JPS58220806A - Polyvinyl alcohol type synthetic fiber having latent solubility in water at low temperature and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled fibers, capable of increasing the dissolving temperature in water, reducing the dissolving temperature in water after the treatment with an alkali, and having improved drying efficiency, by spinning a polyvinyl alcohol (PVA) having introduced carboxyl groups into a coagulation bath of Glauber's salt, treating the resultant fibers in an acidic bath, drying the resultant fibers, and heat-treating the dried fibers. CONSTITUTION:A polyvinyl alcohol (PVA) having 0.02-0.4mol/100g introduced carboxyl groups is dissolved in water to give an aqueous solution, which is then spun into a coagulation bath of Glauber's salt. The resultant fibers are then treated in an acidic bath of 2-6pH, and dried with the stuck Glauber's salt. The dried fibers are further heat-treated at 150 deg.C-the melting point to increase the dissolving temperature in water to 90 deg.C or above. The resultant fibers are washed with water to remove the stuck Glauber's salt, and if necessary an oiling agent is applied thereto. The oiled fibers are dried and treated with an alkali to afford the aimed PVA fibers having <=80 deg.C dissolving temperature in water. EFFECT:The high dissolving temperature in water as high as 90 deg.C or above facilitates the drying in the preparation process, and the removal of the stuck Glauber's salt is possible at 80 deg.C or below in the dissolving and removing step thereof. USE:Binder fibers for nonwoven fabrics, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) synthetic fiber that has the property of potentially dissolving in water at low temperatures. ``PVA is a polymer that originally has the property of dissolving in water, and fibers of this polymer are manufactured by spinning its aqueous solution using a wet or dry method.

The fiber is generally dried, stretched, and heat treated after spinning, and if necessary undergoes an acetalization reaction, etc., and is consumed in large quantities primarily for industrial material applications as a highly water-based, high-strength, high-Young's-modulus fiber. .

On the other hand, it is also used in various fields as a water-soluble fiber that takes full advantage of the original property of PVA to dissolve in water after drying the water contained in the fiber after spinning.

For example, dry-processed, wet-processed nonwovens, fibers for textile binders.

Fibers for chemical lace base fabrics and the like are known. Among them, binder fibers for wet-laid non-woven fabrics are typically used. Main fibers cut into several layers and PVA-based water-soluble binder fibers are mixed in an appropriate ratio to make a slurry. The process involves making a wet sheetra and drying it to make a wet non-woven fabric, which is called paper.
During the drying process, the binder fibers dissolve and form a fine film at the intersections of the main fibers, which solidify as water evaporates and develop paper strength.

As mentioned above, there are two methods for producing PVA-based water-soluble fibers: the dry method and the wet method.As will be understood later, the present invention is particularly effective in the wet method, so the following will be based on the wet method. I will explain.

In the known wet method for producing water-soluble fibers, PVAt having an appropriate degree of saponification and degree of polymerization is dissolved in water and spun as a total coagulation bath of a saturated sodium sulfate solution. Eventually it must be removed or dried.

However, since fibers are inherently water-soluble, if the temperature rises while still containing water during drying, depending on the temperature, the fibers may be fused, or even if they are not fused, the surface of the fibers may be partially dissolved. As the moisture evaporates, the single fibers adhere to each other, resulting in a total loss of commercial value. Therefore, the fibers are dried at a temperature below the water dissolution temperature,
Drying efficiency will be significantly reduced.

Various efforts have been made to avoid this problem.

For example, in the case of binder fibers for wet-processed nonwoven fabrics, the fibers are usually formed using a Glauber's salt bath as a coagulating bath, but the Glauber's salt is dried without washing and cut into suitable fiber lengths for use for the purpose.

In this case, due to the coagulation and dehydration ability of the sulfate that adheres to the fibers, no melting or adhesion will occur even if the fibers are dried at a temperature higher than the melting temperature of the fibers in water, making it possible to dry efficiently. be.

