JP2008013859A - Method for bleaching non-wood pulp without chlorine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for bleaching a non-wood pulp so as to have a high whiteness while minimizing the increase of bleaching cost and also maintaining the viscosity of the pulp not using a chlorine-based chemical but using only a peroxide in bleaching the non-wood pulp. <P>SOLUTION: This method for bleaching the non-wood pulp in a high whiteness includes treating the pulp with a chelating agent or an acid, performing a first stage of bleach treatment by adding a peroxide to the treated pulp and then further adding the peroxide without washing the pulp to perform a second stage of bleach treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for bleaching non-wood pulp, and more particularly to a method for bleaching non-wood pulp without using any chlorine bleach.

  Non-wood pulp is pulp obtained from fibers other than wood fibers. Non-wood plants used for papermaking are mulberry, mitsumata, ganpi, flax, cannabis, kenaf, choma, jute, sunn hemp, cotton, monocotyledonous plants, Manila hemp, sisal, esparto, bamboo, rice straw, wheat straw, sugar cane There are bagasse and reeds.

These plants are pulped by cooking. Examples of the cooking process include a soda method (NaOH), a sulfite method (Na ₂ SO ₄ , NaOH), a kraft method (Na ₂ S, NaOH), a soda ash method (Na ₂ CO ₃ ), and the like. After cooking, beat and wash with a beater. Next, after dust removal, it is bleached by a poucher, a tower or the like. As a bleaching method, hemp pulp (flax, cannabis, jute, etc.) is bleached in three stages of sodium hypochlorite and chlorine-alkali-sodium hypochlorite. Wood bast pulp is bleached with bleaching powder, sodium hypochlorite, sodium chlorite, and the like. Manila hemp pulp is bleached with hydrogen peroxide, bleached powder, chlorine, etc. depending on the application. Grain straw pulp is bleached in three stages: hypochlorite, chlorine-alkali-sodium hypochlorite. Sugarcane bagasse pulp is bleached in three stages: hypochlorite, hydrogen peroxide, chlorine-alkali-sodium hypochlorite.

  As a method of bleaching non-wood pulp with high whiteness, a bleaching method is disclosed in which bast fibers are pulped with an enzyme and then an oxidizing agent, a reducing agent, or a combination thereof (see Patent Document 1). According to this method, a pulp having a high whiteness is obtained when bleached with a chlorine bleach or a combination thereof, but there is a problem that an organic chlorine compound such as dioxin or chloroform is produced and pollutes the environment. Further, when hydrogen peroxide is used as an oxidizing agent, hydrogen peroxide is wastefully decomposed due to a large amount of heavy metals in the pulp, and it is difficult to bleach to high whiteness.

  Non-wood contains a large amount of metal in the fiber because it grows faster than wood and contains a large amount of metal even after pulping. It is difficult to increase the whiteness of non-wood pulp.

  As a method of bleaching with hydrogen peroxide, a bleaching method using a bleaching agent mainly composed of hydrogen peroxide is disclosed as a bleaching method of coconut fiber (see Patent Document 2). This method is a method of bleaching with caustic soda, soda salt and surfactant in addition to hydrogen peroxide. As a hydrogen peroxide stabilizer, a stabilizer containing soda salt as a main component (which seems to be sodium silicate). Is used. However, this stabilizer is insufficient when bleaching at high whiteness, and there is a problem such as generation of scale when used in a large amount.

  As a bast raw material, a mixture of oxalic acid or oxalate, hydrogen peroxide or a hydrogen peroxide generator, an alkali metal carbonate, a chelating agent and water, or a mixture of anthraquinones added thereto, 60 A method of cooking at a temperature of ˜130 ° C. is disclosed (see Patent Document 3). This method discloses cooking, and does not disclose any measures for preventing the decomposition of hydrogen peroxide by heavy metals in the raw material, and the bast pulp cannot be made high in whiteness.

  Although the use of hydrogen peroxide is disclosed as an improved alkaline peroxide treatment method for non-woody lignocellulosic substrates, the objective is to obtain non-woody lignocellulosic agricultural residues that are edible for humans or ruminants It is not intended to bleach to high whiteness (see Patent Document 4).

