JPH08291490A - Deinking and bleaching method of extra-lightweight waste newspaper - Google Patents

Abstract

PURPOSE: To obtain regenerated pulp having high quality with excellent whiteness without extension and strengthening of washing equipment or increasing of a bleaching agent in a bleaching process by using waste newspaper mainly composed of extra-lightweight waste newspaper as a raw material. CONSTITUTION: Waster newspaper mainly composed of extra-lightweight waste news paper is used as a raw material and fed in a pulper, broken, dehydrated and resultant raw material is blended with sodium hydroxide in an amount of 1-3wt.% based on the raw material and sodium silicate in 2-5 weight times of the adding amount of the sodium hydroxide in an agitator under a light pressure, aged at 50-70 deg.C for >=3hr, subjected to a flotation treatment and washed to obtain deinked regenerated pulp. Then, the regenerated pulp is blended with a prescribed amount of hydrogen peroxide, 2-5wt.% sodium hydroxide and sodium silicate in 2-5 weight times of the adding amount of the sodium hydroxide in an agitator under a light pressure, subjected to peroxide bleaching at 60-100 deg.C for 1-5hr, washed, thus subjected to a reducing and bleaching treatment by using sodium hydrosolfite or thiourea dioxide and washed to obtain the objective bleached regenerated pulp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deinking bleaching method for waste newspaper, and in particular, when an ultralight newspaper waste is used as a main raw material, a deinking bleaching method for obtaining a deinked pulp with little residual ink and high whiteness. It is about the method.

[0002]

2. Description of the Related Art Recently, from the standpoint of protecting the global environment, it has been strongly desired to collect and recycle more waste paper.
The recovery rate of used paper as a raw material for papermaking in Japan is about 50% of the raw material for producing paper and paperboard. Therefore, in order to further increase the recovery rate of used paper, it is an important issue to stably obtain inexpensive deinked pulp with high quality (particularly high whiteness).

However, in recent years, especially regarding newspapers,
With the changes in speed, visualization, and weight reduction, the paper and ink are also undergoing major changes. For example, shift to offset printing for high-speed printing, color photo printing for visualization,
For example, the weight reduction of newsprint is reduced. These changes have a negative effect on the deinking of used paper, and especially for the ultra-lightweight newspaper, which has been rapidly increasing in recent years, the increase in the amount of ink per pulp is obvious, which is a major problem for paper makers. There is.

Many proposals have been made for the deinking bleaching method for offset printed newspapers, and Japanese Patent Laid-Open No. 55-408.
No. 50 discloses that a deinking agent consisting of an alkali, a surfactant and a hydrogen peroxide bleaching agent are added to printed waste paper containing offset waste paper to obtain a concentration of 15% or more and 5.0 g / l.
There is seen a method in which a refiner, a kneader or the like is used in the above alkaline concentration (as NaOH) and mechanical stirring is performed while applying a compressive force under heating.

Further, as an improvement of JP-A-55-40850, JP-A-63-28992 discloses a mechanical stirring treatment followed by aging for 0.5 hours or more, and a concentration of 15 to 2 again.
A method of performing mechanical stirring treatment at 5% is disclosed. These methods have been introduced with some effect on old newspapers using conventional plain newspapers, but they are satisfactory especially for the deinking bleaching of ultra-lightweight newspapers, which has recently been rapidly increasing. Instead of such a method, the establishment of a deinking bleaching method for ultra-lightweight newspaper waste was urgently needed.

When paper is produced using deinking pulp which has not been sufficiently deinked, spotted or whisker-like dust is generated on the obtained paper, which lowers the commercial value. In addition, if the bleaching treatment is not sufficient, the whiteness of the deinked pulp is low, which causes a drawback that the use of paper and the range of use of the deinked pulp are limited. Therefore, in order to use a large amount of ultra-lightweight newspaper waste paper for high-quality paper, it is important to use deinked pulp with high whiteness.

Japanese Unexamined Patent Publication No. 6-49792 discloses a kneading step, an aging step, although it is not a method for treating ultra-lightweight waste newspaper.
A method of repeating the floating selection step and the washing step two to three times is disclosed. This method is a very effective means for obtaining high-quality deinked pulp, but the equipment such as a chemical mixing device, an aging tower, a floating sorting device, and a washing machine is enormous. There is a problem with economic efficiency such as expenses and drug costs. In order to effectively use waste paper, which is an inexpensive raw material,
At the same time as the quality of deinked pulp, the economic efficiency of process equipment and chemicals is an important key for waste paper processing.

