JPH075817B2 - Fluororesin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a fluororesin composition having excellent melt moldability and sliding properties, such as a sealing material and a bearing which require sliding properties. The present invention relates to a fluororesin composition applicable to injection molded products.

(Prior Art) Fluorocarbon resins are used in a wide range of fields due to their excellent properties (heat resistance, chemical resistance, weather resistance, etc.), but there are many examples of applications in which excellent sliding properties are applied. In the field of such sliding materials, tetrafluoroethylene resin (PTFE) has been regarded as the most excellent material and is widely used. However, since PTFE has a high melt viscosity even at temperatures above its melting point, it cannot be applied to melt molding such as extrusion molding and injection molding, which are used in general-purpose thermoplastic resins, and it has to be commercialized by cutting. Have

Therefore, a method is known in which a sliding filler such as PTFE powder or graphite is mixed with various thermoplastic resins to improve the sliding characteristics. (Plastic age 19
April 1986 issue P.162-171). Regarding the thermoplastic fluororesin, a sliding material having good friction and wear characteristics is obtained by a method of mixing vinylidene fluoride resin and PTFE into a soft fluororesin disclosed by the present inventors in Japanese Patent Publication No. 62-324324. This is disclosed in JP-A-62-195035.

(Problems to be Solved by the Invention) In many cases, thermoplastic fluororesins generally have high crystallinity and are unsuitable for mixing fillers that are likely to enter an amorphous portion. Therefore, in order to obtain a material having excellent melt moldability such as extrusion and injection and having good slidability while making use of the characteristics such as chemical resistance and oil resistance of the fluororesin, the soft fluororesin, like the amorphous fluororesin, is used. It is desirable to use a resin that combines a quality polymer and a crystalline polymer. In that sense, the method disclosed in JP-A-62-195035 is effective, but vinylidene fluoride resin (PVDF) is used to adjust the hardness and wear resistance of the mixed resin of soft fluororesin and PTFE. Since it is used, there are problems that the heat resistance is low, that the linear expansion coefficient is large, and that the shrinkage factor during molding is large.

Conventionally used PTFE sealing materials have a melting point of 327.
Although it is as high as ℃, PVDF is as low as 165 to 175 ℃, and some crystals start melting even below the melting point, so it is actually possible to use it only at a lower temperature.
Furthermore, in the measurement by the inventors, the linear expansion coefficient of the composition disclosed in JP-A-62-195035 is 25 to 29 × 10 ⁻⁵ cm / cm.
℃ and PTFE is larger than 7-12 × 10 ^-5 cm / cm ・ ℃. This property is particularly important in the sealing material used when the operating temperature rises and falls, and it is desirable that the sealing material have a numerical value as low as possible. On the other hand, the shrinkage rate at the time of molding is particularly important in the case of injection molding, but it is known that PVDF is larger than other thermoplastic fluororesins (1987 Plastic Material Commerce Handbook).

The present invention has been made to solve the problems of the injection-moldable sliding material formed by mixing the soft fluororesin, PTFE and PVDF.

(Means for Solving Problems) The present inventors completed the present invention as a result of various studies on the types of soft fluororesins to be used and the types of crystalline fluororesins to be mixed in order to control the melt fluidity. One or more monomers containing at least one fluorine-containing monomer as a soft fluororesin, and a monomer having at least one carbon-carbon double bond and a peroxy bond in the molecule (unsaturated peroxide). To produce a fluorine-containing copolymer (trunk polymer) having a glass transition temperature of room temperature or lower, and 100 to 100 parts by weight of this trunk polymer, a mixed monomer of ethylene and fluoroolefin is added in an amount of 10 to 80%. By weight of the soft fluororesin (A) graft-copolymerized, the ethylene-fluoroolefin copolymer (B) in the same combination as that used for the graft copolymerization is used. In addition, it has been found that by mixing the slidable filler (C), it is possible to obtain a fluororesin slidable material excellent in melt moldability with improved heat resistance, linear expansion coefficient and molding shrinkage. is there.

