RELEASE AGENT FOR TIRE BLADDER, TIRE BLADDER, AND PNEUMATIC TIRE

Abstract

A release agent for being coated onto a tire bladder made of a zinc-oxide-incorporated butyl rubber during pneumatic-tire molding, the release agent containing (A) organopolysiloxane, which contains a carboxy group indicated by the general formula (1) below

##STR00001##

(in the formula, R.sup.1 is a substituted or unsubstituted C1-C30 monovalent hydrocarbon group excluding R.sup.2, R.sup.2 is a carboxy-group-substituted C1-C30 monovalent organic group, R.sup.3 is R.sup.1 or R.sup.2, and n is an integer of 3 to 2000.). This release agent produces a longer service life of a tire bladder and leads to reduced tire production cost because the amount of silicone that migrates to the tire side is low when the tire is released, and repeated mold-release performance is enhanced.

Claims

1. A release agent for application to a tire bladder made of zinc oxide-containing butyl rubber when molding pneumatic tires, comprising: (A) a carboxyl group-containing organopolysiloxane of general formula (1) ##STR00011## wherein R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 30 carbon atoms other than R.sup.2, R.sup.2 is a carboxyl group-substituted monovalent organic group of 1 to 30 carbon atoms, R.sup.3 is R.sup.1 or R.sup.2, and n is an integer from 3 to 2,000.

2. A release agent for application to a tire bladder made of zinc oxide-containing butyl rubber when molding pneumatic tires, which release agent is an aqueous emulsion composition comprising: (A) 100 parts by weight of the organopolysiloxane of general formula (1) in claim 1, (B) from 1 to 30 parts by weight of a surfactant, and (C) from 30 to 10,000 parts by weight of water.

3. The release agent for a tire bladder of claim 1 or 2, wherein the carboxyl group-containing organopolysiloxane of general formula (1) in component (A) includes: (A-1) a carboxyl group-containing organopolysiloxane wherein n is an integer of 3 or more and less than 150, and (A-2) a carboxyl group-containing organopolysiloxane wherein n is an integer of 150 or more and not more than 2,000.

4. The release agent for a tire bladder of claim 3, wherein the blending ratio of components (A-1) and (A-2), expressed by weight, is from 95:5 to 10:90.

5. A method of producing a tire bladder for molding pneumatic tires, comprising the step of applying the release agent of the composition of claim 1 to a tire bladder surface made of zinc oxide-containing butyl rubber and subsequently heating at a temperature of between 80 and 250 C.

6. A pneumatic tire molded using the tire bladder obtained by the method of claim 5.

Description

EXAMPLES

[0074] The invention is illustrated more fully below by way of Working Examples and Comparative Examples, although these Examples are not intended to limit the invention. In the following Examples, unless noted otherwise, all references to percent (%) are by weight.

[Evaluation of Adherence to Zinc Oxide-Containing Butyl Rubber]

[0075] Gauze impregnated with organopolysiloxane or organopolysiloxane emulsion was used to apply organopolysiloxane or organopolysiloxane emulsion to a 2 mm thick sheet of butyl rubber formulated with zinc oxide, following which the rubber sheet was placed in a thermostatic chamber set to 150 C. and heated for 50 minutes. The rubber sheet was then immersed for 10 minutes in 1-butanol, in addition to which the side of the sheet to which organopolysiloxane or organopolysiloxane emulsion had been applied was wiped with a 1-butanol-impregnated gauze. After 24 hours of air drying, the amount of organopolysiloxane remaining on the butyl rubber sheet was measured using a fluorescence x-ray spectrometer.

[Test of Tire Bladder Releasability]

[0076] A test piece obtained by applying organopolysiloxane or organopolysiloxane emulsion to slab rubber (cured) from a cured bladder and then rinsing the rubber with butanol was laminated to a tire inner liner (uncured) and repeatedly press-cured at 190 C. for 15 minutes. The force when pulling these apart after carrying out the above operation ten or more times was determined.

##STR00005##

Working Example 1

[0077] The organopolysiloxane of average formula (4) below having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol was furnished for use.

