Dynamic covalent hyperbranched structure tough facing base paper and preparation method thereof

Abstract

The invention provides dynamic covalent hyperbranched structure tough facing base paper and a preparation method thereof. The facing base paper is prepared from the following raw materials in parts by weight: 10 to 40 phr of bleached softwood pulp, 60 to 90 phr of bleached hardwood pulp, 0.1 to 10 phr of dynamic copolymerized hyperbranched polymer, 5 to 30 phr of titanium dioxide, 3 to 5 phr of PAE wet strength agent, 5 to 7 phr of AKD and 1 to 3 phr of cationic starch. The dynamic covalent hyperbranched polymer is prepared from maleic anhydride, glycerol and a modifier, and the modifier is 4-carboxyphenylboronic acid or 1, 4-butanediol divinyl ether. According to the invention, the dynamic covalent hyperbranched polymer is adopted as a modifier to synchronously realize reinforcement and toughening of the facing base paper, so that the problems of wood fiber aggregation caused by increase of the use amount of long-chain wood fibers and paper brittleness increase caused by crosslinking of strong covalent bonds are avoided, and the base paper has high tensile strength and anti-cracking performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, in particular to a decorative base paper and a preparation method thereof. BACKGROUND

[0002] The annual output of wood-based panels in China is about 300 million cubic meters, and the volume of production and sales exceeds that of steel and plastic, playing an important role in the national economic construction. Decorative base paper is a kind of industrial special paper made of wood pulp, titanium dioxide and additives, which is used for the decoration of wood-based panels after printing and resin impregnation, and has important significance for giving wood-based panel substrates aesthetic appearance, protecting the substrate and improving the surface quality of the substrate.

[0003] With the rapid development of decorative wood-based panel industry and people's pursuit of high-quality life, the market demand for decorative base paper is rising. However, the decorative surface of decorative wood-based panels is prone to cracking during use, which seriously restricts its popularization and application. The quality of the decorative surface of decorative wood-based panels depends largely on the quality and performance of the decorative base paper. The decorative base paper is mainly prepared by using broadleaf wood pulp with short-chain fibers, resulting in fewer bonding points between wood fibers, low interfacial bonding strength, easy pulling of wood fibers from the paper, and low strength of broadleaf wood fibers, leading to poor tensile strength and fracture toughness of the decorative base paper. In the production of decorative base paper, about 30% of mineral filler-titanium dioxide is often added, which significantly reduces the interfacial bonding strength between wood fibers, and the weak bonding between wood fibers and titanium dioxide is mainly achieved by electrostatic force and hydrogen bond, resulting in increased brittleness and reduced tensile strength of the decorative base paper.

[0004] Patent document CN117306298A mentions a decorative base paper with uniform distribution of titanium dioxide, which has high brittleness and low tensile strength; patent document CN119352338A mentions a base paper for carrier tape, which has insufficient crack resistance and poor fracture toughness. The existing technology has low tensile strength and crack resistance of the decorative base paper, high brittleness of the paper, and a non-simple preparation method. SUMMARY

[0005] One object of the present application is to solve the problem of low tensile strength and crack resistance of the decorative base paper, and to provide a dynamic covalent hyperbranched polymer for modification, to improve the tensile strength and crack resistance of the decorative base paper.

[0006] Another object of the present application is to improve the problem of high brittleness of the paper, and to provide a dynamic covalent hyperbranched polymer and a processing aid, which cross-link long-chain wood fibers through strong covalent bonds, to improve the brittleness of the paper.

[0007] Another object of the present application is to have excellent water absorption performance, and the paper prepared by mixing wood pulp and dynamic covalent hyperbranched polymer has a good pore structure, which improves the liquid absorption capacity, and provides conditions for the preparation of other modified papers based on the paper.

