TIRE OBJECT PROVIDED WITH AN ELASTOMER LAYER MADE OF A THERMOPLASTIC ELASTOMER IN THE FORM OF AN (A-B-(A-METHYLSTYRENE-CO-B))N-B-C BLOCK COPOLYMER

Abstract

A pneumatic object is provided with an elastomer layer which is gastight to inflation gases, said elastomer layer comprising, as predominant elastomer, a thermoplastic elastomer in the form of a block copolymer which comprises: (a) an elastomeric block comprising at least units derived from isobutylene, and having a glass transition temperature of less than or equal to 20 C., and (b) one or more thermoplastic blocks, the thermoplastic block(s) each comprising at least one first block consisting of units derived from at least one polymerizable monomer and at least one second block, said second block(s) being a random copolymer consisting of units derived from -methylstyrene and of units derived from -pinene. A process for rendering a pneumatic object gastight to inflation gases is also disclosed.

Claims

1.-24. (canceled)

25. A pneumatic object provided with an elastomer layer which is gastight to inflation gases, said elastomer layer comprising, as predominant elastomer, a thermoplastic elastomer in the form of a block copolymer which comprises: (a) an elastomeric block comprising at least units derived from isobutylene, and having a glass transition temperature of less than or equal to 20 C., and (b) one or more thermoplastic blocks, the one or more thermoplastic blocks each comprising at least one first block consisting of units derived from at least one polymerizable monomer and at least one second block, said at least one second block being a random copolymer consisting of units derived from -methylstyrene and of units derived from -pinene.

26. The pneumatic object according to claim 25, wherein the block copolymer has a structure in which the elastomeric block is connected at one of its ends to a thermoplastic block.

27. The pneumatic object according to claim 25, wherein the block copolymer has a linear structure in which the elastomeric block is connected at each of its ends to a thermoplastic block.

28. The pneumatic object according to claim 25, wherein the block copolymer has a star-branched structure, the elastomeric block being central and being connected to 3 to 12 branches, each branch consisting of a thermoplastic block.

29. The pneumatic object according to claim 25, wherein the at least one polymerizable monomer is selected from styrene monomers.

30. The pneumatic object according to claim 29, wherein the at least one polymerizable monomer is styrene.

31. The pneumatic object according to claim 25, wherein the block copolymer has a weight-average molecular weight ranging from 30 to 300 kg/mol.

32. The pneumatic object according to claim 31, wherein the block copolymer has a weight-average molecular weight ranging from 120 to 250 kg/mol.

33. The pneumatic object according to claim 25, wherein a content of units derived from -pinene ranges from 0.5 to 25 mol % relative to the number of mole of units of the block copolymer.

34. The pneumatic object according to claim 33, wherein the content of units derived from -pinene ranges from 0.8 to 5 mol % relative to the number of moles of units of the block copolymer.

35. The pneumatic object according to claim 25, wherein the one or more thermoplastic blocks represent from 5 to 30% by weight relative to the total weight of the block copolymer.

36. The pneumatic object according to claim 35, wherein the one or more thermoplastic blocks represent from 10 to 20% by weight relative to the total weight of the block copolymer.

37. The pneumatic object according to claim 25, wherein the elastomeric block has a glass transition temperature of less than or equal to 40 C.

38. The pneumatic object according to claim 37, wherein the elastomeric block has a glass transition temperature of less than or equal to 50 C.

39. The pneumatic object according to claim 25, wherein the elastomeric block comprises from 0.5 to 6% by weight of units derived from one or more conjugated dienes relative to the total weight of the elastomeric block.

40. The pneumatic object according to claim 39, wherein the elastomeric block comprises from 1.5 to 5% by weight of units derived from one or more conjugated dienes relative to the total weight of the elastomeric block.

41. The pneumatic object according to claim 40, wherein the one or more conjugated dienes are selected from the group consisting of isoprene, 1,3-butadiene, 1-methylbutadiene, 2-methylbutadiene, 2,3-dimethyl-1,3-butadiene, 2,4-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3-methyl-1,3-hexadiene, 4-methyl-1,3-hexadiene, 5-methyl-1,3-hexadiene, 2,3-dimethyl-1,3-hexadiene, 2,4-dimethyl-1,3-hexadiene, 2,5-dimethyl-1,3-hexadiene, 2-neopentylbutadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-vinyl-1,3-cyclohexadiene, and mixtures thereof.

