JP2022122905A - Heat resistant silane crosslinked resin molded body and manufacturing method therefor, and heat resistant product using heat resistant silane crosslinked resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a heat resistant silane crosslinked resin molded body capable of manufacturing the heat resistant silane crosslinked resin molded body excellent in appearance without black point due to burn by suppressing volatilization of a silane coupling agent, the heat resistant silane crosslinked resin molded body excellent in appearance without black point due to burn, and a heat resistant product using the same.

SOLUTION: There are provided a manufacturing method of a heat resistant silane crosslinked resin molded body having a process (a) for melting and mixing a resin composition containing a polyolefin resin and an inorganic filler at specific amounts, a process (b) for mixing the resulting molten mixed article, organic peroxide and a silane coupling agent at specific amounts, a process (c) for grafting reacting a silane graft resin to a polyolefin resin by melting and mixing the resulting mixture at a decomposition temperature of the organic peroxide, a process (d) for melting and mixing a silane master batch obtained in the process (c) and a silanol condensation catalyst and then molding them, and a process (e) for contacting the resulting molded body and water, a heat resistant silane crosslinked resin molded body and a heat resistant product.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a heat-resistant silane-crosslinked resin molded article, a method for producing the same, and a heat-resistant product using the heat-resistant silane-crosslinked resin molded article.

Wiring materials such as insulated wires, cables, cords, optical fiber core wires, and optical fiber cords used for internal and external wiring of electrical and electronic equipment must have flame retardancy, heat resistance, and mechanical properties (e.g., tensile properties, wear resistance, etc.). Various properties are required, such as flexibility). As a material used for these wiring materials, a resin composition containing a large amount of metal hydrate such as magnesium hydroxide or aluminum hydroxide is used.

In addition, wiring materials used in electrical and electronic equipment may be heated to 80 to 105° C., or even up to about 125° C., when used for a long period of time. In such a case, a method of cross-linking the coating material by an electron beam cross-linking method, a chemical cross-linking method, or the like is adopted for the purpose of imparting high flame retardancy to the wiring material.
Conventionally, as a method of cross-linking polyolefin resin such as polyethylene, an electron beam cross-linking method in which electron beams are irradiated to cross-link (also referred to as cross-linking), and an organic peroxide etc. is decomposed by applying heat after molding. Chemical cross-linking methods such as a cross-linking method in which a cross-linking reaction is performed using a hydrolyzable silane coupling agent and a silane cross-linking method using a hydrolyzable silane coupling agent are known. Among these cross-linking methods, the silane cross-linking method in particular does not require special equipment in many cases, and thus has advantages in terms of production.

The silane cross-linking method is obtained by grafting a hydrolyzable silane coupling agent having an unsaturated group to a resin in the presence of an organic peroxide to obtain a silane graft resin, and then adding water in the presence of a silanol condensation catalyst. By contacting with, the silane coupling agent is subjected to silanol condensation to obtain a crosslinked product of the silane graft resin.
In the silane cross-linking method, each component such as a resin, a hydrolyzable silane coupling agent, an organic peroxide and an additive is generally melt-kneaded together. For example, in Patent Document 1, a resin component obtained by mixing a polyolefin-based resin and a maleic anhydride-based resin is added with an inorganic filler surface-treated with a silane coupling agent, a silane coupling agent, an organic peroxide, and a cross-linking catalyst. A method has been proposed in which the mixture is sufficiently kneaded with a kneader, extruded with a single-screw extruder, and then immersed in warm water.

Japanese Patent Application Laid-Open No. 2001-101928

However, in the conventional silane cross-linking method described above, the silane coupling agent tends to volatilize during melt-kneading in a Banbury mixer or kneader. In particular, when the blending amount of the silane coupling agent is set to be large, or when the blending amount of the inorganic filler is set to be small, the volatilization amount of the silane coupling agent increases.
If the silane coupling agent evaporates during melt-kneading, black spots are generated in the melt-kneaded product, and the resulting crosslinked molded product is not only burnt, but desired heat resistance cannot be imparted. In the present invention, the term "burn" refers to a cross-linked molded product or a burned product or carbonized material of its material that occurs on the surface or inside of the cross-linked molded product. Become.

An object of the present invention is to provide a method for producing a heat-resistant silane-crosslinked resin molded article that suppresses volatilization of a silane coupling agent and that can produce a heat-resistant silane-crosslinked resin molded article that is free from black spots due to burning and has an excellent appearance. and Another object of the present invention is to provide a heat-resistant silane-crosslinked resin molded article excellent in appearance without black spots due to burning, and a heat-resistant product using the same.

In the silane cross-linking method, the present inventors discovered that during melt-kneading, a large amount of the silane coupling agent volatilized by friction or the like rapidly reacts with the organic peroxide to generate heat, and the melt-kneaded product exceeds the flash point. It was found that excessive reaction (combustion reaction) is a factor in the formation of black spots in the melt-kneaded product. As a result of further investigation, in the silane crosslinking method, a melt-kneaded product obtained by previously melt-kneading a resin and an inorganic filler, a silane coupling agent, and an organic peroxide were once mixed (while suppressing the grafting reaction). It was found that when melt-kneading (grafting reaction) is performed later, volatilization of the silane coupling agent can be suppressed to prevent the formation of black spots, and it is possible to produce a heat-resistant silane-crosslinked resin molded article having an excellent appearance without black spots caused by burning. Based on this knowledge, the present inventors have made further studies and completed the present invention.

That is, the objects of the present invention have been achieved by the following means.
<1> A method for producing a heat-resistant silane-crosslinked resin molding comprising the following steps (a) to (e).
Step (a): A step of melt-kneading a resin composition containing a polyolefin resin and 1 to 400 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin composition Step (b): Obtained in step (a) The resulting melt-kneaded product, 0.01 to 0.6 parts by mass of an organic peroxide per 100 parts by mass of the resin composition in the melt-kneaded product, and a graftable site of a polyolefin resin and a graft Step (c) of mixing 0.5 to 15 parts by mass of a silane coupling agent having a site capable of undergoing a chemical reaction at a temperature lower than the decomposition temperature of the organic peroxide: the mixture obtained in step (b) is melt-kneaded in the absence of a silanol condensation catalyst at a temperature higher than the decomposition temperature of the organic peroxide, and the silane coupling agent is grafted to the polyolefin resin by radicals generated from the organic peroxide, thereby silane grafting Step (d) of preparing a silane masterbatch containing a resin: Step (e) of molding after melt-kneading the silane masterbatch and a silanol condensation catalyst Step (e): The molded body obtained in step (d) and water <2> The method for producing a heat-resistant silane crosslinked resin molded article according to <1>, wherein the amount of the inorganic filler is 1 to 80 parts by mass with respect to 100 parts by mass of the resin composition.
<3> The polyolefin resin is an ethylene-vinyl acetate copolymer, an ethylene-(meth)acrylic acid copolymer, an ethylene-alkyl(meth)acrylate copolymer, a low-density polyethylene, or a linear low-density polyethylene. , ultra-low density polyethylene, ethylene rubber and styrene elastomer.
<4> The method for producing a heat-resistant silane-crosslinked resin molded article according to any one of <1> to <3>, wherein the polyolefin resin contains ethylene rubber.
<5> The method for producing a heat-resistant silane crosslinked resin molding according to <4>, wherein the ethylene rubber is ethylene-propylene-diene rubber or ethylene-propylene rubber.
<6> The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <5>, wherein the silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane.
<7> The inorganic filler is at least one selected from the group consisting of silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, antimony trioxide, clay, magnesium carbonate, zinc borate, zinc hydroxystannate and talc. The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <6>.
<8> The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <8>, wherein the melt mixing in the step (c) is performed using an extrusion device.
<9> A heat-resistant product comprising a heat-resistant silane-crosslinked resin molded article produced by the method for producing a heat-resistant silane-crosslinked resin molded article according to any one of <1> to <8> above.
<10> The heat-resistant product according to <9>, which is an electric wire or an optical fiber cable provided with a coating layer comprising the heat-resistant silane-crosslinked resin molded article.
<11> A heat-resistant silane-crosslinked resin molded article produced by the method for producing a heat-resistant resin molded article according to any one of <1> to <8> above, wherein the polyolefin resin is formed through a silanol bond. A heat-resistant silane-crosslinked resin molding containing a silane-crosslinked resin crosslinked by

In the present specification, a numerical range represented by "to" means a range including the numerical values before and after "to" as lower and upper limits.

