JPS5838727A - Preparation of polyolefin pipe crosslinked in the presence of water - Google Patents

Abstract

PURPOSE:To obtain the titled pipe usable as a piping for drinking water, by molding a polyolefin resin composition crosslinked in the presence of water into a pipe, and heat-treating the resultant pipe under specific conditions to decompose and volatilize the residual harmful organic components. CONSTITUTION:A polyolefin resin composition crosslinkable in the presence of water (hereinafter referred to as a composition) is molded into a pipe, which is then heat-treated under the conditions expressed by the formula[t0 is the heating time (hr);(d) is the pipe wall thickness (mm.); T is the heating temperature ( deg.K)]. The heat treatment is preferably carried out before the crosslinking of the composition generally in an anhydrous inert liquid, e.g. silicone oil, in a circulating air at 50-120 deg.C. The composition is preferably obtained by mixing (A) a polyolfein, e.g. polyethylene, with (B) vinyltriethoxysilane, etc., (C) dicumyl peroxide, etc. and (D) dibutyltin dilaurate.

Description

[Detailed Description of the Invention] A pipe made of crosslinked polyolefin has excellent heat resistance, mechanical strength, and especially environmental stress cracking resistance.
It is seen as promising for water pipes, hot water supply pipes, etc.

The present inventors constructed a water-crosslinked polyolefin pipe by combining the organic components, i.e., unreacted grafting agent (e.g., vinyltrimethoxysilane), decomposition products of the crosslinking agent as a graft initiator,
It was discovered that methanol produced by the graft reaction and other toxic organic components remained in abundance outside the fort, making it completely unusable as a drinking water pipe. Even after one month has passed since manufacture, the amount remaining is
It reaches as much as 100 to 800 ppin.

The inventors of the present invention have conducted extensive research to solve these new technical challenges and make water-crosslinked polyolefin pipes usable as drinking water piping, and have found that under the following specific conditions: By heat-treating water-crosslinked (uncross-linked 4I&) polyolefin pipes, any harmful organic components remaining therein can be decomposed and dissipated to obtain water-crosslinked polyolefin pipes that can be used as drinking water piping. This discovery has been made and the present invention has been completed.

Eggs are also a novel technological invention! 1! We found a problem and solved the problem by further research based on this, and when manufacturing the water-crosslinked polyurethane reflex,
After molding the water-crosslinkable polyolefin resin compound into a pipe shape, to≧20d” exp (0,
75X10' (?) - ±) ) [However, member is the heating time, d is the pipe wall thickness (drunk), and T is the heating temperature ('K)
This is a method for producing a water-crosslinked polyolefin pipe used as drinking water piping, which is heat-treated under the following conditions.

In the present invention, the water-crosslinked polyolefin resin composition used as a raw material is, for example, (a) polyolefin (preferably polyethylene, whose density is generally 0.91 to 0.970). ] to (b) general formula R
R' SiY, (R is a hydrocarbon group containing monovalent olefinic unsaturation or a hydrocarbonoxy group, Y is a hydrolyzable organic group 1. R' is a group it or a group Y) and a compound represented by , (c) a compound that generates free radicals in the polyolefin at a temperature of 140° C. or higher, and (d) a silanol condensation catalyst.

(a) Components include homopolymers such as polymethylene, polyethylene, and polystyrene; copolymerized monopolymers mainly composed of methylene with ethylene, propylene, etc.; copolymerized monomers composed mainly of ethylene with methylene, propylene, butene, etc., mainly composed of propylene. Examples include copolymers of olefins such as those copolymerized with other olefins, and copolymers of olefins such as ethylene, propylene, and butene with other monomers (e.g., vinyl acetate, acrylic acid, and methacrylic acid).

Component (b) may be a known silane compound such as vinyltriethoxysilane or vinylmethyldimethoxysilane.

Component (C) includes organic peroxide crosslinking agents such as dicumyl peroxide, 45-dimethyl-2,5-di(t-butylperoxy)-hexyne-8, and azobis-isobutyronitrile. , azo compounds such as dimethyl azo isodibutyrate, etc.

Component (d) may include carboxylates such as dibutyltin dilaurate, stannous acetate, lead naphthenate, and zinc caprylate, and organometallic compounds such as titanate esters and chelate compounds.

The blending ratio of these components may be arbitrarily selected, but for example, 0.1 to 50 parts of component (b), preferably 0.5 to 1 part of component (11)
0 parts, component (C) 0.05 to 1.5 parts, preferably 0.0 parts.
01 to 0.2 parts, component (d) 0.005 to 5 parts, preferably 0. 1 to 0.5 parts of O.

