JPH01104820A - Production of high-strength acrylic fiber - Google Patents

Abstract

PURPOSE:To obtain the titled fiber with high strength and high modulus, useful for tire cords, reinforcing fibers for composite materials etc., by dry-wet spinning of a stock solution of a high-molecular weight acrylonitrile-based polymer into a coagulating both retained at low temperatures followed by drawing at high draw ratio. CONSTITUTION:A stock solution prepared by dissolving in an organic solvent (pref. DMF or dimethylacetamide) an acrylonitrile-based polymer containing >=95wt.% of acrylonitrile, with a weight-average molecular weight of >=1,000,000 is subjected to dry-wet spinning into a coagulating both retained at <=-40 deg.C (pref. a mixed solvent of organic solvent/alcohol) followed by drawing so as to be >=20 for the overall draw ratio, thus obtaining the objective fiber having the following characteristics: 1. tenacity...>=22g/d 2. tensile modulus...>=250g/d 3. degree of orientation (pi) measured by X-ray spectrometry...pref. >=95% 4. crystallinity parameter (beta)...<=0.8 deg. 5. knot strength...>=4g/d 6. knot modulus...>=150g/d.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the production of high-strength acrylic fibers useful as industrial fibers such as tire cords and reinforcing fibers for composite materials.

[Conventional technology]

Traditionally, acrylic fibers have been produced in large quantities for clothing, but at present they are rarely used for industrial or industrial purposes because they do not have sufficient mechanical strength.
Many attempts have been made to produce acrylic fibers with mechanical properties that can be used as industrial or sex industry material fibers.

For example, Japanese Patent Application Laid-open No. 57-51819 discloses that fibers obtained by wet or wet-dry spinning are wet-stretched, dried under no tension, and then contact-stretched on a heating plate to increase the effective stretching ratio to 9 times. It has been proposed to make acrylic fibers with a high elastic modulus by 25 times or less. On the other hand, JP-A-57-161
No. 117 discloses that an acrylonitrium-based polymer having a relative viscosity of 2-5 to &0 is spun by dry or wet processes, washed, or wet-stretched after washing, dried on a heated row μ under two tensions, and heat-treated under dry heat. A method is proposed. In addition, Japanese Patent Application Publication No. 5
Publication No. 9-199809 describes acryl μ with a molecular weight of 400,000.
After the spinning stock solution obtained by dissolving the polymer in the solvent under reduced pressure and defoaming is spun and solidified, it is stretched in multiple stages at higher temperatures in subsequent steps, and then dried under tension at 130°C or less. It is described that acrylic fibers having a weight of 20 g/d or more can be produced by using K and K.

[Problem that the invention seeks to solve]

The gist of all of these known techniques is to improve tensile strength, and such improvement in tensile strength often reduces other mechanical properties, such as tensile modulus and knot strength. In addition, it does not comprehensively improve or improve other mechanical properties such as elastic modulus and knot strength. Unlike fibers, it does not satisfy the fiber properties required for reinforcing fibers in composite materials.

Therefore, the present inventors developed an acrylonitrile with a high degree of polymerization with a weight average molecular f11 million or more! J/L'-based polymers are used to remove the puffiness of the mechanical properties of fibers, and high-strength acrylic with a small amount of copolymerized components (second component) is used to improve chemical resistance and weather resistance. As a result of extensive research into fiber manufacturing methods, we have developed industrially advantageous high-strength acrylic fibers that have significantly improved mechanical strength compared to conventional acrylic fibers by using an extremely low temperature coagulation bath of -40°C. They discovered a manufacturing method and completed the present invention.

[Means for solving problems]

The gist of the present invention is to prepare a spinning stock solution obtained by dissolving an acrylonitrile polymer containing 95% by weight or more of acrylonitrile and having a weight average molecular weight of 1 million or more in an organic solvent in a coagulation bath maintained at a temperature of -40°C or less. Wet-dry spinning and stretching the total stretching ratio to 20 times or more to achieve a strength of 22
The objective is to produce high-strength acrylic fibers with a g/d or more and an elastic modulus of 250 g/d or more.

