Ethylene vinyl acetate sole

Poly(vinyl acetate) (PVA) and ethylene-vinyl acetate (EVA) copolymer adhesives have much in common, yet represent extremes in the degree of sophistication of their production processes. Both products are stable suspensions in water of a film-forming polymer, the particles of which are generally spherical. They are made by emulsion polymerization, which uses a free-radical addition mechanism to polymerize the monomer in the presence of water and stabilizers. Vinyl acetate is the sole or major monomeric raw material. 

Adhesive applications can be widespread including contact cmnents, pressure-sensitive adhesives and hot melts. In solid compounded articles footwear is a large volune application such as molded-ln-place soling or unit soles to be cemented to uppers. Additional uses are in toys, milk tubing, cove base, mats and miscellaneous coatings or molded parts. Potential uses include blends with ethylene-propylene rubber and ethylene-vinyl acetate copolymers to provide ozone-resistant fomulations or blends to improve crack- or impact-resistance of plastics. 

Ethylene]vinyl acetate. Symbolized as E/VAC according to ISO 1043 but the abbreviation of EVA is extensively used in the literature. Copolymer of ethylene and vinyl acetate. Its flexibility is similar to that of the plasticized PVC but in this case it is an inherent property due to the chemical structure without any incorporation of a plasticizer. As a thermoplastic, it is processed by extrusion or injection moulding. Strainability of E/VAC films is higher than that of LDPE. Applications injection moulded shoe soles, bathing sandals, and other consumer goods impact modifier for rigid PVC. Trade names Levapren (FRG), Ultrathene (USA). 

Polyethylene has limited adhesion to paints and inks. This is because it is a non-polar hydrocarbon incapable of forming hydrogen bonds. Adhesion can be improved by copolymerizing ethylene with polar monomers such as ethyl acrylate or vinyl acetate to give ethylene ethyl acrylate (EEA) copolymers or ethylene vinyl acetate (EVA) copolymers. EVA is often used for shoe soles. 

Depending on fashion, each year different materials have been and are currently used in the manufacturing of shoes, ranging from rubber soles (vulcanized styrene-butadiene rubber (SBR), thermoplastic rubber, EPDM) to different polymers (leather, polyurethanes, ethylene-vinyl acetate (EVA) copolymers, polyvinyl chloride (PVC), polyethylene, Phylon). To produce adequate adhesive joints, surface preparation of those materials is required (see part B Surface treatments). Surface preparation procedures for these materials must be quickly developed and the validity of these treatments is generally too short. Several procedures have been established to optimize the upper to sole bonding, most of them are based in the use of organic solvents. Due to environmental and health issues, solvents should be removed from the surface preparation procedure and several environmental friendly procedures for the surface preparation of several materials have been proposed. 

This regioselectivity is practically not influenced by the nature of subsituent R. 3,5-Disubstituted isoxazolines are the sole or main products in [3 + 2] cycloaddition reactions of nitrile oxides with various monosubstituted ethylenes such as allylbenzene (99), methyl acrylate (105), acrylonitrile (105, 168), vinyl acetate (168) and diethyl vinylphosphonate (169). This is also the case for phenyl vinyl selenide (170), though subsequent oxidation—elimination leads to 3-substituted isoxazoles in a one-pot, two-step transformation. 1,1-Disubstituted ethylenes such as 2-methylene-1 -phenyl-1,3-butanedione, 2-methylene-1,3-diphenyl- 1,3-propa-nedione, 2-methylene-3-oxo-3-phenylpropanoates (171), 2-methylene-1,3-dichlo-ropropane, 2-methylenepropane-l,3-diol (172) and l,l-bis(diethoxyphosphoryl) ethylene (173) give the corresponding 3-R-5,5-disubstituted 4,5-dihydrooxazoles. 

In 1969, 90% of vinyl acetate was manufactured by this process. By 1975 only 10% was made from acetylene, and in 1980 it was obsolete. Instead, a newer method based on ethylene replaced this old acetylene chemistry. A Wacker catalyst is used in this process similar to that for acetic acid. Since the acetic acid can also be made from ethylene, the basic raw material is solely ethylene, in recent years very economically advantageous as compared to acetylene chemistry. An older liquid-phase process has been replaced by a vapor-phase reaction run at 70-140 psi and 175-200°C. Catalysts may be (1) C—PdCb—CuCb, (2) PdClj—AI2O3, or (3) Pd—C, KOAc. The product is distilled water, acetaldehyde, and some polymer are... 

It has been found that in the development of EVA polymers for heat seal applications by emulsion polymerization that the concentration of vinyl acetate and ethylene in the polymer is not solely responsible for its use as a heat seal adhesive (2). 

Also itermolecular photochemical [2+2] cycloaddition based on 2-trifluoromethylquinazoline 1286 was studied. In a similar conditions the reaction with ethylene gives compound 1287 in 17 % yield as a sole product probably due to low solubility of ethylene in methanol. Ene-type product 1288 was isolated in 65 % yield when isobutylene was used in the reaction, showing that biradical intermediate is involved in the transformation. In a case of ethyl vinyl ether acetal 1292 was formed as product of methanolysis of intermediate azetidine 1289. Similarly was used intermediate azetidine 1290 was not isolated when dichloroethylene and its formation was proved by isolation of methanolysis product 1293 in 89 % yield. It should be noted, that treatment of product 1288 with base leads to elimination of CFs-group as in a case of 1284 (Scheme 298) [797]... 

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