CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to US Provisional Application No. 63/349,428 filed June 6, 2022, the disclosure of which is incorporated herein by reference. FIELD

[0002] This application relates to a method for making sulfur copolymers from elemental sulfur and various comonomers in an extrusion process.

BACKGROUND

[0003] Sulfur copolymers are polymers produced from reacting elemental sulfur and one or more monomers. The production of sulfur copolymers is sometimes referred to as inverse vulcanization and produces a polymer with long linear chains of sulfur with interspersed monomer chains. Traditional sulfur vulcanized polymers are crosslinked whereby the sulfur chain is only one or two sulfur atoms long. Sulfur copolymers are characterized as having relatively high molecular weight, long chains of sulfur atoms, and high sulfur content. Sulfur copolymers have many applications such as in electrochemical cells, optics, as FUS donors, and antimicrobial materials. The sulfur copolymer can be a thermoplastic or a thermoset for use in elastomers, resins, lubricants, coatings, antioxidants, cathode materials for electrochemical cells, dental adhesives /restorations, and polymeric articles such as polymeric films and free-standing substrates.

[0004] Presently, sulfur copolymers are prepared by combining molten sulfur with monomers and catalyst in a batch reactor. The melt phase is then introduced into and cured in a mold. The melt phase reaction is extremely slow requiring batch times of greater than 30 minutes to accomplish full reaction due to inefficient mixing. Sulfur copolymers produced by melt phase reaction must be further purified to remove unreacted elemental sulfur. The requirement for melt phase reaction of solid feeds has limited the production of sulfur copolymers at larger scales.

SUMMARY

[0005] Disclosed herein is an example method of producing a sulfur copolymer comprising introducing at least elemental sulfur into a screw extruder; mixing the elemental sulfur and a reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer. [0006] Further disclosed herein is an example method of forming a sulfur copolymer comprising introducing elemental sulfur and a polymeric material into a screw extruder; depolymerizing at least a portion of the polymeric material in the screw extruder to from a reactive monomer; mixing the elemental sulfur and the reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer.

[0007] Further disclosed herein is an example method of forming a sulfur copolymer comprising introducing a rubber tire material, an unsaturated compound, a metathesis catalyst, and elemental sulfur into a screw extruder; reacting the rubber tire material with the unsaturated compound in the presence of the metathesis catalyst in the screw extruder to form a reactive monomer; mixing the elemental sulfur and the reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer.

[0008] These and other features and attributes of the disclosed method for making sulfur copolymers from elemental sulfur and various comonomers in an extrusion process of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

[0010] FIG. 1 is a gel permeation chromatogram of a polymer produced in accordance with certain embodiments of the present disclosure.

[0011] FIG. 2 is a gel permeation chromatogram of a polymer produced in accordance with certain embodiments of the present disclosure.

[0012] FIG. 3 is an X-ray diffractogram of a polymer produced in accordance with certain embodiments of the present disclosure.

[0013] FIG. 4 is a gel permeation chromatogram of a polymer produced in accordance with certain embodiments of the present disclosure.

[0014] FIG. 5 is a gel permeation chromatogram of a polymer produced in accordance with certain embodiments of the present disclosure.

[0015] FIG. 6 is an X-ray diffractogram of a polymer produced in accordance with certain embodiments of the present disclosure. DETAILED DESCRIPTION

[0016] Disclosed herein are methods of continuous production of sulfur copolymers, and, more particularly, disclosed are methods of producing sulfur copolymers using a reactive extruder. The methods generally include introducing elemental sulfur, a reactive monomer, and an optional a sulfur linking catalyst into a reactive extruder, mixing the elemental sulfur, reactive monomer, and sulfur linking catalyst in a mixing zone within the reactive extruder, reacting the sulfur and the reactive monomer in the presence of the sulfur linking catalyst, and extruding the sulfur copolymer. In embodiments, the reactive monomer is sources from a postconsumer polymer stream such as a post-consumer tires, water bottles, milk jugs, and the like. The reactive extruder typically includes a barrel, one or more screws disposed within the barrel, and a drive motor operable to turn the screws within the barrel. The screws typically include different zones for mixing and conveying material through the barrel, where the mixing zones are configured to shear and knead the material to promote thorough mixing. In further embodiments, the reactive extruder can include a die such that the sulfur copolymer can be formed into a desired shape. The present methods have several advantages over the melt phase methods for producing sulfur copolymers, including continuous production and flexibility of reactive monomer choice.

