* GB785148 (A)

Description: GB785148 (A) ? 1957-10-23

Method for the preparation of low molecular weight polymers of esters ofmethacrylic acid

Description of GB785148 (A)

JeD: e PATENT SPECIFICATION Date of Application and filing Complete Spec No 26293/55 Application made in Italy on Sept 24, 1954. Complete Specification Published: Oct 23, 1 ' Ification: Sept 14, 19 785 148 P 55. P 57. Index atacceptance:-Classes 2 ( 3), C 3 A 1 OE 4 (A 2: B 1: C), C 3 A 1 OE 5 (B: E); and 2 ( 6), P 8 (D 2 82: FX: P 6 X: TIX) International Classification:-CO 7 c CO 8 f. COMPLETE SPECIFICATION, Method for the preparation of Low Molecular Weight Polymers of Esters of Methacrylic Acid We, MONTECATINI SOCIETA GENERALE PER L'INDUSTRIA MINERARIA E CHIM Ic A, a Body Corporate organised and existing under the laws of Italy, of 18, Via Filippo Turati, Milan, Italy, do hereby dedlare the invention, for which we pray that a patent may be grantedl to us, and the method by which it is to be performed, to be particularly described in and by' the following statement: - The object of the present invention is the preparation, from esters of unsaturated carboxylic acids, in particular of esters of methacrylic acid, of low molecular weight polymer O ranging from dimers to polymers having a degree of polymerisation up to 50. Low polymers of this type, especially those of methyl methacrylate, have been prepared and described previously Thus, the diner of methyl methacrylate has been obtained by low pressure distillation of the distillation residues. of the monomer and identified as dimethyl t 1 a-dimethyldihydromuconate (U S Patent No 2,244,487) Subsequently this dimer has also been obtained, together with an isomer identified as

the dimethyl ester of anna,'-trimethyl-glutaconic acid (U S Patent No. 2,244,645) by direct dimerisation of the monomer in vapour phase in the presence of dehydrating catalysts Further, a series of low polymers (diner, trimer and higher) of the same methacrylate has been obtained-by controlled polymerisation in the presence of polymerisation inhibitors (U S Patent No. 2,232,785). The present invention provides an improved process for the preparation of low polymers, and their mixtures, of methyl methacrylate and of other esters of methacrylic acid. In fact, the processes kiown up-to now for 4 Q the preparation of such products, which can be. of considerable interest as intermediates for organic synthesis, as plasticisers for synthetic resins and for other applications, do not give yields which are useful in practice, and prelPrice 3 s 6 d l sent various difficulties This is true in particular for the processes described in the already mentioned U S Patents relating to the preparation of the dimer of methyl methacrylate, but also for the liquid-phase polymeriation process described in the U S Patent No 2,232,785, according to which, even with very prolonged reaction times, not more than 50-60 % of the monomer is converted to use-' ful low polymers The process described in the above mentioned patent consists essentially in heating the monomer at temperatures not higher than 2250 C, in the liquid phase and in the presence of a polymerisation inhibitor. Under these temperature conditions, polymerisation of methylmethacrylate occurs still -to a considerable extent according to a radical chain 1 mechanismr with a successioui of concatenated reactions, some of which are very rapid, which lead to a practically irreversible formation of macromolecules This process is hindered only to a very small extent by the -presence of a polymerisation inhibitor, which, on the other hand, can cause a certain delay in the start of the conversion of the monomer, while the product of the reaction, when carried out to high conversions, contains considerable percentages of polymers with al high degree of polymerisation Further, the presence of an inhibitor often causes a marked discolouration of the products It has now been found that considerably better results can be obtained if the process is conducted within a temperature range, which varies from monomer to monomer, but in general is withi the limits 2250-3500 C, in which the radical chain polymerisation reaction is replaced to al practically complete extent b-y a step reaction composed of a sequence' of bimolecular reactions of a type: Mm + Mn > Mm+n (wherein M is a monomer molecule; m, N are price 25 iindices which can have the values: 1,2,3) separating, in the case of

the more volatile -This type of reaction, in contrast to radical monomers, fractions corresponding to the chain reactions, has an equilibrium, which is various polymers (dimer, trimer, tetramer, temperature controlled and is not influenced by pentamer, etc) and a mixture of higher polythe presence of inhibitors or of molecular mers having a degree of polymerisation higher 70 oxygen Within certain limits, it can be con than 5 With the increase of the degree of trolied not only by varying the temperature but polymerisation, a separation of the individual also by varying the reaction time, affording, polymeric terms becomes practically impossible products of varying compositions, with since the boiling temperatures tend to become differem proportions of dimer, trimer, tetra closer and closer; moreover, above 3000 C, 75 mer, pentamer, etc O until the equilibrium ist the products tend to pyrolyse From the rereached; action product some small amounts of resinBy this purely thermal polymerisation pro ous, high molecular weight polymers can be cess, without addition of any reagent, it is separated, they proportions of which vary l 5 possible to obtain, as is apparent from the depending on the temperature at which the re 80 examples which will be given, very high, some action has been conducted Thus, for methyl times nearly quantitative yields of mixtures of methacrylate, the percentage of resinous polylow polymers of a composition which can be mers on-the total of polymer obtained is 7 5 % controlled within certain limits, and it is also when the reaction is conducted at 2250 C and possible to obtain, starting from mixtures of only of 2 % after an equal reaction time at 85 monomer and a determined polymer (e g, 2750 C; it is likely that in the latter case the dimer, or trimer) or from a determined poly high polymers are formed in practice only mer, mixtures of low polymers with propor during the time of initial heating On the tions of the individual components which cane other hand, at 2000 C a prevailing formation be controlled within certain limits of high polymers occurs, since at this tem go The convenience of operating at tempera- perature the radical-chain polymerisation pretures higher than those of the U S Patent No vails, which gradually disappears as the tem2,232,785 appears evident on examination of plerature increases. the variation of the average molecular weight As regards the reaction conditions, the of the products as a} function of the polymer minimum temperature, as already stated, 95 ilsation temperature varies from monomer to monomer The presFor methyl methacrylate, for example, the sure is autogenous, that is, the pressure of the behaviouxA shown in the accompanying graph natural equilibrium of the system, equal to the (wherein trepresents absolute temperature and total vapour pressure below the critical temM represents molecular weight) is observed,

perature and depending on the charging ratio 100 where the molecular weights obtained ins of the autoclave above the critical temperature. thermal polymerisations are indicated: EI by We have found that in practice it is not essenSchulz and Blaschke (see, for example, Z tial, as would appear from the U S Patent No. Phlys Chemie B 50, 305, 1941); A by Wall 2,232,785, to operate with the monomermin ing-and Briggs '(J Am Chem Soc 68, 1141, liquid phase, and that the critical temperature 105 1946); O by us All molecular weight data does not represent a top limit, no solution of have been obtafned by viscosimetfric methods continuity being observed at this temperature applying the Schulz and Dinglinger correction in the reaction mechanism, especially when the (J Prakt Chemie 159, 136, 1941) except our reaction is conducted at high concentrations, data on polymers obtained at 2250, 2500 and comparable with those of a liquid phase Of 110 2750 C which are derived from cryoscopic course, if the temperature is raised above about measurements 3000 C, the influence of pyrolytic reactions It is' clear that the usual law of the becomes perceptible; the rate of these reactions Arrhenius type, which indicates a radical chain is however relatively moderate and their conmechanism, is followed up to about 150 C squences can be minimised when the process 115 Between about 150 and 2250 C there is a is conducted with short reaction times The range of mechanism transition, and above 2250 reaction time can be regulated in dependence C the reaction becomes a reaction of addition, on the temperature, the higher temperatures by steps aallowing similar results to be obtained in much Our process may be performed by introduc shorter reaction times It must be noted that 120 ing the monomer, or one of the above men the reactions are exothermic and that theretioned mixtures, into a sinless-steel autoclave fore, with an adequate construction of the rewhich isr heated' rapidly to the reaction term gction equipment, it is not necessary to furnish perature by means of a thermostatic oil bath; further heat,, apart from the initial heat necespreferably the monomer or mixture is injected sary to bring the equipment to the required 125 into, the pre-heated autodlave In-practice it is temperature; in certain cases it will be neces-4 possible to operate either in a continuous or sary to employ a cooling system The process discontinuous manner The Jiquid pioducts is carried out, as already stated, in absence of are immediately submitted to-a fractional dis polymerisation inhibitors; the presence of tillation, under a pressure of a few mm of Hg, oxygen, which under these conditions has prac 130 785,148 _ For the dimer of methyl methacrylate, the already known structure corresponding prewvalently to the methyl a,al-dinethyldihydromuconate isomer has been confirmed By-operating as described above, with various monomers and at various temperatures,

