JPS6360125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pill-resistant wholly aromatic polyamide fiber and a method for producing the same. More specifically, the present invention relates to a polymetaphenylene isophthalamide fiber having improved pill resistance and a method for industrially producing the fiber.

Prior art A spinning solution in which a wholly aromatic polyamide obtained from an aromatic diamine and an aromatic dicarboxylic acid is dissolved in an organic polar solvent such as N-methyl-2-pyrrolidone or N,N-dimethylacetamide is prepared by a dry method or a wet method. Spinning is known from numerous patents and documents (Japanese Patent Publication No. 47-41743,
50-12322 etc.). In particular, polymetaphenylene isophthalamide fibers are known as "Cornetx" in Japan.
It is commercially available under the name (registered trademark), and its excellent heat resistance has established its use in protective clothing, sports clothing, filters, etc.

However, conventional wholly aromatic polyamide fibers have been found to cause significant pilling in clothing and interior applications, particularly in clothing that involves a lot of movement, such as protective workwear and sports clothing, which has become a practical problem.

Purpose of the Invention In view of the problems with conventional wholly aromatic polyamide fibers, the present inventors aimed to obtain wholly aromatic polyamide fibers with improved pill resistance, particularly polymetaphenylene isophthalamide fibers. As a result of extensive research, we have arrived at the fiber of the present invention and its manufacturing method.

That is, the object of the present invention is to provide a wholly aromatic polyamide fiber, particularly a polymetaphenylene isophthalamide fiber, which has significantly improved anti-pilling properties compared to conventional wholly aromatic polyamide fibers, as well as special additives and The object of the present invention is to provide a method for producing wholly aromatic polyamide fibers with good anti-pilling properties, particularly polymetaphenylene isophthalamide fibers, without requiring additional treatments.

Composition of the Invention The polymetaphenylene isophthalamide fiber of the present invention, which has excellent pill resistance, is a wholly aromatic polyamide in which 85 mol% or more, preferably 95 mol% or more of the polymer repeating units are metaphenylene isophthalamide units. A solution prepared by dissolving in an organic polar solvent is wet-spun into an aqueous coagulation bath containing calcium chloride,
A fiber obtained by carrying out water washing and wet stretching using a high-temperature water washing bath or stretching bath in which the concentration of an organic polar solvent is within a specific range that is much higher than usual, followed by dry heat stretching at a high temperature. and the apparent density (da) of the amorphous portion in the fiber is 1.335 g/cm ³ or less, preferably 1.334 g/cm ³ or less, and
The degree of crystal orientation (fc) is 90% or more, preferably 92% or more. characterized by

Here, the wholly aromatic polyamide in which 85 mol% or more of the repeating units are metaphenylene isophthalamide units refers to polymethphenylene isophthalamide whose homolimer or copolymer component does not exceed 15 mol%. A copolymer whose main component is As an example of a copolymer,
Examples include polymetaphenylene paraphenylene isophthalamide copolymer, polymetaphenylene isophthalamide copolymer, and the like.

In addition, especially when a high degree of heat resistance is required, it is preferable that 95 mol% or more of the repeating units are metaphenylene isophthalamide units.

The apparent density (da) of the amorphous part is a measure of the density of the amorphous part of the fiber, and the fiber of the present invention has a da of 1.335 g/cm ³ or less, which is higher than that of ordinary polymethane. This value is extremely small compared to nylene isophthalamide fiber. This means that the fiber of the present invention has a structure in which the amorphous portions are extremely sparse.

Here, the apparent density (da) of the amorphous portion is determined by the following formula.

[Apparent density da of amorphous part]

da=(ρ ₂₅ −11.45Xc)/1−Xc) Here, ρ ₂₅ ; Specific gravity of the fiber at 25 _° C It is measured by

[Specific gravity of fiber ρ ₂₅ ] Measured by floating and sinking a sample in a mixture of carbon tetrachloride and n-heptane. The procedure is as follows.

