JPH02307971A - Production of water-absorbing polyester fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having excellent water-absorption, fibrillation resistance, etc., by producing a specific highly oriented hollow fiber with a polyester containing a sulfonic acid metal salt and treating the hollow fiber with an aqueous solution of an alkali compound. CONSTITUTION:In the synthesis of a polyester containing an alkylene terephthalate as a main unit, a sulfonic acid metal salt compound of formula (M and M, are metal; R is H or ester forming functional group; n is 1 or 2) is added in an amount of 0.3-15mo% based on the acid component. The polyester is melt-spun to obtain a highly oriented hollow fiber having a crystal size on (100) plane of >=40Angstrom , amorphous orientation degree na of 0.09-0.03 and an alkali thinning parameter K of >=0.3. The objective fiber containing fine pores distributed on the crosssection of the fiber, oriented in the direction of fiber axis and partly connected to the hollow part of the fiber can be produced by treating the hollow fiber with an aqueous solution of an alkali compound until 2-50wt.% of the fiber is dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing polyester fibers having water absorption properties. More specifically, it has excellent water absorption and wear resistance (
The present invention relates to a method for producing water-absorbing polyester fibers having special micropores and having significantly improved fibril resistance.

(Prior art) Polyester has many excellent properties and has a wide range of uses as a synthetic fiber. However, since polyester fiber is hydrophobic, it is required to have water absorption and hygroscopic properties. Its use in the field is restricted.

Conventionally, as a method for imparting water absorbency to polyester fibers, a method has been proposed in which a hydrophilic compound, such as a polyalkylene glycol and a sulfonic acid metal salt, is blended before fiber formation, but the fibers obtained by such a method are All had insufficient water absorption.

Furthermore, hollow fibers made of modified polyester obtained by adding a specific metal sulfonate, such as sodium 3-carbomethoxy-benzenesulfonate-5-sodium carboxylate, are treated with an aqueous alkali solution to have a special shape. However, a method has also been proposed (Japanese Patent Publication No. Sho 61-31231, etc.) in which water absorption is improved by forming micropores in which at least some of the holes are open. However, although the polyester fibers obtained by this method have excellent water absorption properties, the requirements for dust-free clothing used in IC manufacturing sites have become stricter in recent years, so further improvement in fibril resistance is desired. ing.

As a method to improve fibril resistance, it is possible to reduce the number of micropores by reducing the amount of sulfonic acid metal salt added or by using mild conditions for treatment with an alkaline aqueous solution in the method described above. This method cannot be put to practical use because the water absorbency is also significantly reduced.

(Object of the invention) The object of the present invention is to provide a method for producing polyester fiber that has excellent water absorption comparable to that of natural fibers and has dramatically improved fibril resistance and abrasion and discoloration resistance. It is in.

(Structure of the Invention) In order to achieve the above-mentioned object, the present inventors have intensively studied the fibril resistance and microstructure of polyester fibers having micropores, and found that only in the case of polyester fibers having a specific structure. It was discovered that water absorption and abrasion resistance (fibril resistance) can be achieved at the same time, and the present invention was achieved.

That is, according to the present invention, when synthesizing a polyester whose main structural unit is alkylene terephthalate, a sulfonic acid metal salt compound represented by the following general formula (I>) is added to the polyester at any stage until the polycondensation reaction is completed. The following (a) is added by adding 0.3 to 15 mol% to the acid component, and melt-spinning the obtained polyester.
- Highly oriented hollow fibers that simultaneously satisfy the formula (a) (100) crystal size (X): 40 people ≦X (BL consumption part orientation degree (∆na): 0.03≦∆na≦ 0.09 (e) Alkali weight loss parameter (K): 0.3≦Then, the hollow fiber is treated with an aqueous solution of an alkali compound to elute 2 to 50% by weight from the hollow fiber. are scattered in the cross section of the fiber and arranged in the fiber axis direction,
There is also provided a method for producing a water-absorbing polyester fiber, which is characterized by forming micropores, some of which communicate with the hollow portion.