In the case of binder fibers for wet-laid non-woven fabrics, as mentioned above, water is used in the paper-making process to form a slurry, so Glauber's salt is removed, and therefore no Glauber's salt is present in the finished wet-laid non-woven fabric. Therefore, even if it is coated with Glauber's salt, there is no problem as a binder fiber for wet-laid nonwoven fabrics.

However, the fibers to which Glauber's salt is attached can be used for limited purposes such as the above-mentioned wet-laid nonwoven fabric, but cannot be used for general purposes.

For example, for water-soluble staples, textile filaments, etc. that require spinning, adhesion of Glauber's salt is fatal to their ability to pass through processing steps such as spinning and weaving.

In general, in order to improve the passage through the processing process, oils that have been carefully examined for smoothness, antistatic properties, winding properties, and various other factors are used, and the selection of the oil is important. It is a fact that those skilled in the art often experience that if they make a mistake, they will not pass the process at all.

Furthermore, it is highly unlikely that the fabric will not pass through the spinning and weaving processes if it has Glauber's salt attached to it.

A known wet manufacturing method for water-soluble fibers for applications where glauber's salt adhesion is not allowed will be described in more detail.

As described above (spun the FVA aqueous solution mainly into a high-concentration sodium sulfate coagulation bath, wet-stretched as appropriate, wash off the adhering sodium sulfate, apply an oil and dry. In the case of filaments, cheese The yarn is then wound, twisted, and subjected to the weaving process.

In the case of staples, they are used in the dry non-woven fabric manufacturing process or the spinning process, so they are wound and then cut into appropriate lengths. Another manufacturing method is to wash the dried product after the wet stretching with water to remove the mirabilite, coat it with an oil agent, and then dry it. In the case of filament, it is made into a cheese roll, and in the case of staple, it is crimped, and the post-cutting process is performed. It is an offering to

In either method, water, which has high solubility and is economical, is used for cleaning the sodium sulfate, and a drying step is required after applying the oil.

Originally, water-soluble fibers are mostly or completely dissolved in the presence of water when the temperature exceeds the water dissolution temperature of the fibers.

Further, even below that temperature, swelling is large and even partial dissolution may occur, and this tendency becomes stronger as the temperature of the water present in the fiber approaches the water dissolution temperature.

Therefore, the key points in manufacturing water-soluble PVA fibers using a wet process that does not cause mirabilite adhesion are to suppress fiber swelling in the washing process of mirabilite to eliminate dissolved components, and to prevent fibers from melting and wetting due to dissolution in the drying process. Then there is K.

In response to this problem, various studies have been made from the viewpoint of how to economically obtain materials with a low water dissolution temperature.

In the sodium sulfate washing process, the swelling of PVA is suppressed, but solvents that are soluble in sodium sulfate are being considered. For example, methanol has a low solubility for mirabilite and PVA
The dissolution and diffusion of Glauber's salt inside the fibers is the rate-limiting factor in order to suppress the swelling of the sulfate, which requires an extremely long time to wash, and because it is a flammable chemical, it requires a large investment in equipment. As a result, the manufacturing cost increases significantly.

Therefore, in the end, there is no need to use water to wash Glauber's salt; at best, the water temperature can be forcibly lowered to an economically viable level, or the fibers can be put under as much tension as possible to suppress swelling, but even then, there is no problem. The reality is that if this is to occur, it is unavoidable to raise the water dissolution temperature of the fibers.

On the other hand, in the drying process, as mentioned above, the problem is how to dry efficiently without cutting the fibers or adhering the fibers to each other.

Water-soluble fibers dissolve in the presence of water when heated to a temperature equal to or higher than the water-soluble fiber.

Therefore, during drying, most of the time must be spent at a temperature considerably lower than the water dissolution temperature of the fiber.

The reason why the temperature must be kept very low is that, as mentioned above, the fibers swell significantly even below the water dissolution temperature, and in some cases may partially dissolve. This tendency becomes more noticeable as the temperature approaches the water dissolution temperature.

Generally, drying is done at a temperature about 10°C lower than the water dissolution temperature! Ru.

