JP2000248011A - Thermally reversibly thickening, water-soluble resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally reversibly thickening, water-soluble resin composition which has a more excellent resin migration-inhibiting effect than conventional resin compositions in thermal drying treatments and can particularly suitably be used as a paper-strengthening agent or a surface-sizing agent. SOLUTION: This thermally reversibly thickening, water-soluble resin composition comprises (A) a (co)polymer which is produced by (co)polymerizing (a) a radically polymerizable monomer containing at least 50 wt.% of (a1) a vinylic monomer giving its homopolymer having a heat-sensitive gelling property. Therein, the component (a) is (co)polymerized in a heterogeneous state in the presence of the aqueous solution of (B) a heat-insensitive gelling, water-soluble resin adjusted to a temperature not lower than the transition temperature of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble resin composition, and more particularly to a thermoreversible water-soluble resin composition which can be suitably used as a paper strength enhancer or a paper surface sizing agent.

[0002]

2. Description of the Related Art Conventionally, in the papermaking industry, paper strength agents,
Examples of the water-soluble resin used for the surface sizing agent, the retention aid, the binder for pigment coating, and the like include polyacrylamide, starch, polyvinyl alcohol, polyethyleneimine, polycationic resin, polystyrenesulfonic acid sodium salt, and polyethylene glycol. Are known. These are usually heated and dried after being impregnated or applied to paper in the form of an aqueous solution. However, during heating and drying,
In the case of impregnation, as water moves to the substrate surface,
As the resin migrates to the surface of the base material, the internal resin concentration decreases and the paper strength is reduced; in the case of surface application, the resin penetrates into the base material as water permeates into the base material. There is a problem that the surface concentration of the resin decreases due to the movement, and the surface sizing property decreases. In order to solve such a problem, a method has been proposed in which a paper strength enhancer or a surface sizing agent comprising a non-thermosensitive gelling water-soluble resin and a thermosensitive gelling agent are used in combination (for example, Japanese Patent Application Laid-Open No. No.-131084).

[0003]

However, if a temperature-sensitive gelling agent is simply added to a paper strength enhancer or a surface sizing agent and used, the resin component moves to the surface of the substrate or inside the substrate (hereinafter referred to as migration). ) May not always be sufficiently suppressed.

[0004]

Means for Solving the Problems In view of the above problems, the present inventors have made extensive studies on a method for sufficiently exhibiting thermosensitive gelling properties and sufficiently suppressing migration of a resin. In the presence of a gelling water-soluble resin,
The object can be achieved by using a water-soluble resin composition obtained by (co) polymerizing a radical polymerizable monomer containing a specific amount or more of a vinyl monomer that gives a homopolymer having a thermosensitive gelling property. Found and arrived at the present invention.

