Silane-containing carboxy-terminated polymers

Abstract

Polymers are functionalized at chain ends thereof with silane-containing carboxyl groups of the formula (I) ##STR00001##
where R.sup.1 and R.sup.2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl or aralkoxy radical; R.sup.3 and R.sup.4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical; and A is a divalent organic radical.

Claims

1. End group-functionalized polymers comprising a polymer chain terminated by a silane-containing carboxyl group of the formula (I) ##STR00012## wherein the silane containing carboxyl group is bonded with the polymer chain via one or more divalent structural elements of the formula (V) ##STR00013## where R is H, R.sup.1, R.sup.2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl, or aralkoxy radical R.sup.3, R.sup.4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical, A is a divalent organic radical, n=3-6, and R.sup.5, R.sup.6 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical wherein the polymers are diene polymers or diene copolymers.

2. The end group-functionalized polymers according to claim 1, wherein the polymer is obtained by reaction of reactive ends of the polymer chain with one or more silalactone functionalizing reagents, wherein the silalactones are compounds of the formula (III) ##STR00014##

3. The end group-functionalized polymers according to claim 2, wherein: any alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl, aralkoxy, or divalent organic radical may contain one or more heteroatoms; the silalactones are compounds of the formula (III) ##STR00015## and the one or more divalent structural elements of the formula (V) are derived from cyclosiloxanes of the formula (IV) ##STR00016##

4. The end group-functionalized polymers according to claim 3, wherein: the heteroatoms are O, N, S and Si; the cyclosiloxanes are a member of the group consisting of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or dodecamethylcyclcohexasiloxane; the silalactones comprise one or more of 2,2-diethyl-1-oxa-2-silacyclohexan-6-one, 2,2,4-trimethyl-1-oxa-2-silacyclohexan-6-one, 2,2,5-trimethyl-1-oxa-2-silacyclohexan-6-one, 2,2,4,5-tetramethyl-1-oxa-2-silacyclohexan-6-one, 2,2-diethyl-1-oxa-2-silacyclohexan-6-one, 2,2-diethoxy-1-oxa-2-silacyclohexan-8-one, 2,2-dimethyl-1,4-dioxa-2-silacyclohexan-6-one, 2,2,5-trimethyl-1,4-dioxa-2-silacyclohexan-6-one, 2,2,3,3-tetramethyl-1,4-dioxa-2-silacyclohexan-6-one, 2,2-dimethyl-1-oxa-4-thia-2-silacyclohexan-6-one, 2,2-diethyl-1-oxa-4-thia-2-silacyclohexan-6-one, 2,2-diphenyl-1-oxa-4-thia-2-silacyclohexan-6-one, 2-methyl-2-ethenyl-1-oxa-4-thia-2-silacyclohexan-6-one, 2,2,5-trimethyl-1-oxa-4-thia-2-silacyclohexan-8-one, 2,2-dimethyl-1-oxa-4-aza-2-silacyclohexan-6-one, 2,2,4-trimethyl-1-oxa-4-aza-2-silacyclohexan-6-one, 2,4-dimethyl-2-phenyl-1-oxa-4-aza-2-silacyclohexan-6-one, 2,2-dimethyl-4 trimethylsilyl-1-oxa-4-aza-2-silacyclohexan-6-one, 2,2-diethoxy-4-methyl-1-oxa-4-aza-2-silacyclohexan-6-one, 2,2,4,4-tetramethyl-1-oxa-2,4-disilacyclohexane-6-one, 3,4-dihydro-3,3-dimethyl-1H-2,3-benzoxasilin-1-one, 2,2-dimethyl-1-oxa-2-silacyclopentan-5-one, 2,2,3-trimethyl-1-oxa-2-silacyclopentan-5-one, 2,2-dimethyl-4-phenyl-1-oxa-2-silacyclopentan-5-one, 2,2-di(tert-butyl)-1-oxa-2-silacyclopentan-5-one, 2-methyl-2-(2-propen-1-yl)-1-oxa-2-silacyclopentan-5-one, 1,1-dimethyl-2,1-benzoxasilol-3(1H)-one, and 2,2-dimethyl-1-oxa-2-silacycloheptan-7-one; the polymers comprise at least one of polybutadiene, polyisoprene, butadiene-isoprene copolymer, butadiene-styrene copolymer, isoprene-styrene copolymer, and butadiene-isoprene-styrene terpolymer; and the polymers have mean molar masses of 100,000 to 1,000,000 g/mol, and glass transition temperatures of ?110? C. to 0? C.