For this reason, in order to obtain water-soluble fibers that melt at low temperatures, it is necessary to lower the drying temperature, which results in a significantly longer drying time, which significantly reduces productivity. The resulting water-soluble fibers are extremely expensive.

Therefore, various attempts have been made to increase the drying efficiency as much as possible. That is, an attempt is made to bring the drying temperature as close as possible to the water dissolution temperature.

For example, various attempts have been made to apply an anti-adhesion agent before drying in an attempt to prevent single fibers from adhering to each other.
Even if mineral oil or the like is applied, it is only slightly effective, and no dramatic effects have been achieved.

In addition, in order to prevent fibers with moisture from swelling during the drying process and resulting in fibers adhering to each other, it is relatively effective to apply tension in the fiber axis direction, but this can approach the water dissolution temperature slightly. That's about it.

Furthermore, when the amount of water contained in the fibers decreases, it tends to become difficult for the fibers to adhere to each other due to dissolution of the fibers.

The present inventors made various studies regarding this point before arriving at the present invention, but it was found that 100 to 200%
It was found that until the moisture content of the fiber reaches about 10%, it cannot be raised above the water dissolution temperature of the fiber, and therefore most of the drying must be done at a low temperature.

As described above, the only way to significantly improve drying efficiency is to increase the water dissolution temperature of the fibers.

However, if the water dissolution temperature is raised, efficient production is possible in the fiber manufacturing process, but depending on the intended use of the fiber, it is necessary to dissolve or remove it in the processing process. In addition to being extremely difficult and expensive to operate due to the high temperature, it also has a fatal defect in that the physical properties of the main fiber are significantly impaired due to the high temperature treatment.

As mentioned above, fibers that are soluble in water at low temperatures have low productivity and are very expensive, and high-temperature soluble fibers can be manufactured at relatively low cost, but the processing process of dissolving or dissolving them requires significant costs. In addition, it also poses a qualitative problem.

Therefore, products using dry non-woven fabrics and knitted fabrics using water-soluble fibers will be expensive even if K is eventually used.

The present inventors have arrived at the present invention as a result of intensive research to solve the above-mentioned problems.

That is, the present invention relates to a water-soluble fiber that can achieve its purpose at a high water dissolution temperature of 9°C or higher in the manufacturing process of water-soluble fiber, but at a low temperature of 80°C or lower in the dissolution or dissolution/removal process. It is.

More specifically, by introducing carboxyl groups into the fibers and subjecting them to heat treatment, the water dissolution temperature in the fiber manufacturing process is increased to 90°C or higher, making it easier to wash and subsequently dry the sodium sulfate, and in the processing process. Then apply alkali treatment.
The present invention provides a PVA-based fiber whose water dissolution temperature is as low as 80° C. or lower to facilitate dissolution and removal, and a method for producing the same.

J・＼ The present invention will be described in detail below.

Introducing a force boxy ρ group into PVA fibers is an important requirement of the present invention, and the following three methods are effective.
be.

(1) Spinning PVA into which a carboxyl group has been introduced; (2) Spinning a mixture of the PVA into which a carboxyl group has been introduced and ordinary PVAI; (5) Water-soluble polymers having carboxyl groups such as polyacrylic acid and polymethacrylic acid. and ordinary PVA are mixed and spun.

The fibers thus obtained dissolve at low temperatures, but
To raise the water dissolution temperature to 90°C or higher, the spun fibers should be
It is important to treat with H2-6 solution, dry with the Glauber's salt still attached, and then heat-treat at 150°C.

In the wet manufacturing method of PVA fibers, the spinning dope is usually discharged into a coagulation bath consisting of a sodium sulfate solution and coagulated to form a thread, which is then introduced into a higher temperature of a sodium sulfate solution and heated to an appropriate temperature. □The process is to undergo stretching at a certain magnification, then drying, further stretching, and heat treatment if necessary.
The treatments under 2 to 6 may be performed using a coagulation bath, or an acidic bath using a subsequent higher temperature sodium sulfate bath (2 baths), or an acidic bath other than the above-mentioned baths. In order to perform drying and heat treatment to prevent adhesion at a later stage, it is preferable to use 1cI'i and the above two baths as acidic baths.

