KR20040060141A - Resin composition for optical fiber loose tube - Google Patents

Abstract

PURPOSE: Provided is a resin composition for a loose tube of optical fiber, which has excellent extrudability and structural stability and thus increases communication speed through the optical fiber. CONSTITUTION: The resin composition for a loose tube of optical fiber comprises polybutylene terephthalate and polycarbonate. The polybutylene terephthalate has an intrinsic viscosity of 1.20-1.35 dl/g and the polycarbonate has a viscosity average molecular weight of 17,000-30,000. Particularly, the resin composition comprises 49-76 wt% of polybutylene terephthalate and 24-51 wt% of polycarbonate. Additionally, the resin composition optionally further comprises 0.01-0.05 parts by weight of a surface lubricant based on 100 parts by weight of the resin composition.

Description

Resin composition for optical fiber loose tube {RESIN COMPOSITION FOR OPTICAL FIBER LOOSE TUBE}

The present invention relates to a resin composition for loose tube included in the configuration of an optical cable.

An optical cable is made of bundles of optical fibers, specifically a bundle of fiber-shaped waveguides for the purpose of light transmission. The structure has a double-cylindrical shape in which a core called a core is wrapped around a cladding, and the outer surface is coated with one or two synthetic resin coats to protect it from impact.

The synthetic resin sheath for protecting the optical cable from external impact is called a loose tube, and the loose tube is formed through (1) an extruder. (2) Because optical cables generally require about 20 years of durability, the materials used for loose tubes must also have excellent durability. (3) Because of the purpose of communication, the optical fiber communication rate must not be lowered. .

Currently, polymer materials used for loose tubes include polybutylene terephthalate (hereinafter referred to as "PBT"), nylon, polypropylene, and the like. Among them, PBT is the most used polymer material.

The polymer material is known to satisfy both moldability, durability, and the like, which are required for the loose tube, but there is a problem about communication rate. In order to exhibit the excellent communication rate, when forming a loose tube, it must first have characteristics such as stable discharge amount, shape stability of the tube, and shrinkage rate regardless of meltability and time in the extruder.

(1) meltability

In case of PBT, PBT for loose tube uses high viscosity products of 1.25 ㎗ / g or higher manufactured through melt polymerization and solid state polymerization process, whereas intrinsic viscosity of commonly used products is 0.8 ~ 1.1 ㎗ / g. If the high degree of crystallinity is not good meltability is not completely melted in the extruder may appear as a projection on the tube surface. Since the protrusions lower the communication rate, the PBT should exhibit high viscosity and excellent meltability.

(2) discharge

Regardless of the above materials, if the discharge amount is not constant with time, the pressure of the extruder head part is not kept constant, so the diameter of the tube may fluctuate with time, which may hinder the communication rate. to be. In order to have a constant discharge amount, the friction force between the raw materials, or between the raw materials and the screw should be lowered to facilitate the transfer of the raw materials in the extruder.

(3) tube shape stability

Extrusion of loose tube is done in the horizontal direction rather than vertical direction, so when the solidification rate, the crystallization rate is low, or the melt tension is small, the eccentricity of the cross section of the tube is formed into an elliptical shape instead of a circular shape (optical fiber deviates from the center of the tube). Since this may interfere with the communication rate, a material having a high solidification rate or high melt tension should be selected.

(4) shrinkage

In addition, all polymers have a property of shrinkage during solidification after melting, so that the material used in the manufacture of loose tube also shrinks during solidification, but if the shrinkage is excessive, the optical fiber in the loose tube becomes bent, rather than straight, and thus communicates. Low shrinkage properties are also important, as they can affect.

