JPH0949195A - Production of fluorescent whitened paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain fluorescent whitened paper having improved light fastness as the largest problem by treating highly whitened paper using a stilbene-based fluorescent whitening agent with a reducer. SOLUTION: A stilbene-based fluorescent whitening agent is added to a raw pulp slurry together with a reducer such as sodium thiosulfate, sodium sulfite or sodium hydrogensulfite and subjected to papermaking to obtain fluorescent whitened paper. Otherwise, the reducer may be applied on the paper during the papermaking after adding the stilbene-based fluorescent whitening agent to the raw pulp, or may be applied after the papermaking.

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 fluorescent whitening paper, and more particularly to a method for producing a fluorescent whitening paper having good light resistance (fastness to light). Therefore, the fluorescent brightening paper produced by the present invention can be suitably used for a book cover, a file paper, a poster, a catalog and the like which require light resistance.

[0002]

2. Description of the Related Art Optical brightening paper is generally dyed with a stilbene optical brightening agent in the same manner as a direct dye. That is, a method of adding to a pulp slurry having a raw material concentration of 4 to 5%, fixing it to pulp with aluminum sulfate together with a sizing agent, a wet paper strength improver, etc., and making paper, and a method of applying the paper-making chemical together with a size press on a paper machine. After the papermaking, a coating machine is used for coating with a papermaking chemical.

[0003]

The fluorescent whitening paper manufactured in this way has a weak light resistance, and the secondary product using this paper does not meet the user's requirements. Dye manufacturers and paper manufacturers have made diligent efforts to improve this problem, but the present situation is that even after about 40 years have passed since the domestic production of fluorescent dyes, it has not been improved. The stilbene-based fluorescent whitening agent used as a whitening agent for paper is required to have various light fastnesses depending on its use, and how to maximize the light fastness is the biggest problem. Generally, in the textile industry, when light fastness is required, disperse dye-based optical brighteners are used to secure light fastness, but the dyeing method is thermosol method, high temperature dyeing method, carrier method. In the paper making process, it is difficult to use the dyeing method depending on the dyeing conditions, and a dyeing method that cannot be used for producing inexpensive paper is adopted. Therefore, for dyeing fluorescent whitening paper, it is unavoidable to use a direct dye type stilbene fluorescent brightening agent that can be dyed at room temperature under dyeing conditions.

The present invention aims to obtain a fluorescent whitening paper which can be used in a wide variety of applications by improving the weakness of light resistance, which is a problem of the fluorescent whitening paper dyed with the above-mentioned stilbene-based fluorescent whitening agent, and increasing the commercial value. It is an issue.

[0005]

The cause of the weak light resistance of fluorescent whitening paper dyed with a stilbene-based fluorescent whitening agent is explained as follows. Stilbene optical brightener is 350
It absorbs UV rays around nm and reflects around 420 nm, but at that time, the double bond part of stilbene shifts from trans type to cis type and does not absorb the UV rays around 350 nm necessary for fluorescent whitening. . Fading due to oxidation and decomposition by light energy.

The present inventors have focused on the fact that one of the causes of fading of fluorescent whitening paper dyed with a stilbene-based optical brightening agent is fading due to oxidation and decomposition due to light energy, and have studied a method for reducing the effect. The present invention has been completed earnestly. That is, the gist of the present invention is that when a high-white paper is produced using a stilbene-based optical brightening agent, a reducing agent is added.
Developed a method for producing fluorescent whitening paper with good light resistance by using the method of adding together with a stilbene whitening agent to the stock slurry, the method of coating during papermaking, the method of coating after papermaking Is.

The papermaking fibers used in the present invention include softwood bleached kraft pulp (NBKP), hardwood kraft pulp (LBKP) and softwood bleached sulfite pulp (NB).
SP) Hardwood bleached sulfite pulp (LBSP), chemical pulp such as dissolving pulp (DP), groundwood pulp (GP),
Mechanical pulp such as thermomechanical pulp (TMP), seed fiber fiber pulp such as cotton pulp and linter pulp, etc.
Non-wood fiber pulps such as bast fiber pulps such as hemp, swordfish, ganpi, and sanpei, and semi-synthetic fibers such as rayon fibers are used, and sulfite pulps are most effective. As a paper-making chemical, a sizing agent, a dry paper-strengthening agent, and a wet paper-strengthening agent which are generally used can be appropriately used in combination, but the cationic chemical has a bad influence on the light resistance.
Although it is possible to use a filler, it has a negative effect on the fluorescent whitening effect due to the masking effect. In particular, titanium oxide also reduces the effect of the reducing agent.

The stilbene whitening agents used in the present invention include 4,4'-diaminostilbene disulfonic acid derivative, stilbentriazinyl derivative, 4,4'-bistriazinylaminostilbene-2,2 '. And disulfonic acid derivatives.

