JPS6088117A - Preparation of high-modulus yarn - Google Patents

Abstract

PURPOSE:To obtain the titled yarn efficiently without causing thermal deterioration, by subjecting optically anisotropic dope prepared by dissolving poly(p- phenylene terephthalamide) (PPTA for short) in conc. sulfuric acid to wet spinning, applying tension to the yarn under specific conditions, drying the yarn. CONSTITUTION:PPTA is dissolved in 95-101wt% conc. sulfuric acid in such a way that the polymer concentration is >=17wt%, and the dope is adjusted to a proper temperature to show optical anisotropy. Firstly, the dope is extruded into a gas, and then into a coagulating solution. The coagulated yarn is drawn out, washed with water, 1-10g/d tension (with the proviso that denier is based on yarn after drying) is applied to the yarn in >=50wt% water content state, the length of the yarn is made not to change >=0.5% during the application of tension, and the yarn is dried at room temperature -200 deg.C, to give the desired yarn. EFFECT:Having a few fluff and small unevenness of sectional area of fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides high modulus poly(p-7 enylene terephthalamide) (hereinafter sometimes abbreviated as PPTA).

) This invention relates to a method for producing fibers, and particularly relates to an improved method for producing fibers efficiently and with less fluff without thermal deterioration.

It is known that high-strength, high-modulus fibers can be produced from PPTA (for example, JP-A-47-39458 and JP-A-47-43419).

In particular, Japanese Patent Application Laid-Open No. 47-43419 discloses that high modulus type PPTA fibers can be obtained by air-discharge wet spinning from a high-concentration PPTAO dope followed by tension heat treatment. Then, Kevlar 49 is used as the fiber produced by this method.

However, the disadvantage of these fibers is that they are prone to fibrillation [e.g., S. L., Phoenix et al.; Text,
Res, J, December issue, page 934 (1974)
) has been pointed out. High modulus type PP
Many methods for producing TA fibers have been disclosed since then, but all of them involve tension heat treatment accompanied by stretching, and according to the knowledge obtained by the present inventors, they suffer from the above-mentioned drawbacks, i.e., they tend to become fibrillated. It is inevitable that the occurrence of fluff will increase. Furthermore, thermal deterioration is often observed during heat treatment.

The present inventors have developed a high modulus PP without such drawbacks.
In the process of conducting various research for the purpose of producing TA fibers, a specially limited amount of P-zo was spun in the air, and a specific range of tension was applied to the fiber in a specific water content state while or after washing with water. They discovered that by drying the fibers at the same length, that is, without changing the length, it was possible to obtain highly modulus fibers that did not show heat deterioration and had little fuzz. The present invention was completed after repeated research.

That is, in the present invention, poly(p-phenylene terephthalamide) is added to concentrated sulfuric acid having a concentration of 95 to 101% by weight and shortness of at least 1%.
The optically anisotropic dope dissolved to a polymer concentration of 7% by weight was extruded from a spinneret into a gas and then into a coagulation bath, and the coagulated yarn was taken out from the coagulation bath and washed with water or after 50%. After applying a tension of 1 to 10 f/d (denier is based on the fiber after drying) to the yarn in a water-containing state of more than 100%, the fiber length at the time of applying the tension is 0.5% or more. Room temperature to 200℃ without changing
This is a method for producing high modulus fibers that is characterized by drying.

The polymer used in the present invention consists essentially of PPTA. Here, the meaning of "essentially" means that PP is used in a small amount within a range that does not impede the constituent elements and effects of the present invention.
Polymers other than TA [e.g., poly-(m-phenylene terephthalamide), poly=(p-phenylene terephthalamide), poly-(m-phenylene phthalamide), poly-(polymethylene terephthalamide), aliphatic polyamide, alicyclic polyamide, polyester, polyimide, polyurethane, polyurea, etc.) or PPTA with other repeating units (e.g., nuclear-substituted p-phenylene units, nuclear-substituted or unsubstituted p-phenylene units, etc.). Biphenylene units, I)-phenylene units, m-phenylene units, (poly)methylene units, pyridylene units, bonding units such as esters, urethanes, ureas, ethers, thioethers, etc.) are copolymerized, various additives, This means that compounding agents (for example, dyes, antioxidants, ultraviolet absorbers, brighteners, pigments, etc.) may be added.