That is, the present invention relates to a method for producing a radical polymerizable monomer (a) containing at least 50% by weight of a vinyl monomer (a1) which gives a homopolymer having a thermosensitive gelling property. In a thermo-reversible thickening water-soluble resin composition comprising a (co) polymer (A) polymerized (co) polymerized below, a non-thermosensitive gelling aqueous solution controlled at a temperature not lower than the transition temperature of (A) In the presence of the aqueous solution of the water-soluble resin (B),
A thermoreversible thickening water-soluble resin composition characterized in that (a) is (co) polymerized in a heterogeneous state; and a paper-strengthening agent or paper surface sizing agent comprising the resin composition. .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A vinyl monomer (a1) used in the present invention to provide a homopolymer having a thermosensitive gelling property
As, for example, (A) vinyl alkyl (C 1 -C
6) Ether (vinyl methyl ether, etc.); (b) N-
Monosubstituted (meth) acrylamide [N-isopropyl (meth) acrylamide, N-methoxypropyl (meth) acrylamide, etc.]; (c) N, N-disubstituted (meth) acrylamide [N, N-diethyl (meth) acrylamide; N- (meth) acryloylpyrrolidine and the like];
(D) Mono (meth) acrylate of polyoxyalkylene (degree of polymerization: 3 to 40) monool or diol having 2 to 4 carbon atoms of an alkylene group [tetraethylene glycol monoethyl ether mono (meth) acrylate, pentaethylene glycol mono Butyl ether mono (meta)
Acrylate, methoxytrioxypropylene tetraoxyethylene (meth) acrylate, mono (meth) acrylate of ethylene oxide 6 mol adduct of tetrapropylene glycol, etc.); (e) polyoxyalkylene having 2 to 4 carbon atoms in alkylene group (polymerization Degree 3-40) monovinyl phenyl ether of monool or diol (tetraethylene glycol monomethyl ether monovinyl phenyl ether, pentaethylene glycol monoethyl ether monovinyl phenyl ether, methoxypentaoxypropylene tetraoxyethylene vinyl phenyl ether, ethylene oxide of tetrapropylene glycol 8) (F) monoalkyl phenyl ether of a molar adduct); (f) alkylene of a cyclic amine (2-4 carbon atoms)
(Meth) acrylic acid ester of an adduct of 1 to 40 moles of an oxide [such as a monomer described in JP-A-6-9848, such as morpholinoethyl (meth) acrylate]; (g) an acyclic amine having 5 or more carbon atoms (Meth) acrylic acid ester of 1 to 40 mol of alkylene (C2-4) oxide adduct [diisopropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, etc.] Etc.];
(H) Vinyl monomers having a polyiminoethylene group (degree of polymerization of 2 to 50) [such as tetraethyleneimine mono (meth) acrylamide and the like and the monomers described in JP-A-9-12781]; (Meth) acrylamide having an amino group or an alkylamino group having 5 or more carbon atoms such as an alkyl group [N-morpholinoethyl (meth) acrylamide and the like] and the like. These can be used alone or in combination of two or more.

[0007] Of these, (d), (e),
The vinyl monomers (f) and (g) are preferred in that a composition having a high temperature-sensitive gelling property can be obtained, and (f) and (g) are particularly preferred.

The homopolymer (a1) has a temperature-sensitive gelling property, and has a temperature (transition temperature) at which hydrophilicity and hydrophobicity reversibly change at a certain temperature as a boundary. , Usually 20 to 100 ° C, preferably 40 to 80 ° C. The transition temperature is determined by gradually heating a 1% by weight (solid content) aqueous solution of the homopolymer and measuring the temperature at which the aqueous solution starts to become cloudy or gel.

The composition of the present invention comprises, in the presence of a non-thermosensitive gelling water-soluble resin (B), a vinyl monomer (a1) which gives a homopolymer having a thermosensitive gelling property, and optionally a vinyl monomer (a1). A monomer (mixture) (a) comprising another vinyl monomer (a2) to be used is heated to a temperature not lower than the transition temperature of the (co) polymer (A) of (a) in the presence of a radical polymerization initiator. By radical (co) polymerization. (A) in (a)
The content of 1) is usually 50% by weight or more, preferably 70% by weight.
% By weight or more, more preferably 80% by weight or more.
When the content of (a1) is less than 50% by weight, the composition does not exhibit sufficient thermosensitive gelling properties.

