Silane crosslinkable resin composition, silane crosslinked resin molded product, production methods for these, and wiring material

Abstract

Provided is a silane crosslinkable resin composition containing: 100 parts by mass of a base resin including a polyolefin resin; a silane coupling agent graft-bonded to the base resin; 1-60 parts by mass of a compound having two or more imide structures; and 0.01-5 parts by mass of a silanol condensation catalyst. Also provided are a silane crosslinked resin molded product of the silane crosslinkable resin composition, and a wiring material having said molded product. Further provided are production methods for a silane crosslinkable resin compound and a silane crosslinked resin molded product, said methods comprising melting and mixing, at specific percentages, a base resin, a silane coupling agent, a compound having two or more imide structures, an inorganic filler, an organic peroxide, and a silanol condensation catalyst.

Description

Silane-crosslinkable resin composition, silane-crosslinked resin molded body, their manufacturing methods, and wiring material

[0001] The present invention relates to a silane-crosslinkable resin composition, a silane-crosslinked resin molded article, methods for producing the same, and a wiring material.

[0002] Wiring materials, such as insulated wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables) used in the fields of electrical and electronic equipment and industry, include coating layers (insulators, sheaths, etc.) formed from various resin molded bodies or rubber molded bodies. Such molded bodies (coating layers) are required to have various properties depending on the application and usage of the wiring material, such as appearance characteristics and heat resistance from the standpoint of safety and reliability. A representative technique for improving the heat resistance of wiring materials is to form a coating layer using a crosslinked molded body obtained by crosslinking a resin or rubber. Methods for crosslinking such resins or rubbers can generally be electron beam crosslinking, chemical crosslinking, etc.; among chemical crosslinking methods, the silane crosslinking method is widely used because it allows for crosslinking a silane-crosslinkable resin composition in the crosslinking step easily and with high productivity without requiring special equipment. As an example of an insulated wire having a coating layer formed by such a silane crosslinking method, Patent Documents 1 and 2 describe an insulated wire having a wire coating material obtained by water-crosslinking a composition for a wire coating material containing a silane-grafted polyolefin, an unmodified polyolefin, a polyolefin modified with a specific functional group, a brominated flame retardant having a phthalimide structure, a crosslinking catalyst, zinc sulfide, and the like.

[0003] JP 2012-057080 A JP 2016-046084 A

[0004]

[0003] Conventionally, the properties of crosslinked resin molded articles (coating layers) produced by the silane crosslinking method have been considered to be affected not only by the types and contents of the components constituting the crosslinked resin molded article, but also by the occurrence and reaction rate of the grafting reaction of the silane coupling agent, and the direct crosslinking reaction between resins or rubbers, and various studies have been conducted on these properties. From this perspective, the present inventors have investigated the properties of crosslinked resin molded articles, but have encountered the problem that even when various improvements or modifications are made based on the above perspective, it is not possible to achieve both the appearance properties and heat resistance of the crosslinked resin molded article. However, Patent Documents 1 and 2 do not address this problem at all.

[0005] An object of the present invention is to provide a silane-crosslinked resin molded article that combines excellent appearance characteristics (in which poor appearance and the generation of protruding agglomerates (lumps) are suppressed) with sufficient heat resistance due to increased crosslinking density, and a method for producing the same. Another object of the present invention is to provide a silane-crosslinkable resin composition that can form a silane-crosslinked resin molded article having the above-mentioned excellent properties, and a method for producing the same. A further object of the present invention is to provide a wiring material that has a silane-crosslinked resin molded article having the above-mentioned excellent properties as a coating layer.

[0006] The present inventors continued to investigate the problem of the inability to achieve both excellent appearance and heat resistance in the silane crosslinking method and discovered that the reaction rate (crosslinking rate) of the final crosslinking reaction (silanol condensation reaction) affects the properties of the crosslinked resin molded product, particularly the appearance and heat resistance. Based on this finding, the present inventors further investigated and found that by adding a compound having two or more imide structures to the silanol condensation catalyst in a specific ratio during the final crosslinking reaction of a silane crosslinkable resin composition containing a polyolefin resin grafted with a silane coupling agent in a specific ratio, the final crosslinking reaction can proceed at a moderate rate, forming a sufficient (dense) crosslinked structure through the silanol condensation reaction while suppressing the occurrence of poor appearance and lumps. As a result, they found that silane crosslinked resin molded products that combine excellent appearance and sufficient heat resistance can be produced with high productivity. Based on this finding, the present inventors further investigated and developed the present invention.

[0007] That is, the object of the present invention has been achieved by the following means. <1> A silane-crosslinkable resin composition containing 100 parts by mass of a base resin containing a polyolefin resin, a silane coupling agent graft-bonded to the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, and 0.01 to 5 parts by mass of a silanol condensation catalyst. <2> The silane-crosslinkable resin composition according to <1>, wherein the base resin does not contain a modified polyolefin resin modified with any of a carboxylic acid group, a methacrylic group, and an epoxy group. <3> The silane-crosslinkable resin composition according to <1> or <2>, wherein the compound having two or more imide structures does not contain a brominated flame retardant having a phthalimide structure. <4> The silane-crosslinkable resin composition according to any one of <1> to <3>, wherein 1 to 200 parts by mass of an inorganic filler is contained relative to 100 parts by mass of the base resin. <5> A silane-crosslinkable resin molded product of the silane-crosslinkable resin composition according to any one of <1> to <4> above. <6> A wiring material having the silane-crosslinked resin molded product according to <5> above as a coating layer.

[0008] <7> A method for producing a silane-crosslinkable resin composition, comprising: a step (1) of melt-mixing, relative to 100 parts by mass of a base resin containing a polyolefin resin, 2 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction to the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, 1 to 200 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 5 parts by mass of a silanol condensation catalyst, to obtain a silane-crosslinkable resin composition, wherein, in performing the step (1), if the entire base resin is melt-mixed in the following step (a), the step (1) comprises the following steps (a) and (c), and on the other hand, if only a part of the base resin is melt-mixed in the following step (a), the step (1) comprises the following steps (a), (b), and (c): step (a): mixing all or a part of the base resin, the inorganic filler, and a step of melt-mixing the silane coupling agent and the organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide to prepare a silane masterbatch; a step of melt-mixing the remainder of the base resin with the silanol condensation catalyst to prepare a catalyst masterbatch; and a step of melt-mixing the silane masterbatch with the silanol condensation catalyst or the catalyst masterbatch. A method for producing a silane crosslinkable resin composition, wherein the compound having two or more imide structures is mixed in at least one of the steps (a) and (b). <8> The method for producing a silane crosslinkable resin composition according to <7>, wherein the entire amount of the compound having two or more imide structures is mixed in the step (b).<9> A method for producing a silane-crosslinked resin molded product, comprising the following steps (1), (2), and (3): step (1): melt-mixing 2 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction with the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, 1 to 200 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 5 parts by mass of a silanol condensation catalyst, relative to 100 parts by mass of a base resin containing a polyolefin resin, to obtain a mixture; step (2): molding the mixture obtained in step (1) to obtain a molded product; and step (3): contacting the molded product obtained in step (2) with water to obtain a silane-crosslinked resin molded product. In carrying out the step (1), when the entire base resin is melt-mixed in the step (a), the step (1) comprises the following steps (a) and (c); on the other hand, when a portion of the base resin is melt-mixed in the step (a), the step (1) comprises the following steps (a), (b), and (c): step (a): melt-mixing all or a portion of the base resin, the inorganic filler, the silane coupling agent, and an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide to prepare a silane masterbatch; step (b): melt-mixing the remainder of the base resin and the silanol condensation catalyst to prepare a catalyst masterbatch; and step (c): melt-mixing the silane masterbatch with the silanol condensation catalyst or the catalyst masterbatch. A method for producing a silane-crosslinked resin molded product, comprising mixing the compound having two or more imide structures in at least one of the steps (a) and (b). <10> A method for producing a silane-crosslinked resin molded product according to <9>, comprising mixing the entire amount of the compound having two or more imide structures in the step (b). <11> A silane-crosslinkable resin composition produced by the production method according to the above <7> or <8>.<12> A silane-crosslinked resin molded article produced by the method described in <9> or <10> above. <13> A wiring material having the silane-crosslinked resin molded article described in <12> above as a coating layer.

[0009] The present invention can provide a silane-crosslinked resin molded article that combines excellent appearance characteristics, in which the occurrence of appearance defects and bumps is suppressed, with sufficient heat resistance due to increased crosslinking density (due to the high density of the crosslinked structure), and a method for producing the same. The present invention can also provide a silane-crosslinkable resin composition that can form a silane-crosslinked resin molded article having the above-mentioned excellent properties, and a method for producing the same. Furthermore, the present invention can provide a wiring material that has a silane-crosslinked resin molded article having the above-mentioned excellent properties as a coating layer. The above and other features and advantages of the present invention will become more apparent from the description below.

[0010] In the present invention, when the content, physical properties, etc. of a component are described using a numerical range, and when the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, in the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. Note that in the present invention, when multiple numerical ranges are set and described, the upper and lower limits forming the numerical range are not limited to the specific combination written before and after "to" as a specific numerical range, and can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Furthermore, in the present invention, "(meth)acrylic acid" represents either or both of acrylic acid and methacrylic acid, and "(meth)acrylic acid ester" represents either or both of an acrylic acid ester and a methacrylic acid ester.

[0011] [Silane Crosslinkable Resin Composition] The silane crosslinkable resin composition of the present invention contains, per 100 parts by mass of a base resin containing a polyolefin resin, a silane coupling agent grafted to the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, and 0.01 to 5 parts by mass of a silanol condensation catalyst. As will be described in detail below, the silane crosslinkable resin composition of the present invention contains a silane crosslinkable resin in which the silane coupling agent and the base resin are grafted (grafted), and contains a compound having two or more imide structures and a silanol condensation catalyst in a mixed state with the base resin. Furthermore, a preferred form of the silane crosslinkable resin composition described below contains, in addition to the compound having two or more imide structures and the silanol condensation catalyst, a silane crosslinkable resin in which the silane coupling agent bonded or dissociated with an inorganic filler is grafted (grafted) to the base resin.

