JPH02117945A - Fluoroelastomer composition - Google Patents

Abstract

PURPOSE:To obtain the title composition outstanding in compression set characteristics, mechanical characteristics and processability by blending a specific high-molecular weight three-dimensional fluoroelastomer with a specific two-dimensional fluoroelastomer at specified proportion. CONSTITUTION:The objective composition can be obtained by blending (A) 100 pts.wt. of a fluoroelastomer made up of vinylidene fluoride unit (VDF), hexafluoropropylene unit (HFP) and tetrafluoroethylene unit, 68-71wt.% in fluorine content, 25-45wt.% in HFP content and 100-300ml/g in intrinsic viscosity with (B) 1-30 (pref. 1-20) pts.wt. of a second fluoroelastomer made up of VDF and HFP, 64-67wt.% in fluorine content and 10-50ml/g in intrinsic viscosity. It is preferable that this composition be cured with a polyhydroxyl compound.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to novel fluoroelastomer compositions with improved vulcanization properties, and more particularly to improved vulcanization customization and processability to provide high performance fluororubbers. The present invention relates to a fluoroelastomer composition.

Conventional technology Because fluoroelastomers have excellent heat resistance, solvent resistance, and chemical resistance, they have been used as sealing materials such as O-rings, oil seal packings, and gaskets, and diaphragms used under harsh conditions. Although widely used,
In recent years, as mechanical parts have become smaller and more complex in shape,
In terms of physical properties such as workability, compression set, and mechanical properties, there is a growing demand for materials with excellent properties. For example, it is important for sealing materials processed primarily by compression molding to have low compression set, but with recent technological innovations, the usage conditions for sealing materials are becoming increasingly harsh, and they are resistant to chemicals, solvents, etc. The demand for sex is increasing. However, if the fluorine content is increased in order to improve the chemical resistance and solvent resistance of the fluoroelastomer, the compression set resistance tends to increase and the roll processability tends to decrease.

Until now, as a fluoroelastomer, for example, vinylidene fluoride (hereinafter referred to as VdF) unit 6
0 to 15% by weight and hexafluoropropylene (hereinafter referred to as RF
A copolymer polymerized at a charging ratio of 40 to 85% by weight of units (denoted as P) (Japanese Patent Publication No. 33-7394), containing 3 to 35% by weight of tetrafluoroethylene (hereinafter referred to as TFE) units, and VdF units. and the sum of P units is 97-65
% by weight, and a copolymer in which the weight ratio of VdF units to HFP units is in the range of 2.33:l to 0.667:1 (Japanese Patent Publication No. 36-3495), TFE units 10
-30% by weight, the sum of VdF units and HFP units is 90 to 70% by weight, and the weight ratio of VdF units to RFP units is 1.6:! , 0-4. o: copolymer in the range of t, o (Japanese Patent Publication No. 48-18957), V
A copolymer consisting of 57-61% by weight of dF units, 27-31% by weight of HFP units and 10-14% by weight of TFE units (
Japanese Patent Publication No. 53-149291) and the like have been proposed, but these cannot necessarily be said to be satisfactory in terms of the balance between workability and compression set resistance.

On the other hand, there are methods to improve the physical properties by adjusting the molecular weight distribution of fluoroelastomers, such as two-stage polymerization (continuous polymerization), in which a high molecular weight copolymer is first polymerized, and then a low molecular weight copolymer is polymerized. A method for producing copolymers with two molecular weight distributions (Japanese Patent Publication No. 51-25279), and a method for producing copolymers or terpolymers with low Mooney viscosity and excellent processability by suspension polymerization (Japanese Patent Publication No. 51-25279). Publication No. 49-29630, Special Publication No. 51-84
32) and a high molecular weight fluoroelastomer with a bimodal molecular weight distribution (European Patent Application Publication No. 0186180A2), but these methods also make it possible to obtain a fluoroelastomer that satisfies the above requirements. I couldn't do that.

By the way, in general, in fluoroelastomers,
Increasing the low molecular weight component makes it easier to process, but the compression set resistance and mechanical properties deteriorate; on the other hand, increasing the high molecular weight component improves the compression set resistance and mechanical properties. Processing tends to become difficult, and especially in high fluorine content elastomers, if the low molecular weight component is increased for the purpose of improving processability, vulcanization characteristics and physical properties inevitably deteriorate.

