Wood-plastic co-extrusion composite board and preparation method thereof

Abstract

The present application relates to the technical field of wood-plastic board, and particularly relates to a wood-plastic co-extrusion composite board and a preparation method thereof. The wood-plastic co-extrusion composite board comprises a core layer and a cladding layer. The core layer is made of first raw materials comprising recycled resin, first wood powder and first additives. The cladding layer is made of second raw materials comprising new resin, second wood powder and second additives. The second raw materials further comprise a cladding material with polyurethane containing ethylene ether chain segments as core material and melamine resin as wall material. The present application introduces a material capable of swelling in water after breaking in the cladding layer to improve the nail holding force of the board.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood-plastic boards, and particularly relates to a wood-plastic co-extrusion composite board and a preparation method thereof. BACKGROUND

[0002] Wood-plastic composite board is a new green decorative material made of wood powder as the main material, mixed with plastic and processing additives, and then extruded by mold equipment. It has the performance and characteristics of wood and plastic, and can replace wood and plastic. Wood-plastic boards have many advantages, such as excellent water resistance and corrosion resistance, good dimensional stability, flexible production process, little damage to equipment, use of recycled waste wood and plastic as raw materials, and recyclability, etc. Therefore, as a new type of engineering material, wood-plastic boards have a wide range of applications in many fields.

[0003] The current second-generation co-extrusion wood-plastic board refers to a board with new material as the cladding layer and recycled material as the core layer. For example, a double-layer PE co-extrusion wood-plastic board and a preparation method thereof are disclosed in a patent document with the publication number CN107933028A. The surface layer formula A takes 25-28% modified plastic, and simultaneously adds wood powder 54-57%, filler 14-17%, coupling agent 3-6%, antioxidant 0.15-0.4%, and the rest is additive. The core layer formula B takes 25-28% modified plastic, and simultaneously adds wood powder 54-57%, filler 14-17%, coupling agent 3-6%, antioxidant 0.15-0.4%, flame retardant 2-5%, mildew-proof agent 2-5%, and the rest is additive. The sum of the components of the surface layer formula A and the core layer formula B respectively meets 100%. The core layer uses recycled waste material, and the production cost is relatively reduced.

[0004] However, the existing wood-plastic board mainly uses wood powder as the main material, and the long fibers of wood in the wood powder are broken, so compared with the traditional composite board mainly using virgin wood board as the main material and having long fibers, the nail holding force is still lacking. In addition, the interfacial bonding strength between the core layer and the cladding surface layer is also a problem that needs to be considered for the current co-extrusion wood-plastic board. SUMMARY

[0005] The present application solves the above problems and provides a wood-plastic co-extrusion composite board and a preparation method thereof.

[0006] The technical solution for solving the problem of the present application is to provide a wood-plastic co-extrusion composite board, which comprises a core layer and a cladding layer. The core layer is made of a first raw material comprising recycled resin, first wood powder and first additive. The cladding layer is made of a second raw material comprising new resin, second wood powder and second additive. The second raw material further comprises a cladding material with polyurethane containing ethylene ether chain segments as the core material and melamine resin as the wall material.

[0007] The core material in the coating material, the polyurethane containing ethylene ether segments, is a water-swelling material. The oxygen atom in the ethylene ether segment has a pair of unshared electron pairs, which can be connected with the hydrogen atom in the water molecule to form a hydrogen bond. Due to the formation of the hydrogen bond, the molecular chain is changed from a twisted state to a relaxed state, and the macroscopic performance is swelling deformation. The content of the ethylene ether segment is preferably more than 20%. The wall material in the coating material, the melamine resin, is hardly soluble in water, and the heat distortion temperature is up to 180℃. Therefore, the core material can be well wrapped in the co-extrusion process. Based on this, the application introduces a coating material which can swell in water after being broken into the coating layer of the composite board to improve the nail holding force of the board. That is, when the nail is driven into the composite board and the wall material of the coating material near the nail is broken, the core material is exposed and can react with the water in the air and swell in volume. In other words, the structure of the board near the nail swells in volume, and the nail is clamped, so that the nail holding force is improved.

[0008] The preparation method of the polyurethane containing ethylene ether segments is not limited. Since the polyurethane needs to be coated and the application is the cured material, the polyurethane can be one-component or two-component.