[0012] The silane-crosslinkable resin composition of the present invention contains a specific amount of a compound having two or more imide structures in combination with a specific amount of a silanol condensation catalyst. This allows the silanol condensation reaction to occur and proceed at a moderate reaction rate under mild conditions, while eliminating the need for special crosslinking equipment such as a chemical crosslinking tube or an electron beam crosslinker. As a result, the occurrence of poor appearance and bumps due to the accelerated silanol condensation reaction can be suppressed, resulting in excellent appearance characteristics. In the present invention, poor appearance refers to defects due to foaming and defects such as unevenness and roughness, known as melt fracture, on the surface (appearance) of a silane-crosslinked resin molded product (coating layer) obtained from the silane-crosslinkable resin composition. Furthermore, bumps refer to gel-like protruding aggregates (gel bumps) formed by the final crosslinking (silanol condensation reaction) or aggregated bumps formed by the aggregation of incompatible raw materials, which are present on the surface of the silane-crosslinked resin molded product (coating layer). Furthermore, it is possible to suppress the delay in the formation of crosslinked structures (delay in crosslink construction), which is caused by a slower silanol condensation reaction, and thus the decrease in crosslink density (decreased heat resistance) and deterioration in productivity. In the present invention, the appropriate (suitable) reaction rate (crosslinking rate) for the silanol condensation reaction cannot be uniquely determined depending on the content of the silanol condensation catalyst, the contact conditions with water, etc. Whether the reaction rate of the silanol condensation reaction is appropriate can be judged and evaluated by maintaining the catalytic activity of the silanol condensation catalyst and passing, for example, the appearance property test and the heat distortion test described in the Examples below.

[0013] As described above, the silane-crosslinkable resin composition of the present invention can adjust the reaction rate of the silanol condensation reaction to an appropriate reaction rate, thereby realizing a silane-crosslinked resin molded article that achieves a good balance between the appearance properties and heat resistance, which are contradictory properties depending on whether the silanol condensation reaction is fast or slow. Therefore, the silane-crosslinkable resin composition of the present invention is suitably used for the silane-crosslinked resin molded article and wiring material of the present invention.

[0014] [Silane-Crosslinked Resin Molded Article] The silane-crosslinked resin molded article of the present invention is a crosslinked molded article of the silane-crosslinkable resin composition of the present invention. Specifically, it is a crosslinked resin molded article (molded article made of a silanol condensate of the silane-crosslinkable resin composition) obtained by molding the silane-crosslinkable resin composition of the present invention into a predetermined shape and size and then silane-crosslinking (silanol condensation reaction) the composition. As will be described in detail later, the silane-crosslinked resin molded article of the present invention is formed by a silanol condensation reaction at an appropriate reaction rate using a compound having two or more imide structures and a silanol condensation catalyst, and has a crosslinked structure in which the base resin is appropriately silane-crosslinked (a crosslinked structure via a silane coupling agent or its silanol condensate). Therefore, the silane-crosslinked resin molded article of the present invention exhibits a good balance between excellent appearance characteristics and sufficient heat resistance. Furthermore, it is believed that a preferred form of the silane-crosslinked resin molded article described later has an inorganic filler incorporated into part of the crosslinked structure, as described below. Therefore, a preferred embodiment of the silane-crosslinked resin molded article, as described below, has a well-balanced structure between crosslinked structures between base resins (without the involvement of an inorganic filler) and crosslinked structures involving an inorganic filler, thereby exhibiting excellent appearance characteristics and sufficient heat resistance at a high level. The silane-crosslinked resin molded article of the present invention is molded into an appropriate shape and dimensions depending on the application, for example, the application of the wiring material of the present invention described below.

[0015] Each component used in the present invention will be described below. One or more of each component may be used. In the present invention and this specification, the term "resin" simply refers to a resin that has not undergone a grafting reaction with a silane coupling agent. On the other hand, a resin that has undergone a grafting reaction with a silane coupling agent may be referred to as a silane crosslinkable resin, a silane grafted resin, or the like. In addition, the term "(co)polymer" is used to include the resin or rubber.

[0016] <Base Resin> The silane-crosslinkable composition of the present invention contains a polyolefin resin as its base resin, and is preferably composed of a polyolefin resin. As described above, this base resin contains a polyolefin resin (silane-crosslinkable resin, silane graft resin) obtained by grafting a silane coupling agent. The silane graft resin contained in the base resin is formed from a silane coupling agent (described below) and a polyolefin resin, and is a resin obtained by grafting the silane coupling agent to the polyolefin resin. In this silane graft resin, the graft reaction amount of the silane coupling agent is not particularly limited. Generally, it is sufficient that the graft reaction amount obtained by reacting the silane coupling agent with the polyolefin resin in the blending amount described below is sufficient. The silane graft resin may be appropriately synthesized or may be a commercially available product. The silane graft resin is obtained by reacting a polyolefin resin with a silane coupling agent at a temperature equal to or higher than the decomposition temperature of the organic peroxide. The specific reaction conditions are not particularly limited, but suitable examples include the melt-mixing conditions of step (1) or step (a) described below, with the organic peroxide content set within the range described below. Commercially available silane-grafted resins include Linklon (trade name, manufactured by Mitsubishi Chemical Corporation).

[0017] (Polyolefin Resin) The polyolefin resin (before the grafting reaction) from which the silane graft resin is formed is not particularly limited as long as it is a resin composed of a polymer obtained by polymerizing or copolymerizing a compound having an ethylenically unsaturated bond (olefin compound), and known resins used in conventional resin compositions can be used. In the present invention, the term "polyolefin resin" encompasses not only resins composed of polymers obtained by polymerizing or copolymerizing the above-mentioned olefin compounds, but also elastomers and rubbers composed of such polymers. The polyolefin resin has a graftable moiety (e.g., an unsaturated bond moiety in the carbon chain or a carbon atom containing a hydrogen atom) that undergoes a grafting reaction with the grafting reaction moiety of the silane coupling agent. Examples of such polyolefin resins include polyethylene (PE), polypropylene (PP), ethylene-α-olefin copolymers, resins such as copolymers containing an acid copolymerization component or an acid ester copolymerization component, and styrene-based elastomers.

[0018] Polyethylene Resin Polyethylene resin (PE) is not particularly limited as long as it is a polymer resin whose main component is ethylene, and examples thereof 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). Of these, linear low-density polyethylene and low-density polyethylene resins are preferred.

[0019] - Polypropylene Resin - Polypropylene resin (PP) is not particularly limited as long as it is a polymer resin whose main component is propylene, and examples thereof include propylene homopolymers, as well as random polypropylene and block polypropylene resins.

[0020] Ethylene-α-olefin copolymer resin: The ethylene-α-olefin copolymer resin is preferably a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms (excluding those included in the polyethylene resins and polypropylene resins described above). Examples of the copolymer include ethylene-propylene copolymer resin (excluding those included in the polypropylene resins), ethylene-butylene copolymer resin, and ethylene-α-olefin copolymer resin synthesized in the presence of a single-site catalyst.

[0021] - Copolymer resin having an acid copolymerization component or an acid ester copolymerization component - The compound that derives the acid copolymerization component or acid ester copolymerization component in the copolymer resin having an acid copolymerization component or an acid ester copolymerization component is not particularly limited, and examples thereof include carboxylic acid compounds such as (meth)acrylic acid, and acid ester compounds such as vinyl acetate and (meth)acrylic acid esters. The (meth)acrylic acid ester is not particularly limited, but examples thereof include alkyl (meth)acrylates. The alkyl group of the alkyl (meth)acrylate is preferably one having 1 to 12 carbon atoms. The copolymer resin having an acid copolymerization component or an acid ester copolymerization component is not particularly limited, but examples thereof include ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, ethylene-alkyl (meth)acrylate copolymer, and other resins. Specific examples of ethylene-alkyl (meth)acrylate copolymer resins include ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA).

[0022] - Styrenic Elastomer - A styrene-based elastomer refers to an elastomer made of a polymer having a component derived from an aromatic vinyl compound within the molecule. Examples of such styrene-based elastomers include block copolymers and random copolymers of conjugated diene compounds and aromatic vinyl compounds, as well as hydrogenated products thereof. Specific examples include 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), and hydrogenated acrylonitrile-butadiene rubber (HNBR).

[0023] - Modified Polyolefin Resin - The base resin may contain a resin obtained by modifying a polyolefin resin. Examples of modified polyolefin resins include modified polyolefin resins modified with any of a carboxylic acid group, a methacrylic group, and an epoxy group, as well as modified polyolefin resins modified with any of a carboxylic acid group, an acid anhydride group, an amino group, an acrylic group, a methacrylic group, and an epoxy group. Such modified polyolefin resins are not particularly limited, and examples include resins composed of a polymer obtained by graft polymerizing a compound having at least one of the above groups onto a polyolefin resin, and resins composed of a polymer obtained by copolymerizing a compound having at least one of the above groups with an olefin compound. Specific examples include maleic acid-modified polyethylene resins, maleic acid-modified polypropylene resins, resins composed of ethylene-glycidyl methacrylate (E-GMA) copolymers, and resins composed of ethylene-methyl methacrylate (EMMA) copolymers. As for the modified polyolefin resin and the compound having at least one of the above-mentioned groups (corresponding to the "compound that introduces a functional group" in each patent document), reference can be made, as appropriate, to the contents described in Patent Document 1 or Patent Document 2, the contents of which are incorporated as is into this specification as part of their description.

[0024] - Oil - The polyolefin resin may optionally contain various oils used as plasticizers or softeners. Examples of such oils include oils used as plasticizers for polyolefin resins or mineral oil softeners for rubber. As the oil, aromatic oils, paraffin oils, and naphthenic oils are preferably used, and paraffin oils are more preferred.

[0025] (Composition of Base Resin) The base resin may contain each of the above resins alone or multiple resins. In the present invention, the base resin preferably contains a polyethylene resin. However, in terms of improving manufacturability and mechanical properties, it may also contain a polyethylene resin and a polyolefin resin other than a polyethylene resin. It is more preferable that the base resin is composed of a polyethylene resin. However, it is preferable that the base resin does not contain the above-mentioned modified polyolefin resin. If the base resin does not contain the above-mentioned modified polyolefin resin, the appearance characteristics can be further improved without impairing sufficient heat resistance, and a silane-crosslinked resin molded product that combines high appearance characteristics and sufficient heat resistance can be realized. In the present invention, "the base resin does not contain a modified polyolefin resin" means that the base resin does not actively contain or mix a modified polyolefin resin, but does not exclude the inevitable inclusion or mixing of the modified polyolefin resin. For example, the content of the modified polyolefin resin in the base resin can be 4.0% by mass or less, preferably less than 0.5% by mass, based on 100% by mass of the base resin.