Mix appropriate amounts of carbon tetrachloride and n-heptane,
Prepare a liquid whose specific gravity at 20℃ is slightly larger than the sample's specific gravity.

Extract with methanol using a Soxhlet extractor, and place the dried samples (n=5) together with the mixed liquid into a test tube with a common grinder.

Cool to -10℃, aspirate for 30 seconds with an aspirator, and then seal tightly.

Transfer to a constant temperature bath at 20.0℃ and let stand for 15 minutes, then repeat heating by 0.3℃ and leaving for 15 minutes.

The temperature at which each sample settles is recorded, and the average settling temperature of the five samples is defined as t (℃) (40℃
If all the sample has not settled by then, start over from )).

Using an Ostwald hydrometer, this liquid was measured at 20°C.
Measure the specific gravity at 30°C and 40°C, create a calibration curve, and read the specific gravity ρt at temperature t (°C) from the calibration curve.

Assuming that the coefficient of expansion of the fiber is 3.0×10 ^-4 , calculate the specific gravity of the sample at 25°C using the following formula.

ρ ₂₅ = [1+3.0×10 ^-4 (t-25)]×ρt [Crystallinity Xc of fiber by X-ray diffraction] Determined from X-ray scattering intensity by the following procedure. The device used is Rigaku Denki RU-3H, and the scattering intensity was 2θ.
= Measured in the range of 6° to 40°.

Set the aligned fiber sample on a rotating sample stage and rotate it to obtain the scattering intensity curve (A).

Fix the fiber sample and obtain a scattering intensity curve in the meridian direction. Based on this curve, 2θ = 6°, 13°, 20°, 26°,
Find a smooth curve (B) that passes through each point at 31°, 36°, and 40°.

Obtain the scattering intensity curve (C) without the sample.

Let Sc be the area surrounded by curve A and curve B in the range of 2θ=6° to 40°, and let S _A be the area surrounded by curve B and curve C.

Determine the crystallinity Xc using the following formula.

Xc=Sc/Sc+S _A The degree of crystal orientation (fc) is a measure of the degree of orientation of crystal parts, and is determined by X-ray diffraction as follows.

[Crystal orientation (fc)]

The counter is fixed at 2θ=27.3° and the sample is rotated to calculate the half-width H (°) of the X-ray diffraction intensity curve using the following formula.

Degree of crystal orientation (fc) = 180-H/H x 100 (%) In the fiber of the present invention, the fc is 90% or more, which means that the crystal portions are sufficiently oriented.

In addition, the crystallinity (Xc) of the fiber of the present invention is 25
~36%, which is equivalent to normal (high tenacity type) polymetaphenylene isophthalamide fiber.

The denier of the fibers of the present invention is suitably 1 to 10 denier/filament, and the cross-sectional shape of the fibers can be any shape such as circular, oval, or cocoon-shaped. The fibers may be used as stable fibers or as multifilament yarns.

The fibers may also contain additives such as matting agents, colorants, and stabilizers, and may also be provided with oils and other finishing agents.

Such pill-resistant polymetaphenylene isophthalamide fibers can be produced by the method of the present invention as shown below.

That is, a polar solvent solution of a wholly aromatic polyamide polymer in which 85 mol% or more of the repeating units are metaphenylene isophthalamide units is extruded into an aqueous coagulation bath containing calcium chloride under specific conditions, washed with water, and wet stretched. When producing fully aromatic polyamide fibers by drying and dry heat stretching, the organic polar solvent concentration C (%) and temperature T (°C) of at least one of the water washing bath and/or wet stretching bath are determined by the following formula: (A), (B) 25≦C≦45 ……(A) 150−2C≦T≦100 ……(B) Washing with water and wet stretching are performed at the same time, and then drying at 290 to 350°C. By hot stretching, a pill-resistant polymetaphenylene isophthalamide fiber is produced.

The polar organic solvents used in the method of the present invention include N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), N , N,N',N'-tetramethylurea (TMU), etc. Particularly preferably NMP
or DMAC and mixtures thereof.

