CN110587749A - Complexing wood shavings, complexing shaving board and manufacturing method thereof - Google Patents

Abstract

The invention relates to a complex wood shavings, a complex shaving board and a manufacturing method thereof, belonging to the technical field of artificial board processing. The complex shaving board is composed of complex shavings and an adhesive, wherein a plant polyphenol metal salt complex is introduced into the complex shavings, and metal ions are fixed on the surfaces, cell walls, cell cavities and/or cell gaps of the shavings through plant polyphenol, so that the color of the shaving board is effectively changed, and the performances of the shaving board, such as water resistance, corrosion resistance, mildew resistance and the like, are improved.

Description

A kind of complex particle, complex particle board and manufacturing method thereof

technical field

The invention relates to the technical field of wood-based board processing, in particular to a complexed particle board, a complexed particle board and a manufacturing method thereof.

Background technique

Particleboard, also known as particle board, is made of wood or other wooden materials after shavings are applied, and then glued together under heat and pressure to form a wood composite material. Due to its good physical and mechanical properties and easy processing, it has been widely used in the fields of panel furniture, building structural materials, and decorative materials. With the continuous development of particleboard in the field of home decoration, and people's continuous pursuit of a better life. In decoration, the pursuit of wood products has undergone a huge change from practicality to individualization and functionality. The existing particleboard processing technology is difficult to achieve the unity of functionality and individualization. For example, increasing the color of particleboard requires Dye the particle board; increase the water resistance of the particle board is mainly to add water repellents such as paraffin; increase the anti-corrosion performance needs to increase the preservative; increase the anti-mold performance requires anti-mold agent; In process.

Contents of the invention

In order to solve the problems existing in the prior art, the invention provides a kind of entangled shavings, entangled particleboard and a manufacturing method thereof. The preparation of the complexed particleboard by the invention not only effectively changes the color of the particleboard, but also increases the advantages of the particleboard such as waterproof, anti-corrosion, anti-mildew, etc., and can effectively prevent the particleboard from cracking.

In order to solve the above technical problems, the present invention provides the following technical solutions:

On the one hand, the present invention provides a kind of complex shavings, which is prepared from shavings, plant polyphenols and metal salts; the plant polyphenols and metal salts exist in the form of complexes in the shavings and are distributed on the surface of the shavings , cell walls, cell lumens and/or intercellular spaces.

Further, the plant polyphenols are polygallates and/or polyflavans plant polyphenols; the gallate polyphenols contain at least one polyol and a plurality of phenolic carboxylic acids, and the polyalcohol passes through The ester bond is connected with the phenol carboxylic acid; the molecular weight of the polyflavan polyphenol is 500-3000, the polymer is 2-10, the units are connected by C-C bonds, and the molecular skeleton is C ₆ ·C ₃ · C ₆ structure, a three-carbon chain (C~2, C~3, C~4) is connected between two phenolic aromatic rings (A ring, B ring), one of the carbon atoms is connected to the 8a position of the A ring Oxygen atoms are linked to form a pyran ring (C ring).

On the other hand, the present invention also provides a kind of preparation method of above-mentioned complex shavings, comprising

Step 1: Prepare an appropriate amount of shavings;

Step 2: introduce plant polyphenols into shavings to obtain polyphenol shavings;

Step 3: introducing metal salt into polyphenol shavings to obtain polyphenol metal salt shavings;

Step 4: drying the above shavings to obtain complex shavings.

Further, the step 2 is:

21) dissolving plant polyphenols in water, and stirring evenly to form a plant polyphenol aqueous solution;

22) immersing the above-mentioned shavings in an aqueous solution of plant polyphenols;

23) Drying the shavings impregnated with the aqueous plant polyphenol solution.

Preferably, the concentration of the plant polyphenol aqueous solution is 1g/L-25.0g/L, the average molecular weight is 170-50000, which is 1-40 polymers; the immersion time of the wood shavings in the plant polyphenol aqueous solution is 10min- 48h, the impregnation temperature is 0-80°C, and the impregnation method is normal pressure or pressurized;

The plant polyphenol is one or more mixtures of tannin extract, tannin, tannic acid, endogalic acid and pyrogallic acid.

