Method for manufacturing a composite fibre board

Abstract

The present invention relates to a method for manufacturing a composite fibre board and to a composite fibre board thus obtained. The present invention furthermore relates to a laminate comprising a stack of composite fibre boards, as well to its use. An object of the present invention is to provide a composite fibre board that has a low surface sound and is dimensional stable.

Description

[0001] Title: Method for manufacturing a composite fibre board

[0002] Description:

[0003] The present invention relates to a method for manufacturing a composite fibre board and to a composite fibre board thus obtained. The present invention furthermore relates to a laminate comprising a stack of composite fibre boards, as well to its use.

[0004] A method for manufacturing a composite fibre board is known in the art.

[0005] For example, International application W02007020657 discloses a process for manufacturing a composite material component comprising a step of forming a slurry with resin solution, fillers and optional additives, a step of impregnation, spraying, coating of bamboo and jute provided separately or combined in a ratio of 1 :99 to 99 :1 mixture of resin, additives and filler into the slurry with or without other natural fibres selected from Bulrush (Hogla), Hem, Banana and pine apple, in amount of 1% - 90% by wt. of reinforcement material when present, a step of drying the impregnated / sprayed / coated reinforcement material in oven at temperature of 50 °C to 200°C and cutting the impregnated / sprayed / coated and dried fibres or panels into required size and a step of pressing the impregnated / sprayed / coated dried cut pieces of bamboo and jute with or without the other natural fibres multi-layered according to require thickness and pressed in the hydraulic press at a pressure 0.1 to 20 tons per square inches for a definite period at a defined temperature.

[0006] GB1435195A discloses a method of manufacturing a laminate sheet, wherein a wood veneer is covered on one side only with a layer of a polymer which is bonded to the veneer by heating under pressure, and the veneer is then bonded by glueing on its uncoated side to a wood substrate, wherein the veneer is covered with the polymer at a temperature of between 140-170 °C at a pressure of 440 kgf / cm2for 15-30 minutes.

[0007] CN 108797192 relates to a glue-free straw fiber board, which is prepared by hot-pressing a wet billet obtained by uniformly mixing straw fibers and auxiliary materials, wherein the mass fraction of the straw fibers is 20% to 80%, and the balance is auxiliary materials selected from one or more of wood fiber, bamboo fiber and chemical fiber. The preparation method of the glue-free straw fibreboard comprises a step of expanding the straw in an extruder to obtain straw fibers, a step of mixing the straw fiber with water to obtain a straw fiber slurry, a step of pulping the straw fiber slurry with auxiliary materials, wherein the suspension obtained by pulping is made into a wet billet by the drawing method comprising dehydration, filtration and compacting. When the wet billet reaches the required thickness, it is transferred from the forming cylinder to a hot press machine operating at a temperature of 180-220° C to produce a glue-free straw fibreboard.

[0008] WO 2012 / 009514 relates to a biolaminate structure, comprising a first cellulosic layer, a second cellulosic layer, and a first bio-based polymer comprising one of polylactic acid and lactic acid that impregnates the first cellulosic layer and the second cellulosic layer, wherein the first cellulosic layer and the second cellulosic layer are fused together.

[0009] US 2018 / 162093 relates to a composite melded article in which aliphatic polyester-based resin expanded beads and a thermosetting resin cured product containing a reinforcing fiber, which is formed between the expanded beads, are integrally fixed, wherein the aliphatic polyester-based resin is a crystalline polylactic acid-based resin.

[0010] US 2009 / 004941 relates to a bio-disintegratable board for use in a vehicle comprising at least two layers of nonwoven fabric, wherein said nonwoven fabric comprises a sheath-core type conjugate fiber and a natural fiber, wherein the sheathcore type conjugate fiber comprises 30-70 wt. % of polylactic acid as a sheath component, and 30-70 wt. % of a resin selected from the group consisting of polyethyleneterephthalate, polytrimethyleneterephthalate, polypropylene and polyethylene as a core component, wherein said natural fiber is kenaf fiber.

[0011] JP 2007-196500 relates to a method for producing a composite board, wherein 10 to 70% by weight of polylactic acid short fibers having an average fiber length in the range of 20 to 100 mm and 90 to 10% by weight of natural fibers having an average fiber length in the range of 5 to 100 mm are mixed, and the resulting cloth-like material is laminated, and then paper is laminated on at least one side of the cloth-like material laminate, and the laminate and the paper are integrally molded by heating and compressing. The composite board has a laminated structure in which paper is bonded integrally to the surface of the fiber-based board, and polylactic acid resin is used as the binder.