For this reason, there has been a strong desire to develop a fluoroelastomer that has excellent compression set resistance and mechanical properties as well as excellent workability.

Problems to be Solved by the Invention The object of the present invention is to provide a fluoroelastomer composition that can meet these demands in terms of both excellent compression set resistance, mechanical properties, and processability. It was made for the purpose of

Means for Solving the Problems As a result of intensive research to develop a fluoroelastomer that is excellent in both physical properties and processability, the present inventors found that VdF units, HFP units, and TFE The excellent performance of the ternary fluoroelastomer can be achieved by blending a specific low molecular weight binary fluoroelastomer consisting of VdF units and )IFP units in a predetermined ratio with a specific high molecular weight ternary fluoroelastomer consisting of units. The present inventors have discovered that the processability can be improved without impairing the processability, and have completed the present invention based on this knowledge.

That is, the present invention (consists of AWdF units, HFP units and TFE units, and has a fluorine content of 68 to 71% by weight, an RFP unit content of 25 to 45% by weight, and an intrinsic viscosity of 100 to 300 ml/g) To 100 parts by weight of the fluoroelastomer, 1 to 30 parts by weight of a fluoroelastomer (consisting of BWdF units and HFP units, with a fluorine content of 64 to 67% by weight, and an intrinsic viscosity of 10 to !50 ml/9) is blended. The present invention provides a fluoroelastomer composition comprising:

The present invention will be explained in detail below.

The fluoroelastomer composition of the present invention comprises a ternary fluoroelastomer composed of VdF units, HFP units and TFE units as the component (A), and a binary fluoroelastomer composed of VdF units and HFP units as the component (B). The ternary fluoroelastomer of component (A) has a fluorine content in the range of 68 to 71% by weight, and an RFP unit content in the range of 25 to 45% by weight. It is necessary that there be. The fluorine content is 6
If it is less than 8% by weight, the solvent resistance against solvents such as methanol will not be sufficient, and if it exceeds 71% by weight, the polymer will tend to become plastic-like and its elasticity will decrease. Further, if the content of HFP units is less than 25% by weight, the properties as an elastomer may not be fully exhibited, and if it exceeds 45% by weight, workability during roll kneading etc. tends to decrease.

Furthermore, the intrinsic viscosity of the ternary elastomer is 100 to 3
It is necessary to be in the range of 00ml/9. This intrinsic viscosity is an indicator of the molecular weight of the polymer, and from the viewpoint of vulcanization physical properties, a larger one is preferable, but polymers exceeding 300+12/g are technically difficult to manufacture, especially when they have a high fluorine content. However, if it is less than 100 ml/g, the compression set resistance will be insufficient.

-J, the binary fluoroelastomer of component (B) needs to have a fluorine content in the range of 64 to 67% by weight. If the fluorine content is less than 64% by weight, the polymer will become plastic-like and have insufficient elasticity, while if it exceeds 67% by weight, the content of HFP units will increase, resulting in a marked decrease in the polymerization rate, and if the polymer has a high molecular weight. Since it becomes difficult to obtain, it lacks practicality. Furthermore, the binary fluoroelastomer has an intrinsic viscosity of 10 to 50 ml/
It is necessary to have a low molecular weight in the range of 9.

When the intrinsic viscosity is less than 10 m<1/g, the molecular weight is low, and its blending causes deterioration of the overall physical properties.

Moreover, if it exceeds 50 m (i/g), the effect of improving the processability of the high molecular weight ternary fluoroelastomer will not be sufficiently exhibited.

In the fluoroelastomer composition of the present invention, the amount of the low molecular weight binary fluoroelastomer (B) is 1 to 30 parts by weight per 100 parts by weight of the high molecular weight ternary fluoroelastomer (A). , preferably 1
-20 parts by weight. If this amount is less than 1 part by weight, the effect of improving processability will not be sufficiently exhibited;
If it exceeds 0 parts by weight, the amount of low molecular weight components increases too much, resulting in a decrease in compression set resistance after vulcanization.

