Flame-retardant thin high-pressure decorative laminate bendable at small angles and its production

Abstract

Proposed is a flame-retardant thin high-voltage decorative laminated board which can be bent at a small angle and a preparation method thereof. Kraft paper is soaked in a benzene tri-melamine ethanol solution, taken out and pre-dried, then soaked in a 5'-guanylic acid disodium aqueous solution, taken out and dried to obtain a pretreated flame-retardant modified kraft paper. Benzene tri-melamine, 5'-guanylic acid disodium and cellulose are combined by a reaction including hydrogen bonding as shown in the formula. The pretreated kraft paper is impregnated in a guanidino acetic acid-chitosan composite modified phenolic resin, dried after impregnation to make the resin in a pre-cured state. Multiple papers are assembled and subjected to hot-pressing treatment, pressure is released and demoulding is performed to obtain a high-voltage decorative laminated board. The local stress concentration is reduced while the high curing degree and flame-retardant performance are maintained, so that a small bending radius is obtained.

Description

Technical Field

[0001] This invention relates to the field of engineered wood products, specifically to a flame-retardant thin high-pressure decorative laminate that can be bent at a small angle and its preparation. Background Technology

[0002] High-pressure decorative laminates, often referred to as "fireproof boards" in the market, are primarily made from paper impregnated with thermosetting resin through assembly and hot pressing, and are widely used in furniture and interior decoration. Since their main raw materials are paper and resin, existing products typically improve their flammability by adding flame retardants or using flame-retardant-treated paper. With the trend towards thinner and curved surfaces, thin high-pressure decorative laminates also need to possess good small-radius bending performance. Existing phenolic resins have relatively high rigidity after curing, while the addition of flame-retardant components can easily further reduce the flexibility of the paper and board, causing problems such as cracking and delamination when the board is bent at a small radius. Therefore, how to balance flame retardancy and small-radius bending performance is a problem that existing technologies need to solve. Summary of the Invention

[0003] In view of the above-mentioned research and development issues, this invention provides a process method for composite material of phenolic resin modification and kraft paper pretreatment, a novel flame retardant, and a corresponding preparation process.

[0004] Firstly, a method for preparing a flame-retardant thin high-pressure decorative laminate that can be bent at a small angle is provided, including: (1) Phenolic resin modification: Chitosan was added to a 1.0 wt% aqueous acetic acid solution and stirred at 50-60℃ for 30-60 min to fully dissolve the chitosan. Guanidoacetic acid was then added to the solution, with a mass ratio of chitosan to guanidoacetic acid of 2:(0.2-0.4). The mixture was stirred for another 20-40 min to obtain a uniform guanidoacetic acid-chitosan composite modified solution. 100 parts by weight of phenol and 130-150 parts by weight of 37 wt% formaldehyde aqueous solution were added to a reaction vessel, and 1.5-2.5 parts by weight of 30 wt% NaOH aqueous solution were added. The reaction was carried out at 65-75℃ for 30-60 min, and then the temperature was raised to 80-85℃ for 40-60 min to obtain phenolic resin prepolymer. Cool the prepolymer to 55-60℃, slowly add 15-25 parts by weight of guanidinoacetic acid-chitosan composite modified solution, stir for 20-30 min, adjust the pH of the system to 8.0-9.0, raise the temperature to 70-80℃ and continue the reaction for 30-60 min, or stop the reaction and cool when the viscosity of the resin at the reaction temperature reaches 40-100 mPa·s to obtain guanidinoacetic acid-chitosan composite modified phenolic resin; (2) Flame-retardant impregnation modification of kraft paper: Kraft paper is immersed in a 0.03-0.06 g / mL benzomelamine ethanol solution for 2-5 min, then removed and pre-dried at 50-70℃ for 3-8 min, and then immersed in a 0.04-0.08 g / mL 5'-guanylate disodium aqueous solution for 2-5 min, and then dried at 80℃ for 10-20 min to obtain pretreated flame-retardant modified kraft paper. In the above process, benzomelamine, disodium 5'-guanylate, and cellulose undergo the following reaction, which includes ionic bonding:

[0005] (3) Press forming: Pretreated flame-retardant modified kraft paper is impregnated in guanidinoacetic acid-chitosan composite modified phenolic resin, and the amount of dry resin is controlled to be 50-65% of the oven-dry weight of the kraft paper. After impregnation, it is dried at 100-115℃ for 20-30 seconds to allow the resin to be in a pre-cured state. Take multiple sheets of the obtained impregnated paper preforms and perform hot pressing treatment under a pressure of 7~10MPa: heat up to 170℃ at a heating rate of 8~12℃ / min, keep at 170℃ and pressurize for 20~30min, then maintain the pressure and cool down to 50℃ at a cooling rate of 8~12℃ / min; release the pressure and demold to obtain the flame-retardant thin high-pressure decorative laminate that can be bent at a small angle.

