JP2023107031A - Heat-resistant silane crosslinked resin molded body, silane crosslinked resin composition and methods for producing them, and wiring material - Google Patents

Abstract

To provide a heat-resistant silane crosslinked resin molded body which exhibits high heat resistance at 150°C or higher while using a polyolefin resin, and is excellent in appearance characteristics such as a smooth surface and no foam, and a method for producing the heat-resistant silane crosslinked resin molded body, a silane crosslinked resin composition which enables formation of a heat-resistant silane crosslinked resin molded body and a method for producing the silane crosslinked resin composition, and wiring material using a heat-resistant silane crosslinked resin molded body.SOLUTION: A silane crosslinked resin composition is provided which contains boehmite, a silane coupling agent portion, a silanol condensation catalyst, a hindered phenolic antioxidant, and a benzimidazole-based antioxidant with respect to a base resin including at least one ethylene copolymer of an ethylene-vinyl acetate vinyl copolymer and an ethylene-(meth)acrylate copolymer, in specific ratios, and does not contain aluminum hydroxide. A heat-resistant silane crosslinked resin molded body using the silane crosslinked resin composition, and methods for producing the silane crosslinked resin composition and the heat-resistant silane crosslinked resin molded body, and wiring material having a coating layer formed of the heat-resistant silane crosslinked resin molded body are also provided.SELECTED DRAWING: None

Description

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

Wiring materials for insulated wires, cables, cords, optical fiber core wires, and optical fiber cords (optical fiber cables) used in electrical and electronic equipment and industrial fields require heat resistance, etc. from the standpoint of safety and reliability. be done.
2. Description of the Related Art In recent years, the performance and functionality of electrical and electronic equipment have been improved, and wiring materials used in these devices are required to have higher heat resistance. For example, wiring materials for automobiles (especially cables mounted in the engine room of automobiles, cross-linked electric wires) are required to have extremely high heat resistance. As a heat resistance test (aging resistance test), it is specified that the tensile elongation after 10,000 hours at 150 ° C. is 100% or more (elongation rate is 100% or more), and it is required to satisfy this. ing.
As a wiring material that satisfies such high heat resistance, conventionally, there is a wiring material in which an insulating coating layer provided around a conductor is formed from a composition containing silicone, fluororubber, fluororesin, or the like as a base material. However, silicone materials have problems with oil and solvent resistance, and are not suitable for applications where they may come into contact with engine oil or battery fluid. In addition, fluororubber and fluororesin are very expensive, and the density of the material is high, and the weight of the wiring material is also large.
In view of the above problems, a method has been developed for producing a wiring material (crosslinked electric wire) with excellent heat resistance by forming a covering layer by crosslinking an inexpensive and lightweight polyolefin resin as a base material.
For example, in Patent Document 1, a resin composition containing a sulfur-based antioxidant, a hindered phenol-based antioxidant, a metal hydroxide and zinc oxide is irradiated with an electron beam in a base resin mainly composed of polyethylene or the like. A method for cross-linking to produce non-halogen insulated wires is described.
Further, in Patent Document 2, as a method for producing a heat-resistant silane crosslinked resin molding that forms a coating layer of a wiring material, a base resin, an organic peroxide, a metal hydrate, a brominated flame retardant, antimony trioxide, A method for silane-crosslinking a crosslinkable resin molding containing a silane coupling agent and a silanol condensation catalyst in specific proportions is described.
Furthermore, Patent Document 3 describes a method for producing a flame-retardant crosslinked resin molded article that forms a coating layer of a wiring material by using a base resin containing a specific resin component such as ethylene rubber, an organic peroxide, and boehmite. , a method for silane-crosslinking a flame-retardant crosslinkable resin composition containing a silane coupling agent and a silanol condensation catalyst in specific proportions.

Japanese Patent Application Laid-Open No. 2007-207642 JP 2016-121203 A JP 2017-179235 A

In the production method described in Patent Document 1, in order to achieve high heat resistance at 150° C. for 10,000 hours, in addition to the hindered phenolic antioxidant and zinc oxide, aluminum hydroxide as a metal hydroxide Alternatively, it is necessary to use a complex thereof together with 2-mercaptobenzimidazole as a sulfur antioxidant. However, when a large amount of aluminum hydroxide is used, the resin composition tends to foam in the melt-mixing process or the molding process, making it impossible to produce a coating layer (wiring material) with a desired appearance. In particular, in the silane cross-linking method, which requires the melt mixing process and the molding process to be performed under higher temperature conditions than the electron beam cross-linking method, the surface smoothness of the molded product decreases (rough appearance) and lumps (agglomerates) Defects in appearance are likely to occur due to the occurrence (occurrence of appearance lumps), and furthermore, the occurrence of foaming becomes conspicuous unless production conditions such as melt-mixing conditions and molding conditions are strictly controlled.
In addition, the heat-resistant silane crosslinked resin molded article or the flame-retardant crosslinked resin molded article produced by the production methods described in Patent Documents 2 and 3 exhibit a certain degree of heat resistance, but have excellent appearance and high heat resistance. There is room for further study in order to achieve both.

The present invention solves the above-mentioned problems, and while using a polyolefin resin, exhibits a high heat resistance of, for example, 150 ° C. or higher, and has a smooth surface with no bumps or bubbles. An object of the present invention is to provide a resin molding and a manufacturing method capable of manufacturing the molding while suppressing foaming. Another object of the present invention is to provide a silane-crosslinkable resin composition capable of forming this heat-resistant silane-crosslinked resin molded article, and a method for producing the same. A further object of the present invention is to provide a wiring material provided with a heat-resistant silane-crosslinked resin molded article obtained by a method for producing a heat-resistant silane-crosslinked resin molded article as a coating layer.

In the silane cross-linking method using a base resin having a polyolefin resin as an essential component, the present inventors have used a specific ethylene copolymer as the polyolefin resin, boehmite as the inorganic filler, a hindered phenolic antioxidant and a benzo A silane crosslinkable resin composition prepared by a specific process by containing two kinds of imidazole-based antioxidants in a specific content and avoiding the inclusion of aluminum hydroxide as an inorganic filler, The present inventors have found that it is possible to suppress the occurrence of pimples and foaming in the melt-mixing process and the molding process, and to form a silane-crosslinked resin molded article having a smooth surface and exhibiting high heat resistance. Based on this knowledge, the present inventors have made further studies and completed the present invention.

That is, the object of the present invention has been achieved by the following means.
<1> 9 to 80 parts by mass of boehmite per 100 parts by mass of a base resin containing at least one ethylene copolymer selected from an ethylene-vinyl acetate copolymer and an ethylene-(meth)acrylate copolymer, 1 to 15 parts by mass of a silane coupling agent grafted to the base resin, 0.01 to 0.5 parts by mass of a silanol condensation catalyst, a hindered phenol antioxidant, and a benzimidazole antioxidant A method for producing a heat-resistant silane-crosslinked resin molded article, comprising silane-crosslinking a silane-crosslinkable resin composition containing and not containing aluminum hydroxide,
The step (a), step (b), step (c), step (d) and step (e) are provided below, and the hindered phenol-based oxidation is performed in at least one step of step (a) and step (b). A method for producing a heat-resistant silane-crosslinked resin molding, comprising mixing an inhibitor or the benzimidazole-based antioxidant.
Step (a): Part of the base resin, the boehmite, and grafting to the base resin
a silane coupling agent having a reactive grafting reaction site;
0.01 to 0.5 parts by mass of an organic peroxide with respect to 100% by mass of the resin,
The silane mass is melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Step (b) of preparing a turbatch: melt-mixing the remainder of the base resin and the silanol condensation catalyst to form a catalyst matrix;
Process for preparing a starbatch Step (c): Dry blending the silane masterbatch and the catalyst masterbatch
Step (d) of obtaining a silane crosslinkable resin composition: Molding the silane crosslinkable resin composition to obtain a molded body Step (e): Contacting the molded body with water to heat-resistant Step <2> of obtaining a silane crosslinked resin molded article according to <1>, wherein the hindered phenol-based antioxidant is contained in an amount of 0.5 to 5 parts by mass with respect to 100 parts by mass of the base resin. Production method.
<3> The production method according to <1> or <2>, wherein the benzimidazole antioxidant is contained in an amount of 4 to 12 parts by mass with respect to 100 parts by mass of the base resin.
<4> The production method according to any one of <1> to <3>, wherein the ethylene copolymer is contained at a rate of 10 to 70% by mass based on 100% by mass of the base resin.
<5><1> to <4>, wherein each ethylene copolymer contained in the base resin contains vinyl acetate or (meth)acrylic acid ester at a rate of 10 to 30% by mass in each ethylene copolymer. The manufacturing method according to any one of the items.
<6> The production method according to any one of <1> to <5>, wherein the boehmite is contained in an amount of 9 to 50 parts by mass with respect to 100 parts by mass of the base resin.
<7> The production method according to any one of <1> to <6>, wherein the base resin contains a styrene elastomer and an organic oil.
<8> 9 to 80 parts by mass of boehmite per 100 parts by mass of a base resin containing at least one ethylene copolymer selected from an ethylene-vinyl acetate copolymer and an ethylene-(meth)acrylate copolymer, 1 to 15 parts by mass of a silane coupling agent grafted to the base resin, 0.01 to 0.5 parts by mass of a silanol condensation catalyst, a hindered phenol antioxidant, and a benzimidazole antioxidant And a method for producing a silane crosslinkable resin composition containing no aluminum hydroxide,
The hindered phenol-based antioxidant or the benzimidazole-based antioxidant in at least one of the steps (a) and (b), comprising the following steps (a), (b), and (c): A method for producing a silane crosslinkable resin composition by mixing
Step (a): Part of the base resin, the boehmite, and grafting to the base resin
a silane coupling agent having a reactive grafting reaction site;
0.01 to 0.5 parts by mass of an organic peroxide with respect to 100% by mass of the resin,
The silane mass is melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Step (b) of preparing a turbatch: melt-mixing the remainder of the base resin and the silanol condensation catalyst to form a catalyst matrix;
Process for preparing a starbatch Step (c): Dry blending the silane masterbatch and the catalyst masterbatch
and step <9> of obtaining a silane crosslinkable resin composition.
<10> A silane crosslinkable resin composition produced by the production method according to <8> above.
<11> A wiring material having a coating layer on the outer periphery of a conductor,
A wiring material, wherein the coating layer is a layer of the heat-resistant silane crosslinked resin molding according to <9>.
<12> The wiring material according to <11>, which is a heat-resistant wire or cable.

