JPS58164627A - Production of electroconductive ultrahigh-molecular polyethylene sinter - Google Patents

Abstract

PURPOSE:To produce the titled sinter having electroconductivity uniform throughout the sinter including its interior and surface, by ram-extruding a mixture prepared by mixing a specified ultrahigh-MW PE with an electroconductivity-imparting agent, a lubricant and an organic peroxide. CONSTITUTION:A mixture is obtained by uniformly mixing and dispersing 100 pts.wt. ultrahigh-MW PE powder, average MW by a viscosity method >=1,000,000 that by light scattering >=3,000,000, with 0.5-10pts.wt. electroconductivity-imparting agent (e.g., acetylene black), below 10pts.wt. lubricant (e.g., polyethylene wax) and 0.01-0.50pts.wt. organic perioxide having a 10hr half life of 90- 130 deg.C, e.g., dicumyl peroxide. Then, this mixture is introduced from a material feed part 3 into the cylinder 1 of a ram extruder equipped with heating means Nos. 1-3 set at 200-300 deg.C for the high-temperature part and at 150-200 deg.C for the low-temperature part and extruded by a ram 2 into a sinter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes conductive ultra-high molecular weight polyethylene (hereinafter referred to as UHM).
During ram extrusion molding of UHMW-PH (abbreviated as W-PH),
A cross-linked type that has uniform conductivity from the inside to the surface layer by blending pHi with a conductivity imparting agent, a lubricant to reduce extrusion pressure, and an organic peroxide as a cross-linking agent, uniformly dispersed, and sintered. The present invention relates to a method for molding a U HMW-PK sintered body.

UHMW-PKd has superior properties such as abrasion resistance, low-temperature properties, impact resistance, and resistance to stress cracking compared to ordinary polyethylene. It is considered useful for lining hoppers, chutes, etc. that require wear resistance, and as a material for bearings, gears, rollers, guide rails, etc. that require self-lubricity, low friction coefficient, and wear resistance. However, - side, volume 1.1+! resistance is 10I
8ocrn or more, the surface resistance is 1 O" or higher, and the electrical insulation is high, so the surface is easily charged with static electricity, and the static electricity tends to cause dust to adhere to the product surface, causing hygiene problems. Nurses say that it cannot be used in environments where organic solvents are used, or in atmospheres where combustible powder such as coal or coke is likely to form, or where organic solvents are used. There is.

Therefore, since HUHMW-PK alone is not suitable for applications where problems occur due to static electricity,
It is necessary to provide conductivity.

By the way, carbon black and carbon fiber are generally used as conductivity imparting agents to impart conductivity.

Metal powders, etc. are used, but when these conductivity imparting agents are mixed with UHMW-PIH powder and subjected to ram extrusion molding to obtain a sintered body, the blending amount is 2 parts by weight per 100 parts by weight of UHMW-PK. When the amount exceeds 1 part by weight, the extrusion pressure increases extremely and ram extrusion becomes difficult, so it is necessary to add an appropriate lubricant to reduce this extrusion pressure. but,
Addition of a lubricant reduces the extrusion pressure and facilitates the molding of conductive UHMW-PK, but it has the disadvantage of reducing the conductivity near the surface layer of the extruded product.

Therefore, in order to eliminate the above-mentioned conventional drawbacks, the inventors of the present invention have conducted intensive studies for some time, and as a result, added a small amount of organic peroxide to the conventional conductive UHMW-PI formulation. It has been found that by crosslinking, a conductive UHMW-BE sintered body in which the conductivity near the surface layer does not decrease can be obtained.

That is, the feature of the present invention is that the UHMW-PK
The method involves blending an organic peroxide with a conductivity imparting agent and a lubricant into a powder, uniformly dispersing them, and molding the resulting mixture into a sintered body by ram extrusion.

