Vinyl chloride polymers commercial

Raw Materials. PVC is inherently a hard and brittle material and very sensitive to heat it thus must be modified with a variety of plasticizers, stabilizers, and other processing aids to form heat-stable flexible or semiflexible products or with lesser amounts of these processing aids for the manufacture of rigid products (see Vinyl polymers, vinyl chloride polymers). Plasticizer levels used to produce the desired softness and flexibihty in a finished product vary between 25 parts per hundred (pph) parts of PVC for flooring products to about 80—100 pph for apparel products (245). Numerous plasticizers (qv) are commercially available for PVC, although dioctyl phthalate (DOP) is by far the most widely used in industrial appHcations due to its excellent properties and low cost. For example, phosphates provide improved flame resistance, adipate esters enhance low temperature flexibihty, polymeric plasticizers such as glycol adipates and azelates improve the migration resistance, and phthalate esters provide compatibiUty and flexibihty (245). 

X-ray studies indicate that the vinyl chloride polymer as normally prepared in commercial processes is substantially amorphous although some small amount of crystallinity (about 5% as measured by X-ray diffraction methods) is present. It has been reported by Fuller d in 1940 and Natta and Carradini in 1956 that examination of the crystalline zones indicates a repeat distance of 5.1 A which is consistent with a syndiotactic (i.e. alternating) structure. Later studies using NMR techniques indicate that conventional PVC is about 55% syndiotactic and the rest largely atactic in structure. 

Solution viscosities are involved in quality control of a number of commercial polymers. Production of poly(vinyl chloride) polymers is usually monitored in terms of relative viscosity (tj/tjo) while that of some fiber forming species is related to IV [inherent viscosity, c ln(> /)/ )]. The magnitudes of these parameters depends primarily on the choices of concentration and solvent and to some extent on the solution temperature. There is no general agreement on these experimental conditions and comparison of such data from di I ferent manufacturers is not always straightforward. 

Many linear aliphatic polyesters are produced commercially. They are relatively low in molecular weight, less than 10,000. The main use of these materials is as plasticizers for poly(vinyl chloride) polymers and copolymers. Such polyesters are usually formed from dicarboxylic acids and glycols. Often, monocarboxylic acids or monohydroxy compounds are added towards the end of the reaction, in... 

Omitting the construction and demolition debris from the calculations, the composition (by volume this time) is as follows paper and paperboard 50%, plastics 14%, metals 12%, glass 4%, organics 6%, and miscellaneous 14%. All plastic packaging (post-consumer, industrial, commercial, and institutional) represented about 8% of the overall refuse. It is a reasonable assumption that the composition of plastics discarded in landfills is a reflection of the quantities produced for packaging applications the commodity plastics polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) should be well represented (see Ethylene POLYMERS PROPYLENE Polymers (PP) Styrene Polymers Vinyl Chloride Polymers). 

Table 4.1. Comparative properties of typical commercial grades of vinyl chloride polymers.

In practice, however, vinyl chloride polymerized commercially does not have regular tacticity because the growing end of the chain is a free radical at an sp hybridized carbon center which can freely rotate. This rotation rate varies with temperature by polymerizing vinyl chloride at very low temperature the rotation can be slowed significantly, preferentially trapping certain conformations and allowing for polymerization of a more syndiotactic polymer. 

An example of a commercial semibatch polymerization process is the early Union Carbide process for Dynel, one of the first flame-retardant modacryhc fibers (23,24). Dynel, a staple fiber that was wet spun from acetone, was introduced in 1951. The polymer is made up of 40% acrylonitrile and 60% vinyl chloride. The reactivity ratios for this monomer pair are 3.7 and 0.074 for acrylonitrile and vinyl chloride in solution at 60°C. Thus acrylonitrile is much more reactive than vinyl chloride in this copolymerization. In addition, vinyl chloride is a strong chain-transfer agent. To make the Dynel composition of 60% vinyl chloride, the monomer composition must be maintained at 82% vinyl chloride. Since acrylonitrile is consumed much more rapidly than vinyl chloride, if no control is exercised over the monomer composition, the acrylonitrile content of the monomer decreases to approximately 1% after only 25% conversion. The low acrylonitrile content of the monomer required for this process introduces yet another problem. That is, with an acrylonitrile weight fraction of only 0.18 in the unreacted monomer mixture, the low concentration of acrylonitrile becomes a rate-limiting reaction step. Therefore, the overall rate of chain growth is low and under normal conditions, with chain transfer and radical recombination, the molecular weight of the polymer is very low. 

AUoys of ceUulose with up to 50% of synthetic polymers (polyethylene, poly(vinyl chloride), polystyrene, polytetrafluoroethylene) have also been made, but have never found commercial appUcations. In fact, any material that can survive the chemistry of the viscose process and can be obtained in particle sizes of less than 5 p.m can be aUoyed with viscose. 

Antagonism between antimony oxide and phosphoms flame retardants has been reported in several polymer systems, and has been explained on the basis of phosphoms interfering with the formation or volatilization of antimony haUdes, perhaps by forming antimony phosphate (12,13). This phenomenon is also not universal, and depends on the relative amounts of antimony and phosphoms. Some useful commercial poly(vinyl chloride) (PVC) formulations have been described for antimony oxide and triaryl phosphates (42). Combinations of antimony oxide, halogen compounds, and phosphates have also been found useful in commercial flexible urethane foams (43). 

