RU2407753C2 - Vinylidene fluoride-based bromine-containing copolymers for thermo-aggressive resistant materials - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: described are vinylidene fluoride-based bromine-containing copolymers of general formula -[CF₂R]_n-[CF(R_F) CF₂]_m-[CF(CF₂O(CF₂)KCF₂Br)CF₂]_P-, where R=-CH₂; mixture of -CH₂ and -CF₂, in which content of the R=CH₂ component is not less than 60 mol %; R_F=-CF₃; -OCF₃; -OCF₂CF₂CF₂OCF₃; -OCF₂CF₂(OCF₂)₂OCF₃; n=64.0 - 85.0 mol %.; p=0.3 - 3.0 mol %.; m= the rest up to 100 mol %; k=1-3.

EFFECT: obtaining vinylidene fluoride-based bromine-containing copolymers which do not contain gel, vulcanisates with high strength and elasticity.

16 ex, 3 tbl

Description

The present invention relates to the field of production of copolymers of the general formula

where R = -CH ₂ ; (a mixture of —CH ₂ and —CF ₂ , in which the content of the component R =) —CH _{2 is} not less than 60 mol%;

R _F = —CF ₃ ; -OCF ₃ ; —OCF ₂ CF ₂ CF ₂ OCF ₃ ; —OCF ₂ CF ₂ (OCF ₂ ) ₂ OCF ₃ ;

n = 64.0-85.0 mol.%; k is 1-3;

p = 0.3-3.0 mol%;

m = the rest is up to 100 mol.%.

and can be used in industry SK to obtain sealing materials that work in aggressive environments at high temperatures.

Known bromine-containing copolymers based on vinylidene fluoride (VDF) obtained by water emulsion copolymerization of VDF, hexafluoropropylene (HFP) and bromine-containing monomer (BSM) selected from the group consisting of bromotrifluoroethylene (BTFE) or 4-bromo-tetrafluoro-3,4,4,4 at 105 ° C and a pressure of 4.5-6.3 MPa. These copolymers are easily vulcanized by peroxides. Vulcanizates based on them have the following indicators:

- tensile strength - 14.4-15.4 MPa - elongation at break - 170-185% - residual deformation after compression (ODS) after 70 hours at 204 ° C - 25-27%

(U.S. Pat. No. 4,035,505 publ. 12.07.77, C08F 214/16).

The disadvantage of such copolymers is that they contain a significant amount of insoluble fraction (gel), which significantly complicates their processing. It should also be noted the need to use to obtain a sufficiently high pressure.

Known bromine-containing copolymers based on VDF obtained by water-emulsion copolymerization of VDF, tetrafluoroethylene (TFE), perfluoroalkyl vinyl ether (PFAVE) and BSM. As PFAVE, perfluomethyl vinyl ether (PFMVE) or perfluoropropyl vinyl ether (PFVVE) is used, and bromoperfluoropropyl vinyl ethers are used as BSM. The copolymerization process is carried out at 80 ° C, a single charge and autogenous pressure for 24 hours. The resulting copolymers do not contain a gel (completely soluble in methyl ethyl ketone), are easily vulcanized by peroxides, and vulcanizates based on them have the following properties:

- tensile strength - 13.5-15.7 MPa - elongation at break - 207-262% - Shore hardness - 65-68 - ODS (70 h at 200 ° C) - 31-34%

(U.S. Pat. No. 4,831,085, publ. 16.05.89, C08C 19/04, C08F 8/00).

As can be seen from the description of the patent, vulcanizates based on such copolymers have an ODS of at least 31%. To obtain copolymers with a good yield, a sufficiently long copolymerization process is required. It should also be noted that carrying out the process with a single charge and autogenous pressure leads to the production of polymers that are heterogeneous in composition. The above disadvantages limit the scope of their use.