  In bleaching non-wood pulp with hydrogen peroxide, a method of performing hydrogen peroxide bleaching after pretreatment with hypochlorite and a chelating agent is disclosed as a measure to prevent wasteful decomposition of hydrogen peroxide by a large amount of heavy metals. (See Patent Document 5). This method improves the efficiency of the subsequent hydrogen peroxide bleaching by removing heavy metals, and can be bleached with high whiteness. However, since chlorine compounds are used, organochlorine compounds are produced, which is preferable for the environment. There is no.

As a method for producing high-whiteness non-wood mechanical pulp, a method of producing pulp by bleaching sodium percarbonate or alkali carbonate and hydrogen peroxide as a bleaching solution, and then mechanically defibrating the bleached fiber raw material Is disclosed (see Patent Document 6). In this method, no measures are taken against heavy metals in the pulp, and the pulp cannot be bleached to high whiteness.
JP 54-68402 A JP 60-181390 A JP-A 63-264991 Japanese Patent Laid-Open No. 2-119551 JP 2001-140181 A JP 2003-147690 A

  The object of the present invention is the bleaching of non-wood pulp, using no chlorinated chemicals as a bleaching agent, using only peroxides, minimizing the increase in bleaching cost and maintaining pulp viscosity. It is bleaching wood pulp to high whiteness.

  As a result of diligent research on the bleaching method of non-wood pulp, the present inventors treated non-wood pulp with a chelating agent or acid, and then bleached without washing during the two-stage peroxide treatment. The present inventors have found that a non-wood pulp having a high whiteness can be obtained very effectively. That is, the present invention is as follows.

(1) In the method of bleaching non-wood pulp with high whiteness, the pulp is treated with a chelating agent or acid, a peroxide is added to the treated pulp, the first stage bleaching treatment is performed, and then the washing is not performed. A non-chlorine bleaching method for non-wood pulp, further comprising adding a peroxide to perform the second stage bleaching treatment.
(2) The chlorine-free bleaching method for non-wood pulp according to (1), wherein sodium silicate is added in the first stage bleaching treatment.
(3) The chlorine-free bleaching method for non-wood pulp according to (1), wherein a chelating agent and a magnesium salt are added in the first stage bleaching treatment.
(4) The chlorine-free non-wood pulp according to (1), wherein the chelating agent is at least one selected from an aminocarboxylic acid chelating agent and an aminoalkyl phosphoric acid chelating agent represented by the general formula (1) Bleaching method.

（式中のＸは水素、アンモニウムまたはアルカリ金属を示し、ｍは２〜３の整数、ｎは０〜３の整数を示す。）

(X in the formula represents hydrogen, ammonium or alkali metal, m represents an integer of 2 to 3, and n represents an integer of 0 to 3.)

(5) The chlorine-free bleaching method for non-wood pulp according to (1), wherein the acid treatment temperature is 85 ° C. or higher.
(6) The chlorine-free bleaching method for non-wood pulp according to the above (1), wherein the ratio of the added amount of the first-stage and second-stage peroxides is 1: 9 to 5: 5.
(7) The chlorine-free bleaching method for non-wood pulp according to (1), wherein the peroxide is hydrogen peroxide.
(8) The chlorine-free bleaching method for non-wood pulp according to (1), wherein the non-wood pulp is abaca, kenaf, straw, or bacus.

  According to the present invention, a high whiteness non-wood pulp can be economically obtained using a small amount of hydrogen peroxide. In addition, since hydrogen peroxide is used, harmful substances such as organochlorine compounds remain or are not discharged in the pulp or in the wastewater, so that a very clean pulp can be economically produced. Furthermore, since the chlorine-based compound is not used in the physical properties of the obtained pulp, there is a merit that it can be used for applications that dislike the residue of the chlorine-based compound.