In the present invention, a melt-kneaded product obtained by melt-kneading a resin composition and an inorganic filler in advance, a specific amount of an organic peroxide and a silane coupling agent are mixed, and then melt-kneaded to obtain a polyolefin-based A resin composition containing a resin and a silane coupling agent are effectively prevented from volatilizing before and/or during melt-kneading to produce a heat-resistant silane crosslinked resin molded article and a heat-resistant article containing the molded article. can produce sex products. Furthermore, a highly heat-resistant silane-crosslinked resin molded article to which a large amount of inorganic filler is added can be produced without using a special machine such as an electron beam crosslinking machine.
Therefore, the present invention can provide a method for producing a heat-resistant silane-crosslinked resin molded article that suppresses volatilization of the silane coupling agent and produces a heat-resistant silane-crosslinked resin molded article that has an excellent appearance without black spots due to burning. In addition, the present invention can provide a heat-resistant silane-crosslinked resin molded article excellent in appearance without black spots due to burning, and a heat-resistant product using the same.

First, each component used in the present invention will be described.
<Resin composition>
The resin composition used in the present invention contains a polyolefin resin, and may further contain an organic oil, a plasticizer, and the like, if necessary.

- Polyolefin resin -
The polyolefin resin is a resin composed of a homopolymer or copolymer of a compound having an ethylenically unsaturated bond, and is grafted with a silane coupling agent in the presence of radicals generated from an organic peroxide to be described later. A polymer resin having a site capable of reacting (referred to as a graft reaction site) and a site capable of grafting reaction in the main chain or at its end is used. Examples of sites that can be grafted include unsaturated bond sites of carbon chains, carbon atoms having hydrogen atoms, and the like.
As such a polyolefin-based resin, those used in conventional heat-resistant resin compositions can be used without particular limitation. For example, resins such as polyethylene, polypropylene, ethylene-α-olefin copolymer, polyolefin copolymer having an acid copolymerization component (including an acid ester copolymerization component), rubbers or elastomers of these polymers, etc. is mentioned. Examples of rubbers or elastomers include ethylene rubbers, styrene-based elastomers, copolymer rubbers of alkyl acrylate and ethylene (ethylene acrylic rubbers), and the like.
In particular, polyolefin copolymers with acid copolymer components have high acceptability (miscibility) for various inorganic fillers such as metal hydrates, and can maintain mechanical strength even when a large amount of inorganic filler is blended. Polymer resin (ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl copolymer), polyethylene (low density polyethylene, linear low density polyethylene, ultra It preferably contains at least one resin selected from the group consisting of low-density polyethylene), ethylene rubber, and styrenic elastomer. The polyolefin resin more preferably contains ethylene rubber.
The polyolefin-based resin and each resin described below may be used alone or in combination of two or more.

(polyethylene resin)
The polyethylene resin may be a polymer resin containing an ethylene component, and may be an ethylene homopolymer or a copolymer of ethylene and an α-olefin (preferably 5 mol % or less) (excluding polypropylene). ), and resins composed of copolymers of ethylene and non-olefins (preferably 1 mol % or less) having only carbon, oxygen and hydrogen atoms in functional groups. As the α-olefins and non-olefins mentioned above, known ones conventionally used as copolymerization components of polyethylene can be used without particular limitation.
Polyethylene resins include high density polyethylene (HDPE), low density polyethylene (LDPE), ultra high molecular weight polyethylene (UHMW-PE), linear low density polyethylene (LLDPE) and very low density polyethylene (VLDPE). Among them, low density polyethylene, linear low density polyethylene or ultra-low density polyethylene is preferable, and low density polyethylene or linear low density polyethylene is more preferable.

(polypropylene resin)
The polypropylene resin may be a polymer resin containing propylene as a main component, such as a propylene homopolymer (homopolypropylene resin), an ethylene-propylene random copolymer, an ethylene-propylene block copolymer, and the like. can be used.

(Ethylene-α-olefin copolymer resin)
Ethylene-α-olefin copolymer resins preferably include resins of copolymers of ethylene and α-olefins having 3 to 12 carbon atoms (excluding those corresponding to the polyethylene and polypropylene described above). .

(Polyolefin copolymer resin having an acid copolymer component)
The acid copolymerization component (including the acid ester copolymerization component) in the polyolefin copolymer resin having an acid copolymerization component is not particularly limited, but may be a carboxylic acid compound such as (meth)acrylic acid, vinyl acetate, or Examples include acid ester compounds such as alkyl (meth)acrylates (preferably having 1 to 12 carbon atoms). Polyolefin copolymer resins having an acid copolymer component include, for example, ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, ethylene-alkyl(meth)acrylate copolymer, and the like. each resin of. Among them, ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate copolymer are preferable, because of their acceptability to inorganic fillers and heat resistance. Ethylene-vinyl acetate copolymer resin is more preferable from the viewpoint of properties.

(ethylene rubber)
Ethylene rubber is not particularly limited as long as it is a copolymer rubber of ethylene and α-olefin. For example, ethylene rubber is preferably a binary copolymer rubber of ethylene and α-olefin (preferably having 1 to 12 carbon atoms), ethylene and α-olefin (preferably having 1 to 12 carbon atoms) and α- A rubber composed of a terpolymer with a third component having an unsaturated bond other than an olefin may be mentioned. The third component includes conjugated or non-conjugated dienes, specifically butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB), 1,4-hexadiene and the like. Binary copolymer rubbers include ethylene-propylene rubber (EPM), and terpolymer rubbers include ethylene-propylene-diene rubber (EPDM).

(Styrene-based elastomer)
Styrene-based elastomers refer to those having an aromatic vinyl compound as a constituent component in the molecule. Examples of such styrene-based elastomers include block copolymers and random copolymers of conjugated diene compounds and aromatic vinyl compounds, or hydrogenated products thereof. Examples of such styrene-based elastomers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymer. polymer (SBS), hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-butadiene rubber (SBR), Examples include hydrogenated styrene-butadiene rubber (HSBR).

The polyolefin resin (each resin or rubber described above) may be acid-modified. The acid used for acid modification is not particularly limited, and commonly used unsaturated carboxylic acids and the like can be mentioned.

(organic oil)
Organic oils include aromatic oils, paraffinic oils, naphthenic oils, or mixed oils containing these three. As the organic oil, those commonly used in resin compositions can be used without particular limitation, and paraffinic oils and naphthenic oils are preferred. The organic oil is preferably used together with the styrenic elastomer. One type of organic oil may be used alone, or two or more types may be used in combination.

- Content of resin composition -
The content of the polyolefin resin in the resin composition is not particularly limited, but the total content with the organic oil is preferably 15 to 100% by mass. The content of the organic oil in the resin composition (when the resin composition contains a plasticizer, the total content with the plasticizer) is not particularly limited, but is preferably 0 to 40% by mass, and 0 to 35% by mass. % is more preferred.

In the present invention, the content of each of the resins included in the polyolefin resin in the resin composition is appropriately set within a range that satisfies the above content of the polyolefin resin. set.
The polyethylene resin content is preferably 0 to 98% by mass, more preferably 5 to 90% by mass. The polypropylene resin content is preferably 0 to 40% by mass, more preferably 2 to 30% by mass, and even more preferably 2 to 25% by mass. The content of the ethylene-α-olefin copolymer resin is preferably 0 to 98% by mass. The content of the polyolefin copolymer resin having an acid copolymer component is preferably 0 to 90% by mass, more preferably 0 to 70% by mass. The ethylene rubber content is preferably 0 to 98% by mass, more preferably 0 to 90% by mass. The content of the styrene elastomer is preferably 0 to 40% by mass, more preferably 0 to 30% by mass.

