A formaldehyde-free adhesive for formaldehyde-free impregnated special decorative paper and a preparation method thereof

Abstract

This invention discloses a formaldehyde-free adhesive for impregnating specialty decorative paper and its preparation method, relating to the field of formaldehyde-free adhesive technology. The formaldehyde-free adhesive for impregnating specialty decorative paper contains 60-75% composite impregnation adhesive, 5-15% amino-functionalized cellulose nanofibers, 0.8-1.5% carbodiimide, 0.2-0.6% modified cerium oxide nanoparticles, and deionized water. The composite impregnation adhesive is prepared by blending polymethylhydrosiloxane-modified acrylic resin and water-based nano-terminated polyurethane resin at a mass ratio of (7-9):(1-3). The preparation method involves impregnation followed by segmented hot-pressing curing. The decorative paper prepared with this formaldehyde-free adhesive has no formaldehyde release and possesses excellent abrasion resistance, light fastness, water resistance, and dimensional stability, making it suitable for interior decoration, furniture veneer, vehicle interiors, ship decoration, and other applications.

Description

Technical Field

[0001] This invention relates to the field of formaldehyde-free adhesive technology, specifically to a formaldehyde-free adhesive for impregnating special decorative paper and its preparation method. Background Technology

[0002] Existing impregnated decorative papers mostly use formaldehyde-containing resin adhesives, which release formaldehyde during use, posing a health hazard. They also suffer from insufficient abrasion resistance, poor lightfastness, yellowing, high water absorption, and poor dimensional stability. Furthermore, traditional products are functionally limited and lack environmentally friendly value-added features, failing to meet the high-quality demands of modern interior decoration for formaldehyde-free, environmentally friendly, and multifunctional integrated products, thus restricting their application scope.

[0003] Therefore, it is of great significance to invent a formaldehyde-free adhesive for impregnating special decorative paper. Summary of the Invention

[0004] The purpose of this invention is to provide a formaldehyde-free adhesive for impregnating special decorative paper and its preparation method, so as to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A formaldehyde-free adhesive for impregnating specialty decorative paper, wherein the formaldehyde-free adhesive for impregnating specialty decorative paper comprises the following components by mass percentage: 60-75% composite impregnating adhesive, 5-15% amino-functionalized cellulose nanofibers, 0.8-1.5% carbodiimide, 0.2-0.6% modified cerium oxide nanoparticles, and the remainder being deionized water; Furthermore, the composite impregnating adhesive is prepared by blending polymethylhydrosiloxane modified acrylic resin and waterborne nano-terminated polyurethane resin in a mass ratio of (7-9):(1-3).

[0006] Furthermore, the preparation method of the polymethylhydrosiloxane modified acrylic resin includes the following steps: adding polymethylhydrosiloxane and divinylbenzene into a reaction vessel, adding a platinum catalyst, heating to 150-155℃ and reacting for 30-60 minutes, cooling to room temperature, and obtaining modified polymethylhydrosiloxane. Modified polymethylhydrosiloxane, styrene, isooctyl acrylate, hydroxyethyl acrylate, and glycidyl methacrylate were added to a reaction vessel, along with benzoyl peroxide. The mixture was stirred until homogeneous and then added dropwise to a xylene / butyl acetate mixed solvent at 90-95°C. After the addition was complete, the mixture was heated to 110-115°C and reacted for 6-8 hours. The mixture was then cooled to room temperature to obtain polymethylhydrosiloxane-modified acrylic resin.

[0007] Furthermore, in the preparation process of the modified polymethylhydrosiloxane, the molar ratio of polymethylhydrosiloxane to divinylbenzene is 2:1, and the amount of platinum catalyst added is 0.5-0.6% of the total mass of polymethylhydrosiloxane and divinylbenzene.

[0008] Furthermore, in the preparation process of the polymethylhydrosiloxane modified acrylic resin, the mass ratio of the total mass of modified polymethylhydrosiloxane: styrene, isooctyl acrylate, hydroxyethyl acrylate, and glycidyl methacrylate to benzoyl peroxide is (5-20):(78-94):(0.8-2); wherein, the mass ratio of styrene: isooctyl acrylate: hydroxyethyl acrylate: glycidyl methacrylate is (25-35):(30-40):(15-20):(10-15); Furthermore, the xylene / butyl acetate mixed solvent is 30-50% of the total mass of the polymethylhydrosiloxane modified acrylic resin.

