RU2480496C2 - Elastomeric composition based on copolymer of tetrafluoroethylene and perfluoroalkylvinyl esters - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: elastomeric composition for sealing materials based on a copolymer of tetrafluoroethylene and perfluoromethylvinyl ester and perfluoroalkyl vinyl esters which contain a cyano group, contains perfluorodiimidoyl amidine as a curing agent and further contains nano-sized nickel metal in the presence of a perfluorinated dispersant.

EFFECT: improved processability of rubber mixtures, vulcanisates have high nominal tensile strength, good physical and mechanical properties, resistance to nitric acid, high heat resistance after ageing for 70 hours.

2 tbl, 12 ex

Description

The present invention relates to the field of production of rubber mixtures based on perfluorinated rubbers, namely, triple or quaternary copolymers of tetrafluoroethylene (TFE), perfluoromethyl vinyl ether (PFMVE), and perfluoroalkyl vinyl ethers (PFAVE) containing a cyano group.

Such compositions are intended for use in the chemical and oil refining industries, as well as in other branches of technology as sealing materials, where high thermal aggressive properties are required.

Known elastomeric composition based on a copolymer containing 42-70 mol.% Units of TFE, 25-55 mol.% Units of PFMVE, 1-4 mol.% Units of perfluoroalkyl vinyl ether of the formula

and 1-7 mol.% units of perfluoroalkylvinyl ether of the formula

The composition contains 1.5 parts by weight vulcanizing agent - bis 4,4 'dioxi-3,3' diaminodiphenylhexafluoropropane (BOAF) and 25 parts by weight filler (carbon black P-701) per 100 parts by weight copolymer (US Pat. RF 2137781, C08F 214/26, prior. 05.08.98).

Vulcanizates based on such a composition are well processed on standard equipment and have good physical and mechanical properties. The disadvantages of this composition is that the vulcanizates even in the unfilled state have a significant color and have insufficiently high heat resistance in the stressed state, so if for 24 hours at 275 ° C the ODS fluctuates within 12-15%, then at 300 ° C, according to the authors of this application, it is 26-51%, in addition, the vulcanizates of such a composition are not sufficiently resistant to concentrated nitric acid.

A known composition based on a copolymer of tetrafluoroethylene, perfluoromethyl vinyl ether and one or more perfluoroalkyl vinyl ether containing a cyano group, including an amidine-containing vulcanizing agent of the general formula X-Y- (Z) _n , where X is a group of formula I

in which each R independently may be, for example, H, an optionally substituted alkyl, alkenyl, aryl or alkenylaryl group, Y is a covalent bond or linking group, Z is H or a group of formula I, which may be the same as X, or differ from it, n = 1-3, in the amount of 0.1-10 wt.h. per 100 parts by weight of copolymer.

The composition may also contain a filler, for example carbon black, in an amount of 1-70 parts by weight per 100 parts by weight copolymer and additional vulcanizing agent, for example, ammonium-forming compounds, substituted or unsubstituted triazine derivatives, peroxides, bis-aminophenols, bis-amido oximes, organotin compounds (US 2004/0072959 A1, priority from 11.10.02, C08F 8/00, C08K 5/00 )

The vulcanizates of this composition have good physical and mechanical properties and resistance to nitric acid, however, their heat resistance in the stressed state is not high enough, so according to the data given in the description of the application, even at 300 ° C the ODS can be 58%. According to the authors of this application, when reproducing examples 2 and 3, the ODS of the obtained vulcanizates at 330 ° C was 80-85%.

It should also be noted that the use of salts as a curing agent

can cause corrosion of technological equipment, since the latter in the conditions of manufacture of products emit acids of the formula R'COOH.

A known composition based on tetrafluoroethylene, perfluoromethyl vinyl ether and a third monomer containing a functional group selected from the group consisting of perfluoro (4-cyanobutyl vinyl ether), perfluoro (2-phenoxypropyl vinyl ether), perfluoro (8-cyano-5methyl-3,6-dioxa 1-octene), a bromine-containing olefin using fibrillated polytetrafluoroethylene with a fiber length of 1.17 ÷ 0.104 mm as a reinforcing filler (US Pat. US 4520170, B29C 43/00, C08L 27/00, prior dated 09.20.1982).

However, according to the authors of this application, the vulcanizates of such a composition have poor heat resistance in the stressed state. So, the ODS at 300 ° C cannot even be measured, since the test cylinders simply collapse under these conditions.

