POLYMERIC COMPOSITION COMPRISING A THERMOPLASTIC ELASTOMER WITH BUTADIENE AND STYRENE BLOCKS AND A COMPATIBLE PLASTICIZER

Abstract

A polymer composition comprises: a) at least one block thermoplastic elastomer comprising at least one elastomer block and at least one thermoplastic block, the elastomer block(s) predominantly comprising units derived from butadiene, the thermoplastic block(s) consisting of units derived from one or more styrene monomers, b) at least one plasticizer selected from butadiene oligomers with: b1) the molar content of 1,2-polybutadiene units in said plasticizer is within a range of from 70% to 130% of that in the elastomer block of the thermoplastic elastomer, and the molar mass of the plasticizer is greater than 1500 and less than 50 000 g/mol, or else b2) the molar content of 1,2-polybutadiene units in the plasticizer is less than 70%, or greater than 130%, of that in the elastomer block of the thermoplastic elastomer, and the molar mass of the plasticizer is greater than 4000 and less than 50 000 g/mol.

Claims

1.-10. (canceled)

11. A polymer composition comprising: (a) at least one block thermoplastic elastomer comprising at least one elastomer block and at least one thermoplastic block, the at least one elastomer block predominantly comprising units derived from butadiene, and the at least one thermoplastic block consisting of units derived from one or more styrene monomers; (b) at least one plasticizer selected from butadiene oligomers, it being understood that: (b1) a molar content of 1,2-polybutadiene units in the at least one plasticizer is within a range of from 70% to 130% of a molar content of 1,2-polybutadiene units in the at least one elastomer block of the at least one block thermoplastic elastomer, and a molar mass of the at least one plasticizer is greater than 1500 g/mol and less than 50,000 g/mol, or else (b2) a molar content of 1,2-polybutadiene units in the at least one plasticizer is less than 70%, or greater than 130%, of a molar content of 1,2-polybutadiene units in the at least one elastomer block of the at least one block thermoplastic elastomer, and a molar mass of the at least one plasticizer is greater than 4000 g/mol and less than 50,000 g/mol.

12. The polymer composition according to claim 11, wherein the at least one elastomer block further comprises units derived from one or more styrene monomers.

13. The polymer composition according to claim 12, wherein the one or more styrene monomers of the at least one elastomer block are selected from the group consisting of styrene, o-, m- or p-methyl styrene, alpha-methyl styrene, beta-methyl styrene, 2,6-dimethyl styrene, 2,4-dimethylstyrene, alpha-methyl-o-methyl styrene, alpha-methyl-m-methyl styrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methyl styrene, beta-methyl-m-methyl styrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethyl styrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethyl styrene, beta-methyl-2,4-dimethyl styrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chlorostyrene, alpha-chloro-m-chlorostyrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorostyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, and styrene derivatives substituted with a silyl group.

14. The polymer composition according to claim 13, wherein the one or more styrene monomers of the at least one elastomer block are selected from styrene and alpha-methylstyrene.

15. The polymer composition according to claim 11, wherein the one or more styrene monomers of the at least one thermoplastic block are selected from styrene, o-, m- or p-methylstyrene, alpha-methyl styrene, beta-methyl styrene, 2,6-dimethyl styrene, 2,4-dimethylstyrene, alpha-methyl-o-methyl styrene, alpha-methyl-m-methyl styrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methyl styrene, beta-methyl-m-methyl styrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethyl styrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6-dimethyl styrene, beta-methyl-2,4-dimethyl styrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chl orostyrene, alpha-chloro-m-chloro styrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, alpha-chloro-2,6-dichlorstyrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, and styrene derivatives substituted with a silyl group.

16. The polymer composition according to claim 15, wherein the at least one thermoplastic block predominantly comprises units derived from the alpha-methylstyrene monomer.

17. The polymer composition according to claim 16, wherein the at least one thermoplastic block consists of units derived from the alpha-methylstyrene monomer.

18. The polymer composition according to claim 11, wherein the at least one thermoplastic block consisting of units derived from one or more styrene monomers represents at most 35% by weight, relative to a weight of the at least one thermoplastic elastomer.

