JPH11189925A - Production of sheath-code conjugated fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process for a sheath-code conjugated fiber that can increase the through-put her a unit time, i.e., increase of productivity and, can improve conventional defects e.g. deteriorations of fiber properties such as Young's modulus or elongation elastic recovery rate by using a specific polymer as the core component in the production of a poly(propylene terephthalate) fiber. SOLUTION: Substantially, a poly(propylene terephthalate) polymer is used as a sheath component, while a polymer A that has a larger temperature dependency in elongation viscosity than that of the poly(propylene terephthalate) polymer is used as a core component. This sheath-core conjugated fiber is spun so that the amount of the polymer A may become 0.1-10 wt.% based on the whole conjugated fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a core-sheath conjugate fiber which can contribute to an improvement in productivity and has improved defects such as a decrease in fiber properties such as a Young's modulus and an elongation recovery rate.

[0002]

2. Description of the Related Art Polyester fibers have various excellent properties including mechanical properties, and are therefore widely used in apparel and industrial materials.

Hitherto, in order to obtain polyester fibers, a so-called two-step method in which a polymer is melt-spun and then stretched has been generally used. Such a fiber that has just been melt-spun has not developed the internal structure of the fiber and has poor mechanical properties and dimensional stability. Therefore, it is necessary to form and fix the structure by stretching in another process. . The draw ratio depends on the melt spinning conditions, particularly the take-up speed, and setting an excessive ratio leads to yarn breakage and a reduction in texture, so there is a limit to the draw ratio.

In general, the productivity in the spinning process largely depends on the discharge amount per unit time. In order to obtain a fiber having a desired denier, since the draw ratio is limited as described above, the denier of the undrawn fiber, that is, the discharge amount of the spinning is naturally limited, and the improvement in productivity in the two-step method is limited. is there.

In recent years, in particular, the take-up speed of polyethylene terephthalate (hereinafter abbreviated as PET) has been increased to 5000 m /
A high-speed spinning method for obtaining a practical fiber in one step without increasing the speed at a speed of not less than one minute is being industrially adopted. In addition, the productivity in the spinning process greatly depends on the discharge amount per unit time.
The productivity of the process method is improved.

However, even in the high-speed spinning method,
For example, PET fibers and the like exhibit practically preferable mechanical properties at a spinning speed of about 6000 to 7000 m / min, but when the speed is further increased, the strong elongation is reduced, which causes a practical problem. Therefore, there is a limit to sufficiently exhibit the effect of improving productivity.

As described above, conventionally, there has been a limitation on the discharge amount in both the two-step method and the high-speed spinning method (one-step method). Therefore, if the molecular orientation can be suppressed and a fiber having a larger residual elongation can be obtained even at the same spinning speed, it is possible to further increase the spinning speed, that is, to increase the discharge rate and increase the production efficiency.

In this regard, spinning methods have been proposed in which a small amount of incompatible polymer is blended with the matrix polymer. For example, JP-A-58-98414 and JP-A-60-209015 disclose that a polymer incompatible with a matrix polymer is added in an amount of 0.1 to 10% by weight to suppress molecular orientation. A spinning method is disclosed. Japanese Patent Application Laid-Open No. 57-11211 discloses a method of adding a liquid crystal polymer. Furthermore, JP-A-56-91013, JP-A-57-47912, and JP-A-62-21817 also show that addition of a small amount of a polyolefin-based polymer to polyester suppresses molecular orientation. Is disclosed.

[0009] However, even if the molecular orientation is suppressed by these methods, there is an adverse effect due to the added polymer. For example, when a polymer having a low softening point such as polystyrene is added, fusion occurs when a process such as false twisting that requires a high-temperature heat treatment is performed due to the low softening point polymer present in the surface layer. There are cases. In addition, they may be cloudy due to incompatibility, or the coloring properties of the dyed product may be poor. Furthermore, since it is very difficult to uniformly blend a small amount of a different kind of polymer with the polyester, there is a problem that a blend unevenness is liable to occur, yarn breakage frequently occurs, and stains are caused.

On the other hand, polypropylene terephthalate fibers are disclosed in JP-A-52-5320 and JP-A-52-812.
It has been known for a long time as seen in No. 4
It has excellent elongation elastic recovery, low Young's modulus, good dyeability, and is chemically stable, and is a fiber suitable for clothing.

However, since 1,3 propanediol as a raw material is relatively expensive, it has not been used as a synthetic fiber until now.

[0012]

DISCLOSURE OF THE INVENTION The present invention can improve productivity by increasing the discharge amount of polypropylene terephthalate fiber, and can also improve the drawbacks of deterioration of fiber properties such as Young's modulus and elongation elastic recovery. It is an object of the present invention to provide a method for producing a core-sheath composite fiber.

