JP4093939B2 - Low shrinkage polyester fiber - Google Patents

Description

  The present invention relates to a low-shrinkage polyester fiber suitable for use in industrial materials, particularly for squeezing and fixing to protect a main core portion of a cable such as an optical cable.

  Conventionally, aramid fibers and glass fibers have been used as press-wound yarns for bundling several cores made of optical fibers and several protective layers (clads) that cover and protect them in optical cables using industrial materials, especially optical fibers in the core. It has been.

  However, these are all expensive and cannot cope with the low price accompanying the rapid expansion of the optical cable market in recent years.

  In order to solve this problem, an inexpensive polyester fiber is used as a low-priced presser winding thread. The characteristic required for the presser winding is low heat shrinkability.

  On the other hand, as described in Patent Document 1, for example, a polyester low heat shrink yarn is obtained by drawing a polyester partially oriented yarn (POY yarn) at a certain draw ratio and heat-treating it at a high temperature of 190 to 240 ° C. to limit shrinkage. It is known to be obtained. However, in this case, it is related to low-elongation yarns such as sewing threads, and problems such as frequent yarn breakage and fluffing occur in the twisting process and the process of joining the optical cable. was there. Moreover, although the dry heat shrinkage rate at 150 ° C. is described, any of them has a large shrinkage rate and cannot be employed for an optical cable.

  And as a thing with a still lower dry heat shrinkage rate, in Patent Document 2, the strength is 7.9 to 10.2 cN / dtex, the elongation at break is 18 to 30%, and the dry heat shrinkage rate at the time of 1 minute treatment at 177 ° C. A low shrinkage polyester fiber having a -1 to 3% ratio has been proposed.

  However, this uses polyester having a very high intrinsic viscosity of 0.92, which is expensive because a special apparatus is required for spinning. In addition, it is a fiber suitable for industrial materials such as tire cords, and has high strength but low elongation and poor handleability. Further, in the minus region where the shrinkage rate is less than 0%, the fiber stretches during the heat treatment, so that it is unstable to wind and fix the inner layer portion like a press winding of an optical cable.

  Patent Document 3 proposes a polyester fiber useful for high-toughness tarpaulins and the like, but this is also expensive because it uses a solid-phase polymerized polyester having a high intrinsic viscosity. Moreover, the dry heat shrinkage was also high.

  On the other hand, as an inexpensive low-shrinkage polyester fiber, as described in Patent Document 4, unstretched POY yarn is drawn at a low draw ratio and heat treated to produce a low-shrinkage or self-stretched yarn. Fiber is known.

  However, in this case, since the strength is low and the elongation is high, even if it is used as a clothing material, it is unstable and cannot be used as an industrial material.

  As described above, low-shrinkage polyester fibers are largely divided into two types, one is high-strength low-stretch fibers using high-viscosity resins such as tire cords, and low-strength high-stretch for inexpensive clothing. There was no low-shrinkage polyester fiber that can be used for both clothing and industrial materials.

Japanese Patent Publication No.58-4089 JP 52-99317 A JP 2000-27029 A JP 2000-328381 A

  The present inventors have solved the problems of the prior art, are inexpensive and excellent in handleability, and stably protect the core portion as a presser winding thread in the cable manufacturing process and in the product. An object of the present invention is to provide a low-shrinkage polyester fiber suitable for a press-wound yarn of an optical cable.

As a result of intensive studies to solve the above problems, the present inventors have reached the present invention.
That is, the gist of the present invention is a polyester fiber having ethylene terephthalate as a main repeating unit, which satisfies the following (1) to (4), and is characterized by low shrinkage polyester fiber for optical fibers.
(1) Intrinsic viscosity 0.55 to 0.70
(2) Elongation at break 28-38%
(3) Dry heat shrinkage at 130 ° C. 0 to 0.5%
(4) Shrinkage start temperature in thermal stress curve 180 ° C

  The low-shrinkage polyester fiber of the present invention has the physical properties within the scope of the present invention, so that it can maintain stable operability without yarn breakage even if it is subjected to combined yarn or twisted, and the physical properties are reduced even if heat treatment is performed. There is no heat shrinkage. Further, since the viscosity is not high, it can be produced at low cost by a spinning machine for clothing. For this reason, even if it uses for holding | wound winding yarns, such as an optical cable, the performance of the main core part is not impaired by heat shrink.

