JP2011032419A - Functional group-modified resin, flame-retardant resin composition, and insulated wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functional group-modified resin, a flame-retardant resin composition, and an insulated wire excellent in cold resistance and abrasion characteristics. <P>SOLUTION: The flame-retardant resin composition in which the functional group-modified resin with a coefficient of elasticity of 2,000 MPa or more obtained by adding 1 pt.mass or more of a functional group-containing compound and 0.5 pt.mass or more of a polymerization initiator to 100 pts.mass of homopolypropylene and bringing them into reaction, an unmodified polypropylene resin, magnesium hydroxide, and an antioxidant are mixed, is extrusion molded around a conductor to form an insulator layer, so that the insulated wire is obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a functional group-modified resin, a flame retardant resin composition using the functional group-modified resin, and an insulated wire using the flame retardant resin composition, and particularly for automobiles, electrical / electronic devices, and the like. The present invention relates to a functional group-modified resin, a flame retardant resin composition, and an insulated wire that are suitably used.

  Various properties such as mechanical properties, flame retardancy, heat resistance, and cold resistance are required for members and insulating materials used in automobiles, electronic / electrical devices, and the like. Conventionally, a polyvinyl chloride compound or a compound containing a halogen-based flame retardant containing a bromine atom or a chlorine atom in the molecule has been mainly used as the material.

  A large amount of corrosive gas may be generated when the above materials are incinerated during disposal. For this reason, a non-halogen flame retardant material that does not cause the generation of corrosive gas has been proposed (see, for example, Patent Document 1). Moreover, as seen in Patent Documents 2 to 4 and the like, as a non-halogen flame retardant resin composition, a composition using a surface-treated magnesium hydroxide as a flame retardant is known.

JP 2004-83612 A Japanese Patent No. 3339154 Japanese Patent No. 3636675 JP 2004-189905 A

  As the conventionally proposed non-halogen flame retardant resin composition, a polyolefin resin filled with magnesium hydroxide is generally used. However, the conventional flame retardant resin composition has a problem that it is not sufficiently provided with cold resistance and wear when used as an insulator of an insulated wire.

  The problem to be solved by the present invention is to solve the above-mentioned problems, and an object thereof is to provide a functional group-modified resin, a flame-retardant resin composition and an insulated wire excellent in cold resistance and wear resistance. And

  In order to solve the above problems, the functional group-modified resin of the present invention is a functional group-modified resin having an elastic modulus of 2000 MPa or more obtained by reacting at least homopolypropylene, a functional group-containing compound, and a polymerization initiator. The homopolypropylene is obtained by adding 1 part by mass or more of the functional group-containing compound and 0.5 part by mass or more of the polymerization initiator to 100 parts by mass and reacting them. is there.

  The functional group-modified resin is obtained by graft copolymerization of the functional group-containing compound and the homopolypropylene, or the functional group of the functional group-containing compound is a carboxylic acid group, an acid anhydride group, an epoxy group, It is at least one functional group selected from a hydroxyl group, an amino group, an alkenyl cyclic imino ether group, and a silane group, the polymerization initiator is an organic peroxide, and the organic peroxide is , Cumene hydroperoxide, di-t-butyl peroxide, di-α-cumyl peroxide, addition amount of the polymerization initiator (Y part by mass) and the functional group The mass ratio (Z = X / Y) of the addition amount (X part by mass) of the group-containing compound is preferably 5 or more.

  The summary of the flame retardant resin composition of the present invention is to contain at least the functional group-modified resin and the flame retardant.

  The gist of the insulated wire of the present invention is that an insulator layer using the flame retardant resin composition is formed around a conductor.

  The present invention relates to a functional group having a modulus of elasticity of 2000 MPa or more obtained by adding 1 part by mass or more of a functional group-containing compound and 0.5 part by mass or more of a polymerization initiator to 100 parts by mass of homopolypropylene. Since it is a modified resin, when a flame retardant resin composition using the functional group-modified resin is used as an insulating film, an insulated wire excellent in cold resistance and wear resistance can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. The functional group-modified resin of the present invention is reacted by mixing 1 part by mass or more of a functional group-containing compound and 0.5 part by mass or more of a polymerization initiator with respect to 100 parts by mass of homopolypropylene, and melt-mixing the mixture. The resulting resin is a modified resin in which at least a part of the modifying agent composed of the functional group-containing compound is bonded to the main chain composed of homopolypropylene.

