JP5367732B2 - Flame retardant resin composition and optical fiber cord using the same - Google Patents

Description

  The present invention relates to a flame retardant resin composition excellent in flame retardancy and an optical fiber cord excellent in flame retardancy and bending rigidity using the same.

  Optical fiber cords are required to have various characteristics such as mechanical characteristics and flame retardancy. For this reason, polyvinyl chloride (PVC) is used as a coating material used for conventional optical fiber cords. However, when such materials are discarded without appropriate treatment and landfilled, plasticizers and heavy metal stabilizers blended in the coating material may be eluted. In addition, when burned, harmful gases may be generated from the halogen compounds contained in the coating material.

  In view of such an environmental impact, an optical fiber cord using a non-halogen flame retardant coating material in which a high concentration of metal hydrate is filled in a polyolefin resin component has been proposed (for example, Patent Documents). 1). However, when the optical fiber cord described in Patent Document 1 is used, when used for a long period of time, the coating material may shrink and the optical fiber or the optical fiber core wire may protrude, which may cause trouble in the connection between the fibers. . Further, when the metal hydrate is filled at a high concentration, a resin component having a low elastic modulus is often used, so that it is difficult to obtain a predetermined bending rigidity necessary for the optical fiber cord.

JP-A-9-33770

  The present invention solves the above-described problems, and a flame-retardant resin composition excellent in flame retardancy and bending rigidity, and an optical fiber using the same and having reduced flame retardancy, bending rigidity, and optical fiber protrusion The challenge is to provide code.

  As a result of intensive studies in view of the above problems, the present inventors have found that a flame retardant resin composition using a specific polyolefin resin containing polypropylene, a metal hydrate, and a crystallization nucleating agent is flame retardant and flexural rigidity. It was found that the heat shrinkage rate is small. Furthermore, the present inventors have found that an optical fiber cord having this flame retardant resin composition as a coating layer has a low thermal shrinkage rate of the coating layer even when used for a long period of time, and can reduce fiber protrusion. The present invention has been made based on this finding.

That is, the present invention
<1> The thermoplastic resin component (A) is (a) 70 to 95% by mass of an unmodified acid-containing polyolefin resin containing polypropylene, but the non- acid-modified polypropylene resin among the polyolefin resins of the (a) component. 10 to 70% by weight in the thermoplastic resin component (a), and (b) 5 to 30 wt% acid-modified polyolefin resin respectively containing organic, to the thermoplastic resin component (a) 100 parts by mass of 30 to 150 parts by mass of magnesium hydroxide (B) and 1 to 30 parts by mass of a crystallization nucleating agent (C) selected from an organic nucleating agent and silica having a BET specific surface area of 175 to ²⁰⁰ m ² / g. A flame retardant resin composition,
<2> The flame retardant resin composition according to <1>, wherein the component (a) is a polyolefin resin selected from polypropylene and polyethylene ,
<3> The flame-retardant resin composition according to <1> or <2>, wherein the acid-modified polyolefin resin is an acid-modified polyethylene, and <4> the above <1> to <1>3> An optical fiber cord, wherein a coating layer is formed on the outer periphery of an optical fiber core wire using the flame retardant resin composition according to any one of 3
Is to provide.

  INDUSTRIAL APPLICABILITY The present invention can provide a flame retardant resin composition excellent in flame retardancy and bending rigidity, and an optical fiber cord excellent in flame retardancy and bending rigidity using the same and having reduced fiber protrusion. .

It is a schematic sectional drawing which shows one Embodiment of the optical fiber cord of this invention. It is explanatory drawing which shows the evaluation method of the bending rigidity of an optical fiber cord.

  A preferred embodiment of the optical fiber cord according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an optical fiber cord of the present invention. In the figure, reference numeral 1 denotes an optical fiber cord, 2 denotes an optical fiber core wire, 3 denotes a tensile strength fiber layer provided as necessary, and 4 denotes a coating layer as a jacket.

  In the present invention, the flame retardant resin composition used as the coating layer of the optical fiber cord contains a thermoplastic resin component (A), magnesium hydroxide (B), and a crystallization nucleating agent (C). First, each component which comprises the thermoplastic resin component (A) among the flame-retardant resin compositions of this invention is demonstrated.

