Composition and absorbent material

Abstract

To provide a composition suitably usable in a variety of fields where water absorption is needed, as a water-absorbing material excellent in coefficient of water absorption, speed of water absorption, and long-term stability in a swollen state.SOLUTION: A composition includes: a copolymer containing an olefin unit, and maleic acid or maleic acid anhydride unit; and polyvinyl alcohol whose saponification degree is 70 mol% or less. A content of the polyvinyl alcohol is 7-25 pts.mass relative to 100 pts.mass of the copolymer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composition and a water-absorbing material.

Background Art

[0002] In recent years, water-absorbing materials using highly water-absorbent resins that absorb tens to hundreds of times their own weight of water have been proposed. Regarding such water-absorbing materials, in the field of sanitary products, they are being developed for use in a wide range of fields, such as menstrual pads and disposable diapers; in the field of agriculture and horticulture, as water retention materials; and in the fields of civil engineering and architecture, as coagulation materials for sludge, dew prevention materials, water stop materials, etc. Specific examples of highly water-absorbent resins include hydrolyzates of starch-acrylonitrile graft polymers, starch-acrylic acid graft polymers, hydrolyzates of vinyl acetate-acrylic acid ester copolymers, polyacrylate cross-linked products, carboxymethylated cellulose, olefin-(anhydrous) maleic acid copolymers, and the like.

[0003] Water-absorbing materials are required to have the ability to quickly absorb a large amount of water and also the ability to stably maintain the swollen state after absorbing water. In contrast, for example, in Patent Document 1, a method for producing a water-absorbent resin composition is disclosed, which is characterized in that when adding water and a cross-linking agent to a powder of a water-absorbent resin in the presence of an inert inorganic powder to carry out a cross-linking reaction and water evaporation, a poly(meta)acrylic acid alkali metal salt is added together with the water and the cross-linking agent.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a composition that is suitably used as a water-absorbing material excellent in water absorption rate, water absorption speed, and temporal stability in a swollen state. [Means for solving the problem]

[0006] The inventors have found that when an olefin-(anhydrous) maleic acid copolymer is used as the water-absorbent resin, by using polyvinyl alcohol in combination and by keeping the degree of saponification and content of the polyvinyl alcohol within a predetermined range, excellent water absorption rate, water absorption rate, and stability over time in the swollen state can be obtained.

[0007] The present invention includes the following aspects. [1] A composition comprising an olefin unit and a copolymer containing maleic acid or maleic anhydride units, and polyvinyl alcohol having a degree of saponification of 70 mol% or less, wherein the polyvinyl alcohol content is 7 to 25 parts by mass per 100 parts by mass of copolymer. [2] The composition according to [1], wherein the degree of saponification is 20 mol% or more. [3] The composition according to [1] or [2], used as an absorbent material. [4] An absorbent material comprising any of the compositions described in [1] to [3]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a composition that is suitable for use as a water absorbent material that is excellent in water absorption rate, water absorption rate, and stability over time in a swollen state. [Modes for carrying out the invention]

[0009] One embodiment of the present invention is a composition containing an olefin unit, a copolymer containing maleic acid or maleic anhydride units (hereinafter also referred to as "(maleic anhydride) units") (hereinafter also referred to as "olefin-(maleic anhydride) copolymer"), and polyvinyl alcohol.

[0010] The number of carbon atoms in an olefin unit may be, for example, 2 or more, 3 or more, or 4 or more, or 6 or less, 5 or less, or 4 or less, or 4. The olefin may be linear or branched. The olefin is preferably a 4-carbon olefin (butylene), and more preferably a 4-carbon branched olefin (isobutylene).

[0011] In an olefin-(anhydride)maleic acid copolymer, the mass ratio of olefin units to (anhydride)maleic acid units (olefin units / (anhydride)maleic acid units) may be 2 / 8 or more, 3 / 7 or more, or 4 / 6 or more, and may be 8 / 2 or less, 7 / 3 or less, or 6 / 4 or less.

[0012] The weight-average molecular weight of the olefin-(anhydride) maleic acid copolymer may be 10,000 or more, 30,000 or more, or 50,000 or more, and may be 500,000 or less, 300,000 or less, or 100,000 or less.

[0013] The content of the olefin-(anhydride) maleic acid copolymer may be 70% by mass or more, 80% by mass or more, or 90% by mass or more, or 93% by mass or less, based on the total nonvolatile content of the composition.

[0014] Polyvinyl alcohol has a degree of saponification of 70 mol% or less. By using such polyvinyl alcohol in combination with an olefin-(anhydride) maleic acid copolymer, a suitable composition can be obtained as a water absorbent with excellent water absorption rate, water absorption rate, and long-term stability in the swollen state. From the viewpoint of further improving water absorption rate, the degree of saponification of the polyvinyl alcohol is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 39 mol% or more, particularly preferably 46 mol% or more, preferably 65 mol% or less, more preferably 60 mol% or less, even more preferably 55 mol% or less, and particularly preferably 53 mol% or less.

