Plant-based resin, preparation method thereof and quick-drying high-flexibility coating

Abstract

According to the plant-based resin, the preparation method thereof and the quick-drying high-flexibility coating, compared with the prior art, high-purity tannic acid is adopted as a raw material, and maleic anhydride is introduced into a polyhydroxy structure of the tannic acid for grafting treatment, so that the high-flexibility quick-drying coating is obtained; a carboxyl functional group generated after grafting and an epoxy group of allyl glycidyl ether are subjected to an epoxy ring-opening esterification reaction to further expand grafting, and meanwhile, the unsaturation degree of the product is greatly increased. The ultraviolet curing efficiency of the product is higher, and rapid curing is realized; on the other hand, the grafted molecular chain is relatively long, so that the compound not only retains the compactness brought by a macromolecular benzene ring but also retains the spatiality of the grafted molecular chain in a spatial three-dimensional structure, and the flexibility after film formation is obviously improved.

Description

Technical Field

[0001] The invention belongs to the field of plant-based coating preparation, and specifically relates to a plant-based resin and a preparation method thereof, and a quick-drying high-flexibility coating. Background Art

[0002] As oil resources are becoming increasingly depleted, oil-based paints not only consume precious oil resources, but also emit a large amount of harmful solvent gases into the air. The development of environmentally friendly paints has become a top priority, especially plant-based paints, which have become the main development direction of paints. End consumers, paint industry manufacturers, and global government agencies have begun to demand safer and more sustainable decorative or protective paints. With the continuous development of environmentally friendly paints such as plant-based / bio-based, the demand for plant-based paints in all walks of life is growing.

[0003] However, the mainstream plant-based coatings on the market are currently plagued by problems such as long curing time and poor coating performance after curing due to the composition of the glue material. For example, some plant-based coatings need to undergo a secondary curing process of UV curing + thermal curing, which seriously limits the production capacity bottleneck and application scope of some coating processes; some plant-based coatings have poor coating performance after curing, have high requirements for the coating substrate, and are easily ineffective due to changes in the surface morphology of the substrate (expansion, cracks, etc.).

[0004] For example, the Chinese patent with publication number CN 116716033 A published on September 8, 2023, discloses a UV-curable anti-tannic acid coating and a preparation method thereof, comprising the following components in parts by weight: 10-40 parts of fluorine-modified polyurethane acrylate, 10-40 parts of polyurethane acrylate, 2-5 parts of polyethylene glycol, 2-5 parts of 2,4-diisocyanate toluene, 0.2-1 parts of modified cellulose nanocrystals, 2-7 parts of benzophenone, 2-7 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 5-15 parts of trimethylolpropane triacrylate, 10-30 parts of tripropylene glycol diacrylate, 5-10 parts of 1,6-hexanediol diacrylate, 0.5-10 parts of nano-silicon dioxide, and 3-6.5 parts of titanium dioxide modified white clay. The disclosed curing method is: UV curing first, then thermal curing, with a curing energy of 300-650mj / cm 2 The thermal curing temperature is 70-80° C. It does not disclose a technical solution for rapid curing.

[0005] Therefore, it is necessary to provide a plant-based fast-drying and highly flexible coating. Summary of the invention

[0006] The object of the present invention is to provide a plant-based resin and a preparation method thereof, wherein high-purity tannic acid is used as a raw material, maleic anhydride is introduced into the polyhydroxy structure of tannic acid for grafting treatment, and then the carboxyl functional group generated after grafting is subjected to epoxy ring-opening esterification reaction with the epoxy group of allyl glycidyl ether to further expand the grafting, and at the same time greatly increase the unsaturation of the product. The preparation method of the present invention is simple and the raw material cost is low.

