JPH09248453A - Hydrophilic resin molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the shape retention of a molded body without separating a water absorbable resin from the molded body after water absorption by dispersing particles of a water absorbeble resin in a thermoplastic resin molded body with a specific particle size and a distribution index. SOLUTION: A water absorbable resin having specific properties is dispersed in a thermoplastic resin molded body composed of an ethylene polymer containing particles of a water absorbable resin (A-component) such as (meth) acrylate polymer crosslinked matter. The number average particle size of the water absorbable resin is set to 5μm or less and the particle size distribution index(DQ) thereof is set to 1.0-3.0 [particle size distribution index(DQ)=(wt. average particle size)/(number average particle size)]. Since the water absorbable resin particles are uniformly and finely dispersed in the resin molded body, good shape retention is shown without separating the water absorbable resin particles from the molded body after water absorption.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is excellent in that water-absorbent resin particles are uniformly finely dispersed in a molded article, so that the water-absorbent resin particles do not detach from the molded article after absorbing water. The present invention relates to a hydrophilic resin molded product having excellent shape retention.

[0002]

2. Description of the Related Art Conventionally, polyolefins, which have been widely used as packaging materials, containers, etc. due to their excellent moldability and mechanical strength, have poor printability, adhesiveness and hydrophilicity due to their poor reactivity. Because of the fact that it has not reached the point required as the application of, the usage method was limited. In order to improve this, a resin composition in which a water absorbent resin is mixed with polyolefin has been proposed. However, it is difficult to uniformly and finely disperse the water-absorbent resin in these resins, the dispersed particle size is large at 20 to 60 μm, and the dispersion is non-uniform. It was dissociated from the sample, and the shape retention was poor, and only mechanical strength was unsatisfactory.

Therefore, several methods have been proposed as a method for uniformly and finely dispersing the water absorbent resin. For example, as the water-absorbent resin, a fine powder obtained by polymerizing a cross-linked product of vinyl acetate / methyl acrylate copolymer, or a fine powder obtained by mechanically crushing the cross-linked product with a device such as a jet mill is used as a polyolefin. A method of compounding and molding (Japanese Patent Laid-Open No. 56-33032) has been proposed. However, with such a method, although the hydrophilicity level is slightly improved, the dispersed particle size is still as large as 10 to 50 μm, so that a satisfactory level is not obtained.
It requires a grinding process and is economically disadvantageous.

Further, a method of melt-kneading a water-absorbent resin containing a carboxylate group and a glycidyl methacrylate / ethylene copolymer (Japanese Patent Laid-Open No. 61-266427).
JP-A-63-31733) has been proposed. However, in such a method, although the hydrophilicity level is improved, a satisfactory molded article cannot be obtained in terms of imparting uniform hydrophilicity, shape retention after absorbing water, and mechanical strength. was there.

Further, a sheet or film having polyamide or polyester as a continuous phase and water-absorbent resin particles having a dispersed particle size of 10 to 100 μm as a dispersed phase (JP-A-61-161).
No. 62529) has been proposed. However,
Although this product has an improved hydrophilicity level, its shape retention property after absorbing water is not satisfied because the dispersed particle size of the water-absorbent resin particles is large.

In addition to the above, a resin composition (JP-A-57-190046) in which a polyamide is mixed with a water-absorbent resin containing acrylic acid as a main component has been proposed. However, this product also has an improved level of hydrophilicity, but the level is insufficient, and the shape retention property after water absorption is not satisfied because the dispersed particle size of the water-absorbent resin is much larger than 5 μm. .

[0007]

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to obtain a hydrophilic resin molded article having a good shape retention without the water-absorbent resin being detached from the molded article after absorbing water. To provide.

[0008]

The present invention provides a thermoplastic resin molding containing water-absorbent resin particles (component A),
The water-absorbent resin particles (component A) have a number average particle diameter of 5 μm or less in the thermoplastic resin molding, and have the following formula (I):
And a particle size distribution index (DQ) of 1.0 to 3.0 dispersed therein.

[0009]

## EQU00002 ## Particle size distribution index (DQ) = (weight average particle size) / (number average particle size) (I)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

[Detailed Description of the Invention] [I] Production of Material for Molding Hydrophilic Resin Composition (1) Raw Material (A) Water-Absorbing Resin (Component A) As the water-absorbing resin (component A), a generally known material is appropriately used. Can be selected and used. Specific examples of the water absorbent resin include
(Meth) acrylic acid polymer crosslinked product, (meth) acrylic acid ester / vinyl acetate copolymer saponified product or crosslinked product thereof, starch / (meth) acrylic acid graft copolymer saponified product, starch / acrylonitrile Examples thereof include crosslinked products of saponified graft copolymers and crosslinked products of saponified starch / (meth) acrylic acid ester graft copolymers, which can be preferably used. Among these,
It is more preferable to use a crosslinked (meth) acrylate polymer.

