A bio-based rubber dispersant and its preparation method

Abstract

This invention relates to the field of rubber additives technology and discloses a bio-based rubber dispersant and its preparation method. The dispersant comprises a C16 polyhydroxy fatty acid oligomer containing terminal alkenyl groups. The oligomer is formed by 2-6 C16 polyhydroxy fatty acid structural units linked by ester bonds. Some hydroxyl groups form an ester structure with a monocarboxylic acid containing terminal carbon-carbon double bonds, while retaining free hydroxyl groups and / or free carboxyl groups. The preparation method includes: subjecting plant epidermal material rich in C16-type keratin to limited depolymerization, acidification precipitation, washing, and drying to obtain a C16 polyhydroxy fatty acid oligomer; after dehydration, partially esterifying it with a monocarboxylic acid containing terminal carbon-carbon double bonds, and then post-processing to obtain the dispersant. This invention can improve the dispersibility of silica, the storage stability of rubber compounds, elongation at a given point, and dynamic fatigue performance, while maintaining the strength and toughness of vulcanized rubber.

Description

Technical Field

[0001] This invention relates to the field of rubber additives technology, and in particular to a bio-based rubber dispersant and its preparation method. Background Technology

[0002] Silica has good reinforcing properties and is widely used in tires and other rubber products. However, silica contains a lot of silanol groups on its surface, which can easily form strong interactions between particles, causing silica to agglomerate in rubber. This affects the processing performance of the rubber compound, the dispersion state of the filler, and the overall performance of the vulcanized rubber. To improve the dispersion of silica in rubber, organic dispersants or processing aids are usually added to the rubber composition.

[0003] For example, Chinese Patent CN116178791A discloses a high-performance silica dispersant and its preparation method and application. Its raw materials include fatty acids, inorganic alkalis, wax additives and fatty acid esters, which are used to improve the processing and dispersion properties of silica-filled rubber compounds. Chinese Patent CN121378883A discloses the application of a bio-based fatty acid amine ester dispersant. The dispersant is prepared by reacting organic acids with organic alcohol amines, preferably using methyl diethanolamine stearate. The above dispersants mainly improve the dispersion effect by improving the wettability of silica and the flowability of the rubber compound. However, while reducing filler agglomeration, it may still be difficult to take into account the reinforcing properties of the vulcanizate, the storage stability of the rubber compound and its long-term performance.

[0004] To address these issues, existing research proposes using depolymerized suberin derivatives (C-DSDs) derived from cork in silica-filled rubber. C-DSDs contain long-chain aliphatic structures and polar groups such as hydroxyl and carboxyl groups, which can regulate the interfacial interaction between silica and rubber and improve the tensile strength, toughness, and energy absorption properties of vulcanizates. However, the improvement of the static modulus of vulcanizates by C-DSDs is still limited, and there is still room for reduction in the silica agglomerate size and filler network strength in the filling system. Furthermore, the interfacial stability of the C-DSDs system under long-term repeated deformation and humid heat environments lacks sufficient verification. Summary of the Invention

[0005] The technical problem to be solved by this invention is that existing organic rubber dispersants are difficult to maintain the strength and toughness of vulcanized rubber while taking into account the dispersibility of silica, the storage stability of rubber compound, the elongation at a given point and the dynamic fatigue performance. Some low molecular weight dispersing components also have the tendency to migrate or be extracted. To address this, we propose a bio-based rubber dispersant and its preparation method.

[0006] To address the aforementioned technical problems, this invention provides a bio-based rubber dispersant comprising a C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups.

[0007] The C16 polyhydroxy fatty acid oligoester containing terminal alkenyl groups comprises: an oligomer segment formed by ester bonds connecting 2-6 C16 polyhydroxy fatty acid structural units, free hydroxyl groups and / or free carboxyl groups retained in the oligomer segment, and a terminal alkenyl fatty acid ester structure formed by the reaction of some hydroxyl groups of the oligomer segment with a monocarboxylic acid containing a terminal carbon-carbon double bond.

[0008] In some embodiments, the C16 polyhydroxy fatty acid oligoester containing terminal alkenyl groups can be represented by the structural schematic shown in formula (I):

[0009] (I)

[0010] Among them, A i denoted as C16 aliphatic skeleton in the i-th C16 polyhydroxy fatty acid structural unit; B represents a hydrocarbon group containing a terminal carbon-carbon double bond; n represents the number of C16 polyhydroxy fatty acid structural units in the low polyester molecule, and n≥2; xi represents the number of free hydroxyl groups retained in the i-th C16 polyhydroxy fatty acid structural unit; yi represents the number of hydroxyl groups forming a terminal alkenyl fatty acid ester structure in the i-th C16 polyhydroxy fatty acid structural unit.

