JP2005154958A - Fibrillated acrylic fiber, method for producing the same and structure containing the fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fibrillated acrylic fiber produced from a stably spinnable fiber, enabling easy fibrillation and having excellent thermal stability and provide a method for producing the fibrillated acrylic fiber and a structure containing the fiber. <P>SOLUTION: The fibrillated acrylic fiber is produced by beating a raw material fiber having a water-absorption rate of ≥0.15 g/g and a water absorption of ≥20 wt.% and produced by spinning a spinning dope composed of a polymer mixture comprising 95-99 wt.% acrylonitrile polymer containing ≥80 wt.% acrylonitrile bonded in the polymer and 1-5 wt.% hydrophilic acrylonitrile resin containing 10-70 wt.% acrylonitrile bonded in the resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a fibrillated acrylic fiber, a method for producing the same, and a structure containing the fiber.

Fibers having fine fineness such as ultrafine fibers and fibrillated fibers are widely used as paper or non-woven materials, friction materials, cement reinforcing materials, or the like. Acrylic fibers are excellent in water resistance and chemical resistance, and have the characteristics of being hardly fusible, and are suitable materials for such applications. For this reason, various attempts have been made to obtain acrylic fibers having a fine fineness, but the most common method is to beat the fibers to form a fibril.

However, it is difficult to fibrillate general-purpose acrylic fibers even after a beating process. For this reason, methods using an additive have been proposed. For example, in Patent Documents 1 and 2, cellulose acetate or an acrylic resin that is incompatible with the acrylonitrile-based polymer constituting the fiber is added to the spinning dope and spun to form a phase separation structure in the fiber. After obtaining the acrylic fiber which has, the method of beating a fiber and making it a fibril is disclosed. However, in these methods, the incompatible substances added are united and the area of the incompatible substances in the fiber tends to be large, so that yarn breakage frequently occurs during spinning, and the fiber splitting property deteriorates. Have problems.

Patent Documents 3 and 4 disclose fibrillated acrylic fibers made of two types of acrylonitrile polymers having different acrylonitrile bond contents. In these cases, the difference in the acrylonitrile bond content between the two types of acrylonitrile polymers used is small and phase separation is unlikely to occur, so a high rate of raw fiber with a moisture content of several hundred percent is fibrillated. As such high moisture content raw material fibers, so-called gel fibers that have not been heat-treated are used. Fibrilized acrylic fibers obtained by beating such raw fibers have poor heat stability and have the problem of shrinking in the drying process when producing the final product paper or nonwoven fabric.
Japanese Patent Laid-Open No. 10-158928 JP 11-293516 A JP 2000-73229 A JP 2003-166118 A

It is an object of the present invention to provide a fibrillated acrylic fiber improved in the present situation, a method for producing the same, and a structure containing the fiber.

As a result of diligent investigations to achieve the above-mentioned object, the present inventor has obtained a certain degree of compatibility with the polymer in the spinning solution of the acrylonitrile polymer, and has a hydrophilic property. It has been found that the raw material fiber obtained by using the resin-containing material has good splitting properties and can be easily fibrillated by beating.

（５）（１）〜（４）のいずれかに記載のフィブリル化アクリル繊維を含有する構造物。
（６）８０重量％以上のアクリロニトリルを結合含有するアクリロニトリル系重合体９５〜９９重量％および１０〜７０重量％のアクリロニトリルを結合含有するアクリロニトリル系親水性樹脂１〜５重量％の重合体混合物からなる紡糸原液を湿式紡糸するに際し、延伸後の未乾燥繊維の水分率を５０〜１３０重量％とし、該未乾燥繊維を１０５〜１３０℃の温度で湿熱処理して得られる繊維を叩解することを特徴とするフィブリル化アクリル繊維の製造方法。 That is, the present invention is achieved by the following means.
(1) Containing a polymer mixture of 95 to 99% by weight of acrylonitrile-based polymer containing 80% by weight or more of acrylonitrile and 1 to 5% by weight of acrylonitrile-based hydrophilic resin containing 10% to 70% by weight of acrylonitrile. A fibrillated acrylic fiber obtained by beating a raw fiber having a water absorption rate of 0.15 g / g or more and a water absorption of 20% by weight or more, which is obtained by spinning a spinning dope.
(2) The fibrillated acrylic fiber according to (1), wherein the raw fiber has a water retention of 120% by weight or less.
(3) The acrylonitrile-based hydrophilic resin has at least one selected from the group consisting of a polyalkylene oxide chain, a polyether amide chain, and a polyether ester chain as a hydrophilic component (1) or (2) ) Fibrillated acrylic fiber.
(4) The fibrillated acrylic fiber according to (1) or (2), wherein the acrylonitrile-based hydrophilic resin contains 30 to 90% by weight of a monomer represented by the following chemical formula 2 as a copolymerization component.

