Preparation method and application of repulpable gallic acid-based waterproof and oil-proof agent

Abstract

The invention discloses a preparation method and application of a repulpable gallic acid-based waterproof and oil-proof agent, and belongs to the technical field of bio-based oil-proof hydrophobic paper surface coatings. The preparation method comprises the following steps: by taking alkyl gallate and epoxy chloropropane as raw materials, preparing alkyl gallate epoxy through epoxidation reaction; and uniformly mixing the alkyl gallate epoxy resin with an acid anhydride / phenol compound to obtain the alkyl gallate epoxy resin series waterproof and oil-proof agent. The structure of the bio-based waterproof and oil-proof agent prepared by the invention contains groups such as a non-polar long alkyl chain, an epoxy group and an amino group, a compact cross-linked coating can be formed on the surface and the interior of paper, and gaps between paper cellulose are filled, so that permeation of oil, water and gas is blocked, meanwhile, the adhesive force between the coating and the paper is increased, and the waterproof and oil-proof effects are improved. The fibers are more tightly combined together; non-polar long alkyl chains and benzene ring groups in the structure can endow the paper with excellent oil-proof, hydrophobic and mechanical properties, and flexible chain segments (alkyl carbon chains) with different lengths are introduced to adjust the flexibility of the coating, so that the flexibility and tensile strength of the paper can be effectively adjusted; the coating paper can be recycled and reused in an alcoholysis mode. The raw materials are easy to obtain and renewable, paper can be re-pulped after being coated, and the paper has the potential of replacing plastic packaging and meets the performance requirements of paper packaging on specific scenes such as water resistance and oil resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of bio-based oil-repellent and hydrophobic paper surface coating, and particularly relates to a preparation method and application of a reslurryable gallic acid-based water- and oil-repellent agent. BACKGROUND

[0002] Paper packaging has become an essential part of people's high-quality life due to its lightness and low price, and is widely used in food, medicine, medical devices, children's toys and other fields. Under the background of global "plastic limit order", paper has become one of the most important choices to replace disposable plastic products due to its renewable, degradable and low-cost advantages. Paper is composed of cellulose, but the strong hydrophilicity and porous structure of natural cellulose lead to the easy penetration of water, oil and oxygen, which seriously limits its application in high-end packaging fields such as food and medicine; it is generally necessary to coat it or use fluorine-containing materials for coating treatment to meet the industrial application requirements. However, coated paper (such as polyethylene, polyethylene, polypropylene, fluorocarbon compound coated paper) has the problems of non-reslurry, difficult recycling, and difficult degradation, etc. Although polyethylene laminated paper has excellent barrier properties, its poor interfacial compatibility with cellulose fibers leads to serious fiber damage during the regeneration process, and the recycling rate is less than 30%. Fluorine-containing additives (such as polyfluoroalkyl substances (PFAS)) will produce harmful substances during use, which seriously threatens human health, and has been restricted in developed countries and regions. Developing environmentally friendly paper coating with good water and oil resistance and recyclability has become the key to the high-quality development of paper packaging materials.

[0003] Biomass resources are renewable, abundant, easily degradable, and biocompatible, and more importantly, they reduce the use of fossil resources from the source. Bio-based coatings mainly use natural polysaccharides (such as chitosan), proteins (such as zein), and plant oil derivatives, starch as the core, and through chemical modification or composite technology to endow paper with multifunctionality. Patent CN 112029146A discloses a super-hydrophobic coating based on protein particles and its preparation method. The super-hydrophobic coating uses long-chain fluorine-free alkanes to modify starch, avoiding the potential impact of fluorine-containing modifiers on the water environment. The modified coating has excellent water and oil resistance; although the oil resistance of protein is excellent, its hydrophilicity is very strong, and it needs very complex modification methods, and protein is very strict on temperature, if in high temperature environment will cause protein irreversible denaturation, thus leading to the performance and stability of the coating material. In addition, the preparation process of the above coating is complex, which hinders its large-scale industrial production. Zhang et al. (ACS Applied Polymer Materials 2024 6(5), 2877-2888) used oxidized cellulose nanofiber (OCNF) as raw material, prepared a nanocellulose-based coating solution with high barrier property by sodium periodate, and then compounded with chitosan solution (CTS), and then coated on the substrate paper. It is widely used in paper coating due to its film-forming property and high barrier property, but its hydrophilicity leads to poor moisture resistance, and the mechanical strength of chitosan coating is limited, and the price is expensive, which limits the large-scale industrial application of the coating. Tian et al. (Journal of Colloid and Interface Science, 2022. 610: p. 1043-1056.) stabilized soybean oil-based Pickering emulsion by silanization modification of nanocellulose, which improved the water vapor barrier property of the coating by 33%, and was sustainable, but due to its poor water dispersibility, its application is challenged. In summary, bio-based composites have shown excellent application potential in paper packaging materials.

