High-performance australian eucalyptus composite board and preparation method therefor

Abstract

An Australian eucalyptus composite board and a preparation method therefor. Australian eucalyptus wood is used as a raw material, a surface layer material is pretreated, and meanwhile, a specific adhesive is applied to the surface layer material and a core layer material, so that a force can be uniformly distributed on the prepared surface layer structure and core layer structure, the comprehensive performance is obviously improved, the static bending strength of the product can be up to 25 MPa, the screw holding capability of the board surface and the board edge reaches 1200 N or above, moreover, the lowest formaldehyde emission amount of the product is only 0.06 mg / L, and the 24-hour absorption expansion rate is less than 3%.

Description

A high-performance Australian eucalyptus composite board and its preparation method Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to a high-performance Australian eucalyptus composite board and a preparation method thereof. Background Art

[0002] Australian eucalyptus (abbreviated as Australian eucalyptus) has better mechanical strength and corrosion resistance than other varieties of eucalyptus. At the same time, due to its abundant resources, low price, and uniform and beautiful texture, it has been widely introduced in recent years and has begun to be used in the field of decorative and fitting boards.

[0003] However, because eucalyptus is less tough than other woods, its performance when processed into composite boards is lower than that of general composite boards. In addition, since composite boards are often made of sandwich structures made of wood of different sizes, the stress conditions of the surface and the interlayer are uneven, so they are often easily broken. This also leads to the need to use high-strength urea-formaldehyde glue as an adhesive for eucalyptus composite boards, resulting in a higher formaldehyde emission rate for some performance-enhanced eucalyptus composite boards. In addition, eucalyptus wood itself will also release a certain amount of formaldehyde, so the environmental friendliness of such products has been difficult to improve.

[0004] Summary of the Invention

[0005] Based on the defects of the existing technology, the purpose of the present invention is to provide a high-performance Australian eucalyptus composite board. The product uses Australian eucalyptus wood as raw material, pre-treats the surface material, and applies a specific adhesive to the surface material and the core material. The prepared surface structure and core structure are not only uniformly stressed, but also have significantly improved overall performance. The static bending strength of the product can reach up to 25MPa, and the screw holding force of the board surface and board edges reaches more than 1200N. At the same time, the formaldehyde emission of the product is as low as 0.06mg / L, and the 24h absorption expansion rate is less than 3%.

[0006] A high-performance Australian eucalyptus composite board comprises two surface layers and a core layer located between the surface layers; the wood particles in the surface layers have a mesh size of 3 to 12, and the mass content of water-soluble metal salt in the wood particles is 3 to 6 wt%; the mesh size of the wood particles in the core layer is ≤ 2 mesh;

[0007] The surface layer and the core layer contain adhesives, wherein the adhesive of the surface layer contains modified hydrophobic soybean protein; and the adhesive of the core layer contains xanthan gum, with a mass content of ≥25wt%.

[0008] In existing products, composite boards, especially particleboard composite boards, are mainly prepared with wood particles of different sizes to prepare the core layer and the surface layer respectively, and then composited to form a sandwich structure. Compared with raw wood materials, these composite boards are easier to process, have higher strength, and better corrosion and moisture resistance. However, such products require the use of wood with better texture as raw materials. If the Australian eucalyptus wood described in the present invention is used as raw material, the prepared product has poor strength and a high breakage rate during use. Therefore, in the technical solution of the present invention, based on the preparation of the Australian eucalyptus wood particleboard, the inventors add a specific content of water-soluble metal salt to the surface particles. Modified hydrophobic soy protein is introduced as a component in the surface adhesive. Due to the action of water-soluble metal salts, the connection density of wood molecules in the surface wood particles becomes higher. At the same time, this component will react with the modified hydrophobic soy protein in the adhesive to cause secondary modification of the modified hydrophobic soy protein, so that its molecular chain is further spread and tightly connected with the surface fibers of the wood particles and other components of the adhesive. With the cooperation of the adhesive with high xanthan gum content in the core layer, the surface and core layers of the overall product have high uniformity of force, and its strength is significantly improved without using high-strength urea-formaldehyde adhesive.

[0009] Preferably, the water-soluble metal salt is a monovalent inorganic metal halide salt.

[0010] More preferably, the monovalent metal salt is at least one of LiCl, NaCl, KCl, LiBr, NaBr, and KBr.

