A wet strength dissociating agent and its usage method

Abstract

The present invention provides a wet strength dissociating agent and a method for using the same, belonging to the technical field of papermaking. The wet strength dissociating agent includes the following raw material types in terms of the percentage by weight of waste paper: 5-20% of a solution containing an oxidizing agent, 0.1-1% of sodium chloride, 0-6% of sulfate, 0-0.1% of a non-ionic surfactant, and 0.01-0.05% of a stabilizer. The wet strength dissociating agent of the present invention has a better dissociation effect on the wet strength agent, is not only applicable to dissociating different wet strength agents, but also has a fast dissociation speed for waste paper, little influence on the fiber length and strength in the waste paper, etc.

Description

Technical Field

[0001] The present invention relates to the recycling and reuse of wet-strength paper, and particularly to a wet-strength dissociating agent used in the process of recycling and reusing wet-strength paper, belonging to the field of papermaking technology. Background Art

[0002] With the development of society and the demand for energy conservation and emission reduction, the papermaking industry will use more recycled waste paper as raw materials for production. Waste paper pulping means that the fiber quality in the pulp of waste paper can still be maintained at a relatively high level after recycling treatment. With the high requirements for paper properties, many papers are added with wet-strength agents to improve paper properties, but the presence of wet-strength agents affects the effect of waste paper recycling and the properties of the finished paper.

[0003] Therefore, the research on wet-strength dissociating agents has become urgent and necessary. At present, the papermaking industry mainly uses auxiliaries such as sulfates and hypochlorites to treat wet-strength waste paper, so as to replace expensive wet-strength dissociating agents and cumbersome waste paper repulping processes. However, although using these two auxiliaries, sulfates and hypochlorites, to treat wet-strength waste paper can achieve the purpose of cost saving and simplifying the repulping process, there are still certain problems. Sulfates cannot treat all wet-strength agents well. For example, magnesium sulfate has a good dissociating effect on MF wet-strength paper, but the dissociating effect on PAE wet-strength paper is average; hypochlorites have pollution problems due to the presence of chlorine, and the addition amount needs to be strictly controlled, otherwise it will affect the properties of the paper.

[0004] In view of the above problems, developing a safe, environmentally friendly and efficient wet-strength dissociating agent is an urgent problem to be solved. Summary of the Invention

[0005] In view of the above problems, the present invention provides a wet-strength dissociating agent and its use method to improve the dissociating effect of the wet-strength dissociating agent and expand the applicable range of the wet-strength dissociating agent.

[0006] To achieve the above object, the technical solution of the present invention is: a wet-strength dissociating agent, which is used for pulping when recycling wet-strength waste paper. Calculated by weight percentage of the waste paper, the wet-strength dissociating agent includes the following raw material types: 5-20% of a solution containing an oxidant, 0.1-1% of sodium chloride, 0-6% of sulfate, 0-0.1% of a non-ionic surfactant, and 0.01-0.05% of a stabilizer.

[0007] Further, the solution containing an oxidant is a circulating solution in the production process of persulfate. The circulating solution is the centrifugal filtrate in the production process of potassium peroxymonosulfate, a solution after composition adjustment or a solution prepared according to a ratio, wherein the hydrogen peroxide content is 3-4%, the persulfate is 6-8%, the sulfuric acid is 4-6%, and the rest is water.

[0008] Further, the oxidant-containing solution is a mixed solution prepared from persulfate, hydrogen peroxide, concentrated sulfuric acid and water.

[0009] Further, the persulfate is at least one of potassium persulfate, sodium persulfate or potassium peroxymonosulfate compound salt.

[0010] Further, the mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid and water in the mixed solution is 6-8:3-4:4-6:87-82.

[0011] Further, the sulfate includes at least one of magnesium sulfate and aluminum sulfate; the stabilizer is at least one of HEDP, EDTA, citric acid, sodium hexametaphosphate and sodium silicate.

[0012] Further, the non-ionic surfactant includes at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and fatty acid methyl ester ethoxylate.

[0013] The usage method of the above wet strength dissociating agent includes the following steps:

[0014] S1. Add a predetermined amount of water to the waste paper for pre-soaking;

[0015] S2. Add the oxidant-containing solution to the pre-soaked waste paper and mix well;

[0016] S3. Add sodium chloride, sulfate, non-ionic surfactant and stabilizer to the solution in step S2 and mix well;

[0017] S4. Pulverize to obtain pulp.

[0018] Further, in step S1, the temperature of the pre-soaking is 10-50 °C, the time of the pre-soaking is 5-30 min, and the pre-soaking is carried out in a hydrapulper.

