JPH05222615A - Sheath-core type polyester conjugate fiber - Google Patents

Abstract

PURPOSE:To provide the subject fiber containing polyethylene naphthalate having a specific intrinsic viscosity as the core component and polyethylene terephthalate having a specified intrinsic viscosity as the sheath component, having a high strength, a high elastic modulus and high dimensional stability and useful for reinforcing rubbers, etc. CONSTITUTION:(A) Polyethylene naphthalate having an intrinsic viscosity [eta]of >=0.6 and mainly containing ethylene-2,6-naphthalate units and (B) polyethylene terephthalate having an intrinsic viscosity [eta] of >=0.95 and mainly containing ethylene terephthalate units are used as the core component and the sheath component, respectively. The melted products of the components are fed into a conjugate spinning pack so that the ratio of the core part occupying in the conjugate fiber is 50-90wt.%, spun from a sheath-core type spinneret, quenched, solidified, oiled and subsequently drawn to obtain the objective sheath- core type polyester conjugate fiber having a Young modulus of >=100g/d at 120 deg.C, a dry heat shrinkage degree of <=2% at 150 deg.C, a high strength, a high elastic modulus and good thermal dimensional stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester composite fiber having high strength and high elastic modulus. In detail, high strength,
The present invention relates to a polyester composite fiber suitable for industrial materials having excellent mechanical properties such as high modulus and good thermal dimensional stability, and particularly when the polyester fiber of the present invention is used for reinforcing rubber, thermal deformation recovery property of rubber ( (For example, flat spot resistance, etc.) can be significantly improved.

[0002]

2. Description of the Related Art A polyester fiber, particularly a polyethylene terephthalate fiber, has a Young's modulus higher than that of polyamide fiber and is about the same as that of rayon, and has a better balance of physical properties than other fiber materials. It is widely used as a rubber reinforcing material for cords.

However, although polyethylene terephthalate fiber has a relatively high Young's modulus at room temperature,
When heated, the Young's modulus decreases and the dimensional stability becomes poor. Therefore, even a high Young's modulus polyethylene terephthalate fiber manufactured for industrial materials such as rubber reinforcement has a drawback that its Young's modulus is lowered to the same degree as that of a normal clothing polyethylene terephthalate fiber when heated.

On the other hand, the polyethylene naphthalate fiber which has been subjected to a sufficient drawing heat treatment has a Young's modulus at room temperature which is almost twice that of the polyethylene terephthalate fiber. Moreover, such polyethylene naphthalate fiber has 10
The tire cord has a high Young's modulus of 100 g / d or more even under heating conditions of 0 ° C. or higher and excellent thermal dimensional stability of 2% or less in dry heat shrinkage at 150 ° C. Attempts have been made to use it as a rubber reinforcing material.

However, polyethylene naphthalate fiber is inferior in adhesiveness to rubber as compared with polyethylene terephthalate fiber, and particularly when used as a tire cord, heat generated during running of a vehicle accumulates in the tire. At a high temperature, it has a drawback that it loses adhesiveness with rubber and causes peeling.

[0006] For the purpose of improving the above-mentioned drawbacks caused when polyethylene naphthalate fiber is used as a tire cord, the core component is composed of polyethylene naphthalate, and the sheath component is made of polyamide or polyethylene naphthalate and polyamide. In recent years, a core-sheath type composite fiber composed of a blend has been proposed (Japanese Patent Laid-Open No. 3-146).
713, JP-A-3-161514 and JP-A-3-161516).

However, since the polyester and the polyamide are originally difficult to adhere to each other, the above-mentioned composite fiber containing polyester as the core component and polyamide as the sheath component is
There is a drawback that the core portion and the sheath portion are easily separated. Further, when a blend of polyethylene naphthalate and polyamide is used as a sheath component, both polymers are not uniformly mixed in the sheath portion, and it is difficult to obtain a composite fiber having good physical properties.

In addition, a so-called flat spot phenomenon often occurs in a tire reinforced with a fiber, which greatly impairs the riding comfort of an automobile. In the flat spot phenomenon, the temperature of the tire is reinforced by the internal heat generated while the automobile is running. When the secondary transition point (hereinafter referred to as "Tg") of the tire cord is exceeded, the Young's modulus of the tire cord decreases and deformation occurs, and this deformation is not recovered even when the automobile is not running (cooling) while cooling. This is a phenomenon that occurs because of this.

