Production method of dry-process paper pulp molding

Abstract

The invention belongs to the technical field of paper pulp molding, and particularly relates to a production method of a dry paper pulp molding, which utilizes a foaming agent and strictly controls the use amount relationship of the foaming agent and fibers and the foaming temperature, and expands the fibers in the process of realizing the thermal expansion of the foaming agent, so that the fibers are in a completely fluffy state, thereby avoiding fiber agglomeration and improving the production efficiency. The free sliding among the fibers is realized; meanwhile, the foaming agent has the characteristics that the foaming agent expands after being heated, and the microspheres generate volume but are not broken and maintain the original shape when being heated, so that gaps among fibers can be effectively filled in the high-temperature shaping process, and the mechanical property of the product is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of pulp moulds, and in particular relates to a production method of a dry pulp mould. Background Art

[0002] Pulp molding is a three-dimensional papermaking technology that uses plant fibers as the basic raw material and uses waste paper, dry pulp, and wet pulp as feed materials. Paper products of a certain shape are molded into special molds on the molding machine. Pulp molding has gradually become a substitute for traditional plastic packaging and foam plastics due to its biodegradable, recyclable and renewable properties. It is widely used in food packaging, electronic product cushioning packaging, agricultural seedling cups and other fields. The raw materials for pulp molding are bamboo pulp, wood pulp, grass pulp, sugarcane pulp, recycled waste paper pulp and other plant fiber pulp or mixed pulp. Usually, the pulping process needs to be carried out in a pulp mill. The pulp mill is a process that removes sugars, pectin and other substances from plants (such as bamboo, sugarcane, grass, wood, etc.) to leave the cellulose or hemicellulose required for pulp molding or papermaking. After the pulp is prepared by the pulp mill, it needs to be dried at low temperature to enter the market in the form of dry pulp board. Pulp molding companies need to disperse the pulp dry pulp board with water before use.

[0003] At present, the production methods of pulp molding include the following: 1. Wet molding process, whose preparation steps are pulping → drying → beating (adding 5-10 times water) → adsorption molding → drying process. Due to the large amount of water required, the operating cost is high, the efficiency is low, and the area occupied is large. Attention should be paid to changes in water quality at all times, and the return water needs to be replaced regularly. In addition, the drying process consumes a lot of heat energy, resulting in high energy consumption. 2. Injection molding process, whose preparation steps are pulping → mixing and granulation → injection molding → cooling and demolding, but it has the disadvantages of expensive injection molding equipment, high energy consumption caused by high temperature and high pressure operation, and the need to use adhesives, waterproofing agents and other additives in the granulation process; 3. Dry molding process, which directly uses pulp board for processing, without dehumidification and drying process, has the advantages of low production cost and low energy consumption, and is an important method for the development of pulp molding. If pulp board is used directly to produce pulp molding, there will also be corresponding technical barriers. The reason is: when pulp is produced into pulp board in the pulp mill, plant fibers rely on hydrogen bonds or cross-fibers to form pulp boards. At this time, it is difficult for fibers to slide against each other, so directly using pulp board to press products is prone to tearing defects.

[0004] A semi-dry pulp molding production process and its production line (patent number: ZL202310541812.6) and a dry pulp molding forming method (patent number: ZL202110942444.7) both introduce the production method of dry pulp molding. The technical route is to loosen and crush the pulp board, reorganize it into a net through air flow and other means after crushing, spray adhesive and then mold it. The fibers are dispersed by physical methods and then reorganized. However, due to factors such as static electricity between fibers during physical dispersion, the fibers will cause the fibers to clump, making it difficult to achieve an ideal dispersion state.

[0005] Patent publication number CN104074105A discloses a pulp molding production method, comprising the following steps: 1) crushing, sanding, and grinding raw materials to obtain pulp fibers; 2) mixing a binder, an additive, and water in a weight ratio of 10-15:1:10-15 to form a paste; 3) adding the prepared pulp fibers and the paste to a mixer for mixing; 4) cutting the mixture to obtain mixed particles; 5) adding a foaming agent to the mixed particles and injecting them into a mold; 6) forming; 7) cooling and demoulding. The foaming agent transforms the thin-walled solid structure of the product into a foamed porous structure, thereby improving the structural strength and cushioning performance, reducing labor intensity and improving operating conditions. The patent adopts an injection molding process to realize the molding of the product, but the injection molding process requires the material to have good fluidity, which is difficult to achieve with plant fibers. On the other hand, the purpose of adding a foaming agent in the patent is to obtain a porous structure. It is feasible to transform the thin-walled solid structure of the product into a foamed porous structure for cushioning packaging materials, but it will cause oil and water immersion when used on food packaging. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention proposes a production method for dry pulp molding. An appropriate amount of foaming agent is added during the pulping process of the pulp mill and dried together with the pulp board before entering the market. When in use, it is first baked at high temperature, and the foaming agent expands the pulp to obtain a fluffy "pulp board" for the purpose of obtaining a better sliding space for the fibers during molding and facilitating the molding of the product. During molding, a higher temperature is applied to melt the foaming agent PS shell and integrate it with the fibers to obtain better mechanical properties. The foaming agent used is a core-shell structure foaming agent, the shell of which is a polystyrene material and the interior is a material that expands when heated. The difference between the present invention and the aforementioned patent is that the purpose of using the foaming agent in this patent is to expand the agglomerated plant fibers so that there is more space for the fibers to slide rather than to transform the thin-walled solid structure into a foamed porous structure. At the same time, the foaming agent shell can also provide bonding properties to improve the strength of the product.

