JP2837677B2 - Injection molding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an injection-molded product obtained from a resin composition containing ultra-high molecular weight polyethylene, and more particularly, to excellent slidability. The present invention relates to an injection-molded article excellent in heat resistance and rigidity as well as wear resistance.

(Prior art) Ultrahigh molecular weight polyethylene is superior to general-purpose polyethylene in impact resistance, abrasion resistance, chemical resistance, tensile strength and the like, and its use as an engineering plastic is expanding. However, ultra-high molecular weight polyethylene has a very high melt viscosity and poor fluidity compared to general-purpose polyethylene, so it is very difficult to mold it by ordinary extrusion or injection molding, and most of it is formed by compression molding. At present, some rods are extruded at an extremely low speed.

(Problems to be Solved by the Invention) When such ultra-high molecular weight polyethylene having inferior melt fluidity is molded by a usual injection molding method, a shear fracture flow occurs in the process of filling the resin into the mold cavity, and a molded product is formed. , Delamination occurs in a mica-like manner, and not only cannot a molded article exhibiting the excellent properties of ultra-high molecular weight polyethylene be obtained, but also it is usually inferior to a general-purpose polyethylene molded article.

The present inventors previously, ultra-high molecular weight polyethylene having an intrinsic viscosity of 10 to 40 dl / g measured in a 135 ° C decalin solvent, and the intrinsic viscosity is a low molecular weight to high molecular weight polyethylene lower than the ultra high molecular weight polyethylene. And the ultra-high molecular weight polyethylene is present in an amount of 15 to 40% by weight based on the total amount of both, and the intrinsic viscosity [η] _{c of} 3.5 to 15 dl / g measured as a whole and less than 4.5 kg · cm The olefin resin composition having a melting torque T can be used for general-purpose injection molding while substantially retaining the excellent slidability, abrasion resistance, impact resistance, chemical resistance, tensile strength, etc. of ultra-high molecular weight polyethylene. It has been found that it can be easily formed using a machine.

The present inventors, when blending a certain amount of a fine particle inorganic filler into this olefin resin composition, have the following characteristics of the olefin resin composition: (1) a wear coefficient, and (2) dynamic friction. It has been found that the heat resistance, rigidity and moldability can be improved without substantially impairing the coefficient, (3) the limit PV value.

(Means for Solving the Problems) According to the present invention, ultrahigh molecular weight polyethylene having an intrinsic viscosity of 10 to 40 dl / g measured in a decalin solution at 135 ° C.
10 to 100 parts by weight of a resin composition comprising 15 to 40% by weight and 60 to 85% by weight of a low to high molecular weight polyethylene having an intrinsic viscosity of 0.1 to 5 dl / g under the above measurement conditions.
An injection-molded article obtained by injection-molding an inorganic filler-containing composition obtained by blending from 30 to 30 parts by weight of a fine particle inorganic filler, wherein the ultra-high molecular weight polyethylene and the low molecular weight to high molecular weight polyethylene are Resin composition has an intrinsic viscosity
3.5 to 15 dl / g, melting torque T is 4.5 kg · cm or less, the fine particle inorganic filler has a median diameter measured by a Coulter counter method in a range of 0.1 to 30 μm, and the injection molded product has a flexural elasticity. Rate (ASTM D790) is 23000
kg / cm ² or more, a heat distortion temperature (ASTM D648) is 94 ° C. or higher, and injection molded articles is provided which melted limit PV value is equal to or in the range of more than ^{330kg / cm 2 · m / min} .

(Operation) In the composition of the present invention, the ultra-high molecular weight polyethylene has excellent sliding properties such as a low coefficient of wear, a low coefficient of kinetic friction and a high critical PV value, and has impact resistance, tensile strength, and chemical resistance. It is an indispensable component because it has excellent properties. The ultrahigh molecular weight polyethylene has an intrinsic viscosity (hereinafter, the intrinsic viscosity means the one obtained by this measuring method) measured in a decalin solvent at 135 ° C. [η] _u is 10 to 40 dl / g, particularly 15
It is also important to be in the range of ~ 35dl / g. If [η] _u is smaller than the above range, the sliding characteristics and mechanical properties will be inferior to those in the above range, while if [η] _u is larger than the above range, it will be described below. Even when used in combination with the components, the injection moldability is reduced, and the appearance of the molded product is poor, and the occurrence of a flow mark occurs,
In addition, it is inferior in abrasion resistance, for example, delamination easily occurs.