5. The end group-functionalized polymers according to claim 1, wherein the polymers have mean molar masses of 10,000 to 2,000,000 g/mol.

6. The end group-functionalized polymers according to claim 1, wherein the polymers have glass transition temperatures of ?110? C. to +20? C.

7. A process for preparing the end group-functionalized polymers according to claim 1, the process comprising adding one or more silalactones to polymers having reactive ends on the polymer chain.

8. The process according to claim 7, further comprising adding the silalactones to the polymers after completion of polymerization.

9. The process according to claim 7, further comprising using an excess or a stoichiometric amount or a deficiency of silalactones, based on the amount of polymer.

10. The process according to claim 9, wherein the amount of silalactones is from 0.005 to 2% by weight, based on the amount of polymer.

11. The process according to claim 7, wherein prior to addition of the silalactones, the process further comprises: polymerizing monomers to form polymer chains having reactive chain ends, and reacting reactive chain ends with cyclosiloxanes of the formula (IV) ##STR00017## where n=3-6, and where R.sup.5, R.sup.6 in formula (IV) are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical.

12. The process according to claim 11, further comprising reacting the reactive chain ends with 0.002 to 4% by weight of the cyclosiloxanes of the formula (IV) based on the amount of polymer.

13. The process according to claim 11, wherein a ratio of silalactone to cyclosiloxane is from 20:1 to 1:1.

14. Vulcanizable rubber compositions comprising: a) end group-functionalized polymers according to claim 1, and b) ageing stabilizers, oils, fillers, rubbers and/or further rubber auxiliaries.

15. Mouldings produced from vulcanizable rubber compositions comprising the end group-functionalized polymers according to claim 1.

Description

EXAMPLES

Example 1: Synthesis of Styrene-Butadiene Copolymer, Unfunctionalized (Comparative Example)

(1) An inertized 20 l reactor was charged with 8.5 kg of hexane, 1185 g of 1,3-butadiene, 315 g of styrene, 8.6 mmol of 2,2-bis(2-tetrahydrofuryl)propane and 11.3 mmol of butyllithium, and the contents were heated to 60? C. Polymerization was effected while stirring at 60? C. for 25 minutes, Subsequently, 11.3 mmol of cetyl alcohol were added to cap the anionic ends of the polymer chains, the rubber solution was discharged and stabilized by addition of 3 g of Irganox? 1520 (2,4-bis(octylthiomethyl)-6-methylphenol), and the solvent was removed by stripping with steam. The rubber crumbs were dried at 65? C. under reduced pressure.

Example 2: Synthesis of Silanolate-Terminated Styrene-Butadiene Copolymer by Reaction with Cyclosiloxane (Comparative Example)

(2) The procedure was as in Example 1. In place of the cetyl alcohol, however, an amount of hexamethylcyclotrisiloxane equimolar to that of butyllithium was added (as a solution in cyclohexane) and the reactor contents were then heated to 60? C. for a further 20 minutes.

Example 3: Synthesis of Silane-Containing Carboxyl-Terminated Styrene-Butadiene Copolymer by Reaction with Cyclosiloxane and then Silalactone (Inventive)

(3) The procedure was as in Example 2. 20 minutes after addition of the hexamethylcyclotrisiloxane, an amount of 2,2-dimethyl-1-oxa-4-thia-2-silacyclohexan-6-one equimolar to that of butyllithium and hexamethylcyclotrisiloxane was added (as a solution in toluene) and the mixture was heated to 60? C. for a further 20 minutes.

