A method for improving the performance of waste pulp with high lignin content

Abstract

The present invention belongs to the field of waste paper pulp performance recovery, and specifically relates to a method for improving the performance of waste paper pulp with high lignin content, comprising the following preparation steps: placing waste paper pulp in a sealed bag, dripping propyl acetoacetate into the waste paper pulp, and kneading it thoroughly to make it evenly mixed; adding sulfuric acid solution to the evenly mixed waste paper pulp, and kneading it thoroughly to make it evenly mixed; heating the evenly mixed waste paper pulp to react, kneading it during the reaction, and washing it with water after the reaction to obtain modified waste paper pulp. The process of the present invention is simple, easy to operate, and convenient for industrial application. The swelling property of the modified waste paper pulp fiber is improved, and the strength of the paper made of the modified waste paper pulp is improved, which expands the application scenarios of waste paper pulp.

Description

Technical Field

[0001] The invention belongs to the field of waste paper pulp performance recovery, and in particular relates to a method for improving the performance of waste paper pulp with high lignin content. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] With the strengthening of environmental protection awareness and the increasing shortage of plant resources, the recycling and utilization of waste paper has received more and more attention from pulp and paper companies. Waste paper is cheap and widely available, which can effectively solve the shortage of papermaking raw materials. In addition, it is also conducive to solving the pollution to the environment during the pulping and papermaking process. However, as the number of recycling increases, the fiber undergoes multiple swelling, high-temperature drying, pressing and other processes, and the fiber becomes keratinized, resulting in a decrease in the strength of the finished paper, which to a certain extent limits the recycling of waste paper.

[0004] At present, the paper strength of waste paper pulp is improved by many methods such as mechanical pulping, chemical additive addition, and biological enzyme pretreatment. Among the existing pulping methods, mechanical pulp occupies a large share in the entire pulping industry due to its simple process, low cost, high yield, and low pollution. However, this pulping method retains most of the lignin in the raw material, which makes it easy to turn yellow during subsequent use and the mechanical strength of the paper is low, which greatly limits the recycling of this type of waste paper. Many researchers have found that after treating waste paper pulp with a high lignin content with the help of laccase and then grafting and modifying it with amino acids, the carboxyl content on the surface of the waste paper pulp fibers is significantly increased, thereby increasing the swelling of the fibers, improving the softness of the fibers, and increasing the bonding energy of the fibers in the paper sheet, and improving the paper strength of the waste paper pulp. However, the above method requires the use of biological enzymes for treatment, and the reaction conditions are relatively harsh, making it difficult to achieve large-scale application. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, an object of the present invention is to provide a method for improving the performance of waste paper pulp with high lignin content.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for improving the properties of waste paper pulp with a high lignin content, comprising the following steps:

[0008] S1. Put waste paper pulp in a sealed bag, add propyl acetoacetate dropwise into the waste paper pulp, and knead thoroughly to mix the waste paper pulp evenly;

[0009] S2, adding sulfuric acid solution to the mixed waste paper pulp, and kneading it thoroughly to make it mixed evenly;

[0010] S3, heating the uniformly mixed waste paper pulp to react, kneading it during the reaction, and washing it with water after the reaction to obtain modified waste paper pulp.

[0011] In a second aspect, the present invention provides modified waste paper pulp obtained by the method for improving the properties of waste paper pulp with high lignin content described in the first aspect.

[0012] In a third aspect, the present invention provides the use of the modified waste paper pulp described in the second aspect in waste paper making.

[0013] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0014] (1) Compared with the enzyme treatment method, the method provided by the present invention has simple process, mild reaction conditions, readily available raw materials, easy operation, and convenient industrial application.

[0015] (2) The method for improving the performance of waste paper pulp with high lignin content obtained by the present invention has improved swelling properties of fibers in the modified waste paper pulp, improved paper strength, and expanded application scenarios of the waste paper pulp. DETAILED DESCRIPTION

[0016] A first typical embodiment of the present invention is a method for improving the properties of waste paper pulp with high lignin content, comprising the following steps:

[0017] S1. Put waste paper pulp in a sealed bag, add propyl acetoacetate dropwise into the waste paper pulp, and knead thoroughly to mix the waste paper pulp evenly;

[0018] S2, adding sulfuric acid solution to the mixed waste paper pulp, and kneading it thoroughly to make it mixed evenly;

[0019] S3, heating the uniformly mixed waste paper pulp to react, kneading it during the reaction, and washing it with water after the reaction to obtain modified waste paper pulp.