  The functional group-modified resin may be either a graft polymer obtained by grafting a functional group-containing compound onto homopolypropylene or a copolymer of a functional group-containing compound and homopolypropylene, but is preferably a graft polymer.

  The homopolypropylene before modification used for the functional group-modified resin is a propylene homopolymer having an elastic modulus of 2000 MPa or more. If the homopolypropylene before modification has an elastic modulus of 2000 MPa or more, a modified resin after modification can also be obtained having an elastic modulus of 2000 MPa or more.

  When the elastic modulus of the functional group-modified resin is less than 2000 MPa, sufficient wear resistance and cold resistance cannot be obtained in the insulating coating formed from the flame retardant resin composition using the functional group-modified resin. The upper limit of the elastic modulus of the functional group-modified resin is preferably 4000 MPa. If the elastic modulus of the functional group-modified resin exceeds 4000 MPa, the insulation coating may be cracked in a winding test at a low temperature. The preferable elastic modulus range of the functional group-modified resin is in the range of 2000 to 3500 MPa. In the present invention, the value of elastic modulus is measured according to JIS K7161.

  Although the homopolypropylene before modification used for the functional group-modified resin can be used regardless of the melt flow rate (MFR), the MFR is preferably 0.01 to 10000 g / min. When the MFR is less than 0.01 g / min, mixing is difficult, and when the MFR exceeds 10,000 g / min, there is a possibility that mixing is difficult. In the present invention, the MFR values are all measured according to JIS K7210 (temperature 230 ° C., load 2.16 kg).

  The addition amount (X part by mass) of the functional group-containing compound used in the functional group-modified resin may be 1 part by mass or more, preferably 1.5 parts by mass or more with respect to 100 parts by mass of homopolypropylene. More preferably, it is 2.0 parts by mass or more. In addition, unless otherwise indicated, the addition amount of a functional group containing compound and a polymerization initiator in this invention is the value of the mass part with respect to 100 mass parts of homopolypropylene. If the addition amount of the functional group-containing compound is less than 1 part by mass, the effects of the present invention cannot be exhibited. Moreover, it is preferable that the addition amount of a functional group containing compound is 10 mass parts or less. When the addition amount of the functional group-containing compound exceeds 10 parts by mass, unreacted substances may increase.

  Examples of the functional group of the functional group-containing compound include at least one functional group selected from a carboxyl group, an acid anhydride group, an epoxy group, a hydroxyl group, an amino group, an alkenyl cyclic imino ether group, and a silane group. It is done. The functional group-containing compound used in the functional group-modified resin may be used singly or in a plurality of types. In the functional group-modified resin, a functional group-containing compound is reacted with homopolypropylene to introduce a functional group into the main chain made of homopolypropylene, so that insulation of insulated wires from a flame-retardant resin composition containing the functional group-modified resin is performed. When the body layer is formed, the adhesion between the insulator layer and the conductor can be improved.

  Examples of the functional group-containing compound containing a functional group such as a carboxyl group or an acid anhydride group include α, β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itaconic acid, or anhydrides and acrylic acids thereof , Unsaturated monocarboxylic acids such as methacrylic acid, furanic acid, crotonic acid, vinyl acetic acid and pentenoic acid.

  Examples of the functional group-containing compound containing an epoxy group include glycidyl acrylate, glycidyl methacrylate, itaconic acid monoglycidyl ester, butenetricarboxylic acid monoglycidyl ester, butenetricarboxylic acid diglycidyl ester, butenetricarboxylic acid triglycidyl ester, α-chloro Examples include glycidyl esters such as acrylic acid, maleic acid, crotonic acid, and fumaric acid, vinyl glycidyl ether, allyl glycidyl ether, glycidyl oxyethyl vinyl ether, glycidyl ethers such as styrene-p-glycidyl ether, and p-glycidyl styrene. .

  Examples of the functional group-containing compound containing a hydroxyl group include 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and hydroxyethyl (meth) acrylate.

  Examples of the functional group-containing compound containing an amino group include aminoethyl (meth) acrylate, propylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, Examples include aminopropyl (meth) acrylate, phenylaminoethyl (meth) acrylate, cyclohexylaminoethyl (meth) acrylate, and the like.

