JP2619844B2 - Method for producing polyurethane elastic yarn - 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 polyurethane elastic yarn, and more particularly, to a method for melt continuous polymerization,
The present invention relates to a method for producing a polyurethane elastic yarn having excellent heat resistance and uniformity by a direct spinning method.

[0002]

2. Description of the Related Art Conventionally, there are a one-shot method and a prepolymer method as a method for polymerizing a polyurethane elastic material. However, the uniformity of the resulting polymer and, consequently, the spinnability are greatly improved. In addition, the prepolymer method is superior in quality in that yarn breakage in the spinning process can be reduced. Further, there are a batch method and a continuous method as a method for producing a prepolymer, but the batch method has many problems in terms of industrially using continuous equipment. On the other hand, as a continuous method, a method of producing a reaction tube having a static mixing function is disclosed in
Although it is disclosed in Japanese Patent Application Laid-Open No. 9636, there is a problem in that it is mixed uniformly. Generally, a wet spinning method or a dry spinning method is used for producing a polyurethane elastic yarn, and there are relatively few examples in which a melt spinning method is used. This is because polyurethane elastomers generally have poor thermal stability during melting, making long-term stable operation difficult.In addition, polyurethane elastic yarns obtained by melt spinning have poor heat resistance and are subject to deformation at high temperatures. It is considered that there is a problem such as insufficient recovery.

[0003] Several methods have been proposed to improve the thermal properties of urethane yarn obtained by the melt spinning method. For example, Japanese Patent Publication No. 44-20247 proposes a method of adding a special polyfunctional compound during the synthesis of polyurethane. Japanese Patent Publication No. 43-7426 proposes a method of synthesizing a polyurethane using a polyfunctional polyol and melt-spinning the polyurethane. However, a method of improving the heat resistance of polyurethane elastic yarn by giving a cross-linking to polyurethane with these polyfunctional compounds is that if sufficient cross-linking is provided to improve the heat resistance, the softening temperature of the polymer becomes higher, so that the spinning temperature becomes higher. Therefore, there is a problem that the polyurethane tends to be thermally decomposed and spinning becomes unstable.

A method in which a polyisocyanate compound is added to a melted polyurethane elastic material, mixed and spun (Japanese Patent Publication No. Sho 5)
No. 8-46573) has good heat resistance and spinning operability of the obtained polyurethane elastic yarn. However, since the polyurethane is polymerized into pellets and then spun, the two steps of the polyurethane production step and the spinning step are carried out. The process is necessary and complicated.

[0005]

The inventors of the present invention have studied for the purpose of solving the above-mentioned problems, and as a result, have conducted a continuous melt polyaddition reaction of the polyurethane and continuously spun the resulting molten polyurethane directly. As a result, the present inventors have found that a polyurethane elastic yarn having excellent physical properties can be stably manufactured by a simple process, and arrived at the present invention.

That is, in the method for producing a polyurethane elastic yarn of the present invention, a prepolymer obtained by reacting a polyol having an average molecular weight of 500 to 6000 with an organic diisocyanate and a diol having a molecular weight of 500 or less are continuously supplied to a kneading extruder. Polyurethane is produced and then discharged from a spinning head connected to the extruder tip to produce polyurethane elastic yarn.Polyisocyanate compound is added to and kneaded with polyurethane produced by a kneading extruder, and then spun. The isocyanate group content is set to 0.5% by weight or more. By such a method, a polyurethane elastic yarn having better physical properties at high temperatures is produced.

[0007] Polyols having a molecular weight of 500 to 6000 suitable for the present invention are prepared by polycondensation and addition polymerization (for example, ring-opening polymerization).
Alternatively, it is a diol of a polymer compound obtained by polyaddition or the like, and typical examples include polyester diol, polyether diol, polycarbonate diol, and co-condensates thereof (for example, polyester ether diol). These may be used alone or as a mixture of two or more.

The polyester diols include propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-methyl 2-10 carbon atoms such as propanediol
Alkane diols or mixtures thereof with glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid or other aliphatic or aromatic dicarboxylic acids having 4 to 12 carbon atoms or mixtures thereof The resulting saturated polyester diols or polylactone diols such as polycaprolactone glycol, polypropiolactone glycol and polyvalerolactone glycol are preferably used. As the polyether diol, polyalkylene ether diols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol are preferably used.

The above-mentioned polycarbonate diols include those having 2 to 12 carbon atoms such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol and 1,10-decanediol.
And aliphatic or alicyclic diols, or a polycarbonate diol obtained by subjecting diphenyl carbonate or phosgene to polycondensation with a mixture thereof is preferably used.

