JP2006259418A - Flame-retardant primary coated optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary coated optical fiber having high flame retardancy and excellent adhesiveness with epoxy resin and usable even in a high temperature and high humidity environment. <P>SOLUTION: The primary coated optical fiber comprises a primary coating layer 2 formed around a fiber 1 and a secondary coating layer further formed around the primary coating layer and is characterized in that: the secondary coating layer is composed of at least two layers or more; the inner layer 3 of the secondary coating layer comprises a resin composition containing a metal hydride in 100 parts by mass of a base resin consisting of 20 to 70 mass% of a thermoplastic elastomer and 30 to 80 mass% of an ethylenic copolymer; the outer layer 4 of the secondary coating layer contains a base resin comprising a polyester elastomer and/or an ethylene-vinylacetate copolymer saponification product; and the thickness ratio of the inner layer to the outer layer is 1.5 to 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical fiber, and more particularly to an optical fiber that has high flame retardancy, exhibits excellent adhesion to an epoxy resin, and can be used even under high temperature and high humidity.

  As shown in FIG. 1, the optical fiber has a structure in which the outer periphery of the fiber 1 is covered with a primary coating material 2 and the outer periphery of the primary coating material 2 is further covered with a secondary coating material 3. The primary coating layer is generally formed of two or more layers of silicone resin or ultraviolet curable resin. A secondary coating layer is formed on the outer periphery by coating a resin such as a polyester elastomer. The optical fiber is fixed to the connector with an adhesive such as an epoxy resin, and the connector is abutted and joined. However, the optical fiber is not projected by the use environment such as heat cycle. The secondary coating layer and the primary coating layer are sufficiently adhered (see, for example, Patent Document 1 and Patent Document 2).

JP-A-5-157950 JP 2002-162543 A

  The optical fiber is usually provided with flame retardancy by using a flame retardant resin composition in the secondary coating layer, but as a flame retardant blended therefor, harmful heavy metals and phosphorus compounds Other halogen compounds are currently used. However, when a flame retardant wire in which a secondary coating material is coated with a resin composition containing a halogen-based flame retardant is incinerated, there arises a problem that a large amount of smoke or corrosive gas is generated. For this reason, the examination of the technique which expresses a flame retardance without using a halogenated flame retardant is performed actively. As a general flame retardant technique, there is a method of blending metal hydrate, but in order to impart high flame retardancy, it must be blended in large quantities, resulting in significant mechanical strength and other properties. The decline was inevitable.

In particular, in a secondary coating layer used in an optical fiber, a significant decrease in adhesiveness with an epoxy resin used as an adhesive for the primary coating layer or connector is fatal.
The present inventors have also confirmed that when a non-halogen flame retardant in an amount that can satisfy the flame retardancy is blended with the polyester elastomer, the mechanical strength and adhesive strength of the coating layer are remarkably lowered and cannot be used. In that case, it is difficult to maintain the moisture and heat resistance, and it is difficult to maintain the moisture and heat resistance corresponding to 2000 hours at 85 ° C. and 85% shown in the Telcordia standard, which is a typical standard required for communication equipment. Met.

  As a result of intensive studies based on these findings, the present invention has a good appearance, excellent productivity, very little fiber protrusion during actual use, excellent adhesion to epoxy resin, even under high temperature and high humidity. Invented a non-halogen moisture-resistant flame-retardant optical fiber that can be used and does not generate a large amount of smoke or halogen gas during incineration.

That is, the present invention
(1) An optical fiber in which a primary coating layer is formed on the outer periphery of a fiber and a secondary coating layer is further formed on the outer periphery of the primary coating layer, and the secondary coating layer includes at least two or more layers And the inner layer of the secondary coating layer contains 50 to 200 parts by mass of metal hydrate with respect to 100 parts by mass of the base resin composed of 20 to 70% by mass of the thermoplastic elastomer and 30 to 80% by mass of the ethylene copolymer. The outermost layer of the secondary coating layer is composed of 0 to 60 parts by mass of filler with respect to 100 parts by mass of the base resin composed of polyester elastomer and / or saponified ethylene-vinyl acetate copolymer. A flame retardant optical fiber comprising a composition,
(2) The ratio of the metal hydrate in the resin composition constituting the inner layer is 2 or more by mass ratio with respect to the proportion of the filler in the resin composition constituting the outermost layer ( 1) Flame retardant optical fiber as described in
(3) The flame retardant optical fiber according to (1) or (2), wherein a thickness ratio of the inner layer to the outer layer is 1.5 to 20;
(4) The flame-retardant optical fiber according to any one of (1) to (3), wherein the thermoplastic elastomer is at least one selected from a polyester elastomer, a polyurethane elastomer, and a polyamide elastomer. ,
(5) The outermost layer is composed of a resin composition containing at least one selected from the group consisting of melamine cyanurate compounds, clays and metal hydrates (1) to (4) ) A flame retardant optical fiber according to any one of the above,
Is to provide.

