JP2005082948A - Bulky deinked pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide bulky deinked pulp having whiteness the same as that of conventional hydrogen peroxide bleaching processed pulp without using an additive and without treating to age for a long time in a deinked pulp production process including a bleaching process. <P>SOLUTION: The bulky deinked pulp is produced by adding an alkaline agent and hydrogen peroxide in a preceeding step and adding an organic peracid precursor which produces peracetic acid by reacting with hydrogen peroxide in a deinking pulp production process including a bleaching process comprising 2 steps, the preceeding step and a latter step. Preferably, the bleaching time of the bulky deinked pulp after adding the organic peracid precursor is 1-30 minutes and pH is 8-10.5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to deinked pulp, and more particularly, to a bulky deinked pulp processed by a deinked pulp manufacturing process including a bleaching process, and in particular, the bleaching process is composed of two stages, a first stage and a second stage, and an alkali is used in the first stage The present invention relates to a bulky deinked pulp produced by adding chemicals and hydrogen peroxide and adding an organic peracid precursor at a later stage.

The importance of recycling recycled paper is increasing from the viewpoint of effective use of resources and environmental protection. In the used paper recycling process, generally used paper is depulverized together with alkaline chemicals and surfactants using a pulping machine such as a pulper, and then used paper pulp is added. The pulp fiber is bleached with an alkaline chemical, the pulp fiber is swollen with alkaline chemicals, the ink is peeled off from the pulp, and the whiteness of the pulp is increased with hydrogen peroxide. Next, in the flotation process, ink particles are attached to and floated on the bubbles, and the ink particles are separated from the pulp.

In the hydrogen peroxide bleaching step, alkaline chemicals such as sodium hydroxide and potassium hydroxide are added to perform bleaching under high pH conditions in order to enhance the bleaching effect. In addition, sodium silicate or the like may be used in combination in order to suppress wasteful decomposition of hydrogen peroxide.

However, there are some problems with recycled paper made from waste paper. Among them, it was an important problem in expanding the use of waste paper that the bleaching process was brought to a high pH condition by alkali chemicals, the flexibility of deinked pulp was increased, and the bulkiness was lowered.

As a method for producing a bulky paper from deinked pulp, a method using a bulking agent and an additive for recycling used paper is shown (for example, see Patent Documents 1 and 2). However, the method using these additives does not modify the deinked pulp itself to a bulky property.

As a method for producing a bulky deinked pulp in the deinked pulp manufacturing process, a method for controlling the interface potential between the ink particles and the pulp in the flotation process is shown (for example, see Patent Document 3). However, this method requires new equipment that can measure and control the interface potential in the flotation process. Moreover, after aging a used printing paper with an alkali, the method of neutralizing with an acid and applying a high shear force and performing disaggregation and ink peeling is shown (for example, refer patent document 4). However, this method is not sufficiently improved in bulkiness and needs to be neutralized with an acid after alkali ripening, which requires complicated operations. Furthermore, it is necessary to newly establish an aging process, and it requires steam and alkaline chemicals, which is difficult in terms of economy.

As a technique for modifying the pulp itself to be bulky, a method using pulp treated with an enzyme that decomposes polysaccharides or a microorganism that produces the enzyme is shown (for example, see Patent Document 5). However, since this method requires a reaction time of 1 to 10 days for the enzyme treatment, it is necessary to newly establish a treatment process and control the pH and temperature during that time. There is difficulty in economy. Furthermore, in the enzyme treatment, a decrease in pulp yield and a decrease in pulp viscosity are also problematic. Moreover, the method of utilizing a partial mercerized pulp is shown (for example, refer patent document 6). However, this partial mercerization requires a long time for the treatment, and the cellulose structure of the partial mercerized pulp is different from that of normal papermaking pulp.