Low molecular weight to high molecular weight polyethylene having an intrinsic viscosity lower than that of ultrahigh molecular weight polyethylene used in the present invention is an indispensable component for imparting injection moldability to ultrahigh molecular weight polyethylene. In _order to keep the intrinsic viscosity and the melting torque of the entire composition within the ranges specified in the present invention, the intrinsic viscosity [η] _n determined by the method described in detail below is 0.1 to 5 dl / g, particularly 0.5 to 3 dl / g.
Should be in the range of dl / g. When [η] _n is smaller than the above range, inconveniences such as bleeding on the surface of the injection-molded article are liable to occur. On the other hand, when _n is larger than the above range, the melt fluidity is reduced and the moldability of the entire composition is reduced. Tends to decrease.

In the present invention, the ultrahigh molecular weight polyethylene and the low molecular weight to high molecular weight polyethylene are formed into a composition under certain conditions, so that the composition is provided with excellent injection moldability and has low friction. It can have a modulus and a wear coefficient as well as a high critical PV value. First, the ultra high molecular weight polyethylene should be present in an amount of 15 to 40% by weight, especially 20 to 35% by weight, based on the whole olefin resin composition. When the amount of the ultrahigh molecular weight polyethylene is smaller than the above range, the friction coefficient, wear resistance and the like become inferior to those in the above range. On the other hand, if the amount is more than the above range, the moldability is reduced and the abrasion resistance such as delamination is reduced.

Next, this olefin resin composition was 3.5
It should have an intrinsic viscosity [η] _c of 1515 dl / g, especially 4.0-10 dl / g. That is, if this [η] _c is lower than the above range, the dynamic friction coefficient and abrasion resistance will be inferior to those within the above range, and if it is higher than the above range, the moldability will decrease. , Wear resistance is also reduced. The melting torque T in this specification is measured using a JSR Curast Meter (manufactured by Imanaka Kikai Kogyo KK) under the conditions of a temperature of 240 ° C., a pressure of 5 kg / cm ² , an amplitude of ± 3 °, and a frequency of 6 CPM. If the melting torque T exceeds 4.5 kg · cm, it will not bite into a normal screw and cannot be injection molded with a general-purpose injection molding machine. Therefore, T should be 4.5 kg · cm or less. is there.

The injection-molded article of the present invention has a median diameter of 0.1 to 30 μm as measured by the Coulter counter method.
The composition is obtained by injection-molding an inorganic filler-containing composition containing a fine particle inorganic filler in the range of (1).

In the present invention, the fine particle inorganic filler is blended in an amount of 10 to 30 parts by weight per 100 parts by weight of the resin composition comprising ultrahigh molecular weight polyethylene and low molecular weight to high molecular weight polyethylene. By injection-molding such an inorganic filler-containing composition, an injection-molded article having excellent heat resistance and rigidity can be obtained without impairing the inherent sliding properties of the resin composition. For example, the injection molded product of the present invention
Flexural modulus of g / cm ² or more, heat deformation temperature of 94 ° C or more and 330
It has a melting limit PV value of more than kg / cm ² · m / min.

Generally, it is widely used to add a filler to a plastic molded article for the purpose of increasing the amount or for improving impact resistance, heat resistance, abrasion resistance, electric insulation and the like. However, the ultra high molecular weight polyethylene according to the present invention-
The combination of the low molecular weight to high molecular weight polyethylene composition and the fine particle inorganic filler improves heat resistance at about 40 ° C. or more in terms of heat deformation temperature and rigidity which reaches about twice as much in terms of flexural modulus. And an unexpected improvement in these properties is due to the presence of the olefin composition (1).
This is possible without substantially impairing the excellent sliding characteristics of a low wear coefficient, (2) a low dynamic friction coefficient, and (3) a high limit PV value.

