Silane crosslinkable resin composition, silane crosslinked resin molded product, and electrical wire

Abstract

The present invention provides: a silane crosslinkable resin composition that contains at least one silanol condensation catalyst represented by a specific formula and having a mass reduction rate of less than 10.0% when heated at 100°C for 30 min, and that does not contain a tin-containing silanol condensation catalyst; and a silane crosslinked resin molded product and an electrical wire that use said silane crosslinkable resin composition.

Description

Silane-crosslinkable resin composition, silane-crosslinked resin molded body, and electric wire

[0001] The present invention relates to a silane-crosslinkable resin composition, a silane-crosslinked resin molded article, and an electric wire.

[0002] Wiring materials such as insulated wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables) used in electrical and electronic devices and automobiles have a tubular molding formed of a crosslinked resin as an insulating coating layer (also simply referred to as a coating layer) on the outer periphery of a conductor, etc. Among crosslinked resins, silane crosslinked resins in particular are widely used as materials for the coating layer of electric wires because they can be crosslinked and cured by a silane crosslinking method, which allows crosslinking of a silane crosslinkable resin composition easily and with high productivity without requiring special equipment.

[0003] The silane crosslinking method involves a silanol condensation reaction as the final crosslinking reaction. Various compounds can be used as silanol condensation catalysts to initiate or accelerate this condensation reaction. Among these, organotin compounds are frequently used because of their high catalytic activity and the ability to achieve appropriate crosslinking rates and crosslinking densities. These organotin compounds can exhibit endocrine disrupting effects, raising safety concerns. Therefore, efforts are being made to convert these compounds to tin-free silanol condensation catalysts. Examples include organic sulfonic acids and zinc carboxylates. Furthermore, Patent Document 1 describes "organometallic compounds other than organotin compounds," specifically, so-called organic carboxylate metal salts, such as zinc laurate, zinc octoate, zinc stearate, aluminum adipate, aluminum laurate, and calcium adipate. Furthermore, Patent Document 2 describes "silanol condensation catalysts characterized by containing an organoaluminum compound," specifically, "aluminum acetylacetonate, aluminum lactate, aluminum tristearate, bis(2-ethylhexanoato)hydroxyaluminum, and aluminum glycinate."

[0004] However, organic sulfonic acids, zinc carboxylates, and the like generate irritating odors during the crosslinking reaction, for example, during the production of silane-crosslinked resin molded articles, posing environmental and worker safety problems. Furthermore, when a silanol condensation catalyst decomposes under high-temperature conditions, the reaction rate (crosslinking rate) of the silanol condensation reaction increases, resulting in poor appearance and the formation of bumps on the surface of the molded article, resulting in a deterioration in appearance. On the other hand, a slow reaction rate (crosslinking rate) of the silanol condensation reaction results in a decrease in crosslink density immediately after production. Therefore, when using a silanol condensation catalyst that can generate odor, production must be carried out at low temperatures to suppress odor generation and to prevent excessive crosslinking rate acceleration. This creates a trade-off between odor suppression and crosslinking rate acceleration, and crosslink density (suppression of slowing down the crosslinking rate), leading to problems with manufacturability and crosslinking rate. Patent Documents 1 and 2 do not address these issues of manufacturability and crosslinking rate.

[0005] JP 2002-146150 A JP 2014-193944 A

[0006] The present invention aims to provide a silane-crosslinkable resin composition that uses a silanol condensation catalyst that is free from the problem of endocrine disrupters, yet is capable of causing a crosslinking reaction at an appropriate (moderate) crosslinking rate while suppressing odor generation, and that can produce a silane-crosslinked resin molded article having excellent appearance and high crosslink density. Another object of the present invention is to provide a silane-crosslinked resin molded article and an electric wire that use the silane-crosslinkable resin composition.

[0007] The present inventors have conducted extensive research into silane-crosslinkable resin compositions and have found that the use of a silanol condensation catalyst having a specific chemical structure represented by formula (1) described below and exhibiting a mass loss rate of less than 10.0% by mass under the conditions described below can suppress odor generation during the production of silane-crosslinked resin molded articles, particularly during melt mixing, and can also allow the silanol condensation reaction to proceed at an appropriate crosslinking rate, thereby enabling the production of silane-crosslinked resin molded articles with excellent appearance and high crosslink density with excellent manufacturability. Based on this finding, the present inventors have conducted further research and have arrived at the present invention.

[0008] That is, the object of the present invention has been achieved by the following means: <1> A silane-crosslinkable resin composition containing at least one silanol condensation catalyst represented by the following formula (1), which exhibits a mass loss rate of less than 10.0% when heated at 100°C for 30 minutes, and which does not contain a tin-containing silanol condensation catalyst. Formula (1): M(R １ ) ａ (R ２ ) ｂ In formula (1), M represents aluminum, titanium, zirconium, or zinc. １ represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxy group, a hydroxy group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group. ２ represents an alkyl or arylcarbonyloxy group, or a substituent not containing nitrogen. a is an integer of 1 to 4, and b is an integer of 0 to 3. <2> The R １ represents acetylacetone, ethyl acetoacetate, or a conjugate base thereof. <3> The silane-crosslinkable resin composition according to <1> or <2>, wherein M represents aluminum, zirconium, or zinc. <4> The silane-crosslinkable resin composition according to any one of <1> to <3>, comprising a base resin, the base resin comprising a polyolefin resin. <5> The silane-crosslinkable resin composition according to any one of <1> to <4>, comprising a base resin, the content of the silanol condensation catalyst being 0.01 to 1 part by mass per 100 parts by mass of the base resin. <6> The silane-crosslinkable resin composition according to any one of <1> to <5>, comprising a base resin, the content of an inorganic filler being 0.5 to 400 parts by mass per 100 parts by mass of the base resin. <7> A silane-crosslinkable resin molded product of the silane-crosslinkable resin composition according to any one of <1> to <6> above. <8> An electric wire having the silane-crosslinked resin molded product according to <7> above as a coating layer.

[0009] The present invention provides a silane-crosslinkable resin composition that uses a silanol condensation catalyst that is free from the problem of endocrine disrupters, yet can proceed with a crosslinking reaction at an appropriate crosslinking rate while suppressing odor generation, and can produce a silane-crosslinked resin molded article having excellent appearance and high crosslink density. The present invention also provides a silane-crosslinked resin molded article and an electric wire that use the silane-crosslinkable resin composition. The above and other features and advantages of the present invention will become more apparent from the following description.

[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 that form 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.