The poly(-, phenylene terephthalamine P) used in the method of the present invention has a molecular weight of at least 2.0, more preferably 3.
．． Intrinsic viscosity of 0 or more, more preferably 3.5 or more (at 25°C
(measured in concentrated sulfuric acid).

As a solvent for dope preparation used for spinning, 95 to 10
Concentrated sulfuric acid is used in a concentration of 1% by weight, preferably 97.5-100.5% by weight. Specifically, the key is:
The type of polymer, intrinsic viscosity, and concentration of the polymer dissolved in the P-zo used for spinning should be appropriately selected. When the concentration of concentrated sulfuric acid is less than 95% by weight, the solubility of the polymer is poor, and therefore a suitable dope cannot be obtained during spinning, and the viscosity of the dope increases, making it difficult to transport and filter. , the mechanical properties of the resulting fibers are unsatisfactory. On the other hand, if the concentration of concentrated sulfuric acid exceeds 101, ie, fuming sulfuric acid containing a large excess of sog, it is difficult to handle, and the polymer hardly dissolves. It is known that fuming sulfuric acid at a concentration of 101% or less with a small excess of SO3 provides good solubility of the polymer and provides a preferred spinning dope. However, there was a large excess of 80% in concentrated sulfuric acid. The presence of these causes large voids in the internal structure of the resulting fibers, resulting in a dull appearance, poor mechanical properties, and a slow withdrawal rate (from the coagulation bath).

The dope used for spinning must be prepared to contain 17% by weight or more of poly(-p-phenylene terephthalamide) in order to achieve high modulus. This concentration should be determined specifically by the intrinsic viscosity and type of polymer used and the concentration of concentrated sulfuric acid.

The temperature of the spinning dope is preferably any temperature between the lowest temperature at which the dope exhibits optical anisotropy and has sufficient fluidity to be handled, up to about 100°C. spinning r-
Specifically, the temperature of the spinneret should be determined as appropriate, taking into consideration the polymer concentration, type, sulfuric acid concentration of the solvent, spinneret orifice diameter, linear discharge speed, etc.

The dope thus prepared must be extruded through a spinneret into a gas and then into a coagulation bath. The dope is degassed, filtered, and needled before passing through the spinneret.
This would be particularly preferred for industrial production. The shape of the spinneret, the number of holes, the size of the holes, etc. are not particularly limited. The hole size is usually 0. Those with a diameter of O1 to 0.5 fins are used. The linear speed of the r-pull extruded from the spinneret is not particularly limited, and may be determined solely based on requirements such as productivity and draft, which will be described later. It is important that the dope stream extruded from the spinneret first passes through a gas. This is because when the fibers are suddenly extruded from the spinneret into a coagulation bath without passing gas, it is difficult to increase the draft to more than 1.5, and the resulting fibers have low density and low strength and elongation. This is because it is small. Examples of the gas include air, 90%, Alzan, oxygen, and the like. Air is the most preferred method due to its economic advantages and ease of use. The thickness of the gas, ie, the distance between the spinneret and the coagulation surface, is suitably about 0.2 to 50 centimeters. The P-flow pushed out into the gas is
It then needs to be extruded into a coagulation bath where it undergoes coagulation.

Water is preferably used as the coagulating liquid, but methyl alcohol, ethylene glycol, glycerin, isopro)R
Monohydric or polyhydric alcohols such as alcohol, mixtures of water and the above-mentioned alcohols, aqueous solutions of acids such as sulfuric acid, aqueous alkaline solutions such as ammonium hydroxide, and aqueous solutions of various salts such as calcium chloride are used. The temperature of the dope or coagulation liquid during this wet spinning is not particularly limited, but it is generally desirable to be in the range of -1θ to 40°C.

The shape of the coagulation bath is not particularly limited. However, in industrial production, from the viewpoint of increasing the spinning speed to a high level, it would be preferable to use a so-called funnel-shaped coagulation bath as shown in Figure 3 of JP-A-55-122012. .

The dope stream extruded into the coagulation bath undergoes coagulation in the coagulation bath, and then the coagulated thread is removed from the coagulation bath by at least 30 minutes.
It is desirable and more preferable to draw at a speed that produces a draft of 0 in order to obtain fibers with high strength and high modulus.4.
It is a draft of 0 or more.