(5) A structure containing the fibrillated acrylic fiber according to any one of (1) to (4).
(6) Containing a polymer mixture of 95 to 99% by weight of acrylonitrile-based polymer containing 80% by weight or more of acrylonitrile and 1 to 5% by weight of acrylonitrile-based hydrophilic resin containing 10% to 70% by weight of acrylonitrile. When wet-spinning the spinning dope, the moisture content of the undried fiber after stretching is 50 to 130% by weight, and the fiber obtained by wet-heat treatment of the undried fiber at a temperature of 105 to 130 ° C. is beaten. A method for producing a fibrillated acrylic fiber.

Since the raw fiber employed in the present invention can be spun with good operability without using a special apparatus and can be easily fibrillated in a short time by beating, the fibrillation of the present invention Acrylic fibers can be manufactured at low cost. Therefore, the cost of these products can be reduced by using paper, non-woven fabrics, or friction materials, reinforcements, and industrial materials that are often required for low-cost materials. Can contribute.

Further, the acrylonitrile-based hydrophilic resin contained in the raw fiber employed in the present invention can play a role as a binder. For this reason, when using the fibrillated acrylic fiber of this invention as a paper raw material, the quantity of a binder can be reduced rather than usual, and it can also make it non-use depending on the case.

Furthermore, according to the present invention, the splitting property of the raw material fibers can be maintained even after the wet heat treatment, and a thermally stable fibrillated acrylic fiber can be obtained, which is suitable for applications requiring dimensional stability. Can be used.

The present invention is described in detail below. The acrylonitrile-based polymer of the present invention is not particularly limited as long as it is used in the production of conventionally known acrylic fibers, but it is necessary to contain 80% by weight or more of acrylonitrile, and more preferably 88% by weight or more. When the acrylonitrile bond content is less than 80% by weight, the difference from the acrylonitrile bond content of the acrylonitrile-based hydrophilic resin described later is small, and the fiber splitting property is lowered.

In the acrylonitrile-based polymer, the monomer that can be copolymerized with acrylonitrile may be a vinyl compound, and a plurality of types may be copolymerized. Typical examples include acrylic acid, methacrylic acid, or esters thereof; acrylamide, methacrylamide, or N-alkyl substituted products thereof; vinyl esters such as vinyl acetate; vinyl chloride, vinyl bromide, vinylidene chloride, and the like. Examples of known monomers that can be copolymerized with acrylonitrile, such as unsaturated sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, or salts thereof. be able to.

In addition, as an acrylonitrile-type polymer, you may use multiple types of polymers which satisfy | fill the above-mentioned composition.

Next, the acrylonitrile-based hydrophilic resin of the present invention needs to contain 10 to 70% by weight of acrylonitrile, more preferably 15 to 50% by weight, and still more preferably 15 to 30% by weight. . If the acrylonitrile bond content is in the range of 10 to 70% by weight, it can have a certain degree of compatibility with the acrylonitrile polymer described above. In other words, if it is out of the range, the compatibility with the acrylonitrile polymer is too low or too high, and yarn breakage may occur frequently in the spinning process, or the fiber splitting property may be reduced. .

In preparing the spinning dope, the acrylonitrile polymer is 95 to 99% by weight and the acrylonitrile hydrophilic resin is 1 to 5% by weight with respect to the total amount of the polymer used. If it is out of this range, problems in production such as nozzle clogging and yarn breakage during spinning and problems in characteristics such as inability to obtain sufficient splitting properties occur.

The raw fiber of the present invention has a water absorption rate of 0.15 g / g or more and a water absorption of 20% by weight or more when measured under the conditions described later. When the raw fiber has these characteristics, a fibrillated acrylic fiber having good thermal stability can be obtained while maintaining the fiber splitting property.

