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

Abstract

The invention provides a silane cross-linkable resin composition, a silane cross-linked resin molded article using the silane cross-linkable resin composition, and an electric wire. The silane-crosslinkable resin composition 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 DEG C for 30 minutes, and does not contain a tin-containing silanol condensation catalyst.

Description

Technical Field

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

[0002] Wiring materials such as insulated wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables) used in electrical / electronic equipment and automobiles have a tubular molded article formed of a crosslinked resin around the outer periphery of a conductor, etc., as an insulating coating (also simply referred to as a coating). Among crosslinked resins, silane crosslinked resins are particularly widely used as materials for wire coatings because they can be crosslinked and cured using the silane crosslinking method, which allows for simple and high-productivity crosslinking of silane crosslinkable resin compositions without the need for specialized equipment.

[0003] However, in the silane crosslinking method, a silanol condensation reaction is carried out as the final crosslinking reaction. As a silanol condensation catalyst to initiate or promote this condensation reaction, various compounds can be used. Among them, organotin compounds are often used because of their high catalytic activity and ability to achieve an appropriate crosslinking rate and crosslinking density.

[0004] This organotin compound sometimes exhibits environmental hormone effects, raising concerns about its safety.

[0005] Therefore, research is underway to convert tin-free silanol condensation catalysts. Examples include organic sulfonic acids and zinc carboxylates. Furthermore, Patent Document 1 specifically lists as "organometallic compounds other than organotin compounds" so-called organic carboxylic acid metal salts such as zinc laurate, zinc octoate, zinc stearate, aluminum adipate, aluminum laurate, and calcium adipate. Furthermore, Patent Document 2 specifically lists as "silanol condensation catalysts characterized by containing an organoaluminum compound" "aluminum acetylacetonate, aluminum lactate, aluminum tristearate, bis(2-ethylhexanoic acid)hydroxyaluminum, and aluminum glycinate."

[0006] However, organic sulfonic acid, zinc carboxylate etc. produce odors such as pungent smells when cross-linking reaction, for example, when manufacturing silane cross-linked resin moldings, which has problems in terms of environmental load and operator's safety. Moreover, when silanol condensation catalyst decomposes under high temperature conditions and causes the reaction speed (cross-linking speed) of silanol condensation reaction to become faster, the problem of appearance deterioration such as poor appearance and granular material is generated on the surface of molding. On the other hand, if the reaction speed (cross-linking speed) of silanol condensation reaction is slow, the problem of cross-linking density reduction just after manufacturing will be generated. Therefore, when using a silanol condensation catalyst that can produce odor, in order to suppress the generation of odor, and then in order to suppress the excessive high speed of cross-linking speed, it is necessary to manufacture at low temperatures, the generation suppression of odor and the high speed suppression of cross-linking speed and the cross-linking density (low speed suppression of cross-linking speed) become a compromise relationship, causing the problem of manufacturability and cross-linking speed. About such manufacturability and cross-linking speed problem, no research is carried out in patent documents 1 and 2.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-146150

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-193944 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] The present invention aims to provide a silane crosslinkable resin composition that uses a silanol condensation catalyst that is free of environmental hormone issues, allows a crosslinking reaction to proceed at an appropriate (moderate) crosslinking rate while suppressing odor generation, and enables the production of a silane crosslinked resin molded article having an excellent appearance and a high crosslinking density. Furthermore, the present invention aims to provide a silane crosslinked resin molded article and an electric wire using the above-described silane crosslinkable resin composition.

[0013] Means for solving problems

[0014] The present inventors have conducted intensive research on silane crosslinkable resin compositions and have discovered that, when a silanol condensation catalyst having a specific chemical structure represented by formula (1) described below and having a mass reduction rate of less than 10.0% by mass under the conditions described below is used as a silanol condensation catalyst, the generation of odor can be suppressed, for example, during the production of a silane crosslinked resin molded article, particularly during melt mixing, and the silanol condensation reaction can proceed at an appropriate crosslinking rate. As a result, a silane crosslinked resin molded article having an excellent appearance and a high crosslinking density can be produced with excellent manufacturability. Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0015] That is, the subject of the present invention is achieved by the following means.

[0016] <1> A silane crosslinkable resin composition comprising at least one silanol condensation catalyst represented by the following formula (1) and having a mass reduction rate of less than 10.0% when heated at 100°C for 30 minutes, and containing no tin-containing silanol condensation catalyst.

[0017] Formula (1): M(R1) a (R2) b

[0018] In formula (1), M represents aluminum, titanium, zirconium or zinc.

[0019] R1 represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxyl group, a hydroxyl group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group.

[0020] R2 represents an alkyl group or an arylcarbonyloxy group, or a substituent not containing nitrogen.

[0021] a is an integer of 1-4, and b is an integer of 0-3.

[0022] <2> <1> The silane crosslinkable resin composition, wherein the above R1 represents acetylacetone, ethyl acetoacetate or a conjugate base thereof.

[0023] <3> <1> or <2> The silane crosslinkable resin composition, wherein the M is aluminum, zirconium or zinc.

[0024] <4> <1> ~ <3> The silane crosslinkable resin composition described in any one of the preceding claims contains a base resin, and the base resin contains a polyolefin resin.

[0025] <5> <1> ~ <4> The silane crosslinkable resin composition described above contains a base resin, wherein the content of the silanol condensation catalyst is 0.01 to 1 parts by mass based on 100 parts by mass of the base resin.

[0026] <6> <1> ~ <5> The silane crosslinkable resin composition according to any one of the preceding claims contains a base resin and 0.5 to 400 parts by mass of an inorganic filler relative to 100 parts by mass of the base resin.

[0027] <7> One of the above <1> ~ <6> A silane crosslinking resin molded article of the silane crosslinking resin composition according to any one of the preceding claims.

[0028] <8> An electric wire having the above <7> The silane crosslinking resin molded body serves as a covering layer.

[0029] Effects of the Invention

[0030] The present invention provides a silane crosslinkable resin composition that uses a silanol condensation catalyst that is free of environmental hormone issues, allows a crosslinking reaction to proceed at an appropriate crosslinking rate while suppressing odor generation, and enables the production of a silane crosslinked resin molded article having an excellent appearance and a high crosslinking density. Furthermore, the present invention provides a silane crosslinked resin molded article and an electric wire using the silane crosslinkable resin composition.

[0031] The above and other features and advantages of the present invention will become more apparent from the following description. DETAILED DESCRIPTION

[0032] In the present invention, when describing the content and physical properties of a component by showing a numerical range, when describing the upper limit and lower limit of the numerical range respectively, any upper limit and lower limit can be appropriately combined to set to a specific numerical range. On the other hand, in the present invention, the numerical range represented by "to" refers to a range including the numerical values ​​recorded before and after "to" as the lower limit and upper limit. It should be noted that, in the present invention, when describing a plurality of numerical ranges, the upper limit and lower limit forming the numerical range are not limited to the specific combination recorded before and after "to" as a specific numerical range, and can be set to a numerical range formed by appropriately combining the upper limit and lower limit of each numerical range.

[0033] [Silane crosslinkable resin composition]

[0034] The silane crosslinkable resin composition of the present invention (hereinafter sometimes referred to simply as the crosslinkable composition of the present invention) contains at least one silanol condensation catalyst represented by formula (1) described below and having a mass reduction rate of less than 10.0% when heated at 100°C for 30 minutes.

[0035] On the other hand, the crosslinkable composition of the present invention does not contain a tin-containing silanol condensation catalyst. Here, a tin-containing silanol condensation catalyst refers to an organotin compound containing tin as a constituent element that functions as a catalyst for a silanol condensation reaction, and various well-known organotin compounds can be cited. For example, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, dibutyltin diacetate, etc. can be cited. In the present invention, the silane crosslinkable resin composition does not contain a tin-containing silanol condensation catalyst, which means that the silane crosslinkable resin composition does not actively contain or mix a tin-containing silanol condensation catalyst, but does not exclude the inevitable inclusion or mixing of a tin-containing silanol condensation catalyst. For example, the crosslinkable composition of the present invention may contain a tin-containing silanol condensation catalyst of 0.001 parts by mass or less relative to 100 parts by mass of the base resin.

