GB2028831A

GB2028831A - Moisture-curable polymer composition

Info

Publication number: GB2028831A
Application number: GB7923560A
Authority: GB
Original assignee: Mitsubishi Petrochemical Co Ltd
Current assignee: Mitsubishi Petrochemical Co Ltd
Priority date: 1978-07-05
Filing date: 1979-07-05
Publication date: 1980-03-12
Also published as: FR2430432A1; GB2028831B; JPS559611A; JPS6223777B2; DE2926830C3; FR2430432B1; DE2926830C2; DE2926830A1

Abstract

A crosslinkable polyethylene resin composition comprises (A) a copolymer of ethylene and an ethylenically unsaturated silane compound, wherein the content of the ethylenically unsaturated silane compound unit is 0.001 to 15 percent by weight, and (B) a silanol condensation catalyst, e.g. dibutyl tin dilaurate. The copolymer may further comprise a further monomer, e.g. vinyl acetate or methyl acrylate. The composition may also comprise a foaming agent, e.g. an azodicarbonamide.

Description

SPECIFICATION Crosslinkable Polyethylene Resin Compositions This invention relates generally to crosslinkable polyethylene resin compositions. More particularly, the invention relates to polyethylene resin composition the resins of which are crosslinkable by exposure to water, each composition comprising a random copolymer of ethylene and an ethylenically unsaturated silane compound having a hydrolysable silane group as a crosslinkable group and a crosslinking reaction catalyst.

The procedure of crosslinking low-density polyethylenes and other polyethylene resins thereby to improve their mechanical strength, heat resistance, and other properties, and various crosslinking techniques for this purpose are known.

One crosslinking technique of this character which has been proposed comprises adding an organic peroxide as a crosslinking agent to a polyethylene and heating these materials to a high temperature to decompose the peroxide and thereby to initiate the crosslinking reaction. In this case, however, since crosslinking due to the decomposition of the peroxide is carried out prior to the step of forming the polyethylene, the quality of the formed product is frequently defective, and, in extreme cases, the forming step cannot be carried out satisfactorily.

If the crosslinking is to be carried out after the forming step, a high-temperature effective peroxide which can withstand the forming temperature must be used. In order to decompose a peroxide of such a character, the formed articles must be heated to a temperature higher than the forming temperature. As a result, variations due to softening of the formed article will occur in the crosslinking step, and the quality of the formed product will still be defective.

An example of a polyethylene whose manufacture is not accompanied by such problems encountered in chemical crosslinking is a silicone-grafted polyethylene as disclosed, for example, in Japanese Patent Publication Number 1711/1 973, Japanese Patent As Laid Open No.8389/1972, Japanese Patent As Laid Open No. 138042/1975, and Japanese Patent As Laid Open No. 9073/1977.

When a silicone-grafted polyethylene is exposed to water, its silicone part is hydrolysed, and the crosslinking reaction progresses. Since this hydrolysis occurs at a relatively low temperature, the larne- scale equipment normally required for chemical crosslinking becomes unnecessary. For this reason applications to crosslinked moulded products have been considered. In this case, however, a plurality of process steps for producing the base polyethylene and for grafting the silicone onto the base polyethylene are necessary. Moreover, a polyethylene article produced and crosslinked in this manner, such as, for example, a sheet, is unsatisfactory with respect to its odour, mechanical strength, heat resistance and heat welding property.

On the other hand, a method of causing crosslinking of copolymers of ethylene and a vinyl alkoxysilane by heating or by mechanical working has been disclosed in U.S. Patents Nos. 3,225,018 and 3,392,1 56. This method is advantageous relative to the above mentioned grafting method in that a crosslinkable polyethylene is obtained with a single process step, that is, with only the copolymerization step. In this case, however, since the crosslinking unavoidably must be carried out prior to the forming process, the same problems as in the case of the above-mentioned chemical crosslinking are encountered. Moreover, the mechanical strength of a formed article produced by forming after the crosslinking reaction is not satisfactory.

It is an object of this invention to provide solutions to the above-described problems encountered in the prior art. It is contemplated in accordance with this invention to achieve this and other objects thereof by combining a random copolymer comprising a unit of ethylene and a unit of an ethylenically unsaturated silane compound which is crosslinkable by exposure to water and a catalyst for crosslinking by exposure to water.

According to this invention, briefly summarised, there are provided crosslinkable polyethylene resin compositions each comprising (A) a copolymer comprising a unit of ethylene and a unit of an ethylenically unsaturated silane compound, wherein the content of the unitofethylenically unsaturated silane compound is from 0.001 to 1 5 percent by weight, and (B) a silanol condensation catalyst.

According to this invention, crosslinking upon exposure to water is imparted to a polyethylene resin having a silane group introduced into polyethylene molecules, not by grafting, but by random copolymerization. The term "copolymers" as used herein does not normally include graft copolymers.

However, it does not exclude graft copolymers which may unavoidably be produced concurrently.

A crosslinked formed article obtained by forming a composition of this invention and exposing it to water thereby to cause crosslinking therein not only has excellent mechanical strength and heat resistance but, in the form of a crosslinked sheet article (a sheet article being one of the formed articles of a composition of this invention), has a high performance equivalent in practice to that of an ordinary low-density polyethylene sheet with respect to its heat welding property, which has given rise to the greatest difficulty in crosslinked polyethylene sheets of the prior art, as well as even high performance relative to heat resistance.

While there is no grafting step in this invention, a polyethylene wherein an unsaturated silane compound is copolymerized must be made separately instead. Furthermore, partly because the quantity of the unsaturated silane compound used is small, the production of the silanated copolymers is made possible by carrying out this copolymerization by substantially the same method, as in the homopolymerization of ethylene, and may be considered to be within the diversification of polyethylenes.