the results iudiicated in the following examples were obtained, where the hours relate to the time of permanence at the indicated temperature, whereas the " yield " (total product freed from the monomer) and the percentages of the individual polymeric terms are always referred to the weight of the starting monomer. tically no influence on the polymerisation, does not interfere The lower polymers obtained are esters of diner, trimer, tetramer carboxylic acids; their exact structure is not easily established, but they are probably highly branched, in consequence of the way in which they are formed, by successive addition of monomer molecules to molecules of a low polymer, or of molecules of low polymers one to the other. This appears to be confirmed by the fact that the higher terms of the series are liquid at a temperature slightly higher than room term perature, instead of being solid, as would polymers having a scarcely branched structure. EXAMPLE 1 METHYL METHACRYLATE Temperature 225 C. Hours Yield Dimer Trimer Tetramer Higher Terms 22 81 29 7 18 9 9 8 22 6 96 2 17 7 24 2 18 8 35 5 98 3 4 7 16 7 20 4 56 5 EXAMPLE 2 METHYL METHACRYLATE Temperature 2500 C. Hours Yield Dimer Trimer Higher Terms % o/% % (+tetramer) % 1 1/4 46 30 5 9 3 6 2 3 68 35 5 18 3 14 2 6 83 2 27 9 27 9 27 4 -92 3 19 1 29 7 435 13 3/4 95 3 13 9 26 2 55 2 16 96 1 11 1 24 61 23 97 2 6 1 19 7 71 4 33 97 8 6 19 72 8 98 5 2 19 73 8 46 98 5 1 19 73 9 785,148 i t i 71 i i 785,148 L EXAMPLE 3 METHYL METHACRYLATE Temperature 2750 C Autoclave of 200 ml capacity Initial monomer charged 100 g. Hours Yield Dimer Trimer Tetramer Higher Ti erms 1 65 35 16 8 7 3 91 18 24 19 30 96 10 -23 23 40 99 6 21 26 46 99 4 21 27 47 24 99 4 21 27 47 EXAMPLE 4 METHYL METHACRYLATE Temperature 350 C. Hours Yield Dimer Trimer Tetramer Higher Terms 3 82 3 24 6 21 5 13 3 22 9 The relatively low yield obtained at this temperature is to parallel pyrolytic reactions. be ascribed to a concurrence of EXAMPLE 5. The following table shows, for the case of methyl methacrylate, how mixtures of polymers can be obtained by employmig, as starting materials for the process, mixtures of Monomer and low polymers or low polymer alone. Starting Time Temperature Yield Dimer Trimer Tetramer Higher Terms compound hours 'C. % monomer + 50 % 24 275 98 5 4 5 19 27 48 dimer J Dimer 9 250 100 39 2 60 8 Trimer 9 250,, 78 2 21 8 Tetramer 40 275,, 0 5 3 5 50 46 The

process according to the present invention may be applied not only to methyl meth-. -;acrylate but also methacrylates of alcohols of higher molecular weights, following examples: as is shown by the EXAMPLE 6. By operating with monomeric butyl methacrylate under the conditions described, the following results are obtained: Temperature Time 0 (. Yield Dimer hunirs Trimer Tetramer Higher terms 0/o 0/o 0/O 9 1 Ev 1 r 1 1 u/9/ /v 250 19 92 15 2 27 22 28 275 24 98 8 6 11 5 23 6 54 3 EXAMPLE 7. With 2-ethyl-hexyl methacrylate, by heating for 1 hour at 275 G, the following results are obtained: yield of polymers 62 Q%, of which 36 % dimer, 19 i% trimer and 7 6 % higher terms. The lower polymeric terms contained in the products obtained in the experiments which have been described in the foregoing examples, have been characterised on the basis of their boiling point, specific gravity, refractive index 15 and saponification value, as shown in the following table: MATERIALS Molecular Boiling Density at Refractive Saponification weight Point/2 200 C index at value mm Hg (D 2 20) 200 C. C N 20 METHYL METHACRYLATE Dimer 200 88 90 1 0447 1 4466 560 Trimer 300 148 150 1 073 1 464 560 Tetramer 400 195 200 1 094 1 468 560 Pentamer 500 230 240 1 112 1 472 560 BUTYL METHACRYLATE Dimer 284 130 135 0 958 1 445 394 Trimer 426 187 185 0 982 1 475 394 Tetramer 568 240 245 0 975 1 462 294 2-ETHYL-HEXYL-METHACRYLATE Dimer 396 180 185 0 927 1 454 283 Trimer 595 240 245 0 932 1 458 283

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* GB785149 (A)

Description: GB785149 (A) ? 1957-10-23

Improvements in or relating to rotary fluid control valves

Description of GB785149 (A)

PATENT SPECV I F ICATION \ PATENT SPECIFICATION tbate of Application and filing Complete Specification: Sept 20, 1955. 785,149 No 26895/55. Application made in United States of America on Feb 16, 1955. Complete Specification Published: Oct 23, 1957. Index at Acceptance:-Class 135, VE( 1 H: 5 B: 6 B), VM 3 B, VN 3. International Classification:-F 06 k. The inventors of this invention in the sense of being the actual devisers thereof within the meaning of Section 16 of the Patents Act, 1949, are VINCENT KILEY VAN ALLEN and DAVID LUKE MORGAN both of Bridgeport Thermostat Division, Robertshaw-Fulton Controls Company, 1225 Connecticut Avenue, Bridgeport 1, Connecticut, United States of America, both citizens of the United States of America. COMPLETE SPECIFICATION Improvements in or relating to Rotary Fluid Control Valves We, ROBERTSHAW-FULTON CONTROLS COM having a chamber therein, a first rotary valve PANY, a Corporation organized under the laws closure member within said chamber movable of the State of Delaware, United States of between first and second positions and having a America, of 110, East Otterman Street, port for high pressure fluid and a port for low 45 Greensburg, Pennsylvania, United States of pressure fluid, said ports selectively interAmerica, do hereby declare the invention, for connecting said conduits when said first valve which we pray that a patent may be granted to member is in either of its two positions, said us, and the method by which it is to be per first valve member having a first passageway formed, to be particularly described in and by establishing communication between said high 50 the following statement: pressure port and said chamber to normally This invention relates to rotary fluid control maintain a fluid pressure in said chamber valves and more particularly to valves for use which tends to force said first valve member in refrigerating or air conditioning systems against said header and a second passageway It has been customary in such devices to for allowing flow of fluid from said chamber 55 provide a rotary member rotatably mounted on to said low pressure port, a second valve a header having a plurality of parallel conduits closure r 2 member pivotally mounted on said first therethrough The rotary member is usually rotary valve member and-being rotatable about provided with ports which selectively inter

its pivotal mounting from an inoperative posiconnect the conduits as the rotary member is tion wherein flow of fluid through said second 60 rotated Although effective when used in low passageway is prevented to an operative pressure applications, this arrangement has position where flow of fluid is permitted been found to be unsatisfactory -when used in through the second passageway to reduce the a high pressure application, such as a refriger fluid pressure in said chamber tending to force ating system said first valve member against said header, 65 If the pressure within one of the conduits is the second valve member being rotatable high, it will tend to force the rotary member from an inoperative position to an operative from the header, thus presenting a sealing position when the first valve member is moved problem To overcome this, some devices between its positions, there being a manually permit the flow of high pressure fluid into a operable lever having one end available beyond 70 sealed chamber on the other side of the header the housing and the other end received in the The high pressure fluid then tends to force the second valve member for moving the first valve rotary member against the header Although member-between its two positions, said manuthis arrangement eliminates the sealing prob ally operable means first moving the second lem, it has been found that rotation of the valve member over the first valve -member to 75 rotary member is more difficult due to the said operative position and then effecting moveincreased friction between the rotary member ment of the first valve member from one of its and the header, positions to the other. According to the present invention there is The invention will now be further described provided a rotary fluid-control valve com with reference to the accompanying drawings 80 prising a housing including a header having a wherein: plurality of conduits therethrough, said housing Fig 1 is a front elevation partly in section of lPrice 3 s6 d l 785,149 a rotary fluid, control valve; Fig 2 is awsection taken on the line II-II of Fig 1,_ Fig 3 is a section taken on the line Hi-IAf ig 1 Referring more particularly to the drawing, the valve includes a hollow: casing 10 of generally cylindrical configuration and having a conical shaped end portion defining a chamber 11 therein The casing 10 is provided with two annular indentations 12, 12 in the wall. thereof which are adapted to be received in two annular recesses 14, 14 in a wall of a header 16 later to be described. The conical shaped end of the casing 10 is provided with a flarned end portion 18 carrying a fiang 2-) having a= second flange 22 attached thereto and provided with an annular boss 24. The header 16 is held in a fixed position in the lower end of the casing 10 by the annularindentations 12, 12 in the annular recesses

