Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/18—Introducing halogen atoms or halogen-containing groups
  • C08F8/20—Halogenation

Definitions

• the present invention relates to a halogenated butyl polymer. In another of its aspects, the present invention relates to a process for production of a butyl polymer.
• Butyl polymer or rubber is well known in the art, particularly in its application in the production of tires.
• halogenated butyl rubbers are known since such rubbers have particularly advantageous adhesion behaviour, flexural strength, service life and impermeability to air and water.
• the present invention provides a halogenated butyl polymer having improved curing and/or aging properties, the butyl polymer derived from a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C 14 multiolefin monomer and a styrenic monomer.
• the present invention provides a process for preparing a halogenated butyl polymer having improved curing and/or aging properties, the process comprising the steps of: contacting a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C 14 multiolefin monomer and a styrenic monomer with a catalyst system to produce a te ⁇ olymer; and halogenating the te ⁇ olymer to produce the halogenated butyl polymer.
• the present invention provides a vulcanizate derived from a vulcanizable mixture comprising: a halogenated butyl polymer derived from a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C 14 multiolefin monomer and a styrenic monomer; a filler; and a vulcanization agent.
• butyl rubber polymers relates to butyl rubber polymers.
• the terms "butyl rubber”, “butyl polymer” and “butyl rubber polymer” are used throughout this specification interchangeably and each is intended to denote polymers prepared by reacting a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C 14 multiolefin monomer and a styrenic monomer.
• halogenating a te ⁇ olymer derived from a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C I4 multiolefin monomer and a styrenic monomer results in a polymer having improved properties compared to a polymer produced by halogenating a copolymer derived from a monomer mixture comprising a C 4 to C 8 monoolefin monomer and a C 4 to C 14 multiolefin monomer.
• the improved properties include faster cure, higher maximum torque, higher delta torque, relatively stable modulus over time, improved hot air aging properties and improved aged flexure properties. These improved properties are believed to result from direct interaction between the styrenic moieties in the polymer backbone with a crosslinking agent added to vulcanize the halogenated butyl rubber.
• Figures 1 and 2 illustrate the (Raman infrared) R.I. and (ultraviolet) U.V. (256 ran) traces of the GPC chromatogram of te ⁇ olymers in accordance with the present invention
• Figure 3 illustrates a depiction of various bromine containing structures
• Figure 4 illustrates the cure behaviour of a conventional polymer
• Figures 5 and 6 illustrate the cure behaviour of te ⁇ olymers in accordance with the present invention
• Figures 7 and 8 illustrate hot air aging properties of te ⁇ olymers in accordance with the present invention.
• the present te ⁇ olymers are derived and the present process relates to the use of a monomer mixture comprising a C 4 to C 8 monoolefin monomer, a C 4 to C 14 multiolefin monomer and a styrenic monomer.
• the monomer mixture comprises from about 80% to about 99% by weight C 4 to C 8 monoolefin monomer, from about 0.5% to about 5% by weight C 4 to C 14 multiolefin monomer and from about 0.5% to about 15% by weight styrenic monomer. More preferably, the monomer mixture comprises from about 85% to about 99% by weight C 4 to C 8 monoolefin monomer, from about 0.5% to about 5% by weight C 4 to C, 4 multiolefin monomer and from about 0.5% to about 10%) by weight styrenic monomer.
• the monomer mixture comprises from about 87%o to about 94% by weight C 4 to C 8 monoolefin monomer, from about 1% to about 3% by weight C 4 to C 14 multiolefin monomer and from about 5%> to about 10%> by weight styrenic monomer.
• the preferred C 4 to C 8 monoolefin monomer may be selected from the group comprising isobutylene, 2-methylpropene-l, 3-methylbutene-l, 4-methylpentene-l, 2-methylpentene-l, 4- ethylbutene-1, 4-ethylpentene-l and mixtures thereof.
• the most preferred C 4 to C 8 monoolefin monomer comprises isobutylene.
• the preferred C 4 to C 14 multiolefin monomer may be selected from the group comprising isoprene, butadiene- 1,3, 2,4-dimethylbutadiene-l,3, piperyline, 3-methylpentadiene-l,3, hexadiene- 2,4, 2-neopentylbutadiene-l,3, 2-methlyhexadiene-l,5, 2,5-dimethlyhexadiene-2,4, 2- methylpentadiene-1,4, 2-methylheptadiene-l,6, cyclopentadiene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof.