In the present invention, an elastic copolymer having a composition of fluororubber is suitable for the trunk polymer of the soft fluororesin to be used, which is a binary system of vinylidene fluoride (VDF) and hexafluoropropene (HFP), and VDF. Examples include monomer compositions such as a ternary system of HFP and tetrafluoroethylene (TFE) and a binary system of VDF and chlorotrifluoroethylene (CTFE). Unsaturated peroxides used in the production of the trunk polymer include t-butylperoxymethacrylate and t-butylperoxymethacrylate.
Examples thereof include unsaturated peroxyesters such as butylperoxycrotonate and unsaturated peroxycarbonates such as t-butylperoxyallylcarbonate and p-menthaneperoxyallylcarbonate.

Furthermore, a copolymer of ethylene and fluoroolefin is suitable as a crystalline fluororesin that is graft-polymerized to this trunk polymer, and its melting point is 200 ° C by copolymerizing with ethylene.
Examples of fluoroolefins that give the above copolymers include chlorotrifluoroethylene, tetrafluoroethylene, hexafluoroisobutene, and dichlorodifluoroethylene.

Further, the ethylene-fluoroolefin copolymer in the present invention may include a terpolymer in which 0.1 to 10 mol% of the third monomer is added. Examples of the third monomer include a fluorine-based monomer such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, hexafluoroisobutene, perfluoroalkyl vinyl ether, fluorinated butadiene and hydrocarbon. Examples include system monomers such as propylene, isobutene, isoprene, butadiene, acrylic acid ester, methacrylic acid ester, and vinyl ester.

In the present invention, a resin having a desired high melting point, a low linear expansion coefficient and a low molding shrinkage ratio can be obtained by a combination of a soft fluororesin, an ethylene copolymer and a slidable filler,
The mixing ratio of the ethylene copolymer (B) with respect to 100 parts by weight of the soft fluororesin (A) is 10 to 1000 parts by weight, preferably 30 to 1000 parts by weight, depending on the hardness of the intended product, the type of slidable filler, and the amount added. Selected between 300 parts by weight. When the mixing amount of the ethylene copolymer is high, the hardness is high and the viscosity at the time of melt molding is lower, but the crystallinity of the mixed resin is increased, and when the filler is mixed in a large amount, it becomes brittle.

As the slidable filler mixed with the mixed resin,
What is generally known as a slidable filler can be used, such as PTFE powder, carbon black, graphite, metal powder such as copper, bronze and tungsten, and phenol resin.

Sliding filler (C) that is mixed with 100 parts by weight of a mixed resin of a soft fluororesin (A) and an ethylene copolymer (B)
1 to 150 parts by weight, preferably 10 to 100 parts by weight is suitable. If it is less than this range, the effect of the filler will not be exhibited, and if it exceeds this range, the melt viscosity of the finally obtained mixed resin will increase and the moldability of the intended injection molding etc. will be impaired. Be seen.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Examples 1 to 5 1-1 Production of soft fluororesin (I) 120 kg pure water, 0.4 kg potassium persulfate, ammonium perfluorooctanoate in a 300 stainless steel autoclave
0.05kg, potassium dihydrogen phosphate 0.5kg and CFC R113
After adding 0.2 kg of t-butylperoxyallyl carbonate diluted to 5% by means of, exhausting and nitrogen substitution were repeated, 15 kg of vinylidene fluoride and 12.2 kg of chlorotrifluoroethylene were separately charged in 6 times and stirred for 10 to 10 Polymerization was carried out at 13 kg / cm ² G at 50 ° C for 10 hours.

As a product, latex 147 having a solid content of 16.5% by weight.
5 kg was obtained.

This latex 13 in a 300 stainless steel autoclave
Add 6.7 kg (solid content 22.56 kg), pure water 45.5 kg, ammonium perfluorooctanoate 0.05 kg, repeat evacuation and nitrogen substitution, then add 5% sodium sulfite aqueous solution 1, add chlorotrifluoroethylene 15.4 kg and ethylene.
3.7kg is divided into 3 times and charged, 3 to 12k while stirring
Polymerization was carried out at 40 ° C. for 16 hours at g / cm ² G.

