JPH01148890A - Method for bleaching wood pulp - Google Patents

Abstract

PURPOSE: To bleach wood pulp using an oxidative bleaching agent under a low-toxic condition at a low cost without any scale trouble by using a specific water-soluble copolymer as an auxiliary. CONSTITUTION: Wood pulp is bleached using a peroxide together with, as a bleaching-promotive auxiliary, 0.05-1 wt.%, based on the dry pulp, of a water-soluble copolymer 1,000-80,000 in molecular weight made from (A) 50-99.9 mol% of an unsaturated monocarboxylic acid-based monomer selected from acrylic acid, methacrylic acid and salts thereof and (B) 0.1-50 mol% of an unsaturated sulfonic acid-based monomer selected from sulfonic acid group-contg. monomers and salts thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for bleaching wood pulp, and more specifically, peroxide is used to bleach mechanical pulp (MP) and chemical mechanical pulp (C).
High-yield pulp such as GP), deinked pulp (DIP)
When bleaching chemical pulp such as soda pulp (AP) and kraft pulp (KP) obtained by cooking with an alkaline solution of hydrogen peroxide, a specific water-soluble copolymer is used as a bleaching improvement aid. Relating 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 hydrosulfide, zinc hydrosulfide, etc. Although reduction bleaching has the advantage of being a relatively inexpensive bleaching method, it does not have sufficient bleaching properties and is limited to low whiteness pulps.
In recent years, the number of days in which reducing bleach is used has been decreasing.

Deinked pulp (DIR) has shown a significant increase in recent years,
As a bleaching method, an oxidative bleaching method using hydrogen peroxide is mainly used.

Bleaching of chemical pulp such as soda pulp (AP) and kraft pulp (KP) is performed using chlorine-based oxidizing bleaches such as chlorine, bleaching powder, chlorine dioxide, and sodium chlorite, as well as thiosulfates, sulfites, and bisulfites. A so-called multi-stage bleaching method that combines sulfur-containing reducing bleaching agents 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 mentioned above, the usage of peroxide bleaching agents has been rapidly increasing in the bleaching of wood pulp such as high-yield pulp, deinked pulp, and chemical pulp.

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 auxiliaries include, for example, ethylenediaminetetraacetic acid (E
DTA)・Diethylenediaminepentaic acid M (DTPA)
)・Nitrilotriacetic acid III (NTA)・Aminocarboxylate salts such as diethylenetriaminepentamethylene phosphate (DTPMPA), condensed phosphates such as sulfites, silicates, and tripolyphosphates, alkaline earth metals such as magnesium and calcium. Scrap compounds, aluminum compounds, etc. 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. In addition, 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. This tends to cause scaling problems, such as the formation of clogged areas on the finer plate. Condensed phosphate is
It flows into the sea through rivers as wastewater and becomes a causative agent of red tide. Furthermore, when used at high temperatures such as Ritziner bleaching, the condensed phosphate is decomposed into phosphoric acid, forming insoluble salts with the above-mentioned polyvalent metals, which tends to cause skenyl trouble. 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, Japanese Patent Application Laid-Open No. 52-1033
No. 86 proposes the use of α-hydroxyacrylic acid-based polymers. However, this polymer does not have good bleaching properties when used as an aminocarboxylic acid auxiliary agent, and is extremely expensive, so it has not been put to practical use yet.

(Problems to be solved by the invention) The present invention solves the problems of hydrogen peroxide, sodium peroxide, percarbonate,
When bleaching wood pulp using oxidizing bleaches such as perborate, peracetic acid, and ozone, use a specific inexpensive auxiliary agent that exhibits a remarkable bleaching enhancement effect even in relatively low amounts. The present invention provides a method for bleaching wood pulp that can overcome the above-mentioned problems of conventional auxiliary agents.

(Means and effects for solving the problems) The present invention has the following features:
When bleaching wood pulp with peroxide, an unsaturated monocarboxylic acid selected from acrylic acid, methacrylic acid, and their salts is used as a bleaching improvement aid.
99.9 mol% and 0.1 of an unsaturated sulfonic acid monomer selected from sulfonic acid group-containing monomers and their salts
The intermolecular ratio obtained by using a proportion in the range of ~50 mol% is 1
．． 000~s o, o o o 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, water-soluble copolymer (I)
When used as an auxiliary agent, ■ delignification is promoted, ■
Mn 1CU eluted from wood pulp or present in industrial water.

By chelating polyvalent metal ions such as Fe, Ni, Go, etc., wasteful peroxide decomposition is suppressed; ■Autoxidation of chromophores, especially quinones, in wood is suppressed; ■l”e, C
Possible effects include preventing insoluble substances such as colored metal hydroxides such as u and Ni from (re)adhering to the 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 with 21iii 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; alkanols such as monoethanolamine, jetanolamine, triethanolamine, monoisopropanolamine, and dimethylethanolamine. Amines; examples include pyridine. 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-acrylamido-2-methylpropanesulfonic acid,
3-7 Ryloxy 2-hydroxypropanesulfonic acid,
Sulfoethyl (meth)acrylate, sulfopropyl (
meth)acrylate, 2-hydroxysulfopropyl (
Examples include sulfonic acid group-containing monoproducts such as meth)acrylate and sulfoethylmaleimide, or partially or completely neutralized products thereof with monovalent metals, divalent metals, ammonia, and organic amines. Monovalent metals include sodium, potassium, etc., and divalent metals include calcium, magnesium, zinc, etc. Also,
Organic amines include alkylamines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, and triethylamine; alkanolamines such as monoethanolamine, jetanolamine, triethanolamine, monoisopropanolamine, and dimethylethanolamine. ; Examples include pyridine. Among them, sodium is the most preferred because it is inexpensive and industrially easily available.

