JP3354769B2 - Optical fiber coated tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary coating material (loose tube) for an optical fiber cable, and more particularly to an optical fiber coated tube having excellent durability such as heat resistance and heat and humidity resistance.

[0002]

2. Description of the Related Art An optical fiber-coated tube (loose tube) directly protects an optical fiber. An optical fiber passes through the tube, and several optical fiber-coated tubes are bundled. It becomes an optical fiber cable. BACKGROUND ART Conventionally, polybutylene terephthalate resin has been widely used for optical fiber coated tubes because of its excellent mechanical strength and chemical resistance. However, the conventional secondary tubing for optical fiber cables made of polybutylene terephthalate resin has excellent mechanical strength, rigidity and oil resistance, but has been placed in a high-temperature atmosphere or a high-temperature, high-humidity atmosphere for a long time. In this case, thermal degradation and hydrolysis of the resin occur, and the mechanical strength and the like decrease.Therefore, there is a problem that the optical fiber in the tube is affected, transmission loss occurs, and the performance as a secondary coated tube is reduced. Yes, these measures are required.

[0003]

According to the present invention, as a result of intensive studies to solve the conventional problems, a tube obtained by extruding a specific polybutylene terephthalate resin shows excellent dimensional stability. The present inventors have found that this is a coated tube for an optical fiber cable, which maintains excellent performance for a long period of time, and has reached the present invention. That is, in the present invention, a polybutylene terephthalate resin having an intrinsic viscosity of 1.0 or more is extruded, and the heat of crystal fusion ΔH _m is 40 J /
g or more .

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polybutylene terephthalate resin in the present invention means a polyester whose main repeating unit is butylene terephthalate, and specifically, a polyester obtained by condensing 1,4-butanediol with terephthalic acid or a lower alcohol ester thereof. Yes, it may be a copolymer. Here, the copolymer is mainly composed of terephthalic acid or its lower alcohol ester as a dibasic acid component, and a polyester composed of 40 mol% or less of other dibasic acid components, or 1,1 as a glycol component.
Mainly 4-butanediol and other glycol components
Refers to a polyester composed of 0 mol% or less. Furthermore, the main component is terephthalic acid or its lower alcohol ester.
1,4-Butanediol, which also includes polyesters in which the total of other dibasic acid components and other glycol components is less than 40 mol%. Here, as the dibasic acid component other than terephthalic acid or its lower alcohol ester, isophthalic acid, phthalic acid, adipic acid, sebacic acid, succinic acid, oxalic acid, dodecane diacid, and the like or lower alcohol esters thereof can be used. As the glycol component other than 1,4-butanediol, ordinary alkylene glycols such as ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, hexamethylene glycol, neopentyl glycol, and cyclohexane dimethanol can be used. or,
It may be a branched polymer mainly composed of a so-called butylene terephthalate unit and branched by adding a polyfunctional compound. Examples of the polyfunctional compound that can be used here include trimesic acid, trimellitic acid, pyromellitic acid and their lower alcohol esters, glycerin, trimethylolethane, trimethylolpropane,
Pentaerythritol and the like. The addition amount of these polyfunctional compounds is 1 mol% or less as an acid component or a glycol component.

[0005] The polybutylene terephthalate resin used in the present invention is required to have an intrinsic viscosity of 1.0 or more. If a material having an intrinsic viscosity of less than 1.0 is used, a circular cross section cannot be obtained, and only a flat coated tube can be obtained. If the coated tube is flat, it is bulky when the coated tubes are bundled (usually used in a bundle), which undesirably hinders the advantages of the optical fiber. In addition, the intrinsic viscosity
If it is less than 1.0, the polymer molecular weight is small, the mechanical strength is reduced due to thermal deterioration, etc., and the coating tube is cracked or broken by a slight external force, and the optical fiber is protected from moisture or external force Is gone. It should be noted that the upper limit of the intrinsic viscosity does not need to be particularly defined, but if the intrinsic viscosity is too large, the production cost of the polybutylene terephthalate resin increases, melt fracture and the like are likely to occur, and the moldability of the tube decreases. Therefore, it is preferable to be about 1.6 or less. Here, the adjustment of the intrinsic viscosity is performed by controlling the polycondensation time in the same manner as the viscosity adjustment of a general polyester resin. It is better to use the phase polymerization method
Polymer quality and economical preference. In addition, this solid-phase polymerization method is carried out at a high temperature, for example, at 160 ° C. under an inert gas flow.
A general solid-phase polymerization method of heating to the melting point or lower may be used.

