JPH01182335A - Polyolefin resin composition - Google Patents

Abstract

PURPOSE:To obtain a polyolefin resin composition, containing a specific polyethylene and specified mica powder as essential components, having sliding and mechanical characteristics, dimensional accuracy and economical efficiency and effectively usable for molding structural parts having sliding parts. CONSTITUTION:A polyolefin resin composition containing (A) polyethylene having 500000-1200000 viscosity-average molecular weight and 0.94-0.97g/cm<3> density, (B) 5-60wt.% mica powder having <=200 weight-average flake diameter and >=10 weight-average aspect ratio and, as necessary, (C) a silane coupling agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition for sliding members that has excellent sliding properties, mechanical properties, and dimensional accuracy and is relatively inexpensive. More specifically, the sliding material contains specific polyethylene and specific mica powder as essential components, and has excellent sliding properties such as friction resistance and abrasion resistance, mechanical properties such as elastic modulus, strength and strength, and dimensional accuracy. The present invention relates to a resin composition for parts. The resin composition of the present invention is particularly effectively used in molding structural parts having sliding parts by taking advantage of its excellent sliding properties, mechanical properties, dimensional accuracy, and cost.

[Conventional technology]

Conventionally, various thermoplastic resins and thermosetting resins containing carbon fiber, fluororesin powder, and oil have been used for sliding parts, but although these resins have excellent sliding properties, they are expensive. It is expensive, and there are economical problems when using it for molding large parts. Furthermore, since these resins are formulated for use in sliding parts, when used as materials for structural parts, their properties such as elastic modulus, toughness (elongation, impact strength), and strength are unsatisfactory. there were.

On the other hand, although it has long been known that ultra-high molecular weight polyethylene has excellent sliding properties, the melt viscosity of this polyethylene is extremely high, making injection molding impossible. Recently, a new polyethylene that has both injection moldability and sliding properties has been developed.
l 38, Plate 3, P78) Although this resin is suitable as a material for structural parts with sliding parts due to its sliding properties and economic efficiency, it is necessary to further improve the friction and wear properties. 'In addition, the purpose of the present invention is to improve mechanical properties such as elastic modulus, strength, and thermal deformation temperature. More specifically, the goal is to improve the wear resistance, elastic modulus, strength, and heat distortion temperature of polyethylene without impairing its sliding properties and economic efficiency. The most commonly used method for improving the elastic modulus, strength, and heat distortion temperature of resin is glass fiber filling.
Resin filled with glass fiber wears the mating metal in the sliding part, and is not recommended for reasons such as poor dimensional accuracy, cracks, and unsatisfactory roundness of the sliding part. As a result of intensive research into improving the above-mentioned problems, the inventors have developed polyethylene whose molecular weight and density are within a specific range, and mica powder whose weight-average flake diameter and weight-average aspect ratio are within a specific range. We discovered that by combining these and keeping the mica powder blend within a specific range, we could obtain a composition that was excellent in terms of F, sliding properties, force characteristics, V-method accuracy, and economical efficiency. The present invention has now been completed.

That is, the present invention has a viscosity average molecular weight of 500,000 to 1,200,000,
Contains polyethylene with a degree of 0.94 to 0.97 g/cm3 and mica powder as essential components, the weight average flake diameter of the mica powder is 200 μm or less, the weight average aspect ratio is 10 or more, and the blending ratio is 5 to 60. The polyethylene used in the present invention, which is a resin composition with a weight of -, must have a viscosity average molecular weight of 500,000 to 1,200,000 and a density of 0.94 to 0.97 f/d. . Compositions using polyethylene with a molecular weight of less than 500,000 have insufficient wear resistance, and compositions using polyethylene with a molecular weight of more than 1.2 million are difficult to mold by injection molding, extrusion molding, etc. .

