Strength-thermal insulation-decorative integrated sandwich structure wood composite material and preparation method thereof

Abstract

The application discloses a strength-heat preservation-decoration integrated laminated structure wood composite material and a preparation method thereof, and comprises at least two pieces of outer layer materials and an intermediate layer; the outer layer material is wood containing nanocellulose and water-based resin; and the intermediate layer is a blend of cork particles and polylactic acid. The nanocellulose and the water-based resin are dissolved in an alkaline solution to obtain a mixed solution, the mixed solution is treated by impregnation into the wood, and the outer layer material is obtained after hot pressing; the cork particles and the polylactic acid are blended and hot-pressed to obtain the intermediate layer; the two pieces of outer layer materials and the piece of intermediate layer are cold-pressed and glued together to obtain a three-layer composite material of outer layer material-intermediate layer-outer layer material; and a customized pattern is directly printed on the surface of the three-layer composite material by using a digital jet printing technology, so that the strength-heat preservation-decoration integrated laminated structure wood composite material is prepared. The application solves the problem of lack of multifunctional integrated wood materials in fabricated wood structure buildings.

Description

Technical Field

[0001] This invention relates to the field of prefabricated wood structure technology, specifically to a sandwich structure wood composite material integrating strength, insulation, and decoration, and its preparation method. Background Technology

[0002] Wood is a green, environmentally friendly, renewable, and biodegradable material widely used in the construction and home furnishing industries. Especially in recent years, prefabricated wood-structure buildings have seen a surge in demand, creating a growing need for multi-functional integrated building units that combine structure, insulation, and decoration. However, such materials are still in short supply. While wood itself has a certain degree of low thermal conductivity, its direct application cannot meet the insulation performance requirements of buildings. In prefabricated buildings, fossilized polymers, such as polyurethane foam and polystyrene foam, are commonly used as wall insulation materials. However, these materials have drawbacks such as poor environmental friendliness and flammability, which do not align with the concept of green and sustainable development. Furthermore, high-quality wood is currently scarce. The main type of wood meeting the requirements for wood-structure buildings is pine, which is primarily imported. While my country has abundant fast-growing tree species such as poplar, eucalyptus, and fir, these suffer from low mechanical strength, poor structural stability, and limited surface patterns, making them unsuitable for direct use as structural or surface decoration materials, resulting in very low added value. Therefore, using abundant and renewable green resources to construct wood materials that integrate strength, insulation, and decoration is of positive significance for promoting sustainable economic and social development and improving the application efficiency of prefabricated buildings. Summary of the Invention

[0003] In view of the above-mentioned prior art, the purpose of this invention is to provide a sandwich-structured wood composite material integrating strength, thermal insulation, and decoration, and its preparation method. This invention prepares a three-layered wood composite material with an inner thermal insulation layer, two outer reinforcing layers, and a digitally patterned decorative outer surface, solving the problem of the scarcity of multifunctional integrated wood materials in prefabricated wood structure buildings.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A first aspect of the present invention provides a sandwich structure wood composite material integrating strength, heat insulation and decoration, comprising at least two outer layers and an intermediate sandwich layer disposed between the outer layers;

[0006] The outer layer material is wood containing nanocellulose and water-based resin; the thickness of the outer layer material is 1-100 mm.

[0007] The intermediate interlayer is a blend of cork particles and polylactic acid; the thickness of the intermediate interlayer is 2-200 mm.

[0008] Preferably, a customized pattern is printed on the surface of the outer layer material;

[0009] Preferably, the cork particles have a particle size of 10-500 mesh; the cork particles are derived from oak bark;

[0010] Preferably, the polylactic acid has a particle size of 10 to 100 mesh.

[0011] A second aspect of the present invention provides a method for preparing a sandwich-structured wood composite material integrating strength, thermal insulation, and decoration, comprising the following steps:

[0012] (1) Preparation of outer layer material: Nanocellulose and aqueous resin are dissolved in an alkaline solution to obtain a mixture. The mixture is impregnated into the wood and then hot-pressed to obtain the outer layer material.

[0013] (2) Preparation of intermediate sandwich layer: Cork particles are blended with polylactic acid and hot-pressed to obtain intermediate sandwich layer;

[0014] (3) Bonding: Two outer layer materials obtained in step (1) and one intermediate interlayer obtained in step (2) are bonded together by cold pressing to obtain a three-layer composite material of outer layer material-intermediate interlayer-outer layer material;

[0015] (4) Surface digital printing: Customized patterns are printed directly on the surface of the three-layer composite material obtained in step (3) using digital inkjet printing technology, thereby producing a sandwich structure wood composite material that integrates strength, heat preservation and decoration.

