Process for halogenating isobutylene-isoprene copolymers

Abstract

The present invention relates to a method for halogenating an isobutylene-isoprene copolymer. By using the method of the present invention, the hydrogen halide byproduct can be quickly recycled as a halogenating agent and reused. Therefore, a halogenated isobutylene-isoprene copolymer having a high content of secondary allyl halogen functional groups can be prepared by increasing the participation ratio of the halogenating agent in the reaction and suppressing the rearrangement of the secondary allyl halogen functional groups. The halogenated isobutylene-isoprene copolymer prepared according to the present invention can be effectively used in a crosslinking reaction with other rubbers and is industrially useful.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority based on Korean Patent Application Nos. 2020-0120299 and 2020-0120663 filed on September 18, 2020, the entire contents of which are incorporated into this specification by reference. Technical Field

[0004] The present invention relates to a process for halogenating isobutylene-isoprene copolymers. Background Art

[0005] Butyl rubber (isobutylene-isoprene rubber, IIR) is an isobutylene-isoprene copolymer containing isobutylene and about 1% to 6% of isoprene, and has excellent chemical resistance, moisture resistance, electrical insulation, etc., and is therefore used as an adhesive composition, an adhesive sheet, etc. Isobutylene is the main component of butyl rubber, which exhibits excellent gas barrier properties, oxidation resistance and thermal stability, but has no additional functional groups in the polymer chain and cannot participate in cross-linking reactions. In order to make up for these defects, a certain amount of isoprene with unsaturated functional groups is included in butyl rubber after polymerization. However, butyl rubber has a low isoprene content and still has the defect of insufficient cross-linking reactivity.

[0006] In order to solve the above defects, the double bonds of isoprene are subjected to an additional bromination reaction to convert butyl rubber into brominated butyl rubber, and the brominated butyl rubber is crosslinked / mixed with other rubbers before use. The brominated butyl rubber is characterized in that it does not show air permeability, and therefore, is widely used as a main material for inner tubes and inner liners of tires.

[0007] In the case of bromination, hydrogen bromide (HBr) is generated during the bromination process, and the ratio of the actual bromination of the isobutylene-isoprene copolymer to the bromine molecules (Br2) used in the bromination reaction is limited. In addition, the hydrogen bromide generated as a by-product after the bromination reaction needs to be neutralized with an alkaline substance, and according to the neutralization reaction, there is a defect that a large amount of alkali metal bromide is handled and consumed.

[0008] Generally, in order to improve the degree of bromination in the bromination reaction of butyl rubber, an oxidant such as hydrogen peroxide is used to oxidize hydrogen bromide again to bromine molecules to participate in the bromination reaction again. However, even if bromine molecules are used again, the actual degree of bromination is not significant compared with the injection amount of bromine molecules. Therefore, there is still a need to develop a method for further improving the economic feasibility and efficiency of the bromination reaction.

[0009] [Prior art literature]

[0010] [Patent Document]

[0011] Japanese Patent Publication No. 2020-513055 Summary of the invention

[0012] Technical issues

[0013] An object of the present invention is to provide a method for preparing a halogenated isobutylene-isoprene copolymer containing a high content of secondary allyl halogen functional groups having a terminal double bond by suppressing a side reaction of rearranging the secondary allyl halogen functional groups into primary allyl functional groups in the halogenation reaction of the isobutylene-isoprene copolymer.

[0014] Technical Solution

[0015] In order to solve the above-mentioned task, the present invention provides a method for halogenating an isobutylene-isoprene copolymer, comprising: (S1) preparing a mixed solution comprising an isobutylene-isoprene copolymer, an organic hypochlorite and a hydrocarbon solvent; and (S2) reacting the mixed solution with a halogenating agent to halogenate the isobutylene-isoprene copolymer.

[0016] Beneficial Effects

[0017] By using the method of the present invention, the hydrogen halide byproduct can be quickly recycled as a halogenating agent and reused. Therefore, by increasing the participation ratio of the halogenating agent in the reaction and suppressing the rearrangement of the secondary allyl halogen functional group, a halogenated isobutylene-isoprene copolymer with a high content of secondary allyl halogen functional groups can be prepared.

