JP2002194688A - Method for cleaning in papermaking and screening process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for cleaning in a paper making and screening process, having high safety and slight influence on drain, with which impurities of chemicals consisting essentially of a sizing agent in a screening process can be effectively removed. SOLUTION: This method for cleaning in the paper making and screening process, an aqueous dispersion liquid consisting essentially of D-limonene and caustic soda is added to a screening system and circulated to remove impurities derived from each chemical consisting essentially of the sizing agent. Preferably the weight ratio of the caustic soda to the D-limonene in the aqueous dispersion liquid is 5-50 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method in a paper making process which can effectively remove impurities of various chemicals, mainly sizing agents, in the paper making process.

[0002]

2. Description of the Related Art (1) The selection process is a process mainly including a tank, a screen for removing foreign substances, a cleaner, piping, and a pump, and having almost no opening. For that reason,
Until now, the method of cleaning the inside of the fine selection process has been a method of removing dirt at a flow rate in a pipe by circulating with a pump using water (hot water). (2) When the stain in the process is caused by the chemical compounded in the paper, the concentration is 0.5 to 2% by weight in water (hot water).
The caustic soda was mixed and washed similarly by circulating. (3) In order to increase the washing efficiency with caustic soda, a method of increasing the concentration to about 2 to 5% by weight was applied, but there was no feasibility due to drainage regulations and safety issues. (4) Therefore, in the above method, dirt (foreign matter) is often not removed, and physical cleaning is performed by removing pipes and the like.

[0003] In the conventional washing with caustic soda, for removing impurities by mixing various chemicals contained in paper,
Not always effective. In addition, when the concentration of caustic soda was increased, adverse effects such as effects on drainage and safety problems occurred.

As mentioned above, there is no effective cleaning chemical to solve these problems, and the solution has been awaited.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-safety, low-impact effect on wastewater, and to effectively remove impurities of various chemicals, mainly sizing agents, in a paper-making process. It is intended to provide a washing method in a paper making selection step that can be performed.

[0006]

Means for Solving the Problems As a result of intensive studies in view of the above, the present inventor has invented a washing method in the paper making selective step of the present invention.

That is, in the washing method in the papermaking screening step of the present invention, an aqueous dispersion mainly composed of D-limonene and caustic soda is added to a screening system, and the mixture is circulated to remove impurities derived from various chemicals mainly containing a sizing agent. It is characterized by being removed.

In the present invention, the weight ratio of caustic soda in the aqueous dispersion is 5 to 5 with respect to D-limonene.
It is preferably 0% by weight.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the paper-making selection step
This is the step of circulating the white water of the paper making, and also the step of removing foreign substances by a cleaner and a screen. If impurities are generated during the selection process and are not removed by the cleaner and the screen, the impurities adhere to the paper product, resulting in a defect and failing to function as a product. for that reason,
It is necessary to minimize impurities in the papermaking process, but since the organic chemicals are blended to stabilize the quality of the paper, the mixture is washed for a certain period of time.
Need to be removed. In the present invention, D-
It has been found that by adding an aqueous dispersion of limonene and caustic soda, dissolution and removal of mixed impurities of various chemicals, which have been ineffective conventionally, can be efficiently performed.

In the present invention, the weight ratio of D-limonene to caustic soda is 5 to 50% by weight of D-limonene, so that it can be efficiently removed. Here, if the amount of caustic soda is less than 5% by weight, the removal rate decreases. On the other hand, when the content exceeds 50% by weight, drainage after circulation and safety are hindered.

The purpose of mixing caustic soda with D-limonene is to promote the dissolving effect of D-limonene.

Here, it has been confirmed from analysis results that impurities removed by D-limonene contain 80% or more of organic substances in composition. Regarding the generation of impurities, it is often observed in systems where acid paper and neutral paper are mutually formed.In particular, the sizing agent is obtained by mutual papermaking of saponified rosin size with acid paper and alkyl ketene dimer with neutral paper. Is specifically recognized in certain systems.