In general, PBT is a crystalline polymer, and the shrinkage rate of injection molding under normal conditions shows a shrinkage of 1.5 to 2.5% .In the manufacture of optical fiber loosetubes, the tube thickness is thin, quenched, Because the tension is relaxed again, the shrinkage is about 0.05%, which is smaller than this. After measuring the long-term shrinkage after manufacture of loose tube, the shrinkage is about 0.1%. If the shrinkage is 0.15% or more, the communication rate of the optical fiber is significantly reduced. Therefore, when manufacturing the tube in consideration of post-shrinkage, the shrinkage rate is usually 0.05% or less. In order to reduce the shrinkage rate, there is a method of increasing the molecular weight of the material, a method of forming a constant tension in the tube after the tube is manufactured, or a method of storing at a low temperature, but in a method of significantly increasing the molecular weight, There is a problem, such as how to give a constant tension to the tube or low temperature storage has a problem that the effect is insignificant.

U.S. Patent Nos. 4,917,845 and 5,536,810 disclose methods for obtaining high molecular weight PBT resins by rapid solid phase polymerization or for obtaining suitable solid phase polymerization conditions. In addition, US Pat. No. 5,334,343 discloses a method of improving the crystallization rate of PBT resin to be used in the extrusion process, US Pat. Nos. 5,229,432 and 4,071,503 improve the melt tension of PBT resin to be used for blow molding The manufacturing method of is disclosed. However, the above patent only refers to a method of preparing a high molecular weight PBT, a method of increasing the crystallization rate, a method of increasing the melt tension using a branching agent or a chain extender.

On the other hand, polycarbonate (hereinafter referred to as "PC") is an amorphous polymer, which has a low surface hardness but has excellent mechanical strength, particularly melt tension and impact strength, so that it is used in bottled water bottles, automobile headlamps, bumpers, and soundproof walls. Mold shrinkage is 0.6 ~ 0.8%, which is significantly lower than PBT and post shrinkage does not progress.

Thus, the present inventors prepared a new resin composition for optical fiber loose tube by mixing polycarbonate with PBT resin in order to improve the problem of the conventional resin composition for optical fiber loose tube, the optical fiber loose tube by the composition is extrudable and melted The present invention was completed by finding excellent tension and low molding shrinkage.

An object of the present invention is to provide a resin composition for a novel optical fiber loose tube.

Specifically, it is an object of the present invention to provide a resin composition for an optical fiber loose tube that is excellent in extrudability and structural stability and can maintain a communication rate.

In order to achieve the above object, the present invention provides a resin composition for an optical fiber loose tube containing polybutylene terephthalate and polycarbonate.

Hereinafter, the present invention will be described in detail.

The present invention provides a resin composition for an optical fiber loose tube containing polybutylene terephthalate and polycarbonate.

Polybutylene terephthalate (hereinafter referred to as "PBT") is a crystalline polymer, and the main repeating unit means butylene terephthalate, which means that it is produced through melt polymerization and solid state polymerization process. In the present invention, the intrinsic viscosity is 1.20 ~ 1.35 dl / g, but if the intrinsic viscosity of the PBT exceeds the above range, not only the production of PBT itself is difficult, but also the fluidity is significantly lowered, the processing temperature is increased and the end groups are increased. It appears that if less than the above range because the melt tension is low, eccentricity may occur and the shrinkage rate is also high.

The content of the PBT is 49 to 76% by weight based on the resin composition for optical fiber loose tube of the present invention. If the range is exceeded, problems such as shrinkage and eccentricity of the PBT have appeared, and if the range is less than the above range, the solidification rate is too fast when the tube is processed due to the influence of polycarbonate, thus making it difficult to produce a tube having a desired thickness.

The present invention mixes polycarbonate in order to increase the melt tension and to reduce the shrinkage of the product in the PBT produced through melt polymerization and solid state polymerization process.

Polycarbonate (hereinafter referred to as "PC") is an amorphous polymer having a low surface hardness but excellent mechanical strength, particularly melt tension and impact strength, and is significantly lower than that of the PBT at about 0.6 to 0.8% of mold shrinkage under general conditions. Shrinkage also has a feature that does not proceed, in the present invention, it is preferable to use a viscosity average molecular weight of 17,000 to 30,000.

