JPH01192815A - Water absorbing fiber - Google Patents

Abstract

PURPOSE:To obtain the title tough fiber, excellent in water absorbability, showing the neutral pH in absorbing water, by spinning a mixture consisting of an alkaline metal salt of a copolymer of an alpha-olefin or vinyl compound and maleic anhydride and PVA and carrying out heat treatment thereof. CONSTITUTION:A mixture of (A) an alkaline metal salt of a copolymer of an alpha-olefin or vinyl compound and maleic anhydride, (B) PVA (preferably, having 80-100mol% saponification degree) is formed into a fiberform and subsequently heat-treated preferably at 120-150 deg.C to provide the aimed fiber showing the neutral pH in absorbing water. Further, a resin with 0.2-0.5 neutralization value obtained by partially neutralizing an isobutylene-maleic anhydride copolymer having 0.2-5dl/g intrinsic viscosity in DMF solution at 30 deg.C with NaOH or KOH is preferably used as the component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to water-absorbing fibers that are strong and have excellent water-absorbing properties, and which are neutral when absorbing water.

[Conventional technology]

In recent years, superabsorbent resins that can absorb distilled water tens to hundreds of times their own weight have been developed and are used in disposable diapers, sanitary products, etc., but most of the current superabsorbent resins are It is used in powder or granular form and in combination with powder, matrix, nonwoven fabric, etc., but it has drawbacks such as difficulty in uniform dispersion because of the powder, and a tendency to cause migration in the final product. A fibrous water-absorbing resin is desired as a solution to these drawbacks, but it is inexpensive and has excellent performance (for impact applications, in addition to high water-absorbing performance, the pH at the time of water absorption is
There are very few commercially available water-absorbing fibers.

[Problem to be solved by the invention]

A method for obtaining a super absorbent resin by adding a crosslinking agent to an alkali metal salt of a copolymer of α-olefin or a vinyl compound and maleic anhydride is known, and for example, in JP-A-56-36504, cross-linking A polyvalent epoxy compound is used as a crosslinking agent, and JP-A-57-73007 describes a polyvalent amine as a crosslinking agent.

However, in the example of JP-A-57-73007, high-temperature heat treatment is required for crosslinking, and the alkali metal salt is liberated during the heat treatment, resulting in -
It is extremely difficult to make it neutral.

In the example of JP-A-56-36504 using a polyvalent epoxy compound, the problem of voice can be solved because crosslinking can be done at low temperatures, but the resulting water-absorbing resin is hard and brittle, and if left as it is, it will not be suitable for fibers. It is not suitable for being molded and used.

Furthermore, %Kokai No. 62-30125 describes polyhydric alcohols such as polyethylene glycol and glycerin as cross-linking agents, but in this case too, high-temperature heat treatment is required for cross-linking. It is difficult to make the - of the water absorbent resin neutral. That is, with conventionally known techniques, it is difficult to obtain water-absorbing fibers that are strong, have excellent water-absorbing properties, and have a neutral pH when absorbing water.

[Means to solve the problem]

According to the present invention, the above-mentioned problem can be solved by molding a mixture consisting of two components of an alkali metal salt (I) of a copolymer of an α-olefin or a vinyl compound and maleic anhydride and polyvinyl alcohol (II) into a fibrous shape. After that, the problem was solved by heat treatment to obtain a fibrous water-absorbing resin.

In other words, since polyvinyl alcohol (hereinafter simply referred to as rPVA J), which is an ID component, has many crosslinkable functional groups (OH groups) in its molecule, it is difficult for ordinary polyhydric alcohols to cause crosslinking. SiK<1 relatively low temperature (I20 ~
150° C.), a crosslinking reaction effective to obtain a water-absorbing resin occurs. Therefore, the alkali metal in component (I) is not liberated during heat treatment, and a water-absorbing resin having a neutral pH upon water absorption can be obtained.

Furthermore, the added PVA improves the hard and brittle properties of component (I), resulting in water absorption that is strong and has excellent processability.