[0018] The halogenated isobutylene-isoprene copolymer prepared according to the present invention can be effectively used in a crosslinking reaction with other rubbers and is industrially useful. DETAILED DESCRIPTION

[0019] Hereinafter, the present invention will be described in more detail to help understanding of the present invention.

[0020] It should be understood that the words or terms used in the specification and claims of the present invention should not be understood as the meanings defined in commonly used dictionaries. It should also be understood that, based on the principle that the inventor can appropriately define the meanings of words or terms to best illustrate the invention, the words or terms should be understood to have meanings consistent with their meanings in the technical concept of the present invention.

[0021] The method for halogenating an isobutylene-isoprene copolymer of the present invention is characterized by comprising: (S1) preparing a mixed solution comprising an isobutylene-isoprene copolymer, an organic hypochlorite and a hydrocarbon solvent; and (S2) reacting the mixed solution with a halogenating agent to halogenate the isobutylene-isoprene copolymer.

[0022] In the case of a bromination reaction performed by reacting an isobutylene-isoprene copolymer with a halogenating agent, for example, a brominating agent, a bromine atom is partially inserted into the isoprene repeating unit (Structure I). Then, a portion exists as the isoprene repeating unit itself, repeating units of secondary allyl bromide (Structure II, exo-allyl bromide) and primary allyl bromide (Structure III, endo-allyl bromide) are generated from the isoprene repeating unit, and hydrogen bromide (HBr) is generated as a by-product.

[0023]

[0024] Although hydrogen bromide remains in the mixed solution, it will not participate in the bromination reaction unless it is converted into another substance, and will show toxicity. In the case of using an alkaline substance to neutralize hydrogen bromide to remove it, alkali metal bromide is generated, and there is a problem of waste generation.

[0025] In addition, in the case where hydrogen bromide continues to remain in the solution, an additional reaction with the isobutylene-isoprene copolymer that has been brominated isobutylene-isoprene copolymer is caused. In this case, a side reaction that causes a structural rearrangement from structure II to structure III occurs, and causes a problem that the brominated isobutylene-isoprene copolymer becomes undesirable crosslinking properties. In order to constantly maintain the crosslinking properties of the halogenated isobutylene-isoprene copolymer, it is important to prevent such structural rearrangement.

[0026]

[0027] In order to suppress the side effects and structural rearrangement caused by the residue of hydrogen bromide, it is important that hydrogen bromide is recycled as Br2 as a brominating agent and is used again in the bromination reaction. For this reason, an oxidant can be used together in the bromination reaction system. The oxidant oxidizes hydrogen bromide (HBr) to HOBr, and then HOBr reacts with another hydrogen bromide molecule to be converted into bromine molecules. The bromine molecules thus formed can be used as a brominating agent again, thereby helping to improve the efficiency of the bromination reaction.

[0028] HOBr+HBr→Br2+H2O

[0029] However, hydrogen peroxide or the like, which is a commonly used oxidant, has very low solubility in the organic layer and is present in the water layer of the mixed solution, while the isobutylene-isoprene copolymer and the bromine molecules are present in the organic layer of the mixed solution, and the hydrogen bromide produced therefrom is also present in the organic layer. Therefore, in order to make the oxidant contact and react with hydrogen bromide, it is necessary to move the hydrogen bromide to the water layer. This inhibits the reaction of the oxidant and hydrogen bromide, and acts as a factor that prevents the hydrogen bromide from being recycled into bromine molecules.

[0030] The inventors of the present invention conducted research to improve the bromination efficiency of isobutylene-isoprene copolymer and further promote the recycling of hydrogen bromide to bromine molecules, and used an organic hypochlorite that is easily dissolved in an organic layer as an oxidant. By doing so, hydrogen bromide generated as a byproduct can easily and quickly contact the organic hypochlorite to promote the regeneration reaction of hydrogen bromide. By doing so, if the same amount of bromine molecules is used, the bromine utilization rate (%) indicating the degree to which bromine molecules actually participate in and form bonds with the isobutylene-isoprene copolymer can be improved.

