Sulfur-free, zinc-free cure system for halobutyl and halogen containing polymers

Abstract

This invention discloses a sulfur free and ZnO free cross-linking composition comprising a multifunctional phosphine crosslinking agent and halobutyl polymers or halogen containing polymers.

Claims

1. A cured, sulfur free and ZnO free compound comprising a halogen containing polymer crosslinked with bis(2-diphenylphosphinophenyl)ether.

2. The compound according to claim 1, wherein the halogen containing polymer is at least one halobutyl polymer selected from bromobutyl polymers, chlorobutyl polymers, and mixtures thereof.

3. The compound according to claim 1, wherein the halogen containing polymer is at least one halogen containing polymer selected from bromine containing polymers, chlorine containing polymers, and mixtures thereof.

4. The compound according to claim 1, wherein the halogen containing polymer is selected from the group consisting of brominated isobutylene para-methylstyrene, brominated isoprene isobutylene p-methylstyrene terpolymer, starbranch brominated butyl, and mixtures thereof.

5. The compound according to claim 1, further comprising at least one filler and at least one process aid.

6. The compound according to claim 5, wherein the filler is selected from the group consisting of carbon black, white fillers, and mixtures thereof.

7. A cured, sulfur free and ZnO free compound comprising: a halogenated butyl rubber formed from isobutylene and less than 2.2 mol % isoprene; and a multifunctional phosphine crosslinking agent of the structure ##STR00004## wherein n?3.

8. The compound according to claim 7, wherein the halogenated butyl polymer is a bromobutyl polymer or a chlorobutyl polymer.

9. The compound according to claim 7, wherein the polymer is selected from the group consisting of brominated isobutyiene para-methylstyrene, brominated isoprene isobutylene p-methylstyrene terpolymer, and star branch brominated butyl.

10. The compound according to claim 7, further comprising a filler and a process aid.

11. The compound according to claim 10, wherein the filler is selected from the group consisting of carbon black, white filler, and mixtures thereof.

12. The compound according to claim 7, wherein the multifunctional phosphine crosslinking agent is selected from the group consisting of 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane, 1,6-bis(diphenyl-phosphino)hexane, and 1,8-bis(diphenylphosphino)octane.

13. The compound according to claim 7, wherein a molar ratio of allylic halide to multifunctional phosphine is 0.01:15 to 15:0.01.

14. The compound according to claim 7, wherein a molar ratio of allylic halide to multifunctional phosphine ratio is 0.01 to 15.

15. The compound according to claim 7, wherein a molar ratio of multifunctional phosphine to allylic halide is 0.01 to 15.

16. A process for preparing a cross-linked rubber compound, the process comprising contacting a halogenated butyl rubber formed from isobutylene and less than 2.2 mol % isoprene, with a multifunctional phosphine crosslinking agent of the structure ##STR00005## wherein n?3.

17. The process according to claim 16, wherein the halogenated butyl rubber is a bromobutyl rubber or a chlorobutyl rubber.

18. The process according to claim 16, wherein: the halogenated butyl rubber is a bromobutyl rubber; and the contacting comprises reacting the polymer with the multifunctional phosphine crosslinking agent for about 10 to 90 minutes at a temperature of 140 to 200?C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described by way of reference to the drawings, in which:

(2) FIG. 1 shows the effects of the alkyl spacer on bisphosphine nucleophiles on the cure behavior of bromobutyl rubber;

(3) FIG. 2 shows the cure behavior of bromobutyl and Bis(2-diphenylphosphinophenyl)ether (DPEphos);

(4) FIG. 3 shows the effects of the level of bisphosphine on the cure behavior of bromobutyl rubber;

(5) FIG. 4 shows the cure behavior for various bromine containing polymers;

(6) FIG. 5 shows the cure behavior for chlorobutyl rubber;

(7) FIG. 6 shows the effects of black and white fillers; and

(8) FIG. 7 shows the comparative study of bisphosphine cure versus standard pharmaceutical.

