JP2009235625A - Method for producing waste paper pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing high-ash and high-whiteness waste paper pulp from waste paper, which enables the mechanical strength of the pulp to be improved stably without being affected by impurities in waste pulp such as mechanical pulp, anionic substance and suspended colloidal substance. <P>SOLUTION: The method for producing waste paper pulp includes the disaggregating step 1 of making waste paper D into pulp slurry, the step 2 of removing dust from the pulp slurry, the step 3 of deinking the pulp slurry, and the step 5 of bleaching the pulp slurry, followed by the step of scrubbing the pulp slurry with a scrubbing liquid W, the step 7 of dewatering the pulp slurry, the step 9 of stocking the dewatered pulp, and the step of conveying the stocked pulp. In this method, an enzyme is added to the pulp in either one of the step 9 and the conveying step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing waste paper pulp, and relates to a method for producing waste paper pulp capable of obtaining higher pulp strength than conventional waste paper pulp while containing pulp fibers that have been repeated several times in recent years. It is.

  Conventionally, various beating methods, classification of raw pulp, and blending of paper strength enhancers have been studied and adopted for improving pulp strength in raw pulp. The method that has been adopted most often is a single formulation of a synthetic polymer using a cationic polymer.

  Also, in the used paper recycling process, in order to improve pulp strength without being affected by fine fibers, fillers, etc., earnest research has been conducted on the recovery of ash in floss and the recovery of fine fibers. . However, in the used paper recycling process, it is necessary to remove stains derived from used paper and printing inks such as carbon black, so the use of enzymes in the process involving the removal of these inhibitors is included in the used paper. It was thought that the effect could not be exhibited due to the influence of mechanical pulp, anionic substances, suspended colloidal substances and the like.

  Therefore, in the conventional general waste paper pulp manufacturing method, waste paper pulp is manufactured through the steps of disaggregation, dust removal, deinking, bleaching and washing, regardless of the ash content in the waste paper raw material, and the ash content in the washing step. The method of carrying out the removal and producing waste paper pulp with a low ash content was the mainstream for ensuring the pulp strength.

In recent years, methods for deinking waste paper pulp and improving drainage by adding a polysaccharide hydrolase in the used paper recycling treatment process have been disclosed (see, for example, Patent Documents 1 to 3 and Non-Patent Document 1). ). However, in this method, the enzyme is used for the purpose of improving deinking, and the effect of the enzyme is consumed by deinking. Therefore, the use of the enzyme at the deinking stage can obtain an effect of improving pulp strength. Can not. Moreover, there is no description or suggestion related to the pulp strength improvement.
JP 59-9299 A JP-A-63-59494 JP-A 63-145495 Tappi, 72 [6], 187 [1989]

  The main problem to be solved by the present invention is a method for producing waste paper pulp that can stably improve the pulp strength without being affected by mechanical pulp, anionic substances, suspended colloidal substances, etc. contained in the waste paper. Is to provide.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
A disaggregation process to turn waste paper into pulp slurry;
A dust removal step, a deinking step, and a bleaching step of the pulp slurry;
Following these steps, a washing step for washing the pulp slurry with a washing liquid, a dehydrating step for dehydrating the pulp slurry, a stock step for stocking dehydrated pulp, and a conveying step for conveying the stocked pulp,
A method for producing waste paper pulp having
In at least one of the stock process and the transport process, an enzyme is added to the pulp to obtain waste paper pulp.
A method for producing waste paper pulp, characterized in that

[Invention of Claim 2]
The stock process comprises a stock tower having an upper stage for transferring the dehydrated pulp, and a lower stage for diluting the dehydrated pulp that has been added to the dehydrated pulp from the upper stage,
Adding the enzyme into the lower part,
A method for producing waste paper pulp according to claim 1.

