JPH0425290B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vulcanizable fluorine-containing copolymer that can provide a vulcanized rubber with excellent mechanical strength. A fluorine-containing copolymer consisting of fluoroisobutene (hereinafter abbreviated as HFIB) and hexafluoropropene (hereinafter abbreviated as HFP), and in addition to these monomer units, tetrafluoroethylene (hereinafter abbreviated as TFE).
The present invention relates to a fluorine-containing copolymer containing a unit (abbreviated as ). Conventionally, fluorine-containing copolymers such as VdF and HFP
It is known that copolymers obtained by copolymerizing are vulcanized with various vulcanizing agents to produce elastomers with excellent heat resistance and chemical resistance.
This elastomer is used for various purposes as O-rings, sheets, and various other molded products.
However, when this fluorine-containing elastomer is used in applications that require mechanical strength, such as heat-resistant and corrosion-resistant belts, diaphragms, or various sliding members, it is difficult to maintain tensile strength, especially 100% tensile stress or tear strength. The drawback was that it was not strong enough. In order to improve the mechanical strength of such fluorine-containing elastomers, various methods have been used so far, such as improving the tensile stress by 100% by adding reinforcing agents such as various carbon blacks, and adding inorganic fibers ( JP-A-50-23441), combination of heat-resistant organic fibers (JP-A-53-8649), or combination of fibrillated TFE emulsion polymer (JP-A-53-8650). Several methods have been proposed to improve the strength. However, since all of these methods involve adding additives during vulcanization and compounding, there are difficulties in processability during kneading or molding. In view of these circumstances, the present inventors have developed a fluorine-containing elastomer that is 100% elastomer without impairing its physical properties such as heat resistance and solvent resistance, and its moldability.
As a result of intensive research to obtain a fluorine-containing elastomer with excellent mechanical strength such as tensile stress and tear strength, we have developed a fluorine-containing elastomer that has excellent mechanical strength such as tensile stress and tear strength.
The inventors have discovered that the objective can be achieved by improving the fluorine-containing copolymer itself, and have completed the present invention based on this knowledge. That is, the present invention contains 40 to 80 mol% of VdF units,
Consisting of 0.5 to 20 mol% of HFIB units and 5 to 30 mol% of HFP units, and 35% in methyl ethyl ketone solution
A fluorine-containing copolymer with an intrinsic viscosity of 0.5 to 1.5 dl/g measured at °C, and 40 to 80 mol% of VdF units, 0.5 to 20 mol% of HFIB units, and 5 to 20 HFP units.
mol% and TFE units from 5 to 20, and has an intrinsic viscosity measured at 35°C in methyl ethyl ketone solution.
The present invention provides a fluorine-containing copolymer having a content of 0.5 to 1.5 dl/g. The fluorine-containing copolymer of the present invention is a copolymer in which the content of each monomer is 60 to 75 mol% of VdF units, 2 to 10 mol% of HFIB units, and 15 to 30 mol% of HFP units,
or 60 to 75 mol% of VdF units, 2 to 10 mol% of HFIB units, 5 to 20 mol% of HFP units, and 5 to 5 mol% of TFE units.
Preference is given to copolymers that are 20 mol%. Furthermore, in the copolymer of the present invention, in addition to the above-mentioned monomer units, other monomer units may be added as desired.