Here, "(meth) acry" means methacryl and acryl, and the same applies below. In addition,
Unless it imparts unfavorable performance to the water-absorbent resin, it is a copolymer in which physical properties and the like are improved by copolymerizing the components of these specific examples with other copolymerizable monomers. It doesn't matter. Examples of such a monomer that imparts preferable properties to the water absorbent resin include carboxylic acid or a salt thereof, phosphoric acid or a salt thereof, sulfonic acid or a salt thereof, or a water-soluble monomer having a group derived from them as a functional group. Mention may be made of ethylenically unsaturated monomers. In addition to the water-soluble ethylenically unsaturated monomer, as copolymerizable monomers, for example, (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, (poly) ethylene glycol mono (meth) acrylate, 2-hydroxyethyl (meth) acrylate and the like can be mentioned, and these can be used alone or in combination of two or more in an amount that does not significantly deteriorate the performance of the water absorbent resin.

These water absorbent resins may be of a salt type, and examples thereof include alkali metal salt types of Na, K and the like, and alkaline earth metal salt types of Mg, Ca and the like. However, the alkali metal salt type is particularly preferable. It should be noted that it is possible to use two or more kinds of the above water-absorbent resins in combination as the water-absorbent resin. Particles made of such a water-absorbent resin are contained in a thermoplastic resin molding described later in an amount of 0.1% by weight or more, have a number average particle diameter of 5 μm or less, and have a particle diameter distribution index (DQ) of 1.0 to 3. It is uniformly dispersed at 0.0.

(B) Ethylene polymer (B) having a functional group capable of chemically bonding or affinity with the water-absorbent resin particles (component A)
Component) The component B ethylene polymer is a thermoplastic ethylene polymer, has a functional group capable of chemically bonding or having an affinity with the water-absorbent resin, and has a melting point measured by DSC (differential scanning calorimeter). (Peak temperature) is 80 to 120 ° C., preferably 82
It is an ethylene-based polymer in the range of ~ 115 ° C, particularly preferably 85-110 ° C (hereinafter sometimes referred to as modified ethylene-based polymer).

If the melting point is too high, it becomes difficult to finely disperse the water-absorbent resin, the hydrophilicity of the molded article is insufficient, and the shape retention after absorbing water tends to be poor. On the other hand, if it is too low, the heat resistance of the molded article will be low, such being undesirable. This modified ethylene polymer is
Ethylene as the main component, with this hydroxyl group, acid anhydride group,
Carboxyl group, amino group, glycidyl group, nitro group,
A method of copolymerizing an unsaturated monomer having a functional group such as other group, or an ethylene-based polymer having a functional group such as a hydroxyl group, an acid anhydride group, a carboxyl group, an amino group, a glycidyl group, or another group. It can be obtained by a method of subjecting an unsaturated monomer to a graft reaction condition, a method of thermally decomposing an ethylene-based polymer, or the like.

Here, as the ethylene-based polymer, for example, an ethylene homopolymer, ethylene as a main component and other α
Random or block copolymers containing olefins as subcomponents are preferably used. Other α-olefins are, for example, propylene, butene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, heptene-.
1, octene-1, decene-1 and the like.

Examples of unsaturated monomers having a hydroxyl group, a carboxyl group, an acid anhydride group, an amino group, a glycidyl group, and other functional groups include hydroxyl group-containing unsaturated monomers such as hydroxyethyl methacrylate and hydroxypropyl methacrylate. Carboxylic acid ester; maleic anhydride,
Unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, methacrylic acid and crotonic acid or anhydrides thereof; amino group-containing unsaturated monomers such as amino (meth) acrylate and aminoalkoxyvinylsilane; glycidyl (meth) acrylate Glycidyl group-containing unsaturated carboxylic acid esters such as; vinyl acetates such as vinyl acetate and vinyl butyrate;
Examples thereof include unsaturated carboxylic acid esters such as methyl (meth) acrylate and ethyl (meth) acrylate; unsaturated carboxylic acid metal salts such as sodium (meth) acrylate and zinc (meth) acrylate.

The content in the modified ethylene polymer of the structural unit based on the unsaturated monomer having these hydroxyl group, carboxyl group, acid anhydride group, amino group, glycidyl group and other functional groups is 0. 05 to 20% by weight, preferably 0.1 to 15% by weight, particularly preferably 0.1 to 10% by weight. If this content is too low, the desired effect cannot be expected, and if it is higher than this, the production method becomes complicated, which is not preferable.

Among these modified ethylene-based polymers, preferred are specifically, for example, ethylene / glycidyl (meth) acrylate copolymer, ethylene. (Meth)
Acrylic acid copolymer, ethylene / vinyl acetate copolymer,
Examples thereof include ethylene / (meth) acrylic acid ester copolymers and metal salts of ethylene / (meth) acrylic acid ester copolymers (ionomers such as sodium salts and zinc salts).
These modified ethylene polymers may be used alone or in combination of two or more.

