BG113585A - METHOD FOR MANUFACTURING HEMP PANEL PLATES - Google Patents

Abstract

The invention relates to a method for the production of ecological boards from hemp pazder (particles and short fibers), which are used in the construction, furnishing and furniture industry. Through the created boards of hemp particles and short fibers from the stems of industrial hemp, a replacement of the traditionally used wood is provided, which in the future leads to a reduction of deforestation. Improved physico-mechanical indicators compared to the standard required indicators for chipboard and MDF have been proven. The method, according to the invention, includes: 1/ processing industrial hemp stalks in a decorticator to separate hemp wood particles and short fibers with a size of 0.1 mm to 20 mm; 2/ storage; 3/ crushing the particles to no more than 5 mm; 4/ separation of dust and particles smaller than 1 mm in size; 5/ sifting to leave only those particles with a size of no more than 5 mm; 6/ drying the particles to 18% humidity; 7/ gluing with binding emulsions in a gluing mixer; 8/ laying of the obtained material to create a sheet material/carpet in the requested size of the plate; 9/ cold pressing of the carpet from hemp particles; 10/ edging the thus created carpet to the required dimensions; 11/ feeding the prepared and sized plates into the hot multi-stage press for heat treatment according to a program depending on the thickness and density of the plate, by performing three-stage hot pressing and thermoforming; 12/ followed by cooling; 13/ sizing to desired size; 14/ grinding; 15/ as if necessary and smoothing. The used hemp particles in the board with a binder content as an amount relative to dry mass in the range of 8% to 14% were bonded with an adhesive composition of 90% urea formaldehyde resin, 10% melamine formaldehyde resin and paraffin emulsion and subjected to a three-stage hot pressing with a multi-functional possibility to set duration, temperature and pressure.

Description

Field of technique

The invention relates to a method for the production of ecological boards from hemp pazder (particles and short fibers), which are used in the construction, furnishing and furniture industry.

Prior art

Hemp is one of the oldest cultivated lico-fibrous plants. It is grown for its fiber and its seeds are used to extract oil. Hemp fiber is very strong and resistant to rotting in water. In terms of these qualities, it surpasses all other plant fibers and is therefore irreplaceable and widely used in a number of cases. The long hemp fiber is used in the textile industry, and the fine, or short fiber, together with crushed parts of the wood, has applications in construction and furniture.

After the primary processing of the hemp stalks, a large amount of wood is obtained (wood pulp - hemp particles and short fibers). Wood constitutes 70-75% of the weight of air-dry defoliated stems. With an average yield of 800-1000 kg of stalks per hectare, high-stemmed hemp ensures the extraction of 550-700 kg of wood, or 3-4 times more than the annual growth of 1 decre of forest. It has been proven that 1 acre of hemp plantations (growing in 4 months) can produce as much raw material as 4 acres of forest growing in 20 years.

Wood particle boards (chipboard) are known, which are produced using the technology of hot pressing and gluing with synthetic resins. Their disadvantages are the low water resistance, the lack of possibility of relief treatments (milling) and dangerous levels of formaldehyde emissions from the surface layer of the plates, which are dangerous for human health.

Also known are medium density fiberboards (Medium Density Fiberboard - MDF), which are produced from soft wood by the method of dry pressing at high pressure and temperature. The wood particles are ground into pulp and bound together with lignin and paraffin. A disadvantage is the impossibility of wood-fiber boards to withstand a large load, as cracking and splitting occurs under pressure.

A method is known (CN109483 686A) for the production of artificial boards without formaldehyde from hemp stems, in which the stem of hemp culture is used as a raw material, which is pulverized to 20-50 mesh (0.841-0.297 mm), polymer MDI glue is added with 2%-8% by weight of the dry mass of hemp stems and a formaldehyde modifier of 2%-5% by weight of the dry mass of hemp stems and the artificial boards are produced by mixing and stirring, pressing and post-processing. A disadvantage of the method is that the resulting artificial boards are of low strength, which limits their use and application.

