A method for preparing decorative paper impregnated with thermoplastic melamine adhesive

Abstract

This invention relates to the field of decorative paper technology, specifically to a method for preparing thermoplastic melamine adhesive-impregnated decorative paper, comprising the following steps: Step (1) base paper pretreatment; Step (2) thermoplastic melamine adhesive preparation; Step (3) impregnation: impregnating the pretreated base paper with thermoplastic melamine adhesive, drying, cooling, shearing, stacking, laying, and hot pressing to obtain thermoplastic melamine adhesive-impregnated decorative paper. This method introduces compounds containing flexible segments onto the melamine molecule, and improves extensibility by precisely controlling the temperature, pH value, and reaction time of the synthesis reaction; a modified nano-silica dispersion is coated on the surface of the base paper, and modified nano-silica is embedded in the gaps of the base paper to improve the interfacial bonding force between the filler and the resin, allowing the filler to play a better role, thereby improving the overall performance of the resin adhesive.

Description

Technical Field

[0001] This invention relates to the field of decorative paper technology, and specifically to a method for preparing decorative paper impregnated with thermoplastic melamine adhesive. Background Technology

[0002] Currently, the preparation methods for melamine-impregnated decorative paper mainly include adhesive preparation, impregnation, drying, and cooling. Regarding adhesive preparation, melamine-formaldehyde resin is typically prepared by reacting melamine with formaldehyde, or urea-formaldehyde resin is prepared by reacting urea with formaldehyde, or a mixture of both is used. CN107164992B discloses a low-formaldehyde melamine-impregnated decorative paper and its preparation method. This method includes steps such as preparing urea-formaldehyde adhesive resin, preparing melamine adhesive resin, primary impregnation, and secondary impregnation. By controlling the raw material ratio and process parameters, the formaldehyde release of the prepared impregnated paper can be effectively controlled to ≤0.3 mg / L.

[0003] Regarding impregnation processes, CN107724172A discloses a novel impregnated paper production process. This process involves two impregnations: first, a lower-cost urea-formaldehyde resin is used for the first impregnation, followed by a higher-cost but higher-performance melamine resin for the second impregnation. This reduces manufacturing costs while ensuring the surface performance of the impregnated paper. CN107354812A discloses a production process for high-gloss, low-cost impregnated paper, including steps such as one impregnation, one drying, spraying, coating, secondary drying, and cutting. Through improvements to the impregnation process, a glossy finish is achieved on the surface of the flooring or furniture after pressing, significantly enhancing surface gloss.

[0004] To address the issue of high formaldehyde release from melamine-impregnated paper, CN117385671A proposes a method for preparing low-formaldehyde-release melamine-impregnated paper. This method involves modifying melamine with a low-molar urea-formaldehyde resin, reacting benzoic acid with formaldehyde, and adding a formaldehyde scavenging agent to create the resin. The method also controls the temperature, time, pH value, and amount of raw materials added during the impregnation process. CN108130796A discloses a method for preparing decorative paper capable of purifying formaldehyde. This method uses a mixture of urea-formaldehyde resin, modified starch, and water-soluble chitosan to obtain an impregnation solution, which is then dried in a mixed atmosphere of dry air and ammonia. This results in decorative paper with excellent formaldehyde capture and removal capabilities.

[0005] However, existing melamine-impregnated decorative papers generally suffer from insufficient ductility, easily breaking when bent or stretched, failing to meet the application requirements of special packaging or decoration fields where surface materials have a certain degree of deformability. This is mainly because the network structure formed after the curing of traditional melamine-urea-formaldehyde resin is too rigid and lacks sufficient flexibility. Although CN117385671A mentions adding isocyanate ester during the melamine resin softening process to improve toughness, it still fails to completely solve the ductility problem of impregnated paper in specific application scenarios. Summary of the Invention

[0006] To address the technical problem that traditional melamine-impregnated decorative paper lacks extensibility and is prone to breakage when bent or stretched, failing to meet the application requirements of special packaging or decoration fields for surface materials with a certain degree of deformation capability, this invention provides a method for preparing thermoplastic melamine-impregnated decorative paper to improve the extensibility of impregnated decorative paper, enhance the impregnation effect, optimize the production process, and achieve special functions.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0009] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper, with a coating amount of 8-12 g / m². 2 The paper is then dried at 0.001–0.02 MPa and 40–50 °C to obtain pretreated base paper.