[0012] FR 3006693 relates to a method for manufacturing a composite material, wherein a mixture of natural organic fibers, such as straw, is prepared, pasteurized and seeded with mycelium obtained from fungal species to form a mycelial substrate, whereafter the mycelial substrate is compressed by heating.

[0013] US 2010 / 0093245 relates to a method of preparing a non-woven fabric composite material comprising the following steps of obtaining a natural fiber, milling the natural fiber to a desired fiber length, mixing the milled natural fiber with a thermoplastic fiber, creating a matted or felted material from the blended fibers using carding and needle punching, air deposition of fibers sprayed with a light glue to give a matted non-woven fabric composite material.

[0014] CN 101691045 relates to a method for producing a plate, comprising steps of mixing PLA fiber and degummed hemp fiber for obtaining fiber felt, wetting the fiber felt with a treatment liquid comprising one or more of a flame retardant, an antibacterial agent, an antioxidant, a tackifier and a gelling agent, drying the impregnated fiber felt, and roll and shape the dried fiber felt to make hemp fibreboard.

[0015] JP 2007-270417 relates to a method for producing a fiber board, comprising laminating a fiber board having an apparent density of 0.8 to 1.1 g / cm3on a cloth-like material obtained by mixing short fibers of polylactic acid fibers and short fibers of natural fibers having an average fiber length of 5 to 100 mm, and heating and compressing the laminate or simultaneously carrying out heating and compression.

[0016] CN 102085680 relates to a method for preparing an ecological composite material of crop straw fibers, comprising the steps of mechanical separation of crop straw, subjecting the short straw to alkali treatment at a temperature of 80-100°C during 1-2 hours, washing with water and neutralizing to a pH of 7, drying at a temperature of 60 to 80° C for 2 to 10 hours to obtain straw fibers as a reinforcing phase and polylactic acid material as a matrix to obtain a composite material by hot pressing at a temperature of 170-180°C, a pressure of 3-6MPa, and a hot pressing time of 1-5min.

[0017] CN 106738181 relates to a method for preparing a modified crop straw fiber ecological composite material, comprising the steps of cooking the crop straw with a 4% by mass phosphoric acid solution at 60-80°C for 40 minutes, washing, drying and mechanically separating the crop straw into short straws, treating the short straw with alkali in a sodium hydroxide solution at a treatment temperature of 80-100° C for 1-2 h, adding a mixed grafting modifier of a silane coupling agent and acrylic acid, and a mixed solution of ethanol and water, and reacting for 30-40 minutes, drying the mixture at 160-180° C for 4-6 h, layering and mixing the obtained straw fibers with polylactic acid fibers, and hot pressing the fibers on a hot press to obtain the modified crop straw fiber ecological composite material.

[0018] KR 2011 / 0034518 relates to a method for manufacturing a bamboo fiber- reinforced composite material for automobiles, comprising the steps of drying bamboo fibers, cutting the dried bamboo fibers into a predetermined size, performing a delignification process as a pretreatment for the cut bamboo fibers, laminating and mixing polylactide pellets or polylactide fibers on the bamboo fibers subjected to the delignification process, and performing compression molding under high temperature and pressure.

[0019] Material from paper industry material, such as old, corrugated cardboard (OCC), office paper, newspaper, silicon coated paper (SCP) is nowadays collected and recycled as starting material for making new paper and cardboard. Waste from other industries, such as spent brewers’ grains (SBG), spent coffee ground (SCG), egg husks can be converted into a feed additive for animals. Furthermore, it is known to develop products from agricultural waste, such as light wallboards made by heat compression of rice straw and shell corn as raw material and adhesives and synthetic urea formaldehyde 13% acting as adhesives.

[0020] The mechanical properties of a composite board can vary widely depending on the materials used, their proportions, and the manufacturing process. Composite boards are typically made by combining two or more different materials to create a board with improved properties compared to the individual materials. Some of the key mechanical properties that are relevant for composite boards are: strength, e.g. tensile strength (resistance to pulling forces), compressive strength (resistance to crushing forces), and flexural strength (resistance to bending), stiffness, e.g. modulus of elasticity (Young's modulus), hardness, dimensional stability, surface sound and thickness swelling.