[0026] When the base resin contains multiple resins, the resins or oils may be contained in a content that totals 100% by mass, and this content is appropriately set depending on the physical properties, application, etc. of the silane-crosslinked resin molded product. For example, the content of polyethylene resin in 100% by mass of the base resin is preferably 20 to 100% by mass, and more preferably 30 to 90% by mass. Setting the lower limit of the polyethylene resin content to 70% by mass is also a preferred embodiment. Furthermore, the content of polypropylene resin, ethylene-α-olefin copolymer resin, or copolymer resin having an acid copolymerization component or an acid ester copolymerization component in 100% by mass of the base resin is preferably 0 to 80% by mass, and more preferably 10 to 70% by mass. Meanwhile, the content of styrene-based elastomer in 100% by mass of the base resin is preferably 0 to 50% by mass, and more preferably 5 to 20% by mass. The oil content in 100% by mass of the base resin is preferably 0 to 50% by mass, and more preferably 5 to 20% by mass. When the base resin contains a modified polyolefin resin, the content of the modified polyolefin resin in 100% by mass of the base resin is not particularly limited, but can be 5 to 70% by mass, 5 to 40% by mass, or 10 to 30% by mass.

[0027] <Compounds Having Two or More Imide Structures> Compounds having two or more imide structures (hereinafter, sometimes referred to as polyimide compounds) have a structure in which two carbonyl groups are bonded to an amino group (—NR—) or ammonia: —CO—NR ２ It is a compound having two or more —CO— groups in its molecular structure. ２ represents a hydrogen atom, a substituent, or a bond. ２The substituent that can be taken as the imide group is not particularly limited, and examples thereof include an alkyl group, an alkenyl group, an aryl group, and the like. In the polyvalent imide compound, the imide structure may be a linear imide structure, but is preferably a cyclic imide structure (an imide structure is incorporated to form a ring). In the cyclic imide structure, one or more imide structures may be incorporated into one ring (cyclic chain). In the present invention, a compound having two or more imide structures generally includes a form in which two imide structures exist independently via an atom or a linking group (for example, a compound represented by formula (1) or formula (2) described below), a form in which a carbonyl group, an amino group, or ammonia of one imide structure is shared with the other imide structure (for example, a compound having an isocyanurate ring structure described below), and a form in which the above two forms are mixed. Examples of a form in which a carbonyl group, an amino group, or ammonia of one imide structure is shared with the other imide structure include, for example, -CO-NR ２ -CO-NR ２ -CO-(R ２ is as described above.) and this compound is interpreted as having two imide structures. The chain may be incorporated into a ring in a polyimide compound, and an example of a ring structure consisting of three imide structures is an isocyanurate ring structure.

[0028] Examples of the cyclic imide structure include ring structures having one imide structure in the ring, such as a maleimide ring structure, a succinimide ring structure, a glutarimide ring structure, or a ring structure in which a benzene ring is condensed with any of these ring structures, and ring structures having two or more imide structures in the ring, such as an isocyanurate ring structure. A ring structure having one imide structure in the ring is preferred, and a maleimide ring structure or a ring structure in which a benzene ring is condensed with a maleimide ring structure (for example, a phthalimide structure) is more preferred. The bonding portion in the cyclic imide structure may be any atom, but is preferably an atom forming a cyclic structure, and is preferably a nitrogen atom (the above-mentioned R ２ ) is more preferable.

[0029] The polyimide compound may have two or more imide structures per molecule. When the polyimide compound is a high molecular weight compound, preferably a polymer, the number of imide structures present in one molecule can be appropriately set depending on the molecular weight of the high molecular weight compound, and can be, for example, 2 to 100. On the other hand, when the polyimide compound is a low molecular weight compound, usually a non-polymer compound (also referred to as a monomer compound), the number of imide structures present in one molecule is preferably, for example, 2 to 4, and more preferably 2. The two or more imide structures may be different from one another, but are preferably the same. The polyimide compound may be a high molecular weight compound (polymer), but is preferably a low molecular weight compound (non-polymer). As described below, various compounds can be used as such polyimide compounds. From the viewpoint of environmental compatibility, compounds other than brominated flame retardants having a phthalimide structure (i.e., the polyimide compound does not contain a brominated flame retardant having a phthalimide structure) are preferred, compounds other than flame retardants (i.e., the polyimide compound does not contain a flame retardant) are more preferred, and compounds other than polyimide compounds having halogen atoms (i.e., the polyimide compound does not contain a polyimide compound having a halogen atom) are even more preferred. In the present invention, "the polyimide compound does not contain a brominated flame retardant or the like" means that the polyimide compound does not actively contain or mix a brominated flame retardant or the like, but does not exclude the polyimide compound from inevitably containing a brominated flame retardant or the like. For example, the polyimide compound may contain a brominated flame retardant or the like in an amount of 0.5% by mass or less relative to 100% by mass of the polyimide compound.

[0030] The polyimide compound is not particularly limited, and examples thereof include monomer compounds that form bismaleimide resins. An imide compound having two cyclic imide structures represented by the following formula (1) or formula (2) is preferred, and a compound represented by the following formula (1) is more preferred.

[0031] In formula (1) and formula (2), R each represents a linking group. The linking group that can be taken as R is not particularly limited, and examples thereof include an alkylene group, an alkenylene group, an arylene group, an oxygen atom (—O—), a sulfur atom (—S—), an imino group, or a group relating to a combination thereof. The alkylene group that can be taken as R is not particularly limited, and may be any of a linear chain, branched chain, and cyclic chain, with a linear chain or branched chain being preferred. The number of carbon atoms in the alkylene group is not particularly limited, and is preferably, for example, 1 to 12, more preferably 1 to 6, and even more preferably 1 to 3. The bonding positions of the alkylene groups are not particularly limited, and may be the same carbon atom or different carbon atoms. When different carbon atoms are used as bonding positions, the carbon atoms located at both ends of the longest carbon chain forming the alkylene group are preferred. The alkenylene group that can be taken as R is not particularly limited, and may be any of a linear chain, branched chain, and cyclic chain, with a linear chain or branched chain being preferred. The number of carbon atoms in the alkenylene group is not particularly limited, but is preferably 2 to 6, and more preferably 2 or 3, for example.

[0032] The arylene group that can be taken as R is not particularly limited, and may be a monocyclic arylene group or a polycyclic arylene group, but a monocyclic arylene group is preferred. The number of carbon atoms in the arylene group is not particularly limited, but for example, it is preferably 6 to 24, more preferably 6 to 10, and even more preferably 6. In the case of a monocyclic arylene group (phenylene group), the bonding position is not particularly limited, and may be any of a 1,2-phenylene group, a 1,3-phenylene group, and a 1,4-phenylene group, but a 1,3-phenylene group or a 1,4-phenylene group is preferred, and a 1,4-phenylene group is more preferred. The imino group that can be taken as R is not particularly limited, and may be -NR Ｎ - is an example of a group represented by the above R Ｎ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and preferably a hydrogen atom.

[0033] The groups relating to the above combinations that can be taken as R are not particularly limited, and appropriate groups or atoms can be combined. The number of groups and atoms constituting the group relating to the combination is not particularly limited, and can be, for example, 2 to 10, preferably 3 to 7. Examples of the groups relating to the above combinations include a group formed by a combination containing an alkylene group and an arylene group, a group formed by a combination containing an arylene group and an oxygen atom, a group formed by a combination containing an alkylene group, an arylene group and an oxygen atom, and a group formed by a combination containing an alkylene group and a sulfur atom. Examples of groups formed by a combination containing an alkylene group and an arylene group include an arylene group-alkylene group-arylene group. Examples of groups formed by a combination containing an arylene group and an oxygen atom include an arylene group-oxygen atom-arylene group. Examples of groups formed by a combination containing an alkylene group, an arylene group and an oxygen atom include an arylene group-oxygen atom-arylene group. Examples of groups formed by a combination containing an alkylene group, an arylene group and an oxygen atom include an arylene group-oxygen atom-arylene group. Examples of the group formed by a combination containing an alkylene group and a sulfur atom include alkylene group-sulfur atom-sulfur atom-alkylene group. The arylene group contained in the group relating to the combination is preferably a phenylene group, and more preferably a 1,4-phenylene group.

[0034] In the present invention, the number of atoms constituting the linking group R is not particularly limited, but can be 3 to 100, and more preferably 20 to 70. The number of linking atoms of the linking group is preferably 50 or less, more preferably 5 to 30, and even more preferably 7 to 20. The number of linking atoms refers to the minimum number of atoms connecting the nitrogen atoms contained in the two maleimide rings. For example, when the linking group R is -(1,4-phenylene group)-CH ２ In the case of -(1,4-phenylene group)-, the number of atoms constituting the linking group is 23, but the number of linking atoms is 9.

[0035] The linking group that can be taken as R is preferably an alkylene group, an arylene group, a group formed by a combination containing an alkylene group and an arylene group, or a group formed by a combination containing an alkylene group, an arylene group, and an oxygen atom.

[0036] The compound represented by the above formula (1) or formula (2) may be unsubstituted or may have a substituent. The substituents that these compounds may have are not particularly limited, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, heterocyclic groups, alkoxy groups, amino groups, and halogen atoms. Among these, it is preferable that the compound does not contain a halogen atom, and an alkyl group is preferred, for example. The number of carbon atoms in the alkyl group is not particularly limited, and is preferably 1 to 20, and more preferably 1 to 6. The number of carbon atoms in the alkenyl group and alkynyl group is not particularly limited, and is preferably 2 to 20. The number of carbon atoms in the aryl group is the same as the number of carbon atoms in the arylene group that can be taken as R. Examples of heterocyclic groups include cyclic groups having at least one oxygen atom, sulfur atom, or nitrogen atom, and are preferably 5- or 6-membered heterocyclic groups having 2 to 20 carbon atoms. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups. The number of carbon atoms in the alkyl group constituting the alkoxy group is not particularly limited, and is the same as the number of carbon atoms in the alkyl group. The amino group may be an unsubstituted amino group (-NH ２ In addition to the above, the halogen atom includes an amino group in which one or two hydrogen atoms are substituted with an alkyl group, an aryl group, or a heterocyclic group. The halogen atom is not particularly limited, and examples thereof include a fluorine atom, a chlorine atom, and a bromine atom, with a bromine atom being preferred.

