JP2513651B2 - Hot water soluble copolyester - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hot water-soluble copolyester. More specifically, it relates to a copolyester which is used as a component of a composite fiber and can be easily formed into an ultrafine fiber or a specially shaped cross-section yarn by dissolving and removing with hot water.

[Prior Art] Conventionally, as a method for producing ultrafine fibers, the direct spinning method is very difficult in terms of operability during spinning / drawing, yarn quality of the ultrafine yarn, and easiness of handling up to a higher-order processing stage. It is considered difficult at the current technological stage. For this reason, there is known a means for dissolving and removing at least a part or swelling and splitting after forming a composite fiber of different components (a cross-sectional shape is a sea-island type, a blend type, a splittable multi-layer type, etc.).

However, in the above-mentioned dissolution removal or swelling division, chemicals had to be used. For example, formic acid is conventionally used to dissolve and remove polyamide, hot aqueous solution of caustic soda is used to dissolve and remove polyester, and trichloroethylene is used to dissolve and remove polystyrene.

The handling of these chemicals is dangerous and special equipment was required to dissolve and remove the polymer. For this reason, there are problems in terms of worker safety and health and manufacturing costs.

On the other hand, JP-B-58-39926 discloses that the content of 5-
It has been proposed that a water-soluble polyester copolymerized with sodium sulfoisophthalate is blend-spun and then dissolved and removed during stretching.

However, if such a large amount of sodium salt of 5-sulfoisophthalic acid is added, it is difficult to obtain a polymer having a sufficient degree of polymerization due to the foaming / thickening action during the polycondensation reaction, so that the spinnability is not always satisfactory. . Further, since a part of this type of polymer is eluted even in cold water, cold water cannot be used to turn the molten polymer after polymerization reaction into gut by discharge cooling, and a special device is required.

As a water-soluble polyester, there are many proposals for applications such as adhesives, sizing agents, and paints (eg
-40873, 57-26309, 60-1334, etc.). However, these were not always satisfactory for fiber formation due to melt spinning.

Further, JP-B-55-1374 describes a water-soluble polyamide.

However, this copolymer is said to have poor spinnability due to thermal stability at high temperatures and oligomers and monomers. Especially when the water-insoluble component is polyester
A spinning temperature of 280 to 290 ° C was required, and there was a problem in thermal stability and spinning stability. Also, the melting temperature cannot be kept high,
There was a limit in maintaining the cross-sectional shape of the composite yarn. In order to obtain a composite yarn by melt spinning, it is necessary to maintain appropriate heat resistance, viscosity, and spinnability even when melted at high temperature. In particular, in order to obtain an arbitrary composition ratio of the component X and the component Y in composite yarns having various cross-sectional shapes, at least the components X and Y must maintain the same level of viscosity. Due to the difference in the viscosity levels of the two components, the cross-sectional shape differs for each single-filament filament, and changes depending on the progress of spinning. Furthermore, it took a long time for the polymer to dissolve in hot water.
That is, there is a limit to the improvement of the conjugate fiber that can be obtained by dissolving and removing one component with hot water to obtain an ultrafine fiber.

[Problems to be Solved by the Invention] An object of the present invention is to have suitable heat resistance, viscosity, and spinnability even at high temperature without the above-mentioned drawbacks, and when applied as at least one component of a composite fiber, An object is to provide a copolyester that is insoluble in cold water and easily soluble in hot water.

[Means for Solving the Problems] The above object of the present invention is obtained from 5-sodium sulfoisophthalic acid, isophthalic acid, a C ₃ -C ₂₀ aliphatic dicarboxylic acid or a C ₃ -C ₂₀ aliphatic dicarboxylic acid. As an acid component other than the polyanhydride to be used, substantially only terephthalic acid as a constituent component, and as a diol component other than the polyalkylene glycol or its derivative having a number average molecular weight of 400 to 6000, substantially only ethylene glycol. In the polyester as a component, the following (I) ~
A hot water-soluble copolymerized polyester for forming fibers, which contains the amount of the components represented by the formula (V) and has a number average molecular weight of at least 12,000.