[0016] Preferably, in step (1), the mass concentration of the aqueous resin in the mixture is 10-50%; the amount of nanocellulose added is 0.1-2% of the mass of the aqueous resin; and the pH of the alkaline solution is 8-10.

[0017] Preferably, the aqueous resin is selected from styrene-acrylic acid copolymer resin, phenolic resin, and melamine resin with a molecular weight of less than 10,000;

[0018] Preferably, the mixture contains a curing agent, and the content of the curing agent accounts for 5-20% of the mass of the water-based resin;

[0019] Preferably, the curing agent is a curing agent that is compatible with the water-based resin, such as aziridine curing agent, ammonium chloride curing agent, etc.

[0020] Aqueous resins can be dissolved in alkaline solutions by stirring and heating, ensuring that all the aqueous resins are dissolved in the alkaline solution.

[0021] The timber can be of any tree species and any size, and is especially suitable for fast-growing tree species, such as poplar, eucalyptus, and fir.

[0022] Preferably, the nanocellulose is cellulose with carboxyl functional groups, an aspect ratio of 100 to 1000, and a diameter of 1 to 100 nm.

[0023] Preferably, in step (1), the impregnation treatment is performed by vacuuming at 0.01-0.09 MPa for 0.1-10 hours, followed by pressurizing at 0.1-1.5 MPa for 0.1-10 hours.

[0024] The hot pressing is performed at 5-10 MPa and 50-70°C for 0.1-10 hours, followed by heating to 70-90°C for 0.1-10 hours, and finally heating to 90-120°C until the moisture content of the outer layer material is less than 10%.

[0025] Preferably, in step (2), the mass of polylactic acid accounts for 10-40% of the total mass of polylactic acid and cork particles; the intermediate interlayer also contains a mixture of nanocellulose and glycerol; the amount of nanocellulose and glycerol mixture added accounts for 1-10% of the total mass of polylactic acid and cork particles, and the mass ratio of nanocellulose to glycerol is 1:5.

[0026] Preferably, in step (2), the hot pressing pressure is 2 to 10 MPa, the hot pressing temperature is 180°C, and the hot pressing time is 2 to 10 min / mm.

[0027] The hot pressing time is determined based on the thickness of the intermediate interlayer. For an intermediate interlayer with a thickness of 1 mm, the hot pressing time is 2 to 10 minutes; and so on.

[0028] Preferably, in step (3), the cold pressing bonding is as follows: applying polyurethane structural adhesive, and then assembling the outer layer material, the middle interlayer, and the outer layer material along the grain direction of the wood to form an interlayer structure, and pressing it at 1~100Mpa and room temperature for ≥24h.

[0029] Preferably, the amount of polyurethane structural adhesive is 300 g / m². 2 .

[0030] Preferably, in step (4), the customized printing pattern involves spraying UV ink as a primer onto the surface of the three-layer composite material. While the ink is being sprayed from the printhead according to the customized pattern, a UV light lamp cures the ink layer printed on the surface. After printing, two layers of topcoat are applied, with a total coating weight of 80 g / m². -3 .

[0031] A third aspect of the present invention provides the application of a sandwich structure wood composite material integrating strength, thermal insulation, and decoration in prefabricated wood structure buildings and home furnishings.

[0032] The beneficial effects of this invention are:

[0033] (1) The three-layer wood composite material prepared by the present invention, which has sandwich insulation, two outer outer layer reinforcement and digital pattern decoration on the outer surface, solves the problem of the scarcity of wood materials that integrate three functions in prefabricated wood structure buildings.

[0034] (2) In this invention, water-based resin and nanocellulose are introduced into wood. During curing, they are further cross-linked and combined with the hydroxyl groups of wood to form a whole. The dense outer surface of wood is obtained by hot pressing and curing, which reduces the roughness of the rough wood surface and meets the requirements of digital inkjet printing.

[0035] (3) The intermediate insulation interlayer of the present invention has certain strength and toughness, and can be cold-pressed and glued with the outer layer material to combine the multi-layer material together. The wood layer of the present invention organically combines the reinforcing toughness effect of nanocellulose, the filling and reinforcing effect of resin, the characteristics of sealing pores and firmly bonding patterns, and also gives full play to the advantage of hot pressing to make the wood surface flat and smooth. Ultimately, the wood layer can perfectly integrate the strength and stability required by structural wood and the pattern customization requirements required by decorative materials. Attached Figure Description

[0036] Figure 1 Photograph of the strength-insulation-decorative integrated material with surface-printed plain floral patterns prepared in Example 1;

[0037] Figure 2 Photograph of the strength-insulation-decorative integrated material for surface printing watercolor patterns prepared in Example 2. Detailed Implementation

[0038] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0039] As introduced in the background section, fast-growing tree species such as poplar, eucalyptus, and fir have bottleneck problems such as low mechanical strength, poor structural stability, and limited surface patterns, making them difficult to use directly as structural materials and surface decoration materials, resulting in very low added value.

