RU2471827C1 - Elastomeric composition based on copolymer of tetrafluoroethylene and perfluoroalkyl vinyl esters - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: elastomeric composition is based on a ternary or quaternary copolymer of tetrafluoroethylene and perfluoroalkyl vinyl esters which contain a cyano group, which contains perfluorodiimidoyl amidine as a vulcanising agent. The composition additionally contains 0.5-5.0 pts.wt oxides of group I, II, III, IV, V, VI, VIII metals or mixtures thereof. Components of the composition are in the following ratio: copolymer 100 pts.wt; vulcanising agent 1-4 pts.wt; metal oxide 0.5-5 pts.wt.

EFFECT: obtaining an elastomeric composition with shorter optimum time for the vulcanisation process, higher maximum torque during vulcanisation, the vulcanisates have good physical and mechanical properties, resistance to nitric acid, heat resistance after ageing for 70 hours, and can be used to obtain colour compositions without using expensive dyes.

9 cl, 2 tbl, 17 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 of a curing agent - bis4,4'-dioxi-3,3'-diaminodiphenylhexafluoropropane (BOAF) and 25 parts by weight of filler (carbon black P-701) per 100 parts by weight of copolymer (US Pat. RF 2137781, C08F 214/26, priority from 08/05/98).

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 an unfilled state, have a significant color and have insufficiently high heat resistance in the stressed state, so that if for 24 hours at 275 ° C the ODS fluctuates within 12-15%, then at 300 ° C, according to 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, perfluoromethylvinyl ether and one or more perfluoroalkylvinyl 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 an amount of 0.1-10 wt.h. per 100 parts by weight 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 10.10.02, 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 an amount of 1-4 parts by weight per 100 parts by weight copolymer (RF patent 2319717, C08L 27/18, prior. 10.07.06). Vulcanizates of such a composition have a high complex of initial properties, good ODS and resistance to nitric acid. However, after aging vulcanizates at 300 ° C for 70 hours, their tensile strength decreases significantly (by about 30-35%). The technological disadvantage of making the composition is a rather high optimal time of the first stage of vulcanization:

t ₉₀ min. 30.5.

Stage I vulcanization - pressing, as a rule, is limited by the number of products placed in the press, and the size of the plates. This stage determines the performance. Stage II is carried out in a thermostat with a one-time loading of a large amount of rubber goods, accumulated in stage I after the press. The disadvantages of making the composition also include the low value of the maximum torque (M _HF , H * m 3.2) at stage I, which determines the vulcanization characteristics of the composition associated with the density of the vulcanization network. In addition, for the production of products, such as insulation of electrical wires, tubes, etc., it is necessary to have colored compositions, which requires the additional use of expensive dyes that do not impair the properties of the composition. The above disadvantages somewhat limit the scope of their use.

The objective of the proposed technical solution is to develop a composition whose vulcanizates have a reduced time of stage I vulcanization and an increased torque value, along with good initial physical and mechanical properties, heat resistance during aging at high temperature and resistance to concentrated nitric acid.

The problem is achieved in that the elastomeric composition based on a triple or quaternary copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ethers containing a cyano group, including perfluorodiimidoylamidine as a vulcanizing agent, additionally contains 0.5-5 parts by weight. metal oxides of I, II, III, IV, V, VI, VIII groups of the Periodic Table of D.I. Mendeleev or their mixtures in the following ratio of components, parts by weight:

copolymer one hundred curing agent 1-4 metal oxides 0.5-5.

As the curing agent, DIPIA of the general formula II is used. Preferred according to this invention are metal oxides: Ag ₂ O (I g); BaO (II gr); Nd ₂ O ₃ , La ₂ O ₃ (lanthanides III gp); Pb ₃ O ₄ (IV gr); Sb ₂ O ₃ , V ₂ O ₅ (V gr); Mo ₂ O ₅ (VI gr); NiO, CoO (VIII gr); CoO + Al ₂ O ₃ .