[0011] It should be noted that the quantitative detection method of the water-soluble metal salt in the surface wood shavings of the present invention can be performed by thermogravimetric method or elemental analysis method. Specifically, in the present invention, after the wood chips are dried and dehydrated, they are calcined by a calcination method to obtain inorganic ash, and the component contents of lithium, sodium and potassium ions in the ash are determined (monovalent metal salts basically do not become complex oxides or composite salts after thermogravimetric pyrolysis at 1000°C, so the content of metal salts can basically be determined by the molar amount of metal ions), and the loading amount of water-soluble metal salts in the actual components can be known. If the actual loading amount of the additionally applied water-soluble metal salts is to be determined (excluding the interference of inorganic salts contained in the original wood), it is necessary to further test the original wood and then compare the raw material results. However, since the ash content of eucalyptus wood is extremely low and the basic ash is calcium salts or oxides (the ash content of the trunk of the wood is generally 0.5-5wt%, and the mass proportion of calcium salts or oxides in the ash reaches more than 50wt%), the water-soluble metal salts contained in the original wood can also be ignored, and it is considered that the water-soluble metal salts in the ash are all additionally applied later.

[0012] Preferably, the mass content of xanthan gum in the adhesive of the core layer is 25 to 40 wt%.

[0013] More preferably, the core layer adhesive comprises a water-dispersible component and a glue component in a mass ratio of (8:2) to (7:3); the water-dispersible component comprises the following components in parts by weight: 15 to 20 parts of polyvinyl alcohol, 35 to 45 parts of xanthan gum, 15 to 20 parts of acetic acid acrylic emulsion, and 10 to 25 parts of soy protein; the glue component comprises a plasticizer and MDI glue in a mass ratio of (9:1) to (8:2).

[0014] Among common formaldehyde-free adhesives, MDI glue as the main component can exert excellent bonding properties, but such products need to be compounded with a certain amount of bio-glue to solve the problems of poor initial adhesion of MDI glue, unformed slabs, and easy clogging. However, when applied to particleboard, especially particleboard made of Australian eucalyptus wood, people generally use the same adhesive to glue the core layer and surface materials, and do not pay attention to the uneven force problem caused by the differences in the size and hot pressing degree of the surface and core layer materials, resulting in the core layer material composed of large-sized particle materials being too strong. However, if the amount of adhesive added to the core layer material is reduced, the bonding uniformity of the core layer material will decrease, and material falling will be likely to occur. Therefore, in order to match the surface wood shavings, the inventor adjusted the adhesive composition of the core layer accordingly, increased the content of xanthan gum, and increased the initial viscosity while improving the compatibility and wettability of the adhesive, and appropriately reduced the continuous viscosity, thereby balancing the strength of the surface and core layers of the product; on the other hand, if the amount of xanthan gum added is too much, exceeding 40wt%, the initial viscosity of the adhesive will increase significantly, the processing difficulty will increase, and the product performance will decline to a certain extent.

[0015] Preferably, the surface adhesive comprises a water-dispersible component and a glue component in a mass ratio of (8:2) to (7:3); the water-dispersible component comprises the following components in parts by weight: 25 to 35 parts of polyvinyl alcohol, 25 to 35 parts of xanthan gum, 25 to 35 parts of acetic acid acrylic emulsion, and 10 to 20 parts of modified hydrophobic soy protein; the glue component comprises a plasticizer and MDI glue in a mass ratio of (9:1) to (8:2).

[0016] Preferably, the modified hydrophobic soy protein is urea-modified soy protein.

[0017] Soy protein was used to prepare adhesives in the early days of the industry. It is not only inexpensive but also has excellent environmental protection. However, this component is not water-resistant and has low strength. It is not easy to compound with other adhesives and has gradually been replaced by urea-formaldehyde adhesives. In the technical solution of the present invention, the inventor modified soy protein with urea and used it as an adhesive component. Because the connecting hydrogen bonds in the high-molecular protein and polymer contained in it are destroyed by urea, the hydrophobic groups inside the overall structure are exposed, and the water resistance is improved. At the same time, it can be combined with other components in the adhesive, such as MDI glue and xanthan gum. Moreover, because the water-soluble metal salts in the surface wood chips will continue to react with the modified soy protein, the bonding effect of the overall adhesive can be significantly improved. In addition, due to the effect of the modified hydrophobic soy protein, the moisture resistance of the surface wood chips can also be improved, and the absorption rate of the overall product is reduced.

