JPH10130953A - Method for producing polyurethane elastic fiber - Google Patents

Abstract

(57) [Problem] To provide a method for obtaining polyurethane elastic fibers having uniform physical properties and uniformity. SOLUTION: A prepolymer obtained by reacting a high molecular diol and an organic diisocyanate and a chain extender are continuously supplied to a kneading extruder to produce polyurethane, and then the polyurethane elastic fiber is directly fed. A polyurethane elasticity characterized in that, at the time of spinning, the temperature of the input portion of the chain extender is higher than the melting point of the hard segment component of the polyurethane comprising the chain extender and the organic diisocyanate by 3 ° C. or more. Fiber manufacturing method.

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 polyurethane elastic fiber, and more particularly to a method for producing a polyurethane elastic fiber having excellent uniformity by melt continuous polymerization and melt spinning.

[0002]

2. Description of the Related Art In recent years, there has been an increase in demand for stockings using a support panty-stocking, that is, a covering yarn obtained by winding a nylon filament yarn around a polyurethane elastic yarn together with stretchable fabrics such as swimwear and foundations. Are steadily increasing. At present, polyurethane elastic yarn is produced by three types of methods: wet spinning, dry spinning, and melt spinning, and the mainstream is dry spinning. However, in recent years, attention has been paid to the characteristics of polyurethane elastic yarns obtained by the melt spinning technique because they are compatible with the full support of the pantyhose section, and at the same time, quantitative expansion is progressing.

One of the problems with such melt spinning is that polyurethane itself is susceptible to oxygen and water. As a characteristic of the segmented polyurethane, there is a problem that once the hard segments are once aggregated, it becomes difficult to re-melt. In order not to cause this problem, it has been considered that it is preferable to directly produce a fiber without solidifying after synthesizing the polyurethane, that is, a direct-polymerized spinning. In other words, chips are once formed by the conventional melt spinning method, but in the manufacturing process of such chips, in most cases, they pass through a cooling step with water, so that urea bonds may be formed or oxygen may be oxidized by contact with air. Is big. Further, upon re-melting, it is extremely difficult to completely remove water and oxygen adsorbed in the polyurethane, so that the influence greatly affects the process passability and the obtained fiber properties.

However, this polymerization direct spinning method also has many problems in stabilizing polyurethane and removing unreacted substances, and several proposals have been made to solve such problems. JP-A-6-10211 discloses a direct polymerization spinning method in which the isocyanate content of polyurethane discharged from a spinning head is specified.
Japanese Patent Publication No. 305226 proposes a direct polymerization spinning method in which degassing is performed under reduced pressure during or after the melt polymerization step. These proposals have reduced the amount of lumps present in polyurethane elastic fibers, but have not yet eliminated uniformity of physical properties of polyurethane elastic fibers and unevenness of fineness.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a polyurethane elastic fiber by a direct polymerization spinning method, in which a uniform property and uniform yarn (fiber) are obtained. is there.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned current situation, the present inventors have studied to eliminate unevenness in the fineness of polyurethane elastic fiber and obtain a uniform yarn in the polymerization direct spinning method. As a result, the present invention has been achieved. One-shot method and prepolymer method are known as polyurethane polymerization. The one-shot method is a method in which all the raw materials of polyurethane are simultaneously charged into a reactor at a set molar ratio. Met. In pursuit of this cause, a white crystal-like foreign substance was mixed in the polymerized polyurethane, and the presence of the foreign substance caused unevenness in the fineness of the fiber. There was found.
When the foreign matter was analyzed, it was analyzed that it was composed of diisocyanate, which is a raw material of polyurethane, and a chain extender, and that the hard segment portion of polyurethane was aggregated without being incorporated into the polyurethane main chain. Was.
As a cause of the formation of such aggregates, in the one-shot method, a high-molecular diol, a diisocyanate, and a chain extender, which are raw materials of polyurethane, are simultaneously charged into a reactor.
It is presumed that the diisocyanate and the chain extender react instantaneously to generate an unnecessarily long hard segment. There is also a prepolymer method in which a prepolymer composed of a diisocyanate and a polymer diol is first synthesized in a separate tank, and a chain extender is charged into a reactor with a delay in charging the synthesized prepolymer. In this case, since the released diisocyanate is present in excess, white foreign matter is generated as in the one-shot method.

Accordingly, in the present invention, when the polyurethane is polymerized by the prepolymer method, the temperature of the portion where the chain extender is introduced is controlled by adjusting the temperature of the hard segment composition of the polyurethane comprising the chain extender and the organic diisocyanate. By making the melting point higher than the melting point by 3 ° C. or more, the generation of the white foreign matter described above could be suppressed.

The polymer diol used in the present invention is a polymer compound obtained by polycondensation, addition polymerization or the like.
Polyester diol having a molecular weight of 1,000 to 3,000,
Examples thereof include polyetherdiol, polycarbonate-todiol, and co-condensates thereof (eg, polyester-ether-diol, polyestercarbonate-todiol, and the like). These may be used alone or in combination of two or more. When the molecular weight is less than 1,000, heat resistance and elastic recovery are reduced, while the molecular weight is less than 30.
If it exceeds 00, spinnability may decrease, which is not preferable.