[0011] [Silane Crosslinkable Resin Composition] The silane crosslinkable resin composition of the present invention (hereinafter sometimes simply referred to as the crosslinkable composition of the present invention) contains at least one silanol condensation catalyst represented by the formula (1) described below, which exhibits a mass loss rate of less than 10.0% when heated at 100°C for 30 minutes. On the other hand, the crosslinkable composition of the present invention does not contain a tin-containing silanol condensation catalyst. Here, the tin-containing silanol condensation catalyst refers to an organotin compound that functions as a catalyst for the silanol condensation reaction among organotin compounds containing tin as a constituent element, and includes various known organotin compounds. Examples include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate. In the present invention, the absence of a tin-containing silanol condensation catalyst in the silane crosslinkable resin composition means that the silane crosslinkable resin composition does not intentionally contain or mix a tin-containing silanol condensation catalyst, but does not exclude the inevitable inclusion or mixing of the tin-containing silanol condensation catalyst. For example, the crosslinkable composition of the present invention may contain a tin-containing silanol condensation catalyst in an amount of 0.001 parts by weight or less per 100 parts by weight of the base resin.

[0012] The crosslinkable composition of the present invention contains at least one silanol condensation catalyst represented by the following formula (1), which exhibits a mass loss rate of less than 10.0% when heated at 100°C for 30 minutes. By containing this silanol condensation catalyst, the crosslinkable composition of the present invention allows the crosslinking reaction to proceed at an appropriate crosslinking rate while suppressing odor generation, thereby enabling the production of silane-crosslinked resin molded articles with excellent appearance and high crosslink density with excellent manufacturability. The crosslinkable composition of the present invention preferably contains one or two types of silanol condensation catalyst. In the present invention, whether the "crosslinking rate" is appropriate cannot be determined uniquely by the content of the silanol condensation catalyst, the conditions for contact with water, and the like. Whether the crosslinking rate is appropriate can be judged and evaluated by maintaining the catalytic activity of the silanol condensation catalyst and passing, for example, the appearance test and crosslink density test (heat deformation rate) described in the Examples below.

[0013] <Silanol condensation catalyst represented by formula (1)> The silanol condensation catalyst contained in the crosslinkable composition of the present invention is represented by the following formula (1), and is a compound that does not normally correspond to an environmental hormone (endocrine disruptor). Formula (1): M(R １ ) ａ (R ２ ) ｂ In formula (1), M represents a metal species, specifically aluminum, titanium, zirconium, or zinc. Among these, aluminum, zirconium, and zinc are preferred in terms of crosslinking rate.

[0014] R １ represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxy group, a hydroxy group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group. In the present invention, a ligand having a specific group includes a ligand consisting of only the specific group, and a ligand composed of the specific group and a group, atom, or structure other than the specific group. For example, a ligand having an alkylcarbonyloxy group includes a ligand consisting of only an alkylcarbonyloxy group, and a β-ketoester compound composed of an alkylcarbonyloxy group and another group. The above group contained in the ligand may take the form of an ion, a conjugate base, or the like, as long as it is coordinated to the metal species M. １ The ligand that can be taken as R preferably has one to three of the above groups, and more preferably has one or two of them. １ Among the above groups, the ligands that can be taken as R are preferably ligands having at least one group selected from the group consisting of an alkyl group, a carbonyl group, an alkoxy group, and an arylcarbonyloxy group. Substituents formed by combining two or more of the above groups are not particularly limited, and examples thereof include a combination of an alkyl group and a carbonyl group (an alkylcarbonyl group), a combination of an aryl group and a carbonyl group (an arylcarbonyl group), and the like. １ Examples of the ligand that can be used include a ligand having an alkylcarbonyl group and an alkylcarbonyloxy group (for example, a ketoester compound), a ligand having two alkylcarbonyl groups (for example, a diketone compound), and the like.

[0015] R １ The alkyl group that can be contained in the ligand is not particularly limited and may be a straight chain, branched chain, or dry chain, with a straight chain or branched chain being preferred. The number of carbon atoms in the alkylene group is not particularly limited, but is preferably 1 to 40, more preferably 1 to 20, even more preferably 1 to 10, and particularly preferably 1 to 5. R １ The alkoxy group that can be contained in the ligand is not particularly limited, and R １ An example of the alkyl group is an alkyloxy group in which an oxygen atom is bonded to the terminal of the alkyl group that the ligand may have. However, within the above range, the number of carbon atoms in the alkyl group of the alkoxy group is preferably 1 to 24, and more preferably 1 to 20. １ The aryl group that can be contained in the ligand is not particularly limited, and may be a monocyclic aryl group or a polycyclic aryl group. The number of carbon atoms in the aryl group is not particularly limited, but is preferably 6 to 40, more preferably 6 to 20, and even more preferably 6 to 10. １ The alkylcarbonyloxy group that the ligand may have is not particularly limited, and may be any of R １ Examples of the R include a group in which a carbonyloxy group is bonded to the terminal of an alkyl group that the ligand may have (an alkyl-COO- group). １ The arylcarbonyloxy group that the ligand may have is not particularly limited, and R １ Examples of the aryl group include a group in which a carbonyloxy group is bonded to the terminal of an aryl group that the ligand may have (aryl-COO- group).

[0016] R １ Examples of the ligand that can be used include diketone compounds such as acetylacetone, and β-ketoester compounds such as ethyl acetoacetate. １The diketone compound that can be used as the silanol condensation catalyst is not particularly limited, but includes 1,3-diketone compounds and 1,4-diketone compounds, and 1,3-diketone compounds are preferred in that they provide a high stability of the silanol condensation catalyst and can reduce the mass loss rate described below.

[0017] The 1,3-diketone compound includes R Ａ -CO-C(R Ｂ ) ２ -CO-R Ｃ It is expressed as: R Ａ and R Ｃ R includes an alkyl group, an aryl group, an alkoxy group, a carbonyl group, a carboxy group, a ketone group, etc., and is preferably an alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 5. Ａ and R Ｃ may be the same or different. Ａ and R Ｃ The alkyl group, aryl group and alkoxy group that can be taken as R １ The alkyl group, aryl group, and alkoxy group that the ligand may have are the same as those that may be included in the ligand. Ａ and R Ｃ Examples of the ketone group that can be taken as R include a group represented by -CO-R. Here, R is not particularly limited, and examples thereof include an alkyl group and an aryl group. The alkyl group and aryl group that can be taken as R are not particularly limited, and examples thereof include R Ａ and R Ｃ The alkyl and aryl groups that can be represented by R are the same as those that can be represented by R. Ｂ Examples of the two R include a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a carbonyl group, a carboxy group, a ketone group, and an alkylcarbonyl group, and a hydrogen atom is preferred. Ｂ may be the same or different, and are preferably all hydrogen atoms. Ａ and R Ｃ and R 1 and R 2 are preferably alkyl groups, for example, acetylacetone, in which both are methyl groups.