[0020] In one or more examples of this embodiment, the waste paper pulp includes mechanical pulp or chemical mechanical pulp that is recycled, and the mechanical pulp or chemical mechanical pulp is derived from coniferous wood, hardwood and grass raw materials.

[0021] The main reason for the yellowing and brittleness of waste paper pulp with high lignin content is the phenolic hydroxyl groups in lignin. With the help of acetoacetate and sulfuric acid, the phenolic hydroxyl groups can react to improve the yellowing. In addition, the strength of the paper fiber after modification is significantly improved.

[0022] In one or more examples of this embodiment, the content of lignin in the waste paper pulp is 10-15%.

[0023] In one or more examples of this implementation mode, in step S1: the purity of the propyl acetoacetate is 92-95%; the mass ratio of the waste paper pulp to the propyl acetoacetate is 20-30:1; and the dripping speed of the propyl acetoacetate is 2-5 mL / min.

[0024] In one or more examples of this embodiment, the mass ratio of sulfuric acid to propyl acetoacetate is 1:5-8.

[0025] In one or more examples of this implementation mode, in step S2: the kneading temperature is 1-4° C., and the kneading time is 0.5-1.5 h.

[0026] In one or more examples of this embodiment, the temperature is raised to 20-40° C. in step S3 .

[0027] In one or more examples of this implementation mode, the reaction time in step S3 is 4-5 hours, and the kneading is performed at intervals of 30-60 minutes.

[0028] The second typical embodiment of the present invention is the modified waste paper pulp obtained by the method for improving the properties of waste paper pulp with high lignin content described in the first typical embodiment.

[0029] A third typical embodiment of the present invention is the use of the modified waste paper pulp described in the second typical embodiment in waste paper making.

[0030] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0031] Example 1

[0032] Take poplar chemical mechanical pulp waste paper (lignin content 12%) and place it in a sealed bag, then add 92% purity acetoacetate to the waste paper pulp, the drop rate is 2mL / min, the mass ratio of waste paper pulp to acetoacetate is 20:1, and knead it thoroughly. The mixed waste paper pulp is placed at 1°C, sulfuric acid solution is added, the mass ratio of acetoacetate to sulfuric acid is 5:1, and it is kneaded thoroughly to make it evenly mixed. After 0.5h, the temperature of the mixed system is increased to 25°C, and the reaction is continued for 4h, and kneading is performed every 30min. After the reaction is completed, it is washed with water to obtain modified waste paper pulp.

[0033] Control group: Poplar chemical mechanical pulp waste paper (lignin content 12%) was placed in a sealed bag, and then deionized water was added to the waste paper pulp at a dropping speed of 2mL / min. The mass ratio of waste paper pulp to deionized water was 20:1, and it was fully kneaded. The mixed waste paper pulp was placed at 1°C, deionized water was added, and it was fully kneaded to make it evenly mixed. After 0.5h, the temperature of the mixed system was increased to 25°C, and the reaction was continued for 4h, during which it was kneaded every 30min. After the reaction was completed, it was washed with water to obtain modified waste paper pulp.

[0034] The modified waste paper pulp was made into paper (with a basis weight of 60 g / m 2 ), and the physical strength of the finished paper was measured. The test results are shown in Table 1.

[0035] Table 1 Comparison of physical strength of waste paper pulp before and after modification

[0036]

[0037] From the data in Table 1, it can be seen that the tensile index of paper made from modified waste paper pulp prepared by the above method has increased from the original 23.52N·m·g -1 Increased to 29.56N·m·g -1 The burst resistance index is increased from 1.21KPa·m 2 ·g -1 Increased to 1.53KPa·m 2 ·g -1 The tear index is increased from 2.35mN·m 2 ·g -1 Increased to 2.87mN·m 2 ·g -1 The above results confirm that this method can effectively improve the paper strength of waste paper pulp and improve the performance of waste paper pulp.

[0038] Example 2

[0039] Take the straw chemical mechanical pulp waste paper (lignin content 10%) and put it in a sealed bag, then add 95% purity acetoacetate to the waste paper pulp, the drop rate is 5mL / min, the mass ratio of waste paper pulp to acetoacetate is 25:1, and knead it thoroughly. The mixed waste paper pulp is placed at 1°C, sulfuric acid solution is added, the mass ratio of acetoacetate to sulfuric acid is 8:1, and it is kneaded thoroughly to make it evenly mixed. After 1 hour, the temperature of the mixed system is increased to 40°C, and the reaction is continued for 5 hours, and kneading is performed every 45 minutes. After the reaction is completed, it is washed with water to obtain modified waste paper pulp.