[0021] An object of the present invention is to provide an advanced environmentally sustainable composite board as an alternative for wood-based products.

[0022] Another object of the present invention is to provide a method for manufacturing a composite fibre board wherein a plurality of its components are natural based components and / or recycled components. Another object of the present invention is to provide a composite fibre board that has a low surface sound and is dimensional stable.

[0023] The present invention as mentioned above relates to a method for manufacturing a composite fibre board via thermopressing, the method comprising the steps of: i) providing a mixture of raw materials comprising fibres, ii) thermopressing the mixture of i) in a temperature range of 120 °C to 210 °C, a pressure in a range from 3 to 200 kg / cm2and a reaction time from 1 to 20 minutes, wherein the raw material mixture comprises 1 - 35 wt.% silicone coated paper, 60 - 98 wt.% agricultural materials and 0,5 - 10 wt.% polylactic acid fibres, based on the total weight of the raw material mixture, and the sum total of the separate constituents in the raw material mixture is always 100 wt.%.

[0024] The present inventors found that one or more of the above objects can be achieved by providing a specific mixture of raw materials comprising 1 - 35 wt.% silicone coated paper, 60 - 98 wt.% agricultural materials and 0,5 - 10 wt.% polylactic acid fibres. The present inventors were able to provide a method for manufacturing a composite fibre board via thermopressing wherein the mixture of raw materials is recyclable, biobased, sustainable, environmentally friendly and / or biodegradable.

[0025] The present composite fibre board is not a laminated structure in which paper is bonded integrally to the surface of the fiber-based board, since there is no paper layer in the present composite fibre board. In addition, the present method does not include a step of placing paper on at least one side of a fiber board, as recited in the aforementioned JP 2007-196500.

[0026] In the present method there is no use in the raw material mixture of any mycelium obtained from fungal species to form a mycelial substrate as recited in FR 3006693.

[0027] In the present method there is no step of mixing a milled natural fiber with a thermoplastic fiber, let alone a step of creating a matted or felted material from the blended fibers as recited in US 2010 / 0093245.

[0028] In the present method there is no presence of degummed hemp fiber, let alone obtaining a fiber felt, as recited in CN 101691045. In the present method there is no alkali treatment or neutralizing step, as recited in CN 102085680.

[0029] In the present method there are no steps such as cooking, mixing with phosphoric acid solution, treating with alkali in a sodium hydroxide and adding a mixed grafting modifier as recited in CN 106738181.

[0030] In the present method there are no steps of drying bamboo fibers and performing a delignification process as recited in KR 2011 / 0034518.

[0031] In an example the agricultural materials are chosen from the group of wheat straw, corn straw or silage, rice straw, cotton, hemp, kenaf, sugarcane bagasse, bamboo, soya straw, miscanthus, rapeseed straw, sunflower straw, agave, and other fibres resulting from underutilized or waste streams as a result of agri-business or manufacturing processes, such as coffee grounds, nut shells, husks, and eggshells, or a combination thereof. This means that the present method for manufacturing a composite fibre board may be conducted by a mixture of several types of straw, such as straw originating from soya, hemp, and wheat.

[0032] In an example the raw material mixture further comprises 1 -35 wt.% natural paper based cellulose fibres chosen from the group of recycled cardboard, recycled craft or kraft paper, recycled office paper, and recycled newsprint, or a combination thereof, based on the total weight of the raw material mixture, and the sum total of the separate constituents in the raw material mixture is always 100 wt.%.

[0033] In an example the length of the polylactic acid fibres is at most 15 mm, preferably at most 10 mm and at least 2 mm, preferably at least 4 mm. The present inventors found that shorter polylactic acid (PLA) fibers are more preferable than longer PLA fibers as shorter PLA fibers obtain better dispersion in the wet pulp and obtain better connection with agricultural fibers and other components of the raw material mixture, such as silicone coated paper (SCP) and for example old, corrugated containers (OCC).

[0034] In an example the polylactic acid fibres have a denier in a range of 1.5-2.4 dtex, preferably in a range of 1.7-2.2 dtex. In the present context "dtex" is a unit of measurement that stands for decitex and is used to measure the linear density of fibers or yarns, specifically the mass in grams per 10,000 meters of the material. The present inventors found that a dtex value in the range as mentioned above has a beneficial effect for the present composite fibre board on both strength and durability on the one hand and abrasion resistance on the other hand.

