A low-migration rubber additive masterbatch and a method for its preparation

Abstract

The application relates to the technical field of rubber auxiliary master batch, and discloses a low-migration rubber auxiliary master batch and a preparation method thereof; the master batch comprises 50-75 parts of organic rubber auxiliary agents, 12-30 parts of polymer carriers, 5-20 parts of branched polysulfide compounds and 0.1-5 parts of processing aids in terms of weight parts; the branched polysulfide compound contains 3 or 4 sulfide groups and C12-C18 hydrophobic alkyl branched chains; during preparation, the organic rubber auxiliary agents are premixed with the branched polysulfide compound, and then the premixed product is mixed, extruded and granulated with the polymer carriers and the processing aids; the obtained master batch can reduce the extraction amount of auxiliary agent related target objects after long-term heat aging, does not substantially affect the vulcanization characteristics of the rubber material and the initial mechanical properties of the vulcanized rubber, and can also improve the retention rate of the mechanical properties of the vulcanized rubber after aging.

Description

Technical Field

[0001] This invention relates to the field of rubber additive masterbatch technology, and in particular to a low-migration rubber additive masterbatch and its preparation method. Background Technology

[0002] Antioxidants, accelerators, plasticizers, and other rubber additives are typically added during the processing, storage, and use of rubber products to improve the properties of rubber materials. However, some rubber additives have low molecular weights and limited binding capacity with the rubber matrix. They are prone to migrating from the interior of the rubber to the surface under the influence of concentration gradients, temperature changes, and external media. This results in a reduction in the effective content of the additives, precipitation or contamination of the rubber surface, and consequently affects the performance stability of the rubber products. Therefore, reducing the migration and extraction of rubber additives in the rubber matrix has become a problem that needs to be solved in the field of rubber additive technology.

[0003] To address the aforementioned problems, existing technologies have proposed solutions. For example, Chinese Patent Publication No. CN114044897A discloses a method for preparing antioxidant 6PPD, which involves reacting a cashew nut phenol derivative with antioxidant 6PPD to obtain a macromolecular antioxidant containing a cashew nut phenol structure. Chinese Patent Publication No. CN113462022A discloses a rubber antioxidant composition and its preparation method and application, which combines an organic compound containing an active group, an amine antioxidant, and a modified antioxidant formed therefrom to reduce antioxidant migration while also taking into account the antioxidant properties of rubber.

[0004] Existing low-migration technologies mainly control the initial migration of organic rubber additives, without fully considering the potential changes in the migration and extractability of transformation products after chemical transformation during service aging. McMinn et al., in their paper "In-depth chemical profiling of tire and artificial turf crumb rubber: aging, transformation products, and transport pathways" published in *Environmental Science: Processes & Impacts*, also pointed out that solvent extraction, leaching, and bioavailability extraction revealed changes in the types, abundance, polarity, and molecular weight of organic compounds in rubber materials with different service lives. Therefore, the low initial migration of organic rubber additives in their unaged state does not necessarily indicate a low overall migration throughout the entire service aging cycle. Furthermore, measures to reduce migration must avoid significantly affecting the vulcanization characteristics and mechanical properties of the rubber compound. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing rubber additive masterbatches, during long-term thermal aging, are difficult to reduce the migration of the rubber additives themselves and their aging conversion products from the rubber matrix without significantly affecting the normal vulcanization of the rubber compound and the initial mechanical properties of the vulcanized rubber. Therefore, it is difficult to balance long-term low migration performance and the retention of mechanical properties after aging. To this end, we propose a low-migration rubber additive masterbatch and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention provides a low-migration rubber additive masterbatch, which, by weight, comprises 50-75 parts of organic rubber additive, 12-30 parts of polymer carrier, 5-20 parts of branched polysulfide compound and 0.1-5 parts of processing aid, wherein the branched polysulfide compound is a reaction product formed by the addition of a polythiol compound to a terminal monoolefin via a mercapto-olefin reaction.

