JPH09228291A - Binder for water-soluble paper and water-soluble paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain water-soluble paper which has high paper strength after drying and wet strength and readily dissolves into water with slight agitation by using a modified polyvinyl alcohol prepared by subjecting a vinyl compound to the Michael addition reaction. SOLUTION: Acrylamide and/or 2-acrylamide-2-methylpropanesulfonic acid or its salt is used to effect the Michael addition reaction with polyvinyl alcohol with a saponification degree of >=80%, preferably 100%, then the product is hydrolyzed with an alkali or the like to prepare a modified polyvinyl alcohol with a weight - average molecular weight of 8,000-390,000. This modified polyvinyl alcohol is directly dried or purified with a small amount of methanol or isopropyl alcohol then dried to prepare the objective powdery binder. This binder is added to pulp slurry and the slurry is subjected to sheet making to give the objective water-soluble paper.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a binder for water-disintegrating paper and a water-disintegrating paper obtained by using the binder.
More specifically, the present invention relates to a binder having a paper strength and a wet strength, and a binder which gives a paper which is hydrolyzed by a little stirring when wet, and a water-made paper made by using the binder.

[0002]

2. Description of the Related Art Recently, paper products have been used as cleaning tools in various fields because they are inexpensive and can be disposable. In particular, paper products containing a disinfectant component are often used as cleaning tools for toilets. These are used for toilets and are often thrown away after use because they are discarded. For this reason, paper products that are not water-degradable do not dissolve in the toilet clogs or septic tanks, and may float forever, causing problems. To solve these problems, various hydrolyzed papers and their binders have been researched and developed.

Japanese Patent Publication No. 40-968, Japanese Patent Publication No. 43-12
JP-A-62-141199 discloses a method in which carboxymethyl cellulose is mixed with a paper-making raw material such as pulp and then the carboxymethyl cellulose is converted into its alkali metal salt with an alkali agent.
A sheet having a binder of hydrogel fibers of a mixture of alginic acid and glycol ester of alginic acid is disclosed. Further, JP-A-6-220793 discloses a compounded product of specific CMC and powdered organic acid as a binder.

[0004]

However, according to Japanese Patent Publication No. 40-968 and Japanese Patent Publication No. 43-1214, the complexity of taking a two-step process and the method disclosed in Japanese Patent Publication No. 62-141199. In the thing,
The complexity of the production of the fiber binder poses a problem, and neither is practical. Further, in JP-A-6-220793, the water decomposability and the wet strength are still insufficient,
We haven't reached the level of satisfaction yet.

An object of the present invention is to provide a binder capable of giving a hydrolyzed paper having an excellent water decomposability and an excellent wet strength, which is hydrolyzed by a slight stirring when wet, and a hydrolyzed paper made by using the binder. .

[0006]

The present invention has been earnestly studied in view of the above circumstances, and it was found that the above problems can be overcome by using a specific modified polyvinyl alcohol (hereinafter referred to as modified PVA). Was completed. That is, modified PVA having a weight average molecular weight of 8000 to 390000 obtained by subjecting polyvinyl alcohol (hereinafter referred to as PVA) to a Michael addition reaction of a vinyl compound.
It is a binder for hydrolyzed paper containing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION P used as a raw material of the present invention
The degree of saponification of VA is not particularly limited, but when a strong alkali is used as a catalyst, it is preferably 80% or more, and more preferably 99% or more of completely saponified product. This is to prevent the alkali of the catalyst from being consumed by saponification and to suppress the amount of by-products (acetate) generated by saponification.

The degree of polymerization of PVA is preferably 50 to 8,000, and more preferably 300 to 4000 in terms of easiness of production.

A modified product of PVA may be used as the PVA which is the reaction base (raw material). Examples of the modified product include carboxyl-modified PVA obtained by saponifying a copolymer of vinyl acetate and a dibasic acid such as maleic acid and itaconic acid, and a copolymer of vinyl acetate and 2-acrylamido-2-methylpropanesulfonic acid (salt) monomer. There is a sulfonic acid-modified PVA obtained by saponifying a polymer.

PVA may be previously dissolved in water, or may be used in the reaction as a solid. When PVA is reacted as a solid, it is preferable that the average particle size is 1000 μm or less. If it exceeds 1000 μm, there is a possibility that a catalyst and a vinyl compound are difficult to permeate.

