JPS60240748A - Ultra-high-molecular-weight polyethylene composition - Google Patents

Abstract

PURPOSE:To improve the moldability of an ultra-high-molecular-weight polyethylene without deteriorating the physical properties, by adding thereto a polyethylene having a lower molecular weight and a specified intrinsic viscosity. CONSTITUTION:An ultra-high-molecular-weight polyethylene composition consisting of 99-50wt% ultra-high-molecular-weight polyethylene (A) having an intrinsic viscosity [eta] of 6dl/g or higher and preferably having an average particle diameter of 20-500mum and a particle size distribution within the range of 5- 2,000mum; and 1-50wt% polyethylene (B) having an intrinsic viscosity [eta] of 1.5-4.5dl/g and preferably having an average particle diameter of 20-400mum and a particle size distribution within the range of 5-500mum. In addition, a heat stabilizer, a weathering stabilizer, pigments, dyes, a lubricant, an inorganic filler or reinforcement such as carbon black, talc, and glass fibers, a flame retardant, a neutron shielding agent, etc. may be added in an amount within limits not detrimental to the object.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention has excellent molding processability, and has the inherent characteristics of ultra-high molecular weight polyethylene, such as abrasion resistance, impact resistance, self-lubricating property,
The present invention relates to an ultra-high molecular weight polyethylene composition having stress crack resistance and the like.

[Conventional technology]

Ultra-high molecular weight polyethylene has superior impact resistance, abrasion resistance, chemical resistance, tensile strength, etc. compared to general-purpose polyethylene, and its use as an engineering plastic is expanding. However, compared to general-purpose polyethylene, the melt viscosity is extremely high and the fluidity is poor, so it is extremely difficult to mold by extrusion molding or injection molding.Most of the polyethylene is molded by compression molding, and some rods etc. Currently, extrusion molding is carried out at very low speeds.

As a method for improving the moldability of ultra-high molecular weight polyethylene, the Japanese Patent Publication No. 43-24525
A method of adding a lubricant such as a higher fatty acid salt has been proposed, as in Japanese Patent Publication No. 49-15948, but when the amount of such lubricant is increased, the abrasion resistance, which is the original characteristic of ultra-high molecular weight polyethylene, has been proposed. Since the properties, impact resistance, etc. are reduced, it is necessary to keep the amount added to a small amount, and as a result, it is currently impossible to significantly improve moldability.

On the other hand, as in JP-A No. 57-193319, ultra-high molecular weight polyethylene is mixed with a flowability improver that is solid at room temperature.
Method of adding 0 parts by weight, or JP-A-57-1770
36, a method of adding 10 to 60 parts by weight of polyethylene with a molecular weight of 5,000 to 20,000 has been proposed, but paraffin wax such as the former, petroleum resin,
Addition of a large amount of low molecular weight compounds such as higher alcohols may impair the inherent properties of ultra high molecular weight polyethylene, and there is also a possibility that the low molecular weight compounds may ooze out onto the surface of the molded product and contaminate other articles. Furthermore, even when a large amount of low molecular weight polyethylene such as the latter is added, it is currently impossible to suppress the deterioration of the physical properties of ultra-high molecular weight polyethylene.

[Problem that the invention seeks to solve]

In view of this situation, the present inventors conducted various studies to improve the moldability of ultra-high molecular weight polyethylene without causing any deterioration in its physical properties. It was found that the object of the present invention (1) can be achieved by adding the following, and the present invention was completed.

[Means for solving problems]

That is, in the present invention, the intrinsic viscosity [η] is at least 6C1
99 to 50% by weight of ultra-high molecular weight polyethylene (A) of 1/g or more and an intrinsic viscosity [η] of 1.5 to 4.5C1
1/fj polyethylene (B) 1 to 50% by weight, without any loss of wear resistance, impact resistance, self-lubricating property, stress crank resistance, etc., which are the original characteristics of ultra-high molecular weight polyethylene. The object of the present invention is to provide an ultra-high molecular weight polyethylene composition that has improved moldability without causing any problems.

[For production]

The ultra-high molecular weight polyethylene (A) used in the present invention has an intrinsic viscosity [η] of at least 6 (11/f1 or more, preferably 12 to 2
5 d679, preferably melt fluorate (
MFR: ASTM D1238, F) is 0.019/
I Qwn or less, density (D: ASTM D1505) is 0.92011/cni or more, melting point (Tm; ASTM
D3417) is an ethylene homopolymer with a temperature of 115°C or higher,
Or a copolymer mainly composed of ethylene and a small amount of other α-olefin such as evapropylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc., which is a crystalline resin. It is. Preferably in powder form,
Particularly preferably, the average particle size is in the range of 20 to 500μ, and the particle size distribution is in the range of 5 to 2000μ.

[η] of 6 dl/fl Ungrooved ones have inferior wear resistance, impact resistance, etc., while those with [η] exceeding 25 dl/fl may not improve moldability even if added with polyethylene (B), which will be described later. .

The polyethylene (B) used in the present invention has an intrinsic viscosity [η] of 1.5 to 4.5 d1/, measured at 135°C in a decalin solvent! 9, preferably 2 to 4 dl/I
preferably melt fluorate tMFR.