As described above, according to the present invention, a high molecular weight ternary fluoroelastomer which has excellent solvent resistance and excellent mechanical properties and compression set resistance of the vulcanized product, has a relatively low vulcanizability even with a low molecular weight. By blending a small amount of a low molecular weight binary fluoroelastomer with excellent compression set resistance, the vulcanization properties are improved and the excellent physical properties originally possessed by the high molecular weight ternary fluoroelastomer are almost completely impaired. However, the processability can be improved.

In the present invention, the fluoroelastomer used as component (A) can be produced by a method conventionally used in the production of fluoroelastomers, such as an emulsion polymerization method, a suspension polymerization method,
It can be produced by any method such as a solution polymerization method.

For example, according to the suspension polymerization method, first a predetermined amount of tsummer (prepared tsummer) dissolved in an inert organic solvent is suspended in an aqueous medium, and then a suspension stabilizer and an oil-soluble catalyst? After adding, reduce the temperature to 50℃ while stirring mechanically.
Maintain at ~60°C, pressure 5~20kg/crs'・
Polymerization is proceeded by adding a new composition of additives (continuously added monomer) so that G becomes constant. The feed composition is determined so that the amount of fluoroelastomer produced is equal to the amount of the monomer added, and the composition of the fluoroelastomer is the same as the composition of the monomer added.

The charged seven-mer composition and the continuous addition composition can be measured by gas chromatography (G, C,), and the composition of monomer units in the fluoroelastomer can be measured by FNMR after dissolving the elastomer in acetone.

The inert organic solvent used in this suspension polymerization method is selected from organic solvents that do not have carbon-hydrogen bonds that are likely to cause chain transfer.
1,2,2-trifluoroethane is preferred in terms of performance and economy. Methyl cellulose can be used as a suspension stabilizer, and dialkyl peroxydicarbonates, which can be used at high temperatures, are suitable as oil-soluble catalysts. Furthermore, in this polymerization, a chain transfer agent may be used as necessary to adjust the molecular weight.

There are no particular limitations on the method for preparing the fluoroelastomer composition of the present invention, and for example, a general method of blending using a roll, Banbury mixer, kneader, etc. can be employed.

Although the fluoroelastomer compositions of the present invention can be vulcanized with polyamine compounds and polyhydroxy compounds, the improved performance of the fluoroelastomer compositions of the present invention is even more pronounced when vulcanized with polyhydroxy compounds. Ru.

Next, an example of a vulcanization method using the polyhydroxy compound will be explained.

The fluoroelastomer composition of the present invention is mixed with an acid binder, a polyhydroxy compound, a vulcanization accelerator, and a filler used if necessary, and then heated and vulcanized.

As a compounding agent, a divalent metal oxide or hydroxide, such as an oxide or hydroxide of magnesium, calcium, zinc, lead, etc., is used, and the amount used is 1 per 100 parts by weight of the fluoroelastomer composition. -30 parts by weight, preferably 2 to 20 parts by weight.

As a polyhydroxy compound, hydroquinone, 2.2
-Bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(4-hydroxyphenyl)
Perfluoropropane (bisphenol AF), 4, C
-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenylmethane, 2,2-bis(4-hydroxyphenyl)butane, etc., from 0.1 to IO parts by weight, preferably from 0.6 to 5 parts by weight, per 100 parts by weight of the composition. Used as a percentage.

As the vulcanization accelerator, quaternary onium salt compounds, quaternary phosphonium salts, quaternary ammonium salts or iminium salts, such as tetramethylammonium chloride, tetraethylammonium chloride, tetrapropylammonium chloride, tetrabutylammonium chloride, tetra Butylammonium bromide, bis(benzyldiphenylphosphine)iminium chloride, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride, benzyltrioctylphosphonium chloride, etc. are suitable, and 0.0% per 100 parts by weight of the composition.
0.05 to 2 parts by weight, preferably 0.1 to 1 parts by weight. As the filler reinforcing agent, for example, carbon black, silica, clay, talc, etc. are used as necessary.

A mixture of a fluoroelastomer composition, an acid binder, a polyhydroxy compound, a vulcanization accelerator, and a filler used as necessary is kneaded using a roll or a Banbury mixer, and then put into a mold and pressurized for primary vulcanization. Then, secondary vulcanization is performed. Generally, the temperature condition for primary vulcanization is 100-200°C1
Vulcanization time 10-180 minutes, pressure 20-100h97c
It is selected from the range of m3・G, and the secondary vulcanization conditions are a temperature of 15
It is selected from the range of 0 to 300°C and vulcanization time of 0 to 30 hours.

