JP2013241510A - Flame-retardant polyolefin resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame-retardant polyolefin resin composition having excellent mechanical characteristics such as strength and elongation, heat resistance, flexibility, and flame retardancy, and further having excellent oil resistance, especially the oil resistance at a high temperature; and to provide a flame-retardant polyolefin resin composition having excellent mechanical characteristics, heat resistance, flexibility, flame retardancy and oil resistance, and suitable for a resin for covering an electric wire.SOLUTION: A flame-retardant polyolefin resin composition obtained by crosslinking a resin composition containing a thermoplastic resin and a metal hydroxide is regulated so that the flame-retardant polyolefin resin composition may contain a crosslinkable polyolefin having density of 0.905-0.940 g/cmas the thermoplastic resin, and the gel content in the thermoplastic resin after the crosslinking is ≥35 wt.%.

Description

The present invention relates to a flame retardant polyolefin resin composition. Specifically, the present invention relates to a flame retardant polyolefin resin composition that is excellent in mechanical properties such as strength and elongation, heat resistance, flexibility, flame retardancy, and oil resistance.
The present invention relates to a flame retardant polyolefin resin composition which is excellent in mechanical properties such as strength and elongation, heat resistance, flexibility, flame retardancy and oil resistance, and suitable as a resin for coating an electric wire.

  Polyvinyl chloride resin composition has excellent electrical insulation and self-extinguishing flame retardancy, so it has been widely used for wire coating, tubes, tapes, building materials, automotive parts, home appliance parts, etc. Yes. However, since the polyvinyl chloride resin composition contains chlorine in the molecular structure, hydrogen chloride gas, which is a corrosive gas, is generated during combustion, and toxic gas may be generated depending on the combustion conditions. For this reason, as a part of countermeasures against recent environmental problems, a material that does not contain halogen (hereinafter, the fact that halogen is not contained is sometimes referred to as “non-halogen”) has been used.

  Examples of the non-halogen material include polyolefin resins and styrene resins typified by polypropylene and polyethylene, but these resins are not flame retardant and need to be flame retardant depending on the application. As a countermeasure, a method of adding a halogen-based flame retardant has been performed for a long time. However, since halogen-based flame retardants can also generate toxic gases during combustion, recently, as a non-halogen-based flame retardant, a method of incorporating a metal hydroxide such as magnesium hydroxide or aluminum hydroxide has been adopted. (For example, refer to Patent Document 1).

Although the flame-retardant resin composition containing such a metal hydroxide can prevent the generation of halogen-based gas during combustion, since the resin composition melts due to the high temperature during combustion, The so-called drip phenomenon of falling or the shape retention at high temperatures has not been improved.
As a technique for improving the heat resistance in order to solve the above-mentioned problems in the polyolefin-based flame retardant resin composition, a method of crosslinking the resin composition by a method such as electron beam irradiation, chemical crosslinking, or water crosslinking is known. (See, for example, Patent Documents 2 and 3). Among these, the water crosslinking method is suitably used because it does not require special crosslinking equipment and can be easily crosslinked as compared with the electron beam irradiation method and the chemical crosslinking method.

On the other hand, when using a polyolefin-based flame retardant resin composition for applications such as wire coating, oil resistance is required in addition to flame retardancy and heat resistance. However, simply by crosslinking the resin composition as described above to make a flame retardant resin composition, the heat resistance is improved, but the oil resistance is not improved sufficiently, especially at a high temperature of 100 ° C. or higher. Performance that satisfies the characteristics has not been obtained.
In Patent Document 4, as a method for improving the oil resistance and flexibility of a polyolefin-based flame retardant resin composition, a resin composition comprising a crystalline polyolefin, a peroxide-crosslinked elastomer, a metal hydrate, etc. is organically used. A method of crosslinking with peroxide is disclosed.

JP 2000-109638 A JP 7-25939 A JP 2000-38481 A JP 2004-285185 A

According to the present inventors, even in the method of Patent Document 4, the oil resistance at a high temperature of 100 ° C. or higher is insufficient, the flame resistance resin is still excellent in flexibility and heat resistance and excellent in oil resistance. The present condition is that the composition is not found.
The present invention has been made in view of the above circumstances, and its purpose is excellent in mechanical properties such as strength and elongation, heat resistance, flexibility, flame resistance, and oil resistance, particularly oil resistance at high temperatures. It is providing the flame-retardant polyolefin resin composition excellent in property.
Another object of the present invention is to provide a flame retardant polyolefin resin composition that is excellent in mechanical properties, heat resistance, flexibility, flame retardancy, and oil resistance and that is suitable as a resin for coating electric wires.

  As a result of intensive studies in view of the above problems, the present inventors have determined the density of the crosslinkable polyolefin in a specific range in a crosslinked resin composition obtained by crosslinking a resin composition containing a crosslinkable polyolefin and a flame retardant. And it discovered that said problem could be solved by making the crosslinking degree of a crosslinked resin composition into a specific range, and completed this invention.

That is, the gist of the present invention is the following [1] to [8].
[1] A flame-retardant polyolefin resin composition obtained by crosslinking a resin composition containing a thermoplastic resin and a metal hydroxide, and the density of the thermoplastic resin is 0.905 to 0.940 g / cm ^3. A flame retardant polyolefin resin composition containing a crosslinkable polyolefin, wherein the thermoplastic resin after crosslinking has a gel content of 35% by weight or more.
[2] The flame retardant polyolefin resin composition according to [1], wherein the crosslinkable polyolefin is a silane-grafted polyolefin obtained by graft-modifying a polyolefin resin with an unsaturated silane compound.
[3] In [1] or [2], the crosslinkable polyolefin has a crosslinkable polyolefin having a density of 0.860 to 0.900 g / cm ³ and a crosslink having a density of 0.920 to 0.960 g / cm ^3. Flame retardant polyolefin resin composition, which is a mixture with a functional polyolefin.
[4] The flame-retardant polyolefin resin composition according to any one of [1] to [3], which contains 40% by weight or more of a metal hydroxide.
[5] The flame retardant polyolefin resin composition according to any one of [1] to [4], further containing an ethylene / vinyl acetate copolymer as the thermoplastic resin.
[6] The flame retardant polyolefin resin composition for covering electric wires according to any one of [1] to [5]. [7] A molded product formed by molding the flame retardant polyolefin resin composition according to any one of [1] to [5].
[8] An electric wire formed by coating the flame retardant polyolefin resin composition according to any one of [1] to [5].

