Highly weather-resistant formaldehyde-free finishing paper and preparation method thereof

Abstract

Disclosed are highly weather-resistant formaldehyde-free facing paper and a preparation method thereof, belonging to the technical field of impregnated paper. The highly weather-resistant formaldehyde-free facing paper is obtained from plain base paper or printed decorative paper through a four-step process of impregnation with impregnating glue, primary drying for pre-crosslinking, coating with a rubber roller, and secondary drying for pre-curing. The obtained highly weather-resistant formaldehyde-free facing paper has a wet strength of 5.74-6.17 MPa, a tensile strength of 7.10-7.43 MPa, an adhesion grade of 1, a surface bonding strength of 1.64-1.73 MPa, a surface abrasion value of 22-27 mg / 100r, a surface dry heat resistance of 5, a surface resistance to hot and cold cycles without cracks, bubbling, discoloration, or wrinkling, a surface cracking resistance of 5, a surface water vapor resistance of 5, a surface light color fastness of 5, and a formaldehyde emission of 0 mg / L.

Description

Technical Field

[0001] The invention relates to highly weather-resistant formaldehyde-free facing paper and a preparation method thereof, belonging to the technical field of impregnated paper. Background Art

[0002] Facing paper, also known as decorative paper, is used to protect and decorate the surface of wood-based panels. Not only does it create a rich, stylish, and beautiful surface, it also imparts numerous properties, including wear resistance, heat resistance, weather resistance, and stain resistance. Facing paper has traditionally been impregnated with aldehyde-based adhesives such as urea-formaldehyde resin and melamine-formaldehyde resin. The harmful effects of free formaldehyde are unavoidable, making the use of formaldehyde-free facing paper a top priority for the wood-based panel industry and related industries.

[0003] At present, the formaldehyde-free adhesives with the widest application range and high research popularity in the impregnation of facing paper are mostly water-based polyurethane and water-based acrylic resin adhesives. The structure and performance of these two types of adhesives can be adjusted greatly, and their film-forming properties and paper covering power are relatively ideal. In addition, corresponding adhesive products can be developed according to the performance of decorative base paper and the quality requirements of artificial board products.

[0004] While water-based polyurethane and water-based acrylic resin adhesives for facing paper offer advantages such as being environmentally friendly, formaldehyde-free, fast drying, and excellent film-forming properties, they also suffer from issues such as poor surface hardness and scratch and abrasion resistance after impregnation. Rapid film formation during production can lead to paper sticking to steel rollers and breaking, as well as poor weather resistance during subsequent use. Therefore, when using adhesives based on water-based polyurethane or water-based acrylic resins in the production of formaldehyde-free facing paper, it is necessary to enhance the mechanical properties and weather resistance of these adhesives. Furthermore, the dry / wet tensile strength of the base paper needs to be substantially improved to accommodate the demands of rapid film formation and high-speed production.

[0005] Chinese patent CN114293402A discloses a formaldehyde-free hot-pressed impregnated decorative paper and its preparation method. The method involves selecting a water-based acrylic resin, water-based polyurethane, or a mixture of the two and adding a certain amount of water to form an impregnating adhesive. Decorative base paper is then immersed in the impregnating adhesive for a certain period of time to produce decorative paper with varying amounts of impregnation. The impregnated decorative paper is then bonded to a wood-based panel and hot-pressed in a hot press at a specific temperature and pressure to produce the impregnated hot-pressed decorative paper. While this patent uses adhesives based on water-based acrylic resins and water-based polyurethanes, it avoids formaldehyde release. However, it does not address the poor mechanical properties and weather resistance of the decorative paper associated with these two resin adhesives, nor does it improve the base paper's dry and wet tensile strength to prevent breakage.

[0006] Chinese patent CN109537355A discloses a long-lasting formaldehyde-free impregnated paper and its preparation method. The raw materials of the long-lasting formaldehyde-free impregnated paper include base paper and a modified impregnating resin; the raw materials of the modified impregnating resin include formaldehyde solution, 2-methyl-2-butanol, sodium hydroxide solution, formaldehyde-removing reinforcing phase emulsion, phenol, and acetic acid solution; the raw materials of the formaldehyde-removing reinforcing phase emulsion include formaldehyde-removing reinforcing phase matrix powder, surface deposition liquid, and n-octadecyl alcohol; the raw materials of the surface deposition liquid include hydrochloric acid, potato starch, dicyclohexyl peroxydicarbonate, nonylphenol polyoxyethylene ether, methyl methacrylate, blocked isocyanate, and sodium hydroxide solution; and the raw materials of the reinforcing phase matrix include nano-coconut fiber carbon, anhydrous ethanol, anhydrous acetic acid, and an ammonia solution. Compared with the prior art, the long-lasting formaldehyde-free impregnated paper according to the embodiments of the present invention can significantly improve the impregnation bonding performance and storage characteristics; improve transparency and weight, and will not cause harm to the human body and the environment during long-term use. This patent does not avoid the use of formaldehyde. Although the use process of impregnated paper can achieve zero formaldehyde release, the formaldehyde pollution problem in the production process is difficult to completely avoid. Moreover, the patented impregnated paper uses liquid carbon dioxide supercritical treatment during the shaping process. This harsh treatment condition will undoubtedly increase production costs.

[0007] From the above, we can see that the current formaldehyde-free facing paper still has problems such as low mechanical properties, poor weather resistance, low dry / wet tensile strength of the base paper, and difficulty in matching adhesives with fast film-forming speeds. Therefore, it is of great practical significance to develop a highly weather-resistant formaldehyde-free facing paper to promote the solution of the above problems. Summary of the Invention

[0008] In response to the shortcomings of the above-mentioned prior art, the present invention provides a highly weather-resistant formaldehyde-free facing paper and a preparation method thereof, to achieve the following invention objectives: to prepare formaldehyde-free facing paper with good mechanical properties, good weather resistance, and base paper dry / wet tensile strength that is suitable for the high-speed production rate of water-based quick-drying adhesives.

[0009] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0010] A highly weather-resistant formaldehyde-free facing paper and a preparation method thereof, wherein the highly weather-resistant formaldehyde-free facing paper is prepared from one of plain base paper and printed decorative paper through a four-step process of impregnation with an impregnating adhesive, primary drying and pre-crosslinking, coating with a rubber roller, and secondary drying and pre-curing;

[0011] The impregnation glue is mainly composed of dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine, a cross-linking agent, and deionized water;

[0012] The coating glue is mainly composed of water-based polyacrylate emulsion, cyclodextrin-embedded diallyl phthalate, modified titanium dioxide, ammonium polyacrylate, and deionized water;

[0013] The preparation method of the highly weather-resistant formaldehyde-free facing paper comprises nine steps: preparation of a dialdehyde carboxymethyl chitosan aqueous solution, preparation of cyclodextrin-embedded diallyl phthalate, preparation of modified titanium dioxide, preparation of an impregnating adhesive, preparation of a coating adhesive, impregnation of the impregnating adhesive, primary drying and pre-crosslinking, coating with a coating adhesive roller, and secondary drying and pre-curing.