[0018] More preferably, the method for preparing the modified hydrophobic soy protein comprises the following steps:

[0019] The soy protein is ground and then dispersed in water, urea is then added and mixed, and the mixture is stirred and reacted at 30-40° C. for 20-30 minutes, and filtered to obtain the modified hydrophobic soy protein; the mass ratio of the soy protein to urea is 1:(0.4-0.6).

[0020] Because urea has a strong tendency to hydrogen bond with protein molecules in soy protein, soy protein modification can be achieved by simply mixing and dispersing the urea and soy protein under relatively mild conditions. However, the degree of modification should be kept low, as this may lead to difficulty or uneven dispersion during adhesive preparation, reducing the effectiveness of the adhesive. It should also be noted that the modified hydrophobic soy protein described herein is not completely hydrophobic and can still disperse to a certain extent in water.

[0021] Another object of the present invention is to provide a method for preparing the high-performance Australian eucalyptus composite board, comprising the following steps:

[0022] (1) Cutting, slicing and drying the Australian eucalyptus wood to obtain primary wood chips;

[0023] (2) screening the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the primary screening is 2 to 3 meshes;

[0024] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 8 to 12 meshes;

[0025] (4) placing 20-40 wt% of surface wood chips into a solution containing a water-soluble metal salt and heating it to 60-80° C. for 24-30 hours, wherein the concentration of the water-soluble metal salt is 0.8-1.2 g / L;

[0026] (5) drying the surface wood chips soaked in step (4), and then mixing with the remaining untreated surface wood chips, applying the surface adhesive after drying, and applying the core adhesive to the core wood chips;

[0027] (6) The core layer shavings and the surface layer shavings after gluing are paved, hot pressed, cured, and sawed in sequence to obtain the high-performance Australian eucalyptus composite board.

[0028] In order to make water-soluble metal salt fully enter the surface wood shavings inside, it is necessary to adopt the mode of heating and soaking to introduce this component, if just introduce with the pattern of traditional sizing, then be difficult to realize ideal doping effect.Simultaneously, this component also can with the modified hydrophobic protein and the xanthan gum effect in the surface adhesive, its molecular structure is fully spread, promote the bonding degree of adhesive component inside and with wood shavings, but because water-soluble metal salt is higher for the hydroxyl coordination trend in the modified hydrophobic soy protein molecule, if all contain water-soluble metal salt in all surface wood shavings, just will cause modified hydrophobic soy protein to spread excessively, overall adhesive hydrophobicity is too strong, finally cause the bonding effect variation of adhesive, the intensity deficiency of product.Therefore, in the preparation method of product of the present invention, need mix with the surface wood shavings after the untreated surface wood shavings of part with the impregnation, after applying adhesive, water-soluble metal salt only can contact with part adhesive and component is modified, and whole presents good bonding effect.

[0029] Preferably, the Australian eucalyptus is Eucalyptus grandiflora, and the ash content is 2-5wt%.

[0030] Preferably, the primary wood chips in step (1) have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm.

[0031] Preferably, the amount of adhesive used in step (5) is 30-40 kg / m 3 .

[0032] More preferably, in step (5), the moisture content of the surface wood chips and the core wood chips after gluing is 8-10 wt%.

[0033] Preferably, the mass ratio of the core layer material to the surface layer material during paving in step (6) is (1-2):1.

[0034] Preferably, the temperature during hot pressing in step (6) is 200-220° C., the speed is 200-220 mm / s, and the applied pressure is 3-4 bar.

[0035] The beneficial effect of the present invention is that the present invention provides a high-performance Australian eucalyptus composite board and a preparation method thereof. The product uses Australian eucalyptus wood as raw material, pre-treats the surface material, and applies a specific adhesive to the surface material and the core material. This can ensure that the prepared surface structure and core structure are not only uniformly stressed, but also significantly improve the overall performance. The static bending strength of the product can reach up to 25MPa, and the screw holding force of the board surface and board edge reaches more than 1200N. At the same time, the formaldehyde emission of the product is as low as 0.06mg / L, and the 24h absorption expansion rate is less than 3%. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples. Its purpose is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all conventional common reagents and instruments unless otherwise specified.

