A method for producing a pulp molded article and a pulp molded article produced thereby

Abstract

The present invention relates to a method for producing a pulp molded article and a pulp molded article produced thereby. According to the method of the present invention, high smoothness can be achieved while maintaining low hardness by the combined use of short fibers, low pressure molding, staged drying, and a high light mold, so that vibration wear of the pulp molded article can be reduced.

Description

Technical Field

[0001] This invention relates to the field of packaging, specifically to a method for preparing pulp molded articles and pulp molded articles prepared therefrom, and also to a method for mitigating vibration wear of pulp molded articles. Background Technology

[0002] Laptops often use molded pulp cushioning packaging. During random vibration tests, the contact points between the molded pulp and the machine frequently experience wear, lint, or fiber shedding due to friction. This is mainly caused by insufficient fiber bonding or weak surface strength, leading to the shedding of fine particles during mechanical friction. This not only affects the appearance but may also pollute the environment or the computer product itself.

[0003] To address this issue, one could add or modify the bags used to package the laptops during vibration testing, or modify the shape of the pulp molded parts (e.g., reducing the height at wear locations). However, these methods are either environmentally unfriendly or lead to poor test results. A more fundamental solution is to improve the quality of the pulp molded products. Therefore, it remains necessary to provide higher-quality pulp molded products to reduce wear during random vibration testing. Summary of the Invention

[0004] Based on theoretical analysis and practical testing, the inventors of this invention discovered that while making the paper-plastic surface smooth, by adjusting fiber length, pulp dissociation, adding various additives, adjusting drying methods, and adjusting hot-pressing parameters, the strength and hardness of the pulp can be appropriately reduced, thus most effectively solving the wear problem. Based on this, the inventors completed this invention.

[0005] One object of the present invention is to provide a method for preparing a pulp molded article and a pulp molded article prepared therefrom, thereby reducing vibration wear of the pulp molded article.

[0006] According to one aspect of the present invention, the method for preparing the pulp molded article includes the following steps: S1: Add 10-20% by weight of water to fiber pulp board paper with a fiber length of 1-3 mm and beat it with a blade pulper at a speed of 1500-2500 rpm to make the pulp freeness in the range of 30°SR-40°SR. S2: Add inorganic salts, surfactants, defoamers, wet strength agents, and food-grade gelatin to the slurry and mix evenly. Then, transport the mixture to the slurry suction tank and perform slurry suction molding. S3: The wet blank after slurry molding is dried in stages. First, it is pre-dried at a low temperature of 60-80℃ for 5-8 hours, or dried until there is no moisture on the surface; then it is dried with infrared light for 1-2 hours, or dried until the moisture content is below 5%; then the product is placed at room temperature and 40%-50% humidity for 3-7 hours. S4: Grind the hot press mold with 400 mesh → 800 mesh → 1200 mesh gauze in sequence, and then apply matte water-based paint and polyurethane varnish in sequence to make the surface roughness of the hot press mold 3-5 µm. S5: The dried product from step S3 is hot-pressed and shaped in the hot-press mold processed in step S4 under a hot-pressing pressure of 0.3-0.5MPa, a hot-pressing temperature of 100-120℃, and a vacuum of 0.06-0.08MPa to obtain a pulp molded product.

[0007] In step S3, low-temperature pre-drying can slowly remove surface moisture and prevent local shrinkage and deformation; infrared drying can heat evenly and avoid local overheating caused by hot air drying; reduce surface cracks; finally, maintaining the ambient humidity at 40%-50% can prevent the product from becoming brittle due to over-drying; in step S5, under the specific hot pressing pressure, hot pressing temperature and vacuum conditions, water vapor generated by hot pressing can be removed in time, reducing bubble residue and improving surface smoothness.

[0008] According to one embodiment of the present invention, in step S1, The fiber length is 2.2-2.8 mm, preferably 2.3-2.7 mm, the added water content is 13-17% by weight, preferably 15% by weight, and the slurry freeness is in the range of 32°SR-38°SR, preferably in the range of 35°SR.

[0009] According to one embodiment of the present invention, The slurry concentration in step S1 is 3%-5%, and In step S2, based on the weight of the slurry solids in the suction tank, the inorganic salts include: 3%-5% talc and less than 5% modified precipitated calcium carbonate; the surfactant dosage is 0.1%-0.3%, and the surfactant is fatty alcohol polyoxyethylene ether (AEO); the defoamer dosage is 0.05%-0.1%, and the defoamer is polydimethylsiloxane; the wet strength agent dosage is 1%-2%, and the wet strength agent is polyamide epichlorohydrin; and the food-grade gelatin dosage is 3%-7%.