  Non-wood used in the present invention includes mulberry, mitsumata, ganpi, flax, hemp, kenaf, choma, jute, sunn hemp, cotton, manila hemp, sisal hemp, esparto, bamboo, rice straw, wheat straw, sugar cane bagasse, reed, etc. . These non-woods are pulped by a cooking method such as a soda method, a sulfite method, a kraft method, or a soda ash method. These non-wood species and cooking methods are not particularly limited.

  The non-wood pulp cooked by these cooking methods is first treated with a chelating agent (sometimes abbreviated as Q or Q stage). Depending on the state of the pulp, for example, the pulp concentration is 1 to 40% by weight, preferably 2 to 10% by weight, the temperature is 5 to 80 ° C., preferably 10 to 60 ° C., and the treatment time is 5 to 300 minutes, preferably 30 For ~ 180 minutes, the pH is 4-9, preferably 5-8. The Q-staged pulp is separated by a dehydrator and preferably subjected to washing.

  The chelating agent used is at least one chelating agent selected from aminocarboxylic acid chelating agents and aminoalkyl phosphoric acid chelating agents represented by the general formula (1).

（式中のＸは水素、アンモニウムまたはアルカリ金属を示し、ｍは２〜３の整数、ｎは０〜３の整数を示す。）

(X in the formula represents hydrogen, ammonium or alkali metal, m represents an integer of 2 to 3, and n represents an integer of 0 to 3.)

  Specific examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), N-hydroxyethylethylenediamine-N, N ′, N ″ -triacetic acid (HEDTA), and nitrilotriacetic acid (NTA). ), Cyclohexanediaminetetraacetic acid (CyDTA), etc., and salts thereof, aminotrimethylenephosphonic acid (ATMP), ethylenediaminetetramethylenephosphonic acid (EDTMPA), diethylenetriaminepentamethylenephosphonic acid (DTPMPA) as aminoalkyl phosphate chelating agents , Propylenediaminetetramethylene phosphonic acid (PDTMPA), etc., and salts thereof The amount used varies depending on the amount of heavy metals contained in the pulp and water, but is 0 per dry pulp. 01 to 5.0% by weight, preferably 0.05 to 1.0 wt%.

  As a pretreatment for peroxide bleaching, an acid treatment (abbreviated as A or A stage) can be performed instead of the Q stage. Depending on the state of the pulp, for example, the pulp concentration is 1 to 40% by weight, preferably 2 to 10% by weight, the temperature is 5 to 100 ° C, preferably 85 ° C to 95 ° C, and the treatment time is 5 to 300 minutes, preferably 90-180 minutes, the pH is carried out at 1-3.5. The pulp of stage A treatment is separated by a dehydrator and preferably subjected to washing. As the acid for the A-stage treatment, hydrochloric acid, sulfuric acid, nitric acid, sulfurous acid, formic acid, acetic acid and other inorganic acids and organic acids are used.

  The pulp after the A-stage or Q-stage treatment is subjected to the first stage peroxide bleaching (may be abbreviated as P1 or P1 stage). In this treatment, the pulp is bleached by peroxide. As peroxides in the P1 stage, 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. In general, hydrogen peroxide is preferably used. The amount of hydrogen peroxide to be used is 0.05 to 10% by weight, preferably 0.5 to 5% by weight, based on 100% by weight hydrogen peroxide per dry bone pulp.

  Caustic soda, caustic potash, lime, soda ash, etc. can be used as the alkaline agent when hydrogen peroxide is used as the peroxide. Among these, caustic soda can be preferably used because it is inexpensive. The amount of the alkaline agent used is an amount for adjusting the initial bleaching pH to 10.5 to 11.5.

  In the present invention, high-whiteness non-wood pulp can be obtained without a stabilizer, but it may be more preferable to use a peroxide stabilizer depending on the type of non-wood pulp. As the stabilizer, sodium silicate, a magnesium compound, and a chelating agent are used. The amount of sodium silicate used is 1 to 10% by weight per absolutely dry pulp. As the chelating agent, those similar to those used in the Q stage of the pretreatment are used. The amount used is 0.05 to 1% by weight per absolutely dry pulp. When using a chelating agent, it is particularly preferable to use a magnesium compound in combination. As the magnesium compound, magnesium sulfate, magnesium hydroxide, and a magnesium nitrate compound can be used, but generally magnesium sulfate is used. The usage-amount of a magnesium compound is 0.005-1.0 weight% as magnesium ion, Preferably it is 0.01-0.5 weight%.