Effects of the Invention The fluoroelastomer composition of the present invention has an excellent balance between physical properties and processability, including extremely excellent compression set resistance and mechanical properties, as well as good processability. For example, it can be advantageously used as a material for O-rings, oil seal sealing materials, diaphragms, solenoid valves, needle valves, copying machine blades, fixing rolls, various industrial valves, or composite parts with other different materials.

Examples Next, the present invention will be explained in more detail with reference to examples.
The present invention is not limited in any way by these examples.

The physical properties and processability of the fluoroelastomer and composition were determined by the following methods.

(1) Intrinsic viscosity; Methyl ethyl ketone 0-11? /loO+IIff concentration solution is measured at 35°C using a capillary viscometer.

(2) Mechanical properties of vulcanizate; Polyol vulcanization standard conditions Fluoroelastomer: 100 fEt parts Highly active maggot oxide: 3 parts by weight Calcium hydroxide
= 6 parts by weight Bisphenol AF: 2 parts by weight Bis(benzyldiphenylphosphine)iminium chloride = 0.3 parts by weight Medium thermal carbon: 30 parts by weight Kneading method Two-roll primary heat press vulcanization: Secondary oven at 177°C for minutes Vulcanization: 232°C x 24 hours A polyol vulcanized sheet with a thickness of 21 m1 was prepared under the above-mentioned standard vulcanization conditions, and No. 3 dumbbell-shaped test pieces were punched out from this sheet to meet JIS-K 63.
Using a tensile tester [manufactured by Toyo Seiki Co., Ltd.] according to 01,
Mechanical properties are measured at a tensile rate of 50 c++/min.

(3) Vulcanization characteristics: Measured using a disc rheometer manufactured by Toyo Seiki Co., Ltd., disc type BL, amplitude angle of 3°, and frequency of 3Cp111.

(4) Compression set; P-24 type 0- polyol vulcanized under the above standard vulcanization conditions.
Using a ring, the temperature was maintained at 200'C for 72 hours under 25% compression according to JIS-K 6301, and then
After cooling to room temperature for 0 minutes, the thickness is measured using a thickness meter (manufactured by Kyoto Kobunshi Keiki).

(5) Roll processability: Evaluate the workability during roll kneading, processing, and molding under the polyol vulcanization standard conditions.

That is, the adhesion to the roll, tearing, powder insertion time, and sheet dispensing texture are comprehensively considered and evaluated according to the following criteria.

○: Excellent, △: Average, X: Poor Reference example 1 An autoclave with an internal volume of approximately 1512 mm equipped with an electromagnetic induction stirrer was sufficiently purged with nitrogen gas, and the process of depressurization-N and filling was repeated three times. 5,800 g of pure 1.1.2-trichloro-
1,2,2-trifluoroethane (hereinafter referred to as Freon 113) 13359 and methyl cellulose (viscosity 50 cp) 5.89 as a suspension stabilizer were charged, and the mixture was heated at 600 r.
The temperature was maintained at 50°C while stirring at pm. Next, a monomer mixture consisting of 4.8% by weight of VdF units, 91.8% by weight of HFP units, and 3.4% by weight of human TFE units was charged as a charging gas until it reached 15 kg/cII+3·G. Next, 25 g of a Freon 113 solution containing 10.5% by weight of diisopropyl peroxydicarbonate was charged as a catalyst to initiate polymerization. Due to polymerization, the pressure is 14.5 kg/cII! When it drops to 3・G, VdF
Unit 39.2% by weight, HFP unit 40.2IItj1%
, a mixed monomer consisting of 20.6% by weight of TFE units was continuously added as a continuous gas, and the pressure was again increased to 15 kg/cta3.
Returned to G. These operations were repeated to carry out the polymerization reaction for 17 hours. After the polymerization reaction was completed, the remaining mixing material was scavenged, and the resulting suspension was dehydrated using a centrifuge, thoroughly washed with water, and then dried under vacuum at 100°C to obtain about 5 kg of elastomer. The obtained fluoroelastomer was
Analyzed by NMR, VdF unit 38.9% by weight, RFP unit 42.9% by weight, TFE unit 18.2
% by weight, and the fluorine content is 69.5% by weight, (V)
was 157TA<17g.

