A reactive bio-based plasticizer and a preparation method and application thereof

Abstract

This invention provides a reactive bio-based plasticizer, its preparation method, and its application. The method involves a ring-opening esterification reaction of bio-based dimer acid and glycidyl methacrylate in the presence of a catalyst and a polymerization inhibitor to generate the reactive bio-based plasticizer. The reactive bio-based plasticizer prepared by this invention is linked to active carbon-carbon double bond groups from glycidyl methacrylate via ester bonds. During rubber vulcanization, these double bonds participate in free radical cross-linking reactions initiated by sulfur or peroxides, thereby chemically bonding to the three-dimensional network structure of the rubber in the form of covalent bonds. This avoids the migration, volatilization, and extraction problems caused by weak intermolecular forces in physical plasticizers, retains the good plasticizing and lubricating effects of long-chain molecules, improves the mixing and processing fluidity of rubber, and its reactivity contributes to the cross-linking network after vulcanization, preventing excessive softening and resulting in a good balance of mechanical properties in rubber products.

Description

Technical Field

[0001] This invention relates to the field of rubber additives technology, specifically to a reactive bio-based plasticizer, its preparation method, and its application. Background Technology

[0002] Plasticizers, commonly known as rubber oils or processing oils, are indispensable components in rubber processing. They are used to improve the processing properties of rubber compounds during mixing, extrusion, and calendering, and to adjust the hardness, elasticity, and low-temperature properties of vulcanized rubber. Traditional petroleum-based plasticizers, such as aromatic oils and naphthenic oils, primarily interact with the rubber matrix through physical entanglement and van der Waals forces. During long-term use, these plasticizers are prone to migration, volatilization, or solvent extraction, leading to hardening, brittleness, shrinkage, performance degradation, and shortened service life. Furthermore, traditional petroleum-based products rely on non-renewable resources, and some contain polycyclic aromatic hydrocarbons, posing environmental and health risks.

[0003] However, most existing bio-based plasticizers are still physical plasticizers, and the migration problem has not been fundamentally solved. Therefore, the existing technology needs further development. Summary of the Invention

[0004] To address the shortcomings of existing technologies and solve the aforementioned problems, a reactive bio-based plasticizer, its preparation method, and its applications are proposed, along with the following technical solution: A method for preparing a reactive bio-based plasticizer, wherein bio-based dimer acid and glycidyl methacrylate are reacted via ring-opening esterification in the presence of a catalyst and a polymerization inhibitor to generate the reactive bio-based plasticizer.

[0005] Furthermore, the molar ratio of the bio-based dimer acid to glycidyl methacrylate is 1:(1.0-2.5).

[0006] Furthermore, the molar ratio of the bio-based dimer acid to glycidyl methacrylate is 1:(1.8-2.2).

[0007] Furthermore, the reaction temperature is 80-130℃, and the reaction time is 2-8 hours.

[0008] Furthermore, the bio-based dimer acid is an octadecane-unsaturated fatty acid.

[0009] Furthermore, the catalyst is selected from one or more of triethylamine, triphenylphosphine, tetrabutylammonium bromide, and N,N-dimethylethanolamine.

[0010] Furthermore, the polymerization inhibitor is selected from hydroquinone, methylhydroquinone, and 2,6-di-tert-butyl-p-cresol.

[0011] In addition, the present invention also provides a reactive bio-based plasticizer prepared by the above preparation method.

[0012] This invention also provides the application of reactive bio-based plasticizers as plasticizers in rubber compositions.

[0013] Furthermore, the rubber composition, by weight, comprises the following components: raw rubber: 100 parts; reactive bio-based plasticizer as described in claim 8: 5-50 parts; reinforcing filler: 20-80 parts; vulcanizing agent: 0.5-3 parts; accelerator: 0.5-5 parts.

