GB1590749A - Isoolefin-cyclodiolefin copolymers and terpolymers - Google Patents
Isoolefin-cyclodiolefin copolymers and terpolymers Download PDFInfo
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
- C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
- C08L23/22—Copolymers of isobutene; Butyl rubber ; Homo- or copolymers of other iso-olefins
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Description
(54) ISOOLEFIN-CYCLODIOLEFIN COPOLYMERS
AND TERPOLYMERS
(71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of
America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The present invention relates to substantially gel-free copolymers of an iso-olefin and cyclopentadiene. According to this invention a substantially gel-free copolymer consists essentially of a major portion of an isoolefin having 4 to 10 carbon atoms per molecule and 5 to 45 mole % of cyclopentadiene or methylcyclopentadiene, said copolymer having a number average molecular weight (Mn) of at least 30,000 to less than 90,000.
Also said copolymers may also contain another conjugated diene, eg an acyclic diolefin.
Preferred acyclic diolefins include isoprene and piperylene, preferably isoprene. The unsaturation is 5 to 45 mole %, preferably 8 to 40 mole % and Mn's are at least 30,000 to less than 90,000, preferably 50,000-90,000, more preferably 60,000-90,000, most preferably 70,000-90,000.
The physical properties and oil extensibility of these polymers are quite unexpectedly acceptable for major tyre applications and other major applications, heretofore limited to
Butyl rubber or halobutyl rubber having a minimum Mn of about 120,000. These new polymers of the present invention clearly solve the problem of how to reduce the Mn of an elastomer while maintaining its physical properties thereby effectively creating a production cost saving.
The polymerization of the monomers to produce the copolymers of the present invention is carried out in the presence of not more than 40 vol %, based on the total monomers plus cosolvent of a cosolvent which is a solvent for the polymer at the polymerization temperature, and at a temperature of less than -80"C, e.g. -80" to -1100C. The catalyst may be an aluminium halide or hydrocarbyl aluminium dihalide as disclosed in U. S. Patent 3,856,763 wherein the aluminium halide must be introduced into the reaction zone dissolved in a polar solvent.
The quantity of cosolvent used is varied with the temperature in order to control molecular weight effectively. The optimum cosolvent level is determined by selecting the minimum solvent-monomer ratio at which the copolymer to be prepared remains in solution at the polymerization temperature.
To possess good physical properties, it is imperative that the copolymers and terpolymers of the invention incorporate critical levels of cyclopentadiene or methyl cyclopentadiene.
These critical levels are related to the Mn of the polymer. For example, at Mn of 30,000 the minimum cyclodiolefin content must be about 35 mole % (e.g. 37%), while at an Mn of 50,000 the minimum is about 20 mole % (e.g. 23%), at Mn's of 60,000 and 70,000 the critical minimum unsaturations are about 15% (e.g. 18 mole % and 10 mole %) cyclodiolefin respectively. Non-cyclic diolefins may also be present in these polymers but they have little effect on the relationship of cyclodiolefin critical levels with Mn. The cyclodiolefins which may be used are cyclopentadiene or methylcyclopentadiene or a combination of the two. Preferred acyclic diolefins include isoprene and piperylene, preferably isoprene. The co- and terpolymers of the present invention can be used as a direct replacement for Butyl rubber.
An object of the present invention is to provide blend compositions of the co- and terpolymers with oils and fillers for improvement in both physical and rheological properties.
Another object of the present invention is to provide blend compositions of the co- and terpolymers of the present invention with natural rubber, SBR rubbers, EPDM terpolymers, polybutadiene, butyl rubbers and halo butyl rubbers and mixtures thereof wherein the physical properties as well as ozone resistance are markedly improved.
One of the major properties of elastomers is the level of strength which can be achieved in its networks. Strength of elastomers is now known to be related to many survival properties of rubber materials. These survival properties include, for example, rupture, tearing, fatigue, cracking, etc. Tensile strength is considered to be a simple but excellent measure of the overall survival characteristics of elastomers. Tensile strength could thus serve as a measure to establish a base reference of the survival properties of polyisobutylene. This now can be achieved through the medium of Butyl rubbers.It can be demonstrated that tensile strength does not vary significantly with the compositional variations available in Butyl rubbers ( 97.5 to - 99.0 mole % isobutylene), and the values for tensile strength obtained on such networks could be considered representative of crosslinked polyisobutylene.
The elastomers of this invention represent a range of compositional change of isoolefin starting at ~ 95 mole %. According to the principles of this invention, the isoolefin units can be replaced by cyclopentadiene residues until the isoolefin content has been reduced to 55 mole %. If the Butyl rubbers serve as an appropriate reference for the strength of polyisobutylene then use of this reference can be continued in use to follow the effects of very great compositional changes both as to amount and type represented by isobutylene.
isoprene and isobutylene-cyclopentadiene copolymers. (See Figure 6).
It was found that modifications of compositions of Butyl rubber by increasing the isoprene content at lower number average molecular weights produced little effect on the maximum achievable tensile strength relative to the references. (See Figure 7). Thus, a combination of results from copolymers with isoprene contents in the range of the Butyl rubbers of commerce (1.19 to 2.68 mole %), with those selected from the higher mole % unsaturation range of the present invention continued to show minimal effect on the maximum achievable tensile strength.Unexpectedly, the presence of cyclodiolefin such as cyclopentadiene in the copolymers produced marked compositional effects on the maximum achievable tensile strength. (See Figure 8 and Figure 99. The compositionaleffect of cyclopentadiene in the copolymers was found to be represented by the equation: Mn* = aebx, where Mn* is the minimum number average molecular weight associated with reference strength values and a = number average molecular weight of the reference ("cross-linked" polyisobutylene) and equal to 120,000 and x = mole % concentration of cyclopentadiene as determined in a standardized test formulation.The value for b was found to be equal to -0.0377. As the equation indicates, the required number average molecular weight to provide strength values equivalent to the references decreases with increase of cyclopentadiene content in the copolymer. For example, at 8 and 40 mole % cyclopentadiene, the required number average molecular weights were about 89,000 and 27,000, respectively. The terpolymer networks of isobutylene-isoprene-cyclopentadiene show that the strength dependence on Mn is primarily related to the cyclopentadiene content.