[0018] The 1,4-diketone compound includes R Ａ -CO-C(R Ｄ ) ２ -C(R Ｅ ) ２ -CO-R Ｃ It is expressed as: R Ａ and R Ｃ is R of the 1,3-diketone compound Ａ and R Ｃ It is synonymous with R Ｄ and R Ｅ are R of the 1,3-diketone compound. Ｂ However, a hydrogen atom or an alkylcarbonyl group is preferred. Ｄ and R Ｅ may be the same or different, and are preferably all hydrogen atoms. Ａ and R Ｃ and R 1 and R 2 are each an alkyl group, and examples thereof include 2,5-hexanedione (also called acetonylacetone) and 3,4-diacetyl-2,5-hexanedione.

[0019] R １ The β-ketoester compound that can be used as R Ｆ -CO-C(R Ｂ ) ２ -COO-R Ｇ Preferred is a β-ketoester compound represented by R Ｆ is R of the 1,3-diketone compound Ａ It is synonymous with R Ｂ is R of the 1,3-diketone compound Ｂ It is synonymous with R Ｇ R is an alkyl group, an aryl group, an alkoxy group, a carbonyl group, a carboxy group, a ketone group, etc., and an alkyl group is preferred. Ｇ The alkyl group, aryl group and alkoxy group that can be taken as R １ The alkyl, aryl and alkoxy groups that can be contained in the ligands that can be represented by R ＧThe number of carbon atoms in the alkyl group that can be represented by R is preferably 1 to 40, more preferably 1 to 30, even more preferably 1 to 25, and particularly preferably 1 to 20. Ｇ The ketone group that can be used as R Ａ and R Ｃ As a β-ketoester, R Ｆ and R Ｇ are both alkyl groups, and examples thereof include methyl acetoacetate (methyl acetoacetate), ethyl acetoacetate (ethyl acetoacetate), methyl pivaloyl acetate, methyl isobutyroyl acetate, ethyl benzoyl acetate, ethyl para-anisoyl acetate, methyl caproyl acetate, methyl lauroyl acetate, and methyl palmitoyl acetate.

[0020] The conjugate base of the diketone compound or β-ketoester compound includes a compound obtained by removing one hydrogen atom from the above-mentioned diketone compound or β-ketoester compound, and usually, R Ｂ or R Ｄ Or R Ｅ Preferred examples of the compound include compounds in which one hydrogen atom has been removed.

[0021] R １ Examples of the ligand (including its conjugate base) having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxy group, a hydroxy group, an alkoxy group, an aryl group, an alkyloxy group, and an arylcarbonyloxy group include, in addition to the diketone compounds and β-ketoester compounds described above, alcohol compounds having an alkoxy group such as methoxy, isopropoxy, n-butoxy, n-propoxy, 2-ethylhexoxy, and stearyloxy; carboxylic acid compounds such as adipic acid, lactic acid, and stearic acid; dodecylbenzenesulfonic acid; octylene glycol; octanol; phosphate esters; various ethers; and phenols.

[0022] R １As the R in formula (1), acetylacetone, ethyl acetoacetate, or a conjugate base thereof is preferred, since the crosslinking rate (catalytic activity of the silanol condensation catalyst) can be adjusted to an appropriate rate and both appearance and crosslink density can be achieved at a high level. １ In the silanol condensation catalyst represented by formula (1), may be bonded to M as a monodentate ligand or may be bonded to M as a bidentate ligand.

[0023] R in formula (1) ２ is a substituent bonded to the metal atom M in formula (1) by a chemical bond (usually a covalent bond or an ionic bond) other than a coordinate bond, and represents an alkyl or arylcarbonyloxy group, or a substituent not containing nitrogen. ２ The alkylcarbonyloxy group that can be taken as R is not particularly limited as long as it is an anion of an aliphatic carboxylic acid, and examples thereof include alkylcarbonyloxy groups having a total carbon number of 2 to 40 including the carbon atom of the carbonyl group, and alkylcarbonyloxy groups having a total carbon number of 2 to 20 are preferred. Examples of alkylcarbonyloxy groups include the anion of stearic acid. ２ The arylcarbonyloxy group which can be taken as the arylcarbonyloxy group is not particularly limited as long as it is an anion of an aromatic carboxylic acid, and examples thereof include arylcarbonyloxy groups having a total of 7 to 40 carbon atoms including the carbon atom of the carbonyl group, and an arylcarbonyloxy group having a total of 7 to 20 carbon atoms is preferred.

[0024] R ２ The nitrogen-free group that can be taken as the aryl group is not particularly limited, and any appropriate group can be adopted.

[0025] R in formula (1) ２ In the silanol condensation catalyst represented by formula (1), is usually bonded to M at one bond, but is not limited thereto.

[0026] In formula (1), a is an integer of 1 to 4, preferably an integer of 2 to 4. b is an integer of 0 to 3, preferably 1 or 2. However, a+b is an integer of 8 or less, preferably an integer of 1 to 4.

[0027] The silanol condensation catalyst represented by the above formula (1) is preferably a silanol condensation catalyst in which M is aluminum or zirconium and R is a silanol condensation catalyst in which M is aluminum or zirconium and R is a silanol condensation catalyst in which R is aluminum or zirconium, ... １ is preferably acetylacetone, ethyl acetoacetate, or a conjugate base thereof, and further, when a is 1 or more, a silanol condensation catalyst in which b is 0 is more preferred.

[0028] Examples of the silanol condensation catalyst represented by the above formula (1) include zirconium acetylacetonate, zinc acetylacetonate, aluminum tris(ethylacetoacetate), acetylacetonate aluminum bis(ethyl acetylacetoacetate), titanium tetraacetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate, and aluminum tris(acetoacetate).

[0029] The silanol condensation catalyst contained in the crosslinkable composition of the present invention exhibits a mass loss rate of less than 10.0% when heated at 100°C for 30 minutes. Specifically, the mass loss rate before and after heating is less than 10.0% by mass, as measured by the mass loss rate measurement method described in the Examples. This mass loss rate was devised as an index for evaluating the thermal stability (thermal decomposition property) and odor generation of a silanol condensation catalyst, based on the discovery that many odor-causing compounds have boiling points or decomposition temperatures of 100°C or less at 1 atmosphere. When the silanol condensation catalyst represented by Formula (1) exhibits a mass loss rate of less than 10.0% by mass, odor generation can be suppressed without reducing the crosslinking rate (catalytic activity of the silanol condensation catalyst). In the present invention, the mass loss rate of the silanol condensation catalyst is preferably 5.0% by mass or less, since odor generation can be highly suppressed. The lower limit of the mass loss rate is ideally 0% by mass, but in practice is 0.0001% by mass or more.

