Flame-retardant polyolefin resin composition, flame-retardant polyolefin resin molded article, and polymer insulator

Abstract

The present invention provides a flame-retardant polyolefin resin molded article with excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, a flame-retardant polyolefin resin composition capable of producing this molded article, and a polymer insulator. [Solution] A flame-retardant polyolefin resin composition containing 30 to 120 parts by mass of an inorganic filler and 10 to 35 parts by mass of a brominated flame retardant per 100 parts by mass of a base resin containing a polyolefin resin, wherein the inorganic filler contains 30 parts by mass or more of boehmite per 100 parts by mass of the base resin; a flame-retardant polyolefin resin molded article; and a polymer insulator having this flame-retardant polyolefin resin molded article.

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant polyolefin resin composition, a flame-retardant polyolefin resin molded article, and a polymer insulator. [Background technology]

[0002] Various resin or rubber molded products are used as covering layers (insulators, sheaths, etc.) for wiring materials such as insulated wires, cables, cords, optical fiber cores, or optical fiber cords (optical fiber cables) used in the fields of electrical and electronic equipment and industrial applications. Furthermore, while insulators attached to power transmission lines were conventionally made of porcelain, polymer insulators, which consist of a core made of glass fiber reinforced plastic (FRP) or the like with an outer sheath (surface layer) made of polymer material covering the outer periphery (surface), have become widely used in recent years to overcome problems such as being heavy and brittle. As mentioned above, the coating layer of wiring materials, and the surface layers of various molded products, polymer insulators, etc., require various properties depending on the application and usage.

[0003] For example, polymer insulators and their surface layers installed outdoors are required to have properties such as insulating properties, as well as properties that suppress the occurrence of tracking phenomena (sometimes called "tracking resistance"), deliquescence resistance (also called "acid resistance"), and flame retardancy. Patent Document 1 describes the following "silicone rubber composition for high-voltage electrical insulators" as a material that can improve the acid resistance of polymer insulators when used as a material to form the surface layer of polymer insulators. (A) Organic peroxide curing type or addition reaction curing type organopolysiloxane composition: 100 parts by mass (B) Organic compounds that are solid at room temperature (25°C) and have two or more ester bonds in one molecule: 0.15 to 20 parts by mass, (C) Aluminum hydroxide with an average particle size of 20 μm or less: 30 to 400 parts by mass A silicone rubber composition for high-voltage electrical insulators characterized by containing the following:

[0004] On the other hand, wiring materials and their coating layers are required to have properties such as flame retardancy, mechanical properties, and appearance properties, and various resin compositions for forming the coating layer of wiring materials are being investigated. For example, Patent Document 2 describes "a flame-retardant resin composition characterized in that, per 100 parts by mass of resin component (a) mainly composed of an ethylene copolymer, or an ethylene copolymer and a polyolefin resin and / or a styrene elastomer, it contains 70 to 250 parts by mass of magnesium hydroxide, 10 to 150 parts by mass of aluminum hydroxide, and 0 to 100 parts by mass of melamine cyanurate, and the total amount of magnesium hydroxide and aluminum hydroxide is 150 to 300 parts by mass per 100 parts by mass of resin component (a)." According to Patent Document 2, this flame-retardant resin composition has excellent mechanical properties, heat resistance, etc., and is said to be easy to form a coating that has both excellent flame retardancy that conforms to strict flame retardancy standards and high weather resistance. Furthermore, Patent Document 3 describes a "flame-retardant crosslinked resin molded article" manufactured by the "method for manufacturing a flame-retardant crosslinked resin molded article" described below. According to Patent Document 3, this flame-retardant crosslinked resin molded article is said to have excellent appearance, mechanical strength, acid resistance, and flame retardancy. (a) A step of preparing a silane masterbatch by melting and mixing 0.003 to 0.3 parts by mass of organic peroxide, 30 to 300 parts by mass of boehmite and aluminum hydroxide in total, and more than 2 parts by mass but no more than 15.0 parts by mass of a silane coupling agent having graft reaction sites capable of grafting onto the base resin, at a temperature above the decomposition temperature of the organic peroxide, and causing the graft reaction. Step (b) involves mixing the silane masterbatch obtained in step (a) with the silanol condensation catalyst and then molding it. The process involves bringing the molded body obtained in step (b) into contact with water to cause crosslinking (c), It has, The mass ratio of the boehmite content to the aluminum hydroxide content [boehmite content:aluminum hydroxide content] is 85:15 to 15:85. "Method for manufacturing flame-retardant crosslinked resin molded articles" [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-234311 [Patent Document 2] Japanese Patent Publication No. 2009-114230 [Patent Document 3] International Publication No. 2018 / 180689 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, rubber compositions containing a large amount of aluminum hydroxide in silicone rubber, which has excellent weather resistance, have been widely used as materials for forming the surface layer of polymer insulators, as described in Patent Document 1. However, because silicone rubber is soft, the surface layer made of silicone rubber is easily scratched, and the risk of damage from flying objects, birds, and animals is particularly high. If the surface layer is damaged and it can no longer perform its intended function, the functions and properties of the polymer insulator, such as insulation, will be impaired. Therefore, the surface layer of polymer insulators is required to have properties that make it resistant to damage (also called "scratch resistance"). However, Patent Document 1 does not consider this aspect.

[0007] Generally, the resistance to trauma can be improved by using various resins instead of silicone rubber. However, conventional flame-retardant resin compositions were not intended for application to the surface layer of polymer insulators and could not meet the required properties of polymer insulators, particularly tracking resistance and deliquescence resistance, at the level required for polymer insulators. Furthermore, conventional flame-retardant resin compositions frequently use magnesium hydroxide and aluminum hydroxide as inorganic fillers, and sometimes boehmite is also used. However, flame-retardant resin compositions containing these inorganic fillers have unique problems due to the inorganic fillers, which can adversely affect the properties of polymer insulators. For example, the flame-retardant resin composition described in Patent Document 2, which contains a specific resin component, magnesium hydroxide, and aluminum hydroxide, is said to have excellent mechanical properties, heat resistance, flame retardancy, and weather resistance. However, due to the magnesium hydroxide, deliquescence resistance is reduced, and due to the foaming of aluminum hydroxide, surface defects or internal defects (such as voids) may occur. Therefore, unless some countermeasures are taken, molded articles (coating layers) formed from this flame-retardant resin composition are unsuitable for use in environments where they may be exposed to acidic gases such as exhaust gases, like polymer insulators, and may not exhibit stable properties. Furthermore, since boehmite has inferior flame-retardant properties compared to magnesium hydroxide and aluminum hydroxide, flame-retardant resin molded articles containing boehmite cannot exhibit sufficient flame retardancy unless some countermeasures are taken. The flame-retardant crosslinked resin molded article described in Patent Document 3 is said to exhibit excellent flame retardancy by containing aluminum hydroxide in addition to boehmite. Similar to the flame-retardant resin composition described in Patent Document 2, it has problems caused by aluminum hydroxide.

[0008] The present invention aims to provide a flame-retardant polyolefin resin molded article with excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, and a flame-retardant polyolefin resin composition capable of producing this molded article. Furthermore, the present invention aims to provide a polymer insulator containing the above-mentioned excellent flame-retardant polyolefin resin molded article. [Means for solving the problem]

[0009] The inventors of the present invention have been investigating a technique to improve the required properties of molded articles such as polymer insulators while resolving the specific problems associated with inorganic fillers in a flame-retardant polyolefin resin composition that exhibits superior trauma resistance compared to silicone rubber. They concluded that simply selecting inorganic fillers used in conventional flame-retardant resin compositions would not allow for the resolution of the aforementioned specific problems and the satisfaction of the required properties. Therefore, they continued their investigation of flame-retardant polyolefin resin compositions and found that by using an inorganic filler and a brominated flame retardant in a specific ratio with a base resin containing polyolefin resin, and by using boehmite, which does not exhibit sufficient flame retardancy contrary to the common technical practice of using highly flame-retardant inorganic fillers in highly flame-retardant resin compositions, as part or all of the inorganic filler, it is possible to realize a flame-retardant polyolefin resin molded article that satisfies the required properties of various applications while exhibiting high flame retardancy, while resolving the specific problems associated with aluminum hydroxide and magnesium hydroxide. Based on this finding, the inventors conducted further investigations and arrived at the present invention.

[0010] In other words, the objectives of the present invention were achieved by the following means. <1> A flame-retardant polyolefin resin composition comprising 100 parts by mass of a base resin containing a polyolefin resin, 30 to 120 parts by mass of an inorganic filler, and 10 to 35 parts by mass of a brominated flame retardant, A flame-retardant polyolefin resin composition wherein the inorganic filler contains 30 parts by mass or more of boehmite per 100 parts by mass of the base resin. <2> The melt flow rate (measured at a temperature of 190°C and a load of 10 kg) is 4.0 g / 10 min or higher. <1> The flame-retardant polyolefin resin composition described above. <3> A silicone compound containing 1 to 30 parts by mass, <1> or <2> The flame-retardant polyolefin resin composition described above. <4> It is a bridge structure. <1> ~ <3> A flame-retardant polyolefin resin composition according to any one of the following items. <5> the above <1> ~ <4> A flame-retardant polyolefin resin molded article of a flame-retardant polyolefin resin composition according to any one of the items. <6>A polymer insulator comprising the flame-retardant polyolefin resin molded article according to <5> on an outer periphery of a core. [[Effects of the Invention]]

[0011] The present invention can provide a flame-retardant polyolefin resin molded article excellent in deliquescence resistance, foaming suppression, flame retardancy and tracking resistance, and a flame-retardant polyolefin resin composition capable of producing this molded article. The present invention can also provide a polymer insulator comprising the above-described excellent flame-retardant polyolefin resin molded article. [[Mode for Carrying Out the Invention]]

[0012] In the present invention, when a numerical range is used to describe the content, physical properties and other characteristics of components, if the upper limit and lower limit of the numerical range are described separately, any upper limit and any lower limit may be combined as appropriate to form a specific numerical range. On the other hand, when a plurality of numerical ranges expressed using "~" are set for description, the upper limits and lower limits forming the numerical ranges are not limited to combinations of the specific upper limits and lower limits described before and after "~" as a specific numerical range, and a numerical range obtained by appropriately combining the upper limit and lower limit of each numerical range may be obtained. Note that in the present invention, a numerical range expressed using "~" means a range that includes the numerical values described before and after "~" as the lower limit and the upper limit, respectively. In addition, in the present invention, "(meth)acryl" represents either one or both of acryl and methacryl. For example, the term "(meth)acrylic acid ester" represents either one or both of acrylic acid ester and methacrylic acid ester.

[0013] [[Flame-retardant polyolefin resin composition]] The flame-retardant polyolefin resin composition of the present invention contains 30 to 120 parts by mass of an inorganic filler and 10 to 35 parts by mass of a brominated flame retardant per 100 parts by mass of a base resin containing a polyolefin resin. Furthermore, the flame-retardant polyolefin resin composition of the present invention contains boehmite as the inorganic filler, with a boehmite content of 30 parts by mass or more (120 parts by mass or less) per 100 parts by mass of the base resin. The flame-retardant polyolefin resin composition of the present invention having such a composition can realize a flame-retardant polyolefin resin molded article with excellent deliquescence resistance, foam suppression (effect of preventing the occurrence of internal defects by suppressing foam during the manufacture or molding of the flame-retardant polyolefin resin composition), flame retardancy, and tracking resistance. For this reason, the flame-retardant polyolefin resin composition of the present invention is suitable as a material for forming molded articles that require any of the following characteristics: deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, and is particularly suitable as a material for forming the coating layer of wiring materials and the surface layer of polymer insulators.

[0014] The flame-retardant polyolefin resin composition of the present invention may be either a flame-retardant polyolefin resin composition as a non-crosslinked material (also referred to as a "flame-retardant non-crosslinked polyolefin resin composition") or a flame-retardant polyolefin resin composition as a crosslinked material (also referred to as a "flame-retardant crosslinked polyolefin resin composition"), and the necessity of crosslinking is appropriately selected according to the application and required properties. For example, when excellent mechanical properties and high heat resistance are required, such as in the coating layer of wiring materials, a flame-retardant crosslinked polyolefin resin composition is preferable. Here, the flame-retardant non-crosslinked polyolefin resin composition is a resin composition in which a crosslinking reaction has not been actively carried out, and normally the base resin is not crosslinked, but a portion of the base resin may be crosslinked inevitably or to the extent that it does not impair the effects of the present invention. Also, the flame-retardant crosslinked polyolefin resin composition is a resin composition in which a crosslinking reaction has been actively carried out, and normally the base resin is crosslinked, but a portion of the base resin may not be crosslinked depending on the crosslinking conditions or the content of the crosslinking catalyst or crosslinking agent, etc.

[0015] The crosslinking method (crosslinking reaction) for the flame-retardant polyolefin resin composition is not particularly limited, and known resin crosslinking methods, such as those for polyolefin resins, can be applied. For example, electron beam crosslinking, organic peroxide crosslinking, and silane crosslinking are examples, and silane crosslinking is preferred because it allows for crosslinking reaction processing with high productivity without requiring special equipment. In the present invention, electron beam crosslinking refers to a method of crosslinking a base resin, etc., by irradiating a crosslinkable flame-retardant polyolefin resin composition with an electron beam. Organic peroxide crosslinking is one of the chemical crosslinking methods, and refers to a method in which a crosslinkable flame-retardant polyolefin resin composition containing an organic peroxide as a crosslinking catalyst is heated to a temperature above the decomposition temperature of the organic peroxide, and the resins are directly crosslinked by radicals generated from the organic peroxide. Furthermore, the silane crosslinking method, which is a chemical crosslinking method separate from the organic peroxide crosslinking method, refers to a method in which a silane graft resin, formed by a grafting reaction of a silane coupling agent as a crosslinking agent, preferably a crosslinkable flame-retardant polyolefin resin composition further containing a silanol condensation catalyst, is brought into contact with water, thereby causing a silanol condensation reaction of the silane coupling agent and crosslinking the resin via the silane coupling agent.