  The present invention is described in detail below. In order to obtain the low-shrinkage polyester fiber of the present invention at low cost, the present invention uses a polyester mainly composed of ethylene terephthalate.

  If necessary, use a copolymer of acid components such as sodium 5-sulfoisophthalate, adipic acid, sebacic acid, and isophthalic acid, and diol components such as diethylene glycol, triethylene glycol, polyethylene glycol, and cyclohexanedimethanol. By doing so, the functionality of the fiber can be added.

  Moreover, the intrinsic viscosity of this polyester needs to be 0.55-0.70, Preferably it is 0.60-0.65. Within this range, sufficient breaking strength can be obtained even as an optical cable holding winding, and since it is a general-purpose resin, it can be provided at low cost. However, if it is less than 0.55, a fiber having a high breaking strength cannot be obtained, and it is not suitable for industrial materials. If it exceeds 0.70, a special spinning device for industrial materials is required, so the equipment is expensive. It becomes.

  It is important that the elongation at break of the polyester fiber of the present invention is 28 to 38%, preferably 30 to 35%. If it is within this range, the polyester fiber can be twisted to the required fineness, and stable operability can be obtained when it is twisted. Also, since it has an appropriate softness, it is suitable for winding the core portion of the optical cable. ing. If it is less than 28%, there is a problem that yarn breakage frequently occurs during twisting and joining, and if it exceeds 38%, the form stability is insufficient.

  When manufacturing an optical cable, a film such as polyethylene or polypropylene is laminated around the core portion and the protective portion thereof, and a presser wound yarn using the polyester fiber of the present invention is wound in order to fix the film. When this lamination is performed, a dry heat treatment at 120 to 130 ° C. is performed. Therefore, if the presser winding contracts at this temperature, the optical fiber in the core portion is damaged. Therefore, it is important that the dry heat shrinkage at 130 ° C. of the polyester fiber of the present invention is 0 to 0.5%, preferably 0 to 0.3%. Within this range, the optical fiber group can be stably fixed, and the performance of the optical fiber is not impaired. If the thermal expansion is less than 0%, that is, the thermal contraction rate is negative, the optical fiber group cannot be fixed. On the other hand, if it exceeds 0.5%, the optical fiber group is pressed by the contraction, and the performance is impaired.

  Moreover, it is important that the shrinkage start temperature in the thermal stress curve of the polyester fiber of the present invention is 180 ° C. or higher, and preferably 200 ° C. or higher. The shrinkage start temperature is a temperature at the intersection of two tangents of the shrinkage stress curve, as will be described with reference to FIG. This means that the contraction force due to heat does not occur up to the contraction start temperature, and within this range, the contraction force does not impair the performance of the optical fiber.

  A specific method for obtaining the low-shrinkage polyester fiber of the present invention is shown below. The polyester fiber of the present invention employs a method in which a polyester having an intrinsic viscosity of 0.55 to 0.70 is melt-spun, cooled by a known method, and wound up. First, a method in which a drawn yarn is wound up by a direct spinning drawing method (SPD method) and the drawn yarn is subjected to relaxation heat treatment by a multistage drawing machine is preferable. Further, when winding the drawn yarn by the SPD method, each single yarn is individually divided and applied with an oil agent, and if several single yarns are converged and wound without entanglement, the fineness between the single yarns It is further preferable for reducing spots and physical properties. In the prior art, there has been proposed a method of winding by drawing and heat-treating at once by the SPD method, but in this case, strain due to tension during the winding process remains in the fiber. I can't get it.