[0015] In this specification, the degree of saponification of polyvinyl alcohol means the degree of saponification measured by the following method. Precisely weigh approximately 1 g of polyvinyl alcohol, place it in an Erlenmeyer flask, add 40 ml of ethanol, and heat as necessary to dissolve the polyvinyl alcohol. Accurately weigh 20 ml of ethanolic potassium hydroxide reagent and add it, then heat in a water bath with a reflux condenser for 30 minutes, shaking the flask occasionally. After cooling, add a few drops of phenolphthalein reagent and immediately perform a neutralization titration with an appropriate amount of 0.5 mol / L hydrochloric acid (main test). Separately from the main test, perform a neutralization titration using the same procedure as the main test, except that polyvinyl alcohol is not used (blank test). From the results of the neutralization titrations in the main test and the blank test, determine the degree of saponification using the following formula. Saponification degree = (ab) × 28.05 / Amount of polyvinyl alcohol collected (g) a: Amount of 0.5 mol / L hydrochloric acid consumed in a blank test (ml) b: Amount of 0.5 mol / L hydrochloric acid consumed in this test (ml)

[0016] The polyvinyl alcohol content is 7 to 25 parts by mass per 100 parts by mass of olefin-(anhydride) maleic acid copolymer, from the viewpoint of obtaining a composition suitable as a water absorbent with excellent water absorption rate, water absorption rate, and stability over time in the swollen state. The lower limit of the polyvinyl alcohol content is preferably 8 parts by mass, 9 parts by mass, or 10 parts by mass, and more preferably 12 parts by mass, 14 parts by mass, 16 parts by mass, or 18 parts by mass, from the viewpoint of further improving water absorption rate and water absorption rate. The upper limit of the polyvinyl alcohol content is 24 parts by mass, 23 parts by mass, or 22 parts by mass.

[0017] The polyvinyl alcohol content may be 7% by mass or more, 8% by mass or more, or 9% by mass or more, and may be 20% by mass or less, 18% by mass or less, or 17% by mass or less, based on the total nonvolatile content of the composition.

[0018] The composition may further contain other components in addition to the olefin-(anhydride) maleic acid copolymer and polyvinyl alcohol. Examples of other components include inorganic compounds such as silica, thickeners, and defoamers.

[0019] In one embodiment, the composition may be in the form of an aqueous solution. In this case, the composition (aqueous solution) may contain, for example, an olefin-(anhydrous) maleic acid copolymer, polyvinyl alcohol, a basic compound, and water. This composition (aqueous solution) can be obtained, for example, by neutralizing part or all of the olefin-(anhydrous) maleic acid copolymer with an aqueous solution of a basic compound and then further adding polyvinyl alcohol.

[0020] Examples of the basic compound include ammonia; organic amines such as triethylamine, dimethylethanolamine, pyridine, morpholine, and monoethanolamine; and metal base compounds containing Na, K, Li, Ca, etc.

[0021] In another embodiment, the composition may be in the form of a film. In this case, the film-like (film-shaped) composition can be obtained, for example, by pouring the above-mentioned aqueous solution into a container of a desired thickness and then drying it to volatilize water from the aqueous solution.

[0022] In yet another embodiment, the composition may be in the form of a powder. In this case, the powdery composition can be obtained, for example, by using a drying oven, a hot plate, etc. to remove the solvent component from the composition containing the solvent component to form a plate-shaped composition and then grinding it with a grinder.

[0023] The composition described above is suitably used as a water-absorbing material. In other words, another embodiment of the present invention is a water-absorbing material containing the above-described composition. The water-absorbing material is suitably used in various fields where water absorption is required. The water-absorbing material may be used, for example, in sanitary products such as sanitary napkins and disposable diapers, may also be used as a water-retaining material for agricultural and horticultural purposes, and may also be used as a coagulant for sludge, a dew condensation prevention material, a water-stopping material, etc. for civil engineering and construction.

Examples

[0024] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the examples.

[0025] [Example 1] An isobutylene-maleic anhydride copolymer (Isoban 06, manufactured by Kuraray Co., Ltd., weight-average molecular weight: 80,000-90,000) was dissolved in aqueous ammonia to a non-volatile content of approximately 25% by mass to prepare a copolymer solution.