[Invention of Claim 3]
The transporting step includes a pipe line through which the pulp from the stock process is flowed, and a feed pump that is provided in the middle of the pipe to flow the pulp.
The addition of the enzyme is performed in a pipe line upstream of the feed pump, and the pulp to which the enzyme is added passes through the feed pump.
The manufacturing method of the used paper pulp of Claim 1 or Claim 2.

[Invention of Claim 4]
The temperature of the pulp when adding the enzyme is 30 to 55 ° C.,
And the manufacturing method of the used paper pulp of any one of Claims 1-3 which makes the addition amount of the said enzyme 10-10 mass ppm with respect to the absolute dry pulp.

[Invention of Claim 5]
As the enzyme,
A complex cellulase comprising endoglucanase, cellobiohydrolase, and β-glucosidase;
Hemicellulase including xylanase;
The manufacturing method of the used paper pulp of any one of Claims 1-4 which uses the complex enzyme containing this.

  According to the present invention, it is a method for producing waste paper pulp that can stably improve the pulp strength without being affected by mechanical pulp, anionic substances, suspended colloidal substances, etc. contained in the waste paper.

Next, an embodiment of the present invention will be described.
(Outline of this form)
The method for producing waste paper pulp according to the present embodiment includes a disaggregation step to turn waste paper into a pulp slurry, a dust removal step, a deinking step, and a bleaching step of the pulp slurry, and the pulp slurry is washed with a cleaning liquid following these steps. A washing step, a dehydrating step for dehydrating the pulp slurry, a stock step for stocking the dehydrated pulp, and a conveying step for conveying the stocked pulp, and at least one of the stock step and the conveying step, Waste paper pulp is obtained by adding an enzyme to a pulp to be stocked or conveyed (hereinafter also simply referred to as “target pulp”).

  Waste paper pulp made from waste paper collected from the city is used as a used paper that has been made at least once and used, and after making waste paper into a pulp slurry in the disaggregation step, a dust removal step, Through various processes such as deinking process, bleaching process, washing process, dehydration process, when removing impurities and regenerating (manufacturing) recycled paper pulp, the pulp strength of the raw pulp is lower than that of raw pulp made of virgin pulp Show a tendency to

  Furthermore, under the recent situation where many pulp fibers that have been repeatedly recycled are included, waste paper pulp fibers are even shorter and more brittle, and therefore, a decrease in pulp strength is a major problem.

  By the earnest study of the present inventors, mechanical pulp contained in waste paper by adding an enzyme to the target pulp in at least one of the stock process and the transport process, which is a process before completion of used paper pulp in the process of manufacturing waste paper pulp And a method for producing waste paper pulp that can stably improve the pulp strength without being affected by the anionic substances, suspended colloidal substances, and the like.

  Here, the temperature of the target pulp when the enzyme is added is preferably 30 to 55 ° C, and more preferably 40 to 50 ° C. In the case of a normal chemical reaction, the higher the temperature, the more active it is. However, in the case of an enzyme, when it exceeds 55 ° C, which is the upper limit of the optimum temperature, heat denaturation occurs and the activity is lost. If the temperature of the target pulp at the time of adding an enzyme is less than 30 ° C., the enzyme hardly exhibits a reaction activity, and thus the effect of improving the pulp strength by adding the enzyme cannot be obtained.

  Moreover, the pH of the object pulp at the time of adding an enzyme is 5.5-8.5 normally, Preferably it is 6.7-8.0. Below pH 5.5 or above pH 8.5, the three-dimensional structure of the enzyme active site changes and affects the binding with the substrate (cellulose in the fiber, hemicellulose), and the three-dimensional structure of the enzyme active site changes. The bond with the substrate (cellulose in fibers, hemicellulose) is reduced, and the effect of enzyme addition is reduced.

  On the other hand, when the pH exceeds 8.5, when the used waste paper pulp is used as a raw material pulp, the drainage is lowered, the dehydrating property is deteriorated and the operability is lowered, and the flocculant generally used in the papermaking process is reduced. In some cases, the effect of the coagulant may be impaired. Further, when the pH is lower than 5.5, the calcium carbonate contained in the waste paper pulp is decomposed, and the problem of scale generation due to the generation of carbon dioxide and the expression of calcium hydroxide occurs. It may cause an effect inhibition.