[0009] The preparation method of the one-component includes the following steps: mixing ethylene oxide and propylene oxide copolymer diol, polypropylene oxide triol, and heating to 90-110℃; vacuumizing to remove water for 2-4h, and then cooling to 70-90℃; constant temperature for 20-30min; then adding diisocyanate and dibutyltin dilaurate, and reacting for 2-3h to obtain a prepolymer. Mixing the prepolymer, plasticizer and filler, and vacuumizing at 30-40℃ for 1-2h. After back pressure with high-purity nitrogen, adding bis(2-dimethylaminoethyl) ether, KH-560 and trimethyl orthoformate, and mixing uniformly, vacuum stirring for 1-2h, and then extruding into particles, and curing to obtain a water-swelling material. In addition to the ethylene ether segment, the urea group -NHCONH- in the material can also react with water to obtain a space network structure, so that the volume swells.

[0010] The preparation method of the two-component includes the following steps: dehydrating polyether polyol with an average molecular weight of 3000 at 100-120℃ under a vacuum of 8-9kPa for 2-3h until no bubbles are generated; then cooling to below 60℃, adding diisocyanate, and then heating to 80-90℃, and keeping the temperature for 1.5-2h, and then cooling, and sealing to obtain component A. Mixing polyether polyol, plasticizer, curing agent, active diluent and filler uniformly, and sealing to obtain component B. Mixing component A and component B uniformly according to a mass ratio of 1.5:1, vacuum degassing, and then extruding into particles, and curing to obtain a water-swelling material.

[0011] The preparation method of the coating material is not limited, and a conventional melamine resin coating method can be used. For example, melamine, formaldehyde and water are mixed, the pH is adjusted to 8.5-9.0, the solution is heated to 70-75 DEG C and stirred until the solution becomes clear, and then the reaction is timed. The pre-polymer is obtained by keeping the temperature. The core material, dispersant and anhydrous ethanol are mixed and stirred uniformly, the pre-polymer is added to the mixed system and stirred uniformly, the pH is adjusted to 3.0-4.0, and when the pH value is stable, sodium chloride is added, the temperature is increased to 60-80 DEG C, and the reaction is kept for 2 hours. Finally, the pH is adjusted to neutral, and the reaction solution is separated by filtration to obtain the coating material.

[0012] The amount of the coating material should be limited. If it is too low, the effect of improving the nail holding force cannot be achieved. As a preferred embodiment of the present application, the mass of the coating material in the second raw material is 50%-100% of the mass of the second wood powder.

[0013] The particle size of the coating material should be limited. If the particle size is too small, it will be difficult to break the microcapsule structure of the nail. As a preferred embodiment of the present application, the particle size of the coating material is substantially the same as that of the second wood powder. In general, the particle size of wood powder in a wood-plastic board is 20-40 mesh, i.e. 0.425-0.85 mm. Therefore, as a preferred embodiment of the present application, the particle size of the coating material is 0.4-1 mm.

[0014] When the polyurethane containing ethylene ether segments swells in water, if the constraint is not enough, it will swell freely in all directions, which will reduce the contact pressure acting on the nail and also cause deformation of other parts of the composite board. Therefore, it is preferred to improve the mechanical strength of the coating layer and reduce the deformation rate of the coating layer. As a preferred embodiment of the present application, the second wood powder is a hydrophobically modified wood powder. The hydrophobically modified wood powder improves the polarity of the surface of the wood powder, improves the compatibility of the wood powder with the newly formed resin, improves the mechanical strength of the coating layer, and makes it less likely to deform. On the other hand, it reduces the problem that the wood powder absorbs water and causes the board to easily deform. In some embodiments, the use of hydrophobically modified wood powder with coating material causes only the structure of the board near the nail to swell, while the volume of the structure of the board in other parts remains unchanged, so that the swelling deformation occurs in the direction of the nail, further tightening the nail.

[0015] The method for hydrophobically modifying the second wood powder is not limited, and the hydroxyl groups on the surface of the wood powder can be reacted into hydrophobic groups by any method, such as reacting carboxylic acid into ester groups, reacting aldehyde into ether bonds; or the wood powder can be coated with a hydrophobic shell. As a preferred embodiment of the present application, the hydrophobically modified wood powder is obtained by the following steps: reacting the hydroxyl groups on the surface of the wood powder into ether bonds. The aldehyde group reacts with the hydroxyl group on the wood powder to form an acetal, which is hydrophobically modified and forms a cross-linked structure, which can improve the mechanical strength of the coating layer.

[0016] As a preferred embodiment of the present application, the second raw material further comprises an aldehyde-based compound. The aldehyde-based compound is preferably a non-formaldehyde cross-linking agent, and is preferably one or both of glyoxal and glutaraldehyde, so as to avoid excessive formaldehyde content in the composite board.