The content of the PC is 24 to 51% by weight based on the resin composition for optical fiber loose tube of the present invention. If the above range is exceeded, the rate of solidification during tube processing is too high, making it difficult to produce a tube having a target thickness. If the diameter is less than the above range, the effect of adding a PC is not large.

In order to further provide a desired characteristic, the resin material used for this invention etc. can add and use the well-known substance generally added to a thermoplastic resin etc. in addition. For example, it is possible to mix stabilizers such as antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, lubricants, colorants such as dyes and pigments, lubricants and plasticizers.

Specifically, the internal lubricant is added to improve meltability and fluidity, and paraffin wax, pentaerythritol ester-based wax, or paraffin-based high wax is preferable. The content of the internal lubricant is 0.03 to 0.05% by weight with respect to the resin composition for the optical fiber loose tube of the present invention, when exceeding the above range is a cause of coming out of the surface of the resin when the high temperature drying more than 120 ℃ to contaminate the inside of the dryer, If less than the above range, the effect of the addition is insignificant.

Antioxidants of PBT include octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Octadecyl-3- ( 3,5-di-t-butyl-4-hydroxylphenyl) propionate) is used, and in view of color and effect, an antioxidant of a thiol ester type is preferable. The content of the antioxidant of the PBT is preferably 0.05 to 0.2% by weight based on the resin composition for optical fiber loose tube of the present invention.

PC's antioxidants include phosphite-based tris (2,4-di-t-butylophenyl) phosphate and cyclic neopentanetetraribis (octadecyl Phosphate) (Cyclic neopentantetraly bis (octadecyl phosphate), hereinafter referred to as "CNBOP") or bis (2,4-di-t-butylphenyl) penterythritol diphosphite (Bis (2,4-di-t-butylphenyl) penterythritol diphosphite), preferably CNBOP. The content of the PC antioxidant is preferably 0.05 to 0.2% by weight.

In addition, the resin composition for an optical fiber loose tube of the present invention further includes a surface lubricant.

Loose tube has to form a certain structure in order to increase the communication rate. To this end, a certain amount of resin must be added to the extruder head to maintain a constant pressure. In addition, the frictional force of the surface must be low for constant transfer of the resin, for this purpose is added to the surface lubricant.

The surface lubricants include calcium stearate; Or an internal lubricant such as paraffin wax, pentaerythritol ester system wax, or paraffin high wax, and preferably calcium stearate.

In the present invention, the amount of the surface lubricant is 0.01 to 0.05 parts by weight, and preferably 0.02 to 0.04 parts by weight, based on 100 parts by weight of the resin composition for the optical fiber loose tube. In the case of exceeding the above range, when the lubricant is eluted around the nozzle during extrusion and the amount is increased, the lubricant sticks to the surface of the tube to form protrusions and lowers the communication rate. Not desirable.]

The resin composition for an optical fiber loose tube made of the PBT and PC is prepared by injecting each composition into an extruder and then extruding to prepare a mixture, and by adding a surface lubricant to the mixture and then heating and surface coating the obtained optical fiber loose tube. An optical fiber loose tube can be manufactured by extruding the resin composition for a film.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the examples.

Example 1 Preparation of Resin Composition for Optical Fiber Loose Tube of the Present Invention

75.% by weight of PBT having an intrinsic viscosity of 1.30 dl / g and PC having a viscosity average molecular weight of 22,000; Other mixtures were prepared by carrying out the temperature conditions as shown in Table 1 below in the extruder having a twin screw, 0.1 wt% of the Siol ester antioxidant and 0.1 wt% of CNBOP and 0.05 wt% of paraffin wax. 0.03 parts by weight of calcium stearate was added to the prepared mixture as a surface lubricant.

Feeding part Melting part Nozzle part Extrusion speed Extrusion Temperature (℃) 230 260-270 265 10 kg / hr

Example 2 Preparation of Resin Composition for Optical Fiber Loose Tube of the Present Invention 2

50 wt% of PBT having an intrinsic viscosity of 1.30 dl / g and 49.75 wt% of PC having a viscosity average molecular weight of 22,000 were prepared in the same manner as in Example 1 above.