Furthermore, by adding a particulate inorganic filler to the specific olefin resin composition, the dimensional stability of the injection-molded article is improved, and so-called "sink" and "slipping" which are likely to occur in the injection-molded article are reduced. Also, remarkable advantages are obtained in terms of moldability, such as improvement in appearance characteristics and mechanical accuracy of the molded article, and shortening of the molding cycle.

It is also important that the amount of the filler is within the above range,
If less than the above range, compared to those within the range,
If the degree of improvement in heat resistance, rigidity and moldability is small, and if it is more than the above range, the melt fluidity will decrease and the injection moldability will worsen, and the sliding characteristics of the molded article will also decrease.

(Preferred Embodiment of the Invention) Olefin resin composition The ultrahigh molecular weight polyethylene and the low molecular weight to high molecular weight polyethylene used in the present invention are a homopolymer of ethylene or ethylene containing ethylene as a main component and other α-olefins such as propylene. 1-butene, 1-pentene, 1
-Hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 3-methyl-1-pentene and the like.

The olefin resin composition used in the present invention can be produced by blending the above-mentioned ultra-high molecular weight polyethylene and low molecular weight to high molecular weight polyethylene at a polymerization amount ratio, and melt-kneading the mixture. From the standpoint of forming the composition, it is particularly desirable to produce by a multi-stage polymerization method. That is, in the presence of a Ziegler-type catalyst composed of a highly active solid titanium catalyst component and an organoaluminum compound catalyst component and in the absence of hydrogen, an olefin mainly composed of ethylene is polymerized to produce an ultrahigh molecular weight polyethylene, The olefin is then polymerized in the presence of hydrogen to produce a low to high molecular weight polyethylene. The highly active solid titanium-based catalyst preferably contains magnesium, titanium and halogen as essential components.

The specific Ziegler-type catalyst used is basically a specific type of catalyst formed from a solid titanium catalyst component and an organoaluminum compound catalyst component. As the solid titanium catalyst component, for example, it is preferable to use a highly active fine powder catalyst component having a narrow particle size distribution, an average particle size of about 0.01 to 5 μm, and several microspheres fixed. . A highly active fine powdered titanium catalyst component having such properties is, for example, a solid titanium catalyst component disclosed in JP-A-56-811, which is obtained by contacting a liquid state magnesium compound with a liquid state titanium compound to form a solid. It can be produced by strictly adjusting the precipitation conditions when depositing the product. For example, in the method disclosed in the publication,
When a hydrocarbon solution in which magnesium chloride and a higher alcohol are dissolved and titanium tetrachloride are mixed at a low temperature, and then heated to about 50 to 100 ° C. to precipitate a solid product,
A small amount of about 0.01 to 0.2 mol of a monocarboxylic acid ester coexists with 1 mol of magnesium chloride, and the precipitation is carried out under strong stirring conditions. If necessary, it may be washed with titanium tetrachloride. Thus, a solid catalyst component satisfying both the activity and the particle shape can be obtained. Such a catalyst component can be, for example, titanium from about 1 to about 6
% By weight, and halogen / titanium (atomic ratio) is about 5%.
From about 90 to about magnesium / titanium (atomic ratio) from about 4 to about 50.

Further, the particle size distribution obtained by subjecting the slurry of the solid titanium catalyst component prepared as described above to a shear treatment at a high speed is narrow, and the average particle diameter is usually 0.01 to 5 μm, preferably 0.05 to 3 μm. Spheres are also suitably used as a highly active fine powdered titanium catalyst component. As a method of the high-speed shearing treatment, specifically, for example, a method of appropriately treating a slurry of a solid titanium catalyst component in an inert gas atmosphere using a commercially available homomixer is employed. At that time, for the purpose of preventing a decrease in catalyst performance, a method in which an organoaluminum compound in an equimolar amount to titanium is added in advance may be adopted. Further, a method of filtering the slurry after the treatment with a sieve to remove coarse particles may be employed. By these methods, a highly active fine powdered titanium catalyst component having the above-mentioned fine particle diameter can be obtained.