The wood shavings are soaked in a polyphenol solution, and the wood shavings cell wall gradually swells under the action of water, and the plant polyphenols are gradually introduced into the wood shavings surface, cell wall, cell cavity and/or intercellular space until the preset impregnation amount is reached The shavings are taken out, placed in a drying kiln or in the air, so that the water in the shavings is gradually evaporated, and the concentration of plant polyphenols in the cells increases, and when it reaches the isoelectric point, it begins to precipitate, and the hydrogen bond and/or hydrophobic bond Under the action, the plant polyphenols are solidified in the shavings to form polyphenol shavings.

Further, the step 3 is:

31) dissolving the metal salt in water and stirring evenly to form an aqueous solution of the metal salt;

32) Soak the above polyphenol shavings in the metal salt solution.

Preferably, the concentration of the metal salt solution is 0.3g/L-30.0g/L; the immersion time of the wood shavings in the metal salt solution is 10min-24h, the immersion temperature is 0-80°C, and the immersion method is normal pressure or pressure;

The metal salt is one or more mixtures of iron salt, copper salt and metal borate salt.

The polyphenol shavings are soaked in metal salts, and the shavings cell walls gradually swell under the action of water, and the metal salts are gradually introduced into the shavings surface, cell walls, cell lumens and/or intercellular space until the preset impregnation amount is reached ; The plant polyphenols and metal salts are complexed in the shavings, and the shavings and the plant polyphenol metal salt complexes are mainly bound by hydrogen bonds, dispersing bonds, and covalent bonds, and the polyphenol metal salt complexes It is formed by chelating the five-membered ring formed by the adjacent diphenolic hydroxyl group of plant polyphenols and ions.

In yet another aspect, the present invention also provides a complexed particleboard, which comprises 1-95% of the above-mentioned complexed particleboard.

Plant polyphenol metal salts are provided on the surface of the shavings and/or in the cell lumen, cell wall, and/or interstitial spaces in the shavings, and the shavings are arranged along the grain orientated and/or randomly, and glued by an adhesive into a whole.

In yet another aspect, the present invention also provides a method for preparing complexed particleboard, comprising the above-mentioned complexed particleboard, including:

101) drying

Using the air flow method, dry the complexed shavings to a moisture content of 2-5%, the inlet air temperature during drying is 370-400°C, the drying medium temperature is 160-190°C, and the oxygen content of the drying medium is 13-18%;

102) Sizing

Using spray sizing method, phenolic resin or urea-formaldehyde resin is evenly sprayed on the surface of the complexed shavings. If it is phenolic resin, the sizing amount is 5% to 10%; if it is urea-formaldehyde resin, the sizing amount is 8-12%. %

103) Paving molding

Adopt air-flow paving method to pave the above-mentioned dry shavings into a slab with a surface density of 0.15-0.45g/cm ² ;

104) Hot pressing

The above-mentioned slab is sent into a multi-layer hot press machine or a continuous hot press machine, and after hot pressing, it is made into a particle board with a density of 0.65-1.10 g/cm ³ .

Existing studies believe that there are many reasons for particleboard cracking, the most important of which is that the polysaccharides (cellulose, hemicellulose, etc.) in the shavings absorb or release water during the moisture absorption and desorption process, causing the shavings to expand or shrink, resulting in The shavings are dimensionally unstable.

Compared with the prior art, the present invention has the following beneficial effects:

In the present invention, plant polyphenols are firstly introduced into wood shavings. Since the phenolic hydroxyl groups of plant polyphenols are combined with the alcoholic hydroxyl groups in cellulose and hemicellulose in wood shavings through hydrogen bonds, loosening bonds, and covalent bonds, on the one hand, they are hydrophilic in wood shavings. On the other hand, the phenolic hydroxyl groups and benzene rings of plant polyphenols make them hydrophilic and hydrophobic. When the phenolic hydroxyl groups of plant polyphenols are combined with cellulose and hemicellulose in shavings and After the metal ions are complexed, its hydrophobic benzene ring structure means that the complexed shavings show a hydrophobic function, thereby increasing the water resistance of the shavings;

At the same time, the introduction of metal salts can effectively increase the anti-corrosion and anti-mildew properties of the particleboard, and also change the color of the particleboard to a certain extent, so that the particleboard has the color of metal salts, and the metal salt ions and plant polyphenols are complexed in wood , the existence is relatively stable and not easy to fade.