Polyester as used in the present invention includes terephthalic acid as the main acid component, and alkylene glycols having 2 to 6 carbon atoms, such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol,
The target is a polyester whose main structural unit is alkylene terephthalate and whose main glycol component is at least one glycol selected from hexamethylene glycol, particularly preferably ethylene glycol and tetramethylene glycol. It may also be a polyester in which part of the terephthalic acid component is replaced with another difunctional carboxylic acid component, and/or a polyester in which part of the glycol component is replaced with a diol component other than the above-mentioned glycol. good.

Examples of difunctional carboxylic acids other than terephthalic acid used here include isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, adipic acid, sebacic acid, and 1,4-cyclohexane dicarboxylic acid. Aromatic, aliphatic, and alicyclic difunctional carboxylic acids can be mentioned. Examples of diol compounds other than the above-mentioned glycols include aliphatic, alicyclic, and aromatic diol compounds such as cyclohexane-1,4-dimetatool, neopentyl glycol, bisphenol A, and bisphenol S.

Such polyesters may be synthesized by any method. For example, in the case of polyethylene terephthalate, usually terephthalic acid and ethylene glycol are directly esterified, a lower alkyl ester of terephthalic acid such as dimethyl terephthalate is transesterified with ethylene glycol, or terephthalic acid and ethylene glycol are transesterified. The first stage reaction is to react with terephthalic acid to produce a glycol ester and/or its low polymer, and the first stage reaction product is heated under reduced pressure until the desired degree of polymerization is achieved. It is produced by a second step of polycondensation reaction.

The sulfonic acid metal salt compound used in the present invention is represented by the following general formula (1). In the formula, M and M' are metals, and M is particularly an alkali metal, an alkaline earth metal,
Mn 1/2, Co 1/2 or 7. o 1/2 is preferred, especially Li, Na, K, Ca 1/2,
Mg 1/2 is particularly preferred, and M' is particularly preferably an alkali metal or alkaline earth metal, especially Li
, Na, K, Ca 1/2, and Mg 1/2 are particularly preferred. M and M' may be the same or different. n
is 1 or 2.

R is a hydrogen atom or an ester-forming functional group, and the functional group is -COOR' (where R' is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group) or -Co
-EO(CH2) t ) pOH (where 1 is an integer of 2 or more, p is an integer of 1 or more), etc. are preferred.

Preferred specific examples of such sulfonic acid metal salt compounds include 3-carbomethoxybenzenesulfonic acid Na-5
-Sodium carboxylate, 3-carbomethoxy-benzenesulfonic acid Na-5-carboxylic acid K, 3-carbomethoxy-
-5-carboxylic acid K, 3-hydroxyethoxycarbonyl benzenesulfonic acid Na-5 to benzenesulfonic acid
- Sodium carboxylate, Na 3-carboxy benzenesulfonate, Na 5-carboxylate, Na 3-hydroxyethoxycarbonyl benzenesulfonate, Mg 5-carboxylate 1/2, Na-3,5-dicarboxylate benzenesulfonate Examples include Na acid, Na benzenesulfonic acid, Mg172-3,5-dicarboxylic acid, and the like.

The above-mentioned sulfonic acid metal salt compounds may be used alone or in combination of two or more. It may be added at any stage before the polycondensation reaction of the polyester is completed; for example, it may be added to the raw material of the polyester.
It may also be added during the synthesis of polyester. In any case, it is preferable to mix the components in a molten state after addition.

If the amount of the above-mentioned compound added is too small, the water absorbency and hygroscopicity of the hollow fibers finally obtained will be insufficient, whereas if it is too large, it will be difficult to obtain a polyester with a sufficient degree of polymerization. Therefore, the amount added should be in the range of 0.3 to 15 mol%, preferably 0.5 to 5 mol%, based on the acid component constituting the polyester to be added.

In the present invention, it is important to melt-spun the polyester obtained as described above to obtain a highly oriented hollow fiber that simultaneously satisfies the following formulas (a) to (C1), and then to perform an alkali weight loss treatment.

(a) (100) crystal size (X): 40 people ≦X 7(b) Amorphous part orientation degree (Δna): 0.03≦Δna≦0.09 (C) Alkali weight loss parameter (K) 2 0.3≦ Here, K is defined as follows.

