ljepila polikloropren
TRANSCRIPT
Sticks. Polychloroprene for contact adhesives with
high initial strength at low process temperatures
Baypren®
1. Description . . . . . . . . . . . . . . . . . . . . . . . 3
2. Range of properties . . . . . . . . . . . . . . . . 4
3. Product range . . . . . . . . . . . . . . . . . . . . . 5
4. Formulation of adhesives . . . . . . . . . . . 6
4.1 Selection of the Baypren® grades . . . . . 6
4.2 Choice of solvent . . . . . . . . . . . . . . . . . . 8
4.3 Metal oxides . . . . . . . . . . . . . . . . . . . . . . 9
4.4 Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5 Chlorinated rubber . . . . . . . . . . . . . . . . 10
4.6 Fillers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.7 Antioxidants . . . . . . . . . . . . . . . . . . . . . 10
4.8 Addition of Desmodur® . . . . . . . . . . . . 11
5. Mastication or direct-dissolve process . . . . . . . . . . . . 12
6. Formulation examples . . . . . . . . . . . . . 13
7. Supply form . . . . . . . . . . . . . . . . . . . . . 18
8. Packaging . . . . . . . . . . . . . . . . . . . . . . . 18
9. Storage . . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Baypren®
Description
3
Baypren® is a 2-chloro-butadiene-(1,3)polymer (polychloroprene) produced bystate-of-the-art processes.Its excellent solubility in many organicsolvents and its high rate of crystallizingmake it ideal for the production of con-tact adhesives.
2. Baypren®
Range of properties
4
Baypren® adhesives are used widely allover the world, the main reason for theirpopularity being that, after brief surfacedrying, they are able during their opentime to produce a bond of immediatelymeasurable strength (Fig. 1).Following momentary adhesion, thepolychloroprene begins immediately tocrystallize, with the result that the bondcures rapidly and its strength rises ac-cordingly (Fig. 2).The demand for contact adhesives basedon Baypren® is particularly high in theshoe industry, in furniture production, inthe construction and automotive indus-tries and in the do-it-yourself sector.Apart from their simple, economical pro-cessing, these products are distin-guished by their excellent adhesion to awide range of materials and guaranteeoutstanding results.
Fig. 1: Initial strength as a function of open timeand applied pressure
Initial bond strength
Peel
str
engt
h
Open time withlow pressure
Open time with higher pressure
Fig. 2: Increase in strength through crystallization
Str
engt
h
Curing time
Fast crystallizing Baypren® grades
Grade Chip-size [mm] Viscosity [mPa·s]10 % solution in Toluene
Standard grades310-1 2.5 – 3.0 70 – 220310-2 2.5 – 3.0 220 – 380320-1 2.5 – 3.0 350 – 550 320-2 2.5 – 3.0 550 – 810330-1 2.5 – 3.0 700 – 1,000330-2 2.5 – 3.0 900 – 1,400340-1 2.5 – 3.0 1,130 – 1,800340-2 2.5 – 3.0 1,800 – 2,500350-1 1.5 – 2.0 2,200 – 4,000350-2 1.5 – 2.0 2,500 – 5,300
TETD modified grades321-1 2.5 – 3.0 350 – 550321-2 2.5 – 3.0 550 – 810331-1 2.5 – 3.0 700 – 1,000 331-2 2.5 – 3.0 900 – 1,400
Special grades (MMA grafting)320-1p 2.5 – 3.0 350 – 550320-2p 2.5 – 3.0 550 – 810
5
3. Baypren®
Product range
To satisfy the varied demands arising inindustrial practice, Baypren® is suppliedwith varying crystallization rates, viscosi-ties and chip sizes (Table 1).
First digit: Indication of the crystallization rate
2 = medium
3 = rapid
Second digit: Indication of the viscosity
1 = low
2 + 3 = medium
4 = high
5 = very high
Third digit: Indication of special properties
0 = standard grade
1 = thiuram-based
3 = special grade in terms of crystallization
p = special grade for “grafting”
Table 2: Nomenclature of the Baypren® adhesivegrades
Table 1: Baypren® adhesive grades
The meaning of the suffix is shown in Table 2.