[0004] Natural plant polyphenols are widely concerned in the field of functional materials due to their rich active functional groups (such as phenolic hydroxyl, ester bond) and natural antioxidant properties. Natural plant polyphenols are considered as one of the potential ideal raw materials for preparing environmentally friendly papermaking additives because of their wide sources, renewability, low price, adjustable structure, non-toxicity and biodegradability. Patent CN202311530938.X invents a biodegradable high-barrier (water, oil, oxygen, water vapor) paper-based packaging material and its preparation method. The coating has five layers in turn, which are base paper layer, starch layer, polyethylene layer, polyepoxy oil resin layer and polyacrylic acid resin layer. However, its preparation process is relatively complicated, which is not conducive to industrial production. Patent CN 108383970 A invents a preparation method of high-temperature alkali-resistant waterborne polyurethane coating, which can form a polyurethane coating on the surface of paper that is resistant to high-temperature sodium hydroxide solution. However, its preparation process requires a variety of complex raw materials, and all of them are non-renewable petroleum-based raw materials, which limits its wide application and sustainable development. Patent CN 102875740 A invents a preparation method of epoxy resin modified styrene-acrylic emulsion. However, the surface strength of the coated paper is poor and the emulsion itself has poor water resistance. The process has poor safety and needs to be further optimized. It has become a key to the high-quality development of the paper packaging industry to develop environmentally friendly bio-based paper waterproof / oil repellent agents with waterproof and oil-repellent functions and a feasible preparation process that can give paper excellent performance. SUMMARY

[0005] In this context, the purpose of the present application is to propose a bio-based epoxy waterproof and oil-repellent agent with rewettability based on gallic acid as the core raw material: In view of the above-mentioned problems existing in the prior art, (1) the first technical problem solved by the present application is to provide a preparation method of a series of gallic acid alkyl ester epoxy resins with different alkyl chain lengths and rewettability; (2) the second technical problem solved by the present application is to provide a series of waterproof and oil-repellent agents prepared by the method; (3) the third technical problem solved by the present application is the specific application of the waterproof and oil-repellent agent as a paper oil-repellent and hydrophobic surface coating.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present application are as follows:

[0007] The application discloses a preparation method of a reslurryable gallic acid epoxy waterproof and oil-proof agent, and selects three different carbon chain length epoxy resins including methyl gallate, octyl gallate and lauryl gallate to prepare a gallic acid epoxy waterproof and oil-proof agent, wherein the lauryl gallate epoxy resin (DG-EP) is taken as an example and the preparation method comprises the following steps: taking the lauryl gallate, epoxy chloropropane and liquid alkali as raw materials, and performing an epoxidation reaction under the action of a phase transfer catalyst to prepare the lauryl gallate epoxy resin, then adding an acid anhydride and a phenol curing agent into the lauryl gallate epoxy resin and fully blending to prepare the gallic acid-based paper waterproof and oil-proof agent.

[0008] Further, the structure of the lauryl gallate is as follows:

[0009]

[0010] Further, the preparation method of the gallic acid-based waterproof and oil-proof surface coating is as follows: the lauryl gallate, the epoxy chloropropane and the phase transfer catalyst are put into a reaction kettle with a thermometer and a reflux device, heating and stirring are performed, the raw material ratio, the reaction temperature, the reaction time and the catalyst dosage are controlled, the catalyst and the generated salt are removed through water washing after the reaction, the water washing is performed until neutral, and the epoxy chloropropane and water are removed through reduced pressure distillation.

