Liquid silane-grafted olefin composition, silane-crosslinked cured product thereof, and production methods for same

Abstract

Provided are: a liquid silane-grafted olefin composition containing 1-200 parts by mass of an inorganic filler and a liquid silane-grafted olefin obtained by grafting 10-150 parts by mass of a silane coupling agent with respect to 100 parts by mass of a liquid olefin polymer; a silane-crosslinked cured product thereof; and a production method comprising a specific step for grafting, at a temperature of 50-200°C, 10-150 parts by mass of a silane coupling agent to 100 parts by mass of a liquid olefin polymer in the presence of 0.2-5.0 parts by mass of an organic peroxide.

Description

Liquid silane-grafted olefin composition, silane-crosslinked cured product thereof, and methods for producing the same

[0001] The present invention relates to a liquid silane-grafted olefin composition, a silane-crosslinked cured product thereof, and methods for producing these.

[0002] Various resin or rubber molded articles are used as coating layers (insulators, sheaths, etc.) provided on wiring materials such as insulated wires, cables, cords, optical fiber cores, and optical fiber cords (optical fiber cables) used in the fields of electrical and electronic equipment and industry, and as various molded articles such as packing and sheets. Crosslinkable compositions such as crosslinkable resin compositions and crosslinkable rubber compositions are often used as materials for forming such molded articles. For example, Patent Document 1 proposes a rubber composition that "contains a liquid modified ethylene-based random copolymer (A) and a rubber component (B), wherein the liquid modified ethylene-based random copolymer (A) is an ethylene-based random copolymer (a0) graft-copolymerized with an unsaturated silane compound component" and satisfies specific requirements (a-1) to (a-5) (requirements (a-1) to (a-5) are omitted), and also proposes a "molded article obtained by crosslinking this rubber composition." Furthermore, Patent Document 2 proposes a specific "liquid modified ethylene random copolymer in which an unsaturated silane compound is graft-copolymerized onto an ethylene random copolymer" as a modifier for resins or silicon-containing rubbery polymers, as well as a rubbery polymer composition containing this liquid modified ethylene random copolymer, a specific elastic copolymer, a silicon-containing rubbery polymer, and other components.

[0003] JP 2021-024912 A JP 61-246215 A

[0004] As a material for forming the above-mentioned molded body, a solid crosslinkable composition containing a high-molecular-weight, solid polymer (resin or rubber) as a main component is usually used. For example, the rubber composition described in Patent Document 1 contains a liquid modified ethylene random copolymer (A) as a modifier for the rubber composition, but since the main component is a rubber component (B), the composition as a whole is solid. Such a solid crosslinkable composition is heated to a temperature at which it becomes molten, and then molded to carry out the final crosslinking reaction. As such, a solid crosslinkable composition requires a heating step for plasticization during molding, and therefore must be handled in a molten state using manufacturing equipment such as an extruder or injection molding machine, which is inefficient to work with. Moreover, this also leads to increased manufacturing costs. The same applies to the rubber polymer composition described in Patent Document 2.

[0005] On the other hand, liquid crosslinkable compositions containing low-molecular-weight polybutadiene or the like are also known as materials for forming the above-mentioned molded bodies. Although such liquid crosslinkable compositions do not need to be heated to a molten state during molding, the final crosslinking reaction must be carried out by external forces such as heat or light. Therefore, even liquid crosslinkable compositions still require special crosslinking equipment (e.g., a crosslinking tube), which reduces workability and increases production costs. Furthermore, liquid crosslinkable compositions can easily become discolored due to uneven mixing, and if a discolored crosslinkable composition is subjected to a final crosslinking reaction (silanol condensation reaction), the appearance of the resulting crosslinked cured product will be impaired.

[0006] As described above, conventional crosslinkable compositions, whether solid or liquid, used as materials for forming molded articles require a heating step and heating equipment or special crosslinking equipment during molding or the final crosslinking reaction, resulting in poor workability and in the failure to obtain crosslinked cured products with good appearance. On the other hand, conventional liquid crosslinkable compositions require heating conditions in the final crosslinking reaction, otherwise crosslinking does not proceed sufficiently and sufficient mechanical properties are not obtained after the crosslinking reaction. Patent Documents 1 and 2 specifically describe rubber compositions containing 10 parts by mass of a liquid modified ethylene random copolymer and 50 parts by mass of white carbon per 120 parts by mass of rubber. However, these rubber compositions contain five times the amount of white carbon relative to the liquid modified ethylene random copolymer, and neither patent document considers liquid crosslinkable compositions that do not contain rubber or the like, including the white carbon content, from the above-mentioned perspective.

[0007] The present invention aims to provide a liquid silane-grafted olefin composition that does not discolor or the like and has excellent workability, which eliminates the need for a heating step or heating device during molding, and which does not require a crosslinking device such as a crosslinking tube during the final crosslinking reaction while allowing the final crosslinking reaction to proceed quickly, thereby producing a silane-crosslinked cured product with excellent appearance and mechanical properties, and a silane-crosslinked cured product (silanol condensation cured product) of the liquid silane-grafted olefin composition as a crosslinked molded product with excellent appearance and mechanical properties. Another object of the present invention is to provide methods for producing the liquid silane-grafted olefin composition and the silane-crosslinked cured product thereof.

[0008] The present inventors have conducted extensive research into materials for forming molded articles and have found that grafting a silane coupling agent onto a liquid olefin polymer can produce a liquid silane-grafted olefin while suppressing discoloration and other problems, and that using this liquid silane-grafted olefin in combination with an inorganic filler can increase the amount of silane coupling agent used for the grafting reaction. Furthermore, they have found that by combining a liquid silane-grafted olefin and an inorganic filler to produce a liquid silane-grafted olefin composition that is silane-crosslinkable and maintains a liquid state as a whole, no heating step or heating device is required during molding, thereby achieving excellent workability. Furthermore, they have found that this crosslinkable liquid composition can be rapidly crosslinked (silanol condensation reaction) under mild conditions and with simple operations, resulting in a solid silane-crosslinked cured product with excellent appearance and mechanical properties, without the need for a crosslinking device such as a crosslinking tube. As described above, the present inventors have found that the above-mentioned crosslinkable liquid composition can simultaneously solve the problems of both conventional solid and liquid compositions. Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0009] That is, the object of the present invention has been achieved by the following means. <1> A liquid silane-grafted olefin composition containing a liquid silane-grafted olefin obtained by grafting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a site that undergoes a grafting reaction with the liquid olefin polymer, and 1 to 200 parts by mass of an inorganic filler per 100 parts by mass of the liquid olefin polymer. <2> The liquid silane-grafted olefin composition according to <1>, wherein the amount of the silane coupling agent to be grafted is 10 to 80 parts by mass. <3> The liquid silane-grafted olefin composition according to <1> or <2>, containing 10 to 150 parts by mass of the inorganic filler. <4> The liquid silane-grafted olefin composition according to <1> or <2>, wherein the inorganic filler has a BET specific surface area of ​​10 m ２<5> The liquid silane-grafted olefin composition according to any one of <1> to <3>, comprising 1 to 30 parts by mass of an inorganic filler having a BET specific surface area of ​​more than 100 m / g. ２ <6> The liquid silane-grafted olefin composition according to any one of <1> to <4>, comprising 1 to 30 parts by mass of an inorganic filler having a BET specific surface area of ​​more than 100 m / g. ２ <7> A silane-crosslinked cured product of the liquid silane-grafted olefin composition according to any one of <1> to <6> above. <8> A method for producing a liquid silane-grafted olefin composition according to any one of <1> to <6>, comprising a step of grafting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a site that undergoes a graft reaction with the liquid olefin polymer in the presence of 0.2 to 5.0 parts by mass of an organic peroxide at a temperature of 50 to 200°C, wherein in carrying out the step, the grafting reaction is carried out in the co-presence of a total amount of 1 to 200 parts by mass of an inorganic filler relative to 100 parts by mass of the liquid olefin polymer, or the grafting reaction is carried out in the co-presence of a part of the inorganic filler or in the absence of the inorganic filler, and then the liquid silane-grafted olefin composition is mixed with the remainder or all of the inorganic filler. <9> A method for producing a silane-crosslinked cured product, comprising contacting the liquid silane-grafted olefin composition obtained by the method for producing a liquid silane-grafted olefin composition described in <8> above with water in the presence of a silanol condensation catalyst to produce a silane-crosslinked cured product of the liquid silane-grafted olefin composition.

