Dispersion acrylic adhesive

Acrylic acid, the main precursor to acrylic adhesives had been synthesized in the mid 1800s and the first acrylic acid esters were made and characterized at the turn of the century [62]. The first commercial launch of acrylic polymers in the form of poly(methylmethacrylate) took place in 1927 when the German company Rohm and Haas AG introduced this new plastic to the market. Soon after, other companies such as BASF introduced acrylic dispersions. 

Urethanes have also been used to toughen vinyl-terminated acrylic adhesives for improved impact resistance. Thus rubber-toughened urethane acrylates [79,80], water-dispersible urethane acrylates [81], and high-temperature-performance urethane-acrylate structural adhesives have been reported [82]. Polyurethanes terminated with acrylic functionality are also used for anaerobic or radiation-cured adhesives with improved toughness [83]. 

EcoSynthetix markets EcoSphere biolatex binder dispersions as a replacement for petroleum-based styrene butadiene latex. EcoSphere biolatex binders are based on starch derived from crops such as com, potatoes, and tapioca. Although the product was originally developed for the paper coating industry, it can also be applied in the textile coating industry. EcoSynthetix also produces EcoMer , a biobased building block to synthesize waterborne sugar-acrylic adhesives and resins. 

The second means of transforming a liquid adhesive entirely into a solid without the loss of a solvent or dispersion medium is to produce solidification by a chemical change rather than a physical one. Such reactive adhesives may be single-part materials that generally require heating or exposure to electron beam or UV or visible radiation (see Radiation-cured adhesives) to perform the reaction, and which may be solids (that must be melted before application), liquids or pastes. The alternative two-part systems require the reactants to be stored separately and mixed only shortly before application. The former class is exemplified by the fusible, but ultimately reactive, epoxide film adhesives and the latter by the two-pack Epoxide adhesives and Polyurethane adhesives and by the Toughened acrylic adhesives that cure by a free-radical Chain polymerization mechanism. 

Binders in coatings include polyvinyl acetate and copolymers, polyvinyl butyral, polyesters, acrylic polymers, epoxies and polyurethanes (see Ethylene-vinyl acetate copolymers. Acrylic adhesives, Epoxide adhesives and Polyurethane), polyvinyl chloride, polyvinylidene fluoride and aUcyds (oxygen-convertible media containing polyol esters of long-chain unsaturated acids). All these potential film-formers can adhere through dispersion forces, (which are probably weak). Many binders, however, also contain... 

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. 

Flexible PVC tapes of various types are predominately used for electrical insulation purposes and to a lesser extent, for pipe insulation. In Europe, acrylate dispersions have been used in the manufacture of electrical tapes for more than four decades. Coating weights of ca. 25 g dry adhesive m are typically used. Their advantage is that they can be coated on to flexible PVC films without a primer. However, the use of dispersions requires a high level of knowledge of the compositions and interactions between particular flexible PVC substrates and acrylic adhesives. As a result, suitable dispersions must be carefully selected and in many cases, it is necessary to use more than one dispersion type to achieve required performance levels. Of prime... 

The most widely used emulsion based additives are the all-acrylic or MBS coreshell polymers. Methacrylate-based shell compositions are generally not highly miscible with the various engineering resin compositions, creating a challenge for proper impact modifier dispersion and adhesion. Common approaches to this problem... 

Emulsion Polymerization. Emulsion polymerization is the most important industrial method for the preparation of acryhc polymers. The principal markets for aqueous dispersion polymers made by emulsion polymerization of acryhc esters are the paint, paper, adhesives, textile, floor pohsh, and leather industries, where they are used principally as coatings or binders. Copolymers of either ethyl acrylate or butyl acrylate with methyl methacrylate are most common. 

For some applications, such as for repulpable type PSAs, it may be advantageous to incorporate high levels of acrylic acid because this makes the polymer more hydrophilic. At the same time, high levels of acid also improve the water-dispersibility of the adhesive, especially at higher pH where the acid groups are converted to the more water-soluble neutralized salt form. Since the high level of acid increases the of the resulting polymer, a non-tacky material results. To make the adhesive pressure sensitive, the polymer can be softened with water-dispersible or soluble plasticizers, such as polyethers [68]. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Emulsion-based primer plus alkyd finish These are based on acrylic resin dispersions and have the advantage of a rapid rate of drying. They generally have excellent adhesion and flexibility but lack the sealing properties of aluminum primers. 

P.V.D.F. Polyvinylidene fluoride (p.v.d.f. or p.v.f.2) dispersions are applied by the coil-coating process. They are blends of p.v.d.f. resin and acrylic. The combination produces a system which has excellent weather-ability and which can be bonded via an adhesive primer to a galvanised steel or aluminium substrate. 

The important role Transmission Electron Microscopy (TEM) can play in this process is demonstrated on the development of an oxidation catalyst for the production of acrylic acid. Acrylic acid is produced by BASF in quantities of several 100.000 tons per year in a two step gas phase oxidation process starting from propene, which is oxidised to acrolein in the first step and then further oxidised to acrylic acid in a second step, each step requiring a special developed catalyst. Acrylic acid is used as a base material for the production of superabsorbents for nappies, dispersions and emulsions for adhesives and construction materials. 

Acrylic acid and its salts are raw materials for an important range of esters, including methyl, ethyl, butyl, and 2-ethylhexyl acrylates. The acid and its esters are used in polyacrylic acid and salts (32%, including superabsorbent polymers, detergents, water treatment chemicals, and dispersants), surface coatings (18%), adhesives and sealants (15%), textiles and non-wovens (12%), plastic modifiers (5%), and paper coating (3%). 

Poly(acrylic acid) is water soluble. Because of its water solubility and its ability to increase the viscosity of water, it is used as a thickener. It is also a good flocculent for sewage treatment and is added as a pigment dispersant in latex paints, and is used in binders and adhesives. Polymers and copolymers containing acrylic or/and methacrylic acid are manufactured at a rate of about 2,000,000 metric tons yearly. 

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