The invention is now described in detail.

1. Copolymer of ethylene and unsaturated silane compound (Silanated copolymer) For brevity, the copolymer comprising units of ethylene and an unsaturated silane compound is referred to as "the silanated copolymer". We may use as the unsaturated silane compound, various compounds each having a hydrolysable silane group and an ethylenically unsaturated bond which is copolymerizable with ethylene.

A compound of this character can be represented by the following general formula: R Si Rtn Y3~n wherein R designates an ethylenically unsaturated hydrocarbyl or hydrocarbylether group; R' designates an aliphatic saturated hydrocarbyl group; Y designates a hydrolysable organic group; and n is0, 1 or 2. When a plurality of Ys exist, they need not be the same.

More specific examples of these unsaturated silane compounds are those wherein, for example, R is vinyl, ally, isopropenyi, butenyl, cyclohexenyl or y-methacryloxypropyl; Y is methoxy, ethoxy, formyloxy, acetoxy,propionyloxy, alkylamino or arylamino; and R' is methyl, ethyl, propyl, decyl or phenyl.

A particularly desirable unsaturated silane compound is represented by the following formulas.

C H2 = C H Si (OZ)3 wherein Z is a hydrocarbyl group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms.

In the most desirable case, this compound is vinyl trimethoxysilane, vinyl triethoxysilane or vinyl triacetoxysilane.

The copolymerization of the ethylene and the unsaturated silane compound is carried out under appropriate conditions which will bring about the copolymerization of these two monomers.

More specifically, these copolymerization conditions include, for example: a pressure of 500 to 4,000 kg/cm2, preferably 1,000 to 4,000 kg/cm2; a temperature of 100 to 4000 C, preferably 1 50 to 3500C; the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, and the use of an autoclave, tubular reactor or the like, preferably an autoclave reactor wherein the two monomers are caused to contact simultaneously or in stepwise manner.

In this invention, any of the radical polymerization initiators and chain transfer agents known to be suitable for the polymerization or copolymerization of ethylene can be used. Examples of such polymerization initiators are organic peroxides such as lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide and t-butyl peroxyisobutyrate; molecular oxygen; and azo compounds such as azobisisobutyronitile and azoisobutylvaleronitrile. Examples of such chain transfer agents are paraffins such as methane, ethane, propane, butane and pentane; cr-olefins such as propylene, butene-1, and hexene-1; aldehydes such as formaldehyde, acetaldehyde and nbutylaldehyde; ketones such as acetone, methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons and chlorohydrocarbons.

The copolymer used in the composition of this invention has a content of a unit of the unsaturated silane compound of from 0.001 to 15 percent, preferably 0.01 to 5 percent, particularly preferably 0.05 to 2 percent, all percentages being by weight. In general, the silanated copolymer which has a high content of a unit of an unsaturated silane compound, after crosslinking has taken place upon exposure to water, possesses excellent mechanical strength and heat resistance. However, if this content is excessively high, the tensile elongation and heat welding property will deteriorate. The content range of 0.001 to 1 5 percent by weight as determined on this basis.

2. Sllanol condensation catalyst In general, chemicals which can be used as catalysts for promoting dehydration condensation between silanols of silicone are suitable for use in this invention. A silanol condensation catalyst of this character is, in general, any of the carboxylates of metals such as tin, zinc, iron, lead and cobalt, organic bases, inorganic acids and organic acids.

Specific examples of the silanol condensation catalyst are dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate; ethylarnines, dibutylamine, hexylamines, pyridine; inorganic acids such as sulfuric acid and hydrochloric acid; and organic acids such as toluenesulfonic acid, acetic acid, stearic acid and maleic acid. Carboxylates of tin are particularly desirable.

The quantity in which the silanol condensation catalyst is used can be suitabiy determined with respect to the given catalyst for the given copolymer with reference to the examples of practice set forth hereinafter. Generally speaking, the quantity of the catalyst to be blended into the composition is in the range of 0.001 to 10 percent by weight, preferably 0.01 to 5 percent by weight, particularly preferably 0.03 to 3 percent by weight, relative to the quantity of the silanated copolymer in the composition.

3. Preparation of composition The compositions of this invention can be prepared by any of the methods and means which can be used for blending various additives into thermoplastic resins.

The process of preparing the composition of this invention, in general, is one which is ordinarily accompanied by melting or dissolving (particularly the former) the silanated copolymer and/or the silanol catalyst For example, the copolymer, the silanol condensation catalyst (as it is or in the form of a solution or dispersion), and, when necessary, adjuvants-are kneaded in an extruder and then extruded into desired formed articles such as, for example, moulded articles, bars, tubes, sheets, and other articles or materials such as pellets.

Furthermore, the quantity of the silanol condensation catalyst is small in comparison with that of the copolymer mentioned hereinbefore. Accordingly, a convenient procedure, which is frequently resorted to in the blending of ingredients in small quantities, is to prepare a master batch by blending the silanol condensation catalyst in a high concentration in a dispersion medium such as polyethylene, and to blend this master batch dispersion into the copolymer in a quantity such that catalyst concentration attains a specific value.

Another possible process comprises forming the copolymer into a desired formed article and thereafter immersing the formed article in a solution or a dispersion containing the silanol catalyst thereby to impregnate the article with the catalyst By this process, a composition of this invention in a formed state can be obtained.

As frequently seen in resin compositions, the composition of this invention may contain various adjuvant materials. Examples of such adjuvant materials are miscible thermoplastic resins, stabilizers, lubricants, fillers, colouring agents and foaming agents.

4. Crosslinking When a formed article of a composition of this invention is exposed to water, a crosslinking reaction occurs. It should be understood, however, that crosslinking is not a requisite of this invention.

