JP2003138465A - Method for weight reduction processing of polyester fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a method for weight reduction processing of a polyester fiber by which an alkylene glycol and a divalent aromatic carboxylic acid can effectively be recovered and reused. SOLUTION: At least a part of the alkylene glycol is separated and recovered by distillation from waste liquid produced by the weight reduction of the polyester fiber with the alkylene glycol and a weight-reducing agent and methanol is added to the residue after distillation and carried out transesterification, and then, a divalent aromatic carboxylic acid dimethyl ester is recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing the weight of polyester fibers, and more particularly, to a waste liquid containing alkylene glycol and divalent aromatic carboxylic acid ester generated during weight reduction of polyester fibers. The present invention relates to a weight reduction processing method capable of recovering these active ingredients.

[0002]

2. Description of the Related Art Polyesters, especially polyalkylene terephthalates, have been produced and used in large quantities in daily life related materials such as fibers because of their excellent chemical stability. However, when this is used as a clothing material, there is a big problem in terms of texture.

In order to solve this problem, an alkali weight reduction processing method (UK Patent Specification No. 652948) is proposed in which the texture is improved by treating it in an aqueous solution of sodium hydroxide at a temperature of 60 ° C. or higher and hydrolyzing it. Was done.

The alkali reduction processing is carried out at a reduction rate of several% to 50% in order to obtain a texture suitable for the purpose, but the waste liquid (hereinafter referred to as alkali reduction waste liquid) contains a large amount of alkylene glycol and A divalent aromatic carboxylic acid salt (eg disodium terephthalate) is included.

Many methods have been proposed for recovering the divalent aromatic carboxylic acid component from the alkali reduction waste liquid as a valuable resource. The method is to precipitate the divalent aromatic carboxylic acid by acid precipitation with sulfuric acid or the like, This is what is separated.

A method is proposed in which a crude divalent aromatic carboxylic acid is reacted with methanol to give a dimethyl ester of the divalent aromatic carboxylic acid (eg dimethyl terephthalate), which is purified by distillation or the like to obtain a polyester raw material. (Japanese Patent Publication No. 5-59899, etc.). However, since it is necessary to add a large amount of acid to a large amount of alkali, it is difficult to call it an economical method.

Further, no proposal has been made on an effective method for recovering the alkylene glycol generated in the weight reduction processing.

As described above, the conventionally proposed methods for reducing the amount of polyester fiber have a big problem in terms of resource saving and environmental load.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art and to reduce the amount of alkylene glycol component and divalent aromatic carboxylic acid removed from polyester fiber. The purpose is to establish a method for reducing the weight of polyester fibers, which enables effective recovery and utilization of the components.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies in view of the above-mentioned prior art, and completed the present invention.

That is, the object of the present invention is to reduce the weight loss of polyester fibers produced from a divalent aromatic carboxylic acid and / or its ester and an alkylene glycol when the weight reduction treatment is performed using the alkylene glycol and the weight reducing agent. Recovering at least a part of the alkylene glycol from the waste liquid generated during the treatment by distillation, and then recovering the divalent aromatic carboxylic acid dimethyl ester obtained by transesterification by adding methanol to the distillation residue. Can be achieved by a method for reducing the weight of a polyester fiber.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester fiber to be subjected to weight reduction processing in the present invention is a polyester fiber produced from alkylene glycol and a divalent aromatic carboxylic acid or its ester, and a woven fabric consisting of polyester fiber only, Not only knitted fabrics and non-woven fabrics, but also blended yarns, cloths and the like containing natural fibers such as cotton can be the objects of the weight reduction processing of the present invention.

The alkylene glycol of the polyester fiber to be subjected to weight reduction processing can be used as long as it is known as a polymer material for fibers. Further, as the divalent aromatic carboxylic acid, any known one as a polymer material for fibers can be used.

In the present invention, the polyester fiber is soaked in a weight-reducing agent comprising an alkylene glycol and a weight-reducing agent in a weight-reducing processing bath, and the target wind is appropriately adjusted depending on the combination of the weight-reducing agent concentration, temperature and treatment time. It is processed up to the weight loss rate suitable for the case. The weight reduction processing may be performed either batchwise or continuously.

The alkylene glycol used is
Although any one can be used, an alkylene glycol having 2 to 4 carbon atoms is preferable from the viewpoint of handling and price, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol and the like. You can Further, if the alkylene glycol used for weight reduction is the same as the alkylene glycol constituting the polyester fiber, the separation step can be simplified, which is preferable.

As the weight reducing agent to be used, any one can be selected as long as it has a function of reducing the weight of the fiber in alkylene glycol. Among them, carbonates, oxides, hydroxides and alkaline earth metals of alkali metals can be selected. It is preferable to use at least one metal compound selected from the group consisting of carbonates, oxides, and hydroxides of group metals.

The weight-reduced fibers are taken out of the fiber weight-reduction processing bath and, if necessary, subjected to a dewatering machine to absorb the fibers.
After draining a part of the adhered liquid, wash with a washer.
The fibers that have been thoroughly washed are dried in a drying facility to become product fibers whose weight has been reduced.

The waste liquid discharged from the weight reduction processing bath contains
It contains residual alkylene glycol, residual weight reducing agents, alkylene glycol liberated from the fibers and di-alkylene glycol esters of divalent aromatic carboxylic acids. In addition, depending on the raw material polyester fiber, inorganic substances contained in the fiber may be present in the waste liquid. On the other hand, the waste liquid discharged from the washer contains a detergent and a residual alkylene glycol, a residual weight reducing agent, a diol liberated from the fiber, and a di-alkylene glycol ester of a divalent aromatic carboxylic acid.

