LU83777A1 - TREATED BLADDER FOR VULCANIZATION OF PNEUMATIC OR SEMI-PNEUMATIC ENVELOPES OR BANDAGES, TREATMENT COMPOSITION THEREFOR AND METHOD FOR VULCANIZATION OF ENVELOPES - Google Patents

Description

I *

The present invention relates to lubricating compositions for the vulcanization bladders of envelopes, or bandages, to the vulcanization bladders of envelopes coated externally with these lubricating compositions and to a method of vulcanizing the envelopes using a bladder thus coated.

Pneumatic rubber casings or tires for vehicles are usually produced by molding and vulcanizing a raw, or unvulcanized and unshaped, casing in a molding press in which the green casing is pressed outward against the surface of a mold by means of a bladder expandable by an internal fluid. By this process, the green envelope is shaped against the surface of the external mold which defines the design of the tread 15 of the tire and the configuration of the sidewalls.

. The envelope is vulcanized by heating. In general, the bladder is expanded by the internal pressure of a fluid such as hot gas, hot water and / or steam, which also participates in the heat transfer necessary for vulcanization.

The tire is then allowed to cool a little in the mold, sometimes helping this cooling by introducing cold or cooler water into the bladder. Then the mold is opened, the bladder deflates by releasing the pressure of its internal fluid, and the envelope is removed from the envelope mold. This use of envelope vulcanization bladders is well known to specialists.

It is known that there is a significant relative movement between the outer contact surface of the bladder and the inner surface of the envelope during the phase of dilation of the bladder before the vulcanization of the envelope is complete. Likewise, there is considerable relative movement between the outer contact surface of the bladder and the vulcanized inner surface of the envelope after the envelope has been molded and vulcanized, during deflation. extraction of the bladder from the envelope.

If adequate lubrication is not provided between the bladder and the inner face of the envelope, the bladder generally tends to curl, which results in deformation of the envelope in the mold and also has the effect to overuse and roughen the surface of the bladder itself. In addition, the surface of the bladder may tend to stick to the inner face of the envelope when the envelope is vulcanized and during the stage of cycle 10 of vulcanization of the envelope during which the bladder deflates. In addition, there is a potential risk of trapping air bubbles between the surfaces of the bladder and of the envelope, these bubbles promoting vulcanization defects of the envelopes due to the absence of heat transfer. 15 their adequate ..

For this reason, it is conventional to pre-coat with a lubricant the internal face of the raw or unvulcanized envelope in order to carry out lubrication between the external face of the bladder and the internal face of the envelope during 20 'operation of shaping and molding of the envelope. The lubricant is sometimes referred to as "lining cement". Usually, the inner face of the green casing, which is generally a mixture of rubber gum, is simply spray coated, in a closed spray booth, with a lubricant which may for example be based on polymer of silicone. Other additives such as mica, polymer polyols, cellulosic ethers, clay such as bentonite, etc. can also be used in the lubricant composition. Some lubricants are solvent-based and others are water base. Aqueous solutions of soaps are often used.

Numerous lubricant compositions for this application have been described in the art.

However, the conventional practice of coating, rt * · 3 spraying the internal face of the raw casing with a lubricating composition can constitute an operation requiring a relatively large workforce, which can add appreciably at the cost of producing the envelope. The envelope must be brought into the spray booth and removed from it, and the sprayed lubricant coating must be allowed to dry.

It is therefore desirable to have an improved lubrication system with regard to its composition and its use for molding or shaping and vulcanizing raw casings.

According to the invention, there is provided a lubricating composition which results from mixing: (A) from about 10 to about 40, preferably from about 25 to about 35 parts by weight of bentonite having the same particle size. about 0.149 to about 0.03 mm, preferably about 0.074 to about 0.037 mm; (B) from about 15 to about 45, preferably about 25 to about 35 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity in the range of from about 15 million to about 25 million centist okes at 25 ° C; (C) from about 15 to about 45, preferably from about * to about 35 parts by weight of a polydimethylsilo-25 xane characterized in that it has a viscosity between about 40,000 and about 120 000, preferably between about 50,000 and about 70,000 centistokes at 25 ° C; (D) from about 12 to about 36, preferably from about 20 to about 30 parts by weight of a poly (ethylene glycol and / or propylene glycol), characterized in that it has a molecular weight in l range from about 1500 to about 2200 d (E) from about 10 to about 25, preferably from about 15 to about 20 parts by weight of surfactants.

r (4 for these polydimethylsiloxanes and this poly (alkylene glycol); and (F) if desired, from about 4 to about 12 parts by weight of a stabilizer relative to the total of the 5-dimethylsiloxanes.