The concentration of the polymer in the spinning dope is preferably 10 to 30% by weight, particularly 15 to 25% by weight. In addition, to increase the stability of the solution, a small amount of metal halide salt,
For example, calcium chloride, lithium chloride, etc. may be included.

This solution is made into a fiber by wet spinning,
The aqueous coagulation bath containing calcium chloride used in wet spinning is preferably a coagulation bath with a calcium chloride concentration of 35% by weight or more and a bath temperature of 60° C. or more.

The fibers drawn from the coagulation bath are then subjected to water washing and wet stretching. The water washing bath and wet stretching bath may be used as long as the solvent concentration and temperature are within the above ranges, but particularly preferable results can be obtained under the following conditions. That is, (a) the wet stretching bath is 25≦C≦45 and 150−2C≦T≦
It is particularly preferable to select water washing conditions such that the amount of residual agent in the fibers subjected to drying is 5% or less by further washing with water if necessary.

Wet stretching is performed in one or more stages, and the total wet stretching ratio is preferably 2 to 4 times.

Although the drying method and conditions for drying after wet stretching can be arbitrarily selected, it is not preferable to set the drying temperature to 200°C or higher, particularly 250°C or higher.

Dry stretching performed subsequent to drying is carried out at 290 to 390°C,
Particularly preferably, the temperature is 300 to 360°C. The dry heat stretching ratio is preferably 1.1 times or more, and the total stretching ratio including wet stretching is preferably 3.0 to 5.5 times.

The fibers of the present invention inherently have excellent heat resistance, but in order to develop sufficient heat resistance (especially high-temperature dimensional stability), it is desirable to increase crystallization by dry heat drawing. The dry heat stretching temperature is 290~ as mentioned above.
Generally applicable within the range of 390℃. If the temperature is lower than 290°C, the degree of crystallinity will increase sufficiently, and if the temperature is higher than 390°C, not only will the fiber deteriorate significantly, but the degree of crystallinity will not increase. The yarn heating time in dry heat drawing varies depending on the temperature and the bundled state of the yarn (large tows deteriorate heat transfer), but is generally preferably 0.5 to several seconds. The crystallinity (Xc) of the obtained fibers is 25~
36%, which is almost the same as normal (high strength type) polymetaphenylene isophthalamide fiber. When Xc is less than 25%, it is desirable to strengthen the dry heat stretching conditions (temperature and/or time).

Effects of the Invention The polymetaphenylene isophthalamide fiber of the present invention having the above-mentioned microstructure has superior pill resistance compared to conventional fibers of the same type.

In the past, attempts have been made to lower the strength of fibers to improve anti-pilling properties, and measures such as changing the coagulation conditions (changing to conditions that are unfavorable for the purpose of obtaining high strength) and lowering the draw ratio have been considered. Ta. Regarding the former, the process condition deteriorates significantly (yarn breakage/single yarn breakage), and it is impossible to find conditions that can be adopted industrially, and regarding the latter, the strength decreases and the elongation increases, It was not an effective measure from the viewpoint of anti-pilling properties.

In contrast, according to the method of the present invention, it is possible to reduce the strength without deteriorating the process condition or increasing the elongation, and it is possible to reduce the strength of the anti-pilling polymetaphenylene isophthalamide fiber. Industrial production becomes possible.

Although the mechanism by which the effects of the present invention are expressed has not yet been fully elucidated, the dry yarn (before dry heat stretching) obtained by the method of the present invention has a clear crystal structure observed in X-rays, and this It is thought that it brings about special effects.

In other words, due to the presence of crystals (nuclei) before dry heat drawing, some of the amorphous chains exhibit strong tension during dry heat drawing.
Moreover, it is presumed that the amorphous portion as a whole remains in a sparse structure because the uniform stretching effect in dry stretching is inhibited by the presence of crystals. It is thought that such a special microstructure exerts the remarkable effect of good anti-pilling properties.

Therefore, the polymetaphenylene isophthalamide fiber of the present invention is particularly suitable for use in the fields of protective workwear and sports clothing.