[0008] In order to achieve the above-mentioned purpose, the application provides a dynamic covalent hyperbranched structure strong and tough finishing base paper, which comprises, by weight parts, 10-40 phr of bleached coniferous pulp, 60-90 phr of bleached broadleaf pulp, 0.1-10 phr of dynamic covalent hyperbranched polymer and 5-30 phr of titanium dioxide. The fibers of the bleached coniferous pulp are long and thin, and have high strength and toughness; the fibers of the bleached broadleaf pulp are short and wide, and have good softness, which can provide high strength and high toughness; the titanium dioxide can improve the whiteness and hiding power, and can improve the surface flatness of the paper; the boric acid or vinyl ether in the dynamic covalent hyperbranched polymer can form a dynamic borate ester bond or an acetal bond with the hydroxyl groups on the surface of the wood fibers and fillers, the formation of the dynamic covalent bond can enhance the tensile strength of the base paper, and at the same time, can preferentially break and dissipate energy when the paper breaks, thereby improving the tensile properties of the paper in cooperation with the toughening properties of the hyperbranched polymer; in addition, the intramolecular cavity of the hyperbranched polymer can increase the free volume fraction of the base paper, thereby improving the absorption performance of the glue solution.

[0009] Preferably, the base paper comprises, by weight parts, 20-30 phr of bleached coniferous pulp, 70-80 phr of bleached broadleaf pulp, 3-8 phr of dynamic covalent hyperbranched polymer, 10-20 phr of titanium dioxide and 9-15 parts of additives.

[0010] Preferably, the beating degree of the wood pulp is 30-45°SR, and the wet weight is 2-3 g.

[0011] Preferably, the dynamic covalent hyperbranched polymer is prepared from maleic anhydride, glycerol and a modifier; the modifier is one or both of 4-carboxyphenylboronic acid and 1,4-butanediol divinyl ether.

[0012] Preferably, the mass ratio of the maleic anhydride and the glycerol in the dynamic covalent hyperbranched polymer is 1:1.5-2.

[0013] Preferably, the additives comprise 3-5 phr of polyamide-epichlorohydrin resin (PAE) wet strength agent, 5-7 phr of alkyl alkene ketone dimer (AKD) and 1-3 phr of cationic starch. The PAE wet strength agent is a cationic and water-soluble thermosetting resin, and the main component is a polycondensate of polyamide polyamine and epichlorohydrin, which can give the paper wet strength; the cationic groups of the PAE are adsorbed on the hydroxyl groups on the surface of the fibers, and the epoxy groups form ether bonds with the fibers to form a three-dimensional network structure; a stable thermosetting structure is formed; the AKD is a reactive neutral sizing agent, and the internal lactone ring reacts with the hydroxyl groups of the cellulose to form a hydrophobic structure.

[0014] A preparation method of a dynamic covalent hyperbranched structure strong and tough finishing base paper, comprising the following steps: S1, reacting maleic anhydride and glycerol to synthesize a hydroxyl-terminated hyperbranched polymer; S2, reacting the hydroxyl-terminated hyperbranched polymer with a modifier to synthesize a dynamic covalent hyperbranched polymer; S3, adding the dynamic covalent hyperbranched copolymer, titanium dioxide and an additive into wood pulp to mix uniformly to obtain a slurry; S4, obtaining a wet paper sheet after the slurry is web-formed, and then performing pressing, drying and calendering to obtain a surface paper.

[0015] Preferably, the reaction temperature in step S1 is 100-150 DEG C, and the reaction time is 5-10 hours.

[0016] Preferably, the mass ratio of the hydroxyl-terminated hyperbranched polymer to the modifier in step S2 is 1:1.2-2, the reaction temperature is 100-120 DEG C, and the reaction time is 1-3 hours.

[0017] Preferably, the pressing pressure in step S4 is 0.2-0.5 MPa, the drying temperature is 100-105 DEG C, the drying time is 10-20 min, the calendering speed is 10-15 m / min, the calendering pressure is 30-50 N / mm, and the calendering temperature is 70-80 DEG C.

[0018] The present application has the following advantages:

[0019] The dynamic covalent hyperbranched polymer is used as the modifier, the hyperbranched polymer can improve the toughness of paper through cavity effect and stress branching, and the problem of wood fiber aggregation caused by increasing the content of long-chain wood fibers to improve toughness is avoided.

[0020] The intramolecular cavity formed by the hyperbranched polymer and the wood pulp can improve the free volume fraction in the paper and promote the absorption performance of the base paper to the glue solution.

[0021] The dynamic covalent hyperbranched polymer can introduce dynamic covalent bonds, further improve the tensile strength and anti-cracking toughness of the base paper, solve the problem that titanium dioxide wrapping and chemical modification thereof are difficult to enhance the interfacial bonding force between wood fibers and between wood fibers and titanium dioxide, and avoid the problem of brittleness enhancement of paper caused by the interfacial cross-linking structure of strong covalent bonds. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present application clearer, the following examples clearly and completely describe the technical scheme in the present application. Obviously, the described examples are part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] The advantages of the present application will be described below in combination with specific examples and comparative examples.