[0010] Step (2) Preparation of thermoplastic melamine adhesive: Mix 1200-1400 parts of formaldehyde with 90-110 parts of ammonia water by weight, adjust the pH to 8.8-9.2, and when the reaction temperature rises to 55-65℃, add 180-220 parts of melamine and stir for 10 minutes. Then add 380-420 parts of urea, heat to 83-90℃, keep warm and evaporate until the water content is 20%-30% by mass. When the temperature drops to 60℃, add 70-90 parts of diethylene glycol and continue to cool to 30-40℃. Then add 20%-30% of acrylic resin by mass and stir evenly to obtain thermoplastic melamine adhesive. Note that in the chemical formula, "1200-1400 parts of formaldehyde" refers to the mass of 37% formaldehyde aqueous solution (formalin), not pure formaldehyde gas.

[0011] Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue, dry, cool, cut, stack, lay, and hot press to obtain thermoplastic melamine glue impregnated decorative paper.

[0012] From a functional group perspective, melamine consists of a six-membered ring formed by alternating links of three carbon atoms and three nitrogen atoms, with each carbon atom also bonded to an amino group. The three carbon atoms and three nitrogen atoms are connected by covalent bonds in an alternating pattern of single and double bonds, forming a six-membered heterocyclic ring. This six-membered heterocyclic structure endows melamine with certain stability and unique physicochemical properties. Melamine adhesive is formed by the condensation polymerization of melamine and formaldehyde. The molecule contains a triazine ring structure, which possesses high bond energy and symmetry, allowing it to remain stable within a certain temperature range and preventing molecular chain breakage or rearrangement. During the curing process, melamine adhesive forms a highly cross-linked three-dimensional network structure. For these reasons, the formulation is adjusted before curing to ensure the melamine adhesive retains its ductility.

[0013] This scheme mainly involves introducing a compound containing flexible segments onto the melamine molecule through step (2), and improving its extensibility by precisely controlling the temperature, pH value and reaction time of the synthesis reaction.

[0014] Secondly, this method involves coating a modified nano-silica dispersion onto the surface of the base paper. Utilizing the gaps in the base paper, the modified nano-silica is embedded within, improving the interfacial bonding between the filler and the resin, allowing the filler to function more effectively, thereby enhancing the overall performance of the resin adhesive, including its ductility. The pressure conditions in this method allow for faster moisture evaporation and enable the modified nano-silica to embed into the fiber gaps of the base paper. It can form hydrogen bonds or covalent bonds with the hydroxyl groups of the fiber paper, increasing the tensile strength and folding endurance of the base paper. It can also fill the micropores between fibers, reducing stress concentration points and inhibiting crack propagation. Furthermore, the organic segments of the modified nano-silica form an interpenetrating network with the subsequent thermoplastic melamine adhesive, improving interfacial shear strength. The modified nano-silica coating, acting as a pre-coating layer, balances the surface energy difference between the base paper and the thermoplastic melamine adhesive, reducing adhesive rejection and fluctuations in adhesive application during subsequent impregnation.

[0015] Preferably, in step (1), the modified nano-silica dispersion comprises: 5%–10% modified nano-silica by mass percentage, 1%–3% hydroxyethyl acrylate, 1%–2% acrylic acid, and the remainder being water.

[0016] Preferably, the modified nano-silica dispersion contains acrylic acid-grafted nano-silica.

[0017] Acrylic acid-grafted nano-silica dispersion can be prepared by the following method: 1 part by weight of nano-silica is dispersed in 30-35 parts of deionized water, ultrasonically treated, and then 0.3-0.9 parts of vinyltrimethoxysilane are added. The pH of the system is adjusted to 9-11 with ammonia water, and the mixture is stirred and reacted at 80-85℃ for 5-8 hours. After drying, silane-modified nano-silica is obtained. Then, an aqueous solution containing 5%-10% by mass of silane-modified nano-silica, 1%-3% of hydroxyethyl acrylate and 1%-2% of acrylic acid is prepared, and 0.01-0.1 parts of potassium persulfate initiator are added. The mixture is reacted at 80-90℃ for 1-2 hours to obtain the modified nano-silica dispersion.