19. The polymer composition according to claim 11, wherein the at least one plasticizer represents from 5 to 50 phr.

20. A tire comprising the polymer composition according to claim 11.

Description

EXAMPLES

[0099] Determination of the distribution of molar masses by PS equivalent RI SEC

[0100] It is determined by polystyrene equivalent size exclusion chromatography (SEC). SEC makes it possible to separate macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the bulkiest being eluted first. Without being an absolute method, SEC makes it possible to comprehend the distribution of the molar masses of a polymer. The various number-average molar masses (Mn) and weight-average molar masses (Mw) can be determined from commercial standards and the polymolecularity or polydispersity index (PI=Mw/Mn) can be calculated via a “Moore” calibration.

[0101] Preparation of the polymer: There is no specific treatment of the polymer sample before analysis. The latter is simply dissolved in chloroform at a concentration of approximately 2 g/l. The solution is then filtered through a filter with a porosity of 0.45 μm before injection.

[0102] SEC analysis: The apparatus used is an Agilent 1200 chromatograph. The elution solvent is chloroform. The flow rate is 1 ml/min, the temperature of the system is 30° C. and the analytical time is 30 min. A set of three Agilent columns in series which are preceded by a filter, with commercial names “PLgel 10 μm (pre-column)” and two “PLgel 10 μm mixed B”, is used. The volume of the solution of the polymer sample injected is 100 μd. The detector is an Agilent 1200 differential refractometer and the software for processing the chromatographic data is the Chemstation system. The calculated average molar masses are relative to a calibration curve produced from Agilent-KIT PS commercial polystyrene standards.

[0103] Proton nuclear magnetic resonance (.sup.1H NMR):

[0104] The contents of the various monomer units and their microstructures within the copolymer are determined by an NMR analysis. The spectra are acquired on a Bruker 500 MHz spectrometer equipped with a BBI Z-grad “broad band” 5 mm probe. The quantitative .sup.1H NMR experiment uses a 30° single pulse sequence and a repetition time of 5 seconds between each acquisition. The samples are dissolved in CDCl.sub.3. The integration zones considered for quantification are the spectral signature zones of the monomer units known to those skilled in the art.

[0105] Differential scanning calorimetry (DSC):

[0106] Measurement of the Tg of the copolymers

[0107] The characterization of the Tg values of the elastomer block and of the poly(alpha-methylstyrene) blocks is carried out by a DSC measurement (DSC1 instrument from Mettler Toledo). The instrument operates under a helium atmosphere. 10 to 20 mg of TPE elastomer are sampled and placed in a crucible conventionally used by those skilled in the art for carrying out Tg measurements. The sample is first placed under isothermal conditions at +25° C. for 2 minutes and then cooled to −150° C. at a rate of 50° C. per minute. An isotherm is then applied at −150° C. for 10 minutes. First heating then starts from −150° C. to +10° C. at a rate of 20° C. per minute, and is continued from 10° C. to 250° C. at a rate of 50° C. per minute. The sample then undergoes quenching to reach −150° C. at the maximum rate permitted by the instrument. The sample is then maintained under isothermal conditions at −150° C. for 15 minutes.

[0108] Second heating then starts from −150° C. to +10° C. at a rate of 20° C. per minute (range for measuring the Tg of the elastomer part of the TPE) and continues from +10° C. to +250° C. at a rate of 50° C. per minute (range for measuring the Tg of the poly(alpha-methylstyrene) blocks). In this measurement, only the second heating is processed.

[0109] Method for measurement of the dynamic properties under strain

[0110] The dynamic properties, complex moduli G*, are measured on a viscosity analyser (Metravib DMA+450), according to standard ASTM D 5992-96. The response is recorded of a sample of desired composition (cylindrical test specimen with a thickness of 2 mm and a cross section of 78 mm.sup.2), subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz. A sweep is carried out from −80° C. to +150° C. at a rate of 1.5° /min at a stress of 0.7 MPa.

[0111] The samples are moulded at 180° C. (diameter 25 mm, thickness 2 mm) for 5 minutes, then cut to a diameter of 10 mm with a hollow punch.

[0112] The complex modulus G* is measured.

[0113] The objective of the examples is to verify the compatibility and the selectivity of certain plasticizers used according to the invention with the elastomer phase of various thermoplastic elastomers.

[0114] The thermoplastic elastomers TPE1, TPE2 and TPE3 used are linear triblock copolymers having a poly(alpha-methylstyrene) thermoplastic block/styrene-butadiene elastomer block/poly(alpha-methylstyrene) thermoplastic block sequence. The block referred to as the central block is therefore in this macrostructure the elastomer block.