The acrylonitrile polymer used in the present invention needs to have a weight average molecular weight of 1,000,000 or more, preferably 1,200,000 or more. In order to produce the high-strength acrylic fiber of the present invention, it is necessary to perform high stretching of 20 times or more.
When such a polymer is used, it is impossible to perform such high stretching, and therefore the high strength acrylic fiber of the present invention cannot be obtained. The acrylonitrile) l171z-based polymer having a weight average molecular weight of 1 million or more used in the present invention can be produced by ordinary suspension polymerization, emulsion polymerization, and solution polymerization.
The method described in Publication No. 1510, that is, acrylic ::)!
JA/10-70% by weight, organic solvent 15-60% by weight,
A method in which a mixture of 16 to 60 parts by weight of water is polymerized in the presence of a physical initiator, and then 1 to 10 parts by weight of water and/or an organic solvent is added to 1 part by weight of the monomer to polymerize the fibers. This is preferable in that a high molecular weight polymer suitable for shaping can be stably obtained.

The organic solvent used here is DMF
DMAc (dimethylacetamide), r-
Examples include petilofucton and DM80 (dimethyl sulfoxide). Further, the composition of the acrylonitrile polymer used here can be freely selected depending on the purpose of use of the acrylic fiber, but from the viewpoint of the physical properties of the fiber, it is preferable that the copolymerization ratio is 5 weight or less. If more than 5% by weight of the copolymerization component is copolymerized, the advantages of the acrylic fiber, such as its weather resistance and alkali resistance, will be reduced. Specific examples of copolymer components include methyl acrylate or methacrylate, methyl acrylate or methacrylate, n-
or iso- or t-butyl acrylate-F or methacrylate V-), 2-ethyμhexyμ acrylate or methacrylate, α-chloroacrylonitrile, 2-
Examples include unsaturated monomers such as hydroxyethyl acrylate, hydroxyethyl acrylate, hydroxyalkyl acrylate or methacrylate V-), vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl acetate, but other than these Any monomer can be used as long as it can be copolymerized with acrylonitrile, and it can be copolymerized with acrylonitrile alone or in combination.

In order to produce the high-strength acrylic fiber of the present invention, the above-mentioned high molecular weight acrylonitrile polymer is mixed with DMF and DMA.
c. A spinning stock solution is prepared by dissolving in an organic solvent such as DMSO or γ-butyrofuctone. In order to obtain high-strength fibers, the entire molecular chains constituting the fibers are stretched in the fiber axis direction.
It is necessary to approach the so-called stretched chain state, and it is important to prepare a polymer solution (spinning dope) in which the molecular chains are sufficiently loosened to make it easier to align the polymer molecular chains during the spinning and stretching stages. It is. Further, when spinning is performed by a dry-wet spinning method, it is preferable to set the viscosity of the spinning dope in the range of 500 to 1500 poise at 45° C. in view of its operability.

When spinning is performed using a spinning dope with a viscosity exceeding 1500 poise, extremely high pressure is applied to the spinning equipment, including the spinning nozzle and dope spinning machine, reducing the durability of the spinning machine. Furthermore, it is possible to lower the viscosity by heating the spinning stock solution to a high temperature, but in this case, a problem arises in that the stability of the solvent and the stock solution decreases. On the other hand, if a spinning dope having a diameter of less than 5001 is used, the spinnability deteriorates and stable spinning cannot be performed by the dry-wet spinning method. Further, in order to obtain a spinning stock solution of 500 to 1,500 poise using an acrylonitrile polymer having a weight average molecular weight of 1 million or more, the concentration of the stock solution must be 10% by weight or less. However, Acryloni 1μ is 95
An acrylonitrile polymer having a weight average molecular weight of 1,000,000 or more and having a weight average molecular weight of 1,000,000 or more can be obtained by coagulating a low-concentration spinning stock solution with a polymer concentration of 10- or less using a conventional coagulation bath consisting of two components of water and an organic solvent. Since the polymer concentration is low, solvent removal occurs rapidly during the coagulation process, and as a result, voids are likely to occur, and even if such an undrawn yarn is drawn, desired fiber properties cannot be developed. As a method to eliminate such structural defects, even if attempts are made to lower the temperature of the coagulation bath and gradually remove the solvent during the formation of coagulated threads, the melting point of the conventional coagulation bath consisting of a two-component system of water and organic solvent is low. Due to the relationship between It cannot be said that reducing the temperature in such a water/organic solvent system coagulation bath is a preferable method. However, for example, by using a coagulation bath consisting of a mixed solvent of organic solvent/alcoholic solvent, even from a low-concentration spinning stock solution, voids can be generated compared to a two-component system of water/organic solvent, although the reason is not clear. The occurrence of structural defects is suppressed, and spinning can be performed under a wide range of coagulation conditions. Furthermore, its melting point is significantly lower than that of a two-component system of water/organic solvent, and the viscosity of this coagulated liquid hardly increases in the cryogenic region below -40°C, making spinning at cryogenic temperatures possible. became.