[0011] In each structural unit, xi and yi are independent non-negative integers, and xi+yi does not exceed the number of reactive hydroxyl groups in the corresponding C16 polyhydroxy fatty acid structural unit other than the hydroxyl groups involved in the formation of the low polyester backbone. At least one yi in the low polyester molecule is not 0, and the low polyester molecule as a whole retains at least one free hydroxyl group and / or free carboxyl group.

[0012] Preferably, the C16 polyhydroxy fatty acid is selected from one or more of 10,16-dihydroxyhexadecanoic acid, 9,16-dihydroxyhexadecanoic acid, and 9,10,16-trihydroxyhexadecanoic acid.

[0013] Preferably, the oligomer segment is formed by 2-6 C16 polyhydroxy fatty acid structural units, more preferably by 2-4 of the structural units.

[0014] Preferably, the monocarboxylic acid containing a terminal carbon-carbon double bond is a terminal enoic acid containing 8-18 carbon atoms, more preferably 10-undecenoic acid.

[0015] Preferably, the molar ratio of the monocarboxylic acid containing the terminal carbon-carbon double bond to the initial free hydroxyl group in the oligomeric segment is 0.05:1-0.70:1, more preferably 0.10:1-0.45:1.

[0016] Preferably, the C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups has a number average molecular weight of 500-2500, a hydroxyl value of 60-260 mgKOH / g, an acid value of 15-130 mgKOH / g, and an iodine value of 5-60 gI2 / 100g.

[0017] In one embodiment, the bio-based rubber dispersant is composed of the C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups.

[0018] In another embodiment, the bio-based rubber dispersant further includes a bio-based fatty acid ester carrier and / or a state-conditioning component. By mass, the bio-based rubber dispersant preferably includes 60-95 parts of a C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups, 5-35 parts of a bio-based fatty acid ester carrier, and 0-10 parts of a state-conditioning component.

[0019] Preferably, the bio-based fatty acid ester carrier is selected from monoglyceride fatty acid esters, diglyceride fatty acid esters, and mixtures thereof; the condition-modifying component is selected from one or two of rice bran wax and carnauba wax.

[0020] This invention also provides a method for preparing a bio-based rubber dispersant, comprising the following steps:

[0021] S1: A mixture of C16 polyhydroxy fatty acid low polyester, monocarboxylic acid containing terminal carbon-carbon double bonds and esterification catalyst;

[0022] S2: Add an esterification catalyst to the mixture obtained in step S1, and carry out the esterification reaction of the mixture obtained in step S1 at 100-170℃ for 1-8 hours under inert gas protection, and remove the water generated in the reaction.

[0023] S3: After the reaction is completed, the resulting reactants are cooled and post-treated to form a bio-based rubber dispersant with C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups as the dispersing active ingredient.

[0024] Preferably, the C16 polyhydroxy fatty acid oligopolyester in step S1 is obtained through the following steps: washing, drying, and pulverizing plant epidermal material containing C16 type keratin to obtain plant epidermal material powder; adding the plant epidermal material powder to an alkaline medium with an alkali concentration of 0.3-1.2 mol / L and treating it at 75-110℃ for 30-240 min; performing solid-liquid separation on the obtained system to obtain a liquid phase containing C16 polyhydroxy fatty acid and its oligomer salt; acidifying the liquid phase to a pH of 4.5-6.5 to precipitate the C16 polyhydroxy fatty acid oligopolyester; and performing solid-liquid separation, washing, and drying on the precipitate to obtain the C16 polyhydroxy fatty acid oligopolyester.

[0025] Preferably, the plant epidermal material is tomato skin.

[0026] Preferably, the esterification catalyst in step S2 is selected from one or both of p-toluenesulfonic acid and methanesulfonic acid.

[0027] Preferably, a polymerization inhibitor is also added in step S2, wherein the polymerization inhibitor is selected from hydroquinone, p-hydroxyanisole, and combinations thereof.

[0028] Preferably, the post-processing in step S3 includes cooling, removal of unreacted monocarboxylic acids, removal of esterification catalyst, and one or more of pulverization, flake formation, or granulation.

[0029] The present invention also provides a method for preparing a composite bio-based rubber dispersant, comprising melting and mixing the above-mentioned C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups with a bio-based fatty acid ester carrier and optional state-conditioning components, homogenizing and then cooling and granulating to obtain a composite bio-based rubber dispersant.

[0030] Preferably, the melting and mixing temperature is 70-120°C; by mass, the composite bio-based rubber dispersant comprises 60-95 parts of C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups, 5-35 parts of bio-based fatty acid ester carrier, and 0-10 parts of physical state conditioning components.