  Next, the drawn yarn is put into a 3 to 4 multi-stage drawing machine. In this case, after drawing to give tension, heat treatment is performed at a temperature below the crystal melting point of the polyester, and the non-heated roller A method in which the film is relaxed between and wound with a winder is preferable. The relaxation rate during the relaxation heat treatment may be selected as appropriate so that the physical property value of the present invention is obtained, but the relaxation rate is set so as not to be taken by the heat treatment roller.

  The fineness of the polyester fiber of the present invention is not particularly limited, but is suitable for an optical fiber, and is preferably 167 to 400 dtex for inexpensive production using the SPD method and the drawing method described above. .

An example of a process for producing a press-wound yarn for an optical cable using the low-shrinkage polyester fiber of the present invention is shown below.
First, several low shrinkable polyester fibers of the present invention are combined and twisted with a twister. At this time, fluid entanglement is performed with a fluid such as air in order to improve convergence. After that, a dyeing process is performed to obtain a presser winding thread of the optical cable.

  The press-wound yarn obtained in this way is used to wind and bundle several bundled optical fibers around the outer side of the clad layer that protects the outer side as a core.

  Hereinafter, the present invention will be described in more detail with reference to examples. The characteristic values in the following examples are measured by the following methods.

(1) Intrinsic viscosity The intrinsic viscosity [η] was measured by an ordinary method using an automatic viscometer in a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio) at 20 ° C.

(2) Breaking strength / breaking elongation Using an autograph tensile tester (manufactured by Shimadzu Corporation), a tensile test was carried out until breakage with an initial length of 200 mm, a strain rate of 100% / min, and an initial load of 1/30 cN / dtex, The breaking strength and breaking elongation were determined.

(3) Dry heat shrinkage at 130 ° C. A load of 1/30 cN / dtex was applied to the polyester fiber of the present invention, and the length at this time was defined as L0. Next, heat treatment was performed in an oven at 130 ° C. for 1 hour under no load, cooled for 1 hour at room temperature, fiber length L after heat treatment was measured under a load of 1/30 cN / dtex, and calculated by the following formula: did.
130 ° C. dry heat shrinkage (%) = (L0−L) / L0 × 100

(4) Thermal stress curve shrinkage start temperature (Ts)
An initial load of 1/600 cN / dtex is applied to 100 mm of the polyester fiber of the present invention, and the temperature is increased from room temperature to 250 ° C. at a temperature increase rate of 120 ° C./min with a thermal stress tester KE-2S (manufactured by Kanebo Engineering). A curve of shrinkage stress with respect to temperature at the time of drawing was drawn, and the temperature at the intersection of two tangents shown in FIG. 1 was evaluated as Ts (° C.).

(5) Boiling water shrinkage The initial length L1 is obtained by suspending a 200 mg load on the polyester fiber 500 mm of the present invention, and immersed in boiling water for 15 minutes with the load suspended, and the length L2 after air drying is measured. The shrinkage was calculated by the following formula.
Boiling water shrinkage rate (%) = (L1-L2) / L1 × 100

(6) Yarn breakage at the time of twisting Nine polyester fibers of the present invention are twisted together and subjected to air entanglement treatment. Evaluation was made with a rate of 70-90% as Δ and a value less than 70% as x.

(7) Presser winding performance The expert evaluated the presser wound yarn using the polyester fiber of the present invention as ◯ when it can be used for an optical cable, and × when it cannot be used.