The average molecular weight of these polyols is 50
It is preferably from 0 to 6000, and more preferably from 500 to 2500. If the average molecular weight is too small, the compatibility with the organic diisocyanate is too good and the elasticity of the produced polyurethane is poor.On the other hand, if the average molecular weight is too large, the compatibility with the organic diisocyanate becomes poor and mixing in the polymerization process does not work well, A lump of a gel-like substance is generated or a stable polyurethane cannot be obtained.

The molecular weight used in the present invention is 500
The low molecular weight diols less than ethylene glycol, propylene glycol, 1,4-butanediol, 1,5
Aliphatic, alicyclic or aromatic diols such as -pentane glycol, 3-methylpentane glycol, 1,6-hexanediol, and 1,4-bishydroxyethylbenzene. These may be used alone or in combination of two or more.

The organic diisocyanate used in the present invention includes 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, 2,2'-dimethyl-isocyanate.
4,4'-diphenylmethane diisocyanate, 1,3
-Or 1,4-bis (isocyanatomethyl) benzene, 1,3- or 1,4-bis (isocyanatomethyl) cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, aromatic, alicyclic or aliphatic such as isophorone diisocyanate Group diisocyanates. These organic diisocyanates may be used alone or as a mixture of two or more.

According to the method described in JP-A-2-47306, the above-mentioned organic diisocyanate, high-molecular diol and low-molecular diol are reacted at once (one-shot method). Due to the difference in reactivity between the polymer diol and the polymer diol, a large number of lumps are formed due to the crystalline hard segments, and the viscosity also varies greatly. However, by using a so-called prepolymer method in which the organic diisocyanate and the polymer diol are reacted in advance in a molar ratio of usually from 4: 1 to 2: 1, more preferably from 2.5: 1 to 2: 1. 1 kg
Lumps can be significantly reduced to 500 or less (preferably 200 or less) per mass. Such a prepolymer can be suitably obtained by a method in which the above raw materials are mixed in advance by a high-speed mixer, and then generated while rectifying and flowing down by a perforated plate having a rectifying action provided in a reaction tube. For example, the raw materials are supplied at a predetermined molar ratio using, for example, a metering pump, and the number of rotations is 1,000 to 5,000 r.
pm, preferably at 2000 to 4000 rpm. The raw material uniformly mixed by the high-speed mixer has an open area ratio of 3 to 60%, preferably 5 to 40%.
Is supplied to a reaction tube provided with three or more perforated plates. The L / D of the reaction tube is usually in the range of 2 to 30, preferably 3 to 2
0. The average residence time in the reaction tube is usually 15 to 12
0 minutes, preferably 30 to 80 minutes, and the reaction temperature is 50 to 1 minute.
20 ° C, preferably 70 to 90 ° C. It is preferable to control the supply of the raw material to the reaction tube so that the level on the uppermost perforated plate is constant, for example.

In the polymerization of the polyurethane elastomer, the prepolymer and the low molecular weight diol are first uniformly mixed at a temperature of 100 ° C. or lower, and then supplied to a screw type extruder for polymerization. As a screw type extruder, a single screw or a twin screw extruder such as a mixing screw having a kneading action can be used, and a twin screw is particularly preferable. A high-quality urethane resin having a low viscosity variation and an extremely small amount of lump by melt-polymerizing at a rotation speed of 30 to 300 rpm, a cylinder temperature of a polymerization zone of 210 to 245 ° C., and a tip extrusion pressure of 20 to 100 kg / cm ^2. Is obtained. The average residence time depends on the screw diameter and L / D, but is usually continuously extruded for 2 to 20 minutes.

When the polyurethane elastic fiber is produced according to the present invention, a known coloring agent, antioxidant,
A slipping agent, a weathering agent, a heat-resistant agent and the like can be added to the screw-type extruder or dispersed in the prepolymer.

In the present invention, the active isocyanate group content of the polyurethane discharged from the kneading extruder is set at 0.5.
% By weight or more, more preferably 0.9% by weight or more.
When the isocyanate group concentration is low, the heat resistance of the obtained polyurethane elastic yarn decreases. The content of active isocyanate groups in the polyurethane is measured by dissolving the polyurethane in dimethyl sulfoxide (DMSO) and reacting with excess dibutylamine, and then back titrating residual dibutylamine with an ethanolic solution of hydrochloric acid to obtain [NCO]. Converted weight%
Expressed by

As a method for increasing the content of active isocyanate groups, the ratio (R) of the number of moles of isocyanate groups of the organic diisocyanate compound used as the raw material for polymerization to the number of moles of hydroxyl groups of polyol and diol is preferably 1.0 or more, and more preferably 1. There are a method of spinning before the completion of the polyaddition reaction as a value of 02 to 1.05, a method of adding and mixing a polyisocyanate compound to a polyurethane in which the polyaddition reaction has proceeded and the isocyanate group concentration has been reduced, and spinning in the present invention. Method is adopted. Since the method of adding the polyaddition before completion of the polyaddition reaction spins the polyurethane before the molecular weight is not sufficiently large, the spinnability is poor, and the wound filaments may be liable to stick. On the other hand, a method of adding a polyisocyanate compound to a polyurethane having undergone polymerization is more preferable because of good spinnability.