There is a known method (CN108656300A) for the production of an ecological hemp core board, comprising the following steps: (1) grinding the hemp core into a powder with a particle size of 10 mm to 200 mm, and then adding rod-shaped, blocky or granular solid material; (2) drying at a drying temperature of 105°C to 125°C in a rotary dryer or channel dryer of the solid material to a moisture content of 2%-18% by mass; (3) bonding the solid material by soaking, brushing, or spraying, the amount of the bonding agent being 1%-15% of the dry bulk of the solid material; (4) layering the solid material to produce sheet material; (5) hot pressing the board to obtain an environmental hemp core board, where in step (5) the hot pressing pressure is 3 MPa to 5 MPa, the hot pressing time is 0.4 min/mm to 1.2 min/mm, and the hot pressing temperature is 170°C to 200°C. The method further includes the step of cooling, cutting and grinding the plate. A disadvantage of the method is that wood material is also used to achieve the required properties of the plates, which increases the price of the necessary raw materials and makes it difficult to supply them.

The purpose of the invention is the creation of a method for the use of hemp pulp as a raw material source for the production of panels for furniture and furnishings, by replacing the traditionally used wood, which in the future will lead to a reduction in deforestation and the preservation of ecologically valuable wood. plants. In addition, the produced hemp-based boards (particles and short fibers) must have a different amount of binder and density, as well as improved physico-mechanical properties compared to the standard requirements for particleboards.

Technical essence of the invention

The task of the present invention is to create a method for the production of hemp pazder plates (hemp particles and short fibers), and according to the invention, a product is created from non-woody lignocellulosic raw material, which solves the stated problems from the level of the technique, and more specifically:

provides a raw material source for the production of boards for furniture and furnishings, by replacing the traditionally used wood;

utilizes agricultural waste from hemp stalks;

in perspective leads to a reduction of deforestation and preservation of ecologically valuable woody plants;

creates plates with different amount of binder;

uses an adhesive composition with minimal formaldehyde emissions (formaldehyde emissions comparable to those of natural wood), which will significantly reduce the risk to the health of people using this material in their interior;

has improved physico-mechanical indicators compared to the standard required indicators for particle boards and significantly surpasses those of chipboard and MDF.

An additional task of the invention is to provide the possibility of producing hemp pazder plates (particles and short fibers) with different densities.

These and other tasks are solved by a method for the production of hemp pazder plates, according to the invention, which includes the following technological phases: 1/ processing industrial hemp stems in a decorticator to separate hemp wood particles and short fibers with a size of 0.1 mm to 20 mm; 2/ storage; 3/ crushing of the particles to no more than 5 mm; 4/ separation of dust and particles smaller than 1 mm in size; 5/ sieving to leave only those particles with a size of no more than 5 mm; 6/ drying the particles to 18% humidity; 7/ gluing with binding emulsions in a gluing mixer; 8/ laying of the obtained material to create a sheet material/carpet in the requested size of the plate; 9/ cold pressing of the carpet from hemp particles; 10/ edging the thus created carpet to the required dimensions; 11/ feeding the prepared and sized plates into the hot multi-level press for heat treatment according to a program depending on the thickness and density of the plate, by performing three-stage hot pressing and thermoforming at a temperature of the countertops in the range between 120°C and 220°C: First stage - duration from 1 to 2 min at pressure from 3 MPa to 4.5 MPa; Second stage - duration from 1 to 3 min at pressure from 0.5 MPa to 2.5 MPa; Third stage - from 0.3 to 1.2 MPa; 12/ followed by cooling; 13/ sizing to desired size; 14/ grinding; 15/ as if necessary and smoothing. The process can be carried out manually and/or automatically using a purpose-built program.

The hot pressing machine has a multifunctional possibility of settings with different operation mode, such as: duration, temperature, pressure, etc.

The strength of the plates is inversely proportional to the drying humidity of the particles. Drying the particles to 18% humidity is optimal in terms of time and effect.

