JPS61194299A - Enhancement of yield of filler in neutral papermaking - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for improving the yield of calcium carbonate added as a filler in a neutral papermaking process in the paper industry.

(Prior Art) In the paper manufacturing process, conventionally, it has been most common to add sulfuric acid to acidify the paper stock. This is because a large amount of sulfuric acid band is required for fixing rosin-based sizing agents, anionic polymer paper formulations, and fillers such as clay, talc, and kaolin. However, papermaking at a low pH promotes corrosion of the equipment and has the disadvantage that the paper-made product deteriorates due to long-term storage. Furthermore, in order to reduce wastewater as much as possible due to pollution problems, and due to the lack of water resources and lower unit water consumption, a large amount of recycled water is being used, and fAJriL1! Using a large amount of l-band increases the salt concentration in the water, causing various problems.

Therefore, neutral paper making methods that do not use sulfuric acid bands have been studied, and neutral paper making has already been carried out in many factories.

Since rosin-based sizing agents are not effective in neutral papermaking, synthetic sizing agents for neutral papermaking have been developed, and several types of neutral sizing agents are currently commercially available and in use.

Furthermore, in the production of stamp paper, fillers are added to improve the printing effect, but in conventional acid paper production, fillers such as kaolin, Merck, and clay have been used. These fillers cannot be produced domestically in good quality and have mostly been dependent on rotation. Calcium carbonate, which is produced in large quantities in Japan, has not been used because it foams and dissolves in acidic conditions, but it can be used in neutral papermaking, which is extremely advantageous for Japan's paper manufacturing industry. The effect and whiteness are also excellent.

The fillers used in both acidic and neutral papermaking are mostly fine particles of inorganic mineral substances, and when added during the papermaking process, it is extremely difficult for them to remain in the paper product. Therefore, it is customary to use a polymer electrolyte as a retention aid.

The materials used in acidic paper making, such as kaolin, merck, and clay, have a fairly strong negative surface charge, so they aggregate extremely sharply with cationic polymers, and pulp fibers are also negatively charged, so both It becomes a composite floc and improves the yield of filler. However, in the case of calcium carbonate, its surface charge is extremely weak, and it does not cause sharp aggregation with polymers. Therefore, even if a retention agent is used, the yield is considerably inferior to that of acid paper making, and a large amount of calcium carbonate flows out into the white water.

Cationic polymers are mainly used as filler retention aids, and in acidic papermaking, cationic modified products obtained by Mannich conversion of polyacrylamide are most commonly used. Since this cationic polymer is a tertiary amine, when the pH of the system becomes alkaline, dissociation becomes extremely poor and the properties as a cationic polymer are lost. Therefore, in neutral papermaking, it is necessary to use a quaternary amine, and the one currently used in large amounts is a copolymer of (meth)acryloyl oxyethyl trimethylammonium salt and acrylamide. However, even if this polymer is used, the filler retention effect is currently considerably inferior compared to acid papermaking.

(Objective of the invention) It is an object of the present invention to increase the yield of calcium carbonate filler in neutral paper making.

(Problems to be Solved by the Invention) Calcium carbonate fillers in neutral papermaking have a weak surface charge, making it difficult to form flocs due to the cationic polymer, and the resulting flocs are fine particles, which can be easily removed from the wire during papermaking. It falls off and escapes into the white water, and the yield does not improve as expected. This can be considered because the solid content in white water reaches as much as 4000 to 5000 pHXn in factories that use cationic polymer retention aids to make neutral paper. This is thought to be because pulp fibers coagulate more easily than calcium carbonate, so the polymer acts more on the pulp fibers, forming a pulp that is almost entirely pulp, leaving calcium carbonate behind. It will be done. Therefore, in order to improve the yield of calcium carbonate, it is necessary to coagulate calcium carbonate itself more fully. It can be said that the current amount of polymer retention agents added is insufficient for this purpose. Currently, the amount of polymer added is o, oos ~ 0.0
It is about 3%, but it is added to increase the yield effect.
= It will be necessary to increase it significantly. However, adding a large amount of high molecular weight polymer increases the aggregation of pulp fibers and significantly deteriorates the formation of paper. Therefore, by minimizing the amount of polymer added,
Moreover, it is necessary to improve the yield of calcium carbonate.

The present invention solves this problem.

