Method of producing fiber product from natural fibers using pressure and vibration

Abstract

A method of compressing plant fibers using a combination of pressure and vibration is described. The method can achieve higher density at given process parameters, densify voids or hard to compress volumes, and densify surfaces and fiber bonds. The method can be used to create flat and 3D structures in fiber materials, densify specific areas of objects, and make advanced formations not possible to achieve with plain or isostatic pressure.

Description

[0001] METHOD OF PRODUCING FIBER PRODUCT FROM NATURAE FIBERS

[0002] USING PRESSURE AND VIBRATION

[0003] TECHNICAL FIELD

[0004] This invention relates to a production method and system for fiber based cellulose material products by means of converting blanks or portions of web, into shaped products, wherein there is provided a production space including an intermittently converting production unit, a supply station and a supply path.

[0005] BACKGROUND

[0006] Natural materials and fiber based cellulose materials in specific are sensitive for moisture content when being converted. This includes creasing (when materials are locally delaminated to introduce folds), cutting (when materials and fibers are cut or separated), and press-forming (when materials are reshaped with or without delamination or fusing of fibers into new bonds and structures). The moisture content is extra important if fiber bonds are broken or if new bonds is to be formed in the operation.

[0007] If too much water is introduced in or with the material and are needed to be dried away in or after the converting process, this leads to excessive need of heat or energy. Optimizing the moisture content therefor helps optimizing not only the quality of the product but also the energy consumption. It is to be understood that the invention does not relate to the continuous production of paper and board, wherein there is continuous feeding of a web from a wet end to a roll-up end, resulting in a product in the form of a roll including numerous layers of paper / board. Instead the invention preferably relates to production of intermittently produced objects.

[0008] In a typical operation flat material are fed from as sheets, pre -cut shapes or from a roll before the actual operation. In some operations for example in sheet cutting or dry-forming the material might be manufactured direct before the converting operation.

[0009] Typical process conditions are 150-250 C and pressure 100- 10000 bar (200- 2000 Bar). Moisture content typically less than 20% water. The fibre product may be a hollow product such as a package or a closure. Products can be formed from a web of the material and punched / cut during forming. Typically, for example, a round is cut to form a round package.

[0010] The forming is typically done with two tools where both the outer tool, the pad, and the inner tool, the punch, may consist of several parts to allow for the ejection of the finished product. Typically, the pad is opened while the punch is collapsed. The punch, parts of the punch or parts of the pad may also be made of a compressible material, which allows the tool material to be reshaped during compression.

[0011] A capsule may be formed by lining a mould partially or completely internally with a loosely bonded fibrous material. The fibrous material may be draped into the mould or fed into the mould in a form, for example rolled like a cylinder. The mould may be closed or partially open when the material is introduced. Examples of known methods described above are shown in EP 3 736 099 and WO 2020 / 165780.

[0012] SUMMARY OF THE INVENTION

[0013] This innovation relates to a method of producing fiber product from natural fibers using pressure and vibration, in accordance with claim 1.

[0014] Thanks to the invention plant fibers, including wood fibers, can be efficiently compressed and / or shaped using a combination of pressure and vibration. Both shearing, out of plane and combination of these forces can be used. Frequencies between 0,1 and 40 kHz can be used. Temperature intervals of 50-250 deg Celsius are relevant, as is moisture content ranging from 3 to 50% , more preferred 5-20%. There are several advantages. Higher density can be achieved at given process parameters, at least in a surface layer. Voids or hard to compressed volumes can be densified, surfaces on subject will have better density and fiber bonds and areas with surfaces perpendicular or close to perpendicular to the given pressure force can be densified, at least in a surface layer. There are several applications for this including making flat and 3d structures in fiber material’s, densifying specific areas of objects such as edge or week spots or to make advanced formations not possible to achieve with just plain or isostatic pressure. DETAILED DESCRIPTION

[0015] Plant fibers, including wood fibers, are widely used in the manufacturing of various items, such as packaging materials, closures, and food service items, due to their biodegradability and sustainability. However, dry natural fibers typically require very high pressure to achieve the desired density, which can be time-consuming and inefficient. To address this issue, a method of compressing plant fibers using a combination of pressure and vibration has been developed. This method can achieve higher density at given process parameters, densify voids or hard to compress volumes, and densify surfaces and fiber bonds. It can be used to create flat and 3D structures in fiber materials, densify specific areas of objects, and make advanced formations not possible to achieve with plain or isostatic pressure.

[0016] The method according to the invention is based on producing a fiber product using pressure and vibration, comprising the steps as defined in claim 1.

[0017] In one embodiment the vibration frequency is between 0,1 -100 Hz arranged to provide increased compression. Tests have shown that the use of such frequencies may provide increased compression in a layer adjacent the surface being applied in combination with high pressure and moderate or high temperature, whereby increased compression may be obtained, at least within a surface layer, within a depth ranging from 20 pm to a depth of at least 1000 pm of the produced product. In some applications increased compression to a depth of 3000 pm was achieved. Tests have shown that plant fibers that have been compressed in accordance with the invention may have a higher density than the original plant fibers at the same process parameters and that the compressed plant fibers may have densified surfaces and fiber bonds.