75 de/fJ in a boiling NaOH aqueous solution of 35 g/fJ
If the weight loss rate (%) after soaking a 36fil (single yarn 2.1de) round cross-section (perfect circle) multifilament (tube knit) with no hollow part for 30 minutes is ΔW/WX100, it is expressed by the following formula. It will be done.

K = 1/30XΔW/WX 100 Since the actual alkali weight loss rate is proportional to the specific surface area (surface area per unit weight) of the fiber, it changes depending on the single yarn denier, density, and cross-sectional shape. Therefore, it is necessary to convert to the value under the above conditions.

That is, if the specific surface area under the above conditions is So, the specific surface area of the measurement sample is S, and the apparent alkali raw material parameter when the measurement sample is reduced in alkali according to the above conditions is S.

K = -X K' becomes.

As described above, the highly oriented hollow fibers used in the present invention have a larger crystal size than ordinary polyester fibers,
Because the degree of orientation of the amorphous portion is low and the alkali weight loss parameter is large (usually about 0.2), the final water-absorbing polyester with micropores has excellent abrasion resistance and does not generate fibrils when washed, etc. This results in a significant decrease.

Here, if the crystal size (X) is less than 40 or the degree of orientation of the amorphous part (Δna) exceeds 0.09, the entanglement of the amorphous molecular chains (tie molecular chains) connecting the crystals should be considered. As a result, wear resistance decreases and fibrillation becomes more likely to occur. On the other hand, when Δna is less than 0.03, the material is easily deformed during the weaving and knitting process, and the quality of the final woven or knitted product is degraded.

In addition, when the alkali weight loss parameter is less than 0.3, that is, when the alkali weight loss rate becomes slow, this is thought to be because the mobility of the molecular chains in the amorphous region decreases (the cohesiveness of the molecular chains improves). This decreases the elasticity and makes it easier for fibrillation to occur.

゛It should be noted that as the alkali weight loss parameter increases by 0.3 or more, the fibril resistance improves, but if it increases to 0.8 or more, it tends to reach a plateau, so it is particularly preferably 0.5 to 0.8.

In addition, among such highly oriented hollow fibers, the following (d) to (
A material that satisfies the fiber characteristics f) is preferable because a woven or knitted fabric that is uniform and has a soft feel can be obtained in the end.

(d) Birefringence (Δn) + 0.05<80 (e) Thermal stress peak (ST): 100°C≦5T (f) Diving shrinkage (BWS): BWS≦15% Here, Δn is 0 If the ST is less than .05 or the BWS exceeds 15%, the level dyeing property will deteriorate or shrinkage spots will tend to occur, and if the ST is less than 100°C, the texture of the resulting woven or knitted fabric will be hard. There is a tendency to become a thing.

Among these fiber properties, in particular Δn is 0.08 to 0.1.
4.ST is 110-130℃ and BWS is 5-10%
It is preferable that

Highly oriented hollow fibers having the characteristics described above can be easily and industrially obtained by, for example, high-speed spinning using the method shown in FIG. That is, in FIG. 1, the polyester containing the aforementioned sulfonic acid metal salt compound was melted and discharged from a spinneret (1) in which a hollow space was formed, and was cooled and solidified by cooling air blown from a cooling device (3). After that, it is lubricated by the lubricant applicator (4), then taken over by the first godet roller (5), and then passed through the godet roller (6), and then transferred to the winder (7).
Wind it up.

At this time, the molten polymer maintained at 285 to 300°C is passed from a spinneret heated to 290 to 300°C.
Discharge into an atmosphere heated to 250-300°C at a position 10 mm below the face of the mouthpiece, and continue at least 9 mm below the face of the mouthpiece.
After cooling and solidifying by blowing cooling air over a length of 60 cm or more from the 0 mm point, the draft rate is 150 to 40.
0 at 3500 m/min or more (preferably 4000 to 80 m/min
00 m7 minutes), the crystal size is 4
Polyester fibers having a diameter of 0 Å or more, an amorphous orientation degree of 0.03 to 0.09, and an alkali weight loss parameter of 0.3 or more can be obtained industrially.