[0024] Total examples:

[0025] Raw materials: bleached softwood pulp 10-40 phr, bleached hardwood pulp 60-90 phr, dynamic covalent hyperbranched polymer (boronic acid-terminated hyperbranched polymer or vinyl ether-terminated hyperbranched polymer) 0.1-10 phr, titanium dioxide 5-30 phr, PAE wet strength agent 3-5 phr, AKD 5-7 phr, cationic starch 1-3 phr.

[0026] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: according to the mass ratio of 1:1.5-2, maleic anhydride and glycerol are added, and the hydroxyl-terminated hyperbranched polymer is synthesized by reacting at 100-150℃ for 5-10 hours; according to 40-50 mass parts of hydroxyl-terminated hyperbranched polymer and 50-70 mass parts of 4-carboxyphenylboronic acid, the boronic acid-terminated hyperbranched polymer is synthesized by reacting at 100℃-120℃ for 1-3 hours; S2: Pulping: bleached softwood pulp and bleached hardwood pulp are mixed, and boronic acid-terminated hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added, and the pulp is obtained after mixing uniformly; S3: After the pulp is web-formed, wet paper sheet is obtained, and after pressing, drying and calendering, the surface paper is obtained: the pressure of pressing is 0.2-0.5 MPa; the drying temperature is 100-105℃; the drying time is 10-20 min; the calendering temperature is 70℃; the calendering speed is 10-15 m / min; the calendering pressure is 30-50 N / mm.

[0027] Example 1: Raw materials: bleached softwood pulp 20 phr, bleached hardwood pulp 80 phr, boronic acid-terminated hyperbranched polymer 1 phr, titanium dioxide 20 phr, PAE wet strength agent 4 phr, AKD 6 phr, cationic starch 2 phr.

[0028] The amount of dynamic covalent hyperbranched polymer added in this example is very small, which may result in too few dynamic covalent bonds, thereby affecting the tensile strength of the paper.

[0029] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: according to the mass ratio of 1:1.5, maleic anhydride and glycerol are added, and the hydroxyl-terminated hyperbranched polymer is synthesized by reacting at 140℃ for 7 hours; according to 43 mass parts of hydroxyl-terminated hyperbranched polymer and 61 mass parts of 4-carboxyphenylboronic acid, the boronic acid-terminated hyperbranched polymer is synthesized by reacting at 120℃ for 3 hours; S2: Pulping: bleached softwood pulp and bleached hardwood pulp are mixed, and boronic acid-terminated hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added, and the pulp is obtained after mixing uniformly; S3: The pulp is web-formed to obtain wet paper sheet, and then the surface base paper is obtained after pressing, drying and calendering: the pressure of pressing is 0.5 MPa; the drying temperature is 105°C; the drying time is 20 min; the calendering temperature is 70°C; the calendering speed is 13 m / min; and the calendering pressure is 40 N / mm.

[0030] Example 2: Raw materials: bleached softwood pulp 25 phr, bleached hardwood pulp 75 phr, boronic acid-terminated hyperbranched polymer 3 phr, titanium dioxide 20 phr, PAE wet strength agent 3.5 phr, AKD 5.5 phr, cationic starch 2 phr.

[0031] The amount of dynamic covalent hyperbranched polymer is increased in this example, and the tensile strength of the paper is expected to be improved.

[0032] The formulation of this example uses moderate amounts of raw materials, and the expected effect is moderate, with high cost performance.

[0033] The preparation method of this example is the same as that of Example 1.

[0034] Example 3: Raw materials: bleached softwood pulp 30 phr, bleached hardwood pulp 70 phr, boronic acid-terminated hyperbranched polymer 5 phr, titanium dioxide 20 phr, PAE wet strength agent 5 phr, AKD 7 phr, cationic starch 3 phr.

[0035] The boronic acid group can undergo condensation reaction with adjacent cellulose hydroxyl groups to form stable borate ester bonds to enhance interfacial adsorption; the boron atom in the boronic acid group can form a coordination bond with the oxygen atom of the cellulose hydroxyl group to enhance interfacial adsorption; at the same time, the hydroxyl group of the boronic acid group and the oxygen atom of the cellulose hydroxyl group can form a hydrogen bond, and the non-covalent bond and covalent bond synergistically form a "strong-weak" gradient bonding network, taking into account the bonding strength and toughness.