[0007] The branched polysulfide compound is an organic compound containing 3 or 4 thioether groups and having 3 or 4 hydrophobic alkyl branches, wherein the hydrophobic alkyl branches have 8-24 carbon atoms, and the main component has the structure shown in Formula I and / or Formula II:

[0008] C2H5C[CH2OC(O)CH2CH2SR]3 (Equation I)

[0009] C[CH2OC(O)CH2CH2SR]4 (Equation II)

[0010] In Formula I and Formula II, R is a C12-C18 straight-chain or branched alkyl group.

[0011] The compound shown in Formula I is prepared by thiol-ene addition of trimethylolpropane tris(3-mercaptopropionic acid) ester and a monoalkenyl compound; the compound shown in Formula II can be prepared by thiol-ene addition of pentaerythritol tetra(3-mercaptopropionic acid) ester and a monoalkenyl compound.

[0012] The general structural formula of the terminal monoolefin is CH2=CH—R¹, where R¹ is a straight-chain or branched alkyl group of C6-C22, and R is —CH2—CH2—R¹.

[0013] The terminal monoalkenyl compound is selected from one or more of 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

[0014] Preferably, after the branched polysulfide compound is aged in air at 100°C for 72 hours, the oxidation ratio of the sulfide groups is 15%-45%, and the temperature of the main endothermic peak of DSC is increased by 8-25°C compared with that before aging.

[0015] The branched polysulfide compound has a mercapto conversion rate of not less than 97% and an unreacted monoalkenyl compound mass fraction of not more than 0.5%.

[0016] Test results show that after the branched polysulfide compound is treated with hot air, some of the sulfide sulfur is converted into sulfoxide sulfur and sulfone sulfur. At the same time, the temperature of its main endothermic peak in DSC changes. Based on the test results of extractability, vulcanization performance and mechanical properties, it is speculated that the branched structure, hydrophobic alkyl chain, changes in sulfur-containing chemical state during aging and the corresponding thermal transformation behavior jointly affect the extractability of organic rubber additives and their aging conversion products.

[0017] The organic rubber additive is selected from one or more of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, polymeric 2,2,4-trimethyl-1,2-dihydroquinoline, or 2,2′-methylenebis(4-methyl-6-tert-butylphenol).

[0018] The polymer carrier is selected from one or more of ethylene-vinyl acetate rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, nitrile rubber, and ethylene-vinyl acetate copolymer. Preferably, the polymer carrier is ethylene-vinyl acetate rubber or styrene-butadiene rubber.

[0019] The vinyl acetate structural unit in the ethylene-vinyl acetate rubber has a mass fraction of 40%-80%; the vinyl acetate structural unit in the ethylene-vinyl acetate copolymer has a mass fraction of 5%-40%.

[0020] The processing aid is selected from one or more of naphthenic oil, paraffin oil, fatty acids, and fatty acid esters.

[0021] This invention also provides a method for preparing low-migration rubber additive masterbatch, comprising the following steps:

[0022] S1: Mix polythiols and monoalkenyl compounds at a molar ratio of thiol to carbon-carbon double bond of 1:(0.98-1.05), and carry out thiol-alkene addition in the presence of a free radical initiator. After the reaction is completed, perform vacuum devolatilization at 60-140℃ and 0.1-5kPa until the mass fraction of unreacted monoalkenyl compounds is not higher than 0.5%, to obtain branched polysulfide compounds.

[0023] S2: Premix the organic rubber additive with the branched polysulfide compound obtained in step S1 at 40-80℃ for 5-30 min to obtain a premix;

[0024] S3: After plasticizing the polymer carrier, add the premix obtained in step S2 and processing aids, mix at 60-100℃ for 3-20 minutes, then extrude, cool and pelletize to obtain low migration rubber additive masterbatch.

[0025] In step S1, the amount of free radical initiator is 0.1%-2.0% of the total mass of the polythiol compound and the monoalkenyl compound, preferably 0.3%-1.0%.