[0017] The coating material uses melamine resin as the wall material, and a small amount of free aldehyde is inevitably left over during the preparation process. As a preferred embodiment of the present application, the free aldehyde in the coating material is used to react the hydroxyl groups on the surface of the wood powder into ether bonds. The free aldehyde in the coating material can be used to reduce the formaldehyde content of the composite board. At the same time, through acetalization, the wood powder can be cross-linked and combined with the melamine resin wall material of the coating material to a certain extent, thereby improving the sealing property of the coating material and further improving the mechanical strength of the composite board. In addition, through cross-linking of the wood powder and the melamine resin, the wood powder serves as a second layer of wall material of the coating material, so that the appearance of the wood-plastic board is closer to that of a natural wood board. In order to promote the second coating of the wood powder on the surface of the coating material, the wood powder can be dispersed in polyvinyl alcohol first, and then mixed and reacted with the coating material and the aldehyde-based compound.

[0018] The other components in the second raw material of the coating layer are not limited, and the components and amounts commonly used in existing wood-plastic boards can be used. As a preferred embodiment of the present application, the new resin is high-density polyethylene resin, and the amount of the new resin in the first raw material is 15% to 25%, such as 15%, 18%, 20%, 22%, or 25%. As a preferred embodiment of the present application, the second additive comprises, by mass fraction, 10 to 15 parts of a filler, such as 10 parts, 12 parts, 14 parts, or 15 parts, which can be calcium powder, silicon powder, etc.; 2 to 5 parts of a lubricant, such as 2 parts, 3 parts, 4 parts, or 5 parts; 0.2 to 0.8 parts of an antioxidant, such as 0.2 parts, 0.4 parts, 0.6 parts, or 0.8 parts; 0.2 to 0.8 parts of an ultraviolet-resistant agent, such as 0.2 parts, 0.4 parts, 0.6 parts, or 0.8 parts; and 1 to 1.5 parts of a pigment, such as 1 part, 1.2 parts, or 1.5 parts, which can be iron red or carbon black.

[0019] The above is an adjustment of the formula of the second raw material of the coating layer in the composite board. In general, the nails can be clamped through partial expansion of the board structure in the coating layer. In some embodiments, as a preferred embodiment of the present application, the coating material is also included in the first raw material to further improve the nail holding force.

[0020] Since the core layer is completely covered by the coating layer, the wood powder in the core layer is not easy to contact water and deform by absorbing water, and therefore the wood powder in the core layer can not be subjected to hydrophobic modification.

[0021] In the case of using an aldehyde-based compound as the second raw material of the coating layer, since the wood powder is also included in the core layer, the excess of the aldehyde-based compound can be adjusted to promote the cross-linking of the aldehyde-based compound in the coating layer with the first wood powder having a hydroxyl group on the surface in the core layer during the co-extrusion process, thereby improving the interface bonding strength between the core layer and the coating layer. As a preferred embodiment of the present application, the first wood powder is wood powder treated by immersion in an ammonium persulfate solution. The ammonium persulfate is used as a catalyst to promote the cross-linking of the aldehyde-based compound in the coating layer with the first wood powder having a hydroxyl group on the surface in the core layer at the temperature of the co-extrusion process.

[0022] The other components in the first raw material of the core layer are not limited and can be the components and amounts commonly used in the existing wood-plastic boards. As a preferred embodiment of the present application, the recycled resin is a polyethylene recycled resin, and the amount of the recycled resin in the first raw material is 15% to 25%, such as 15%, 18%, 20%, 22%, or 25%. As a preferred embodiment of the present application, the first additives include, by mass fraction, 10 to 15 parts of a filler, such as 10 parts, 12 parts, 14 parts, or 15 parts, which can be calcium powder, silicon powder, or the like; 2 to 5 parts of a lubricant, such as 2 parts, 3 parts, 4 parts, or 5 parts; 0.2 to 0.8 parts of an antioxidant, such as 0.2 parts, 0.4 parts, 0.6 parts, or 0.8 parts; and 0.2 to 0.8 parts of an anti-ultraviolet agent, such as 0.2 parts, 0.4 parts, 0.6 parts, or 0.8 parts. No pigment is needed in the core layer.

[0023] Another object of the present application is to provide a preparation method of the wood-plastic co-extrusion composite board, which comprises the following steps:

[0024] S1. Granulating the first raw material and the second raw material, respectively;

[0025] S2. Feeding the first raw material particles and the second raw material particles into different extruders, respectively, to obtain melts at 120 to 180°C, and combining the two melts in a coating co-extrusion die to form a core layer and a coating layer, respectively.

[0026] The present application has the following beneficial effects:

[0027] 1. The present application provides a wood-plastic co-extrusion composite board, which realizes the improvement of the nail holding force of the board by introducing a material that can swell in water after being broken into the coating layer.