[0009] Furthermore, in the xylene / butyl acetate mixed solvent, the mass ratio of xylene to butyl acetate is 2:1; Furthermore, the dripping time is 3-3.5 hours.

[0010] Furthermore, the preparation method of the waterborne nano-terminated polyurethane resin includes the following steps: adding polyethylene adipate-1,4-butanediol diol to a reaction vessel, heating to 60-65°C, adding isophorone diisocyanate and an organic bismuth catalyst, further heating to 75-80°C and reacting for 2-3 hours, cooling to 40-45°C, adding 1,4-butanediol, stirring and reacting for 30-40 minutes, adding sulfonate hydrophilic chain extender AESA, maintaining the temperature for 1-1.5 hours, adding methyl ethyl ketone oxime, further cooling to 30-35°C, adding deionized water during stirring, and after the addition is complete, shearing emulsification and vacuum degassing are performed to obtain the waterborne nano-terminated polyurethane resin.

[0011] Furthermore, in the preparation process of the waterborne nano-terminated polyurethane resin, the mass ratio of polyethylene adipate-1,4-butanediol diol: isophorone diisocyanate: organic bismuth catalyst: 1,4-butanediol: sulfonate hydrophilic chain extender AESA: methyl ethyl ketone oxime: deionized water is 100:(20.3-28.5):(0.1-0.14):(2.25-4.95):(3.73-6.22):(7.67-8.04):(139-399); the deionized water addition rate is 5-10 mL / min. Furthermore, the stirring speed during the shear emulsification process is 8000-10000 r / min, and the time is 30-40 min; Furthermore, the vacuum degassing process is performed at a vacuum level of -0.08 to -0.09 MPa, with a stirring speed of 200 to 250 rpm and a time of 15 to 20 min.

[0012] Furthermore, the preparation method of the amino-functionalized cellulose nanofibers includes the following steps: ultrasonically dispersing 2.5-3 wt% cellulose nanofibers in deionized water, adding 3-(2-aminoethylamino)propylmethyldimethoxysilane, heating to 90-95℃ and reacting for 3-6 h, adding 0.25-0.3 mol / L calcium chloride solution, cooling to 50-60℃ and stirring, and replacing the solvent with 50%, 75%, and 100% tert-butanol at 8-hour intervals to obtain amino-functionalized cellulose nanofibers.

[0013] Furthermore, in the preparation process of the amino-functionalized cellulose nanofibers, the amount of 3-(2-aminoethylamino)propylmethyldimethoxysilane added is 3-8% of the mass of the cellulose nanofibers.

[0014] Furthermore, the preparation method of the modified cerium oxide nanoparticles includes the following steps: ultrasonically dispersing cerium oxide nanoparticles in deionized water to form a cerium oxide nanoparticle dispersion; adjusting the pH of the dispersion to 4.5 using hydrochloric acid; adding 3-glycidyloxypropyltrimethoxysilane; and heating to 60-65℃ for 8-8.5 h to obtain modified cerium oxide nanoparticles.

[0015] Furthermore, in the preparation process of the modified cerium oxide nanoparticles, the solid content of the cerium oxide nanodispersion is 20-25%; the mass ratio of cerium oxide nanoparticles to 3-glycidyloxypropyltrimethoxysilane is 3:1.

[0016] Furthermore, the base paper layer is made of hardwood pulp with a density of 0.50-0.55 g / cm³. 3 ; Furthermore, the cerium oxide nanoparticles have a particle size of 15-20 nm; A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper includes the following steps: adding polymethylhydrosiloxane-modified acrylic resin, amino-functionalized cellulose nanofibers, carbodiimide, modified cerium oxide nanoparticles, and deionized water sequentially into a reaction apparatus, heating to 20-25℃ and mixing evenly to obtain the formaldehyde-free adhesive for impregnating special decorative paper.

[0017] Furthermore, the pressure during the hot-press curing process is 0.3-0.5 MPa.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention forms a composite impregnation adhesive by blending water-based nano-terminated polyurethane resin and polymethylhydrosiloxane-modified acrylic resin in a certain proportion. The nano-sized adhesive particles can significantly improve the permeability of the adhesive in the gaps between the base paper fibers. The end-terminated structure ensures its compatibility with polymethylhydrosiloxane-modified acrylic resin. The elastic segments and the rigid structure of the acrylic resin form a complementary rigid-flexible structure, which not only improves the flexibility and interlayer adhesion of the adhesive layer, but also does not damage the original hydrophobic and lightfast system. At the same time, its hydrophilic modified structure is compatible with the dispersibility of each functional component in the system, further synergistically strengthening the overall density and stability of the composite impregnation adhesive layer. This solves the problem that polymethylhydrosiloxane-modified acrylic resin alone is not sufficient for impregnating dense base paper and has a slightly brittle adhesive layer.