[0030] As will be described later, the crosslinkable composition of the present invention contains the above-mentioned silanol condensation catalyst, which is free from the problem of endocrine disrupters, yet is capable of causing a crosslinking reaction at an appropriate crosslinking rate while suppressing the generation of odor, and can produce a silane-crosslinked resin molded article that exhibits excellent appearance and high crosslink density.

[0031] Each component (excluding the silanol condensation catalyst) used in the present invention is described below. One or more of each component may be used. In the present invention and this specification, the term "resin" refers to a resin to which a silane coupling agent is not grafted. On the other hand, a resin to which a silane coupling agent is grafted is sometimes referred to as a silane-crosslinkable resin, a silane-grafted resin, or the like. Furthermore, the term "(co)polymer" is used to include the resin or rubber.

[0032] <Silane-Crosslinkable Resin> The crosslinkable composition of the present invention contains a silane-crosslinkable resin. The silane-crosslinkable resin is not particularly limited, and may be in the form of a composition (mixture) containing a base resin that serves as the base of the crosslinkable composition and a silane coupling agent (in an unreacted state), or in the form of a silane-crosslinkable resin to which the silane coupling agent is grafted.

[0033] In the form of a composition, the silane crosslinkable resin preferably contains a base resin and a silane coupling agent, and further contains an organic peroxide.

[0034] The silane crosslinkable resin is formed from a silane coupling agent and a base resin, as described below, with the silane coupling agent grafted to the base resin. The graft reaction amount of the silane coupling agent in this silane crosslinkable resin is not particularly limited. Generally, the graft reaction amount obtained by reacting the silane coupling agent with the base resin in the amount described below in the form of a composition is sufficient. The silane crosslinkable resin may be synthesized by the method described below, or a commercially available product. The silane crosslinkable resin may be obtained by reacting the base resin and the silane coupling agent described below at a temperature equal to or higher than the decomposition temperature of the organic peroxide described below. 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 crosslinkable resins include Linkron (trade name, manufactured by Mitsubishi Chemical Corporation).

[0035] (Base Resin) The base resin forming the silane graft resin and the base resin when used in the form of a composition (the base resin before the grafting reaction with the silane coupling agent) are not particularly limited, but include resins composed of various (co)polymers, with polyolefin resins being preferred. - Polyolefin Resin - The polyolefin resin 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, and known polyolefin resins used in conventional resin compositions can be used. The polyolefin resin has a graftable moiety (e.g., an unsaturated bond moiety in a 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, polyolefin resin copolymers having an acid copolymerization component or an acid ester copolymerization component, and styrene-based elastomers.

[0036] The polyethylene is not particularly limited as long as it is a polymer resin containing ethylene as a main component, 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).

[0037] The polypropylene is not particularly limited as long as it is a polymer resin containing propylene as the main component, and examples thereof include propylene homopolymers, as well as random polypropylene and block polypropylene resins.

[0038] The ethylene-α-olefin copolymer preferably includes a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms (excluding those included in the above-mentioned polyethylene and polypropylene). Examples include an ethylene-propylene copolymer (excluding those included in the above-mentioned polypropylene), an ethylene-butylene copolymer, and an ethylene-α-olefin copolymer synthesized in the presence of a single-site catalyst. Furthermore, examples of ethylene-α-olefin copolymer rubber include ethylene-propylene rubber (EPM) as a binary copolymer rubber, as well as ethylene-propylene-diene rubber (EPDM), which is a terpolymer rubber with a conjugated diene compound or a non-conjugated diene compound.

[0039] In the polyolefin resin copolymer having an acid copolymerization component or an acid ester copolymerization component, the compound that derives the acid copolymerization component or the 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, and examples thereof include alkyl (meth)acrylates. The alkyl group of the alkyl (meth)acrylate preferably has 1 to 12 carbon atoms. The polyolefin resin copolymer having an acid copolymerization component or an acid ester copolymerization component is not particularly limited, and examples thereof include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA).

[0040] Styrenic elastomers refer to elastomers made of polymers containing components derived from aromatic vinyl compounds within the molecule. Examples of such styrene 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 copolymers (SEBS), styrene-isoprene-styrene block copolymers (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymers (SBS), hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymers (SEEPS), styrene-ethylene-propylene-styrene block copolymers (SEPS), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber (HSBR), and hydrogenated acrylonitrile-butadiene rubber (HNBR).

[0041] The polyolefin resin may be acid-modified with an unsaturated carboxylic acid compound such as maleic acid (anhydride).

[0042] The polyolefin resin may contain various oils used as plasticizers or softeners as desired. Examples of such oils include oils used as plasticizers for polyolefin resins or mineral oil softeners for rubber. Suitable oils include aromatic oils, paraffin oils, and naphthenic oils.

[0043] - Composition of Polyolefin Resin - The polyolefin resin may contain the above-mentioned specific resin alone or multiple resins. In the present invention, the polyolefin resin may contain only polyethylene. However, it is preferable that the polyolefin resin contain polyethylene, a styrene-based elastomer, and an oil, in order to enhance the effect of improving mechanical properties by increasing crosslink density. When the polyolefin resin contains multiple resins, the content of each of the above resins or oils should be 100% by mass in total, and this content can be appropriately set depending on the physical properties and application of the silane-crosslinked resin molded product. For example, the content of polyethylene in 100% by mass of the polyolefin resin is preferably 5 to 100% by mass, more preferably 10 to 80% by mass, and particularly preferably 15 to 70% by mass. Furthermore, the content of the styrene-based elastomer in 100% by mass of the polyolefin resin is preferably 5 to 70% by mass, more preferably 10 to 40% by mass, and even more preferably 10 to 35% by mass. The content of oil in 100% by mass of the polyolefin resin is preferably 0 to 40% by mass, and more preferably 5 to 25% by mass.

[0044] Silane Coupling Agents—The silane coupling agents (before the grafting reaction) that form the silane crosslinkable resin, and the silane coupling agents used in the form of a composition, are not particularly limited as long as they have a grafting reaction site (group or atom) that can undergo a grafting reaction with a grafting reaction site of the base resin in the presence of radicals generated by decomposition of an organic peroxide, and a hydrolyzable silyl group as a reaction site capable of silanol condensation. Examples of such silane coupling agents include silane coupling agents that have traditionally been used in silane crosslinking methods. Among these, those having a vinyl group and an alkoxysilyl group at the terminal are preferred. Examples of such silane coupling agents 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, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred. The silane coupling agents forming the silane graft resin may be used alone or in combination of two or more.