  The pulp concentration in the P1 stage is 5 to 35%, preferably 10 to 30% by weight. The temperature is 35 to 90 ° C, preferably 40 to 70 ° C. The processing time is 15 to 120 minutes.

  The pulp obtained by Q or A-P1 of the present invention is bleached by the second stage hydrogen peroxide bleaching (sometimes abbreviated as P2 or P2 stage) without washing. The P2 stage is not bleached and is subsequently bleached with hydrogen peroxide and alkaline agent. The amount of hydrogen peroxide to be used is 0.05 to 10% by weight, preferably 0.5 to 5% by weight, based on 100% by weight hydrogen peroxide per dry pulp. The alkaline agent is the same as P1, and the amount used is an amount for adjusting the initial bleaching pH to 10.5 to 11.5. The P2 stage pulp concentration is 5-30%, preferably 10-30% by weight. The temperature is 35 to 90 ° C, preferably 40 to 70 ° C. The treatment time is 15 to 300 minutes, preferably 30 to 180 minutes.

Next, the method of 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 non-wood pulp used and the method of analytical evaluation are as follows.
Pulp type: Philippine Abaca pulp (caustic soda cooking)
Hunter whiteness: 39.1%
Metal content: Cu1.3ppm Fe104ppm Mn87ppm
Hexeneuronic acid (HexA) amount: 35.20 μmol / g Pulp analysis evaluation ・ Whiteness: JIS-P8123 (Hunter whiteness method)
Discoloration test: put in an oven at 80 ° C.-RH 65% and heat-treated for 24 hours. Thereafter, the whiteness was measured and the PC value was calculated.

Example 1
Philippine abaca pulp was bleached with Q-P1P2 according to the following conditions.
・ Q treatment (chelating agent treatment)
1) DTPA: 0.2%, treatment initial pH: 6.0, pulp concentration: 10%, treatment temperature: 30 ° C., treatment time: 2 hours.
2) After the treatment, it was diluted with water to a pulp concentration of 2.5% and then dehydrated to a pulp concentration of 20%.
P1 treatment (peroxide treatment)
3) H ₂ O ₂ : 1.5%, NaOH: 0.8%, pulp concentration: 10%, treatment temperature: 70 ° C, treatment time: 2 hours.
・ No cleaning ・ P2 treatment (peroxide treatment)
4) H ₂ O ₂ : 1.5%, NaOH: 0.2%, pulp concentration: 10%, treatment temperature: 70 ° C, treatment time: 2 hours.
-Washing and paper making 5) After completion of the reaction, the pulp was diluted and disaggregated to a pulp concentration of 0.8% with water, adjusted to pH 5.5 with sulfite water and dehydrated on a Buchner funnel.
6) Hunter whiteness was measured after air drying overnight.

Example 2
The same procedure as in Example 1 was performed except that 3% of sodium silicate was added during the P1 treatment of Example 1.

Example 3
The same procedure as in Example 1 was performed except that DTPA 0.25% and MgSO ₄ 1.5% were added during the P1 treatment of Example 1.

Comparative Example 1
The pulp after the Q treatment in Example 1 was carried out in the same manner as in Example 1 except that the pulp was bleached with a single stage of hydrogen peroxide under the following conditions.
H ₂ O ₂ : 3.0%, NaOH: 2.0%, pulp concentration: 10%, treatment temperature: 70 ° C., treatment time: 3 hours.