[0014] The following are further improvements to the above technical solution:

[0015] Step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution

[0016] Carboxymethyl chitosan is added to deionized water, and the temperature is raised and kept constant at 60-80° C. while controlling the stirring rate at 600-900 rpm. 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide are then added. After they are completely dissolved, hydrogen peroxide is added dropwise at a rate of 0.5-30 g / min. After the hydrogen peroxide is added dropwise, the reaction is continued at a constant temperature with stirring for 3-7 hours, and then the temperature is lowered to room temperature to stop the reaction to obtain a dialdehyde carboxymethyl chitosan aqueous solution.

[0017] The carboxymethyl chitosan has a deacetylation degree of 60-95%, a carboxylation degree of 60-85%, and a molecular weight of 1.0×10 5 ~3.5×10 5 g / mol;

[0018] The mass concentration of hydrogen peroxide in the hydrogen peroxide is 8-20wt%;

[0019] The mass ratio of the carboxymethyl chitosan, deionized water, 2,2,6,6-tetramethylpiperidinium oxide, N-chlorosuccinimide and hydrogen peroxide is 40-110:55-120:0.5-1.5:0.5-1.0:10-40.

[0020] Step 2: Preparation of cyclodextrin-encapsulated diallyl phthalate

[0021] β-cyclodextrin is stirred and dissolved in hot water at 65-80°C to obtain a β-cyclodextrin aqueous solution. The stirring speed is controlled at 400-700 rpm and the temperature is constant at 35-55°C. The ethanol solution of diallyl phthalate is slowly added dropwise. After the addition is completed, the mixture is stirred and reacted at a constant temperature for 4-9 hours. The mixture is allowed to stand at 0-4°C for 20-30 hours. The mixture is then discharged and filtered at 0-4°C. The filtrate is freeze-dried at -10-0°C for 8-14 hours to obtain cyclodextrin-encapsulated diallyl phthalate, which is then stored in a cool and dry environment.

[0022] In the β-cyclodextrin aqueous solution, the mass fraction of β-cyclodextrin is 1-20wt%;

[0023] The ethanol solution of diallyl phthalate is slowly added dropwise at a rate of 1 to 35 g / min, and the mass of the added solution is 1 to 3 times the mass of the β-cyclodextrin aqueous solution;

[0024] The ethanol solution of diallyl phthalate has a mass ratio of diallyl phthalate to ethanol of 20-100:300.

[0025] Step 3: Preparation of modified titanium dioxide

[0026] After drying the nano-titanium dioxide at 70-110° C. for 10-19 hours, the dried nano-titanium dioxide, oleic acid diethanolamide borate, and ethyl acetate are added to a high-speed dispersion kettle, and then dispersed at a high speed of 5000-8000 rpm for 5-9 hours. The temperature is then raised and kept constant at 50-65° C., and the dispersion rate is reduced to 1000-3000 rpm. 3-isocyanate propyltriethoxysilane is then added, and the amino-terminated hyperbranched polyamide is added after the constant temperature reaction for 6-18 hours. The stirring and dispersion are continued, and after the reaction is continued for 5-11 hours, the temperature is cooled to room temperature and centrifuged. The obtained solid is washed with anhydrous ethanol 2-4 times and dried at 50-80° C. for 4-8 hours to obtain the modified titanium dioxide.

[0027] The nano titanium dioxide is rutile and has a particle size of 1 to 100 nm;

[0028] The amino group number of the amino-terminated hyperbranched polyamide is 4 to 11 mol / mol and the molecular weight is 200 to 1000 g / mol;

[0029] The mass ratio of the dried nano-titanium dioxide, oleic acid diethanolamide borate, ethyl acetate, 3-isocyanate propyl triethoxysilane, and amino-terminated hyperbranched polyamide is 20-50:0.1-2:150-250:3-7:2-9.

[0030] Step 4: Preparation of impregnation glue

[0031] The specific formula of the impregnating glue is as follows in parts by weight:

[0032] 15-40 parts of dialdehyde carboxymethyl chitosan aqueous solution,

[0033] 0.5-10 parts of polyvinyl alcohol,

[0034] 4-9 parts of polyethyleneimine aqueous solution,

[0035] Cross-linking agent 0.1~1 part,

[0036] Defoaming agent polyether-siloxane copolymer 0.1~0.2 parts,

[0037] 60-90 parts of deionized water;

[0038] The molecular weight of the polyvinyl alcohol is 10,000 to 250,000 g / mol;

[0039] The mass fraction of polyethyleneimine in the polyethyleneimine aqueous solution is 10-30wt%, and the molecular weight of polyethyleneimine is 20000-100000 g / mol;

[0040] The cross-linking agent is one of bishydroxyethyl sulfone, 1,3-bishydroxymethyl urea, and dihydroxymethyl dihydroxyethylene urea resin;

[0041] According to the specific formula of the impregnation glue in parts by weight, dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine aqueous solution, crosslinking agent, defoaming agent polyether-siloxane copolymer, and deionized water are added to a stirring kettle, and the transparent liquid obtained after complete dissolution by stirring is the impregnation glue.

[0042] Step 5: Preparation of coating glue

[0043] The specific formula of the coating glue is calculated in parts by weight:

[0044] 55~100 parts of water-based polyacrylate emulsion,

[0045] Cyclodextrin embedded diallyl phthalate 1-9 parts,

[0046] 1~10 parts of modified titanium dioxide,

[0047] Dispersant ammonium polyacrylate 0.5~3 parts,

[0048] Defoaming agent polyether-siloxane copolymer 0.1~0.2 parts,

[0049] 40-100 parts of deionized water;

[0050] The aqueous polyacrylate emulsion has a solid content of 45-65%, a viscosity of 1000-5000 mPa·s, and a pH value of 6-8.5;

[0051] According to the specific formula of the coating glue in parts by weight, deionized water, defoaming agent polyether-siloxane copolymer, dispersant ammonium polyacrylate, and modified titanium dioxide are placed in a high-speed dispersing kettle. After high-speed dispersion at a dispersion rate of 7500-11000 rpm for 5-11 hours, the dispersion rate is reduced to 3500-5000 rpm, and cyclodextrin-embedded diallyl phthalate and aqueous polyacrylate emulsion are added. After continuing to disperse for 3-6 hours, the coating glue is discharged.

[0052] Step 6: Dipping Glue

[0053] The plain base paper or printed decorative paper is unwound by a paper pulling machine at a speed of 10-35 m / min. The unwound plain base paper or printed decorative paper passes through a counterweight roller and a pulling roller in sequence, and then enters an impregnation tank for impregnation. The impregnation temperature is controlled at 20-35°C, and the impregnation time is controlled at 3-11 seconds. The impregnated plain base paper or printed decorative paper passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue on both sides of the plain base paper or printed decorative paper to obtain a pre-impregnated base paper with neat edges.

[0054] Step 7: One-time drying and pre-crosslinking

[0055] The pre-impregnated collagen paper enters the oven for pre-crosslinking under the action of the traction roller. The oven is controlled at 60-90°C and the pre-crosslinking time is controlled at 10-35 seconds. After leaving the oven, it is naturally cooled to obtain pre-crosslinked paper.

[0056] Step 8: Apply rubber roller

[0057] The pre-cross-linked paper enters the glue coating tank under the traction of the traction roller and is roller coated on both sides. The temperature of the coating glue is controlled at 20~35℃ and the roller coating time is controlled at 4~9 seconds. The pre-cross-linked paper after roller coating passes through the metering roller to make the glue layer evenly distributed, and then passes through the scraper to scrape off the glue on both sides of the pre-cross-linked paper to obtain coated paper with neat edges.