[0026] In step S1, the free radical initiator can be a photoinitiator or a thermal initiator. The photoinitiator is selected from one or both of 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,2-dimethoxy-2-phenylacetophenone. The thermal initiator is selected from one or both of azobisisobutyronitrile and benzoyl peroxide.

[0027] In step S1, when photoinitiation is used, the reaction temperature is 25-45℃, the irradiation wavelength is 320-405nm, and the reaction time is 2-6h; when thermal initiation is used, the reaction temperature is 55-90℃, and the reaction time is 3-8h.

[0028] In step S1, for high-boiling-point raw materials such as 1-octadecene, depressurization devolatilization is difficult. Unreacted monoalkenyl compounds can be removed by thin-film evaporation, solvent washing, or recrystallization.

[0029] Steps S2 and S3 are carried out without the addition of an exogenous oxidant, and the total processing time of steps S2 and S3 does not exceed 40 minutes, in order to reduce the pre-oxidation of branched polysulfide compounds in the masterbatch preparation stage.

[0030] The technical effects and advantages of this invention are as follows:

[0031] Compared with existing technologies, this invention introduces unoxidized branched polysulfide compounds into organic rubber additive masterbatches. By utilizing the restriction effect of their branched hydrophobic structure on the migration of additives, and combining the dynamic antioxidant effect of sulfide groups during thermal aging, the formation and migration of the additive masterbatch and its aging transformation products are synergistically regulated. This technical approach differs from schemes that rely solely on linear sulfide antioxidants or pre-increase the oxidation degree of sulfur-containing groups. It helps to reduce the extractable amount of additive-derived substances after long-term thermal aging and improve the retention of mechanical properties after aging, with less impact on the vulcanization characteristics of the rubber compound and the initial mechanical properties of the vulcanized rubber. Attached Figure Description

[0032] 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:

[0033] Figure 1 A schematic diagram of the reaction for preparing a four-armed C12-branched polysulfide compound from pentaerythritol tetra(3-mercaptopropionic acid) ester and 1-dodecene.

[0034] Figure 2A schematic diagram of the reaction for preparing a three-armed C12-branched polysulfide compound from trimethylolpropane tris(3-mercaptopropionic acid) ester and 1-dodecene.

[0035] Figure 3 A schematic diagram of the reaction for preparing a four-armed C18 branched polysulfide compound from pentaerythritol tetra(3-mercaptopropionic acid) ester and 1-octadecene.

[0036] Figure 4 The curves show the changes in the total extractable amount of the target compound from 6PPD in the samples of Example 1 and Comparative Examples 1-3 at different aging times;

[0037] Figure 5 To prepare the branched polysulfide compound obtained in Example 1 1 H nuclear magnetic resonance spectrum;

[0038] Figure 6 The S 2p high-resolution X-ray photoelectron spectra of the branched polysulfide compound obtained in Example 1 before and after aging;

[0039] Figure 7 The high-resolution X-ray photoelectron spectroscopy peak fitting diagram of the S 2p peaks of the branched polysulfide compound obtained in Example 1 after aging;

[0040] Figure 8 Differential scanning calorimetry (DSC) curves of the branched polysulfide compound obtained in Example 1 before and after aging;

[0041] Figure 9 The above are comparative liquid chromatograms of the extracts from vulcanized rubber samples of Example 1, Comparative Example 1, and Comparative Example 2 after aging in hot air at 100°C for 336 hours. Detailed Implementation

[0042] The following examples are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, all raw materials used are industrial grade or analytical grade reagents; the amounts of each component are by weight.

[0043] In this embodiment, PETMP represents pentaerythritol tetra(3-mercaptopropionic acid) ester, TMPMP represents trimethylolpropane tri(3-mercaptopropionic acid) ester, DLTDP represents dilaurylate thiodipropionate, EVM represents ethylene-vinyl acetate rubber, and 6PPD represents N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine.