Other vinyl monomers (a2) optionally used together with (a1) include, for example, (cyclo) alkyl (C 1-22) (meth) acrylate [methyl (meth) acrylate, Ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; (Meth) acrylate [benzyl (meth) acrylate, etc.]; hydroxyl-containing (meth) acrylate [2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate, glycerin mono (meth) acrylate (Meth) acrylamide or a derivative thereof ((meth) acrylamide, N, N-dibutyl (meth) acrylamide, cyclohexyl (meth) acrylamide, N-) Methyl (meth) acrylamide, N-methylol (meth) acrylamide, diacetone acrylamide, etc.]; cyano group-containing monomer [(meth) acrylonitrile, 2-cyanoethyl (meth) acrylate, 2-cyanoethyl acrylamide, etc.]; Meth) acrylate [ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 2,2-bis (4-hydroxyethylphenyl) propane di (meth) acryl Styrenes (styrene, α-methylstyrene, vinyltoluene, divinylbenzene, etc.); diene monomers (butadiene, isoprene, chloroprene, etc.); vinyl esters (vinyl acetate, vinyl propionate, etc.); Epoxy group-containing monomers [glycidyl (meth) acrylate, allyl glycidyl ether, etc.]; monoolefins (ethylene, propylene, 1-butene, etc.); halogen-containing monomers (vinyl chloride, vinylidene chloride, etc.); Monomers (N-vinyl-2-pyrrolidone, N-methylolmaleimide, N-vinylsuccinimide, etc.); unsaturated dibasic acid dialkyl esters [dialkyl maleate (C1-8) ester, dialkyl itaconate (carbon Number 1
8) Ester, etc.]; Silyl group-containing monomer [3-trimethoxysilylpropyl (meth) acrylate, etc.]; Anionic group-containing monomer [(meth) acrylic acid, (anhydride) maleic acid, fumaric acid, itacone Acid, vinyl sulfonic acid,
(Meth) acryloyloxyethylsulfonic acid, styrenesulfonic acid, vinylbenzoic acid, alkyl (1 to
10) Allyl sulfosuccinic acid, (meth) acryloyl polyoxyalkylene (polymerization degree 2 to 15) sulfate, etc. and salts thereof (alkali metal salt, ammonium salt, etc.)]; cationic group-containing monomer [N, N- Dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-dimethylaminoethyl ( (Meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, vinylaniline, vinylimidazole, p-aminostyrene, N
-Vinylcarbazole, 2-vinylpyridine and the like and salts thereof (inorganic acid salts such as hydrochloric acid and phosphoric acid, and organic acid salts such as formic acid and acetic acid)] and combinations of two or more thereof.

As the non-thermosensitive gelling water-soluble resin (B) used in the present invention, those usually used for paper processing or fiber processing, specifically, polyvinyl alcohol or a modified product thereof (polyvinyl) Alcohols, partially saponified ethylene-vinyl acetate copolymers, partially acetalized polyvinyl alcohols, etc.); starch or modified products thereof (oxidized starch, phosphorylated esterified starch, cationized starch, casein, soy protein, synthetic protein, Polyacrylamides [acrylamide polymer, acrylamide-sodium (meth) acrylate copolymer, Mannich modified polyacrylamide, etc.]; formalin-based resins (urea-formalin resin, melamine-formalin) Resin, etc.); Gin-based water-soluble resin agents (gum rosin, wood rosin, tall oil rosin, maleated rosin, etc.); carboxylic acid group or sulfonic acid group-containing resin [poly (meth) acrylic acid, styrene-maleic acid copolymer, (meth) acrylic Acid alkyl ester- (meth)
Acrylic acid copolymers, alkali metal salts or ammonium salts such as polystyrene sulfonic acid, etc.]; polyethylene glycol, polyethylene imine, and mixtures of two or more thereof. The weight average molecular weight of (B) by GPC is usually 1,000 to 1,000,000, preferably 2,000 to 500,000.

Among them, polyvinyl alcohol having a degree of polymerization of 100 to 500 or a modified product thereof (especially, 88 to 99% saponified ethylene-vinyl acetate copolymer) and starch or Modified forms thereof (particularly oxidized starch and cationized starch) are preferred.

