JP3325102B2 - Polyester-based composite molded article and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite molded article excellent in flame retardancy, airtightness and adhesion, and a method for producing the same. The present invention relates to a composite molded article suitable for various equipment parts in the automobile and electric / electronic fields. Goods.

[0002]

2. Description of the Related Art Crystalline resins such as polybutylene terephthalate (PBT resin) and polyethylene terephthalate (PET resin) are known for their mechanical properties, electrical properties, and other physical and chemical properties. It is used as an engineering plastic in a wide range of applications such as automobiles and electric / electronic parts because of its excellent workability and good workability. In recent years, these electric / electronic and automotive parts have been required to have not only flame retardancy but also various advanced characteristics. On the other hand, flame-retardant polyalkylene terephthalates are flame-retarded by adding a flame-retardant, so that the properties of the flame-retardant tend to be inferior to those of non-flame retardants. Various additives are added to improve the deterioration of physical properties,
These may also deteriorate physical properties other than the intended physical properties, and when conflicting requirements are made for one part,
In some cases, one type of material cannot be used. As one method of solving such a case, a composite molded part has been developed in which materials adapted to different requirements are combined and integrated. Generally, as a method of integrally molding two kinds of materials, partially different characteristics are obtained by a dual molding method in which a dissimilar resin is secondarily molded on a primary molded article of the resin and the interface is fused and fixed. It is known to obtain composite molded articles having the same. However, in the case of a composite molded article using high-crystalline thermoplastic polyester for multiple molding, the interface between the resin on the primary side and the resin on the secondary side is insufficiently fused, easily peeled by an external force, and warped. Etc. tend to occur and often do not satisfy the function as an integrally molded product in use. In order to compensate for the fusion strength at the interface between the two resins, there have been attempts to provide a mechanical structure with a mechanical anchor effect, such as providing an undercut or through hole in the primary molded product, or apply an adhesive to the primary molded product. However, the shape is complicated and the process is complicated, which is economically disadvantageous, and is not desirable in terms of production efficiency. In particular, polybutylene terephthalate, polypropylene terephthalate, or polyethylene terephthalate have high crystallinity, so they are molded by a double molding method, and a composite molded product with high fusion strength at the interface between resins can be efficiently manufactured by a simple method. It was very difficult to produce well.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have developed a polyalkylene terephthalate resin which is an integrally molded product having excellent mechanical properties, chemical properties, thermal properties, etc. As a result of intensive studies to economically and efficiently obtain a flame-retardant composite molded product having a high fusion strength between resins by a simple multiple molding method without using any method, the present invention has been achieved. That is, the present invention is obtained by integrally molding a resin material (A) represented by the following (I) or (II) and a flame-retardant resin material (B) represented by the following (III) by a multiple molding method. A flame-retardant composite molded article excellent in airtightness and adhesion and a method for producing the same. (I) A copolymer mainly composed of polyalkylene terephthalate (alkylene group having 2 to 4 carbon atoms) and containing 1 to 40 mol% of another comonomer unit. (II) Polyalkylene terephthalate is added to the copolymer of the above (I). (III) (a) a polyalkylene terephthalate (having 2 to 4 carbon atoms of an alkylene group) as a main component and not more than 40 mol% other comonomer units polymer 40 to 97 wt% you weight of (b) halogen-based flame retardant 3-25% by weight (C) below the flame retardant resin material consisting of 0 to 15 wt% antimony compounds, present invention The constituent material of the integrally molded article and the molding method thereof will be described in detail.