The alkali metal salt of the copolymer used in the present invention <1) is
It is obtained by partially neutralizing a copolymer of an α-olefin or a vinyl compound and maleic anhydride with an alkali metal compound, and an alkali metal compound is an oxide of an alkali metal such as sodium, potassium, or lithium. Or hydroxide, among which sodium hydroxide or potassium hydroxide is preferably used.

The copolymer of α-olefin or vinyl compound and maleic anhydride is a copolymer of maleic anhydride and at least one monomer selected from the group consisting of α-olefin or vinyl compound. The α-olefin herein means a linear or branched unsaturated hydrocarbon having 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms. Examples include ethylene, propylene, butene-1, butene-2, isobutylene, n
-, (1-tene, isogrene, 2-methyl-1-butene, n-hexene, 2-methyl-1-pentene, 3-methyl-1-intene, 4-methyl-1-pentene, 2-ethyl-1- Butene, diisobutylene, 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1
, 3-octadiene, 2-methyl-4-dimethyl-1-
Examples include pentene and 2-methyl-4-dimethyl-2-pentene. Here, inbutylene also means return BB containing inbutylene.

Furthermore, vinyl compounds refer to unsaturated compounds that can be copolymerized with maleic anhydride, such as styrene, vinyl chloride, vinyl acetate, acrylonitrile, methyl vinyl ether,
(meth)acrylic'IIR-r-sf, etc.

These monomers may be used alone or in combination of two or more. Among these monomers, α-olefins such as ethylene and isobutylene, styrene or methyl vinyl ether are preferably used.
The use of α-olefins, especially isobutylene, is also consistent with the objectives of the invention.

The α-olefin in the copolymer is bicarbonate.

The composition ratio of the nil compound and maleic anhydride may be at any level as long as the reaction product obtained by reacting the produced copolymer with an alkaline substance is soluble in water. . In the case of a copolymer of ethylene, isobutylene, styrene, or methyl vinyl ether and maleic anhydride, which is preferably used in the present invention, about 1 to 3 moles of ethylene, isobutylene, ethylene, or haftyl vinyl ether per 1 mole of maleic anhydride. In most cases, it is about 1 mole.

Such maleic anhydride copolymers can be used alone or in combination of two or more.

The molecular weight of these copolymers is such that the intrinsic viscosity [η] measured in dimethyl formaldehyde solution at 30°C is 0.1 to
8 (dt/j9), particularly preferably 0.2 to 5 (
#, #) is preferable.

When the intrinsic viscosity is less than 0.1, the molecular weight is too small and a water absorbent fiber with a high water absorption capacity cannot be obtained.

- If the size is larger than that, the viscosity of the solution will be high, causing problems in workability and production during the production of water-absorbent fibers.

In the present invention, the reaction ratio of the alkali metal compound to the copolymer of α-olefin or vinyl compound and maleic anhydride, that is, the degree of neutralization, is determined to be alkaline to 1 mole of maleic anhydride groups present in the copolymer. substance 2
When the degree of neutralization when molar equivalents are reacted is 1, it is important that the degree of neutralization is between 0.1 and 0.6.

That is, if the degree of neutralization is less than 0.1, it is not only difficult to form the copolymer into an aqueous solution, but also fibers with a high water absorption capacity cannot be obtained. On the other hand, if the degree of neutralization exceeds 0.6, the resultant water-absorbent fiber becomes alkaline when it absorbs water, which is not preferable. From these viewpoints, the degree of neutralization of the copolymer is 0.1
-0.6, preferably 0.2-0.5.

The polyvinyl alcohol used in the present invention is obtained by saponifying vinyl acetate polymer, and the degree of saponification is 6.
It is 0 to 100 mol%, preferably 80 to 100 mol%.

In addition, the degree of polymerization of polyvinyl alcohol is 300 to 3.00.
Preferably, it is within the range of 0. Cal again? xyl group,
It is also possible to use polyvinyl alcohol modified by copolymerizing a copolymerizable monomer having a sulfonic acid group or the like.