[0019] Further, in step S4, start the motor during pulverization, and the pulverization time is 30-120 min.

[0020] The beneficial effects of the wet strength dissociating agent and its usage method of the present invention are as follows:

[0021] The wet strength dissociating agent of the present invention uses an oxidant-containing solution, which contains persulfate, hydrogen peroxide, stabilizer and sulfuric acid, etc. The dissociation effect on the wet strength agent is better. It is not only applicable to different wet strength agents, but also has a fast dissociation speed for waste paper, and has little influence on the fiber length and strength in the waste paper, etc.

[0022] The wet strength dissociating agent of the present invention uses an oxidant-containing solution as the main active ingredient, sodium chloride is a synergist for the oxidation of persulfate, and at the same time the sulfate plays an auxiliary synergistic role in the formula. Each formula ingredient cooperates synergistically to achieve the effective dissociation of the wet strength paper.

[0023] The wet strength dissociating agent of the present invention has a pulping yield of over 92% when dissociating waste paper with different wet strength dosages and types for 30 - 120 minutes at a solution pH of 5 - 6. Detailed implementation manners

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar promotions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0025] A wet strength dissociating agent for recycling waste paper pulping, calculated by weight percentage of waste paper, the wet strength dissociating agent includes the following raw material types: 5 - 20% of a solution containing an oxidant, 0.1 - 1% of sodium chloride, 0 - 6% of sulfate, 0 - 0.1% of a non - ionic surfactant, and 0.01 - 0.05% of a stabilizer. Preferably, the solution containing an oxidant is a circulating solution in the production process of persulfate. The circulating solution is the centrifugal filtrate in the production process of potassium peroxymonosulfate, the solution after composition adjustment or the solution prepared according to a ratio, wherein the hydrogen peroxide content is 3 - 4%, the persulfate is 6 - 8%, the sulfuric acid is 4 - 6%, and the rest is water; or the solution containing an oxidant is a mixed solution prepared from persulfate, hydrogen peroxide, concentrated sulfuric acid and water. Preferably, the persulfate in the mixed solution is at least one of potassium persulfate, sodium persulfate or potassium peroxymonosulfate complex salt, and the mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid and water is 6 - 8:3 - 4:4 - 6:87 - 82.

[0026] In the above - mentioned wet strength dissociating agent, the sulfate includes at least one of magnesium sulfate and aluminum sulfate, the stabilizer is at least one of HEDP, EDTA, citric acid, sodium hexametaphosphate and sodium silicate, and the non - ionic surfactant includes at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and fatty acid methyl ester ethoxylate.

[0027] The usage method of the above - mentioned wet strength dissociating agent includes the following steps:

[0028] S1. Add a predetermined amount of water to the waste paper for pre - soaking; preferably, the pre - soaking temperature is 10 - 50 °C, the pre - soaking time is 5 - 30 minutes, and the pre - soaking is carried out in a hydraulic pulper; the predetermined amount of water is determined according to the target concentration of the final pulp. The target concentration of the pulp is generally 8 - 15%, and the predetermined amount of water is calculated according to the following formula: pulp concentration = waste paper amount / (waste paper amount + water amount) * 100%;

[0029] S2. Add the solution containing an oxidant to the pre - soaked waste paper and mix evenly;

[0030] S3. Add sodium chloride, sulfate, non-ionic surfactant, and stabilizer to the solution in step S2 and mix well;

[0031] S4. Pulverize the pulp. Start the motor during pulverization, and the pulverization time is 30 - 120 min; when the pulverization is complete, during the stirring process, the pulp does not adhere or take a small amount of pulp and add it to water, and observe that the pulp is completely dispersed into flocs in water without residual shredded paper in chunks.

[0032] Example 1

[0033] A wet strength dissociating agent for recycled waste paper pulping. By weight percentage of the waste paper, the wet strength dissociating agent includes the following raw material types: 5% of a solution containing an oxidant, 1% of sodium chloride, 1% of magnesium sulfate, 0.1% of fatty alcohol polyoxyethylene ether, and 0.05% of citric acid. The solution containing an oxidant is a circulating solution in the production process of persulfate. The circulating solution is the centrifugal filtrate in the production process of potassium peroxymonosulfate. After component adjustment, the hydrogen peroxide content is 3 - 4% (4% in this example), the persulfate is 6 - 8% (6% in this example), the sulfuric acid is 4 - 6% (6% in this example), and the rest is water;

[0034] The usage method of the above wet strength dissociating agent includes the following steps:

[0035] S1. Add a predetermined amount of water to MF wet strength waste paper for pre-soaking; the pre-soaking temperature is 50 °C, the pre-soaking time is 5 min, and the pre-soaking is carried out in a hydrapulper;

[0036] S2. Add the solution containing an oxidant to the pre-soaked waste paper and mix well;

[0037] S3. Add sodium chloride, magnesium sulfate, fatty alcohol polyoxyethylene ether, and citric acid to the solution in step S2 and mix well;

[0038] S4. Pulverize the pulp. Start the motor during pulverization, the pulverization time is 120 min, the pH of the obtained pulp solution is 5.7, and the pulping yield is 96%; the pulping yield is calculated as follows: Pulping yield = (1 - amount of incompletely pulverized waste paper / amount of waste paper) * 100%, and the incompletely pulverized waste paper is the waste paper remaining after screening through a vibrating screen with a sieve slot of 0.15 mm. The above amounts of paper are all absolute dry masses.

[0039] Example 2

[0040] A wet strength dissociating agent for recycled waste paper pulping. By weight percentage of the waste paper, the wet strength dissociating agent includes the following raw material types: 20% of a solution containing an oxidant, 0.1% of sodium chloride, 6% of aluminum sulfate, 0.05% of alkylphenol polyoxyethylene ether, and 0.01% of sodium hexametaphosphate. The solution containing an oxidant is a circulating solution in the production process of persulfate. The circulating solution is the centrifugal filtrate in the production process of potassium persulfate hydrogen sulfate. After component adjustment, the hydrogen peroxide content is 3-4% (3% in this example), the persulfate content is 6-8% (8% in this example), the sulfuric acid content is 4-6% (4% in this example), and the rest is water;

[0041] The usage method of the above wet strength dissociating agent includes the following steps:

[0042] S1. Add a predetermined amount of water to the PAE wet strength waste paper for pre-soaking; the pre-soaking temperature is 10°C, the pre-soaking time is 30 min, and the pre-soaking is carried out in a hydrapulper;

[0043] S2. Add the solution containing an oxidant to the pre-soaked waste paper and mix evenly;

[0044] S3. Add sodium chloride, aluminum sulfate, alkylphenol polyoxyethylene ether, and sodium hexametaphosphate to the solution in step S2 and mix evenly;

[0045] S4. Pulverize the pulp. When pulverizing, start the motor, the pulverizing time is 30 min, the pH of the obtained pulp solution is 5.1, and the pulping yield is 94%.

[0046] Example 3

[0047] A wet strength dissociating agent for recycled waste paper pulping. By weight percentage of the waste paper, the wet strength dissociating agent includes the following raw material types: 15% of a solution containing an oxidant, 0.5% of sodium chloride, 2% of magnesium sulfate, 2% of aluminum sulfate, 0.1% of fatty acid methyl ester ethoxylate, and 0.03% of sodium silicate. The solution containing an oxidant is a mixed solution prepared from persulfate (potassium persulfate in this example), hydrogen peroxide, concentrated sulfuric acid, and water. In the mixed solution, the mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid, and water is 6:4:4:86.

[0048] The usage method of the above wet strength dissociating agent includes the following steps:

[0049] S1. Add a predetermined amount of water to the MF wet strength waste paper for pre-soaking; preferably, the pre-soaking temperature is 30°C, the pre-soaking time is 20 min, and the pre-soaking is carried out in a hydrapulper;

[0050] S2. Add the solution containing an oxidant to the pre-soaked waste paper and mix evenly;

[0051] S3. Add sodium chloride, magnesium sulfate, aluminum sulfate, fatty acid methyl ester ethoxylate, and sodium silicate to the solution in step S2 and mix evenly;

[0052] S4. Pulverize the pulp. Start the motor during pulverization. The pulverization time is 80 min. The pH of the obtained pulp solution is 5.3, and the pulping yield is 97%.

[0053] Example 4

[0054] A wet strength dissociating agent for recycling waste paper pulping. By weight percentage of waste paper, the wet strength dissociating agent includes the following raw material types: 8% of a solution containing an oxidant, 0.7% of sodium chloride, 4% of aluminum sulfate, 0.05% of fatty alcohol polyoxyethylene ether, 0.05% of alkylphenol polyoxyethylene ether, and 0.03% of HEDP. The solution containing an oxidant is a mixed solution prepared from persulfate (sodium persulfate in this example), hydrogen peroxide, concentrated sulfuric acid, and water. The mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid, and water in the mixed solution is 8:3:6:83.