In the present invention, plant polyphenols and metal salts are introduced into the cell walls of the shavings, and the plant polyphenols and metal salts are complexed in the shavings. Valence bonding, polyphenol metal salt complexes are formed by chelating five-membered rings formed by the adjacent diphenolic hydroxyl groups of plant polyphenols and ions. The adjacent cellulose/hemicellulose molecular chains are cross-linked into a network structure, as if several scaffolds are supported on the cellulose/hemicellulose molecular chains, so that it reduces or even does not cause swelling during moisture absorption or desorption or contraction; on the basis of the above, a large number of hydrogen bonds (plant polyphenolic phenolic hydroxyls and shavings are combined to form multi-point hydrogen bonds) and coordination bonds (plant polyphenolic phenolic rings) are formed in the cellulose skeleton. The ortho-hydroxyl on the metal complexes with the metal salt to form a coordination bond) consisting of multiple sacrificial bond networks. Since the bond energy of the sacrificial bond is smaller than that of the covalent bond (the covalent bond network is formed between cellulose, hemicellulose, lignin and phenolic resin), when the shavings are subjected to internal stress or external force, the sacrificial bond is broken preferentially over the covalent bond . The dynamic effect of the continuous breaking and reconstruction of sacrificial bonds dissipates a large amount of energy in the particle system, eliminates or weakens the internal stress, and protects the integrity of the covalent bond network of the cellulose skeleton. This provides a new method for solving the cracking problem of wood shavings.

In the present invention, plant polyphenols are firstly introduced into the shavings to make the shavings swollen; then metal salts are introduced into the shavings, and the plant polyphenols combine with the cellulose and hemicellulose in the shavings to form multi-point hydrogen bonds. Phenol complexes with metal salts, combining "cellulose-plant polyphenols-metal salts" into one, as if forming a number of scaffolding supports in the cellulose skeleton molecule; then, with the evaporation and oxidation of water, "cellulose -Plant polyphenols-metal salts" are further cross-linked and oxidized to finally form complexed shavings. The "cellulose-plant polyphenol-metal salt" dynamic multiple sacrificial bond network structure of the present invention supports cellulose and/or hemicellulose so that it reduces or even does not cause expansion or shrinkage during moisture absorption or desorption, while sacrificing bonds The dynamic effect of continuous fracture and reconstruction dissipates a large amount of energy in the wood-recombined material system, eliminates or weakens internal stress, protects the integrity of the covalent bond network of the cellulose skeleton, and solves the problem of easy cracking of shavings from the molecular level .

Description of drawings

Fig. 1 is the shaving situation before and after processing in the embodiment of the present invention 1;

Fig. 2 is the contact angle of water on the surface of radiata pine shavings before and after treatment in the embodiment of the present invention 1;

Fig. 3 is the shaving situation before and after processing in the embodiment of the present invention 2;

Fig. 4 is the contact angle of water on the surface of eucalyptus shavings before and after treatment in the embodiment of the present invention 2;

Fig. 5 is the oriented strand board that the embodiment of the present invention 4 manufactures;

Fig. 6 is the chipboard that the embodiment 5 of the present invention manufactures.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will describe in detail in conjunction with specific embodiments.

In the present invention, the materials and reagents used can be obtained from commercial sources unless otherwise specified.

Example 1

A preparation method of complexed radiata pine shavings, comprising

Step 1: Prepare an appropriate amount of radiata pine shavings;

Saw radiata pine into 1000-2000mm wood sections, after peeling, use a planer to plan and form flat shavings; after drying, use airflow sorting to obtain flat shavings, as shown in Figure 1(a) , belongs to the prior art.

Step 2: introduce plant polyphenols into shavings to obtain polyphenol shavings;

21) Dissolving tannin with an average molecular weight of 170 and a polymer of 1 in water, and stirring uniformly to form an aqueous tannin solution with a concentration of 1.0 g/L;

22) Immerse the above-mentioned shavings in an aqueous tannin solution under normal pressure, the immersion time is 48 hours, and the immersion temperature is 25°C;

23) Dry the shavings impregnated with the aqueous tannin solution.

Step 3: introducing metal salt into polyphenol shavings to obtain polyphenol metal salt shavings;

31) Dissolving ferric chloride in water and stirring evenly to form an aqueous ferric chloride solution with a concentration of 1.0 g/L;

32) Immerse the above-mentioned polyphenol shavings in an aqueous solution of ferric chloride under normal pressure for 24 hours and at a temperature of 25°C.