Resin material (A) effective for the composite molded article of the present invention
(I) constituting one of the above is mainly composed of polyalkylene terephthalate (alkylene group having 2 to 4 carbon atoms) and 1 to 40
A copolymer containing at least one mol% of another comonomer unit, specifically, a poly (ethylene glycol) obtained by a polycondensation reaction between terephthalic acid or an ester-forming derivative thereof and an alkylene glycol having 2 to 4 carbon atoms or an ester-forming derivative thereof. It is mainly composed of alkylene terephthalate, and includes, for example, a copolymer containing polyethylene terephthalate, polypropylene terephthalate or polybutylene terephthalate as a main component, into which 1 to 40 mol% of another comonomer unit is introduced. The third component (comonomer) constituting such a copolymer includes isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylethanedicarboxylic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, and dodecanediacid. Examples of such known dicarboxylic acids and their alkyl, alkoxy or halogen-substituted products. These dicarboxylic acid compounds can also be used as a comonomer component in the form of a derivative capable of forming an ester, for example, a lower alcohol ester such as dimethyl ester, for polycondensation. Examples of the dihydroxy compound used as the third component for constituting the copolymer include ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hydroquinone, resorcinol, Dihydroxyphenyl, naphthalene diol, dihydroxydiphenyl ether, cyclohexanediol, 2,2-bis (4
-Hydroxyphenyl) propane, relatively low molecular weight dihydroxy compounds such as diethoxylated bisphenol A, and alkyl, alkoxy or halogen substituted products thereof. These comonomer components may be introduced by mixing two or more kinds. In the present invention, the above-mentioned compound can be used as a comonomer component, and a thermoplastic polyester copolymer produced by polycondensation can be used alone or as a mixture of two or more kinds as the resin material (A) of the present invention. The resin material mainly composed of polyalkylene terephthalate constituting the integrally molded product in the present invention (A) is a material having characteristics as an original engineering plastic and having both excellent airtightness and excellent adhesiveness, The content of the copolymer component is in the range of 1 to 40 mol%,
Preferably it is in the range of 3-35 mol%.

In general, such a resin material (A) is used as a primary molded product, and a secondary material (B) is molded and fused thereon. In molding, the surface (interface) of the resin material (B) must be temporarily melted, and its melting point must be considered. Therefore, the melting point of the resin material (A) is desirably 250 ° C. or less, preferably 240 ° C. or less. If the melting point of the resin material (A) is too high, it is necessary to further raise the molding resin temperature of the resin material (B) in the secondary molding, which tends to cause thermal decomposition, etc. Harm and not preferred. On the other hand, if the melting point of the resin material (A) is too low, the primary material tends to be deformed during the secondary molding, which is not preferable. The melting point of the resin material (A) is adjusted according to the type of the polyalkylene terephthalate resin used, the type and amount of the copolymer component, and the like. Particularly preferred from this point of view are mainly polyethylene terephthalate, polypropylene terephthalate or polybutylene terephthalate,
It is a copolymer having a copolymer component of about 35 mol%. Further, as a resin material (A) effective for the composite molded article of the present invention, poly (alkylene terephthalate (alkylene group having 2 to 4 carbon atoms) is added to the copolymer (I) in an amount of 1 to 95% by weight based on the total amount. Mixed blends (II) are also mentioned. The mixing amount of polybutylene terephthalate, polypropylene terephthalate or polyethylene terephthalate to be blended is 95% by weight or less, preferably 90% by weight, based on the total amount of (II) from the viewpoint of imparting airtightness and fusibility of the molded article and melting point of the mixture. % By weight or less is preferred.

Further, the resin material constituting the molded article of the present invention
As (A), a small amount of another thermoplastic resin may be supplemented in addition to the resin represented by (I) or (II) in order to impart desired properties. As such an auxiliary thermoplastic resin, for example, a polyolefin-based polymer,
Polyamide-based polymer, polycarbonate-based polymer, polyarylate-based polymer, polyester polymer other than the main component (for example, completely aromatic polyester), styrene-based polymer (for example, AS or ABS resin), polyphenylene oxide-based polymer, Acrylate-based polymers, polyacetals, polysulfones, polyethersulfones, polyetherimides, polyetherketones, polyarylenesulfide-based polymers, fluororesins, olefin-based thermoplastic elastomers (eg, EPDM or ionomer), styrene-based thermoplastic elastomers (eg, SBS or SEB
S), a urethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, a polyether-based thermoplastic elastomer, or a modified product thereof, and the like. Two or more kinds of these thermoplastic resins are mixed. You can also use
As described above, it is necessary to consider the rigidity, melting point, and the like of the compound even when such other thermoplastic resin is compounded supplementarily.