Example 3 Preparation of Resin Composition for Optical Fiber Loose Tube of the Present Invention 3

It prepared in the same manner as in Example 1 except adding 24.75% by weight of a PC having a viscosity average molecular weight of 17,000.

Example 4 Preparation of Resin Composition for Optical Fiber Loose Tube of the Present Invention 4

Except for adding 49.75% by weight of PC having a viscosity average molecular weight of 17,000 was prepared in the same manner as in Example 2.

Comparative Example 1 Preparation of Resin Composition for Optical Fiber Loose Tube 1

99.9% by weight of PBT having an intrinsic viscosity of 1.30 dl / g and 0.1% by weight of a thiol ester antioxidant were prepared, followed by the same method as in Example 1.

Comparative Example 2 Preparation of Resin Composition for Optical Fiber Loose Tube 2

90 wt% of PBT having an intrinsic viscosity of 1.30 dl / g and 9.75 wt% of PC having a viscosity average molecular weight of 17,000 were prepared in the same manner as in Example 1.

Comparative Example 3 Preparation of Resin Composition for Optical Fiber Loose Tube 3

It was prepared in the same manner as in Example 1 except that calcium stearate as a surface lubricant was not added.

Comparative Example 4 Preparation of Resin Composition for Optical Fiber Loose Tube 4

It was prepared in the same manner as in Example 1, except that 25 wt% of PBT having an intrinsic viscosity of 1.30 dl / g and 74.75 wt% of PC having a viscosity average molecular weight of 22,000 were added thereto.

Comparative Example 5 Preparation of Resin Composition for an Optical Fiber Loose Tube 5

99.85% by weight of PC having a viscosity average molecular weight of 22,000, 0.1% by weight of CNBOP and 0.05% by weight of paraffin wax were prepared in the same manner as in Example 1.

Comparative Example 6 Preparation of Resin Composition for an Optical Fiber Loose Tube 6

It prepared in the same manner as in Comparative Example 5 except that 99.85 wt% of PC having a viscosity average molecular weight of 17,000 was added.

Comparative Example 7 Preparation of Resin Composition for an Optical Fiber Loose Tube 7

Except that a PBT having an intrinsic viscosity of 1.10 dl / g was prepared in the same manner as in Example 1.

Comparative Example 8 Preparation of Resin Composition for Optical Fiber Loose Tube 8

Except that a PC having a viscosity average molecular weight of 30,000 was prepared in the same manner as in Example 1.

The compositions and contents of Examples 1 to 4 and Comparative Examples 1 to 8 are shown in Table 2 below.

Experimental Example

The content of PC in PBT was 0 to 100% by weight, and the physical properties thereof were confirmed through the measurement method as follows.

Melt Flow Index (MI)

The melt index was measured at 260 ° C. and 2.16 kg by ASTM D-1238. The results are shown in Table 3 below.

The preferred melt flow index for loose tube extrusion is 3 to 15 g / 10 min, more preferably 5 to 12 g / 10 min. If the melt flow index is 5 g / 10min or less, tube extrusion is possible at 270 ℃ or more, and PBT is pyrolyzed to increase the end group.If it exceeds 12 g / 10min, eccentricity occurs during extrusion and shrinkage is also increased. Will increase.

2. Melt Tension

Melt tension was measured using Extensional Rheomete (Goffert REOTENS 71.97). The capillary die was measured to have a diameter of 2 mm and a length of 32 mm to pull out at a speed of 250 mm / sec to exit at a speed of 46.9 mm / sec. At this time, the melting temperature inside the die was 260 ° C, and the distance between the exit of the die and the winding roller was 85 mm. The results are shown in Table 3 below.

3. Mechanical Properties

Tensile and flexural properties were measured by ASTM D 638, 790. The results are shown in Table 3 below.

4. Impact strength

Measured by ASTM D 256, but measured at room temperature (23 ℃). The results are shown in Table 3 below.

