SU68062A1 - The method of obtaining porous plastics - Google Patents

Description

Methods are known for producing porous plastics based on polymers and pore formers.

It has been established that from any polymer that possesses the pa of the definition stage by thermoplasticity, melting or expandability when heated, depending on the conditions, half a porous material of different density can be obtained.

If some azo compounds are added to such polymers, taken as a powder, decompose when heated to release carbonic acid, hydrogen or other gases, and then, with appropriate heating, pressurized under a certain pressure in an airtight mold, under specially selected conditions the polymer is melted or softened, the added azo compound is decomposed and the evolved gases are distributed in the polymer. If the mold is then cooled to a temperature of 20 °, the obtained pressed product is removed from it and reheated, the polymer softens, the gases in it expand, and the polymer acquires a microporous structure, which significantly increases in volume. then cooled.

For this purpose the most are:

1) esters or amines of azodicarboxylic acids;

2) acyclic, hydroaromatic and aromatic azodinitriles, azodicarboxylic acids or amides of azodicarboxylic acids;

3) aromatic, acyclic azoimidines or mixtures thereof.

Depending on the pressing conditions (pressure, temperature, time) and heating conditions after pressing (temperature, time), porous LT materials of different density, structure, and pore sizes are obtained.

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The main saKOHONrepHOCTHs are also determined, which determine the required number of pore-forming agents, the pressure developed during decomposition in the nress-form and when the extruded billet is inflated, the residual pressure inside the pores of the resulting porous material, the expansion of the polymer and the associated relaxation effect.

One of the indispensable conditions for obtaining a porous material is the absence of chemical interaction of the pore forming material with polymer molecules.

It is also important that the decomposition of the blowing agent does not generate too much heat, under the action of which the polymer can decompose in the inner layers of the extruded billet. For example, diazo aminobenzene, when used together with PVC or chlorinated PVC, causes decomposition of these polymers as a result of a large exothermic effect upon decomposition. It is also important that the plasticity temperature of the polymer coincides with the decomposition temperature of the blowing agent.

The structure of the polymer is essential for the mechanism of the formation of pores in the polymer and for the degree of its swelling. Polymers with a linear molecular structure, such as polystyrenes, are capable of "inflating almost infinitely, up to beats. weights of 0.01 or less, while polymers with a branched molecular structure, for example, polyvinyl chloride, "inflate sparingly. The size and character of the holes in the first case are determined by the ease of orientation of the molecules and the relatively low viscosity of the polymer; in the second case, the orientation is difficult and the viscosity is much higher, which leads to a different character and pore size.

As a rule, isolated, non-communicating pores are formed in polymers.

The described process and basic principles are applicable to many polymeric substances and result in porous light materials with a bulk weight or density from 0.01 to 0.5-0.8 and high specific strength.

It is easy to use a plastic , cellulose acetate, ethyl and benzyl cellulose and other cellulose ethers, polymers of various natural and synthetic acids, salts of these acids and other poly ernye substances capable soften or melt and form a pressurized under heating plastics.

Depending on the requirements for the porous material, the polymer can be added before mixing it with the blowing agent or thereafter various fillers (fibrous, crystalline and amorphous), plasticizers or solvents, accelerators and catalysts, as well as substances that form such additives in the process of making porous material.

Example I. 100 wt. powdered polystyrene, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene, acetylcellulose, or some other polymer that meets the requirements outlined above, are mixed in a ball mill or in another apparatus from 1-30 wt. h (depending on the desired density of the porous material) azodicarboxylic ether or any other

a blowing agent belonging to the series of azo compounds indicated by you, or their mixtures until a homogeneous mixture is formed within 1-12 hours. The resulting mixture is then pressed in a hermetic mold of the norshne type into a product of the desired shape at a temperature of from 100 to 200, depending on the softening temperature of the polymer and the decomposition temperature of the pore-forming agent, and a pressure of from 50 to 1000 / sg / s. the number of applied blowing agent. The incubation time for heating and under pressure is 1-5 minutes per 1 mm of the thickness of the product. At the end of the extrusion, the mold is cooled to a temperature of 20-30 ° under pressure at a cooling rate of not more than 30 minutes and the product is removed from the mold.

Not later than 12 hours after pressing, the extruded product is subjected to "inflation by heating or in a liquid (water, glycerin, oils, etc.) or heated air, high-frequency currents, infrared rays or some other method at a temperature of 80-150 ° , depending on the softening temperature of the polymer, for 10-90 minutes, depending on the desired density of the porous material and the residual pressure inside the pores.

Example 2. 100 weight. Threshold polymethyl methacrylate, or any polymer of the methacrylic or acrylic ester polymer, or some other suitable polymer, is shifted in a ball mill or in any other apparatus with I-30 wt. including a pore former, belonging to the series of azo compounds listed above, or mixtures for 1-12 hours. Methyl methacrylate monomer or some other appropriate monomer is introduced into the resulting mixture for 1-2 hours, in which the catalyst is previously: 1 dissolved, for example, benzoyl peroxide or some other, with or without it, taken in an amount of 20-100 wt. h. After that, the mixture is pressed, cooled and the resulting product is “inflated, as indicated in example 1.

Example 3. In carrying out the process described in Example 2, di-tri or tetrafunctional monomer is additionally used both by itself and in mixture with the corresponding polymers, monomers in the amount of 0.5-20% to the polymer and catalysts, the purpose of combining the polymer, converting it into a thermo-reactive state and obtaining a non-meltable and insoluble product. For example, ethylene glycol dimethacrylic ester is used in the case of polymers of methacrylic or acrylic acid esters, allyl esters of two-, three-, and polybasic acids and other di-tri- and tetrafunctional monomers.

Example 4. When mixing the components, the processes described in examples 1, 2 and 3 add fillers (glass, cellulose and wood fibers, cork, mineral fillers) in an amount from 0.5 to 50% to the polymer or plasticizers, see dyes or solvents in an amount of from 1 to 50% to the polymer.

The invention

A method of producing porous plastics based on polymers and pore formers, characterized in that hot melt polymers or copolymers or mixtures thereof with mono-di-tri and tetra-functional monomers in a mixture with fillers, plasticizers, solvents, accelerators and catalysts or without them displaced with decomposing when heated with the release of gaseous substances, such as carbon dioxide, nitrogen, ammonia or hydrogen, azo compounds such as esters or amines of azodicarboxylic acids, azodinitriles, azodicarboxylic acids Ota, amides of azodicarboxylic acid

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and azoimidines, or mixtures thereof, are pressed in a hermetic mold at the softening temperature of the polymer and decomposition of the azo compound, followed by cooling under pressure and "inflating the material obtained by heating to the required porosity.