This exposure to water is suitably carried out by causing the formed article to be contacted by water (in liquid or vapour state) at a temperature in the range of from room temperature to 2000C, ordinarily in the rangeoffrom room temperature to 1000C,fora contact time in the range of from 10 seconds to 1 week, ordinarily in the range of from 1 minute to 1 day. This contacting with water can be carried out under increased pressure. In order to increase the wetness of the formed article, the water may contain a wetting agent, a surfactant, a water-soluble organic solvent, or the like. In addition to ordinary water, the water can be in other forms such as heated water vapour or moisture in the air.

In addition, by exposing to water the composition of this invention during its preparation and forming, the preparation and forming of the composition and the crosslinking reaction can be carried out simulataneously.

5. Modifications A variety of modifications relating to the composition of this invention are possible.

In one such modification, in addition to the two ingredients, namely, the ethylene and the ethylenically unsaturated silane compound, a terpolymer of these two monomers and another monomer copolymerizable therewith is used as the aforementioned copolymer. This comonomer can be selected from various monomers which are copolymerizable with the two monomers, the ethylene and the ethylenically unsaturated silane compound, and, moreover, are compatible with the unsaturated silane and/or the crosslinking reaction thereof.Examples of such comonomers are vinyl esters such as vinyl acetate, vinyl butyrate, vinyl pivalate and the like; (meth)acrylates such as methyl(meth)acrylate, butyl(meth)acrylate, and the like; olefinically unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid and the like; derivatives of (meth)acrylic acid such as (meth)acrylamide, (meth)acrylonitrile and the like; and vinyl ethers such as vinyl methyl ether, vinyl phenyl ether and the like. Particularly desirable comonomers are vinyl esters and (meth)acrylic esters. The content of this comonomer unit within the copolymer is generally up to 40 percent by weight, preferably 0.5 to 35 percent by weight, more preferably 1 to 25 percent, by weight of the copolymer.

Another modification comprises introducing a foaming agent into the composition of this invention thereby to render the composition foamable or expandable. The copolymer within the composition in this case, in addition to being a copolymer comprising substantially the ethylene unit and the ethylenically unsaturated silane unit, may be a copolymer comprising these two monomer units and, further, a third comonomer as described above. In the modifications set forth hereinafter, it is to be understood that the copolymer in the composition can be either of these two kinds of copolymers.

Foaming agents which can be used for this purpose are those which are known to be suitable for the foaming of ethylenic resins.

Typical examples of such foaming agents are chemical foaming agents such as azodicarbonamide, d initrosopentamethylenetetramine, p,p'-oxybi s(benzenesulfonylhydrnzide), N,N'-d imethyl-N,N' dinitrosoterephthalamide and the like, and physical foaming agents such as hydrocarbons (for example, butane or pentane) and halogenated hydrocarbons (for example, methylchloride). Among the chemical foaming agents, azodicarbonamide is preferable in view of its stability and decomposition temperature.

The above-enumerated foaming agents can be used singly or as mixtures of a plurality thereof. A foaming agent (C) is normally used in a quantity which is, ordinarily, 0.2 to 30 percent by weight, preferably 0.5 to 20 percent by weight, on the basis of the sum (A + C) where (A) represents the copolymer.

Still another modification comprises blending with this composition a polyolefin compatible therewith. Examples of this polyolefin are low-density, medium-density and high-density polyethylene, polypropylene, chlorinated polyethylene, and various copolymers comprising ethylene and one or more other monomers (for example, vinyl acetate, methyl acrylate, propylene, butene, hexene and the like).

The above-mentioned polyolefin can be used singly or as mixtures of a plurality thereof. The content of the polyolefin in the composition is up to 70 percent by weight based on the sum of the quantities of this polyolefin and this copolymer. Furthermore, the content of the ethylenically unsaturated silane compound unit is based on this sum of the quantities of this polyolefin and this copolymer.

In a further modification, a fine inorganic filler is blended with this composition. Examples of this inorganic filler are silicates such as kaolin, purophanite, talc, montmorillonite, zeolite, mica, diatomaceous earth, silica, white carbon, calcium silicate, asbestos, glass powder, glass fiber, calcium carbonate, gypsum, magnesium carbonate, magnesium hydroxide, carbon black, titanium oxide and the like. The content of this inorganic filler is up to 60 percent by weight on the basis of the sum of quantities of this filler and this copolymer.

One specific, concrete example of the composition according to this invention is in the form of a film. The thickness of this film is ordinarily in the range of 5-500 microns. This film may be in the form of a laminate with one or more other films.

In order to indicate more fully the nature and features of this invention, the following specific examples of practice constituting preferred embodiments of this invention and comparison examples are set forth, it being understood that these examples are presented as illustrative only and that they are not intended to limit the scope of the invention. Throughout these examples, all quantities specified in percentages or parts are by weight.

EXAMPLES 1,2 AND 3 Ethylene-vinyltrimethoxysilane copolymers were continuously synthesised, in each case, by supplying a mixture of ethylene, vinyltrimethoxysilane and propylene as a chain transfer agent to a stirred autoclave reactor of 1.5-liters capacity and adding thereto t-butylperoxyisobutyrate as a polymerization initiator under the conditions of a pressure of 2,400 kg/cm2 and a temperature of 2200C. The formed products thus obtained were almost odourless. The polymerization conditions and the properties of the formed copolymers are shown in Table 1 below.

To each of these copolymers, 5 percent of a master batch comprising 1 percent of dibutyltin dilaurate and 99 percent of low-density polyethylene ("YUKALON EH-30" (trade mark) manufactured by Mitsubishi Petrochemical Co. Ltd., Japan) was added, and these materials were mixed for 7 minutes in a roll mill at a temperature of 120 to 1 250C and formed into a pressed sheet, which was immersed in hot water at 1 000C for one day to cause crosslinking. The tensile strength and elongation and heat welding property of the sheet'thus obtained were measured whereupon the results shown in Tables 2 and 3 were obtained.

