KR20170079043A - Method for producing paper with reduced fluorescent whitening agent content using cellulase - Google Patents

Abstract

The present invention is not only to induce quenching of a fluorescent whitening agent by simply introducing a cellulase and dissociating it but to induce desorption of the fluorescent whitening agent remaining on the surface of paper to decrease the fluorescence index, Ink particles attached to the surface can be removed. Therefore, it is not necessary to carry out the floating float treatment process for deinking treatment, so that the white board paper manufacturing company can reduce the processing cost and time for recycling the white paper paper waste, and can reduce the cost of paper. In addition, it can contribute to the protection of domestic forest resources and the environment by reducing pollutants such as wastewater generated by the oxidizing agent used to reduce the content of the fluorescent whitening agent.

Description

TECHNICAL FIELD The present invention relates to a method for producing a paper having reduced fluorescent whitening agent content by using a cellulase agent,

The present invention relates to a method of producing a paper having a reduced content of a fluorescent whitening agent by using a cellulase agent and a paper of reduced content of a fluorescent whitening agent prepared by the method.

The use of toilet paper and napkins as hygienic paper is continuously increasing in proportion to the improvement of economic and cultural level. At present, the consumption of toilet paper per capita has rapidly increased, and this trend is expected to continue in the future. The raw materials of toilet paper are natural pulp, bleached kraft pulp, and recycled waste paper such as CPO (computer printout) and white ledger. Natural pulp is used only for the production of the finest premium beauty tissue, and most of the commonly used toilet paper is made from recycled raw materials. CPO, which is the main raw material of sanitary paper, and printing paper such as paper bound paper require very high whiteness and strength. Therefore, producers are forced to use a large amount of fluorescent whitening agent, and as the quality requirement for printing paper increases, the use of the fluorescent whitening agent is further increased.

On the other hand, fluorescent whitening agents are additives that are most widely used in production of printing paper, which is a quality standard of whiteness, and are entangled in pulp or chest, or escaped to the surface together with starch or polyvinyl alcohol in size press. In this way, the fluorescent whitening agent contained in the inside, the surface and the coating layer of the paper necessarily causes the fluorescent whitening agent to remain on the paper again when the paper is recycled. The risks to the human body of residual fluorescent brighteners are known to have a generally bad effect. In particular, since hygiene paper is used in contact with skin, skin side effects and possible carcinogenesis are constantly being raised. The Ministry of Health and Welfare also regulates the addition of a fluorescent whitening agent in food packaging paper. Therefore, when recycling the paper to which the fluorescent whitening agent has been added, it is important to remove the fluorescent whitening agent remaining on the paper. As a method for removing such a fluorescent whitening agent, there is a method of adding a liquid containing a triazin UVA compound in the course of treating a fluorescent whitening agent as proposed in Japanese Laid-Open Patent Publication No. 2003-502517 . However, since it contains chemical substances such as ammonium group (-NH ₂ ) and sulfone group (-SO ₃ ), it is accompanied by toxicity and odor, is not environmentally friendly, and is difficult to handle in the field. In addition, methods such as decomposition with an oxidizing agent, masking with a cationic polymer, and addition of a raw material having an ultraviolet absorbing property have been proposed. However, this method also causes the use of excessive chemicals and the problem that the removal amount of the fluorescent whitening agent is insufficient.

Korean Patent Laid-Open Publication No. 2014-0107640 discloses a method of reducing fluorescence in pulp. However, a method for producing a paper with reduced fluorescent whitening agent content using the cellulase of the present invention has not yet been disclosed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned needs, and it is an object of the present invention to provide a method of repulping a cellulase in a white paper sheet in order to induce desorption of a fluorescent whitening agent remaining on a white paper sheet, The fluorescence index, whiteness, and brightness of the herb were measured without flotation. As a result, the present invention has accomplished the present invention by confirming that not only the content of the fluorescent whitening agent on the paper surface is reduced but also the ink particles are removed to further improve the whiteness and white brightness of the paper .

In order to solve the above-described problems, the present invention provides a method for producing pulp, comprising: 1) introducing a cellulase into raw pulp containing a fluorescent whitening agent at a temperature of 28 to 48 ° C and a pH of 7 to 8, Dissociating; 2) adding fresh water to the raw pulp dissociated in the step 1) to dilute the raw pulp to 0.3 ~ 0.8%, and selecting the pulp from the diluted raw pulp; And 3) compressing the selected feedstock in the step 2) and drying the reduced feedstock.