Step 4: drying the above shavings to obtain complex shavings.

The complexed shavings were dried to a moisture content of 3% by the airflow method, the inlet air temperature was 400°C, the drying medium temperature was 160°C, and the oxygen content of the drying medium was 13%, as shown in Figure 1(b).

Analyzed by a colorimeter, the Lab values of the shavings before treatment were 67.90, 2.71 and 20.49, showing light yellow, and the Lab values of the shavings after complexation treatment were 47.87, 0.14 and 8.80, which were black.

The shavings before and after treatment were analyzed by contact angle. As shown in Figure 2, the contact angle of radiata pine shavings after complexation treatment increased, and the water resistance was enhanced.

Example 2

A preparation method of complexed eucalyptus shavings, comprising

Step 1: Prepare an appropriate amount of shavings;

Saw the eucalyptus into 1300mm wood sections, and use a rotary cutter to cut into 1.0mm veneers. After cutting, a large piece of regular shavings is formed. After drying, eucalyptus shavings are made, as shown in Figure 3(a) Show.

Step 2: Introduce black wattle bark extract (polyflavanoid plant polyphenols) into shavings to obtain polyphenol shavings;

21) Dissolving black wattle bark extract in water and stirring evenly to form an aqueous solution of black wattle bark extract with a concentration of 1 g/L;

22) Immerse the above shavings in the black wattle bark extract solution, the immersion pressure is 0.4MPa, the immersion time is 10min, and the immersion temperature is 20°C;

23) Dry the shavings impregnated with the aqueous solution of black wattle bark extract.

Step 3: introducing metal salt into polyphenol shavings to obtain polyphenol metal salt shavings;

31) Dissolving ferrous sulfate in water and stirring evenly to form an aqueous ferrous sulfate solution with a concentration of 3.0 g/L;

32) Immerse the above-mentioned polyphenol shavings in an aqueous solution of ferrous sulfate, the immersion pressure is 0.4MPa, the immersion time is 30min, and the immersion temperature is 20°C.

Step 4: drying the above shavings to obtain complex shavings.

The complexed shavings were dried to a moisture content of 3% by the airflow method, the inlet air temperature was 400°C, the drying medium temperature was 160°C, and the oxygen content of the drying medium was 13%, as shown in Figure 3(b).

Using a colorimeter for analysis, the Lab values of the shavings before treatment were 82.21, 1.48 and 23.41, showing pink, and the Lab values of the shavings after complexation treatment were 50.73, 0.16 and 1.26, which were dark black.

The wood shavings before and after treatment were analyzed by contact angle. As shown in Figure 4, the contact angle of poplar wood shavings after complexation treatment increased, and the water resistance was enhanced.

Example 3

A preparation method for complex poplar wood shavings, comprising

Step 1: Prepare appropriate amount of poplar wood shavings;

Poplar or poplar branches are cut into wood chips with a chipper, and then planed into rod-shaped shavings with a double-drum planer, which belongs to the prior art;

Step 2: import bayberry extract (polygallate plant polyphenol) into shavings to obtain polyphenol shavings;

21) Dissolving red bayberry extract in water and stirring evenly to form an aqueous solution of red bayberry extract with a concentration of 3.0 g/L;

22) Immerse the above-mentioned shavings in the plant polyphenol aqueous solution under normal pressure, the immersion time is 8 hours, and the immersion temperature is 25°C;

23) Drying the shavings impregnated with the aqueous solution of bayberry extract.

Step 3: introducing metal salt into the shavings of bayberry extract to obtain metal salt shavings of bayberry extract;

31) 500g of zinc borate and 500g of copper sulfate were dissolved in 1000L of water, and after stirring evenly, a mixed salt solution of zinc borate and copper sulfate was formed;

32) Immerse the above-mentioned polyphenol shavings in the metal salt aqueous solution under normal pressure, the immersion time is 4 hours, and the immersion temperature is 25°C.

Step 4: drying the above shavings to obtain complex shavings.

Example 4

A complexing oriented particle board, comprising the complexing shavings prepared in Example 1, tannins are arranged on the surface of the shavings and/or the cell lumen, the cell wall, and/or the intercellular space in the shavings, and the shavings are oriented After paving, it is glued together with an adhesive, as shown in Figure 5.