[0007] Another object of the present invention is to provide a fast-drying high-flexibility coating, which is obtained by mixing the plant-based resin prepared above with a photoinitiator. The monomer prepared from the above raw materials, on the one hand, greatly increases the unsaturation of the product, making the UV curing efficiency of the product higher and achieving rapid curing; on the other hand, due to the longer grafted molecular chain, this type of compound retains both the compactness brought by the macromolecular benzene ring and the spatiality of the grafted molecular chain in the spatial stereostructure, and the flexibility is significantly improved after film formation.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A plant-based resin with the structural formula:

[0010] In the structural formula, b is

[0011]

[0012] The present invention provides a method for preparing a plant-based resin, comprising the following steps:

[0013] 1) adding tannic acid to maleic anhydride, heating for reaction, and obtaining a prepolymer;

[0014] 2) The prepolymer and allyl glycidyl ether are heated to react in the presence of a catalyst to obtain a plant-based resin.

[0015] The step 1) is carried out under a protective atmosphere, preferably a N2 protective atmosphere;

[0016] In step 1), tannic acid is added to maleic anhydride at 70° C. to 80° C.;

[0017] In step 1), the molar ratio of tannic acid to maleic anhydride is 1:25-27;

[0018] In step 1), the heating reaction refers to heating to 100-120° C. and reacting for 2 hours;

[0019] In step 1), the prepolymer prepared has the structural formula:

[0020] In the structural formula, a is

[0021] The step 2) is carried out under a protective atmosphere, preferably a N2 protective atmosphere;

[0022] In step 2), the ratio of the molar amount of -COOH groups contained in the prepolymer to the molar amount of allyl glycidyl ether is 1:1 to 1.2;

[0023] In step 2), the amount of the catalyst used is 1% of the total mass of all raw materials in step 2);

[0024] In step 2), the catalyst is aluminum acetylacetonate;

[0025] In step 2), the heating reaction refers to heating to 140°C-160°C for 2-3h;

[0026] Preferably, step 2) is specifically as follows: adding a catalyst to allyl glycidyl ether, stirring, heating to 100°C-120°C, adding the prepolymer prepared in step 1), protecting with nitrogen, heating to 140°C-160°C, and reacting for 2-3h.

[0027] Step 2) reacting, and filtering to obtain a plant-based resin.

[0028] The main functions of allyl glycidyl ether in the present invention are two points. The first point is that it has an epoxy group, and the second point is that it has -C=C-, and the functional groups are distributed at the head and tail. The epoxy group is to be able to undergo an epoxy ring-opening esterification reaction with a carboxyl group (-COOH), thereby connecting the molecular chain to the main product, and -C=C- is a necessary group as a functional group of the UV-curable resin. The higher the unsaturation (the number of -C=C- functional groups), the faster the photocuring rate.

[0029] The invention provides a quick-drying high-flexibility coating, which adopts the plant-based resin as a raw material.

[0030] The fast-drying high-flexibility coating comprises a plant-based resin and a photoinitiator;

[0031] The mass of the photoinitiator is 1-2% of the total mass of the plant-based resin and the photoinitiator.

[0032] The photoinitiator is photoinitiator model BASF ingacure 184;

[0033] The curing conditions of the quick-drying high-flexibility coating are as follows: the film thickness of the quick-drying high-flexibility coating is 20 μm, UV curing is performed under an ultraviolet lamp with a power of 4 KW; the surface drying time is 5 seconds; and the actual drying time is 0.2 hours.

[0034] The fast-drying high-flexibility coating is used for photocurable coatings, especially for semiconductor packaging.

