JPH049232B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for bleaching wood pulp, and more specifically, the present invention relates to a method for bleaching wood pulp, using peroxide to bleach high-yield pulp such as mechanical pulp (MP) and chemical mechanical pulp (CGP), deinked pulp (DIP), etc. ), a specific water-soluble copolymer is used as a bleaching agent when bleaching chemical pulp such as soda pulp (AP) and kraft pulp (KP) obtained by cooking with an alkaline solution of hydrogen peroxide. The present invention relates to a bleaching method characterized by: (Prior Art) Oxidative bleaching methods using hydrogen peroxide, sodium peroxide, peracetic acid, etc. are methods for bleaching so-called high-yield pulps such as wood pulps such as mechanical pulp (MP) and chemical mechanical pulp (CGP). There is a reduction bleaching method that uses sodium hydrosulfite, zinc hydrosulfite, etc. Reductive bleaching has the advantage of being a relatively inexpensive bleaching method, but
Due to insufficient bleaching properties, it is limited to low whiteness pulp,
In recent years, the amount of reducing bleach used has been on the decline. The number of deinking pipes (DIP) has increased significantly in recent years, and oxidative bleaching using hydrogen peroxide is mainly used as the bleaching method. Soda pulp (AP) and kraft pulp (KP)
Bleaching of chemical pulp such as chlorine, bleaching powder, chlorine dioxide, sodium chlorite, and other chlorine-based oxidizing bleaches and sulfur-containing reducing bleaches such as thiosulfate, sulfite, and bisulfite are used in combination. A so-called multi-stage bleaching method is used. However, chlorine-based oxidizing bleaches severely corrode bleaching equipment when residual chlorine increases or temperatures rise. Further, although chlorine dioxide is one of the most frequently used chlorine bleaching agents and exhibits excellent bleaching properties, it has the drawbacks of being expensive and increasing the wastewater load. In order to eliminate these drawbacks of chlorine bleach, the use of peroxide bleach has recently begun to be considered. As described above, the amount of peroxide bleaching agents used in bleaching wood pulp such as high-yield pulp, deinked pulp, and chemical pulp has been rapidly increasing. Such peroxide bleaching agents, such as hydrogen peroxide, do not have sufficient bleaching properties even when used alone, and are usually used in combination with a bleaching aid (hereinafter referred to as "aid" for simplicity). Known auxiliary agents include, for example, aminocarboxylate salts such as ethylenediaminetetraacetic acid (EDTA), diethylenediaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), and diethylenetriaminepentamethylene phosphate (DTPMPA), sulfite salts, and silicic acid. Salts, condensed phosphates such as tripolyphosphate, alkaline earth metal compounds such as magnesium and calcium, and aluminum compounds are used. However, although aminocarboxylate-based auxiliaries exhibit relatively good bleaching properties, their use is severely limited due to their high cost and relatively strong toxicity. Also,
Sulfites and silicates are often used as inexpensive auxiliaries, but they combine with polyvalent metals in wood and alkaline earth metal compounds and aluminum compounds added as auxiliaries to form insoluble salts. For example, scaling problems such as clogging on the refiner plate are likely to occur. Condensed phosphates flow into the sea through rivers as wastewater and become a causative agent of red tide. Furthermore, when used at high temperatures such as in refiner bleaching, the condensed phosphate is decomposed into phosphoric acid, producing insoluble salts with the above-mentioned polyvalent metals, which tends to cause scale problems. Although alkaline earth metal compounds and aluminum compounds are relatively inexpensive, they are not sufficiently effective, and addition of these polyvalent metals promotes scale damage. In order to overcome these problems,
No. 103386 proposes the use of α-hydroxyacrylic acid-based polymers. However, this polymer does not have as good a bleaching property as an aminocarboxylic acid-based auxiliary agent, and is extremely expensive, so it has not been put into practical use yet. (Problems to be Solved by the Invention) The present invention provides solutions for bleaching wood pulp using oxidizing bleaches such as hydrogen peroxide, sodium peroxide, percarbonate, perborate, peracetic acid, and ozone. ,
A method for bleaching wood pulp that can overcome the above-mentioned problems of conventional auxiliaries by using an inexpensive specific auxiliary that exhibits a remarkable bleaching enhancement effect even in relatively low amounts. It provides: (Means and effects for solving the problems) The present invention uses acrylic acid and
50 to 99.9 mol% of unsaturated monocarboxylic acid monomers selected from methacrylic acid and their salts, and 0.1 to 99.9 mol% of unsaturated sulfonic acid monomers selected from sulfonic acid group-containing monomers and their salts. 50 mol%
