KR101788630B1 - Co-polyester having excellent heat stability and low temperature thermal water extractable, and method for manufacturing thereof - Google Patents

Abstract

The present invention relates to a copolyester for use in low temperature hot water which is excellent in thermal stability and a method for producing the same. More particularly, the present invention relates to a copolyester having high solubility under low temperature conditions, To a low-temperature hot-water-soluble copolyester excellent in thermal stability and excellent in thermal properties, and a process for producing the same.

Description

[0001] The present invention relates to a co-polyester having excellent heat stability and a method for producing the same,

The present invention relates to a copolyester for use in low temperature hot water which is excellent in thermal stability and a method for producing the same. More particularly, the present invention relates to a copolyester having high solubility under low temperature conditions, To a low-temperature hot-water-soluble copolyester excellent in thermal stability and excellent in thermal properties, and a process for producing the same.

Conventional extraction type composite yarns are produced by composite spinning of an extraction component, which is an alkali-soluble polymer, and a fiber-forming polymer, and are mainly produced for the purpose of producing microfibers or hollow fibers. In general, copolymerized polyester is mainly used as an extracting component polymer because it is extracted from an alkali solution and a weight loss facility widely used for weight reduction processing of a general polyester without using an organic solvent having a high cost of a special device and a recovery process. This is because the components can be eluted.

Polyamides and polyesters are mainly used as the polymer of the fiber-forming component. In recent years, cellulose ester, polytrimethylene terephthalate, polybutylene terephthalate and the like have been used for the purpose of imparting functionality.

Alkali-active polyesters used as extraction component polymers have been prepared in a variety of ways. A method of copolymerizing a dimethylisophthalate sulfonate salt or a low molecular weight polyalkylene glycol in a polyester polymerization process, a method of blending a second polyester with a high molecular weight polyalkylene glycol, and a method of blending a dimethylisobutylate sulfonate or a low molecular weight poly A method of copolymerizing or blending phthalatesulfonate salt with polyalkylene glycol, and the like. In addition, polystyrene or polyethylene is mainly used as the polymer dissolved by the above-mentioned solvent.

However, when the fiber-forming component is polyester, there is a problem that the fiber-forming component is also dropped in the aqueous solution of alkylliol when the extraction component is eluted, thereby deteriorating the physical properties.

Further, when the alkali is reduced, it may be detrimental to the health of workers, and the cost of using an alkali solution is additionally required, which is not environmentally friendly.

Accordingly, research on extraction components that can be extracted into water, which is not alkali, has been continued so as not to affect the fiber-forming components, and water-soluble polyesters are a typical extract component for this.

The water-soluble polyester is a polycondensation product of ethylene glycol and terephthalic acid, which is produced by condensing and condensing various diols, various dicarboxylic acids and water-soluble components. Examples of such water-soluble polyesters include those disclosed in International Patent Publication No. WO2002-57334 A) preparing an aqueous or methanolic slurry comprising 1,4-cyclohexanedimethanol (CHDM) and dicarboxylic acid, maintaining the slurry at a temperature below the melting point of CHDM, b) contacting the slurry to a reactor , C) esterifying the slurry, optionally in the presence of a suitable catalyst, at a temperature and pressure sufficient to effect the esterification, d) forming a prepolymer, and e) performing polycondensation Comprising polycondensing a prepolymer in the presence of a suitable catalyst at a temperature and pressure sufficient to form the polyester Manufacturing method "and proposes a method for producing a water-soluble polyester containing CHDM.

The conventional water-soluble polyesters conventionally have a high melting point and / or a high glass transition temperature during the weight loss process, so that the high-temperature elution is carried out at a temperature of 90 ° C or higher. At lower temperatures, It is impossible to carry out the reduction process at a low temperature.

However, the weight loss process performed at such a high temperature has a problem in that it is difficult to obtain the desired final fiber by changing the physical properties of the fiber forming component such as changing the degree of surface crystallization of the fiber forming component coextensive with the water-soluble polyester polymer. Also, the use of high temperature hot water may increase the cost of energy use and the risk of working environment.

In addition, even if the weight loss process can be performed at a low temperature condition, if the thermal stability is low, heat shrinkage occurs during processing and the process loss ratio is high, and the polymer needs to be dried for a long time in order to make it into a fiber.

Therefore, it is easy to dissolve even at low temperature, and it is used in water which is not alkali. Therefore, it is possible to prevent the alkali of the fiber forming component, harm to the health of workers, cost of alkali solution and environmental pollution, It is necessary to develop a water-soluble copolyester which does not cause a change in the physical properties of the fiber-forming component.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in an effort to solve the above-mentioned problems, and an object of the present invention is to provide a thermoplastic resin composition having excellent melting point and excellent thermal stability and excellent usability at a temperature significantly lower than a temperature at which a conventional weight- At the same time, it is possible to prevent defective dyeing non-uniformity of fibers produced by uniform elution, and to prevent the alkaline infiltration of the fiber forming component due to dissolution by water, which is not alkali, and also to prevent worker health harm and environmental pollution. An excellent low temperature hydrothermal utilization copolyester and a process for producing the same.

In order to solve the above-mentioned first problem, the present invention provides a process for producing an aromatic polycarboxylic acid comprising an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate A reacted esterification reagent comprising an acid component and a diol component; And polyethylene glycol; And a mid-condensation copolyester,
The copolyester has a melting point of at least 200 ° C, a dissolution rate (%) at 70 ° C in hot water of not less than 98% by the following method,
The aromatic polycarboxylic acid having 6 to 14 carbon atoms in the acid component includes terephthalic acid and isophthalic acid, and contains 5 to 15 mol% of isophthalic acid in the acid component, and provides a thermostable low temperature hot water-soluble copolyester .
* Determination of copolyester dissolution rate (%)
1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate To obtain

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According to a preferred embodiment of the present invention, the esterification reaction product may include monomers and acid component and diol component in a molar ratio of 1: 1.1 to 2.0.