In addition to having the above-described characteristics, the raw fiber employed in the present invention desirably has a water retention rate of 120% by weight or less, preferably 70% by weight or less, and more preferably 40% by weight or less. If it has the characteristics mentioned above and a water retention is 120 weight% or less, it will become possible to improve the thermal stability of the obtained fibrillated acrylic fiber, maintaining the division property of a fiber.

The hydrophilic component of the acrylonitrile-based hydrophilic resin of the present invention is not particularly limited as long as it has hydrophilicity, and examples thereof include a hydroxyl group and an amino group. Particularly, a polyalkylene oxide chain, a polyether, etc. When amide chain, polyether ester chain, etc. are adopted, the thermoplasticity of the resin increases and it becomes possible to play a role as a binder, so the fibrillated acrylic fiber finally obtained is suitable for paper raw materials .

As a method for incorporating the hydrophilic component, a method for copolymerizing a vinyl monomer having a hydrophilic component on its side chain with acrylonitrile, or a method for copolymerizing a vinyl monomer having a reactive functional group with acrylonitrile. Thereafter, a method in which a reactive compound containing a hydrophilic component is grafted is exemplified.

In the former method, as the vinyl monomer in which the hydrophilic component is incorporated on the side chain, the monomer represented by Chemical Formula 2 is easy to handle and is typical. The bond content of the monomer is 30 to 90% by weight, preferably 50 to 85% by weight, and more preferably 70 to 85% by weight. If it is 30-90 weight%, it will become easy to obtain raw material fiber with favorable splitting property, maintaining the mechanical strength of a fiber. The lower alkyl group in the chemical formula 2 generally means a group having 5 or less carbon atoms, and more practically 3 or less. In the copolymerization with acrylonitrile, other vinyl compounds may be copolymerized in addition to the above vinyl monomers.

Preferable examples of the vinyl monomer having a hydrophilic component incorporated on the side chain include a reaction product of 2-methacryloyloxyethyl isocyanate and polyethylene glycol monomethyl ether. Suitable examples of methoxypolyethylene glycol (30 mol) methacrylate, methoxypolyethylene glycol (30 mol) acrylate, polyethylene glycol-2,4,6-tris-1-phenylethylphenyl ether methacrylate (number average molecular weight of about 1600). In addition, in the case of the graft reaction which is the latter method, suitable examples of the vinyl monomer having a reactive functional group include 2-hydroxyethyl methacrylate, acrylic acid, methacrylic acid, N-hydroxymethylacrylamide, N, N-dimethylaminoethyl methacrylate, glycidyl methacrylate, 2-methacryloyloxyethyl isocyanate, and the like. Suitable examples of the reactive compound containing a hydrophilic component include polyethylene glycol monomethyl ether and polyethylene glycol monomethacrylate. Etc.

As other properties of the acrylonitrile-based hydrophilic resin of the present invention, it is desirable to have a water swelling degree of 10 to 300 g / g, preferably 20 to 150 g / g. When the degree of water swelling exceeds 300 g / g, troubles such as yarn breakage are likely to occur in the spinning process. Various methods can be used to adjust the degree of water swelling, such as copolymerizing a crosslinkable monomer or changing the size of the monomer 1 or m shown in Chemical Formula 2. It can be illustrated.

Further, the acrylonitrile-based hydrophilic resin may be soluble in water and the solvent of the acrylonitrile-based polymer, but is preferably insoluble in water and the solvent of the acrylonitrile-based polymer and stable in the solvent described on the left. It is desirable to have the property of dispersing in The insolubility in water and the solvent of the acrylonitrile polymer suppresses the dissolution of the acrylonitrile hydrophilic resin from the fiber in the spinning process. Therefore, the fibrillated acrylic fiber finally obtained has a binder-like property as described above. The property of being able to have a function and being stably dispersed contributes to stable spinning in order to suppress troubles such as nozzle clogging and yarn breakage in the spinning process.

The method for synthesizing the acrylonitrile-based polymer described above is not particularly limited, and well-known polymerization means such as suspension polymerization method, emulsion polymerization method, solution polymerization method and the like can be used. In addition, the polymerization method can be used as a method for synthesizing the acrylonitrile-based hydrophilic resin. In some cases, as described above, a graft reaction can also be used to introduce the hydrophilic component.