The vinyl compound used in the present invention includes acrylonitrile, acrylamide, acrylic acid or a salt thereof, acrylic ester, and 2-acrylamide-2.
-Methyl propane sulfonic acid or its salt (for example, sodium salt, potassium salt, ammonium salt), vinyl sulfonic acid or its salt, nonionic such as vinyl sulfoxide, vinyl sulfone, maleic acid, maleic acid diester, and anionic vinyl compounds To N, N-dimethylaminoethyl acrylate or a quaternary salt thereof, N, N-
Examples thereof include cationic vinyl compounds such as dimethylaminopropyl acrylamide or a quaternary salt thereof. Moreover, these can also be used in combination of 2 or more types. Of these, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, or a salt thereof is preferable because it has high reactivity, the water-degradability of the paper made is good, and the adhesive strength to the paper is strong.

The method for producing the modified PVA used in the present invention includes the following methods, but any method may be used.

(A) A method in which a vinyl compound is subjected to a Michael addition reaction in a PVA aqueous solution. B) A method in which a vinyl compound is subjected to a Michael addition reaction with PVA in a solvent suspension system. C) A method of performing a Michael addition reaction between solid PVA and a liquid vinyl compound under solid-liquid reaction conditions.

The above-mentioned "solid-liquid reaction conditions" in (c) means that solid PVA is reacted with a liquid vinyl compound (or vinyl compound solution) to produce a modified PVA. The PVA of (1) is not dissolved in the vinyl compound through the reaction (even if it is slightly dissolved), the chemical reaction with the vinyl compound is allowed to proceed while maintaining the solid state (powder state), Refers to the conditions for denaturation.

Among the above-mentioned production methods (a)-(b) and (c), the method (c) is preferable in view of high reactivity, stability of the manufactured product and high purity. The method (c) will be described in detail.

As for the procedure of compounding, first, solid PVA is used.
To the catalyst, a catalyst such as NaOH, KOH, triethylamine or the like is added, and then a vinyl compound is added. The order of addition in the present invention is not limited to this, but in any case, it is desirable to add as uniformly as possible. In this case, a method of adding a drug under high-speed stirring of PVA, a method of spray-adding a drug, or the like is also desirable in order to carry out the reaction uniformly. The amount of the catalyst used in the reaction is preferably 0.5 to 100 mol% with respect to PVA, and the amount of the vinyl compound is preferably 1 to 150 mol%.

These are agitated while maintaining the solid form of PVA with a horizontal blender or the like, and a Michael addition reaction is carried out for 30 minutes to 10 hours. Suitable temperatures for carrying out the Michael addition reaction are in the range 5 to 90 ° C, preferably 20 to 70 ° C.
Range. Depending on the type of vinyl compound (eg, acrylonitrile, acrylamide, etc.), an alkali or the like may be added after this for hydrolysis. In this case, it can be partially hydrolyzed or completely hydrolyzed depending on the use. The hydrolyzate also corresponds to the modified PVA of the present invention.

For the hydrolysis, NaOH, KOH, LiO
In addition to alkaline preparations such as H, Na ₂ CO ₃ and NH ₄ OH,
Alkylamines such as dimethylamine and alkanolamines such as monoethanolamine can also be used.

Further, by substituting the system with nitrogen during the reaction, it is possible to prevent coloring of the product and breakage of the molecular chain due to radicals.

The finally obtained product may be dried as it is, or may be purified with 1 to 5 parts by weight of methanol, isopropyl alcohol or the like per 1 part by weight of the obtained product (modified PVA) and then dried. A powder product (average particle size 150 to 1000 μm) can be easily obtained (drying can use a known method).

As described above, in order to easily obtain a powder product after the reaction, it is necessary that the water content of the reaction system is 0 to 70% by weight, preferably 0 to 50% by weight throughout the reaction.
It is necessary to: If the water content of the reaction system exceeds 70% by weight, not only powdering becomes difficult but also the reaction rate is difficult to increase. If the water content exceeds 70% by weight,
It becomes difficult for PVA to maintain a powder state throughout the reaction. The closer the water content of the reaction system is to 0% by weight, the easier it is to obtain a powder product, and the higher the reaction rate can be expected.

When the water content of the reaction system is 0% by weight, the vinyl compound is originally liquid, or even when a solid vinyl compound is used, it is dissolved using a solvent other than water. Whether the catalyst is solid or liquid, it is used as it is, or is dissolved or diluted in a solvent other than water before use.

It is also possible to add a PVA insoluble solvent. The PVA-insoluble solvent is a solvent that does not dissolve PVA and can be dispersed in the solvent to form a slurry of PVA, and specific examples thereof include methanol, isopropyl alcohol, acetone, and methyl ethyl ketone. By adding a PVA insoluble solvent, PVA (including those already modified) can be added during the reaction.
It also has the effect of preventing the formation of dumplings (lumps).