[0035] The present invention furthermore relates to a composite fibre board obtained according to a method as discussed above and having a thickness of 0,5-50 mm and a density of 300-1100 kg / m3.

[0036] In an example of a composite fibre board obtained according to a method as discussed above the formaldehyde emission as tested under ASTM D6007 using analytical method ASTMD5197 renders an emission standard of less than 0.01 ppm, preferably less than 0.007 ppm and more preferably less than 0.006 ppm.

[0037] The present invention furthermore relates to a laminate comprising a stack of composite fibre boards as discussed above, wherein the composite fibre boards are laminated using a polyvinyl acetate based adhesive.

[0038] In another example the present invention relates to a laminate comprising a stack of composite fibre boards as discussed above, wherein the composite fibre boards are laminated using an adhesive not containing any formaldehyde or formaldehyde derivatives.

[0039] In an example of a laminate the formaldehyde emission as tested under ASTM D6007 using analytical method ASTMD5197 renders an emission standard of less than 0.01 ppm, preferably less than 0.005 ppm and more preferably less than 0.004 ppm.

[0040] The present invention also relates to the interior and / or exterior use of a composite board as discussed above or a laminate as discussed above as a construction material chosen from the group of flooring, furniture, wall coverings, facades, and ceilings.

[0041] In an embodiment of flooring application the thickness swelling and click tensile strength of the final panel is <12% and > 500N, respectively.

[0042] In an example of the method for manufacturing a composite fibre board via thermopressing existing machines and equipment from paper milling industry and existing machines for harvesting and milling agricultural products were used and combined in order to achieve proper blended mixture of raw materials. By this way fibres from raw material are processed to proper size, especially <1 ,2mm. In further process, by proper process conditions such as heat, especially 160-210°C, and pressure, especially 3-200 kg / cm2) and time, especially 1-20 min, the process of activating of lignin from the fibres is initiated and the activated lignin can be seen as a natural glue.

[0043] The thickness of the manufactured board is in a range of 0,5-50 mm and the density is in a range of 300-1100 kg / m3.

[0044] The final laminate may contain additional components, such as flame retardants, plasticizers, pigments, dyes, fillers, emulsifiers, surfactants, thickeners, rheology modifiers, heat, and radiation stabilization additives, defoamers, levelling agents, anti-cratering agents, fillers, sedimentation inhibitors, U.V. absorbers, and antioxidants.

[0045] In order to further understand the techniques, means and effects of the present disclosure, the following detailed descriptions and examples are hereby referred to, such that, and through which, the purposes, features and aspects of the present disclosure can be thoroughly and concretely appreciated; however, the appended examples are merely provided for reference and illustration, without any intention to be used for limiting the present disclosure.

[0046] In the examples the abbreviation SCP means Silicone Coated Paper, also known as a “release liner”, OCC means: Old Corrugated Containers according to EN 643, PLA means polylactic acid, WOP means waste office paper, MDF means Medium Density Fibreboard, HDF means High Density Fibreboard and LDF means Low Density Fibreboard.

[0047] The surface soundness is measured according to EN311 , and thickness swelling is measured according to EN317.

[0048] Examples 1-10 and Comparative examples 1.1-8.1

[0049] Example 1

[0050] A mixture of raw materials was prepared. The mixture comprised Soya : Wheat : Hemp : OCC : SCP:PLA= 30%:30%:30%:4%:5%:1 % (all on weight percentage basis). The PLA used here is PLA fibers having a length of 10 mm and denier 1 ,7 dtex. The processed raw materials size was <1 mm. The total amount of solids before pressing was 70%. The process conditions for manufacturing a composite fibre board were: T= 200°C; P= 7kg / cm ; t= 385 s. The thickness of composite fibre board (medium density fibreboard) thus obtained was 3mm having a density of 741 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table. Comparative Example 1.1

[0051] A similar mixture of raw materials as for Example 1 was prepared, except for the PLA. The process conditions as applied in Example 1 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0052] Example 2

[0053] A mixture of raw materials was prepared. The mixture comprised Soya : SCP: PLA= 84% : 14%:2% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 5mm and denier 2,2 dtex. The processed raw materials size was <0,8mm. The total amount of solids before pressing was 68%. The process conditions for manufacturing a composite fibre board were: T= 200°C; P= 14 kg / cm2; t= 350 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 2mm having a density of 898 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0054] Comparative Example 2.1