[0010] The present invention provides a liquid silane-grafted olefin composition that does not discolor or otherwise exhibits excellent workability and that can produce a silane-crosslinked cured product with excellent appearance and mechanical properties by eliminating the need for a heating step or heating device during molding and eliminating the need for a crosslinking device such as a crosslinking tube during the final crosslinking reaction while still allowing the final crosslinking reaction to proceed rapidly, and also provides a silane-crosslinked cured product of the liquid silane-grafted olefin composition that is a crosslinked molded product with excellent appearance and mechanical properties.The present invention also provides a method for producing the liquid silane-grafted olefin composition and the silane-crosslinked cured product thereof.These and other features and advantages of the present invention will become more apparent from the description below.

[0011] In the present invention, when describing the content, physical properties, etc. of a component by indicating a numerical range, if 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, when describing multiple numerical ranges expressed using "to", the upper and lower limits forming the numerical range are not limited to the specific combination written before and after "to" as a specific numerical range, but can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that 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 upper and lower limits.

[0012] [Liquid Silane-Grafted Olefin Composition] The liquid silane-grafted olefin composition of the present invention contains a liquid silane-grafted olefin and an inorganic filler, as described below, and maintains a liquid state as a whole. However, the inorganic filler is usually dispersed in a solid state (e.g., particulate) in the liquid silane-grafted olefin, although this varies depending on the type and content of the inorganic filler. In the present invention, "liquid" means that the composition is liquid at room temperature (25°C) and normal pressure (1 atm), i.e., is liquid. Specifically, it means that the (absolute) viscosity measured with a Brookfield viscometer at room temperature and normal pressure is 100 Pa s or less. In the present invention, the viscosity at room temperature and normal pressure is preferably 3 Pa s or less. On the other hand, in the present invention, the term "solid (state)" refers to a state that does not exhibit fluidity at room temperature and normal pressure, and for example, means that the (absolute) viscosity measured with a Brookfield viscometer at room temperature and normal pressure is 10,000 Pa s or more.

[0013] The liquid silane-grafted olefin composition is a composition containing a liquid silane-grafted olefin obtained by grafting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a site for grafting reaction, and 1 to 200 parts by mass of an inorganic filler per 100 parts by mass of the liquid olefin polymer. This liquid silane-grafted olefin composition is a silane-crosslinkable liquid composition containing a liquid silane-grafted olefin in which the silane coupling agent is grafted to the liquid olefin polymer, and an inorganic filler. Here, the inorganic filler may be bonded to or adsorbed to the silane coupling agent. This liquid silane-grafted olefin and liquid silane-grafted olefin composition are preferably prepared by the method for producing a liquid silane-grafted olefin composition of the present invention, which will be described later.

[0014] In the liquid silane-grafted olefin composition of the present invention, the kinematic viscosity at 100°C under normal pressure is not particularly limited, but is preferably 1,000 mm ２ / s or less, and ２When the liquid silane-grafted olefin composition exhibits a kinematic viscosity within the above range, the composition can be easily removed from the vessel after the reaction and the efficiency of purification by separation is improved.

[0015] The liquid silane-grafted olefin composition of the present invention is liquid under normal temperature and pressure conditions, and as described below, when contacted with water by a silane crosslinking method, it cures to form a solid composition (a silane-crosslinked cured product). Therefore, by utilizing its liquid properties, this liquid silane-grafted olefin composition eliminates the need for a heating step or heating device during molding, demonstrating excellent workability. Furthermore, because the liquid silane-grafted olefin composition of the present invention is silane-crosslinkable, it eliminates the need for an excessively high-temperature heating step using a crosslinking device such as a crosslinking tube, and can be contacted with water under mild conditions, resulting in high workability. Furthermore, the final crosslinking reaction (silanol condensation reaction) proceeds rapidly, establishing a sufficient crosslinked structure and resulting in a crosslinked cured product with excellent appearance and mechanical properties.

[0016] [Silane-Crosslinked Cured Product of Liquid Silane-Grafted Olefin Composition] The silane-crosslinked cured product of the liquid silane-grafted olefin composition of the present invention (hereinafter referred to as the silane-crosslinked cured product of the present invention) is a crosslinked cured product (silanol condensation cured product) obtained by subjecting the silanol condensation-capable reactive sites of the silane coupling agent of the liquid silane-grafted olefin composition of the present invention, particularly the liquid silane-grafted olefin, to a silanol condensation reaction. As described below, this silane-crosslinked cured product contains a crosslinked olefin polymer obtained by crosslinking a liquid olefin polymer via a silane coupling agent or a silanol condensate thereof, and also a crosslinked olefin polymer obtained by incorporating an inorganic filler and crosslinking. In this way, the crosslinked olefin polymer has a crosslinked structure via the silane coupling agent or a silanol condensate thereof, and also a crosslinked structure initiated by the inorganic filler. The liquid silane-grafted olefin composition of the present invention is converted from a liquid composition (liquid composition) to a solid composition (crosslinked cured product) by contacting it with water in the presence of a silanol condensation catalyst using a silane crosslinking method. The lan-crosslinked cured product of the present invention is usually a molded product, but may also be in a shapeless (unmolded) bulk state.

[0017] Each component used in the present invention will be described below. Each component may be used alone or in combination of two or more.

[0018] <Liquid Olefin Polymer> The liquid olefin polymer may be a (co)polymer of an olefin compound that is liquid at room temperature and normal pressure, and any known (co)polymer may be used without any particular limitation. In the present invention, the olefin compound refers to a compound having an ethylenically unsaturated group, and includes alkene compounds having one ethylenically unsaturated group in the molecule, such as ethylene and propylene, as well as polyene compounds having two or more ethylenically unsaturated groups in the molecule. Examples of polyene compounds include conjugated diene compounds such as butadiene and isoprene.

[0019] The liquid olefin polymer preferably has a site in the main chain or at its terminal that can undergo grafting reaction with a silane coupling agent (described later) by radicals generated from an organic peroxide. Examples of the site that can undergo grafting reaction include an unsaturated bond site in a carbon chain and a carbon atom having a hydrogen atom.

[0020] The liquid olefin polymer is not particularly limited, and examples thereof include ethylene random copolymers, liquid diene polymers, organic mineral oils, and hydrogenated or modified products thereof. Examples of liquid diene polymers include liquid butadiene polymers, liquid isoprene polymers, and liquid styrene-butadiene copolymers. Of these, ethylene random copolymers, liquid butadiene polymers, and liquid isoprene polymers are preferred. Examples of modified products include acid-modified products.

[0021] (Ethylene-Based Random Copolymer) Examples of the ethylene-based random copolymer include copolymers having a constituent component derived from ethylene and a constituent component derived from an α-olefin. The α-olefin is not particularly limited, but is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 3 to 10 carbon atoms, and even more preferably propylene. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene. The ethylene-based random copolymer may have one or more constituent components derived from an α-olefin.

[0022] The ethylene random copolymer may contain a constituent component derived from at least one other monomer selected from polar group-containing compounds, aromatic vinyl compounds, and cyclic olefins.