[0018] Preferably, in step (1), the moisture content of the pretreated base paper is 6% to 8%.

[0019] Excessive moisture content will dilute the melamine adhesive, leading to insufficient curing and defects such as bubbles and blistering during hot pressing; insufficient moisture content will increase the brittleness of the base paper, making it prone to breakage during impregnation.

[0020] Preferably, the density of the thermoplastic melamine adhesive is 1.0-1.3 g / cm³. 3 .

[0021] As a preferred option, in step (3), the process of impregnating the pretreated base paper with thermoplastic melamine glue is as follows: the pretreated base paper is first passed through a back coating roller, then the excess glue is wiped off with a metering roller, and then passed through a drying oven at a drying temperature of 110-135℃, so that the moisture content of the impregnated paper is 12% to 15% and the glue application amount is 60-70g / cm², and then cooled.

[0022] Preferably, before wiping away excess glue with a metering roller, air is filtered out using a curved breathing roller.

[0023] Preferably, in step (3), the drying method is a seven-section drying oven with the temperature of the first section oven being 110℃, the temperature of the second section oven being 125℃, the temperature of the third section oven being 135℃, the temperature of the fourth section oven being 130℃, the temperature of the fifth section oven being 130℃, the temperature of the sixth section oven being 130℃, and the temperature of the seventh section oven being 120℃.

[0024] Preferably, in step (3), the acrylic resin is a hydroxy acrylate-organosilicon copolymer.

[0025] Preferably, in step (3), the cooling method is to cool the paper surface to 25-30°C by blowing natural cold air through an oven and then cooling it to 25-30°C by water cooling with rollers.

[0026] The impregnated paper produced by this method, used in special packaging or decoration fields, can meet the product's requirements for ductility to a certain extent after special design. It is not easy to break when bent or stretched, and can adapt to some applications that require the surface material to have a certain deformation ability.

[0027] Compared to existing technologies, the advantages of this solution are:

[0028] 1. This method introduces compounds containing flexible segments into the melamine molecule and improves its ductility by precisely controlling the temperature, pH value, and reaction time of the synthesis reaction;

[0029] 2. In this method, the modified nano-silica dispersion is coated on the surface of the base paper. The modified nano-silica is embedded in the gaps of the base paper, which can improve the interfacial bonding force between the filler and the resin, allowing the filler to play a better role and thus improving the overall performance of the resin adhesive. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the following examples and comparative examples, the modified nano-silica dispersion was prepared as follows: The acrylic acid-grafted nano-silica dispersion can be prepared by the following method: by weight, 1 part of nano-silica is dispersed in 30 parts of deionized water, ultrasonically treated, and then 0.5 parts of vinyltrimethoxysilane are added. The pH of the system is adjusted to 10 with ammonia water, and the mixture is stirred and reacted at 83°C for 6 hours. After drying, silane-modified nano-silica is obtained. Then, an aqueous solution containing 8% silane-modified nano-silica, 2% hydroxyethyl acrylate, and 1.5% acrylic acid by mass fraction is prepared, and 0.05 parts of potassium persulfate initiator are added. The mixture is reacted at 85°C for 1.5 hours to obtain the modified nano-silica dispersion.

[0032] Example 1

[0033] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0034] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0035] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0036] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The pretreated base paper is first passed through the back coating roller, and the air is discharged by the curved breathing roller. Then the excess glue is wiped off by the metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling of the roller. It is then cut, stacked, laid out, and hot-pressed to obtain thermoplastic melamine glue impregnated decorative paper.

[0037] Example 2

[0038] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0039] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 9 g / m². 2 The paper was then dried at 0.008 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0040] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1200 parts of 37% formaldehyde aqueous solution with 110 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 390 parts of urea, heat to 88℃, and keep warm to evaporate until the water content is 28% by mass. When the temperature drops to 60℃, add 75 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0041] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The pretreated base paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 28℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0042] Example 3

[0043] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0044] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 11 g / m². 2 The paper is then dried at 0.01 MPa and 40-50℃ to obtain pretreated base paper with a moisture content of 6% to 8%.