A slurry was obtained as the product. The slurry was filtered by a centrifuge, and the hydropolymer was dried at 80 ° C for 2 days. The yield of the polymer [soft fluororesin (I)] is 35.7k.
The ECTFE content in the polymer was 36.8% by weight.

As a result of elemental analysis, the ECTFE of the polymer had a molar composition ratio of chlorotrifluoroethylene and ethylene of 53:47. Further, the melting point by DSC showed a clear peak at 18.1 ° at 2θ by 223 ° C and X-ray diffraction.

1-2 mixture Soft fluororesin (I) powder and ethylene-chlorotrifluoroethylene copolymer (ECTFE resin) (trade name: Halar, product of Ausimont, USA, grade 300)
No., a copolymer of chlorotrifluoroethylene and ethylene in a 1: 1 molar ratio, MI value 5kg / 10min 275 ° C, 2.16kg, melting point 241
C.) powder and the slidable filler were mixed in the weight ratios shown in Examples 1 to 5 in Table 1. For mixing, use Kawada Seisakusho Co., Ltd. 20 super mixer (20 volumes) 1000
Mix for 5 minutes at rpm.

1-3 Production of pellets of mixed resin The mixed resin powder obtained in 1-2 was passed through an extruder with a diameter of 30 mm manufactured by Tanabe Plastic Co., Ltd. to obtain pellets. The pellets are produced by the strand cut method, and the operating conditions of the extruder are an extrusion temperature of 230 to 250.
It was carried out at a temperature of 30 ° C and a rotation speed of 30 rpm.

1-4 Measurement of Melt Properties of Pellets To evaluate the melt moldability of the pellets obtained in 1-3, pellets were obtained at 270 ° C. and 100 kgf using a high-performance flow tester CFT-500 manufactured by Shimadzu Corporation. Flow value (ml / sec)
Was measured.

1-5 Preparation of flat plate for measuring physical properties and measurement of molding shrinkage Using injection molding machine IS-75E manufactured by Toshiba Machine Co., Ltd., using pellet obtained in 1-3, 2 mm thick, 100 × 130 mm flat plate shape A molded product of

The injection temperature was 250 to 270 ° C., and the injection pressure was 700 to 1000 kgf / cm ^{2 under} the operating conditions. At this time, the mold shrinkage in the flow direction and the direction perpendicular to the flow direction was measured from the dimension measurement of the obtained molded product.

1-6 Measurement of friction coefficient A 40 mmφ disc was punched out from the flat plate-shaped molded product obtained in 1-5 and the friction coefficient between this disc and iron (S45C) was measured by ORIENTEC CORPORATION's friction tester EFM- 5 kgf / cm ² using III-EN
Was measured at a pressure of 0.2 m / sec. The friction coefficient was a value one hour after the start of measurement.

1-7 Measurement of Wear Amount In the test of 1-6, the weight of the test piece after 120 minutes was measured, and the wear amount was calculated from the difference from the weight before the test.

1-8 Measurement of melting start temperature About 10 mg of a thin piece was scraped from the flat plate obtained in 1-5, and the rising temperature of the melting peak was measured using a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer Co., Ltd.).

1-9 Measurement of linear expansion coefficient 1 mm x 5 mm x 15 mm test piece was carved out from the flat plate obtained in 1-5, and a thermomechanical analyzer TMA (TM-700 manufactured by Vacuum Riko Co., Ltd.)
0) was used to measure the average linear expansion coefficient at 23 ° C to 100 ° C. Table 1 shows the measurement results of these 1-4 to 1-9.

Comparative Example 1 100 parts by weight of the soft fluororesin (I) obtained in Example 1-1 was added to 80 parts of PVDF (Solef1008 manufactured by Solvey) and PTFE.
Powder (Cefural Lube I manufactured by Central Glass Co., Ltd.)
90 parts were mixed in the same manner as in Example 1-2, and Example 1-
An attempt was made to pelletize by the same method as described in 3, but the elongation of the molten resin strand was poor, and continuous pellet production was impossible.

