Waterproof paper holder manufacturing process

Abstract

The invention discloses a waterproof paper support manufacturing process which comprises the following steps: before paper pulp is conveyed into a pulp barrel of a forming machine, firstly adding a waterproof agent into the pulp according to a formula proportion of 3-7% of the weight of oven dry pulp, then stirring for 20 minutes at a rotating speed of 200r / min, finally conveying the paper pulp to the forming machine, forming a wet paper blank on the forming machine provided with a mold by virtue of vacuum adsorption, and finally, carrying out vacuum drying on the wet paper blank to obtain the waterproof paper support. And forming the shape set by the mold. Compared with a traditional method, the waterproof agent is added into the paper pulp, the waterproof agent can permeate into a capillary structure of the paper pulp to form a waterproof layer, water permeation is effectively prevented, and therefore the waterproof performance of the paper support can be improved from the interior, and secondly, the waterproof agent is evenly distributed in the paper pulp and is not prone to losing efficacy due to abrasion or scratching, and the waterproof performance of the paper support is improved. And the waterproof effect of the paper holder is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of paper trays, and more particularly to a process for manufacturing waterproof paper trays. Background Art

[0002] Paper trays are mainly used for transportation cushioning and protection of poultry eggs and small electronics. They can also be made into beverage cup holders, medical utensils, disposable flower pots, etc. They are made from carton scraps, newsprint, white pure wood pulp, etc., which are crushed and mixed into a slurry with a certain concentration. They are then formed by vacuum adsorption on a CNC mold customized according to product design and then dried to form environmentally friendly paper products of different types and uses.

[0003] Since the paper tray is made of 100% recycled paper material, which has the characteristics of absorbing moisture, its waterproof performance is poor. Secondly, during the manufacturing process of the paper tray, it is easy to cause problems such as dents, shrinkage holes and sandwiching on the paper tray, which in turn affects the overall waterproof performance of the paper tray.

[0004] In order to improve the waterproof performance of paper trays, the traditional waterproof paper tray manufacturing process usually improves the waterproof performance of paper trays by coating waterproof coating on the surface of paper trays, but this method may not completely cover the capillary structure inside the paper tray, which can easily lead to water penetration of the paper tray. In addition, the traditional waterproof coating has poor wear resistance. Once it is worn or scratched, water can penetrate. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a waterproof paper tray manufacturing process to solve the problem of poor waterproofness of the prior paper tray.

[0006] The technical solution of the present invention is as follows: a waterproof paper tray production process, before the pulp is transported into the pulp barrel of the forming machine, a waterproofing agent is first added to the pulp at a formula ratio of 3% to 7% of the absolute dry pulp weight, and then stirred at a speed of 200r / min for 20 minutes.

[0007] The waterproof paper tray production process includes the following steps:

[0008] Step 1: pretreating the raw material to obtain a pulp suspension, and then filtering the pulp suspension to obtain a first slurry;

[0009] Step 2: Add the first slurry into the slurry preparation tank, stir at a speed of 200 r / min, continue stirring for 60 minutes to make the first slurry fully uniform, and slowly heat it to 60°C;

[0010] Step 3: Add the additive to the slurry preparation tank, and then add the waterproofing agent to the first slurry at a ratio of 3% to 7% of the absolute dry slurry weight after an interval of 10 minutes, and stir at a speed of 200 r / min for 20 minutes to obtain the second slurry.

[0011] Step 4: transporting the prepared second slurry to the slurry barrel of the forming machine through a slurry conveying pipeline, and then forming a paper tray intermediate by vacuum adsorption molding;

[0012] Step 5: The paper tray intermediate is dried at 60° C. for 24 hours and then dried to obtain a paper tray.

[0013] Furthermore, the waterproofing agent comprises alkyl ketene dimer and chitosan acetate, and the alkyl ketene dimer accounts for 5% of the total weight of the waterproofing agent.

[0014] Furthermore, the auxiliary agent includes one or more combinations of cationic modified starch, polyvinyl alcohol, carboxymethyl cellulose, and cationic polyacrylamide.

[0015] Furthermore, the amount of cationic modified starch added is 1.5% by weight of the absolute dry pulp.

[0016] Furthermore, the added amount of polyvinyl alcohol accounts for 0.5% to 1% of the weight of the absolute dry pulp.

[0017] Furthermore, the added amount of carboxymethyl cellulose accounts for 0.4% to 0.8% of the weight of the absolute dry pulp.