[0008]

In view of the above situation, the present inventors have made earnest studies on a deinking bleaching method for ultra-lightweight newspaper waste paper, and as a result, have considered the following. That is, in the conventional deinking method, which includes the disaggregation step, the kneading step, the aging step, the floating sorting step, and the washing step, which are found in Japanese Patent Laid-Open No. 55-40850, the case where ultra-lightweight waste newspaper is used as a raw material , A defect that the entire deinked pulp was dull was confirmed. Also, even if a large amount of bleaching agent is added to bleach in order to forcibly increase the whiteness in the bleaching step after deinking treatment,
The reaction efficiency is poor, which causes an increase in cost and drainage load.

The reason for this is that the ultra-lightweight newspaper has a larger amount of ink per pulp than the ordinary newspaper, and the surface of the newspaper forms a starch film with a gate trol coater, etc. Adhesion of ink to the paper is judged to be quite different from that of ordinary newspapers. Therefore, if it is a process that strengthens the mechanical stirring process that is a conventional deinking method, the unpeeled ink and the already peeled ink are also dispersed and subdivided, and the redeposition and twisting of the ink particles on the fiber It seems that it is even complicated. Furthermore, since the ink particles are extremely fine, the effect of the floating sorting step after aging is also reduced, and the entire deinked pulp becomes dull. Therefore, for waste paper with a large amount of ink such as ultra-lightweight newspapers, it is necessary to increase equipment costs and chemical costs, such as adding or strengthening a washing device and increasing the amount of bleaching agent in the bleaching process.

The present invention is a deinking bleaching method for solving the above-mentioned problems, which is different from the conventional deinking method.
A method for deinking and bleaching used newspaper, which is mainly made of ultra-lightweight used newspaper, which is sequentially subjected to an aging step, a floating sorting step, a washing step, a hydrogen peroxide bleaching step, a washing step, a reduction bleaching step and a washing step. In each of the step and the hydrogen peroxide bleaching step, as a chemical mixture during aging and hydrogen peroxide bleaching, stirring and mixing treatment is performed in a state where the compression force is weak. In addition, as a chemical formulation for aging and bleaching with hydrogen peroxide, 1 to 5% by weight of caustic soda is added to waste paper, and the amount of sodium silicate is 2 to 5 times the amount of the caustic soda added. Without using a mechanical mixer with strong mechanical stirring such as a kneader as a chemical mixer at the time of aging and hydrogen peroxide bleaching, a steam mixer, a chemical mixer, a mica processor, etc. By using an agitator with a weak compression force, the ink is peeled off to a size that can be easily removed without extremely subdividing the ink, and a high-whiteness deinked pulp can be used even with ultra-lightweight waste newspaper as a raw material. The present invention has been completed and the present invention has been completed.

That is, since the present invention is for expanding the use of waste paper, even if the waste paper mainly composed of ultra-lightweight waste paper is used as a raw material, the whiteness is high by the treatment of the present invention,
An object of the present invention is to provide a deinking bleaching method for ultra-lightweight newspaper waste paper, which produces waste paper deinking pulp that has little dust and can be highly blended with high-quality paper.

[0012]

In the present invention, as a method for obtaining high quality deinked pulp from ultra-lightweight waste newspaper,
With the method of performing deinking and bleaching at the same time, there is a limit to the increase in whiteness, and since many speckled or whisker-like dusts remain, the deinking process and the bleaching process are separated, and further bleaching is performed after the deinking process. Take the method of doing.

