JPH071836A - Production of highly water absorbable paper - Google Patents

Abstract

PURPOSE:To obtain paper having a high water absorbing capacity preventing the blur of aq. ink and suitable for the printing of a sharp image. CONSTITUTION:Fine particles of a temp.-sensitive water absorbable resin composed of a crosslinked N-isopropylacrylamide polymer are mixed with a paper stock and this paper stock is supplied to a paper making process in such a state that the water absorbing capacity of the temp.-sensitive resin is lost by heating the resin to temp. higher than the phase transition temp. thereof to easily produce water absorble paper having high water absorbing capacity at room temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a paper having a good water absorbing ability, and an object thereof is to prevent the ink from bleeding by using it for information paper using an aqueous ink such as an ink jet.

[0002]

2. Description of the Related Art Inkjet systems are widely used as printers used in computers and word processors. Since this ink contains water, it has deficiencies such as bleeding along the pulp fibers in the paper, and the absorption on the paper is delayed and the ink adheres to other parts to stain the characters.

In order to solve this problem, a method of mixing a highly water-absorbent resin composed of a cross-linked product of sodium polyacrylate into paper has been studied, but when the water-absorbent resin is mixed in the paper material, the highly water-absorbent resin is obtained. Cannot absorb the water and swell, resulting in poor drying. In addition, the calcium ion and aluminum ion in the paper material reduce the water absorbing ability, failing to achieve the initial purpose.

Further, Japanese Patent Laid-Open No. 58-21597 discloses a method of making a paper by adding a water-insoluble polymer to a paper material. The purpose of the paper making is to increase paper strength. No improvement in Noh can be expected.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent bleeding of water-based ink and to easily obtain a paper having a high water-absorbing ability suitable for printing a clear image.

[0006]

In order to achieve the above object, the present invention is constructed as follows. That is, the present invention is N-
It is characterized in that a paper material containing fine particles of a temperature-sensitive water-absorbent resin composed of a cross-linked product of an isopropyl acrylamide polymer is heated to a temperature higher than the phase transition temperature of the temperature-sensitive resin, and the water-absorbing ability is lost. Further, in the present invention, the particle size of the above superabsorbent resin fine particles is 30 μm or less in a dry state, and the mixing ratio in the paper material is 0.5 to 5.
It is characterized by being 0% by weight.

[0007]

The crosslinked product of the N-isopropylacrylamide polymer is temperature-sensitive, and if it is below the phase transition temperature, it becomes a gel state that it absorbs water, and it disappears in water above the phase transition temperature. A common papermaking method is a method in which a paper stock obtained by suspending pulp or the like in water is filtered with a wire to form a wet web, and the paper is pressed and dried.
-When the isopropylacrylamide polymer crosslinked fine particles are mixed, if the temperature of the paper stock is equal to or higher than the phase transition temperature, the resin loses its water absorbing ability and is easily dispersed in an aqueous liquid,
No trouble occurs in each process from paper making to drying. When the synthetic paper is used, it is customary to use it at room temperature. Since the temperature is not higher than the phase transition temperature, the resin has recovered its water absorbing ability and can prevent bleeding of the aqueous ink.

[0008]

EXAMPLE As described above, the present invention uses a paper material in a state where the crosslinked fine particles of the N-isopropylacrylamide polymer are heated to a temperature higher than the phase transition temperature of the resin and the water absorbing ability of the resin fine particles disappears. It is characterized by doing. Papermaking temperature is 3
It can be appropriately selected within the range of 0 ° C. or higher and 50 ° C. or lower depending on the phase transition temperature of the resin. N-isopropylacrylamide can be copolymerized with various water-soluble monomers, and if the copolymerization ratio of the hydrophilic monomer is high, the phase transition temperature becomes high. Water-soluble monomers copolymerizable with N-isopropylacrylamide include nonionic monomers such as (meth) acrylamide, acrylonitrile, vinyl acetate, and anions such as (meth) acrylic acid, acrylamidomethylpropylsulfonic acid, fumaric acid, and itaconic acid. Examples thereof include cationic monomers such as a polymerizable monomer, dialkylaminoalkyl (meth) acrylate or a quaternary product thereof, dialkylaminoalkyl (meth) acrylamide or a quaternized product thereof.

