JPH0533212A - Production of acrylic precursor yarn for carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the title high-strength yarn causing little fluff even in stretching at a high draw ratio by drawing undrawn yarn of acrylic yarn in hot water at a specific draw ratio, drying, densifying and then subjecting to two-stage pressure steam drawing under a specific condition. CONSTITUTION:First, an acrylic polymer solution is spun and drawn in a hot water bath at 3-5 draw rations. Then, the drawn yarn is dried, densified and subjected to two-stage drawing in pressurized steam under a condition satisfying the formula >>n1-n2>=1 and T1<T2 (n1 is draw ratio in the first-stage pressurized steam; n2 is draw ratio in the second-stage pressurized stage; T1 and T2 are temperatures of the first-stage and the second stage pressurized steam) to give 10-25 times total draw rations. The temperature of the pressurized steam is 110-160 deg.C. Before drying and densifying, oiling is preferably carried out in order to prevent fusing of yarn and to maintain bundling of yarn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic precursor for carbon fibers, and more particularly to a method for producing a high-strength acrylic precursor for carbon fibers with less yarn fluff and yarn breakage. It is a thing.

[0002]

2. Description of the Related Art One of the important applications of acrylic fibers is acrylic raw yarn for carbon fiber, which requires high strength and high orientation fiber performance.

As a method for producing an acrylic precursor for carbon fibers which satisfies this requirement, it is known to carry out high-stretching using pressurized steam. In order to further densify the fiber and to prevent devitrification of the yarn after drawing in pressurized steam, after spinning washing, draw once in hot water, then dry densify and press steam draw. This is known as the preferred method.

Further, the high-magnification drawing by pressure steam also increases the yarn-making speed of the yarn, and is therefore considered to be a method which also contributes to the improvement of productivity.

[0005]

Generally, however, the acrylic fiber as a precursor for carbon fiber has a single fineness of 0.7 to 1.5.
Since it is denier and extremely thin, fluff is likely to be generated by high-strength drawing, and particularly in steam drawing, fluffing frequently occurs and it cannot be used as an acrylic precursor for carbon fiber, which is a neck of high-strength drawing.

Various improvements have been made to the steam stretching machine and the apparatus, but the stretching ratio is only about 8 to 10 times, and no sufficient solution has been taken yet.

The present invention has been obtained as a result of investigations for solving such a problem, and its object is to reduce the generation of fluff even when a high draw ratio of 10 to 25 times is used as a total draw ratio. It is to provide a method for obtaining a high-strength acrylic precursor for carbon fibers.

[0008]

Means and Actions for Solving the Problems In order to achieve the above object, the present invention provides a method of spinning an acrylic polymer solution, stretching in a hot water bath to dry densify, and then pressure steam stretching. After stretching in the bath to be 3 to 5 times, it is stretched in two stages in pressure steam, and the total stretching ratio is 10 to 25.
And the stretching condition is | n ₁ −n ₂ | <1.0, T
_The main constitution is a method for producing an acrylic precursor for carbon fiber, wherein ₁ <T ₂ . Where n
₁ is the draw ratio in the first-stage pressure steam, n ₂ is the draw ratio in the second-stage pressure steam, and T ₂ and T ₂ are the pressure steam temperatures of the first and second stages, respectively.

Hereinafter, the present invention will be described in more detail along with its operation. The acrylic polymer used in the present invention contains at least 95 mol% of acrylonitrile and is a copolymer of one or more comonomers. As the unsaturated monomer used in the present invention as a comonomer, acrylic acid, methacrylic acid, acrylic acid esters, acrylamide, methacrylamide, N-hydroxymethylacrylamide, vinyl chloride, vinylidene chloride, vinyl acetate, 2 vinyl pyridine , Allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, p-styrene sulfonic acid and salts thereof, but of course, are not limited to these.

The intrinsic viscosity of the polymer at this time is 1.4 to
It should be 2.5, preferably 1.5 to 2.2. If the intrinsic viscosity is too small, high-strength fibers cannot be obtained, and if it is too large, it becomes difficult to adjust the spinning dope and the spinnability is significantly deteriorated.