[0045] - Organic Peroxide - It is preferable to use an organic peroxide when synthesizing a silane crosslinkable resin, and it is also preferable to contain an organic peroxide when used in the form of a composition as a base resin. The organic peroxide generates radicals at least by thermal decomposition, and serves to cause a grafting reaction by radical reaction between the silane coupling agent and the base resin. Such organic peroxides are not particularly limited as long as they generate radicals, 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.

[0046] <Inorganic Filler> The crosslinkable composition of the present invention preferably contains an inorganic filler regardless of the form of the silane crosslinkable resin. In particular, when the silane crosslinkable resin is used in the form of a composition, the coexistence of an inorganic filler can suppress the volatilization of the silane coupling agent and the condensation reaction between silane coupling agents. Therefore, a silane crosslinked resin molded article with excellent appearance, strength, and crosslink density can be produced. The inorganic filler is not particularly limited as long as it is a commonly used inorganic filler, but it is preferable that the inorganic filler has a site on its surface that can chemically bond with the silanol condensation reactive site of the silane coupling agent via a hydrogen bond, a covalent bond, or an intermolecular bond. The site that can chemically bond with the silanol condensation reactive site of the silane coupling agent is not particularly limited, but examples thereof include an OH group (a hydroxyl group, a water molecule of water of water or crystallization, 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 exhibiting high crosslink density (heat resistance, strength, etc.) can be formed. 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.

[0047] 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. 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.

[0048] <Additives> The 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 silanol condensation catalyst in the silane crosslinkable resin composition is not particularly limited and can be set appropriately. For example, it can be 0.005 to 2 parts by mass relative to 100 parts by mass of the base resin (i.e., the base resin before the grafting reaction with the silane coupling agent). In terms of being able to proceed with the crosslinking reaction at an appropriate crosslinking rate while suppressing the generation of odor, the content is preferably 0.01 to 1 part by mass, more preferably 0.03 to 0.5 parts by mass, and even more preferably 0.05 to 0.5 parts by mass.

[0050] The content of the silane coupling agent in the silane crosslinkable resin composition is not particularly limited, but is preferably 1 to 15 parts by mass, more preferably 2 to 15 parts by mass, even more preferably 3 to 15 parts by mass, and particularly preferably 3 to 8 parts by mass, per 100 parts by mass of polyolefin resin, in order to suppress the formation of protruding aggregates (gel particles) due to crosslinked gel, etc., and the volatilization of the silane coupling agent, thereby enabling the production of a silane crosslinked resin molded product having excellent appearance and sufficient crosslinking density. Here, for convenience, the content of the silane coupling agent in the silane crosslinkable resin 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] In the silane-crosslinkable resin composition, when the base resin is used in the form of a composition, the content of the organic peroxide in the silane-crosslinkable resin composition is not particularly limited, but is preferably 0.01 to 0.6 parts by mass relative to 100 parts by mass of the base resin, and is preferably 0.1 to 0.2 parts by mass from the viewpoint of further improving the appearance, crosslink density, etc. of the silane-crosslinked resin molded article.

[0052] The content of the inorganic filler in the silane-crosslinkable resin composition is not particularly limited, but is, for example, preferably 0.5 to 400 parts by mass relative to 100 parts by mass of the base resin, more preferably 30 to 280 parts by mass, even more preferably 50 to 250 parts by mass, and particularly preferably 50 to 100 parts by mass, in terms of being able to further improve the appearance of the silane-crosslinked resin molded article.

[0053] 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.

[0054] [Silane-crosslinked resin molded article] The silane-crosslinked resin molded article of the present invention is a crosslinked resin molded article of the silane-crosslinkable resin composition of the present invention described above. Specifically, it is a crosslinked, cured product obtained by molding the silane-crosslinkable resin composition of the present invention into a predetermined shape and size, and then contacting it with water to cause a silanol condensation reaction. This silane-crosslinked resin molded article has a crosslinked structure in which the base resin is silane-crosslinked, and as described below, an inorganic filler may be incorporated into the crosslinked structure. The crosslinked structure is preferably a crosslinked structure mediated by a silane coupling agent or a silanol condensate thereof, and a structure in which an inorganic filler is incorporated into a part of the crosslinked structure. The silane-crosslinked resin molded article of the present invention has excellent appearance and a high crosslinking density.

[0055] The content of each component in the silane-crosslinked resin molded product of the present invention is generally the same as the content of each component in the crosslinkable composition of the present invention. However, the organic peroxide and silanol condensation catalyst are usually decomposed and not present. The content of the silane coupling agent is the content before the grafting reaction and silanol condensation reaction, and the content of the base resin is the content before crosslinking.

[0056] The silane-crosslinked resin molded article of the present invention has an excellent appearance and a high crosslink density, and can be suitably used in various products (including semi-finished products, parts, and components). Specific examples include insulating coating layers (including sheaths) for wiring materials, molding materials, power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, packings, gaskets, cushioning materials, and vibration-proofing materials. It is particularly suitable for use as insulating coating layers for insulated electric wires for vehicles such as automobiles and trains, and sheaths for cabtire cables.

[0057] [Electric Wire] The electric wire of the present invention has the above-described silane-crosslinked resin molded product formed into a tubular shape as an insulating layer that coats the outer periphery of a conductor. The electric wire of the present invention has a coating layer formed from a silane-crosslinked resin molded product exhibiting excellent appearance and high crosslink density, and therefore has an excellent appearance free of gel particles and also high heat resistance and strength. Unless otherwise specified, the electric wire of the present invention refers to a wiring material used for internal or external wiring of electric and electronic devices, and includes insulated electric wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables). The electric wire of the present invention is the same as conventional electric and electronic devices and industrial wires, except that the coating layer is formed from the silane-crosslinked resin molded product of the present invention. When the coating layer of an electric wire is composed of multiple layers, it is sufficient that at least one of the layers is formed from the silane-crosslinked resin molded product of the present invention. The coating layer formed from the silane-crosslinked resin molded product of the present invention is provided on the outer periphery of a conductor directly or via another layer. The presence or absence of other layers, and the materials thereof, are appropriately determined depending on the type, application, required characteristics, etc. of the electric wire. The conductor may be a conventional one, such as a single wire or a stranded wire (in which tensile strength fibers are laid longitudinally or twisted together) made of soft copper, copper alloy, or aluminum. In addition to bare wires, tin-plated wires or wires with an enamel-coated insulating layer may also be used. The thickness of the coating layer formed from the silane-crosslinked resin molded product of the present invention is not particularly limited, but is usually about 0.15 to 5 mm.