Known bromine-containing VDF copolymers obtained by water-emulsion copolymerization of VDF, TFE, perfluoropolyalkoxyalkyl vinyl ethers (PFAAVE) and BSM at 20-35 ° C and a pressure of 1.75 MPa. Esters of the general formula CF ₂ = CFOCF ₂ CF ₂ (OCF ₂ ) _x OCF ₃ , where x = 3-4, were used as PFAAVE, and bromotrifluoroethylene or a compound of the formula CF ₂ = CFO (CF ₂ ) ₃ OCF ₂ CF as BSM ₂ Br. Vulcanizates based on copolymers in which a compound of the formula CF ₂ = CFO (CF ₂ ) ₃ OCF ₂ CF ₂ Br is used as BSM have good elasticity (elongation 205-475%), but have high ODS values at 200 ° C (38 -50%), and copolymer-based vulcanizates, in which bromotrifluoroethylene was used as BSM, have good ODS at 200 ° C but low elongation (130-135%), while the copolymers themselves contain a significant amount of gel. It should also be noted that vulcanizates based on the copolymers described in this patent have low strength properties - tensile strength 5.5-6.7 MPa (US Pat. US 6294627, publ. 25.09.01, C08F 116/12).

The closest analogue in structure are bromine-containing copolymers on an axial VDF containing 65-85 mol% of VDF, 0-10 mol% of TFE, 0-25 mol% of PFMVE, 0.5-30 mol% of PFAAVE. (U.S. Pat. No. 6,380,337, publ. 30.04.02, C08F 214/22, C08F 214/26). As BSM use bromoperfluoroethyl ether. The copolymers are prepared by water-emulsion copolymerization of comonomers at 50 ° C for 8 hours using an oxidation-reduction initiation system based on ammonium persulfate (PSA) and sodium bisulfite. The resulting copolymers do not contain a gel, and vulcanizates based on such copolymers have good strength characteristics (tensile strength 9.7-14.6 MPa) with a relative elongation of 260-280%.

The patent does not contain data on ODS, however, as shown by studies of the authors of the present invention, vulcanizates based on the described copolymers have ODS (200 ° C, 24 hours) - 35-45%.

The objective of this technical solution is to create bromine-containing copolymers based on VDF that do not contain a gel (completely soluble), vulcanizates based on which have a combination of good strength, elastic properties and values of ODS.

The problem is solved by the synthesis of a copolymer of General formula I

where R = -CH ₂ ; (a mixture of —CH ₂ and —CF ₂ , in which the content of the component R = —CH _{2 is} not less than 60 mol%);

R _F = —CF ₃ ; -OCF ₃ ; —OCF ₂ CF ₂ CF ₂ OCF ₃ ; —OCF ₂ CF ₂ (OCF ₂ ) ₂ OCF ₃ ;

n = 64.0-85.0 mol%; k is 1-3;

m = 15.0-35.0 mol%;

p = 0.3-3.0 mol%;

m = rest up to 100 mol%

The proposed copolymers are preferably prepared by water-emulsion copolymerization of VDF, or a mixture of VDF with TFE (containing at least 60 mol.% VDF) with a perfluorinated comonomer selected from the group consisting of HFP and PFAVE, and with a bromine-containing comonomer. As an emulsifier, ammonium salts of perfluorocarboxylic or perfluoroxacarboxylic acids are used. Ammonium persulfate or a redox system based on PSA and sodium metabisulfite (MBS) are used as an initiator. The amount of initiator is usually 0.05-2 wt.% Based on the aqueous phase and the copolymerization process is usually carried out for 2-5 hours at a temperature of 35-70 ° C and a pressure of 0.8 MPa. The copolymer yield (based on the monomer mixture used) is 81-94 wt.% Upon conversion (based on the reacted monomers) 93-99 wt.%.

As PFAVE, perfluoromethylvinyl ether (PFMVE), perfluoromethoxypropyl vinyl ether (PFMPVE) or perfluoroalkoxyvinyl ether of the formula CF ₂ = CFOCF ₂ CF ₂ (OCF ₂ ) ₂ OCF ₃ (PFAOVE) are used. As the bromine-containing comonomer, ω-bromoperfluoroalkylallyl ether (BPFAAE) of the general formula II is used

where k = 1-3.

From latex, the copolymers are isolated by high-speed mechanical stirring with the addition of nitric acid, washed with water, ethanol and dried at 50-70 ° C under vacuum or in a stream of dry air.

