Ethylene ethyl acrylate, adhesives

This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

Ethylene Copolymers. Ethylene copolymers probably are the most important materials in hot-melt formulations. Ethylene-vinyl acetate and ethylene-ethyl acrylate polymers are very versatile and available in a wide range of grades offering different co-monomer contents and viscosities. The melts are stable and compatible with various modifying resins, waxes, extenders, and fillers. Adhesion to many substrates is good—including the polyolefin plastics, which are difficult to bond with most other types of adhesive unless the surfaces are pre-treated. 

Ethylene-ethyl acrylate copolymers can produce very tough flexible materials and can vary from very rubbering low temperature melting products to polyethylene-like materials. EEA is used as a hot melt adhesive, for disposable gloves, tubing and sheeting. 

Polyethylene, linear low density film, food-contact Polyvinyl alcohol film, food-contact polyolefin o-Methylstyrene/vinyltoluene copolymer, hydrogenated film, food-contact PP Terpene resin film, food-packaging Ethylene/ethyl acrylate copolymer Ethylene/methyl acrylate copolymer 1,2-Polybutadiene Polystyrene Silica, fumed Vinylidene chloride/methyl acrylate copolymer film, food-packaging pressure-sensitive adhesives... 

In 2003 Dow introduced three classes of compatibiliser, i.e., maleated polyolefins, ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers, all imder the Amplify name. They were intended to improve the impact and viscosity characteristics of engineering thermoplastics and polyolefins for use in domestic appliance and automotive components, as well as for coatings and adhesives. 

This copolymer is also widely used as a blending compound with olefin homopolymers as well as with polyamides, polyesters, and polycarbonate to improve impact strength and toughness and either to increase heat seal response or to promote adhesion. EMA is also used in soft blow-molded articles such as squeeze toys, tubing, disposable medical gloves, and foamed sheet. EMA copolymers and ethylene ethyl acrylate (EEA) copolymer containing up to 8% ethyl acrylate are approved by the FDA for food packaging. 

Uses in the manufacturing of acrylic resins for use in paint formulations, industrial coatings and latexes in the manufacturing of plastics, such as ethylene ethyl acrylate in the manufacturing of poly-acrylate elastomers and acrylic rubber in the forming of denture materials water-emulsion vehicle for paints, textiles and paper coatings, leather finishes, resins and adhesives lends flexibility to hard films A... 

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. 

Blends of ethylene copolymers (such as ethylene-vinyl acetate, ethylene-ethyl acrylate, ethylene-acrylic acid copolymers) have been typically added to LDPE, HDPE and LLDPE to improve filler and additive acceptance, balance film properties, improve environmental stress crack resistance, tear resistance, toughness and surface properties. These blends are particularly prevalent in film formulations and as such are rarely disclosed by the manufacturer. Equistar has introduced functionalized polyolefins (Integrate ) to improve dispersion and adhesion in wood fiber filled and mineral filled polyolefin composites. Arkema Group offers Lotryl ethylene-acrylate (methyl, butyl and 2-ethyl hexyl) copolymers and notes the wide range of compatibility with other polyolefins as well as polyamides and polyesters. 

Two types of hot melt adhesives are used in this application, which stresses high strength and shear resistance. Low molecular weight polyethylene based adhesive is exemplified by Eastman s Eastobond A-39. Competitive products are primarily based on ethylene-ethyl acrylate polymers. These ethylene-acrylate polymers are chosen because they give slightly higher shear strength performance than ethylene-vinyl acetate based products. A typical adhesive formulation is illustrated in Table 20. 

The early hot melt adhesives were not strictly definable as rubber-based adhesives. Most rubber polymers such as natural rubber and random SBR are of such molecular weight and structure that they do not melt readily to a workable coating consistency at a temperature below which thermal degradation and decomposition take place. Certain synthetic polymers, however, lend themselves to the formulation of a wide range of hot melt adhesive compositions. Polyamide and polyester resins, ethylene-vinyl acetate (EVA) copolymers, ethylene-ethyl acrylate (EEA) copolymers, low molecular weight polyethylene and amorphous polypropylene, and certain vinyl ethers have found application in hot melt adhesives. These adhesives have found wide use in packaging, industrial, and construction applications. 

Ethylene Ethyl Acrylate (EEA) (Diek, 1987) - A much narrower range of EEA polymers are available than for EVA. This has reduced the number of hot melt adhesives developed using EEA to a few speeialty formulations in which EEA imparts superior properties. These include superior adhesion to polyethylene and polypropylene, improved thermal stability and lower price. 

A hot melt adhesive is heated to a viscosity of approximately 10 000 cP and can be coated at speeds as high as 800 mpm, typically onto papers and films. Most hot melt coating processes apply either pressure-sensitive adhesives or permanent adhesives. Pressure sensitive adhesives are applied within the converting industry in web width ranges over 2 m with a coating thickness up to approximately 100 g/m. The adhesives include ethylene vinyl acetate (EVA) copolymers, sty-rene-isoprene-styrene (SIS) copolymers, styrene-butadiene-styrene (SBS) copolymers, ethylene ethyl acrylate copolymers (EEA), and polyurethane reactive (PUR) pressure sensitive formulations. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

Poly(vinyl alcohol) is utilized as a component of starch-based adhesives.11121114 Other patents report the use of partially oxidized starch,1115 dextrins,1116 dextrins and urea,1117 borax,1118 boric acid,1119 and vinyl methyl ether-maleic acid copolymers.1120 Other patents indicate the use of poly (vinyl alcohol) with partially hydrolyzed poly(vinyl acetate),1121 nonhy-drolyzed poly(vinyl acetate),1122 and poly(vinyl chloride).1123 A few patents have reported such poly acrylic additives as poly (acrylic acid)1124 and its salts,1125 poly(acrylamide),1126 1127 A-methylacrylamide or poly(A-acryl-amide),1128 and polyethyleneimine.1129 Polystyrene has also been used,1130 as well as more complex copolymers such as a maleic acid monobutyl ester-methyl vinyl ether copolymer, together with dextrin and polyacrylamide),1131 carboxylated ethyl acrylate-styrene zinc salt copolymer,1132 ethylene-methyl acrylate-vinyl acetate copolymer,1133 vinyl acetate-vinyl pyr-rolidone copolymer,1134 and ethylene-vinyl acetate copolymer.1135 Some adhesives are compounded with SBR latex1136 1138 and phenol-formaldehyde resins.1139... 