[0036] The crosslinkable composition of the present invention contains at least one silanol condensation catalyst represented by the following formula (1) and having a mass reduction 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 the generation of odor. As a result, a silane crosslinked resin molded article having an excellent appearance and a high crosslinking density can be produced with excellent manufacturability. The crosslinkable composition of the present invention preferably contains one or two silanol condensation catalysts.

[0037] In the present invention, whether the "crosslinking rate" is appropriate cannot be determined solely by the content of the silanol condensation catalyst, the conditions of contact with water, etc. The appropriateness of the crosslinking rate can be determined and evaluated by maintaining the catalytic activity of the silanol condensation catalyst, for example, by passing the appearance test and the crosslinking density test (heating deformation rate) described in the Examples below.

[0038] <Silanol condensation catalyst represented by formula (1)>

[0039] The silanol condensation catalyst contained in the crosslinkable composition of the present invention is a compound represented by the following formula (1) and generally does not correspond to an environmental hormone (endocrine disruptor).

[0040] Formula (1): M(R1) a (R2) b

[0041] In formula (1), M represents a metal species, specifically aluminum, titanium, zirconium, or zinc. Among them, aluminum, zirconium, and zinc are preferred from the viewpoint of crosslinking speed.

[0042] R1 represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxyl group, a hydroxyl group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group.

[0043] In the present invention, the ligand having a specific group includes a ligand composed solely of 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 composed solely of an alkylcarbonyloxy group and a β-ketoester compound composed of an alkylcarbonyloxy group and other groups.

[0044] The above-mentioned groups contained in the ligand may be in the form of ions, conjugate bases, etc. as long as they coordinate to the metal species M. The ligand that can be used as R1 preferably has one to three of the above-mentioned groups, and preferably one or two.

[0045] Among the ligands that can be used as R1, a ligand having at least one of an alkyl group, a carbonyl group, an alkoxy group, and an arylcarbonyloxy group is preferred. 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 (alkylcarbonyl), and a combination of an aryl group and a carbonyl group (arylcarbonyl).

[0046] Examples of the ligand that can be used as R1 include a ligand having an alkylcarbonyl group and an alkylcarbonyloxy group (for example, a ketoester compound), and a ligand having two alkylcarbonyl groups (for example, a diketone compound).

[0047] The alkyl group that can be a ligand for R1 is not particularly limited and can be any of a linear, branched, dry, or cyclic chain, preferably a linear or branched chain. 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.

[0048] The alkoxy group that can be a ligand for R1 is not particularly limited, and examples thereof include an alkoxy group having an oxygen atom bonded to the terminal of an alkyl group that can be a ligand for R1. The number of carbon atoms in the alkyl group of the alkoxy group is preferably 1 to 24, more preferably 1 to 20, within the above range.

[0049] The aryl group that can be a ligand for R1 is not particularly limited and can be a monocyclic or 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.

[0050] The alkylcarbonyloxy group which may be a ligand for R1 is not particularly limited, and examples thereof include a group in which a carbonyloxy group is bonded to the terminal of an alkyl group which may be a ligand for R1 (alkyl-COO- group).

[0051] The arylcarbonyloxy group which may be a ligand for R1 is not particularly limited, and examples thereof include a group in which a carbonyloxy group is bonded to the terminal of an aryl group which may be a ligand for R1 (aryl-COO- group).

[0052] Examples of the ligand that can be used as R1 include diketone compounds such as acetylacetone and the like, and β-ketoester compounds such as ethyl acetoacetate and the like.

[0053] The diketone compound that can be used as R1 is not particularly limited, and examples thereof include 1,3-diketone compounds and 1,4-diketone compounds. 1,3-diketone compounds are preferred because they provide high stability of the silanol condensation catalyst and can reduce the mass loss rate described below.

[0054] As a 1,3-diketone compound, RA -CO-C(R B )2-CO-R C As R A and R C , respectively, include alkyl, aryl, alkoxy, carbonyl, carboxyl, keto, etc., preferably alkyl. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 5. A and R C Can be the same or different. A and R C The alkyl, aryl and alkoxy groups used are the same as the alkyl, aryl and alkoxy groups that can be used as R1. A and R C As for the ketone group, the group represented by -CO-R can be cited. Here, R is not particularly limited, and alkyl and aryl groups can be cited. The alkyl and aryl groups that can be used as R are not particularly limited, and are respectively the same as those used as R. A and R C The same alkyl and aryl groups can be used.

[0055] As R B , and may be a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a carbonyl group, a carboxyl group, a keto group, an alkylcarbonyl group, etc., preferably a hydrogen atom. B They may be the same or different, but are preferably both hydrogen atoms.

[0056] As the 1,3-diketone compound, R A and R C The compound in which all the groups are alkyl groups is preferably, for example, acetylacetone in which all the groups are methyl groups.

[0057] As a 1,4-diketone compound, R A -CO-C(R D )2-C(R E )2-CO-R C Indicates. R A and R C R with 1,3-diketone compounds A and R C Same meaning. As R D and R E , respectively with the R B The same meanings as above, preferably hydrogen atom, alkylcarbonyl group. D and R E They may be the same or different, but are preferably both hydrogen atoms.

[0058] As the 1,4-diketone compound, R A and R CExamples of the compounds each containing an alkyl group include 2,5-hexanedione (also referred to as acetonylacetone) and 3,4-diacetyl-2,5-hexanedione.

[0059] There is no particular limitation on the β-ketoester compound that can be used as R1. F -CO-C(R B )2-COO-R G The β-ketoester compound shown.

[0060] R F R with 1,3-diketone compounds A Same meaning. B R with 1,3-diketone compounds B Same meaning. G Examples thereof include an alkyl group, an aryl group, an alkoxy group, a carbonyl group, a carboxyl group, and a keto group, and an alkyl group is preferred.

[0061] For R G The alkyl group, aryl group and alkoxy group that can be used are the same as the alkyl group, aryl group and alkoxy group that can be used as the ligand of R1. G The number of carbon atoms in the alkyl group that can be used is preferably 1 to 40, more preferably 1 to 30, further preferably 1 to 25, and particularly preferably 1 to 20. G The ketone group that can be used as R A and R C The same keto groups can be used.

[0062] As β-ketoester, R F and R G Examples of the compounds all containing alkyl groups include methyl acetoacetate, ethyl acetoacetate, methyl pivaloyl acetate, methyl isobutyryl acetate, ethyl benzoyl acetate, ethyl p-methoxybenzoyl acetate, methyl hexanoyl acetate, methyl lauroyl acetate, and methyl palmitoyl acetate.

[0063] Examples of the conjugate base of the diketone compound or β-ketoester compound include compounds obtained by removing one hydrogen atom from the above diketone compound or β-ketoester compound. In general, preferably, one of the conjugate bases of R B or R D or R E The compounds can be obtained by adopting hydrogen atoms.

[0064] As for the ligand (including its conjugate base) having at least one of an alkyl group, a carbonyl group, a carboxyl group, a hydroxyl group, an alkoxy group, an aryl group, an alkoxy group, and an arylcarbonyloxy group that can be used as R1, in addition to the above-mentioned diketone compounds and β-ketoester compounds, there can be mentioned, for example, alcohol compounds having alkoxy groups such as methoxy, isopropoxy, n-butoxy, n-propoxy, 2-ethylhexyloxy, and stearyloxy, carboxylic acid compounds such as adipic acid, lactic acid, and stearic acid, dodecylbenzenesulfonic acid, octanediol, octanol, phosphate esters, various ethers, phenol, and the like.

[0065] R1 is preferably acetylacetone, ethyl acetoacetate, or a conjugate base thereof, from the viewpoint of being able to adjust the crosslinking rate (catalytic activity of the silanol condensation catalyst) to an appropriate rate and achieving both high appearance and crosslinking density.

[0066] In the silanol condensation catalyst represented by formula (1), R1 in formula (1) may bond to M as a monodentate ligand or as a bidentate ligand.

[0067] R2 in formula (1) is a substituent bonded to the metal atom M in formula (1) via a chemical bond other than a coordinate bond (usually a covalent bond or an ionic bond), and represents an alkyl group or an arylcarbonyloxy group, and a substituent not containing nitrogen.