<Inorganic filler>
The inorganic filler used in the present invention is not particularly limited as long as it is commonly used in conventional heat-resistant resin compositions. Those having sites that can be chemically bonded by isoforms or intermolecular bonds are preferred. Examples of sites that can be chemically bonded to hydrolyzable silyl groups include OH groups (OH groups such as hydroxyl groups, water molecules containing water or water of crystallization, and carboxyl groups), amino groups, SH groups, and the like.
Examples of inorganic fillers include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, and hydrated aluminum silicate. , hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, talc, and other compounds having a hydroxyl group or water of crystallization. Boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon, clay, zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, zinc borate, white carbon, Also included are zinc borate, zinc hydroxystannate, zinc stannate and the like.
Among them, at least one selected from the group consisting of metal hydrates, silica, antimony trioxide, zinc borate and zinc hydroxystannate is preferable, and silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, antimony trioxide, clay , magnesium carbonate, zinc borate, zinc hydroxystannate and talc, and more preferably aluminum hydroxide or magnesium hydroxide.

The inorganic filler can also be used after being surface-treated with various surface-treating agents. Examples of magnesium hydroxide surface-treated with a silane coupling agent include Kisuma 5L and Kisuma 5P (both trade names, manufactured by Kyowa Chemical Industry Co., Ltd.).
An inorganic filler may be used individually by 1 type, and may use 2 or more types together.

When the inorganic filler is used as a powder, the average particle size is preferably 0.2 to 10 μm, more preferably 0.3 to 8 μm, even more preferably 0.4 to 5 μm, 0.4 to 3 μm is particularly preferred.
When the average particle size of the inorganic filler is within the above range, it is possible to prevent secondary aggregation and obtain a molded article having an appearance without lumps.
The average particle size of the inorganic filler is determined by dispersing the inorganic filler in alcohol or water and using an optical particle size analyzer such as a laser diffraction/scattering particle size distribution analyzer.

<Organic Peroxide>
The organic peroxide used in the present invention generates radicals by at least thermal decomposition, and serves as a catalyst for grafting reaction by radical reaction of the silane coupling agent to the polyolefin resin (grafting reaction site of the silane coupling agent and It is a covalent bond forming reaction with a graftable site of a polyolefin resin, which is also called a (radical) addition reaction.). For example, when the silane coupling agent contains an ethylenically unsaturated group as a grafting reaction site, a grafting reaction by a radical reaction between the ethylenically unsaturated group and the polyolefin resin (including a hydrogen radical abstraction reaction from the polyolefin resin) is performed. act to give rise to
The organic peroxide is not particularly limited as long as it performs the above functions. For example, compounds represented by the general formula: R ¹ -OO-R ² , R ³ -OO-C(=O)R ⁴ or R ⁵ C(=O)-OO(C=O)R ⁶ are preferred. Here, R ¹ to R ⁶ each independently represent an alkyl group, an aryl group or an acyl group. Among R ¹ to R ⁶ of each compound, it is preferable that all of them are alkyl groups, or that one of them is an alkyl group and the rest are acyl groups. As such organic peroxides, those used in radical polymerization or conventional silane cross-linking methods can be used without particular limitation, and include benzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2, 5-di-(tert-butylperoxy)hexane or 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3 are preferred.

The decomposition temperature of the organic peroxide is preferably 80 to 195°C, particularly preferably 125 to 180°C. In the present invention, the decomposition temperature of an organic peroxide refers to the temperature at which an organic peroxide of a single composition, when heated, causes itself to decompose into two or more compounds within a certain temperature or temperature range. means. Specifically, it refers to the temperature at which heat absorption or heat generation starts when heated from room temperature at a heating rate of 5° C./min in a nitrogen gas atmosphere by thermal analysis such as DSC method.
One type of organic peroxide may be used, or two or more types may be used.

<Silane coupling agent>
The silane coupling agent used in the present invention includes a site (group or atom) capable of grafting reaction to the site capable of grafting reaction of the polyolefin resin in the presence of radicals generated by decomposition of the organic peroxide, and silanol. There is no particular limitation as long as it has a condensable hydrolyzable silyl group. Examples of such a silane coupling agent include silane coupling agents used in conventional silane cross-linking methods. Among them, for example, a compound represented by the following general formula (1) can be used.

In general formula (1), R _a11 is a group containing an ethylenically unsaturated group, R _b11 is an aliphatic hydrocarbon group, a hydrogen atom or Y ¹³ . Y ¹¹ , Y ¹² and Y ¹³ represent hydrolyzable organic groups. Y ¹¹ , Y ¹² and Y ¹³ may be the same or different.
The R _a11 group corresponds to a graft reaction site, and examples of groups that can be used as R _a11 include a vinyl group, a (meth)acryloyloxyalkylene group, and a p-styryl group, with a vinyl group being preferred.
Aliphatic hydrocarbon groups that can be used as R _b11 include aliphatic hydrocarbon groups having 1 to 8 carbon atoms excluding aliphatic unsaturated hydrocarbon groups. R _b11 is preferably Y ¹³ described later.
Y ¹¹ , Y ¹² and Y ¹³ represent reactive sites (hydrolyzable organic groups) capable of silanol condensation. Examples thereof include an alkoxy group having 1 to 6 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, and an acyloxy group having 1 to 4 carbon atoms, and an alkoxy group is preferred. Specific examples of hydrolyzable organic groups include methoxy, ethoxy, butoxy, acyloxy and the like. Among them, methoxy or ethoxy is preferable from the viewpoint of reactivity of the silane coupling agent.

Such a silane coupling agent is preferably a silane coupling agent having an unsaturated group with a high hydrolysis rate, more preferably R _b11 is Y ¹³ and Y ¹¹ , Y ¹² and Y ¹³ are the same is a silane coupling agent. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, vinyltriacetoxysilane. vinylsilane such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and (meth)acryloxysilane such as methacryloxypropylmethyldimethoxysilane. Among them, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred.
One type of silane coupling agent may be used, or two or more types may be used.
The silane coupling agent may be used as it is or diluted with a solvent.

<Silanol condensation catalyst>
The silanol condensation catalyst used in the present invention causes (promotes) the silanol condensation reaction of the silane coupling agent grafted onto the polyolefin resin in the presence of water. Based on the action of this silanol condensation catalyst, the polyolefin resin is crosslinked via the silane coupling agent. As a result, a silane-crosslinked resin molded article having excellent heat resistance can be obtained.
Such silanol condensation catalysts are not particularly limited, and examples thereof include organotin compounds, metallic soaps, platinum compounds and the like. Specifically, organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, dibutyltin diacetate, zinc stearate, lead stearate, barium stearate, calcium stearate, sodium stearate, lead naphthenate, sulfuric acid Examples include lead, zinc sulfate, and organoplatinum compounds. Organotin compounds are preferred.
One type of silanol condensation catalyst may be used, or two or more types may be used.

<Carrier resin>
In the present invention, the silanol condensation catalyst may be used as it is or as a mixture with a resin. The resin to be melt-kneaded (supported) with the silanol condensation catalyst (referred to as a carrier resin) is not particularly limited, but the polyolefin-based resin described in the resin composition can be used. A polyethylene resin is preferable because it has a high affinity with a silanol condensation catalyst and can impart high heat resistance. One type of carrier resin may be used, or two or more types may be used.

<Additive>
Various additives can be used in the present invention. Examples of additives include various additives commonly used in electric wires, electric cables, electric cords, automobile members, OA equipment, construction members, miscellaneous goods, sheets, foams, tubes, pipes, and the like. Examples of such additives include antioxidants, cross-linking aids, lubricants, metal deactivators, flame retardants (auxiliaries), and resins other than the above polyolefin resins.
As the antioxidant, those commonly used in conventional heat-resistant resin compositions can be used without particular limitation, and examples thereof include benzimidazole antioxidants, amine antioxidants, and phenol antioxidants , sulfur-based antioxidants, hydrazine-based antioxidants, and the like.