In order to obtain the desired number average molecular weights of the co- and terpolymer of the present invention, the reaction must be carried out below -800C., more preferably -90 C. to -1100C. To obtain the desired number average molecular weight in a substantially gel-free polymer, a homogeneous polymerization is required and this is achieved by carrying out the reaction in a vehicle which is a solvent for the copolymer at the reaction temperature. The vehicle comprises predominantly the monomers to be polymerized in conjunction with an inert cosolvent or mixtures of inert cosolvents. The vehicle (monomers plus cosolvent) must of course be liquid at the polymerization temperature.
It is essential in carrying out the process of this invention that the cosolvent comprise at least 5% by volume and not more than 40% by volume of the total cosolvent-monomers system. Preferably, 5 to 30 volume % cosolvent is used, more preferably 5 to 20 volume %, most preferably 5 to 15 volume %, e.g., 10 volume %.
The optimum amount of cosolvent to be used is the minimum amount necessary to avoid gelation. If too little cosolvent is used gelation of the product results. Too high a level results in undesirable lowering of number average molecular weight below the minimum desired Mn as indicated in Figure 10.
For the purposes of this invention, it is convenient to define the volume % of inert cosolvent as that calculated based on the volume of monomers at about -78 C. (dry ice temperature) while the volume of cosolvent is determined at 25"C. The volume % of cosolvent as calculated is uncorrected for volume changes and cooling for the cosolvent to reaction conditions.
The minimum quantity of a given cosolvent required to produce gel-free polymers is a function of the cosolvent, the conjugated cyclomultiolefin used and the polymerization temperature. Having selected the composition of the blend of monomers and the cosolvent to be used the minimum quantity of cosolvent required is readily determined by carrying out the polymerization using varying amounts of cosolvent. The minimum quantity of cosolvent necessary is that amount required to maintain a homogeneous system; that is to prevent precipitation of polymer during polymerization.
The term "cosolvent" as used in the specification means the inert solvent which, together with the monomer feed, comprises the vehicle for the reaction. The cosolvent and monomers must be mutually soluble and the blend of monomers plus cosolvent must be a solvent for the copolymer at the polymerization temperature. The term "inert" means that the cosolvent will not react with the catalyst or otherwise enter into the polymerization reaction. The cosolvent must not contain substituents in its molecule which will interfere with the polymerization reaction. Aliphatic and cycloaliphatic hydrocarbons are suitable cosolvents. The preferred cosolvents are paraffinic hydrocarbons, cycloaliphatic hydrocarbons and carbon disulfide and mixtures thereof. Preferably, the paraffinic hydrocarbon or cycloaliphatic hydrocarbon solvent is a C5-C10 hydrocarbon, more preferably a C5-C8 hydrocarbon.Illustrative examples of the hydrocarbon solvents are pentane, isopentane, methylpentane, hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, heptane, isooctane, 1,2,3,3-tetramethyl hexane, tetramethyl cyclohexane, etc. Generally any paraffin, whether normal, branched or cyclic which is a liquid under polymerization conditions, may be used. The term "paraffin" as used in the specification includes normal paraffins, cycloparaffins and branched paraffins. The preferred cosolvents are cycloparaffins or paraffinic mixtures containing cycloparaffins, preferably C6-C7 cycloparaffins (i.e.
cyclohexane, methylcyclohexane), utilized at about 5 to 30 volume %, e.g., 10 to 20 volume
It will be evident to those skilled in the art that since the monomers act as part of the solvent system for the polymer, the conversion level of the polymerization must not be so great as to result in precipitation of the copolymer as a result of depletion of solvent.
Preferably, the conversion level is 2 to 30, more preferably about 3 to 15%, most preferably about 5 to about 13%, e.g. 10%.
In preparing the polymers of this invention, the catalyst is an aluminum halide or a hydrocarbyl aluminum dihalide. Where an aluminum halide is used, it must be in the form of a homogeneous solution of submicron dispersion of catalyst particles, e.g., colloidal dispersion. Therefore, the catalyst must be dispersed or dissolved in a suitable catalyst solvent or mixture of solvents. The catalyst solvent must be a polar solvent. Illustrative examples of suitable aluminum halides are AICl3 and AlBr3. The preferred aluminum halide catalyst is aluminum chloride.
It is essential that the aluminum halide catalyst be in solution in the polar organic solvent prior to introduction of the catalyst to reaction medium. Combining the polar organic solvent with the reaction medium and thereafter adding the aluminum halide catalyst thereto will not result in the production of the desired Mn, high unsaturation polymers of this invention.
Use of the term "solution" with reference to the polar organic solvent/aluminum halide systems is intended to include both true solutions and colloidal dispersions since they may exist concurrently in the same system.
The aluminum halide/polar solvent catalyst preferably comprises 0.01 to 2 wt. % aluminum halide, more preferably 0.05 to 1, most preferably 0.1 to 0.8.
As previously noted, the catalyst may also be a hydrocarbylaluminum dihalide. Where the hydrocarbylaluminum halide is the catalyst, wherein the hydrocarbyl group can be a C1-C18 straight chain, branched or cyclic group. Both cycloaliphatic and aromatic substituents can comprise the hydrocarbyl radical. Alkyl groups, especially lower alkyl groups, e.g. C1-C4, are preferred because of their general availability and economy of use.
The halide can be bromine or chlorine, preferably chlorine. The term "dihalide" as used in the specification and claims means dichloride or dibromide.
Illustrative examples of these hydrocarbylaluminum dihalides are methylaluminum dichloride, ethylaluminum dichloride, isobutylaluminum dichloride, methylaluminum dibromide, ethylaluminum dibromide, benzylaluminum dichloride, phenylaluminum dich loride, xylylaluminum dichloride, toluylaluminum dichloride, butylaluminum dichloride, hexylaluminum dichloride, octylaluminum dichloride, cyclohexylaluminum dichloride, etc.