(A) Thermoplastic resin component The thermoplastic resin component (A) in the present invention is (a) 70 to 95% by mass of a non-acid-modified polyolefin resin containing polypropylene, but among the polyolefin resins of the (a) component, polypropylene resins that are not acid-modified contains thermoplastic resin component (a) 10 to 70 wt% in, and (b) an acid modified polyolefin resin 5-30 wt%, respectively.

(A) Polyolefin resin not modified with acid including polypropylene As the component (a) in the present invention, at least one of the constituent components is an olefin homopolymer or copolymer that is not acid-modified. Can do. Examples of the non-acid-modified one include polyolefin resins that are not modified with an unsaturated carboxylic acid such as acrylic acid or methacrylic acid. Examples of the component (a) in the present invention include polypropylene resins and ethylene-α-olefin copolymers.
As the polypropylene resin of the component (a), propylene homopolymer (homopolypropylene), ethylene-propylene random copolymer, ethylene-propylene block copolymer, propylene and other small amount of α-olefin (for example, 1 -Butene, 1-hexene, 4-methyl-1-pentene, etc.), polypropylene having atactic PP, block copolymer of polypropylene and ethylene copolymer rubber, and the like. In this specification, the copolymer having a propylene component and an ethylene component as constituent components is a polypropylene resin.

  As the polypropylene resin, an ethylene-propylene block copolymer is preferable. The ethylene-propylene block copolymer has a structure in which a polyethylene phase is dispersed in a propylene homopolymer via an ethylene-propylene rubber phase. For this reason, even if it fills highly the below-mentioned magnesium hydroxide, it can prevent making the rigidity of the flame-retardant resin composition of this invention too high. As a component (a), by using an ethylene-α-olefin copolymer in combination, a flame-retardant resin composition having an appropriate rigidity in which the ethylene-α-olefin copolymer is dispersed in the vicinity of the polyethylene phase. Can be obtained.

  The ethylene-α-olefin copolymer of component (a) is preferably a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms. Specific examples of the α-olefin include propylene, Examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like. Examples of the ethylene-α-olefin copolymer include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), very low density polyethylene (VLDPE), ethylene-propylene copolymer rubber (EPR), and ethylene-butylene copolymer. Polymerized rubber (EBR), ethylene-α-olefin copolymer synthesized in the presence of a single site catalyst, and the like.

In the present invention, one or more of the above polyolefin resins may be used, and a polypropylene resin is included from the viewpoint of improving crystallinity. (A) The amount of the polypropylene resin in the component is preferably from 10 to 70 mass% in the thermoplastic resin component (A), rather more preferably to be 40 to 60 mass%, in the present invention 10 -70 mass% is contained . If the blending amount of the polypropylene resin is too small, the rigidity is lowered, and if it is too much, the flame retardant cannot be retained and the low temperature characteristics are lowered.
(A) Content of a component is 70-95 mass% in a thermoplastic resin component (A), Preferably it is 75-85 mass%. If the content is too small, the required rigidity is not satisfied. If the content is too large, the flame retardant cannot be retained and the mechanical properties are deteriorated.

(B) Acid-modified polyolefin resin The component (b) in the present invention is an acid-modified polyolefin resin. Here, as the polyolefin resin, the same polyolefin resin as the component (a) can be exemplified. Examples of the component (b) include those obtained by acid-modifying a polyolefin resin by reacting an unsaturated carboxylic acid such as acrylic acid or methacrylic acid in the presence of an organic peroxide.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride, fumaric anhydride, and the like.
It is considered that the acid-modified polyolefin resin sufficiently disperses magnesium hydroxide in the resin component by reacting the acid-modified portion with magnesium hydroxide described later.
In the present invention, from the viewpoint of affinity with the component (a), the component (b) is preferably acid-modified polyethylene, and particularly preferably polyethylene modified with maleic acid and / or acrylic acid.
(B) Content of a component is 5-30 mass% in a thermoplastic resin component (A), Preferably it is 15-25 mass%. By setting the content of the component (b) within this range, the flame retardant resin composition of the present invention can be melt-kneaded with a resin component or the like with an appropriate viscosity even when highly filled with magnesium hydroxide as described later. Can be obtained. The cause of this is not clear, but the acid-modified polyolefin resin reacts with magnesium hydroxide or preferably a silane coupling agent surface-treated with magnesium hydroxide, and smoothly melt-kneads with other resin components. Seems to do.
When the content of the component (b) is too small, it is easy to bend and when an optical fiber cord is formed by forming a coating layer on the outer periphery of the optical fiber core using the flame retardant resin composition of the present invention, It may remain in a state where stress is applied to the optical fiber core, which is not preferable. When there is too much content of (b) component, the load at the time of extrusion will increase, and it will interfere with manufacture.