8 ≦ A ≦ 16 (I) 5 ≦ B ≦ 40 (II) 0 ≦ C ≦ 20 (III) 0 ≦ D ≦ 20 (IV) 0 ≦ E ≦ 20 (V) In the formula, A is 5-sodium sulfoisophthalic acid, B is isophthalic acid, C is a C ₃ -C ₂₀ aliphatic dicarboxylic acid, and D is D.
Is a polyanhydride obtained from a C _{3 to} C ₂₀ aliphatic dicarboxylic acid, E is a copolymerization amount of polyalkylene glycol or its derivative having a number average molecular weight of 400 to 6000, and A to C
Is mol% based on the total acid component, and D and E are% by weight based on the total polymer. Further, C, D and E do not become 0 at the same time and contain at least one component. Can be achieved by

The hot-water-soluble copolyester of the present invention (hereinafter, simply referred to as hot-water-soluble polymer) has terephthalic acid and ethylene glycol as main constituent components, and has the copolymerization components shown in the formulas (I) to (V). In addition, 5-sodium sulfoisophthalic acid, isophthalic acid, a C _{3 to} C ₂₀ aliphatic dicarboxylic acid, a polyanhydride obtained from a C _{3 to} C ₂₀ aliphatic dicarboxylic acid, and a polyanhydride having a number average molecular weight of 400 to 6000. A specific amount of alkylene glycol or its derivative is copolymerized.

That is, 5-sodium sulfoisophthalic acid as a copolymer component requires 8 to 16 mol%, preferably 10 to 15 mol%. If it is less than 8 mol%, the desired hot-water-soluble substance cannot be obtained. On the other hand, if it exceeds 16 mol%, it is difficult to handle in practice, even if the produced polymer is soluble in hot-water, but partially elutes in cold water. Occurs.

Also, with the 5-sodium sulfoisophthalic acid,
It is necessary to copolymerize 40 mol%, preferably 10-36 mol% isophthalic acid. When isophthalic acid is less than 5 mol%, flaky insoluble matter remains when dissolved in hot water.
If the ol% is exceeded, the polycondensation reaction rate will be slow, the softening point of the obtained polymer will be 100 ° C or less, drying before melt spinning cannot be sufficiently performed, and a polymer having a high melt viscosity at high temperature can be obtained. There is a practical adverse effect such as not occurring.

The hot water-soluble polymer of the present invention further comprises a C _{3 to} C ₂₀ aliphatic dicarboxylic acid, a polyanhydride obtained from a C _{3 to} C ₂₀ aliphatic dicarboxylic acid, and a number average molecular weight of 400 to 6000.
It is necessary to copolymerize a specific amount of at least one component of the polyalkylene glycol or its derivative. This not only improves hot water solubility, but also imparts flexibility to the discharge gut after the completion of polymerization, and features such as easy cutting.

Examples of the C _{3 to} C ₂₀ aliphatic dicarboxylic acid here include malonic acid, succinic acid, glutaric acid, adipic acid, corkic acid, azelaic acid, sebacic acid, dodecanedioic acid, and the like. Preferred components are adipic acid, azelaic acid, sebacic acid, dodecanedioic acid.

As the copolymerization amount of these C _{3 to} C ₂₀ aliphatic dicarboxylic acids, the upper limit is 20 mol%, and when it exceeds 20 mol%, like the above-mentioned isophthalic acid, the polycondensation reaction rate, the polymer softening point,
And problems such as melt viscosity will occur.

The preferred copolymerization amount of the aliphatic dicarboxylic acid is 15 mol% or less when the polyacid anhydride of the aliphatic dicarboxylic acid and / or polyalkylene glycol or a derivative thereof is used in combination, and the aliphatic dicarboxylic acid is also used. 5 to 20 when polyanhydride of acid and / or polyalkylene glycol or its derivative is not used in combination
mol%. The polyanhydride obtained from the aliphatic dicarboxylic acid has the following formula In the formula, it can be represented by m = 1 to 18 and n = 2 to 10. Specific examples thereof include polyadipic acid anhydride, polyazelaic acid anhydride, polysebacic acid anhydride, and polydodecanedioic acid anhydride. Of these, polydodecanedioic acid anhydride is preferable.

The copolymerization amount of the polyanhydride obtained from these aliphatic dicarboxylic acids has an upper limit of 20% by weight, preferably 15% by weight or less. When it exceeds 20% by weight, problems such as polycondensation reaction rate, polymer softening point, and melt viscosity occur as in the case of isophthalic acid.

