LU83805A1 - IMPROVED BLADDER FOR VULCANIZING ENVELOPES OR TREATED PNEUMATIC BANDAGES, TREATMENT COMPOSITION THEREFOR AND METHOD FOR VULCANIZING ENVELOPES - Google Patents

Description

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The present invention relates to lubricant compositions for vulcanization bladders for envelopes or pneumatic tires, vulcanization bladders for envelopes coated externally with these lubricant compositions and a method for vulcanization of envelopes using a bladder thus treated.

Usually, rubber tires for vehicles are produced by molding and vulcanizing a green, i.e. unvulcanized and unshaped, envelope in a molding press in which the green envelope is pressed towards outside against the surface of a mold by means of a bladder expandable by an internal fluid. By this process, the raw shell is shaped against the surface of the outer mold which defines the pattern of the tread of the shell and the shape of the sidewalls. The envelope is vulcanized by heating. In general, the bladder is expanded by the internal pressure supplied by a fluid such as a hot gas, from. hot water and / or steam, which also participates in heat transfer for vulcanization. The envelope is then allowed to cool a little in the mold, sometimes with the addition of cold or cooler water in the bladder. Then the mold is opened, the bladder is deflated by releasing the pressure of its internal fluid and the envelope is removed from the envelope mold. This use of tire vulcanization bladders is. 25 well known to specialists.

It is known that there is a significant relative movement between the external contact surface of the bladder and the internal surface of the envelope during the dilation phase of the bladder before the vulcanization of the envelope.

/ '30 loppe. Similarly, there is also a considerable relative movement between the external contact surface of the bladder and the vulcanized internal surface of the envelope after molding and vulcanization of the envelope during deflation and extraction of the envelope bladder. J

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. . 2 Unless adequate lubrication is provided between the bladder and the inner surface of the envelope, the bladder generally tends to curl, resulting in deformation of the envelope in the mold and also excessive wear and etching. from the surface of the bladder itself.

The surface of the bladder also tends to stick to the inner surface of the envelope after vulcanization of the envelope and during the part of the vulcanization cycle of the envelope corresponding to the deflation of the bladder. In addition, air bubbles are likely to be trapped between the surfaces of the bladder and the envelope, favoring the appearance of vulcanization defects in the envelopes due to inadequate heat transfer.

For this reason, there is usually a prior coating of the raw or unvulcanized casing with a lubricant to lubricate the outer surface of the bladder and the inner surface of the casing during the shaping and molding operation. the envelope. The lubricant is sometimes referred to as “lining cement” (lining 20 surround). Usually, the internal surface of the green envelope, which is generally a mixture of rubber gum, is simply spray coated in a closed, ventilated spray booth, with a lubricant which may for example be based on silicone polymer. . Other additives can also usually be used in the lubricant composition, such as mica, polymer polyols, cellulose ethers, clays such as bentonite, etc. Some lubricants are based on solvents, others are water-based. Aqueous solutions of soaps are often used.

‘Λ / 30 Many lubricant compositions have been described in the art for this application.

However, the usual practice of spray coating the inner surface of a green casing with a lubricant composition can lead to a / 3 operation which requires a relatively large workforce, which can appreciably increase the cost. envelope manufacturing. The envelope should be transported to and from the spray booth, and the coating of sprayed lubricant should be left 5 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 envelopes.

According to the invention there is provided a lubricant composition which results from the mixture of: (A) from about 10 to about 40, preferably about 25 to about 35 parts by weight of a bentonite having a size of particles between about 0.149 and about 0.03, preferably between about 0.074 and about 0.037 mm; (B) about 15 to about 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 „; (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 approximately 1500 to approximately 2500 , preferably from about 1800 to about 2200; (D) about 10 to about 25, preferably about 15 to about 20 parts by weight of surfactants for this polydimethylsiloxane and this poly (alkylene glycol); and (E) if desired, about 4 to about 12 parts by weight of a stabilizer.