The molecular weight obtained by using the ratio in the range of 1000 ~
The present invention relates to a method for bleaching wood pulp, characterized in that 80,000 water-soluble copolymer I is used in an amount of 0.05 to 1 weight percent based on bone dry pulp. The reason why the bleaching properties of wood pulp improve when water-soluble copolymer I is used as an auxiliary agent is not clear, but it is speculated as follows. That is, when water-soluble copolymer I is used as an auxiliary agent, delignification is promoted, and Mn, Cu, Fe, Ni,
It chelates polyvalent metal ions such as Co and suppresses wasteful peroxide decomposition. It suppresses the autooxidation of chromophores, especially quinones, in wood. Fe, Cu,
Possible effects include preventing insoluble substances such as colored metal hydroxides such as Ni from (re)adhering to wood pulp as scale. The unsaturated monocarboxylic acid monomer, which is one of the raw material monomers for obtaining the water-soluble copolymer I used in the present invention, includes acrylic acid, methacrylic acid, monovalent metals thereof, divalent metals, etc. Examples include partially neutralized products and completely neutralized products with metals, ammonia, and organic amines. Monovalent metals include sodium, potassium, etc., and divalent metals include calcium, magnesium, zinc, etc. In addition, organic amines include alkylamines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamine; monoethanolamine,
Examples include alkanolamines such as diethanolamine, triethanolamine, monoisopropanolamine, and dimethylethanolamine; pyridine; and the like. Among them, sodium is the most preferred because it is inexpensive and industrially easily available. In addition, examples of the unsaturated sulfonic acid monomer, which is the other raw material monomer for obtaining the water-soluble copolymer I used in the present invention, include vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, ,
Styrene sulfonic acid, 2-acrylamide-2-
Methylpropanesulfonic acid, 3-allyloxy-2
-Hydroxypropanesulfonic acid, sulfoethyl (meth)acrylate, sulfopropyl (meth)
Sulfonic acid group-containing monomers such as acrylate, 2-hydroxysulfopropyl (meth)acrylate, and sulfoethylmaleimide, or one thereof
Examples include partially neutralized products and completely neutralized products using valent metals, divalent metals, ammonia, and organic amines. Monovalent metals include sodium, potassium, etc., and divalent metals include calcium, magnesium, zinc, etc. In addition, organic amines include alkylamines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamine; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, and dimethylethanolamine; and pyridine. etc. can be given. Among them, sodium is the most preferred because it is inexpensive and industrially easily available. In order to obtain the water-soluble copolymer I used in the present invention, these raw unsaturated monocarboxylic acid monomers and unsaturated sulfonic acid monomers may be polymerized using known techniques. For example, in the case of aqueous polymerization, persulfates such as sodium persulfate and potassium persulfate; hydrogen peroxide, 2,2'-azobis(2-amidinopropane) hydrochloride, 4,4'-azobis-4-cyanovaleric acid, etc. It can be produced by a conventional method using a water-soluble azo compound or the like as a polymerization catalyst. In the case of polymerization in organic solvents such as alcohols such as methanol and isopropyl alcohol, ethers such as tetrahydrofuran and dioxane, aromatic threads such as benzene, xylene and toluene, or ketones such as methyl ethyl ketone and methyl isobutyl ketone, Organic peroxides such as benzoyl peroxide, lauroyl peroxide, peracetic acid; azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,
It can be produced by a conventional method using an oil-soluble azo compound such as (4-dimethylvaleronitrile) as a polymerization catalyst. In addition, when obtaining the water-soluble copolymer I, other monomers copolymerizable with the unsaturated monocarboxylic acid monomer and the unsaturated sulfonic acid monomer may be used within a range that does not impair the effects of the present invention. It is of course possible to copolymerize. Examples of other copolymerizable monomers include amide monomers such as (meth)acrylamide and t-butyl (meth)acrylamide; (meth)acrylic acid esters, styrene, 2-methylstyrene, vinyl acetate, etc. hydrophobic monomer; 3-
Methyl-3-buten-1-ol (isoprenol), 3-methyl-2-buten-1-ol (prenol), 2-methyl-3-buten-2-ol (isoprene alcohol), 2-hydroxyethyl (meth) ) acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol monoisoprenol ether, polypropylene glycol monoisoprenol ether, polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether, glycerol monoallyl ether, Hydroxyl group-containing unsaturated monomers such as α-hydroxyacrylic acid, N-methylol (meth)acrylamide, glycerol mono(meth)acrylate, and vinyl alcohol; dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, etc. Cathinic monomer; Nitrile monomer such as (meth)acrylonitrile; (meth)acrylamide methanephosphonic acid, (meth)acrylamide methanephosphonic acid methyl ester, 2-