[0040] Based on this, the purpose of this invention is to provide a sandwich-structured wood composite material integrating strength, thermal insulation, and decoration, and its preparation method. The sandwich-structured wood composite material includes at least two outer layers and an intermediate layer disposed between the outer layers. The outer layer material is wood containing nanocellulose and water-based resin; the water-based resin, through its functional groups, dissolves in alkali solution and achieves self-curing and cross-linking through a curing agent; the nanocellulose, through its high aspect ratio and surface functional groups, entangles and cross-links within the resin matrix, reinforcing the resin; when these are introduced into the wood as a whole, they can further cross-link and composite with the hydroxyl groups of the wood during curing; in the heat curing stage, hot pressing is introduced, which both transfers heat to cure the resin and densifies the wood surface, reducing the surface roughness from tens of micrometers to meet the roughness requirements of a few micrometers for direct digital inkjet printing. Simultaneously, the resin fills and seals the wood surface, making the wood surface structure more compact.

[0041] The middle interlayer is a blend of cork particles and polylactic acid. The cork particles are synthesized into a whole block layer with the help of polylactic acid melt adhesive. Glycerin promotes the uniform mixing of cork particles, nanocellulose and polylactic acid particles. Nanocellulose promotes the interfacial fusion of cork and polylactic acid and strengthens the tough polylactic acid adhesive layer, thereby obtaining a heat insulation layer with a certain bonding strength.

[0042] The three-layer adhesive composite sandwich structure, forming a strength-insulation-decorative integrated wood-based composite material, eliminates the need for sanding and puttying required for digital printing on ordinary wood surfaces. This simplifies the process, reduces printing costs, and improves efficiency. Furthermore, the main component of the digital printing ink droplets is acrylic resin, which has strong polarity, similar to the polarity of the resin filling the wood surface and the nanocellulose. This results in a strong bond between the digitally printed pattern and the wood surface, exhibiting high adhesion. Therefore, the wood layer of this invention organically combines the reinforcing toughness effect of nanocellulose, the filling and strengthening properties of resin, the ability to close pores, and the strong bonding of patterns. It also leverages the advantage of hot pressing to create a smooth and flat wood surface, ultimately enabling the wood layer to perfectly integrate the strength and stability required for structural wood with the customized patterns required for decorative materials.

[0043] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0044] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0045] Example 1: Preparation of a sandwich-structured wood composite material integrating strength, thermal insulation, and decoration:

[0046] 1) Preparation of outer layer material: First, prepare a triethylamine aqueous solution with pH=10. Then, add styrene-acrylic acid copolymer resin (acrylic resin) with a molecular weight of 1700 to the alkaline liquid and heat and stir at 70℃ to dissolve it, obtaining an acrylic resin alkaline solution with a solid content of 25wt%. Then, after cooling the liquid to room temperature, add carboxylated nanocellulose (aspect ratio 1000, diameter 10nm) and 10% aziridine curing agent at a mass ratio of 1wt% of the acrylic resin, and stir evenly to obtain an acrylic resin solution. Vacuum at 0.09MPa for 1h, then pressurize at 1.1MPa for 1h to impregnate poplar wood with the acrylic resin solution to a thickness of 10mm. Under hot pressing pressure of 10MPa, first heat to 60℃ and hold for 1h, then heat to 80℃ and hold for 5h, and finally dry the moisture content of the outer layer material to below 10% at 110℃ to obtain the outer wood reinforcement layer of the sandwich structure.

[0047] 2) Preparation of the intermediate interlayer: 100-mesh cork oak particles and 40-mesh polylactic acid (PLA) particles are mixed at a mass ratio of 10:2. Then, a mixture of nanocellulose and glycerol (mass ratio of 1:5) accounting for 10 wt% of the total mass of the two mixtures is added and stirred evenly. The blend and mold are then placed in a hot press and hot-pressed at 180°C for 200 min under a pressure of 10 MPa. After cooling to room temperature, a cork insulation layer with a thickness of 50 mm is obtained.