The closest analogue to the composition of the composition and the achieved result is a composition based on a triple or quadruple copolymer of TFE and perfluoroalkyl vinyl ethers containing a cyano group. The composition contains a vulcanizing agent - perfluorodiimidoylamidine (DPIA) of the formula

where n = 2 ÷ 8, m = 2 ÷ 8

in the amount of 1-4 parts by weight per 100 parts by weight copolymer (RF patent 2319717, C08L 27/18, prior. 07/10/06). Vulcanizates of this composition have a high complex of initial properties, good ODS and resistance to nitric acid. However, after aging vulcanizates at 300 ° C for 70 h, their tensile strength decreases significantly (by about 30-35%). A technological disadvantage of making the composition is the relatively poor processability of the rubber compound, which is expressed by the high value of the minimum torque M _L , N · m (> 1.0). The disadvantages of the composition also include a low conditional tensile strength (≤13.0 MPa).

The objective of the proposed technical solution is to develop a composition whose rubber compounds have good processability, and vulcanizates have an increased value of conditional tensile strength, along with good initial physical and mechanical properties, heat resistance during aging at high temperature and resistance to concentrated nitric acid.

This object is achieved in that the elastomeric composition based on a triple or quaternary copolymer of tetrafluoroethylene perfluoromethyl vinyl ether and perfluoroalkyl vinyl ethers containing a cyano group, including perfluorodiimidoylamidine as a vulcanizing agent, additionally contains nanosized metal nickel in the presence of a perfluorinated dispersant with the following mass ratios:

copolymer - one hundred curing agent - 1-3 nanoscale metallic nickel - 0.5-5 perfluorinated dispersant - 0.5-4

The perfluorinated dispersant allows to increase the aggregative stability of nanosized metallic nickel particles.

As the vulcanizing agent, DIPIA of the general formula P.

As the basis of the composition, ternary and quaternary copolymers based on TFE, PFMVE and perfluoroalkyl vinyl ethers containing a cyano group can be used, for example, copolymers of the following formulas.

where n = 42-70 mol. %, m = 25-55 mol. %, p = 1-7 mol. %, a = 0.3-7 mol. %

The composition may also contain a filler, which is used, for example, carbon black (T-900), Aerosil (A-175).

The mixing of the components of the rubber mixture is carried out on rollers, or in closed-type rubber mixers.

First, a polymer, nano-sized metallic nickel in the presence of a perfluorinated dispersant is fed, and then a curing agent.

Vulcanization is carried out in two stages, first in the press at 160 ° C, for 10-20 minutes, and then in a thermostat with a stepwise rise in temperature from 30 ° C to 280 ° C, for 38-40 hours.

Used curing agents (structure 11) are obtained by a known method (Thomas Goft and I. L. Zollinger, Ind. Eng. Chem. Prod. Res. Develop, v.13, No. 2, 1997).

Nanoscale metallic nickel, it is most preferable to use nanoscale nickel with a particle diameter of 215-1050 nm, a perfluorinated dispersant, for example, perfluorinated UPI oil or 6MF-320 perfluorinated polyester, which is a commercial product, can be used as a perfluorinated dispersant.

Tests of vulcanizates are carried out on the following guests:

- elastic strength characteristics, GOST 270-75;

- Shore hardness, GOST 263-75;

- accumulation of relative residual compression deformation at 250 ° C, 300 ° C, 330 ° C for 24 hours at 20% compression, aging at 300 ° C for 70 hours, GOST 9.029-74;

- determination of vulcanization characteristics on a vulcanometer for rubber compounds, GOST 12535 - 84, 100S rheometer from Monsanto.

Resistance to nitric acid is evaluated by the coefficient of swelling by volume (%) after keeping in a 60% HNO ₃ solution at 80 ° C for 70 hours. The following examples illustrate the invention.

Example 1

On the rollers at a roll temperature of 25 ° C, 100 mass parts are mixed. a copolymer of formula V (n = 62, m = 35.2, p = 2.5, a = 0.3) with a Mooney viscosity of MB (1-10) 100 ° C 93 units, 1 part by weight nanosized metallic nickel with a particle diameter of 215 nm in the presence of 2 parts by weight perfluorinated oil UPI and 3 parts by weight DIPIA for 10 minutes The resulting crude rubber mixture is subjected to vulcanization, first in a press at 160 ° C for 10 minutes, and then in a thermostat with a stepwise rise in temperature from 30 ° C to 280 ° C for 40 hours.

Vulcometric characteristics of the composition:

M _L , Nm 0.80

Physico-mechanical properties of vulcanizates:

Stress at 100% elongation, MPa 2.6 Conditional tensile strength, MPa 16,0 Elongation at Tension,% 220 Residual elongation after rupture,% one Shore Hardness 70 Resistance to HNO ₃ (60%, 80 ° С, 70 h) 0.12 ODS, 20% compression 24 h × 300 ° C 14.0 ODS, 20% compression 24 h × 330 ° C 28.0

Properties of vulcanizates after aging, 300 ° C × 70 h:

Stress at 100% elongation, MPa 2.2 Conditional tensile strength, MPa 11.5 Elongation at Tension,% 240 Shore Hardness 64 ODS, 20% compression 22

The results of measurements of the properties of rubber compounds and vulcanizates with other compositions of the rubber mixture are shown in table 1 and 2.