According to another preferred embodiment of the present invention, the aromatic polycarboxylic acid having 6 to 14 carbon atoms may further include at least one of dimethyl terephthalate and dimethyl isophthalate.

According to another preferred embodiment of the present invention, the aliphatic polycarboxylic acid having 2 to 16 carbon atoms is selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, , Sebacic acid, nonanoic acid, decanoic acid, dodecanoic acid, and hexanodecanoic acid.

According to another preferred embodiment of the present invention, the diol component is selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol and 1,6- And may include any one or more selected.

According to another preferred embodiment of the present invention, 1 to 7 mol% of the aliphatic polycarboxylic acid having 2 to 16 carbon atoms and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate are contained in the acid component can do.

According to another preferred embodiment of the present invention, the aromatic polycarboxylic acid having 6 to 14 carbon atoms in the acid component includes terephthalic acid and isophthalic acid, and may contain 5 to 15 mol% of isophthalic acid in the acid component .

According to another preferred embodiment of the present invention, the acid component comprises 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate, .

According to another preferred embodiment of the present invention, the copolyester may contain polyethylene glycol in an amount of 1 to 10 parts by weight based on 100 parts by weight of the esterification reaction product.

According to another preferred embodiment of the present invention, the polyethylene glycol may have a weight average molecular weight of 400 to 10,000.

According to another preferred embodiment of the present invention, the copolyester may have an intrinsic viscosity of 0.5 to 0.9 dl / g.

According to another preferred embodiment of the present invention, the imago copolyester has a dissolution rate (%) of 60% or more in hot water at 60 캜 and a dissolution rate of 70% or more in 50 캜 of hot water.

The present invention also relates to a process for producing a polyester resin composition comprising (1) an acidic component comprising an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate, ≪ / RTI > to produce a reacted esterification reactant; And
(2) condensing / condensing the esterification reaction product and polyethylene glycol (PEG); ≪ / RTI > to produce a copolyester,
The copolyester has a melting point of at least 200 DEG C and a dissolution rate (%) at 70 DEG C in water of the copolyester measured by the following method of 98%
Wherein the esterification reaction product comprises terephthalic acid and isophthalic acid as aromatic polycarboxylic acids having 6 to 14 carbon atoms in the monomer as the acidic component, and using the low temperature hot water containing 5 to 15 mol% of the isophthalic acid in the acid component To provide a method for producing a co-polyester.

* Copolyester  How to measure dissolution rate (%)

1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate .

According to a preferred embodiment of the present invention, the esterification reaction product of the step (1) is formed by reacting the acid component and the diol component in a molar ratio of 1: 1.1 to 2.0,
Wherein the acid component is an aromatic polycarboxylic acid having 6 to 14 carbon atoms and further containing at least one of dimethyl terephthalate and dimethyl isophthalate;
But are not limited to, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, fimaric acid, azelaic acid, sebacic acid, nonanoic acid, decanoic acid, dodecanoic acid and hexanodecanoic acid At least one aliphatic polycarboxylic acid having 2 to 16 carbon atoms; And sodium 3,5-dicarbomethoxybenzenesulfonate; Or more,
The diol component may include one or more selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol.

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According to another preferred embodiment of the present invention, in the step (1), the esterification reaction product is an aromatic polycarboxylic acid having 6 to 14 carbon atoms in the acid, which is a monomer, and includes terephthalic acid and isophthalic acid, Containing 5 to 15 mol% of phthalic acid, 1 to 7 mol% of aliphatic polycarboxylic acid having 2 to 16 carbon atoms, and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate .

According to another preferred embodiment of the present invention, the esterification reaction product is an acidic component containing 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid, sodium 3,5-dicarbomethoxybenzenesulfo And 5 to 12 mol% of nate.

According to another preferred embodiment of the present invention, the polyethylene glycol may have a weight average molecular weight of 400 to 10,000, and may be a polycondensation product containing 1 to 10 parts by weight of polyethylene glycol per 100 parts by weight of the esterification reaction product.

According to another preferred embodiment of the present invention, the copolyester may have an intrinsic viscosity of 0.5 to 0.9 dl / g.

According to another preferred embodiment of the present invention, the copolyester has a dissolution rate (%) of 60% or more in hot water at 60 캜 and a dissolution rate of 70% or more in 50 캜 of hot water.

Hereinafter, the terms used in the present invention will be described

The term " superfine paper " used in the present invention means grass paper having a basis weight of 20 g / m ² or less, and the 'grass paper' In a state where the paper has not been subjected to a dehydration, dehydration and / or drying process, and contains a paper-making-forming component and a binder component.

The copolyester of the present invention has a remarkably high melting point, so that it has excellent thermal properties, minimizes changes in the product with time, minimizes the process loss during processing, and can radiate as a single product, Thereby preventing changes in the physical properties of the fiber forming components occurring at the time of performing the weight loss process at a high temperature and preventing the defects such as uneven dyeing of the final fiber and deterioration of the mechanical properties after the weight loss process because the weight loss is uniform. In addition, it is possible to prevent alkaline infiltration of the fiber forming component due to its excellent utilization in non-alkali water, and it can contribute to the safety and alkaline cost reduction such as the health of workers during the weight reduction process, the cost for alkali wastewater treatment, have. Furthermore, it possesses biodegradable properties, enabling self-decomposition at the time of landfill disposal, environmentally friendly, and has wide applications in products such as fibers and films.

