Preparation method of surface sizing agent based on water-resistant phenolic compound starch

Abstract

The present invention discloses a preparation method of a surface sizing agent based on water-resistant phenolic compounded starch. Alkali is added to a reaction kettle, and a solvent is added. After adding substrate a and substrate b, the reaction kettle is closed, and the reaction is carried out at 100-250 °C for 0.2-12 h. After the reaction is completed, it is cooled to room temperature, and acid is added to adjust the pH value to neutral, and then freeze-dried to obtain anionic polymer A; Anionic polymer A is dissolved with deionized water and sodium hydroxide to prepare solution A; Sodium hydroxide is dissolved in water, and p-hydroxystyrene is added under stirring to obtain solution B; The starch solution is made into a gelatinized starch solution, solution A or solution B is added, aluminum sulfate or aluminum chloride is added under stirring, and acid is added to adjust the pH to obtain the surface sizing agent. The surface sizing agent obtained by compounding the lignin-based phenolic sizing agent with starch in the present invention can achieve the same water resistance enhancement effect as the styrene-acrylic sizing agent compounded with starch.

Description

Technical Field

[0001] The present invention belongs to the technical field of paper sizing agents, and particularly relates to a preparation method of a surface sizing agent based on water-resistant phenolic compounded starch. Background Art

[0002] Oxidized starch, enzymatically hydrolyzed starch or cationic starch-based surface sizing agents are used to enhance the dry strength of paper. They are particularly widely used for corrugated paper because corrugated paper now uses a large amount of waste paper, and its strength will decrease as the number of fiber recycling times increases. Therefore, starch-based surface sizing agents are needed to perform surface sizing on this kind of paper to increase its dry strength.

[0003] However, starch-based surface sizing agents have poor water resistance and need to be combined with internal sizing to achieve the water resistance enhancement effect, or combined with chemically synthesized reagents such as AKD, ASA or styrene-acrylic glue for surface sizing. The disadvantages of these synthetic chemical sizing agents are high price, difficult biodegradation, and they all use fossil resources as raw materials. In the future, with the exhaustion of fossil resources, the raw material sources of sizing agents will be limited.

[0004] Methyl p-hydroxycinnamate and methyl ferulate can be obtained in high yields from grass lignin (Li Jiankui (2019). Catalytic depolymerization based on lignin priority and hierarchical conversion of biomass whole components [D]. Doctoral thesis, Beijing Forestry University, Beijing, China.). These two products can be hydrolyzed to obtain p-hydroxycinnamic acid and ferulic acid. The lignin oxidative depolymerization products p-hydroxybenzaldehyde and vanillin can react with p-hydroxycinnamic acid and ferulic acid through the Pekin reaction (Mialon L, Pemba AG, Miller SA. Biorenewable polyethylene terephthalate mimics derived from lignin and acetic acid [J]. Green Chemistry, 2010, 12(10): 1463 - 9262.), and these two products can be decarboxylated to obtain p-hydroxystyrene and 4-vinylguaiacol.

[0005] ZL201811619939.0 and CN202010086330.2 introduce a method for preparing 4-vinylphenol or 4-vinylguaiacol by a one-step method using p-hydroxyacetophenone and vanillone. Vanillone can be obtained by lignin oxidative depolymerization. Lignin hydrogenolysis can obtain p-hydroxyethylbenzene in high yields. 4-Ethylguaiacol is also one of the depolymerization products of lignin, and it can be oxidized to p-hydroxyacetophenone or vanillone respectively.

[0006] Therefore, both 4-vinylphenol and 4-vinylguaiacol can be derived from lignin. If they are derivatized into macromolecules while maintaining the phenolic structure, the derivatives will have the same biodegradable function as lignin. Substituting p-hydroxyacetophenone or vanillone with the reduction products of p-hydroxyacetophenone and vanillone, namely 4-hydroxy-3-methoxy-α-methylbenzyl alcohol and 4-hydroxy-α-methylbenzyl alcohol, and then increasing the carboxyl content of the derivatives using the carboxylic acids containing carboxyl groups obtained from the depolymerization of lignin, can also be biodegradable.