[0115] Synthesis of TPE3:

[0116] 20 g of methylcylohexane, 10 g of alpha-methylstyrene and 1.25 mmol of tetrahydrofurfuryl ethyl ether are introduced into a 500 ml reactor. After neutralizing the impurities with n-butyl lithium, 0.25 mmol of s-butyl lithium are introduced. After 2 h 30 min at T=5° C., the conversion to alpha-methylstyrene measured by solids content is 70%. Analysis of the polymer by size exclusion chromatography shows the presence of a main population: Mn=20 400 g/mol.

[0117] At the end of these 2 h 30 min at 5° C., 2 g of butadiene are introduced into the reactor and then, two minutes after this addition of butadiene, a mixture containing 16.75 g of butadiene and 100 g of methylcyclohexane, the impurities of which were neutralized beforehand with n-butyl lithium, is introduced into the reactor. The reaction medium is maintained at 5° C. for 15 minutes. After these 15 minutes, the butadiene conversion is 83%.

[0118] 0.12 mmol of dimethyldichlorosilane is then introduced into the reactor. The reaction medium is maintained at 5° C. for 30 minutes. The polymer obtained at the end of this coupling step is a triblock poly(apha-methylstyrene)-b-polybutadiene-b-poly(alpha-methylstyrene) polymer, which has a molar mass by SEC analysis: Mn=139 600 g/mol and 2 Tg values measured by DSC analysis: 181° C. and −25° C.

[0119] TPE1 and TPE2 are prepared according to a similar process.

[0120] The structures of the thermoplastic elastomers used according to the invention and tested are given in Tables 1 and 1a.

TABLE-US-00001 TABLE 1 % % Thermoplastic Elastomer % STY/ % 1,2-PB/ % 1,4-PB TPE (PAMS) (SBR) Elastomer Elastomer Elastomer name Block Block block block block TPE1¤ 26.6¤ 73.4¤ 7.9¤ 76.9¤ 15.2¤ TPE2¤ 30.4¤ 69.6¤ 0.7¤ 87.8¤ 11.6¤ TPE3¤ 23.9¤ 76.1¤ 0.8¤ 80.1¤ 19.1¤

TABLE-US-00002 TABLE 1a Tg DSC Tg DSC elastomer thermoplastic TPE Mn SEC PI SEC block block name (g/mol) (g/mol) (° C.) (° C.) TPE1 113300 1.25 −8 175 TPE2 132400 1.05 −13 174 TPE3 139600 1.03 −25 181

[0121] % Thermoplastic (PAMS) Block: wt % of the poly(alpha-methylstyrene) thermoplastic block in the TPE

[0122] % Elastomer (SBR) Block: wt % of the SBR elastomer block in the TPE

[0123] % STY/Elastomer block: mol % of styrene units in the elastomer block

[0124] % 1,2-PB/Elastomer block: mol % of 1,2-PB units in the elastomer block

[0125] % 1,4-PB/Elastomer block: mol % of 1,4-PB units in the elastomer block

[0126] Polymer compositions are prepared comprising a thermoplastic elastomer and a plasticizer in solution. In a 5 1 reactor fitted with a stirring paddle, 100g of TPE and 20g of plasticizer are introduced for a composition containing 20 phr of plasticizer. 2 litres of methylcyclohexane are added and the whole is stirred for 12 h. The solution is recovered and dried under vacuum or stripped with water vapour to remove the solvent.

[0127] The plasticizers used are butadiene oligomers.

[0128] The characteristics of the plasticizers used are presented in Table 2.

[0129] Table 2a shows their contents in the compositions, the glass transition temperatures of the elastomer block and of the poly(alpha-methylstyrene) thermoplastic blocks of the thermoplastic elastomers in the compositions.

[0130] Finally, Table 2a shows the complex moduli G* of the compositions.