The pressing temperature depends on and is a function of the plate density.

In three-stage hot pressing, the pressing time is a function of plate thickness.

In the hemp pazder plates produced by the method according to the invention, the content of the binder as an amount relative to dry mass is in the range of 8% to 14% depending on the strength and purpose of the plates. The adhesive composition of the plates consists of 90% urea formaldehyde resin (CFC) and 10% melamine formaldehyde resin (MFS). As a water-repellent substance, a paraffin emulsion was used, in which the paraffin content relative to the absolutely dry particles was 0.5%, and the emulsion was introduced at a concentration of 50%.

In a preferred embodiment, the hemp pazder plates have a density of 750 to 850 kg/m ³ . Hemp particles are pre-dried to a moisture content of 6.5%. The adhesive composition of the plates consists of MFS in a content of 10% relative to the absolutely dry particles. As a water-repellent substance, a paraffin emulsion was used, in which the paraffin content relative to the absolutely dry particles was 0.5%, and the emulsion was introduced at a concentration of 50%.

Advantages:

The advantage is that the use of the hemp padder, as a raw material source for the production of panels for furniture and furnishings, by replacing the traditionally used wood, will in the future lead to a reduction of deforestation and the preservation of ecologically valuable woody plants. Agricultural waste from the hemp stalks is also utilized.

Another main advantage of the hemp particle and fiber boards created according to the method of the invention is that they are an environmentally friendly product, both in terms of raw material (during its rapid growth, industrial hemp absorbs significant amounts of carbon dioxide (CO2)) and relation to the bonding materials (emulsions) with low formaldehyde content used in the production of the plates. The adhesive composition used has minimal formaldehyde emissions (formaldehyde emissions comparable to those of natural wood (super EO class - below 1.5 mg/100 g)), which will significantly reduce the health risk of people using this material in the interior you are.

According to the invention, the advantage of the proposed method is that it implies additional processing of the material, which allows to achieve the necessary and better properties of the plates made only of hemp particles. Boards made of hemp pazder have very good physical and mechanical indicators, superior to boards made of wood particles and wood fibers. This is due to their low bulk density, respectively high compression coefficient, and the presence of fine fibers filling the pore space in the plates and increasing the contact area between the particles. In terms of bending strength and modulus of elasticity, the created material is comparable to medium-density fiberboard (MDF), and in terms of transverse tensile strength it even surpasses it.

Due to the significant homogeneity of this type of boards and the high compression ratio, they have between two and three times better screw retention on the edge than factory-produced three-layer chipboard. In factory chipboards, larger particles are used for the intermediate layer, which are significantly less compacted, which is also reflected in their screw retention along the edge. The good screw retention along the edge of hemp pazder boards makes them particularly suitable for furniture production.

The obtained hemp pazder boards with a density of 750 to 850 kg/m ³ have very good performance values. As a result of the very high compression ratio (8 and 8.5 times), boards with a density of 800 and 850 kg/m ³ have values of their performance indicators significantly exceeding the most stringent requirements, namely those of MDF for load-bearing structures and use in a humid environment. The presence of fine fibers in the hemp pazder also has an additional beneficial effect on the indicators of the plates. In this way, the contact area increases, and hence the adhesion and cohesion bonds between the hemp particles. This makes these boards an extremely suitable ecological material for applications such as flooring and other elements subject to load in a humid environment.

It is possible to add flame retardant chemicals that slow down the burning according to the requirements of different countries.

Examples of implementation of the invention

In more detail, the invention is explained with exemplary non-limiting embodiments of the method for the production of hemp pazder plates.