It can be contained in a range of less than mol%. Examples of this monomer unit include chlorotrifluoroethylene, 1-hydropentafluoropropene-1, ethylene, propylene, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and the like. If the content of HFIB units in the copolymer of the present invention is too small, the effect of improving mechanical strength, which is a feature of the present invention, will be insufficient, and if it is too large, rubber elasticity will be impaired. Therefore, preferred copolymers are obtained when the content of HFIB units is in the range from 2 to 10 mol%. Also, VdF unit, HFP
The content of the TFE unit is appropriately selected within the above-mentioned predetermined range from the viewpoints of rubber elasticity, heat resistance, and solvent resistance. The copolymer of the present invention can be obtained by copolymerizing each monomer in the presence of a radical initiator using a known polymerization method such as bulk polymerization, suspension polymerization, emulsion polymerization, or solution polymerization. . Among the above polymerization methods, a preferred polymerization method is suspension polymerization or emulsion polymerization, in which case ammonium persulfate, sodium persulfate, potassium persulfate, perphosphoric acid, perboric acid, sodium percarbonate, Potassium percarbonate, ammonium percarbonate, etc. are used, and among these, the most preferred initiator is ammonium persulfate. The amount of initiator used is usually in the range of 0.01 to 5 parts by weight per 100 parts by weight of the total monomers. The above radical initiator may be used alone, but if necessary, it may be used in combination with a reducing agent such as a sodium, potassium or ammonium salt such as sulfite, bisulfite, hyposulfite, thiosulfate, phosphorous acid, or hypophosphorous acid. It may be used in combination, or a ferrous compound,
It can also be used in combination with cupric compounds and other easily oxidized metal compounds. Furthermore, in the production of the fluorine-containing copolymer of the present invention, surfactants known to be useful, particularly fluorine-containing surfactants, can be used as necessary. Examples of the fluorine-containing surfactant include fluorine-containing aliphatic carboxylic acids or sulfonic acids and salts thereof. Further, a known chain transfer agent can also be used to adjust the degree of polymerization if necessary. The copolymerization reaction is usually carried out under a pressure of 2 to 45 Kg/cm ² , and the polymerization temperature is appropriately selected depending on the type of radical initiator used. For example, when a persulfate is used as the radical initiator, Normally 50~90℃
The polymerization reaction takes place at a temperature of . Polymerization can be carried out either in a batch method, in which the predetermined comonomers are charged all at once, or by continuously supplying a mixed gas of comonomers adjusted to a predetermined molar ratio at a constant pressure. Although a continuous method may be used in which polymerization is carried out, a copolymer obtained by a batch method has a greater effect of improving mechanical strength after vulcanization, and therefore a batch method is preferable as a polymerization operation. After performing the copolymerization reaction in this manner, the copolymer is solidified from the resulting polymer latex by a known method, for example, by adding an inorganic electrolyte such as magnesium chloride or ammonium chloride, or by freezing. Then, it is separated by a method such as filtration or centrifugation, thoroughly washed with pure water, and then dried. In the fluorine-containing copolymer of the present invention thus obtained, the HFIB unit can be confirmed and the composition of each monomer unit can be analyzed by infrared absorption spectrum or 19F-NMR. In other words, in the infrared absorption spectrum, at 1450 cm ^-1

