JP3305915B2 - Method for producing polyurethane / polyamide composite elastic fiber - Google Patents

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 composite elastic fiber having a polyurethane elastomer as a core component and a polyamide as a sheath component.

[0002]

2. Description of the Related Art Generally, an elastic yarn made of 100% polyurethane exhibits large extensibility only by its own rubber elasticity.
Its elongation reaches 400 to 600%, making it difficult to use as it is. Therefore, the elongation is 300-400%
A so-called covering yarn in which a crimped yarn or a flat yarn or the like is wrapped single or double around an urethane elastic yarn is used as a method for suppressing such a phenomenon. However, such covering yarns are inferior in productivity, and furthermore, the cost is high due to the addition of the covering step, and furthermore, the covering yarn cannot be expected to have the bulkiness of the crimped yarn. It is.

On the other hand, in order to eliminate the drawbacks of the covering yarn, one component is a polyurethane elastomer and the other component is a polyamide, which is a heat-shrinkable polymer different from each other, and is bonded to a side-by-side type or an eccentric sea core type. Conjugate fiber with latent crimp ability
No. 36725 and Japanese Patent Publication No. 55-27175. Such composite fibers have excellent crimp performance,
The elastic properties of polyurethane elastomers themselves are rarely exploited. In these conjugate fibers, the urethane elastomer exhibiting elasticity itself is used, but only the use of crimpability in the form of conjugate fibers is used. The use of the above-mentioned "elasticity" and the high stretch by the synergistic use of crimpability and elasticity No attention was paid to the conversion.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve the disadvantages of the prior art, and as a result, have made the polyurethane elastomer and the polyamide into a specific core-sheath state, and subsequently stretched, relaxed, and heat-treated. The present inventors have found a method for easily and inexpensively producing an elastic fiber having not only bulkiness and strength but also elasticity characteristic of an elastomer by integration of (dry heat) treatment, and have reached the present invention.

[0005]

That is, the present invention relates to a method for continuously drawing, relaxing and heat-treating an undrawn yarn obtained by composite melt-spinning a composite fiber having a crosslinked polyurethane elastomer as a core component and a polyamide as a sheath component. In the case of performing the method, the cross-sectional area ratio of the core / sheath of the composite fiber is 3 to 99, and the relaxation rate is 80 to
200 %, the heat treatment is dry heat and the treatment temperature is 13
A method for producing a composite elastic fiber, characterized in that the condition that the temperature is higher than 0 ° C and not higher than 150 ° C is satisfied.

[0006] Here, the polyurethane elastomer refers to a polyurethane in a broad sense having a urethane bond or a urea bond in a molecule. As long as it is thermoplastic, a linear urethane or a urethane having a partially cross-linked bond can be used.

The crosslinked polyurethane elastomer having a core component constituting the present invention is not a usual thermoplastic polyurethane but a crosslinked polyurethane. The crosslinks of the polyurethane are preferably formed by allophanate linkages mainly by reaction with the polyisocyanate contained therein.

As a method for producing such a crosslinked polyurethane, a polyisocyanate and a molten thermoplastic polyurethane are mixed during the spinning to react during or after the spinning, and the allophanate crosslinked structure is mainly active in the molecule. Method, for example,
8-46573).

The hardness of the thermoplastic polyurethane is preferably in the range of 60 to 95 according to JIS-A. Hardness is 60
If it is less than 10%, the resulting yarn has poor recovery power and strength, which is not preferable because problems such as whitening occur. Conversely, when the hardness is high, the strength and the resilience are excellent, and problems such as whitening can be solved. Therefore, the range of 92 to 95 is most preferable.

The polyisocyanate used in the present invention generally has a molecular weight of 300 or more, preferably 400 or more.
More preferably, one or a mixture of polyfunctional polyols having a bifunctional or trifunctional hydroxyl group of 800 or more and 5000 or less, and a polyfunctional isocyanate (for example, diphenylmethane diisocyanate, trifunctional isocyanate,
Or a mixture thereof). The average functionality of the polyol is from 2.0 to 2.
It is preferable to use those in the range of 8. When the polyol component has a functionality of only 2.0, it is desirable that free polyfunctional isocyanate is present in the polyisocyanate. In this way, the ratio of the number of moles of isocyanate groups / the number of moles of hydroxyl groups may be more than 2.0.

The amount of the polyisocyanate in the core component is preferably 5 to 40% by weight based on the total amount of the mixture of the thermoplastic polyurethane and the polyisocyanate to be spun. The amount added depends on the type of polyisocyanate used, but the amount added is 40% by weight.
If the ratio is more than 1, the mixing becomes uneven and the spinning becomes unstable or the mechanical properties of the yarn are unsatisfactory. On the other hand, if it is less than 5% by weight, the heat resistance of the obtained yarn is insufficient. .

