CN115787346B

CN115787346B - Efficient dispersion method of aramid fiber

Info

Publication number: CN115787346B
Application number: CN202211531090.8A
Authority: CN
Inventors: 李霞; 韩文佳; 姜亦飞; 丁其军; 娄江; 柳竹青
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2022-12-01
Filing date: 2022-12-01
Publication date: 2023-09-22
Anticipated expiration: 2042-12-01
Also published as: CN115787346A

Abstract

The invention belongs to the field of aramid fiber paper-based materials, and provides a method for efficiently dispersing aramid fibers. The method comprises the steps of simple irradiation treatment, and then adding aluminum salt and nanocellulose in sequence. The method of the invention mainly uses the electronegative functional group and Al generated after the irradiation treatment of the surface of the aramid fiber ³⁺ The strong charge interaction and the easy dispersibility of the nanocellulose, and the high suspension stability realize the efficient dispersion of the aramid fiber. Meanwhile, a large amount of hydroxyl groups on the surface of the nanocellulose can form hydrogen bond combination after being dried, so that the strength performance of the aramid fiber paper can be effectively improved, the method has important significance for development of an aramid fiber material, and particularly the aramid fiber paper-based material with high uniformity can be prepared.

Description

Efficient dispersion method of aramid fiber

Technical Field

The invention belongs to the technical field of aramid fiber paper-based materials, and particularly relates to a method for efficiently dispersing aramid fibers.

Background

The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.

Aramid fibers are aromatic polyamides artificially synthesized in the last century. The polyamide compound is defined as a polyamide compound in which at least 85% of amide bonds in a long chain are directly connected with two benzene rings, and is roughly classified into three types according to the difference of molecular structures: para-aramid fiber, meta-aramid fiber, and heterocyclic aramid fiber. It has unique characteristics such as high strength, high modulus, good thermal stability, low density, good wear resistance, etc. The aramid paper prepared from the aramid fibers by the wet papermaking forming process has the characteristics of low density, high specific strength, high specific stiffness, shock resistance, outstanding corrosion resistance, self-extinguishing property, good high-temperature stability, electromagnetic wave permeability and the like, and is widely applied to the fields of high-temperature insulating materials, aerospace, high-performance electronic equipment and the like.

The aramid fiber has strong hydrophobicity, has poor wettability to aqueous medium, affects the dispersion of the fiber in the aqueous medium, and can not be well dispersed in water only by mechanical stirring in the pulping and papermaking process, and the dispersed fiber can generate new flocculation in the streaming process, thereby causing poor paper formation uniformity and affecting the quality of paper. Secondly, in order to ensure that the aramid fiber paper has sufficient mechanical strength, the aramid fibers must have sufficient length, generally longer than conventional plant fibers, further resulting in difficulty in dispersion, especially in slurry tanks, pumps and pipes, etc. in which the flocculation is entangled if a vortex is encountered, and dispersion of the flocculated fiber mass is particularly difficult. Meanwhile, the flocked fiber bundles are in a cloud shape in an aqueous medium, the true density of the flocked fiber bundles is higher than that of water, the flocked fiber bundles sink in the water under the condition of full wetting, but the dry fibers are easy to absorb tiny bubbles in the water and float upwards. Thus, the sinking of the fibers and the sheet forming time are increased in the papermaking process, the opportunity of flocculation of the fibers in water is increased, and the distribution of the fibers in the thickness direction of the paper is further affected. Therefore, how to efficiently disperse the aramid fibers is a problem to be solved in making high-performance aramid fiber paper.