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

It should be noted that the polydimethylsiloxane may have hydroxyl end groups as an ingredient (precursor) for the preparation of the composition.

The invention further provides a caustic bladder for the vulcanization of expandable envelopes, coated with such a composition (in particular after elimination of the water). In practice, bladder rubber is generally butyl or butyl rubber (a copolymer of isoprene and isobutylene). The term "butyl type" denotes various modified basic butyl rubbers, such as halogen-substituted butyl rubbers, such as chlorobutyl rubber and bromobutyl rubber.

The invention further relates to a method of manufacturing a pneumatic or semi-pneumatic rubber envelope in which a raw envelope is placed in an envelope mold, the coated expandable bladder of the invention is arranged therein. ci, the mold is closed and the bladder is expanded by applying an internal hot fluid pressure to apply the envelope outward against the surface of the mold so as to shape and vulcanize the envelope, after which it is opened the mold, the bladder is deflated and the shaped and vulcanized envelope is removed. The bladder is generally connected to an internal part of the envelope mold itself.

In more detail, this process for molding .30 pneumatic or semi-pneumatic envelopes comprises the following operations: (A) obtaining or manufacturing a raw envelope with elements which will form its external tread intended for come into contact with the ground, two separate inextensible heels 5, flanks extending radially outwards. from the heels to join the tread, a support carcass comprising reinforcing elements and an internal surface of rubber compound; 5 (B) introduce the raw envelope into a mold press for envelopes and have a vulcanization bladder for envelopes coated with the invention inside the raw envelope, the bladder being fixed to an interior part of the envelope press.

10 (C) close the envelope mold and expand the coated envelope vulcanization bladder, by means of an internal heated fluid, towards the outside, against the internal gum mixture surface of the envelope, to press the envelope hot and pressurized outward to form and vulcanize the envelope; (D) open the envelope mold, deflate the bladder and remove the vulcanized envelope, generally torox-shaped.

The term "pneumatic enclosure" refers to enclosures, the proper functioning of which, when mounted on a rim, relies on an internal fluid, such as pressurized air in their enclosure cavity, and the expression "semi-pneumatic envelope" relates to envelopes which contain an internal fluid, such as air, in their cavity, but the correct functioning of which, when mounted on a rim, does not completely depend on its pressure .

In the practice of the invention, the aqueous emulsion or dispersion of the lubricant composition can be conveniently obtained by the method of: (A) mixing under high shear about 10 to about 40, preferably about 25 to about 35 parts by weight of a bentonite having a particle size of between about 0.149 and about 0.03 mm, preferably between about 0.074 and about 0.037 mm, with about 500 to about. 1500, preferably about 600 to about 800 parts by weight of water at a temperature between about 20 and about 95 ° C, the water preferably being preheated to a temperature of about 50 to about 85 ° C, up to 'the mixture appears to have thickened; (B) mix with the preceding mixture approximately 15 to approximately 45, preferably approximately 25 to approximately 35 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity of between approximately 40,000 and approximately 120,000, preferably between about 50,000 and about 70,000 centisto-kes at 25 ° C, about 12 to about 36, preferably about 20 to about 30 parts by weight of poly (ethylene glycol and / or pxopylene glycol), characterized in that it has a molecular mass of between approximately 1500 and approximately 2500, preferably between approximately 1800 and approximately 2200, and a surfactant, in a proportion which is preferably from approximately 4 to approximately 10 parts by weight, for this polydimethylsiloxane and this poly (alkylene glycol); (C) mixing, if desired, with the foregoing mixture about 2 to about 10 parts by weight of an additional surfactant to reduce friction between the bladder and the shell; (D) mixing, if desired, with the foregoing mixture about 2 to about 8 parts by weight of a corrosion inhibitor; (E) mixing, if desired, with the above mixture about 0.2 to about 1.0 part by weight of an anti-foaming agent; (F) mix, if desired, with the above mixture / about 30 to about 10 parts by weight of stabilizer.