In addition to being composed of a non-halogen agent, the flame-retardant optical fiber of the present invention has the effect of maintaining excellent flame retardancy without deteriorating moisture and heat resistance and adhesion to an epoxy resin. Play.
In the present invention, the secondary coating layer is composed of at least two layers, and the base resin of the outermost layer is made of a polyester elastomer and / or a saponified ethylene-vinyl acetate copolymer. The resin composition constituting the inner layer of the two layers is composed of a thermoplastic elastomer and an ethylene copolymer as a base resin, and a metal hydrate is blended so as to ensure sufficient flame retardancy. However, there is an effect that the mechanical characteristics as the strand are not impaired.

Hereinafter, the present invention will be described in detail.
First, the primary coating layer of the moisture and heat resistant flame retardant optical fiber of the present invention will be described. The primary coating layer of the flame retardant optical fiber of the present invention is preferably formed of an ultraviolet curable resin. Although it does not specifically limit as ultraviolet curable resin, For example, polyether type, polyester type, an epoxy type, and a polybutadiene type urethane acrylate can be mentioned.
By using the ultraviolet curable resin described above, the adhesion strength with a secondary coating layer described later is improved. Therefore, it functions to suppress the protruding amount of the fiber protruding from the end face when the strand is used.

Next, the secondary coating layer of the flame-retardant optical fiber of the present invention will be described. The secondary coating layer is composed of at least two layers. These can be formed by a conventionally known method, and may be extrusion-coated at the same time, or may be further extrusion-coated after forming a coating layer once.
Among these, the base resin of the resin composition constituting the inner layer of the secondary coating layer is composed of 20 to 70% by mass of a thermoplastic elastomer and 30 to 80% by mass of an ethylene copolymer. Here, each component will be described.

(1) Thermoplastic Elastomer The thermoplastic elastomer used in the present invention can be used without particular limitation as long as it has a hard segment and a hard segment. Among them, a polyester elastomer, a polyurethane elastomer, and a polyamide elastomer are preferable. Any one of these may be used alone, or two or more may be used in combination. When a thermoplastic elastomer is used for the outer layer of the secondary coating layer described later, it is particularly preferable to use a polyester elastomer. In that case, the soft segment is preferably composed only of the polyalkyl glycol shown below. This is because when the aliphatic polyester is used as the soft segment, the heat and humidity resistance may be lowered.

  Further, the hard segment of the polyester elastomer may be either a polyalkylene terephthalate represented by the following chemical formula 2 or a polyalkylene isophthalate represented by the following chemical formula 3. Both may be included.

  Further, when a polyester elastomer is used as the thermoplastic elastomer for the inner layer of the secondary coating layer, the melting point is preferably 200 ° C. or less. In this case, the heat and moisture resistance and the workability during wiring are good, and the primary coating layer is less likely to foam when the coating layer is coated. The melting point of the polyester elastomer is preferably 120 ° C to 195 ° C, more preferably 150 ° C to 190 ° C. This is because, if the melting point is too low, the wiring performance may be significantly reduced.

  The amount of the thermoplastic elastomer used in the inner layer of the present invention is 20 to 70% by mass in the resin component. If it is less than 20% by mass, the adhesiveness with the primary coating layer is lowered, and if it exceeds 70% by mass, the amount of the ethylene copolymer, which is the other resin component described later, is reduced, thereby reducing the flame retardancy. It is.

(2) Ethylene-based copolymer In the present invention, an ethylene-based copolymer is used in addition to the thermoplastic elastomer for the base resin of the resin composition used as the inner layer of the secondary coating layer. Specific examples of the ethylene copolymer that can be used in the present invention include, for example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-ethyl acrylate copolymer, and an ethylene-methacrylate copolymer. Is mentioned. These may be used alone or in combination of two or more. From the viewpoint of improving flame retardancy, an ethylene-vinyl acetate copolymer is preferred. Further, in order to improve flame retardancy, the content of copolymerized components copolymerized with ethylene (for example, VA content for ethylene-vinyl acetate copolymer, EA content for ethylene-ethyl acrylate copolymer) is 40% or more of the ethylene copolymer is preferable, more preferably 60% or more, and particularly preferably 70% or more.

