JP2001247736A - Fluororesin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluororesin composition without deteriorating mechanical characteristics even when a large amount of a filler is compounded. SOLUTION: This fluororesin composition is obtained by using a mixture of 98.0-99.9 wt.% of polytetrafluoroethylene with 0.1-2.0 wt.% of a melt-flowable fluororesin which has 0.1-0.5 μm number-average particle diameter of primary particles as a fluororesin in the fluororesin composition comprising 40-99.9 pts.wt. of the fluororesin and 0.1-60 pts.wt. of the filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fluororesin composition, and more particularly, to a fluororesin composition containing polytetrafluoroethylene and a filler and having excellent moldability and mechanical properties.

[0002]

2. Description of the Related Art Polytetrafluoroethylene (hereinafter PT)
FE) has excellent properties such as heat resistance, chemical resistance, weather resistance, electrical insulation, water / oil repellency, non-adhesiveness, and self-lubricating properties. Widely used for industrial purposes.

[0003] Practical molding PTFE is roughly classified into two types: fine powder and molding powder (or granular resin). Fine powder is a powder obtained by aggregating, separating and drying PTFE from a latex obtained by an aqueous dispersion (emulsion) polymerization method, and is generally processed by paste extrusion molding performed by mixing a liquid lubricant, and used for sealing. Used for materials, tubes, wire covering materials, etc. On the other hand, molding powder is obtained by finely pulverizing granular PTFE obtained by a suspension polymerization method, and is generally a powder having an average particle size of 20 to 100 μm, and is processed by compression molding or ram extrusion molding, and is used for bearings, sliding pads. Such as sliding material, packing,
It is widely used as a sealing material for gaskets, seal rings, valve seats and the like.

[0004] As described above, PTFE molding powder is generally mainly used for sliding materials and seal materials. For example, when used for valve seats, particularly excellent barrier performance is required. However, in general, PTFE alone may not satisfy mechanical properties such as abrasion resistance and compression creep resistance, and various fillers are added to molding powder to improve mechanical properties. As the filler, generally, an inorganic filler such as glass fiber, graphite, carbon fiber, molybdenum disulfide, and bronze powder, or an organic filler such as aromatic polyester, polyimide, and polyphenylene sulfide is known. Mixed with molding powder alone or in combination.

[0005] The molding powder and the filler-containing molding powder are generally formed into a final product by compression molding, firing and then cutting. However, in addition to being required to satisfy the above-mentioned mechanical properties, it is necessary to satisfy the powder characteristics. Better fluidity and higher bulk density are desired.

Although various sizes of compression molds are used depending on the application, the molding powder itself and the powder obtained by mixing the molding powder and the filler have almost no fluidity. It is known that the powder density in a mold is inferior due to low bulk density. However, when a mold having a thin resin filling portion is used or when automatic molding is performed, particularly excellent filling properties are required, and excellent fluidity and high bulk density of the raw material powder are required.

In order to impart fluidity to the molding powder and the filler-containing molding powder and to improve the bulk density, the molding powder having an average particle diameter of several tens μm is generally converted into granular particles having an average particle diameter of several hundred μm. And granulate. As a method of granulation, for example, in the presence of water and an organic liquid that has little solubility in water and can wet PTFE, the mixture is stirred with a molding powder or a molding powder containing a filler to form a droplet of the water-insoluble organic liquid. A method of coagulation and granulation is known (JP-B-56)
-8044, JP-A-57-18730, JP-A-10-251413 and the like).

[0008]

As described above, it is desired that the molding powder and the filler-containing molding powder have better fluidity and higher bulk density from the viewpoint of productivity during processing. In order to improve the fluidity of the granulated powder, generally, the density of the granulated particles is increased, that is, the bulk density of the granulated powder is increased, the shape of the granulated particles is more round, and the surface of the granulated particles is increased. It is known that smoother and harder is preferable.