(C) Crystallization nucleating agent The flame-retardant resin composition of the present invention contains a crystallization nucleating agent. When the resin component is melted and kneaded by heating and then cooled and molded, the crystallization nucleating agent promotes crystallization of the resin component, particularly the polypropylene resin. For this reason, as a crystallization nucleating agent, what improves the crystallization speed of a polypropylene resin by adding to a polypropylene resin can be used preferably.
The crystallization nucleating agent that can be used in the present invention include inorganic nucleating agents and organic nucleating agent, in the present invention, Ru is selected from the organic nucleating agent and a BET specific surface area 175~200m 2 / ^g of silica. Moreover, you may use together an inorganic nucleating agent and an organic nucleating agent. In the present invention, an inorganic nucleating agent is preferably used as the crystallization nucleating agent from the viewpoint of improving the crystallinity of the polypropylene resin in the component (a).

Examples of the inorganic nucleating agent in the present invention include silica, talc, mica, calcium carbonate, titanium oxide, zinc oxide nanoparticle, layered silicate, and metal particle. Among these, silica is preferable, and an untreated one or one using a silane coupling agent can be used.
In the present invention, when silica is used as the inorganic nucleating agent, BET specific surface area of silica is rather preferable those 175~225m ² / g, are used in the present invention that of 175~200m ² / g. In addition, the BET specific surface area of the silica in this invention shall mean the value which measured the dry powder sample of the silica by the liquid nitrogen adsorption method by JISZ8830.

  As the organic nucleating agent in the present invention, a phosphate metal salt compound is preferable. Specifically, sodium-2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2′-ethylidene-bis (4,6-di-t-butyl) Phenyl) phosphate, lithium-2,2′-methylene-bis- (4,6-di-t-butylphenyl) phosphate, lithium-2,2′-ethylidene-bis (4,6-di-t-) Butylphenyl) phosphate, sodium-2,2′-ethylidene-bis (4-i-propyl-6-tert-butylphenyl) phosphate, lithium-2,2′-methylene-bis (4-methyl-6- t-butylphenyl) phosphate, lithium-2,2′-methylene-bis (4-ethyl-6-tert-butylphenyl) phosphate, sodium-2,2′-butylidene- Sus (4,6-di-methylphenyl) phosphate, sodium-2,2'-butylidene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2'-t-octylmethylene -Bis (4,6-di-methylphenyl) phosphate, sodium-2,2'-t-octylmethylene-bis (4,6-di-t-butylphenyl) phosphate, calcium-bis- (2, 2'-methylene-bis (4,6-di-t-butylphenyl) phosphate), magnesium-bis [2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate], Barium-bis [2,2′-methylene-bis (4,6-di-t-butylphenyl) phosphate], sodium-2,2′-methylene-bis (4-methyl-6) t-butylphenyl) phosphate, sodium-2,2′-methylene-bis (4-ethyl-6-tert-butylphenyl) phosphate, sodium-2,2′-ethylidene-bis (4-m-butyl-) 6-t-butylphenyl) phosphate, sodium-2,2′-methylene-bis (4,6-di-methylphenyl) phosphate, sodium-2,2′-methylene-bis (4,6-di-) Ethylphenyl) phosphate, potassium-2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate, calcium-bis [2,2′-ethylidene-bis (4,6-di-) t-butylphenyl) phosphate], magnesium-bis [2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate], Barium-bis [2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate], aluminum-tris [2,2′-methylene-bis (4,6-di-t-butylfell) ) Phosphate] and aluminum-tris [2,2′-ethylidene-bis (4,6-di-t-butylphenyl) phosphate]. Of these, sodium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate is preferred.