[0037] In each embodiment and comparative example,

[0038] The Australian eucalyptus wood is large-leaf eucalyptus produced in Guangxi, and has an ash content of 2.6 wt%;

[0039] The polyvinyl alcohol is a 1999 brand product produced by Wanwei Company;

[0040] The xanthan gum is 9270 product produced by Renqiu High-Tech Chemical;

[0041] The acetic acid acrylic emulsion is DC-7039 produced by Guangzhou Franklin;

[0042] The soy protein is produced by Jiangxi Hengding Food Co., Ltd.

[0043] The DOP plasticizer is a dioctyl ester product produced by Shandong Evonik;

[0044] The DBP plasticizer is a dibutyl ester product produced by Shandong Evonik;

[0045] The MDI glue is CW-20 product produced by Wanhua Chemical.

[0046] In addition, the raw materials used in the examples and comparative examples of the present invention are all common commercially available products, and the same raw materials are used in the parallel experiments in each example and comparative example.

[0047] Example 1

[0048] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention comprises the following steps:

[0049] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0050] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0051] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0052] (4) placing 30 wt% of the surface wood shavings into a solution containing a water-soluble metal salt, heating it to 75° C. and maintaining it for 24 hours, wherein the concentration of the water-soluble metal salt is 1 g / L; the water-soluble metal salt is a potassium chloride solution;

[0053] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0054] (6) the core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order in a mass ratio of 1.5:1 to obtain the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is about 5wt%; the temperature during hot pressing is 210°C, the speed is 220mm / s, and the applied pressure is 3.5bar;

[0055] The surface adhesive comprises a water-dispersible component and a glue component in a mass ratio of 8:2. The water-dispersible component comprises the following components in parts by weight: 30 parts polyvinyl alcohol, 30 parts xanthan gum, 30 parts acetic acid acrylic emulsion, and 10 parts modified hydrophobic soy protein. The glue component comprises a plasticizer and MDI glue in a mass ratio of 8:2, wherein the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1. The modified hydrophobic soy protein is prepared by mixing 1g of ground soy protein and 0.5g of urea in 100mL of deionized water, stirring at 35°C for 30 minutes, and filtering to obtain the modified hydrophobic soy protein.

[0056] The core layer adhesive includes a water-dispersible component and a glue component, and the mass ratio of the two is 8:2; the water-dispersible component includes the following components in parts by weight: 20 parts of polyvinyl alcohol, 40 parts of xanthan gum, 20 parts of acetate-acrylic emulsion, and 20 parts of soy protein; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0057] The surface adhesive and core adhesive can be prepared using conventional preparation methods, or with certain adjustments based on the method described in CN108504320A. Specifically, the preparation method of the surface adhesive and core adhesive described in this embodiment is as follows: the water-dispersible components are added to an appropriate amount of water in the order of the recipe to uniformly disperse them (the added solvent water is not included in the weight of the adhesive and the components), and then the pH is adjusted to neutral or weakly alkaline so that the entire mixed solution does not precipitate, thereby obtaining Precursor I; the glue components are then mixed uniformly according to the recipe and heated and stirred under a nitrogen atmosphere until the mixture is stable and does not stratify, thereby obtaining Precursor II. During the sizing process, Precursor I and Precursor II are mixed uniformly and sizing is performed. At the same time, the amount of water added to the water-dispersible components ensures that the modified hydrophobic soy protein can be dispersed to form a suspension without precipitation or suspension stratification.

[0058] Example 2

[0059] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention comprises the following steps:

[0060] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0061] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0062] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0063] (4) placing 40 wt% of the surface wood chips into a solution containing a water-soluble metal salt, heating it to 65° C. and maintaining it for 30 hours, wherein the concentration of the water-soluble metal salt is 1.2 g / L; the water-soluble metal salt is a lithium bromide solution;

[0064] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0065] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is approximately 5.3 wt %; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar;

[0066] Among them, the surface adhesive includes a water-dispersible component and a glue component, and the mass ratio of the two is 8.5:1.5; the water-dispersible component includes the following components in parts by weight: 25 parts of polyvinyl alcohol, 35 parts of xanthan gum, 25 parts of acetate-acrylic emulsion, and 15 parts of modified hydrophobic soy protein; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0067] The core layer adhesive includes a water-dispersible component and a glue component, and the mass ratio of the two is 8.5:1.5; the water-dispersible component includes the following components in parts by weight: 20 parts of polyvinyl alcohol, 35 parts of xanthan gum, 20 parts of acetate-acrylic emulsion, and 25 parts of soy protein; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0068] The rest is the same as Example 1.

