Лако-красочные материалы — производство

A Loop continuous reactor uses a broadly similar formulation to the batch case, but the poly(vinyl alcohol)-containing solution is pumped in continuously rather than added to the reactor initially. Also, a redox initiator is used: Parts by weight (kg) 1. Initial reactor filling Process water 46.3 Poly(vinyl alcohol) (88% hydrolyzed) 2.2 Poly(vinyl alcohol) (98% hydrolyzed) […]

A. Poly(vinyl acetate) Homopolymers 1. Batch Process A simple formulation by the batch process is as follows: Parts by weight (kg) 1. Initial reactor charge Process water 360.5 Poly(vinyl alcohol) (88% hydrolyzed) 12.6 Presolution Nonyl phenol (15 M) ethyl oxide condensate 6.6 Linear C12 sulfate, sodium salt 0.3 Sodium bicarbonate 1.6 Antifoam (nonsilicone) 0.4 Water […]

PVA and EVA products are often sold with rather limited information. Often solids content, viscosity range, and pH are the only real specifications given. Minimum filming temperature (or in some cases, glass transition temperature) may be quoted, together with comonomer type, if any, and some brief application recommendations. Manufacturers may in production test for more […]

The majority of standard product formulations for PVA and EVA adhesives use poly(vinyl alcohol) as the main protective colloid and thickener. Poly(vinyl alcohol) can be obtained in a number of grades produced from poly(vinyl acetate) by hydrolysis. As a consequence, almost all products are effectively vinyl acetate/vinyl alcohol copolymers. Lower levels of hydrolysis, 88% most […]

Addition polymerization is exothermic, and one of the major constraints to high produc­tion rates is the problems associated with heat removal. In processes using ethylene, the pressure of the gas determines solubility in the liquid phases (i. e., water and vinyl acetate monomer droplets) and in the polymer particles. This concentration of ethylene at the […]

The essential property of any polymer used as an adhesive is that it should have good cohesion and stick to the surfaces it joins. This can occur only if the polymer forms a film on application or at some stage during the joining process. In the case of a water suspen­sion such as a PVA […]

Vinyl acetate is characterized by having an activated double bond. While being an accep­tably stable material under normal ambient storage, it is readily attacked by a free radical. This simple addition gives another free radical, and the addition of a series of monomer units results in a polymer chain. Thus CH2=CH—C—CH, + • S07 ^ […]

Ken Geddes Crown Berger Limited, Darwen, Lancashire, England I. INTRODUCTION Poly(vinyl acetate) (PVA) and ethylene-vinyl acetate (EVA) copolymer adhesives have much in common, yet represent extremes in the degree of sophistication of their produc­tion processes. Both products are stable suspensions in water of a film-forming polymer, the particles of which are generally spherical. They are […]

The use of polyurethanes in the pressure-sensitive adhesives market has been relatively small. Polyurethanes have been somewhat limited to being used as additives to pressure — sensitive adhesives to improve their cohesive strength. Recent developments in the institu­tional carpet backing or automotive carpet floor mat markets suggest that pressure — sensitive urethanes can succeed commercially […]

Polyurethane reactive hot melts are 100% solid, hot-melt thermoplastic prepolymers that moisture cure slowly after application. Conventional hot melts are known for their quick setting, excellent green strength, ease of application, and low toxicity. Their primary limitation is low heat resistance (at elevated temperatures, the adhesive will soften and flow) and poor adhesion to some […]