[0028] 2. In an optional embodiment, the present application cross-links the hydroxyl groups on the wood powder in the coating layer by acetalization, which further improves the nail holding force in multiple aspects such as reducing the water absorption of the wood powder and forming a network structure by cross-linking.

[0029] 3. In an optional embodiment, the present application soaks the wood powder in the core layer in an ammonium persulfate solution to promote the cross-linking of the aldehyde-based compound in the coating layer with the wood powder having a hydroxyl group on the surface in the core layer, thereby improving the bonding strength between the core layer and the coating layer. DETAILED DESCRIPTION

[0030] The following is a detailed description of the application and further describes the technical solutions of the application, but the application is not limited to these examples.

[0031] Example 1

[0032] A wood-plastic co-extrusion composite board is prepared by the following steps:

[0033] S1. Crush and grind the recycled polyethylene resin until the particle size is 1 mm. Crush the poplar and pass it through a 30-mesh sieve to obtain wood powder with a particle size of 0.6 mm. According to the mass fraction, 20 parts of recycled polyethylene resin, 50 parts of wood powder, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, and 0.4 parts of ultraviolet resistant agent are batched into an extruder for mixing. After high-speed mixing at 160℃ and 80r / min, low-speed mixing at 10r / min is carried out. Mix for 15 minutes; then extrude at a temperature of 160℃ and a pressure of 20MPa. After extrusion, cut the particles to obtain core layer particles.

[0034] S2. Prepare the core material: Mix the ethylene oxide and propylene oxide copolymer diol, and the polyoxypropylene triol according to a mass ratio of 20:1. Stir while heating to 100℃, then vacuum dehydrate for 4h, and cool to 80℃. Keep the temperature constant for 30min; then add 30% of the mass of the ethylene oxide and propylene oxide copolymer diol of diphenylmethane-4,4-diisocyanate and a small amount of dibutyltin dilaurate, and react for 3h to obtain a prepolymer. Mix the prepolymer, dioctyl phthalate dehydrated by vacuum drying, fumed white carbon black, carbon black, and sodium-based bentonite according to a mass ratio of 110:30:3:7:52. Vacuum for 2h at 35℃; back pressure with high-purity nitrogen, then add a small amount of bis(2-dimethylaminoethyl) ether, 3% of the mass of the prepolymer of KH-560, and 2% of the mass of orthoformic acid trimethyl ester, and mix uniformly; vacuum stir the product for 2h, then extrude into particles with a particle size of 0.6mm, and solidify to obtain the core material.

[0035] Prepare the coating material A1: Mix melamine and formaldehyde according to a molar ratio of 1:2.5, then adjust the pH to 8.5 with a base, heat the solution to 70℃, and stir until the solution becomes clear. Start timing after 30min of incubation to obtain a prepolymer. Mix the above-mentioned core material, sodium dodecyl sulfate, NP-10, and anhydrous ethanol according to a mass ratio of 100:2:0.5:400 and stir uniformly to obtain a mixed system. Add the prepolymer to the mixed system, adjust the pH to 3.0 with an acid, and add sodium chloride when the pH value is stable. Heat to 80℃ and incubate for 2h. After cooling, adjust the pH to neutral with a base, separate the reaction solution by suction filtration to obtain the coating material A1.

[0036] Preparation of the coated layer particles: The high-density polyethylene resin was crushed and ground until the particle size was 1 mm. The poplar wood was crushed and passed through a 30-mesh screen to obtain wood powder with a particle size of 0.6 mm. According to the mass parts, 20 parts of high-density polyethylene resin, 50 parts of wood powder, 40 parts of coating material A1, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, 0.4 parts of anti-ultraviolet agent, 0.9 parts of iron red, and 0.2 parts of carbon black were batched into an extruder for mixing. After high-speed mixing at 80 r / min and 160 °C, low-speed mixing at 10 r / min was performed. The mixing was performed for 15 min. Then, the mixture was extruded at a temperature of 160 °C and a pressure of 20 MPa. After extrusion, the mixture was cut into particles to obtain the coated layer particles.

[0037] S3. The core layer particles were added to the main extruder, and the coated layer particles were added to the auxiliary extruder. The two melts were heated to 180 °C to form a melt that could flow. The two melts met in a coating co-extrusion die to form a core layer and a coated layer, respectively. The core layer and the coated layer passed through a designed flow channel to form a melt embryo with a certain shape. The melt embryo was shaped, cooled, pulled, and cut to obtain a composite board.

[0038] Example 2

[0039] This example is basically the same as Example 1, except that the preparation method of the core material is different.