Here, the draft is defined as the value obtained by dividing the linear velocity of the coagulated filament when it is drawn out from the coagulation bath by the linear velocity of the dope passing through the spinneret.

The coagulated filament drawn out from the coagulation bath is washed with water. Washing with water is carried out in one or more stages, and in order to perform this effectively, it may be combined with an alkaline aqueous solution such as caustic soda. It is preferable to extract and remove the solvent as much as possible by washing with water. For example, if sulfuric acid is used as the solvent, about 1
Preferably, the residual amount is less than % by weight. The method of washing with water is not particularly limited, and may be a known technique, for example, a method of running in a water bath, a method of pouring water on a rotating roller, method 1, +
? The method may be selected from a method in which the material is washed with water while being sprinkled on a bottle or cloth, a method in which it is deposited on a net and water is sprinkled on it, or a method in which these methods are combined.

The washed fibers are applied with an oil or the like if necessary and dried, but it is important in the method of the present invention that the steps from washing to drying be carried out in a special manner. That is, while washing with water, make small holes in the V/LV,.../U, and apply a tension of 1 to 10 g/d to the yarn in a state of water content of more than % by weight (however, the denier is based on the fiber after drying). ) and drying at room temperature to 200° C. so that the fiber length does not change by more than 0.5% when tension is applied. In the method of the present invention, the step of applying tension to the water-containing yarn may be carried out during washing or after washing is completed, and if washing is in the middle, washing may be carried out at the same time. The method of applying tension can be achieved, for example, by using a plurality of Nelson rollers or by using a roller with a chi/ξ. Also, as an experimental method, it is possible to increase the load on the so-called dancer roller of the winding machine, but in either case, the tension applied to the water-containing yarn is 1 to 10 t/d. There must be. It is presumed that when such tension is applied, the yarn is slightly stretched. At a tension of 12/d or less, it is possible to increase the modulus to some extent by adjusting the temperature or residence time during drying, but the effect is not sufficient and is not preferred.

10- On the other hand, if the tension exceeds 1 Of/d, the fiber structure is destroyed due to excessive stretching, and although the modulus increases, the strength decreases significantly and fuzz is generated. The tension applied to the water-containing yarn is preferably 2 to 81/d.

The yarn thus tensioned in a water-containing state is then dried under a knitting condition in which its length does not change by more than 0.5%. In order to carry out drying at a fixed length industrially and conveniently,
It would be preferable to carry out drying in a step directly after applying tension in a wet state.

As a method for drying at a fixed length, it is convenient to dry the yarn on a heated roller without causing it to slip, or to wrap the yarn around a bobbin, wire, or frame.

In the present invention, drying refers to the act of reducing the moisture content from a moisture content of 50% by weight or more to an equilibrium moisture content (about several %) or less.

The drying temperature should be selected from room temperature to 200°C; if it exceeds 200°C, although the modulus increases, it is not preferable because thermal deterioration of the fibers, decrease in stiffness, and even the occurrence of fluff are observed. In other words, in order to suppress thermal deterioration of the fibers, maintain strength, and greatly increase the modulus, and obtain fibers without fuzz, the temperature should be between room temperature and 200°C, and the temperature should be 50 to 1.
A temperature of 50°C is more preferable, and a temperature of 80 to 1 Mo°C is most effective.

In the method of the present invention, the change in fiber length during drying is 0.5
It is extremely important not to exceed %. This is because, when stretched by 0.5% or more during drying, more fuzz will occur. On the other hand, conventionally known methods for producing high modulus PPTA fibers all involve drawing in a drying and/or heat treatment step, which inevitably leads to the generation of fluff and unevenness in the cross-sectional area of the fibers. The change in fiber length during drying should preferably be suppressed to 0.3% or less, more preferably 0.92% or less, which is substantially constant length drying.

One of the characteristics of the method of the present invention is that after applying tension to the yarn in a water-containing state, it is dried at a relatively low temperature. At this time, if the water content is less than 50% by weight, the strength will decrease and fuzz will easily occur. The water content is preferably 80% by weight or more.

The fiber produced by the method of the present invention can be produced by the conventional method, as described above.
That is, compared to fibers produced by hot drawing, the fibers have high modulus and strength, have less fluff, and have less irregularities in fiber cross-sectional area. Furthermore, there is less thermal deterioration during spinning.

