JPS601237A - Foaming polyethylene composition - Google Patents

Abstract

PURPOSE:To provide a polyethylene compsn. which can give easily and simply various shaped foams in addition to sheets, by incorporating a specified catalyst for crosslinking and a vinylalkoxysilane-grafted (copolymerized) polyethylene. CONSTITUTION:A foaming polyethylene compsn. contains a vinylalkoxysilane- grafted polyethylene or a vinylalkoxysilane-copolymerized polyethylene and a catalyst of the formula (wherein R1 is alkyl, R2 is 1-16C alkyl) for crosslinking. This compsn. may contain resin compoments such as polyethylene in addition to said vinylalkoxysilane-grafted or-copolymerized polyethylene. Further, additives such as filler (e.g., talc), colorant, antioxidant, etc. may be added to the compsn. Preferred R1 includes 8C or lower long-chain alkyl groups, among which methyl, butyl and n-octyl are particularly preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyethylene compositions for use in the production of polyethylene foams.

Conventionally, crosslinkable polyethylene grafted with vinyl alkoxysilane has been used in the production of polyethylene foam to improve physical properties such as heat resistance.

Since the crosslinking of this crosslinkable polyethylene is carried out at a relatively slow rate by moisture in the presence of a silanol condensation catalyst, in order to obtain a good foam, it is necessary to add a silanol condensation catalyst and a pyrolytic foaming side to the crosslinkable polyethylene. The usual method is to add and knead the mixture, extrude it into a sheet-shaped cap, treat it with hot water to effect crosslinking, and then heat and foam it. However, with this method, the process is complicated because the material is first formed into a sheet, and it is difficult to obtain a good foam using the so-called general foaming method, in which a foaming agent is injected midway through the extruder and foaming is performed at the same time as extrusion. It is also difficult to produce foams with large wall thicknesses, tubes, or other shapes other than sheets.

In view of the vinyl alkoxysilane blank polyethylene foaming method described above, the present invention provides a method for producing a modified polyethylene foam that is simpler and allows for the production of foams in shapes other than sheet shapes. Mono-r:;he), its gist is that it contains vinylalkoxysilane blank polyethylene or vinylalkoxysilane copolymerized polyethylene and a crosslinking catalyst represented by the following general formula' (l-Characteristics It consists in a polyethylene composition for foaming.

R1-Sn-0-C-R.

111 0 0 (R1n alkyl group, RM is an alkyl group of 01 to 6)
1) Vinyl alkoxysilane contained in the foaming polyethylene composition of the present invention7 Polyethylene is polyethylene, vinyl alkoxysilane such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyljethoxysilane, etc. is mixed with organic peroxide, etc. Furthermore, the vinyl alkoxysilane copolymerized polyethylene contains ethylene and the above-mentioned vinyl alkoxysilane as copolymerization components in the main chain. All of these polymers condense and crosslink in the presence of moisture using dibutyltin silacrate and other silanol condensation catalysts, so they have been known to be used for the purpose of modifying polyethylene, such as improving its heat resistance. It is something that

Next, the compound of the general formula used in the present invention is used as a crosslinking catalyst for the polymer, and the crosslinking catalyst is converted into an alkoxysilane blat in the presence of water like a conventional silanol condensation catalyst. It has the effect of crosslinking a polymer or a cage copolymer, and also has the effect of promoting crosslinking of an alkoxysilane-containing polymer by heating at about ioθ to 150°C even in the absence of water.

That is, the present invention was made based on the discovery for the first time that the above-mentioned action of the compound represented by the general formula as a thermal cross-linking catalyst can be applied to the production of foams to obtain immediate effects. It is something.

In addition, although R1 is an alkyl group in the above general formula,
R is preferably a long brocade-shaped alkyl group having 8 or less carbon atoms, such as a methyl group, a butyl group, or a normal octyl group.

Specific examples of the compound preferably used in the present invention include lamps,
Methyl-tin oxide-octylate (CH, -5n
O-0COC, H, ), normal petite loose tin oxide lacrate (nC4)1. SnOococ,
, u, 3), normal octyl-tin oxide-stearate, normal butyl-tin oxide-acetate, and the like.