[0007] This is achieved specifically through the following technical solutions:

[0008] A method for producing a dry pulp mold comprises the following steps:

[0009] 1) Pulping: mixing plant fiber pulp, microsphere foaming agent, oil repellent, and waterproofing agent to prepare slurry;

[0010] 2) Low temperature drying: The pulp is dried at low temperature to produce pulp board;

[0011] 3) Baking and foaming: Baking the pulp board at 90-180°C to obtain a foamed pulp board;

[0012] 4) Shaping: Place the foamed pulp board in a mold and shape it at high temperature to obtain a pulp molded product.

[0013] The slurry comprises the following components in parts by weight: 95-98 parts of plant fiber, 0.5-2 parts of microsphere foaming agent, 0.5-1 parts of oil repellent, and 0.5-1 parts of waterproofing agent.

[0014] The plant fiber pulp is any one or more of bamboo pulp, sugarcane pulp, wood pulp and straw pulp.

[0015] The plant fiber pulp is prepared according to a traditional pulp and papermaking method, including any one of a caustic soda method, a sulfite method, a sulfate method, a mechanical pulping method, a bleached chemical thermomechanical pulping method, and an alkaline hydrogen peroxide pulping method.

[0016] The foaming agent is polystyrene microspheres.

[0017] Furthermore, the foaming agent is polystyrene microspheres with a particle size of 2-15 μm and a foaming ratio of 2-10 times.

[0018] Furthermore, the foaming agent is any one or more of polystyrene microsphere foaming agents 031du40, 043du80, F-30, F-36, and F-48.

[0019] The low-temperature drying temperature is ≤80° C., and the pulp board is baked until the moisture content is ≤10%.

[0020] The pulp board is baked at 90-180° C. for 1-3 minutes.

[0021] The high temperature setting temperature is 180-220° C. and the time is 30-120 seconds.

[0022] Beneficial effects:

[0023] The present invention utilizes a foaming agent and strictly controls the amount of foaming agent and fiber, as well as the foaming temperature. During the thermal expansion of the foaming agent, the fibers are stretched and fully fluffed, preventing fiber clumping and enabling free interfiber movement. The foaming agent can be added during the pulping process and dried along with the pulp board, reducing energy consumption. The foaming agent can then be heated and foamed for use in pulp molding.

[0024] The method of the present invention can meet the production requirements of pulp molded products with various structures without using a large amount of water and high-end equipment.

[0025] The foaming agent used in the present invention has a core-shell structure, in which the shell is PS (polystyrene) and the core is a liquid that expands when heated. The foaming agent expands the fibers during the first foaming, and during the second high-temperature setting, the shell (PS) melts and acts as a bond to the fibers, further improving the strength of the finished product and ensuring the mechanical properties.

[0026] Molding properties of wet pulp: stiffness ≥ 200mN, bursting index ≥ 2.0Kpa.m 2 / g, tensile index ≥5N.m / g. The mechanical properties of the pulp molded product produced by the method of the present invention are: stiffness ≥300mN, bursting index ≥3.0Kpa.m 2 / g, tensile index ≥6N.m / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The effects of different foaming agents on the foaming of pulp board at different baking temperatures;

[0028] Figure 2 The influence of different setting temperatures on product stiffness, bursting index and tensile index. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments. Any improvement or replacement based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0030] Example 1

[0031] A method for producing a dry pulp mold comprises the following steps:

[0032] 1) Pulping: 9.5 kg of bamboo pulp prepared by a sulfite process, 0.05 kg of a microsphere foaming agent, 0.05 kg of an oil-proofing agent perfluoroalkyl phosphate, and 0.05 kg of a waterproofing agent AKD were mixed uniformly to prepare a slurry;

[0033] 2) Low temperature drying: The pulp board was dried at 80°C for 8 hours, and the moisture content of the pulp board was tested to be 5% to obtain the pulp board;

[0034] 3) High temperature baking: bake the pulp board at 130°C for 2 minutes to obtain a foamed pulp board;

[0035] 4) Shaping: Place the foamed pulp board in a mold and shape it at 180°C to obtain a pulp molded product.

[0036] The foaming agent is polystyrene microsphere foaming agent F-30 with a particle size of 2-15 μm.