  Examples of the functional group-containing compound containing an alkenyl cyclic imino ether group include 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-vinyl-5,6-dihydro-4H-1,3-oxazine, 2-isopropenyl-5,6-dihydro-4H-1,3-oxazine and the like can be mentioned.

  Examples of the functional group-containing compound containing a silane group include unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetylsilane, and vinyltrichlorosilane.

  The addition amount (Y parts by mass) of the polymerization initiator used for the functional group-modified resin may be 0.5 parts by mass or more, preferably 0.6 parts by mass or more with respect to 100 parts by mass of homopolypropylene. More preferably, it is 0.7 parts by mass or more. If the addition amount of the polymerization initiator is less than 0.5 parts by mass, the effect of the present invention cannot be exhibited. Moreover, it is preferable that the addition amount of a polymerization initiator is 5 mass parts or less. When the addition amount of the polymerization initiator exceeds 5 parts by mass, there is a possibility that the decomposition proceeds excessively and the processing cannot be performed efficiently.

  As the polymerization initiator used in the functional group-modified resin, an organic peroxide is preferably used because radicals can be efficiently generated by heating. As the organic peroxide used as the polymerization initiator, various commercially available organic peroxides can be used.

  Examples of the organic peroxide used as the polymerization initiator include ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, isobutyryl peroxide, bis (3,5,5, -trimethylhexanoyl) peroxide, Diacyl peroxides such as lauroyl peroxide and benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, di-isopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetra Hydroperoxides such as methylbutyl hydroperoxide, di-t-butyl peroxide, t-butyl-α-cumyl peroxide, di-α-cumyl peroxide, 1,4 (or 1,3 ) Bis [(t-butylperoxy) isopropyl] benzene, 1,1-bis (t-butylperoxy) cyclohexane, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2, Dialkyl peroxides such as 5-dimethyl-2,5-bis (t-butylperoxy) -3-hexyne, n-butyl = 4,4-bis (t-butylperoxy) valerate, 2,2-bis Peroxyketals such as (t-butylperoxy) butane, t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxyoctoate, t-butylperoxypivalate, t-butyl Peroxyneodecanoate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxybenzoate alkyl peresters such as t-butylperoxylaurate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, bis- (2-ethylhexyl) peroxydicarbonate, diisopropylperoxydicarbonate, Di-sec-butyl peroxydicarbonate, di-n-propyl peroxydicarbonate, bis (2-ethoxyethyl) peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, t-butylisopropyl Examples include peroxycarbonates such as percarbonate.

  As the organic peroxide, it is possible to use at least one compound selected from cumene hydroperoxide, di-t-butyl peroxide, and di-α-cumyl peroxide from the viewpoint of radical generation efficiency and price. preferable. These may be used individually by 1 type, or may mix and use 2 or more types.

  Furthermore, the ratio (Z = X / Y) of the addition amount (X part by mass) of the functional group-containing compound used in the functional group-modified resin and the addition amount (Y part by mass) of the polymerization initiator is preferably 5 or more. If this ratio is 5 or more, it is possible to improve the graft amount of the functional group-containing compound. As a result, it is possible to further improve the wear resistance of an insulated wire having an insulator containing a flame retardant resin composition using a functional group-modified resin.

  The graft amount is the amount of the functional group compound that is directly chemically bonded to the homopolypropylene main chain to form a true graft in the functional group-modified resin.

  Furthermore, the ratio (Z) of the addition amount of the functional group-containing compound and the polymerization initiator is preferably 5.5 or more from the viewpoint of increasing the graft amount. Moreover, the upper limit of the ratio (Z) of the addition amount of the functional group-containing compound and the polymerization initiator is preferably 20 or less from the viewpoint of suppressing unreacted substances as much as possible.

  The functional group-modified resin can be produced by putting the above components into a kneader or the like, mixing, heating, melting, and reacting. In this case, the heating temperature, reaction time, and the like can be appropriately selected.

  The flame retardant resin composition of the present invention comprises, for example, (a) a polyolefin-based resin, (b) the above functional group-modified resin, (c) a flame retardant, (d) other additives such as an antioxidant, and the like. be able to. In addition, the flame-retardant resin composition of this invention should just contain said functional group modified resin and a flame retardant at least. Hereinafter, the flame retardant resin composition will be described.

