SU274741A1 - METHOD OF OBTAINING POLYAMIDE - Google Patents

Description

The invention relates to polyamides suitable for the manufacture of fibers, with aromatic cycles in the chain and possessing excellent thermal properties, in particular, high resistance to prolonged heating at high temperature in the presence of air.

It is known that polyamides with a chain formed by aromatic cycles bound by amide groups have an increased heat resistance and are able to withstand, without decomposing, a temperature of the order of 300-400 ° C. In addition, these polyamides possess such physicochemical and mechanical properties that allow them to be widely used in the manufacture of fibers, films, coatings, and molded products.

However, the extrusion of aromatic polyamides in the molten state is practically impossible, since in order to provide the necessary viscosity it is necessary to work at very high temperatures, which causes some decomposition of the polymer.

In addition, the solubility of aromatic polyamides in commonly used solvents is usually low, as a result of which it is difficult to obtain solutions of sufficient concentration, which can be extruded in a dry or wet state. Their solubility can be increased by adding

mineral salts that are soluble and dissociate into ions in a solvent, but subsequently these salts are almost impossible to completely remove from the finished products released from these solutions. In addition, these salts are fillers capable of impairing certain properties of the polymer.

The invention relates to polyamides of increased heat resistance, capable of producing relatively concentrated solutions in common solvents.

A method for the preparation of polyamides by condensation of 15 dicarboxylic chlorides with diamines of the formula

Hjn

NH2

20

where R is hydrogen or alkyl containing 25 to 6 carbon atoms; R is alkyl, hydrogen.

2H, N

Chloroanhydrides of predominantly aromatic dicarboxylic acids, for example isophthalic, terephthalic, are used in the reaction.

To obtain copolyamides, one or more amino derivatives with one or more acid derivatives can be introduced into the reaction.

The melting point of polyamides is above 300 ° C, most often around 350 ° C. During molding, they are able to withstand, without decomposition, temperatures higher than 150 ° C (further up to 200 ° C), with quite satisfactory mechanical properties. Their electrical properties, in particular the resistivity in the transverse direction and the dielectric constant, depend much less on temperature than on conventional polyamides. The properties of polyamides do not deteriorate appreciably with prolonged exposure to high temperatures (on the order of 200 ° C) in an inert atmosphere and even in the presence of air.

Aromatic polyamides, derivatives of 1,1-bis- (4-aminophenyl) -2-phenylalkanes, substituted or unsubstituted, dissolve in metacresol at 25 ° C, in dimethylformamide, dimethyl acetamide, dimethyl sulfoxide, etc., to form a rather viscous concentrated solutions suitable for dry or wet molding. These solutions can be extruded in the form of fibers, films, or cast in the form of films or plates used in the manufacture of varnishes, binders for laminates, etc.

Polyamides, in particular derivatives of iso-terephthalic acids, are more resistant to hydrolysis in a neutral alkaline or acidic medium than aliphatic polyamides.

Example 1. In a laboratory apparatus with a mixer (mixer) pour a solution of 13.7 wt. including bis- (4-amiophenyl) phenylmethane in 130 weight. including tetrahydrofuran and a solution of 10.6 wt. including carbon dioxide in 100 weight. h of water. A solution of 10.15 wt. including terephthalic acid chloride in 130 weight. including anhydrous tetrahydrofuran and stirred for 5 minutes A white, viscous solution is obtained, to which 1000 wt. including water, and the polymer precipitates as a precipitate. The latter is washed, dried, and a yield (yield 95%) of a polymer with a viscosity (characteristic) of 1.57, determined in W-cresol at 25 ° C and 0.5% concentration.

In the study of thermal balance with a rate of increase in temperature of 2.2 ° C / min, it is noted:

in a nitrogen atmosphere, the weight loss starts at 344 ° C, remains insignificant to 342 ° C and increases, starting at 432 ° C; in the presence of air, there was a slight increase in weight up to 323 ° C and a significant loss, starting at 425 ° C.

It is possible to obtain highly concentrated solutions of the said polyamide in dimethylformamide, dimethylacetamide, hexamethylphosphoramide, dimethyl sulfoxide, N-methylpyrrolidone. By pouring onto a glass plate and evaporating the solvent in a cabinet at 100 ° C, a film with the following mechanical properties can be obtained from a 20% solution in dimethylformamide.

This film after 30 hours in air at 170 ° C still has a tensile strength of 0.9 kg / mm, an elongation at break of 2.3% and a modulus (elasticity) of 47 kg / mm.

Example 2. Under the conditions of example 1, replacing the terephthalic acid chloride with the isophthalic acid chloride, a polymer with a characteristic viscosity of 0.80, determined in metacresol at a solution concentration of 0.5 and 25%, is obtained.