Medium crystallizing Baypren® grades
Grade Chip-size [mm] Viscosity [mPa·s]10 % solution in Toluene
Standard grades213-1 2.5 – 3.0 70 – 220213-2 2.5 – 3.0 220 – 380223-1 2.5 – 3.0 350 – 550 223-2 2.5 – 3.0 550 – 810233-1 2.5 – 3.0 700 – 1,000233-2 2.5 – 3.0 900 – 1,400243-1 2.5 – 3.0 1,130 – 1,800243-2 2.5 – 3.0 1,600 – 2,500253-1 1.5 – 2.0 2,200 – 4,000253-2 1.5 – 2.0 2,500 – 5,300
4. Baypren®
Formulation of adhesives
6
For adhesive production, use is madepredominantly of Baypren® grades with ahigher rate of crystallization (B 310 to350). Adhesives formulated with themgive bonds with high initial strength thatcure very quickly indeed.
4.1 Selection of the Baypren® grades
Thiuram grades for easiermastication
Baypren® 321 and 331 differ from the ot-her Baypren® grades in that they are mo-dified with thiuram disulfide. This additi-ve makes mastication easier, increasescompatibility with many other adhesivecomponents (resins, for example) andextends the storage stability of the adhe-sives.
Fig. 3: Crystallization
Time [h]
Test temperature: -5 °C n 300 gradesn 200 gradesH
ardn
ess
[Sho
re A
]
0.130
40
50
60
70
80
90
100
1 10 100 1,000
7
When bonding sensitive, light-coloredmaterials such as white leather or PVCfilm, it is advisable to use the thiuram-free Baypren® grades. Under unfavorableconditions, e.g. in the presence of cer-tain leather greases or plasticizers, thereis a danger with light-colored materialsthat the thiuram contained in the Bay-pren® may migrate out of the adhesivefilm onto the surface of the material andproduce a yellowish discoloration. Itmust also be taken into account thatBaypren® adhesives containing thiuramcan become discolored on contact withiron, copper or brass due to the thiuramin them.
In cases where high initial bond strengthis not needed, use can be made of themedium crystallizing Baypren® grades ofthe 200 range. They are cheaper andprolong the open time of the adhesives –a factor that also enhances processingreliability.
The medium crystallizing Baypren® gra-des can be used both on their own andin combination with rapidly crystallizingBaypren® grades.
Because there is nowadays an increa-sing demand for high-viscosity polychlo-roprene for economic reasons, we haveextended our range of rapidly and medi-um crystallizing grades. Baypren® 350and 253 are two new products that canbe used in combination with low-viscosi-ty Baypren®. To align the longer dissol-ving time of high-viscosity Baypren® gra-des with the dissolving time of low-vis-cosity grades, Baypren® 350 and Bay-pren® 253 are produced in the form ofextremely thin chips.
Fig. 4: Dissolving time in relation to chip thickness
Dissolving time [min]0 100 200 300 400
Baypren® 340
Baypren® 350
Baypren® 243
Baypren® 253
Thiuram-free grades for light-colored materials
Baypren® 310, 320, 330, 340 Baypren® 350 (approx. 1 mm)(approx. 2 mm)
8
Baypren® adhesive raw materials are sol-uble in many organic solvents and sol-vent mixtures.The solvent or solvent mixture used toproduce the adhesive is chosen accord-ing to both economic and technical con-siderations. It has to be taken into ac-count, for example, that the solvent canhave a considerable influence on:- the viscosity of the adhesive,- the compatibility of the adhesive with
an added crosslinking agent,- the behavior of the adhesive during
storage at low temperatures,- the occurrence of phase separation
during the storage of resin-containingadhesives
- the wetting of the adhesive surface,- the drying of the adhesive film,- the open time of the adhesive film,- the curing rate of the bond.
Apart from the influence on the technicalproperties of the adhesives, the physio-logical effect of the solvents also has tobe considered.The use of certain solvents is subject torestrictions or is completely banned insome countries. Furthermore, attentionmust be paid to the flammability of manysolvents and their ability to form explo-sive mixtures with air.