[0040] In step S2, the core material was prepared as follows: Polyether polyol with an average molecular weight of 3000 was dehydrated at 110 °C under a vacuum of 8.5 kPa for 3 h until no bubbles were present. Then, the temperature was lowered to below 60 °C, and diisocyanate was added. The temperature was then increased to 85 °C, and the mixture was incubated for 2 h. After cooling, the mixture was sealed to obtain component A. Polyether polyol, plasticizer, curing agent, active diluent, and filler were stirred uniformly to obtain component B. Components A and B were mixed uniformly at a mass ratio of 1.5:1. After vacuum degassing, the mixture was extruded into particles with a particle size of 0.6 mm. After curing, the core material was obtained.

[0041] Preparation of coating material A2: Melamine and formaldehyde were mixed at a molar ratio of 1:2.5. The pH of the solution was adjusted to 8.5 with a base. The solution was heated to 70 °C and stirred until the solution became clear. The reaction was timed, and the solution was incubated for 30 min to obtain a prepolymer. The core material, sodium dodecyl sulfate, NP-10, and anhydrous ethanol were mixed at a mass ratio of 100:2:0.5:400 and stirred uniformly to obtain a mixed system. The prepolymer was added dropwise to the mixed system, and the pH was adjusted to 3.0 with an acid. When the pH was stable, sodium chloride was added, and the temperature was increased to 80 °C. The mixture was incubated for 2 h. After cooling, the pH was adjusted to neutral with a base. The reaction solution was separated by suction filtration to obtain coating material A2.

[0042] Preparation of the coated layer particles: The high-density polyethylene resin was ground until the particle size was 1 mm. The poplar wood was ground and passed through a 30-mesh screen to obtain wood powder with a particle size of 0.6 mm. According to parts by mass, 20 parts of the high-density polyethylene resin, 50 parts of the wood powder, 40 parts of the coating material A2, 14 parts of calcium powder, 3 parts of a lubricant, 0.4 parts of an antioxidant, 0.4 parts of an ultraviolet inhibitor, 0.9 parts of iron red, and 0.2 parts of carbon black were batched into an extruder for mixing. After high-speed mixing at 80 r / min and low-speed mixing at 10 r / min at 160 °C for 15 min, the mixture was extruded at a temperature of 160 °C and a pressure of 20 MPa. After extrusion, the mixture was cut into particles to obtain the coated layer particles.

[0043] Example 3

[0044] This example is basically the same as Example 1, except that the wood powder in the coated layer is different.

[0045] In step S2, the poplar wood was ground and passed through a 30-mesh screen to obtain wood powder with a particle size of 0.6 mm. The wood powder was dried at 105 °C until the weight was constant, then added to dimethyl sulfoxide for swelling. Then, the modified agent phthalic anhydride and the catalyst p-dimethylaminopyridine were added, and the mixture was reacted at 70 °C for 3 h. After that, the esterified modified wood powder was obtained by precipitation with acetone.

[0046] The same mass of the esterified modified wood powder was used to replace the wood powder.

[0047] Example 4

[0048] This example is basically the same as Example 1, except that the wood powder in the coated layer is different.

[0049] In step S2, the poplar wood was ground and passed through a 30-mesh screen to obtain wood powder with a particle size of 0.6 mm. The impregnation solution was prepared, in which the concentration of glyoxal was 20% and the concentration of ammonium persulfate was 2%. The wood powder was dried at 105 °C until the weight was constant, then added to the impregnation solution for vacuum impregnation for 30 min at a vacuum degree of 0.1 bar. After that, the etherified modified wood powder was obtained by curing at 120 °C for 4 h.

[0050] The same mass of the etherified modified wood powder was used to replace the wood powder.

[0051] Example 5

[0052] This example is basically the same as Example 1, except that the wood powder was added in the step of preparing the coating material A1.

[0053] Step S2: Preparation of coating material A1: melamine and formaldehyde were mixed in a molar ratio of 1:2.5, and the pH was adjusted to 8.5 with a base. The solution was warmed to 70°C and stirred until the solution became clear, and then the reaction was timed. The solution was kept at 70°C for 30 min to obtain a prepolymer. The core material, sodium dodecyl sulfate, NP-10, and anhydrous ethanol were mixed in a mass ratio of 100:2:0.5:400 and stirred uniformly to obtain a mixed system. The prepolymer was added dropwise to the mixed system, and the pH was adjusted to 3.0 with an acid. When the pH was stable, sodium chloride was added, and the temperature was raised to 80°C. The reaction was kept at 80°C for 2 h.

[0054] The temperature was reduced to 60°C, and then wood powder that was crushed to 0.6 mm and dried and 2% ammonium persulfate were added. After stirring for 10 min, the pH was adjusted to 3.5 with an acid, and the reaction was kept at 60°C for 7 h.