The more preferable copolymerization amount of the polyanhydride obtained from the aliphatic dicarboxylic acid is 10% by weight or less when the aliphatic dicarboxylic acid and / or polyalkylene glycol or a derivative thereof is used in combination, When the polyanhydride of the aliphatic dicarboxylic acid and / or the polyalkylene glycol or its derivative is not used in combination, the amount is 3 to 15% by weight.

Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like, and examples of the derivative of the polyalkylene glycol include ethylene oxide, propylene oxide, butylene oxide and the like on the phenolic hydroxyl group of the bisphenol compound such as bisphenol A. Polyether compounds and the like obtained by ring-opening addition can be mentioned, but polyethylene glycol is particularly preferable.

These polyalkylene glycols or their derivatives require a number average molecular weight of 400 to 6000, preferably 600 to 4000. If the number average molecular weight is less than 400, the melting point of the produced polymer is greatly lowered and the polymer is insufficiently dried. For example, when the fiber is formed, the water content of the polymer causes a large decrease in the degree of polymerization during spinning, resulting in fiber formation. Will cause problems. On the other hand, when the number average molecular weight exceeds 6000, phase separation is likely to occur in the polymer, and the effects of hot water solubility and imparting flexibility to the gut are reduced.

The copolymerization amount of the polyalkylene glycol or its derivative is 20% by weight at the upper limit, preferably 15% by weight or less. When the amount of copolymerization exceeds 20% by weight, problems such as swelling of the polymer in cold water and marked deterioration of heat resistance of the polymer occur.

The more preferable copolymerization amount of the polyalkylene glycol or its derivative is 10 when the aliphatic dicarboxylic acid and / or its polyanhydride is used in combination.
3% to 15% by weight when the aliphatic dicarboxylic acid and / or its polyanhydride is not used in combination.
Is.

Further, the hot water soluble polymer should have a number average molecular weight of at least 12,000, preferably 15,000 to 35,000.

That is, when the number average molecular weight of the polymer is less than 12,000, the melt viscosity is small on the discharge surface during polymer synthesis, and the discharge of the polymer becomes unstable. Further, since the cooled polymer gut becomes brittle, process troubles such as frequent occurrence of polymer scraps (chip shape with abnormal length, polymer powder, etc.) are likely to occur in the process of finely granulating the polymer. Furthermore, the mechanical properties (strength, elongation, etc.) of polymers are basically inferior, which causes problems in the application of polymers.

On the other hand, if the number average molecular weight of the polymer is too large, the melt viscosity of the polymer increases, so the melt temperature of the polymer is set considerably higher than its melting point in order to maintain an appropriate polymer flow during molding. Need to do. Therefore, the polymer is severely deteriorated by a thermal decomposition reaction, and the thermal decomposition product is contained in the molded body, which causes a problem in quality and quality of the molded body.

When the polymer is used as, for example, one component of the conjugate fiber, it must have a melt viscosity similar to that of the other component. If the molecular weight is out of the above range, for example, a suitable melt viscosity or drawability in the composite spinning with polyethylene terephthalate. This is also because it is difficult to obtain threadiness. Since the melt viscosity of the hot water-soluble polymer of the present invention varies not only with the molecular weight but also with the polymer composition, it is necessary to select an appropriate molecular weight according to the polymer composition and other components of the composite spinning.

In the hot water-soluble polymer, among its copolymerization components, 5-sodium sulfoisophthalic acid,
Isophthalic acid and C ₃ -C ₂₀ aliphatic dicarboxylic acids are preferably kept in a total amount in the range of ₂₀ to 60 mol%, particularly 25 to 55 mol%.

Next, a synthesis example of the hot water-soluble polymer will be described.

To synthesize the hot water-soluble polymer, terephthalic acid, ethylene glycol, 5-sodium sulfoisophthalic acid, isophthalic acid, C _{3 to} C ₂₀ aliphatic dicarboxylic acid,
The polyanhydride obtained from the aliphatic dicarboxylic acid and the polyalkylene glycol having a number average molecular weight of 400 to 6000 or a derivative thereof are used as raw materials, and the synthesis is carried out by a known method.