4.2 Choice of solvent
Baypren® 320-p is a polychloroprenewich is suitable as a starting material forthe grafting reaction with methyl-methacrylate (MMA). These graft adhe-sives are commonly used in the shoe in-dustry for bonding plasticized PVC andother substrates that are otherwise diffi-cult to bond, such as EVA (ethylene-vinylacetate copolymer) and SBS (styrene-bu-tadiene-styrene block copolymer).
Graft adhesive with outstanding resistance to discoloration
9
As a rule, magnesium oxide and zincoxide are added to Baypren® adhesives.The presence of the metal oxides has afavorable effect on the storage stabilityof the adhesive and the stability of thebonds. This is because the polychloro-prene splits off traces of hydrogen chlo-ride over the course of time and the met-al oxides serve as acceptors for them.The very fine-particle zinc oxides, Bay-oxide® Z aktiv and Bayoxide® Z trans-parent, are ideal for use with Baypren®
adhesives.
4.3 Higher bond stability
with metal oxides
Fig. 5: Bayoxide® Z aktiv
4.4 Addition of resins for faster curing
Resins are an excellent way of improvingthe adhesive properties of the Baypren®
solutions. Through the addition of aresin, the open time can be adjustedover a broad range and curing can be ac-celerated. The final crystallization stateof the Baypren® is barely affected by theresins, with the result that the adhesivefilms retain a high level of cohesivestrength. However, these valuable prop-erties can only be attained if the rightquantity of the right resin is added, de-pending on the particular application.
Heat-activated alkyl-phenol resins orhigh-melting rosin esters are preferredwhenever rapid curing of the bonds isneeded. To prolong the open time, for-mulators generally use terpene-phenolicresins, coumarone-indene resins, or low-melting rosin esters.
10
Through the addition of chlorinated rub-ber, the initial strength of the bonds canbe significantly increased. Chlorinatedrubber of medium solution viscosity isgenerally used, e.g. Pergut® S 40 orPergut® S 90.
4.5 Chlorinated rubber for improved initial strength
Fig. 6: Influence of Pergut® on the strength increase of Baypren® bonds
4.6 Addition of fillers All kinds of fillers can be added toBaypren® adhesives. Typical examplesare chalk, heavy spar and silica.
4.7 Antioxidants Baypren® itself is considerably more re-sistant to aging than many of the resinsused for adhesive production. Rosinesters, coumarone resins and terpene-phenolic resins, being unsaturated com-pounds, are prone to oxidation over thecourse of time. This phenomenon startswith embrittlement or softening of theadhesive layer in the outer edges of thebond, and can finally lead to its com-plete destruction. The aging of Baypren® bonds can becountered by the addition of suitable an-tioxidants.The ideal antioxidants for resin-basedBaypren® adhesives are sterically hin-dered phenols such as Vulkanox®
BHT, Vulkanox® DS and Vulkanox® BKF(Lanxess AG).
Time [hours]
n with Pergut®
n without Pergut®Peel
str
engt
h [N
/mm
]
00
1
2
3
4
5
6
2 6 24
11
Although for many applications com-pletely satisfactory strength characteris-tics are obtained with one-componentBaypren® adhesives, the addition ofDesmodur® (polyisocyanate), e.g. Desmo-dur® RE, RFE, RC or RN, can significantlyimprove the bonding properties, in par-ticular the– heat resistance of the bonds,– initial strength of the bonds,– resistance of the bonds to grease
and oil,– adhesion to critical materials.
Desmodur® RE and Desmodur® RFE havethe highest peel strength.