On the other hand, many of the conventionally proposed deinking pulp bleaching methods are related to improving the whiteness of the deinked pulp and improving the ink peelability, and the bulkiness of the deinked pulp sheet has been sufficiently studied. It's hard to say. For example, a method has been shown in which waste paper raw materials are disaggregated, dehydrated, the raw materials are digested, delignification treatment with oxygen is performed, and further, multistage bleaching is performed (see, for example, Patent Document 7). Similarly, a method of using dithionite or thiourea dioxide after bleaching waste paper with hydrogen peroxide while disaggregating it in the earth kettle is disclosed (for example, see Patent Document 8). Moreover, the method of implementing an alkali immersion process for 30 minutes or more by strong alkalinity is shown (for example, refer patent document 9). Furthermore, a method using on-site production thiourea dioxide is shown (for example, see Patent Documents 10 to 11). However, any of the above methods improves the bleaching effect or ink peeling effect of deinked pulp, and is not necessarily effective as a measure for increasing the bulk. In addition, a pulp bleaching method using an agglomerate containing a bleach activator is shown (for example, see Patent Document 12). However, this method is a one-step bleaching method using a peracid generated by a bleach activator and aims to improve the bleaching effect, and does not show a bulking effect. Since it is necessary to bleach the pulp, it is assumed that the flexibility of the pulp increases and the bulkiness decreases. In addition, a method is shown in which an aromatic organic anhydride is added to a pulp after hydrogen peroxide treatment and reacted with residual hydrogen peroxide (see, for example, Patent Document 13). However, this method also improves the bleaching effect of the pulp, and no bulk increase effect is shown. Also, the amount of aromatic organic acid added to the pulp is large, which is not realistic.
JP 2003-96693 A JP 2002-129497 A JP 09-324381 A Japanese Patent Laid-Open No. 11-200269 Japanese Patent Application Laid-Open No. 07-54293 Japanese Patent Application Laid-Open No. 07-189168 JP 2000-27085 A Japanese Patent Laid-Open No. 08-35188 JP 2002-249993 A Japanese Patent Laid-Open No. 07-82243 JP 2001-316994 A Japanese translation of PCT publication No. 2002-525453 Japanese Patent Laid-Open No. 06-158574

When trying to obtain a bulky deinked pulp in the deinked pulp manufacturing process, a method of using an additive, a method of manufacturing a bulky deinked pulp in the deinked pulp manufacturing process, or modifying the pulp itself to be bulky However, there are many methods that require long-time treatment, those that require new equipment, and those that cannot be sufficiently improved in bulkiness.

That is, the present invention provides a whiteness equivalent to that in a normal hydrogen peroxide bleaching step without using additives, aging for a long time, or processing in a deinked pulp manufacturing process including a bleaching step. The present invention provides a bulky deinked pulp.

In order to solve the above-mentioned problems, the present inventors have intensively studied a bleaching process that replaces the hydrogen peroxide bleaching process. As a result, in the deinking pulp bleaching process consisting of two stages, the first stage and the second stage, the first stage is bleached with less alkaline chemicals and hydrogen peroxide, and the second stage is an organic that reacts with hydrogen peroxide to produce peracetic acid. It has been found that the object can be effectively achieved by bleaching with a peracid precursor.
That is, the present invention includes the following inventions.
(1) In a deinked pulp manufacturing process including a bleaching process, the bleaching process is composed of two stages, a first stage and a second stage, and an alkali chemical and hydrogen peroxide are added in the first stage and reacted with hydrogen peroxide in the second stage. A bulky deinked pulp produced by adding an organic peracid precursor that produces peracetic acid.
(2) The bulky deinked pulp according to (1) above, wherein the bleaching time after addition of the organic peracid precursor is 1 to 30 minutes.
(3) The bulky deinked pulp according to the above (1) to (2), wherein the pH after the preceding bleaching step is 8 to 10.5.
(4) The bulky deinked pulp according to (1) to (3) above, wherein the amount of the organic peracid precursor added is 30 to 50% of the amount of hydrogen peroxide added.
(5) above (1) to a main component bulky deinked pulp according to any one of (4), bulk density ^is bulky paper is 0.50g / m ³ ~0.60g / m 3 .

The present inventors consider as follows why the method according to the present invention provides a bulky deinked pulp than the conventional method. That is, since the waste paper pulp is bleached with hydrogen peroxide under a little alkali addition condition, the swelling and softening of the pulp fiber is suppressed, so that the pulp itself remains rigid even after bleaching and obtained from the pulp. It is estimated that standard handsheets will also be bulky.