[0068] The alkylcarbonyloxy group that can be used as R2 is not particularly limited as long as it is an anion of an aliphatic carboxylic acid. Examples thereof include alkylcarbonyloxy groups having a total carbon number of 2 to 40, including the carbon atom of the carbonyl group, and preferably alkylcarbonyloxy groups having a total carbon number of 2 to 20. Examples of the alkylcarbonyloxy group include the anion of stearic acid.

[0069] The arylcarbonyloxy group that can be used as R2 is not particularly limited as long as it is an anion of an aromatic carboxylic acid. Examples include arylcarbonyloxy groups having a total carbon number of 7 to 40, including the carbon atoms of the carbonyl group. Preferably, the arylcarbonyloxy group has a total carbon number of 7 to 20.

[0070] There are no particular limitations on the nitrogen-free group that can be used as R2, and any appropriate group can be used.

[0071] In the silanol condensation catalyst represented by the formula (1), R2 in the formula (1) is usually bonded to M via one bonding portion, but is not limited thereto.

[0072] In formula (1), a is an integer of 1 to 4, and preferably an integer of 2 to 4.

[0073] b is an integer of 0 to 3, and preferably 1 or 2.

[0074] Here, a+b is an integer of 8 or less, preferably an integer of 1-4.

[0075] As the silanol condensation catalyst represented by the above formula (1), from the perspective of maintaining an appropriate crosslinking rate (catalytic activity of the silanol condensation catalyst) and being able to achieve excellent appearance and high crosslinking density, a silanol condensation catalyst in which M is aluminum or zirconium and R1 is acetylacetone, ethyl acetoacetate or their conjugate base is preferred. Furthermore, when a is greater than 1, a silanol condensation catalyst in which b is 0 is more preferred.

[0076] Examples of the silanol condensation catalyst represented by the above formula (1) include zirconium acetylacetonate, zinc acetylacetonate, tris(ethylacetoacetoxy)aluminum, acetylacetonate aluminum bis(ethylacetoacetate), titanium tetraacetylacetonate, bisethylacetoacetate aluminum monoacetylacetonate, and tris(acetoacetate)aluminum.

[0077] The silanol condensation catalyst contained in the crosslinkable composition of the present invention has a mass reduction rate of less than 10.0% when heated at 100°C for 30 minutes. Specifically, the mass reduction rate before and after heating in the mass reduction rate measurement method described in the Examples is less than 10.0% by mass. Since many compounds that cause odor have a boiling point or decomposition temperature of 100°C or less at 1 atmosphere, the mass reduction rate has been proposed as one of the indicators for evaluating the thermal stability (thermal decomposition) and odor generation of silanol condensation catalysts. When the silanol condensation catalyst represented by formula (1) shows a mass reduction 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).

[0078] In the present invention, the mass reduction rate of the silanol condensation catalyst is preferably 5.0% by mass or less from the perspective of highly suppressing the generation of odor. The lower limit of the mass reduction rate is ideally 0% by mass, but is practically 0.0001% by mass or more.

[0079] As described below, the crosslinkable composition of the present invention contains the aforementioned silanol condensation catalyst, which is free of environmental hormone issues, and can carry out a crosslinking reaction at an appropriate crosslinking rate while suppressing the generation of odor, thereby enabling the production of a silane crosslinked resin molded article exhibiting an excellent appearance and a high crosslinking density.

[0080] Hereinafter, each component (excluding the silanol condensation catalyst) used in the present invention will be described.

[0081] Each component can be used alone or in combination of two or more.

[0082] It should be noted that in the present invention and this specification, when simply referred to as resin, it refers to a resin that is not grafted with a silane coupling agent. On the other hand, a resin that is grafted with a silane coupling agent is sometimes referred to as a silane crosslinking resin, a silane grafted resin, etc.

[0083] In addition, when referring to a (co)polymer, it is used to include the resin or rubber.

[0084] <Silane-crosslinking resin>

[0085] The crosslinkable composition of the present invention contains a resin exhibiting silane crosslinkability.

[0086] The resin exhibiting silane crosslinking properties is not particularly limited, and includes, for example, two forms: a composition (mixture) comprising a base resin serving as a basis for a crosslinkable composition and a silane coupling agent (in an unreacted state); and a silane crosslinking resin to which a silane coupling agent is graft-bonded.

[0087] In the form of a composition of a resin exhibiting silane crosslinking properties, it is preferred that the composition contain a base resin and a silane coupling agent, and further contain an organic peroxide.

[0088] The silane crosslinkable resin is formed from a silane coupling agent (described below) and a base resin, with the silane coupling agent being graft-bonded to the base resin. The graft reaction amount of the silane coupling agent in the 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 blending amount described below in the form of a composition will suffice.

[0089] The silane crosslinking resin may be synthesized by the method described below, or a commercially available product may be used. The silane crosslinking resin is obtained by reacting a base resin described below with a silane coupling agent described below at a temperature above the decomposition temperature of an organic peroxide described below. Specific reaction conditions are not particularly limited, but the melt mixing conditions of step (1) or step (a) described below are preferably used, provided that the content of the organic peroxide is set within the range described below. Commercially available silane crosslinking resins include Linklon (trade name, manufactured by Mitsubishi Chemical Corporation).

[0090] (Base resin)

[0091] The base resin forming the silane grafted 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, and resins including various (co)polymers can be mentioned, and polyolefin resins are preferred.

[0092] -Polyolefin resin-

[0093] 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 site (e.g., an unsaturated bond site of a carbon chain, a carbon atom having a hydrogen atom) that can undergo a grafting reaction with the grafting reaction site of a silane coupling agent. Examples of such polyolefin resins include polyethylene (PE), polypropylene (PP), ethylene-α-olefin copolymers, polyolefin resin copolymers having an acid copolymer component or an acid ester copolymer component, and styrene-based elastomers.

[0094] As polyethylene, there is no particular limitation as long as it is a polymer resin with ethylene as the main component. Examples include high-density polyethylene (HDPE), low-density polyethylene (LDPE), ultra-high molecular weight polyethylene (UHMW-PE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (VLDPE).

[0095] The polypropylene is not particularly limited as long as it is a polymer resin containing propylene as a main component. For example, in addition to a propylene homopolymer, there can be mentioned resins of random polypropylene and block polypropylene.

[0096] Preferred examples of ethylene-α-olefin copolymers include copolymers of ethylene and α-olefins having 3 to 12 carbon atoms (excluding the copolymers contained in polyethylene and polypropylene mentioned above). Examples include ethylene-propylene copolymers (excluding those contained in polypropylene), ethylene-butene copolymers, and ethylene-α-olefin copolymers synthesized in the presence of a single-site catalyst.

[0097] Furthermore, ethylene-α-olefin copolymer rubbers include ethylene-propylene rubber (EPM) which is a binary copolymer rubber and ethylene-propylene-diene rubber (EPDM) which is a ternary copolymer rubber with a conjugated diene compound or a non-conjugated diene compound.

[0098] The compound introduced into the resin of the polyolefin resin copolymer having an acid copolymer component or an acid ester copolymer 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 ester. The (meth)acrylic acid ester is not particularly limited, and examples thereof include alkyl (meth)acrylates. The alkyl group of the alkyl (meth)acrylate is preferably an alkyl group having 1 to 12 carbon atoms.

[0099] The polyolefin resin copolymer having an acid copolymer component or an acid ester copolymer 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).

[0100] Styrene-based elastomer refers to the elastomer that is made up of the polymer having the constituent from aromatic vinyl compound in molecule.As such styrene-based elastomer, block copolymer and random copolymer or their hydride etc. of conjugated diene compound and aromatic vinyl compound can be enumerated.Specifically, styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymer (SBS), hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber (HSBR), hydrogenated acrylonitrile-butadiene rubber (HNBR) etc. can be enumerated.

[0101] The polyolefin resin may be acid-modified with an unsaturated carboxylic acid compound such as (anhydrous) maleic acid.

[0102] Polyolefin resins may contain various oils used as plasticizers or softeners as needed. Examples of such oils include plasticizers used in polyolefin resins or mineral oil softeners for rubber. As oils, aromatic oils, paraffin oils, and naphthenic oils are preferably used.