4.8 Addition of Desmodur ®
to improve the bonding properties
Fig. 7: Colors of the various Desmodur ® R-grades
Fig. 8: Initial strength of the bonds after storage inheat (30 min/50 °C), substrate: Nora rubber
% by weight crosslinking agent calculated on Baypren® adhesive
Init
ial p
eel s
tren
gth
[N/m
m]
0.5
Desmodur® RE Desmodur® RFE Desmodur® RC Desmodur® RN
0
1
1.5
2
2.5
3
3.5
4
4.5
5
Desmodur® RE
Desmodur® RFE
Desmodur® RC
Desmodur® RN
0 1 2 3 4 5 6 7 8 9
5. Mastication or direct-dissolve process
12
Formerly, mastication of the polychloro-prene before dissolving was an integralpart of the formulation procedure in the ad-hesives industry. It also enabled adhesiveswith acceptable properties to be producedfrom polychloroprene raw materials of av-erage quality.As a result of continuing research, it hasnow become possible to guarantee consis-tent polychloroprene quality. Contact adhe-sives based on Baypren® can therefore beformulated without previous masticationusing the so-called direct-dissolve process.Polychloroprene solutions also have elasticcharacteristics in addition to their purelyviscous properties. These elastic propertiesmean that extra force is needed to applythe solution to the substrate (Fig. 9).Studies carried out on solutions of theBaypren® 300 grades show that the level ofelasticity, measured as normal stress, is de-pendent on the viscosity of the Baypren®
solution. With increasing viscosity of thesolution, the normal stress rises (at con-stant solids concentration) (Fig. 10).The mastication of Baypren® results inproducts with lower viscosities and normalstresses. However, the pairs of values liewithin the normal stress/viscosity bandthat applies to the unmasticated Baypren®
300 grades, i.e. although the values formasticated Baypren® 330 are lower, theydo not differ from the normal stress/viscos-ity data of an unmasticated Baypren® 320of equal viscosity. Bonding tests on formu-lated adhesives produce the same bondingdata for masticated as for unmasticatedBaypren® of the same viscosity.Baypren® can thus be used for formulatingadhesives with optimum rheological andbonding properties even without the timeand cost-intensive procedure of mastica-tion prior to dissolving.
Fig. 9: Adhesive application of viscous and visco-elastic solutions
Pulling direction F ViscousDoctor blade
Gap
Layer thickness = film thickness
Pulling direction F Viscous
GapLayer thickness ≠ film thickness
Substrate
F Elastic
Substrate
Fig. 10: Viscosity and normal stress after masticati-on of Baypren® 330
Nor
mal
str
ess
[Pa]
0
1
2
3
4
5
Viscosity [Pas]0 2 4 6 8 10
Mastication time Unmasticated
1 min
2 min
3 min
5 min
7 min10 min
Table 3: Formulation examples for Baypren®
contact adhesives
6. Formulation examples
13
Table 3 shows typical formulation exam-ples for Baypren® contact adhesives.By adding more of the given solvent mix-ture, the solution viscosity of the adhe-sives can be set to the desired level.With the adhesive prepared according toformulation no. 3, 10 pbw Desmodur® REor RFE can be added as a crosslinkingagent to 100 pbw adhesive immediatelybefore application.
Formulation no. #1 # 2 # 3 # 4 # 5
Baypren® 320 100 100 100 100 —
Baypren® 233 — — — — 100
Magnesium oxide 4 4 4 4 4
Bayoxide® Z aktiv 4 4 4 4 4
Pergut® S 40 — — — var —
Heat-reactive alkyl-phenolic resin (SPF 121H*) 30 30 — var var
Terpene-phenolic resin (SP 553*) — — 30 var —
Ethyl acetate 120 35 35 35 35
White spirit (boiling range 65–95 °C) 120 70 70 70 70
Toluene 120 — — — —
Cyclohexane — 140 140 140 140
Methylethylketone — 105 105 105 105
It frequently happens that a bond is sub-jected to a high level of stress at a veryearly stage – for example when bondingcurved soles in the shoe industry orcurved surfaces of wood or plastic in fur-niture production. In such cases, highinitial strength and rapid curing are es-sential. This is no problem for adhesivesformulated with the rapidly crystallizingBaypren® grades.
High initial strength
* Schenectady Europe S.A., Bethune, France
14
Figs. 11–14 show how the initial strengthof the bonds can be adjusted by varyingthe Pergut® content, resin content andopen time. The highest initial strength isobtained in resin-free formulations con-taining Pergut® (formulation no. 4). Onthe other hand, Pergut® has no influencewhatsoever on the final strength of thebonds. Here, the addition of resins has apositive effect.
Fig. 12: Influence of Pergut® on the initial strength with the addition of various resins (no. 4, open time 60 min)
Peel
str
engt
h [N
/mm
]
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
Open time [min] Pergut® content [parts]
3060
900
5
10
Fig. 11: Influence of Pergut® on the initial strengthin a formulation without resin (no. 4)
Peel
str
engt
h [N
/mm
]
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
Varying resin content
withoutSP 553
SPF 121H0
5
10
Varying the initial and final strength
Pergut® content [parts]
15
If high initial bond strength is not ab-solutely essential, medium crystallizinggrades can also be used (for example,for laying flexible floorcoverings). Theresin content can be varied over a widerange in such formulations.