[0023] The polar group-containing compound is not particularly limited, and examples thereof include α,β-unsaturated carboxylic acid compounds such as acrylic acid, methacrylic acid, fumaric acid, and maleic anhydride, and metal salt compounds thereof such as sodium salts; α,β-unsaturated carboxylic acid ester compounds such as methyl acrylate, ethyl acrylate, n-propyl acrylate, methyl methacrylate, ethyl methacrylate, and n-propyl methacrylate; vinyl ester compounds such as vinyl acetate and vinyl propionate; and unsaturated glycidyl compounds such as glycidyl acrylate and glycidyl methacrylate. The aromatic vinyl compound is not particularly limited, and examples thereof include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, methoxystyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylbenzyl acetate, hydroxystyrene, p-chlorostyrene, divinylbenzene, α-methylstyrene, and allylbenzene. The cyclic olefin is not particularly limited, and a cyclic olefin having 3 to 30 carbon atoms is preferred, and a cyclic olefin having 3 to 20 carbon atoms is more preferred. Examples of the cyclic olefin include cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, and tetracyclododecene.

[0024] The content of ethylene-derived components (also referred to as ethylene content) relative to all components in the ethylene-based random copolymer is not particularly limited and is appropriately set taking into consideration the range in which the crystalline and liquid state of the ethylene-based random copolymer can be maintained. The ethylene content is, for example, preferably 30 to 90 mol%, more preferably 30 to 80 mol%, even more preferably 40 to 75 mol%, and particularly preferably 40 to 60 mol%. The ethylene content can be determined by the method described in Patent Document 1. The content of α-olefin-derived components (also referred to as α-olefin content) relative to all components in the ethylene-based random copolymer is not particularly limited and is appropriately set taking into consideration the ethylene content, etc. The content of components derived from other monomers in the ethylene-based random copolymer is not particularly limited and can be, for example, 20 parts by mass or less, preferably 10 parts by mass or less, relative to 100 parts by mass of the total of the ethylene-derived components and the α-olefin-derived components.

[0025] The molecular weight (number average molecular weight, weight average molecular weight, etc.) of the ethylene random copolymer is not particularly limited and may be appropriately set within a range in which the copolymer can be maintained in a liquid state. The molecular weight distribution of the ethylene random copolymer is also not particularly limited and may be appropriately set.

[0026] The ethylene random copolymer may be a commercially available product or may be appropriately synthesized. Examples of commercially available products include LUCANT (trade name, manufactured by Mitsui Chemicals, Inc., ethylene-α-olefin oligomer). When synthesizing an ethylene random copolymer, ethylene and an α-olefin can be polymerized by a known polymerization method. For example, the contents of Patent Document 1 can be appropriately referenced, and the contents thereof are incorporated herein in their entirety as part of the present specification.

[0027] (Liquid Diene Polymer) The liquid diene polymer is not particularly limited, but examples thereof include polymers obtained by polymerizing at least a conjugated diene compound, and, if necessary, copolymerizing both a conjugated diene compound and a vinyl-substituted aromatic compound. The liquid diene polymer may have one or more constituent components derived from a conjugated diene compound. Furthermore, the liquid diene polymer may not have a constituent component derived from a vinyl-substituted aromatic compound, and when it has a constituent component derived from a vinyl-substituted aromatic compound, it may have one or more constituent components derived from a vinyl-substituted aromatic compound.

[0028] The conjugated diene compound is not particularly limited as long as it is a polymerizable monomer compound, but a conjugated diene compound having 4 to 12 carbon atoms is preferred, and a conjugated diene compound having 4 to 8 carbon atoms is more preferred. Examples of such conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-heptadiene. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of ease of industrial availability. The vinyl-substituted aromatic compound is not particularly limited as long as it is a monomer copolymerizable with the conjugated diene compound, but a monovinyl aromatic compound is preferred. Examples of monovinyl aromatic compounds include styrene, p-methylstyrene, α-methylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene, and styrene is preferred from the viewpoint of ease of industrial availability.

[0029] Preferred liquid diene polymers include homopolymers of 1,3-butadiene, homopolymers of isoprene, copolymers of 1,3-butadiene and styrene (SBR), copolymers of isoprene and styrene, and hydrogenated versions of these.

[0030] In the homopolymer of 1,3-butadiene and the homopolymer of isoprene, the amount of vinyl groups in the constituent component derived from 1,3-butadiene or isoprene is not particularly limited and may be set appropriately.

[0031] The copolymer of 1,3-butadiene and styrene may be a random copolymer or a block copolymer, but a random copolymer is preferred. In the copolymer of 1,3-butadiene and styrene, the content of the styrene-derived component is not particularly limited, but for example, it is preferably more than 0% by mass and not more than 50% by mass, and more preferably more than 0% by mass and not more than 20% by mass, relative to 100% by mass of all components of the copolymer. Furthermore, in the copolymer of 1,3-butadiene and styrene, the amount of vinyl groups in the 1,3-butadiene-derived component is not particularly limited and may be set appropriately.

[0032] The molecular weight (number average molecular weight, weight average molecular weight, etc.) of the liquid diene polymer is not particularly limited and may be appropriately set within a range in which the liquid state can be maintained. The molecular weight distribution of the liquid diene polymer is also not particularly limited and may be appropriately set.

[0033] The liquid diene polymer may be a commercially available product or may be appropriately synthesized. Examples of commercially available products include LBR (trade name, manufactured by Kuraray Co., Ltd., liquid butadiene), LIR (trade name, manufactured by Kuraray Co., Ltd., liquid isoprene), and LSBR (trade name, manufactured by Kuraray Co., Ltd., liquid styrene butadiene). When synthesizing a liquid diene polymer, a conjugated diene compound and an appropriate vinyl-substituted aromatic compound can be polymerized by a known polymerization method.

[0034] (Organic Mineral Oil) Examples of organic mineral oils include those that are commonly used in resin compositions and the like, such as paraffin-based oils and various other synthetic oils.

[0035] <Silane Coupling Agent> The silane coupling agent has a grafting site (a functional group such as a group or an ethylenically unsaturated group) that can undergo grafting reaction with a grafting site of a liquid olefin polymer in the presence of radicals generated by decomposition of an organic peroxide. The silane coupling agent also has a hydrolyzable silyl group (e.g., an alkoxysilyl group) as a silanol condensable reactive site.

[0036] The silane coupling agent is not particularly limited, and includes silane coupling agents conventionally used in silane crosslinking methods.Specific examples include vinylalkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, and vinyltriacetoxysilane, and (meth)acryloxyalkoxysilanes such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane.Among these, vinyltrimethoxysilane or vinyltriethoxysilane is particularly preferred.The grafting rate of the silane coupling agent to the liquid olefin polymer (the amount of silane coupling agent grafted and bonded to the liquid olefin polymer through a grafting reaction with the liquid olefin polymer) is not particularly limited, and is within the range achieved by the grafting reaction according to the method for producing the liquid silane-grafted olefin composition of the present invention described below.

[0037] <Inorganic Filler> The liquid silane-grafted olefin composition of the present invention contains an inorganic filler. While any commonly used inorganic filler may be used, those having a site on their surface that can chemically bond with the silanol condensation-capable reactive site of the silane coupling agent via a hydrogen bond, covalent bond, or intermolecular bond are preferred. Sites that can chemically bond with the silane coupling agent include, but are not limited to, OH groups (hydroxyl groups, water molecules containing water or crystallization, OH groups such as carboxyl groups), amino groups, and SH groups. When an inorganic filler having a site that can chemically bond is used, particularly when the inorganic filler is present during the grafting reaction between the liquid olefin and the silane coupling agent, two liquid silane-grafted olefins can be formed: one in which the silane coupling agent that is weakly bonded to the inorganic filler undergoes a grafting reaction, and the other in which the silane coupling agent that is strongly bonded to the inorganic filler undergoes a grafting reaction. By crosslinking these two types of liquid silane-grafted olefins, a silane-crosslinked cured product with excellent appearance and mechanical properties can be formed. Here, examples of weak bonds with the inorganic filler include interactions due to hydrogen bonds, interactions between ions, partial charges or dipoles, and actions due to adsorption. Examples of strong bonds with the inorganic filler include chemical bonds with sites on the surface of the inorganic filler that can form chemical bonds.