The method for deinking and bleaching the ultra-lightweight waste newspaper of the present invention will be described below. That is, the method for deinking and bleaching the ultra-lightweight waste paper of the present invention is carried out by first disaggregating the raw waste paper in an aqueous medium and dehydrating it, and then adding 1 to 3% by weight of caustic soda to the waste paper. -2 to 5 times the amount of added sodium silicate-
After adding the hydrogen peroxide and the deinking agent, the mixture is uniformly agitated by a mixer having a relatively low mechanical compression force such as a steam mixer or a chemical mixer, and then aged, and then the float. -Selection (floating selection). After the flotation, the peeling ink that could not be removed is removed in the washing process. After washing, the pulp was dewatered again, 2 to 5% by weight of caustic soda was added to the waste paper again, and 2 to 5 times the amount of the caustic soda added soda silicate was added. , Hydrogen peroxide bleaching chemicals added, steam mixer and chemical mixer
Bleaching is performed by uniformly stirring the mixture with a mixer having a relatively small mechanical compression force, and allowing it to stay for about 3 hours. This allows
Although a deinked pulp having a whiteness of about 70 can be obtained, it is preferable to use a reducing bleaching agent in order to further increase the whiteness. As the reducing bleaching agent, it is desirable to bleach with hydrosulfite or thiourea dioxide.

When deinking and bleaching waste newspaper mainly consisting of ultra-lightweight waste newspaper, the chemicals are mixed with a mechanically agitating mixer such as a kneader conventionally used in the deinking method of offset printing newspaper. It was confirmed that the method did not sufficiently increase the whiteness. The reason for this is that if chemicals are mixed with a mechanical mixer such as a kneader that has strong mechanical agitation, ink will be screwed in or re-adsorbed in ultra-lightweight newspaper waste paper, and bleaching chemicals such as hydrogen peroxide will be used in the subsequent bleaching. Even if the amount is increased, the whiteness does not increase easily.

The deinking bleaching method of the present invention is characterized in that it is used for deinking bleaching of newspaper wastepaper mainly consisting of ultra-lightweight newspaper wastepaper without using a mechanical mixer such as a kneader having strong mechanical agitation. , A chemical mixer, a mica processor, etc. are used to mix and process chemicals by using an agitator having a weak compression force. By this method, we have completed a deinking bleaching method that can obtain deinked pulp with a high whiteness, which has never been obtained with newspaper wastepaper mainly made of ultra-lightweight newspaper.

Regarding the pulp concentration at the time of aging and bleaching with hydrogen peroxide, since the compression force of the mixer is weak, sufficient mixing cannot be achieved. On the other hand, if it is too low, hydrogen peroxide is wasted due to impurities in water, and the practical range is 10 to 25%. The temperature and time are high and the longer the better, but the practical range is 50 to 70 at the time of aging.
Desirably, the temperature is about 3 to 20 hours. Further, it is desirable that the bleaching with hydrogen peroxide is carried out at 60 to 100 ° C. for about 1 to 5 hours.

Regarding the amount of caustic soda added, the larger the amount added, the higher the effect. However, if it exceeds 5%, the drainage load will increase conversely, which is not practical. On the other hand, if the amount is too small, the bleaching effect is low, the amount of unreacted hydrogen peroxide is large, and it does not contribute much to the whiteness increase of pulp. As a practical range, about 1 to 3% by weight is desirable at the time of aging. Further, it is desirable that the content of hydrogen peroxide is about 2 to 5% by weight when bleaching.

As the sodium silicate used in the present invention, No. 3 sodium silicate specified in JIS K-1408 used industrially is used. When the amount of soda silicate added is less than twice the weight of the caustic soda added, an unfavorable phenomenon of yellowing of the pulp due to the caustic soda occurs, and the bleaching effect is significantly reduced. Sliding occurs in the chemical mixing machine and sufficient mixing cannot be performed. Regarding the upper limit of the amount of soda silicate added, there is no particular adverse effect on bleaching due to high addition, but soda silicate also increases drainage load due to high addition, as with caustic soda. .
The preferred amount of soda silicate added is 2 to 5 times the weight of the caustic soda added.

Since it is difficult to obtain a sufficient whiteness only by bleaching with hydrogen peroxide, it is necessary to carry out further reduction bleaching. Also, increasing the amount of caustic soda added during bleaching with hydrogen peroxide will reduce the increase in whiteness, but by combining reduction bleaching, the whiteness will be greatly improved.
It is necessary to carry out reduction bleaching after bleaching with hydrogen peroxide. As the reducing bleaching agent, it is desirable to use hydrosulfite or thiourea dioxide (hereinafter abbreviated as FAS).