[0006] The thickness of the kraft paper raw material is 0.24 mm.

[0007] The thickness of the laminate produced is 0.69 mm.

[0008] The purity of guanidinoacetic acid is >97.0%.

[0009] The amount of dry resin applied is controlled to be 50-65% of the oven-dry weight of the kraft paper, which is controlled by controlling the pressure of the glue roller.

[0010] The resulting laminate meets the performance specifications of GB / T7911-2024.

[0011] GB / T 7911-2024: High-pressure decorative laminates (HPL) made of thermosetting resin impregnated paper.

[0012] The present invention also provides a flame-retardant thin high-pressure decorative laminate that can be bent at a small angle, prepared by the above method.

[0013] Under normal circumstances, after kraft paper undergoes phosphorus and nitrogen flame retardant treatment and the nitrogen content and cross-linking degree of phenolic resin are increased, laminated boards often become further hardened and brittle, thus their small radius bending performance is generally expected to decrease. However, this invention combines guanidinoacetic acid-chitosan composite modified phenolic resin with flame-retardant modified kraft paper, and employs a controlled heating-high temperature curing-pressurized controlled cooling process to improve flame retardant performance while maintaining a small bending radius of R3 to R3.5 mm.

[0014] According to the present invention, chitosan contains a large number of amino and hydroxyl groups, and guanidinoacetic acid contains guanidinyl and carboxyl groups. Both form strong hydrogen bonds and multi-point intermolecular interactions at the interface between the phenolic resin and the fiber. During hot pressing, the amino groups of chitosan can also participate in the subsequent curing of the phenolic system. Simultaneously, controlling the heating rate allows the resin to fully impregnate and redistribute before complete cross-linking. After curing, the resin is cooled under pressure at approximately 10°C / min, gradually releasing the stress generated by interlayer thermal shrinkage. This reduces localized stress concentration while maintaining a high degree of curing and flame retardant properties, thereby achieving a small bending radius. Detailed Implementation

[0015] The specific embodiments of this invention are provided to enable those skilled in the art to fully understand the invention and are intended to effectively support the claims of this invention. This section also involves the explanation or definition of the features and terms of the technical solutions of this invention. Those skilled in the art should understand the scope of the claims of this invention in conjunction with the explanation of specific features and terms in the specification, and should not arbitrarily misinterpret the true meaning represented by the features and terms of this invention.

[0016] It must be understood that, in any work involving the definition of the scope of the claims of this invention, the specific embodiments provided by this invention can be used to fully support appropriate equivalent or superior solutions derived therefrom, and the scope of the claims should never be construed as not exceeding the examples themselves. Similarly, it must be understood that, with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this application will also be equally applicable to similar technical problems without any inventive effort by those skilled in the art, and the scope of protection of this invention should not be limited to the examples described in the specific embodiments of this invention.

[0017] The following examples and comparative examples were verified using kraft paper of the same size and specifications, wherein the purity of guanidinoacetic acid was >97.0%.

[0018] Example 1:

[0019] (1) Phenolic resin modification

[0020] Weigh 19.54g of an aqueous solution of acetic acid with a mass concentration of 1.0wt%, add 0.40g of chitosan, and stir at 55℃ for 45min to fully dissolve the chitosan; then add 0.06g of guanidinoacetic acid and continue stirring for 30min to obtain 20.0g of a uniform guanidinoacetic acid-chitosan composite modified solution, wherein the mass ratio of chitosan to guanidinoacetic acid is 2:0.3.

[0021] 100.0g of phenol and 140.0g of 37wt% formaldehyde aqueous solution were weighed and added to a reaction vessel. 6.67g of 30wt% NaOH aqueous solution was added, of which the actual amount of NaOH added was 2.0g. The mixture was stirred and reacted at 70℃ for 45min. Then the temperature was raised to 82℃ and the reaction was continued for 50min to obtain phenolic resin prepolymer.

