Water-based tackifiers

In static oven aging at 40°C (104°F) of a rosin ester tackifier (Fig. 10) the rate of hydroperoxide formation was reduced significantly using AO-2, with even better results using AO-3. The hydroperoxides are fairly stable at room temperature. At temperatures associated with hot-melt compounding or drying of solvent- and water-based formulations, hydroperoxides decompose spontaneously. The decomposition products initiate further reactions, which can result in the formation of color species. The addition of AO-2 and AO-3 which reduces the level of hydroperoxides formed, subsequently reduces the level of tackifier discoloration after oven aging (Fig. 11). 

Elastomers used in water-based systems include various rubber latices, especially natural rubber and SBR, and occasionally, polychloroprene. The bulk of the market in water-based adhesives is now held by acrylic dispersions. Although these are designed for use without modification, it is normal to formulate, especially by addition of tackifiers. Commonly used tackifying resins include soft resins, or hard resins in solution, which may... 

Uses Flame refardant, plasticizer, tackifier for water-based coatings and adhesives, rubber coatings, inks, carpetbackings, paper and fabric coaf-ings... 

Uses Tackifier resin for water-based adhesives and sealants based on acrylic, S/B, nat. rubber, neoprene, and PVAc, esp. for pressure-sensitive adhesives, and for coatings Features Solv.-free... 

Uses Tackifier for rubbers, lacquers, ink vehicles, varnishes, adhesives extender for shellac in water-based inks, paints, coatings, paper coatings, adhesives, wax emulsions film-former in cosmetics glazing agent in foods plasticizer in chewing gum in food-contact articles and coatings... 

PSA (solvent-based or water-based) - elastomer (e.g., NR, SBR/CSBR, Butyl/Polyisobutylene, acrylic), tackifier resin, plasticizers, fillers, stabilizers. 

Water-based dispersions or emulsions such as polyvinyl acetate, acrylics, polyvinyl chloride and polyvinyl alcohol with plasticizers and tackifiers. In addition, this range can include urea formaldehyde and phenolic adhesives, resins, natural adhesives produced from starch, dextrin, casein, animal glues (see Polyvinyl alcohol in adhesives, Phenolic adhesives single-stage resoles. Phenolic adhesives two-stage novolacs. Animal glues and technical gelatins) and rubber latex (see Emulsion and dispersion adhesives). Solvent-free 100% solids such as polyurethane. Hot melt adhesives include Ethylene-vinyl acetate copolymers, polyolefins, polyamides, polyesters with tackifiers and waxes. More recent additions include cross-linkable systems. 

A summary is presented of topics discussed at a conference on adhesive tapes organised in Athens by AFERA. These included the use of iodopropynyl butyl carbamate for the protection of water-based adhesives from biological attack, the formulation of NR latex based adhesives with tackifiers in aqueous dispersion, the effects of silicon contamination on adhesion to plastics film supports treated in different ways, possible harmful effects... 

A water-based acrylic phenolic adhesive system was first developed by Fry, when he used a phenolic resin tackifier for an acrylic latex. The... 

In the final paper, Azrak, Joesten and Hale illustrate the effect of reformulation of acrylic contact adhesives from solvent-based to water-based systems. Requirements on the tackifier and polymer latex are discussed which lead to an adhesive with the proper balance of open time and green strength. 