[0019] 2. Polymethylhydrosiloxane-modified acrylic resin forms a hydrophobic surface layer through self-stratification, and Si-O bonds enhance its heat and corrosion resistance. The amino groups on the surface of amino-functionalized cellulose nanofibers form hydrogen bonds with the carboxyl and hydroxyl groups in the polymethylhydrosiloxane-modified acrylic resin, and simultaneously undergo ring-opening reactions with the epoxy groups of glycidyl methacrylate, strengthening the interfacial bonding between the resin and the base paper fibers. The self-stratified hydrophobic layer of polymethylhydrosiloxane-modified acrylic resin and the internal cross-linking of amino-functionalized cellulose nanofibers enhance the formation of a structure with both surface corrosion resistance and strong internal adhesion, solving the problem of imbalance between surface function and internal adhesion in impregnated paper prepared by traditional impregnation adhesives. At the same time, the amino-functionalized cellulose nanofibers fill the voids in the polymethylhydrosiloxane-modified acrylic resin, further improving the resin's density. 3. The -N=C=N- groups in carbodiimide undergo an acylation reaction with the carboxyl groups on the surface of polymethylhydrosiloxane-modified acrylic resin and amino-functionalized cellulose nanofibers to form stable acylurea bonds. At the same time, it consumes the carboxyl groups generated by hydrolysis, blocks the hydrolysis chain reaction, strengthens the stability of the cross-linked network, and inhibits hydrolysis. In synergy with the heat resistance of the Si-O bonds of polymethylhydrosiloxane-modified acrylic resin and the size stability of amino-functionalized cellulose nanofibers, the formaldehyde-free adhesive prepared in this application can increase the thermal decomposition temperature of decorative paper and improve its resistance to damp heat aging. 4. The 4f electron structure of cerium oxide can effectively shield 280-350nm ultraviolet rays, inhibiting resin molecular chain breakage and yellowing. After modification with 3-glycidoxypropyltrimethoxysilane, epoxy groups are introduced on the surface, which react with the hydroxyl and amino functionalized cellulose nanofibers of polymethylhydrosiloxane-modified acrylic resin, improving dispersion uniformity and preventing particle aggregation. The UV shielding function of modified cerium oxide synergistically with the light resistance of polymethylhydrosiloxane-modified acrylic resin, avoiding resin degradation and yellowing caused by UV irradiation. The organosilane modification groups on the surface of cerium oxide have good compatibility with the silicon-oxygen structure of polymethylhydrosiloxane-modified acrylic resin, and do not affect the self-layering and hydrophobic effect of the resin adhesive. Detailed Implementation

[0020] 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.

[0021] The following examples illustrate the preparation method of polymethylhydrosiloxane-modified acrylic resin, which includes the following steps: adding polymethylhydrosiloxane and divinylbenzene to a reaction vessel, adding a platinum catalyst, heating to 150°C and reacting for 30 minutes, and cooling to room temperature to obtain modified polymethylhydrosiloxane. In the preparation process of the modified polymethylhydrosiloxane, the molar ratio of polymethylhydrosiloxane to divinylbenzene is 2:1, and the amount of platinum catalyst added is 0.5% of the total mass of polymethylhydrosiloxane and divinylbenzene. Modified polymethylhydrosiloxane, styrene, isooctyl acrylate, hydroxyethyl acrylate, and glycidyl methacrylate were added to a reaction vessel, benzoyl peroxide was added, and the mixture was stirred evenly. The mixture was then added dropwise to a xylene / butyl acetate mixed solvent at 90°C for 3 hours. After the addition was complete, the mixture was heated to 110°C and reacted for 6 hours. The mixture was then cooled to room temperature to obtain polymethylhydrosiloxane modified acrylic resin.

[0022] In the preparation process of the polymethylhydrosiloxane modified acrylic resin, the mass ratio of modified polymethylhydrosiloxane: styrene, isooctyl acrylate, hydroxyethyl acrylate, glycidyl methacrylate to benzoyl peroxide is 13:86:1; wherein, the mass ratio of styrene: isooctyl acrylate: hydroxyethyl acrylate: glycidyl methacrylate is 30:35:20:15. The xylene / butyl acetate mixed solvent is 40% of the total mass of the polymethylhydrosiloxane modified acrylic resin.