Example 4: Synthesis of Silane-Containing Carboxyl-Terminated Styrene-Butadiene Copolymer Having a Tertiary Amino Group at the Start of the Chain by Reaction with Cyclosiloxane and then Silalactone (Inventive)

(4) The procedure was as in Example 3. Prior to addition of the butyllithium, however, an amount of pyrrolidine equimolar to that of butyllithium was added.

Example 5: Synthesis of Silane-Containing Hydroxyl-Terminated Styrene-Butadiene Copolymer by Reaction with 1-Oxa-2-Silacycloalkanes (Comparative Example)

(5) The procedure was as in Example 2. In place of the hexamethylcyclotrisiloxane, however, an amount of 2,2,4-trimethyl-1-oxa-4-aza-2-silacyclohexane equimolar to that of butyllithium was added (as a solution in hexane).

(6) The polymer properties of the styrene-butadiene copolymers from Examples 1-5 are summarized in Table 1. It is apparent from Table 1 that the inventive silane-containing carboxyl-terminated polymers of Examples 3 and 4, with the same molecular weight and polydispersity level as the polymers of Comparative Examples 1, 2 and 5, have much higher Mooney viscosities and much reduced cold flow values. Low cold flow values are advantageous, since the corresponding rubbers have a lesser tendency to flow and hence improved dimensional stability in the course of storage.

Examples 6 a-e: Rubber Compositions

(7) Tyre tread rubber compositions comprising the styrene-butadiene copolymers of Examples 1-5 were produced. The constituents are listed in Table 2. The rubber compositions (apart from sulphur and accelerator) were produced in a 1.5 l kneader. The sulphur and accelerator constituents were subsequently mixed in on a roller at 40? C.

(8) TABLE-US-00001 TABLE 1 Properties of the styrene-butadiene copolymers of Examples 1-5 Styrene Functionalizing Vinyl content.sup.a) content.sup.a) Tg.sup.b) M.sub.n.sup.c) ML1 + 4.sup.d) Cold flow.sup.e) SSBR from Ex. reagent [% by wt.] [% by wt.] [? C.] [kg/mol] M.sub.w/M.sub.n.sup.c) [ME] [mg/min] 1 51.5 20.9 ?23 244 1.10 42 21 (comparative) 2 hexamethyl- 50.6 21.3 ?24 239 1.10 41 21 (comparative) cyclotrisiloxane 3 1. hexamethyl- 50.7 21.0 ?24 246 1.09 79 0 (inventive) cyclotrisiloxane 2. silalactone 4 1. hexamethyl- 49.9 21.9 ?24 183 1.22 56 9 (inventive) cyclotrisiloxane 2. silalactone 5 1-oxa-2- 50.9 21.5 ?23 220 1.15 37 25 (comparative) silacycloalkane .sup.a)determination of vinyl and styrene contents by FTIR .sup.b)determination of glass transition temperature by DSC .sup.c)determination of molar mass M.sub.n and polydispersity M.sub.w/M.sub.n by GPC (PS calibration) .sup.d)determination of Mooney viscosity at 100? C. .sup.e)determination of cold flow at 50? C.