[0037] The number of substituents possessed by the compound represented by formula (1) or formula (2) is not particularly limited, and may be one or more and not more than the number of hydrogen atoms possessed by these compounds. In the compound represented by formula (2), all four hydrogen atoms of each benzene ring may be substituted. The substitution positions of the substituents possessed by the compound represented by formula (1) or formula (2) are not particularly limited.

[0038] Examples of the compound represented by formula (1) include phenylmethane maleimide, o-, m-, or p-phenylene bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6-bismaleimide(2,2,4-trimethyl)hexane, 4,4'-diphenylmethane bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4,4'-diphenyl ether bismaleimide, alkylene bismaleimides having 1 to 6 carbon atoms, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene, etc. Examples of the compound represented by formula (2) include bromine-based flame retardants such as ethylene bis(tetrabromophthalimide) and ethylene bis(tribromophthalimide).

[0039] Examples of polyimide compounds having an isocyanurate ring structure include triallyl isocyanurate, and also include bromine-based flame retardants such as tris(2,3-dibromopropyl)isocyanurate.

[0040] <Silanol condensation catalyst> The silanol condensation catalyst functions to promote the condensation reaction of the silanol condensable reactive site of the silane coupling agent grafted to the base resin in the presence of water (moisture). Based on the function of this silanol condensation catalyst, the base resin is crosslinked via the silane coupling agent. Such silanol condensation catalyst is not particularly limited, and examples thereof include organic tin compounds, metal soaps, platinum compounds, etc. Examples of organic tin compounds include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, dibutyltin diacetate, etc.

[0041] <Silane Coupling Agent> The silane crosslinkable resin composition of the present invention contains a silane coupling agent grafted to a polyolefin resin (base resin). The polyolefin resin grafted with the silane coupling agent is preferably prepared by grafting the silane coupling agent with the polyolefin resin using the method described below. The silane coupling agent (before the grafting reaction) that forms the silane graft resin is not particularly limited as long as it has a grafting reaction site (group or atom) that can undergo a grafting reaction with a graft-reactive site of the polyolefin resin in the presence of radicals generated by decomposition of an organic peroxide, and a silanol condensation-capable reactive site. The silane coupling agent used in the present invention is preferably one that has a hydrolyzable silyl group, particularly an alkoxysilyl group, as the silanol condensation-capable reactive site, since the final crosslinking reaction (particularly the silanol condensation reaction) exhibits equivalent reactivity. Examples of such silane coupling agents include silane coupling agents conventionally used in silane crosslinking methods. Suitable examples of the silane coupling agent include silane coupling agents having an ethylenically unsaturated group and a hydrolyzable silyl group (e.g., an alkoxysilyl group), and specifically include vinylalkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, and vinyltriacetoxysilane, and (meth)acryloxysilanes such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane. Among these, in the present invention, vinylalkoxysilanes are preferred, and vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred, in that the grafting reaction and silanol condensation reaction with the polyolefin resin proceed quickly. One type of silane coupling agent may be used, or two or more types may be used. The compound may be used as it is or after diluting with a solvent or the like.

[0042] <Inorganic Filler> The silane crosslinkable composition of the present invention also preferably contains an inorganic filler. In particular, when a silane coupling agent and a polyolefin resin are subjected to a grafting reaction during the preparation of the silane crosslinkable resin composition, the coexistence of an inorganic filler is preferred in that it can suppress the volatilization of the silane coupling agent and the condensation reaction between the silane coupling agents, thereby further improving the appearance characteristics and heat resistance. The inorganic filler is not particularly limited as long as it is a commonly used inorganic filler, but it is preferable that it has a site on its surface that can chemically bond with the silanol condensable reactive site of the silane coupling agent through a hydrogen bond, a covalent bond, or an intermolecular bond. The site that can chemically bond with the silane coupling agent is not particularly limited, but examples thereof include an OH group (a hydroxyl group, a water molecule of water containing water or crystal water, an OH group such as a carboxyl group), an amino group, an SH group, etc. When such an inorganic filler is present during the silane grafting reaction, a silane-grafted resin can be formed by grafting a silane coupling agent weakly bonded to the inorganic filler, and a silane-grafted resin can be formed by grafting a silane coupling agent strongly bonded to the inorganic filler. By crosslinking these two types of silane-grafted resins, a silane-crosslinked resin molded product can be formed that exhibits high crosslink density (heat resistance) without impairing its excellent appearance characteristics. Examples of weak bonds with the inorganic filler include interactions due to hydrogen bonds, interactions between ions, partial charges or dipoles, and adsorption. Examples of strong bonds with the inorganic filler include chemical bonds with sites on the inorganic filler surface that can be chemically bonded.

[0043] Examples of inorganic fillers include those typically used in resin compositions, such as metal hydrates such as compounds having hydroxyl groups or crystal water, such as aluminum hydroxide, magnesium hydroxide, boehmite, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, and talc. Other examples include boron nitride, silica (crystalline silica, amorphous silica, etc.), carbon black, clay (calcined clay), zinc oxide, tin oxide, titanium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, zinc borate, white carbon, zinc borate, zinc hydroxystannate, and zinc stannate. Of these, aluminum hydroxide or magnesium hydroxide is preferred.

[0044] In the present invention, when the polyimide compound does not contain a brominated flame retardant having a phthalimide structure, it is preferable that the inorganic filler does not contain antimony trioxide. In the present invention, not containing antimony trioxide as an inorganic filler means that antimony trioxide is not actively contained or mixed, and does not exclude the silane-crosslinkable resin composition and the silane-crosslinked resin molded product from inevitably containing antimony trioxide as an inorganic filler. For example, the silane-crosslinkable resin composition and the silane-crosslinked resin molded product may contain less than 30 parts by mass of antimony trioxide per 100 parts by mass of the base resin, and preferably less than 10 parts by mass.

[0045] The inorganic filler is preferably in the form of particles, and its 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, and particularly preferably 0.4 to 3 μm. The average particle size 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. Inorganic fillers that have been surface-treated with various surface treatment agents can also be used. One type of inorganic filler may be used alone, or two or more types may be used in combination.

[0046] <Organic Peroxide> It is preferable to use an organic peroxide when synthesizing the silane graft resin. The organic peroxide generates radicals by thermal decomposition, thereby initiating and promoting the grafting reaction between the silane coupling agent and the base resin through a radical reaction. Such organic peroxides are not particularly limited, and examples thereof include organic peroxides represented by the general formula: R １Ａ -OO-R ２Ａ , R ３Ａ -OO-C(=O)R ４Ａ , R ５Ａ C(=O)-OO(C=O)R ６Ａ In this case, a compound represented by the formula: １Ａ ~R ６Ａ Each of R independently represents an alkyl group, an aryl group, or an acyl group. １Ａ ~R ６Ａ Among these, those in which all groups are alkyl groups, or those in which one is an alkyl group and the remaining is an acyl group, are preferred. The decomposition temperature of the organic peroxide, as measured by the method described in JP 2016-121203 A, is preferably 80 to 195°C, and particularly preferably 125 to 180°C. Examples of such organic peroxides include those described in paragraph

[0036] of JP 2016-121203 A, the contents of which are incorporated herein by reference. Among these, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Perhexa 25B), and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3 are preferred.

[0047] <Carrier Resin> The above-mentioned silanol condensation catalyst is mixed with a resin or rubber as desired and used. Such a resin or rubber (also referred to as a carrier resin) is not particularly limited, but the components described for the base resin can be used. In terms of compatibility with the base resin, the carrier resin is preferably at least one of the components constituting the base resin, and preferably contains the same components as the base resin.

[0048] <Additives> The silane-crosslinkable composition of the present invention may contain various additives that are commonly used in resin compositions, such as antioxidants, lubricants, metal deactivators, plasticizers, flame retardants, flame retardant assistants, and (co)polymers other than those described for the base resin.

[0049] (Composition of Silane Crosslinkable Resin Composition) The content of the compound having two or more imide structures in the silane crosslinkable resin composition is 1 to 60 parts by mass relative to 100 parts by mass of the base resin. When the silane crosslinkable resin composition contains a compound having two or more imide structures in this range, the silanol condensation reaction as the final crosslinking reaction proceeds at an appropriate rate together with the silanol condensation catalyst, thereby building a sufficient crosslinked structure through the silanol condensation reaction and suppressing the occurrence of poor appearance and bumps, thereby realizing a silane crosslinked resin molded product that combines appearance properties and heat resistance. In order to achieve a high level of balance between the appearance properties and heat resistance of the silane crosslinked resin molded product, the content of the compound having two or more imide structures in the silane crosslinkable resin composition is preferably 2 to 60 parts by mass, more preferably 5 to 50 parts by mass, and even more preferably 7.5 to 45 parts by mass relative to 100 parts by mass of the base resin. In addition, when the polyimide compound has reacted or decomposed, the content is calculated as the mass before the reaction or decomposition.

[0050] The content of the silane coupling agent in the silane-crosslinkable resin composition is not particularly limited, but is preferably 2 to 15 parts by mass, more preferably 2.5 to 10 parts by mass, and even more preferably 3 to 7.5 parts by mass, relative to 100 parts by mass of the base resin, in order to produce a silane-crosslinked resin molded product having excellent appearance characteristics and sufficient crosslink density (heat resistance) while suppressing appearance defects, the formation of bumps, and volatilization of the silane coupling agent. Here, in the silane-crosslinkable resin composition, the silane coupling agent is graft-bonded to the polyolefin resin, but for convenience, the content of the silane coupling agent is the content converted into the mass before the grafting reaction with the polyolefin resin (the content of the silane coupling agent used in combination with the polyolefin resin).