[0044] The thiol conversion rate was determined by iodometric titration to identify the residual thiol content in the reaction product, and calculated based on the molar amount of thiol added before the reaction and the molar amount of residual thiol after the reaction. The residual monoalkenyl compound content was determined by gas chromatography, with the corresponding monoalkenyl compound used as an external standard for quantification. The oxidation ratio of thioether groups was determined by S 2p high-resolution X-ray photoelectron spectroscopy, and calculated as the percentage of the sum of the peak areas of sulfoxide and sulfone sulfur to the total peak area of ​​sulfur elements after peak fitting. The thermal transition temperature was determined by differential scanning calorimetry, with the temperature increased from 20℃ to 90℃ at a rate of 10℃ / min under a nitrogen atmosphere. The peak temperature of the main endothermic peak was taken as the thermal transition temperature. All tests were performed in triplicate, and the average value was taken.

[0045] The formula for the thiol conversion rate is shown below:

[0046]

[0047] Where n0 is the molar amount of thiol added before the reaction; n1 is the molar amount of residual thiol in the reaction product.

[0048] The formula for the oxidation ratio of thioether groups is shown below:

[0049]

[0050] Among them, A 硫醚 A 亚砜 and A 砜 These represent the fitted peak areas of the S 2p region corresponding to the chemical state of sulfur.

[0051] The 6PPD masterbatch was prepared according to the formula shown in Table 1. The EVM used contained 50% vinyl acetate by mass, and the Mooney viscosity ML(1+4) at 100°C was 20. The processing oil was naphthenic oil.

[0052] Table 1. 6PPD masterbatch formulations for Examples 1-3 and Comparative Examples 1-3

[0053]

[0054] 1. Preparation of branched polysulfide compounds

[0055] Preparation Example 1: Branched polysulfide compound A

[0056] 100.0 g of PETMP, 139.2 g of 1-dodecene, and 1.2 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to a photochemical reactor equipped with a stirrer and a nitrogen protection device. The system was heated to 40 °C and nitrogen was purged for 20 min. The reaction was stirred for 4 h under 365 nm ultraviolet light irradiation. After the reaction was completed, the system was subjected to reduced pressure treatment at 90 °C and 1.5 kPa for 1 h to remove residual 1-dodecene, yielding a four-armed C12 branched polysulfide compound A.

[0057] like Figure 1 As shown, the main structure of branched polysulfide compound A is C[CH2OC(O)CH2CH2SC]. 12 H 25 ]4, the molecular formula is C 65 H 124 O8S4 yielded a light yellow waxy substance with a yield of 98.2%.

[0058] Take a small amount of the obtained branched polysulfide compound and use deuterated chloroform as a solvent to perform... 1 H NMR spectroscopy, with chemical shifts based on tetramethylsilane, yielded the following results: Figure 5 As shown.

[0059] like Figure 5 As shown, the obtained product exhibits characteristic signals of methylene groups adjacent to the ester group near δ 4.1 ppm, characteristic signals of methylene groups on both sides of the thioether group and methylene groups adjacent to the carbonyl group in the δ range of 2.5-2.8 ppm, and characteristic signals of methylene groups in long-chain alkyl groups and terminal methyl groups in the δ ranges of 1.2-1.4 ppm and 0.8-0.9 ppm, respectively. 1 The H NMR spectrum is consistent with the expected branched polysulfide structure.

[0060] The prepared branched polysulfide compound was used as the sample before aging; another branched polysulfide compound from the same batch was aged in an air atmosphere at 100℃ for 72h, and then cooled to room temperature as the sample after aging. X-ray photoelectron spectroscopy was performed on the sample before and after aging, respectively. Monochromatic Al Kα rays were used as the excitation source, and high-resolution S 2p spectra were collected. Charge correction was performed using the binding energy of the C 1s peak of 284.8eV.

[0061] Background subtraction and peak fitting were performed on the S 2p high-resolution spectra of the aged samples to determine the fitted peak areas of sulfide sulfur, sulfone sulfur and sulfone sulfur respectively, and the oxidation ratio of sulfide groups was calculated according to the percentage of the sum of the peak areas of sulfone sulfur and sulfone sulfur to the total fitted peak area of ​​sulfur elements.