The composition intended for application to the surface of the bladder is an emulsion or an aqueous dispersion of the compositions. For example, the application composition also contains (D) about 500 to about 1500, preferably about 600 to about 800 parts by weight of water which, after application to the bladder, is removed by evaporation. More water can certainly be used, although further dilution of the composition reduces the effectiveness of its application.

It is generally preferred that polydimethylsiloxane. of (B) or (C) carries terminal hydroxyl groups, as an ingredient for the preparation (precursor) of the composition.

The poly (alkylene glycol) of (D) is chosen from a poly (ethylene glycol), a poly (propylene glycol) or a mixture thereof. Poly (propylene glycol) is preferred.

The invention further relates to a vulcanizing bladder for expandable envelopes, made of rubber, coated with this coating composition (in particular after removal of the water). In practice, the rubber constituting the bladder is generally a butyl rubber or of the bu-tyle type (copolymer of isoprene and isobutylene). By "butyl type rubber" is meant various modified basic butyl rubbers such as halogen-substituted butyl rubbers, for example chlorobutyl or bromobutyl rubbers.

The invention also relates to a process for the preparation of a pneumatic or semi-pneumatic rubber casing which consists in placing, in a tire mold, a raw casing in which is arranged an expandable bladder / 5 of the invention, close the mold and expand the bladder by introducing a hot fluid inside it to force the envelope outward against the surface of the mold so as to shape and vulcanize the envelope, after whereby the mold is opened, the bladder is deflated and the shaped and vulcanized envelope is removed.

Such a method of molding a pneumatic or semi-pneumatic envelope more precisely comprises the following operations: (A) a raw envelope is obtained or constructed comprising elements which will form its external tread intended to come into contact with the ground, two separate inextensible heels, sides extending radially outward from the heels to join the tread, a support carcass with reinforcing elements, and an inner face of rubber compound; (B) this green envelope is introduced into a molding press for envelopes and there is a vulcanization bladder for the envelopes, coated in accordance with the invention inside the raw envelope, the bladder being fixed to an internal part the envelope press; (C) the envelope mold is closed and the vulcanization bladder of the coated envelopes is expanded outwards, by means of a heated internal fluid, against the surface of the internal rubber mixture of the envelope to press the envelope towards the outside under temperature and pressure conditions making it possible to shape and vulcanize the envelope; (D) the envelope mold is opened, the bladder is deflated and the vulcanized envelope which generally has a toroxdale shape is removed from the mold.

The expression "pneumatic envelope" designates envelopes whose correct operation, when mounted on a rim, is based on an internal fluid such as 6 of the pressurized air in the cavity of the envelope and the expression " will be pneumatic ”means envelopes which contain an internal fluid, such as air, in their cavity, but which do not completely depend on its pressure to function properly when they are mounted on a rim.

It is important to realize that various lubricant mixtures or compositions have been evaluated prior to the discovery and use of the composition of the invention for envelope bladder coatings.

For example, lubricant compositions containing a silicone compound based on organic solvents have been evaluated. However, difficulties have been encountered apparently due to the fact that the organic solvent of the composition ends up damaging or degrading the rubber surface of the bladder itself. The organic solvent poses potential flammability and toxicity problems. It was further observed that the coating compositions based on organic solvents evaluated, deposited on the vulcanization bladder, only had a useful life of approximately 4 to 6 cycles of vulcanization of the envelopes until whether it is considered necessary or useful to re-coat the surface of the bladder. This frequency of re-coatings is considered to have a marginal economic advantage in view of the potential dangers which are linked.

