Butyl rubber with new sequence distribution

Abstract

The invention relates to an efficient polymerization process and its use to produce novel copolymers with a specific microstructure. In particular, the invention relates to butyl rubbers with novel microstructure, preferably those obtainable by copolymerization of monomer mixtures comprising isobutylene and isoprene. In a further aspect the invention relates to halogenated copolymers obtainable from such novel copolymers by halogenation.

Claims

1. Copolymers of isobutylene and isoprene having a copolymer sequence distribution defined by equation (I)
F=mA/(1+mA).sup.2(eq. I) wherein A is the molar ratio of isoprene to isobutylene in the copolymer as determined by .sup.1H NMR; and F is the isobutylene-isoprene-isoprene triad fraction in the copolymer as determined by .sup.13C NMR; and m is in the range of
[1.27(0.025MOC)]m[1.17(0.025MOC)] whereby MOC is the content of isoprene in the copolymer in mol-% as determined by .sup.1H NMR, and m is 1.12 or less.

2. The copolymers according to claim 1, wherein the isobutylene content is 85.0 to 99.5 mol.-% and the isoprene content is 0.5 to 15.0 mol.-%.

3. The copolymers according to claim 1, wherein the isobutylene content is 96.2 to 99.5 mol.-% and the isoprene content is 0.5 to 3.8 mol.-%.

4. The copolymers according to claim 1 wherein the copolymers are halogenated copolymers.

5. The copolymers according to claim 4, wherein the copolymers have an amount of halogen of 0.1 to 8.0 wt.-% by weight of the halogenated copolymer.

6. A process for the preparation of the copolymers according to claim 1, the process comprising: a) contacting a diluent and a monomer mixture comprising isobutylene and isoprene in a mass ratio of monomer mixture to diluent of 5:95 to 95:5 to form a reaction medium; b) polymerizing the monomer mixture within the reaction medium in the presence of an initiator system to form a copolymer solution comprising the copolymer which is at least substantially dissolved in the reaction medium comprising the diluent and residual monomers of the monomer mixture; and c) separating residual monomers of the monomer mixture and additionally diluent from the reaction medium to obtain the copolymer whereby step b) is carried out at a temperature of 95 C. to 60 C., and whereby the diluent comprises at least 95.0 wt.-% of one or more aliphatic hydrocarbons having a boiling point of 5 C. to 95 C. at a pressure of 1013 hPa and comprises at maximum 1.0 wt.-% of halogenated hydrocarbons or is free of such halogenated hydrocarbons.

7. The process according to claim 6, wherein, for the diluent, the aliphatic hydrocarbons having a boiling point in the range of 5 C. to 95 C. at a pressure of 1013 hPa comprise linear (n-alkanes) and the content of the linear (n-alkanes) does not exceed 85 wt.-%.

8. The process according to claim 6, wherein, for the diluent, the aliphatic hydrocarbons include cyclic hydrocarbons having a boiling point in the range of 5 C. to 95 C. at a pressure of 1013 hPa, and the content of cyclic hydrocarbons does not exceed 25 wt.-%.

9. Process according to claim 6, wherein the initiator system comprises ethyl aluminum sesquichloride generated by mixing equimolar amounts of diethyl aluminum chloride and ethyl aluminum dichloride in a diluent.

10. The process according to claim 6, wherein, for the initiator system, water and/or alcohols are used as a proton source.

11. A process for the preparation of the halogenated copolymers according to claim 4, the process comprising: a) contacting a diluent and a monomer mixture comprising isobutylene and isoprene in a mass ratio of monomer mixture to diluent of 5:95 to 95:5 to form a reaction medium; (b) polymerizing the monomer mixture within the reaction medium in the presence of an initiator system to form a copolymer solution comprising the copolymer which is at least substantially dissolved in the reaction medium comprising the diluent and residual monomers of the monomer mixture; c) separating residual monomers of the monomer mixture to separate copolymer from the monomers; and d) halogenating the copolymer.

12. The process according to claim 11, wherein the halogenation is carried out using elemental chlorine (Cl.sub.2) or bromine (Br.sub.2) as halogenation agent.