In addition, if the take-up speed (■1) is 8000 m or less, the stretching ratio is <1.8-vt/10000)
It is preferable that the stretching be performed within a range of not more than 2 times. However, within the above range, not all fibers have the fiber properties that are essential in the present invention, and it is necessary to set the spinning and drawing conditions appropriately within this range.

Furthermore, the fiber properties also change depending on the melt viscosity of the polymer, the shape of the spinneret hole, the cooling conditions of the spun yarn, and the heat treatment after drawing. Therefore, it is important to select other spinning conditions appropriately.

The above-mentioned spinning and drawing process does not necessarily need to be divided into two processes, and may be continuous, that is, a direct drawing method may be adopted. In this case, the advantage of process rationalization can also be obtained.

In the present invention, the spinning conditions are further adjusted so that the fiber properties of the resulting fibers are as follows (satisfying the ladle is:
This is preferable because it improves the feel of the woven or knitted fabric finally obtained.

(a) Young's modulus (E): 400 < E < 1200 g/mm2 In addition, in Fig. 1, stretching is performed between the first godet roller (5) and the second godet roller (6), and the second godet roller is heated. It is also preferable to perform heat treatment as a roller and then wind it up.

The stretching ratio and heat treatment temperature in this method should be adjusted so that the resulting fibers simultaneously satisfy the following fiber properties (b) to (d), as this will improve the feel of the final woven or knitted fabric. preferable.

(b) Birefringence (Δn): 0. l≦Δn (darkness 10
Strength at % elongation (S1o): 2. Og/de≦5I
O(d) Boiling water shrinkage (BWS): 5%≦BWS In the present invention, if the hollowness of the highly oriented hollow fibers obtained in this way is too low, the effect of improving water absorption and hygroscopicity by making them hollow will decrease. If it is too high, the hollow part will be easily soaked, and once soaked, the water absorption and hygroscopicity will decrease. is preferably 5 to 50%, particularly 8 to 20%. Generally, the higher the hollowness ratio,
Since fibril resistance tends to decrease, it is preferable to adjust it appropriately depending on the purpose of use.

Further, the outer shape and the hollow part shape in the cross section of the hollow fiber may have any shape. For example, when the outer shape and the hollow part are both circular, one of the outer shape and the hollow part is circular and the other is irregularly shaped. In this case, both the outer shape and the hollow portion may have similar or dissimilar shapes. Further, there is no need to particularly limit the size of the outer diameter.

Furthermore, when spinning hollow fibers, a two-layer or more multilayer composite hollow fiber may be obtained by using a modified polyester to which the above compound is added and an unmodified polyester to which the compound is not added. When spinning composite hollow fibers to be bent, it is necessary to arrange the modified polyester component to which the above-mentioned compound is added so as to reach the hollow portion from the fiber surface.

Part of the modified polyester can be easily removed from the hollow fibers thus obtained by subjecting them to stretching heat treatment or false twisting as necessary, or by immersing them in an aqueous solution of an alkaline compound after forming them into a fabric. can be done.

The alkaline compounds used include sodium hydroxide,
Examples include potassium hydroxide, tetramethylammonium hydroxide, sodium carbonate, potassium carbonate, and the like. Among these, sodium hydroxide and potassium hydroxide are particularly preferred.

The concentration of such an aqueous solution of an alkali compound varies depending on the type of alkali compound, processing conditions, etc., but is usually 0.01.
A range of 40% by weight is preferred, and a range of 0.1 to 30% by weight is particularly preferred. The treatment temperature is preferably in the range of room temperature to 100°C, and the treatment time is usually in the range of 1 minute to 4 hours. Further, the amount of modified polyester to be eluted and removed by treatment with this aqueous solution of an alkali compound should be in the range of 2 to 50% by weight based on the weight of the fiber. By processing in this manner, polyester fibers having micropores that are scattered in the cross section of the hollow fibers, arranged in the fiber axis direction, and some of which communicate with the hollow portion can be obtained.

