JP2005154937A - Bleaching method with metal-disubstitued deleted type heteropolyoxometalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bleaching method for stains on papermaking chemical pulp, textile materials and clothes and fungi stuck to teeth, towels and tiles and the like. <P>SOLUTION: The bleaching method comprises making a treatment with a metal-substituted bideleted γ-Keggin type heteropolyoxometalate and an oxidizing agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bleaching method for molds attached to chemical pulp and fiber materials for paper manufacture, clothing stains, teeth, towels, tiles, and the like. In particular, the field of the present invention is that organic peracids such as hydrogen peroxide and peracetic acid, oxygen, sodium percarbonate, sodium perborate, etc. are obtained by using a two-deficient γ-Keggin type tungstosilicic acid substituted with a metal atom. This is a method for activating the oxidizing agent bleaching effect.

  Conventionally, chlorine chemicals have been used as bleaching agents for bleaching chemical pulp for papermaking and fiber materials. In chemical pulp for papermaking, specifically, a combination of chlorine (abbreviated as C), hypochlorite (H) and chlorine dioxide (D), for example, C-E-H-D, C / D Bleaching by a sequence such as -EHD (C / D is a combined bleaching stage of chlorine and chlorine dioxide, E is an alkali extraction stage) has been performed.

  However, these chlorine bleaching chemicals produce organic chlorine compounds that are harmful to the environment at the time of bleaching, and environmental pollution of bleaching wastewater containing these organic chlorine compounds has become a problem. The most effective way to reduce or prevent by-products of organochlorine compounds is to reduce the amount of chlorinated chemicals used or not at all. Pulp produced by a method that does not use any chlorine bleach such as chlorine, hypochlorites, and chlorine dioxide is called TCF (total chlorin-free) pulp.

  As a bleaching method using no chlorine bleach, a method using a peroxide bleach such as hydrogen peroxide has been conventionally performed, which is a known technique. This peroxide bleaching agent is used at high temperatures and is used for bleaching chemical pulp for papermaking and cotton cloth. However, the effect of peroxide bleaching agents is inadequate. For this reason, the use of transition metal complexes as activation catalysts has been studied. However, conventional transition metal complexes cannot provide a sufficient bleaching effect. There was also a problem of damaging the fiber.

  Waynestock et al. Have proposed that vanadium-substituted polyoxometalates are effective for bleaching and delignification of wood pulp (see Patent Document 1). Low and heteropolyacids are used as stoichiometric bleaching chemicals, leaving the problem of being not economical.

Palen Aalto et al. Proposed a method for bleaching and delignification using hydrogen peroxide as an oxidizing agent by heteropolyoxometalate obtained by condensing metal oxides such as tungstic acid, molybdic acid and silicic acid in the reaction solution. However, there is no description of hardwood pulp containing a large amount of non-phenolic lignin which is difficult to bleach and delignify.
Japanese Patent No. 3169020 Japanese National Patent Publication No. 10-501588

  The object of the present invention is to utilize an oxidizing agent in bleaching chemical pulp for papermaking or cotton cloth. More specifically, by improving the bleaching effect of the oxidizing agent, it is possible to achieve high whiteness without causing deterioration of the fiber. It is to provide a bleaching method that advances the process.

  As a method of bleaching and delignification in bleaching of chemical pulp for papermaking and cotton cloth, the present inventors have prepared a solution containing a two-deficient γ-Keggin type heteropolyoxometalate substituted with a metal atom as shown in FIG. The mixture of oxidants such as hydrogen peroxide, peracid, oxygen, and ozone shows higher whitening effect with higher activity than previously proposed polyoxometalates without damaging the fiber. I found it.

  That is, the present invention relates to a bleaching method characterized by treatment with a two-deficient γ-Keggin type heteropolyoxometalate substituted with a metal atom and an oxidizing agent, and particularly to a bleaching method for chemical pulp for papermaking. Is.

  According to the bleaching method of the present invention, an extremely high bleaching effect and delignification effect can be achieved without damaging the fiber. Furthermore, no chlorine-based chemicals are used as bleaching chemicals, no organic chlorine compounds are produced, and it is industrially possible to greatly reduce environmental pollution caused by bleaching wastewater.