On the other hand, if the density of the polyethylene used in the present invention is less than 0.94 f/-, the wear resistance and mechanical properties of the composition will be unsatisfactory. There is no particular restriction on the upper limit of the density of polyethylene used in the present invention, but
In regions that do not contain large amounts of copolymerized monomers, the upper limit of the density of polyethylene is substantially 0.97 t/aA.

The polyethylene used in the present invention is preferably modified by copolymerization with a monomer having a polar group. Examples of monomers having a polar group include unsaturated carboxylic acids or derivatives thereof, and representative examples thereof include monobasic carboxylic acids having at most 10 carbon atoms and at least one double bond. acid (e.g. acrylic acid, methacrylic acid) and a carbon number of at most 1
Examples include dicarboxylic acids having at least 5 double bonds and at least one double bond (e.g. maleic acid 1!2) and anhydrides of said dicarboxylic acids (e.g. maleic anhydride, hymic anhydride). However, luic acid and maleic anhydride are particularly preferably used. Modification of polyethylene with these polar group-containing monomers can be carried out using known methods such as liquid phase method, suspension method, melting method, etc., and there is no restriction at all, and in the composition of the present invention.

It is not necessarily necessary that the entire amount of the polyethylene component used be polyethylene modified with polar groups, and only a portion of the polyethylene component used may be polyethylene modified with polar groups.

In addition, the polyethylene used in the present invention may contain other monomers such as propylene, butene-1, pentene, 4-methylpentene-1, α-olefins such as hexane, octene, and decene, diolefins such as butadiene and isogrene, and cycloolefins such as cyclopentene, cyclohexene, cyclopentadiene, and norbornene may be copolymerized.

The type of mica powder used in the present invention is not particularly limited, and can be selected from a wide range of muscovite, phlogopite, synthetic phlogovite, and sericite. The mica powder needs to have a weight average flake diameter of 200 μm or less and a weight average aspect ratio of 10 or more.

The weight average flake diameter j of mica powder in the present invention is
The powder is classified using microsieves or sieves with various openings, and the results are plotted on a Rosin-R 1ar diagram. Using sheep's eye opening jso (
This is the value defined by equation 1) or (2).

When using microsheep 1=lso (
1) When using a sieve 1=4-1so(
2) Here, the part of the mica powder with a large particle size is classified by a sieve, and the part with a fine particle size is classified by a microsiep.

The weight average flake diameter of the mica powder used in the present invention must be 200 μm or less, and must be 15 to 1
00 μm is desirable. Compositions using mica powder with a weight average flake diameter exceeding 200 μm cannot be used because the wear properties will be poor. On the other hand, there is no particular restriction on the lower limit of the weight average flake diameter of the mica powder used in the present invention, but mainly from the viewpoint of economic efficiency, be. .

In the present invention, the weight average aspect ratio α of mica powder is calculated using the weight average flake diameter l, the weight average flake thickness d of the mica powder measured by the following method, and the equation (8). is the value.

α=l/d (The weight average flake thickness d of mica powder in equation 81(8) is C,
Water surface single-particle film properties (C, E) reported by Capes et al.
, Capes and R.C., Coleman,
Ind, Eng, Chem.

Fundam, 12.124 (1973)) K! D.I.
This is a value calculated according to equation (4) using the occupied area S of the flakes on the water surface where the IQ is determined tL.

Here, W is the weight of the mica powder used for measurement, p is the density of mica, and (1-ε) is the occupancy rate when the mica powder is in the closest packed state on the water surface. The weight average aspect ratio of the mica powder used in the composition of the present invention is 10.
It is necessary that the number is 15 or more, and it is desirable that the number is 15 or more. Compositions using mica powder with a weight average aspect ratio of less than 10 are not only unsatisfactory in mechanical properties such as modulus of elasticity, strength, and heat/deformation temperature, but also have poor dimensional accuracy of molded products, such as recoil and roundness. cannot be used because it is unsatisfactory. Note that there is no particular restriction on the upper limit of the weight average aspect ratio of the mica powder used in the present invention.