5. Loose tube shrinkage

The loose tube was cut by 7 m to separate the optical fiber and the tube in the tube, and then the length of the optical fiber was measured. The method uses the property that the polymer resin melts and then cools and shrinks when the tube is extruded, but the optical fiber does not shrink. The results are shown in Table 4 below.

6. Eccentricity

The cross section of the manufactured tube was cut and the tube outer diameter was measured in four directions at right angles, and a large value was selected from the value obtained by subtracting the small outer diameter from the large outer diameter. The results are shown in Table 4 below.

7. Communication rate

1 m of the prepared tube was cut and irradiated with a certain intensity of light on one side, and the loss rate was measured by measuring the intensity of light on the other side. The results are shown in Table 4 below.

As shown in Table 3 above, when the PC is added to the PBT, the mechanical strength and the melt tension are improved at all contents, but such physical properties do not coincide with improving the properties of the loose tube.

Table 4 is a result of the tube shape, shrinkage, communication rate after the actual loose tube production, as shown in the table can be seen to exhibit excellent characteristics in the content of a certain PC. In this case, the loose tube had an outer diameter of 2.8 mm and an inner diameter of 2.4 mm.

Indeed, as shown in Table 4, which is an important result when manufacturing loose tubes, loose tube characteristics of 49 to 76 wt% PBT and 24 to 51 wt% PC were better than PBT alone or PC alone. When the PBT alone or the PC content is reduced, the eccentricity is large due to the low melt tension of the PBT, and the shrinkage rate is also high, which causes the communication rate of the optical fiber to be hindered. On the other hand, when the PC alone or the content of PBT is low, there is a structural problem of the tube due to the rapid solidification of the PC, which inhibits the communication rate. In addition, even if the communication ratio is good, as in Comparative Example 3, when the lubricant is not coated on the surface, the raw material is not transferred normally from the feeding part of the extruder due to the friction between the raw material and the raw material and the raw material and the screw during tube manufacturing. Therefore, since the pressure of the extruder head portion is difficult to be kept constant, the thickness of the tube changes with time, which increases the eccentricity and inhibits the communication rate. In addition, as in Comparative Example 7, lowering the intrinsic viscosity of PBT increases the eccentricity and shrinkage rate during tube processing, thereby decreasing the communication rate.When using a PC having a high viscosity-average molecular weight as in Comparative Example 8, the fluidity is lowered, so that the processing temperature is higher than 280 ° C. It is not preferable to increase the terminal group due to the thermal decomposition of PBT, thereby inhibiting the durability of the optical cable.

As described above, the present invention, in the construction of the raw material for manufacturing optical fiber loose tube, by mixing the PC resin with high crystallization rate and high shrink tension and low shrinkage rate to PBT resin with a high crystallization rate to increase the melt tension and at the same time lower the eccentricity of the tube By reducing the mold shrinkage rate, an optical fiber loose tube can be produced which increases the optical fiber communication rate.

Claims (6)

Resin composition for an optical fiber loose tube containing polybutylene terephthalate and polycarbonate. The resin composition for an optical fiber loose tube according to claim 1, wherein the polybutylene terephthalate has an intrinsic viscosity of 1.20 to 1.35 dl / g, and the polycarbonate has a viscosity average molecular weight of 17,000 to 30,000. The resin composition for an optical fiber loose tube according to claim 1, wherein the polybutylene terephthalate is 49 to 76 wt% and the polycarbonate is 24 to 51 wt%. The resin composition for an optical fiber loose tube according to claim 1, wherein the resin composition for an optical fiber loose tube further comprises 0.01 to 0.05 part by weight of a surface lubricant based on 100 parts by weight of the resin composition. The resin composition according to claim 4, wherein the surface lubricant is selected from the group consisting of pentaerythritol ester wax, paraffin wax and calcium stearate. An optical fiber loose tube obtained by extruding the resin composition for optical fiber loose tube of claim 1.