The crystallization nucleating agent in the present invention is mixed with the resin component, and then the resin component is melt-kneaded at a melting temperature or higher, and then cooled and molded.
In this invention, it is preferable that the compounding quantity of the crystallization nucleating agent of a polypropylene is 1-30 mass parts with respect to 100 mass parts of thermoplastic resin components (A), and it is more preferable that it is 3-15 mass parts. If the amount is too large, the rigidity is too high, which is not preferable. When the amount of the crystallization nucleating agent is too small, crystallization is insufficient and heat shrinkage is likely.

(B) Magnesium hydroxide Magnesium hydroxide that can be used in the present invention includes non-surface treated ones ("Kisuma 5" (trade name, manufactured by Kyowa Chemical Co., Ltd.)), fatty acids such as stearic acid and oleic acid. Surface-treated (“Kisuma 5A” (trade name, manufactured by Kyowa Chemical Co., Ltd.), phosphate-treated (“Kisuma 5J” (trade name, manufactured by Kyowa Chemical Co., Ltd.)), vinyl group or epoxy There are those treated with a silane coupling agent having a terminal group (“Kisuma 5L” (trade name, manufactured by Kyowa Chemical Co., Ltd.)). In the present invention, surface treatment with a silane coupling agent is more preferable.

When maintaining flame retardancy, the blending amount of magnesium hydroxide is 30 to 150 parts by mass, preferably 80 to 120 parts by mass with respect to 100 parts by mass of the thermoplastic resin component (A). If the amount of magnesium hydroxide is too large, the mechanical strength, electrical properties, and heat resistance will be significantly reduced or the appearance will be poor. If the amount of magnesium hydroxide is too small, the desired flame retardancy cannot be maintained.
Further, BET specific surface area of magnesium hydroxide preferably has 2~18m ² / g, especially balance of dispersibility and extrudability those 4~10m ² / g is better preferred.
In addition, the BET specific surface area of magnesium hydroxide in the present invention refers to a value obtained by measuring a dry powder sample of magnesium hydroxide by a liquid nitrogen adsorption method according to JIS Z 8830.

  The flame retardant resin composition of the present invention includes various commonly used additives such as antioxidants, metal deactivators, flame retardant (auxiliary) agents, fillers, lubricants, and the like. It can mix | blend suitably in the range which does not impair the objective.

  Antioxidants such as 4,4′-dioctyl diphenylamine, N, N′-diphenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, etc. Agent, pentaerythrityl-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate Phenolic antioxidants such as 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, bis (2-methyl-4- ( 3-n-alkylthiopropionyloxy) -5-tert-butylphenyl) sulfide, 2-mercaptoben ヅ imidazole and its zinc salt, pentaerythri Lumpur - tetrakis (3-lauryl - thiopropionate) and the like sulfur-based antioxidant such.

Examples of metal deactivators include N, N′-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hydrazine, 3- (N-salicyloyl) amino-1,2,4. -Triazole, 2,2'-oxamidobis- (ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) and the like.
In addition, flame retardants (auxiliaries) and fillers include carbon, clay, zinc oxide, tin oxide, titanium oxide, magnesium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, talc, calcium carbonate, magnesium carbonate, white For example, carbon.
Examples of the lubricant include hydrocarbons, fatty acids, fatty acid amides, esters, alcohols, and metal soaps.