The thermoreversible thickening water-soluble resin composition of the present invention comprises a copolymer (A) comprising a monomer (a) and a radical polymerization initiator (c) in the presence of the aqueous solution (B). ) Is obtained by radical (co) polymerization in a heterogeneous state at a temperature equal to or higher than the transition temperature. As the polymerization method (a), for example, a temperature (normally 40 to 100 ° C., preferably 5 to 100 ° C.) or higher, which is equal to or higher than the transition temperature of the (co) polymer (A) under a nitrogen gas atmosphere.
A method of polymerizing (a) in a heterogeneous state by adding (c) to a mixture of the aqueous solution of (B) and (a) whose temperature has been adjusted to 0 to 90 ° C. (during polymerization, The polymer becomes water-insoluble particles, and after the polymerization is completed, a uniform aqueous solution can be obtained by cooling to a temperature lower than the transition temperature of (A). ]
Is mentioned. The polymerization time is not particularly limited.
４０40 hours, preferably 2-20 hours. The above method has the advantage that the process is simple and the polymerization system has a low viscosity. The polymerization of (a) is most preferably performed by the above method, but may be performed by the following method if necessary. In a nitrogen gas atmosphere, the mixture of (a) and the aqueous solution of (B), which has been adjusted to a temperature lower than the transition temperature of (A) (usually 5 to 60 ° C., preferably 20 to 50 ° C.), requires (c) (A) is polymerized while maintaining the temperature at a temperature lower than the transition temperature of (A) [during polymerization, the polymer (A) of (a) is soluble in water, An aqueous solution is obtained. A water-soluble organic solvent (for example, at least one selected from methanol, ethanol, isopropanol, butanol, acetone, dioxane, and tetrahydrofuran) or a mixed solvent of the solvent and water as a solvent under a nitrogen gas atmosphere; Temperature (usually 20-100 ° C, preferably 4
A method of polymerizing (a) in a homogeneous state by adding (c) to the mixture of (A) and the solution of (B) whose temperature has been adjusted to 0 to 90 ° C. [During polymerization, the polymer of (a) is polymerized. Becomes a homogeneous state in which the solvent is soluble. After the polymerization is completed, water is added, the solvent is removed by a method such as distillation, and the mixture is cooled to the transition temperature of (A) or lower to obtain a uniform aqueous solution. ];

In the above polymerization, the ratio of (B) to (a) is such that (a) is usually 0.1 to 500 parts by weight, preferably 10 to 200 parts by weight, per 100 parts by weight (solid content) of (B). It is. If (a) is less than 0.1 part by weight, the thermosensitive gelling property is not sufficiently exhibited, and if it exceeds 500 parts by weight, the viscosity of the composition tends to be too high.

As the radical polymerization initiator (c), organic peroxides (cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, benzoyl peroxide, lauroyl peroxide, etc.), inorganic peroxides [Persulfates (sodium persulfate, ammonium persulfate, potassium persulfate, etc.), hydrogen peroxide, etc.]; Azo compounds (azobisisobutyronitrile, azobisisovaleronitrile, azobisisovaleric acid, 2,2 ′) -Azobis (2,4-dimethylvaleronitrile) and the like, and combinations of two or more of these. Of these, organic peroxides and / or inorganic peroxides are preferable because (a) is easily graft-polymerized to (B). The amount of the polymerization initiator used is (a)
Usually 0.01 to 5% by weight, preferably 0.
1 to 3% by weight.

If necessary, together with (c), a reducing agent [sodium pyrobisulfite, sodium sulfite, sodium hydrogensulfate, ferrous sulfate, glucose, sodium formaldehyde sulfoxylate, L-ascorbic acid (salt), etc.], Additives such as chelating agents (glycine, alanine, sodium ethylenediaminetetraacetate, etc.) and pH buffers (sodium tripolyphosphate, potassium tetrapolyphosphate, etc.) may be used in combination. The amount of these additives used is
(A) 0 to 5% by weight based on the total amount, preferably 0 to 5% by weight
3% by weight.

If necessary, a known chain transfer agent can be used for the purpose of adjusting the molecular weight of the polymer. Examples of the chain transfer agent include α-methylstyrene dimer (2,4-diphenyl-4-methyl-1-pentene and the like), terpinolene, terpinene, dipentene, an alkyl mercaptan having 8 to 18 carbon atoms, and an alkylene having 8 to 18 carbon atoms. Examples include dithiol, alkyl thioglycolate, dialkylxanthogen disulfide, tetraalkylthiuram disulfide, chloroform, carbon tetrachloride and the like. These can be used alone or in combination of two or more. The amount of the chain transfer agent to be used is generally 0 to 15% by weight, preferably 0 to 5% by weight, based on the total amount of the monomer (mixture) (a).

GP of (co) polymer (A) comprising (a)
The weight average molecular weight by the C method is usually 1,000 to 1,0.
00,000, preferably 5,000 to 500,000
It is.

The composition of the present invention has a temperature-sensitive gelling property, and hydrophilicity and hydrophobicity are reversibly changed at a certain temperature as a boundary. Temperature) is usually 20 to 100 ° C, preferably 40 to 80 ° C.
It is. The transition temperature is determined by gradually heating a 1% by weight (solid content) aqueous solution of the composition and measuring the temperature at which the aqueous solution starts to become cloudy or gel.