[0051] The content of the silanol condensation catalyst in the silane crosslinkable resin composition is 0.01 to 5 parts by mass relative to 100 parts by mass of the base resin. When the silane crosslinkable resin composition contains the silanol condensation catalyst in this range, the silanol condensation reaction as the final crosslinking reaction, together with the compound having two or more imide structures, can proceed at an appropriate rate to build a sufficient crosslinked structure through the silanol condensation reaction, thereby suppressing the occurrence of poor appearance and bumps, and thereby realizing a silane crosslinked resin molded product that combines appearance properties and heat resistance. In order to achieve a high level of balance between the appearance properties and heat resistance of the silane crosslinkable resin molded product, the content of the silanol condensation catalyst in the silane crosslinkable resin composition is preferably 0.05 to 4 parts by mass, more preferably 0.075 to 3.5 parts by mass, even more preferably 0.1 to 3 parts by mass, and even more preferably 0.1 to 1 part by mass relative to 100 parts by mass of the base resin. In the silane-crosslinkable resin composition, the mass ratio of the content of the polyimide compound to the content of the silanol condensation catalyst [content of the polyimide compound / content of the silanol condensation catalyst] is not particularly limited and can be set appropriately. For example, the mass ratio [content of the polyimide compound / content of the silanol condensation catalyst] can be set to 0.2 to 6,000, preferably 10 to 600, in order to achieve a good balance between the appearance properties and heat resistance of the silane-crosslinked resin molded article at a high level.

[0052] In the present invention, in order to achieve a good balance between the appearance characteristics and heat resistance of the silane-crosslinked resin composition at a high level, the contents of the compound having two or more imide structures, the silane coupling agent, and the silanol condensation catalyst can be set by appropriately combining the preferred ranges of each component.

[0053] The content of the inorganic filler in the silane-crosslinkable resin composition is not particularly limited, but is preferably 0.5 to 400 parts by mass, more preferably 1 to 200 parts by mass, per 100 parts by mass of the base resin, in order to further improve the appearance and heat resistance of the silane-crosslinked resin molded article. In the present invention, the use of a compound having two or more imide structures can dramatically increase the gel fraction, and reducing the content of the inorganic filler can improve the extrusion appearance. In this case, the content of the inorganic filler can be, for example, 1 to 300 parts by mass, more preferably 5 to 250 parts by mass, particularly preferably 10 to 200 parts by mass, and most preferably 20 to 100 parts by mass, per 100 parts by mass of the base resin.

[0054] When an organic peroxide is used in the grafting reaction between a silane coupling agent and a base resin in a silane-crosslinkable resin composition, the amount of organic peroxide used is not particularly limited, but is preferably 0.01 to 0.6 parts by mass, more preferably 0.05 to 0.5 parts by mass, and even more preferably 0.1 to 0.2 parts by mass, relative to 100 parts by mass of the base resin, in order to efficiently initiate and progress the grafting reaction between the silane coupling agent and the base resin. However, in the silane-crosslinkable resin composition, the organic peroxide is usually decomposed during the grafting reaction.

[0055] The total content of additives in the silane-crosslinkable resin composition is not particularly limited and can be set appropriately within a range that does not impair the effects of the present invention. For example, the content of antioxidant is not particularly limited, but is preferably 0.2 to 8 parts by mass per 100 parts by mass of the base resin.

[0056] (Composition of silane-crosslinked resin molded body) The silane-crosslinked resin molded body is formed by molding a silane-crosslinkable resin composition and then contacting it with water to cause a silanol condensation reaction, so the contents of the above-mentioned components in this molded body are usually the same as those in the silane-crosslinkable resin composition. However, the organic peroxide and silanol condensation catalyst are usually decomposed. 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 crosslinking.

[0057] In the silane-crosslinkable resin composition and silane-crosslinked resin molded product of the present invention, the polyimide compound is generally not thought to undergo a direct crosslinking reaction with the polyolefin resin. However, depending on the type of polyimide compound, it is possible that the polyimide compound may be hydrolyzed (the imide bond is cleaved) and react with other components.

[0058] [Method for Producing Silane-Crosslinkable Resin Composition] The silane-crosslinkable resin composition of the present invention can be prepared by mixing the above-mentioned components. In an embodiment using a silane-grafted resin, the silane-grafted resin, a compound having two or more imide structures, a silanol condensation catalyst, and optionally an inorganic filler and additives can be melt-mixed to prepare the silane-crosslinkable resin composition. The melt-mixing method and conditions can be the method and conditions of step (1) or step (a) described below. On the other hand, in an embodiment in which a polyolefin resin and a silane coupling agent are subjected to a grafting reaction during the preparation of the silane-crosslinkable resin composition, the composition can be prepared by mixing a polyolefin resin, a silane coupling agent, an organic peroxide, a compound having two or more imide structures, a silanol condensation catalyst, and optionally an inorganic filler and additives. The mixing method (mixing order) and conditions are not particularly limited, but the composition can preferably be produced by a method in which the inorganic filler is optionally mixed in the preferred method for producing a silane-crosslinkable resin composition described below. A preferred embodiment of the silane-crosslinkable resin composition containing an inorganic filler can be prepared by mixing the components as described above, except that the inorganic filler is an essential component. However, it is preferable to prepare the composition by a preferred embodiment of the silane-crosslinkable resin composition manufacturing method described below (hereinafter, sometimes referred to as a manufacturing method of a preferred crosslinkable resin composition of the present invention).

[0059] [Method for producing silane-crosslinked resin molded article] The silane-crosslinked resin molded article of the present invention can be produced by molding the silane-crosslinkable resin composition of the present invention and then contacting it with water to cause a crosslinking reaction (silanol condensation reaction). The method and conditions for molding the silane-crosslinkable resin composition, and the method and conditions for contacting it with water, are not particularly limited, and the methods and conditions described in steps (2) and (3) below can be applied. A preferred form of silane-crosslinked resin molded article containing an inorganic filler can be produced in the same manner as the silane-crosslinked resin molded article of the present invention, except for using a preferred form of silane-crosslinkable resin composition. However, it is preferable to produce it by a preferred method for producing a silane-crosslinked resin molded article described below (hereinafter, sometimes referred to as a suitable method for producing a molded article of the present invention).

[0060] [Method for producing a preferred crosslinkable resin composition of the present invention and method for producing a preferred molded article of the present invention] A preferred method for producing a crosslinkable resin composition of the present invention and a preferred method for producing a preferred molded article of the present invention (both production methods may be collectively referred to as the preferred production methods of the present invention) are described below. Both production methods involve a grafting reaction between a polyolefin resin and a silane coupling agent during the preparation of the composition.

[0061] Step (1): melt-mixing 2 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction to the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, 1 to 200 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 5 parts by mass of a silanol condensation catalyst relative to 100 parts by mass of a base resin containing a polyolefin resin to obtain a mixture (a preferred form of a silane-crosslinkable resin composition); Step (2): molding the mixture obtained in Step (1) to obtain a molded product; Step (3): contacting the molded product obtained in Step (2) with water to obtain a silane-crosslinked resin molded product.

[0062] The step (1) includes the following steps depending on the use mode (compounding mode) of the base resin. That is, when performing this step (1), if the entire base resin is melt-mixed in the step (a), the step (1) includes the steps (a) and (c), while if only a portion of the base resin is melt-mixed in the step (a), the step (1) includes the steps (a), (b), and (c). Furthermore, a compound having two or more imide structures can be mixed in at least one of the steps (a) and (b), and it is preferable to mix the entire amount in the step (b) because this can further improve appearance properties while maintaining sufficient heat resistance. Step (a): A step of melt-mixing all or a part of the base resin, an inorganic filler, a silane coupling agent, and an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide to prepare a silane masterbatch. Step (b): A step of melt-mixing the remainder of the base resin and a silanol condensation catalyst to prepare a catalyst masterbatch. Step (c): A step of melt-mixing the silane masterbatch with a silanol condensation catalyst or a catalyst masterbatch.

[0063] In a preferred manufacturing method of the present invention, the mixed amounts of each component used as the base resin are the same as the above-described contents of the base resin composition. The mixed amounts of the compound having two or more imide structures, the silanol condensation catalyst, and the additives are the same as the contents in the silane-crosslinkable resin composition described above. The mixed amount of the silane coupling agent is the same as the content in the silane-crosslinkable resin composition described above, except that it is 2 to 15 parts by mass per 100 parts by mass of the base resin. The mixed amount of the inorganic filler is the same as the content in the silane-crosslinkable resin composition described above, except that it is 1 to 200 parts by mass per 100 parts by mass of the base resin.

[0064] In a preferred manufacturing method of the present invention, the mixture obtained in step (1) may contain 100 parts by mass of the base resin. For example, step (a) may include an embodiment in which the entire amount (100 parts by mass) of the base resin is mixed, and an embodiment in which only a portion of the base resin is mixed. When a portion of the base resin is mixed in step (a), the proportion is preferably 60 to 95% by mass, and more preferably 70 to 85% by mass, of the 100% by mass of the base resin mixed in steps (a) and (b). The remainder of the base resin (carrier resin) mixed in step (b) is appropriately determined depending on the portion of the base resin mixed in step (a). When a portion of the base resin is mixed in step (a), the components mixed may be one type or two or more types.

[0065] Although a portion of the inorganic filler can be used in a step other than step (a), such as step (b), it is preferable to use the entire amount in step (a) in order to achieve a well-balanced construction of a crosslinked structure between base resins (without the inorganic filler) and a crosslinked structure involving the inorganic filler. When an inorganic filler is used in step (b), the amount used is not particularly limited and is determined appropriately. Various additives may be mixed in either step (a) or step (b).

[0066] <Step (1)> In a preferred production method of the present invention, step (1) is carried out in which a base resin, a silane coupling agent, a compound having two or more imide structures, an inorganic filler, an organic peroxide, and a silanol condensation catalyst are melt-mixed in the above-mentioned amounts to prepare a silane-crosslinkable resin composition in a preferred form as a mixture. Step (1), i.e., melt-mixing of the base resin, silane coupling agent, compound having two or more imide structures, inorganic filler, organic peroxide, and silanol condensation catalyst, is carried out in the following order:

[0067] (Step (a)) In a preferred production method of the present invention, step (a) is carried out to prepare a silane master batch (silane MB) by melt-mixing all or a part of the base resin, an inorganic filler, a silane coupling agent, an organic peroxide, and, optionally, a compound having two or more imide structures in the above-mentioned amounts at a temperature equal to or higher than the decomposition temperature of the organic peroxide.

[0068] In step (a), the mixing temperature for melt-mixing (also referred to as melt-kneading) the above-mentioned components is equal to or higher than the decomposition temperature of the organic peroxide, preferably equal to or higher than the decomposition temperature of the organic peroxide + (25 to 110)°C, more preferably 150 to 230°C, and even more preferably 175 to 210°C. Here, the decomposition temperature of the organic peroxide, which is used as the reference for the melt-mixing temperature, is the temperature under normal pressure (approximately 0.1 MPa). Mixing conditions such as mixing time can be set appropriately. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes. By melt-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 progressing the grafting reaction.