[0011] Further, the structure of the lauryl gallate epoxy resin is as follows:

[0012]

[0013] Further, the molar ratio of the hydroxyl group of the lauryl gallate, the liquid alkali of the epoxy chloropropane and the phase transfer catalyst in the reaction is 1:10-20:1-1.5, and the catalyst dosage is 0.05%-0.5% of the total mass of the reaction system.

[0014] Further, the liquid alkali is specifically a sodium hydroxide aqueous solution, and the mass fraction of the liquid alkali is 20%-40%; the phase transfer catalyst is specifically benzyltriethylammonium chloride.

[0015] Further, the epoxy ring-opening reaction temperature is 80-120 DEG C, the epoxy ring-opening reaction time is 4-10 hours, the epoxy ring-closing reaction temperature is 30-50 DEG C, and the epoxy ring-closing reaction time is 2-8 hours.

[0016] Further, the acid anhydride compound is taken as a curing agent, and the methyl tetrahydrophthalic anhydride is specifically selected.

[0017] Further, the phenol curing accelerator is specifically dimethylaminomethylphenol.

[0018] Further, the mass ratio of the gallic acid lauryl ester epoxy resin to the acid anhydride curing agent and the phenol curing accelerator is 100:10-30:1-3.

[0019] Further, the obtained gallic acid bio-based waterproof and oil-proof agent is uniformly dropped onto the surface of the paper, uniformly rolled on the surface of the paper by a coating machine, and then subjected to a crosslinking reaction at 70-90 DEG C for 1-5 h to obtain the rewettable gallic acid-based coated paper.

[0020] Further, the above-mentioned rewettable gallic acid-based lauryl ester epoxy resin is applied as a waterproof and oil-proof agent surface coating of paper.

[0021] Further, the rewettable paper is prepared by selecting ethylene glycol as a solvent, alcoholysis at 120 DEG C-160 DEG C for 2-6 h, and then filtering, washing, dissociating and papermaking.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] The present application aims to solve the problems of poor waterproof and oil-proof performance of paper packaging, and proposes a series of rewettable bio-based epoxy waterproof and oil-proof agent based on gallic acid as a core material: (1) the present application utilizes the polyphenol hydroxyl group and the special benzene ring rigid structure of gallic acid to construct an environmentally friendly resin matrix as a waterproof and oil-proof agent through an epoxidation reaction, which can form a dense crosslinked coating on the paper, fill and block the gaps between the cellulose fibers, thereby blocking the penetration of oil, water and gas; and different lengths of flexible segments (alkyl carbon chains) are introduced to adjust the flexibility of the coating, effectively improving the flexibility and strength of the paper; (2) the additional value utilization of gallic acid in the paper coating field is realized, and the coating performance is increased through the inherent functions (antibacterial and antioxidant) of gallic acid, which can reduce the dependence on subsequent additives. At the same time, the raw material has the advantages of wide source, renewable and green renewable, and the production process is green and sustainable. (3) the series of bio-based gallic acid ester epoxy resin paper has 100% rewettable performance, realizing the rewettable recycling of the paper with the coating. The present application develops a series of bio-based gallic acid ester epoxy resin waterproof and oil-proof agent for paper, which has a wide application and practical prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a gallic acid ester epoxy resin series waterproof and oil-proof agent raw material and equation formula diagram;

[0025] Figure 2 is a crosslinked structure diagram of the gallic acid ester epoxy resin series waterproof and oil-proof agent;

[0026] Figure 3is the infrared spectrogram of gallic acid methyl ester (GA-MG) and gallic acid methyl ester epoxy resin (MG-EP) ;

[0027] Figure 4 is the infrared spectrogram of gallic acid octyl ester (GA-OG) and gallic acid octyl ester epoxy resin (OG-EP) ;