In the practice of the invention, the aqueous emulsion or dispersion of the lubricating composition can be conveniently obtained by the method of (A) mixing under high shear mixing conditions from about 10 to about 40, preferably about 25 to about 35 parts by weight of a bentonite having a particle size between about 0.149 and about 0.03 mm, preferably between about 0.074 and 0.037 mm, with about 500 to about 1500, preferably about 600 to about J- 7 ron 800 parts by weight of water at a temperature between about 20 ° C and about 95 ° C, the water preferably being preheated to a temperature of about 50 to about 80 ° C, until let the mixture appear thickened; 5 (B) mix with this suspension, under conditions of high shear, approximately 15 to approximately 45, preferably approximately 25 to approximately 35 parts by weight of a polydimethylsi-loxane characterized in that it has a viscosity of between approximately 15 million and approximately 25 million centis-ÎO tokes at 25 ° C, and approximately 3 to approximately 25 parts by weight of surfactant active for this polydimethylsiloxane j (C) mix with the composition obtained approximately 15 to approximately 45 , preferably about 25 to about 35 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity between about 40,000 and about 120,000, preferably between about 50,000 and about 70,000 centistokes at 25 ° C, approximately 12 to approximately 36, preferably approximately 20 to approximately 30 parts by weight of a poly (ethylene glycol and / or propylene glycol) characterized in that it has a molecular mass of between approximately 1500 and approximately 2500 , preferably between around 1800 and approx iron 2200, and about 4 to about 10 parts by weight of surfactant for this polydimethylsiloxane and this poly (alkylene glycol); (D) mixing, if desired, the composition obtained about 25 to about 10 parts by weight of a surfactant to reduce the friction between the bladder and the tire; i (E) mixing, if desired, the composition obtained approximately 2 to approximately 8 parts by weight of a corrosion inhibitor; (F) mixing, if desired, the composition obtained approximately 0.2 to approximately 1.0 part by weight of anti-foaming agent; (G) mix, if desired, with the composition obtained, from about 2 to about 10 parts by weight of stabilizer.

Note that one can use in the practice of the invention various relatively well-known anti-foam agents and various stabilizers which are generally well known to specialists.

The aqueous emulsion or dispersion is simply applied, for example by spraying, to the bladder and it is dried by evaporation at a temperature which is for example in the range of from about 20 ° C to about 110 ° C.

It is preferred that the bladder, for this application, be at-. about 80 - 150% of its position or dilated state for vulcanization of the envelope (and not in the deflated or collapsed state), although this is not considered necessary "and bladders have been coated with success in a somewhat deflated state.

It should be noted that various lubricant compositions with emulsion or aqueous dispersion, based on silicone or siloxane, have been formulated previously and evaluated as coatings for vulcanization bladders. In fact, such a composition has been previously tested with the viscous polydimethylsiloxane fluid (C). With this composition, it has been experimentally found that when a rubber bladder is coated with it, only 6 to 9 envelopes can be molded with this bladder (6 to 9 cycles of vulcanization of the envelopes) until excessive adhesion occurs between the outer contact surface of the bladder and the inner surface of the envelope, resulting in their tendency to stick excessively to one another during deflation of the bladder after vulcanization of the envelope. After adding the viscous polyorganosiloxane polymer to the mixture, it has been found that about 10 to about 15 envelopes t can be shaped and molded with the bladder (10 to 15 cycles) before excessive adhesion occurs ( bonding) between surfaces.

<t ί 9

An important feature of the lubricant composition is obviously the presence of two types of polydimethylsiloxane polymers (of B and C) which comprise both a high viscosity polymer and a fluid having a certain viscosity. Note, however, that a coating made of these materials has been found to be somewhat greasy unless bentonite is also used, which tends to both combat the greasy appearance of the surface of the coated bladder. , and also, apparently, to a large extent allow potentially trapped air to escape from the surface. The optional additional soap or surfactant may be beneficial, as it can apparently increase the slip between the bladder and the envelope.

The optional defoaming agent may consist of an aqueous polydimethylsiloxane emulsion which is advantageous because it prevents or inhibits the formation of foam during mixing.

The following nonlimiting examples are given by way of illustration of the invention. Unless otherwise indicated, all parts and percentages are by weight.

EXAMPLE I

A lubricating conqaosition is prepared according to the formula indicated in Table I.