[0055] The usage method of the above wet strength dissociating agent includes the following steps:

[0056] S1. Add a predetermined amount of water to the UF wet strength waste paper for pre-soaking; the pre-soaking temperature is 10 - 50 °C, the pre-soaking time is 5 - 30 min, and the pre-soaking is carried out in a hydrapulper;

[0057] S2. Add the solution containing an oxidant to the pre-soaked waste paper and mix evenly;

[0058] S3. Add sodium chloride, aluminum sulfate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and HEDP to the solution in step S2 and mix evenly;

[0059] S4. Pulverize the pulp. Start the motor during pulverization. The pulverization time is 60 min. The pH of the obtained pulp solution is 5.5, and the pulping yield is 94%.

[0060] Example 5

[0061] A wet strength dissociating agent for recycling waste paper pulping. By weight percentage of waste paper, the wet strength dissociating agent includes the following raw material types: 18% of a solution containing an oxidant, 0.4% of sodium chloride, 3% of magnesium sulfate, 0.03% of fatty alcohol polyoxyethylene ether, 0.03% of alkylphenol polyoxyethylene ether, 0.04% of EDTA, and 0.03% of fatty acid methyl ester ethoxylate. The solution containing an oxidant is a circulating solution in the production process of persulfate. The circulating solution is the centrifugal filtrate in the production process of potassium peroxymonosulfate. After component adjustment, the hydrogen peroxide content is 3 - 4% (3.5% in this example), the persulfate is 6 - 8% (7% in this example), the sulfuric acid is 4 - 6% (5% in this example), and the rest is water.

[0062] The method for using the above wet strength dissociating agent includes the following steps:

[0063] S1. Add a predetermined amount of water to the MF wet strength waste paper for pre-soaking; the pre-soaking temperature is 40 °C, the pre-soaking time is 20 min, and the pre-soaking is carried out in a hydrapulper;

[0064] S2. Add a solution containing an oxidant to the pre-soaked waste paper and mix evenly;

[0065] S3. Add sodium chloride, magnesium sulfate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid methyl ester ethoxylate, and EDTA to the solution in step S2 and mix evenly;

[0066] S4. Pulverize the pulp. When pulverizing, start the motor, the pulverizing time is 40 min, the pH of the obtained pulp solution is 5.2, and the pulping yield is 98%.

[0067] Example 6

[0068] A wet strength dissociating agent for recycling waste paper pulping, calculated by weight percentage of the waste paper, the wet strength dissociating agent includes the following raw material types: 10% of a solution containing an oxidant, 0.6% of sodium chloride, 3% of magnesium sulfate, 3% of aluminum sulfate, 0.03% of fatty alcohol polyoxyethylene ether, 0.03% of alkylphenol polyoxyethylene ether, 0.02% of citric acid, 0.02% of sodium silicate, and 0.03% of fatty acid methyl ester ethoxylate. The solution containing an oxidant is a mixed solution prepared from persulfate (in this example, potassium monopersulfate compound salt), hydrogen peroxide, concentrated sulfuric acid, and water. The mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid, and water in the mixed solution is 7:4:5:84.

[0069] The method for using the above wet strength dissociating agent includes the following steps:

[0070] S1. Add a predetermined amount of water to the PAE wet strength waste paper for pre-soaking; the pre-soaking temperature is 20 °C, the pre-soaking time is 25 min, and the pre-soaking is carried out in a hydrapulper;

[0071] S2. Add a solution containing an oxidant to the pre-soaked waste paper and mix evenly;

[0072] S3. Add sodium chloride, magnesium sulfate, aluminum sulfate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid methyl ester ethoxylate, citric acid, and sodium silicate to the solution in step S2 and mix evenly;

[0073] S4. Pulverize the pulp. When pulverizing, start the motor, the pulverizing time is 50 min, the pH of the obtained pulp solution is 5.6, and the pulping yield is 98%.

[0074] Comparative Example 1

[0075] Comparative Example 1 is a comparative test of Example 1. The difference is that sodium chloride is not added in Comparative Example 1, and the other conditions and parameters are the same as those in Example 1. When pulping the same MF wet-strength waste paper, after pulping for the same 120 minutes, the pH of the obtained pulp solution is 5.8, and the pulping yield is 90%.

[0076] Comparative Example 2

[0077] Comparative Example 2 is a comparative test of Example 1. The difference is that sulfate (magnesium sulfate) is not added in Comparative Example 2, and the other conditions and parameters are the same as those in Example 1. When pulping the same MF wet-strength waste paper, after pulping for the same 120 minutes, the pH of the obtained pulp solution is 4.5, and the pulping yield is 89%.

