JPH09157472A - Polytetrafluoroethylene powder composition and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of giving molded products hard to draw and break, low in coefficient of friction under sliding in the presence of lubricant and excellent in abrasion resistance, with filler hard to eliminate, and damaging no material as sliding partner. SOLUTION: This powder composition comprises 1-20wt.% of PTFE (polytetrafluoroethylene) fine powder 1-1000μm in average particle diameter, 10-50wt.% of talc powder 0.5-40μm in average particle diameter, and 30-89wt.% of PTFE molding powder 5-100μm in average particle diameter. This powder composition is obtained pref. by first mixing PTFE fine powder with talc powder to effect fibrillation of part of the PTFE fine powder and coating the talc powder with the fibrillated PTFE fine powder and then by mixing the resultant mixed powder with the PTFE molding powder.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention produces a molded product which is resistant to stretch breakage, has low friction and abrasion resistance in sliding in the presence of lubricating oil, and does not damage the mating material. Possible polytetrafluoroethylene (hereinafter P
TFE) powder composition and a method for producing the same.

[0002]

2. Description of the Related Art Filler-containing PTFE is widely used as a sliding material, a sealing material and the like. In such applications, many properties are required such that the molded product is difficult to stretch and break, has a low coefficient of friction, is excellent in wear resistance, and is excellent in heat resistance and chemical resistance, and does not damage the mating material. It The PTFE used here is a molding powder which is a powder for compression molding, while the filler is an inorganic filler such as glass fiber, carbon fiber, graphite, molybdenum disulfide, bronze powder, or an aromatic polyester, a polyimide, Organic fillers such as pophenylene sulfide are known (Japanese Patent Publication No. 49-36081).
JP-A-57-105442 and JP-A-58-193.
97 gazette). Furthermore, as an example of the special combination, PTFE powder (molding powder) having an average particle diameter of 5 to 500 μm and P having an average primary particle diameter of 0.05 to 0.5 μm are used.
A filler-containing PTFE composition comprising a TFE fine powder and a filler is also known (Japanese Patent Laid-Open No. HEI-1).
-225652). This composition is produced by adding an aqueous dispersion containing PTFE fine powder (fine powder) to a mixed powder of a molding powder and a filler, and then drying.

[0003]

However, in a sliding material or a sealing material formed from a conventional PTFE molding powder containing a filler, since PTFE itself has a non-adhesive property, the PTFE and the filler are not filled. Since the adhesiveness is poor with the adhesive, it is easy to break by stretching, the filler is easily separated from PTFE on the sliding surface and the sealing surface, and the filler exposed on the sliding surface damages the mating material that makes sliding contact or slides. There are problems such as causing an increase in resistance. In recent years, the material of the mating material with which the sliding material and the sealing material are in sliding contact has been changed to aluminum in order to save energy, reduce weight, and maintain free. In the conventional PTFE containing filler, the PTFE itself wears out. Although the material of the filler is designed so as not to do so, the PTFE resin itself and the mating material are greatly worn against the aluminum material and cannot be used.

[0004]

Means for Solving the Problems The present invention provides a molded article which is unlikely to be stretched and fractured, has a low friction coefficient in sliding in the presence of lubricating oil and is excellent in abrasion resistance, and is difficult to remove the filler. As a result of intensive studies aimed at providing a PTFE composition which does not damage a sliding partner, PTFE fine powders 1 to 20 having an average particle diameter of 1 to 1000 μm
10% by weight of talc powder having an average particle size of 0.5 to 40 μm
PTF consisting of 50% by weight and 30 to 89% by weight of PTFE molding powder having an average particle size of 5 to 100 μm
The present invention has been completed by discovering that the E powder composition is effective for the above purpose.

A molded article obtained by compression-molding such a powder composition and then firing the composition has improved adhesion between the PTFE molding powder and talc, and thus is unlikely to be stretch-broken, and the PTFE fine powder is gradually added when sliding. Since the surface of the talc powder is covered with the fiberized PTFE, the talc powder is less likely to be exposed and detached. As a result, the wear of the molded product itself and the wear of the mating material are small. Furthermore, it has good compatibility with lubricating oil and has a very small wear coefficient.