[0058] The electric wire of the present invention can be produced by forming the silane-crosslinkable resin composition of the present invention into an annular layer (tubular) on the outer surface of a conductor, and then contacting the layer with water to cause a crosslinking reaction (silanol condensation reaction). Preferably, the electric wire can be produced by changing the molding step (2) in the method for producing a silane-crosslinked resin molded article of the present invention described below to a step of co-extrusion molding the silane-crosslinkable resin composition onto the outer surface of the conductor using a coating device (extruder).

[0059] The silane-crosslinked resin molded product of the present invention exhibits the above-mentioned excellent properties and can therefore be used for various purposes other than as a coating layer for electric wires. Examples of such uses include as a substitute for resin molded products, such as heat-resistant sheets, heat-resistant films, power plugs, connectors, tubes, and vibration-proof materials.

[0060] [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, the 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 using a composition containing a resin and a silane coupling agent as the base resin, i.e., 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 the base resin, the silane coupling agent, the organic peroxide, the 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 step (1) of preparing the silane-crosslinkable resin composition of the present invention described below.

[0061] [Method for Producing Silane-Crosslinked Resin Molded Articles] The silane-crosslinked resin molded article of the present invention (hereinafter sometimes referred to as the molded article manufacturing method of the present invention) can be produced by molding the silane-crosslinkable resin composition of the present invention and then subjecting it to a crosslinking reaction (silanol condensation reaction). A preferred example of such a manufacturing method includes the following steps (1) to (3). The molded article manufacturing method of the present invention is suitably applicable to an embodiment using a composition containing a base resin and a silane coupling agent. In an embodiment using a silane-grafted resin, the following steps (2) and (3) can be applied to a mixture of the silane-grafted resin, a silanol condensation catalyst, and, if appropriate, an inorganic filler. Step (1): Melt-mixing the base resin with the silane coupling agent, an organic peroxide, a silanol condensation catalyst, and preferably an inorganic filler to obtain a silane-crosslinkable resin composition. Step (2): Molding the silane-crosslinkable resin composition to obtain a molded article. Step (3): Contacting the molded article with water to obtain a silane-crosslinked resin molded article.

[0062] In the above step (1), although the components can be mixed all at once, it is preferable to carry out the following steps depending on the use mode (compounding mode) of the base resin. That is, when carrying out this step (1), if the entire base resin is melt-mixed in the following step (a), step (1) comprises the following steps (a) and (c). On the other hand, if a portion of the base resin is melt-mixed in the following step (a-2), step (1) comprises the following steps (a), (b), and (c). Step (a): A step of melt-mixing all or a portion of the base resin, a silane coupling agent, an organic peroxide, and preferably an inorganic filler 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 the molded article manufacturing method of the present invention, the blending amounts of each polymer component used as the base resin are the same as the above-described contents of the base resin composition. Furthermore, the blending amounts of the silane coupling agent, inorganic filler, silanol condensation catalyst, and additives are the same as the contents in the silane-crosslinkable resin composition described above. In the molded article manufacturing method of the present invention, the mixture obtained in step (1) only needs to contain 100 parts by mass of the base resin. For example, in step (a), the blending amount may include blending the entire amount (100 parts by mass) of the base resin, and blending only a portion of the base resin. When blending a portion of the base resin in step (a), the blending amount is preferably 60 to 95% by mass, more preferably 70 to 85% by mass, of the 100% by mass of the base resin blended in steps (a) and (b). The remaining portion of the base resin (carrier resin) blended in step (b) is appropriately determined depending on the portion of the base resin blended in step (a). When a part of the base resin is mixed in step (a), the component to be mixed may be one kind or two or more kinds.

[0064] When an inorganic filler is used, a portion of the inorganic filler can be used in a step other than step (a), such as step (b), but 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 (not via 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).

[0065] <Step (1)> In the method for producing a molded article of the present invention, step (1) is carried out in which a base resin, a silane coupling agent, an organic peroxide, a silanol condensation catalyst, preferably an inorganic filler, and appropriate additives are melt-mixed in the above-mentioned amounts to prepare the silane-crosslinkable resin composition of the present invention as a mixture. Step (1), i.e., melt-mixing of the base resin, silane coupling agent, inorganic filler, organic peroxide, and silanol condensation catalyst, is carried out in the following order:

[0066] (Step (a)) In the method for producing a molded article 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, a silane coupling agent, an organic peroxide, preferably an inorganic filler, and appropriate additives in the above-mentioned mixed amounts at a temperature equal to or higher than the decomposition temperature of the organic peroxide.

[0067] 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.

[0068] 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.

[0069] In the present invention, the order of mixing is not specified, and the above components may be mixed in any order. For example, the above components can be melt-mixed all at once, or they can be mixed in the following order by the following steps (a-1) and (a-2). In particular, when an inorganic filler is used, it is preferable to perform step (a) by the following steps (a-1) and (a-2) in the following order: 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.

[0070] In step (a-1), by premixing the inorganic filler and the silane coupling agent, a good balance can be achieved between 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. This effectively prevents the volatilization of the silane coupling agent and the condensation reaction between unadsorbed silane coupling agents during the melt-mixing in step (a-2). As a result, a silane-crosslinked resin molded article can be produced that exhibits improved appearance and has improved mechanical properties (tensile strength) and heat resistance due to the silane crosslinking method.

[0071] 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.

[0072] 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).

[0073] 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 a silane MB (step (a-2)). This produces a silane master batch containing a silane-grafted resin. 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 step (a-2) are not particularly limited, and the melt-mixing method and conditions for step (a) can be applied.

[0074] 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.

[0075] 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.

[0076] The Silane MB prepared in step (a) contains a reaction mixture of a base resin, a silane coupling agent, and preferably 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 (2) 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.

[0077] (Step (b)) In the molded body 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) and a silanol condensation catalyst are melt-mixed to prepare a catalyst master batch (catalyst MB). The melt-mixing method and conditions in step (b) are not particularly limited, and the melt-mixing method and conditions for 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, and is 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, and preferably 3 to 20 minutes. The catalyst MB is preferably in the form of pellets or powder.

[0078] (Step (c)) In the molded body 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 performed 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 in 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).

[0079] In this way, 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, and preferably an inorganic filler. When the silane-crosslinkable resin composition contains an inorganic filler, the silanol-condensable reactive site of the silane coupling agent in the silane-grafted resin 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.