Hereinafter, the manufacturing method of the flame-retardant resin composition of this invention is demonstrated.
Add the metal hydrate (B), the crystallization nucleating agent (C), and, if necessary, other resins and additives to the thermoplastic resin component (A) comprising the components (a) and (b), and heat Knead. When the thermoplastic resin component (A) is melted and kneaded, the crystallization nucleating agent (C) is dispersed in the thermoplastic resin component (A). In this dispersion, the crystalline portion in the thermoplastic resin component (A), for example, a polypropylene resin or other resin is cooled in the subsequent cooling and solidification step, starting from the place where the crystallization nucleating agent (B) is present. Crystallize. At this time, the polypropylene resin in the thermoplastic resin component (A) forms very fine crystallites starting from the crystallization nucleating agent (C). The kneading temperature is preferably 160 to 240 ° C., and the kneading conditions such as the kneading temperature and the kneading time can be appropriately set at the temperature at which the resin components (a) and (b) are melted. The kneading method can be satisfactorily used as long as it is a method usually used for rubber, plastic and the like. As the apparatus, for example, a single screw extruder, a twin screw extruder, a roll, a Banbury mixer or various kneaders are used. The components may be kneaded in any order, and may be melt-kneaded after dry blending at room temperature. By this step, a flame retardant resin composition in which each component is uniformly dispersed can be obtained. Although there is no restriction | limiting in particular in the conditions of a cooling solidification process, Conditions can be selected suitably if desired.

  The optical fiber cord of the present invention is manufactured by extrusion coating around an optical fiber strand or around an optical fiber core line in which tensile strength fibers are longitudinally or twisted. The temperature of the extruder at this time is preferably about 180 ° C. in the cylinder portion and about 200 ° C. in the cross head portion, although it depends on the conditions of the take-off speed of the type of resin and optical fiber. The optical fiber cord of the present invention includes all of the optical fiber strands or core wires coated on the outer periphery of the above-described composition as a coating layer, and the structure thereof is not particularly limited. The thickness of the coating layer and the type and amount of the tensile strength fiber that is vertically attached or twisted to the optical fiber core wire vary depending on the type and use of the optical fiber cord, and can be appropriately set.

(Example)
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these.

[Examples 1 to 12, Reference Examples 1 and 2, and Comparative Examples 1 to 8]
Tables 1 and 2 show Examples 1 to 12, Reference Examples 1 and 2 and Table 3 shows the contents of each component of the resin compositions of Comparative Examples 1 to 8 (numbers in the table are parts by mass unless otherwise specified). ). Each component shown in the table was dry blended at room temperature, and melt kneaded using a Banbury mixer to produce each resin composition.

Each component material shown in the table is as follows.
(A) Non-acid-modified polyolefin resin containing polypropylene, LLDPE
Product Name: Umerit 2525F, Ube Maruzen Polyethylene, Random Polypropylene Product Name: PB222A, Sun Allomer, Block Polypropylene Product Name: PB270A, Sun Allomer, Homo Polypropylene Product Name: PL400A, Sun Allomer (b) Acid-modified Polyolefin resin, acid-modified polyethylene Product name: Admer DU8300, manufactured by Nippon Polyethylene

(B) Magnesium hydroxide The following magnesium hydroxide was obtained, and the BET specific surface area was measured by a liquid nitrogen adsorption method for these dry powder samples of magnesium hydroxide according to JIS Z 8830. This value was 6.0 m ² / g as shown below.
Magnesium hydroxide surface-treated with a silane coupling agent Product name: Kisuma 5L, manufactured by Kyowa Chemical Co., Ltd., BET specific surface area: 6.0 m ² / g
(C) Crystallization nucleating agent / silica Product name: Aerosil V200, manufactured by Nippon Aerosil Co., Ltd., BET specific surface area: 200 m ² / g,
・ Phosphate product name: NA-902, manufactured by ADEKA (other additives)
・ Antioxidant Product name: Irganox 1010, manufactured by BASF ・ Lubricant calcium stearate, manufactured by Shinagawa Chemical