[0023] A method for preparing waterborne nano-terminated polyurethane resin includes the following steps: 100 parts of polyethylene adipate-1,4-butanediol diol are added to a reaction vessel and heated to 60°C. 20.3 parts of isophorone diisocyanate and 0.1 parts of an organic bismuth catalyst are added, and the mixture is further heated to 75°C and reacted for 2 hours. The mixture is then cooled to 40°C, 2.25 parts of 1,4-butanediol are added, and the mixture is stirred for 30 minutes. 3.76 parts of sulfonate hydrophilic chain extender AESA are added, and the mixture is kept at this temperature for 1-1.5 hours. 7.67 parts of methyl ethyl ketone oxime are added, and the mixture is further cooled to 30°C. During stirring, 139 parts of deionized water are added at a rate of 5 mL / min. After the addition is complete, the mixture is sheared and emulsified, and then degassed under vacuum to obtain the waterborne nano-terminated polyurethane resin.

[0024] The preparation method of amino-functionalized cellulose nanofibers includes the following steps: 2.5 wt% cellulose nanofibers are ultrasonically dispersed in deionized water, 3-(2-aminoethylamino)propylmethyldimethoxysilane is added, the mixture is heated to 90℃ and reacted for 3 h, 0.25 mol / L calcium chloride solution is added, the mixture is cooled to 50℃ and stirred, and the solvent is replaced with 50%, 75%, and 100% tert-butanol at 8-hour intervals to obtain amino-functionalized cellulose nanofibers; In the preparation of the amino-functionalized cellulose nanofibers, the amount of 3-(2-aminoethylamino)propylmethyldimethoxysilane added is 6% of the mass of the cellulose nanofibers.

[0025] The preparation method of modified cerium oxide nanoparticles includes the following steps: ultrasonically dispersing cerium oxide nanoparticles in deionized water to form a cerium oxide nanoparticle dispersion with a solid content of 20%; adjusting the pH of the dispersion to 4.5 with hydrochloric acid; adding 3-glycidyloxypropyltrimethoxysilane; heating to 60°C and reacting for 8 hours to obtain modified cerium oxide nanoparticles. In the preparation of the modified cerium oxide nanoparticles, the mass ratio of cerium oxide nanoparticles to 3-glycidyloxypropyltrimethoxysilane is 3:1.

[0026] Example 1: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 70wt% composite impregnation adhesive, 10wt% amino-functionalized cellulose nanofibers, 1.1wt% carbodiimide, 0.4wt% modified cerium oxide nanoparticles, and 8.5wt% deionized water sequentially into a reaction apparatus, heating to 20°C and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; In the composite impregnation adhesive, the mass ratio of polymethylhydrosiloxane-modified acrylic resin to waterborne nano-terminated polyurethane resin is 8:2.

[0027] The formaldehyde-free impregnated special decorative paper prepared in Example 1 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The method for preparing the formaldehyde-free impregnated special decorative paper includes the following steps: S1: Pre-treating the surfaces of three base paper layers to remove impurities, and set them aside for later use; S2: Pour formaldehyde-free impregnated special decorative paper into a polytetrafluoroethylene container with formaldehyde-free glue, place three layers of base paper in it, impregnate at room temperature for 5 minutes, and absorb the residual resin on the surface to obtain a base paper composite with an impregnated glue layer. S3: Place the base paper composite with the impregnated adhesive layer into a polytetrafluoroethylene vacuum-sealed bag, heat to 30°C and hot-press for 2 hours, then heat to 180°C and hot-press for 0.5 hours, and cool to room temperature to obtain formaldehyde-free impregnated special decorative paper.