By the way, polyamide fiber has a low Young's modulus and a low Tg (for example, Tg = 45 of nylon 6).
˜50 ° C., Tg of nylon 6,6 = 40 ° C.), and when used for tire cords, the above-mentioned flat spot phenomenon tends to appear prominently. Therefore, it is described in the above publication using polyamide as a sheath component. With the conventional core-sheath type composite fibers described above, it is difficult to avoid the flat spot phenomenon when used as a tire cord.

[0010]

From the above points, the present inventors have high strength and high modulus and excellent thermal dimensional stability,
Research has been continued for the purpose of obtaining polyester fibers suitable for industrial materials, particularly as a rubber reinforcing material for tire cords and the like. As a result, polyethylene naphthalate mainly composed of ethylene-2,6-naphthalate units having a specific intrinsic viscosity was used as a core component, and polyethylene terephthalate mainly composed of ethylene terephthalate units having a specific intrinsic viscosity was used as a sheath component. It has been found that when combined to form a composite fiber, the composite fiber is subjected to a specific treatment to obtain a fiber having high strength, high modulus and good thermal dimensional stability, which is suitable as an industrial material, particularly as a rubber reinforcing material. And completed the present invention.

That is, the present invention provides (a) an intrinsic viscosity [η]
Of polyethylene-2,6-naphthalate having a ratio of 0.6 or more as a core component, and polyethylene terephthalate having a limiting viscosity [η] of 0.95 or more as a main component of ethylene terephthalate Core-sheath type polyester conjugate fiber formed by using as a sheath component; (b) the proportion of the core portion in the conjugate fiber is 50 to 90% by weight; (c) Young's modulus at 120 ° C. is 100 g / d. And above; and (d) 150 ° C
The core-sheath type polyester conjugate fiber has a dry heat shrinkage ratio of 2% or less;

The core-sheath type composite fiber of the present invention has, as a core component, an intrinsic viscosity [η] of 0.6 or more and ethylene-
It is necessary to form the bicomponent fiber using polyethylene naphthalate (hereinafter referred to as "PEN") having 2,6-naphthalate units as a main component.

In the present invention, the intrinsic viscosity of PEN [η]
Dissolves PEN in a mixed solvent of p-chlorophenol and tetrachloroethane (weight mixing ratio 1: 1) at 30 ° C.
The value obtained from the viscosity measured in step 1. Intrinsic viscosity of PEN
When [η] is less than 0.6, 120 of the composite fiber of the present invention is obtained.
The Young's modulus at ° C cannot be 100 g / d or more, and a high modulus composite fiber cannot be obtained. The intrinsic viscosity [η] of PEN is particularly preferably 0.7 or more. In the present invention, it is preferable that the intrinsic viscosity [η] of PEN in the conjugate fiber after spinning is 0.55 or more.

Further, in the present invention, "ethylene-2,
"Mainly composed of 6-naphthalate units" means that PEN 95
It means that more than mol% is composed of ethylene-2,6-naphthalate units. PE used in the present invention
N has a Tg of usually 100 to 120 ° C., preferably 1
The temperature is from 10 to 120 ° C., which falls within the category of polymers having a high Tg among the thermoplastic resins. Ethylene in PEN-
When the proportion of 2,6-naphthalate units is less than 95 mol%, the Tg of the composite fiber of the present invention is lowered, and further, a high melting point composite fiber cannot be obtained, and the thermal dimensional stability and strength of the composite fiber are high. This leads to a decrease in elongation and Young's modulus.

The PEN used in the present invention is naphthalene-
Derivatives such as 2,6-dicarboxylic acid or its ester and ethylene glycol or its derivative, together with a small amount (usually less than 5 mol%) of a third component, if necessary, are added in the presence of a catalyst by a method known per se. It can be produced by condensation.

When a third component is used, one or more appropriate third components are added before the completion of the PEN polymerization, and the ethylene-2,6-naphthalene copolymerized with the third component is added. -Tocopolymer can be obtained. Examples of the third component that can be used are diethylene glycol, neopentyl glycol, cyclohexanedimethanol, isophthalic acid, sulfoisophthalic acid and their sodium salts, polyalkylene glycol, naphthalene-2,7-.
Dicarboxylic acid, naphthalene-2,7-dicarboxylic acid-4
-Sulfonic acid sodium salt and the like can be mentioned.