Here, the addition of the organic peroxide is an important point in the method of the present invention, and when the organic peroxide is added, the UHMW-Pl
d Due to crosslinking, the migration of the lubricant to the surface layer is inhibited by an increase in melt viscosity during the sintering process. Therefore, the concentration of the conductivity imparting agent in the surface layer is almost the same as that in the inner layer, and a molded article with uniform conductivity can be obtained. On the other hand, when no organic peroxide is added, the lubricant is UH
Since the melt viscosity is lower than the melt viscosity of MW-pIc, the extrusion pressure: migrates to the surface layer and rubbles, resulting in a decrease in the concentration of the conductivity imparting agent in the surface layer and a decrease in conductivity near the surface layer.

In the present invention, if a lubricant is not added, the extrusion pressure will increase significantly, and in order to reduce this, it is necessary to add a lubricant.

The UHMW-PIc powder used in the present invention has a molecular weight of 3 million or more according to the light scattering method and 10 million according to the viscosity method.
For example, Hoechst's Ho5talen GUR, Mitsui Petrochemical Industries, Ltd.'s Hl-ZQX M
illion), etc.

In addition, as the conductivity imparting agent in the present invention, acetylene black [trade name: Denka Black: Denki Kagaku Kogyo Co., Ltd.
Conductive carbon black such as Ketschen Black (trade name: Ketschen Black IDC manufactured by Nippon Easy Co., Ltd.), carbon fibers, or metal powders such as copper powder, iron powder, silver powder, etc. are used. When performing lamb extrusion molding, the amount of these conductivity imparting agents is 0.5 to 10 parts by weight per 100 parts by weight of UHMW-PIC in order to suppress the pressure increase during extrusion.
Parts by weight, preferably 1 to 5 parts by weight.

The lubricants used in the present invention include montanic acid ester waxes, various polyethylene waxes, hydrocarbon waxes, and fatty acid transparent waxes.

(dicarboxylic acid ester, glycerin fatty acid ester,
Powdered products such as amide wax, etc.) can be mentioned.

The amount of these additives added is preferably 10 parts by weight or less, preferably 5 parts by weight or less, per 100 parts by weight of UHMW-PlC. If it exceeds 100 parts by weight, the mechanical properties will deteriorate and should be avoided.

Further, the organic peroxide of the crosslinking agent having the characteristics described above used in the present invention includes dialkyl peroxide such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and dicumyl peroxide; .

90~ of peroxyketals such as 1-bis(t-butylperoxy)3,3.5-trimethylmicrohexane, etc.
UHMW-PI! is a general term for organic peroxides commonly used for crosslinking polyethylene that have a 10-hour half-life temperature of 135°C. : It is desirable to use it in powder form considering its dispersion into powder. And the amount added is UKMW-p
The overlapping portion may be 0.01 to 0.50 parts by weight, preferably 0.05 to 0.2 parts by weight. If 0.5 parts by weight or more is added, cracks may occur on the surface of the molded product during extrusion molding.

Next, the ram extrusion device used in the present invention is generally known, and includes, for example, a plunger type device as shown in FIG. This is composed of a cylinder (1) equipped with a heating device (4) in, for example, three stages (A 1 + A 2 , A 3 ), a ram (2) that reciprocates in the cylinder, and a raw material supply section (3). ing.

The extrusion speed during extrusion molding must be appropriately adjusted depending on the inner diameter and length of the cylinder of the ram extrusion device, the cylinder heater capacity, and the heater temperature. ,
Preferably 220-270°C, 150-200°C in the low temperature part
℃, preferably 160 to 180℃. 300
At temperatures above 15°C, UHMW-PI deteriorates due to thermal decomposition.
At temperatures below 0°C, thermal expansion is large and the extrusion molded product becomes smelli
Both are unfavorable since they may cause NG Marks or insufficient sintering.

Hereinafter, further specific examples of the present invention will be shown. However, it goes without saying that the present invention is not limited to these examples.

Example I UHMW-PIC (trade name Ho5talen GUR4
12; manufactured by Hoechst Co., Ltd.) to 100 parts by weight of acetylene black (trade name: Denka Black; manufactured by Denki Kagaku Kogyo Co., Ltd.)
W) 5 parts by weight, montanic acid ester (trade name: Hoech
st Wachs In; manufactured by Hoechst) 3 parts by weight,
01 parts by weight of 2,5-dimethyl-2,5-di(1-butylperoxy)hexane (trade name Perhexa 25B40; manufactured by NOF Corporation) diluted to 40% by weight with calcium carbonate was blended. Henschel mixer: - Uniformly dispersed for 20 minutes. This uniform blend ・1:
' Then the raw material with an inner diameter of 50101. Using a ram extruder with a 2 m long insulated heater (electrical capacity N'KW) and 3-banded ram extruder, press the ram extruder tbb under the extrusion conditions shown in Table 1 above.
x*b-'ctniiwa48-01□Yu, it. picture
1 law was formed.