[0010] Preferably, in step S2, based on the weight of the slurry solids in the suction tank, the inorganic salt comprises: 4% talc and 3% modified precipitated calcium carbonate; the surfactant is used at a rate of 0.2%, and the surfactant is fatty alcohol polyoxyethylene ether (AEO); the defoamer is used at a rate of 0.08%, and the defoamer is polydimethylsiloxane; the wet strength agent is used at a rate of 1.5%, and the wet strength agent is polyamide epichlorohydrin; and the food-grade gelatin is used at a rate of 5%.

[0011] According to one embodiment of the present invention, in step S3, The low-temperature pre-drying temperature is 70℃, and the drying time is 6 hours; the infrared drying time is 1.5 hours; then the product is placed at room temperature and 40%-50% humidity for 6 hours.

[0012] According to one embodiment of the present invention, in step S5, The hot pressing pressure is 0.4 MPa, the hot pressing temperature is 110℃, and the vacuum degree is 0.07 MPa.

[0013] like Figure 4 As shown, there is no restriction on the order of steps S4 and S1-S3 in this invention.

[0014] According to another aspect of the invention, a pulp molded article prepared by the above method is provided.

[0015] According to another aspect of the present invention, a method for mitigating vibration wear of pulp molded articles is provided, the method comprising conducting vibration tests using the pulp molded articles prepared as described above.

[0016] Beneficial effects According to the method of the present invention, by combining short fibers, low-pressure molding, staged drying, and high-gloss molds, high smoothness can be achieved while maintaining low hardness, thereby reducing vibration and wear of pulp molded products. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a random vibration test of a laptop packaging.

[0018] Figure 2 Is Figure 1 The diagram shown illustrates the wear phenomenon during a random vibration test, where powder is shed from the packaging at the edge of the machine.

[0019] Figure 3 This is a schematic diagram of the surface of a conventional pulp molded product in Comparative Example 1 (left image, conventional pulp molded product surface) and the surface of a pulp molded product prepared in Example 1 of the present invention (right image, new pulp molded product surface).

[0020] Figure 4 This is a process flow diagram of the pulp molding product of the present invention. Detailed Implementation

[0021] The present invention will be described in detail below through embodiments. The specific embodiments described below are merely illustrative and are not intended to limit the invention or its uses. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following specific embodiments or examples.

[0022] Unless otherwise specified, all raw materials used in this invention are commercially available or prepared by methods known in the art, and the instruments used are conventional testing instruments.

[0023] In this invention, "room temperature" can refer to a temperature of 0-40°C, preferably 10-30°C, or 20-25°C. The value of "approximately xx" refers to a value within the range of ±10%, ±5%, ±2%, ±1%, or ±0.5% of the original value.

[0024] Example 1 (1) Add 15% by weight of water to fiber pulp board paper with a fiber length of 2.3-2.7 mm and beat it with a blade pulper at a speed of 2000 rpm to make the pulp freeness 35°SR; (2) Add about 4% talc, about 3% modified precipitated calcium carbonate, about 0.2% surfactant fatty alcohol polyoxyethylene ether (AEO), 0.08% defoamer polydimethylsiloxane, 1.5% wet strength agent polyamide epichlorohydrin, and 5% food grade gelatin, then stir, mix evenly and perform suction molding. (3) The wet blank after the suction molding in step (2) is first pre-dried at a low temperature of about 70°C for about 6 hours until there is no moisture on the surface; then it is dried with infrared light for about 1.5 hours until the moisture content is below 5%; then the product is placed in room temperature and 40%-50% humidity for about 6 hours. (4) Use sandpaper (400 mesh → 800 mesh → 1200 mesh) to polish the hot press mold in sequence, and then apply matte water-based paint and polyurethane clear varnish in sequence to ensure that the surface smoothness of the hot press mold is 3-5 µm. (5) The dried product from step (3) is hot-pressed and shaped in the hot-press mold treated in step (4) under a hot-pressing pressure of about 0.4 MPa, a hot-pressing temperature of about 110°C, and a vacuum of about 0.07 MPa to obtain a pulp molded product.

[0025] Comparative Example 1 The normal paper-plastic preparation method is as follows: Purchase standard bamboo pulp and sugarcane pulp for pulping. No special requirements are placed on fiber length, which meets industry standards. The fiber length distribution is wider than that described in this application. The only additive is a reinforcing agent (amphoteric polyamide modified resin (polyamide-epoxychloropropane resin, PAE)). The mixture is naturally dried at room temperature (10-40℃) for approximately 5 days. The hot-pressing mold is only lightly sanded to remove rough edges and uneven areas after machining; no fine polishing is performed. The results are as follows... Figure 3 As shown on the left.