<Method for producing heat-resistant silane-crosslinked resin molding>
Next, the method for producing the heat-resistant silane-crosslinked resin molding of the present invention (hereinafter sometimes referred to as the production method of the present invention) will be specifically described.
The production method of the present invention has the following steps (a) to (e).
Step (a): A step of melt-kneading a resin composition containing a polyolefin resin and 1 to 400 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin composition Step (b): Obtained in step (a) The melt-kneaded product, 0.01 to 0.6 parts by mass of an organic peroxide per 100 parts by mass of the resin composition in the melt-kneaded product, and a graftable site of the polyolefin resin for grafting Step (c) of mixing 0.5 to 15 parts by mass of a silane coupling agent having a reactive site at a temperature below the decomposition temperature of the organic peroxide: the mixture obtained in step (b) , In the absence of a silanol condensation catalyst, the silane graft resin is melt-kneaded at a decomposition temperature of the organic peroxide or higher, and the silane coupling agent is grafted to the polyolefin resin by radicals generated from the organic peroxide. Step (d): Step (e) of molding after melt-kneading the silane masterbatch and a silanol condensation catalyst Step (e): Contact the molded body obtained in step (d) with water step (e)

In the production method of the present invention, the resin composition, inorganic filler, organic peroxide, silane coupling agent and silanol condensation catalyst, and further additives are collectively melt-kneaded (in the presence of all the components) (melt-mixing ), step (a), step (b), step (c) and step (d) are performed in this order, and each component is melt-kneaded in a specific order. That is, first, the resin composition and the inorganic filler are melt-kneaded, then the obtained melt mixture, the organic peroxide, and the silane coupling agent are premixed (premixed) while suppressing the grafting reaction, and then First, these are melt-kneaded to cause a grafting reaction, and finally the silanol condensation catalyst is melt-kneaded. By melt-kneading the components in this order, volatilization of the silane coupling agent can be suppressed during melt-kneading in the presence of the silane coupling agent (steps (c) and (d)). Therefore, it is possible to suppress the silane coupling agent from reacting with the organic peroxide in a volatilized state, there is no reaction heat, and the temperature in the system is It is maintained below the flash point of the melt-kneaded product of the composition and the inorganic filler and the melt-kneaded product of the silane coupling agent and the organic peroxide). As a result, it is possible to prevent the formation of black spots in the melt-kneaded product and, in turn, the burning (generation of black spots) of the heat-resistant silane crosslinked resin molding.
Although the details of the reason for this are not yet clear, it is considered as follows.
During the melt-kneading of the silane coupling agent and the resin composition or the like, the silane coupling agent may volatilize rapidly and in large amounts due to friction or the like in some cases. The volatilized silane coupling agent rapidly reacts with the organic peroxide present in the vicinity of the surface of the melt-kneaded material, causing a radical polymerization reaction between the silane coupling agents. This radical polymerization reaction is an exothermic reaction, and heat is released with the progress of this polymerization reaction. When the amount of heat generated by this heat radiation increases, the temperature in the system exceeds the flash points of the volatile components and the melt-kneaded material, and the melt-kneaded material tends to generate black spots.
However, in the production method of the present invention, each component is sequentially melt-kneaded in a specific mixing order, so that friction generated during melt-kneading can be reduced, and rapid and large amount of volatilization of the silane coupling agent can be suppressed. Furthermore, since the molten mixture of the resin composition and the inorganic filler, the silane coupling agent, and the cross-linking agent are uniformly dispersed in advance, the reaction (addition reaction, condensation reaction) between the silane coupling agents hardly occurs, The silane coupling agent is stably grafted onto the polyolefin resin. As a result, it is possible to prevent the formation of black spots in the melt-kneaded product and the burning of the heat-resistant silane crosslinked resin molding.

(Step (a))
In the production method of the present invention, before melt-kneading the resin composition, the silane coupling agent and the organic peroxide (grafting reaction of the silane coupling agent to the resin), the resin composition and the inorganic filler are mixed. Melt and knead (step (a)).
In the step (a), the resin composition includes "an aspect in which the entire amount (100 parts by mass) is blended" and "an aspect in which a part of the resin composition is blended". When part of the resin composition is blended in step (a), the remainder of the resin composition may be blended in any step other than step (a), but the step ( It is preferably blended as a carrier resin that supports the silanol condensation catalyst in d). When a part of the resin composition is blended in step (a), the total blending amount of 100 parts by mass of the resin composition blended in step (a) and other steps is used as a standard for the blending amount of each component (for example, step (b) etc.). When the remainder of the resin composition is blended in other steps, particularly in step (d), the resin composition in step (a) is preferably 55 to 99% by mass, more preferably 60 to 95% by mass. and in another step, preferably 1 to 45% by mass, more preferably 5 to 40% by mass.

In step (a), the amount of the inorganic filler compounded is 1 to 400 parts by mass, preferably 30 to 280 parts by mass, per 100 parts by mass of the resin composition. By setting the blending amount to 1 to 400 parts by mass, the grafting reaction of the silane coupling agent in the step (c) becomes uniform, the heat resistance of the heat-resistant silane crosslinked resin molded product is high, and rough appearance is prevented. can. In the present invention, poor appearance due to agglomerates (bubbles) such as crosslinked products between resins, condensates between silane coupling agents, and aggregates of inorganic fillers are referred to as "rough appearance". It is used in distinction from "excellent appearance". Furthermore, the silane coupling agent and the organic peroxide can be uniformly kneaded into the melt-kneaded product of the resin composition and the inorganic filler, and the productivity can be excellent.
In the production method of the present invention, as described above, volatilization of the silane coupling agent can be prevented. Therefore, for the purpose of productivity (reduction of extrusion load), etc., regardless of the above-mentioned preferable blending amount, the blending amount of the inorganic filler is reduced. You can also set it lower. For example, with respect to 100 parts by mass of the resin composition, it can be set to 1 to 80 parts by mass, can also be set to 1 to 60 parts by mass, and can also be set to 1 to 30 parts by mass. .

The melt-kneading in the step (a) may be any method as long as the resin composition and the inorganic filler can be melt-kneaded, and is usually a method in which the resin composition or the polyolefin resin in the resin composition is melted (melt-kneading). is mentioned. That is, the melt-kneading temperature is a temperature higher than the melting point of the resin composition or polyolefin resin, preferably lower than the flash point of the resin composition or polyolefin resin, or lower than the decomposition temperature of the inorganic filler. For example, it can be set to preferably 80 to 250°C, more preferably 100 to 240°C, depending on the melting point and flash point of the resin composition or polyolefin resin. Other conditions such as the kneading time can be appropriately set.
The kneading method is not particularly limited as long as it is a method commonly used for rubbers, plastics and the like. A kneading device is appropriately selected according to, for example, the amount of the inorganic filler. For example, single-screw extruders, twin-screw extruders, rolls, Banbury mixers or various kneaders may be used. Among them, closed mixers such as Banbury mixers and various kneaders are preferable from the standpoint of resin dispersibility.
The melt-kneading method of the resin composition is not particularly limited. For example, a previously prepared resin composition may be melt-kneaded, or the resin, organic oil, or the like to be contained in the resin composition may be separately melt-kneaded.

A melt-kneaded product of the resin composition and the inorganic filler is obtained by the step (a).

(Step (b))
In the production method of the present invention, then, prior to the grafting reaction (step (c)) between the silane coupling agent and the resin, the melt-kneaded product obtained in step (a) and the resin in the melt-kneaded product 0.01 to 0.6 parts by mass of an organic peroxide and 0.5 to 15 parts by mass of a silane coupling agent are mixed with 100 parts by mass of the composition at a temperature below the decomposition temperature of the organic peroxide. (step (b)).

In step (b), the amount of the organic peroxide compounded is 0.01 to 0.6 parts by mass, preferably 0.05 to 0.6 parts by mass, per 100 parts by mass of the resin composition in the melt-kneaded product. 3 parts by mass. By setting the blending amount of the organic peroxide to 0.01 to 0.6 parts by mass, the grafting reaction can be performed in an appropriate range, and no agglomeration due to crosslinked gel or the like is generated. A silane masterbatch having excellent extrudability can be obtained.

The amount of the silane coupling agent compounded is 0.5 to 15 parts by mass, preferably 1 to 8 parts by mass, per 100 parts by mass of the resin composition in the melt-kneaded product. By setting this blending amount to 0.5 to 15 parts by mass, excessive volatilization of the silane coupling agent can be suppressed in the steps (c) and (d) described later, and there is no burning and high heat resistance. can produce a silane crosslinked resin molded product showing Furthermore, condensation between silane coupling agents can be suppressed to produce a heat-resistant silane-crosslinked resin molded article free from rough appearance.
Since volatilization of the silane coupling agent can be prevented in the production method of the present invention, as described above, the compounding amount of the silane coupling agent can be set high for the purpose of improving heat resistance (crosslinking density). For example, it can be set to 3.0 parts by mass or more with respect to 100 parts by mass of the resin composition.