[0069] The mixing method is not particularly limited as long as it is a method commonly used for mixing rubber, plastics, etc. Examples of mixing devices that can be used include a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, or various kneaders, and closed-type mixers such as a Banbury mixer or various kneaders are preferred. The method for mixing the base resin is also not particularly limited. For example, the base resin may be prepared in advance and used, or each component may be used separately.

[0070] In a preferred production method of the present invention, the order of mixing the components in step (a) is not specified, and the components may be mixed in any order. For example, the above components can be melt-mixed all at once, or they can be mixed in the following order in steps (a-1) and (a-2) below. When a compound having two or more imide structures is mixed in step (a), the compound having two or more imide structures may be mixed in any of the following steps. Step (a-1): A step of mixing an inorganic filler and a silane coupling agent to prepare a mixture. Step (a-2): A step of melt-mixing the mixture obtained in step (a-1) with all or part of the base resin in the presence of an organic peroxide at a temperature equal to or higher than the decomposition temperature of the organic peroxide.

[0071] In step (a-1), by premixing the inorganic filler and the silane coupling agent, it is possible to form a well-balanced mixture of the silane coupling agent weakly bonded to or adsorbed on the inorganic filler and the silane coupling agent strongly bonded to or adsorbed on the inorganic filler, which effectively prevents the volatilization of the silane coupling agent and further the condensation reaction between unadsorbed silane coupling agents during the melt-mixing in step (a-2).

[0072] The mixing method and conditions for step (a-1) are not particularly limited, but examples include methods and conditions in which the components are mixed using a known mixer, kneader, or the like, typically at a temperature below the decomposition temperature of the organic peroxide, preferably 10 to 60°C, more preferably around room temperature (20 to 25°C), for several minutes to several hours, by dry or wet mixing. Of these, dry mixing at a temperature below the decomposition temperature of the organic peroxide is preferred. Other conditions for dry mixing are determined appropriately.

[0073] 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 mixed in step (a-2) as long as it is present during the melt mixing in step (a-2), but is preferably mixed in step (a-1).

[0074] Next, the mixture obtained in step (a-1), all or part of the base resin, and the remaining components not mixed in step (a-1) 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 prepare Silane MB (step (a-2)). The melt-mixing in this step can prevent excessive crosslinking between the base resins (the generation of gel particles) while suppressing the volatilization and self-condensation of the silane coupling agent. The melt-mixing method and conditions for this step (a-2) are not particularly limited, and the melt-mixing method and conditions for the above-mentioned step (a) can be applied.

[0075] In step (a-2), at least the following modes are conceivable as the grafting reaction between the silane coupling agent and the base resin. That is, a mode in which the silane coupling agent bonded to or adsorbed to the inorganic filler by a weak bond is detached from the inorganic filler and grafted to the base resin. The crosslinked structure formed in step (3) described below from this mode does not incorporate the inorganic filler, and is typically a crosslinked structure via a silanol condensate between silane coupling agents. Alternatively, a mode in which the silane coupling agent bonded to or adsorbed to the inorganic filler by a strong bond undergoes a grafting reaction to the base resin while maintaining its bond or adsorption to the inorganic filler. The crosslinked structure formed in step (3) described below from this mode incorporates the inorganic filler, and is a crosslinked structure originating from the inorganic filler via the silane coupling agent bonded to it. By mixing the crosslinked structures in both of the above modes, a highly developed crosslinked structure, including a crosslinked structure involving the inorganic filler, can be constructed in the silane-crosslinked resin molded product.

[0076] In step (a), additives and the like can also be mixed. However, it is preferable that a silanol condensation catalyst is not substantially mixed in step (a). This makes it possible to suppress the occurrence of a silanol condensation reaction of the silane coupling agent. In the present invention, "substantially not mixed" does not exclude the unavoidably present silanol condensation catalyst, but means that it may be present within a range that can suppress the silanol condensation reaction, for example, within a range of 0.01 parts by mass or less per 100 parts by mass of the base resin.

[0077] The Silane MB prepared in step (a) contains a reaction mixture of a base resin, a silane coupling agent, a compound having two or more imide structures, and an inorganic filler, and contains a silane-grafted resin in which the silane coupling agent and the base resin are grafted to a degree that allows molding in step (b) described below. The silane coupling agent grafted to the base resin includes those that are bonded or adsorbed to the inorganic filler at their silanol condensation-capable reactive sites. Silane MB is preferably in the form of pellets or powder.

[0078] (Step (b)) In a preferred production method of the present invention, step (b) is carried out, either independently of step (a) or subsequent to step (a), in which the remainder of the base resin (carrier resin), a silanol condensation catalyst, and preferably a compound having two or more imide structures are melt-mixed to prepare a catalyst master batch (catalyst MB). The mixing ratio of the carrier resin, silanol condensation catalyst, and compound having two or more imide structures is not particularly limited, but is preferably set so as to satisfy the above-mentioned mixing amounts in step (1). The melt-mixing method and conditions in step (b) are not particularly limited, and the melt-mixing method and conditions of step (a) described above can be applied. For example, the melt-mixing temperature may be equal to or higher than the melting temperature of the base resin, preferably 120 to 200°C, and more preferably 140 to 180°C. Other conditions, such as the mixing time, can be set as appropriate. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes. The catalyst MB is preferably in the form of pellets or powder.

[0079] (Step (c)) In a preferred production method of the present invention, step (c) is then carried out, in which silane MB and a silanol condensation catalyst or catalyst MB are melt-mixed to obtain a mixture. Preferably, silane MB and catalyst MB are melt-mixed. The mixing method is not particularly limited, but is basically the same as the melt-mixing in step (a), and mixing is carried out at a temperature at which at least the base resin melts. The mixing conditions in step (c) are not particularly limited, and the mixing conditions in step (a) above can be applied. For example, the mixing temperature is appropriately selected depending on the melting temperature of the base resin or carrier resin, and is preferably 80 to 250°C, more preferably 100 to 240°C, and even more preferably 120 to 200°C. Other conditions, such as the mixing time, can be set as appropriate. In the melt-mixing of step (c), a melt-mixing method and conditions are set that can maintain the fluidity (moldability) of the mixture. The silane-grafted resin in the mixture is an uncrosslinked product in which the silane coupling agent has not undergone silanol condensation. In practice, when melt-mixing in step (c), partial crosslinking is unavoidable, but the resulting mixture maintains moldability. For example, to avoid the occurrence or progression of a silanol condensation reaction, it is preferable that the silane MB and the silanol condensation catalyst are not kept in a mixed state at a high temperature for a long period of time. In step (c), it is preferable to dry-blend the silane MB and the silanol condensation catalyst or catalyst MB before melt-mixing them. The method and conditions for dry-blending are not particularly limited, and examples include the dry mixing and conditions in step (a-1).

[0080] In this way, a preferred embodiment of the silane-crosslinkable resin composition of the present invention is produced as a mixture. This silane-crosslinkable resin composition contains a silane-grafted resin, a silanol condensation catalyst, an inorganic filler, a compound having two or more imide structures, and the like. In the silane-grafted resin, the silanol-condensable reactive site of the silane coupling agent may be bonded to or adsorbed on the inorganic filler, but is not silanol-condensed. Therefore, the silane-grafted resin includes a silane-grafted resin in which a silane coupling agent bonded to or adsorbed on the inorganic filler is grafted to a base resin, and a silane-grafted resin in which a silane coupling agent not bonded to or adsorbed on the inorganic filler is grafted to a base resin.

[0081] <Step (2)> In the preferred method for producing a molded article of the present invention, the mixture obtained in step (1) (the silane-crosslinkable resin composition according to the preferred embodiment of the present invention) is then molded to obtain a molded article (step (2)). The molding method is not particularly limited and can be appropriately selected depending on the desired product shape. Examples of molding methods include extrusion molding using an extruder, extrusion molding using an injection molding machine, molding using other molding machines, and spiral molding, as described below. When producing wiring materials, extrusion molding is preferred in terms of productivity and the ability to co-extrude with the conductor. The molding conditions (melt-mixing conditions) are not particularly limited as long as they allow uniform mixing and molding and do not cause a silanol condensation reaction in the silane-crosslinkable resin composition according to the preferred embodiment of the present invention. For example, the melt-mixing method and conditions of step (a) can be applied. When using an extruder, the temperature of the extruder is preferably 120 to 180°C in the cylinder and approximately 160 to 200°C in the crosshead (die), although this will depend on various conditions such as the type of base resin and the take-up speed of the conductor, etc. The screw rotation speed and molding speed (linear speed) of the extruder in extrusion molding are not particularly limited and can be set appropriately depending on the characteristics or performance of the extruder, the extrusion amount (coating amount), etc. The linear speed can usually be set to 1 to 20 m / min.

[0082] Step (2) can be carried out simultaneously with or consecutively to step (c). For example, a series of steps can be employed in which the silane MB and the silanol condensation catalyst or catalyst MB are mixed by dry blending or the like immediately before the coating device (extruder) and then melt-mixed in the coating device (step (c)). Alternatively, the silane MB and the silanol condensation catalyst or catalyst MB are separately introduced into the coating device and then melt-mixed (step (c)), followed by (co-extrusion) molding (step (2)) onto the outer circumferential surface of a conductor or the like.

[0083] In this way, a molded article (uncrosslinked molded article) of the silane-crosslinkable resin composition of the preferred embodiment of the present invention is obtained. Like the preferred silane-crosslinkable resin composition, this molded article is in a partially crosslinked state that maintains moldability in step (2), although partial crosslinking of the silane-crosslinkable resin is unavoidable. Therefore, the preferred silane-crosslinked resin molded article of the present invention is made into a crosslinked or final-crosslinked molded article by carrying out step (3).