[0069] Example 3

[0070] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention comprises the following steps:

[0071] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0072] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0073] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0074] (4) placing 20 wt% of surface wood shavings into a solution containing a water-soluble metal salt, heating it to 80° C. and maintaining it for 26 hours, wherein the concentration of the water-soluble metal salt is 0.8 g / L; the water-soluble metal salt is a potassium chloride solution;

[0075] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0076] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is approximately 3.8 wt %; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar.

[0077] The rest is the same as Example 1.

[0078] Example 4

[0079] An embodiment of the high-performance Australian eucalyptus composite board and preparation method thereof according to the present invention differs from Example 1 only in that the core layer adhesive includes a water-dispersible component and a glue component, with the mass ratio of the two being 8:2; the water-dispersible component includes the following components in parts by weight: 15 parts of polyvinyl alcohol, 55 parts of xanthan gum, 20 parts of acetic acid acrylic emulsion, and 10 parts of soy protein; the glue component includes a plasticizer and MDI glue, with the mass ratio of the two being 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0080] Example 5

[0081] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention differs from Example 1 only in that the modified hydrophobic soy protein is prepared by mixing 1 g of ground soy protein and 0.2 g of urea and dispersing the mixture in 100 mL of deionized water, stirring and reacting at 35° C. for 40 minutes, and filtering to obtain the modified hydrophobic soy protein.

[0082] Example 6

[0083] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention differs from Example 1 only in that the modified hydrophobic soy protein is prepared by mixing 1 g of ground soy protein and 0.8 g of urea and dispersing the mixture in 100 mL of deionized water, stirring and reacting the mixture at 35°C for 20 minutes, and filtering to obtain the modified hydrophobic soy protein.

[0084] Example 7

[0085] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention differs from Example 1 only in that the modified hydrophobic soy protein is prepared by mixing 1 g of ground soy protein, 0.3 g of urea, and 0.2 g of potassium chloride and dispersing them in 100 mL of deionized water, stirring and reacting at 35°C for 20 minutes, and filtering to obtain the modified hydrophobic soy protein.

[0086] Comparative Example 1

[0087] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0088] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0089] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0090] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0091] (4) Apply the surface adhesive to the surface wood chips and the core adhesive to the core wood chips at the same time; the amount of the surface adhesive is 35kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0092] (5) the core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order in a mass ratio of 1.5:1 to obtain the high-performance Australian eucalyptus composite board; the mass content of the water-soluble metal salt in the surface layer shavings is about 1.2 wt% (i.e., the substance contained in the original wood material); the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar;

[0093] The core layer adhesive and the surface layer adhesive are the same, including a water-dispersible component and a glue component, and the mass ratio of the two is 8:2; the water-dispersible component includes the following components in parts by weight: 30 parts of polyvinyl alcohol, 30 parts of xanthan gum, 30 parts of acetate-acrylic emulsion, and 10 parts of soy protein; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0094] Comparative Example 2

[0095] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0096] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0097] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0098] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0099] (4) soaking the surface wood chips and the core wood chips in a solution containing a water-soluble metal salt and heating the solution to 75° C. for 24 hours, wherein the concentration of the water-soluble metal salt is 1 g / L; the water-soluble metal salt is a potassium chloride solution;

[0100] (5) Drying the soaked surface shavings and core shavings in step (4), and applying the surface adhesive and core adhesive to the dried surface shavings and core shavings respectively; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0101] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar;

[0102] The core layer adhesive and the surface layer adhesive are the same, including a water-dispersible component and a glue component, and the mass ratio of the two is 8:2; the water-dispersible component includes the following components in parts by weight: 30 parts of polyvinyl alcohol, 30 parts of xanthan gum, 30 parts of acetate-acrylic emulsion, and 10 parts of soy protein; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0103] Comparative Example 3

[0104] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0105] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0106] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0107] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0108] (4) Apply the surface adhesive to the surface wood chips and the core adhesive to the core wood chips at the same time; the amount of the surface adhesive is 35kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0109] (5) The core layer shavings and the surface layer shavings after gluing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar.

[0110] Comparative Example 4

[0111] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0112] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0113] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0114] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0115] (4) placing 60 wt% of the surface wood chips into a solution containing a water-soluble metal salt, heating it to 75° C. and maintaining it for 24 hours, wherein the concentration of the water-soluble metal salt is 1 g / L; the water-soluble metal salt is a potassium chloride solution;

[0116] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0117] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is approximately 8.4 wt %; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar.