The PTFE fine powder used in the present invention has an average particle size of 0.05 to 0.5 obtained by emulsion polymerization.
Homopolymer of 0.5 μm tetrafluoroethylene (TFE), or polymer in which 1.0% by weight or less of a monomer copolymerizable with TFE (eg hexafluoropropylene or perfluoroalkyl vinyl ether) is copolymerized. The primary particles are coagulated and dried to form secondary particles. The particle size of the PTFE fine powder is not limited, but the average particle size may be 1 to 1000 μm, and a powder having an average particle size of 300 to 500 μm which is commercially available as a molding powder for paste extrusion is economically advantageous. Therefore, it is preferably used. It is known that the PTFE fine powder is fibrillated when compressed and sheared by a mixer or the like.

The PTFE fine powder for covering the surface of talc with the fibrous substance of PTFE tends to cover the surface of talc with the increase of the addition amount of the fibrous substance, but the addition of PTFE fine powder When the amount is large, the fluidity of the powder composition is lowered, and the handling property as a molding powder composition is deteriorated. Therefore, the amount of PTFE fine powder added is 1 in the range in which the surface of talc is sufficiently covered with fibrous PTFE and the fluidity of the powder composition is good.
-20% by weight, preferably 4-15% by weight.

The talc powder used in the present invention has an average particle size of 0.5 to 40 μm, preferably 1 to 30 μm. For powders having an average particle size of less than 0.5 μm, it becomes difficult to uniformly disperse them, and even for powders having an average particle size of more than 40 μm, it becomes difficult to uniformly disperse them. The blending ratio of such talc powder is 10 to 50% by weight, preferably 10 to 40% by weight. 10% by weight
If the amount is less than 50%, the PTFE molded product will be greatly worn, and if the amount added exceeds 50% by weight, the moldability will be poor and the mechanical properties of the molded product will be deteriorated.

The PTFE molding powder used in the present invention comprises a homopolymer of TFE obtained by suspension polymerization, or a monomer copolymerizable with TFE (for example, hexafluoropropylene or perfluoroalkyl vinyl ether). It is a pulverized product of a copolymerized product of not more than 0.0% by weight. The particle size of the PTFE molding powder is 5 to 100 μm, preferably 10 to 50 μm. The finely powdered PTFE molding powder is advantageous for uniformly mixing with the talc powder and the PTFE fine powder. The amount of the PTFE molding powder added is 30 to 89% by weight, preferably 45 to 86% by weight. If the amount added is less than 30% by weight, the moldability will deteriorate and the mechanical properties of the molded product will also deteriorate. If the amount added exceeds 89% by weight, the improvement of sliding characteristics such as abrasion resistance cannot be remarkably recognized.

The PTFE powder composition of the present invention preferably comprises 1 to 20 parts by weight of PTFE fine powder having an average particle size of 1 to 1000 μm and 10 to 50 parts by weight of talc powder having an average particle size of 0.5 to 40 μm. Then, the mixed powder is mixed with 30 to 89 parts by weight of PTFE molding powder having an average particle size of 5 to 100 μm to obtain a total amount of 100.
It is manufactured by adjusting the amount to be by weight. By mixing in this order, the surface of the talc powder, which is the filler, is sufficiently covered with the fibrous substance of PTFE.
Adhesion with the molding powder is improved, and it is possible to obtain effects such as prevention of detachment of talc powder in the subsequent steps. A molded product obtained by compression-molding the powder composition produced in this way and then firing it is difficult to stretch and break, and has effects such as a low coefficient of friction and excellent wear resistance. Note that P
A mixed powder of TFE fine powder and talc coated with a fibrous substance of PTFE is mixed with P having an average particle size of 5 to 100 μm.
Even in the step of mixing with 30 to 89 parts by weight of TFE molding powder, a part of the PTFE fine powder is further made into fibers, and the PTFE molding powder and PT
The mixed powder of talc coated with FE fibrous material is overlaid and coated with PTFE fibrous material.