[0028] Figure 5 is the infrared spectrogram of gallic acid lauryl ester (GA-DG) and gallic acid lauryl ester epoxy resin (DG-EP) ;

[0029] Figure 6 is the hydrogen nuclear magnetic spectrogram of gallic acid methyl ester (GA-MG) and gallic acid methyl ester epoxy resin (MG-EP) ;

[0030] Figure 7 is the hydrogen nuclear magnetic spectrogram of gallic acid octyl ester (GA-MG) and gallic acid octyl ester epoxy resin (MG-EP) ;

[0031] Figure 8 is the hydrogen nuclear magnetic spectrogram of gallic acid lauryl ester (GA-DG) and gallic acid lauryl ester epoxy resin (DG-EP) ;

[0032] Figure 9 is the flow chart of waterproof and oil-proof agent coated paper of gallic acid ester epoxy resin series for testing the repulpability of the paper; DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described below in combination with specific examples. In the following examples, the technical means used are all conventional means well known to those skilled in the art, unless otherwise specified.

[0034] The raw materials and reagents used in the following examples are as follows: gallic acid octyl ester in the examples, analytical grade, provided by Shandong Keyuan Biochemical Co., Ltd.; gallic acid methyl ester, gallic acid lauryl ester, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, dimethylaminomethylphenol, analytical grade, provided by Shanghai Maikelin Biochemical Technology Co., Ltd.; sodium hydroxide, potassium hydroxide, analytical pure, provided by Nanjing Chemical Reagent Co., Ltd.; acetic acid, hydrochloric acid, methyltetrahydrophthalic anhydride, industrial grade, provided by China National Pharmaceutical Group Chemical Reagent Co., Ltd.; epichlorohydrin, industrial grade, provided by Anhui Xinyuan Technology Co., Ltd.

[0035] Example 1

[0036] A preparation method of a reslurryable gallic acid-based epoxy resin paper waterproof and oil-proof agent, comprising the following steps: adding methyl gallate, epichlorohydrin and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the methyl gallate is 9.21 g, the epichlorohydrin is 83.32 g, and the benzyl triethyl ammonium chloride is 0.46 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the NaOH is 6.6 g, n(methyl gallate):n(ECH):n(NaOH)=1:6:1.1, then heating to 90°C, reacting for 5 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 3 h at 40°C; after the reaction, removing the generated salt by filtration, neutralizing with acetic acid and washing with water, and finally removing the epichlorohydrin and water in the system by reduced pressure distillation. A methyl gallate epoxy resin (MG-EP) is obtained, which is a transparent light yellow viscous liquid with an epoxy value of 0.66 mol / 100 g. The reaction equation is as follows: Figure 1 e in the figure.

[0037] Example 2

[0038] A preparation method of a reslurryable gallic acid-based epoxy resin paper waterproof and oil-proof agent, comprising the following steps: adding octyl gallate, epichlorohydrin and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the octyl gallate is 14.1 g, the epichlorohydrin is 83.25 g, and the benzyl triethyl ammonium chloride is 0.48 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the NaOH is 6.6 g, n(octyl gallate):n(ECH):n(NaOH)=1:6:1.1, then heating to 90°C, reacting for 5 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 3 h at 40°C; after the reaction, removing the generated salt by filtration, neutralizing with acetic acid and washing with water, and finally removing the epichlorohydrin and water in the system by reduced pressure distillation. An octyl gallate epoxy resin (OG-EP) is obtained, which is a transparent light yellow viscous liquid. The epoxy value is 0.51 mol / 100 g. The reaction equation is as follows: Figure 1 e in the figure.

[0039] Example 3

[0040] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding methyl gallate, epichlorohydrin and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the amount of methyl gallate is 17 g, the amount of epichlorohydrin is 92.5 g, and the amount of benzyltriethylammonium chloride is 0.5 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the amount of NaOH is 6.6 g, n(methyl gallate) : n(ECH) : n(NaOH) = 1 : 6 : 1.1, then heating to 90 DEG C, reacting for 5 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 3 h at 40 DEG C; after the reaction is completed, removing the generated salt by suction filtration, neutralizing with acetic acid and washing with water, and finally removing the epichlorohydrin and water in the system by vacuum distillation. A methyl gallate epoxy resin (MG-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature. The epoxy value is 0.41 mol / 100 g. The reaction equation is as follows: Figure 1 e.