At present, the dispersion performance of the aramid fiber is improved mainly by adopting the following methods: (1) The viscosity of the fiber suspension is increased by adding a dispersing agent, the degree of freedom of the fiber in water is limited, meanwhile, hydrophilic groups are contained in molecules, the wettability of the fiber suspension to water is increased, and common dispersing agents include polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAM) and the like. (2) The electronegative anionic surfactant is added to change the electrokinetic charge of the aramid fibers in the suspension, so that the electronegativity of the aramid fibers is increased, the repulsive force among the fibers is increased, the collision among the fibers is reduced to a certain extent, the flocculation degree is reduced, and common surfactants include sodium dodecyl benzene sulfonate and the like. (3) Physical treatment methods, such as pretreatment of the fibers by using a beater, promote dispersion of the fiber bundles into individual fibers; the dispersion effect of the fiber is improved by the impact and shearing action of high-speed micro-jet flow and shock wave generated by ultrasonic treatment on the fiber. These methods have a good effect of improving the dispersion of the fibers, but have problems such as an increase in drainage time due to an increase in viscosity, a foaming problem due to the addition of a surfactant, and the like. Therefore, how to realize the dispersion of the aramid fiber more efficiently and environmentally friendly is still a problem to be solved.

Disclosure of Invention

In order to solve the problems, the invention provides a method for efficiently dispersing aramid fibers. The method mainly comprises the steps of firstly carrying out simple irradiation treatment, and then sequentially adding aluminum salt and nanocellulose to realize efficient dispersion of the aramid fiber. The principle of the method mainly utilizes the electronegative functional group and Al generated after the irradiation treatment of the surface of the aramid fiber ³⁺ The strong charge interaction and the easy dispersibility of the nanocellulose, and the high suspension stability realize the efficient dispersion of the aramid fiber. Meanwhile, a large amount of hydroxyl groups on the surface of the nanocellulose can form hydrogen bond combination after being dried, so that the strength performance of the aramid fiber paper can be effectively improved, the method has important significance for development of an aramid fiber material, and particularly the aramid fiber paper-based material with high uniformity can be prepared.

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

in a first aspect of the present invention, there is provided a method for efficiently dispersing aramid fibers, comprising:

carrying out irradiation treatment on the aramid fiber;

dispersing the aramid fiber subjected to the irradiation treatment into an aluminum salt solution, and treating for 30s-10min;

adding nano cellulose, and continuing to treat for 10 s-5 min to obtain the nano-cellulose;

based on the method and the aramid fiber, the invention also researches the dosage of irradiation metering, aluminum salt, nanocellulose and the like. Verified that the irradiation measurement is 10-80kGy/h; the concentration of the aramid fiber is 0.01% -1%; the dosage of the aluminum salt is 0.01% -0.3%; when the dosage of the nanocellulose is 0.1-10%, the dispersing effect of the aramid fiber is remarkably improved.

Principle of action of the invention

The efficient dispersion of the aramid fiber of the invention mainly has 3 action principles.

(1) Through irradiation treatment, active groups on the surface of the aramid fiber are increased, and the wettability to water is improved; meanwhile, the generation of negative groups also provides binding sites for the subsequent adsorption of aluminum ions.

(2) Al in aluminum salt ³⁺ The surface of the aramid fiber is enabled to form a layer of uniform water slide film, the friction force of the surface of the aramid fiber is reduced, the winding among the fibers is reduced, meanwhile, the electrokinetic charge of aluminum ions on the surface of the fiber is endowed with positive charges, the aramid fiber is enabled to have certain Zeta potential, and the dispersibility of the aramid fiber is improved.

(3) The nanocellulose has good dispersibility and suspension stability, has a larger specific surface area, can be adsorbed and flocculated on the surface of the aramid fiber, has good hydrophilic performance, and can effectively improve the dispersibility of the aramid fiber.

In a second aspect of the present invention, there is provided an aramid fiber suspension prepared by the above method.

In a third aspect of the present invention, there is provided an aramid fiber paper-based material, the raw materials comprising: the aramid fiber suspension described above.

In a fourth aspect of the invention, the application of irradiation treatment, aluminum salt and nanocellulose in improving the dispersibility of aramid fibers is provided.

The beneficial effects of the invention are that

Firstly, the irradiation treatment method is simple and efficient.