[0016] In the present invention, among the flame-retardant polyolefin resin compositions of the present invention, those compositions intended for crosslinking but not subjected to crosslinking treatment (uncrosslinked) are referred to as "crosslinkable flame-retardant polyolefin resin compositions," and are distinguished from the above-mentioned flame-retardant non-crosslinked polyolefin resin compositions that are not intended for crosslinking. In the present invention, crosslinkable flame-retardant polyolefin resin compositions suitably applicable to electron beam crosslinking, organic peroxide crosslinking, or silane crosslinking may be referred to as electron beam crosslinkable flame-retardant polyolefin resin compositions, peroxide crosslinkable flame-retardant polyolefin resin compositions, or silane crosslinkable flame-retardant polyolefin resin compositions, respectively. In the present invention, unless otherwise specified, the term "flame-retardant polyolefin resin composition" is used as a general term that includes flame-retardant non-crosslinked polyolefin resin compositions, flame-retardant crosslinked polyolefin resin compositions, and crosslinkable flame-retardant polyolefin resin compositions.

[0017] The flame-retardant polyolefin resin composition of the present invention preferably further contains, in addition to the above components, components essential for or suitable for the crosslinking method described later, depending on whether or not crosslinking is performed and the crosslinking method applied. Among the flame-retardant polyolefin resin compositions of the present invention, the flame-retardant non-crosslinked polyolefin resin composition is, as described above, a mixture of a base resin, an inorganic filler containing boehmite, and a brominated flame retardant in a specific mass ratio, and may contain other components as appropriate.

[0018] The crosslinkable flame-retardant polyolefin resin composition of the present invention is a mixture of a base resin, an inorganic filler containing boehmite, and a brominated flame retardant in a specific mass ratio, and may contain other components as appropriate, and it is preferable that the other components include a crosslinking catalyst, a crosslinking agent and / or a crosslinking aid. For example, an electron beam crosslinkable flame-retardant polyolefin resin composition is a mixture of a base resin, an inorganic filler containing boehmite, and a brominated flame retardant in a specific mass ratio, and preferably contains other components as appropriate, particularly crosslinking agents and / or crosslinking aids. The peroxide crosslinkable flame-retardant polyolefin resin composition is a mixture of a base resin, an inorganic filler containing boehmite, and a brominated flame retardant in a specific mass ratio, and preferably further contains an organic peroxide as a crosslinking catalyst and a crosslinking aid. This resin composition may optionally contain other components. On the other hand, the peroxide crosslinkable flame-retardant polyolefin resin composition usually does not contain a silanol condensation catalyst, nor does it contain a silane coupling agent. Not containing a silanol condensation catalyst includes, for example, a configuration in which it is contained in an amount of 0.001 parts by mass or less per 100 parts by mass of the base resin. Furthermore, the silane coupling agent not included in the peroxide crosslinkable flame-retardant polyolefin resin composition refers to a silane coupling agent used to form a silane crosslinked structure by grafting reaction with the base resin, and does not include, for example, a silane coupling agent used as a surface treatment agent for inorganic fillers, etc. "Not containing a silane coupling agent" includes a configuration in which a silane coupling agent for forming a silane crosslinked structure is included, for example, in an amount of 0.5 parts by mass or less per 100 parts by mass of the base resin.

[0019] The silane-crosslinkable flame-retardant polyolefin resin composition is a mixture of a base resin, an inorganic filler containing boehmite, and a brominated flame retardant in a specific mass ratio, and contains a silane coupling agent grafted onto the base resin. Preferably, this resin composition further contains a silanol condensation catalyst, and may contain other components as appropriate. Specifically, the silane-crosslinkable flame-retardant polyolefin resin composition is preferably a silane-crosslinkable composition containing a silane-grafted resin (also called a "silane-crosslinkable resin") in which a silane coupling agent is grafted onto a base resin, an inorganic filler containing boehmite, a brominated flame retardant in a specific mass ratio, and further containing a silanol condensation catalyst and other components as appropriate. The silane-grafted resin is formed from a silane coupling agent and a base resin, and is a resin formed by a grafting reaction between the silane coupling agent and the base resin. In this silane-grafted resin, the amount of grafting reaction (amount of grafting) of the silane coupling agent is not particularly limited. Typically, the amount of grafting reaction obtained by reacting the silane coupling agent with the base resin in the proportions shown in the silane crosslinking method for manufacturing molded articles described later is sufficient. The silane graft resin may be synthesized as appropriate or a commercially available product may be used. The silane graft resin is obtained by reacting a base resin and a silane coupling agent at a temperature above the decomposition temperature of the organic peroxide, preferably in the presence of an inorganic filler containing boehmite, in a specific content as described later (for example, step (a) described later). There are no particular limitations on the specific reaction conditions, but the melt mixing conditions of step (1) or step (a) described later are preferred, with the organic peroxide content set to the range described later.

[0020] In the silane-crosslinkable flame-retardant polyolefin resin composition, the silane coupling agent only needs to be grafted to the base resin in some part, and may also contain silane coupling agents that are not grafted. Furthermore, in the silane-crosslinkable flame-retardant polyolefin resin composition of the present invention, the silane coupling agent may be bound to or adsorbed to boehmite or an inorganic filler other than boehmite. That is, the silane-crosslinkable flame-retardant polyolefin resin composition of the present invention may contain a silane graft resin in which a silane coupling agent bound to or dissociated with boehmite or an inorganic filler other than boehmite is grafted (grafted reaction) to the base resin, together with an inorganic filler containing boehmite. The silane-crosslinkable flame-retardant polyolefin resin composition of the present invention is preferably prepared by the silane crosslinking method for producing molded articles (step (1)) described later, but it can also be prepared by appropriately mixing the above components in addition to this manufacturing method.

[0021] The flame-retardant crosslinked polyolefin resin composition of the present invention is prepared by crosslinking a crosslinkable flame-retardant polyolefin resin composition. The flame-retardant crosslinked polyolefin resin composition has a crosslinked structure in which at least the base resin (or the (co)polymer, etc., constituting it) is crosslinked directly or via a crosslinking agent, and preferably exhibits high heat resistance and excellent mechanical properties while maintaining excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance.

[0022] The crosslinked structure of flame-retardant crosslinked polyolefin resin compositions varies depending on the type of crosslinking reaction (crosslinking method) and cannot be clearly and generally defined. For example, a flame-retardant crosslinked polyolefin resin composition obtained by irradiating an electron beam crosslinkable flame-retardant polyolefin resin composition with an electron beam (also called an "electron beam crosslinked resin composition") has a crosslinked structure in which the base resin (or the resins that constitute it) is directly crosslinked. A flame-retardant crosslinked polyolefin resin composition (also called a "peroxide crosslinked resin composition") obtained by crosslinking a peroxide crosslinkable flame-retardant polyolefin resin composition has a crosslinked structure in which the base resin (or the resins that constitute it) is directly crosslinked, preferably a crosslinked structure in which it is crosslinked via a crosslinking agent and / or a crosslinking aid. A flame-retardant crosslinked polyolefin resin composition obtained by crosslinking a silane-crosslinkable flame-retardant polyolefin resin composition (also referred to as a "silane-crosslinked resin composition") has a crosslinked structure in which at least the base resin (or the resins constituting it) is mediated by a silane coupling agent or its silanol condensate. Preferably, boehmite or an inorganic filler other than boehmite is incorporated into a part of this crosslinked structure. As described later, a silane-crosslinked resin composition having such a crosslinked structure exhibits high heat resistance and excellent mechanical properties while maintaining the excellent four properties described above by constructing a crosslinked structure between base resins (without mediated by boehmite or an inorganic filler other than boehmite) and a crosslinked structure involving boehmite or an inorganic filler other than boehmite (a crosslinked structure originating from boehmite or an inorganic filler other than boehmite) in a balanced manner.

[0023] The flame-retardant polyolefin resin composition of the present invention is typically an unmolded product that has not been molded into a shape applicable to a predetermined use. For example, it may be in a shapeless (unmolded) bulk state, or it may be a strand or pellet.

[0024] The flame-retardant polyolefin resin composition of the present invention, whether or not it is crosslinked, can realize flame-retardant polyolefin resin molded articles with excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance (hereinafter sometimes simply referred to as "four properties"). In particular, the crosslinkable flame-retardant polyolefin resin composition can realize flame-retardant polyolefin resin molded articles (crosslinked products) that exhibit high heat resistance and excellent mechanical properties while maintaining the excellent four properties mentioned above, and more preferably also have excellent appearance properties. Furthermore, the flame-retardant polyolefin resin composition of the present invention preferably also exhibits high fluidity (moldability). Therefore, the flame-retardant polyolefin resin composition of the present invention is suitable as a material for forming the surface layer of a flame-retardant polyolefin resin molded article, in particular, a material for forming the surface layer of a polymer insulator where the four properties mentioned above are required.

[0025] The flame-retardant crosslinked polyolefin resin composition of the present invention, particularly the flame-retardant non-crosslinked polyolefin resin composition and the crosslinked flame-retardant polyolefin resin composition, preferably exhibit excellent fluidity. Flame-retardant crosslinked polyolefin resin compositions exhibiting excellent fluidity can realize flame-retardant polyolefin resin molded articles that have excellent moldability even when containing inorganic fillers, exhibit excellent properties uniformly, and also have excellent appearance characteristics. The melt flow rate (measured at a temperature of 190°C and a load of 10 kg), which is one of the indicators for evaluating the fluidity of the flame-retardant crosslinked polyolefin resin composition, is not particularly limited, but it is preferably 4.0 g / 10 min or higher in that it exhibits high fluidity, excellent moldability, and also excellent appearance characteristics. The melt flow rate is more preferably 7.0 g / 10 min or higher, and even more preferably 10.0 g / 10 min or higher, in that it exhibits even better moldability while maintaining excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance. The upper limit of the melt flow rate is not particularly limited; for example, it can be 50.0 g / 10 min or less, and more preferably 40.0 g / 10 min or less. In this invention, the melt flow rate (MFR) is the value measured under the conditions of a measurement temperature of 190°C and a load of 10 kg, based on the method specified in Japanese Industrial Standard (JIS) K 7210-1.

[0026] The content of each component in the flame-retardant crosslinked polyolefin resin composition of the present invention will be described later.

[0027] [[Flame-retardant polyolefin resin molded product]] The flame-retardant polyolefin resin molded article of the present invention is a resin molded article obtained by molding the flame-retardant polyolefin resin composition of the present invention into a predetermined shape and dimensions, and then subjecting it to an appropriate crosslinking reaction treatment. In particular, the silane crosslinked resin composition is a crosslinked resin molded article (a molded article consisting of a silanol condensate of the silane crosslinkable flame-retardant polyolefin resin composition) obtained by molding the silane crosslinkable flame-retardant polyolefin resin composition of the present invention and then performing silane crosslinking (silanol condensation reaction). Since the flame-retardant polyolefin resin molded articles of the present invention are molded articles of the flame-retardant polyolefin resin composition of the present invention, the flame-retardant polyolefin resin molded articles of the present invention also include flame-retardant non-crosslinked polyolefin resin molded articles, flame-retardant crosslinked polyolefin resin molded articles, and crosslinkable flame-retardant polyolefin resin molded articles, similar to the flame-retardant polyolefin resin composition of the present invention.

[0028] When molding a flame-retardant polyolefin resin composition, the composition can be molded into appropriate shapes and dimensions depending on its intended use. The molding method for the flame-retardant polyolefin resin composition is not particularly limited, and various molding methods that can be commonly applied to resin compositions can be used, specifically the molding methods described in step (2) below.

[0029] The flame-retardant polyolefin resin molded articles of the present invention exhibit excellent four properties as described above, preferably high heat resistance and excellent mechanical properties, and also have excellent appearance characteristics. Furthermore, since the base resin containing the polyolefin resin is harder than rubber such as silicone rubber, it is inexpensive and exhibits high resistance to trauma. Therefore, the flame-retardant polyolefin resin molded articles of the present invention are suitable for molded articles used in various applications, and in particular as materials for forming the surface layer of polymer insulators where the four properties described above are required.

[0030] The content of each component in the flame-retardant polyolefin resin molded article of the present invention will be described later.

[0031] The flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded articles of the present invention may exhibit insulating, semiconductive, or conductive properties depending on the application. When used as a coating layer for wiring materials, a surface layer for polymer insulators, etc., insulating properties are used. In the present invention, insulating properties are not particularly limited and refer to exhibiting insulating properties to the degree required for the intended application.

[0032] The components and their contents used in this invention are described below. The flame-retardant crosslinked polyolefin resin composition and flame-retardant polyolefin resin molded article of the present invention may contain one or more of each component. In this invention and specification, the term "resin" simply refers to a resin in which the silane coupling agent has not undergone a grafting reaction.

[0033] [Base resin] The flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded article of the present invention may contain resins other than polyolefin resin, or elastomers, oils, etc., as long as they contain a polyolefin resin as their base resin. In this invention, even when the resin composition and resin molded article contain various rubbers such as ethylene rubber or styrene-based elastomers, they will be referred to as resin composition, resin molded article, etc. for convenience, but this does not exclude elastomer compositions and elastomer molded articles from the technical scope of this invention.

[0034] By including polyolefin resin in the base resin, the resistance to trauma can be improved when a flame-retardant polyolefin resin molded product is formed. Other resins or elastomers (also referred to as "other resins or elastomers" in the present invention) that may be included in the base resin are not particularly limited to any resins or elastomers commonly used in various resin compositions. Examples of other resins or elastomers include acid-modified polyolefin resins, fluororesins, chlorinated polyethylene resins, ethylene rubber, silicone rubber, acrylic rubber, fluororubber, synthetic rubber, styrene-based elastomers, ethylene-α-olefin copolymer rubber, oils, and the like.

[0035] The base resin preferably further contains ethylene rubber and / or a styrene-based elastomer in addition to the polyolefin resin, and more preferably further contains ethylene rubber and a styrene-based elastomer. If the base resin contains a styrene-based elastomer, it is preferable that it also contains oil. In a crosslinkable flame-retardant polyolefin resin composition, it is preferable that at least one of the resins (including elastomers) that may be included in the base resin is a resin having crosslinkable parts. Examples of resins having crosslinkable parts include polyolefin resins, ethylene rubber, acid-modified polyolefin resins, chlorinated polyethylene resins, silicone rubber, acrylic rubber, fluororubber, styrene-based elastomers, and ethylene-α-olefin copolymer rubber.