[0007] Currently, there is no research report on using these two lignin-based monomer phenols or their derivatives to be compounded with starch for surface sizing to improve the water resistance of starch surface sizing agents. Summary of the Invention

[0008] The purpose of this section is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract, and the title. However, such simplifications or omissions shall not be used to limit the scope of the present invention.

[0009] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0010] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for a surface sizing agent based on water-resistant phenolic compounded starch.

[0011] To solve the above technical problems, the present invention provides the following technical solution: A preparation method for a surface sizing agent based on water-resistant phenolic compounded starch, including,

[0012] Preparing anionic polymer A: Adding an alkali to a reaction kettle, adding a solvent, adding substrates a and b, closing the reaction kettle, reacting at 100 - 250 °C for 0.2 - 12 h. After the reaction is completed, cooling to room temperature, adding an acid to adjust the pH value to neutral, filtering, taking the filter residue and performing Soxhlet extraction with water. Monitor the aqueous solution in the Soxhlet extractor using thin-layer chromatography. When substrate b in the aqueous solution of the Soxhlet extractor disappears in thin-layer chromatography, then freeze-drying to obtain anionic polymer A;

[0013] Dissolving anionic polymer A in deionized water and sodium hydroxide to prepare solution A;

[0014] Dissolving sodium hydroxide in water, adding p-hydroxystyrene with stirring to obtain solution B, where B is at least one of 4-vinylguaiacol and 4-vinylphenol;

[0015] Configure the surface sizing agent: Prepare a gelatinized starch solution from a starch solution, add solution A or solution B, or add both solution A and solution B simultaneously, add aluminum sulfate or aluminum chloride under stirring, and add an acid to adjust the pH to 5 - 11 to obtain the surface sizing agent;

[0016] Among them, the solvent is at least one of ethanol, methanol, DMF, and water;

[0017] The substrate a is at least one of 4 - hydroxy - 3 - methoxy - α - methylbenzyl alcohol, 4 - hydroxy - α - methylbenzyl alcohol, p - hydroxycinnamic acid, and ferulic acid;

[0018] The substrate b is at least one of p - hydroxybenzoic acid, p - hydroxyphenylacetic acid, p - hydroxyphenylpropionic acid, vanillic acid, homovanillic acid, and dihydroferulic acid.

[0019] As a preferred embodiment of the preparation method of the present invention, among them: the base is at least one of sodium hydroxide, potassium hydroxide, potassium acetate, sodium acetate, calcium oxide, calcium hydroxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, ammonia water, triethylamine, DBU (1,8 - diazabicyclo[5.4.0]undec - 7 - ene).

[0020] As a preferred embodiment of the preparation method of the present invention, among them: after adding the substrate a and the substrate b, close the reaction kettle, wherein the concentrations of the base and a are both 0.01 - 0.5 kg / L, and the mass - volume concentration of b is 0 - 0.5 kg / L.

[0021] As a preferred embodiment of the preparation method of the present invention, among them: after adding the substrate a and the substrate b, close the reaction kettle, wherein the time taken to heat up to the specified temperature is within 30 minutes.

[0022] As a preferred embodiment of the preparation method of the present invention, among them: the mass concentration of solution A is 0.01 - 0.5 kg / L, and the pH value of solution A is above 12.

[0023] As a preferred embodiment of the preparation method of the present invention, among them: the mass concentration of solution B is 0.01 - 0.5 kg / L, the pH value of solution B is above 12, wherein the total content of phenolic monomers and their self - polymerized oligomers in B is more than 90%, and the content of monomers is more than 10%.

[0024] As a preferred embodiment of the preparation method of the present invention, among them: the starch is at least one of industrial - grade cationic starch, oxidized starch, and enzymatically hydrolyzed starch, and the mass concentration of the starch is 0.01 - 0.5 kg / L.

[0025] As a preferred embodiment of the preparation method of the present invention, wherein: the acid is at least one of industrial-grade sulfuric acid and hydrochloric acid; the mass of aluminum sulfate or aluminum chloride is between 1% and 4% of the mass of the added starch.

[0026] As a preferred embodiment of the preparation method of the present invention, wherein: the mass concentration of A and B in the sizing agent is 0 - 0.3 kg / L.

[0027] Another object of the present invention is to overcome the deficiencies in the prior art and provide a product prepared by a preparation method of a surface sizing agent based on water-resistant phenolic compound starch.