Furthermore, in order to obtain deinked pulp with high whiteness by bleaching with hydrogen peroxide under a small amount of alkali addition, some treatment for further improving whiteness is required. The present inventors have found that it is extremely suitable for bleaching such deinked pulp to be bleached for a short time using an organic peracid precursor that reacts with hydrogen peroxide to generate peracetic acid as a subsequent stage. The headline and the present invention were completed. The reason why short-time bleaching using an organic peracid precursor is effective is that the organic peracid precursor reacts with hydrogen peroxide remaining in the pulp after the hydrogen peroxide bleaching to cause excess polymerization. Since acetic acid is produced and the produced peracetic acid reacts quickly with the pulp, it is presumed that short-time bleaching is possible. As a result, it is presumed that pulp bleaching is performed extremely effectively. Moreover, it is generally known that yellowing of pulp due to alkali can be prevented by leaving a small amount of hydrogen peroxide after bleaching with hydrogen peroxide. In the present invention, although residual hydrogen peroxide is consumed, It is presumed that alkali burn does not occur because acetic acid is generated after the reaction of peracetic acid with peracetic acid and the pH is lowered.

With respect to the bulky deinked pulp of the present invention, in a bleaching process comprising two stages, a first stage and a second stage, an alkaline chemical and hydrogen peroxide are added in the first stage, and an organic catalyst that reacts with hydrogen peroxide in the second stage to produce peracetic acid. By adding an acid precursor and bleaching, it becomes possible to produce a bulky deinked pulp having a whiteness equivalent to that in a normal hydrogen peroxide bleaching step.

In addition to newspaper waste paper, the waste paper targeted by the present invention includes printed waste paper such as flyers, colored paper, imitation paper, and other low-quality waste paper.

In the pre-bleaching step of the present invention, hydrogen peroxide and at least one kind of alkaline chemicals are used. As the alkaline chemicals, sodium hydroxide and sodium silicate are preferable.
Hydrogen peroxide is added in the range of 0.3 to 3% by mass with respect to the pulp.

Alkaline chemicals are added so that the system pH after bleaching in the pre-stage bleaching step of the present invention is 8 to 10.5. If the pH is less than 8, the bleaching effect is lowered due to the decrease in oxidation ability. If the pH is more than 10.5, swelling and softening of the pulp are promoted, and the bulking effect may not be obtained.

The bleaching time in the pre-stage bleaching step of the present invention is 30 to 180 minutes, preferably 60 to 120 minutes. When bleaching for less than 30 minutes, hydrogen peroxide cannot react sufficiently, and the bleaching effect is reduced. When bleaching for 180 minutes or more, hydrogen peroxide is consumed unless the addition rate is excessive, In addition to the color development of lignin, the effect of the organic peracid precursor is not obtained.

The bleaching temperature in the pre-stage bleaching step of the present invention is 45 to 85 ° C, preferably 60 to 80 ° C. When bleaching is performed at a temperature of less than 45 ° C. in the bleaching process, the reaction rate is lowered and the reaction time is increased. On the other hand, if it exceeds 85 ° C., a decomposition reaction of hydrogen peroxide occurs, which is not suitable.

The pulp density | concentration in the pre-stage bleaching process of this invention is 15-40 mass%, Preferably it is 20-35 mass%. If the concentration in the bleaching step is less than 15% by mass, the chemical and the pulp do not sufficiently react, the reaction rate decreases, and the reaction time increases. On the other hand, a concentration exceeding 40% by mass is not suitable because it is difficult to uniformly disperse and react the bleaching chemical.

As the organic peracid precursor used in the subsequent bleaching step of the present invention, at least one organic peracid precursor that reacts with hydrogen peroxide to produce peracetic acid is used. Examples of the organic peracid precursor include tetraacetylethylenediamine (TAED), tetraacetylglycol (TAGU), glucose pentaacetate (GPAC) acetoxybenzene sulfonic acid, and the like, but two molecules per organic peracid precursor molecule. Tetraacetylethylenediamine capable of producing peracetic acid is preferred because of its high efficacy.