TABLE-US-00003 TABLE 2 Mn Content plasticizer of 1,2-PB Plasticizer name (g/mol) (%) bdf 1.5 k (1) 1530 15.2 bdf 2.7 k (2) 2700 12.9 bdf 4.7 k (3) 4700 10.9 bdf 10 k (4) 10000 7 bdf 18 k (5) 18000 7.7 bdf 47 k (6) 47000 7 bdt 1.5 k (7) 1500 88 bdt 3.2 k (8) 3200 80.4 Ricon 130 (9) 3400 22.9 Ricon 150 (10) 4300 42.1 Ricon 156 (11) 2000 50.3 Ricon 184 (12) 8600 26 Polybutadiene 5 k (13) 5300 14 Polybutadiene 150 k (14) 180000 4 (1) bdf 1.5 k from PSS Polymer Standards Service GmbH (2) bdf 2.7 k from PSS Polymer Standards Service GmbH (3) bdf 4.7 k from PSS Polymer Standards Service GmbH (4) bdf 10 k from PSS Polymer Standards Service GmbH (5) bdf 18 k from PSS Polymer Standards Service GmbH (6) bdf 47 k from PSS Polymer Standards Service GmbH (7) bdt 1.5 k from PSS Polymer Standards Service GmbH (8) bdt 3.2 k from PSS Polymer Standards Service GmbH (9) Ricon 130 from Cray Valley (10) Ricon 150 from Cray Valley (11) Ricon 156 from Cray Valley (12) Ricon 184 from Cray Valley containing between 10 and 16 mol % of styrene (13) Polybutadiene 5 k having an Mn of 5300 g/mol, a PI = 1.05, and having a percentage of 1,2-PB of 14 wt % (14) Polybutadiene 150 k having an Mn of 150 000 g/mol, a PI = 1.9, and having a percentage of 1,2-PB of 4 wt %, of cis-1,4-PB of 93 wt % and of trans-1,4-PB of 3 wt % Content of 1,2-PB: molar content of 1,2-polybutadiene units in the plasticizer

TABLE-US-00004 TABLE 2a Composition 1 2 3 4 5 6 7 8 9 10 11 12 TPE1 100 100 100 100 100 100 100 100 100 100 100 TPE2 100 TPE3 bdf 1.5k 20 bdf 2.7k 20 bdf 4.7k 20 bdf 10k 20 bdf18k 20 bdf47k 20 bdt 1.5k 20 bdt 3.2k 20 Ricon 130 20 Ricon 150 Ricon 156 20 Ricon 184 Polybutadiene 5k Polybutadiene 150k Tg elastomer −8 −37 −38 −37 −34 −38 −12 −14 −10 −33 −20 −13 block (° C.) Tg thermoplastic 175 104 1301 144 160 163 167 145 158 136 136 174 block (° C.) G* 40° C. (MPa) 2.96 0.47 5.22 G*40° C. 1 0.16 1 (plasticized)/G *40° C. (non-plasticized Composition 13 14 15 16 17 18 19 20 TPE1 TPE2 100 100 100 TPE3 100 100 100 100 100 bdf 1.5k 20 bdf 2.7k bdf 4.7k bdf 10k bdf18k bdf47k bdt 1.5k bdt 3.2k Ricon 130 Ricon 150 10 20 Ricon 156 Ricon 184 20 Polybutadiene 5k 2.0 20 Polybutadiene 20 150k Tg elastomer −32 −25 −24 −45 −36 −28 block (° C.) Tg thermoplastic 155 181 161 158 160 166 block (° C.) G* 40° C. (MPa) 0.79 0.54 0.48 1.34 1.06 0.41 0.7 1.18 G*40° C. 0.15 1 0.8 0.31 0.53 0.88 (plasticized)/G *40° C. (non-plasticized Tg elastomer block: Tg of the elastomer central block of the TPE with or without plasticizer measured by DSC Tg thermoplastic block: Tg of thermoplastic block of the plasticized TPE measured by DSC G*.sub.40° C. (plasticized)/G*.sub.40° C. (non-plasticized): G* of the plasticized TPE/G* of the TPE alone

[0131] Table 2a shows that the plasticizers bdf 10k, bdf 18k, bdf 47k, bdt 3.2k and polybutadiene 5k are compatible with and selective for the elastomer phase because they significantly lower the Tg of the elastomer central block (or at the very least the Tg(non-plasticized TPE E block)—Tg(plasticized TPE E block)/((Tg(non-plasticized TPE E block)—Tg(plasticizer)) ratio is high) without lowering the Tg of the thermoplastic blocks by more than 25° C.

[0132] Moreover, the complex moduli G* show a drop in the rigidity on the compositions measured, which confirms that the plasticizers according to the invention do indeed make it possible to adjust the rigidity of the composition.