The preferred catalysts are methylaluminum dichloride, ethylaluminum dichloride and isobutylaluminum dichloride.
The hydrocarbylaluminum dihalide catalyst may be added neat or in solution. Preferably where a catalyst solvent is used, it is a liquid paraffin solvent or cycloparaffin solvent. It is advantageous though not necessary to use paraffins of low freezing point. Methylcyclohexane is particularly useful since catalyst solutions of about 1% concentration do not freeze at -120"C.
The concentration of the catalyst is not critical. Very dilute catalyst solutions, however, are not desirable since substantial fractions of the catalyst may be deactivated by impurities.
Very concentrated solutions are undesirable since at polymerization temperatures catalyst may be lost by freezing out of solution.
In carrying out the polymerization, those skilled in the art will be aware that only catalytic amounts of catalyst solution are required. Preferably, the volume ratio of monomer plus cosolvent to catalyst solution is 100/1 to 9/1, more preferably 80/1 to 10/1, most preferably 50/1 to 20/1.
The term "polar solvent" as used in the specification means non-aromatic, organic solvents having a dielectric constant at 250C. of at least 4, preferably 4 to 20, more preferably 6 to 17, most preferably 9 to 13. These polar solvents, however, must not contain sulfur, oxygen, phosphorus or nitrogen in the molecule since compounds containing these elements will react with or otherwise deactivate the catalyst.
The preferred polar solvents are inert halogenated aliphatic hydrocarbons; more preferably halogenated paraffinic hydrocarbons and vinyl or vinylidene halides, most preferably primary or secondary chlorinated paraffinic hydrocarbons. The halogenated hydrocarbon is preferably a Cl-C5 paraffin hydrocarbon; more preferably a C1-C2 paraffin.
The ratio of carbon atoms to halogen atoms in the polar solvent is preferably 5 or less.
Preferably the halogen is chlorine.
Illustrative examples of these polar organic solvents are methylchloride, ethyl chloride, propyl chloride, methyl bromide, ethyl bromide, chloroform, methylene chloride, vinyl chloride, vinylidene chloride, dichloroethylene, etc. Preferably, the polar solvent is methyl chloride or ethyl chloride. Generally, any inert halogenated organic compound which is normally liquid under polymerization conditions and has a dielectric constant of at least 4.0 may be used.
In practising the process of this invention, it is essential that the polymerization be carried out in the homogeneous phase without the precipitation of polymer. Conventional slurry processes are inapplicable for the preparation of the high unsaturation polymers of this invention since by their nature they result in polymer precipitation with gelation of the polymer as a consequence.
The amount of cosolvent required in order to maintain the polymerization reactants and product in solution throughout the polymerization is a function of the cyclopentadiene and its concentration in the monomer feed. The polymerization temperature at which precipitation of polymer will occur is itself a function of the amount of and type of cosolvent and the cyclopentadiene.
The term "critical homogeneous polymerization temperature" as depicted in Figure 1 as used in the specification and claims means that polymerization temperature below which precipitation of polymer will occur, when no cosolvent is included in the reaction mixture, i.e., the only solvent for the reactants and product being the monomer feed.
Characterization of polymers prepared by bulk polymerization, i.e., without cosolvent shows that the polymers formed are low in number average molecular weight (Mn). In order to increase Mn, the lowering of polymerization temperature is an obvious expedient.
However, in the absence of cosolvent, the result is gelation.
The problem of gelation is obviated by the addition of a cosolvent which permits the lowering of polymerization temperature below the critical homogeneous polymerization temperature. It has been found that the polymerization temperature below -800C is necessary in order to achieve Mn values of at least 30,000 for cyclopentadiene copolymer and terpolymers. At least 5 volume % inert solvent based on the monomer feed is necessary in order to carry out the polymerization in solution at these low temperatures.
The necessity for utilizing low polymerization temperatures is exemplified by Figure 2 which shows the exponential decrease in number average molecular weight with increasing temperature. The criticality of selecting the proper quantity of cosolvent is demonstrated in
Figure 3. Too little cosolvent results in precipitation of the polymer with reactor fouling or gelation. Further benefits of low temperature and proper selection of appropriately low cosolvent concentration are demonstrated in Figures 4 and 5. Figure 4 shows that reactivity is favored by low temperatures (in addition to the molecular weight benefit). Figure 5 shows that catalyst efficiency is favored by low cosolvent concentration (in addition to the molecular weight benefit).
In practising the process of this invention, one skilled in the art may proceed as follows in order to determine the preferred reaction conditions.
First, a convenient polymerization temperature below about -80"C. is selected. Next the desired feed composition, i.e. monomers and ratio of isoolefin to cyclopentadiene and the cosolvent to be used are selected. Polymerization reactions are carried out using successively greater amounts of solvent. The initial polymerization reaction is carried out using 5 volume % based on the total of monomer plus solvent of the cosolvent since lesser amounts will be inadequate. In each successive run an additional 5 volume % is added. The procedure is continued until the reaction medium remains clear throughout the reaction.
Turbidity is indicative of precipitation of polymer which leads to reactor fouling or gelation.
The polymer formed is characterized for Mn and mole % unsaturation. Where a higher
Mn is desired, it may be achieved by either lowering the polymerization temperature or where possible using slightly less solvent than determined by the above method, e.g., 1-2 volume % less, provided that turbidity does not occur. Reduction of polymerization temperature may result in a greater cosolvent requirement. Hence, the aforegoing procedure of adding additional solvent to the reaction medium must be continued until the reaction medium is again clear throughout the polymerization.
Where the mole % unsaturation is to be adjusted, somewhat more or less of the cyclopentadiene is used depending on whether a slightly higher or lower unsaturation is desired. Change in feed composition and/or conversion may require readjusting the cosolvent requirement. Generally, increasing the cyclopentadiene content of the monomer feed increases the cosolvent requirement.