[0031] The technical effects and advantages of this invention are as follows:

[0032] Compared to ordinary C16 polyhydroxy fatty acids, this invention forms an oligomeric structure, allowing a single oligoester molecule to simultaneously retain multiple free hydroxyl and / or free carboxyl groups. These free hydroxyl and / or free carboxyl groups can interact polarly with the silanol groups on the surface of silica, and may undergo dehydration or condensation reactions under mixing conditions, which is beneficial for enhancing the adsorption and retention of the oligoester on the silica surface. The terminal alkenyl groups introduced through partial esterification enable the oligoester to participate in crosslinking reactions under sulfur vulcanization conditions, while the C16 aliphatic segments are beneficial for improving the compatibility between the oligoester and the rubber phase. The synergistic effect of these structures is beneficial for improving the dispersion state of silica in rubber and the stability of the silica-rubber interface.

[0033] Compared with C-DSDs, this invention does not directly modify the complex depolymerization mixture. Instead, it selects the relatively concentrated C16 polyhydroxy fatty acid oligomer segments as the basic skeleton and introduces terminal alkenyl groups through partial esterification. This makes it easier to control the degree of terminal alkenyl group introduction and the content of residual polar groups, thereby improving the compatibility between silica dispersion and rubber interface properties. Attached Figure Description

[0034] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings:

[0035] Figure 1 RPA strain scan curves for different dispersant systems;

[0036] Figure 2 This is a particle size distribution diagram of silica agglomerates;

[0037] Figure 3 The stress-strain curve of the vulcanized rubber;

[0038] Figure 4 This is the fatigue crack growth curve;

[0039] Figure 5 The Fourier transform infrared spectrum of Example 2;

[0040] Figure 6 The washed samples from Example 2 and Comparative Example 3 1 H nuclear magnetic resonance spectrum;

[0041] Figure 7 The thermogravimetric curves are for Example 2 and Comparative Example 3. Detailed Implementation

[0042] Unless otherwise stated, low polyester in this specification refers to oligomeric organic compounds formed by at least two C16 polyhydroxy fatty acid structural units linked by ester bonds and used as organic compounding components rather than rubber matrices.

[0043] Partial esterification refers to the process of forming ester bonds between only a portion of the free hydroxyl groups in the low-polyester and the terminal olefinic acid, resulting in a product containing both terminal alkenyl structures and unreacted free hydroxyl groups.

[0044] C-DSDs references refer to suberin depolymerization derivatives obtained from cork or other suberin-rich plant materials through depolymerization, acidification, and separation.

[0045] The raw material amounts and target hydroxyl esterification rates for Examples 1-4 are shown in Table 1. The specific preparation steps are as follows:

[0046] 1000g of washed, seed-removed, dried and crushed tomato peel powder was added to a reactor equipped with a stirring, condensing and temperature control device. 8.0L of 0.65mol / L sodium hydroxide aqueous solution was added. The mixture was heated to 95℃ under nitrogen protection and stirred for 90min. After the reaction was completed, the mixture was filtered while hot and the filtrate was collected.

[0047] The filtrate was cooled to below 50°C, and hydrochloric acid was added dropwise under stirring to adjust the pH to 5.5. The precipitate was allowed to stand and collected by pressure filtration or centrifugation. The precipitate was washed with deionized water until the pH of the washing solution was 6-7 and the inorganic salt content met the set control requirements. The resulting wet material was vacuum dried at 65°C until the moisture content was no higher than 1.5%, resulting in a C16 polyhydroxy fatty acid mixed low polyester, denoted as basic low polyester A.

[0048] The results of testing on basic low-polyester A showed that its acid value was 72.4 mgKOH / g, hydroxyl value was 219.6 mgKOH / g, number-average molecular weight was 980, weight-average molecular weight was 1540, and molecular weight distribution was 1.57. The content of C16 structural units in basic low-polyester A was 89.6%, the content of free C16 polyhydroxy fatty acid monomers was 7.8%, the moisture content was 0.46%, and the ash content was 0.72%.

[0049] The following examples use a measured hydroxyl value of 219.6 mg KOH / g for basic low-polyester A as a feeding example. In actual production, the amount of 10-undecenoic acid should be calculated based on the measured hydroxyl value of the basic low-polyester. The amount of hydroxyl substances contained in 100g of basic low-polyester A is approximately 0.392 mol.

[0050] All embodiments adopted the following basic operation: basic low polyester A, 10-undecenoic acid, p-toluenesulfonic acid and p-hydroxyanisole were added to the reactor, heated to 135°C under nitrogen protection and held for 2 hours; then the temperature was raised to 145°C and gradually reduced to -0.08 MPa, the reaction was continued for 2 hours and the reaction water was removed, and the acid value, hydroxyl value and iodine value were measured. When the target residual hydroxyl value was reached and the terminal alkenyl group and newly added ester group could be confirmed by FTIR or NMR, the reaction was terminated by cooling. If necessary, adsorption filtration was used to reduce residual catalyst and free 10-undecenoic acid.