The polybutylene terephthalate resin or its composition used in the present invention preferably satisfies the following formula (1). _Tm − _Tic ≦ 30 (1) _Tm : heating rate by differential thermal analysis based on JIS K7121
Melting point of resin measured at 10 ° C / min T _ic : Rate of temperature decrease by differential thermal analysis based on JIS K7121
Extrapolated crystallization initiation temperature of resin measured at 10 ° C / min. Those satisfying the above formula, when used as an optical fiber-coated tube, can be obtained as described later, and have excellent dimensional stability, as described below. It will be.

The polybutylene terephthalate resin used in the present invention has a carboxy group content at the molecular chain end of 45.
It is preferably at most meq / kg. 45 carboxy groups
If it is larger than meq / kg, the hydrolysis resistance becomes poor, which is not preferable. Optical fiber is used under high temperature and high humidity environment,
When the coated tube is hydrolyzed, the mechanical strength is reduced, and the coated tube is cracked or broken by a slight external force, and the function of protecting the optical fiber from moisture or external force is lost, which is not preferable.

In the present invention, it is also preferable to use a composition obtained by blending the above-mentioned polybutylene terephthalate resin with various additives as a tube material. A particularly preferred additive is a crystal nucleating agent, and its compounding amount is 0.005 to 2.0 parts by weight based on 100 parts by weight of the polybutylene terephthalate resin. If the nucleating agent is added in an amount of 0.005 parts by weight or more, dimensional stability is improved in a high-temperature and high-humidity environment, which is preferable. here,
If the dimensional change of the coated tube is large, the dimensional change of the coated tube is influenced by bending of the optical fiber and the like, and the transmission loss increases, which is not preferable. The term “dimensional stability” as used herein means post-shrinkage or the like in a high-temperature and high-humidity environment, and the heat of crystal fusion ΔH _m of an optical fiber-coated tube obtained by extrusion molding is 40 J / g or more. preferable. Heat of crystal fusion Δ of optical fiber coated tube
When H _m is less than 40 J / g, not promoted crystallization of the coating tube, occurs recrystallization in an environment of high temperature and high humidity,
Post-shrinkage may increase, which is not preferable. The heat of crystal fusion ΔH _m refers to a rate of temperature increase of 10 ° C. by differential thermal analysis.
/ Min. The content of the nucleating agent is
If the amount is more than 2.0 parts by weight, the coated tube becomes brittle, which is not preferable. As the crystal nucleating agent used here, any of an organic substance and an inorganic substance can be used. As inorganic substances,
Zn powder, Al powder, graphite, or alone such as carbon _{black, ZnO, MgO, Al 2 O} 3, TiO 2, MnO 2, SiO 2, Fe
Metal oxides such as ₃ O ₄ , aluminum nitride, silicon nitride, titanium nitride, nitrides such as boron nitride, Na ₂ CO ₃ , CaCO
₃ , inorganic salts such as MgCO ₃ , CaSiO ₃ , BaSO ₄ , and Ca ₃ (PO ₄ ) ₃ ; and clays such as talc, kaolin, clay, and clay can be used alone or in combination of two or more. Examples of organic substances include organic salts such as calcium oxalate, sodium oxalate, calcium benzoate, calcium phthalate, calcium tartrate, magnesium stearate, and polyacrylate, and polymers such as polyester, polyethylene, and polypropylene, and polymers. Can be used alone or in combination of two or more. Particularly preferred are boron nitride and talc.

[0009] Compositions containing a phosphorus compound are also preferred for obtaining good thermal stability. The compounding amount of the phosphorus compound is polybutylene terephthalate resin 100
0.01 to 1.0 part by weight, preferably 0.1 to 1.0 part by weight.
0.5 parts by weight. If the amount is less than 0.01 part by weight, the effect of addition is not exhibited. If the amount is more than 1.0 part by weight, the hydrolysis resistance is rather deteriorated, which is not preferable. As the phosphorus-based compound used here, phosphite-based and phosphite-based organic compounds are preferable. For example, triallyl phosphite such as triphenyl phosphite, tri (nonylphenyl) phosphite, and distearyl pentaerythritol dithiol phosphite are preferred. Phosphite, cyclic neopentanetetrayl-bis- (2,4-di-t-butylphenyl-phosphite), di- (2,6-di-t-butyl-
Heat-resistant phosphites such as 4-methylphenyl) pentaerythritol diphosphite, tetrakis (2,4
Phosphonite compounds such as-(di-t-butylphenyl) -4,4-biphenylenephosphonite are typical examples. Preferably, bis- (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4-biphenylenephosphonite, bis −
(2,4-di-t-butylphenyl) pentaerythritol diphosphite.