To obtain the water-soluble copolymer (I) used in the present invention,
These raw material 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. Also,
When polymerizing in organic solvents such as alcohols such as methanol and isopropyl alcohol, ethers such as tetrahydrofuran and dioxane, aromatics such as benzene, xylene and toluene, or ketones such as methyl ethyl ketone and methyl isobutyl ketone, peroxidation Organic peroxides such as benzoyl, lauroyl peroxide, peracetic acid, etc.; oil-soluble azo compounds such as azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc. It can be produced by a conventional method as a polymerization catalyst.

It is of course possible to copolymerize other monomers that are copolymerizable with the spinning wheel convex body and the unsaturated sulfonic acid monomer. Examples of other monopolymers that can be copolymerized include (meth)acrylamide, t-butyl (meth)acrylamide, and other amide mu-forms; (meth)acrylic esters, styrene, 2-methylstyrene, vinyl acetate; Hydrophobic monomers such as 3-methyl-3-buten-1-ol (isoprenol), 3-methyl-2-buten-1-ol (prenol), 2-methyl-3-buten-2-ol (isoprenol) 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,
Hydroxyl group-containing unsaturated monomers such as polypropylene glycol monoallyl ether, glycerol monoallyl ether, α-hydroxyacrylic acid, N-methylol (meth)acrylamide, glycerol mono(meth)acrylate, and vinyl alcohol; dimethylaminoethyl (meth) Cationic bodies such as acrylate and dimethylaminopropyl: Nitrile-based 01 suspensions such as (meth)acrylonitrile; (meth)acrylamide methanephosphonic acid, (meth)acrylamide methanephosphonic acid methyl ester, 2-(meth)acrylamide-2- Phosphorous monomers such as methylpropanephosphonic acid; ethylene, propylene, 1-butene, isobutylene, α-amylene, 2-methyl-1-butene, 3-methyl-1-butene (α-isoamylene), 1-hexene, 1 Examples include α-olefin monomers such as -heptene; crotonic acid: unsaturated dicarboxylic acid monomers such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and aconitic acid.

The intermolecular distance of water-soluble copolymer (I) is 1,00
0-8 0. A value in the range 0 0 0 is effectively used. Those outside this molecular layer range do not have sufficient bleaching properties.

In order to bleach wood pulp with peroxide in the method of the present invention using the water-soluble copolymer (I) as an auxiliary agent, conventionally known peroxide bleaching techniques may be used, and specifically, the method described below may be used. This should be clearer than the example.

In the present invention, the water-soluble copolymer (I) is used in an amount of 0.05 to 11111 percent based on the bone dry pulp. If the number of containers used is less than the above range, sufficient bleaching properties cannot be obtained. Furthermore, even if the amount used is greater 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 addition, when carrying out the present invention, water-soluble copolymer (I)
can be used in combination with conventionally used auxiliaries such as aminocarboxylate, sulfite, silicate, condensed phosphate such as tripolyphosphate, alkaline earth metal compounds such as magnesium and calcium, and aluminum compounds. Of course, it is also possible to use it.

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 a chlorine-based agent such as chlorine, bleaching powder, chlorine dioxide, and chlorite, although the effect is slightly inferior. It is also effective as an auxiliary agent for oxidizing bleaches and sulfur-containing reducing bleaches such as sodium hydrosulfide, zinc hydrosulfide, thiosulfates, sulfites, and bisulfites.

Furthermore, the 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 moe 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. Incidentally, parts and % in the examples indicate heavy weight and weight %, respectively.

Example 1 Volume ff1500ad! 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%), is placed in a beaker, and then the final pulp concentration is 12%. Added the necessary water. Add a molecular layer of 20% to this as an auxiliary agent under low speed stirring. OOO acrylic M/3-allyloxy 2-hydroxypropanesulfonic acid (molar ratio 75/25
) 1.2 parts of 5% aqueous solution of copolymer sodium salt (0.2% based on pulp), 1.2 parts of 35% hydrogen peroxide solution as peroxide.
71 parts (2% based on pulp) and 10% as alkaline agent
After adding 6.0 parts of sodium carbonate aqueous solution (2% based on pulp), p + was reduced to 10 parts using 3% sodium hydroxide aqueous solution.
．． It was set as 8.

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 adjusted to 60° C. for 3 hours.

A portion of the thus bleached pulp slurry was diluted to 3% and adjusted to pH 6.0 using sulfite water.