The spinning may be carried out in a coagulating bath, or may be carried out in the air and then immersed in a coagulating liquid. As the coagulating liquid, a dimethylacetamide aqueous solution, a dimethylformamide aqueous solution, a dimethylsulfoxide aqueous solution, or the like is used. The coagulated yarn is washed with warm water to sufficiently remove the solvent. The yarn after desolvation needs to be stretched 3 to 5 times in a hot water bath at 85 to 100 ° C.

If the draw ratio in the hot water bath is too small, devitrification occurs in the yarn due to dry densification, and if it is too large, the draw ratio in the pressurized steam becomes extremely small and the total draw ratio becomes Fibers with a low degree of orientation cannot be obtained.

After the drawing in the hot water bath, in order to make the internal structure of the fiber densified, a heating roller at 110 to 180 ° C.
Dry densification treatment is performed for 5 to 5 seconds. It is preferable to perform oiling prior to the dry densification treatment in order to prevent the fusion of the yarns and maintain the sizing property. After the dry densification, it is stretched by the first stage pressure steam and then by the second stage pressure steam to give a total stretching ratio of 10 to 25 times. Compared with the method in which the pressure steam drawing is performed in only one step, the drawing is performed in two steps, the difference in the draw ratio is less than 1, and the method in which the drawing temperature in the latter stage is kept higher than that in the former stage is fluff. It is possible to perform high-magnification stretching with less occurrence of

The temperature of the pressurized steam must be in the range of 110 to 160 ° C. It is presumed that when the drawing is excessively performed in only one stage, fluffing is likely to occur because spots are likely to appear in the drawing location of each single fiber in the pressure steam drawing machine. Therefore, by dividing the drawing into two stages and making the draw ratio of the same degree in each stage, the draw unevenness between the single fibers is reduced, and at the same time the draw resistance is increased. It is considered that high-stretching is achieved.

When the total draw ratio is lower than 10 times, high strength and highly oriented yarn cannot be obtained, and when it is higher than 25 times, fluff is generated due to single yarn breakage and crazes and cracks in the fiber. Occurrence of is seen.

After the pressure steam drawing, if necessary, 110 to 110
Treatment with a heating roller at 250 ° C. can be performed, and further, oiling for improving the focusing property can be added.

As described above, the feature of the present invention is that an acrylic fiber having a high strength and a high degree of orientation which is imparted with an extremely high draw ratio and has no fluff due to single yarn breakage is obtained. As a precursor, it has become possible to produce a high-quality precursor that has not been obtained in the past with high productivity.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 70% of a dimethylacetamide solution containing 20% by weight of a copolymer having an intrinsic viscosity of 2.1 obtained by copolymerizing 96.0% by weight of acrylonitrile and 4.0% by weight of methyl acrylate. After spinning at 30 ° C. into a coagulation bath of an aqueous dimethylacetamide solution and passing through a warm bath at 85 ° C. for washing, 95
It was stretched in a hot water bath at ℃ and dried on a 110 ° C heating roller, and then a silicon-based oil agent was applied, and dried and densified on a 143 ° C heating roller. Subsequently, stretching was performed in a pressure steam stretching machine at 125 ° C., and the breaking ratio thereof was examined. The stretch ratio in the hot water bath and the steam stretch ratio at break were as shown in Table 1.

[0020]

[Table 1]

The yarn drawn 3 to 5 times in a hot water bath at 95 ° C. does not show devitrification due to densification by drying, and has a large total draw ratio at break.

Example 2 In Example 1, the hot water draw ratio was fixed to 4.0, and the heating steam draw was changed to two stages, and the steam draw machine temperatures were as shown in Table 2. The appearance of fluff on the wound yarn was visually observed. The results are shown in Table 2.

[0023]

[Table 2]

From Table 2, it is more advantageous to increase the temperature of the second stage than that of the first stage steam drawing temperature in terms of fuzz formation.
Further, it can be said that it is advantageous not to increase the difference between the respective draw ratios.

Example 3 An experiment similar to that of Example 2 was conducted. The first stage of the pressure steam drawing machine was 115 ° C. and the second stage was 130 ° C. The fiber strength, the presence or absence of crazes in the fibers, and the degree of fluff formation were examined. The results are shown in Table 3.

[0026]

[Table 3]

From Table 3, the strength (orientation) is insufficient when the total draw ratio is 10 times or less. When it exceeds 25 times, generation of crazes is recognized, and further generation of fluff is observed.