Fig. 14: Initial strength when using medium crystallizing grades (no. 5, with heat-reactive alkyl-phenolic resin [SPF 121H*])
Fig. 13: Influence of Pergut on the final strength after 9 days with the addition of various resins (no. 4, open time 60 min)
Peel
str
engt
h [N
/mm
]
0.00without
SPF 121H
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Varying resin content
0
5
10
Peel
str
engt
h [N
/mm
]
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Resin content [phr]
0 30 60 90 12015
30
45
60
Pergut® content [parts]
Open time [min]
* Schenectady Europe S.A., Bethune, France
SP 553
Peel
str
engt
h [N
/mm
]
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Open time [min]
15 30 60 90 120immediately
1 d
3 d
9 d
16
Peel strength of toluene-free formulations
Because of the negative physiologicaleffect of toluene, its use is subject torestrictions or is banned entirely as anadhesives solvent in many countries. Ifwe look at formulations 1 (Fig. 15) and 2(Fig. 16), it can be seen that comparablebond strength can also be attained withtoluene-free Baypren® adhesives.
Fig. 15: Formulation 1, peel strength with a toluene-based adhesive
Fig. 16: Formulation 2, peel strength with a toluene-free adhesive
Peel
str
engt
h [N
/mm
]
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Open time [min]
15 30 60 90 120immediately
1 d
3 d
9 d
Storage time
Storage time
17
Baypren® adhesives to which Desmodur®
is added before application to increasethe heat resistance are extremely valu-able, for example, in floorcoverings neara radiator or for table-tops that need towithstand hot dishes and plates.The adhesion-improving effect ofDesmodur® additives is utilized, amongother things, in shoe production forbonding rubber materials that are other-wise difficult to bond.
Crosslinking with Desmodur
Fig. 17: Heat resistance of Baypren®/Desmodur®
bonds – adhesive formulation based on Baypren®
320/terpene-phenolic resin + 5 % crosslinking agent, substrate: SBR rubber
Sof
teni
ng p
oint
mea
sure
d to
AS
TM 8
16 [°
C]
0
20
40
60
100
80
120
140
160
Withoutcrosslin-ker
DesmodurRE
DesmodurRFE
DesmodurRC
DesmodurRN
18
Baypren® adhesives are supplied in theform of flat chips. To ensure consistentpourability, the chips and the granulesare powdered with talc (max. 1 %).
For transport purposes, the Baypren®
grades are packed in sacks of 25 kg. Thesacks are made of multi-ply kraft paperlined inside with polyethylene. Each sackis labeled clearly with details of thegrade. 35 such sacks are stacked on aone-trip pallet and the pallet is thenshrink-wrapped with polyethylene film.
All Baypren® adhesives have excellentstorage stability if stored under theproper conditions (i.e. 25 °C and 50 %relative humidity). To maintain perfectsolubility, the product must be protectedfrom heat and direct sunlight.In isolated cases, the Baypren® chips inthe bootom sacks of pallet may stick to-gether due to the dead load of the prod-uct. The chips can be separated by lightly shaking the sacks. Baypren® chipstend to clump if stored improperly. thechips can then no longer be separartedby shaking.
7. Supply form
8. Packaging
9. Storage
This information and our technical advice – whether verbal,
in writing or by way of trials – are given in good faith but
without warranty, and this also applies where proprietary
rights of third parties are involved. Our advice does not
release you from the obligation to verify the information
currently provided – especially that contained in our safety
data and technical information sheets – and to test our
products as to their suitability for the intended processes
and uses. The application, use and processing of our pro-
ducts and the products manufactured by you on the
basis of our technical advice are beyond our control and,
therefore, entirely your own responsibility. Our products are
sold in accordance with the current version of our General
Conditions of Sale and Delivery.
Edition: 07-2007 Order No.: MS007133
Printed in Germany · E
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www.bayeradhesives.com