TABLE I

25 Matter Parts

Bentonite clay (0.044 mm) 31.2

Water 712.1

Polydimethylsiloxane1 (at the ends of hydroxyl chairs). 42.8 2 30 Polydimethylsiloxane 62.8 1

6.25 surfactant

Corrosion inhibitor (sodium benzoate) 5

Anti-foam 0.33

Stabilizer 6.25 10 1. Indicated as being a polydimethylsiloxane having a viscosity of the order of 20 million centistokes in a mixture consisting of approximately 31.3 parts of the polydimethylsi-loxane and approximately 11.6 parts of agent surfactant for this 5.

2. Indicated as being a viscous polydimethylsiloxane fluid having a viscosity of approximately 60,000 centistokes in a mixture consisting of approximately 31.3 parts of this polydimethylsiloxane, approximately 25 parts of polypropylene glycol having a molecular weight d 'about 200 and about 6.3 parts surfactant therefor · 3. Sodium soap from a vegetable oil, considered optional.

The aqueous emulsion was prepared according to the following procedure: (A) heating the water to a temperature of about 60 ° C and adding the clay. Mix at 2500 rpm in a Cowles mixer for about 2 to 5 minutes, during which the appearance of the mixture indicates that it has thickened.

(B) add the mixture of polyorganosiloxane polymers under high shear at 2500 rpm. to prepare an aqueous emulsion.

(C) Add the viscous fluid mixture of polyorganosiloxane and polyglycol by mixing under high shear.

(D) add the additional surfactant.

(E) add the corrosion inhibitor intended to protect the application device.

30 (F) add the silicone antifoam.

(G) add the stabilizer at a rate of 10% of the total of the polysiloxane and of the siloxane concentrate (B and C).

The mixture is applied by spraying onto the external face of the vulcanization bladder of the rubber casings maintained in the expanded state. The coating is left to dry at approximately 65 ° C. The coating is reapplied after approximately 4 cycles of vulcanization of the envelopes, with a maximum of 4 to 4 hours between coating applications.

The coating is dried for about one minute on the hot (65 ° C) surface of the bladder to form a coating of lubricant composition thereon.

The bladder itself is butyl rubber, its general shape is toroidal with an overall diameter in the expanded state of about 990 mm and a tubular diameter of about 250 mm. Its surface was pretreated by washing with a hydrocarbon solvent then drying to remove surface oils etc ...

15 A raw radial envelope of dimensions 11 R 22.5 is manufactured.

The envelope is placed in an envelope mold and the coated bladder fixed to the mold is introduced inside the envelope. The mold is closed and the bladder 20 is dilated with steam at about 190 ° C. to apply it strongly against the internal surface of the envelope and press the external face of the envelope to shape the envelope in the same way. - re desired and vulcanize it.

The mold is then opened, the bladder 25 is deflated and the envelope is removed therefrom. By operating in this way, it can be observed that approximately 10 to approximately 15 envelopes can be molded with the bladder in approximately 8 to 13 hours (vulcanization cycles) before it is necessary to reapply lubricant composition. on the bladder.

30 In general, a new application is considered to be necessary when the bladder exaggeratedly sticks to the internal face of the vulcanized envelope when the dilated bladder is deflated after the vulcanization operation ·, 4 12

The inner face of the envelope is generally a mixture of rubber which may consist of various rubbers such as natural rubber, cis-1,4-polyisoprene, cis-1,4-polybutadiene, butadiene copolymers. sty-5 rein, butyl rubber, halo-butyl rubbers, for example chlorobutyl and bromobutyl rubbers and EDPT (terpolymer of ethylene, propylene and a small amount of a diene) ·

In this example, the preparation of a radial carcass envelope is described. Although the invention can often be considered more adaptable to the production of radial carcass envelopes than of diagonal carcass envelopes, because the bladders generally have to expand. further during the vulcanization cycle of the envelopes with a diagonal carcass, which stretches the surface coating of the bladder, the invention is considered to be entirely acceptable for the production of envelopes with a diagonal carcass and is not limited the manufacture of envelopes with a radial carcass.