[0036] For example, in a silane-crosslinkable flame-retardant polyolefin resin composition, it is preferable that at least one of the base resins (including elastomers) contains a resin having graft reaction sites and graft-reactive sites for the silane coupling agent described later in the main chain or at its ends, as crosslinkable sites by radicals generated from organic peroxides. The crosslinkable sites only need to have a structure suitable for each crosslinking method. For example, crosslinkable sites and graft-reactive sites include unsaturated bond sites in carbon chains and carbon atoms having hydrogen atoms. Examples of such resins include polyolefin resins, ethylene rubber, acid-modified polyolefin resins, chlorinated polyethylene resins, silicone rubber, acrylic rubber, fluororubber, styrene-based elastomers, and ethylene-α-olefin copolymer rubbers.

[0037] (Polyolefin resin) Polyolefin resins are not particularly limited as long as they consist of polymers obtained by polymerizing or copolymerizing compounds having ethylenically unsaturated bonds (olefin compounds), and known resins used in various resin compositions can be used. Examples include polyethylene, polypropylene, ethylene-α-olefin copolymers, block copolymers of polypropylene and ethylene-α-olefin copolymers, copolymers having acid copolymer components, and copolymers having acid ester copolymer components. Also, rubber or elastomers (excluding ethylene rubber and styrene-based elastomers) made from these copolymers can be used. The polyolefin resin preferably contains at least one of the following resins: polyethylene, polypropylene, copolymers having acid copolymer components, and copolymers having acid ester copolymer components. It is more preferable to contain polyethylene resin and polypropylene resin in order to achieve a good balance of deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, and it is even more preferable to contain polyethylene resin, polypropylene resin, and a copolymer resin having acid copolymer components and / or a copolymer resin having acid ester copolymer components.

[0038] - Polyethylene resin - Polyethylene resin (PE) is not particularly limited as long as it is a polymer resin mainly composed of ethylene. Examples include high-density polyethylene (HDPE), low-density polyethylene (LDPE), ultra-high molecular weight polyethylene (UHMW-PE), linear low-density polyethylene (LLDPE), and very low-density polyethylene (VLDPE). Among these, linear low-density polyethylene and low-density polyethylene are preferred. The MFR of the polyethylene resin (measured at a temperature of 190°C and under a load of 2.16 kg) is not particularly limited, but is preferably 1.0 to 20.0 g / 10 min, and more preferably 1.5 to 15.0 g / 10 min. In this invention, the MFR of the polyethylene resin is the value measured under the conditions of a measurement temperature of 190°C and a load of 2.16 kg, based on the method specified in JIS K 7210-1.

[0039] - Polypropylene resin - Polypropylene resin (PP) is not particularly limited as long as it is a polymer resin mainly composed of propylene. Examples include propylene homopolymers, as well as random polypropylene and block polypropylene resins.

[0040] - Ethylene-α-olefin copolymer resin - Preferably, the ethylene-α-olefin copolymer resin is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms (excluding those included in the polyethylene resin and polypropylene resin mentioned above). The ethylene-α-olefin copolymer resin includes various resins such as random copolymers or alternating copolymers of ethylene and α-olefin, and block copolymers containing ethylene segments and α-olefin segments. Examples of ethylene-α-olefin copolymer resins include ethylene-propylene copolymer resin (excluding those included in polypropylene resin), ethylene-butylene copolymer resin, ethylene-octene copolymer resin, and ethylene-α-olefin copolymer resin synthesized in the presence of a single-site catalyst.

[0041] - Copolymer resin having acid copolymer components - The compound used to introduce the acid copolymer in a copolymer resin having an acid copolymer is not particularly limited, and examples include carboxylic acid compounds such as (meth)acrylic acid. The copolymer resin having an acid copolymer is not particularly limited, but examples include resins made of ethylene-(meth)acrylic acid copolymer.

[0042] - Copolymer resin having acid ester copolymer components - The compounds used to derive the acid ester copolymer in copolymer resins having an acid ester copolymer are not particularly limited, and include acid ester compounds such as vinyl acetate and (meth)acrylic acid esters. The (meth)acrylic acid ester is not particularly limited, but alkyl (meth)acrylates are a good example. The alkyl group of the alkyl (meth)acrylate has 1 to 12 carbon atoms, which is preferable. Examples of copolymer resins having an acid ester copolymer (excluding those contained in polyethylene resins) include ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), and other ethylene-alkyl (meth)acrylate copolymer resins.

[0043] The vinyl acetate content (also referred to as "VA content") in the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 10 to 50% by mass, and more preferably 15 to 35% by mass. In the present invention, the VA content is the value determined in accordance with JIS K 7192. The alkyl (meth)acrylate content (also referred to as "AA content") in the ethylene-alkyl (meth)acrylate copolymer is not particularly limited, but is preferably 15 to 60% by mass, more preferably 15 to 35% by mass, and even more preferably 15 to 30% by mass. In the present invention, the alkyl (meth)acrylate content can be determined using an infrared spectrometer to determine the ratio of the absorbance due to the carbonyl and methylene in the acrylic acid ester portion. Furthermore, the MFR (measurement temperature 190°C, load 2.16 kg) of the copolymer resin having an acid ester copolymer component is not particularly limited, but is preferably 1.0 to 20.0 g / 10 min, and more preferably 1.5 to 15.0 g / 10 min. In the present invention, the MFR of the copolymer resin having an acid ester copolymer component is the value measured under the conditions of a measurement temperature of 190°C and a load of 2.16 kg, based on the method specified in JIS K 7210-1.

[0044] Depending on the application or required properties, one or more of the above-mentioned resins can be used as polyolefin resins.

[0045] (Acid-modified polyolefin resin) Acid-modified polyolefin resins include resins obtained by modifying the above-mentioned polyolefin resin with an unsaturated carboxylic acid compound (also simply called "unsaturated carboxylic acid") or its anhydride. Acid-modified polyethylene resin is a preferred example of an acid-modified polyolefin resin. The amount of modification by the unsaturated carboxylic acid in the acid-modified polyolefin resin is not particularly limited, but is preferably 0.1 to 2.0% by mass, and more preferably 0.2 to 1.0% by mass, relative to the (pre-modification) polyolefin resin. The above unsaturated carboxylic acid (including anhydrides) is not particularly limited, and carboxylic acids having an unsaturated bond that can react with the above copolymer, etc. (e.g., by radical addition reaction) are preferred. This unsaturated carboxylic acid may have one carboxyl group or two or more. Preferred unsaturated carboxylic acids include, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid, and their metal salts or organic salts, as well as unsaturated carboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, and fumaric anhydride. The unsaturated carboxylic acid that modifies the polyolefin resin may be one or two or more. Maleic anhydride or acrylic acid are preferred as the unsaturated carboxylic acid.

[0046] (Ethylene rubber) The ethylene rubber is not particularly limited as long as it is a rubber (including elastomers) made of a copolymer obtained by copolymerizing compounds having ethylenically unsaturated bonds, and known types can be used. Preferred ethylene rubbers include binary copolymer rubber of ethylene and α-olefin, and terpolymer rubber of ethylene, α-olefin, and diene. The diene compound constituting the terpolymer may be a conjugated diene compound or a non-conjugated diene compound, but a non-conjugated diene compound is preferred. As the α-olefin, α-olefins having 3 to 12 carbon atoms are preferred. As the conjugated diene compound, examples include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and others, with butadiene compounds being preferred. Specific examples of non-conjugated diene compounds include dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and 1,4-hexadiene. As the binary copolymer rubber, ethylene-propylene rubber (EPM) is preferred, and as the ternary copolymer rubber, ethylene-propylene-diene rubber (EPDM) is preferred.

[0047] (Styrene-based elastomer) Styrene-based elastomers refer to elastomers composed of polymers having constituent components derived from aromatic vinyl compounds within their molecules. Examples of such styrene-based elastomers include block copolymers and random copolymers of conjugated diene compounds and aromatic vinyl compounds, or hydrogenated versions thereof. Examples of styrene-based elastomers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated SIS, styrene-butadiene-styrene block copolymer (SBS), hydrogenated SBS, styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), styrene-ethylene-propylene-styrene block copolymer (SEPS), styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber (HSBR), and hydrogenated acrylonitrile-butadiene rubber (HNBR).

[0048] (Acrylic rubber) While not particularly limited, acrylic rubber (ACM) is preferably a rubber elastic body made of a copolymer obtained by copolymerizing an alkyl acrylate, such as ethyl acrylate or butyl acrylate, with an unsaturated hydrocarbon or a monomer having various functional groups. The monomer copolymerized with the alkyl acrylate is not particularly limited, but examples include ethylene, 2-chloroethyl vinyl ether, methyl vinyl ketone, acrylic acid, acrylonitrile, or butadiene.

[0049] (Silicone rubber) The silicone rubber can be any rubber made of a polymer having a polysiloxane structure (organopolysiloxane), and those commonly used in rubber compositions can be used without particular limitations. While there are no particular limitations on the silicone rubber, examples include various silicone rubbers such as methylpolysiloxane, dimethylpolysiloxane, methylvinylpolysiloxane, phenylpolysiloxane, and methylphenylpolysiloxane.

[0050] (Fluororesin) Fluororesins are typically obtained by (co)polymerizing monomers containing fluorine atoms. While not particularly limited, examples of such fluororesins include tetrafluoroethylene-hexafluoropropylene resin, tetrafluoroethylene-perfluoroalkyl ether resin, ethylene-tetrafluoroethylene resin, ethylene-tetrafluoroethylene-hexafluoropropylene resin, chlorotrifluoroethylene resin, and polyvinylidene fluoride resin.

[0051] (Chlorinated polyethylene resin) The chlorinated polyethylene resin is not particularly limited as long as it is polyethylene in which hydrogen atoms bonded to the polyethylene main chain are replaced by chlorine atoms. Examples include those obtained by chlorinating ethylene (co)polymers. The weight-average molecular weight of the chlorinated polyethylene is not particularly limited and can be set appropriately depending on its properties and applications. Chlorinated polyethylene may be amorphous, semi-crystalline, or crystalline, but amorphous is preferred. In this invention, amorphous polyethylene is defined as having a heat of fusion of less than 5 J / g as measured by a differential scanning calorimeter. The chlorine content of chlorinated polyethylene is not particularly limited and can be set as appropriate, for example, 20% by mass or more, and preferably 30% or more and less than 38%.

[0052] (Fluororubber) The fluororubber used is not particularly limited, and conventional fluororubbers used in various rubber molded products can be used. Examples of fluororubbers include tetrafluoroethylene-propylene copolymer rubber (FEPM), tetrafluoroethylene-fluorinated (e.g., hexafluoro)propylene copolymer rubber, tetrafluoroethylene-perfluorovinyl ether copolymer rubber (FFKM), and vinylidene fluoride rubber (FKM, e.g., vinylidene fluoride-hexafluoropropylene copolymer rubber).

[0053] (oil) Examples of oils that may be contained in the base resin include oils used as plasticizers in polyolefin resins or as mineral oil softeners for rubber. Such oils are not particularly limited, but include organic oils or mineral oils, such as soybean oil, paraffin oil, naphthenic oil, and aromatic oils.

[0054] Each component contained in the base resin may be one type or two or more types.

[0055] (Composition of the base resin) In the present invention, the base resin may contain a polyolefin resin, and may also contain other resins or elastomers depending on the physical properties and applications of the flame-retardant polyolefin resin composition and the flame-retardant polyolefin resin molded article. The composition (components and their content) of the base resin in this case is appropriately selected and determined. Preferably, the content of each component of the base resin is appropriately determined from the following range so that the total content of each component is 100% by mass.

[0056] The total content of polyolefin resin in 100% by mass of the base resin can be appropriately determined, and is preferably 50 to 100% by mass, more preferably 55 to 90% by mass, and even more preferably 60 to 80% by mass, in which deliquescence resistance, foam suppression, flame retardancy, and tracking resistance can be improved, and furthermore, high trauma resistance can be observed. The polyethylene content in 100% by mass of the base resin can be appropriately determined considering the total content of the polyolefin resin, etc. For example, in terms of deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, it is preferably 35 to 100% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 65% by mass. The polypropylene content in 100% by mass of the base resin can be appropriately determined considering the total content of the polyolefin resin, etc. For example, in terms of deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, it is preferably 0 to 15% by mass, more preferably 3 to 12% by mass, and even more preferably 5 to 10% by mass. In 100% by mass of the base resin, the content of copolymer resin having an acid copolymer component and copolymer resin having an acid ester copolymer component can be appropriately determined considering the total content of the polyolefin resin, etc. For example, in terms of deliquescence resistance, foam suppression, flame retardancy and tracking resistance, it is preferably 0 to 15% by mass, more preferably 3 to 12% by mass, and even more preferably 5 to 10% by mass. The content of ethylene-α-olefin copolymer resin in 100% by mass of the base resin can be appropriately determined considering the total content of the polyolefin resin, etc.

[0057] In 100% by mass of the base resin, the total content of other resins or elastomers is preferably 0 to 50% by mass, more preferably 10 to 45% by mass, and even more preferably 20 to 40% by mass, in order to improve mechanical properties (especially elongation at break), fluidity (MFR), etc., while maintaining deliquescence resistance, foam suppression, flame retardancy, and tracking resistance.

[0058] In 100% by mass of the base resin, the total content of styrene-based elastomer and ethylene rubber can be appropriately determined considering the total content of the other resins or elastomers mentioned above. For example, while maintaining deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, the content is preferably 0 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass, in terms of fluidity, mechanical properties, and heat resistance. The content of styrene-based elastomer in 100% by mass of the base resin can be appropriately determined considering the total content of the other resins or elastomers mentioned above, the total content of styrene-based elastomer and ethylene rubber, etc. For example, while maintaining deliquescence resistance, foam suppression, flame retardancy and tracking resistance, the content is preferably 0 to 20% by mass, more preferably 3 to 15% by mass, and even more preferably 5 to 15% by mass in terms of fluidity, mechanical properties and heat resistance. The ethylene rubber content in 100% by mass of the base resin can be appropriately determined considering the total content of the other resins or elastomers, the combined content of styrene-based elastomers and ethylene rubber, etc. For example, while maintaining deliquescence resistance, foam suppression, flame retardancy and tracking resistance, the ethylene rubber content is preferably 0 to 20% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass, in terms of fluidity, mechanical properties and heat resistance.

[0059] In 100% by mass of the base resin, the respective content of each resin or elastomer other than the styrene-based elastomer and ethylene rubber mentioned above can be appropriately determined considering the total content of the other resins or elastomers, for example, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass.

