JPH0441706A - Polyvinyl alcohol-based fiber having high toughness and its production - Google Patents

Abstract

PURPOSE:To obtain the title fiber having high strength and high initial modulus and useful as a fishing net and rope as well as reinforcing material such as rubber or plastic. CONSTITUTION:Water and/or alcohol is applied to a fiber consisting of PVA having 1500-7000, preferably 3000-5000 polymerization degree and subjected to thermal stretching, and the fiber is heat-treated under relax ratio of 0.5-10%, preferably 2-10% at >=150 deg.C, preferably 180-260 deg.C, for 3-20 sec to provide the objective fiber having >=14g/d tensile strength, >=250g/d initial modulus and >=40g/d toughness.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides polyvinyl alcohol (hereinafter referred to as "polyvinyl alcohol") which has high strength, high initial modulus, and high toughness.

It is abbreviated as PVA. ) type polymer and its manufacturing method.

(Conventional technology) PVA fiber has the highest strength among general purpose fibers.

Has a high initial modulus of elasticity, rubber hoses, conveyor belts, fibers for cement reinforcement, sewing thread for materials 1 tatami thread, fishing nets, land nets 1
It is widely used as a fiber for industrial materials such as heavy fabrics and ropes.

In recent years, various attempts have been made to further increase the strength and initial elastic modulus of PVA fibers in response to increasingly sophisticated market demands.
A method is disclosed in which a glycerin solution of PVA having a weight average molecular weight of 500,000 or more is gel-spun in a cooling bath, the glycerin of the solidified yarn is removed, and then hot-stretched. Further, JP-A-60-126312 discloses a method in which a DMSO solution of PVA having a degree of polymerization of 1,800 or more is dry-wet-spun in a methanol bath, and the resulting undrawn yarn is hot-stretched.

However, with these methods, the higher the stretching ratio, the lower the elongation at break, so although it was possible to improve the strength and initial elastic modulus to some extent, it was not possible to improve the toughness.

On the other hand, the method of subjecting fibers after stretching to a relaxing treatment is generally well known and is applied not only to polyamide and polyester fibers but also to PVA fibers.

However, these methods merely apply further heat to the stretched fibers to increase the degree of crystallinity and stabilize the fiber structure.

It was not intended to improve toughness.

In industrial material applications, fibers are rarely used in their final form as they are; they undergo secondary and tertiary processing such as weaving, knitting, and single-strand braiding before becoming final products. It is common to However, fibers with low cutting elongation and low toughness often break single filaments during post-processing or have a significant decrease in tenacity, resulting in a significant decrease in the strength of the processed product even if the strength of the raw yarn is high. There was a problem with this. For this reason, there has been a strong desire to develop PVA fibers that have both high strength and high toughness.

(Problems to be Solved by the Invention) As mentioned above, PVA having high strength and high initial elastic modulus
Various types of fibers have been proposed, but PVA fibers, which have high strength, high initial elastic modulus, and high toughness and are suitable for industrial material applications, especially for rubber reinforcement, are not known to have improved toughness. There wasn't.

Therefore, the first object of the present invention is high strength.

The object of the present invention is to provide a PVA fiber having a high initial modulus of elasticity and moderately high toughness for use in rubber reinforcement.

A second object of the present invention is to use such high toughness PVA.
An object of the present invention is to provide a method for manufacturing fibers with high productivity.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have found that after applying water, alcohol, or a mixture thereof to hot-stretched PVA fibers, relaxing The present invention was achieved by discovering that by heat-treating the material, the elongation at break can be increased and the toughness can be improved without causing a significant decrease in strength.

That is, the present invention has the following configuration.

(1) Made of polyvinyl alcohol with a degree of polymerization of 1500 or more and 7000 or less, with a tensile strength of 14 g/d or more,
A high toughness polyvinyl alcohol fiber having an initial elastic modulus of 250 g/d or more and a toughness of 40 g/d% or more.

(2) After applying water, alcohol, or a mixture thereof to a hot-stretched fiber made of polyvinyl alcohol with a degree of polymerization of 1,500 or more and 7,000 or less,
A method for producing high-toughness polyvinyl alcohol fibers, which is characterized by heat treatment at a temperature of 150° C. or higher under a relaxation rate of 10%.