To carry out the method of producing hemp particle board and short fibers, it is preferred to use industrial hemp stalks, baled (may be with leaves and/or seeds), which are allowed to dry for about 20 days in the field before starting of the process. Baled hemp does not need to be stored indoors. The method includes the following steps sequentially. Industrial hemp stalks are processed in a decorticator, where hemp wood particles and short fibers with a size of 0.1 mm to 20 mm are separated. The particles are stored in a silo until the required amount is accumulated for the next stage. The amount of particles passes through a drum crusher, where they are crushed to no more than 5 mm and the crushed mass goes to a pulverizer to separate the dust and particles smaller than 1 mm in size. After that, the particles are sifted through a sieve, leaving only those with a size of no more than 5 mm. In the dryer, the particles reach optimal humidity by drying to 18% humidity. Having reached the required humidity, they enter a pasting mixer, where under certain revolutions the particles are pasted together with the emulsions connecting them in exemplary proportions. Coming out of the mixer, the resulting material is spread in a carpet laying machine, which creates a carpet according to the desired size of the slab. The carpet of hemp particles continues into the cold press machine, which presses it and prepares it for the hot press. After the cold pressing, the carpet created in this way is trimmed to the required dimensions by a movable circular saw. The prepared and dimensioned slabs are fed automatically or manually into the hot multi-deck press, where they are fired according to a program depending on thickness and density. The hot press machine provides a multi-functional setting option with different operation mode, such as: time, temperature, pressure. The cut slabs are placed in a hot multi-deck press where they go through three compression cycles. The duration of the pressure is in three stages as follows: First stage - from 1 min to 2 min at a pressure of 3 MPa to 4.5 MPa; Second stage - from 1 min to 3 min at a pressure of from 0.5 MPa to 2.5 MPa; Third stage - from 0.3 MPa to 1.2 MPa. The pressure factor is between 45 s.mm' ¹ and 65 s.mnT ¹ . The pressing temperature is in the range between 120°C and 220°C, depending on the density of the plate. The pressing time depends on the thickness of the plate. After that, the plates are cooled, sized, sanded, and if necessary, they can also go through the modern smoothing press. Leaving the hot press, the already finished plates are cooled in a specialized mechanism for several hours. Cooled they go into a multipurpose circular saw for sizing. Ready-to-size plates go through a grinding machine, which removes any irregularities. A modern pressing system is optional, after which the slabs are stacked on the pallet and stored ready for transport.

In a preferred but non-limiting exemplary embodiment of the invention, the hemp pazder boards (particles and short fibers) are produced with a binder content as an amount relative to dry weight in certain percentages depending on the strength and purpose of the boards as follows:

- Plates with 8% - designed for unloaded furniture;

- Plates with 10% - for mass furniture;

- Plates with 12% - for use in rooms with increased humidity;

- Slabs with 14% - with increased strength, can be used for flooring.

When implementing the invention, the adhesive composition of the plates consists of 90% KFS and 10% MFS. The corresponding resins have the following indicators: CFC - mole ratio 1.07; dry content 50%, dynamic viscosity 23.76±0.52 mPas and MFS - mole ratio 1.76; dry content 54%, dynamic viscosity 2H0.76 tRa. As a chemical catalyst, ammonium sulfate was used in a content of 2% relative to the absolutely dry binder. Ammonium sulfate is introduced in the form of a solution with a concentration of 30%. As a water-repellent substance, a paraffin emulsion was used, in which the paraffin content relative to the absolutely dry particles was 0.5%, and the emulsion was introduced at a concentration of 50%. Hot pressing is carried out at a table temperature of 175°C. The hot pressing mode is three-stage: First stage - pressure 4.0 MPa and duration 1 min; Second stage - pressure 1.2 MPa and duration 1 min; Third stage - pressure 0.6 MPa and duration 14 min. The compression factor is 60 s.mm' ¹ .