13. A polymer product comprising cured or uncured copolymers according to claim 1.

14. The copolymers according to claim 1, wherein the isobutylene content is 96.3 to 99.0 mol.-% and the isoprene content is 1.0 to 3.7 mol.-%.

15. The copolymers according to claim 1, wherein the copolymers are halogenated copolymers and have an amount of halogen of 0.8 wt.-% to 3 wt.-% by weight of the halogenated copolymer.

16. The copolymers according to claim 1, wherein the copolymers are halogenated copolymers and have an amount of halogen of 1.8 to 2.3 wt.-% by weight of the halogenated copolymer.

17. The copolymers according to claim 1, wherein: the copolymers are halogenated and have an amount of halogen of 0.1 to 8.0 wt.-% by weight of the halogenated copolymer; and the isobutylene content is 85.0 to 99.5 mol.-% and the isoprene content is 0.5 to 15.0 mol.-%.

18. The copolymers according to claim 1, wherein: the copolymers are halogenated and have an amount of halogen of 1.8 to 2.3 wt.-% by weight of the halogenated copolymer; and the isobutylene content is 96.3 to 99.0 mol.-% and the isoprene content is 1.0 to 3.7 mol.-%.

19. The copolymers according to claim 1, wherein m is 0.95 to 1.12.

Description

EXAMPLES

(1) General Procedures

(2) All polymerizations were performed in an MBraun MB-200G dry box equipped with a pentane cooling bath and a reactor and bath temperature recorder. The diluent employed was dried using an MBraun MB-SPS solvent purification system and piped directly into the dry box for use. The diluent was consisting of: less than 0.1 wt.-% aliphatic hydrocarbons having a boiling point below 45 C. at a pressure of 1013 hPa, 98.7 wt.-% aliphatic hydrocarbons having a boiling point in the range of 45 C. to 80 C. at a pressure of 1013 hPa, the residual amount to 100.0 wt.-% aliphatic hydrocarbons having a boiling point above 80 C. at a pressure of 1013 hPa.

(3) The total amount of cyclic aliphatic hydrocarbons present in the solvent was 18.7 wt. % (methylcyclopentane, cyclopentane and cyclohexane). The total amount of cyclohexane present in the solvent was 1.4 wt. %. The total amount of branched, non-cyclic aliphatic hydrocarbons present in the solvent was 34.4 wt. % (2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, 2,2-dimethylpentane).

(4) Isobutylene (i.e. isobutene) was used without further purification. Ethyl aluminum dichloride (EADC) 1.0 M in hexanes and diethyl aluminum chloride (DEAC) 1.0 M in hexanes were used as received. Isoprene was dried over CaH.sub.2 for 24 hours under an inert atmosphere before being vacuum distilled to a separate flask and then introduced into the dry box where it was stored at 2 C. until used.

(5) Initiator Preparation

(6) A master-batch of EASC/H.sub.2O catalyst was prepared by mixing 100 mL of 1.0 M EADC and 100 mL of 1.0 M DEAC in a 1 L Erlenmeyer flask in a dry box. After mixing for 15 minutes the solution was diluted with 800 mL of the diluent as specified above and stirring was continued for 1 h. 4.0 mL of de-ionized water was then added to the stirred solution. After the water was added the solution was left stirring for 1 h. The solution was then filtered using 0.45 m filter discs.

(7) Polymerization Procedure

(8) A general polymerization recipe was followed with any deviations noted in the following discussion. A 500 mL 3-neck round-bottomed flask was cooled to the reaction temperature (80 C.) and 40 mL of the diluent as specified above was added. Isobutylene (80 mL) was measured into a chilled graduated cylinder in the cooling bath allowing time to reach the bath temperature before it was added to the reactor flask. Isoprene (ranging from 3.75 to 14 mL) was measured into the reaction flask using a pipette at room temperature. The solution was then stirred at 330 rpm and once the temperature was stabilized the polymerization was initiated with EASC pipetted into the reaction flask with no further cooling. Reactions were run for 30 minutes and were stopped using a solution of ethanol containing about 1 wt % NaOH. The raw polymer cement was removed from the dry box and about 100 mL of hexanes was added with 1.0 mL of an anti-oxidant solution (1 wt % Irganox 1076 in hexanes). The solution was then coagulated into about 600 mL of stirring ethanol. The rubber was collected and dried in the vacuum oven at 60 C. for 48 hours. Yields were determined gravimetrically.