[0017] A mentioned above, the sulfur copolymer is produced from reaction of a reactive monomer with sulfur in the presence of a sulfur linking catalyst. While elemental sulfur can be polymerized, the resulting polymer is only stable at higher temperatures and will quickly depolymerize at standard temperature and pressure to more stable forms such as Ss. Under extrusion polymerization conditions within the reactive extruder, the sulfur ring undergoes an equilibrium ring-opening polymerization (ROP) of the Ss monomer into a linear polysulfidic chain of the form of (5" — (S) _n — 5") where n is a whole number typically between 1 and 6 and where 5' are radical chain ends. Reaction 1 shows the reversible ring opening of sulfur under heat to form polysulfidic chain

Reaction 1

[0018] Reaction 2 illustrates the formation of sulfur copolymer from the reaction of linear polysulfidic chain with a reactive monomer containing ethylenic unsaturation. Radical chain ends of the linear polysulfidic chain react with the ethylenic unsaturation to form a covalent bond thereby producing the sulfur copolymer. In embodiments a sulfur linking catalyst is provided which can lower reaction temperature, increase yield of reaction, and make sulfur copolymers with higher glass transition temperatures. Catalysts also allow relatively unreactive monomers such as ethylene glycol dimethacrylate to be utilized to produce sulfur copolymers.

Reaction 2

[0019] Reactive monomers suitable for forming sulfur copolymers include, without limitation, amines, thiols, sulfides, alkynyl unsaturated monomers, nitrones, aldehydes, ketones, thiiranes, ethylenically unsaturated monomers, epoxides, and combinations thereof.

[0020] In embodiments, the reactive monomer can be sourced from recovered streams or recycled streams. Sulfur compounds made with reactive monomers from recovered streams can be a cost-effective way to upgrade the reactive monomer from a relatively lower value material to a relatively higher value sulfur copolymer. The present process of extrusion polymerization does not require the reactive monomer to be isolated or purified prior to polymerization and is particularly suitable for processes whereby the reactive monomer in included as part of a larger bulk material where the reactive monomer is not readily recoverable on its own.

[0021] As discussed above the reactive monomer can be recovered from post-consumer polymer streams. Some suitable sources of reactive monomer containing materials may include, without limitation, un-hydrogenated polymer waxes such as polyethylene wax and polypropylene wax, steam cracker tar, unsaturated solid resin such as vinyl esters, unsaturated polyoctene, vinyl cyclobutane, styrene, unsaturated poly alpha olefins, and other unsaturated compounds. While not being limited by theory , any material which is reactive to sulfur under extrusion polymerization conditions can be utilized in the present process. In some embodiments, materials can be treated to increase the availability of the reactive monomer therein. For example, polyethylene can be thermally degraded under pyrolysis conditions to form polyethylene wax containing a mixture of alkanes, alkenes, and alkynes. [0022] In further embodiments, the reactive monomer can be produced in situ in the reactive extruder from depolymerization of a polymeric material. For example, a polymeric material which contains unsaturated bonds or is capable of reacting to form unsaturated bonds under extrusion polymerization conditions can be used as a source of reactive monomer. In some embodiments, a polymeric material may be at least partially depolymerized in the reactive extruder to form the reactive monomer. Depolymerization can be carried out in the reactive extruder using the heat and shear generated within the reactive extruder barrel which can at least partially thermally depolymerize some materials to form reactive monomers. Alternatively, or in addition to thermal depolymerization, depolymerization can be carried out with a catalyst to promote chain scission. Some materials which can be depolymerized to produce reactive monomers include, without limitation, natural and synthetic elastomers such as acrylic rubbers, butadiene rubbers, butyl rubbers, chlorosulfonated polyethylene, ethylene propylene diene monomer (EPDM), fluoroelastomers such as those based on vinylidene fluoride, isoprene rubber, nitrile rubber, perfluoroelastomer, polychloroprene, neoprene, polysulfide rubber, silicone rubber, styrene butadiene rubber, butadiene rubber, and combinations thereof. Further materials which can be depolymerized to produce reactive monomers include, without limitation, polyolefins such as polyethylene, polypropylene, polyisobutylene, polymethylpentene, and combinations thereof. In embodiments, some specific recovered materials which can be depolymerized in the present process include, without limitation, rubber tire materials such as tires, tire scraps, water bottles, garbage containers, milk bottles, oil bottles, water bottles, and the like. In embodiments, the polymeric materials are sourced from a post-consumer polymer stream.

[0023] There are several suitable chemical routes to depolymerize the polymeric material, only some of which are alluded to herein. One method to depolymerize the polymeric material includes olefin metathesis where an unsaturated compound such as an unsaturated wax is mixed with the polymeric matenal and a metathesis catalyst, and the mixture is introduced into the reactive extruder. The unsaturated compound reacts with the polymeric material in the presence of the metathesis catalyst through olefin metathesis reactions in the barrel of the reactive extruder to produce ethylenically unsaturated reactive monomers. For olefin metathesis reactions, heterogeneous catalysts such as organoaluminium, organotin, organomolybdenum, organotungsten, or organoruthenium, catalysts can be used. Some specific catalysts include Schrock and Grubbs catalysts such as Grubbs Catayst® 1 ^st and 2 ^nd generations, or the Hoveyda-Grubbs Catalyst ® and analogs thereof. In embodiments, the catalyst can include any of dichloro(3-phenyl-lH-inden-l- ylidene)bis(tricyclohexylphosphine)ruthenium(II), benzylidene- bis(tricyclohexylphosphine)dichloromthenium, dichloro[l,3-bis(2,4,6-trimethylphenyl)-2- imidazolidinylidene](3-phenyl-17/-inden-l-ylidene)(tricycloh exylphosphine)mthenium(II), benzylidene[l,3-bis(2,4,6-trimethylphenyl)-2- imidazolidinylidene]dichloro(tricyclohexylphosphine)rutheniu m, (l,3-Bis-(2,4,6- trimethylphenyl)-2-imidazolidinylidene)dichloro(o-isopropoxy phenylmethylene)mthenium, Dichloro[l,3-bis(2,6-isopropylphenyl)-2-imidazolidinylidene] (2- isopropoxyphenylmethylene)ruthenium(II), dichloro[l,3-bis(2,4,6-trimethylphenyl)-2- imidazolidinylidene][(2-isopropoxy)(5-trifluoroacetamido)ben zyhdene]ruthenium(II), and combinations thereof. In embodiments, depolymerization can be achieved without a catalyst by using heat and shear generated within an extruder.

[0024] As mentioned above, reactive monomers suitable for forming sulfur copolymers include, without limitation, amines, thiols, sulfides, alkynylly unsaturated monomers, nitrones, aldehydes, ketones, thiiranes, ethylenically unsaturated monomers, epoxides, and combinations thereof. Amine monomers are monomers that are polymerizable by amine groups. Suitable Amine monomers include, but are not limited to, m-phenylenediamine, and p-phenylenediamine, 1,3-phenylenediamine, and combinations thereof. Thiol monomers are monomers that are polymerizable by thiol groups. Suitable thiol monomers include, but are not limited to, 4,4'-thiobisbenzenethiol.

[0025] Alkynylly unsaturated monomers are monomers which are polymerizable through an alkynyl unsaturation. In one embodiment, aromatic alkynes, both internal and terminal alkynes, multi-functional alkynes may be used. Examples of alkynylly unsaturated monomers include, but are not limited to, ethynylbenzene, 1 -phenylpropyne, 1,2-diphenylethyne, 1 ,4-diethynylbenzene, l,4-bis(phenylethynyl)benzene, 1,4-diphenylbuta-l, 3-diyne, and combinations thereof.

[0026] Nitrone monomers are monomers that are polymerizable through a nitrone group. In one embodiment, nitrones, dinitrones, and multi -nitrones may be used. Examples of suitable nitrones include, but are not limited to, N-benzylidene-2-methylpropan-2-amine oxide.

[0027] Aldehyde monomers are monomers that are polymerizable through an aldehyde group. In one embodiment, aldehydes, dialdehydes, and multi-aldehydes may be used. Ketone monomers are monomers that are polymerizable through a ketone group. In one embodiment, ketones, dikitones, and multi-ketones may be used. Epoxide monomers are monomers that are polymerizable through an epoxide group(s). Non-limiting examples of such monomers include, generally, mono- or polyoxiranylbenzenes, mono- or polyglycidylbenzenes, mono- or polyglycidyloxybenzenes, mono- or polyoxiranyl(hetero)aromatic compounds, mono- or polyglycidyl(hetero)aromatic compounds, mono- or polyglycidyloxy(hetero)aromatic compounds, diglycidyl bisphenol A ethers, mono- or polyglycidyl(cyclo)alkyl ethers, mono- or polyepoxy(cyclo)alkane compounds, oxirane-terminated oligomers, and combinations thereof. In a particular embodiment, the epoxide monomers include benz l glycidyl ether and tris(4-hydroxyphenyl)methane triglycidyl ether. In certain embodiments, the epoxide monomers may include a (hetero)aromatic moiety such as, for example, a phenyl, a pyridine, a triazine, a pyrene, a naphthalene, or a polycyclic (hetero)aromatic ring system, bearing one or more epoxide groups. For example, in certain embodiments, the one or more epoxide monomers are selected from epoxy(hetero)aromatic compounds, such as styrene oxide and stilbene oxide and (hetero)aromatic glycidyl compounds, such as glycidyl phenyl ethers (e.g., resorcinol diglycidyl ether, glycidyl 2-methylphenyl ether), glycidylbenzenes (e.g., (2,3-epoxypropyl)benzene) and glycidyl heteroaromatic compounds (e.g., N-(2,3-epoxypropyl)phthalimide).

[0028] Thiirane monomers are monomers which are polymerizable through a thirane group(s). Non-limiting examples of thiirane monomers include, mono- or polythiiranylbenzenes, mono- or polythiiranylmethylbenzenes, mono- or polythiiranyl(hetero)aromatic compounds, mono- or polythiiranylmethyl(hetero)aromatic compounds, dithiiranylmethyl bisphenol A ethers, mono- or polydithiiranyl (cyclo)alkyl ethers, mono- or polyepisulfide(cyclo)alkane compounds, thiirane-terminated oligomers, and combinations thereof. In some embodiments, thiirane monomers may include a (hetero)aromatic moiety such as, for example, a phenyl, a pyridine, a triazine, a pyrene, a naphthalene, or a poly cyclic (hetero)aromatic ring system, bearing one or more thiirane groups.