[0078] An organopolysiloxane mixture which had a viscosity of 34,000 mm.sup.2/s and a carboxyl amount of 59,600 g/mol and was composed of the organopolysiloxane of average formula (5) below having a carboxyl group at one end of the molecular chain, the organopolysiloxane of average formula (6) below having carboxyl groups at both ends of the molecular chain and the dimethylpolysiloxane of average formula (7) below in the weight ratio 5:2.5:2.5 was furnished for use.

[0079] The organopolysiloxane of average formula (4) in an amount of 300 g was mixed together with 200 g of the mixture of the organopolysiloxanes of average formulas (5), (6) and average formula (7). Using the resulting mixture, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

##STR00006##

Working Example 2

[0080] An amount of 250 g of the organopolysiloxane of average formula (4) having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol was mixed with 250 g of the organopolysiloxane of average formula (6) below having carboxyl groups at both ends of the molecular chain, a viscosity of 66,700 mm.sup.2/s and a carboxyl amount of 27,200 g/mol. Using the resulting mixture, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

Working Example 3

[0081] An organopolysiloxane mixture which had a viscosity of 60 mm.sup.2/s and a carboxyl amount of 1,440 g/mol and was composed of the organopolysiloxane of average formula (8) below having a carboxyl group at one end of the molecular chain, the organopolysiloxane of average formula (9) below having carboxyl groups at both ends of the molecular chain and the dimethylpolysiloxane of average formula (10) below in the weight ratio 5:2.5:2.5 was furnished for use.

[0082] The organopolysiloxane of average formula (6) above having carboxyl groups at both ends of the molecular chain, a viscosity of 66,700 mm.sup.2/s and a carboxyl amount of 27,200 g/mol was furnished for use.

[0083] The mixture of organopolysiloxanes of average formulas (8), (9) and (10) in an amount of 350 g and 150 g of the organopolysiloxane of average formula (6) were mixed together and dissolved. Using the resulting mixture, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

##STR00007##

Working Example 4

[0084] A 300 mL glass beaker was charged with 60 g of the organopolysiloxane of average formula (4) having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol. To this was added 40 g of an organopolysiloxane mixture which had a viscosity of 34,000 mm.sup.2/s and a carboxyl amount of 59,600 g/mol and was composed of the organopolysiloxane of average formula (5) having a carboxyl group at one end of the molecular chain, the organopolysiloxane of average formula (6) having carboxyl groups at both ends of the molecular chain and the dimethylpolysiloxane of average formula (7) in the weight ratio 5:2.5:2.5. Using a homogenizing mixer, the beaker contents were mixed together at a speed of 2,000 rpm. Next, 9 g of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=8 moles (available from Kao Corporation under the trade name Emulgen 1108), 2 g of a 60% aqueous solution of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=50 moles (available from Kao Corporation under the trade name Emulgen 1150S-60) and 27 g of water were added. Using a homogenizing mixer, the beaker contents were stirred at a speed of 7,000 rpm, whereupon an oil-in-water system formed and an increase in viscosity was confirmed. Stirring was continued for another 15 minutes. Next, under stirring at 2,000 rpm, 112 g of water was added, after which the beaker contents were transferred to a 1-liter glass beaker, 750 g of a 2% aqueous solution of carboxymethylcellulose sodium (available from DKS Co., Ltd. under the trade name Cellogen F) was added and the system was stirred at 2,000 rpm, giving a white emulsion.

[0085] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

Working Example 5

[0086] A 300 mL glass beaker was charged with 50 g of the organopolysiloxane of average formula (4) having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol, and 50 g of the organopolysiloxane of average formula (6) having carboxyl groups at both ends of the molecular chain, a viscosity of 66,700 mm.sup.2/s and a carboxyl amount of 27,200 g/mol. Using a homogenizing mixer, the beaker contents were mixed together at a speed of 2,000 rpm. Next, 9 g of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=8 mol (available from Kao Corporation under the trade name Emulgen 1108), 2 g of a 60% aqueous solution of a polyoxyethylene alkyl ether for which the number of molecules of ethylene oxide added=50 moles (available from Kao Corporation under the trade name Emulgen 1150S-60) and 27 g of water were added. Using a homogenizing mixer, the beaker contents were stirred at a speed of 7,000 rpm, whereupon an oil-in-water system formed and an increase in viscosity was confirmed. Stirring was continued for another 15 minutes. Next, under stirring at 2,000 rpm, 112 g of water was added, after which the beaker contents were transferred to a 1-liter glass beaker, 750 g of a 2% aqueous solution of carboxymethylcellulose sodium (available from DKS Co., Ltd. under the trade name Cellogen F) was added and the system was stirred at 2,000 rpm, giving a white emulsion.