When the third component is copolymerized, the Tg of the ethylene-2,6-naphthalate copolymer obtained is 10
It is necessary to select the kind and the use ratio so as not to fall below 0 ° C., and the copolymerization ratio of the third component should usually be less than 5 mol%. The copolymerization ratio of the third component is 5 mol% or more, that is, ethylene-
When the proportion of 2,6-naphthalate units is less than 95 mol%, as described above, the Tg of the conjugate fiber is lowered and the melting point is not high, and the thermal dimensional stability and the strength and elongation of the conjugate fiber are low. ,
Young's modulus etc. decreases.

In the composite fiber of the present invention, the composite fiber is formed by using polyethylene terephthalate (hereinafter referred to as "PET") having an intrinsic viscosity [η] of 0.95 or more and mainly ethylene terephthalate units as a sheath component. It is necessary to. In the spun conjugate fiber, the intrinsic viscosity [η] of PET is preferably 0.90 or more. In the present invention, the intrinsic viscosity [η] of PET is P
Similar to the case of EN, PET is a mixed solvent of p-chlorophenol and tetrachloroethane (weight mixing ratio 1: 1).
It is a value obtained from the viscosity of the substance dissolved in the solution and measured at 30 ° C.

In the conjugate fiber of the present invention, the melt viscosity of PET and PEN to be composite-spun is usually quite high, and therefore the head temperature of the spinning machine during melt-spinning is usually 290-3.
Although a high temperature of 10 ° C., particularly 300 to 310 ° C. is usually adopted, when the intrinsic viscosity [η] of PET is less than 0.95,
The melt viscosity of PET in the head portion is considerably lower than the melt viscosity of PEN, and the difference in melt viscosity between the two becomes large. As a result, the cross-sectional shape of the spun conjugate fiber does not become uniform and concentric, and eccentricity occurs, or the fiber diameter becomes uneven and a good core-sheath type conjugate fiber cannot be obtained. The sex becomes worse. Moreover, fluff is generated even in the drawing step after spinning, and the obtained drawn yarn has poor physical properties, particularly mechanical properties, heat resistance, and thermal dimensional stability.

Therefore, in the present invention, 290 to 310.
In order to minimize the difference with the melt viscosity of PEN at the time of melt spinning at a high temperature of 300 ° C., particularly 300 to 310 ° C., the PET constituting the sheath portion has an intrinsic viscosity [η] of 0.95 or more. It is necessary to use a composite fiber having a good cross-sectional shape, a uniform fiber diameter, and various physical properties, particularly mechanical properties, heat resistance and thermal dimensional stability. From such a point, it is more preferable that the intrinsic viscosity [η] of PET is 1.0 or more.

In the present invention, "mainly containing ethylene terephthalate units" means that 90 mol% or more of PET is composed of ethylene terephthalate units. When the proportion of ethylene terephthalate units in PET is less than 90 mol%, the Tg of the composite fiber of the present invention is lowered, and a composite fiber having a high melting point cannot be obtained, and thermal dimensional stability, strength and elongation of the composite fiber, This leads to a decrease in Young's modulus and the like. The PET used in the present invention contains a derivative of terephthalic acid or an ester thereof and ethylene glycol or a derivative thereof in a small amount (usually 10 mol%).
It can be produced by polycondensing in the presence of a catalyst with a third component of (less than 1) by a method known per se.

When a third component is used, it is preferable to add one or more suitable third components before the completion of the polymerization of PET, whereby ethylene terephthalate is copolymerized with the third component. A copolymer can be obtained. Examples of the third component that can be used include diethylene glycol, neopentyl glycol, cyclohexanedimethanol, isophthalic acid, sulfoisophthalic acid and sodium salts thereof, polyalkylene glycol and the like.

Further, in the conjugate fiber of the present invention, one or both of PEN which is the core component and PET which is the sheath component, may be a matting agent such as titanium oxide, a gloss improving agent, a flame retardant, etc., if necessary. May be contained.