In the present invention, the amount of the ethylene-based copolymer is 30 to 80% by mass in the base resin. This is because if the amount is less than 30% by mass, the flame retardancy is lowered, and if it is more than 80% by mass, the amount of the thermoplastic elastomer as the other resin component is reduced, thereby lowering the adhesiveness to the primary coating layer. More preferably, it is 40-70 mass%.
For the secondary coating inner layer, a thermoplastic elastomer and an ethylene-based copolymer are used as a base resin. The thermoplastic elastomer can improve the adhesion strength between the primary coating layer and the secondary coating outermost layer. On the other hand, ethylene-based copolymers can reduce the blending amount of metal hydrates blended in order to exhibit flame retardancy, avoid a significant decrease in mechanical strength, and also have hydrolysis resistance. Can be improved.

(3) Metal Hydrate The inner layer of the secondary coating layer in the present invention includes a resin composition in which a metal hydrate is blended with respect to 100 parts by mass of the base resin composed of the thermoplastic elastomer and the ethylene-based copolymer. Is done.
The type of metal hydrate that can be used in the present invention is not particularly limited. For example, aluminum hydroxide, magnesium hydroxide, hydrated aluminum silicate, hydrated magnesium silicate, basic magnesium carbonate, aluminum orthosilicate, Examples thereof include metal compounds having a hydroxyl group or crystal water such as hydrotalcite, and these may be used alone or in combination of two or more. Of these metal hydrates, aluminum hydroxide and magnesium hydroxide are preferred.

  The metal hydrate may be untreated or surface-treated. Examples of the aluminum hydroxide that can be used in the present invention include those that have not been surface-treated (Hidilite H42M (trade name, manufactured by Showa Denko), etc.) and those that have been surface treated with fatty acids such as stearic acid and oleic acid (Hijilite). H42S (trade name, manufactured by Showa Denko) and the like. Magnesium hydroxide that can be used in the present invention includes those that have not been surface-treated (Kisuma 5 (trade name, manufactured by Kyowa Chemical Co., Ltd.)) and those that have been surface-treated with fatty acids such as stearic acid and oleic acid ( Kisca 5A (trade name, manufactured by Kyowa Chemical Co., Ltd.), phosphate-treated (Kisuma 5J (trade name, manufactured by Kyowa Chemical Co., Ltd.), etc.), silane coupling agent having a vinyl group or an epoxy group at the terminal There is a surface-treated product (Kisuma 5L (trade name, manufactured by Kyowa Chemical Co., Ltd.)).

The flame retardant test methods include horizontal flame retardant, inclined flame retardant, and vertical flame retardant. When maintaining vertical flame retardant, the amount of metal hydrate is 100 parts by mass of the inner layer base resin. On the other hand, it is preferable to set it as 50-200 mass parts. If it exceeds 200 parts by mass, mechanical strength and adhesiveness may be reduced, hydrolysis resistance may be reduced, and appearance may be deteriorated.
Moreover, if it is a grade which does not inhibit adhesiveness with an epoxy resin, you may mix | blend a metal hydrate with the outer layer of a secondary coating layer, and in this case, it is 0 with respect to 100 mass parts of resin components which comprise an outer layer. It is preferable to add about 50 parts by mass.

(4) Polyester elastomer In the present invention, a polyester elastomer and / or a saponified ethylene-vinyl acetate copolymer is used as a base polymer in the resin composition constituting the outer layer of the secondary coating layer.
The polyester elastomer in the present invention generally has a structure of an (AB) n-type multi-block copolymer composed of a crystalline (hard) segment A and an amorphous (soft) segment B, and is structurally hard. The segments are polyesters such as polybutylene terephthalate and polybutylene isophthalate, and the soft segment includes two types of polyether types such as polyethylene glycol and polypropylene glycol and polyester types such as aliphatic polyesters, both of which should be used. Can do.

The polyester elastomer used for the outermost layer of the secondary coating layer is not particularly limited for both the hard segment and the soft segment, but a polyester elastomer consisting only of the above (1 type) can be preferably used as the soft segment.
Furthermore, the melting point of the polyester elastomer used for the outermost layer of the secondary coating layer can be used without any particular limitation.
In the present invention, the polyester elastomer may be used alone or in combination of two or more. Further, the outermost layer of the secondary coating layer may be used by mixing with the following saponified ethylene-vinyl acetate copolymer.