[0051] Table 1. Raw material dosage and target hydroxyl esterification rate for Examples 1-4

[0052]

[0053] Example 5

[0054] 80 parts by weight of U-C16O-25 prepared in Example 2, 15 parts by weight of glyceryl monostearate and 5 parts by weight of rice bran wax were added to a melt mixer and mixed at 90°C for 20 min. After cooling and granulation by steel belt, composite particulate dispersant PU-C16O was obtained.

[0055] Example 6

[0056] 10 kg of washed, deseeded, dried and crushed tomato peels were added to 80 L of 0.55 mol / L sodium hydroxide aqueous solution and stirred at 95 °C for 90 min. After the reaction solution was filtered through a plate and frame filter, hydrochloric acid was added to the filtrate to adjust the pH to 5.5. After pressure filtration, washing with water and vacuum drying at 65 °C, a C16 polyhydroxy fatty acid mixed low polyester without preparative chromatography or multiple solvent fractionation was obtained. Based on the measured hydroxyl value of the mixed low polyester, 10-undecenoic acid was added at a target hydroxyl esterification rate of 25%, and partial esterification was carried out according to the conditions described in Example 2 to obtain the industrial simplified product IU-C16O-25.

[0057] Comparative Example 1

[0058] A C16 polyhydroxy fatty acid mixture with 10,16-dihydroxyhexadecanoic acid as the main component is used as a dispersant, denoted as C16-M. By mass percentage, the C16 polyhydroxy fatty acid mixture includes 95.6% 10,16-dihydroxyhexadecanoic acid, 2.8% other C16 dihydroxy fatty acids, 1.1% C16 trihydroxy fatty acids, and 0.5% other fatty acids and impurities.

[0059] Comparative Example 2

[0060] Basic low-polyester A is used as the dispersant, denoted as C16-O.

[0061] Comparative Example 3

[0062] Weigh 100 parts by weight of base low polyester A and 18.1 parts by weight of 10-undecenoic acid, add them to a reaction vessel, heat to 80°C under nitrogen protection and stirring, and keep warm and mix for 20 minutes. No esterification catalyst or polymerization inhibitor is added during the mixing process, and no dehydration is performed under reduced pressure. After mixing, the mixture is cooled and discharged to obtain a physical mixture of base low polyester A and 10-undecenoic acid, denoted as PM-C16O / UDA. According to the mass of the feed materials, the obtained PM-C16O / UDA includes 84.7% base low polyester A and 15.3% 10-undecenoic acid, and its raw material mass ratio is the same as that in Example 2.

[0063] Comparative Example 4

[0064] Weigh 100 parts by mass of base low polyester A, and according to the hydroxyl value of base low polyester A, add 50.7 parts by mass of 10-undecenoic acid according to the target esterification rate of 70% for the initial free hydroxyl group. Except for the different amount of 10-undecenoic acid added, the types and amounts of esterification catalyst and polymerization inhibitor, reaction temperature, reaction time, nitrogen protection, reduced pressure dehydration and post-treatment steps are the same as in Example 2. A highly esterified C16 polyhydroxy fatty acid low polyester is obtained, which is denoted as U-C16O-70.

[0065] Comparative Example 5

[0066] The comparative example uses depolymerized cork suberin derivatives from the paper "Natural cork / potato periderm derivatives enabled interface engineering of elastomer composites for tunable energy-absorbing capabilities" published by Bumyong Yoon et al. in Industrial Crops & Products as a comparative dispersant, denoted as C-DSDs. The cork raw material was dried, pulverized, and sieved to obtain cork powder. 100 parts by weight of cork powder were weighed and 1000 parts by weight of a 5% sodium hydroxide alcohol aqueous solution were added. The mass ratio of ethanol to water in the alcohol aqueous solution was 70:30.

[0067] The mixture was heated to 90°C under stirring and kept at that temperature for 4 hours. After the reaction was completed, the mixture was filtered to remove insoluble residues. The residues were then washed with an alcohol-water solution. The filtrates and washing solutions were combined, and the ethanol was removed under reduced pressure. Hydrochloric acid was added to adjust the pH of the system to 2.5, causing the depolymerized suberin derivatives to precipitate. After solid-liquid separation, water washing, and vacuum drying at 60°C, C-DSDs were obtained.