[0103] - Composition of polyolefin resin -

[0104] The polyolefin resin may contain the above-mentioned specific resin alone or a plurality of resins. In the present invention, the polyolefin resin may contain only polyethylene, but preferably contains polyethylene, a styrene-based elastomer, and oil in view of the effect of improving mechanical properties by increasing crosslinking density.

[0105] When the polyolefin resin contains multiple resins, as long as the above-mentioned resins or oils are contained in a total content of 100% by mass, it can be appropriately set according to the physical properties, application, etc. of the silane crosslinked resin molded body. 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. In addition, the content of 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 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.

[0106] -Silane coupling agent-

[0107] The silane coupling agent (before the grafting reaction) used to form the silane crosslinking resin, and the silane coupling agent used in the form of a composition, are not particularly limited as long as they have a grafting reaction site (group or atom) capable of grafting with the grafting reaction site of the above-mentioned base resin in the presence of free radicals generated by the 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 those conventionally used in silane crosslinking methods. Among them, those having vinyl and alkoxysilyl groups at the ends are preferred. Examples of such silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, and vinyltriacetoxysilane; and (meth)acryloxysilanes such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane. Among these, vinyltrimethoxysilane and vinyltriethoxysilane are particularly preferred.

[0108] The silane coupling agent forming the silane grafted resin may be used alone or in combination of two or more.

[0109] -Organic peroxides-

[0110] When synthesizing a silane crosslinking resin, it is preferred to use an organic peroxide. Furthermore, when used as a base resin in the form of a composition, it is preferred to contain an organic peroxide. The organic peroxide has the following function: at least by thermal decomposition, it generates free radicals, and the free radical reaction promotes the grafting reaction between the silane coupling agent and the base resin. Such an organic peroxide is not particularly limited as long as it is a substance that generates free radicals. For example, it is preferably a substance having the general formula: R1A -OO-R 2A 、R 3A -OO-C(=O)R 4A 、R 5A C(=O)-OO(C=O)R 6A The compound shown. Here, R 1A ~R 6A Each independently represents an alkyl group, an aryl group or an acyl group. Preferably, R 1A ~R 6A All of them are alkyl groups, or any one of them is alkyl and the rest are acyl groups.

[0111] The decomposition temperature of the organic peroxide is preferably 80° C. to 195° C., particularly preferably 125° C. to 180° C., as measured by the method described in JP-A-2016-121203.

[0112] Examples of such organic peroxides include those described in paragraph

[0036] of JP-A-2016-121203, which is incorporated herein by reference, and the contents thereof are incorporated herein as part of the description of this specification. Among these, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Perhexa25B), and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne are preferred.

[0113] (Inorganic filler)

[0114] 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 presence of an inorganic filler can suppress volatilization of the silane coupling agent and condensation reactions between silane coupling agents. Consequently, it is possible to produce a silane crosslinked resin molded article having an excellent appearance, high strength, and high crosslinking density.

[0115] The inorganic filler is not particularly limited as long as it is a commonly used inorganic filler. However, it is preferably an inorganic filler having a site on its surface that can chemically bond to the reactive site of the silane coupling agent capable of undergoing silanol condensation via a hydrogen bond, a covalent bond, or an intermolecular bond. The site that can chemically bond to the reactive site of the silane coupling agent capable of undergoing silanol condensation is not particularly limited, and examples thereof include OH groups (hydroxyl groups, water molecules containing water or crystal water, OH groups such as carboxyl groups), amino groups, and SH groups.

[0116] If such an inorganic filler is coexisted during the silane grafting reaction, a silane grafted resin formed by a grafting reaction of a silane coupling agent that is weakly bonded to the inorganic filler and a silane grafted resin formed by a grafting reaction of a silane coupling agent that is strongly bonded to the inorganic filler can be formed. By subjecting these two silane grafted resins to a cross-linking reaction, a silane cross-linked resin molded body exhibiting a high cross-linking density (heat resistance, strength, etc.) can be formed. Here, examples of weak bonding with the inorganic filler include interactions based on hydrogen bonds, interactions between ions, partial charges or dipoles, and effects based on adsorption. In addition, examples of strong bonding with the inorganic filler include chemical bonding to chemically bondable sites on the surface of the inorganic filler.

[0117] As the inorganic filler, the inorganic filler commonly used in the resin composition can be enumerated, for example, aluminum hydroxide, magnesium hydroxide, boehmite, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum nitride, aluminum borate, whisker, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, hydrotalcite, talc and the like metal hydrates with compounds of hydroxyl or crystal water. In addition, boron nitride, silicon dioxide (crystalline silicon dioxide, amorphous silicon dioxide, etc.), carbon, clay (calcined clay), zinc oxide, tin oxide, titanium dioxide, molybdenum oxide, antimony trioxide, organosilicon compound, quartz, zinc borate, white carbon black, zinc borate, hydroxy zinc stannate, zinc stannate etc. can be enumerated. Among them, aluminum hydroxide or magnesium hydroxide are preferred.

[0118] The inorganic filler is preferably a particle, 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.

[0119] Inorganic fillers surface-treated with various surface treatment agents may be used.

[0120] The inorganic filler may be used alone or in combination of two or more.

[0121] <Additives>

[0122] The crosslinkable composition of the present invention may contain various additives commonly used in resin compositions. Examples of such additives include antioxidants, lubricants, metal deactivators, plasticizers, flame retardants, flame retardant aids, and (co)polymers other than those described for the base resin.

[0123] (Composition of Silane Crosslinkable Resin Composition)

[0124] The content of the silanol condensation catalyst in the silane crosslinkable resin composition is not particularly limited and can be appropriately set. 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). From the perspective of enabling the crosslinking reaction to proceed at an appropriate crosslinking rate while suppressing the generation of odor, it 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.

[0125] The content of the silane coupling agent in the silane crosslinkable resin composition is not particularly limited. However, from the perspective of suppressing the formation of protruding aggregates (gel particles) caused by crosslinked gel and the volatilization of the silane coupling agent, and enabling the production of a silane crosslinked resin molded article having an excellent appearance and a sufficient crosslinking density, the content 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 the polyolefin resin. For convenience, the content of the silane coupling agent in the silane crosslinkable resin is the amount calculated as the mass before the grafting reaction with the polyolefin resin (the amount of the silane coupling agent used in combination with the polyolefin resin).

[0126] In the case where the base resin is used in the form of a composition in the silane crosslinkable resin 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. From the perspective of further improving the appearance and crosslinking density of the silane crosslinkable resin molded article, it is preferably 0.1 to 0.2 parts by mass.

[0127] The content of the inorganic filler in the silane crosslinkable resin composition is not particularly limited. For example, it is preferably 0.5 to 400 parts by mass relative to 100 parts by mass of the base resin. From the perspective of further improving the appearance of the silane crosslinkable resin molded article, it is more preferably 30 to 280 parts by mass, further preferably 50 to 250 parts by mass, and particularly preferably 50 to 100 parts by mass.

[0128] The total content of additives in the silane crosslinkable resin composition is not particularly limited and can be appropriately set within a range that does not impair the effects of the present invention. For example, the content of the antioxidant is not particularly limited but is preferably 0.2 to 8 parts by mass per 100 parts by mass of the base resin.

[0129] [Silane crosslinked resin molded article]

[0130] 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. 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.

[0131] The silane crosslinked resin molded article has a crosslinked structure in which a base resin is silane-crosslinked. As described below, an inorganic filler may be introduced into the crosslinked structure. Preferably, the crosslinked structure is crosslinked via a silane coupling agent or a silanol condensate thereof, and the inorganic filler is introduced into a portion of the crosslinked structure.

[0132] The silane crosslinked resin molded article of the present invention has an excellent appearance and a high crosslinking density.

[0133] The contents of the various components in the silane crosslinked resin molded article of the present invention are generally substantially the same as those in the crosslinkable composition of the present invention. However, the organic peroxide and silanol condensation catalyst are generally decomposed and no longer present. The silane coupling agent content refers to the content before the grafting reaction and silanol condensation reaction, while the base resin content refers to the content before crosslinking.