[0048] 3) Three-layer structural bonding: The outer wood reinforcement layer obtained in step 1) is coated with polyurethane structural adhesive on one side, with an adhesive application rate of 300g / m². 2 Then, two outer wood reinforcement layers and one middle interlayer are assembled along the grain of the wood to form an interlayer structure. The assembled layers are then pressed for 24 hours under 5MPa pressure and room temperature to obtain a three-layer structural strength-insulation interlayer wood composite material consisting of outer material, middle interlayer, and outer material.

[0049] 4) Surface digital printing: First, white UV ink is sprayed onto the surface of the three-layer structural strength-insulation interlayer wood composite material obtained in step 3) as a primer. The coating amount of UV ink is 40g / m². 2Then, the pre-designed JPEG format floral pattern is imported into the digital printer service software "Fiery XF Client," and the image is converted to digital format. The interface is then designed, and inkjet printing begins. During printing, the conveyor roller transports the three-layer structural strength-insulation interlayer wood composite material, while the inkjet head moves back and forth in a straight line along a trajectory perpendicular to the direction of movement of the outer layer material. Simultaneously, a UV light lamp cures the ink layer printed on the outer layer material surface. After printing, two coats of UV-cured acrylic resin varnish (total coating weight 80g / m²) are applied using a coating machine. 3 This process reinforces the protective layer while improving surface wear resistance, thus completing the entire digital printing process and producing a poplar composite material that integrates strength, insulation, and decoration (see...). Figure 1 ).

[0050] Tests showed that the material has an elastic modulus of 13600 MPa, a static bending strength of 98 MPa, and an impact toughness of 67 KJ / m. 2 The tensile strength is 89 MPa, exceeding the strength grade TCT40 index value in GB 50005-2017 "Standard for Design of Timber Structures"; the thermal conductivity is 0.072 W / (m·K), and the water absorption rate is 27%; the surface has a clear plain floral pattern, the abrasion value is only 80 mg / 100 r, the surface stain resistance is level 5, the adhesion reaches level 2, the gloss is 6.5, and the formaldehyde emission is 0.08 mg / m³. 3 The lightfastness reaches level 4. Overall performance meets the requirements for use in prefabricated timber structure buildings.

[0051] Example 2: Preparation of a sandwich-structured wood composite material integrating strength, thermal insulation, and decoration

[0052] 1) Preparation of outer layer material: First, prepare an aqueous solution of phenolic resin with pH=10, molecular weight of 400, and solid content of 20wt%. Then, add 1wt% carboxylated nanocellulose (aspect ratio 800, diameter 20nm) and 10wt% ammonium chloride curing agent to the solution, and stir evenly to obtain a composite resin solution. Vacuum at 0.08MPa for 0.5h, then pressurize at 1.0MPa for 0.5h to impregnate poplar wood with the composite resin solution to a thickness of 5mm. Under a hot-pressing pressure of 15MPa, first heat to 60℃ and hold for 1h, then heat to 80℃ and hold for 2h, and finally dry the material at 110℃ to a moisture content of less than 10wt%, thus obtaining the outer wood reinforcement layer of the sandwich structure.

[0053] 2) Preparation of the intermediate interlayer: 50-mesh cork oak particles and 50-mesh polylactic acid (PLA) particles are mixed at a mass ratio of 10:3. Then, a mixture of nanocellulose and glycerol (mass ratio of 1:5) accounting for 8 wt% of the total mass of the two mixtures is added and stirred evenly. The blend and mold are then placed in a hot press and hot-pressed at 180°C for 180 min under a pressure of 12 MPa. After cooling to room temperature, a cork insulation layer with a thickness of 60 mm is obtained.

[0054] 3) Three-layer structural bonding: The outer wood reinforcement layer obtained in step 1) is coated with polyurethane structural adhesive on one side, with an adhesive application rate of 300g / m². 2 Then, two outer wood reinforcement layers and one middle interlayer are assembled along the grain of the wood to form an interlayer structure. The assembled layers are then pressed for 30 hours under 8MPa pressure and room temperature to obtain a three-layer structure of strength-insulation interlayer wood composite material consisting of outer material, middle interlayer, and outer material.

[0055] 4) Surface digital printing: First, spray white UV ink onto the surface of the outer layer material obtained in step 3) as a primer, with a coating amount of 40g / m². 2 Then, the pre-designed JPEG format watercolor pattern is imported into the digital printer service software "Fiery XF Client," and the image is converted to digital format. The interface is then designed, and inkjet printing begins. During printing, the conveyor roller transports the three-layer structural strength-insulation interlayer wood composite material, while the inkjet head moves back and forth in a straight line along a trajectory perpendicular to the direction of movement of the outer layer material. Simultaneously, a UV light lamp cures the ink layer printed on the poplar surface. After printing, two coats of UV-cured acrylic resin varnish (total coating weight 80g / m²) are applied using a coating machine. 3 This process reinforces the protective layer while improving surface wear resistance, thus completing the entire digital printing process and producing a poplar composite material that integrates strength, insulation, and decoration (see...). Figure 2 ).