1 is a cross-sectional view of a cis-core type conjugate fiber according to a preferred embodiment of the present invention.
2 is a cross-sectional view of a sea-island type conjugate fiber according to a preferred embodiment of the present invention.
3 is a cross-sectional view of a side-by-side type composite fiber according to a preferred embodiment of the present invention.
4 is a cross-sectional view of a divided pie-type conjugate fiber according to a preferred embodiment of the present invention.
5 is a cross-sectional view of a mosaic-type conjugate fiber according to a preferred embodiment of the present invention.
6 is a cross-sectional view of a matrix-dispersed type composite fiber according to a preferred embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

As described above, the conventional water-soluble polyester has a high melting point or a high glass transition temperature, so that the high-temperature elution is usually carried out at a temperature of 90 ° C or higher in the course of the weight reduction step. It is impossible to carry out a weight loss process at a low temperature in the production of composite fibers such as yarn. Accordingly, inevitably, the weight reduction process performed at a high temperature may change the surface crystallinity of the fiber-forming component co-spun together with the water-soluble polyester polymer, thereby changing the physical properties of the fiber-forming component and making it difficult to obtain final fibers having desired physical properties , High energy is required depending on high temperature conditions, and there is a problem in safety of workers. In addition, in the case of the alkali-utilizing copolyester, by performing the weight reduction process with the alkali solution, the alkali-impregnated fiber-forming component causes alkaline infiltration to cause deterioration of the physical properties of the fiber-forming component and requires a separate alkali solution, The wastewater treatment cost of the alkaline solution after the weight reduction process is generated, which may be detrimental to the health of the operator, and is not environmentally friendly.

Accordingly, the present invention provides a process for producing a polyurethane foam which comprises reacting an acid component containing an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate, An esterification reagent; And a polyethylene glycol; wherein the copolyester has a melting point of not less than 200 ° C and a solubility (%) at 70 ° C in the hot water of the copolyester measured by the following method: ) Is 98% or more. The present invention has been made to solve the above-mentioned problems by providing a low-temperature hot water-soluble copolyester having excellent heat stability.

* Copolyester  How to measure dissolution rate (%)

1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate .

As a result, copolyester has remarkably high melting point, so it has excellent thermal properties, minimizing changes of product over time, minimizing process loss during processing, and being capable of spinning as a single product, The change in the physical properties of the fiber forming component that occurs upon elution at high temperature is prevented and the elution is uniform so that the defective dyeing nonuniformity of the final fiber after the weight loss process is prevented. In addition, it can prevent alkaline infiltration of fiber forming components due to its excellent use in low-temperature water, which is not an alkali, and furthermore it can reduce the cost of safety and alkali, such as worker's health during the weight loss process, reduce alkali wastewater treatment cost, You can contribute. Furthermore, it can be biodegradable, self-degradable at the time of landfill disposal, and can be a more environmentally friendly polymer.

The low temperature hot water-soluble copolyester of the present invention is formed by condensation and condensation of an esterification reaction product and polyethylene glycol, and the esterification reaction product is a reaction product containing an acid component and a diol component.

First, each compound included in the acid component will be described.

Wherein said acidic component mainly comprises polyvalent carboxylic acid and sodium 3,5-dicarbomethoxybenzenesulfonate, said polyvalent carboxylic acid being selected from the group consisting of aromatic polycarboxylic acids having 6 to 14 carbon atoms and aliphatic polyvalent carboxylates having 2 to 16 carbon atoms Acid.

However, depending on the purpose, the polycarboxylic acid may include a dicarboxylic acid including a heterocycle, and as the non-limiting examples of the dicarboxylic acid, 2,5-furandicarboxylic acid, 2,5- And 2,5-pyrrolic dicarboxylic acid, and the like.

The aromatic polycarboxylic acid having 6 to 14 carbon atoms may be any one or more selected from the group consisting of terephthalic acid, dimethyl terephthalate, isophthalic acid and dimethyl isophthalate, and preferably terephthalic acid and isophthalic acid to improve water solubility and water- . ≪ / RTI >

The aliphatic polycarboxylic acid having 2 to 16 carbon atoms is preferably selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, pimelic acid, azelaic acid, sebacic acid, Dodecanoic acid, and dodecanoic acid, and hexanodecanoic acid. Preferably, it may be at least one of adipic acid, succinic acid and glutaric acid, and even more preferably it may be adipic acid to further improve water availability. The aliphatic polycarboxylic acid having 2 to 16 carbon atoms can increase the fluidity of the low-temperature hot-water-soluble copolyester polymer chain and the surface area of the low-temperature hot-water-soluble copolyester polymer to adhere to water, so that the water-reducing process can be performed even at low temperatures.

Next, the present invention includes sodium 3,5-dicarbomethoxybenzenesulfonate which is a sulfonic acid metal salt capable of inducing adsorption of water molecules as an acid component.

Sodium 3,5-dicarbomethoxybenzenesulfonate can induce the polymer adsorption of water molecules, which further improves the water solubility, and thus may enable a weight loss process even at low temperatures. In addition to the above sodium 3,5-dicarbomethoxybenzenesulfonate, there may be used one or more selected from among lithium 3,5-dicarbomethoxybenzenesulfonate, 5-sulfoisophthalic acid monosodium salt, Sulfonic acid metal salt.

According to a preferred embodiment of the present invention, each of the monomers contained in the above-mentioned acid component may contain 1 to 7 mol% of an aliphatic polycarboxylic acid having 2 to 16 carbon atoms in the acid component, sodium 3,5-dicarbonate And 5 to 12 mol% of an aromatic polycarboxylic acid having 6 to 14 carbon atoms.