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

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

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

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

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

First, a polymer, a metal oxide, and then a curing agent are supplied.

Vulcanization is carried out in two stages, first in a press at 160 ° C, and then in a thermostat with a stepwise rise in temperature from 30 ° C to 280 ° C.

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

Metal oxides - commercial products

Tests of vulcanizates are carried out according to the following GOSTs:

- elastic strength characteristics, GOST 270-75,

- Shore hardness, GOST 263-75,

- accumulation of relative residual compressive strain 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, rheometer 100S 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 rollers at a temperature of rolls of 25 ° C, a mixing of 100 parts by weight is carried out. copolymer with Mooney viscosity MB (1-10) 100 ° C 1 wt.h. Ag ₂ O and 3 parts by weight DIPIA. The resulting crude rubber mixture is subjected to vulcanization, first in a press at 160 ° C for 2 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:

t ₉₀ min 2 M _HF , Hm 4.06

Physico-mechanical properties of vulcanizates:

Stress at 100% elongation, MPa 4.1 Conditional tensile strength, MPa 13.6 Elongation at Tension,% 220 Residual elongation after rupture,% one Shore Hardness 72 Resistance to HNO ₃ (60%, 80 ° С, 70 h) 0.1 ODS, 20% compression 24 h × 300 ° C 14.0 ODS, 20% compression 24 h × 330 ° C 22.0

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

Stress at 100% elongation, MPa 3,5 Conditional tensile strength, MPa 13.6 Elongation at Tension,% 270 Shore Hardness 69 ODS, 20% compression 23 Color the black

The results of measurements of the properties of rubber compounds and vulcanizates with other curing activators are shown in tables 1 and 2.

As follows from the data given in tables 1 and 2, the introduction into the composition of the elastomeric composition of metal oxides I-VI, VIII groups of the periodic system of elements leads to

reducing the optimal time of the process of stage I vulcanization (t ₉₀ , min);

increase in maximum torque (M _HF , H · m) during vulcanization up to 1.5 times;

vulcanizates have good physical and mechanical properties, resistance to nitric acid, heat resistance after aging at 300 ° C for 70 hours;

the ability to obtain color compositions without the use of expensive dyes.