In order to give the composite elastic fiber sufficient functions of recoverability and heat resistance, the core component polyurethane has a crosslinking density Y (μmol / g) of 15 or more and a core / sheath composite ratio. X + the crosslink density Y, X + Y ≧ 35
It is preferable that the relational expression is always satisfied. Here, the cross-link density is the amount of cross-links such as allophanate bonds formed in the polyurethane, and is represented by the molar equivalent of cross-links per unit weight of the polyurethane. The measurement of the amount can be carried out, for example, by the method described in JP-A-4-11021.
That is, when the crosslinking density of the polyurethane in the core component is low, it is necessary to increase the composite ratio X (accordingly, the ratio of the core component) according to the above formula. Conversely, when the crosslinking density of the polyurethane in the core component is high, Expanding the scope of the compound ratio,
That is, the ratio of the sheath component can be increased.

The polyamide used for the sheath component in the present invention can be nylon 6, nylon 12, nylon 66, or a copolymer thereof, but nylon 12 is preferred. Among the nylons 12, it is preferable that the viscosity is low because the draw draft of the conjugate fiber can be increased and the elastic properties of the yarn are improved.

Having described both the core and sheath components, the composite ratio of the core and sheath will now be described. The composite ratio of the core / sheath component is in the range of 3 to 99 in terms of cross-sectional area ratio, and preferably 10 to
70, more preferably 20 to 50. This ratio is 3
When the ratio is less than the above, the elastic recovery, recovery at high temperature, and heat resistance of the obtained yarn are insufficient. Conversely, when the ratio exceeds 100, the sheath component is broken or the core component is easily exposed on the yarn surface. It is not preferable because it has a bad effect on spinnability and the like.

Next, as the composite form of the core-sheath, an eccentric core-sheath composite fiber or a concentric core-sheath composite fiber may be used, but a concentric core-sheath composite fiber is preferred. The cross-sectional shape of the composite fiber may be a non-circular shape such as a circle or an ellipse.

Next, a method for producing the composite elastic fiber of the present invention will be described. The melt conjugate spinning for producing the composite elastic fiber of the present invention comprises a portion for melt-extruding a thermoplastic polyurethane, a portion for adding and mixing a polyisocyanate for forming a crosslink, a portion for melt-extruding a sheath component, and a known method. And a spinning head having a core-sheath composite spinneret. As a device used for adding the polyisocyanate during spinning, a known device can be used. It is also possible to use a kneading device having a rotating part in the portion where the polyisocyanate is added to and mixed with the polyurethane in a molten state, but it is more preferable to use a mixing device having a static kneading element. A well-known mixing device having a stationary kneading element can be used. The shape and number of static kneading elements vary depending on the conditions used, but they should be selected so that the thermoplastic polyurethane and polyisocyanate are sufficiently mixed before being discharged from the composite die. Is essential, and usually 20 to 90 elements are provided. The polyurethane mixed with the polyisocyanate is used as a core component, the sheath component is melted by another extruder, and both are guided to a known core-sheath composite spinneret to be spun to obtain the composite fiber according to the present invention. Can be Incidentally, the composite ratio of the core and the sheath can be easily adjusted by changing the discharge amount of both components.

The conjugated fiber thus obtained is rich in the fitting property and excellent in dimensional stability which are the objects of the present invention.
In order to form a stretchable elastic yarn, the obtained spun yarn is subjected to relaxation heat (dry heat) treatment simultaneously with stretching. FIG. 1 shows a conceptual diagram of a stretching heat treatment apparatus for that purpose. The supplied undrawn yarn is drawn between the feed roller 1 and the first roller 2. Subsequently, relaxation heat treatment is performed by the second roller 3 which is rotated at a lower speed than the first roller and is heated to a predetermined temperature, and is wound up via the third roller 4. It is important that the relaxation heat treatment satisfies the following conditions. Relaxation rate 80-200
% Range is required, but can be appropriately selected depending on the draft for drawing. If the stretching draft is high, dimensional stability and elongation recovery, which is a characteristic of the polyurethane elastomer, may not be exhibited unless the relaxation rate is increased.
In particular, it is important to adjust the range of the relaxation rate to 80 to 200% in accordance with the drawing draft in order to remarkably exhibit the elongation recovery property which is a characteristic of the elastomer. If the relaxation rate at this time is less than 80%, the characteristic of polyurethane elastomer, elongation recovery cannot be brought out,
It is not possible to obtain a composite elastic fiber having an elongation recovery property, which is an object of the present invention, which is rich in bulkiness. Conversely, the relaxation rate is 20
If it exceeds 0%, the slack of the yarn becomes large and the yarn is easily broken. The relaxation rate is determined by the following equation.