As the organic aluminum compound catalyst component, for example, triethylaluminum, trialkylaluminum such as triisobutylaluminum, diethylaluminum chloride such as diethylaluminum chloride, alkylaluminum sesquichloride such as ethylaluminum sesquichloride, or these Is preferably used.

In the polymerization step for producing the ultra-high-molecular-weight polyethylene, a highly active titanium catalyst component (A) is used as a catalyst, for example, about 0.001 to about 20 mg atoms, particularly about 0.005 to about 10 mg atoms, as titanium atoms per medium,
The organoaluminum compound catalyst component (B) is preferably used in such a ratio that the Al / Ti (atomic ratio) is about 0.1 to about 1000, particularly about 1 to about 500. The temperature of the polymerization step for producing the ultra-high molecular weight polyethylene is usually from about -20 to about
It is in the range from 120 ° C, preferably from about 0 to about 100 ° C, particularly preferably from about 5 to about 95 ° C. Further, the pressure during the polymerization reaction is a pressure range in which liquid phase polymerization or gas phase polymerization is possible at the above temperature, for example, from atmospheric pressure to about 1000 kg / cm ² , preferably from atmospheric pressure to about 50 kg / cm ² It is. The polymerization time in the polymerization step may be set so that the amount of ultra-high molecular weight polyethylene produced is about 1000 g or more, preferably about 2000 g or more, per 1 mg atom of titanium in the highly active titanium catalyst component. In addition, in the polymerization step, in order to produce the ultrahigh molecular weight polyethylene, it is preferable to carry out the polymerization reaction in the absence of hydrogen. Furthermore, after performing the polymerization reaction, the polymer can be once isolated and stored in an inert medium atmosphere.

Examples of the inert medium that can be used in the polymerization step for producing the ultrahigh molecular weight polyethylene include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, and kerosene; cyclopentane, cyclohexane, and the like. Alicyclic hydrocarbons; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as dichloroethane, methylene chloride and chlorobenzene; and mixtures thereof. In particular, the use of aliphatic hydrocarbons is desirable.

In the production of the olefin resin composition of the present invention, a polymerization reaction of the remaining olefin is carried out in the presence of hydrogen in a polymerization step other than the polymerization step for producing the ultrahigh molecular weight polyethylene.

The supply ratio of hydrogen in the polymerization steps other than the ultrahigh molecular weight polyolefin production polymerization step is usually 0.01 to 50 mol, preferably 0.05 to 30 mol, per 1 mol of the olefin supplied to each polymerization step.

The concentration of each catalyst component in the polymerization product solution in the polymerization tank in the polymerization step other than the ultra-high molecular weight polyethylene production polymerization step is about 0.001 to about 0.1 in terms of titanium atom per one polymerization volume in terms of the treated catalyst. Milligram atoms, preferably from about 0.005 to about 0.1 milligram atoms, and polymerized Al
/ Ti (atomic ratio) is about 1 to 1000, preferably about 2 to about 5
It is preferable to prepare to be 00. For this purpose, an organoaluminum compound catalyst component (B) can be additionally used as necessary. In the polymerization system, a hydrogen / electron donor, a halogenated hydrocarbon, and the like may be coexistent for the purpose of adjusting the molecular weight distribution and the like.

The polymerization temperature is a temperature range in which slurry polymerization and gas phase polymerization can be performed, and about 40 ° C. or more, more preferably about 50 to about 100 ° C.
Is preferable. Further, the polymerization pressure can be recommended, for example, in the range of from atmospheric pressure to about 100 kg / cm ² , particularly, from atmospheric pressure to about 50 kg / cm ² . The polymerization time should be set so that the amount of the polymer produced is about 1000 g or more, particularly preferably about 5000 g or more per 1 mg atom of titanium in the titanium catalyst component.