COMPARISON EXAMPLE 1 2 Percent of vinyltrimethoxysilane and 0.1 percent of dicumylperoxide were dispersed in a lowdensity polyethylene ("YUKALON EH-30" (trade mark) manufactured by the Mitsubishi Petrochemical Co. Ltd., Japan) having a melt index of 2 g/1 0 min and a density of 0.919 g/cc. The resulting dispersion was caused to undergo graft polymerization by the use of a 50-mm diameter Dulmage-screw extruder with an LID value of 24 at an extrusion temperature of 2000 C. The silicone-grafted polyethylened thus obtained which had a very strong odour, was used further to form a pressed sheet which was caused to undergo crosslinking by the process set forth in Examples 1, 2 and 3.

COMPARISON EXAMPLE 2 The ethylene-vinyltrimethoxysilane copolymer described in Example 3 of U.S. Patent 3,392,156 was subjected to thermal and mechanical processing in a roll mill at a temperature of from 145 to 1 500C for 3 hours to effect cross-linking. The cross-linked material thus obtained was formed into a pressed sheet.

COMPARISON EXAMPLE 3 A low-density polyethylene ("YUKALON ZF-30" (trade mark) manufactured by the Mitsubishi Petrochemical Co. Ltd., Japan) having a melt index of 1 g/l 0 min and a density of 0.920 g/cc was formed into a pressed sheet.

The properties of the crosslinked sheets obtained in Comparison Examples 1, 2 and 3 are shown in Tables 2 and 3 as follows: TABLE 1 Polymerization conditions and properties of copolymers formed.

Polymerization conditions Properties of copolymer Initiator Ethylene Melt# Vinyl# feed rate conversion index silane content g/Hr % g/10 min % by weight 2.0 15 1.0 0.34 2.4 15 1.0 0.72 *' Test method:Japanese Industrial Standards JIS K 760 *2 Analysis by fluorescent X-rays TABLE 2 Tensile properties

aS Tensile strength and elongation at break \ \ | point 23"C Vinyl *t \ elongation at Gel a2 silane content content t Strength i Elongation \Example 2 6.05 32 Strength Example li-xample 1 1 0.05 1 32 1 190 1 550 0.72 Example 2 | 0.34 | 71 | 200 | 450 Example Example 3 | 0.72 | 79 | 115 350 Comparison Example 1 | 0.72 | 70 1 165 1 370 2 2 1 OJ2 1 68 1 105- 68 190 'S 3 0 0 170 600 Continuation of Table 2

Tensile strength and elonga tion at break point *3 80 C- Strength Elongation Kg/cm2 % Example 1 55 510 Example 2 75 430 Example 3 75 340 Comparison Example 1 60 370 2 2 40 230 3 15 # 390 al Analysis by fluorescent X-rays *2' Extraction with boiling xylene for 10 hours *3 Measured by JIS K6760 TABLE 3 Heat welding property *4

Peeling strength (kg/10mm) Gel content 160 C 180 C 200 C % by weight Example 1 5.0 5.4 5.3 32 ,. 2 3.8 4.3 4.7 71 .. 3 3.2 4.0 4.2. 79 Comparison Example 1 1.0 1.8 2.0 70 ., 2 3.1 3.8 4.0 68 .. 3 5.3 5.2 5.4 0 *4 Test method: From a sheet of 0.5-mm thickness, several test pieces, each of 1 0-mm width and 100-cm length, were made.A number of test specimens, each comprising two test pieces superposed on each other and welded together under pressure, were prepared by preheating pairs of the test pieces respectively at 1600C, 1800C, and 2000C in a steam pressing machine for one minute, and thereafter pressing each pairfortwo minutes at a pressure of 6 kg/cm2. The 90-degree peeling strength of the welded part of each test specimen thus prepared was measured by means of an autograph at a tensile speed of 500 mm/minute.

EXAMPLES 4 to 8 Ethylene-vinyltrimethoxysilane copolymers (A) were continuously synthesized, in each case, by supplying a mixture of ethylene, vinyltrimethoxysilane and propylene into a stirred autoclave reactor of 1.5-liters capacity and adding thereto t-butylperoxyisobutylate as a polymerization initiator under the conditions of a pressure of 2,400 kg/cm2 and a temperature of 2000 C. The polymerization conditions and the properties of the expanded copolymers are shown in Table 4 below.

To 100 parts of each of the copolymers thus obtained, 5 parts of a master batch containing 1 percent of dibutyltin dilaurate (B) and a specific quantity of an azodicarbonamide-based foaming agent ("VINYFOR DG &num;5" (trade mark) manufactured by trhe Eiwa Kasei Company, Japan) (C) were added, and these materials were mixed for 5 minutes in a roll mill at a temperature of 120 to 1 250C. The colour of the resulting composition was thereaftere uniform, from which it was determined that the distribution of the foaming agent within the mixture was uniform. A crosslinking reaction was not evident during this mixing. That is, the gel content was zero percent in all cases.

The mixture was next made into a sheet and taken out of the mill. This mixture in sheet state was heated for 10 minutes in a Geer oven at a temperature of 1 900C and thereby caused to expand.

The results of foaming and the heat adhesive property of the product thus obtained are set forth in Tables 5 and 6 below.

EXAMPLE9 An expandable compositioin comprising an ethylenevinyltrimethoxysilane copolymer (A), dibutyltin dilaurate (B), and a foaming agent (C) was prepared by the procedure of Example 7 and was placed in a mould with a depth of 10 mm and measuring 1 50 mm square. This mould was placed between press plates for 10 minutes under a pressure of 100 kg/cm2 and at a temperature of 1 900C.