[0087] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

Working Example 6

[0088] A 300 mL glass beaker was charged with 60 g of the organopolysiloxane of average formula (4) having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol. To this was added 40 g of an organopolysiloxane mixture which had a viscosity of 34,000 mm.sup.2/s and a carboxyl amount of 59,600 g/mol and was composed of the organopolysiloxane of average formula (5) having a carboxyl group at one end of the molecular chain, the organopolysiloxane of average formula (6) having carboxyl groups at both ends of the molecular chain and the dimethylpolysiloxane of average formula (7) in the weight ratio 5:2.5:2.5. Using a homogenizing mixer, the beaker contents were mixed together at a speed of 2,000 rpm. Next, 9 g of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=8 moles (available from Kao Corporation under the trade name Emulgen 1108), 2 g of a 60% aqueous solution of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=50 moles (available from Kao Corporation under the trade name Emulgen 1150S-60) and 27 g of water were added. Using a homogenizing mixer, the beaker contents were stirred at a speed of 7,000 rpm, whereupon an oil-in-water system formed and an increase in viscosity was confirmed. Stirring was continued for another 15 minutes. Next, while stirring at 2,000 rpm, 112 g of water was added. The beaker contents were transferred to a 1-liter glass beaker, 5 g of an emulsion containing 42% of the dimethylpolysiloxane of average formula (13) below having a viscosity of 1,950,000 mm.sup.2/s and 745 g of a 2% aqueous solution of carboxymethylcellulose sodium (available from DKS Co., Ltd. under the trade name Cellogen F) were added, and the system was stirred at 2,000 rpm, giving a white emulsion.

[0089] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

##STR00008##

Working Example 7

[0090] A 300 mL glass beaker was charged with 67.5 g of the organopolysiloxane of average formula (4) having carboxyl groups at both ends of the molecular chain, a viscosity of 126 mm.sup.2/s and a carboxyl amount of 880 g/mol. To this was added 22.5 g of an organopolysiloxane mixture which had a viscosity of 60 mm.sup.2/s and a carboxyl amount of 1,440 g/mol and was composed of the organopolysiloxane of average formula (8) having a carboxyl group at one end of the molecular chain, the organopolysiloxane of average formula (9) having carboxyl groups at both ends of the molecular chain and the dimethylpolysiloxane of average formula (10) in the weight ratio 5:2.5:2.5. To this was further added 10 g of the organopolysiloxane of average formula (14) having amino groups on side chains of the molecule, a viscosity of 55,100 mm.sup.2/s and an amino amount of 10,500 g/mol. Using a homogenizing mixer, the beaker contents were mixed together at a speed of 2,000 rpm. Next, 9 g of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=8 moles (available from Kao Corporation under the trade name Emulgen 1108), 2 g of a 60% aqueous solution of a polyoxyethylene alkyl ether having a number of moles of ethylene oxide added=50 moles (available from Kao Corporation under the trade name Emulgen 1150S-60) and 27 g of water were added. Using a homogenizing mixer, the beaker contents were stirred at a speed of 7,000 rpm, whereupon an oil-in-water system formed and an increase in viscosity was confirmed. Stirring was continued for another 15 minutes. Next, under stirring at 2,000 rpm, 112 g of water was added. The beaker contents were transferred to a 1-liter glass beaker, 320 g of a 2% aqueous solution of hydroxypropyl methylcellulose (available from Shin-Etsu Chemical Co., Ltd. under the trade name Metolose 90SH-100000) and 430 g of water were added, and the system was stirred at 2,000 rpm, giving a white emulsion.

[0091] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

##STR00009##

Working Example 8

[0092] Mica (available from Shiraishi Calcium Kaisha, Ltd. under the trade name Takaramica M-101) in an amount of 5 g was added to 1,000 g of an emulsion obtained in the same way as in Working Example 10. Using a homogenizing mixer, the system was mixed for 5 minutes at a speed of 2,000 rpm.