[0118] Comparative Example 5

[0119] An embodiment of the high-performance Australian eucalyptus composite board and its preparation method according to the present invention comprises the following steps:

[0120] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0121] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0122] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0123] (4) soaking the surface wood shavings in a solution containing a water-soluble metal salt and heating it to 50° C. for 20 hours, wherein the concentration of the water-soluble metal salt is 0.8 g / L; the water-soluble metal salt is a potassium chloride solution;

[0124] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0125] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is approximately 4.7 wt %; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar.

[0126] Comparative Example 6

[0127] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0128] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0129] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0130] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0131] (4) placing 10 wt% of surface wood shavings into a solution containing a water-soluble metal salt, heating it to 90° C. and maintaining it for 30 hours, wherein the concentration of the water-soluble metal salt is 1.2 g / L; the water-soluble metal salt is a potassium chloride solution;

[0132] (5) Drying the surface shavings after soaking in step (4), and then mixing with the remaining untreated surface shavings, applying the surface adhesive after drying, and applying the core adhesive to the core shavings at the same time; the amount of the surface adhesive applied is 35 kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0133] (6) The core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order according to a mass ratio of 1.5:1, thereby obtaining the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is approximately 3.9 wt %; wherein the temperature during hot pressing is 210° C., the speed is 220 mm / s, and the applied pressure is 3.5 bar.

[0134] Comparative Example 7

[0135] An Australian eucalyptus composite board and a preparation method thereof, which differ from Example 1 only in that the surface adhesive includes a water-dispersible component and a glue component, with the mass ratio of the water-dispersible component and the glue component being 8:2; the water-dispersible component includes the following components in parts by weight: 30 parts of polyvinyl alcohol, 30 parts of xanthan gum, 30 parts of acetic acid acrylic emulsion, and 10 parts of soy protein; the glue component includes a plasticizer and MDI glue, with the mass ratio of the plasticizer and the MDI glue being 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0136] Comparative Example 8

[0137] An Australian eucalyptus composite board and a preparation method thereof, the difference from Example 1 being that the preparation method comprises the following steps:

[0138] (1) cutting, slicing, and drying Eucalyptus globulus wood until the moisture content is less than 3 wt % to obtain primary wood chips; the primary wood chips have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm;

[0139] (2) performing a first-stage screening on the primary wood shavings to obtain core wood shavings and screened material; the mesh size of the screen used for the first-stage screening is 2 mesh;

[0140] (3) performing secondary screening on the screened material to obtain surface shavings; the mesh size of the screen used for the secondary screening is 10 mesh;

[0141] (4) Apply the surface adhesive to the surface wood chips and the core adhesive to the core wood chips at the same time; the amount of the surface adhesive is 35kg / m 3 The amount of adhesive applied to the core layer is 30kg / m 3 After sizing, the moisture content of the wood chips is controlled to be within 10 wt%;

[0142] (5) the core layer shavings and the surface layer shavings after sizing are paved, hot pressed, cured, and sawed in a predetermined order in a mass ratio of 1.5:1 to obtain the high-performance Australian eucalyptus composite board. The composition analysis of the product shows that the mass content of water-soluble metal salts in the surface layer shavings is about 5wt%; the temperature during hot pressing is 210°C, the speed is 220mm / s, and the applied pressure is 3.5bar;

[0143] Among them, the surface adhesive includes a water-dispersible component and a glue component, and the mass ratio of the two is 8:2; the water-dispersible component includes the following components in parts by weight: 30 parts of polyvinyl alcohol, 30 parts of xanthan gum, 30 parts of acetic acid acrylic emulsion, 9.8 parts of modified hydrophobic soy protein, and 0.2 parts of potassium chloride; the glue component includes a plasticizer and MDI glue, and the mass ratio of the two is 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0144] Comparative Example 9

[0145] An Australian eucalyptus composite board and a preparation method thereof, which differ from Example 1 only in that the core layer adhesive includes a water-dispersible component and a glue component, with the mass ratio of the water-dispersible component and the glue component being 8:2; the water-dispersible component includes the following components in parts by weight: 30 parts of polyvinyl alcohol, 25 parts of xanthan gum, 30 parts of acetic acid acrylic emulsion, and 15 parts of soy protein; the glue component includes a plasticizer and MDI glue, with the mass ratio of the plasticizer and the MDI glue being 8:2, and the plasticizer is a mixture of DOP plasticizer and DBP plasticizer in a mass ratio of 1:1.

