JPH049233B2 - - 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. Deinked pulp (DIP) has shown a significant increase 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 bleaching powder, uses a combination of chlorine-based oxidizing bleaches such as bleaching powder, chlorine diate, and sodium chlorite, and sulfur-containing reducing bleaches such as thiosulfates, sulfites, and bisulfites. 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. In the bleaching of wood pulp such as high-yield pulp, deinked pulp, and chemical pulp as described below, the amount of peroxide bleaching agents used is 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 simply referred to as an aid). . Known auxiliary agents include aminocarboxylate salts, sulfites, and silicates such as ethylenediaminetetraacetic acid (EDTA), diethylenediaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), and diethylenetriaminepentamethylene phosphate (DTPMPA). , condensed phosphates such as tripolyphosphate, alkaline earth metal compounds such as magnesium and calcium, and aluminum compounds. 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 by dissolving 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 salts thereof, 3-methyl-3-buten-1-ol, polyethylene glycol mono-3-methyl-3-butene-1
- The molecular weight obtained by using a hydroxyl group-containing monomer selected from all ether, glycerol monoallyl ether, and 2-hydroxyethyl (meth)acrylate in a proportion ranging from 0.1 to 50 mol%
The present invention relates to a method for bleaching wood pulp, characterized in that a water-soluble copolymer (I) of ~80,000 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 the water-soluble copolymer (I) is used as an auxiliary agent, delignification is promoted, and Mn eluted from wood pulp or present in working water,
Chelates polyvalent metal ions such as Cu, Fe, Ni, and Co, suppressing wasteful peroxide decomposition, and suppressing autooxidation of chromophores, especially quinones, in wood.
Possible effects include preventing insoluble substances such as colored metal hydroxides such as Fe, Cu, and 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, or monovalent metals thereof, Examples include partially neutralized products and completely neutralized products using 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. Further, as the other hydroxyl group-containing monomer of the raw material monomer for obtaining the water-soluble copolymer (I) used in the present invention, 3-methyl-3-buten-1-ol (isoprenol) , polyethylene glycol mono-3-methyl-3-butene-1
At least one selected from -ol ether, glycerol monoallyl ether, and 2-hydroxyethyl (meth)acrylate can be mentioned. In order to obtain the water-soluble copolymer (I) used in the present invention, these raw material unsaturated monocarboxylic acid monomers and hydroxyl group-containing 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 addition, alcohols such as methanol and isopropyl alcohol,
In the case of polymerization in organic solvents such as ether systems such as tetrahydrofuran and dioxane, aromatic systems such as benzene, xylene, and toluene, or ketone systems such as methyl ethyl ketone and methyl isobutyl ketone, benzoyl peroxide, lauroyl peroxide, peracetic acid, etc. organic peroxide system; azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4
It can be produced by a conventional method using an oil-soluble azo compound such as -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 hydroxyl group-containing monomer may be added to the extent that the effects of the present invention are not impaired. Of course, copolymerization is possible. 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; 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)acrylate, 2-hydroxysulfopropyl (meth)acrylate, sulfoethylmaleimide or their monovalent metals , divalent metals, ammonia, unsaturated sulfonic acid monomers such as partially neutralized products and completely neutralized products with organic amines; cationic monomers such as dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, etc. Nitrile monomers such as (meth)acrylonitrile; Phosphorus-containing monomers such as (meth)acrylamidomethanephosphonic acid, (meth)acrylamidemethanephosphonic acid methyl ester, and 2-(meth)acrylamido-2-methylpropanephosphonic acid Monomers; α- such as ethylene, propylene, 1-butene, isobutylene, α-amylene, 2-methyl-1-butene, 3-methyl-1-butene (α-isoamylene), 1-hexene, 1-heptene, etc. Examples include olefinic monomers; crotonic acid; unsaturated dicarboxylic acid monomers such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and aconitic acid. The molecular weight of the water-soluble copolymer (I) is 1000
~80000 can be effectively used. If the molecular weight is outside this range, the bleaching properties will not be sufficient. In order to peroxide bleach the wood pulp in the method of the present invention using the water-soluble copolymer (I) as an auxiliary agent, a conventional peroxide bleaching method may be used.
More specifically, this will be clear from the Examples described later. In the present invention, the water-soluble copolymer () 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. Further, even if the amount used is larger than the above range, bleaching properties commensurate with the increased amount cannot be obtained, and on the contrary, the COD load of the wastewater increases, which is not preferable. In carrying out the present invention, the water-soluble copolymer (I) may include conventionally used aminocarboxylate salts, sulfites, silicates, condensed phosphates such as tripolyphosphate, magnesium, calcium, etc. Of course, it is also possible to use it in combination with auxiliary agents such as alkaline earth metal compounds and aluminum compounds. In addition, the water-soluble copolymer (I) can be used not only as an auxiliary agent in peroxide bleaching as in the present invention, but also as chlorine, bleaching powder, chlorine dioxide, etc., although the effect is slightly inferior.
It is also effective as an auxiliary agent for chlorine-based oxidizing bleaches such as chlorite, and sulfur-containing reducing bleaches such as sodium hydrosulfite, zinc hydrosulfite, thiosulfate, sulfite, and bisulfite. In addition, water-soluble copolymer (I) can be used not only as an auxiliary agent during bleaching with peroxide.
It also exhibits an excellent bleaching enhancement effect when used in the so-called pre-treatment process 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%. This was mixed with 1.2 parts of a 5% aqueous solution (0.2% based on the pulp) of acrylic acid/isoprenol (molar ratio 75/25) copolymer sodium salt having a molecular weight of 20,000 as an auxiliary agent and 35% peroxide as a peroxide under low-speed stirring. Hydrogen oxide water 1.71 parts (2% based on pulp)
After adding 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 the whiteness was measured using an air-dried Hunter whiteness meter. The results obtained are shown in Table 1. Examples 2 to 13 A predetermined amount of the water-soluble copolymer (I) shown in Table 1 was used as an auxiliary agent in place of the acrylic acid/isoprenol (molar ratio 75/25) copolymer sodium salt used in Example 1. The whiteness of the handmade sheet was measured in exactly the same manner as in Example 1, except that . 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 The same procedure was carried out 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. The whiteness of the handmade sheet was measured in exactly the same manner as in Example 1. The results obtained are shown in Table 1.