[0060] The oil content in 100% by mass of the base resin can be determined as appropriate. For example, in terms of fluidity, mechanical properties, and heat resistance, it is preferably 0 to 20% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass.

[0061] [Inorganic filler] The flame-retardant polyolefin resin composition of the present invention contains an inorganic filler. The inorganic filler may contain boehmite, or it may contain boehmite and other inorganic fillers. By using at least boehmite as an inorganic filler in combination with the brominated flame retardant described later, the low flame retardant effect of boehmite can be reinforced while improving deliquescence resistance, foaming, and appearance defects caused by aluminum hydroxide and magnesium hydroxide. When the flame-retardant polyolefin resin composition of the present invention is a silane-crosslinkable flame-retardant polyolefin resin composition, it is preferable that the boehmite and inorganic fillers other than boehmite have on their surfaces sites that can chemically bond with the silanol-condensable reaction sites of the silane coupling agent by hydrogen bonds, covalent bonds, or intermolecular bonds. Such chemically bondable sites are not particularly limited, but examples include oxygen atoms, OH groups (hydroxyl groups, water molecules in water containing water or crystal water, OH groups such as carboxyl groups), amino groups, SH groups, etc.

[0062] <Boehmite> Boehmite is a type of aluminum oxide hydrate (Al2O3·H2O). In the present invention, boehmite acts as a filler or flame retardant and also exhibits the ability to retain coexisting silane coupling agents. In the present invention, it is preferable to use boehmite without surface treatment. The average secondary particle size of boehmite is not particularly limited, but is preferably 0.3 to 5 μm, and more preferably 0.4 to 2 μm. When the average secondary particle size is 0.3 to 5 μm, flame retardancy can be imparted without impairing elongation and strength. In addition, when mixed with a silane coupling agent, boehmite is less likely to undergo secondary aggregation, resulting in an excellent appearance. The average secondary particle size can be determined by dispersing boehmite in alcohol or water and using an optical particle size analyzer such as a laser diffraction / scattering particle size distribution analyzer. The shape of boehmite is not particularly limited, and it can be used in granular, plate-like, or needle-like forms, with plate-like forms being preferred. When it is in plate-like form, the aspect ratio is preferably 1 to 60, and from the viewpoint of balancing strength and flexibility, 1 to 3 is preferred. The BET specific surface area of ​​boehmite is not particularly limited, but in terms of tensile strength or flexibility, it is between 0.8 and 30 m². 2 / g is preferred, and 1.2 to 25m 2 / g is more preferable. The BET specific surface area is a value measured using nitrogen gas as the adsorbate, in accordance with the "carrier gas method" of JIS Z 8830:2013. For example, it is a value measured using the specific surface area and pore distribution analyzer "FlowSorb" (manufactured by Shimadzu Corporation).

[0063] <Inorganic fillers other than boehmite> Other inorganic fillers besides boehmite are not particularly limited, and those commonly used as fillers in resin compositions, etc., can be used without any particular restrictions. Inorganic fillers other than boehmite are not particularly limited and include, for example, 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, quartz, zinc borate, white carbon, zinc borate, zinc hydroxystannate, and zinc stannate.

[0064] Inorganic fillers other than boehmite can be one or more of the above fillers, and preferably contain one or more of calcium carbonate, antimony trioxide, talc, silica (crystalline silica, amorphous silica, etc.), carbon black, and clay (calcined clay). It is preferable to include antimony trioxide as it can further improve flame retardancy and also provides excellent mechanical properties and fluidity (moldability) in addition to deliquescence resistance, foam suppression, and tracking resistance.

[0065] The shape of inorganic fillers other than boehmite is not particularly limited, and granular, plate-shaped, needle-shaped, etc., can be used. Inorganic fillers other than boehmite are usually used as powders or particles. The average particle size in this case is not particularly limited, but 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 fillers other than boehmite in alcohol or water and using an optical particle size analyzer such as a laser diffraction / scattering particle size distribution analyzer.

[0066] Boehmite and other inorganic fillers can also be used after being surface-treated with various surface treatment agents. Examples of surface treatment agents include silane coupling agents, titanate coupling agents, phosphate esters, fatty acids, and fatty acid metal salts.

[0067] [Bromine-based flame retardant] The flame-retardant polyolefin resin composition of the present invention contains a brominated flame retardant. Brominated flame retardants are not particularly limited as long as they contain bromine atoms, and include those commonly used in flame-retardant resin compositions. Examples include brominated ethylene bisphthalimide compounds, bisbrominated phenyl terephthalamide compounds, brominated bisphenol (e.g., tetrabromobisphenol A) compounds, 1,2-bis(bromophenyl)ethane compounds, polybromodiphenyl ether (e.g., decabromodiphenyl ether) compounds, polybromodiphenyl (e.g., tribromophenyl) compounds, hexabromocyclododecane, brominated polystyrene, and hexabromobenzene, which are organic brominated flame retardants. Among these, 1,2-bis(bromophenyl)ethane is preferred, and commercially available products include, for example, Cytex (trade name, manufactured by Albemarle) and Firemaster (trade name, manufactured by Chemtura Japan). As for brominated flame retardants, the contents described in Japanese Patent Publication No. 2016-121203 may be referenced as appropriate, and those contents are incorporated as is as part of this specification.

[0068] [Other ingredients] The flame-retardant polyolefin resin composition of the present invention may contain, in addition to the base resin, inorganic filler, and brominated flame retardant, various components such as additives commonly used in resin compositions (referred to as "other components"), to the extent that they do not impair the objectives of the present invention. Examples of other components include silicone compounds, antioxidants (anti-aging agents), lubricants, metal deactivators, plasticizers, flame retardants other than brominated flame retardants, and flame retardant aids. Furthermore, for crosslinkable flame-retardant polyolefin resin compositions, it is preferable to appropriately include crosslinking agents, crosslinking aids, crosslinking catalysts, crosslinking accelerators, etc., depending on the type of crosslinking reaction applied. The other components that may be contained in the flame-retardant polyolefin resin composition may be one or two or more of each type.

[0069] <Silicone compounds> When the flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded article of the present invention contain a silicone compound, water repellency is improved, water film formation on the surface becomes less likely, and high insulation performance is exhibited even in humid environments. Therefore, the flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded article of the present invention containing a silicone compound can be particularly suitably applied to the surface layer of polymer insulators where insulation performance in humid environments may be required. The silicone compound is not particularly limited and includes silicone polymers such as polysiloxanes and organopolysiloxanes. The silicone compound may be used alone or as a mixture with a filler such as silica.

[0070] <Antioxidant> The antioxidant is not particularly limited, but examples include amine antioxidants, phenol antioxidants, or sulfur antioxidants. Examples of phenol antioxidants include pentaerythritol-tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

[0071] <Lubricant> The lubricant is not particularly limited, but examples include silicone compounds, fatty acid metal salts, and fatty acid amides, with silicone compounds being preferred. The silicone compound used as a lubricant can be any compound that functions as a lubricant, and examples include compounds different from the silicone compounds that exhibit the above-mentioned water-repellent properties.

[0072] <Flame retardants other than brominated flame retardants> Flame retardants other than bromine-based flame retardants are not particularly limited, but examples include chlorine-based flame retardants and phosphorus-based flame retardants.

[0073] <Organic peroxide> The peroxide-crosslinkable flame-retardant polyolefin resin composition preferably contains one or more organic peroxides as crosslinking catalysts. Furthermore, when preparing the silane graft resin contained in the silane-crosslinkable flame-retardant polyolefin resin composition, it is preferable to use one or more organic peroxides. Organic peroxides generate radicals through thermal decomposition, and as catalysts, they induce and promote crosslinking reactions between resins, or induce and accelerate grafting reactions between silane coupling agents and base resins (a covalent bond formation reaction between grafting sites of silane coupling agents and graftable sites of base resins, also known as (radical) addition reactions). The organic peroxide is not particularly limited, and those used in radical polymerization reactions or conventional silane crosslinking methods can be used without particular limitation. 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 compounds represented by are preferred. Here, R 1 to R 6 each independently represent an alkyl group, an aryl group, or an acyl group. Among R 1 to R 6 , those in which all are alkyl groups, or those in which one is an alkyl group and the remainder are acyl groups, are preferred.

[0074] The decomposition temperature (exothermic onset temperature) of the organic peroxide, measured by the method described in Japanese Patent Application Laid-Open No. 2016-121203, is preferably 80 to 195°C, and particularly preferably 125 to 180°C. Examples of such organic peroxides include the organic peroxides described in paragraph

[0036] of Japanese Patent Application Laid-Open No. 2016-121203, the content of which is incorporated herein by reference as part of the description of the present specification. Among these, dicumyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Perhexa 25B), and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3 are preferred.

[0075] <Silane coupling agent> In the present invention, it is preferable that the electron beam crosslinkable flame-retardant polyolefin resin composition contains one or more silane coupling agents as crosslinking agents. On the other hand, when preparing the silane graft resin contained in the silane crosslinkable flame-retardant polyolefin resin composition, one or more silane coupling agents are used, and the silane crosslinkable flame-retardant polyolefin resin composition contains one or more silane coupling agents as crosslinking agents. The silane coupling agents contained in the silane crosslinkable flame-retardant polyolefin resin composition are usually graft-bonded to the base resin. Silane coupling agents (including silane coupling agents before graft bonding to the base resin) have graft reaction sites (groups or functional groups such as ethylenically unsaturated groups) that can graft onto graft-reactive sites in the base resin in the presence of radicals generated by electron beam irradiation or decomposition of organic peroxides. Silane coupling agents used in the silane crosslinking method further have hydrolyzable silyl groups (e.g., alkoxysilyl groups) as silanol condensation-reactive sites. It is preferable that these silanol condensation-reactive sites can interact with and / or react with chemically bonding sites of the boehmite or other inorganic fillers. Examples of interactions include chemical or physical adsorption or adhesion, or chemical reactions.

[0076] Such silane coupling agents are not particularly limited and include silane coupling agents conventionally used in electron beam crosslinking or silane crosslinking methods. Preferred silane coupling agents include those having an ethylenically unsaturated group and a hydrolyzable silyl group (e.g., an alkoxysilyl group). Specific examples of silane coupling agents include vinyl alkoxysilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinyldimethoxyethoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, allyltrimethoxysilane, allyltriethoxysilane, and vinyltriacetoxysilane, and (meth)acryloxysilanes such as methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane. Among these, vinyltrimethoxysilane or vinyltriethoxysilane are particularly preferred. Silane coupling agents may be used individually or in combination of two or more types. They may also be used as is or diluted with a solvent.

[0077] <Silanol condensation catalyst> The silane-crosslinkable flame-retardant polyolefin resin composition preferably contains one or more silanol condensation catalysts. The silanol condensation catalyst has the function of promoting the condensation reaction of the silanol-condensable reaction sites of the silane coupling agent grafted onto the base resin in the presence of water (moisture). Based on the function of this silanol condensation catalyst, the base resin is crosslinked via the silane coupling agent and, as appropriate, boehmite or other inorganic fillers. Such silanol condensation catalysts are not particularly limited and include, for example, organotin compounds, metal soaps, and platinum compounds. Examples of organotin compounds include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, and dibutyltin diacetate.

[0078] <Crosslinking agents and crosslinking aids> When a crosslinkable flame-retardant polyolefin resin composition is crosslinked by electron beam crosslinking, the crosslinkable flame-retardant polyolefin resin composition may contain one or more crosslinking agents and crosslinking aids. The crosslinking agents and crosslinking aids can be those commonly used in electron beam crosslinking without particular limitation. Examples include polyfunctional compounds, such as (meth)acrylate compounds like polypropylene glycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate, allyl compounds like triallyl cyanurate, maleimide compounds, and divinyl compounds.

[0079] <Carrier resin> When crosslinking a crosslinkable flame-retardant polyolefin resin composition by a silane crosslinking method, it is preferable to use a resin or rubber (referred to as a carrier resin) to form a mixture with a silanol condensation catalyst during its production. That is, it is preferable that the silanol condensation catalyst is used mixed with the carrier resin. Such a carrier resin is not particularly limited, but the components described for the base resin can be used. In terms of compatibility with the base resin, the carrier resin is preferably at least one of the components constituting the base resin, and preferably contains the same components as the base resin.

[0080] [Composition of flame-retardant polyolefin resin composition] In the flame-retardant polyolefin resin composition of the present invention, the total content of the inorganic filler containing boehmite is 30 to 120 parts by mass per 100 parts by mass of the base resin, which is preferable in that it enables the realization of a flame-retardant polyolefin resin molded article that is excellent in deliquescence resistance, foam suppression, flame retardancy and tracking resistance, and preferably also has excellent mechanical properties, and also enables the flame-retardant polyolefin resin composition to exhibit excellent fluidity (moldability). The total content of the inorganic filler is preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more, per 100 parts by mass of the base resin, in order to particularly enhance tracking resistance, balance the above four properties, and further improve mechanical properties. On the other hand, the total content of the inorganic filler is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of the base resin, in order to maintain the excellent above four properties while also improving mechanical properties and moldability.

[0081] The boehmite content in the flame-retardant polyolefin resin composition of the present invention can be appropriately determined considering the total content of inorganic fillers, etc. For example, in terms of excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, it is 30 parts by mass or more (120 parts by mass or less) per 100 parts by mass of base resin. In terms of exhibiting a good balance of deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, the boehmite content is preferably 35 to 100 parts by mass, more preferably 40 to 80 parts by mass, and even more preferably 50 to 70 parts by mass, per 100 parts by mass of base resin. The total content of inorganic fillers other than boehmite in the flame-retardant polyolefin resin composition of the present invention can be appropriately determined considering the total content of inorganic fillers, etc., and is preferably 5 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 7 to 15 parts by mass per 100 parts by mass of base resin, in terms of being able to improve flame retardancy while maintaining deliquescence resistance, foam suppression and tracking resistance, and also improving mechanical properties and fluidity. The antimony trioxide content in the flame-retardant polyolefin resin composition of the present invention can be appropriately determined considering the total content of inorganic fillers and the total content of inorganic fillers other than boehmite, for example, in order to further improve flame retardancy, mechanical properties and fluidity while maintaining deliquescence resistance, foam suppression and tracking resistance, it is preferably 0 to 25 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 5 to 15 parts by mass per 100 parts by mass of base resin.

