JPS588748A - Crosslinked polyolefin composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which has improved extrudability, does not suffer from accumulation of resinous matter around a die during extrusion, and is useful for wire covering, by adding a metallic soap to a hydrolytically crosslinkable compsn. composed mainly of a silicone-grafted polyolefin. CONSTITUTION:100pts.wt. polyolefin such as PE, 1-4pts.wt. ethylenically unsaturated silane compd. having a hydrolyzable org. group such as vinyltriethoxysilane, 0.02-1pts.wt. free radical-generating agent such as dicumyl peroxide, 0.01-5pts.wt. silanol condensation catalyst such as dibutyltin dilaurate and 0.1- 0.7pts.wt. metallic soap such as lithium stearate or processing aid composed of a mixture of said metallic soap and an org. acid (ester) having a m.p. of 60 deg.C or higher, are kneaded together to obtain the titled compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydrolytically crosslinked polyolefin composition mainly composed of a silicone-grafted polyolefin having excellent extrusion processability.

Silicone-grafted polyolefin is extruded using an ordinary extruder and then cross-linked in the presence of water, so it does not require special equipment like chemical cross-linking and is easy to process. As a crosslinked polyolefin, it has been applied to molded products such as electric wire coatings.

However, when extruding wire coatings, pipes, etc. using a hydrolytically crosslinkable polyolefin composition mainly composed of silicone-grafted polyolefin (hereinafter abbreviated as silane crosslinked polyolefin), the lip of the die may The problem is that a gel-like substance (hereinafter referred to as sludge) adheres and accumulates on the surface of the molded product, causing scratches on the surface of the molded product, and that this sludge adheres to the surface of the molded product, significantly impairing the appearance of the molded product. . Therefore, the generated meyani is processed by a method such as burning it with a burner,
Not only is the operation complicated, but especially when the buildup generated on the mandrel during tube forming adheres to the inner surface of the pipe.
Since its removal is also difficult and poses a serious problem, preventing the formation of smear during extrusion molding of silane-crosslinked polyolefins is an important issue.

The present invention was completed based on the discovery that by adding a specific processing aid to a silane-crosslinked polyolefin, the occurrence of smear during extrusion processing can be prevented and extrusion processability can be significantly improved.

That is, an object of the present invention is to provide a silane-crosslinked polyolefin composition having excellent extrusion processability. A crosslinked polyolefin composition characterized in that 0.1 to 0.7 parts by weight of an extrusion processing aid is blended in 1 part by weight. That is, the composition according to the present invention comprises a polyolefin, a silane compound, a radical generator, a silanol condensation catalyst, and an extrusion processing aid.

The extrusion processing aid used in the present invention is a metal soap (hereinafter referred to as A
Sometimes called ingredients. ) It is preferable to combine component A with an organic acid having a melting point of 60°C or higher or an ester thereof (sometimes referred to as organic acid, etc.) and/or silicone oil (hereinafter referred to as B).
Sometimes called ingredients. ) consists of a combination system. The metal soap is preferably a metal salt of stearic acid or 12-hydroxystearic acid, such as calcium, zinc,
Mention may be made of the metal salts of magnesium, aluminum and lithium. When component A is used alone, lithium stearate is particularly preferred.

Preferred examples of the organic acid used as component B include stearic acid, 12-hydroxystearic acid, palmitic acid, and stearin.

In a system in which lithium stearate and 12-hydroxystearic acid are used in combination, a combination of lithium stearate and 12-hydroxystearic acid is particularly preferred.

Also, silicone oil has a temperature of 350 to 60 at 5°C.
00008 Preferably, a liquid having a viscosity of 1000 to 1000008 and a liquid at room temperature is used. In a system used in combination with silicone oil, calcium stearate or lithium stearate is preferred as component A.

The blending ratio of A component and B component is A, /B (weight ratio) 05
-5, preferably 1-2 is appropriate.

The blending amount of component A and component B is 0.05 to 0.5 parts by weight, preferably 0.05 to 0.05 parts by weight, per 100 parts by weight of polyolefin.
, 1 to 04 parts by weight, and the combined amount of both is 01 to 04 parts by weight.
-07, preferably 02-05 parts by weight. If it is less than 0.01 parts by weight, it will not be effective in preventing the formation of stickiness, and if it exceeds 0.07 parts by weight, the composition will slip in the extruder and the extrusion stability will be impaired.

Examples of the polyolefin used in the present invention include α-olefin homopolymers and copolymers such as high-pressure and low-pressure low-density polyethylene, high-density polyethylene, and polypropylene. It can also contain a copolymer of a vinyl monomer copolymerizable with an α-olefin and a vinyl monomer copolymerizable with an α-olefin.

As the ethylenically unsaturated silane compound having a hydrolyzable organic group, those having R8i Zs (R is an ethylenically unsaturated group and Z is a hydrolyzable organic group) are suitable, and preferred examples are: As 0H2=0H8i
(OR')s (Rf represents a hydrocarbon group having 1 to 8 carbon atoms), specific examples of which include Teha, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane and their like. A combination is preferred.

The radical generator is not particularly limited as long as it generates free radicals in the polyolefin under the reaction conditions, but examples include benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2°5-di(1 -butylperoxy)hexyne-3, azobisisobutyronitrile, and a particularly preferred example is dicumyl peroxide.