The mixing in step (b) may be any method as long as the melt-kneaded material, the organic peroxide and the silane coupling agent can be mixed, and dry mixing (dry blending) in which they are mixed with or without heating is preferred. The mixing conditions are usually a temperature lower than the decomposition temperature of the organic peroxide, and the above components are mixed while suppressing the occurrence of the grafting reaction. The mixing temperature is preferably 10 to 50° C., more preferably room temperature (25° C.) to 40° C., and can be set for several minutes to several hours. For the mixing in step (b), a commonly used mixer such as the kneading device described in step (a) can be used.
The mixing in step (b) is preferably performed in the absence of a silanol condensation catalyst to suppress the condensation reaction of the silane coupling agent. Melt-kneading in the absence of a silanol condensation catalyst is as explained in the following step (c).

A (preliminary) mixture of the melt-kneaded material, the organic peroxide, and the silane coupling agent is obtained by the step (b).

(Step (c))
In the production method of the present invention, the mixture obtained in step (b) is then melt-kneaded at a temperature higher than the decomposition temperature of the organic peroxide in the absence of a silanol condensation catalyst (step (c)).
In the present invention, melt-kneading in the absence of a silanol condensation catalyst means melt-kneading without substantially mixing a silanol condensation catalyst. In other words, it does not exclude the presence of a silanol condensation catalyst that is inevitably present, and means that it may be present to the extent that the following kneadability and moldability problems due to silanol condensation of the silane coupling agent do not occur. do. For example, the silanol condensation catalyst may be present in an amount of 0.01 parts by mass or less with respect to 100 parts by mass of the resin composition.
By performing the melt-kneading in the absence of a silanol condensation catalyst, it is possible to suppress the condensation reaction of the silane coupling agent in this step, resulting in excellent kneading (easy melt-kneading) and excellent moldability ( can be extruded into the desired shape).

The melt-kneading in step (c) is performed at a temperature higher than the decomposition temperature of the organic peroxide, preferably at the decomposition temperature of the organic peroxide + (25 to 110)°C, for example, at a temperature of 150 to 230°C. This decomposition temperature is preferably set after the resin composition is melted. Other melt-kneading conditions, such as kneading time, can be appropriately set.
In step (c), radicals generated from the organic peroxide cause a grafting (bonding) reaction between the grafting reaction sites of the silane coupling agent and the graftable sites of the polyolefin resin. If kneading is performed below the decomposition temperature of the organic peroxide, the silane grafting reaction does not occur, and the desired heat resistance cannot be obtained. Sometimes you can't.
Melt-kneading in step (c) can be performed using the kneading device described in step (a), and is preferably performed using an extrusion device (single-screw extruder, twin-screw extruder).

In step (c), a silane graft resin in which a silane coupling agent is covalently bonded to a polyolefin resin is synthesized by a grafting reaction, and a silane masterbatch containing this silane graft resin is prepared as a reaction composition. can do. In this grafting reaction, one molecule of the silane coupling agent is usually added to one graftable site, but the present invention is not limited to this.
In the silane graft resin contained in the resulting silane masterbatch (silane MB), the silane coupling agent is grafted to the resin to such an extent that it can be molded by the step (d). The inorganic filler in the silane MB may or may not be bonded with a silane coupling agent (hydrolyzable silyl group).

(Step (d))
In the production method of the present invention, the silane masterbatch obtained in step (c) and the silanol condensation catalyst are then melt-kneaded and molded (step (d)).

In the melt-kneading of the step (d), it is preferable to melt-knead the silanol condensation catalyst and the carrier resin in advance to prepare a catalyst masterbatch (catalyst MB) and use it.
When a part of the resin composition is melt-kneaded in the step (a), the rest of the resin composition is used as the carrier resin. In this case, the blending ratio of the remainder of the resin composition and the silanol condensation catalyst is not particularly limited, and is set so as to satisfy the blending amount of the resin composition and the blending amount of the silanol condensation catalyst. Further, as the carrier resin, a resin other than the above resin composition can be used. In this case, the amount of the carrier resin compounded is preferably 1 to 60 parts by mass, more preferably 2 to 50 parts by mass, and still more preferably 2 to 40 parts by mass with respect to 100 parts by mass of the resin composition.
Furthermore, the catalyst MB may contain inorganic fillers. The content of the inorganic filler in the catalyst MB is not particularly limited, but is preferably 350 parts by mass or less with respect to 100 parts by mass of the carrier resin. If the amount of filler is too large, the silanol condensation catalyst may be difficult to disperse, and the silanol condensation reaction may be difficult to proceed. On the other hand, if the amount of the carrier resin is too large, the degree of cross-linking of the molded product may decrease, and the desired heat resistance may not be obtained.
The melt-kneading of the carrier resin and the silanol condensation catalyst may be carried out under the condition that the resin composition is melted. This melt-kneading can be performed in the same manner as the melt-kneading in the step (a). For example, the kneading temperature can be set to 80-250°C, more preferably 100-240°C. Other conditions such as the kneading time can be appropriately set.

In step (d), the silane MB and the silanol condensation catalyst (the silanol condensation catalyst itself or the catalyst MB) are melt-kneaded.
The amount of the silanol condensation catalyst is preferably 0.01 to 0.6 parts by mass, more preferably 0.001 to 0.4 parts by mass, per 100 parts by mass of the resin composition. When the amount of the silanol condensation catalyst is within the above range, the cross-linking reaction due to the silanol condensation reaction of the silane coupling agent tends to proceed almost uniformly, the heat resistance of the heat-resistant silane cross-linked resin molded product is increased, and the external appearance and physical properties are improved. can be prevented from decreasing, and productivity is also improved.
The melt-kneading in the step (d) may be any method as long as it is performed while the resin composition is molten, and can be performed, for example, in the same manner as the melt-kneading in the step (a). Step (d) is performed while suppressing the silanol condensation reaction of the coupling agent grafted onto the polyolefin resin. For example, step (d) is preferably carried out under conditions where the amount of water present is small, and it is preferred that the silane MB and the silanol condensation catalyst are not kept in a kneaded state at a high temperature for a long time.
Before melt-kneading in step (d), each component can be mixed, for example dry-blended, without melting the polyolefin resin or carrier resin. The dry blending method and conditions are not particularly limited, and examples thereof include dry blending in step (b) and its conditions.
Thus, a heat-resistant silane-crosslinkable resin composition, which is a melt-kneaded product of the silane MB and the silanol condensation catalyst, is obtained.

In step (d), the heat-resistant silane crosslinkable resin composition is molded.
Molding of the heat-resistant silane-crosslinkable resin composition is sufficient as long as the heat-resistant silane-crosslinkable resin composition can be molded, and an appropriate molding method and molding conditions are selected according to the form of the resin-crosslinked molded product. The molding method includes extrusion molding using an extruder, extrusion molding using an injection molding machine, and molding using other molding machines.
Extrusion is preferably applied when the heat resistant product of the present invention is a wiring material, especially an electric wire or an optical fiber cable. Extrusion can be performed using a general-purpose extruder. The extrusion molding temperature depends on various conditions such as the type of resin composition or carrier resin and the extrusion speed (take-up speed). It is preferable to set it to a degree.

In step (d), melt-kneading and molding can be performed simultaneously or sequentially. That is, as one embodiment of melt-kneading, for example, a mode of melt-kneading molding materials (silane MB and silanol condensation catalyst (catalyst MB)) during or immediately before extrusion molding can be mentioned. For example, the mixture obtained by mixing (dry blending) the silane MB and the silanol condensation catalyst at room temperature or at a high temperature (in a non-melted state) may be introduced into a molding machine and melt-kneaded. Alternatively, the silane MB and the silanol condensation catalyst may be melt-kneaded and pelletized, and then introduced into the molding machine and melt-kneaded again. More specifically, a series of steps can be adopted in which a mixture of silane MB and a silanol condensation catalyst is melt-kneaded in a coating device, then extrusion-coated on the outer peripheral surface of a conductor or the like, and molded into a desired shape.
A molded article of the heat-resistant silane-crosslinkable resin composition is obtained as described above.