[0018] Furthermore, the amount of cationic polyacrylamide added is 0.3% to 0.8% of the absolute dry pulp weight.

[0019] Furthermore, the amount of the waterproofing agent used is 5% by weight of the absolute dry pulp.

[0020] The present invention according to the above scheme has the following beneficial effects:

[0021] (1) The present invention provides a waterproof paper tray manufacturing process. Before the pulp is transported into the pulp barrel of the forming machine, a waterproof agent is first added to the pulp at a formula ratio of 3% to 7% of the absolute dry pulp weight, and then stirred at a speed of 200r / min for 20 minutes. Finally, the pulp is transported to the forming machine, and a wet paper blank is formed by vacuum adsorption on the forming machine equipped with a mold to form a shape set by the mold. Compared with the traditional method, the present process adds a waterproof agent to the pulp, and the waterproof agent can penetrate into the capillary structure of the pulp to form a waterproof layer, effectively preventing the penetration of water, thereby improving the waterproof performance of the paper tray from the inside. Secondly, because the waterproof agent is evenly distributed in the pulp, it is not easy to fail due to wear or scratches, thereby improving the waterproof effect of the paper tray.

[0022] (2) The present invention provides a waterproof paper tray manufacturing process. Before the pulp is conveyed into the pulp barrel of the forming machine, a waterproof agent is first added to the pulp at a formula ratio of 3% to 7% of the absolute dry pulp weight to ensure that the fibers in the pulp are tightly combined together, thereby increasing the density of the paper tray, so that the paper tray has a larger mass under the same volume, which helps to improve its bearing capacity and stability. Secondly, the combination of the waterproof agent and the pulp fiber enhances the interaction force between the fibers, thereby enhancing the overall hardness of the paper tray, so that the paper tray is not easily deformed or broken when subjected to external forces.

[0023] (3) The present invention provides a waterproof paper tray production process. Before conveying the pulp into the pulp barrel of the forming machine, a waterproofing agent is first added to the pulp at a formula ratio of 3% to 7% of the absolute dry pulp weight, and then stirred at a speed of 200r / min for 20 minutes to enable the waterproofing agent to be evenly distributed between the pulp fibers and fill the gaps between the pulp fibers. This makes the surface of the paper tray smoother and flatter after it is formed, and it is not easy to generate paper scraps and dust. The improved smoothness of the paper tray surface provides a good foundation for watermark printing. The ink can be evenly attached to the paper tray to form clear patterns and texts. Secondly, the smooth surface also reduces the penetration and diffusion of ink during the printing process, thereby improving the accuracy and aesthetics of printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The present invention is a flowchart of the process for producing a waterproof paper tray in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0027] In order to better understand the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0028] Preparation of waterproofing agent:

[0029] First, 1 mL of pure acetic acid was added to 99 mL of deionized water to prepare an acetic acid solution with a volume fraction of 1% and a pH value of about 3.38.

[0030] An appropriate amount of chitosan powder was gradually added to a 1% acetic acid solution, and stirred at a stirring speed of 500 r / min for 4 h until the chitosan was completely dissolved, to prepare chitosan acetic acid solutions with mass fractions of 0.5%, 1%, 1.5%, 2% and 2.5%, and allowed to stand for defoaming overnight for use.

[0031] (1) Preparation of waterproofing agent 1

[0032] AKD wax (alkyl ketene dimer) is heated to 5-10°C above its melting point under vacuum conditions to ensure complete melting and avoid oxidation, which can improve the purity and reactivity of AKD wax. Chitosan solution is slowly heated to 65-70°C. Before adding hot melt AKD, a small amount of non-ionic surfactant (such as polysorbate) is added to the chitosan acetic acid solution to reduce interfacial tension and improve emulsification efficiency. Then, hot-melt AKD was slowly added to the chitosan acetic acid solution with a mass fraction of 0.5%, and the speed of the high-speed shear emulsifier was adjusted to 8000 r / min-10000 r / min to reduce the damage of the shear force to the molecular structure of chitosan, while maintaining sufficient shear force to form a stable emulsion for 15-20 minutes to ensure that the AKD wax and the chitosan solution were fully mixed to form a uniform emulsion. The emulsion was then cooled at 10°C for 10 minutes and then gradually lowered to -10°C to avoid rapid temperature changes that could cause the emulsion to rupture. Finally, waterproofing agent 1 was obtained, in which the AKD wax was added at 5% (relative to the total mass of the mixture).

