Preparation method and application of a fully bio-based oil-proof and hydrophobic paper surface coating

Abstract

The present application discloses a method for preparing a fully bio-based oil-proof and hydrophobic paper surface coating, and belongs to the technical field of bio-based oil-proof and hydrophobic surface coatings. The present application uses natural monophenol and dimer acid glycidyl ester as raw materials, and prepares fully bio-based monophenol grafted dimer acid glycidyl ester through ring-opening etherification. The prepared fully bio-based monophenol grafted dimer acid glycidyl ester is used as an oil-proof and hydrophobic surface coating for paper. The polar hydroxyl groups and ether bonds in the structure of the bio-based monophenol grafted dimer acid glycidyl ester prepared in the present application can increase the adhesion between the coating and the paper, making the fibers more closely combined; and the non-polar long alkyl chains and benzene ring groups in the structure can give the paper good oil-proof and hydrophobic and mechanical properties. The present application is simple to operate, has low cost, can be used for industrial large-scale production, and has good practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of bio-based oil-proof and hydrophobic surface coatings, and specifically relates to a preparation method of a fully bio-based monophenol grafted glycidyl ester oil-proof and hydrophobic paper surface coating and its application in paper. Background Art

[0002] Packaging materials play a fundamental role in the material protection process and have become an indispensable part of human high-quality life. In 2021, the global packaging materials market size exceeded US$1 trillion, and it is increasing year by year. Among the many packaging materials, paper packaging is considered to be one of the most environmentally friendly packaging materials due to its advantages such as light weight, easy to carry, low cost, renewable and degradable. It has been widely used in many fields such as food and pharmaceutical packaging, medical and health care, and electronic products. However, paper is composed of plant fibers, and there are a large number of hydroxyl groups in its molecular structure to form a loose and porous structure, which is easy to absorb moisture, resulting in a decrease in its own mechanical properties, making it difficult to meet the needs of industrial applications. In order to improve the moisture-proof performance of paper, the traditional method is to coat the surface of the paper (such as petroleum-based polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET)) or to coat the surface of the paper with fluorine-containing waterproof / oil-proof agents. Petroleum-based plastic films are non-renewable and difficult to degrade in the natural environment, which will inevitably cause environmental pollution; and fluorinated waterproof / oil-proof agents have been banned in many countries because they produce perfluorooctanoic acid / perfluorooctane sulfonyl compounds (PFOA / PFOS) that are harmful to humans and the environment during preparation and use. The development of green, environmentally friendly, degradable, oil-proof and hydrophobic coatings has become a "bottleneck" problem that restricts the high-quality development of the paper packaging industry.

[0003] Natural polymers (such as starch, chitosan, zein and collagen fibers) are considered to be potential ideal materials for preparing green, environmentally friendly, degradable, oil-proof and hydrophobic coatings because of their non-toxic, renewable and degradable advantages. Although polysaccharides (starch, chitosan, cellulose) and proteins (zein, casein) have good oil-proof properties, their polyhydroxy structures lead to poor hydrophobic properties and usually need to be used in combination with hydrophobic materials. Khairuddin et al. (Journal of Physics: Conference Series, 2019, 1153 (1): 12092-12097) double-coated starch and shellac with good water barrier properties, first applied starch on the paper surface, and then applied shellac on the starch surface, to obtain a double-layer coated paper with good water vapor barrier properties, and the oil resistance of the coating is better than that of conventional paper coatings, but the preparation process of double-layer coated paper is cumbersome, and it has been coated and dried twice, which greatly increases energy consumption and production costs, limiting its further industrialization. Kansal et al. (Journal of Applied Polymer Science, 2021, 138 (3): 49692) developed a fully bio-based chitosan grafted epoxy sunflower oil coating coated paper with good hydrophobic and oil-resistant properties. However, chitosan is expensive, which limits the large-scale industrial application of the coating. CN 113583368 A discloses a modified starch PVA-based composite film and a preparation method thereof. The modified starch PVA-based composite film has excellent hydrophobicity, but PVA is a petroleum-based plastic, which is non-renewable, difficult to degrade and has limited oil-proof effect. CN 112029146 A discloses a super-hydrophobic coating based on protein particles and a preparation method thereof. The super-hydrophobic coating uses long-chain fluorine-free alkanes to modify starch to avoid the potential impact of fluorine-containing modifiers on the water environment, but the preparation process is very complicated and cumbersome, and only has hydrophobic properties. Patent CN114957739 A has developed a chitosan tannin extract-based water-based paper oil-proofing agent using chitosan and natural tannin extract as raw materials. The natural tannin extract is subjected to ethylene oxide / propylene oxide ring opening, epichlorohydrin etherification and chitosan grafting reaction to synthesize a chitosan tannin extract-based water-based paper oil-proofing agent, which forms a dense film to impart good water and oil-proof properties to paper. However, the water and oil-proofing agent needs to be liquefied by ethylene oxide / propylene oxide, has poor process safety and a relatively complicated preparation process. In addition, the production cost of the raw material chitosan used is high, which is not conducive to industrial production.

