Preparation method of in-pulp additive for enhancing ring crush strength and tensile strength of paper

Abstract

The invention discloses a preparation method of an in-pulp additive for enhancing ring crush compression strength and tensile strength of paper, which comprises the following steps: by taking optimized and screened bamboo powder as a raw material, carrying out alkali treatment and (3-chloro-2-hydroxypropyl) trimethyl ammonium chloride modification, then adding the bamboo powder into fiber pulp, and uniformly stirring to obtain the in-pulp additive for enhancing ring crush compression strength and tensile strength of paper. And then carrying out processes of bubbling, suction filtration, squeezing, drying and the like to prepare paper with relatively high ring crush compression resistance and tensile strength. The method adopts low-price biomass raw materials, is green and pollution-free, and greatly reduces the production cost. Meanwhile, the modified bamboo powder can keep long-term stability and is easy to store and transport. The paper reinforcing auxiliary agent has good hydrophilicity and biocompatibility, the retention rate of fine fibers is increased, the bonding strength between the fibers can be improved, and a powerful solution is provided for the paper reinforcing problem in the papermaking industry.

Description

Technical Field

[0001] The invention relates to the field of pulping and papermaking, and also belongs to the field of chemistry and chemical engineering, and in particular to a method for preparing an additive added to pulp for enhancing the ring crushing and tensile strength of paper. Background Art

[0002] Paper is formed by the interweaving of hydrogen bonds between fibers. Its strength is greatly affected by environmental factors. For example, changes in temperature and humidity can weaken hydrogen bonds, thereby reducing the mechanical properties of paper. How to improve the physical properties of specialty paper, such as tensile strength and ring crush strength, has become a key technical problem that needs to be solved urgently. High-strength paper needs to maintain structural integrity under high-intensity pressure to meet the use requirements in complex application scenarios and ensure the stability and durability of paper under various stress conditions. In order to improve the mechanical properties of specialty paper, such as tensile strength, ring crush strength and folding resistance, researchers are constantly exploring new materials and processes. Due to the limited fiber bonding force in traditional papermaking processes, it is difficult to meet the needs of high-strength paper by relying solely on hydrogen bonds between fibers. Therefore, the introduction of paper enhancers has become an effective means to improve paper strength. Paper enhancers significantly improve the physical properties of paper by improving the bonding force between fibers or forming additional reinforcement structures in the fiber network, providing a new way to meet the high-strength requirements of various specialty papers.

[0003] Paper reinforcing agents are usually added in two ways: adding into the pulp before pulp forming and applying on the surface after forming. The principle of paper reinforcing agents is to improve the mechanical properties of formed paper by increasing the hydrogen bonding force between fibers. Current paper reinforcing agents include polyacrylamide, starch and its modified products, chitosan and its modified products, and some inorganic substances, organic polymers, etc.

[0004] Polyacrylamide-based reinforcing agents are one of the most widely used and high-performance papermaking reinforcing agents. The molecular weight of this type of reinforcing agent is generally between 100,000 and 1,000,000. The molecular weight can be adjusted according to the fiber characteristics and the specific requirements of the paper type to achieve different reinforcing effects. Polyacrylamide adjusts the charge balance in the slurry (such as the anion / cation ratio) and combines with the charged groups on the fiber surface to enhance the binding force between fibers and significantly improve the tensile strength and compressive strength of the paper. At present, many types of polyacrylamide have been developed, including cationic, anionic and amphoteric types. In addition, based on the excellent chemical properties of polyacrylamide, acrylamide grafting chitosan or compounding with other compounds to further improve the physical properties of paper such as tensile strength and burst resistance has also become an important direction for the development of reinforcing agents.

[0005] Starch and its modified products are also commonly used paper strengtheners. As a renewable water-soluble natural high molecular carbohydrate, starch can not only be added to paper to strengthen it, but also improve the surface strength of paper by surface sizing. However, the direct addition of starch is likely to cause the slurry to aggregate or agglomerate. Therefore, modified starch products suitable for different application scenarios have been developed, such as cationic starch and anionic starch. These modified starches can be added to the slurry or surface sized according to the charge characteristics of the slurry, thereby enhancing the strength and water resistance of the paper.