(5) Saponified ethylene-vinyl acetate copolymer In the present invention, a saponified ethylene-vinyl acetate copolymer in which a part or all of the acetate groups of the vinyl acetate copolymer is substituted with a hydroxyl group is used in the outermost layer. be able to.
In the present invention, the saponified ethylene-vinyl acetate copolymer may be used alone or in combination of two or more. Moreover, you may mix and use the said polyester elastomer.

(6) Melamine cyanurate compound In this invention, a melamine cyanurate compound can be mix | blended with the outer layer of a secondary coating layer. The particle size is preferably fine, and the average particle size is 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. Moreover, the melamine cyanurate compound surface-treated from the dispersible surface is used preferably. Examples of the melamine cyanurate compound that can be used in the present invention include MCA-1 (trade name, manufactured by Mitsubishi Chemical Corporation), MC600, and MC860 (both trade names, manufactured by Nissan Chemical Industries, Ltd.). Examples of the melamine cyanurate compound surface-treated with a fatty acid include MC610 and MC640 (both are trade names, manufactured by Nissan Chemical Co., Ltd.). Examples of the melamine cyanurate compound that can be used in the present invention include melamine cyanurate having the following structure.

In this invention, the compounding quantity of a melamine cyanurate compound is 0-40 mass parts with respect to 100 mass parts of outermost layer resin components, Preferably it is 5-30 mass parts. If the amount of the melamine cyanurate compound is too small, the effect of improving the flame retardancy will not be exhibited. If the amount is too large, the mechanical strength and the adhesive strength are lowered, and the appearance of the fiber strand is markedly deteriorated.
Further, it is preferable to add the melamine cyanurate compound to the secondary coating inner layer in combination with the organic clay described below, whereby the amount of metal hydrate in the secondary coating inner layer can be greatly reduced.

(7) Clay Clay can be blended in the outermost layer of the secondary coating layer of the present invention. Clay (clay mineral) is a silicate mineral or the like having a layered structure and is a substance having a layered structure formed by laminating a large number of sheets. Among the above sheets, some are tetrahedron sheets formed by bonding a large number of tetrahedrons made of silicic acid in the plane direction, and some are bonded by a large number of octahedrons containing Al, Mg, etc. in the plane direction. It is an octahedron sheet formed as described above. The layered structure of the sheet, the types of elements constituting the sheet, and the like vary depending on the individual clay. In the present invention, among such clays, for example, montmorillonite, saponite, hectorite, beidellite, stevensite, nontronite, vermiculite, halloysite, mica, fluorinated mica, kaolinite, pyrophyllolite and the like are used. be able to. Moreover, natural products or synthetic products may be used.

  For the resin composition constituting the outer layer of the secondary coating layer of the present invention, an organic clay obtained by organizing clay (clay mineral) with an organic agent can be preferably used. Various onium ions can be used as the organic agent. These various onium ions are primary to quaternary ammonium ions, such as hexyl ammonium ion, octyl ammonium ion, 2-ethylhexyl ammonium ion, dodecyl ammonium ion, lauryl ammonium ion, octadecyl ammonium ion, dioctyl dimethyl ammonium ion, trioctyl ammonium ion. Ions, dioctadecyldimethylammonium ions, trioctylammonium ions, dioctadecyldimethylammonium ions, trioctadecylammonium ions, and the like can be used.

In this invention, the compounding quantity of clay is 0-30 mass parts with respect to 100 mass parts of outermost layer resin components, Preferably it is 3-15 mass parts. When the blending amount of clay is too small, the effect as a flame retardant aid is not expressed, and when it is too large, the mechanical strength and the adhesive strength are remarkably lowered. Among the clays, it is preferable to use an organic clay from the viewpoint of dispersibility in the resin composition.
In addition, the organic clay is added to the inner layer of the secondary coating layer in combination with the melamine cyanurate compound described above and added to the inner layer of the secondary coating to significantly reduce the amount of metal hydrate in the inner layer of the secondary coating. Can be preferred.

  Furthermore, in the present invention, by using a melamine cyanurate compound as a flame retardant in addition to a metal hydrate as a flame retardant and clay as a flame retardant aid in the outer layer of the secondary coating layer, The generation of nitrogen gas by the nurate compound and the clay uniformly dispersed in the resin composition play a role of slowing down the burning rate of the resin composition, and thus are considered to have high flame retardancy. In addition, because of this effect, high flame retardancy can be maintained even if the metal hydrate is reduced, so the mechanical strength, adhesion strength between the primary coating layer and the epoxy resin is higher than when a large amount of metal hydrate is blended. Can be improved.