[0013]

Means for Solving the Problems In order to achieve the above object, a method for producing a core-sheath conjugate fiber according to the present invention uses substantially polypropylene terephthalate as a sheath component polymer,
The core component polymer contains polymer A whose elongational viscosity has a greater temperature dependency than that of the above-mentioned polypropylene terephthalate polymer, and the polymer A is contained in an amount of 0.
The core-sheath composite spinning is performed so as to be 1 to 10% by weight.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, polypropylene terephthalate is substantially used as the sheath component polymer, and the core component polymer contains polymer A whose elongational viscosity has a greater temperature dependency than that of the above polypropylene terephthalate polymer, and the polymer A is 0% with respect to the entire composite fiber. The core-sheath composite spinning is performed so as to be 0.1 to 10% by weight.

The polypropylene terephthalate in the present invention is a polyester obtained by using terephthalic acid as a main acid component and 1,3 propanediol as a main glycol component. However, it may contain another copolymer component capable of forming an ester bond at a ratio of 20 mol%, more preferably 10 mol% or less.

Examples of the copolymerizable compound include dicarboxylic acids such as isophthalic acid, succinic acid, cyclohexanedicarboxylic acid, adipic acid, dimeric acid and sebacic acid;
On the other hand, examples of the glycol component include, but are not limited to, ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol.

Titanium dioxide as a matting agent, fine particles of silica or alumina as a lubricant, hindered phenol derivatives, coloring pigments and the like as antioxidants can be added as required.

The core component polymer must contain a polymer A (hereinafter sometimes simply referred to as polymer A) in which the temperature dependence of the extensional viscosity is larger than that of the sheath component polypropylene terephthalate. The temperature dependency of the elongational viscosity referred to here is determined as follows. That is, the sheath component polypropylene terephthalate (hereinafter sometimes simply referred to as PPT) and the polymer A to be examined are each melt-spun, and the yarn temperature (T (K)) and yarn speed (V
(M / sec)), and the birefringence (Δn) is measured online. Then, the deformation speed (dV / dx) is obtained from the yarn speed according to the following formula, the spinning stress (σ) is obtained from the birefringence index using the stress optical coefficient, and the elongational viscosity (η) is obtained from the deformation speed gradient and the spinning stress. Is calculated by the following equation. Where x
Is the distance (m) from the base.

Η = σ / (dV / dx) Since the yarn temperature T (x) is also measured, {1 / T (x)}
The temperature dependence of the elongational viscosity is determined from the figure of −log η (x).

From the comparison of the relative temperature dependence with PPT, polymer A is particularly preferably polystyrene from the viewpoints of cost, availability, spinnability and the like.

The core component may be a polymer A having a temperature dependency of elongational viscosity greater than that of the sheath component PPT alone or a blend with another polymer. In order not to impair the elongation elastic recovery property of the fiber, from the viewpoint of physical properties, the core component polymer has a temperature dependence of elongation viscosity such that the ratio of the polymer A larger than that of the sheath component PPT falls within a predetermined range.
It is preferably blended with T. In this case, the ratio of the polymer A having a large temperature dependency of the elongational viscosity to the core component polymer becomes considerably large as compared with the conventional method of blending the whole polymer, so that the blending becomes easy, and the blending becomes easier than the conventional method. Defects due to spots can be significantly reduced.

The core-sheath shape is not particularly limited, and may be a concentric core-sheath or an eccentric core-sheath, may have a plurality of cores, or may have a sea-island structure. It is preferably from 95 to 20/80. Particularly preferably, it is in the range of 7/93 to 15/85. That is, it is important that the polymer A in the core component is continuously present in a constant amount in the fiber axis direction and is not exposed on the fiber surface.

By the way, the content of the polymer A whose elongational viscosity is largely temperature-dependent is determined by the fact that the obtained fiber substantially exhibits the characteristics as a PPT fiber, in particular, the elongation recovery property. 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less.

Japanese Patent Publication No. 43-23879 discloses a thermoplastic amorphous polymer (PMM in Examples).
A), a core-sheath conjugate fiber in which a thermoplastic crystalline polymer (nylon 6 in the example) is disposed in a sheath portion is disclosed. However, this merely shows core / sheath = amorphous polymer / crystalline polymer, and does not show any combination of polymers having different temperature dependences of elongational viscosity. Means that it is meaningful to cold-draw the fiber wound at a low speed and partially cut the core polymer.There is no explanation about the effect of suppressing the molecular orientation by high-speed spinning and the fact that this effect is manifested in a very small amount. Not shown. Further, in this case, the composite ratio of the core polymer is 20% by weight or more of the entire conjugate fiber, and in this case, the characteristics of the core polymer are strongly exhibited, and the characteristics of the sheath polymer cannot be utilized.