When the aliphatic polycarboxylic acid having 2 to 16 carbon atoms in the acid component is contained in an amount of less than 1 mol%, the intended water-solubility and water-solubility characteristics are difficult to be exhibited, It may be a copolyester having a lowered heat resistance, a lowered glass transition temperature and a glass transition temperature and no melting point, when the polymer is contained in an excess amount, There is a problem that the shrinkage characteristics are remarkably exhibited, which may cause deterioration in workability of the post-processing step.

If the amount of sodium 3,5-dicarbomethoxybenzenesulfonate contained in the acid component is less than 5 mol%, the desired water-solubility can not be obtained, so that the step of reducing at low temperature may be difficult, and when 12 mol% The polymerization efficiency of the copolyester is remarkably lowered, the melt viscosity is increased, the spinning workability is significantly lowered, and the excessive production of diethylene glycol (DEG), which is a by-product of the process, There is a problem that it causes the silk thread and the pack pressure rise.

According to a preferred embodiment of the present invention, the aromatic polycarboxylic acid having 6 to 14 carbon atoms contained in the remaining amount of the acid component includes terephthalic acid and isophthalic acid, and the acid component contains 5 to 15 mol% of isophthalic acid . If the content of isophthalic acid in the acid component is less than 5 mol%, the desired water-solubility characteristics can not be obtained, so that it may be difficult to dissolve in water other than alkali and may not be eluted at low temperature. If 15 mol% It may be a copolyester in which the melting point is lowered or the melting point itself is not present, so that the thermostability of the copolyester is lowered, and the fiber produced has a large change with the lapse of time and the fiber processing work may be difficult.

More preferably, the acid component may contain 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid, and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate, To 14 aromatic polycarboxylic acids, which can achieve the desired remarkable water solubility characteristics and thus good availability at low temperatures.

Next, the diol component included as a monomer together with the acid component will be described.

The diol component may include an aliphatic diol component having 2 to 14 carbon atoms and polyethylene glycol.

First, the aliphatic diol component having 2 to 14 carbon atoms is specifically exemplified by ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, trimethyl From the group consisting of glycol, tetramethylene glycol, pentamethyl glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol and tridecamethylene glycol And may be any one or more selected. Preferably, it may be any one or more of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol.

The polyethylene glycol may have a weight average molecular weight of 400 to 10,000. If the weight average molecular weight is less than 400, it is difficult to carry out the weight loss process at a low temperature because the polyethylene glycol can not have desired water solubility characteristics. If the weight average molecular weight If it is more than 10,000, there is a problem that the polymerization reactivity is lowered and the glass transition temperature of the copolyester formed becomes too low or the melting point does not appear, resulting in poor heat stability.

Among the monomers described above, an acid component containing an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate is reacted with a diol component The esterification reaction product may contain the acid component and the diol component in a molar ratio of 1: 1.1 to 2.0. If the diol component is contained in an amount less than 1.1 molar ratio, there is a problem that the polymerization degree is lowered due to the lowered reactivity, and when the molar ratio exceeds 2.0 mol, adverse reaction products such as diethyl glycol may be generated, And there is a problem that an excessive use of diol may increase the manufacturing cost.

In the low temperature hydrothermal copolyester of the present invention, the esterification reaction product and the polyethylene glycol are condensed with each other. According to a preferred embodiment of the present invention, the copolyester contains polyethylene glycol in an amount of 1 To 10 parts by weight. If the amount of the polyethylene glycol is less than 1 part by weight, the desired water-solubility characteristics can not be obtained. Therefore, there is a problem that the weight loss process at low temperatures is difficult to perform. If the amount exceeds 10 parts by weight, It is too low and the thermal stability may become poor.

On the other hand, the copolyester of the present invention containing the monomer as described above satisfies a dissolution rate (%) of 70% in hot water of 98% or more, preferably a dissolution of 95% or more in 60% of hot water , And still more preferably 70% or more in dissolution rate in hot water at 50 占 폚.

In the case of conventional alkali-soluble copolyesters or water-soluble copolyesters, the reduction process was carried out almost at 90 ° C or higher, preferably 100 ° C or higher. However, the weight loss process at a high temperature causes a change in the physical properties of the fiber-forming component and the like, so that the physical properties of the desired fiber can not be completely obtained, and the alkali loss-reducing solution causes the alkali-breaking of the fiber-forming component. Accordingly, the inventors of the present invention have found that water can be used to prevent alkali-impregnation of a fiber forming component in a weight loss solution and can be reduced at a low temperature of 50 to 70 캜, The inventors of the present invention have solved the problems of the prior art by inventing copolyesters having a remarkably high solubility of copolyester at a temperature.

The dissolution rate of the copolyester was determined by adding 1 g of the usable copolyester chip to 60 g of hot water having a predetermined temperature, reducing the volume for 25 minutes, filtering paper having a pore diameter of 2 to 3 탆 (trade name: Filter Paper Quantitative Ashless 53 -110 mm, manufactured by Hyundai Micro Co.), and the weight can be calculated by the following calculation formula.

Dissolution rate (%) =

The copolyester of the present invention satisfies a dissolution rate at 70 캜 of not less than 98%. If the dissolution rate at 70 캜 is less than 98%, the intended encapsulation at a low temperature can not be obtained, The fiber-forming component coextracted together with the copolyester according to the present invention has a problem of difficulty in changing the physical properties of the resultant fiber due to the different degree of surface crystallinity in the composite fiber state and in the post-reduction state .