The pressure was removed after this pressure step to allow the composition to expand.

The result of foaming thus obtained is indicated in Table 5.

COMPARISON EXAMPLES 4 AND 5 To two lots of a low-density polyethylene ("YUKALON EH-30" (trade mark) manufactured by the Mitsubishi Petrochemical Co. Ltd., Japan) with a melt index of 2 g/1 0 min and a density of 0.919 g/cc, two lots of vinyl trimethoxysilane were respectively added each in a quantity of 2 percent relative to the quantity of the corresponding lot of the polyethylene. The two lots of the vinyl trimethoxysilane respectively contained 0.06 and 0.1 percent of dick my peroxide dispersed therein. Each of the two mixtures thus obtained was subjected to graft polymerization by means of a 50-mm diameter extruder with an L/D ratio of 24 at an extrusion temperature of 2000C.

The two kinds of vinylsilane-grafted polyethylene thus obtained (hereinafter referred to as graft A and graft B) respectively had a melt index of 1.6 g/1 0 min and a silane content of 0.5 percent (graft A), and a melt index of 1.3 g/1 0 min and a silane content of 0.7 percent (graft B).

Then, by the procedure set forth in Examples 4 to 8, a mixture of vinylsilane-grafted polyethylene, dibutyltin dilaurate, and a foaming agent was obtained for each of the grafts A and B, and, by heating each expandable composition for 10 minutes in a Geer oven at a temperature of 1900 C, it was caused to expand. Here the above-mentioned expandable compositions underwent partial cross-linking at the time of mixing in the roll mill and were found ta contain, respectively, 17 and 32 percent of gel.

The foaming results and the heat adhesive properties of the products thus obtained are shown in Tables 5 and 6 below.

TABLE 4 Polymerization conditions and properties of copolymers formed

Polymerization conditions Ethylene Vinylsilane Propylene Pressure Temperature feed rate feed rate feed rate KgIcm2 "C Kg/Hr giHr lit./Hr Copolymer A 2400 220 43 13 600 Copolymer B 2400 220 43 25 550 Copolymer C 2400 220 43 130 400 Continuation of Table 4

Polymerization conditions Properties of copolymer Initiator Melt *' Vinylsilane *2 feed rate Conversion index content g/Hr % g/10-min % by weight Copolymer A 1.6 15 1.0 0.05 Copolymer B 1.7 15 1.0 0.10 Copolymer C 2.2 15 1.0 0.50 *1 Test method: JIS K6760 *2 Analysis by fluorescent X-rays.

TABLE 5 Foaming Results Blend proportions: a and b based on a + b, c based on a.

Example 4 4 5 6 7 8 I Copolymer A 91% - - B - 99.8% 91% 70% o " C - 910Jo a Graft A - - - 0 E o ~ b Foaming Agent 9% 0.2to 9% 30% 9% Catalyst c master batch 5% 5% 5% 5% 5% Expandability O (i) * O ** () . * Cell structure uniform uniform uniform uniform uniform Apparent 2 o density 0.065 0.75 0.060 0.021 0.061 glce Gel content 23% 46 48 47 78 TABLE 5 continued

Example Comparison Example 9 4 < 4 5 Copolymer A - B - = 910/0 0 a Graft A - 91% E .. B ~ ~ 91% 0 O b Foaming agent 9% 9% 9% Catalyst c master batch 5% 5% 5% Expandability ' Expandabi 0 it - 0 (i) A*** X * X**,e Cell structure ' uniform not uniform a, Apparent 0.060 0.076 measurement density impossible 73 L Gel content 75 51 73 Note: all quantitative percentages by weight.

* Very good ** Good Not good (voids present) Very bad (cannot be called expanded structure) TABLE 6 Heat adhesive property of foamed structure*

Gel content Heat adhesion rate ( h) % by weight 160 C 180 C 200 C Example 4 23 100 100 100 " 6 1 48 90 100 100 " 8 78 60 95 100 Comparison Example 4 51 5 20 95 * Four steel plates, each measuring 50 mm square and 2-mm thickness, were placed for 5 minutes in each of three Geer ovens respectively adjusted to temperatures of 1600C, 1805C and 200 C as shown in Table 6. The four plates from each oven were immediately thereafter placed respectively on the surfaces of samples of the four foamed structures of Examples 4, 6 and 8 and Comparison Example 4, and were thus pressed against the samples for 30 seconds, after which the resulting laminated combinations of steel plate and foamed structure were left to cool naturally. The temperature to which each steel plate was heated was taken as the best adhesion temper ature, and the adhered state at the respective heat adhesion temperature was examined with respect to each foamed structure.In Table 6, the heat adhesion rate is an index indicating the state of adhesion between the steel plate and the foamed structure and is the percentage, with respect to the adhesion surface area at the time of adhesion, of the foamed structure remaining in an adhering state on the steel plate when, after adhesion, the foamed structure is peeled away from the steel plate.

EXAMPLES 10 TO 12 Ethylene-vinyltrimethoxysilane-vinyl acetate copolymers were continuously synthesized, in each case, by supplying a mixture of ethylene, vinyltrimethoxysilane, vinyl acetate and propylene as a chain transfer agent into a stirred autoclave reactor of 1.5-liters capacity and adding thereto t butyleroxyisobutyrate as a polymerization initiator under the conditions of a pressure of 2,400 kg/cm2 and a temperature of 2O9-2220C. The polymerization conditions and the properties of the formed copolymers are shown in Table 7 below.

Each of the copolymers thus produced was formed into a sheet by means of a steam press. Each sheet thus produced was immersed in a solution of dibutyltin dilaurate in xylene in 1096 by weight concentration and was then immersed in water of 700C for a dae, thereby to effect cross-linking of the copolymer. The properties of the sheets are shown in Table 8 below.