14, 14 A plurality, in tbis instance four parallel. conduits 26, 2 8; 30 and 32 for fltuid extendthrough the header 16 Each of the parallel. conduitss,26, 2 &, 30 S 32 is provided with a recess 34 in the Qutiter end thereof to -receive-a section. Of copper tubng 30-which engbles each f the conduit 26, 28,,'30, 32 to be connected to a. system now,-to be described. The, coniduits 26, 28 are adapted to be connectedrrespectvely by means of the tubing 36. to the-high,'pressiire (discharge-) side-and to thez ow.pre u nside of Ccompressor @t shpu,) in a refrigerating or air condtioning syspein, N The,: condfits 30, 32 are adapted ta be c Rocted respectively bym means of the. t g>,t 3, o,heat exchangers (not sh Qwn) such -ds-al condenser, and evaporator in a ref 1 ger'atingsyse Imnl 1 iorthe rorma Iw operati Qnof the system, conduits 26, 30 sh.ogiu 4 b Jeintirceomnected and comnduits 28, 32 s 1 on 1 ('be, interconrsiectedto allow -flow -of fluid from the discharge side of the corm pressor into condoimt 26 aindt out conduit 30; tlirough. thetwo heat e-chan-g-ers, into' conduit 32, -out, condut 28 Yand into ti lqeow-pressure side of -tlhecomp ressor. Tintt-rcoit ne ct the conduits 22 28, 30, 32 as aboa_ desr'd, a rotary -valfve member. 38 io'ro lysoun(ted, og the top of the. headier i 16, The rotairyvalve ntmeiber-38-is of generally, dricalconfiglration and has an, -enddface 39, th end colwiic seats upo,,the top sfacw e of,the header 46 Th matingsurfaces of the headei 16 and the end face -39 of the- rotary valge, nmber, 38 are highly. -1 appedsrfaces, to insuge -no leakage of fluidtherebetwen A, Xdividing wafll,40 is formed: wvithin tbaerot'ary v 4 emeinber-38 and defines two chambers 42 44 with the rotary valve member, 38 In the position shown, the chambex, 4,26 e 6 nel-pos th&e coduits 28, 32, and the chamber 44-wich Partially surrounds. the chaxpbemr 42 e vvelops Fthe coniduits -26 30,,. thus theconduits 28 ' 3 '2 and c 6 ncduits 26,' 30 are interconnected. It will be noted that if the rotary valve member 38 is rotated 1800, the chamber 42 will interconnect the conduits 28, 30 and the chamber 44 will interconnect the conduits 70 26, 32, thus reversing the flow of fluid through the heat exchangers To provide for rotation of the rotary valve member 38, a recess 46 is formed in the conduit 28 near the top of the header 16 A bushing 48 has a portion fixed 75 within the recess 46 and a portion projecting from the header 16 which is

slidably received in a recess 50 formed in the dividing wall 40. Thus, the rotary valve member 38 is rotatable on the bushing 48 to selectively interconnect 80the conduits 26, 28, 30,,32. It should now be noted that the high pressure fluid in the chamber 44 will tend to force the rotary member 38 away from the header 16 and that it is necessary to provide a force which 85 tends to force the rotary valve member 38 tgward the header 16 if leakage between their mating surfaces is to be prevented: To this end, a port 52 is provided in the wall of the rotary valve member 38 to allow communica 90 tion between the chamber 44 and the chamber 11 Thus, flow of fluid is permitted from chamber 44 to chamber 11, and a-fluid pressure is maintained in chamber 11 which is equal to the fluid-pressure in chamber 44 However, it 95 can be seen that fluid pressure in the chamber 11 acts on a larger area of the rotary valve member than does the fluid pressure within, chamber 44, thus a resultant force is created which tends to-force the rotary valve member 100 38 toward the header 16. Although the pressure in the chamber 11 tends to force-the rotary valve member 38 toward the header 16 and effect a seal between. their mating surfaces, the friction between the 105 mating surfaces is increased and manual rotation of the rotary valve member 38 would be, difficult if the high pressure fluid were maintained in chamber 11 during, rotation of the rotary valve member To permit easier 110 rotation of the rotary valve meimber 38, a means is provided which reduces thie fluid: pressure inthe-chamber 1-1 during rotation of _ the rotary valve member A An equalizing selector-54 forming a valve closure -member is-, 115 pivoted on a raised surface 56 of the rotarym valve-member 38-;by a pin 58 andjis, free, to rotate -ab out the pin 58 between two stops 60,: 62 The-equalizing selector 54 is biased to the 1 stop A 62 by the spring 64 which has, one end 120 attached to a pin 66 projecting from the rotary valve, member 38 a d the opposite end fixed, by a suitable means to the-equalizing selector 54 The spring 64-mounted in ten sion between the equalizing selector -54:-and: 125 the, pin 66 normally holds the equaliving. selector 54 in engagement with the stop 62 A port 68 is positioned on a-curved Raised I surface -70:which-is engqged by the free-end-of-' the equalizing selector 54 duirjng-1 rotati N 130 785,149thereof' The port 68 is of larger diameter than the port 52 and extends through the wall of the' rotary member 38 ' to establish communication between the chamber 11 and' the chamber 42. When the-eqdalizing selector 54 is in engagement with, the-stop 62 as shown; it covers the port 68 and-prevents flow of flui dtherethrough.

However, if the-equalizing selector 54 is rotated: counterclockwise to, engage the stop, 60; the port 68 will; be uncovered and the pressure in the chamber 11 will cause fluid to-flow throughthe port 68 and into the low pressure chamber 42 Since the port 68 is of larger diameter than port 523 the flow of fluid through port 68 will be greater and the pressure in the chamber will decrease reducing' the force tending to force the rotary valve member 38 against the headen 16 thus, effecting easier' rotation-of-the rotary valve member 38 The equalizing selector 54 is provided witir a recess 72 in the top thereof which is adapted to receive an operating end 74 of a lever assembly including a flexible bellows 76 The opposite end of the bellows 76 is attached to the flanged end portion 18 of the housing 10. Thus, the bellows 76 hermetically seals the chamber 11 A curved operating shaft 78 extends through the bushing 24 and into the bellows 76 to have one end in engagement with the inner side of the operating end 74 The opposite end of the shaft 78 extends exteriorly of the housing 10 to receive a manually rotatable knob 80 Rotation of the knob 80 will cause rotation of the curved shaft 78 and the operating end 74 of the flexible bellows 76. When the operating shaft 78 is rotated, the equalizing selector 54 will be rotated until it engages the stop 60 uncovering the port 68, which permits flow of fluid from the chamber 11 into the chamber 42 to reduce the pressure forcing the rotary valve member 38 against the header 16 Since the equalizing selector 5 is in engagement with the stop 60, further rotation of the knob 80 causes the rotary valve member 38 to be rotated about the bushing 48. When the rotary valve member 38 has been thus rotated 180 the knob 80 is released and the spring 64 causes the equalizing selector 54 to rotate until it engages the stop 62 and covers the port 68 thus, allowing pressure to build up again in the chamber 11. OPERATION The conduit 26 and the conduit 28 are connected respectively to the high pressure (discharge) side and low pressure (suction) sides of a compressor in a refrigerating or air conditioning system by means of the tubing 36. The conduits 30, 32 are connected one each to the two heat exchangers (condenser and evaporator) by means of the tubing 36 In the position shown, fluid will flow from the compressor into the conduit 26 and the chamber 44, out the conduit 30, through the two heat exchangers, into the conduit 32 and the chamber 42 and back into the compressor by the conduit 28Should it be desired to reverse the flow: through the two heat exchangers, the knob 80) is rotated counterclockwise Rotation of the 70 X knob 80 first rotates the equalizing selector 54counterclockwise until: it engages the stop