[0055] After cooling, the pH was adjusted to neutral with a base. The reaction solution was separated by suction filtration to obtain a mixture of coating material A1 and wood powder.

[0056] Preparation of coated particles: high-density polyethylene resin was crushed and ground until the particle size was 1 mm. According to the mass parts, 20 parts of high-density polyethylene resin, 90 parts of the mixture of coating material A1 and wood powder, 14 parts of calcium powder, 3 parts of a lubricant, 0.4 parts of an antioxidant, 0.4 parts of an ultraviolet-resistant agent, 0.9 parts of iron red, and 0.2 parts of carbon black were added to an extruder in batches for mixing. After high-speed mixing at 80 r / min and low-speed mixing at 10 r / min at 160°C for 15 min, the mixture was extruded at a temperature of 160°C and a pressure of 20 MPa. The extruded product was cut into particles to obtain coated particles.

[0057] Example 6

[0058] This example is basically the same as Example 5, except that:

[0059] An impregnation solution was prepared, in which the concentration of glyoxal was 20%, and the concentration of ammonium persulfate was 2%.

[0060] Step S2: Preparation of coating material A1: melamine and formaldehyde were mixed in a molar ratio of 1:2.5, and the pH was adjusted to 8.5 with a base. The solution was warmed to 70°C and stirred until the solution became clear, and then the reaction was timed. The solution was kept at 70°C for 30 min to obtain a prepolymer. The core material, sodium dodecyl sulfate, NP-10, and anhydrous ethanol were mixed in a mass ratio of 100:2:0.5:400 and stirred uniformly to obtain a mixed system. The prepolymer was added dropwise to the mixed system, and the pH was adjusted to 3.0 with an acid. When the pH was stable, sodium chloride was added, and the temperature was raised to 80°C. The reaction was kept at 80°C for 2 h.

[0061] The temperature was lowered to 60°C, then the wood powder which was crushed to 0.6mm and dried, the impregnation solution was added, after stirring for 10 minutes, the pH was adjusted to 3.5, and the reaction was carried out at 60°C for 7h.

[0062] After cooling, the pH was adjusted to neutral with alkali, and the reaction solution was separated by suction filtration to obtain a mixture of coating material A1 and wood powder.

[0063] Example 7

[0064] This example is basically the same as Example 1, the only difference is that the excess of glyoxal in the coating layer.

[0065] In step S2, the coating layer particles were prepared: the high-density polyethylene resin was crushed and ground until the particle size was 1mm.

[0066] The poplar was crushed and passed through a 30-mesh sieve to obtain wood powder with a particle size of 0.6mm. The impregnation solution was prepared, the concentration of glyoxal in the impregnation solution was 20%, and the concentration of ammonium persulfate was 2%. After drying the wood powder to a constant weight at 105°C, it was added to the impregnation solution and vacuum impregnated for 30 minutes at a vacuum degree of 0.1bar. After impregnation, it was taken out and cured at 120°C for 4h to obtain etherified modified wood powder.

[0067] According to the mass fraction, 20 parts of high-density polyethylene resin, 50 parts of etherified modified wood powder, 10 parts of glyoxal, 40 parts of coating material A1, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, 0.4 parts of anti-ultraviolet agent, 0.9 parts of iron red, and 0.2 parts of carbon black were batched into an extruder for mixing, mixed at a high speed of 80r / min at 160°C, then switched to a low speed of 10r / min, and mixed for 15 minutes; then extruded at a temperature of 160°C and a pressure of 20MPa, and after extrusion, the particles were cut to obtain the coating layer particles.

[0068] Example 8

[0069] This example is basically the same as Example 1, the only difference is that the excess of glyoxal in the coating layer, and the wood powder in the core layer is treated with ammonium persulfate solution.

[0070] In step S1, the recycled polyethylene resin was crushed and ground until the particle size was 1mm. The poplar was crushed and passed through a 30-mesh sieve to obtain wood powder with a particle size of 0.6mm; a 2% ammonium persulfate solution was prepared. After drying the wood powder to a constant weight at 105°C, it was added to the ammonium persulfate solution and vacuum impregnated for 30 minutes at a vacuum degree of 0.1bar.

[0071] According to mass parts, 20 parts of recycled polyethylene resin, 50 parts of impregnated wood powder, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, 0.4 parts of anti-ultraviolet agent are batched into an extruder for mixing, high-speed mixing at 80 r / min and then low-speed mixing at 10 r / min after 160 ℃, mixing for 15 min; then extruding at a temperature of 160 ℃ and a pressure of 20 MPa, and cutting the particles after extruding to obtain core layer particles.

