Printing papers

a printing paper and paper technology, applied in papermaking, non-fibrous pulp addition, coatings, etc., can solve the problems of uv absorption, change in brightness, and inability to last, so as to improve discoloration, reduce discoloration, and improve environmental friendliness

Inactive Publication Date: 2006-10-26
NIPPON PAPER IND CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0026] Discoloration of paper is greatly reduced by providing a method for improving discoloration comprising preparing a paper containing a pulp irradiated with UV visible light in the presence of at least one compound selected from the group consisting of reducing agents, oxidizing agents and hydrogen-donating organic compounds or irradiating prepared paper with UV / visible light in the same manner, and especially such benefits as environmental friendliness are achieved because light and bulky papers can be prepared from smaller amounts of wood resources by treating MP having a high yield or MP-containing papers.PREFERRED EMBODIMENTS OF THE INVENTION
[0027] Pulps used in printing papers of the present invention include raw pulps such as bleached or unbleached mechanical pulps, semichemical pulps, chemical pulps and deinked pulps derived from wood. Either one member or a mixture of two or more members of these pulps may be used. The term “bleached” here means that the pulp has gone through e.g., a normal multi-stage bleaching process or a short sequence bleaching process in contrast to unbleached pulps. The present invention is preferably directed to bleached mechanical pulps because the invention works very effectively in the case of pulps showing significant discoloration,
[0028] Compounds that can be used to improve discoloration of pulp used in the present invention include known reducing agents, oxidizing agents and hydrogen-donating organic compounds commonly used as bleaching / decoloring agents. The pulps are treated in the presence of at least one compound among these groups.
[0029] Such reducing agents include, for example, sulfite or bisulfite ion, hydrosulfites, borohydride compounds, etc. The borohydride compounds are normally represented by general formula (1) or (2) below. M(BR4-nHn)m  (1) wherein n=an integer from 1 to 4, m=an integer from 1 to 3, M=a metal ion, organic ion or inorganic ion, R=a hydrocarbon group or substituted hydrocarbon group or BR3-nHn  (2) wherein n=an integer from 1 to 3, R=a hydrocarbon group or substituted hydrocarbon group. In general formula (1) above, the metal ion includes monovalent metal ions such as alkali metals, divalent metal ions such as alkali earth metals, and trivalent metal ions; and the organic ion may be any stable ion, especially a quaternary ammonium ion. Substituents for R include aliphatic hydrocarbon groups preferably containing 1 to 20, more preferably 1 to 10 carbon atoms, aromatic hydrocarbon groups preferably 6 to 20, more preferably 6 to 14 carbon atoms, alkyl-substituted hydrocarbon groups preferably containing 7 to 40, more preferably 7 to 24 carbon atoms, etc. When two or more substituents for R exist, R may be the same or different. Especially preferred borohydride compounds for use in the present invention are sodium borohydride or tetrabutylammonium borohydride. Sodium borohydride or tetrabutylammonium borohydride or mixtures thereof can also be used.
[0030] Preferred oxidizing agents are peroxides. As for peroxides, both organic peroxides and inorganic peroxides can be used. Organic peroxides that can be used are compounds represented by general formula (3) below: ROOR′  (3) wherein R and R′ may be the same or different and represent a hydrocarbon group, alkylcarbonyl group, arylcarbonyl group, alkoxycarbonyl group, aryloxycarbonyl group, formyl group or hydrogen.
[0031] The hydrocarbon group includes aromatic hydrocarbon groups such as phenyl, naphthyl, biphenyl and anthryl groups; aliphatic hydrocarbon groups; and substituted forms thereof; and the alkylcarbonyl group includes acetyl, ethylcarbonyl and propionylcarbonyl groups and substituted forms thereof. The arylcarbonyl group includes benzoyl, naphthylcarbonyl and biphenylcarbonyl groups and substituted forms thereof. The alkoxycarbonyl group includes methoxycarbonyl and ethoxycarbonyl groups and substituted forms thereof. The aryloxycarbonyl group includes phenoxycarbonyl, naphthoxycarbonyl and biphenyloxycarbonyl groups and substituted forms thereof. Specific examples of these organic peroxides include, for example, peracids such as perbenzoic acid and derivatives thereof, peracetic acid and performic acid; esters of these peracids; and percarbonic acid and esters thereof. Inorganic peroxides include hydrogen peroxide, sodium percarbonate, sodium peroxide, etc. Other oxidizing agents. include those containing no halogens such as ozone and oxygen.