[0078] Comparative Examples 3 - 5

[0079] Comparative Examples 3 - 5 are comparative tests of Example 1. The differences are that the solution containing oxidant is not added in Comparative Example 3, the addition amount of the solution containing oxidant is 3% of the weight of the waste paper in Comparative Example 4, and the addition amount of the solution containing oxidant is 25% of the weight of the waste paper in Comparative Example 5. The other conditions and parameters are the same as those in Example 1. When pulping the same MF wet-strength waste paper, after pulping for the same 120 minutes, the pH of the pulp solution obtained in Comparative Example 3 is 7.0, and the pulping yield is 13%; the pH of the pulp solution obtained in Comparative Example 4 is 6.5, and the pulping yield is 68%; the pH of the pulp solution obtained in Comparative Example 5 is 3.5, and the pulping yield is 96%.

[0080] Comparative Example 6

[0081] Comparative Example 6 is a comparative test of Example 1. The difference is that the stabilizer is not added in Comparative Example 6, and the other conditions are the same as those in Example 1. When pulping the same MF wet-strength waste paper, the time required for complete pulping is 150 minutes. After complete pulping, the pH of the obtained pulp solution is 5.6, and the pulping yield is 97%.

[0082] Test Example

[0083] The pulp prepared in the above Examples 1 - 6 and Comparative Examples 1 - 6 was tested for the strength of pulp fibers. The testing method:

[0084] Take 0.1 g (absolute dry) of the pulp for dispersion, and then use a fiber test analyzer to analyze the number-average fiber length of the fibers.

[0085] The fiber strength is characterized by the strength of the formed paper:

[0086] After the handsheets are placed in a thermo-hygrostat with a relative humidity of (50±2)% and a temperature of (23±1)°C for 24 h to balance the moisture, relevant physical properties are measured respectively in accordance with the national standards GB / T 455---2002 "Determination of Tear Strength of Paper and Paperboard", GB / T 22898--2008 "Paper and Paperboard - Determination of Tensile Strength - Constant Rate Elongation Method (100 mm / min)", etc.

[0087] The test results are as follows:

[0088] Table 1

[0089]

[0090]

[0091] The larger the tensile index and tear index of the paper, the stronger the relative fiber strength. The number-average fiber length shows the change in fiber length to a certain extent, and a small value indicates that the fibers are damaged to a certain extent. The above test results show that the wet strength dissociating agent of the present invention not only has a good dissociation effect but also has little influence on the fiber length and strength in waste paper.

[0092] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A wet strength dissociating agent, which is used for pulping when wet strength waste paper is recycled. It is characterized in that Calculated by weight percentage of wet strength waste paper, the wet strength dissociating agent includes the following raw material types: 5-20% of a solution containing an oxidant, 0.1-1% of sodium chloride, 0-6% of sulfate, 0-0.1% of a non-ionic surfactant, and 0.01-0.05% of a stabilizer. The solution containing an oxidant is a mixed solution prepared from persulfate, hydrogen peroxide, concentrated sulfuric acid and water. The mass ratio of persulfate, hydrogen peroxide, concentrated sulfuric acid and water in the mixed solution is 6-8:3-4:4-6:87-82.

2. A wet strength dissociating agent according to claim 1, It is characterized in that The persulfate is at least one of potassium persulfate, sodium persulfate or potassium peroxymonosulfate compound salt.

3. A wet strength dissociating agent according to claim 1 or 2, It is characterized in that The sulfate includes at least one of magnesium sulfate and aluminum sulfate; the stabilizer is at least one of HEDP, EDTA, citric acid, sodium hexametaphosphate and sodium silicate.

4. A method for using the wet strength dissociating agent according to claim 1 or 2, It is characterized in that It includes the following steps: S1. Add a predetermined amount of water to the waste paper for pre-soaking. S2. Add the solution containing an oxidant to the pre-soaked waste paper and mix evenly. S3. Add sodium chloride, sulfate, non-ionic surfactant and stabilizer to the solution in step S2 and mix evenly. S4. Pulverize to obtain pulp; the pH value of the obtained pulp is 5.1-5.7, and the pulp yield is 94%-98%.

5. A method for using the wet strength dissociating agent according to claim 5, It is characterized in that In step S1, the pre-soaking temperature is 10-50°C, the pre-soaking time is 5-30 min, and the pre-soaking is carried out in a hydrapulper.

6. A method for using the wet strength dissociating agent according to claim 5, It is characterized in that In step S4, start the motor during pulverization, the pulverization time is 30-120 min, and the concentration of the obtained pulp is 8-15%. ​ ​ ​

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