polymer industries

Industrial Polymers

PLASTICS-FILMS-FIBRES-ELASTOMERS

Plastic, Man-Made Fiber and Film Industries

Plastic Industries

Overview

• A plastic is a material that contains a polymerized organic substance of large molecular weight as an essential ingredient, is solid in its finished state, and at some stage in its manufacture or its processing into finished articles can be shaped by flow.

• The plastic industries have developed and grown then, since their discovery. Plastics can be used in various applications because of their toughness, water resistance, excellent resistance to corrosion, ease of fabrication, and remarkable color range.

History

• The development of commercial phenolic resin in 1909 by Baekland was the start of the synthetic plastic industry. His discovery stimulated the search for other plastics.

• The first plastic of industrial significance was cellulose

nitrate (Celluloid) and was discovered about the middle of the nineteenth century. It was first used in 1869 by Hyatt who was searching for an ivory substitute.

Classification

• Thermosetting plastics are processed by heat curing to produce an infusible or insoluble product.

• Thermoplastics are processed by heating to

soften them and cooling to harden them. • On the basis of derivation, they may also be

grouped as natural resins, cellulose derivatives, protein products, and synthetic resins.

Applications and Uses Common Resin Types and Applications

Resin Type Applications

Polyesters Construction, auto repair putty, laminates, skis,

fishing rods, boats and aircraft component,

coatings, decorative fixtures, bottles

Polyurethanes Insulation, foam inner liners for clothing, rocket fuel

binders, elastomers, adhesives

Polyethers Coatings, pump gears, water-meter parts, bearing

surfaces, valves

Applications and Uses Common Resin Types and Applications

Resin Type Applications

Epoxies Laminates, adhesives, flooring, linings, propellers,

surface coatings

Polyethylene Packaging films and sheets, containers, wire cable

insulation, pipe, linings, coatings, molds, toys,

housewares

Polypropylene Housewares, medical equipment (can be sterilized),

appliances, toys, electronic components, tubings and

pipes, fibers and filaments, coatings

Applications and Uses Common Resin Types and Applications

Resin Type Applications

Polyvinyl chloride Pipe and tubing, pipe fittings, adhesives, raincoats

and baby pants, building panels

Acrylics Decorative and structural panels, massive glazing

domes, automotive lens systems, illuminated

translucent floor tiles, windows, and canopies

Polystyrene Insulation, pipe, foams, cooling towers, thin-walled

containers, appliances, rubbers, automotive

instruments and panels

Plastics in Everyday Life

Standard Symbols

Raw Materials

• Monomers: vinyl chloride, ethylene, propylene and similar simple hydrocarbons

• Chemical intermediates : phenol, formaldehyde, hexamethylenetetramine, phthalic anhydride, methyl acrylate and methacrylate

• Other raw materials: plasticizers, fillers, and reinforcements are also added to alter the properties of the plastic products.

Manufacturing Processes

• is carried out in the liquid or vapor state.

• The monomers and activator are mixed in a reactor and heated or cooled as needed.

Bulk Polymerization

• is used when the exothermic heat is too great to be controlled in bulk polymerization.

• The monomer and initiator are dissolved in a nonreactive solvent which serves to slow the reaction and thus moderate the heat given off.

Solution Polymerization

Manufacturing Processes

• is the process where the monomer is suspended in water by agitation.

• stabilizers (i.e. talc, fuller’s earth, and bentonite) are added to stabilize the suspension and prevent polymer globules from adhering to each other.

Suspension Polymerization

• is similar to suspension polymerization but the monomer is broken up into droplets that form aggregates called micelles.

•The monomer is on the interior of the micelles, and the initiator is in the water. Soap or another emulsifying agent is used to stabilize the micelles.

Emulsion Polymerization

Polyethylene

• It is the first and the largest in production of polyolefin plastic.

• High-density polyethylene (HDPE), produced by

low-pressure methods, is used mainly for blow-molded containers and injection-molded articles and pipe.

• Low-density polyethylene (LDPE), produced by high-pressure methods, is used mainly for plastic films.

Polyethylene

The Process Flow of LDPE Production

Individual Process Descriptions

1. Demethanization and Deethanization – The feed for the process is a mixture of methane, ethane, and ethylene. Since ethylene is the monomer to be used ethylene has to be separated from methane and ethane. High purity ethylene is used (99.8%).

Individual Process Descriptions

2. Compression of Ethylene and Catalyst - Ethylene and the catalyst (free-radical yielding such as oxygen or peroxide) are compressed to operating pressure (150 MPa).

Individual Process Descriptions

3. Solution Polymerization – In a tubular reactor maintained at 190°C, solution polymerization occurs to convert ethylene to polyethylene. About 30% conversion is achieved per pass.

Individual Process Descriptions

4. Pressure Separation

– At this stage, the unconverted ethylene is removed and recycled.

Individual Process Descriptions

5. Extrusion and Pelletizing – The polyethylene is extruded and pelletized.

Individual Process Descriptions

6. Quench Cooling – This hardens the polyethylene pellets by addition of cold water.

Individual Process Descriptions

7. Water Separation and Drying – These involve the removal of water from the pellets to obtain the final product.

Man-Made Fiber and Film Industries

Classification According to Spinning Procedures

• Melt spinning involves pumping molten polymer through capillaries or spinnerets and the polymer streams that emerge are solidified by quenching in cool air.