Meanwhile, the specific dissolution condition according to the method of measuring the dissolution rate is only one method for indicating the physical properties of the copolyester according to the present invention, and may be different from the weight loss condition in the conjugate fiber containing the copolyester, The conditions are not particularly limited in the invention. In addition, the specific losing time may vary depending on the specific conditions of the weight loss process, for example, the temperature of the hot water, the addition of additives for increasing the rate of loss to hot water, and the like.

Further, according to a preferred embodiment of the present invention, the intrinsic viscosity of the copolyester may be 0.5 to 0.9 dl / g. If the intrinsic viscosity is less than 0.5 dl / g, there is a problem that the mechanical strength of the conjugate fiber is remarkably weakened during the composite spinning with the fiber, resulting in poor post-processing. If the intrinsic viscosity is more than 0.9 dl / g, There is a problem that elution at low temperature becomes difficult.

As described above, the low-temperature hot water-soluble copolyesters include (1) aromatic polycarboxylic acids having 6 to 14 carbon atoms, aliphatic polycarboxylic acids having 2 to 16 carbon atoms, and sodium 3,5-dicarbomethoxybenzenesulfonate ≪ / RTI > comprising the steps of: preparing a reacted esterification reactant comprising an acid component and a diol component; And (2) subjecting the esterification reaction product and polyethylene glycol (PEG) to condensation and condensation, wherein the copolyester has a melting point of 200 ° C or higher, And a dissolution rate (%) of the copolyester in hot water at 70 占 폚 is 98% or more.

* Copolyester  How to measure dissolution rate (%)

1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate .

Dissolution rate (%) =

First, as step (1), an acid component containing an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms, and sodium 3,5-dicarbomethoxybenzenesulfonate and a diol component To prepare a reacted esterification reaction product.

The acid component mainly comprises polyvalent carboxylic acid and sodium 3,5-dicarbomethoxybenzenesulfonate, and the polyvalent carboxylic acid is again an aromatic polyvalent carboxylic acid having 6 to 14 carbon atoms and an aliphatic polyvalent carboxylic acid having 2 to 16 carbon atoms And includes a carboxylic acid.

However, depending on the purpose, the polycarboxylic acid may include a dicarboxylic acid including a heterocycle, and as the non-limiting examples of the dicarboxylic acid, 2,5-furandicarboxylic acid, 2,5- And 2,5-pyrrolic dicarboxylic acid, and the like.

The aromatic polycarboxylic acid having 6 to 14 carbon atoms may be any one or more selected from the group consisting of terephthalic acid, dimethyl terephthalate, isophthalic acid and dimethyl isophthalate, and preferably terephthalic acid and isophthalic acid to improve water solubility and water- . ≪ / RTI >

The aliphatic polycarboxylic acid having 2 to 16 carbon atoms may be selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, pimelic acid, azelaic acid, sebacic acid, An acid, a dodecanoic acid, and a hexanodecanoic acid. Preferably, it may be at least one of adipic acid, succinic acid and glutaric acid, and even more preferably it may be adipic acid to further improve water availability.

The aliphatic polycarboxylic acid having 2 to 16 carbon atoms has been improved in fluidity of the low-temperature hot-water-soluble copolyester polymer chain and the surface area of bonding with water, so that the weight loss process can be performed even at low temperature in water-soluble properties.

Next, the present invention includes sodium 3,5-dicarbomethoxybenzenesulfonate which is a sulfonic acid metal salt capable of inducing adsorption of water molecules as an acid component.

Sodium 3,5-dicarbomethoxybenzenesulfonate can induce the polymer adsorption of water molecules, which further improves the water solubility, and thus may enable a weight loss process even at low temperatures. In addition to the above sodium 3,5-dicarbomethoxybenzenesulfonate, there may be used one or more selected from among lithium 3,5-dicarbomethoxybenzenesulfonate, 5-sulfoisophthalic acid monosodium salt, Sulfonic acid metal salt.

According to a preferred embodiment of the present invention, each of the monomers contained in the above-mentioned acid component may contain 1 to 7 mol% of an aliphatic polycarboxylic acid having 2 to 16 carbon atoms in the acid component, sodium 3,5-dicarbonate And 5 to 12 mol% of an aromatic polycarboxylic acid having 6 to 14 carbon atoms.

When the aliphatic polycarboxylic acid having 2 to 16 carbon atoms in the acid component is contained in an amount of less than 1 mol%, the desired water-solubility and water-solubility characteristics are difficult to be exhibited, and elution at low temperatures may be difficult. , There is a problem that the heat resistance and the glass transition temperature of the produced copolyester are lowered, resulting in the morphological stability of the formed polymer and deterioration of the processability of the composite fiber.

If the amount of sodium 3,5-dicarbomethoxybenzenesulfonate contained in the acid component is less than 5 mol%, the desired water-solubility can not be obtained, so that the step of reducing at low temperature may be difficult, and when 12 mol% (DEG), which is a by-product of the process, and the resultant unreacted material remains in the spinning process, the process efficiency of the copolyester polymerization process is remarkably lowered, the melt viscosity is increased, There is a problem that it causes the silk thread and the pack pressure rise.

According to a preferred embodiment of the present invention, the aromatic polycarboxylic acid having 6 to 14 carbon atoms contained in the remaining amount of the acid component includes terephthalic acid and isophthalic acid, and the acid component contains 5 to 15 mol% of isophthalic acid . If the content of isophthalic acid in the acid component is less than 5 mol%, there is a problem that the desired water-solubility characteristics can not be obtained and low-temperature elution can not be performed. If the isophthalic acid content is more than 15 mol% There is a problem that the copolyester which is not expressed in itself can be produced, the change of the fiber produced over time due to the decrease in heat resistance of the copolyester is large, and the fiber processing work may be difficult.