Next, the manufacturing method of the fibrillated acrylic fiber of this invention is described. In the fibrillated acrylic fiber raw material fiber of the present invention, in order to facilitate fibrillation by beating, acrylonitrile-based hydrophilic resin is dispersed in the acrylonitrile-based polymer inside the fiber, and the acrylonitrile-based polymer and acrylonitrile-based hydrophilic are dispersed. It is desirable that a microvoid is formed at least at a part of the boundary with the functional resin, and that each microvoid is connected. In order to obtain a raw material fiber having such a structure, it is preferable to select the following means.

That is, the case of wet spinning using an aqueous solution of an inorganic salt such as sodium thiocyanate as a solvent is as follows. First, after dissolving the above-mentioned acrylonitrile polymer in an aqueous solution of an inorganic salt such as sodium thiocyanate, a spinning stock solution is prepared by adding and mixing the above-mentioned acrylonitrile-based hydrophilic resin directly or in a dissolved or dispersed state in water or a solvent. Then, after spinning from the nozzle, the water content of the undried fiber after stretching is 50 to 130% by weight, preferably 60 to 120% by weight, through the steps of coagulation, water washing and stretching. Subsequently, wet heat treatment is performed at 105 ° C to 130 ° C, preferably 110 ° C to 125 ° C.

Here, when the moisture content of the undried fiber after drawing is less than 50% by weight, the microvoids formed inside the fiber are not connected, so that the fiber splitting ability is reduced, and more than 130% by weight. In this case, a large number of large voids are formed inside the fiber, and the spinnability is lowered, which is not preferable. Although there are many methods for controlling the moisture content of the undried fiber after stretching, in order to control within the above range, the coagulation bath temperature is about 5 to 15 ° C., and the stretching ratio is about 7 to 15 times. desirable.

In addition, when the heat treatment is less than 105 ° C., the heat stability is inferior, and when it exceeds 130 ° C., microvoids are blocked. In addition, the wet heat treatment here means a treatment for heating in an atmosphere of saturated steam or superheated steam.

The fibrillated acrylic fiber of the present invention can be obtained by beating the raw fiber after the wet heat treatment obtained as described above into an appropriate length without being dried and beating in a state dispersed in water. However, it goes without saying that the beating treatment may be performed after the raw fiber is dried. However, in this case, it is desirable that the drying temperature does not exceed the temperature during the wet heat treatment. If the drying temperature exceeds the temperature at the time of the wet heat treatment, the microvoids are clogged, so that the fiber partitionability is lowered, and the target fibrillated acrylic fiber may not be obtained.

As described above, the case where an inorganic salt such as sodium thiocyanate is used as a solvent has been described. However, the above conditions are the same even when an organic solvent is used. However, since the types of solvents are different, it is desirable to set the coagulation bath temperature to 40 ° C. or higher in order to control the moisture content of the undried fibers after drawing within the above range. In addition, the evaluation method of the moisture content of the undried fiber after extending | stretching is mentioned later.

The raw material fiber obtained as described above has an acrylonitrile-based hydrophilic resin dispersed in the acrylonitrile-based polymer inside the fiber, and a microvoid at least part of the boundary between the acrylonitrile-based polymer and the acrylonitrile-based hydrophilic resin. Are formed, and each microvoid is connected to each other. Under the conditions described later, the water absorption rate is 0.15 g / g or more and the water absorption rate is 20% by weight or more. The structure can maintain the mechanical strength of the fiber, and can be easily treated by beating even if wet heat treatment is performed to improve thermal stability and the water retention is reduced to about 120% by weight or less. It is possible to fibrillate.

Needless to say, in order to form the above structure, the acrylonitrile-based polymer and the acrylonitrile-based hydrophilic resin having the above-described characteristics must be used in a proportion within the above-described range.

Such a raw fiber structure is considered to be brought about for the following reasons. First, as a constitution of the raw material fiber, an acrylonitrile-based hydrophilic resin having a certain degree of compatibility with the acrylonitrile-based polymer is dispersed and contained. By having this “some degree of compatibility”, the acrylonitrile-based polymer is included. Although a void is formed by phase separation at the interface between the acrylonitrile-based hydrophilic resin and the phase separation occurs only partially, it becomes a microvoid instead of a large void. In addition, by “dispersing”, the formed microvoids are also dispersed in the fiber. Furthermore, it is thought that each microvoid is connected by controlling the moisture content of the undried fiber after drawing.

