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
  • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F210/04—Monomers containing three or four carbon atoms
  • C08F210/08—Butenes
  • C08F210/10—Isobutene
  • C08F210/12—Isobutene with conjugated diolefins, e.g. butyl rubber

Definitions

• the present invention relates to a butyl polymer having improved processability. In another of its aspects, the present invention relates to a process for production of such a butyl polymer.
• Butyl polymer or rubber is well known in the art, particularly in its application in the production of tires .
• butyl polymer and butyl rubber are well known, interchangeably used terms of art and, as will be described in more detail hereinbelow, relate to a copolymer of an isoolefin and a conjugated diene.
• commercial butyl polymer is prepared in a low temperature cationic polymerization process using Lewis acid-type catalysts, of which a typical example is aluminum trichloride.
• Lewis acid-type catalysts of which a typical example is aluminum trichloride.
• the process used most extensively employs methyl chloride as the diluent for the reaction mixture and the polymerization is conducted at temperatures on the order of less than -90°C, resulting in production of a polymer in a slurry of the diluent .
• the polymer in a diluent which acts as a solvent for the polymer (e.g., hydrocarbons such as pentane, hexane, heptane and the like) .
• a diluent which acts as a solvent for the polymer
• the product polymer may be recovered using conventional techniques in the recovery of rubbery polymers .
• Elastomers go through a multitude of operations in the process of making a rubbery article. They are exposed to different shear rates and stresses during operations such as storage, mixing, milling, calendering, extrusion, injection molding and forming.
• the rheological behavior of the elastomers in the raw or compounded form is critical from the viewpoint of processability. These rheological properties are ultimately determined by the structural characteristics of the elastomer.
• processability issues and their relationship to rheological behavior, as well as structural characteristics of the polymer see, for example, J. L. White and N. Tokita: J. Applied Polymer Science, vol. 11, pp. 321-3.34 (1967) or J. White: Rubber Chem. Technol, vol. 50, pp. 163 - 185 (1976).
• the polymer have certain strength in order to resist cold flow during storage or transportation. Higher elasticity or green strength can also be beneficial in forming operations to prevent excessive flow of the compound as it is shaped or formed. In this respect a high viscosity material is preferred, showing a high degree of elastic memory. It is generally believed that resistance to cold flow can be improved by increasing the molecular weight of the polymer or by increasing long chain branching. In contrast, during extrusion or injection molding it is often desirable to have a polymer with low viscosity and reduced elasticity in order to ensure high extrusion rates and dimensional stability.
• Rapid relaxation of stresses during these operations is also desirable so that the extruded article does not change its shape during the post-extrusion handling of the material .
• Increasing molecular weight or long chain branching can have a negative impact on these operations because of the increased elasticity.
• Very high elastic memory can also result in poor filler incorporation in a mixer or on a mill .
• the molecular weight distribution (MWD) of the elastomer is equally important. For example, narrow molecular weight distribution is believed to result in crumbling of the elastomer on a mill or in a mixer. Broadening of MWD can help to eliminate this problem. However, as MWD is increased, elasticity of the polymer will increase, resulting in an increase of die swell or compound shrinkage .
• Dynamic testing is often used to assess rheological and processability characteristics of polymers.
• the key values derived from dynamic testing are the Storage Modulus (G' ) , Loss Modulus (G") and Tangent Delta (tan ⁇ ) .
• the Storage Modulus is a measure of stored energy or elasticity.
• the Loss Modulus is a measure of lost energy or viscous property.
• the prior art contains numerous examples oriented toward the improvement of the processability of elastomers.
• increasing long chain branching can reduce cold flow.
• One method of increasing long chain , branching is the introduction of a multifunctional monomer, such as divinyl benzene (DVB) , into the polymerization mixture.
• DVB divinyl benzene
• DVB divinyl benzene
• Using very low concentration of DVB will produce mostly linear chains containing only a few pendant vinyl aromatic groups . However, some of the growing chains will react with these pendant groups and the chain will grow through, resulting in an X-shaped molecule.
• tensile strength and elongation of the cured rubber decreased.
• the partially crosslinked rubber would not be able to homogeneously mix with the curatives and filler.