More preferably, the acid component may contain 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid, and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate, To 14 aromatic polycarboxylic acids, which can achieve the desired remarkable water solubility characteristics and thus good availability at low temperatures.

Next, the diol component included as a monomer together with the acid component will be described.

Non-limiting examples of the diol component may include an aliphatic diol component having from 2 to 14 carbon atoms.

Examples of the aliphatic diol having 2 to 14 carbon atoms include ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, propylene glycol, trimethylglycol, But are not limited to, those selected from the group consisting of tetramethylene glycol, tetramethylene glycol, pentamethyl glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol and tridecamethylene glycol It can be any one or more. Preferably, it may be any one or more of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol.

Among the monomers described above, an acid component containing an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate is reacted with a diol component The esterification reaction product may contain the acid component and the diol component in a molar ratio of 1: 1.1 to 2.0. If the diol component is contained in an amount less than 1.1 molar ratio, there is a problem that the polymerization degree is lowered due to the lowered reactivity, and when the molar ratio exceeds 2.0 mol, adverse reaction products such as diethyl glycol may be generated, And there is a problem that an excessive use of diol may increase the manufacturing cost.

The time for mixing the acid component and the diol component to produce the esterification reaction of step (1) is not limited, and may further include a catalyst. The catalyst may be a catalyst usually used in the production of polyester, and is not particularly limited thereto, and can be produced, for example, as a non-limiting example, a metal acetate catalyst.

The esterification reaction in step (1) can be preferably carried out at a temperature of 200 to 270 ° C and a pressure of 1100 to 1350 Torr. If the above condition is not satisfied, the esterification reaction time may be prolonged or the reactivity may be lowered to cause a problem that an esterification reaction product suitable for the polycondensation reaction can not be formed.

Next, as step (2), the esterification reaction product and poly (ethylene glycol) (PEG) are condensed and condensed.

The polyethylene glycol preferably has a weight average molecular weight of 400 to 10,000. According to a preferred embodiment of the present invention, the step (2) is a step of dissolving polyethylene glycol in an amount of 1 to 10 And can be condensed to weight. If the weight average molecular weight is less than 400 and / or the polyethylene glycol is less than 1 part by weight, it can not have the desired water-solubility characteristic and it is difficult to carry out the weight loss process at low temperature. If the weight average molecular weight exceeds 10,000 and / When the amount of the glycol is more than 10 parts by weight, the polymerization reactivity is lowered, and the melting point (and / or the glass transition temperature) of the formed copolyester becomes too low, resulting in poor heat stability.

The timing of introduction of the polyethylene glycol is not limited and may be added during the esterification reaction of the esterification reaction product or may be mixed with the reaction product after completion of the esterification reaction.

Preferably, the condensation-condensation reaction in step (2) can be carried out at a temperature of 250 to 300 ° C and a pressure of 0.3 to 1.0 Torr. If the above conditions are not satisfied, the reaction time delay, polymerization degree, And the like.

The step (2) may further include a catalyst during the condensation / condensation reaction. The catalyst may be an antimony compound or a phosphorus compound to prevent discoloration of the color due to pyrolysis at a high temperature in order to ensure proper reactivity and lower the production cost.

Examples of the antimony compound include antimony oxides such as antimony trioxide, antimony trioxide, and antimony pentoxide, antimony halides such as antimony trisulfide, antimony trifluoride, antimony trichloride, antimony triacetate, antimony benzoate, antimony tristearate, Can be used.

The amount of the antimony compound used as the catalyst is preferably 100 to 600 ppm based on the total weight of the polymer obtained after the polymerization.

As the phosphorus compound, phosphoric acid, trimethylphosphoric acid monomethylphosphoric acid, phosphoric acid such as tributylphosphoric acid, and derivatives thereof are preferably used. Of these, trimethylphosphoric acid, triethylphosphoric acid or triphenylphosphoric acid is particularly preferred, The amount of the phosphorus compound used is preferably 100 to 500 ppm based on the total weight of the polymer obtained after the polymerization.

On the other hand, the copolyester produced through the step (2) described above satisfies the dissolution rate (%) in the hot water at 70 ° C of 98% or more and preferably 100% A dissolution rate of not less than 95%, more preferably not less than 70%, in a hot water of 50 캜. This makes it possible to reduce water at a low temperature of not more than 90 ° C., which is not higher than a usual high temperature, even at a weight loss condition, at a low temperature of 70 ° C., and at a weight loss rate of 70 ° C. 98% or more, and the weight loss rate is remarkably excellent. Since the critical significance of the dissolution rate is the same as described above, a detailed description thereof will be omitted.

Further, according to a preferred embodiment of the present invention, the intrinsic viscosity of the copolyester produced may be 0.5 to 0.9 dl / g. If the intrinsic viscosity is less than 0.5 dl / g, there is a problem that the mechanical strength of the conjugate fiber is remarkably weakened during the composite spinning with the fiber, resulting in poor post-processing. If the intrinsic viscosity is more than 0.9 dl / g, There is a problem that elution at low temperature becomes difficult.

On the other hand, a conjugated fiber can be obtained by using the copolyester produced by the above-described method as an eluting component (hereinafter referred to as a second component) and a fiber-forming component (hereinafter referred to as a first component).

The fiber forming component is usually contained in a conjugate fiber, and a resin capable of being spinnable as a fiber may be used. Preferably, the fiber forming component is a polyester resin, a polyamide resin, an acrylic resin, an olefin resin and a polyurethane resin ≪ / RTI > However, the fiber-forming component may be modified to realize a fiber having desired physical properties, and is not limited to the following specific examples.