[0134] The silane crosslinked resin molded article of the present invention has an excellent appearance and a high crosslinking density and is suitable for use in a variety of products (including semi-finished products, parts, and components). Specifically, it can be used as insulating coatings (including sheaths) for wiring materials, molding materials, power plugs, connectors, sleeves, cases, tape substrates, tubes, sheets, gaskets, spacers, cushioning materials, and shockproof materials. It is particularly suitable for use as insulating coatings for insulated wires used in vehicles such as automobiles and electric trains, and as sheaths for rubber-insulated cables.

[0135] [electric wire]

[0136] The electric wire of the present invention comprises the aforementioned silane crosslinked resin molded article, molded into a tubular shape, as an insulating layer covering the outer periphery of the conductor. Since the coating layer is formed from the silane crosslinked resin molded article exhibiting excellent appearance and a high crosslinking density, the electric wire of the present invention exhibits an excellent appearance free of gel particles and the like, and furthermore, exhibits high heat resistance and strength. Unless otherwise specified, the electric wire of the present invention refers to wiring materials used for internal or external wiring of electrical / electronic equipment, including insulated wires, cables, cords, optical fiber core wires, or optical fiber cords (optical fiber cables).

[0137] The electric wire of the present invention is similar to conventional electric wires used in various electrical and electronic equipment and industrial fields, except that the coating is formed from the silane crosslinked resin molded article of the present invention. When the electric wire coating comprises multiple layers, at least one layer may be formed from the silane crosslinked resin molded article of the present invention. The coating formed from the silane crosslinked resin molded article of the present invention is applied directly to the outer peripheral surface of the conductor or via other layers. The presence or absence of other layers and the materials used are appropriately determined depending on the type, application, and required properties of the electric wire.

[0138] Conventional conductors can be used, such as single or twisted wires (wires formed by longitudinally adding or twisting tensile fibers) of soft copper, copper alloy, or aluminum. In addition to bare wire, tinned materials or materials with an enameled insulating layer can also be used. The thickness of the coating formed from the silane crosslinked resin molded article of the present invention is not particularly limited, but is generally approximately 0.15 to 5 mm.

[0139] The electric wire of the present invention can be produced by molding the silane crosslinkable resin composition of the present invention into an annular layer (tubular shape) on the outer peripheral surface of a conductor, and then contacting the layer with water to cause a crosslinking reaction (silanol condensation reaction). Preferably, in the method for producing a silane crosslinkable resin molded article of the present invention described below, the molding step (2) can be configured as a step of co-extrusion molding the silane crosslinkable resin composition onto the outer periphery of the conductor using a coating device (extruder).

[0140] The silane crosslinked resin molded article of the present invention exhibits the above-mentioned excellent properties and can therefore be used in various applications other than the coating layer of electric wires, for example, as a substitute for resin molded articles such as heat-resistant sheets, heat-resistant films, power plugs, connectors, pipes, and vibration-proof materials.

[0141] [Method for producing silane crosslinkable resin composition]

[0142] The silane crosslinkable resin composition of the present invention can be prepared by mixing the above-mentioned components.

[0143] In the case of using a silane grafted resin, the silane grafted resin, silanol condensation catalyst, inorganic filler, and additives can be melt-mixed to prepare a silane crosslinkable resin composition. The melt-mixing method and conditions can be the same as those described in step (1) or step (a) below.

[0144] On the other hand, in a method using a composition containing a resin and a silane coupling agent as a base resin, that is, in a method in which a polyolefin resin and a silane coupling agent are subjected to a graft reaction when preparing a silane crosslinkable resin composition, the base resin, silane coupling agent, organic peroxide, silanol condensation catalyst, inorganic filler, and additives can be appropriately mixed to prepare the composition. The mixing method (mixing order) and conditions are not particularly limited, and the composition can preferably be produced by the step (1) of preparing the silane crosslinkable resin composition of the present invention described below.

[0145] [Method for producing a silane crosslinked resin molded body]

[0146] The silane crosslinked resin molded article of the present invention (hereinafter sometimes referred to as the molded article production 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 production method includes the following steps (1) to (3).

[0147] The method for producing a molded article of the present invention can be preferably applied to a method using a composition comprising a base resin and a silane coupling agent. In a method 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, an appropriate inorganic filler, and the like.

[0148] Step (1): A step of mixing a silane coupling agent, an organic peroxide, a silanol condensation catalyst and preferably an inorganic filler with a base resin to obtain a silane crosslinkable resin composition.

[0149] Step (2): Step of molding the silane crosslinkable resin composition to obtain a molded body

[0150] Step (3): a step of bringing the molded body into contact with water to obtain a silane crosslinked resin molded body

[0151] The above-mentioned step (1) may be performed by mixing the components all at once, but is preferably performed through the following steps depending on the usage (blending method) of the base resin.

[0152] That is, when performing step (1), if the entire base resin is melt-mixed in 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 step (a-2), step (1) comprises the following steps (a), (b), and (c).

[0153] Step (a): melt-mixing all or part of the base resin, the silane coupling agent, the organic peroxide, and preferably an inorganic filler at a temperature above the decomposition temperature of the organic peroxide to prepare a silane masterbatch.

[0154] Step (b): melt-mixing the remaining portion of the base resin with the silanol condensation catalyst to prepare a catalyst masterbatch

[0155] Step (c): melt-mixing the silane masterbatch with the silanol condensation catalyst or catalyst masterbatch

[0156] In the method for producing a molded article of the present invention, the blending amounts of the respective polymer components used as the base resin are the same as the aforementioned contents described above as part of the composition of the base resin. Furthermore, the blending amounts of the silane coupling agent, inorganic filler, silanol condensation catalyst, and additives are the same as those in the aforementioned silane crosslinkable resin composition.

[0157] In the method for producing a molded article of the present invention, the mixture obtained in step (1) may contain 100 parts by mass of the base resin. For example, in step (a), both the total amount (100 parts by mass) of the base resin and the part of the base resin may be mixed.

[0158] When a portion of the base resin is mixed in step (a), the proportion thereof is preferably 60% to 95% by mass, and more preferably 70% to 85% by mass, based on 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 based on the portion of the base resin mixed in step (a).

[0159] In addition, when a part of a base resin is mixed in step (a), the mixed component may be one kind or two or more kinds.

[0160] When an inorganic filler is used, a portion of the inorganic filler may be used in a step other than step (a), such as step (b). However, from the perspective of being able to construct a well-balanced crosslinked structure between the base resins (not through the inorganic filler) and a crosslinked structure involving the inorganic filler, it is preferred that the entire amount of the filler be used in step (a). When an inorganic filler is used in step (b), the amount used is not particularly limited and can be appropriately determined.

[0161] Various additives may be mixed in either step (a) or step (b).

[0162] <Process (1)>

[0163] In the method for producing a molded article of the present invention, step (1) is performed: 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 aforementioned mixing amounts to prepare the silane crosslinkable resin composition of the present invention as a mixture.

[0164] Step (1), namely, melt mixing of the base resin, the silane coupling agent, the inorganic filler, the organic peroxide, and the silanol condensation catalyst, is performed in the following order.

[0165] (Step (a))

[0166] In the method for producing a molded article of the present invention, step (a) is performed: all or part of the base resin, a silane coupling agent, an organic peroxide, preferably an inorganic filler, and appropriate additives are melt-mixed in the aforementioned mixing amounts at a temperature above the decomposition temperature of the organic peroxide to prepare a silane masterbatch (silane MB).

[0167] In step (a), the mixing temperature for melt mixing (also referred to as melt kneading) of the above components is above the decomposition temperature of the organic peroxide, preferably 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 used as a reference for the melt mixing temperature is the temperature under normal pressure (about 0.1 MPa). Mixing conditions such as the mixing time can be appropriately set. For example, the mixing time can be set to 1 minute to 25 minutes, preferably 3 minutes to 20 minutes. By melt mixing at a temperature above the decomposition temperature of the organic peroxide, the organic peroxide is thermally decomposed to generate free radicals, thereby carrying out a grafting reaction.

[0168] As mixing method, as long as it is the method normally used in the mixing of rubber, plastics etc., it is not particularly limited.As mixing apparatus, for example, single screw extruder, twin screw extruder, roller, Banbury mixer or various kneaders etc. can be used, preferably closed mixers such as Banbury mixer or various kneaders.

[0169] The mixing method of 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.

