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Adhesives made from film forming materials that can disperse or dissolve in water are water-based adhesives and are often referred to as waterborne adhesives. Among them, film forming materials are generally organic polymers. Animal glue, starch, dextrin, serum protein, albumin, methyl cellulose and polyvinyl alcohol all belong to this kind of adhesive, and some soluble intermediates of phenolic aldehyde and urea formaldehyde resin also belong to this kind. Some of the adhesive film forming materials can be dissolved in or dispersed in water by lye, such as casein, rosin, shellac, vinyl acetate or acrylate copolymer containing carboxyl groups (such as PAS, methacrylic acid or maleic anhydride), and carboxymethyl fibrin. Many water-based adhesives are made from latex.
At first, latex refers to the natural rubber dispersions from rubber trees. The term is now used to refer to synthetic resins and synthetic rubber latex produced by emulsion polymerization. Such latex examples include synthetic rubber by emulsion polymerization of butadiene, styrene, butadiene acrylonitrile and chlorobutadiene, and synthetic resins by emulsion polymerization of vinyl acetate, (methyl) acrylic acid (ester), vinyl chloride, two chloroethylene, and styrene. Aqueous dispersions can also be obtained by emulsifying or dispersing solid rubber or resin. Recycled gum, butyl gum, rosin, rosin derivatives, bitumen, coal tar, and dispersion of synthetic resins derived from coal tar and petroleum can be obtained by this method. In 1970s, the water based gum, which was made from solid rubber as base material and a variety of additives, was already available, in which synthetic hydrocarbon resins or rosin soap derivatives were added to increase the strength properties. Water based water based water based adhesives use water as its flow carrier, and its adhesive particles are dispersed in water, thereby reducing the viscosity of the colloid, so that it can be used in various adhesives at different thickness. During the curing period of the adhesive, the volatilization of the flow carrier usually occurs in the large oven, but the volatilization and curing can also occur under mild and unheated open conditions. It is necessary to point out that the existing water based adhesives are not all solvent - free l00%, and may contain a limited amount of volatile organic compounds as additives for their aqueous media, so as to control viscosity or fluidity. To sum up, water-based adhesives can be classified as follows.

(1) aqueous solution based water-based adhesives include the following types. (1) natural or modified natural polymer solutions such as some starch or dextrins, cellulose and protein adhesives. (II) synthetic polymer aqueous solutions such as polyvinyl alcohol (PVA).
(2) water dispersive or emulsion type water based adhesives include the following categories. Synthetic resin latex, such as polyvinyl acetate (PVAC), polyacrylate, etc. synthetic rubber latex, such as butadiene, Ding Jing, neoprene latex, etc.
Classification of water based adhesives
(3) water dispersions such as water based reclaimed rubber or butyl rubber made from solid rubber or resin through emulsification or dispersion.
(4) other water-based polyurethane, which can be emulsified or dispersed during the synthesis of non chain polymerization, can also be prepared by an already made ionic polyurethane solid emulsion or dispersion. In addition, there are water-based inorganic adhesives, mainly silicate or sodium silicate adhesives. But strictly speaking, they do not belong to the category of adhesives (Adhesives). Among them, water based water based water based adhesives have various kinds, different properties, wide use and complex formulation and preparation technology, which represents the mainstream of solvent free water based adhesives. According to the hydrophilic and water dispersibility of the polymer, it can be divided into self emulsifying and emulsifying agent (surface active agent) emulsified dispersive water base adhesive, and can also be divided into cationic, anionic and non ionic types according to the type of emulsifier. Water soluble adhesives made from water-soluble polymers are generally poor in water resistance and limited in application and development potential. It should be noted that adhesives can be classified and described in terms of chemical composition, function, physical form, curing mode and so on (Table 1).
According to curing methods, it can be divided into solvent base, water base, hot melt, pressure sensitive, reactive type, anaerobic and UV curing adhesive. Most of the adhesives are overlapped in different categories. Some synthetic polymers can be prepared as solvent based adhesives and water based adhesives. Therefore, it is difficult to specify a particular polymer as a solvent based or water based adhesive. In addition, some water-based adhesives can be sold in solid form and dissolved or dispersed when water is used. Water based acrylic pressure sensitive adhesives are also produced in large quantities. The main polymers used for water-based and solvent based adhesives are listed in Table 2.
Table 1 Classification Methods for classification of adhesives, characteristic examples of irreversible curing of thermosetting under heating and heating and pressure, and the ability to soften and flow acetate cellulose, polyacetyl acetate and polyvinyl alcohol elastomer at heating and pressure after heating and compression. The high elasticity with excellent flexibility and peeling strength is synthesized from two different resins, natural rubber and polybutadiene alloy adhesive. Phenolic aldehyde, nitrile. Phenolic aldehyde is used in industrial assembly by functional adhesive. It helps maintain the structure of the whole polyurethane, epoxy, phenolic, polyimide, and C Unstructured gum of eNIC acid ester combination of light material together with animal and plant product glue in physical form, liquid glue, low viscosity polyvinyl acetate paste, high viscosity starch adhesive tape rubber powder, granular acrylate, styrene block copolymer
Table 2 the main polymer water based and solvent based adhesives for water based starch and dextrin gum animal glue albumin silica sodium casein carboxymethyl cellulose sodium lignosulpose solvent based nitrocellulose acetate butyrate cellulose acetate recirculating polyisobutylene water base or solution base agent polyvinyl acetate Copolymer polyacrylate and polymethacrylate polyurethane PVC and copolymer polyvinyl ether polyvinylidene vinyl ether polyvinylidene chloride and copolymer polyamide UF and phenolic rosin ester natural rubber butadiene rubber butyl rubber butadiene rubber butadiene rubber rubber reclaimed rubber. It is worth noting that the adhesives and people in the living body are in the body. The earliest types of adhesives (such as bone glue, egg white, paste, etc.) are not solvent based adhesives, but mainly water-based adhesives. "Nature is the most brilliant teacher", it seems to have shown that one of the right directions of adhesives water-based adhesives. In depth study of these natural or biological adhesives, mankind will take a lot of detours in the development of solvent free adhesives, and will achieve faster and greater progress. In the era of intelligent materials, the development and development of bionic, smart or intelligent adhesives will be inseparable from the development of water-based adhesives.