The optimum reaction conditions are those which give the desired Mn at the highest (warmest) temperature for the desired unsaturation level. Economic considerations dictate the use of the warmest temperature practical for polymerization. Use of lower temperatures will necessitate the use of greater amounts of cosolvent.
In an alternative approach to determine the necessary quantity of cosolvent, the reactions are carried out in bulk wihout using cosolvent. For each different cyclopentadiene content monomer feed, polymerizations are carried out at progressively lower temperatures until the critical homogeneous polymerization temperature for the feed composition is determined. The polymerization is repeated for different feed compositions and the data obtained are the critical homogeneous polymerization temperatures as a function of cyclopentadiene content of the feed. A plot of these data gives the critical homogeneous polymerization temperature curve analogous to that of Figure 1. The polymer formed is analyzed for cyclopentadiene content and a determination is made of the correlation mole % unsaturation in the polymer and volume % cyclopentadiene in the feed.The polymer formed in bulk copolymerization of isobutylene and cyclopentadiene is unsuitable for commercial use since it has a very low Mn. In order to control the Mn of the polymer between 30,000 to 90,000, it is necessary to carry out the polymerization at lower temperatures, e.g., less than -80 C., which requires the addition of cosolvent to prevent precipitation of polymer during polymerization.
The quantity of solvent used should be kept to a minimum since excess cosolvent results in the lowering of Mn. In determining the amount of solvent to be used, the monomer feed composition is determined. A convenient polymerization temperature below -80 C. is selected.
The minimum cosolvent requirements for isoolefin-cyclopentadiene may be determined by carrying out the polymerization at the critical homogeneous polymerization temperature for the isoolefin-cyclopentadiene feed composition, terminating the polymerization by destroying the catalyst and, with constant stirring, lowering the temperature of the system to the desired polymerization temperature. The polymer which, of course, is by definition insoluble below the critical homogeneous polymerization temperature will precipitate out and the system will appear turbid. The polymer will not be gelled, however, since polymerization was terminated prior to precipitation. The cosolvent selected is then added in incremental amounts until the turbidity disappears.The quantity of solvent so added is a good approximation of the minimum solvent requirements for a given isoolefin-multiolefin feed to be polymerized at a given temperature.
The term "solution polymerization" as used in the specification and claims means a polymerization carried out so that the polymer product remains dissolved throughout the reaction.
Utilizing the process of this invention, it is now possible to prepare such cyclodiene copolymers having as little as 5 mole % unsaturation and as high as 45 mole % unsaturation; more preferably 8 to 40 mole % and more preferably the unsaturation is at least about 20 mole % for polymers of Mn between 30,000 and 50,000, at least 15 mole % forn between 50,000 and 60,000, at least 10 mole % for Mn of between 60,000 and 90,000 and at least 5 mole % for Mn between 70,000 and 90,000. As a result of the relatively lower reactivity of the olefinic residue, copolymers having incorporated therein 2-4 mole % cyclic diene are about as reactive as Butyl rubber having an isoprene content of 0.5 to 1.5 mole % and therefore require ultra acceleration for practical sulfur vulcanization.The higher unsaturation copolymers and terpolymers, e.g., at least 5 mole %, preferably at least 8 mole %, of cyclopentadiene may be sulfur vulcanized using the delayed action accelerator cure systems.
In general, the copolymers of this invention must not contain more than 45 mole % unsaturation. When the multiolefin is a cyclic multiolefin above 45 mole % unsaturation, the glass transition temperature of the polymer is too high. As a result, the polymers have poor low temperature characteristics. The terpolymers of this invention have 5 to 45 mole % cyclopentadiene unsaturation, more preferably at least 8 to 40 mole %, and most preferably the unsaturation is at least 20 mole % ycclopentadiene for polymers with Mn between 30,000 and 50,000, at least 15 mole % for Mn between 50,000 and 60,000, at least 10 mole % for Mn between 60,000 and 70,000, and at least 5 mole % for Mn between 70,000 and 90,000.The total unsaturation for isoprene and cyclopentadiene is preferably between 8 mole % and 45 mole %, more preferably between 8 and 40 mole %, and most preferably between 12 and 30 mole %.
The products of this invention offer a number of important advantages over the commercially available Butyl rubbers. In addition to possessing superior cold flow and green strength properties while retaining the low air permeability and mechanical damping characteristics of conventional low unsaturation isoolefin copolymers, the products of this invention offer greater versatility in vulcanization techniques. Furthermore, while the vulcanization of conventional isoolefin-multiolefin copolymers requires the use of ultra-accelerator type cures, e.g., thiuram (Tuads) or dithiocarbamates (Tellurac), the products of this invention may be vulcanized using the thiazole, e.g., mercaptobenzothiazole, type cures currently used in the vulcanization of general purpose rubbers, e.g., natural rubber, SBR, polybutadiene, etc. (The word 'Tuads' is a Registered Trade Mark).
Because of certain factors of which premature vulcanization (scorch) is a prime example, modern practice has tended towards the use of a special class of thiazoles called delayed action accelerators. These delayed action accelerators permit the processing of the compounded rubber (including vulcanizing agents) at elevated temperature for a predetermined period of time before vulcanization commences. Such cure techniques are not possible with conventional isoolefin copolymers. The delayed action accelerators are, however, used advantageously in the vulcanization of the isoolefin copolymers of this invention.
The delayed action accelerators suitable for use in vulcanizing the products of this invention include the benzothiazole sulfenamides having the general formula:
wherein X is an amino group. The amino group is mono- or diorganosubstituted and may be cyclic including heterocyclic. For example, X may be
or
- N - R2 where R1 is H or R and R is organo or cycloorgano. R2 is a divalent organo radical.