The polyisocyanate compound applied to the present invention is a compound having at least two isocyanate groups in the molecule. For example, a polyol used for the synthesis of polyurethane is added with and reacted with at least twice the amount of an organic diisocyanate. Can be combined. Further, a trifunctional or higher functional polyol can also be used. The number of isocyanate groups contained in one molecule of the polyisocyanate compound is 2 to 4, particularly preferably 2 diisocyanate compounds. If the amount of isocyanate groups is too large, the viscosity of the polyisocyanate increases and handling becomes difficult.

The polyisocyanate compound has an average molecular weight of usually 500 or more, particularly preferably from 1,000 to 3,000. If the average molecular weight is smaller than this, when adding to and mixing with the molten polyurethane, the vapor pressure is high at that temperature, which is inconvenient in operation, and because the activity is too large, it is liable to be deteriorated during storage and uneven during spinning. It is easy to cause a reaction. On the other hand, if the molecular weight is too large, it is necessary to increase the amount of the polyisocyanate compound to be added, and spinning after mixing tends to be unstable, which is not preferable.

Examples of suitable polyisocyanate compounds include polyols having a molecular weight of 500 to 3,000, such as polyethers, polyesters, polylactones, polyesteramides, polycarbonates, and block copolymers thereof, and the like. Compounds obtained by reaction with diisocyanates such as p, p'-diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and the like.

The molecular weight of the polyisocyanate compound used in the present invention means an apparent molecular weight calculated from the isocyanate group content measured by the amine titration method.

The addition amount of the polyisocyanate compound of the present invention is 3 to 30 with respect to the mixture of the thermoplastic polyurethane elastic material to be spun and the polyisocyanate compound.
(% By weight) is preferable, and particularly preferably, 5 to 20%.
(Weight)%. The polyurethane discharged from the spinning nozzle has an isocyanate group content of 0.5% by weight or more, preferably 1.0% by weight or more. The addition amount varies depending on the type of the polyisocyanate compound to be used. However, if the addition amount is small, the thermal properties of the target urethane yarn are insufficiently improved, which is not preferable. On the other hand, if the amount is too large, the spinning becomes unstable, which is not preferable.

A method of adding and mixing a polyisocyanate compound to a polyurethane in a molten state is performed by using an apparatus for mixing and spinning using a rotary kneader (for example, JP-B-46-432).
No. 46) can be used, but it is more preferable to use a mixing device having a static kneading element. Known mixing devices having a static kneading element include Kenics'"StaticMixer", Sakura Seisakusho's "Scare Mixer", Tsubaki Kogyo's "Honeycomb Mixer", and Tokushu Kika Kogyo's "TK-ROSSISG Mixer". Can be used. The shape and number of these static kneading elements vary depending on the conditions used, but are selected so that kneading is completed sufficiently before the polyurethane elastomer and the polyisocyanate compound are discharged from the spinneret. .

[0024]

The present invention will be described more specifically with reference to the following examples. The 190 ° C. elongation recovery rate for evaluating the heat resistance of the polyurethane elastic yarn is measured as follows. (1) 100 mm of polyurethane elastic yarn is stretched to 130 mm and left in an oven at 190 ° C. for 1 minute. (2) Let stand at 130 ° C. for 2 minutes at 20 ° C. (3) Two minutes after releasing the extension, the length L (mm) is measured. 190 ° C. elongation recovery rate (%) = (130−L) / (130
-100) x 100

Example 1 Polyester diol of adipic acid and 1,4-butanediol (polybutanediol adipate: PB
A) a mixture of polyester diol (polyhexanediol adipate: PHA) of adipic acid and 1,6-hexanediol (PHA and PHA in a molar ratio of 1: 1) and a polyol having a molecular weight of 2,000 and 66.5.
Part and 4,4'-diphenylmethane diisocyanate (M
DI) 27.1 parts of each pre-melted at 70 ° C. were reacted for 2 hours in a preparation tank with a stirrer maintained at 85 ° C. to prepare a prepolymer.