[0062] Test results are as follows Figure 6 and Figure 7 As shown, by Figure 6 It can be seen that the S 2p signal of the sample before aging is mainly concentrated in the binding energy region corresponding to the thioether state sulfur; the signal of the sample after aging is enhanced in the higher binding energy region, indicating that some thioether groups are transformed into sulfur-containing groups with higher oxidation state during the aging process.

[0063] Peak fitting was performed on the S 2p high-resolution spectrum of the aged sample, and the results are as follows: Figure 7 As shown, the S 2p spectrum of the aged sample can be decomposed into signals corresponding to thioether sulfur, sulfoxide sulfur, and sulfone sulfur.

[0064] The obtained branched polysulfide compounds were taken as samples before aging and samples after aging, respectively. The samples after aging were obtained by aging the branched polysulfide compounds in air at 100°C for 72 hours. Differential scanning calorimetry (DSC) was performed on the samples before and after aging, respectively. The test was carried out in a nitrogen atmosphere, with the temperature increased from 20°C to 90°C at a rate of 10°C / min. The heat flow changes during the heating process were recorded, and the peak temperature of the main endothermic peak was taken as the main endothermic peak temperature of DSC.

[0065] Test results are as follows Figure 8 As shown, compared with the sample before aging, the main endothermic peak of the sample after aging shifts towards higher temperatures, indicating that the thermal transformation behavior of branched polysulfide compounds changes after air aging.

[0066] Preparation Example 2: Branched polysulfide compound B

[0067] 100.0 g of TMPMP, 127.8 g of 1-dodecene and 1.1 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to the reactor, and photoinitiation and depressurization removal were carried out according to the method of Preparation Example 1 to obtain three-armed C12 branched polysulfide compound B.

[0068] like Figure 2 As shown, the main structure of branched polysulfide compound B is C2H5C[CH2OC(O)CH2CH2SC]. 12 H 25 ]3, the molecular formula is C 51 H 98 O6S3 yielded a light yellow, viscous, waxy substance with a yield of 97.6%.

[0069] Preparation Example 3: Branched polysulfide compound C

[0070] 100.0 g of PETMP, 208.6 g of 1-octadecene, and 1.5 g of 2-hydroxy-2-methyl-1-phenylpropanone were added to the reactor. The system was maintained at 55 °C, and nitrogen gas was purged for 20 min. The reaction was then stirred for 5 h under 365 nm ultraviolet light. After the reaction was completed, the system was subjected to reduced pressure treatment at 105 °C and 1.0 kPa for 1.5 h to obtain the four-armed C18 branched polysulfide compound C.

[0071] like Figure 3 As shown, the main structure of branched polysulfide compound C is C[CH2OC(O)CH2CH2SC]. 18 H 37 ]4, the molecular formula is C 89 H 172 O8S4 yielded a pale yellow solid wax with a yield of 96.8%.

[0072] Preparation Example 4: Branched polysulfide compound D

[0073] The branched polysulfide compound A obtained in Preparation Example 1 was dissolved in dichloromethane. At 0-5°C, a solution of m-chloroperoxybenzoic acid was added dropwise at a rate of 0.8 mol equivalent of the sulfide group. After the addition was completed, the temperature was raised to 25°C and reacted for 3 hours. The mixture was washed successively with sodium bisulfite aqueous solution and deionized water, and the solvent was removed under reduced pressure to obtain a pre-oxidized branched polysulfide compound D. X-ray photoelectron spectroscopy showed that the proportion of sulfoxide and sulfone sulfur in the total sulfur was 74.1%. This retainer was used to evaluate the effect of pre-forming a static polar phase.

[0074] 2. Basic properties of branched polysulfide compounds

[0075] Branched polysulfide compound AC was treated in air at 100℃ for 72h. The main endothermic peak temperature, sulfide oxidation ratio and mass retention rate of DSC before and after treatment were tested. The results are shown in Table 2.