-60decreasing the fluid pressure within the chamber 11 tending to force the rotary valvemember 38 toward the header 16 Further 75 ' rotation of the knob 80 causes the assembly of the rotary valve member 38, equalizing selector 54 and' spring 6-4 to rotate about the bushing 48 When-the rotary member has-beenrotated -1809 ', the -knob 8 T is released, andithe 80 " equalizing selector 54:is returned to its-originalposition by the spring 64-to-engage the stop-62. The chamber 42 now envelopes the conduits 28-fi 30: andl the chambern 44 envelopest the conduits 3, 2 '6, Thus, the fl Tobwtlhtilkai the 85 heat exchangers is reversed. It will be apparent that the device herein disclosed is not limited to use with refrigerating or air conditioning systems, but may easily We used with any pneumatic or hydraulic applica 90 tion requiring a flo W reversing means It will also be apparent that various changes may be made in the form and arrangement of parts and in the details of construction herein disclosed 95

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* GB785150 (A)

Description: GB785150 (A) ? 1957-10-23

Improvements relating to the treatment of distillation of synthesis gases

Description of GB785150 (A)

COMPLETE SPECIFICATION Improvements relating to the treatment of Distillation of Synthesis Gases We, SIMON-CARVES LIMITED, a British Com- pany, of Bird Hall Lane, Cheadle Heath, Stockport, Cheshire, do hereby declare the invention (Communicated by DR. C. OTTO &

COMPANY, a German Company, of Bochum, Germany), for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly-described in and by the following statement :- This invention relates to a method for extracting valuable substances which are capable of being extracted from a liquid - by passing the liquid through an ion exchanger, from gases obtained by distillation or synthesis, in particular ammonia from gases obtained in the distillation of coal, by means of a step-bystep gas washing process. Normally the percentage of the substances to be removed by washing is very small compared with the total quantity of gas. In order to be able to remove the substance concerned at least nearly entirely, which is mostly desirable in order to keep the gas clean, very large quantities of liquid are required, whose further processing for the purpose of extracting the substances absorbed by the liquid involves expensive installations and considerable operating costs. - Thus, for instance, when separating the ammonia from the liquor obtained in the normal gas washing process, so much live steam is. required that frequently the entire process of extracting the ammonia becomes uneconomical. Similar conditions obtain in the extraction of other valuable substances, such as sulphur compounds. Many proposals for the reduction of the cost of removing the quid diluting the washed-out valuable substance are almost without exception based on the idea of extracting the valuable substance only partly and rendering- the remainder of the liquid in some way-harmless. Mostly this involves again considerable costs, because normally it is not permissible to let the residual water run into natural rivers or lakes, because of its dangerous effects on the flora and fauna. It is the purpose of the invention to make the extraction of the valuable substances from the washing liquid of the gas washing process as complete as possible, but with a very considerable reduction of the processing costs. According to the invention, the washer liquid in the first stage in the path of the gas is brought to a concentration as high as possible of the valuable substance to be recovered, without talking the washing effect into consideration. This can be achieved without difficulty by a corresponding adjustment of the operating conditions, that is to say, by selecting the -most favourable conditions of pressure, quantity, temperature, and time of application of the washing liquid. For instance, - the ammonia concentration of the outlet liquid of the first stage, which in the hitherto generally used ammonia recovery process amounts to about 10 to 12 grammes per litre, can be increased to about 50 to 100

grammes per litre. Oa the other hand, the washing liquid in the second stage is enriched with the substance to be washed out only to such an extent and under such conditions that the final gas is sufficiently pure. From the small. quantities of the outlet liquid of the first stage, the valuable substance present in a high concentration is extracted in the usual manner, preferably by driving it off by means of steam, and from the larger quantities of outlet liquid from the second stage the substance is removed by passing this second outlet liquid, containing a low concentration of the valuable substance, through an ion exchanger. After the exchanger mass has been enriched sufficiently, the valuable substance in question is recovered by regenerating the mass. The method according to the invention offers a number of considerable advantages. For the removal of the small quantity of liquid obtained froin the first washing stage a fraction only of the quantity of live steam which was required in the past is necessary. Also, the concentration of the valuable substance in the vapours driven off is much higher than hitherto, so that also the quantity of accompanying steam can be reduced approximately in proportion with the increase in the concentration of the valuable substance in the liquid to be removed, which correspondingly cheapens the sub sequent processing of the vapours. Frequently the enriched outlet liquid must be processed chemically before or during the driving off of the desired substance, and thereby absorbs solids which may render further processing uneconomical. In the processing of ammonia liquor, this is, for instance, the known treatment of the liquor with milk of lime. In order to carry out the method according to the invention for recovering ammonia, the milk of lime column of the separating plant can be dispensed with completely. The outflow from the separator, which is now no- longer fouled by lime, is according to a further feature of the invention passed together with the outlet liquid from the second washing stage through the ion exchanger, which retains also the ammonia which has not been driven off from the separator outflow. The liquid leaving

the ion exchanger contains no impurities, apart from small quantities of free acids, and can be left to flow without clarification into natural rivers or lakes, possibly after purification in an acid exchanger. The outlet water from the ion exchanger is in general practically free from the valuable substance washed out of the gas, - and can therefore be used for many purposes. Preferably it can be returned partly or completely to the circulation in the second washing stage. It is convenient to use as the washing liquid for the first stage a part of the outlet liquid from the second stage, which contains already a small concentration of the valuable substance to be washed out In this case, the liquid drawn off must be replaced- by admitting fresh liquid, if the washing liquid of the second stage is to circulate. If the washing Iiquid for the second stage absorbs in addition to the substance to be washed out also other components ofthe gas, for instance, in addition to ammonia also hydrogen suLphide, carbon dioxide, and the like, these substances remain more or Iess in the outlet liquid of the ion exchanger. According to a further development of the invention, the liquids obtained in a preliminary treatment of the gas before the first washing stage, which obtain the valuable substance to be washed out, are admitted to one of the two washing - liquids of the stage-by-stage gas washing process, according to the concentration of this substance. Normally it is advisable to add them to- the liquid obtained from the second washing stage. In the preliminary processing of gases obtained in the distillation of coal it is mainly a question of dealing with -the flushing liquid or bathe gas collector main or the flow branched off the circulating liquid and the condensate obtained in the cooling of the gas. In the circulation of the washing liquid, an equilibrium is soon obtained in the various substances involved, that is to say, the washing liquid in the second stage absorbs practically only the valuable substance which is to be washed out. In the processing of gas obtained in the distillation of coal also

residual quantities of what is known as fixed acids, for instance, hydrochloric acid, thiocyanic acid, and the like, are washed out in the second washing stage and produce in the liquid passing to the ion exchanger a certain content of fixed ammonia salts. When these fixed salts are decomposed in the ion exchanger; acids- are formed which do not escape in the form of gas, as do for instance, carbon dioxide, hydrogen sulphide, and hydro-cyanic acid, or cannot be removed from the exchanger outlet liquid by densifying or evaporation. If the exchanger outlet liquor is used as the washing liquid in the second washing stage, the acids remain in the liquid circulation of this stage. If, according to a further development of the invention, the liquid obtained in the preliminary processing of the gas, i.e. before~ the first washing stage, which contains one or several ofthevaluable substances which are to be washed out, is also passed to the ion exchanger, the free acid contents- of the exchanger outflow is further increased. The content of free acids, which may reach a pHvalue of 2 to 3, has a very favourable effect on the washing process in the second washing stage. In the further processing of the mass of the ion exchanger with the absorbed valuable substance, by means of a suitable regenerating agent, a highly concentrated solution is obtainted. This solution can be processed preferably together with the separator vapours, which are also highly concentrated, in order to extract the valuable substance in a common installation, for instance, if ammonia is to be extracted, in an ammonium salt saturator. Referring to the accompanying drawings Figure 1 shows diagrammatically an installation employed to carry out the method according to the invention. All parts of the installation such as the gas exhauster, liquid pumps, heat exchangers, stop valves, and by-passes, not essentiaI to the understanding of the nature of the invention are not shown, in- order to improve the clarity of the illustration. An installation for the indirect extraction of ammonia from gas obtained in- the distillation of coal has been assumed as an example of an ~ embodiment of the invention. All numerical data refer to I tonof coal throughput in the distilling furnaces. The various figures denote the quantities of liquid passing through the various pipes concerned, in litres, and the numbers in- brackets indicate the ammonia content of these liquids. in grammes per litre. A gas collector main 1,. a gas cooling instal lation 2, and: the two stages 3 and 4 of an ammonia washing installation are connected consecutively into the crude gas pipe 10. from the distilling furnace. This washing installation is operated in such