Comparative Example 2
The pulp after the Q treatment of Example 2 was carried out in the same manner as in Example 2 except that the pulp was bleached with a single stage of hydrogen peroxide under the following conditions.
H ₂ O ₂ : 3.0%, NaOH: 2.0%, sodium silicate: 3.0%, pulp concentration: 10%, treatment temperature: 70 ° C., treatment time: 3 hours

Comparative Example 3
The pulp after the Q treatment in Example 3 was carried out in the same manner as in Example 3 except that the pulp was bleached with a single stage of hydrogen peroxide under the following conditions.
H ₂ O ₂ : 3.0%, NaOH: 2.0%, DTPA 0.25%, MgSO ₄ 1.5%, Pulp concentration: 10%, Treatment time: 3 hours

  As shown in Table 1, in the case of the present invention, higher whiteness was obtained even without a stabilizer during hydrogen peroxide bleaching, compared to hydrogen peroxide single-stage bleaching. In the present invention, the stability of the hydrogen peroxide in the P2 stage is greatly improved.

Example 4
Instead of the Q process of Example 1, the same process as in Example 1 was performed except that the A process under the following conditions was performed.
・ A treatment (acid treatment)
1) H2SO4: 2%, initial treatment pH: 2.0, pulp concentration: 10%, treatment temperature: 50 ° C., treatment time: 2 hours.

Example 5
The same procedure as in Example 2 was performed except that the A process was performed instead of the Q process in Example 2.

Example 6
The same procedure as in Example 3 was performed except that the A process was performed instead of the Q process in Example 3.

Comparative Example 4
The same procedure as in Example 1 was performed except that the A process was performed instead of the Q process in Comparative Example 1.

Comparative Example 5
It carried out similarly to the comparative example 2 except having implemented A process instead of Q process of the comparative example 2.

Comparative Example 6
It carried out similarly to the comparative example 3 except having implemented A process instead of Q process of the comparative example 3.

  As the pretreatment in Table 2, the effect of the present invention when acid treatment was performed was described. As a result, the present invention was excellent in the A process as well as the Q process.

Example 7
The same procedure as in Example 4 was performed except that the treatment temperature A in Example 4 was 85 ° C.

Examples 8-11
In Example 1, the ratio of the addition amount of hydrogen peroxide of P1 and P2 was set to 1: 9, 2.5: 7.5, 7.5: 2.5, 9: 1. Went to.

  The ratio of P1 and P2 is shown in Table 4. As a result, the range of 1: 9 to 5: 5 showed the best bleaching result. By treating with a small amount of hydrogen peroxide at P1, the stability of hydrogen peroxide at P2 is improved and a high whiteness pulp is obtained. Therefore, in terms of equipment, P1 may be a smaller bleaching tower than P2, and there is an advantage that the equipment cost for bleaching at high whiteness can be minimized.

Claims (8)

  In the method of bleaching non-wood pulp to a high degree of whiteness, the pulp is treated with a chelating agent or acid, peroxide is added to the treated pulp, the first stage is bleached, and then further peroxidized without washing. A chlorine-free bleaching method for non-wood pulp, characterized in that a second stage bleaching treatment is performed by adding a product.   The chlorine-free bleaching method for non-wood pulp according to claim 1, wherein sodium silicate is added in the first stage bleaching treatment.   The chlorine-free bleaching method for non-wood pulp according to claim 1, wherein a chelating agent and a magnesium salt are added in the first stage bleaching treatment. The non-wood pulp chlorine-free bleaching method according to claim 1, wherein the chelating agent is at least one selected from an aminocarboxylic acid chelating agent and an aminoalkyl phosphoric acid chelating agent represented by the general formula (1).

(X in the formula represents hydrogen, ammonium or alkali metal, m represents an integer of 2 to 3, and n represents an integer of 0 to 3.)   The chlorine-free bleaching method for non-wood pulp according to claim 1, wherein the acid treatment temperature is 85 ° C or higher.   The method for chlorine-free bleaching of non-wood pulp according to claim 1, wherein the ratio of the added amount of the peroxide in the first stage and the second stage is 1: 9 to 5: 5.   The method for chlorine-free bleaching of non-wood pulp according to claim 1, wherein the peroxide is hydrogen peroxide.   The chlorine-free bleaching method for non-wood pulp according to claim 1, wherein the non-wood pulp is abaca, kenaf, straw or bacus.