• the presence of gel, especially in high amounts, in an interpolymer such as butyl polymer is not desirable because it makes the even dispersion of fillers and curatives normally used during vulcanization difficult. This increases the likelihood of under- and over-cured areas within the rubbery article, rendering its physical properties inferior and unpredictable .
• Powers particularly prefers, as the functional reagent, such cationically active agents which do not contain active branching (crosslinking) functionality - i.e., the growing butyl chain can not propagate further if attached to the reactive site of the additive - column 15, lines 14-21. Indeed, Powers does not teach or suggest the use of a crosslinking agent during production of the butyl polymer and gives preference in the Examples to polymeric modifiers which tend to terminate the chain after attachment .
• crosslinking active branching
• butyl rubber which has an improved balance of (lower) cold flow, (higher) green strength, (faster) filler incorporation, (higher degree) of filler dispersion, (higher) stress relaxation rate and (lower) melt viscosity at high shear rates.
• the present invention provides a butyl polymer having improved processability, the butyl polymer being derived from a reaction mixture comprising :
• the present invention provides a process for preparing a butyl polymer having improved processability, the process comprising the steps of contacting a reaction mixture comprising :
• 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 7 monoolefin monomer and a C to C i4 multiolefin monomer or ⁇ -pinene.
• the butyl polymer may be halogenated or non-halogenated.
• the monomer mixture may contain small amounts of one or more polymerizable co-monomers.
• a butyl rubber having an improved balance of green strength, filler incorporation and stress relaxation rate can be obtained by adding to the monomer mixture a multiolefin cross-linking agent and a chain transfer agent.
• the resulting butyl polymer has overall improved processability. More specifically, such butyl polymers have a highly desirable combination of rheological properties.
• the viscosity and elasticity of the butyl polymer at very low shear rates is higher than that of a comparable copolymer of an isoolefin and a conjugated diene, rendering the present butyl polymer more resistant to cold flow.
• the viscosity and elasticity of the butyl polymer at high shear rates is lower than that of a comparable copolymer of an isoolefin and a conjugated diene, resulting in improved mixing properties, higher extrusion rate and reduced die swell for the present butyl polymer.
• These improved properties are believed to result from the combination of the monomer mixture, the multiolefin cross-linking agent and the chain transfer agent.
• the present invention provides a means to purposefully alter the rheological properties of polymers. It has been discovered that this may be achieved by the amount of crosslinking agent added to the process, and by the control of the intensity of the chain transfer reaction. The latter can be achieved by the addition of chain transfer agent in the desired concentration, or by changing the polymerization temperature. It is known that chain transfer in cationic polymerization processes is strongly influenced by temperature .
• the product obtained is suitable for compounding and curing - i.e., it has sufficient molecular weight or elasticity for conventional rubber- handling operations.
• the first two points imply that logarithm tangent delta - logarithm frequency curves of a linear polymer and of a polymer with branched chains has to have a crossover point .
• Butyl polymers having widely different tangent delta - frequency relationships can be produced.
• the crossover point between the tangent delta curve of the linear polymer and the near-gel point polymer can be shifted.
• gel free polymers with frequency-independent tangent delta can be made and the tangent delta value can be changed by the control of the polymerization reaction.
• the polymers obtained can be processed, compounded and cured by conventional methods and they display a significantly improved processability.
• Figure 1 is a double logarithmic plot showing the tangent delta as a function of the angular frequency of conventional butyl polymers with different Mooney viscosity.
• Figure 2 is a double logarithmic plot showing the complex viscosity as a function of the angular frequency of conventional butyl polymers with different Mooney viscosity.
• Figure 3 is a double logarithmic plot showing the tangent delta as a function of the angular frequency of polymers of different solubility made in the presence of DVB and different amounts of chain transfer agent .
• Figure 4 is a double logarithmic plot showing the complex viscosity as a function of the angular frequency of polymers of different solubility made in the presence of DVB and different amounts of chain transfer agent.
• Figure 5 is a double logarithmic plot showing the tangent delta as a function of the angular frequency of completely soluble polymers made in the presence of different amounts of DVB and chain transfer agent.
• Figure 6 is a double logarithmic plot showing the complex viscosity as a function of the angular frequency of completely soluble polymers made in the presence of different amounts of DVB and chain transfer agent.
• Figure 7 is a plot of torque as function of time showing the torque development of conventional linear and a DVB branched butyl sample during their mixing with carbon black.