The amount of the crosslinking catalyst to be used is 0.005 to 0.5 parts by weight, particularly 0.01 to 0.5 parts by weight, per 100 parts by weight of vinyl alkoxysilane brat or copolymerized polyethylene.
It is preferable to use 0.1 part by weight.

In addition, in the composition of the present invention, it is also possible to include a resin component other than the vinyl alkoxysilane grater or copolymerized polyethylene, such as polyethylene, and additives other than the resin component such as talc or other additives. It is also possible to add fillers, coloring agents, anti-deterioration agents, and the like.

Next, in order to produce a polyethylene foam using the composition of the present invention, a composition containing vinyl alkoxysilane brat or copolymerized polyethylene and the above-mentioned crosslinking catalyst, and other resins and additives added as necessary. All you have to do is heat and knead it with an extruder, give it foaming properties, give it a shape by extrusion, etc., and foam it. This crosslinks the resin component, resulting in a crosslinked product with improved physical properties such as heat resistance. A polyethylene foam is obtained.

For example, the composition of the present invention is fed into an extruder, heated and melted in an extrusion-like cylinder, and then 7 Leon gas or other blowing agent is injected through an injection hole installed in the middle of the extruder cylinder, and then kneaded. By extruding from the mold of the extruder,
Crosslinking progresses due to heating during extrusion in the acid form, and foaming occurs simultaneously with extrusion due to the action of the foaming agent, yielding a polyethylene crosslinked foam all at once.

The polyethylene composition for foaming of the present invention has the above-mentioned structure and contains a crosslinking catalyst with a particular structure, so the process of imparting foamability to the composition and simply heat-molding it is necessary. Modified polyethylene foam with improved physical properties such as heat resistance through crosslinking can be easily produced without the need for complicated processes such as hot water crosslinking! In particular, the composition of the present invention is suitable for manufacturing foams of various shapes by applying it to a one-stage foaming extrusion method in which the composition is extruded together with a foaming agent to foam and mold at once. It is something.

The unexploded 8A will be explained below with reference to seven examples.

In addition, in the following, parts mean parts by weight.

EXAMPLE For extrusion, 295 parts of vinyl trimethoxysilafugu 2ft polyethylene and 5 parts of pellets prepared from a mixture of 25 parts of talc, 1 part of n-butyl-tin oxide-laurate and 100 parts of polyethylene were mixed and supplied,
Heat kneading L in the extruder, 7 Leon 113 was continuously press-in and mixed from the middle of the extruder Schilling at 180°C so that the pressure inside the cylinder was maintained at 50 atm, and the mixed melt was mixed. Extruded from the mold. The extruded melt started foaming at the same time as extrusion, and a foam with a foaming ratio of 27.3 times was obtained.

Regarding this foam, the crosslinked gel fraction (extruded foam as it is/using it as a sample,
After time extraction, the weight ratio of the unextracted resin to the sample piece (expressed in %) was 0.80.6.
%Met.

Further, the foam was heated to 120° C. for 3 hours, and then the total volume was measured, and the volume retention rate was found to be 94.1%.

Comparative Example The melt was extruded from an extruder in the same manner as in Example 1, except that 1 part of digtyltin silacrate was used in the pellet preparation instead of n-butyl-tin oxy F-laurate, and the foaming ratio was 28.1. A double foam was obtained. The crosslinked gel fraction and volume retention rate of this foam were measured in the same manner as in Example 1. The crosslinked gel fraction was 14%, and the volumetric fiber #'f
The rate was 22%.

patent applicant Sekisui Chemical Co., Ltd. Representative: Mototoshi Yorinuma

Claims (1)

[Claims] 1. Vinyl alkoxysilane blank polyethylene or h
A polyethylene composition for foaming, characterized in that it contains vinyl alkoxysilane copolymerized polyethylene and a crosslinking catalyst represented by the following general formula. RI-Sn -0-C-R2 111 0 (R1h alkyl group, R2-C8-1. alkyl group)