[0056] Tests showed that the material has an elastic modulus of 13,300 MPa, a static bending strength of 97 MPa, and an impact toughness of 75 KJ / m. 2 The tensile strength is 82 MPa, exceeding the strength grade TCT40 index value in GB 50005-2017 "Standard for Design of Timber Structures"; the thermal conductivity is 0.056 W / (m·K), and the water absorption rate is 8%; the surface has a clear watercolor pattern, the abrasion value is only 80 mg / 100 r, the surface stain resistance is level 5, the adhesion reaches level 2, the gloss is 6.5, and the formaldehyde emission is 0.08 mg / m³. 3The lightfastness reaches level 4. Overall performance meets the requirements for use in prefabricated timber structure buildings.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A sandwich-structure wood composite material integrating strength, thermal insulation, and decoration, characterized in that, Prepared by the following method: (1) Preparation of outer layer material: Nanocellulose and aqueous resin are dissolved in an alkaline solution to obtain a mixture. The mixture is impregnated into the wood and then hot-pressed to obtain the outer layer material. The mass concentration of aqueous resin in the mixture is 10-50%. The amount of nanocellulose added is 0.1-2% of the mass of aqueous resin. The pH of the alkaline solution is 8-10. The aqueous resin is selected from phenolic resin, melamine resin or styrene-acrylic copolymer resin with a molecular weight of less than 10,000. The nanocellulose is cellulose with carboxyl functional groups, an aspect ratio of 100-1000, and a diameter of 1-100 nm. The impregnation treatment is vacuumed at 0.01-0.09 MPa for 0.1-10 h, and then pressurized at 0.1-1.5 MPa for 0.1-10 h. The hot pressing is performed under a pressure of 5~10MPa, first heating at 50℃~70℃ for 0.1~10h, then raising the temperature to 70℃~90℃ and heating for 0.1~10h, and finally heating at 90℃~120℃ until the moisture content of the outer layer material is less than 10%; the thickness of the outer layer material is 1~100mm; the mixture contains a curing agent, and the content of the curing agent accounts for 5~20% of the mass of the water-based resin; (2) Preparation of the intermediate sandwich layer: Cork particles are blended with polylactic acid and hot-pressed to obtain an intermediate sandwich layer; the thickness of the intermediate sandwich layer is 2~200mm; the cork particles are derived from oak bark; the particle size of the cork particles is 10~500 mesh; the particle size of the polylactic acid is 10~100 mesh; the mass of the polylactic acid accounts for 10~40% of the total mass of polylactic acid and cork particles; the intermediate sandwich layer also contains a mixture of nanocellulose and glycerol; the amount of nanocellulose and glycerol mixture added accounts for 1~10% of the total mass of polylactic acid and cork particles, and the mass ratio of nanocellulose to glycerol is 1:5; the hot-pressing pressure is 2~10MPa, the hot-pressing temperature is 180℃, and the hot-pressing time is 2~10min / mm; (3) Adhesion: Two outer layer materials obtained in step (1) and one intermediate interlayer obtained in step (2) are bonded together by cold pressing to obtain a three-layer composite material of outer layer material-intermediate interlayer-outer layer material; the cold pressing is as follows: polyurethane structural adhesive is applied, and then the outer layer material-intermediate interlayer-outer layer material are assembled into an interlayer structure along the grain direction of the wood, and pressed for ≥24h under 1~100MPa and room temperature conditions; (4) Surface digital printing: Customized patterns are printed directly on the surface of the three-layer composite material obtained in step (3) using digital inkjet printing technology, thereby producing a sandwich structure wood composite material that integrates strength, heat preservation and decoration. The customized printing pattern is achieved by spraying UV ink as a primer onto the surface of a three-layer composite material. While the ink is being sprayed from the printhead according to the customized pattern, a UV light irradiation lamp will perform a light curing treatment on the ink layer sprayed on the surface. After printing, apply two coats of topcoat, with a total coating weight of 80 g / m². 3 .

2. The application of the integrated strength-insulation-decoration sandwich structure wood composite material as described in claim 1 in prefabricated wood structure buildings and home furnishings.

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