The telopolyoxometalate of the present invention has a hetero atom of silicon, a poly atom of tungsten, a two-deficient structure site, and at least one kind selected from a transition metal atom and a typical metal atom at the deficit site. A metal disubstituted deficient tungstosilicic acid having an atom inserted therein is preferably represented by the following general formula. M is preferably iron, manganese, lanthanum or palladium.
[SiM ₂ W ₁₀ O ₄₀ ] ^q- (1)
(In the formula, M represents a transition metal atom or a typical metal atom. Q is a positive integer.

As counter cations of the metal disubstitution-deficient γ-tungstosilicate, H, Li, K, Na, Rb, Cs, Ca, Mg, Sr, Ba, Al, PR ¹ R ² R ³ R ⁴ , NR ¹ R ² R ³ R ⁴ (R ¹ , R ² , R ³ and R ⁴ are the same or different and are H, C ₁ -C ₂₀ -alkyl, C ₅ -C ₈ -cycloalkyl or C ₆ -C ₂₄ -aryl. ) One or more cations selected from the group consisting of:

The metal disubstituted γ-tungstosilicate used in the present invention is a compound that is stable in air and easy to handle. For example, an iron-substituted product is described in Inorganic Chemistry, Vol. 38, No. 25, page 5724 (1999). In addition, the manganese-substituted product can be synthesized by the method described in Inorganic Chemistry, Vol. 35, No. 1, p. 30 (1996). The raw material, deficient Keggin type K ₈ [γ-SiW ₁₀ O ₂₆ ] 12H ₂ O, can be synthesized by the method described in Inorganic Synthesis, Vol. 27, page 85 (1990).

  Examples of the oxidizing agent in the present invention include hydrogen peroxide, adducts of hydrogen peroxide and inorganic salts, sodium peroxide, persulfates, perborates, performic acid, peracetic acid and other inorganic and organic peroxidations. Or oxygen can be used. The form of the bleaching agent may be powdery or liquid, and may contain a surfactant, a metal sequestering agent and the like in addition to the above essential components.

  In the present invention, the digested chemical pulp is preferably subjected to chelate treatment (abbreviated as Q-stage treatment) in order to remove heavy metals derived from wood raw materials, for example, iron, manganese and copper. This prevents the decomposition of hydrogen peroxide, peracid, and the like by these heavy metals and the resulting decrease in viscosity. Suitable chelating reagents include DTPA (diethylenetriaminepentaacetic acid), but other chelating agents such as EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), and the like are possible.

  The pH of the pulp-containing water in the Q stage treatment is adjusted to an appropriate value depending on the chelating agent used. In the Q-stage treatment of the present invention, depending on the properties of the pulp, the pulp concentration is usually 0.5 to 20%, preferably 1 to 10%, temperature 50 to 90 ° C, preferably 60 to 80 ° C. Is performed for 60 minutes to 240 minutes, preferably 90 minutes to 180 minutes. The pulp after the Q stage treatment is washed and dehydrated, and then subjected to a peroxide treatment (abbreviated as Pcat stage treatment) in the presence of the metal disubstitution-deficient γ-tungstosilicate catalyst.

  The treatment in the Pcat stage is performed by adjusting the pH of the pulp-containing water to 7.5 or less, preferably 4.0 to 5.0. In the Pcat stage treatment of the present invention, the pulp concentration is usually 0.5 to 40%, preferably 1 to 30%, more preferably 5 to 20%, and the temperature 70 to 110 ° C., although it depends on the properties of the pulp. Is performed at 80 to 100 ° C. and the treatment time is 60 to 300 minutes, preferably 60 to 210 minutes.

  As the Pcat stage peroxide, inorganic and organic peroxides such as hydrogen peroxide, adducts of hydrogen peroxide and inorganic salts, sodium peroxide, persulfates, performic acid and peracetic acid can be used. Preferably hydrogen peroxide is used. The amount of peroxide used is 0.01 to 5%, preferably 0.5 to 3%, per 100% dry pulp in terms of 100% hydrogen peroxide.