  In this embodiment, the amount of the enzyme added is preferably 10 to 100 ppm by weight, more preferably 25 to 50 ppm by weight. If the addition amount is less than 10 ppm by mass, the effect may not be obtained. On the other hand, if the addition amount exceeds 100 ppm by mass, there is little improvement in the effect, it is uneconomical, and there is a possibility that the system may become dirty. .

  Furthermore, as the enzyme, endoglucanase (EG) that randomly cleaves amorphous cellulose (hydrated cellulose) swollen with water, cellobiohydrolase (CBHI), EG, CBHI, which sequentially cleaves from the non-reducing end of crystalline cellulose, It is preferable to use a complex enzyme containing a complex cellulase containing β-glucosidase that decomposes the cellooligosaccharide cleaved by II into a monosaccharide and a hemicellulase containing xylanase. Since this complex enzyme has a slow production rate to decompose to a monosaccharide, it can stably modify the cellulose fiber without reducing the mechanical strength of the fiber. Can be expected. When an enzyme is added to the pulp, fine fibrillation (fluffing) occurs in the cell wall of the fiber, and the enzyme selectively acts on the fiber fibrils generated by physical shearing forces such as the disaggregation process and dust removal process. It is considered that the effect of fibrillation in a microscopic state is developed even for the waste paper pulp fiber that acts and is repeatedly and repeatedly brittle while maintaining the fibril state generated in the fiber wall. And since this fibrillated fine fiber has a wide specific surface area, the number of hydrogen bonds inevitably increases, and the bond between fibers becomes stronger when it becomes paper, resulting in excellent adhesion performance, increasing the bond area between fibers, Mechanical strength is improved by increasing the density of paper. In addition, fibrillation can be produced even for long fibers that are difficult to receive physical shearing force, and fine fibers adhere to each other, so that it is possible to improve the pulp strength of the obtained waste paper pulp.

  In general, an enzyme has a substrate specificity that only reacts with one substrate and a reaction specificity that is limited to only one reaction and does not cause other side reactions. Therefore, in the preferred production method of this embodiment, a complex enzyme is used. Further, according to the knowledge of the present inventors, a complex cellulase containing endoglucanase, cellobiohydrolase, and β-glucosidase, and xylanase are used. By using a complex enzyme containing hemicellulase, it reacts only with cellulose and hemicellulose, and has a characteristic that it is difficult to react with other chemicals such as sizing agent and pulp strength agent, so sizing agent and pulp strength agent, etc. There is no risk of disturbing the effects of other chemicals.

  Moreover, since the complex enzyme is a nonionic substance and does not contain a surfactant, inorganic ions, or the like, there is no possibility of affecting the performance of the rosin sizing agent. Conversely, by adding the above complex enzyme, there is a possibility that the amount of rosin sizing agent used can be reduced, and even with waste paper pulp that has a high ash content derived from waste paper, waste paper pulp with high pulp strength and high whiteness It has the potential to be obtained.

  The possibility of reducing the amount of rosin sizing agent used is said to be due to the tendency of the complex enzyme to concentrate on the fine fibers in the pulp slurry and to exert its effect. It is considered that since the amount of fibers decreases, the consumption of the sizing agent by the fine fibers cut short is reduced, and the rosin sizing agent is efficiently fixed to the long fibers or the fibrillated fine fibers.

  When the complex enzyme is used as an enzyme, it is more preferable that the component content of each enzyme used in the complex enzyme is 20% (vs. total enzyme mass) or less. This is because the heavy use of enzymes leads to the cutting of cellulose constituting the pulp fibers, which in turn leads to finer pulp fibers and reduced pulp strength.