[0055] A similar mixture of raw materials as for Example 2 was prepared, except for the PLA. The process conditions as applied in Example 2 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0056] Example 3

[0057] A mixture of raw materials was prepared. The mixture comprised Soya : Wheat : Hemp : Rapeseed : OCC : SCP : PLA = 15% : 40% : 8,5% : 15% : 10% : 10% : 1 ,5% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 5 mm and denier 2 dtex. The processed raw materials size was <1 ,2 mm. The total amount of solids before pressing was 73%. The process conditions for manufacturing a composite fibre board were: T= 200°C; P= 3 kg / cm2; t= 1195 s. The thickness of composite fibre board (low density fibreboard) thus obtained was 20mm having a density of 399 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0058] Comparative Example 3.1 A similar mixture of raw materials as for Example 3 was prepared, except for the PLA. The process conditions as applied in Example 3 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0059] Example 4

[0060] A mixture of raw materials was prepared. The mixture comprised Miscanthus : Sunflower: OCC : SCP : SBG (spent brewers’ grain) : PLA= 30% : 30% : 15% : 15%: 9,5% : 0,5% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 5 mm and denier 1 ,5 dtex. The processed raw materials size was <0,8mm. The total amount of solids before pressing was 67%. The process conditions for manufacturing a composite fibre board were: T= 190°C; P= 13 kg / cm2; t= 520 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 2,5 mm having a density of 884 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0061] Comparative Example 4.1

[0062] A similar mixture of raw materials as for Example 4 was prepared, except for the PLA. The process conditions as applied in Example 4 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0063] Example 5

[0064] A mixture of raw materials was prepared. The mixture comprised Wheat : Rapeseed : SCP : WOP (waste office paper) : PLA = 50% : 30% : 9% : 8% : 3% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 10 mm and denier 2 dtex. The processed raw materials size was <0,8 mm. The total amount of solids before pressing was 71 %. The process conditions for manufacturing a composite fibre board were: T= 200°C; P= 14 kg / cm2; t= 360 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 3,5 mm having a density of 904 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0065] Comparative Example 5.1 A similar mixture of raw materials as for Example 5 was prepared, except for the PLA. The process conditions as applied in Example 5 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0066] Example 6

[0067] A mixture of raw materials was prepared. The mixture comprised Miscanthus : Typha latifolia :OCC : SCP : SCG (spent coffee ground): PLA = 40% : 20% :20% : 10% : 6% : 4% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 5 mm and denier 1 ,9 dtex. The processed raw materials size was <0,8 mm. The total amount of solids before pressing was 72%. The process conditions for manufacturing a composite fibre board were: T= 150 °C; P= 12 kg / cm2; t= 375 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 2,2 mm having a density of 854 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0068] Comparative Example 6.1

[0069] A similar mixture of raw materials as for Example 6 was prepared, except for the PLA. The process conditions as applied in Example 6 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0070] Example 7

[0071] A mixture of raw materials was prepared. The mixture comprised Soya : Wheat : Hemp : SCP : Cocoa shells: Peanut husks : PLA = 34% : 40% : 10% : 5%: 5% : 5%: 1% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 12 mm and denier 2,2 dtex. The processed raw materials size was <0,9 mm. The total amount of solids before pressing was 65%. The process conditions for manufacturing a composite fibre board were: T= 205 °C; P= 14 kg / cm2; t= 590 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 3,5 mm having a density of 903 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0072] Comparative Example 7.1 A similar mixture of raw materials as for Example 7 was prepared, except for the PLA. The process conditions as applied in Example 7 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0073] Example 8

[0074] A mixture of raw materials was prepared. The mixture comprised Soya : Wheat: Corn : Hemp: SCP : PLA = 40% : 20% : 20% : 10% : 8,5% :1,5% (all on weight percentage basis). The PLA used here is PLA fibers having a length of 5 mm and denier 1 ,5 dtex. The processed raw materials size was <0,8 mm. The total amount of solids before pressing was 64%. The process conditions for manufacturing a composite fibre board were: T= 200 °C; P= 14 kg / cm2; t= 360 s. The thickness of composite fibre board (high density fibreboard) thus obtained was 3,2 mm having a density of 865 kg / m3. The board having a smooth and even surface was dimensional stable and flat. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0075] Comparative Example 8.1

[0076] A similar mixture of raw materials as for Example 8 was prepared, except for the PLA. The process conditions as applied in Example 8 were repeated here. The data for the surface soundness (EN311) and thickness swelling (EN317) are shown in the Table.