[0022] The phenolic resin prepolymer was cooled to 58°C, and 20.0 g of the guanidinoacetic acid-chitosan composite modified solution was slowly added while stirring continuously. After the addition was complete, stirring was continued for 25 min. The pH of the system was adjusted to 8.5 using a 10 wt% NaOH aqueous solution, and then the temperature was raised to 75°C and the reaction was continued for 45 min. After the reaction was completed, the mixture was cooled to room temperature, and a small amount of deionized water was added as needed to adjust the resin solid content to 50.0 wt%. The viscosity of the resin at 25°C was controlled to be approximately 75 mPa·s, thus obtaining the guanidinoacetic acid-chitosan composite modified phenolic resin.

[0023] (2) Flame-retardant impregnation modification of kraft paper

[0024] Weigh 25.0 g of benzomelamine, add ethanol and dilute to 500 mL to prepare a benzomelamine ethanol solution with a concentration of 0.05 g / mL. Separately weigh 30.0 g of disodium 5'-guanylate, add deionized water and dilute to 500 mL to prepare a disodium 5'-guanylate aqueous solution with a concentration of 0.06 g / mL.

[0025] Take three sheets of kraft paper (0.24 mm thick) of the same size and weight, immerse them completely in the above-mentioned phenyl melamine ethanol solution for 4 min, remove them and pre-dry them at 60 °C for 5 min; then immerse them completely in the 5'-guanylate disodium aqueous solution for another 4 min, remove them and dry them at 80 °C for 15 min to obtain pretreated flame-retardant modified kraft paper.

[0026] (3) Press plate forming

[0027] Take three sheets of the pretreated flame-retardant modified kraft paper, with each sheet having an oven-dry weight of 20.0g. Impregnate each sheet with the guanidinoacetic acid-chitosan composite modified phenolic resin prepared in step (1). Control the dry resin coating amount of each kraft paper to 12.0g through impregnation and extrusion, i.e., the dry resin coating amount is 60% of the oven-dry weight of the kraft paper. Since the solid content of the modified phenolic resin used is 50.0wt%, the resin liquid adsorption amount of each kraft paper is controlled to be approximately 24.0g.

[0028] After impregnation, the impregnated paper is dried at 107℃ for 25 seconds to allow the resin to reach a pre-cured state. Three sheets of the obtained impregnated paper, each approximately 0.29 mm thick, are assembled and fed into a hot press for hot pressing at 8.5 MPa. The temperature is increased to 170℃ at a rate of 10℃ / min and held at 170℃ for 25 minutes. Subsequently, the pressure is maintained at 8.5 MPa, and the temperature is decreased to 50℃ at a rate of 10℃ / min. The pressure is released and the material is demolded to obtain a 0.69 mm thick, flame-retardant, thin, high-pressure decorative laminate that can be bent at a small angle.

[0029] performance: The oxygen index is 44%. 2- The combustion growth rate index FIGRA is 120 W / s. 3- The minimum post-forming bending radius R is 3.1 mm.

[0030] 4- Surface abrasion resistance meets the requirements of ≥2 level in GB / T7911-2024 "Thermosetting Resin Impregnated Paper High Pressure Decorative Laminate (HPL)", small ball impact resistance meets the requirements of ≥2 level in GB / T7911-2024, and large ball impact resistance meets the requirements of GB / T7911-2024 with an impact height of 600mm and an indentation diameter of ≤10mm.

[0031] Comparative Example 1:

[0032] (1) Preparation of ordinary phenolic resin

[0033] 100.0 g of phenol and 140.0 g of a 37 wt% formaldehyde aqueous solution were weighed and added to a reaction vessel. 6.67 g of a 30 wt% NaOH aqueous solution was added, with the actual amount of NaOH added being 2.0 g. The mixture was stirred at 70 °C for 45 min. The temperature was then raised to 82 °C and the reaction continued for 50 min, followed by a decrease to 75 °C and another 45 min. After the reaction was complete, the mixture was cooled to room temperature. A small amount of deionized water was added as needed to adjust the resin solid content to 50.0 wt%. The viscosity of the resin at 25 °C was controlled to be approximately 75 mPa·s, yielding ordinary phenolic resin.