[0014] Beneficial effects: 1. The reactive bio-based plasticizer prepared in this invention is linked to a carbon-carbon double bond group from glycidyl methacrylate via an ester bond. During the rubber vulcanization process, this double bond participates in the free radical cross-linking reaction initiated by sulfur or peroxide, thereby chemically bonding to the three-dimensional network structure of the rubber in the form of a covalent bond, avoiding the migration, volatilization and extraction problems caused by the weak intermolecular forces of physical plasticizers.

[0015] 2. The reactive bio-based plasticizer prepared by this invention retains the good plasticizing and lubricating effects of long-chain molecules, improves the mixing and processing fluidity of rubber, and its reactivity can contribute to the cross-linking network after vulcanization, avoiding excessive softening and enabling rubber products to obtain a good balance of mechanical properties.

[0016] 3. Using bio-based dimer acids as raw materials reduces dependence on petroleum resources, and the product does not contain polycyclic aromatic hydrocarbons. Attached Figure Description

[0017] Figure 1 This is the infrared spectrum of the product of Example 1 of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application.

[0019] According to embodiments of the present invention, a method for preparing a reactive bio-based plasticizer is provided. The reactive bio-based plasticizer is generated by ring-opening esterification of bio-based dimer acid and glycidyl methacrylate in the presence of a catalyst and a polymerization inhibitor. The reactive bio-based plasticizer prepared by the present invention is linked to active carbon-carbon double bond groups from glycidyl methacrylate via ester bonds. During rubber vulcanization, these double bonds participate in free radical cross-linking reactions initiated by sulfur or peroxides, thereby chemically bonding to the three-dimensional network structure of the rubber in the form of covalent bonds. This avoids the migration, volatilization, and extraction problems caused by weak intermolecular forces in physical plasticizers, retains the good plasticizing and lubricating effects of long-chain molecules, improves the mixing and processing fluidity of rubber, and its reactivity contributes to the cross-linking network after vulcanization, preventing excessive softening and achieving a good balance of mechanical properties in rubber products.

[0020] Dimer acids are long-chain, multifunctional polymeric fatty acids. At high temperatures, the carboxyl groups of dimer acids undergo various reactions. A common one is the reaction with amines to form amides. Dimer acids typically contain trace amounts of monomeric fatty acids and small amounts of trimer acids. Under certain temperature conditions, this product exhibits stable performance, is non-toxic, non-volatile, has a high flash point and ignition point, and does not freeze at low temperatures. It also possesses relatively high viscosity and adhesive strength. In the following examples, the octadecane-unsaturated fatty acids used are dimer acids from Linyi Daming Bioenergy Co., Ltd., model DMD-80, with an acid value of 190-198 mgKOH / g, a saponification value of 192-202 mgKOH / g, a viscosity of 6500-9000 mPa·s at 25℃, a dimer content of 80-85%, a trimer content of 13-18%, and a monomeric acid content of 3%. Example 1 In a 250 mL four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet, 100 g of octadecane-unsaturated fatty acid and 0.3 g of hydroquinone as a polymerization inhibitor were added. Nitrogen gas was introduced for protection, and the mixture was stirred and heated to 100 °C to ensure the octadecane-unsaturated fatty acid was uniformly melted. Then, 0.8 g of triethylamine catalyst was added, followed by the slow dropwise addition of 20 g of glycidyl methacrylate. The dropping rate was controlled to maintain the system temperature at 100-110 °C. After the addition was complete, the reaction was maintained at 110 °C for 6 hours. During the reaction, the acid value was periodically measured until it was less than 5 mg KOH / g. After the reaction was complete, the mixture was distilled under reduced pressure at 120 °C and -0.098 MPa for 1 hour to remove unreacted glycidyl methacrylate and byproducts, yielding a brownish-yellow viscous, transparent liquid.

[0021] Example 2 The operation steps are the same as in Example 1, except that the amount of glycidyl methacrylate added is changed so that the molar ratio of octadecane unsaturated fatty acid to glycidyl methacrylate is 1:1.8.