[0080] <Step (2)> In the method for producing a silane-crosslinked resin molded article of the present invention, the mixture (silane-crosslinkable resin composition) obtained in step (1) is next 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 electric wires, 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 of the present invention. For example, the melt-mixing method and conditions of step (c) can be applied. When using an extrusion molding machine, the temperature of the extrusion molding machine 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.

[0081] 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 surface of a conductor or the like.

[0082] In this way, a molded article (uncrosslinked molded article) of the silane-crosslinkable resin composition of the present invention is obtained. Like the silane-crosslinkable resin composition of the present invention, this molded article is in a partially crosslinked state that maintains moldability in step (2), although partial crosslinking of the silane-grafted resin is unavoidable. Therefore, the silane-crosslinked resin molded article of the present invention is made into a crosslinked or final-crosslinked molded article by carrying out step (3).

[0083] <Step (3)> In the molded body production method of the present invention, the molded body obtained in step (2) is then contacted with water to produce the silane-crosslinked resin molded body of the present invention in step (3). Since the molded body obtained in step (2) is an uncrosslinked silane-grafted 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 body in which the silane coupling agent has undergone silanol condensation and crosslinked can be obtained. Contact of the uncrosslinked molded body with water can be carried out by a conventional method. The silanol condensation reaction proceeds simply by leaving the uncrosslinked molded body 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 promoting the silanol condensation reaction (crosslinking reaction), active contact of the uncrosslinked molded body 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.

[0084] In this way, 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 graft resin) is condensed via a siloxane bond. Furthermore, when the silane-crosslinked resin molded article contains an inorganic filler, the silane-crosslinked inorganic filler 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, thereby 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).

[0085] The molded article production method of the present invention can suppress the generation of odors due to decomposition of the silanol condensation catalyst during the melt-mixing of steps (1), (b), (c), and (2), particularly during the melt-mixing of step (b). Therefore, the silanol condensation catalyst with excellent catalytic activity represented by formula (1) can be contained up to step (3) without reducing its content, allowing the silanol condensation reaction (final crosslinking reaction) to proceed at an appropriate reaction rate (crosslinking rate). As a result, a silane-crosslinked resin molded article with excellent appearance and high crosslink density can be produced.

[0086] The present invention will be described in more detail below based on examples, but the present invention is not limited to these. In Tables 1-1 and 1-2 (collectively referred to as Table 1), the numerical values ​​relating to the blending amount (content) of each example represent parts by mass unless otherwise specified. Furthermore, a blank space for each component means that the blending amount of the corresponding component is 0 parts by mass.

[0087] Details of each compound used in the examples and comparative examples are shown in Table 1 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. 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. <Silane coupling agent> KBM-1003: vinyl trimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. <Organic peroxide> Perhexa 25B: chemical substance name 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, decomposition temperature 154°C, manufactured by NOF Corporation <Inorganic filler> Magnesium hydroxide: Magseeds FK621 (product name), manufactured by Konoshima Chemical Co., Ltd.

[0088] <Silanol condensation catalyst> Dioctyltin dilaurate: Adekastab OT-1 (trade name), manufactured by ADEKA Corporation Acetylacetone zirconium: Nursem Zr (trade name), manufactured by Nippon Chemical Industry Co., Ltd. Acetylacetone zinc: Nursem Zn (trade name), manufactured by Nippon Chemical Industry Co., Ltd. Tetrastearyl titanate: TA-90 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Aluminum tris(ethyl acetoacetate): AL-3215 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Aluminum tri-2-butoxide: AL-3001 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Acetylacetonatoaluminum bis(ethyl acetylacetoacetate): AL-3200 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Titanium tetraacetylacetonate: TC-401 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Tetrastearyl titanate normal butyl titanate: TA-21 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd. Alkylamine, zirconium compound: K-KAT672 (trade name), manufactured by KING INDUSTRIES Alkylamine, zinc carboxylate: K-KAT670 (trade name), manufactured by KING INDUSTRIES Zinc compound, alkylamine: K-KAT635 (trade name), manufactured by KING INDUSTRIES Carboxylate metal salt: K-KAT633 (trade name), manufactured by KING INDUSTRIES Zinc compound, amine compound: K-KAT614 (trade name), manufactured by KING INDUSTRIES Alkyl aromatic sulfonic acid: NACURE CD-2150 (trade name), manufactured by KING INDUSTRIES Dinonylnaphthalenedisulfonic acid: NACURE 155 (product name), manufactured by KING INDUSTRIES

[0089] Examples 1 to 12 and Comparative Examples 1 to 13 In each of the Examples and Comparative Examples, a portion of the base resin (specifically, the LLDPE shown in the "Catalyst MB" column of Table 1) was used as a carrier resin for catalyst MB in the mass ratio shown in that column. The components shown in the "Silane MB" column of Table 1 were melt-mixed at 170 to 200°C using a Banbury mixer, followed by pelletizing to prepare pellets of silane MB (step (a)). Additionally, the components shown in the "Catalyst MB" column of Table 1 were melt-mixed at 170 to 200°C using a Banbury mixer in the mass ratio shown in that column, followed by pelletizing to prepare pellets of catalyst MB (step (b)).

[0090] 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 to obtain a dry blend (dry blending step (c)). The mixing ratio of silane MB to catalyst MB was the mass ratio shown in the "Silane MB" and "Catalyst MB" columns in Table 1. Next, a 25 mm (screw diameter) extruder with an L / D (ratio of effective screw length L to diameter D) = 25 was used, with a die temperature of 200°C. The extrusion temperature conditions were set to C3 = 170°C, C2 = 150°C, and C1 = 80°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 40 rpm (the melt-mixing step of step (c), up to this point, step (1)), the wire speed was adjusted to extrusion-coat a 0.8 mmφ bare annealed copper wire conductor to an outer diameter of 2.4 mmφ and a thickness of 0.8 mm, thereby obtaining 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 3 hours in an environment of room temperature (25°C) and a relative humidity of 55%, allowing 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.

[0091] Examples 13 and 14 Electric wires having a coating layer formed of a silane-crosslinked resin molded product were produced in the same manner as in Example 1, except that in step (1) of Example 1, step (b) was not performed and a silanol condensation catalyst was directly dry-blended instead of catalyst MB in step (c), the dry-blending step.

[0092] Examples 15 and 16 Electric wires having a coating layer formed of a silane-crosslinked resin molded product were produced in the same manner as in Example 1, except that in step (1) of Example 1, step (a) was not performed and a silane-grafted resin was used as silane MB in step (c).