By the way, in consideration of the processability and the process stability at the time of drawing or drawing false twisting by the two-step method, it is preferable that the obtained fibers are oriented to some extent. Therefore, the spinning speed is preferably 4000 m / min or more. More preferably, it is 5000 m / min or more. In addition, in order to obtain a fiber having a high elongation characteristic comparable to a high-speed spun fiber only by spinning, the spinning speed is preferably 7000 m / min or more,
More preferably, it is at least 10,000 m / min. However, when the spinning speed exceeds 12000 m / min, the residual elongation decreases, and the success rate of automatic switching of the bobbin during winding decreases.

By adopting the above-mentioned production method, a PPT fiber with suppressed molecular orientation can be obtained, but the mechanism is that the spinning stress share ratio between polymers changes on the spinning line (cooling process). That is, if the temperature dependence of the elongational viscosity of the polymer A is high with respect to PPT, the P
Since the spinning stress share ratio of the PT decreases, the orientation of the PPT is suppressed. For example, the spinning stress burden ratio in the high temperature region below the die is polymer A / PPT = 30/70, and the polymer A / P is at the 95% thinning end point which is a relatively low temperature region.
It happens that PT = 70/30.

The degree of orientation suppression can be evaluated by, for example, the birefringence and residual elongation of the wound yarn. In the case of a core-sheath composite yarn, measuring the birefringence of only the sheath portion takes a considerable amount of time, so it is easier to use the residual elongation as an evaluation standard.

The polypropylene terephthalate fiber obtained according to the present invention has a low Young's modulus and a good elongation elastic recovery property, like the conventional polypropylene terephthalate fiber. As processing yarn, stretch materials such as pantyhose, tights, swimwear, socks and other conventional uses such as innerwear, sportswear, brushes, campuses, and lining, slacks,
It can be suitably used for clothing such as blousons and blouses, and for materials such as ribbons, tapes and belts.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. In addition, the measuring method in the Example used the following method.

A. Intrinsic viscosity [η] Measured at 25 ° C. in orthochlorophenol.

B. Stress-elongation curve A load-elongation curve was determined using a tensile tester manufactured by Orientec under the conditions of a sample length of 200 mm and a tensile speed of 200 mm / min. Next, the load value was divided by the initial fineness, which was used as the tensile stress, and the elongation was divided by the initial sample length to obtain the elongation.

C. Boiling water shrinkage rate Using a measuring machine with a frame circumference of 0.5 m, apply an initial load and rewind at a speed of 60 turns / min to make a small case with 10 turns, and apply a load 20 times the initial load to apply a case. Measure the length. Next, the load was removed, the sample was immersed in boiling water at 100 ° C. for 15 minutes, taken out, air-dried, re-loaded and the length of the scab was measured, and the hot water shrinkage was calculated by the following equation.

D. Hot water shrinkage (%) = (L0−L1) / L × 100 where L0: length before immersion (mm) L1: length after air drying (mm) Periodic spots in the fiber longitudinal direction Continuous heat shrinkage spot measuring system F manufactured by Toray Engineering Co., Ltd.
The continuous wet heat stress was measured at a measurement temperature of 100 ° C. by TA-500. Yarn speed 10m / min, chart speed 6c
m / min.

E. Elastic recovery rate The sample was subjected to a constant speed elongation type tensile tester equipped with a self-recording device, and subjected to an initial load of 1/30 g per denier for 20 c.
At a grip distance of m, the stretching speed is set to 10% of the grip distance and stretched to a predetermined elongation. Immediately, from the stress-strain curve recorded by removing the weight at the same speed, the constant elongation up to a predetermined elongation was α, and the recovery elongation reduced until the stress became equal to the initial load was β, which was determined by the following formula.

Elastic recovery (%) = (β / α) × 100 Example 1 140 ° C. to 230 ° C. using 19.4 kg of dimethyl terephthalic acid and 15.2 kg of 1,3-propanediol as catalyst using tetrabutyl titanate as a catalyst. After the transesterification reaction was carried out while distilling off methanol at, polymerization was further carried out for 3 hours at a constant temperature of 250 ° C. to obtain a polypropylene terephthalate having an intrinsic viscosity [η] of 0.89.