Polyester diols include propylene glycol, 1,4-butanediol, 1,5-pentaneddiol, 1,6-hexanediol, and 3-methyl-diol.
1,5-pentaneddiol, 1,8-octanediol
2-methyl-1,8-octanediol, 1,9-
Alkanediol having 2 to 10 carbon atoms such as nonandiol, neopentyl glycol, 2-methyl-propanediol or a mixture thereof, and glutaric acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, Saturated polyester diol, polycaprolactone glycol, polypropiolactone glycol, polyvalerolactone glycol obtained from an aliphatic or aromatic dicarboxylic acid having 4 to 12 carbon atoms such as isophthalic acid or a mixture thereof. Polylactone diols such as toluene are preferably used.

Examples of the polyetherdiol include polyalkylene etherdiols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol. Is preferably used.

Polycarbonate diols such as 1,4
-Butanediol, 1,5-pentanediole, 1,6
-Hexanediol, 3-methyl-1,5-pentaneddiol, 1,8-octanediol, 2-methyl-1,
Condensation of diphenyl carbonate or phosgene with an alkanediol having 2 to 10 carbon atoms, such as 8-octanediol, 1,9-nonandiol, neopentyl glycol, 2-methyl-propanediol, or a mixture thereof, is carried out. Polycarbonatediol obtained by polymerization is preferably used.

The organic diisocyanate used in the present invention includes 4,4'-diphenylmethane diisocyanate,
Tolylene diisocyanate 2,2'-dimethyl-4,
Aromatics such as 4'-diphenylmethane diisocyanate, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane, 4,4'-dicyclohexylmethane diisocyanate and isophorone diisocyanate And alicyclic or aliphatic diisocyanates.
These organic diisocyanates may be used alone or in combination of two or more.

The chain extender used in the present invention is a chain extender commonly used in polyurethane polymerization, that is, a low molecular weight compound having a molecular weight of 400 or less and containing at least two hydrogen atoms capable of reacting with diisocyanate, for example, ethyleneglycol. Aliphatic, alicyclic or aromatic diols such as propylene glycol, 1,4-butanediol, 1,5-pentaneddiol, 1,6-hexanediol and 1,4-bishydroxyethylbenzene. Can be cited. These may be used alone or as a mixture of two or more.

The polyurethane is polymerized by a prepolymer method in which a chain extender is mixed with the prepolymer. As a method of charging the prepolymer to the reactor, a method of simultaneously charging diisocyanate and polymer diol to the reactor,
There is a method in which diisocyanate and polymer diol are reacted in another reactor, and a prepolymer obtained is charged into the reactor. The timing of mixing the prepolymer and the chain extender is important. In the polymerization of polyurethane, the raw material is supplied to a single screw such as a mixing screw having a kneading action or a screw type extruder such as a twin screw extruder. Among them, a twin-screw extruder having an L / D (reactor cylinder length / screw diameter) of 37 or more is preferable, and the twin-screw is filled with polyurethane in the latter half of the L / D of 18 from the entrance side. A twin screw extruder provided with a portion to be formed is preferable. A decompression portion may be provided at the rear of the filling portion to remove air and low molecular components mixed in the polyurethane. By using a twin-screw extruder, kneading is performed efficiently, and the polymerization of polyurethane is performed uniformly.

In such a screw type extruder,
The conditions for adding the chain extender depend on the reaction temperature and the L / D of the extruder, but it is desirable that the L / D of the extruder be introduced in the range of 13 to 22, more preferably 16 to 18. At this stage, the prepolymer reaction between the polymer diol and the organic diisocyanate is almost completed, and the effect of adding a chain extender to the prepolymer is sufficiently obtained. If the chain extender is charged at an early stage, it is undesirable because it reacts with an excess of unreacted organic diisocyanate and generates a large amount of long-chain hard segment aggregates.

The temperature at which the chain extender is introduced is 3 ° C. or higher, preferably 5 ° C. or higher than the melting point of the reaction product of the chain extender and the organic diisocyanate, which is a polyurethane hard segment constituent. It is necessary. By setting the temperature to 3 ° C. or higher, the above-described hard segment-like crystalline foreign matter can be melted and incorporated into the polyurethane long chain,
This makes it possible to suppress the generation of unnecessarily long hard chain segments. Therefore, stable spinning can be performed and the resulting fiber has a high degree of uniformity.

If the temperature is higher than the melting point of the above-mentioned reactant by less than 3 ° C., the foreign matter is transferred to the next zone of the extruder and polymerized before it is completely melted. The effect of suppressing the occurrence of the occurrence is lost. The upper limit of the temperature of the charging section is not particularly limited.
The temperature is preferably lower than the thermal decomposition temperature of the organic isocyanate. In the present invention, "the temperature of the portion where the chain extender is charged" indicates the temperature of the cylinder of the screw type extruder into which the chain extender is charged.