(9) TABLE-US-00002 TABLE 2 Constituents of the tyre tread rubber compositions (figures in phr: parts by weight per 100 parts by weight of rubber) Comparative Comparative Inventive Inventive Comparative Example Example Example Example Example 6a 6b 6c 6d 6e styrene-butadiene copolymer from Example 1 70 0 0 0 0 styrene-butadiene copolymer from Example 2 0 70 0 0 0 styrene-butadiene copolymer from Example 3 0 0 70 0 0 styrene-butadiene copolymer from Example 4 0 0 0 70 0 styrene-butadiene copolymer from Example 5 0 0 0 0 70 high-cis polybutadiene 30 30 30 30 30 (BUNA? CB 24 from Lanxess Deutschland GmbH) silica (Ultrasil? 7000) 90 90 90 90 90 carbon black (Vulcan? J/N 375) 7 7 7 7 7 TDAE oil (Vivatec 500) 36.3 36.3 36.3 36.3 36.3 processing aid (Aflux 37) 3 3 3 3 3 stearic acid (Edenor C 18 98-100) 1 1 1 1 1 ageing stabilizer 2 2 2 2 2 (Vulkanox? 4020/LG from Lanxess Deutschland GmbH) ageing stabilizer 2 2 2 2 2 (Vulkanox? HS/LG from Lanxess Deutschland GmbH) zinc oxide (Rotsiegel zinc white) 3 3 3 3 3 wax (Antilux 654) 2 2 2 2 2 silane (SI 69? from Evonik) 7.2 7.2 7.2 7.2 7.2 diphenylguanidine (Rhenogran DPG-80) 2.75 2.75 2.75 2.75 2.75 sulfenamide (Vulkacit? NZ/EGC from Lanxess Deutschland GmbH) 1.6 1.6 1.6 1.6 1.6 sulphur (Chancel 90/95 ground sulphur) 1.6 1.6 1.6 1.6 1.6 sulfonamide (Vulkalent? E/C) 0.2 0.2 0.2 0.2 0.2

Examples 7 a-e: Vulcanizate Properties

(10) The tyre tread rubber compositions of Examples 6a-e according to Table 2 were vulcanized at 160? C. for 20 minutes. The properties of the corresponding vulcanizates are listed in Table 3 as Examples 7a-e. The vulcanizate properties of the vulcanized sample from Comparative Example 7a comprising the unfunctionalized styrene-butadiene copolymer are given the index 100. All values greater than 100 in Table 3 mean a corresponding percentage improvement in the respective test property.

(11) TABLE-US-00003 TABLE 3 Vulcanizate properties Comparative Comparative Inventive Inventive Comparative Example Example Example Example Example 7a 7b 7c 7d 7e Styrene-butadiene copolymer in the vulcanizate: styrene-butadiene copolymer from Example 1 X styrene-butadiene copolymer from Example 2 X styrene-butadiene copolymer from Example 3 X styrene-butadiene copolymer from Example 4 X styrene-butadiene copolymer from Example 5 X Vulcanizate properties: tan ? at 0? C. (dynamic damping at 10 Hz) 100 112 125 125 115 tan ? at 60? C. (dynamic damping at 10 Hz) 100 110 143 145 117 tan ? maximum (MTS amplitude sweep at 1 Hz, 60? C.) 100 115 134 139 117 ?G* (G*@0.5%-G*@15% from MTS amplitude sweep) 100 159 254 255 189 [MPa] Resilience at 60? C. [%] 100 113 118 121 114 Abrasion (DIN 53516) [mm.sup.3] 100 119 135 130 113

(12) The resilience at 60? C., the dynamic damping tan ? at 6000, the tan ? maximum in the amplitude sweep and the module difference ?G* between low and high strain in the amplitude sweep are indicators of rolling resistance in the tyre. As apparent from Table 3, the vulcanizates of Inventive Examples 7c and 7d feature particularly high improvements in these rolling resistance-relevant properties.

(13) The dynamic damping tan ? at 0? C. is an indicator of the wet skid resistance of the tyre. As apparent from Table 3, the vulcanizates of Inventive Examples 7c and 7d feature particularly high improvements in this wet skid-relevant property.

(14) The DIN abrasion is an indicator of the abrasion resistance of the tyre tread. As apparent from Table 3, the vulcanizates of Inventive Examples 7c and 7d feature particularly high improvements in this property.