[0041] Example 4

[0042] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding methyl gallate, epichlorohydrin and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the amount of methyl gallate is 17 g, the amount of epichlorohydrin is 92.5 g, and the amount of benzyltriethylammonium chloride is 0.5 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the amount of NaOH is 6.6 g, n(methyl gallate) : n(ECH) : n(NaOH) = 1 : 6 : 1.1, then heating to 90 DEG C, reacting for 5 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 3 h at 40 DEG C; after the reaction is completed, removing the generated salt by suction filtration, neutralizing with acetic acid and washing with water, and finally removing the epichlorohydrin and water in the system by vacuum distillation. A methyl gallate epoxy resin (MG-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature. The epoxy value is 0.41 mol / 100 g. The reaction equation is as follows: Figure 1 e.

[0043] Example 5

[0044] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding methyl gallate, epichlorohydrin, and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel, and thermometer, wherein the methyl gallate is 9.21 g, the epichlorohydrin is 83.32 g, and the benzyltriethylammonium chloride is 0.46 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the NaOH is 6.6 g, n(methyl gallate):n(ECH):n(NaOH)=1:6:1.1, then heating to 70°C, and reacting for 5 h; dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 4 h at 30°C; after the reaction, removing the generated salt by filtration, neutralizing with acetic acid, and washing with water; and finally removing the epichlorohydrin and water in the system by reduced pressure distillation. A methyl gallate epoxy resin (MG-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature. The epoxy value is 0.56 mol / 100 g. The reaction equation is as follows: Figure 1 e in the formula.

[0045] Example 6

[0046] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding octyl gallate, epichlorohydrin, and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel, and thermometer, wherein the octyl gallate is 14.1 g, the epichlorohydrin is 83.32 g, and the benzyltriethylammonium chloride is 0.48 g; adding a 32% sodium hydroxide solution into the constant pressure funnel, wherein the NaOH is 6.6 g, n(octyl gallate):n(ECH):n(NaOH)=1:6:1.1, then heating to 90°C, and reacting for 3 h; dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, and reacting for 2 h at 40°C; after the reaction, removing the generated salt by filtration, neutralizing with acetic acid, and washing with water; and finally removing the epichlorohydrin and water in the system by reduced pressure distillation. An octyl gallate epoxy resin (OG-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature, and the epoxy value is 0.39 mol / 100 g. The reaction equation is as follows: Figure 1 e in the formula.

[0047] Example 7

[0048] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding gallic acid octyl ester, epoxy chloropropane and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the gallic acid octyl ester is 14.1 g, the epoxy chloropropane is 83.32 g and the benzyl triethyl ammonium chloride is 0.48 g, adding a 32% sodium hydroxide solution into the constant pressure funnel, taking 6.6 g of NaOH, n(gallic acid octyl ester):n(ECH):n(NaOH) = 1:6:1.1, then heating to 70 DEG C, reacting for 5 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, reacting for 4 h at 30 DEG C, after the reaction, removing the generated salt by filtration, neutralizing with acetic acid and washing with water, and finally removing the epoxy chloropropane and water in the system by reduced pressure distillation. A gallic acid lauryl ester epoxy resin (OG-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature, and the epoxy value is 0.41 mol / 100 g. The reaction equation is as follows: Figure 1 e in the formula.

[0049] Example 8

[0050] A preparation method of a reslurry gallic acid-based epoxy resin paper waterproof and oil repellent agent, comprising the following steps: adding gallic acid lauryl ester, epoxy chloropropane and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the gallic acid lauryl ester is 17 g, the epoxy chloropropane is 92.5 g and the benzyl triethyl ammonium chloride is 0.5 g, adding a 32% sodium hydroxide solution into the constant pressure funnel, taking 6.6 g of NaOH, n(gallic acid lauryl ester):n(ECH):n(NaOH) = 1:6:1.1, then heating to 90 DEG C, reacting for 3 h, dropping the sodium hydroxide solution in the constant pressure funnel into the reaction kettle, reacting for 2 h at 40 DEG C, after the reaction, removing the generated salt by filtration, neutralizing with acetic acid and washing with water, and finally removing the epoxy chloropropane and water in the system by reduced pressure distillation. A gallic acid lauryl ester epoxy resin (GA-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature. The epoxy value is 0.30 mol / 100 g. The reaction equation is as follows: Figure 1 e in the formula.