[0077] Example 9

[0078] A panel was manufactured by laminating four individual layers according to the invention (medium density fiberboard MDF having a thickness of 3 mm and a density of 741 kg / m3) and using polyvinyl alcohol (Vinavil 2252M) as an adhesive. The lamination press conditions were: T= 85 °C; P= 7 kg / cm2and t= 210 s. The panel characteristics thus obtained are a thickness of 12 mm and a density of 741 kg / m3.

[0079] The laminated board having a smooth and even surface was dimensional stable and flat.

[0080] Example 10

[0081] A panel was manufactured by laminating five individual layers according to the invention (high density fiberboard HDF having a thickness of 2.0 mm and a density of 898 kg / m3) and using polyvinyl alcohol (Kleiberit 303.0) as an adhesive. The lamination conditions were: T= 80°C; P= 14 kg / cm2and t = 300s. The board characteristics of composite fibre board thus obtained are a thickness of 10 mm and a density of 898 kg / m3.

[0082] Both individual layers and laminated board are HDF (high density fiberboard). The laminated board having a smooth and even surface was dimensional stable and flat.

[0083] Table: properties of fibre boards according to Examples 1 -8 and Comparative Examples 1.1-8.1.

Claims

CLAIMS1. A method for manufacturing a composite fibre board via thermopressing, the method comprising the steps of: i) Providing a mixture of raw materials comprising fibres, ii) Thermopressing the mixture of a) in a temperature range of 120 °C to 210 °C, a pressure in a range from 3 to 200 kg / cm2and a reaction time from 1 to 20 minutes, wherein the raw material mixture comprises 1 - 35 wt.% silicone coated paper, 60 - 98 wt.% agricultural materials and 0,5 - 10 wt.% polylactic acid fibres, based on the total weight of the raw material mixture, and the sum total of the separate constituents in the raw material mixture is always 100 wt.%.

2. A method according to claim 1 , wherein the agricultural materials are chosen from the group of wheat straw, corn straw or silage, rice straw, cotton, hemp, kenaf, sugarcane bagasse, bamboo, soya straw, miscanthus, rapeseed straw, sunflower straw, agave, and other fibres resulting from underutilized or waste streams as a result of agri-business or manufacturing processes, such as coffee grounds, nut shells, husks, and eggshells, or a combination thereof.

3. A method according to claim 1 , wherein the raw material mixture further comprises 1-35 wt.% natural paper based cellulose fibres chosen from the group of recycled cardboard, recycled craft or kraft paper, recycled office paper, and recycled newsprint, or a combination thereof, based on the total weight of the raw material mixture, and the sum total of the separate constituents in the raw material mixture is always 100 wt.%.

4. A method according to any one or more of the preceding claims, wherein the length of the polylactic acid fibres is at most 15 mm, preferably at most 10 mm and at least 2 mm, preferably at least 4 mm.

5. A method according to any one or more of the preceding claims, wherein the polylactic acid fibres have a denier in a range of 1.5-2.4 dtex, preferably in a range of 1.7-2.2 dtex.

6. A composite fibre board obtained according to a method according to any one or more of the preceding claims having a thickness of 0,5-50 mm and a density of SOO- 1100 kg / m3.

7. A composite fibre board according to claim 6, wherein the formaldehyde emission as tested under ASTM D6007 using analytical method ASTMD5197 renders an emission standard of less than 0.01 ppm, preferably less than 0.007 ppm and more preferably less than 0.006 ppm.

8. A laminate comprising a stack of composite fibre boards according to any one of claims 6-7, wherein the composite fibre boards are laminated using a polyvinyl acetate based adhesive.

9. A laminate comprising a stack of composite fibre boards according to any one of claims 6-7, wherein the composite fibre boards are laminated using an adhesive not containing any formaldehyde or formaldehyde derivatives.

10. A laminate according to any one or more of claims 8-9, wherein the formaldehyde emission as tested under ASTM D6007 using analytical method ASTMD5197 renders an emission standard of less than 0.01 ppm, preferably less than 0.005 ppm and more preferably less than 0.004 ppm.

11. The interior and exterior use of a composite fibre board according to any one of claims 6-7 or a laminate according to any one of claims 8-10 as a construction material chosen from the group of flooring, furniture, wall coverings, facades, and ceilings.

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