[0028] Example 2: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 60wt% composite impregnation adhesive, 5wt% amino-functionalized cellulose nanofibers, 0.8wt% carbodiimide, 0.2wt% modified cerium oxide nanoparticles, and 34wt% deionized water sequentially into a reaction apparatus, heating to 20°C and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The formaldehyde-free impregnated special decorative paper prepared in Example 2 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0029] Example 3: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 75wt% composite impregnation adhesive, 15wt% amino-functionalized cellulose nanofibers, 1.5wt% carbodiimide, 0.6wt% modified cerium oxide nanoparticles, and 7.9wt% deionized water sequentially into a reaction apparatus, heating to 20°C and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The formaldehyde-free impregnated special decorative paper prepared in Example 3 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0030] Comparative Example 1: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 70wt% of commercially available water-based acrylic resin, 10wt% of amino-functionalized cellulose nanofibers, 1.1wt% of carbodiimide, 0.4wt% of modified cerium oxide nanoparticles, and 8.5wt% of deionized water sequentially into a reaction apparatus, heating to 20℃ and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The commonly available water-based acrylic resin is a polymer emulsion made of styrene and acrylate copolymer; The formaldehyde-free impregnated special decorative paper prepared in Comparative Example 1 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0031] Comparative Example 2: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 80wt% composite impregnating adhesive, 1.1wt% carbodiimide, 0.4wt% modified cerium oxide nanoparticles, and 9.5wt% deionized water sequentially into a reaction apparatus, heating to 20℃ and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The formaldehyde-free impregnated special decorative paper prepared in Comparative Example 2 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0032] Comparative Example 3: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 70.4 wt% composite impregnating adhesive, 10 wt% amino-functionalized cellulose nanofibers, 1.1 wt% carbodiimide and 8.9 wt% deionized water sequentially into a reaction device, heating to 20°C and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The formaldehyde-free impregnated special decorative paper prepared in Comparative Example 3 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0033] Comparative Example 4: A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper, comprising the following steps: adding 70 wt% polymethylhydrosiloxane modified acrylic resin, 10 wt% amino-functionalized cellulose nanofibers, 1.1 wt% carbodiimide, 0.4 wt% modified cerium oxide nanoparticles, and 8.5 wt% deionized water sequentially into a reaction apparatus, heating to 20°C and mixing evenly to obtain a formaldehyde-free adhesive for impregnating special decorative paper; The formaldehyde-free impregnated special decorative paper prepared in Comparative Example 4 was used to prepare formaldehyde-free impregnated special decorative paper. The performance of the prepared formaldehyde-free impregnated special decorative paper was tested to verify the technical effect of the formaldehyde-free adhesive. The remaining steps are the same as in Example 1.

[0034] Performance testing: The free formaldehyde content of the formaldehyde-free adhesives prepared in the embodiments and comparative examples of this application was tested: the free formaldehyde content of the adhesives was tested by acetylacetone spectrophotometry according to GB 18583-2008 and GB / T 23993-2009. Lightfastness test: UV accelerated aging was performed according to ASTM D1925-2013, with parameters of 60 kWh·m. -2 Conduct testing; Water resistance test: The water absorption rate was tested in 24 hours according to GB / T 17657-2013, and the mass change rate after immersion in water was measured. Test of resistance to damp heat aging: The bond strength retention rate was determined after damp heat aging at 85℃ / 85%RH for 168h in accordance with GB / T 17657-2013. Mechanical property testing: According to GB / T 17657-2013, the 180° peel test was conducted to determine the bond strength and compressive strength. Abrasion resistance test: According to GB / T 17657-2013, Taber abrasion test, load is 500g.

[0035] The test results are shown in Table 1 below.

[0036] Table 1 Performance Test Data of Formaldehyde-Free Impregnated Specialty Decorative Paper Conclusion: The examples effectively solve the problems of formaldehyde content, limited performance, and poor stability of impregnated paper prepared by traditional impregnating adhesives through the synergistic effect of components such as composite impregnation adhesive and amino-functionalized cellulose nanofibers. They achieve a multi-functional integration of formaldehyde-free environmental protection with wear resistance, light resistance, and water resistance, with stable and reliable performance and broad application prospects.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A formaldehyde-free adhesive for impregnating special decorative paper, characterized in that: The formaldehyde-free adhesive for impregnating special decorative paper comprises the following components by mass percentage: 60-75% composite impregnating adhesive, 5-15% amino-functionalized cellulose nanofibers, 0.8-1.5% carbodiimide, 0.2-0.6% modified cerium oxide nanoparticles, and the remainder being deionized water. The composite impregnation adhesive is prepared by blending polymethylhydrosiloxane modified acrylic resin and water-based nano-terminated polyurethane resin in a mass ratio of (7-9):(1-3).

2. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 1, characterized in that: The preparation method of the waterborne nano-terminated polyurethane resin includes the following steps: adding polyethylene adipate-1,4-butanediol diol to a reaction vessel, heating to 60-65°C, adding isophorone diisocyanate and an organic bismuth catalyst, further heating to 75-80°C and reacting for 2-3 hours, cooling to 40-45°C, adding 1,4-butanediol, stirring and reacting for 30-40 minutes, adding sulfonate hydrophilic chain extender AESA, maintaining the temperature for 1-1.5 hours, adding methyl ethyl ketone oxime, further cooling to 30-35°C, adding deionized water during stirring, and after the addition is complete, shearing emulsification and vacuum degassing are performed to obtain the waterborne nano-terminated polyurethane resin.

3. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 2, characterized in that: In the preparation of waterborne nano-terminated polyurethane resin, the mass ratio of polyethylene adipate-1,4-butanediol diol: isophorone diisocyanate: organic bismuth catalyst: 1,4-butanediol: sulfonate hydrophilic chain extender AESA: methyl ethyl ketone oxime: deionized water is 100:(20.3-28.5):(0.1-0.14):(2.25-4.95):(3.73-6.22):(7.67-8.04):(139-399); the deionized water addition rate is 5-10 mL / min.

4. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 1, characterized in that: The preparation method of the polymethylhydrosiloxane modified acrylic resin includes the following steps: adding polymethylhydrosiloxane and divinylbenzene into a reaction vessel, adding a platinum catalyst, heating to 150-155℃ and reacting for 30-60 min, cooling to room temperature, and obtaining modified polymethylhydrosiloxane. Modified polymethylhydrosiloxane, styrene, isooctyl acrylate, hydroxyethyl acrylate, and glycidyl methacrylate were added to a reaction vessel, along with benzoyl peroxide. The mixture was stirred until homogeneous and then added dropwise to a xylene / butyl acetate mixed solvent at 90-95°C. After the addition was complete, the mixture was heated to 110-115°C and reacted for 6-8 hours. The mixture was then cooled to room temperature to obtain polymethylhydrosiloxane-modified acrylic resin.

5. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 4, characterized in that: In the preparation of modified polymethylhydrosiloxane, the molar ratio of polymethylhydrosiloxane to divinylbenzene is 2:1, and the amount of platinum catalyst added is 0.5-0.6% of the total mass of polymethylhydrosiloxane and divinylbenzene. In the preparation of polymethylhydrosiloxane modified acrylic resin, the mass ratio of the total mass of modified polymethylhydrosiloxane, styrene, isooctyl acrylate, hydroxyethyl acrylate, and glycidyl methacrylate to benzoyl peroxide is (5-20):(78-94):(0.8-2); wherein, the mass ratio of styrene:isooctyl acrylate:hydroxyethyl acrylate:glycidyl methacrylate is (25-35):(30-40):(15-20):(10-15); The xylene / butyl acetate mixed solvent is 30-50% of the total mass of the polymethylhydrosiloxane modified acrylic resin.

6. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 1, characterized in that: The preparation method of the amino-functionalized cellulose nanofibers includes the following steps: ultrasonically dispersing 2.5-3 wt% cellulose nanofibers in deionized water, adding 3-(2-aminoethylamino)propylmethyldimethoxysilane, heating to 90-95℃ and reacting for 3-6 h, adding 0.25-0.3 mol / L calcium chloride solution, cooling to 50-60℃ and stirring, and replacing the solvent with 50%, 75%, and 100% tert-butanol at 8-hour intervals to obtain amino-functionalized cellulose nanofibers.

7. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 6, characterized in that: In the preparation of amino-functionalized cellulose nanofibers, the amount of 3-(2-aminoethylamino)propylmethyldimethoxysilane added is 3-8% of the mass of the cellulose nanofibers.

8. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 1, characterized in that: The method for preparing modified cerium oxide nanoparticles includes the following steps: ultrasonically dispersing cerium oxide nanoparticles in deionized water to form a cerium oxide nanoparticle dispersion; adjusting the pH of the dispersion to 4.5 using hydrochloric acid; adding 3-glycidyloxypropyltrimethoxysilane; and heating to 60-65℃ for 8-8.5 h to obtain modified cerium oxide nanoparticles.

9. The formaldehyde-free adhesive for impregnating special decorative paper according to claim 8, characterized in that: In the preparation of modified cerium oxide nanoparticles, the solid content of the cerium oxide nanodispersion is 20-25%; the mass ratio of cerium oxide nanoparticles to 3-glycidyloxypropyltrimethoxysilane is 3:

1.

10. A method for preparing a formaldehyde-free adhesive for impregnating special decorative paper according to any one of claims 1-9, characterized in that: The process includes the following steps: adding polymethylhydrosiloxane-modified acrylic resin, amino-functionalized cellulose nanofibers, carbodiimide, modified cerium oxide nanoparticles, and deionized water sequentially into a reaction apparatus, heating to 20-25℃ and mixing evenly to obtain formaldehyde-free adhesive for impregnating special decorative paper.

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