In the present invention, at least a part of the alkylene glycol is separated and recovered from the waste liquid discharged from the weight reduction processing bath or the like by distillation, and methanol is added to the residue to cause a transesterification reaction to divalent aromatic compounds. The carboxylic acid dimethyl ester is obtained, and the divalent aromatic carboxylic acid dimethyl ester is recovered, whereby the divalent aromatic carboxylic acid dimethyl ester and the alkylene glycol are respectively recovered from the polyester weight loss processing waste liquid.

As the distillation apparatus for separating at least a part of alkylene glycol from the waste liquid discharged from the weight reduction processing bath or the like, a known distillation apparatus can be used, and either normal pressure or reduced pressure is possible, and a continuous method is also a batch method. Is also possible. The recovered alkylene glycol can be used again for the weight reduction processing of the polyester fiber.

The remaining components obtained by separating and recovering at least a part of the alkylene glycol by distillation include the residual alkylene glycol, the residual weight reducing agent, the alkylene glycol liberated from the fiber and the di-alkylene glycol ester of the divalent aromatic carboxylic acid. There is.

Methanol was added to this to esterify,
Divalent aromatic carboxylic acid dimethyl ester. This reaction can be carried out near the boiling point of methanol, and if necessary, it can be carried out using a transesterification catalyst such as an alkali metal carbonate to accelerate the reaction. For the esterification reaction, for example, a tank reactor with a stirrer attached to a reflux device, a tower reactor having a multi-stage perforated plate tray or the like installed therein, and the like can be used.

The divalent aromatic carboxylic acid dimethyl ester produced by the esterification reaction is separated and purified from impurities such as alkylene glycol, residual methanol, and inorganic salt by a known method such as distillation / crystallization to give polyester again. The divalent aromatic carboxylic acid can be used as a raw material. Further, the alkylene glycol can be used again for the weight reduction processing of the polyester fiber.

[0024]

EXAMPLES Examples of the present invention will now be described in detail, but the present invention is not limited thereto. In the examples, "parts" means "parts by weight" unless otherwise specified, and the weight of the fabric before and after the weight reduction treatment is dried in a steam dryer kept at 90 ° C. and then cooled to a constant temperature before measurement. did.

[Example 1] As a fiber-reducing processing bath mixed solution, 2.4 parts of reagent sodium carbonate was added to 240 parts of reagent ethylene glycol in a flat container made of stainless steel to prepare a solution containing 1.0% by weight of a reducing agent. A slurry of ethylene glycol was prepared. This flat container was placed on a stirring heating plate and heated so that the internal temperature became 115 ° C.

After the internal temperature of the solution reached 115 ° C., 7.0 parts of a plain weave fabric composed of polyethylene terephthalate fiber was used as an outer upper roller and a lower part centered at a liquid depth of about 40 mm in the fiber weight reduction processing bath. It was set between the rollers and a small motor was driven so that the upper roller rotated at 35 rpm. The diameter of the upper roller was 37 mm and the diameter of the lower roller was 15 mm.

After the fabric was soaked in the bath for 120 minutes, the fabric was removed from the roller and washed with 500 parts of warm water at 50 ° C. Washing with water was carried out twice, and dried with the above steam dryer. The weight of the woven fabric after the weight reduction treatment was 5.7 parts, and the weight loss rate was 19%.

The above weight reduction operation was repeated 10 times by repeatedly using the same ethylene glycol slurry to obtain 190 parts of the residual weight reduction waste liquid. The cleaning waste liquid is charged into a simple distillation apparatus and subjected to atmospheric distillation, and ethylene glycol 1
25 parts were collected.

About 50 parts of methanol was added to the distillation residual liquid to give about 7
The transesterification reaction was carried out under methanol reflux conditions at 0 ° C for 10
The reaction was carried out for 0 minutes, and the reaction product was cooled to 20 ° C. and filtered to obtain 11.2 parts of dimethyl terephthalate.

[0030]

EFFECTS OF THE INVENTION According to the method of the present invention, the active ingredient in the waste liquid generated in the weight reduction processing of polyester fiber can be effectively recovered, and the resource saving and the environmental load reduction can be realized to a large extent.

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Claims (4)

[Claims] 1. When a polyester fiber produced from a divalent aromatic carboxylic acid and / or its ester and an alkylene glycol is subjected to a weight reduction treatment using an alkylene glycol and a weight reducing agent, a waste liquid generated during the weight reduction treatment, At least a part of the alkylene glycol is separated and recovered by distillation, then, methanol is added to the distillation residue to obtain an ester exchange reaction, and a divalent aromatic carboxylic acid dimethyl ester is recovered. Method for reducing the weight of system fibers. 2. An alkali metal carbonate, oxide or hydroxide as a weight reducing agent, an alkaline earth metal carbonate or oxide,
The weight reduction processing method according to claim 1, wherein at least one metal compound selected from the group consisting of hydroxides is used. 3. The weight reduction processing method according to claim 1, wherein the alkylene glycol is at least one diol selected from the group consisting of ethylene glycol, 1,3-propanediol and 1,4-butanediol. 4. The weight reduction processing method according to claim 1, wherein an alkali metal carbonate is added as a catalyst during the transesterification reaction.