[0035] Compared with the prior art, the present invention is based on tannic acid extracted from plant gallnut, and maleic anhydride is introduced into the polyhydroxy structure of tannic acid for grafting treatment, and then the carboxyl functional group generated after grafting and the epoxy group of allyl glycidyl ether are subjected to epoxy ring-opening esterification reaction to further expand the grafting, and at the same time, the unsaturation of the product is increased, so that the ultraviolet curing efficiency of this product is higher; on the other hand, due to the longer grafted molecular chain, this type of compound retains both the compactness brought by the macromolecular benzene ring and the spatiality of the grafted molecular chain in the spatial stereostructure, and the flexibility is significantly improved after film formation. The coating prepared after reaction modification, in addition to high bonding strength, also has the characteristics of rapid curing, high flexibility, etc., which solves the problems of slow curing speed of conventional coatings, poor flexibility after curing, easy cracking, and the need to consume petrochemical resources for coating preparation. The improvement of the toughness of the coating of the present invention can significantly improve the crack resistance and impact resistance of the coating, significantly expand the application range of the coating, and reduce the requirements for the coating substrate. It can be used as a variety of protection solutions that have high requirements on coating flexibility and curing rate, such as protective coatings in semiconductor packaging processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the process of preparing the prepolymer of formula (II) in step 1) of Example 1;

[0037] Figure 2 The process of preparing the product of formula (I) in step 2) of Example 1;

[0038] Figure 3 The photos are of the prepolymer and product of Example 1, with the prepolymer on the left and the final product on the right;

[0039] Figure 4 This is the infrared spectrum of the raw material tannic acid in Example 1;

[0040] Figure 5 The infrared spectrum of the prepolymer of formula (II) prepared in Example 1;

[0041] Figure 6 This is the infrared spectrum of the product of formula (I) prepared in Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0044] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0045] Example 1

[0046] A method for preparing a plant-based resin comprises the following steps:

[0047] 1) Add 25 mol of maleic anhydride to a 1000 ml flask, heat to 80°C, add 1 mol of tannic acid, stir, protect with nitrogen, heat to 120°C and react for 2 hours to obtain a prepolymer of formula (II). The reaction process is as follows: Figure 1 As shown; pictures of the products are as follows Figure 3 As shown;

[0048] 2) Add 25 mol of allyl glycidyl ether to a 1000 ml flask, add 1% of the total mass of the raw materials in this step, add aluminum acetylacetonate, stir, heat to 100°C, add the prepolymer of formula (II) containing 25 mol of -COOH groups synthesized in step 1), protect with nitrogen, heat to 140°C and react for 3 hours. The final product is filtered to obtain the product of formula (I). The reaction process is as follows Figure 2 As shown; pictures of the products are as follows Figure 3 shown.

[0049] The infrared images of tannic acid and prepolymer II are as follows: Figure 4 and Figure 5 As shown in the figure, when the phenolic hydroxyl group in tannic acid reacts with the anhydride in maleic anhydride (MAH) to undergo a ring-opening esterification reaction, MAH is connected to the long-chain molecule of tannic acid, the phenolic hydroxyl group in tannic acid disappears, and a carboxyl group is generated. It can be seen from the infrared spectrum that at 3400 cm -1 -3200cm -1 The absorption peak of phenolic hydroxyl group has disappeared and is replaced by the absorption peak at 3500cm -1 The carboxyl group has a strong absorption peak. At the same time, at 1710 cm -1The carbonyl absorption peak on the carboxyl group appeared on the left and right, further proving the formation of prepolymer II.

[0050] Figure 6 is the infrared spectrum of the product of formula (Ⅰ). When the epoxy group in allyl glycidyl ether undergoes epoxy ring-opening esterification reaction with the carboxyl group of prepolymer Ⅱ, hydroxyl groups will be regenerated. The corresponding 3600cm -1 The hydroxyl stretching vibration absorption peak was restored at 1160cm -1 A strong absorption peak appeared at 1640 cm, which corresponds to the stretching vibration of CO, indicating that the carboxyl group of prepolymer II and the epoxy group of allyl glycidyl ether underwent a ring-opening esterification reaction, proving the existence of prepolymer I. -1 The obvious enhancement of the stretching vibration peak of C=C also confirms the existence of the target product.