• Figure 8 is a plot showing the remaining stress at 120 s as a function of initial slope of black filled linear and branched samples.
• Figure 9 is a plot showing the remaining stress at 120 s as a function of initial stress of black filled linear and branched samples.
• Figure 10 is a plot showing the running die swell
• Figure 11 is a plot showing the relaxed die swell (determined by MPT measurements) as a function of the initial stress (determined by stress relaxation measurements) of black filled linear and branched samples .
• Figure 12 is a plot showing the apparent viscosity
• Figure 13 is a plot showing the area under the Mooney relaxation curve of the raw polymers as a function of their remaining stress at 120 s determined by stress relaxation measurements using the black filled compounds.
• Figure 14 is a double logarithmic plot showing the tangent delta as a function of the angular frequency of samples made in continuous polymerization.
• the present butyl polymer is derived from, and the present process relates to, the use of a monomer mixture comprising a C to C 7 monoolefin monomer and a C to C 14 multiolefin monomer or ⁇ -pinene.
• the monomer mixture comprises from about 80% to about 99% by weight of a C to C 7 monoolefin monomer and from about 1.0 % to about 20% by weight of a C to C ⁇ 4 multiolefin monomer or ⁇ -pinene. More preferably, the monomer mixture comprises from about 85% to about 99% by weight of a C 4 to C 7 monoolefin monomer and from about 1.0% to about 10% by weight of a C 4 to C i multiolefin monomer or ⁇ -pinene.
• the monomer mixture comprises from about 95% to about 99% by weight of a C 4 to C 7 monoolefin monomer and from about 1.0% to about 5.0% by weight of a C 4 to C i4 multiolefin monomer or ⁇ -pinene.
• the preferred C 4 to C 7 monoolefin monomer may be selected from the group comprising isobutylene, 2-methyl-
• C 7 monoolefin monomer comprises isobutylene.
• the preferred C 4 to C i4 multiolefin monomer may be selected from the group comprising isoprene, butadiene, 2-methylbutadiene, 2 , 4-dimethylbutadiene, piperyline, 3- methyl-1 , 3-pentadiene, 2 , 4-hexadiene, 2- neopentylbutadiene, 2-methly-l, 5-hexadiene, 2 , 5-dimethly- 2 , 4-hexadiene, 2-methyl-1, 4-pentadiene, 2-methyl-1, 6- heptadiene, cyclopenta-diene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof.
• the most preferred C 4 to C ⁇ 4 multiolefin monomer comprises isoprene.
• the monomer mixture may contain minor amounts of one or more additional polymerizable co- monomers.
• the monomer mixture may contain a small amount of a styrenic monomer.
• the preferred styrenic monomer may be selected from the group comprising p-methylstyrene, styrene, ⁇ -methyl- styrene, 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 styrenic monomer in an amount of up to about 5.0% by weight of the monomer mixture .
• the butyl polymer may be halogenated.
• the halogenated 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 1.0 % to about 3.0%, by weight of the polymer .
• the halogenated butyl polymer may also be produced by halogenating a previously-produced butyl polymer derived from the monomer mixture described hereinabove .
• the reaction mixture used to produce the present butyl polymer further comprises a multiolefin cros - linking agent.
• the choice of the cross-linking agent is not particularly restricted.
• the cross- linking comprises a multiolefinic hydrocarbon compound. Examples of these are norbornadiene, 2- isopropenylnorbornene, 2-vinyl-norbornene, 1,3,5- hexatriene, 2-pheny1-1, 3 -butadiene, divinylbenzene, diisopropenylbenzene, divinyltoluene, divinylxylene and Ci to C 20 alkyl-substituted derivatives thereof.
• the multiolefin crosslinking agent is selected from the group comprising divinyl-benzene, diisopropenylbenzene, divinyltoluene, divinyl-xylene and Ci to C 2o alkyl substituted derivatives thereof. Most preferably the multiolefin crosslinking agent comprises divinylbenzene and diisopropenylbenzene.
• the amount of crosslinking agent used in the reaction mixture depends upon the type of multifunctional crosslinking agent employed.
• the amount of DVB can range from 0.01 to 3 weight% (where weight percent is defined as DVB/ (IB+IP+DVB) *100) .
• the preferred range is 0.05 to 1 weight%, the most preferred is 0.1 to 0.4 weight%.
