MXPA99001101A - Low bromine isobutylene-co - Google Patents

Abstract

Tire curing bladders are made from poly(isobutylene-co-4-bromomethylstyrene) with a benzylic bromine content of from 0.15 to 0.45 mole percent, vulcanized with a cure system of 1, 6-hexamethylene-bis(sodium thiosulfate) and zinc oxide. The vulcanizate has low residual benzylic bromine content which leads to enhanced stability under severe duty applications, reduced hot tension set, and reduced adhesion or co-cure to halobutyl tire innerliners.

Description

COMPOSITIONS OF ISOBUTILENE-CQ-4-BROMOMETILESTIRENE WITH LOW CONTENT OF BROMO, FOR APPLICATIONS OF SEVERE WORK ELASTOMERS Field of the Invention The present invention relates to poly (isobutylene-co-4-methylstyrene), vulcanizable mixtures containing the brominated copolymer and a curing gasket, and the resulting vulcanizates. The invention also relates to products made from vulcanized which are useful at elevated temperatures and other severe conditions. Background of the Invention Curing vesicles are commonly used in presses to mold and cure useful articles such as tires. The tire curing vesicles are typically inflated with steam, for example at 200 psi and 190 ° C, to press the uncured tire out against a negative mold surface. The pressure exerted by the vesicle forms the rim in the desired shape for the pattern configuration of the tread and the side walls. The application of heat and pressure cures the rim to vulcanize the rubberized polymers that comprise the material of the rim. The tire curing vesicles are ordinarily made of butyl rubber cross-linked or vulcanized to form a polymer having good thermal and physical stability properties. Even in this case, due to the high temperature and extreme wear conditions caused by the repeated expansion and contraction of the tire curing bladder, the vesicles made from these polymers have a limited shelf life. Recently, isobutylene-co-4-bromomethylstyrene polymers have been used to make tire curing vesicles. These polymers are inherently more resistant to oxidation due to the saturated polymer backbone. However, these brominated polymers can be bonded or co-cured with the internal halobutyl liners used in the rims, so that separation of the gall bladder from the rim after curing the rim can be more difficult. One approach to solving this problem has been the use of a graphite additive in the brominated copolymer of isobutylene and p-methylstyrene, as described in EP 0 711 642 A2, Goodyear Tire and Rubber Company. It is said that graphite improves lubricity, reduces the adhesion of the inner lining of cured rim to the tire curing vesicle, and reduces setting by hot tension (vesicle growth during the service life). U.S. Patent No. 5,385,459, issued to Graves et al. Discloses grafting polyethers, polylactones or polyesters into brominated p-methylstyrene-isobutylene copolymers to make tire curing vesicles that are said to have self-detachment properties. It has been known to use 1,6-hexamethylene bis (sodium thiosulfate (HTS) as a stabilizing agent, more specifically as a reversal inhibitor, in vulcanized masterbatches in general purpose rubber sulfur.) See U.S. Patents 4,417,012. 4,520,154, and 4,587,296, issued to Moniotte, and 5,508,354, issued to Taima et al., More recently, it has been pointed out that HTS and zinc oxide can be used to accelerate the curing of black rim sidewall compounds based on poly elastomers. (brominated isobutylene-co-p-methylstyrene) (BIMS) Ignatz-Hoover et al., Black Tire Sidewall Compounds Based on Brominated Poly (Iso-butylene-co-p-Methylstyrene) Elastomer and Accelerated with 1,6-Hexamethylene- bis (Sodium Thiosulfate), "presented at a meeting of the rubber division, American Chemical Society, Cleveland, Ohio, United States, document No. 110, October 17-20, 1995. This document discloses vulcanizing two elastomers BIMS with HTS and zinc oxide. The BIMS elastomers contained 0.75 mole% benzylic bromide and 5 mole% p-methylstyrene co-monomer; and 1.2 mole% of benzyl bromide and 7.5 mole% of p-methylstyrene co-monomer. Another study reports the distribution of additives between phases in physical mixtures of rubber containing poly (isobutylene-co-4-methylstyrene) bromide. This study presents the results of the curative distribution and migration in physical mixtures of a copolymer of brominated isobutylene-methylstyrene and styrene-butadiene rubber, with and without HTS. Dias et al., "Cura-tive Migration in Rubber Compounds Containing Brominated Poly-isobutylene-co-4-Methylstyrene", presented at a meeting of the rubber division, American Chemical Society, Cleveland, Ohio, United States, document No. 96 , October 17-20, 1995. SUMMARY OF THE INVENTION It has been found that poly (isobutylene-co-4-methylstyrene-no) that