  In the present invention, the composition excluding the base resin in the resin composition is generically referred to as a filler, and in the resin composition constituting the outermost layer, the total is 0 to 60 parts by mass with respect to 100 parts by mass of the base resin. Blended. When it is possible to maintain sufficient flame retardancy with the resin composition of the inner layer, it is not necessary to add a flame retardant to the outermost layer, but when it is insufficient to retain the flame retardant with the flame retardant compounded in the inner layer The outermost layer is filled with a filler.

  In the insulating resin composition of the present invention, various additives commonly used in electric wires and cables, such as antioxidants, metal deactivators, flame retardants (auxiliaries), fillers, A lubricant and the like can be appropriately blended within a range not impairing the object of the present invention. Further, a resin other than the polyester elastomer can be mixed as long as the characteristics are not impaired. Although the range which can be mixed is not specifically limited, Generally it is 30 mass% or less.

  Antioxidants include amine-based antioxidants such as 4,4'-dioctyl diphenylamine, N, N'-diphenyl-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer Agents, pentaerythrityl-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate , 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene and other phenolic antioxidants, bis (2-methyl-4- ( 3-n-alkylthiopropionyloxy) -5-t-butylphenyl) sulfide, 2-mercaptobenzimidazole and its zinc salt, pentaerythritol-tetrakis (3-lauryl-thiopropionate) And sulfur-based antioxidants.

  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).

Examples of fillers and other flame retardants include carbon, zinc oxide, tin oxide, titanium oxide, magnesium oxide, molybdenum oxide, antimony trioxide, silicone compounds, quartz, talc, calcium carbonate, magnesium carbonate, and white carbon. It is done.
Examples of lubricants include hydrocarbons, fatty acids, fatty acid amides, esters, alcohols, and metal soaps. Among these, wax E, wax OP (both trade names, manufactured by Clariant), etc. Examples include ester-based, alcohol-based, and metal soap-based materials that exhibit both lubricity and external lubricity. However, if these lubricants, antioxidants, and metal deactivators are added too much, the adhesion to the underlying fiber strands will be significantly reduced, causing problems such as fiber sticking out during actual use.

Furthermore, in the present invention, by adding the colorant only to the inner layer material, the problem of color fading that occurs when the secondary coating layer is a single layer is also solved.
In the present invention, the problem of die scum is solved by adopting a method of simultaneously extruding the inner layer material and the outer layer material as a method of manufacturing an optical fiber. This is because an inner layer material containing a large amount of additives such as metal hydrates due to die scum is extruded while being covered with an outer layer material having relatively less additives. The thickness ratio of the inner layer to the outermost layer is preferably 1.5 to 20 because the flame retardant / moisture and heat resistance effect of the inner layer and the adhesive effect of the outermost layer with the epoxy resin can be satisfied in a well-balanced manner.

An ultraviolet curable resin (thickness: 0.14 mm) was applied to the outer periphery of a fiber having a diameter of 0.125 mm, and a primary coating layer was formed by irradiating with 300 mJ / cm ³ of ultraviolet rays. Then, the secondary coating layer was formed by the thickness of 0.25 mm-0.30 mm with the extrusion temperature of 210 to 260 degreeC for the material described in Table 1.
For each obtained optical fiber, the following items were evaluated. The results are shown in Table 1.
Extrusion moldability: The amount of die scum when an optical fiber core wire was produced 1000 m under the above conditions was visually observed.
The case where the amount was relatively small, or the case where the amount was not generated was rated as ◯, and the case where the amount was large as x.

-Flame retardance: The vertical combustion test of UL1581 was conducted, and the average time (unit: second) until the optical fiber was self-extinguished when the test was performed five times was calculated. Within 60 was considered acceptable.
Adhesiveness: The strands were bonded to an aluminum plate with an epoxy resin, and the strength (unit: N) for peeling the strands was measured. 5N or more was accepted.
Protrusion: The optical fiber was cut to 1.00 m, and a heat shock test at −30 / 80 ° C. was performed. The number of cycles was 100 cycles, and each holding time was 2 hours.
A projecting amount of less than 0.2 mm was indicated by ◯, and a projecting amount of 0.2 mm or more was indicated by x.
Moisture and heat resistance: It was left under 85 ° C. and 85% wet heat for 1000 hours and 2000 hours, wound around a 50 mm mandrel 6 times, and confirmed whether cracks occurred in the coated part. The case in which a crack was generated after being left for 1000 hours was rated as “X”, the case in which a crack was not generated after being wound in 1000 hours was marked as “◯”, and the case in which no crack was generated after 2000 hours was marked as “A”.
Color fading: The optical fiber was lightly wiped with an absorbent cotton impregnated with ethanol, and the color of the absorbent cotton was visually observed. The case where the color of the covering material adhered to the absorbent cotton was indicated as x, and the case where it did not adhere was indicated as ◯.