• the reaction mixture used to produce the present butyl polymer further comprises a chain transfer agent.
• the chain transfer agent should preferably be a strong chain transfer agent - i.e., it should be capable of reacting with the growing polymer chain, terminate its further growth and subsequently initiate a new polymer chain.
• the type and amount of chain transfer agent is dependent upon the amount of crosslinking agent. At low concentrations of crosslinking agent low amounts of chain transfer agent and/or a weak chain transfer agent can be employed. As the concentration of the crosslinking agent is increased, however, the chain transfer agent concentration should be increased and/or a stronger chain transfer agent should be selected.
• the strength of the chain transfer agent may be determined conventionally - see, for example, J. Macromol . Sci.-Chem., Al (6) pp. 995-1004 (1967) [Kennedy et al . ] .
• a number called the transfer constant expresses its strength. According to the values published in this paper, the transfer constant of 1-butene (used in Exxon 's DVB patents) is 0.
• the chain transfer agent has a transfer coefficient of at least about 10, more preferably at least about 50.
• useful chain transfer agents are piperylene, 1-methylcycloheptene, 1- methyl-cyclopentene, 2-ethyl-l-hexene, 2 , 4 , 4-trimethyl-l- pentene, indene and mixtures thereof.
• the most preferred chain transfer agent is 2 ,4, 4-trimethyl-1-pentene.
• the amount of chain transfer agent employed depends upon the amount and type of the multifunctional crosslinking agent used.
• the preferred range is 0.01 to 1.4 weight %, based on the amount of isobutylene used
• the present process comprises contacting the reaction mixture described above with a catalyst system.
• the process for producing the butyl polymer is 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.
• the butyl polymer may be produced by polymerization in solution or by a slurry polymerization method. Polymerization is preferably conducted in suspension (the slurry method) - see, for example, Ullmann's Encyclopedia of Industrial Chemistry
• the process is conducted in the presence of an aliphatic hydrocarbon diluent (such as n-hexane) and a catalyst mixture comprising a major amount (from about 80 to about 99 mole percent ) of a dialkylaluminum halide (for example diethylaluminum chloride) , a minor amount (from about 1 to about 20 mole percent ) of a monoalkylaluminum dihalide (for example isobutylaluminum dichloride) , and a minor amount (from about 0.01 to about 10 ppm ) of at least one of a member selected from the group comprising water, aluminoxane (for example methylaluminoxane ) and mixtures thereof .
• a dialkylaluminum halide for example diethylaluminum chloride
• a minor amount from about 1 to about 20 mole percent
• a monoalkylaluminum dihalide for example isobutylaluminum dichloride
• butyl polymer which is useful herein - see, for example, "Cationic Polymerization of Olefins: A Critical Inventory” by Joseph P. Kennedy (John Wiley & Sons, Inc. ⁇ 1975) . If it is desired to produce a halogenated butyl polymer, the butyl polymer prepared according to the above process may be halogenated in a conventional manner. See, for example, United States patent 5,886,106.
• the halogenated butyl rubber may be produced either by treating finely divided butyl rubber with a halogenating agent such as chlorine or bromine, or by producing brominated butyl rubber by the intensive mixing, in a mixing apparatus, of brominating agents such as N-bromosuccinimide with a previously made butyl rubber.
• 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. See, for more detail, Ullmann's Encyclopedia of Industrial Chemistry (Fifth, Completely Revised Edition, Volume A23; Editors Elvers et al . ) .
• the amount of halogenation during this procedure may be controlled so that the final terpolymer has the preferred amounts of halogen described hereinabove.
• the butyl rubbers may be used for the production of vulcanized rubber products.
• useful vulcanizates may be produced by mixing the butyl rubber with carbon black, silica and/or other known ingredients (e.g., other fillers, other additives, etc.) and crosslinking the mixture with a conventional curing agent in a conventional manner.
• Vulcanizates of halogenated butyl rubber may be similarly prepared.
• TMP-1 titanium trichloride
• methyl chloride methyl chloride
• ethanol 10 mL
• the resulting polymer was dissolved in hexane, stabilized by the addition 0.2 phr Irganox-1010TM and coagulated in hot water. Residual moisture and monomer were removed by drying samples on a hot- mill at 140 °C. Results are shown in Table 1.