Example 1
A polyethylene terephthalate polymer having an intrinsic viscosity of 0.630 and containing 0.4% by weight of titanium dioxide (TiO ₂ ) is melted at 296 ° C., extruded from a 12-hole die, cooled, and each single yarn is individually treated with oil. It was made to give, and it extended | stretched between the heating goded roller and the heat set goded roller, 12 pieces were converged, and the drawn yarn of 267dtex / 12 filament was obtained by SPD method. Thereafter, the drawn yarn is fed into a first roller (non-heated), a second roller (80 ° C.), a third roller (100 ° C.), a fourth roller (220 ° C.), a fifth roller (non-heated), and a winder. The stretching ratio between the first roller and the second roller is 1.005 times, the stretching ratio between the second roller and the third roller is 1.000 times, and the stretching ratio between the third roller and the fourth roller is 1. A low shrinkage polyester fiber having physical properties shown in Table 1 of 280 dtex / 12 filaments, subjected to relaxation heat treatment at 000 times, 0.936 times between the fourth roller and the fifth roller at a total draw ratio of 0.941 times Got. Then, nine polyester fibers were converged with a twister to produce a presser wound yarn. As shown in Table 1, this presser wound yarn has a low dry heat shrinkage rate and is thermally stable, and can be used as an optical cable.

(Examples 2 and 3)
A low-shrinkage polyester fiber of 280 dtex / 12 filaments was obtained in the same manner as in Example 1 except that the temperature of the fourth roller was 210 ° C. in Example 2 and 225 ° C. in Example 3. As shown in Table 1, this presser wound yarn could be used as an optical cable.

(Comparative Examples 1 and 2)
Comparative Example 1 is the same as Example 1 except that the stretching ratio of the third roller and the fourth roller is 1.10 times, and Comparative Example 2 is that the stretching ratio of the fourth roller and the fifth roller is 0.925 times. Stretched. In Comparative Example 1, the elongation at break was lower than that of the present invention. In Comparative Example 2, the elongation at break exceeded the range of the present invention, and the strength was low and the shape stability as a presser wound yarn was applied.

(Comparative Examples 3 and 4)
The polyester chips having the intrinsic viscosity shown in Table 1 were melt-spun at 285 ° C. in Comparative Example 3 and 310 ° C. in Comparative Example 4, and the SPD drawn yarn was wound and stretched in the same manner as in Example 1. Comparative Example 3 is low in intrinsic viscosity and low in strength, so it is subjected to the form stability of the presser wound yarn. Comparative Example 4 is expensive because it is a solid-phase polymerization chip, and the spinning machine used is special for industrial materials. Expensive and expensive. Moreover, since the strength was too high, there was a lot of fluffing at the time of twisting, and the presser wound yarn was too hard to wind.

(Comparative Example 5)
Spinning and stretching were performed in the same manner as in Example 1 except that the temperature of the fourth roller was 195 ° C. The dry heat shrinkage at 130 ° C. exceeded the range of the present invention and was unsuitable for presser winding yarns.

(Comparative Example 6)
An undrawn yarn (POY yarn) was wound at 3200 m / min using a polyester chip having an intrinsic viscosity shown in Table 1. With the same stretching machine as in Example 1, the stretching ratio of the third roller and the fourth roller is 1.3 times, the temperature of the fourth roller is 150 ° C., and the stretching ratio of the fourth roller and the fifth roller The self-stretched yarn was wound up at 0.950. Both the boiling water shrinkage and the 130 ° C. dry heat shrinkage were negative, that is, they were elongated by heat treatment. The fibers had low strength and lacked shape stability.

(Comparative Example 7)
Spinning and stretching were performed in the same manner as in Example 1 except that the temperature of the fourth roller was 185 ° C. and the stretching ratio of the fourth roller and the fifth roller was 0.945. Since the shrinkage start temperature is outside the range of the present invention and the shrinkage force of the presser wound yarn is expressed at a low temperature, the core portion is pressed by heat treatment during the production of the optical cable.

It is an example of the thermal stress curve of the low shrinkable polyester fiber of this invention. The temperature at the intersection of two tangents in the curve was defined as the shrinkage start temperature (Ts).

Claims (1)

A low-shrinkage polyester fiber for an optical cable , which is a polyester fiber having ethylene terephthalate as a main repeating unit and satisfying the following (1) to (4).
(1) Intrinsic viscosity 0.55 to 0.70
(2) Elongation at break 28-38%
(3) Dry heat shrinkage at 130 ° C. 0 to 0.5%
(4) Shrinkage start temperature in thermal stress curve 180 ° C

Images