The amount of the organic peracid precursor added in the subsequent bleaching step of the present invention is 30 to 100% by mass of the amount of hydrogen peroxide added. If the addition is less than 30% by mass, a sufficient bleaching effect may not be obtained. Further, even when more than 100% by mass is added, it is difficult to further improve the whiteness.

As a method for adding the organic peracid precursor, warm water in which the organic peracid precursor is dissolved may be added to the pulp and stirred, but it may be directly added to the pulp as it is and stirred.

The bleaching time in the latter stage bleaching process of this invention is 1 to 30 minutes. If bleaching is performed for less than 1 minute, the pulp and peracetic acid cannot sufficiently react, and the bleaching effect may not be obtained uniformly. Further, when bleaching exceeds 30 minutes, it is difficult to improve the whiteness.

The bleaching temperature in the latter-stage bleaching step of the present invention is 45 to 85 ° C., preferably 60 to 80 ° C., and it is preferable to maintain the temperature in the former-stage bleaching step as it is. As in the previous bleaching step, bleaching at a bleaching step temperature of less than 45 ° C. reduces the reaction rate of hydrogen peroxide, causing an increase in reaction time. On the other hand, if it exceeds 85 ° C., a decomposition reaction of hydrogen peroxide occurs, which is not suitable.

The pulp density | concentration in the latter stage bleaching process of this invention is 15-40 mass%, Preferably it is 20-35 mass%. If the concentration in the bleaching step is less than 15% by mass, the reaction rate between the organic peracid precursor and hydrogen peroxide decreases, causing an increase in the reaction time. On the other hand, a concentration exceeding 40% by mass is not suitable because it is difficult to uniformly disperse and react the organic peracid precursor.

The bulky deinked pulp of the present invention, bulk density of handsheets were created in accordance with JIS P 8222 is a deinking pulp becomes 0.50g / cm ³ ~0.60g / cm ³ using a該脱Sumi pulp .

EXAMPLES Next, although this invention is demonstrated in detail based on an Example, an Example does not limit this invention at all. In this example, the percentage (%) means mass% except whiteness, and the chemical addition rate is expressed by mass% per dry pulp. The quality of the deinked pulp was evaluated by the pulp whiteness according to JIS P 8212 and the tightness according to JIS P 8223.

Example 1
Printed newspaper waste paper: Flyer = Warm water at 30 ° C. was added to waste paper blended at a ratio of 6: 4, and it was disaggregated under the following conditions with a test pulper and dehydrated to a concentration of 25%.
Pulp concentration 2%
Caustic soda addition rate ......... 0.4%
Next, the pulp was treated as a pre-bleaching step under the following conditions. The pH after bleaching was 9.9.
Pulp concentration: 25%
Bleaching time ………………… 2 hours bleaching temperature ………………… 60 ℃
Caustic soda addition rate ......... 0.4%
Sodium silicate addition rate: 0.5%
Hydrogen peroxide addition rate ......... 1.0%
(Net equivalent) Same as below)
Next, the pulp was treated as a subsequent bleaching step under the following conditions. The pH after bleaching was 7.6.
Pulp concentration: 25%
Processing time ………………… 30 minutes Processing temperature …………………… 60 ℃
Organic peracid precursor addition rate: 0.5%
(Tetraacetylethylenediamine (TAED) manufactured by Kao Corporation, and so on)
Next, handsheets were prepared according to JIS P 8222 and air-dried. Handsheets were measured for pulp whiteness and tightness and are shown in Table 1 as Example 1.

Example 2
In Example 1, the caustic soda addition rate in the first stage bleaching step is 0.7%, the sodium silicate addition rate is 0.9%, the hydrogen peroxide addition rate is 1.0%, and the organic peracid precursor addition rate in the second stage bleaching step Was bleached in the same manner as in Example 1 except that it was carried out at 0.9%. The handsheet was measured for pulp whiteness and is shown in Table 1 as Example 2.