[0028] Advantages of the present invention:

[0029] The present invention provides a preparation method of a surface sizing agent based on water-resistant phenolic compound starch and its product. The surface sizing agent obtained by mixing lignin-based phenolic sizing agent and starch can achieve the effect of water resistance enhancement compared with the styrene-acrylic compound starch sizing agent. At the same time, the lignin-based phenolic sizing agent can be completely biodegradable, and it can use lignin as a source without relying on fossil resources, meeting the country's requirements for carbon neutrality and carbon peak. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0031] Figure 1 It is a possible mechanism diagram of the alkaline catalytic curing of B on paper in the present invention, where n is the total degree of polymerization and m is the degree of polymerization of the polymerization of vinyl groups;

[0032] Figure 2 It is a possible mechanism diagram for simply explaining the preparation of A with p-hydroxybenzoic acid as the lignin-derived acid in the present invention, where n is the total degree of polymerization and m is the degree of polymerization of the polymerization of vinyl groups;

[0033] Figure 3 It is a side view of the contact angle of the base paper in the present invention;

[0034] Figure 4 It is a side view of the contact angle of the paper treated with 30% oxidized starch in Examples 1 - 3 of the present invention;

[0035] Figure 5 It is a side view of the contact angle of the paper treated in Example 1 of the present invention;

[0036] Figure 6Side view of the contact angle of the treated paper in Embodiment 2 of the present invention. Detailed implementation manners

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0039] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments.

[0040] The main principle of the sizing agent of the present invention:

[0041] Phenolic monomers can be chemically cross-linked and cured under acid-base catalysis during the heating and drying process on paper as a water-resistant enhancer, or the polymer prepared from phenolic monomers can be used as a water-resistant enhancer first and then physically cross-linked and cured on paper as a water-resistant enhancer, or the polymer prepared from phenolic monomers and the monomer are added simultaneously and then chemically cross-linked and cured under acid-base catalysis as a water-resistant enhancer. Starch and phenolic substances can improve the intermolecular force between the phenolic sizing agent and starch through the coordination bridging of aluminum sulfate, making the strengthening effect of starch more obvious, and at the same time, it can also serve the purpose of being a dispersant for anionic phenolic latex.

[0042] Under acid or alkaline catalysis, the benzyl group of p-hydroxystyrene substances will generate a carbocation, which may trigger a stepwise polymerization reaction similar to phenolic resin with the ortho position of the phenolic hydroxyl group, and at the same time, it may also trigger an ionic polymerization reaction of the side-chain double bond by the benzyl carbocation. Due to the complex mechanism, the possible mechanism diagram of the alkaline-catalyzed curing of the present invention B on paper is as Figure 1 , and such polymers can achieve the purpose of enhancing the paper strength through the coordination bridging of aluminum ions with starch or paper.

[0043] Since the coordination ability of the phenolic hydroxyl group is relatively poor, molecules with carboxyl groups can be grafted onto it to improve its coordination ability with aluminum ions and also improve its dispersibility in the solution. Taking p-hydroxybenzoic acid as a lignin-derived acid, the possible mechanism diagram for the preparation of A is briefly described, as Figure 2As shown, p-hydroxycinnamic acid substances decarboxylate to form p-hydroxystyrene substances under alkaline catalysis. Under alkaline catalysis, the benzyl group of p-hydroxystyrene substances will form a carbocation, which may trigger a stepwise polymerization reaction similar to phenolic resin with the ortho-position of the phenolic hydroxyl group, and at the same time, it may also trigger an ionic polymerization reaction of the side-chain double bond initiated by the benzyl carbocation.

[0044] Due to the low oxygen content of A, the contact angle of the paper after sizing is large, but it is not easily dispersed in an aqueous solution under near-neutral conditions. However, B is more easily dispersed in the starch solution due to the presence of carboxyl groups on the molecule. Therefore, after B is mixed with A, B can act as a dispersant for A, and at the same time, B and A can continue to polymerize on the paper, reducing the oxygen content, increasing the contact angle, and also increasing the molecular weight to achieve the strengthening purpose.