Also, a resin material constituting the molded article of the present invention
(A) may contain an inorganic filler. Such a filler is preferably blended in order to obtain excellent properties such as mechanical strength, heat resistance, dimensional stability, and electrical properties, and is particularly effective for increasing rigidity. For this purpose, a fibrous, powdery or plate-like filler is used depending on the purpose. Examples of the fibrous filler include glass fiber, asbestos fiber, carbon fiber, silica fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, stainless steel, aluminum, titanium, Inorganic fibrous substances such as fibrous materials of metals such as copper and brass can be used. Particularly typical fibrous fillers are glass fibers. In addition, a high melting point organic fibrous substance such as polyamide, fluororesin, and acrylic resin can also be used. On the other hand, as the particulate filler, carbon black, silica, quartz powder, glass beads, glass powder,
Silicates such as calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, wollastonite,
Oxides of metals such as iron oxide, titanium oxide and alumina, carbonates of metals such as calcium carbonate and magnesium carbonate,
Sulfates of metals such as calcium sulfate and barium sulfate, other silicon carbide, silicon nitride, boron nitride, and various metal powders. Examples of the plate-like filler include mica, glass flake, various metal foils, and the like. These inorganic fillers can be used alone or in combination of two or more. The combined use of a fibrous filler, particularly a glass fiber or a carbon fiber, and a granular or plate-like filler is a preferable combination, particularly in terms of having both mechanical strength, dimensional accuracy, electrical properties and the like. The amount of the inorganic filler added is 40% by weight or less based on the total amount of the resin material (A). If it is more than this, the moldability and toughness are impaired, which is not preferable. Particularly preferably, it is at most 30% by weight.

Further, a resin material constituting the molded article of the present invention
(A) may contain a halogen-based flame retardant.
Such a flame retardant may be any organic halogen compound which is generally used as a flame retardant of a thermoplastic polyester to obtain flame retardancy, such as halogenated phenyl, halogenated diphenyl ether, halogenated aromatic bisimide compound, and halogenated aromatic bisimide. Aromatic epoxy compounds, low molecular weight organic halogen compounds of bisphenol A, halogenated polycarbonates, halogenated polystyrenes and the like. Here, the halogen is generally preferably bromo. The flame retardants may be used alone or in combination of two or more. The object of the present invention can be achieved by using any of the above flame retardants, but in particular, halogenated aromatic bisimide compounds, halogenated aromatic epoxy compounds, halogenated polycarbonates, halogenated benzyl acrylates, halogenated polystyrenes Use is preferred. The addition amount of such a flame retardant can be arbitrarily added according to the required flame retardancy level.However, from the viewpoint of the mechanical properties of the molded article, moldability, thermal stability and cost, the total amount of the resin material (A) is 0 to
It is preferably 15% by weight, particularly preferably 3 to 10% by weight. Further, an inorganic flame retardant may be added to the resin material (A) of the present invention to assist the effect of the flame retardant. Typical examples thereof include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimonate and the like. The amount of the flame retardant aid can be arbitrarily added according to the required flame retardancy.However, from the viewpoint of the mechanical properties, moldability, thermal stability and cost of the molded product, the amount of the resin material (A) is It is preferably from 0 to 10% by weight, particularly preferably from 2 to 7% by weight.

Next, (III) constituting the flame-retardant resin material (B) for forming the other part of the composite molded article is composed of (a) a polyester resin such as polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate; or these as a main component and a polymer obtained by introducing 40 mol% or less of other comonomer units to, (b) halogen-based flame retardant 3-25% by weight and (c) antimony compound 0
It is a flame-retardant resin material composed of 15% by weight. Examples of the third component (comonomer) constituting the copolymer (a) include the same dicarboxylic acid compounds and dihydroxy compounds as those described for the resin material (A). May be introduced. In the present invention, the above-mentioned compound can be used as a comonomer component, and a thermoplastic polyester copolymer produced by polycondensation can be used alone or as a mixture of two or more kinds as the resin material (a) of the present invention. Since the flame-retardant resin material (B) constituting the integrally molded article in the present invention is a material originally having properties as an engineering plastic, the content of the copolymer (a) component is at most 40 mol% or less. And preferably at most 35 mol%.