  As the (a) polyolefin resin in the flame retardant resin composition, a homopolymer or copolymer of olefin such as polyethylene resin or polypropylene resin is used. Among these, a polypropylene resin is preferable, and a homopolymer of propylene may be used, or a copolymer with another monomer may be used. In the case of a copolymer, the polyolefin resin may contain 50% by mass or more of the propylene component, but preferably contains 60% by mass or more of the propylene component. The polyolefin resin may be either a modified resin modified with a compound containing a functional group such as a polar group or an unmodified unmodified resin. However, from the viewpoint of low cost, an unmodified resin is used. Is preferred.

  When an unmodified polypropylene resin is used as the polyolefin resin, the melt flow rate (MFR) is preferably in the range of 0.01 to 1000 g / min (measured at 230 ° C.). When an unmodified polypropylene resin is used as the polyolefin resin, the elastic modulus is preferably in the range of 500 to 4000 MPa.

  In the flame retardant resin composition, (b) the content of the functional group-modified resin is preferably 5 to 30% by mass in the flame retardant resin composition. When the content of the functional group-modified resin is less than 5% by mass, there is a possibility that sufficient wearability may not be obtained when the insulating layer of the insulated wire is used. On the other hand, when the content of the functional group-modified resin exceeds 30% by mass, the cold resistance may be lowered when the insulating layer of the insulated wire is used. Moreover, it is preferable that content of functional group modified resin is the range of 10-60 mass% in all the resin components in a flame-retardant resin composition.

  As the flame retardant (c) used in the flame retardant resin composition, those containing magnesium hydroxide as a main component are preferable. Examples of magnesium hydroxide include synthetic magnesium hydroxide, natural magnesium hydroxide obtained by pulverizing natural minerals, and the like.

  The particle size of the flame retardant is from 0.1 to 20 μm, preferably from 0.2 to 10 μm, more preferably from 0.5 to 5 μm, in terms of average particle size. When the average particle diameter of the flame retardant is less than 0.1 μm, secondary aggregation is likely to occur, and the mechanical properties are deteriorated. Moreover, when the average particle diameter of a flame retardant exceeds 20 micrometers, when it uses for the insulator layer of an insulated wire, there exists a possibility that it may become the external appearance defect of an insulator layer.

  The addition amount of the flame retardant in the flame retardant resin composition is usually 30 to 250 parts by mass with respect to 100 parts by mass of the resin component. The addition amount of a preferable flame retardant is 50-200 mass parts with respect to 100 mass parts of resin components, More preferably, it is 60-180 mass parts.

  Further, the flame retardant may have a surface treated with a surface treating agent on the surface of magnesium hydroxide or the like. As the surface treating agent, a homopolymer of α-olefin such as 1-heptene, 1-octene, 1-nonene, 1-decene, a mutual copolymer, or a mixture thereof is used. The surface treatment agent may be modified.

  The modification of the surface treatment agent for the flame retardant is, for example, a method in which an unsaturated carboxylic acid or a derivative thereof is used as a modifier, and a carboxyl group (acid) is introduced into the polymer such as the above-mentioned α-olefin polymer for acid modification. Is mentioned. Specific examples of the modifier include maleic acid and fumaric acid as unsaturated carboxylic acid, and maleic anhydride (MAH), maleic acid monoester, maleic acid diester and the like as derivatives thereof. As the modifier, maleic acid and maleic anhydride are preferable. These modifiers may be used alone or in combination of two or more. Examples of the acid modification method for introducing an acid into the surface treatment agent include graft polymerization and a direct method. Moreover, the usage-amount of the said modifier is about 0.1-20 mass% with respect to the said polymer, Preferably it is 0.2-10 mass%, More preferably, it is 0.2-5 mass%.

  The surface treatment method of the flame retardant is not particularly limited, and various treatment methods can be used. Examples of the surface treatment method of the flame retardant include a method performed simultaneously with the pulverization of the flame retardant, and a method of mixing the previously pulverized flame retardant and the surface treatment agent and treating them later. Further, the surface treatment method for the flame retardant may be either a wet treatment method using a solvent or a dry treatment method not using a solvent.

  Solvents used for wet processing of the flame retardant include aliphatic hydrocarbons such as pentane, hexane, and heptane, and aromatic hydrocarbons such as benzene, toluene, and xylene. Further, the surface treatment of the flame retardant may be a method in which a surface treatment agent is added to the flame retardant and the resin at the time of preparing the flame retardant resin composition and the composition is kneaded at the same time.