[0082] The flame-retardant polyolefin resin composition of the present invention is preferable because it does not contain aluminum hydroxide as an inorganic filler, that is, the inorganic filler does not contain aluminum hydroxide, in that it can suppress foaming caused by aluminum hydroxide during melt mixing or molding, thereby realizing a flame-retardant polyolefin resin molded article that suppresses the occurrence of internal defects, and also improves the appearance characteristics of the flame-retardant polyolefin resin molded article. In the present invention, the statement that the composition does not contain aluminum hydroxide includes not only the embodiment in which the content of aluminum hydroxide per 100 parts by mass of base resin in the composition is 0 parts by mass, but also the embodiment in which aluminum hydroxide is contained in a content that does not impair the effects of the present invention. The content in this case cannot be uniquely determined because the foaming suppression effect varies depending on the adjustment of manufacturing conditions, etc., but for example, it is preferable that it is 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less per 100 parts by mass of base resin in the composition.

[0083] The flame-retardant polyolefin resin composition of the present invention is preferable in terms of deliquescence resistance if it does not contain magnesium hydroxide as an inorganic filler, that is, if the inorganic filler does not contain magnesium hydroxide. In the present invention, the statement that the composition does not contain magnesium hydroxide includes not only the embodiment in which the magnesium hydroxide content in the composition is 0 parts by mass per 100 parts by mass of the base resin, but also the embodiment in which magnesium hydroxide is contained in a content that does not impair the effects of the present invention. The content in this case cannot be uniquely determined, but for example, it is preferable to have 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less per 100 parts by mass of the base resin in the composition.

[0084] In the flame-retardant polyolefin resin composition of the present invention, the content of the brominated flame retardant is 10 to 35 parts by mass per 100 parts by mass of the base resin, in which, when used in combination with an inorganic filler containing boehmite in the above-mentioned amount, it combines deliquescence resistance, foam suppression, flame retardancy, and tracking resistance at excellent levels. If the content of the brominated flame retardant is too low, sufficient flame retardancy will not be exhibited, while if the content of the brominated flame retardant is too high, tracking resistance tends to decrease. Therefore, the content of the brominated flame retardant is preferably 10 to 30 parts by mass, more preferably 15 to 30 parts by mass, and even more preferably 20 to 30 parts by mass, in which excellent deliquescence resistance and foam suppression can be maintained while flame retardancy and tracking resistance are well balanced at a high level. In the flame-retardant polyolefin resin composition of the present invention, the mass ratio of the boehmite content to the brominated flame retardant content [boehmite content / brominated flame retardant content] is not particularly limited and can be set as appropriate. For example, the mass ratio [boehmite content / brominated flame retardant content] can be 46 / 54 to 92 / 8, preferably 55 / 45 to 85 / 15, and more preferably 60 / 40 to 80 / 20, in order to achieve a good balance of flame retardancy and tracking resistance at a high level while maintaining excellent deliquescence resistance and foam suppression.

[0085] In the flame-retardant polyolefin resin composition of the present invention, the total content of inorganic fillers (particularly the content of boehmite) and the total content of brominated flame retardants can be appropriately determined according to the above-mentioned respective content. For example, in order to maintain the excellent four properties described above while suppressing a decrease in mechanical properties and fluidity, the total content is preferably 55 to 130 parts by mass, more preferably 65 to 120 parts by mass, and even more preferably 80 to 110 parts by mass per 100 parts by mass of base resin.

[0086] The total content of other components and the content of each of the other components in the flame-retardant polyolefin resin composition of the present invention are 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 silicone compound in the flame-retardant polyolefin resin composition is not particularly limited and can be, for example, 0 to 50 parts by mass per 100 parts by mass of the base resin. However, it is preferably 1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, in order to maintain excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance while exhibiting high water repellency. The content of the antioxidant in the flame-retardant polyolefin resin composition is not particularly limited and should be set within a range that does not impair the effects of the present invention. For example, it can be 0.1 to 15 parts by mass, and preferably 0.1 to 10 parts by mass.

[0087] In a crosslinkable flame-retardant polyolefin resin composition, the content of organic peroxides is not particularly limited and is set appropriately according to the crosslinking method, etc. For example, in a peroxide crosslinkable flame-retardant polyolefin resin composition, the content of organic peroxides can be 0.01 to 7 parts by mass, preferably 0.01 to 5 parts by mass, and more preferably 0.03 to 2 parts by mass, per 100 parts by mass of the base resin. On the other hand, in silane-crosslinkable flame-retardant polyolefin resin compositions, organic peroxides usually decompose during the grafting reaction. When using organic peroxides in the grafting reaction between a silane coupling agent and a base resin in the preparation of a silane-crosslinkable flame-retardant polyolefin resin composition, the amount of organic peroxide used is not particularly limited, but for example, it is preferable to use 0.001 to 0.6 parts by mass, more preferably 0.01 to 0.5 parts by mass, and even more preferably 0.05 to 0.2 parts by mass per 100 parts by mass of the base resin, in order to efficiently cause and advance the grafting reaction between the silane coupling agent and the base resin.

[0088] In a silane-crosslinkable flame-retardant polyolefin resin composition, the content of the silane coupling agent is set as appropriate. For example, it is preferable that the content is 0.5 to 16 parts by mass per 100 parts by mass of the base resin, in order to establish a sufficient crosslink density and achieve high mechanical properties and high heat resistance while maintaining excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, and furthermore, to achieve an excellent appearance. The above content of the silane coupling agent is preferable to be 0.5 to 10 parts by mass, more preferably 1 to 6 parts by mass, and even more preferably 1 to 4 parts by mass, per 100 parts by mass of the base resin, in order to exhibit even better fluidity. Here, in a silane-crosslinkable flame-retardant polyolefin resin composition, the silane coupling agent is grafted to the base resin, but for convenience, the above content of the silane coupling agent is the content converted to the mass before the graft reaction with the base resin (content of the silane coupling agent used in combination with the base resin). As mentioned above, the peroxide crosslinkable flame-retardant polyolefin resin composition does not contain a silane coupling agent for forming a silane crosslinked structure.

[0089] In a silane-crosslinkable flame-retardant polyolefin resin composition, the content of the silanol condensation catalyst is preferably 0.01 to 0.6 parts by mass, more preferably 0.03 to 0.3 parts by mass, and more preferably 0.05 to 0.2 parts by mass, per 100 parts by mass of the base resin. This is because it allows for the establishment of a sufficient crosslink density, thereby achieving high heat resistance while maintaining excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, and furthermore, it allows for the suppression of appearance defects, the formation of blemishes, and the volatilization of the silane coupling agent, resulting in an excellent appearance. As mentioned above, the peroxide crosslinkable flame-retardant polyolefin resin composition does not contain a silanol condensation catalyst.

[0090] In a crosslinkable flame-retardant polyolefin resin composition, the total content of the crosslinking agent and crosslinking aid is not particularly limited and is set appropriately according to the crosslinking method, etc. For example, in an electron beam crosslinkable flame-retardant polyolefin resin composition, the total content of the crosslinking agent and crosslinking aid is preferably 0.5 to 8 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the base resin. In a peroxide crosslinkable flame-retardant polyolefin resin composition, the total content of the crosslinking agent and crosslinking aid is preferably 0.1 to 3 parts by mass, and more preferably 0.3 to 2 parts by mass, per 100 parts by mass of the base resin.

[0091] The total content of components other than those mentioned above, and the content of each component in the flame-retardant polyolefin resin composition, are 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 lubricants, metal deactivators, plasticizers, flame retardants other than brominated flame retardants, and flame retardant aids in the flame-retardant polyolefin resin composition can each be, for example, 0 to 5 parts by mass per 100 parts by mass of resin.

[0092] The composition of the flame-retardant crosslinked polyolefin resin composition of the present invention is usually the same as the types and contents of each component in the flame-retardant polyolefin resin composition of the present invention described above. However, the content of the base resin is converted to the content before crosslinking. In the silane crosslinked resin composition, the content of the silane coupling agent is converted to the content before the grafting reaction and the silanol condensation reaction. Note that the organic peroxide and silanol condensation catalyst are usually decomposed.

[0093] [Method for producing flame-retardant polyolefin resin composition] The method for producing the flame-retardant polyolefin resin composition of the present invention can be applied without being particularly limited to conventional methods for producing resin compositions, and for example, the production method described later is preferred. <Preparation of flame-retardant non-crosslinked polyolefin resin composition and crosslinked flame-retardant polyolefin resin composition> Both of the above compositions can be prepared by melting and mixing the above components. The mixing method is not particularly limited, as long as it is a method commonly used for mixing rubber, plastics, etc. Mixing equipment can include, for example, a single-screw extruder, twin-screw extruder, rolls, a Banbury mixer, or various types of kneaders, with closed-type mixers such as Banbury mixers or various types of kneaders being preferred. Mixing conditions such as mixing temperature and mixing time are not particularly limited and can be appropriately set within a temperature range above the melting temperature of the base resin. The mixing temperature is preferably, for example, the melting mixing conditions in step (1) described later, for example, 120 to 200°C. When preparing the peroxide-crosslinkable flame-retardant polyolefin resin composition, the temperature should be set below the decomposition temperature of the organic peroxide. The order in which the components are mixed is not particularly restricted; the components can be mixed (melted) all at once, or they can be mixed sequentially in any order that suits the situation.

[0094] The silane-crosslinkable flame-retardant polyolefin resin composition may also be prepared by the following method, regardless of the above preparation method, and is preferably prepared by step (1) of the molded article manufacturing method by the silane crosslinking method described later. For example, in the preparation of a silane crosslinkable flame-retardant polyolefin resin composition, in an embodiment using a silane graft resin, the silane graft resin, an inorganic filler containing boehmite, a brominated flame retardant, a silanol condensation catalyst, and other components as appropriate can be mixed or melt-mixed in the above-mentioned amounts. The method and conditions for melt-mixing at this time can be those of step (1) or step (a) described later. On the other hand, in an embodiment in which a graft reaction is carried out between a base resin and a silane coupling agent during the preparation of a silane crosslinkable flame-retardant polyolefin resin composition, the composition can be prepared by mixing the base resin, silane coupling agent, organic peroxide, inorganic filler containing boehmite, brominated flame retardant, silanol condensation catalyst, and other components as appropriate in the above-mentioned amounts (mixture amounts). Preferably, it can be produced by step (1) described later.

[0095] As described above, a non-crosslinked or crosslinkable (uncrosslinked) flame-retardant polyolefin resin composition can be obtained in which each component is dispersed (mixed).

[0096] <Preparation of flame-retardant crosslinked polyolefin resin composition> The flame-retardant crosslinked polyolefin resin composition of the present invention can be prepared by performing the above-described crosslinking reaction treatment on the above-described crosslinkable flame-retardant polyolefin resin composition. The flame-retardant crosslinked polyolefin resin composition may be crosslinked in an unmolded state or after molding. Furthermore, a flame-retardant crosslinked polyolefin resin molded article can be produced by crosslinking the flame-retardant crosslinked polyolefin resin composition after molding.

[0097] When a crosslinkable flame-retardant polyolefin resin composition is subjected to a crosslinking reaction by electron beam crosslinking, the crosslinkable flame-retardant polyolefin resin composition prepared as described above is irradiated with an electron beam. The electron beam irradiation conditions are not particularly limited as long as the crosslinkable flame-retardant polyolefin resin composition (resin) can be crosslinked. For example, the electron beam irradiation dose can be 1 to 30 Mrad, and the acceleration voltage during irradiation can be 500 to 750 keV.

[0098] When a crosslinkable flame-retardant polyolefin resin composition is subjected to a crosslinking reaction using an organic peroxide crosslinking method, the crosslinkable flame-retardant polyolefin resin composition prepared as described above is heated to a temperature above the decomposition temperature of the organic peroxide. The heating conditions should be such that they are above the decomposition temperature of the organic peroxide contained in the crosslinkable flame-retardant polyolefin resin composition, and the heating time is not particularly limited. As heating conditions, for example, the melt mixing conditions of step (1) described later can be applied.

[0099] When a crosslinkable flame-retardant polyolefin resin composition is subjected to a crosslinking reaction by a silane crosslinking method, it is preferable to bring the silane-crosslinkable flame-retardant polyolefin resin composition, which contains a silane graft resin formed by a silane coupling agent graft reaction, into contact with moisture.

[0100] [Method for manufacturing flame-retardant polyolefin resin molded articles] The flame-retardant polyolefin resin molded article of the present invention can be manufactured by molding a flame-retardant polyolefin resin composition, or by molding a crosslinkable flame-retardant polyolefin resin composition before or after crosslinking treatment. The molding method and molding conditions for each resin composition are selected appropriately according to the shape and form after molding. For example, the molding method and molding conditions of step (2) described later can be applied.

[0101] <Method for producing flame-retardant crosslinked polyolefin resin molded articles by silane crosslinking method> As a method for producing flame-retardant crosslinked polyolefin resin molded articles by the silane crosslinking method, a method comprising the following steps (1), (2), and (3) (hereinafter sometimes referred to as the "method for producing molded articles by the silane crosslinking method") is preferred.

[0102] Process (1): Base resin, inorganic filler containing boehmite, brominated flame retardant, and silang A coupling agent, an organic peroxide, a silanol condensation catalyst, and as appropriate... The other components are melted and mixed to form a molten mixture (silane crosslinkable flame retardant polyole Steps to obtain a fin resin composition Step (2): A step in which the molten mixture obtained in step (1) is molded to obtain a molded body. Step (3): The molded body obtained in step (2) is brought into contact with water to form a flame-retardant crosslinked polyolefin. Process for obtaining a resin molded product

[0103] In the silane crosslinking method for manufacturing molded articles, the mixing amounts of each component used as the base resin shall be the same as the content percentages described above for the composition of the base resin. Furthermore, the mixing amounts of boehmite, inorganic fillers other than boehmite, brominated flame retardants, silane coupling agents, silanol condensation catalysts, and other components shall be the same as the content percentages in the flame-retardant polyolefin resin composition described above. In addition, in the silane crosslinking method for manufacturing molded articles, the mixing amount of organic peroxide shall be the same as the amount of organic peroxide used in the grafting reaction between the silane coupling agent and the base resin described above.