In order to further improve heat resistance, a polybutylene terephthalate resin is added in addition to the phosphorus compound.
It is preferable that the hindered phenol compound or the thioether compound is contained in an amount of 0.01 to 0.5 part by weight based on part by weight. An example of the hindered phenol compound used here is 1,6-hexanediol bis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis [3- (3,
5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- (3-
t-butyl-5-methyl-4-hydroxyphenyl) propionate]. Examples of the thioether compound include dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, tetrakis [methylene-3- (dodecylthio) propionate] methane, dialkyl ( C ₁₂ ~C ₁₈₎ -3,3 - such as thiodipropionate and the like. Preferably, it is a hindered phenol compound. Particularly preferably, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol bis [3- (3-t-butyl-5-
Methyl-4-hydroxyphenyl) propionate].

The resin material used in the present invention may be used in combination with a known substance generally added to a thermoplastic resin or the like in order to further impart desired properties. For example,
It is possible to incorporate stabilizers such as antioxidants, ultraviolet absorbers and light stabilizers, antistatic agents, lubricants, coloring agents such as dyes and pigments, lubricants, plasticizers, and the like. The optical fiber-coated tube of the present invention is a tube formed by extruding a specific polybutylene terephthalate resin, and can be manufactured by a usual tube forming apparatus. Since the optical fiber-coated tube of the present invention preferably has advanced crystallization in terms of post-shrinkage and the like, the cooling temperature of the tube is 30 to 70 ° C.
Is preferable, and particularly preferably 50 to 70 ° C.

An optical fiber-coated tube comprising the polybutylene terephthalate resin of the present invention or a composition thereof,
It not only has excellent mechanical strength, rigidity and oil resistance, but also exhibits excellent dimensional stability even when placed in a high-temperature atmosphere or a high-temperature, high-humidity atmosphere for a long time. Extremely low strength, maintaining excellent performance over a long period. Furthermore, since the polybutylene terephthalate resin used in the present invention also has excellent tube moldability, it can sufficiently cope with high-speed molding at several hundred m / min, and has the advantage of being inexpensive to produce.

[0013]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but it is needless to say that the present invention is not limited to these examples. Examples 1 to 3 and Comparative Examples 1 to 3 Using various polybutylene terephthalate resin compositions shown in Table 1, using a tube extrusion molding apparatus, a resin temperature of 250 was used.
The tube was molded under the conditions of ° C and a cooling temperature (water bath temperature) of 30 ° C, and the tube formability was examined. Furthermore, for the obtained tube with an outer diameter of 2.5 mm and an inner diameter of 1.7 mm, heat resistance,
Tests were made for wet heat resistance and dimensional stability. Table 1 shows the results. The evaluation method and evaluation criteria for each test item are shown below. Formability: The outer diameter of a tube having a length of 1 m was measured at 10 points, the ratio of the maximum value to the minimum value was determined, and the ratio was evaluated according to the following criteria. ○: those with a maximum / minimum value of less than 1.05 ×; those with a maximum / minimum value of 1.05 or more ・ Heat resistance: tubes heated at 180 ° C in a hot air dryer for a certain period at 23 ° C, 50% RH After standing for 24 hours in a thermo-hygrostat, the tensile strength and tensile elongation were measured and evaluated according to the following criteria. ；: The period in which the retention of the tensile strength and the tensile elongation is 80% or more is 48 hours or more. Δ: The period in which the retention of the tensile strength and the tensile elongation is 80% or more is 24 hours or more. The retention rate of either tensile strength or tensile elongation becomes less than 80% when left for 24 hours under heating.-Moist heat resistance: Tubes left at 23 ° C, 50% for a certain period of time in an atmosphere of 80 ° C and 95% RH. After being left in a RH constant temperature and humidity chamber for 24 hours, the tensile strength and tensile elongation of the tube were measured and evaluated according to the following criteria. ；: The period during which the retention of the tensile strength and the tensile elongation is 80% or more is 3 weeks or more. Δ: The period when the retention of the tensile strength and the tensile elongation is 80% or more is 2 weeks or more. The retention rate of either tensile strength or tensile elongation becomes 80% or less after leaving for 2 weeks.-Dimensional stability: Tubes left in a hot-air dryer at 85 ° C for 24 hours at 23 ° C, 50% RH After standing for 24 hours in a thermo-hygrostat, the change rate (%) of the length of the tube was measured. Here, T _m , T _ic and ΔH _m are DSCs manufactured by PerkinElmer.
It is a value measured by.