• Mooney and Mooney relaxation were measured at 125 °C. Relaxation time was set at eight minutes. Mooney values, as well as the area under the curve registered during relaxation, are listed in Table 1. The results clearly show that TMP-1 is an effective chain transfer agent. Mooney decreased from about 49 to about 23 as the amount of TMP-1 was increased from 0 to 0.21 g in the charge. Results also show that the chain transfer agent had no effect on the conversion or catalyst efficiency.
• This Example illustrates how the solubility of a DVB cross-linked polymer can be increased by the addition of strong chain transfer agents to the polymerization mixture and still obtain polymers with sufficiently high viscosity.
• composition of the mixture was measured to be 57 wt% meta-divinylbenzene (m-DVB) , 24 wt% para-divinylbenzene (p-DVB) , 9.9 wt% meta- ethylvinylbenzene and 9.1 wt % para-ethylvinylbenzene .
• TMP-1 diisobutylene (2, 4, 4-trimethyl-l-pentene)
• the resulting polymer was dissolved in hexane, stabilized by the addition 0.2 phr Irganox-1010TM and coagulated in hot water. Residual moisture and monomer were removed by drying the samples on a hot mill at 140°C.
• the Mooney viscosity of the polymer samples obtained in this Example decreased from about 44 to about 18 with increasing solubility. However, even at the highest chain transfer agent concentration an elastic material was obtained which was suitable for compounding and curing.
• the frequency independent tangent delta is achieved by producing an elastomer which is close to its gel point.
• a polymer at its gel point is in a transition state between liquid and solid.
• the complex viscosity obtained from dynamic testing can be used to predict the apparent viscosity of sample in capillary flow according to the Cox-Merz rule (W. P. Cox and E. H. Merz: J. Polymer Sci, Vol 28, p 619 (1958)).
• the Cox-Merz rule states that the complex viscosity at a given angular frequency is equal to the apparent viscosity measured under steady shear rate in a capillary viscometer. This has been confirmed very recently by measuring the viscosity of different elastomers using RPA and MPT (Monsanto Processability Tester) (J. S. Dick: Comparison of shear thinning behavior of different elastomers using capillary and rotorless shear rheometry, Paper No. 50, ACS Rubber Division Meeting Dallas, Texas, April 4-6, 2000.)
• Mooney stress relaxation measurements were also conducted using these samples to determine the ability of the samples to resist cold flow by an independent method.
• the selected relaxation time was eight minutes.
• the area under the torque - time curve was used to compare the samples. Table 2 shows the results. All DVB modified samples except the very low Mooney one (Mooney 17.6) has a higher area under curve value than the linear control sample of this example or any linear samples produced in Example 1. Even the 17.6 Mooney sample has very similar area under curve value to that of the linear control.
• the higher are under curve indicates a higher ability of the sample to resist flow under low shear rates, i.e., to resist cold flow.
• This example shows the effect of different degrees of branching on dynamic properties.
• Figure 5. And 6 show the results of dynamic testing. Tangent delta of the DVB modified samples was measured to be lower at low frequencies (1 rad/s or below) than that of the linear samples. This confirms the results of the Mooney relaxation measurements, i.e., they are able to resist cold flow more than the linear samples.
• All DVB modified samples showed a cross over point with the tangent delta - frequency curve of the two control samples. At frequencies higher than about 1 rad/s, all DVB modified samples displayed a higher tangent delta. This indicates that at higher shear rates these samples will have less elasticity. Lower elasticity at higher shear rates is preferred in order to obtain a material which is less nervy or swells less as it exits the die of an extruder.
• samples were prepared using a low and constant DVB concentration, varying the diisobutylene concentration in order to prepare samples having identical degrees of branching but different Mooney viscosity.
• Experimental conditions were identical to that of the previous examples. Experimental results are listed in Table 4.
• samples prepared at this low concentration of DVB are still able to resist cold flow better than comparable or even higher Mooney linear samples.
• the 28.1 Mooney sample of this example (Experiment No. 21) has an area under curve value of 609.
• the 32.4, 35.8 and even the 46.2 Mooney linear samples of Example 1 have a lower are under curve value (see Table 1.) .