42. The pneumatic object according to claim 25, wherein the elastomer layer which is gastight to inflation gases further comprises an extending oil.

43. The pneumatic object according to claim 42, wherein the extending oil is selected from the group consisting of polyolefinic oils, paraffinic oils, naphthenic oils, aromatic oils, mineral oils and mixtures thereof.

44. The pneumatic object according to claim 43, wherein the extending oil is selected from olefinic oils.

45. The pneumatic object according to claim 44, wherein the extending oil is a polyisobutylene oil.

46. The pneumatic object according to claim 42, wherein the extending oil has a number-average molar mass ranging from 350 to 4000 g/mol.

47. The pneumatic object according to claim 46, wherein the extending oil has a number-average molar mass ranging from 400 to 3000 g/mol.

48. The pneumatic object according to claim 42, wherein the extending oil has a content of greater than 5 phr.

49. The pneumatic object according to claim 48, wherein the extending oil has a content between 5 and 100 phr.

50. The pneumatic object according to claim 25, wherein the elastomer layer has a thickness of greater than or equal to 0.05 mm.

51. The pneumatic object according to claim 50, wherein the elastomer layer has a thickness ranging from 0.1 to 10 mm.

52. The pneumatic object according to claim 51, wherein the elastomer layer has a thickness ranging from 0.1 to 2 mm.

53. The pneumatic object according to claim 25, wherein the elastomer layer is arranged on the inner wall of the pneumatic object.

54. The pneumatic object according to claim 25, wherein the pneumatic object is a pneumatic tire.

55. A process for rendering a pneumatic object gastight to inflation gases comprising the step of: incorporating the elastomer layer which is gastight to inflation gases into the pneumatic object according to claim 25 during the manufacture of the pneumatic object or after the manufacture of the pneumatic object.

56. The process according to claim 55, wherein the elastomer layer is arranged on the inner wall of the pneumatic object.

57. The process according to claim 55, wherein the pneumatic object is a pneumatic tire.

58. The process according to claim 57, wherein the incorporating step includes depositing the elastomer layer on a tire-building drum before covering said elastomer layer a remainder of the structure of the pneumatic tire.

Description

EXAMPLE 1: PREPARATION OF A REFERENCE BLOCK COPOLYMER (POLYMER 1)STYRENE/ISOBUTYLENE/STYRENE BLOCK COPOLYMER

[0182] The block copolymer (polymer 1) is synthesized as follows:

[0183] A 500 ml separable round-bottomed flask (polymerization container) is placed under nitrogen, and n-hexane (dried over molecular sieves, 23.8 ml) and butyl chloride (dried over molecular sieves, 214.4 ml) are then added by means of a syringe. The polymerization container is then cooled by immersion in a dry ice/methanol bath at 70 C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (75 ml, 794 mmol), the isobutylene is added to the polymerization container by means of a nitrogen pressure. p-Dicumyl chloride (0.1248 g, 0.540 mmol) and -picoline (0.1026 g, 1.10 mmol) are then added. Titanium tetrachloride (0.84 ml, 7.70 mmol) is then added so as to start the polymerization. After stirring for one hour at the same temperature (70 C.), a sample of the polymerization solution (approximately 1 ml) is extracted from the total polymerization solution.

[0184] Styrene (9.79 g, 94.1 mmol), previously cooled to 70 C., is then added to the polymerization container. 45 min after addition of the styrene, the polymerization solution is poured into hot water (500 ml) in order to stop the reaction and this mixture is then stirred for 30 min. The polymerization solution is then washed with deionized water (3500 ml). The solvent and the analogues are evaporated from the washed crude reaction product under reduced pressure at 80 C. for 24 hours to obtain the block copolymer. The weight-average molecular weights of the central block (polyisobutylene) and of the total block copolymer are measured by gel permeation chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I below.