[0006] In contrast, the application of chitosan and its modified products is relatively rare, mainly concentrated in areas with high requirements for paper, such as food packaging and medical barrier materials. By carboxylating, cationizing or grafting chitosan with other compounds, not only can its hydrophilicity and surface activity be improved, but also the hydrogen bond strength between fibers can be further improved by compounding inorganic or organic reinforcing agents, thereby significantly enhancing the mechanical properties of paper.

[0007] In addition, some other paper enhancers, such as guar gum, pectin, polyvinyl alcohol and hemicellulose polysaccharides, have also been studied. However, due to the high cost, limited enhancement effect or certain toxicity, the practical application and promotion of these enhancers are relatively slow.

[0008] Paper enhancers are mainly used to improve the strength of paper and enable it to meet certain usage requirements in harsh environments. Therefore, the research focus of paper enhancers is to significantly improve the performance of paper after adding enhancers to paper. Fibers are hydrophilic and are evenly dispersed in water through decomposition. Then, through vacuum filtration, the fibers are intertwined with each other to form strong hydrogen bonds, and finally paper is formed. However, some enhancers have insufficient surface charge and weak hydrophilicity, and are easy to agglomerate in water. They also have poor bonding with fibers and low retention rates. After forming paper, they cannot play a good reinforcing role, but affect the uniformity of the paper and even cause powdering. On the other hand, paper enhancers have a certain reinforcing effect on paper through modification or grafting. However, chemical reactions and excessive drug additions not only greatly increase the cost of the enhancers, but also increase toxicity, which limits the application of paper. For example, polyacrylamide enhancers have developed anionic, cationic or amphoteric properties through modification. However, it is a petroleum-based product, and its production and use will cause harm to the environment. The enhanced paper is prohibited from use in food packaging and other fields due to its uncontrollable toxicity. Starch is a friendly product. Modified cationic starch can bind to fibers through ionic bonds to enhance paper, but the cost remains high. Some other enhancing products, such as chitosan, are also limited in application due to their high cost. Summary of the invention

[0009] In order to solve the problems of the prior art, the present invention provides a method for preparing an additive added into pulp for enhancing the ring crushing and tensile strength of paper.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A method for preparing a pulp-added auxiliary agent for enhancing the ring crushing and tensile strength of paper comprises the following steps:

[0012] The bamboo powder raw material is prepared into slurry water, and then an alkaline solution is added, and ultrasonication is performed. Thereafter, the mixed solution is kept at 40-80° C. for 10-40 minutes, and then (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution is added and mixed evenly, and the mixture is kept at 40-80° C. for 0.5h-2h to obtain an additive for adding into the slurry.

[0013] Furthermore, the bamboo powder is bamboo powder that has passed through a 30-800 mesh sieve.

[0014] Furthermore, the concentration of bamboo powder in the slurry is 1%-80%, preferably 10%-50%.

[0015] Furthermore, the alkaline solution is one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and ammonia solution.

[0016] Furthermore, the mass concentration of the alkaline solution is 10-30%. The alkaline solution is added to create an alkaline environment and the pH is adjusted to a range of 8-10.

[0017] Furthermore, the ultrasonication time is 10-30 min.

[0018] Furthermore, the concentration of the (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution is 50-70wt%, and the amount of (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution added is 5%-40% of the mass of the bamboo powder.

[0019] A method for preparing reinforced paper comprises the following steps:

[0020] The additives added into the pulp are mixed with the pulp slurry for 1-10 minutes, and then the paper is made by dispersing and papermaking to prepare the reinforced paper.

[0021] Furthermore, the pulp slurry is fiber pulp, one or more of coniferous wood pulp, broadleaf wood pulp, wheat straw pulp, straw pulp, waste paper pulp, and bamboo pulp.

[0022] Further, the concentration of the pulp slurry is less than 1%.

[0023] Furthermore, the amount of the additive added into the pulp is 5-30% of the pulp slurry, preferably 5-20%.

[0024] Furthermore, the weight of the reinforced paper is 60-200 g / m 2 .

[0025] Further, the wet paper web is subjected to a pressing dehydration treatment at 80-105° C. and 0.05-0.15 MPa for 10 min-20 min.

[0026] Furthermore, papermaking includes processes such as bubbling, filtration, pressing, and drying.