Further, in the composite fiber of the present invention, the proportion of the core portion made of PEN is 50 to 90% by weight, that is, PET.
It is necessary that the ratio of the sheath portion consisting of 50 to 10% by weight. If the ratio of the core part (PEN) is less than 50% by weight, the covering ratio of the sheath part (PET) in the composite fiber becomes too large, and the thermal dimensional stability and high Young's high temperature which are the characteristics of the PEN fiber are high. The property of rate cannot be imparted to the composite fiber, and it becomes impossible to obtain the target composite fiber suitable as an industrial material. on the other hand,
When the proportion of the core portion (PEN) exceeds 90% by weight, when the composite fiber is used for reinforcing rubber, the adhesiveness with the rubber becomes poor. From the viewpoints of thermal dimensional stability, high Young's modulus at high temperature, adhesiveness to rubber, etc., it is preferable that the proportion of the core portion (PEN) in the composite fiber is particularly 75 to 90% by weight.

In order for the conjugate fiber of the present invention to have the above-mentioned physical properties that the Young's modulus at 120 ° C. is 100 g / d or more and the dry heat shrinkage percentage at 150 ° C. is 2% or less, the conjugate fiber is It is necessary that both the core PEN and the sheath PET that make up be highly oriented and crystallized. PEN for core and P for sheath
Any method can be adopted as long as it is a method for highly orienting and crystallizing both ET, for example, a high-speed spinning method for producing a conjugate fiber in which linear stretching orientation and crystallization is performed by performing high-speed spinning, Direct spinning method in which the spun composite fiber is continuously drawn and oriented / crystallized without being wound, and a method in which the spun composite fiber is once wound and then stretched to be oriented / crystallized, etc. It can be adopted, and the process can be rationalized in the case of the high speed prevention method and the spinning direct drawing method in which the spinning is followed by the drawing treatment.

In the case of the spinning direct drawing method or the method of spinning and once winding and then drawing, PEN forming the core portion has a crystallization rate of about 7.5 as compared with PET forming the sheath portion. It is twice as slow and it is difficult to achieve orientation and crystallization sufficiently in one stage of stretching, so it is better to carry out stretching in two or more stages under heating (for example, using a heating roller) than in one stage. Well, it is particularly preferable to carry out in 3 stages or more. By carrying out the above-mentioned orientation / crystallization treatment, the Young's modulus at 120 ° C. is 100 g / d or more, and the dry heat shrinkage rate at 150 ° C. is 2% or less, thus having a high Young's modulus and high thermal dimensional stability. The core-sheath type composite fiber of the present invention can be obtained.

In the conjugate fiber of the present invention, the cross-sectional shape of the whole conjugate fiber and the cross-sectional shape of the core are not particularly limited,
It may have any shape such as a circle, an ellipse, a rectangle, a triangle, and a polygon, but it is usually preferable that the entire cross section and the core have a circular cross-sectional shape in order to obtain uniform physical properties. In addition, it is desirable for the use of industrial materials that the single fiber fineness of the composite fiber of the present invention after the stretching treatment (after orientation / crystallization) is about 3 to 10 denier. The total fineness is 50
About 0 to 1000 denier is preferable. The composite fiber of the present invention is a monofilament, a short fiber, or a
Filament yarn, slab, spun yarn, woven fabric, non-woven fabric,
It can be used in any form such as a net and a tire cord.

Although not limited, a general method for producing the core-sheath type polyester conjugate fiber of the present invention will be described below. Intrinsic viscosity of the core part of one of the two extruders
ethylene having an [η] of 0.6 or more, preferably 0.7 or more
280 is supplied by supplying PEN mainly composed of 2,6-naphthalate units and melting at a temperature of 290 to 310 ° C., while supplying PET mainly composed of ethylene terephthalate units constituting the sheath portion to the other extruder. ~ 30
Melts at a temperature of 0 ° C. Then each molten polymer stream was heated to 300-3 ° C. with a head temperature of 300-310 ° C. and a length of 10 cm-100 cm just below the spinneret.
A core-sheath type composite fiber in which PEN is the core part and PET is the sheath part is spun out from the spinneret by introducing it to a composite spinning device equipped with a heat-retaining / heating cylinder for forming a heating atmosphere at 20 ° C After passing through the heating cylinder, it is rapidly cooled and solidified by cooling air, and an oil agent is added to produce a core-sheath type polyester composite fiber.