Comparative Examples 2 to 4 2-1 Manufacture of Soft Fluorine Resin (II) (A) Manufacture of Trunk Polymer 15 kg of water, 30 g of potassium persulfate, ammonium perfluorooctanoate 4 in a 30-volume stainless steel autoclave.
0 g and t-butyl peroxyallyl carbonate 30 g
After exhausting, 3.8 kg of vinylidene fluoride monomer and 2.3 kg of chlorotrifluoroethylene monomer were charged, and the polymerization reaction was carried out at a temperature of 51 ° C for 19 hours while stirring, and the rotation speed of stirring was increased at the end of the reaction. By doing so, the polymer was precipitated to obtain a powdery polymer. The yield after washing with water and drying was 5.0 kg, and the amount of active oxygen based on t-butylheroxyallyl carbonate in the copolymer was determined to be 0.041% by the iodometric titration method.

(B) Production of graft copolymer 2.16 kg of trunk polymer obtained by the above copolymerization reaction and CFC
22.5 kg of R113 was charged into a 30-volume stainless autoclave, and after evacuation, 1.5 kg of vinylidene fluoride monomer was charged and graft polymerization was carried out at 98 ° C. for 22 hours. The produced polymer was separated from the solvent, washed with water and dried to obtain 3.36 kg of a white powder of the soft fluororesin (II).

The melting point of this resin (endothermic peak temperature in DSC measurement) is 1
It was measured to be 67 ° C.

2-2 Blending, molding and measurement of physical properties The soft fluororesin and PVDF (Solef1008 manufactured by Solvey Co.) obtained in 2-1 and the slidable filler were used as Comparative Examples 2-4 in Table 1.
Were mixed in a weight ratio shown in Example 1 to produce pellets by the same operation as described in Example 1-3 (the molding temperature was 200 to 220).
Flow rate measurement (measurement temperature 220
C.), injection molding (molding temperature 220 to 240.degree. C.) of a flat plate-shaped molded article and measurement of physical properties described in 1-6 to 1-10.

The results obtained are shown in Table 1.

As can be seen from Table 1, heat resistance (melting start temperature) and molding shrinkage are significantly improved. Further, Comparative Example 3 is an improvement of Comparative Example 2 and is improved in friction and wear characteristics, but is inferior to Example 2 in terms of melting start temperature, shrinkage rate, and linear expansion coefficient.

It can be seen that the friction coefficient is lower than PVDF and ECTFE alone and the wear characteristics are superior to PTFE in both Examples and Comparative Examples.

(Effect of the Invention) By mixing the soft fluororesin used in the present invention with the ethylene-fluoroolefin copolymer and the slidable filler, a fluororesin molded article having excellent melt moldability and sliding properties can be obtained. it can.

Further, the fluororesin composition of the present invention has improved heat resistance, is superior in shrinkage characteristics during molding and dimensional stability due to temperature change, as compared with conventionally known sliding materials having excellent melt moldability. It is clear.

Claims (3)

[Claims] 1. A method comprising copolymerizing at least one monomer containing at least one fluorine-containing monomer with a monomer having a carbon-carbon double bond and a peroxy bond at the same time in a molecule, A fluorinated copolymer (trunk polymer) having a glass transition temperature below room temperature was produced, and 10 to 80 parts by weight of a mixed monomer of ethylene and fluoroolefin was graft-copolymerized with 100 parts by weight of this trunk polymer. A fluororesin composition having excellent melt moldability and slidability, which is obtained by mixing the soft fluororesin (A) with the above-mentioned copolymer (B) of ethylene and fluoroolefin and the slidable filler (C). 2. The mixing ratio of (A) and (B) is 100, which is (A).
10 to 1000 parts by weight of (B) with respect to 1 part by weight, and 1 to 150 parts by weight of the slidable filler is mixed with 100 parts by weight of the mixed resin of (A) and (B). The fluororesin composition according to claim 1. 3. The fluororesin composition according to claim 1, wherein the copolymer of ethylene and fluoroolefin has a melting point of 200 ° C. or higher.