As follows from the data given in tables 1 and 2, the introduction of nanosized metallic nickel dispersed in perfluorinated oil into the composition of the elastomeric composition leads to a significant improvement in the processability (reduction of the minimum torque M _L to 20%) of rubber mixtures, while the vulcanizates have an increased the value of conditional tensile strength, good physical and mechanical properties, resistance to nitric acid, increased heat resistance after aging at 300 ° C for 70 hours.

Table 1 The composition of the rubber compounds Structure No. of examples 2 3 four 5 6 7 8 9 10 eleven 12 (counter) The copolymer, parts by weight one hundred one hundred one hundred one hundred one hundred one hundred one hundred one hundred one hundred one hundred one hundred Formula where V V V V V V III IV V V V n 62 62 62 62 62 62 62 62 43 62 62 The composition of the copolymer, mol.% m 35,2 35,2 35,2 35,2 35,2 35,2 35,2 35,2 54,2 35,2 35,2 p 2,5 2,5 2,5 2,5 2,5 2,5 2,8 - 2,5 2,5 2,5 but 0.3 0.3 0.3 0.3 0.3 0.3 - 2,8 0.3 0.3 0.3 Mooney viscosity MB (1-10) 100 ° C 93 93 93 93 93 93 67 120 93 93 93 The vulcanizing agent DIPIA, parts by weight 3 3 3 3 3 3 3 3 one 3 3 Composition of DIPIA n 2 8 6 6 6 6 6 6 6 6 6 m 8 2 5 5 5 5 5 5 5 5 5 Nanodispersed metallic nickel, parts by weight 1,0 1,5 2.0 1,0 1,0 1,0 1,0 1,0 5,0 0.5 - The number average particle diameter, nm 447 447 447 447 215 1050 447 447 447 447 - Perforated dispersant UPI Perforated Oil 0.5 2 2 one 2 2 2 2 four - - Simple perforated polyester 6MF-320 - - - - - - - - - 3 - Carbon black T-900 - - - - - - - - 25 - - Aerosil F-172 - - - - - - - - - 5 -

table 2 Properties of rubber compounds and vulcanizates based on them Indicators No. of examples 2 3 four 5 6 7 8 9 10 eleven 12 (counter) Vulcometric characteristics of rubber compounds (vulcanization in the press at T = 160 ° C *) M _L , Nm 0.81 0.84 0.83 0.85 0.81 0.82 0.79 0.83 0.82 0.9 1,02 Physico-mechanical properties of vulcanizates Stress at 100% elongation, MPa 2,5 2.7 3,1 2.6 2.6 2.6 1.9 2.9 7 5 2.1 Conditional tensile strength, MPa 14.5 14.1 14.1 14.0 16,0 14.2 14.8 14.0 17 15,5 13.0 Elongation at break,% 220 211 180 220 220 215 200 290 220 200 190 Residual elongation after rupture,% 2 2 one one one one one one one one 2 Shore Hardness 70 73 75 70 70 70 63 76 85 80 68 Resistance to HNO ₃ (60%, 80 ° С, 70 h) 0.11 0.12 0.11 0.11 0.12 0.11 0.11 0.11 0.12 0.11 0.10 ODS, 20% compression 24 h × 300 ° C fourteen fifteen fifteen 13 13 fourteen fifteen 13 12 fourteen fifteen 24 h × 330 ° C 27 28 29th 27 26 27 28 25 25 27 29th Properties of vulcanizates after aging, 300 ° C × 70 h Stress at 100% elongation, MPa 2.1 2,3 3,1 2.2 2.2 2.2 1.4 3,1 5.5 4.0 1,5 Conditional tensile strength, MPa 12.1 11.0 11.1 11.5 11.5 eleven 11.5 11.5 13.0 11.0 9 Relative extension, % 250 240 230 220 240 240 230 230 240 250 300 Shore Hardness 65 68 70 65 64 65 62 71 81 76 62 ODS, 20%, 300 ° C,% 24 twenty 22 25 25 24 25 24 19 21 35

Claims (1)

An elastomeric composition for sealing materials based on a triple or quaternary copolymer of tetrafluoroethylene, perfluoromethylvinyl ether and perfluoroalkylvinyl ethers containing a cyano group, including perfluorodiimidoylamidine as a vulcanizing agent, characterized in that the composition additionally contains a nanosized metallic nickel in the presence of a perfluorinated dispergiene, perfluorinated oil. hours:
copolymer one hundred curing agent 1-3 nanoscale metallic nickel 0.5-5 perfluorinated dispersant 0.5-4