EXAMPLES The content and effects of the present invention will be explained below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In addition, various measured values in the examples are based on the following methods.

[Intrinsic viscosity ()] 30 by Ostwald viscometer for a polymer solution with a concentration of 0.5 g/100 ml in concentrated sulfuric acid (98% sulfuric acid)
Obtain the specific viscosity ηr at °C, and use the following formula to obtain the intrinsic viscosity ()
seek.

=ln ηr/0.5 [Mechanical properties] The strength and elongation of the single yarn were measured using an Instron tensile tester. Measurement conditions: sample length 20mm, tensile speed
100%/min, n=20 Single yarn denier is determined from the weight of the yarn (or tow) and the number of filaments.

[Anti-pilling property]

The product yarn is crimped and cut to obtain a crimped fabric with a fiber length of 51 mm, and the spun yarn obtained from this is used as a surge fabric and its anti-pilling properties are measured. Anti-pilling property is JISL1076
-67, measured using an ICI type pilling tester.

In addition, "part" and "%" indicating concentration in the examples are based on weight unless otherwise specified.

Example 1 Intrinsic viscosity obtained by copolymerization of metaphenylene diamine, isophthalic acid chloride, and terephthalic acid chloride (copolymerization molar ratio = 97/3)
20.5 parts of fully aromatic polyamide of 1.83% and 79.5 parts of N,
Dissolved in N-dimethylacetamide (DMAC). This was degassed to obtain a spinning stock solution at 40°C, which was extruded through a spinneret with a pore diameter of 0.05 mmφ and 2000 holes into a coagulation bath consisting of an aqueous solution with a calcium chloride concentration of 38% and a temperature of 70°C. After passing through a coagulation bath of approximately 1.0 m, it was washed in a 20°C water bath containing 12% DMAC.
After washing in a 60°C water bath containing 3% DMAC, the film was stretched 3.1 times in a bath with a DMAC concentration of 40% and a temperature of 90°C. After further washing with water, it was dried on a drying roller at 120°C. The dried thread contained about 3% DMAC, and the X-ray diffraction photograph showed a clear crystal diffraction pattern. This fiber was further stretched 1.3 times on a hot plate at 340°C. The physical properties of the obtained fiber were as follows.

Apparent density of amorphous part (da) 1.331g/cm ^3Crystal orientation (fc) 92% Crystallinity (Xc) 28.4% Fineness 2.3de Strength 2.83g/de Elongation 18.0% The spinning and drawing condition was good. .

The obtained fibers (staple fibers) were spun into a serge fabric, and the anti-pilling properties were evaluated using an ICI pilling tester, and were found to be good at grade 4 to 5.

Comparative Example 1 A polymetaphenylene isophthalamide fiber and a serge fabric were obtained in the same manner as in Example 1 except that the DMAC concentration in the drawing bath was 1% or less. The physical properties of the obtained fibers and anti-pilling properties of the fabric were as follows.

Apparent density of amorphous part (da) 1.346g/cm ^3Crystal orientation (fc) 92% Crystallinity (Xc) 29.1% Fineness 2.3de Strength 5.1g/de Elongation 23.% Pill resistance Grade 1-2 comparison Example 2 A polymetaphenylene isophthalamide fiber and a surge fabric were obtained in the same manner as in Comparative Example 1, except that the in-bath stretching ratio was 2.8 times and the hot plate stretching ratio was 1.1 times. The physical properties of the obtained fibers and anti-pilling properties of the fabric were as follows.