(C) Thermoplastic Polymer (Component C) For the purpose of improving moldability and physical properties of the molded product, a thermoplastic polymer other than the above-mentioned component B used in the base resin material of the hydrophilic resin molded product of the present invention. Examples of the combination (C component) include polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polymethyl methacrylate, polyvinyl acetate,
Polyvinyl alcohol, polyvinyl ether, polyvinyl butyrate, polyvinyl formal, cellulosic resin, polyamide, polyester, polycarbonate, polyphenylene ether, polyphenylene sulfide, polysulfone, polyimide, polyamideimide, polyetherimide, polyetherketone, polyetheretherketone, polyacetal , Polyarylate, polyallylamine, polyethylene oxide and the like. Among these, polyolefin, polyamide,
It is preferable to use polyester, particularly polyolefin, and particularly crystalline polyolefin. These thermoplastic polymers can also be used as a mixture of plural kinds.

As the polyolefin, for example, ethylene, propylene, butene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, heptene-
1, homopolymers of α-olefins such as octene-1, decene-1, copolymers of two or more kinds of these α-olefins such as random or block, and other copolymerizability mainly containing α-olefins Random, block, or graft copolymers containing a monomer as a subcomponent, or a combination thereof may be used.

Here, as the other copolymerizable monomer,
As long as it is different from the modified ethylene polymer of the component B, an unsaturated monomer having a constituent component such as a hydroxyl group, an acid anhydride group, a carboxyl group, an amino group, a glycidyl group, and other functional groups is used. I don't mind. Among these, it is preferable to use an ethylene polymer containing ethylene as a main component and a propylene polymer containing propylene as a main component, and specifically, a homopolymer of ethylene or propylene, or a main component of ethylene or Propylene and other α-olefins as subcomponents (Ethylene and propylene are in the relationship of other α-olefins with each other, and the other α-olefins may be two or more kinds. The same applies hereinafter.) Random or block copolymer with ethylene, propylene with the most components (optionally other α-olefins may be included) and other copolymerizable monomer with a secondary component, block or graft, etc. And the like, or a combination thereof.

In particular, an ethylene polymer is preferable from the viewpoint of adhesiveness and workability, and a melting point (peak temperature) by DSC of a propylene polymer or the like is 130 from the viewpoint of heat resistance.
℃ or more, especially 135-180 ℃, especially 140 ℃ -17
Polymers at 0 ° C are preferred. In addition, JIS K 7210
Compliant melt flow rate (MFR; melt flow coefficient, 190 ° C, 2.16 kg load for ethylene polymer, 230 ° C, 2.16 for propylene polymer)
(kg load) is 0.1 to 200 g / 10 minutes, especially 0.3
Polymers of up to 150 g / 10 min are preferred from the viewpoint of moldability and mechanical strength.

Polyamides are also thermoplastic and crystalline and / or amorphous high molecular weight solid polymers containing homopolymers, copolymers and / or terpolymers having repeating amide units in the polymer chain, preferably Softening point or melting point of 100 ° C or higher, preferably 160 to 280 ° C
Is nylon. Specifically, for example, nylon 6
Polylactams such as (polycaprolactam), nylon 3 (polypropiolactam), nylon 7 (polyenanthlactam), nylon 8 (polycapryllactam), nylon 12 (polylauryllactam); nylon 11
Homopolymers of amino acids such as (polyaminodecanoic acid); nylon 4 (polypyrrolidinone); nylon 6,6
(Hexamethylene adipamide), nylon 4,6 (polytetramethylene adipamide), nylon 4,2 (polytetramethylene oxalamide), nylon 6,10
(Polyhexamethylene sebacamide), nylon 6,1
(Polyhexamethylene isophthalamide), nylon 6,12 (polyhexamethylene dodecanoic acid) and other dicarboxylic acid copolymers with diamines; aromatic and partially aromatic polyamides; nylon 6/6, 6 (caprolactam and hexamethylene azide) Copolyamides such as poamide); nylon 6 / 6,6 / 6,1
0, such as terpolyamide; block copolymers, such as polyether polyamide. Among these, nylon 6 is preferable, and these can be used together.

Furthermore, polyester is a polymer chain
A linear crystalline and / or amorphous high molecular weight solid polymer having a repeating group of -CO-O- containing an O-CO-O- group,
A polyester having a softening point or a melting point of 100 ° C. or higher, and preferably 160 to 280 ° C. is preferable. Specifically, for example, polyethylene terephthalate (PE
T), polyalkylene tetraphthalates such as polybutylene terephthalate (PBT); polyalkylene isophthalates such as polyethylene isophthalate and polytetramethylene isophthalate; polyalkylenes such as polyethylene 2,6 naphthalate and polybutyne 2,6 naphthalate Examples thereof include naphthalate. Among these, it is preferable to use PET or PBT.