a way that the ammonia content of the. gases leaving the last washing stage 4 corresponds normally to a maximum of 2 grammes per 100.N cubic meters. It is assumed that the quantity of the liquid obtained in the preliminary treatment of the gas in the collector main 1 and the cooling -installation 2, after removal of the gas tar in the tar separator 6, amounts to 110 litres. per ton of coal throughput, with an average ammonia concentration of 9~grammes per litre. In. the-first- washing stage 3 in the path of the gas, the g3. is washed with a part of the liquid obtained from the second washing stage 4, the quantity being 27 litres. of liquid per ton of coali throughput, the ammonia content of which may amount to about 0.6 g/l. After its passage through the washing stage 3, this quantity of liquid has been enriched to about 60 g/l and reaches a separating column 7, in which the ammonia is driven off by means of live steam, so that the ammonia content drops to about 2 girl. The remainder of the liquid obtained from the second washing stage, which is not passed through the stage 3, 95, litres- per ton of coal throughput, is combined with the outlet liquid of the separator 7 and the ammonia solution obtained from the tar separator 6. The total quantity of liquid, 23S litres, with an ammonia content of 4.7 g/l,. flows into an ion exchanger, which consists of two installations 5 and 5a operated alternately. The ion exchanger 5, which is the one in operation, retains a practically all the ammonia from the liquid passing through it, so that the ammonia content of the outlet liquid from the exchanger amounts only to about 0.02 g/l. About one half of this outlet liquid, 122 l/t coal throughput, flows in circulation back to the second washing stage 4, while the other half may be used for any other purposes or can be piped to the drain. It is convenient to admit through the head of the washer 4 about 10 litres of fresh water per ton of coal throughput, while the fresh water requirements of the normal indirect method of extracting ammonia amount to about 150 Vi coal throughput. In the usual

process this large quantity of fresh water eventually becomes the outflow liquid from the separator 7; fouled with lime and therefore unusable. However, in the method according to the invention, the lime column of the separator installation can be omitted com pletely. The mass enriched with ammonia, of the ion exchanger Sa, which is disconnected from the path of the liquid, is regenerated with sulphuric acid. The outlet liquid flows to an ammonia saturator 8. The vapours from the separator 7, complaining a high. concentration: of ammonia, flow alsoi into this ammonia saturator and are further processed in this.. saturator 8 together with the regenerated solution, with a further addition Of sulphuric acid, so that ammonium sulphate. is obtained. The total quantity of ammonia obtained from the crude gas is therefore recovered at this point The costs of constructing an installation: for carrying out the process according to the 'in- vention are approximately equal to the costs of an installation of the. usual type for the indirect recovery of ammonia The lime column and lime processing installation, which are no longer required, are replaced by an ion exchanging installation 5, 5a. As in the usual type of installation, the outlet - vapours from. the separator column 7 can be further processed to obtain a concentrated ammonia liquor instead of ammonium salts in the. saturator 8. Apart from. the fact that for carrying out the method of the invention only a very small fraction of the quantity of fresh water previously required for the ammonia washing installation is necessary, a further essential advantage of the invention lies in the fact that a considerable quantity of live steam for the separator column 7 is saved. Figure 2 shows the graph. of the steam re- quirement of the separator column Z, referred to- the ammonia concentration of the outlet water from the ammonia washer 3. In the usual ammonia extraction method, the outlet vapour of the separator column 7 contain about 8 parts of accompanying steam. to one part of ammonia. The graphs shown datted are based- on this ratio z=8. It is known that the steam consumption of the separator column depends to a considerable extent on the inlet temperature tAw of the admitted ammonia-containing water. It amounts to about 6.4 kilogrammes per kilogramme of ammonium sulphate, if nonpreheated water at 25"C, with an ammonia content of 10 g/l, the usual concentration of ammonia in the indirect process, is

passed through the separator. The steam consumption is reduced with an increase in the ammonia content to about 60 g/l, which can easily be achieved in the outlet liquid of the first working stage 3, to about 3 kilograms of steam per kilogramme of ammonium sulphate, all other conditions remaining equal. Owing to the high ammonia-concentration of the liquid passing into the separating installation, the process according to the invention is still very satisfactory for a sufficient removal of ammonia at a ratio z=4 of the accompanying steam to ammonia in the outlet steam coming from the separator column 7. - It must be taken into account here that the ammonia still contained in the outlet of the separator column 7 is practically entirely retained in the ion exchanger 5, 5a, so that it is not lost. The graphs of Figure 2 drawn in full lines, referred to an accompanying steam ratio of z=4, show that in the method according to the invention only 1.7 to about 2kg of live steam are required per kilogramme of ammonium sulphate in the separator, according to the preheating of the liquid passing into the separator column. The main disadvantage of the indirect method of extracting ammonia, as used hitherto, is the high live steam requirements ofthe ammonia separator column, so that this is considerably reduced by the present invention. All advantages of this method, in particular the simple and orderly arrangement of the- operation of the installation, are fully retained. What we claim is :- 1. A method for the extraction of valuable substances from distillation or synthesis gases by means of a stage-by-stage washing process, in which-the washing liquid of the first stage in the path of the gas is-brought to a concentration as high as possible of the substance to be washed out, by means of a corresponding regulation of the operating conditions, and the washing liquid of the second stage is enriched with this substance under conditions enabling the valuable substance to be extracted from the gas to a sufficient degrce, the washed out substance being driven off from the washing liquid of the first stage by the usual method, preferably by means of steam, and being recovered from the washing liquid of the second stage by passing this liquid into an ion exchanger, and subsequently regenerating the enriched exchanger mass. 2. A method according to Claim 1, in which a part of the liquid from the second washing stage is employed as the washing liquid for the first stage. 3. A method according to Claims 1 and 2, in which the liquid flowing out of the ion exchanger and freed from the washed-out

valuable substance is returned to the circulation at the second washing stage. 4. A method according to Claims 1 to 3, in which vapours or liquids obtained by passing the washing liquid of the first stage through a separating stage, and in the regeneration process ofthe ion exchanger mass, are processed further together, order to recover the valuable substance contained in them, which was washed out of the gas, for instance, in the case where ammonia is being recovered, in an ammonium sulphate saturator. 5. A method according to Claims 1 to 4, in which liquids obtained in preliminary treat ment of the gas and containing the valuable - substance to be washed out, are added according to the concentration of the valuable substance to one of the washing liquids of the stage-by stage gas washing process, preferably to the outlowing liquid of the second washing stage. 6. A method of recovering valuable sub stances from distillation or synthesis gases, substantially as described.

* GB785151 (A)

Description: GB785151 (A) ? 1957-10-23

Means for arresting aircraft and other mobile objects

Description of GB785151 (A)

: - PATENT SPECIFICATION Inventors: 'ROBDRMT B, COTTON and DONALD B DOOLITTLE 785,151 Date of Application and filing Complete Specification: Sept 21, 1955. No 26978/55. Complete Specification Published: Oct 23, 1957.

Index at acceptance:-Classes 4, G( 4: 7); and 108 ( 3), 58 M 2 A. International Classification:-B 64 f F 06 f. -C Oi MPLETE SPECIFICATION Means for Arresting Aircraft and other Mobile Objects We, ALL AMERICAN ENGINEERING COMPANY, a corporation of the State of Delaware, United States, of America, and having -its principal place of business at Du Pont Airport, 'Wilmington, lDelaware, United' States of America, do hereby declare the invention, for which we pray, that a patent may be granted to us, and, the method by, which it is, to be performed, to be particularly described' in and by, the following statement: - The present invention' relates to means for arresting aircraft and other mobile objects traversing a surface, a landing strip in the case of aircraft The principal object of the invention is to provide an expeditionary form of arresting gear readily transported and set up in various localities, within a minimum time. Accordingto the invention, there is provided an, arresting means for aircraft and, other mobile objects traversing a surface and, adapted for engagement withh an arrest cable stretched across the surface, comprising a unit in the form of an elongated tube adapted to 'be filled with liquid and sealed with an arrest. piston normally at a starting position at one end of said tube, said piston being adapted to permit displacement of liquid past itself as it is pulled' through -the tube so as to establish a predetermined resistance to the pulling force, means for connecting said' arrest cable to the piston through 'a cable outlet at the opposite end' of the tube for applying the pulling force to the piston to effect forward displacement thereof through the tube, retrieving means for returning the piston to the starting position and means which restrict or make up loss of liquidl at the outlet as the piston is pulled through the tube. -The arresting unit and the arrangement thereof 'in conjunction with a landing strip according to the invention willi be further described with reference to the accompanying drawings which show several embodiments by way of example. I 1 N the drawings, wherein like pants are given like reference numerals and are thus identified throughout the following description: Fig 1 is a general layout perspective view of a landing runway with arresting units according to the invention mounted adjacent thereto for operation; Fig 2 is an assembled elevational view partly in cross section of one form of the complete arresting units; c S o lFig, 3 ' is a longitudinal cross section view of one form of valved arrest piston used in the arresting unit; Fig 4 is a transverse section through the housing 'tube or cylinder for the arrest piston showiing in elevation, the centrifugal circulating pumlps and motor for