[0045] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1400 parts of 37% formaldehyde aqueous solution with 90 parts of ammonia water, adjust the pH to 9.0, and when the reaction temperature rises to 58℃, add 190 parts of melamine and stir for 10 minutes. Then add 390 parts of urea, heat to 88℃, and keep warm to evaporate until the water content reaches 26% by mass. When the temperature drops to 60℃, add 86 parts of diethylene glycol, and continue to cool to 35℃. Then add 26% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0046] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The pretreated base paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 14% and the glue amount is 66g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 28℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0047] Example 4

[0048] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0049] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 9 g / m². 2 The paper was then dried at 0.012 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0050] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9.0, and when the reaction temperature rises to 55-65℃, add 190 parts of melamine and stir for 10 minutes. Then add 410 parts of urea, heat to 88℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 38℃. Then add 26% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0051] Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue. The pretreated base paper is first passed through the back coating roller, and the air is discharged by the filtration roller with an arc. Then, the excess glue is wiped off with the metering roller. The paper is then dried in an oven to make the moisture content of the impregnated paper 13% and the glue amount 65g / cm². The paper is then cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 28℃ by water cooling with rollers. The paper is then cut, stacked, laid out, and hot-pressed to obtain thermoplastic melamine glue impregnated decorative paper.

[0052] Example 5

[0053] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0054] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0055] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0056] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The pretreated base paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². The paper is cooled to a surface temperature of 25℃ by blowing natural cold air in the oven. It is then cut, stacked, laid out, and hot-pressed to obtain thermoplastic melamine glue impregnated decorative paper.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that the nano-silica dispersion was not coated:

[0059] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0060] Step (1) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0061] Step (2) Impregnation: The base paper is impregnated with thermoplastic melamine glue. The pre-treated base paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first section oven is 110℃, the temperature of the second section oven is 125℃, the temperature of the third section oven is 135℃, the temperature of the fourth section oven is 130℃, the temperature of the fifth section oven is 130℃, the temperature of the sixth section oven is 130℃, and the temperature of the seventh section oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that the nano-silica dispersion is coated:

[0064] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0065] Step (1) Base paper pretreatment: Coat the surface of the base paper with a nano-silica dispersion at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0066] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0067] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0068] Comparative Example 3

[0069] The difference from Example 1 is that conventional melamine adhesive is directly applied:

[0070] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0071] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0072] Step (2) Impregnation: The pretreated base paper is impregnated with melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, thermoplastic melamine glue impregnated decorative paper is obtained.

[0073] Comparative Example 4

[0074] The difference from Example 1 is that the modified nano-silica dispersion was not subjected to low-pressure treatment after coating:

[0075] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0076] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2The paper is dried at 45°C to obtain pretreated base paper with a moisture content of 7%.

[0077] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0078] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0079] Comparative Example 5

[0080] The difference from Example 1 is that the moisture content of the pretreated base paper exceeded the standard, reaching 9%.

[0081] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0082] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 9%.

[0083] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0084] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0085] Comparative Example 6

[0086] The difference from Example 1 is that no acrylic resin was added during the preparation of the thermoplastic melamine adhesive:

[0087] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0088] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0089] Step (2) Preparation of thermoplastic melamine adhesive: By proportion, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, keep warm and evaporate until the water content is 25% by mass, cool down to 60℃ and add 80 parts of diethylene glycol, continue to cool down to 35℃, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0090] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the amount of acrylic resin added is excessive:

[0093] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0094] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0095] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 85℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 60℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 40% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0096] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0097] Comparative Example 8

[0098] The difference from Example 1 lies in the order of material addition during the preparation of the thermoplastic melamine adhesive:

[0099] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0100] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0101] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 60℃, add 80 parts of diethylene glycol, followed by 200 parts of melamine, stir for 10 minutes, then add 400 parts of urea, heat to 85℃, keep warm and evaporate until the water content is 25% by mass, continue to cool to 35℃, then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0102] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0103] Comparative Example 9

[0104] The difference from Example 1 lies in the temperature control during the preparation of the thermoplastic melamine adhesive:

[0105] A method for preparing decorative paper impregnated with thermoplastic melamine adhesive includes the following steps:

[0106] Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper at a coating amount of 10 g / m². 2 The paper was then dried at 0.005 MPa and 45°C to obtain pretreated base paper with a moisture content of 7%.