[0031] - Bromine utilization rate = (number of bromine atoms bonded to the isobutylene-isoprene copolymer) / (number of bromine atoms injected in the bromination reaction) × 100

[0032] Step (S1)

[0033] Step (S1) is a step of preparing a mixed solution containing an isobutylene-isoprene copolymer, an organic hypochlorite and a hydrocarbon solvent, and is a step of preparing a reactant for a halogenation reaction.

[0034] In the present invention, the isobutylene-isoprene copolymer may contain 1 mol % to 10 mol %, 1 mol % to 8 mol % or 1 mol % to 5 mol %, or 1 mol % to 3 mol % of isoprene-derived units compared to the isobutylene-isoprene copolymer, but a copolymer having an appropriate composition or molecular weight may be selected according to the purpose or use and applied to the present invention without limitation.

[0035] In the present invention, step (S1) can be performed by mixing the isobutylene-isoprene copolymer and the hydrocarbon solvent to first prepare the isobutylene-isoprene copolymer solution (butyl rubber solution), and then mixing the organic hypochlorite. In the process of preparing the butyl rubber solution, after mixing the isobutylene-isoprene copolymer and the hydrocarbon solvent, a stirring step can also be performed to fully dissolve the isobutylene-isoprene copolymer.

[0036] In addition, step (S1) may include the step of mixing the isobutylene-isoprene copolymer, the organic hypochlorite and the hydrocarbon solvent, and stirring for 10 seconds to 60 minutes, and the stirring time may be 10 seconds or more, 20 seconds or more, 30 seconds or more, 50 seconds or more and 60 minutes or less, 30 minutes or less, 20 minutes or less, 10 minutes or less, or 3 minutes or less.

[0037] For example, step (S1) may be performed by preparing a butyl rubber solution of a mixture of an isobutylene-isoprene copolymer and a hydrocarbon solvent, injecting an organic hypochlorite to prepare a mixed solution, and stirring for 10 seconds to 60 minutes.

[0038] As described above, the dispersibility of the organic hypochlorite in the mixed solution can be enhanced by pre-stirring the mixed solution before reacting it with the brominating agent. This contributes to a more favorable performance of the reaction of the organic hypochlorite with hydrogen bromide after the bromination reaction, thus promoting the circulation of hydrogen bromide to bromine molecules to improve the regeneration efficiency.

[0039] In the present invention, the organic hypochlorite may be a compound represented by Formula 1 below.

[0040] [Formula 1]

[0041]

[0042] In formula 1,

[0043] R is an alkyl group of 1 to 10 carbon atoms.

[0044] Specifically, R may be an alkyl group of 4 to 10 carbon atoms, and in view of ensuring stability to exposure, the carbon adjacent to the oxygen atom of Formula 1 may preferably be a tertiary carbon. For example, R may be a tert-butyl group, a tert-amyl group, a 2-methylpentane-2-yl group, a 2,3-dimethylbutane-2-yl group, a 2-methylhexane-2-yl group, a 2,4-dimethylpentane-2-yl group, a 2,3-dimethylpentane-2-yl group, a 2,3,3-trimethylbutane-2-yl group, and the like, without limitation.

[0045] In the present invention, based on 1 equivalent of the halogenating agent, the organic hypochlorite may be 0.1 equivalent to 2.0 equivalents, specifically, 0.1 equivalent or more, 0.2 equivalent or more and 2.0 equivalent or less, 1.0 equivalent or less, 0.8 equivalent or less, 0.6 equivalent or less, less than 0.5 equivalent, 0.4 equivalent or less. The halogenating agent may be, for example, a brominating agent.

[0046] If the organic hypochlorite is used in an excess amount, the organic hypochlorite reacts with HCl to generate chlorine molecules (Cl 2 ), and this reacts with the unreacted isobutylene-isoprene copolymer to induce a side reaction of undergoing chlorination.

[0047] HOCl+HCk→Cl2+H2O

[0048] If partial chlorination occurs instead of bromination, the chlorine-carbon bond has a higher binding energy than the bromine-carbon bond and has poor leaving ability and a reduced crosslinking rate, and the crosslinking (vulcanization) properties of the compounding ingredients after the rubber is prepared will change, and it will be difficult to ensure the optimal physical properties required for business. Therefore, the target degree of crosslinking cannot be achieved within the set time, and defects that deteriorate the physical properties may be caused.