retrieing the piston; Fig, 5 is a transverse cross section of one of the arresting cable sheavesl; lFig ' 6 is a top planl view showing the sheaves and arresting cable in position for an arrest; Fig 7 is a cross section view of a second' form of valved, piston used' in the arresting device; -Fig '8 is, a cross section view of a third form'of piston;' Fig 9 is a cross section view of the cylinder and of a fourth form of piston in elevation; lFigure 10 is a cross section view of ithe front end of the cylinder showing 'the piston's position after an arrest and' showing the retrievinig and leakage replenishing mechanisms; and Figure 11 is an enlarged view showing the cable 'guides and connections to the piston head. Referring to the drawing in detail and, first with particular reference to the installation layout of t Figure l, there is shown any well known aircraft landing deck, mat or runway A with arresting gear units R and 'C arranged longitudinally along opposite sides thereof The unit B is positioned ahead' of the unit 'C in the direction of 'travel of the landing aircraft, whereby a series of arresting cable legs 'D, 11, 12: and 13 ' (Figure 1) are provided' across the X i 1 i i 1 i 785,151 runway-A in a manner to enable anyone of the same to engage with the arresting hook 14 of the aircraft 15, In Figure 1 the aircraft arresting hook has caught the cable leg 12. I From Figures 1 and 6, it will be appreciated that a single arrest cable may be looped to form a plurality of legs, the ends' of the cable being anchored to the arrest piston in one of the units, Each of the units B and C is identical in structure the B unit being arranged on the left side of the landing deck A, and the 'C on the right sidethereof. Each unit comprises an elongated hydi aulic fluid 'holding tube or cylinder 16 formed of a plurality of sections 17 with coupling flanges 108 boltedi together, see Figures 1 and 2. Within the cylinder is an arrest piston 19, one form thereof being illustrated in Figure 3. The piston 19 is a valved piston and the head or forward end of the piston is coupled to the cable ends of the arrest cable which may be looped around rectangularly spaced and, positioned sheaves 21, 22, 231 and 24, see Figures 1, 2 and-" 6 'For convenience of reference the arrest cables are also generally; indentified as deck pendants or loops ID -Each sheave is shielded byma cover or'housing 26 open on the side leading into the deck pendant arresing lip, i D,' which housing, is mounted on a base plate 27 and anchored, to the ground by stay wires 28 secured from each : corner of the base plate Two coupling ferrules with, bifurcated ends 31, see Figure 3, are arranged' side by side to hold the -cable ends and said ends 31 -are connected by a pin 7 32 to a valve actuatiiig lever 33 The lever 33 in turn connects to a

bell-crank lever 34 pivoted to the valve head 316, saidr bell-crank having 'one arm 35 in endwise abutment with the valve -loading pistaon 361 of the valve 37. The valve 3 '7 is pressure loaded to its seat -40 by, suitable means, such as fluid inlet conduit 3 '8 leading from a pressure source into the hollow -loading -chamber 39 rearward of the valve leading piston 36 ' The valve seat 40 is formed on the rearwardly extending skirt 41 -spaced apart from the centre of the valve' head -36 by a spide T structure 42 through which fluids may pass to force open the valve 3 i 7 at -pretdetermined arresting loads Also, 'it is tortbe noted that when load; is applied to the cable arresting loop Dl, the bell-crank arm 35 boosts the pull 'against the resistance of the loading piston 361 8 so 'that 'the valve 37 is cracked -open and then remains open by the flow' of fluid -therethrough as the arrest piston' continues to be drawn forward through the tube 16 The present system is a fluid system constantly maintained loaded with hydraulic fluid by a replenishing pump 43 in line 44, see Figure 2 'h-is pump is large enough to only provide an output sufficient to replenish the leakage at the cable outlets and calibrated low enough in output so as not to cause premature retrieving of the cable at the end of the arrest. In the present system the fluid is kept stationary by passing a valved piston through the fluid instead of forcing the fluid through a 70 valve In order to adjust the valve and piston a closure 37 a is provided in the cylinder head, see Fig 2. RETRIEVING EQUIPMENT The retrieving of the cable after an arrest is 75 accomplished by the by-pass conduit 45 extending from side connections 46 at the tail end of the cylinder assembly longitudinally and parallel thereto into side connection 47 at the head of the cylinder assembly The con 80 duit 45 at the junction with side connection 47 connects to the replenishing line 44 as in Figs 2, 6 and 10 to the head, of the cylinder. Interposed in the retrieving conduit 45 is a pump, such as a centrifugal pump 48 driven 85 -by a -suitable motor 49 and interposed in the conduit 45 t between the output side of the pump and the -side connection 47 is a retrieving control, valve 50, such as a gate valve with an operating lever 51 90 INITIAL ACCELERATION TIME DELAY Connected into the side of the cylinder 16 at the tail end by connections 52 and 53 and preferably on anm opposite side from the connection 46 is a time delay by-pass line 54, 93 which may have interposed in the line a relief valve 55 set to blow off at about 12 S P S l. With the initial, pull on the cable and forward movement thereby imparted to the piston the fluid is allowed to by-pass through the 103 time delay tube, until the piston passes the -port of connection 53

After passing the port at 53 the fluid must then pass through the fluid loaded valve in the piston 19 as the result of the cable payout For example, at maximum 105 cable load the pressure built up in the cylinder is approximately 1600 'P S I and the fluid or air loaded valve keeps' the cable load substantially constant. Different forms of pistons with or without 110 valve structures may be used in the system. The piston may be solid with _a relatively smaller outside diam -ter than ithe arrest tube bore and, for example, a second form; of piston with an-airloaded valve is illustrated in Fig 115 -7.<T'his form comprises a head portion 55 with a hollow cylindrical nose 56 formed with fluid intake ports 5 7 and a leading end plate 58 formed with apertures to hold the headed cable couplers 59 The shell 60 of the piston 120 -is surrounded by a packing ring 61 and, is interiorly formed with an integral flange 62 which is secured as by bolts '63 to a valve seat body 64 A hollow valve body 65 is concenr trically mounted within the piston shell in rim 125 abutting engagement with the shouldered flat face of the valve seat:64 The rim of the hollow valve body is formed with a flange 66 into which threads the end of the valve seat securing bolts 63 In the piston shell above the 130 in Fig 10 and the cable is then, retrieved by fluid through valve 50 and connection 47 to the head of the piston 49 ' The p'articular form shown is that illustrated in Fig 7. OPERATION 70 The arrest is made upon engagement of the deck 'pendant D by the arresting hook of an aircraft 15, which exerts a load on the cable of the pendant, This load is transmitted to the piston 19 During the first few feet of 75 cable playout the fluid is allowed to bypass through the time delay by-pass, sothat a hydraulic load only sufficient to pre-tension the cable, approximately '100 P S I willf be exerted in the cable during initial acceleration of 80 the cable After sufficient payout pulls the piston past the time delay by-pass port the fluid must pass through the fluid loaded valve incorporated in the piston 19 or be squeezed between the outer diameter of the piston and 85 the arrest tube bore, and resistance is thus set up to arrest the aircraft. As previously stated, at maxim urn cable load the pressure built up in the cylinder is approximately 1600 'P IS 1 L and during the cable p ay, 90 out the cable load is substantially constant as determined by the fluid load" constant pressure valve Any leakage during use i's replenished by the above described replenishing pump 95 After the arrest the piston is forward as in Fig 10 and when the cable is removed from the arresting hook the cable is retrieved. This is accomplished' by opening the gate valve, which allows the centrifugal pump to 100 pump the fluid from one side of the piston to

the other This pump may lbe operated continuously during landing operations.

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* GB785152 (A)

Description: GB785152 (A) ? 1957-10-23

Preparation of -a - hydroxycarboxylic acids and derivatives thereof

Description of GB785152 (A)

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The EPO does not accept any responsibility for the accuracy of data and information originating from other authorities than the EPO; in particular, the EPO does not guarantee that they are complete, up-to-date or fit for specific purposes.