[0045] Example 1

[0046] (1) Prepare anionic polymer A, and the method and steps are as follows:

[0047] Add 5 g of sodium hydroxide to the reaction kettle, add 50 ml of water to the reaction kettle, then add 7 g of substrate a (4-hydroxycinnamic acid) and 2 g of substrate b (p-hydroxybenzoic acid), then close the reaction kettle, react at 160 °C for 1 hour, and the time to rise to the specified temperature is within 30 minutes. After the reaction is completed, cool to room temperature and then add acid to adjust the pH value to neutral. The obtained filter residue is subjected to Soxhlet extraction with water. The aqueous solution in the Soxhlet extractor is monitored by thin-layer chromatography, and substrate b in the aqueous solution of the Soxhlet extractor disappears on the thin-layer chromatography. Then freeze-dry and weigh the solid weight as 5 g. Dissolve it with 20 ml of deionized water and 1 g of sodium hydroxide, and make up the volume to a constant volume with a 25-ml volumetric flask with a PP plastic stopper for standby. After detection, the pH is 12.7, and this solution is recorded as the solution of A.

[0048] (2) Add 8.75 g of oxidized starch to 80 ml of deionized water, gelatinize at 80 °C for half an hour. When the temperature drops to about 40 °C, add 5 ml of the solution of A, stir and add an aluminum sulfate solution. The mass of aluminum sulfate is 1.75% of the mass of the starch. Then add 10% sulfuric acid to adjust the pH to 7.9, and continue to add deionized water dropwise until the solution volume is 100 ml to obtain a surface sizing enhancer.

[0049] Apply this sizing agent to 40 g / m of paper without applying any chemicals 2The paper is sized with an amount of 2% of the absolute dry weight of the paper, and the tensile strength of the paper is as follows: According to the national standard GB / T 453-1989, four specimens with a length of (150 ± 10) mm and a width of (15 ± 0.1) mm are taken longitudinally, and their dry tensile properties are measured with a tensile strength tester. The measurement length is (100 ± 0.5) mm, and the tensile rate is (50 ± 2) mm / min. The calculation is carried out according to the following formula, and the average value is taken.

[0050] S = F / Lw

[0051] In the formula:

[0052] S --- Tensile strength, N / mm;

[0053] F --- Average tensile force, N;

[0054] Lw --- Width of the test paper strip, mm.

[0055] According to YC / T 424-2011, for the contact angle of the paper, at least three specimens are cut and fixed flat on the sample stage. A 2 μL liquid droplet is dripped, and the contact time does not exceed 1 s. The contact angle is measured with contact angle measurement software, and the average value is taken.

[0056] The results show that the sizing agent increases the tensile strength of the paper from 1.82 N / mm (longitudinal tensile strength of the original paper) to 3.68 N / mm, an increase of 1.02 times, and the surface contact angle of the paper increases from 17.2 degrees (surface contact angle of the original paper) to 69.17 degrees, an increase of 3.02 times.

[0057] Compared with the sizing of the paper under the same conditions with a higher concentration (30%) of oxidized starch sizing agent (tensile strength is 2.763 N / mm, contact angle is 29.8 degrees), the strength is increased by 33%, and the contact angle is increased by 1.32 times; Note: Generally, 30% oxidized starch surface sizing is used in industry.

[0058] For the side view of the contact angle of the original paper, see Figure 3 , and the longitudinal tensile strength diagram of the original paper is shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] For the side view of the contact angle of the paper treated in Example 1, see Figure 5 , and its longitudinal tensile strength is shown in Table 2.

[0063] Table 2

[0064] Tensile strength (N) Breaking deformation (mm) Maximum value 56.98 2.839 Minimum value 51.90 2.029 Average value 55.26 2.571 1 51.90 2.029 2 56.98 2.839 3 56.98 2.729 4 55.17 2.686 Elongation at break 2.571％ Tensile strength 3.684 N / mm Tensile index 92.093 N·m / g Energy absorption <![CDATA[57.777 J / m 2 > Absorption index 1444.427 J / g Length at break 9.397 km

[0065] Side view of the contact angle of the oxidized starch sized paper with 30% Figure 4 , and its longitudinal tensile strength diagram is shown in Table 3.