The above-mentioned composite spinning is usually about 1000 m /
It is preferable to perform the spinning at a spinning speed of not less than a minute, and in that case, it is important to control the heating atmosphere immediately below the spinneret in order to sufficiently orientate and crystallize the composite fiber in the subsequent drawing step. When the core-sheath type polyester composite fiber of the present invention oriented and crystallized by spinning is directly obtained, the spinning speed is 1500 m /
It is better to perform high speed spinning for more than a minute.

When an unstretched yarn is produced by spinning and subjected to a linear stretching process in which it is wound or a winding process after once winding, the temperature of the heating supply roller is set to 7
The temperature is set to 0 to 130 ° C., preferably 100 to 120 ° C., and multi-stage drawing is preferably performed thereafter. In multi-stage stretching, the temperature of the final stage stretching roller is 180 to 240 ° C., preferably 200 to 2
Stretching heat treatment is performed at 20 ° C. When the temperature of the drawing roller at the final stage is out of this range, particularly lower than 180 ° C., the composite fiber having the Young's modulus and the dry heat shrinkage ratio aimed at by the present invention cannot be obtained, and the heat resistance of the composite fiber is not obtained. Will be inferior.

By such multi-stage drawing with the heating roller, the characteristic of PEN forming the core portion appears in the composite fiber even though the sheath portion of the composite fiber is made of PET, and at 120 ° C. It is possible to obtain a core-sheath type polyester composite fiber having a Young's modulus of 100 g / d or more and a dry heat shrinkage rate at 150 ° C. of 2% or less. The composite fiber has excellent thermal stability and does not cause thermal deformation such as a flat spot phenomenon when used as an industrial material such as a tire cord.

The core-sheath type polyester conjugate fiber of the present invention obtained as described above is suitable for industrial materials, and is particularly excellent as a rubber reinforcing material, especially for tire cords. Generally, PET fiber is inferior in adhesiveness to rubber as compared with polyamide fiber,
In the core-sheath type polyester conjugate fiber of the present invention, it is possible to maintain sufficient adhesive strength with the rubber by selecting the type of oil agent used during spinning.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited thereto. In the following examples, the intrinsic viscosity [η] of each polymer before spinning is measured by the method described above, and the intrinsic viscosity [η] of each polymer in the fiber after spinning, the strength of the obtained fiber, and the elongation The degree, Young's modulus, dry heat shrinkage, adhesiveness with rubber and heat resistant adhesiveness were measured by the following methods.

Intrinsic viscosity of each polymer in the fiber after spinning
Measurement of [η]: (1) Intrinsic viscosity of each polymer in core-sheath type composite fiber
[η]: The core-sheath type composite fiber was dissolved in a p-chlorophenol / tetrachloroethane mixed solvent (weight ratio 1: 1) to give 30
The intrinsic viscosity [η] ₀ of the conjugate fiber is obtained by measurement under the condition of ° C. On the other hand, after the same core-sheath type composite fiber is subjected to alkali weight reduction treatment to dissolve and remove the sheath part, the intrinsic viscosity of the core part (PEN) is measured in the same manner as above, and the intrinsic viscosity is defined as [η] ₁ . .. The intrinsic viscosity of PET constituting the sheath portion is taken as _{[η] 2, [η]} 0, the relationship is established as shown in Equation 1 below between [eta] ₁ and [eta] _2.

[0035]

[Equation 1] [η] ₀ = ([η] ₁ + [η] ₂ ) / 2 Therefore, from Equation 1 above, the intrinsic viscosity [η] ₂ of PET that constitutes the sheath portion of the composite fiber is expressed by the following equation Calculated from 2.

[0036]

[Equation 2] [η] ₂ = 2 [η] ₀ − [η] ₁

(2) Intrinsic viscosity [η] of polymer in single fiber (fibers of Comparative Example 1 and Comparative Example 3): In the same manner as described above, the single fiber obtained in Comparative Example 1 or Comparative Example 3 was p. −
It was dissolved in a chlorophenol / tetrachloroethane mixed solvent (weight ratio of 1: 1) and measured at 30 ° C. to obtain the intrinsic viscosity [η].

Measurement of fiber strength, elongation and Young's modulus:
The strength, elongation and Young's modulus of the fiber are measured according to JIS L101.
It was measured according to the definition and measuring method of 7. Measurement of dry heat shrinkage of fiber: According to JIS L1013, the heat treatment temperature was 150 ° C., and the heat treatment time was 30 minutes.