Examples of coagulation baths that allow spinning at such extremely low temperatures include alcoholic solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol, as well as ketones, esters, Examples include ethers and halogenated hydrocarbons.

Although these may be used alone, it is preferable to use a mixed solvent with the organic solvent used for preparing the spinning dope, and the preferred weight ratio of organic solvent/alcoholic solvent is 0 to 70/100. ~30, more preferably 1
0-60790-40.

In the conventional dry-wet spinning method, the temperature of the coagulation bath is high, so when the spinning stock solution comes into contact with the coagulation bath, first the solvent is removed and then gelation occurs.However, as in the present invention, the coagulation bath temperature is high. When using this method, gelation of the spinning solution first proceeds, and then the solvent is removed. In the coagulated threads obtained in this way, the high concentration polyacrylonitrile polymer separates into a network in a low concentration due to Subinoda μ decomposition, and it is better to use a coagulation bath at a lower temperature to make the polymer more homogeneous. A coagulated thread in which the fibers are dispersed is obtained, and by drawing such a coagulated thread, a high-strength acrylic fiber can be produced.

The diameter of the nozzle for spinning is preferably α3 or larger. When using a high molecular weight polymer as in the present invention, it is necessary to lower the polymer concentration in the spinning dope, and therefore the discharge rate must be set higher than when using a spinning dope with a high polymer concentration. It is necessary to spin,
When a spinning nozzle with a hole diameter of 0.31 m11 or less is used, increasing the discharge rate lowers the spinning draft, causing slack in the yarn in the coagulation bath and even yarn unevenness, which is not preferable.

The coagulated thread obtained in this way is stretched while washing the organic solvent contained in the coagulated thread with hot water with a temperature gradient so that the temperature becomes higher in the later steps, and then stretched at a temperature exceeding 100°C. It is necessary to perform stretching. 1 like this
Examples of stretching at a temperature exceeding 00° C. include steam stretching and stretching in a moist heat atmosphere using a high boiling point solvent as a heating medium. Note that the high boiling point solvent includes water-soluble polyhydric alcohols such as ethylene glycol and diethylene glycol.
μ, triethylene glyco-μ, glycerin, and the like.

The drawn yarn thus obtained may be recycled if necessary.

After thorough washing, oil treatment, drying and baking at a temperature of 100 to 150°C, and more preferably dry heat stretching of 1.05 to 1.2 times at a temperature of 150 to 250°C. The total stretching ratio must be 20 times or more.

The acly fiber of the present invention obtained in this way has physical properties such as a single fiber strength of 22 g/d or more and an elastic modulus of 250 g/d or more, and is used in many fields for industrial use, industrial use, or fiber reinforcement. , Specifically, campus and asbestos fees lol
It can be used for industrial purposes such as , m yarn, hoses, heavy fabrics, and tire coats, and as a reinforcing fiber for composite materials.

〔Example〕

Hereinafter, the present invention will be specifically explained using Examples.

The weight average molecular weight (Mvr) is a value calculated by the following formula by measuring the intrinsic viscosity [η] of the polymer at 25° C. using dimethylformamide as a solvent.

[η) = A 35 X 'I O-'(My)'
The strength and elongation were calculated from the SS curve.

C. The degree of orientation and crystallinity parameters were measured by X-ray diffraction according to the following procedure.

(a) Degree of orientation (π) Obtain a diffraction profile in the azimuth direction for the reflection near the scattering angle 2θ = 176 in the equatorial direction of the acrylic fiber, and draw a pace fin on the graph to calculate the half-width H of the peak (in degrees). It was calculated using the following formula.

) Crystalline Puffmeter @ A diffraction profile of the acrylic fiber at all scattering angles was obtained, a pace fin was drawn on the graph, and the half-width B of the peak was calculated using the following formula.

(β) = Bl - b2 (where b is the half width of the standard sample (silicon powder)) The degree of orientation (π) and crystallinity parameter ■ were measured using RAD-A manufactured by Rigaku Denki under the following conditions. .

Tube voltage, tube current: 40KV, 200mA (π) Tube voltage, tube current: 40KV, 2 Q 0rnk (1) N1
Filter Use Example 1, Comparative Example 1 Using polyacrylonitrile/L' (AN100) with a weight average molecular weight of 850,000 and 1,090,000 prepared by suspension polymerization method,
The viscosity at 45℃ shown in Table 1 is 600-80
A spinning stock solution of 0 poise was obtained. This spinning stock solution was transferred from a spin tank maintained at 50°C using a nozzle with a pore diameter α of 55 days and a number of holes of 50 to methyl alcohol/L//DMAc-90/1.
0 (weight) and spun into a coagulation bath at a temperature of -50°C using a dry-wet spinning method. The distance between the nozzle surface and the coagulation bath is 5■
And so. The coagulated thread obtained in this way was heated three times in 70°C water, and then in boiling water! After stretching L5 times and further 2.4 times in glycerin at 200°C, oil treatment and drying at 140°C, dry heat stretching was further performed at 200°C 1.15 times, resulting in a total stretching ratio of 211L9 times. Achieved. Table 1 shows the physical properties of the acrylic fiber thus obtained.