COMPLETE SPECIFICATION Preparation of cc - Hydroxycarboxylic acids and derivatives thereof We, NATIONAL RESEARCH CORPORATION, a corporation organized and existing under the laws of the State of Massachusetts, United States of America, located at 70 Memorial Drive, Cambridge 42, State of Massachusetts,

United State of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the production of valuable chemicals and in particular to the production of alpha hydroxy carboxylic acids and esters thereof. A principal object of the present invention is to provide an economical, integrated process for making alpha hydroxy carboxylic acids and esters thereof from organic compounds containing an alpha olefinic linkage. Another object of the invention is to provide an economical, integrated process for making methacrylic acid and esters thereof from isobutylene. Another object of the invention is to provide an improved process for the production of the valuable intermediate compound alpha hydroxyisobutyric acid. Still another object of the invention is to provide a process for converting isobutylene to esters of alpha hydroxyisobutyric -acid. Other objects of the invention will in part be obvious and will in part appear hereinafter. For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing which is a flow sheet illustrating one preferred embodiment of the present invention. A particular aspect of the present invention is directed to the conversion of organic compounds containing an alpha olefinic linkage to the corresponding alpha hydroxy carboxylic acid by means of a nitric acid solution containing dinitrogen tetroxide. The resultant alpha hydroxy carboxylic acid may subsequeatly be dehydrated or esterified or subjected to both a dehydration and an esterification. In one preferred embodiment of the invention, isobutylene is converted to alpha hydroxyisobutyric acid by means of a nitric acid solution containing dinitrogea tetroxide. The resultant alpha hydroxyisobutyric acid may subsequently be dehydrated or esterified or subjected to both a dehydration and an esterification to methacrylic acid or suitable esters thereof. The reaction between an organic compound containing an alpha olefinic linkage and a nitric acid solution containing dinitrogen tetroxide takes place when the nitric add solution has a HNOs concentration above 25 percent by weight and contains a quantity of dinitrogen tetroxide above 10 percent by weight of the nitric acid. The nitric acid is preferably used in at least the stoichiometric amount required to convert the alpha unsaturated organic compound to the corresponding

alpha hydroxy carboxylic acid. This reaction is carried out at relatively low temperatures in particular at temperatures below20"C. Referring now to the drawing, there is illustrated a flow sheet which embodies one preferred continuous method of practicing the present invention. The drawing will be described as illustrating the conversion of isobutylene to alpha hydroxyisobutyric acid and esters thereof, it being understood that this continuous method is applicable to the conversion of other organic compounds containing alpha olefinic linkage to alpha hydroxy carboxylic acids and esters thereof. In-the flow sheet, there is shown a reactor 2 charged with a nitric acid solution containing dinitrogen tetroxide. Isobutylene is passed into the nitric acid solution in the reactor 2 at a predetermined rate. Upon completion of the controlled reaction between the isobutylene and the nitric acid solution containing dinitrogen tetroxide, the reaction mixture is drained into a vacuum still 4 and the nitric acid and nitrogen oxides present are removed by distillation. The recovered nitric add is recycled back to a suitable storage means. If desired, a suitable purifying and/or concentrating means may be employed for processing all the nitric acid recovered prior to returning it to storage. The dinitrogen tetroxide recovered may also be recycled back to a suitable storage means. The nitric oxide recovered may be mixed with air to form dinitrogen tetroxide which may also be recycled back to a suitable storage means. If desired, a suitable purifying means may-be employed for processing the dinitrogen tetroxide recovered prior to returning it to storage. A portion of the recovered dinitrogen tetroxide may be bubbled through water with air to form a -nitric add solution suitable for the reaction. The reaction mixture, substantially free of nitric acid and oxides of nitrogen, is then treated in a dissolver 6 with a suitable solvent. - The resulting solution is- drained into a crystalliying tank 8 wherein the alpha hydroxyiso butyric acid is crystallized out of the solvent. The alpha hydroxyisobutyric add and its mother liquor are drained into a centrifuge 10 and separated. The mother liquor may be further processed to recover the last traces of the alpha hydroxyisobutyric acid. The solvent,

which comprises the majority of the mother liquor, may be recycled back to the dissolver 6 via suitable purifying means (not shown). The crude add. may be subjected to~further purification, if desired. - The alpha hydroxyisobutyric add is fed to an esterification and dehydration reactor 12 and esterified and dehydrated to methyl rnetha crylate by any of the well-known techniques. The esterification of the alpha hydroxy carboxylic adds can be accomplished by the general procedures. desribed by Clinton and Laskowski, "Journal of American Chemical Soaety" -70, 3135 (1948). The procedures described in this article are as follows: "For each mole of aliphatic carboxyl group there are used 96 g. (3 moles) of commercial methanol, 300 ml. of ethylene dichloride, and 3 ml. of concentrated sulfuric acid. If the acid is aromatic, the amount of sulfuric acid is increased to 14 ml. per mole of carboxyl group. The mixture is refluxed for from six to fifteen hours. Progress of esterification is usually, but not invariably, indicated by the development of cloudiness and the separation of an upper layer containing water, methanol and sulfuric add. The cooled reaction mixture is washed successively with water, sodium bicarbonate solution and- again with water. The ethylene dichloride layer is then distilled at atrnospheric pressure or in vacuo, and the residual methyl ester processed by distillation or rrystallization." In connection with the specific flow sheet illustrated in the drawing, it should be pointed out that numerous modifications may be made in the various techniques employed without departing from the scope of the invention. For example, upon completion of the controlled reaction, the product, alpha hydroxyisobutyric acid, instead of being recovered by distilling the nitric add and nitrogen oxides therefrom, can be recovered from the nitric acid solution directly by means of a suitable solvent extraction. Likewise, instead of treating the nitricadd and nitrogen-oxide-free reaction mixture, with a suitable solvent to dissolve the alpha hydroxyisobutyric- acid, the desired acid may be crystallized directly without admixture of an additional solvent. Also if methacrylic acid is the desired end product rather than the methacrylate, the esterification step can be eliminated and

the alpha hydroxyisobutyric acid can be simply dehydarted to methacrylic add. If esters of alpha hydroxyisobutyric acid are- the desired end products, then the dehydration step can be eliminated and the alpha hydroxyisobutyric andean be simply esterified with the desired alcohol. The desired acids or esters can also be prepared by esterifying or dehydrating or esterifying and dehydrating or dehydrating and esterifying the reaction mixtures directly, thus eliminating the necessity of any isolation of the intermediate alpha hydroxyisobutyric add. Equally, many esters of methacrylic acid other than the methyl esters may be made by utilizing a different alcohol. Examples of such suitable alcohols are the ali- phatic alcohols ethyl, propyl and butyl. Specific detailed methods of practicing the present invention are set forth in the following non-limiting examples which are directed more specifically to the step of converting isobutylene to alpha hydroxyisobutyric add. v - ~ EXAMPLE I 1100 grams of 100% nitric acid and 215 grams of dinitrogen tetroxide (2NO2=N204) were charged to a reaction vessel and cooled to a temperature of 5"C. i 5", after which time isobutylene was slowly bubbled therethrough. 107 grams of isobutylene were added to the reaction mixture as it was stirred over a period of about 5 hours while maintaining the temperature below about 10"C. After all the isobutylene had been fed, the reaction mixture was allowed to stand for about=16 hours at ice temperature (0 C.). The resulting mixture was distilled in a vacuum to remove the nitric acid and nitrogen oxides. The residue was then dissolved in benzene and extracted with water. The resulting aqueous phase was separated from the organic phase. A second quantity of water was mixed with the organic phase, and the resulting aqueous phase was decanted therefrom and combined with the first aqueous phase. The - water was removed by vacuum distillation, and the residue was combined with the residue obtained from the organic phase on removal of the benzene. The combined residues were added to 1650 mls. of a 2N aqueous solution of NaOH. The mixture was then subjected to continuous oxygen bubbling and stirring at 60"C. for about 47 hours. Oxygen was bubbled through the heated mixture at a rate of about 450 mls. per minute. After acidification and ether extraction of the saponification mixture, evaporation of the ether led to a solid residue. The solid residue, .recrystallized from a small volume of benzene,