[0014]

[Table 1]

Note: PBT; polybutylene terephthalate resin (in addition, intrinsic viscosity
In the case of 1.0 or more, solid-state polymerization is performed.) Intrinsic viscosity; value measured in orthochlorophenol at 25 ° C; CEG content; carboxy group content at the molecular chain end of polybutylene terephthalate resin Content; PBT resin 100 The content is based on parts by weight, and is indicated by parts by weight. Phosphorus compound; tetrakis (2,4-di-t-butylphenyl) -4,4-biphenylene phosphite hindered phenol compound; pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxy) Phenyl) propionate] Thioether compound; Tetrakis [methylene-3 (dodecylthio) propionate] methane Crystal nucleating agent; Boron nitride Example 4 Tube forming in the same manner as in Example 1 except that the cooling temperature (water bath temperature) was 60 ° C. And evaluated similarly. Table 2 shows the results.

[0016]

[Table 2]

[0017]

The polybutylene terephthalate resin composition of the present invention is excellent not only in mechanical strength, rigidity and oil resistance but also in long-term durability such as heat resistance, wet heat resistance and dimensional stability. Most suitable for coated tube of optical fiber. Furthermore, by using this polybutylene terephthalate resin composition, an optical fiber coated tube having excellent functions can be obtained for a long period of time even in a high-temperature atmosphere or a high-temperature, high-humidity atmosphere.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-330385 (JP, A) JP-A-6-206991 (JP, A) JP-A-5-57763 (JP, A) JP-A-2- 258864 (JP, A) JP-A-2-212339 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/44

Claims (9)

(57) [Claims] 1. An optical fiber coated tube having a heat of crystal fusion ΔH _m of 40 J / g or more, obtained by extrusion molding a polybutylene terephthalate resin or a composition thereof having an intrinsic viscosity of 1.0 or more. Wherein the following formula (1) extruding a satisfactory polybutylene terephthalate resin or a composition comprising billing
Item 2. An optical fiber-coated tube according to Item 1 . _Tm − _Tic ≦ 30 (1) _Tm : heating rate by differential thermal analysis based on JIS K7121
Melting point of resin measured at 10 ° C / min T _ic : Rate of temperature decrease by differential thermal analysis based on JIS K7121
Extrapolated crystallization onset temperature of resin measured at 10 ° C / min 3. The optical fiber-coated tube according to claim 1, wherein the polybutylene terephthalate resin composition comprises 0.005 to 2.0 parts by weight of a nucleating agent per 100 parts by weight of the polybutylene terephthalate resin. 4. The optical fiber coated tube according to claim 2, wherein the nucleating agent is boron nitride and / or talc. 5. The polybutylene terephthalate resin has a carboxyl group content at a molecular terminal of 45 meq / kg or less.
The optical fiber-coated tube according to any one of claims 4 to 4. 6. The optical fiber coating according to claim 1, wherein the polybutylene terephthalate resin composition contains 0.01 to 1.0 parts by weight of a phosphorus compound with respect to 100 parts by weight of the polybutylene terephthalate resin. tube. 7. A polybutylene terephthalate resin composition comprising 0.01 to 1.0 parts by weight of a phosphorus compound and 0.01 to 2.0 parts by weight of a hindered phenol compound or a thioether compound per 100 parts by weight of a polybutylene terephthalate resin. The optical fiber coated tube according to claim 1. 8. The optical fiber-coated tube according to claim 6, wherein the phosphorus-based compound is a phosphite-based and / or phosphite-based organic compound. 9. The maximum cross section of an optical fiber coated tube.
The optical fiber coated tube according to any one of claims 1 to 8, wherein a ratio of the value to the minimum value is less than 1.05 .