Example 2 Spinning was carried out in the same manner as in Example 1 using an acrylonitrile polymer prepared by suspension polymerization and having a weight average molecular weight of 1,050,000 and copolymerized with 3 weights of methacrylic acid. The physical properties of the obtained acrylic fiber are: fineness 1.14 d, strength (knot strength) 22.4 (6,1) g/d, elongation (knot elongation) EL5.
(2,1)-1 elastic modulus (nodule elastic modulus) 261 (158)
g/d, X-ray orientation (ff) 9 & 4%, crystallinity z<'y (meter) LL69°.

Example 3 Using the spinning dope having a weight average molecular weight of 1,090,000 used in Example 1, a spinning experiment was conducted under exactly the same conditions except that only the diameter of the spinning nozzle hole was changed. The results are shown in Table 2.

Comparative Example 2 A spinning dope having the composition and viscosity shown in Table 3 was obtained using the polyacrylonide VtV having a weight average molecular weight of 1,090,000 used in Example 1, and a spinning experiment was conducted.

Example 4 Using a weight average molecular weight of 1,340,000 dahliacrylonitrile/L/L/(ANlool) prepared by a suspension polymerization method, it was dissolved in DMAc to prepare a spinning dope having a polymer concentration of 5% by weight. The viscosity at that time was 540 poise (45°C).
．． 35, using a nozzle with 50 holes, methyl alcohol 1μ/
DMAC=90/10 (wt %) and spinning was performed in a coagulation bath at a temperature of -50° C. using a dry-wet spinning method.

Note that the distance between the nozzle surface and the coagulation bath was 5 degrees.

The coagulated thread thus obtained was stretched 5 times in hot water at 70°C, 3 times in boiling water, and 3 times in glycerin at 200°C, treated with an oil agent, dried at 1'40°C, and then stretched for 20
Dry heat stretching was carried out at 0° C. by a factor of 1.1, resulting in a total stretching of 29.7 times. Aku obtained in this way! J/I/Fiber R has a fineness of 1.06 d and a strength (knot strength) of 251 (&4).
g/d, elongation (knot elongation) 7.85 (2,41) 1 elastic modulus (knot elastic modulus 272 (180) g/d% X-ray orientation degree (
π) 96.7%, crystalline Pa'F, +1-gu (/1
It was cL6B°.

Comparative Example 3 Using the spinning dope obtained from the polyacrylonitrile with an average weight fraction of 111,090,000 used in Example 1, a spinning experiment was carried out in the same manner as in Example 1 except that only the temperature of the coagulation bath was changed to 0°C. went. The strength of the obtained acrylic fiber is 19.6
g/d.

Claims (1)

[Claims] 1. Coagulation of a spinning stock solution obtained by dissolving an acrylonitrile polymer containing 95% by weight or more of acrylonitrile and having a weight average molecular weight of 1,000,000 or more in an organic solvent at a temperature of -40°C or less. Wet-dry spinning in a bath, with a total stretching ratio of 2.
Strength 2 characterized by stretching to 0 times or more
A method for producing high-strength acrylic fibers having an elastic modulus of 250 g/d or more and a modulus of elasticity of 2 g/d or more. 2. The method according to claim 1, wherein the coagulation bath is a mixed solvent of an organic solvent/alcoholic solvent. 3. The method according to claim 1, wherein the degree of X-ray orientation (π) of the acrylic fiber is 95% or more, and the crystallinity parameter β is 0.8° or less. 4. The method according to claim 1, characterized in that spinning is carried out using a spinning nozzle with a hole diameter of 0.3 mm or more. 5. The method according to claim 2, wherein the organic solvent is dimethylformamide or dimethylacetamide. 6. The method according to claim 2, wherein the alcohol solvent is methyl alcohol. 7. The method according to claim 1, wherein the viscosity of the spinning dope is 500 to 1500 poise at 45°C. 8. The method according to claim 1, wherein the acrylic fiber has a knot strength of 4 g/d or more and a knot elastic modulus of 150 g/d or more.