In the present invention, a numerical range represented using "to" means a range including the numerical values described before and after "to" as lower and upper limits. In the present invention, when multiple numerical ranges are set for the content, physical properties, etc. of a component, the upper limit and lower limit forming the numerical range are described before and after "-" as a specific numerical range. It is not limited to a specific combination, and can be a numerical range in which the upper limit value and the lower limit value of each numerical range are appropriately combined.

The present invention provides a heat-resistant silane-crosslinked resin molded article that exhibits high heat resistance of, for example, 150° C. or more while using a polyolefin resin, has a smooth surface, and has an excellent appearance with no bumps or bubbles, and this molded article. , it is possible to provide a manufacturing method capable of manufacturing while suppressing foaming. Further, the present invention can provide a silane-crosslinkable resin composition capable of forming this heat-resistant silane-crosslinked resin molded article, and a method for producing the same. Furthermore, the present invention can provide a wiring material having a heat-resistant silane crosslinked resin molded article obtained by a method for producing a heat-resistant silane crosslinked resin molded article as a coating layer.

[Heat-resistant silane cross-linked resin molding]
The heat-resistant silane-crosslinked resin molded article of the present invention is a crosslinked resin molded article (from a silanol condensate of a silane-crosslinkable resin composition) obtained by molding a silane-crosslinkable resin composition described later and then silane crosslinking (silanol condensation reaction). It is a compact). The heat-resistant silane-crosslinked resin molded article of the present invention can be manufactured while suppressing the occurrence of causes of poor appearance, particularly the occurrence of pimples and foaming, and has a smooth surface and an excellent appearance without pimples and foaming. ing. In the present invention, when foaming occurs, air bubbles (cavities) are mainly generated inside the molded body, leading to deterioration of the characteristics of the molded body. 1.
The heat-resistant silane-crosslinked resin molded article of the present invention not only exhibits the excellent appearance described above, but also has high heat resistance of, for example, 150° C. or higher, even though it contains a polyolefin resin. It is possible to achieve high heat resistance that satisfies the prescribed heat resistance test for tensile elongation after 10,000 hours at 150°C. The details of the heat resistance test will be described in the Examples section.

Although the details will be described later, this heat-resistant silane crosslinked resin molded article includes a base resin, usually an ethylene copolymer of at least one of ethylene-vinyl acetate copolymer and ethylene-(meth)acrylic acid ester copolymer. The combination has a silane-crosslinked structure (crosslinked structure via a silane coupling agent or its silanol condensate). As will be described later, this crosslinked structure may incorporate boehmite and an appropriately contained inorganic filler, and it is preferable that boehmite is incorporated as part of the crosslinked structure.
The heat-resistant silane-crosslinked resin molded article of the present invention does not contain aluminum hydroxide, brominated flame retardants, and zinc oxide. The above-described excellent properties are exhibited even if these components are not contained. In the heat-resistant silane-crosslinked resin molded article, "not containing each component" has the same meaning as in the silane-crosslinkable resin composition described later.

The heat-resistant silane-crosslinked resin molded article of the present invention is used for products (including semi-finished products, parts, and members) that require heat resistance. Examples of such products include various wiring materials, heat-resistant sheets, and heat-resistant films. Power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, packings, cushioning materials, and anti-vibration materials are also included. Above all, it is suitably used as a wiring material for automobiles, which requires high heat resistance, particularly as a material for insulating coating layers of cables or cross-linked electric wires mounted in the engine compartment of automobiles.

[Silane crosslinkable resin composition]
The silane-crosslinkable resin composition of the present invention comprises 100 parts by mass of a base resin containing at least one ethylene copolymer selected from an ethylene-vinyl acetate copolymer and an ethylene-(meth)acrylic acid ester copolymer, 9 to 80 parts by mass of boehmite, 1 to 15 parts by mass of a silane coupling agent grafted to the base resin, 0.01 to 0.5 parts by mass of a silanol condensation catalyst, and a hindered phenol antioxidant. , and a benzimidazole-based antioxidant, and does not contain aluminum hydroxide. This silane crosslinkable resin composition is a composition (dry blend) prepared by the method for producing a silane crosslinkable resin composition of the present invention, which will be described later.
Although the details will be described later, in the silane crosslinkable resin composition of the present invention, a silane coupling agent bonded or dissociated with boehmite and an inorganic filler appropriately contained is grafted onto a base resin, particularly an ethylene copolymer. Contains reacted silane crosslinkable resin. This silane cross-linkable resin composition is formed by a silane cross-linking method (silanol condensation reaction), while suppressing volatilization of the silane coupling agent and foaming during melt-mixing, while suppressing volatilization of the silane coupling agent and foaming during melt-mixing. It can be manufactured, and is suitably used in the method for manufacturing the heat-resistant silane-crosslinked resin molding of the present invention.

The silane crosslinkable resin composition of the present invention contains boehmite as an inorganic filler, but does not contain aluminum hydroxide. As a result, it is possible to effectively suppress foaming in the steps of preparing and molding the silane-crosslinkable resin composition without impairing the high heat resistance of the heat-resistant silane-crosslinked resin molded article, thereby improving the appearance characteristics. In the present invention, the composition does not contain aluminum hydroxide means that the content of aluminum hydroxide with respect to 100 parts by mass of the base resin in the composition is 0 parts by mass, and in addition, the content of aluminum hydroxide to some extent It encompasses the containing embodiment. The content at this time cannot be unambiguously determined because the effect of suppressing foaming varies depending on the adjustment of manufacturing conditions, etc., but for example, it should be 10 parts by mass or less with respect to 100 parts by mass of the base resin in the composition. is preferred, 5 parts by mass or less is more preferred, and 3 parts by mass or less is even more preferred.
In the present invention, the aluminum hydroxide contained in the composition includes not only aluminum hydroxide used as an arbitrary inorganic filler but also aluminum hydroxide remaining in or complexed with boehmite, which will be described later.

It is one of preferred embodiments that the silane crosslinkable resin composition of the present invention does not contain a brominated flame retardant. In this aspect, a non-halogen resin molded article can be obtained without impairing the high heat resistance of the heat-resistant silane-crosslinked resin molded article. The brominated flame retardant is not particularly limited, and examples thereof include the brominated flame retardant described in Patent Document 2. In the present invention, the composition does not contain a brominated flame retardant means that the content of the brominated flame retardant with respect to 100 parts by mass of the base resin in the composition is 0 parts by mass, and the content is 10 parts by mass or less. This content is preferably 5 parts by mass or less.

It is also one of preferred aspects that the silane crosslinkable resin composition of the present invention does not contain zinc oxide. In the present invention, the composition does not contain zinc oxide, in addition to the aspect in which the content of zinc oxide with respect to 100 parts by mass of the base resin in the composition is 0 parts by mass, the content is 5 parts by mass. It includes the following aspects. This content is preferably 3 parts by mass or less.