Examples of acid modified polyolefins are the copolymers of ethylene with acrylic acid or methacrylic acid. Variations include the partially neutralised acid copolymers with metal ions (ionomers) or terpolymers of ethylene, an acid and an acrylate such as methyl acrylate or isobutyl acrylate. Acid-containing extrudable adhesives are widely used to bond to aluminium foil. Examples of anhydride-modified polyolefins include terpolymers of ethylene, maleic anhydride and acrylates such as ethyl acrylate or butyl acrylate and the anhydride-grafted polyolefins. Some typical applications and stmctures of a variety of multilayer materials with extruded polymer tie-layer adhesives, as described in Du-Pont trade literature, are detailed in Table 16.2. 

Yan et al. [52] explored the use of IPN techniques to produce a composite vinyl-acrylic latex. The first-formed polymer was produced using VAc and divinyl benzene (DVB), while the second formed polymer constituted a BA/DVB copolymer. In both cases the DVB was added at 0.4 wt%. They compared this product with another product, a bidirectional interpenetrating netwodc (BIPN) in which VAc was again polymerized over the first IPN. They noted that the compatibility between the phases was more pronounced in the BIPN than in the IPN as determined using dynamic mechanical measurements and C nuclear magnetic resonance spectroscopy. The concept of polymer miscibility has also been used to produce composite latex particles and thus modify the pafamance properties of VAc latexes. Bott et al. [53] describe a process whereby they bloid VAc/ethylene (VAc/E) copolymers with copolymers of acrylic acid or maleic anhydride and determine windows of miscibility. Apparently an ethyl acrylate or BA copolymer with 10-25 wt% AA is compatible with a VAc/E copolymer of 5-30 wt% ethylene. The information obtained from this woik was then used to form blends of latex polymers by polymerizing suitable mixtures of monomers into preformed VAc/E copolymers. The products are said to be useful for coating adhesives and caulks. 

Ethylene can be free radically copolymerized with vinyl acetate. Copolymerization with 0%-35% vinyl acetate is carried out in bulk at 1000-2000 bar, that of 35%-100%at 100-400 bar in /-butanol, and that of 60%-100%at 1-200 bar in emulsion. Products with vinyl acetate contents of over 10% give shrinkable films those with up to 30% vinyl acetate give thermoplastic films, and those with over 40% vinyl acetate give clear films. Products of still higher vinyl acetate content are elastomers, fusion, and solvent adhesives or modifiers for PVC. The products can be cross-linked with lauroyl peroxide on the addition of, for example, triallyl cyanurate. Copolymers of ethylene and ethyl acrylate have similar properties. 

These are mentioned occasionally in the polyblend literature. For example, when ethylene/methyl acrylate copolymer was blended with polybutylene terephthalate, maleating the copolymer improved interfacial adhesion and impact strength [208]. Blends of ethy-lene thyl acrylate copolymers with PE are mentioned as commercial thermoplastic elastomers [24]. Ethylene copolymers with ethyl acrylate and carbon monoxide, with acrylonitrile, and with dimethyl acrylamide all provided strong hydrogen bonding, producing miscibility... 

The hot melt adhesives are based on ethylene-vinyl acetate or ethyl acrylate copolymers or styrene block copolymers, because of the need to adhere to polyester. The starting point formulation for a PET bottle adhesive is given in Table 19 ... 

Poly(ethyl methacrylate) (PEMA) yields truly compatible blends with poly(vinyl acetate) up to 20% PEMA concentration (133). Synergistic improvement in material properties was observed. Poly(ethylene oxide) forms compatible homogeneous blends with poly(vinyl acetate) (134). The T of the blends and the crystaUizabiUty of the PEO depend on the composition. The miscibility window of poly(vinyl acetate) and its copolymers with alkyl acrylates can be broadened through the incorporation of acryUc acid as a third component (135). A description of compatible and incompatible blends of poly(vinyl acetate) and other copolymers has been compiled (136). Blends of poly(vinyl acetate) copolymers with urethanes can provide improved heat resistance to the product providing reduced creep rates in adhesives used for vinyl laminating (137). 

Specialty waxes include polar waxes for more polar adhesive systems. Examples would be castor wax (triglyceride of 12-hydroxy stearic acid) or Paracin wax N- 2 hydroxy ethyl)-12-hydroxy stearamide) which are used in polyester, polyamide, or with high VA EVA copolymer-based systems. Other common polar waxes are maleated polyethylenes, which are used to improve the specific adhesion of polyethylene-based adhesives, and low molecular weight ethylene copolymers with vinyl acetate or acrylic acid, which are used to improve low temperature adhesion. High melting point isotactic polypropylene wax (7 155°C) and highly refined paraffin wax (7,n 83°C) are used where maximum heat resistance is critical. Needless to say, these specialty waxes also command a premium price, ranging from 2 to 5 times that of conventional paraffin wax. 

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