• the most preferred C 4 to C 14 multiolefin monomer comprises isoprene.
• the preferred styrenic monomer may be selected from the group comprising p- methylstyrene, styrene, ⁇ -methylstyrene, p-chlorostyrene, p-methoxystyrene, indene (including indene derivatives) and mixtures thereof.
• the most preferred styrenic monomer may be selected from the group comprising styrene, p-methylstyrene and mixtures thereof.
• the butyl polymer is halogenated.
• the butyl polymer is brominated or chlorinated.
• the amount of halogen is in the range of from about 0.1 to about 8%), more preferably from about 0.5%> to about 4%, most preferably from about 1.5% to about 3.0%), by weight of the polymer.
• the halogenated butyl polymer may be produced by halogenating a previously produced butyl polymer derived from the monomer mixture described hereinabove.
• the manner by which the butyl polymer is produced is conventional and within the purview of a person of ordinary skill in the art.
• the process for producing the butyl polymer may be conducted at a temperature conventional in the production of butyl polymers (e.g., in the range of from about -100°C to about +50°C; usually less than -90°C) in the presence of a conventional catalyst (e.g., aluminum trichloride).
• the butyl polymer may be produced in a conventional manner, by polymerization in solution or by a slurry polymerization method.
• Polymerization is preferably conducted in suspension (the slurry method).
• the slurry method For more information on the production of butyl rubber, see, for example, any of the following: 1. Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A23; Editors Elvers et al.).
• the butyl polymer may then be halogenated in a conventional manner. See, for example,
• the halogenated butyl rubber may be produced either by treating finely divided butyl rubber with a halogenating agent, such as chlorine or bromine, preferably bromine, or by producing brominated butyl rubber by intensive mixing, in a mixing apparatus, of brominating agents such as N-bromosuccinimide with a previously made butyl rubber.
• a halogenating agent such as chlorine or bromine, preferably bromine
• brominating agents such as N-bromosuccinimide
• the halogenated butyl rubber may be produced by treating a solution or a dispersion in a suitable organic solvent of a previously made butyl rubber with corresponding brominating agents.
• the present halogenated butyl rubber may be used for the production of vulcanized rubber products.
• useful vulcanizates may be produced by mixing the halogenated butyl rubber with carbon black and/or other known ingredients (additives) and crosslinking the mixture with a conventional curing agent in a conventional manner.
• the polymerizations were terminated with the addition to the reactor of 10 mL of ethanol.
• the polymer was recovered by dissolving in hexane, followed by ethanol coagulation.
• the polymer was then dried in a vacuum oven at 40°C until a constant weight was reached.
• Example 1 As will be apparent, neither p-MeSt nor St were used in Example 1. Accordingly, this Example is provided for comparative piuposes only and is outside the scope of the invention.
• Figures 1 and 2 illustrate the R.I. and U.V. (256 ran) traces of the GPC chromatogram of a p-MeSt te ⁇ olymer (Example 4) and a St te ⁇ olymer (Example 7), respectively.
• Comparison of the R.I. and U.V. traces provides information about the compositional homogeneity of the polymer as a function of molecular weight.
• the R.I. signal is proportional to the total mass of the polymer chain.
• the U.V. signal is proportional to the number of aromatic monomer units inco ⁇ orated into the chain, since U.V. abso ⁇ tion of IB and IP units are negligible at 256 nm compared to that of the aromatic ring.
• the R.I. and U.V. traces of the pMeSt te ⁇ olymer show near complete overlapping.
• the U.V./R.I. ratio which is proportional to the p-MeSt content of the given molecular weight fraction, is substantially constant over the entire molecular weight range.
• the styrene content of the polymer increases by a factor of about four as molecular weight decreases (elution volume increases), which is an indication that St acts as a chain transfer agent and has lower reactivity toward the IB capped growing cation than IB.
• the polymer product was dissolved in hexane to produce a polymer cement to which 0.08 phr octylated diphenylamine (ODPA) and 0.017 phr IrganoxTM 1010 was added. Thereafter, the cement was solvent stripped and mill dried.
• ODPA octylated diphenylamine
• the resulting homogeneous rubber was once again cut into pieces and redissolved in hexane.