  In the Pcat stage treatment of the present invention, as a reaction catalyst, depending on the delignification conditions of pulp, 1 to 5000 ppm, preferably 10 to 2000 ppm, more preferably 100 to 1000 ppm of the above-mentioned metal disubstituted defect type γ, depending on pulp delignification conditions. -Add tungstosilicic acid. If it is less than 1 ppm, the catalytic effect is insufficient, and if it is more than 5000 ppm, the effect is not increased, which is disadvantageous in terms of cost. As for the method of adding the acid, peroxide and reaction catalyst to the pulp, each may be sequentially mixed with the pulp, or the acid, peroxide and reaction catalyst may be mixed in advance and then mixed with the pulp.

  The reaction catalyst contained in the Pcat stage of the present invention facilitates the reaction in which the peroxide decomposes or modifies the lignin or pigment contained in the pulp, and the delignification or bleaching effect in the subsequent treatment with the peroxide in an alkaline medium. It exerts the effect of improving.

  The pulp after the Pcat stage treatment can be washed and dehydrated and then subjected to the above-described Q stage treatment to remove excess reaction catalyst. The pulp after the Q-stage treatment is washed and dehydrated, and then subjected to a delignification / bleaching step with a peroxide in an alkaline medium (this step is abbreviated as Ep-stage treatment).

  In the Ep stage, the pulp is subject to delignification and bleaching action by peroxide in an alkaline medium. As the alkaline agent in the Ep stage, caustic soda, caustic potash, lime, soda ash and the like can be used. The amount of the alkali agent used is 0.05 to 5.0%, preferably 0.1 to 1.0%, per dry bone pulp in terms of caustic soda. When the amount of alkali used is less than this, the delignification / bleaching effect is lowered, and when it is more than this, the viscosity of the pulp is remarkably lowered.

  As peroxides in the Ep stage, inorganic and organic peroxides such as hydrogen peroxide, adducts of hydrogen peroxide and inorganic salts, sodium peroxide, persulfates, formic acid, and peracetic acid can be used. In general, hydrogen peroxide is preferably used. The amount of peroxide used is 0.05 to 8%, preferably 0.2 to 2.0%, per 100% dry pulp in terms of 100% hydrogen peroxide. If the amount of peroxide used is less than this, the delignification / bleaching effect is low, and if it is more than this, the efficiency of the peroxide decreases.

  The pulp concentration in the Ep stage of the present invention is preferably 7 to 30%, more preferably 10 to 20%. The temperature is preferably 40 to 120 ° C, more preferably 60 to 95 ° C. The treatment time is preferably 15 to 150 minutes, more preferably 30 to 120 minutes.

  The bleaching method of the present invention can be applied not only to chemical pulp for papermaking, but also to bleaching of textile materials, clothing stains, cotton products such as towels, molds attached to tiles, teeth and the like.

  Next, the present invention will be described specifically by way of examples. The amount of each chemical used is indicated by weight percent per dry pulp, and the amount of hydrogen peroxide used is 100% hydrogen peroxide equivalent. The pulp used for the bleaching is crafted L material pulp (hunter whiteness 49.7%, K value 6.6, viscosity 0.0299 Pa · s). A series of analytical evaluations were performed by the following methods.

・ Whiteness: JIS-P8123 (Hunter whiteness method)
K value: TAPPI K value method Viscosity TAPPI No. 44 method delignification rate (%) = [1-((K value after bleaching) / (K value before bleaching))] × 100

Reference Example 1 [Synthesis of iron disubstitution-deficient γ-tungstosilicate]
8.9 g of two-deficient Keggin type K ₈ [γ-SiW ₁₀ O ₃₆ ] 12H ₂ O is dissolved in 90 ml of pure water and adjusted to pH 3.9 with an aqueous nitric acid solution. Add 15 ml of pure water in which 2.4 g of iron (III) nitrate nonahydrate is dissolved, and stir for 5 minutes. Subsequently, 20 g of cesium nitrate is added. The solid matter that has been stirred for 15 minutes and collected is collected by filtration. 10 ml of pure water was added to this and washed twice to obtain 5.1 g of iron disubstituted deficient γ-tungstosilicate cesium salt.