The blending ratio of mica powder in the composition of the present invention is 5 to 60
It is necessary that the weight is -, preferably 10 to 5
0% by weight, more preferably 15 to 45% by weight◇
When the blending ratio of mica powder is less than 5% by weight, the effect of improving mechanical properties such as sliding properties, elastic modulus, strength, and heat distortion temperature is unsatisfactory. On the other hand, if the blending ratio of mica powder exceeds 60% by weight, the viscosity of the composition during molding will be extremely high and molding will become extremely difficult. It's inappropriate.

In the composition of the present invention, it is preferable that a silane coupling agent is used in addition to the polyethylene x mother powder. The blending of a silane coupling agent is effective in improving the sliding properties of the composition of the present invention as well as mechanical properties such as strength, elastic modulus, and heat distortion temperature. There are no restrictions on the type of silane coupling agent used for 54IP, but
Silane coupling agents that form amino groups, epoxy groups, or double bonds, such as T-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Methacryloxypropyltrimethoxysilane and the like are particularly preferably used. There is no particular restriction on the addition rate of the silane coupling agent in the composition of the present invention, but numerically it is 0.00% by weight of the mica powder blended into the composition.
The amount is 2 to 2% by weight, preferably 0.3 to 1% by weight. The silane coupling agent is attached to the surface of the mica powder in advance,
The silane coupling agent-treated mother powder may be used by melt-kneading polyethylene, or it may be added directly to polyethylene during melt-kneading.

In order to further improve sliding properties and friction/wear properties, the composition of the present invention may contain various additives other than mica powder, such as carbon fiber, fluororesin powder, molybdenum disulfide, and glass beads. In addition, in order to improve the mechanical properties, electrical properties, etc. of the composition, reinforcing materials such as glass fibers may be added to the extent that it does not immediately affect the sliding properties. It is free to add various fillers such as talc, carbonized calcium, barium sulfate, and wollastonite, whiskers such as potassium titanate, and conductivity improving fillers such as carbon black, carbon fiber, and metal powder. . Other 1 In the composition of the present invention, various known additives, such as deterioration inhibitors, colorants, lubricants, mold release agents, antistatic agents, etc., may be appropriately added within the range that does not impair its performance. , there is no problem in adding it.

The composition in the present invention is produced by kneading each component using equipment such as a single screw extruder, a twin screw extruder, a kneader and one twin screw roll. Although there are no particular restrictions on the type of cross-wire material used or the cross-wire conditions, the polyethylene component used in the present invention has a high melt viscosity, so it is possible to improve the dispersibility of mica powder in polyethylene and prevent cross-wires. In order to minimize damage to the mica powder inside, it is desirable to set the thermal resistance divided by crosstalk to a slightly higher value than that of general polyethylene.

The f1 product in the present invention is injection molded or extruded.

It can be molded into any shape by compression molding, blow molding, etc., such as electrical parts, electronic parts, mechanical parts, automobile parts, structural parts, sheets, profile extrusions, rods, pipes, etc., and used for various purposes. However, by taking advantage of its excellent friction, wear characteristics, dimensional accuracy, and rigidity, it can be used for molded products that require sliding properties, such as copying machines, printers, paper sheet conveyance rollers for facsimile machines, idle pulleys for belts, gears, etc. It is preferably used as a replacement part for the sliding part where cams and cross roller bearings were conventionally used, and as plungers for keyboard keyswitches used in computers, etc.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but these are not intended to limit the present invention in any way. [Examples] Example 11 Comparative Example 1 Viscosity average molecular weight 800,000, density 0.965 f/ Phlogopite having a weight-average fushik diameter of 40 μm and a weight-average aspect ratio of 30 was added to and mixed with polyethylene of clI, and the mixture was melt-kneaded and pelletized using a single-screw extruder with a cylinder temperature set at 275°C. The obtained pellet was molded using an in-line screw injection molding machine under the conditions of a cylinder temperature of 275°C, an injection pressure of aooKg/ffl, and a mold temperature of 80°C.
Vertical 80■, Yo: +B□m, thickness 3vm flat plate test piece (
(for friction and wear test), length 127cm, width 13cm,
A square bar test piece (for measuring flexural modulus) with a thickness of 6.41E1 was prepared, and physical properties were measured by the method shown below.