That is, each of the direct acid or its lower alcohol ester, the aliphatic dicarboxylic acid and / or its polyanhydride, polyalkylene glycol or its derivative is esterified and / or transesterified under ethylene glycol excess, and further excess A method of distilling off ethylene glycol under reduced pressure is adopted. At this time, all the constituent components may be present from the initial stage of the reaction, or a part of the components may be reacted with ethylene glycol to form a low polymer, and the remaining components may be added to the polycondensation. Further, some stages of polycondensation may be performed in a solid phase. As reaction catalysts and additives, alkali metal compounds, alkaline earth metal compounds, cobalt compounds, antimony compounds, germanium compounds, titanium compounds,
Known compounds such as tin compounds, manganese compounds, zinc compounds and phosphorus compounds are adopted. Further, an antioxidant such as a hindered phenol compound may be contained.

As an example, the direct polycondensation method (batch type) will be described. At least terephthalic acid, isophthalic acid, and the aliphatic dicarboxylic acid and these acid components are used.
Charge 1.2 mol times ethylene glycol into an esterification can, and add water from the rectification column while stirring at a temperature from normal pressure to around ² kg / cm ² (gauge pressure) and above the boiling point of ethylene glycol to around 250 ° C. The esterification reaction is carried out while distilling off.

Next, the esterification reaction product is transferred to a polycondensation vessel, and while stirring, methyl ester or ethylene glycol ester of 5-sodium sulfoisophthalic acid (SI), a polyanhydride obtained from the aliphatic dicarboxylic acid , And polyalkylene glycol were added, and then polycondensation catalyst and antimony trioxide and phosphoric acid were added as stabilizers, and then ethylene glycol was distilled out of the reaction system at 250-290 ° C under reduced pressure (1 mmHg or less). Meanwhile, the polycondensation reaction may be carried out until the desired hot water-soluble polymer is obtained.

The obtained polymer is discharged from a polycondensation can by a usual method to be finely divided.

The hot water-soluble polymer thus obtained is particularly useful when applied to a composite fiber.

That is, the conjugate fiber as referred to herein is an ultrafine fiber generation type conjugate fiber such that one of the constituent components is dissolved and removed to obtain an ultrafine fiber, more specifically, a sea-island type conjugate fiber, a mixed spun conjugate fiber, and separation separation. Multi-component composite fiber such as type composite fiber,
A composite fiber that forms various deformed cross-sections by removing one component, or a composite fiber that can impart special bulkiness and rigidity by removing one component from the knitted fabric after setting.

The hot water-soluble polymer is one that is insoluble in cold water and soluble in hot water. This property of being insoluble in cold water and soluble in hot water is very advantageous in manufacturing synthetic fibers. That is, when it is soluble in cold water as well, when the molten polymer is discharged into a gut after completion of the polycondensation reaction, discharge cooling in a water bath that is usually used becomes impossible, and special cooling equipment is required. To do. In addition, when the composite fiber is handled, it is deformed by moisture in the air, which makes post-processing difficult. For example, when a composite fiber is made into a woven fabric, knitted fabric, or non-woven fabric, it enters the machine base for fabric formation through a thread or carding process, but during this time, the yarn breaks, fuzzing, or tangles of the composite fiber. It becomes difficult to process. Therefore, the hot water-soluble polymer of the present invention can be used as one component of the composite fiber together with other water-insoluble polymer components.

In this case, the water-insoluble components include polyamides such as nylon 4, nylon 6, nylon 7, nylon 11, nylon 12, nylon 66, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyolefins such as polyethylene and polypropylene. The class, and copolymers and modified products of these are preferably used.
The water-insoluble component is not limited to one component, and may be two or more components. In any case, the hot water-soluble polymer may be a conjugate fiber having a cross-sectional morphology occupying at least a part of the fiber surface. by this,
For example, if a hot water-soluble polymer is used as the sea component of the sea-island type composite fiber, ultrafine fibers can be obtained very easily by removing the hot water. Further, in the case of a conjugate fiber in which various arrangements of the hot water-soluble polymer are taken into consideration, a modified cross-section yarn having a shape corresponding to the arrangement can be obtained.

Furthermore, after setting the knitted fabric of the composite fiber, the hot water-soluble polymer can be appropriately removed to give a silky feel having a unique bulk and elasticity. Of course, these conjugate fibers show only one application example of the polymer of the present invention, and are not limited to these.