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[Procedure amendment]

[Submission date] July 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title of the invention: Method for producing acrylic precursor yarn for carbon fiber

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an acrylic precursor for carbon fibers, and more particularly, to the production of an acrylic precursor yarn for high-strength carbon fibers with less yarn fluff and yarn breakage with excellent productivity. It is about the method.

[0002]

2. Description of the Related Art One of the important applications of acrylic fibers is acrylic raw yarn for carbon fiber, which requires high strength and high orientation fiber performance.

As a method for producing an acrylic precursor yarn for carbon fibers which satisfies this requirement, it is known to carry out high-magnification drawing using pressurized steam. Further densify the fiber,
Moreover, in order to prevent devitrification of the yarn after drawing in pressurized steam, it is preferable to carry out drawing in hot water after spinning washing, then dry densification, and then pressure steam drawing. Known as.

Further, the high-magnification drawing by pressure steam also increases the yarn-making speed of the yarn, and is therefore considered to be a method which also contributes to the improvement of productivity.

[0005]

However, in general, the acrylic fiber as the precursor yarn for carbon fiber has a single fineness of 0.7 to
Since it is extremely thin at 1.5 denier, fluffing is likely to occur due to high-strength drawing, and fluffing frequently occurs especially in steam drawing, and it cannot be used as an acrylic precursor yarn for carbon fiber. There is.

Various improvements have been made to the steam stretching machine and the apparatus, but the stretching ratio is only about 8 to 10 times, and no sufficient solution has been taken yet.

The present invention has been obtained as a result of investigations for solving such a problem, and its object is to reduce the generation of fluff even when a high draw ratio of 10 to 25 times is used as a total draw ratio. It is intended to provide a method for obtaining a high-strength acrylic precursor yarn for carbon fiber.

[0008]

Means and Actions for Solving the Problems In order to achieve the above object, the present invention provides a method of spinning an acrylic polymer solution, stretching in a hot water bath to dry densify, and then pressure steam stretching. After stretching in the bath to be 3 to 5 times, it is stretched in two stages in pressure steam, and the total stretching ratio is 10 to 25.
And the stretching condition is | n ₁ −n ₂ | <1.0, T
_The main constitution is a method for producing an acrylic precursor yarn for carbon fibers, wherein ₁ <T ₂ . Here, n ₁ is the draw ratio in the first-stage pressure steam, n ₂ is the draw ratio in the second-stage pressure steam, and T ₂ and T ₂ are the first-stage and second-stage pressure steam temperatures, respectively. Is.

Hereinafter, the present invention will be described in more detail along with its operation. The acrylic polymer used in the present invention contains at least 95 mol% of acrylonitrile and is a copolymer of one or more comonomers. As the unsaturated monomer used in the present invention as a comonomer, acrylic acid, methacrylic acid, acrylic acid esters, acrylamide, methacrylamide, N-hydroxymethylacrylamide, vinyl chloride, vinylidene chloride, vinyl acetate, 2 vinyl pyridine , Allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, p-styrene sulfonic acid and salts thereof, but of course, are not limited to these.

The intrinsic viscosity of the polymer at this time is 1.4 to
It should be 2.5, preferably 1.5 to 2.2. If the intrinsic viscosity is too small, high-strength fibers cannot be obtained, and if it is too large, it becomes difficult to adjust the spinning dope and the spinnability is significantly deteriorated.

The spinning may be carried out in a coagulating bath, or may be carried out in the air and then immersed in a coagulating liquid. As the coagulating liquid, a dimethylacetamide aqueous solution, a dimethylformamide aqueous solution, a dimethylsulfoxide aqueous solution, or the like is used. The coagulated yarn is washed with warm water to sufficiently remove the solvent. The yarn after desolvation needs to be stretched 3 to 5 times in a hot water bath at 85 to 100 ° C.

If the draw ratio in the hot water bath is too small, devitrification occurs in the yarn due to dry densification, and if it is too large, the draw ratio in the pressurized steam becomes extremely small and the total draw ratio becomes Fibers with a low degree of orientation cannot be obtained.