The composite fiber comprising the first component and the second component may be a sheath-core type, an island in the sea type, a side by side type, and a segmented pie, A mosaic type, a matrix-dispersed type, a nebulous type, and the like, and is not particularly limited to this, and it is preferable that the composite fiber is in the form of a composite fiber including a first component and a second component separately.

1 is a cross-sectional view of a sheath-core type conjugate fiber according to a preferred embodiment of the present invention. As shown in FIG. 1, the sheath-core type conjugate fiber is more preferable than the sheath- , The first component may be a core component (21), and the second component may be a sheath component (20). On the other hand, when the second component is used as a core component and the first component is used as a sheath component, yarns of three degrees of fineness having an excellent dyeability and excellent sensitivity to a soft touch can be obtained.

2 is a cross-sectional view of island-in-the-sea type conjugated fiber according to a preferred embodiment of the present invention. In case of island-in-the-sea type fiber, 30) and the second component is the island component 31 (island in the sea).

By incorporating the first component as the sea component 30, a microfine yarn containing a cast component (second component) can be obtained.

On the other hand, when the second component is a sea component and the first component is a component, it is possible to obtain multiple hollow fibers after elution, and light weight and warmth effect can be obtained depending on the amount of the hollow component.

FIG. 3 is a sectional view of a side by side type composite fiber according to a preferred embodiment of the present invention, FIG. 4 is a sectional view of a segmented pie type composite fiber, FIG. 5 is a cross- Fig. 6 is a cross-sectional view of the matrix-dispersion type. In the case of the composite fiber form shown in FIGS. 3 to 6, since the positions of the first and second components of the present invention are the same, the first and second components May be not particularly limited.

The present invention will now be described more specifically with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

≪ Example 1 >

First, 7 mol% of isophthalic acid, 4 mol% of adipic acid, 10 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate and 79 mol% of terephthalic acid were added as acid components to the esterification reaction product, Ethylene glycol as a diol component was added in a molar ratio of 1: 1.2 based on terephthalic acid in the acid component. Thereafter, esterification reaction was carried out at 250 ° C under a pressure of 1140 Torr to obtain an ester reaction product, and the reaction rate was 97.5%.

The resulting ester reactant was transferred to a condensation polymerization reactor, and 7 parts by weight of polyethylene glycol (PEG) having a molecular weight of 4,000 was added to 100 parts by weight of the ester reactant. Then, 400 ppm of antimony trioxide was added as a condensation polymerization catalyst to a final pressure of 0.5 Torr The temperature was raised to 285 DEG C while gradually decompressing to conduct condensation polymerization reaction, and copolyester was prepared.

≪ Examples 2 to 9 &

The copolyesters shown in Table 1 below were prepared in the same manner as in Example 1,

≪ Comparative Example 1 &

The copolyesters shown in Table 1 below were prepared in the same manner as in Example 1,

<Experimental Example>

The following properties of the copolyester resin prepared through the above Examples and Comparative Examples were measured and are shown in Table 1.

1. Intrinsic viscosity

Using Ortho-Chloro Phenol as a solvent, 2.0 g / 25 ml

, And the mixture was incubated at 25 DEG C for 30 minutes and analyzed by an automatic viscometer connected to a CANON viscometer.

2. Glass transition temperature

The glass transition temperature was measured using a differential thermal calorimeter. The analysis conditions were a heating rate of 20 ° C / min.

3. Assessment of acceptability by water temperature

The water dissolution rate and the filter permeability were evaluated by varying the elution temperature as shown in Table 1 below,

The dissolution rate (%) was determined by adding 1 g of the usable copolyester chip to 60 g of hot water having a specific water elution temperature, dissolving the solution for 25 minutes, filtering paper having a pore diameter of 2 to 3 탆 (trade name: Filter Paper Quantitative Ashless 53-110 mm, manufacturer: Hyundai Micro Co.), and the dissolution rate was determined by the following formula.

Dissolution rate (%) =

At this time, the filter permeability was evaluated in the order of ⊚, ◯, △, and × as the degree of passing of the copolyester solution through the filter was reduced by using a filter capable of removing particles of 0.2 μm.

4. Radiation workability evaluation

The yield of copolyester fiber without shrinkage was calculated by the following equation when the copolyester was spun through a conventional polyester melt spinning apparatus and spinning with a full 9 kg drum.

로 계산되며

And

When the yield of the calculation result is 100 to 95%, it is divided into?, 95 to 90% when? And less than 90%, respectively.

As can be seen from Tables 1 to 3, in the case of Comparative Examples 1 to 4, it was confirmed that the water receptivity at 70 ° C in hot water was less than 75%, which is not significantly better than in the Examples.

On the other hand, in the case of Examples 1 to 4, the acceptability of the copolyester prepared by the same composition was evaluated by temperature, and it was confirmed that the acceptability was 70% or more at hot water at 50 ° C, Is 100%, it can be confirmed that the acceptance at a low temperature is very excellent.

In addition, in Example 5, it was confirmed that the heat resistance was not remarkably low due to the excessive amount of isophthalic acid, and it was confirmed that it was unsuitable for single spinning. In addition, in Example 6, it can be confirmed that the acceptance of water in low-temperature hot water is not very good as isophthalic acid is contained too much.

In addition, in Example 7, adipic acid was inferior due to the undesirable inclusion of adipic acid. In Example 8, adipic acid was contained in an excessive amount, and therefore, acceptance in low temperature hot water was improved, And the spinning workability is lowered.

In addition, in the case of Example 9, the acceptance of the metal sulfonate was inferior due to the inclusion of the sulfonic acid metal salt. In Example 10, the acceptance of the metal sulfonate in the hot water was good, It can be confirmed that the property is remarkably deteriorated.