Friction and wear test: ■Using a friction and wear tester manufactured by Orientic, using 545c as the mating material, the friction speed was 503 /
see, load 15 Kg/1 tAf), the specific wear amount (unit distance,
The wear volume per unit load) and the coefficient of dynamic friction were determined.

In addition, the friction speed was kept constant and the load was increased stepwise, and the operation was carried out for one hour under each load to determine the limit load that would cause the test piece to melt and the frictional force to increase rapidly, and the surface pressure P (
The limit Pv value was determined by the product of Kp/-) and friction velocity V (cm/lee).

Flexural modulus: Measured according to ASTM D-790.

The measurement results are shown in Table-1. Polyethylene alone (comparative example 1
), it is clear that the addition of mica powder with a specific shape greatly improves the specific wear amount, friction coefficient, and elastic modulus, resulting in a composition with excellent sliding properties and mechanical properties. It is.

Example 2 A test piece was prepared in the same manner as in Example 1 except that polyethylene with a viscosity average molecular weight of 600,000 and a density of 0.968 g/cm3 was used, and the results of characteristic evaluation are shown in Table IK. Like the composition of Example 1, it has excellent wood sliding properties and mechanical properties.

Comparative Examples 2 and 3 Test pieces were prepared in the same manner as in Example 1 and Comparative Example 1, except that polyethylene with a viscosity average molecular weight of 300,000 and a density of 0.965 f/c4 was used, and the results of characteristic evaluation are shown below. -1. As is clear from Table 1, no improvement in sliding properties was observed due to the addition of mica powder, which is different from that in Example 1.

Comparative Example 4 A test piece was prepared in the same manner as in Example 1, except that polyethylene with a viscosity average molecular weight of 800,000 and a density of 0.930 g/cm3 was used, and its characteristics were evaluated. The results are shown in Table-1. Flexural modulus is unsatisfactory.

Example 3 Polyethylene with a viscosity average molecular weight of 1 million and a density of 0.96 f/cIA and muscovite powder with a weight average particle size of 90 μm and a weight average aspect ratio of 50 were mixed in the formulation shown in Table 1,
Using the same extruder as used in Example 1, the mixture was melt-kneaded and pelletized at a cylinder temperature of 280°C, and then injection molded to obtain a test piece. The injection pressure at this time was 850-/-. Table 1 shows the results of characteristic evaluation. This composition has excellent sliding and mechanical properties.

Comparative Example 5 Using polyethylene with a viscosity average molecular weight of 2 million and a density of 0.93F/-, pelletization was attempted in the same manner as in Example 1 with the formulation shown in Table 1, but the load on the drive motor of the extruder was significant. In addition, the dispersion of the mica powder in the extrudate was extremely poor, making it impossible to obtain satisfactory pellets. Further, pelletization was attempted again using a twin-screw extruder and the cylinder temperature was set at 300°C, but the above extrusion situation could not be resolved.

Example 4.5 The mixing ratio of polyethylene was 60% by weight - 1 The mixing ratio of phlogopite was 40% by weight (Example 4), or the mixing ratio of polyethylene was 50% by weight and the mixing ratio of phlogopite was 50% by weight (Example 4). Example 5
) A test piece was prepared in the same manner as in Example-1, except for the following. Since the composition of Example 5 had a rather high viscosity, it was injection molded at a cylinder temperature of 280° C. to obtain a test piece. The characteristics evaluation results are shown in Table-1. All compositions had excellent sliding properties and mechanical properties. Comparative Examples 6 and 7 Phlogopite with a weight average particle size of 230 μm and a weight average aspect ratio of 65 (Comparative Example-6) and d weight average particle size. A test piece was prepared in the same manner as in Example 1 except that muscovite having a weight average aspect ratio of 15 μm and 7 was used (Comparative Example 7), and the results of characteristic evaluation are shown in Table 1. The composition of Comparative Example 6 has unsatisfactory sliding properties, and the composition of Comparative Example 8 has unsatisfactory flexural modulus.