[0034] (2) Press plate forming

[0035] Three sheets of ordinary kraft paper of the same specifications and weight (same as in Example 1) were taken, each with an oven-dry weight of 20.0g. Without flame-retardant pretreatment, they were directly impregnated in the aforementioned ordinary phenolic resin. The amount of dry resin applied to each sheet was controlled to be 12.0g through impregnation and compression, i.e., 60% of the oven-dry weight of the kraft paper. Since the solid content of the ordinary phenolic resin used was 50.0wt%, the amount of resin liquid absorbed by each sheet was controlled to be approximately 24.0g.

[0036] After impregnation, the impregnated paper was dried at 107℃ for 25 seconds to allow the resin to reach a pre-cured state. Three sheets of the obtained impregnated paper, each approximately 0.29 mm thick, were assembled and fed into a hot press for hot pressing at a pressure of 8.5 MPa. The temperature was increased to 170℃ at a rate of 10℃ / min and held at 170℃ for 25 minutes. Subsequently, the pressure was maintained at 8.5 MPa, and the temperature was decreased to 50℃ at a rate of 10℃ / min. The pressure was released and the material was demolded to obtain the high-pressure decorative laminate of Comparative Example 1.

[0037] performance: 1. The oxygen index is 26%; 2. The combustion growth rate index FIGRA is 245 W / s; 3. The minimum post-forming bending radius R is 4.3mm; 4. The surface abrasion resistance meets the requirements of ≥2 level in GB / T7911-2024 "Thermosetting Resin Impregnated Paper High Pressure Decorative Laminate (HPL)", the small ball impact resistance meets the requirements of ≥2 level in GB / T7911-2024, and the large ball impact resistance meets the requirements of GB / T7911-2024 with an impact height of 600mm and an indentation diameter of ≤10mm.

[0038] Comparative Example 2:

[0039] (1) Preparation of ordinary phenolic resin

[0040] 100.0 g of phenol and 140.0 g of a 37 wt% formaldehyde aqueous solution were weighed and added to a reaction vessel. 6.67 g of a 30 wt% NaOH aqueous solution was added, with the actual amount of NaOH added being 2.0 g. The mixture was stirred at 70 °C for 45 min. The temperature was then raised to 82 °C and the reaction continued for 50 min, followed by a decrease to 75 °C and another 45 min. After the reaction was complete, the mixture was cooled to room temperature. A small amount of deionized water was added as needed to adjust the resin solid content to 50.0 wt%. The viscosity of the resin at 25 °C was controlled to be approximately 75 mPa·s, yielding ordinary phenolic resin.

[0041] (2) Flame-retardant impregnation modification of kraft paper

[0042] Weigh 25.0 g of benzomelamine, add ethanol and dilute to 500 mL to prepare a benzomelamine ethanol solution with a concentration of 0.05 g / mL. Separately weigh 30.0 g of disodium 5'-guanylate, add deionized water and dilute to 500 mL to prepare a disodium 5'-guanylate aqueous solution with a concentration of 0.06 g / mL.

[0043] Take three sheets of kraft paper of the same specifications and quality (same as in Example 1), immerse them completely in the above-mentioned phenyl melamine ethanol solution for 4 minutes, remove them and pre-dry them at 60°C for 5 minutes; then immerse them completely in the 5'-guanylate disodium aqueous solution for another 4 minutes, remove them and dry them at 80°C for 15 minutes to obtain pretreated flame-retardant modified kraft paper.

[0044] (3) Press plate forming

[0045] Take three sheets of the pretreated flame-retardant modified kraft paper, each with an oven-dry weight of 20.0g. Impregnate each sheet with the above-mentioned ordinary phenolic resin. Control the dry resin coating amount of each kraft paper to 12.0g through impregnation and compression, i.e., the dry resin coating amount is 60% of the oven-dry weight of the kraft paper. The resin liquid adsorption amount of each kraft paper is controlled to be approximately 24.0g.

[0046] After impregnation, the impregnated paper was dried at 107℃ for 25 seconds to allow the resin to reach a pre-cured state. Three sheets of the obtained impregnated paper, each approximately 0.29 mm thick, were assembled and fed into a hot press for hot pressing at a pressure of 8.5 MPa. The temperature was increased to 170℃ at a rate of 10℃ / min and held at 170℃ for 25 minutes. Subsequently, the pressure was maintained at 8.5 MPa, and the temperature was decreased to 50℃ at a rate of 10℃ / min. The pressure was released and the material was demolded to obtain the high-pressure decorative laminate of Comparative Example 2.