It is important to note that the shell of this example was made by directly expanding the coated bladder against the interior gum mixture surface of the shell to press the shell outward under temperature and temperature conditions. pressure allowing to shape and vulcanize it. The coated bladder effectively prepared the envelope without applying a coating of lubricant or liner cement to the inside of the raw envelope. This fact is considered to be important, because it clearly shows that the coated bladder according to the invention allows adequate lubrication for a series of successive cycles of vulcanization of the envelopes under conditions of temperature and pressure, expansion and contraction. , without the prior application of lining cement or conventional lubricant on the internal face of the envelope.

i "ft 13

It can reasonably be considered that this will allow considerable savings in manpower and material in the preparation of the pneumatic casings. Although it is recognized that a pre-coating of lubricant can be used, if desired, on the inner face of the raw shell, in association with the coated bladder, it is considered important that this example demonstrates that this is not necessary.

<t «

Claims (18)

1. Lubricating composition, characterized in that it comprises: (A) about 10 to about 40 parts by weight of a bentonite having a particle size of from about 0.149 to about 0.03 mm; (B) about 15 to about 45 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity between * about 15 million and about 25 million centistokes at 25 ° C; (C) about 15 to about 45 parts by weight of a polydimethylsiloxane having a viscosity in the range of from about 40,000 to about 120,000 centistokes at 25 ° C; * 15 (D) approximately 12 to approximately 31 parts by weight of a poly (ethylene glycol and / or propylene glycol), characterized in that it has a molecular mass of between approximately 1500 and approximately 2500 d. (Fî) approximately 10 to about 25 parts by weight of surfactants for polydimethylsiloxanes and poly (alkylene glycol); (F) optionally about 4 to about * 12 parts by weight of stabilizer. 2. Lubricating composition according to claim 25 1, characterized in that at least one of the polydimethylsilo xanes of (B) and (C) carries terminal hydroxyl groups. 3. Composition according to claim 1, characterized in that the poly (alkylene glycol) is poly (propylene glycol). 30 4 - Composition according to claim 3, characterized in that the polydimethylsiloxane of (B) carries terminal hydroxyl groups. 5. Lubricating composition according to claim 1, characterized in that it is an aqueous emulsion </ "15 containing about 500 to about 1500 parts of water by weight. 6. Lubricating composition according to claim 2, characterized in that it is an aqueous emulsion containing about 500 to about 1500 parts by weight of water. 7. Composition according to claim 4, charac terized in that it is an aqueous emulsion containing about 500 to about 1500 parts by weight of water. 8. Composition according to claim 5, characterized in that it contains approximately 500 to approximately 1500 10 parts by weight of water. 9. Vulcanizing bladder for envelopes or tires made of vulcanized rubber, expandable, characterized in that it carries a coating of the composition according to claim 1 on its exposed external face. 15 10 - Vulcanization bladder for butyl rubber or vulcanized butyl type envelopes, expandable, toroidal, for a pneumatic or semi-pneumatic tire, characterized in that it carries a coating of the composition according to claim 2 on its face external. 20 11 “Vulcanizing bladder for butyl rubber or vulcanized butyl rubber, expandable, for a pneumatic or semi-pneumatic tire, characterized in. that it carries a coating of the composition according to claim 3 on its external face. 25 12 - Vulcanizing bladder for expandable vulcanized rubber envelopes, characterized in that it carries a coating of the composition according to claim 4 on its external face. 13. Process for preparing the composition according to any one of claims 1 to 3, characterized in that (A) about 10 to about 40 parts by weight of a bentonite having high shear conditions is mixed. a particle size of about y / AX η 16 0.149 to about 0.03 mm with about 500 to about 1500 parts by weight of water preheated to a temperature between about 20 and about 95 ° C until the mixture appears thickened; 5 (B) this suspension is mixed with high shear about 15 to about 45 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity of between about 15 million and about 25 million centistokes at 25 ° C and about 3 to about 25 parts by weight of a surfactant for this polydimethylsiloxane; (C) mixed with. this composition about 15 to about 45 parts by weight of a polydimethylsiloxane. characterized in that it has a viscosity between about 40,000 to about 120,000 centistokes at 25 ° C, about 12 * to about 36 parts in weight of poly (ethylene glycol and / or propylene glycol), characterized in that it has a molecular mass of approximately 1500 to approximately 2500, and approximately 4 to approximately 10 parts by weight of a surfactant for the polydimé -20 thylsiloxane and alkylene oxide polyol; (D) if desired, mix with this composition about 2 to about 10 parts by weight of additional surfactant j (B) if desired mix with this composition about 2 to about 8 parts by weight d 'corrosion inhibitor; (F) mixing, if desired, with this composition about 0.2 to about 1.0 part by weight of anti-foaming agent; > 30 (G) if desired, this composition is mixed with this composition approximately 2 k approximately 10 parts by weight of stabilizer. <. 