[0037] Example 2

[0038] A method for producing a dry pulp mold comprises the following steps:

[0039] 1) Pulping: 9.8 kg of sugarcane pulp prepared by a sulfite process, 0.2 kg of a microsphere foaming agent, 0.1 kg of a perfluoroalkyl chromium complex as an oil repellent, and 0.1 kg of a rosin paraffin glue as a waterproofing agent were mixed uniformly to prepare a slurry;

[0040] 2) Low-temperature drying: drying the pulp at 60°C for 10 hours to produce a pulp board;

[0041] 3) High temperature baking: bake the pulp board at 140°C for 2 minutes to obtain a foamed pulp board;

[0042] 4) Shaping: Place the foamed pulp board in a mold and shape it at 200°C to obtain a pulp molded product.

[0043] The foaming agent is polystyrene microsphere foaming agent 031du40 or F-36 with a particle size of 2-15 μm.

[0044] Example 3

[0045] A method for producing a dry pulp mold comprises the following steps:

[0046] 1) Pulping: 9.6 kg of bamboo pulp prepared by a sulfite process, 0.1 kg of a microsphere foaming agent, 0.06 kg of an oil-proofing agent perfluoroalkyl copolymer, and 0.09 kg of a waterproofing agent paraffin latex were mixed uniformly to prepare a slurry;

[0047] 2) Low-temperature drying: drying the pulp at 50°C for 12 hours to produce a pulp board;

[0048] 3) High temperature baking: bake the pulp board at 160°C for 3 minutes to obtain a foamed pulp board;

[0049] 4) Shaping: Place the foamed pulp board in a mold and shape it at 220°C to obtain a pulp molded product.

[0050] The foaming agent is a polystyrene microsphere foaming agent 043du80 with a particle size of 2-15 μm.

[0051] The pulp molded products prepared in Examples 1-3 were tested for stiffness, bursting index, tensile strength and tensile strength index.

[0052]

[0053] Example 4

[0054] A method for producing a dry pulp mold comprises the following steps:

[0055] 1) Pulping: 9.5 kg of bamboo pulp prepared by a sulfite process, 0.05 kg of a microsphere foaming agent, 0.05 kg of an oil-proofing agent perfluoroalkyl phosphate, and 0.05 kg of a waterproofing agent AKD were mixed uniformly to prepare a slurry;

[0056] 2) Low temperature drying: The pulp board was dried at 45°C for 8 hours, and the moisture content of the pulp board was tested to be 5% to obtain the pulp board;

[0057] 3) High temperature baking: bake the pulp board at 90-180°C for 2 minutes to obtain a foamed pulp board;

[0058] 4) Shaping: Place the foamed pulp board in a mold and shape it at 180°C to obtain a pulp molded product.

[0059] The foaming agent is polystyrene microsphere foaming agent F-30, F-36, F-48, 031du40, 043du80 with a particle size of 2-15 μm, and its foaming ratio is as follows Figure 1 shown.

[0060] The best foaming agent was F-36. The effect of setting temperature on pulp molding products was further studied. The setting temperature range was 180-220℃. The results were as follows: Figure 2 shown.

Claims

1. A method for producing a dry pulp mold, characterized in that: The steps are as follows: 1) Pulping: mixing plant fiber pulp, microsphere foaming agent, oil repellent, and waterproofing agent to prepare slurry; 2) Low temperature drying: The pulp is dried at low temperature to produce pulp board; 3) Baking and foaming: Baking the pulp board at 90-180°C to obtain a foamed pulp board; 4) Shaping: Place the foamed pulp board in a mold and shape it at high temperature to obtain a pulp molded product.

2. The method for producing a dry pulp mold according to claim 1, wherein: The slurry comprises the following components in parts by weight: 95-98 parts of plant fiber, 0.5-2 parts of microsphere foaming agent, 0.5-1 parts of oil repellent, and 0.5-1 parts of waterproofing agent.

3. The method for producing a dry pulp mold according to claim 2, wherein: The plant fiber pulp is any one or more of bamboo pulp, sugarcane pulp, wood pulp and straw pulp.

4. The method for producing a dry pulp mold according to claim 1, wherein: The foaming agent is polystyrene microspheres.

5. The method for producing a dry pulp mold according to claim 4, wherein: The foaming agent is polystyrene microspheres with a particle size of 2-15 μm and a foaming ratio of 2-10 times.

6. A method for producing a dry pulp mold according to claim 4 or 5, characterized in that: The foaming agent is any one or more of polystyrene microsphere foaming agents 031du40, 043du80, F-30, F-36, and F-48.

7. The method for producing a dry pulp mold according to claim 1, wherein: The low-temperature drying temperature is ≤80° C., and the pulp board is baked until the moisture content is ≤10%.

8. The method for producing a dry pulp mold according to claim 1, wherein: The baking and foaming temperature is 90-180° C. and the time is 1-3 minutes.

9. The method for producing a dry pulp mold according to claim 1, wherein: The high temperature setting temperature is 180-220° C. and the time is 30-120 seconds.

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