JPH06220720A - Flat acrylic fiber and method for producing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] Acrylic fiber with a special flat cross section that has excellent luster and soft texture by the dry spinning method. [Constitution] 92% by weight or more of acrylonitrile and 0 to
Thermoplastic with an acrylonitrile polymer (I) consisting of a monomer containing 1.5% by weight of a strong acid group and 0 to 8% by weight of an acrylonitrile and a monoethylenic vinyl monomer having copolymerizability as a sheath The length (A) between both ends of the fiber cross section, the thickness (B) at the maximum tip portion and the thickness (C) at the necked portion, which are obtained by dry spinning using the polymer (II) as the core, are A / C ≧
Flat acrylic fiber satisfying 5 and B / C ≧ 1.2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic fiber having a special flat cross section having a softer texture while making use of the excellent luster obtained by a dry spinning method.

[0002]

2. Description of the Related Art In dry spinning, a circular filament immediately after being ejected from a nozzle forms a skin layer while shrinking due to evaporation of a solvent from the surface, while the volume of the central portion is increased as the solvent in the central portion evaporates. As a result, a fiber with a unique dumbbell-shaped cross section and a soft texture that is difficult to obtain by wet spinning is obtained.

[0003]

However, in the normal dry spinning, in order to avoid yarn breakage right under the nozzle to ensure spinning stability, and to avoid generation of adhesive yarn right under the nozzle, the spinning stock solution immediately before discharge. In order to keep the viscosity at 20 poise or higher, the polymer concentration in the spinning dope needs to be increased to 23-40%. As a result, the flatness of the dumbbell-shaped cross section, which is small in the volume contraction effect of the central portion, is the flatness (A
The ratio of / C) is less than 5.

On the other hand, in order to obtain a flat cross section by dry spinning, JP-A 63-316212 and 63-3162 are used.
There is a method of discharging from a special flat-shaped nozzle as disclosed in Japanese Patent No. 13, but compared with wet spinning,
Since a nozzle having a higher flatness is required, the resulting fiber is limited to a thick denier product, and the cross-sectional shape has a flatness (B / C) ratio of less than 1.2 according to the present invention. The desired soft texture cannot be obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to monoethylene copolymerizable with 92% by weight or more of acrylonitrile, 0 to 1.5% by weight of a strong acid group-containing monomer and 0 to 8% by weight of acrylonitrile. Of an acrylonitrile-based polymer (I) made of a polymerizable vinyl-based monomer and a thermoplastic polymer (I
The length (A) between both ends of the fiber cross section obtained by dry spinning using I) as a core, the thickness (B) at the maximum tip portion and the thickness (C) at the necked portion are A / C ≧ 5 and B / It is a flat acrylic fiber that satisfies C ≧ 1.2.

Further, in the present invention, a core-sheath type composite nozzle is used as the nozzle used in the dry spinning in the above, and the spinning stock solution having a viscosity of 20 poise or more at the time of discharging the polymer (I) is discharged to the core part. The polymer (II) concentration is 15% by weight
Dry spinning under the following conditions, using a spinning dope having a viscosity of 1 voise or more at the time of nozzle discharge, and a ratio of the amount of the spinning dope to be supplied to the core is 10 to 60% by weight of the total amount of the spinning dope. The manufacturing method is characterized by

The present invention will be described in detail below. Acrylonitrile polymer (I) used for the sheath portion in the present invention
Is at least 92% by weight of acrylonitrile and 0 to
1.5% by weight, preferably 0 to 1% by weight, of a strong acid group-containing monomer, and 0 to 8% by weight, preferably 3 to 8% by weight, of a monoethylenic vinyl-based monomer copolymerizable with acrylonitrile. It is necessary to contain.

When the amount of the strong acid group-containing monomer is more than 1.5% by weight, the obtained fiber has an amorphous shape which includes not only the dumbbell-shaped cross-section but also various different cross-sections such as a trilobal shape. If the amount of the monoethylenic vinyl-based monomer having copolymerizability with acrylonitrile exceeds 8% by weight, the evaporation of the solvent from the fiber surface is slow, and the resulting fiber has a flatness (A / C) of 5 or more and a flatness. It has a cross section close to a circle, not a dumbbell-shaped cross section with a degree (B / C) of 1.2 or more.