[0058] Step 9: Secondary drying and pre-curing

[0059] Under the action of the traction roller, the coated paper enters the oven for pre-curing treatment. The oven is divided into two temperature control sections. The temperature of the first section is controlled at 80~110℃, and the second section is controlled at 110~130℃. The pre-curing treatment time is controlled at 10~40 seconds. After the pre-curing is completed, it leaves the oven and enters the air cooling channel. After air cooling to room temperature, it is rolled up to obtain highly weather-resistant formaldehyde-free finishing paper.

[0060] Compared with the prior art, the present invention achieves the following beneficial effects:

[0061] 1. The present invention uses relatively mild oxidants 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide, in conjunction with the process of slowly adding hydrogen peroxide, to carry out precise and controllable directional oxidation of carboxymethyl chitosan. The hydroxyl groups on the carboxymethyl chitosan are directional oxidized to aldehyde groups. The generated dialdehyde carboxymethyl chitosan contains a large number of polar functional groups, such as aldehyde groups, amino groups and unoxidized hydroxyl groups, so it has a strong adsorption and penetration effect on the base paper. The above-mentioned polar functional groups and the hydroxyl groups in the base paper fibers also have a strong Hydrogen bonding greatly improves the wet strength of the base paper. In the single drying pre-crosslinking step, dialdehyde carboxymethyl chitosan can undergo self-crosslinking reactions based on the large number of aldehyde groups it carries, and is also very easy to undergo crosslinking reactions with polyvinyl alcohol and polyethyleneimine contained in the impregnating glue. These crosslinking reactions can quickly improve the mechanical strength of the initial impregnated base paper, thereby avoiding the problem of paper breakage due to insufficient strength in the subsequent roller coating process. At the same time, it also plays a very important role in improving the mechanical properties of the final high-weather-resistant formaldehyde-free facing paper.

[0062] 2. In the impregnation glue formula designed by the present invention, polyethyleneimine and polyvinyl alcohol have very strong affinity and penetration with the base paper. Combined with the polar functional group effect contained in dialdehyde carboxymethyl chitosan, the combination of these three can quickly improve the wet strength of the base paper, so that the base paper can adapt to the high guide speed in the impregnation step of the impregnation glue, maintain a high paper feed speed without paper breakage problems, and the cross-linking agents such as bishydroxyethyl sulfone, 1,3-bishydroxymethyl urea, and dihydroxymethyl dihydroxyethylene urea resin added to the impregnation glue cooperate with the cross-linking effect of the aldehyde groups contained in dialdehyde carboxymethyl chitosan. After the base paper is impregnated with glue and during the one-time drying and pre-cross-linking process, polyethyleneimine, polyvinyl alcohol, cross-linking agent and dialdehyde carboxymethyl chitosan undergo pre-cross-linking reaction, thereby giving the base paper extremely strong wet strength and tensile strength, which can not only improve the mechanical properties of the final finishing paper product, but also avoid the problem of paper breakage at high paper feed speeds;

[0063] 3. The present invention prepares cyclodextrin-embedded diallyl phthalate, uniformly disperses the oily diallyl phthalate into an aqueous coating adhesive system, and during the secondary drying and pre-curing process, the diallyl phthalate overflows from the cyclodextrin cavity under the action of heat, undergoing a certain degree of cross-linking reaction with the aqueous polyacrylate undergoing a film-forming reaction. During the final high-pressure heat bonding process of the artificial board, the diallyl phthalate and the aqueous polyacrylate undergo a more complete curing and cross-linking reaction, thereby significantly improving the hardness, wear resistance, weather resistance, bonding strength, and other mechanical properties of the facing paper surface by increasing the cross-linking and curing density of the facing paper resin system.

[0064] 4. The present invention modifies the surface of nano-titanium dioxide. First, under the dispersing effect of oleic acid diethanolamide borate, the nano-titanium dioxide is dispersed into ethyl acetate by relying on a high-speed dispersion process. The hydroxyl groups on the surface of the nano-titanium dioxide dispersed at the nanoscale first react with 3-isocyanate propyltriethoxysilane, and the hydroxyl groups on the surface of the nano-titanium dioxide are converted into silanol groups and isocyanate groups. These two functional groups then react with the terminal amino groups of the amino-terminated hyperbranched polyamide, thereby coating the surface of the nano-titanium dioxide with a layer of amino-terminated hyperbranched polyamide. The amino-terminated hyperbranched polyamide has strong polarity and can be uniformly dispersed in an aqueous system. This avoids the agglomeration of nano-titanium dioxide in the coating adhesive system. The surface-modified nano-titanium dioxide is dispersed in the coating adhesive system at the nanoscale. After being coated on the facing paper and undergoing the pre-curing reaction and the high-pressure heat bonding reaction in the artificial board manufacturing process, the nano-titanium dioxide can still maintain its nano-scale dispersion state. In addition, the terminal amino group of the amino-terminated hyperbranched polyamide coated on the surface of the nano-titanium dioxide will also undergo a cross-linking reaction with the water-based polyacrylate. In this way, the nano-titanium dioxide can not only give the facing paper excellent weather resistance in the form of nano-scale particles, but also greatly improve the mechanical properties of the facing paper due to its participation in the cross-linking and curing reaction.

[0065] 5. The impregnating glue and coating glue designed by the present invention do not contain formaldehyde in their formulas, and the entire production process of the facing paper does not involve any formaldehyde components. Therefore, the production of highly weather-resistant formaldehyde-free facing paper using the technical solution of the present invention can achieve formaldehyde-free production throughout the entire process.

[0066] 6. The high-weather-resistant formaldehyde-free facing paper obtained by the present invention has a wet strength of the initial impregnated collagen base paper of 1.08~1.32 MPa, a tensile strength of the initial impregnated collagen base paper of 1.86~2.05 MPa, a wet strength of the pre-crosslinked paper of 2.20~2.42 MPa, a tensile strength of the pre-crosslinked paper of 2.95~3.38 MPa, a wet strength of the high-weather-resistant formaldehyde-free facing paper of 5.74~6.17 MPa, a tensile strength of the high-weather-resistant formaldehyde-free facing paper of 7.10~7.43 MPa, an adhesion grade of 1, a surface bonding strength of 1.64~1.73 MPa, a surface abrasion value of 22~27 mg / 100r, a surface dry heat resistance of 5, a surface resistance to cold and hot cycles without cracks, bubbling, discoloration, or wrinkling, a surface cracking resistance of 5, a surface water vapor resistance of 5, a surface light color fastness of 5, and a formaldehyde release of 0 mg / L. DETAILED DESCRIPTION

[0067] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0068] Example 1: A method for preparing highly weather-resistant formaldehyde-free facing paper

[0069] Step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution

[0070] Carboxymethyl chitosan was added to deionized water, and the temperature was raised and kept constant at 75°C while controlling the stirring rate at 800 rpm. 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide were then added. After they were completely dissolved, hydrogen peroxide was added dropwise at a rate of 10 g / min. After the addition of hydrogen peroxide was completed, the mixture was stirred at a constant temperature for 4 hours, and then cooled to room temperature to stop the reaction to obtain a dialdehyde carboxymethyl chitosan aqueous solution.