In addition, the present invention provides a reduced content of fluorescent whitening agent produced by the above production method.

The present invention is not only to induce quenching of a fluorescent whitening agent by simply introducing a cellulase and dissociating it but to induce desorption of the fluorescent whitening agent remaining on the surface of paper to decrease the fluorescence index, Ink particles attached to the surface can be removed. Therefore, it is not necessary to carry out the floating float treatment process for deinking treatment, so that the white board paper manufacturing company can reduce the processing cost and time for recycling the white paper paper waste, and can reduce the cost of paper. In addition, it can contribute to the protection of domestic forest resources and the environment by reducing pollutants such as wastewater generated by the oxidizing agent used to reduce the content of the fluorescent whitening agent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a method for producing a paper having a reduced content of a fluorescent whitening agent using a cellulase according to an embodiment of the present invention. FIG.

In order to accomplish the present invention, the present invention provides a method for producing pulp, comprising: 1) introducing a cellulase into raw pulp containing a fluorescent whitening agent at a temperature of 28 to 48 ° C and a pH of 7 to 8, Dissociating; 2) adding fresh water to the raw pulp dissociated in the step 1) to dilute the raw pulp to 0.3 ~ 0.8%, and selecting the pulp from the diluted raw pulp; And 3) compressing the selected feedstock in the step 2) and drying the reduced feedstock.

In the method according to one embodiment of the present invention, the fluorescent whitening agent has stilbene as a basic structure. Since stilbene is an unsaturated hydrocarbon having a double bond between carbon and carbon in the middle, the fluorescent whitening agent may be a compound represented by the following formula (1) or an isomer thereof, but is not limited thereto.

At this time, the fluorescent whitening agent is divided into three types, disulpho, tetrasulpho and hexasulpho depending on the number of the sulfone groups introduced. The fluorescent whitening agent is prepared by introducing a substituent such as a sulfone group using 4,4'-diaminostilbene-2,2'-disulfonic acid as a basic structure The number of sulfone groups is determined. The types of fluorescent whitening agents vary depending on the R ₁ and R ₂ substituents of the general formula (1). Table 1 shows the kinds of substituents depending on the type of fluorescent whitening agent. A constant substituent always attaches to the position of R ₁ irrespective of the type of the fluorescent whitening agent but the kind of the fluorescent whitening agent varies depending on the substituent having a different number of sulfone groups at the position of R ₂ .

In the method according to one embodiment of the present invention, the cellulase may be added in an amount of 0.3 to 1.8 parts by weight based on 100 parts by weight of the raw pulp, but is not limited thereto.

In the method according to one embodiment of the present invention, the papermaking process generally includes a dissolving step, a paper finishing step, and a papermaking step. First, in the dissociation stage, the pulp is loosened and dissolved in water using a high-speed dissociator. At this time, the raw pulp may be subjected to a sizing treatment in which a colloidal material having water resistance is mixed, or a filler or a dye may be further added, but the present invention is not limited thereto.

In the method according to one embodiment of the present invention, the raw pulp may be, but not limited to, a surface-sizing treated paper or printing paper.

In the method according to an embodiment of the present invention, the flotation treatment may not be performed after the step 1), but the present invention is not limited thereto. It is important not to apply floating treatment after the injection of cellulase. It is because it is difficult to expect decrease of fluorescence index because desorbed fluorescent whitening agent is re-adsorbed on pulp fiber when floating.

In addition, the present invention provides a reduced content of fluorescent whitening agent produced by the above production method.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not limited thereto.

Materials and methods

1. Materials Preparation

In the present invention, a liquid type industrial cellulase (Cellusoft, 2.5 L) purchased from Novozymes was used. The white-ledger used in the domestic white board makers is the raw materials that are used in actual use. Since the types of white paper are very various, they are crushed by using a crusher to ensure uniformity of quality, Respectively.