The polyurethane elastic fiber of the present invention may optionally include a matting agent (light shielding agent) such as titanium oxide and zinc oxide,
It can contain antioxidants, ultraviolet absorbers, etc.,
These can be added to any of the polymerization raw materials,
An addition port may be provided in the middle of the reactor for addition.

After the melt spinning, the polyurethane elastic fiber of the present invention can be subjected to a heat treatment in a dry atmosphere, if necessary.

[0020]

EXAMPLES The present invention will be described below in detail, but the present invention is not limited to these examples. The physical property values in the examples were measured and calculated by the following methods. (1) Unevenness of elastic fiber fineness Using a Uster Eveness Tester (manufactured by USTER), at a measuring slit corresponding to the total fineness of the yarn, at a winding speed of 100 m / min (feed speed of 50 m / min). It was measured. The U% value is measured at any five locations on the measurement sample, with two measurements for 20 minutes, and the average value is shown. Further, a fineness variance exceeding ± 25% was referred to as imocov, and the number of imocovs in a given yarn length was counted. (2) Strength (g / denier) and elongation (%) of elastic fiber Using an Instron type tensile tester, under the conditions of a sample length of 10 cm, an initial load of 0.001 g / denier, and a tensile speed of 500% / min. It was measured. The measurement is made at any five points of the measurement sample, and the average value is shown.

Example 1 Polyesterdiol having a molecular weight of 1900 (hereinafter referred to as PMAZ) comprising 3-methyl-1,5-pentaneddiol and azelaic acid, and 4,4'-diphenylmethanediisocyanate (Hereinafter referred to as MDI) in a molar ratio of PMAZ: MDI = 1: 3.3 continuously under a nitrogen seal under a 30φ twin screw extruder (L
/ D = 44), and 1,4-butanediol (hereinafter, referred to as BD) as a chain extender is continuously supplied from the position where L / D is 17 so as to be equimolar to PMAZ. ,
Polymerization was performed by a prepolymer method. At this time, a screw segment having a reverse feed capability was installed at a position where the L / D was 34, a filling portion was provided, and then a vent portion was provided. Also,
The cylinder temperature of the BD charging section was set at 235 ° C.
(The melting point of the gel state material composed of MDI and BD is 230 ° C.
Met. )

The melt-polymerized polyurethane was directly supplied to a spinning nozzle, and melt-spun. Silicon oil was applied as a spinning oil agent and wound up in a cheese at a speed of 500 m / min to obtain 40 denier elastic fibers. The wound cheese was aged in a furnace at a temperature of 80 ° C. for 9 hours under a dry atmosphere at a dew point of −30 ° C., and further aged in a furnace at 25 ° C. and 50% RH. The spinning was extremely stable and no breakage was observed. No stains near the spinneret were found. The replacement cycle of the nozzle pack and the filter was 15 days. Table 1 shows the physical properties of the obtained fiber.

Comparative Example 1 Melt polymerization and melt spinning were carried out in the same manner as in Example 1 except that the temperature of the BD charging portion was changed to 225 ° C. Foreign matter like white crystals was observed in the resin spun from the spinneret, and the yarn was frequently broken and stable spinning was not possible. Further, the pressure of the spinning nozzle pack was increased within a short time, and spinning was disabled. The replacement cycle of the nozzle pack and the filter was 3 days. When the nozzle pack was disassembled and observed when the operation was stopped, a white gel was clogged in the filter portion. When this gel was analyzed, it was a hard segment comprising MDI and BD. Table 1 shows the physical properties of the obtained fibers, although the number of yarn breaks was large.

Comparative Example 2 Melt polymerization and melt spinning were carried out in the same manner as in Example 1 except that the temperature of the BD charging portion was 232 ° C. Foreign matter like white crystals was observed in the resin spun from the spinneret, and although not as much as in Comparative Example 1, thread breakage occurred and stable spinning was not possible. In addition, the pressure of the spinning nozzle pack increased gradually, and spinning became impossible. The replacement cycle of the nozzle pack and the filter was 7 days. Although there was a thread break,
Table 1 shows the physical properties of the obtained fiber.

Example 2 Melting polymerization and melt spinning were carried out in the same manner as in Example 1 except that the temperature of the BD charging portion was 240 ° C. No white crystal-like foreign matter was found in the resin spun from the spinneret, and the spinning could be performed stably. Also, there was no increase in the pressure of the spinning nozzle pack.
The replacement cycle was 16 days. Table 1 shows the physical properties of the obtained fiber.

[0026]

[Table 1]

[0027]

According to the production method of the present invention, a fiber having a high degree of uniformity can be obtained stably for a long period without breakage and no nozzle contamination in the direct polymerization spinning method. In addition, since the life of the spin pack is long, it is advantageous in terms of cost performance.

Claims (1)

[Claims] A polyurethane is produced by continuously supplying a prepolymer obtained by reacting a polymer diol with an organic diisocyanate and a chain extender to a kneading extruder to produce polyurethane elastic fibers. In direct spinning, the temperature of the portion where the chain extender is charged is controlled by the chain extender and the organic diisocyanate.
A method for producing a polyurethane elastic fiber, wherein the melting point is higher than the melting point of the hard segment component of the polyurethane by at least 3 ° C.