[0033] (2) Preparation of Waterproofing Agent 2

[0034] Heat the AKD wax to 5-10°C above its melting point under vacuum conditions to ensure complete melting and avoid oxidation, which can improve the purity and reactivity of the wax. Slowly heat the chitosan solution to 65-70°C, and before adding the hot melt AKD, add a small amount of non-ionic surfactant (such as polysorbate) to the chitosan acetic acid solution to reduce interfacial tension and improve emulsification efficiency. Then, hot-melt AKD was slowly added to the chitosan acetic acid solution with a mass fraction of 1.0%, and the speed of the high-speed shear emulsifier was adjusted to 8000 r / min-10000 r / min to reduce the damage of the shear force to the molecular structure of chitosan, while maintaining sufficient shear force to form a stable emulsion for 15-20 minutes to ensure that the AKD wax and the chitosan solution were fully mixed to form a uniform emulsion. The emulsion was then cooled at 10°C for 10 minutes and then gradually lowered to -10°C to avoid rapid temperature changes that could cause the emulsion to rupture. Finally, waterproofing agent 2 was obtained, in which the AKD wax was added at 5% (relative to the total mass of the mixture).

[0035] (3) Preparation of Waterproofing Agent 3

[0036] Heat the AKD wax to 5-10°C above its melting point under vacuum conditions to ensure complete melting and avoid oxidation, which can improve the purity and reactivity of the wax. Slowly heat the chitosan solution to 65-70°C, and before adding the hot melt AKD, add a small amount of non-ionic surfactant (such as polysorbate) to the chitosan acetic acid solution to reduce interfacial tension and improve emulsification efficiency. Then, hot-melt AKD was slowly added to the chitosan acetic acid solution with a mass fraction of 1.5%, and the speed of the high-speed shear emulsifier was adjusted to 8000 r / min-10000 r / min to reduce the damage of the shear force to the molecular structure of chitosan, while maintaining sufficient shear force to form a stable emulsion for 15-20 minutes to ensure that the AKD wax and the chitosan solution were fully mixed to form a uniform emulsion. The emulsion was then cooled at 10°C for 10 minutes and then gradually lowered to -10°C to avoid rapid temperature changes that could cause the emulsion to rupture. Finally, waterproofing agent 3 was obtained, in which the AKD wax was added at 5% (relative to the total mass of the mixture).

[0037] (4) Preparation of Waterproofing Agent 4

[0038] Heat the AKD wax to 5-10°C above its melting point under vacuum conditions to ensure complete melting and avoid oxidation, which can improve the purity and reactivity of the wax. Slowly heat the chitosan solution to 65-70°C, and before adding the hot melt AKD, add a small amount of non-ionic surfactant (such as polysorbate) to the chitosan acetic acid solution to reduce interfacial tension and improve emulsification efficiency. Then, hot-melt AKD was slowly added to the chitosan acetic acid solution with a mass fraction of 2.0%, and the speed of the high-speed shear emulsifier was adjusted to 8000 r / min-10000 r / min to reduce the damage of the shear force to the molecular structure of chitosan, while maintaining sufficient shear force to form a stable emulsion for 15-20 minutes to ensure that the AKD wax and the chitosan solution were fully mixed to form a uniform emulsion. The emulsion was then cooled at 10°C for 10 minutes and then gradually lowered to -10°C to avoid rapid temperature changes that could cause the emulsion to rupture. Finally, waterproofing agent 4 was obtained, in which the AKD wax was added at 5% (relative to the total mass of the mixture).

[0039] (5) Preparation of Waterproofing Agent 5

[0040] Heat the AKD wax to 5-10°C above its melting point under vacuum conditions to ensure complete melting and avoid oxidation, which can improve the purity and reactivity of the wax. Slowly heat the chitosan solution to 65-70°C, and before adding the hot melt AKD, add a small amount of non-ionic surfactant (such as polysorbate) to the chitosan acetic acid solution to reduce interfacial tension and improve emulsification efficiency. Then, hot-melt AKD was slowly added to the chitosan acetic acid solution with a mass fraction of 2.5%, and the speed of the high-speed shear emulsifier was adjusted to 8000 r / min-10000 r / min to reduce the damage of the shear force to the molecular structure of chitosan, while maintaining sufficient shear force to form a stable emulsion for 15-20 minutes to ensure that the AKD wax and the chitosan solution were fully mixed to form a uniform emulsion. The emulsion was then cooled at 10°C for 10 minutes and then gradually lowered to -10°C to avoid rapid temperature changes that could cause the emulsion to rupture. Finally, waterproofing agent 5 was obtained, in which the AKD wax was added at 5% (relative to the total mass of the mixture).