• the ability of the compounded samples to relax under stress was determined using the stress relaxation program of the RPA 2000 (Rubber " Process Analyzer) instrument. During this measurement a constant strain is applied to the sample by the rapid movement of the lower die and the stress is measured at the upper die as a function of time. This measurement is similar to the ' Mooney relaxation measurement in principle. Therefore, stresses detected at longer times can be used to characterize the ability of a sample to resist cold flow. A higher remaining stress is an indication of higher resistance to cold flow. The remaining stress at two minutes was selected for the characterization of the cold flow resistance of the samples.
• the initial rate of stress decay enables one to determine the sample ability to relax when it is exposed to a large strain for a very short period of time.
• An example of this is the extrusion of rubber or its compound through a short and narrow die at a high shear rate. As the rubber enters the die, it is exposed to a high strain for a short period of time.
• the initial stress detected shortly after the application of strain can be used to characterize the die swell behavior of the sample. A lower initial stress value implies that the sample will swell less after exiting the die.
• the initial slope of the log (stress) - log (time) curve in the 0.01 - I s interval and the stress detected at 1 s were selected.
• Figure 9 shows the remaining stress at two minutes as a function of the initial slope.
• Figure 9 shows the remaining stress at two minutes as a function of stress detected at 1 s.
• the Figures clearly demonstrate the difference between branched and linear samples and the superior properties of branched samples. For example, at the same remaining stress at 2 minutes their initial relaxation is faster and their initial stress is lower. On the other hand at the same initial slope or initial stress their remaining stress at longer time is higher. This implies that cold-flow and extrusion properties can be improved at the same time.
• the die swell of the compounded samples listed in Tables 5 and 6 were determined using a capillary viscometer (Monsanto Processability Tester (MPT) ) .
• Figures 10 - 13 are provided to illustrate the ability of the values determined by stress relaxation measurement to describe the processability characteristics of the samples.
• Figure 10 shows that there is a strong correlation between the running die swell and the initial stress and this correlation is independent of the structure of the polymer.
• Figure 11 shows that there is a strong correlation between the relaxed die swell and the initial stress and this correlation is independent of the structure of the polymer.
• Figure 12 shows that there is a strong correlation between the apparent viscosity and the initial slope of the stress relaxation curve and this correlation is independent of the structure of the polymer.
• Figure 13 shows that there is a strong correlation between the area under the curve determined by Mooney relaxation measurements conducted on the raw polymers and the remaining stress determined by stress relaxation measurement. This correlation is also independent of the structure of the polymer.
• Cold flow properties of the compounded samples were determined using the so-called deformational (DEFO) measurements.
• the measurement is conducted using a 30 mm diameter and 13 mm high compression molded disk. On this disk a load (8 N) is applied and the height of the disk is measured as a function of time. Samples with higher resistance to cold flow will retain more of their original height . Table 5 and 6 lists the remaining height of the samples. According to the results, the remaining height of branched samples is higher than that of a similar Mooney linear sample. For example, the 36.9 Mooney branched sample remaining height was 11.3 mm. In contrast, the 35.8 Mooney linear sample remaining height was 10.9 mm. Only the significantly higher Mooney linear sample (Mooney 46.2) could resist to cold flow as much as the 36.9 Mooney branched sample.
• This example shows that combination of improved properties can also be achieved in continuous polymerization.
• the Mooney of the samples is listed in Table 8, along with the measured area under the Mooney relaxation curve.
• test results of a linear control sample of identical Mooney viscosity is included in Table 8. This sample was also made in continuous polymerization. However, the monomer feed contained no DVB or TMP-1. The increased cold flow resistance is clearly shown by the higher area under the relaxation curve of the samples made in the presence of DVB and TMP- 1.
• FIG. 14 shows the results of measurements done at 125°C using 0.72 degree arc in the 0.05 - 209 rad/s angular frequency range. According to the results, the tangent delta of the DVB modified samples is lower at low frequencies than that of the linear sample. On the other hand it is higher at high frequencies and the cross over point is clearly present.
• Example 5 The two samples of Example 5 along with the linear control sample were compounded with 60 phr N660 black.
• MPT and cold flow DEFO measurements confirmed that the samples made in the presence of DVB and TMP-1 has an improved combination of processing properties. Their increased resistance to cold flow is indicated by the higher remaining height values . According to the MPT measurements, this increased resistance to cold flow did not result in increased die swell. In fact, the running and relaxed die swell of the DVB modified samples was measured to be lower.

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