The composition and structure of the obtained copolymers are determined using ^l9 F / ¹ H NMR spectroscopy and X-ray fluorescence spectroscopy (XRF). The molar ratio of VDF, TFE, BPFAAE and HFP (or PFAVE) is calculated from the NMR spectra of the samples in an acetone-d ₆ solution (unless otherwise specified) using hexafluoro-p-xylene (Bruker AM-500 spectrometer). The content of bound bromine is calculated from the XPS spectra (Spectroscan MAKC-G spectrometer).

The intrinsic viscosity is determined on a Ubbelode viscometer at 25 ± 0.1 ° C in a solution of tetrahydrofuran (unless otherwise specified). The Mooney viscosity of the obtained copolymers is determined according to GOST 10722-26.

The glass transition temperature is determined according to GOST 12254-66.

The proposed copolymers are subjected to peroxide vulcanization at 170-180 ° C for 15-20 minutes, followed by temperature control at 200-250 ° C for 6-12 hours. Various peroxides can be used as a vulcanization agent, but preferably 2,5-bis (tert-butylperoxy) -2,5-dimethylhexane sold under the trademarks Luperox ^® 101XL, Varox ^® DBPH-50, etc. The process is carried out in the presence of a vulcanization coagent, for which preferred is triallyl isocyanurate, marketed under the trademark Diak ^® №7. As a filler, various carbon blacks can be used, for example, T 900, No. 990. Additionally, metal oxides and hydroxides are used in the composition, for example, Ca (OH) ₂ , ZnO, PbO, etc.

Physical and mechanical parameters of vulcanizates, namely: Shore hardness, stress at 100% elongation, conditional tensile strength, elongation at break and relative residual deformation after compression are determined according to relevant standards (GOST 263-76, GOST 12535-78, GOST 9.029-74).

The following examples illustrate the invention.

Example 1

Into a 0.7 L stainless steel reactor previously evacuated and evacuated, equipped with a shielded drive motor, a mechanical propeller stirrer (1500 rpm), temperature and pressure sensors, a thermostatic jacket and two reagent nozzles, 370 is loaded without access to air g of a freshly prepared aqueous phase consisting of a solution of 3.7 g of ammonium perfluorooctanoate and 0.74 g of ammonium persulfate in distilled water. the pH of the aqueous phase is 4.3.

The mixer is turned on and the contents of the reactor are heated to 70 ° C in 10 minutes, after which 16 g of a pre-prepared mixture of monomers containing 73.8 mol.% VDF, 25.5 mol.% HFP are fed into the gas phase of the reactor from a metal ampoule (balloon) equipped with a siphon and 0.7 mol.% BPFAAE (k = 1) until a pressure of 0.8 MPa is reached.

In the process of copolymerization, when the pressure in the reactor is lowered to 0.7 MPa, the next portion of the mixture of monomers is fed to a pressure of 0.8 MPa, maintaining the process temperature within 70 ± 0.5 ° C. The copolymerization is carried out for 2.6 hours and 140 g of a mixture of monomers are fed, after which the reactor is cooled to room temperature. Unreacted monomers are trapped for recycling and 496 g of latex are recovered with a solids content of 25.6 wt.% Latex pH 3.0.

The latex copolymer is isolated by high-speed mechanical stirring with the addition of an aqueous solution of nitric acid, washed with hot water, then with a mixture of water and ethanol, squeezed and dried in a vacuum oven at a temperature of 60 ° C and a residual pressure of 3 mm Hg. to constant weight.

The resulting copolymer (122 g) had an intrinsic viscosity of 1.24 dl / g, a Mooney viscosity of 60, and was completely soluble in acetone. The yield of copolymer (for the used mixture of monomers) is 87.1%. Conversion (to reacted monomers) - 98.4%.