The hot water-soluble polymer in the composite fiber is
It is desirable to use a substance that does not leave a foreign matter residue with hot water without using any auxiliary agent, such as a substance that dissolves to form a transparent liquid or a substance that forms an emulsion finely dispersed state.

[Effects of the Present Invention] The hot water-soluble copolyester of the present invention is obtained by adding isophthalic acid, C ₃ in addition to 5-sodium sulfoisophthalic acid.
To C ₂₀ aliphatic dicarboxylic acid, polyanhydride obtained from the aliphatic dicarboxylic acid, and number average molecular weight of 400 to 600
Since it is composed of 0 polyalkylene glycol or its derivative, it exhibits the property of being insoluble in cold water and soluble in hot water. In addition, it has excellent heat resistance at high temperatures and spinnability, so it can be used for fiberizing by melt spinning. Especially, it can be used as one component of composite fiber and extra fine fiber or special fiber obtained by dissolving and removing it. It is useful in the field of deformed yarn cutting.

Hereinafter, the present invention will be specifically described with reference to examples. In this example, parts mean parts by weight. Further, the number average molecular weight and polymer evaluation of the hot water-soluble polymer in the present invention were carried out according to the following methods.

(1) Number average molecular weight Using a polymer chip as an orthochlorophenol solution, the molecular weight distribution was measured by gel permeation chromatography (GPC) according to a conventional method, and the number average molecular weight was calculated. A polystyrene standard sample was used to calibrate the molecular weight.

(2) Softening point Polymer chips were heat treated (70 ° C x 3 hr) and then measured with a penetrometer. The softening point was the temperature at which a chip with a thickness of 3 mm was deformed by 0.1 mm at a heating rate of 10 ° C / min.

(3) Change in cold water After immersing a chip (about 3mmφ x 5mm length) in water at 30 ° C for 20 hours, the surface condition, chip shape, and weight change of the chip were observed.

(4) Solubility in hot water 1 g of chips (about 3 mmφ x 5 mm length) were put into 100 g of hot water at 95 ° C, and the solubility was observed while stirring with a magnetic stirrer.

(5) Heat resistance After the chips were vacuum-dried at a temperature 10 ° C lower than the softening point for 8 hours, the viscosity and spinnability at a melt storage time of 10 minutes and 30 minutes at 285 ° C were observed with a melt indexer.

Example 1 112.7 parts dimethyl terephthalate (DMT), 32.7 parts dimethyl isophthalate (DMI), dimethyl adipate (DMA) 1
3.0 parts, 117.5 parts of ethylene glycol (EG), and 0.15 parts of calcium acetate were charged into a flask, and transesterification was performed at 130 to 230 ° C while distilling generated methanol. Next, the transesterification reaction product was transferred to a polymerization vessel, where there was methyl ester of 5-sodium sulfoisophthalic acid (SI) dimethyl 5-sodium sulfoisophthalate 33.3 parts, antimony trioxide 0.06 parts, phosphoric acid 0.02 parts. ,
And 0.6 part of lithium acetate are added, and after reacting at 230 to 250 ° C. for 1 hour, 11.3 parts of polyethylene glycol (PEG) having a number average molecular weight of 600 is additionally added, and the temperature is gradually raised from 250 ° C. While gradually reducing the pressure from 280 ℃,
Polycondensation was performed for 3.5 hours under the condition of 1 mmHg or less. After the polymerization, the polymer was discharged in a gut shape in a room temperature water bath to obtain chips.

The polymer thus obtained had a number average molecular weight of 27,000 and a softening point of 124 ° C. When the characteristics of this chip were evaluated, as shown in Table 1, the chip did not change in cold water, was soluble in hot water, and had good heat resistance.

Example 2 85.8 parts of terephthalic acid (TPA), isophthalic acid (IPA) 2
2.9 parts, 27.7 parts of dodecanedioic acid (DA), and 81.7 parts of EG are charged into an esterification reaction can, and atmospheric pressure ~ 2.0 Kg / cm ² G, 230 ~
An ester reaction was carried out while distilling generated water at 250 ° C. Next, the ester reaction product was transferred to a polymerization vessel, where 30.7 parts of SI ethylene glycol ester, 18.6 parts of PEG having a number average molecular weight of 2000, 0.07 part of antimony trioxide, and phosphoric acid were used.
0.02 parts, and 0.8 parts of lithium acetate are added, while gradually increasing the temperature from 250 ° C. and gradually reducing the pressure from normal pressure,
Finally, polycondensation was carried out at 280 ° C. and 1 mmHg or less for 4 hours.
After the polymerization, the polymer was discharged in a gut shape in a room temperature water bath to obtain chips.