Reference Example 2 [Synthesis of Manganese (III) Disubstituted Deficient γ-Tungstosilicate]
5.9 g of the two-deficient Keggin type K ₈ [γ-SiW ₁₀ O ₃₆ ] 12H ₂ O is dissolved in 25 ml of pure water and adjusted to pH 3.9 with an aqueous nitric acid solution. Thereafter, the pH is adjusted to 3.8 to 4.5 until precipitate formation. Pour 10 ml of pure water in which 0.78 g of manganese (II) acetate tetrahydrate is dissolved, and stir for 2 minutes. Subsequently, 10 ml of pure water in which 0.17 g of potassium permanganate is dissolved is added. After stirring for 5 minutes, 10 g of cesium nitrate is added, and the mixture is stirred for 15 minutes and the precipitated solid is recovered by filtration. To this was added 10 ml of pure water and washed twice to obtain 4.3 g of manganese (III) disubstituted deficient γ-tungstosilicate cesium salt.

Reference Example 3 [Synthesis of lanthanum disubstituted deficient γ-tungstosilicate]
The procedure was the same as that of the iron-substituted product except that 2.5 g of lanthanum nitrate hexahydrate was added instead of iron (III) nitrate nonahydrate and the pH was adjusted to 3.8.

Examples 1 and 2 (Q-Pcat-Q-Ep)
Q (Chelating agent treatment)
An aqueous sulfuric acid solution was added to the L-wood pulp after kraft cooking, 0.2% of DTPA was added, and the mixture was treated for 120 minutes under the conditions of pulp concentration 5.0%, pH 5.6, and temperature 70 ° C. After completion of the treatment, it was diluted with water to a pulp concentration of 2.5% and then dehydrated to a pulp concentration of 20%.

Pcat (peroxide treatment in the presence of catalyst)
To the pulp obtained as described above, 0.05% of iron disubstitution-deficient γ-tungstosilicate silicate salt and 1.0% of H ₂ O ₂ were added, and the pulp concentration was 10%, pH 4.0 or 7.0. , And treated at a temperature of 90 ° C. for 180 minutes. After completion of the treatment, the pulp was diluted with water to a pulp concentration of 2.5%, and then adjusted to a pulp concentration of 20%.

Q (Chelating agent treatment)
The obtained pulp was treated by the same method as the Q-stage treatment.
Ep (alkali peroxide bleaching)
0.3% of H ₂ O ₂ was added to the pulp obtained by treating the above three steps, and treated for 60 minutes under the conditions of pulp concentration 10%, pH 11.2, and temperature 70 ° C. After completion of the treatment, the pulp was diluted with water to a pulp concentration of 2.5%, and then dehydrated to a pulp concentration of 20% to obtain a bleached pulp.

Examples 3 and 4
Bleaching operation as in Examples 1 and 2 except that in Pcat of Examples 1 and 2, manganese (III) di-substituted γ-tungstosilicate was used instead of iron di-substituted γ-tungstosilicate Went.

Examples 5 and 6
The same bleaching operation as in Examples 1 and 2 was carried out except that lanthanum disubstitution-deficient γ-tungstosilicate was used in place of iron disubstitution-deficient γ-tungstosilicate in Pcat of Examples 1 and 2. .

Examples 7 and 8
The same bleaching operation as in Examples 1 and 2 was carried out except that palladium disubstitution-deficient γ-tungstosilicate was used instead of iron disubstitution-deficient γ-tungstosilicate in Pcat of Examples 1 and 2. .

Comparative Examples 1 and 2
The same bleaching operation as in Examples 1 and 2 was performed except that iron disubstitution-deficient γ-tungstosilicate cesium salt was not added to Pcat in Examples 1 and 2.

Comparative Examples 3 and 4
The same bleaching operation as in Examples 1 and 2 was performed except that unsubstituted tungstosilicic acid was used in place of the iron disubstitution-deficient γ-tungstosilicate in Pcat of Examples 1 and 2.

Polyhedral diagram of the molecular structure of two-deficient γ-Keggin heteropolyoxometalates substituted by metal atoms

Claims (4)

A bleaching method comprising treating with a deficient γ-Keggin type heteropolyoxometalate substituted with a metal atom and an oxidizing agent. The bleaching method according to claim 1, wherein the bleaching object is chemical pulp for papermaking. The bleaching method according to claim 1, wherein the heteropolyoxometalate is represented by the following general formula (1).
[SiM ₂ W ₁₀ O ₄₀ ] ^q- (1)
(In the formula, M represents a transition metal atom or a typical metal atom. Q is a positive integer.) The bleaching method according to claim 1, wherein the oxidizing agent is hydrogen peroxide, peracetic acid, oxygen, sodium percarbonate or sodium perborate.

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