[0170] In the present invention, the order of mixing is not particularly limited, and the above-mentioned components can be mixed in any order. For example, the above-mentioned components can be melt-mixed at once, or they can be mixed in the following mixing order through the following steps (a-1) and (a-2). In particular, when an inorganic filler is used, it is preferred that step (a) be mixed through the following steps (a-1) and (a-2) in the following mixing order.

[0171] Step (a-1): a step of mixing an inorganic filler and a silane coupling agent to prepare a mixture

[0172] 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 higher than the decomposition temperature of the organic peroxide.

[0173] In step (a-1), by premixing the inorganic filler and the silane coupling agent, a well-balanced silane coupling agent can be formed, which is weakly bonded or adsorbed to the inorganic filler and strongly bonded or adsorbed to the inorganic filler. This effectively prevents volatilization of the silane coupling agent and condensation reactions between unadsorbed silane coupling agents during melt mixing in step (a-2). As a result, a silane-crosslinked resin molded article can be produced that exhibits a superior appearance and has improved mechanical properties (tensile strength) and heat resistance due to the silane crosslinking method.

[0174] The mixing method and mixing conditions in step (a-1) are not particularly limited. Examples include dry or wet mixing using a known mixer, kneader, etc., typically at a temperature below the decomposition temperature of the organic peroxide, preferably 10°C to 60°C, more preferably around room temperature (20°C to 25°C), for a period of several minutes to several hours. Dry mixing (dry blending) at a temperature below the decomposition temperature of the organic peroxide is preferred. Other dry mixing conditions can be appropriately determined.

[0175] In step (a-1), the base resin may be mixed as long as the temperature is kept lower than the above-mentioned decomposition temperature.

[0176] The organic peroxide only needs to be present during the melt mixing in step (a-2). It may be mixed in step (a-2), but is preferably mixed in step (a-1).

[0177] Next, the mixture obtained in step (a-1), all or a portion 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 above the decomposition temperature of the organic peroxide to prepare silane MB (step (a-2)). This produces a silane masterbatch containing a silane-grafted resin. The melt mixing in this step can suppress volatilization and self-condensation of the silane coupling agent while preventing excessive cross-linking reactions between the base resins (eg, the formation of gel particles).

[0178] The melt mixing method and conditions in the step (a-2) are not particularly limited, and the melt mixing method and conditions in the above-mentioned step (a) can be applied.

[0179] In step (a-2), there are at least the following considerations as to how the silane coupling agent and the base resin undergo a grafting reaction. Specifically, a method in which the silane coupling agent, which is weakly bonded or adsorbed to the inorganic filler, separates from the inorganic filler and undergoes a grafting reaction with the base resin. The cross-linked structure formed in step (3) described later by this method does not incorporate the inorganic filler and generally becomes a cross-linked structure via a silanol condensate between the silane coupling agents. Alternatively, a method in which the silane coupling agent, which is strongly bonded or adsorbed to the inorganic filler, undergoes a grafting reaction with the base resin while maintaining the bond or adsorption to the inorganic filler. The cross-linked structure formed in step (3) described later by this method incorporates the inorganic filler and becomes a cross-linked structure starting from the inorganic filler via the silane coupling agent bonded thereto. By combining the cross-linked structures of the two methods, a highly developed cross-linked structure can be constructed, which includes a cross-linked structure in which the inorganic filler is entangled in the silane cross-linked resin molded body.

[0180] In step (a), additives and the like may also be mixed. However, in step (a), it is preferred that a silanol condensation catalyst is not substantially mixed. Thus, the occurrence of the silanol condensation reaction of the silane coupling agent can be suppressed. In the present invention, "substantially not mixed" means that the silanol condensation catalyst that is inevitably present is not excluded, and the silanol condensation catalyst may be present as long as it is within a range that can suppress the silanol condensation reaction, for example, within a range of 0.01 parts by mass or less relative to 100 parts by mass of the base resin.

[0181] The silane MB prepared in step (a) comprises 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 is graft-bonded to the base resin to such an extent that the silane coupling agent can be formed in step (2) described below. The silane coupling agent graft-bonded to the base resin includes a silane coupling agent bonded to or adsorbed on the inorganic filler at a reactive site capable of silanol condensation.

[0182] Silane MB is preferably in the form of pellets or powder.

[0183] (Step (b))

[0184] In the method for producing a molded article of the present invention, step (b) is performed independently of step (a) or after step (a) to prepare a catalyst masterbatch (catalyst MB) by melt-mixing the remainder of the base resin (carrier resin) and the silanol condensation catalyst.

[0185] The melt mixing method and conditions in step (b) are not particularly limited, and the melt mixing method and conditions described in step (a) 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, more preferably 140 to 180°C. Other conditions, such as mixing time, can be appropriately set. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes.

[0186] Catalyst MB is preferably in the form of pellets or powder.

[0187] (Step (c))

[0188] In the method for producing a molded article of the present invention, the step (c) of melt-mixing the silane MB and the silanol condensation catalyst or the catalyst MB to obtain a mixture is then performed. Preferably, the silane MB and the catalyst MB are melt-mixed.

[0189] The mixing method is not particularly limited and is essentially the same as the melt mixing in step (a), requiring mixing at least at a temperature at which the base resin melts. The mixing conditions in step (c) are not particularly limited, and the mixing conditions described in step (a) can be applied. For example, the mixing temperature is appropriately selected based on the melting temperature of the base resin or carrier resin, preferably from 80°C to 250°C, more preferably from 100°C to 240°C, and even more preferably from 120°C to 200°C. Other conditions, such as mixing time, can be appropriately adjusted.

[0190] In the melt mixing of step (c), a melt mixing method and conditions are set to maintain the fluidity (formability) of the mixture. The silane grafted resin in the mixture is an uncrosslinked body in which the silane coupling agent has not undergone silanol condensation. In practice, if melt mixing is performed in step (c), partial crosslinking (partial crosslinking) is unavoidable, but the resulting mixture maintains formability. For example, in order to avoid the occurrence or progress of the silanol condensation reaction, it is preferred not to maintain the silane MB in a high temperature state for a long time while mixed with the silanol condensation catalyst.

[0191] In step (c), silane MB and silanol condensation catalyst or catalyst MB are preferably dry-mixed before melt-mixing. The dry-mixing method and conditions are not particularly limited, and examples thereof include the dry-mixing and conditions in step (a-1).

[0192] In this manner, the silane crosslinkable resin composition of the present invention is produced as a mixture.

[0193] The 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 reactive sites of the silane coupling agent capable of undergoing silanol condensation in the silane grafted resin may be bonded to or adsorbed on the inorganic filler, but silanol condensation does not occur. Therefore, the silane grafted resin includes a silane grafted resin formed by grafting a silane coupling agent bonded to or adsorbed on the inorganic filler and a base resin, and a silane grafted resin formed by grafting a silane coupling agent not bonded to or adsorbed on the inorganic filler and a base resin.

[0194] <Process (2)>

[0195] In the method for producing a silane crosslinked resin molded article of the present invention, the following step (2) is performed for molding the mixture (silane crosslinkable resin composition) obtained in the step (1) to obtain a molded article.

[0196] The molding method is not particularly limited and can be appropriately selected according to the form of the target product. 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 described below. When manufacturing wires, extrusion molding is preferred from the perspectives of productivity and the ability to co-extrude with a conductor.

[0197] The molding conditions (melt mixing conditions) are not particularly limited as long as they allow uniform mixing and molding and the silane crosslinkable resin composition of the present invention does not undergo silanol condensation reaction. For example, the melt mixing method and conditions of step (c) can be applied.

[0198] When using an extruder, the temperature of the extruder also depends on various conditions such as the type of base resin and the pulling speed of the conductor, but is preferably 120-180°C in the barrel and approximately 160-200°C in the crosshead (die). The screw speed and molding speed (line speed) of the extruder during extrusion molding are not particularly limited and can be appropriately set based on the characteristics and performance of the extruder, the extrusion volume (coating volume), etc. The line speed can generally be set to 1-20 m / min.

[0199] Step (2) can be carried out simultaneously with or continuously with 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 entering the coating device (extruder), followed by melt mixing in the coating device (step (c)), or the silane MB and the silanol condensation catalyst or catalyst MB are separately introduced into the coating device and melt mixed (step (c)), followed by (co-extrusion) molding onto the outer peripheral surface of a conductor or the like (step (2)).