(Function and Effect) The present invention involves adding polyaluminum chloride to the paper stock or calcium carbonate dispersion liquid prior to adding the retention agent polymer, coagulating the calcium carbonate particles to some extent in advance, and then adding the retention agent polymer to produce pulp fibers. The purpose is to improve the yield of calcium carbonate filler by forming a composite floc of calcium carbonate and calcium carbonate.

Although polyaluminum chloride has extremely weak cohesiveness with respect to pulp fibers, it has quite good cohesiveness with calcium carbonate. Therefore, when polyaluminum chloride is added to a stock containing calcium carbonate filler, mainly calcium carbonate particles agglomerate. The aggregation is not as strong as the aggregation of cationic polymers such as Merck, and the flocs are relatively small. When a retention agent polymer is added to this, a composite floc with pulp fibers is formed and the content of calcium carbonate in the paper after papermaking is improved.

Polyaluminum chloride can be added at any stage after the calcium carbonate filler is added to the pulp slurry but before the retention agent polymer is added, but it is generally added in the mixing chest or machine chest. It would be appropriate to do so. Retention agent polymers are typically added at the fan pump inlet, screen inlet or outlet, etc.

The yield effect can also be improved by adding polyaluminum chloride to a slurry of calcium carbonate alone before adding it to the stock, flocculating it, and then mixing it with the pulp slurry, but the flocculated calcium carbonate particles tend to settle. It is quite difficult to operate in the field and may cause trouble. It may be dangerous if sufficient measures are not taken.

The amount of polyaluminum chloride added seems to have little effect on the effect. Of course, if it is extremely small, the effect will be affected, but if it is 0.001% or more based on the solids in the paper stock, the effect can be expected. Adding a large amount improves the effectv
cFi is useless and increases the salt concentration in the white water, which is rather undesirable. 0.003 to 0.051 (AmuO Fuji conversion) is preferable.

Currently, some factories that produce neutral paper add small amounts of sulfuric acid to the paper stock. Although it is not clear what the purpose is, one possibility is to adjust the pH to 1. However, the pH due to calcium carbonate is 8.5, for example, 8.0.
I can't think of any benefit even if I adjust it to this point.

As long as calcium carbonate is used, the pH must be kept on the alkaline side, so there is almost no need for the PHal1m clause. Further, as to whether the addition of sulfuric acid can improve the yield of calcium carbonate, almost no effect was observed. Unlike polyaluminum chloride, sulfate band has no effect on calcium carbonate aggregation.

Therefore, it is natural that the addition of sulfuric acid has no effect on the yield of calcium carbonate.

Comparative example 1. I, BKP was beaten with a beater to give a freeness of 08F350-. This pulp slurry was preliminarily mixed with water and a nine-dimensional calcium carbonate filler was adjusted so that the ratio of pulp to filler was 7:3, and 0.5% of cationic starch was added to the solid content. A neutral sizing agent f0.3% was added to prepare a furnish. The yield effect test was conducted using a drop-type dynamic jar.

The measurement was carried out at a paper stock concentration of 0.6 cm, - initial stage of superhydration of 100 -
Comparative Example 2.
Acryloyl was added to the furnish of Comparative Example 1 as a retention aid.
After adding 1.02% of a copolymer of oxyethyl trimethylammonium and acrylamide, the yield rate was measured.

Comparative example 3. 0.02% of sulfuric acid was added to the furnish of Comparative Example 1.
1 (in terms of Am O3), and 0.02 g of the retention aid of Comparative Example 2 was added thereto to measure the retention rate.

Example 1. 0.005% of polyaluminum chloride was added to the furnish of Comparative Example 1, and then 0.02 g of the retention aid of Comparative Example 2 was added to measure the retention of calcium carbonate.

Example 2. The amount of polyaluminum chloride added is 0.01%
The yield of calcium carbonate was measured under the conditions described in Example 1 except for the following conditions.

Example 3. Addition amount of polyaluminum chloride to, 02%
The yield was measured under the following conditions as described in Example 1 except for the following conditions.

Example 4. Addition of polyaluminum chloride to, o
All yields were measured under the conditions described in Example 1 except that ss was used.

Example 5. Polyaluminum chloride was added to a 30% dispersion of calcium carbonate to coagulate it, and this was mixed with paper stock so that the total solid content of calcium carbonate was 30%, and a retention agent was added. 0.02% polymer
In addition, the yield was measured.

Claims (1)

[Claims] A method of improving the retention of calcium carbonate filler in neutral papermaking by adding polyaluminum chloride to the paper stock or calcium carbonate filler dispersion before adding a polymer retention improver.