[0104] <Process (1)> In the silane crosslinking method for manufacturing molded articles, step (1) is performed in which a base resin, an inorganic filler containing boehmite, a brominated flame retardant, a silane coupling agent, an organic peroxide, a silanol condensation catalyst, and other components as appropriate are melt-mixed in the above-mentioned proportions to prepare a flame-retardant polyolefin resin composition as a mixture. The mixing order of each component in step (1) is not particularly limited, and each component can be mixed together. The mixing conditions in this case can be those of step (a) described later. In the silane crosslinking method for manufacturing molded articles, it is preferable to (melt) mix the base resin, an inorganic filler containing boehmite, a brominated flame retardant, a silane coupling agent, an organic peroxide, a silanol condensation catalyst, and other components as appropriate, and then mix the resulting mixture (silane masterbatch) with the silanol condensation catalyst, in order to suppress the silanol condensation reaction of the silane coupling agent before the grafting reaction of the silane coupling agent into the base resin. In this case, "mixing the base resin, an inorganic filler containing boehmite, a brominated flame retardant, a silane coupling agent, an organic peroxide, a silanol condensation catalyst, other components as appropriate, the silane coupling agent, and the organic peroxide" does not specify the mixing order, but means that they can be mixed in any order. In the present invention, it is preferable to pre-mix the inorganic filler containing boehmite with the silane coupling agent.

[0105] Step (1), namely the melting and mixing of the base resin, an inorganic filler containing boehmite, a brominated flame retardant, a silane coupling agent, an organic peroxide, a silanol condensation catalyst, and other components as appropriate, is preferably carried out in the following order of steps (a) to (c). In other words, when performing step (1) above, if the entire base resin is mixed in step (a) below, step (1) comprises steps (a) and (c) below. On the other hand, if only a portion of the base resin is mixed in step (a) below, it is preferable that step (1) comprises steps (a), (b), and (c) below.

[0106] Process (a): All or part of the base resin, an inorganic filler containing boehmite, and a brominated flame retardant. The agent, the silane coupling agent, and the organic peroxide, the decomposition temperature of the organic peroxide A silane masterbatch (silane MB) is prepared by melting and mixing at a temperature of 10°C or higher. The process Step (b): The remaining base resin and the silanol condensation catalyst are melt-mixed to form a catalyst master. Process for preparing a batch (catalyst MB) Step (c): A silane masterbatch and a silanol condensation catalyst or catalyst masterbatch Mixing process

[0107] In the silane crosslinking method for producing molded articles, it is sufficient that the flame-retardant polyolefin resin composition obtained in step (1) contains 100 parts by mass of base resin. For example, step (a) may include a configuration in which the entire amount (100 parts by mass) of the base resin is mixed, or a configuration in which a portion of the base resin is mixed. In step (1), it is preferable for the base resin to be mixed in both step (a) and step (b) for the sake of mixability. When a portion of the base resin is mixed in step (a), of the 100% by mass of base resin to be mixed in steps (a) and (b), preferably 70 to 99% by mass, more preferably 75 to 95% by mass is melt-mixed in step (a), and preferably 1 to 30% by mass, more preferably 5 to 25% by mass is melt-mixed in step (b).

[0108] The base resins mixed in step (a) may be one type or two or more types, and there are no particular restrictions on their types. For example, polyolefin resins can be used as base resins in step (a), and other examples may include ethylene rubber, styrene-based thermoplastic elastomers, oils, etc., as needed. The remaining portion of the base resin (carrier resin) mixed in step (b) is determined appropriately according to a portion of the base resin mixed in step (a).

[0109] Boehmite and other inorganic fillers are usually mixed in process (a) because they allow for a good balance between cross-linked structures between base resins (without involving the boehmite-containing inorganic filler) and cross-linked structures involving the boehmite-containing inorganic filler. However, some may be mixed in process (b).

[0110] (Step (a)) In step (a), all or part of the base resin, an inorganic filler containing boehmite, a silane coupling agent, an organic peroxide, and other components as appropriate are melt-mixed in the above-mentioned proportions at a temperature above the decomposition temperature (exothermic onset temperature) of the organic peroxide to prepare a silane masterbatch (silane MB). This melt-mixing causes a grafting reaction between the silane coupling agent and the base resin, and a silane MB containing a silane graft resin in which the silane coupling agent is grafted can be prepared.

[0111] In step (a), the mixing temperature for melting and mixing (also called melting and kneading or kneading) the above-mentioned components is above the decomposition temperature of the organic peroxide, preferably at a temperature of the decomposition temperature of the organic peroxide + (25 to 110) °C, more preferably at 150 to 230 °C, and even more preferably at 175 to 210 °C. Here, the decomposition temperature of the organic peroxide used as the reference for the melting and mixing temperature is the temperature under normal pressure (approximately 0.1 MPa). At the above mixing temperature, the above-mentioned components can melt and mix sufficiently, and the organic peroxide can decompose and act to carry out the necessary grafting reaction. Other conditions, such as the mixing time, can be set as appropriate. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes.

[0112] The mixing method is not particularly limited, as long as it is a method commonly used for mixing rubber, plastics, etc. Mixing equipment can be, for example, a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, or various types of kneaders, with closed-type mixers such as Banbury mixers or various types of kneaders being preferred. The method of mixing the base resin is not particularly limited. For example, if the base resin contains two or more components, the base resin may be prepared in advance and used, or each component may be used separately.

[0113] In step (a), the mixing order of each component is not specified, and the components may be mixed in any order. For example, the above components can be melted and mixed all at once, or they can be melted and mixed in a specific order. In the silane crosslinking method for manufacturing molded articles, it is more preferable to carry out the following steps (a-1) and (a-2). Step (a-1): Mix an inorganic filler containing boehmite with a silane coupling agent. The process of preparing a mixture Step (a-2): The mixture obtained in step (a-1) and all or part of the base resin, As appropriate, combine with other components in the presence of organic peroxides. A process of melting and mixing at a temperature above the melting temperature.

[0114] In step (a-1), first, an inorganic filler containing boehmite and a silane coupling agent are mixed to prepare a mixture. By mixing the inorganic filler containing boehmite and the silane coupling agent, a balanced mixture of silane coupling agent weakly bonded or adsorbed to boehmite or other inorganic fillers and silane coupling agent strongly bonded or adsorbed to boehmite or other inorganic fillers can be formed. Here, weak bonds with boehmite or other inorganic fillers include interactions by hydrogen bonding, interactions between ions, partial charges or dipoles, and effects by adsorption. Strong bonds with boehmite or other inorganic fillers include chemical bonds. By forming the above-mentioned silane coupling agent in a balanced manner, volatilization of the silane coupling agent and condensation reactions between unadsorbed silane coupling agents can be effectively prevented during melt mixing in step (a-2). As a result, flame-retardant cross-linked polyolefin resin molded articles can be manufactured that exhibit superior appearance while maintaining high levels of mechanical properties and heat resistance.

[0115] The mixing method and conditions for step (a-1) are not particularly limited, but examples of mixing methods and conditions include using a known mixer, kneader, etc., and mixing by dry or wet method for several minutes to several hours at a temperature below the decomposition temperature of the organic peroxide, preferably 10 to 60°C, more preferably near room temperature (20 to 25°C). Among these, dry mixing (dry blending) at a temperature below the decomposition temperature of the organic peroxide is preferred. Other conditions for dry mixing can be determined as appropriate.

[0116] In step (a-1), the base resin may be mixed in as long as the temperature below the above-mentioned decomposition temperature is maintained. The organic peroxide only needs to be present during the melt mixing in step (a-2), and may be mixed in step (a-2) or in step (a-1). When the organic peroxide is mixed in step (a-1), it may be mixed with the silane coupling agent and then with the inorganic filler containing boehmite, or it may be mixed separately with the inorganic filler, apart from the silane coupling agent.

[0117] (Process (a-2)) In step (a-2), the mixture obtained in step (a-1), all or part of the base resin, and the remaining components not mixed in step (a-1) are melt-mixed in the presence of an organic peroxide at a temperature above the decomposition temperature of the organic peroxide to prepare silane MB. In this melt-mixing step, excessive cross-linking reactions (generation of gel particles) between the base resins can be prevented while suppressing the volatilization and self-condensation of the silane coupling agent mentioned above. The melt-mixing method and conditions in step (a-2) are not particularly limited, and the melt-mixing method and conditions in step (a) above can be applied.

[0118] In steps (a-1) and (a-2), and especially in step (a-2), it is preferable to melt-mix the above-mentioned components without substantially mixing in the silanol condensation catalyst. This suppresses the condensation reaction of the silane coupling agent, facilitates melt-mixing, and allows for obtaining the desired shape during extrusion molding. Here, "without substantially mixing in the silanol condensation catalyst" does not mean eliminating the unavoidably present silanol condensation catalyst, but rather means that it may be present to an extent that does not cause the above-mentioned problems due to silanol condensation of the silane coupling agent. For example, in step (a-2), the silanol condensation catalyst may be present if it is 0.01 parts by mass or less per 100 parts by mass of the base resin.

[0119] In step (1), and especially in steps (a-1) and (a-2), it is preferable that the crosslinking agents and crosslinking aids other than the silane coupling agent are not substantially mixed. When the crosslinking agents and crosslinking aids are not substantially mixed, crosslinking between the base resins is less likely to occur during melt mixing, resulting in a superior appearance and heat resistance of the flame-retardant polyolefin resin composition.

[0120] As described above, silane MB is prepared by mixing each component together or by performing steps (a-1) and (a-2). This silane MB contains a reaction mixture of a base resin, an inorganic filler including boehmite, and a silane coupling agent, and contains a silane graft resin in which the silane coupling agent and the base resin have undergone a graft reaction to the extent that it can be molded by step (2) described below. The silane coupling agent grafted to the base resin includes those that are bound to or adsorbed to boehmite or an inorganic filler other than boehmite at the reaction sites where silanol condensation is possible. Silane MB is preferably in pellet or powder form.

[0121] During the combined mixing of each component and in step (a-2), at least the following modes of grafting reaction between the silane coupling agent and the base resin are conceivable. Specifically, one mode involves the silane coupling agent, which is weakly bonded or adsorbed to boehmite or an inorganic filler other than boehmite, detaching from the boehmite or the inorganic filler other than boehmite and undergoing a grafting reaction with the base resin. In this mode, the crosslinked structure formed in step (3) described later does not incorporate boehmite or the inorganic filler other than boehmite, and is usually a crosslinked structure via silanol condensates between silane coupling agents. Another mode involves the silane coupling agent, which is strongly bonded or adsorbed to boehmite or an inorganic filler other than boehmite, undergoing a grafting reaction with the base resin while maintaining its bond or adsorption to the boehmite or the inorganic filler other than boehmite. In this embodiment, the crosslinked structure formed in step (3) described later incorporates boehmite or an inorganic filler other than boehmite, and is a crosslinked structure that starts with boehmite or an inorganic filler other than boehmite and is bonded to by a silane coupling agent. By mixing the crosslinked structures in the above two embodiments, a highly developed crosslinked structure including a crosslinked structure incorporating boehmite or an inorganic filler other than boehmite can be constructed in the flame-retardant crosslinked polyolefin resin molded body. In particular, in the preferred step (a) in which steps (a-1) and (a-2) are performed, a good balance can be achieved between a crosslinked structure that does not incorporate boehmite or an inorganic filler other than boehmite and a crosslinked structure that incorporates boehmite or an inorganic filler other than boehmite.

[0122] (Step (b)) In step (b), independently of or following step (a), the remainder of the base resin (carrier resin) and the silanol condensation catalyst are melt-mixed to prepare a catalyst masterbatch (catalyst MB). The mixing ratio of the carrier resin and the silanol condensation catalyst is not particularly limited, but is preferably set to satisfy the above-mentioned mixing amount in step (1). The melting and mixing method and conditions in step (b) are not particularly limited, and the melting and mixing method and conditions of step (a) above can be applied. For example, the melting and mixing temperature should be above the melting temperature of the base resin, preferably 120 to 200°C, and more preferably 160 to 200°C. Other conditions, such as the mixing time, can be set as appropriate. For example, the mixing time can be 1 to 25 minutes, preferably 3 to 20 minutes. In step (b), another resin can be used as a carrier resin in place of or in addition to the remainder of the base resin. When another resin is used as the carrier resin, the grafting reaction in step (a) can be promoted, and defects are less likely to occur during molding. The amount of the other resin to be mixed is preferably 1 to 60 parts by mass, more preferably 2 to 50 parts by mass, and even more preferably 2 to 40 parts by mass, per 100 parts by mass of the base polymer. Catalyst MB is preferably in pellet or powder form.

[0123] Other components may be mixed in any of steps (a-1), (a-2), or (b). The silicone compound only needs to be present when carrying out step (c), and may be mixed in any of the steps. It is preferable that the silicone compound be mixed in step (b) in order to prevent the water-repellent effect from being impaired by the seepage of low-molecular-weight silicone components as the silicone compound forms a cross-linked structure and becomes high molecular weight. The antioxidant only needs to be present during step (c), and may be mixed in any of the steps. It is preferable that the antioxidant be mixed in step (b) in order to allow the grafting reaction between the silane coupling agent and the base resin to occur and proceed efficiently without inhibiting it. When mixing in step (a-1) or step (a-2), it is preferable that the amount of antioxidant mixed is 0.5 parts by mass or less per 100 parts by mass of the base resin. The flame retardant and flame retardant aid may be present during step (c) and may be mixed in any of the steps. It is preferable that the flame retardant and flame retardant aid be mixed in step (b) in order to efficiently induce and proceed with the grafting reaction between the silane coupling agent and the base resin without inhibiting it.

[0124] (Process (c)) In step (c), silane MB and silanol condensation catalyst or catalyst MB are mixed to obtain a mixture. Preferably, silane MB and catalyst MB are melt-mixed. In step (c), when mixing the silanol condensation catalyst, it can be mixed either alone or as a mixture of the silanol condensation catalyst with other rubber or resin. The mixing method is not particularly limited, but is basically the same as the melt mixing in step (a), and is mixed at a temperature at which the base resin melts. The mixing conditions in step (c) are not particularly limited, and the mixing conditions of step (a) above can be applied. For example, the mixing temperature is appropriately selected according to the melting temperature of the base resin or carrier resin, for example, 80 to 250°C is preferred, 100 to 240°C is more preferred, and 120 to 200°C is even more preferred. Other conditions, such as the mixing time, can be set as appropriate. In step (c), a mixing method and conditions are set that can maintain the fluidity (moldability) of the mixture. The silane graft resin in the mixture is an uncrosslinked form in which the silane coupling agent has not undergone silanol condensation. In practice, some crosslinking may occur when mixing in step (c), but the resulting mixture is expected to maintain its moldability. For example, to avoid the occurrence or progression of a silanol condensation reaction, it is preferable that the silane MB and silanol condensation catalyst are not kept at high temperatures for a long time in a mixed state. In step (c), it is preferable to dry blend the silane MB and the silanol condensation catalyst or catalyst MB before mixing them. The method and conditions for dry blending are not particularly limited and include, for example, the dry mixing in step (a-1) and the conditions thereunder.

