Acrylic sensitive adhesives industry

New Energy Saving Reactive Acrylic Liquid Polymers for the Pressure Sensitive Adhesives Industry... 

Acrylics are some of the most common and most versatile materials used in the PSA industry. Although the basic monomers and some of the acrylic polymers have been known for about a century, their commercial application as pressure sensitive adhesives did not happen until after the Second World War. 

Among the different pressure sensitive adhesives, acrylates are unique because they are one of the few materials that can be synthesized to be inherently tacky. Indeed, polyvinylethers, some amorphous polyolefins, and some ethylene-vinyl acetate copolymers are the only other polymers that share this unique property. Because of the access to a wide range of commercial monomers, their relatively low cost, and their ease of polymerization, acrylates have become the dominant single component pressure sensitive adhesive materials used in the industry. Other PSAs, such as those based on natural rubber or synthetic block copolymers with rubbery midblock require compounding of the elastomer with low molecular weight additives such as tackifiers, oils, and/or plasticizers. The absence of these low molecular weight additives can have some desirable advantages, such as ... 

Recently, Dowbenko et al (Ref. 4) of PPG Industries described two approaches to the development of energy-curable pressure sensitive adhesives. One Involved the incorporation of low molecular weight acrylic polymers into hot melt formulations the second employed radiation polymerization of monomer-polymer syrups. 

Instak. [Polynter Industries] Vinyl-acrylic emulsion aq. pressure-sensitive adhesive. 

The PSA tape is manufactured by Compac Industries, Inc. (manufacturer part number 807). The backing is 51 microns thick aluminum foil with a 31 microns thick acrylic pressiare sensitive adhesive. The surface of each sensor was washed with isopropyl alcohol and then blown dry with nitrogen prior to applying the pressure sensitive adhesive tape. Tests were conducted at room temperature using acetone as the liquid. 

Adhesives as materials can be classified in a number of ways such as chemical structure or functionality. In this book, adhesives have been classified into two main classes natural and synthetic. The natural group includes animal glue, casein- and protein-based adhesives, and natural rubber adhesives. The synthetic group has been further divided into two main groups industrial and special compounds. Industrial compounds include acrylics, epoxies, silicones, etc. An example of the specialty group is pressure-sensitive adhesives. 

Other polymers of the mono(meth)acrylate type are mostly used in industry. Leather finishes, adhesives, paints, printing inks and coatings are examples of practical applications. Butyl acrylate is sometimes used in spectacle frames. Often, 2-ethylhexyl acrylate is used in the manufacture of pressure-sensitive adhesives, but a wide range of other acrylates are also used in this field. 

Due to the continuing increase in the cost of raw materials, new low-cost acrylated tackifying oligomers have been developed for formulating UV-/EB-curable pressure-sensitive adhesives. All types of adhesive performance, such as removable adhesives, sheet stock and general purpose industrial pressure-sensitive adhesives,... 

The field of solvent-free pressure-sensitive adhesives is an upcoming industrial technology. Such products find application as self-adhesive technical and medical products. The main aim is to manufacture solvent-free acrylic PSAs (A-PSAs), which have excellent performance and provide a good balance between adhesive and cohesive strengths. PSAs can act as extruder adhesives or UV-polymerised adhesives. Such adhesives, through their viscoelastic fluid state, can build joints without any requirement to change this flow state during or after application. 

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. 

Before adhesion occurs, wetting of the surface must occur, which implies that the molecules of the adhesives must come close with those of the surface to interact. After the solvent evaporates, a permanent bond sets between the surfaces to be joined. Pressure-sensitive adhesives are special nonreacting ones that do not lose their tackiness even when the solvent evaporates. This is because the polymer used is initially in the liquid stage and it remains so even after drying. The most common adhesive used industrially is polymer dispersion of a copolymer of 2-ethyl hexyl acrylate, vinyl acetate, and acrylic acid in water... 

Another important application area for PSAs in the electronic industry focuses on the manufacturing, transport and assembly of electronic components into larger devices, such as computer disk drives. Due to the sensitivity of these components, contamination with adhesive residue, its outgassing products, or residue transferred from any liners used, needs to be avoided. Cleanliness of the whole tape construction becomes very critical, because residuals like metal ions, surfactants, halogens, silicones, and the like can cause product failures of the electronic component or product. Due to their inherent tackiness, acrylic PSAs are very attractive for this type of application. Other PSAs can be used as well, but particular attention has to be given to the choice of tackifier or other additives needed in the PSA formulation. The choice of release liner also becomes very critical because of the concern about silicone transfer to the adhesive, which may eventually contaminate the electronic part. 

The advantages of a cationic adhesive formulation over that of a free radical one are the lack of oxygen sensitivity, less shrinkage on curing, and better adhesion. The disadvantages are that the photoinitiators are sensitive to moisture and basic materials and that the addic species can promote corrosion. Consequently, the majority of UV formulations used in industry are acrylate based and cured by a free radical mechanism. 

Acrylic adhesives first appeared about 1937 the acrylic resins may be considered as belonging to the vinyl family [1, p. 305], Today, acrylic adhesives appear in many forms as both pressure-sensitive and non-pressure sensitive formulations in organic solvent and emulsion forms as monomer and polymer cements as anaerobics as cyanoacrylates as so-called reactive or honeymoon two-part systems and as radiation curing formulations. Commercial production of acrylic polymers began in the late 1920s, but it was not until 1958 that the first aerylie sealant was developed [10, p. 226]. The solvent-based acrylic sealants were first introdueed to the eonstruction industry in about 1960 ... 

Lamination (sticking together of layers) of fabric, foam and film, in various combinations, can be performed using latex- and solvent-based or fusible adhesives (see Adhesive classification). In addition, adhesives are sometimes applied from solution or latex for subsequent reactivation by heat during lamination. Acrylic dispersions are the main type of latex-based adhesives used in the laminating industry butadiene rubbers and polyurethanes are also utilized in smaller quantities. The latex-based adhesives are used for aesthetic reasons and also on heat-sensitive or open-structured fabrics. The solvent-based adhesives, for example rubbers and polyurethanes, are used in applications similar to those for latex adhesives. 

Acetone and methyl ethyl ketone are components of solvent blends in urethane, nitrile rubber, and neoprene industrial adhesives. Acetone is the primary solvent in resin-type adhesives and pressure sensitive chlorinated rubber adhesives. Methyl isobutyl ketone is a solvent component for nitrile rubber and acrylic adhesives as well as in polyvinyl chloride and polyvinyl chloride-polyvinyl acetate copolymer bonding adhesives. Again, the desired evaporation rate of the adhesive formulation will often determine the ketone selected. 

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