[0047] performance: 1. The oxygen index is 38%; 2. The combustion growth rate index FIGRA is 168 W / s; 3. The minimum post-forming bending radius R is 4.6mm; 4. The surface abrasion resistance meets the requirements of ≥2 level in GB / T7911-2024 "Thermosetting Resin Impregnated Paper High Pressure Decorative Laminate (HPL)", the small ball impact resistance meets the requirements of ≥2 level in GB / T7911-2024, and the large ball impact resistance meets the requirements of GB / T7911-2024 with an impact height of 600mm and an indentation diameter of ≤10mm.

[0048] Comparative Example 3:

[0049] (1) Phenolic resin modification

[0050] Weigh 19.54g of an aqueous solution of acetic acid with a mass concentration of 1.0wt%, add 0.40g of chitosan, and stir at 55℃ for 45min to fully dissolve the chitosan; then add 0.06g of guanidinoacetic acid and continue stirring for 30min to obtain 20.0g of uniform guanidinoacetic acid-chitosan composite modified solution.

[0051] 100.0g of phenol and 140.0g of 37wt% formaldehyde aqueous solution were weighed and added to a reaction vessel. 6.67g of 30wt% NaOH aqueous solution was added, of which the actual amount of NaOH added was 2.0g. The mixture was stirred and reacted at 70℃ for 45min. Then the temperature was raised to 82℃ and the reaction was continued for 50min to obtain phenolic resin prepolymer.

[0052] The phenolic resin prepolymer was cooled to 58°C, and 20.0 g of the guanidinoacetic acid-chitosan composite modified solution was slowly added while stirring continuously. After the addition was complete, stirring was continued for 25 min. The pH of the system was adjusted to 8.5 using a 10 wt% NaOH aqueous solution, and then the temperature was raised to 75°C and the reaction was continued for 45 min. After the reaction was completed, the mixture was cooled to room temperature, and a small amount of deionized water was added as needed to adjust the resin solid content to 50.0 wt%. The viscosity of the resin at 25°C was controlled to be approximately 75 mPa·s, thus obtaining the guanidinoacetic acid-chitosan composite modified phenolic resin.

[0053] (2) Flame-retardant impregnation modification of kraft paper

[0054] Weigh 25.0 g of benzomelamine, add ethanol and dilute to 500 mL to prepare a benzomelamine ethanol solution with a concentration of 0.05 g / mL. Separately weigh 30.0 g of disodium 5'-guanylate, add deionized water and dilute to 500 mL to prepare a disodium 5'-guanylate aqueous solution with a concentration of 0.06 g / mL.

[0055] Take three sheets of kraft paper of the same specifications and quality (same as in Example 1), immerse them completely in the above-mentioned phenyl melamine ethanol solution for 4 minutes, remove them and pre-dry them at 60°C for 5 minutes; then immerse them completely in the 5'-guanylate disodium aqueous solution for another 4 minutes, remove them and dry them at 80°C for 15 minutes to obtain pretreated flame-retardant modified kraft paper.

[0056] (3) Press plate forming

[0057] Take three sheets of the pretreated flame-retardant modified kraft paper, with each sheet having an oven-dry weight of 20.0g. Impregnate each sheet with the above-mentioned guanidinoacetic acid-chitosan composite modified phenolic resin. Control the dry resin coating amount of each kraft paper to 12.0g and the resin liquid adsorption amount of each kraft paper to approximately 24.0g through impregnation and extrusion.

[0058] After impregnation, the impregnated paper was dried at 107℃ for 25 seconds to allow the resin to reach a pre-cured state. Three sheets of the obtained impregnated paper, each approximately 0.29 mm thick, were assembled into a preform. The hot press platen was preheated to 170℃, and the assembled impregnated paper was directly fed into the hot press. The press was held at 8.5 MPa pressure and 170℃ platen temperature for 25 minutes without any programmed temperature control at 10℃ / min. Subsequently, the pressure was maintained at 8.5 MPa, and the temperature was lowered to 50℃ at a rate of 10℃ / min. The pressure was released and the paper was demolded to obtain the high-pressure decorative laminate of Comparative Example 3.