If necessary, the composition of the present invention may further contain a non-thermosensitive gelling water-soluble resin (B) after completion of the polymerization. In this case, the amount of (B) to be added is usually 50 to 1000 parts by weight, preferably 100 to 5 parts by weight, per 100 parts by weight of the (co) polymer (A).
00 parts by weight.

If necessary, various clays, kaolin, calcium carbonate, satin white, titanium oxide, aluminum hydroxide, barium sulfate, zinc oxide, calcium sulfate, talc, plastic pigment (polystyrene, styrene / butadiene copolymer) , Styrene / acrylic copolymer beads, etc.), known fillers, defoamers (mineral oil-based defoamers, silicon-based defoamers, etc.) and other additives [dyes, pH adjusters, preservatives Agent etc.] can be contained. The content of these additives is
Usually 0 to 20% by weight based on the total weight of (B) and (A)
It is.

Next, a method of using the composition of the present invention as a paper strength agent will be exemplified. The composition of the present invention is diluted with water or the like as necessary, and then a known fixing agent, internal sizing agent, filler, and the like are added as necessary to obtain a paper strength enhancer-containing liquid.

The solid content of the water-soluble resin composition of the present invention in the paper strength enhancer-containing liquid is usually 0.01 to 50% by weight, preferably 5 to 30% by weight.

The paper strength-enhancing agent-containing liquid is added to a pulp slurry obtained by mixing a waste paper pulp with a pulp dispersion obtained by beating the pulp dispersion. The amount of the solid content of the paper strength enhancer composition based on the pulp solid content is usually 0.05 to 5% by weight, preferably 0.2 to 1% by weight, based on the pulp.

The paper is obtained by making the above-mentioned pulp slurry with an ordinary paper machine. Papermaking is usually performed by dewatering in a wire part following a flow box, squeezing in a press part, drying in a dryer part, and smoothing with a machine calendar.

Examples of the paper machine include a fourdrinier paper machine. The basis weight of the paper is usually from 20 to 500 g / m ² .

Drying is performed by steam heating, hot air heating, or the like. Dryers include drum dryers, air cap dryers, air wheel dryers, air conditioner bear dryers and combinations thereof. The drying temperature varies depending on the type of dryer, but the temperature inside the dryer is usually 50 to 200 ° C, preferably 1 to 200 ° C.
00-150 ° C.

When the water-soluble resin composition of the present invention is used as a paper strength enhancer, the paper strength enhancer is evenly distributed inside the paper, so that a paper having high strength can be obtained. For this reason, the obtained paper has high paper strength, newsprint, writing paper, printing paper,
It can be suitably used as base paper for coated paper, cardboard case, cement bag, wrapping paper, foster paper, photosensitive paper, decorative board base paper, outdoor poster, tissue paper, paper towel, napkin and the like.

Further, a method for using the composition of the present invention as a surface sizing agent for paper will be exemplified. The sizing agent-containing paint can be obtained by diluting the composition of the present invention with water or the like as necessary, and then blending a water-soluble polymer, a resin latex, a paper strength enhancer and the like as necessary.

The solid content of the water-soluble resin composition of the present invention in the sizing agent-containing paint is usually 1 to 80% by weight.

The paper coated with the sizing agent-containing paint is applied to neutral or acidic high-quality paper, medium-grade paper or lower-grade paper using a sizing agent-containing paint using a coating machine and dried with a dryer. It can be obtained by smoothing with a machine calendar or the like as necessary.

Examples of the coating machine include an on-machine or off-machine roll coater (size press, gate roll coater, etc.), a bar coater and the like. The coating amount is
Usually 0.001 to 10 g / m ² as the weight after drying, preferably 0.01-5 g / m ^2.

Drying is performed by steam heating, hot air heating, or the like. Dryers include drum dryers, air cap dryers, air wheel dryers, air conditioner bear dryers and combinations thereof. The drying temperature varies depending on the type of dryer, but the temperature inside the dryer is usually 50 to 200 ° C, preferably 1 to 200 ° C.
00-150 ° C.