Measurement of adhesiveness with rubber: JIS L101
It was measured according to 7-3.3.1A. Measurement of heat-resistant adhesion: According to JIS L1017-3.3.1A, the heat treatment during vulcanization was performed at 170 ° C. for 60 minutes.

Examples 1 to 3 Intrinsic viscosity [η] = 0.85
No.2 PEN was melted at 300 ° C with a 30Φ melt extruder, and PET with an intrinsic viscosity [η] = 1.2 was melted with a 30Φ melt extruder at 2
After melting at 95 ° C., the melt flow of each polymer was introduced into the composite spinning pack at the ratio shown in Table 1 below, and the nozzle hole diameter was 0.
A core / sheath composite spinning spinneret with a 4 mm, 96-hole spinneret having a heating atmosphere temperature of 310 ° C. and 320 ° C. under the spinneret and a heating cylinder length of 20 c.
Under the condition of m, the core-sheath type composite fiber was spun out so that the core portion was PEN and the sheath portion was PET, and after being kept warm and passed through the heating cylinder, it was rapidly cooled and solidified with cooling air at a temperature of 25 ° C. Was wound at a spinning speed of 1000 m / min.

The spinning raw yarn obtained above was heated at a heating roller temperature of 110 ° C., a first stretching roller temperature of 170 ° C., and a second stretching roller temperature of 170 ° C.
Two-stage drawing was carried out under heating conditions of a drawing roller temperature of 210 ° C. to obtain a drawn yarn having a total draw ratio of 4.4 times. At that time,
The draw ratio between the heating supply roller and the first drawing roller is 4.0.
The stretching ratio between the first stretching roller and the second stretching roller was 1.1.

In the above spinning and drawing processes, the spinning amount of the polymer during spinning was adjusted so that the fineness of the drawn yarn was 500 denier / 96 filaments. The drawn yarn obtained above is combined into two yarns, and 1000 denier /
The physical properties of the 192 filament were measured by the methods described above. The results are shown in Table 1 below.

Comparative Example 1 PEN having an intrinsic viscosity [η] = 0.85 was melted at 300 ° C. with a 30Φ melt extruder, and then introduced into a single spinning pack to have a nozzle hole diameter of 0.4 mm and a hole number of 96 holes. The spin spinning spinneret with the spinneret attached to the spinneret spins the PEN single fiber under the conditions of heat insulation and heating cylinder length of 20 cm under the spinneret having a heating atmosphere temperature of 310 ° C and 320 ° C. After being rapidly cooled and solidified with cooling air at a temperature of 25 ° C., an oil agent is applied, and then the spinning speed is 100.
It was wound at 0 m / min.

The spinning yarn obtained above was heated to a temperature of 130 ° C. for a supply roller, a first drawing roller temperature of 170 ° C. and a second drawing roller temperature.
A two-stage roller drawing was carried out under a heating condition of a drawing roller temperature of 210 ° C. to obtain a drawn yarn having a total draw ratio of 4.0 times. At that time,
The stretching ratio between the heating supply roller and the first stretching roller is 3.6.
The stretching ratio between the first stretching roller and the second stretching roller was 1.11 times.

Also in the above spinning and drawing treatments, as in Examples 1 to 3, the spinning amount of the polymer during spinning is adjusted so that the fineness of the drawn yarn is 500 denier / 96 filaments. , The obtained two drawn yarns are combined and 10
As a 00 denier / 192 filament, its physical properties were measured by the methods described above. The results are shown in Table 1 below.

Comparative Example 2 The ratio of PEN and PET supplied to the composite spinning pack was 30% as shown in Table 1 below.
Except for the number 70, spinning and drawing were performed in the same manner as in Examples 1 to 3, two drawn yarns obtained were combined, and
As a 1000 denier / 192 filament, its physical properties were measured by the methods described above. The results are shown in Table 1 below.

Comparative Example 3 P of Intrinsic Viscosity [η] = 1.2
After ET was melted at 295 ° C. with a 30Φ melt extruder, it was introduced into a single spinning pack and the nozzle hole diameter was 0.4 mm and the hole number was 9
From a single spinneret with a 6-hole spinneret, PEN single fiber is spun out under the conditions of heat insulation and heating cylinder length of 20 cm under the spinneret having a heating atmosphere temperature of 305 ° C and 310 ° C. After passing, it is rapidly cooled and solidified with cooling air at a temperature of 25 ° C., an oil agent is applied, and then a spinning speed of 1000.
It was wound up at m / min.