DETAILED DESCRIPTION OF THE INVENTION

(9) Halobutyl Polymer

(10) The halobutyl polymers used in the present invention are copolymers of at least one isoolefin monomer and one or more multiolefin monomers or one or more alkyl substituted aromatic vinyl monomers or both.

(11) In one embodiment, the halobutyl polymers used in the formation of the ionomer of the present invention comprises at least one allylic halo moiety, or at least one halo alkyl moiety or both.

(12) In one embodiment, the halobutyl polymers comprises repeating units derived from at least one isoolefin monomer and repeating units derived from one or more multiolefin monomers. In such an embodiment, one or more of the repeating units derived from the multiolefin monomers comprise an allylic halo moiety.

(13) In one embodiment, the halobutyl polymers is obtained by first preparing a copolymer from a monomer mixture comprising one or more isoolefins and one or more multiolefins (also referred to as multiolefin butyl rubber polymer), followed by subjecting the resulting copolymer to a halogenation process to form the halobutyl polymers. Halogenation can be performed according to the process known by those skilled in the art, for example, the procedures described in Rubber Technology, 3rd Ed., Edited by Maurice Morton, Kluwer Academic Publishers, pp. 297-300 and further documents cited therein.

(14) During halogenation, some or all of the multiolefin content of the copolymer is converted to units comprising allylic halides. The total allylic halide content of the halobutyl polymers cannot exceed the starting multiolefin content of the parent copolymer.

(15) In one embodiment, the monomer mixture used in preparing the multiolefin butyl rubber comprises from about 80% to about 99.5% by weight of at least one isoolefin monomer and from about 0.5% to about 20% by weight of at least one multiolefin monomer. In one embodiment, the monomer mixture comprises from about 83% to about 98% by weight of at least one isoolefin monomer and from about 2.0% to about 17% by weight of a multiolefin monomer.

(16) In one embodiment, the multiolefin butyl polymer comprises at least 0.5 mol % repeating units derived from the multiolefin monomers. In one embodiment, the repeating units derived from the multiolefin monomers are at least 0.75 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 1.0 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 1.5 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 2.0 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 2.5 mol %.

(17) In one embodiment, the multiolefin butyl polymer comprises at least 3.0 mol % repeating units derived from the multiolefin monomers. In one embodiment, the repeating units derived from the multiolefin monomers are at least 4.0 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 5.0 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are at least 6.0 mol %. In one embodiment, the repeating units derived from the multiolefin monomers at least 7.0 mol %.

(18) In one embodiment, the repeating units derived from the multiolefin monomers are from about 0.5 mol % to about 20 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are from about 0.5 mol % to about 8 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are from about 0.5 mol % to about 4 mol %. In one embodiment, the repeating units derived from the multiolefin monomers are from about 0.5 mol % to about 2.5 mol %.

(19) In one embodiment, the halobutyl polymers for use in the present invention includes a brominated butyl rubber formed from isobutylene and less than 2.2 mol % isoprene, which is commercially available from LANXESS Deutschland GmbH and sold under the names Bromobutyl 2030?, Bromobutyl 2040?, Bromobutyl X2?, and Bromobutyl 2230?.

(20) In one embodiment, the halobutyl polymers for use in the present invention includes a high isoprene brominated butyl rubber formed from isobutylene and at least 3 mol % isoprene or at least 4% mol % isoprene, as described in Canadian Patent Application No. 2,578,583 and 2,418,884, respectively.

(21) In one embodiment, the halobutyl polymers of the present invention comprise copolymers of at least one isoolefin and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more of the repeating units derived from the aromatic vinyl monomers comprise a halo alkyl moiety.

(22) In one embodiment, these type of halobutyl polymers are obtained by first preparing a copolymer from a monomer mixture comprising one or more isoolefins and one or more alkyl substituted aromatic vinyl monomers, followed by subjecting the resulting copolymer to a halogenation process to form the halobutyl polymers. During halogenation, some or all of the alkyl groups of the repeating units derived from the aromatic vinyl monomers are halogenated.