Next, using a general-purpose extrusion coating apparatus, the resulting composition was extrusion coated at a thickness of 0.35 mm on the outer periphery of an optical fiber nylon core wire having an outer diameter of 0.90 mm with tensile strength fibers (aramid fibers). An optical fiber cord having the structure 1 was manufactured.
The following evaluation was performed on the manufactured optical fiber cord. The evaluation results of Examples 1 to 14 obtained are shown in Tables 1 and 2, and the evaluation results of Comparative Examples 1 to 8 are shown in Table 3.
(1) Tensile properties The flame-retardant resin composition was heat-press molded to produce a sheet having a thickness of 1.0 mm ± 0.15 mm. A dumbbell No. 2 type test piece based on JIS K 7113 was produced from this sheet and subjected to a tensile test. The test was conducted at 25 mm between marked lines and at a tensile speed of 200 mm / min. A material having a tensile strength (TS) of 10 MPa or more and a tensile elongation (EL) of 200% or more was regarded as acceptable.
(2) Bendability An optical fiber cord was wound around a mandrel having an outer diameter of 14 mm and left for 5 minutes. The optical fiber cord was released from the mandrel, and the radius of curvature R after 120 minutes was compared. Those having a radius of curvature of 83 mm or more were considered to have passed the bending property. The thing with a curvature radius of 85 mm or more is preferable.
(3) Thermal Shrinkage The shrinkage rate after a sample cut out of 250 mm from the above cord was held in a constant temperature layer at 60 ° C. for 18 hours was measured. 1% or less was accepted.
(4) Bending stiffness Using the bending stiffness test apparatus 10 shown in FIG. 2, the optical fiber cord is bent with a bending diameter D = 30 mm so that the distance between the upper plate 11 of FIG. 2 and the upper surface of the load cell balance 13 is 30 mm. The repulsive force W was measured with a load cell, and the bending stiffness EI was calculated based on the following (Equation 1). The bending rigidity EI was 15-30 N · mm ² as acceptable.
EI = 0.3483WD ² (Formula 1)
(5) Flame retardancy A horizontal combustion test was conducted based on JIS C 3005. Those with a fire spread of less than 60 seconds passed, those with a fire spread of 60 seconds or more were rejected, and in Table 2, pass was indicated as ◯, and failure was indicated as x.

As can be seen from Tables 1 to 3, the optical fiber cord of Comparative Example 1 using the composition not containing the component (C) had a large heat shrinkage rate and was unacceptable. In addition, the optical fiber cord of Comparative Example 2 using a composition with a small amount of component (C) also had a large thermal shrinkage rate and failed. The optical fiber cord of Comparative Example 3 having a large amount of component (C) was largely bent and rejected. The optical fiber cord of Comparative Example 4 containing no component (b) was unacceptable due to excessive bending. (B) The optical fiber cord of Comparative Example 5 with a large amount of component was unacceptable because of the large thermal shrinkage rate. The composition of Comparative Example 8 not containing component (b) could not be melt kneaded. Could not be manufactured. The flame retardant of the optical fiber cord of Comparative Example 9 using a composition with a small amount of component (B) was rejected. The optical fiber cord of Comparative Example 10 using a composition in which the blending amount of the component (B) was too large failed in mechanical properties and bending.
On the other hand, the optical fiber cords of Examples 1 to 12 passed all the tensile properties, bending, thermal contraction rate, bending rigidity, and flame retardancy, and exhibited excellent properties. Example 13 has a small amount of polypropylene resin in component (a), and Reference Example 2 has a small amount of bending due to a large amount of blended polypropylene resin in component (a), but 83 mm, which is a sufficiently usable level. there were.

DESCRIPTION OF SYMBOLS 1 Optical fiber cord 2 Optical fiber core wire 3 Tensile fiber layer 4 Coating layer 10 Bending rigidity test apparatus 11 Upper plate 12 Slider 13 Load cell type balance 14 Base

Claims (4)

The thermoplastic resin component (A) is: (a) 70 to 95% by mass of a non-acid-modified polyolefin resin containing polypropylene; however, among the polyolefin resins of the component (a), the non-acid-modified polypropylene resin is the heat thermoplastic resin component (a) 10 to 70 wt% in, and (b) an acid modified polyolefin resin 5-30 wt% respectively containing organic, the thermoplastic resin component (a) 100 parts by mass of contrast, hydroxide 30 to 150 parts by mass of magnesium (B) and 1 to 30 parts by mass of a crystallization nucleating agent (C) selected from an organic nucleating agent and silica having a BET specific surface area of 175 to ²⁰⁰ m ² / g Flame retardant resin composition. The flame retardant resin composition according to claim 1, wherein the component (a) is a polyolefin resin selected from polypropylene and polyethylene.   The flame retardant resin composition according to claim 1 or 2, wherein the acid-modified polyolefin resin is acid-modified polyethylene. An optical fiber cord comprising a coating layer formed on the outer periphery of an optical fiber core wire using the flame retardant resin composition according to any one of claims 1 to 3.

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