[0072] In step S2, the cladding layer particles are prepared: the high-density polyethylene resin is crushed and ground until the particle size is 1 mm. The poplar is crushed and passed through a 30-mesh sieve to obtain wood powder with a particle size of 0.6 mm. The impregnation solution is prepared, and the concentration of glyoxal in the impregnation solution is 20%, and the concentration of ammonium persulfate is 2%. After drying the wood powder to a constant weight at 105 ℃, it is added to the impregnation solution for vacuum impregnation for 30 min at a vacuum degree of 0.1 bar. After impregnation, it is taken out and cured at 120 ℃ for 4 h to obtain etherified modified wood powder.

[0073] According to mass parts, 20 parts of high-density polyethylene resin, 50 parts of etherified modified wood powder, 10 parts of glyoxal, 40 parts of cladding material A1, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, 0.4 parts of anti-ultraviolet agent, 0.9 parts of iron red, and 0.2 parts of carbon black are batched into an extruder for mixing, high-speed mixing at 80 r / min and then low-speed mixing at 10 r / min after 160 ℃, mixing for 15 min; then extruding at a temperature of 160 ℃ and a pressure of 20 MPa, and cutting the particles after extruding to obtain cladding layer particles.

[0074] Example 9

[0075] This example is basically the same as example 1, and the only difference is that the cladding material A1 is also included in the core layer.

[0076] In step S1, according to mass parts, 20 parts of recycled polyethylene resin, 50 parts of wood powder, 40 parts of cladding material A1, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, and 0.4 parts of anti-ultraviolet agent are batched into an extruder for mixing, high-speed mixing at 80 r / min and then low-speed mixing at 10 r / min after 160 ℃, mixing for 15 min; then extruding at a temperature of 160 ℃ and a pressure of 20 MPa, and cutting the particles after extruding to obtain core layer particles.

[0077] Example 10

[0078] This example is basically the same as example 1, and the only difference is that:

[0079] In step S1, 22.5 parts of recycled polyethylene resin, 55 parts of wood powder, 15 parts of calcium powder, 2 parts of lubricant, 0.6 parts of antioxidant, and 0.6 parts of anti-ultraviolet agent are batched into an extruder for mixing at 150°C at a high speed of 60 r / min, and then at a low speed of 8 r / min for 20 min. Then, extrusion is carried out at a temperature of 150°C and a pressure of 15 MPa, and the extruded product is cut into particles to obtain core layer particles.

[0080] In step S2, 22.5 parts of high-density polyethylene resin, 55 parts of wood powder, 55 parts of coating material A1, 15 parts of calcium powder, 2 parts of lubricant, 0.6 parts of antioxidant, 0.6 parts of anti-ultraviolet agent, 1 part of iron red, and 0.5 part of carbon black are batched into an extruder for mixing at 150°C at a high speed of 60 r / min, and then at a low speed of 8 r / min for 20 min. Then, extrusion is carried out at a temperature of 150°C and a pressure of 15 MPa, and the extruded product is cut into particles to obtain coating layer particles.

[0081] In step S3, the core layer particles are added to the main extruder, and the coating layer particles are added to the auxiliary extruder. The two kinds of melt are heated at a temperature of 160°C to form a melt that can flow. The two kinds of melt meet in a coating co-extrusion die to form a core layer and a coating layer, respectively. The core layer and the coating layer pass through a designed flow channel to form a melt embryo with a certain shape. The melt embryo is shaped, cooled, pulled, and cut to obtain a composite board.

[0082] Comparative Example 1

[0083] This comparative example is basically the same as Example 1, except that in step S2, the coating material A1 is not contained.

[0084] In step S2, the coating layer particles are prepared: 20 parts of high-density polyethylene resin, 50 parts of wood powder, 14 parts of calcium powder, 3 parts of lubricant, 0.4 parts of antioxidant, 0.4 parts of anti-ultraviolet agent, 0.9 parts of iron red, and 0.2 parts of carbon black are batched into an extruder for mixing at 160°C at a high speed of 80 r / min, and then at a low speed of 10 r / min for 15 min. Then, extrusion is carried out at a temperature of 160°C and a pressure of 20 MPa, and the extruded product is cut into particles to obtain coating layer particles.

[0085] Comparative Example 2

[0086] This comparative example is basically the same as Example 1, except that in step S2, the coating material A1 is replaced by a mixture of core material and melamine resin.

[0087] Grip strength detection

[0088] The detection was performed according to the provisions of 4.21 in GB / T 17657-2013 Wood-based panels and veneered wood-based panels-Determination of formaldehyde content, and the detection results are shown in Table 1.

