Method for manufacturing lightweight wood composites using hemp shives

Abstract

Method for manufacturing lightweight wood composites using hemp shives involves the following steps: producing wood particles and hemp shive particles in the form of shavings; drying the shavings; mixing the shavings with adhesive; forming a shavings mat; pre-pressing it; and pressing it. In this process, the chip mat is formed as a three-layer structure, with the two outer layers consisting of wood chips and the inner layer formed by mixing wood chips with hemp shives at a mass ratio of wood chips to hemp shives selected from the range of 75:25%, 50:50%, and 25:75%.

Description

The utility model belongs to the woodworking industry, in particular to manufacturing technologies wood composites (particle board, oriented strand board (OSB), fiberboards, wood-polymer boards, etc.) with reduced density, and can be used in the production of construction, heat-insulating and furniture board materials, household goods or industrial use, etc. Particleboard (PCB) is one of the main wood composites in world trade. In recent years global demand and production of JVs have increased due to factors such as relatively low cost, satisfactory physical and mechanical properties, high demand for wood composites and the presence of a large quantity of raw materials. Today, the traditional raw materials for the production of wood composites are wood. Glue and wood chips are the two main components of the JV. The cost of the raw materials used, namely glue and wood chips, accounts for the majority of the cost of the final SP. The total cost materials accounts for 40-60% of the total cost of production. Other main cost components, such as energy, labor and processing costs of the SP, are about 15-20%, 5-20% and 25-30%, respectively. Wood chips are the second most expensive component after glue in the production of JV, on which accounts for approximately 20% of total production costs. Thus, it is an undeniable fact that that the cost of materials, which includes the cost of glue and wood chips, is often more half of the total cost of production. However, if the prices of wood raw materials in recent years increased, the estimated price of agricultural waste is at least 50% lower than the price wood chips. As a result, replacing wood chips with alternative, non-wood raw materials can lead to significant cost savings. Optimization of available wood and lignocellulosic raw materials, as well as the search for alternative natural raw materials derived from renewable agricultural waste to replace wood in manufacturing, joint ventures are a viable strategy for reducing negative environmental impacts environment and increasing resource efficiency in the woodworking industry. Agricultural waste is a huge pool of unused biomass resources. Thus, Although wood remains the traditional raw material for the production of composites, fibers agricultural waste is becoming popular for the production of composite panels with the aim of sustainable forest management. The density of traditional SP is usually 600-750 kg / m3. According to the CEN / TS standard 16368:2014, lightweight boards are considered to be boards with a density of less than 600 kg / m3. Lightweight SPs have a number of advantages for manufacturers, designers and end users compared to standard slabs. Their use expands the possibilities of interior design (use of more massive elements, reducing the load during installation), simplifies installation and processing, facilitates transportation and machining, and also allows to reduce transportation and raw material costs. The weight of the material is the third most important criterion for consumers when choosing furniture - after design and cost. One important approach to reducing the density of wood-based panels is to use raw materials from annual and perennial plants, as well as a combination of wood with fibrous plant materials materials of agricultural origin. Thus, one of the directions of reducing wood costs in the production of SP and reducing their density is the use of agricultural waste and annual plants. Currently agricultural waste is not used as efficiently as we would like, and landfilling landfilling or open burning are common practices for this resource, which creates significant environmental problems. Thus, the use of agricultural waste as a raw material for production of JV can reduce the rate of deforestation in many countries and transform such resources for wood materials with added value. This problem is especially relevant now in Ukraine, because forests are being destroyed in Ukraine due to Russia's military aggression, and we are also forced to spend a lot of wood on building fortifications for the military and building houses for refugees. One such agricultural waste is hemp husk, a by-product cultivation of hemp (Cannabis sativa L.). Industrial hemp is cultivated as an industrial crop in in many countries, including Ukraine. According to the Food and Agriculture Organization According to the UN, in 2023, approximately 34,076 tons of hemp seeds were harvested worldwide, of which about 2119 tons were produced in Europe and approximately 580 tons in Ukraine. After primary processing of the plant 30% of the fibers and 70% of the husks are obtained, waste from mechanical processing of the stems, which can be used in