[0036] The preparation method of this example is the same as that of Example 1.

[0037] Example 4: Raw materials: bleached softwood pulp 25 phr, bleached hardwood pulp 75 phr, boronic acid-terminated hyperbranched polymer 7 phr, titanium dioxide 20 phr, PAE wet strength agent 4 phr, AKD 6 phr, cationic starch 2 phr.

[0038] The preparation method of this example is the same as that of Example 1.

[0039] Example 5: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 9 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 4 phr of PAE wet strength agent, 6 phr of AKD, and 2 phr of cationic starch. The preparation method in this embodiment is the same as that in Example 1.

[0040] Example 6: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 10 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 4 phr of PAE wet strength agent, 6 phr of AKD, and 2 phr of cationic starch.

[0041] This embodiment incorporates the largest amount of dynamically covalently hyperbranched polymer, and the paper's tensile strength is expected to be the highest.

[0042] The preparation method in this embodiment is the same as that in Example 1.

[0043] Example 7: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 5 phr of end-boronic acid group hyperbranched polymer, 10 phr of titanium dioxide, 4 phr of PAE wet strength agent, 6 phr of AKD, and 2 phr of cationic starch.

[0044] The preparation method in this embodiment is the same as that in Example 1.

[0045] Example 8: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 5 phr of end-boronic acid group hyperbranched polymer, 15 phr of titanium dioxide, 4 phr of PAE wet strength agent, 6 phr of AKD, and 2 phr of cationic starch.

[0046] The preparation method in this embodiment is the same as that in Example 1.

[0047] Example 9: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 5 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 3 phr of PAE wet strength agent, 5 phr of AKD, and 1 phr of cationic starch.

[0048] The preparation method in this embodiment is the same as that in Example 1.

[0049] Example 10: Raw materials: 25 phr of bleached softwood pulp, 75 phr of bleached hardwood pulp, 5 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 5 phr of PAE wet strength agent, 7 phr of AKD, and 3 phr of cationic starch.

[0050] The preparation method in this embodiment is the same as that in Example 1.

[0051] Example 11: Raw materials: 10 phr of bleached softwood pulp, 90 phr of bleached hardwood pulp, 3 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 3.5 phr of PAE wet strength agent, 5.5 phr of AKD, and 2.5 phr of cationic starch.

[0052] The preparation method in this embodiment is the same as that in Example 1.

[0053] Example 12: Raw materials: 40 phr of bleached softwood pulp, 60 phr of bleached hardwood pulp, 3 phr of end-boronic acid group hyperbranched polymer, 20 phr of titanium dioxide, 3.5 phr of PAE wet strength agent, 5.5 phr of AKD, and 2.5 phr of cationic starch.

[0054] The preparation method in this embodiment is the same as that in Example 1.

[0055] Example 13: Raw materials: The raw material formula in this embodiment is the same as that in Example 2.

[0056] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: Maleic anhydride and glycerol were added at a mass ratio of 1:2 and reacted at 100℃ for 7 hours to synthesize a hydroxyl-terminated hyperbranched polymer; 42 parts by mass of the hydroxyl-terminated hyperbranched polymer and 71 parts by mass of 4-carboxyphenylboronic acid were reacted at 120℃ for 3 hours to synthesize a borate-terminated hyperbranched polymer. S2: Pulping: Bleached softwood pulp and bleached hardwood pulp are mixed, and terminal borate-based hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added. After mixing evenly, the pulp is obtained. S3: After the pulp is wired and formed into a wet paper sheet, it is then pressed, dried and calendered to obtain the decorative base paper: the pressing pressure is 0.5MPa; the drying temperature is 105℃; the drying time is 20min; the calendering temperature is 70℃; the calendering speed is 13m / min; and the calendering pressure is 40N / mm.

[0057] Example 14: Raw materials: The raw material formula in this embodiment is the same as that in Example 2.