[0200] In this manner, a molded article (uncrosslinked molded article) of the silane crosslinkable resin composition of the present invention is obtained. This molded article, like the silane crosslinkable resin composition of the present invention, cannot avoid partial crosslinking of the silane grafted resin, but is in a partially crosslinked state, maintaining the moldability that allows molding in step (2). Therefore, the silane crosslinkable resin molded article of the present invention is made into a crosslinked or finally crosslinked molded article by carrying out step (3).

[0201] <Process (3)>

[0202] In the method for producing a molded article of the present invention, the molded article obtained in step (2) is then contacted with water to produce the silane crosslinked resin molded article of the present invention. In the molded article obtained in step (2), the silane grafted resin is uncrosslinked. Therefore, in this step, a silanol condensation reaction (dehydration condensation reaction) occurs at the reaction sites capable of silanol condensation of the silane coupling agent grafted and bonded to the base resin, and is promoted (promoted), ultimately leading to silane crosslinking. In this manner, a silane crosslinked resin molded article crosslinked by silanol condensation of the silane coupling agent can be obtained.

[0203] The contact of the uncrosslinked molded body with water can be carried out by a common method. As long as the silanol condensation reaction is in the presence of water, it can be carried out even if it is placed in a temperature environment of about room temperature, for example, 20 to 25°C, so it is not necessary to actively contact with water. From the viewpoint of promoting the silanol condensation reaction (crosslinking reaction), it is preferred to actively contact the uncrosslinked molded body with water. As a contact method, the method (condition) commonly used in the silane crosslinking method can be mentioned, for example, a method of contact under a normal pressure environment can be mentioned, specifically, exposure to a saturated water vapor atmosphere, exposure to a high humidity environment, immersion in room temperature water or warm water (for example, 50°C to 90°C), placement in a wet heat tank, exposure to high-temperature water vapor, etc. can be mentioned. In addition, in order to allow water to penetrate into the interior during contact, pressure can also be applied.

[0204] In this manner, the silane crosslinked resin molded article of the present invention is produced.

[0205] The silane crosslinked resin molded article comprises a silane crosslinked resin formed by condensing a base resin (silane grafted resin) via a siloxane bond. Furthermore, when the silane crosslinked resin molded article contains an inorganic filler, the silane inorganic filler can bond to the silane coupling agent of the crosslinked base resin. Therefore, it is believed that the silane crosslinked resin includes: a crosslinked resin in which multiple base resins are bonded or adsorbed to the inorganic filler via a silane coupling agent, thereby bonding (crosslinking) the inorganic filler and the silane coupling agent; and a crosslinked resin in which the silane coupling agent grafted and bonded to the base resin undergoes a silanol condensation reaction by hydrolysis of the reactive sites capable of silanol condensation, thereby crosslinking the silane coupling agent (siloxane bond) (without the inorganic filler).

[0206] The method for producing a molded article of the present invention can suppress the generation of odors caused by decomposition of the silanol condensation catalyst during melt mixing in steps (1), (b), (c), and (2), particularly during melt mixing in step (b). Therefore, the silanol condensation catalyst having excellent catalytic activity represented by formula (1) can be included until step (3) without reducing its content, and the silanol condensation reaction (final crosslinking reaction) can proceed at an appropriate reaction rate (crosslinking rate). As a result, a silane crosslinked resin molded article having an excellent appearance and a high crosslinking density can be produced.

[0207] Example

[0208] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[0209] In Tables 1-1 and 1-2 (collectively referred to as Table 1), the numerical values ​​related to the compounding amount (content) of each example represent parts by mass unless otherwise specified. In addition, for each component, a blank column means that the compounding amount of the corresponding component is 0 parts by mass.

[0210] The details of each compound used in Examples and Comparative Examples are shown in Table 1 and below.

[0211] <Base resin>

[0212] (Silane grafted resin)

[0213] Linklon XCF 730M (trade name): silane-grafted polyethylene, silane coupling agent content 5% by mass, manufactured by Mitsubishi Chemical Corporation

[0214] (Polyolefin resin)

[0215] LLDPE: Evolue SP 0540 (trade name), linear low-density polyethylene, manufactured by PRIMEPOLYMER

[0216] SEEPS: SEPTON 4077 (trade name), styrene-ethylene-ethylene-propylene-styrene block copolymer, manufactured by KURARAY CO., LTD.

[0217] Oil: Cosmo Neutral 500 (trade name), paraffin oil, manufactured by Cosmo Oil Lubricants

[0218] <Silane coupling agent>

[0219] KBM-1003: Vinyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.

[0220] <Organic Peroxides>

[0221] PERHEXA25B: Chemical substance name, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, decomposition temperature 154°C, manufactured by NOF Corporation

[0222] (Inorganic filler)

[0223] Magnesium hydroxide: Magseeds FK 621 (trade name), manufactured by Kamishima Chemical Industry Co., Ltd.

[0224] <Silanol Condensation Catalyst>

[0225] Dioctyltin dilaurate: Adekastab OT-1 (trade name), manufactured by ADEKA Corporation

[0226] Zirconium acetylacetonate: NacemZr (trade name), manufactured by Nippon Chemical Industry Co., Ltd.

[0227] Zinc acetylacetonate: NacemZn (trade name), manufactured by Nippon Chemical Industry Co., Ltd.

[0228] Tetrastearyl titanate: TA-90 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0229] Tris(ethylacetoacetate)aluminum: AL-3215 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0230] Aluminum tri-sec-butoxide: AL-3001 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0231] Aluminum acetylacetonate bis(ethylacetoacetate): AL-3200 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0232] Titanium tetraacetylacetonate: TC-401 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0233] Tetrastearyl titanate n-butyl titanate: TA-21 (trade name), manufactured by Matsumoto Fine Chemical Co., Ltd.

[0234] Alkylamine, zirconium compound: K-KAT 672 (trade name), manufactured by KING INDUSTRIES

[0235] Alkylamine, zinc carboxylate: K-KAT 670 (trade name), manufactured by KING INDUSTRIES

[0236] Zinc compound, alkylamine: K-KAT 635 (trade name), manufactured by KING INDUSTRIES

[0237] Carboxylic acid metal salt: K-KAT 633 (trade name), manufactured by KING INDUSTRIES

[0238] Zinc compound, amine compound: K-KAT 614 (trade name), manufactured by KING INDUSTRIES

[0239] Alkyl aromatic sulfonic acid: NACURE CD-2150 (trade name), manufactured by KING INDUSTRIES

[0240] Dinonylnaphthalene disulfonic acid: NACURE 155 (trade name), manufactured by KING INDUSTRIES

[0241] <Examples 1 to 12 and Comparative Examples 1 to 13>

[0242] 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 at the mass ratio shown in the same column.

[0243] The components shown in the "Silane MB" column of Table 1 were melt-mixed at 170 to 200°C using a Banbury mixer and pelletized to prepare pellets of the obtained silane MB (step (a)).

[0244] Separately, the components listed in the "Catalyst MB" column of Table 1 were melt-mixed at the mass ratios shown in the same column using a Banbury mixer at 170 to 200°C and pelletized to obtain Catalyst MB pellets (step (b)).

[0245] Next, the prepared silane MB pellets and catalyst MB pellets were dry-mixed for 2 minutes at room temperature (25°C) using a tumble mixer immediately prior to extrusion molding to obtain a dry blend (dry-mixing step (c)). The mixing ratio of silane MB to catalyst MB at this time was the mass ratio shown in the "Silane MB" and "Catalyst MB" columns of Table 1.

[0246] Next, a 25 mm (screw diameter) extruder with L / D (ratio of screw effective length L to diameter D) = 25 was divided into three zones on the feeder side of the barrel portion at a die temperature of 200°C or less, and the extrusion temperature conditions were set to C3 = 170°C, C2 = 150°C, and C1 = 80°C. The prepared dry blend was fed into the extruder and melt-mixed at a screw speed of 40 rpm (melt mixing step of step (c), which is step (1) up to this point) while being subjected to a process of mixing the dry blended material in a molten copper wire. The outer diameter of the conductor becomes Extrusion coating was performed by adjusting the line speed so as to achieve a thickness of 0.8 mm to obtain a coated conductor (step (2)). In this case, the dry blend was melt-mixed in an extruder before extrusion molding to prepare a silane crosslinkable resin composition.