On the other hand, to each of the copolymers, 5 percent of a master batch comprising 1 percent by weight of dibutyltin dilaurate and 99 percent of low-density polyethylene was added, and each of the mixtures was kneaded at 1 2O0C for 5 minutes and was then formed into a pressed sheet of 0.5 mm thickness. Each of the sheets was immersed in water at 700 C for a day thereby to effect cross-linking of the copqlymer.

From each of these sheets of the cross-linked copolymers was prepared a test piece of 10 mmwidth and 100 mm-length, the two test pieces were superposed and the end portion of the assembled pieces was welded along the width thereof by means of a steam press at a pressure of 6 kg/cm2 for 2 minutes after being preheated at 1 200C, 1 400C or 1 800C for 1 minute. The 900 peeling strength of each of the welded test pieces was determined by means of an autograph at a peeling rate of 500 mm/min. at a room temperature. The results obtained are shown in Table 9 below.

EXAMPLE 13 The procedure of Examples 10 to 12 was followed except that vinyl acetate was replaced by methyl acrylate thereby to produce ethylene-methyl acrylatevinyltrimethoxysilane copolymer, which was subjected to sheeting and then to cross-linking. The properties of the sheet were determined, and the results obtained are shown in Tables 7 to 9 below.

TABLE 7 Polymerization conditions and properties of copolymers formed

Polymerization conditions Ethylene VA*4 or MA Vinylsilane Propylene Pressure Temperature feed rate feed rate feed rate feed rate Example Kg/cm C Kg/Hr g/Hr lit./Hr g/Hr 10 2400 220 32 VAS.6 52 150 11 2400 218 32 VA8.0 54 40 12 2400 215 32 VA8.0 125 80 13 2400 220 32 MA0.6 43 440 TABLE 7 continued

Polymerization conditions Properties of copolymer Initiator VA or *2 Vinylsilane *3 feed rate Conversion Melt *1 index Ma content content Example g/Hr % g/10 min. % by wt. % by wt.

10 0.8 12 3.0 14 0.15 11 0.7 12 3.2 18 0.15 12 0.8 12 3.1 18 0.50 13 1.1 12 3.4 13 0.15 *1 Test method: Japanese Industrial Standards JIS K 6760 *2 Analysis by infrared absorption spectrum *3 Analysis by fluorescent X-rays *4 VA: vinyl acetate MA : methyl acrylate TABLE 8 Property

Tensile *1 | Tensile *l Flexural *2 1 Heat Gel strength strenGtil | elongation rigidity t distortion 1 Content Example 1 k9/cm2 l % kg/cm2 | % by wt.

1- = -I t t io i 235 1 610 680 \ 56 10 236 810 680 56 11 | 240 | 650 510 | 61 | 56 12 13 240 | 530 1 49O \ 26 1 78 13 1 235 1 620 1 720 60 58 TABLE 9.Heat welding property

Peeling strength (kg/lO mm) at: 1 ExamI 10 6.2 6.6 6.5 6.7 11 6.3 11 1 6.3 6.6 1 6.5 6.7 1 12 5.8 6.1 6.4 s3 13 6.1 1 6.4 1 6.7 ! 6.5 Note: *l Test method: JIS K 6760 *2 Test method: ASTM D 747 *s Heat distortion was determined as follows: In an oil bath at 1200C, a load of 3 kg was applied on a flat test piece of 2 mm-thick ness and 10 cm square, and the distortion after an hour was determined.

*4 Gel content was determined by the method of extraction with boiling xylene for 10 hours.

EXAMPLES 14 TO 17 To each of the copolymers shown in Examples 10 to 13 was added 5% by weight of a master batch comprising 1 % by weight of dibutyltin dilaurate and 99% by weight of low-density polyethylene, and each of the mixtures thus obtained was formed into an inflation film of 50 micron-thickness by an inflation method where the extruder had a 40 mm diameter and an LID value of 24, the extrusion temperature was 1 500C, and the blow ratio was 1.5:1. Each of the films thus obtained was placed in a room maintained constantly at a temperature of 400C and a relative humidity of 80% for a week thereby to effect cross-linking of the copolymer.

Each of the films was subjected to welding wherein two sheets of film were heat-sealed by means of a hot plate, heat-sealing machine at a sealing temperature of 1 200C, 1 400C, 1 600C or 1 800C and at a pressure of 2 kg/cm2 for one second. Test pieces of 2 cm-width and 10 cm-length were prepared from the heat-sealed film, the heat sealed portion lying along the width, and were then subjected to a 900 peeling strength determination by means of an autograph at a peeling rate of 500 mm/min. The results obtained are shown in Table 10 as follows: TABLE 10.Heat seal property

Peeling strength (g/20 mm) at: | Gel content Example Example | 12000 | 14000 | 160-C | 180-C | % by weight 1400 1450 14 1 1300 1 1400 1 1450 \ 1450 1 58 15 1 1350 1400 1 14six \ 1400 8 58 16 1 125it 1300 | 1400 | 1400 | 78 17 | 1350 1 1400 | 1450 | 1450 | 58 EXAMPLES 18 TO 20 To each of the copolymers obtained by the process of Examples 1 to 3 was added 5% by weight of a master batch comprising 1% by weight of dibutyltin dilaurate and 99% by weight of low-density polyethylene. Each of the mixtures thus obtained was formed into an inflation film of 60 micron thickness by an inflation method wherein the extruder was a full flight screw extruder of 40 mm diameter with an L/D value of 24, the extrusion temperature was 1 700C, and the blow ratio was 1.5:1.