The heat treatment is carried out at any step after the tubular shape, specifically before, during, and after crosslinking, and the removal of toxic organic components can be achieved satisfactorily by the heat treatment in any of these steps.

By the way, since non-crosslinked polyolefin pipes are much easier to joint than crosslinked pipes, they are heat treated before crosslinking, shipped uncrosslinked, jointed and laid, and then water crosslinked while passing water through them. 14J et al., the preferable heat treatment period is before crosslinking.

Heat treatment before crosslinking is generally performed in circulating air or in an inert liquid that does not contain water (e.g. silicone oil, polyalkylene glycol oil, etc.), and the heating temperature is above room temperature and below the melting point of the uncrosslinked polyolefin pipe. (Generally from 50℃
]20°C).

The heat treatment during crosslinking is carried out in heated water, steam, etc., and the heating temperature is as determined before crosslinking.

Heat treatment after crosslinking is carried out in circulating air, heated water, steam,
Heating is done in an inert liquid that does not contain water, and the heating temperature is room temperature (
The treatment is carried out at as high a temperature as possible, for example, about 400°C, within a range that does not cause deterioration of the water-crosslinked polyolefin pipe. □For molding and crosslinking of the water-crosslinkable polyolefin pipe according to the present invention, known molding and crosslinking means can be used. For example, extruded, uncrosslinked polyolefin pipe can be easily formed and crosslinked by exposing it to an aqueous atmosphere (e.g., immersion in water, water passage, steam) with or without subjecting it to the heat treatment described above. .

In the context of the present invention, the wall thickness of the water-crosslinked polyolefin pipe is generally from 1 to 50, preferably from 1 to 20.

After making it into a water-crosslinked polyethylene pipe under the conditions, it was supervised by the Ministry of Health and Welfare's Environmental Sanitation Bureau, Water Supply Environment Department: Chapter 15, "Potassium Permanganate Consumption" of "Testing Methods for Water Supply - 1978 Edition" (published by the Japan Water Works Association in 1982). Table 1 shows the consumption of potassium permanganate measured according to the method described in ``.

100 parts of polyethylene 2.2 parts of vinyltrimethoxysilane 0.2 parts of dibutyl-tin-dilaurate 0.05 parts of procedural amendment No. 1, case description 1982 Patent Application No. 136.821 2. Title of the invention Method for producing water-crosslinked polyolefin pipe 3.
Relationship with the case of the person making the amendment Patent applicant Name: Dainichi Nichifuden Wire Co., Ltd. 7, Subject of amendment (1) Li Detailed Declaration Page 1 Description of scope of patent claims Annex No. Correct.

(2), page 3, line 9, “heating time” is followed by t.
Add ``(hr,)'' 〇(3) Ministry of Finance, page 7, w, line 4 [1-50J, then rm
Join B.

(4) On page 7 of the same V#, line 4, “1~2oJ is followed by r,
Joined J-kai.

Attachment Claims (1) When producing a water-crosslinked polyolefin resin composition - [however, t
o is the heating time (hr-J), d is the pipe wall thickness (IOI)
Manufacturability of a water-crosslinked polyolefin pipe for use as drinking water piping, characterized in that it is heat-treated under conditions of J k and T are heating temperatures CK).

(2) A binary system for a water-crosslinked polyolefin pipe according to claim (1), in which the heat treatment performed before crosslinking is expressed as a percentage.

Special release day? U38- 38727 (4) Procedural Amendment (Voluntary) November 26, 1980 Commissioner of the Patent Office Tol Indication of Case 1982 P#: fF Condyle No. 136821 2.
Title of the invention Method for manufacturing a water-crosslinked polyolefin pipe 3 Relationship with the case of the person making the amendment Patent applicant 7, subject of the amendment (1) Page 7, line 8 of the specification: [After making a water-crosslinked polyethylene pipe, wo "After making it into a pipe, JIS
The sample water is collected in accordance with the method described in Sections 6 and 5 of K6762-1966, and the correction is made to ``About the sample water.''

Claims (2)

[Claims] (1) When manufacturing a water-crosslinked polyolefin pipe, 1 to ≧ 20d" exp (0,76X10' (-y
-BT) ) [where, to represents the heating time, d represents the pipe wall thickness, and T represents the heating temperature ('K)]. Method for manufacturing water-crosslinked polyolefin pipes used as (2) A method for producing a water-crosslinked polyolefin pipe according to claim (1), characterized in that heat treatment is performed before crosslinking.