The molded article of the heat-resistant silane-crosslinkable resin composition (silane-grafted resin contained in this molded article) is an uncrosslinked body in which the hydrolyzable silyl groups derived from the silane coupling agent are not silanol-condensed. Practically, partial cross-linking (partial cross-linking) is unavoidable due to the melt-kneading in the step (d), but it is preferable that at least the moldability at the time of molding is maintained in the resulting molded product.
The hydrolyzable silyl group of the silane graft resin in the molded article may or may not be bonded or adsorbed to the inorganic filler.

In the production method of the present invention, the additives may be kneaded or mixed in any step, and the order of mixing in each step is not particularly limited.
Additives are preferably added to the carrier resin, and particularly antioxidants and metal deactivators are preferably added to the carrier resin so as not to inhibit the grafting reaction of the silane coupling agent to the resin. A lubricant is also preferably added to the carrier resin. Furthermore, it is preferred that the cross-linking coagent is not substantially mixed during the preparation of the catalyst MB in steps (a), (c) and (d). If the cross-linking aid is not substantially mixed, the cross-linking reaction between the resin components through the cross-linking aid is unlikely to occur during melt-kneading, and rough appearance due to gelation can be prevented. In addition, the grafting reaction of the silane coupling agent to the resin is likely to occur, resulting in excellent heat resistance. Here, the fact that the cross-linking aid is not substantially mixed does not mean that the cross-linking aid that is inevitably present is not excluded, and means that the cross-linking aid may be present to an extent that does not impair the above advantages.
In the production method of the present invention, the amount of the additive to be added is not particularly limited, and can be appropriately set within a range that does not impair the intended effect. The blending amount of the antioxidant can be appropriately set, but is preferably 0.1 to 15.0 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the resin composition.

(Step (e))
In the production method of the present invention, the molded body of the heat-resistant silane crosslinkable resin composition obtained in step (d) is then brought into contact with water to crosslink (step (e)). In step (d), the hydrolyzable silyl groups of the silane coupling agent are hydrolyzed with water to form silanol (OH groups bonded to silicon atoms), and the silanol condensation catalyst present in the molded body causes the hydroxyl groups of the silanol to is (dehydration) condensed and a cross-linking reaction occurs.
Step (e) can be carried out by conventional methods. The condensation reaction proceeds only by storage at room temperature. Therefore, it is not necessary to actively bring the molded body of the heat-resistant silane-crosslinkable resin composition into contact with water. In order to promote this condensation reaction, the molded body of the heat-resistant silane-crosslinkable resin composition can be brought into positive contact with water. Examples of methods for positive contact with water include immersion in water (warm water), introduction into a moist heat bath, exposure to high-temperature steam, and the like. Also, at that time, pressure may be applied to permeate the moisture inside.

Thus, the production method of the present invention is carried out to produce a heat-resistant silane-crosslinked resin molding.

<Heat-resistant silane cross-linked resin molding>
The heat-resistant silane-crosslinked resin molded article of the present invention is produced by the production method of the present invention and contains a silane-crosslinked resin in which a polyolefin resin is crosslinked via silanol bonds. This silane crosslinked resin has a crosslinked portion in which the hydrolyzable silyl groups derived from the silane coupling agent in the above-mentioned silane graft resin are silanol-bonded, and some of the hydrolyzable silyl groups are bonded to the inorganic filler or It may be adsorbed.
This heat-resistant silane-crosslinked resin molded article is produced by suppressing volatilization of the silane coupling agent, has an excellent appearance without black spots due to burning, and exhibits high heat resistance.

As described above, the production method of the present invention suppresses volatilization of the silane coupling agent, minimizes burning and rough appearance of the finally obtained molded body, and has a good appearance. It becomes possible to manufacture a molded article. It is particularly effective when the amount of the inorganic filler compounded is reduced or when the amount of the silane coupling agent compounded is increased. The production method of the present invention greatly reduces burning and poor dispersion of the molded body compared to the method of melting and mixing the resin composition, inorganic filler, organic peroxide, silane coupling agent and silanol condensation catalyst all at once. It can be improved (suppressed). Moreover, burning of the molded body can be improved even in comparison with the method of mixing the inorganic filler, the silane coupling agent and the organic peroxide, and then melt-kneading the resin composition.
In the method for producing a heat-resistant silane crosslinked resin molding, if a large amount of the silane coupling agent volatilizes, black spots are generated in the melt-kneaded product, and in the worst case, there is a possibility of ignition, which raises safety concerns. However, the production method of the present invention can suppress the volatilization of the silane coupling agent and ensure high safety.

<Application of manufacturing method for heat-resistant products and silane-crosslinked resin moldings>
(Heat resistant product)
The heat-resistant product of the present invention is a product containing a silane-crosslinked resin molded article (including semi-finished products, parts, members, etc.), and may be a product consisting only of a silane-crosslinked resin molded article. Such heat-resistant products include, for example, other heat-resistant flame-retardant wire parts, flame-retardant heat-resistant sheets, flame-retardant heat-resistant films, and various other heat-resistant moldings, specifically power supply plugs, connectors, sleeves, and boxes. , tape substrates, tubes, sheets, wiring materials used for internal and external wiring of electric and electronic equipment, and molded parts such as electric wire insulators and sheaths.
The heat-resistant product of the present invention is preferably a wiring material, particularly an electric wire or an optical fiber cable, having a silane-crosslinked resin molding as a coating layer.

(Application of manufacturing method for silane crosslinked resin molding)
The production method of the present invention can be applied to the production of heat-resistant products containing silane-crosslinked resin moldings, such as the heat-resistant products of the present invention. The production method of the present invention is suitably applied to the production of wiring materials, and can form a covering layer (insulator, sheath) of wiring materials.
When manufacturing a wiring material by the manufacturing method of the present invention, preferably, the silane MB obtained in step (c), the silanol condensation catalyst, and (molding material) are melt-kneaded in an extruder (extrusion coating device), The obtained heat-resistant silane crosslinkable resin composition is extruded around the outer circumference of the conductor or the like. Thus, a wiring material can be produced by coating a conductor or the like with a heat-resistant silane-crosslinkable resin composition.
Such heat-resistant products can be produced by extruding and coating heat-resistant silane crosslinked resin moldings that are highly heat-resistant and do not melt even at high temperatures, even when a large amount of inorganic filler is added, without the use of special machines such as electron beam crosslinkers. It can be molded using an apparatus. The conductor to be used may be a single wire or stranded wire of annealed copper or the like, or a conductor tandemly provided with tensile strength fibers, and may be a bare wire or a tin-plated or enamel-coated wire. Examples of metal materials for forming conductors include annealed copper, copper alloys, and aluminum. Although the thickness of the insulating layer (coating layer made of the heat-resistant resin composition of the present invention) formed around the conductor is not particularly limited, it is usually about 0.15 to 5 mm.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.
In Tables 1 and 2, the numerical values relating to the compounding amounts in each example represent parts by mass unless otherwise specified. A blank column for each component means that the amount of the corresponding component is 0 parts by mass.

Details of each component (compound) shown in Tables 1 and 2 are shown below.
<Resin composition>
UE-320: Novatec LL (trade name), LLDPE, manufactured by Mitsubishi Yuka Evolue SP1540: trade name, LLDPE, manufactured by Prime Polymer)
EC9: Novatec PP (trade name), polypropylene resin, EV360 manufactured by Japan Polypropylene Corporation: Evaflex EV360 (trade name), ethylene-vinyl acetate copolymer, manufactured by Mitsui-DuPont Polychemicals)
Septon 4077: trade name, styrene elastomer (SEEPS), Kuraray Diana Process PW90: trade name, paraffin oil, Idemitsu Kosan Co., Ltd. Mitsui EPT0045H: trade name, EPM, Mitsui Chemicals Mitsui EPT3092EPM: trade name, EPDM (Ethylene-propylene-diene rubber), Mitsui Chemicals Co., Ltd. Nodel 3720: trade name, EPDM (ethylene-propylene-ethylidenenorbornene rubber), Dow Chemical Company <inorganic filler>
Magnesium hydroxide: Kisuma 5L (trade name), average particle size 0.8 μm, aluminum hydroxide manufactured by Kyowa Chemical Industry Co., Ltd.: OL-104 (trade name), average particle size 1.2 μm, calcium carbonate manufactured by HYUBER: Softon 2200 (trade name), average particle size 1.5 μm, antimony trioxide manufactured by Bihoku Funka Co., Ltd.: PATOX-C (trade name), average particle size 3.5 μm, silica manufactured by Nippon Seiko Co., Ltd.: Crystallite 5X (trade name) , Average particle size 1.2 μm, manufactured by Tatsumori <Organic peroxide>
Perhexa 25B: trade name, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, decomposition temperature 179° C., manufactured by NOF CORPORATION <Silane coupling agent>
KBM-1003: trade name, vinyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. KBE-1003: trade name, vinyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. <Silanol condensation catalyst>
ADEKA STAB OT-1: trade name, dioctyltin dilaurate, manufactured by ADEKA <Antioxidant>
Irganox 1010: trade name, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], manufactured by BASF