The water dissolution temperature in this application means that a fiber of appropriate length and thickness is fixed at the upper end of the scale, and 10'00" is fixed at the lower end of the scale.
/ Place it in the water with a denier-equivalent weight.

This is the temperature at which the sinker melts and falls along with the weight from the melted part when the water is immersed vertically and the water temperature is raised from room temperature at a rate of 1°C per minute. Note that the water dissolution temperature after alkali treatment is the dissolution temperature measured by the above measurement method after treatment with caustic soda IQ/l.

There are various methods for introducing carboxy μ groups into PTA, but
The following methods are effective.

(b) A method of copolymerizing with a monomer that can be copolymerized with vinyl ester and saponifying it; (b) A method of graft polymerizing to PVA or graft polymerizing to polyvinyl ester and saponifying it. There are methods such as chemical reaction, but method (a) is more economical.

More specifically, method (a) involves the use of unsaturated basic acids, unsaturated tribasic acids, and anhydrides thereof that can be copolymerized with organic acid vinyl esters such as vinyl formate, vinyl acetate, or vinyl propionate. , take these esters, such as acrylic acid, methacrylic acid, crotonic acid,
maleic acid, fumaric acid, itaconic acid, maleic anhydride,
By saponifying a copolymer of itaconic anhydride, or by saponifying the copolymer of itaconic anhydride, or the above-mentioned hinyl esters,
By saponifying a copolymer of methacrylnitrile and acrylamide, the desired PVA1 having a carboxyl group in the molecule can be produced.

Method (b) includes a method in which acrylonitrile or acrylamide is graft-polymerized to PTA or polyvinyl acetate and then saponified.

Method (c) involves reacting PVA with a dibasic acid, such as maleic acid, 7-malic acid, ga, malonic acid, succinic acid, adipic acid, or anhydride thereof, and introducing a carboxyl group through a partial esterification reaction. be able to.

It is not clear why the temperature of the aqueous layer increases when carboxyl groups are introduced into PVA fibers and is heat-treated, but it decreases significantly when treated with alkali, but it is probably due to the formation of esters between the carboxyl groups and the hydroxyl groups present between or within the molecules. It is thought that the temperature of the aqueous layer increases due to the formation of bonds, and that when treated with alkali, the ester bonds, which are weak against alkali, are broken, resulting in a significant drop.

The amount of carboxyl groups in PVA is preferably from 0.02 mol to 0.4 mol, more preferably from 0.04 to 0.18 mol, per 100 g of polymer.

If the amount is less than 0.02 mol, the effect of the presence of carboxyl groups is small, and therefore the difference between the aqueous layer temperature and the aqueous layer temperature after alkali treatment is large, so if the aqueous layer temperature is raised to above PO°C in the fiber manufacturing process, processing will be difficult. The temperature of the aqueous layer after the alkaline aqueous solution treatment does not fall below 80°C.

Moreover, if it is more than 0.4 mol, it is difficult to make it into fibers. That is, the coagulation state during spinning is not good and the spinning condition is poor. Furthermore, the swelling during the drying process before heat treatment is too large, causing adhesion of single fibers even in the presence of Glauber's salt, which is a problem.

The saponification degree is preferably 80% or more, and the polymerization degree is 400%.
~3000 is appropriate.

When mixing and spinning the PVA into which carboxyl groups have been introduced in method (2) and ordinary PVA without carboxyl groups, the amount of carboxyl groups in 100 g of the mixed PVA polymer is 0.02 to 0.4. It is sufficient to include moles. For example, if 50% by weight of PVA with 0.16 mol of carboxyl groups and 50% by weight of normal PVA without carboxyl groups are mixed in 10'Og of PVA polymer, polymer 1009
Having 0.08 mol of carboxyl group per K
Become.