[0029] Ethylenically unsaturated monomers are monomers that are polymerizable through an ethylenic unsaturation. Some suitable ethylenically unsaturated monomers include, without limitation, vinyl monomers, (meth)acryl monomers, unsaturated hydrocarbon monomers, and ethylenically -terminated oligomers. Examples of such monomers include, generally, mono- or polyvinylbenzenes, mono- or polyisopropenylbenzenes, mono- or polyvinyl(hetero)aromatic compounds, mono- or polyisopropenyl(hetero)aromatic compounds, alkylene di(meth)acrylates, bisphenol A di(meth)acrylates, benzyl (meth)aciylates, phenyl(meth)acrylates, heteroaryl (meth)acrylates, terpenes (e.g., squalene) and carotene. Ethylenically unsaturated monomers include a (hetero)aromatic moiety such as, for example, phenyl, pyridine, triazine, pyrene, naphthalene, or a polycyclic (hetero)aromatic ring system, bearing one or more vinylic, acrylic or methacrylic substituents. Examples of such monomers include benzyl (meth)acrylates, phenyl (meth)acrylates, divinylbenzenes (e.g., 1,3-divinylbenzene, 1,4-divinylbenzene), isopropenylbenzene, styremcs (e.g., styrene, 4-methylstyrene, 4-chlorostyrene, 2,6-dichlorostyrene, 4-vinylbenzyl chloride), diisopropenylbenzenes (e g., 1,3-diisopropenylbenzene), vinylpyridines (e.g., 2-vinylpyridine, 4-vinylpyridine), 2,4,6-tris((4-vinylbenzyl)thio)-l,3,5-triazine and divinylpyridines (e.g., 2,5-divinylpyridine). In certain embodiments, the one or more ethylenically unsaturated monomers (e.g., including an aromatic moiety) bears an amino (i.e., primary or secondary) group, a phosphine group or a thiol group One example of such a monomer is vinyldiphenylphosphine. Ethylenically unsaturated monomers can further include linear and branched chain diene and alkene hydrocarbons with carbon numbers from Cis to Cso and above. [0030] The elemental sulfur may be of any natural or synthetic allotrope or polymorph, including without limitation, Se, S7, Ss a-Sulfur, Ss P-Sulfur, Ss y-Sulfur, and combinations thereof. The sulfur can be provided in any suitable form such as a powder or be provided dissolved in a suitable liquid such as carbon disulfide. Under standard conditions (101.325 kPa and 25°C), elemental sulfur primarily exists in an eight-membered ring form (Ss) which has a melting point in a range of 120°C - 130°C. The sulfur ring undergoes an equilibrium ringopening polymerization (ROP) of the Ss monomer into a linear polysulfidic chain of the form of (5" — (S) _n — 5 ) where n is a whole number typically between 1 and 6 and where S' are radical chain ends. While Ss is generally the most available and least expensive feedstock, many other allotropes of sulfur can be used such as allotropes derivable by melt-thermal processing of Ss. Any sulfur species that yield diradical or anionic polymerizing species when heated as described herein can be used in the polymerizing extrusion process described herein. [0031] The sulfur and reactive monomer can be provided in any suitable ratio. For example, the sulfur and reactive monomer can be mixed in a weight ratio of 1 : 99 sulfur to reactive monomer to 50 : 50 sulfur to reactive monomer or, alternatively from 10 : 90 sulfur to reactive monomer to 40 : 60 sulfur to reactive monomer, from 20 : 60 sulfur to reactive monomer to 30 : 70 sulfur to reactive monomer, or any ranges therebetween.

[0032] The sulfur linking catalyst includes any catalyst capable of accelerating or promoting the formation of the linear polysulfidic chain and reactive monomer. Some suitable sulfur linking catalysts include, but are not limited to, metal dialkyldithiocarbamates, where the metal is zinc, iron, cobalt, copper, or nickel, such as zinc dimethyldithiocarbamate (Zn(DMDC)2, zinc diethyldithiocarbamate (Zn(DEDC)2), zinc di-/7-butyldithiocarbamate (Zn(DBDC)2) and zinc di-w-octyldithiocarbamale (Zn(DODC)2), thiuram zinc stearate, 2-cyano-2-propylbenzodithioate, hexamethylene tetramine. 1,3-diphenylguanidine, N,N'-diorthotolyl guanidine, 2-mercaptobenzothiazole, 2,2'-dithiobis(benzothiazole), zinc-2-mercaptobenzothiazole, zinc O,O-di-n-butylphosphorodithioate, N-cyclohexyl-2- benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfonemide, 2-(4-morpholinothio)- benzothiazole, N,N'-dicyclohexyl-2-benzothiazole sulfenamide, ethylene thiourea, di-pentamethylene thiourea, dibutyl thiourea, zinc-isopropyl xanthate, sodium isopropyl xanthate, potassium isopropyl xanthate, zinc ethyl xanthate, sodium ethyl xanthate, potassium ethyl xanthate, zinc methyl xanthate, sodium methyl xanthate, potassium methyl xanthate, and combinations thereof.

[0033] As discussed above, the method of producing a sulfur copolymer generally includes introducing elemental sulfur, a reactive monomer, and an optional sulfur linking catalyst into a reactive extruder. The elemental sulfur, a reactive monomer, and sulfur linking catalyst can be added to the reactive extruder in any order or at any point along the barrel of the reactive extruder. In some embodiments, the sulfur, reactive monomer, and sulfur linking catalyst are added all at once to the reactive extruder. In further embodiments, one or more of the elemental sulfur, reactive monomer, or sulfur linking catalyst are introduced into the reactive extruder separately. In some embodiments, one or more of the elemental sulfur, a reactive monomer, or sulfur linking catalyst are introduced into the reactive extruder at multiple locations in the barrel of the reactive extruder.

[0034] In embodiments where the reactive monomer is generated within the reactive extruder, such as in depolymerization of polymeric material embodiments, the polymeric material is introduced into the reactive extruder first, along with any other depolymerization compounds required such as depolymerization catalysts and unsaturated compounds as discussed above. The depolymerization reaction occurs in the barrel of the reactive extruder to produce reactive monomers, thereafter which sulfur and sulfur linking catalyst can be introduced separately or together into the barrel to be mixed with the reactive monomers. Alternatively, the polymeric material can be mixed with any of depolymerization catalysts, depolymerization compounds, sulfur linking catalyst, elemental sulfur, or combinations thereof.

[0035] The reactive extruder is operated extrusion polymerization conditions including a suitable pressure and temperature to form the linear polysulfidic chain as described above and to react the linear polysulfidic chain with the reactive monomer. In embodiments, the reactive extruder is operated at a pressure between 50 bar to 350 bar. Alternatively, at a pressure between 70 bar to 120 bar, 120 bar to 200 bar, 200 bar to 350 bar, or any ranges therebetween. In embodiments, the reactive extruder, either the barrel or a reaction zone, is operated at a temperature between 100°C to 300°C. Alternatively, at a temperature between 100°C to 150°C, at a temperature between 150°C to 200°C, at a temperature between 200°C to 250°C, at a temperature between 250°C to 300°C or any ranges therebetween. In some embodiments, the reactive extruder can be operated with differing temperatures at different points in the barrel. In embodiments, the reactive extruder can be operated with a residence time between 60 seconds to 5 minutes. Alternatively, a residence time between 1 minute to 2 minutes, between 2 minutes to 3 minutes, between 3 minutes to 5 minutes, or any ranges therebetween. [0036] As mentioned above, the reactive extruder can be any type of screw extruder such as single screw or double screw extruder. The reactive extruder can have any suitable L/D ratio such as between 20: 1 to 40: 1 or greater.

[0037] The compositional makeup of the sulfur copolymer is affected by the choice of reactive monomer used to make the sulfur copolymer. In embodiments where the reactive monomer is incorporated with other bulk materials, such when depolymerized tire scraps are used as the source of reactive monomer, the bulk materials can be incorporated into in the final sulfur copolymer product. In embodiments where sulfur and reactive monomer are the primary compounds, the resulting sulfur copolymer generally contains 10-99 wt. % of sulfur, and 5-50 wt % of reactive monomer. Alternatively, from 10-40 wt. % of sulfur, 40-60 wt. % of sulfur, 60-90 wt. % of sulfur, 90-99 wt. % of sulfur, or any ranges therebetween.

[0038] The sulfur copolymers can be synthesized to have any suitable weight average molecular weight (Mw), as measured by gel permeation chromatography (GPC) analysis, for example. For example, the sulfur copolymers can have a weight average molecular weight (Mw) of at least 10,000 g/mole. Alternatively, the sulfur copolymer can have a weight average molecular weight (Mw) between 10,000 g/mole to 100,000 g/mole, from 10,000 g/mole to 30,000 g/mole, 30,000 g/mole to 60,000 g/mole, or any ranges therebetween.

Additional Embodiments

[0039] Accordingly, the present disclosure may provide method for making sulfur copolymers from elemental sulfur and various comonomers in a continuous extrusion process. The methods/systems/compositions/tools may include any of the various features disclosed herein, including one or more of the following statements.

[0040] Embodiment 1. A method of producing a sulfur copolymer comprising: introducing at least elemental sulfur into a screw extruder; mixing the elemental sulfur and a reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer. [0041] Embodiment 2. The method of embodiment 1 further comprising introducing a sulfur linking catalyst into the screw extruder.

[0042] Embodiment 3. The method of embodiment 2 wherein the sulfur linking catalyst comprises a catalyst selected from the group consisting of zinc, iron, cobalt, copper, or nickel metal dialkyldithiocarbamates, tetramine, thiazole, thiophosphate, guanidine, mercaptobenzothiazole, thiourea, xanthate, sulfonamide, thiuram zinc stearate, 2-cyano-2- propylbenzodithioate, hexamethylene tetramine, 1,3-diphenylguanidine, N,N'-diorthotolyl guanidine, 2-mercaptobenzothi azole, 2,2'-dithiobis(benzothiazole), zinc-2- mercaptobenzothiazole, zinc O,O-di-n-butylphosphorodithioate, N-cyclohexyl-2- benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfonemide, 2-(4-morpholinothio)- benzothiazole, N,N'-dicyclohexyl-2-benzothiazole sulfenamide, ethylene thiourea, di-pentamethylene thiourea, dibutyl thiourea, zinc-isopropyl xanthate, sodium isopropyl xanthate, potassium isopropyl xanthate, zinc ethyl xanthate, sodium ethyl xanthate, potassium ethyl xanthate, zinc methyl xanthate, sodium methyl xanthate, potassium methyl xanthate, and combinations thereof.

[0043] Embodiment 4. The method of embodiment 1 wherein the reactive monomer comprises at least one reactive monomer selected from the group consisting of an amine, a thiol, a sulfide, an alkynyl unsaturated monomers, a nitrone, an aldehyde, a ketone, a thiirane, an ethylenically unsaturated monomer, an epoxide, and any combination thereof.

[0044] Embodiment 5. The method of embodiment 1 wherein the reactive monomer comprises at least one olefin containing compound selected from the group consisting of steam cracker tar, vinyl esters, unsaturated polyoctene, vinyl cyclobutane, styrene, unsaturated poly alpha olefins, and combinations thereof.

[0045] Embodiment 6. The method of embodiment 1 wherein the reactive monomer is derived from a post-consumer polymer comprising at least one post-consumer polymer selected from the group consisting of tires, tire scraps, water bottles, garbage containers, milk bottles, oil bottles, water bottles, and any combinations thereof.

[0046] Embodiment 7. The method of any of embodiments 1-6 wherein the screw extruder is operated at a pressure in a range of 50 bar to 350 bar and a temperature in a range of 100°C to 300°C.

[0047] Embodiment 8. The method of embodiments 1-7 wherein the sulfur copolymer comprises sulfur in an amount of about 10 wt. % to about 99 wt. %.

[0048] Embodiment 9. A method of forming a sulfur copolymer comprising: introducing elemental sulfur and a polymeric material into a screw extruder; depolymerizing at least a portion of the polymeric material in the screw extruder to from a reactive monomer; mixing the elemental sulfur and the reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer.

[0049] Embodiment 10. The method of embodiment 9 wherein the polymeric material comprises a material selected from the group consisting of acrylic rubbers, butadiene rubber, butyl rubbers, chlorosulfonated polyethylene, ethylene propylene diene monomer (EPDM), vinylidene fluoride, isoprene rubber, nitrile rubber, perfluoroelastomer, polychloroprene, neoprene, polysulfide rubber, silicone rubber, styrene butadiene rubber, polyolefins, and combinations thereof.

[0050] Embodiment 11. The method of embodiment 10 wherein the reactive monomer comprises at least one reactive monomer selected from the group consisting of amines, thiols, sulfides, alkynylly unsaturated monomers, nitrones, aldehydes, ketones, thiiranes, ethylenically unsaturated monomers, epoxides, and combinations thereof.

[0051] Embodiment 12. The method of embodiment 10 wherein the reactive monomer is derived from a post-consumer polymer comprising at least one post-consumer polymer selected from the group consisting of tires, tire scraps, water bottles, garbage containers, milk bottles, oil bottles, water bottles, and any combinations thereof.

[0052] Embodiment 13. The method of any of embodiments 9-12 further comprising introducing a depolymerization catalyst into the screw extruder.

[0053] Embodiment 14. The method of any of embodiments 9-13 wherein the screw extruder is operated at a pressure in a range of 50 bar to 350 bar and a temperature in a range of lO°C to 300°C.

[0054] Embodiment 15. The method of any of embodiments 9-14 wherein the sulfur copolymer comprises sulfur in an amount of about 10 wt. % to about 99 wt. %.

[0055] Embodiment 16. A method of forming a sulfur copolymer comprising: introducing a rubber tire material, an unsaturated compound, a metathesis catalyst, and elemental sulfur into a screw extruder; reacting the rubber tire material with the unsaturated compound in the presence of the metathesis catalyst in the screw extruder to form a reactive monomer; mixing the elemental sulfur and the reactive monomer in a mixing zone in the screw extruder; and reacting the elemental sulfur and the reactive monomer to form a sulfur copolymer comprising sulfur and the reactive monomer. [0056] Embodiment 17. The method of embodiment 16 wherein the metathesis catalyst comprises a heterogeneous catalyst selected from the group consisting of organoaluminium, organotin, organomolybdenum, organotungsten, organoruthenium, and combinations thereof. [0057] Embodiment 18. The method of any of embodiment 9 wherein the screw extruder is operated at a pressure in a range of 50 bar to 350 bar.

[0058] Embodiment 19. The method of any of embodiments 16-17 wherein the screw extruder is operated at a temperature in a range of 10°C to 300°C.

[0059] Embodiment 20. The method of any of embodiments 16-18 wherein the sulfur copolymer comprises sulfur in an amount of about 10 wt. % to about 99 wt. %.

[0060] To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the disclosure.

EXAMPLES

General Methodology

[0061] In these examples, sulfur copolymers were prepared from a low-density polyethylene wax in an extrusion polymerization process. The extruder used was an 11 mm co-rotating twin screw extruder with an L/D ratio of 40 sourced from Thermoscientific Inc. The extruder has eight heating zones as well as a die block. Further, the barrel is separable into two pieces such that the barrel can be split during the polymerization such that observations of the polymerization reaction can be tracked. The maximum extruder speed is 900 rpm and maximum pressure at the end of extruder is 90 bar. The extruder includes one solid feed and one liquid feed port with a throughput of 20 to 600 g/hr, depended on the material characteristics and extruder rpm. The screws include mixing elements and distributive elements which have different angles and thickness such that various mixing intensity levels can be achieved for different mixing sections. For each of the examples, the screws were configured with four mixing zones mixing zone 1, mixing zone 2, mixing zone 3, and mixing zone 4.

Polyethylene Wax Preparation and Characterization

[0062] Low density polyethylene was subjected to pyrolysis using a fluidized bed reactor to produce polyethylene wax. The polyethylene pyrolysis product is predominantly normal hydrocarbons with some minor non-normal hydrocarbon content. The normal hydrocarbons are a mixture of olefin (diene and alkene) and alkane hydrocarbons, which is commonly associated with pyrolysis of a polyethylene material. [0063] A gas chromatogram (GC) analysis of the polyethylene wax was performed. It was observed that the GC demonstrated a characteristic, repeating pattern of ‘triplet’ peaks that correspond to the presence of diene, alkene and alkane hydrocarbons. The GC confirmed that the polyethylene was produced from the pyrolysis process includes a mixture of paraffinic and olefinic hydrocarbons with both normal and non-normal structures and carbon numbers ranging from Cis and Cso+. Typically, Cis is commonly the lowest carbon number detected in paraffinic waxes, while the upper carbon number detected varies depending on the feed but typically ranges between C40 to Cso+. A gel permeation chromatography test of the polyethylene was indicated that the number average molecular weight was 538 daltons and weight average molecular weight was 685 daltons. Several further tests were performed including congealing point tests according to ASTM D938, auto drop melting point according to ASTM D3954, kinematic viscosity at 135°C according to ASTM D445, needle penetration at 25°C according to ASTM D1321, oil content test according to ASTM D721, solvent extractable according to ASTM D3235, and ASTM color test according to ASTM D6045. The results of all the tests are summarized in Table 1.

Table 1

Polyethylene Wax Polymer Synthesis

[0064] Polyethylene wax produced from pyrolysis was blended with sulfur in a 2: 1 weight ratio with 0.01 grams of zinc diethyldithiocarbamate (ZnDEDC) per gram of polyethylene wax. A sample of polyethylene wax was prepared according to Table 2. The polyethylene was introduced into the extruder previously described. The screw speed and throughput rate were maintained at 200 RPM and 71 g/h, respectively. The residence time in the extruder was about 10 minutes. Each of the extruder barrels were operated according to Table 3 for this test. Table 2

Table 3

[0065] After a period of time, the barrel was separated to observe and test the material at each of the four mixing zones in the extruder. It was observed that color change started in mixing zone 1 with some hardened materials at the end of mixing zone 1. It was further observed that the material was further mixed and reacted in mixing zone 2. It was further observed that the material felt like polymer in mixing zone 3 and mixing zone 4. In the extruder screws leading into mixing zone 1 the mixture of sulfur and polyethylene wax appeared to be unreacted. As the material proceeded further downstream in mixing zone 2, 3, and 4 the color of the mix progressively changed from a yellowish to a greyish material which is indicative of the material reacting. No H2S was detected at any zones in the extrusion reactor.

Polyethylene Wax Polymer Analysis

[0066] Material from each of the mixing zones and was sampled and subjected to gel permeation chromatography (GPC) analysis. The results of the GPC analysis are shown in FIG. 1 and FIG. 2. FIG. 1 clearly demonstrates the formation of sulfur-polyethylene copolymers within the extruder. The increased high molecular weight tail exemplifies this reaction. FIG. 2. is a zoomed version of FIG. 1 showing the high molecular weight region. As the sulfur-polyethylene blend moves along the extruder barrel the reaction proceeds further producing more higher molecular weight polymeric species. A summary of the results of the GPC analysis is shown in Table 4. It was observed that polyethylene wax had a low molecular weight of Mn=764, Mw= 1066, and Mx=1416. Mixing zone 1 contains a nearly physical blend of PE wax/Sulfur. The molecular weights of mixing zone 1 is nearly same as PE wax. As the reaction proceeds in mixing zone 2, 3, and 4 it was observed that the molecular weight progressively increases from ~1 kg/mol to 15 kg/mol to 30 kg/mol. All the samples still show a prominent low molecular weight peak centered around -1000 g/mol which is similar to polyethylene wax. This indicates that there remains a portion of saturated polyethylene wax fraction in the original pyrolysis product. The sulfur likely reacted with all available unsaturation to produce the high molecular weight fractions.

Table 4

[0067] An x-ray scattering test was performed on material on sulfur, polyethylene wax, material from mixing zone 1 and material from mixing zone 4. The results of the x-ray scattering test are shown in FIG. 3. As shown in FIG. 3, it can be observed from the scattering peaks that elemental sulfur shows multiple crystalline peaks corresponding to rhombic crystalline structure. Similarly, polyethylene wax samples show diffraction peaks corresponding to the 110 and 200 planes. The mixing zone 1 material is a physical blend of Sulfur with polyethylene and retains most of the scattering peaks corresponding to sulfur. This indicates that sulfur and polyethylene wax have not reacted in the earlier mixing zones. On the other hand, the samples collected from mixing zone 4 is fully reacted product. As seen from the diffractograms, all the peaks associated with sulfur have completely disappeared and the sample only retains peaks that are present in the original wax sample. This indicates that the sulfur can be fully reacted with polyethylene wax using a continuous extrusion process. The absence of crystalline unreacted sulfur is evidence of the usefulness of extrusion process in producing sulfur copolymers.

Depolymerized Tire Preparation and Characterization

[0068] In this example, tire granules were depolymerized for use as a starting material to produce sulfur copolymers. Cross-metathesis in the presence of an unsaturated wax was chosen as the depolymerization method. A ruthenium-based Hovey da-Grubbs Catalyst ® M73 SiPr (Dichloro[l,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylide ne][(5- isobutoxycarbonylamino)-(2-isopropoxy)benzylidene]ruthenium( II)) catalyst was used at the depolymerization catalyst. The catalyst contains sterically demanding aryl substituents at the N-heterocyclic carbene ligand and additional donor functionalities at the alkylidene moiety. The depolymerization experiments with ruthenium-based catalyst were carried on air without any protection from oxy gen or moisture. It was found that rubbers in tire granules can be fully depolymerized into a soluble fraction at the catalyst loadings of 5 mg catalyst per gram of tire granules.

[0069] Tire granules, C?6 wax, and a ruthenium-based catalyst were mixed and introduced into the extruder. The extrusion operating conditions and composition used for depolymerization work is shown in Table 5 below. After the material was introduced into the extruder and run for a period of time, the barrel was separated to sample and observe the progress of the depolymerization reaction It was observed that mixing zone 1 had nearly unreacted tire granules. In mixing zones 2, 3, and 4, it was observed that the tire granules are depolymerized as evidenced by cleaner screw elements. The output of the extruder was a physical blend of carbon black, fillers with depolymerized oligomers.

Table 5

Depolymerized Tire Polymer Synthesis

[0070] A 27 g sample of depolymerized tire granules was mixed with 13.5 gram of sulfur and ZnDEDC. Previous testing showed the depolymerized tire granules contain about 50 wt. % carbon black. The sample was into the extruder at a feed rate of 71 g/h and screw speed of 200 RPM. The temperature was maintained at 170°C along the reaction zones. After a period of time the barrel was separated to observe the reaction progression. It was observed that the materials in mixing zone 1 were soft, material in mixing zone 2 was harder, and the material in mixing zone 3 and 4 were even harder. Die pressure was in 35-40bar, while torque was in 45- 50%; both responses were in moderate ranges. No H2S was detected in the barrel.

Table 6

Sulfur Crosslinked Polymer Analysis

[0071] Material from each of the mixing zones and was sampled and subjected to gel permeation chromatography (GPC) analysis. The results of the GPC analysis are shown in FIG. 4 and FIG. 5. FIG. 4 clearly demonstrates the formation of sulfur-tire depolymerized copolymers within the extruder. The increased high Mw tail exemplifies this reaction. FIG. 5. is a zoomed version of FIG. 4 showing the high molecular weight region. As the sulfur-tire depolymerized monomer blend moves along the extruder barrel the reaction proceeds further producing more higher Mw polymeric species. It was observed that mixing zone 1 had lower molecular weight compared to the finished product that showed a fully reacted high molecular weight sample.

Table 7

[0072] An x-ray scattering test was performed on material on sulfur and material from mixing zones 1, 2, and 4. The results of the test are shown in FIG. 6. I was observed from the scattering peaks that sulfur shows the classic rhombic crystal peaks. In mixing zone 1 and 2, samples also show sulfur peaks which is indicative of unreacted sulfur blended with the depolymerized tire granules. In mixing zone 4 sample shows no sulfur peaks and appears to be completely amorphous. This indicates that the sulfur has completed reacted with the depolymerized granules forming fully amorphous copolymer.

[0073] While the disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the disclosure as disclosed herein. Although individual embodiments are discussed, the present disclosure covers all combinations of all those embodiments.

[0074] While compositions, methods, and processes are described herein in terms of “comprising,” “containing,” “having,” or “including” various components or steps, the compositions and methods can also “consist essentially of’ or “consist of’ the various components and steps. The phrases, unless otherwise specified, “consists essentially of’ and “consisting essentially of’ do not exclude the presence of other steps, elements, or materials, whether or not, specifically mentioned in this specification, so long as such steps, elements, or materials, do not affect the basic and novel characteristics of the disclosure, additionally, they do not exclude impurities and variances normally associated with the elements and materials used.

[0075] All numerical values within the detailed description are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0076] Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.