:ASTM D1238, E) 1.0 to 0.01
/1Q+m, more preferably 0.1 to 0.01.9
/10 mm, preferably with a density of 0.920 to 0.
97017/14° Preferably melting point is 115 to 1
Homopolymers of ethylene, or ethylene and small amounts of other α-olefins such as propylene, 1
-butene, 1-hexene, 1-octene, 4-methyl-
It is a crystalline resin that is a copolymer mainly composed of ethylene such as 1-pentene, 1-decene, and 1-tetradecene.

From the viewpoint of dispersibility with the ultra-high molecular weight polyethylene, it is preferably in powder form, particularly preferably with an average particle size of 20 to 400.
A fine powder having a particle size distribution of 5 to 500 μ is desirable.

[η] is 1.5C11/I! If less than 4.5 dJ/! is added to the ultra-high molecular weight polyethylene (A), the abrasion resistance, impact resistance, etc. will decrease. If it exceeds li', there is no effect of improving the moldability of ultra-high molecular weight polyethylene (A).

In addition, in the present invention, when [η] is 1.561/fi, the viscosity average molecular weight is 42,000, and [η] is 2.
(1179 is equivalent to 60000.

The ultra-high molecular weight polyethylene composition of the present invention comprises the ultra-high molecular weight polyethylene (A) in an amount of 99 to 50% by weight, preferably 97 to 70% by weight, and the polyethylene (B) in an amount of 1 to 50% by weight, preferably 6 to 30% by weight. If the amount of added polyethylene (B) consisting of
If it exceeds 0% by weight, wear resistance, impact resistance, self-lubricating properties,
Stress crack resistance etc. deteriorate.

The ultra-high molecular weight polyethylene composition of the present invention can be obtained by mixing ultra-high molecular weight polyethylene (A) and polyethylene (B) in the above-mentioned range using a Henschel mixer, a -plender, a ribbon blender, a tumbler blender, or the like.

The ultra-high molecular weight polyethylene composition of the present invention includes heat-resistant stabilizers, weather-resistant stabilizers, pigments, dyes, lubricants, inorganic fillers or reinforcing agents such as carbon black, talc, and glass fiber,
Compounding agents such as flame retardants and neutron shielding agents that are usually added to polyolefins may be added to the extent that the object of the present invention is not impaired.

〔Effect of the invention〕

Compared to conventional compositions, the ultra-high molecular weight polyethylene composition of the present invention can be molded without sacrificing the characteristics inherent to ultra-high molecular weight polyethylene, such as wear resistance, impact resistance, self-lubricating properties, and stress crack resistance. Since the processability is improved, for example, in extrusion molding, profiles with complicated cross-sections, such as round bars with a diameter of 20 to 200 mm, can be easily extruded with low load and low resin pressure.

In compression molding, the melt flowability during heating and pressing has been improved, so it is now possible to easily mold thin sheets of 2 to 5 yran t, which previously had many problems due to unfired parts due to poor deaeration. Ta.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples as long as they do not go beyond the gist of the invention.

Examples 1 to 3 As ultra-high molecular weight polyethylene (A), intrinsic viscosity [η]
: 22.7C1l/! 70.90 and 95% by weight of ultra-high molecular weight polyethylene powder (UMPE-I) with average particle size of 160μ and polyethylene (B
) as the limiting viscosity [η): '6.8C1l191M
FR: 0.03 g/10wn, density: 0.950
．． ! After mixing 30.10% by weight and 5% by weight of polyethylene powder (HDPE-■) with il/cpI and average particle size of 80μ, respectively, in a Henschel mixer,
- 65mmφ screw extrusion method described in Publication No. 35139 (screw rotation speed = 20 rpm, resin temperature =
A 50 mmφ round bar was melt-extruded using a temperature of 240° C.), and the extrusion characteristics (motor load, resin pressure) were recorded. In addition, test pieces were prepared by cutting, and physical properties were measured using the following method.

. Tensile test: ASTM D638, but the test piece shape is AS
Using No. TM4 and a tensile speed of 50 mm/cm, the tensile strength at break (TS: kli'/c) and elongation at break (EL: %
).

Izot impact strength (1, ZOD: kg・cm/Cm
): ASTM D256, notched, specimen thickness = 3
．． 2-way taper wear test: JIS K6902, however, H-22 was used as the wear wheel, and the amount of wear (g) after 1000 rotations was measured.

The results are shown in Table 1.

Comparative Example 1 Instead of HDPE-I used in Example 3, intrinsic viscosity C
η]: 1.2d6#i'XMFR:13,9/10
Cabinet, density: 0.965. ! i+/- and average particle size: 80
The same procedure as in Example 6 was carried out except that μ polyethylene powder (HDPE-11) was used.

The results are shown in Table 1.

Comparative Example 2 Intrinsic viscosity [η):
Example 1 was carried out in the same manner as in Example 1, except that ultra-high molecular weight polyethylene powder (UMPE-It) having 1β/g and an average particle size of 200μ was used. The results are shown in Table 1.

Claims (1)

[Claims] (1) 99 to 50% by weight of ultra-high molecular weight polyethylene (A) having an intrinsic viscosity [η] of at least 6 dl/i or more
and 1 to 50% by weight of polyethylene (B) having an intrinsic viscosity [η] of 1.5 to 4.5 dl/g.