[0027] Using cheap bamboo powder under optimized screening conditions as raw material, the activity of the surface groups of the bamboo powder is stimulated by alkali treatment, and then (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution is added to modify the bamboo powder, improve the hydrophilicity of the bamboo powder, and make it better dispersed in water. The fiber slurry is mixed with the modified bamboo powder, and after dispersion, the modified bamboo powder enhancer is combined with the fiber in the water medium. In the papermaking process, it can not only improve the retention rate of fine fibers, but also greatly enhance the strength of the paper. Since the microscopic morphology of bamboo powder is long strips, it has a certain supporting effect on the paper, and the ring crush strength of the paper is also significantly improved.

[0028] Firstly, by optimizing and screening suitable bamboo powder raw materials, selecting the appropriate slurry concentration, adjusting the appropriate alkali concentration to stimulate the active sites of the bamboo powder, and then adjusting the amount of 3-chloro-2-hydroxypropyl)trimethylammonium chloride solution added to modify the bamboo powder, finally obtaining bamboo powder enhancers with different degrees of modification.

[0029] There are few studies on using cheap bamboo powder as a paper strengthener, and it has not yet been widely used on cellulose acetate flat membranes. At the same time, bamboo powder is a green and renewable biomass raw material with a low price. Bamboo powder modified with 3-chloro-2-hydroxypropyl)trimethylammonium chloride has the characteristics of high hydrophilicity and long-term stability. It has a significant enhancement effect on the ring crush strength and tensile strength of paper and can be used on a large scale and commercially.

[0030] Bamboo powder with a specific mesh size is screened as a raw material to prepare an additive for pulp addition for enhancing the ring crush strength and tensile strength of paper, which has the following characteristics: 1) Bamboo powder, as a natural plant raw material, has the advantages of short growth cycle, abundant raw materials, low cost, etc., is green and pollution-free, and greatly reduces production costs; 2) The paper enhancing additive of the present invention has good hydrophilicity and biocompatibility, and the modified bamboo powder can be fully and evenly dispersed in water, which can not only improve the retention rate of fine fibers, but also increase the bonding strength between fibers, providing a powerful solution to the problem of paper enhancement in the papermaking industry; 3) The modified bamboo powder can maintain long-term stability and is easy to store and transport. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1It is a scanning electron microscope comparison picture of bamboo powder and modified bamboo powder (modified bamboo powder prepared by using bamboo powder and 65wt% (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution in a mass ratio of 5:1).

[0032] Figure 2 It is a comparison chart of the ring compression strength of bamboo powder and modified bamboo powder (modified bamboo powder prepared by using bamboo powder and 65wt% (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution in a mass ratio of 5:1).

[0033] Figure 3 It is a comparison chart of the tensile strength of bamboo powder and modified bamboo powder (modified bamboo powder prepared by using bamboo powder and 65wt% (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution in a mass ratio of 5:1).

[0034] Figure 4 This is a picture of modified bamboo powder (modified bamboo powder prepared by mixing bamboo powder with 65 wt % (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution in a mass ratio of 5:1) after storage for 30 days. DETAILED DESCRIPTION

[0035] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0036] Example 1

[0037] 1. Preparation of additives added to pulp

[0038] Obtain 400 mesh bamboo powder through optimization screening, weigh 50g, add it to 100g deionized water, fully swell it, and then stir it evenly. Then prepare a 20% concentration of sodium hydroxide solution, and add 20mL of the prepared sodium hydroxide solution to the bamboo powder-water mixture that has been stirred evenly, then use an ultrasonic generator to ultrasonicate for 20min, and stir it with a glass rod for 1min every 5min. After the ultrasonication is completed, put the mixed solution in a 70℃ water bath pot and keep it warm for 30min, then add 65wt% (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution (respectively 0g, 5g, 10g, 15g, 20g, corresponding to the mass ratio of bamboo powder to 65wt% (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution of 50:0, 10:1, 5:1, 10:3, 10:4), stir it to make it fully mixed, then keep it warm at 70℃ for 2h, and stir it with a glass rod for 1min every 30min to obtain the slurry adding additive. The samples of additives added into the pulp modified by 0g, 5g, 10g, 15g and 20g of ammonium chloride solution were named A-1, A-2, A-3, A-4 and A-5 respectively.