[0059] performance: 1. The oxygen index is 43%; 2. The combustion growth rate index FIGRA is 128 W / s; 3. The minimum post-forming bending radius R is 4.5mm; 4. The surface abrasion resistance meets the requirements of ≥2 level in GB / T7911-2024 "Thermosetting Resin Impregnated Paper High Pressure Decorative Laminate (HPL)", the small ball impact resistance meets the requirements of ≥2 level in GB / T7911-2024, and the large ball impact resistance meets the requirements of GB / T7911-2024 with an impact height of 600mm and an indentation diameter of ≤10mm.

[0060] The comparative design follows the principle of single variable and elimination item by item. That is, under the premise of keeping other factors such as raw material usage, assembly method and hot pressing conditions as consistent as possible, the three key technical measures of kraft paper flame retardant pretreatment, modified phenolic resin and controlled heating and cooling are respectively eliminated or replaced. By comparing item by item, the actual contribution of each technical measure to flame retardant performance and small radius bending performance is judged, and the necessity of the combination scheme of the present invention is verified.

Claims

1. A method for preparing a flame-retardant thin high-pressure decorative laminate that can be bent at a small angle, characterized in that, include: (1) Phenolic resin modification: Chitosan was added to a 1.0 wt% aqueous acetic acid solution and stirred at 50-60℃ for 30-60 min to fully dissolve the chitosan. Guanidoacetic acid was then added to the solution, with a mass ratio of chitosan to guanidoacetic acid of 2:(0.2-0.4). The mixture was stirred for another 20-40 min to obtain a uniform guanidoacetic acid-chitosan composite modified solution. 100 parts by weight of phenol and 130-150 parts by weight of 37 wt% formaldehyde aqueous solution were added to a reaction vessel, and 1.5-2.5 parts by weight of 30 wt% NaOH aqueous solution were added. The reaction was carried out at 65-75℃ for 30-60 min, and then the temperature was raised to 80-85℃ for 40-60 min to obtain phenolic resin prepolymer. Cool the prepolymer to 55-60℃, slowly add 15-25 parts by weight of guanidinoacetic acid-chitosan composite modified solution, stir for 20-30 min, adjust the pH of the system to 8.0-9.0, raise the temperature to 70-80℃ and continue the reaction. When the viscosity of the resin at the reaction temperature reaches 40-100 mPa·s, stop the reaction and cool to obtain guanidinoacetic acid-chitosan composite modified phenolic resin. (2) Flame-retardant impregnation modification of kraft paper: Kraft paper is immersed in a 0.03-0.06 g / mL benzomelamine ethanol solution for 2-5 min, then removed and pre-dried at 50-70℃ for 3-8 min, and then immersed in a 0.04-0.08 g / mL 5'-guanylate disodium aqueous solution for 2-5 min, and then dried at 80℃ for 10-20 min to obtain pretreated flame-retardant modified kraft paper. In the above process, benzomelamine, disodium 5'-guanylate, and cellulose undergo the following reaction, which includes ionic bonding: ； (3) Press forming: Pretreated flame-retardant modified kraft paper is impregnated in guanidinoacetic acid-chitosan composite modified phenolic resin, and the amount of dry resin is controlled to be 50-65% of the oven-dry weight of the kraft paper. After impregnation, it is dried at 100-115℃ for 20-30 seconds to allow the resin to be in a pre-cured state. Take multiple sheets of the obtained impregnated paper preforms and perform hot pressing treatment under a pressure of 7~10MPa: heat up to 170℃ at a heating rate of 8~12℃ / min, keep at 170℃ and pressurize for 20~30min, then maintain the pressure and cool down to 50℃ at a cooling rate of 8~12℃ / min; release the pressure and demold to obtain the flame-retardant thin high-pressure decorative laminate that can be bent at a small angle.

2. The preparation method according to claim 1, wherein, The thickness of the kraft paper raw material is 0.24mm.

3. The preparation method according to claim 1, wherein, The thickness of the laminate produced is 0.69 mm.

4. The preparation method according to claim 1, wherein, The purity of guanidinoacetic acid is >97.0%.

5. A high-pressure decorative laminate prepared by the preparation method according to any one of claims 1 to 4.

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