[0009]

【Example】

Example 1 30 parts by weight of bleached softwood kraft pulp (NBKP) and 70 parts by weight of bleached hardwood kraft pulp (LBKP) (dry weight part, hereinafter the same) were beaten with a refiner to give a freeness of 400 ml C.I. S. F. (Canadian Freeness). To this, 0.5% by weight of a stilbene optical brightening agent (CI. FB-166) was added to the pulp, and 10% by weight of sodium thiosulfate pentahydrate was added to the pulp, and a sizing agent (trade name " 2.5 parts by weight of Size Pine "manufactured by Arakawa Chemical Industry Co., Ltd., 4.0 parts by weight of a dry paper strengthening agent (trade name" Polystron "manufactured by Arakawa Chemical Industry Co., Ltd.), and 5 parts of liquid aluminum sulfate. A slurry containing 0.0 part by weight was prepared, and an optical brightening paper having a basis weight of 150 g / m ^{2 was} made into paper by using a Fourdrinier paper machine according to a conventional method.

Comparative Example 1 A fluorescent brightening paper was made under the same conditions as in Example 1 except that sodium thiosulfate pentahydrate was not added, and used as a comparative example.

Example 2 A pulp composed of 30 parts by weight of bleached softwood kraft pulp (NBKP) and 70 parts by weight of bleached hardwood kraft pulp (LBKP) (dry weight part, hereinafter the same) was beaten with a refiner to give a freeness of 400 ml C.I. S. F. The stilbene-based fluorescent whitening agent (CIFB-1
76) was added to pulp in an amount of 0 to 5% by weight, and a sizing agent (trade name "Size Pine" manufactured by Arakawa Chemical Industry Co., Ltd.) was added thereto.
2.5 parts by weight, 4.0 parts by weight of a dry paper strengthening agent (trade name "Polystron" manufactured by Arakawa Chemical Industry Co., Ltd.), and 5.0 parts by weight of liquid aluminum sulfate were added to prepare a slurry. Paper was made using a Fourdrinier paper machine. Using a size press machine in the middle of papermaking, 5 parts by weight sodium sulfite, 3 parts by weight starch (trade name "Mermaid M200", manufactured by Shikishima Starch Co., Ltd.), acrylic surface strength improver (trade name "Polymerset 600", Arakawa) Chemical Co., Ltd.) 10 parts by weight, 82 parts by weight of water while applying a coating liquid, basis weight 1
A 50 g / m ² fluorescent whitening paper was produced.

Comparative Example 2 Sodium sulfite in the size press liquid was removed, and a fluorescent whitening paper was made under the same conditions as in Example 2 to make a comparative example.

Example 3 50 parts by weight of softwood bleached sulfite pulp (NBSP),
Linter pulp 50 parts by weight (dry weight part, the same applies hereinafter)
The pulp consisting of the mixture of No. 1 and No. 3 was beaten with a refiner to give a freeness of 400 ml C. S. F. The stilbene-based fluorescent whitening agent (CI FB-86) was added to the raw material in an amount of 0 to 5% by weight based on the pulp, and a sizing agent (trade name "Size Pine" Arakawa Chemical Industry Co., Ltd. 25 parts by weight), 4.0 parts by weight of a dry paper strength enhancer (trade name "POLISTRON" manufactured by Arakawa Chemical Industry Co., Ltd.), and 5.0 parts by weight of liquid aluminum sulfate to prepare a slurry. After making a paper having a basis weight of 150 g / m ² using a Fourdrinier paper machine according to the usual method, 5 parts by weight of sodium bisulfite and Mermaid M200 (manufactured by Shikishima Starch Co., Ltd.) were used using an Aeknife coating machine.
3 parts by weight, 10 parts by weight of Polymer Set 600 (manufactured by Arakawa Chemical Co., Ltd.), and 82 parts by weight of water were applied to produce a fluorescent brightened paper.

Comparative Example 3 Sodium bisulfite in the coating liquid was removed, and a fluorescent whitening paper was made under the same conditions as in Example 3 to make a comparative example.

Table 1 shows the evaluation results of each example and comparative example. In addition, the evaluation was performed by illuminating the paper made in the examples and comparative examples with a carbon fade meter (manufactured by Suga Test Instruments Co., Ltd.) for 3 hours, and measuring the fluorescence intensity (Zf value by the UV filter method) before and after the irradiation with a spectral white photometer (Tokyo). Colorimetry was performed by Denshoku Co., Ltd. and the rate of decrease in fluorescence intensity was compared.

[0016]

[Table 1]

From the comparison between Example 1 and Comparative Example 1 in Table 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, it can be seen that the light resistance is improved by the treatment with the reducing agent.

[0018]

As described above, according to the present invention, it has become possible to improve the light resistance, which is the greatest problem of the stilbene type brightener. The high-white paper obtained by using the present invention is a paper that can be suitably used for a book cover, a file paper, a poster, a catalog, etc., which requires light resistance, which is a field that cannot be used conventionally.

Claims (5)

[Claims] 1. A method for producing a fluorescent whitening paper, which comprises treating a fluorescent whitening paper obtained by inner surface dyeing or surface dyeing with a stilbene whitening agent with a reducing agent. 2. The method for producing a fluorescent brightening paper according to claim 1, wherein the reducing agent is added to the raw material slurry together with the stilbene-based brightening agent. 3. The method for producing an optical brightening paper according to claim 1, wherein a reducing agent is applied to the paper making. 4. The method for producing an optical brightening paper according to claim 1, wherein a reducing agent is applied after the optical brightening paper is made. 5. The method for producing a fluorescent brightened paper according to claim 1, wherein the reducing agent is sodium thiosulfate, sodium bisulfite, sodium bisulfite or the like.