[0146] Effect Example 1

[0147] In order to verify the performance of the high-performance Australian eucalyptus composite board of the present invention, the products of each embodiment and comparative example (2440×1220×18 mm) were treated at a constant temperature and humidity of 20°C and 50% relative humidity for 24 hours, and then left at room temperature and humidity for 24 hours, and the following performance tests were performed:

[0148] (1) Static bending strength test: carried out in accordance with GB / T 4897-2015 Particleboard;

[0149] (2) Elastic modulus test: carried out according to GB / T 4897-2015 Particleboard;

[0150] (3) Screw holding force (board surface) test: carried out in accordance with GB / T 4897-2015 "Particleboard";

[0151] (4) Screw holding force (board edge) test: carried out in accordance with GB / T 4897-2015 "Particleboard".

[0152] The test results are shown in Table 1.

[0153] Table 1

[0154] As shown in Table 1, the high-performance Australian eucalyptus composite board of the present invention exhibits high strength, with static bending strength reaching 18 MPa or above, reaching a maximum of 25 MPa, and an elastic modulus exceeding 2850 MPa. Furthermore, the board exhibits high screw-holding strength, with a small difference in average values ​​between the board surface and the board edge. Compared to this product, Comparative Example 1, produced using conventional particleboard processing and a formaldehyde-free adhesive, demonstrates that while this product meets the GB / T 4897-2015 "Particleboard" standard, its performance is significantly inferior to that of the various examples of the present invention, resulting in a very limited scope of application, a short service life, and a high breakage rate. The product of Comparative Example 2 is based on the product of Comparative Example 1, in which the wood particles are pre-soaked in salt water. The strength performance of the product is improved to a certain extent, but not significantly. The product of Comparative Example 3 replaces the formaldehyde-free adhesive used in the product of Comparative Example 1 with the specific adhesive described in the present invention. The product performance is improved to a certain extent, but since the modified hydrophobic soy protein in the adhesive can only rely on hydrogen bonds for bonding reinforcement, it still does not meet the expected goals. From the comparison of the performance of the products of Comparative Examples 4 to 6 with the product of Example 1, it can be seen that the loading amount of the surface wood particles when impregnating and loading the water-soluble metal salt needs to be appropriate. If too little is added, the adhesive in the product cannot fully play its role. However, the loading amount cannot be too much, otherwise the secondary modification of the modified hydrophobic soy protein in the adhesive will be excessive, which will have a greater impact on the performance of the product, especially the static bending strength. Even if the loading amount is controlled within an appropriate range, if the loading area of ​​the water-soluble metal salt is too large, the adhesive will also be excessively modified, and close bonding between the components cannot be achieved. As can be seen from Comparative Examples 7 products, after carrying out suitable impregnation treatment, if only common formaldehyde-free adhesive is used, although water-soluble metal salt can still carry out certain modification to soy protein, obviously there is no significant change compared with Comparative Example 1 product, and is weaker than Comparative Examples 2 products, illustrating that specific impregnation treatment means of the present invention is only suitable for collocation adhesive formulation of the present invention. Comparative Example 8 products do not soak surface wood particles, but add an amount of potassium chloride in adhesive, and potassium chloride is introduced into the surface wood particles in adhesive sizing process, and from the result, this performance improvement effect is not obvious compared with Example 1, possible reasons may also be that modified hydrophobic soy protein cannot maintain suitable degree of modification except that potassium chloride cannot fully make the surface fiber of wood particles be closely connected. As can be seen from Comparative Examples 9 products, after surface wood particles are modified and sizing, core layer wood particles equally need to carry out specific sizing to ensure that the performance of product is effectively improved, and this product uses the core layer adhesive with lower xanthan gum content, although product performance meets testing standard, elastic modulus is lower.From the comparison between Example 1 and Examples 5 to 7, it can be seen that the modification degree of the modified hydrophobic soy protein also has a certain influence on the performance of the product. However, insufficient modification of the soy protein with urea or excessive modification will reduce the static bending strength of the product, and excessive modification will also reduce the elastic modulus of the product. If part of the urea is replaced with a water-soluble metal salt during the urea modification stage, it will work together with the urea to cause excessive modification of the soy protein and reduce the product performance.