[0107] Step (2) Preparation of thermoplastic melamine adhesive: By weight, mix 1300 parts of 37% formaldehyde aqueous solution with 100 parts of ammonia water, adjust the pH to 9, and when the reaction temperature rises to 50℃, add 200 parts of melamine and stir for 10 minutes. Then add 400 parts of urea, heat to 65℃, and keep warm to evaporate until the water content reaches 25% by mass. When the temperature drops to 40℃, add 80 parts of diethylene glycol, and continue to cool to 35℃. Then add 25% by mass of hydroxyl acrylate-organosilicon copolymer, and stir evenly to obtain a density of 1.2 g / cm³. 3 Thermoplastic melamine adhesive;

[0108] Step (3) Impregnation: The pretreated base paper is impregnated with thermoplastic melamine glue. The impregnated paper is first passed through a back coating roller, and the air is discharged by filtering the liquid with a curved breathing roller. Then, the excess glue is wiped off with a metering roller. It is then dried in a seven-section oven. The temperature of the first oven is 110℃, the temperature of the second oven is 125℃, the temperature of the third oven is 135℃, the temperature of the fourth oven is 130℃, the temperature of the fifth oven is 130℃, the temperature of the sixth oven is 130℃, and the temperature of the seventh oven is 120℃, so that the moisture content of the impregnated paper is 13% and the glue amount is 65g / cm². It is cooled by blowing natural cold air in the oven, and then cooled to the paper surface temperature of 25℃ by water cooling with rollers. After cutting, stacking, laying, and hot pressing, the thermoplastic melamine glue impregnated decorative paper is obtained.

[0109] The test methods and results are shown in Table 1.

[0110] Table 1

[0111]

[0112] Examples 1-5 show significant performance improvements compared to Comparative Examples 1-9. Examples 4 and 5, for instance, show that although the drying and cooling processes differ from Example 1, the performance is still superior to Comparative Examples 1-9, indicating that these two conditions have a promoting effect on performance, rather than a decisive one.

[0113] The difference between Comparative Example 1 and Example 1 is that the base paper was not pretreated, and the performance improvement brought by the modified nano silica was missing compared to Example 1.

[0114] The difference between Comparative Example 2 and Example 1 is that unmodified silica was used. Due to the aggregation of surface hydroxyl groups, it cannot effectively penetrate the fiber gaps and has no surface grafting groups to participate in the subsequent network construction. Instead, it acts as a defect point, causing stress concentration and significantly weakening the reinforcement effect.

[0115] The difference between Comparative Example 3 and Example 1 is that conventional melamine adhesive was used, which lacks the toughening effect of flexible segments of acrylic resin. The brittle cross-linked network is prone to microcracks and propagation when bent.

[0116] The difference between Comparative Example 4 and Example 1 is that the atmospheric pressure drying in step (1) causes the modified nano silica to be adsorbed only on the surface of the base paper and fails to form a mechanical interlock with the fiber, making it easy to peel off from the interface under external force.

[0117] The difference between Comparative Example 5 and Example 1 is that the increased moisture content of the base paper dilutes the concentration of the impregnating adhesive, resulting in a decrease in the density of the resin film after curing. At the same time, moisture catalyzes the hot pressing side reaction, releasing formaldehyde.

[0118] The difference between Comparative Example 6 and Example 1 is that the adhesive lacks acrylic resin, the melamine rigid network lacks toughening and buffering, and the impact energy absorption capacity drops sharply.

[0119] The difference between Comparative Example 7 and Example 1 is that excess acrylic resin occupies the crosslinking sites of melamine, inhibiting the formation of a three-dimensional network, and the density and strength decrease simultaneously.

[0120] The difference between Comparative Example 8 and Example 1 is that the premature addition of diethylene glycol triggers a formaldehyde disproportionation side reaction, and the byproduct formic acid catalyzes the formation of weak bonds such as methylene ether bonds, which reduces network stability.