[0004] Compared with natural polymers, vegetable oils are widely available, cheap, structurally adjustable, renewable, non-toxic and biodegradable, and are considered to be one of the potential ideal raw materials for the preparation of environmentally friendly papermaking additives; at the same time, the long-chain alkyl groups in the structure of vegetable oil-derived coatings can give paper excellent waterproof properties. Cao et al. (ACS Appl. Mater. Interfaces 2020, 12, 18987-18996) used palm oil and furfuryl alcohol as raw materials to design a low-cost waterproof paper coating. After coating, the water contact angle of the paper reached 120° and the water vapor permeability decreased by 22%; however, the furfuryl alcohol used in the coating is a Class 2B carcinogen, and the oil-proof performance of the coating has not been reported. Patent CN202110521109.X reports a new method for preparing a dimer acid-based waterborne polyurethane paper surface sizing agent with waterproof and oil-proof functions using plant oil-derived dimer acid as a raw material. The long-chain alkyl group in its structure and the dense film formed give the paper good waterproof and oil-proof properties; however, the surface sizing agent not only has a lengthy preparation process (involving reactions such as esterification, amination, and neutralization), but also more than 90% of the structure comes from petroleum-based raw materials, and there is still huge room for improvement in sustainability. The development of all-biobased paper waterproof / oil-proof agents with both waterproof and oil-proof functions is an inevitable development trend for the high-quality development of the papermaking industry and the industry's realization of the "dual carbon" strategy. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing an oil-proof and hydrophobic surface coating. The prepared monophenol grafted dimer acid glycidyl ester oil-proof and hydrophobic paper surface coating is non-toxic and biodegradable.

[0006] The technical problems to be solved by the present invention are as follows: (1) providing a preparation method of the all-biobased monophenol grafted dimer acid glycidyl ester; (2) providing an application of the all-biobased monophenol grafted dimer acid glycidyl ester as an oil-proof and hydrophobic surface coating for paper.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a fully bio-based oil-proof and hydrophobic surface coating, which uses natural monophenol and dimeric acid glycidyl ester as raw materials and prepares fully bio-based monophenol grafted dimeric acid glycidyl ester through ring-opening etherification.

[0009] Furthermore, the preparation method of the all-biobased oil-proof and hydrophobic surface coating comprises the following steps: putting natural monophenol, dimer acid diglycidyl ester, catalyst and solvent into a reactor equipped with a thermometer and a water separator, introducing nitrogen, heating and stirring, controlling the raw material ratio, reaction temperature, time and amount of catalyst, removing the catalyst by water washing after the reaction is completed, washing with water until neutral, and finally removing the solvent, excess monophenol and water in the system by reduced pressure distillation to obtain all-biobased monophenol grafted dimer acid glycidyl ester.

[0010] Furthermore, the natural monophenol is any one of cardanol and eugenol.

[0011] Furthermore, the molar ratio of the dimer acid diglycidyl ester to the natural monophenol is 1:2-5.

[0012] Furthermore, the catalyst is any one of potassium hydroxide, sodium hydroxide, boron trifluoride etherate and sodium phenolate.

[0013] Furthermore, the solvent is any one of xylene, ethyl acetate, acetylacetone, cyclohexane and toluene.