Example 6 Using polyethylene with a viscosity average molecular weight of 800,000 and a density of 0.965 g/cm3, phlogopite powder with a weight average particle size of 40 μm and a weight average aspect ratio of 30, and γ-aminopropyltriethoxysilane, the results shown in Table 1 were prepared. A test piece with the composition shown was prepared and its characteristics were evaluated.

The results are shown in Table-1. Compared to the composition of Example 1, the sliding properties are further improved.

Example 7 Viscosity average molecular weight 600,000, density 0.965 t/d (D
Polyethylene with 0.0% maleic anhydride. I x 10""
rthol/f-PE, t-butyl hydroperoxide 0.03X I Q-' moj/f-PE were tri-blended in a Henschel mixer, then melt-kneaded in a single-screw extruder to form maleic anhydride-modified polyethylene ( A) was obtained. The modified polyethylene, a weight average particle diameter of 40 μm,
Using phlogopite having a weight average aspect ratio of 30, test pieces of the compositions shown in Table 1 were prepared and their characteristics were evaluated.

The results are shown in Table-1. Compared to the composition of Example 1, further improvement in sliding properties is observed.

Example 8 Viscosity average molecular weight 800,000, density 0.965 f/cIII
of polyethylene, maleic anhydride-modified polyethylene (B) with a density of 0.94 f/aJ, and a weight average particle size of 40 μm.
Using phlogopite with a weight average aspect ratio of 30 and T-aminopropyltriethoxysilane, specimens having the compositions shown in Table 1 were prepared and their characteristics were evaluated.

The results are shown in Table IK. This composition has excellent sliding and mechanical properties.

Example 9 Viscosity average molecular weight 600,000, density 0.968 f/eIAf
) A test piece with the composition shown in Table 1 was prepared using polyethylene, modified polyethylene (B), white limestone with a weight average particle size of 25 μm and a weight average aspect ratio of 40, and γ-7 minoprobyl triethoxysilane. It was manufactured and its characteristics were evaluated. The results are shown in Table-1. The composition has extremely excellent sliding and mechanical properties.

Example 10 All the above Examples and Comparative Examples 1 to 4. A driven pulley for a flat belt for conveyance was manufactured by injection molding using the same composition as in Comparative Example 6.7. In molding the composition of Comparative Example 1.3, the size of the molded product varied widely, requiring low-temperature molding using a refrigerator.

When the obtained molded products were mounted on a paper sheet conveying device and a continuous use test was conducted, the parts made of the compositions of all the examples showed a sufficient lifespan, but the parts made of the compositions of the comparative examples When installed, the load torque on the pulley due to belt tension will be large.

This resulted in an increase in the power required for the main motor, and the wear on the pulley was large.

Margins below [Effects of the Invention] According to the present invention, it has become possible to obtain a polyethylene-based resin composition having excellent sliding properties, mechanical properties, etc. that have not been achieved with polyethylene as a conventional sliding material.

Patent applicant: RiRashi Co., Ltd. Tateishi Electric Co., Ltd.

Claims (1)

[Claims] 1. The viscosity average molecular weight is 500,000 to 1.2 million, and the density is 0.
94 to 0.97 g/cm^3 polyethylene and mica powder are essential components, and the weight average flake diameter of the mica powder is 2
00μ or less, a weight average aspect ratio of 10 or more, and a blending ratio of 5 to 60% by weight. 2. The resin composition according to claim 1, which contains a silane coupling agent. 3. The resin composition according to claim 1 or 2, characterized in that polyethylene in which a polar group is copolymerized is used. 4. A sliding component molded using the resin composition according to any one of claims 1 to 3.