[0071] The carboxymethyl chitosan has a deacetylation degree of 85%, a carboxylation degree of 80%, and a molecular weight of 2.5×10 5 g / mol;

[0072] The mass concentration of hydrogen peroxide in the hydrogen peroxide is 12wt%;

[0073] The mass ratio of the carboxymethyl chitosan, deionized water, 2,2,6,6-tetramethylpiperidinoxide, N-chlorosuccinimide and hydrogen peroxide is 70:100:1:0.7:30.

[0074] Step 2: Preparation of cyclodextrin-encapsulated diallyl phthalate

[0075] β-cyclodextrin was stirred and dissolved in 70°C hot water to obtain a β-cyclodextrin aqueous solution. The stirring speed was controlled at 600 rpm and the temperature was constant at 40°C. The ethanol solution of diallyl phthalate was slowly added dropwise. After the addition was completed, the reaction was continued at a constant temperature with stirring for 6 hours. After standing at 1°C for 27 hours, the product was discharged and filtered at 1°C. The filtrate was freeze-dried at -6°C for 11 hours to obtain cyclodextrin-encapsulated diallyl phthalate, which was then stored in a cool and dry environment.

[0076] In the β-cyclodextrin aqueous solution, the mass fraction of β-cyclodextrin is 13wt%;

[0077] The ethanol solution of diallyl phthalate is slowly added dropwise at a rate of 20 g / min, and the mass of the added solution is twice the mass of the β-cyclodextrin aqueous solution;

[0078] The ethanol solution of diallyl phthalate has a mass ratio of diallyl phthalate to ethanol of 70:300.

[0079] Step 3: Preparation of modified titanium dioxide

[0080] After the nano-titanium dioxide was dried at 100° C. for 13 hours, the dried nano-titanium dioxide, oleic acid diethanolamide borate, and ethyl acetate were added to a high-speed dispersion kettle, and then dispersed at a high speed of 6500 rpm for 8 hours. The temperature was then raised and kept constant at 63° C., and the dispersion rate was reduced to 1700 rpm. 3-isocyanate propyltriethoxysilane was added, and the amino-terminated hyperbranched polyamide was added after constant temperature reaction for 13 hours. Stirring and dispersion were continued, and the reaction was continued for 7 hours. The temperature was cooled to room temperature and centrifuged. The obtained solid was washed with anhydrous ethanol three times and dried at 75° C. for 5 hours to obtain modified titanium dioxide.

[0081] The nano titanium dioxide is rutile and has a particle size of 40 nm;

[0082] The amino group number of the amino-terminated hyperbranched polyamide is 7 mol / mol and the molecular weight is 650 g / mol;

[0083] The mass ratio of the dried nano-titanium dioxide, oleic acid diethanolamide borate, ethyl acetate, 3-isocyanate propyl triethoxysilane, and amino-terminated hyperbranched polyamide is 40:1:210:4:5.

[0084] Step 4: Preparation of impregnation glue

[0085] The specific formula of the impregnating glue is as follows in parts by weight:

[0086] 22 parts of dialdehyde carboxymethyl chitosan aqueous solution,

[0087] 3 parts of polyvinyl alcohol,

[0088] 5 parts of polyethyleneimine aqueous solution,

[0089] 0.7 parts of cross-linking agent,

[0090] Defoaming agent polyether-siloxane copolymer 0.16 parts,

[0091] 75 parts of deionized water;

[0092] The molecular weight of the polyvinyl alcohol is 80000 g / mol;

[0093] The mass fraction of polyethyleneimine in the polyethyleneimine aqueous solution is 18 wt %, and the molecular weight of polyethyleneimine is 70,000 g / mol;

[0094] The cross-linking agent is bishydroxyethyl sulfone;

[0095] According to the specific formula of the impregnation glue in parts by weight, dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine aqueous solution, crosslinking agent, defoaming agent polyether-siloxane copolymer, and deionized water are added to a stirring kettle, and the transparent liquid obtained after complete dissolution by stirring is the impregnation glue.

[0096] Step 5: Preparation of coating glue

[0097] The specific formula of the coating glue is calculated in parts by weight:

[0098] 80 parts of water-based polyacrylate emulsion,

[0099] Cyclodextrin embedded diallyl phthalate 6 parts,

[0100] 7 parts of modified titanium dioxide,

[0101] Dispersant ammonium polyacrylate 1 part,

[0102] Defoaming agent polyether-siloxane copolymer 0.13 parts,

[0103] 65 parts of deionized water;

[0104] The aqueous polyacrylate emulsion has a solid content of 60%, a viscosity of 2000 mPa·s, and a pH value of 7;

[0105] According to the specific formula of the coating glue in parts by weight, deionized water, defoaming agent polyether-siloxane copolymer, dispersant ammonium polyacrylate, and modified titanium dioxide are placed in a high-speed dispersing kettle. After high-speed dispersion at a dispersion rate of 10,000 rpm for 9 hours, the dispersion rate is reduced to 4,500 rpm, and cyclodextrin-embedded diallyl phthalate and aqueous polyacrylate emulsion are added. After continuing to disperse for 4 hours, the coating glue is discharged.

[0106] Step 6: Dipping Glue

[0107] The plain base paper or printed decorative paper is unwound by a paper pulling machine at a speed of 20 m / min. The unwound plain base paper or printed decorative paper passes through a counterweight roller and a pulling roller in sequence, and then enters an impregnation tank for impregnation. The impregnation temperature is controlled at 25°C, and the impregnation time is controlled at 6 seconds. The impregnated plain base paper or printed decorative paper passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue on both sides of the plain base paper or printed decorative paper to obtain a pre-impregnated base paper with neat edges.

[0108] Step 7: One-time drying and pre-crosslinking

[0109] The pre-impregnated collagen paper enters the oven for pre-crosslinking under the action of the traction roller. The oven is controlled at 70°C and the pre-crosslinking time is controlled at 18 seconds. After leaving the oven, it is naturally cooled to obtain pre-crosslinked paper.

[0110] Step 8: Apply rubber roller

[0111] The pre-cross-linked paper enters the glue coating tank under the traction of the traction roller and is roller coated on both sides. The temperature of the coating glue is controlled at 28°C and the roller coating time is controlled at 5 seconds. The pre-cross-linked paper after roller coating passes through the metering roller to make the glue layer evenly distributed, and then passes through the scraper to scrape off the glue on both sides of the pre-cross-linked paper to obtain coated paper with neat edges.

[0112] Step 9: Secondary drying and pre-curing

[0113] Under the action of the traction roller, the coated paper enters the oven for pre-curing treatment. The oven is divided into two sections for temperature control. The temperature of the first section is controlled at 90°C and the second section is controlled at 125°C. The pre-curing treatment time is controlled at 30 seconds. After the pre-curing is completed, it leaves the oven and enters the air cooling channel. After air cooling to room temperature, it is rolled up to obtain highly weather-resistant formaldehyde-free finishing paper.

[0114] Example 2: Preparation method of highly weather-resistant formaldehyde-free facing paper

[0115] Step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution

[0116] Carboxymethyl chitosan was added to deionized water, and the temperature was raised and kept constant at 60°C while controlling the stirring rate at 600 rpm. Then, 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide were added. After they were completely dissolved, hydrogen peroxide was added dropwise at a rate of 0.5 g / min. After the addition of hydrogen peroxide was completed, the mixture was stirred at a constant temperature for 3 hours, and then cooled to room temperature to stop the reaction to obtain a dialdehyde carboxymethyl chitosan aqueous solution.