In another preferred embodiment, the hemp pazder boards have different densities of 750, 800 and 850 kg/m ³ . Hemp particles are pre-dried to a moisture content of 6.5%. The adhesive composition of the plates consists of MFS in a content of 10% relative to the absolutely dry particles. The melamine formaldehyde resin has indicators: MFS - molar ratio 1.76; dry content 54%; dynamic viscosity 21±0.76 shRa. As a water-repellent substance, a paraffin emulsion was used, in which the paraffin content relative to the absolutely dry particles was 0.5%, and the emulsion was introduced at a concentration of 50%. Hot pressing is carried out at a table temperature of 160°C. The hot pressing mode is three-stage: First stage - pressure 4.0 MPa and duration 1 min; Second stage - pressure 1.2 MPa and duration 1 min; Third stage pressure 0.6 MPa and duration 14 min. The compression factor is 90 s.mm' ¹ .

Using the utility model

The composition of the exemplary boards is indicated in table 1. For control, a board obtained from wood particles with a 10% binder content is used.

Table 1: Composition of hemp particle and fiber boards

Plate, type Type of raw material Binder content, % CFC content, % MFS content, % Paraffin content, % Hemp 8 Hemp pazder 8 7.2 0.8 0.5 Hemp 10 Hemp pazder 10 9.0 1.0 0.5 Hemp 12 Hemp pazder 12 10.8 1,2 0.5

Hemp 14 Hemp pazder 14 12.6 1.4 0.5 REF 10 Wood particles 10 9.0 1.0 0.5

The results for density, water absorption and thickness swelling of the exemplary boards are presented in Table 2.

Table 2: Density, Water Absorption and Thickness Swelling of Hemp Particle Boards and Fibers

Plate, type Density p, kg/m ³ Water absorption A, % Swelling no thickness Gt, % Hemp 8 660 76.76 26.00 Hemp 10 662 69.45 20.64 Hemp 12 661 63.72 16.41 Hemp 14 659 47.10 12.81 REF 10 671 79.99 31.36

The physical and mechanical parameters of the plates are determined according to the requirements of the current BDS EN:

- BDS EN 323:2001. Wooden boards. Determination of density;

- BDS EN 310:1999. Wooden boards. Determination of flexural modulus and flexural strength;

- BDS EN 319:2002. Particleboard and fiberboard.

Determination of tensile strength perpendicular to the plane of the plate;

- BDS EN 309:2006. Particle boards. Definition and classification;

- BDS EN 312:2010. Particle boards. Requirements.

Based on their density, in accordance with БДС EN 309:2006, the obtained boards are classified as structural, medium-heavy boards (density 500 kg/m ³ - 700 kg/m ³ ), that is, boards intended for the production of furniture (type P2).

For hemp pazder boards with increasing binder content from 8 to 14%, water absorption decreased by 1.63 times (63% improvement in index values). The most significant improvement of 1.35 times was observed when the binder content increased from 12 to 14%. All boards obtained from hemp pazder had lower index values compared to those of the control board REF 10, obtained from wood particles and with 10% binder content.

According to BDS EN 312:2010, the requirement for boards of type РZ (chipboard for application in a humid environment) is at most 13%. The requirement for MDF for use in a dry environment is at most 12% (БДС EN 622-5:2010). For plates type P2 for interior furnishings, including furniture, with application in a dry environment, determination of swelling by thickness is not required. For all types of MDF, regardless of whether they are for a dry or wet environment, a thickness swelling determination is required.

The binder content has a very strong influence on the thickness swelling of the hemp pazder boards. When increasing the binder content from 8 to 14%, the thickness swelling decreases (improves) by 2.03 times, and the boards with 14% binder meet the requirements for chipboard type PZ (for use in humid environments) and approach the requirements for MDF for application in a dry environment.

Hemp particleboard and fiberboard had better (low) through-thickness swelling than the control particleboard. Thus, the Hemp 10 board has 1.52 times lower thickness swelling compared to the control chipboard obtained with the same binder content.

The flexural modulus, flexural strength, and transverse tensile strength data of the exemplary plates are presented in Table 3.