Using this diluted and pH-adjusted pulp slurry, T
Two handmade sheets were prepared using the APP1 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 M/3-allyloxy 2-hydroxypropanesulfone WI used in Example 1 (molar ratio 75/25)
Example 1 except that a predetermined amount of the water-soluble copolymer shown in Table 1 was used as an auxiliary agent instead of the copolymer sodium salt.
The whiteness of the handmade sheet was measured in exactly the same manner.

The results obtained are shown in Table 1.

Example 14 ゛The white color of the handmade sheet was prepared in the same manner as in Example 1 except that 6.0 parts of 10% sodium silicate aqueous solution was used instead of 6.0 parts of 10% sodium carbonate aqueous solution in Example 1. The degree of The results obtained are shown in Table 1.

Examples 15-16 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 the same manner as in Example 1 except that the whiteness of the handmade sheet was measured. The results obtained are shown in Table 1.

Comparative Examples 1 to 16 In place of the acrylic acid/3-allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) copolymer sodium salt used in Example 1, a predetermined amount of auxiliary agent shown in Table 2 was used. 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 2.

Example 17 1500 parts of 65°C warm water and 7 pieces of waste newspaper shredded into 2zX2z were placed in a standard disintegrator according to JIS P-8209.
5 parts were added and lightly disintegrated for 1 to 2 minutes. The waste paper pulp slurry obtained by scraping off the sample adhering to the propeller and inner wall contains 20. OOO acrylic acid/3-allyloxy-2-human 0oxypropanesulfonic acid (molar ratio 75/25) copolymer sodium salt 0.1% (based on pulp), hydrogen peroxide 1.5% (based on pulp) , 1.5% sodium hydroxide (based on pulp), 3% sodium silicate No. 3 (based on pulp), and 0.2% deinking agent (sodium oleate) (based on pulp) were added, and 6
Disintegration was carried out at 0°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%, subjected to a 70-station at 30°C for 10 minutes, filtered through a standard mesh sieve, and dehydrated to a concentration of 10 parts. 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 weight of 100 g/7 FL2 was prepared using a Tarapy 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 to 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, and the whiteness of the sheets 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 0 hydrogen peroxide instead of 1.5% hydrogen peroxide (based on pulp)
．． A handmade sheet was prepared in exactly the same manner as in Example 17, except that 5% (based on pulp) and peracetic acid 1.0% (based on pulp) were used, and its whiteness was measured.

The results obtained are shown in Table 3.

Comparative Examples 17 to 30 Handmade sheets were prepared in exactly the same manner as in Example 17, except that the auxiliaries shown in Table 4 were used, and the whiteness of the sheets 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 obtained results are shown in Table 4.

Example 32 ■First step 5 In an autoclave made of LIS316, cedar chips with a length of about 4 cm and a width of about 4 CIRN thickness of about 0.5α and a cedar chip with an absolute dry weight of 20 OOO as an auxiliary agent were added.
Acrylic R/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 41/9 was added, and the mixture was cooked at 170°C for 1.5 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.), and the yield was 41.
．． A 5% graded soda pulp was obtained. 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 has an intermolecular content of 20% as an auxiliary agent. Acrylic acid that is OOO/3-
10.1% sodium allyloxy-2-hydroxypropanesulfonic acid (molar ratio 75/25) copolymer, 3% hydrogen peroxide and 4% sodium hydroxide were added, and bleaching was performed at 90°C for 1 hour. Table 5 shows the physical properties of the bleached soda pulp obtained.

(2) Second step, second step, second step, first step was repeated to perform bleaching. Table 5 shows the physical properties of the bleached soda pulp obtained.

Examples 33 to 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.

Comparative Examples 32 to 43 Cooking and bleaching were carried out in exactly the same manner as in Example 32, except that the specified cans of auxiliaries shown in Table 6 were used.

The results obtained are shown in Table 6.

(Effect of the invention) When bleaching wood pulp using a peroxide bleaching agent, 0.05 to 1 weight percent m of a specific water-soluble copolymer (I) is used as an auxiliary agent based on the bone dry pulp. According to the bleaching method of the present invention used, compared to conventional bleaching methods using auxiliary agents such as aminocarboxylate, sulfite, silicate, condensed phosphate, alkaline earth metal compound, etc.
Bleaching properties are significantly improved with a small amount of auxiliary agent m.

In addition, the water-soluble copolymer (I) does not generate insoluble salts during bleaching operations, so it does not cause scaling problems and does not cause environmental pollution problems such as corrosion of bleaching equipment and red tide. There is no.

Claims (1)

[Scope of Claims] 1. An unsaturated monocarboxylic acid monomer selected from acrylic acid, methacrylic acid, and their salts as a bleaching improvement aid when bleaching wood pulp with peroxide.
Unsaturated sulfonic acid monomer selected from 0 to 99.9 mol% and sulfonic acid group-containing monomers and their salts 0
．． A water-soluble copolymer (I) with a molecular size of 1,000 to 80,000 obtained using a proportion in the range of 1 to 50 mol%
A method for bleaching wood pulp, which comprises using 0.05 to 1 percent by weight of 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. The bleaching method according to claim 1, wherein the wood pulp is kraft pulp (KP) or soda pulp (AP).