[0039] 2. Preparation of reinforced paper

[0040] According to 100g / m 2 The paper was made by quantitatively printing paper, and the modified additive (additive added in the pulp) samples were added into bleached kraft hardwood pulp (concentration of 0.05%) at an addition amount of 5%, 10%, 15% and 20% respectively, the pulp and the additive were evenly dispersed by a fiber defibriller, most of the water was removed by bubbling, filtration and other processes to form a formed wet paper web, and then it was pressed and dehydrated at 90°C and 0.1MPa for 10 minutes and dried to obtain enhanced paper samples. The additives added in the pulp were 5%, 10%, 15% and 20% respectively, and they were named B-1, B-2, B-3, B-4 and B-5 respectively).

[0041] Figure 1 This is a scanning electron microscope comparison of bamboo powder and modified bamboo powder (modified bamboo powder prepared by mixing bamboo powder with 65wt% (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution at a mass ratio of 5:1). From the SEM image, the modified bamboo powder is wrapped compared to the bamboo powder, and the surface of the bamboo powder is wrapped with a layer of something like grease, gathering together.

[0042] Figure 2 This is a comparison chart of the ring crush strength of bamboo powder and modified bamboo powder (modified bamboo powder prepared by adding bamboo powder to 65wt% (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution at a mass ratio of 5:1). When bamboo powder and modified bamboo powder are added to paper, the ring crush strength of the paper shows a significant downward trend compared to the base paper as the amount of bamboo powder added increases, while the modified bamboo powder shows a significant increasing trend as the amount of added increases. The ring crush strength of the reinforced paper with a 20% modified bamboo powder addition increases by more than 2.5 times compared to the base paper.

[0043] Figure 3 This is a comparison chart of the tensile strength of bamboo powder and modified bamboo powder (modified bamboo powder prepared by adding bamboo powder to 65wt% (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution at a mass ratio of 5:1). When bamboo powder and modified bamboo powder are added to paper, the tensile strength of the paper shows a slow downward trend compared to the base paper as the amount of bamboo powder added increases, while the modified bamboo powder shows a significant increasing trend as the amount of addition increases. The tensile strength of the reinforced paper with a 20% modified bamboo powder addition increases by more than 1.5 times compared to the base paper.

[0044] Figure 4 This is a picture of modified bamboo powder (modified bamboo powder prepared by mixing bamboo powder with 65wt% (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution in a mass ratio of 5:1) after storage for 30 days. The modified bamboo powder remained stable and its properties did not change after being stored at room temperature for one month.

Claims

1. A method for preparing a pulp additive for enhancing the ring crush and tensile strength of paper, characterized in that: The steps include: The bamboo powder raw material is prepared into slurry water, and then an alkaline solution is added, and ultrasonication is performed. Then, the mixed solution is kept at 40-80°C for 10-40 minutes, and then (3-chloro-2-hydroxypropyl) trimethylammonium chloride solution is added and mixed evenly, and the mixture is kept at 40-80°C for 0.5-2 hours to obtain an additive for adding into the slurry.

2. The preparation method according to claim 1, characterized in that: The bamboo powder is bamboo powder that has passed through a 30-800 mesh sieve.

3. The preparation method according to claim 1, characterized in that: The concentration of bamboo powder in the slurry is 1%-80%.

4. The preparation method according to claim 1, characterized in that: The alkaline solution is one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, and ammonia solution; the mass concentration of the alkaline solution is 10-30%, and the pH is adjusted to 8-10 by adding the alkaline solution.

5. The preparation method according to claim 1, characterized in that: The ultrasonic time is 10-30 minutes.

6. The preparation method according to claim 1, characterized in that: The concentration of the (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution is 50-70wt%, and the added amount of the (3-chloro-2-hydroxypropyl)trimethylammonium chloride solution is 5%-40% of the mass of the bamboo powder.

7. A method for preparing reinforced paper, characterized in that: The steps include: The additives added into the pulp are mixed with the pulp slurry for 1-10 minutes, and then the paper is made by dispersing and papermaking to prepare the reinforced paper.

8. The preparation method according to claim 7, characterized in that: The paper pulp is fiber pulp, which is one or more of softwood pulp, hardwood pulp, wheat straw pulp, straw pulp, waste paper pulp and bamboo pulp; the concentration of the paper pulp is less than 1%.

9. The preparation method according to claim 7, characterized in that: The amount of the additive added into the pulp is 5-30% of the pulp slurry.

10. The preparation method according to claim 7, characterized in that: The weight of reinforced paper is 60-200g / m 2 The wet paper web is subjected to a pressing and dehydration treatment at 80-105°C and 0.05-0.15MPa for 10-20min.

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