[0041] The conductivity and viscosity of the waterproofing agent 1, waterproofing agent 2, waterproofing agent 3, waterproofing agent 4 and waterproofing agent 5 were tested, and the test results are as follows:

[0042] Table 1 Viscosity and conductivity of waterproofing agent

[0043]

[0044] 1. Changes in conductivity:

[0045] From the data in Table 1, it can be seen that as the mass fraction of chitosan acetic acid solution increases, the conductivity of the waterproofing agent also increases. This may be because the amino functional groups on the chitosan molecular chain ionize positive charges in water, increasing the ion concentration of the solution and thus improving the conductivity.

[0046] When the mass fraction of chitosan acetate solution increased from 0.5% to 2.5%, the conductivity increased from 187.2μs / cm to 695.4μs / cm, with a large increase, indicating that the concentration of chitosan has a significant effect on the conductivity.

[0047] 2. Changes in viscosity:

[0048] Similarly, as the mass fraction of chitosan acetate solution increases, the viscosity of the waterproofing agent also gradually increases. This may be because the long molecular chain structure of chitosan is entangled with each other in the solution, forming a more complex network structure, thereby increasing the viscosity of the solution.

[0049] When the mass fraction of chitosan acetate solution increased from 0.5% to 2.5%, the viscosity increased from 16.3 mPa·s to 24.7 mPa·s.

[0050] It can be seen that the hydroxyl and amino functional groups on the chitosan molecular chain interact with water and oil, promoting the adsorption of chitosan at the AKD / water interface and in the aqueous phase. This adsorption helps to reduce the particle size of the AKD emulsion and stabilize it, thereby forming a stable emulsion structure. Chitosan exists in the form of positively charged amino functional groups in the acetic acid solution, which helps to stabilize the uniform dispersion of AKD particles in water and form a stable waterproofing agent.

[0051] However, high conductivity means that it contains more charged ions or functional groups. When these charged ions or functional groups come into contact with pulp, they will interact with the charges on the fiber surface, thereby affecting the bonding force between the fibers. Too high conductivity will accelerate the migration and penetration of ions, affecting the uniformity and structural stability of the pulp. Secondly, as the viscosity increases, the fluidity of the waterproofing agent in the pulp is poor, and it is difficult to disperse evenly in the pulp, which can easily lead to uneven waterproofing performance of the paper support and poor local waterproofing effect. Based on this, the waterproofing agent in this embodiment uses a waterproofing agent 3 with a mass fraction of 1.5%.

[0052] See also Figure 1 As shown, a waterproof paper tray manufacturing process provided by an embodiment of the present invention includes the following steps:

[0053] 1. Use rice straw, bagasse, wheat straw, waste paper, corrugated cardboard, etc. as raw materials, and make pulp suspension through physical processes such as crushing and grinding;

[0054] 2. Filter the pulp suspension through a filter screen to remove impurities and residues therein to obtain a first slurry.

[0055] 3. The paper tray intermediate is formed by vacuum adsorption molding by a molding machine, which specifically includes the following steps:

[0056] S3.1: Add the first slurry into the slurry preparation tank, stir at a speed of 200r / min, continue stirring for 60min, make the first slurry fully uniform, and slowly heat it to 60℃;

[0057] S3.2: Add the additive to the slurry preparation tank, add the waterproofing agent to the first slurry at a ratio of 3% to 7% of the absolute dry slurry weight after an interval of 10 minutes, and stir at a speed of 200 r / min for 20 minutes to obtain the second slurry;

[0058] S3.3: transporting the prepared second slurry to the slurry barrel of the molding machine through the slurry conveying pipeline, and then forming a paper tray intermediate by vacuum adsorption molding;

[0059] 4. The paper tray intermediate is dried at 60° C. for 24 hours and then oven dried to obtain a paper tray.

[0060] In the above step S3.2, the auxiliary agent includes one or more combinations of cationic modified starch, polyvinyl alcohol, carboxymethyl cellulose, and cationic polyacrylamide.

[0061] The following specific embodiments 1 to 8 adopt the above waterproof paper tray manufacturing process to produce paper trays with waterproof function.