[0089] Bond strength detection

[0090] The detection was performed according to the provisions of 4.20 in GB / T 17657-2013 Wood-based panels and veneered wood-based panels-Determination of formaldehyde content, and the detection results are shown in Table 1.

[0091] Table 1.

[0092]

[0093] As shown in Table 1, through the comparison of Example 1 and Comparative Examples 1 and 2, it can be seen that the addition of the coating material with the water-swelling polyether polyurethane as the core material in the coating layer can effectively improve the nail holding force; and if no coating is performed, the board deformation and the nail holding force will be greatly reduced due to the strong water absorption of the core material. Through the comparison of Example 1 and Examples 3-6, it can be seen that the hydrophobic modification of the wood powder can improve the nail holding force, and the etherification modification and the etherification modification of the free aldehyde in the coating material are better. In addition, although the addition of the coating material in the coating layer will cause the reduction of the bonding strength between the core layer and the coating layer, through the comparison of Example 4 and Examples 7-8, it can be seen that the use of the excess glyoxal in the coating layer and the wood powder treated by the ammonium persulfate soaking in the core layer can avoid this problem and improve the bonding strength between the core layer and the coating layer.

[0094] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or use similar ways to replace, but will not deviate from the spirit of the present application or exceed the scope defined by the appended claims.

Claims

1. A wood-plastic co-extrusion composite board, comprising a core layer and a cladding layer, the core layer is made of a first raw material comprising recycled resin, first wood powder and first additives, and the cladding layer is made of a second raw material comprising virgin resin, second wood powder and second additives; characterized in that: the first wood powder is wood powder treated by immersion in an ammonium persulfate solution; the second raw material further comprises a coating material with polyurethane containing ethylene ether segments as core material and melamine resin as wall material, and an aldehyde compound; the first raw material further comprises the coating material; in the second raw material, the mass of the coating material is 50%-100% of the mass of the second wood powder; the second wood powder is hydrophobically modified wood powder; the hydrophobically modified wood powder is obtained by reacting the hydroxyl groups on the surface of the wood powder into ether bonds; the hydroxyl groups on the surface of the wood powder are reacted into ether bonds by free aldehyde in the coating material; the first and second additives each independently comprise, by mass, 10-15 parts of filler, 2-5 parts of lubricant, 0.2-0.8 parts of antioxidant, and 0.2-0.8 parts of anti-ultraviolet agent; the second additive further comprises 1-1.5 parts of pigment; comprising the following steps: S1. granulating the first and second raw materials respectively; S2. feeding the first and second raw material particles into different extruders respectively, obtaining melt at 120-180℃, and the two melts meet in a co-extrusion die head to form the core layer and the cladding layer respectively. 2.The wood-plastic co-extrusion composite board according to claim 1, wherein the wood powder treated by immersion in an ammonium persulfate solution is wood powder treated by immersion in an ammonium persulfate solution at a concentration of 0.5%-1%. 3.The wood-plastic co-extrusion composite board according to claim 1, wherein the hydrophobically modified wood powder is obtained by reacting the hydroxyl groups on the surface of the wood powder into ether bonds through the following steps: S1. preparing a solution of 0.5%-1% ammonium persulfate; S2. immersing the wood powder in the solution of step S1 for 1-2 hours; S3. washing the wood powder with deionized water; S4. drying the wood powder; S5. adding the wood powder of step S4 to a solution of 0.5%-1% sodium borohydride; S6. stirring the solution of step S5 for 1-2 hours; S7. washing the wood powder with deionized water; and S8. drying the wood powder. 4.The wood-plastic co-extrusion composite board according to claim 1, wherein the aldehyde compound is formaldehyde.

2. The wood-plastic co-extrusion composite board according to claim 1, characterized in that: 5.The wood-plastic co-extrusion composite board according to claim 1, wherein the coating material is prepared by the following steps: S1. preparing a solution of 0.5%-1% ammonium persulfate; S2. immersing the wood powder in the solution of step S1 for 1-2 hours; S3. washing the wood powder with deionized water; S4. drying the wood powder; S5. adding the wood powder of step S4 to a solution of 0.5%-1% sodium borohydride; S6. stirring the solution of step S5 for 1-2 hours; S7. washing the wood powder with deionized water; and S8. drying the wood powder.

3. The wood-plastic co-extrusion composite board according to claim 1, characterized in that: ​ 4. The wood-plastic co-extrusion composite board according to claim 3, characterized in that: ​ 5. The wood-plastic co-extrusion composite board according to claim 4, characterized in that: ​ 6. The wood-plastic co-extrusion composite board according to claim 1, characterized in that: ​ 7. A method for manufacturing the wood-plastic co-extrusion composite board according to any one of claims 1-6, characterized in that: ​ ​ ​

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