[0093] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

Comparative Example 1

[0094] An amount of 300 g of the dimethylpolysiloxane of average formula (11) having a viscosity of 101 mm.sup.2/s and 200 g of the dimethylpolysiloxane of average formula (12) having a viscosity of 30,200 mm.sup.2/s were mixed together and dissolved. Using this mixture, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

##STR00010##

Comparative Example 2

[0095] A 300 mL glass beaker was charged with 60 g of the dimethylpolysiloxane of average formula (11) having a viscosity of 101 mm.sup.2/s and 40 g of the dimethylpolysiloxane of average formula (12) having a viscosity of 30,200 mm.sup.2/s. Using a homogenizing mixer, the beaker contents were mixed together at a speed of 2,000 rpm. Next, 9 g of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=8 moles (available from Kao Corporation under the trade name Emulgen 1108), 2 g of a 60% aqueous solution of a polyoxyethylene alkyl ether for which the number of moles of ethylene oxide added=50 moles (available from Kao Corporation under the trade name Emulgen 1150S-60) and 10 g of water were added. Using a homogenizing mixer, the beaker contents were stirred at a speed of 7,000 rpm, whereupon an oil-in-water system formed and an increase in viscosity was confirmed. The homogenizing mixer was changed to a homogenizing disperser and the system was stirred at a speed of 2,000 rpm for 15 minutes. Next, the stirrer was returned once again to a homogenizing mixer, 119 g of water was added and the system was stirred at 2,000 rpm. The contents were then transferred to a 1-liter glass bearer, 750 g of a 2% aqueous solution of carboxymethylcellulose sodium (available from DKS Co., Ltd. under the trade name Cellogen F) was added, and the system was stirred at 2,000 rpm, giving a white emulsion.

[0096] Using the emulsion thus prepared, the evaluation of adherence to butyl rubber and the releasability test described above were carried out. The results are presented in Table 1.

TABLE-US-00001 TABLE 1 Evaluation of adherence to Tire bladder bladder rubber (amount of releasability organopolysiloxane, g/m.sup.2) test Working Example 1 2.28 good Working Example 2 2.93 fair Working Example 3 1.90 good Working Example 4 1.67 good Working Example 5 2.25 fair Working Example 6 1.65 good Working Example 7 1.14 good Working Example 8 1.10 good Comparative Example 1 0.009 NG Comparative Example 2 0.004 NG

[0097] Compared with the carboxyl group-lacking methylpolysiloxanes and emulsions thereof in Comparative Examples 1 and 2, the carboxyl group-containing organopolysiloxanes or organopolysiloxane mixtures containing the same, and emulsions thereof, in Working Examples 1 to 8, when applied to a butyl rubber sheet which was subsequently rinsed with butanol, resulted in a higher amount of polysiloxane remaining thereon and also better releasability

Working Example 9

[0098] Toluene (700 g) was added to 300 g of the organopolysiloxane prepared in Working Example 1, and mixing and dissolution carried out. The resulting solution was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Working Example 10

[0099] The emulsion prepared in Working Example 4 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Working Example 11

[0100] The emulsion prepared in Working Example 5 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Working Example 12

[0101] The emulsion prepared in Working Example 6 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Working Example 13

[0102] The emulsion prepared in Working Example 7 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Working Example 14

[0103] The emulsion prepared in Working Example 8 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

Comparative Example 3

[0104] The emulsion prepared in Comparative Example 2 was applied with a spray to the surface of a tire bladder made of zinc oxide-containing butyl rubber, and subsequently heated at 150 C. for 50 minutes. Tire curing/molding was carried out using the resulting bladder, and the bladder life was evaluated. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Working Working Working Working Working Working Example Example Example Example Example Comparative Example 9 10 11 12 13 14 Example 3 Bladder 130 120 110 150 110 110 100 life Note: Values indicated are relative to an arbitrary value of 100 for the bladder life in Comparative Example 3.

[0105] Compared with the carboxyl group-lacking methylpolysiloxane and emulsion thereof in Comparative Example 3, the organopolysiloxanes containing the carboxyl group-containing organopolysiloxanes and emulsions thereof, in Working Examples 9 to 14, resulted in a longer bladder life.