In Examples 1 to 10 and Comparative Examples 1 to 7, of 100% by mass of the resin composition, part (95% by mass) was used in step (a), and the remainder (5% by mass) was used as a carrier in step (d). used as a resin.
<Examples 1 to 10>
The resin, organic oil, and inorganic filler shown in the resin composition column of Table 1 are put into a 2L Banbury mixer manufactured by Nippon Roll in the amounts shown in Table 1, and melt-kneaded at a kneading temperature of 180 to 190 ° C. for about 8 minutes. , and discharged at a material discharge temperature of 180 to 190° C. to obtain a melt-kneaded product (step (a)).
Next, the resulting melt-kneaded product, silane coupling agent, and organic peroxide are put into a 10 L Henschel mixer manufactured by Toyo Seiki Co., Ltd. at the blending ratio shown in Table 1, and 8 minutes at room temperature in the absence of a silanol condensation catalyst. Mixing (dry blending) was performed to obtain a dry blend as a preliminary mixture (step (b)).
Then, the resulting dry blend was charged into a 40 mm single screw extruder (with vent holes), without charging (in the absence of) a silanol condensation catalyst, the extruder temperature was adjusted to the decomposition temperature of the organic peroxide. was melted and kneaded by setting the head temperature to 200°C and extruding. The extruded strand was water-cooled and then cut to obtain silane MB pellets (step (c)).

On the other hand, each component (carrier resin, silanol condensation catalyst and antioxidant) shown in the column of components for catalyst MB shown in Table 1 is melt-kneaded at 180 to 190 ° C. in a Banbury mixer at the blending amount shown in Table 1, and the material is discharged. The temperature was set to 180-190° C. to obtain catalyst MB. Next, after dry blending the silane MB and the catalyst MB at the ratio shown in Table 1 (the ratio of the resin composition used in step (a) and the carrier resin used for preparing the catalyst MB together to 100% by mass), It was introduced into an extruder equipped with a screw having a diameter of 40 mm (ratio of screw effective length L to diameter D: L/D 24, compression section screw temperature 190°C, head temperature 200°C). While melt-kneading the silane MB and the catalyst MB in the extruder (preparing a heat-resistant silane cross-linking resin composition), the outside of the 1/0.8 TA conductor is extruded to a thickness of 1 mm (heat-resistant silane cross-linking resin composition A molded article was formed) to obtain a covered conductor having an outer diameter of 2.8 mm (step (d)).
The resulting coated conductor is left for 24 hours in an environment with a temperature of 80° C. and a relative humidity of 95%, and the heat-resistant silane cross-linkable resin composition molded body is brought into contact with water to form a heat-resistant silane cross-linked resin molded body. An electric wire (heat-resistant product) having a coating layer consisting of was manufactured (step (e)).

<Comparative Examples 1 to 7>
Each component (resin, organic oil, inorganic filler, silane coupling agent and organic peroxide) shown in the column for silane MB components in Table 2 was put into a 2L Banbury mixer manufactured by Nippon Roll Co., Ltd. in the amount shown in Table 2, After melt-kneading at a kneading temperature of 160 to 200° C. for about 8 minutes, the material was discharged at a discharge temperature of 200° C. to obtain a silane masterbatch.
On the other hand, each component (carrier resin, silanol condensation catalyst, and antioxidant) shown in the column of components for catalyst MB shown in Table 2 is melt-kneaded at 180 to 190 ° C. in a Banbury mixer at the blending amount shown in Table 2, and the material is discharged. The temperature was set to 180-190° C. to obtain catalyst MB.
Next, after dry-blending the silane MB and the catalyst MB at the ratio shown in Table 2 (the ratio of the resin composition used for preparing the silane MB and the carrier resin used for preparing the catalyst MB together to 100% by mass), It was introduced into an extruder equipped with a screw having a diameter of 40 mm (ratio of screw effective length L to diameter D: L/D 24, compression section screw temperature 190°C, head temperature 200°C). While melt-kneading the silane MB and the catalyst MB in this extruder, the outside of the 1/0.8 TA conductor was extrusion-coated with a thickness of 1 mm to obtain a coated conductor with an outer diameter of 2.8 mm.
The resulting coated conductor is left for 24 hours in an environment of a temperature of 80° C. and a relative humidity of 95%, and the extruded coating of the coated conductor is brought into contact with water to form a coating layer made of a heat-resistant silane crosslinked resin molding. Made a wire.

<Test>
The silane MB prepared above and the wire produced were evaluated in the following tests, and the results are shown in Tables 1 and 2.
(Test 1: Extrusion test)
Silane MB was prepared five times in the same manner as in each example. The obtained silane MB was extruded into an extruder equipped with a screw with a diameter of 25 mm (ratio of screw effective length L to diameter D: L/D = 25, cylinder temperature was set to 180°C, and head temperature was set to 190°C. ) to extrude a sheet having a thickness of 1 mm and a width of about 8 mm.
The surface of the obtained sheet with a length of 50 cm was visually evaluated for the presence or absence of black spots due to burning and appearance roughness.
- Presence or absence of black spots -
As for the presence or absence of black spots, those in which no black spots occurred (confirmed) on all five sheets (accepted) were evaluated as "○", and those in which black spots occurred (confirmed) on even one of the five sheets ( failed) was set as "x".
- Presence or absence of rough appearance -
In addition, "○" indicates that no lumps with a diameter of 1 mm or more were generated (confirmed) on all five sheets (accepted), and two out of the five sheets had no lumps with a diameter of 1 mm or more. "△" indicates that none of them occurred (confirmed) (accepted), and "x" indicates that all of the five sheets produced (confirmed) a particle with a diameter of 1 mm or more (failed). did.

(Test 2: Appearance roughness test of electric wire)
The presence or absence of external roughness for a length of 3 m was visually confirmed for the electric wires produced in each example and comparative example.
In the rough appearance test, "O" was given to those in which no particles with a diameter of 1 mm or more could be generated (confirmed) (passed), and those in which 2 to 4 particles with a diameter of 1 mm or more could be generated (confirmed) (passed). Δ”, and those in which 5 or more pimples with a diameter of 1 mm or more were generated (confirmed) (failed) were evaluated as “x”.

(Test 3: Heat deformation characteristic test)
A heat deformation test was conducted to test the heat resistance of the electric wire (coating layer). The heat deformation test was performed according to JIS C 3005, using the electric wire as it was as a test piece, at a measurement temperature of 120° C. and a load of 5N. In the heat deformation test, samples with a thickness reduction rate (%) of 40% or less were passed.
In the heat deformation characteristic test, the wire coating layer (heat-resistant silane crosslinked resin molded article) with a thickness reduction rate of 40% or less was found to have a polyolefin resin crosslinked through a silanol bond in the wire coating layer. It can be confirmed that it contains a silane crosslinked resin formed by
Comparative Examples 2 and 5 were both very poor in appearance, and could not be subjected to a heat deformation characteristic test.

The results in Tables 1 and 2 reveal the following.
In a comparative example in which a silane crosslinkable resin composition (sheet) was prepared by a production method that does not undergo the steps specified in the present invention, at the time of preparation (molding) of the silane crosslinkable resin composition, from an organic peroxide in a Banbury mixer. The generated radicals acted on the silane coupling agent, and an explosion sound was confirmed, which was presumed to have caused the silane coupling agent to react. In addition, black spots or rough appearance was confirmed in the molded article (sheet) of the obtained silane crosslinkable resin composition. Moreover, in Comparative Examples 1 to 5, the coating layer (silane crosslinked resin molding) of the electric wire was burnt and the appearance was rough, and it was found that the appearance was poor.
On the other hand, in Examples 1 to 10, in which heat-resistant silane crosslinked resin moldings were produced by the production method of the present invention, volatilization of the silane coupling agent was effectively suppressed, no burning occurred, and the appearance was rough. It has an excellent appearance (it passed the extrudability test and the electric wire roughening test), and also exhibits excellent heat resistance with a thickness reduction rate of 40% or less in the heat deformation test.