the production of SP without additional grinding. Unlike other agricultural waste, Hemp fescue has a relatively uniform particle size and low lignin content, which provides uniform bonding and increased dimensional stability of the boards. This gives reason to consider it advisable using hemp husk as a raw material for the production of wood composites. A known method of manufacturing particle boards using straw, which includes the operations preparation of chips, drying of chips, mixing of chips with glue, shaping and pressing chip carpet, pressing of boards, according to which the outer layers of the boards are formed from wood particles, and the inner layer is made of wood particles with the addition of up to 20% particles from wheat straw, and urea-formaldehyde resin was used as the glue [1]. The disadvantage of the known method is unsatisfactory bonding strength and low content of straw particles (up to 20%) due to poor bonding with urea-formaldehyde adhesives. There is a known method for manufacturing wood composites using rapeseed waste, which includes operations of manufacturing wood particles, drying particles, mixing particles with glue, forming and pressing of carpet, pressing, which is characterized in that the carpet for making composites are formed from wood particles with the addition of up to 30% of particles made from rapeseed waste, and urea-formaldehyde resin was used as the glue [2]. The disadvantage of the known method is unsatisfactory bonding strength and low content of rapeseed particles (up to 30%) due to poor bonding with urea-formaldehyde adhesives. A hemp-based wood panel and a method of manufacturing it, including forming and production of panels 500-750 kg / m3 from hemp stems glued with isocyanate glue (pMDI) with weight hemp stalks at least 70% and glue within 5-20%, hemp is used in the form of mixtures of particles 1-5 cm long and fibers up to 60 cm long with a weight ratio between particles and fiber 1:5 and 3:2 [3]. The disadvantage of the known method is the high density of the panels, the use of expensive isocyanate glue (pMDI) and its high content, the use of long particles and fibers, which makes it difficult to apply glue to them and mix them, which collectively leads to an increase in price finished products. The utility model is based on the task of improving the method of manufacturing lungs wood composites by rational use of hemp fescue particles in the structure composite in order to reduce its density and improve its performance properties. In addition, due to the fact that in the method of manufacturing lightweight wood composites, part of the wood chips is replaced by particles from hemp coir, expanding the raw material base for production composites, valuable wood raw materials are saved, and the cost of finished composites is reduced. The problem is solved by the fact that in the method of manufacturing lightweight wood composites from using hemp straw, which includes operations for producing wood particles and particles from hemp fescue in the form of chips, drying the chips, mixing the chips with glue, forming a chip carpet, pressing it and pressing it, according to the utility model, The chip carpet is formed into a three-layer structure, with the two outer layers formed from wood pulp. shavings, and the inner layer is formed by mixing wood shavings with particles from fescue hemp at a mass ratio of wood chips to hemp husk particles selected from the series 75:25%, 50:50%, 25:75%. Method for manufacturing lightweight wood composites (particle boards) with a density of 350-550 kg / m3 from using hemp straw includes operations for the production of wood particles and particles from hemp fescue in the form of chips, drying the chips, mixing the chips with glue, forming of chip carpet, its pressing and pressing. Chip carpet is formed into a three-layer, in which the two outer layers are formed from wood chips, and the inner layer is formed by mixing wood chips with hemp fescue particles in a mass ratio wood chips to hemp fescue particles selected from the following range: 75:25%, 50:50%, 25:75%. When Urea-formaldehyde resin is used as the glue. Method for manufacturing lightweight wood composites, in particular lightweight particle boards with a density 350-550 kg / m3 using hemp fescue is carried out as follows. Wood raw materials and hemp straw are crushed to make wood chips and hemp fescue particles and dried. Dried wood chips and fescue particles hemp is fed to the mixing operation. During the mixing process, a urea-formaldehyde glue. After mixing with glue, a three-layer chipboard is formed carpet, with the two outer layers formed from wood chips, and the inner layer formed from by mixing wood chips with hemp fescue particles in a mass ratio of wood chips to hemp fescue particles selected from the following range: 75:25%, 50:50%, 25:75%. The ratio between the outer and inner layers is 33:67%. Formed carpet is pressed and fed to the plate pressing operation. The plate pressing is carried out under a pressure of 2.5 MPa and at a temperature of 190 °C. Additionally, for comparative evaluation of properties, control samples were made from in the ratio of 100:0% and 0:100%, which are not included in the scope of legal protection of the claimed useful models. Samples for mechanical testing were cut from the pressed plates. The strength was determined