[0049] Within the above range, the organic hypochlorite can sufficiently function as an oxidant to reduce hydrogen bromide to a brominating agent, and can significantly improve the bromide utilization rate or the bromide content of brominated isobutylene-isoprene.

[0050] In the present invention, the mixed solution may contain less than 15 wt % or less than 10 wt % of water, based on the total weight of the mixed solution, preferably less than 10 wt %, less than 5 wt %, less than 3 wt %, preferably less than 1 wt %.

[0051] The material used as conventional oxidant is water-soluble, and water is added to the mixed solution alone to form an emulsion. If water is not used, the oxidant is not fully dispersed in the mixed solution, thereby reducing the reactivity with hydrogen bromide. Therefore, the process of recycling hydrogen bromide as a brominating agent is not well performed, and ultimately, there is a defect of inducing the bromine utilization rate in the bromination reaction of isobutylene-isoprene copolymer to reduce. However, if water is used in the mixed solution, it may cause other defects that reduce the solubility of isobutylene-isoprene copolymer and increase the probability of precipitation, and the improvement of bromine utilization rate and the prevention of precipitation of isobutylene-isoprene copolymer are both difficult to achieve.

[0052] At the same time, the organic hypochlorite used as an oxidant in the present invention can be easily dissolved in the organic layer, and there is no need to form a separate emulsion to react with hydrogen bromide. Therefore, except for the minimum amount of water contained as an impurity in part of the reactants, no water is contained in the mixed solution, and the water content in the mixed solution can be minimized. In the present invention, although water is not used in the mixed solution, there is no problem with the dispersibility of the organic hypochlorite, and the precipitation of the isobutylene-isoprene copolymer can be prevented while maintaining the bromine utilization rate at the same level.

[0053] In the present invention, the hydrocarbon solvent may be an aliphatic hydrocarbon solvent or an aromatic hydrocarbon solvent. For example, the aliphatic hydrocarbon solvent may be one or more selected from butane, pentane, neopentane, hexane, cyclohexane, methylcyclohexane, heptane and octane, and the aromatic hydrocarbon solvent may be one or more selected from benzene, toluene, xylene and ethylbenzene. More preferably, the hydrocarbon solvent may be hexane without limitation.

[0054] In the present invention, the mixed solution may further contain alcohol.

[0055] Although the hydrogen halide and the organic hypochlorite are reacted to be recycled and used as the halogenating agent as described above, part of the hydrogen halide still remains in the organic layer, and the possibility of inducing the rearrangement of the structure II cannot be completely eliminated. Therefore, by further including an alcohol in the mixed solution, the hydrogen halide that is not recycled as the halogenating agent can be dissolved in the water layer to prevent physical contact with the halogenated isobutylene-isoprene copolymer in the organic layer.

[0056] In addition, alcohol is used instead of water to form the water layer, and since the intrinsic pKa of the oxonium ion is small, the ionization tendency of the hydrogen halide is reduced together, and therefore, the number of halogen ions is reduced and structural rearrangement can be effectively suppressed.

[0057] As described above, it is important to separate the hydrogen halide quickly in a separate water layer after the isobutylene-isoprene copolymer is halogenated and before the additional reaction with the hydrogen halide. Therefore, it is preferred that water is not added separately during the halogenation reaction, but alcohol is injected into the reaction system before starting the halogenation as in step (S1).

[0058] In the present invention, the alcohol may be 0.1 to 20 parts by weight, specifically, 0.1 to 100 parts by weight, specifically, 0.1 to 10 parts by weight and 20 to 15 parts by weight, based on 100 parts by weight of the hydrocarbon solvent.

[0059] Within the range, the alcohol sufficiently achieves the effect of suppressing by-products, and can prevent rearrangement of the isobutylene-isoprene copolymer, and can prevent excessive energy from being consumed in a drying process after the halogenation reaction is completed without reducing economic feasibility.