Further, as the flame retardant (b) to be blended with the flame retardant resin material (B), a halogen-based flame retardant can be used. Such a flame retardant (b) is generally a thermoplastic polyester flame retardant (b)
Can be used, but the flame-retardant ability and the flame-retardant resin material (B) are 2
It is preferable to use the flame retardant (b) having good heat resistance because it is used for heavy molding and is molded at a high temperature. As such a flame retardant (b), a halogenated bisimide compound (preferably alkylene bistetrabromophthalimide or arylenebistetrabromophthalimide), a brominated epoxy resin having a molecular weight of 10,000 or more, or a polypentabromo compound Benzyl acrylate or polydibromostyrene and / or polytribromostyrene are preferred. The addition amount of such a flame retardant can be arbitrarily added according to the required flame retardant level, but from the viewpoint of cost, mechanical properties and moldability, the resin material (B)
It is preferably from 3 to 25% by weight, particularly preferably from 3 to 10% by weight, based on the total amount.

Further, the flame-retardant resin material (B) of the present invention includes:
In order to help the effect of the flame retardant, an inorganic flame retardant can be added. Typical examples thereof include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimonate and the like. The amount of the flame retardant aid can be arbitrarily added according to the required flame retardancy. However, in view of the mechanical properties of the molded product, moldability, heat stability and cost, the resin material is
(B) The amount is preferably from 0 to 15% by weight, particularly preferably from 2 to 7% by weight, based on the total amount.

The flame-retardant resin material (B) constituting the molded article of the present invention may contain a thermoplastic resin and / or various fillers in addition to the resin represented by the above (III). . Examples of the thermoplastic resin and filler to be compounded are the same as those used in the resin material (A).

The resin material (A) used in the present invention
And (B) are known substances other than the above, which are generally added to a thermoplastic resin in order to impart desired properties to one or both of them, that is, various kinds of substances such as antioxidants and ultraviolet absorbers. It is of course possible to add a stabilizer, an antistatic agent, a coloring agent such as a dye or a pigment, a lubricant, a plasticizer, a crystallization accelerator, a nucleating agent, a release agent, and the like.

[0014] The composite molded article of the present invention comprises the above (A) and (B) 2
It is molded by a so-called multiple molding method using various kinds of resin materials. As a molding method, injection molding, compression molding and other molding methods are applied, but injection molding is generally preferred.
Either resin material (A) or (B) is molded in advance to form a primary molded product, and then another resin material is molded, fused and integrated, and the shape and structure of the molded product or purpose Any of the primary side molded products may be used depending on the application.However, it is generally better to perform primary molding with the resin material (A) and then secondary mold the resin material (B) when the molded product loses its shape or during molding or during molding. It is preferable in order to prevent deformation later.

In this case, in order to perform strong fusion, it is necessary in the secondary molding that the surface layer (interface) of the primary molded article is melted by the resin temperature of the resin material (B).
For this reason, the resin temperature in the secondary molding needs to be at least the melting point of the resin material (A) of the primary molded article, and the resin temperature of the secondary material at the time of contact in the secondary molding is set to be 10 degrees below the melting point of the primary material. It is preferable to carry out the secondary molding by raising the temperature to 120 ° C, preferably 30 to 100 ° C. However, if the resin temperature of the secondary material is too high, the secondary material may be decomposed and deteriorated.
It is not preferable that the melting point of (A) is too high. Generally, as described above, the melting point of the primary material is 250 ° C. or less, preferably 24 ° C.
0 ° C. or lower, which can be adjusted by the copolymerization component of the polyalkylene terephthalate-based resin of the resin material (A) constituting the primary molded article and its introduction amount, auxiliary components and its blending amount, etc. Since such adjustment also affects the rigidity of the material itself, the composition of the resin material is selected depending on the balance.