EXAMPLE 2: PREPARATION OF A COMPARATIVE BLOCK COPOLYMER (POLYMER 2)--PINENE-CO-STYRENE/ISOBUTYLENE/-PINENE-CO-STYRENE BLOCK COPOLYMER

[0185] The block copolymer (polymer 2) is synthesized as follows:

[0186] A 2 litre separable round-bottomed flask (polymerization container) is placed under nitrogen, and n-hexane (dried over molecular sieves, 192 ml) and butyl chloride (dried over molecular sieves, 768 ml) are then added by means of a syringe. The polymerization container is then cooled by immersion in a dry ice/methanol bath at 70 C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (175 ml, 1852 mmol), the isobutylene is added to the polymerization container by means of a nitrogen pressure. p-Dicumyl chloride (0.1413 g, 0.611 mmol) and -picoline (1.709 g, 18.3 mmol) are then added. Titanium tetrachloride (5.36 ml, 48.9 mmol) is then added so as to start the polymerization. After stirring for 65 minutes at the same temperature (70 C.), a sample of the polymerization solution (approximately 1 ml) is extracted from the total polymerization solution.

[0187] Styrene (28.9 ml, 251 mmol) is then added. Once the styrene addition has ended, -pinene (3.64 ml, 23.2 mmol) is added dropwise for 40 min. Once the -pinene addition has ended, titanium tetrachloride (1.79 ml, 16.3 mmol) is once again added and the mixture is stirred for 50 min. Afterwards, the polymerization solution is poured into hot water (2 litres) in order to stop the reaction and this mixture is then stirred for 30 min. The polymerization solution is then washed with deionized water (32 litres). The solvent and the analogues are evaporated from the washed crude reaction product under reduced pressure at 80 C. for 24 hours to obtain the block copolymer. The weight-average molecular weights of the central block (polyisobutylene) and of the total block copolymer are measured by gel permeation chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I below.

EXAMPLE 3: PREPARATION OF A COMPARATIVE BLOCK COPOLYMER (POLYMER 3)--PINENE/STYRENE/ISOBUTYLENE/STYRENE/-PINENE BLOCK COPOLYMER

[0188] The block copolymer (polymer 3) is synthesized as follows:

[0189] A 2 litre separable round-bottomed flask (polymerization container) is placed under nitrogen, and n-hexane (dried over molecular sieves, 192 ml) and butyl chloride (dried over molecular sieves, 768 ml) are then added by means of a syringe. The polymerization container is then cooled by immersion in a dry ice/methanol bath at 70 C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (175 ml, 1852 mmol), the isobutylene is added to the polymerization container by means of a nitrogen pressure. p-Dicumyl chloride (0.1413 g, 0.611 mmol) and -picoline (1.7091 g, 18.3 mmol) are then added. Titanium tetrachloride (5.36 ml, 48.9 mmol) is then added so as to start the polymerization. After stirring for 90 minutes at the same temperature (70 C.), a sample of the polymerization solution (approximately 1 ml) is extracted from the total polymerization solution.

[0190] The styrene (28.9 ml, 251 mmol) is then added and the medium is stirred until the degree of conversion of the styrene has reached 70%. The conversion of the styrene is monitored by gas chromatography. Then, the -pinene (3.64 ml, 23.2 mmol), previously cooled to 70 C., is added to the polymerization container.

[0191] After 30 minutes, titanium tetrachloride (0.30 ml, 2.74 mmol) is added again and the medium is stirred for 20 minutes. The polymerization solution is then poured into hot water (2 litres) in order to stop the reaction and this mixture is then stirred for 30 min. The polymerization solution is then washed with deionized water (32 l). The solvent and the analogues are evaporated from the washed crude reaction product under reduced pressure at 80 C. for 24 hours to obtain the block copolymer. The weight-average molecular weights of the central block (polyisobutylene) and of the total block copolymer are measured by gel permeation chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I below.

EXAMPLE 4: PREPARATION OF A BLOCK COPOLYMER WHICH CAN BE USED IN THE PNEUMATIC OBJECT ACCORDING TO THE INVENTION (POLYMER 4)-(-PINENE-CO--METHYLSTYRENE)/STYRENE/ISOBUTYLENE/STYRENE/(-PINENE-CO--METHYLSTYRENE) BLOCK COPOLYMER