According to the present invention, there is provided a flame retardant polyolefin resin composition having excellent mechanical properties such as strength and elongation, heat resistance, flexibility, flame retardancy, and excellent oil resistance. In particular, according to the present invention, a flame retardant polyolefin resin composition excellent in oil resistance at a high temperature of 100 ° C. or higher is provided.
Moreover, according to this invention, it is excellent in a mechanical characteristic, heat resistance, a softness | flexibility, a flame retardance, and oil resistance, and the flame-retardant polyolefin resin composition suitable as an electric wire coating resin is provided.

Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
The flame retardant polyolefin resin composition of the present invention is obtained by crosslinking a resin composition containing a thermoplastic resin and a metal hydroxide, and contains a crosslinkable polyolefin as the thermoplastic resin, at least the crosslinkable polyolefin being Cross-linked.

<Thermoplastic resin>
The thermoplastic resin in the present invention is a crosslinkable resin and contains at least a crosslinkable polyolefin described in detail below.

<Crosslinkable polyolefin>
The crosslinkable polyolefin in the present invention means a polyolefin resin that can undergo a crosslinking reaction but has not yet been crosslinked. That is, it means a polyolefin resin before crosslinking as a raw material constituting the flame-retardant polyolefin resin composition of the present invention obtained by crosslinking.
Here, the crosslinking degree of the crosslinkable polyolefin does not need to be 0, and it is sufficient that the crosslinkable polyolefin has a thermoplasticity that can substantially be melt-molded. Specifically, the degree of crosslinking of the crosslinkable polyolefin is usually 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, and still more preferably 5% by weight as the gel content in the measurement method described later. Hereinafter, it is particularly preferably 3% by weight or less, and the lower limit is 0% by weight.

In the present invention, the crosslinkable polyolefin is not limited as long as it is a polyolefin resin that can be crosslinked by a crosslinking reaction. Here, the type of the crosslinking reaction is not limited, and may be crosslinking by peroxide, but is usually crosslinking by moisture (water crosslinking). Therefore, as the crosslinkable polyolefin, a polyolefin resin modified or copolymerized so as to be water-crosslinkable is preferably used.
The polyolefin resin used as the raw material to be modified is not limited. For example, homopolymers such as ethylene, propylene, and 1-butene, those α-olefins or those α-olefins and 3-methyl-1-butene, 1- Other α-olefins having about 4 to 20 carbon atoms such as pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, vinyl acetate, (meth) acrylic acid, (meth) acrylic Examples thereof include copolymers with acid esters and the like.

Specific examples of the polyolefin resin include, for example, low, medium and high density polyethylene (branched or linear) ethylene homopolymer, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene 4-methyl-1-pentene copolymer, ethylene / 1-hexene copolymer, ethylene / 1-octene copolymer, ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, ethylene / Ethylene resins such as (meth) ethyl acrylate copolymer; propylene homopolymer, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, propylene / 4 A propylene-based resin such as methyl-1-pentene copolymer; and 1-butene homopolymer, 1-butene / ethylene copolymer, 1- 1-butene-based resins such as ten-propylene copolymer. These polyolefin resins can be used alone or in combination of two or more.
Here, the ethylene-based resin, the propylene-based resin, and the 1-butene-based resin each mean a resin having ethylene, propylene, or 1-butene as a main component of the monomer unit, and more preferably, each monomer unit. Is a resin containing 50% by weight or more of the composition.

Among these, as the polyolefin resin used for the raw material of the crosslinkable polyolefin, an ethylene resin is preferable. As described later, the crosslinkable polyolefin in the present invention is preferably one obtained by grafting a silane compound by a graft reaction with a free radical generator, but if the polyolefin resin used as a raw material is an ethylene resin, grafting is preferably performed. Since it is made, it is preferable. Moreover, if the polyolefin resin used as a raw material is an ethylene-based resin, it is preferable when the flame-retardant polyolefin resin composition of the present invention is used for coating an electric wire because heat resistance and flame retardancy are improved.
The polyolefin resin used as a raw material for the crosslinkable polyolefin is, among ethylene resins, ethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 1-octene copolymer. An ethylene / vinyl acetate copolymer is particularly preferred.

The crosslinkable polyolefin in the present invention can be suitably obtained by modifying the polyolefin resin so that water crosslinking is possible. Although the modification method is not limited, it is preferable to graft the polyolefin resin with an unsaturated silane compound. Hereinafter, a resin obtained by grafting a polyolefin resin with an unsaturated silane compound (hereinafter sometimes referred to as silane-grafted polyolefin) will be described in detail.
In the present invention, examples of the silane-grafted polyolefin include a modified polyolefin resin obtained by subjecting the polyolefin resin to a graft reaction step of an unsaturated silane compound in the presence of a radical generator such as an organic peroxide. It is also possible to obtain a crosslinkable polyolefin by copolymerization instead of grafting, and in that case, it can be obtained by radical copolymerization of the monomer constituting the polyolefin resin and the unsaturated silane compound.

In order to graft the unsaturated silane compound onto the polyolefin resin, for example, a known method, that is, a method in which a predetermined amount of an unsaturated silane compound and a radical generator are melt kneaded into the polyolefin resin can be used.
Here, the unsaturated silane compound is not limited, and specific examples include compounds represented by the following general formula (I).

R1 · SiR2 _n Y _3-n (I)
In formula (I), R1 represents an ethylenically unsaturated hydrocarbon group, R2 represents a hydrocarbon group, Y represents a hydrolyzable organic group, and n is an integer of 0-2.
Here, as R1, an ethylenically unsaturated hydrocarbon group having 3 to 10 carbon atoms is preferable, and examples thereof include a propenyl group, a butenyl group, a cyclohexenyl group, and a γ- (meth) acryloyloxypropyl group. R2 is preferably a hydrocarbon group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a decyl group, and a phenyl group. Y is preferably a hydrolyzable organic group having 1 to 10 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a formyloxy group, an acetoxy group, a propionyloxy group, an alkylamino group, and an arylamino group.
Specific examples of such unsaturated silane compounds include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloyloxypropyltrimethoxysilane, etc. Among these, odor etc. From the viewpoint, vinyltrimethoxysilane is preferred.

  The amount of the unsaturated silane compound added is not limited, but is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more with respect to 100 parts by weight of the polyolefin resin, while preferably 10 parts by weight or less. More preferably, it is 5 parts by weight or less.