Secondly, the added aluminum salt solution is easy to recycle, and cannot cause environmental pollution; the added nanocellulose biomass is environment-friendly and renewable, and is beneficial to the formation of the aramid fiber in the subsequent drying process.

In summary, the method is an environment-friendly and efficient aramid fiber dispersing method, avoids the use of a large amount of petroleum-based products in the traditional dispersing method, and reduces the pollution to the environment.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

The method comprises the following steps:

(1) Irradiation pretreatment of aramid fiber

The aramid fiber raw materials include, but are not limited to, aramid chopped fibers, aramid pulp, and the like, and are pretreated with ionizing radiation.

(2) Addition of aluminium salts

Under the action of a dispersing machine, the aramid fiber after irradiation treatment is dispersed into an aluminum salt solution, and the aluminum salt comprises aluminum sulfate, aluminum chloride and the like.

(3) Addition of nanocellulose

And continuing to add the suspension of the nanocellulose, wherein the nanocellulose comprises various different types of nanocellulose such as nanofiber crystals, nanocellulose microfibrils, bacterial cellulose and the like, and the nanocellulose mixed suspension compounded by the nanocellulose, and stirring and adsorbing for a certain time to form the uniformly-dispersed aramid fiber dispersion suspension.

In some embodiments, the irradiation rate of step (1) is 10-80kGy/h.

In some embodiments, the concentration of the aramid fiber of step (2) is 0.01% to 1%.

In some embodiments, the aluminum salt in step (2) is aluminum sulfate in an amount of 0.01% -0.3% for 30s-10min.

In some embodiments, the nanofibers of step (3) are predominantly nanocellulose microfibrils with a large aspect ratio (> 50) and bacterial cellulose.

In some embodiments, the nanocellulose of step (3) is used in an amount of 0.1% -10%.

In some embodiments, the dispersing time of step (3) is 10s to 5min.

The invention will now be described in further detail with reference to the following specific examples, which should be construed as illustrative rather than limiting.

In the following examples and comparative examples, the aspect ratio of bacterial cellulose was about 100.

Example 1

The irradiation rate of the aramid fiber is 30kGy/h, the irradiated aramid fiber is dispersed into 0.01% aluminum sulfate solution with the concentration of 0.01%, stirred and dispersed for 10min, then 0.1% bacterial cellulose is added, and stirred and dispersed for 5min.

Example 2

The irradiation rate of the aramid fiber is 50kGy/h, the irradiated aramid fiber is dispersed into 0.05% concentration aluminum sulfate solution at 0.1%, stirred and dispersed for 5min, and then bacterial cellulose with the dosage of 1% is added, stirred and dispersed for 3min.

Example 3

The irradiation rate of the aramid fiber is 50kGy/h, the irradiated aramid fiber is dispersed into 0.1% concentration aluminum sulfate solution at 0.5%, stirred and dispersed for 1min, and then bacterial cellulose with the dosage of 5% is added, stirred and dispersed for 1min.

Example 4

The irradiation rate of the aramid fiber is 60kGy/h, the irradiated aramid fiber is dispersed into 0.2% concentration aluminum sulfate solution at 0.5%, the mixture is stirred and dispersed for 1min, and then bacterial cellulose with the dosage of 5% is added, and the mixture is stirred and dispersed for 1min.

Example 5

The irradiation rate of the aramid fiber is 80kGy/h, the irradiated aramid fiber is dispersed into 0.3% concentration aluminum sulfate solution at 1% concentration, stirred and dispersed for 30s, then 10% amount of bacterial cellulose is added, and stirred and dispersed for 30min.

Comparative example 1

The aramid fiber is directly dispersed into 0.1% concentration aluminum sulfate solution at 0.5% concentration without irradiation treatment, stirred and dispersed for 1min, and then bacterial cellulose with 5% dosage is added, stirred and dispersed for 1min.