[0022] Example 3 The operation steps are the same as in Example 1, except that the amount of glycidyl methacrylate added is changed so that the molar ratio of octadecane unsaturated fatty acid to glycidyl methacrylate is 1:2.2.

[0023] Example 4 The operation steps are the same as in Example 1, except that the amount of glycidyl methacrylate added is changed so that the molar ratio of octadecane unsaturated fatty acid to glycidyl methacrylate is 1:1.

[0024] Example 5 The operation steps are the same as in Example 1, except that the amount of glycidyl methacrylate added is changed so that the molar ratio of octadecane unsaturated fatty acid to glycidyl methacrylate is 1:2.5.

[0025] Example 6 The operating steps are the same as in Example 1, except that the reaction temperature is adjusted to 80°C.

[0026] Example 7 The operating steps are the same as in Example 1, except that the reaction temperature is adjusted to 130°C.

[0027] Example 8 The operation steps are the same as in Example 1, and the reaction is carried out at 110°C for 2 hours.

[0028] Example 9 The operation steps are the same as in Example 1, and the reaction is carried out at 110°C for 8 hours.

[0029] Example 10 The operating procedure is the same as in Example 1, except that the catalyst is replaced with an equimolar amount of triphenylphosphine.

[0030] Example 11 The operating steps are the same as in Example 1, except that the catalyst is replaced with an equimolar amount of tetrabutylammonium bromide.

[0031] Example 12 The operation steps are the same as in Example 1, except that the polymerization inhibitor hydroquinone is replaced with an equal mass of methylhydroquinone.

[0032] Comparative Example 1 The operation steps were the same as in Example 1, but without the addition of the catalyst triethylamine. After the reaction was carried out at 110°C for 6 hours, the acid value was still as high as 180 mg KOH / g or more, indicating that almost no reaction occurred.

[0033] Comparative Example 2 The operation steps are the same as in Example 1, but without the polymerization inhibitor hydroquinone. During the addition of glycidyl methacrylate and in the early stage of the reaction, the viscosity of the system increased sharply and a large amount of insoluble gel-like material appeared, indicating that the double bonds in glycidyl methacrylate underwent a self-polymerization side reaction and the target plasticizer could not be obtained.

[0034] Comparative Example 3 The operation steps are the same as in Example 1, except that 100g of octadecane unsaturated fatty acid is replaced with an equimolar amount of oleic acid, and the molar ratio of carboxyl group to glycidyl methacrylate is kept at 1:2.

[0035] Comparative Example 4 The reaction was carried out by conventional acid-carboxyl esterification of methacrylic acid and octadecane unsaturated fatty acids, catalyzed by concentrated sulfuric acid.

[0036] Comparative Example 5 Commercially available epoxidized soybean oil was used as a comparison. Epoxidized soybean oil is a common physical plasticizer. Comparative Example 6 Commercially available environmentally friendly naphthenic oils were used as a comparison. Environmentally friendly naphthenic oils are commonly used physical plasticizers in the industry.

[0037] The product obtained in Example 1 was characterized using infrared spectroscopy. The infrared spectrum is shown below. Figure 1 As shown, octadecane unsaturated fatty acids are long-chain fatty acid dimers containing two carboxyl groups (-COOH); glycidyl methacrylate contains an epoxy group and an acryloxy group. The essence of the reaction is that the -OH group of the carboxyl group nucleophilically attacks the C atom of the epoxy group, leading to ring opening of the epoxy group and the formation of an ester group (-COO-) and a hydroxyl group.