[0076] Table 2. Basic properties of branched polysulfide compounds

[0077]

[0078] 3. Preparation of Masterbatch

[0079] First, 6PPD and the corresponding branched polysulfide compound were premixed at 60°C for 10 min. In Example 3, the premixing temperature was 75°C. EVM was added to a mixer and plasticized at 70°C and 60 r / min for 2 min. The premix and naphthenic oil were added, and mixing continued for 5 min, controlling the discharge temperature not to exceed 95°C. After discharge, the mixture was extruded through a twin-screw extruder and pelletized to obtain masterbatch with a particle size of 2-4 mm. In Comparative Example 1, no branched polysulfide compound was added. In Comparative Example 2, an equal amount of DLTDP was used to replace the branched polysulfide compound. In Comparative Example 3, an equal amount of pre-oxidized branched polysulfide compound D was used to replace branched polysulfide compound A.

[0080] Experimental Example 1

[0081] The masterbatches from Examples 1-3 and Comparative Examples 1-3 were added to natural rubber / styrene-butadiene rubber blends, respectively. The basic formulation, by weight, included 50 parts of natural rubber, 50 parts of styrene-butadiene rubber, 45 parts of carbon black N330, 5 parts of naphthenic oil, 3 parts of zinc oxide, 2 parts of stearic acid, 1.5 parts of sulfur, and 1.2 parts of accelerator CBS. The amount of each masterbatch added was 3.64 parts, so that the actual amount of 6PPD added was 2.0 parts.

[0082] The rubber compound was prepared using a two-stage mixing process and vulcanized at 160℃ according to the positive vulcanization time. The vulcanized samples were divided into an unaged group and a hot air aged group. The unaged group was not subjected to hot air aging, and its aging time was recorded as 0h. The hot air aged group was placed in a 100℃ hot air aging chamber and aged for 168h and 336h respectively.

[0083] After reaching the appropriate aging time, the sample was cut into small pieces of about 2 mm square. 1.0 g of the sample was weighed and 20 mL of 20% (v / v) ethanol aqueous solution was added. The sample was extracted by shaking at 40 °C for 24 h. After extraction, the extract was filtered, and 6PPD, 6PPD-quinone, and identifiable 6PPD derivatives were determined by liquid chromatography-mass spectrometry. Quantification was performed using a 6PPD standard curve. The identifiable 6PPD derivatives were converted into 6PPD equivalents, and the sum of the contents of 6PPD, 6PPD-quinone, and the derivatives was recorded as the total extractable content of 6PPD.

[0084] Each group of experiments had three parallel samples. The test results are expressed as mean ± standard deviation. The test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 3. The total extractable content of Examples 1 and Comparative Examples 1-3 at different aging times was plotted as curves, and the results are as follows. Figure 4 As shown.

[0085] To further compare the extraction of 6PPD and its conversion products after aging of different samples, vulcanized rubber samples from Example 1, Comparative Example 1, and Comparative Example 2, aged at 100℃ for 336 hours, were selected. Extracts were prepared according to the above method, and detected under the same liquid chromatography-tandem mass spectrometry (LC-MS / MS) conditions. All samples used the same sample mass, extract volume, dilution factor, and injection volume. The resulting chromatographic curves used the same vertical axis response ratio and were equidistantly shifted along the vertical axis. This shifting was only used to distinguish the chromatographic curves of different samples and did not change the retention time, peak area, or relative response relationship between different samples. The test results are as follows: Figure 9 As shown.