[0117] The carboxymethyl chitosan has a deacetylation degree of 60%, a carboxylation degree of 60%, and a molecular weight of 1.0×10 5 g / mol;

[0118] The mass concentration of hydrogen peroxide in the hydrogen peroxide is 8wt%;

[0119] The mass ratio of the carboxymethyl chitosan, deionized water, 2,2,6,6-tetramethylpiperidinoxide, N-chlorosuccinimide and hydrogen peroxide is 40:55:0.5:0.5:10.

[0120] Step 2: Preparation of cyclodextrin-encapsulated diallyl phthalate

[0121] β-cyclodextrin was stirred and dissolved in 65°C hot water to obtain a β-cyclodextrin aqueous solution. The stirring speed was controlled at 400 rpm and the temperature was constant at 35°C. The ethanol solution of diallyl phthalate was slowly added dropwise. After the addition was completed, the reaction was continued at a constant temperature with stirring for 4 hours. The mixture was allowed to stand at 0°C for 20 hours, and then the mixture was discharged and filtered at 0°C. The filtrate was freeze-dried at -10°C for 8 hours to obtain cyclodextrin-encapsulated diallyl phthalate, which was then stored in a cool and dry environment.

[0122] In the β-cyclodextrin aqueous solution, the mass fraction of β-cyclodextrin is 1wt%;

[0123] The ethanol solution of diallyl phthalate is slowly added dropwise at a rate of 1 g / min, and the mass of the added solution is 1 times the mass of the β-cyclodextrin aqueous solution;

[0124] The ethanol solution of diallyl phthalate has a mass ratio of diallyl phthalate to ethanol of 20:300.

[0125] Step 3: Preparation of modified titanium dioxide

[0126] After the nano-titanium dioxide is dried at 70° C. for 10 hours, the dried nano-titanium dioxide, oleic acid diethanolamide borate, and ethyl acetate are added to a high-speed dispersion kettle, and then dispersed at a high speed of 5000 rpm for 5 hours. The temperature is then raised and kept constant at 50° C., and the dispersion rate is reduced to 1000 rpm. 3-isocyanate propyltriethoxysilane is then added. After the constant temperature reaction for 6 hours, the amino-terminated hyperbranched polyamide is added, and stirring and dispersion are continued. After the reaction for 5 hours, the mixture is cooled to room temperature and centrifuged. The obtained solid is washed twice with anhydrous ethanol and dried at 50° C. for 4 hours to obtain modified titanium dioxide.

[0127] The nano titanium dioxide is rutile and has a particle size of 1 nm;

[0128] The amino group number of the amino-terminated hyperbranched polyamide is 4 mol / mol and the molecular weight is 200 g / mol;

[0129] The mass ratio of the dried nano-titanium dioxide, oleic acid diethanolamide borate, ethyl acetate, 3-isocyanate propyl triethoxysilane, and amino-terminated hyperbranched polyamide is 20:0.1:150:3:2.

[0130] Step 4: Preparation of impregnation glue

[0131] The specific formula of the impregnating glue is as follows in parts by weight:

[0132] 15 parts of dialdehyde carboxymethyl chitosan aqueous solution,

[0133] 0.5 parts of polyvinyl alcohol,

[0134] 4 parts of polyethyleneimine aqueous solution,

[0135] 0.1 part of cross-linking agent,

[0136] Defoaming agent polyether-siloxane copolymer 0.1 part,

[0137] 60 parts of deionized water;

[0138] The molecular weight of the polyvinyl alcohol is 10000 g / mol;

[0139] The mass fraction of polyethyleneimine in the polyethyleneimine aqueous solution is 10wt%, and the molecular weight of polyethyleneimine is 20000g / mol;

[0140] The cross-linking agent is 1,3-bis(hydroxymethyl)urea;

[0141] According to the specific formula of the impregnation glue in parts by weight, dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine aqueous solution, crosslinking agent, defoaming agent polyether-siloxane copolymer, and deionized water are added to a stirring kettle, and the transparent liquid obtained after complete dissolution by stirring is the impregnation glue.

[0142] Step 5: Preparation of coating glue

[0143] The specific formula of the coating glue is calculated in parts by weight:

[0144] 55 parts of water-based polyacrylate emulsion,

[0145] Cyclodextrin-encapsulated diallyl phthalate 1 part,

[0146] 1 part of modified titanium dioxide,

[0147] Dispersant ammonium polyacrylate 0.5 parts,

[0148] Defoaming agent polyether-siloxane copolymer 0.1 part,

[0149] 40 parts of deionized water;

[0150] The aqueous polyacrylate emulsion has a solid content of 45%, a viscosity of 1000 mPa·s, and a pH value of 6;

[0151] According to the specific formula of the coating glue in parts by weight, deionized water, defoaming agent polyether-siloxane copolymer, dispersant ammonium polyacrylate, and modified titanium dioxide are placed in a high-speed dispersing kettle. After high-speed dispersion at a dispersion rate of 7500 rpm for 5 hours, the dispersion rate is reduced to 3500 rpm, and cyclodextrin-embedded diallyl phthalate and aqueous polyacrylate emulsion are added. After continuing to disperse for 3 hours, the coating glue is discharged.

[0152] Step 6: Dipping Glue

[0153] The plain base paper or printed decorative paper is unwound by a paper pulling machine at a speed of 10 m / min. The unwound plain base paper or printed decorative paper passes through a counterweight roller and a pulling roller in sequence, and then enters an impregnation tank for impregnation. The impregnation temperature is controlled at 20°C, and the impregnation time is controlled at 3 seconds. The impregnated plain base paper or printed decorative paper passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue on both sides of the plain base paper or printed decorative paper to obtain a pre-impregnated base paper with neat edges.

[0154] Step 7: One-time drying and pre-crosslinking

[0155] The pre-impregnated collagen paper enters the oven for pre-crosslinking under the action of the traction roller. The oven is controlled at 60°C and the pre-crosslinking time is controlled at 10 seconds. After leaving the oven, it is naturally cooled to obtain pre-crosslinked paper.

[0156] Step 8: Apply rubber roller

[0157] The pre-cross-linked paper enters the glue coating tank under the traction of the traction roller and is roller coated on both sides. The temperature of the coating glue is controlled at 20℃ and the roller coating time is controlled at 4 seconds. The pre-cross-linked paper after roller coating passes through the metering roller to make the glue layer evenly distributed, and then passes through the scraper to scrape off the glue on both sides of the pre-cross-linked paper to obtain coated paper with neat edges.

[0158] Step 9: Secondary drying and pre-curing

[0159] Under the action of the traction roller, the coated paper enters the oven for pre-curing treatment. The oven is divided into two temperature control sections. The temperature of the first section is controlled at 80°C and the second section is controlled at 110°C. The pre-curing treatment time is controlled at 10 seconds. After the pre-curing is completed, it leaves the oven and enters the air cooling channel. After air cooling to room temperature, it is rolled up to obtain highly weather-resistant formaldehyde-free finishing paper.

[0160] Example 3: Preparation method of highly weather-resistant formaldehyde-free facing paper

[0161] Step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution

[0162] Carboxymethyl chitosan was added to deionized water, and the temperature was raised and kept constant at 80° C. while controlling the stirring rate at 900 rpm. 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide were then added. After they were completely dissolved, hydrogen peroxide was added dropwise at a rate of 30 g / min. After the addition of hydrogen peroxide was completed, the mixture was stirred at a constant temperature for 7 hours, and then cooled to room temperature to stop the reaction to obtain a dialdehyde carboxymethyl chitosan aqueous solution.