The raw material waste paper used in the deinking bleaching method of the present invention is intended for ultra-lightweight newspaper waste paper, but it may be 30% or less even if ordinary newspapers or heavy newspapers are mixed.
Also, it can be applied to coated paper such as leaflets and used magazine paper. The pulp obtained by deinking and bleaching ultra-lightweight waste newspaper by the deinking and bleaching method of the present invention has a whiteness of about 75%.
It is a feature that a deinked pulp with a high whiteness, which cannot be obtained by using a conventional mixer having a high compression force such as a kneader, can be obtained.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

In the following Examples and Comparative Examples,
The bleaching conditions of the pulp and the measurement of the obtained pulp were as follows, unless otherwise specified. Also,% shown here
Indicates weight% unless otherwise specified, and the addition amount indicates the amount based on the absolutely dried pulp.

Treatment in the disaggregation step Water was added to the pulper for the test so that the pulp concentration was 5%, and 1% of caustic soda, 2% sodium silicate and deinking agent were used for the dry weight of pulp. (Kao Corporation, trade name; DI-76
7) After adding 0.2% and stirring well, newspaper wastepaper containing 80% ultra-lightweight newspaper waste was added to the pulper to charge and separate, and then dehydrated to a concentration of 18%.

Example 1 Pulp after caustic soda 1.
5% Sodium silicate 3%, Deinking agent (above) 0.2%, Hydrogen peroxide 1.5% After mixing with a steam mixer,
Aging was performed at a temperature of 60 ° C. for 12 hours. After aging, it was disintegrated at a concentration of 2%, further diluted to 1%, subjected to a flotation treatment for 6 minutes using a test floater, dehydrated and deinked at a concentration of 18%. Regenerated pulp was obtained. Further, 2% of caustic soda, 6% of sodium silicate and 3% of hydrogen peroxide were added to the obtained recycled pulp, and the mixture was mixed in a steam mixer and bleached at a temperature of 70 ° C. for 3 hours. Then dilute to 3%, 15
%, And pulp was obtained after bleaching with hydrogen peroxide.

The bleached pulp obtained above was diluted to 3% and 1% of hydrosulfite was added, bleached at 65 ° C. for 30 minutes and then dehydrated to 15% to obtain a finished pulp.

Example 2 Pulp after bleaching with hydrogen peroxide obtained in Example 1 was caustic soaked.
0.2% DA and 0.5% FAS were added and bleached at 70 ° C. for 50 minutes to obtain a finished pulp.

Comparative Example 1 In Example 1, a steam mixer was used as a mixer for the chemicals during aging.
A finished pulp was obtained in the same manner as in Example 1 except that a kneader was used instead of the mumixer.

Comparative Example 2 In Example 1, a steam mixer was used as a chemical mixer for bleaching.
A finished pulp was obtained in the same manner as in Example 1 except that a kneader was used instead of the mumixer.

Comparative Example 3 Completed in the same manner as in Example 1, except that the amount of caustic soda added was 0.5% and the amount of sodium silicate added was 3%, and the aging was performed. The pulp was obtained.

Comparative Example 4 Completed in the same manner as in Example 1 except that the caustic soda was added in an amount of 1.5% and the sodium silicate was added in an amount of 2%. The pulp was obtained.

Comparative Example 5 As in Example 1, except that the amount of caustic soda added during bleaching with hydrogen peroxide was 1% and the amount of soda silicate added was 6%, and bleaching was performed. A finished pulp was obtained in the same manner.

Comparative Example 6 As in Example 1, except that the amount of caustic soda added during bleaching with hydrogen peroxide was 2% and the amount of soda silicate added was 3%, and bleaching was performed. A finished pulp was obtained in the same manner.

Comparative Example 7 In Example 1, 50% of ultra-lightweight waste newspaper was used as a raw material.
A finished pulp was obtained in the same manner as in Example 1 except that the used newspaper waste containing was added to the pulper and disintegrated.

Example 3 A finished pulp was obtained in the same manner as in Example 1 except that the amount of caustic soda added was 3% and the amount of sodium silicate additive was 6%. It was

Example 4 Example 1 was repeated except that bleaching was carried out by changing the amount of caustic soda added to 4% and the amount of sodium silicate added to 8% during bleaching with hydrogen peroxide. A finished pulp was obtained in the same manner.