Comparative example 2

The irradiation rate of the aramid fiber is 50kGy/h, the irradiated aramid fiber is dispersed into an aqueous solution without adding aluminum salt at the concentration of 0.5 percent, stirred and dispersed for 1min, and then bacterial cellulose with the dosage of 5 percent is added, stirred and dispersed for 1min.

Comparative example 3

The irradiation rate of the aramid fiber is 50kGy/h, the irradiated aramid fiber is dispersed into 0.1% concentration aluminum sulfate solution at 0.5%, the mixture is stirred and dispersed for 1min, bacterial cellulose is not added any more, and the stirring and the dispersion are continued for 1min.

Comparative example 4

The irradiation rate of the aramid fiber is 50kGy/h, the irradiated aramid fiber is dispersed into 0.1% concentration aluminum sulfate solution at 0.5%, stirred and dispersed for 1min, and then 5% dosage of nano cellulose crystal (length-diameter ratio is less than 30) is added, stirred and dispersed for 1min.

And (3) testing the dispersion performance of the aramid fiber:

the method for testing the dispersing effect of the aramid fiber comprises the following steps: the dispersed aramid fiber suspension is manufactured and molded by using a Frank PTI Zhang Chao sheet machine, and the ration is 60g/m ² . After drying, the uniformity properties of the aramid paper were measured using a paper uniformity tester (2 DLAB F/SENSOR, germany) and expressed as a uniformity index, which refers to the number of sheets per square meter of wadding polymer in units of Flocs/m ² . The smaller the uniformity index, the less the wadding polymer in the unit area of the aramid fiber paper is, and the better the dispersing effect of the aramid fiber is; the larger the uniformity index, the more the wadding per unit area of the aramid fiber paper, and further the worse the dispersing effect of the aramid fibers.

TABLE 1 measurement results of the uniformity Properties of the aramid fibers of examples 1-5 and comparative examples 1-3

From Table 1, it can be seen from the examples that the aramid fiber dispersion system of the present invention has a high dispersing effect. From analysis of example 3 and comparative example 4, it can be seen that bacterial cellulose (about 100) with a larger aspect ratio has a better dispersion effect than nanocellulose crystals (< 30) with a smaller aspect ratio. Analysis of example 3 and comparative examples 1, 2, and 3, respectively, showed that good dispersion of the aramid fibers could not be achieved without any steps of irradiation treatment, addition of aluminum salt, addition of nanocellulose.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method of efficiently dispersing aramid fibers comprising:

carrying out irradiation treatment on the aramid fiber, wherein the irradiation rate is 10-80kGy/h;

dispersing the aramid fiber subjected to the irradiation treatment into an aluminum salt solution, treating for 30s-10min, adding nano cellulose, and continuously treating for 10 s-5 min to obtain the aramid fiber;

the concentration of the aramid fiber is 0.01% -1%;

the dosage of the aluminum salt is 0.01% -0.3%;

the dosage of the nanocellulose is 0.1% -10%;

the aspect ratio of the nanocellulose is > 50.

2. The method of efficiently dispersing aramid fiber of claim 1 wherein the aluminum salt is aluminum sulfate or aluminum chloride.

3. The method of efficiently dispersing aramid fibers of claim 1 wherein the nanocellulose is at least one of nanofiber crystals, nanocellulose microfibrils, bacterial cellulose.

4. The method of efficiently dispersing aramid fiber of claim 1 wherein the aramid fiber is an aramid chopped fiber or an aramid pulp.

5. The method of efficiently dispersing aramid fiber of claim 1 wherein the irradiation uses ionizing radiation.

6. An aramid fiber suspension prepared by the method of any one of claims 1-5.

7. An aramid fiber paper-based material, characterized in that the raw materials comprise: the aramid fiber suspension of claim 6.

8. An aramid fiber paper-based material characterized in that it is obtained by forming an aramid fiber suspension according to claim 6.

9. Use of the method for efficiently dispersing aramid fiber according to any one of claims 1 to 5 for improving the dispersibility of aramid fiber.