[0062] Example 1

[0063] The auxiliary agent in this embodiment 1 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 1 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 3% of the weight of the absolute dry pulp.

[0064] Example 2

[0065] The auxiliary agent in this embodiment 2 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 2 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 4% of the weight of the absolute dry pulp.

[0066] Example 3

[0067] The auxiliary agent in this embodiment 3 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 3 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 5% of the weight of the absolute dry pulp.

[0068] Example 4

[0069] The auxiliary agent in this embodiment 4 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 4 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 6% of the weight of the absolute dry pulp.

[0070] Example 5

[0071] The auxiliary agent in this embodiment 5 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 5 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 7% of the weight of the absolute dry pulp.

[0072] Example 6

[0073] The auxiliary agent in this embodiment 6 is polyvinyl alcohol, and the amount of polyvinyl alcohol added is 0.5% to 1% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 6 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 7% of the weight of the absolute dry pulp.

[0074] Example 7

[0075] The auxiliary agent in this embodiment 7 is carboxymethyl cellulose, and the amount of carboxymethyl cellulose added is 0.4% to 0.8% of the weight of the absolute dry pulp. The waterproofing agent in this embodiment 7 is the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 7% of the weight of the absolute dry pulp.

[0076] Example 8

[0077] The auxiliary agent in this embodiment 8 is cationic polyacrylamide, and the amount of cationic polyacrylamide added is 0.3% to 0.8% of the absolute dry pulp weight. The waterproofing agent in this embodiment 8 is the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 7% of the absolute dry pulp weight.

[0078] Comparative Example 1

[0079] The auxiliary agent in this comparative example 1 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this comparative example 1 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent used is 0.5% of the weight of the absolute dry pulp.

[0080] Comparative Example 2

[0081] The auxiliary agent in this comparative example 2 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this comparative example 2 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent used is 1% of the weight of the absolute dry pulp.

[0082] Comparative Example 3

[0083] The auxiliary agent in this comparative example 3 is cationic modified starch, and the amount of cationic modified starch added is 1.5% of the weight of the absolute dry pulp. The waterproofing agent in this comparative example 3 adopts the above-mentioned waterproofing agent 3, and the amount of the waterproofing agent is 2% of the weight of the absolute dry pulp.

[0084] The performance test of the paper trays prepared in Examples 1 to 8 and Comparative Examples 1 to 3 was performed

[0085] Effect of the amount of waterproofing agent on the moisture resistance of paper tray

[0086] Water resistance test method: Pour clean water into the paper tray and observe the water penetration time of the sample at room temperature. The test results are shown in Table 2 below.

[0087] Table 2 Waterproofness test of paper trays prepared in Examples 1 to 8 and Comparative Examples 1 to 3

[0088] Additives Waterproofing Waterproofing agent dosage / % Penetration time / h Example 1 Cationic modified starch Waterproofing agent 3 3％ 20 Example 2 Cationic modified starch Waterproofing agent 3 4％ 23 Example 3 Cationic modified starch Waterproofing agent 3 5％ 25 Example 4 Cationic modified starch Waterproofing agent 3 6％ 28 Example 5 Cationic modified starch Waterproofing agent 3 7％ 29 Example 6 Polyvinyl alcohol Waterproofing agent 3 7％ 29 Example 7 Carboxymethyl cellulose Waterproofing agent 3 7％ 28 Example 8 Cationic polyacrylamide Waterproofing agent 3 7％ 30 Comparative Example 1 Cationic modified starch Waterproofing agent 3 0.5％ 3 Comparative Example 2 Cationic modified starch Waterproofing agent 3 1％ 7 Comparative Example 3 Cationic modified starch Waterproofing agent 3 2％ 13

[0089] It can be seen from the data in Table 2 above that when the dosage of the waterproofing agent (with cationic modified starch as an auxiliary agent) increases from 0.5% to 3%, the water penetration time of the paper tray increases significantly, indicating that the waterproof performance is rapidly improved.

[0090] When the amount of waterproofing agent exceeds 3%, the increase rate of water resistance slows down, but still shows an upward trend. This may be because as the amount of waterproofing agent increases, the coverage of the waterproofing agent on the fiber surface gradually increases, but after reaching a certain level, the effect of increasing the amount of waterproofing agent on improving water resistance is no longer significant.