Each film thus obtained was placed in a room maintained constantly at a temperature of 400C and at a relative humidity of 80% for a week thereby to effect cross-linking of the copolymer. The results obtained are shown in Tables 11 and 12, as follows: TABLE 11. Heat sealing property *l

Heat seal strength | Vinylsilane \ (gt20 mm) at: content Gel content Example | 1600C 1 1800C | 200 C L by'wt. %by wt.

18 | 1450 1 1560 | 1650 1 0.05 1 29 19 | 1400 I 1500 | 1550 j 0.34 63 20 1 1350 1 1450 1 1500 1 0.7 1 72 Note: *t The heat sealing property was determined as follows: Strips of 20 mm-width and 100 mm-lengthswere prepared from film to be tested of 60 micron-thickness. Two of the strips were superposed and the superposed assembly was subjected to heat sealing by meanarof 9 heat-bar heat sealing machine at a heat-bar temperature of 160, 180 and 200C and at a pressure of 1 kg/cm2 for a second along the width.The test piece thus produced was subjected to a 90 peeling strength determination by means of an autograph at a peeling rate of 500 mm/min.

TABLE 12 Tensile strength and elongation at break point*

- D s 230C 80-C 1 23"C 8tress Elongation | Stress | Elongation kg/cm tElongation Example \ kglcm2 9E kgcm2 18 210 650 60- 5210 225 600 85 480 20 225 450 95 400 Note: * Test method :JlSK6760 EXAMPLE 21 Ethylene-vinyltrimethoxysilane copolymer was continuously synthesized by supplying a mixture of 43 kg/Hr of ethylene, 190 g/Hr of vinyltrimethoxysilane and 400 lit/Hr of propylene as a chain transfer agent, into a stirred autoclave of 1.5-liters capacity and adding thereto 2.4 g/Hr of t butylperoxyisobutyrate as a polymerization initiator under the conditions of a pressure of 2,400 kg/cm2 and a temperature of 2200C. The product obtained had a melt index of 1 g/1 0 min. and a vinylsilane content of 0.75% by weight, and was almost odourless.

To the copolymer was added 5% by weight of the copolymer of a master batch comprising 1% by weight of dibutyltin dilaurate and 99% by weight of low-density polyethylene and there was further added low-density polyethylene ("YUKALON ZF-30" (trade mark) manufactured by Mitsubishi Petrochemical Co. Ltd., Japan) having a melt index of 1 g/1 0 min. and density of 0.920 g/cm3 in a quantity of 5% by weight of the total of the copolymer and the low-density polyethylene. The mixture thus obtained was formed into an inflation film of 60 micron-thickness by an inflation method where the extruder was a full flight screw extruder of 40 mm diameter, the LID being 24, the extrusion temperature 1 700C and the blow ratio 1.5:1. The film thus obtained as placed in a room maintained constantly at a temperature of 400C and a relative humidity of 80% for a week thereby to effect cross linking of the copolymer.

On the other hand,the same mixture of the copolymer, dibutyltin dilaurate and the low-density polyethylene as was formed into inflation film in the above procedure was milled over a roll mill at 120 to 1 250C for 7 minutes and formed into a pressed sheet, which was then immersed in water at 100C for a day thereby to effect cross-linking of the copolymer.

EXAMPLE 22 To the mixture of the copolymer and dibutyltin dilaurate obtained by the procedure of Example 21 was further added low-density polyethylene which was the same as was used in Example 21 in a quantity of 10% by weight of the total of the copolymer and the low-density polyethylene.

The mixture was processed into inflation film and a pressed sheet, which were subjected to crosslinking of the copolymer, as in Example 21.

EXAMPLE 23 To the mixture of the copolymer and dibutyltin dilaurate obtained by the procedure of Example 21 was further added low-density polyethylene which was the same as was used in Example 21 in a quantity of 30% by weight of the total of the copolymer and the low-density polyethylene.

EXAMPLE 24 To the mixture of the copolymer and dibutyltin dilaurate obtained by the procedure of Example 21 was further added low-density polyethylene which was the same as was used in Example 21 in a quantity of 50% by weight of the total of the copolymer and the low-density polyethylene.

The mixture was processed into inflation film and a pressed sheet, which were subjected to crosslinking, as in Example 21.

EXAMPLE 25 To the mixture of the copolymer and dibutyltin dilaurate obtained by the procedure of Example 21 was further added low-density polyethylene which was the same as was used in Example 21 in a quantity of 70% by weight of the total of the copolymer and the low-density polyethylene.

The welding property, heat resistance and tensile property of the crosslinked products obtained in Examples 21 to 25 are shown in Table 13, as follows: TABLE 13

Tensile strength and elongation at break Heat seal strength at *2 point *4 Gel *1 Heat "! content 160C 180'C 2000C distortion Strength Elongation Example % by wt. 9/2 cm % kgIc 21 70 1,350 1,500 1,500 26 225 1 480 22 68 1,400 1,500 1,550 30 225 550 23 59 1,450 1,500 1,600 41 225 810 24 48 1,500 1,600 1,600 49 220 630 25' 25 1,550 1,600 1,600 62 215 640 Note: *I See note *4 for Table 9.

Heat seal property was determined as follows: Superposed two sheets of film of 60 micron-thickness was subjected to heat sealing by means of a heat-plate heat sealing machine at a sealing temperature of 160"C, 180"C or 200"C at a pressure of 2 kg/cm2 for 1 second, and from the heat-sealed film was prepared a test piece of 2 cm-width and 10 cm-length, the heat sealed portion lying along the width, which was then sub jected to 900 peeling strength determination by means of a Schopper machine at a peeling rate of 500 mm/min.

See note *3 for Table 9.

*4 Elongation was determined in accordance with Japanese Industrial Standards, JIS Z 1702.