[0040] Control group: Propyl acetoacetate and sulfuric acid were replaced with an equal amount of deionized water to obtain modified waste paper pulp as the control group.

[0041] The modified waste paper pulp was made into paper (with a basis weight of 60 g / m 2 ), and the physical strength of the finished paper was measured. The test results are shown in Table 2.

[0042] Table 2 Comparison of physical strength of waste paper pulp before and after modification

[0043]

[0044] From the data in Table 2, it can be seen that the tear length of paper made from modified waste paper pulp prepared by the above method is increased from the original x3.65Km to 3.98Km, and the bursting index is increased from the original 2.26KPa·m 2 ·g -1 Increased to 2.93KPa·m 2 ·g -1 The tear index is increased from 2.84mN·m 2 ·g -1 Increased to 3.01mN·m 2 ·g -1 The above results confirm that this method can effectively improve the paper strength of waste paper pulp and improve the performance of waste paper pulp.

[0045] Example 3

[0046] Take eucalyptus peroxide hydroperoxide mechanical pulp waste paper (lignin content 15%) and place it in a sealed bag, then add 95% purity acetoacetate to the waste paper pulp, the drop rate is 2mL / min, the mass ratio of waste paper pulp to acetoacetate is 20:1, and knead it thoroughly. The mixed waste paper pulp is placed at 1°C, sulfuric acid solution is added, the mass ratio of acetoacetate to sulfuric acid is 5:1, and it is fully kneaded to make it evenly mixed. After 0.5h, the temperature of the mixed system is increased to 25°C, and the reaction is continued for 4h, and kneading is performed every 30min. After the reaction is completed, it is washed with water to obtain modified waste paper pulp.

[0047] Control group: Propyl acetoacetate and sulfuric acid were replaced with an equal amount of deionized water to obtain modified waste paper pulp as the control group.

[0048] The modified waste paper pulp was made into paper (with a basis weight of 60 g / m 2 ), and the physical strength of the finished paper was measured. The test results are shown in Table 3.

[0049] Table 3 Comparison of physical strength of waste paper pulp before and after modification

[0050]

[0051] From the data in Table 3, it can be seen that the tensile index of paper made from modified waste pulp prepared by the above method is increased from the original 2.75Km to 2.92Km, and the bursting index is increased from the original 1.89KPa·m 2 ·g -1 Increased to 2.07KPa·m 2 ·g -1 The tear index is increased from 2.16mN·m 2 ·g -1 Increased to 2.38mN·m 2 ·g -1 The above results confirm that this method can effectively improve the paper strength of waste paper pulp and improve the performance of waste paper pulp.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the properties of waste paper pulp with high lignin content, characterized in that: The following steps are involved: S1. Put waste paper pulp in a sealed bag, add propyl acetoacetate dropwise into the waste paper pulp, and knead thoroughly to mix the waste paper pulp evenly; S2, adding sulfuric acid solution to the mixed waste paper pulp, and kneading it thoroughly to make it mixed evenly; S3, heating the uniformly mixed waste paper pulp to react, kneading it during the reaction, and washing it with water after the reaction is completed to obtain modified waste paper pulp; In step S1: the mass ratio of the waste paper pulp to propyl acetoacetate is 20-30:1; the dripping speed of the propyl acetoacetate is 2-5 mL / min; The mass ratio of sulfuric acid to propyl acetoacetate is 1:5-8; In step S2: the kneading temperature is 1-4°C, and the kneading time is 0.5-1.5 h; In step S3, the temperature is raised to 20-40°C; In step S3, the reaction time is 4-5 h, and the kneading is performed at intervals of 30-60 min; The content of lignin in the waste paper pulp is 10-15%.

2. A method for improving the properties of waste paper pulp with high lignin content as claimed in claim 1, characterized in that: The waste paper pulp includes mechanical pulp or chemical mechanical pulp that is recycled, and the mechanical pulp or chemical mechanical pulp is derived from coniferous wood, broad-leaved wood and grass raw materials.

3. The method for improving the properties of waste paper pulp with high lignin content according to claim 1, characterized in that: In step S1: the purity of the propyl acetoacetate is 92-95%.

4. Modified waste paper pulp obtained by the method for improving the properties of waste paper pulp with high lignin content according to any one of claims 1 to 3.

5. Use of the modified waste paper pulp according to claim 4 in waste paper making.

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