In the case of (5), poly□′)□□acrylic acid, polymer
Chrysanthemum... PV that does not have acid or its salts, etc. and carboxyl group
Regarding mixed spinning with A, it is only necessary to perform gradient mixing so that the average amount of carboxyl after mixing becomes 0.02 to 0.47 microns per 100 f of polymer.

The concentration of the PVA-based aqueous solution having carboxyl groups thus obtained is preferably 8 to 20% by weight, and more preferably 13% by weight.
~17%.

The spinning stock solution is mainly spun into a concentrated Glauber's salt bath, then introduced into a hotter Glauber's salt solution, subjected to wet stretching at an appropriate ratio, and treated in an acidic bath with a pH of 2 to 6, with the Glauber's salt still attached. dry.

If the pH is lower than 2, it is not preferable because V) PVA deteriorates during the subsequent heat treatment. Moreover, at pH 6 or higher, the temperature of the aqueous layer increases even with heat treatment, and therefore the difference from the temperature of the aqueous layer after alkali treatment is small. It is assumed that the carboxyl group is present in the form of a carbonate salt, reducing reactivity.

Subsequently, the film is heat-treated at a temperature of 150°C or higher and lower than the melting point by constant length or slight stretching to bring the temperature of the aqueous layer to 90°C or higher.

If the temperature is below 150°C, an aqueous layer temperature of 90°C or above cannot be obtained.

In order to use the fibers for dry nonwoven fabrics, weaving, and textile applications, it is important to remove Glauber's salt and add an oil agent. Although washing of Glauber's salt is carried out with water, in the case of the present invention, Ly)
dixyl group? As the water solubility temperature is increased, there is no need to lower the water temperature in particular, and washing under normal tension is sufficient, and the washing process is much easier than with normal P'VA-based water-soluble fibers. be. As the anti-oil agent, any known oil agent may be appropriately selected. □Drying after applying the oil agent is the most distinctive feature of the present invention, and drying is performed below the water dissolution temperature of the fiber until the moisture content reaches 10 to 20 culm attack degree. Generally about 10
°C or less, but in the case of the present invention, it is approximately 50 °C.
C or so is sufficient, and in addition to the aqueous layer temperature being originally high at 90°C or higher, the drying temperature only needs to be lowered by a small amount from the aqueous layer temperature, and therefore a higher drying temperature can be set, resulting in a remarkable drying efficiency. If you increase , it becomes k.

It is not clear why the drying temperature may be slightly lower than the water dissolution temperature in the case of the present invention, but in the case of ordinary PVA, its water resistance is only due to the physical factor of crystallization, but the present invention It is presumed that this is because it is more stable against moist heat due to the chemical reaction between phoxyl and hydroxyl groups.

In the case of staples, the dried fibers are crimped if necessary and cut into appropriate lengths. In the case of filament, it is usually rolled into cheese after drying.

Although the fiber thus obtained has a high aqueous group temperature of 90° C. or higher, it becomes 80° C. or lower if treated in an alkaline bath, and can be dissolved or removed at low temperatures.

The fibers are made into woven and knitted fabrics as filaments and spun yarns,
For example, it can be used in various applications such as chemical lace base fabrics and high-grade terry cloth, where it is ultimately dissolved and removed, and in various applications as binder fibers such as binders for dry-laid non-woven fabrics as staples.

Note that the scope of use is not limited to the above example, as a matter of course.

The present invention □ will be explained below with reference to examples, but it is not limited to these examples.

Example 1 Vinyl acetate and itaconic acid were copolymerized using methanol as a solvent using 2,2'-azobisisobutyronitrile as a catalyst, and then saponified with an alkali to convert itaconic acid into 2
Degree of polymerization introduced in mol%: 1800. Ken (tjtpa, s
Mo/l/% polyvinyl 7 luco 7v (PVAloog
A *, b force #boxy # group zO, 087 mo #) was obtained.

A 16% by weight aqueous solution of this PVA gold was used as a spinning dope.