Specific examples of the strong acid group-containing monomer include (meth) acrylic acid, (meth) allylsulfonic acid, vinylbenzenesulfonic acid and salts thereof. Also,
Examples of the monoethylenic vinyl-based monomer copolymerizable with acrylonitrile include (meth) acrylic acid esters such as methyl acrylate and methyl methacrylate, vinyl acetate, styrene, and acrylamide.

On the other hand, the thermoplastic polymer (II) used in the core portion is not particularly limited as long as it can be dissolved in a solvent of an ordinary acrylonitrile polymer, but is not compatible with the acrylonitrile polymer (I) used in the sheath portion. It is necessary that it is good and does not peel off. The cross-sectional shape of the fiber obtained in the present invention is governed by the acrylonitrile polymer (I) used in the sheath portion, and the thermoplastic polymer (II) used in the core portion has almost no effect.

The polymer used in the present invention can be produced by any method such as ordinary suspension polymerization, solution polymerization and emulsion polymerization. The degree of polymerization of the polymer is preferably 0.1 to 0.2 in terms of its specific viscosity.

The stock solution for spinning of the sheath and the core is prepared by dissolving the polymer (I) and the polymer (II) in a solvent of a usual acrylonitrile polymer such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. However, dimethylformamide is particularly preferable in terms of polymer solubility and solvent recovery.

The spinning stock solution used for the sheath portion must have a viscosity at the time of discharge of 20 poises or more in order to avoid yarn breakage immediately below the nozzle and generation of adhesive yarn immediately below the nozzle. The polymer concentration in the spinning dope is slightly different depending on the degree of polymerization of the polymer (I) and the temperature of the spinning dope at the time of discharge, but it is in the range of 23 to 43%. It is preferably low also in the sense of increasing A / C).

The spinning dope to be used for the core must maintain the viscosity of the spinning dope immediately before discharge to 1 poise or more in order to avoid the destruction of the core-sheath structure and the generation of the adhesive yarn just below the nozzle. The polymer concentration in the spinning dope is slightly different depending on the degree of polymerization of the polymer (II) and the temperature of the spinning dope at the time of discharge, but especially from the meaning of enhancing the volume shrinkage effect at the center of the fiber cross section and increasing the flatness (A / C). Also needs to be 15% or less. It goes without saying that a plasticizer substance, a whiteness improving agent, a heat stabilizer, titanium oxide and the like can be added to the spinning dope used for the sheath or core in the present invention.

The two kinds of spinning dope prepared as described above are heated to 100 to 150 ° C., and then 160 to 280 through a sheath-core type composite nozzle having an ordinary circular hole shape.
It is discharged into an inert gas at ℃ to evaporate the solvent and obtain an undrawn yarn. The supply amount ratio of the spinning dope for the core portion is required to be 10 to 60% by weight, preferably 20 to 50% by weight, based on the total amount of the spinning dope to be supplied. When this ratio is less than 10% by weight, the volume shrinkage effect of the central portion of the fiber cross section is insufficient, and the flatness (A / C) of the obtained fiber cross section is smaller than 5. On the other hand, when the ratio of the core portion exceeds 60% by weight, a complete core-sheath structure cannot be obtained, and there arises a problem of thread adhesion and thread breakage immediately below the nozzle. The heating temperature of the spinning dope and the temperature of the inert gas are preferably high in the sense that the evaporation of the solvent is increased and the flatness of the cross section is increased.

The undrawn yarn thus spun is subsequently drawn 3 to 6 times in hot water at 80 to 100 ° C., and 80 to 100 at the same time as or before and after the drawing treatment.
Washed in hot water at ℃. The amount of residual solvent after cleaning is usually 2
% Or less. The stretch-washed yarn is then dried and relaxed. Generally, the flatness of the cross section of the fiber finally obtained by the drawing treatment is lower than that of the undrawn yarn, but the flatness defined in the present invention means the flatness of the finally obtained fiber.