[0038] 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. Among these, aluminum hydroxide, magnesium hydroxide, silica, talc, and calcium carbonate are preferred.

[0039] The inorganic filler contained in the liquid silane-grafted olefin composition of the present invention can improve the mechanical properties of the silane-crosslinked cured product while maintaining an excellent appearance. In particular, the effect of improving the mechanical properties can be achieved by adjusting the BET specific surface area (in the present invention, simply referred to as "specific surface area") of the inorganic filler, and the specific surface area of ​​the inorganic filler can be appropriately set in consideration of the appearance and mechanical properties. Specifically, in terms of the silane-crosslinked cured product, maintaining an excellent appearance while having a high effect of improving the mechanical properties even with a small content, it is preferable that the inorganic filler have a large specific surface area, for example, 10 m ２ More preferably, it is greater than 100m ２ More preferably, it is greater than 300m ２ In this case, the upper limit of the specific surface area is not particularly limited, but in practice it is 400 m ２ / g or less.

[0040] In the present invention, even inorganic fillers with a small specific surface area can be used in the liquid silane-grafted olefin composition of the present invention because they are effective in improving the mechanical properties of the silane-crosslinked cured product. Examples of inorganic fillers with a small specific surface area include inorganic fillers with a specific surface area of ​​10 m or less. ２ / g or less is preferred, ２ The lower limit of the specific surface area is not particularly limited, but in practice it is 0.1 m ２ / g or more, and 1m ２ / g or more is preferable. The specific surface area of ​​the inorganic filler is a value measured in accordance with the "carrier gas method" of JIS Z 8830:2013 using nitrogen gas as an adsorbate. For example, it can be measured using a specific surface area / pore distribution measuring device "Flowsorb" (manufactured by Shimadzu Corporation). The specific surface area can be adjusted and set by adjusting the particle size through the manufacturing method or classification, as well as by changing the shape depending on the chemical species or crystalline structure, or by selecting a porous material.

[0041] 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. The inorganic filler may also be surface-treated with various surface treatment agents.

[0042] The total content of inorganic fillers in the liquid silane-grafted olefin composition is 1 to 200 parts by mass per 100 parts by mass of the liquid olefin polymer constituting the liquid silane-grafted olefin. When the silane-grafted olefin composition of the present invention contains inorganic fillers in this range, a crosslinked cured product having excellent appearance and mechanical properties can be formed without impairing the workability, etc. of the composition. In order to achieve high levels of both appearance and mechanical properties of the silane-crosslinked cured product without impairing the properties of the composition, the total content of inorganic fillers in the composition is preferably 3 to 150 parts by mass, more preferably 10 to 150 parts by mass, even more preferably 10 to 100 parts by mass, and particularly preferably 10 to 55 parts by mass.

[0043] In the present invention, either the inorganic filler having a large specific surface area or the inorganic filler having a small specific surface area can be used as the inorganic filler, but it is preferable to use the inorganic filler having a large specific surface area in combination with the inorganic filler having a small specific surface area, in that the liquid silane-grafted olefin composition has good workability, can achieve a uniform mixed state, and can uniformly proceed with the crosslinking reaction to achieve high levels of both appearance and mechanical properties of the silane-crosslinked cured product. The content of the inorganic filler having a large specific surface area among the inorganic fillers can be determined in consideration of the total content of the inorganic fillers, whether it is used alone or in combination with the inorganic filler having a small specific surface area. For example, in the composition, ２ / g (specific surface area is 100 m ２ / g) can be 0 to 50 parts by mass, but is preferably 1 to 30 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 3 to 10 parts by mass, in order to achieve high levels of both appearance and mechanical properties of the silane-crosslinked cured product without impairing the workability of the composition and the uniformity of the crosslinking reaction. ２The content L100 of the inorganic filler exceeding 1 / g can be set to 0 to 35 parts by mass, but is preferably 1 to 30, more preferably 1 to 10 parts by mass, and even more preferably 3 to 10 parts by mass, in that the workability of the composition is not impaired and the uniformity of the crosslinking reaction is more excellent, thereby achieving high levels of both appearance and mechanical properties of the silane-crosslinked cured product.

[0044] In the composition, a specific surface area of ​​10 m ２ The content S of the inorganic filler having a specific surface area of ​​0.05 to 1.0 g / g or less can be set to 0 to 200 parts by mass either when used alone or when used in combination with the inorganic filler having a large specific surface area. However, from the viewpoint of achieving high levels of both the appearance and mechanical properties of the silane-crosslinked cured product without impairing the workability of the composition or the uniformity of the crosslinking reaction, the content S is preferably 0 to 150 parts by mass, more preferably 10 to 150 parts by mass, even more preferably 10 to 100 parts by mass, and particularly preferably 10 to 50 parts by mass.

[0045] In the present invention, in either case where an inorganic filler having a large specific surface area and an inorganic filler having a small specific surface area are used in combination, the ratio [S / (L10 or L100)] of the content L10 or L100 of the inorganic filler having a large specific surface area to the content S of the inorganic filler having a small specific surface area (excluding the case where L10 or L100 is 0 parts by mass) is not particularly limited and can be determined appropriately. For example, taking into consideration the workability of the liquid silane-grafted olefin composition, the mixed state, the uniformity of the crosslinking reaction, and further the appearance and mechanical properties of the silane-crosslinked cured product, it can be, for example, more than 0 and 70 or less, preferably 1 to 50, and more preferably 0.2 to 10.

[0046] <Organic Peroxide> In the present invention, when obtaining a liquid silane-grafted olefin, it is preferable to use an organic peroxide. The organic peroxide generates radicals by thermal decomposition and acts as a catalyst to initiate a grafting reaction of the silane coupling agent to the liquid olefin polymer by radical reaction. There are no particular limitations on the organic peroxide, and any organic peroxide used in a conventional silane crosslinking method can be used without any particular limitations. Examples of such organic peroxides include those represented by the general formula: R １ -OO-R ２ , R ３ -OO-C(=O)R ４ , R ５ C(=O)-OO(C=O)R ６ In this case, a compound represented by the formula: １ ~R ６ Each of R independently represents an alkyl group, an aryl group, or an acyl group. １ ~R ６ Among these, those in which all groups are alkyl groups, or those in which one is an alkyl group and the other is an acyl group, are preferred.Specific examples include benzoyl peroxide, dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3.

[0047] <Silanol Condensation Catalyst> In the present invention, the liquid silane-grafted olefin composition may or may not contain a silanol condensation catalyst. A liquid silane-grafted olefin composition that does not contain a silanol condensation catalyst is preferably contacted with the silanol condensation catalyst together with water during the silanol condensation reaction. The silanol condensation catalyst used in the present invention promotes the silanol condensation reaction (dehydration condensation reaction) of silanol condensable reactive sites of the silane coupling agent grafted onto the liquid olefin polymer in the presence of water. This condensation reaction crosslinks the liquid olefin polymer via the silane coupling agent. The silanol condensation catalyst is not particularly limited, and examples thereof include organotin compounds, organoaluminum compounds, organozirconium compounds, organozinc compounds, metal soaps, and platinum compounds. Organotin compounds and organoaluminum compounds are preferred. Examples of organotin compounds include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate. Examples of organoaluminum compounds include acetylacetonate aluminum, aluminum tris(ethylacetoacetate), aluminum tri-2-butoxide, and acetylacetonatoaluminum bis(ethylacetylacetoacetate). When the liquid silane-grafted olefin composition contains a silanol condensation catalyst, the content of the silanol condensation catalyst in the liquid silane-grafted olefin composition is not particularly limited and may be determined appropriately. For example, the content is preferably 0.0001 to 1.5 parts by mass, more preferably 0.0001 to 0.5 parts by mass, and even more preferably 0.001 to 0.2 parts by mass, per 100 parts by mass of the liquid olefin polymer.