yielded a crop of crystals amounting to 114.8 grams. The yield of alpha hydroxyisobutyric acid was thus 57.8% based on the original quantity of isobutylene fed to the reactor. EXAMPLE II 830 grams of 100% nitric acid and 420 grams of dinitrogen tetroxide (2NO2=N204) were charged to a reaction vessel and cooled to a temperature of 5 C.i5 , after which time isobutylene was slowly bubbled therethrough. 80.8 grams of isobutylene were added to the reaction mixture as it was stirred over a period of about 5 hours while maintaining the temperature below about 10 C. After all the isobutylene had been fed, the reaction mixture was distilled in a vacuum to remove the nitric acid and nitrogen oxides. The residue was then allowed to stand for about 16 hours at ice temperature (O"C.). The residue was worked up in a manner similar to that illustrated in. Example I with the exception of the saponification time. In this run, the saponification one portion of the mixture was terminated after 19 hours, while the saponification of the remainder of the reaction mixture was terminated after 43 hours. The yield of crystals obtained from the residue resulting from the 19 hours saponification amounted to 45.0 grams. The yield of crystals obtained from the residue resulting from the 43 hours saponification amounted to 46.5 grams. Thus if the saponification were terminated after 19 hours, the yield of alpha hydroxyisobutyric acid would amount to 60% based on the original quantity of isobutylene fed to the reactor. Termination of the saponification after 43 hours would produce a yield of alpha hydroxyisobutyric acid amounting to 62% based on the original quantity of isobutylene fed to the reactor. EXAMPLE III 1561 grams of 70% nitric acid solution and 323 grams of dinitrogen tetroxide (2NO2 N204) were charged to a reaction vessel and cooled to a temperature of 0 C.i5 , after which time isobutylene was slowly bubbled therethrough. 109 grams of isobutylene were added to the reaction mixture as it. was stirred over a period of about 5 hours while maintaining the temperature below about 5"C. After all the isobutylene had been fed, the reaction mixture was allowed to stand for about 16 hours at ice temperature (0 C.). The resulting mixture was distilled in a vacuum to remove the nitric acid and nitrogen oxides. Benzene was added to the residue and the insoluble solid material was filtered off. This material identified as alpha hydroxyisobutyric acid

amounted to 91 grams. The organic phase was worked up in. a manner similar to that illustrated in Example I. The yield of crystals obtained in this run amounted to 44.7 grams. The yield of alpha hydroxyisobutyric acid was thus 68.7% based on the original quantity of isobutylene fed to the reactor. In order to obtain a direct comparison between the use of nitric acid solutions containing dinitrogen tetroxide, illustrated in the above examples, and nitric acid solutions containing substantially no dinitrogen tetroxide, a reaction of the type generally described in the above examples was provided. In this case, however, 59.5 grams of isobutylene was slowly bubbled into 560 grams of 100% nitric acid maintained at a temperature below 15 C.i5 . The yield of alpha hydroxyisobutyric acid obtained from this reaction amounted to 36.4% based on the original quantity of isobutylene fed to the reactor. Thus the yields of alpha hydroxyisobutyric acid obtained using the nitric acid-dinitrogen tetroxide solutions of the present application were more. than .one and one-half times as great as those obtained using only nitric acid. The process set forth for the conversion of isobutylene to alpha hydroxyisobutyric acid is equally applicable to the conversion of other organic compounds containing an alpha olefinic linkage to alpha hydroxy carboxylic acids. By organic materials containing an alpha olefinic linkage," it is meant to include generally organic compounds which contain at least one terminal double bond between two carbon atoms. Such alpha unsaturated organic compounds may. contain functional. groups, such as hydroxyl, halide, cyano, ester, ether, keto, carboxyl and like functional groups. Thus, according to the present invention, it is possible to convert alpha unsaturated organic com pounds such as, for example, isobutylene, allyl chloride, methyl methacrylate, methacrylonitrile, vinyl acetate, allyl alochol, methyl allyl alcohol, methyl vinyl ketone, methyl vinyl ether, acrylic acid, methacrylic acid, butadiene, methyl pentadiene, diallyl, styrene, alpha methyl styrene, para divinyl benzene, alpha vinyl pyridine and the like, to the corresponding alpha hydroxy carboxylic acids or derivatives thereof. The alpha hydroxy carboxylic acid obtained contains the same number of carbon atoms as the alpha unsaturated organic compound from which it is produced. The conversion of alpha unsaturated organic compounds to high yields of the corresponding alpha hydroxy carboxylic acids is carried out by means of a nitric acid solution containing substantial quantities of dinitrogen tetroxide. Nitric acid solutions with a HNO3 concentratin of from 25 percent to

100 percent by weight and containing a quantity of dinitrogen tetroxide above 10 per cent by weight of the nitric acid have been found usable for the reaction. As illustrated in Examples I, II and III, the use of nitric acid solutions with a HN03 concentration of 70 percent by weight and above of the nitric acid resulted in high yields of the desired alpha hydroxy acid. The quantity of nitric acid employed in the reaction is at least equal to the stoichiometric amount required to convert the alpha unsaturated organic compound to the corresponding alpha hydroxy carboxylic acid. However, better results have been obtained when the nitric acid is present in excess over the stoichiometric amount required for the conversoin. As used in the specification and claims, "nitric acid solutions" will- refer not only to aqueous solutions having a HNO3 concentration above about 25 per cent by weight but also to 100 percent nitric acid. Also dinitrogen tetroxide is an equilibrium mixture of the monomer (NO2) and the dinner (N2O4). The equilibrium concentration of the monomer is a function of temperature, as described in "Inorganic Chemistry" by Ephraim, page 667, Third Edition, Nordehous When used in the specification and the claims, the expression "dinitrogen tetroxide" is intended to include the equilibrium concentration of the monomer at the temperature employed. The reaction is carried out at relatively low temperatures i.e., at temperatures below 20"C. Generally, it has been found that reaction temperatures below about 10"C. have beenpreferable. The time of reaction may be varied so that, for example, very much shorter periods than those given in the examples are satisfactory. The structure of the product resulting directly from the reaction between an organic compound containing an alpha olefinic linkage and a nitric acid solution containing a substantial quantity of dinitrogen tetroxide is not yet known with absolute certainty? However, it is known that material capable of being converted to the desired alpha hydroxy-carboxylic acid is one of the products. This is supported by the fact that the desired alpha hydroxy carboxylic aad.is obtained, in some instances, only after the reaction mi:ture, freed of nitric acid and nitrogen oxides, is treated with water and/or bases and/or acids. Thus, in Example I and II, which employed 100% nitric acid, the desired alpha hydroxy acid was obtained after a suitable base hydrolysis. The function of this caustic hydrolysis was to saponify and to form material capable of being converted to the desired alpha hydroxy carboxylic acid, such as, for example, nitrate esters of the desired hydroxy acid. In Example III, which employed a 70% aqueous nitric acid solution, the major portion of the desired alpha hydroxy

acid was recovered without any hydrolysis treatment. This may be due to the fact that the water in the nitric acid solution made possible, in the reaction mixture, the hydrolysis of any material capable of being converted to the desired hydroxy acid. If desired, a suitable quantity of air or oxygen can be introduced into the reactor during the reaction so as to react with any nitric oxide present to produce dinitrogen tetroxide directly within the reactor. This dinitrogen tetroxide then becomes available for the reaction. What we claim is- 1. A process of forming alpha hydroxy carboxylic acids from organic compounds containing an alpha olefinic linkage, charac terized by reacting an alpha unsaturated organic compound as herein defined with a nitric acid solution containing dinitrogen tetroxide at a temperature below 20 C., the nitric acid solution having a HNOa concen tration above 25 percent by weight and con taining a quantity of dinitrogen tetroxide above 10 percent by weight of the nitric acid, the nitric acid being used in at least the stoichio metric amount required to convert the alpha unsaturated organic compound to the cor responding alpha hydroxy carboxylic acid. 2. A modification of the process claimed in claim 1, wherein 100% nitric acid is employed and the reaction mixture is subsequently hydrolysed. 3. A process according to claim 1 or 2 characterized by esterifying the alpha hydroxy carboxylic acid with an alcohol and isolating the corresponding ester of the alpha hydroxy carboxylic acid. 4. A process according to claim 1 or 2 in which isobutylene is converted to alpha hydroxyisobutyric acid. 5. A process according to claim 4 in which the esters of alpha hydroxyisobutyric acid are produced by esterifying the acid with an alcohol to form the corresponding ester.

6. A process according to any ofclaims 1--5 in which methacrylates are produced by con verting isobutylene to alpha hydroxyisobutyric acid, esterifying the alpha hydroxyisobutyric acid with an alcohol to form the corresponding ester, and dehydrating the ester to form the methacrylate. 7. A process according to claim 4 in which methacrylic acid is produced by dehydrating alpha hydroxyisobutyric acid to form methacry licacid. 8. A process for the production of alpha hydroxy carboxylic acids from organic compounds as claimed in claim 1 substantially as set forth and described hereinbefore.