According to ¹⁹ F / ¹ H NMR spectroscopy, the structure of the obtained copolymer contained VDF units - 72.3 mol%, HFP - 27.0 mol%, BPFAAE (k = 1) - 0.7 mol%, and according to the data of X-ray fluorescence analysis, the copolymer contains 0.66 wt.% bound bromine. Thus, the resulting copolymer corresponds to the formula I, where:

R _F = —CF ₃ ; k = 1

n = 72.3 mol%

m = 27.0 mol%

p = 0.7 mol%

The copolymerization conditions, composition and properties of the copolymers obtained according to this and the following examples, for ease of consideration are summarized in tables 1 and 2.

Example 2

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 1, but a redox system based on PSA and MBS is used as the initiator of the copolymerization. The process is carried out at 50 ° C and a mixture of monomers containing VDF - 73.7 mol.%, HFP - 25.6 mol.% And BPFAAE (k = 1) - 0.7 mol.% Is used.

Example 3

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 1, but Na ₂ HPO ₄ · 12H ₂ O buffer (1.5 mol%) is used to control the pH of the aqueous phase and a mixture of monomers containing VDF - 76.9 mol%, HFP - 22.3 is used mol.% and BPFAAE (k = 1) - 0.8 mol.%.

Example 4

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 1, but KH ₂ PO ₄ (1.5 mol%) is used as a buffer and a mixture of monomers containing VDF - 76.6 mol.%, HFP - 22.6 mol.% And BPFAAE (k = 1) - 0.8 mol%.

Example 5

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 1, but using a mixture of monomers containing VDF - 48.5 mol.%, HFP - 25.8 mol.%, BPFAAE (k = 1) - 0.7 mol.% And TFE -25.0 mol.% .

Example 6

376 g of a freshly prepared aqueous phase is loaded into the apparatus described in Example 1, consisting of a solution of 3.76 g of a mixture of ammonium perfluoroheptanoate and ammonium perfluorononanoate (60:40 by weight), 0.75 g of ammonium persulfate in distilled water.

After heating the reactor to 60 ° C, a mixture of monomers is fed containing VDF - 73.5 mol.%, PFMVE - 25.8 mol.% And BPFAAE (k = 1) - 0.7 mol.%, Until a pressure of 0.8 MPa is reached and is maintained by periodic feeding of this the same mixture of monomers for 2.7 hours. The isolation process and methods of analysis of the obtained copolymer are similar to those described in example 1.

Example 7

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but as the initiator of the copolymerization, a redox system based on PSA and MBS is used. The process is carried out at 50 ° C and a mixture of monomers containing VDF - 73.8 mol.%, PFMVE - 25.5 mol.% And BPFAAE (k = 1) - 0.7 mol.% Is used.

Example 8

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but instead of BPFAAE (k = 1), BPFAAE (k = 3) is used in a mixture of monomers containing VDF - 73.6 mol%, PFMVE - 25.7 mol% and BPFAAE (k = 3 ) - 0.7 mol%.

Example 9

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but using a mixture of monomers containing VDF - 74.0 mol.%, PFMVE - 25.7 mol.%, BPFAAE (k = 1) - 0.3 mol.%.

Example 10

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but using a mixture of monomers containing VDF - 73.5 mol.%, PFMVE - 23.4 mol.%, BPFAAE (k = 1) - 3.1 mol.%.

Example 11

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but using a mixture of monomers containing WDF - 76.6 mol.%, PFMVE - 18.6 mol.%, BPFAAE (k = 1) - 0.8 mol.% And TFE - 4.0 mol.% .

Example 12

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 6, but use a mixture of monomers containing VDF - 72.5 mol.%, PFMVE - 18.7 mol.%, BPFAAE (k = 1) - 0.8 mol.% And TFE - 8.0 mol.% .

Example 13

The apparatus described in Example 1 was charged with 438 g of a freshly prepared aqueous phase consisting of a solution of 8.76 g of ammonium salt of perfluoroxacarboxylic acid based on trimer of hexafluoropropylene oxide and 0.66 g of ammonium persulfate and 0.13 g of sodium metabisulfite in distilled water.

After heating the reactor to 35 ° C, a mixture of monomers is fed containing VDF - 73.7 mol%, BPFAAE (k = 1) - 0.7 mol% and perfluoromethoxypropyl vinyl ether (PFMPVE) - 25.6 mol% until a pressure of 0.8 MPa is reached.

