阅读说明：本技术 造纸白水净化剂及其使用方法、包含其的改性纸浆及改性纸 (Papermaking white water purifying agent, using method thereof, modified paper pulp containing papermaking white water purifying agent and modified paper ) 是由 张金柱 张延伟 王鹏辉 于 2020-05-11 设计创作，主要内容包括：本发明提供了一种造纸白水净化剂及其使用方法、包含其的改性纸浆及改性纸,所述造纸白水净化剂包括改性或未改性的纳米纤维素类材料。本发明提供的造纸白水净化剂可以替代目前现有技术中的无机盐类絮凝剂,降低造纸白水中细小纤维、无机填料等悬浮固形物含量以及木质素、半纤维素、添加助剂等溶解物的含量,并且减轻对设备腐蚀损坏,降低机械的停机率；同时,加入造纸白水中的造纸白水净化剂可以作为浆内添加助剂使用,改善纸浆的性能,进而可以提高最后得到的改性纸的抗张强度等。(The invention provides a papermaking white water purifying agent, a using method thereof, modified paper pulp containing the papermaking white water purifying agent and modified paper. The papermaking white water purifying agent provided by the invention can replace inorganic salt flocculating agents in the prior art, reduce the content of suspended solid matters such as fine fibers and inorganic fillers and the content of dissolved matters such as lignin, hemicellulose and additive in papermaking white water, reduce the corrosion damage to equipment and reduce the shutdown rate of machinery; meanwhile, the papermaking white water purifying agent added into the papermaking white water can be used as an additive in the pulp to improve the performance of the paper pulp, so that the tensile strength and the like of the finally obtained modified paper can be improved.)

1. A purifying agent for papermaking white water, which is characterized by comprising a modified or unmodified nano cellulose material.

2. The papermaking white water purifying agent according to claim 1, wherein the nanocellulose-based material comprises any one or a combination of at least two of nanocellulose, micro-nanocellulose, lignin micro-nanocellulose, or lignin nanocellulose;

preferably, the modified or unmodified nanocellulose-based material has a diameter of 8-100nm, an aspect ratio of 50-5000, more preferably a diameter of 8-30nm, and an aspect ratio of 50-500.

3. The papermaking white water purifying agent according to claim 1 or 2, characterized in that the papermaking white water purifying agent comprises a modified nanocellulose-based material;

preferably, the modified nanocellulose material comprises any one or a combination of at least two of an oxidation-modified nanocellulose material, an esterification-modified nanocellulose material, a carboxylation-modified nanocellulose material, a cation-modified nanocellulose material, an etherification-modified nanocellulose material, or a graft polymerization-modified nanocellulose material, more preferably a carboxylation-modified nanocellulose material and/or a cation-modified nanocellulose material, and even more preferably a cation-modified nanocellulose material.

4. Use of a paper making white water scavenger according to any one of claims 1-3, characterized in that it comprises: mixing a papermaking white water purifying agent with paper pulp;

preferably, the mixing is performed in a mixing tank;

preferably, the amount of the papermaking white water purifying agent is 0.1-5%, and more preferably 0.8-1.2% of the oven dry mass of the pulp;

preferably, the papermaking white water purifying agent is mixed with the pulp in the form of a dispersion.

5. A modified pulp, characterized in that it comprises the papermaking white water purifying agent of any one of claims 1 to 4.

6. The modified pulp according to claim 5, characterized in that the amount of said papermaking white water purifying agent added to said modified pulp is 0.1-5%, more preferably 0.8-1.2% of the oven dry mass of the pulp.

7. The modified pulp of claim 5 or 6, further comprising an inorganic filler.

8. Modified paper produced from the modified pulp according to any one of claims 5-7.

9. The method for preparing modified paper according to claim 8, characterized in that the method comprises the steps of:

(1) mixing paper pulp, a paper making white water purifying agent, paper making white water and optional inorganic filler to obtain modified paper pulp;

(2) and defibering, homogenizing and papermaking the modified paper pulp to obtain the modified paper.

10. The production method according to claim 9, wherein the pulp is selected from any one of softwood pulp, hardwood pulp, bamboo pulp, plant pulp, or secondary recycled pulp or a combination of at least two thereof;

preferably, the papermaking white water includes white water that has not been subjected to a cleaning treatment.

Technical Field

The invention belongs to the technical field of papermaking production, and relates to a papermaking white water purifying agent, a using method thereof, modified paper pulp containing the purifying agent and modified paper.