The intrinsic viscosity [η] _n of the low to high molecular weight polyethylene contained in the olefin resin composition obtained by the above multistage polymerization method cannot be directly determined, but the density of the ultrahigh molecular weight polyethylene is _Du and the composition ratio W ₁ Assuming that the density of the low to high molecular weight polyethylene is D _n , the composition ratio is W ₂ , and the density of the composition is D _c , Is satisfied, the density D _{n of the} low molecular weight to high molecular weight polyethylene is obtained from the equation (1).
An MFR (melt flow rate) having a one-to-one correspondence with D _n from D _n and [η] _n having a one-to-one correspondence are obtained from the MFR.

In the above-mentioned preparation method, the polymerization to the ultrahigh molecular weight polyethylene is performed in the first stage, and the polymerization to the low molecular weight to high molecular weight polyethylene is performed in the second and subsequent stages, but the polymerization in the reverse order is also possible. It should be understood that.

Fine particle inorganic filler As the fine particle inorganic filler used in the present invention,
Silicas such as dry-process amorphous silica (Aerosil), wet-process amorphous silica (white carbon), crystalline silica (Cristobalite, Quartz), and diatomaceous earth; alumina (α-alumina), aluminum hydroxide or alumina gel Aluminas such as (gibbsite, boehmite); aluminum silicates such as synthetic aluminum silicate (amorphous) and natural aluminum silicate (kaolin, calcined kaolin);
Natural magnesium silicate (talc), synthetic magnesium silicate, synthetic basic magnesium silicate; natural or synthetic smectite group viscous minerals (bentonite, montmorillonite); synthetic aluminosilicate (zeolite); calcium carbonate, magnesium carbonate, barium sulfate And the like; alkaline earth metal salts such as magnesium oxide and magnesium hydroxide.

In the present invention, the fine particle inorganic filler has a median diameter (coulter counter method) of 0.1 to 30 μm,
In particular, those having a range of 0.5 to 10 μm are used.

Particularly desirable particulate inorganic fillers are those known as lubricants, such as talc, magnesium oxide, aluminum silicate, barium sulfate, aluminum hydroxide and the like.

Composition In the present invention, it is necessary that the fine particle inorganic filler is dispersed as finely and uniformly as possible in the resin composition to be injection molded. Such fine dispersion is achieved by supplying the olefin resin composition and the fine particle inorganic filler to a single-screw or twin-screw extruder and melt-kneading them. Of course, at the time of the kneading, a known compounding agent for an olefin resin, for example, an antioxidant, a release agent, a pigment or the like can be compounded according to a known formulation.

It is a remarkable advantage that the molding of the blend can be performed using a general-purpose injection molding machine. The injection molding conditions are
Although not particularly limited, it is generally preferable to carry out at a cylinder temperature of 200 to 290 ° C. and an injection pressure of 1000 to 4000 kg / cm ² .
Injection molding can, of course, be performed in one stage or in multiple stages.

INDUSTRIAL APPLICABILITY The injection molded product of the present invention is useful for various mechanical parts requiring sliding performance, such as various bearings, gears, cams, sliders, rollers, reels, cylinders, pistons, and the like.

(Effect of the Invention) In the injection molded article of the present invention, the specific composition of ultrahigh molecular weight polyethylene and low molecular weight to high molecular weight polyethylene is used as a base material, thereby preserving the inherent characteristics of ultrahigh molecular weight polyethylene. Not only can high-precision processing into mechanical parts and the like be possible, but by blending a fine particle inorganic filler in this composition in a fixed amount ratio, the low wear coefficient and low wear of the olefin resin composition are reduced. Without substantially compromising the kinetic coefficient of friction, and the high critical PV value,
Remarkable improvements in heat resistance, rigidity, and formability were obtained, such as improving the heat distortion temperature, improving the flexural modulus, and eliminating "sink" and "warpage".

(Examples) The composition of the present invention will be specifically described by examples.

The production of the olefin resin composition used in the examples is shown below.