[0058] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: Maleic anhydride and glycerol were added at a mass ratio of 1:2 and reacted at 120℃ for 7 hours to synthesize a hydroxyl-terminated hyperbranched polymer; 42 parts by mass of the hydroxyl-terminated hyperbranched polymer and 51 parts by mass of 4-carboxyphenylboronic acid were reacted at 120℃ for 3 hours to synthesize a borate-terminated hyperbranched polymer. S2: Pulping: Bleached softwood pulp and bleached hardwood pulp are mixed, and terminal borate-based hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added. After mixing evenly, the pulp is obtained. S3: After the pulp is wired and formed into a wet paper sheet, it is then pressed, dried and calendered to obtain the decorative base paper: the pressing pressure is 0.5MPa; the drying temperature is 105℃; the drying time is 20min; the calendering temperature is 70℃; the calendering speed is 13m / min; and the calendering pressure is 40N / mm.

[0059] Example 15: Raw materials: The raw material formula in this embodiment is the same as that in Example 2.

[0060] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: Maleic anhydride and glycerol were added at a mass ratio of 1:2 and reacted at 140℃ for 7 hours to synthesize a hydroxyl-terminated hyperbranched polymer; 42 parts by mass of the hydroxyl-terminated hyperbranched polymer and 61 parts by mass of 4-carboxyphenylboronic acid were reacted at 120℃ for 3 hours to synthesize a borate-terminated hyperbranched polymer. S2: Pulping: Bleached softwood pulp and bleached hardwood pulp are mixed, and terminal borate-based hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added. After mixing evenly, the pulp is obtained. S3: After the pulp is wired and formed into a wet paper sheet, it is then pressed, dried and calendered to obtain the decorative base paper: the pressing pressure is 0.3MPa; the drying temperature is 104℃; the drying time is 15min; the calendering temperature is 75℃; the calendering speed is 13m / min; and the calendering pressure is 40N / mm.

[0061] Examples 13-15 describe the effect of changes in reaction conditions on the tensile strength of the prepared decorative base paper.

[0062] Example 16 Raw materials: 30 phr of bleached softwood pulp, 70 phr of bleached hardwood pulp, 5 phr of end-vinyl ether hyperbranched polymer, 20 phr of titanium dioxide, 4 phr of PAE wet strength agent, 5 phr of AKD, and 3 phr of cationic starch.

[0063] Preparation method: S1: Preparation of dynamic covalent hyperbranched polymer: Maleic anhydride and glycerol were added at a mass ratio of 1:2 and reacted at 140℃ for 7 hours to synthesize a hydroxyl-terminated hyperbranched polymer; 42 parts by mass of the hydroxyl-terminated hyperbranched polymer and 60 parts by mass of 4-carboxyphenylboronic acid were reacted at 120℃ for 3 hours to synthesize a borate-terminated hyperbranched polymer. S2: Pulping: Bleached softwood pulp and bleached hardwood pulp are mixed, and terminal borate-based hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD and cationic starch are added. After mixing evenly, the pulp is obtained. S3: After the pulp is wired and formed into a wet paper sheet, it is then pressed, dried and calendered to obtain the decorative base paper: the pressing pressure is 0.3MPa; the drying temperature is 104℃; the drying time is 15min; the calendering temperature is 75℃; the calendering speed is 13m / min; and the calendering pressure is 40N / mm.

[0064] The end-vinyl ether hyperbranched polymer used in this embodiment undergoes an etherification reaction with the cellulose hydroxyl groups to form stable covalent bonds, which directly enhances the surface bonding strength of the fiber. The ether oxygen atoms of the vinyl ether groups can still form strong hydrogen bonds with the atoms of the cellulose hydroxyl groups, enhancing the polarity of the fiber surface and the density of binding sites. The high reactivity of the vinyl ether groups can crosslink and copolymerize with other substances to form a complex crosslinking network, thereby improving the tensile strength of the paper.

[0065] Table 1 Raw material ratio table for Examples 1-12

[0066] Examples 1-12 are studies on different proportions of several substances; Examples 1-3 are studies on the relationship between the amount added to the overall formulation; it is expected that the decorative base paper of Example 3 has the best tensile strength; Examples 3-6 are studies on the effect of the amount of dynamically covalently hyperbranched polymer added on the performance of decorative base paper; Examples 7-9 are studies on the effect of the amount of titanium dioxide added on the performance of decorative base paper; Examples 2 and 9-10 are studies on the effect of the addition of processing aids on the performance of decorative base paper; Examples 2 and 11-12 are studies on the effect of the ratio of two wood pulp matrices on the performance of decorative base paper.