2. Cellulase after dissolution ( repulping ) Conducted

The white-ledger sampling material that has been crushed to an appropriate size is diluted to 2% with distilled water after being precipitated in distilled water of pH 7 to 8 and then diluted with distilled water. Cellulase is then added to the sample for disintegrator, Daeill machinery, Korea) was used for dissociation (Table 2). The dissociation condition was dissociated for about 33 minutes at 8,000 rpm and the fibers were completely fused. The temperature of the fresh water at Harry was set at 30 ° C and 45 ° C, respectively, and wrapped in blanket so that the temperature could be maintained. The dissociated material was diluted to 0.5% with the addition of fresh water and a basis weight of 100 ± 10 g / m ² was prepared according to TAPPI standard method sp-02 using the diluted material. Which produced a few seconds for 5 minutes and then pressed at 3.5kg _f / cm ² pressure condition and dried with a cylinder dryer for laboratory. Then, conditioning was carried out at 23 ° C and 50% RH (relative humidity), and fluorescence index, whiteness and white brightness were measured using an Elrepho spectrophotometer Respectively. Cellulase injections and repulping were performed using the difference between the fluorescence index of the waterless soil without cellulase and the fluorescence index of the water containing cellulase And the reduction effect of the fluorescence index was confirmed (Fig. 1).

3. Cellulase after dissolution ( repulping ) And floating ( flotation ) Conducted

Flotation is a method in which ink particles dispersed in a stock are adhered to the surface of bubbles by physical and chemical methods, floated, and then removed and deinked. In the present invention, the floating flotation method is used to induce desorption of the fluorescent whitening agent on the surface of white-ledger and fiber, thereby reducing the fluorescence index. Floating flotation treatment using a flotator (Deaill, Korea) was carried out after dissociation into a high-speed dissociation apparatus by injecting a cellulase into the disintegrated white paper as in the method of inducing desorption of a fluorescent whitening agent using a high-speed dissociation apparatus 2). 75 g of pulp and 4925 liters of fresh water were added to the laboratory floating dewaxing machine, which had a total volume of 5 liters, and the suspension was floated for 5 minutes at the air level of 8. During the floating process, the ink particles separated from the pulp and rising to the surface were removed together with the air bubbles, and the suspended material was diluted to 0.5% by adding fresh water. Based on the TAPPI standard method sp-02, the diluted material was used to produce a basis weight 100 ± 10 g / m ² . Which produced a few seconds for 5 minutes and then pressed at 3.5kg _f / cm ² pressure condition and dried with a cylinder dryer for laboratory. Thereafter, conditioning was performed under conditions of 23 ° C and 50% RH (relative humidity), and the fluorescence index was measured using an elrepho spectrophotometer (FIG. 1).

The enzymes and physical treatment conditions used in the present invention Experimental conditions Repulping Repulping + floating flotation pH 7-8 (Neutral)
The pH value of the material is pH 7-8. Temperature (℃) 30 and 45 enzyme Cellulase

Example  1. Cellulase after dissolution ( repulping ) Fluorescence index, whiteness degree and White sensitivity  Measure

The fluorescence index (%) was measured by the amount and temperature of the cellulase. As a result, when the cellulase was injected and dissociated only as shown in Table 3, the fluorescence index was the lowest when the cellulase dosage was 1.5% at 30 ° C and 45 ° C.

In addition, as shown in Table 4, fluorescence index reduction value was obtained by subtracting the fluorescence index measurement value when the cellulase treatment was performed without injecting the cellulase at the fluorescence index measurement value when the cellulase was injected and only the dissociation was performed, Respectively. As a result, the degree of decrease of the fluorescence index can be easily compared by representing the difference of each value as a delta (Δ) value based on the fluorescence index measurement value when the cellulase is not added. The closer the delta value is to (-), the lower the fluorescence index when the cellulase is added and the dissociation only, the lower the fluorescence index when the cellulase is not added, and the closer to (+) the cellulase The fluorescence intensity was higher than the fluorescence intensity when it was not used. It was found that the delta (DELTA) value when the cellulase treatment and dissociation alone were performed showed a value close to (-), so that the present invention had an effect of reducing the fluorescence index.

In addition, whiteness and white brightness of the paddy field were measured by applying a cellulase rule and dissociating only. As a result, in comparison with amylase, which is known to decrease the fluorescence index, as shown in Table 5, when the cellulase was treated, the whiteness of the water-base paper was measured at 30 ° C and 45 ° C, It was confirmed that the white sensitivity was further improved.