• the so-produced polymer cement was then transferred to a 12 litre baffled reactor equipped with a mechanical stirrer and two syringe ports.
• the cement container was rinsed with hexane and dichloromethane. Water was then added to the reactor and the mixture was stirred for several minutes.
• Bromination of the polymer product was started by injecting the appropriate amount of bromine into the reactor. After 4 minutes of reaction time, the reaction was terminated by the injection of caustic solution (6.4 wt%> NaOH). The mixture was allowed to stir for an additional 10 minutes and a stabilizer solution containing 0.25 phr epoxidized soybean oil (ESBO), 0.02 phr ODPA and 0.003 phr IrganoxTM 1076 was then added to the mixture. The brominated rubber mixture was then washed three times after which additional ESBO (0.65 phr) and calcium stearate (1.5 phr) were added to the cement prior to steam stripping. The polymer was finally dried on a hot mill.
• Bromine concentration, rubber concentration (solids), water content and reaction time were all kept constant.
• 30 vol%> dichloromethane was used as a polar co-solvent in order to obtain improved control over the extent of reaction and, thereby, to obtain the same concentration of brominated structures (approximately 1.0 mol%) in all brominated polymer products.
• Stabilizer and antioxidant levels of the brominated te ⁇ olymers were kept constant.
• Calcium stearate level was set at 1.5 phr and ESBO level at 0.9 phr.
• composition of the brominated te ⁇ olymers is reported in Table 2.
• the p-MeSt and St content determined before and after bromination are substantially consistent with one another. According to the results, the amount of primary brominated structures was lower in the te ⁇ olymer than in the control and decreased with increasing p-MeSt or St content.
• 1,4-IP enchainments The presence of a brominated aromatic ring was estimated from a mass balance: total bromine content of the samples minus the amount of bromine attached to the 1,4-IP units. The total bromine content of the samples was determined by oxygen flask combustion. Further, the amount of bromine attached to the 1,4-IP units was calculated from the HNMR results.
• the two values for bromine content are reasonably matched in Example 2, indicating that the bromination of the aromatic ring is negligible.
• the two values for bromine content deviate indicating that the aromatic ring underwent bromination.
• the deviation between the two values is even more pronounced in the case of the styrene te ⁇ olymers (i.e., Examples 5-7). This is not su ⁇ rising since, from a steric hinderance viewpoint, the more accessible para-position is not blocked in the case of styrene, and the ortho and para orienting affect of the alkyl group (polymer backbone).
• a gum vulcanizate was prepared by adding 1 phr of stearic acid and 5 phr of zinc oxide to the brominated polymer on a mill set to 40°C (i.e., no filler or oil was used during vulcanization). Cure behaviour was determined by ODR Monsanto Rheometer (3 degree arc,
• the rubber produced in Example 1 shows a large trough or long induction period before the onset of curing. Specifically, the copolymer produced in Example 1 reaches a Tc50 point (half cured state) in approximately 13 minutes and a Tc90 point in approximately ⁇ 20 minutes.
• the te ⁇ olymers produced in Examples 2 ( low p- MeSt content te ⁇ olymer) and 6 (medium St content te ⁇ olymer) possess narrower torque curves and are observed to reach their Tc50 point in less than half the time in spite of the fact that the Examples 2 and 6 te ⁇ olymers contained 10 - 35 % less Exo than the Example 1 copolymer. This is evidence that the aromatic rings take part in the curing reaction.
• the rubber was cured at 166°C for 30 minutes.
• the cured sheets were placed at room temperature for a period of sixteen hours prior to cutting them into tensile test pieces according to standard test methods (ASTM D412-68).
• Each vulcanizate was subjected to hot air aging tests (ASTM D573-81) under two different conditions: 120°C for 168 hours and 140°C for 168 hours.
• Table 5 also summarizes the imaged stress strain results of the St te ⁇ olymers and the results of the limited hot air aging study carried out using the low St content te ⁇ olymer (Example 5).
• the modulus of the te ⁇ olymers is somewhat higher than that of the control.
• the 100%) modulus of the St te ⁇ olymer decreased by 30% and the 300% modulus by 16%> as a result of 168 hrs/140°C hot air aging, indicating a better aging resistance over the copolymer of Example 1.

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