[0163] The carboxymethyl chitosan has a deacetylation degree of 95%, a carboxylation degree of 85%, and a molecular weight of 3.5×10 5g / mol;

[0164] The mass concentration of hydrogen peroxide in the hydrogen peroxide is 20wt%;

[0165] The mass ratio of the carboxymethyl chitosan, deionized water, 2,2,6,6-tetramethylpiperidinium oxide, N-chlorosuccinimide and hydrogen peroxide is 110:120:1.5:1.0:40.

[0166] Step 2: Preparation of cyclodextrin-encapsulated diallyl phthalate

[0167] β-cyclodextrin was stirred and dissolved in 80°C hot water to obtain a β-cyclodextrin aqueous solution. The stirring speed was controlled at 700 rpm and the temperature was constant at 55°C. The ethanol solution of diallyl phthalate was slowly added dropwise. After the addition was completed, the reaction was continued at a constant temperature with stirring for 9 hours. The mixture was allowed to stand at 4°C for 30 hours. The mixture was then discharged and filtered at 4°C. The filtrate was freeze-dried at 0°C for 14 hours to obtain cyclodextrin-encapsulated diallyl phthalate, which was then stored in a cool and dry environment.

[0168] In the β-cyclodextrin aqueous solution, the mass fraction of β-cyclodextrin is 20wt%;

[0169] The ethanol solution of diallyl phthalate is slowly added dropwise at a rate of 35 g / min, and the mass of the added solution is 3 times the mass of the β-cyclodextrin aqueous solution;

[0170] The ethanol solution of diallyl phthalate has a mass ratio of diallyl phthalate to ethanol of 100:300.

[0171] Step 3: Preparation of modified titanium dioxide

[0172] After the nano-titanium dioxide is dried at 110° C. for 19 hours, the dried nano-titanium dioxide, oleic acid diethanolamide borate, and ethyl acetate are added to a high-speed dispersion kettle, and then dispersed at a high speed of 8000 rpm for 9 hours. The temperature is then raised and kept constant at 65° C., and the dispersion rate is reduced to 3000 rpm. 3-isocyanate propyl triethoxysilane is then added. After the constant temperature reaction for 18 hours, the amino-terminated hyperbranched polyamide is added. Stirring and dispersion are continued. After the reaction is continued for 11 hours, the mixture is cooled to room temperature and centrifuged. The obtained solid is washed with anhydrous ethanol four times and dried at 80° C. for 8 hours to obtain modified titanium dioxide.

[0173] The nano titanium dioxide is rutile and has a particle size of 100 nm;

[0174] The amino group number of the amino-terminated hyperbranched polyamide is 11 mol / mol and the molecular weight is 1000 g / mol;

[0175] The mass ratio of the dried nano-titanium dioxide, oleic acid diethanolamide borate, ethyl acetate, 3-isocyanate propyl triethoxysilane, and amino-terminated hyperbranched polyamide is 50:2:250:7:9.

[0176] Step 4: Preparation of impregnation glue

[0177] The specific formula of the impregnating glue is as follows in parts by weight:

[0178] 40 parts of dialdehyde carboxymethyl chitosan aqueous solution,

[0179] 10 parts of polyvinyl alcohol,

[0180] 9 parts of polyethyleneimine aqueous solution,

[0181] 1 part cross-linking agent,

[0182] Defoaming agent polyether-siloxane copolymer 0.2 parts,

[0183] 90 parts of deionized water;

[0184] The molecular weight of the polyvinyl alcohol is 250,000 g / mol;

[0185] The mass fraction of polyethyleneimine in the polyethyleneimine aqueous solution is 30wt%, and the molecular weight of polyethyleneimine is 100000g / mol;

[0186] The cross-linking agent is dimethylol dihydroxyethylene urea resin;

[0187] According to the specific formula of the impregnation glue in parts by weight, dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine aqueous solution, crosslinking agent, defoaming agent polyether-siloxane copolymer, and deionized water are added to a stirring kettle, and the transparent liquid obtained after complete dissolution by stirring is the impregnation glue.

[0188] Step 5: Preparation of coating glue

[0189] The specific formula of the coating glue is calculated in parts by weight:

[0190] 100 parts of water-based polyacrylate emulsion,

[0191] Cyclodextrin embedded diallyl phthalate 9 parts,

[0192] 10 parts of modified titanium dioxide,

[0193] Dispersant ammonium polyacrylate 3 parts,

[0194] Defoaming agent polyether-siloxane copolymer 0.2 parts,

[0195] 100 parts of deionized water;

[0196] The aqueous polyacrylate emulsion has a solid content of 65%, a viscosity of 5000 mPa·s, and a pH value of 8.5;

[0197] According to the specific formula of the coating glue in parts by weight, deionized water, defoaming agent polyether-siloxane copolymer, dispersant ammonium polyacrylate, and modified titanium dioxide are placed in a high-speed dispersing kettle. After high-speed dispersion at a dispersion rate of 11,000 rpm for 11 hours, the dispersion rate is reduced to 5,000 rpm, and cyclodextrin-embedded diallyl phthalate and aqueous polyacrylate emulsion are added. After continuing to disperse for 6 hours, the coating glue is discharged.

[0198] Step 6: Dipping Glue

[0199] The plain base paper or printed decorative paper is unwound by a paper pulling machine at a speed of 35 m / min. The unwound plain base paper or printed decorative paper passes through a counterweight roller and a pulling roller in sequence, and then enters an impregnation tank for impregnation. The impregnation temperature is controlled at 35°C, and the impregnation time is controlled at 11 seconds. The impregnated plain base paper or printed decorative paper passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue on both sides of the plain base paper or printed decorative paper to obtain a pre-impregnated base paper with neat edges.

[0200] Step 7: One-time drying and pre-crosslinking

[0201] The pre-impregnated collagen paper enters the oven for pre-crosslinking under the action of the traction roller. The oven is controlled at 90° C. and the pre-crosslinking time is controlled at 35 seconds. After leaving the oven, it is naturally cooled to obtain pre-crosslinked paper.

[0202] Step 8: Apply rubber roller

[0203] The pre-cross-linked paper enters the glue coating tank under the traction of the traction roller and is roller coated on both sides. The temperature of the coating glue is controlled at 35℃ and the roller coating time is controlled at 9 seconds. The pre-cross-linked paper after roller coating passes through the metering roller to make the glue layer evenly distributed, and then passes through the scraper to scrape off the glue on both sides of the pre-cross-linked paper to obtain coated paper with neat edges.

[0204] Step 9: Secondary drying and pre-curing

[0205] Under the action of the traction roller, the coated paper enters the oven for pre-curing treatment. The oven is divided into two temperature control sections. The temperature of the first section is controlled at 110°C and the second section is controlled at 130°C. The pre-curing treatment time is controlled at 40 seconds. After the pre-curing is completed, it leaves the oven and enters the air cooling channel. After air cooling to room temperature, it is rolled up to obtain highly weather-resistant formaldehyde-free finishing paper.