(Manufacturing method of this embodiment)
Next, an embodiment of the method for producing waste paper pulp of the present invention will be described in detail with reference to FIG.
In the manufacturing method of the used paper pulp P of this form, the used paper D is disaggregated with the pulper 1 at a disaggregation process, and it is set as a pulp slurry. The pulp slurry is dedusted by the screen 2 in the dust removing process, and after adding a deinking agent such as higher alcohol and fatty acid in the deinking process, the ink is floated and removed by a flotation process by the flowator 3. Next, after selection in the cleaner 4 in the selection process, in the bleaching process, bleaching agents such as hydrogen peroxide and formamidinesulfinic acid, buffering agents such as sodium silicate and alkaline chemicals such as caustic soda are added, and then in the alkali soaking tower 5 Bleaching and alkali soaking are performed, and in the subsequent deinking step, the ink is subjected to a flotation process by the flowator 6 and separated and removed.

  Subsequent to these steps, in the washing step and the dehydration step, the dehydrator 7 performs washing and dehydration while supplying water W as a washing liquid, and sends the obtained dehydrated pulp to the stock tower 9 provided in the stock step.

  In this embodiment, the stock tower 9 includes an upper stage portion 9A that transfers the dehydrated pulp and a lower stage portion 9B that communicates with the upper stage portion 9A. In the lower stage portion 9B, dehydrated pulp is introduced from the upper end portion 9A, and the introduced dehydrated pulp is diluted with the dilution water W to form a slurry. The diluted pulp slurry is fed to a paper making process (not shown) through a conveying process.

  In this embodiment, in the transporting process, the pipe 12 through which the diluted pulp slurry from the stock tower 9 is fed and the diluted pulp slurry provided in the middle of the pipe 12 are flown. And a feed pump 11 for feeding.

  Here, in the method for producing waste paper pulp of this embodiment, an enzyme is added to the pulp in at least one of the stock process and the transport process. Although various places can be considered as the place where this enzyme is added, typically, the form (form A) and the pipe line 10B are added to the upper stage 9A of the stock tower 9 through the pipe line 10A. A form that is added into the lower stage 9B of the stock tower 9 by passing it through (form B), a form that is added into the pipe line 12 upstream of the flow pump 11 by passing through the pipe 10C (form C), Or a combination is conceivable.

  According to the knowledge of the present inventors, it is preferable to select the addition amount, concentration, and location in consideration of the pulp strength of the used waste paper pulp as the effect of the enzyme.

  For example, when waste paper pulp is being shortened or when the fiber is brittle, it is preferable to slowly and slowly advance the reaction with the enzyme, and form A and / or form B is suitably employed. be able to.

  On the other hand, for example, when it is desired to grasp the pulp strength in a timely manner and optimize the addition amount, it is preferable to use the form C with a small time lag from the paper making process. In this case, a form to be added into the pipe 12 downstream of the flow pump 11 is also conceivable, but according to this form, the time lag until the paper making process is shortened, and the reaction time may be too short. According to the form C, the pulp to which the enzyme has been added passes through the feed pump 11 and is stirred in the feed pump 11, so that dispersion unevenness is reliably prevented, so that the form A and / or the form In comparison with the addition in B, Form C is most preferred.

  The form A is a case where the enzyme is added at a stage where the pulp concentration is high, and the concentration at this time is preferably adjusted to 15 to 35%, more preferably 20 to 30% by the dehydrator 7 or the like. If the pulp concentration is less than 15%, the added enzyme may be diluted, and the effect of the enzyme addition may be difficult to express. Thus, it is necessary to add a relatively large amount of enzyme to the pulp raw material. However, if a large amount of enzyme is added, there may be a problem that quality variation is likely to occur, for example, the strength of the pulp may be reduced.

  On the other hand, when the pulp concentration exceeds 35%, uniform dispersion and reaction between the pulp and the enzyme are difficult to occur, and the pulp strength may be uneven.

