BG4395U1 - Hemp awn slab - Google Patents

Abstract

The present utility model relates to an ecological slab of hemp awn (particles and short fibres) obtained from the stalks of industrial hemp and used in the construction industry, in furnishings and in the furniture industry. It serves to replace traditionally used timber which in the longer term will lead to abatement of deforestation. It has been proven that the physicomechanical properties of the hemp awn slab exceed the standard requirements for chipboards and MDF boards. The hemp particles used in the slab contain a binder the content of which versus the dry mass ranges from 8% to 14% and, after being dried to a certain moisture content, are treated with an adhesive compound made of 90% urea formaldehyde resin and 10% melamine formaldehyde resin and paraffin emulsion. The so prepared slab is laid in a hot multilevel press for thermal treatment according to a program which depends on the thickness and density of the slab and includes three-step hot pressing and thermoforming with multifunctional choice of settings for various operational modes, such as duration, temperature, pressure, etc.

Description

Field of technique

The utility model relates to an ecological board of hemp pazder (particles and short fibers) used in the construction, furnishing and furniture industries.

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 stems 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 hazardous to human health levels of emitted formaldehyde emissions from the surface layer of the plates.

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.

The purpose of the utility model is to create a product from a non-woody lignocellulosic raw material that utilizes agricultural waste from hemp particles and short fibers, and is a substitute for traditionally used wood materials.

Technical nature of the utility model

The object of the present utility model is to create a hemp pazder plate (hemp particles and short fibers) that solves the stated problems of the prior art, and more specifically:

- provides a raw material source for the production of plates 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 requirements for particle boards and significantly surpasses those of chipboard and MDF.

An additional task of the utility model is to provide the possibility for hemp pazder plates (particles and short fibers) to be of different densities.

These and other tasks are solved by creating a hemp pazder plate, according to the useful model, in which 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 plate. The adhesive composition of the plate 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 sheet has a density of 750 kg/m ³ 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:

An advantage is that the use of the hemp plant as a raw material source for the production of furniture and furnishing plates, 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 utility model hemp particle and fiber board is that it is an environmentally friendly product, both in terms of the raw material (during its rapid growth, industrial hemp absorbs significant amounts of carbon dioxide (CO ₂ )) and in terms of of the binding 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 (class super E0 - below 1.5 mg/100 g)), which will significantly reduce the risk to the health of people using this material in the interior you are

According to the utility model, the hemp pazder board has physico-mechanical properties superior to particle board and wood fiber board. This is due to the 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 board and the high compression ratio, it has 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 board makes it particularly suitable for furniture production.

The resulting hemp pazder board with a density of 750 to 850 kg/m ³ has very good performance values. As a result of the very high compression ratio (8 and 8.5 times), the board with a density of 800 and 850 kg/m ³ has performance values significantly exceeding the most stringent requirements, namely those of MDF for load-bearing structures and use in a humid environment. An additional favorable influence on the parameters of the plate is also the presence of fine fibers in the hemp pazder. In this way, the contact area is increased, and hence the adhesion and cohesive bonds between the hemp particles. This makes this board an extremely suitable ecological material for applications such as flooring and other elements subjected to loading in wet environments.

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 utility model

In more detail, the utility model is explained with exemplary non-limiting embodiments of the utility model for the manufacture of a hemp padder plate.

For the production of hemp particle board and short fiber, it is preferred to use industrial hemp stalks, baled (may be with leaves and/or seeds), which are allowed to dry in the field for about 20 days before starting the process. Baled hemp does not need to be stored indoors. 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 below 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 18% humidity by drying, which is optimal in terms of time and effect. The strength of the plates is proportionally dependent on the drying humidity of the particles. Having reached the required humidity, they enter a pasting mixer, where, under certain revolutions, the particles are pasted with their binding emulsions in exemplary proportions of 90% urea-formaldehyde resin (KFS) 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%. 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. 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 pressing machine provides a multifunctional possibility of settings 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 pressure 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 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.mm ^-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 utility model, the hemp pazder board (particles and short fibers) has a binder content as an amount by dry weight in certain percentages depending on its strength and purpose as follows:

- Plate with 8% - designed for unloaded furniture;

- Plate with 10% - for mass furniture;

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

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

The adhesive composition of the plate 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 mPa.s and MFS - mole ratio 1.76; dry content 54%, dynamic viscosity 21±0.76 m₽as 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 mPa.s. 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 listed in Table 1. A board made from wood particles with a 10% binder content is used as a control.

Table 1. Composition of hemp particle and fiber boards

Plate^ type VND of the raw material Binder content % Our CFC content, % MFS content, % Paraffin content, % Hemps Hemp vs 8 7.2 0.8 0.5 Hemp 10 Kpiopep jigsaw puzzle 10 9.0 1.0 0.5 ; Hemp 12 Hemp Mon. Wed 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

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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, Water absorption A, % Swelling but 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

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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 resulting 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 the 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 dry or wet environments, a determination of thickness swelling 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 Nftnnr Bending strength Jin, N/mm^ Strength of transverse tension /Ϊ, N/mm' 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

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According to BDS EN 312:2010, the elasticity requirement (for P2 chipboard boards intended for furniture production) is at least 1500 N/mm ² . Requirement for elasticity 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 a binder content of 10% and more 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 14% binder content also meet the requirements for the indicator for MDF for use in a dry environment - at least 20 N/mm ² (BDS EN 6225:2010).

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). A requirement for MDF for use in a dry environment is at least 0.55 N/mm ² (БДС EN 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 N/mm ¹ Ni news holding perpendicular to the edge /s, N/mm ^: Hemp 8 77.04 5534 Hemp 10 88.94 59.46 Hemp 12 90.37 66.13 Hemp 14 97.92 71.01 REF 10 61.98 22.67 I Three-layered chipboards 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

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Slab, guy, Flesh! . o st r* kg.nr Water absorption A, % Swelling pi thickness 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.™- ¹ Modulus of elasticity Em, N/mm ² Strength when bending /t, N/mm ³ Transverse tensile strength D N/mm ¹ 750 2970 24.38 0.98 800 3805 31.20 L19 850 3879 32.17 1.23

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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 6225:2010).

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 ratio, 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 (KFS): Composition - molar ratio - 0.85-1.17, dry content 35%-65%, dynamic viscosity - 23.76±0.52 Mpa.s.; Melamine formaldehyde 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 dyes; Paraffin emulsion - concentrate 45%-65%; Ammonium sulfate solution at a concentration of 18%-36%; Ammonium polyphosphate.

An example of the ratio of weight units of a plate 1200 mm x 2400 mm x 12 mm 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 sulfate - 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 of % of all binder: FCS % - from 6% to 8.2%; MFS % - from 0.5% to 0.9%; Paraffin emulsion - from 0.35% to 0.60%; Ammonium sulfate - 0.15% to 0.30% in form with a concentration of 18% to 36%; Lingusulphate - of the entire binder from 15% to 25%.

Claims (1)

Hemp pazder board consisting of hemp particles and short fibers from industrial hemp stalks, characterized in that the hemp particles used in the board with a binder content as an amount relative to dry mass in the range of 8% to 14% are glued with an adhesive composition of 90% urea formaldehyde resin, 10% melamine formaldehyde resin and paraffin emulsion