has been brominated at a relatively low bromine content can be effectively vulcanized to form a vulcanizate suitable for work severe such as tire curing vesicles. These vulcanizates are cross-linked very efficiently, and leave an extremely low benzylic benzylic content. The low residual benzylic bromine contributes to the stability of the vulcanized polymer by reducing the number of reactive sites, and also facilitates inhibiting the. co-curing or adhesion of tire curing vesicles made from vulcanized to internal halobutyl tire liners, when used in tire manufacturing. Accordingly, in one aspect, the present invention provides a vulcanizable mixture of brominated poly (isobutylene-co-4-methyl-styrene) and a curing package, wherein the brominated poly (isobutylene-co-4-methylstyrene) contains from 0.10 to 0.45, preferably 0.15 to 0.35 molar% benzylic bromine. The curing package preferably comprises 1,6-hexamethylene-bis (sodium thiosulfate) (HTS), zinc oxide, an optional accelerator and an optional retarder. Another aspect of the invention is a poly (isobutylene-co-4-bromomethylstyrene) especially adapted for use in the vulcanizable mixture just described. The polymer is a poly (isobutylene-co-4-brornomethylstyrene-co-methylstyrene) comprising from 0.1 to 0.45, preferably 0.15 to 0.35 molar% of benzylic bromine, where the total content of bromomethylstyrene and methylstyrene is less than 2% molar, preferably from 0.2 to 1 molar%. In another aspect, the present invention provides a poly (isobutylene-co-4-bromomethylstyrene) obtained by vulcanizing the vulcanizable mixture just described. The invention also provides a vulcanizate of a poly- (isobutylene-co-4-bromomethylstyrene) comprising from 0.1 to 0.45, preferably 0.15 to 0.35 molar% of vulcanized 4-bromomethylstyrene to a degree where the vulcanizate is essentially free of benzylic bromine. . In another aspect, the present invention provides a tire curing bladder, high temperature hose, packing, and other temperature resistant articles made from the vulcanizates. In another aspect of the invention, pharmaceutical closures are provided having extremely low levels of halogen. A further aspect of the invention is a method for vulcanizing poly (isobutylene-co-4-methylstyrene). The method includes brominating the poly (isobutylene-co-4-methylstyrene) to obtain a poly (isobutylene-co-4-bromomethylstyrene) containing from 0.1 to 0.45% molar of benzylic bromine. As another step, the poly (isobutylene-co-4-bromomethylstyrene) is combined with a curing package. The method then includes the step of heating the composite mixture to obtain a vulcanizate. The cured package in the vulcanizable mixture and method described above includes 0.2 to 6 phr of HTS, 0.1 to 6 phr of zinc oxide, 0 to 8 phr of a fatty acid or metal salt of fatty acid, and 0 to 8 phr of a retardant. More preferably, the curing package includes 0.5 to 5 phr of HTS, 2 to 4 phr of zinc oxide, 0 to 2 phr of stearic acid and 0 to 2 phr of retardant. Detailed Description of the Invention Brominated poly (isobutylene-co-4-bromomethylstyrene) (BIMS) is well known in the art. The preparation of C4-C7 isoolefin copolymers / p-alkylstyrene is generally disclosed, for example, in U.S. Patent No. 5,162,445, issued to Powers et al., And the statutory registration of invention H1475, of Newman et al. collaborators, which are incorporated herein by reference. BIMS with a relatively high bromine level, usually at least 0.5% olar of benzylic bromine, is commercially available from Exxon under the designation Exxpol ™. According to the present invention, the BIMS has a relatively low level of bromination, in the order of 0.1 to 0.45 mol% of benzylic bromine. Below this range, the crosslinking density obtained after vulcanization may be too low to be useful. Above this range, the polymer will be crosslinked too narrowly using the same curing package to have useful properties, for example, it will become stiff or brittle, or there may be benzylic bromine if reacted, which can lead to instability. In a tire curing bladder, this will result in reduced life of the vulcanized, and undesirably increased adhesion or tendency to co-cure with internal halobutyl wheel liners. Within the range according to the invention, the bromine content, as well as the other properties of the polymer and the selection of the curing package, can be adjusted and optimized to obtain desired properties of the resulting vulcanizate. In general, the bromination level of the BIMS is controlled by limiting the amount of the bromine reagent, using the procedures and techniques disclosed in United States Patent 5,162,445, Powers et al., And United States registration H1475 of Newman et al. collaborators, mentioned above.