[0066] Table 3

[0067]

[0068]

[0069] Example 2

[0070] (1) Prepare the solution of B. Dissolve 0.45 g of sodium hydroxide in 20 ml of water, and add 1 g of p-hydroxystyrene while stirring to obtain the target solution. Note: Since the monomer of B is very prone to self-polymerization, even when stored at low temperature, self-polymerization will occur to obtain the oligomer of B. Therefore, the total content of phenolic monomers and their self-polymerized oligomers in the selected B is more than 90%, and the content of the monomer is more than 10%. B needs to maintain a certain amount of monomer to initiate the cross-linking reaction;

[0071] The preparation method of p-hydroxystyrene is as follows: Take 15 g of p-hydroxycinnamic acid in a reaction kettle, add 0.1 g of potassium acetate and 50 mL of DMF, react at 150 °C for 2 hours, take out the reacted liquid, pour it into 120 mL of water, separate the precipitated oil through a separatory funnel, and wash it twice with deionized water. Then take the lower layer liquid as p-hydroxystyrene.

[0072] (2) Add 8.75 g of oxidized starch to 60 ml of deionized water, gelatinize at 80 °C for half an hour. When the temperature drops to about 40 °C, add all the B solution, add the aluminum sulfate solution while stirring. The mass of aluminum sulfate is 1.75% of the mass of starch. Then add 10% sulfuric acid to adjust the pH to 7.9, and continue to add deionized water until the volume of the solution is 100 ml to obtain the surface sizing enhancer.

[0073] Apply this sizing agent to the paper with a basis weight of 40 g / m 2 without adding any chemicals, size it in an amount of 2% of the oven-dry weight of the paper, and detect the longitudinal tensile strength and contact angle according to the method described in Example 1. The results show that the sizing agent increases the tensile strength of the paper from 1.82 N / mm to 2.36 / mm, an increase of 0.295 times, and the contact angle of the paper surface increases from 17.2 degrees to 84.52 degrees, an increase of 3.9 times. The side view of the contact angle of the paper after treatment in Example 2 of the present invention is shown in Figure 6 , and its tensile strength diagram is shown in Table 4.

[0074] Table 4

[0075]

[0076]

[0077] Compared with sizing the paper under the same conditions with a higher concentration (30%) of oxidized starch sizing agent, the strength decreased by 15%, and the contact angle increased by 1.63 times.

[0078] Example 3

[0079] (1) Prepare anionic polymer A, and the method and steps are as follows:

[0080] Add 5 g of sodium hydroxide to the reaction kettle. Put 50 ml of water into the reaction kettle, then add 7 g of substrate a (4-hydroxycinnamic acid) and 2 g of substrate b (p-hydroxybenzoic acid). Then close the reaction kettle and react at 160 °C for 1 hour. The time to raise the temperature to the specified temperature is within 30 minutes. After the reaction is completed, cool to room temperature and then add acid to adjust the pH value to neutral. The obtained filter residue is subjected to Soxhlet extraction with water. The aqueous solution in the Soxhlet extractor is monitored by thin-layer chromatography, and substrate b in the aqueous solution of the Soxhlet extractor disappears on the thin-layer chromatography;

[0081] Then freeze-dry, weigh the solid weight as 5 g, dissolve it with 20 ml of deionized water and 1 g of sodium hydroxide, and make up the volume to a constant volume with a 25-ml volumetric flask with a PP plastic stopper for standby. After detection, the pH is 12.7, and this solution is recorded as the solution of A.

[0082] (2) Prepare the solution of B. Dissolve 0.45 g of sodium hydroxide in 20 ml of water, and add 1 g of p-hydroxystyrene during stirring to obtain the target solution. The p-hydroxystyrene is the same as in Example 2.

[0083] (3) Add 8.75 g of oxidized starch to 60 ml of deionized water, gelatinize at 80 °C for half an hour. When the temperature drops to about 40 °C, add 5 ml of the solution of A. Add the aluminum sulfate solution during stirring. The mass of aluminum sulfate is 1.75% of the mass of the starch. Add all of the solution of B, then add 10% sulfuric acid to adjust the pH to 7.9, and continue to add deionized water until the volume of the solution is 100 ml to obtain the surface sizing enhancer.

[0084] Use this sizing agent for the paper with a basis weight of 40 g / m 2 and size it in an amount of 2% of the oven-dry weight of the paper. The tensile strength of the paper is increased from 1.82 N / mm to 3.78 N / mm, an increase of 1.07 times. The surface contact angle of the paper is increased from 17.2 degrees to 96.3 degrees, an increase of 4.60 times.