[0014] Furthermore, the amount of the catalyst used is 1% to 7% of the mass of the dimer acid glycidyl ester.

[0015] Furthermore, the amount of the solvent is 50% to 100% of the diglycidyl dimer acid ester.

[0016] Furthermore, the ring-opening etherification reaction temperature is 100°C to 160°C.

[0017] Furthermore, the ring-opening etherification time is 4h to 10h.

[0018] Furthermore, the all-biobased monophenol grafted dimer acid glycidyl ester is prepared by the above-mentioned method for preparing the all-biobased oil-proof and hydrophobic surface coating.

[0019] Furthermore, the all-biobased monophenol grafted dimer acid glycidyl ester is used as an oil-proof and hydrophobic surface coating for paper.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The polar hydroxyl group and ether bond in the structure of the bio-based monophenol grafted dimer acid glycidyl ester prepared by the present invention can increase the adhesion between the coating and the paper, making the fibers more tightly combined; while the non-polar long alkyl chain and benzene ring group in the structure can give the paper good oil-proof, hydrophobic and mechanical properties;

[0022] (2) The raw materials of the present invention are all derived from biomass, which has a wide range of sources and is inexpensive, biodegradable, green and non-toxic, meeting the major strategic needs of the sustainable development of my country's materials industry;

[0023] (3) The present invention provides a method for preparing a high-quality, environmentally friendly, all-biobased paper oil-proof and hydrophobic surface coating, which is simple to operate, low in cost, and has broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a structural diagram of a monophenol grafted dimer acid glycidyl ester oil-proof and hydrophobic surface coating, a is a structural diagram of cardanol grafted dimer acid glycidyl ester, and b is a structural diagram of eugenol grafted dimer acid glycidyl ester;

[0025] Figure 2 is the H NMR spectrum of cardanol grafted dimer acid glycidyl ester (CDGE);

[0026] Figure 3 is the H NMR spectrum of cardanol grafted dimer acid glycidyl ester (CDGE);

[0027] Figure 4 is the H NMR spectrum of cardanol grafted dimer acid glycidyl ester (CDGE);

[0028] Figure 5 is the H NMR spectrum of cardanol grafted dimer acid glycidyl ester (CDGE);

[0029] Figure 6 This is the H NMR spectrum of eugenol grafted dimer acid glycidyl ester (EDGE);

[0030] Figure 7 This is the H NMR spectrum of eugenol grafted dimer acid glycidyl ester (EDGE);

[0031] Figure 8 This is the H NMR spectrum of eugenol grafted dimer acid glycidyl ester (EDGE). DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art.

[0033] The cardanol in the examples is industrial grade and provided by the Institute of Forest Chemical Industry, Chinese Academy of Forestry; all-biobased dimer acid diglycidyl ester (epoxy value is 0.21 moL / 100g) is industrial grade and provided by Anhui Xinyuan Technology Co., Ltd.; soluble starch and toluene are provided by Sinopharm Chemical Reagent Co., Ltd.; eugenol, xylene, ethyl acetate, acetylacetone, cyclohexane, sodium phenolate are analytical grade and provided by Shanghai MacLean Biochemical Technology Co., Ltd.

[0034] Example 1

[0035] A method for preparing an oil-proof and hydrophobic surface coating of cardanol grafted dimer acid glycidyl ester, comprising the following steps: adding 89.8g of cardanol, 100.0g of dimer acid diglycidyl ester, 1.0g of sodium phenolate and 50.0g of xylene to a reactor, replacing it with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating it to 140°C and reacting for 9 hours. After the reaction is completed, wash it three times with deionized water to remove the sodium phenolate, and finally remove the xylene and water in the system by vacuum distillation. Cardanol grafted dimer acid glycidyl ester (CDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 2 shown.

[0036] Example 2

[0037] A method for preparing an oil-proof and hydrophobic surface coating of cardanol grafted dimer acid glycidyl ester, comprising the following steps: adding 89.8g of cardanol, 100.0g of dimer acid diglycidyl ester, 3.0g of sodium phenolate and 70.0g of acetylacetone to a reactor, replacing with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating to 150°C and reacting for 7 hours. After the reaction is completed, wash three times with deionized water to remove the sodium phenolate, and finally remove the acetylacetone and water in the system by reduced pressure distillation. Cardanol grafted dimer acid glycidyl ester (CDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 3 shown.