The spinning stock solution was spun into a coagulation bath consisting of a saturated mirabilite bath at 40°C, stretched twice between rollers, and further stretched at 80°C and P.
After stretching 2 times in a saturated sodium sulfate bath adjusted to H4.5,
After drying at 0°C, heat treatment was performed at 210°C for 30 seconds at a constant length. The obtained fiber has a single fiber thickness of 2 denier,
The aqueous group temperature was 100°C or higher. (100°
After washing the Glauber's salt with room temperature water under tension and treating it with an anionic oil, it was dried with hot air at 97°C until the moisture content reached 10%, and the remaining water was washed with water Q[,,120 °C
It was dried. No adhesion between single fibers was observed.

The aqueous group temperature after treating the fiber under tension with an aqueous solution of caustic soda at a concentration of 19/l) and a temperature of 50''C is:

It melted at a very low temperature of °C. That is, in the fiber manufacturing process, efficient production is possible due to the high aqueous group temperature, and in the processing process, it is possible to dissolve or remove by dissolution at a low temperature of 60°C as long as alkaline earth metal is applied.

Comparative Example 1 Polymerization degree of 1750 made by ■Gurare, which does not contain carboxyl groups
, PVAi with saponification degree of 98.5 moIv% (7) was used, and the treatment was performed under exactly the same conditions as in Example 1 up to the oil treatment step.

The aqueous group temperature of the obtained fiber was 70°C.

When drying after the oil treatment was carried out under the same conditions as in Example 1, fusing occurred, and the single fibers strongly adhered to each other, resulting in a rod-like shape.

Therefore, up to 10 moisture particles can be dried at 60°C, and less than 10 particles can be dried at 60°C.
Dry at 20°C. Although the adhesion was suppressed to a slight extent, the drying time was more than 20 times that of Example 1, which was completely out of the question for industrial production.

Note that Example 1. The aqueous group temperature after treatment with a caustic soda aqueous solution was measured in the same manner as above, and it was exactly the same as 70°C without treatment.

Comparative Example 2 - Polymerization degree 1700 manufactured by Kuraray, which does not contain carboxyl groups
Completely saponified PVA with a saponification degree of 99.9 mol % was produced under the same conditions as in Example 1.

Although the aqueous group temperature was 90°C, severe adhesion between single fibers was observed during the drying process after oil treatment.

Therefore, the moisture content is reduced to 80°C and dried.
Thereafter, the temperature was raised to 120°C to dry the remaining moisture.

Although no adhesion between single fibers was observed, the aqueous group temperature was 90
The temperature was high, and the drying time was five times that of Example 1.

As in Comparative Example 1, even when treated with an aqueous caustic soda solution, the aqueous group temperature was no different from 90°C in the case without treatment.

In comparison with Comparative Example 1.2, Example 1 clearly shows that it is possible to efficiently produce PVA-based fibers with low-temperature water solubility.

Examples 2-5. Comparative Examples 3 to 4 Vinyl acetate and itaconic acid were mixed using methanol as a solvent.
After copolymerizing with 2'-zobisisobutylnitrile, the polymerization degree was 16o by saponification with an alkali.

~1700. Itaconic acid copolymerized PVA with a saponification degree of 98.0 to 98.6 mo/L'% was obtained. By changing the itaconic acid copolymerization number, the amount of carboxyl groups contained in 100 g of polymer was 0.014 mol (Comparative Example 3), o, o3 + mo/
I/(Example 2), o, o66mo/L/C Example 3)
, C1,21 mo/L/(Example 4), 0.31 mole (Example 5).

It was set to 0.53 mo/I/ (Comparative Example 4).

Using each itaconic acid copolymerized PVAN, production was performed under exactly the same conditions as in Example 1 up to the oil treatment step.

The subsequent drying conditions were as follows: (aqueous group temperature -5°C)
), and the moisture content of the residue was raised to 120°C. ,,・.

1□, ゎeh, -5-ru 1□8eh.

In Comparative Example 3, the aqueous group temperature after alkali treatment was as high as 90°C, and in Comparative Example 4, adhesion was large during drying before heat treatment during spinning, and the spinning condition was not good.