【table】

[Table] Comparative Examples 1 to 16 Examples were carried out except that the predetermined amount of auxiliary agent shown in Table 2 was used in place of the acrylic acid/isoprenol (molar ratio 75/25) copolymer sodium salt used in Example 1. The whiteness of the handmade sheet was measured in exactly the same manner as in Example 1. 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.
1,500 copies and 75 copies of 2 cm x 2 cm shredded newspaper waste 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 was added to acrylic acid/isoprenol with a molecular weight of 20,000 as an auxiliary agent (mole ratio 75/isoprenol).
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
Disaggregated for 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°C for 10 minutes, and then filtered through a standard mesh sieve and dehydrated to a concentration of 10%. Next, the pulp slurry was diluted to a concentration of 1% and adjusted to pH 5.3 using aluminum sulfate. 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/isoprenol (mol 75/
25) 0.3% copolymer sodium salt, 0.1% anthraquinone, 3% hydrogen peroxide, 25% sodium hydroxide, and ion-exchanged water with a liquid ratio of 4/Kg were charged and cooked at 170°C for 15 hours. next,
After washing with water, it 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 0.1% of acrylic acid/isoprenol (mole ratio 75/25) copolymer sodium salt with a molecular weight of 20,000 as an auxiliary agent and peroxide are added to the selected soda pulp obtained in the first step. 3% hydrogen and 4% sodium hydroxide were added and bleaching was carried out at 90°C for 1 hour. Table 5 shows the physical properties of the bleached soda pulp obtained. 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】

[Table] Comparative Example 44 Instead of the acrylic acid/isoprenol (molar ratio 75/25) copolymer sodium salt used in Example 32, an acrylic acid/α-hydroxyacrylic acid (molar ratio 75/25) copolymer with a molecular weight of 20,000 was used. The physical properties of soda pulp were measured in the same manner as in Example 32, except that the same amount of polymer sodium salt was used. The results obtained are shown in Table 7.

[Table] (Effects of the invention) When bleaching wood pulp using a peroxide bleaching agent, a specific water-soluble copolymer (I) in an amount of 0.05 to 1 weight percent based on the bone dry pulp is used as an auxiliary agent. According to the bleaching method of the present invention, which is used as Bleaching performance is significantly improved with a small amount of auxiliary agent. Moreover, the water-soluble copolymer (I) does not generate insoluble salts during bleaching operations, so it does not cause scaling problems, nor does it cause environmental pollution problems such as corrosion of bleaching equipment or 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. Mol% and hydroxyl group-containing monomer selected from 3-methyl-3-buten-1-ol, polyethylene glycol mono-3-methyl-3-buten-1-ol ether, glycerol monoallyl ether, and 2-hydroxyethyl (meth)acrylate. The molecular weight obtained by using the polymer in a proportion in the range of 0.1 to 50 mol% is 1000 to 1000.
1. A method for bleaching wood pulp, which comprises using a water-soluble copolymer (I) of 80,000 in an amount of 0.05 to 1 percent by weight based on bone dry pulp. 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.