[0068] By mass percentage, the resulting C-DSDs comprise 74.6% C18-C24 aliphatic hydroxy acids and dicarboxylic acid derivatives, 8.2% C16 fatty acids and their derivatives, 8.7% aromatic components containing ferulic acid structures, 4.1% glycerol and other low-molecular-weight ester components, and 4.4% other components.

[0069] Comparative Example 6

[0070] To prepare a fatty acid alcohol ester type silica dispersant, denoted as FAAE, the vegetable oil fatty acid mixture used includes, by mass percentage, 42.6% oleic acid, 35.4% linoleic acid, 12.1% palmitic acid, 4.8% stearic acid, and 5.1% other fatty acids.

[0071] Weigh 100 parts by weight of the vegetable oil fatty acid mixture, 50.8 parts by weight of triethanolamine and 0.15 parts by weight of hypophosphite, add them to a reaction vessel, heat to 150°C under nitrogen protection and stirring, and keep the temperature for 4 hours; then heat to 165°C and continue the reaction under reduced pressure for 2 hours, remove the water generated in the reaction, cool down and filter after the reaction is completed to obtain fatty acid triethanolamine ester type dispersant FAAE.

[0072] By mass percentage, the resulting FAAE comprises 61.5% fatty acid triethanolamine monoester, 23.4% fatty acid triethanolamine diester, 4.6% fatty acid triethanolamine triester, 6.1% unreacted fatty acids, and 4.4% free triethanolamine and other components.

[0073] Comparative Example 7

[0074] The rubber composition was formulated according to the basic formulation of Experimental Example 2. The amount of TESPT was 6.4 parts by mass based on a total mass of 100 parts by mass of solution-polymerized styrene-butadiene rubber and cis-butadiene rubber. No organic rubber dispersant was added. The other components and their amounts were the same as those in the basic formulation of Experimental Example 2. Rubber compounds and vulcanized rubber samples were prepared according to the mixing, resting, re-mixing, final mixing and vulcanization process described in Experimental Example 2. The resulting test group was denoted as TESPT-F.

[0075] Comparative Example 8

[0076] The rubber composition was formulated according to the basic formulation of Experimental Example 2. The amount of TESPT was 3.2 parts by mass based on a total mass of 100 parts by mass of solution-polymerized styrene-butadiene rubber and cis-butadiene rubber. No organic rubber dispersant was added. The other components and their amounts were the same as those in the basic formulation of Experimental Example 2. Rubber compounds and vulcanized rubber samples were prepared according to the mixing, resting, re-mixing, final mixing and vulcanization process described in Experimental Example 2. The resulting test group was denoted as TESPT-R.

[0077] The dispersants used in each experimental group are shown in Table 2.

[0078] Table 2 Experimental Groups

[0079]

[0080] Experimental Example 1

[0081] The acid value, hydroxyl value, iodine value, and number-average molecular weight of the dispersants obtained in the examples and comparative examples were determined, and the structure was analyzed by infrared spectroscopy and nuclear magnetic resonance. In order to distinguish between the covalent introduction and physical mixing of terminal alkenyl groups, each sample was thoroughly washed with petroleum ether to remove free 10-undecenoic acid and other soluble small molecules. After drying, the iodine value was determined again, and the content of free 10-undecenoic acid in the samples was determined by gas chromatography. The test results are shown in Table 3.

[0082] Table 3. Structure and physicochemical properties of dispersants

[0083]

[0084] As shown in Table 3, U-C16O-15, U-C16O-25, U-C16O-35, U-C16O-45, and U-C16O-70 all exhibit characteristic absorption of terminal alkenyl groups, while the absorption of ester carbonyl groups is enhanced. Proton signals corresponding to the terminal alkenyl groups can be observed in the NMR results. The iodine value of the physical mixture PM-C16O / UDA decreased after washing, while the esterified oligomers of each part still retained most of their unsaturated structures after washing. This indicates that the terminal alkenyl groups are mainly connected to the C16 polyhydroxy fatty acid oligomer segments through ester bonds, rather than existing in the form of free 10-undecenoic acid. With the increase of esterification degree, the hydroxyl value of the oligomers gradually decreased, while the iodine value and number-average molecular weight gradually increased. Example 2 retains more free hydroxyl groups while having a clear terminal alkenyl structure, which can take into account both the functional groups of silica and the functional structure of the rubber phase. The product obtained by the industrial simplified route has similar physicochemical properties to that of Example 2, indicating that fine classification is not a necessary condition for obtaining the product of this invention.

[0085] Experiment Example 2

[0086] The basic formulation of the rubber composition is shown in Table 4.

