Modified PVA paint and its prepn process

Abstract

The present invention discloses one kind of modified PVA paint, which consists of PVA, regulator, inorganic matter, tackifier and water. The tackifier is polyethylene imine and/or polyoxyethylene; the inorganic matter is clay and/or nanometer titania or the mixture of clay, nanometer silica and nanometer titania. The preparation process includes mixing PVA, regulator, inorganic matter, and water through stirring, heating to and maintaining at 90-95 deg.c to dissolve PVA completely, cooling to normal temperature, and adding tackifier through stirring. The product of the present invention has excellent machinability, and the formed coating has high water resistance, excellent ultraviolet ray and infrared ray reflecting property, high wear resistance and other excellent performance.

Description

1. Technical field [0001] The invention belongs to a polyvinyl alcohol coating solution and a production process thereof. 2. Background technology [0002] In barrier packaging materials, it is an effective way to rationally develop and utilize high barrier polymers. Due to the characteristics of molecular structure, these polymers have high density and can effectively prevent gas permeation. They are used as barrier layers to compound with other materials. Finally, the comprehensive performance is good, especially the oxygen permeability is low, and the representative ones are polyvinyl alcohol PVA, polyvinylidene chloride PVDC, and ethylene-vinyl alcohol copolymer EVOH. Polyvinylidene chloride PVDC is the earliest barrier material developed. Because its molecular chain unit contains two chlorine atoms, and the plasticizing temperature is very close to the decomposition temperature, it is difficult to process and cannot be recycled. A large amount of dioxins are produced du...

AI Technical Summary

Problems solved by technology

Therefore, developed countries have gradually turned to use EVOH and PVA. EVOH is a modified variety of PVA, but EVOH is relatively expensive and is a polar polymer. It cannot be directly compounded with general-purpose materials. Adhesive resins and Expensive multi-layer co-extrusion equipment can produce this kind of film, and the cost is very high. Like PVA, this kind of material has the same performance as PVA, and its performance of blocking oxygen and other gases is greatly affected by humidity. In addition, 30 %-40% of the ethylene component is polymerized with PVA, so the oxygen transmission rate increases. For example, if a five-layer co-extrusion equipment is used, the middle layer uses EVOH as a barrier layer with a thickness of 5 μm, and the thickness of other materials is 95 μm. The oxygen transmission rate is 8cm 3 / m 2 ·24h·0.1Mpa

Polyvinyl alcohol PVA is a polyhydric polar polymer with the molecular formula CH 2 -CHOHn has strong water absorption and can be dissolved in water. Due to the effect of intermolecular hydrogen bonds, it has high density and excellent gas barrier properties, but its melting point is as high as 220-240 ° C, and its decomposition temperature is low. It begins to etherify at 160 ° C. It begins to decompose at 200°C, making it difficult to process thermoplastically. Most of the currently available PVA films are produced by tape casting, but the disadvantages of tape casting are: long production cycle, low production efficiency, film thickness, unstable quality, and low cost. High, thereby limiting the popularization and application of PVA film, and in the prior art, because in the material of modified PVA adopted, the addition amount of plasticizer, modifying agent etc. is too large, makes its purity reduce, and oxygen permeability increases Large, the base film is polypropylene PP, the thickness is 25μm, the thickness of the polyvinyl alcohol coating is 10μm, and the oxygen transmission rate is 3cm 3 / m 2 ·24h·0.1Mpa, the water vapor transmission rate is 4g / m 2 24 hours, and must be produced by expensive proprietary coating machines, low output and high energy consumption, so its manufacturing cost is high, and its air permeability is greatly affected by humidity, which restricts its wide application

However, the use of aluminum foil as a barrier layer cannot be applied to occasions that require transparent packaging due to its opacity, and its price is also relatively high, which cannot meet the social requirements for high-barrier packaging.