In particular, the cationic monomer copolymer has a positive charge and is easily adsorbed on the pulp surface, which is advantageous for improving the yield of the water-absorbent resin fine particles. A plurality of these monomers can be used together and copolymerized with N-isopropylacrylamide. The particle diameter of the water-absorbent resin fine particles is 30 μm or less in the dry state, and it is particularly desirable that the particle diameter is 15 μm or less. If the particle size is excessively large, the paper surface will have large irregularities and the printability will deteriorate. In order to produce such fine particles, the method of finely pulverizing the polymer is easy, and it is also easy to obtain the fine particles at the time of polymerization by emulsion polymerization or the like. In the present invention, the amount of the water-absorbent resin fine particles mixed in the paper stock is 0.
A range of 5 to 5% by weight is preferable, if it is too small, it is invalid, and if it is too large, the cost becomes high. The present invention will be specifically described below with reference to examples.

Example 1 A mixed solution of 70 g of N-isopropylacrylamide, 5 g of acryloyloxyethyltrimethylammonium chloride and 25 g of deionized water was added to 2 g of a 1% aqueous solution of methylenebisacrylamide and 2,2'-azobis (2-amidinopropane) hydrochloric acid. 1 g of a 1% salt aqueous solution was added and mixed, and the mixture was polymerized in a Teflon container to obtain a lump polymer. This resin had a water absorption capacity of 85 times and a phase transition temperature of 36 ° C. This resin is finely pulverized, and the fine powder that has passed through a sieve with an opening of 0.015 mm is referred to as Resin-1. LBKP 70%, NBK
Pulp consisting of P30% mixing ratio was beaten to 400 ml Canadian standard freeness, 8% talc and 0.4% emulsion size were mixed with Resin-1 and 3% liquid band was added to bring the pH to 5.5. After the adjustment, papermaking was performed at a temperature of 45 ° C. The addition amount of each chemical is a weight ratio per pulp. The wet paper web was calendered at a linear pressure of 500 kg / cm to make the paper surface smooth and then dried to be used in the test.

[0011]

[Effects of the Invention] Various test papers are fed at room temperature of 25 ° C using an ink jet printer HG-4000PC manufactured by Seiko Epson, and after printing on one page of B-5 size paper, the copy paper is immediately pressed on the surface. The presence or absence of transfer and the bleeding of the print were observed. The paper made under the conditions of Example 1 had no transfer to copy paper and no ink bleeding was observed at a mixing ratio of resin-1 of 1% and 2%. On the other hand, with the resin-free paper, the characters were transferred to the copy paper and the printing was blurred. Further, the resin-mixed paper produced at 30 ° C. was not suitable for printing because fine holes were generated on the paper surface. The resin-containing paper of the present invention is easy to manufacture, has an excellent ink absorbing effect, suppresses a phenomenon called show-through, and produces clear printing.

Claims (3)

[Claims] 1. A paper stock mixed with fine particles of a temperature-sensitive water-absorbent resin comprising a cross-linked N-isopropylacrylamide polymer is heated to a temperature higher than the phase transition temperature of the temperature-sensitive resin so that the water-absorbing ability is lost. A method for producing a highly water-absorbent paper characterized by: 2. The water-absorbent resin fine particles have a particle size of 30 μm in a dry state.
It is m or less, The manufacturing method of the super absorbent paper of Claim 1 characterized by the above-mentioned. 3. The method for producing super absorbent paper according to claim 1, wherein the mixing ratio of the water-absorbent resin fine particles is 0.5 to 5.0% by weight with respect to the pulp in a dry state.