[0026] The obtained copolymer solution was mixed with an aqueous solution of polyvinyl alcohol (hereinafter also referred to as "PVA1") having a degree of saponification of 39-46 mol% ("Gosenex LW-100" manufactured by Mitsubishi Chemical Corporation) to obtain a composition, such that the PVA1 (non-volatile content) content was 10 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0027] [Example 2] A composition was obtained in the same manner as in Example 1, except that the content of PVA1 (non-volatile content) was changed to 20 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0028] [Example 3] A composition was obtained in the same manner as in Example 1, except that polyvinyl alcohol with a degree of saponification of 46-53 mol% (Mitsubishi Chemical Corporation's "Gosenex LW-200", hereinafter also referred to as "PVA2") was used instead of PVA1.

[0029] [Example 4] A composition was obtained in the same manner as in Example 3, except that the content of PVA2 (non-volatile content) was changed to 20 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0030] [Comparative Example 1] A composition was obtained in the same manner as in Example 1, except that PVA1 was not used.

[0031] [Comparative Example 2] A composition was obtained in the same manner as in Example 1, except that the content of PVA1 (non-volatile content) was changed to 5 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0032] [Comparative Example 3] A composition was obtained in the same manner as in Example 1, except that the content of PVA1 (non-volatile content) was changed to 30 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0033] [Comparative Example 4] A composition was obtained in the same manner as in Example 1, except that polyvinyl alcohol with a degree of saponification of 80 mol% (Kuraray Poval 35-80, manufactured by Kuraray Co., Ltd., hereinafter also referred to as "PVA3") was used instead of PVA1.

[0034] [Comparative Example 5] A composition was obtained in the same manner as in Comparative Example 4, except that the content of PVA3 (non-volatile content) was changed to 20 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0035] [Comparative Example 6] A composition was obtained in the same manner as in Example 1, except that polyvinyl alcohol with a degree of saponification of 89 mol% (Mitsubishi Chemical Corporation's "Nichigo G Polymer AYB8041W", hereinafter also referred to as "PVA4") was used instead of PVA1.

[0036] [Comparative Example 7] A composition was obtained in the same manner as in Comparative Example 6, except that the content of PVA4 (non-volatile content) was changed to 20 parts by mass per 100 parts by mass of isobutylene-maleic anhydride copolymer (non-volatile content).

[0037] The following evaluations were performed using each of the obtained examples and comparative compositions. The results are shown in Table 1.

[0038] (Evaluation of water absorption rate) An equal amount of deionized water was added to the copolymer solution and thoroughly mixed, then poured into a 100mm square, 30mm high silicone case. The silicone case was covered with a breathable material such as paper to prevent contamination, and dried at room temperature for 72 hours. Subsequently, the sample was dried in a box-type dryer at 80°C for 1 hour, followed by heat treatment at 150°C for 10 minutes to obtain an evaluation film. The obtained film was cut into test pieces of approximately 10mm x 20mm, and resin samples were prepared by sandwiching the test pieces in a brass mesh. The weight of these resin samples (weight before testing) was measured. These resin samples were placed in a 70ml glass bottle, filled with deionized water, and the lid was closed. The sample immersed in water was heated in a 60°C oven for 72 hours, and then cooled to room temperature. Next, the sample was removed from the water, excess water was removed, and the weight (weight after testing) was measured to calculate the water absorption rate (=weight after testing / weight before testing × 100 (%)).

[0039] (Evaluation of water absorption rate) 1.5 g of the resin sample and 67 g of deionized water were accurately weighed, and the resin sample was placed in a 70 ml glass bottle. Next, the deionized water was added, and the time it took for the resin sample to absorb the deionized water and become gel-like was measured. In Table 1, "<1 min" and "<2 min" mean that the resin sample became gel-like within 1 minute and 2 minutes, respectively.

[0040] (Evaluation of stability over time in a swollen state) After evaluating the water absorption rate as described above (after water absorption), the viscosity of the resin samples was measured at approximately 25°C under the conditions of a rotational viscometer rotor number 4 and a rotation speed of 30. Furthermore, after the viscosity measurement, the resin samples were stored at approximately 25°C for one week, and the viscosity of the stored resin samples was measured again in the same manner as above. The results are shown in Table 1. Examples 1-4 showed small viscosity changes before and after storage, indicating excellent temporal stability. In Table 1, "Gel-free" means that the resin dissolved in water and no gel was present, while "Low swelling" means that gel was formed in the water, but a large amount of water remained that was not absorbed by the resin. Viscosity measurements were not performed in either case.

[0041] [Table 1]

Claims

1. A copolymer containing olefin units and maleic acid or maleic anhydride units, It contains polyvinyl alcohol with a degree of saponification of 70 mol% or less, A composition in which the polyvinyl alcohol content is 7 to 25 parts by mass per 100 parts by mass of the copolymer.

2. The composition according to claim 1, wherein the degree of saponification is 20 mol% or more.

3. The composition according to claim 1 or 2, used as a water absorbent.

4. A water-absorbing material comprising the composition according to claim 1 or 2.

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