[0087] Table 4 Basic Formulation of Rubber Compositions

[0088]

[0089] Solution-polymerized styrene-butadiene rubber (SBR) and butadiene rubber (BR) were added to an internal mixer for plasticizing. Then, silica, processing oil, appropriate dispersants, and silane coupling agents were added in batches, followed by zinc oxide, stearic acid, antioxidants, and protective wax. The mixing temperature after adding silica was controlled to ensure each group underwent a similar high-temperature silanization process. After discharge, cooling, and resting, the mixture was re-mixed. Finally, sulfur and accelerators were added at a lower temperature, and after uniform mixing, the mixture was sheeted. The vulcanization characteristics of each group were measured using a rotorless vulcanizer. Flat vulcanization was performed according to the optimal vulcanization time for each group to obtain corresponding vulcanized rubber samples. The processing, vulcanization, and initial dispersion performance test results for each group are shown in Table 5. G0, G1, G2, G4, G5, and G7 were selected as representative test groups, and their RPA strain scan curves and silica agglomerate particle size distribution curves are shown in Table 5. Figure 1 and Figure 2 As shown.

[0090] Table 5 Processing, vulcanization and initial dispersion properties

[0091]

[0092] As can be seen from Table 5, the dispersant of the present invention can reduce the viscosity of the rubber compound and the network strength of the silica filler, and increase the content of the binder. The examples with a moderate degree of esterification showed good initial dispersion effect, and the degree of silica agglomeration was lower than that of C-DSDs, ordinary C16 monomers, unmodified low polyester and physical mixtures. After excessive esterification, the dispersion performance of silica decreased due to the reduction of free hydroxyl groups. The scorch time and positive vulcanization time of each example were similar to those of the full-volume TESPT control group and the reduced-volume TESPT blank group, and there was no significant shortening or lengthening.

[0093] Depend on Figure 1 It can be seen that the storage modulus G′ of each group of rubber compounds decreases with increasing strain, but the magnitude of the decrease varies. The low-strain storage modulus of the reduced TESPT blank group G0 is relatively high, and the storage modulus decreases significantly during the strain scan, indicating that its silica filler network is strong. The storage modulus of group G7 corresponding to Example 2 of this invention decreases less, indicating that it can reduce the interaction between silica particles and inhibit the formation of filler network.

[0094] Depend on Figure 2 It can be seen that the silica agglomerates in group G0 have a wide particle size distribution and large particle size tails; the particle size distribution of groups G2, G4 and G5 shifts to the direction of smaller particle size to varying degrees; the particle size distribution of group G7 is further concentrated in the smaller particle size region, and the proportion of large particle size agglomerates is low. The above results are consistent with the changes in agglomerate d50 and the proportion of large particle size agglomerates shown in Table 5.

[0095] Experiment Example 4

[0096] The vulcanized rubber was cut into standard tensile specimens, and Young's modulus, stress at 100% elongation, stress at 300% elongation, tensile strength, and elongation at break were measured at room temperature. The toughness of the vulcanized rubber was calculated based on the integral area of ​​the tensile stress-strain curve. The test results are shown in Table 6, and the stress-strain curves are as follows: Figure 3 As shown.

[0097] Table 6 Static Mechanical Properties of Vulcanizates

[0098]

[0099] As can be seen from Table 6, C-DSDs can improve the tensile strength, elongation at break and toughness of vulcanizates, but the elongation at a given elongation is relatively limited. The dispersant with a moderate degree of esterification in this invention improves Young's modulus and stress at a given elongation while maintaining strength, elongation and toughness, thus achieving a balance between rigidity and toughness. As the degree of esterification continues to increase, the number of free hydroxyl groups decreases, and the strength and toughness begin to decline, indicating that moderate partial esterification is necessary.

[0100] Depend on Figure 3It can be seen that group G2 has higher elongation at break and tensile strength, but the stress in its medium strain range is relatively low; group G7 maintains higher elongation at break and tensile strength while exhibiting higher stress levels in the medium-high strain range. The above results show that Example 2 of the present invention can take into account the constant elongation performance, tensile strength and toughness of the vulcanizate.

[0101] Experimental Example 5

[0102] Temperature scanning of the vulcanized rubber was performed using a dynamic mechanical analyzer, and the loss factors near 0℃ and 60℃ were recorded. The temperature rise under cyclic loading was evaluated by compression heat generation test, and the wear volume, resilience and Shore hardness were measured. The test results are shown in Table 7.

[0103] Table 7 Dynamic properties of vulcanizates

[0104]

[0105] As can be seen from Table 7, the dispersant of the present invention improves the elongation performance without increasing compression heat generation and wear. The examples with a moderate degree of esterification show low high-temperature loss and compression temperature rise, and maintain a good low-temperature loss level, indicating that its improvement on the dispersion and interfacial interaction of silica does not come at the cost of significantly sacrificing dynamic performance.