[0048] <Other Components> The liquid silane-grafted olefin composition of the present invention may contain optional components (other components) other than the above-mentioned components. Examples of other components include various components such as additives commonly used in resin compositions, such as (co)polymers other than liquid olefin polymers, flame retardants, flame retardant aids, antioxidants (antioxidants), lubricants, crosslinking agents, crosslinking aids, etc. The content of other components in the liquid silane-grafted olefin composition is not particularly limited and may be appropriately set within a range that does not impair the object of the present invention, particularly within a range that does not impair the liquid state.

[0049] The liquid silane-grafted olefin composition of the present invention preferably does not contain, as a polymer component, a solid (co)polymer, such as various resins or rubbers, etc. In the present invention, "not containing a solid (co)polymer" includes an embodiment in which the content of the solid (co)polymer is 0 parts by mass relative to 100 parts by mass of the liquid olefin polymer, as well as an embodiment in which the content is 5 parts by mass or less.

[0050] [Method for Producing Liquid Silane-Grafted Olefin Composition] The liquid silane-grafted olefin composition of the present invention can be prepared by any suitable method, for example, by mixing or melt-mixing the liquid silane-grafted olefin, inorganic filler, and optionally other components. However, it is preferred to produce the liquid silane-grafted olefin composition by the method for producing the liquid silane-grafted olefin composition described below, since this method suppresses discoloration and other problems during preparation and enables the production of a silane-crosslinked cured product exhibiting excellent appearance and mechanical properties. The method for producing the liquid silane-grafted olefin composition of the present invention (sometimes simply referred to as the method for producing the liquid composition of the present invention) comprises the step of reacting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a moiety capable of undergoing a grafting reaction with the liquid olefin polymer in the presence of 0.2 to 5.0 parts by mass of an organic peroxide at a temperature of 50 to 200°C. In this step, the grafting reaction is carried out in the presence of all of 1 to 200 parts by mass of the inorganic filler, or the grafting reaction is carried out in the presence of a portion of the inorganic filler or in the absence of the inorganic filler, and then mixed with the remainder or all of the inorganic filler.

[0051] The method for producing a liquid composition of the present invention can use a reactor capable of stirring, such as an open-type reactor or a closed-type reactor (a reactor capable of being sealed). In the present invention, a closed-type reactor is preferred because it allows the grafting reaction to proceed uniformly, suppresses discoloration or coloration, and produces a liquid silane-grafted olefin composition with a uniform viscosity, thereby producing a silane-crosslinked cured product with excellent appearance and mechanical properties. Examples of the reactor include a general reaction vessel, an autoclave, an autoclave equipped with a stirrer, etc., and a general closed-type reaction vessel or an autoclave equipped with a stirrer is preferred.

[0052] In the liquid composition production method of the present invention, the amount of silane coupling agent mixed (used) is 10 to 150 parts by mass per 100 parts by mass of the liquid olefin polymer. When the amount of silane coupling agent mixed is within this range, the grafting reaction proceeds uniformly without discoloration, and the silanol condensation reaction proceeds rapidly under mild conditions, allowing the preparation of a liquid silane-grafted olefin composition capable of building a sufficient crosslinked structure. Furthermore, it becomes possible to produce a silane-crosslinked cured product that exhibits excellent appearance and mechanical properties. The amount of silane coupling agent mixed is more preferably 10 to 80 parts by mass, and even more preferably 30 to 80 parts by mass, per 100 parts by mass of the liquid olefin polymer, in order to achieve a high level of both suppression of discoloration and rapid progress of the silanol condensation reaction.

[0053] In the liquid composition production method of the present invention, the amount of organic peroxide mixed (used) is 0.2 to 5.0 parts by mass per 100 parts by mass of the liquid olefin polymer. When the amount of organic peroxide mixed is within this range, the grafting reaction proceeds efficiently, suppressing discoloration and other problems while allowing the silanol condensation reaction to proceed rapidly under mild conditions, making it possible to prepare a liquid silane-grafted olefin composition capable of building a sufficient crosslinked structure. It also makes it possible to produce a silane-crosslinked cured product that exhibits excellent appearance and mechanical properties. The amount of organic peroxide mixed is more preferably 0.5 to 5.0 parts by mass, and even more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of the liquid olefin polymer, in terms of achieving high levels of suppression of discoloration and other problems while allowing the silanol condensation reaction to proceed rapidly.

[0054] In the method for producing a liquid composition of the present invention, the amount of inorganic filler mixed (used) is the same as the content of inorganic filler in the above-mentioned liquid silane-grafted olefin composition of the present invention.

[0055] In the method for producing a liquid composition of the present invention, a liquid olefin polymer and a silane coupling agent are subjected to a grafting reaction at a temperature of 50 to 200°C in the above-mentioned mixed amounts. This reaction can be carried out in the presence of an organic peroxide, and is preferably carried out by mixing the liquid olefin polymer, silane coupling agent, and organic peroxide in the above-mentioned mixed amounts at a temperature of 50 to 200°C. More preferably, the reaction is carried out by injecting (charging) the liquid olefin polymer into a reactor (preferably a sealed reactor) set at 50 to 200°C, and then injecting (charging, adding) the silane coupling agent and organic peroxide together or separately into the liquid olefin polymer at 50 to 200°C, preferably the liquid olefin polymer heated to 50 to 200°C, thereby mixing the liquid olefin polymer, silane coupling agent, and organic peroxide. In this more preferred mixing method, the injection time (injection rate) of the silane coupling agent and organic peroxide cannot be uniquely determined depending on the apparatus used, and is set appropriately depending on the type, performance, etc. of the apparatus. For example, a flow rate of 2 to 10 mL / min per 100 g of liquid olefin polymer is preferred. When the silane coupling agent and the organic peroxide are injected into a reactor together, a mixture of the silane coupling agent and the organic peroxide is prepared. The silane coupling agent and the organic peroxide are mixed using a known mixer or the like, typically under non-heated or low-temperature heated conditions, preferably at 10 to 60°C, more preferably near room temperature (20 to 35°C), for several minutes to several hours, by dry or wet mixing methods and conditions. Preferably, dry mixing (dry blending) is performed under non-heated or low-temperature heated conditions.

[0056] In the method for producing a liquid composition of the present invention, the reaction temperature is set to 50 to 200°C, in a temperature range of at least the one-hour half-life temperature and at most the one-minute half-life temperature of the organic peroxide. The reaction temperature may be the installation temperature of the reactor, but is preferably the temperature of the liquid olefin polymer, or a normal heating temperature. The reaction time is set appropriately depending on the progress of the grafting reaction, but is preferably, for example, 10 minutes or more, more preferably 30 minutes to 2 hours, and even more preferably 45 minutes to 1 hour. The reaction time is defined as the elapsed time from the time (starting point) when the liquid olefin polymer, silane coupling agent, and organic peroxide are mixed at a predetermined temperature. Stirring is continued during the reaction, with the stirring speed and other factors being set appropriately. In the reaction between the liquid olefin polymer and the silane coupling agent, it is preferable to substantially eliminate the presence of a silanol condensation catalyst. Here, "substantially free of silanol condensation catalyst" does not mean excluding the unavoidably present silanol condensation catalyst, and for example, the silanol condensation catalyst may be present in an amount of 0.01 part by mass or less per 100 parts by mass of the liquid olefin polymer.

[0057] In the method for producing a liquid composition of the present invention, the grafting reaction in the above step may be carried out in the presence or absence of an inorganic filler. When the grafting reaction is carried out in the presence of an inorganic filler, a mixture containing a liquid silane-grafted olefin and the inorganic filler (including cases where the inorganic filler is bound to or adsorbed to the silane coupling agent) is obtained, and when the grafting reaction is carried out in the absence of an inorganic filler, a liquid silane-grafted olefin is obtained.