In a preferred embodiment, the BIMS comprises from 0.5 to 10 mol% of p-methylstyrene, of which approximately 5 to 30% has been converted to bromomethylstyrene, more preferably 0.5 to 4 mol% methylstyrene, of which approximately 10% has been converted to bromomethylstyrene. In a particularly preferred embodiment, the BIMS has up to 2 mol%, especially 0.2 to 1 mol%, of total bromomethylstyrene and methylstyrene. For use in tire curing vesicles and other severe work applications, BIMS generally has a heavy average molecular weight of from about 50,000 to about 500,000, preferably from about 300,000 to about 450,000. Mooney viscosities at 125 ° C of 30 to 50 or 60 are common, being typical of about 45. The particular molecular weight distribution of the BIMS will depend on the particular properties desired for the vulcanized application. For example, the crosslinked BIMS according to the present invention, because it will have a relatively low extractable components content and high stability, is contemplated as useful in medical and pharmaceutical applications, such as plugs or closures, tubes, packaging and pharmaceutical caps used to handle blood and other biological fluids, and the like. A preferred curing package according to the present invention comprises 1,6-hexamethylene-bis (sodium thiosulfate (HTS) and zinc oxide.) 1,6-hexamethylene-bis (sodium thiosulfate) is commercially available under the designation commercial Duralink HTS, which is sold as a reversal inhibitor for use in general purpose vulcanized rubber In general, the curing package includes 0.2 to 6 parts by weight of HTS and 0.1 to 6 parts by weight of zinc oxide , per 100 parts of BIMS and any other lubricated polymers present The HTS is generally used in stoichiometric excess relative to the benzylic bromo functionality of the BIMS, preferably 1 to 2 moles of HTS per mole of benzylic bromine in the BIMS. Zinc oxide is generally used in stoichiometric excess, typically around 2.5 moles of zinc oxide per mole of HTS In a preferred embodiment, the curing package includes 0.5 to 5 phr of HTS and 2 to 4 zinc oxide phr. The curing package may also include conventional accelerators and retarders. Accelerators include, for example, fatty acids such as stearic acid and metal salts of fatty acids. Accelerators and retarders are preferably used in the curing package at up to 8 phr, more preferably from 0 to 2 phr. The vulcanizable mixture of BIMS and curing pack can also be combined with other additives conventionally used in the manufacture of tire curing vesicles and other severe working elastomers, such as fillers, including reinforcing fillers such as carbon black, antioxidants and anti-ozonants, oils and waxes, and the like. Typically, the BIMS is first incorporated into a masterbatch in an internal mixer such as a Banbury mixer or its equivalent, with the desired additives, except the ingredients of the curing package, and physically mixed until a predetermined temperature is reached, usually 150. at 165 ° C. The master charge is then emptied and cooled. The master batch is then mixed at a lower temperature, usually less than 115 or 100 ° C, with the ingredients of the curing pack (HTS, zinc oxide, accelerator (s) and retarder (s)), in a two-mill rollers or an internal mixer, to form the vulcanizable mixture of BIMS and the components of the curing package. The vulcanizable BIMS / curing mixture is then shaped or molded and cured using conventional vulcanization equipment. For example, tire curing vesicles can be molded from the vulcanizable mixture by means of a compression molding machine, injection or transfer. A curing dispenser is commonly used to determine the optimum curing time and temperature, although the actual curing time depends on the heating rate and the thickness of the tire curing bladder. The vulcanizates of the present invention can also be used to make other molded articles resistant to temperature, such as hoses, gaskets and the like, for use at temperatures above 100 or 150 ° C, for example. Because the Bvulcanizates herein are highly stable, inert and have a low content of extractable components, they can also be used to make molded articles having utility in the medical and pharmaceutical fields where inert, stable materials are required, such as for example, hoses, tubes, gaskets, seals and closures used to contain blood, urine, physiological saline, medications and other biological and therapeutic fluids. Examples In the following examples, poly (isobutylene-co-p-methylstyrene) (B brominated poly (isobutylene-co-p-methylstyrene) brominating compound was obtained essentially as described in US Patent 5,162,445, issued to Powers. and collaborators. Some master charges were also prepared from copolymers of isobutylene-p-methylstyrene physically blended with the most highly brominated Bof the state of the art for comparison purposes. The compositions (determined by proton NMR, unless otherwise indicated), and the Mooney viscosities of the various polymers used in the examples, are listed in Table 1.

