Method for producing fibrous products from natural fibers using pressure and vibration

Abstract

The invention discloses a method for compressing plant fibers by combining pressure and vibration. The method can achieve higher density under given process parameters, compact voids or volumes that are difficult to compress, and densify surface and fiber bonds. The method can also be used for forming planar and three-dimensional structures in the fiber material and carrying out densification treatment on a specific area of an article to form a complex forming structure which cannot be realized only through common pressure or isostatic pressing.

Description

Technical Field

[0001] This invention relates to a method and system for producing fiber-based cellulose material products, specifically involving the conversion of raw materials or a portion of fiber webs into molded products, wherein a production space is provided, the production space including an intermittent conversion production unit, a supply station and a supply path. Background Technology

[0002] Natural materials, especially cellulose-based materials, are highly sensitive to moisture content during conversion. The conversion process includes pleating (partial delamination of the material to form folds), cutting (cutting or separating the material and fiber webs), and compression molding (reshaping the material, regardless of whether the fibers are delaminated or fused to form new bonds and structures). Moisture content is particularly important if fiber bonds are broken or new bonds need to be formed during the process.

[0003] If too much moisture is introduced into the material, or if moisture enters the material and needs to be dried during or after the conversion process, it will lead to excessive heat or energy consumption. Therefore, optimizing the moisture content not only helps improve product quality but also optimizes energy consumption. It should be understood that this invention does not relate to the continuous production of paper and paperboard, but rather preferably to the intermittent production of products, wherein the fiber web is continuously fed from the wet end to the winding end, and the final product is a roll containing multiple layers of paper / paperboard.

[0004] In typical operations, flat material is fed in sheet, pre-cut shape, or roll form before actual processing. In some operations (such as sheet cutting or dry forming), the material can be manufactured directly before the conversion operation.

[0005] Typical process conditions are a temperature of 150–250°C, a pressure of 100–10000 bar (200–2000 bar), and a moisture content typically below 20%. The fiber product can be a hollow product, such as a packaging container or cap. The product can be formed from the fiber web of the material and stamped / cut during the forming process, for example, cut into circles to form circular packaging containers.

[0006] The molding process typically employs two sets of molds: an outer mold (a backing plate) and an inner mold (a punch). Both can consist of multiple components to eject the finished product. Typically, the punch retracts when the backing plate opens. The punch, a portion of the punch, or a portion of the backing plate can also be made of compressible material, allowing the mold material to be reshaped during compression.

[0007] The capsule can be made by partially or completely lining the interior of a mold with a loosely bonded fibrous material. The fibrous material can be placed inside the mold or formed into a specific shape (such as a cylindrical roll) and fed into the mold. The mold can be closed or partially opened during material feeding. Examples of the above-mentioned known methods can be found in EP 3 736 099 and WO 2020 / 165780. Summary of the Invention

[0008] This invention relates to a method for manufacturing fiber products from natural fibers using pressure and vibration, specifically as described in claim 1.

[0009] This invention enables the efficient compression and / or molding of plant fibers (including wood fibers) through a combination of pressure and vibration. Shear force, out-of-plane force, and combinations thereof can be used, with a frequency range of 0.1–40 kHz, an applicable temperature range of 50–250 °C, and a moisture content range of 3%–50%, more preferably 5%–20%. This invention offers several advantages: higher density can be achieved (at least in the surface layer) under given process parameters; voids or difficult-to-compress volumes can be compacted; the density and fiber bonding of the product surface are improved; and surface areas perpendicular or nearly perpendicular to the given pressure direction can be densified (at least in the surface layer). This invention has various applications, including: forming planar and three-dimensional structures in fibrous materials; densifying specific areas of a product (such as edges or weak points); and forming complex molding structures that cannot be achieved solely through ordinary pressure or isostatic pressing. Detailed Implementation

[0010] Plant fibers (including wood fibers) are widely used in the manufacture of various products such as packaging materials, caps, and food service products due to their biodegradability and sustainability. However, dried natural fibers typically require extremely high pressure to achieve the desired density, a time-consuming and inefficient process. To address these issues, this invention proposes a method for compressing plant fibers using a combination of pressure and vibration. This method can achieve higher densities under given process parameters, compacting voids or difficult-to-compress volumes, improving surface density and fiber bonding. The method can also be used to form planar and three-dimensional structures in fibrous materials, densify specific areas of a product, and create complex molding structures that cannot be achieved solely through ordinary pressure or isostatic pressing.

[0011] The method of the present invention utilizes pressure and vibration to prepare fiber products, and the specific steps are as defined in claim 1.

[0012] In one embodiment, the vibration frequency is 0.1–1000 Hz to increase compressibility. Tests show that, combined with high pressure and moderate or high temperature, using this frequency can increase the compressibility of adjacent layers of the compressed surface, thereby achieving an increase in compressibility (at least at the surface level) to a depth ranging from 20 µm to at least 1000 µm in the manufactured product. In some applications, the depth of the increased compressibility can reach 3000 µm. Test results show that plant fibers compressed using the method described in this invention have a higher density than the original plant fibers under the same process parameters, and the compressed plant fibers have a denser surface and fiber bond.