[0192] The block copolymer (polymer 4) is synthesized as follows: A 1 litre separable round-bottomed flask (polymerization container) is placed under nitrogen, and n-hexane (dried over molecular sieves, 121 ml) and butyl chloride (dried over molecular sieves, 485 ml) are then added by means of a syringe. The polymerization container is then cooled by immersion in a dry ice/methanol bath at 70 C. A Teflon feed tube is connected to a pressure-resistant glass collection flask equipped with a three-way tap and containing isobutylene (100 ml, 1059 mmol), the isobutylene is added to the polymerization container by means of a nitrogen pressure. p-Dicumyl chloride (0.0808 g, 0.350 mmol) and -picoline (0.9773 g, 10.5 mmol) are then added. Titanium tetrachloride (3.07 ml, 28.0 mmol) is then added so as to start the polymerization. After stirring for 120 minutes at the same temperature (70 C.), a sample of the polymerization solution (approximately 1 ml) is extracted from the total polymerization solution.

[0193] The styrene (0.80 ml, 6.99 mmol) is added and the medium is stirred for 15 minutes. Then, titanium tetraisopropoxide (2.73 ml, 9.22 mmol) is added and the medium is stirred for 10 min. Then, -pinene (2.08 ml, 13.3 mmol) and -methylstyrene (18.8 ml, 143 mmol) are added and the medium is stirred until the degree of conversion of the -methylstyrene has reached 70%. The conversion of the styrene is monitored by gas chromatography.

[0194] The polymerization solution is then poured into hot water (1 litre) in order to stop the reaction and this mixture is then stirred for 30 min. The polymerization solution is then washed with deionized water (31 l). The solvent and the analogues are evaporated from the washed crude reaction product under reduced pressure at 80 C. for 24 hours to obtain the block copolymer. The weight-average molecular weights of the central block (polyisobutylene) and of the total block copolymer are measured by gel permeation chromatography (GPC) as defined above and the glass transition temperature is measured according to the DMA method as defined above. These data are collated in Table I below.

TABLE-US-00001 TABLE I This table collates the values for weight-average molar mass (Mw), the contents of units derived from -pinene in moles relative to the number of moles of units of the block copolymer (% -pinene) and the percentage by weight of the thermoplastic block(s) relative to the total weight of the block copolymer (% TP blocks). Tg of Mw elastomeric (kg/mol) % -pinene % TP blocks block Polymer 1 100 0 15 60 C. Polymer 2 200 1.1 15 62 C. Polymer 3 200 1.1 15 60 C. Polymer 4 200 1.2 15 61 C.

EXAMPLE 5: PREPARATION AND EVALUATION OF ELASTOMER LAYER WHICH IS GASTIGHT TO INFLATION GASES AND WHICH CAN BE USED IN THE PNEUMATIC OBJECT ACCORDING TO THE INVENTION (MATRIX 100% BLOCK COPOLYMER)

[0195] The block copolymers obtained (polymers 1 to 4) were formulated in layers that are gastight to inflation gases, consisting of 100% of block copolymer (layers 1 to 4, respectively).

[0196] The gastight elastomer thermoplastic layers of the invention are prepared in a conventional manner, for example by incorporation of the block copolymer into a twin-screw extruder, so as to melt the matrix, followed by the use of a flat die for preparing the thermoplastic layer. More generally, the thermoplastic layer may be formed via any method known to a person skilled in the art: extrusion, calendering, extrusion-blow moulding, injection moulding or cast film.

[0197] The properties of these gastight layers were then evaluated.

[0198] The data are collated in Table II below.

TABLE-US-00002 TABLE II This table collates the standardized values (relative to layer 1) for gastightness, adhesion and heat resistance of the elastomer layers prepared by means of the above block copolymers synthesized beforehand. Gastightness Adhesion Heat resistance Layer 1 100 100 100 Layer 2 100 320 113 Layer 3 92 520 118 Layer 4 122 480 119

[0199] The elastomer layer which can be used according to the invention (layer 4) has an unexpected synergistic effect, especially in terms of gastightness.

[0200] In particular, with the same content of -pinene and the same percentage by weight of the thermoplastic block(s) as the comparative layers 2 and 3, the layer which can be used according to the invention, 4, has equivalent adhesion and heat resistance but better gastightness, even though layers 2 and 3 already show good results.

[0201] This reflects the effect of the particular architecture and of the particular composition of the block copolymer constituting the elastomer layer which can be used according to the invention, and in particular of the presence of -methylstyrene.