 The results of evaluating the characteristics of this polymer are shown in Table 1.

Examples 3 to 5 and Comparative Examples 1 to 5 The case of changing the amount of the copolymerization component of the hot water-soluble copolymerized polyester was carried out in the same manner as in Example 2. The results are shown in Table 1.

In the case of Example 4, instead of PEG having a number average molecular weight of 2000, polydodecanedioic acid anhydride (PDA) having an average degree of polymerization of n = 3.2 was copolymerized.

Example 6 The chips obtained in Example 1 were vacuum-dried at 100 ° C. for 10 hours, and the homopolyethylene terephthalate (PET) chips (IV; 0.70) vacuum-dried at 150 ° C. for 6 hours were separately separated. It was melted (280 ° C) by a screw extruder and sent by a gear pump to a sea-island type spinneret of 18 groups of 16 islands for composite spinning. The polymer of Example 1 is a sea component, and the discharge amount is 5.
28 / min, PET was an island component with a discharge rate of 20.8 g / h, spun from a spinneret hole, air-cooled, oiled with modified olefins, and then wound at 1000 m / min. The obtained undrawn yarn was drawn 3.2 times by passing through a hot roll of 90 ° C. and a hot plate of 120 ° C. to obtain a drawn yarn of 75 denier 18 filaments.
Almost no yarn breakage occurred during spinning and drawing.

Then, a tubular knit fabric was prototyped using this drawn yarn and
It was immersed for 10 minutes and then dried. Weight before soaking 7.4g (knitted fabric approx. 1m
The long one weighed 5.9 g after the immersion treatment, and the touch was very soft and supple. Furthermore, the cross section of the drawn yarn
18 filaments were divided into 288 filaments of ultrafine fibers.

Example 7 According to Example 6, using a spinneret in which the fiber has a trilobal cross-sectional shape and the polymer of Example 1 is arranged in a tapered wedge shape from the apex of the trilobal direction toward the fiber inward direction. The yarn was then subjected to a spinning process to obtain a composite fiber of 75 denier 36 filaments.

Then, a tubular knitted fabric was formed according to Example 6, followed by immersion treatment with boiling water for 10 minutes. As a result, the hot water-soluble polymer was removed, and the apex of three lobes was formed into a wedge-shaped taper toward the inside of the fiber. A dent was formed to give a silky, elegant luster and texture.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-58-83046 (JP, A) JP-A-57-133125 (JP, A) JP-A-55-5938 (JP, A) JP-A-54- 3848 (JP, A)

Claims (1)

(57) [Claims] 1. 5-Sodium sulfoisophthalic acid, isophthalic acid, C ₃ -C ₂₀ aliphatic dicarboxylic acid or C ₃ -C ₂₀
As an acid component other than the polyanhydride obtained from the aliphatic dicarboxylic acid, substantially only terephthalic acid as a constituent component, and as a diol component other than a polyalkylene glycol having a number average molecular weight of 400 to 6000 or a derivative thereof, A polyester having substantially only ethylene glycol as a constituent component, containing a component amount represented by the following formulas (I) to (V) and having a number average molecular weight of at least 12,0:
00 is a hot water soluble copolyester for fiber formation. 8 ≦ A ≦ 16 (I) 5 ≦ B ≦ 40 (II) 0 ≦ C ≦ 20 (III) 0 ≦ D ≦ 20 (IV) 0 ≦ E ≦ 20 (V) In the formula, A is 5-sodium sulfoisophthalic acid, B is isophthalic acid, C is a C ₃ -C ₂₀ aliphatic dicarboxylic acid, and D is C.
₃ -C polyacid anhydride derived from aliphatic dicarboxylic acids _20, E represents the copolymerization amount of the polyalkylene glycol or derivative thereof having a number average molecular weight 400 to 6000, A through C is mol% of total acid component, D and E are wt% based on the total polymer. Further, C, D and E do not become 0 at the same time and contain at least one component.