9 The tensile strength and initial elastic modulus in the present invention are based on JIS
-L-1013, the measurement is performed at a gripping interval of 25 cm and a pulling speed of 30 CO+/min.

Moreover, toughness is determined by integrating the area between the load-elongation curve and the elongation axis obtained in the above measurement.

The present invention will be explained in more detail below.

The PVA fiber of the present invention has a tensile strength of 14 g/d or more and an initial elastic modulus of 250 g/d or more, which is much higher performance than general-purpose polyamide or polyester fibers. Moreover, while conventional PVA fibers had a toughness of only about 30 g/d%, the PVA fiber of the present invention has a toughness of 40 g/d% or more, which is a typical high toughness fiber. It has a toughness close to that of PVA fiber, and its elongation is about 4 to 5% for ordinary high-strength PVA fibers.

Since it usually has an elongation of 5.5% or more, it is extremely useful industrially.

In other words, as mentioned above, in industrial material applications,
Although post-processing such as weaving, knitting, and twist braiding is generally performed before the final product is obtained, the PVA fiber of the present invention has a high toughness of 40 g/d% or more. Therefore, during post-processing, single yarns are less likely to be cut or the strength decreases, and it is possible to prevent a decrease in the strength of the processed product.

The fineness and number of filaments of the PVA fiber of the present invention are not particularly limited, and may be 1200d1500f,
Even if it is a multifilament such as 1500d/300f.

The monofilament may have a fineness of 100 deniers or more.

The PVA used in the present invention has a degree of polymerization of 1500 or more.

It must be 7000 or less, preferably 3000 or more.

5000 or less. A degree of polymerization of less than 1500 is unsuitable because the tensile strength, initial elastic modulus, etc. of the final product will be lower than the desired values. Also, the degree of polymerization is 7000
PVA that exceeds 100% has a high polymer cost, leading to an increase in the cost of the final product, making it difficult to widely apply it to industrial material applications.

In the production method of the present invention, the spinning method of the PVA fiber serving as the supply system is not particularly limited.

For example, patent application No. 1-12203 proposed by the present inventors
The dry/wet (gel) spinning method described in No. 0 can be adopted.

That is, a spinning stock solution prepared by dissolving PVA with a degree of polymerization of 1,500 or more in a solvent mainly composed of DMSO is dry/wet-spun, and the resulting undrawn yarn is hot-stretched to form PVAm,! can be produced by performing dry/wet spinning using a spinneret having a discharge hole protruding from the spinning dope exit side, followed by hot stretching.

In addition, conventionally known spinning method 1, for example, a PVA aqueous solution containing boric acid or a boric acid salt is used as the spinning stock solution.

It can also be produced by a wet spinning method using a coagulation bath of alkali hydroxide, sodium sulfate, or the like.

In the present invention, after applying water, alcohol, or a mixture thereof to these hot-stretched PVA fibers, heat treatment is performed at a relaxation rate of 0.5 to 10%.

In other words, 1. In normal hot stretching, industrially, a pair of rollers with different circumferential speeds (the one with the lower circumferential speed is the supply roller,
Use the taller one as the stretching roller. ), run the yarn between
This is done by heating the yarn between the rollers by various means, and further.

Although this may be carried out in multiple stages, in the present invention, a relaxation roller is further provided after the stretching roller of the second final stretching stage, and between the stretching roller and the relaxing roller, water, alcohol, or After applying these mixtures, heat treatment is performed at a temperature of 150° C. or higher under a relaxation rate of 0.5 to 10% defined by the following formula.

Even if undrawn yarn is heat-treated by adding water or the like, no increase in toughness will be achieved.9 Therefore, in the present invention, it is necessary to implement the drawn yarn as a supply system, and preferably 85% of the maximum drawing ratio.
or more stretching, more preferably 90% or more stretching,
It is preferable to use hot-drawn yarn with a breaking elongation of 5% or less.

As a result of detailed study on the relationship between relaxation rate and toughness, the present inventors found that when PVA fibers are directly heat-treated after hot drawing, when the relaxation rate is increased, the elongation at break increases, but the strength increases. It has been found that, while the decrease is large and the toughness does not increase, when water, alcohol, or a mixture thereof is applied and heat treated, the elongation increases while suppressing the decrease in strength by 1, and the toughness increases. Furthermore, the inventors have also found that the higher the relaxation rate, the smaller the decrease in strength and the greater the cutting elongation, which makes it possible to increase toughness more effectively.

In addition, when adding water, although the decrease in strength by 1 is small,
The upper limit of the possible relaxation rate is about 5%, whereas when alcohol is added.

It was also found that although the upper limit of the possible relaxation rate is 10%, a decrease in strength of 1 is larger than in the case of water.

Based on the above facts, in the present invention, it is necessary to set the relaxation rate during heat treatment to 0.5 to 10%, preferably 2 to 10%, and it is preferable that it be as high as possible within this range.

If the relaxation rate is less than 0.5%, the increase in cutting elongation will be small and the toughness will not exceed 40 g/d, and if it is greater than 10%, the tension applied to the yarn during heat treatment will be too low. , which is not preferable because the threads may be fused and cut.

In the present invention, examples of the alcohol to be applied to the PVA fiber after hot drawing include methanol, ethanol, propatool, etc., but ethanol is preferably used, and a mixture of water and ethanol is more preferable. A mixture of water and ethanol is particularly preferable because the higher the relaxation rate, the higher the toughness. This is because although the relaxation rate can be high, the reduction in strength by one level is large, so the advantages of both can be taken advantage of. The volume mixing ratio of water and alcohol is 90:10~50:50
A range of is preferred.

In the present invention, these liquids include hydrochloric acid and phosphoric acid.

Catalysts for promoting dehydration reactions such as para-toluenesulfonic acid,
Oil agents, pigments, etc. may be mixed.

The method of applying liquid such as water is not particularly limited, and methods such as applying with a so-called oiling roller, immersing in these liquids, and spraying the liquid can be used.

The amount applied is not particularly limited, but 0 to the fiber
．． It is preferable to apply 1 to 3.0% by weight of the liquid.

In addition, heat treatment may be performed after applying these liquids and performing continuous drying treatment, but in that case, the shrinkage stress during drying will spread to the heat treatment process and the tension during heat treatment will decrease. It is best to avoid doing so.

The tension during heat treatment is preferably 0.1 to 1.0 g/d.

The heat treatment must be performed at a temperature of 150°C or higher, but the upper limit is the melting point of the fiber, preferably 180 to 260°C, and 1
It is preferable to carry out for ~60 seconds, especially for 3 to 20 seconds.

If the heat treatment temperature is less than 150° C., sufficient stress relief from the fibers cannot be achieved, and the desired high toughness cannot be obtained.

(Function) In the present invention, high toughness PVA fibers of 40 g/d% or more can be obtained because the applied water and alcohol molecules enter the PVA molecular chains constituting the fibers and break down the PVA molecular chains. This is believed to be due to the fact that, since the fibers are shrunk, the tension of the threads is maintained during the heat treatment even under a relaxation rate of 0.5 to 10%, which removes the strain in the PVA molecular chains.

(Example) Next, one embodiment of the present invention will be specifically explained using examples.

Example 1 Polymerization degree 3900 (7) PVA (saponification degree 99.9%
Jl/%) was prepared, and this spinning stock solution was passed through a stainless steel cylindrical capillary tube 3 with an inner diameter of 0.54 mm.
Dry/wet spinning was carried out using a spinneret embedded so that 00 fibers protruded 3a+m toward the outlet side of the spinning dope through a 10mm air gap in a methanol coagulation bath at a linear discharge speed of 4m1 min and a spinning draft of 4.0. After extracting DMSO, it was dried to obtain an undrawn yarn.

Next, this undrawn yarn is drawn with hot air provided between a supply roller and a drawing roller, with an inlet temperature of 205°C and an outlet temperature of 265°C, and a water/ethanol mixture ( After applying 0.7% by weight of 70/30 volume ratio) with an oiling roller, 60! > Dry for a while. Furthermore, this yarn was passed through a heat treatment machine with an internal temperature of 220 tons for 3
Run it for seconds, grip it with a relaxing roller, and then wind it up.
A fiber of 1500d/300f was obtained. At this time, the speed ratio of the stretching roller and relaxing roller is 1:0.95, which is 5
% relaxation rate.

The tension during heat treatment was 0.7 g/d.

The fiber obtained above had a tensile strength of 15.5 g/d, an initial elastic modulus of 298 g/d, an elongation of 5.6%, and a toughness of 49.
It had an extremely excellent performance of 5 g/d%.

Comparative Example 1 PVA-based fibers were produced in the same manner as in Example 1 except that the water/ethanol mixture was not applied.

The obtained fiber had a tensile strength of 12.5 g/d, an initial modulus of elasticity of 220 g/d, an elongation of 5.5%, and a toughness of 39.2 g/d.
It was only a percentage.

Comparative Example 2 PVA-based fibers were produced in the same manner as in Example 1 except that the internal temperature of the heat treatment machine was set at 145°C. The obtained fibers had a tensile strength of 14.8 g/d and an initial elastic modulus of 317.
g/d, elongation was 4.5%, but toughness was 38.0
It was only g/d%.

Comparative Example 3.4 The speed ratio of the stretching roller and relaxing roller is 0.997
(relaxation ratio 0.3%) and 1:0.85 (relaxation ratio 15%) in the same manner as in Example 1.
produced fibers.

The fiber obtained when the relaxation ratio was 0.3%.

The tensile strength was 15.3 g/d and the initial elastic modulus was 312 g/d.

The elongation was decreased to 4.5% and the toughness was decreased to 32.3 g/d%. Furthermore, when the relaxation ratio was 15%, the fibers were frequently fused and cut in the heat treatment machine, making it impossible to collect samples.

Example 2. Comparative Example 5 PVA with a polymerization degree of 1300 (saponification degree 99.9 mol%)
29 wt% DMSO solution of and PV with a degree of polymerization of 1700
A 24% by weight DMS○ solution of A (saponification degree 99.7 mol%) was prepared, and these spinning stock solutions were dried in the same manner as in Example 1.
An unstretched product was obtained by wet spinning.

Next, this undrawn yarn was subjected to the same hot stretching, application of a water/methanol mixture, drying, and heat treatment as in Example 1.

Fiber obtained from PVA with a degree of polymerization of 1300 (Comparative Example 5)
Although the elongation at break was 5.7%, the tensile strength was 1
2.5g/d, initial elastic modulus 230g/d, toughness 30
．． It was only 7 g/d%.

On the other hand, fibers obtained from PVA with a degree of polymerization of 1700 1/# (
Example 2) has a tensile strength of 14.2 g/d and an initial elastic modulus of 260 g/d%.

It had satisfactory performance with cutting elongation of 5.6% and toughness of 41.3 g/d%.

(Effects of the Invention) The PVA-based fiber of the present invention has high toughness close to that of polyamide fiber. This is an unprecedented PVA-based fiber, which not only makes it possible to expand its use in fishing nets and ropes, which are the typical uses of PVA fibers, but also allows for secondary processing such as weaving, knitting, and single-twist braiding. Rubber because the strength loss is small.

It can also be used as a reinforcing material for plastics, etc.
It is a fiber suitable for various industrial material applications.

Furthermore, according to the method for producing high-toughness PVA-based fibers of the present invention, it is possible to produce PVA-based fibers having the above-mentioned advantages with good productivity and at low cost.

Claims (2)

[Claims] (1) It is made of polyvinyl alcohol with a degree of polymerization of 1500 or more and 7000 or less, has a tensile strength of 14 g/d or more, an initial elastic modulus of 250 g/d or more, and a toughness of 40 g/d% or more. High toughness polyvinyl alcohol fiber. (2) After applying water, alcohol, or a mixture thereof to a hot-stretched fiber made of polyvinyl alcohol with a degree of polymerization of 1,500 or more and 7,000 or less,
A method for producing high-toughness polyvinyl alcohol fiber, characterized by heat treatment at a temperature of 150° C. or higher under a relaxation rate of 0%.