Table 1 The composition of the rubber compounds Structure No. of examples 2 3 four 5 6 7 8 9 10 eleven 12 13 fourteen fifteen 16 17 (count.) 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 one hundred one hundred one hundred one hundred one hundred The composition of the copolymer, mol.% Formula where V V V V V V V V V V V III IV V V V n 43 43 43 43 62 43 43 43 43 43 43 62 68 43 43 43 m 54,2 54,2 54,2 54,2 35,2 54,2 54,2 54,2 54,2 54,2 51,2 35,2 28.8 54,2 54,2 54,2 R 2,5 2,5 2,5 2,5 2,5 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 0.3 0.3 0.3 0.3 2,5 - 2,8 0.3 0.3 0.3 Mooney viscosity MB (1-10), 100 ° C 85 85 85 85 85 85 85 85 85 85 85 67 120 85 85 85 Vulcanizing agent, parts by weight DIPIA 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Composition of DIPIA n 6 6 6 6 6 6 6 2 8 6 6 6 6 6 6 6 m 5 5 5 5 5 5 5 8 2 5 5 5 5 5 5 5 Metal oxide, parts by weight Ag ₂ O 0.5 Wow one Nd ₂ O ₃ 5 La ₂ o ₃ 5 5 5 Pb ₃ O ₄ one V ₂ O ₅ 5 Sb ₂ O ₃ 2 Bi ₂ O ₃ 5 MoO ₃ 5 Soo 5 Nio 5 0.8 CoO ₃ +0.2 Al ₂ O ₃ 5 0.7 CoO ₃ +0.3 Al ₂ O ₃ one Fillers, parts by weight Soot T-900 25 Aerosil A-175 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 13 fourteen fifteen 16 17 (counter) Vulcometric characteristics of rubber compounds (vulcanization in the press at T = 160 ° C *) t ₉₀ min 7.5 2.7 19.0 18.0 14.0 19.5 10.1 12.1 18.5 18.0 17.5 17.5 18.5 17.0 17.5 30.5 M _HF , Nm 4.0 4,59 4.01 4.06 4.01 3,7 3.79 3.73 3.6 3.6 3.6 3,7 4.6 4.1 4.2 3.2 Physico-mechanical properties of vulcanizates Stress at 100% elongation, MPa 3.6 3.4 3.3 3.4 3,5 3.4 3.4 3,5 3.65 3.8 3,5 3.6 5.8 9.5 7.0 3.2 Conditional tensile strength, MPa 13.5 14.1 13,2 13.6 14.5 13.5 14.1 13.5 13.3 13.6 13.9 13.5 13.0 19.0 15.1 13.1 Elongation at break,% 180 190 210 220 210 220 220 260 250 260 220 210 220 250 260 220 Residual elongation after rupture,% one one 2 one 1,0 one one one one one 2 one one one 2 2 Shore Hardness 83 81 69 71 85 70 75 69 68 70 71 78 75 85 73 73 Resistance to HNO ₃ (60%, 80 ° С, 70 h) 0.10 0.10 0.11 0.11 0.13 0.10 0.14 0.11 0.12 0.13 0.13 0.11 0.12 0.10 0.14 0.10 0.11 0.10 0.12 ODS, 20% 24 h × 300 ° C 12 eleven eleven 12 12 12 eleven eleven 12 12 eleven eleven 12 9 12 10 compression 24 h × 330 ° C 22 21 22 23 23 22 22 23 27 22 27 22 21 17 21 22 Properties of vulcanizates after aging, 300 ° C × 70 h Stress at 100% elongation, MPa 3,7 3,5 3,1 3,7 3.6 3,5 3.4 3.4 3,5 2,5 2,4 3.3 5.5 8.5 6.5 3.3 Conditional tensile strength, MPa 12.6 10.6 11.5 11.6 13,4 12.5 13.3 11.0 12 11.5 10.1 12.5 12.1 17.1 13.1 12.0 Relative extension, % 190 200 280 270 220 230 230 290 270 280 300 280 270 250 250 280 Shore Hardness 80 79 67 69 80 65 69 66 65 66 68 77 69 78 72 71 ODS, 20%, 300 ° C,% 21 22 23 22 21 22 23 21 22 21 22 21 21 19 22 23 Color mustard. b / w b / w b / w white b / w b / w b / w 6/3 b / w black blue blue black white brown

Claims (9)

1. An elastomeric composition based on a triple or quaternary copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ethers containing a cyano group, including perfluorodiimidoylamidine as a vulcanizing agent, the composition further comprising 0.5-5.0 parts by weight metal oxides of I, II, III, IV, V, VI, VIII groups of the periodic system of elements of D. I. Mendeleev or their mixtures in the following ratio of components, parts by weight:
Copolymer one hundred Vulcanizing agent 1-4 Metal oxide 0.5-5 2. The elastomeric composition according to claim 1, which consists in the fact that it contains silver oxide as a metal oxide. 3. The elastomeric composition according to claim 1, which consists in the fact that it contains barium oxide as a metal oxide. 4. The elastomeric composition according to claim 1, which consists in the fact that as the metal oxide, it contains lanthanum oxide or niodeum oxide. 5. The elastomeric composition according to claim 1, which consists in the fact that it contains lead oxide as a metal oxide. 6. The elastomeric composition according to claim 1, which consists in the fact that it contains vanadium oxide as a metal oxide. 7. The elastomeric composition according to claim 1, which consists in the fact that it contains molybdenum oxide as a metal oxide. 8. The elastomeric composition according to claim 1, which consists in the fact that, as a metal oxide, it contains nickel oxide or cobalt oxide. 9. The elastomeric composition according to claim 1, which consists in the fact that, as a metal oxide, it contains a mixture of aluminum oxide and cobalt oxide.