Apparent density of amorphous part (da) 1.348g/cm ^3Crystal orientation (fc) 89% Crystallinity (Xc) 28.3% Fineness 3.1de Strength 2.8g/de Elongation 48% Pill resistance Grade 1-2 Examples 2. 79.5 parts of a fully aromatic polyamide with an intrinsic viscosity of 1.90 obtained from a copolymer of metaphenylene isophthalamide, isophthalic acid chloride, and terephthalic acid chloride (copolymerization molar ratio = 97/3)
of N-methyl-2-pyrrolidone (NMP). This is degassed and filtered to obtain a spinning stock solution at 60℃, which is extruded at 380 g/min through a spinneret with a hole diameter of 0.08 mmφ and 15,000 holes installed at the bottom of a cylindrical spinning tube (coagulation bath) with a depth of 1.5 m. did. The coagulating liquid supplied to the spinning tube has a calcium chloride concentration of 42% and an NMP concentration of 2.
%, the coagulated fiber bundle was washed in a 25°C water bath containing about 10% NMP, then washed in a 60°C water bath containing about 2% NMP, and then washed with 35% NMP. Stretched 2.5 times in a bath at 95°C. After further washing in a water bath at 60°C, it was dried on a roller with a surface temperature of 120°C. The amount of residual solvent in the dried yarn was 4.3%, and the X-ray diffraction photograph of the fiber showed a clear crystal diffraction pattern. Subsequently, after stretching to 1.6 times on a hot plate at 340℃,
After giving about 13 crimps per inch, it was cut to 51 mm. The physical properties of the obtained fiber were as follows.

Apparent density of amorphous part (da) 1.328g/cm ^3Crystal orientation (fc) 92.5% Crystallinity (Xc) 26.1% Fineness 2.1de Strength 2.6g/de Elongation 16.% Obtained fiber (staple fiber) was spun into a serge fabric, and its anti-pilling properties were evaluated using an ICI pilling tester, and the anti-pilling properties were evaluated to be grade 4 to 5, which was good.

Comparative Example 3 Fibers and serge fabrics were obtained in the same manner as in Example except that the NMP concentration in the drawing bath was 1% or less. The physical properties and pill resistance evaluation results were as follows.

Apparent density of amorphous part (da) 1.351g/cm ^3Crystal orientation (fc) 92.3% Crystallinity (Xc) 31.0% Fineness 2.1de Strength 5.2g/de Elongation 3.2% Pill resistance Grade 1-2

Claims (1)

[Scope of Claims] 1 A solution of a wholly aromatic polyamide in an organic polar solvent in which 85 mol% or more of the repeating units are composed of metaphenylene isophthalamide is wet-spun into an aqueous coagulation bath containing calcium chloride, and then spun in a water washing bath and /Or organic polar solvent concentration C (%) of at least one stretching bath
Water washing and wet stretching are carried out under the conditions that the temperature T (°C) simultaneously satisfies the following formulas (A), (B) 25≦C≦45 ……(A) 150−2C≦T≦100 ……(B) The fiber is dry-heat stretched at 290 to 390°C, so that the apparent density (da) of the amorphous part in the fiber is 1.335 g/cm ³ or less and the degree of crystal orientation (fc) is 90% or more. Pill-resistant polymetaphenylene isophthalamide fiber. 2. A solution of a wholly aromatic polyamide in an organic polar solvent in which 85 mol% or more of the repeating units are composed of metaphenylene isophthalamide is placed in an aqueous coagulation bath with a calcium chloride concentration of 35% by weight or more and a liquid temperature of 60°C or higher. Wet spinning is carried out, and then the organic solvent concentration C (%) and temperature T (°C) of at least one of the washing bath and/or stretching bath are determined by the following formulas (A), (B) 25≦C≦45... (A) 150−2C≦T≦100 ……(B) A fiber of 1.335 g/cm, which is characterized by dry heat drawing at 290 to 390°C, which has been subjected to water washing and wet drawing under conditions that simultaneously satisfy the following. A method for producing an anti-pilling polymetaphenylene isophthalamide fiber having an apparent density (da) of an amorphous part of ³ or less and a degree of crystal orientation (fc) of 90% or more. 3. The method for producing pill-resistant polymetaphenylene isophthalamide fibers according to claim 2, wherein the organic polar solvent is N-methyl-2-pyrrolidone or N,N-dimethylacetamide. 4. The method for producing anti-pilling polymetaphenylene isophthalamide fiber according to claim 3 or 4, wherein the wet stretching ratio is 2.0 to 4.0 and the total stretching ratio is 3.0 times or more.