[0086] Table 3 Extractability of 6PPD-derived target compounds after aging

[0087]

[0088] As shown in Table 3, compared with Comparative Example 1 which does not contain branched polysulfide compounds, Examples 1-3 showed lower total extractables in the initial state and after aging, and reduced the extraction amount of the representative conversion product 6PPD-quinone. Although Comparative Example 2 added conventional linear sulfides, its total extractables after aging were still higher than those of the Examples. Comparative Example 3 had a certain retention effect in the initial stage, but it lacked a continuous transition from a low polarity state to a high polarity state during aging, and its long-term test results differed from those of the Examples. The results of Example 1 were better than those of Examples 2 and 3, indicating that the degree of branching and the length of the hydrophobic chain affect the initial compatibility, oxidation response rate, and the motion state of the retained phase after oxidation. The four-armed C12 structure showed a more suitable balance in this experimental formulation.

[0089] like Figure 4 As shown, as the aging time increased from 0 h to 336 h, the total extractable content of each group of vulcanized rubber samples showed an increasing trend. Under the same aging time, the total extractable content of Example 1 was lower than that of Comparative Examples 1-3, indicating that the masterbatch containing branched polysulfide compounds is beneficial to reducing the extractable amount of 6PPD and its aging conversion products.

[0090] like Figure 9 As shown, under the same sample mass, extraction conditions, and detection conditions, the response of the chromatographic peak corresponding to the main target analyte in the extract of Example 1 was lower than that of Comparative Example 1 and Comparative Example 2. This trend is consistent with Table 3 and Figure 4 The quantitative results shown are consistent.

[0091] Experimental Example 2

[0092] The sample from Example 1, aged for 336 h, was cryosectioned. X-ray photoelectron spectroscopy was used to determine the apparent proportions of subsulfonate sulfur and sulfone sulfur in the internal regions relative to total sulfur. The total extractable amount of the target compound from the 6 PPD source in the same sample was also tested. The results are shown in Table 4. Since the rubber compound also contains sulfur, accelerator CBS, and its vulcanization reaction products, the apparent proportions are only used for relative comparisons between examples under the same basic formulation and testing conditions, and are not used to absolutely attribute the source of each sulfur-containing component. The results are shown in Table 4.

[0093] Table 4. Correspondence between apparent high-oxidized sulfur ratio and total extractable amount of target compounds from 6PPD.

[0094]

[0095] As shown in Table 4, all three examples showed an increase in the apparent high-oxidized sulfur ratio after aging. However, there was no simple monotonic correspondence between this ratio and the total extractable amount of the target compound from 6 PPD: Example 2 had the highest apparent high-oxidized sulfur ratio, but its total extractable amount was not the lowest; Example 1 had a moderate apparent high-oxidized sulfur ratio, but obtained the lowest total extractable amount. Combined with the DSC main endothermic peak temperatures of different branched polysulfide compounds in Table 2, it can be seen that the long-term low migration effect of the present invention does not depend solely on the sulfide content or oxidation degree, but is related to the combined effect of branching structure, hydrophobic chain length, and thermal transformation behavior.

[0096] Experimental Example 3

[0097] The vulcanization characteristics of rubber compounds were determined according to GB / T 9869.3-2025 "Determination of vulcanization properties of rubber by vulcanizer - Part 3: Rotorless vulcanizer", and the tensile properties of vulcanized rubber were determined according to GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". After the samples were aged in hot air at 100℃ for 168h, the tensile strength retention rate and elongation at break retention rate were calculated. The results are shown in Table 5.

[0098] Table 5 Vulcanization and Mechanical Properties

[0099]

[0100] The positive vulcanization time and unaged mechanical properties of the examples and comparative examples are similar, indicating that the branched polysulfide compounds do not significantly interfere with the vulcanization of the rubber compound at the stated addition amount; the mechanical properties of the examples after aging have a high retention rate, which is consistent with their low additive loss.

[0101] Experiment Example 4

[0102] To investigate the applicability of this invention to different types of organic rubber additives, the 6PPD in Example 1 was replaced with an equal amount of 2,2′-methylenebis(4-methyl-6-tert-butylphenol) to prepare a hindered phenol antioxidant masterbatch. A control masterbatch without branched polysulfide compounds and supplemented with EVM was also prepared. The two masterbatches were added to the EPDM rubber formulation to make the actual amount of hindered phenol antioxidant added 2.0 parts, and aged in hot air at 125°C for 168 hours. The total extractable amount of hindered phenol masterbatch and its derivatives was calculated based on the peak area of ​​liquid chromatography according to the extraction steps of Example 1.