[0060] In the present invention, there is no limitation on the type of alcohol, but considering the easy drying of the isobutylene-isoprene copolymer after the halogenation reaction is completed, the alcohol may be an alcohol having 1 to 4 carbon atoms, for example, methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol, tert-butanol or a mixture thereof.

[0061] Step (S2)

[0062] Step (S2) is a step of halogenating the isobutylene-isoprene copolymer by reacting the mixed solution prepared in step (S1) with a halogenating agent, in which case a halogen atom is located at a hydrogen position of the isobutylene-isoprene copolymer to generate hydrogen halide as a by-product.

[0063] In the present invention, the halogenating agent may be a bromine molecule (Br2) or a chlorine molecule (Cl2), specifically, a bromine molecule (Br2).

[0064] In the present invention, the halogenating agent may be 0.2 to 0.8 equivalents, specifically, 0.2 equivalents or more, 0.3 equivalents or more, 0.4 equivalents or more and 0.8 equivalents or less, 0.7 equivalents or less, 0.6 equivalents or less, for example, 0.5 equivalents, based on 1 equivalent of the isobutylene-isoprene copolymer.

[0065] Within the above range, the halogenation reaction of the isobutylene-isoprene copolymer may be sufficiently performed while suppressing the deterioration of physical properties of the isobutylene-isoprene copolymer due to an excessive amount of remaining hydrogen halide that is not recycled.

[0066] In the present invention, halogenating agent can be used as composition type by being dissolved in hydrocarbon solvent, and hydrocarbon solvent can be aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent.For example, described aliphatic hydrocarbon solvent can be one or more selected from butane, pentane, neopentane, hexane, cyclohexane, methylcyclohexane, heptane and octane, and described aromatic hydrocarbon solvent can be one or more selected from benzene, toluene, dimethylbenzene and ethylbenzene.More preferably, described hydrocarbon solvent can be hexane, without restriction.

[0067] The hydrocarbon solvent used to dissolve the halogenating agent may be the same as or different from the hydrocarbon solvent used to prepare the mixed solution in step (S1), and preferably, hexane may also be used.

[0068] In the composition including the halogenating agent, the content of the halogenating agent may be 10 wt % or more, 15 wt % or more and 50 wt % or less, 30 wt % or less, for example, 20 wt % based on the composition without limitation.

[0069] In the present invention, the halogenation in step (S2) can be performed at 10°C to 80°C, 10°C or more, 30°C or more, 40°C or more and 80°C or less, 60°C or less, for example, 40°C.

[0070] Within the above range, the halogenation reaction of the isobutylene-isoprene copolymer may be easily performed while preventing the amount of the structure III in the halogenated isobutylene-isoprene copolymer from increasing due to an excessive reaction of halogenation, thereby preventing deterioration of physical properties.

[0071] In the present invention, the halogenation in step (S2) can be performed for 10 seconds to 60 minutes, specifically, more than 10 seconds, more than 30 seconds, more than 3 minutes and less than 60 minutes, less than 30 minutes, less than 10 minutes, less than 7 minutes, for example, 5 minutes.

[0072] Within the range, the halogenation reaction can be performed for a sufficient time, the halogenation degree of the isobutylene-isoprene copolymer can be high, and the amount of structure III in the halogenated isobutylene-isoprene copolymer can be prevented from increasing due to excessive halogenation reaction to cause deterioration of physical properties.

[0073] The present invention may further include: (S3) a step of reacting with an alkaline substance.

[0074] Even if the above step (S2) is performed, part of the hydrogen halide still remains, which can react with the alkaline substance to be neutralized through an acid-base reaction.

[0075] In the present invention, the alkaline substance may use a substance having a pH of 10 to 14, specifically, alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, etc., for example, potassium hydroxide, sodium hydroxide, calcium hydroxide, potassium carbonate, sodium carbonate, calcium carbonate, etc., without limitation.

[0076] In the present invention, step (S3) can be performed at 10° C. to 40° C., specifically, 10° C. or more, 15° C. or more, 18° C. or more and 40° C. or less, 30° C. or less, 25° C. or less, for example, 20° C. In addition, step (S3) can be performed for 3 minutes to 30 minutes, specifically, 3 minutes or more, 5 minutes or more, 7 minutes or more and 30 minutes or less, 20 minutes or less, 15 minutes or less, for example, 10 minutes.