(23) In one embodiment, the halobutyl polymers of the present invention comprise copolymers of at least one isoolefin, one or more multiolefin monomers, and one or more alkyl substituted aromatic vinyl monomers. In such an embodiment, one or more units derived from the multiolefin monomers comprise an allylic halo moiety and/or one or more units derived from the substituted aromatic vinyl monomers comprise a haloalkyl moiety.

(24) In one embodiment, the monomer mixture used in preparing the copolymer of isoolefin, the multiolefin and the alkyl substituted aromatic vinyl monomers comprise from about 80% to about 99% by weight of isoolefin monomers, from about 0.5% to about 5% by weight the multiolefin monomers, and from about 0.5% to about 15% by weight of the alkyl substituted aromatic vinyl monomers. In one embodiment, the monomer mixture comprises from about 85% to about 99% by weight of isoolefin monomer, from about 0.5% to about 5% by weight the multiolefin monomer and from about 0.5% to about 10% by weight alkyl substituted aromatic vinyl monomer.

(25) The halobutyl polymers should have allylic bromide content from 0.05 to 2.0 mol %, more preferably from 0.2 to 1.0 mol % and even more preferably from 0.5 to 0.8 mol %. The high multiolefin halobutyl polymers should also contain residual multiolefin levels ranging from 2 to 10 mol %, more preferably from 3 to 8 mol % and even more preferably from 4 to 7.5 mol %.

(26) Halogen Containing Polymers

(27) Halogen containing polymers that may be used to demonstrate the scope of the invention are bromobutyl, chlorobutyl, brominated high isoprene butyl rubber, brominated isobutylene para-methylstyrene (BIMSM), brominated isoprene isobutylene p-methylstyrene terpolymer, starbranch brominated butyl (SBB) and chlorobutyl.

(28) Formation of Bisphosphine Cross-Linking Butyl Ionomer Network

(29) Shown in Scheme 1 below is an illustrative example, where bromobutyl rubber is reacted with alkyl bisphosphine at about 160? C. to provide bisphosphine crosslinked butyl ionomer.

(30) ##STR00001##

(31) The reaction provides the simultaneous formation of bisphosphine cross-linking butyl ionomer. As a person skilled in the part would readily appreciate that the bisphosphine agents as shown may be of different alkyl lengths, as well as similar bisphosphine nucleophiles containing aromatics, heteroaromatics, cycloalkanes, heteroalkanes and heterocycloalkanes or combination thereof in between the two phosphine moieties or as the phosphine side groups can also be use, reacting with halobutyl or halogen containing polymers to form other types of ionomers.

(32) Nucleophiles

(33) According to the present invention, the halobutyl or bromine containing polymers can be reacted with the bisphosphine nucleophiles, i.e., symmetrical or unsymmetrical bisphosphine compounds with the structure:
(R.sub.2).sub.2PR.sub.1P(R.sub.3).sub.2 wherein R1=alkyl, alkenyl, cycloalkyl, aryl, heteroaryl, heteroalkyl, heteroalkenyl, heterocycloalkyl; R2=R3=alkyl, alkenyl, cycloalkyl, aryl, heteroaryl, heteroalkyl, heteroalkenyl, heterocycloalkyl; R25?R3=alkyl, alkenyl, cycloalkyl, aryl, heteroaryl, heteroalkyl, heteroalkenyl, heterocycloalkyl.

