Envelope sealing adhesives

Envelope sealing adhesives are usually remoistenable, and typically blends of dextrin and compatible polyvinyl aeetate homopolymers as well as all dextrin or all resin types. Some water-borne and hot melt pressure sensitive adhesives based on acryhc or rubber resin liquids and rubber resin hot melts are also used. Natural rubber latex is the basis for self sealing envelopes. 

Envelope front seal adhesives are made from solutions of dextrins in water. They require high solid contents, usually 60 to 70%. Which of the two dextrin types (white or yellow) would be more suitable as adhesives for envelope seals ... 

Animal glues are used widely in a variety of ways with paper. For example, they have been the dominant adhesive for rewettable gummed paper tapes, labels, and envelope seals [69]. They are an important coadditive with synthetic wet-strength resins and rosin sizes for coated paper products [70]. They have been a primary binder for the grit that forms sandpaper [71]. 

Large quantities of starch are consumed as a component of adhesives for paper and paperboard, especially in the production of corrugated board. Dextrins, derived from com or potato starch, are used as adhesives for laminated products and as gums for envelope construction and sealing. 

This mechanism of adhesion advanced and originally promoted by the Soviets (1963) is of the greatest importance to applications where a material is being adhered to itself, such as in the self tack of rubber. Another familiar example is the application of the same adhesive to two diflerent surfaces from a solvent system, allowing the solvent to dry partially or totally, and then comhining the treated surfaces, such as in the use of contact cement or self-sealing envelopes. 

Natural rubber adhesive, or latex, is used in self-seal applications, where it makes use of its unique ability to bond only to itself with pressure. Applications include selfseal envelopes, press-to-seal cases, and cold-seal candy wraps. Natural rubber latex is also used in adhesives for lamination of polyethylene film to paper, such as in multiwall hags. 

Dextrins have many applications, with adhesives being their primary market (11,96). Dextrins are used as adhesives for case and carton sealing. For this application, borax is often added to the dextrin to add stability and increase viscosity. Dextrins are added to adhesives used in the laminating of products such as paperboard and shipping containers. The paper industry adds dextrins in adhesives for tube winding and bag adhesives. Library pastes, bottle label adhesives, envelop adhesives, gummed tape, and wall covering adhesives all benefit fiom dextrin addition. 

First, the adhesive must be able to be conveniently applied to the substrate using a manual or mechanized method of apphcation. Second, the adhesive must wet the surface to which it is applied. Third, the adhesive must achieve a permanently solid state via evaporation of a solvent, removal of pressure, a drop in temperature, or the occurrence of chemical reaction. The conversion must occur within a time period amenable to the nse of the bonded part. Fourth, before it is put into service, the adhesively bonded part mnst have been provided with a bond that is strong enough to resist normally imposed stresses. The stresses normally imposed on a sealed envelope are very dilferent from those imposed on a tiled wall or a bonded vehicle frame. Fifth, the adhesive mnst maintain the bond through the joint s fimctional lifetime, withstanding all environments to which the joint is normally exposed. 

Coating and binding products used for carpet backings, adhesives, adhesive tapes, self-seal envelopes, etc. 

Natural rubber has an excellent flexibility, high initial tack, and good tack retention properties. Typical applications include its use as an adhesive in self-sealing envelopes, and, in general, as pressure sensitive adhesive. It also has wide applications in the footwear and upholstery industries, for the attachment of leather, fabrics, and ruhher to one another or to wood and metal, bonding of paper, felt and textiles in the manufacturing of stationery, packaging, etc. 

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. 

Uses Binder, carrier, compounding agent, dispersant, stabilizer, protective colloid in polymerizations for textiles, paper, cement/plaster additive, films, ceramics, molded prods., mold release useful for remoistenable adhesives, wood adhesives, envelope, label, bookbinding, padding, carton sealing applies. 

Nonfood hydroxyethyl starch applications are in the paper industry for surface sizing and coating, as quality enhancer for pigmented papers, as wet-end additives in textiles for warp sizing as an adhesive component for bag pastes, case sealing and enveloping materials. Hydroxypropyl starches with higher DS are used routinely in pharmacy as a blood plasma extender. 

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