  On the other hand, when it is desired to add an enzyme at a stage where the pulp concentration is low, it is preferable to use Form B or Form C. The concentration at this time is preferably adjusted by adjusting the amount of dilution water W in the lower stage portion 9B. It is adjusted to 2.5 to 5.0%, more preferably 3.0 to 4.5%. If the pulp concentration is less than 2.5%, the effect of the enzyme is hardly exhibited, and the workability in the paper making process may be reduced due to a decrease in the feed concentration of the raw pulp. On the other hand, when the pulp concentration exceeds 5.0%, the contact reaction between the enzyme and the pulp is hindered, and there is a possibility that unevenness in the pulp strength improving effect may occur, and the fibrillated fibers are likely to fall off. It becomes a factor of decline.

  The reaction time between the enzyme and the target pulp is preferably 0.3 to 2.5 hours, more preferably 0.5 to 2.0 hours. If the time is less than 0.3 hours, the reaction may not proceed sufficiently. On the other hand, if the time exceeds 2.5 hours, the reaction proceeds excessively, which may lead to a decrease in pulp strength.

  Of course, the addition of the enzyme does not have to be performed at one place, but can be carried out at two or more places in which forms A to C and addition at other places are appropriately combined.

  In this embodiment, the used paper D is a used paper product, which is general paperboard, paper, cutting waste of paperboard, and the like, and includes waste paper, but usually used paper is mainly used.

  As described above, in the present embodiment, the used paper pulp P that has undergone the disaggregation process, the dust removal process, the deinking process, the bleaching process, the washing process, the dehydration process, the stock process, and the transport process is provided for the papermaking process. Then, in at least one of the stock process and the transport process before being subjected to the papermaking process, the enzyme is supplied from the enzyme tank 10 to the pulp (dehydrated pulp) in the stock tank 9 or to the pulp (usually pulp slurry) being transported. Added.

  By adding enzymes to the pulp after washing and dewatering treatment in this way, it does not interfere with the deinking and bleaching effects, and mechanical pulp, anionic substances and suspended colloids contained in waste paper The pulp strength can be remarkably improved without being affected by substances and the like, and the waste paper pulp having high ash content and high whiteness can be obtained. Thus, an environmentally friendly method for producing waste paper pulp can be provided.

Next, examples of the present invention will be described.
First, warm water at 30 ° C. was added to waste printed paper consisting of 70% waste paper for offset printing and 30% waste paper for flyers, and the slurry was disaggregated with a standard disaggregator (compliant with JIS P 8220) to obtain pulp slurry. This pulp slurry was adjusted so that the pulp concentration was 5%, and caustic soda (addition rate 0.5%), deinking agent (addition rate 0.4%, nonionic surfactant R-6000 manufactured by Lion Corporation) ) Was added. This pulp slurry was once dehydrated to a concentration of 17%, diluted to a pulp concentration of 5% with warm water at 30 ° C, and aged for 1 hour in a warm bath at 30 ° C. After aging, the mixture was stirred for 2 minutes with a deflaker. Next, after the pulp concentration was diluted to 1%, the pulp was put into a laboratory flotator and flotated for 10 minutes at an air flow rate of 120 L / hr. The floated pulp slurry was dehydrated to a pulp concentration of 10% and then bleached with hydrogen peroxide (additional dry pulp addition rate of 1%) for 1 hour. Next, the pulp concentration was diluted to 3% with hot water at 30 ° C., and then dehydrated again. After the concentration, temperature, and pH shown in Table 1, the enzyme was added, and a flattening treatment (linear pressure 100 kg) was performed using a test calendar. / Cm), a test piece was obtained and used for each test. The results are shown in Table 1. Various conditions such as the type of enzyme and the location of addition were also changed as shown in Table 1. The details of various conditions and measurement methods shown in the table are as follows.