Table 3: Flexural Modulus, Flexural Strength and Transverse Tensile Strength of Hemp Particle and Fiber Boards

Plate, type Modulus of elasticity Em, N/mm ² Flexural strength fm, N/mm ² Transverse tensile strength ft, N/mm ² Hemp 8 2197 18.55 0.69 Hemp 10 2265 19.17 0.72 Hemp 12 2483 20.15 0.85 Hemp 14 2783 21.53 0.93 REF 10 1525 10.33 0.37

According to BDS EN 312:2010, the elasticity requirement (for P2 chipboard boards intended for furniture production) is at least 1500 N/mm ² . Elasticity requirement MDF for use in a dry environment is at least 2200 N/mm ² (БДС EN 622-5:2010. Wood fiber boards. Requirements. Part 5: Requirements for boards produced by the dry method (MDF))

As the binder content increased from 8 to 14%, the modulus of elasticity of hemp pazder boards increased by 1.27 times. All of the Hemp Pazder boards had higher values for the flexural modulus of elasticity than the control particle board. Hemp 10 board has 1.49 times better index values compared to chipboard obtained with the same binder content.

All boards made of hemp particles and fibers significantly exceed the standard requirement for the indicator, for chipboard type P2 - for furniture production (BDS EN 312:2010). Boards with 10% and more binder content meet the requirements for the flexural modulus of elasticity for MDF for a dry environment (БДС EN 622-5:2010).

As the binder content increased from 8 to 14%, their flexural strength improved by 1.16 times. All boards made of hemp particles and fibers significantly exceed the requirements for the indicator for chipboard type P2 (chipboard intended for furniture production) - at least 11 N/mm ² (BDS EN 312:2010). Hemp pazder boards with a 14% binder content also meet the requirements for the indicator for MDF for use in a dry environment - at least 20 N/mm ² (БДС EN 622-5:2010).

All hemp particleboards and fiberboards had significantly higher flexural strength than the control particleboard. The Hemp 10 board has 1.86 times the flexural strength of the control board made from wood particles with the same binder content.

The bending strength requirement for boards of type P2 (chipboard intended for furniture production) is at least 11 N/mm ² (BDS EN 312:2010). A requirement for MDF for use in a dry environment is at least 20 N/mm ² (БДС EN 622-5:2010).

The transverse tensile strength requirement for P2 type boards (chipboard intended for furniture production) is at least 0.30 N/mm ² (BDS EN 312:2010). The requirement for MDF for use in a dry environment is at least 0.55 N/mm ² (БДС ΕΝ 622-5:2010)

In the hemp particle and fiber boards, as the binder content increased from 8 to 14%, the transverse tensile strength improved by 1.35 times. This type of boards, due to the low bulk density of the material and the participation of short fibers in their structure, have a transverse tensile strength exceeding the requirements for MDF for use in a dry environment at least 0.55 N/mm ² (БДС EN 622-5: 2010).

Board with 10% binder content has 1.95 times higher transverse tensile strength compared to particle board at the same binder content.

Data on screw retention (pullout resistance of fasteners) perpendicular to the broad side are given in Table 4.

Table 4: Screw retention perpendicular to the wide side and to the edge

Plate, type Screw retention perpendicular to the wide side fc, N/mm ² Screw retention perpendicular to the edge fc, N/mm ² Hemp 8 77.04 55.34 Hemp 10 88.94 59.46 Hemp 12 90.37 66.13 Hemp 14 97.92 71.01 REF 10 61.98 22.67 Industrially produced chipboard 65.03 25.07 Industrially produced MDF 86.48 16.09

As the binder content increased from 8 to 14%, the screw retention perpendicular to the broad side improved by a factor of 1.27 in hemp pazder plates. All hemp-based boards have higher values of screw retention perpendicular to the broad side than both industrially produced and laboratory-produced particleboard. Hemp pazder boards with 10% binder content have a higher value of screw retention perpendicular to the wide side than factory-made MDF.

In hemp pazder boards with increasing binder content from 8 to 14%, screw retention perpendicular to the edge improved by 1.28 times.

The results for density, water absorption and thickness swelling of the exemplary boards of different densities are presented in Table 5.