Next, 1,4-butanediol (1,4-BD) was prepared in a storage tank at 80 ° C. as a low molecular weight diol. 13.7kg /
At a time of 1.3 kg / hour, the mixture was continuously supplied and mixed by a high-speed mixer at 4000 rpm, and then injected into a 45φ twin-screw extruder (rotating in the same direction) to carry out polymerization. The cylinder temperature of the twin screw extruder was 210 ° C. The relative viscosity of the polymer collected at the extruder tip was 2.10, and the isocyanate content was 0.03%.

On the other hand, dihydroxy poly ε having a hydroxyl value of 150
1500 parts of caprolactone and 1000 parts of p, p'-diphenylmethane diisocyanate were reacted at 80 ° C. to obtain a viscous polyisocyanate compound. This had an isocyanate content of 6.74% and a molecular weight of 1250.

The polymer produced is divided at the tip of the extruder, and a part of the polymer is discharged into water from a 2.4φ die to form pellets. The other part was injected with a polyisocyanate compound, kneaded using a mixing device having a static kneading element, weighed with a gear pump, and using a nozzle having a diameter of 1.0 mm and a winding speed of 5 mm.
A 40 denier monofilament was spun at 00 m / min. Table 1 shows the results of spinning while changing the amount of the polyisocyanate compound added to the polyurethane.

[0029]

[Table 1]

[0030] The yarn quality was measured after standing for 2 days at room temperature after spinning. The lump in the yarn is 1000
The number was good at 1 or less in m.

Example 2 A prepolymer was prepared by mixing 719 parts of polytetramethylene glycol having a hydroxyl group at both terminals having a molecular weight of 1,000 and 258 parts of 4,4'-diphenylmethane diisocyanate at 80 ° C.

Then, 1,4-butanediol as a low molecular weight diol was heated to 80 ° C. and supplied to the twin-screw extruder used in Example 1 through separate injection holes. The cylinder temperature of the extruder was set at 220 ° C. The feed rate of the prepolymer was kept constant at 14.5 kg / hour, and the spinning was performed while changing the isocyanate content in the polymer by changing the feed rate of 1,4-butanediol. Table 2 shows the results.

[0033]

[Table 2]

The isocyanate content immediately after being discharged from the nozzle increased when the supply amount of 1,4-butanediol was reduced. On the other hand, the heat resistance of the filament measured after standing at room temperature for 2 days after spinning increased with the isocyanate content.

Example 3 The polyol used in Example 1 was used at 13.4 kg / h, MD
I was fed at 5.4 kg / hr and mixed with a high-speed mixer rotating at 4000 rpm, then the mixture was continuously 200 mm in inner diameter and 800 mm in height so that the residence time was 60 minutes.
A perforated plate having an aperture ratio of 40% and a diameter of 40 mm was supplied to a reaction tube provided with six sheets, and the prepolymer was discharged from the lower portion at a rate of 18.8 kg / hour (see FIG. 2). Next, after polymerizing polyurethane in the same manner as in Example 1-3, a polyisocyanate compound was added, and a monofilament was spun.

Example 4 A prepolymer was produced in the same manner as in Example 3 except that polytetramethylene glycol was used as a polyol. Then, a polyurethane was polymerized, and then a polyisocyanate compound was added to spin a monofilament. Table 1 shows that the polyurethane elastic yarns of Examples 3 and 4 are more excellent in quality.

[0037]

According to the production method of the present invention, it has become possible to produce polyurethane elastic yarn of excellent quality stably and continuously. In addition, since this polyurethane elastic yarn does not contain lumps even when manufactured continuously for a long period of time, it is useful without causing defects such as perforations in knitted products such as stockings, swimwear, and inners, and weft steps in fabrics. is there.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an apparatus suitable for the production method of the present invention.

FIG. 2 is a schematic view of an example of an apparatus for prepolymer purification suitable for the production method of the present invention.

Claims (3)

(57) [Claims] 1. A polyurethane obtained by continuously feeding a prepolymer obtained by reacting a polyol having an average molecular weight of 500 to 6000 with an organic diisocyanate and a diol having a molecular weight of 500 or less to a kneading extruder, and then forming a polyurethane at the tip of the extruder. A method for producing a polyurethane elastic yarn, characterized in that when the polyurethane elastic yarn is directly spun by discharging from a connected spinning head, the content of active isocyanate groups of the discharged polyurethane is 0.5% by weight or more. 2. The method according to claim 1, wherein a polyisocyanate compound is added to the polyurethane produced by the kneading extruder, kneaded, and then spun. 3. A prepolymer in which a polyol and an organic diisocyanate are preliminarily mixed by a high-speed mixer, and then rectified by a perforated plate having a rectifying action disposed in a reaction tube.
2. The method according to claim 1, wherein the material is generated while flowing down.
The described method.