The amount of the PVA-insoluble solvent added is PV
0.1 to 5 parts by weight to A1 part by weight is appropriate. If it is less than this, the contribution to uniformity is small, and if it is more than this, it is difficult to form a slurry.

The modification ratio of the PVA modified product obtained by the above-mentioned production method can be determined by NMR or IR, and the modification ratio is 0.5 to 45 mol%. Other means for determining the modification rate include colloid titration for anion modification and semi-micro Kjeldahl method for modification with a nitrogen-containing compound.

The weight average molecular weight of the modified PVA obtained by the above-mentioned production method was measured by GPC to be 8000-3.
The range is 90,000, and the preferred range is 20000.
It is 250,000. If it is less than 8,000, the adhesiveness to paper will be insufficient, and if it exceeds 390000, the water-decomposability of the paper will be poor.

A 0.1N NaCl aqueous solution was used as an eluent, and four columns (TSKgelG) manufactured by Tosoh Corporation were used.
2500PW, G4000PW, G5000PW) were connected in series and measured.

Modified P obtained by using, for example, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) or its Na salt as a vinyl compound.
VA comprises the following structural units. Acrylamide (if hydrolyzed)

[0029]

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Acrylamide (when partially hydrolyzed)

[0031]

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Acrylamide (when not hydrolyzed)

[0033]

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For AMPS

[0035]

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Combined use of acrylamide and AMPS (when hydrolyzed)

[0037]

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The modified PVA used in the present invention is usually added as a binder in an amount of 2 to 30% by weight based on the total amount of the pulp raw material and the binder.

The modified PVA used in the present invention can be used as a mixture with alginic acid, carboxymethyl cellulose or the like, as long as the performance is not impaired. The hydrolyzed paper of the present invention can be obtained by mixing the binder of the present invention and pulp raw materials such as pulp, regenerated cellulose fiber and synthetic fiber, and making paper by a known method.

[0040]

EXAMPLES Production Example 1 PVA (Kuraray PVA-117) 440 having a polymerization degree of 1700 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, powdered NaOH 12 g and acrylonitrile 265
g was added, and the mixture was stirred at 50 ° C. for 6 hours. At this time, the water content of the reaction system was 0% by weight. 500 g of the obtained product
Was purified with isopropyl alcohol and dried to obtain 660 g of white powder (average particle size: 520 μm).

When the obtained powder was analyzed by NMR,
Cyanoethylation degree (modification rate) is 45 mol%, reaction rate is 9
It was 0%. The weight average molecular weight measured by GPC was 90000.

Production Example 2 PVA (Kuraray PVA-117) 440 having a polymerization degree of 1700 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, 400 g of 30% -NaOH aqueous solution and 426 g of 50% acrylamide aqueous solution were added, and the mixture was stirred at 20 ° C. for 4 hours. The water content of the reaction system at this time was 39% by weight. The obtained product was purified with 500 g of methanol and then dried to obtain 630 g of white powder (average particle size 400 μm).

When the obtained powder was analyzed by NMR,
The degree of carbamoylethylation (modification rate) was 23 mol%, and the reaction rate was 77%. The weight average molecular weight measured by GPC was 85,000.

Production Example 3 PVA (Kuraray PVA-124) 440 having a polymerization degree of 2400 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, 30% -NaOH aqueous solution 200 g and 50% acrylamide aqueous solution 284 g were added, and the mixture was stirred at 30 ° C. for 2 hours under N ₂ stream. The water content of the reaction system at this time was 31% by weight.
Met.

Next, 50 g of 50% NaOH was added,
Hydrolysis was carried out at 0 ° C for 1 hour. At this time, the water content of the reaction system was 32%. The obtained product was directly dried to obtain 610 g of white powder (average particle size: 630 μm).

When the obtained powder was analyzed by NMR and IR, the degree of carbamoylethylation was 2 mol%, the degree of carboxyethylation was 13 mol% (total modification rate was 15 mol%), and the reaction rate was 75%. It was The weight average molecular weight was measured by GPC and found to be 120,000.

Production Example 4 PVA (Kuraray PVA-205) 490 having a saponification degree of 88% and a polymerization degree of 500 was placed in a horizontal blender having a capacity of 4 liters.
g, 50% -NaOH aqueous solution 320 g, acrylic acid 23
5 g and isopropyl alcohol 200 g (vs PVA
0.4 times the amount) was added and the mixture was stirred in a slurry state at 60 ° C. for 8 hours. The water content of the reaction system at this time was 13% by weight.
The obtained product was purified with 300 g of methanol and then dried to obtain 640 g of white powder (average particle size: 590 μm).