[0091] After research, it was found that the surface of paper fibers carries a negative charge. This is because the cellulose molecules in the pulp contain hydroxyl groups (-OH). In aqueous solution, these hydroxyl groups can dissociate into hydroxide ions (OH-), making the fiber surface negatively charged. However, one end of the synthetic waterproofing agent is positively charged, so it is adsorbed on the fiber surface and tightly combined with the fiber and other fillers, improving the retention rate of fine fibers and other fillers, filling the pores between the fiber network, forming a network structure with strong binding ability, and effectively preventing the penetration of water molecules. In addition, AKD (alkyl ketene dimer) is melted and filled in the fiber network. During the hot pressing process, water and acetic acid evaporate instantly, providing conditions for the chemical reaction between AKD and cellulose. AKD reacts chemically with cellulose, causing the chemical properties of the fiber surface to change from hydrophilic to hydrophobic. This chemical change improves the waterproof performance of the paper tray and can more effectively resist water penetration and erosion.

[0092] It is worth mentioning that the surface of paper fibers usually carries a negative charge, which is determined by the chemical structure of cellulose and the processing conditions in the papermaking process. In addition to the fibers themselves, the slurry also contains other anionic substances, such as certain fillers, additives or dissolved organic matter. The waterproofing agent in this embodiment carries a positive charge. If it is directly added to the fiber slurry, it may be preferentially bound by anionic substances and fail to exert its effectiveness.

[0093] Based on this, Example 1 first adds cationic modified starch to the pulp preparation tank. Cationic modified starch is obtained by chemically modifying starch to give it cationic properties. After the cationic modified starch is added to the pulp preparation tank, negative charges such as anionic garbage will be preferentially combined in the fiber slurry, and then the waterproofing agent 3 is added. The waterproofing agent 3 can combine with more fine fibers, increase the attachment of fine fibers, and also promote the surface binding of long fibers, thereby providing more favorable conditions for paper support molding and further improving the quality of paper support. Secondly, after the cationic modified starch is added to the pulp preparation tank, hydrogen bonds are formed between the fibers and starch molecules, which can effectively improve the strength performance of the paper support.

[0094] The inventors found that as the amount of cationic modified starch added gradually increases, the absolute value of the Zeta potential of the fiber system will decrease. This change will affect the uniformity of the paper support, thereby damaging the strength of the paper support during molding, and will also cause the fiber system to drain water for a longer time and reduce production efficiency. After analysis, it was found that the optimal addition amount of cationic modified starch is 1.0% to 2.0% of the weight of the absolute dry pulp.

[0095] In Example 6, polyvinyl alcohol is first added to the pulp mixing tank, and then the waterproofing agent 3 is added. The chemical formula of polyvinyl alcohol (PVA) is C2H4On, where n represents the number of repeating units. PVA is a water-soluble high molecular polymer formed by polymerization of vinyl alcohol monomer (C2H4O). During the polymerization process, the hydroxyl groups (-OH) of vinyl alcohol can be partially or completely hydrogen-bonded to form a long-chain structure of PVA. In addition, due to the hydrogen bonding within and between the molecules of polyvinyl alcohol, the bonding area between fibers can be increased, thereby strengthening the bonding ability between fibers, and thus improving the tensile strength and burst resistance of the paper support.

[0096] The inventors have found through experimental analysis that as the amount of polyvinyl alcohol increases, the tensile strength and bursting resistance of the paper tray gradually increase and then tend to stabilize or slightly decrease. Therefore, the optimal amount of polyvinyl alcohol added is 0.5% to 1% of the weight of the absolute dry pulp.

[0097] In Example 7, carboxymethyl cellulose is first added to the pulp preparation tank, and then the waterproofing agent 3 is added. Carboxymethyl cellulose is an anionic ether natural polymer compound obtained by chemically modifying cellulose, and its molecular formula is (C6H7O2(OH)3)n, where n is the degree of polymerization. Since the molecules contain hydroxyl groups and carboxyl groups, they can form a strong bond between molecules through hydrogen bonds. When carboxymethyl cellulose is dissolved in water, a transparent viscous solution is formed, which can be evenly coated on the pulp. The bridging effect between fibers and the large number of hydrogen bonds formed enhance the bonding force between fibers. Carboxymethyl cellulose has an affinity with fibers and fillers, so it can produce a retention effect and reduce the loss of fillers and fine fibers. When carboxymethyl cellulose is fully combined with the pulp first, a stable fiber network structure can be formed. On this basis, after adding the waterproofing agent 3, the waterproofing agent 3 can be effectively distributed and fixed in the fiber network structure, thereby improving the waterproof performance of the paper support. The waterproofing agent 3 can provide good hydrophobicity, and after combining with carboxymethyl cellulose, the hydrophobic functional groups of the waterproofing agent 3 face the outside of the pore wall, so that the surface of the pore acquires hydrophobicity, which can effectively improve the waterproof performance of the paper support.