In order to obtain the fibrillated acrylic fiber of the present invention, a beating process is performed, and the method of the beating process is not particularly limited, and a normal beating method can be employed. A typical example is a fibrillation method using a beater such as a beater or refiner.

Examples of the structure containing the fibrillated acrylic fiber of the present invention include a nonwoven fabric, paper, a sheet-like material, a laminate, and a cotton-like material (including spherical and massive materials). Further, in forming the structure, the fibrillated acrylic fiber of the present invention may be used alone, and if necessary, natural fiber, organic fiber, semi-synthetic fiber, synthetic fiber, inorganic fiber, glass fiber, etc. You may use together a fiber, a thermosetting resin, rubber | gum, etc. In addition, what is necessary is just to select suitably the ratio for which the fibrillated acrylic fiber of this invention accounts in a structure satisfies the mechanical characteristics etc. which are calculated | required in the use of this structure.

The fibrillated acrylic fiber of the present invention can also be used as a reinforcing material for concrete or a resin plate, or a friction material such as a clutch plate or a brake shoe. In particular, when an acrylonitrile-based hydrophilic resin obtained by copolymerization of a monomer represented by Chemical Formula 2 is used, the ability as a binder is increased, so that it is very useful as a paper raw material.

Furthermore, when a fiber having a water retention rate of 120% by weight or less is used as the raw material fiber, the thermally stable fibrillated acrylic fiber of the present invention is obtained, and the degree of deformation due to heating is small. Among applications, it can be suitably used particularly for applications requiring dimensional stability.

Examples are shown below for facilitating the understanding of the present invention. However, these are merely examples, and the gist of the present invention is not limited thereto. In the examples, parts and percentages are shown on a weight basis unless otherwise specified. In addition, the water swelling degree of the acrylonitrile-based hydrophilic resin described in the examples, the moisture content of the undried fibers after stretching, the water absorption rate, the water absorption rate, and the water retention rate of the raw fiber are measured by the following methods.

(1) Degree of water swelling About 0.5 g of acrylonitrile-based hydrophilic resin is immersed in pure water, and after 24 hours at 25 ° C., the water-swelled acrylonitrile-based hydrophilic resin is sandwiched between filter papers and water between the resins. Remove. The weight (W1) of the sample thus prepared is measured. Next, the sample is dried to a constant weight in a vacuum dryer at 80 ° C., and the weight (W0) is measured. From the above results, the degree of water swelling is calculated according to the following formula.
Water swelling degree (g / g) = (W1-W0) / W0

(2) Moisture ratio of undried fiber after stretching After immersing the undried fiber after stretching in ion-exchanged water, centrifugal acceleration 1100G (G by a centrifugal dehydrator (TYPE H-770A manufactured by Kokusan Centrifuge Co., Ltd.)) Dehydrated for 2.5 minutes. After dehydration, the weight is measured (W3), the undried fiber is dried at 120 ° C. for 15 minutes, the weight is measured (W2), and the following formula is calculated.
Moisture content of undried fiber after stretching (%) = (W3−W2) / W2 × 100

(3) About 5 g of raw fiber dried at a water absorption rate of 105 ° C. is defibrated, wrapped in gauze, and immersed in ion-exchanged water adjusted to 30 ° C. for 30 seconds. Immediately after the immersion, the sample is immediately dehydrated for 2 minutes under a centrifugal acceleration of 1100 G with a centrifugal dehydrator (same as above) while being wrapped in gauze. After dehydration, the fiber is taken out from the gauze and weighed (W5), dried at 80 ° C., weighed (W4), and calculated by the following formula.
Water absorption rate (g / g) = (W5-W4) / W4

(4) About 10 g of raw fiber dried at a water absorption rate of 105 ° C. is wrapped in gauze and immersed in ion exchange water at 25 ° C. for 24 hours, and then dehydrated for 2 minutes under a centrifugal acceleration of 1100 G using a centrifugal dehydrator (same as above). Remove the water between the fibers. The fiber weight after dehydration is measured (W7), dried in a vacuum dryer at 80 ° C. until a constant weight is measured, and the weight is measured (W6).
Water absorption (%) = (W7−W6) / W6 × 100