In the case of Example 11, the content of polyethylene glycol was inferior to that of Example 11, and thus the acceptance of the polyethylene glycol in the low temperature hot water was not very good. In Example 12, the polyethylene glycol was contained in an excessive amount, It can be confirmed that the property is remarkably deteriorated.

Claims (19)

An esterified reactant reacted with an acid component comprising an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate, and a diol component; And a polyethylene glycol, wherein the core-condensed copolyester comprises:
The copolyester has a melting point of at least 200 ° C, a dissolution rate (%) at 70 ° C in hot water of not less than 98% by the following method,
The aromatic polycarboxylic acid having 6 to 14 carbon atoms in the acidic component includes terephthalic acid and isophthalic acid, and contains 5 to 15 mol% of isophthalic acid in the acid component.
* Determination of copolyester dissolution rate (%)
1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate .

The method according to claim 1,
Wherein the esterification reaction product comprises a monomer and an acid component and a diol component in a molar ratio of 1: 1.1 to 2.0.
The method according to claim 1,
Wherein the aromatic polycarboxylic acid having 6 to 14 carbon atoms further comprises at least one of dimethyl terephthalate and dimethyl isophthalate.
The method according to claim 1,
The aliphatic polycarboxylic acid having 2 to 16 carbon atoms is preferably selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, pimelic acid, azelaic acid, sebacic acid, Wherein the low-temperature hot water-soluble copolyester is at least one selected from the group consisting of dodecanoic acid and hexanodecanoic acid.
The method according to claim 1,
Wherein the diol component comprises any one or more selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol and 1,6-hexanediol Useful low-temperature hot water-soluble copolyester with excellent thermal stability.
The method according to claim 1,
Characterized in that the acid component contains 1 to 7 mol% of an aliphatic polyvalent carboxylic acid having 2 to 16 carbon atoms and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate. Use cast copolyester.
delete The method according to claim 1,
Wherein the acid component comprises 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate, Sexual copolyester using hot water.
The method according to claim 1,
Wherein the copolyester comprises polyethylene glycol in an amount of 1 to 10 parts by weight based on 100 parts by weight of the esterification reaction product.

The method according to claim 1,
The polyethylene glycol has a weight average molecular weight of 400 to 10,000. The low-temperature hot water-soluble copolyester excellent in thermal stability.
The method according to claim 1,
Wherein the copolyester has an intrinsic viscosity of 0.5 to 0.9 dl / g.
The method according to claim 1,
Wherein the copolyester has a dissolution rate (%) of 60% or more in hot water at 60 占 폚 of 95% or more and a dissolution rate of 50% or more in hot water of 70% or more.
(1) reacted ester comprising an acid component including an aromatic polycarboxylic acid having 6 to 14 carbon atoms, an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and sodium 3,5-dicarbomethoxybenzenesulfonate, and a diol component Preparing a reaction product; And
(2) subjecting the esterification reaction product and polyethylene glycol (PEG) to condensation and condensation to prepare a copolyester,
The copolyester has a melting point of at least 200 DEG C and a dissolution rate (%) at 70 DEG C in water of the copolyester measured by the following method of 98%
Wherein the esterification reaction product comprises terephthalic acid and isophthalic acid as aromatic polycarboxylic acids having 6 to 14 carbon atoms in the monomer as the acidic component, and using the low temperature hot water containing 5 to 15 mol% of the isophthalic acid in the acid component &Lt; / RTI &gt;
* Determination of copolyester dissolution rate (%)
1 g of copolyester chip was added to 60 g of hot water having a predetermined temperature and dissolved for 25 minutes. Then, the weight of the remaining amount after filtration was measured using a filter paper having a pore diameter of 2 to 3 탆 and the dissolution rate .

14. The method of claim 13,
The esterification reaction product in the step (1) is formed by reacting an acid component and a diol component in a molar ratio of 1: 1.1 to 2.0,
Wherein the acid component is an aromatic polycarboxylic acid having 6 to 14 carbon atoms and further containing at least one of dimethyl terephthalate and dimethyl isophthalate;
But are not limited to, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, citric acid, fimaric acid, azelaic acid, sebacic acid, nonanoic acid, decanoic acid, dodecanoic acid and hexanodecanoic acid At least one aliphatic polycarboxylic acid having 2 to 16 carbon atoms; And
Sodium 3,5-dicarbomethoxybenzenesulfonate,
Wherein the diol component comprises any one or more selected from the group consisting of ethylene glycol, diethylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol and 1,6-hexanediol Which is excellent in thermal stability.
14. The method according to claim 13, wherein in the step (1)
The esterification reaction product is a product obtained by reacting 1 to 7 mol% of an aliphatic polycarboxylic acid having 2 to 16 carbon atoms and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate in an acid component as a monomer Which is characterized by excellent thermal stability.
14. The method according to claim 13, wherein in the step (1)
The esterification reaction product is a reaction product in which an acidic component containing 5 to 15 mol% of isophthalic acid, 1 to 7 mol% of adipic acid and 5 to 12 mol% of sodium 3,5-dicarbomethoxybenzenesulfonate as an acidic monomer Which is characterized by excellent thermal stability.
14. The method of claim 13, wherein in step (2)
Wherein the polyethylene glycol has a weight average molecular weight of 400 to 10,000 and is polycondensed by containing 1 to 10 parts by weight of polyethylene glycol per 100 parts by weight of the esterification reaction product. Way.
14. The method of claim 13,
Wherein the copolyester has an intrinsic viscosity of 0.5 to 0.9 dl / g.
14. The method of claim 13,
Wherein the copolyester has a dissolution rate (%) of 60% or more in hot water at 60 占 폚 of 95% or more and a dissolution rate of 50% or more in hot water of 70% or more.

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