during static bending (according to DSTU EN 310: 1993), modulus of elasticity during static bending (according to DSTU EN 310: 1993), tensile strength perpendicular to the plane of the plate (according to DSTU EN 319: 1993). The values ​​of the determined indicators were compared with the requirements of international standards for lightweight particleboard (EN 16368 and ANSI A208.1). Mechanical properties of the resulting boards are given in Table 1. Lightweight three-layer particle boards with inner layer formed by mixing are obtained wood chips with hemp fescue particles at a mass ratio of wood chips to particles of hemp fescue, selected from the range: 75:25%, 50:50%, 25:75%, characterized by high mechanical properties compared to standard requirements for lightweight boards. In particular, in terms of strength values ​​during static bending, plates with a density of 450 kg / m3 correspond to requirements for LP1 type slabs according to EN 16368 and LD-1 and LD-2 according to ANSI A208.1, and a density of 550 kg / m3 requirements for LP1 and LP2 plates according to EN 16368 and LD-1 and LD-2 according to ANSI A208.1; by values The modulus of elasticity of a plate with a density of 350 kg / m3 meets the requirements for LP1 and LD-1 type plates according to EN 16368 and ANSI A208.1, respectively, and with a density of 450 and 550 kg / m3, the requirements for LP1 and LP2 type slabs according to EN 16368 and LD-1 and LD-2 according to ANSI A208.1. Tensile strength values perpendicular to the plane of the slab with a density of 550 kg / m3 meet the requirements for LP1 type slabs according to EN 16368, and boards with a density of 450 and 550 kg / m3 meet the requirements for boards of type LD-1 and LD-2 according to ANSI A208.1. This indicates that the hemp fescue particles stick together well both among themselves and with wood shavings. The characteristics of the mechanical properties of the obtained lightweight plates are given in the table. Table Comparative characteristics of mechanical properties of the obtained lightweight boards with the requirements of the standards Indicator Density plates (kg / m3) Correlation particles wooden shavings to fescue particles hemp Proposed way Requirements according to EN 16368 Requirements according to with ANSI A208.1 type LP1 type LP2 type LD- 1 type LD- 2 Tensile strength at static bending, MPa 350 100:0 1.7 4.0 8.0 3.0 5.0 75:25 2.5 50:50 3.0 25:75 2.9 0:100 3.4 450 100:0 4.9 75:25 5.5 50:50 5.8 25:75 5.9 0:100 6.5 550 100:0 8.2 75:25 8.6 50:50 8.6 25:75 8.9 0:100 9.6 Modulus of elasticity, MPa 350 100:0 371 550 1000 550 1025 75:25 585 50:50 637 25:75 644 0:100 953 450 100:0 1005 75:25 1160 50:50 1196 25:75 1201 0:100 1402 550 100:0 1639 75:25 1736 50:50 1755 25:75 1757 0:100 1852 Tensile strength at stretching perpendicularly 350 100:0 0.20 0.28 0.40 0.10 0.15 75:25 0.20 50:50 0.20 to the plane of the plate, MPa 25:75 0.19 0:100 0.19 450 100:0 0.25 75:25 0.25 50:50 0.25 25:75 0.24 0:100 0.23 550 100:0 0.30 75:25 0.30 50:50 0.30 25:75 0.29 0:100 0.27 The advantage of the utility model is that the proposed lightweight wood composite has a small weight, but still maintains sufficient mechanical stability. In addition, the manufacturing process the corresponding utility model of a lightweight wood composite is simple; there is no need for re-equipment of existing installations for the production of light wooden products corresponding to the utility model plates. The claimed method can be implemented in industrial conditions using standard equipment for the production of particleboard and is suitable for mass production. Therefore, the proposed method of manufacturing lightweight wood composites allows to expand raw material base for their production thanks to the involvement of agricultural waste, namely hemp slats, reduce the cost of finished boards and, accordingly, save valuable wood raw materials, which is extremely relevant for sparsely forested regions of Ukraine. Another of The advantages of using hemp fescue are that it is a cheap and annually renewable species. raw materials. Sources of information: 1. Utility model patent No. 21441, Ukraine, MPK B27N 3 / 00. Method of manufacturing chipboard plates / Bekhta P.A., Salabai R.G. - Application number u200610411; statement 02.10.06; published 15.03.07, Bul. No 3. 2. Utility model patent No. 95233, Ukraine, MPK B27N 3 / 00. Method of manufacturing wooden composites using rapeseed waste / Bekhta P.A., Kopansky M.M., Salabai R.G. - Issue applications a2014 07983; statement 15.07.14; published 10.12.14, Bull. No. 23. 3. NOPENS Ingmar, VERSTRAETE Frederik, CORDEEL Filip. Hemp-based wood and its manufacturing method-European Patent Application EP 4 501 564 A2, Date of publication: 05.02.2025 Bulletin 2025 / 06.

Claims

Method for manufacturing lightweight wood composites using hemp straw, which includes operations for the production of wood particles and hemp coir particles in in the form of chips, drying chips, mixing chips with glue, forming chipboard carpet, its pressing and pressing, which is characterized in that the chip carpet is formed into a three-layer structure, with the two outer layers formed from wood chips, and the inner layer is formed by mixing wood chips with fescue particles hemp at a mass ratio of wood chips to hemp straw particles, selected from the range 75:25%, 50:50%, 25:75%.