The preparation method of above-mentioned complexed particleboard comprises:

101) drying

Using the airflow method, dry the complexed shavings to a moisture content of 3%, the inlet air temperature is 400°C during drying, the drying medium temperature is 160°C, and the oxygen content of the drying medium is 13%;

102) Sizing

Adopt spray sizing method, phenolic resin is evenly sprayed on the surface of described complex shavings, if it is phenolic resin sizing amount is 8%;

103) Paving molding

Adopt the air-flow laying method, the above-mentioned dried shavings are directional paved into a slab with a surface density of 0.15g/cm ² ;

104) Hot pressing

The above-mentioned slab is sent into a continuous hot press machine, and after hot pressing, it is made into an oriented strand board with a density of 0.65 g/cm ³ .

According to "Oriented Strand Board" GB/T 4897-2015, the physical and mechanical properties of the above-mentioned complexed OSB were tested, and the results are shown in Table 1. As can be seen from Table 1, the various properties of the board have reached the requirements of the national standard, and after the complexation treatment, the value of the 24h water absorption thickness expansion rate is significantly reduced, which proves that the dimensional stability of the complexed particle board prepared by the present invention is significantly improved. .

Table 1 Comparison of properties of oriented strand board before and after complexation treatment

Example 5

A kind of complex particle board, is made up of the complex shavings prepared by 45% embodiment 3, 45% common shavings and 10% phenolic resin; After mixing common shavings and complex shavings; Described shavings are randomly lapped and stacked, A phenolic adhesive is provided at the overlapping joint, and is glued into a whole by the adhesive. The density of the complexed particle board is 0.90 g/cm ³ , as shown in FIG. 6 .

The preparation method of above-mentioned complexed particleboard comprises:

101) drying

Using the air flow method, dry the above-mentioned complexed shavings after sizing to a moisture content of 5%, when drying, the inlet air temperature is 370-400°C, the temperature of the drying medium is 160-190°C, and the oxygen content of the drying medium is 13-18%;

102) Sizing

Adopt spray sizing method, spray phenolic resin on the surface of described complexed shavings and ordinary shavings respectively evenly, the sizing amount of complexed shavings is 12%; The sizing amount of ordinary shavings is 8%;

103) Paving molding

Adopt the air-flow paving method, weigh the complexed shavings and ordinary shavings after sizing according to the set density, and after mixing evenly, adopt random paving, and pave the slab with a density of 0.30g/cm ² ;

104) Hot pressing

After the above slab is sent into a multi-layer hot press, after hot pressing, it is made into a particle board with a density of 0.90 g/cm ³ .

According to GB/T4897-2003, the physical and mechanical properties of particleboard are tested, and the results are shown in Table 2. From Table 2, it can be seen that after complexation treatment, the density, strength and elastic modulus of the material remain basically unchanged; The stability is greatly increased; the anti-corrosion, anti-mildew and flame-retardant properties of the material have been greatly improved, and the loss of imported metal ions (zinc ions, copper ions) has been greatly reduced.

Table 2 Comparison of properties of poplar particleboard before and after complexation treatment

Performance Ordinary particle board Complex particle board Density (g/cm³) 0.90 0.90 Bending strength (MPa) 48.2 48.6 Flexural modulus of elasticity (MPa) 5400 5300 Internal bonding strength (MPa) 1.10 1.12 Surface bonding strength (MPa) 1.23 1.25 Internal bonding strength after 2h boiling water (MPa) 0.42 0.48 24h water absorption thickness swelling rate (%) 6.7 4.3 Flame retardant B2 B1 Mildew resistance level 4 level 2 Anti-corrosion properties Level IV (Incorruptible) Class II (corrosion resistance) Copper ion loss - 15% Zinc ion loss - 17%

In summary, it can be seen that the complexed particleboard prepared by using the complexed shavings of the present application has the color of metal salt, and the metal salt ion is complexed with plant polyphenols in wood, which is relatively stable, not easy to fade, and has both anti-corrosion and anti-mildew properties. , flame retardant and other properties.