Each component used in the present invention is described below.
Each component can use 1 type(s) or 2 or more types, respectively.
<Base resin>
The base resin used in the present invention may contain at least one ethylene copolymer selected from ethylene-vinyl acetate copolymers and ethylene-(meth)acrylate copolymers. When the base resin contains an ethylene copolymer, it is possible to form a silane-crosslinked resin molded article exhibiting high heat resistance by using both boehmite and two kinds of antioxidants.
The base resin can contain, in addition to the ethylene copolymer, a polyolefin resin, a rubber or elastomer such as a polymer forming the polyolefin resin, an organic oil, and the like. Among them, it preferably contains at least one of polyethylene, polypropylene, ethylene rubber, styrene elastomer and organic oil, and more preferably contains styrene elastomer and organic oil. , polypropylene and ethylene rubber, and particularly preferably polyethylene, polypropylene, ethylene rubber, styrenic elastomer and organic oil.
Each resin component constituting the base resin is usually a graftable site that undergoes a grafting reaction with the grafting reaction site of the silane coupling agent, such as an unsaturated bond site of a carbon chain, a carbon atom having a hydrogen atom, in the main chain or at its end. However, in the present invention, since an ethylene copolymer having sites capable of grafting reaction is used, a resin component having no sites capable of grafting reaction can also be used as a resin component other than this.

(ethylene copolymer)
Examples of the ethylene copolymer include at least one selected from the group consisting of ethylene-vinyl acetate copolymer (EVA) and ethylene-(meth)acrylic acid ester copolymer. is more preferred. By using an ethylene copolymer in combination with boehmite and an antioxidant described later, a silane-crosslinked resin molded article having excellent appearance characteristics and high heat resistance can be produced. The ethylene copolymer contained in the base resin may be of two or more types, and may be two or three types, but preferably one or two types. As two or more ethylene copolymers, EVA or ethylene-(meth)acrylic acid ester copolymer may be used in combination, or EVA and ethylene-(meth)acrylic acid ester copolymer may be combined. can.

- Ethylene-vinyl acetate copolymer -
The ethylene-vinyl acetate copolymer may be an alternating copolymer obtained by alternately polymerizing an ethylene component and a vinyl acetate component as long as it is a copolymer of ethylene and vinyl acetate. A block copolymer in which a polymer block and a polymer block of a vinyl acetate component are combined may be used, or a random copolymer in which an ethylene component and a vinyl acetate component are randomly polymerized may be used.
The content of the vinyl acetate component (EV content) in each ethylene-vinyl acetate copolymer used as the base resin is not particularly limited and can be set appropriately. The content of the vinyl acetate component is preferably 10 to 30% by mass, more preferably 15 to 25% by mass, from the viewpoint of being able to produce a molded article exhibiting excellent appearance characteristics and high heat resistance. more preferred. When multiple ethylene-vinyl acetate copolymers are used, the content of the vinyl acetate component in the entire ethylene-vinyl acetate copolymer is not particularly limited and can be set as appropriate. This vinyl acetate content can be determined according to Japanese Industrial Standards (JIS) K7192.

- Ethylene - (meth) acrylic acid ester copolymer -
Ethylene-(meth)acrylic acid ester copolymer is a copolymer of ethylene and (meth)acrylic acid ester. It may be either a polymer or a random copolymer. Although the (meth)acrylic acid ester is not particularly limited, it is preferably an alkyl (meth)acrylic acid ester, and the number of carbon atoms in the alkyl group is preferably 1 to 12, more preferably 1 to 4. Examples of ethylene-(meth)acrylic acid ester copolymers include ethylene-methyl(meth)acrylate copolymer (EMA), ethylene-ethyl(meth)acrylate copolymer (EEA), ethylene-(meth)acrylic acid butyl copolymer (EBA) and the like.
The content (EA content) of the (meth)acrylic acid ester component in each ethylene-(meth)acrylic acid ester copolymer used as the base resin is not particularly limited and can be appropriately set. The content of the (meth)acrylic acid ester component is preferably 10 to 30% by mass, preferably 15 to 30% by mass, in terms of effectively suppressing the occurrence of pimples and making it possible to obtain a molded product having excellent appearance characteristics. It is more preferably 25% by mass. When using multiple ethylene-(meth)acrylic acid ester copolymers, the content of the (meth)acrylic acid ester component in the entire ethylene-(meth)acrylic acid ester copolymer is not particularly limited, and is set appropriately. can. This (meth)acrylic acid ester content can be determined from the amount of polymerization at the time of manufacture if it is a manufactured product, but if it is a commercial product, the manufacturer's or distributor's materials (catalogs, product information, etc.) can be adopted.

(polyolefin resin)
The polyolefin resin is not particularly limited as long as it is a resin composed of a polymer obtained by homopolymerizing or copolymerizing a compound having an ethylenically unsaturated bond, and is conventionally used in heat-resistant resin compositions. A known one can be used.
Examples thereof include polyethylene (PE), polypropylene (PP), ethylene-α-olefin copolymers, and polyolefin copolymers having an acid copolymerization component or an acid ester copolymerization component (excluding the above ethylene copolymers). .

Polyethylene (PE) is not particularly limited as long as it is a polymer containing ethylene as a main component. Examples include high density polyethylene (HDPE), low density polyethylene (LDPE), ultra high molecular weight polyethylene (UHMW-PE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE).
Polypropylene (PP) is not particularly limited as long as it is a polymer containing a propylene component as a main component. Examples include homopolymers of propylene, as well as random polypropylene and block polypropylene.
Ethylene-α-olefin copolymers preferably include copolymers of ethylene and α-olefins having 3 to 12 carbon atoms (excluding those contained in polyethylene and polypropylene). Examples thereof include ethylene-propylene copolymers (excluding those contained in polypropylene), ethylene-butylene copolymers, and ethylene-α-olefin copolymers synthesized in the presence of a single-site catalyst.
The compound leading to the acid copolymerization component or the acid ester copolymerization component in the polyolefin copolymer having the acid copolymerization component or the acid ester copolymerization component is not particularly limited, and carboxylic acid compounds such as (meth)acrylic acid, etc. mentioned. Examples of polyolefin copolymers having an acid copolymerization component or an acid ester copolymerization component include ethylene-(meth)acrylic acid copolymers.

The polyolefin resin may be acid-modified with a commonly used unsaturated carboxylic acid or derivative thereof.

(rubber or elastomer)
The rubber or elastomer is not particularly limited, and preferably includes, for example, ethylene rubber and styrene elastomer.
- Ethylene rubber -
The ethylene rubber is not particularly limited as long as it is a copolymer rubber obtained by copolymerizing a compound having an ethylenically unsaturated bond, and known rubbers can be used. The ethylene rubber preferably includes a bipolymer rubber of ethylene and α-olefin, a terpolymer rubber of ethylene, α-olefin and a diene compound, and the like. The α-olefin is not particularly limited, and α-olefins having 3 to 12 carbon atoms are preferred.
Further, the diene compound constituting the terpolymer is not particularly limited, and examples thereof include conjugated diene compounds such as butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, dicyclo Examples include non-conjugated diene compounds such as pentadiene (DCPD), ethylidene norbornene (ENB), and 1,4-hexadiene, and non-conjugated diene compounds are preferred. Ethylene-propylene rubber (EPM) is preferred as the bi-copolymer rubber, and ethylene-propylene-diene rubber (EPDM) is preferred as the terpolymer rubber.

- Styrene Elastomer -
The styrene-based elastomer refers to an elastomer composed of a polymer having a component derived from an aromatic vinyl compound in its 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. More specifically, styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymer (SBS) , hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene Rubber (HSBR) etc. are mentioned.

(organic oil)
The base resin may contain various oils, and it is particularly preferable to contain them together with the elastomer. When the base resin contains an elastomer and an organic oil, the moldability of the silane-crosslinkable resin composition is improved, and the appearance characteristics can be enhanced. Such oils include those used as plasticizers for polyolefin resins or as mineral oil softeners for rubbers. The mineral oil softener is a mixed oil containing three of the oils consisting of hydrocarbons having aromatic rings, the oils consisting of hydrocarbons having naphthenic rings, and the oils consisting of hydrocarbons having paraffin chains. Among these, paraffin oil and naphthenic oil are preferably used, and paraffin oil is particularly preferably used.

(Composition of base resin)
The total content of the ethylene copolymer in 100% by mass of the base resin is not particularly limited, but is preferably 10 to 70% by mass, more preferably 15 to 50% by mass, in terms of both appearance characteristics and heat resistance. and more preferably 20 to 40% by mass.
The total content of the polyolefin resin in 100% by mass of the base resin is not particularly limited, but from the viewpoint of both appearance characteristics and heat resistance, it is preferably 10 to 70% by mass, and 15 to 50% by mass. is more preferable, and 20 to 40% by mass is even more preferable.
The content of polyethylene in 100% by mass of the base resin is not particularly limited, and is appropriately set in consideration of the total content of the polyolefin resin. It is more preferably 40% by mass. Similarly, the content of polypropylene in 100% by mass of the base resin is not particularly limited, and is appropriately set in consideration of the total content of the polyolefin resin. For example, it is preferably 3 to 20% by mass. , more preferably 5 to 15% by mass. The content of the ethylene-α-olefin copolymer and the polyolefin copolymer having an acid copolymerization component or an acid ester copolymerization component in 100% by mass of the base resin is not particularly limited, and the total content of the polyolefin resin are appropriately set in consideration of, for example, each can be 0 to 20% by mass.

The content of rubber in 100% by mass of the base resin is not particularly limited, but it is preferable to be 0 to 40% by mass in order to reinforce the improvement of appearance characteristics, especially to suppress foaming by increasing the viscosity of the material. It is preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass. The content of the elastomer in 100% by mass of the base resin is not particularly limited, but is preferably 0 to 40% by mass, more preferably 5 to 30% by mass, in terms of moldability of the silane crosslinkable resin composition. is more preferable, and 10 to 20% by mass is even more preferable.
The content of the organic oil in 100% by mass of the base resin is not particularly limited, but from the viewpoint of moldability of the silane crosslinkable resin composition, for example, it is preferably 0 to 30% by mass, and 5 to 20% by mass. % is more preferred. When the base resin contains an elastomer and an organic oil, the total content of the elastomer and the organic oil is appropriately determined according to each content. preferably 10 to 30% by mass.

<Boehmite>
The boehmite used in the present invention is aluminum oxide hydrate (Al ₂ O ₃ .H ₂ O). Boehmite acts as a filler or flame retardant, but in that it retains the silane coupling agent and contributes to the improvement of mechanical properties and heat resistance. Those having a site (for example, an oxygen atom) that can be chemically bonded by a bond, a covalent bond, or an intermolecular bond are preferred.
Boehmite can usually be synthesized by hydrothermally treating aluminum hydroxide, and a commercially available product can also be used. The boehmite used in the present invention may be boehmite composed of aluminum oxide hydrate after hydrothermal treatment has been completed, or may be a compound compound with aluminum hydroxide obtained by stopping the hydrothermal treatment reaction in the middle. However, in the present invention, the contents of aluminum hydroxide in the silane-crosslinkable resin composition and the heat-resistant silane-crosslinked resin molded product are set within ranges that satisfy the above ranges. In the present invention, depending on whether or not aluminum hydroxide is used as an inorganic filler and the amount of aluminum hydroxide used, the amount of aluminum hydroxide present in the boehmite (composite) is It is determined as appropriate in consideration of the allowable content of aluminum. % by mass is more preferred.
The boehmite may or may not be surface treated. Moreover, it is also preferable that it is in the form of particles. As the boehmite surface treatment agent, an inorganic filler surface treatment agent can be used without particular limitation, and examples thereof include various fatty acids, various coupling agents such as silane coupling agents, and the like. The surface treatment amount of boehmite is not particularly limited, but is, for example, 3% by mass or less.

<Silane coupling agent>
The silane crosslinkable resin composition contains a silane coupling agent grafted to the base resin. The base resin to which the silane coupling agent is grafted is preferably prepared by a grafting reaction between the silane coupling agent and the base resin in step (a) described below.
The silane coupling agent used in the present invention (before the grafting reaction) is a grafting reaction capable of grafting to a graftable site of the base resin in the presence of radicals generated by decomposition of the organic peroxide. It has sites (atoms or functional groups such as ethylenically unsaturated groups). In addition, it preferably has a hydrolyzable silyl group as a reaction site capable of silanol condensation and can react with a site capable of chemical bonding of boehmite or an inorganic filler. Silane coupling agents that can be used in the present invention are not particularly limited, and include silane coupling agents used in conventional silane cross-linking methods.
The silane coupling agent preferably includes a silane coupling agent having an ethylenically unsaturated group and a hydrolyzable silyl group, specifically vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylalkoxysilanes such as vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, vinyltriacetoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, Examples include (meth)acryloxyalkoxysilanes such as methacryloxypropylmethyldimethoxysilane. Among them, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred.

<Silanol condensation catalyst>
The silanol condensation catalyst acts to cause condensation reaction (acceleration) of the silanol-condensable reactive site of the silane coupling agent grafted to the base resin in the presence of moisture. Based on the action of this silanol condensation catalyst, the base resin is crosslinked via the silane coupling agent.
Such silanol condensation catalysts are not particularly limited, and examples thereof include organotin compounds, metallic soaps, platinum compounds and the like. Examples of organic tin compounds include organic tin compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate.

<Hindered Phenolic Antioxidant>
The hindered phenol-based antioxidant is not particularly limited as long as it is an antioxidant having a hindered phenol structure, and known antioxidants such as those commonly used in the field of wiring materials can be used. For example, pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010, manufactured by BASF), 3-(3,5-di-tert- Butyl-4-hydroxyphenyl)stearyl propionate (trade name: Irganox 1076, manufactured by BASF), N,N'-bis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl ) Propionyl]hexamethylenediamine (Irganox 1098 (trade name), manufactured by BASF), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine (adekastab CDA-10 (trade name), manufactured by ADEKA)) and the like.

<Benzimidazole antioxidant>
The benzimidazole-based antioxidant is not particularly limited as long as it is an antioxidant having a benzimidazole structure, and known antioxidants such as those commonly used in the field of wiring materials can be used. For example, 2-mercaptobenzimidazole or its zinc salt (Nocrac MBZ, trade name, 1,3-dihydro-2H-benzimidazole-2-thione 0.5 zinc, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.), 2-methyl mercaptobenzimidazole or its zinc salt, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thione or its zinc salt, and the like.

<Inorganic filler other than boehmite>
In the present invention, inorganic fillers other than boehmite may be used.
This inorganic filler has, on its surface, sites capable of chemically bonding with reactive sites capable of silanol condensation of the silane coupling agent (e.g., hydroxyl groups, water molecules of water containing water or water of crystallization, OH groups such as carboxyl groups, amino groups, SH group, etc.) is preferred. For example, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate, whiskers, hydrated aluminum silicate, hydrated silicon Metal hydrates such as compounds having a hydroxyl group or crystal water such as magnesium acid, basic magnesium carbonate, hydrotalcite, boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon, clay, Zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, talc, zinc borate, white carbon, zinc borate, zinc hydroxystannate, zinc stannate can be used. The inorganic filler may be surface-treated with a surface treatment agent.

<Organic Peroxide>
In the present invention, an organic peroxide is used in preparing the silane crosslinkable resin composition.
The organic peroxide generates radicals by thermal decomposition, and the grafting reaction of the silane coupling agent to the base resin (sharing of the grafting reaction site of the silane coupling agent and the graftable site of the base resin) It is a bond-forming reaction and is also called a (radical) addition reaction.). The organic peroxide is not particularly limited, and examples thereof include general formulas: R ¹ -OO-R ² , R ³ -OO-C(=O)R ⁴ , R ⁵ C(=O)-OO(C= O) A compound represented by ^R6 is preferably used. 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.
The decomposition temperature of the organic peroxide, measured by the method described in Patent Document 2, is preferably 80 to 195°C, particularly preferably 125 to 180°C.
Such organic peroxides include, for example, organic peroxides described in paragraph [0036] of Patent Document 2, and this description is hereby referred to as part of the description of this specification. Take in as Among them, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Perhexa 25B), 2,5-dimethyl-2,5-di-(tert-butylperoxy ) hexyne-3 is preferred.

<Additive>
In the present invention, various additives commonly used in electric wires, electric cables, electric cords and the like can also be used. Examples of such additives include lubricants, metal deactivators, plasticizers, flame retardants, flame retardant auxiliaries, and (co)polymers other than those described in the base resin. Flame retardants (auxiliaries) include brominated flame retardants and/or antimony trioxide.

(Composition of silane crosslinkable resin composition)
The content of boehmite in the silane crosslinkable resin composition is not particularly limited, but it is possible to achieve both excellent appearance characteristics (surface smoothness) and high heat resistance in a well-balanced manner, and to form a sufficient crosslinked structure. The amount is 9 to 80 parts by mass, preferably 9 to 50 parts by mass, more preferably 20 to 40 parts by mass, based on 100 parts by mass of the base resin.
In the silane crosslinkable resin composition, the content of the silane coupling agent grafted to the base resin (content converted to mass before grafting reaction to the base resin) is not particularly limited, but aggregation 1 part per 100 parts by mass of the base resin in that a heat-resistant silane crosslinked resin molded article having a smooth surface and a sufficient crosslinked structure can be produced by suppressing the formation of lumps and foaming due to volatilization. 15 parts by mass, preferably 2 to 10 parts by mass, more preferably 2.5 to 6 parts by mass.
The content of the silanol condensation catalyst in the silane crosslinkable resin composition is not particularly limited, but it is possible to achieve both excellent appearance characteristics (suppression of the occurrence of pimples) and high heat resistance in a well-balanced manner, and to achieve excellent surface smoothness. 0.01 to 0.5 parts by mass, preferably 0.03 to 0.2 parts by mass, and 0.05 to 0.15 parts by mass, based on 100 parts by mass of the base resin Parts by mass are more preferable.

The content of the hindered phenol-based antioxidant in the silane crosslinkable resin composition is not particularly limited, but it can achieve high heat resistance and also improve appearance properties (surface smoothness and suppression of the occurrence of pimples). With respect to 100 parts by mass of the base resin, it is preferably 0.2 to 8 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass. .
The content of the benzimidazole-based antioxidant in the silane crosslinkable resin composition is not particularly limited, but it can achieve high heat resistance and can also improve appearance characteristics (surface smoothness and suppression of the occurrence of pimples). The amount is preferably 2 to 15 parts by mass, more preferably 4 to 12 parts by mass, even more preferably 6 to 10 parts by mass, based on 100 parts by mass of the base resin.

The content of the inorganic filler other than boehmite in the silane crosslinkable resin composition is not particularly limited, and can be appropriately set within a range that does not impair the effects of the present invention. For example, it is preferably 0 to 100 parts by mass, more preferably 0 to 50 parts by mass, based on 100 parts by mass of the base resin. However, when aluminum hydroxide is contained, the content should be within the above range.
The content of the additive in the silane crosslinkable resin composition is not particularly limited, and can be appropriately set within a range that does not impair the effects of the present invention. However, when a brominated flame retardant is contained, the content is preferably within the above range, and antimony trioxide may or may not be contained.

(Composition of heat-resistant silane-crosslinked resin molding)
Since the heat-resistant silane-crosslinked resin molded article is formed by subjecting the silane-crosslinkable resin composition to molding followed by a silanol condensation reaction, the content of each of the above components in the molded article is usually the same as that in the silane-crosslinkable resin composition. is the same as the content in However, in the heat-resistant silane-crosslinked resin molding, the content of the silane coupling agent is the content before the silanol condensation reaction, and the content of the base resin is the content before the crosslinking.

[Method for producing heat-resistant silane-crosslinked resin molding]
The method for producing the heat-resistant silane-crosslinked resin molding of the present invention will be described below.
The silane crosslinkable resin composition of the present invention is produced by performing the following steps (a) to (c) in the method for producing a heat-resistant silane crosslinked resin molded article of the present invention.
The method for producing a heat-resistant silane-crosslinked resin molded article and the method for producing a silane-crosslinkable resin composition of the present invention are sometimes collectively referred to as the production method of the present invention.

The method for producing a heat-resistant silane-crosslinked resin molded article of the present invention comprises the following steps (a) to (e), and the method for producing a silane-crosslinkable resin composition of the present invention comprises the following steps (a) to (c). have. As a result, it is possible to produce a heat-resistant silane-crosslinked resin molded article exhibiting the above properties while suppressing foaming during melt-mixing and molding.

Step (a): a portion of the base resin, boehmite, and a group capable of grafting to the base resin;
a silane coupling agent having a rafting reaction site and an organic peroxide;
Melt and mix at a temperature above the decomposition temperature of the organic peroxide to form a silane master bar.
Step (b): Melt-blending the balance of the base resin and the silanol condensation catalyst to form a catalyst master bar.
Step (c): The silane masterbatch prepared in step (a) and the catalyst masterbatch prepared in step (b).
Step (d) of obtaining a silane-crosslinkable resin composition by dry-blending with Starbatch: Step (e) of molding the silane-crosslinkable resin composition obtained in step (c) to obtain a molded body : The molded article obtained in step (d) is brought into contact with water to obtain a heat-resistant silane crosslinked resin molded article.
the process of obtaining

The hindered phenol-based antioxidant and the benzimidazole-based antioxidant may be mixed in either step (a) or step (b), respectively. It is preferable in that the grafting reaction in step (a) can proceed efficiently. Both antioxidants, particularly hindered phenol-based antioxidants, are mixed in step (a) as long as they do not inhibit the grafting reaction (for example, 1 part by mass or less with respect to 100 parts by mass of the base resin). You can also

In the manufacturing method of the present invention, the mixing amount of each component used as the base resin is the same as the above-mentioned content rate explained as the composition of the base resin. In addition, the mixing amount of boehmite, silane coupling agent, silanol condensation catalyst, hindered phenol antioxidant, benzimidazole antioxidant, inorganic filler other than boehmite, and additives is the same as the above-mentioned silane crosslinkability. The content is the same as in the resin composition.
The amount of the organic peroxide mixed in step (a) is 0.01 to 0.5 parts by mass, preferably 0.1 to 0.2 parts by mass, per 100 parts by mass of the base resin. By setting the amount of the organic peroxide to be mixed within the above range, a heat-resistant silane-crosslinked resin molded article having a smooth surface can be obtained without generating agglomerates (bubs) caused by crosslinked gel or the like.
In the production method of the present invention, part of the base resin to be mixed in step (a) is not particularly limited, and may be a specific resin component or two or more resin components, and may be selected as appropriate. be done. Examples thereof include ethylene copolymers, polyolefin resins, ethylene rubbers, styrene elastomers, organic oils and the like. The rest of the base resin (carrier resin) mixed in step (b) is determined according to a portion of the base resin mixed in step (a), but preferably contains an ethylene copolymer and is a styrene-based elastomer. and more preferably an organic oil. The ratio of the base resin to be mixed in step (a) is preferably 60 to 95% by mass, preferably 70 to 85% by mass, of 100% by mass of the base resin to be mixed in step (a) and step (b). It is more preferable to have

<Step (a)>
In the step (a), a base resin (especially an ethylene copolymer) and a silane coupling agent are subjected to a graft reaction in the presence of boehmite to form a silane crosslinkable resin in which the silane coupling agent is grafted to the base resin. It is a step of preparing a silane masterbatch (silane MB) containing.
In this step, the base resin is heated and mixed with boehmite and a silane coupling agent in the presence of the organic peroxide at a temperature higher than the decomposition temperature of the organic peroxide. This gives the silane MB as a molten mixture.

In the step (a), the mixing temperature for melt-mixing (also referred to as melt-kneading) the above components is the decomposition temperature of the organic peroxide or higher, preferably the decomposition temperature of the organic peroxide + (25 to 110) ° C. temperature, more preferably 150 to 230°C. Mixing conditions such as mixing time can be appropriately set. For example, the mixing time can be 1-40 minutes. By melting and mixing at a temperature equal to or higher than the decomposition temperature of the organic peroxide, the organic peroxide thermally decomposes to generate radicals, thereby promoting the grafting reaction.

As a mixing method, any method generally used for mixing rubbers and plastics may be used. As the mixing apparatus, for example, a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer or various kneaders are used, and closed mixers such as a Banbury mixer or various kneaders are preferred.

In the present invention, the order of mixing is not specified, and the above components may be mixed in any order. For example, the above ingredients can be melt mixed together.
In the production method of the present invention, step (a) is preferably mixed in the following mixing order by following steps (a-1) and (a-2).

Step (a-1): Step of mixing boehmite and a silane coupling agent to prepare a mixture Step (a-2): The mixture obtained in Step (a-1) and part of the base resin are organic peracid
It is melt-mixed at a temperature above the decomposition temperature of the organic peroxide in the presence of the organic peroxide.
process

In the step (a-1), the boehmite and the silane coupling agent are premixed to obtain a silane coupling agent weakly bonded or adsorbed to the boehmite and a silane coupling agent strongly bonded or adsorbed to the boehmite. can be formed in a well-balanced manner. This makes it difficult for the silane coupling agent to volatilize due to the melt-mixing in step (a-2), and prevents the condensation reaction between non-adsorbed silane coupling agents to produce a molded product with excellent appearance. . Here, examples of the weak bond with boehmite include interaction due to hydrogen bonding, interaction between ions, partial charges or dipoles, action due to adsorption, and the like. Further, examples of strong bonding with boehmite include chemical bonding with chemically bonding sites on the surface of boehmite.

The mixing method and mixing conditions of the step (a-1) are not particularly limited, but usually at a temperature lower than the decomposition temperature of the organic peroxide, preferably 10 to 60° C., more preferably 10 to 60° C., using a known mixer. A method and conditions of dry or wet mixing at about room temperature (20 to 25° C.) for several minutes to several hours can be mentioned. Above all, dry mixing (dry blending) at a temperature lower than the decomposition temperature of the organic peroxide is preferred. Other conditions for dry mixing are determined appropriately.

In step (a-1), the base resin can be mixed as long as the temperature is maintained below the decomposition temperature.
The organic peroxide may be present during the melt mixing in step (a-2) and may be mixed in step (a-2), but should be mixed in step (a-1). is preferred.

Next, the mixture obtained in step (a-1) and part of the base resin are melt-mixed in the presence of an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide to obtain a silane MB. is prepared (step (a-2)). A silane masterbatch containing the silane crosslinkable resin is thus prepared. In the melt-mixing in this step, it is possible to prevent excessive cross-linking reaction between the base resins while suppressing volatilization and self-condensation of the above-described silane coupling agent. Furthermore, foaming of the molten mixture can be effectively suppressed for melt mixing. As a result, it is possible to produce a heat-resistant silane-crosslinked resin molded article having a smooth surface and excellent appearance characteristics without blisters and bubbles.
The melt-mixing method and conditions of this step (a-2) are not particularly limited, and the melt-mixing method and conditions of the step (a) can be applied.