[0077] Under the temperature and time conditions, the remaining hydrogen halide and unreacted halogenating agent can be removed by reaction with an alkaline substance, thereby terminating the reaction and preparing a high-purity halogenated isobutylene-isoprene copolymer. If the reaction time of step (S3) is less than 3 minutes, the reaction cannot be fully terminated, and unreacted halogenating agent will remain, which risks acting as a toxic substance.

[0078] At the same time, since an organic hypochlorite is used as an oxidant in the present invention to convert hydrogen halide into a halogenating agent for repeated use in the reaction, the amount of hydrogen halide remaining after the reaction is very small. Therefore, the alkali metal halide produced by the reaction of hydrogen halide with an alkaline substance is small, the time and cost required for processing the alkali metal halide can be saved, and the defects related to toxicity can be solved.

[0079] Example

[0080] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

[0081] Example 1

[0082] 0.5 g of isobutylene-isoprene copolymer (isoprene content = 1.8 mol%) and 2.8 g of n-hexane were injected into a vibrator and dissolved for more than 12 hours, and then stirred for 30 minutes in a heating mantle adjusted to a reaction temperature of 40° C. to prepare a butyl rubber solution. Then, 2.2 mg of organic hypochlorite t-BuOCl (0.25 equivalent based on 1 equivalent of the brominating agent) was injected as an oxidizing agent to prepare a mixed solution. Thereafter, stirring was performed for 1 minute for premixing.

[0083] After the premixing was completed, 0.08 mL of a bromine solution (20 wt % solution in hexane) containing 13.0 mg of Br2 brominating agent (0.5 equivalent based on 1 equivalent of isobutylene-isoprene copolymer) was injected into the mixed solution, and the bromination reaction was carried out at 40°C for 5 minutes.

[0084] Then, 0.16 mL of a NaOH aqueous solution (1 M) was injected and neutralized at 20° C. for 10 minutes, and then dried in a vacuum oven to prepare a brominated isobutylene-isoprene copolymer.

[0085] Example 2

[0086] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1 except that no premixing was performed.

[0087] Example 3

[0088] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of water was further included in the mixed solution.

[0089] Example 4

[0090] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of water was additionally included in the mixed solution and premixing was not performed.

[0091] Example 5

[0092] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 4.4 mg (0.50 equivalent based on 1 equivalent of the brominating agent) of organic hypochlorite t-BuOCl was additionally used as an oxidizing agent.

[0093] Example 6

[0094] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of water was further included in the mixed solution and 4.4 mg (0.50 equivalent based on 1 equivalent of the brominating agent) of organic hypochlorite t-BuOCl was used as an oxidizing agent.

[0095] Example 7

[0096] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of methanol was additionally injected into the mixed solution.

[0097] Example 8

[0098] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of ethanol was additionally injected into the mixed solution.

[0099] Example 9

[0100] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.28 g (10 parts by weight based on 100 parts by weight of hexane) of isopropyl alcohol was further included in the mixed solution.

[0101] Example 10

[0102] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that 0.14 g (5 parts by weight based on 100 parts by weight of hexane) of methanol was further included in the mixed solution.

[0103] Comparative Examples 1 to 10

[0104] A brominated isobutylene-isoprene copolymer was prepared by the same method as in Example 1, except that the reaction conditions were changed as shown in Table 1 below.

[0105] [Table 1]

[0106]

[0107]

[0108] Experimental Example 1

[0109] According to the following equation, the utilization rate (%) of bromine actually used in the bromination reaction of the injected bromine molecules was calculated.