The radical generator is not limited as long as an unsaturated silane compound can be grafted to the polyolefin resin, but an organic peroxide or an azo compound is preferable.
The organic oxide is not limited, but specifically, 1,1-bis (t-butylperoxy)
-3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) ) Peroxyketals such as valerate, 2,2-bis (t-butylperoxy) butane; di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α, α'-bis (t-butylperoxy) ) Dialkyl peroxides such as diisopropylbenzene, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3; acetyl Peroxide, isobutyl peroxide, octanoyl peroxide, decanoyl peroxide, laur Diacyl peroxides such as rhoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, benzoyl peroxide, 2,5-dichlorobenzoyl peroxide, m-trioyl peroxide; t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-butylperoxylaurate, t-butylperoxybenzoate, di-t-butylperoxyisophthalate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane , T-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, cumylperoxyoctate, and other peroxyesters; di (2-ethylhexyl) peroxydicarbonate, di ( -Methyl-3-methoxybutyl) peroxydicarbonates, etc .; t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1 , 1,3,3-tetramethylbutyl hydroperoxide and the like. Among these, t-butylperoxybenzoate, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxy-2-ethylhexanoate, dicumyl peroxide and the like are preferable.
The azo compound is not limited, but specifically, azobisisobutyronitrile, dimethylazoisobutyrate, or the like can be used.

  The addition amount of the radical generator is not limited, and a larger amount is desirable for grafting the unsaturated silane compound onto the polyolefin resin to obtain a sufficient crosslinking effect, but a smaller amount is desirable from the viewpoint of workability. Specifically, it is preferably 0.001 part by weight or more, more preferably 0.01 part by weight or more, still more preferably 0.03 part by weight or more with respect to 100 parts by weight of the polyolefin resin, while preferably 3 parts by weight. It is not more than parts by weight, more preferably not more than 2 parts by weight, still more preferably not more than 1 part by weight.

  The method of grafting the unsaturated silane compound onto the polyolefin resin is not limited, and can be obtained, for example, by melt-kneading a polyolefin resin, an unsaturated silane compound, and a radical generator at a temperature of 80 to 250 ° C. At this time, if water is contained, a water crosslinking reaction is performed, and therefore, it is preferable to melt and knead in a state not containing water.

The graft amount of the silane-grafted polyolefin is not limited, but is usually 0.5% by weight or more, preferably 0.7% by weight or more, and usually 8% by weight or less, preferably 5% by weight or less. When the graft amount is less than the lower limit, crosslinking of the thermoplastic resin portion is insufficient, so that the tensile properties of the flame retardant polyolefin resin composition of the present invention may be insufficient. On the other hand, if the graft amount exceeds the upper limit, the degree of cross-linking of the thermoplastic resin portion is too high and the moldability tends to be lowered.
Here, the measurement of the graft amount of the silane-grafted polyolefin can be confirmed by an analysis method using an infrared absorption spectrum, ¹ H-NMR, a high-frequency plasma emission analyzer (ICP) or the like.

The melt flow rate (MFR) of the crosslinkable polyolefin is not limited, but is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more, still more preferably 0.5 g / 10 min or more, preferably Is 50 g / 10 min or less, more preferably 30 g / 10 min or less, and still more preferably 20 g / 10 min or less.
Here, MFR means a value at 230 ° C. and 21.2 N (2.16 kg) load when the polyolefin resin is a propylene resin, and the polyolefin resin is an ethylene resin, 1-butene resin or other polyolefin. In the case of resin, it means a value at 190 ° C. and 21.2 N load. If the MFR of the polyolefin resin is less than the lower limit value, the fluidity is too low and the load on the extruder tends to increase and the productivity tends to decrease. If the MFR exceeds the upper limit value, the fluidity is too high. It tends to be difficult to form a strand by an extruder.

In the present invention, the density of the crosslinkable polyolefin is in the range of 0.905 to 0.940 g / cm ³ . When the density of the crosslinkable polyolefin is less than the lower limit, the oil resistance deteriorates, which is not preferable. Moreover, when the density of crosslinkable polyolefin exceeds the said upper limit, since tensile elongation will deteriorate, it is unpreferable. By setting the density of the crosslinkable polyolefin within the above range, the flexibility and oil resistance of the flame retardant polyolefin resin composition of the present invention are improved. This is achieved by optimizing the density of the crosslinkable polyolefin. This is probably because the balance between the crystal part that improves oil resistance and the non-crystal part (amorphous part) that controls flexibility is improved. As a result, it is thought that the physical property fall by oil can be suppressed, maintaining a softness | flexibility.
Incidentally, the density of the crosslinkable polyolefin, for the same reason as described above, preferably 0.910 g / cm ³ or more, more preferably 0.915 g / cm ³ or more, more preferably 0.920 g / cm ³ or more is desirable, whereas, preferably 0.935 g / cm ³ or less and more preferably 0.930 g / cm ³ or less.

In the present invention, two or more different crosslinkable polyolefins may be used in combination. For example, when using a silane grafted polyolefin as the crosslinkable polyolefin, when using a modified polyolefin resin in combination, using a modified with a different unsaturated silane compound, or modified with a different graft amount Is used in combination.
In the case where two or more different types of crosslinkable polyolefin are used in combination, the above density value may be obtained by actually measuring the density of the mixed crosslinked polyolefin, or may be obtained by calculation from each density and blending ratio. .

Among these, as an embodiment in which two or more different types of crosslinkable polyolefins are used in combination, a method of using two or more types of crosslinkable polyolefins obtained using polyolefin resins having different densities as raw materials is suitably employed. This is because with a single polyolefin resin, it may be difficult to set the density of the crosslinkable polyolefin within the above range.
Conventionally, many attempts at flame retardant polyolefin resin compositions have not been made at densities in the range specified in the present invention. This is because such a density range is difficult to achieve with a single resin unless a targeted adjustment is made. In the present invention, it has been found that such a special density range is purposely selected, and further has an effect of improving oil resistance by setting the gel content in a specific range as described later. As a means for achieving the density range, an embodiment in which two or more different types of crosslinkable polyolefin are used in combination is suitable.

When a specific density range is achieved by using two or more different crosslinkable polyolefins, it is preferable to use a crosslinkable polyolefin having a relatively low density and a crosslinkable polyolefin having a high density in combination. Specifically, for example, it is preferable to use a crosslinkable polyolefin having a density of 0.860 to 0.900 g / cm ³ and a crosslinkable polyolefin having a density of 0.920 to 0.960 g / cm ³ in combination. It is.
The low density cross-linkable polyolefin, preferably a density 0.870~0.895g / cm ^3, as a dense crosslinking polyolefins, that the density 0.930~0.950g / cm ³ preferable.

In particular, when two or more crosslinkable polyolefins having the above density range are used in combination, the crosslinkable polyolefin is preferably a polyethylene resin, and more preferably silane-grafted polyethylene. That is, it is preferable to use two or more kinds of a crosslinkable polyethylene having a relatively low density and a crosslinkable polyethylene having a high density.
In addition, it can also be set as one crosslinkable polyolefin by grafting an unsaturated silane compound using 2 or more types of polyolefin resin together as a raw material.