[0026] Experimental Example 1 The tensile strength, elongation at break, density, Shore hardness, and surface roughness of the paper-plastic composites of Example 1 and Comparative Example 1 were measured using measurement methods commonly used in the art, and the results are listed in Table 1 below.

[0027] Use such as Figure 1 The random vibration test shown was performed on the paper-plastic composites of Example 1 and Comparative Example 1. As shown in Table 1 below, Comparative Example 1 showed powder shedding after 300 tests, while Example 1 showed no powder shedding after 1400 tests.

[0028] The appearance of Example 1 and Comparative Example 1 is as follows Figure 3 As shown in the photo.

[0029] Depend on Figure 3 It can be seen that the surface of the pulp molded product of Example 1 is significantly smoother than that of the pulp molded product of Comparative Example 1.

[0030] As can be seen from Table 1 below, the paper-plastic prepared in Example 1 of the present invention has slightly lower strength and hardness than the conventional paper-plastic in Comparative Example 1, and its surface is smoother (lower roughness), showing better wear resistance.

[0031] Table 1

[0032] The results of the above experimental examples show that, under the conditions of Example 1 of the method of the present invention, the surface of the prepared pulp molded product is significantly smoother, and no powder falls off during random vibration testing.

[0033] In contrast, in Comparative Example 1, the prepared pulp molded products had a rough surface and significant powder shedding.

Claims

1. A method for preparing a pulp molded article, the method comprising the following steps: S1: Add 10-20% by weight of water to fiber pulp board paper with a fiber length of 1-3 mm and beat it with a blade pulper at a speed of 1500-2500 rpm to make the pulp freeness in the range of 30°SR-40°SR. S2: Add inorganic salts, surfactants, defoamers, wet strength agents, and food-grade gelatin to the slurry and mix evenly. Then, transport the mixture to the slurry suction tank and perform slurry suction molding. S3: The wet blank after slurry molding is dried in stages. First, it is pre-dried at a low temperature of 60-80℃ for 5-8 hours; then it is dried with infrared light for 1-2 hours; then the product is placed at room temperature and 40%-50% humidity for 3-7 hours. S4: Grind the hot press mold with 400 mesh → 800 mesh → 1200 mesh gauze in sequence, and then apply matte water-based paint and polyurethane varnish in sequence to make the surface roughness of the hot press mold 3-5 µm. S5: The dried product from step S3 is hot-pressed and shaped in the hot-press mold processed in step S4 under a hot-pressing pressure of 0.3-0.5MPa, a hot-pressing temperature of 100-120℃, and a vacuum of 0.06-0.08MPa to obtain a pulp molded product.

2. The preparation method according to claim 1, in step S1, The fiber length is 2.2-2.8 mm, the added water content is 13-17% by weight, and the pulp freeness is in the range of 32°SR-38°SR.

3. The preparation method according to claim 1, in step S1, The fiber length is 2.3-2.7 mm, the added water content is 15% by weight, and the pulp freeness is 35°SR.

4. The preparation method according to claim 1, wherein, The slurry concentration in step S1 is 3%-5%, and In step S2, based on the weight of the slurry solids in the suction tank, the inorganic salts include: 3%-5% talc and 1%-5% modified precipitated calcium carbonate; the surfactant is used in an amount of 0.1%-0.3%, and the surfactant is fatty alcohol polyoxyethylene ether (AEO); the defoamer is used in an amount of 0.05%-0.1%, and the defoamer is polydimethylsiloxane; the wet strength agent is used in an amount of 1%-2%, and the wet strength agent is polyamide epichlorohydrin; and the food-grade gelatin is used in an amount of 2%-5%.

5. The preparation method according to claim 1, wherein, In step S2, based on the weight of the slurry solids in the suction tank, the inorganic salts include: 4% talc and 3% modified precipitated calcium carbonate; the surfactant dosage is 0.2%, and the surfactant is fatty alcohol polyoxyethylene ether (AEO); the defoamer dosage is 0.08%, and the defoamer is polydimethylsiloxane; the wet strength agent dosage is 1.5%, and the wet strength agent is polyamide epichlorohydrin; and the food-grade gelatin dosage is 5%.

6. The preparation method according to claim 1, wherein, In step S3, The low-temperature pre-drying temperature is 70℃, and the drying time is 6 hours; the infrared drying time is 1.5 hours; then the product is placed at room temperature and 40%-50% humidity for 6 hours.

7. The preparation method according to any one of claims 1 to 6, wherein, In step S5, The hot pressing pressure is 0.4 MPa, the hot pressing temperature is 110℃, and the vacuum degree is 0.07 MPa.

8. A pulp molded article, which is prepared by the preparation method according to any one of claims 1-7.

9. A method for mitigating vibration wear of molded pulp articles, the method comprising performing a vibration test using the molded pulp article according to claim 8.

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