[0016]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. Examples 1 to 20, Comparative Examples 1 to 5 A polyalkylene terephthalate (a) and / or a halogen-based flame retardant (b) and optionally an inorganic filler (d) were added and mixed in the proportions shown in Table 1, and were extruded. To obtain a resin composition (A). Further, to the polyalkylene terephthalate (a), a halogen-based flame retardant (b), an antimony-based compound (c), and optionally an inorganic filler (d) are added at a ratio shown in Table 2, mixed, and pelletized by an extruder. Was obtained as resin material (B). Table 3 shows the composition and physical properties of the polyalkylene terephthalate resin used. Next, using the resin materials (A) and (B), composite molded articles were prepared in combinations shown in Tables 4 and 5, and the adhesion strength was evaluated. The results are shown in Tables 4 and 5. In addition, it was used in the following examples.
Details of each component are as follows. (A) Polyalkylene terephthalate PBT copolymer (a-1) Production method) 169.74 parts by weight of dimethyl terephthalate, dimethyl isophthalate
24.25 parts by weight of chill, 126 parts by weight of 1,4-butanediol
And titanium tetrabutoxide 0.12 parts by weight,
Equipped with a reactor and a distillation column,
The temperature inside the reactor to 140 ° C, and gradually
The methanol by-produced is distilled off, and the transesterification
Responded. Distilled methanol becomes 85% by weight of theoretical amount
At which point the temperature of the reactants was increased to 185 ° C. and then
This was transferred to another reactor at a temperature of 210 ° C, and 1.0 torr
Melting polycondensation was carried out by continuously stirring at a pressure of r for 2.0 hours.
The melt is extruded as a strand from the spout, and the
Cut the strand and measure 2mm in diameter and 3mm in length.
A colored, cylindrical polymer chip was obtained. PBT copolymer (a-2) production method) 184.3 parts by weight of dimethyl terephthalate,
9.7 parts by weight of chill, 126 parts by weight of 1,4-butanediol
And 0.12 parts by weight of titanium tetrabutoxide,
A polymer chip was obtained by the same production method as in (a-1). PBT copolymer (a-3) production method) 199 parts by weight of dimethyl terephthalate, ethylene glycol
18 parts by weight, 103 parts by weight of 1,4-butanediol and
Using 0.12 parts by weight of titanium tetrabutoxide, (a-
A polymer chip was obtained by the same production method as in 1). PBT resin trade name) Polyplastics Co., Ltd., DURANEX 400F
(P PET resin trade name) manufactured by Kanebo Co., Ltd., Bellpet EFG-10 (b) halogen-based flame retardant trade name) ethylenebistetrabromophthalimide; albemarle
BT-93W brominated polycarbonate; Teijin Chemicals Ltd., FG-7
500 brominated epoxy resin; manufactured by Dead Sea Bromin Co., F23
00 polypentabromobenzyl acrylate; dead sieve
Lomin, FR-1025 polydibromostyrene; Ferro, Pyrocheck 6
8PB brominated epoxy oligomer; Dainippon Ink and Chemicals, Ltd.
Co., Ltd., EP-100 (c) Antimony compound trade name) antimony trioxide; Nippon Seiko Co., Ltd., PATOX-M (d) Inorganic filler trade name) glass fiber; Nitto Boseki Co., Ltd. , CS3PE-94
1

The adhesion strength was evaluated as follows. [Adhesion Strength Evaluation Method] First, a half of an ASTM No. 1 dumbbell shown in FIG. Next, this molded piece is subjected to ASTM
Attach to the mold of No. 1 dumbbell, perform secondary molding by changing resin temperature using resin material (B) as secondary material, and FIG. 1 (b)
A dumbbell-shaped composite molded product having a joint at the center as shown in (1) was obtained. The adhesion strength of the composite molded article was measured using a tensile tester.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