1) Hytrel 4057
Toray DuPont Co., Ltd. Polyester elastomer Melting point: 163 ° C
Hard segment: (Chemical formula 2), (Chemical formula 3)
Soft segment: Polyethylene glycol

2) Hytrel 4777
Toray DuPont Co., Ltd. Polyester elastomer Melting point: 200 ° C
Hard segment: (Chemical formula 2) only Soft segment: Polyethylene glycol

3) Mersen H6960
Tosoh Corporation Ethylene-vinyl acetate copolymer saponified product 4) Resamine P-2288
Dainichi Seika Kogyo Co., Ltd. Polyurethane Elastomer

5) Pebax 4033
Atofina Polyamide Elastomer 6) Revaprene 800HV
Bayer ethylene-vinyl acetate copolymer VA content: 80%

7) Kisuma 5A
Kyowa Chemical Industry Co., Ltd. Magnesium hydroxide 8) Melamine cyanurate MC640
Nissan Chemical Industries, Ltd. Melamine cyanurate

9) Nanofil 32
Sud Chemie Organic Organized Clay 10) Calcium stearate Calcium stearate Calcium stearate

As can be seen from the results of the table, Comparative Example 1 in which the polyester elastomer of the inner layer of the secondary coating is 10%, which is less than 20% of the base resin, has a problem of protrusion, but Comparative Example 2 in which 80% exceeds 70%. However, there were problems with flame retardancy and heat and humidity resistance. In Comparative Examples 3 and 4 in which the total mass of the filler contained in the resin composition constituting the outermost layer exceeds 60 parts, a large amount of dies is generated at the time of extrusion, so there is a problem in extrusion moldability. Further, Comparative Example 5 in which the amount of the metal hydrate in the secondary coating inner layer exceeds 200 parts has a problem with moisture and heat resistance, and Comparative Example 6 with less than 50 parts has a problem in flame retardancy. In Comparative Examples 7 to 11 in which the secondary coating layer is composed of only one layer, the color fading when wiped with absorbent cotton impregnated with ethanol was remarkable. Further, in Comparative Examples 7, 9, 10, and 11, the amount of die scum generated was significant and there was a problem in extrusion moldability.
On the other hand, in Examples 1-17, there was no problem in any item and the favorable characteristic was shown as a flame-retardant optical fiber strand.

It is sectional drawing of an optical fiber strand.

Explanation of symbols

1. 1. Optical fiber Primary covering material3. Secondary covering material (inner layer)
4). Secondary covering material (outer layer)

Claims (5)

An optical fiber having a primary coating layer formed on the outer periphery of a fiber and a secondary coating layer formed on the outer periphery of the primary coating layer, wherein the secondary coating layer comprises at least two layers, The resin composition in which the inner layer of the secondary coating layer contains 50 to 200 parts by mass of metal hydrate with respect to 100 parts by mass of the base resin comprising 20 to 70% by mass of the thermoplastic elastomer and 30 to 80% by mass of the ethylene copolymer. And the outermost layer of the secondary coating layer is composed of a composition comprising 0 to 60 parts by mass of filler with respect to 100 parts by mass of a base resin consisting of a polyester elastomer and / or a saponified ethylene-vinyl acetate copolymer. A flame-retardant optical fiber, characterized in that it is constructed. The ratio of the metal hydrate in the resin composition constituting the inner layer is 2 or more by mass ratio with respect to the ratio of the filler in the resin composition constituting the outermost layer. Flame retardant optical fiber. The flame retardant optical fiber according to claim 1 or 2, wherein a thickness ratio of the inner layer to the outermost layer is 1.5 to 20. The flame-retardant optical fiber according to any one of claims 1 to 3, wherein the thermoplastic elastomer is at least one selected from a polyester elastomer, a polyurethane elastomer, and a polyamide elastomer. The outermost layer is composed of a resin composition containing at least one selected from the group consisting of a melamine cyanurate compound, clay and metal hydrate. The flame-retardant optical fiber according to the item.

Images