Background

At present, in the white water for papermaking, colloids such as lignin, fine fibers, fillers and the like with negative charges in the white water are polymerized by adding a flocculating agent into the white water after papermaking to form large particles, so that the colloid particles are easy to precipitate or float and separate, most flocculating agents are salt-containing compounds, and the addition of the flocculating agents can increase the salt content in the white water, have a certain corrosion effect on equipment and increase the cost of later-stage water purification.

CN101285278A discloses a white water recovery process for papermaking by static precipitation method, which is to introduce the white water generated in the papermaking process into one or more settling ponds, to let stand until the turbidity of the supernatant fluid is reduced to less than 40ppm, to draw the supernatant fluid for use, and to collect the precipitate. The patent application can recycle the white water of papermaking, but the settling ponds are arranged, and the occupied area is wider. CN106629970A discloses a method for treating and recycling papermaking white water, placing a graphene aerogel macroscopic integral material in an adsorption tower, filtering the papermaking white water from top to bottom, allowing purified wastewater to flow out from the bottom, intercepting fine fibers on the surface layer by using the porous structure of the graphene aerogel macroscopic integral material so as to be convenient for recycling, adsorbing soluble substances in the papermaking white water by using the adsorption effect of the graphene aerogel macroscopic integral material so as to reduce the influence of the accumulation of the soluble substances on the quality of subsequent water in a closed cycle process, and ensuring the quality of treated water by periodically activating the filled graphene aerogel macroscopic integral material. The patent application can realize the reutilization of the white water in the paper making, but has higher cost, and on the other hand, can not generate any powerful aftereffect on the paper pulp.

Therefore, there is a need to develop a material that can both purify the white water of paper making and improve the properties of paper to further meet the application requirements.

Disclosure of Invention

The invention aims to provide a papermaking white water purifying agent, a using method thereof, modified paper pulp containing the purifying agent and modified paper. The papermaking white water purifying agent provided by the invention can replace inorganic salt flocculating agents in the prior art, reduce the content of suspended solid matters such as fine fibers and inorganic fillers and the content of dissolved matters such as lignin, hemicellulose and additive agents in the papermaking white water, reduce the corrosion damage to equipment and reduce the shutdown rate of machinery; meanwhile, the papermaking white water purifying agent added into the papermaking white water can be used as an additive in the pulp to improve the performance of the paper pulp, so that the tensile strength and the like of the finally obtained modified paper can be improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a papermaking white water purifying agent comprising a modified or unmodified nanocellulose-based material.

The modified or unmodified nanocellulose material provided by the invention is a micro-nano or nano-sized cellulose, has a higher specific surface area and a higher length-diameter ratio, contains a large number of hydroxyl groups on the surface, has high surface activity, and has stronger adsorption capacity on salts, fine fibers, lignin, hemicellulose, inorganic matters and papermaking auxiliary agents in papermaking white water, so that the modified or unmodified nanocellulose material provided by the invention can replace a flocculating agent commonly used in the prior art, can be used as a papermaking white water purifying agent, can obviously reduce the content of suspended solid matters such as fine fibers and inorganic fillers in the papermaking white water and the content of dissolved matters such as lignin, hemicellulose, an additive and the like, and further reduces the indexes such as the conductivity, the total solid matter content and the COD (chemical oxygen demand) of the papermaking white water.

The papermaking white water purifying agent provided by the invention can replace the currently common salt flocculating agent, so that the salt content in the white water can be reduced, the corrosion damage to equipment can be reduced, the machine outage rate is reduced, the circulation frequency of the papermaking white water is increased, the operating cost of a paper mill is reduced, zero emission is gradually realized, and the pollution to the environment is reduced.

In the invention, the nano cellulose material comprises any one or a combination of at least two of nano cellulose, micro-nano cellulose, lignin micro-nano cellulose or lignin nano cellulose.

Preferably, the diameter of the modified or unmodified nanocellulose material is 8-100nm, such as 8-20nm, 10-50nm, 30-80nm, 40-100nm, 50-80nm, 30-90nm, etc., the aspect ratio is 50-5000, such as 50-100, 50-500, 100-.

Preferably, the papermaking white water purifying agent comprises a modified nanocellulose-based material.

Preferably, the modified nanocellulose material comprises any one of or a combination of at least two of an oxidation-modified nanocellulose material, an esterification-modified nanocellulose material, a carboxylation-modified nanocellulose material, a cation-modified nanocellulose material, an etherification-modified nanocellulose material or a graft polymerization-modified nanocellulose material, more preferably a carboxylation-modified nanocellulose material and/or a cation-modified nanocellulose material, and still more preferably a cation-modified nanocellulose material.