• In dry spinning, the polymer is dissolved in a suitable organic solvent. The solution is forced through spinnerets and dry filaments are formed upon evaporation of the solvent.

• Wet spinning involves spinning of a solution of polymer and coagulation of the fiber in a chemical bath.

Overview

• Fibers were originally of natural origin and were produced from wool, silk, cotton, flax, and similar materials.

• The first man-made fibers were made by Swan in 1883 when he squirted a solution of cellulose nitrate in acetic acid through holes.

• Fibers have three important general properties:

length, crimp and denier.

Synthetic Fibers and their Applications

• Polyamides –They are used in home furnishings, especially carpets.

• Acrylics and Modacrylics – polyacrylonitrile is the major component of several industrial textile fibers.

• Spandex – It is used in foundation garments, hose, swimwear and other elastic products.

Vinyls and Vinylidines

• Saran is the copolymer of vinyl chloride and and vinylidene chloride. It is resistant to mildew, bacterial and insect attack. Automobile seat covers and home upholstery are its prime applications.

• Vinyon is the trade name of copolymers of 90% vinyl chloride and 10% vinyl acetate. Resistance to acids and alkalies, sunlight, and aging makes Vinyon useful in heat-sealing fabrics and clothing.

Other Synthetic Fibers

• Polyolefins – They excel in special cases, such as ropes, laundy nets, carpets, blankets and backing for tuffed carpets, but are difficult to dye and their melting point is low.

• Fluorocarbons – It is widely used in pump packings and shaft bearings.

• Glass Fibers – are used for electrical insulation in motors and generators, structural reinforcement of plastics, fire-proof wall coverings and tire cords.

Multicomponent fibers

• Multicomponent fibers have been prepared

which possess superior properties to either

component if spun alone. They correspond to

better dyeability, permanent crimp, or silklike

feel, etc.

Finishing and Dyeing of Textiles

• Dyeing, bleaching, printing, and special finishing (such as for crease recovery, dimensional stability, resistance to microbial attack and ultraviolet light) involve unit operations such as filtering, heating, cooling, evaporation and mixing.

Films • are made from

different polymers such as polyesters, polyvinyl chloride, etc.

3 Common Types of Film Processing

• Slit-die process – produces flat sheets by extruding the molten polymer through a slit-die into a quenching water bath or onto a chilled roller.

• Blow-extrusion Process – produces tubular film by using air pressure to force the molten polymer around a mandrel.

• Calendering – preparation of film is produced by feeding a plastic mix of polymer, stabilizer, and plasticizers between two heated roll where it is squeezed into a film.

Nylon 6.6

• Nylon 6.6 was the first all-synthetic fiber made commercially and opened up the entire field.

• It is the product resulting from the polymerization of adipic acid and hexamethylene diamine.

PFD for Nylon Production

Raw Materials

• The raw materials for fiber production are just the same as in plastics production and will depend on the type of material the fiber is made up of.

• For the production of nylon yarn, however, the raw materials cited are adipic acid and hexamethylene diamine (“hexa”).

• Utilities such as steam and water will also be used.

Individual Process Description

1. Nylon Salt Formation - The reaction between equimolar proportions of the two raw materials produces nylon salt solution. Acetic acid is added to the (“hexa”) to to stabilize chain length.

Individual Process Description

2. Evaporation – The water produced from the reaction is evaporated in an evaporator and a jacketed autoclave.

• In the jacketed autoclave, pure nitrogen at 175-345 kPa forces the material downward. TiO2 dispersion is also added.

Individual Process Description

3. Casting Wheel – Each 900-kg batch is extruded as rapidly as possible. • A ribbon of polymer about 30 cm wide and 6 mm thick flows on the 1.8-m cat

drum. • Water sprays on the inside cools and harden the underside of the ribbon, the

outer is cooled by air and water.

Individual Process Description

4. Blender and Hopper – The ribbons are cut into small chips or flakes, blended and emptied to hoppers.

Individual Process Description

• Melt Spinning – A typical spinning unit is composed of a metal vessel surrounded by a Dowtherm vapor heated jacket which keeps the temperature of the vessel above melting temperature (263°C).

• As the nylon flake enters the vessel, it strikes a grid, where it melts and flows through to the melt chamber below.

• The molten polymer passes through the portholes in this chamber to gear spinning pump.

• They deliver it to a sand filter, which is followed by screens and a spinneret plate.

• The filaments are solidified by air and passed in a bundle through steam-humidifying chamber.

Melt Spinning

Individual Process Description

6. Cold Drawing – After lubrication on a finish roll, the yarn is stretched or drawn to the desired degree.

7. Bobbin – The nylon yarn passes through a bobbin system and is shipped to various manufacturers for processing.

THANQ -

Reference Austin, G.T. Shreve’s Chemical Process Industries (5th Ed). New York: McGraw-

Hill, Inc., 1984.