That is, the objects of the present invention have been achieved by the following means.
<1> A method for producing a heat-resistant silane-crosslinked resin molding comprising the following steps (a) to (e).
Step (a): A step of melt-kneading a resin composition containing a polyolefin resin and 1 to 100 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin composition Step (b): The melt-kneaded product, 0.01 to 0.6 parts by mass of an organic peroxide per 100 parts by mass of the resin composition in the melt-kneaded product, and a graftable site of the polyolefin resin for grafting Step (c) of mixing 0.5 to 15 parts by mass of a silane coupling agent having a reactive site at a temperature below the decomposition temperature of the organic peroxide: the mixture obtained in step (b) , In the absence of a silanol condensation catalyst, the silane graft resin is melt-kneaded at a decomposition temperature of the organic peroxide or higher, and the silane coupling agent is grafted to the polyolefin resin by radicals generated from the organic peroxide. Step (d) of preparing a silane masterbatch containing: Step (e) of molding after melt-kneading the silane masterbatch and a silanol condensation catalyst Step (e): The molded body obtained in step (d) and water Contacting step <2> The method for producing a heat-resistant silane crosslinked resin molded article according to <1>, wherein the amount of the inorganic filler compounded is 1 to 80 parts by mass with respect to 100 parts by mass of the resin composition.
<3> The polyolefin resin is an ethylene-vinyl acetate copolymer, an ethylene-(meth)acrylic acid copolymer, an ethylene-alkyl (meth)acrylate copolymer, a low density polyethylene, a linear low density polyethylene, The method for producing a heat-resistant silane crosslinked resin molding according to <1> or <2>, which contains at least one resin selected from the group consisting of ultra-low density polyethylene, ethylene rubber and styrene elastomer.
<4> The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <3>, wherein the polyolefin resin contains ethylene rubber.
<5> The method for producing a heat-resistant silane crosslinked resin molding according to <4>, wherein the ethylene rubber is ethylene-propylene-diene rubber or ethylene-propylene rubber.
<6> The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <5>, wherein the silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane.
<7> The inorganic filler is at least one selected from the group consisting of silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, antimony trioxide, clay, magnesium carbonate, zinc borate, zinc hydroxystannate and talc. The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <6>.
<8> The method for producing a heat-resistant silane crosslinked resin molding according to any one of <1> to <8>, wherein the melt mixing in the step (c) is performed using an extrusion device.
<9> A heat-resistant product comprising a heat-resistant silane-crosslinked resin molded article produced by the method for producing a heat-resistant silane-crosslinked resin molded article according to any one of <1> to <8> above.
<10> The heat-resistant product according to <9>, which is an electric wire or an optical fiber cable provided with a coating layer comprising the heat-resistant silane-crosslinked resin molded article.
<11> A heat-resistant silane-crosslinked resin molded article produced by the method for producing a heat-resistant resin molded article according to any one of the above <1> to <8>, wherein the polyolefin resin is formed through a silanol bond. A heat-resistant silane-crosslinked resin molding containing a crosslinked silane-crosslinked resin.

First, each component used in the present invention will be described.
<Resin composition>
The resin composition used in the present invention contains polyolefin resin (also referred to as polyolefin resin) , and may further contain organic oil, plasticizer, and the like, if necessary.

In Examples 1 to 10 , Reference Examples 3 and 9, and Comparative Examples 1 to 7, of 100% by mass of the resin composition, part (95% by mass) was used in step (a), and the remainder (5% by mass) was used. It was used as a carrier resin in step (d).
<Examples 1 to 10 and Reference Examples 3 and 9 >
The resin, organic oil, and inorganic filler shown in the resin composition column of Table 1 are put into a 2L Banbury mixer manufactured by Nippon Roll in the amounts shown in Table 1, and melt-kneaded at a kneading temperature of 180 to 190 ° C. for about 8 minutes. , and discharged at a material discharge temperature of 180 to 190° C. to obtain a melt-kneaded product (step (a)).
Next, the resulting melt-kneaded product, silane coupling agent, and organic peroxide are put into a 10 L Henschel mixer manufactured by Toyo Seiki Co., Ltd. at the blending ratio shown in Table 1, and 8 minutes at room temperature in the absence of a silanol condensation catalyst. Mixing (dry blending) was performed to obtain a dry blend as a preliminary mixture (step (b)).
Then, the resulting dry blend was charged into a 40 mm single screw extruder (with vent holes), without charging (in the absence of) a silanol condensation catalyst, the extruder temperature was adjusted to the decomposition temperature of the organic peroxide. was melted and kneaded by setting the head temperature to 200°C and extruding. The extruded strand was water-cooled and then cut to obtain silane MB pellets (step (c)).

Claims (11)

A method for producing a heat-resistant silane-crosslinked resin molding having the following steps (a) to (e).
Step (a): A step of melt-kneading a resin composition containing a polyolefin resin and 1 to 400 parts by mass of an inorganic filler with respect to 100 parts by mass of the resin composition Step (b): Obtained in step (a) The melt-kneaded product obtained, 0.01 to 0.6 parts by mass of an organic peroxide per 100 parts by mass of the resin composition in the melt-kneaded product, and a graftable site of the polyolefin resin Step (c) of mixing 0.5 to 15 parts by mass of a silane coupling agent having a site capable of grafting reaction at a temperature lower than the decomposition temperature of the organic peroxide: the obtained in step (b) The mixture is melt-kneaded in the absence of a silanol condensation catalyst at a temperature higher than the decomposition temperature of the organic peroxide, and the silane coupling agent is grafted onto the polyolefin resin by radicals generated from the organic peroxide. Step (d) of preparing a silane masterbatch containing a silane graft resin: Step (e) of molding after melt-kneading the silane masterbatch and a silanol condensation catalyst: The molded body obtained in step (d) contact with water 2. The method for producing a heat-resistant silane crosslinked resin molding according to claim 1, wherein the amount of the inorganic filler compounded is 1 to 80 parts by mass with respect to 100 parts by mass of the resin composition. The polyolefin resin is an ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl copolymer, low density polyethylene, linear low density polyethylene, ultra-low 3. The method for producing a heat-resistant silane-crosslinked resin molded article according to claim 1 or 2, which contains at least one resin selected from the group consisting of density polyethylene, ethylene rubber and styrenic elastomer. The method for producing a heat-resistant silane crosslinked resin molded article according to any one of claims 1 to 3, wherein the polyolefin resin contains ethylene rubber. 5. The method for producing a heat-resistant silane crosslinked resin molding according to claim 4, wherein the ethylene rubber is ethylene-propylene-diene rubber or ethylene-propylene rubber. The method for producing a heat-resistant silane crosslinked resin molding according to any one of claims 1 to 5, wherein the silane coupling agent is vinyltrimethoxysilane or vinyltriethoxysilane. 2. The inorganic filler is at least one selected from the group consisting of silica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, antimony trioxide, clay, magnesium carbonate, zinc borate, zinc hydroxystannate and talc. 7. The method for producing a heat-resistant silane crosslinked resin molding according to any one of items 1 to 6. The method for producing a heat-resistant silane-crosslinked resin molded article according to any one of claims 1 to 8, wherein the melt-mixing in the step (c) is performed using an extruder. A heat-resistant product comprising a heat-resistant silane crosslinked resin molded article produced by the method for producing a heat-resistant silane crosslinked resin molded article according to any one of claims 1 to 8. 10. The heat-resistant product according to claim 9, which is an electric wire or an optical fiber cable provided with a coating layer comprising the heat-resistant silane crosslinked resin molded product. A heat-resistant silane crosslinked resin molded article produced by the method for producing a heat-resistant resin molded article according to any one of claims 1 to 8, wherein the silane is obtained by crosslinking a polyolefin resin via a silanol bond. A heat-resistant silane crosslinked resin molding containing a crosslinked resin.