Pressure sensitive tape solvent

Working with less dilute solutions of elastomers one cannot fail to notice the influence (the stiffer the greater the effect) of molecular structure on the onset and course of non-Newtonion flow, on gelation and swelling, and the influence of the solvent as expressing itself by virial coefficients, molecular dimensions in solution, spinnability, and film forming. The sensitivity with which the tack of adhesives, demonstrated by pressure sensitive tapes which at that time reached the market, depends on the structure and composition of the elastomer was similarly striking and raised the question, which molecular structure or state was best suited to exhibit tacky adhesion, or adhesion per se. 

Early adhesive uses of butyl rubber generally consisted of solvent-based dispersions, or tape and rope extrusion of formulated solid rubber. Extensive use was made of butyl rubber s inherent tackiness in highly saturated grades of the polymer to make pressure sensitive tapes and precoated films. The polymers are also extensively used as major components of hot-melt adhesives, solid rubber sealing tapes, and caulking grades of sealants and mastics, of which most were high solids content solvent-based formulations. 

Pressure-sensitive adhesives fall into three broad product categories water based, solvent based, and hot melt. Application areas tend to overlap, and all three types can be used in most of the application areas. Despite this overlap, tapes tend to be produced from solvent-based adhesives, while water-based adhesives are preferred for label stock. Hot melts are used in both applications. Pressure-sensitive tapes for a variety of uses, such as masking, packaging, and insulation, are the largest application area, followed... 

Most often, NR adhesives are supplied either as a solvent dispersion or as latex for coating onto surfaces. Viscosity can range from very low viscous solutions for spray application to higher viscous mastics suitable for troweling. NR adhesives can also be pre-coated onto fabric, paper or film to provide pressure-sensitive tapes. 

A pressure-sensitive adhesive (PSA) is a viscoelastic material that adheres without the need of more than light pressure and requires no activation by water, solvent, or heat. The bond that is formed should be a permanent bond in the sense that the PSA remains bonded imless removal is desired and activated by the user. The Pressure Sensitive Tape Council suggests a number of other desirable features of many PSAs, including aggressive tack, the ability to adhere to a variety of surfaces, and to be removed cleanly without leaving residue. A common element to all PSAs is a polymeric network. This network may be uncross-linked or cross-linked, and it may also contain nonpolymeric additives that affect adhesive properties. 

Terpene Resins are low molecular weight hydrocarbon resins prepared by cationic polymerization of certain terpenes. They are used as tackifiers in pressure-sensitive tapes, masking tapes, hot melt coatings and adhesives, laminating adhesives and rubber solution adhesives. Terpene resins can be considered as solid solvents for a rubber which function by solubilizing the smaller tack-bestowing molecules from their dispersion in the mass of a rubber. 

Water-borne emulsions and solvent solutions - used in non-structural applications, such as pressure-sensitive tapes and labels. Information on these types, of which there are many, is not given in this book. Those specifically for wood bonding are included. 

Elastomeric adhesives are natural or synthetic polymers with superior toughness and elongation. Examples of elastomeric adhesives include natural rubber, reclaimed rubber, butyl rubber, polyisobutylene, nitrile rubber, styrene-butadiene-rubber, etc.l Elastomeric adhesives are supplied as solvent solutions, latex cements, pressure sensitive tapes, and single- or multi-component nonvolatile liquid or pastes.[ 1 However, they are usually supplied in liquid form. Most are solvent dispersions or water emulsions. The service temperature is up to 204°C (400°F). They never melt, have excellent flexibility, but low bond strength. The main application of elastomeric adhesives is on unstressed joints on lightweight materials (e.g., joints in flexure). Hence, they are not considered structural adhesives. 

Tackifying Resins. These are advantageous when the dried surface of the adhesive is intended to be permanently tacky, as with a pressure-sensitive tape, or at least to remain tacky for a long while after removal of solvent. Various naturally occuring resins and their derivatives are used, such as rosin and rosin esters, terpene, and coumarone and coumarone-in-dene. Resins synthesized from petroleum are widely used, often in combination with those from biological sources. 

The process of masticating and dissolving natural rubber is important for pressure sensitive formulation as well as for solvent cement production. Pressure sensitive tapes and labels based on natural rubber are a significant part of the rapidly growing pressure sensitive adhesive... 

Environmental concerns, which have resulted in restrictions on the use of organic solvents, have been the impetus for a strong interest in the use of rubber latexes in the formulation of pressure sensitive tapes and labels, can sealants, and contact adhesives. The availability of suitable rubber latexes and tackifying resin dispersions have made this change pos-... 

Pressure sensitive tapes and labels are offered with a variety of backing materials such as crepe paper, aluminum foil, fabric, cellophane, kraft paper, cellulose acetate, polyester film, polyethylene, polypropylene, plasticized poly (vinyl chloride), woven glass fiber cloth, or other flexible materials. Pressure sensitive adhesives may be applied from solvent, latex, hot melt, or radiation cured 100% solids systems. A wide variety of coating methods are utilized such as roll coating, calendering, slot die, and transfer coating. 

If the ratio of solvent to ambient air is within a given range the mix is explosive in the presence of fire or electric sparks. In areas where these solvents are used all the equipment and electric equipment should be spark proof, and the solvent vapors should be eliminated by exhaust fans (but now in some countries it is unlawful to release large quantities of noxious solvents in the ambient air so that very large users may need some system for recycling of solvents, for instance those who coat very large surfaces of pressure-sensitive tapes and labels or laminate plastic films for flexible packaging). 

Rubber-based solvent cements are adhesives made hy combining one or more rubbers or elastomers in a solvent. These solutions are further modified with additives to improve the tack or stickiness and the degree of peel strength, flexibility, and the viscosity, or body. Rubber-based adhesive is used in a wide variety of applications, such as contact adhesive from plastic laminates used for counter tops, cabinets, desks, and tables. Adhesive is used on pressure-sensitive tapes as floor tile adhesive and carpeting adhesive. Self-sealing envelopes and shipping containers use rubber cements. Solvent-based rubber adhesives have been the mainstay of the shoe and leather industry. 

Cellulosics. CeUulosic adhesives are obtained by modification of cellulose [9004-34-6] (qv) which comes from cotton linters and wood pulp. Cellulose can be nitrated to provide cellulose nitrate [9004-70-0] which is soluble in organic solvents. When cellulose nitrate is dissolved in amyl acetate [628-63-7] for example, a general purpose solvent-based adhesive which is both waterproof and flexible is formed. Cellulose esterification leads to materials such as cellulose acetate [9004-35-7], which has been used as a pressure-sensitive adhesive tape backing. Cellulose can also be ethoxylated, providing hydroxyethylceUulose which is useful as a thickening agent for poly(vinyl acetate) emulsion adhesives. Etherification leads to materials such as methylceUulose [9004-67-5] which are soluble in water and can be modified with glyceral [56-81-5] to produce adhesives used as wallpaper paste (see Cellulose esters Cellulose ethers). 

SBR adhesives can be used as latices or as solvent-borne, pressure-sensitive and tape adhesives. 

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