Other Polymers. Besides polycarbonates, poly(methyl methacrylate)s, cycfic polyolefins, and uv-curable cross-linked polymers, a host of other polymers have been examined for their suitabiUty as substrate materials for optical data storage, preferably compact disks, in the last years. These polymers have not gained commercial importance polystyrene (PS), poly(vinyl chloride) (PVC), cellulose acetobutyrate (CAB), bis(diallylpolycarbonate) (BDPC), poly(ethylene terephthalate) (PET), styrene—acrylonitrile copolymers (SAN), poly(vinyl acetate) (PVAC), and for substrates with high resistance to heat softening, polysulfones (PSU) and polyimides (PI). 

Uses. Phthabc anhydride is used mainly in plasticizers, unsaturated polyesters, and alkyd resins (qv). PhthaUc plasticizers consume 54% of the phthahc anhydride in the United States (33). The plasticizers (qv) are used mainly with poly(vinyl chloride) to produce flexible sheet such as wallpaper and upholstery fabric from normally rigid polymers. The plasticizers are of two types diesters of the same monohydric alcohol such as dibutyl phthalate, or mixed esters of two monohydric alcohols. The largest-volume plasticizer is di(2-ethylhexyl) phthalate [117-81-7] which is known commercially as dioctyl phthalate (DOP) and is the base to which other plasticizers are compared. The important phthahc acid esters and thek physical properties are Hsted in Table 12. The demand for phthahc acid in plasticizers is naturally tied to the growth of the flexible poly(vinyl chloride) market which is large and has been growing steadily. 

Poly(vinyl chloride) is Hsted on the TSCA inventory and the Canadian Domestic Substances List (DSL) as ethene, chloro-, homopolymer [9002-86-2]. Because polymers do not appear on the European Community Commercial Chemical Substances listing or EINECS, poly(vinyl chloride) is listed through its monomer, vinyl chloride [75-01-4]. In the United States, poly(vinyl chloride) is an EPA hazardous air pollutant under the Clean Air Act Section 112 (40 CER 61) and is covered under the New Jersey Community Right-to-Know Survey N.J. Environmental Hazardous Substances (EHS) List as "chloroethylene, polymer" with a reporting threshold of 225 kg (500 lb). 

The largest volume commercial derivatives of 1-butanol are -butyl acrylate [141-32-2] and methacrylate [97-88-1] (10). These are used principally ia emulsion polymers for latex paints, ia textile appHcations and ia impact modifiers for rigid poly(vinyl chloride). The consumption of / -butanol ia the United States for acrylate and methacrylate esters is expected to rise to 182,000—186,000 t by 1993 (10). 

Chloroformates are versatile, synthetic intermediates, based on the affinity of the chlorine atoms for active hydrogen atoms. Chloroformates should be considered as intermediates for syntheses of pesticides, perfumes, dmgs, polymers, dyes, and other chemicals. Some of these products, eg, carbonates, are used as solvents, plastici2ers, or as intermediates for further synthesis. A significant use of chloroformates is for conversion to peroxydicarbonates, which serve as free-radical initiators for the polymeri2ation of vinyl chloride, ethylene, and other unsaturated monomers. The most widely used percarbonate initiators are diisopropyl peroxydicarbonate (IPP), di-2-ethyIhexylperoxydicarbonate (2-EHP), and di-j -butylperoxydicarbonate (SBP). The following Hst includes most of the commercially used percarbonates. 

A variety of waxy hydrophobic hydrocarbon-based soHd phases are used including fatty acid amides and sulfonamides, hydrocarbon waxes such as montan wax [8002-53-7], and soHd fatty acids and esters. The amides are particularly important commercially. One example is the use of ethylenediamine distearamide [110-30-5] as a component of latex paint and paper pulp blackHquor defoamer (11). Hydrocarbon-based polymers are also used as the soHd components of antifoaming compositions (5) examples include polyethylene [9002-88-4], poly(vinyl chloride) [9002-86-2], and polymeric ion-exchange resins. 

Diesters. Many of the diester derivatives are commercially important. The diesters are important plasticizers, polymer intermediates, and synthetic lubricants. The diesters of azelaic and sebacic acids are useflil as monomeric plasticizing agents these perform weU at low temperatures and are less water-soluble and less volatile than are diesters of adipic acid. Azelate diesters, eg, di- -hexyl, di(2-ethylhexyl), and dibutyl, are useflil plasticizing agents for poly(vinyl chloride), synthetic mbbers, nitroceUulose, and other derivatized ceUuloses (104). The di-hexyl azelates and dibutyl sebacate are sanctioned by the U.S. Food and Dmg Administration for use in poly(vinyl chloride) films and in other plastics with direct contact to food. The di(2-ethylhexyl) and dibenzyl sebacates are also valuable plasticizers. Monomeric plasticizers have also been prepared from other diacids, notably dodecanedioic, brassyflc, and 8-eth5lhexadecanedioic (88), but these have not enjoyed the commercialization of the sebacic and azelaic diesters. 

It is an interesting paradox that one of the least stable of commercially available polymers should also be, in terms of tonnage consumption at least, one of the two most important plastics materials available today. Yet this is the unusual position held by poly(vinyl chloride) (PVC), a material whose commercial success has been to a large extent due to the discovery of suitable stabilisers and other additives which has enabled useful thermoplastic compounds to be produced. 

In addition to homopolymers of varying molecular and particle structure, copolymers are also available commercially in which vinyl chloride is the principal monomer. Comonomers used eommercially include vinyl acetate, vinylidene chloride, propylene, acrylonitrile, vinyl isobutyl ether, and maleic, fumaric and acrylic esters. Of these the first three only are of importance to the plastics industry. The main function of introducing comonomer is to reduce the regularity of the polymer structure and thus lower the interchain forces. The polymers may therefore be proeessed at much lower temperatures and are useful in the manufacture of gramophone records and flooring compositions. 

---