[0051] Example 2

[0052] A fast-drying high-flexibility coating, comprising a plant-based resin and a photoinitiator prepared in Example 1; the specific method of use is: the product of Example 1 is mixed with a BASF ingacure 184 photoinitiator and then applied to a wire bonding board, the thickness is controlled to be about 20 μm, and UV curing is performed under a 4KW ultraviolet lamp. The amount of the photoinitiator is 1.5% of the total mass of the product of Example 1 and the BASF ingacure 184 photoinitiator. The surface drying time and the actual drying time are measured. In addition, the existing glue on the market is subjected to the same test under the same curing conditions for comparison, and the test results of the cured resin performance are shown in Table 1. The coating flexibility is measured in accordance with GB / T 1731-93.

[0053] According to GB / T 9286-88: Determination of coating adhesion; according to GB / T 6739-2022, pencil hardness test.

[0054] Table 1 Test results of cured resin properties

[0055]

[0056] The principle of the present invention is as follows: the hydroxyl group and the anhydride group react to generate the carboxyl group; the carboxyl group and the epoxy group react to generate the hydroxyl group, and the reaction is performed to synthesize a new prepolymer. Each step of the reaction continuously improves the unsaturation of the prepolymer, and each step of the reaction introduces the -C=C- functional group, such as maleic anhydride (anhydride group and -C=C-); allyl glycidyl ether (epoxy group and -C=C-), so that the resin generated has the characteristics of plant base (derived from tannic acid) and light curing (multiple unsaturation). The present invention uses specific raw materials to react, such as the hydroxyl group of tannic acid reacts with maleic anhydride (maleic anhydride has both anhydride and -C=C-) to generate a carboxyl group. The carboxyl group of the product of the first step reacts with the epoxy group of allyl glycidyl ether (allyl glycidyl ether has both epoxy group and -C=C-) to generate a hydroxyl group. The final product has a high degree of unsaturation, so it can be quickly photocured. On the other hand, since the grafted molecular chain is relatively long, this type of compound retains both the compactness brought by the macromolecular benzene ring and the spatiality of the grafted molecular chain in the spatial stereostructure, and the flexibility is significantly improved after film formation. Glycidyl ethers of other structures cannot be used for the preparation of the present invention and are prone to failure. The main advantage of the allyl glycidyl ether of the present invention is that its main reactive functional groups are just at the head and tail, the epoxy functional group is used to participate in the reaction, and the double bond functional group is used for subsequent ultraviolet light curing. The same is true for maleic anhydride. Epoxy group + double bond group can realize the present invention.

[0057] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A plant-based resin, characterized in that: The structural formula of the plant-based resin is: In the structural formula, b is 2. A method for preparing a plant-based resin according to claim 1, characterized in that: The preparation method comprises the following steps: 1) adding tannic acid to maleic anhydride, heating for reaction, and obtaining a prepolymer; 2) The prepolymer and allyl glycidyl ether are heated to react in the presence of a catalyst to obtain a plant-based resin.

3. The preparation method according to claim 2, characterized in that: In step 1), the molar ratio of tannic acid to maleic anhydride is 1:25-27.

4. The preparation method according to claim 2 or 3, characterized in that: In step 1), the heating reaction refers to heating to 100-120° C. and reacting for 2 hours.

5. The preparation method according to claim 2, characterized in that: In step 1), the prepolymer prepared has the structural formula: In the structural formula, a is 6. The preparation method according to claim 2, characterized in that: In step 2), the ratio of the molar amount of -COOH groups contained in the prepolymer to the molar amount of allyl glycidyl ether is 1:1 to 1.

2.

7. The preparation method according to claim 2, characterized in that: The amount of the catalyst used is 1% of the total mass of all raw materials in step 2).

8. The preparation method according to claim 2 or 7, characterized in that: The catalyst is aluminum acetylacetonate.

9. The preparation method according to claim 2, characterized in that: In step 2), the heating reaction refers to heating to 140°C-160°C for 2-3h.

10. A quick-drying, highly flexible coating, characterized in that: The plant-based resin described in claim 1 is used as a raw material.

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