[0058] The grafting reaction is preferably carried out in the presence of an inorganic filler, since this allows the grafting reaction to proceed while suppressing the volatilization and condensation reaction of the silane coupling agent, and allows for the formation of a balanced mixture of the silane coupling agent weakly bonded to the inorganic filler and the silane coupling agent strongly bonded to the inorganic filler. In this case, the inorganic filler may be used in its entirety or in part. When a portion of the inorganic filler is present during the grafting reaction, the amount of the inorganic filler may be a portion of the total content. For example, assuming the total content (1 to 200 parts by mass) is 100% by mass, the amount of the inorganic filler may be 3% by mass or more but less than 100% by mass, and preferably 10% by mass or more but less than 100% by mass. It is preferable that the inorganic filler to be present is an inorganic filler with a large specific surface area, as described above, in terms of the dispersibility of the resulting mixture and, further, the dispersibility of the liquid silane-grafted olefin composition. When the grafting reaction is carried out in the presence of an inorganic filler, the method for mixing the components is not particularly limited. The liquid olefin polymer, silane coupling agent, organic peroxide, and inorganic filler may be mixed all at once or sequentially. For example, the inorganic filler may be mixed alone, or may be premixed with a silane coupling agent and then mixed with the liquid olefin polymer. Similarly to the silane coupling agent, the inorganic filler can be added to a liquid olefin polymer heated to 50 to 200°C. However, it is preferable that the inorganic filler be added to the reaction apparatus in advance (before heating) either together with or separately from the liquid olefin polymer. The method for mixing the liquid olefin polymer and the silane coupling agent is as described above. Even when the grafting reaction is carried out in the presence of an inorganic filler, the reaction method and reaction conditions for the grafting reaction are the same as those described above.

[0059] When the grafting reaction is carried out in the presence of a portion of the inorganic filler, or when the grafting reaction is carried out in the absence of the inorganic filler, the remaining or all of the inorganic filler is mixed in after the grafting reaction. That is, the mixture of the liquid silane-grafted olefin or inorganic filler obtained by the grafting reaction is mixed with the remaining or all of the inorganic filler. The mixing method and mixing conditions are not particularly limited, and can be, for example, the method and conditions used in the grafting reaction. The grafting reaction and the subsequent mixing can also be carried out continuously.

[0060] In the liquid composition production method of the present invention, when a liquid silane-grafted olefin composition containing a silanol condensation catalyst is produced, the liquid silane-grafted olefin composition and the silanol condensation catalyst are mixed, for example, under the conditions for preparing the mixture of the silane coupling agent and the organic peroxide. The amount of the silanol condensation catalyst mixed (used) is not particularly limited and can be set appropriately. In order to allow the silanol condensation reaction to proceed rapidly under mild conditions, the amount of the silanol condensation catalyst mixed can be set in the same range as the content of the silanol condensation catalyst in the liquid silane-grafted olefin composition.

[0061] In this manner, a liquid silane-grafted olefin composition containing a liquid silane-grafted olefin and an inorganic filler can be produced.

[0062] [Method for producing a silane-crosslinked cured product] The silane-crosslinked cured product (silanol condensation cured product) of the present invention can be produced by any suitable method for subjecting silanol-condensable reactive sites of a silane coupling agent in a liquid silane-grafted olefin composition to a silanol condensation reaction, and is preferably produced by the method for producing a silane-crosslinked cured product of the present invention described below, since it is possible to produce a silane-crosslinked cured product having a sufficient crosslinked structure and excellent appearance and mechanical properties. The method for producing a silane-crosslinked cured product of the present invention (sometimes simply referred to as the method for producing a cured product of the present invention) comprises a step of contacting the liquid silane-grafted olefin composition obtained by the method for producing a liquid silane-grafted olefin composition of the present invention with water in the presence of a silanol condensation catalyst.

[0063] In this step, the amount of silanol condensation catalyst used is not particularly limited, and for example, is preferably 0.0001 to 1.5 parts by mass, more preferably 0.0001 to 0.5 parts by mass, and even more preferably 0.001 to 0.2 parts by mass, per 100 parts by mass of the liquid olefin polymer in the liquid silane-grafted olefin composition. In this step, the method for contacting the liquid silane-grafted olefin composition (including the molded article described below) with water in the presence of the silanol condensation catalyst is not particularly limited, and examples include a method of contacting a liquid silane-grafted olefin composition containing a silanol condensation catalyst with water, and a method of contacting a liquid silane-grafted olefin composition not containing a silanol condensation catalyst with a silanol condensation catalyst and water. The contact of the liquid silane-grafted olefin composition with water can be carried out by a method commonly used in silane crosslinking methods. The silanol condensation reaction proceeds in the presence of moisture even under mild conditions, such as leaving the composition at room temperature, for example, at a temperature of about 20 to 25°C. This eliminates the need for a special crosslinking device such as a crosslinking tube, and does not require active contact with water. From the perspective of promoting the silanol condensation reaction (crosslinking reaction), it is preferable to actively contact the liquid silane-grafted olefin composition with water. Examples of contacting methods include methods (conditions) typically applied to silane crosslinking methods, such as contacting the composition with water under mild conditions in an ambient pressure environment. Specific examples include exposure to a saturated water vapor atmosphere, exposure to a high-humidity environment, immersion in room-temperature water or hot water (e.g., 50 to 90°C), and placement in a moist heat bath. The composition can be contacted with water under agitation to increase the efficiency of contact with water, and pressure can be applied during contact to allow water to penetrate the composition.

[0064] In the method for producing a cured product of the present invention, the liquid silane-grafted olefin composition can be molded into an appropriate shape before contacting the liquid silane-grafted olefin composition with water. The molding method and molding conditions are appropriately selected depending on the shape and form of the molded product. Examples of molding methods include molding, coating (spray coating, brush coating), and other methods such as impregnating fibers or dipping other molded products. Coating methods can be used to mold film- or plate-shaped molded products. While molding conditions are not particularly limited, the liquid silane-grafted olefin composition is liquid at room temperature and normal pressure, eliminating the need for a heating step or heating device that would require heating to a temperature high enough to melt a solid crosslinkable composition. Therefore, non-heating or low-temperature heating can be used. For example, the molding temperature can be 0 to 60°C, preferably 5 to 40°C. When the liquid silane-grafted olefin composition is molded under the above molding conditions, the silanol condensation reaction of the silane coupling agent can be effectively suppressed (hardening and solidification during molding can be suppressed), and a silane-crosslinked cured product with excellent appearance can be produced.

[0065] In this way, a solid silane-crosslinked cured product having a sufficient crosslinked structure, excellent appearance, and excellent mechanical properties can be produced from the liquid silane-grafted olefin composition. It is believed that this silane-crosslinked cured product contains a crosslinked polymer formed via the silane coupling agent (siloxane bond) through hydrolysis of the silanol condensation-capable reactive sites of the silane coupling agent grafted to the liquid olefin polymer, which undergo a silanol condensation reaction with each other. This crosslinked polymer also includes a crosslinked polymer formed via a silanol condensate between silane coupling agents, in which the silane coupling agent weakly bonded to the inorganic filler in the liquid silane-grafted olefin composition detaches from the inorganic filler and then undergoes a silanol condensation reaction, resulting in the liquid silane-grafted olefin composition condensing via a siloxane bond. It is also believed that the product contains a crosslinked polymer formed via a silane coupling agent bonded to the inorganic filler, in which the silanol condensation-capable reactive sites of the silane coupling agent grafted to the liquid olefin polymer are bonded or adsorbed to the inorganic filler as the starting point for crosslinking. This crosslinked polymer is formed from liquid silane-grafted olefin, which is contained in the liquid silane-grafted olefin composition and to which a silane coupling agent that is strongly bonded to an inorganic filler is graft-bonded, and has a crosslinked structure that involves the inorganic filler.