In the step (a-2), at least the following are conceivable modes of grafting reaction of the silane coupling agent to the base resin. In other words, the silane coupling agent bound or adsorbed to the boehmite by a weak bond desorbs from the boehmite and undergoes a grafting reaction with the base resin. From this aspect, the crosslinked structure formed in step (e) to be described later does not incorporate boehmite, and usually becomes a crosslinked structure via a silanol condensate between silane coupling agents. Also, in this embodiment, the silane coupling agent bound or adsorbed to boehmite with a strong bond undergoes a grafting reaction to the resin while maintaining the bond or adsorption to boehmite. From this aspect, the crosslinked structure formed in step (e), which will be described later, incorporates boehmite and becomes a crosslinked structure via the silane coupling agent bound to boehmite as a starting point.

In step (a), antioxidants, inorganic fillers other than boehmite, additives, and the like can also be mixed. However, it is preferred that substantially no silanol condensation catalyst is mixed in step (a). Thereby, the occurrence of the silanol condensation reaction of the silane coupling agent can be suppressed. Here, "substantially not mixed" does not mean that the silanol condensation catalyst that is inevitably present is also excluded, and the range that can suppress the silanol condensation reaction, for example, 0.01 per 100 parts by mass of the base resin It means that it may be present as long as it is in the range of parts by mass or less.

The silane MB prepared in step (a) contains a reaction mixture of a base resin, boehmite and a silane coupling agent, and the silane coupling agent is incorporated into the base resin to the extent that it can be molded by step (b) below. It contains a silane crosslinkable resin (silane graft polymer) that is grafted. The silane coupling agent grafted to the base resin includes those bonded or adsorbed to boehmite and optionally present inorganic fillers other than boehmite at its silanol-condensable reaction sites.
The silane MB is preferably pelletized or powdered.

<Step (b)>
In the production method of the present invention, the remainder of the base resin and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch (catalyst MB).
The melt-mixing method and conditions in step (b) are not particularly limited, and the melt-mixing method and conditions in step (a) can be applied. For example, the melt-mixing temperature may be higher than the melting temperature of the base resin, preferably 120 to 200°C, more preferably 140 to 180°C.
Catalyst MB is preferably in the form of pellets or powder.

<Step (c)>
In the production method of the present invention, the silane masterbatch and the catalyst masterbatch are then dry blended to prepare a silane crosslinkable resin composition.
The mixing method and conditions are not particularly limited, but from the viewpoint of suppressing the occurrence or progress of the silanol condensation reaction, it is preferable to adopt a dry blending method and conditions under non-high temperature conditions, for example, in step (a-1) Dry mixing methods and conditions are included.

Thus, the silane crosslinkable resin composition of the present invention is produced.
This silane crosslinkable resin composition contains a silane crosslinkable resin, boehmite, a silanol condensation catalyst, and the like. In this silane crosslinkable resin, the reaction site capable of silanol condensation of the silane coupling agent may bind or adsorb to boehmite, but is not silanol-condensed. Therefore, the silane cross-linkable resin is composed of a silane cross-linkable resin in which a silane coupling agent bound or adsorbed to boehmite is grafted onto a base resin, and a silane coupling agent that is not bound or adsorbed to boehmite is grafted onto a base resin. and an attached silane crosslinkable resin.

<Step (d)>
In the production method of the present invention, the silane crosslinkable resin composition is then molded to obtain a molded body. In step (d), the silane crosslinkable resin composition, which is usually a dry blend, is melt-blended and molded.
The molding method is not particularly limited, and is appropriately selected according to the form of the desired product. Examples of the molding method include extrusion molding using an extruder, extrusion molding using an injection molding machine, and molding using other molding machines. When manufacturing a wiring material, the extrusion molding method is preferable from the viewpoint of productivity, co-extrusion with a conductor, and the like.
Molding conditions (melt-mixing conditions) are not particularly limited as long as they can be uniformly mixed, and for example, the melt-mixing method and conditions of step (a) can be applied. For example, the melt-mixing temperature in this step is the temperature at which the base resin melts or higher, preferably 80 to 250°C, more preferably 100 to 240°C, and even more preferably 120 to 200°C. In this melt-mixing, the melt-mixing method and conditions are set while maintaining the moldability of the melt mixture of the silane crosslinkable resin composition. The silane crosslinkable resin in the molten mixture is an uncrosslinked body in which the silane coupling agent is not silanol-condensed. In practice, melt-mixing in step (d) inevitably results in partial cross-linking (partial cross-linking), but the resulting melt mixture retains moldability. For example, in order to avoid the occurrence or progress of a silanol condensation reaction, it is preferable that the melt-mixed silane crosslinkable resin composition is not kept at a high temperature for a long period of time.

Step (d) can be performed simultaneously with step (c) or sequentially. For example, a series of processes can be adopted in which the silane MB and the catalyst MB are dry-blended in a coating device (extruder), melt-mixed, and then molded (co-extrusion molding) on the outer peripheral surface of a conductor or the like.

<Step (e)>
In the production method of the present invention, the molded article obtained in step (d) is then brought into contact with water to produce a heat-resistant silane-crosslinked resin molded article. Since the molded product obtained in the step (d) is an uncrosslinked product, this step causes a silanol condensation reaction at the reaction site capable of silanol condensation of the silane coupling agent grafted to the base resin, Proceed (accelerate) to obtain a final crosslinked molded body.
Contact between the uncrosslinked molded article and water can be carried out by a usual method. Although the silanol condensation reaction proceeds by simply leaving it in a temperature environment of normal temperature, for example, about 20 to 25° C., it is preferable to actively contact with water to accelerate the silanol condensation reaction (crosslinking reaction). As the contact method, methods (conditions) normally applied to the silane cross-linking method can be mentioned. For example, each contact method such as immersion in warm water, introduction into a moist heat bath, exposure to high temperature steam, etc. can be applied. .

Thus, the heat-resistant silane-crosslinked resin molding of the present invention is produced.
This heat-resistant silane crosslinked resin molding contains a crosslinked resin obtained by condensing a base resin through siloxane bonds. Further, the heat-resistant silane crosslinked resin molded article contains boehmite, and this boehmite may be bonded to the silane coupling agent of the crosslinked resin. Therefore, the crosslinked resin is composed of a plurality of base resins bonded or adsorbed to boehmite by a silane coupling agent and bonded (crosslinked) via the boehmite and the silane coupling agent, and a crosslinked resin grafted to the base resin. A crosslinked resin crosslinked via the silane coupling agent (siloxane bond) (not via boehmite) by hydrolyzing the hydrolyzable groups of the silane coupling agent in the silane coupling agent and causing a silanol condensation reaction with each other. it is conceivable that.

In the method for producing a heat-resistant silane-crosslinked resin molded product of the present invention, in the melt-mixing step, the kneaded product contains boehmite in the above-mentioned content and further contains an antioxidant, thereby reducing the viscosity of the kneaded product (kneadability (fluidity) The above series of steps can be carried out by suppressing volatilization and self-condensation reaction of the silane coupling agent, as well as foaming during melt-mixing. Therefore, the method for producing a heat-resistant silane-crosslinked resin molded article of the present invention uses a lightweight and inexpensive polyolefin resin, even though it is a silane-crosslinking method that is simple but has problems with appearance characteristics. It is possible to produce a heat-resistant silane-crosslinked resin molded article that exhibits heat resistance, has a smooth surface, and is free from pimples and bubbles and has excellent appearance characteristics.
The heat-resistant silane-crosslinked resin molded article of the present invention exhibits high heat resistance with an estimated 40,000-hour life expectancy temperature of 125° C. or higher as defined by JASO, and an estimated 10,000-hour life expectancy temperature of 150° C. or higher. , shows higher heat resistance that is required in recent years.

[Wiring material]
The wiring material of the present invention is a wiring material having a coating layer on the outer circumference of a conductor. It is a wiring member formed of a crosslinked resin molding. Therefore, the wiring material of the present invention exhibits high heat resistance of, for example, 150° C. or more, and is excellent in appearance characteristics. It is also cheaper and lighter.
The wiring material of the present invention is the same as those commonly used in the fields of various electric/electronic devices and industries, except that the coating layer is formed of the heat-resistant silane crosslinked resin molding of the present invention. . The coating layer formed of the heat-resistant silane crosslinked resin molded article of the present invention is provided directly on the outer peripheral surface of the conductor or via another layer. The presence or absence of the layer, materials, etc. are appropriately determined. Usual conductors can be used, for example, copper or aluminum single wires or stranded wires (tensile fibers are tandemly arranged or twisted together). In addition to bare wires, tin-plated wires or wires having an enamel-coated insulating layer can also be used. The thickness of the coating layer formed from the heat-resistant silane-crosslinked resin molded article of the present invention is not particularly limited, but is usually about 0.15 to 5 mm.
The wiring material of the present invention can be produced by disposing the silane crosslinkable resin composition of the present invention in a layer on the outer periphery of a conductor, followed by a cross-linking reaction (silanol condensation reaction). For example, in the above-described method for producing a heat-resistant silane crosslinked resin molded article of the present invention, the molding step (d) is performed by co-extrusion of the silane crosslinkable resin composition on the outer periphery of the conductor using a coating device (extruder). It can be manufactured by a molding process. Specific coextrusion molding is as described above.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these.