On the other hand, the heat (dry heat) treatment temperature immediately after stretching is 1
It is necessary to exceed 30 ° C. and 150 ° C. or less.
When the treatment temperature is 130 ° C. or lower, the strength and stress are weak, the shrinkage of boiling water is large, which is not preferable in terms of dimensional stability, and the elongation recovery characteristic of the polyurethane elastomer may not be remarkably exhibited. Not preferred. On the other hand, if the treatment temperature exceeds 150 ° C., the physical properties of the fiber due to heat are remarkably reduced, and the strength and the elongation recovery are deteriorated.

[0019]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. In the examples,
The characteristic value of the yarn was measured by the following measurement method using a sample obtained by leaving the spun conjugate fiber at room temperature for 5 days and further subjecting the fiber to a stretching and relaxation heat (dry heat) treatment. (Each measuring method of boiling water shrinkage rate, elongation rate, elongation recovery rate) Take the yarn after relaxation heat treatment in a scalpel, apply a load of 40 mg / de,
The sample was subjected to a shrinkage treatment in boiling water for 20 minutes, and then air dried all day and night under the same load, at 20 ± 3 ° C.
The yarn was suspended under the temperature and humidity of 65 ± 3% RH by the following method. I. Yarn length: 250 mm (yarn length L0 under initial load suspension)
B. Initial load: 4 mg / de c. Test load: 400 mg / de (suspend each load so as not to rotate to the yarn end) d. Load suspension time: 2 minutes e. Measure the yarn length L1 when the test load is suspended, and apply the initial load again after removing the load. The initial load is applied and the yarn length L2 after 2 minutes is measured. G. The formula for elongation rate and elongation recovery rate is as follows.

Example 1 A thermoplastic polyurethane (diphenylmethane diisocyanate / polyethylene adipate / 1, 4-butanediol system, JIS-A hardness 90) was melted by an extruder, while a polyisocyanate compound ("AP-" manufactured by Nippon Polyurethane Co., Ltd.) was melted. 40 ″ and a degree of functionality of 2.3) are injected into the thermoplastic polyurethane by a supply device so as to be 15% by weight, and both components are kneaded with a kneading device having 30 static kneading elements to obtain a core component. . On the other hand, as a sheath component,
Using m-cresol as a solvent, a concentration of 0.5% and a temperature of 25
Nylon 12 having a relative viscosity of 1.6 measured at 0 ° C. is melted by another extruder, and both core and sheath components are guided to a concentric core / sheath composite spinneret (nozzle diameter 0.5 mm) to determine the composite ratio of core / sheath. It was spun at a constant rate and wound up on a bobbin at a winding speed of 500 m / min to obtain a composite elastic fiber having a 40 denier monofilament and a composite ratio (core / sheath) of 12/1. The crosslink density of the core component of the composite elastic fiber was 29 μmol / g.

Next, the obtained undrawn yarn was processed by a drawing heat treatment apparatus of the SDTY system in which all of the drawing and relaxation (heat) processing steps were directly connected. At this time, the stretching draft was set to 3.0, 3.5, or 4.0, and subsequently the treatment was performed at a relaxation rate of 66.7, 100, or 130%. 130,
Alternatively, it was set at 150 ° C. and wound up. Table 1 shows the stretching and relaxation heat treatment conditions and the physical properties of the obtained composite elastic yarn.

[0022]

[Table 1]

As shown in Table 1, the product of the present invention No. 6,
In the samples of 11, 15, 20, and 24, the boiling water shrinkage rate is 25 to
An excellent result of 30% was obtained, and an elastic fiber having no problem in dimensional stability could be provided. In addition, both the elongation recovery rate and the strength show good results. On the other hand, when the roller heater temperature is room temperature, the strength is about 30% to 40% less than that of the product of the present invention. Further, even when the heater temperature is 110 ° C. , some effects are observed as compared with those at room temperature, but it is not sufficient compared with the product of the present invention.

[0024]

As described above, according to the present invention,
By spinning a polyurethane elastomer and a polyamide in a specific composite shape and then processing them under the above-mentioned processing conditions, a composite elastic fiber can be produced that can fully exploit the elongation recoverability of the polyurethane elastomer itself. Can do things. The obtained composite elastic fiber has an unprecedented high elasticity and excellent resilience, is excellent in dimensional stability and fit, and is extremely useful for a pantyhose king, a stretch woven or knitted fabric and the like.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of a stretching relaxation heat treatment apparatus according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 feed roller 2 first roller (drawing roller) 3 second roller (roller heater) 4 third roller 5 winding yarn

Claims (1)

(57) [Claims] An undrawn yarn obtained by composite melt-spinning a composite fiber having a crosslinked polyurethane elastomer as a core component and a polyamide as a sheath component is continuously stretched, relaxed, and heat-treated. The conditions that the core / sheath cross-sectional area ratio is 3 to 99, the relaxation rate is 80 to 200%, the heat treatment is dry heat, and the treatment temperature exceeds 130 ° C. and is 150 ° C. or less are satisfied. A method for producing a composite elastic fiber, characterized in that: