Novel rubber cross-linking agent and preparation method thereof

Abstract

The invention relates to a novel sulfur-olefin adduct, which has more excellent mixing performance in rubber as a rubber cross-linking agent and can provide a vulcanized rubber composite material with more excellent dynamic physical properties. The present invention also relates to a process for preparing a novel sulfur-olefin adduct comprising reacting sulfur with an olefin compound in the presence of a catalyst.

Description

Technical Field

[0001] This invention relates to rubber crosslinking agents, particularly novel sulfur-olefin adducts used as crosslinking agents in the manufacture of natural and / or synthetic rubber products. The invention also relates to a novel sulfur-olefin adduct prepared by a specific catalytically controlled polymerization method comprising reacting sulfur with an olefin to form a sulfur-olefin adduct, which exhibits excellent properties and product morphology as a crosslinking agent. Specifically, the invention relates to a catalytically controlled reverse vulcanization method of sulfur, resulting in a sulfur-olefin adduct exhibiting better physical properties in terms of thermal stability and product morphology, and, when introduced into rubber, showing better performance in terms of rapid dispersion in rubber, anti-blooming properties, dynamic physical properties, and other vulcanization characteristics. Background Technology

[0002] Vulcanization is a process that uses sulfur to form a three-dimensional rubber network through chemical cross-linking between the linear macromolecules of natural or synthetic rubber and the sulfur vulcanizing agent, thereby increasing the elasticity of the rubber and enabling rubber products to be used practically.

[0003] Effective vulcanization methods require the addition of a relatively large amount of sulfur. However, high-sulfur rubber can exhibit an undesirable phenomenon of sulfur migration from the bulk to its surface, commonly known as "blooming." Sulfur tends to bloom on the rubber surface when its concentration exceeds its maximum solubility in rubber at storage temperatures. This results in reduced tackiness of the rubber compound surface and can negatively impact the tire-forming process, as rubber compound tackiness plays a crucial role.

[0004] In the rubber industry, two types of sulfur are commonly used: elemental sulfur with an S8 ring structure (rubber-soluble) and polymeric sulfur (rubber-insoluble) with long-chain polysulfide macromolecules called insoluble sulfur. Developing insoluble sulfur is crucial to overcoming blooming in rubber processing, a critical issue in the tire manufacturing industry. Insoluble sulfur is typically prepared by rapidly quenching molten sulfur at ambient temperatures above 159°C (preferably >250°C) or by vaporizing sulfur in a carbon disulfide (CS2) solvent at >600°C. Methods for preparing polymeric sulfur (insoluble sulfur) are generally unattractive due to the energy-intensive processes and the safety hazards posed by the high flammability of CS2. Therefore, current manufacturing processes present not only technical and engineering challenges but also significant safety concerns due to the extremely high flammability of CS2. Insoluble sulfur products primarily consist of long-chain sulfur molecules and a smaller amount of soluble S8 rings.

[0005] Insoluble sulfur is a better vulcanizing agent than rhombic sulfur (conventional rubber-grade sulfur), but it cannot completely solve the blooming problem. If exposed to high curing temperatures, long storage times, etc., the long-chain molecules of insoluble sulfur tend to revert to a more stable soluble form. Before or after insoluble sulfur is incorporated into the rubber composition, it partially reverts to soluble sulfur, leading to blooming because the solubility of soluble sulfur in the rubber exceeds saturation levels at a given temperature. Furthermore, if processed at excessively high temperatures, the rubber composition is prone to scorching.

[0006] Therefore, a crosslinking agent is needed that is easy to prepare industrially and easy to handle when added to mixing equipment for compounding. Banbury internal mixers, two-roll mills, and similar equipment also offer reduced blooming and better physical and curing properties in rubber composites, making them highly favored in the rubber industry.

[0007] Numerous existing technical documents teach the use of copolymers of sulfur with non-conjugated dienes, which are believed to enhance compatibility with rubber. This polymer structure is also thought to improve the stability of sulfur chains against decomposition into soluble S8 units at normal storage and processing temperatures, while simultaneously allowing for easy release of sulfur for crosslinking at vulcanization temperatures.

[0008] US 2989513A teaches a method for preparing a vulcanizing agent, which involves heating sulfur and olefins in a near 1:1 weight ratio at a temperature of 145-180°C to obtain a viscous liquid.

[0009] US 3259598 discloses a method for preparing a vulcanizing agent, comprising heating sulfur, linseed oil, and styrene at a temperature of 128-135°C for 5-50 hours to obtain a brittle copolymer that must be pulverized before use in rubber. Similarly, US 3264239A discloses a copolymer prepared by heating sulfur, linseed oil, and dicyclopentadiene (DCPD) as described above.

[0010] US 3523926 discloses a sulfiding agent obtained by reacting a diene such as cyclopentadiene and dicyclopentadiene with sulfur at 140°C, using an amine as a catalyst; however, the product is separated from the reactants by dissolving the product in CS2 and evaporating the CS2.

[0011] US 4902775 and US 4739036 disclose a vulcanizing agent prepared by heating 1-50 parts by weight of sulfur and 1 part by weight of one or more olefins in an aqueous reaction medium in the presence of an alkali and a dispersant at a temperature of 120-200°C with stirring. Products in bead morphology of various sizes are obtained.

[0012] WO1999048966A1 highlights the disadvantages of the product obtained by the method described in US 4739036, which is unsuitable for introduction into rubber compounds due to the relatively large particle size of the product, and describes the process equipment for obtaining a product with a specific particle size distribution, wherein 90 wt% of the composition particles are no larger than 20 micrometers.

[0013] US6747122B2 describes a method for preparing polysulfide from polythiocyclopentanediyl at 140°C and 70 bar in the presence of an amine as a catalyst and H2S.

[0014] Recently, numerous studies have involved a method called “reverse vulcanization” (i.e., polymerizing sulfur by adding a small amount of olefin, as opposed to adding a small amount of sulfur to unsaturated rubber in conventional vulcanization to obtain vulcanized rubber). This term was described by Pyun & Chung in “Nature Chemistry, 2013 DOI: 10.1038 / NCHEM.1624” as a method for preparing chemically stable and processable polymeric materials by direct copolymerization of elemental sulfur with ethylene monomers, and the production of polymers containing sulfur atom chains, where sulfur atoms are bridged together with small dienes / olefins or longer organic molecules.

[0015] Jakub Wr czycki et al. published a conference paper (2018) in... The International Scientific-Technical Conference (APGIP-9) described sulfur / organic copolymers as curing agents for rubber and the application of such products as vulcanizing agents in rubber. However, these products are synthesized by bulk polymerization without any solvent and are obtained in the form of hard solids, which are difficult to separate from the reactor, thus posing a problem for scaling up the method to an industrial scale.

[0016] In a study by Ronaldo P. Parreño Jr. et al., presented at IOP Conf 2020, Ser.: Mater. Sci. Eng. 778 012023, entitled “Sulfur copolymers (S-DIB) from inversevulcanization of elemental sulfur (S8) for polymer blend,” they found that the evolution of the sulfur copolymer structure involved branching to hyperbranching as the comonomer DIB (diisopropylbenzene) increased. For S-DIB with a high sulfur content (90 wt%), the copolymer structure consisted of longer polysulfide rings, while a higher DIB proportion (20-50 wt%) produced copolymers with a hyperbranched structure.

[0017] Reverse vulcanization is a relatively new trend and is still under extensive investigation to provide a detailed understanding of its mechanisms, as highlighted by the Hassel group in “NATURE COMMUNICATIONS | (2019) 10:64”. Most existing discussions describe reverse vulcanization as a bulk radical copolymerization of unsaturated comonomers with liquid sulfur, proposing that sulfur diradicals add to the olefin double bond while partially removing α-hydrogen and generating H2S.

[0018] A review of prior art disclosures (patents and recent references) regarding the preparation of sulfur-olefin adducts reveals that the reaction products of sulfur and one or more olefins yield viscous liquids or hard solids that adhere to the reactor and are difficult to handle even on a laboratory scale, posing even greater challenges on an industrial scale. Furthermore, due to the physical properties and morphology of sulfur-olefin adducts, the products from this reaction mixture must be pulverized before they can be incorporated into rubber elastomers. Additionally, sulfur-olefin adducts prepared by earlier methods are typically difficult to disperse in the rubber matrix during compounding. These are the drawbacks faced by the aforementioned methods when scaling up to a commercial scale.

[0019] To economically produce the large quantities of vulcanizable rubber compositions required in the tire and rubber specialty industries, automated methods and systems for the transport / delivery of sulfur and other components, along with strict time scheduling, are crucial for the mixing and other operations used in the preparation of vulcanizable rubber compositions. To adhere to these time schedules, the component materials of the vulcanizable composition must meet certain stringent standards regarding the speed and ease of transport / delivery, as well as uniform integration into the rubber compound. Currently, it is difficult to add powdered common sulfur or insoluble sulfur to internal mixing units because they are difficult to flow into the mixing equipment. Furthermore, powdered sulfur (rubber-grade and insoluble sulfur) adheres to the mixing equipment, causing further problems in the mixing of the compound.

[0020] In some cases, particulate polymer-bound sulfur is used, which is expensive and requires higher dosage levels to compensate for the polymer content.

[0021] The inventors of this invention have surprisingly discovered that the aforementioned disadvantages and problems can be overcome by this invention, which provides a novel sulfur-olefin adduct comprising sulfur and polymerized sulfur. This novel sulfur-olefin adduct is obtained by catalytically suspending the polymerization of sulfur and olefin in water under stirring conditions in the presence of an alkali and a dispersant at 160°C-170°C, and by adding a catalyst in a small dosage range to control the sulfur polymerization and maintaining it at the desired temperature for 1-24 hours to obtain a free-flowing powder / particle product of the sulfur-olefin adduct and a mixture of sulfur. This product is easily introduced into rubber and has relatively little leakage in a twin-roll mill type mixing system.

[0022] Purpose of the invention The object of this invention is to provide novel sulfur-olefin adducts that can be used as crosslinking agents in the compounding of natural and / or synthetic rubbers for the manufacture of rubber products.

[0023] Another object of the present invention is to provide novel sulfur-olefin adducts that exhibit better physical properties in terms of thermal stability and product morphology, are more easily introduced into rubber with less leakage during mixing in a two-roll mill, and exhibit comparable or better performance in terms of dispersibility, blooming, dynamic physical properties and other vulcanization characteristics compared to soluble sulfur.

[0024] Another object of the present invention is to provide a rubber crosslinking agent, such as a sulfur-olefin adduct, in an easily usable product form, i.e., tablets or granules. Its softening or melting point is much lower than the melting temperature of elemental sulfur, so that it can be incorporated into rubber at a much lower temperature than when elemental sulfur is used.

[0025] Another object of the present invention is to provide novel sulfur-olefin adducts for use in rubber formulations, wherein the sulfur-olefin adducts are used directly or loaded onto a suitable support such as carbon black, silica, etc.

[0026] Another object of the present invention is to provide a rubber crosslinking agent, such as a sulfur-olefin adduct, to prevent the tendency of rubber composites to char before vulcanization, and also to obtain the advantage of mixing at relatively low temperatures in conventional mixing equipment.

[0027] Another object of the present invention is to provide a rubber crosslinking agent that has anti-blooming properties compared to sulfur.

[0028] Another object of the present invention is to provide a novel catalytically controlled polymerization method comprising reacting sulfur with olefins to form sulfur-olefin adducts, which, as crosslinking agents, exhibit excellent properties and product morphology.

[0029] Another object of the present invention is to provide an efficient and industrial-scale method for producing sulfur-olefin adducts, most likely in the form of sulfur-olefin copolymers / terpolymers, which can be used as novel crosslinking agents for unsaturated rubbers / elastomers and are economically attractive. Summary of the Invention

[0030] According to one aspect of the invention, a sulfur-olefin adduct is provided, wherein the adduct comprises sulfur and polymeric sulfur in a ratio of 1.5:1 to 9:1, the sulfur-olefin adduct being completely soluble in carbon disulfide, wherein, by DSC characterization, the sulfur adduct has an onset melting point of about 90°C to about 100°C and a final melting temperature below 110°C.

[0031] According to another aspect of the present invention, the present invention provides a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts, wherein sulfur is reacted with aliphatic olefins and / or aromatic olefins or mixtures of olefins in a stirred reactor system in the presence of water, alkali, dispersant and catalyst to obtain sulfur-olefin adducts, wherein at the start of the reaction, the weight ratio of sulfur to olefins is from 5:1 to 9.5:0.5, and the weight ratio of water to the mixture of sulfur and olefins is from 1.5:1 to 10:1.

[0032] According to another aspect of the present invention, the present invention provides a catalytically controlled reverse sulfurization method, comprising heating and stirring sulfur and an olefin or olefin mixture in an alkaline aqueous solution reaction medium at a temperature above 100°C in the presence of a dispersant, and adding an optimal dose of catalyst to control the polymerization of sulfur to form a sulfur-olefin adduct.

[0033] According to another aspect of the present invention, the present invention provides a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts, wherein the method includes the following steps; a. Sulfur is added to an olefin or olefin mixture in the presence of water, alkali, dispersant and catalyst in a stirred reactor system; b. Heat the reaction mixture to 120°C to 200°C with stirring for at least 2 hours; c. Cooling and separating the sulfur-olefin adduct in powder / particulate form; d. Optionally, wash the powder / particle product with a suitable solvent to remove impurities; e. Optional drying of the product; f. Optionally, tablets may be formed by compression or granulation using suitable equipment.

[0034] According to another aspect of the invention, the present invention provides a free-flowing powder / particle form of a sulfur-olefin adduct, which is readily introduced into the rubber vulcanization process to form vulcanized articles for use in the tire and non-tire industries.

[0035] According to another aspect of the present invention, a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts in powder / particulate form as crosslinking agents for rubber is provided, comprising the following steps: a. Reaction of sulfur, olefins or mixtures of olefins, water, alkali, dispersant and catalyst in a suitable stirred reactor system, under reaction conditions such that a powder / particle form of polymeric sulfur and a mixture of sulfur is produced that is easily separable from the reactor, wherein at the start of the reaction, the weight ratio of sulfur to olefins or mixtures of olefins is 5:1 to 9:1, and the weight ratio of water to sulfur plus olefins or mixtures of olefins is 2:1 to 10:1. b. Heat the reaction mixture to 150°C to 180°C with stirring for 4-6 hours to form a powder / particle crosslinking agent; c. Cooling and separation of sulfur-olefin adducts in powder / particulate form by filtration; d. Optionally wash the powder / granular product with water to remove impurities; e. Dried products; f. Forming tablets by compression or granulation using suitable equipment; g. Use the obtained product in rubber formulations for various rubber products. Detailed Implementation

[0036] At temperatures above 159°C, molten sulfur (S8 monomer) undergoes ring-opening polymerization (ROP), resulting in the formation of linear sulfur diradicals. These diradicals polymerize into two forms of sulfur: insoluble and soluble sulfur, the composition of which depends on the reaction temperature, time, and cooling conditions. Compared to soluble sulfur, insoluble sulfur is insoluble in carbon disulfide (CS2) or toluene solvents, and therefore can be separated from soluble sulfur by solvent extraction.

[0037] The production of insoluble sulfur involves hazardous operations, including high temperatures (250°C to 650°C) and the handling of large quantities of flammable and dangerous carbon disulfide. The method is energy-intensive and involves numerous safety concerns requiring a high level of process control and automation, thus increasing production costs.

[0038] According to some embodiments, the present invention provides a sulfur-olefin adduct, wherein the adduct comprises sulfur and polymeric sulfur in a ratio of 1.5:1 to 9:1, the sulfur-olefin adduct being completely soluble in carbon disulfide, wherein, by DSC characterization, the sulfur adduct has an onset melting point of about 90°C to about 100°C and a final melting temperature below 110°C.

[0039] According to other embodiments, the present invention provides a simple, novel and safe method for manufacturing sulfur-olefin adducts that exhibit good physical properties in terms of thermal stability and product morphology, and when incorporated into rubber, exhibits comparable or better properties than insoluble sulfur, blooming, dynamic physical properties and other curing properties, and can be effectively used as a crosslinking agent in the natural and synthetic rubber industries and is economically attractive.

[0040] According to other embodiments, the present invention provides a rubber crosslinking agent, such as a sulfur-olefin adduct, having an easy-to-use product form, i.e., a rubber crosslinking agent form. The powder, tablet, or granules have a softening point or melting point much lower than the melting temperature of elemental sulfur, allowing them to be incorporated into rubber at much lower temperatures than when using elemental sulfur alone, preventing the rubber compound from scorching prior to vulcanization, and also providing the advantage of mixing at relatively low temperatures in conventional mixing equipment.

[0041] According to some other embodiments, the present invention provides a rubber crosslinking agent that has anti-frost whitening properties compared with rubber-grade sulfur.

[0042] According to other embodiments, the present invention provides a novel catalytically controlled polymerization method comprising reacting sulfur with olefins to form sulfur-olefin adducts, which have excellent properties as crosslinking agents and product morphologies.

[0043] According to other embodiments of the invention, a sulfur / olefin reaction product is obtained by suspension polymerization, yielding a sulfur-olefin adduct composition containing a mixture of polymeric macromolecules and free soluble sulfur. This composition is found to be thermally stable and provides properties similar to insoluble sulfur during rubber processing. Furthermore, it is surprisingly found that the product is completely soluble in CS2. However, the toluene solubility of the product varies with the initial sulfur and olefin composition and the polymerization reaction time, with the soluble component accounting for 25% to 99% of the total weight, unlike insoluble sulfur which is insoluble in both CS2 and toluene.

[0044] Therefore, the product obtained by the method according to the present invention, having a polymeric sulfur component (soluble in CS2 and soluble in toluene to varying degrees), differs from the polymeric form of insoluble sulfur used in rubber vulcanization. The toluene-soluble component of the product of the present invention most likely exists in the form of a mixture of oligomeric sulfur-olefin copolymers and amorphous supercooled liquid sulfur, and does not exhibit blooming tendency except that it exists in a soluble form.

[0045] US 4902775 discloses a sulfur-olefin adduct containing about 39% to about 46% by weight of free elemental sulfur, expressed in terms of blooming and 300% modulus, which is suitable for use as a crosslinking agent. In contrast, the novel sulfur-olefin adduct of the present invention, although containing more than 60% sulfur, more preferably 70-85% by weight, as analyzed by HPLC, exhibits better blooming and modulus.

[0046] According to some other embodiments, the rubber crosslinking agent provided by the present invention is in an easy-to-use product form, i.e., the form of a rubber crosslinking agent. The powder, tablet, or granules have a softening point or melting point much lower than the melting temperature of elemental sulfur, allowing them to be incorporated into rubber at much lower temperatures than when elemental sulfur is used, thus preventing the rubber compound from scorching before vulcanization, and also providing the advantage of mixing at relatively low temperatures in conventional mixing equipment.

[0047] According to yet another embodiment, the rubber crosslinking agent provided by the present invention has anti-frost whitening properties compared to ordinary sulfur.

[0048] According to some other embodiments, the present invention provides an efficient and industrially scalable method for producing sulfur-olefin adducts that can be used as novel crosslinking agents for unsaturated rubbers and are economically attractive.

[0049] According to some other embodiments, the present invention provides a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts, which involves reacting sulfur with aliphatic olefins and / or aromatic olefins or mixtures of olefins in a stirred reactor system in the presence of water, alkali, dispersant and catalyst to obtain sulfur-olefin adducts, wherein at the start of the reaction, the weight ratio of sulfur to olefins is from 5:1 to 9.5:0.5, and the weight ratio of water to the mixture of sulfur and olefins is from 1.5:1 to 10:1.

[0050] According to other embodiments, novel compositions of sulfur-olefin adducts are prepared in an intermittent or continuous manner by a catalytically controlled reverse sulfurization method, the method comprising the steps of heating and stirring sulfur and an olefin or olefin mixture in an alkaline aqueous reaction medium at a temperature above 100°C in the presence of a dispersant, and adding an optimal dose of catalyst to control the polymerization of sulfur to form sulfur-olefin adducts.

[0051] According to some other embodiments, the present invention provides a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts, wherein the method includes the following steps; a. Sulfur is added to an olefin or olefin mixture in the presence of water, alkali, dispersant and catalyst in a stirred reactor system; b. Heat the reaction mixture to 120°C to 200°C with stirring for at least 2 hours; c. Cooling and separating the sulfur-olefin adduct in powder / particulate form; d. Optionally, wash the powder / particle product with a suitable solvent to remove impurities; e. Optional drying of the product; f. Optionally, tablets may be formed by compression or granulation using suitable equipment.

[0052] According to some other embodiments, the present invention provides an industrially economical suspension polymerization method in which sulfur is reacted with an olefin or a mixture of olefins in an aqueous suspension of alkali and a dispersant, in the presence of a catalyst catalyzing the copolymerization of sulfur and olefins, at a temperature of 120°C to 200°C, preferably 160°C to 180°C, more preferably 160°C to 170°C, and held for 1-24 hours, more preferably 3-8 hours, and most preferably 5-6 hours before cooling.

[0053] According to other embodiments, the present invention provides a novel sulfur-olefin adduct, which is obtained by suspension polymerization of sulfur and olefins under stirred conditions, in water, in the presence of an alkali and a dispersant, at 160°C to 170°C, with the addition of a small amount of catalyst to control sulfur polymerization, to obtain a product comprising soluble sulfur and a polymerized sulfur-olefin adduct as a free-flowing powder / particle. These remarkable properties are achieved by a catalytic suspension polymerization method for sulfur-olefin adducts.

[0054] Water, along with a dispersant and an alkali, is used as a medium in which sulfur can melt and react with olefins at a given time, under autogenous pressure and with effective mixing and the addition of an optimal amount of catalyst, at higher temperatures >159°C. When the reaction mixture is cooled, sulfur-olefin adducts in small particulate or powder form are obtained and can be separated by filtration. Water acts as a heat dissipation medium for any exothermic reaction, and the alkali can neutralize any acidic components, i.e., H₂S, formed in the process. Catalysis is controlled to copolymerize to obtain free-flowing polymer materials in powder / particulate form. Therefore, this invention provides a novel catalytically controlled polymerization method for preparing novel sulfur-olefin adducts, which can be readily scaled up to industrial production scale.

[0055] According to another aspect of the present invention, the present invention provides a catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts in powder / particulate form as crosslinking agents for rubber, comprising the following process steps: a. React sulfur, olefins or mixtures of olefins, water, alkali, dispersant and catalyst in a suitable stirred reactor system, the reaction conditions being such that at the end of the reaction, a powder / particle form of polymeric sulfur and a mixture of sulfur is produced that is easily separable from the reactor, wherein at the beginning of the reaction, the weight ratio of sulfur to olefins or mixtures of olefins is 5:1 to 9:1, and the weight ratio of water to sulfur plus olefins or mixtures of olefins is 2:1 to 10:1. b. Heat the reaction mixture to 150°C to 180°C with stirring for 4-6 hours to form a powder / particle crosslinking agent; c. Cooling and separation of sulfur-olefin adducts in powder / particulate form by filtration; d. Optionally, wash the powder / particle product with water to remove the impurities; e. Dried products; f. Forming tablets by compression or granulation using suitable equipment; g. Use the obtained product in rubber formulations for various rubber products.

[0056] According to other embodiments of the present invention, HPLC analysis shows that the sulfur-olefin adduct contains >60% by weight of sulfur.

[0057] More specifically, in this invention, by DSC characterization, the melting point of the sulfur-olefin adduct measured at a heating rate of 0.5 °C / min is between 90 °C and 100 °C.

[0058] Furthermore, when measured at 150°C, the viscosity of the sulfur-olefin adduct obtained by the present invention is higher than that of sulfur. The viscosity of sulfur measured at 150°C is about 8 to 9 cP (centipoise), and the viscosity of the sulfur-olefin adduct of the present invention at 150°C is about 35 to about 45 cP.

[0059] Further Fourier transform infrared (FTIR) spectroscopy studies showed that, using diffuse reflectance technology on powder samples, the sulfur-olefin adducts obtained in this invention exhibited high performance at 1500-2000 cm⁻¹. -1 The region exhibits a distinct infrared band, unlike sulfur or the product obtained according to the method of Example 18 of US4902775.

[0060] More specifically, in this invention, the dropping point of the sulfur-olefin adduct is lower than that of sulfur and the product obtained by Example 18 of US4902775, which is closest to the prior art.

[0061] The distinguishing features of the sulfur-olefin adduct of the present invention compared to the product obtained in Example 18 of US 4902775 and compared to sulfur are described in Table I below: Table I: Comparative Study of the Sulfur-Olefin Adducts of the Present Invention with Sulfur and Sulfur-Olefin Adducts from the Prior Art (US4902775, Example 18)

[0062] According to other specific embodiments of the present invention, a sulfur-olefin adduct containing about 25% to about 98% by weight of a toluene-soluble component is further disclosed, which is prepared according to a method comprising the following steps: i) In an autoclave, under autogenous pressure and with effective stirring, an aqueous suspension containing sulfur and at least one olefin or a mixture of olefins (preferably two different olefins), an alkali, a dispersant, and an optimal amount of catalyst is heated to a temperature of 120°C to about 200°C, preferably 160-180°C, and more preferably 160-170°C, wherein the aqueous suspension is heated for a time sufficient to form the sulfur-olefin adduct in powder / particle form; and ii) Separate the sulfur-olefin adduct in powder / particulate form by filtration, followed by washing with water and drying; and iii) Optionally, tablets or granules of the resulting solid sulfur-olefin adduct are prepared by melting and pressing in a suitable tableting or granulating apparatus.

[0063] The products of this invention have been found to be stable during long-term storage and heating to -105°C. Therefore, products containing polymeric sulfur-olefin adducts in the form of sulfur-olefin copolymers / terpolymers and amorphous soluble sulfur exhibit stable properties compared to insoluble sulfur (which reverts to normal soluble sulfur upon heating). Thus, in rubber processing, particularly in tire manufacturing, they offer significant advantages over both soluble and insoluble sulfur. Adding ethylene monomers to molten sulfur as a crosslinking agent allows the formation of crosslinked chains with stable structures.

[0064] In other embodiments, a tablet or granular product made by melting and / or granulating powder is disclosed to obtain a uniform product form for final application in rubber compounding and to be easily handled in mixing equipment.

[0065] The novel reverse-vulcanized sulfur-olefin adducts produced according to the present invention comprise sulfur and sulfur polymers. Specific olefin compounds that can be used in the present invention include, but are not limited to, aliphatic and aromatic olefins, such as isobutylene, isopentenene, diisobutylene, triisobutylene; cycloalkenes, such as cyclopentene and cyclohexene; unsaturated terpenes, such as pinene, dipentene, camphene, and myrcene; aromatic olefins, such as styrene, dihydronaphthalene, indene, α-methylstyrene; and polyolefins, such as butadiene, isoprene, chloroprene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, vinylcyclohexene, 1,7-octadiene, cyclooctadiene, etc. Preferred olefin compounds are styrene, α-methylstyrene, cyclopentadiene, and dicyclopentadiene, with a particularly preferred combination of styrene and dicyclopentadiene.

[0066] The olefin reactants used are not limited to the specific olefin reactants mentioned above, but other olefin reactants that form compounds, polymers or copolymers with sulfur, which are commonly used by those skilled in the art, can also be used to form equivalent non-blooming crosslinking agents.

[0067] When using more than one olefin, the weight ratio between the olefins can be varied widely depending on the desired properties of the specific olefin and sulfur-olefin adduct.

[0068] According to some preferred embodiments, the weight ratio of styrene to dicyclopentadiene (DCPD) can be from about 1:1 to about 5:1. In a particularly preferred embodiment, the weight ratio of styrene to DCPD is from about 5:1 to about 1:5, more preferably 9:1, and most preferably 4:1. The weight ratio of the olefin used, such as styrene, to DCPD is related to the properties of the dispersion of the sulfur-olefin curing agent in the rubber. Higher amounts of DCPD have been found to produce adducts that are difficult to disperse in the rubber matrix.

[0069] According to some embodiments, the preferred ratio of water to sulfur is such that the resulting product can be freely stirred and suspended as a slurry in the aqueous reactants, with a slurry concentration of approximately 10-40% (weight / weight), more preferably 15-25% (weight / weight). The weight ratio of water to sulfur can be approximately 2:1 to 10:1, preferably 2:1 to 8:1, and most preferably 2:1 to 6:1. According to some implementations, the preferred ratio of sulfur to olefin reactants is to maximize the available sulfur while exhibiting good dispersion characteristics, and to have just enough olefin reactants to prevent blooming.

[0070] According to other embodiments, the proportion of sulfur in the sulfur-olefin mixture is from about 80% to about 95% by weight, preferably from about 85% to 90% by weight, and most preferably 90% by weight, to obtain the best performance, dispersion, tensile properties, etc. relative to the rubber, and the proportion of unsaturated olefin reactants is from about 5% to about 15% by weight relative to sulfur, more preferably 10% by weight of sulfur, to obtain cost and performance advantages.

[0071] According to another embodiment, the base used for the reaction of sulfur-olefin adducts includes, but is not limited to, calcium carbonate (CaCO3), sodium carbonate, zinc carbonate, sodium hydroxide, and organic amines (e.g., triethylamine (TEA)). CaCO3 is the most preferred base because it is inexpensive and readily available. According to other embodiments, the weight ratio of base to sulfur can be from 1:10 to 1:25. The amount of base used should maintain the pH of the reactants between 7 and 10, more preferably between 8 and 9.

[0072] According to other embodiments, the catalyst used for "controlled reverse sulfidation" in this invention is derived from a class of compounds, such as, but not limited to, metal salts of dialkyl dithiocarbamates, preferably zinc diethyl dithiocarbamate (ZDC), thiuram disulfide (preferably TMTD), and mixtures thereof.

[0073] According to some other embodiments, the optimal dosage of the catalyst relative to the total feed of sulfur-added olefins is 1-5000 ppm, preferably 500-5000 ppm, and most preferably 1000-3000 ppm. The very low and very high dosages of the catalyst result in the product being difficult to separate from the reactor system because it forms large clumps, but surprisingly, it exhibits performance comparable to powder / granular products in rubber.

[0074] According to other embodiments, the dispersants used in the sulfur-olefin copolymerization method include, but are not limited to, polyethylene oxide, fatty alcohol polyoxyethylene ether, polysorbate, carboxymethyl cellulose, polyvinyl alcohol, and mixtures thereof. The amount of dispersant used is 0.1% to 10% by weight of the sulfur used in the method.

[0075] According to some other embodiments, the sulfur-olefin adduct used as the crosslinking agent of the present invention is prepared at a temperature of 120°C to 200°C, preferably 140°C to 170°C, and most preferably the reaction is carried out at at least 160°C to 165°C. At temperatures below 145°C, the separated particulate products agglomerate and form lumpy substances. Since the reaction takes place above the boiling point of water, the reaction must be carried out in a pressure reactor system.

[0076] According to other embodiments, the present invention provides a method in which the mother liquor is recycled in a manner that makes the method more economical after appropriate treatment. Studies have found that after multiple recycling cycles, the mother liquor can be reused by adding only a small amount of dispersant before discharge, a fact easily determined by those skilled in the art.

[0077] According to other embodiments, the present invention discloses optimal ratios of sulfur and olefins, such as styrene and DCPD, reaction temperature, and time, which provide sulfur-olefin adducts and optionally recycle the mother liquor, making the method economically attractive for industrial-scale production. As other embodiments of the method, it can be carried out in a batch or continuous manner, by appropriately optimizing the process parameters in a manner readily apparent to those skilled in the art.

[0078] According to other embodiments, the novel sulfur-olefin adduct of the present invention is used in rubber formulations, wherein the sulfur-olefin adduct can be used directly or loaded onto a suitable support such as carbon black, silica, etc.

[0079] Vulcanized rubbers prepared from the sulfur-olefin adducts of the present invention can be used in non-tire rubber compounds, such as retreaded tires, conveyor belts, bicycle tires, hoses, molded and extruded products, and tire components, such as tire compounds, treads, tire sidewalls, steel belts and gussets, and steel wire coated compounds. Other products that can be used with the present invention include rollers, colored rubber products, and any stable elastomer that does not exhibit sulfur blooming and has better dispersibility in rubber than insoluble sulfur.

[0080] According to other embodiments, the vulcanization method using the product of the present invention includes preparing a masterbatch comprising rubber, carbon black, vulcanization activator, anti-degradation agent, and processing oil in a mixing process outside the production stage, such as a Banbury mixer or an open two-roll mill. Subsequently, a vulcanization system comprising polysulfide and a vulcanization accelerator is added to the masterbatch in a mixing process outside the production stage, such as a Banbury mixer or an open two-roll mill. After mixing, the uncured rubber composition is cured for 24 hours, and then vulcanized by heating at 140-180°C for 6 hours, more preferably 3 hours, for example by compression molding, transfer molding, and injection molding.

[0081] In other embodiments, after placing the sulfur-olefin adduct prepared according to the method of the present invention at 105°C for 8 hours, the rubber was evaluated compared with similar treatment of insoluble sulfur. The results showed that the product obtained according to the method of the present invention has better thermal and storage stability compared with insoluble sulfur. It was found that the product has better thermal stability compared with insoluble sulfur.

[0082] The present invention also relates to sulfur-olefin adducts, which, by DSC characterization, have a DSC melting point onset between 90°C and 100°C when measured at a DSC heating rate of 0.5°C / min. More preferably, the DSC melting point onset is between 97°C and 100°C when measured at a DSC heating rate of 0.5°C / min, and most preferably, the DSC melting point onset is between 98°C and 100°C when measured at a DSC heating rate of 0.5°C / min. An important aspect of the sulfur-olefin adducts of the present invention is that they have been unexpectedly found to have lower melting points relative to other forms of sulfur (rubber grade and insoluble), and are therefore considered particularly suitable for use as crosslinking agents for rubber.

[0083] In industrial practice involving the processing of rubber using insoluble sulfur, particularly in the tire industry, productivity, output, and processing speed are limited due to the need to control processing temperatures below 100°C to prevent the conversion of insoluble sulfur to soluble sulfur, and considering blooming and tack loss. Therefore, the sulfur-olefin adduct of the present invention is found to be more thermally stable, offering a significant advantage in maximizing productivity in rubber processing, thus proving economically beneficial.

[0084] Analysis method: Differential scanning calorimetry (DSC): The differential scanning calorimetry (DSC) used to measure the melting point onset and melting range of the sulfur-olefin adducts of this invention includes a first heating scan, thereby determining the melting peak temperature and the exothermic peak temperature. The instrument used was a Mettler-Toledo-DSC-1 Star. The method used is as follows. The instrument was calibrated according to the manufacturer's "User Manual". A similar method was used for the sulfur-olefin adduct sample. The aluminum pan and cap were balanced on a balance. Approximately 6.0–7.0 mg of the sulfur-olefin adduct was placed in the tare pan, covered with the tare cap, and pressed tightly using a sample capping device. An empty, pressed aluminum pan and cap were prepared in a similar manner as a reference. The sample pan and reference pan were placed in the DSC tray and sample cell at room temperature. The sample was heated from 50°C to 130°C at a rate of 0.5°C / min in the presence of nitrogen. The "DSC melting point onset" was defined as the temperature at which endothermic melting begins. Data analysis was performed using Mettler Staresoftware-DBV-15.00.

[0085] Droplets: The dropping point of the sulfur-olefin adduct was analyzed using a Mettler-Toledo DP-70 instrument equipped with a One-Click user interface. The sample was placed in the sample holder, which was then placed in the heater. The temperature was increased from 50°C to 130°C at a programmed rate of 2°C / min. The dropping point was recorded when the sample melted and the droplet slowly descended in the cell. The instrument automatically displayed the dropping point.

[0086] Fourier transform infrared (FTIR) spectroscopy: Sulfur-olefin adduct samples were analyzed using diffuse reflectance infrared Fourier transform spectroscopy with a Jasco FTIR 4600, and the spectra were compared with those of elemental sulfur. The adduct samples were pulverized and placed in sample cups, and a large amount of data was collected and recorded using Spectra-Manager software.

[0087] HPLC analysis of sulfur content: The sulfur-olefin adduct was dissolved in THF (25 mg in 25 mL THF), and 20 μL of sample was injected into an Agilent 1260 Infinity-II HPLC system mounted on a Waters Microbondapak C-18 column (10 μm / 3.9 × 300 mm). A PDA-UV detector was used for measurements at λ254 nm. Data analysis was performed using Agilent CDS-ChemState software.

[0088] The external standard method using sulfur as a standard was used for quantitative analysis. The sulfur content in the adduct was expressed as % w / w in the adduct sample taken by HPLC analysis.

[0089] Toluene solubility was determined by Soxhlet extraction, using 10 g of sample extracted in a Soxhlet apparatus for 24 hours. Solubility is expressed as weight / weight (w / w), i.e., the weight percentage of toluene soluble from the initial weight.

[0090] Solubility in CS2, measured at ambient temperature (-30°C), is determined by dissolving the sulfur-olefin adduct in CS2 until saturation and expressed as g / 100g CS2, i.e., the amount of adduct soluble in 100g CS2 solvent, in grams.

[0091] Viscosity was measured using a Brookfield Viscometer DV2 LT according to standard methods and expressed as centipoise (cP) at 150°C.

[0092] Rubber mixing methods: Rubber compounding is carried out according to known rubber compounding methods. A masterbatch of rubber, carbon black, stearic acid, zinc oxide, processing oil, and anti-degradation agent is mixed in an internal mixer (Banbury, dumping temperature 140-160°C). Subsequently, the sulfur-olefin adduct prepared according to the method of the present invention, the accelerator, and the masterbatch are mixed on a two-roll mill at 50-90°C and cured for 24 hours. The rubber compound is vulcanized by compression molding at 140°C, the compression molding time being equal to the optimal vulcanization time (t). 90- Rheometer diagram). After cooling, the vulcanized sheet was left to stand for 24 hours, and its properties were determined according to ASTM standard method D412.

[0093] The following examples illustrate certain embodiments of the present invention and are for illustrative purposes only. It should be understood that many changes can be made to the specifically disclosed ingredients, proportions, and conditions without departing from the spirit of the invention, and the scope of the invention is not limited.

[0094] Example: Comparative Examples 1-3 provide information on the bulk copolymerization of sulfur-olefins, while Comparative Example 4 describes a catalyst-free suspension polymerization as presented in the prior art.

[0095] Comparative Example 1: Reaction of DCPD with sulfur (S:DCPD weight ratio = 91:9) (Reference: Jakub Wr) czycki et al. in “Advance in Petroleum and Gas Industry and Petrochemistry” (APGIP-9)) 363.6 g of sulfur was placed in a 1000 ml flask equipped with a temperature controller, thermocouple sheath, and mechanical stirrer. The flask was purged with nitrogen, and the mixture was heated to 140 °C. Stirring was started when the sulfur melted. 36.4 g of DCPD was added to the molten sulfur at 140 °C. The reaction was exothermic, reaching 165 °C, and became too viscous to stir within 25–30 minutes. The product solidified at 165 °C and adhered to the impeller and thermocouple sheath, resembling concrete upon cooling. Removing the reaction product from the flask was very difficult.

[0096] Comparative Example 2: Reaction of DCPD and styrene with sulfur (S:DCPD:styrene weight ratio = 87:8.7:4.3) (Reference: Jakub Wr) czycki et al. in “Advance in Petroleum and Gas Industry andPetrochemistry” (APGIP-9)) Add 435 g of sulfur, 43.5 g of DCPD, and 21.5 g of styrene to a 1000 ml 4-necked flask equipped with a temperature controller, thermocouple sheath, and mechanical stirrer. Purge the flask with nitrogen and heat the mixture to 140 °C. Begin stirring when the sulfur melts. The reaction is exothermic, reaching 165 °C, and becomes very viscous within 25-30 minutes, making stirring impossible. Maintain the material at 140-150 °C for 3 hours. The product becomes rubbery and solidifies, adhering to the impeller and thermocouple sheath. Removing the reaction product from the flask is very difficult.

[0097] Comparative Example 3: Reaction of DCPD and styrene with sulfur in an autoclave (weight ratio of S:DCPD:styrene = 87:8.7:4.3) Add 435g sulfur, 43.5g DCPD, and 21.5g styrene to a 1L autoclave equipped with a temperature controller, thermocouple sheath, and mechanical stirrer. Heat the mixture to 160°C. Begin stirring at ~120°C (when the sulfur melts). The reaction is exothermic, reaching 165°C, and becomes very viscous within 25-30 minutes, making stirring impossible. Maintain the material at 160-170°C for 3 hours. The product becomes rubbery and solidifies, adhering to the impeller and thermocouple sheath. Removing the reaction product from the autoclave is very difficult.

[0098] Comparative Example 4: The reaction of DCPD and styrene with sulfur was carried out according to the prior art US 4902775 Ex-18 (List IV, 11) (weight ratio of S: DCPD: styrene = 85:13.5:1.5). In a 1-liter autoclave equipped with a stirrer, 500 g water, 4 g CaCO3, 6.4 g CMC, 85 g sulfur, 13.5 g DCPD, and 1.5 g styrene were added. The autoclave was sealed and heated to 160 °C with stirring. The mixture was maintained at 160 °C for 5 hours. It was then cooled and discharged with stirring. The powdered product was filtered, washed with water, and dried. The isolated sulfur-olefin product yield was ~90% (by weight) as a brown powder. Toluene solubility: 12% w / w (by Soxhlet extraction) and CS2 solubility: 38.8 g / 100 g CS2; sulfur content (HPLC determination ~41%): DSC: onset -96.9 °C, peak 99.02 °C, termination 101.72 °C.

[0099] This invention: Example 1: This example illustrates the optimization parameters required for this method. (S: weight ratio of styrene to DCPD = 90:8:2) In a 1 Lt autoclave equipped with a stirrer, add 700 g water, 5.6 g CaCO3, 8.9 g CMC (carboxymethyl cellulose) or 1.26 g fatty alcohol polyoxyethylene ether, 126 g sulfur (S), 11.2 g styrene, 2.8 g DCPD, and the required amount of catalyst. Seal the autoclave and heat to 160 °C with stirring. At 160 °C, the catalyst concentration is 5-7 kg / cm³. 2The product was kept under autogenous pressure for 3-6 hours. It was then cooled and discharged with stirring. The product was filtered, washed with water, and dried. The separation yield was 97.2% (wt), and the product was a brownish-yellow granular sulfur-olefin adduct. HPLC characterization showed that the sulfur-olefin adduct contained 76.8% (wt) sulfur. DSC showed a melting point onset of 93.5 °C, peaks at 102.1 and 106.6 °C, and a termination melting point of 109.3 °C, which is significantly different from the insoluble sulfur and sulfur (melting point onset 101.7 °C, peaks at 102 and 118 °C, termination at 118.4 °C). CS2 solubility: ~35.9 g / 100 g CS2 (completely dissolved).

[0100] The mother liquor from the previous batch can be reused up to three times after proper treatment, and the resulting product is similar to the product obtained in Example 1 above.

[0101] Example 2: Effect of catalyst loading on product formation and properties: This example illustrates the effect of the optimal catalyst concentration for processing batch reaction feedstock on the product separation powder / particle morphology. Batch production was conducted by varying the catalyst amount (ppm relative to the weight of S) between 0 ppm and 5000 ppm, while other feedstocks remained the same as described below.

[0102] In a 1-liter autoclave equipped with a stirrer, 700 g of water, 5.6 g of CaCO3, 8.9 g of CMC, 126 g of S, 11.2 g of styrene, 2.8 g of DCPD, and catalysts in varying amounts according to Table 1 were added. The autoclave was sealed and heated to 160 °C with stirring. The mixture was maintained at 160 °C for 3 hours. It was then cooled with stirring and discharged. The product was filtered, washed with water, and dried.

[0103] Table 1: Effect of catalyst loading

[0104] To properly discharge the reactants from the reactor and separate the reaction products, the optimal catalyst concentration was found to be greater than about 1000 ppm and less than 5000 ppm.

[0105] Example 3: Different sulfur to olefin ratios: Examples 3.1-3.6 illustrate the effects of varying the sulfur-to-olefin ratio on reactant discharge, product separation, and applications in rubber during a batch suspension polymerization reaction. The reaction was carried out in an autoclave batch process as described in Example 1, but the sulfur-to-olefin ratio was varied as shown in Table 2.

[0106] Table 2: Effect of sulfur-olefin ratio on product formation and separation

[0107] Example 4: This example illustrates the results of a pilot-scale reaction of this method. (S: styrene: DCPD = 90:8:2 by weight) Example 4-(A): In a 40-liter autoclave equipped with a stirrer, 24.5 liters of water, 350 g of CaCO3, 150 g of fatty alcohol polyoxyethylene ether, 8000 g of sulfur, 178.4 g of DCPD, 710.4 g of styrene, and the required amount of catalyst were added. The autoclave was sealed and heated to 160°C with stirring. The temperature was 6-7 kg / cm². 2 The mixture was kept at 160°C for 6 hours under autogenous pressure. It was then cooled and discharged with stirring. The product was filtered, washed with water, and dried. The separation yield was 98.5%, as a yellowish-brown powdery granular product.

[0108] The product showed ~98% toluene-soluble fraction (assessed by Soxhlet extraction with toluene); DSC showed melting at 94.8℃, with two peaks at 101.2 and 106.4℃, and melting terminated at 107.6℃, which is significantly different from insoluble sulfur and sulfur. CS2 solubility: 35.86 g / 100 g CS2, and sulfur content determined by HPLC was 78.5 w / w.

[0109] Example 4 (B): In a 40-liter autoclave equipped with a stirrer, 28 liters of water, 224 g of CaCO3, 100.8 g of fatty alcohol polyoxyethylene ether, 5040 g of sulfur, 112 g of DCPD, 448 g of styrene, and the required amount of catalyst were added. The autoclave was sealed and heated to 160°C with stirring. The catalyst concentration was 6-7 kg / cm³. 2 The mixture was kept at 160°C for 6 hours under its own pressure. It was then cooled and discharged with stirring. The product was filtered, washed with water, and dried. The separation yield was 98.5% (wt), as a yellowish-brown powdery granular product.

[0110] The product showed ~64-66% toluene-soluble fraction (assessed by Soxhlet extraction with toluene); DSC showed melting at 96.1℃ with two peaks at 102.3℃ and 107.3℃, terminating melting at 109.7℃, which is significantly different from insoluble sulfur and sulfur. CS2 solubility ~36.01 g / 100 g CS2, sulfur content: 78.4% w / w as determined by HPLC.

[0111] Example 5: Rubber Properties: The product obtained according to the optimal method of Example 4(A) was used together with Control-1 containing sulfur (S) and Control-2 containing insoluble sulfur to assess the product properties of natural rubber (NR) blends. Considering a 90% concentration of active sulfur, a blend using the product of Example-4(A) was prepared. The mixing and performance evaluation results in Table 3 are summarized in Table 4.

[0112] Table 3: Rubber Compound Components

[0113] Table 4: Performance Evaluation Data

[0114] As can be seen from Table 4, it is evident that the vulcanized rubber properties of the sulfur-olefin adduct of Example 4(A), particularly at 90% sulfur content, are comparable to or, in some cases, superior to, insoluble sulfur. Compared to insoluble sulfur, no blooming was observed in the unvulcanized samples containing the sulfur-olefin adduct from Example 4(A), even after 60 days of storage.

[0115] Example 6: Rubber Properties: Sulfur-olefin adduct products obtained from various combinations, i.e., sulfur-olefin adducts. Prior art (Comparative Example 4), Example 3.5 (higher DCPD ratio), and Control-1 containing sulfur (S) and Control-2 containing insoluble sulfur (IS). The compounding is shown in Table 5, and the performance evaluation results are shown in Table 6.

[0116] Table 5 details the rubber compounding of different sulfur-olefin adducts.

[0117]

[0118] Table 6: Performance Evaluation Results

[0119] As can be seen from Table 6 above, it is clear that the product with higher DCPD in the reaction leads to uneven product dispersion, and therefore does not exhibit the desired performance under all parameters.

[0120] Furthermore, compared to the product obtained by the present invention, the product from Comparative Example 4 (Goodyear US4902775) exhibits a relatively low modulus performance of 300%.

[0121] Example 7: Thermal and storage stability study.

[0122] To determine the thermal stability of the sulfur-olefin copolymer obtained by the present invention to insoluble sulfur, the material obtained from Example 4(A) was kept together with insoluble sulfur in an oven at 105°C for 8 hours (Table 7). After 8 hours, both were removed and cooled to room temperature. Both were evaluated in rubber according to ASTM methods (Table 8). The product prepared according to Example 4(A) was stored for 90 days, and the storage stability of the product of the present invention and its performance compared with insoluble sulfur were evaluated in rubber (Table 9). In addition, the DSC and CS2 solubilities were measured and compared with the material before heat treatment (Table 7).

[0123] Table 7: Comparison of thermal stability between Example 4(A) and insoluble sulfur

[0124] Table 8: Evaluation and comparison of Example 4(A) and insoluble sulfur before and after heating at 105°C for 8 hours.

[0125] Table 9: Storage Stability Studies

[0126] As can be clearly seen from Table 9 above, the product of the present invention is stable (90 days) and the dynamic physical properties of the rubber are comparable to those of the product obtained with insoluble sulfur.

[0127] Figure 1: Comparison of DSC studies of ordinary sulfur, sulfur-olefin adducts according to US4902775, and sulfur-olefin adducts of the present invention.

[0128] Figure II: Comparison of diffuse reflectance FTIR spectra of ordinary sulfur, sulfur-olefin adduct according to US4902775, and sulfur-olefin adduct of the present invention.

Claims

1. A sulfur-olefin adduct, wherein, The adduct comprises sulfur and polymeric sulfur in a ratio of 1.5:1 to 9:1, characterized in that the sulfur-olefin adduct is completely soluble in carbon disulfide, wherein, by DSC characterization, the onset of melting of the sulfur-olefin adduct is about 90°C to 100°C, and the final melting temperature is below 110°C.

2. The sulfur-olefin adduct according to claim 1, wherein, The polymerized sulfur is obtained by reacting sulfur with an olefin, wherein the weight ratio of reactant sulfur to olefin is from 5:1 to 9.5:0.

5.

3. The sulfur-olefin adduct according to claim 1, wherein, Depending on the process parameters and the molar ratio of the reactants, the solubility of the sulfur-olefin adduct in toluene is 25-99%.

4. The sulfur-olefin adduct according to claim 1, wherein, The olefin is selected from isobutylene, isopentenene, diisobutylene, triisobutylene; cycloolefins, such as cyclopentene and cyclohexene; unsaturated terpenes, such as dipentene, pinene, camphene, and myrcene; aromatic olefins, such as styrene, divinylbenzene, dihydronaphthalene, indene, and α-methylstyrene; and polyolefins, such as butadiene, isoprene, chloroprene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, vinylcyclohexene, 1,7-octadiene, cyclooctadiene, or mixtures thereof.

5. The sulfur-olefin adduct according to claim 1, wherein, The olefin compounds are selected from aromatic olefins of styrene and α-methylstyrene and aliphatic olefins selected from cyclopentadiene, dipentene and dicyclopentadiene or mixtures thereof.

6. The sulfur-olefin adduct according to claim 5, wherein, The weight ratio of the aromatic olefin to the aliphatic olefin is 1:1 to 10:1, preferably 1:1 to 4:

1.

7. The sulfur-olefin adduct according to claim 5, wherein, The aliphatic olefin is dicyclopentadiene, and the aromatic olefin is styrene.

8. A catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts, characterized in that, The method involves reacting sulfur with aliphatic olefins and / or aromatic olefins or mixtures of olefins in a stirred reactor system in the presence of water, alkali, dispersant and catalyst to obtain sulfur-olefin adducts, wherein at the start of the reaction, the weight ratio of sulfur to olefins is from 5:1 to 9.5:0.5, and the weight ratio of water to the mixture of sulfur and olefins is from 1.5:1 to 10:

1.

9. The catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts according to claim 8, wherein, The weight ratio of aromatic olefins to aliphatic olefins is 1:1 to 10:1, preferably 1:1 to 4:

1.

10. The catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts according to claim 8, wherein, This method Includes the following steps; a. Sulfur is added to an olefin or olefin mixture in the presence of water, alkali, dispersant and catalyst in a stirred reactor system; b. Heat the reaction mixture to 120°C to 200°C with stirring for at least 2 hours; c. Cooling and separating the sulfur-olefin adduct in powder / particulate form; d. Optionally, wash the powder / particle product with a suitable solvent to remove impurities; e. Optional drying of the product; f. Optionally, tablets may be formed by compression or granulation using suitable equipment.

11. The method according to claim 8, wherein, The alkali is selected from inorganic alkalis and organic alkalis, including alkali metal carbonates, alkaline earth metal carbonates, alkali metal hydroxides, tetraalkylammonium hydroxides, tertiary amines, primary amines, and secondary amines.

12. The method according to claim 11, wherein, The base is selected from calcium carbonate, sodium carbonate, sodium hydroxide, triethylamine and / or mixtures thereof.

13. The method according to claim 8, wherein, The dispersant is selected from fatty alcohol polyoxyethylene ether, carboxymethyl cellulose, polysorbate, anionic tristyrene phenol phosphate, or mixtures thereof.

14. The method according to claim 8, wherein, The catalyst is selected from metal salts of dialkyl dithiocarbamate, thiuram disulfide, or mixtures thereof.

15. The method according to claim 14, wherein, The amount of catalyst or catalyst mixture relative to sulfur is 500 ppm to 5000 ppm.

16. The method according to claim 8, wherein, The aqueous suspension is heated at a temperature of about 125°C to about 180°C for a reaction time of about 1-24 hours; more preferably 1-8 hours, and most preferably 5-6 hours.

17. The method according to claim 16, wherein, The aqueous suspension is heated at a temperature of approximately 150°C to 170°C for 5-6 hours.

18. The method according to claim 8, wherein, The mother liquor obtained after solid-liquid separation is then recycled to the main reaction of sulfur and olefins after optionally undergoing appropriate purification steps.

19. A catalytically controlled suspension polymerization method for preparing sulfur-olefin adducts in powder / particulate form as rubber crosslinking agents, characterized in that, This method includes the following process steps: (a) Reaction of sulfur, olefin or mixture of olefins, water, alkali, dispersant and catalyst in a suitable stirred reactor system, wherein the reaction conditions result in the final production of a powder / particle form of polymeric sulfur and a mixture of sulfur that is easily separable from the reactor, wherein at the start of the reaction, the weight ratio of sulfur to olefin or mixture of olefins is 5:1 to 9:1 and the weight ratio of water to sulfur plus olefin or mixture of olefins is 2:1 to 10:

1. (b) Heat the reaction mixture to 150°C to 180°C for 4-6 hours with stirring to form a powder / particle crosslinking agent; (c) Cooling and separating the sulfur-olefin adduct in powder / particulate form by filtration; (d) Optionally wash the powder / granular product with water to remove impurities; (e) Dried product; (f) Forming tablets by compression or granulation using suitable equipment; (g) Use the obtained product in rubber formulations for various rubber products.

20. The sulfur-olefin adduct according to claim 1, wherein, It is used in rubber formulations, where the sulfur-olefin adduct is used directly or loaded onto a carrier such as carbon black, silica, or a mixture thereof.

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