The method of obtaining heat-resistant fiber

 

(57) Abstract:

Usage: obtain fibres for technical purposes. The inventive prepare for a solution polymethacrylamide in an organic solvent in two stages. First conduct the synthesis of its oligomers. Then copolycondensation adding 1-15 wt.%. -diaminocyclohexane with the number of duplicate links-OSi(CH3)2- equal 29-79. The solution is formed into a water-dimethylacetamide the precipitation bath. Conduct orientation plastification pulling the freshly formed fibers in an aqueous solution of dimethylacetamide. Washed, dried and termwithout. table 1.

The invention relates to methods of producing synthetic fibers, in particular modified heat-resistant fibers on the basis of polymethacrylamide.

A method of obtaining heat-resistant fibers of polymethacrylamide forming from a solution of polymer orientation plastification pulling, shaded from the solvent and drying. The method comprises the subsequent heat treatment of the dry oriented amorphous fibers at 300-350oC [1]

The disadvantage of this method is aviakosmicheskaya polyamides extrusion spinning of the polymer solution in a precipitation bath with subsequent plastification pulling the obtained fibers with 0-50oC in a water bath containing 50-70% (mol.) the solvent of the polymer, by the washing of solvent and heat treatment [2]

However, the fiber obtained by this method has stable properties.

As a prototype the selected method of obtaining heat-resistant fibers [3] comprising preparing a solution polymethacrylamide in dimethylacetamide two-stage low-temperature polycondensation: in the first stage synthesis of the oligomer, in the second stage copolycondensation, forming a solution in water dimethylacetamide the precipitation bath, plastification pulling the freshly formed fibers in an aqueous solution of dimethylacetamide, washing, drying and thermolytic.

The disadvantage of this method is that the resulting fiber has a low elasticity and a large number of external defects. In addition, when receiving fiber there is a significant drop number of elementary fibers.

According to the present invention is a method of obtaining heat-resistant fibers include the preparation of the solution polymethacrylamide in dimethylacetamide two-stage low-temperature polycondensation, comprising the synthesis of the oligomer and seopolico the e freshly formed fibers in an aqueous solution of dimethylacetamide, washing, drying and thermolytic. At this stage copolycondensation in the reaction medium was further added 1-15% by weight polymethacrylamide-diaminocyclohexane with the number of duplicate links-OSi(CH3)2equal 29-79.

Introduction to the main chain polymethacrylamide silicone segments allows you to modify the polymer. This way, the block copolymers with the General formula (I):

NH2-[Ph-NHCO-Ph-CONH-Ph] n-NHCO-Ph-CONH-(CH2)3- Si(CH3)2-[OSi(CH3)2]m-(CH2)3-NHCO-Ph-CO-. (I)

where

n is the average number of links equal to 20;

m 29-79.

These polymeric materials are of considerable practical interest, because the contributions of the different nature of the blocks form a complex of specific properties. Thermodynamic incompatibility of organic and organosilicon units leads to in such systems microphase separation, which allows to consider them as pseudanabaena. Studies have shown that the surface polyorgano-polysiloxane always enriched component with lower surface energy, i.e., a polysiloxane, which provides the modifying effect. Crcesus radial macropolicy and formed uniformly distributed over the volume of the fiber microcapillaries), that helps to improve the elasticity of the fibers and, as a consequence, to reduce the number of breakages of elementary fibers and external defects.

The method is as follows.

The spinning solution obtained by the method of two-stage low-temperature polycondensation in solution.

At the first stage in the solution of dimethylacetamide (DMAA) synthesize oligomers polymethacrylamide (PFIA) with terminal amino groups (II) under the scheme:

nH2N-Ph-NH2+(n-p)ClOC-Ph-COCl H2N-[Ph-NHCO-PH-CONH-Ph]n-NH2+(n-p)HCl (II)

where p=(0,2-0,03)n.

In the reactor with stirring under cooling with ice water loaded organic solvent DMAA and m-phenylenediamine (MPDA). After dissolution with stirring, add softlinked (IPC) in the amount of 80-97% of stoichiometric. The temperature is brought to room.

To the obtained solution of the oligomer PFIA in the second phase at room temperature add 1-15% by weight of PFIA-diaminocyclohexane (DAOS) with the number of repeating units [-OSi(CH3)2-]mm 29-79.

a-diaminocyclohexane with m 29-79 get well-known technique [Brandt P. A. Sudramanian R. N ° P. M. Ward T. C. McGrath, J. E. Polymer Preprints 1985, v.26, N. 2, p.2130.