[0110] - Bromine utilization rate (%) = (number of bromine atoms bonded to the isobutylene-isoprene copolymer) / (number of bromine atoms injected in the bromination reaction) × 100

[0111] [Table 2]

[0112]

[0113]

[0114] The bromination utilization rate indicates the degree of the compound actually inserted into the isobutylene-isoprene copolymer and causing bromination among the compounds used as the brominating agent, and indicates that, if the bromination utilization rate increases, the bromination of the isobutylene-isoprene copolymer can be increased to a higher level with the same amount of the brominating agent. In the case of Examples 1 to 10 in which the isobutylene-isoprene copolymer was brominated according to the method proposed in the present invention, a higher bromination utilization rate was confirmed compared to Comparative Examples 1 and 2 in which no oxidant was used, Comparative Examples 3 to 5 in which hydrogen peroxide was used as the oxidant, and Comparative Examples 6 to 10 in which metal hypochlorite was used.

[0115] Specifically, when metal hypochlorite was used as the oxidant, more than twice the equivalent of the oxidant was used in Comparative Examples 8 to 10 compared with Example 4, but the degree of actual insertion into bromine was delayed, resulting in poor bromination utilization.

[0116] In addition, Examples 1 to 3 in which the organic hypochlorite was injected and premixed were performed more actively reacted with the organic hypochlorite and hydrogen bromide to improve the regeneration efficiency, and showed improved bromination utilization compared to Examples 2 and 4 in which the premixing was omitted.

[0117] In addition, in the case of using an organic hypochlorite as an oxidant, the water content can be minimized, and the bromination utilization rates of Examples 1 and 3 are shown to be the same as those of Examples 2 and 4. In contrast, when Comparative Examples 4 and 5 are compared with Comparative Examples 6 and 7, it can be found that Comparative Examples 4 and 6 show poor bromination utilization rates compared with Comparative Examples 5 and 7, respectively.

[0118] Experimental Example 2

[0119] For the brominated isobutylene-isoprene copolymers of Examples and Comparative Examples, 1 H NMR (CDCl3) analysis was used to calculate the ratio of the internal structure.

[0120]

[0121] (1) Structure I (isoprene repeating unit) content (mol %)

[0122] -Structure I content (mol%) = [(Structure I mole number) / (Structure A mole number + Structure I mole number + Structure II mole number + Structure III mole number)] × 100

[0123] The structure I content (mol %) indicates the ratio of isoprene repeating units in which bromine is not inserted into one chain of the isobutylene-isoprene copolymer chain but remains as it is.

[0124] (2) Bromination content (mol%)

[0125] - Bromination content (%) = [(moles of structure II + moles of structure III) / (moles of structure A + moles of structure I + moles of structure II + moles of structure III)] × 100

[0126] The bromide content (mol %) indicates the ratio of repeating units into which bromine is inserted in one chain of the isobutylene-isoprene copolymer chain and is an index showing the degree of progress of the bromination reaction with respect to the isobutylene-isoprene copolymer.

[0127] (3) Chloride content (mol%)

[0128]

[0129] - Chloride content (mol%) = [(mol number of structure IV + mole number of structure V) / (mol number of structure A + mole number of structure I + mole number of structure II + mole number of structure III)] × 100

[0130] The chlorinated content (mol %) indicates the ratio of repeating units into which chlorine is inserted in one chain of the isobutylene-isoprene copolymer chain.

[0131] (4) Structure II ratio (%)

[0132] -Ratio of structure II (%) = [(moles of structure II) / (moles of structure II + moles of structure III)] × 100

[0133] The Structure II ratio (%) indicates the ratio of Structure II in the brominated repeating units (Structure II and Structure III).

[0134] [Table 3]

[0135]

[0136]

[0137] In Examples 1 to 10, isobutylene-isoprene copolymers having higher bromide contents than those of Comparative Examples can be prepared, indicating that brominated isobutylene-isoprene copolymers having excellent crosslinking properties can be prepared by using an organic hypochlorite as an oxidizing agent.

[0138] Specifically, Example 4 using t-BuOCl as an oxidant exhibited a higher bromination content than Comparative Example 3 using the same equivalent of hydrogen peroxide as an oxidant. In addition, it was confirmed that Example 2 and Example 4 using t-BuOCl as an oxidant exhibited higher bromination contents than Comparative Examples 6 and 7 using the same equivalent of NaOCl as an oxidant, respectively.