In the copolymerization process, when the pressure in the reactor is lowered to 0.7 MPa, the pressure is restored by periodic feeding of a mixture of monomers of the same composition for 4.2 hours (184 g of a mixture of monomers). After that, the feed is stopped and the copolymerization is continued for another 2.0 hours until the monomers are fully developed.

The process of isolating the obtained copolymer is similar to that described in example 1. But in the analysis process, solutions of the copolymers in a mixture of hexafluorobenzene - acetone-d ₆ (50:50 vol.%) Were used to take ¹⁹ F / 'H NMR spectra. The intrinsic viscosity was determined under the conditions of example 1, but in a solution of hexafluorobenzene.

Example 14

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 13, but using a mixture of monomers containing VDF - 65.9 mol.%, PFMPVE - 33.3 mol.% And BPFAAE (k = 1) - 0.8 mol.%.

Example 15

The process of copolymerization, isolation and analysis of the copolymer is carried out analogously to example 13, but using a mixture of monomers containing VDF - 60.2 mol.%, PFMPVE - 19.6 mol.%, BPFAAE (k = 1) - 0.7 mol.% And TFE - 19.5 mol.% .

Example 16

The copolymerization, isolation and analysis of the copolymer is carried out analogously to example 13, but instead of the PFMPVE monomer, the PFAOVE monomer and a mixture of monomers containing VDF - 73.4 mol.%, PFAOVE - 25.8 mol.% And BPFAAE (k = 1) - 0.8 mol.% Are used.

Of the copolymers synthesized according to examples 1-16, compositions containing:

copolymers 1-12 100.0 wt. hours soot T900 25.0 wt. hours calcium hydroxide 3.0 wt. hours Luperox ^® 101XL (45% active) 2.5 wt. hours triallyl isocyanurate (Diak ^® # 7) 2.5 wt. hours

The compositions are cured in a press at 177 ° C for 15 minutes, followed by heating from room temperature to 230 ° C for 3 hours and thermostating at 230 ° C for 6 hours. The vulcanized compositions are released in the form of plates (120 × 120 × 1 ) mm for testing physical and mechanical properties and cylinders (10 × 10) mm for testing ODS.

The properties of the vulcanizates are shown in table 3.

Thus, as can be seen from the data given in the examples and in the tables, the proposed copolymers do not contain a gel (completely soluble), and the vulcanizates based on them have, along with good ODS at 200 ° C, high strength and elasticity. At the same time, their use does not require the use of high pressures and a long process time.

Table 3 Properties of vulcanizates room Hardness Stress at 100% elongation, MPa Tensile strength, MPa Elongation at break,% Relative deformation after compression by 20% (24 h × 200 ° C) one 72 8.0 20.2 200 23 2 75 12.1 20.4 180 21 3 74 9.5 19.4 190 22 four 73 9.1 18.3 210 22 5 76 11.2 19.5 180 eighteen 6 66 6.6 15.7 220 25 7 72 6.9 15.2 190 21 8 65 6.5 14.2 180 23 9 65 5.2 11.2 260 24 10 75 7.2 19.2 160 twenty eleven 68 7.0 15.2 200 24 12 68 7.3 16.0 190 23 13 62 4.5 10.8 200 29th fourteen 60 4.2 9.2 210 28 fifteen 70 5.3 14.5 180 29th 16 60 4.2 9.0 260 28

Claims (1)

Vinylidene fluoride-based bromine copolymers of the general formula

where R = -CH ₂ ; a mixture of —CH ₂ and —CF ₂ , in which the content of the component R = CH _{2 is} not less than 60 mol%;
R _F = —CF ₃ ; -OCF ₃ ; —OCF ₂ CF ₂ CF ₂ OCF ₃ ; —OCF ₂ CF ₂ (OCF ₂ ) ₂ OCF ₃ ;
n = 64.0-85.0 mol%; k = 1-3
p = 0.3-3.0 mol.%
m = the rest is up to 100 mol.%,
for heat resistant materials.