[0084] <Step (3)> In the preferred method for producing a molded article of the present invention, the molded article obtained in step (2) is then contacted with water to produce a preferred embodiment of a silane-crosslinked resin molded article of the present invention in step (3). Since the molded article obtained in step (2) contains an uncrosslinked silane-crosslinked resin, this step initiates and advances (accelerates) a silanol condensation reaction (dehydration condensation reaction) at the silanol condensable reactive sites of the silane coupling agent grafted to the base resin, ultimately resulting in silane crosslinking. In this way, a silane-crosslinked resin molded article in which the silane coupling agent has undergone silanol condensation and crosslinked can be obtained. Contact of the uncrosslinked molded article with water can be carried out by a conventional method. The silanol condensation reaction proceeds simply by leaving the uncrosslinked molded article at room temperature, e.g., about 20 to 25°C, in the presence of moisture; therefore, active contact with water is not necessary. From the viewpoint of accelerating the silanol condensation reaction (crosslinking reaction), active contact of the uncrosslinked molded article with water is preferred. The contact method may be a method (condition) normally applied to the silane crosslinking method, for example, a method of contacting in an ordinary pressure environment, specifically, exposure to a saturated water vapor atmosphere, exposure to a high humidity environment, immersion in room temperature water or hot water (for example, 50 to 90°C), immersion in a moist heat bath, exposure to high temperature water vapor, etc. Furthermore, pressure may be applied during contact to allow moisture to penetrate the interior.

[0085] In this way, a preferred embodiment of the silane-crosslinked resin molded article of the present invention is produced. This silane-crosslinked resin molded article contains a silane-crosslinked resin in which a base resin (silane-crosslinkable resin) is condensed via a siloxane bond. The silane-crosslinked resin molded article also contains an inorganic filler, which may be bonded to the silane coupling agent of the crosslinked base resin. Therefore, the silane-crosslinked resin is considered to contain a crosslinked resin in which multiple base resins are bonded or adsorbed to the inorganic filler via the silane coupling agent, resulting in bonding (crosslinking) via the inorganic filler and the silane coupling agent, and a crosslinked resin in which the silanol-condensable reactive sites of the silane coupling agent grafted to the base resin are hydrolyzed and undergo a silanol condensation reaction with each other (without the inorganic filler being involved) via the silane coupling agent (siloxane bond).

[0086] In the preferred method for producing a molded article of the present invention, a compound having two or more imide structures is present when the final crosslinking reaction in step (3) is initiated and progressed, so that the final crosslinking reaction (silanol condensation reaction) in step (3) can proceed at an appropriate reaction rate, and a silane-crosslinked resin molded article can be produced that achieves a good balance between appearance properties and heat resistance, which are conflicting properties depending on the speed of the silanol condensation reaction.

[0087] The silane-crosslinked resin molded article of the present invention has excellent appearance characteristics and high heat resistance, and can be suitably used in various products (including semi-finished products, parts, and components). Specific examples include resin molded article substitutes such as insulating coating layers (including sheaths) for wiring materials, molding materials, power plugs, connectors, sleeves, boxes, tape substrates, tubes, heat-resistant sheets, heat-resistant films, packings, gaskets, cushioning materials, and vibration-proofing materials. Taking advantage of the excellent properties of the silane-crosslinked resin molded article of the present invention, it can be suitably used as insulating coating layers for insulated electric wires for vehicles such as automobiles and trains, and sheaths for cabtire cables.

[0088] [Wiring Material] The wiring material of the present invention has a tubular silane-crosslinked resin molded product of the present invention or a preferred embodiment of the silane-crosslinked resin molded product of the present invention as a coating layer (insulating layer, sheath, etc.) that coats the outer periphery of a conductor. The wiring material (coating layer) of the present invention exhibits excellent appearance characteristics and high heat resistance. Unless otherwise specified, the wiring material of the present invention refers to a wiring material used for internal or external wiring of electric or electronic devices, and includes insulated wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables). The wiring material of the present invention is the same as conventional wiring materials used in various electric and electronic devices and industrial fields, except that the coating layer is formed of the silane-crosslinked resin molded product of the present invention or a preferred embodiment of the silane-crosslinked resin molded product of the present invention. Here, when the coating layer of the wiring material is composed of multiple layers, it is sufficient that at least one of the layers is formed of the silane-crosslinked resin molded product of the present invention or a preferred embodiment of the silane-crosslinked resin molded product of the present invention. The coating layer formed from the silane-crosslinked resin shaped product of the present invention or a preferred embodiment of the silane-crosslinked resin shaped product of the present invention is provided on the outer peripheral surface of the conductor directly or via another layer, and the presence or absence of other layers, as well as the materials thereof, are determined appropriately depending on the type, application, required characteristics, etc. of the electric wire. Conventional conductors can be used, such as solid or stranded wires (wires with tensile strength fibers longitudinally attached or twisted together) of soft copper, copper alloy, or aluminum. In addition to bare wires, tin-plated wires and wires with an enamel-coated insulating layer can also be used. The thickness of the coating layer formed from the silane-crosslinked resin shaped product of the present invention or a preferred embodiment of the silane-crosslinked resin shaped product of the present invention is not particularly limited, but is usually about 0.15 to 5 mm.

[0089] The wiring material of the present invention can be produced by molding the silane-crosslinkable resin composition of the present invention or a preferred embodiment of the silane-crosslinked resin molded article of the present invention into an annular layer (tubular) on the outer surface of a conductor, and then contacting the molded article with water to cause a crosslinking reaction (silanol condensation reaction). Preferably, in the preferred method for producing a molded article of the present invention described above, the molding step (2) is performed by co-extrusion molding the preferred embodiment of the silane-crosslinkable resin composition of the present invention onto the outer periphery of the conductor using a coating device (extruder). In addition, by not mixing an inorganic filler in the preferred method for producing a molded article of the present invention, a wiring material having a coating layer formed from the silane-crosslinkable resin composition of the present invention can be produced by performing the step of co-extrusion molding the silane-crosslinkable resin composition of the present invention onto the outer periphery of the conductor.

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0091] Details of the compounds used in the examples and comparative examples are shown in Tables 1 to 3 and below. <Base Resin> (Silane Graft Resin) Linkron XCF730M (trade name): silane grafted polyethylene, silane coupling agent content 5% by mass, manufactured by Mitsubishi Chemical Corporation (Polyolefin Resin) LLDPE: Evolue SP0540 (trade name), linear low-density polyethylene, manufactured by Prime Polymer Co., Ltd. PP: PB222A (trade name), manufactured by SunAllomer Co., Ltd., random polypropylene resin EVA: Evaflex EV360 (trade name), ethylene-vinyl acetate copolymer resin, manufactured by Dow Mitsui Polychemicals Metallocene Plastomer: Kernel KS-240T (trade name), polyethylene, manufactured by Japan Polyethylene Co., Ltd. SEEPS: Septon 4077 (trade name), styrene-ethylene-ethylene-propylene-styrene block copolymer, manufactured by Kuraray Co., Ltd. Oil: Cosmo Neutral 500 (trade name), paraffin oil, manufactured by Cosmo Oil Briquettes Co., Ltd. Malein-modified PP: Admer QE800 (product name), manufactured by Mitsui Chemicals, Inc. Epoxy-modified PE: Bondfast E (product name), manufactured by Sumitomo Chemical Co., Ltd.

[0092] <Compounds Having Two or More Imide Structures> 4,4'-Diphenylmethane bismaleimide: BMI-1000H, manufactured by Daiwa Chemical Industry Co., Ltd. Bisphenol A diphenyl ether bismaleimide: BMI-4000, manufactured by Daiwa Chemical Industry Co., Ltd. 3,3'-Dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide: BMI-5100, manufactured by Daiwa Chemical Industry Co., Ltd. Phenylmethane maleimide: BMI-2300, manufactured by Daiwa Chemical Industry Co., Ltd. Triallyl isocyanurate: TAIC (trade name), manufactured by Mitsubishi Chemical Corporation Tris(2,3-dibromopropyl)isocyanurate: TAIC-6B (trade name), manufactured by Mitsubishi Chemical Corporation Ethylene bis(tetrabromophthalimide): CG-952, manufactured by Sun Chemical Co., Ltd.

[0093] <Silane coupling agent> Silane coupling agent: KBM-1003 (trade name), manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane <Organic peroxide> Organic peroxide: Perhexa 25B (trade name), manufactured by NOF Corporation, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, decomposition temperature 154°C <Inorganic filler> Magnesium hydroxide: Magseeds FK640 (trade name), manufactured by Konoshima Chemical Co., Ltd.

[0094] <Silanol condensation catalyst> Dioctyltin dilaurate: Adekastab OT-1 (trade name), manufactured by ADEKA Corporation

[0095] (Examples 1 to 25 and Comparative Examples 1 to 4) Examples 1 to 25 and Comparative Examples 1 to 4 were each carried out using the components shown in Tables 1 to 3. In Tables 1 to 3, the numerical values ​​relating to the blending amount (content) of each example represent parts by mass unless otherwise specified. Furthermore, a blank cell for each component means that the blending amount of the corresponding component is 0 parts by mass. In each example (except for Example 11) and comparative example, a portion (30% by mass) of the base resin was used as a carrier resin for catalyst MB.

[0096] The silane-grafted resin or polyolefin resin, modified polyolefin resin, inorganic filler, organic peroxide, silane coupling agent, and polyimide compound shown in the "Silane MB" column of Tables 1 to 3 were melt-mixed in a Banbury mixer at 170 to 200°C in the mass ratios shown in the same column, followed by pelletization to prepare pellets of Silane MB (step (a)). Meanwhile, the carrier resin, silanol condensation catalyst, and polyimide compound shown in the "Catalyst MB" column of Tables 1 to 3 were melt-mixed in a Banbury mixer at 170 to 200°C in the mass ratios shown in the same column, followed by pelletization to prepare pellets of Catalyst MB (step (b)).

[0097] Next, the prepared Silane MB pellets and Catalyst MB pellets were dry-blended in a tumbler mixer at room temperature (25°C) for 2 minutes immediately before extrusion molding in the mass ratios shown in the "Silane MB" and "Catalyst MB" columns of Tables 1 to 3 to obtain a dry blend (dry blending step (c)). Next, a 25 mm (screw diameter) extruder with an L / D (ratio of effective screw length L to diameter D) of 25 was used, with a die temperature of 200°C. The extrusion temperature conditions were set to C3 = 180°C, C2 = 160°C, and C1 = 140°C, with the extrusion being divided into three zones toward the feeder side of the cylinder. The prepared dry blend was introduced into the extruder, and while melt-mixing at a screw speed of 10 to 40 rpm (the melt-mixing step of step (c)), the wire speed was adjusted to extrusion-coat a 1.9 mm diameter conductor made of tin-plated copper stranded wire to an outer diameter of 2.6 mm and a thickness of 0.35 mm, yielding a coated conductor (step (2)). At this time, the dry blend was melt-mixed in the extruder before extrusion molding, thereby preparing a silane-crosslinkable resin composition. The obtained coated conductor was left to stand for 12 hours in an environment at room temperature (25°C) and a relative humidity of 50% RH to allow the silane-crosslinkable resin composition to come into contact with water (step (3)). In this way, an electric wire having a coating layer formed from a silane-crosslinked resin molded product was produced.