Olefin resin composition [Catalyst preparation] 47.6 g (0.5 mol) of anhydrous magnesium chloride, 0.25 of decane
And 2-ethylhexyl alcohol 0.23 (1.5mo
l) was heated at 130 ° C. for 2 hours to form a homogeneous solution, and 7.4 ml (50 mmol) of ethyl benzoate was added. This homogeneous solution was kept at -5C. It was added dropwise with stirring to 1.5 TiCl ₄ over 1 hour. The reactor used was glass 3
And the stirring speed was 950 rpm. After the dropwise addition, the temperature was raised to 90 ° C., and the reaction was performed at 90 ° C. for 2 hours. After the completion of the reaction, a solid portion was collected by filtration, and further sufficiently washed with hexane to obtain a highly active fine powdery titanium catalyst component. The catalyst component contained 3.8 wt% titanium atoms.

[Polymerization] Continuous polymerization was carried out using a continuous two-stage polymerization apparatus in which two polymerization tanks having an inner volume of 220 were connected in series. First polymerization tank of the continuous two-stage polymerization apparatus (hereinafter abbreviated as polymerization tank 1)
N-hexane 130 was added to the mixture, and the temperature was raised to 40 ° C. 35 mg / hr of n-hexane, 45 mM / hr of triethylaluminum, 1.0 mg atom / hr using a titanium catalyst as a titanium atom, and ethylene gas were continuously introduced into the polymerization tank 1 at a rate of 6.0 Nm ³ / hr. The slurry of the polymerization mixture in the polymerization tank 1 was sent to the subsequent polymerization tank (hereinafter abbreviated as polymerization tank 2) using a pump, and the level of the polymerization tank 1 was maintained at 130. At that time, the polymerization pressure in the polymerization tank 1 was 4.8 kg / cm ² G.

In the polymerization tank 2, in addition to the polymerization mixture slurry sent from the polymerization tank 1, n-hexane 25 / hr, ethylene gas 18N
It was introduced continuously at a rate of m ³ / hr. Further, an appropriate amount of hydrogen gas is added to adjust the composition (molar ratio) of the gas phase portion of the polymerization tank 2 to ethylene.
The hydrogen was adjusted to 30 for 1000. The slurry generated by the polymerization reaction was intermittently withdrawn from the lower portion of the polymerization tank 2 using a timer valve, and the level of the polymerization tank 2 was reduced to 120.
Kept. The polymerization temperature of the polymerization tank 2 was 65 ° C, and the polymerization pressure was 4.
It was 1 kg / cm ² G. The obtained polymer and solvent were separated by a centrifugal separator and dried under a stream of N ₂ .

[Η] and content of each component of the obtained polyolefin composition, [η] of the composition, and melting torque T were measured by the following methods.

[Η]: Intrinsic viscosity measured in 135 ° C decalin solvent [η] _c = 5.5 dl / g Melting torque (T): Using a JSR Curast Meter (manufactured by Imanaka Kikai Kogyo) at a temperature of 240 ° C and a pressure of 5 kg / g cm ² , amplitude ± 3 ゜,
This is the torque of the sample in the molten state measured at a frequency of 6 CPM.

T = 1.3 kg · cm In the present invention, physical properties were evaluated in accordance with the following methods using test pieces injection-molded under the conditions described in Example 1.

Heat distortion temperature (° C): Using a heat distortion tester (manufactured by Toyo Seiki), according to ASTM D648.

Test piece: 12.7 × 12.7 × 127mm load: 4.64kg / cm ² Flexural modulus (kg / cm _2): conforms to ASTM D790.

Test piece: 2 × 12.7 × 63.5mm Dynamic friction coefficient: Using a Matsubara friction and wear tester (manufactured by Toyo Baldwin), compressive load 7.5 kg / cm ² , sliding speed 12 m / m
The test was performed for 30 minutes under the condition of "in" to determine the friction coefficient. Opponent material is SUS
304, the sliding surface roughness was processed to 6 s before use.

Test piece: Injection molded square plate (130 × 120 × 2 mm) was used.