, 1 The obtained round bar was cut and the surface resistance in the cross section was measured from the surface of the round bar to the center using a tester (the distance between the measurement terminals was 8101). As shown in the figure, from the surface to the center (
The surface resistance was on the order of 103.

Comparative Example 1 On the other hand, the crosslinking agent used in Example 1 (Perhexa 25
A conductive round bar was extruded in the same manner as in Example 1, except that the raw material formulation excluding B40) was used, and the extrusion pressure was 862 to 902, which was slightly lower than in Example 1. (see Table 1)).

When the surface resistance of the cross section was measured in the same manner as in Example 1, as shown in FIG. 2, the surface resistance near the surface layer of the extruded round bar increased rapidly. Therefore, in applications that require a surface resistance of less than 1O, the surface layer is partially 1 to 2 m thick.
It was found that this required cutting, resulting in a large loss of raw materials.

Example 2 Using the same raw materials as in Example 1, a ram with an outer diameter of 795 m + 11° and a length of 400 cm, a mandrel with an outer diameter of 501111 cm, a length of 800 cm, and a cylinder with an inner diameter of 80 cm and a length of 1000 vum [insulated □ heater (electric Using a ram extruder with a capacity IKW) with 2 bands, extrude the product under the extrusion conditions shown in Table 2 to obtain an external diameter of 751111 + inner diameter of approximately 4711111.
1 conductive cross-linked type UHMW-pH! The pipe was formed.

When the obtained pipe was cut and the surface resistance at its cross section was measured, it was found to be a fairly uniform value from the outer surface to the inner surface of the pipe, as shown in FIG.

Comparative Example 2 On the other hand, using a ram extruder having the same ram, mandrel, and cylinder as in Example 2, the same raw material formulation without the addition of a crosslinking agent as in Comparative Example 1 was used to extrude the ram, and the outer diameter was approximately 751,011 mm, and the internal conductivity was 451,111 mm. When a UHMW-PIC vibe was molded and the surface resistance of its cross section was measured in the same manner as in Example 2, the surface resistance changed rapidly near the outer and inner surface layers of the pipe, as shown in Figure 3. It was rising.

As described above, the present invention suppresses the rapid increase in surface resistance near the surface (outer surface, inner surface) that occurs during lamb extrusion molding of conductive UHMW-PI, and achieves uniform conductivity from the inside to the surface. By making it possible to manufacture ram extrusion molded products with a high surface resistance, it is possible to reduce the surface resistance. It is something to play.

[Brief explanation of drawings]

Figure 1 is a longitudinal sectional view of the extrusion device used in the present invention, Figure 2 is a diagram showing the relationship between the distance from the surface of a round bar and surface resistance, and Figure 3 is a diagram showing the relationship between the distance from the surface and surface resistance of a pipe. It is a figure showing a relationship. Patent applicant Mitsuboshi Belting Co., Ltd.

Claims (1)

[Scope of Claims] L: An ultra-high molecular weight polyethylene powder having an average molecular weight of 1 million or more as determined by the viscosity method and 3 million or more as determined by the light scattering method, mixed with a conductivity imparting agent, a lubricant, and an organic peroxide and dispersed therein. 1. A method for producing a conductive ultra-high molecular weight polyethylene sintered body, which comprises forming a mixture into a sintered body by ram extrusion. 2 A patent claim in which 0.5 to 10 parts by weight of a conductivity imparting agent, 10 parts by weight or less of a lubricant, and 0.01 to 0.50 parts by weight of an organic peroxide are blended with the ultra-high molecular weight polyethylene powder. A method for producing an ultra-high molecular weight polyethylene sintered body having electrical conductivity according to item 1.