[0051] Example 9

[0052] A preparation method of a reslurryable gallic acid-based epoxy resin paper waterproof and oil-proof agent, comprising the following steps: adding lauryl gallate, epoxy chloropropane and phase transfer catalyst into a reaction kettle provided with mechanical stirring, condensation reflux device, constant pressure funnel and thermometer, wherein the lauryl gallate is 17 g, the epoxy chloropropane is 92.5 g, and the benzyl triethyl ammonium chloride is 0.5 g; adding a 32% mass fraction sodium hydroxide solution into the constant pressure funnel, wherein the NaOH is 6.6 g, n(lauryl gallate):n(ECH):n(NaOH) = 1:6:1.1, then heating to 70 DEG C and reacting for 5 h; adding the sodium hydroxide solution in the constant pressure funnel into the reaction kettle and reacting for 4 h at 30 DEG C; after the reaction is completed, removing the generated salt by filtration, neutralizing with acetic acid and washing with water, and finally removing the epoxy chloropropane and water in the system by reduced pressure distillation. A lauryl gallate epoxy resin (GA-EP) is obtained, which is a transparent light yellow viscous liquid at room temperature and a white solid at room temperature. The epoxy value is 0.45 mol / 100 g. The reaction equation is as follows: Figure 1

[0053] Example 10

[0054] A preparation method of a reslurryable bio-based methyl gallate epoxy resin paper waterproof and oil-proof agent, comprising the following steps: fully stirring and uniformly dispersing the obtained methyl gallate epoxy resin, MTHPA (methyl tetrahydrophthalic anhydride) and DPM-30 (dimethylaminomethyl phenol) in a proportion, wherein the mass ratio of the components is 10:2:0.2, to obtain a methyl gallate epoxy resin waterproof and oil-proof agent. The obtained bio-based methyl gallate waterproof and oil-proof agent is uniformly dropped to one end of the surface of paper along a roller coating rod, and the coating is uniformly applied to the surface of the paper with a quantitative value of 75 g / m 2 at a uniform speed by using a rod coating machine, the coating amount of each group is controlled to be almost the same (10-15 g / m 2 ), and then the coated paper is subjected to crosslinking reaction in an 80 DEG C constant temperature and pressure oven for 5 h, to obtain the reslurryable bio-based coated paper.

[0055] Example 11

[0056] A preparation method of a reslurryable bio-based octyl gallate epoxy resin paper waterproof and oil-proof agent, comprising the following steps: fully stirring and uniformly dispersing the obtained octyl gallate epoxy resin, MTHPA (methyl tetrahydrophthalic anhydride) and DPM-30 (dimethylaminomethyl phenol) in a proportion, wherein the mass ratio of the components is 10:2:0.2, to obtain an octyl gallate epoxy resin waterproof and oil-proof agent. The obtained bio-based octyl gallate waterproof and oil-proof agent is uniformly dropped to the surface of paper along a roller coating rod, and the coating is uniformly applied to the surface of the paper with a quantitative value of 75 g / m 2 ​A4 paper surface, and the coating machine with uniform speed roller coating to evenly coat the paint on the paper surface, control the coating amount of each group almost the same (10-15g / m 2 ), then the coated paper in 80℃ constant temperature constant pressure oven for crosslinking reaction 5h, to prepare the said pulpable bio-based coating paper.