[0038] Example 3

[0039] A method for preparing an oil-proof and hydrophobic surface coating of cardanol grafted dimer acid glycidyl ester, comprising the following steps: adding 89.8g of cardanol, 100.0g of dimer acid diglycidyl ester, 5.0g of sodium phenolate and 80.0g of toluene to a reactor, replacing it with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating it to 140°C and reacting for 5 hours. After the reaction is completed, wash it three times with deionized water to remove the sodium phenolate, and finally remove the toluene and water in the system by vacuum distillation. Cardanol grafted dimer acid glycidyl ester (CDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 4 shown.

[0040] Example 4

[0041] A method for preparing an oil-proof and hydrophobic surface coating of cardanol grafted dimer acid glycidyl ester, comprising the following steps: adding 89.8g of cardanol, 100.0g of dimer acid diglycidyl ester, 7.0g of sodium phenolate and 100.0g of ethyl acetate to a reactor, replacing with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating to 100°C and reacting for 6 hours. After the reaction is completed, wash three times with deionized water to remove the sodium phenolate, and finally remove the ethyl acetate and water in the system by reduced pressure distillation. Cardanol grafted dimer acid glycidyl ester (CDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 5 shown.

[0042] Example 5

[0043] A method for preparing an oil-proof and hydrophobic surface coating of eugenol grafted dimer acid glycidyl ester, comprising the following steps: adding 48.8g of eugenol, 100.0g of dimer acid diglycidyl ester, 1.0g of sodium phenolate and 50.0g of xylene to a reactor, replacing with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating to 140°C and reacting for 9 hours. After the reaction is completed, wash three times with deionized water to remove the sodium phenolate, and finally remove the excess eugenol, xylene and water in the system by vacuum distillation. Eugenol grafted dimer acid glycidyl ester (EDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 6 shown.

[0044] Example 6

[0045] A method for preparing an oil-proof and hydrophobic surface coating of eugenol grafted dimer acid glycidyl ester, comprising the following steps: adding 85.4g of eugenol, 100.0g of dimer acid diglycidyl ester, 5.0g of sodium phenolate and 70.0g of toluene into a reactor, replacing with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating to 140°C and reacting for 5 hours. After the reaction is completed, wash three times with deionized water to remove the sodium phenolate, and finally remove the excess eugenol, toluene and water in the system by vacuum distillation. Eugenol grafted dimer acid glycidyl ester (EDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 7 shown.

[0046] Example 7

[0047] A method for preparing an oil-proof and hydrophobic surface coating of eugenol grafted dimer acid glycidyl ester, comprising the following steps: adding 122.0g of eugenol, 100.0g of dimer acid diglycidyl ester, 7.0g of sodium phenolate and 100.0g of ethyl acetate into a reactor, replacing with N2 for 3 to 5 times, driving away the air in the device to prevent the product from being oxidized, and then heating to 100°C and reacting for 6 hours. After the reaction is completed, wash three times with deionized water to remove the sodium phenolate, and finally remove the excess eugenol, ethyl acetate and water in the system by vacuum distillation. Eugenol grafted dimer acid glycidyl ester (EDGE) is obtained, and the product hydrogen nuclear magnetic spectrum and structure are as follows Figure 8 shown.

[0048] Comparative Example 1

[0049] Taking oxidized starch (OS) surface sizing agent as a comparative example, 40g oxidized starch and 360g distilled water were weighed into a four-necked flask equipped with an electric stirrer, a condenser and a thermometer, and stirred at room temperature for 10min; then placed in a constant temperature water bath and heated to 90°C for gelatinization, reacted for 30min and discharged, to obtain an oxidized starch (OS) surface sizing agent with a concentration of 10%.