(34) Preferably, the bisphosphine nucleophiles are according to the following formula:

(35) ##STR00002##
wherein n is from 1 to 8. n=1: bis(diphenylphosphino)methane (BDPM) n=2: bis(diphenylphosphino)ethane (BDPE or DIPHOS) n=3: bis(diphenylphosphino)propane (BDPP) n=4: bis(diphenylphosphino)butane (BDPB) n=5: bis(diphenylphosphino)pentane (BDPPe) n=6: bis(diphenylphosphino)hexane (BDPH) n=8: bis(diphenylphosphino)octane (BDPO)

(36) According to one embodiment of the invention, the amount of allylic halide to phosphine is in the range from 15:0.01 molar ratio, more preferable 7:1 molar ratio, more preferable 4:1 molar ratio and even more preferably of about 2:1 molar ratio.

(37) According to another embodiment of the invention, the amount of phosphine to allylic halide is in the range from 15:0.01 molar ratio, more preferable 7:1 molar ratio, more preferable 4:1 molar ratio and even more preferably of about 0.5:1 molar ratio.

(38) The high multiolefin halobutyl polymer and the nucleophile react for about 10 to 90 minutes, preferably from 15 to 60 minutes and more preferably about 10 minutes at temperatures ranging from 140 to 200? C., preferably about 160? C.

(39) Experiments and Results

(40) General

(41) Reactions of bisphosphine nucleophiles with various alkyl spacers and bromobutyl BB2030 as well as with other bromine containing polymers listed in Table 1 were conducted on a lab-scale.

(42) The products were then subjected to compounding and Moving Die Rheometer (MDR) measurements to verify their curability.

(43) Materials

(44) Various halobutyl and halogen containing polymers used in the reactions are outlined in Table 1 below.

(45) TABLE-US-00001 TABLE 1 Polymer BB2030 Bromobutyl 2030 is a halogenated butyl rubber polymer having 0.8-1.5 mol % unsaturation, with about 0.9 mol % allylic bromide and a product of LANXESS Corp. CB1240 Chlorobutyl 1240, is a halogenated butyl rubber polymer having 2.2 mol % unstaturation, with about 1.6 mol % allylic chloride and a product of LANXESS Corp. bromobutyl regular butyl with 4 mol % unsaturation and brominated (4 mol % to 0.8 mol % allylic bromide isoprene) Brominated isoprene isobutylene p-methylstyrene terpolymer Brominated A copolymer of 90.4% isobutylene, 8.2% paramethyl- Terpolymer styrene and 1.4% isoprene; brominated to 0.83 mol % of allylic bromide BIMSM A brominated copolymer of isobutylene paramethylstyrene commercially available from ExxoMobil Chemical (ExxproTM 3035)

(46) Bisphosphine nucleophiles with various alkyl spacers (Table 2) were reacted with unfilled BB2030.

(47) ##STR00003##

(48) TABLE-US-00002 TABLE 2 Nucleo- BDPE philes BDPM (DIPHOS) BDPP BDPB BDPPe BDPH BDPO n 1 2 3 4 5 6 8

(49) Additionally, bis(2-diphenylphosphinophenyl)ether (DPEphos) was used as a nucleophile in the studies.

(50) Crosslinking Reaction

(51) Unfilled Compound

(52) All mixes (Examples 1-17) were performed similarly in a miniaturized internal mixer. The start temperature was approximately at 30? C. and the rotor speed was about 60 rpm. Polymer was put into the mixer at time=0 minute. The bisphosphine nucleophiles were then added to the mixer at time=1 minute; no other curatives were added. Sweeping was at time=3 minutes and dumping at time=6 minutes. The final step of the mixing procedure involved refining the compounds produced from the mixer on the 4?6 mill, performing about 6 endwise passes.

(53) Filled Compound

(54) The mixes (Examples 18-21) were performed similarly as above except that the fillers (white or black) were added along with the bisphosphine agent. For Example 21, the mixing was performed differently where half of the polymer was added at time=0 minute, the other half of the polymer along with the bisphosphine nucleophile, the process aid and the calcined clay were added at time=0.5 minutes. Sweeping was at time=3 minutes and dumped at time=6 minutes.