[0066] Although the details of why the silane-crosslinked cured product of the present invention can achieve both excellent appearance and mechanical properties are still unclear, it is thought that the following applies. Specifically, the silane-crosslinked cured product contains the polymers having the different crosslinking structures described above, and the amount of silane coupling agent used in the grafting reaction is increased, achieving a high crosslink density. This allows the product to exhibit particularly high tensile strength without impairing its excellent appearance. Furthermore, since the silane-crosslinked cured product of the present invention is cured into a solid form from a liquid silane-grafted olefin composition, this corresponds to an increase in the apparent molecular weight of the liquid silane-grafted olefin, and therefore exhibits high flexibility, particularly tensile elongation and tensile modulus. Furthermore, as described above, the grafting reaction and final crosslinking reaction proceed uniformly, further enhancing the effects of improving tensile strength and flexibility.

[0067] [Uses of Silane-Crosslinked Cured Product] The silane-crosslinked cured product of the present invention can be used in various applications in which resin molded products or rubber molded products are usually used, such as insulating coating layers (including sheaths) for wiring materials, molding materials, power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, films, packings, gaskets, cushioning materials, and vibration-proofing materials, as substitutes for resin molded products.

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0069] Details of each compound used in the examples and comparative examples are shown below. <Liquid olefin polymers> LBR-307 (trade name): liquid butadiene, viscosity 0.6 Pa·s, manufactured by Kuraray Co., Ltd. LBR-302 (trade name): liquid butadiene, viscosity 1.5 Pa·s, manufactured by Kuraray Co., Ltd. LUCANT LX004 (trade name): copolymer of ethylene and α-olefin, viscosity 0.82 Pa·s, manufactured by Mitsui Chemicals, Inc. <Silane coupling agents> KBM-1003 (trade name, trimethoxyvinylsilane, manufactured by Shin-Etsu Silicones Co., Ltd.) KBE-1003 (trade name, triethoxyvinylsilane, manufactured by Shin-Etsu Silicones Co., Ltd.) <Organic peroxides> Perhexa 25B (trade name, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, 1-hour half-life temperature 138.1°C, 1-minute half-life temperature 179.8°C, manufactured by NOF Corporation) <Silanol condensation catalysts> ADK STAB OT-1 (trade name, dioctyltin dilaurate, manufactured by ADEKA Corporation)

[0070] <Inorganic filler> Aerosil 130 (product name): silica, specific surface area 130 m ２ / g, Aerosil RX300 (trade name) manufactured by Nippon Aerosil Co., Ltd.: silica, specific surface area 300 m ２ / g, Aerosil 300 (trade name) manufactured by Nippon Aerosil Co., Ltd.: silica, specific surface area 300 m ２ / g, Nano Ace FG-15 (trade name) manufactured by Nippon Aerosil Co., Ltd.: talc, specific surface area 18 m ２ / g, Nippon Talc Co., Ltd. FK610 (trade name): magnesium hydroxide, specific surface area 4.4 m ２ / g, Kisuma 5AL (trade name) manufactured by Konoshima Chemical Co., Ltd.: magnesium hydroxide, specific surface area 6.2 m２ / g, Kyowa Chemical Industry Co., Ltd. BF013S (trade name): aluminum hydroxide, specific surface area 4.7 m ２ / g, Nippon Light Metal Co., Ltd. Softon 2200 (trade name): calcium carbonate, specific surface area 2.2 m ２ / g, manufactured by Bihoku Funka Kogyo Co., Ltd.

[0071] Examples 1 to 27 and Comparative Examples 1 to 5 Examples 1 to 27 and Comparative Examples 1 to 5 were each carried out using the components shown in Tables 1-1 and 1-2 (collectively referred to as Table 1). Specifically, liquid silane-grafted olefin compositions having the compositions shown in Table 1 were prepared by the following production method, and these were then contacted with a silanol condensation catalyst and water to produce silane-crosslinked cured products. In Table 1, the numerical values ​​for the mixed amounts (contents) in each example represent parts by mass unless otherwise specified. Furthermore, a blank cell for each component means that the mixed amount of the corresponding component was 0 parts by mass.

[0072] First, a silane coupling agent and an organic peroxide were mixed in the mass ratio shown in Table 1 and stirred at room temperature (25°C) for 1 minute to obtain a mixture. Next, 100 g of liquid olefin polymer, the mixture, and an inorganic filler were introduced into a sealed reaction vessel (a 1 L autoclave equipped with a stirrer) equipped with a stirrer, and heating was initiated while stirring at 200 rpm. After the temperature of the liquid olefin polymer in the sealed reaction vessel reached the set temperature of 160°C, stirring was continued for 1 hour at the set temperature. Thus, the liquid olefin polymer and the silane coupling agent were grafted in the presence of the organic peroxide and the inorganic filler (total amount), thereby preparing liquid silane-grafted olefin compositions of each Example and Comparative Example. The obtained liquid silane-grafted olefin compositions of each Example contained a liquid silane-grafted olefin obtained by grafting a liquid olefin polymer with a silane coupling agent in the mass ratio shown in Table 1, and an inorganic filler in the mass ratio shown in Table 1.

[0073] Each of the liquid silane-grafted olefin compositions produced in Examples 1 to 27 and Comparative Examples 1 to 5 was liquid at room temperature and normal pressure (with the exception that the inorganic filler was dispersed as solid particles). Each of the produced liquid silane-grafted olefin compositions was subjected to the following tests, and the results are shown in Table 1.

[0074] <Evaluation 1: Mechanical Property (Tensile) Test> Each liquid silane-grafted olefin composition produced was poured into a mold and cured. A Type 3 dumbbell-shaped test piece, as defined in Japanese Industrial Standards (JIS) K 6251 (2017), was prepared from the silane-crosslinked cured product of each liquid silane-grafted olefin composition. Curing was performed by adding 1 part by mass of a silanol condensation catalyst to each composition per 100 parts by mass of the liquid olefin polymer used in the production of each liquid silane-grafted olefin composition, and then leaving the composition in an environment of 60°C and 80% relative humidity for 24 hours, followed by contact with water. Using these dumbbell test pieces, a tensile test was performed in accordance with JIS C 3005 under conditions of a gauge length of 20 mm and a tensile speed of 200 mm / min, and the tensile strength (MPa), tensile elongation (%), and tensile modulus (%) were measured. This test evaluates the mechanical properties of a silane-crosslinked cured product. If the test passes all of the tensile strength (MPa), tensile elongation (%), and tensile modulus (MPa), a silane-crosslinked cured product exhibiting excellent mechanical properties can be produced. Tensile strength of 0.3 MPa or more was evaluated as extremely excellent (◎), 0.1 MPa or more but less than 0.3 MPa was evaluated as excellent (◯), and less than 0.1 MPa was evaluated as unsuccessful (×). Tensile elongation of 40% or more was evaluated as very excellent (◎), 20% or more but less than 40% was evaluated as excellent (◯), and less than 20% was evaluated as unsuccessful (×). Tensile modulus of 1.0 MPa or more was evaluated as extremely excellent (◎), 0.3 MPa or more but less than 1.0 MPa was evaluated as excellent (◯), and less than 0.3 MPa was evaluated as unsuccessful (×).

[0075] <Evaluation 2: Discoloration Test> The liquid silane-grafted olefin compositions produced in each Example and Comparative Example were visually inspected to evaluate the presence or absence of discoloration (usually yellowing). This test evaluates the grafting reaction during the preparation of the liquid silane-grafted olefin composition, the uniformity of the mixed state, and other factors; passing this test indicates the production of a silane-crosslinked cured product with excellent appearance. In the discoloration test, if no discoloration was observed in the produced liquid silane-grafted olefin composition, the result was evaluated as "Good" (passed), and if discoloration was observed, the result was evaluated as "Poor" (failed).