[0018] In another embodiment the vibration frequency vibration frequency is between 0,1-40 kHz arranged to provide increased bonding between fibers in the produced product, at least within a surface layer. Tests have shown that the use of such frequencies may provide increased bonding in a layer adjacent the surface being applied in combination with high pressure and moderate or high temperature, whereby increased bonding may be obtained within a depth ranging from 1 pm to a depth of at least 10 pm of the produced product. In some applications increased bonding to a depth of 20 pm was achieved.

[0019] An advantage that may be obtained is significantly higher production. One aspect in this regard is the fact that most presses used to apply the pressure to dry form the product have a maximum load capacity, e.g. 1500 kN. Mostly a plurality of products is produced during each stroke performed by such a press, implying a limit for how many products that may be produced during each stroke, to achieve a predetermined densification. Hence, when combined with vibrations a larger number of products may be produced during each stroke / pressing operation of the press, thanks to the need of less pressure to achieve a predetermined densification.

[0020] According to a preferred aspect of the invention the pressure force is applied perpendicular or close to perpendicular to at least 50% of surfaces of the plant fibers, preferably at least 90% of the surfaces of the plant fibers . Further, in some applications it may be beneficial that the pressure force is applied using a combination of shear and out-of-plane forces.

[0021] According to another preferred aspect of the invention the pressure is between 200-1000 Mpa. If the fiber product is arranged with undercuts, e.g. threads, test have shown that in some application beneficial results may be achieved by using a pressure that is below 1000 kpa.

[0022] According to another preferred aspect of the invention the compressed plant fibers are used to densify specific areas of the produced fiber product. Test have shown that by means of the invention it is possible to create advanced formations that are not possible to achieve with plain or isostatic pressure.

[0023] The invention may significantly increase productivity and enable the manufacturing of a wide range of items flat or 3D structures from wood fibers, including:

[0024] Packaging items: such as creates, holders, protective packaging, frozen foods packaging, bottles, jars, boxes etc

[0025] Closures and other advanced functional items

[0026] Food service items: such as cutlery, bowls, lids and cups, and other examples Furniture: Compressed wood fibers can be used to make sturdy and eco-friendly furniture pieces, such as chairs, tables, and cabinets.

[0027] Sporting goods: Compressed wood fibers can be used to make high-performance sporting goods, such as skateboards, snowboards, and surfboards. Decorative items: Compressed wood fibers can be used to create decorative items, such as wall panels, picture frames, and sculptures.

[0028] Medical devices: Compressed wood fibers can be used to make medical devices, such as splints and braces, that are biodegradable and eco-friendly.

Claims

Claims:

1. A method of producing a fiber product using pressure and vibration, comprising the steps of: a) providing a source of plant fibers, having a moisture content range of 3-50%, preferably 5-20%; b) placing the plant fibers in a compression mould; c) applying pressure of at least 100 kPa to the plant fibers in the mould; d) applying vibrations of between 0, 1 Hz and 40 kHz to the mould and plant fibers during compression; e) supplying heat within a temperature range between 50-250 degrees Celsius during compression; f) maintaining a moisture content range of 3-50% during compression, preferably a moisture content range 5-20%; g) releasing the pressure and vibration after compression is complete; h) removing a formed product comprising the compressed plant fibers from the mould.

2. The method of claim 1, wherein the vibration frequency is between 0.1 - 1000 Hz arranged to provide increased compression in a surface layer, preferably providing a density increase of at least 5 % within said surface layer, more preferred within the range of 6 -50%.

3. The method of claim 2, wherein the vibration frequency is between 0.1 - 100 Hz arranged to provide increased compression in said surface layer, wherein preferably said increased compression is obtained to a depth of at least 1000 pm, more preferred to a depth of at least 2000 pm of the produced product.

4. The method of claim 1, wherein the vibration frequency is between 0.1 - 40 kHz arranged to provide increased bonding between fibers in the produced product wherein a Scott bond value, according to TAPPI T569, is increased by at least 5%, preferably by 6- 100%, wherein preferably said increased bonding is obtained to a depth of at least 1pm, more preferred to a depth of at least 10 pm of the produced product.

5. The method of claim 1, wherein the pressure force is applied perpendicular or close to perpendicular to at least 50% of the surfaces of the top layer of a fiber sheet-like configuration that is to be molded, preferably at least 90% of the surfaces of the top layer.

6. The method of claim 1, wherein the pressure force is applied using a combination of shear and out-of-plane forces.

7. The method of claim 1, wherein the plant fibers are wood fibers.

8. The method of claim 1, wherein the compressed plant fibers are used to create flat or 3D structures.

9. The method of claim 1, wherein the compressed plant fibers are used to densify specific areas of products.

10. The method of claim 1, wherein the compressed plant fibers are used to create advanced formations not possible to achieve with plain or isostatic pressure.

11. The method of claim 1, wherein the compressed plant fibers have densified surfaces and fiber bonds.

12. The method of claim 1, wherein the pressure is between 200-1000 MPa.

13. The method of claim 1, wherein the pressure is below 1000 kPa, wherein preferably said fiber product is arranged with undercuts, e.g. threads.

14. A fiber product achieved in accordance with a method defined in any of claims 1-13.