A typical method for drying is to pass under tension on a hot roll having a surface temperature of about 115 to 150 ° C. In this case, densification of the fibers is also achieved. On the other hand, it is possible to perform relaxation treatment simultaneously with drying, in which the yarn after hot-water drawing is in a wet state without tension in a heated air in a relative humidity of about 10 to 40% and a temperature of 110 to 160 ° C. Is also a preferred method. As another relaxation heat treatment method, a method of heat-treating the once dried yarn in pressurized steam at a temperature of about 100 to 140 ° C. is also simple and effective. The heat treatment as described above gives the fiber a shrinkage of 10 to 40%. This relaxation shrinkage treatment imparts basic properties such as dyeability and morphological stability required for clothing fibers.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples. In the description, "%" represents% by weight. The "specific viscosity" is 25 g obtained by dissolving 0.1 g of the polymer in 100 ml of dimethylformamide containing 0.1 N of rhodanesoda.
It was measured at ° C. Among the numerical values that define the fiber cross-sectional shape of the present invention, the length (A) between both ends of the fiber cross section indicates the major axis length when the flat dumbbell cross section is extended, and the thickness (B) of the tip maximum part and the constricted part. Thickness (C) indicates the maximum value and the minimum value of the thickness perpendicular to the long axis. (See FIG. 1) The texture is the feel of the finally obtained raw cotton, and is indicated by ⊚: very soft, ◯: soft, ×: hard.

Example 1 (1) Acrylonitrile 93.5%, methyl acrylate 6.0%, sodium methacrylic acid sulfonate 0.5% and an acrylic copolymer having a specific viscosity of 0.161 were added to dimethylformamide. To prepare a stock solution (A) having a polymer concentration of 30%. Separately, (2) an acrylic copolymer of 98% acrylonitrile and 2% sodium methallylsulfonate having a specific viscosity of 0.194 was dissolved in dimethylformamide to prepare a stock solution (B) having a polymer concentration of 12%.

The above stock solution (A) and stock solution (B)
After heating to ℃, 600 holes, orifice hole diameter 0.20
Through the mm-sheath core-sheath type composite nozzle, the stock solution (A) is discharged from the sheath section, and the stock solution (B) is discharged from the core section into the inert gas at 200 ° C while changing the supply ratio of the spinning solution of the core section. An undrawn yarn having a structure was obtained. The viscosities of the stock solution (A) and the stock solution (B) at the time of discharge were 70 poise and 5 poise, respectively.
This undrawn yarn was drawn 3.75 times in hot water at 100 ° C,
Further, the fiber bundle obtained by washing and applying an oil agent in hot water of 95 ° C. was dried and relaxed at a relative humidity of 40% and a temperature of 150 ° C. without tension. The fibers obtained were about 3d. The spinning process passability under each condition and the general shape, flatness (A / C) and flatness (B / C) of the obtained fiber cross section
Is shown in Table 1. Fibers according to the invention (No. 2, 3,
Nos. 4, 5) showed good spinnability, high flatness and very soft texture.

[0021]

[Table 1]

Example 2 (1) An acrylic copolymer of 91% acrylonitrile and 9% vinyl acetate having a specific viscosity of 0.170 was dissolved in dimethylformamide to prepare a stock solution (A) having a polymer concentration of 30%. It was adjusted. (2) An acrylic copolymer of 93% acrylonitrile and 7% vinyl acetate having a specific viscosity of 0.170 was dissolved in dimethylformamide to prepare a stock solution (B) having a polymer concentration of 30%. (3) An acrylic copolymer of 93.5% acrylonitrile, 6% methyl acrylate and 0.5% sodium methallyl sulfonate having a specific viscosity of 0.161 was dissolved in dimethylformamide to obtain a polymer having a polymer concentration of 30%. Stock solution (C) was prepared. (4) Acrylic copolymer of 98% acrylonitrile and 2% sodium methallyl sulfonate having a specific viscosity of 0.194 was dissolved in dimethylformamide to obtain a polymer concentration of 25%.
A stock solution (D) and a stock solution (E) having a polymer concentration of 12% were prepared.