However, if fluidity is required too much, there are many cases where properties such as mechanical strength and barrier properties required for final molded articles are lost. It is related to the very high melt viscosity characteristic of PTFE. Since PTFE has a very high melt viscosity, it is impossible to perform injection molding or extrusion molding by melting a resin used for molding many thermoplastic resins. A special molding method of firing without compression after compression molding is used. Therefore, the compactness in compression molding also affects the compactness of the final molded product, and for example, mechanical properties and gas barrier properties may change.

In general, it is known that PTFE molding powder to which a filler has been added tends to lower the mechanical properties of a molded product as compared to PTFE molding powder alone. As a means for solving this problem, it is known that a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer is blended in an amount of 3 to 30% by weight, but there is a problem in cost due to a large amount of addition. In addition, when the filler is white or light-colored, a coloring problem may occur due to decomposition of volatile components inside the molded article. In addition, when the PTFE molding powder to which the filler is added is granulated into granular particles, the mechanical properties are further reduced.

[0011]

Means for Solving the Problems A conventional PT as described above is used.
In order to solve the problems of FE molding powder, the present invention relates to a fluororesin composition comprising 40 to 99.9 parts by weight of a fluororesin and 0.1 to 60 parts by weight of a filler, wherein the fluororesin is made of PTFE98. 0.099.9% by weight and a melt-flowable fluororesin of 0.1 to 2.0% by weight, and the primary particles of the melt-flowable fluororesin have a number average particle size of 0.1 to 0.5 μm. A fluororesin composition which is

[0012]

DETAILED DESCRIPTION OF THE INVENTION The fluororesin component contained in the fluororesin composition of the present invention preferably has an average particle size of 1 to 100.
μm PTFE and primary particles having an average particle size of 0.1 to 0.5
μm melt-flowable fluororesin. The ratio of the melt-flowable fluororesin to the total amount of the fluororesin component is 0.1 to 0.1.
It is 2.0% by weight, preferably 0.2-1.5% by weight, more preferably 0.6-1.5% by weight. When the proportion of the melt-flowable fluororesin is less than the lower limit, there is almost no improvement in mechanical strength, gas barrier properties and the like. On the other hand, even if the ratio of the melt-flowable fluororesin is increased beyond the upper limit, no further improvement effect can be expected, and if the resin composition is white or light-colored, coloring tends to become a more problematic problem.

The PTFE used in the present invention is usually PTFE obtained by a suspension polymerization method, and includes modified PTFE obtained by copolymerizing a TFE homopolymer or a comonomer. Examples of the comonomer include a compound represented by the formula (I): CF ₂ ＣＦCF—ORf (I) wherein Rf is a perfluoroalkyl group having 1 to 10 carbon atoms, a perfluoro (alkoxyalkyl) group having 4 to 9 carbon atoms, Formula (II):

Embedded image Wherein m is 0 or an integer of 1 to 4, or an organic group represented by the formula (III):

Embedded image (In the formula, n represents an integer of 1 to 4).]

The carbon number of the perfluoroalkyl group is 1
-10, preferably 1-5. By setting the number of carbon atoms of the perfluoroalkyl group within this range, it is possible to obtain an effect of being excellent in creep resistance while maintaining the property of being unable to be melt-molded. Examples of the perfluoroalkyl group include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl, and the like.From the viewpoint of creep resistance and monomer cost, perfluoropropyl is used. Vinyl ether is preferred. When the amount of the comonomer is in the range of 1.0 to 0.001 mol%, an effect of excellent creep resistance can be obtained.

As the melt-flowable fluororesin, tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (hereinafter referred to as PFA), tetrafluoroethylene / hexafluoropropylene copolymer (hereinafter referred to as FEP), tetrafluoroethylene / hexafluoro Examples thereof include a propylene / perfluoroalkyl vinyl ether copolymer (hereinafter referred to as EPA) and a tetrafluoroethylene / perfluoromethyl vinyl ether / perfluoropropyl vinyl ether copolymer (hereinafter referred to as MFA). Among them, PFA is preferable.

As the filler, conventional fillers such as inorganic fillers such as glass fiber, graphite, carbon fiber, molybdenum disulfide, and metal powder (such as bronze powder), and organic fillers such as aromatic polyester, polyimide, and polyphenylene sulfide. The filler added to the PTFE molding powder can be used. Among them, glass fibers are preferred.

When the fluororesin composition of the present invention is used as a granulated powder, the form is preferably a number average particle diameter of 100 to 1000 μm. The expected improvement in handleability cannot be obtained. On the other hand, if it is larger than this, there may be a problem when using a mold having a thin resin-filled portion.

[0018]

The present invention will now be described more specifically with reference to examples and comparative examples. In Examples and Comparative Examples,
The physical properties of the molded article of the fluororesin composition were measured as follows. 1) Apparent density Measured according to JIS K6891-5.3. 2) Tensile strength and elongation A mold having an inner diameter of 100 mm was filled with 25 g of a fluororesin composition sample, and the sample was uniformly leveled.
The pressure is gradually applied until the pressure becomes 9 MPa, and the pressure is further maintained for 2 minutes to perform preforming. The preform is taken out of the mold, put into a hot air circulating furnace preset at 370 ° C., fired for 3 hours, taken out, and cooled to room temperature to obtain a fired body. This fired body was punched out with a JIS No. 3 dumbbell,
According to SK6891-58, the sample is pulled at a tensile speed of 200 mm / min using an autograph having a total load of 500 kg, and the stress (tensile strength) and elongation at break are measured.

3) Gas barrier performance test A cylindrical mold having an inner diameter of 50 mm is filled with 210 g of a sample,
After leveling the sample uniformly, pressurize at 13 mm / min.
Hold at 9 MPa for 2 minutes to perform preforming. The preform is taken out of the mold, placed in a hot air circulating furnace preset at 370 ° C., calcined for 5.5 hours, and then cooled to room temperature at 50 ° C./hour to obtain a cylindrical molded body. This molded body is made to have a thickness of 1.5.
Slice to 0 mm to obtain a gas barrier performance test sample. The obtained test sample is sandwiched between the upper and lower plates of the test jig. The lower plate has a hole of 30 mmφ, and gas pressure can be applied to the test sample from a pipe connected to the hole.
The upper plate has a porous portion having a diameter of 2 mm in a portion facing the hole of the lower plate, and has a structure capable of holding a liquid (water) above the porous portion.
After applying pressure to the test sample with nitrogen gas at 1.96 MPa for 2 hours, the state of leakage of the nitrogen gas is visually determined. A: No leakage B: Bubbles are observed in the upper plate porous portion C: Bubbles continuously leak from the upper plate porous portion

4) Color Check A mold having an outer diameter of 50 mm and an inner diameter of 20 mm is filled with 19 g of the sample, and the sample is uniformly leveled.
Hold at 48.9 MPa for 5 seconds to perform preforming. The preform is taken out of the mold, placed in a hot air circulating furnace preset at 370 ° C., baked for 5.5 hours, and cooled to room temperature at 50 ° C./hour to obtain a sample. The sample is immersed for 2 minutes in a low toxicity dye penetrant F-3B (Eishin Chemical Co., Ltd.) and then washed with water. The side surface of the obtained sample is visually observed, and is determined based on the number of red spots of 0.3 mmφ or more. A: 3 or less B: 4 to 10 C: 11 or more

5) Coloring A cylindrical mold having an inner diameter of 50 mm is filled with 210 g of the sample, and the sample is uniformly leveled.
Hold for 2 minutes at MPa and perform preforming. The preform is taken out of the mold, placed in a hot air circulating furnace preset at 370 ° C., calcined for 5.5 hours, and then cooled to room temperature at 50 ° C./hour to obtain a cylindrical molded body. The molded body is divided horizontally so that the center in the height direction becomes a plane, and Z
Measure the value. Z value is XYZ defined by International Commission on Illumination
It was measured based on the Z value measurement method of the system.