[0038] After the epoxy ring opens, the COC bond breaks, and the COC stretching vibration of the epoxy group disappears at 800–950 cm⁻¹. Following the reaction, the -OH group of the carboxyl group participates in the epoxy ring opening to form the -O- of the ester bond. Therefore, the broad OH peak at 3000–2500 cm⁻¹ weakens; the C=O peak of the carboxylic acid group at 1700–1720 cm⁻¹ disappears and is replaced by the C=O stretching vibration peak of the ester group (1730–1750 cm⁻¹, the wavenumber of the ester group C=O is slightly higher than that of the carboxylic acid group due to the conjugation effect). The ester group is the characteristic functional group of the reaction product; its C=O stretching vibration at 1730–1750 cm⁻¹ shows strong absorption, distinct from the CO stretching vibration of the carboxylic acid group at 1700–1720 cm⁻¹. The asymmetric COC stretching vibration of the ester group shows strong absorption at 1200–1300 cm⁻¹, a characteristic "fingerprint region" of the ester. The C=C double bond of the acryloyloxy group and the C=C double bond connected to the ester group in GMA indicate that GMA participates in the reaction, and this peak disappears. The CH stretching vibration of alkyl groups, particularly saturated alkyl groups, is located near 2920 cm⁻¹ and 2850 cm⁻¹. Since the reaction does not involve alkyl CH groups, this peak is retained and its intensity is stable. By tracking the changes in characteristic peaks such as the epoxy group (800–950 cm⁻¹), carboxyl OH group (3000–2500 cm⁻¹), and ester group (1730–1750 cm⁻¹, 1200–1300 cm⁻¹), it is determined that the carboxyl group of the dimer acid undergoes a ring-opening esterification reaction with the epoxy group of glycidyl methacrylate, generating a product containing an ester bond.

[0039] The products of the above-mentioned embodiments and comparative examples were subjected to performance tests. The relevant data of acid value, viscosity at 25°C and double bond content of the products are shown in Table 1.

[0040] Table 1. Performance test results of the products from Examples 1-12 and Comparative Examples 1-6 First, this invention explored the corresponding conditions for the preparation method. Comparative Examples 1 and 2 did not add catalysts and polymerization inhibitors, respectively, and the reaction could not proceed in the absence of catalysts and polymerization inhibitors. Furthermore, the range of process parameters was explored and optimized through experiments. Regarding the molar ratio, when the molar ratio of the dimer acid carboxyl group to GMA was 1:1.0, the product had a high acid value, indicating incomplete reaction and insufficient introduction of effective double bonds. When the ratio increased to 1:2.5, although the reaction was complete, the product viscosity increased significantly, which may adversely affect subsequent processing. Within the preferred range of 1:1.8 to 1:2.2, the product simultaneously achieved low acid value, moderate viscosity, and high double bond content, achieving the best balance between reaction efficiency, product structure controllability, and processing applicability. Data on reaction temperature and time showed that at 80℃, the reaction required an extension to 10 hours to reach the target, resulting in low efficiency; while at 130℃, although the time could be shortened, the product color darkened, possibly accompanied by thermal side reactions.

[0041] The products of Examples 1-3 and Comparative Examples 3 and 5-6 were added as plasticizers to SBR rubber to prepare rubber compositions comprising, by weight, the following components: 100 parts SBR rubber; 5 parts zinc oxide; 1 part stearic acid; 2 parts antioxidant 4020; 30 parts plasticizer; 50 parts carbon black N330; 1.5 parts accelerator CBS; and 1.8 parts sulfur. The above components were mixed and vulcanized on an open mill using conventional processes to obtain the corresponding products.

[0042] The Mooney viscosity, vulcanization characteristics, hardness, tensile properties, and oil aging resistance of the corresponding products were tested. The oil aging resistance test procedure was as follows: the vulcanized rubber sample was immersed in IRM903 oil at 100°C for 72 hours, removed and dried, and the change in hardness, volume change rate, and tensile property retention rate were tested.

[0043] The test results are shown in Table 2.