When a PBT or PET resin is used as the primary material in preparing a composite molded article by the multiple molding method, the adhesive strength cannot be expected if the resin temperature during the secondary molding is 280 ° C. or less. Further, depending on the flame retardant on the secondary side, if the molding temperature is increased, deterioration occurs, and molding may not be performed. However, according to the present invention, by using the specific resin materials (A) and (B) as described above, an anchor shape can be provided under ordinary molding temperature conditions,
Without using an adhesive, it is possible to easily and economically efficiently produce a composite molded product having a strong interfacial adhesion strength and airtightness that cannot be obtained by the conventional double molding method. In addition, the composite molded article of the present invention has excellent thermal stability, physical properties, mechanical properties, etc. of a polyester engineering plastic, and especially has a chemical stability against chemicals, solvents, lubricants, detergents, etc. It is suitable for many uses in the automotive field and the electric / electronic field where such characteristics are required.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a molded product for measuring adhesion strength used in Examples, (a) is a primary molded product, and (b) is a dumbbell having a joint at the center where a secondary molded product is joined. It is a composite molded article.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary molded article 2 Secondary molded article 3 Joint 4 Gate

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/00 C08L 67/00-67/02

Claims (11)

(57) [Claims] 1. A resin material (A) represented by the following (I) or (II) and a flame-retardant resin material (B) represented by the following (III) are integrally molded by a multiple molding method. Flame-retardant composite molded products with excellent airtightness and adhesion. (I) A copolymer mainly composed of polyalkylene terephthalate (alkylene group having 2 to 4 carbon atoms) and containing 1 to 40 mol% of another comonomer unit. (II) Polyalkylene terephthalate is added to the copolymer of the above (I). (III) (a) a polyalkylene terephthalate (having 2 to 4 carbon atoms of an alkylene group) as a main component and not more than 40 mol% other comonomer units polymer 40 to 97 wt% you weight of (b) halogen-based flame retardant 3-25% by weight (C) a flame retardant resin material consisting of 0 to 15 wt% antimony compounds 2. The resin represented by (I) or (II) contained in the resin material (A) has a melting point of 250 ° C. or less.
The composite molded article according to the above. 3. The composite molded article according to claim 1, wherein the resin material (A) is a composition containing 1 to 40% by weight (based on the total amount of the composition) of an inorganic filler. 4. The resin material (A) contains 3 to 3 halogen-based flame retardants.
The composite molded article according to any one of claims 1 to 3, which is a flame retardant composition containing 25% by weight (based on the total amount of the composition). 5. The flame-retardant resin material (B) comprises an inorganic filler of 1 to 5.
The composite molded article according to any one of claims 1 to 4, which is a composition containing 40% by weight (based on the total amount of the composition). 6. The composite molded article according to claim 1, wherein the flame retardant of the component (b) of the flame retardant resin material (B) is a halogenated bisimide compound. 7. The composite molded article according to claim 1, wherein the flame retardant of the component (b) of the flame retardant resin material (B) is a brominated epoxy resin having a molecular weight of 10,000 or more. 8. The composite molded article according to claim 1, wherein the flame retardant of the component (b) of the flame retardant resin material (B) is polypentabromobenzyl acrylate. 9. The composite molded article according to claim 1, wherein the flame retardant of the component (b) of the flame retardant resin material (B) is polydibromostyrene and / or polytribromostyrene. 10. A resin article (A) represented by the following (I) or (II) is injection-molded to form a primary molded article, and the primary molded article is further subjected to a flame-retardant resin represented by the following (III): Material (B)
And a method for producing a composite molded article having excellent airtightness and adhesiveness, wherein the molded article is secondarily injection-molded and fused and integrated. (I) A copolymer mainly composed of polyalkylene terephthalate (alkylene group having 2 to 4 carbon atoms) and containing 1 to 40 mol% of another comonomer unit. (II) Polyalkylene terephthalate is added to the copolymer of the above (I). (III) (a) a polyalkylene terephthalate (having 2 to 4 carbon atoms of an alkylene group) as a main component and not more than 40 mol% other comonomer units polymer 40 to 97 wt% you weight of (b) halogen-based flame retardant 3-25% by weight (C) a flame retardant resin material consisting of 0 to 15 wt% antimony compounds 11. The method according to claim 10, wherein the resin temperature at the time of secondary injection of the flame-retardant resin material (B) is higher than the melting point of the resin material (A) by 10 ° C. or more.