  When a silane-grafted polyolefin resin is used as the crosslinkable polyolefin in the present invention, a commercially available product can also be used. For example, from Mitsubishi Chemical Co., Ltd. It can be selected or used in combination.

<Metal hydroxide>
In this invention, a metal hydroxide is used in order to provide a flame-retardant action to the flame-retardant polyolefin resin composition of this invention.
The type of metal hydroxide is not limited, but specific examples include magnesium hydroxide, aluminum hydroxide, zirconium hydroxide, potassium hydroxide, hydrotalcite, etc. Among them, magnesium hydroxide and aluminum hydroxide are examples. Preferably used. These metal hydroxides can be used alone or in combination of two or more.

The metal hydroxide used for this invention can use what was surface-treated with the surface treating agent. Examples of the surface treatment agent include silane coupling agents, titanate coupling agents, fatty acids or fatty acid metal salts. As a method for treating the metal hydroxide with these surface treatment agents, known methods such as a wet method, a dry method, and a direct kneading method can be used. By using the surface-treated metal hydroxide, the dispersibility in the obtained flame-retardant polyolefin resin composition may be improved or the mechanical properties may be improved.
The average particle diameter of the metal hydroxide is preferably 4 μm or less from the viewpoint of mechanical properties, dispersibility, and flame retardancy.

  The content of the metal hydroxide is not limited, but is usually 40% by weight or more and preferably 50% by weight or more in the flame-retardant polyolefin resin composition of the present invention, while usually 85% by weight or less. And is preferably 75% by weight or less. If the content of the metal hydroxide is less than the lower limit value, the flame retardancy at the level which is the subject of the present invention tends not to be obtained. On the other hand, when the content of the metal hydroxide exceeds the upper limit, workability and mechanical strength tend to decrease.

  The compounding amount of the metal hydroxide with respect to the crosslinkable polyolefin is not limited, but is usually 100 parts by weight or more and preferably 150 parts by weight or more with respect to 100 parts by weight of the crosslinkable polyolefin, while usually 500 parts by weight. It is below, and it is preferable that it is 400 parts weight or less. If the blending amount of the metal hydroxide is less than the lower limit value, the flame retardancy at the level desired by the present invention tends not to be obtained. On the other hand, when the compounding amount of the metal hydroxide exceeds the upper limit value, workability and mechanical strength tend to be lowered.

Further, the compounding amount of the metal hydroxide with respect to the resin component constituting the flame-retardant polyolefin resin composition of the present invention is not limited, but is usually 100 parts by weight or more and 150 parts by weight or more with respect to 100 parts by weight of the resin component. On the other hand, it is usually 500 parts by weight or less and preferably 400 parts by weight or less. If the blending amount of the metal hydroxide is less than the lower limit value, the flame retardancy at the level desired by the present invention tends not to be obtained. On the other hand, when the compounding amount of the metal hydroxide exceeds the upper limit value, workability and mechanical strength tend to be lowered.

<Crosslinking catalyst>
In this invention, a crosslinking catalyst is used in order to bridge | crosslink said crosslinkable polyolefin.
When silane-grafted polyolefin is used as the crosslinkable polyolefin and water crosslinking is performed as the crosslinking method, the crosslinking catalyst is a compound that can be brought into contact with moisture in the presence of the catalyst to form a crosslinked structure in the polyolefin resin, so-called silanol. A condensation catalyst is selected.
Specific examples of the silanol condensation catalyst include dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, stannous acetate, stannous caprylate, zinc caprylate, lead naphthenate, cobalt naphthenate and the like. Salt. Only one type of crosslinking catalyst may be used, or two or more types may be used in any combination and ratio.

  The amount of the crosslinking catalyst used is not limited, but is usually 0.000005 parts by weight or more, preferably 0.00001 parts by weight or more, and usually 0.05 parts by weight or less, based on 100 parts by weight of the crosslinkable polyolefin. It is preferably 0.01 parts by weight or less. If the amount of the crosslinking catalyst used is less than the lower limit, crosslinking of the crosslinkable polyolefin is insufficient, so that sufficient flame retardancy may not be obtained. On the other hand, when the amount of the crosslinking catalyst used exceeds the upper limit, processability tends to be lowered.

In addition, a crosslinking catalyst can also be used in the state of the masterbatch contained in resin. The resin used as the base of the masterbatch is not limited, but a polyolefin resin is preferable. Moreover, although content of the crosslinking catalyst in a masterbatch is not limited, Since it is normally concentrated and used about 10 to 500 times, it is about 0.0001 to 5.0 weight%.
A commercially available product can be used as the master batch of the crosslinking catalyst. For example, the product can be selected from the trade name “Linkron Catalyst Master Batch” manufactured by Mitsubishi Chemical Corporation.

<Other polyolefin resins>
In the present invention, in addition to the crosslinkable polyolefin, a polyolefin resin that is not crosslinkable (hereinafter sometimes referred to as “other polyolefin resin”) may be used in combination. Such “other polyolefin resin” is also included in the thermoplastic resin in the present invention.
The other polyolefin resin is not limited, but the above-described polyolefin resin used as a raw material for the crosslinkable polyolefin can be used. Furthermore, a polyolefin resin modified with an unsaturated carboxylic acid or the like is also included. Other polyolefin resin may use only 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
Among these, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 1-octene copolymer, ethylene / vinyl acetate copolymer, acid-modified polyolefin, etc. are preferably used. it can.

The amount of other polyolefin resin used is not particularly limited, but the resin component (thermoplastic resin in the present invention) constituting the flame retardant polyolefin resin composition of the present invention is usually 50% by weight or less, The amount is preferably 40% by weight or less, more preferably 30% by weight or less, and usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1.0% by weight or more.
The amount used for 100 parts by weight of the crosslinkable polyolefin when other polyolefin resin is used is not limited, but is usually 0.1 parts by weight or more, preferably 1 part by weight or more, and usually 400 parts by weight or less, preferably Is 250 parts by weight or less.
When other polyolefin resins are used in the above range, the processability, appearance of the molded product and various physical properties may be improved. Flammability may be reduced.

The ethylene / vinyl acetate copolymer that can be suitably used as another polyolefin resin is a copolymer having at least a polymer unit derived from ethylene and a polymer unit derived from vinyl acetate. By containing an ethylene / vinyl acetate copolymer as another polyolefin resin, the flexibility, flame retardancy, and oil resistance of the flame retardant polyolefin resin composition may be improved.
The vinyl acetate content in the ethylene / vinyl acetate copolymer is not limited, but is preferably 10% by weight or more, more preferably 20% by weight or more, while preferably 55% by weight or less, more preferably 45% by weight. It is as follows. Here, vinyl acetate content means the weight ratio of the monomer derived from vinyl acetate among all the monomer units which comprise an ethylene-vinyl acetate copolymer. In the present invention, the measurement of vinyl acetate content means a value measured according to JIS K7192 (1999) using a Fourier transform infrared spectrophotometer.