Example 5 A finished pulp was obtained in the same manner as in Example 1 except that the aging time was 3 hours and the temperature was 60 ° C.

Example 6 A finished pulp was obtained in the same manner as in Example 1 except that bleaching time was 5 hours and hydrogen peroxide was bleached at a temperature of 70 ° C.

Each regenerated pulp thus obtained was put on a standard sheet machine (JIS P-8209) to obtain 60 g.
/ M ² pulp sheet was adjusted, and the whiteness and residual ink amount of the sheet were measured by the following methods.

Whiteness: Measured by Hunter-whiteness according to the method of JIS P-8123.

Remaining ink amount: Using a particle analyzer (manufactured by Nireco, trade name, LUZEX F), the ink area occupied within a certain range was expressed in%.

The results obtained in Examples 1 to 6 and Comparative Examples 1 to 7 are shown in Table 1.

[Table 1]

As shown in Table 1, by applying the deinking method for ultra-lightweight waste newspaper according to the present invention (Examples 1 to 1)
6) It was possible to obtain a recycled pulp with high whiteness and less dust without introducing expensive equipment.

[0043]

EFFECT OF THE INVENTION According to the deinking bleaching method of ultra-lightweight newspaper wastepaper of the present invention, even if wastepaper wastepaper mainly consisting of ultralightweight newspaper wastepaper is used as a raw material, it is possible to add or strengthen the washing device and to improve the bleaching process. It is not necessary to take measures such as increasing the amount of bleaching agents and increasing the amount of bleaching chemicals, and it is possible to obtain high-quality recycled pulp with high whiteness and less dust. Therefore, as a result of obtaining deinked pulp with a high degree of whiteness using ultra-lightweight newspaper waste as a main raw material, it can be used in large quantities in high-quality paper and can be widely applied to paper for various purposes.

Further, as a chemical prescription for aging and bleaching with hydrogen peroxide, caustic soda is added in an amount of 1 to 5% by weight with respect to waste paper, and the caustic soda is added in an amount of 2 to 5 times the amount of caustic soda. Acid source
Without using a mechanical mixer with strong mechanical stirring such as a kneader as a chemical mixer at the time of aging and hydrogen peroxide bleaching, a steam mixer, a chemical mixer, a mica processor, etc. Since it was decided to perform stirring and mixing processing in a state of weak compression force using a stirrer with weak compression force of
The ink can be peeled off to a size that can be easily removed without extremely subdividing the ink, and high-whiteness deinked pulp can be obtained even from ultra-lightweight newspaper waste as a raw material, and the drainage load does not increase. .

Claims (5)

[Claims] 1. Deinking of old waste paper mainly composed of ultra-lightweight old wastepaper, which is sequentially subjected to a disintegration step, an aging step, a floating sorting step, a washing step, a hydrogen peroxide bleaching step, a washing step, a reduction bleaching step and a washing step. A bleaching method, wherein in each of the aging step and the hydrogen peroxide bleaching step, as a chemical mixture at the time of aging and hydrogen peroxide bleaching, an agitated mixing process is carried out in a state of weak compressive force, an ultralight newspaper waste paper. Deinking bleaching method. 2. The chemical mixing at the time of aging and hydrogen peroxide bleaching is performed by using a stirring mixer having a weak compression force such as a steam mixer or a chemical mixer. How to deink and bleach ultra-lightweight newspaper wastepaper. 3. As a chemical for the aging step, 1 to 3% by weight of caustic soda is added to waste paper, and 2 to 5 times the amount of sodium silicate is added to the amount of the caustic soda added. Add and ripen temperature 5
The deinking bleaching method for ultra-lightweight waste newspaper according to claim 1 or 2, wherein the aging is performed at 0 to 70 ° C for 3 hours or more. 4. When bleaching with hydrogen peroxide, 2-5 of caustic soda is added.
2% to 5% by weight of the caustic soda.
Double the sodium silicate, bleaching temperature 60 ~ 100 ℃,
The deinking bleaching method for ultra-lightweight waste newspaper according to claim 1, 2 or 3, wherein the bleaching is carried out for 1 to 5 hours. 5. The deinking bleaching of ultra-lightweight waste newspaper according to claim 1, wherein bleaching is performed using sodium hydrosulfite or thiourea dioxide as a reducing bleaching agent. Method.