[0067] Comparative Example 1 (no modification of the end groups of the hyperbranched polymer) A decorative base paper and its preparation method, comprising the following steps:

[0068] Pulping: Hydroxyl-terminated hyperbranched polymer, titanium dioxide, PAE wet strength agent, AKD, and cationic starch are added to wood pulp and mixed evenly to obtain pulp. The wood pulp contains 20 pr of bleached softwood pulp and 80 pr of bleached hardwood pulp, with a freeness of 43°SR and a wet weight of 2.5 g. The mass of the hydroxyl-terminated hyperbranched polymer is 1 pr of the wood pulp mass, the mass of titanium dioxide is 20 pr of the wood pulp mass, the mass of PAE wet strength agent is 4 pr of the wood pulp mass, the mass of AKD is 6 pr of the wood pulp mass, and the mass of cationic starch is 2 pr of the wood pulp mass. The preparation method of the terminal hydroxyl hyperbranched polymer includes the following steps:

[0069] A hydroxyl-terminated hyperbranched polymer was synthesized by reacting maleic anhydride and glycerol at a mass ratio of 1:1.5 at 130°C for 8 hours.

[0070] Papermaking, pressing, drying and calendering: After the pulp is made into a paper sheet, a wet paper sheet is obtained. After pressing, drying and calendering, the decorative base paper is obtained. The pressing pressure is 0.4 MPa; the drying temperature is 100℃; the drying time is 20 min; the calendering temperature is 70℃; the calendering speed is 13 m / min; and the calendering pressure is 40 N / mm.

[0071] Comparative Example 2 (without adding hyperbranched polymers, only constructing dynamic covalent bonds) A decorative base paper and its preparation method, comprising the following steps:

[0072] Pulping: 1,4-Butanediol divinyl ether, titanium dioxide, PAE wet strength agent, AKD, and cationic starch are added to the wood pulp and mixed evenly to obtain the pulp. The wood pulp contains 30 pr of bleached softwood pulp and 70 pr of bleached hardwood pulp, with a pulp freeness of 43°SR and a wet weight of 2.5 g. The mass of 1,4-Butanediol divinyl ether is 1 pr of the wood pulp mass, the mass of titanium dioxide is 10 pr of the wood pulp mass, the mass of PAE wet strength agent is 5 pr of the wood pulp mass, the mass of AKD is 6 pr of the wood pulp mass, and the mass of cationic starch is 2.5 pr of the wood pulp mass. Papermaking, pressing, drying and calendering: After the pulp is made into a paper sheet, a wet paper sheet is obtained. After pressing, drying and calendering, the decorative base paper is obtained: the pressing pressure is 0.4 MPa; the drying temperature is 100℃; the drying time is 15 min; the calendering temperature is 70℃; the calendering speed is 13 m / min; and the calendering pressure is 40 N / mm.

[0073] Comparative Example 3 (without adding dynamically covalently hyperbranched polymer) A decorative base paper and its preparation method, comprising the following steps: Pulping: Titanium dioxide, PAE wet strength agent, AKD, and cationic starch are added to the wood pulp and mixed evenly to obtain the pulp. The wood pulp contains 25 pr of bleached softwood pulp and 75 pr of bleached hardwood pulp, with a pulp freeness of 40°SR and a wet weight of 2.6 g. The mass of titanium dioxide is 18 pr of the wood pulp mass, the mass of PAE wet strength agent is 3.5 pr of the wood pulp mass, the mass of AKD is 5.5 pr of the wood pulp mass, and the mass of cationic starch is 2.5 pr of the wood pulp mass. Papermaking, pressing, drying and calendering: After the pulp is made into a paper sheet, a wet paper sheet is obtained. After pressing, drying and calendering, the decorative base paper is obtained: the pressing pressure is 0.5 MPa; the drying temperature is 105℃; the drying time is 20 min; the calendering temperature is 75℃; the calendering speed is 12 m / min; and the calendering pressure is 35 N / mm.

[0074] The properties of the decorative base paper prepared in the above embodiments and comparative examples were tested. The basis weight test method was in accordance with GB / T 451.2-2002; the opacity test method was in accordance with GB / T 1543-2005; the tensile strength test method was in accordance with GB / T 12914-2008; the water absorption height test method was in accordance with GB / T 461.1-2002; and the abrasion rate was tested using a CFT-1 material surface performance comprehensive tester.

[0075] Table 2. Performance test results of the base paper for examples 1-12.