  The ethylene / vinyl acetate copolymer may contain other copolymer components in addition to ethylene and vinyl acetate. The copolymerizable component is not limited, and examples thereof include propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-decene. And a copolymer with (meth) acrylic acid, (meth) acrylic acid ester, styrene and the like.

The melt flow rate (MFR) of the ethylene / vinyl acetate copolymer is not limited, but the value measured at 190 ° C. and 21.2 N load is usually 0.1 to 60 g / 10 minutes, preferably 1 to 35 g / 10 minutes. More preferably, the range of 2 to 30 g / 10 min is suitable.
As the ethylene / vinyl acetate copolymer, for example, “Novatech EVA” manufactured by Nippon Polyethylene Co., Ltd., “Evaflex” manufactured by Mitsui DuPont Polychemical Co., Ltd., “Revaprene” manufactured by LANXESS, etc. can be used as appropriate. .

<Other resins>
In the flame-retardant polyolefin resin composition of the present invention, a resin other than the above-mentioned components may be used as “other resin” as necessary within a range that does not significantly disturb the effects of the present invention. Other resin may use only 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.

Specific examples of other resins, that is, resins other than crosslinkable polyolefin and other polyolefin resins include, for example, polyphenylene ether resins; polycarbonate resins; polyamide resins such as nylon 66 and nylon 11; polyethylene terephthalate, poly Examples thereof include polyester resins such as butylene terephthalate; styrene resins such as polystyrene; acrylic / methacrylic resins such as polymethyl methacrylate resins. Furthermore, various thermoplastic elastomers such as styrene, olefin, ester, amide, and urethane can also be suitably used.
In addition to the above “other polyolefin resin”, such “other resin” is also included in the thermoplastic resin in the present invention.

The content in the case of using a resin as the other component is not particularly limited, but is generally 50% by weight or less, preferably 40% by weight or less, more preferably in the total resin component in the flame retardant polyolefin resin composition of the present invention. On the other hand, it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1.0% by weight or more.
In addition, the amount used with respect to 100 parts by weight of the crosslinkable polyolefin when using a resin as the other component is not limited, but is usually 0.1 parts by weight or more, preferably 1 part by weight or more, while usually 400 parts by weight or less, The amount is preferably 250 parts by weight or less.

As the resin used as the other component, a styrene-based elastomer can be preferably used. By containing a styrene elastomer, flexibility may be improved.
The styrene elastomer in the present invention is not limited as long as it has a polymer block mainly composed of a vinyl aromatic compound and a polymer block imparting flexibility. Specifically, a vinyl aromatic compound is It is obtained by hydrogenating a block copolymer having at least two polymer blocks P mainly composed of at least one polymer block Q mainly composed of butadiene and / or isoprene and / or the block copolymer. (Hereinafter, the polymer block P may be abbreviated as “block P” and the polymer block Q may be abbreviated as “block Q”).
Here, “a polymer mainly composed of a vinyl aromatic compound” means a polymer obtained by polymerizing a monomer mainly composed of a vinyl aromatic compound, and “a polymer mainly composed of butadiene and / or isoprene”. The term “polymerized” means a monomer mainly composed of butadiene and / or isoprene. In addition, “mainly” here means 50 mol% or more.

  The monomeric vinyl aromatic compound constituting the block P is not limited, but styrene derivatives such as styrene and α-methylstyrene are preferable. Of these, styrene is the main component. The block P may contain a monomer other than the vinyl aromatic compound as a raw material.

The block Q is more preferably any one of butadiene alone, isoprene alone, butadiene and isoprene. The block Q may contain monomers other than butadiene and isoprene as raw materials.
The block Q may be a hydrogenated derivative obtained by hydrogenating a double bond having after polymerization. The hydrogenation rate of the block Q is not limited, but is preferably 50 to 100% by weight, and more preferably 80 to 100%. By hydrogenating the block Q within the above range, the thermal stability of the laminate of the present invention tends to be improved. The same applies to the case where the block P uses a diene component as a raw material. The hydrogenation rate can be measured by 13C-NMR.

  The weight ratio of the block P in the styrene-based elastomer is not limited, but is usually 5% by weight or more and preferably 10% by weight or more, while it is usually 55% by weight or less and 50% by weight or less. Preferably, it is 45% by weight or less. When the weight ratio of the block P is in the above range, the adhesiveness of the laminate of the present invention tends to be good.

When the copolymer having the block P and the block Q is used as the styrene elastomer, the chemical structure may be any of linear, branched, radial, etc., but the following formula (1) or ( The block copolymer represented by 2) is preferable, and the structure of the following formula (1) is more preferable from the viewpoint of adhesiveness.
Furthermore, the block copolymer represented by the following formula (1) or (2) is more preferably a hydrogenated derivative (hereinafter sometimes abbreviated as a hydrogenated block copolymer). When the copolymer represented by the following formula (1) or (2) is a hydrogenated block copolymer, the adhesiveness of the laminate of the present invention tends to be good.
P- (Q-P) m (1)
(PQ) n (2)
(Wherein P represents the polymer block P, Q represents the polymer block Q, m represents an integer of 1 to 5, and n represents an integer of 2 to 5)
In the formula (1) or (2), m and n are preferably large in terms of lowering the order-disorder transition temperature as a rubbery polymer, but small in terms of ease of production and cost. . In the present invention, m and n are preferably given by integers of 1 to 5, more preferably 2 to 4.

  The block copolymer or hydrogenated block copolymer (hereinafter collectively referred to as “(hydrogenated) block copolymer”) is represented by the formula (2) because it has excellent rubber elasticity. ) A (hydrogenated) block copolymer represented by formula (1) is preferred to a block copolymer, and (hydrogenated) block copolymer represented by formula (1) wherein m is 3 or less. (Hydrogenated) block copolymer represented by the formula (1) in which m is 2 or less is more preferable.

  The number average molecular weight of the styrene-based elastomer in the present invention is not limited, but is usually 20000 or more, preferably 40,000 or more, more preferably as a value in terms of polystyrene measured by gel permeation chromatography (hereinafter sometimes abbreviated as GPC). Is 50000 or more, and is usually 300000 or less, preferably 200000 or less, more preferably 150,000 or less, and still more preferably 100000 or less. If the number average molecular weight of the styrene-based elastomer is within the above range, the adhesiveness and / or affinity with the adhesive resin layer (B) and the polyolefin layer (D) tend to be good.