Example 3
In Example 2, bleaching was performed in the same manner as in Example 2 except that the addition rate of the organic peracid precursor in the subsequent stage bleaching step was 0.1%. The handsheet was measured for pulp whiteness and tightness and is shown in Table 1 as Example 3.

Example 4
Example 1 was carried out except that the caustic soda addition rate in the first stage bleaching step was 1.3%, the sodium silicate addition rate was 1.7%, and the organic peracid precursor addition rate in the second stage bleaching step was 0.9%. Bleached as in Example 1. The handsheet was measured for pulp whiteness and tightness and is shown in Table 1 as Example 4.

Example 5
In Example 4, bleaching was performed in the same manner as in Example 4 except that the caustic soda addition rate in the previous bleaching step was 0.07% and the sodium silicate addition rate was 0.09%. The handsheets were measured for pulp whiteness and tightness and are shown in Table 1 as Example 5.

Example 6
In Example 1, bleaching was carried out in the same manner as in Example 1 except that the caustic soda addition rate in the former bleaching step was 0.7%, the sodium silicate addition rate was 0.9%, and the bleaching time in the latter bleaching step was 60 minutes. . The handsheet was measured for pulp whiteness and tightness and is shown in Table 1 as Example 6.

Example 7
In Example 6, bleaching was performed in the same manner as in Example 6 except that the bleaching time in the subsequent bleaching step was 0.5 minutes. The handsheet was measured for pulp whiteness and tightness and is shown in Table 1 as Example 7.

Comparative Example 1
In Example 1, except that the caustic soda addition rate in the first bleaching step was 0.7%, the sodium silicate addition rate was 0.9%, the bleaching time was 2.5 hours, and the subsequent bleaching step was not performed. Bleached as in Example 1. The handsheet was measured for pulp whiteness and tightness and shown in Table 1 as Comparative Example 1.

Comparative Example 2
In Example 2, it was carried out except that the caustic soda addition rate in the preceding bleaching step was 1.5%, the sodium silicate addition rate was 1.9%, the bleaching time was 2.5 hours, and the subsequent bleaching step was not performed. Bleached as in Example 2. The handsheet was measured for pulp whiteness and tightness and shown in Table 1 as Comparative Example 2.

Comparative Example 3
In Example 4, except that the caustic soda addition rate in the preceding bleaching step was 2.5%, the sodium silicate addition rate was 3.3%, the bleaching time was 2.5 hours, and the subsequent bleaching step was not performed. Bleached as in Example 4. The handsheet was measured for pulp whiteness and tightness and shown in Table 1 as Comparative Example 3.

Comparative Example 4
In Example 6, except that the caustic soda addition rate in the former bleaching step was 1.5%, the sodium silicate addition rate was 1.9%, the bleaching time was 2.5 hours, and the subsequent bleaching step was not performed. Bleached as in Example 6. The handsheet was measured for pulp whiteness and tightness and shown in Table 1 as Comparative Example 4.

In the case of a deinked pulp manufacturing process having a pulp dispersing device such as a disperser or kneader immediately after the bleaching step, in the existing deinking pulp manufacturing process, an organic peracid precursor addition port is attached immediately before the dispersing device. Is also applicable.

Claims (5)

In a deinked pulp manufacturing process including a bleaching process, the bleaching process is composed of two stages, a first stage and a second stage, and an alkaline chemical and hydrogen peroxide are added in the first stage and reacted with hydrogen peroxide in the second stage to react with peracetic acid. A bulky deinked pulp, which is produced by adding an organic peracid precursor that generates water.
2. The bulky deinked pulp according to claim 1, wherein the bleaching time after addition of the organic peracid precursor is 1 to 30 minutes.
The bulky deinked pulp according to claim 1 or 2, wherein the pH after the preceding bleaching step is 8 to 10.5.
The bulky deinked pulp according to claim 1, wherein the addition amount of the organic peracid precursor is 30 to 50% of the addition amount of hydrogen peroxide.
Bulky deinked pulp according to any one of claims 1 to 4 as a main component, bulky paper, wherein the bulk density ^is a ^{0.50g / m 3 ~0.60g / m 3} .