Whether the micropores are connected or not can be determined by measuring the cross section of the fiber at 3000 mm.
It can be observed at a magnification of about 2 times. In particular, the simplest and easiest way to confirm the state of communication from the outer surface of the fiber to the hollow part of the micropores is to observe a single fiber several centimeters in length using an ordinary optical microscope, and then An example of this is a test in which one drop of water (more preferably dyed water) is added to the tube, and the state of communication of the micropores can be easily confirmed by checking whether the water reaches the hollow portion or not.

The micropores possessed by the polyester fiber of the present invention are scattered in the cross section of the fiber, arranged in the fiber axis direction, and have a diameter of 0.01 to 3 μm and a length of 50 times or less than the diameter. It is desirable that there be. The diameter of this micropore is 0.01
If the diameter is less than 3 μm, the water absorption effect tends to decrease, and the diameter is less than 3 μm.
If it exceeds μm, it is difficult to obtain sufficient fiber strength. Furthermore, if the length of the micropores becomes longer than 50 times the diameter, the strength and fibril resistance of the fiber will decrease, which is not preferable.

Note that the hollow fibers obtained by the method of the present invention may contain optional additives, such as catalysts, color inhibitors, heat resistant agents, flame retardants, optical brighteners, matting agents, colorants, and inorganic fine particles, as necessary. etc. may be included.

(Function) As described above, according to the present invention, it is possible to obtain polyester fibers that have excellent water absorption properties and have significantly improved abrasion resistance and fibril resistance. Although the details of this reason are still unknown, it is estimated as follows.

First, the highly oriented polyester hollow fibers used in the present invention are
Since it is composed of polyester containing a specific sulfonic acid metal salt, a part of it is eluted and removed by treatment with an alkaline aqueous solution, forming micropores. Moreover, the micropores are arranged in the fiber axis direction and have a long and narrow shape, and some of them are connected to reach the hollow part, so there is no major deterioration of the fiber properties and it exhibits good water absorption. Polyester fibers are obtained.

゛ Also, because it has a special microstructure, that is, the crystal size is large and the degree of orientation of the amorphous part is small, the entanglement of the amorphous molecular chains (tie molecular chains) that connect the crystals. As a result, it becomes difficult to form fibrils even when stress such as friction is applied.

Furthermore, it has a high alkali weight loss parameter, ie, the molecular chain restraint of the amorphous region is reduced. In other words, since the polyester molecular chains in the amorphous region are movable, even if stress such as friction is applied, it is absorbed by the movement of the amorphous molecular chains, and fibrillation can be avoided.

(Effects of the Invention) As described above, according to the present invention, water-absorbing polyester fibers that are extremely unlikely to generate fibrils can be obtained. Therefore,
This is of great significance, as it can now be applied to the field of dust-free clothing, which was difficult to apply with conventional water-absorbing fibers due to the problem of fibril formation, sports clothing that requires frequent washing, golf wear, etc.

(Example) A detailed explanation will be given below with reference to examples.

Each characteristic value in the examples was measured by the following method.

Water holding rate measurement method A sample obtained by drying a fabric is immersed in water for 30 minutes or more, and then dehydrated for 5 minutes in a dehydrator of a household electric washing machine. It was calculated from the weight of the dry sample and the weight of the sample after dehydration using the following formula.

Sample weight after dehydration - Dry sample weight - Abrasion resistance> According to JIS L1096-6, 17.5E method (Martinsor method). However, if the number of continuous frictions is 2000 times and 5
000 times, and wool was used as the standard friction cloth.

The evaluation was done on a five-point scale from grade 5 (good): no discoloration to grade 1 (poor): Chinese cabbage.

Degree of orientation of amorphous part (Δna)> The degree of orientation of the amorphous portion (Δna) was determined from the following formula.

Δn-fc-Δnc0-Xv where, Δn; birefringence (acoustic propagation velocity method) Xv; crystallinity (density method) fc; degree of crystal orientation (X-ray refraction method) .212 (Polyester) Crystal Size (X)> In the intensity distribution curve measured by X-ray wide-angle diffraction method, find the half width of (010) (1001) and calculate the crystal size using Scherrer's formula.