[0098] The following tests were carried out on each of the manufactured electric wires, and an overall evaluation was made based on the results of each test. The results are shown in Tables 1 to 3. <Overall Evaluation> In the following Tests 1 and 2, if all the wires passed, they were marked with "O" and if even one wire failed, they were marked with "X" and if any one wire failed, they were marked with "Fail".

[0099] <Test 1: Appearance Property Test> The appearance property test for electric wires is an alternative test for evaluating the high crosslinking rate (silanol condensation reaction rate) of the silane-crosslinkable resin composition (silane-crosslinked resin molded product). The surface of the coating layer of each manufactured electric wire was visually observed to evaluate the presence or absence of appearance defects and bumps. Specifically, for "appearance defects," the surface (appearance) of the coating layer was checked for the presence or absence of foaming and the presence or absence of unevenness or roughness. Furthermore, for "bumps," the presence or absence of gel-like protruding aggregates (gel bumps) formed by the final crosslinking reaction (silanol condensation reaction) or aggregated bumps formed by the aggregation of incompatible raw materials was checked on the surface of the coating layer. The evaluation was as follows: when no defective appearance or the presence of lumps was found on the surface of the coating layer, it was evaluated as very good, with a symbol "◎"; when defective appearance or the presence of lumps was found in the electric wire immediately after manufacture (up to a manufactured length of 5 m (excluding 5 m)) but when defective appearance or the presence of lumps was found in the electric wire with a manufactured length of 5 m or more but not including 10 m, it was evaluated as good, with a symbol "◯"; when defective appearance or the presence of lumps was found for the first time in the electric wire with a manufactured length of 10 m or more but not including 50 m, it was evaluated as pass, with a symbol "△"; and when defective appearance or the presence of lumps was found even in the electric wire with a manufactured length of 50 m or more, it was evaluated as fail, with a symbol "×".

[0100] <Test 2: Heat Deformation Test> This test is an alternative test for evaluating the heat resistance (crosslink density) and low crosslinking rate of the coating layer, and the heat deformation rate of each manufactured electric wire was measured in accordance with UL758. Specifically, a load of 2.45 N was applied to each manufactured electric wire in a direction perpendicular to the longitudinal direction at a measurement temperature of 121°C. The deformation rate of the coating layer at this time ([(thickness of coating layer before heating - thickness of coating layer after heating) / thickness of coating layer before heating] x 100) was calculated as the heat deformation rate. A heat deformation rate of less than 30% allows the silanol condensation reaction to proceed quickly, allowing for the construction of a high crosslink density (realizing high heat resistance), and is indicated as very good with a "◎", 30% or more but less than 40% is indicated as good with a "◯", 40% or more but less than 50% is indicated as pass with a "△", and 50% or more is indicated as fail with a "X".

[0101] <Test 3: Hydrogen Halide Gas Generation Test> A test piece (2 g) taken from the coating layer of each manufactured electric wire was quantitatively analyzed for halogen elements in accordance with JCS (Japanese Cable Makers' Association Standard) No. 397A-98, Section 7. Specifically, the test piece was burned in a quartz glass combustion tube at 750°C or higher for 30 minutes, and the generated gas was absorbed in a liquid in an absorption bottle. The absorbed liquid was examined and its pH was measured. This test was a reference test, and the evaluation was performed as follows: a pH of 4.0 or higher was considered good (low generation of hydrogen halide gas) and indicated by "◯", and a pH of less than 4.0 was considered high generation of hydrogen halide gas (failure) and indicated by "X".

[0102]

[0103]

[0104]

[0105] The results shown in Tables 1 to 3 reveal the following. Specifically, in Comparative Examples 1 to 4, in which the content of the silanol condensation catalyst or the compound having two or more imide structures in the silane-crosslinkable resin composition deviates from the range specified in the present invention, it is not possible to produce a silane-crosslinked resin molded article exhibiting excellent appearance characteristics and high heat resistance. In contrast, in Examples 1 to 25, in which a compound having two or more imide structures is coexisted with the silanol condensation catalyst in a specific ratio during the final crosslinking reaction of the silane-crosslinkable resin composition containing the silanol condensation catalyst in a specific ratio, it is possible to produce a silane-crosslinked resin molded article exhibiting excellent appearance characteristics and high heat resistance with excellent manufacturability. This is thought to be because the silanol condensation reaction, which is the final crosslinking reaction in the silane crosslinking method, can proceed at an appropriate reaction rate, i.e., the reaction rate of the silanol condensation reaction can be adjusted to a degree that allows both excellent appearance characteristics and high heat resistance to be achieved. In particular, if the base resin does not contain the above-mentioned modified polyolefin resin, the generation of bumps can be effectively suppressed and the appearance characteristics can be improved to a high level. On the other hand, if the compound having two or more imide structures does not contain a brominated flame retardant having a phthalimide structure or an isocyanurate ring structure, excellent appearance characteristics and high heat resistance can be achieved at the same time, the generation of hydrogen halide gas is suppressed, and environmental compatibility is also excellent.

[0106] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0107] This application claims priority based on Japanese Patent Application No. 2023-049377, filed on March 27, 2023, the contents of which are incorporated herein by reference as part of the present specification.

Claims

1. A silane-crosslinkable resin composition comprising: 100 parts by mass of a base resin containing a polyolefin resin; a silane coupling agent graft-bonded to the base resin; 1 to 60 parts by mass of a compound having two or more imide structures; and 0.01 to 5 parts by mass of a silanol condensation catalyst.

2. 2. The silane-crosslinkable resin composition according to claim 1, wherein the base resin does not contain a modified polyolefin resin modified with any of a carboxylic acid group, a methacrylic group, and an epoxy group.

3. The silane-crosslinkable resin composition according to claim 1, wherein the compound having two or more imide structures does not contain a brominated flame retardant having a phthalimide structure.

4. 2. The silane-crosslinkable resin composition according to claim 1, comprising 1 to 200 parts by mass of an inorganic filler per 100 parts by mass of the base resin.

5. A silane-crosslinked resin molded article of the silane-crosslinkable resin composition according to any one of claims 1 to 4.

6. A wiring material having the silane-crosslinked resin molded product according to claim 5 as a coating layer.

7. A method for producing a silane-crosslinkable resin composition, comprising: (1) melt-mixing 100 parts by mass of a base resin containing a polyolefin resin with 2 to 15 parts by mass of a silane coupling agent having a grafting reaction site capable of undergoing a grafting reaction with the base resin, 1 to 60 parts by mass of a compound having two or more imide structures, 1 to 200 parts by mass of an inorganic filler, 0.01 to 0.6 parts by mass of an organic peroxide, and 0.01 to 5 parts by mass of a silanol condensation catalyst to obtain a silane-crosslinkable resin composition; In carrying out the step (1), when the whole of the base resin is melt-mixed in the step (a), the step (1) comprises the steps (a) and (c) below, while when a part of the base resin is melt-mixed in the step (a), the step (1) comprises the steps (a), (b), and (c) below: Step (a): Mixing all or a part of the base resin, the inorganic filler, and the silane compound. The coupling agent and the organic peroxide are heated to a temperature higher than the decomposition temperature of the organic peroxide. and melt-mixing the mixture at a temperature of 100° C. to prepare a silane masterbatch. Step (b): Melt-mixing the remainder of the base resin with the silanol condensation catalyst, A process for preparing a catalyst masterbatch Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch are mixed. A process of melt-mixing the star batch The method for producing a silane-crosslinkable resin composition includes mixing the compound having two or more imide structures in at least one of the steps (a) and (b).

8. The method for producing a silane-crosslinkable resin composition according to claim 7 , wherein the entire amount of the compound having two or more imide structures is mixed in the step (b).

9. A method for producing a silane-crosslinked resin molded product, comprising the following steps (1), (2), and (3): Step (1): For 100 parts by mass of a base resin containing a polyolefin resin, A silane copolymer having a grafting reaction site capable of grafting to a silane resin. 2 to 15 parts by mass of a pulling agent and 1 to 15 parts by mass of a compound having two or more imide structures 60 parts by mass, 1 to 200 parts by mass of inorganic filler, and 0.0 parts by mass of organic peroxide 1 to 0.6 parts by mass of a silanol condensation catalyst and 0.01 to 5 parts by mass of a silanol condensation catalyst are melted A step of mixing to obtain a mixture Step (2): A step of molding the mixture obtained in step (1) to obtain a molded body. Step (3): The molded body obtained in step (2) is brought into contact with water to form a silane-crosslinked resin. Step of obtaining a molded body In carrying out the step (1), when the whole of the base resin is melt-mixed in the step (a), the step (1) comprises the steps (a) and (c) below, while when a part of the base resin is melt-mixed in the step (a), the step (1) comprises the steps (a), (b), and (c) below: Step (a): Mixing all or a part of the base resin, the inorganic filler, and the silane compound. The coupling agent and the organic peroxide are heated to a temperature higher than the decomposition temperature of the organic peroxide. and melt-mixing the mixture at a temperature of 100° C. to prepare a silane masterbatch. Step (b): Melt-mixing the remainder of the base resin with the silanol condensation catalyst, A process for preparing a catalyst masterbatch Step (c): The silane masterbatch and the silanol condensation catalyst or the catalyst masterbatch are mixed. A process of melt-mixing the star batch The method for producing a silane-crosslinked resin molded product includes mixing the compound having two or more imide structures in at least one of the steps (a) and (b).

10. The method for producing a silane-crosslinked resin molded article according to claim 9 , wherein the entire amount of the compound having two or more imide structures is mixed in the step (b).

11. A silane-crosslinkable resin composition produced by the production method according to claim 7 or 8.

12. A silane-crosslinked resin molded article produced by the method according to claim 9 or 10.

13. A wiring material having the silane-crosslinked resin molded product according to claim 12 as a coating layer.