In the practice of the present invention, first, water is filled in the paper making process. An aqueous dispersion obtained by mixing D-limonene and caustic soda at a predetermined ratio is fed into the papermaking screening process. At this time, the solid concentration of the aqueous dispersion in water is set to 1 to 2% by weight. After the introduction of the aqueous dispersion, the pump in the paper-making process is operated to circulate the dispersion, thereby distributing the dispersion throughout the paper-making process. Subsequently, the mixture is allowed to flow for several hours, and then the dispersion is drained. After drainage is completed, the drain valve is closed, and water (warm water) is filled again in the paper-making process and is circulated. The water (warm water) circulation is repeated two or three times to remove the water outside the paper making process. If the aqueous dispersion remains in the system, the chemicals may be decomposed at the time of production, which may cause an adverse effect on the process. Therefore, it is essential to carry out circulation of water (hot water). Here, it is effective to increase the flow rate in the piping in order to increase the cleaning effect, and it is desirable that the output of the pump in the circulating flow be maximized as much as possible.

[0014]

The present invention will be described below with reference to examples.

Examples 1 to 6 and Comparative Examples 1 to 2 The water held in the cleaning step 30 m ³ was filled with water, and the aqueous solution containing caustic soda shown in Table 1 below was added to the silo.
Liters and 100 liters of D-limonene (active ingredient 10
0%). Thereafter, the pump in the selection process was operated to circulate for 2-3 hours, and after circulating, the aqueous dispersion was drained. After the drainage was completed, water was filled again in the selection process, and circulating was performed with only water for about 30 minutes, and then drained. This circulation with water was performed two or three times, and the aqueous dispersion of caustic soda and D-limonene was excluded from the outside of the selection process.
After washing in the selection process in this way, book paper was made as described below.

LBKP beaten to a freeness of 400 ml and NBKP beaten to a freeness of 480 ml were in a weight ratio of 7: 3.
Into 100 parts of beaten pulp obtained by mixing the above, 6.0 parts of cationic starch (Cato 308, manufactured by NSC) Alkyl ketene dimer sizing agent (AS263, PM of Japan)
C) 1.5 parts Polymethacrylate (High Holder 301, manufactured by Kurita Kogyo) 0.3 part was added. The stock thus blended was machined by a fourdrinier machine to produce book paper. The configuration of Fourdrinier is as follows: wire → press →
Dryer → size press → dryer → calendar →
It is a reeler.

According to the above Examples 1 to 6 and Comparative Examples 1 and 2, the paper made after the washing in the selection step was evaluated by the following evaluation method. The results are shown in Table 1 below.

<Number of paper defects> The number of paper defects is determined by an OMRON electronic paper inspection machine (model KP24YW14, NVPD).
Using Fi), the measurement was performed using a fluorescent lamp as a light source. The numbers before and after washing indicate the number of defects (foreign matter) in 1000 m ² paper. The removal rate (%) is a value (%) obtained by dividing the difference between before and after cleaning by the number before and after cleaning for the number of paper defects.

[0019]

[Table 1]

From the results of Examples 1 to 6 and Comparative Examples 1 and 2, it is possible to increase the foreign matter removal rate of about 40% by setting the weight of caustic soda to D limonene to 5% by weight or more. Further, when the weight of caustic soda is 50% by weight or more, the critical line is reached. For this reason, it was confirmed that the range of 5 to 50% by weight as the weight of caustic soda was appropriate in consideration of cost and safety. On the other hand, in Comparative Examples 1 and 2, D-limonene and caustic soda were used alone, respectively, but both had low removal rates.

[0021]

According to the cleaning method of the present invention, the impurities of various chemicals, mainly sizing agents, which could not be sufficiently removed in the past can be efficiently removed, thereby improving the quality and productivity of the paper. It greatly contributes to Furthermore, by setting the weight ratio of caustic soda to D-limonene to a specific value, the removal effect is also high.

Claims (2)

[Claims] In a washing method in a papermaking screening step, an aqueous dispersion mainly composed of D-limonene and caustic soda is added to a screening system, and the mixture is circulated to remove impurities derived from various chemicals mainly containing a sizing agent. A washing method in a papermaking screening step, characterized by the following. 2. The method according to claim 1, wherein the weight ratio of caustic soda in the aqueous dispersion is 5 to 50% by weight based on D-limonene.