(55) Cure characteristics of all compounds were determined with the use of a Moving Die Rheometer (MDR) according to ASTM 5289. Stress-strain measurements were recorded at 23? C. and done according to ASTM 412 Method A. Hardness (Shore A2) values were determined using an A-scale durometer as described in ASTM 2240.

(56) Additional tests include compression set and permeability. The vulcanizates were cured at 160? C. (t90+10 minutes). The initial compression value was recorded the day after curing then aged in the oven at 70? C. for 72 hours. The final compression value was recorded 30 minutes after taking the sample out of the oven. The oxygen permeability tested on the Mocon overnight, 10 hrs conditioning time at 40? C. conditioning temperature and test temperature.

(57) Effects of the Alkyl Spacer of the Bisphosphine Nucleophiles

(58) Reactions of bisphosphine nucleophiles with various alkyl spacers (in Table 3) and unfilled bromobutyl BB2030 (allylic bromide to bisphosphine at molar ratio of 2:1) were carried out.

(59) TABLE-US-00003 TABLE 3 Ingredient Example Example Example Example Example Example Example Example (phr) 1 2 3 4 5 6 7 8 BB2030 100 100 100 100 100 100 100 BDPM 3.0 BDPE 3.1 (DIPHOS) BDPP 3.3 BDPB 3.4 BDPPe 3.5 BDPH 3.6 BDPO 3.8 DPEphos 4.3 Allylic Br: 2:1 2:1 2:1 2:1 2:1 2:1 2:1 2:1 Bisphosphine Molar Ratio

(60) The effects of the alkyl spacer on the bisphosphine nucleophiles on the cure behavior of BB2030 are studied and the results are summarized in Table 4 and FIGS. 1 and 2.

(61) TABLE-US-00004 TABLE 4 MH ML MH ? ML Example # Nucleophile (dN .Math. M) (dN .Math. M) (dN .Math. M) 1 BDPM 4.14 1.79 2.35 2 BDPE (DIPHOS) 9.31 2.10 7.21 3 BDPP 10.97 2.28 8.69 4 BDPB 10.55 2.12 8.43 5 BDPPe 10.65 2.09 8.56 6 BDPH 10.72 2.09 8.63 7 BDPO 10.32 2.04 8.28 8 DPEphos 5.87 1.85 4.02

(62) The minimum torque (ML), maximum torque (MH) and torque difference (MH-ML) is considered as the parameters to demonstrate the degree of chemical cross-linking. The increase in its value is due to the increasing crosslink density.

(63) The results show that alkyl spacer of n?3 is required on the bisphosphine nucleophiles for maximum crosslinking.

(64) Effects of the Level of Bisphosphine

(65) Reactions of bisphosphine nucleophile BDPB with unfilled bromobutyl BB2030 with allylic bromide to bisphosphine at various molar ratios were carried out (shown in Table 5).

(66) TABLE-US-00005 TABLE 5 Exam- Exam- Exam- Exam- Exam- Ingredient (phr) ple 9 ple 10 ple 4 ple 11 ple 12 BB2030 100 100 100 100 100 BDPB 0.5 2 3.4 5 6.8 Allylic Br:Bis- 13.7:1 3.4:1 2:1 1.4:1 1:1 phosphine Molar Ratio

(67) The results and effects of the level of bisphosphine on the cure behavior of bromobutyl BB2030 are summarized in Table 6 and shown in FIG. 3.

(68) TABLE-US-00006 TABLE 6 bromide to bisphos- MH ML MH ? ML Example # phine molar ratio (dN .Math. M) (dN .Math. M) (dN .Math. M) 9 13.7:1 3.39 2.03 1.36 10 3.4:1 7.96 2.12 5.84 4 .sup.2:1 10.55 2.12 8.43 11 1.4:1 10.50 2.10 8.4 12 .sup.1:1 9.74 2.09 7.65

(69) The results show that the optimal level of crosslinking density was achieved at ca. 3.4 phr of BDPB (equivalent to 2:1 molar ratio of allylic bromide to phosphine).