Problems solved by technology

Thus, MPs are more preferred for an effective utilization of resources and achieving weight reduction of paper, but there is a serious problem of change in brightness over a period of time, i.e., the problem of discoloration, especially in high-brightness papers.
Thus, it is favorable to include the highest possible proportions of MP or DIP in view of the resources problem, and the inclusion of MP would also contribute to weight reduction of paper, but involves the problem of discoloration over a period of time, which is a serious problem especially in the case of paper used in books that are stored and displayed at bookstores for a long period.
However, UV absorbents or the like have the disadvantage that their effect does not last for a long period because they are also lost because of UV light.
On the other hand, when a rhodium catalyst was used for reducing the lignin aromatic ring, it took a long period, such as 5 days to partially hydrogenate the aromatic ring in the hydrogenation reaction of the aromatic ring of the lignin isolated from wood at room temperature in an aqueous alcohol solution, and this catalyst seems very difficult to directly react with the lignin present in pulp fibers because it is used as an emulsion.
Thus, all of these conventional methods have disadvantages such as insufficient anti-fading effect, long processing time, lack of economy or practicability, etc. at present.
In this method, however, large amounts of chemicals or the like must be used to degrade / remove lignin and these treatments cause problems such as yield loss in bleached pulp or strength loss in pulp fibers.
Large amounts of acids are required to remove hexenuronic acid, which also invites the problem of strength loss in pulp fibers.

Method used

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Examples

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Effect test

example 1

[0054] A paper having a basis weight of 46 g / m2 was prepared in an oriented sheet former (Kumagai Riki Kogyo Co.) from a mixed pulp slurry consisting of 10 parts of BCTMP (1) (bleached chemithermomechanical pulp available from Millar Western, ISO brightness 85%, freeness CSF 250 ml) and 90 parts of LBKP (freeness CSF 400 ml) containing 0.9% (based on pulp) of aluminum sulfate, 0.5% of cationized starch as an internal additive (trade name: Cato 3210 available from Nippon Scientific Co., Ltd.), and a blend of light calcium carbonate and talc in a ratio of 6:4 in an amount corresponding to an ash content of 6% in the paper. This sample was immersed in an aqueous 6% sodium borohydride solution (w / v) and then placed on a glass plate. At this point, the impregnant content of sodium borohydride was 18% solids by weight on the basis of the weight of pulp solids. This was irradiated with KrF excimer laser at 40 mJ / cm2 / pulse, 5 Hz for 40 minutes. After completion of laser irradiation, the sam...

example 2

[0055] A similar procedure as in Example 1 was carried out, except that a mixture of 30 parts of BCTMP (1) and 70 parts of LBKP was used.

example 3

[0056] A similar procedure as in Example 2 was carried out except that BCTMP (1) was replaced by BCTMP (2) (Millar Western, ISO brightness 70%, softwood 25%, aspen 75%).

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Abstract

Printing papers with reduced discoloration are obtained by using a pulp with improved discoloration. Printing papers with remarkably improved discoloration can be obtained by including a pulp consisting of one member or a mixed pulp of two or more members of bleached or unbleached mechanical pulps, semichemical pulps, chemical pulps and deinked pulps irradiated with UV and / or visible light in the presence of at least one additive selected from the group consisting of reducing agents, oxidizing agents and hydrogen-donating organic compounds.

Description

TECHNICAL FIELD [0001] The present invention relates to bulky printing papers with reduced loss of brightness, i.e. reduced discoloration, especially printing papers well-suited for books. PRIOR ART [0002] An effective way to utilize papermaking pulp derived from forest resources (in view of the growing concerns of environmentalists), is to prepare paper containing the highest possible proportions of mechanical pulp (hereinafter referred to as MP) having a high yield of about 90% or more, such as stone groundwood pulp, refined ground wood pulp, pressurized groundwood pulp, thermomechanical pulp, chemithermomechanical pulp and bleached chemithermomechanical pulp rather than chemical pulp (hereinafter referred to as CP) having a process yield of about 50% such as kraft pulp, alkaline pulp and sulfite pulp. It is also desirable to improve the utilization ratio of deinked pulp (hereinafter referred to as DIP) made by defiberizing paper once used. [0003] On the other hand, weight reducti...

Claims

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Application Information

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IPC IPC(8): D21H11/00D21H25/00D21C9/10D21C9/00D21H17/63D21H25/04
CPCD21C9/001D21H25/04D21H17/63
InventorOCHI, TAKASHIMIYAWAKI, SHOICHIOUCHI, AKIHIKO
OwnerNIPPON PAPER IND CO LTD