[0050] The surface sizing agent of 10% oxidized starch (OS) in the above comparative example and the all-bio-based monophenol grafted dimer acid glycidyl ester prepared in Examples 1 to 7 were quantitatively mixed to 80 g / m 2 The coating experiment on the kraft paper surface was carried out by spraying. First, fix the kraft paper on the table, pour the diluted monophenol grafted dimer acid glycidyl ester (monophenol grafted dimer acid glycidyl ester: acetone = 1:3) into the spray gun, and spray it evenly on the paper surface. The coating amount is 10g / m 2 ; Place the coated paper in a 55°C constant temperature oven and dry it for 10 minutes; finally, place the treated kraft paper in a constant temperature and humidity room for 24 hours, and then test the physical properties of the paper.

[0051] The water resistance of paper was tested with reference to the determination of water absorption of paper and paperboard GB / T 1540-2002; the oil resistance of paper and paperboard was tested with reference to the determination of fat resistance of paper and paperboard GB / T 22805.2-2008; the tensile strength and elongation of paper were tested with reference to the determination of tensile strength of paper and paperboard GB / T 453-2002. The paper coated with the oxidized starch sizing agent prepared in the above comparative example and the monophenol grafted dimer acid glycidyl ester prepared in Examples 1 to 7 was tested, and the results are shown in Table 1. It can be seen from Table 1 that compared with the comparative example, after being coated with CDGE coating, the 60s Cobb value of the paper increased from 79.21 g / m 2 Down to 38.54g / m 2 The Kit value increases from 0 to 9, and the tensile strength increases from 5.86 kN / m2 Increased to 7.10kN / m 2 After being coated with EDGE coating, the 60s Cobb value of the paper dropped to 13.12g / m 2 , Kit value increased to 10, tensile strength increased to 7.26kN / m 2 The waterproof, oil-proof and mechanical properties of both paper coatings can be significantly improved, and the surface coating effect of eugenol grafted with dimeric acid glycidyl ester is better. This is because the non-polar long-chain alkyl of dimeric acid glycidyl ester and the benzene ring of eugenol give the grafted EDGE excellent hydrophobicity, and the dense cross-linked network structure formed by CDGE (EDGE) can significantly improve the waterproof and oil-proof and mechanical properties of paper.

[0052] Table 1. Physical properties test data of monophenol grafted dimer acid glycidyl ester coated paper

[0053]

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a fully bio-based oil-proof and hydrophobic paper surface coating, characterized in that: Put natural monophenol, dimer acid diglycidyl ester, catalyst and solvent into a reactor equipped with a thermometer and a water separator, introduce nitrogen, heat and stir, control the raw material ratio, reaction temperature, time and catalyst dosage, and carry out a ring-opening etherification reaction. After the reaction, wash with water until neutral to remove the catalyst, and finally remove the solvent, excess monophenol and water in the system by reduced pressure distillation to obtain all-biobased monophenol grafted dimer acid diglycidyl ester; the natural monophenol is any one of cardanol and eugenol; the molar ratio of dimer acid diglycidyl ester to natural monophenol is 1:2-5; the ring-opening etherification reaction temperature is 100°C-160°C, and the ring-opening etherification reaction time is 4h-10h.

2. The method for preparing the all-biobased oil-proof and hydrophobic paper surface coating according to claim 1, characterized in that: The catalyst is any one of potassium hydroxide, sodium hydroxide, boron trifluoride etherate and sodium phenolate.

3. The method for preparing the all-biobased oil-proof and hydrophobic paper surface coating according to claim 1, characterized in that: The solvent is any one of xylene, ethyl acetate, acetylacetone, cyclohexane and toluene.

4. The method for preparing the all-biobased oil-proof and hydrophobic paper surface coating according to claim 1, characterized in that: The amount of the catalyst used is 1% to 7% of the mass of dimer acid diglycidyl ester.

5. The method for preparing the all-biobased oil-proof and hydrophobic paper surface coating according to claim 1, characterized in that: The amount of the solvent used is 50% to 100% of the mass of dimer acid diglycidyl ester.

6. The method for preparing a fully bio-based oil-proof and hydrophobic paper surface coating according to any one of claims 1 to 5, characterized in that: The prepared all-biobased monophenol grafted dimer acid diglycidyl ester is used as an oil-proof and hydrophobic surface coating for paper.

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