Analysis of the thermal balance carried out under the conditions of Example 1 shows:

in a nitrogen atmosphere, the weight loss starts from 322 ° C, remains insignificant to 430 ° C and increases after 430 ° C,

in air, weight loss begins at 340 ° C, remains insignificant to 408 ° C and increases after 408 ° C.

The polymer is dissolved in the same solvents as the polymer from Example 1.

From a 20% strength solution in dimethylformamide, a film with the following mechanical properties can be obtained. Example 3. In a laboratory apparatus with a mixer pour a solution of 28.8 wt. including 1,1-bis (4-aminfeiil) -1-phenylethane, obtained by N. (O-III, by condensation of acetophenone with aniline hydrochloride, 250 parts by weight of tetrahydrofuran and a solution of 21.2 parts by weight of anhydrous (dry) sodium carbonate in 200 parts by weight of water. A solution of 20.3 parts by weight of terephthalic acid chloride in 250 parts by weight of anhydrous tetrahydrofuran is quickly added to the mixture with stirring, stirred for another 5 minutes and 1000 parts of water are added to precipitate polymer, after washing and drying, has an intrinsic viscosity of 1.61, determined in ./-cresole at 0.5% concentration and 25 ° C. With a thermal balance under the same conditions as in the previous examples, it is noted that in air the loss in weight starts from 30 ° C, increases after 416 ° C, and in nitrogen atmosphere both temperatures are slightly shifted up. A 1 liter reactor equipped with a stirrer and thermometer sleeve is charged with 28.8 parts by weight of 1,1-bis- (4-aminophenyl) -1-phenylethane and 300 parts by weight of anhydrous N-methyl-a-pyrrolidone The solution is cooled in a bath with dry ice and acetone to obtain a slurry, then 20.3 wt. Are quickly added. including anhydrous terephthalic acid chloride, the reaction mass is first diluted, then rapidly thickens. The mass is kept for 15 minutes in a bath with dry ice and acetone (after feeding the acid chloride), then it is allowed to reach room temperature, stirred for another 2 hours. Viscosity gradually increased. Dry powdered polymer is obtained by precipitating it with water from a solution in N-methyl-nirrolidone. The viscosity of the polymer in lg-cresol is 1.29. The polymer solution in N-methylpyrrolidone is directly suitable for the production of films or filaments, provided that the hydrochloric acid resulting from the reaction is removed. To do this, a stream of ammonia is passed through the solution, ammonium chloride precipitates, and after filtration, a solution is obtained (directly suitable). From this solution, you can get a film with the following properties. The determination made on the film at 22 ° C, exposed to 30-hour heating in air, at 200 ° C shows that its resistance to rupture is 7.68 kg / mm, and its elongation at break is 6%. This polymer possesses excellent dynamometric properties even after heat treatment, which is clearly better than the polymers of examples 1 and 2. Example 5. Under the conditions of example 4, but with isophthalic acid chlorophydride instead of terephthalic acid chloride, a polymer with characteristic viscosity 1 is obtained, 24 in. And cresole. Thermal balance detects a weight loss starting from 360 ° C and an enhanced weight loss starting from 400 ° C in air. Films prepared from it by the above method have the following properties. Measurements made on the film at 22 ° C, subjected to 30-hour heating at 170 ° C, show that its tensile strength is 6.6 kg / mm, and the elongation at break is 5%. Measurements made on the film with heat-treated at 200 ° C for 30 hours show that its tensile strength is 7.24 kg / mm, and the elongation at break is 4.45%. The same good thermal properties are observed as those of the polymer from Example 4. It is difficult to obtain yarn from the solution obtained in this example, with an increase in the concentration of the solution to 24% (dry matter) MOJKHO it is easy to obtain fibers. The concentrated solution is poured into the head of a spinning cell with a filler of six holes of 0.2 mm each, to which air heated to 300 ° C is supplied and yarns (strands) with a strength of 2.1 g / d and an elongation at break of 21% are obtained. Example 6. For slohe 15.8 wt. including 1,1-bis (4-amino-3-methylphenyl) - 1-phenylethane, 220 weight. including tetrahydrofuran, 10.6 weight. including sodium carbonate and 100 wt. hours of water poured with stirring 10, 15 weight. including acid chloride isophthalic acid, stirred for another 5 minutes and precipitated polymer 100 weight. h of water. The polymer is washed, dried, and then its properties are determined.

Example 7. The isophthalic acid chloride is replaced by terephthalic acid chloride and a polymer is obtained with the following properties; characteristic viscosity 0,84, so pl. above 350 ° C, soluble in dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

Subject invention

The method of producing polyamides by polycondensation of dicarboxylic chlorides

acids and aromatic diamines, characterized in that compounds of formula

where R is hydrogen, alkyl containing up to 6 carbon atoms; R is alkyl, hydrogen.