Texture> The obtained multifilament was knitted into a tube, dyed using a disperse dye in a conventional manner, washed with water, dried, and then set at 180° C. for 1 minute to prepare a sample for texture evaluation.

The texture was evaluated by visual observation and touch.

Example 1 197 parts of dimethyl terephthalate, 1 part of ethylene glycol
24 parts, 3-carbomethoxybenzenesulfonic acid Na
-4 parts of Na-5-carboxylate (1.3 mol% based on dimethyl terephthalate), 0.11 parts of calcium acetate monohydrate
8 parts were placed in a glass flask equipped with a rectification tower, and transesterification was carried out according to a conventional method. After the theoretical amount of methanol had been distilled off, the reaction product was placed in a polycondensation flask equipped with a rectification tower, and 0% trimethyl phosphate was added as a stabilizer. .112 parts and 0.079 parts of antimony dioxide as a polycondensation catalyst were added, and the mixture was heated at a temperature of 280°C for 20 minutes under normal pressure and under a reduced pressure of 39 mmHH.
After reacting for 5 minutes, the reaction was continued for 80 minutes under high vacuum. The final internal pressure was 0.38 mmHg, the intrinsic viscosity of the obtained modified polymer was 0.640, and the softening point was 258°C.

After the reaction was completed, the modified polymer was made into chips according to a conventional method.

After drying the obtained chips, they were cut into widths of 0.
It was extruded at a melt temperature of 300° C. and a spinneret temperature of 290° C. from a spinneret having a spinning hole having an arc-shaped opening with circular slits of 0.07 mm in diameter and 1.0 mm in diameter closed at four locations. The melt-extruded filaments were taken up by the first godet roller (5) shown in FIG. At this time, heat the second godet roller to 120°C and heat set it at the same time.
A multifilament yarn with a de/20fil and a hollow ratio of 15% was obtained.

Next, the obtained threads were made into a plain weave fabric with a gray density of 40 threads/inch, scouring and presetting (170°C x 1
After that, weight loss treatment was carried out in a 3.5% aqueous sodium hydroxide solution at boiling temperature so that the weight loss rate was 20% by weight.

Next, Sumikalon Navy Blue (6%) manufactured by Sumitomo Chemical ■
owf) as a dye, high-pressure dyeing was carried out at 130°C for 45 minutes,
Then, a final set (160'CX 1 minute) was performed.

Table 1 shows the results of the evaluation of the above fiber and fabric samples.

[Brief explanation of the drawing]

FIG. 1 is a route diagram showing an example of a method for manufacturing highly oriented hollow fibers used in the present invention.

Claims (2)

[Claims] (1) When synthesizing a polyester whose main structural unit is alkylene terephthalate, a sulfonic acid metal salt compound represented by the following general formula (I) is added at any stage until the polycondensation reaction is completed. etc.▼...(I) In the formula, M and M' are metals, n is 1 or 2, and R is a hydrogen atom or an ester-forming functional group 0.3 to 15 mol based on the acid component of the polyester % and melt-spun the obtained polyester to form a highly oriented hollow fiber that satisfies the following formulas (a) to (c) at the same time: (a) Crystal size (X) of (100) plane: 40 Å≦X (b) Amorphous part orientation degree (Δna): 0.03≦Δna≦0
．． 09 (c) Alkali weight loss parameter (K): 0.3≦K Next, the hollow fiber is treated with an aqueous solution of an alkaline compound to elute 2 to 50% by weight from the hollow fiber, thereby reducing the cross-section of the hollow fiber. Scattered on the surface, arranged in the fiber axis direction,
A method for producing a water-absorbing polyester fiber, which comprises forming micropores, some of which communicate with the hollow portion. (2) The method for producing water-absorbing polyester fibers according to claim (1), wherein the highly oriented hollow fibers simultaneously satisfy the following formulas (d) to (f). (d) Birefringence (Δn): 0.05<Δn (e) Thermal stress peak (ST): 100°C≦ST (f) Boiling water shrinkage (BWS): BWS≦15%