  Examples of styrene elastomers include commercially available hydrogenated block copolymers such as “KRATON-G” manufactured by Shell Chemicals Japan Co., Ltd., “Septon”, “Hibler” manufactured by Kuraray Co., Ltd., and “Tuftec” manufactured by Asahi Kasei Corporation. In addition, as a commercial product of a non-hydrogenated block copolymer, “KRATON-A” manufactured by Shell Chemicals Japan Co., Ltd., some grades of “Hibler” manufactured by Kuraray Co., Ltd., “Tufprene” manufactured by Asahi Kasei Co., Ltd., etc. Can be appropriately selected and used.

<Other ingredients>
In the flame-retardant polyolefin resin composition of the present invention, additives other than the above-mentioned components and the like may be used as “other components” as necessary, as long as the effects of the present invention are not significantly impaired. Other components may be used alone or in combination of two or more in any combination and ratio.

  Specific examples of additives used as other components include oils, processing aids, plasticizers, crystal nucleating agents, impact modifiers, flame retardant aids, crosslinking agents, crosslinking aids, antistatic agents, and oxidation agents. Examples thereof include an inhibitor, a lubricant, a filler, a compatibilizer, a heat stabilizer, a light stabilizer, an ultraviolet absorber, carbon black, and a colorant. The content of these additives is not limited, but it is preferably used in the range of 50% by weight or less in the flame retardant polyolefin resin composition of the present invention.

  In the flame-retardant polyolefin resin composition of the present invention, a flame retardant other than a metal hydroxide may be used in combination as other components. Flame retardants are roughly classified into halogen-based flame retardants and non-halogen-based flame retardants, and non-halogen-based flame retardants are preferred. Examples of non-halogen flame retardants other than metal hydroxides include phosphorus flame retardants, nitrogen-containing compounds (melamine and guanidine) flame retardants, and inorganic compounds (borate and molybdenum compounds) flame retardants.

Examples of the heat stabilizer and the antioxidant include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and the like.
Fillers are roughly classified into organic fillers and inorganic fillers. Examples of the organic filler include naturally occurring polymers such as starch, cellulose fine particles, wood flour, okara, fir husk, bran, and modified products thereof. Inorganic fillers include talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon Examples thereof include black, zinc oxide, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, and carbon fiber.

The flame retardant polyolefin resin composition of the present invention preferably contains a hydrocarbon rubber softener as oil. The hydrocarbon rubber softener is preferably a mineral oil or synthetic resin softener, more preferably a mineral oil softener.
Mineral oil softeners are generally a mixture of aromatic hydrocarbons, naphthenic hydrocarbons and paraffinic hydrocarbons, with paraffinic oils in which 50% or more of all carbon atoms are paraffinic hydrocarbons, Those in which about 30 to 45% of all carbon atoms are naphthenic hydrocarbons are called naphthenic oils, and those in which 35% or more of all carbon atoms are aromatic hydrocarbons are called carbon atom aromatic oils. ing. As the softener for hydrocarbon rubber in the present invention, any one selected from paraffinic oil, naphthenic oil, and carbon atom aromatic oil is preferably used. Of these, it is more preferable to use paraffinic oil because of its good hue. Examples of the synthetic resin softener include polybutene and low molecular weight polybutadiene.
The hydrocarbon rubber softener may be any one of the above-mentioned various softeners or may be a mixture of plural kinds.

The kinematic viscosity at 40 ° C. of the hydrocarbon rubber softener is preferably lower from the viewpoint of dispersibility and processability, but higher from the viewpoint of suppressing bleed out. Specifically, it is preferably 20 centistokes or more, more preferably 50 centistokes or more, and on the other hand, it is preferably 800 centistokes or less, and preferably 600 centistokes or less.
The flash point (COC method) of the hydrocarbon rubber softener is not limited, but is preferably 200 ° C. or higher, and more preferably 250 ° C. or higher.

The content in the case of using the hydrocarbon rubber softener is not particularly limited, but is usually 25% by weight or less, preferably 15% by weight or less, more preferably 10% by weight in the flame retardant polyolefin resin composition of the present invention. On the other hand, it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1.0% by weight or more.
The content when using a hydrocarbon rubber softener is usually 35% by weight or less, preferably 30% by weight or less, more preferably 25% by weight or less, based on all components except metal hydroxide. On the other hand, it is usually 0.5% by weight or more, preferably 1% by weight or more, more preferably 2% by weight or more.

<Flame-retardant polyolefin resin composition>
The flame retardant polyolefin resin composition of the present invention can be produced by mixing a crosslinkable polyolefin, a metal hydroxide, and a crosslinking catalyst used as necessary at the same time or in any order, and then crosslinking the mixture. .
Specifically, the mixing method is (1) a method in which a cross-linkable polyolefin and a metal hydroxide are mixed first, and a cross-linking catalyst is added later, and (2) a cross-linkable polyolefin and a cross-linking catalyst are mixed in advance, There is a method of adding a substance later, (3) a method of mixing all at once.

In addition, a masterbatch containing a metal hydroxide in a crosslinkable polyolefin and a masterbatch containing a crosslinking catalyst in a resin other than the crosslinkable polyolefin are produced separately, and these are mixed to produce. May be. Thus, if a flame-retardant masterbatch and a catalyst masterbatch are used, it will become possible to mix both at the time of shaping | molding, and it can suppress that a crosslinking reaction advances before obtaining a molded object.
Other components may be added at any timing as long as they can be uniformly dispersed.

Although there is no limitation in the apparatus at the time of mixing each said raw material component, general purpose things, such as a kneader, a Banbury mixer, a roll, a single screw extruder, a twin screw extruder, can be used. The temperature at the time of melt mixing may be a temperature at which at least one of the respective raw material components is in a molten state, but usually a temperature at which all the components used are melted is selected, and is generally performed at 150 to 250 ° C.
In the flame-retardant polyolefin resin composition of the present invention, it is sometimes difficult to measure the melt flow rate (MFR) at 230 ° C. and 21.2 N load even in the resin composition before the crosslinking treatment. However, it has sufficient fluidity for various moldings such as extrusion molding including profile extrusion and compression molding.

<Crosslinking treatment>
When the flame retardant polyolefin resin composition of the present invention is obtained by water crosslinking, a crosslinked structure is usually formed in the resin composition by contacting with water. The water cross-linking treatment is performed by contacting the liquid or vapor water at room temperature to about 200 ° C., usually about room temperature to 100 ° C. for about 10 seconds to 1 week, usually about 1 minute to 1 day. Even if such treatment is not performed, crosslinking can be performed by moisture in the air.
By subjecting the flame retardant polyolefin resin composition of the present invention to a crosslinking treatment, a flame retardant polyolefin resin composition excellent in flame retardancy, mechanical properties, oil resistance and the like can be obtained.