[0121] The difference between Comparative Example 9 and Example 1 is that the low-temperature reaction caused the melamine polycondensation to remain at the linear prepolymer stage, failing to form a highly branched cross-linked structure, resulting in a severe deterioration in overall performance.

[0122] In summary, the implementation of this solution is based on a combination of components and processes; a single component or process cannot achieve the technical effects described in this solution.

Claims

1. A method for preparing decorative paper impregnated with thermoplastic melamine adhesive, characterized in that, Includes the following steps: Step (1) Base paper pretreatment: A modified nano-silica dispersion is coated on the surface of the base paper, with a coating amount of 8-12 g / m². 2 The paper is then dried at 0.001–0.02 MPa and 40–50 °C to obtain pretreated base paper. The modified nano-silica dispersion contains acrylic acid-grafted nano-silica. The acrylic acid-grafted nano-silica dispersion is prepared as follows: 1 part by weight of nano-silica is dispersed in 30–35 parts of deionized water, ultrasonically treated, and then 0.3–0.9 parts of vinyltrimethoxysilane are added. The pH of the system is adjusted to 9–11 with ammonia. The mixture is stirred and reacted at 80–85 °C for 5–8 hours. After drying, silane-modified nano-silica is obtained. Next, an aqueous solution containing 5%–10% silane-modified nano-silica, 1%–3% hydroxyethyl acrylate, and 1%–2% acrylic acid is prepared. 0.01–0.1 parts of potassium persulfate initiator are added, and the mixture is reacted at 80–90 °C for 1–2 hours to obtain the modified nano-silica dispersion. Step (2) Preparation of thermoplastic melamine adhesive: Mix 1200-1400 parts of formaldehyde with 90-110 parts of ammonia water by weight, adjust the pH to 8.8-9.2, add 180-220 parts of melamine when the reaction temperature rises to 55-65℃, stir for 10 minutes, then add 380-420 parts of urea, heat to 83-90℃, keep warm and evaporate until the water content is 20%-30% by weight, cool down to 60℃ and add 70-90 parts of diethylene glycol, continue to cool down to 30-40℃, then add 20%-30% of acrylic resin by weight, stir evenly to obtain thermoplastic melamine adhesive; Step (3) Impregnation: Impregnate the pretreated base paper with thermoplastic melamine glue, dry, cool, cut, stack, lay, and hot press to obtain thermoplastic melamine glue impregnated decorative paper; In step (1), the moisture content of the pretreated base paper is 6% to 8%; In step (3), the acrylic resin is a hydroxy acrylate-organosilicon copolymer.

2. The method for preparing decorative paper impregnated with thermoplastic melamine adhesive as described in claim 1, characterized in that, The density of the thermoplastic melamine adhesive is 1.0-1.3 g / cm³. 3 .

3. The method for preparing decorative paper impregnated with thermoplastic melamine adhesive as described in claim 1, characterized in that, In step (3), the process of impregnating the pretreated base paper with thermoplastic melamine glue is as follows: the pretreated base paper is first passed through the back coating roller, then the excess glue is wiped off with the metering roller, and then passed through the drying oven at a drying temperature of 110-135℃, so that the moisture content of the impregnated paper is 12% to 15% and the glue application amount is 60-70g / cm², and then cooled.

4. The method for preparing decorative paper impregnated with thermoplastic melamine adhesive as described in claim 3, characterized in that, Before wiping away excess glue with the metering roller, use the curved breathing roller to filter out the air.

5. The method for preparing decorative paper impregnated with thermoplastic melamine adhesive as described in claim 1, characterized in that, In step (3), the drying method is a seven-section drying oven. The temperature of the first section of the drying oven is 110℃, the temperature of the second section of the drying oven is 125℃, the temperature of the third section of the drying oven is 135℃, the temperature of the fourth section of the drying oven is 130℃, the temperature of the fifth section of the drying oven is 130℃, the temperature of the sixth section of the drying oven is 130℃, and the temperature of the seventh section of the drying oven is 120℃.

6. The method for preparing decorative paper impregnated with thermoplastic melamine adhesive as described in claim 1, characterized in that, In step (3), the cooling method is to cool the paper surface to 25-30℃ by blowing natural cold air through the oven and then cooling it to 25-30℃ by water cooling through rollers.

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