Compounds used in Examples and Comparative Examples are shown below.
<Base resin>
(1) Evolue SP0540: trade name, manufactured by Prime Polymer Co., Ltd., linear metallocene polyethylene (LLDPE)
(2) VF120T: trade name, manufactured by Ube Maruzen Polyethylene Co., Ltd. EVA, VA content 20% by mass
(3) EVAFLEX EV170: Trade name, manufactured by Mitsui Dow Polychemicals, EVA, VA content 33% by mass
(4) Rexpearl A1150: trade name, manufactured by Mitsubishi Chemical Corporation, EEA, EA content: 15% by mass
(5) EPT3092PM: trade name, manufactured by Mitsui Chemicals, EPDM
(6) PB222A: trade name, manufactured by SunAllomer Co., Ltd., random PP
(7) Tuftec N504: trade name, manufactured by Asahi Kasei Corporation, SEBS
(8) Diana Process Oil PW-90: Product name, manufactured by Idemitsu Kosan Co., Ltd., organic oil (paraffin oil)

<Boehmite>
Boehmite FKB104: trade name, manufactured by Kajima Chemical Co., Ltd., boehmite, aluminum hydroxide residual amount 10% by mass according to the following content measurement method
<Inorganic filler other than boehmite>
(1) BF 013: trade name, manufactured by Nippon Light Metal Co., Ltd., aluminum hydroxide (2) Kisuma 5: trade name, manufactured by Kyowa Chemical Industry Co., Ltd., magnesium hydroxide (3) boehmite composite aluminum hydroxide (using BF 013 as a raw material, Synthesized by the following wet hydrothermal treatment)

(Synthesis of boehmite composite aluminum hydroxide)
4 kg of aluminum hydroxide powder (BF 013) was weighed and put into a 30 L polyethylene container, and 16 L of pure water was added thereto and stirred to prepare an aluminum hydroxide slurry. This slurry was poured into an autoclave having a Hastelloy (registered trademark) C-276 wetted part, and hydrothermally treated at 170° C. for about 6 hours under stirring to synthesize boehmite composite aluminum hydroxide. The hydrothermally treated boehmite slurry cooled to room temperature was dried and then pulverized to obtain a boehmite composite aluminum hydroxide powder. The content of aluminum hydroxide in the obtained boehmite composite aluminum hydroxide was 47% by mass.

(Method for measuring content of aluminum hydroxide)
The content (remaining amount) of aluminum hydroxide in boehmite or boehmite composite aluminum hydroxide was quantified by the following method.
First, the target sample was measured for ignition loss according to JIS R 9301-3-2. However, the ignition loss between 105 and 900°C was measured. In addition, "loss on ignition" is a measurement of the amount of decrease in mass of the target sample when heated, and "loss on ignition between 105 and 900 ° C." is "loss when heated at 900 ° C. minus the mass lost when heated at 105°C from the mass obtained.
After that, the content of aluminum hydroxide was determined using the following formula.

R=(I1-I2)/(I3-I2)×100

The meanings of the symbols in the above formula are shown below.
R: content of aluminum hydroxide (%)
I1: Ignition loss (%) of the target sample determined by the above method
I2: theoretical value of ignition loss of boehmite (%) = 15.0
I3: Theoretical value (%) of ignition loss of aluminum hydroxide = 34.6

<Antioxidant>
(1) Irganox 1076: trade name, manufactured by BASF, hindered phenol antioxidant (2) Irganox 1010: trade name, manufactured by BASF, hindered phenol antioxidant (3) Adekastab CDA-10: Trade name, manufactured by ADEKA, hindered phenol-based antioxidant (4) Nocrack MBZ: trade name, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., benzimidazole-based antioxidant

<Silane coupling agent>
KBM-1003: trade name, manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane <silanol condensation catalyst>
ADEKA STAB OT-1: trade name, manufactured by ADEKA, dioctyltin dilaurate <organic peroxide>
“Perhexa 25B” (trade name, NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, decomposition temperature: 154° C.)
<Lubricant>
X-21-3043: trade name, manufactured by Shin-Etsu Chemical Co., Ltd., silicone gum

(Examples 1 to 13 and Comparative Examples 1 to 12)
Examples 1-13 and Comparative Examples 1-12 were carried out using the components shown in Tables 1 and 2, respectively.
In Tables 1 and 2, numerical values relating to compounding amounts (contents) 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.
In each example and comparative example, part of the base resin (specifically, the "carrier resin" shown in the "catalyst MB" column in Tables 1 and 2) was added to the carrier resin of the catalyst MB at the mass ratio shown in the same column. used as

First, boehmite or an inorganic filler other than boehmite, a silane coupling agent, and an organic peroxide were mixed in a rotary blade mixer (Mazeler PM: product manufactured by Mazeler), and stirred (pre-mixed) for 1 minute at room temperature (25° C.) and a rotation speed of 10 rpm (step (a-1)). A powder mixture was thus obtained.
Then, the powder mixture and the base resin, antioxidant and lubricant shown in the "Silane MB" column of Tables 1 and 2 are mixed in the mass ratio shown in the same column in a kneader (capacity 75 L) heated to 150 ° C. in advance. ), mixed for 5 minutes at a rotation speed of 40 rpm, and then finished kneading (melt mixing) at a rotation speed of 30 rpm for 3 minutes. After confirming that the resin temperature (temperature of the mixture) has reached 180 to 200° C., which is the decomposition temperature of the organic peroxide or higher, the molten mixture is pelletized using a feeder ruder and a pelletizer to obtain silane MB. obtained (step (a) together with step (a-2) and step (a-1)).

On the other hand, the carrier resin, the antioxidant and the silanol condensation catalyst were sequentially introduced into a kneader (capacity: 75 L) heated to 130°C in advance at the mass ratio shown in the "catalyst MB" column in Tables 1 and 2, and the rotation speed was After mixing for 5 minutes at 30 rpm, final kneading (melt mixing) was performed for 3 minutes at 25 rpm. After confirming that the resin temperature (temperature of the mixture) reached about 160° C. and the carrier resin was sufficiently melted, pelletization was carried out using a feeder/ruder and a pelletizer to obtain a catalyst MB (step (b)). .

Next, the pellets of the silane MB and the pellets of the catalyst MB were dry-blended in a tumbler mixer at room temperature (25)° C. for 2 minutes immediately before extrusion molding to obtain a silane crosslinkable resin composition (step (c )). At this time, the mixing ratio of the silane MB and the catalyst MB was the mass ratio shown in the "Silane MB" column and the "Catalyst MB" column in Tables 1 and 2.

Then, the resulting silane crosslinkable resin composition was processed into a 40 mm (screw diameter) extruder with L/D (ratio of screw effective length L to diameter D) = 24 (compression part screw temperature 160°C, head temperature 180°C). ), and the outer peripheral surface of the 1/0.8A conductor was coated with a thickness of 1 mm to obtain an uncrosslinked electric wire with an outer diameter of 2.8 mm (step (d)).

The obtained uncrosslinked electric wire was allowed to stand in an atmosphere of 60° C. and 95% RH for 24 hours to bring the silane crosslinkable resin composition into contact with water (step (e)).
In this way, insulated crosslinked electric wires each having a coating layer formed of a heat-resistant silane crosslinked resin molding were produced.

The manufactured insulated bridged wires were evaluated as follows, and the results are shown in Tables 1 and 2.

<Appearance characteristics>
An appearance characteristic test of the insulated bridged wire was conducted.
Evaluation items were the surface smoothness, the presence or absence of pimples, and the presence or absence of foaming inside the coating layer.
(Surface smoothness)
The smoothness of the entire surface of the coating layer (presence or absence of unevenness) was evaluated by visual observation and touch to evaluate the surface smoothness of a 5-m-long electric wire test piece cut from each insulated bridging electric wire. As a result, "A" indicates that the surface of the coating layer was smooth to the touch, "B" indicates that the surface of the coating layer was slightly rough to the touch but was visually good, and the roughness was visually observed. The case where it could be confirmed was set as "C". "A" and "B" were regarded as acceptable product levels.
(Presence or absence of product)
A 5-m-long wire test piece cut from each insulated bridging wire was evaluated for the presence or absence of lumps on the entire surface of the coating layer by visual inspection and touch. As a result, "A" indicates that no lumps (protruding clumps) can be confirmed visually and by touch on the entire surface, and "B" indicates that no lumps can be confirmed visually but can be confirmed by touch. ", and "C" when a lump was visually confirmed. "A" and "B" were regarded as acceptable product levels.
(Presence or absence of foaming)
The coating layer of the insulated bridging wire with a length of 1 m cut from each insulated bridging wire was sliced into two (semi-cylindrical) on a plane including and along the axis of the insulated bridging wire. The entire cross section of one of the cut coating layers was observed with a binocular stereoscopic microscope with a magnification of 10 times, and the presence or absence of foaming (cavity portions) in the cross section was evaluated. In this evaluation, if at least one cavity with a longest length of 0.05 mm or more measured by shape measurement can be confirmed (exists) in the entire cross section, or if there are 5 or more cavities regardless of size The case where it was possible (exists) was defined as the existence of foaming in the cross section. As a result, "A" was given when foaming could not be confirmed in the cross section, and "C" was given when foaming was confirmed in the cross section. "A" was regarded as a pass as a product level.