Table 1 * Nominal value, real value not measured. ** As determined by FTIR. Master charges were prepared by standard methods, using a Banbury mixer. Unless otherwise indicated, the master charges included 100 parts by weight of BIMS or other rubber, 55 phr of carbon black N330, 7 phr of mineral oil, and 2 phr of paraffin wax, physically mixed in a Banbury mixer until that the temperature reached 165 ° C. The curing additives were physically mixed in the master charge in a two-roll mill, keeping the temperature below 100 ° C. The curing characteristics were evaluated using a Monsanto ODR rheometer (1 ° arc). The delta torque is the maximum torque (MH) minus the minimum torque (ML). Burning safety (Ts2) is the time when torsion rises 2 torsion units (dNm) over ML. Tc (90) is the time to 90% of the delta torque on the minimum torque. The setting by tension was evaluated before and after oven aging by elongating a specimen 300% for 20 minutes at room temperature and measuring the percentage of non-recovery after standing for 20 minutes. The samples were aged in an oven for 48 hours at 177 ° C, followed by rest for 20 minutes, before evaluating the setting by tension. Hot-setting was evaluated by elongating a specimen 200% at 150 ° C for 20 minutes and relaxing the specimen for 20 minutes before evaluating the percentage of non-recovery. Example 1-4 Two BIMS masterbatches were mixed with a curing package of 2 phr of zinc oxide, 0.8 phr of Duralink HTS and 0.25 phr of vulcanization retardant DHT. For comparison purposes, the highly brominated BIMS3 and a physical mixture of BIMS3 (70% by weight) with the IMS1 backbone polymer (30% by weight) were also incorporated in master charges with the same additive recipe. The physical mixture had an overall benzylic bromine content of about 0.35 mol%. The compositions and test results are presented in Table 2.

Table 2 These results show that the vulcanizable mixture of BIMS and the HTS / ZnO curing package has excellent vulcanization properties, as indicated by the good ODR times for Ts2 and Tc (90). The relatively low delta torsion (MH-ML), and the strength and elongation at break, for the physical mixture of Example 4, show that curing the physical mixture of highly brominated BIMS3 with IMS1 backbone copolymer is not comparable with the master loads of BIMSl and BIMS2, even though the overall content of bromine is aximately the same. Note that no vulcanizate of Examples 3 and 4 could elongate to 300%, indicating that these materials were too rigid and brittle (Example 3) or insufficiently and too weakly cross-linked (Example 4) for use in curing vesicles of tires The tensile properties of the materials of Examples 1 and 2 indicate that they are excellent materials for use in tire curing vesicles. The tensile properties of Examples 1 and 2 after oven aging, particularly the setting by stress, are comparable to the properties before oven aging and represent a marked improvement.

Example 5-7 Master fillers were made as in Examples 1-4, with BIMS4 and BIMS5, and mixed with curing packs, as shown together with the curing data and resulting properties in Table 3. Table 3 These examples show that good properties can be obtained with the ZnO / HTS curing package at the low benzylic bromine level of 0.24 and 0.17 mol% of BIMS4 and BIMS5. Example 7 shows that the curing package can be modified to give a faster curing by adding an accelerating ingredient such as stearic acid, to overcome the slow curing resulting from the low bromine content (Example 6). Examples 8-15 A masterbatch was prepared with BIMS6 and 55 phr of carbon black N234, 5 phr of mineral oil, and 5 phr of paraffin wax. This master load was accelerated with a variety of curing packages. Example 8 has a cure package based on ZnO / HTS, while Examples 9-15 are based on historically established cure packages for BIMS polymers. In Table 4, ZDEDC is zinc diethyldithiocarbamate; TMTD is tetramethylthiuram disulfide; DPTTS is dipenta tetrasulfide ethylenethiuram; MBTS is 2-mercaptobenzothia-cyl disulfide; DHT4A2 is magnesium aluminum hydroxycarbonate (CAS No. 11097-59-9); and resin SP1045 is polymethylolol phenol-formaldehyde curing resin, obtained from Schenectady Chemicals, Inc. The resulting curing packets and ODR cure data are shown in Table 4.