[0093] The silanol condensation catalyst used and the produced electric wire (silane-crosslinked resin molded article) were evaluated as follows, as well as during the production process. The results are shown in Table 1.

[0094] <Mass Loss Rate of Silanol Condensation Catalyst> An aluminum cup containing each silanol condensation catalyst (approximately 1.000 g) was placed on a hot plate heated to 100°C for 30 minutes, after which the mass of the silanol condensation catalyst was measured, and the mass loss rate (mass%) before and after heating was calculated using the following formula (W). Table 1 shows the calculated mass loss rates (mass%). A mass loss rate (mass%) of less than 10.0% is indicated as passing with a "◯", and a mass loss rate of 10.0% or greater is indicated as failing with an "X". Formula (W): [(w0 - w) / w0] x 100 (%) In formula (W), w0 is the initial (before heating) catalyst mass (g), and w is the catalyst mass (g) after heating.

[0095] <Appearance Test of Electric Wire> The appearance test of the electric wire was a test to evaluate the high crosslinking rate (silanol condensation reaction rate) of the silane crosslinkable resin composition, and the surface of the coating layer of each electric wire was visually observed to evaluate the occurrence of appearance defects and the presence of bumps. Specifically, a case in which no appearance defects or bumps were observed on the surface of the coating layer was deemed good and indicated by "◯." A case in which appearance defects and bumps were observed on the surface of the coating layer of an electric wire up to (excluding) a manufactured length of 5 m after production, but appearance defects or bumps were no longer observed on the surface of the coating layer of an electric wire after a manufactured length of 5 m was deemed pass and indicated by "Δ." A case in which appearance defects or bumps were observed on the surface of the coating layer of both an electric wire up to (excluding) a manufactured length of 5 m and an electric wire after 5 m, or a case in which appearance defects or bumps were observed only after production of a manufactured length of 5 m or more, was deemed fail and indicated by "X." In this test, "poor appearance" refers to defects on the surface (appearance) of the molded article (coating layer) due to foaming, and defects such as unevenness or roughness known as melt fracture. Also, "lumps" refers to gel-like protruding aggregates (gellums) formed by final crosslinking (silanol condensation reaction) or aggregated lumps formed by incompatible raw materials, which are present on the surface of the molded article (coating layer).

[0096] <Environmental friendliness (problems with endocrine disrupters)> If the silanol condensation catalyst used was not registered as a Substance of Very High Concern (SVHC) under the REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulation, it was deemed to pass and indicated by "◯", and if it was registered, it was deemed to fail and indicated by "X".

[0097] <Measurement of Heat Deformation Rate> The heat deformation rate is a test to evaluate the crosslink density (heat resistance of the coating layer) and the crosslinking rate, and was performed 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 the coating layer before heating - thickness of the coating layer after heating) / thickness of the coating layer before heating] x 100) was calculated as the heat deformation rate. A heat deformation rate of less than 20% allows the silanol condensation reaction to proceed quickly, allowing a high crosslink density to be constructed, and is indicated as very good by "◎". A heat deformation rate of 20% or more but less than 40% is indicated as good by "◯", a heat deformation rate of 40% or more but less than 50% is indicated as pass by "△", and a heat deformation rate of 50% or more is indicated as fail by "X".

[0098] <Overall Evaluation> As a result of the above tests, if a product passed all the tests, it was deemed excellent and was marked with a "◯", and if it failed any of the tests, it was deemed "failed" and was marked with an "X".

[0099]

[0100]

[0101] The results shown in Table 1 reveal the following. Comparative Examples 1 and 2, which used organotin silanol condensation catalysts, exhibited a mass change rate of 0.0% by mass, suppressed odor generation, and had high catalytic activity. However, they were plagued by endocrine disrupting hormones and are likely to become unusable in the future. On the other hand, Comparative Examples 3 to 13, which used silanol condensation catalysts that did not satisfy the formula (1) or mass reduction rate specified in the present invention, all generated odor. Furthermore, Comparative Examples 8, 12, and 13 were unable to advance the crosslinking reaction at an appropriate crosslinking rate. As a result, none of the comparative examples produced silane-crosslinked resin molded articles with excellent appearance and high crosslink density while suppressing odor generation with excellent manufacturability. In contrast, Examples 1 to 16, which used silanol condensation catalysts that satisfied the formula (1) and mass reduction rate specified in the present invention, were able to advance the crosslinking reaction at an appropriate crosslinking rate while suppressing odor generation. As a result, in all Examples, a silane-crosslinked resin molded article having excellent appearance and high crosslink density can be produced with high manufacturability (productivity) even though a silanol condensation catalyst free from the problem of endocrine disrupters is used. This shows that the silane-crosslinkable resin composition of the present invention uses a silanol condensation catalyst, which has high catalytic activity and is free from concerns about endocrine disrupting effects, instead of an organotin compound, and can therefore fully comply with environmental regulations.

[0102] 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.

[0103] This application claims priority based on Japanese Patent Application No. 2023-051164, filed in Japan on March 28, 2023, the contents of which are incorporated herein by reference.

Claims

1. A silane-crosslinkable resin composition containing at least one silanol condensation catalyst represented by the following formula (1), which exhibits a mass loss rate of less than 10.0% when heated at 100°C for 30 minutes, and which does not contain a tin-containing silanol condensation catalyst: Equation (1): M(R) １ ) ａ (R) ２ ) ｂ In formula (1), M represents aluminum, titanium, zirconium, or zinc. R １ represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxy group, a hydroxy group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group. R ２ represents an alkyl or arylcarbonyloxy group, or a nitrogen-free substituent. a is an integer of 1 to 4, and b is an integer of 0 to 3.

2. The R １ The silane-crosslinkable resin composition according to claim 1, wherein represents acetylacetone, ethyl acetoacetate, or a conjugate base thereof.

3. 2. The silane-crosslinkable resin composition according to claim 1, wherein M is aluminum, zirconium, or zinc.

4. The silane-crosslinkable resin composition according to claim 1, comprising a base resin, the base resin comprising a polyolefin resin.

5. 2. The silane-crosslinkable resin composition according to claim 1, comprising a base resin, wherein the content of the silanol condensation catalyst is 0.01 to 1 part by mass per 100 parts by mass of the base resin.

6. 2. The silane-crosslinkable resin composition according to claim 1, comprising a base resin and 0.5 to 400 parts by mass of an inorganic filler per 100 parts by mass of the base resin.

7. A silane-crosslinked resin molded article of the silane-crosslinkable resin composition according to any one of claims 1 to 6.

8. An electric wire having the silane-crosslinked resin molded product according to claim 7 as a coating layer.