(D) Other components In the present invention, in addition to these components, other optional components can be blended and contained as needed in a range that does not significantly impair the effects of the present invention. The optional components include antioxidants, light stabilizers, ultraviolet absorbers, lubricants, colorants, foaming agents, fillers, conductive agents, antistatic agents, physical property modifiers (other resins, rubbers, oils, etc.), Surfactants, neutralizing agents, nucleating agents, clarifying agents, metal deactivators, dispersants, flame retardants, processing aids,
Examples include release agents, bactericides, antifungal agents, and molecular weight modifiers.

In particular, in order to improve hydrophilicity, 0.05 to 10 parts by weight of a surfactant is blended with 100 parts by weight of a molding material constituting a hydrophilic resin molded body, and / or a molding process. 0.1 to 2 parts by weight of an antioxidant is added to 100 parts by weight of a molding material constituting a hydrophilic resin molded body in order to prevent thermal oxidative deterioration at the time of use and to impart durability during use. It is preferable.

As the surface active agent, generally known ones can be appropriately selected and used. Generally, surfactants are classified into anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants according to the structure and the type of charge when they dissociate in the state of an aqueous solution. There is. Examples of the anionic surfactant include fatty acid soap and N-
Carboxylates such as acylamino acid salts, alkyl ether carboxylates, and acylated peptides; alkylsulfonates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, sulfosuccinates, α-olefinsulfonates, N-acylsulfones Sulfates such as acid salts, alkyl sulfoacetates and N-acylmethyl taurines; sulfated oils such as sulfated oils, alkyl sulfates, alkyl ether sulfates, alkyl allyl ether sulfates and alkyl amide sulfates; alkyl phosphorus Examples thereof include phosphoric acid ester salts such as acid salts, alkyl ether phosphates and alkyl allyl ether phosphates.

As the cationic surfactant, for example,
Examples thereof include aliphatic amine salts; aliphatic quaternary ammonium salts; aromatic quaternary ammonium salts such as benzalkonium salts and benzethonium chloride; and heterocyclic quaternary ammonium salts such as pyridinium salts and imidazolinium salts. Examples of the amphoteric surfactants include carboxybetaine type compounds such as alkyldimethylbetaine; sulfobetaine type compounds; aminocarboxylic acid salts; imidazoline derivatives and the like.

Examples of nonionic surfactants include alkyl and alkyl acrylic polyoxyethylene ethers, alkylallyl formaldehyde condensed polyoxyethylene ethers, block polymers having polyoxypropylene as a lipophilic group, and polyoxyethylene poly Ether type such as oxypropyl alkyl ether; ether ester type such as glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether; polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester , Ester types such as propylene glycol ester, sucrose ester; fatty acid alkanolamide, polyoxyethylene fatty acid amide, Polyoxyethylene alkyl amines, nitrogen-containing type such as amine oxides and the like.

Among these surfactants, it is preferable to use anionic surfactants and nonionic surfactants. Among the anionic surfactants, alkylbenzene sulfonates and nonionic surfactants are preferred. Above all, it is particularly preferable to use the ether ester type and the ester type. As the antioxidant, for example, 2,6-di-
t-Butyl-4-methylphenol, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 4,4'-butylidene-bis- (3-methyl-6)
-T-butylphenol), 4,4'-thiobis- (3
-Methyl-6-t-butylphenol), octadecyl-3- (3,5-t-butyl-4-hydroxyphenyl) propionate, tetrakis- [methylene-3-]
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 6- (3,5-di-t
-Butyl-4-hydroxyanilino) -2,4-bis-
Octylthio-1,3,5-triazine, tris-
(3,5-di-t-butyl-4-hydroxybenzyl)
Isocyanurate, tris- (4-t-butyl-2,6)
-Dimethyl-3-hydroxybenzyl) isocyanurate and other phenolic antioxidants; di-lauryl-thio-
Di-propionate, di-tridecyl-thio-di-propionate, di-myristyl-thio-di-propionate, di-stearyl-thio-di-propionate, pentaerythritol-tetrakis- (β-lauryl-thiopropionate), etc. Sulfur antioxidants; tris (isodecyl) phosphite, tris (tridecyl) phosphite, phenyl-di-isooctylphosphite, phenyl-di-tridecylphosphite, diphenylisooctylphosphite, diphenylisodecylphosphite , Diphenyl tridecyl phosphite, phosphonous acid [1,1-biphenyl-4,4'-diylbistetrakis [2,4-bis (1,1-dimethylethyl) phenyl] ester], triphenyl phosphite, tris (Nonylf Yl) phosphite, 4,4 '
-Isopropylidene-diphenylalkyl phosphite, tris (2,4-di-t-butylphenyl) phosphite, tris (buphenyl) phosphite, distearyl pentaerythritol diphosphite, di (2,4
-Di-t-butylphenyl) pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, phenyl-bisphenol A pentaerythritol diphosphite, tetratridecyl 4,
4'-butylidene bis (3-methyl-6-t-butylphenol) -di-phosphite, hexatridecyl-
1,1,3-tris (2-methyl-4-hydroxy-5)
-T-butylphenyl) butane triphosphite, 3,
Examples thereof include phosphorus-based antioxidants such as 5-di-t-butyl-4-hydroxybenzyl phosphite-di-ethyl ester.

Among these, phenolic antioxidants such as tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane and octadecyl-3- (3) are used. , 5-t-butyl-4-hydroxyphenyl) propionate and tris- (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate are preferably used, and these are used in combination with a sulfur-based antioxidant. More preferably.

(2) Content Ratio of Each Component In the molding material for a hydrophilic resin molded product of the present invention, each component of A to C is a component (water-free solid content) 1 to 7
0% by weight and 1 to 100% by weight of a mixture (A + B component) composed of 99 to 30% by weight of B component, and 99% to C of component
It is contained in a proportion of 0% by weight. Here, a preferable content ratio is 2 to 80% by weight of a mixture (A + B component) composed of 2 to 60% by weight of A component and 98 to 40% by weight of B component.
And C component is 98 to 20% by weight.

A preferable content ratio of the component A (water-free solid content) contained in the entire molding material of the hydrophilic resin molding is 0.1% by weight or more, particularly 0.5 to 60% by weight, It is particularly preferably 1 to 50% by weight. If the amount of component A is too small, the desired hydrophilicity will not be obtained, while if it is too large, the mechanical strength of the molded product will be insufficient. On the other hand, if the amount of the component B is too small, the fine dispersion of the component A will be insufficient and the shape retention and mechanical strength after absorbing water will be insufficient. If the amount of component B is too large, the hydrophilicity of the molded product will be insufficient. On the other hand, if the amount of component C is too large, a desired molded article having hydrophilicity cannot be obtained.

[II] Method for preparing hydrophilic resin molding material The water-absorbent resin has a number average particle size of 5 μm or less and a particle size distribution index (D
Q) A molding material which gives a hydrophilic resin molded product uniformly dispersed at 1.0 to 3.0 is prepared by the following method. First, a water-containing water-absorbing resin having a water content of 25 to 80% by weight is kneaded to form a rubbery water-containing water-absorbing resin (component A), and then 1 to 70% by weight of the solid content of the component A and 99 to B component. 1-100% by weight of a mixture composed of 30% by weight and C component 9
9 to 0% by weight (however, the content of the solid content of the water-absorbent resin is 0.1% by weight or more) are simultaneously compounded or sequentially compounded while melt-kneading, and melt-kneaded. Among them, a preferable method is to mix the rubber-like water-containing water-absorbent resin (component A) and the modified ethylene polymer (component B) into a mixture at the time of melt-kneading, and then add the thermoplastic polymer (C Ingredients) are mixed and melt-kneaded.

(A) Preparation of Rubbery Water-Containing Water-Absorbent Resin In preparing a molding material for giving a hydrophilic resin molded article,
First, it is extremely important to knead a water-containing water absorbent resin having a water content of 25 to 80% by weight to obtain a rubbery water-containing water absorbent resin. The water-absorbent resin has a three-dimensional cross-linking structure, the resin swells in a net shape, and absorbs water by containing water in the net, but the state of the resin greatly changes depending on the water content, for example, the water content. If it is less than 25% by weight, the viscosity becomes extremely high due to the cross-linked structure to form a non-adhesive independent granular body, while if it exceeds 80% by weight, it tends to be a jelly-like aggregate.

However, when the water content is 25 to 80% by weight, the water-absorbing water-absorbent resin easily collapses but becomes an aggregate of particles whose surfaces are in close contact with each other. It is easy to knead in this state. It is possible to obtain a rubber-like body which is an irregularly shaped continuous body, and it is possible to finely disperse the rubber-like water-absorbing resin in a molded body only when the water-absorbing resin is used. This was surprising. Among them,
A water content of 30 to 80% by weight, further 30 to 75% by weight,
In particular, the method of kneading the water-containing water-absorbent resin in the range of 30 to 70% by weight is simpler and more preferable.

To obtain such a rubbery water-containing water-absorbent resin, a method of kneading the water-containing water-absorbent resin having a water content of 25 to 80% by weight is convenient. For example, the water content is 80%.
Even with a water-containing water-absorbent resin that is a jelly-like aggregate in excess of wt%, kneading while removing water by volatilization or the like so that the final water content is in the range of 25 to 80 wt%, or Even for a water-containing water-absorbent resin which is an independent granular material having a water content of less than 25% by weight, the desired rubber is obtained by adding water and kneading so that the water content is finally in the range of 25 to 80% by weight. It is also possible to obtain a water-containing water-absorbent resin in the form of water.