[0044] Table 2. Test results of rubber compositions using the products of Examples 1-3 and Comparative Examples 3 and 5-6 as plasticizers. The vulcanizates using the plasticizers of Examples 1-3 of this invention, after being immersed in oil at 100°C for 72 hours, showed only a slight increase in hardness of +3 to +4 degrees, a very low volume expansion rate of only +8% to +9%, and a high retention rate of tensile strength and elongation of over 83%. This contrasts sharply with the two traditional physical plasticizers used in Comparative Examples 5 and 6: vulcanizates made from non-reactive bio-based epoxidized soybean oil and petroleum-based naphthenic oil, which, under the same conditions, exhibited significant increases in hardness, volume expansion, and a substantial decrease in mechanical properties. This difference demonstrates that this invention, by permanently fixing the plasticizer to the rubber network through chemical bonding, can overcome the problem of performance degradation caused by molecular migration and extraction of physical plasticizers.

[0045] The plasticizer of this invention provides excellent anti-migration properties without sacrificing other properties. In terms of processability, its Mooney viscosity is comparable to that of high-efficiency traditional naphthenic oils and superior to epoxidized soybean oil, indicating good plasticizing and lubricating effects, ensuring good processing flow of the rubber compound. Regarding the initial mechanical properties of the vulcanizate, the product of this invention imparts balanced hardness, high tensile strength, and good elongation to rubber products, ensuring ease of processing while enabling the final product to possess high strength, high elasticity, and superior durability—performance that traditional physical plasticizers struggle to achieve simultaneously. Comparative Example 3, using a reactive plasticizer prepared with oleic acid, although also containing active double bonds, exhibited significantly lower initial tensile strength in its vulcanizate than that of this invention, and its performance retention after oil aging was also inferior. This demonstrates that the dimer acid skeleton selected in this invention, with its unique long-chain, flexible, and potentially branched structure, is crucial for forming stronger and more uniform entanglements and cross-linking points in the rubber network. It is not merely a carrier of reactive groups; its structure itself improves the strength, toughness, and durability of the rubber.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a reactive bio-based plasticizer, characterized in that, Bio-based dimer acid and glycidyl methacrylate are converted into reactive bio-based plasticizers through ring-opening esterification in the presence of a catalyst and a polymerization inhibitor.

2. The method for preparing the reactive bio-based plasticizer according to claim 1, characterized in that, The molar ratio of the bio-based dimer acid to glycidyl methacrylate is 1:(1.0-2.5).

3. The method for preparing the reactive bio-based plasticizer according to claim 2, characterized in that, The molar ratio of the bio-based dimer acid to glycidyl methacrylate is 1:(1.8-2.2).

4. The method for preparing the reactive bio-based plasticizer according to claim 1, characterized in that, The reaction temperature is 80-130℃, and the reaction time is 2-8 hours.

5. The method for preparing the reactive bio-based plasticizer according to claim 1, characterized in that, The bio-based dimer acid is an octadecane-unsaturated fatty acid.

6. The method for preparing the reactive bio-based plasticizer according to claim 1, characterized in that, The catalyst is selected from one or more of triethylamine, triphenylphosphine, tetrabutylammonium bromide, and N,N-dimethylethanolamine.

7. The method for preparing the reactive bio-based plasticizer according to claim 1, characterized in that, The polymerization inhibitor is selected from hydroquinone, methyl hydroquinone, and 2,6-di-tert-butyl-p-cresol.

8. A reactive bio-based plasticizer prepared by the preparation method according to any one of claims 1-7.

9. The use of the reactive bio-based plasticizer of claim 8 as a plasticizer in rubber compositions.

10. The application of the reactive bio-based plasticizer according to claim 9 as a plasticizer in a rubber composition, characterized in that, The rubber composition comprises, by weight, the following components: Raw rubber: 100 parts; The reactive bio-based plasticizer as described in claim 8: 5-50 parts; Reinforcing filler: 20-80 parts; Vulcanizing agent: 0.5-3 parts; Accelerator: 0.5-5 parts.

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