Melting limit PV value (kg / cm ² · m / min): Sliding speed 12m / using a Matsubara friction and wear tester (manufactured by Toyo Baldwin)
min, a compressive load from 2.5kg / cm ² to 2.5kg / cm ² jump 40kg / cm
^The PV value (load x speed) at which the resin was melted by frictional heat for 30 minutes under each condition was determined. The partner material is
SUS 304 was used after processing the sliding surface roughness to 6 s.

Test piece: Injection molded square plate (130 × 120 × 2 mm) was used.

Friction and wear test: Using a Matsubara-type friction and wear tester (manufactured by Toyo Baldwin), compressive load 3.4 kg / cm ² , sliding speed 30 m / m
in for 168 hours, the coefficient of friction (× 10 ^-10 cm ³ / kg
m) was determined. The mating material was SUS 304, and the sliding surface roughness was processed to 6 s. The test piece is injection molded square plate (130 × 120
× 2 mm).

Molding shrinkage (%): Vertical and horizontal dimensions were measured using an injection-molded square plate (130 × 120 × 2 mm), and the product shrinkage was measured based on the mold dimensions.

Table 1 shows the results.

Example 1 [η] _c is 5.5 dl / g, density is 0.968 g / cc, and melting torque is
100 parts by weight of the olefin resin composition of 1.3 kg-cm and 10 parts by weight of talc (high filler # 5000PJ: manufactured by Matsumura Sangyo Co., Ltd.) having an average particle size of 1.75 μm as an inorganic filler were mixed with a Henschel mixer. After pelletizing with a single screw extruder, various test pieces were formed using an injection molding machine (IS-50, manufactured by Toshiba Corporation) under the following conditions.

Injection molding conditions Cylinder temperature (° C): 200/230/270/270 Injection pressure (kg / cm ² ): primary / secondary = 1200/800 Screw rotation speed (rpm): 97 Mold temperature (° C): water cooling (27 ° C.) Example 2 The same operation as in Example 1 was carried out except that the amount of talc was changed to 30 parts by weight.

Comparative example 1 It carried out similarly to Example 1 except having used the said olefin resin composition without filler filling.

Comparative example 2 It carried out similarly to Example 1 except having set the filling amount of talc to 3 weight part.

Comparative Example 3 The same operation as in Example 1 was carried out except that the amount of talc was changed to 80 parts by weight and pelletized by a twin-screw extruder.

It was found that the sliding property was remarkably reduced due to too much talc, which was not practical.

Claims (3)

(57) [Claims] An ultrahigh molecular weight polyethylene having an intrinsic viscosity of 10 to 40 dl / g measured in a decalin solution at 135 ° C.
40% by weight, the intrinsic viscosity under the above measurement conditions is 0.1 to 5 dl / g
Injection molding of an inorganic filler-containing composition comprising 10 to 30 parts by weight of a fine particle inorganic filler per 100 parts by weight of a resin composition comprising 60 to 85% by weight of low to high molecular weight polyethylene. The resin composition comprising the ultra-high molecular weight polyethylene and the low molecular weight to high molecular weight polyethylene has an intrinsic viscosity of 3.
5 to 15 dl / g, melting torque T is 4.5 kg · cm or less, the fine particle inorganic filler has a median diameter measured by a Coulter counter method in a range of 0.1 to 30 μm, and the injection molded product has bending elasticity. Rate (ASTM D790) is 23000kg
/ cm ² or more, a heat distortion temperature (ASTM D648) is 94 ° C. or higher, and injection molded articles melting limit PV value is equal to or in the range of more than ^{330kg / cm 2 · m / min} . 2. A resin composition comprising the ultra-high molecular weight polyethylene and a low molecular weight to high molecular weight polyethylene, comprising polymerizing a monomer mainly composed of ethylene in the presence of a polymerization catalyst and in the absence of hydrogen. Claims: It is obtained by a multi-stage polymerization method mainly comprising a pre-polymerization step of producing ultra-high molecular weight polyethylene and a post-polymerization step of producing a low to high molecular weight polyethylene by polymerizing in the presence of a catalyst and hydrogen. 2. The injection molded article according to 1. 3. The injection-molded article according to claim 1, wherein said inorganic filler is talc.