[0125] In this way, a silane-crosslinkable flame-retardant polyolefin resin composition is produced as a mixture (kneaded or molten mixture). The silane-crosslinkable flame-retardant polyolefin resin composition contains each component in the proportions corresponding to the above-mentioned mixing ratios. However, the base resin and the silane coupling agent are graft-bonded to each other, and the organic peroxides usually decompose and disappear. In a silane-crosslinkable flame-retardant polyolefin resin composition, the silane coupling agent grafted to the base resin may interact with boehmite or other inorganic fillers. For example, the silane coupling agent may be bound to or adsorbed to boehmite or other inorganic fillers at the silanol-condensable reaction sites. In this case, the binding or adsorption of the silane coupling agent to boehmite or other inorganic fillers may include both strong and weak binding or adsorption. Therefore, the silane graft resin includes a silane graft resin in which a silane coupling agent bound to or adsorbed with boehmite or other inorganic fillers is grafted to the base resin, and a silane graft resin in which a silane coupling agent not bound to or adsorbed with boehmite or other inorganic fillers is grafted to the base resin. In the silane graft resin, the silanol-condensable reaction sites of the silane coupling agent are not silanol-condensed.

[0126] <Process (2)> In the method for producing molded articles by the silane crosslinking method, the mixture obtained in step (1) (silane crosslinkable flame-retardant polyolefin resin composition) is then molded in step (2) to obtain a molded article. The molding method is not particularly limited and can be appropriately selected depending on the desired product form. Examples of molding methods include extrusion molding using an extruder, extrusion molding using an injection molding machine, and molding using other molding machines. Extrusion molding is preferred in terms of productivity, etc. The molding conditions (melt mixing conditions) are not particularly limited as long as they allow for uniform mixing and molding, and the silane crosslinkable flame-retardant polyolefin resin composition of the preferred form of the present invention does not undergo a silanol condensation reaction. For example, the melt mixing method and conditions of step (a) can be applied. When using an extrusion molding machine, the temperature of the extrusion molding machine is preferably set to 140-200°C in the cylinder section and approximately 160-200°C in the die section, although this depends on various conditions such as the type of base resin and the take-up speed of the conductor, etc. The extrusion conditions (molding conditions) can also be determined as appropriate. For example, the screw rotation speed and molding speed (linear speed) of the extruder in extrusion molding are not particularly limited and can be set as appropriate according to the characteristics or performance of the extruder, the amount of extrusion (coating amount), etc.

[0127] Step (2) can be performed simultaneously with or immediately following step (c). For example, a series of steps can be employed in which silane MB and silanol condensation catalyst or catalyst MB are mixed by dry blending or the like just before the coating device (extruder), and then melt-mixed (step (c)) in the coating device (extruder), or silane MB and silanol condensation catalyst or catalyst MB are separately introduced into the coating device, melt-mixed (step (c)), and then molded (step (2)).

[0128] In this way, a molded article (uncrosslinked molded article) of the silane-crosslinkable flame-retardant polyolefin resin composition is obtained. Similar to the silane-crosslinkable flame-retardant polyolefin resin composition, partial crosslinking of the silane graft resin is unavoidable in this molded article, but it is in a partially crosslinked state that retains moldability that allows it to be molded in step (2). Therefore, the flame-retardant crosslinked polyolefin resin molded article of the present invention becomes a crosslinked or fully crosslinked flame-retardant polyolefin resin molded article by carrying out step (3).

[0129] <Process (3)> In the silane crosslinking method for producing molded articles, step (3) is then performed, in which the molded article obtained in step (2) is brought into contact with water to produce the flame-retardant crosslinked polyolefin resin molded article of the present invention. Since the molded article obtained in step (2) is not crosslinked, this step causes and promotes a silanol condensation reaction (dehydration condensation reaction) at the silanol condensation-capable reaction sites of the silane coupling agent grafted to the base resin, ultimately resulting in silane crosslinking. In this way, a flame-retardant silane crosslinked resin molded article can be obtained in which the silane coupling agent has undergone silanol condensation and crosslinking. Contact between the uncrosslinked molded article and water can be carried out by conventional methods. The silanol condensation reaction proceeds even when left at room temperature, for example, around 20-25°C, in the presence of moisture, so it is not necessary to actively bring the article into contact with water. From the viewpoint of promoting the silanol condensation reaction (crosslinking reaction), it is preferable to actively bring the uncrosslinked molded article into contact with water. As for contact methods, methods (conditions) that are normally applied to the silane crosslinking method can be listed, for example, contact under normal pressure, and specifically include exposure to a saturated water vapor atmosphere, exposure to a high humidity environment, immersion in room temperature water or hot water (for example, 50-90°C), immersion in a humid heat bath, exposure to high temperature water vapor, etc. Pressure may also be applied during contact to allow moisture to penetrate into the interior.

[0130] In this way, flame-retardant crosslinked polyolefin resin molded articles are produced by the silane crosslinking method. This flame-retardant crosslinked polyolefin resin molded article is formed by molding a silane-crosslinked flame-retardant polyolefin resin composition and then bringing it into contact with water to undergo a silanol condensation reaction. Therefore, the content of each component in this molded article is usually the same as the content in the silane-crosslinked flame-retardant polyolefin resin composition. However, in the flame-retardant silane-crosslinked polyolefin resin molded article, the content of the silane coupling agent and the base resin are the same as the content before the grafting reaction and the silanol condensation reaction, respectively. In addition, the silanol condensation catalyst usually decomposes and disappears.

[0131] The flame-retardant silane crosslinked resin molded article contains a crosslinked resin formed by condensation of a base resin (silane crosslinkable resin) via siloxane bonds. The flame-retardant silane crosslinked resin molded article also contains boehmite and, as appropriate, inorganic fillers other than boehmite, and the boehmite or inorganic fillers other than boehmite may be bonded to the silane coupling agent of the crosslinked base resin. Therefore, it is considered that the crosslinked resin contains a crosslinked resin formed by the bonding or adsorption of multiple base resins to boehmite or inorganic fillers other than boehmite via a silane coupling agent, and a crosslinked resin formed via the silane coupling agent (siloxane bonds) (without the need for boehmite or inorganic fillers other than boehmite) through the hydrolysis of silanol condensation reaction sites of the silane coupling agent grafted to the base resin and the subsequent silanol condensation reaction.

[0132] [Applications of flame-retardant polyolefin resin molded products] Because the flame-retardant polyolefin resin molded articles of the present invention exhibit the above-mentioned excellent properties, they can be used as coating materials for wiring materials such as insulated wires, cables, or optical fiber cables, as surface layers for polymer insulators, as materials for rubber-replacement wires and cables, and for other applications such as heat-resistant parts for microwave ovens or gas ranges, heat-resistant wire parts, heat-resistant sheets, and heat-resistant films. Furthermore, they can be suitably used for power plugs, connectors, sleeves, boxes, tape substrates, tubes, sheets, heat-resistant packings, cushioning materials, vibration damping materials, and wiring materials used for internal and external wiring of electrical and electronic equipment, particularly for electric wires and optical fiber cables. In particular, taking advantage of its excellent four properties, and preferably its excellent mechanical properties, heat resistance, and / or appearance properties, it is suitably used as a coating layer for wiring materials and for applications installed outdoors, such as the surface layer of polymer insulators.

[0133] <Polymer insulator> The polymer insulator of the present invention only needs to have a flame-retardant polyolefin resin molded body of the present invention on the outer periphery (surface) of the core. For example, an insulator in which the surface layer of the core of a conventional insulator is replaced with the flame-retardant polyolefin resin molded body of the present invention can be used. As the core, a cylindrical or columnar shape molded from fiber-reinforced plastic (FRP) or the like is usually preferred. The thickness of the surface layer formed from the flame-retardant polyolefin resin molded body of the present invention is appropriately determined according to the shape and size of the insulator (for example, the presence or absence of a cap, its shape, size, spacing, etc.). For example, the thickness of the surface layer is usually 1 mm or more at the thinnest part, and preferably 2 mm or more. The upper limit of the thickness of the surface layer is usually 100 mm or less, and preferably 50 mm or less. The flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded articles of the present invention are composed of a base resin containing polyolefin resin, and are therefore less expensive than conventional rubber compositions and molded articles based on silicone rubber, which have been widely used. They also have excellent resistance to trauma, making them suitable for various applications, particularly as surface layers for polymer insulators. [Examples]

[0134] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0135] Details of each compound used in the examples and comparative examples are shown in Table 1 and below. <Base resin> (Polyolefin resin) (1) Linear low-density polyethylene (LLDPE): Evolu SP0540 (product name, manufactured by Prime Polymer, MFR (measurement temperature 190℃, load 2.16kg) 3.8g / 10min) (2) Linear low-density polyethylene (LLDPE): Evolu SP2520 (product name, manufactured by Prime Polymer Co., Ltd., MFR (measurement temperature 190℃, load 2.16kg) 1.9g / 10min) (3) Linear low-density polyethylene (LLDPE): Evolu SP1071C (product name, manufactured by Prime Polymer, MFR (measurement temperature 190℃, load 2.16kg) 10g / 10min) (4) Ethylene-vinyl acetate copolymer (EVA): Evaflex EV460 (product name, manufactured by Mitsui Dow Polychemicals, VA content 19% by mass, MFR (measurement temperature 190℃, load 2.16kg) 2.5g / 10min) (5) Ethylene-ethyl acrylate copolymer (EEA): Lexpar A4200 (trade name, manufactured by Mitsui Dow Polychemicals, ethyl acrylate content 20% by mass, MFR (measurement temperature 190℃, weight 2.16kg) 5g / 10min) (6) Polypropylene resin (r-PP): PB222A (product name, manufactured by Sun Allomer Co., Ltd.)

[0136] (Other resins or elastomers) (7) Ethylene rubber (EPDM): EPT3092PM (product name, manufactured by Mitsui Chemicals, Ltd., ethylene-propylene-ethylidene norbornene rubber, ethylene content 65% by mass, diene content 4.6% by mass) (8) Styrene-based elastomer: ToughTec N504 (product name, manufactured by Asahi Kasei Corporation, SEBS) (9) Oil: Cosmo Neutral 500 (product name, manufactured by Cosmo Oil Lubricants, paraffin oil)

[0137] <Inorganic filler> (10) Boehmite: FKB104 (product name, manufactured by Kamishima Chemical Industry Co., Ltd., average secondary particle size 1.2 μm, BET specific surface area 6 m²) 2 / g) (11) Magnesium hydroxide: Magsies LN-6 (product name, manufactured by Kamishima Chemical Industry Co., Ltd., average particle size 1.1 μm) (12): Aluminum hydroxide: BF013 (product name, manufactured by Nippon Light Metal Co., Ltd., average particle size 1 μm) (13) Calcium carbonate: Softon 1800 (product name, manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size 1.25 μm) (14) Antimony trioxide: Twinkling Star (product name, manufactured by Meiwa Sangyo Co., Ltd.)

[0138] <Bromine-based flame retardant> (15) Brominated flame retardant: SAYTEX8010 (product name, manufactured by Albemarle)

[0139] <Other ingredients> (16) Antioxidant: Irganox 1076 (trade name, manufactured by BASF, hindered phenol antioxidant) (17) Silicone compound: GENIOPLAST PELLET S (product name, manufactured by Asahi Kasei Wacker Silicone Co., Ltd.) (18) Color masterbatch: PEM 90086-2AL (product name, manufactured by Dainichi Seika Kogyo Co., Ltd., mixture of 60% by mass of LDPE and 40% by mass of carbon black) (19) Crosslinking agent: Ogmont T200 (product name, manufactured by Shin Nakamura Chemical Co., Ltd., trimethylolpropane trimethacrylate (TMPT)) (20) Silane coupling agent: KBM-1003 (product name, manufactured by Shin-Etsu Chemical Co., Ltd., vinyltrimethoxysilane) (21) Organic peroxide: Perhexa 25B (trade name, manufactured by NOF Corporation, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, decomposition temperature 154℃) (22) Silanol condensation catalyst: Adeka Stab OT-1 (product name, manufactured by ADEKA, dioctyl tin dilaurate)

[0140] [Examples 1-15 and Comparative Examples 1-6] Examples 1 to 15 and Comparative Examples 1 to 6 were carried out using the components shown in Tables 1 to 3. Specifically, flame-retardant polyolefin resin compositions with the compositions shown in Tables 1 to 3 were prepared using the manufacturing methods described below, and these were extruded (extruded coating) to produce sheet-like flame-retardant polyolefin resin molded articles. In Tables 1 to 3, the numerical values ​​for the mixing amount (content) in each example are expressed in parts by mass unless otherwise specified. Furthermore, a blank space for each component indicates that the mixing amount of that component is 0 parts by mass. In Tables 1 to 3, the "PEM 90086-2AL" column under "Base Resin" should show both the total mass of the color masterbatch and the converted mass of polyethylene resin contained in the color masterbatch (the value shown in parentheses). Similarly, the "PEM 90086-2AL" column under "Carbon Black" should show both the total mass of the color masterbatch and the converted mass of carbon black contained in the color masterbatch (the value shown in parentheses).

[0141] <Examples 1-13 and Comparative Examples 1-6> The various components shown in Tables 1 to 3 were sequentially added in the parts by mass indicated in the respective columns to a Banbury mixer (2L capacity) preheated to 80°C. The mixture was mixed at 40 rpm for 5 minutes, followed by a final kneading (melt mixing) at 30 rpm for 3 minutes. After confirming that the mixture temperature reached approximately 160°C and the base resin was sufficiently melted, the molten mixture was rolled out to a thickness of approximately 3 mm using an 8-inch open roll and pelletized using a square pelletizer to obtain a flame-retardant non-crosslinked polyolefin resin composition. Next, the obtained flame-retardant non-crosslinked polyolefin resin composition was used to produce tape-shaped molded articles (flame-retardant non-crosslinked polyolefin resin molded articles) with a thickness of 2 mm and a width of 14 mm using an extruder equipped with a screw having an L / D (ratio of effective screw length L to diameter D) of 25 and a screw diameter of 25 mm (cylinder temperature 120-180°C, crosshead temperature 160-200°C).

