Preparation of New Water-resistant Polyvinyl Acetate Emulsion Adhesive (I)

Polyvinyl acetate emulsion is widely used in wood processing, construction and decoration, fabric bonding, because of its unique composition, non-toxic and harmless, non-explosive and flammable, simple production, low price, good performance and convenient application. Bonding of porous materials in the fields of packaging materials, furniture assembly, printing and binding, etc. becomes a relatively large amount of emulsion in synthetic resin emulsions. However, due to its poor water resistance], it limits its scope of use.

This article starts with factors that affect the water resistance of polyvinyl acetate emulsions by using polyvinyl alcohol acetalization as an emulsion stabilizer, emulsion copolymerization of vinyl acetate and methyl methacrylate, and the incorporation of hydrophobic rosin in polymerized monomers. A method of combining resins to develop a water-resistant polyvinyl acetate emulsion adhesive.

1 Experimental section

1.1 Main raw materials and instruments: vinyl acetate (VAc), methyl methacrylate (MMA), polyvinyl alcohol (PVA), light-colored antioxidant rosin modified resin, nonylphenol polyoxyethylene ether (OP-10), Sodium dodecyl sulphate (SLS), formaldehyde, are all industrial products; ammonium persulfate (APS), chemically pure. NDJ-79 rotary viscometer; WE-300 hydraulic universal material testing machine.

1.2 Acetalization of Emulsification Stabilizer (PVA) In a four-necked flask equipped with a stirrer, a feeder, a reflux condenser, and a thermometer, 350 g of deionized water was added, and 45 g of PVA was added. The mixture was stirred and heated to 95° C. to completely dissolve the solution. To 80 °C, add appropriate amount of hydrochloric acid to adjust the pH value of 1-2, start dropping formaldehyde, add 18g after 20min, keep the reaction for 45min; then add the appropriate amount of urea for acetal reaction to prevent unreacted formaldehyde interfere with emulsion polymerization The reaction; then with sodium bicarbonate solution to adjust the pH to be used.

1.3 Emulsion Polymerization The above acetalized PVA solution is cooled to 60° C., an appropriate amount of composite emulsifier composed of SLS and OP-10 is added, dissolved and then heated to 70° C., and the light-colored antioxidant rosin modified resin is added dropwise. The mixed monomers of VAc and MMA, and the initiator APS aqueous solution were added dropwise at a constant temperature of 75° C. for 3 hours. After the addition was completed, the mixture was incubated at 80° C. for 0.5 hours and heated to 90° C. for 1 hour. Then, the temperature was lowered to 60 DEG C, and sodium bicarbonate was added to adjust the pH to 6 to 7. After stirring for 0.5 h, the temperature was lowered to 50 DEG C to obtain a modified PVAc emulsion adhesive.

1 4 Emulsion performance test The prepared PVAc emulsion was adhered to a wood test piece for 24 hours. The water resistance and shear strength were measured according to [5].

2 Results and Discussion

2.1 Effect of acetalization of PVA on water resistance of emulsion

It can be seen from Table 1 that the water resistance of the PVAc emulsion after acetalization of the emulsion stabilizer PVA is significantly improved. This is because PVA is acetalized with formaldehyde to form a six-membered cyclic acetal between the hydroxyl groups of adjacent molecules, which reduces the number of hydroxyl groups on the PVA molecule and enhances the water resistance of the emulsion stabilizer itself, thereby increasing the PVAc. The water resistance of the emulsion after film formation.