Utilizing these characteristics, the fibers obtained by the method of the present invention are useful as reinforcing materials for rubber and plastics such as vertebral belts. When the fibers of the present invention are used for reinforcing these rubbers and plastics, they are usually used in the form of multifilaments, but the fibers of the present invention are not limited thereto, and include monofilaments, roving yarns, It can also be used in the form of cloth, chopped strands, etc., as a reinforcing material for ropes, woven fabrics, plastics, metals, cement, ceramics, etc., and as cotton.

Examples 1 to 3 and Comparative Example 1 PPTA having a logarithmic viscosity of 5.8 was obtained according to the reference example of JP-A-55-122012.

PPTA in 99.6% sulfuric acid with a polymer concentration of 19% by weight 1
The mixture was dissolved at 75°C to a concentration of 3%, and defoamed under reduced pressure for about 2 hours. While filtering the P-pole exhibiting optical anisotropy held at 75 to 80°C, it was extruded through a spinneret having 100 pores with a diameter of 0.065 mm, and after running through approximately 5 tubes of air. , into a 30% by weight aqueous sulfuric acid solution maintained at -5°C. After applying a draft 8 and taking out the coagulated thread from the coagulation bath, it was washed with water on a rotating roller. The water-washed yarn is treated with about 200% sulfuric acid of about 1 to 3% by weight based on the polymer.
While containing ~300% by weight of water, it was wound onto a stainless steel bobbin using a winding machine under various tensions. Tension is applied by changing the load on the dancer roller of the winding machine, and the wound fiber is placed in a water bath to reduce the sulfuric acid content to 1100 pp or less, and then left wound on the bobbin (i.e. at a constant temperature). It was placed in an oven at 120°C and dried for a day and night.

Table I lists the varying conditions and properties of the fibers obtained.
Show K. Fiber strength, elongation, and initial modulus were measured on multifilaments. The number of fluffs is determined by visually counting the number of fluffs on the surface of a sample on a 14-inch Zevin after drying obtained by winding for 20 minutes.

From Table 1, it can be seen that the fibers of the present invention (to which Examples apply) have a higher initial modulus than the fiber of Comparative Example 1, which does not involve additional tensioning in the hydrated state.

Comparative Example 2 The fiber obtained in Comparative Example 1 was passed over a hot plate with a surface temperature of 300°C, and the speed of the front and rear rollers was adjusted to 9 f/
The process was performed under a tension of d.

Table 1 shows the properties of the fibers thus obtained. Although a high modulus fiber is obtained, the strength is significantly lower than the fibers of the present invention shown in Examples 1 to 3, and there is a lot of fuzz.

Example 4 Using PPTA with a logarithmic viscosity of 6.4, 99.9% by weight sulfuric acid, approximately 80
Melt at ~85°C to obtain an optically anisotropic r-p, then ca.
The pressure was reduced to 0.5 to 0.2 tones of Hg and degassed over a period of time. The spinneret temperature was approximately 85°C, the air layer thickness was 10 m,
The draft was set to 9.2, and the coagulation bath was set to 10°C water.

The fibers coming out of the coagulation bath were folded onto a net conveyor to form a yarn pile, and in this state, a 5% Kaseizoda aqueous solution and water were sequentially sprinkled on the yarn and washed for about 30 minutes. The fibers are taken out from the thread pile that has been washed and passed through two Nelson rollers, the roller speed is set so that a tension of 59/d is applied, and then the wet thread (water content approximately 100%) is passed through a heated roller at 120°C. and dried under a fixed length.

The obtained fibers had little fuzz, high modulus, and high strength. The processing conditions and fiber properties are shown in Table 1.

Below margin 171

Claims (1)

[Claims] Poly(p-phenylene terephthalamide) at a concentration of 9
An optically anisotropic dope dissolved in concentrated sulfuric acid of 5 to 101% by weight to a polymer concentration of at least 17% by weight is extruded through a spinneret into a gas and then into a coagulation bath, and from the coagulation bath a coagulated thread is extruded. Take out the yarn, wash it with water, or after washing it with water, apply 1 to tor to the yarn with a water content of 50]i% or more.
After applying a tension of /d (denier is based on the fiber after drying), the fiber length at the time of applying the tension is O,S%
A method for producing high modulus fibers characterized by drying at room temperature to 200°C without causing any change.