After the drawing in the hot water bath, in order to make the internal structure of the fiber densified, a heating roller at 110 to 180 ° C.
Dry densification treatment is performed for 5 to 5 seconds. It is preferable to perform oiling prior to the dry densification treatment in order to prevent the fusion of the yarns and maintain the sizing property. After the dry densification, it is stretched by the first stage pressure steam and then by the second stage pressure steam to give a total stretching ratio of 10 to 25 times. Compared with the method in which the pressure steam drawing is performed in only one step, the drawing is performed in two steps, the difference in the draw ratio is less than 1, and the method in which the drawing temperature in the latter stage is kept higher than that in the former stage is fluff. It is possible to perform high-magnification stretching with less occurrence of

The temperature of the pressurized steam must be in the range of 110 to 160 ° C. It is presumed that when the drawing is excessively performed in only one stage, fluffing is likely to occur because spots are likely to appear in the drawing location of each single fiber in the pressure steam drawing machine. Therefore, by dividing the drawing into two stages and making the draw ratio of the same degree in each stage, the draw unevenness between the single fibers is reduced, and at the same time the draw resistance is increased. It is considered that high-stretching is achieved.

When the total draw ratio is lower than 10 times, high strength and highly oriented yarn cannot be obtained, and when it is higher than 25 times, fluff is generated due to single yarn breakage and crazes and cracks in the fiber. Occurrence of is seen.

After the pressure steam drawing, if necessary, 110 to 110
Treatment with a heating roller at 250 ° C. can be performed, and further, oiling for improving the focusing property can be added.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 70% of a dimethylacetamide solution containing 20% by weight of a copolymer having an intrinsic viscosity of 2.1 obtained by copolymerizing 96.0% by weight of acrylonitrile and 4.0% by weight of methyl acrylate. After spinning at 30 ° C. into a coagulation bath of an aqueous dimethylacetamide solution and passing through a warm bath at 85 ° C. for washing, 95
It was stretched in a hot water bath at ℃ and dried on a 110 ° C heating roller, and then a silicon-based oil agent was applied, and dried and densified on a 143 ° C heating roller. Subsequently, stretching was performed in a pressure steam stretching machine at 125 ° C., and the breaking ratio thereof was examined. The stretch ratio in the hot water bath and the steam stretch ratio at break were as shown in Table 1.

[0019]

[Table 1]

The yarn stretched 3 to 5 times in a hot water bath at 95 ° C. does not show devitrification due to densification by drying and has a large total draw ratio at break.

Example 2 In Example 1, the drawing ratio in hot water was fixed to 4.0 and the heating steam drawing was changed to two steps, and the temperature of each steam drawing machine was set as shown in Table 2. The appearance of fluff on the wound yarn was visually observed. The results are shown in Table 2.

[0022]

[Table 2]

From Table 2, it is more advantageous to increase the temperature of the second stage than that of the first stage steam drawing temperature in terms of fuzz formation.
Further, it can be said that it is advantageous not to increase the difference between the respective draw ratios.

Example 3 An experiment similar to that of Example 2 was conducted, in which the first stage of the pressure steam drawing machine was 115 ° C. and the second stage was 130 ° C. The fiber strength, the presence or absence of crazes in the fibers, and the degree of fluff formation were examined. The results are shown in Table 3.

[0025]

[Table 3]

From Table 3, the strength (orientation) is insufficient when the total draw ratio is 10 times or less. When it exceeds 25 times, generation of crazes is recognized, and further generation of fluff is observed.

[0027]

As is clear from the above description, according to the method of the present invention, it is possible to obtain an acrylic fiber having a high strength and a high degree of orientation, which is imparted with an extremely high draw ratio and has no fluff due to the breakage of a single yarn. As a result, it has become possible to produce a high-quality acrylic precursor yarn for carbon fiber, which has not been obtained in the past, with high productivity. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 25, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

[Table 3]

Front page continued (72) Inventor Akira Hatsukano 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Toshihiro Makishima 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon shares Company Otake Office

Claims (1)

Claim: What is claimed is: 1. When an acrylic polymer solution is spun, stretched in a hot water bath to dry densify and then pressure steam stretched, it is 3 to 5 times in a hot water bath. And then in two stages in pressure steam, the total draw ratio is 10-25.
And | n ₁ −n ₂ | <1.0 T ₁ <T ₂ where n ₁ is the draw ratio in the first stage pressurized steam n ₂ is the draw ratio in the second stage pressurized steam T ₂ , T ₂ are the pressure steam temperatures of the first and second stages, respectively, for the production of the acrylic precursor for carbon fiber.