  It does not specifically limit as a manufacturing method of the said flame-retardant resin composition, A well-known method can be used. The flame retardant resin composition is, for example, an ordinary kneading machine such as a Banbury mixer, a pressure kneader, a kneading extruder, a twin-screw kneading extruder, a roll, etc. It can be obtained by melt-kneading each component such as etc. and uniformly dispersing them.

  The flame retardant resin composition can be used as a member or an insulating material used in automobiles, electronic / electrical devices, and is particularly suitably used as a material for forming an insulating layer of an insulated wire.

  The insulated wire of the present invention coats the conductor by extruding the flame retardant resin composition containing the functional group-modified resin to the periphery of the conductor using an electric wire extrusion molding machine or the like used for production of a normal insulated wire. Thus, an insulator layer using the flame retardant resin composition is formed around the conductor. The conductor used for an insulated wire can utilize what is used for a normal insulated wire. Moreover, the diameter of the conductor of an insulated wire, the thickness of an insulator layer, etc. are not specifically limited, According to the use etc. of an insulated wire, it can determine suitably. The insulator layer may be a single layer or may be composed of two or more layers.

Examples of the present invention and comparative examples are shown below.
(Synthesis of functional group-modified resin)
Synthesis Example 1-A to 1-F, Synthesis Example 1-G to 1-J
Maleic anhydride and di-α-cumyl peroxide (manufactured by NOF Corporation, trade name “Park Mill D”) are added in 100 parts by mass of homopolypropylene (elastic modulus 2100 MPa) in the amounts shown in Tables 1 and 2, After uniformly mixing, the reaction was carried out at a temperature and time shown in Table 1 with a twin-screw kneader to obtain a functional group-modified resin. Tables 1 and 2 show the graft amount and elastic modulus of the functional group-modified resin thus obtained. In addition, the grafting amount in a table | surface was shown with the quantity (mass part) of the functional group containing compound directly couple | bonded with 100 mass parts of homopolypropylene. The graft amount was measured by the following method.

[Measurement method of graft amount]
For the graft amount, first, the total functional group amount (= free functional group amount + bonded functional group amount) of the functional group-modified resin is measured by a predetermined measurement method. Using a solvent having different solubility between the functional group-containing compound and the functional group-modified resin, the free functional group-containing compound is separated and the amount of free functional groups (or the amount of bound functional groups) is measured. From the total functional group amount and free functional group amount (or combined functional group amount), the graft amount is obtained by calculation. As a method for measuring the amount of the functional group, an analytical method such as a titration method or an instrumental analysis method can be used as appropriate depending on the type of the functional group of the functional group-containing compound. For example, when the modifying agent is maleic anhydride, a titration method can be used.

The ratio X between the functional group-containing compound and the polymerization initiator in Synthesis Examples 1-A to 1-C is less than 5, whereas the ratio X in Synthesis Examples 1-D to 1-F is 5 or more. In Synthesis Examples 1-D to 1-F, it can be seen that the graft amount of the functional group-containing compound is higher than that of Synthesis Examples 1-A to 1-C.

Synthesis Example 2-A to 2-C
Synthesis Example 1 except that cumene hydroperoxide (manufactured by NOF Corporation, trade name “Park Mill H”) was used as the polymerization initiator, and the addition amounts of the functional group-containing compound and the polymerization initiator were changed to the addition amounts shown in Table 3. A functional group-modified resin was obtained in the same manner as -A. Table 3 shows the graft amount and elastic modulus of the functional group-modified resin obtained.

Synthesis Examples 3-A to 3-C
A modified functional group-modified resin was obtained in the same manner as in Synthesis Example 1-A, except that acrylic acid was used as the functional group-containing compound, and the addition amounts of the functional group-containing compound and the polymerization initiator were changed to the addition amounts shown in Table 4. . Table 4 shows the graft amount and elastic modulus of the functional group-modified resin obtained.