[0206] Comparative Example 1: Based on Example 1, step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution, was not performed. In step 4, preparation of impregnated glue, 22 parts of dialdehyde carboxymethyl chitosan aqueous solution were replaced by 22 parts of deionized water. The specific operation was as follows:

[0207] Step 1, preparation of dialdehyde carboxymethyl chitosan aqueous solution is not performed;

[0208] The operations of steps 2 and 3 are the same as those in Example 1;

[0209] Step 4: Preparation of impregnation glue

[0210] The 22 parts of dialdehyde carboxymethyl chitosan aqueous solution were replaced by 22 parts of deionized water, and the other operations were the same as in Example 1;

[0211] The operations of steps 5, 6, 7, 8, and 9 are the same as those in Example 1.

[0212] Comparative Example 2: Based on Example 1, step 2, preparation of cyclodextrin-encapsulated diallyl phthalate, was omitted. In step 5, preparation of the coating adhesive, 6 parts of cyclodextrin-encapsulated diallyl phthalate were replaced with 6 parts of deionized water. The specific operation was as follows:

[0213] The operation of step 1 is the same as that of Example 1;

[0214] Step 2, preparation of cyclodextrin-encapsulated diallyl phthalate, was not performed;

[0215] The operations of steps 3 and 4 are the same as those in Example 1;

[0216] Step 5: Preparation of coating glue

[0217] The 6 parts of cyclodextrin-embedded diallyl phthalate were replaced by 6 parts of deionized water, and the other operations were the same as in Example 1;

[0218] The operations of steps 6, 7, 8, and 9 are the same as those in Example 1.

[0219] Comparative Example 3: Based on Example 1, step 3, preparation of modified titanium dioxide, was omitted. In step 5, preparation of coating adhesive, 7 parts of modified titanium dioxide were replaced with 7 parts of titanium dioxide. The specific operation was as follows:

[0220] The operations of steps 1 and 2 are the same as those in Example 1;

[0221] Step 3, preparation of modified titanium dioxide, is not performed;

[0222] The operation of step 4 is the same as that of embodiment 1;

[0223] Step 5: Preparation of coating glue

[0224] 7 parts of modified titanium dioxide were replaced by 7 parts of titanium dioxide, and the other operations were the same as in Example 1;

[0225] The nano titanium dioxide is rutile and has a particle size of 40 nm;

[0226] The operations of steps 6, 7, 8, and 9 are the same as those in Example 1.

[0227] Performance testing:

[0228] The primary impregnated base paper, pre-crosslinked paper, and finally obtained high weather resistant formaldehyde-free facing paper obtained in the intermediate process of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3, as well as the facing artificial board obtained by hot pressing the high weather resistant formaldehyde-free facing paper and the substrate (hot pressing temperature of 140° C., hot pressing pressure of 10 MPa, and hot pressing time of 20 seconds) were prepared with reference to GB / T 465.2-2008 Determination of tensile strength of paper and paperboard after immersion in water, GB / T 12914-2008 Determination of tensile strength of paper and paperboard, GB / T 1720-2020 Paint film circle test, GB / T 7911-2013 Thermosetting resin impregnated paper high pressure decorative laminate (HPL)", GB / T 17657-2022 Test methods for physical and chemical properties of artificial boards and facing artificial boards, GB / T 34722-2017 Impregnated film paper facing plywood and blockboard, and GB / T 28995-2022 Special paper for facing wood-based panels" and "GB / T 15102-2017 Fiberboard and particleboard faced with impregnated film paper" were tested for relevant properties of the above-mentioned paper and wood-based panels. The specific results are shown in Table 1.

[0229] Table 1

[0230]

[0231] From the results in Table 1, it can be seen that in Comparative Example 1, in which no dialdehyde carboxymethyl chitosan aqueous solution is added to the impregnating glue, the wet strength of the initial impregnated glue base paper, the tensile strength of the initial impregnated glue base paper, the wet strength of the pre-crosslinked paper, and the tensile strength of the pre-crosslinked paper are greatly reduced, the wet strength and tensile strength of the high-weather-resistant formaldehyde-free facing paper also decrease slightly, the surface wear resistance decreases slightly, the surface water vapor resistance also decreases, and other indicators do not change significantly. This shows that the dialdehyde carboxymethyl chitosan aqueous solution has a very critical effect on improving the wet strength and tensile strength of the base paper after impregnation, and also has a certain positive effect on improving the wet strength and tensile strength of the final high-weather-resistant formaldehyde-free facing paper; in Comparative Example 2, in which no cyclodextrin is added to the coating glue to embed diallyl phthalate, the wet strength of the initial impregnated glue base paper, the tensile strength of the initial impregnated glue base paper, the wet strength of the pre-crosslinked paper, and the tensile strength of the pre-crosslinked paper do not change , the wet strength and tensile strength of high weather-resistant formaldehyde-free facing paper decreased significantly, and the adhesion, surface bonding strength, surface wear resistance, surface resistance to dry heat, surface resistance to cold and hot cycles, surface cracking resistance, surface resistance to water vapor, and surface light fastness were significantly reduced. This shows that cyclodextrin-encapsulated diallyl phthalate has a very significant effect on improving the mechanical properties and weather resistance of high weather-resistant formaldehyde-free facing paper; in Comparative Example 3, the nano titanium dioxide is not modified, and the wet strength of the initial impregnated collagen paper, the tensile strength of the initial impregnated collagen paper, the wet strength of the pre-cross-linked paper, and the tensile strength of the pre-cross-linked paper are not affected. Except for the above-mentioned indicators, all other indicators have dropped sharply, which shows that if the nano titanium dioxide is not modified, it is difficult to disperse evenly in the colloid, which ultimately leads to a comprehensive decline in various indicators of the high weather-resistant formaldehyde-free facing paper, especially the surface weather resistance, which has a significant decline.