Phosphorus-containing monomers such as (meth)acrylamido-2-methylpropanephosphonic acid; ethylene, propylene, 1-butene, isobutylene, α-amylene, 2-methyl-1-butene, 3-methyl-1-
Butene (α-isoamylene), 1-hexene, 1
-α-olefin monomers such as heptene; crotonic acid; maleic acid, fumaric acid, itaconic acid,
Examples include unsaturated dicarboxylic acid monomers such as citraconic acid and aconitic acid. The molecular weight of water-soluble copolymer I is 1000~
A range of 80,000 is effectively used. If the molecular weight is outside this range, the bleaching properties will not be sufficient. In order to bleach wood pulp with peroxide in the method of the present invention using water-soluble copolymer I as an auxiliary agent, a conventional peroxide bleaching method may be used. It should be obvious. In the present invention, water-soluble copolymer I is used in an amount of 0.05 to 1 weight percent based on the bone-dry pulp. If the amount used is less than the above range, sufficient bleaching properties cannot be obtained. Furthermore, even if the amount used is larger than the above range, bleaching properties commensurate with the increased amount cannot be obtained, and conversely, the CDD load of the wastewater increases, which is not preferable. In carrying out the present invention, water-soluble copolymer I may be prepared from conventionally used aminocarboxylate salts, sulfites, silicate salts, condensed phosphate salts such as tripolyphosphate salts, and alkali salts such as magnesium and calcium. Of course, it is also possible to use it in combination with auxiliary agents such as earth metal compounds and aluminum compounds. In addition, water-soluble copolymer I can be used not only as an auxiliary agent in peroxide bleaching as in the present invention, but also in chlorine-based oxidative bleaching such as chlorine, bleaching powder, chlorine dioxide, and chlorite, although the effect is slightly inferior. It is also effective as an auxiliary agent for sulfur-containing reducing bleaches such as sodium hydrosulfite, zinc hydrosulfite, thiosulfate, sulfite, and bisulfite.
Furthermore, water-soluble copolymer I exhibits an excellent bleaching enhancement effect not only when used as an auxiliary agent in bleaching with peroxide, but also when used in a so-called pre-treatment step in which wood pulp is washed with water. Furthermore, the water-soluble copolymer I can be effectively used as a peroxide bleaching aid not only for wood pulp but also for non-wood pulp. (Examples) Hereinafter, the present invention will be specifically explained using Examples, but the present invention is not limited to these Examples. Note that parts and % in the examples indicate parts by weight and % by weight, respectively. Example 1 30 parts of unbleached refined ground pulp (pulp concentration 16%, whiteness 49.6%), which is a type of high-yield pulp (pulp concentration 16%, whiteness 49.6%), was charged into a beaker with a capacity of 500 ml, and then the final pulp concentration was Added enough water to reach 12%. To this was added 1.2 parts of a 5% aqueous solution of acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) copolymer sodium salt having a molecular weight of 20,000 as an auxiliary agent (0.2% based on the pulp) while stirring at low speed. ), 35 as peroxide
After adding 1.71 parts of % hydrogen peroxide solution (2% based on the pulp) and 6.0 parts of a 10% aqueous sodium carbonate solution (2% based on the pulp) as an alkaline agent, the pH was adjusted to 10.8 using a 3% aqueous sodium hydroxide solution. This was transferred to a polyethylene bag, the inlet was turned back to prevent moisture from evaporating, and then heat treated in a water bath pre-adjusted to 60°C for 3 hours. A portion of the bleached pulp slurry was diluted to 3% and adjusted to pH 6.0 using sulfite water. Using this diluted and PH-adjusted pulp slurry,
Two handmade sheets were prepared using the TAPPI standard method, and after air drying, the whiteness was measured using a Hunter whiteness meter. The results obtained are shown in Table 1. Examples 2 to 13 Acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid used in Example 1 (molar ratio
75/25) The white color of the handmade sheet was prepared in exactly the same manner as in Example 1 except that a predetermined amount of water-soluble copolymer I shown in Table 1 was used as an auxiliary agent instead of the copolymer sodium salt. The degree of The results obtained are shown in Table 1. Example 14 The whiteness of a handmade sheet was measured in the same manner as in Example 1, except that 6.0 parts of a 10% sodium silicate aqueous solution was used instead of 6.0 parts of a 10% sodium carbonate aqueous solution. The results obtained are shown in Table 1. Examples 15-16 Example 1 except that the water-soluble copolymer I shown in Table 1 was used as an auxiliary agent, and 1.71 parts of a 35% aqueous sodium peroxide solution was used instead of 1.71 parts of a 35% hydrogen peroxide solution. Measure the whiteness of the handmade sheet in exactly the same way as above. The results obtained are shown in Table 1.