When the obtained powder was analyzed by colloid titration, the degree of carboxyethylation (modification rate) was 16 mol%,
The reaction rate was 64%. Further, the weight average molecular weight was 22,000 as measured by GPC.

Production Example 5 To a 4-liter horizontal blender, 440 g of PVA having a degree of polymerization of 4000 when completely saponified, 280 g of 50% -NaOH aqueous solution and 828 g of 50% 2-acrylamido-2-methylpropanesulfonic acid aqueous solution were added. 5 at ℃
Stirred for hours. At this time, the water content of the reaction system was 36% by weight. The obtained product was purified with 500 g of isopropyl alcohol and then dried to obtain 710 g of white powder (average particle size 650 μm).

When the obtained powder was analyzed by NMR,
The sulfo group modification ratio was 14 mol% and the reaction ratio was 70%. The weight average molecular weight was measured by GPC and found to be 220,000.

Production Example 6 PVA (Kuraray PVA-124) 440 having a polymerization degree of 2400 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, 40% -NaOH aqueous solution 150 g and 50% N,
621 g of an aqueous solution of N-dimethylaminopropylacrylamide methyl chloride quaternary salt was added, and the mixture was stirred at 40 ° C. for 8 hours. At this time, the water content of the reaction system was 33% by weight. The obtained product was purified with 500 g of isopropyl alcohol and then dried to obtain 630 g of white powder (average particle size 480 μm).

When the cationization degree of the obtained powder was analyzed by colloid titration, the modification rate was 10 mol% and the reaction rate was 6%.
7%. Further, the weight average molecular weight was measured by GPC and found to be 132,000.

Production Example 7 PVA (Kuraray PVA-205) 490 having a saponification degree of 88% and a polymerization degree of 500 was placed in a horizontal blender having a capacity of 4 liters.
g, 50% -NaOH aqueous solution 30 g, and 25% sodium acrylate aqueous solution 1228 g were added, and the mixture was stirred at 60 ° C. for 8 hours. At this time, the water content of the reaction system was 54% by weight. The resulting product has an additional 50% 2-acrylamido-2-
230 g of an aqueous sodium methylpropanesulfonate solution was added, and the mixture was stirred at 70 ° C. for 4 hours. The water content of the reaction system at this time is 5
It was 3%. The obtained product was purified with 500 g of isopropyl alcohol and then dried to obtain 720 g of white powder.
(Average particle size 800 μm) was obtained.

When the obtained powder was analyzed by NMR,
Carboxy modification rate is 17 mol%, Sulfone group modification rate is 3
The reaction rate is 67 in mol% (total modification rate: 20 mol%).
%Met. The weight average molecular weight was measured by GPC and found to be 30,000.

Production Example 8 PVA (Kuraray PVA-117) 440 having a polymerization degree of 1700 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, 30% -NaOH aqueous solution 200 g and 50% acrylamide aqueous solution 284 g were added, and the mixture was stirred at 30 ° C. for 2 hours under N ₂ stream. The water content of the reaction system at this time was 31% by weight.
Met. Then add 50g of 50% NaOH, 90 ℃
Was hydrolyzed for 3 hours. At this time, the water content of the reaction system was 32%. The obtained product was directly dried to obtain 610 g of white powder (average particle size: 760 μm).

When the obtained powder was analyzed by NMR and IR, the degree of carbamoylethylation was 0 mol%, the degree of carboxyethylation was 15 mol% (total modification rate was 15 mol%), and the reaction rate was 75%. It was The weight average molecular weight measured by GPC was 92,000.

Production Example 9 PVA (Kuraray PVA-117) 440 having a polymerization degree of 1700 when completely saponified was placed in a horizontal blender having a capacity of 4 liters.
g, 30% -NaOH aqueous solution 400 g and 50% acrylic acid aqueous solution 426 g were added, and the mixture was stirred at 20 ° C. for 4 hours.
The water content of the reaction system at this time was 39% by weight. The product obtained is purified with 500 g of methanol and then dried,
600 g of white powder (average particle size 400 μm) was obtained.

When the obtained powder was analyzed by NMR,
The degree of carboxyethylation (modification rate) was 19 mol% and the reaction rate was 65%. The weight average molecular weight measured by GPC was 84,000.

Production Example 10 PVA (Kuraray PVA-117) 20 having a polymerization degree of 1700 after complete saponification was placed in a 4-liter separable flask.
0 g and 1500 g of water were added, and the temperature was raised to 80 ° C. and PVA was applied.
Was completely dissolved. Then, 20 g of 50% NaOH and 97 g of acrylamide were added, and the mixture was stirred at 50 ° C. for 10 hours. At this time, the water content of the reaction system was 83% by weight. The resulting reaction solution was poured into a large amount of methanol and sheared with a mixer, so that a powder product could be finally obtained.