Illustrative examples of X are cyclohexylamino, tertiary butyl amino, diisopropyl amino, dicyclohexyl amino, pentamethylene-amino, morpholino, 2-(2,6-dimethyl morpholino), etc. Specific illustrative examples of these sulfenamides are N,N-diethylbenzothiazole-2sulfenamide, N-N-di-isopropyl benzothiazole-2-sulfenamide, N-tertiary butyl benzothiazole-2-sulfenamide, N-cyclohexyl benzothiazole-2-sulfenamide N ,N-dicyclohexyl benzothiazole-2-sulfenamide, 2-(morpholino) benzothiazole sulfenamide, 2-(2,6-dimethyl morpholino) benzothiazole sulfenamide, 2-piperidinyl benzothiazole sulfenamide. In general, any benzothiazole sulfenamide may be used as a delayed action accelerator for the sulfur vulcanization of the polymer of this invention.
The delayed action accelerator is incorporated into the vulcanizable polymer composition at 0.25 to 3.5 wt %, preferably 0.5 to 3.0 wt. %., e.g. 0.5 to 2.5 wt. % based on the weight of copolymer.
It is, of course, obvious to those skilled in the art that the delayed action cures are sulfur cures and sulfur must be incorporated into the polymer blend either as elemental sulfur or as nonelemental sulfur. Suitable nonelemental sulfur is in the form of those compounds which will release sulfur to the polymer under vulcanization conditions. For a description of these nonelemental sulfur compounds, generally, see Vulcanization of Elastomers, Ch.4, J.
C. Ambelang, Reinhold, New York 1964. Illustrative examples of these non-elemental sulfur compounds are dimorpholinyl disulfide and alkyl phenol disulfides. The term "sulfur donor" as used hereinafter in the specification and claims means elemental sulfur as well as the aforementioned nonelemental sulfur compounds. The quantity of sulfur donor required for vulcanization is well known to those skilled in the art. Where the sulfur donor is elemental sulfur, is is incorporated into the polymer at 0.1 to 5 wt. % based on the polymer; preferably 0.25 to 3.5 wt. O/o; more preferably 0.5 to 3.0 wt. %, e.g., 0.5 to 2.5 wt % based on the copolymer. Where the sulfur donor is a nonelemental sulfur compound, it is incorporated at a wt. % of about three times that required for elemental sulfur.The term "nonelemental sulfur compounds" means organic compounds containing sulfur and capable of donating the sulfur to a vulcanization reaction, e.g., disulfides and polysulfides.
The delayed action accelerators may be modified by retarders and activators which will respectively retard or activate the sulfure vulcanization. The addition of the retarder will further delay the time at which vulcanization occurs while the activator will cause vulcanization to occur sooner, e.g., shorter delay time.
The retarders suitable of use in the practice of this invention includes organic compounds having a PKa of about 2 to less than 7; preferably about 3 to about 6.5; more preferably about 4 to about 6, e.g., 5. The term pKa is the dissociation constant as measured in aprotic solvents, see for example Acid-Base Behavior in Aprotic Solvents NBS Monograph 105,
August 1968.
The activators suitable for use in the practice of this invention are metallic oxides, hydroxides and alkoxides of Groups IA and IIA metals of the Periodic Table of Elements and organic compounds having a pKa of about 8 to about 14; preferably about 9 to about 12; more preferably about 9.5 to about 11, e.g. 10. The Periodic Table to which reference is made is that appearing in Notes on the use of the Classification Key of Abridgments of
Patent Specifications.
Illustrative examples of retarders are N-nitroso diphenylamine, N-cyclohexyl thiophthalimide, phthalic anhydride, salicyclic acid, benzoic acid, etc. Generally, the preferred retarders are nitroso compounds, phthalimides, anhydrides and acids.
Illustrative examples of activators are MgO, diphenylguanidine, hexane-1-amine, 1,6-hexane diamine, sodium methoxide, etc. The preferred activators are guanidines and amines.
The retarders and activators are preferably incorporated into the polymer at 0.1 to 5 wt.
more preferably 0.25 to 3.5 wt. %;most preferably 0.5 to 3.0 wt. %, e.g., 0.5 to 2.5 wt.
These copolymers of isoolefins and cyclopentadine or methyl cyclopentadiene e.g., isobutylene and cyclopentadiene possess markedly improved resistance to degradation by ozone over the acyclic diene copolymers. Although it has been postulated that such copolymers would have such improved properties as a result of having the unsaturation located in a side chain rather than in the backbone, it has heretofore not been possible to prepare substantially gel-free isoolefin-cyclodiene copolymers having number average molecular weight below about 90,000 which are commercially acceptable as direct replacements for Butyl rubber.
The highly unsaturated polymers of this invention are substantially as impermeable to air as are commercial low unsaturates, e.g., 1.5 mole % Butyl rubbers. Surprisingly, isoolefin copolymers of CPD or terpolymers of an isolefin, CPD and isoprene are less permeable to air at the higher unsaturation levels than is the low unsaturation Butyl rubber of commerce.
The term "substantially gel-free" as used in the specification and claims means copolymers containing less than 2 wt. % gel; more preferably less than 1% gel, e.g., 1/2% gel. The term "D#", wherein # is an integer means the volume % cyclopentadiene in a monomer mixture, wherein D represents cyclopentadiene and the integer is the volume % diene.
The copolymers and terpolymers of the present invention can be readily blended with other rubbers for modification of physical and chemical properties by techniques well known in the art. These other rubbers are non-polar crystallizable rubbers (i.e.
crystallization either included by low temperature or strain or a mixture thereof), polar crystallizable rubbers, non-polar, non-crystallizable rubbers on polar non-crystallizable rubbers. These rubbers are contained in the blend compositions at a concentration level of 5 to 900 parts by weight per 100 parts of the polymer, more preferably 25 to 500 and most preferably 50 to 300. Typical, but non-limiting examples of each class are: non-polar crystallizable rubbers, natural rubber, low isoprene Butyl rubbers; polar crystallizable rubbers, polychloroprene rubbers (i.e., the neoprene types), non-polar non-crystallizable rubbers-styrene butadiene copolymers, polybutadienes and more highly unsaturated Butyl rubbers; and polar non-crystallizable rubbers-butadiene acrylonitrile copolymers.