14. Process for treating a vulcanization bladder for envelopes made of vulcanized rubber, expandable of </ * "17. toroxdale shape, expandable, for a pneumatic or semi-pneumatic tire, characterized in that the outer face is coated, exposed from the bladder to about 80 to about 150% of its expanded envelope vulcanization position with the aqueous emulsion composition of any of claims 5 to 7, and that this composition is dried by evaporation. 15. A method of molding an envelope or tire of pneumatic or semi-pneumatic rubber, characterized in that it consists in (A) obtaining or constructing a raw envelope comprising elements intended to form its external tread which will be in contact with the ground, two separate inextensible heels, sides extending radially outward from the heels to join the tread, a support carcass with reinforcing elements, and an internal mixing surface rubber gum; (B) introducing the green envelope into an envelope molding press and placing an envelope vulcanization bladder according to any one of claims 9, 10 and 11 inside the green envelope, the bladder being fixed to an internal part of the envelope press; (C) close the envelope mold and expand out the vulcanized coated envelope bladder, using an internal, heated fluid, against the gum mix surface of the envelope, to press the casing outwards under temperature and pressure conditions to shape and vulcanize the casing .; (D) open the envelope mold, deflate the bladder and remove the vulcanized envelope having a general toroxdale shape. 16. A method of molding an envelope or tire i "* 4 <· t IS · of pneumatic or semi" pneumatic rubber, characterized in that (A) a raw envelope is obtained or constructed comprising elements intended to constitute 5 its external tread which will be in contact with the ground, two separate inextensible heels, sides extending radially outward from the heels to join the tread, a support carcass with reinforcing elements and an inner surface of the rubber gum mixture; (B) the green envelope is introduced into "an envelope molding press and a vulcanization bladder of the envelopes according to any one of claims 12 and 13 is placed inside the green envelope, the bladder being fixed to an internal part of the envelope press; (C) the envelope mold is closed and the vulcanized coated envelope bladder is expanded outward by means of an internal fluid heated against the internal rubber mixture of the envelope to press the envelope towards the exterior under conditions of temperature and pressure allowing the shaping and vulcanization of the envelope; (D) the envelope mold is opened, the bladder is deflated and the vulcanized envelope is removed, which generally has a toroidal shape. 17. A method of molding a pneumatic or semi-pneumatic rubber casing, characterized in that: (A) a raw envelope is obtained or constructed comprising elements intended to constitute its external tread which will be in contact with the ground, two separate inextensible heels, sides extending radially outward from the heels to join the tread, a support carcass with elements Λ ",% é r" 19 reinforcing elements and an internal surface of rubber compound; (B) introducing the raw envelope into an envelope molding press and disposing of. the interior of the raw envelope a vulcanization bladder for envelopes according to any one of claims 9, 10 and 11, the bladder being fixed on an internal part of the envelope press; (C) the envelope mold is closed and the bladder is expanded outward by means of an internal heated fluid, the coating of the bladder being directly against the inner surface of the envelope for pressing the casing outwards under temperature and pressure conditions making it possible to shape and vulcanize the casing · 15 18 - Process for molding a pneumatic or semi-pneumatic cauldron casing, characterized in that (A) a raw casing is obtained or constructed comprising elements which will constitute its external tread intended to be in contact with the ground, two separate inextensible heels, flanks extending radially outward from the heels to join the tread, a support carcass with reinforcing elements and an internal surface of rubber compound - 'de rubber; (B) the raw envelope is introduced into an envelope molding press and a vulcanization bladder for envelopes according to any one of claims 12 and 13 is placed inside the raw envelope, the bladder being fixed on an internal part of the 30 envelope press j (C) the envelope mold is closed and the bladder is expanded outwards by means of a heated internal fluid, the coating of this bladder being directly against the internal surface of the envelope to press the envelope 4. ► "" "· * 'v 20 outwards under temperature and pressure conditions allowing the envelope to be shaped and vulcanized. te 4 2M