When the obtained powder was analyzed by NMR,
The carbamoylethylation degree (modification rate) was 4 mol%, and the reaction rate was 13%. The weight average molecular weight measured by GPC was 84,000.

Production Example 11 PVA (Kuraray PVA-117) 4 having a polymerization degree of 1,700 when completely saponified was placed in a 1-liter separable flask.
4g, 30% -NaOH aqueous solution 40g, 50% -acrylamide aqueous solution 43g, and acetone 500g were added, and
Stirred at C for 4 hours. The obtained product was filtered and dried to obtain 60 g of white powder (average particle size: 510 μm).

When the obtained powder was analyzed by NMR,
The carbamoylethylation degree (modification rate) was 21 mol%, and the reaction rate was 70%. Moreover, the weight average molecular weight was 82,000 as measured by GPC.

Production Example 12 PVA (Kuraray PVA-124) 4 having a polymerization degree of 2,400 when completely saponified was placed in a 1-liter separable flask.
4 g, 30% -NaOH aqueous solution 20 g, 50% -acrylamide aqueous solution 28 g, and toluene 600 g were added, and 40
Stirred at C for 7 hours. Next, 5 g of 50% -NaOH was added and hydrolysis was performed at 90 ° C. for 1 hour. The obtained product was filtered, purified with a small amount of methanol, and dried to obtain 55 g of white powder (average particle size: 650 μm).

The obtained powder was analyzed by NMR.
The carbamoylethylation degree (modification rate) was 2 mol%, the carboxyethylation degree was 13 mol% (total modification rate was 15 mol%), and the reaction rate was 75%. Further, the weight average molecular weight was 123,000 as measured by GPC.

Examples 1 to 12 and Comparative Examples 1 to 2 Examples and Comparative Examples were made under the following papermaking conditions and evaluation methods. Papermaking conditions Pulp used: NBKP sheet hydrolyzed in water Pulp / binder blending ratio (weight): 85/15 The binder used was a predetermined amount of the powdered modified PVA obtained in Production Examples 1-12. Basis weight: 30 g / m ² Order of addition: pulp → binder → paper machine Paper machine: Round sheet machine (JIS P-8209) Press conditions: 1 kgf / cm ² × 1 minute Dryer: Rotary dryer (surface temperature 100 ° C × 3 minutes)

Evaluation Method The following three points were evaluated, and the results are shown in Table 1.

Paper making property The paper making article was evaluated according to the following criteria by observing the easiness of peeling when peeled from the wire and the presence or absence of subsequent wire contamination. It is easy to peel off and does not adhere to the wire: ○ It peels off, but there is some adhesion to the wire: △ It does not come off easily, and it adheres to the wire: ×

Water-decomposability After inserting two paper pieces 20 mm x 20 mm into a glass cylindrical tube having an inner diameter of 27 mm and a length of 270 mm, adding pure water up to 200 mm and plugging with a rubber stopper, the operation of flipping the cylindrical tube upside down alternately was continued. , Read the number of times the piece of paper was torn.

Wet strength The paper-made material is cut into a width of 25 mm, moistened with pure water, and excess water is absorbed with a filter paper, and then pulled by a strength tester (JIS-P-8113) to determine the wet strength.

[0070]

[Table 1]

[0071]

EFFECTS OF THE INVENTION By using the binder of the present invention, it is possible to obtain a hydrolyzed paper having good paper-making property and water-decomposability and excellent wet strength.

Claims (5)

[Claims] 1. A weight average molecular weight of 800 obtained by subjecting polyvinyl alcohol to a Michael addition reaction with polyvinyl alcohol.
A binder for hydrolyzed paper containing 0 to 390000 modified polyvinyl alcohol. 2. A binder for hydrolyzable papers, which comprises modified polyvinyl alcohol having a weight average molecular weight of 8000 to 390000, which is obtained by subjecting polyvinyl alcohol to a Michael addition reaction with a vinyl compound and then subjecting it to hydrolysis. 3. A weight average molecular weight of 8000 to 3900, which is obtained by subjecting polyvinyl alcohol to a Michael addition reaction with a vinyl compound or is subjected to a hydrolysis treatment thereafter.
A binder for hydrolyzed paper comprising a modified polyvinyl alcohol powder product obtained by directly drying modified polyvinyl alcohol of No. 00 or purifying with a small amount of an organic solvent and then drying. 4. The vinyl compound according to claim 1, which is acrylamide and / or 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof.
The binder for hydrolyzed paper according to the item. 5. A hydrolyzed paper produced by using the binder according to claim 1.