(5) Water retention rate After the raw material fibers are immersed in ion-exchanged water, they are dehydrated for 2.5 minutes under a centrifugal acceleration of 1100 G with a centrifugal dehydrator (same as above). After dehydration, the weight is measured (W9), the undried fiber is dried at 120 ° C. for 15 minutes, the weight is measured (W8), and the following formula is calculated.
Water retention rate (%) = (W9−W8) / W8 × 100

<Production of acrylonitrile-based polymer and acrylonitrile-based hydrophilic resin>
Aqueous suspension polymerization was performed with the composition shown in Table 1 to prepare acrylonitrile polymers (a1 to a4) and acrylonitrile hydrophilic resins (b1 to b4). As for the acrylonitrile-based hydrophilic resin b2, first, a polyethylene monomer monomethyl ether (number average molecular weight 750) and 2-methacryloyloxyethyl isocyanate are reacted in toluene at 60 ° C. in a nitrogen atmosphere to synthesize a macromonomer. The resulting macromonomer and acrylonitrile were prepared by aqueous suspension polymerization. The abbreviations in the table are: AN: acrylonitrile, MA: methyl acrylate, SMAS: sodium methallylsulfonate, VAc: vinyl acetate, M30: methoxypolyethylene glycol (30 mol) methacrylate, MOI: 2-methacryloyloxy Ethyl isocyanate, PEGME: Polyethylene glycol monomethyl ether. Moreover, about the acrylonitrile-type hydrophilic resin, the water swelling degree calculated | required from the said measuring method was written together.

<Examples 1-3, Comparative Example 1>
A spinning stock solution was prepared by dissolving acrylonitrile polymer in 900% of 50% sodium thiocyanate aqueous solution at a ratio shown in Table 2 and then adding and mixing acrylonitrile hydrophilic resin dispersed in water. The obtained spinning solution is spun and coagulated in a 12% sodium thiocyanate aqueous solution at 5 ° C., then washed with water and stretched 12 times. The resulting undried fiber is steamed at 116 ° C. for 10 minutes. Using the wet heat treatment, a raw material fiber was prepared without performing a drying step. Next, the obtained raw fiber was cut to 5 mm, and weighed so that the weight of the dry fiber would be 50 g. After adding water to adjust to 5 liters and adjusting the water temperature to 20 ° C., Kumagai Riki Kogyo ( Using a Niagara type beater (type BE-10) manufactured by Co., Ltd., it was beaten for 30 minutes under a 2 kg load. The fibrillation state of the obtained fiber was observed with an optical microscope, and the splitting property was evaluated in three stages according to the following criteria.
○: Fibrilized Δ: Fiber surface is fuzzy ×: Almost no fibrillation

Table 2 shows the evaluation results of the fibrillation state, the measurement results of the moisture content of the undried fibers after stretching, and the measurement results of the water absorption rate, the water absorption rate and the water retention rate of the raw fiber.

In Examples 1 to 3, fibrillated acrylic fibers could be easily obtained. On the other hand, in Comparative Example 1, the water absorption rate and the water absorption rate were low, and the splitting property was such that the fiber surface was fluffy. This is because the acrylonitrile bond content in the acrylonitrile-based polymer is small and the difference from the acrylonitrile bond content of the acrylonitrile-based hydrophilic resin is small, so phase separation hardly occurs and microvoids are not sufficiently formed. It is thought that it was because of.

<Examples 4 and 5, Comparative Examples 2 and 3>
Except for changing the ratio of the acrylonitrile-based polymer and the acrylonitrile-based hydrophilic resin of Example 1 as shown in Table 3, a spinning dope, a raw fiber, beating and evaluation were performed in the same manner as in Example 1. Table 3 shows the results.

In each of Examples 4 and 5, fibrillated acrylic fibers could be obtained. In Comparative Example 2, since there was too much acrylonitrile-based hydrophilic resin, nozzle clogging and thread breakage occurred during spinning, and fibers could not be obtained. Further, in Comparative Example 3, since no acrylonitrile-based hydrophilic resin is used, the formation of microvoids is small, and it is considered that the partitionability is poor.

<Examples 6 to 8, Comparative Example 4>
Except for changing the ratio of the acrylonitrile-based polymer and the acrylonitrile-based hydrophilic resin of Example 1 as shown in Table 4, preparation of a spinning dope, preparation of raw fibers, beating and evaluation were performed in the same manner as in Example 1. Table 4 shows the results.