A tip blend of polypropylene terephthalate having an intrinsic viscosity of 0.89 alone, polystyrene (Stylon 685, manufactured by Asahi Kasei Corporation), and polypropylene terephthalate having an intrinsic viscosity of 0.89 in a ratio of 30/70 (weight ratio) was carried out. These were separately melted and filtered through a stainless steel non-woven fabric filter having an absolute filtration diameter of 10 μm, and then a core-sheath composite of polystyrene blend polymer and polypropylene terephthalate on a concentric sheath was discharged from a die 1 having 24 holes. . The core-sheath composite ratio at this time is 1
At 5/85, the ratio of polystyrene to the entire composite fiber was 4.5% by weight. The spinning temperature was adjusted to 260 ° C. and the discharge rate was adjusted to a single yarn fineness of 2d. The discharged yarn is
As shown in FIG. 3, after discharging, air at a room temperature of 25 m / min was blown out from a chimney 2 having a length of 1.0 m, cooled, and then refueled and focused by a refueling guide 3 installed 2 m below the base. Further, confounding was imparted by a confounding device 4 installed 2 m downstream, and the material was taken off at a speed shown in Table 1 by a first take-off roller 5 installed 4 m below the base. Further, the fiber was wound through the second take-up roller 6 by controlling the number of revolutions of the winder 8 so that the winding tension measured by the tensiometer 7 was constant. The speeds of the first take-up roller 5 and the second take-up roller 6 are the same, and the spinning speed is shown in Table 1 (Experiment Nos.
5).

The spinning speed is 6000 m / min and 10,000
The stress-elongation curves of the fibers obtained at m / min are shown in curve A of FIG. 1 and curve A ′ of FIG. 2, respectively. Table 1 shows strength, elongation, shrinkage of boiling water, and periodic unevenness in the fiber longitudinal direction. In addition, Young's modulus when stretched to 40% elongation at a stretching temperature of 60 ° C and a set temperature of 130 ° C using a normal hot roll-hot roll stretching machine,
Table 1 also shows the 10% elongation elastic recovery rate.

As can be seen from Table 1, polystyrene and P
When a core-sheath composite of a PT blend polymer and PPT is used,
The effect of improving the residual elongation is obtained over the entire spinning speed range, and the spinning speed is 6,000 m without impairing the Young's modulus and elongation elastic recovery when stretched, and as is clear from the strong elongation curve (FIG. 1A). Even the / spun yarn is an undrawn yarn. In addition, it can be seen from FIG. 2A 'that even at a spinning speed of 10000 m / min, the yarn has good high elongation characteristics unlike the case of 100% PPT. Further, in this spinning speed region, crystallization is progressing, and the fiber can withstand practical use as it is without drawing or heat treatment.

As a comparative example, spinning was carried out in the same manner as in the example except that a single component of PPT was used, to obtain a wound yarn. Table 2 shows the strength, elongation, shrinkage of boiling water, and periodic unevenness in the fiber longitudinal direction. 600 in the same way as polyethylene terephthalate
It can be seen that the spinning speed of 0 m / min or more is close to the physical properties of the drawn yarn.

[0040]

[Table 1]

[Table 2]

[0041]

According to the method for producing the core-sheath conjugate fiber of the present invention, the discharge rate per unit time can be greatly increased, and the drawbacks of the prior art are the Young's modulus and elongation elastic recovery. Fiber properties such as deterioration can be suppressed.

[Brief description of the drawings]

FIG. 1 is a view showing a stress-elongation curve of a fiber obtained according to the present invention and a comparative example.

FIG. 2 is a view showing a stress-elongation curve of a fiber obtained according to the present invention and a comparative example.

FIG. 3 is a process chart showing an example of a melt spinning method.

[Explanation of symbols]

 1: Cap 2: Chimney 3: Refueling guide 4: Entangling device 5: First take-up roller 6: Second take-up roller 7: Tensiometer 8: Winding machine

Claims (4)

[Claims] 1. A polymer comprising substantially a polypropylene terephthalate as a sheath component polymer, wherein the core component polymer comprises a polymer A having a temperature dependency of elongational viscosity greater than that of the polypropylene terephthalate polymer.
A core-sheath composite spinning so that the content of the core-sheath composite fiber is 0.1 to 10% by weight based on the total weight of the composite fiber. 2. The composite ratio of the core component and the sheath component is from 5/95 to 20.
The method for producing a core-sheath conjugate fiber according to claim 1, wherein the ratio is in the range of / 80. 3. The method for producing a core-sheath conjugate fiber according to claim 1, wherein the polymer A whose elongational viscosity has a greater temperature dependence than that of polypropylene terephthalate is a polystyrene-based polymer. 4. The method for producing a core-sheath conjugate fiber according to claim 1, wherein the spinning speed is 4000 to 12000 m / min.