However, talc powder, which is a filler, is added to PTFE.
When the molding powder is mixed first, the ratio of the talc powder alone covering the surface with the fibrous substance of PTFE is reduced, so that the above-described adhesion effect with the PTFE molding powder and the effect accompanying it are reduced. You also get less. Further, when PTFE fine powder, talc powder, and PTFE molding powder are mixed together at the same time, although a relatively large amount of PTFE fibrous substance is found on the surface of talc powder, talc powder is not enough to obtain the above effects. The surface of the is not covered with PTFE fibrous material.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0013]

Example 1 PTFE fine powder having an average particle size of 430 μm (manufactured by Mitsui DuPont Fluorochemicals; Teflon)
^(R) 6-J) 5% by weight and 35% by weight of talc powder having an average particle size of 20 μm were uniformly mixed in a Henschel mixer,
Next, PTFE molding powder with an average particle size of 35 μm (Mitsui DuPont Fluorochemical Co .; Teflon
^(R) 7-J) 60% by weight was added and uniformly mixed with a Henschel mixer. This composition was preformed at 700 kg / cm ² and fired at 370 ° C. for 3 hours to obtain a cylindrical molded product having a diameter of 50 mm and a height of 100 mm. Outer diameter 50
mm, 2 mm thick disc is cut and processed from AST
The test piece was punched out with a micro dumbbell described in M-1457, and the elongation value was measured and found to be 215%.

[0014]

[Example 2] 60% by weight of PTFE molding powder having an average particle size of 35 µm (manufactured by Mitsui DuPont Fluorochemicals; Teflon ^(R) 7-J), 35% by weight of talc powder having an average particle size of 20 µm, and an average particle size of 430 µm PTFE
5% by weight of fine powder (manufactured by Mitsui DuPont Fluorochemical Co .; Teflon ^(R) 6-J) was mixed uniformly at the same time with a Henschel mixer. A test piece similar to that of Example 1 was molded from this composition, and the elongation value was measured to be 56%.
Met.

[0015]

[Comparative Example 1] 60% by weight of PTFE molding powder (Teflon ^(R) 7-J manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) having an average particle size of 35 μm and 35% by weight of talc powder having an average particle size of 20 μm were uniformly mixed with a Henschel mixer. After mixing, then PTFE fine powder with an average particle size of 430 μm (manufactured by Mitsui DuPont Fluorochemicals; Teflon
5% by weight of ^(R) 6-J) was added and uniformly mixed with a Henschel mixer. A test piece similar to that of Example 1 was molded from this composition, and the elongation value was measured and found to be 35%.

[0016]

[Examples 3 to 5] PTFE fine powder having an average particle diameter of 430 µm (Mitsui DuPont Fluorochemical Co .; Teflon ^(R) 6-J) and talc powder having an average particle diameter of 20 µm were mixed at the ratio shown in Table 1 with a Henschel mixer. After uniformly mixing with PTFE, PTFE molding powder with an average particle size of 35 μm (Mitsui DuPont Fluorochemical Co .; Teflon® ⁾
7-J) was added at a ratio shown in Table 1 and uniformly mixed with a Henschel mixer.

700 g / c of this PTFE powder composition
m ² pre-molded, baked at 370 ° C. for 3 hours, outer diameter 60
A cylindrical molded product having a diameter of 40 mm, an inner diameter of 40 mm and a height of 50 mm was obtained. Outer diameter 50mm, inner diameter 46mm, thickness 2mm
Each of the test pieces was cut into a ring. The dynamic friction coefficient of this test piece was measured by the following friction and wear test method. Using the Matsubara friction and wear tester, A
L alloy die casting (ADC12 specified in JIS 1976 2118) (surface roughness Ra = 3 to 5 μm)
Was used. The dynamic friction coefficient is 10kg / cm ² at a load and 4m / se at a speed in oil for automatic transmission.
The measurement was performed by sliding for 1 hour at c. Table 1 shows the obtained results.

[0018]

[Comparative Example 2] A PTFE powder composition was prepared in the same manner as in Example 2 except that the PTFE fine powder was not added.
After molding, the coefficient of dynamic friction was measured. Table 1 shows the results.

[0019]

[Table 1]

As is clear from Table 1, the PTF of the present invention
It can be seen that the ring molded from the E powder composition has a dynamic coefficient of friction decreased by 42% at the maximum as compared with the ring molded from the powder composition of Comparative Example 2, and the slidability is very excellent.

[0021]

Example 6 PTFE fine powder having an average particle size of 430 μm (manufactured by Mitsui DuPont Fluorochemicals; Teflon)
^(R) 6-J) 10% by weight and 38% by weight of talc powder having an average particle size of 20 μm were uniformly mixed with each other, and then a PTFE molding powder having an average particle size of 35 μm (manufactured by Mitsui DuPont Fluorochemical Co .; Teflon ^{( R)}
7-J) (52% by weight) was added and uniformly mixed with a Henschel mixer. 500 kg / c of this PTFE powder composition
m ² pre-molded, baked at 370 ° C. for 3 hours, outer diameter 60
A cylindrical molded product having a diameter of 40 mm, an inner diameter of 40 mm and a height of 50 mm was obtained. Outer diameter 60mm, inner diameter 40mm, height 2mm
The ring was cut and used as a test piece.

[0022]

[Comparative Example 3] 44% by weight of PTFE molding powder (manufactured by Mitsui DuPont Fluorochemicals; Teflon ^(R) 7-J) having an average particle diameter of 35 μm and 40% by weight of bronze powder (manufactured by Fukuda Metal Foil Powder Co., Ltd .; B-AT350) % Evenly with a Henschel mixer, then the average primary particle size is 0.23 μm
Aqueous dispersion in which primary PTFE particles are dispersed (Mitsui
Dupont Fluorochemical Co .; Teflon ^(R) 30-J)
16% by weight of PTFE was mixed, agglomerated and granulated, and dried at 80 ° C. for 3 hours to obtain a PTFE powder composition. A test piece similar to that in Example 6 was prepared using this PTFE powder composition.

The impregnated amount of oil was measured for these test pieces by the following test method. The weight of each test piece was measured and set as the initial weight X. This was immersed in oil for auto transmission at 100 ° C. for 5 hours, and then the weight of each was measured to obtain Weight A. 11 more test pieces after measurement
After dipping in oil for auto transmission at 0 ° C. for 5 hours, vacuum suction was performed for 5 minutes, and then the pressure was returned to normal pressure. The weight of each of the test pieces was measured and designated as weight B. Further, the surface of the test piece was washed with CFC-113 (Mitsui DuPont Fluorochemical Co., Ltd .; Freon ^(R) 113), and each weight of the test piece was measured and defined as weight C. From the difference between the initial weight X and the weights A, B, and C, the oil impregnation amounts a, b, and c were obtained. Table 2 shows the results.

[0024]

[Table 2]

As is apparent from Table 2, the PTF of the present invention
The ring formed from the E powder composition has a better oil impregnation property than the ring formed from the powder composition of Comparative Example 4, so that the dynamic friction coefficient can be further reduced.

[0026]

EFFECT OF THE INVENTION The PTFE powder composition of the present invention is such that a molded article is less likely to break, has a low dynamic friction coefficient in sliding in the presence of lubricating oil and is excellent in abrasion resistance, and the filler does not easily come off and slide. It shows the sliding characteristics that it does not damage the moving mating material. Moreover, it has excellent heat resistance and chemical resistance.

Claims (4)

[Claims] 1. A polytetrafluoroethylene fine powder having an average particle size of 1 to 1000 μm, 1 to 20% by weight, a talc powder having an average particle size of 0.5 to 40 μm, 10 to 50% by weight, and a polyparticle having an average particle size of 5 to 100 μm. A polytetrafluoroethylene powder composition comprising 30 to 89% by weight of tetrafluoroethylene molding powder. 2. The powder composition according to claim 1, which contains 4 to 15% by weight of polytetrafluoroethylene fine powder. 3. The powder composition according to claim 2, which contains 10 to 40% by weight of talc powder. 4. A polytetrafluoroethylene fine powder having an average particle size of 1 to 1000 μm, 1 to 20 parts by weight, and a talc powder having an average particle size of 0.5 to 40 μm, 10 to 50 parts by weight are first mixed, and then this mixed powder. Average particle size 5 to 1
A method for producing a polytetrafluoroethylene powder composition, which comprises mixing 30 to 89 parts by weight of a polytetrafluoroethylene molding powder having a particle diameter of 00 μm to make the total amount 100 parts by weight.