【table】

[Table] Comparative Examples 1 to 16 Acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid used in Example 1 (molar ratio
75/25) The whiteness of the handmade sheet was measured in the same manner as in Example 1, except that the predetermined amount of auxiliary agent shown in Table 2 was used instead of the copolymer sodium salt.
The results obtained are shown in Table 2.

【table】

[Table] Example 17 Adding hot water at 65℃ to the standard disintegrator described in JIS P-8209.
1500 copies and 75 copies of waste newspapers shredded into 2 cm x 2 cm pieces were charged and gently disintegrated for 1 to 2 minutes. The waste paper pulp slurry obtained by scraping off the sample adhering to the propeller and inner wall has a molecular weight of 20,000 as an auxiliary agent.
Acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) copolymer sodium salt 0.1% (based on pulp), hydrogen peroxide
1.5% (based on pulp), Sodium hydroxide 1.5% (based on pulp), No. 3 sodium silicate 3% (based on pulp)
and deinking agent (sodium oleate) 0.2
% (based on pulp) and disintegrated at 60°C for 20 minutes. After disintegration, the waste paper pulp slurry was transferred to a polyethylene bag, the inlet was folded back to prevent moisture from evaporating, and then aged in a water bath pre-adjusted to 60°C for 2 hours. The aged disintegrated waste paper pulp slurry was diluted to 1%, floated at 30℃ for 10 minutes, and filtered through a standard mesh sieve to give a 10%
Dehydrated to a concentration. Next, dilute the pulp slurry to a concentration of 1% and PH it using aluminum sulfate.
Adjusted to 5.3. Using this PH-adjusted deinked pulp slurry,
A handmade sheet with a basis weight of 100 g/m ² was prepared using a Tatsupee sheet machine, and after air drying, the whiteness was measured using a Hunter whiteness meter. The results obtained are shown in Table 3. Examples 18-29 Handmade sheets were prepared in exactly the same manner as in Example 17, except that the predetermined amounts of auxiliaries shown in Table 3 were used.
Its whiteness was measured. The results obtained are shown in Table 3. Example 30 A handmade sheet was prepared in the same manner as in Example 17 except that 1.5% sodium peroxide (based on pulp) was used instead of 1.5% hydrogen peroxide (based on pulp),
Its whiteness was measured. The results obtained are shown in Table 3. Example 31 Hand papermaking was carried out in the same manner as in Example 17, except that 0.5% hydrogen peroxide (based on pulp) and 1.0% peracetic acid (based on pulp) were used instead of 1.5% hydrogen peroxide (based on pulp). A sheet was prepared and its whiteness was measured. The results obtained are shown in Table 3.