The spun raw yarn obtained above is subjected to two-stage roller stretching under the heating conditions of a heating supply roller temperature of 90 ° C., a first stretching roller temperature of 150 ° C. and a second stretching roller temperature of 200 ° C., and a total stretching ratio of 5 is obtained. A drawn yarn of 2 times was obtained. At that time, the stretching ratio between the heating supply roller and the first stretching roller was 4.7 times, and the stretching ratio between the first stretching roller and the second stretching roller was 1.15 times.

Also in the above spinning and drawing treatments, as in Examples 1 to 3, the spinning amount of the polymer during spinning is adjusted so that the fineness of the drawn yarn is 500 denier / 96 filaments. , The obtained two drawn yarns are combined and 10
As a 00 denier / 192 filament, its physical properties were measured by the methods described above. The results are shown in Table 1 below.

[0050]

[Table 1]

In order for fibers (threads) to be effectively used as a rubber reinforcing material, it is generally necessary that the adhesiveness with rubber is 18 kg or more. This adhesive strength is 90 after heating and before heating.
Must be held at a value of% or higher. From this point, when the results in Table 1 above are examined, the adhesiveness with rubber passed 18 kg or more in all of Examples 1 to 3 and Comparative Examples 1 to 3 before heating, but after the heat resistance test (heating. (After), the PEN single fiber of Comparative Example 1 had a heat-resistant adhesive property (adhesive strength) of 13.6 kg (7 before the heat resistance test).
2.7%), that is, the PEN single fiber has a large decrease in the adhesiveness between the fiber and the rubber by heating, whereas the composite fibers of the present invention of Examples 1 to 3 have Even after that, 90% or more of the adhesive strength before heating was maintained, and it can be seen that the adhesiveness with rubber exceeds the 18 kg pass line.

From the results shown in Table 1, the core portion (PEN)
The composite fiber (drawn yarn) of the present invention of Examples 1 to 3 having a ratio of 50 to 90% has high strength, low elongation and dry heat shrinkage and high Young's modulus. ,
It can be seen that it has excellent dimensional stability, particularly thermal dimensional stability and heat recovery, and is suitable as an industrial material such as a tire cord. On the other hand, the ratio of the core part (PEN) is 5
In the composite fiber of Comparative Example 2 and the PET single fiber of Comparative Example 3 in which the proportion of the sheath portion (PET) exceeds 50% and is less than 0%, the elongation and dry heat shrinkage of the drawn yarn are large, and the Young's modulus is Is small, especially when the Young's modulus at the time of heating at 120 ° C. is reduced to one third or less of the Young's modulus at room temperature, large elongation of the fiber occurs at the time of heating, and the dimensional stability,
In particular, it is found that the thermal dimensional stability and the heat recovery property are poor, and it is not suitable as an industrial material such as a tire cord.

[0053]

The core-sheath type polyester conjugate fiber of the present invention has excellent mechanical properties such as high strength, high modulus and good thermal dimensional stability, and is excellent in adhesion to rubber. Therefore, the core-sheath type polyester conjugate fiber of the present invention is extremely excellent as a rubber reinforcing material and other industrial materials, and particularly when the core-sheath type polyester conjugate fiber of the present invention is used for a tire cord, It is possible to significantly improve the thermal deformation recovery property and prevent the occurrence of the flat spot phenomenon in the tire.

Claims (1)

[Claims] (A) Polyethylene naphthalate having ethylene-2,6-naphthalate units having an intrinsic viscosity [η] of 0.6 or more as a core component, and an intrinsic viscosity of
A core-sheath type polyester conjugate fiber formed by using polyethylene terephthalate mainly composed of ethylene terephthalate units having [η] of 0.95 or more as a sheath component; (b)
The proportion of the core portion in the composite fiber is 50 to 90% by weight; (c) Young's modulus at 120 ° C is 100 g / d or more; and (d) Dry heat shrinkage at 150 ° C is 2
% Or less; A core-sheath type polyester composite fiber characterized by being: