JPH02145809A - Ultrafine gel fiber and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having quick response when used as a reactive element by producing a water-containing fiber by the conjugate spinning of a water-base stock liquid of a PVA polymer and a stock liquid of another water-soluble polymer and subjecting the resultant water-containing fiber to freezing treatment, thawing treatment and removal of the water-soluble polymer. CONSTITUTION:A water-containing fiber produced by the conjugate spinning of a water-base stock liquid of a PVA polymer (preferably containing >=97% of vinyl alcohol unit and having a polymerization degree of >=3,000) and a stock liquid of another water-soluble polymer is subjected to the freezing treatment, the thawing treatment and the removal of the water-soluble polymer to obtain the objective fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to ultrafine gel fibers, and more specifically to hydrous ultrafine gel fibers mainly composed of polyvinyl alcohol polymers and a method for producing the same.

(Conventional technology) Research on high water content gels made of polyvinyl alcohol polymers has been actively conducted, and it has been found that gels with excellent mechanical properties can be obtained by freezing or freezing/thawing an aqueous solution of polyvinyl alcohol polymers. Examples of obtaining water-insoluble high water content gels include Japanese Patent Publication No. 48-30462, Japanese Patent Publication No. 30463-1983, Japanese Patent Application Laid-Open No. 57-130542, Japanese Patent Application Laid-open No. 130543-1983, and Japanese Patent Application Laid-open No. 1982-130542.
It is disclosed in Japanese Patent No. 36630.

However, since the stock solution itself has fluidity, in either case, the stock solution is molded into the desired shape by placing it in a predetermined container or mold and processing it. Therefore, a fibrous molded product has not been obtained.

On the other hand, in JP-A No. 62-90308, a spinning stock solution containing water as a solvent is spun into liquid nitrogen and frozen, then introduced into an extraction bath (methanol) to remove water, and then the dried filament is drawn. There are examples in which polyvinyl alcohol fibers with high strength and high modulus have been obtained by using polyvinyl alcohol, but these are not hydrous ultrafine gel fibers.

On the other hand, research on responsive polymer gels is also actively conducted.
Responsive polymer gels made of various materials that expand, contract, swell, and deform in response to environmental changes have been reported.

However, research on this responsive polymer gel has been conducted since it cannot be used in the form of fibers due to its high water content and low mechanical strength. I can't do it either. Additionally, there was a problem in that the device itself incorporating the responsive polymaglu became large.

Polymer Preprints, Japan Vol, 35, No.
3.771 (1986), Polymer Preprints, Japan Vo 1.36. No.3.881 (1987
) has an example in which responsiveness was confirmed using a hydrogel film with relatively high mechanical strength obtained by repeatedly freezing an aqueous solution containing a blend of polyvinyl alcohol and a polymer electrolyte at -45°C and thawing it at room temperature. There are no examples of hydrous ultrafine gel fibers.

On the other hand, Polymer Preprints, Japan Vo1.36
．． No. 3.878 (1987), an aqueous stock solution of polyvinyl alcohol and polyacrylic acid was spun into a sulfuric acid solution of sodium sulfate, and the wound fiber was heated at 130°C for 30 minutes.
There is 1IiIft, which has been made insolubilized by heat treatment, and its electric field responsiveness has been observed, but this is a fiber with a low water content;
There are no examples of hydrous ultrafine gel fibers.

(Problems to be Solved by the Invention) In view of the current situation, the inventor has made extensive studies and has found that:
The present invention was achieved by confirming that fibers made of polyvinyl alcohol-based polymers have excellent performance as hydrous ultrafine gel fibers.

An object of the present invention is to provide an ultrafine gel fiber that has particularly excellent response speed, high mechanical strength, excellent water resistance, can be formed into any desired shape, and has a wide range of applications, and a method for producing the same.

(Means for solving problems) The present invention has the following configuration.

(1) Ultrafine gel fibers consisting of fine water-containing fibers mainly made of polyvinyl alcohol polymer.

(2) Composite spinning of an aqueous stock solution of polyvinyl alcohol-based polymer and other water-soluble polymer stock solutions to form a hydrated fiber (A>
A method for producing ultrafine gel 11i fibers, which comprises performing a freezing treatment, (B) a thawing treatment, and (C) a water-soluble polymer removal treatment.

(3) Hydrous fiber obtained by composite freeze-spinning of an aqueous stock solution of polyvinyl alcohol-based polymer and another water-soluble polymer stock solution (
A method for producing ultrafine gel fibers, comprising: A) freezing treatment, (B) thawing treatment, and (C) water-soluble polymer removal treatment.

The present invention will be explained in detail below.

The polyvinyl alcohol polymer in the present invention has 50
Any polymer having mole % or more of vinyl alcohol units may be used, such as polyvinyl alcohol, ethylene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acrylic acid, methacrylic acid or sodium acrylate, sodium methacrylate, etc. Examples include, but are not limited to, modified polyvinyl alcohol, which is a copolymer of alkali metal salts, ammonium salts, and esters such as methyl acrylate, methyl methacrylate, and nyl acetate.

Here, the vinyl alcohol unit content is preferably 70
It is preferably mol% or more, more preferably 80 mol% or more, 90 mol% or more, or 97 mol% or more.

In addition, the degree of polymerization of the polyvinyl alcohol polymer is 10
00 or more, preferably 2000 or more, roughly 3000
The above are preferable from the viewpoint of mechanical strength.

The water content of the ultrafine gel fiber of the present invention is high, 30% by weight (hereinafter abbreviated as wt%) or more based on the polymer, and even 8Qw
t% or more, and around 150wt% and even 200wt
Very high values, around %, are also valued at 1q.

The ultrafine gel fibers used in the present invention can be used in any fibrous form, such as strings, filaments, staples, etc., but the thinner the fibers, the larger the specific surface area for reaction, and the more supple they become, allowing them to form into fabrics. When this happens, there is a noticeable difference in responsiveness. In other words, when used as a responsive element, the smaller the fiber diameter is, the better the response speed will be.

The specific fiber diameter is 20μ or less in a hydrated state (10μ or less in an absolutely dry state), preferably 10μ or less (5μ or less in an absolutely dry state).
(below), coarsely less than 5μ (less than 2.5μ when completely dry)
is more preferable.

On the other hand, the cross-sectional shape is not particularly limited, and may be circular, irregularly shaped, solid, or hollow, and the cross-sectional shape may change in the length direction of the fiber.

The aqueous stock solution of the present invention may contain the following polymer electrolytes or other polymers in addition to the polyvinyl alcohol polymer.

In the case of polymer electrolytes, any polymer that contains a dissociative group in the polymer chain and dissociates into polymer ions when dissolved in water is acceptable, and some or all of them become salts and become zero.
The ionic group may be either a cationic group or an anionic group, or may share both.

Examples of polymer electrolytes include polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, poly(acrylamide-acrylic acid) copolymer, and poly(acrylamide-acrylic acid) copolymer.
methacrylic acid) copolymer, poly(acrylamide-trimethyl(N-acryloyl-3-aminopropyl)ammonium iodide) copolymer quaternized product, polyacrylamide-2-methylpropanesulfonic acid, poly(2-methacrylic acid) copolymer,
-acrylamide-2-methylpropanesulfonic acid-2-hydroxylethyl methacrylate) copolymer, poly(2-acrylamide-2-methylpropanesulfonic acid-acrylonitrile) copolymer, alginic acid, carboxymethyl cellulose, or these alkali metal salts, ammonium salts, etc.

Examples of other polymers include polyethylene glycol, polyvinylpyrrolidone, and cellulose derivatives such as hydroxyethyl cellulose, singly or in mixtures. It is not limited to polyelectrolytes or other polymers.

In the present invention, if the blend ratio of the polymer electrolyte or other polymer to the polyvinyl alcohol polymer exceeds 300 wt%, it becomes mechanically weak, which is not preferable. Therefore, the content is preferably 300 wt% or less, preferably 150 wt% or less, and even more preferably 100 wt% or less.

On the other hand, in order to develop responsiveness, it is desirable to blend a polymer electrolyte or a polymer electrolyte salt, and the blend ratio to the polyvinyl alcohol polymer is 10w.
It is not effective unless it is t% or more, preferably 20wt% or more, more preferably 30wt% or more.

The polymer concentration of the aqueous spinning stock solution is preferably 5 wt% or more, preferably 1 Qwt% or more, and further preferably 20 wt% or more.

In addition, the solvent must be aqueous, but 50
A mixed solvent containing a water-soluble solvent may be used as long as it is not more than 3Qwt%, preferably 10wt% or less.
The following is good.

Examples of water-soluble solvents include water-soluble organic solvents such as dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, hexamethylphosphoramide, glycerin, and ethylene glycol, and water-soluble organic solvents such as formic acid and 5A acid. Examples include, but are not limited to, soluble inorganic solvents.

The water-soluble polymer stock solution in the present invention may be any water-soluble polymer stock solution as long as it can be discharged in combination with the water-based stock solution of the polyvinyl alcohol polymer and can be removed leaving behind the polyvinyl alcohol polymer.

Specific examples of such water-soluble polymers include polyethylene glycol-based, polyvinylpyrrolidone-based, alginic acid-based,
Cellulose-based, polypropylene-based, polysulfone-based, polyvinylidene fluoride-based, polysiloxane-based, polyurethane-based, polyamide-based, polyester-based, polyacrylamide-based, polyacrylic acid-based, polymethacrylic acid-based, or mixtures thereof can be selected as the polymer. It is not limited to this.

Solvents include water, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, N
- Water-soluble organic solvents such as methylpyrrolidone and hexamethylphosphoramide, or water-soluble inorganic solvents such as formic acid and riA acid are preferred.

Composite spinning in the present invention can be carried out by wet, dry, or dry-wet spinning methods such as core-sheath fiber spinning and sea-island fiber spinning, which are already known and commonly performed.

It is also possible to carry out composite discharge and freeze-spinning, and composite freeze-spinning is effective when a water-soluble polymer stock solution without an appropriate coagulating liquid is used.

Freeze spinning in the present invention refers to spinning in which an aqueous spinning stock solution is discharged from a spinneret and directly introduced into an environment of -10°C or lower to freeze the aqueous stock solution of a polyvinyl alcohol polymer. A coexisting liquid, liquid nitrogen, or the like can be used as the freezing liquid, but is not particularly limited thereto.

The freezing treatment in the present invention may be carried out at a temperature of -10'C or lower, and specifically can be carried out using a freezer, ice, dry ice, liquid nitrogen, or the like.

The thawing process according to the present invention may be carried out at a temperature of 0'C or higher, but since high temperatures have the negative effect of reducing the mechanical strength of the gel, a temperature of 100'C or lower is preferable, preferably 50'C or higher. 'C or less, preferably 3°C or less.

Freezing and thawing in the present invention may be performed only once, but repeating the freezing and thawing process two or three times increases the mechanical strength, so it is preferably repeated three or more times.

Alternatively, gel fibers with a desired water content can be obtained by dehydrating hydrogel fibers by leaving them under reduced pressure in a frozen state before thawing.

The water-soluble polymer can be removed by elution and removal using a water-soluble solvent, but there is no particular restriction on the method as long as the final water-containing ultrafine gel fibers can be obtained.
Further, it can be removed at any time after the composite discharge.

Further, the blended polymer electrolyte may be subjected to a neutralization treatment in order to turn it into a salt, and specifically, a method of immersing it in an alkali or an acid is preferable.

Furthermore, post-treatment such as stretching can also be performed, which is preferable from the standpoint of improving mechanical strength, dimensional stability, and the like. The timing of implementation may be before, during, or after the freezing/thawing process, or after one change in post-processing.

(Function) In the present invention, since polyvinyl alcohol-based hydrous ultrafine gel fibers are produced by a freezing/thawing method, the fibers have high mechanical strength despite being a hydrous gel. Therefore, it can be used in any form such as cut fibers, single yarns, yarn bundles, nonwoven fabrics, woven fabrics, knitted fabrics, or a combination of these.

It was also found that by employing composite spinning and frozen composite spinning, the handling of ultrafine fibers became much easier and productivity improved.

The ultrafine gel fibers of the present invention can be used as vibration-proofing materials, cushioning materials, water retention materials, cold insulation materials, binding materials, artificial feeds, sustained release materials such as aromatics and chemical solutions, immobilization materials for bacterial cells and microorganisms, and biological tissue repair materials. It can be used in various sensors such as biosensors, diagnostic and therapeutic tools, drug delivery systems, diagnostic agents, pharmaceuticals,
It can be applied to a wide range of fields, including the medical field such as medical tools, the biological field such as bioreactors, and even robots and toys.

In addition, the responsive element made of the hydrous gel fiber of the present invention can be used in these applications, such as artificial muscles, chemical valves, bimetals, pumps, motors, actuators, measuring instruments,
It can also be applied to the electronic industry such as switches.

(Example) The invention will be explained in greater detail by the following examples.

Example 1 Polyvinyl alcohol NH26 (manufactured by Nippon Gosei Kagaku Co., Ltd.>2
50C1 and purified water 10009 were dissolved with stirring at 100'C to obtain stock solution A with PC=20 wt%. Dissolve 80g of sodium alginate (manufactured by Gyudon Kagaku Co., Ltd., 30QCps) and 920g of purified water with stirring at 80℃, PC = 8w.
A stock solution B of t% was obtained. A ratio of 50 parts of stock solution A as an island component and 50 parts of stock solution B as a sea component was discharged at a temperature of 80°C, introduced into a 40'020% calcium chloride aqueous solution, and solidified to form 36 filaments in one filament. 1 q of sea-island composite spun fibers having an island component of The water-containing sea-island type composite spun fibers were immersed in methanol coexisting with dry ice and allowed to stand overnight.The fibers were then taken out and left in the air for about 8 hours to thaw. Then freeze and thaw in the same way.
After repeating the process several times, the gel fibers were immersed in a 1N aqueous sodium hydroxide solution and washed with water to elute and remove the sodium alginate, yielding white hydrated ultrafine gel fibers with a diameter of 8μ (approximately 4μ in an absolutely dry state). .

This hydrous ultrafine gel fiber is sandwiched between stainless steel plates and 1K3
Although the fibers were compressed under a load of Further, even when this hydrous ultrafine gel fiber was left in water for one week, no polymer elution occurred, and the mechanical strength showed almost no change from before the immersion. The water content of this water-containing ultrafine gel fiber was about 60 wt%.

Comparative Example 1 When the sea-island composite spun fiber obtained by spinning in Example 1 was immersed in a 1N sodium hydroxide aqueous solution without freezing and thawing, and then washed with water to elute and remove sodium alginate, polyvinyl alcohol was also dissolved. The fibers lost their shape.

Example 2 A composite discharge stock solution discharged in the same manner as in Example 1 was directly introduced into methanol coexisting with dry ice in a Dewarpine and frozen. After being left in that state overnight, the seabird type composite spun fibers were taken out into a polyethylene bag and left in the air for about 8 hours to thaw.

After repeating freezing and thawing 5 times in the same manner while still in a polyethylene bag, the sodium alginate was eluted and removed by washing with water, and white hydrated ultrafine gel fibers with a diameter of 10μ (approximately 5μ in an absolutely dry state) were obtained. Obtained.

This hydrous ultrafine gel fiber did not exhibit fluidity, and there was no agglutination between the fibers. Subsequently, a compression test and a water immersion test were conducted under the same conditions as in Example 1, but no change was observed in the water-containing ultrafine gel fibers before and after the test. The water content of this water-containing ultrafine gel fiber was about 80W↑%.

Example 3 Polyvinyl alcohol NH26 (manufactured by Nippon Gosei Kagaku Co., Ltd.)
150Cl, polyacrylic acid ACIOLP (manufactured by Nippon Tsumugi Co., Ltd. >100g, purified water 1000ml was dissolved with stirring at 100 ° C. to obtain a stock solution C with PC = 20wt%. 50 parts of this stock solution C as an island component, 1q in the same manner as Example 1
The stock solution B is made up of 50 parts as a sea component, and 80 parts
The fibers were discharged at a temperature of 0.degree. C. and introduced into a 40'C 20% calcium chloride aqueous solution for coagulation to obtain sea-island type composite spun fibers having 36 island components in one filament. The water-containing sea-island type composite spun fibers were immersed in methanol coexisting with dry ice and allowed to stand overnight.The fibers were then taken out and left in the air for about 8 hours to thaw. After repeating freezing and thawing five times in the same manner, the glue fibers were immersed in a 1N aqueous sodium hydroxide solution and washed with water to elute and remove the sodium alginate. A white hydrated ultrafine gel fiber was obtained.

This water-containing ultrafine gel fiber was cut into approximately 10 m long strips, placed in the center of two platinum electrode plates placed in parallel at a distance of approximately 20 m in a slightly alkaline aqueous solution, and a DC current of 40 V and 0.1 A was applied to the fibers. The gender was evaluated.