Table 5: Density, Water Absorption and Thickness Swelling of Hemp Pazder Boards

Plate, type, Density p, kg.nr Water absorption A, % Thickness swelling Gt, % 750 36.59 9.27 800 29.24 7.22 850 24.18 5.91

On the basis of their density, in accordance with BDS EN 309:2006, for example, the hemp pazder boards obtained are classified as heavy boards (density 700-900 kg/m ³ ). The density of the plates is 750, 800 and 850 kg/m ³ .

As the density of hemp pazder boards obtained with melamine formaldehyde resin increases from 750 to 850 kg/m ³ , their water absorption decreases from 36.59% to 24.18%. That is, the improvement in the values of the indicator is 1.51 times. The improvement trend is constant, with a corresponding decrease in water absorption with increasing board density from 750 to 800 kg/m ³ by 1.25, and with increasing density from 800 to 850 kg/m ³ by 1.21 times.

Despite the expected increase in thickness swelling of the plates with increasing their density, this is not noted. In general, this can be explained by a decrease in the water absorption of the slabs, which compensates for having more material to swell in the denser slabs. The total decrease in the values of the indicator is 1.57 times, and the difference in the swelling by thickness of the plate with 800 and 850 kg/m ³ is 1.22 times.

Boards with a density of 800 and 850 kg/m ³ fulfill the most stringent requirements for thickness swelling in the various types of composite wood materials used as load-bearing coatings, namely for MDF for load-bearing structures and use in humid environments, thickness swelling of maximum 8% (БДС EN 622-5:2010).

Data on flexural modulus, flexural strength and transverse tensile strength of the exemplary plates of different densities are presented in Table 6.

Table 6: Flexural Modulus, Flexural Strength and Transverse Tensile Strength of Hemp Particle and Fiber Boards

Density p, kg.m ³ Modulus of elasticity Em, N/mm ² Flexural strength fm, N/mm ² Transverse tensile strength ft, N/mm ² 750 2970 24.38 0.98 800 3805 31.20 1.19 850 3879 32.17 1.23

As the density of the hemp particleboards increased from 750 to 850 kg/m ³ , their flexural modulus increased from 2970 to 3879 N/mm ² . That is, the improvement in the indicator values is 1.31 times. The greatest improvement is reported when the density increases from 750 to 800 kg/m ³ . The difference between the flexural modulus of the plates with a density of 800 and 850 kg/m ³ is only 1.045 times.

All boards meet the most stringent requirement for MDF for load-bearing structures and use in wet environments, a flexural modulus of at least 2700 N/mm ² (БДС EN 622-5:2010).

When the density of the plates increases from 750 to 850 kg/m ³ , their bending strength increases from 24.38 to 32.17 N/mm ² . That is, the overall improvement in the indicator values is 1.32 times. Again, a major improvement is seen as the density increases from 750 to 800 kg/m ³ . The flexural strength values for the 800 and 850 kg/m ³ density boards are similar.

Boards with a density of 800 and 850 kg/m ³ cover the most stringent requirements for the indicator for wood composite materials, namely for MDF for load-bearing structures and moist environments - bending strength of at least 30 N/mm ² .

As the density of the plates increases from 750 to 850 kg/m ³ , their transverse tensile strength increases by 1.26 times. The most significant is the increase, by 1.21 times, when increasing the density from 750 to 800 kg/m ³ .

All boards meet the most stringent requirements for the indicator, namely for MDF for load-bearing structures and use in a humid environment, a transverse tensile strength of at least 0.75 N/mm ² .

In terms of their bending strength and modulus of elasticity, this material is comparable to wood fiber boards (MDF), and in terms of transverse tensile strength it even surpasses it. Due to the significant homogeneity of this type of boards and the high compression factor, they have between 2 and 3 times better screw retention on the edge than factory-produced chipboard and MDF. The good screw retention of PCCs makes them particularly suitable for furniture production.

