JPH02272031A - Method for producing polyolefin crosslinked molded product - Google Patents

Abstract

PURPOSE:To obtain the excellent title molded article improved in lowering of flow processability in molding by bringing a specific silane modified polyolefin into contact with a siloxane condensation catalyst and molding the above mentioned polyolefin and then crosslinking the molded polyolefin. CONSTITUTION:An ethylene-acrylic acid ester copolymer (e.g. ethylene methylacrylate copolymer) used as a raw material polyolefin is blended and thermally reacted with a silane compound (e.g. vinyltrimethoxysilane), radical forming agent (e.g. dicumylperoxide) and other additive, etc., to afford silane modified polyolefin, which is then brought into contact with a siloxane condensation catalyst (e.g. dibutyl tin dilaurate), molded and then brought into contact with water content and thermally crosslinked to provide the aimed molded article.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a crosslinked polyolefin molded article.

[Prior Art] As a conventionally proposed method for producing a polyolefin crosslinked molded article by the silane graft water crosslinking method, a silane grafted polyolefin pellet obtained by subjecting a mixture of a polyolefin, a silane compound, and a radical generator to a heating reaction is used. A commonly used method is to mix it with a catalyst masterbatch containing a silanol condensation catalyst, mold it, bring it into contact with water, heat it, and crosslink it.

[Problems to be Solved by the Invention] However, in the prior art, when the gel fraction, which represents the degree of crosslinking, is set to 50% or more, the melt index of the silane-modified polyolefin decreases to around 50% of the melt index of the raw polyolefin. This has the disadvantage of causing a decrease in fluidity during molding.

An object of the present invention is to provide a method for producing a crosslinked polyolefin molded article that eliminates the drawbacks of the prior art described above and improves fluidity during molding.

[Means and effects for solving the problem] The gist of the present invention lies in the use of a specific polyolefin that exhibits an extremely small decrease in melt index after silane grafting as a raw material polyolefin, thereby making it possible to reduce flow processing during molding. This suppresses the decline in sexual performance.

In the present invention, polyolefins with extremely small decrease in melt index after silane grafting include ethylene-acrylic polyolefins such as ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer (EEA), ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer. Examples include acid ertel copolymers.

By using such a polyolefin, even when the gel fraction after crosslinking is set to 50% or more, the melt index of the silane-modified polymer is 80% or more of the melt index of the initial polymer. This makes it possible to prevent a decrease in fluidity during molding.

The silane compounds include vinyltrimethoxysilane and vinyltriethoxysilane, the radical generators include dicumyl peroxide, benzoyl peroxide, and dichlorobenzoyl peroxide, and the silanol condensation catalysts include dibutyltin dilaurate and dibutyltin. Examples include diacetate and the like.

In the present invention, different polymers, antioxidants, stabilizers, flame retardant aids, fillers, colorants, weather resistance agents, thermal or electrical conductivity agents, etc. may be added as necessary. do not have.

In the present invention, a large amount of flame retardant may be added in order to impart flame retardancy. The flame retardant is preferably an additive flame retardant such as a halogen flame retardant, a phosphorus flame retardant, or an inorganic flame retardant such as aluminum hydroxide or magnesium hydroxide, but is not limited to these.

[Example] Melt index is 3.5.1.2.0.7 (8g/
To 100 parts by weight of pellets of three types of ethylene-ethyl acrylate copolymers (10 minutes), 1.5 parts by weight of vinyltrimethoxysilane, 0.15 parts by weight of dicumyl peroxide, thiodiethylene bis(3,5-di-tert-butyl -4
After mixing 0.1 part by weight of hydroxy) hydrocinnamate, it was put into the hopper of a 40 m/rn single screw extruder, screw IJ, number of revolutions '15 r, p, m, 1 set temperature CI: 150 ° C, C2 :200℃, C3:22
Silane-modified polyethylene pellets were produced by granulating the mixture under the conditions of 0° C. and head = 220° C. while performing a heating reaction.

When the melt flow rate of these pellets was immediately measured, it was confirmed that the melt index was almost the same as that of the raw material EEA.

Next, the pellets were immersed in an emulsion of water and dibutyltin dilaurate (temperature: 80° C.) for 16 hours to crosslink the insulator.

The evaluation results of the gel fraction of the crosslinked product thus obtained are as shown in the lower column of the table, and it had a value of 60% or more.

The gel fraction was determined by n1 after extraction in xylene at 110° C. for 24 hours and thorough drying.

Next, for comparison, when ordinary low density polyethylene (LDPE) was used as the base polymer, the melt index after silane grafting was considerably reduced to 50 to 60% of the melt index of the raw material LDPE.

[Effect of the invention] As explained above, according to the present invention, the gel fraction can be reduced to 50%.
Even if it is set above, there is almost no decrease in the melt index after silane grafting, so the flow processability during molding of the silane-modified polyolefin can be improved, and an excellent crosslinked molded product can be obtained.

Claims (1)

[Claims] 1. A polyolefin crosslinked molded product in which a silane-modified polyolefin obtained by heating a mixture of a polyolefin, a silane compound, and a radical generator is brought into contact with a siloxane condensation catalyst, molded and processed, and then brought into contact with water to be heated and crosslinked. A method for producing a crosslinked polyolefin molded article, characterized in that an ethylene-acrylic acid ester copolymer is used as the polyolefin.