<Heat resistance>
The heat resistance of each of the manufactured insulated bridged wires was evaluated at the estimated 10,000-hour life temperature and the estimated 40,000-hour life temperature. That is, each insulated cross-linked wire produced was heated to a temperature of 170° C., 180° C. or 200° C., and the tensile strength and elongation at break after heating were measured. Tensile strength and elongation at break were measured based on JIS C 3005 (2014) (4.16 Tensile strength of insulator and sheath). Tensile strength (MPa) and tensile elongation (%) were measured by pulling at a speed of 500 mm/min.
At each temperature, the heating time at which the tensile strength after heating reached 3.92 MPa and the heating time at which the elongation at break reached 100% or 50% were determined. Arrhenius plots were prepared for tensile strength and elongation at break from the obtained heating time and heating temperature. From these plots (by extrapolation), the estimated 10,000 hour life temperature and the estimated 40,000 hour life temperature were determined.
In the present invention, "10,000 hour life" means that the elongation at break of the insulated bridge wire becomes 100% after being heated at a specific temperature for 10,000 hours. In addition, "40,000 hour life" means that the tensile strength of the insulated crosslinked wire becomes 3.92 MPa or the elongation at break becomes 50% after being heated at a specific temperature for 40,000 hours. say.
Since the present invention realizes a higher heat resistance than the conventional one, samples with an estimated 10,000-hour life expectancy temperature of 150°C or higher were evaluated as acceptable, and samples with an estimated 10,000-hour life of less than 150°C were evaluated as unacceptable. The 40,000-hour life estimation temperature is a relatively high test for evaluating long-term heat resistance, and was obtained as a reference in the present invention. Therefore, no pass/fail criteria were set.
In Tables 1 and 2, "10,000 hour life estimated temperature" and "40,000 hour life estimated temperature" are expressed as "10,000 Hr heat resistant temperature" and "40,000 Hr heat resistant temperature", respectively.

<Crosslinkability evaluation (heat deformation test)>
Whether or not the coating layer (heat-resistant silane crosslinked resin molding) was sufficiently crosslinked was evaluated by a heat deformation test for each of the manufactured insulated crosslinked wires.
This heat deformation test was performed based on JASO D 625-2 (2020) (4.4 Heat deformation test). Specifically, the insulated bridging wire with a load applied was placed in a constant temperature bath heated to 150° C. for 4 hours, and then quickly placed in cold water within 10 seconds after taking out to cool. After that, the insulated bridging wire was immersed in salt water for 10 minutes, and then a voltage of 1 kV was applied for 1 minute. Samples in which the coating layer did not break until the end of the charging were judged as acceptable, and samples in which the cross-linking was broken were judged as unsatisfactory.

As is clear from the results in Tables 1 and 2, Comparative Examples 1, 5, 7 and 8 containing no ethylene copolymer, boehmite, benzimidazole-based antioxidant or hindered phenol-based antioxidant showed 10, The 000-hour life estimated temperature is less than 150°C, and high heat resistance cannot be achieved.
Moreover, in Comparative Examples 4 and 6, which contain an excessive amount of aluminum hydroxide, foaming during melt mixing cannot be suppressed, and the appearance characteristics are inferior. Comparative Example 2, in which the boehmite content is too low, and Comparative Example 3, in which the boehmite content is too high, cannot achieve high heat resistance, and Comparative Example 2 is also inferior in surface smoothness. Although Comparative Example 3 contained 10 parts by mass of aluminum hydroxide, it contained 90 parts by mass of boehmite.
Comparative Examples 9 and 11, in which the content of the organic peroxide or the silanol condensation catalyst is too small, cannot achieve high heat resistance, fail the heat distortion test, and cannot form sufficient crosslinks. On the other hand, in Comparative Example 10, in which the content of the silane coupling agent is too large, foaming cannot be suppressed and the appearance properties are inferior. In addition, Comparative Example 12, in which the content of the silanol condensation catalyst is too large, cannot suppress the occurrence of pimples, resulting in inferior appearance characteristics and high heat resistance.

On the other hand, Examples 1 to 13 containing an ethylene copolymer, boehmite, a hindered phenolic antioxidant or a benzimidazole antioxidant in a specific proportion and containing no aluminum hydroxide are all In addition to having excellent appearance characteristics, it exhibits high heat resistance at an estimated 10,000-hour lifespan temperature of 150°C or higher. Furthermore, it has also passed the heat deformation test (sufficient cross-linking is formed), and satisfies the properties required for the coating layer of, for example, an insulated cross-linked wire.

Claims (12)

9 to 80 parts by mass of boehmite per 100 parts by mass of a base resin containing at least one ethylene copolymer selected from an ethylene-vinyl acetate copolymer and an ethylene-(meth)acrylic acid ester copolymer; 1 to 15 parts by mass of a silane coupling agent grafted to, 0.01 to 0.5 parts by mass of a silanol condensation catalyst, a hindered phenol antioxidant, and a benzimidazole antioxidant and a method for producing a heat-resistant silane-crosslinked resin molding, comprising silane-crosslinking a silane-crosslinkable resin composition that does not contain aluminum hydroxide,
The step (a), step (b), step (c), step (d) and step (e) are provided below, and the hindered phenol-based oxidation is performed in at least one step of step (a) and step (b). A method for producing a heat-resistant silane-crosslinked resin molding, comprising mixing an inhibitor or the benzimidazole-based antioxidant.

Step (a): Part of the base resin, the boehmite, and grafting to the base resin
a silane coupling agent having a reactive grafting reaction site;
0.01 to 0.5 parts by mass of an organic peroxide with respect to 100% by mass of the resin,
The silane mass is melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Step (b) of preparing a turbatch: melt-mixing the remainder of the base resin and the silanol condensation catalyst to form a catalyst matrix;
Process for preparing a starbatch Step (c): Dry blending the silane masterbatch and the catalyst masterbatch
Step (d) of obtaining a silane crosslinkable resin composition: Molding the silane crosslinkable resin composition to obtain a molded body Step (e): Contacting the molded body with water to heat-resistant Step of obtaining a silane-crosslinked resin molded product The production method according to claim 1, wherein the hindered phenol-based antioxidant is contained in an amount of 0.5 to 5 parts by mass with respect to 100 parts by mass of the base resin. The production method according to claim 1 or 2, wherein the benzimidazole antioxidant is contained in an amount of 4 to 12 parts by mass with respect to 100 parts by mass of the base resin. The production method according to any one of claims 1 to 3, wherein the ethylene copolymer is contained in a proportion of 10 to 70% by mass based on 100% by mass of the base resin. 5. The ethylene copolymer according to any one of claims 1 to 4, wherein each ethylene copolymer contained in the base resin contains vinyl acetate or (meth)acrylic acid ester at a rate of 10 to 30% by mass in each ethylene copolymer. Method of manufacture as described. The production method according to any one of claims 1 to 5, wherein the boehmite is contained in an amount of 9 to 50 parts by mass with respect to 100 parts by mass of the base resin. The production method according to any one of claims 1 to 6, wherein the base resin contains a styrene-based elastomer and an organic oil. 9 to 80 parts by mass of boehmite per 100 parts by mass of a base resin containing at least one ethylene copolymer selected from an ethylene-vinyl acetate copolymer and an ethylene-(meth)acrylic acid ester copolymer; 1 to 15 parts by mass of a silane coupling agent grafted to, 0.01 to 0.5 parts by mass of a silanol condensation catalyst, a hindered phenol antioxidant, and a benzimidazole antioxidant and a method for producing a silane crosslinkable resin composition containing no aluminum hydroxide,
The hindered phenol-based antioxidant or the benzimidazole-based antioxidant in at least one of the steps (a) and (b), comprising the following steps (a), (b), and (c): A method for producing a silane crosslinkable resin composition by mixing

Step (a): Part of the base resin, the boehmite, and grafting to the base resin
a silane coupling agent having a reactive grafting reaction site;
0.01 to 0.5 parts by mass of an organic peroxide with respect to 100% by mass of the resin,
The silane mass is melt-mixed at a temperature equal to or higher than the decomposition temperature of the organic peroxide.
Step (b) of preparing a turbatch: melt-mixing the remainder of the base resin and the silanol condensation catalyst to form a catalyst matrix;
Process for preparing a starbatch Step (c): Dry blending the silane masterbatch and the catalyst masterbatch
to obtain a silane crosslinkable resin composition A heat-resistant silane crosslinked resin molded article produced by the production method according to any one of claims 1 to 7. A silane crosslinkable resin composition produced by the production method according to claim 8 . A wiring material having a coating layer on the outer periphery of a conductor,
The wiring material, wherein the coating layer is a layer of the heat-resistant silane crosslinked resin molding according to claim 9 . The wiring material according to claim 11, which is a heat-resistant wire or cable.