[Formula] Has absorption due to bonding, and according to 19F-NMR, 68.2PPM (standard material

A peak due to the _CF3 group of the HFIB unit is seen in the chemical shift of [Formula]). Furthermore, the intrinsic viscosity of the fluorine-containing copolymer of the present invention (measured at 35°C in a methyl ethyl ketone solution) is 0.5 to
It needs to be 1.5 dl/g. If it deviates from this range, the intended effects of the present invention will not be fully exhibited. The fluorine-containing copolymer of the present invention can be obtained by a known vulcanization method for fluorine-containing elastic copolymers containing VdF units, that is, a method using a vulcanizing agent such as a polyamine compound, a polyhydroxy compound, or an organic peroxide. Can be vulcanized by In the case of vulcanization using the above polyamine compounds,
Such compounds include, for example, hexamethylene diamine,
Alkyl polyamines such as tetraethylenepentamine and triethylenetetramine, or their carbamic acids and cinnamylidenic acids are preferably used. For vulcanization using polyhydroxy compounds,
As the compound, polyhydroxy aromatic compounds such as hydroquinone, bisphenol A, bisphenol AF, and salts thereof are preferably used. Further, fluorine-containing aliphatic diols can also be used. When these polyhydroxy compounds are used as a vulcanizing agent, it is preferable to use, for example, a quaternary phosphorus compound or a quaternary ammonium compound together as a vulcanization accelerator. Furthermore, in the case of vulcanization using an organic peroxide, the peroxide may be, for example, 2,5-dimethyl-
2,5-di(t-butylperoxy)-hexane,
2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3 and the like are preferably used. In this case, it is preferable to use a vulcanization aid in combination.
Suitable examples of the vulcanization aid include triallylisocyanuric acid and triallylcyanuric acid. The amount of the vulcanizing agent, vulcanizing aid, and vulcanizing accelerator used is usually in the range of 1 to 10 parts by weight per 100 parts by weight of the fluorine-containing elastomer. In addition, when vulcanizing the fluorine-containing copolymer of the present invention, other additives commonly used in conventional vulcanization methods, such as metal oxides such as magnesium oxide and lead oxide, hydroxide, etc. Metal hydroxides such as calcium, reinforcing agents such as carbon black and fine silica, etc. can be used. The fluorine-containing copolymer composition containing the above-mentioned vulcanizing agent and other additives is sufficiently uniformly mixed and then heated to a temperature at which a vulcanization reaction occurs to vulcanize it. The mixing is usually carried out using a rubber kneading roll or a Barbary mixer. Vulcanization is often carried out by vulcanizing the composition at a temperature of 120 to 200°C for 1 to 60 minutes using a vulcanization press, mold, extruder, etc. that are commonly used for vulcanization of rubber, plastic, etc. This is done by heating, and in order to further increase the thermal stability and dimensional stability of the vulcanizate, it is heated at a temperature of 180 to 250℃ using a heater etc.
Preferably, the mixture is heated for a period of time. In this way, the vulcanized rubber obtained from the fluorine-containing copolymer of the present invention has excellent heat resistance, chemical resistance, and oil resistance, which are characteristics of fluorine rubber, and also has 100% Mechanical strength such as % tensile stress and tear strength is extremely high. Next, the present invention will be explained in more detail with reference to Examples. Example 1 5000g of purified water in a 15a Sus autoclave
and 8g of ammonium persulfate, close the autoclave, and thoroughly degas the inside of the autoclave.
63 g of HFIB, 189 g of HFP, 55 g of TFE, and 211 g of VdF were sequentially introduced into the autoclave. The molar ratio of each copolymer monomer is VdF60 mol%,
HFIB 7 mol% HFP 23 mol% TFE 10 mol%. Next, while stirring the autoclave at 300 rpm, the internal temperature of the autoclave is raised to 70°C to start the polymerization reaction. Polymerization pressure is initial pressure 12.5Kg/
The pressure gradually decreased from cm ² , and the time from the start of the reaction until no pressure drop was finally observed was 3 hours, and the pressure drop during this period was 11.0 Kg/cm ² . Then, the autoclave was cooled to room temperature,
Purge unreacted monomers. A 5% MgC ₂ aqueous solution was added to the obtained latex, the solid content was separated, thoroughly washed with purified water, and dried in a vacuum dryer at 90°C for 24 hours to obtain a white elastic copolymer.
Got 400g. The composition of each monomer unit of the resulting copolymer is 19F−
NMR confirmed that VdF: 69.9 mol% HFIB: 6.1 mol% HFP: 13.4 mol% TFE: 10.6 mol%, and the intrinsic viscosity η was 0.82 dl/
g (35°C in methyl ethyl ketone solvent), and the Mooney viscosity of this copolymer is ML121°C 1+10 is 72
It was hot. For 100 parts by weight of this copolymer, MT carbon
After kneading 20 parts by weight of MgO, 15 parts by weight, and 3 parts by weight of hexamethylene diamine carbamate using a roll, use an oscillating rheometer (ODR) made by Toyo Seiki.
Vulcanized physical properties were measured using the following method. Further, this vulcanized compound was press-vulcanized at 150℃ for 30 minutes, then heated in an oven at 200℃ for 24 hours to perform post-vulcanization to prepare samples, and the physical properties were measured according to JIS-K-6301. I went there. The results are shown in Table 1. Comparative Example 1 A terpolymer in which the composition of each monomer unit of the copolymer is represented by 63.3 mol% of VdF, 18.7 mol% of HFP, and 18.0 mol% of TFE was produced in the same manner as described in Example 1. Table 1 shows the physical properties of samples cured with the same formulation.