The carboxylation modified nano-cellulose material is any carboxylation modified nano-cellulose material available in the prior art, and the preparation method of the carboxylation modified nano-cellulose material is exemplified as follows:

and (3) placing the nano-cellulose dispersion liquid in a reaction kettle at 60 ℃, adding succinic anhydride for reaction, and washing to obtain a washing product, namely the required carboxylated nano-cellulose.

The cation-modified nanocellulose material of the present invention is any cation-modified nanocellulose material available in the prior art, and an exemplary preparation method of the cation-modified nanocellulose material is as follows:

and (3) placing the nano cellulose dispersion liquid in a reaction kettle at 48 ℃, adding 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and alkali, reacting, washing, and obtaining a washing product, namely the required cation modified nano cellulose material.

The surface activity of the nano-cellulose can be continuously improved by selecting the modified nano-cellulose material, and the action capacity of the nano-cellulose material with solid suspended matters, water-soluble organic matters and inorganic salts in paper pulp is improved. The cation modified nano-cellulose has very high positive charge density, is easy to combine with negative charge substances in paper pulp and has strong combination effect, so that the concentration of solid suspended matters such as fine fibers, lignin, hemicellulose, fillers and various auxiliary agents and medicines with negative charges in white water can be greatly reduced, and the cation modified nano-cellulose has more excellent purification effect.

In a second aspect, the present invention provides a method for using a paper making white water purifying agent, the method comprising: the papermaking white water purifying agent is mixed with the paper pulp.

Preferably, the mixing is performed in a mixing tank.

Preferably, the papermaking white water purifying agent is used in an amount of 0.1 to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc., more preferably 0.8 to 1.2%, for example, 0.9%, 1.0%, 1.1%, etc., of the oven dry mass of the pulp.

Preferably, the papermaking white water purifying agent is mixed with the pulp in the form of a dispersion.

The invention can add paper making white water purifying agent into paper pulp, and the purifying agent can be combined with paper pulp fiber in the paper making process, and the combination strength is high, thereby the aperture diameter between the paper fiber can be reduced, and the micro-net structure filter membrane is self-assembled, thereby the retention rate of fine fiber, inorganic matter, soluble organic matter, lignin, salt, paper making auxiliary agent and the like in the pulp can be improved.

The papermaking white water purifying agent is directly added into the paper pulp, so that the papermaking white water quality can be improved fundamentally, the total solid content of the papermaking white water is lower, a flocculating agent does not need to be added into the papermaking white water, the papermaking white water treatment process is optimized, and the papermaking white water purifying agent can replace the flocculating agent.

In a third aspect, the present invention provides a modified pulp comprising the papermaking white water purifying agent of the first aspect.

The papermaking white water purifying agent provided by the invention can play a role in purifying papermaking white water on one hand, and can retain salts, fine fibers, lignin, hemicellulose, inorganic matters, papermaking additives and the like in the papermaking white water in paper pulp on the other hand, and the papermaking white water purifying agent act together to improve the tensile strength of finally obtained paper. The papermaking white water purifying agent provided by the invention can also be used as an additive in pulp to improve the mechanical property of paper.

The invention improves the retention rate of the fine fiber and the filler in the paper pulp, thereby saving the paper pulp fiber raw material and reducing the papermaking cost.

Preferably, the amount of the papermaking white water purifying agent added to the modified pulp is 0.1 to 5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc., more preferably 0.8 to 1.2%, for example, 0.9%, 1.0%, 1.1%, etc., of the absolute dry mass of the pulp.

Preferably, the modified pulp further comprises an inorganic filler.

In a fourth aspect, the present invention provides a modified paper prepared from the modified pulp of the third aspect.

In a fifth aspect, the present invention provides a method for producing a modified paper according to the fourth aspect, comprising the steps of:

(1) mixing paper pulp, a paper making white water purifying agent, paper making white water and optional inorganic filler to obtain modified paper pulp;

(2) and defibering, homogenizing and papermaking the modified paper pulp to obtain the modified paper.

Preferably, the pulp is selected from any one of softwood pulp, hardwood pulp, bamboo pulp, plant pulp or secondary recycled pulp or a combination of at least two thereof.

Preferably, the papermaking white water includes white water that has not been subjected to a cleaning treatment.