Therefore, in the present invention, the above-mentioned "not kneading a water-containing water-absorbent resin having a water content of 25 to 80% by weight to obtain a rubbery water-containing water-absorbent resin" also includes these aspects. The suitable temperature for kneading during the production of the rubbery water-containing water-absorbent resin is 30 to 90 ° C., but there is also a method of kneading with or without volatilizing water,
It is not necessarily limited to this temperature. The kneading time is 1 to
The shear rate is preferably 50 to 500 sec ^{−1 for} 30 minutes. The water content of the water absorbent resin is adjusted by adding a predetermined amount of water to the water absorbent resin having no water content or a low water content, and mixing with a device such as a stirrer, or the water absorbent resin is an acrylate polymer. In the case of a crosslinked product, it can be carried out by a method of mixing a water-absorbent resin which has not been dried (which already contains water) after the polymerization step with an apparatus such as a stirrer.

(B) Preparation of Thermoplastic Polymer Containing Water-Absorbent Resin The melt-kneading of the water-absorbent resin (A), the modified ethylene polymer (B) and the thermoplastic polymer (C) is carried out by usual melt-kneading. Machine, for example, a single-screw or twin-screw extruder, a Banbury mixer, a mixing roll, a kneader blender, a Brabender plastograph, a horizontal twin-screw reactor, etc., but among them, fine dispersion is easily possible. A twin screw extruder is suitable. The temperature at the time of melt-kneading is preferably selected to be 5 to 100 ° C. higher than the melting point (peak temperature) or softening point of the component B. For example, when using crystalline low density polyethylene having a crystallinity of about 60% Is 130-2
It is preferably selected from the range of 30 ° C. The kneading time is preferably 0.5 to 30 minutes, and the shear rate is preferably 50 to 500 sec ^-1 . If the kneading temperature is too high, heat deterioration of the resin used tends to occur, causing problems such as deterioration of mechanical strength and coloring,
Further, it tends to be difficult to finely disperse the water absorbent resin.

[III] Hydrophilic Resin Molded Body (1) Molding Processing Molding of the molding material for the hydrophilic resin molded body is carried out by various ordinary molding methods, that is, injection molding, injection compression molding, compression molding and extrusion molding. (Pipe molding, sheet molding, film molding, blow molding, various coating molding), gas injection, etc., can be molded into various products such as sheets, containers and fibers.

(2) Physical Properties The thus obtained hydrophilic resin molded product has the content ratio of each of the above-mentioned compounding components, in which the water-absorbent resin particles (water-free solid content) are 0. 1% by weight or more, the upper limit is about 60% by weight or less, preferably 0.5 to 50% by weight, particularly preferably 1 to 40% by weight, and the number average particle diameter is in the thermoplastic resin molded body. Is 5 μm or less and the particle size distribution index (DQ) is 1.0 to 3.0, and the particles are uniformly dispersed.

The number average particle diameter is preferably 0.1 to 4 μm,
It is particularly preferably 0.1 to 3 μm. If the number average particle size is too large, the shape retention property after water absorption and the appearance are deteriorated, the mechanical strength is lowered, and uniform hydrophilicity cannot be imparted. In general, there is a distribution of particle sizes, and even in a system with a large number average particle size, there are stochastic particles with a small particle size. In this case, however, there are many particles with a large particle size. Retention is not preferable. As described above, it is difficult to say that the number average particle size alone sufficiently expresses the particle size of the water absorbent resin with respect to the hydrophilicity. Therefore, the particle size distribution index (DQ) defined by the following equation is used to express the particle size distribution of the water absorbent resin particles in the thermoplastic resin molded body.

[0043]

[Equation 3] DQ = (weight average particle diameter) / (number average particle diameter)

DQ is preferably 1.0 to 2.8, particularly preferably 1.2 to 2.5. DQ never takes a value smaller than 1, and if it is too large, the probability of existence of particles having a large particle size becomes high, which is not preferable for shape retention after water absorption. In other words, regarding the particle size distribution of the water absorbent resin in the thermoplastic resin molded product, the ratio of the number of the water absorbent resin particles having a particle size of more than 5 μm is 20% or less of the total number of the water absorbent resin particles. Is preferred. If it exceeds 20%, the shape retention after water absorption becomes insufficient. Furthermore, with regard to the uniformity of dispersion of the water-absorbent resin, the more uniform it is, the more preferable it is.
Year) ”, and can be evaluated by the P parameter described on pages 458 to 461. That is, specifically, using a photograph of the shape of the water-absorbent resin with a scanning electron microscope,
When the number of divided sections is m, the area of the dispersed particles in the i-th section is bi, and the P parameter is calculated by the following equation.

[0045]

(Equation 4)

P is a value smaller than 1, and the closer it is to 1, the more uniform the dispersion. In the hydrophilic resin molding material of the present invention, it is preferable that the P parameter of the water absorbent resin in the water absorbent resin-containing thermoplastic resin is 0.3 to 1.0, particularly 0.5 to 1.0. . If the water-absorbent resin contained is too small, the desired hydrophilicity cannot be obtained. By making such a molding material into a pellet shape, it becomes easy to use it in the subsequent molding step.

(3) Use The hydrophilic resin molded product of the present invention is particularly useful as an agricultural sheet, a building material, a packaging material, a synthetic paper, a fiber raw material and the like.