[0142] <Example 14> The various components shown in Table 2 were sequentially added in the parts by mass indicated in the same column to a Banbury mixer (capacity 2L) preheated to 80°C. The mixture was mixed at 40 rpm for 5 minutes, followed by a final kneading (melt mixing) at 30 rpm for 3 minutes. After confirming that the mixture temperature reached approximately 160°C and the base resin was sufficiently melted, the molten mixture was rolled thinly to approximately 3 mm using an 8-inch open roll and pelletized using a square pelletizer to obtain an electron beam crosslinkable flame-retardant polyolefin resin composition. Next, the obtained electron beam crosslinkable flame-retardant polyolefin resin composition was used to produce tape-shaped molded articles (tape-shaped molded articles of electron beam crosslinkable flame-retardant polyolefin resin composition) with a thickness of 2 mm and a width of 14 mm using an extruder equipped with an L / D ratio of 25 and a screw diameter of 25 mm (cylinder temperature 150-180°C, crosshead temperature 160-200°C). Next, an electron beam crosslinkable flame-retardant polyolefin resin composition, formed into a tape shape, was irradiated with an electron beam at an accelerating voltage of 500 kV to an irradiation dose of 10 Mrad. In this way, tape-shaped molded articles of electron beam crosslinked resin compositions were manufactured.

[0143] <Example 15> First, the inorganic filler, silane coupling agent, and organic peroxide shown in the "Composition" column of Table 2 were added in the parts by mass indicated in the same column to a rotary blade mixer (Mazeler PM: trade name, manufactured by Mazeler Co., Ltd.) and stirred (pre-mixed) at a rotation speed of 10 rpm for 1 hour at room temperature (25°C) to obtain a powder mixture (step (a-1)). Next, the obtained powder mixture, a portion of the base resin, and a brominated flame retardant were sequentially added in the parts by mass indicated in the same column to a Banbury mixer (capacity 2L, manufactured by Nippon Roll Co., Ltd.) that had been preheated to 80°C and mixed at a rotation speed of 40 rpm for 5 minutes, followed by finish kneading (melt mixing) at a rotation speed of 30 rpm for 3 minutes. The base resin used was 52 parts by mass of linear low-density polyethylene (MFR 10g / 10min), 5 parts by mass of polypropylene resin, 5 parts by mass of ethylene rubber, 5 parts by mass of styrene elastomer, 5 parts by mass of oil, and 5 parts by mass of color masterbatch. After confirming that the temperature of the mixture reached 180-200°C, which is above the decomposition temperature of the organic peroxide, the molten mixture was spread thinly to about 3 mm using an 8-inch open roll and pelletized using a square pelletizer to obtain silane MB (step (a)). The obtained silane MB contains a silane graft resin in which a silane coupling agent has undergone a graft reaction with the base resin.

[0144] Meanwhile, the remaining base resin, silicone compound, antioxidant, color masterbatch, and silanol condensation catalyst were sequentially added to a Banbury mixer (2L capacity, manufactured by Nippon Roll Co., Ltd.) preheated to 80°C, in the mass ratios shown in the "Composition" column of Table 3. After mixing at 40 rpm for 5 minutes, finishing kneading (melt mixing) was performed at 30 rpm for 3 minutes. After confirming that the mixture temperature reached approximately 160°C and that the carrier resin was sufficiently melted, the molten mixture was spread thinly to approximately 3 mm using an 8-inch open roll and pelletized using a square pelletizer to obtain catalyst MB (step (b)).

[0145] Next, the obtained silane MB and catalyst MB were dry-blended in a tumbler mixer at room temperature (25°C) for 2 minutes immediately before extrusion molding, in the mass ratio shown in Table 2, to obtain a dry blend. The obtained dry blend was melt-mixed in an extruder equipped with an L / D=25 screw and a screw diameter of 25 mm (cylinder temperature 150~180°C, crosshead temperature 160~200°C) (step (c), up to step (1)) to obtain a tape molded body with a thickness of 2 mm and a width of 14 mm (a tape-shaped molded body of a silane-crosslinkable flame-retardant polyolefin resin composition) (step (2)). At this time, by melt-mixing the dry blend in the extruder (step (c)), a silane-crosslinkable flame-retardant polyolefin resin composition containing the above-mentioned silane graft resin is prepared as a molten mixture of silane MB and catalyst MB. Next, the tape-shaped molded body was left in an atmosphere of 60°C and 95% RH humidity for 24 hours to come into contact with water (step (3)). In this way, a tape-shaped flame-retardant silane-crosslinked polyolefin resin molded article (a tape-shaped molded article of a silane-crosslinked resin composition) was produced.

[0146] The following tests were conducted on each manufactured tape-shaped molded product, and the results are shown in Tables 1 to 3.

[0147] <Evaluation 1: Extrusion Appearance Test (Reference Test)> In the production of the tape-shaped molded articles of each example and comparative example, if the surface of the obtained tape-shaped molded article was clean with no gel particles observed and had an excellent appearance, it was classified as "A (high quality)". If 1 to 5 gel particles were observed on the surface of the tape-shaped molded article per meter along the long axis of the tape-shaped molded article, but there was no problem with the appearance of the tape-shaped molded article, it was classified as "B (good)". If a large amount of gel particles or roughness were observed on the surface of the tape-shaped molded article and the appearance of the tape-shaped molded article was poor, it was classified as "D (fail)". This test is a reference test for evaluating the moldability of flame-retardant polyolefin resin compositions.

[0148] <Evaluation 2: Extrusion foaming test> In the manufacturing of the tape-shaped molded articles of each example and comparative example, the surface (external appearance) and interior (cross-section when the tape-shaped molded article is cut with a plane perpendicular to the extrusion direction) of the tape-shaped molded article were observed. If no foaming was observed on the surface or inside the tape-shaped molded article, it was classified as "A (good)," and if foaming was observed, it was classified as "D (fail)." This test evaluates the feasibility of manufacturing flame-retardant polyolefin resin molded articles with suppressed foaming of flame-retardant polyolefin resin compositions, i.e., reduced internal defects caused by foaming.

[0149] <Evaluation 3: Mechanical properties test (tensile test, reference test)> Test specimens in the shape of a No. 3 dumbbell, as specified in JIS K 6251, were punched out from the tape-shaped molded bodies produced in each example and comparative example. Using these dumbbell test specimens, tensile tests were 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 strength at fracture (also called tensile strength) and elongation at fracture (also called elongation at fracture) were measured. The tensile strength was evaluated as follows: "A (Excellent)" if the tensile strength was 16 MPa or higher, "B (Good)" if it was between 13 MPa and 16 MPa, "C (Acceptable)" if it was between 10 MPa and 13 MPa, and "D (Fail)" if it was less than 10 MPa. The evaluation of elongation at break was as follows: "A (Excellent)" if the elongation at break was 600% or more, "B (Good)" if it was 500% or more but less than 600%, "C (Acceptable)" if it was 350% or more but less than 500%, and "D (Fail)" if it was less than 350%.

[0150] <Evaluation 4: Fluidity Test (Reference Test)> For each example and comparative example, the melt flow rate (MFR) was measured for the flame-retardant polyolefin resin composition prepared under the conditions of a measurement temperature of 190°C and a load of 10 kg, in accordance with JIS K 7210-1 (2014). In the case of the silane-crosslinkable flame-retardant polyolefin resin composition of Example 15, the MFR could not be measured due to the progression of the silanol condensation reaction during the test; therefore, the MFR of silane MB was measured. The evaluation criteria were as follows: an MFR value (g / 10min) of 10.0g / 10min or higher was rated "A (Excellent)", 7.0g / 10min or higher but less than 10.0g / 10min was rated "B (Good)", 4.0g / 10min or higher but less than 7.0g / 10min was rated "C (Acceptable)", and less than 4.0g / 10min was rated "D (Fail)". The measured values ​​for Examples 3 and 12 are shown in parentheses in the "MFR" column of Tables 1 and 2.

[0151] <Evaluation 5: Flame resistance (flame retardancy) test> The flame resistance of the tape-shaped molded articles produced in each example and comparative example was evaluated in accordance with JIS K 6911 5.24.2 Method B. The flame resistance evaluation was based on whether the flame resistance test results met the requirements for V-0 class ("A" - pass) or not ("D" - fail).

[0152] <Evaluation 6: Tracking Resistance Test> Test specimens were round bars (φ10 mm) molded using the same material as the tape-shaped molded bodies produced in each example and comparative example. In accordance with JIS C 3005, the electrode distance was set to 100 mm, a voltage of 4 kV (50 Hz) was applied, and 0.2% saline solution (conductivity 3000 μS / cm) was sprayed periodically in a cycle of 10 seconds of spraying followed by a 20-second pause. In this test, after performing 101 spray cycles according to the above standard, if no current of 0.5A or more flowed and there were no abnormalities such as combustion, it was classified as "A (Pass)". If a current of 0.5A or more flowed, or if there were abnormalities such as combustion, it was classified as "D (Fail)".

[0153] <Evaluation 7: Dehydration resistance test> A4-sized, 1mm thick press sheet was formed using the same material as the tape-shaped molded bodies produced in each example and comparative example. The mass (W) of the sheet test piece cut from the press sheet into 6cm squares was measured. A The mass (W) was measured. 100 mL of acetic acid (concentration: 99.5% by mass) was placed in a rectangular prism-shaped container with a base of 18 cm x 22 cm and a height of 19 cm. The sheet test piece was placed so as not to come into direct contact with the acetic acid, the lid was closed, and it was left at atmospheric pressure and 23°C for 2 days. After that, the sheet test piece was removed and its mass (W) was measured. B The following was measured. The rate of change in mass of the sheet specimens before and after the test was calculated using the following formula. In this test, samples with a mass change rate of 7% or less were graded "A (Pass)," and those exceeding 7% were graded "D (Fail)." Formula: Mass change rate (%) = [W B (g)-W A (g)] / W A (g) × 100

[0154] <Evaluation 8: Water repellency test (reference test)> Press sheets with an A4 size and a thickness of 1 mm were formed using the same material as the tape-shaped molded bodies produced in each example and comparative example. The press sheets were cut into 3 cm x 1 cm squares, and 1 μL of water was dropped into the center of each cut sheet test piece. Ten seconds after dropping the water, a photograph was taken from the horizontal direction of the sheet using a microscope, and the contact angle between the sheet and the water droplet was measured. The water repellency test was evaluated as follows: "A" if the contact angle was 110° or greater, "B" if it was 100° or greater but less than 110°, "C" if it was 90° or greater but less than 100°, and "D" if it was less than 90°.

[0155] <Evaluation 9: Heat deformation test (reference test)> For each example and comparative example, a heat deformation test was performed on the tape-shaped molded articles produced in accordance with JIS C 3005, and the heat deformation rate (reduction rate) was determined from the thickness after heating and the thickness before heating. The heating temperature was 120°C and the applied load was 10N. This test serves as an indicator for evaluating heat resistance. A deformation rate of less than 40% was assigned an "A," and a deformation rate of 40% or more was assigned a "D."

[0156] [Table 1]

[0157] [Table 2]

[0158] [Table 3]

[0159] The following can be seen from the results shown in Tables 1 to 3. The polyolefin resin compositions of Comparative Examples 1 and 2, which do not contain boehmite, and the flame-retardant polyolefin resin composition of Comparative Example 3, which contains boehmite but does not meet the content specified in the present invention, were inferior in any of the deliquescence resistance test, extrusion foaming test, and tracking resistance test results, and it was not possible to produce flame-retardant polyolefin resin molded articles that possessed deliquescence resistance, foaming suppression, flame retardancy, and tracking resistance. Furthermore, the polyolefin resin compositions of Comparative Examples 4 and 5, which contain boehmite in the content specified in the present invention but do not contain brominated flame retardants in the content specified in the present invention, were inferior in the tracking resistance test or flame resistance test results, and it was not possible to produce flame-retardant polyolefin resin molded articles that possessed deliquescence resistance, foaming suppression, flame retardancy, and tracking resistance. Furthermore, the polyolefin resin composition of Comparative Example 6, which contained boehmite but did not meet the inorganic filler content requirement, performed poorly in tracking resistance and flame resistance tests, and was unable to produce a flame-retardant polyolefin resin molded article that possessed deliquescence resistance, foam suppression, flame retardancy, and tracking resistance. In contrast, the flame-retardant polyolefin resin compositions of Examples 1 to 15, which contain a base resin containing polyolefin resin, an inorganic filler containing boehmite, and a brominated flame retardant in the amounts specified in the present invention, were able to produce flame-retardant polyolefin resin molded articles that possessed deliquescence resistance, foam suppression, flame retardancy, and tracking resistance, regardless of whether they were crosslinked or not. In particular, the flame-retardant crosslinked polyolefin resin compositions were able to produce flame-retardant polyolefin resin molded articles that exhibited high heat resistance while maintaining excellent deliquescence resistance, foam suppression, flame retardancy, and tracking resistance. Furthermore, since the flame-retardant polyolefin resin composition and flame-retardant polyolefin resin molded articles of the present invention contain polyolefin resin as a base resin, it can be understood that they are less expensive and exhibit higher trauma resistance than molded articles using a silicone rubber composition, as described in Patent Document 1.

Claims

1. A flame-retardant polyolefin resin composition comprising 100 parts by mass of a base resin containing a polyolefin resin, 30 to 120 parts by mass of an inorganic filler, and 10 to 35 parts by mass of a brominated flame retardant, A flame-retardant polyolefin resin composition wherein the inorganic filler contains 30 parts by mass or more of boehmite per 100 parts by mass of the base resin.

2. The flame-retardant polyolefin resin composition according to claim 1, wherein the melt flow rate (measured at a temperature of 190°C and a load of 10 kg) is 4.0 g / 10 min or more.

3. The flame-retardant polyolefin resin composition according to claim 1, comprising 1 to 30 parts by mass of a silicone compound.

4. A flame-retardant polyolefin resin composition according to claim 1, wherein the crosslinked material is present.

5. A flame-retardant polyolefin resin molded article of the flame-retardant polyolefin resin composition according to any one of claims 1 to 4.

6. A polymer insulator having a flame-retardant polyolefin resin molded body as described in claim 5 on the outer circumference of the core.

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