(70) Bisphosphine Cross-linking Applied to Other Halogen Containing Polymers

(71) Reactions of bisphosphine nucleophile BDPB with unfilled bromobutyl BB2030 and various other bromine containing polymers with allylic bromide to bisphosphine at 2:1 molar ratio were carried out (shown in Table 7).

(72) TABLE-US-00007 TABLE 7 Exam- Exam- Exam- Exam- Ingredient (phr) ple 13 ple 14 ple 16 ple 17 bromobutyl (4 100 mol % isoprene) Brominated 100 Terpolymer BIMSM 100 CB1240 100 BDPB 2.8 2.9 2.9 3.4 Allylic halide:Bis- 2:1 2:1 2:1 3.3:1 phosphine Molar Ratio

(73) The curing effects of the products are studied and the results summarized in Table 8 below and FIGS. 4 and 5.

(74) TABLE-US-00008 TABLE 8 MH ML MH ? ML Example # Compound (dN .Math. M) (dN .Math. M) (dN .Math. M) Example 13 bromobutyl (4 8.41 1.84 6.57 mol % isoprene) + BDPB Example 14 Brominated 8.56 1.80 6.76 Terpolymer + BDPB Example 16 BIMSM + BDPB 9.67 3.43 6.24 Example 17 CB1240 + BDPB 10.76 1.25 9.51

(75) The results show that reactions with various bromine containing polymers using bisphosphine crosslinking agent is feasible and bromobutyl BB2030 achieved the best crosslink density.

(76) Effects of Fillers

(77) Reactions of bisphosphine nucleophile BDPB with bromobutyl BB2030 with various fillers (Carbon Black, White Filler) were carried out (shown in Table 9).

(78) TABLE-US-00009 TABLE 9 Exam- Exam- Ingredient (phr) ple 18 ple 19 BB2030 100 100 Carbon Black 40 White Filler 40 BDPB 3.4 3.4

(79) The effects of the filler on the cure behavior of BB2030 are shown in Table 10 and FIG. 6.

(80) TABLE-US-00010 TABLE 10 MH ML MH ? ML Example # Compound (dN .Math. M) (dN .Math. M) (dN .Math. M) 18 BDPB + carbon 21.38 3.94 17.44 black 19 BDPB + white filler 15.78 3.51 12.27 (40 phr) 20 BDPB + white filler 20.81 4.48 16.33 (80 phr) + process aid 21 Standard Pharma 10.8 2.7 8.1 Rubber Closure formulation

(81) The results show that fillers have no impact on the crosslinking chemistry, and that mechanical strength of the reaction products increased with the presence of fillers.

(82) Bisphosphine Cure in Rubber Closures

(83) Comparative studies of the properties of cured bisphosphine samples and a typical pharmaceutical rubber closure formulation is shown in Table 11. The results are summarized in Table 12 and shown in FIG. 7.

(84) TABLE-US-00011 TABLE 11 Exam- Exam- ple 23 ple 24 Ingredient (phr) phr phr BB2030 100 100 Calcine clay 80 80 Process aid 2 2 BDPB 3.4 Unbrominated 2 phenol formaldehyde resin ZnO 3

(85) TABLE-US-00012 TABLE 12 Perme- MH- Comp. ability Example MH ML ML set (cm.sup.2/ # Compound (dN.M) (dN.M) (dN.M) (%) (atm sec)) 20 BDPB + 20.81 4.48 16.33 14.8 119 white filler (80 phr) + process aid 21 Typical 10.8 2.7 8.1 24 123 Pharma- ceutical Rubber Closure formulation

(86) Compared to typical pharmaceutical rubber closure formulations, the bisphosphine cure system provides fast cure at high cure state with good compression set and good impermeability.

(87) Vulcanizates based on the new cure system shows significant improvement in compression set properties than the conventional resin cure formulation for bromobutyl.