One of the above stock solutions (A) to (D) is supplied from the sheath, the above stock solution (E) is supplied from the core, and the spinning stock solution is supplied to the core at a ratio of 40%. After heating to 130 ℃, 200 ℃ through a core-sheath type composite nozzle with 600 holes and an orifice hole diameter of 0.20 mmφ
Was discharged into the inert gas of No. 1 to obtain undrawn yarns having a core-sheath structure. The stock solution of the sheath had a viscosity of 50 to 100 poise when discharged, and the stock solution of the core (E) had a viscosity of 5 poise when discharged.

This undrawn yarn was heated in hot water at 100 ° C. for 3.7 minutes.
The fiber bundle was stretched 5 times, further washed in hot water at 95 ° C., and then applied with an oil agent.
%, A temperature of 150 ° C. was used for drying and relaxation treatment. The fibers obtained were about 3d. Table 2 shows the spinning process passability under each condition and the outline, flatness (A / C) and flatness (B / C) of the obtained fiber cross section. No. No. 7 has a substantially circular cross section, No. 7 No. 10 had an irregular cross section in which many trilobes were mixed in addition to dumbbells.

[0025]

[Table 2]

[Example 3] Acrylonitrile 93.5
%, Methyl acrylate 6%, sodium methallylsulfonate 0.5%, an acrylic copolymer having a specific viscosity of 0.161 was dissolved in dimethylformamide to give a polymer concentration of 33%.
A stock solution (A), a stock solution (B) having a polymer concentration of 12% and a stock solution (C) having a polymer concentration of 6% were prepared.

The above stock solution (A) is heated from the sheath, and the stock solution (B) or the stock solution (C) is heated from the core to 130 ° C., respectively, and then a core-sheath type composite nozzle having 600 holes and an orifice hole diameter of 0.20 mmφ. Through changing the supply amount ratio of the spinning dope for the core portion, it was discharged into an inert gas at 200 ° C. to obtain an unstretched yarn having a core-sheath structure. The viscosities of the stock solution (A), the stock solution (B) and the stock solution (C) at the time of discharge were 130 poises, 4 poises and 0.5 poises, respectively.

This undrawn yarn was heated in hot water at 100 ° C. for 3.7 minutes.
The fiber bundle was stretched 5 times, further washed in hot water at 95 ° C., and then applied with an oil agent.
%, A temperature of 150 ° C. was used for drying and relaxation treatment. Table 3 shows the passability in the spinning process under each condition, and the outline, flatness (A / C) and flatness (B / C) of the obtained fiber cross section. Conditions in which the core liquid viscosity is too low (No. 14, 1
In Nos. 5 and 16), adhesive yarn was generated just below the nozzle.

[0029]

[Table 3]

[0030]

EFFECT OF THE INVENTION The fiber according to the present invention can be expected to further enhance the soft texture originally possessed by dry acrylic fiber and to be widely applied to clothing and the like. Further, the present invention can be expected to add functionality by a thermoplastic polymer used for the core or various additives, which is of great industrial significance.

[Brief description of drawings]

FIG. 1 is a fiber cross-sectional shape diagram showing an example of a flat yarn of the present invention.

[Explanation of symbols]

 A Length between both ends B Thickness at maximum tip C Thickness at constriction

Claims (2)

[Claims] 1. Acrylonitrile of 92% by weight or more and 0
To 1.5% by weight of a strong acid group-containing monomer and 0 to 8% by weight of an acrylonitrile-based acrylonitrile polymer (I) comprising a copolymerizable monoethylenic vinyl-based monomer
Of the fiber cross section obtained by dry-spinning with a sheath as a core and a thermoplastic polymer (II) as a core, the thickness (A) at the maximum tip portion (B) and the thickness (C) at the necked portion. Is a flat acrylic fiber satisfying A / C ≧ 5 and B / C ≧ 1.2 2. A core-sheath type composite nozzle is used as a nozzle used for dry spinning, a spinning stock solution having a viscosity of 20 poise or more at the time of discharging the polymer (I) from the nozzle is used for the sheath portion, and a polymer (I) is used for the core portion. II) A spinning dope having a concentration of 15% by weight or less and a viscosity of 1 poise or more at the time of nozzle ejection is used, and the supply ratio of the spinning dope to the core is 10 to 10% of the total spinning dope.
The method for producing a flat acrylic fiber according to claim 1, characterized in that the dry spinning is carried out under the condition of 60% by weight.