[0155] Furthermore, the product of Example 1 with the best performance was subjected to additional performance tests as shown in Table 2 below:

[0156] Table 2

[0157] It can be seen that the other mechanical properties of the high-performance Australian eucalyptus composite board of the present invention are also excellent. At the same time, the product has excellent moisture resistance, with a thickness expansion rate of only 3% after 24 hours of water absorption, and the formaldehyde emission of the product is extremely low, which fully meets environmental protection standards.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-performance Australian eucalyptus composite board, characterized in that: It comprises two surface layers and a core layer between the surface layers; the wood chips in the surface layer have a mesh size of 3 to 12, and the mass content of the water-soluble metal salt in the wood chips is 3 to 6 wt%; the mesh size of the wood chips in the core layer is ≤ 2 mesh; The surface layer and the core layer contain adhesives, the adhesive of the surface layer contains modified hydrophobic soybean protein; the adhesive of the core layer contains xanthan gum, with a mass content of ≥25wt%; The preparation method of the high-performance Australian eucalyptus composite board comprises the following steps: (1) cutting, slicing and drying Australian eucalyptus wood to obtain primary wood chips; (2) subjecting the primary wood shavings to primary screening to obtain core wood shavings and screened material; the mesh size of the screen used for the primary screening is 2 to 3 meshes; (3) subjecting the screened material to secondary screening to obtain surface shavings; the mesh size of the screen used for the secondary screening is 8 to 12 meshes; (4) placing 20-40 wt% of the surface wood chips into a solution containing a water-soluble metal salt, heating it to 60-80° C. and maintaining it for 24-30 hours, wherein the concentration of the water-soluble metal salt is 0.8-1.2 g / L; (5) drying the surface wood chips soaked in step (4), and then mixing with the remaining untreated surface wood chips, applying the surface adhesive after drying, and applying the core adhesive to the core wood chips; (6) The core layer shavings and the surface layer shavings after the gluing are sequentially laid, hot pressed, cured, and sawed to obtain the high-performance Australian eucalyptus composite board.

2. The high-performance Australian eucalyptus composite board according to claim 1, characterized in that: The water-soluble metal salt is a monovalent inorganic metal halide salt; preferably, the monovalent inorganic metal salt is at least one of LiCl, NaCl, KCl, LiBr, NaBr, and KBr.

3. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: The mass content of xanthan gum in the adhesive of the core layer is 25-40wt%.

4. The high-performance Australian eucalyptus composite board as claimed in claim 3, characterized in that: The core layer adhesive comprises a water-dispersible component and a glue component in a mass ratio of (8:2) to (7:3); the water-dispersible component comprises the following components in parts by weight: 15 to 20 parts of polyvinyl alcohol, 35 to 45 parts of xanthan gum, 15 to 20 parts of acetic acid acrylic emulsion, and 10 to 25 parts of soy protein; the glue component comprises a plasticizer and MDI glue in a mass ratio of (9:1) to (8:2).

5. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: The surface adhesive comprises a water-dispersible component and a glue component in a mass ratio of (8:2) to (7:3); the water-dispersible component comprises the following components in parts by weight: 25 to 35 parts of polyvinyl alcohol, 25 to 35 parts of xanthan gum, 25 to 35 parts of acetic acid-acrylic emulsion, and 10 to 20 parts of modified hydrophobic soy protein; the glue component comprises a plasticizer and MDI glue in a mass ratio of (9:1) to (8:2).

6. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: The modified hydrophobic soy protein is urea-modified soy protein; preferably, the preparation method of the modified hydrophobic soy protein comprises the following steps: The soybean protein is ground and then dispersed in water, and then urea is added and mixed and stirred at 30-40° C. for 20-30 minutes, and filtered to obtain modified hydrophobic soybean protein; the mass ratio of the soybean protein to urea is 1:(0.4-0.6).

7. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: The primary wood chips in step (1) have a length of 15 to 25 mm, a width of 8 to 15 mm, and a thickness of 0.5 to 0.8 mm.

8. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: The amount of adhesive applied in step (5) is 30-40 kg / m 3 .

9. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: In the step (5), the moisture content of the surface wood chips and the core wood chips after gluing is 8-10wt%.

10. The high performance Australian eucalyptus composite board according to claim 1, characterized in that: In the step (6), the mass ratio of the core layer material to the surface layer material during paving is (1-2):1; the temperature during hot pressing is 200-220°C, the speed is 200-220 mm / s, and the applied pressure is 3-4 bar.

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