【table】

[Table] Comparative Examples 17 to 30 Handsheets were prepared in exactly the same manner as in Example 17, except that the auxiliaries shown in Table 4 were used, and their whiteness was measured. The results obtained are shown in Table 4. Comparative Example 31 A handmade sheet was prepared in exactly the same manner as in Example 17 except that no auxiliary agent was used, and its whiteness was measured. The results obtained are shown in Table 4.

【table】

[Table] Example 32 1st step In a SUS316 autoclave, about 4 cm in length,
Cedar chips with a width of about 4 cm and a thickness of about 0.5 cm and a molecular weight of 20,000 as an auxiliary agent based on the absolute dry weight of the cedar chips
Acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) copolymer sodium salt 0.3%, anthraquinone 0.1
%, hydrogen peroxide 3%, sodium hydroxide 25%, and ion-exchanged water with a liquid ratio of 4/Kg, and the mixture was cooked at 170°C for 1.5 hours. Next, after washing with water, the pulp was carefully selected using a 6/1000 cut test flat screen (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain selected soda pulp with a yield of 41.5%. The physical properties of the obtained selected soda pulp are shown in Table 5. 2nd step 1st stage The selected soda pulp obtained in the 1st step is mixed with acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) with a molecular weight of 20,000 as an auxiliary agent. 0.1% polymer sodium salt, 3% hydrogen peroxide and 4% sodium hydroxide were added and bleaching was carried out at 90°C for 1 hour. The physical properties of the obtained bleached soda pulp were
Shown in the table. 2nd step, 2nd stage, 2nd step, 1st stage was repeated to perform bleaching. Table 5 shows the physical properties of the bleached soda pulp obtained. Examples 33-44 Cooking and bleaching were carried out in exactly the same manner as in Example 32, except that the predetermined amounts of auxiliaries shown in Table 5 were used.
The results obtained are shown in Table 5.

【table】

[Table] Comparative Examples 32 to 43 Cooking and bleaching were carried out in exactly the same manner as in Example 32, except that the predetermined amounts of auxiliaries shown in Table 6 were used.
The results obtained are shown in Table 6.

[Table] (Effects of the invention) When bleaching wood pulp using a peroxide bleaching agent, a specific water-soluble copolymer I is used as an auxiliary agent in an amount of 0.05 to 1 percent by weight based on the bone dry pulp. According to the bleaching method of the present invention, the amount of Bleaching properties are significantly improved with an amount of auxiliary agent. Moreover, since water-soluble copolymer I does not generate insoluble salts during bleaching operations, it does not cause scaling problems, nor does it cause environmental pollution problems such as corrosion of bleaching equipment and red tide.

Claims (1)

[Scope of Claims] 1. An unsaturated monocarboxylic acid monomer selected from acrylic acid, methacrylic acid, and salts thereof, from 50 to 99.9% as a bleaching improvement aid when bleaching wood pulp with peroxide. A water-soluble monomer with a molecular weight of 1,000 to 80,000 obtained by using an unsaturated sulfonic acid monomer selected from mol% and sulfonic acid group-containing monomers and their salts in a proportion in the range of 0.1 to 50 mol%. Polymer I from 0.05 to bone dry pulp
A method for bleaching wood pulp, characterized in that an amount of 1 percent by weight is used. 2. The bleaching method according to claim 1, wherein the wood pulp is a high-yield pulp. 3. The bleaching method according to claim 1, wherein the wood pulp is deinked pulp (DIP). 4 Claim 1 in which the wood pulp is kraft pulp (KP) or soda pulp (AP)
Bleaching method described in section.