[0048]

〔material〕

(A-1) Preparation of rubbery water-containing water-absorbent resin Cyclohexane was added to a 5-liter four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube.
After 21 kg and 9 g of sorbitan monostearate were added and dissolved, nitrogen gas was introduced to expel residual oxygen. Separately, 300 g of acrylic acid was placed in a conical beaker with a capacity of 3 liters, and while cooling, 123 g of sodium hydroxide having a purity of 95% was dissolved in 796.5 g of water to neutralize 70% of the carbonyl groups of the acrylic acid. .
Next, 150 ppm of sodium hypophosphite, 0.034% of N, N'-methylbisacrylamite and 1.04 g of potassium peroxide were added to and dissolved in this solution, and then nitrogen gas was introduced to remove residual oxygen. Discharged.

The contents of the conical beaker were added to the contents of the four-necked flask described above and stirred, and after bubbling with nitrogen gas, the temperature was raised and the internal temperature was 60 while stirring at a rotation speed of 250 rpm. A water-absorbent resin was obtained by reacting at ˜65 ° C. for 3 hours, which was an aggregate of granular materials having wet surfaces adhered to each other. This water absorbent resin has a number average particle size of 150 μm.
The water-absorbent resin solid content was 37% by weight, the water content was 58% by weight, and the cyclohexane was 5% by weight. this,
The temperature is set to 50 ° C., the rotation speed is set to 100 rpm, and the screw-type twin-screw extruder having four kneading parts is supplied at a speed of 8 kg / hour and kneaded to give a water-absorbent resin solid content of 40% by weight and a water content of 60% % Rubbery water-containing water-absorbent resin was obtained.

(A-2) Independent Granular Water-Absorbing Resin For comparison, an independent granular water-absorbing resin that was not rubber-like was produced in the following manner. That is, the solid content of the water-absorbent resin having the number average particle diameter of 150 μm is 37% by weight, and the water content is 58.
The water-containing water-absorbent resin, which is an aggregate of granular materials whose surfaces are in intimate contact with each other, is formed at a temperature of 1
The number average particle diameter of 180 μm was set at 60 ° C. and a rotation speed of 200 rpm, and kneaded into a screw-type twin-screw extruder having three kneading parts and three devolatilizing parts at a rate of 3 kg / hour and then pelletized. Water-absorbent resin solid content 95.5
An independent granular water absorbent resin having a weight% and a water content of 4.5% by weight was obtained.

(B-1) Modified ethylene-based polymer Glycidyl methacrylate content of 10% by weight, vinyl acetate content of 7% by weight, MFR (190 ° C,
2.16 kg load) 3.0 g / 10 min, melting point (peak temperature) 97 ° C., and crystallinity 16% were used. Mitsubishi Chemical Corporation ethylene / glycidyl methacrylate / vinyl acetate terpolymer.

(B-2) Crystalline ethylene polymer resin MFR (190 ° C., 2.16 kg load) 2.0 g / 10
Min., Melting point (peak temperature) 113 ° C., crystallinity 52%, high-pressure ethylene homopolymer manufactured by Mitsubishi Chemical Corporation. (C-1) Crystalline ethylene polymer MFR (190 ° C, 2.16 kg load) 4.0 g / 10
Min, a melting point (peak temperature) of 106 ° C., and a crystallinity of 47%, an ethylene homopolymer manufactured by Mitsubishi Chemical Corporation was used. (C-2) Crystalline propylene polymer MFR (230 ° C., 2.16 kg load) 0.8 g / 10
A propylene homopolymer manufactured by Mitsubishi Chemical Corp. having a melting point (peak temperature) of 162 ° C. and a crystallinity of 70% was used.

[Evaluation Method] (1) Dispersed Particle Size and Particle Size Distribution of Water-Absorbent Resin Using a molded sheet having a thickness of 2 mm as a test piece, an image analysis device (Japan Mapionix (Japan Mapionix ( Area equivalent circle diameter (di) was measured using "Spica II" manufactured by Co., Ltd., and the number average diameter (Dn) and weight average diameter were calculated according to the following equation, where the number of particles of circle equivalent diameter (di) was ni. (Dw) and particle size distribution index (DQ) were calculated. DQ takes a value larger than 1, and the closer to 1, the narrower the particle size distribution is expressed.

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## EQU00005 ## Dn (.mu.m) =. SIGMA. {(Di). (Ni)} /. SIGMA. (Ni) Dw (.mu.m) =. SIGMA. {(Di) 3. (ni)} /. SIGMA. (N
i) 2 · (ni)} DQ = Dw / Dn

(2) Shape retention after water absorption A molded sheet having a thickness of 50 μm was used as a test piece, and the temperature was 70 ° C. for 2 hours.
It was immersed in pure water for a period of time, and its shape retention was visually evaluated as follows. Good: Even after the dipping treatment, the shape is the same as that before the treatment. Poor: After the immersion treatment, swelling of the water-absorbent resin and separation of the water-absorbent resin from the sheet occurred, and the shape of the surface of the sheet remarkably changed.