In the flame-retardant polyolefin resin composition of the present invention, the gel content in the crosslinked thermoplastic resin is 35% by weight or more. When the gel content in the crosslinked thermoplastic resin is less than the lower limit, the oil resistance deteriorates, which is not preferable.
Here, the gel content in the thermoplastic resin after crosslinking means the gel content in the resin component constituting the flame retardant polyolefin resin composition. That is, it refers to the gel content when the resin component, which is a residue obtained by excluding components (metal hydroxide, other components, etc.) other than the resin from the flame retardant polyolefin resin composition, is 100% by weight.

  Specifically, when the Soxhlet extraction of the resin component in the flame-retardant polyolefin resin composition was conducted in boiling xylene at 144 ° C. for 10 hours, the dry weight of the insoluble matter was measured, and the ratio to the weight before Soxhlet extraction ( (% By weight). In addition, when the resin composition itself before crosslinking is not dissolved in boiling xylene in the first place, it may be measured by appropriately replacing with another solvent.

Oil resistance is optimized by optimizing the gel content in the thermoplastic resin after crosslinking as described above. This is because the main component in the thermoplastic resin is constrained by intermolecular crosslinking. This is considered to be because even when such lubrication penetrates, the molecular entanglement does not loosen and the state before oil immersion can be maintained.
The gel content in the crosslinked thermoplastic resin is preferably 35% by weight or more, more preferably 40% by weight or more, and still more preferably 45% by weight or more for the same reason as described above.
Further, the upper limit of the gel content in the thermoplastic resin after crosslinking is not limited and may be 100% by weight, but is preferably 85% by weight or less from the viewpoint of workability, and is 80% by weight or less. More preferably.

  As described above, the flame-retardant polyolefin resin composition of the present invention contains a crosslinkable polyolefin having a specific density as a thermoplastic resin, and the gel content of the thermoplastic resin after cross-linking is within a specific range. However, due to the synergistic effect, it is possible to obtain a flame retardant polyolefin resin composition having excellent heat resistance, flame resistance and oil resistance, and particularly excellent in oil resistance at a high temperature of 100 ° C. or higher.

In the flame retardant polyolefin resin composition of the present invention, the gel content after crosslinking of the crosslinkable polyolefin is not limited, but is usually 45% by weight or more, preferably 48% by weight or more, more preferably 55% by weight or more. Is desirable. Further, the upper limit of the gel content after crosslinking of the crosslinkable polyolefin is not limited, and may be 100% by weight, but is preferably 85% by weight or less and preferably 80% by weight or less from the viewpoint of workability. It is more preferable. Here, the method for measuring the gel content is the same as described above.
When the gel content after crosslinking of the crosslinkable polyolefin is within the above range, processability and oil resistance tend to be good.

The tensile strength (breaking strength) of the flame retardant polyolefin resin composition of the present invention is preferably 10 MPa or more. When the tensile strength of the flame retardant polyolefin resin composition is in the above range, it can be suitably used for wire coating applications.
The tensile elongation (breaking elongation) of the flame retardant polyolefin resin composition of the present invention is preferably 100% or more. When the tensile elongation of the flame retardant polyolefin resin composition is in the above range, it can be suitably used for wire coating applications.
Here, the tensile strength and the tensile elongation refer to tensile properties when a test is performed at a tensile speed of 200 mm / min using a No. 3 dumbbell test piece according to JIS C-3005.

The flame-retardant polyolefin resin composition of the present invention is immersed in oil adjusted to 121 ° C. (Sun Oil Co., IRM902) for 18 hours, in accordance with JIS C-3005. It is preferable that the tensile strength residual ratio and the tensile elongation residual ratio measured at / min are 30% or more and 40% or more, respectively. Further, it is more preferable that the tensile strength residual rate is 40% or more and the tensile elongation residual rate is 60% or more. By having such oil resistance, it can be suitably used in wire coating applications that require oil resistance, such as excavation, robot cables, and power generation cables.
Here, the tensile strength residual rate and the tensile elongation residual rate mean values obtained by calculating the retention rate for each of the tensile strength and tensile elongation based on the value of a tensile test not immersed in oil (100%). .

  The flame retardancy of the flame retardant polyolefin resin composition of the present invention is preferably 30 or more as an oxygen index measured in accordance with JIS K-7201. By having such flame retardancy, it can be suitably used, for example, in wire coating applications.

<Molded products and applications>
The method of molding the flame retardant polyolefin resin composition of the present invention is not particularly limited to extrusion molding, compression molding, injection molding, etc., but molding is performed by extrusion molding from the viewpoint of fluidity in the molten state of the resin composition. It is desirable to do. The molding temperature is not limited as long as it is higher than the melting temperature of the resin composition, but is preferably 150 ° C to 250 ° C. If the molding temperature is higher than the lower limit, the fluidity of the molten resin composition is high, and it is easy to obtain a molded article having a desired shape. If the molding temperature is lower than the upper limit, foaming due to decomposition of the metal hydroxide is unlikely to occur.

  The flame retardant polyolefin resin composition of the present invention may be molded or processed after the crosslinking treatment. However, since the thermoplasticity is significantly reduced after crosslinking, the desired shape is required before the crosslinking treatment. It is preferable to carry out a crosslinking treatment after molding. Since the flame-retardant polyolefin resin composition of the present invention has good moldability at the stage before crosslinking, for example, when extrusion molding or the like is performed, the surface is smooth and there is no scorch (burn marks) or the like. A molded product having a good appearance can be obtained. Further, by subjecting this molded article to a crosslinking treatment, a molded article of a flame retardant polyolefin resin composition having a good appearance can be obtained as before crosslinking. The flame retardant polyolefin resin composition after crosslinking has the above-described degree of crosslinking, tensile properties, oil resistance, and flame retardancy.

  The use of the flame-retardant polyolefin resin composition of the present invention is not particularly limited, but it has excellent flame retardancy, mechanical properties, heat resistance, and has an excellent appearance. Can be suitably used. In particular, it can be used as a suitable molded article in applications where high oil resistance and flame retardancy are desired.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Production of crosslinkable polyethylene]
The following raw materials were used for the production of the crosslinkable polyethylene.
<Polyethylene>
Polyethylene -1: high-density polyethylene (manufactured by Asahi Kasei Chemicals Corporation, "Cleo Rex K4125", density ^{0.941g / cm 3, MFR (190} ℃, 21.2N load) 2.5 g / 10 min).
Polyethylene-2: ethylene / 1-butene copolymer (Dow Chemical Co., “engage ENR 7256”, density 0.885 g / cm ³ , MFR (190 ° C., 21.2 N load) 2 g / 10 min).
<Unsaturated silane compound>
・ Vinyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.
<Radical generator>
Di-t-butyl peroxide: “Perbutyl D” manufactured by NOF Corporation.