When the resin composition of the present invention is used as a sizing agent, a uniform and thick sizing agent layer is formed with little penetration, so that a paper having high sizing properties can be obtained. Therefore, paper coated with the sizing composition of the present invention has good sizing properties, and is suitable for newsprint paper, writing paper, printing paper, coated paper base paper, wallpaper, cardboard, vinyl paper backing paper, and the like. Can be used for In addition, it can be used not only as a surface sizing agent but also as an internal sizing agent added to pulp slurry or the like.

The paper strength enhancer or surface sizing agent comprising the composition of the present invention has excellent performance (compared to a conventional paper strength enhancer or surface sizing agent simply added with a temperature-sensitive gelling agent). It is not clear why the resin (migration suppression effect of the resin) is exhibited, but it is possible to polymerize the monomer (a) in the presence of the non-thermosensitive gelling water-soluble resin (B). It is presumed that the part is grafted on (B), and as a result, the affinity between the (co) polymers (A) and (B) formed is further improved.

Since the resin composition of the present invention is particularly excellent in the effect of suppressing migration, it is used in applications other than those described above, such as a retention aid, a binder for pigment coating, a warp sizing agent,
It can also be suitably used as a printing paste, a binder for printing ink, a binder for an adhesive or the like.

[0037]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. In the following, parts are parts by weight and% is% by weight.

Example 1 400 parts of water and polyvinyl alcohol ["PVA-117" manufactured by Kuraray Co., Ltd.] were placed in a reaction vessel equipped with a stirrer, a dropping pump, a nitrogen gas inlet tube and a temperature controller.
Parts, 2 parts of morpholinoethyl methacrylate and 0.01 part of t-butyl hydroperoxide were charged, the system was replaced with nitrogen gas under stirring, and reacted at 70 ° C. for 8 hours and further at 85 ° C. for 5 hours, Water-soluble resin composition 1 was obtained. The transition temperature of the composition 1 was 73 ° C.

Example 2 In a reaction vessel equipped with a stirrer, a dropping pump, a nitrogen gas inlet tube and a temperature controller, 400 parts of water and cationized starch [“MS # 2800” manufactured by Nippon Shokuhin Kako Co., Ltd.]
36 parts were added, and the mixture was heated and stirred at 95 ° C. for 60 minutes to be gelatinized and then cooled to 30 ° C. 1.8 parts of diisopropylaminoethyl (meth) acrylate, 0.2 parts of methyl methacrylate and 0.01 parts of t-butyl hydroperoxide were charged therein, and the system was replaced with nitrogen gas under stirring. The reaction was carried out at 85 ° C. for 5 hours, and a water-soluble resin composition 2 was obtained. The composition 2
Was 63 ° C.

Comparative Example 1 400 parts of water and 40 parts of polyvinyl alcohol [“PVA-117” manufactured by Kuraray Co., Ltd.] were mixed and dissolved to obtain a water-soluble resin composition 3 for comparison.

Comparative Example 2 1.8 parts of morpholinoethyl methacrylate, 0.2 part of methacrylic acid and 0.01 part of 2,2′-azobis (2,4-dimethylvaleronitrile) were added to an ampoule, frozen, degassed and sealed. And polymerized at 50 ° C. for 8 hours (transition temperature: 64 ° C.), 400 parts of water and polyvinyl alcohol [“PVA-117” manufactured by Kuraray Co., Ltd.] 3
Eight parts were mixed and dissolved to obtain a water-soluble resin composition 4 for comparison.

Examples 3-4, Comparative Examples 3-4 Each of the water-soluble resin compositions 1-4 was added to a pulp slurry obtained by beating hardwood kraft pulp, and the solid content of the pulp was 0.5%. % By weight, stirred, then made up with a paper machine, squeezed with a roll, and heated with 130 ° C. heated air.
After drying for 0 second, papers 1 to 4 were obtained. The breaking strength and folding strength of each paper were measured. Table 1 shows the results.

[0043]

[Table 1]

Breaking strength: The paper was cut to a width of 25 mm, and the load when the paper was broken was measured by an autograph. Folding strength: The paper was repeatedly bent and spread 90 °, and the number of times of bending until the paper was torn was measured.