The above is the preferred embodiment of the present invention. For those of ordinary skill in the art, without departing from the principle of the present invention, making some improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. a kind of complex wood shavings, it is characterized in that, comprise wood shavings, plant polyphenols and metal salts; Described plant polyphenols and metal salts exist with complex form in described wood shavings, and are distributed on described wood shavings surface, in the cell wall, lumen and/or intercellular spaces. 2. complexing wood shavings according to claim 1, is characterized in that, described plant polyphenol is polygallates and/or polyflavans plant polyphenols; Described gallate polyphenols contain at least A polyhydric alcohol and a plurality of phenolic carboxylic acids, the polyhydric alcohol is connected with the phenolic carboxylic acid through an ester bond; the molecular weight of the polyflavan polyphenol is 500-3000, the polymer is 2-10, and the units are separated by C ~C bonds are connected, the molecular skeleton is C ₆ ·C ₃ ·C ₆ structure, and a three-carbon chain (C~2, C~3, C~4 ), one of the carbon atoms is connected to the oxygen atom at the 8a position of the A ring to form a pyran ring (C ring). 3. complex wood shavings according to claim 1, is characterized in that, described plant polyphenol is one or more of extract, tannin, tannic acid, endogalic acid, pyrogenic endogalic acid mix; The metal salt is one or more mixtures of iron salt, copper salt and metal borate salt. 4. A preparation method of complexed shavings, characterized in that, comprising: Step 1: Prepare an appropriate amount of shavings; Step 2: introduce plant polyphenols into shavings to obtain polyphenol shavings; Step 3: introducing metal salt into polyphenol shavings to obtain polyphenol metal salt shavings; Step 4: drying the above shavings to obtain complex shavings. 5. the preparation method of complexed wood shavings according to claim 4, is characterized in that, described step 2 is: 21) dissolving plant polyphenols in water, and stirring evenly to form a plant polyphenol aqueous solution; 22) immersing the above-mentioned shavings in an aqueous solution of plant polyphenols; 23) Drying the shavings impregnated with the aqueous plant polyphenol solution. 6. The preparation method of complex wood shavings according to claim 5, characterized in that, the concentration of the plant polyphenol aqueous solution is 1g/L～25.0g/L, the average molecular weight is 170～50000, and it is 1～40 polymerization body; the immersion time of the shavings in the plant polyphenol aqueous solution is 10min-48h, the immersion temperature is 0-80°C, and the immersion method is normal pressure or pressurized; The plant polyphenol is one or more mixtures of tannin extract, tannin, tannic acid, endogalic acid and pyrogallic acid. 7. the preparation method of complexed wood shavings according to claim 4, is characterized in that, described step 3 is: 31) dissolving the metal salt in water and stirring evenly to form an aqueous solution of the metal salt; 32) Soak the above polyphenol shavings in the metal salt solution. 8. The preparation method of complexed shavings according to claim 7, characterized in that, the concentration of the metal salt solution is 0.3g/L to 30.0g/L; the immersion time of the shavings in the metal salt solution is 10min -24h, the impregnation temperature is 0-80°C, and the impregnation method is normal pressure or pressurized; The metal salt is one or more mixtures of iron salt, copper salt and metal borate salt. 9. A complexed particle board, characterized in that it comprises the complexed particles according to any one of claims 1-3, which are stacked by random or directional lap joints, and a phenolic adhesive is provided at the lap joints Or urea-formaldehyde adhesive, the density of the particleboard is 0.65-1.10g/cm ³ . 10. A preparation method for complex particleboard, characterized in that, using the complex particle described in any one of claims 1-3 as raw material, comprising: 101) drying Using the air flow method, dry the complexed shavings to a moisture content of 2-5%, the inlet air temperature during drying is 370-400°C, the temperature of the drying medium is 160-190°C, and the oxygen content of the drying medium is 13-18%; 102) Sizing Using spray sizing method, phenolic resin or urea-formaldehyde resin is evenly sprayed on the surface of the complexed shavings. If it is phenolic resin, the sizing amount is 5% to 10%; if it is urea-formaldehyde resin, the sizing amount is 8-12%. %; 103) Paving molding Adopt air-flow paving method to pave the above-mentioned dry shavings into a slab with a surface density of 0.15-0.45g/cm ² ; 104) Hot pressing The above-mentioned slab is sent into a multi-layer hot press machine or a continuous hot press machine, and after hot pressing, it is made into a particle board with a density of 0.65-1.10 g/cm ³ .