Pam:

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Liberated HCl is neutralized with diethylamine. The result is a solution of polyamide-polysiloxane (I) in DMAA, which after filtration and deaeration can be used to produce fibers.

The resulting solution was formed through the die plate in a precipitation bath consisting of a mixture of water DMAA. Freshly formed fibers pull in aqueous solution DMAA, washed from the solvent and dried at 120oC. the Dried fiber is subjected to additional heat treatment. The invention is illustrated by the following examples.

Example 1. In a reactor with a stirrer, cooled with ice water, upload to 12.28 kg of N,N-dimethylacetamide (DMAA) and 1,080 kg (10 mol) of m-phenylenediamine (MPDA). After dilution with vigorous stirring in parts add 1,929 kg (9.5 mol) of isophthalaldehyde (IPC). Stirring is continued for 1 hour while gradually raising the temperature to room, then get 19% (wt.) the solution oligoimide with terminal amino groups in DMAA.

To the resulting solution was added was 0.138 kg (0.045 mol) TAOIST (m=39), which is 5.8% (wt. from polyamide) and stirred the mixture in the reactor for 30 min, then at room temperature and constant stirring for hours getting the solution polyaminopolycarboxylic in DMAA with a dynamic viscosity of 56.5 Pas (25oC). To neutralize the hydrogen chloride released during polycondensation, the reaction solution was added 500 ml of a mixture of diethylamine: DMAA (1:1 vol. ). Then the solution is filtered and molded through a die plate with a hole diameter of 0.08 mm into the precipitation bath consisting of a mixture of water:DMAA (40:60 vol.). Freshly-formed fiber is pulled in 3.4 times in an aqueous solution DMAA (water: DMAA 60:40 vol.), washed from the solvent and dried at 120oC. the Dried fiber is subjected to additional heat treatment, pulling in 1.3 times when heated to 370oC, after which the fiber is made with the characteristics shown in the table.

Example 2. Getting oligoimide carried out according to the method of example 1. To the obtained oligomer with terminal amino groups add 0,024 kg (0,008 mol) or 1% (wt. from polyamide) TAOIST (m=39), stir the mixture in the reactor at room temperature and add in parts stoichiometric quantity (0,103 kg, 0.508 mol) of IPC. The following operations are carried out analogously to example 1 and get the solution blockcopolymer in DMAA with a dynamic viscosity 32,4 Pas, which is formed into a fiber by the method described in example 1.

Example 3. Getting copolymer and forming fibers from him perform tpami add 0,238 kg (0,078 mol) and 10% (wt. from polyamide) TAOIST (m=39), and, accordingly, the stoichiometric amount of IPC is 0,117 kg (0,578 mol).

Example 4. Getting copolymer and forming fibers from him spend according to the method of example 1. As the silicon-containing component use DAOS with the number of the structural units m=79, which is added in the second stage of the synthesis to oligoimide with terminal amino groups in the number 0,048 kg (2 wt. from polyamide).

Example 5. Getting copolymer and forming fibers from him spend according to the method of example 1. The number of DAOS (m=79) is of € 0.195 kg (8.2 wt. from polyamide).

Example 6. Getting copolymer and forming fibers from him spend according to the method of example 1. As the silicon-containing component use DAOS with the number of the structural units m=29 number 0,119 kg (5 wt. from polyamide).

Properties of polyamide-polysiloxane and fibres of them are presented in the table. For comparison, the performance of the fibers from PFIA obtained in similar conditions.

Fibers of the proposed method have at a constant other parameters characteristic of aromatic polyamides, in particular heat-resistant, high resistance surface volokonnogo fiber and facilitates its processing.

The method of obtaining heat-resistant fiber solution preparation polymethacrylamide in dimethylacetamide two-stage low-temperature polycondensation, comprising the synthesis of the oligomer and copolycondensation, forming a solution in volnomyslyaschego the precipitation bath, plastification pulling freshly formed fibers in an aqueous solution of dimethylacetamide, washing, drying, and thermolytic, characterized in that at the stage of copolycondensation in the reaction medium was further added 1 - 15% by weight polymethacrylamide - diaminocyclohexane with the number of duplicate links-OSi(CH3)2is equal to 29 79.

 

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