[0085] Compared with sizing the paper under the same conditions with a higher concentration (30%) of oxidized starch sizing agent, the strength is increased by 36.8%, but the contact angle is increased by 2.22 times.

[0086] The present invention provides a preparation method and a product of a surface sizing agent based on water-resistant phenolic compounded starch. The surface sizing agent obtained by compounding a lignin-based phenolic sizing agent and starch can achieve the same water resistance enhancement effect as that of a styrene-acrylate compounded starch sizing agent. At the same time, the lignin-based phenolic sizing agent can be completely biodegradable, and it can use lignin as a source without relying on fossil resources, meeting the country's requirements for carbon peaking and carbon neutrality.

[0087] 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 preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of a surface sizing agent based on water-resistant phenolic compound starch, characterized in that: Including, Preparing anionic polymer A: Add a base into a reaction kettle, then add a solvent, add substrates a and b, and then close the reaction kettle. React at 100 - 250 °C for 0.2 - 12 h. After the reaction ends, cool to room temperature, add an acid to adjust the pH value to neutral, filter, take the filter residue and perform Soxhlet extraction with water. Monitor the aqueous solution in the Soxhlet extractor by thin-layer chromatography. When substrate b in the aqueous solution of the Soxhlet extractor disappears in the thin-layer chromatography, then perform freeze-drying to obtain anionic polymer A; Dissolve anionic polymer A in deionized water and sodium hydroxide to prepare solution A; Dissolve sodium hydroxide in water, and add p-hydroxystyrene while stirring to obtain solution B, where B is at least one of 4-vinylguaiacol and 4-vinylphenol; Preparing a surface sizing agent: Prepare a gelatinized starch solution from a starch solution, add solution A or solution B, or add both solution A and solution B simultaneously. Add aluminum sulfate or aluminum chloride while stirring, and add an acid to adjust the pH to 5 - 11 to obtain the surface sizing agent; Wherein, the solvent is at least one of ethanol, methanol, DMF, and water; Substrate a is at least one of 4-hydroxy-3-methoxy-α-methylbenzyl alcohol, 4-hydroxy-α-methylbenzyl alcohol, p-hydroxycinnamic acid, and ferulic acid; Substrate b is at least one of p-hydroxybenzoic acid, p-hydroxyphenylacetic acid, p-hydroxyphenylpropionic acid, vanillic acid, homovanillic acid, and dihydroferulic acid; The mass concentrations of A and B in the surface sizing agent are 0.01 - 0.3 kg / L.

2. The preparation method according to claim 1, characterized in that: The base is at least one of sodium hydroxide, potassium hydroxide, potassium acetate, sodium acetate, calcium oxide, calcium hydroxide, zirconium hydroxide, magnesium oxide, magnesium hydroxide, ammonia water, triethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

3. The preparation method according to claim 1 or 2, characterized in that: After adding substrates a and b and then closing the reaction kettle, wherein the concentrations of the base and a are both 0.01 - 0.5 kg / L, and the mass-volume concentration of b is 0 - 0.5 kg / L.

4. The preparation method according to claim 3, wherein: After adding substrates a and b and then closing the reaction kettle, wherein the time taken to heat up to the specified temperature is within 30 minutes.

5. The preparation method according to any one of claims 1, 2 or 4, characterized in that: The mass concentration of solution A is 0.01 - 0.5 kg / L, and the pH value of solution A is above 12.

6. The preparation method according to claim 5, characterized in that: The mass concentration of solution B is 0.01 - 0.5 kg / L, and the pH value of solution B is above 12. Among them, the total content of phenolic total monomers and their self-polymerized oligomers in B is above 90%, and the content of monomers is above 10%.

7. The preparation method according to claim 1, characterized in that: The starch is at least one of industrial-grade cationic starch, oxidized starch, and enzymatically hydrolyzed starch, and the mass concentration of the starch is 0.01 - 0.5 kg / L.

8. The preparation method according to claim 1, characterized in that: The acid is at least one of industrial-grade sulfuric acid and hydrochloric acid; the mass of aluminum sulfate or aluminum chloride is between 1% and 4% of the mass of the added starch.

9. A product prepared by the preparation method according to any one of claims 1 - 8.

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