[0139] In addition, in the examples, the premixed examples 1 and 3 showed higher bromination content than the premixed examples 2 and 4. Meanwhile, the oxidant equivalent was the highest and the bromination content was the largest in examples 5 and 6. However, it can be found that the chlorination content increased due to the excess oxidant and the simultaneous partial chlorination reaction.

[0140] Since t-BuOCl used in the examples was well dispersed in the mixed solution without emulsification, when comparing Examples 1 and 3, and Examples 2 and 4, which used different water contents, the bromination content showed similar degree of excellence, and in Examples 1 and 2, which had a water content of less than 1%, no precipitation of isobutylene-isoprene copolymer was observed. In contrast, the oxidant of the comparative example was difficult to disperse in the mixed solution without using water alone, and the bromination content was low in Comparative Example 4 using NaOCl, and the water content was less than 1% compared to Comparative Example 5, and the bromination content was low in Comparative Example 6, which had a water content of less than 1%, compared to Comparative Example 7. Meanwhile, in Comparative Examples 5 and 7, the bromination utilization rate was slightly increased due to the addition of water, but precipitation of isobutylene-isoprene copolymer was observed with the naked eye.

[0141] Meanwhile, in the case of Examples 6 to 10, t-BuOCl was used as an oxidant and, at the same time, alcohol was injected into the mixed solution, and an even better inhibitory effect of rearrangement of structure II was exhibited, thereby preparing a brominated isobutylene-isoprene copolymer having a very high ratio of structure II.

[0142] The results confirmed that according to the preparation method of the present invention, a brominated isobutylene-isoprene copolymer having a high bromide content can be prepared by using an organic hypochlorite as an oxidant, and an optimal bromination reaction can be performed by controlling the reaction conditions.

Claims

1. A method for halogenating an isobutylene-isoprene copolymer, the method comprising: (S1) preparing a mixed solution comprising an isobutylene-isoprene copolymer, an organic hypochlorite, and a hydrocarbon solvent; and (S2) reacting the mixed solution with a halogenating agent to halogenate the isobutylene-isoprene copolymer, Wherein, step (S1) comprises mixing the isobutylene-isoprene copolymer, the organic hypochlorite and the hydrocarbon solvent and stirring for 10 seconds to 60 minutes.

2. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The organic hypochlorite is a compound represented by the following formula 1: [Formula 1] In formula 1, R is an alkyl group of 1 to 10 carbon atoms.

3. The method for halogenating an isobutylene-isoprene copolymer according to claim 2, wherein: In formula 1, R is an alkyl group of 4 to 10 carbon atoms, The carbon adjacent to the oxygen atom in Formula 1 is a tertiary carbon.

4. The method for halogenating an isobutylene-isoprene copolymer according to claim 2, wherein: In Formula 1, R is tert-butyl, tert-amyl, 2-methylpentane-2-yl, 2,3-dimethylbutane-2-yl, 2-methylhexane-2-yl, 2,4-dimethylpentane-2-yl, 2,3-dimethylpentane-2-yl or 2,3,3-trimethylbutane-2-yl.

5. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The mixed solution includes 15 wt % or less of water based on the total weight of the mixed solution.

6. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The organic hypochlorite is used in an amount of 0.1 to 2.0 equivalents based on 1 equivalent of the halogenating agent.

7. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The halogenating agent is used in an amount of 0.2 to 0.8 equivalents based on 1 equivalent of the isobutylene-isoprene copolymer.

8. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, further comprising (S3) reacting with a basic substance after step (S2).

9. The method for halogenating an isobutylene-isoprene copolymer according to claim 8, wherein: The step (S3) is performed at 10°C to 40°C for 3 minutes to 30 minutes.

10. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The halogenating agent is a bromine molecule (Br2) or a chlorine molecule (Cl2).

11. The method for halogenating an isobutylene-isoprene copolymer according to claim 1, wherein: The mixed solution further comprises alcohol.

12. The method for halogenating an isobutylene-isoprene copolymer according to claim 11, wherein: The alcohol is one or more selected from methanol, ethanol, propanol, isopropanol, 1-butanol, 2-butanol and tert-butanol.

13. The method for halogenating an isobutylene-isoprene copolymer according to claim 11, wherein: The alcohol is present in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the hydrocarbon solvent.

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