An example of an adhesive composition:

Ureaformaldehyde resin (CFC): Composition - molar ratio 0.85 - 1.17, Dry content - 35% - 65%, Dynamic viscosity - 23.76±0.52 Mpa.s.; Melamineformaldehyde resin (MFS): Composition — molar ratio — 1.45 - 1.95, Dry content - 42% - 64%, Dynamic viscosity - 21±0.76; Lingusulphate - 30% - 70% dry content; Formaldehyde acceptor; Ammonium Hydrogen Sulfide - 40% - 85% dry content; Natural colorings; Paraffin emulsion - concentrate 45% - 65%; Ammonium Sulphate solution at a concentration of 18% - 36%; Ammonium Polyphosphate

An example of the ratio of weight units of a plate 1200mm x 2400mm x 12mm with a binder content of 12%:

Hemp wood particles - 22,464 kg; GVW - 2.289 kg; MFS - 0.254 kg; Paraffin - 0.106 kg; Ammonium Sulphate - 0.051 kg; Colorants - 0.450 kg; Lingusulphate - 0.916 kg; Ammonium Hydrogen Sulfide - 0.073 kg; Ammonium Polyphosphate - 2 kg

Exemplary performance in a range of binders for slab - 8%

Content in % of the entire binder: FCS% - from 6% to 8.2%; MFS% - from 0.5% to 0.9%; Paraffin emulsion - from 0.35% to 0.60%; Ammonium Sulphate - 0.15% to 0.30% in form with a concentration of 18% to 36%; Lingusulphate - of the entire binder from 15% to 25%

Claims (10)

1. A method for the production of hemp pazder plates, comprising: grinding the core of a hemp stem; drying and subsequent gluing of the solid material; laying the solid material to obtain sheet material and hot pressing the board, characterized in that the industrial hemp stalks are treated in a decorticator to separate hemp wood particles and short fibers with a size of 0.1 mm to 20 mm , storing and crushing the particles to separate the dust and particles below 1 mm in size by sieving, then after drying the particles to 18% humidity and bonding with binding emulsions the resulting material is laid to create a sheet material/carpet in a requested size of the plate, undergoes cold pressing and edging to the required dimensions, followed by feeding the prepared and sized plates into the hot multi-stage press for heat treatment according to a program, by performing three-stage hot pressing and thermoforming at a table temperature in the range between 120°C and 220° C: first stage duration from 1 to 2 min at pressure from 3 MPa to 4.5 MPa; second stage - duration from 1 to 3 min at pressure from 0.5 MPa to 2.5 MPa; third stage - from 0.3 MPa to 1.2 MPa, and the board thus obtained is subjected to cooling, sizing to the desired size, grinding, if necessary, and smoothing. 2. Method according to claim 1, characterized in that the process can be carried out manually and/or automatically by means of a program created for the purpose. 3. Method according to claim 1, characterized in that the multi-stage hot press has a multi-functional possibility of settings with different operating modes, such as: duration, temperature, pressure I .. Ί And others. 4. Method according to claim 1, characterized in that . the strength of the plates is proportionally dependent on the drying humidity of the particles. 5. A method according to claim 1, characterized in that the pressing temperature is a function of the density of the plate. '· 6. Method according to claim 1, characterized in that in the three-stage hot pressing, the pressing time is a function of the plate thickness. 7. Method according to claim 1, characterized in that with a pressure factor between 45 s.mm-1 and 90 s.mnT ¹ . 1 8. Method according to claim 1, characterized in that the hemp particles used in the plates containing the binder k. substance as an amount relative to dry mass in the range of 8% to 14% and are glued with an adhesive composition of 90% urea formaldehyde resin, 10% melamine formaldehyde resin and paraffin emulsion. 9. Method according to claim 1 and 8, characterized in that the content of the binder as an amount relative to dry mass is dependent on the strength and purpose of the plates. 10. Method according to claim 1, characterized in that the plates have a density of 750 kg/m ³ to 850 kg/m ³ .