Preferred examples of the silanol condensation catalyst include dibutyltin dilaurate, dibutyltin diacetate, dioctyltin simalate, and the like.

The amounts of each component are: 1 to 4 parts by weight of a silane compound, 0.2 to 1 parts by weight of a radical generator, 0.01 to 5 parts by weight of a silanol condensation catalyst, and 01 to 0.7 parts by weight of an extrusion processing aid per 100 parts by weight of polyolefin. A range of is suitable.

In addition to the above-mentioned components, various antioxidants, ultraviolet deterioration inhibitors, antistatic agents, coloring agents, carbon black, etc. that are commonly blended may be contained.

Although the composition according to the present invention can be fed into an extruder and made into pellets, as shown in Japanese Patent Publication No. 1711/1989, a silicone grafted polyolefin and a polyolefin containing a silanol condensation catalyst are prepared separately. Mixing is also possible.

When this composition is used to form pipes, electric wire coatings, or steel pipe coatings, the occurrence of eye stains can be suppressed to a large extent, allowing stable operation over a long period of time, and making it possible to manufacture products with stable quality.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. In each example, p per 100 parts by weight of resin,
2,6-di-1-buty/L-4-methylphenol, tetrakis-[methylene-3-(3',5'di-tert-butyl-4'-hydroxyphenyl]propio, i-1-)
0.005 parts by weight of methane were added in each case.

Example 1 100 parts by weight of polyethylene having a density of 0.945 Ml, 0.1 part by weight of dicumyl peroxide and 2 parts by weight of vinyltrimethoxysilane were blended, and about 200 parts by weight of polyethylene with a density of 0.945 Ml was mixed in a single screw extruder.
A silicone-grafted polyethylene was prepared by extrusion at a temperature of °C. On the other hand, 100 parts by weight of polyethylene, 05 parts by weight of dioctyltin simalate, 20 parts by weight of carbon black
parts by weight, 2 parts by weight of lithium stearate, and 2 parts by weight of 12-hydroxystearic acid, and extruded at a temperature of about 200°C using a single screw extruder to prepare a catalyst masterbatch. 10 parts by weight of a catalyst masterbatch was blended with 90 parts by weight of silicone-grafted polyethylene and extruded using a single-screw extruder at a molding temperature of 200°C to form an O tube with an outer diameter of 4 and a wall thickness of 0.7 mrnO. 2 after starting molding
Even after 4 hours had elapsed, no buildup of dirt was observed, indicating good extrusion moldability.

Example 2 Lithium stearate was mixed with calcium stearate, 1
A tube having an outer diameter of 60 mm and a wall thickness of 5 mm was molded in the same manner as in Example 1, except that 1 part by weight of silicone oil (300008) was added to the 2-hydroxystearic acid double layer. Even after 48 hours had passed since the start of molding, no buildup of dirt was observed, indicating good extrusion moldability.

Example 3 A tube with an outer diameter of 60 mm and a wall thickness of 5 mm was molded in the same manner as in Example 1, except that 1 part by weight of silicone oil (300008) was used instead of 12-hydroxystearic acid. Even after 48 hours had passed since the start of molding, no buildup of dirt was observed, indicating good extrusion moldability.

Comparative Example 1 Same as Example 1 except that lithium stearate and 12-hydroxystearic acid were not blended, but the outer diameter was 60 m.
A tube with a wall thickness of 5 mm was molded.

Ten minutes after the start of molding, a large amount of dirt was observed at the die slip area. After a further 30 minutes, the film from the die slip part is detached and adheres to the inside and outside of the tube, so that only a product with low commercial value can be obtained whose appearance on the inside and outside is significantly impaired.

Comparative Example 2 A tube with an outer diameter of 4 mm and a wall thickness of 0.7 mm was molded in the same manner as in Comparative Example 1.

Three minutes after the start of molding, smearing was already observed at the die slip area. After a further 15 minutes, it was observed that the resin on the die slip part fell off and adhered to the outer surface of the tube. Comparative Example 3 A tube with an outer diameter of 4 mm and a wall thickness of 0.7 mra was molded in the same manner as in Example 1, except that 03 parts by weight of lithium stearate and 03 parts by weight of 12-hydroxystearic acid were used.

Ten minutes after the start of molding, smearing was observed at the die slip area. After another 30 minutes, it was observed that the resin was detached and adhered to the outer surface of the tube.

Comparative Example 4 Same as Example 2 except that 6 parts by weight of calcium stearate and 5 parts by weight of silicone oil were used, but the outer diameter was 60 mm,
A tube with a wall thickness of 5 mm was molded.

Because the formed tube was unstable in screw extrusion in the extruder, the extrusion rate fluctuated and the wall thickness of the tube fluctuated significantly, making it impossible to obtain a tube of the specified dimensions.

Patent applicant: Showa Denko Co., Ltd. Agent Sei Kikuchi

Claims (1)

[Claims] Polyolefin 1 in hydro-crosslinkable polyolefin compositions mainly composed of silicone-grafted polyolefins
A crosslinked polyolefin composition characterized in that 0.1 to 0.7 parts by weight of an extrusion processing aid is blended in 0.00 parts by weight.