Table 4 comment index: R = light reversal SEF = semi-firm F = firm B = blister S / T = soft and sticky Example 8 shows that BIMS6 with low bromine content with ZnO / HTS cured well and gave a satisfactory vulcanization for use like a tire curing bladder. Examples 9-15 show that curants previously established for BIMS did not yield acceptable curing based on MH-ML torsion and appearance, although they are quick cured. Examples 9, 10 and 12-15 also show reversion of curing, which is undesirable for stability to thermal aging. ZnO / HTS, on the other hand, yields good curing data and good appearance of the cured polymer, which is shown in Examples 1-2 and 5-8, which also yield good properties. The present invention is illustrated by the foregoing examples and description. Various changes and modifications will occur to the technicians in the matter in view of this disclosure. All these variations and modifications, which are within the scope and spirit of the appended claims, are intended to be encompassed by them.

Claims (16)

1. CLAIMS 1. A vulcanizable mixture comprising poly (iso-butylene-co-4-bromomethylstyrene) and a curing package comprising 1,6-hexamethylene-bis (sodium thiosulfate), zinc oxide, optionally an accelerator and optionally a retardant, the poly (isobutylene-co-4-bromomethylstyrene) comprising from 0.1 to 0.45% molar of benzylic bromine.
2. 2. The vulcanized product obtained by vulcanizing the mixture of claim 1.
3. 3. A curing vesicle comprising the vulcanized product of claim 2.
4. 4. A hose useful at high temperature, comprising the vulcanized product of claim 2.
5. 5 A package comprising the vulcanized product of claim 2.
6. 6. A pharmaceutical stopper comprising the vulcanized product of claim 2.
7. 7. A vulcanizate prepared from the vulcanizable mixture of claim 1, essentially free of benzylic bromine.
8. The vulcanizate of claim 7, wherein the poly (isobutylene-co-4-bromomethylstyrene) of the vulcanizable mixture comprises 0.1 to 0.45 mol% of 4-bromomethylstyrene.
9. 9. A method for vulcanizing poly (isobutylene-co-4-bromomethylstyrene) containing from 0.1 to 0.45 mol% benzoic bromine, comprising the steps of: combining poly (isobutylene-co-4-bromomethylstyrene) with a packet of cured comprising 1,6-hexamethylene-bis- (sodium thiosulfate), zinc oxide, optionally an accelerator and optionally a retarder; and heating the combined mixture to vulcanize the poly- (isobutylene-co-4-bromomethylstyrene).
10. The method of claim 9, wherein the curing package comprises from 0.2 to 6 phr of 1,6-hexamethylene-bis- (sodium thiosulfate), from 0.1 to 6 phr of zinc oxide, from 0 to 8 phr of a fatty acid or metal salt of fatty acid, and 0 to 8 phr of retardant.
11. The method of claim 9, wherein the curing package comprises 0.2 to 6 phr of 1,6-hexamethylene-bis (sodium thiosulfate), 0.1 to 6 phr of zinc oxide, 0 to 8 phr of a fatty acid or metal salt of fatty acid, and 0 to 8 phr of retardant.
12. The method of claim 10, wherein the curing package comprises 0.5 to 5 phr of 1, β-hexamethylene-bis (sodium thiosulfate), 2 to 4 phr of zinc oxide, 0 to 2 phr of stearic acid, and 0 to 2 phr of retardant.
13. The method of claim 11, wherein the curing package comprises from 0.5 to 5 phr of 1,6-hexamethylene-bis (sodium thiosulfate), from 2 to 4 phr of zinc oxide, from 0 to 2 phr of stearic acid, and 0 to 2 phr of retardant.
14. 14. Poly (isobutylene-co-4-bromomethylstyrene-co-4-methylstyrene) comprising 0.1 to 0.45 mol% benzylic bromine, where the total content of bromomethylstyrene and methylstyrene is less than 2 mol%.
15. 15. The copolymer of claim 14, wherein the total content of bromomethylstyrene and methylstyrene is 0.2 to 1 mol%.
16. 16. A brominated interpolymer of a C4 to C7 isoolefin and a para-alkylstyrene, comprising from 0.1 to 0.45 mol% bromo-substituted para-alkylstyrene and up to 2% total and unsubstituted para-alkylstyrene.