[0106] Experimental Example 6

[0107] Pre-cracked specimens were used for fatigue crack growth tests under fixed tear energy conditions. The number of cycles required to reach a specified crack length was determined using flexural fatigue tests. Separately, vulcanized rubber specimens were subjected to a specified number of cyclic tensile tests. After the cycles, the modulus retention and filler network strength changes were measured, and the debonding of the silica-rubber interface in the fracture surface was observed. The test results are shown in Table 8, and the fatigue crack growth curves of representative test groups are shown below. Figure 4 As shown.

[0108] Table 8 Dynamic fatigue properties of vulcanizates

[0109]

[0110] As can be seen from Table 8, although C-DSDs can provide good strength and toughness, their modulus retention and interfacial stability after cyclic deformation are still lower than those of the low polyester with moderate esterification in this invention. Ordinary C16 monomers and physical mixtures are more prone to filler network recovery and interfacial debonding after repeated deformation. The dispersant of this invention reduces the crack growth rate and improves fatigue life and modulus retention after cycling. The above results are consistent with the explanation that the covalent introduction of terminal alkenyl structures helps to improve interfacial residence stability.

[0111] Depend on Figure 4It can be seen that the fatigue crack growth rate of each group of vulcanizates increases with the increase of tear energy; under the same tear energy, the fatigue crack growth rate of group G7 is lower than that of groups G0, G2, G4 and G5, and is similar to or lower than that of group G1 with full TESPT, indicating that Example 2 of the present invention can suppress crack propagation under cyclic loading.

[0112] Experimental Example 7

[0113] The vulcanized rubber was pulverized to the specified particle size and subjected to Soxhlet extraction with an organic solvent. After deducting the influence of processing oil and other extractables in the blank rubber compound, the relative extractable amount was calculated.

[0114] The extractable amount of the vulcanized rubber was determined again after aging in hot air. The surface precipitation was observed under constant temperature conditions. The degree of surface precipitation was divided into 0-4 levels, where level 0 indicates no visible precipitation and level 4 indicates severe precipitation.

[0115] The samples were placed in an environment of 80℃ and 85% relative humidity for 500 hours. The retention rate of 100% constant elongation stress, the retention rate of tensile strength and the change of filler network strength after wet heat treatment were measured. The test results are shown in Table 9.

[0116] Table 9 Extractability, Migration and Hydrothermal Stability

[0117]

[0118] As can be seen from Table 9, ordinary C16 polyhydroxy fatty acid monomers and physical mixtures have high extractability and surface precipitation tendency, indicating that low molecular weight components or unreacted terminal alkenyl acids are prone to migrate from the rubber system; unmodified oligomers can reduce migration, but the performance after hydrothermal treatment is still lower than that of the embodiments of the present invention; the oligomers of the present invention with moderate esterification degree have low extractability and good hydrothermal stability, indicating that the combination of moderate oligomer structure and terminal alkenyl groups can improve the long-term stability of dispersants at the rubber interface.

[0119] Experimental Example 8

[0120] Samples from Example 2 and Comparative Example 3, washed and vacuum-dried to constant weight under the same conditions, were respectively taken. Fourier transform infrared spectroscopy was performed on Sample 2; Fourier transform infrared spectroscopy was performed on Samples 2 and Comparative Example 3. 1 H NMR spectroscopy and thermogravimetric analysis were performed. Fourier transform infrared spectroscopy was conducted in attenuated total reflectance mode, with a scanning range of 4000-500 cm⁻¹. -1 ; 1 H NMR was performed using deuterated chloroform as a solvent at room temperature; thermogravimetric analysis was conducted under a nitrogen atmosphere, with a temperature range from room temperature to 800℃. The test results are as follows: Figure 5-7 As shown.

[0121] Depend on Figure 5 As can be seen, in Example 2, the depth is approximately 3200-3550 cm. -1 A broad absorption band for the stretching vibration of the hydroxyl group (OH) appears within the range of approximately 2848-2932 cm⁻¹. -1 An aliphatic methylene CH stretching vibration absorption peak appears within the range of approximately 1690-1750 cm⁻¹. -1 Absorption peaks of C=O stretching vibrations in ester and / or carboxyl groups were observed within the range, and correlation absorptions of carbon-carbon double bonds and =CH on unsaturated carbons were also observed. The results indicate that hydroxyl, ester and / or carboxyl groups, aliphatic long chains and unsaturated structures were present simultaneously in Example 2.

[0122] Depend on Figure 6 It can be seen that in Example 2, the corresponding proton signals are still retained in the chemical shift regions corresponding to the terminal alkenyl groups -CH= and =CH2, and characteristic signals appear in the proton regions adjacent to the ester structure. After washing under the same conditions, the terminal alkenyl related signals in Comparative Example 3 are significantly weakened. Combined with the results of iodine value and free 10-undecenoic acid content before and after washing, it is indicated that the terminal alkenyl groups in Example 2 do not mainly exist in the form of free 10-undecenoic acid, and their structural state is different from the physical mixing state of Comparative Example 3.