[0013] In another embodiment, the vibration frequency is 0.1–40 kHz, used to improve the bonding strength between fibers in the manufactured product (at least on the surface). Tests have shown that, combined with high pressure and moderate or high temperature, using this frequency can improve the bonding strength of adjacent layers on the pressure surface, thereby achieving a bonding strength improvement in the manufactured product from a depth range of 1 µm to at least 10 µm. In some applications, the depth of bonding strength improvement can reach 20 µm.

[0014] One advantage of this invention is a significant increase in production efficiency. One aspect is that most presses used to apply pressure to dry-formed products have a maximum load capacity (e.g., 1500 kN) and typically produce multiple products per press, but the number of products per press is limited to achieve a predetermined degree of densification. Therefore, by incorporating vibration, the pressure required to achieve the desired degree of densification is reduced, thereby allowing the press to produce more products per press / pressing operation.

[0015] According to a preferred aspect of the invention, the direction of pressure application is perpendicular or nearly perpendicular to at least 50% of the plant fiber surface, preferably perpendicular or nearly perpendicular to at least 90% of the plant fiber surface. Furthermore, in some applications, it is advantageous to apply the pressure using a combination of shear force and out-of-plane force.

[0016] According to another preferred aspect of the invention, the pressure ranges from 200 to 1000 MPa. If the fiber product has a reversed structure, such as threads, tests have shown that in some applications, pressures below 1000 kPa can yield beneficial results.

[0017] According to another preferred aspect of the invention, the compressed plant fibers are used to densify specific areas of the fiber product. Tests show that the invention can form complex shaped structures that cannot be achieved by ordinary pressure or isostatic pressing alone.

[0018] This invention can significantly improve production efficiency and can utilize wood fiber to manufacture a variety of planar or three-dimensional structural products, including: Packaging products: such as wooden crates, frames, protective packaging, frozen food packaging, bottles, cans, boxes, etc.; Covers and other advanced functional products; Catering supplies: such as tableware, bowls, lids, cups, etc.; Furniture: Compressed wood fiber can be used to manufacture sturdy and environmentally friendly furniture, such as chairs, tables, cabinets, etc. Sporting Goods: Compressed wood fiber can be used to manufacture high-performance sporting goods, such as skateboards, skis, surfboards, etc. Decorations: Compressed wood fiber can be used to make decorations such as wall panels, picture frames, sculptures, etc. Medical devices: Compressed wood fiber can be used to manufacture biodegradable and environmentally friendly medical devices, such as splints and stents.

Claims

1. A method for manufacturing fiber products using pressure and vibration, characterized in that, Includes the following steps: a) Provides a source of plant fiber with a moisture content ranging from 3% to 50%, preferably from 5% to 20%; b) Place the plant fibers into a compression mold; c) Apply a pressure of at least 100 kPa to the plant fibers in the mold; d) During compression, vibrations of 0.1 Hz to 40 kHz are applied to the mold and plant fibers; e) Provide heat within a temperature range of 50–250°C during compression; f) During compression, maintain a moisture content range of 3% to 50%, preferably 5% to 20%; g) After compression is complete, release the pressure and vibration; h) Remove the molded product containing compressed plant fibers from the mold.

2. The method according to claim 1, characterized in that, The vibration frequency is 0.1 to 1000 Hz, used to increase the compressibility of the surface layer, preferably increasing the density of the surface layer by at least 5%, more preferably increasing the density of the surface layer by 6% to 50%.

3. The method according to claim 2, characterized in that, The vibration frequency is 0.1 to 100 Hz, used to increase the compressibility of the surface layer, wherein the increase in compressibility preferably reaches a depth of at least 1000 µm in the manufactured product, and more preferably reaches a depth of at least 2000 µm in the manufactured product.

4. The method according to claim 1, characterized in that, The vibration frequency is 0.1 to 40 kHz, used to improve the bonding strength between fibers in the manufactured product, wherein the Scott bonding strength value measured according to the TAPPI T569 standard is increased by at least 5%, preferably by 6% to 100%, wherein the increase in bonding strength preferably reaches a depth of at least 1 µm in the manufactured product, more preferably reaching a depth of at least 10 µm in the manufactured product.

5. The method according to claim 1, characterized in that, The direction of pressure application is perpendicular or nearly perpendicular to at least 50% of the top surface of the fiber sheet structure to be formed, preferably perpendicular or nearly perpendicular to at least 90% of the top surface.

6. The method according to claim 1, characterized in that, The pressure is applied using a combination of shear force and out-of-plane force.

7. The method according to claim 1, characterized in that, The plant fiber is wood fiber.

8. The method according to claim 1, characterized in that, The compressed plant fibers are used to form planar or three-dimensional structures.

9. The method according to claim 1, characterized in that, The compressed plant fibers are used to densify specific areas of the product.

10. The method according to claim 1, characterized in that, The compressed plant fibers are used to form complex shaped structures that cannot be achieved by ordinary pressure or isostatic pressing alone.

11. The method according to claim 1, characterized in that, The compressed plant fibers have a densified surface and fiber bond.

12. The method according to claim 1, characterized in that, The pressure range is 200–1000 MPa.

13. The method according to claim 1, characterized in that, The pressure is below 1000 kPa, and the fiber product preferably has an undercut structure, such as a thread.

14. A fiber product obtained by the method according to any one of claims 1 to 13.