EXAMPLES 26 TO 31 Two types of ethylene-vinyltrimethoxysilane copolymers were continuously synthesized, in each case, by supplying a mixture of ethylene, vinyltrimethoxysilane and propylene as a chain transfer agent into a stirred autoclave reactor of 1.5-liters capacity and adding thereto t-butylperoxyisobutyrate as a polymerization initiator under the conditions of a pressure of 2,400 kg/cm2 and a temperature of 2200 C. The polymerization conditions and the properties of the copolymers produced are shown in Table 14 below.

Each of the copolymers in the farm of pellets was immersed in a solution of dibutyltin dilaurate in xylene in 10% by weight concentration for one minute and was then immersed in water at 100 C for one day thereby to effect cross-linking of the copolymer. Each of the cross-linked copolymers was subjected to extraction with boiling xylene for 10 hours to give a gel content of 54 and 75% by weight, respectively.

On the other hand, to the copolymer as obtained hereinabove was added a quantity of a master batch comprising 1% by weight of dibutyltin dilaurate and low-density polyethylene ("YUKALON EH-30" (trade mark) manufactured by Mitsubishi Petrochemical Co. Ltd., Japan) and a quantity of kaolin clay with an average particle size of 1.9 microns. The mixture was extruded into strands by means of a double axes extruder of 40 mm diameter, the L/D being 30 at a set temperature of 1700 C.

The gel content and the appearance of the strands as extruded were determined.

Pressed sheets were prepared from the strands thus obtained, which were immersed in water at 1 000C for one day thereby to effect cross-linking of the copolymers. Each of the sheets was subjected to determination of heat distortion.

The results obtained are shown in Table 15.

EXAMPLES 32 AND 33 The production of strands, the determination of the gel content and the appearance of the strands as extruded were carried out in the same way as in Examples 26 to 31 except that calcium carbonate with an average particle size of 0.04 micron was used instead of kaolin clay.

Each of the pressed sheets from the strands was immersed in water at 1 000C for one day thereby to effect cross-linking of the copolymer. The hardness of each of the sheets was determined.

The results obtained are shown in Table 1 6.

EXAMPLES 34 AND 35 The procedure as set forth in Examples 26 to 31 was followed except that gypsum hemihydrate with an average particle size of 6 microns was used instead of kaolin clay. The gel content and the appearance of the strands obtained were determined.

The results obtained are shown in Table 17, below.

TABLE 14

Polymerization conditions \ Ethylene Vinylsilane Propylene Pressure Temperature feed rate I feed rate ' feed rate Copolymer \ Kg/cm2 C Kg/Hr g/Hr lit./Hr A 2400 220 43 25 550 2400 220 43 130 400 TABLE 14 Continued

Polymerization conditions Properties of copolymer Initiator Melt *t Vinylsilane"2 feed rate Conversion index content g/Hr Om 9/10 min. % by wt.

Copolymer \ g/Hr % 9/10 min. % by wt.

15 0.10 A 1.7 15 1.0 0.10 B 2.2 151.00.51 Note. *t, *2 - See Notes *l, *2 for Table 1.

TABLE 15

Example 26 27 28 29 30 31 Copolymer(a) -A 89 89 40 c basedon(a) 8 89 89 40 . + (c) B ~ ~ ~ 89 69 40 8 Graft ~ ~ ~ ~ Cat. master 0 batch based 5 5 5 5 5 5 Co on (a) a o Kaolin clay o based on 11 31 60 11 31 60 (a) +.(c) Gel content *l just after 0 0 0 0 0 0 extrusion, % % by weight Appearance of strand good good good good good good Heat *2 distortion % 56 45 24 23 18 11 Note: *1, *2 : See Note for Table 9.

TABLE 16

Example 32 33 Copolymer (a) A 69 based on 69 8 i (a) + (c) B Graft ow .

Cat. cay. master batch based on (a) 0 CaCO, based on (a) + (c) 31 31 Gel content lust after extrusion % by weight 0 0 Appearance of strand gogd good Hardness (Shore D) 54 57 TABLE 17

Example 34 35 Copolymer (a) A 69 5 based on (a) B ~ 69 > I +(c) s-69 V Graft o Cat. master batch based on (a) 5 5 w o E Gypsum hemihydrate based C Q on (a) + (c) 31 31 Gel content just after extrusion % by weight 0 3 Appearance of strand good fair

Claims

1. A cross-linkable polyethylene resin composition comprising a copolymer comprising a unit of ethylene and a unit of an ethylenically unsaturated silane compound, and a silanol condensation catalyst the content of the unit of an ethylenically unsaturated silane compound being within the range of from 0.001 to 15 percent by weight.

2. A composition according to claim 1 in which the copolymer further comprises up to 40 percent by weight of a unit of a monomer copolymerizabte with the ethylene and the ethylenically unsaturated silane compound, said percentage being based on the weight of the resulting copolymer.

3. A composition according to claim 1 or 2, further comprising a foaming agent of a content which is 0.2 to 30 percent by weight based on the sum of the quantities of the copolymer and of the foaming agent, the composition being thus expandable.

4. A composition according to claim 1 or 2 further comprising a polyolefin of a content up to 70 percent by weight based on the sum of the quantities of the polyolefin and of the copolymer, the content of the unit of an ethylenically unsaturated silane compound being based on the sum of the quantities of the polyolefin and of the copolymer.

5. A composition according to claim 1 or 2 further comprising an inorganic filler of a content up to 60 percent by weight based on the sum of the quantities of the copolymer and of the inorganic filler.

6. A composition according to any of claims 1 to 5 in which the ethylenically unsaturated silane compound may be represented by the formula C =CH Si(OZ)2, wherein Z is a hydrocarbyl group having 1 to 8 carbon atoms.

7. A composition according to any of claims 1 to 6 which is in the form of a film.

8. A composition according to claim 1 substantially as herein described with reference to any of the specific examples.