The most common reason tackifiers are added is to improve the adhesion to non-polar plastics see Table 15.1. Rosin ester tackifiers added at 15-30% will normally increase the peel several fold on polyethylene and polypropylene surfaces. For more polar surfaces, terpene-phenolic or styrene-phenolics are added. Tackifiers are discussed in more detail in Sect. 15.5 below. Acrylics are compatible with only a narrow range of commercial tackifiers. Tackifier dispersions are available for water-based adhesives. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Another important apphcation for 4-/ f2 -octylphenol is ia the production of phenoHc resias. Novolak resias based oa 4-/ f2 -octylpheaol are widely used ia the tire iadustry as tackifiers. The tackiaess of these resias biads the many parts of an automobile tire prior to final vulcanization. A specialty use for novolak resias based oa 4-/ f2 -octylpheaol is the productioa of a ziacated resia, which is formulated as a dispersioa ia water and coated onto paper ia combination with eacapsulated leuco dyes to yield carbonless copy paper (see Microencapsulation). Pressure from writing bursts the encapsulated leuco dye, which is converted from its colorless form to its colored form by the ncated resin (53). Novolak resias based oa 4-/ f2 -octylpheaol are also used ia the productioa of specialty printing inks. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

A second generation of phenolic dispersions, patented by J. S. Fry (33). involved the post dispersion of phenolic resins in a mixture of water and water-miscible solvents. To conform with air pollution regulations, the solvent was held to 20 volume %, or less, of the volatiles. A heat-reactive phenolic resin dispersion (34) and a phenolic-epoxy codispersion have become commercially available based on the above technology. Supplied at 40-45% solids, these products, which have a small particle size (0.75-1.0 ym), are better film formers than the earlier dispersions. Used alone or in blends with other waterborne materials, corrosion-resistant baking coatings may be formulated for coil coating primers, dip primers, spray primer-surfacers, and chemically resistant one-coat systems. Products of this type are also tackifiers for acrylic latexes, and such systems have been employed as contact, heat seal, and laminating adhesives for diverse substrates. 

Chem. Descrip. Aromatic hydrocarbon resin Uses Tackifier in elastomer-based solv., water, and hot-melt sealants and adhesives processing aid, reinforcing agent in rubber compd. and extruding applies. in metallic cold-cut paints food-pkg. and processing applies. 

Chem. Descrip. Glyceryl rosinate CAS 8050-31-5 EINECS/ELINCS 232-482-5 Uses Resin for lacquers, varnishes, adhesives wax modifier tackifier in pressure-sensitive rubber-based adhesives, in solv. and emulsbn types, in EA/A resin wax hot-melt adhesives and coatings modifier (contributes hardness, rapid drying, and resistance to water and alkali) in varnishes improves clarity as a wax modifier Features Pale thermoplastic... 

A low molecular weight PIB is used in many adhesive compositions. It plays role of a plasticizer and/or a tackifier. Adhesive composition based on EPDM rubber, useful in water-tight joints of roofing membranes, contains 5-9 wt% A pressure sensitive... 

The formirlations based on EPDM and brominated butyl rubber are plasticized with PIB to obtain water tight joints of rubber membranes. Peroxide curing causes some degradation of brominated butyl rabber which tackifies product... 

The compositional chemistry of the resins and elastomers has not changed, so the same compatibility should be observed. However, there are additional factors which complicate the situation. Factors such as compatibility of the emulsifier systems must now be taken into consideration. The molecular weight of the polymer which is generally much higher than that found in solvent-based systems, plays a major role. The particulate configurations of the components must also be considered. However, even with all of these complicating factors, in general we can still say that the same types of resins used to tackify specific elastomers in solvent can also be used successfully to tackify those same polymers in water. 

Rosin family s most common form of adhesive is colophony, a hard amorphous substance derived from the oleoresin of the pine tree. This material is applied in solvent solution form as a hot-melt mastic. It has poor resistance to water, is subject to oxidation, and has poor aging properties. Plasticizers are usually added to reduce its brittleness. Bond strengths are moderate and develop rapidly. These materials are used as temporary adhesives in bonding paper and as label varnishes. They are also used as components of PSAs based on styrene-butadiene copolymers and in hot-melt adhesives and tackifiers. These materials have been largely replaced by synthetic-resin adhesives. One specialized form of rosin adhesive is Canada Balsam, covered by the obsolete Military Specification MIL-C-3469C, titled Canada Balsam. This material was intended for cementing optical elements. 

---