[0076] Evaluation 3: Curability Test The liquid silane-grafted olefin compositions produced in each Example and Comparative Example were contacted with water by leaving them in an environment of 60°C and 80% relative humidity for 24 hours in the presence of 0.1 parts by mass of a silanol condensation catalyst per 100 parts by mass of the liquid olefin polymer used to produce each liquid silane-grafted olefin composition. The method for contacting with water in the presence of a silanol condensation catalyst involved adding a predetermined amount of the silanol condensation catalyst to each liquid silane-grafted olefin composition at room temperature and humidity (25°C, 50% RH), stirring at 100 rpm for 1 minute to prepare a mixture, and leaving it in the above environment. This test was conducted to evaluate whether a silanol condensation reaction could be initiated and progressed under mild conditions, without the need for an excessively high-temperature heating step or special crosslinking equipment such as a crosslinking tube, and whether a silane-crosslinked cured product (solid composition) could be produced from the liquid silane-grafted olefin composition. The evaluation of the curability test was made as follows: if the produced liquid silane-grafted olefin composition underwent a silanol condensation reaction (losing its liquid state) and changed into a solid-state composition (silane-crosslinked cured product), it was rated as "Good" (pass); if it remained a liquid composition without losing its liquid state, it was rated as "Poor" (fail).

[0077] <Evaluation 4: Uniformity Test> Five 10 mL test liquid samples were taken from any location of the liquid silane-grafted olefin composition produced in each Example and Comparative Example, and the viscosity of each test sample was measured using a Brookfield viscometer (model number: RVDV2T, manufactured by Brookfield). This test is one of the reference tests for evaluating whether the liquid silane-grafted olefin composition maintains a uniform liquid state; passing this test indicates that the final crosslinking reaction can proceed uniformly, resulting in a silane-crosslinked cured product with approximately uniform appearance and mechanical properties. The uniformity test was evaluated using the average viscosity (ρ ＡＶ ) and the viscosity of each sample (ρ Ｍ ) and the absolute value of the difference (|ρ ＡＶ -ρ Ｍ When the absolute values ​​of all five samples (|ρ ＡＶ -ρ Ｍ |) is the average value (ρ ＡＶ ) was considered to be extremely excellent (◎) (pass), and the absolute values ​​of all five samples (|ρ ＡＶ -ρ Ｍ If the absolute value of at least one sample (|ρ ＡＶ -ρ Ｍ If the difference (|) was more than 10%, it was marked as "×" (fail).

[0078]

[0079]

[0080] The results shown in Table 1 reveal the following: The liquid silane-grafted olefin composition of Comparative Example 1, which does not contain an inorganic filler, does not exhibit sufficient mechanical properties. The liquid silane-grafted olefin composition of Comparative Example 2, in which the amount of silane coupling agent grafted onto the liquid olefin polymer is too small, does not establish a sufficient crosslinked structure even after the crosslinking reaction has progressed, resulting in a silane-crosslinked cured product, and the tensile strength and tensile modulus are also insufficient. On the other hand, the liquid silane-grafted olefin composition of Comparative Example 3, in which the amount of silane coupling agent grafted onto the liquid olefin polymer is too large, exhibits discoloration of the liquid silane-grafted olefin composition itself, resulting in a poor appearance of the silane-crosslinked cured product. This is thought to be due to separation of the inorganic filler in the composition, resulting in a loss of uniformity. Furthermore, the liquid silane-grafted olefin composition of Comparative Example 4, in which the inorganic filler content is too low, does not exhibit sufficient mechanical properties, even when an inorganic filler with a large specific surface area is used. On the other hand, the solid composition of Comparative Example 5, in which the inorganic filler content is too high, exhibits poor tensile elongation.

[0081] In contrast, the liquid silane-grafted olefin compositions of Examples 1 to 27, which contain a liquid silane-grafted olefin obtained by grafting a predetermined amount of silane coupling agent onto a liquid olefin polymer and a specific amount of inorganic filler, are liquid at room temperature and normal pressure even when containing the inorganic filler. Therefore, a heating step and heating device are not required during molding, and discoloration does not occur. Moreover, the final crosslinking reaction, the silanol condensation reaction, proceeds under mild conditions without the use of a special crosslinking device such as a crosslinking tube, to produce a solid silane-crosslinked cured product. Therefore, these compositions exhibit excellent workability (ease of handling), and because they contain a specific amount of inorganic filler, they can produce silane-crosslinked cured products with a sufficient crosslinked structure, excellent appearance, and excellent mechanical properties. In particular, inorganic fillers with a large specific surface area, preferably a specific surface area of ​​100 m or more, are preferred. ２When an inorganic filler having a specific surface area exceeding 1 / g is contained, the composition has high uniformity, and even if the content of the inorganic filler is small, the effect of improving the mechanical properties is enhanced. Furthermore, when an inorganic filler having a large specific surface area and an inorganic filler having a small specific surface area are used in combination, it is possible to achieve a balance of high levels of tensile strength, tensile elongation, and tensile modulus while maintaining excellent discoloration suppression effect and curability.

[0082] 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.

[0083] This application claims priority based on Japanese Patent Application No. 2024-034700, filed on March 7, 2024, the contents of which are incorporated herein by reference as part of the present specification.

Claims

1. A liquid silane-grafted olefin composition comprising a liquid silane-grafted olefin obtained by grafting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a site that undergoes a grafting reaction with the liquid olefin polymer, and 1 to 200 parts by mass of an inorganic filler per 100 parts by mass of the liquid olefin polymer.

2. The liquid silane-grafted olefin composition according to claim 1, wherein the amount of the silane coupling agent to be subjected to the grafting reaction is 10 to 80 parts by mass.

3. The liquid silane-grafted olefin composition according to claim 1, which contains 10 to 150 parts by mass of said inorganic filler.

4. The inorganic filler has a BET specific surface area of ​​10 m ２ 2. The liquid silane-grafted olefin composition according to claim 1, comprising 1 to 30 parts by mass of an inorganic filler having a molecular weight exceeding 1 / g.

5. The inorganic filler has a BET specific surface area of ​​100 m ２ 2. The liquid silane-grafted olefin composition according to claim 1, comprising 1 to 30 parts by mass of an inorganic filler having a molecular weight exceeding 1 / g.

6. The inorganic filler has a BET specific surface area of ​​100 m ２ 2. The liquid silane-grafted olefin composition according to claim 1, comprising 1 to 10 parts by mass of an inorganic filler having a molecular weight exceeding 1 / g.

7. A silane-crosslinked cured product of the liquid silane-grafted olefin composition according to any one of claims 1 to 6.

8. A method for producing a liquid silane-grafted olefin composition according to any one of claims 1 to 6, comprising a step of grafting 100 parts by mass of a liquid olefin polymer with 10 to 150 parts by mass of a silane coupling agent having a site that undergoes a grafting reaction with said liquid olefin polymer in the presence of 0.2 to 5.0 parts by mass of an organic peroxide at a temperature of 50 to 200°C, wherein in carrying out said step, the grafting reaction is carried out in the presence of a total amount of 1 to 200 parts by mass of an inorganic filler relative to 100 parts by mass of said liquid olefin polymer, or the grafting reaction is carried out in the presence of a portion of the inorganic filler or in the absence of the inorganic filler, and then the liquid silane-grafted olefin composition is mixed with the remainder or all of the inorganic filler.

9. A method for producing a silane-crosslinked cured product, comprising contacting the liquid silane-grafted olefin composition obtained by the method for producing a liquid silane-grafted olefin composition according to claim 8 with water in the presence of a silanol condensation catalyst to produce a silane-crosslinked cured product of the liquid silane-grafted olefin composition.