[0123] Depend on Figure 7 It can be seen that the mass changes of both Example 2 and Comparative Example 3 are small below about 200°C, and the main weight loss occurs in the range of about 250-450°C. The thermogravimetric curve of Example 2 shifts to the higher temperature direction relative to Comparative Example 3, indicating that Example 2 has better thermal stability and can meet the temperature requirements of its preparation, granulation and rubber mixing processes.

[0124] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A bio-based rubber dispersant, characterized in that, The bio-based rubber dispersant uses C16 polyhydroxy fatty acid oligoesters containing terminal alkenyl groups as the effective dispersing component. The C16 polyhydroxy fatty acid oligoesters containing terminal alkenyl groups include oligomer segments formed by ester bonds connecting 2-6 C16 polyhydroxy fatty acid structural units, free hydroxyl groups and / or free carboxyl groups retained in the oligomer segments, and terminal alkenyl fatty acid ester structures formed by some of the free hydroxyl groups of the oligomer segments and monocarboxylic acids containing terminal carbon-carbon double bonds.

2. The bio-based rubber dispersant according to claim 1, characterized in that: The C16 polyhydroxy fatty acid is selected from one or more of 10,16-dihydroxyhexadecanoic acid, 9,16-dihydroxyhexadecanoic acid, and 9,10,16-trihydroxyhexadecanoic acid.

3. The bio-based rubber dispersant according to claim 1, characterized in that: The monocarboxylic acid containing a terminal carbon-carbon double bond is a terminal olefinic acid containing 8-18 carbon atoms.

4. The bio-based rubber dispersant according to claim 3, characterized in that: The monocarboxylic acid is 10-undecenoic acid.

5. The bio-based rubber dispersant according to claim 1, characterized in that: The C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups has a number average molecular weight of 500-2500, a hydroxyl value of 60-260 mgKOH / g, an acid value of 15-130 mgKOH / g, and an iodine value of 5-60 gI2 / 100g.

6. The bio-based rubber dispersant according to claim 1, characterized in that: By weight, the rubber dispersant comprises 60-95 parts of the terminal alkenyl C16 polyhydroxy fatty acid low polyester, 5-35 parts of bio-based fatty acid ester carrier, and 0-10 parts of a physical condition adjustment component.

7. The bio-based rubber dispersant according to claim 6, characterized in that: The bio-based fatty acid ester carrier is selected from one or more of glycerol mono-fatty acid esters, glycerol di-fatty acid esters, and mixtures thereof, and the condition-modifying component is selected from one or two of rice bran wax and carnauba wax.

8. A method for preparing a bio-based rubber dispersant as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: A mixture of C16 polyhydroxy fatty acid low polyester, monocarboxylic acid containing terminal carbon-carbon double bonds and esterification catalyst; S2: Add an esterification catalyst to the mixture obtained in step S1, and carry out the esterification reaction of the mixture obtained in step S1 at 100-170℃ for 1-8 hours under inert gas protection, and remove the water generated in the reaction. S3: After the reaction is completed, the resulting reactants are cooled and post-treated to obtain a bio-based rubber dispersant with C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups as the dispersing active ingredient.

9. The method for preparing a bio-based rubber dispersant according to claim 8, characterized in that: The C16 polyhydroxy fatty acid oligopolyester in step S1 is prepared by the following steps: washing, drying and pulverizing plant epidermal material containing C16 type keratin to obtain plant epidermal material powder; adding the plant epidermal material powder to an alkaline medium with an alkali concentration of 0.3-1.2 mol / L and treating it at 75-110℃ for 30-240 min; performing solid-liquid separation on the system obtained to obtain a liquid phase containing C16 polyhydroxy fatty acid and its oligomer salt; acidifying the liquid phase to a pH of 4.5-6.5; and performing solid-liquid separation, washing and drying on the precipitate to obtain the C16 polyhydroxy fatty acid oligopolyester.

10. The method for preparing a bio-based rubber dispersant according to claim 8, characterized in that: The esterification catalyst in step S2 is selected from one or both of p-toluenesulfonic acid and methanesulfonic acid.

11. The method for preparing a bio-based rubber dispersant according to claim 8, characterized in that: The C16 polyhydroxy fatty acid low polyester containing terminal alkenyl groups obtained in step S3 is melt-mixed with a bio-based fatty acid ester carrier and optional state-conditioning components at 70-120°C, homogenized, cooled, and granulated.

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