<Crosslinkable polyethylene-1>
2 parts by weight of an unsaturated silane compound and 0.044 parts by weight of a radical generator are added to 100 parts by weight of polyethylene-1, and this is mixed with a 26 mmφ twin screw extruder (L / D = 49, full flight). The resin was extruded at an extrusion resin temperature of 200 ° C. with a screw). The extruded strand was pelletized with a pelletizer to produce “crosslinked polyethylene-1”. The density of the obtained crosslinkable polyethylene was 0.943 g / cm ³ .

<Crosslinkable polyethylene-2>
“Crosslinked polyethylene-2” was produced in the same manner as crosslinked polyethylene-1, except that polyethylene-1 was changed to polyethylene-2. The density of the obtained crosslinkable polyethylene-2 was 0.892 g / cm ³ .

[Production of resin composition]
The following raw materials were used in addition to the above raw materials for the production of the resin compositions of Examples and Comparative Examples.
<Ethylene / vinyl acetate copolymer (EVA)>
-"Evaflex EV40LX" manufactured by Mitsui DuPont Polychemical Co., Ltd. (density 0.970 g / cm ³ , MFR (190 ° C., 21.2 N load) 2 g / 10 min, vinyl acetate content 41% by weight)
<Acid-modified polyethylene>
-“Modick M122” manufactured by Mitsubishi Chemical Corporation (density 0.92 g / cm ³ , MFR (190 ° C., 21.2 N load) 1 g / 10 min)
<Hydrogenated styrene / butadiene copolymer (SEBS)>
・ “Tuftec N504” manufactured by Asahi Kasei Chemicals Co., Ltd. (density 0.91 g / cm ³ , styrene content 30% by weight)

<Mineral oil>
・ Idemitsu Kosan Co., Ltd., “Diana Process Oil PW90” (mineral oil hydrocarbon)
<Color (pigment) masterbatch>
-Color master batch (black) "PC40B" manufactured by Dainichi Seika Kogyo Co., Ltd.
<Crosslinking catalyst master batch>
・ Mitsubishi Chemical Co., Ltd. “Linkron Catalyst Masterbatch QCM292”
(Polyethylene contains 0.1% by weight of dioctyltin dilaurate as a catalyst)
<Metal hydroxide>
Magnesium hydroxide: manufactured by Kamishima Chemical Industry Co., Ltd., average particle size 1.0 μm, silane coupling agent surface treated product

[Examples 1-5, Comparative Examples 1-7]
What mixed all the raw materials except a crosslinking catalyst with the compounding ratio as described in Table-1 is resin at a rotation speed of 90 rpm using a Banbury kneader (made by Kobe Steel, BB-4 (3L)). After melt-kneading until the temperature reached 200 ° C., a resin composition was produced by pelletizing using an FR extruder (manufactured by Moriyama Co., Ltd.).
After blending 3 parts by weight of the crosslinking catalyst masterbatch with 100 parts by weight of the obtained resin composition, it was extruded at 200 ° C. using a single screw extruder, and an extruded sheet having a width of 50 mm × thickness of 1 mm (before crosslinking) Flame retardant polyolefin resin composition).
The obtained extruded sheet was immersed in warm water at 80 ° C. for 24 hours to perform a water crosslinking treatment to obtain a flame retardant polyolefin resin composition. About the crosslinked sheet of the obtained flame-retardant polyolefin resin composition, the result of having performed the gel content rate, the tension test, and the oil resistance test by the following methods is shown in Table-1.

<Gel content>
The extruded sheet subjected to the crosslinking treatment was subjected to Soxhlet extraction in boiling xylene at 144 ° C. for 10 hours. Next, the weight of the undissolved resin was measured after drying, and the gel content was calculated as the ratio (% by weight) of the unextracted resin to the sample weight before Soxhlet extraction. In addition, about components other than resin, it excluded from calculation of the gel content based on the raw material mixture ratio.

<Tensile test>
Using an extruded sheet (thickness 1 mm) subjected to crosslinking treatment, tensile strength and tensile elongation were measured in accordance with JIS C-3005. The test piece was No. 3 dumbbell, and the tensile speed was 200 mm / min.
Although both the tensile strength and the tensile elongation are preferably higher, the tensile strength is 10 MPa or more and the tensile elongation is 100% or more.

<Oil resistance test>
A No. 3 dumbbell piece punched out from an extruded sheet (thickness 1 mm) subjected to a crosslinking treatment was immersed in oil adjusted to 121 ° C. (IRM902, manufactured by Sun Oil Co., Ltd.) for 18 hours. Then, the adhered oil was wiped off and kept in an environment of 23 ° C. and 50% RH for 24 hours.
The tensile strength and tensile elongation were measured according to C-3005. The tensile speed was 200 mm / min.
Using the value of a tensile test not immersed in oil as a reference (100%), the retention rate was calculated for each of tensile strength and tensile elongation, and the residual tensile strength and residual tensile elongation were obtained. Both the tensile strength residual rate and the tensile elongation residual rate are preferably higher, but the tensile strength residual rate is 30% or more, and the tensile elongation residual rate is 40% or more. It is more preferable that the residual tensile strength is 40% or more and the residual tensile elongation is 60% or more.

Claims (8)

A flame retardant polyolefin resin composition obtained by crosslinking a resin composition containing a thermoplastic resin and a metal hydroxide, wherein the thermoplastic resin has a density of 0.905 to 0.940 g / cm ³ . A flame retardant polyolefin resin composition containing a polyolefin, wherein the thermoplastic resin after crosslinking has a gel content of 35% by weight or more.   The flame-retardant polyolefin resin composition according to claim 1, wherein the crosslinkable polyolefin is a silane-grafted polyolefin obtained by graft-modifying a polyolefin-based resin with an unsaturated silane compound. The crosslinkable polyolefin is a mixture of a crosslinkable polyolefin having a density of 0.860 to 0.900 g / cm ³ and a crosslinkable polyolefin having a density of 0.920 to 0.960 g / cm ^3. The flame-retardant polyolefin resin composition described in 1.   The flame-retardant polyolefin resin composition according to any one of claims 1 to 3, which contains 40% by weight or more of a metal hydroxide.   The flame retardant polyolefin resin composition according to any one of claims 1 to 4, further comprising an ethylene / vinyl acetate copolymer as the thermoplastic resin.   The flame-retardant polyolefin resin composition for electric wire coating | cover in any one of Claims 1-5.   A molded product obtained by molding the flame-retardant polyolefin resin composition according to any one of claims 1 to 5. The electric wire formed by coat | covering the flame-retardant polyolefin resin composition in any one of Claims 1-5.