In each of Examples 6 and 7, fibrillated acrylic fibers could be easily obtained, and in Example 8, fibrillated acrylic fibers were also obtained. On the other hand, Comparative Example 4 had a low water absorption rate and an insufficient fiber splitting property. This is because the acrylonitrile bond content in the acrylonitrile-based hydrophilic resin is large, the hydrophilic component in the resin is reduced, and the difference in the acrylonitrile bond content with respect to the acrylonitrile-based polymer is also reduced. It seems that the connection is less likely to occur.

<Example 9, Comparative example 5>
Using the same spinning dope as in Example 3, the conditions shown in Table 5 were changed with respect to the spinning conditions in Example 3 to prepare, beat and evaluate the raw fibers. Table 5 shows the results.

About Example 9, although the operativity was a little inferior compared with Example 3, the fibrillated acrylic fiber was able to be obtained more easily. In Comparative Example 5, it is considered that by reducing the coagulation bath temperature, the densification of the fibers progressed and the space to be microvoids decreased, resulting in a low water absorption rate and a low water absorption rate, resulting in a decrease in partitionability.

<Examples 10-12, Comparative Examples 6-8>
Using the same spinning dope as in Example 1, the conditions shown in Table 6 were changed with respect to the spinning conditions in Example 1, and the raw fiber was prepared, beaten and evaluated. Table 6 shows the results.

In Examples 10 and 11, fibrillated acrylic fibers were obtained. Comparative Example 7 is considered to have a low water absorption rate and water absorption and low thermal stability. Moreover, all of Comparative Examples 6, 8, and 9 were inferior in separability. This is thought to be because microvoids in the fiber were blocked or reduced due to the changed conditions. In Comparative Example 9, it was considered that the microvoids were clogged because they were dried at a temperature higher than the wet heat treatment temperature.

<Example 12>
A sheet was prepared from the aqueous dispersion of fibrillated acrylic fiber obtained in Example 1 using a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd. The sheet was sandwiched between filter papers, and dried at 130 ° C. using a rotary dryer manufactured by Kumagai Riki Kogyo Co., Ltd. to produce a paper made of fibrillated acrylic fibers of the present invention. The obtained paper was excellent in dimensional stability.

<Comparative Example 10>
A paper was prepared in the same manner as in Example 12 except that the raw material fiber obtained in Comparative Example 7 was used. The resulting paper was severely shrinkable and inferior in dimensional stability. This is because the raw fiber obtained in Comparative Example 7 is low in thermal stability, and the thermal stability of the fibrillated acrylic fiber obtained by beating the fiber is low, and it contracted by heating. This is thought to be the cause.

Claims (6)

A spinning stock solution comprising 95 to 99% by weight of an acrylonitrile-based polymer containing 80% by weight or more of acrylonitrile and a polymer mixture of 1 to 5% by weight of an acrylonitrile-based hydrophilic resin containing 10 to 70% by weight of acrylonitrile. A fibrillated acrylic fiber obtained by beating a raw fiber obtained by spinning and having a water absorption rate of 0.15 g / g or more and a water absorption of 20% by weight or more. The fibrillated acrylic fiber according to claim 1, wherein the raw fiber has a water retention of 120% by weight or less. The fibril according to claim 1 or 2, wherein the acrylonitrile-based hydrophilic resin has at least one selected from the group consisting of a polyalkylene oxide chain, a polyether amide chain, and a polyether ester chain as a hydrophilic component. Acrylic fiber. The fibrillated acrylic fiber according to claim 1 or 2, wherein the acrylonitrile-based hydrophilic resin contains 30 to 90% by weight of a monomer represented by the following chemical formula 1 as a copolymerization component.

The structure containing the fibrillated acrylic fiber in any one of Claims 1-4. A spinning stock solution comprising 95 to 99% by weight of an acrylonitrile-based polymer containing 80% by weight or more of acrylonitrile and a polymer mixture of 1 to 5% by weight of an acrylonitrile-based hydrophilic resin containing 10 to 70% by weight of acrylonitrile. When wet spinning, the dried fiber after stretching has a moisture content of 50 to 130% by weight, and the fiber obtained by wet-heat treatment of the undried fiber at a temperature of 105 to 130 ° C. is beaten. A method for producing fluorinated acrylic fiber.