[Creation of insulated wires]
Examples 1-12
Unmodified polypropylene resin (manufactured by Nippon Polypro Co., Ltd., trade name “EC7”, elastic modulus 1200 MPa, MFR 0.5), functional group-modified resin (Synthesis Examples 1-A to 1-F, 2-A, 2-B, 3 Table 1 shows -A, 3-B), magnesium hydroxide (manufactured by Kyowa Chemical Co., Ltd., trade name “Kisuma 5A”), antioxidant (manufactured by Ciba Specialty Chemicals, trade name “Irganox 1010”). After mixing at 200 ° C. using a twin-screw kneader in the blending amount, the pellet was formed into a pellet with a pelletizer to obtain a flame-retardant resin composition pellet. From the flame retardant resin composition, this pellet was extruded with a thickness of 0.2 mm onto the outer periphery of a conductor (cross-sectional area: 0.5 mm ² ) of an annealed copper wire by twisting seven annealed copper wires using an extrusion molding machine. The insulated wire of Examples 1-12 by which the conductor was coat | covered with the insulator layer which becomes this was obtained.

Comparative Examples 1-6
Except for changing the functional group-modified resin 1-A of Example 1 to the functional group-modified resins 1-G to 1-J, 2-C, and 3-C as shown in Table 7, the same procedure as in Example 1 was performed. An insulated wire was manufactured.

  Using the insulated wires obtained in Examples and Comparative Examples, a cold resistance test and an abrasion test were performed. The test results are shown in Tables 5-7. The cold resistance test method and the wear resistance test method are as follows.

[Cold resistance test method]
This was performed in accordance with JIS C3055. That is, the insulated wires of Examples and Comparative Examples were cut into 38 mm lengths to make test pieces, the test pieces were mounted on a cold resistance tester, cooled to a predetermined temperature, hit with a hitting tool, The condition after hitting was observed. Using five test pieces, the temperature at which all five test pieces were broken was defined as the cold resistant temperature.

[Abrasion test method]
The test was conducted by a blade reciprocation method in accordance with the automobile technical standard “JASO D611-94”. That is, the insulated wire of an Example and a comparative example was cut out to the length of 750 mm, and it was set as the test piece. Then, at a room temperature of 23 ± 5 ° C., the blade is reciprocated at a speed of 10 mm or more in the axial direction with respect to the coating material (insulator layer) of the test piece at a speed of 50 times per minute until the contact with the conductor. The number of times was measured. At this time, the load applied to the blade was 7N. About the frequency | count, the thing 200 times or more was set as the pass, and the thing less than 200 times was set as the disqualification.

  As shown in Tables 5 and 6, Examples 1 to 12 all had good cold resistance, and the wear resistance was acceptable. On the other hand, as shown in Table 7, all of Comparative Examples 1 to 6 were unsatisfactory in wearability.

Claims (11)

A functional group-modified resin having an elastic modulus of 2000 MPa or more obtained by reacting at least homopolypropylene, a functional group-containing compound, and a polymerization initiator,
The functional group-modified resin, wherein the homopolypropylene is obtained by adding 1 part by mass or more of the functional group-containing compound and 0.5 part by mass or more of the polymerization initiator to 100 parts by mass. .   The functional group-modified resin according to claim 1, wherein the functional group-containing compound and the homopolypropylene are graft-copolymerized.   The functional group of the functional group-containing compound is at least one functional group selected from a carboxylic acid group, an acid anhydride group, an epoxy group, a hydroxyl group, an amino group, an alkenyl cyclic imino ether group, and a silane group. The functional group-modified resin according to claim 1 or 2.   The functional group-modified resin according to claim 1, wherein the polymerization initiator is an organic peroxide.   The functional group according to claim 4, wherein the organic peroxide is at least one compound selected from cumene hydroperoxide, di-t-butyl peroxide, and di-α-cumyl peroxide. Modified resin.   The mass ratio (Z = X / Y) of the addition amount (Y part by mass) of the polymerization initiator and the addition amount (X part by mass) of the functional group-containing compound is 5 or more. The functional group-modified resin according to any one of -5.   A flame retardant resin composition comprising at least the functional group-modified resin according to any one of claims 1 to 6 and a flame retardant.   The flame retardant resin composition according to claim 7, further comprising an unmodified polypropylene resin.   The flame retardant resin composition according to claim 7 or 8, wherein the flame retardant is mainly composed of magnesium hydroxide.   The flame retardant resin composition according to any one of claims 7 to 9, wherein the content of the functional group-modified resin is 5 to 30% by mass.   The insulated wire using the flame-retardant resin composition of any one of Claims 7-10 is formed in the circumference | surroundings of a conductor, The insulated wire characterized by the above-mentioned.