Examples 5 to 6 and Comparative Examples 5 to 6 Each of the water-soluble resin compositions 1 to 4 was coated on half paper having a basis weight of 40 g / m ^{2 so} as to have a dry coating amount of 0.5 g / m ² by a bar coater. And dried immediately with 130 ° C. heated air for 30 seconds to obtain papers 5 to 8, respectively. For each paper, the surface sizing was evaluated by measuring the penetration time. Table 2 shows the results.

[0046]

[Table 2]

Surface sizing property: Drops of ion-exchanged water having a diameter of 5 mm were dropped from a height of 1 cm in a constant temperature and humidity room at 25 ° C. and 50% RH, and the time until the water drops disappeared (permeation time) was measured.

[0048]

The thermoreversible thickening water-soluble resin composition of the present invention has the following effects. (1) When used as a paper strength enhancer, the resin composition is immobilized at an early stage by being heated in a heating and drying step after papermaking, and gives paper having a small migration and a uniform resin distribution. As a result, paper having high paper strength can be obtained because the resin works effectively as a paper strength enhancer. (2) When used as a surface sizing agent, it is immobilized at an early stage by being heated in a heating and drying step after coating, and gives a uniform and thick surface sizing agent layer with little penetration. As a result, paper having high sizing properties is obtained because the resin works effectively. Because of the above effects, the water-soluble resin composition of the present invention is used for newsprint, writing paper, printing paper, coated paper base paper, cardboard case, cement bag, wrapping paper,
It can be suitably used as a paper strength enhancer or a surface sizing agent for producing fruit growing paper, photosensitive paper, decorative board base paper, outdoor posters and the like. Further, in addition to the retention aid in the paper industry, binders for pigment coating, etc., warp sizing agents in the textile industry, printing pastes, etc., they can also be suitably used as binders for inks, binders for adhesives, etc. is there.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 19/20 D21H 19/20 B 21/16 21/16 21/18 21/18 F-term (Reference) 4J011 PA53 PA67 PB22 PC02 PC08 4J026 AA03 AA08 AA12 AA17 AA19 AA30 AA38 AA43 AA45 AA50 AA53 AB01 AB20 AB38 BA01 BA02 BA03 BA05 BA07 BA08 BA10 BA15 BA19 BA20 BA25 BA27 BA28 BA29 BA30 BA31 BA32 BA34 BA35 BA40 BA40 BA43 BA40 CE021 CG141 CG171 CH071 CH201 CP011 CP061 PC10 4L055 AG64 AG71 AG73 AH13 AH16 AH18 AH36 EA30 EA32 FA11 FA13 FA17 GA05 GA06 GA15 GA16 GA19 GA22 GA30

Claims (5)

[Claims] 1. A radical polymerizable monomer (a) comprising at least 50% by weight of a vinyl monomer (a1) which gives a homopolymer having a thermosensitive gelling property, in the presence of a radical polymerization initiator. (Co) polymer (A) obtained by (co) polymerization
In a thermoreversible thickening water-soluble resin composition comprising
(A) is polymerized in an inhomogeneous state by (co) polymerization in the presence of an aqueous solution of a non-thermosensitive gelling water-soluble resin (B) which has been adjusted to a temperature not lower than the transition temperature of (A). Thermoreversible thickening water-soluble resin composition. 2. The resin composition according to claim 1, wherein (B) is polyvinyl alcohol or a modified product thereof and / or starch or a modified product thereof. 3. (a1) is a (meth) acrylate of an alkylene oxide adduct of a cyclic amine, and has 5 carbon atoms.
A vinyl monomer selected from the group consisting of the (meth) acrylic acid ester of the alkylene oxide adduct of the acyclic amine, N-monosubstituted (meth) acrylamide and N, N-disubstituted (meth) acrylamide. Item 3. The resin composition according to item 1 or 2. 4. Per 100 parts by weight of the solid content of (B),
The resin composition according to any one of claims 1 to 3, wherein (a) is used in a proportion of 10 to 200 parts by weight. 5. A paper strength enhancer or paper surface sizing agent comprising the resin composition according to claim 1.