[0103] Table 6 Extractability of hindered phenolic antioxidant systems

[0104]

[0105] A decreasing trend in total extractable amount was also observed after aging in the hindered phenol antioxidant system, indicating that the role of the branched polysulfide compounds is not limited to aromatic amine antioxidants. Different additives have different compatibility with the rubber matrix, and in actual use, the degree of branching, alkyl chain length and the amount of branched polysulfide compounds can be adjusted to match the properties.

[0106] 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 low-migration rubber additive masterbatch, characterized in that, By weight, it comprises: 50-75 parts organic rubber additives, 12-30 parts polymer carrier, 5-20 parts branched polysulfide compound, and 0.1-5 parts processing aids, wherein the branched polysulfide compound is a reaction product formed by the addition of a polythiol compound to a terminal monoolefin via a thiol-olefin reaction, and the fully added product of the reaction product has the structure shown in Formula I and / or Formula II: C2H5C[CH2OC(O)CH2CH2SR]3 (Equation I) C[CH2OC(O)CH2CH2SR]4 (Equation II) In Formula I and Formula II, R is a C12-C18 straight-chain or branched alkyl group.

2. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The organic rubber additive is selected from one or more of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, polymeric 2,2,4-trimethyl-1,2-dihydroquinoline, and 2,2′-methylenebis(4-methyl-6-tert-butylphenol).

3. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The polymer carrier is selected from one or more of ethylene-vinyl acetate rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, nitrile rubber, and ethylene-vinyl acetate copolymer.

4. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The terminal monoalkenyl compound is selected from one or more of 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

5. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The branched polysulfide compound has a mercapto conversion rate of not less than 97% and an unreacted terminal monoolefin mass fraction of not more than 0.5%.

6. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The polythiol compound is selected from one or both of trimethylolpropane tris(3-mercaptopropionic acid) ester and pentaerythritol tetra(3-mercaptopropionic acid) ester.

7. The low-migration rubber additive masterbatch according to claim 1, characterized in that: The processing aid is selected from one or more of naphthenic oil, paraffin oil, fatty acids, and fatty acid esters.

8. A method for preparing a low-migration rubber additive masterbatch as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: A polythiol compound and a terminal monoalkenyl compound are mixed at a molar ratio of thiol to carbon-carbon double bond of 1:(0.98-1.05). Thiol-alkene addition is carried out in the presence of a free radical initiator. After the reaction is completed, the compound is subjected to vacuum devolatilization at 60-140℃ and 0.1-5kPa to obtain a branched polysulfide compound. S2: Premix the organic rubber additive with the branched polysulfide compound obtained in step S1 at 40-80℃ for 5-30 min to obtain a premix; S3: After plasticizing the polymer carrier, add the premix and processing aids obtained in step S2, mix at 60-100℃ for 3-20 minutes, then extrude, cool and pelletize to obtain low migration rubber additive masterbatch.

9. The method for preparing a low-migration rubber additive masterbatch according to claim 8, characterized in that: In step S1, the free radical initiator is a photoinitiator or a thermal initiator.

10. The method for preparing a low-migration rubber additive masterbatch according to claim 9, characterized in that: The photoinitiator is selected from one or both of 2-hydroxy-2-methyl-1-phenyl-1-propanone and 2,2-dimethoxy-2-phenylacetophenone, and the thermal initiator is selected from one or both of azobisisobutyronitrile and benzoyl peroxide.

11. The method for preparing a low-migration rubber additive masterbatch according to claim 9, characterized in that: When the free radical initiator is a photoinitiator, the reaction temperature is 25-45℃, the irradiation wavelength is 320-405nm, and the reaction time is 2-6h. When the free radical initiator is a thermal initiator, the reaction temperature is 55-90℃, and the reaction time is 3-8h.

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