(9) Polymer Analysis

(10) NMR spectra were recorded on a Bruker 500 MHz NMR spectrometer using CDCl.sub.3 solutions with a concentration of about 5 mg/mL. A delay time of 10 seconds was used to collect 32 transients at a pulse angle of 90. Chemical shifts are reported in ppm for .sup.1H in relation to TMS (=0).

(11) Determination of Sequence Parameter m

(12) Monomer incorporation was determined by 1H-NMR spectrometry. NMR measurements were obtained at a field strength corresponding to 500 MHz. 1H-NMR spectra were recorded at room temperature on a Bruker Avance NMR spectrometer system using CDCl.sub.3 solutions of the polymers. All chemical shifts were referenced to TMS.

(13) Triad sequence distributions were obtained from .sup.13C NMR spectrometry using a Bruker Avance NMR spectrometer at a field strength of 125.7 MHz and a temperature of 50 degrees centigrade Polymer samples were dissolved into CDCl.sub.3 (containing 1.5 percent wt./v. of chromium (III) acetylacetonate as a relaxation agent) at a concentration of 6 to 8 weight percent. The free induction decays were collected with a 90 degrees pulse, 3.0 second recycle delay and a 2.133 second acquisition time. Each data set consisted of a sweep width of 30,007 Hz and 30,000 scans/transients. All chemical shifts were referenced to tetramethylsilane.

(14) Data processing was performed with TopSpin 2.1.

(15) The isoprene triad resonances were assigned according to information reported by C. Corno, A. Proni, A. Priola, and S. Cesca in Macromolecules 1980, 13, 1092 and J. L. White, T. D. Shaffer, C. J. Ruff, and J. P. Cross in Macromolecules 1995, 28, 3290, both herein incorporated by reference.

(16) For each triad structure, a quaternary carbon and a tertiary carbon resonance was observed. The BII (B=isobutylene, I=isoprene) olefin triad fractions were calculated for each type of carbon, quaternary and tertiary. For example, the BII value for tertiary carbons was calculated by dividing the average of the BII tertiary carbon integral and the IIB tertiary carbon integral by the sum of all the tertiary integrals for BIB, BII, IIB, and III triads. By definition, the BII triad fraction must equal the IIB triad fraction. Once BII triad fractions were calculated for each carbon type, tertiary and quaternary, these values were averaged and used for comparison with the amount of isoprene incorporated into the copolymer. Integrals were calculated for each isoprene resonance based as shown in Table 1.

(17) TABLE-US-00001 TABLE 1 Isoprene centered triads and integration ranges used to quantify relative abundance. Isoprene centered Peak Triad Peak Integral Integral Number Sequece maximum left side right side 1 BII 134.07 134.16 134.01 2 IIB 132.63 132.68 132.58 3 BIB 132.06 132.18 131.94 4 BIB 129.63 129.76 129.53 5 IBIB 129.15 129.22 129.10 6 IIB 128.62 128.69 128.57 7 BII 125.05 125.12 124.97

(18) A plot of the BII fraction (expressed as a percentage of all isoprene centered triads) versus mole percent isoprene incorporated into the copolymer was created and is described below.

(19) Values for the parameter m were determined for each sample using Equation 1 and are given in Table 2.

(20) TABLE-US-00002 TABLE 2 Solution polymerizations performed at 80 C. isoprene Example (mol %) F.sub.BII m 1 2.44 0.026 1.12 2 3.67 0.039 1.11 3 5.71 0.060 1.12 4 7.40 0.072 1.06 5 9.77 0.085 0.95

Example 5Halogenation

(21) The separated rubber solution of Example 2 is halogenated using pilot scale halogenation equipment. Supplemental solvent in an amount of 10% is added to the separated rubber solution in order to lower the viscosity. A brominated butyl polymer containing 1.6% bromine is produced in the separated rubber solution. The halogenated separated rubber solution is then finished using conventional drying and finishing techniques.