[0247] The obtained covered conductor was left to stand in an environment of room temperature (25° C.) and a relative humidity of 55% for 3 hours to allow the silane crosslinkable resin composition to come into contact with water (step (3)).

[0248] In this manner, an electric wire having a coating layer formed of a silane crosslinked resin molded body was produced.

[0249] <Examples 13 and 14>

[0250] An electric wire having a coating layer formed of a silane crosslinked resin molded body was produced in the same manner as in Example 1, except that step (b) was not performed in step (1) of Example 1, and that a silanol condensation catalyst was directly dry-blended in place of catalyst MB in the dry-blending step (c).

[0251] <Examples 15 and 16>

[0252] In step (1) of Example 1, step (a) was omitted, and a silane grafted resin was used as silane MB in step (c). An electric wire having a coating layer formed of a silane crosslinked resin molded body was produced in the same manner as in Example 1.

[0253] The following evaluations were conducted separately during the production process for the silanol condensation catalyst used and the produced electric wire (silane crosslinked resin molded article). The results are shown in Table 1.

[0254] <Mass Reduction Rate of Silanol Condensation Catalyst>

[0255] An aluminum cup containing each silanol condensation catalyst (about 1.000 g) was placed on a hot plate heated to 100° C. for 30 minutes, and the mass of the silanol condensation catalyst was measured. The mass reduction rate (mass %) before and after heating was calculated from the following formula (W).

[0256] Table 1 shows the obtained mass reduction rate (mass %). In addition, the case where the mass reduction rate (mass %) is less than 10.0% is regarded as acceptable and is represented by "0", and the case where it is 10.0% or more is regarded as unacceptable and is represented by "×".

[0257] Formula (W): [(w0-w) / w0]×100(%)

[0258] In the formula (W), w0 represents the initial mass (g) of the catalyst (before heating), and w represents the mass (g) of the catalyst after heating.

[0259] <Appearance Test of Wires>

[0260] The appearance test of the electric wire is a test for evaluating the crosslinking rate (silanol condensation reaction rate) of the silane crosslinkable resin composition. The surface of the coating layer of each electric wire is visually observed to evaluate the occurrence of appearance defects and the presence of particulate matter.

[0261] Specifically, the case where no appearance defects or particulate matter can be confirmed on the surface of the coating layer is rated as good and indicated by "0". The case where an electric wire is manufactured and the occurrence of appearance defects and the presence of particulate matter are confirmed on the surface of the coating layer of an electric wire with a manufacturing length of 5 m (excluding 5 m), but the occurrence of appearance defects or the presence of particulate matter cannot be confirmed on the surface of the coating layer of an electric wire with a manufacturing length of more than 5 m is rated as qualified and indicated by "△". The case where the occurrence of appearance defects or the presence of particulate matter are confirmed on the surfaces of the coating layers of both electric wires with a manufacturing length of 5 m (excluding 5 m) and electric wires of more than 5 m, or the occurrence of appearance defects and the presence of particulate matter can be confirmed only when the manufacturing length is more than 5 m, is rated as unqualified and indicated by "×".

[0262] In this test, "appearance defects" refer to defects on the surface (appearance) of the molded article (coating layer) caused by foaming, as well as defects such as irregularities and roughness known as melt fracture. Furthermore, "granular matter" refers to gel-like protruding aggregates (gel granular matter) present on the surface of the molded article (coating layer) formed by final crosslinking (silanol condensation reaction), or aggregated granular matter formed by incompatibility of the raw materials.

[0263] <Environmental (environmental hormone issues)>

[0264] If the silanol condensation catalyst used is not registered as a substance of very high concern (SVHC) under the REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulations, it is considered as qualified and indicated by "0", and if it is registered, it is considered as unqualified and indicated by "×".

[0265] <Determination of Heating Deformation Rate>

[0266] The heat deformation rate is a low-speed test for evaluating the crosslinking density (heat resistance of the cover layer) and the crosslinking speed, and is conducted in accordance with UL 758.

[0267] 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 was calculated as ([(coating layer thickness before heating - coating layer thickness after heating) / coating layer thickness before heating] × 100) as the heating deformation rate.

[0268] When the heat deformation rate is less than 20%, the silanol condensation reaction proceeds rapidly and a high crosslinking density can be constructed. It is indicated by "◎" as very good, when it is 20% or more and less than 40% as good, it is indicated by "○", when it is 40% or more and less than 50% as acceptable, it is indicated by "△", and when it is 50% or more, it is indicated by "×" as unacceptable.

[0269] <Comprehensive Evaluation>

[0270] The above tests were performed, and the results were expressed as "◯" if all the tests were passed, and "×" if any of the tests were failed, and "failed".

[0271]

[0272]

[0273] The following can be seen from the results shown in Table 1.

[0274] That is, in Comparative Examples 1 and 2, which used a silanol condensation catalyst as an organotin compound, when the mass change rate of the silanol catalyst was 0.0 mass%, the generation of odor could be suppressed and the catalytic activity was high, but there was a problem with environmental hormones, and there was a high possibility that it would become unusable in the future. On the other hand, Comparative Examples 3 to 13, which used a silanol condensation catalyst that did not satisfy the formula (1) or mass reduction rate specified in the present invention, although there was no concern about environmental hormones, all generated odor. Furthermore, Comparative Examples 8, 12, and 13 were unable to undergo a crosslinking reaction at an appropriate crosslinking rate. As a result, none of the comparative examples were able to produce a silane crosslinked resin molded body that suppressed the generation of odor, had an excellent appearance, and had a high crosslinking density with excellent manufacturability.

[0275] In contrast, Examples 1 to 16, which used a silanol condensation catalyst satisfying the formula (1) and mass reduction rate specified in the present invention, were able to carry out the crosslinking reaction at an appropriate crosslinking rate while suppressing the generation of odor. Consequently, in each of these examples, silane crosslinked resin molded articles having excellent appearance and high crosslinking density were produced with high manufacturability (productivity) while using a silanol condensation catalyst that is not subject to environmental hormone effects. This demonstrates that the silane crosslinkable resin composition of the present invention can adequately comply with environmental regulations even when using a silanol condensation catalyst, which has high catalytic activity and is not subject to environmental hormone effects, instead of an organotin compound.

[0276] Although the present invention has been described together with its embodiments, the applicant believes that unless otherwise specified, the present invention is not intended to be limited to any details described and should be broadly interpreted without departing from the spirit and scope of the invention disclosed in the appended claims.

[0277] 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 as a part of the description of this specification.

Claims

1. A silane crosslinkable resin composition comprising at least one silanol condensation catalyst represented by the following formula (1) and having a mass reduction rate of less than 10.0% when heated at 100° C. for 30 minutes, and containing no tin-containing silanol condensation catalyst. Formula (1): M(R1) a (R2) b In formula (1), M represents aluminum, titanium, zirconium, or zinc; R1 represents a ligand having at least one group selected from the group consisting of an alkyl group, a carbonyl group, a carboxyl group, a hydroxyl group, an alkoxy group, an aryl group, an alkylcarbonyloxy group, and an arylcarbonyloxy group; R2 represents an alkyl or arylcarbonyloxy group, or a substituent not containing nitrogen; a is an integer of 1-4, and b is an integer of 0-3.

2. The silane crosslinkable resin composition according to claim 1, wherein The R1 represents acetylacetone, ethyl acetoacetate or their conjugate base.

3. The silane crosslinkable resin composition according to claim 1 or 2, wherein The M is aluminum, zirconium or zinc. 4 . The silane crosslinkable resin composition according to claim 1 , comprising a base resin containing a polyolefin resin. The silane crosslinkable resin composition according to any one of claims 1 to 4, comprising a base resin, wherein the content of the silanol condensation catalyst is 0.01 to 1 part by mass based on 100 parts by mass of the base resin. The silane crosslinkable resin composition according to any one of claims 1 to 5, 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, comprising the silane crosslinked resin composition according to claim 1 . 8 . An electric wire comprising the silane crosslinked resin molded article according to claim 7 as a coating layer.

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