The fillers employed in the present invention are carbon blacks, silica, talcs, ground calcium carbonate, water precipitated calcium carbonate, or delaminated, calcined or hydrated clays or mixtures thereof. These fillers are incorporated into the blend composition at 5 to 350 parts by weight per hundred parts of polymer, more preferably at 25 to 350; and most preferably at 50 to 300. Typically, these fillers have a particle size of 003 to 20 microns, more preferably 0.3 to 10, and most preferably about 0.5 to about 10. The oil absorption as measured by grams of oil absorbed by 100 grams of filler is 10 to 100, more preferably 10 to 85 and most preferably 10 to 75.
The oils employed in the present invention are non-polar process oils having less than 2 wt. % polar type compounds as measured by molecular type clay gel analysis. These oils are selected from paraffinics ASTM Type 104B as defined in ASTM-D-2226-70, aromatics
ASTM Type 102 or naphthenics ASTM Type 104A, wherein the oil has a flash point by the
Cleveland open cup of at least 350 F., a pour point of less than 40"F., a viscosity of 70 to 3000 s.s.u.'s at 100"F. and a number average molecular weight of 300 to 1000, and more preferably 300 to 750. The preferred process oils are paraffinics.
The oils are incorporated into the blend composition at a concentration level of 5 to 200 parts by weight per hundred parts of polymer; more preferably at 25 to 150, and most preferably at 50 to 150.
Other plasticizers suitable for use in the present invention ae medium viscosity ester plasticizers for special high efficiency in increasing resilience particularly at low temperature. Some examples, which are not intended to be limiting in scope are dioctyl phthalate, dioctyl azelate, dioctyl sebacate or dibutyl phthalate. The ester plasticizer is incorporated into the blend composition at a concentration level of 5 to 100 parts by weight per hundred of polymer, more preferably 5 to 75, and most preferably 5 to 50.
The practice of this invention can involve batch or continuous polymerizations either isothermal or multi-temperature. Continuous polymerization is referred since it is more convenient for commercial operation and gives more uniform (homogeneous) products.
Molecular weight distributions (Mw/Mn) are preferably between 2.0 and 20.
The advantages of the physical properties of the compositions of the present invention can be more readily appreciated by reference to the following examples and tables.
Brief description of drawings
Figure I shows the relationship between critical homogeneous polymerization temperature and diene content.
Figure 2 shows the effect of polymerization temperature on number average molecular weight.
Figure 3 shows the effect of cosolvent concentration on molecular weight.
Figure 4 shows the effect of polymerization temperature on total monomer conversion.
Figure 5 shows catalyst efficiency as a function of cosolvent concentration.
Figure 6 shows the relationship between tensile strength and Mn for a base reference--Butyl rubber.
Figure 7 shows the relationship between tensile strength and Mn for an isobutyleneisoprene copolymer, wherein the mole % of isoprene is varied.
Figure 8 shows the relationship between tensile strength and Mn for a copolymer of isobutylene-cyclopentadiene wherein the mole % of cyclopentadiene is varied.
Figure 9 shows the comparative relationship of mole % diolefin (diolefin equivalent in terminology to diene) to Mn* x 10-3 for copolymers of isobutylene-isoprene and isobutylene-cyclopentadiene, required to maintain maximum tensile strength at the reference level.
Figure 10 shows the relationship between mole % of cyclopentadiene of copolymer of isobutylene-cyclopentadiene and Log Mn* (the number average molecular weight required to maintain maximum tensile strength at the reference level).
Example I
The quantities of reactants utilized in the preparation of these copolymers and terpolymers were measured as volume at -780C. Cosolvent (MCH) was measured at 25"C.
Monomer mixes comprising varying quantities of isobutylene and cyclopentadiene and in some cases isoprene also, were polymerized in the presence of an appropriate quantity of methylcyclohexane (MCH) cosolvent. The polymerizations were initiated using an 0.061M solution of ethyl-aluminum dichloride (EADC) in MCH (volume measured at 25"C.) added at a rate such as to maintain the reactor temperature to within 2"C. of the indicated polymerization temperature. In some instances small quantities of an 0.031M solution of
HCI in MCH (volume measured at -780C.) were added to the reactor wherein the HCI serves as a cocatalyst for the polymerization. All polymerizations were conducted in a dry inert atmosphere.The reactions were carried out for the indicated time period at which time they were terminated by the addition of a small quantity of cold 10% propanol in pentane. The reactor solutions were then treated briefly with gaseous NH3 and coagulated by pouring them into hot methanol containing an antioxidant. Polymer samples were dried in vacuo at about 60"C. Polymerization details for some representative products are presented in Table I.
TABLE I
Isobutylene-CPD copolymers and isobutylene-isoprene-CPD terpolymers
Product Feed (ml)
Catalyst Catalyst (ml) (ml)EADC HCl in MCH
No. Mole % Mn x Isobu- CPD Iso- Cosol- Temp. ( C) Time Polymer in MCH 0.0315 M
Unsat. 10-3 tylene prene venta Initial Final (min) Yield(g) 0.061M 24 11.5b 65 3104 96 - 800 -100 -100 45 103 200 36 15.5 82 3104 96 - 800 -106 -106 35 79 250 55 25.1 68 3040 160 - 800 -100 -100 50 105 300 58 27.1 80 3040 160 - 800 -110 -110 50 145 200 76 28.0 48 3040 160 - 800 - 95 - 94 60 127 150 11 77 14.6 40 3104 96 - 800 - 93 - 92 50 110 150 15 78 24.4 39 3230 170 - 600 - 90 - 89 50 105 150 11 79 16.4 36 3929 102 - 600 - 89 - 88 45 100 150 11 84 13.1 60 3104 96 - 800 -107 -107 35 113 100 10 120-2 33.7 65 736 64 - 200 - 90 - 90 80 40 80 15 121-1 21.6 90 760 40 - 200 -111 -110 28 20 20 0.5 26 9/17.8 86 2784 96 320 800 -100 - 99 70 154 215 54 8/12 83 2816 64 320 800 -109 -109 68 109 250 57 7/11 49 2816 64 320 800 -102 -101 70 110 200 23 8.3/15.8 91 2784 96 320 800 -110 -109 35 57 200 a - Cosolvent-methylcyclohexane (MCH) b - Mole % CPD in copolymer c - Mole % isoprene/mole % CPD terpolymer Example 2
Maximum attainable tensile strength
The maximum attainable tensile strength for a given elastomer with a given number average molecular weight in a given compound formulation is determined as follows. After selection of a suitable curing temperature, one vulcanizes the compound at several varying times of curing. Tensile strengths and crosslink densities are measured on the resultant samples. The direction in which the level of the tensile strength trends with changing crosslink density is noted.Further curing times are then employed to allow amplification of the trend until a maximum in the tensile strength level is obtained. This is the maximum attainable tensile strength for the material in question. The strength is dependent on the number average molecular weight of the original polymer and the crosslink density of the specific vulcanizate. The crosslink density is virtually independent of the choice of curing temperature provided extreme high temperatures and extreme duration of curing times are avoided. Such extremes can lead to a reversion in the crosslinking resulting ultimately in a process of "devulcanization".
Some examples of the data developed to appraise the maximum attainable tensile strength in the present instance for two copolymers are given as follows:
TABLE II
Cyclopentadiene Isoprene
Copolymer Copolymer
19.1% Unsat. 14.2% Unsat.
55 000 Mn 80000Mn V X 104 TS, MPaa v x 104 TS, MPa
0.80 5.50 0.45 3.50
1.35 12.0 1.00 12.5
2.00 13.5* 1.20 12.5*
2.90 11.5* 1.85 10.5 a - 1 MPa = 145.0 psi.
v - Crosslink density (moles/cm3) - Reference 1.
* - Maximum attainable tensile strength.
TS - Tensile strength measured at ~ 23C, with a rate of extension'of 20 inches/min.
This method was utilized to determine the maximum tensiles fos~t- various types of coand terpolymers as a function of unsaturation and Mn. The data are presented in Figures 6, 7 and 8.
The compound formulation used to prepare the vulcanizates for test of these experimental elastomers was as follows: polymer 100, zinc stearate 1.65, HAF carbon black 60, hydrocarbon plasticizer oil (Flexon 845, ASTM Type 4) 20, antioxidant (Thermaflex A) 1.11, zinc oxide 5, sulfur 2.5, sulfenamide accelerator (Santocure NS) 0.75. For the compositions containing the "crosslinkable polyisobutylenes" (i.e., the isoprene copolymers with unsaturations in the range of the Butyl rubbers - 1.19 to 2.68 mole percent) the formulation was modified with respect to the curative system. The accelerator (Santocure
NS) was replaced by the ultra-accelerator, combination, Tellurac plus Altax, both at 1.0 phr. (The words 'Flexon', 'Santocure' and 'Altax' are registered Trade Marks). The sulfur content was reduced to 1.5 phr. These modifications were in keeping with the reduced crosslinking capabilities of the indicated isoprene copolymers.
The compound formulation chosen for test of the experimental elastomers was selected on the basis that it represents a practical system with the added attractive economic and commercial feature of being relatively extended in terms of oil plasticizer and carbon black content. However, this test formulation can be varied quite broadly to achieve properties at specific levels related to some end use. Relative to the maximum attainable tensile strength, the trends that would be observed with changes in test formulations would be consistent with information well kown in the art. Examples of such trends are given as follows.
Changing the concentration of carbon black in either direction from the 60 phr level would entail a reduction in the tensile strength. Changing the type of carbon black would affect the tensile strength relative to the particle size of the black. A change to a carbon black of large particle size would result in the reduction in the tensile strength. A change to a carbon black of finer particle size would result in an increase in the tensile strength. Oil plasticizers of low to medium viscosity generally reduce tensile strength as the concentration is increased.
Very viscous or resinous liquid materials in the formulation tend to increase the tensile strength. This is also true of resins. The curative system used for preparation of the vulcanizates can affect the maximum attainable tensile strength. As a broad general rule, the simpler the crosslink at the juncture point which results from a given curative system, the lower the tensile strength. Tensile strengths for example tend to increase as the bond simplicity decreases from C-C, C-S-C, C-S2-C, C-S3-C, etc. and S3+. As practical examples, a peroxide cure would give a simple crosslink juncture (C-C). Next in line of reduced bond simplicity would be a single sulfur atom juncture (S1) resulting from curing a formulation with relatively high accelerator and low sulfur contents. Conversely, curing
with low accelerator and high sulfur contents results in a complex type of bond (S3+).
Maxima in curves relating tensile strength to crosslink density are evident in the results of
Gee2, Flory, Rabjohn and Shaffer3 and Dudek and Bueche4.
The isoolefins which can be employed in the present invention include isobutylene, 2-methyl-1-butene, 3-methyl-1-butene and 4-methyl-1-pentene, wherein isobutylene is preferred. The conjugated dienes which can be employed in the present invention apart from cyclpentadiene and methyl cyclopentadiene include isoprene, piperylene, 2-3 dimethylbutadiene, 2-5 dimethyl hexadi-2,4-ene, cyclohexadiene and mixtures thereof, wherein isoprene is preferred.
References 1. P. J. Flory and J. Rehner, J. Chem. Phys., 11, 512, 521 (1943) 2. G. Gee, J. Polymer Sci., ~, 451 (1947) .3. P.J. Flory, N. Rabjohn and M. C. Shaffer, J. Polymer Sci-, 4, 435 (1949).
4. T. J. Dudek and F. Bueche, J. Appl. Polymer Sci., 8, 555 (1964).
WHAT WE CLAIM IS:
1. A substantially gel-free copolymer consisting essentially of a major portion of an isoolefin having 4 to 10 carbon atoms per molecule and 5 to 45 mole % of cyclopentadiene or methylcyclopentadiene, said copolymer having a number average molecular weight Mn) of at least 30,000 to less than 90,000.
2. A substantially gel-free copolymer consisting essentially of a major portion of an isolefin having 4 to 10 carbon atoms per molecule and 5 to 45 mole % of a mixture of either cyclopentadiene or methylcyclopentadiene or a mixture thereof and another conjugated diene, said polymer having a number average molecular weight of at least 30,000 to less than 90,000.
3. A copolymer according to claim 2 wherein the diene is isoprene, piperylene, 2-3 dimethyl butadiene, 2-5 dimethyl hexadi-2-ene, cyclohexadiene or a mixture thereof.
4. A copolymer according to any one of the preceding claims wherein the isoolefin is isobutylene, 2-methyl-l-butene, 3-methyl-1-butene or 4-methyl-l-pentene.
5. A vulcanizable composition which comprises:
(a) a substantially gel-free copolymer according to any one of the preceding claims
(b) 0.1 to 5.0 wt % based on the copolymer of a sulphur donor; and
(c) 0.25 to 3.5 wt % based on the copolymer of a delayed action accelerator.
6. A composition according to claim 5 which includes 5 to 350 parts by weight per one hundred parts of said copolymer of a filler which is carbon black, silica, talc, ground or water precipitated calcium carbonate or clay, said filler having an oil absorption of from 10 to 100.
7. A composition according to either of claims 5 and 6 which includes 5 to 200 parts by weight based on one hundred parts by weight of said polymer of a non-polar process oil, the oil having less than 2% by weight of polar type compounds.
8. A composition according to any one of claims 5 to 7 which includes 5 to 900 parts by weight per one hundred parts by weight of said polymer of a rubber which is a non-polar crystallizable rubber, a polar crystallizable rubber, a non-polar, non-crystallizable rubber or a polar non-crystallizable rubber.
9. A copolymer according to either of claims 1 and 2 substantially as hereinbefore described with reference to Example 1.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (10)
1. A substantially gel-free copolymer consisting essentially of a major portion of an isoolefin having 4 to 10 carbon atoms per molecule and 5 to 45 mole % of cyclopentadiene or methylcyclopentadiene, said copolymer having a number average molecular weight Mn) of at least 30,000 to less than 90,000.
2. A substantially gel-free copolymer consisting essentially of a major portion of an isolefin having 4 to 10 carbon atoms per molecule and 5 to 45 mole % of a mixture of either cyclopentadiene or methylcyclopentadiene or a mixture thereof and another conjugated diene, said polymer having a number average molecular weight of at least 30,000 to less than 90,000.
3. A copolymer according to claim 2 wherein the diene is isoprene, piperylene, 2-3 dimethyl butadiene, 2-5 dimethyl hexadi-2-ene, cyclohexadiene or a mixture thereof.
4. A copolymer according to any one of the preceding claims wherein the isoolefin is isobutylene, 2-methyl-l-butene, 3-methyl-1-butene or 4-methyl-l-pentene.
5. A vulcanizable composition which comprises:
(a) a substantially gel-free copolymer according to any one of the preceding claims
(b) 0.1 to 5.0 wt % based on the copolymer of a sulphur donor; and
(c) 0.25 to 3.5 wt % based on the copolymer of a delayed action accelerator.
6. A composition according to claim 5 which includes 5 to 350 parts by weight per one hundred parts of said copolymer of a filler which is carbon black, silica, talc, ground or water precipitated calcium carbonate or clay, said filler having an oil absorption of from 10 to 100.
7. A composition according to either of claims 5 and 6 which includes 5 to 200 parts by weight based on one hundred parts by weight of said polymer of a non-polar process oil, the oil having less than 2% by weight of polar type compounds.
8. A composition according to any one of claims 5 to 7 which includes 5 to 900 parts by weight per one hundred parts by weight of said polymer of a rubber which is a non-polar crystallizable rubber, a polar crystallizable rubber, a non-polar, non-crystallizable rubber or a polar non-crystallizable rubber.
9. A copolymer according to either of claims 1 and 2 substantially as hereinbefore described with reference to Example 1.
10. A composition according to claim 5 substantially as hereinbefore described with reference to Example 2.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US05/803,596 US4153773A (en) | 1975-11-13 | 1977-06-06 | Isobutylene cyclodiolefin copolymers and terpolymers |
Publications (1)
Publication Number | Publication Date |
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GB1590749A true GB1590749A (en) | 1981-06-10 |
Family
ID=25186961
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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GB5425777A Expired GB1590749A (en) | 1977-06-06 | 1977-12-30 | Isoolefin-cyclodiolefin copolymers and terpolymers |
Country Status (7)
Country | Link |
---|---|
JP (1) | JPS543190A (en) |
BE (1) | BE866429R (en) |
CA (1) | CA1134996A (en) |
DE (1) | DE2824512A1 (en) |
FR (1) | FR2393820A2 (en) |
GB (1) | GB1590749A (en) |
NL (1) | NL7714530A (en) |
-
1977
- 1977-12-29 NL NL7714530A patent/NL7714530A/en not_active Application Discontinuation
- 1977-12-29 CA CA000294032A patent/CA1134996A/en not_active Expired
- 1977-12-30 GB GB5425777A patent/GB1590749A/en not_active Expired
-
1978
- 1978-01-31 JP JP980178A patent/JPS543190A/en active Pending
- 1978-03-06 FR FR787806375A patent/FR2393820A2/en active Pending
- 1978-04-26 BE BE187153A patent/BE866429R/en active
- 1978-06-03 DE DE19782824512 patent/DE2824512A1/en active Pending
Also Published As
Publication number | Publication date |
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NL7714530A (en) | 1978-12-08 |
CA1134996A (en) | 1982-11-02 |
FR2393820A2 (en) | 1979-01-05 |
BE866429R (en) | 1978-10-26 |
JPS543190A (en) | 1979-01-11 |
DE2824512A1 (en) | 1978-12-14 |
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