Examples 1 to 5 and Comparative Examples 1 to 4 PTFE powder (Polyflon M-1 manufactured by Daikin Industries, Ltd.)
2: average particle size 25 μm) and aqueous dispersion polymerization (emulsion polymerization)
Powder (primary particle size 0.25 μm; 3)
A melt flow rate at 72 ° C. 25 g / 10 min) and glass fibers (average diameter 11 μm; average fiber length 25 μm) previously treated with a silane coupling agent were added to a Henschel mixer having an inner volume of 10 L in an amount shown in Table 1. In addition,
Mix for 10 minutes.

Into a 10-L stainless steel manufacturing vessel equipped with a stainless steel stirring blade and a jacket for temperature control, 7 L of deionized water and 2 kg of the mixture obtained above were charged.
After stirring at 00 rpm for 1 minute, dichloromethane 1.2L
Was added. Furthermore, at room temperature at 1000 rpm, 10
After stirring for 4 minutes, continue stirring at 1000 rpm for 4 minutes.
The temperature was raised to 40 ° C. over 0 minutes, and the stirring was stopped. The obtained granules were separated from water and dried at 160 ° C. for 16 hours using a hot-air circulation dryer. Table 2 shows the physical properties of the composition.

[0024]

[Table 1]

[0025]

[Table 2]

When the results of Examples 1 to 5 and Comparative Examples 2 to 4 are compared with Comparative Example 1 in which the fluororesin component is only PTFE, the ratio of PFA is lower in tensile strength, tensile elongation, gas barrier properties and color check. There is almost no improvement in very few samples, and the effect of improvement is seen in PF
It can be seen that this is the case when the ratio of A is 0.1% or more. Further, as the proportion of PFA increases from 0.1%, the effect of improving these characteristics increases, but even when the ratio exceeds 3.0%, the effect of improvement does not further improve. On the other hand, coloring is PF
As the ratio of A increased, it tended to worsen.

Examples 6-8 and Comparative Examples 5-7 The same PTFE powder, PFA powder and glass fiber as used in Example 1, graphite (manufactured by Chuetsu Graphite Co., Ltd.), Sumika Super (Sumitomo Chemical Industries, Ltd.) The same procedure as in Example 1 was repeated, except that the main component “p-hydroxybenzoic acid polyester”) and molybdenum disulfide (manufactured by Sumiko Lubricants Co., Ltd.) were mixed with the composition shown in Table 3. Granules were produced and their physical properties were measured. Table 4 shows the results
Shown in

[0028]

[Table 3]

[0029]

[Table 4]

From the results shown in Table 4, PFA was added to the fluororesin component.
It can be seen that by adding, regardless of the type of filler, both tensile strength and tensile elongation are improved.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C08L 27/18 (C08L 27/18 27:12) 27:12) (72) Inventor ▲ Hiro ▼ Jiro Honmoto No. 1-1 Nishi-Itsuya, Settsu-shi, Osaka Daikin Industries, Ltd. Yodogawa Works F-term (reference) 4J002 BD15W BD15X BE04X CF04Y CF16Y CM04Y CN01Y DA016 DA026 DA066 DG026 DL006 FA046 FA08 FD01Y FD016 4J100 AC26P AE09Q BA07Q CB18Q

Claims (3)

[Claims] 1. A fluororesin composition comprising 40 to 99.9 parts by weight of a fluororesin and 0.1 to 60 parts by weight of a filler, wherein the fluororesin is polytetrafluoroethylene 9
8.0 to 99.9% by weight and the melt-flowable fluororesin 0.1 to 0.1
A fluororesin composition comprising a 2.0% by weight mixture, wherein the number-average particle diameter of primary particles of the melt-flowable fluororesin is 0.1 to 0.5 μm. 2. The fluororesin composition according to claim 1, wherein the melt-flowable fluororesin is a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer. 3. The fluororesin composition according to claim 1, which is in the form of a granulated powder having a number average particle size of 100 to 1000 μm.