The composition ratio of the alkali metal salt (I) of the copolymer of α-olefin or vinyl compound and maleic anhydride and polyvinyl alcohol (n) is in the range of 90/10 to 50150 as a weight ratio of (I)/<If). It is preferable that the

When the composition ratio is thicker than 90/10, the amount of PVA0 is small, so the temperature (I20 to 15
Heat treatment at 0° C.) hardly causes sufficient crosslinking, and hardly improves the strength of the obtained water-absorbing fibers.

On the other hand, if the composition ratio (50150) is too low, crosslinking will occur too much, and the resulting water-absorbing fiber will have a low water absorption capacity and a low water absorption rate, which is not preferable.

From this point of view, the composition ratio (I) / (ID is 90/10 ~
50150, more preferably 80/20 to 60/40
If it falls within this range, the one most consistent with the purpose of the present invention can be obtained.

A suitable method for producing the water absorbent fibers of the present invention is described below. First, a copolymer of an α-olefin or a vinyl compound and maleic anhydride is reacted with an alkali metal compound in water to prepare an aqueous solution of the salt (I) of the copolymer, and a predetermined amount of polyvinyl alcohol ( An aqueous solution of IO is mixed and stirred to obtain a homogeneous mixed aqueous solution.Next, utilizing the physical properties of this aqueous solution, a sifilament can be formed by a method such as spray drying or melt blowing, or by a conventional wet method or A multifilament composition is obtained by dry spinning.

By heat-treating the fibrous composition thus obtained at a relatively low temperature (I20 to 150°C) that does not cause liberation of alkali metal salts, components (I) and (I0) are crosslinked, and when water is absorbed, A water-absorbing fiber with - neutrality is obtained.

In the present invention, "- is neutral when water is absorbed" means that the pH is 4 to 8.
This means that the indicator methyl orange does not change color when water containing a small amount of methyl orange is absorbed into water-absorbing fibers, and that water containing phenolphthalein is absorbed by water-absorbing fibers. This can be confirmed by not coloring when

Also, whether or not alkali metal salts are liberated during heat treatment can be confirmed by measuring the infrared absorption spectrum of the water-absorbing fibers after heat treatment and checking whether acid anhydride groups derived from maleic anhydride are present. is possible.

The water-absorbing fiber obtained by the above method has a water absorption capacity for distilled water of 10 to 500 times its own weight, preferably 50 to 3.
It exhibits water absorption performance as high as 00 times, and is neutral when water is absorbed, so it is suitable for use in hitting paper diapers, sanitary products, etc., as a substitute for sphagnum moss, and for agricultural and horticultural purposes, such as as a water retaining material for soil.

Furthermore, since the water-absorbing fibers of the present invention are reinforced with polyvinyl alcohol, they can be processed in various ways, and can be processed into strands, yarns, nonwoven fabrics, and woven fabrics depending on the purpose.

The water-absorbing fibers of the present invention contain fillers, pigments, dyes, ultraviolet absorbers, antioxidants, fungicides, bactericides, insecticides, herbicides, fertilizers, fragrances, deodorizers, etc. as necessary. It may also be used.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 Isobutylene-maleic anhydride copolymer (intrinsic viscosity at 30°C in dimethylformamide [η) = 1. O: Co., Ltd.
Kuraray Isopan-10) 100 parts by weight, hydroxide)
Mix 24 parts by weight of IJum and 491 parts by weight of water,
An aqueous solution (degree of neutralization: 0.45°, concentration: 20%) of the Na salt of the inbutylene-maleic anhydride copolymer was prepared by heating and stirring. Polyvinyl alcohol (saponification degree 98%) per 10 parts by weight of this aqueous solution.

Degree of polymerization: 1700. PVA-117) manufactured by Kuraray Co., Ltd.
A uniform mixed aqueous solution was obtained by mixing and stirring 20 parts by weight of the 0% aqueous solution.

This mixed aqueous solution was applied to an Anhydro flat spray dryer (inlet gas temperature 250°C, outlet gas temperature 120°C, residence time 20-30 seconds, feed li
t 15 kg/hr, atomizer-30,00Orp
m) Drying was performed to obtain a fiber composition with a diameter of several microns.