[0057] Example 12

[0058] A preparation method of a pulpable bio-based lauryl gallate epoxy resin waterproof and oil-proof agent for paper, comprising the following steps: the obtained lauryl gallate epoxy resin is fully stirred with MTHPA (methyl tetrahydrophthalic anhydride) and DPM-30 (dimethylaminomethyl phenol) in proportion, and is uniformly dispersed, and the mass ratio of each component is 10:2:0.2, to obtain a lauryl gallate epoxy resin waterproof and oil-proof agent. The obtained lauryl gallate bio-based waterproof and oil-proof agent is uniformly dropped along the roller coating rod to one end of the paper surface, and the coating machine with uniform speed roller coating is used to evenly coat the paint on the surface of A4 paper with a dosage of 75g / m 2 , and the coating amount of each group is controlled to be almost the same (10-15g / m 2 ). Then the coated paper is subjected to crosslinking reaction in an 80℃ constant temperature constant pressure oven for 5h, to prepare the said pulpable bio-based coating paper.

[0059] Example 13

[0060] The paper coated with the lauryl gallate epoxy resin waterproof and oil-proof agent of different chain lengths (1-12 alkyl carbon chains) obtained in examples 10, 11 and 12 is used for pulpability detection of the paper. Part of the waterproof and oil-proof paper is cut into small pieces with scissors, and ethylene glycol is added to a four-necked flask equipped with a mechanical stirrer, a condenser reflux device and a thermometer, and alcoholysis is carried out at 150℃ for 4h. After the end of the reaction, the paper fibers are extracted, and then the paper fibers are washed with ethyl acetate and water several times. The fibers are dissociated into single fibers using a fiber dissociation machine, and then the fibers are used to make paper using a sheet making machine, and the steps are as Figure 8 . The surface of the regenerated paper is uniform and free of impurities, and the mechanical properties are equivalent to those of the original paper, indicating that the waterproof and oil-proof coating has 100% pulpability.

[0061] Comparative example

[0062] Oxidized starch (OS) surface sizing agent is used as a comparative example. 40g of oxidized starch and 360g of distilled water are weighed into a four-necked flask equipped with an electric stirrer, a condenser and a thermometer, and stirred at room temperature for 10min. Then the temperature is raised to 90℃ in a constant temperature water bath for gelatinization, and the reaction is carried out for 30min. The obtained oxidized starch (OS) surface sizing agent with a concentration of 10% is discharged.

[0063] The above-mentioned 10% oxidized starch (OS) surface sizing agent is uniformly dropped along the roller coating rod to one end of the paper surface with a dosage of 75g / m 2The surface of A4 paper was coated, and the oxidized starch (OS) surface sizing agent was added to the surface of the paper at one end of the roller coating rod, and the coating was uniformly applied to the surface of the paper by the roller coating machine at a constant speed. The coating amount of each group was controlled to be almost the same (10-15 g / m 2 ). Then, the coated paper was dried in a constant temperature and pressure oven at 70°C for 1 h to obtain the oxidized starch surface coated paper.

[0064] The water resistance of the paper was tested according to GB / T 1540-2002, the oil resistance of the paper was tested according to GB / T 22805.2-2008, and the tensile strength and elongation of the paper were tested according to GB / T 453-2002. The oxidized starch sizing agent prepared in the above comparative example and the paper coated with the gallic acid epoxy resin series waterproof and oil-proof agent prepared in examples 1-13 and the comparative example were tested, and the results are shown in Table 1.