(3) Hydrophilicity A molded sheet having a thickness of 50 μm was used as a test piece, and this was used at room temperature of 23.
After standing for 48 hours in a thermostatic chamber at 50 ° C. and a relative humidity of 50% to adjust the condition, the sheet is horizontally placed on a sample table of “Goniometer-type contact angle measuring instrument G-1 (trade name)” manufactured by Elma Co., About 1 microliter of pure water was dropped on this sample, and after 5 minutes, the contact angle between the surface of the sample and the left and right droplets was measured. The same measurement was performed 8 times (8 water drops) on the same sample, and the average value was obtained. The smaller the contact angle, the higher the hydrophilicity.

(4) Mechanical Properties A test piece (parallel part length 9 mm, parallel part diameter 1.5 mm) was obtained by melt injection molding a molding material made of a water-absorbent resin-containing thermoplastic resin composition with a minimax compact molding machine. The test piece was prepared and the tensile speed was 1c in accordance with JIS-K7113.
The tensile strength at break (kgf / cm ² ) was measured under the condition of m / min.

Example 1 (First Step) 60% by weight of the rubber-like water-containing water-absorbent resin (A-1) based on the weight of the resin alone and the modified ethylene polymer (B-
1) 40% by weight, temperature 170 ℃, rotation speed 200 rp
It is supplied to "TEX30SST" manufactured by Japan Steel Works, Ltd., which has four kneading parts and three devolatilizing parts set to m,
It was discharged at a rate of 3.0 kg / hour and cut to obtain pellets having a water content of 0.30% by weight.

(Second step) Pellets 40 obtained in the first step
1 part by weight and 60 parts by weight of a propylene polymer resin (C-2) were supplied to "TEX30SST" manufactured by Japan Steel Works, Ltd., which was set at a temperature of 190 ° C. and a rotation speed of 150 rpm.
It was discharged at a rate of 0.0 kg / hour, and this was cut to obtain pellets of a water-absorbent resin-containing resin molding material.

(Molding step) The pellets obtained in the first step and the second step are hot-pressed under the conditions of a temperature of 230 ° C. and a pressure of 100 kg / cm ² to obtain a length of 70 mm, a width of 70 mm and a thickness of 2.
A sheet having a size of 70 mm, a length of 70 mm, a width of 70 mm and a thickness of 50 μm was prepared. Table 1 shows the results of evaluation of these resin compositions and sheets.

[Examples 2 to 8 and Comparative Examples 1 to 7] Pellets and sheets were obtained in the same manner as in Example 1 under the mixing and kneading conditions shown in Tables 1 and 2. The evaluation results are shown in Tables 1 and 2.

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[Table 1]

[0063]

[Table 2]

[0064]

According to the present invention, since the water-absorbent resin particles are uniformly and finely dispersed in the resin-molded body, the water-absorbent resin particles do not detach from the molded body after the molded body absorbs water. Shows good shape retention.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a particle structure of a 2 mm thick molded sheet of a hydrophilic resin obtained in the first step of Example 1 (magnification: 5000 times).

FIG. 2 is an electron micrograph showing a particle structure of a 2 mm thick molded sheet of a hydrophilic resin obtained in the first step of Example 6 (magnification: 5000 times).

Claims (6)

[Claims] 1. A thermoplastic resin molding containing water-absorbent resin particles (component A), wherein the water-absorbent resin particles (component A) have a number average particle size of 5 in the thermoplastic resin molding.
A hydrophilic resin molded product having a particle size distribution index (DQ) represented by the following formula (I) of 1.0 to 3.0 and dispersed in a range of 1.0 μm or less. ## EQU00001 ## Particle size distribution index (DQ) = (weight average particle size) / (number average particle size) (I) 2. A thermoplastic resin molding containing water-absorbent resin particles (component A), wherein the particle diameter is 5 μm in the number of water-absorbent resin particles (component A) having a number average particle diameter of 5 μm or less.
A hydrophilic resin molding, wherein the ratio of the number of water-absorbent resin particles exceeding m is 20% or less. 3. An ethylene-based polymer (component B) 99, wherein the thermoplastic resin molded product has 1 to 70% by weight of water-absorbent resin particles (component A) and a functional group capable of chemical bonding or affinity with the component A. A resin (A + B component) of 1 to 100% by weight and a thermoplastic polymer (component C) other than the B component of 99 to 0% by weight as a base material. The molded product according to claim 1 or 2. 4. The molded product according to claim 1, 2 or 3, wherein the component A is a cross-linked product of a polymer of an acrylate or a methacrylate. 5. The molding material according to claim 3, wherein the component B is an ethylene polymer having a melting point (peak temperature) measured by a differential scanning calorimeter (DSC) of 80 to 120 ° C. 6. The molding material according to claim 3, wherein the C component is selected from polypropylene-based polymers and polyethylene-based polymers.