The fluorescence index of water-base paper pH Enzymes and temperatures Fluorescence index (%) Repulping Repulping + flotation 0% 0.5% 1.0% 1.5% 0% 0.5% 1.0% 1.5% 7-8 Cellulase 30 ℃ 45.21 43.5 43.03 41.36 45.21 48.07 50.08 49.41 45 ° C 44.23 42.68 43.63 42.42 44.23 46.34 44.73 45.53

Difference in fluorescence index of aquatic plants by treatment conditions pH Enzymes and temperatures *? Fluorescence index (%) Repulping Repulping +
Floatation 0.5% 1.0% 1.5% 0.5% 1.0% 1.5% 7-8 Cellulase 30 ℃ -1.71 -2.18 -3.85 2.86 4.87 4.20 45 ° C -1.55 -0.6 -1.81 2.11 0.50 1.30

* △ Fluorescence index = fluorescence index after enzyme treatment - fluorescence index after untreated enzyme.

The whiteness and whiteness measurement results of aquatic plants according to treatment conditions pH Enzymes and temperatures Whiteness and white sensitivity according to enzyme type and dissociation treatment Whiteness (%)
* ISO whiteness White Sensitivity (%)
* CIE brightness 0% 0.5% 1.0% 1.5% 0% 0.5% 1.0% 1.5% 7-8 30 ℃ Amylase 81.4 78.8 80.6 81.0 110.1 99.4 104.3 105.6 Cellulase 81.4 81.3 81.0 80.1 110.1 106.8 106.2 104.4 45 ° C Amylase 80.3 79.1 79.4 78.4 104.5 101.6 102.3 99.6 Cellulase 80.3 80.7 80.8 79.9 104.5 105.5 106.2 104.5

* CIE means the standard colorimetric system of the international standard established by the International Lighting Commission CIE, and ISO means the colorimetric system established by the International Organization for Standardization ISO.

Example  2. Cellulase after dissolution ( repulping ) And floating ( flotation ) Measurement of fluorescence index

In this example, fluorescence index reduction rate of a water-base paper was confirmed (Table 3 and 4) by comparing with the case where the cellulase was added and dissociated, and then the suspension treatment was additionally performed. As a result, it was confirmed that the fluorescence index reduction efficiency was higher when the temperature was 45 ° C than 30 ° C when the suspension was additionally treated after the dissociation, but the fluorescence index was increased more than when the cellulase was applied When the temperature was 30 ℃, the fluorescence index increased more. These results suggest that the fluorescent whitening agent desorbed through the dissociation process is adsorbed to the fiber by the floating fluorescent whitening treatment.

From the above results, it was confirmed that the fluorescence index decreased when the cellulase was injected and dissociated. On the other hand, it was confirmed that the fluorescence index increased when the suspension treatment was additionally performed after the dissociation. It was confirmed that fluorescence index was decreased by inducing desorption of the fluorescent brightener remained on the white paper when the cellulase, which is an industrial enzyme, was added and only dissociated. In the case of only Harry, the fluorescent whitening agent on the fiber surface is well separated due to the action of cellulase, but if the additional floating flotation method is further performed, the desorbed fluorescent whitening agent is reabsorbed in the floating flotation The fluorescence index is expected to rise. Therefore, as the cellulase is injected into the dissociation process without any additional treatment such as suspension treatment, the fluorescence index generated by the fluorescent whitening agent remaining on the white paper can be reduced, and the ink particles can be effectively removed. Whiteness and white sensitivity can be further improved.

Claims (6)

1) introducing a cellulase into raw pulp containing a fluorescent whitening agent at a temperature of 28 to 48 ° C and a pH of 7 to 8 and dissolving the raw pulp using a high-speed dissolver;
2) adding fresh water to the raw pulp dissociated in the step 1) to dilute the raw pulp to 0.3 ~ 0.8%, and selecting the pulp from the diluted raw pulp; And
3) compressing the selected feedstock in step 2) and drying the reduced feedstock, thereby reducing the content of the fluorescent whitening agent. The method according to claim 1, wherein the cellulase is added in an amount of 0.3 to 1.8 parts by weight based on 100 parts by weight of the starting pulp. The fluorescent brightener according to claim 1, further comprising a sizing step of mixing a water-soluble colloidal material with the raw pulp between the step 1) and the step 2), and adding a filler or a dye. A method of making a paper with reduced content. The method of claim 1, wherein the raw pulp is a surface-sizing-treated paper or printing paper. The method of claim 1, wherein the flotation treatment is not performed after the step 1). 6. A paper with reduced content of fluorescent whitening agent prepared by the method of any one of claims 1 to 5.

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