[0232] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A highly weather-resistant formaldehyde-free facing paper, characterized by: The highly weather-resistant formaldehyde-free facing paper is made from one of plain base paper and printed decorative paper through a four-step process of impregnation with an impregnating adhesive, primary drying and pre-crosslinking, coating with a rubber roller, and secondary drying and pre-curing. The specific formula of the impregnating glue is as follows in parts by weight: 15-40 parts of dialdehyde carboxymethyl chitosan aqueous solution, 0.5-10 parts of polyvinyl alcohol, 4-9 parts of polyethyleneimine aqueous solution, Cross-linking agent 0.1~1 part, Defoaming agent polyether-siloxane copolymer 0.1~0.2 parts, 60-90 parts of deionized water; The cross-linking agent is one of bishydroxyethyl sulfone, 1,3-bishydroxymethyl urea, and dihydroxymethyl dihydroxyethylene urea resin; The specific formula of the coating glue is calculated in parts by weight: 55~100 parts of water-based polyacrylate emulsion, Cyclodextrin embedded diallyl phthalate 1-9 parts, 1~10 parts of modified titanium dioxide, Dispersant ammonium polyacrylate 0.5~3 parts, Defoaming agent polyether-siloxane copolymer 0.1~0.2 parts, 40-100 parts of deionized water; The dialdehyde carboxymethyl chitosan aqueous solution is prepared by: adding carboxymethyl chitosan to deionized water, controlling the stirring rate at 600-900 rpm, heating and maintaining the temperature at 60-80° C., then adding 2,2,6,6-tetramethylpiperidinium oxide and N-chlorosuccinimide, and after they are completely dissolved, adding hydrogen peroxide dropwise at a rate of 0.5-30 g / min. After the hydrogen peroxide is added dropwise, continuing the reaction at a constant temperature with stirring for 3-7 hours, then cooling to room temperature and stopping the reaction to obtain the dialdehyde carboxymethyl chitosan aqueous solution; The preparation method of the cyclodextrin-encapsulated diallyl phthalate comprises the following steps: dissolving β-cyclodextrin in hot water at 65-80°C by stirring to obtain a β-cyclodextrin aqueous solution; controlling the stirring speed to 400-700 rpm and the temperature to be constant at 35-55°C; slowly dropping an ethanol solution of diallyl phthalate; continuing the reaction at a constant temperature and stirring for 4-9 hours; standing the solution at 0-4°C for 20-30 hours; then discharging the solution and filtering the solution at 0-4°C; and freeze-drying the filtrate at -10-0°C for 8-14 hours to obtain the cyclodextrin-encapsulated diallyl phthalate, which is then stored in a cool, dry environment. The modified titanium dioxide is prepared by the following method: drying nano-titanium dioxide at 70-110°C for 10-19 hours, adding the dried nano-titanium dioxide, oleic acid diethanolamide borate, and ethyl acetate into a high-speed dispersion kettle, and then dispersing the mixture at a high speed of 5000-8000 rpm for 5-9 hours. The mixture is then heated and kept constant at 50-65°C, and the dispersion rate is reduced to 1000-3000 rpm. 3-isocyanate propyltriethoxysilane is then added, and the mixture is kept constant for 6-18 hours. The amino-terminated hyperbranched polyamide is then added, and the mixture is stirred and dispersed. After the reaction is continued for 5-11 hours, the mixture is cooled to room temperature and centrifuged. The obtained solid is washed with anhydrous ethanol for 2-4 times and then dried at 50-80°C for 4-8 hours to obtain the modified titanium dioxide.

2. The highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: The carboxymethyl chitosan has a deacetylation degree of 60-95%, a carboxylation degree of 60-85%, and a molecular weight of 1.0×10 5 ~3.5×10 5 g / mol; The mass concentration of hydrogen peroxide in the hydrogen peroxide is 8-20wt%; The mass ratio of the carboxymethyl chitosan, deionized water, 2,2,6,6-tetramethylpiperidinium oxide, N-chlorosuccinimide and hydrogen peroxide is 40-110:55-120:0.5-1.5:0.5-1.0:10-40.

3. The highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: In the β-cyclodextrin aqueous solution, the mass fraction of β-cyclodextrin is 1-20wt%; The ethanol solution of diallyl phthalate is slowly added dropwise at a rate of 1 to 35 g / min, and the mass of the added solution is 1 to 3 times the mass of the β-cyclodextrin aqueous solution; The ethanol solution of diallyl phthalate has a mass ratio of diallyl phthalate to ethanol of 20-100:

300.

4. The highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: The nano titanium dioxide is rutile and has a particle size of 1 to 100 nm; The amino group number of the amino-terminated hyperbranched polyamide is 4 to 11 mol / mol and the molecular weight is 200 to 1000 g / mol; The mass ratio of the dried nano-titanium dioxide, oleic acid diethanolamide borate, ethyl acetate, 3-isocyanate propyl triethoxysilane, and amino-terminated hyperbranched polyamide is 20-50:0.1-2:150-250:3-7:2-9.

5. The highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: The molecular weight of the polyvinyl alcohol is 10,000 to 250,000 g / mol; The mass fraction of polyethyleneimine in the polyethyleneimine aqueous solution is 10-30wt%, and the molecular weight of polyethyleneimine is 20000-100000 g / mol.

6. The highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: The water-based polyacrylate emulsion has a solid content of 45-65%, a viscosity of 1000-5000 mPa·s, and a pH value of 6-8.

5.

7. The method for preparing highly weather-resistant formaldehyde-free facing paper according to claim 1, characterized in that: The preparation method of the highly weather-resistant formaldehyde-free facing paper includes nine steps: preparation of a dialdehyde carboxymethyl chitosan aqueous solution, preparation of cyclodextrin-embedded diallyl phthalate, preparation of modified titanium dioxide, preparation of an impregnating glue, preparation of a coating glue, impregnation of the impregnating glue, primary drying and pre-crosslinking, coating with a coating glue roller, and secondary drying and pre-curing.

8. The preparation method according to claim 7, characterized in that: The impregnation glue is prepared by adding a dialdehyde carboxymethyl chitosan aqueous solution, polyvinyl alcohol, polyethyleneimine aqueous solution, a cross-linking agent, a defoaming agent polyether-siloxane copolymer, and deionized water into a stirring kettle according to a specific formula of the impregnation glue in parts by weight, and stirring and dissolving the mixture completely to obtain a transparent liquid, which is the impregnation glue; The coating adhesive is prepared by placing deionized water, a defoaming agent polyether-siloxane copolymer, a dispersant ammonium polyacrylate, and modified titanium dioxide into a high-speed dispersing kettle according to a specific formula of the coating adhesive in parts by weight. After high-speed dispersion at a dispersion rate of 7500-11000 rpm for 5-11 hours, the dispersion rate is reduced to 3500-5000 rpm, and cyclodextrin-embedded diallyl phthalate and an aqueous polyacrylate emulsion are added. After continuing to disperse for 3-6 hours, the coating adhesive is discharged.

9. The preparation method according to claim 8, characterized in that: The impregnation glue is impregnated by unwinding the plain base paper or printed decorative paper under the action of a paper pulling machine, with the unwinding speed controlled at 10-35 m / min. The unwinding plain base paper or printed decorative paper passes through a counterweight roller and a pulling roller in sequence, and then enters the impregnation glue tank for impregnation, with the impregnation glue temperature controlled at 20-35° C. and the impregnation time controlled at 3-11 seconds. The impregnated plain base paper or printed decorative paper passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue impregnated on both sides of the plain base paper or printed decorative paper, thereby obtaining a pre-impregnated base paper with neat edges. The one-time drying pre-crosslinking is that the initially impregnated collagen paper enters an oven for pre-crosslinking under the action of a traction roller, the oven is controlled at 60-90° C., the pre-crosslinking time is controlled at 10-35 seconds, and the paper is naturally cooled after exiting the oven to obtain pre-crosslinked paper.

10. The preparation method according to claim 9, characterized in that: The coating glue roller coating method is as follows: the pre-crosslinked paper is pulled into the coating glue tank by a traction roller, and is double-sidedly coated with a roller. The temperature of the coating glue is controlled at 20-35° C., and the coating time is controlled at 4-9 seconds. The pre-crosslinked paper after roller coating passes through a metering roller to evenly distribute the glue layer, and then passes through an edge scraper to scrape off the glue applied on both sides of the pre-crosslinked paper to obtain coated paper with neat edges; The secondary drying pre-curing is carried out by the coated paper entering an oven for pre-curing treatment under the action of a traction roller. The oven is divided into two temperature control sections, the temperature of the first section is controlled at 80-110°C, and the temperature of the second section is controlled at 110-130°C. The pre-curing treatment time is controlled at 10-40 seconds. After the pre-curing is completed, the paper exits the oven and enters an air cooling channel. After air cooling to room temperature, the paper is rolled up to obtain a highly weather-resistant formaldehyde-free finishing paper.

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