[0065] As can be seen from Table 1, compared with the oxidized starch (OS) surface sizing agent comparative example and the base paper, the 60s Cobb value of the paper coated with the oxidized starch (OS) surface sizing agent was reduced from 72.59 g / m 2 to 58.36 g / m 2 , the Kit value was unchanged at 0 level, the tensile strength was increased from 2.89 kN / m 2 to 3.08 kN / m 2 , and the elongation at break (%) was increased from 1.38% to 1.39%; after coating with the MG-EP waterproof and oil-proof agent, the 60s Cobb value of the paper was reduced from 72.59 g / m 2 to 8.98 g / m 2 , the Kit value was increased from 0 level to 11 level, the tensile strength was increased from 2.89 kN / m 2 to 5.19 kN / m 2 , and the elongation at break (%) was increased from 1.38% to 4.84%; after coating with the OG-EP coating, the 60s Cobb value of the paper was reduced to 7.37 g / m 2 , the Kit value was increased to 12 level, the tensile strength was increased to 6.21 kN / m 2 , and the elongation at break (%) was increased from 1.38% to 3.53%; after coating with the GA-EP coating, the 60s Cobb value of the paper was reduced to 5.54 g / m 2 , the Kit value was increased to 12 level, the tensile strength was increased to 8.27 kN / m 2The elongation at break (%) increased from 1.38% to 2.37%. By comparing with the original paper and the paper coated with the surface sizing agent of oxidized starch (OS), the water and oil repellency and the mechanical properties of the paper coated with the GA-EP water and oil repellent agent were significantly improved, and the effects of the paper coated with the GA-EP water and oil repellent agent were relatively more excellent. This is because the long non-polar alkyl of the GA-EP water and oil repellent agent and the benzene ring in the gallic acid endow the GA-EP after grafting with excellent hydrophobicity, flexibility and tensile strength, and the dense cross-linked network structure formed by the GA-EP can significantly improve the water and oil repellency and the mechanical properties of the paper.

[0066] Table 1. Performance indicators of the paper coated with the GA-EP water and oil repellent agent and the reslurry paper

[0067]

[0068] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a re-sizing gallic acid-based waterproof and oil-repellent agent, characterized in that, include: Alkyl gallate esters with different carbon chain lengths were reacted with epichlorohydrin under the action of a catalyst to obtain a series of bio-based alkyl gallate ester epoxy resins through a two-step epoxidation ring-opening and closing method. Then, using acid anhydride / phenol compounds as curing agents and curing accelerators, they were thoroughly mixed to obtain blended alkyl gallate ester epoxy resins, which are the re-sizing gallic acid-based waterproof and oil-repellent agents.

2. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 1, characterized in that, The structural formulas of the gallic acid alkyl esters with different chain lengths are as follows:

3. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 2, characterized in that, The structural formulas of the gallic acid alkyl ester epoxy resins with different chain lengths are as follows:

4. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 3, characterized in that, The molar ratio of the phenolic hydroxyl group of the gallic acid alkyl ester, epichlorohydrin, and NaOH is 1:10–20:1–1.5; the mass of the phase transfer catalyst is 0.05%–0.5% of the total mass of the reaction system.

5. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 4, characterized in that, The epoxy ring-opening reaction temperature is 80℃~120℃, and the epoxy ring-opening reaction time is 4h~10h; the epoxy ring-closing reaction temperature is 30℃~50℃, and the epoxy ring-opening reaction time is 2h~8h.

6. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 5, characterized in that, The liquid alkali is an aqueous solution of sodium hydroxide or potassium hydroxide, with a mass fraction of 20% to 40%; the phase transfer catalyst is selected from one of benzyltrimethylammonium chloride, benzyltriethylammonium chloride, tetrabutylammonium chloride, and tetrabutylammonium bromide.

7. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 6, characterized in that, The anhydride compound used as the curing agent is selected from one of phthalic anhydride, trimellitic anhydride, methyltetrahydrophthalic anhydride, and methylhexahydrophthalic anhydride. The phenolic curing accelerator is selected from one of dimethylaminomethylphenol, benzyldimethylamine, and triethanolamine.

8. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claim 7, characterized in that, The mass ratio of the gallic acid lauryl ester epoxy resin to the acid anhydride curing agent and the phenol curing accelerator is 100:10-30:1-3.

9. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claims 1 to 8, characterized in that, Gallic water and oil repellents with different alkyl chain lengths were uniformly roller-coated onto the paper surface and crosslinked at 70-90°C for 1-5 hours to obtain the repulpable bio-based coated paper.

10. The preparation method of the re-sizing gallic acid-based waterproof and oil-repellent agent according to claims 1 to 9, characterized in that, In the repulping process, ethylene glycol is selected as the solvent, and alcoholysis is carried out at 120℃~160℃ for 2~6 hours. The repulped paper is obtained by washing, dissociation and papermaking.

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