[Type of enzyme (variety)]
Complex enzyme: Fiberzyme CS (manufactured by Hakuto)
Commercial product A: Lipase E1 ((alkaline lipase) manufactured by Joint Shusei)
Commercial product B: Cellulase ACD (Kao)
Commercial product C: API-21 (manufactured by Showa Denko)
Commercial product D: "Amano" 90 (Amano Enzyme)

[Enzyme addition place]
Conveying step: In this example, the bleached pulp slurry was dehydrated to a pulp concentration of 25%, and further added with hot water when diluted to the target pulp concentration shown in Table 1. In addition, when the enzyme is added at a pulp concentration of 25% in this step and diluted with warm water immediately after that, it corresponds to the above-mentioned form B. Therefore, “form B” is used. Since it corresponds to C, it is written together in the table as “Form C”.
Stock process: In this example, the bleached pulp slurry was diluted with hot water at 30 ° C. to a pulp concentration of 3%, and further dehydrated to the target pulp concentration shown in Table 1 with a filter and screw press. When added. In addition, since this process corresponds to the above-mentioned form A, it was written together in the table as “form A”.
Deinking step: added during the above-described flotation treatment.
Disaggregation step: added during the disaggregation treatment by the standard disaggregator.
Bleaching step: added during the bleaching treatment with hydrogen peroxide.
[Amount of enzyme added]
This is the mass ratio of dry pulp.

[Basis weight (of test piece)]
Measured based on JIS P 8124.

[Whiteness (of specimen)]
Measured based on JIS P 8148.

[Specific tear strength (of specimen)]
Measured based on JIS P 8116.

[Cut length (of specimen)]
Measured based on JIS P 8113.

  INDUSTRIAL APPLICABILITY The present invention is applicable as a method for producing waste paper pulp having high ash content and high whiteness.

It is a flowchart of a used paper pulp manufacturing process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pulper (disaggregation process), 2 ... Screen (dust removal process), 3 ... Flotator (deinking process), 4 ... Cleaner 4 (selection process), 5 ... Alkaline soaking tower (bleaching process), 6 ... Floatator ( Deinking process), 7 ... Dehydrator (cleaning / dehydration process), 9 ... Stock tower (stock process), 9A ... Upper stage, 9B ... Lower stage, 10 ... Enzyme tank, 11 ... Flow pump, 12 ... Pipe line , D ... used paper, P ... used paper pulp, W ... water.

Claims (5)

A disaggregation process to turn waste paper into pulp slurry;
A dust removal step, a deinking step, and a bleaching step of the pulp slurry;
Following these steps, a washing step for washing the pulp slurry with a washing liquid, a dehydrating step for dehydrating the pulp slurry, a stock step for stocking dehydrated pulp, and a conveying step for conveying the stocked pulp,
A method for producing waste paper pulp having
In at least one of the stock process and the transport process, an enzyme is added to the pulp to obtain waste paper pulp.
A method for producing waste paper pulp, characterized in that The stock process comprises a stock tower having an upper stage for transferring the dehydrated pulp, and a lower stage for diluting the dehydrated pulp that has been added to the dehydrated pulp from the upper stage,
Adding the enzyme into the lower part,
A method for producing waste paper pulp according to claim 1. The transporting step includes a pipe line through which the pulp from the stock process is flowed, and a feed pump that is provided in the middle of the pipe to flow the pulp.
The addition of the enzyme into the conduit upstream of the feed pump;
The manufacturing method of the used paper pulp of Claim 1 or Claim 2. The temperature of the pulp when adding the enzyme is 30 to 55 ° C.,
And the manufacturing method of the used paper pulp of any one of Claims 1-3 which makes the addition amount of the said enzyme 10-10 mass ppm of the absolute dry pulp. As the enzyme,
A complex cellulase comprising endoglucanase, cellobiohydrolase, and β-glucosidase;
Hemicellulase including xylanase;
The manufacturing method of the used paper pulp of any one of Claims 1-4 which uses the complex enzyme containing this.

Images