Compared with the prior art, the invention has the following beneficial effects:

(1) the papermaking white water purifying agent provided by the invention has strong adsorption capacity on salts, fine fibers, lignin, hemicellulose, inorganic matters and papermaking auxiliaries in the papermaking white water, and can replace a flocculating agent commonly used for purifying the papermaking white water at present;

(2) the papermaking purifying agent can be mixed with paper pulp, so that the retention rates of fine fibers, inorganic matters, soluble organic matters, lignin, salts, papermaking auxiliaries and the like in the paper pulp are improved, further, papermaking white water is purified from the source, and the cycle number of the papermaking white water is increased;

(3) the papermaking purifying agent can reduce the salt content in the white water, reduce the corrosion damage to equipment, reduce the shutdown rate of machinery and reduce the operating cost of a paper mill;

(4) the papermaking purifying agent provided by the invention can improve the retention rates of fine fibers, inorganic matters, soluble organic matters, lignin, salts, papermaking auxiliaries and the like in paper pulp in the white water while achieving the purpose of purifying the white water for papermaking, and further improves the tensile strength and the like of finally obtained paper;

(5) the papermaking purifying agent is mixed with paper pulp, so that papermaking white water after papermaking of paper can be recycled, wherein the conductivity, the total solid content and the COD of the white water are lower, the conductivity of the papermaking white water is below 4.23ms/cm, the COD value is below 575mg/L, and the total stock content is below 0.43 per mill;

(6) the paper-making purifying agent of the invention is mixed with paper pulp, and the strength of the finally obtained paper can be improved, wherein the tensile index of the paper is more than 60.2 N.m/g, and the optimal tensile index can reach more than 67.2 N.m/g.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Use example 1

The application method of the papermaking white water purifying agent comprises the following steps:

adding nano cellulose into a pulp mixing tank according to the proportion that the adding amount is 0.8 percent of the absolute dry mass of the paper pulp, mixing the nano cellulose with the paper pulp, and papermaking;

wherein the nano-cellulose is added in the form of nano-cellulose dispersion liquid, the solid content of the nano-cellulose dispersion liquid is 0.3 percent, the diameter of the nano-cellulose is 8-20nm, and the length-diameter ratio is 50-300;

wherein the paper pulp is Venus-brand softwood pulp.

Use examples 2 to 4

The difference from use example 1 is that nanocellulose was replaced with lignin nanocellulose (use example 2), carboxylated nanocellulose (use example 3), and cationized nanocellulose (use example 4);

wherein the diameter of the lignin nanocellulose is 8-100nm, the length-diameter ratio is 50-500, the lignin content is 26%, and the lignin content is 26%;

wherein, the preparation methods of the carboxylated nano-cellulose and the cationized nano-cellulose refer to the preparation methods provided in the specification.

Use example 5

The difference from the use example 1 is that the nanocellulose was replaced by nanocellulose having a diameter of 50-80nm and an aspect ratio of 400-1000.

Comparative application example 1

The difference from use example 1 is that no nanocellulose was added to the slurry tank.

Comparative example 2

The difference from the use example 1 is that no nanocellulose was added to the mixing tank, and then an aluminum sulfate flocculant was added to the papermaking white water after papermaking to make a sheet, the amount of which was 0.2% of the total amount of the white water.

Performance test 1

The performance of the papermaking white water produced on the paper sheets of the use examples 1 to 5 and comparative use examples 1 to 2 was tested by the following method:

(1) COD: testing according to the test standard provided by the method for determining the chemical oxygen demand of the water quality HJ 828-2017 dichromate method;

(2) conductivity: testing according to the test standard provided by GB/T11007-2008 conductivity meter test method;

(3) total solid content: testing according to the test standard provided by Water and wastewater monitoring and analyzing method;

the test results are shown in table 1:

TABLE 1

The embodiment and the performance test show that the papermaking white water purifying agent provided by the invention has the function of purifying papermaking white water, can reduce the indexes of the conductivity, the total solid content, COD (chemical oxygen demand) and the like of the papermaking white water, and enables the papermaking white water subjected to papermaking to be recycled in diameter, wherein the conductivity of the papermaking white water is below 4.23ms/cm, the COD value is below 575mg/L, and the total stock content is below 0.43 per thousand.

As can be seen from the comparison of the use examples 1 to 4, in the present invention, the improvement degree of the cationized nanocellulose on the papermaking white water is superior to the carboxylated nanocellulose, the nanocellulose and the lignin nanocellulose. As can be seen from the comparison between the use examples 1 and 5, in the present invention, the modified or unmodified nanocellulose-based material having a diameter of 8 to 30nm and an aspect ratio of 50 to 500 has a better purification effect on white water.

As is clear from the comparison between application example 1 and comparative application example 1, the present invention has a significant purifying effect on the white water of the papermaking; as can be seen from the comparison between the use example 1 and the comparative use example 2, the papermaking purifying agent provided by the invention can replace the conventional papermaking white water flocculant.