[Table] Example 2 Using an autoclave with a volume of 3, the charging molar ratio was VdF 60 mol%, HFIB 5 mol%, HFP 22.5
Example 1 except that mol% and TFE were 12.5 mol%.
The composition of each monomer unit of the copolymer is determined by performing polymerization and post-polymerization treatment according to the polymerization procedure described in
VdF70.0 mol%, HFIB3.4 mol%, HFP13.8 mol%, TFE12.8 mol%, and the intrinsic viscosity is 0.94 dl/
132 g of white elastic body was obtained. This copolymer was vulcanized by the method described in Example 1, and the physical properties were measured. The results are shown in Table 2. Example 3 Purified water in a Sus autoclave with a volume of 3
After charging 1500 g and 4.5 g of ammonium persulfate and thoroughly degassing the inside of the autoclave, a mixed gas with a molar ratio of each monomer gas of VdF 60 mol%, HFIB 7 mol%, HFP 23 mol%, and TFE 10 mol% was added to the autoclave at an internal pressure of 6 Kg/cm ² Then, while stirring the autoclave at 300 rpm, raise the autoclave's internal temperature to 70°C and increase the pressure to 80°C.
The weight was adjusted to Kg/cm ² and polymerization was started. The pressure that decreases as the polymerization reaction progresses is compensated for by continuously feeding the mixed monomer gas of the charged composition with a pressure pump, and the polymerization pressure is increased to 8 kg/cm ²
Polymerization was carried out while maintaining the temperature. The reaction was stopped 5 hours after the start of polymerization, and post-treatment was performed in the manner described in Example 1 to obtain 253 g of a white elastic body. The composition of each monomer unit of this copolymer is
VdF67.5 mol%, HFIB6.4 mol%, HFP17.8 mol%, TFE8.2 mol%, intrinsic viscosity 1.09 dl/g
It was hot. This copolymer was vulcanized using the method and formulation described in Example 1, and the physical properties were measured. The results are shown in Table 2. Example 4 Polymerization was carried out in the same manner as in Example 3 except that the molar ratio of copolymerization monomers was 60 mol% VdF, 10 mol% HFIB, and 30 mol% HFP, and the composition of each monomer unit of the copolymer was , VdF67.3 mol%,
Intrinsic viscosity 0.68 at HFIB6.5 mol%, HFP26.2 mol%
284 g of a white elastic copolymer of dl/g was obtained. This copolymer was vulcanized using the method and formulation described in Example 1, and the physical properties were measured. The results are shown in Table 2. Comparative Example 2 A binary copolymer in which the composition of each monomer unit of the copolymer is represented by 74 mol% of VdF and 26 mol% of HFP was treated according to the same polymerization method, post-treatment, and vulcanization method as in Example 1. Table 2 shows the physical properties of the samples prepared in this manner.

[Table] The following can be understood from Tables 1 and 2. (1) The vulcanizates of the fluorine-containing copolymers of the present invention containing HFIB as a monomer unit shown in Examples 1 to 4 are different from VdF-, which does not contain HFIB units shown in Comparative Examples 1 and 2. HFP binary copolymer or VdF−
It has extremely high 100% tensile stress and tear strength compared to the vulcanized product of HFP-TFE ternary copolymer. (2) Comparison of Example 1 and Example 2 shows that Example 1, which has a higher HFIB unit content, has a greater effect of improving mechanical strength. From this, it is possible to improve the mechanical strength of the fluorine-containing copolymer of the present invention.
It is understood that the contribution of the HFIB unit is large.
However, if the content of HFIB units is too high, the rubber elasticity becomes poor, so it is preferable that the content of HFIB units is 10 mol% or less. (3) Comparing Example 1 and Example 3, it was found that the copolymer vulcanizate that was polymerized in batches was better than the copolymer vulcanizate that was polymerized by continuously blowing mixed gas at a constant pressure. The effect of improving tensile stress and tear strength by 100% is greater than that of a vulcanized copolymer that has been subjected to this process. (4) Comparison of Example 1 and Comparative Example 1 reveals that there is no difference between the two in compression set, heat strength, heat aging test, and oil resistance test. It can be seen that mechanical strength has been improved without impairing oil resistance or oil resistance. Example 5 For 100 parts by weight of the copolymer polymer of Example 1,
MT carbon 30 parts by weight, MgO3 parts by weight, Ca(OH)
₂ 6 parts by weight, Curateve #20 (organic phosphonium salt 33%, fluoroelastomer 67%) 1.8 parts by weight,
Curateve #30 (Dihydroxy Aromatic Compound 50
%, fluoroelastomer 50%) were roll-kneaded, press vulcanized at 177°C for 10 minutes, and then oven-vulcanized at 232°C for 24 hours to produce polyol vulcanized rubber. The vulcanization properties of this vulcanized compound and the mechanical properties of the vulcanized rubber are shown in Table 3.

【table】

Claims (1)

[Scope of Claims] 1 Consists of 40 to 80 mol% vinylidene fluoride units, 0.5 to 20 mol% hexafluoroisobutene units, and 5 to 30 mol% hexafluoropropene units,
A fluorine-containing copolymer having an intrinsic viscosity of 0.5 to 1.5 dl/g when measured in a methyl ethyl ketone solution at 35°C. 2 Consists of 40 to 80 mol% of vinylidene fluoride units, 0.5 to 20 mol% of hexafluoroisobutene units, 5 to 20 mol% of hexafluoropropene units, and 5 to 20 mol% of tetrafluoroethylene units, and in a methyl ethyl ketone solution at 35 °C A fluorine-containing copolymer having a measured intrinsic viscosity of 0.5 to 1.5 dl/g.