摘要:
A pulverulent polymer composition which is readily pourable, has a low tendency to form dust and has good stability on storage is composed of a mixture of a vinyl ester polymer and a small proportion of a hydrophobic silica. The composition is prepared by spray drying an aqueous vinyl ester polymer dispersion in the presence of a hydrophobic silica. The silica is preferably a product from the reaction of a hydrophilic silica with an organochlorosilane. The composition can be redispersed in water and the films produced from such dispersions are transparent; they are suitable for the production of paints, glues and adhesives.
摘要:
For the thermoplastic processing of polyvinyl alcohol, the processing temperature must be below the decomposition temperature of the polyvinyl alcohol; this is attained by incorporating plasticizers. For preparing a plasticizer-containing granular polyvinyl alcohol wherein the plasticizer is homogeneously distributed, there is used as starting material a granular polyvinyl alcohol consisting substantially of particles having a definite diameter. The plasticizer is incorporated in the presence of a small amount of water insufficient to dissolve the polyvinyl alcohol, and the temperature is adjusted in a definite manner during the mixing operation. Simultaneous presence of fine particles of a high molecular weight organic compound soluble or dispersible in water is advantageous. The plasticizer-containing granular polyvinyl alcohol is suitable for the manufacture of any shaped articles, especially films and sheets.
摘要:
The water content of a material, which tends to either absorb water or to release water, is changed with the aid of a film, which at least partially separates the material from the adjacent space and is impermeable to liquid water but permeable to gaseous water. Polyvinyl alcohol with a particular degree of polymerization and degree of hydrolysis is used as the film material. The film can be mechanically or chemically after-treated. The moistening or de-moistening of the material, which is solid, liquid or gaseous, is effected, utilizing a water vapor pressure gradient, under very mild conditions.
摘要:
A molding composition on the basis of polyvinyl alcohol substantially consists of a partially solvolyzed graft copolymer of a vinyl ester and a polyethylene glycol or of a mixture of such graft copolymer with a partially solvolyzed polyvinyl ester as well as of water and optionally a polyhydric alkanol. The composition is obtained by mixing the granular polymers used in each case with the other components. It is water-soluble, flowable and thermoplastically workable and is suitable for the preparation of any shaped articles, especially sheets.
摘要:
A polymer granulate whose particles consist of a core component and a coating component can be prepared by mixing a granular polymer with a pulverulent coating agent. The core component is made of a water-soluble polymer, in particular a polyvinyl alcohol. The coating component is a water-soluble or water-insoluble substance which is applied to the water-moistened particles of the core component. The particles of the polymer granulate have diameters within the range from 0.6 to 6 mm. The granulate has particularly good freeflowing properties; it is especially suitable for preparing adhesives.
摘要:
For the thermoplastic processing of polyvinyl alcohol, the processing temperature must be below the decomposition temperature of the polyvinyl alcohol; this is attained by incorporating plasticizers. For preparing a plasticizer-containing granular polyvinyl alcohol wherein the plasticizer is homogeneously distributed, there is used as starting material a granular polyvinyl alcohol consisting substantially of particles having a definite diameter. The plasticizer is incorporated in the presence of a small amount of water insufficient to dissolve the polyvinyl alcohol, and the temperature is adjusted in a definite manner during the mixing operation. Simultaneous presence of fine particles of a high molecular weight organic compound soluble or dispersible in water is advantageous. The plasticizer-containing granular polyvinyl alcohol is suitable for the manufacture of any shaped articles, especially films and sheets.
摘要:
An encapsulating material for drugs consisting of a modified polyvinyl alcohol which is a partially hydrolized graft copolymer of vinyl acetate on polyethylene oxide.
摘要:
In order to protect the environment from pollution, it is desirable to keep the polyvinyl alcohol content in waste waters as low as possible. Polyvinyl alcohol may be removed from waste waters by means of microorganisms on the the one hand, and on the other according to chemical/mechanical methods by salting-out and precipitation and subsequent separation of the solids. Advantageous is the precipitation in the form of a polyvinyl alcohol/boric acid/didiol complex, especially by means of alkaline earth metal hydroxides in an alkaline medium. Calcium hydroxide is a particularly suitable alkaline earth metal hydroxide.
摘要:
The sieve efficiency can be increased in an improved sieve apparatus in such a way tat the sieve apparatus is equipped with a compulsory mixing device (5). By means of this, during the sieve process, the sieve product, which is moving forward along the main flow direction (1) to a delivery end (11), is thoroughly mixed, which produces the desired increase in sieve efficiency.
摘要:
When polyvinyl alcohol and vinyl acetate/ethylene copolymers are acetalized in an acid aqueous medium in the presence of a wetting agent, an open-pore solid foam is formed, if the reaction mixture contains gas bubbles. These gas bubbles are produced, in particular, by stirring in air. The molded articles obtained are porous, and the pores are uniformly distributed. The dried molded article absorbs many times its weight of water. It is employed as a sponge for household use and in industry.