As a result, when the fibers were placed parallel to the electrode plate, when the current started flowing, the hydrous ultrafine gel fibers began to bend and took on a U-shape after about 3 seconds. Then, when a current was passed in the opposite direction, it began to return to its original position and finally bent in the opposite direction. When the current was stopped in the bent state, it gradually returned to the straight state.

On the other hand, when a hydrous ultrafine gel fiber is placed perpendicular to the electrode plate,
When the current starts flowing, it becomes 1! One end of the fibers began to swell, and finally became a transparent hydrogel whose volume had swelled to about 8 times. When the current was stopped and the temperature was left as it was, the temperature returned to almost the original temperature.

Further, even after being left in water for -week, no elution of the polymer occurred, and there was almost no change in mechanical strength compared to before the start of immersion.

The water content of this water-containing ultrafine gel fiber was about 70 wt%.

Comparative Example 2 The water-containing sea-island type composite spun fiber obtained by spinning in Example 3 was immersed in a 1N aqueous sodium hydroxide solution without freezing and thawing, and then washed with water to elute and remove sodium alginate, and polyvinyl alcohol was also dissolved. The fibers lost their shape.

Example 4 A composite discharge stock solution discharged in the same manner as in Example 3 was directly introduced into methanol coexisting with dry ice in a Dewarpine and frozen. The water-containing sea-island composite spun fibers were then taken out into a polyethylene bag and left in the air for about 8 hours to thaw. After repeating freezing and thawing five times in the same way while still in a polyethylene bag,
The sodium alginate was eluted and removed by washing with water.

Next, the fibers were neutralized by immersion in a 1N aqueous sodium hydroxide solution to obtain white hydrated ultrafine gel fibers with a diameter of 12 μm (6 μm in an absolutely dry state).

This water-containing ultrafine gel fiber does not exhibit fluidity, and there is little adhesion between the fibers. As a result of evaluation in the same manner as in Example 3, when the hydrous ultrafine gel fibers were placed parallel to the electrode plate, when the current started flowing, the gel fibers began to bend and after about 3 seconds, the U
It became a glyph. Then, when a current was passed in the opposite direction, it began to return to its original position and finally bent in the opposite direction. When the current was stopped in the bent state, it gradually returned to the straight state.

On the other hand, when you buy hydrous ultrafine gel fibers perpendicular to the electrode plate,
When an electric current was started to flow, the fibers began to swell from one end and eventually became a transparent hydrogel whose volume swelled to about 10 times. When I stopped the current and left it alone, it returned to almost its original dimensions. Further, even after being left in water for -week, no elution of the polymer occurred, and there was almost no change in mechanical strength compared to before the start of immersion. The water content of this water-containing ultrafine gel fiber was about 90 wt%.

(Effects of the Invention) Since the hydrogel fibers of the present invention are ultrafine fibers, the finer the fibers, the larger the specific surface area for reaction, and the more flexible they are, and the difference in response to reactions is noticeable. In other words, when used as a responsive element, the amount of change is large and the response speed is fast.

Furthermore, in the present invention, since the hydrous ultrafine gel fibers are made by a freezing/thawing method, the mechanical strength is high despite the hydrous gel. For this reason, cut fibers, single yarns, yarn bundles, non-woven fibers, etc.5. Since it can be used in any form such as woven fabrics, knitted fabrics, or any combination of these, it has excellent versatility.

Another feature is that by employing composite spinning and frozen composite spinning, handling of ultrafine fibers becomes much easier and productivity can be improved.

Claims (3)

[Claims] (1) Ultrafine gel fibers consisting of fine water-containing fibers mainly made of polyvinyl alcohol polymer. (2) Water-containing fiber obtained by composite spinning aqueous stock solution of polyvinyl alcohol polymer and other water-soluble polymer stock solution (A)
A method for producing ultrafine gel fibers, which comprises performing a freezing treatment, (B) a thawing treatment, and (C) a water-soluble polymer removal treatment. (3) Hydrous fiber obtained by composite freeze-spinning of an aqueous stock solution of polyvinyl alcohol-based polymer and another water-soluble polymer stock solution (
A method for producing ultrafine gel fibers, comprising: A) freezing treatment, (B) thawing treatment, and (C) water-soluble polymer removal treatment.