[0098] The inventors have found through experimental analysis that as the amount of carboxymethyl cellulose increases, the tensile strength and bursting resistance of the paper tray gradually increase and then slightly decrease. The optimal value is when the amount of carboxymethyl cellulose is 0.4% to 0.8% of the weight of the absolute dry pulp.

[0099] In Example 8, cationic polyacrylamide is first added to the pulp preparation tank, and then waterproofing agent 3 is added. In the fiber slurry system, the fiber surface often has negative charges, which is caused by the ionization of functional groups (such as carboxyl, hydroxyl, etc.) on the fiber surface in water. These negative charges will increase the repulsive force between the fibers, affecting the uniformity and stability of the pulp. Cationic polyacrylamide (CPAM) is a cationic polymer with positive charges (NH 3+ ). When CPAM is added to the fiber slurry, its positive charge will react with the negative charge on the fiber surface to neutralize the charge. This charge neutralization reaction is mainly achieved through electrostatic attraction, that is, the positive charge on the CPAM molecular chain and the negative charge on the fiber surface attract each other, thereby reducing the repulsive force between the fibers. The charge neutralization reaction reduces the repulsive force between the fibers, making it easier for the fibers to approach each other and intertwine, thereby improving the stability and uniformity of the pulp.

[0100] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0101] The above is an exemplary description of the present invention in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A waterproof paper tray manufacturing process, characterized in that: Before conveying the pulp into the pulp barrel of the forming machine, add the waterproofing agent into the pulp at a formula ratio of 3% to 7% of the absolute dry pulp weight, and then stir at a speed of 200r / min for 20 minutes.

2. A waterproof paper tray manufacturing process as claimed in claim 1, characterized in that: The following steps are involved: Step 1: pretreating the raw material to obtain a pulp suspension, and then filtering the pulp suspension to obtain a first slurry; Step 2: Add the first slurry into the slurry preparation tank, stir at a speed of 200 r / min, continue stirring for 60 minutes to make the first slurry fully uniform, and slowly heat it to 60°C; Step 3: Add the additive to the slurry preparation tank, and then add the waterproofing agent to the first slurry at a formula ratio of 3% to 7% of the absolute dry slurry weight after an interval of 10 minutes, and stir at a speed of 200r / min for 20 minutes to obtain the second slurry.

3. A waterproof paper tray manufacturing process as claimed in claim 2, characterized in that: The following steps are also included: Step 4: transporting the prepared second slurry to the slurry barrel of the forming machine through a slurry conveying pipeline, and then forming a paper tray intermediate by vacuum adsorption molding; Step 5: The paper tray intermediate is dried at 60° C. for 24 hours and then dried to obtain a paper tray.

4. A waterproof paper tray manufacturing process as claimed in claim 1, characterized in that: The waterproofing agent comprises alkyl ketene dimer and chitosan acetate, and the alkyl ketene dimer accounts for 5% of the total weight of the waterproofing agent.

5. The waterproof paper tray manufacturing process according to claim 3, characterized in that: The auxiliary agent includes one or more combinations of cationic modified starch, polyvinyl alcohol, carboxymethyl cellulose and cationic polyacrylamide.

6. A waterproof paper tray manufacturing process as claimed in claim 5, characterized in that: The amount of cationic modified starch added is 1.5% by weight of the absolute dry pulp.

7. A waterproof paper tray manufacturing process as claimed in claim 5, characterized in that: The amount of polyvinyl alcohol added is 0.5%~1% of the absolute dry pulp weight.

8. The waterproof paper tray manufacturing process according to claim 5, characterized in that: The added amount of carboxymethyl cellulose accounts for 0.4%~0.8% of the absolute dry pulp weight.

9. A waterproof paper tray manufacturing process as claimed in claim 5, characterized in that: The added amount of cationic polyacrylamide accounts for 0.3%~0.8% of the absolute dry pulp weight.

10. The waterproof paper tray manufacturing process according to claim 1, characterized in that: The dosage of waterproofing agent is 5% of the absolute dry pulp weight.

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