This fibrous composition was heat-treated at 140° C. for 1 hour in a hot air dryer to obtain water-absorbing fibers with a water absorption capacity of 210 times.

The liquid properties of the above-mentioned water-absorbing fibers upon absorption of water showed no coloring due to phenolphthalein, no discoloration due to methyl orange, and could be considered neutral.

Example 2 Styrene-maleic anhydride copolymer (molar ratio of styrene-maleic anhydride 1:1. Intrinsic viscosity [η] = 0.86)
An aqueous solution of Na salt (degree of neutralization: 0.40, concentration: 20%) was prepared by heating and dissolving 100 parts by weight of sodium hydroxide, 15.8 parts by weight of sodium hydroxide, and 579 parts by weight of water. This aqueous solution 10
0 parts by weight of polyvinyl alcohol (degree of curing: 88%)
1 Polymerization degree 1700゜PVA-217 manufactured by Kuraray Co., Ltd.)
A 10% O aqueous solution was mixed and stirred at a ratio of 15 parts by weight to obtain a uniform mixed aqueous solution.

This aqueous solution was dried using a spray dryer in the same manner as in Example 1 to obtain a fibrous composition with a diameter of several microns. This fibrous composition was heat-treated at 150° C. for 30 minutes in a hot air dryer to obtain water-absorbing fibers with a water absorption capacity of 230 times and a neutral − value upon water absorption.

Example 3 Iso-tanol 100Nu salt aqueous solution used in Example 1 10
A mixture of 150 parts by weight of a 15% aqueous solution of PVA-117+7) was extruded using a flow tester and dry-spun to obtain a filamentous composition having a diameter of 400 to 500 μm. This thread-like composition was heat-treated at 140°C for 1 hour to obtain a water-absorbing thread with a water absorption capacity of 95 times. 20℃ of this water absorbent thread, 4
The tensile strength under 0% RH is 710 kl! /crn”
+Elongation was 12%, making the yarn stronger than Comparative Example 1°2.

Comparative Example 1 A solution prepared by mixing 0.3 parts by weight of polyethylene glycol having a molecular weight of 200 with 100 parts by weight of an aqueous solution of Na salt of isopane-10 (degree of neutralization 0.45°, concentration 30%) was mixed with Example 3. Dry spinning was performed in the same way to obtain a diameter of 400 to 500.
A filamentous composition of μ was obtained. This filamentous composition was heated at 180°C
We specialize in water-absorbing yarn that has a water absorption rate of 200 times after being heat-treated for one hour. This water-absorbing thread has an alkaline pH (colored with phenolphthalein) when absorbing water, and is kept at 20°C and 40% R.
The tensile strength under H was 120 Ky/cWL'' *Elongation was 2%.

Comparative Example 2 A solution was prepared by mixing 0.3 parts of glycerin diglycidyl ether (145 parts per epoxy) with 100 parts by weight of an aqueous solution of Na salt of isopane-10 (degree of neutralization 0.45°, concentration 30%). Dry spinning was carried out in the same manner as in Example 3, and the diameter was 400 mm.
A filamentous composition of ~500μ was obtained.

This thread-like composition was heat-treated at 105°C for 1 hour to obtain a water-absorbing thread with a water absorption capacity of 190 times.

This water-absorbing thread had a neutral pH when absorbing water, but at 20°C,
The tensile strength under 40% RH was similar to Comparative Example 1, with a tensile strength of 130 kg/cm" and a small elongation of 2%.

〔Effect of the invention〕

According to the present invention, it is possible to obtain water-absorbing fibers that are strong and have excellent water-absorbing properties, and which have a neutral property when water is absorbed.

Patent applicant Rira Shi Co., Ltd. Agent Patent attorney Ken Honda

Claims (1)

[Claims] A mixture of two components, an alkali metal salt (I) of a copolymer of an α-olefin or a vinyl compound and maleic anhydride, and polyvinyl alcohol (II) is formed into a fiber shape and then heat-treated. Water absorbent fiber with neutral pH