Examples 6-8. Comparative Examples 5 to 6 The same method as in Example 1 was carried out except that the pH in the 80° C. sodium sulfate bath treatment after roller stretching was changed.

The pH was adjusted with sulfuric acid and caustic soda and was 1.5 (Comparative Example 5), 2.5 (Example 6), and 4.0 (Example 7).

5.0 (Example 8) and 8.0 (Comparative Example 6). The aqueous group temperature was measured before and after the alkali treatment, and the results are shown in Table 2.

In Comparative Example 5, the pH was too low, resulting in severe discoloration of the fibers, and the temperature of the aqueous group after alkali treatment was too high.

Although the cause is not clear, it is possible that the main chain of PVA is broken and all crosslinks other than ester bonds are formed between molecules, and the aqueous group temperature decreases by the alkali treatment is too small.

Comparative Example 6 The temperature of the aqueous solution does not rise significantly even after heat treatment. Although the reason is not clear, it is possible that the carboxyl group becomes a salt due to the high pH, reducing its reactivity with the hydroxyl group.

In any case, the aqueous group temperature is low even after heat treatment, and there is almost no decrease in temperature even after alkali treatment.

It is clear how important the pH of the example is.

Examples 9-11. Comparative Examples 7 to 8 The conditions were the same as in Example 1 up to the drying step after spinning, but the heat treatment temperature was variously changed, and the aqueous group temperature was changed to caustic soda 197.
The results are shown in Table 5.

Note that the heat treatment time was 30 seconds as in Example 1.

Table 0-3 The problem with heat treatment at 150°C or lower is that the temperature of the aqueous layer is too low and it takes a long time to dry after oil treatment.

Example 12 Modification degree obtained by saponifying a copolymer of maleic anhydride and vinyl acetate 2 mo) V% (carboxyl group content in 100 g of polymer 0.088 mo/L/) degree of polymerization 1800,
Itaconic acid copolymerized PVA with a saponification degree of 98.5 mol and ordinary completely saponified PTA (the same PVA as in Comparative Example 2) were mixed at a weight ratio of 75:25, rt:')-q- 1
16% by weight PVA water soluble g! with an average carboxyl group amount of 0.066 mol in oog! It was used as a spinning stock solution. After spinning, the spinning solution was treated under exactly the same conditions as in Example 1 to obtain fibers. The fiber has no adhesion and has a water solubility temperature of 100
The temperature of the aqueous layer after treatment with a 1 g/l caustic soda aqueous solution was as low as 73°C.゛Example 15 P obtained by copolymerizing maleic anhydride in Example 12
PV copolymerized with itaconic acid 2 mo/L/gold instead of VA
A (same as in Example 1 - PVA) All were treated under the same conditions as in Example 12, except that i was used.

The resulting fibers had no adhesion at all, and the temperature of the aqueous layer was 100°.
The temperature of the aqueous layer after alkali treatment is 67°C.
It was low.

Patent Issuance Dai Co., Ltd. Attorney Ken Honda

Claims (2)

[Claims] (1) Contains 0.02 to 0.4 moles of carboxyl group in 100 g of polymer forming the fiber, and has a water dissolution temperature of 90
Polyvinyl alcohol-based synthetic fibers that have potential low-temperature water solubility, with a water solubility temperature of 80°C or higher after treatment in an alkaline bath. (2) A polymer containing 02 to 0.4 moles of carboxyl groups in 100 g of the polymer forming the fibers is prepared as an aqueous solution.1. The aqueous solution is wet-spun using Glauber's salt as a coagulating bath, treated with a treatment solution of pH 2 to 6 in the coagulating bath or in a subsequent step, dried with the attached Glauber's salt still attached, and further heat-treated at a temperature above 150°C and below the melting point. Production of polyvinyl alcohol-μ-based synthetic fiber JjlF+, which has a characteristic water solubility temperature of 90°C or higher and a water solubility temperature of 80°C or lower after treatment in an alkali bath, potentially having low-temperature water solubility. law