[0076] As can be seen from the experimental data in Table 2, the base paper prepared by the method of the present invention in Examples 1 to 4 has high opacity, tensile strength and low abrasion rate, good crack resistance and abrasion resistance, and excellent water absorption properties.

[0077] Table 3 Performance test results of Examples 1, 16 and Comparative Examples 1-3

[0078] In Comparative Example 1, no hyperbranched polymer was modified, meaning no dynamic covalent bonds were introduced into the base paper. The tensile strength and abrasion resistance of the base paper were significantly lower than in Examples 1 and 16. In Comparative Example 2, only dynamic covalent bonds were introduced, without introducing hyperbranched polymers. The modifier had poor dispersion in the base paper matrix and could not construct a hyperbranched cross-linked network structure in the base paper. The tensile strength and absorbency of the base paper were significantly lower than in Examples 1 and 16. In Comparative Example 3, no dynamic covalent hyperbranched polymer was introduced, and a dynamic covalent hyperbranched network structure could not be formed. The tensile strength, absorbency, and abrasion resistance of the base paper were significantly lower than in Examples 1 and 16.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamically covalently hyperbranched, strong, decorative base paper, characterized in that, By weight, the raw materials include: 10-40 phr of bleached softwood pulp, 60-90 phr of bleached hardwood pulp, 0.1-10 phr of dynamic covalent hyperbranched polymer, and 5-30 phr of titanium dioxide.

2. The dynamically covalently hyperbranched, strong decorative base paper according to claim 1, characterized in that, By weight, the ingredients include: 20-30 phr of bleached softwood pulp, 70-80 phr of bleached hardwood pulp, 3-8 phr of dynamic covalent hyperbranched polymer, 10-20 phr of titanium dioxide, and 9-15 parts of additives.

3. A dynamically covalently hyperbranched, strong, decorative base paper according to claim 1 or 2, characterized in that, The pulp has a freeness of 30-45°SR and a wet weight of 2-3g.

4. The dynamically covalently hyperbranched, strong decorative base paper according to claim 2, characterized in that, The dynamic covalent hyperbranched polymer is prepared from maleic anhydride, glycerol, and a modifier; the modifier is one or both of 4-carboxyphenylboronic acid and 1,4-butanediol divinyl ether.

5. The dynamically covalently hyperbranched, strong decorative base paper according to claim 4, characterized in that, The mass ratio of maleic anhydride to glycerol added to the dynamic covalent hyperbranched polymer is 1:1.5-2.

6. The dynamically covalently hyperbranched structural tough finishing base paper according to claim 2, characterized in that, The additives include 3-5 phr of polyamide-epoxychloropropane resin (PAE) wet strength agent, 5-7 phr of alkyl ketene dimer (AKD), and 1-3 phr of cationic starch.

7. A method for preparing a dynamically covalently hyperbranched, strong, and durable decorative base paper, characterized in that, A robust decorative base paper with a dynamic covalent hyperbranched structure according to claims 1-6 comprises the following steps: S1. Maleic anhydride and glycerol are reacted to synthesize a hydroxyl-terminated hyperbranched polymer; S2. React the hydroxyl-terminated hyperbranched polymer with a modifier to synthesize a dynamically covalent hyperbranched polymer; S3. Add the dynamic covalent hyperbranched copolymer, titanium dioxide, and additives to the wood pulp and mix them evenly to obtain the pulp. S4. After the pulp is wired and formed into a wet paper sheet, it is pressed, dried and calendered to obtain the decorative base paper.

8. The method for preparing a dynamic covalent hyperbranched structural tough decorative base paper according to claim 7, characterized in that, The reaction temperature in step S1 is 100-150℃, and the reaction time is 5-10 hours.

9. The method for preparing a dynamically covalently hyperbranched, strong, and durable decorative base paper according to claim 7, characterized in that, In step S2, the mass ratio of the terminal hydroxyl hyperbranched polymer to the modifier is 1:1.2-2, the reaction temperature is 100-120℃, and the reaction time is 1-3 hours.

10. The method for preparing a dynamically covalently hyperbranched, strong, and durable decorative base paper according to claim 7, characterized in that, The pressing pressure in step S4 is 0.2-0.5 MPa; the drying temperature is 100-105℃; the drying time is 10-20 min; the calendering speed is 10-15 m / min; the calendering pressure is 30-50 N / mm; and the calendering temperature is 70-80℃.

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