Reference Example 2 In Reference Example 1, the charged gas composition was set to VdF unit 24.
3% by weight, HFP 1st place 69.5% by weight, 6 TFE units
．． 2% by weight, additional twisting gas composition in VdF units 45.4% by weight
, 389 is a fluorocarbon solution containing 31.7% by weight of HFP units, 22.9% by weight of TFE units, and 10.5% by weight of diisopropylperoxydicarbonate,
Polymerization pressure 9.5-10. Okg/clI! Polymerization was carried out in the same manner at 3.G for 16 hours to obtain about 6729 fluoroelastomers. This polymer composition has 48.0 VdF units.
Weight%, npp unit 30.4ffi amount%, TFE unit 2
1.6% by weight, and the fluorine content is 60.8% by weight (
? ) was 175m12/9.

Reference example 3 In reference example 1, pure 600g, Freon 113133
59, and the charged gas composition was 5.6% by weight in VdF units,
RFP unit 90.8% by weight, TFE unit 3.6% by weight,
The additional twisting gas composition was 39.2% by weight of VdF units, 40.1% of iE units for RFP, 20.7% by weight of TFE units, and diisopropyl peroxydicarbonate) 10.5
As a Freon solution containing 329% by weight, the polymerization pressure was 1
9/cm3・G to 4.5-15.0 and 11.5 as well
Polymerization was carried out for a period of time to obtain about 4 kg of fluoroelastomer. The polymer composition was 41.2% by weight of VdF units, R
The FP unit was 40.3% by weight, the TFE unit was 18.5% by weight, the fluorine content was 69.2% by weight, and the (V) was 131% by weight.

Reference example 4 An autoclave with an internal volume of 15Q equipped with an electromagnetic induction stirrer was sufficiently purged with nitrogen gas, and the pressure was reduced to -N and the filling was performed for 3
Pure 6I2, Freon, which was repeatedly purged with nitrogen and deoxidized under reduced pressure! 131.7Q diyodomethane 2
1 g and methylcellulose as suspension stabilizer (viscosity 5
0CI)) was charged and the temperature was maintained at 50°C while stirring at 600 rpm. Next, a mixed monomer consisting of 30.0% by weight of VdF units and 70.0% by weight of P units was used as a charge gas, and 15J21? /CIl! It was prepared until it reached 1.G. Next, as a catalyst, diisopropyl peroxydicarbonate 19. ! 279 of a Freon 113 solution containing 4 parts by weight was charged to start polymerization. When the pressure decreased to 14.57z9/cm"・G due to polymerization, a mixed monomer consisting of 62.7% by weight of VdF units and 37.2% by weight of HFP units was added as a continuous gas, and the pressure was reduced to 15.0% again. #g/ca+'-G. These operations were repeated to carry out the polymerization reaction for 10 hours. After the polymerization reaction was completed, the remaining mixing top was purged, and the resulting suspension was centrifuged. After dehydrating in a machine and washing thoroughly with water,
Vacuum drying at .degree. C. yielded a fluoroelastomer of about 3729. When the obtained fluorine-containing elastomer was analyzed by F NMR, VdF units were 63°8% by weight, )IF
The P unit is 36.2% by weight, and the fluorine content is 65.
4% by weight, (v) was 28rRQ/g.

Examples 1 to 3, Comparative Examples 1 to 3 The polymers obtained in Reference Examples were used alone or in combination as shown in the attached table, and kneaded with rolls. Further, the blending was carried out under the polyol vulcanization conditions described above. The table shows vulcanization properties, processability,
Indicates the physical properties of vulcanized rubber.

Claims (1)

[Scope of Claims] 1(A) Consists of vinylidene fluoride units, hexafluoropropylene units and tetrafluoroethylene units, and has a fluorine content of 68 to 71% by weight and a hexafluoropropylene unit content of 25 to 45% by weight (B) consisting of vinylidene fluoride units and hexafluoropropylene units and having a fluorine content of 64 to 67
A fluoroelastomer composition comprising 1 to 30 parts by weight of a fluoroelastomer having an intrinsic viscosity of 10 to 50 ml/g.