It is clear that various relatively well known defoaming agents and various stabilizers may be used in the practice of the invention, which are well known to those skilled in the art. / / 7 The aqueous emulsion or dispersion is simply applied, for example by spraying, to the bladder and dried little: evaporation at a temperature which will be, for example, from approximately 20 ° C. to approximately 110 ° C. For this re-clothing operation, it is preferred that the bladder be at about 80 to about 150% of its expanded state for the vulcanization of the envelope (and not deflated or collapsed), although this is not considered necessary. and that bladders have been successfully coated in a somewhat deflated condition.

In the practice of the invention, it has been observed that when the coating indicated is used on a rubber bladder, it is possible to mold with this bladder approximately 6 to approximately 9 envelopes (6 to 9 cycles of vulcanization of the envelopes) up to that excessive adhesion is observed between the external contact surface of the bladder and the internal surface of the envelope, manifested by an excessive tendency to sticking during deflation of the bladder after vulcanization of the envelope.

This number of vulcanization cycles is considered to compare favorably with that obtained with previous coating compositions, which are familiar to the Applicant.

An important element of the lubricant composition is obviously the presence of the polydimethylsiloxane fluid.

However, it should be noted that this coating has been found to be somewhat greasy in the absence of bentonite, which not only tends to combat the greasy appearance of the surface of the coated bladder, but also, apparently, in a large extent, trapped air to escape from the surface. The sa-.

% 30 or an optional additional surfactant may be advantageous, as it may apparently increase the slip between the bladder and the envelope.

The optional defoaming agent may be comprised of an aqueous emulsion of polydimethylsiloxane which has the advantage.

4 8 ge to prevent or inhibit foaming during mixing.

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

EXAMPLE 1

A lubricant composition is prepared according to the formula in Table 1 below.

- TABLE 1 10 Material Parts

Bentonite clay (0.044 mm) 12.5

Water 759

Polydimethylsiloxane and polyglycol ^ 62.5

Surfactant 6.25 15 Corrosion inhibitor (sodium benzoate) 5

Anti-foam 0.33

Stabilizer 6,25 ^ described as a viscous fluid of polydimethyl-siloxane having a viscosity of approximately 60,000 centistokes in a mixture consisting of approximately 31.3 paxties of this polydimethyl-siloxane, approximately 25 parts of a polypropylene glycol having a molecular weight of about 2000 and about 6 parts of a surfactant therefor * sodium soap of a vegetable oil, considered optional.

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

(B) Add the mixture of organopolysilo-xane fluid under strong shear at 2500 rpm to make a j r 9 · aqueous emulsion.

(C) Add the additional surfactant.

(D) Add corrosion inhibitor to protect the application device.

5 (E) Add the silicone defoamer.

(F) Add the stabilizer.

The mixture is applied by spraying onto the external surface of the rubber bladder for vulcanization. envelopes in its expanded state. The coating is allowed to dry at about 65 ° C. The coating is reapplied after approximately 4 cycles of vulcanization of the envelopes with a maximum of approximately 6 hours between coating applications "

The coating is dried for about 1 minute on the hot (65 ° C) surface of the bladder to form a coating of lubricant composition therein.

The bladder itself is a butyl rubber type bladder having a generally toroxdale shape 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 ...

A raw envelope with a radial carcass, of dimension 11 R 22.5, is produced.

25 Ch places the envelope in a mold press for envelopes and the coated bladder fixed to the mold is introduced into the envelope. The mold is closed and the bladder is expanded with steam at a temperature of about 190 ° C to apply it forcefully against the inner surface of the envelope and.

'30 the envelope is pressed outwards against the surface of the external mold so that the envelope is shaped in the desired manner and vulcanized.

Then open the mold, deflate the bladder and remove the envelope. By operating in this way, it is observed that it is possible to mold approximately 6 to approximately 9 envelopes with the bladder in a period of approximately 8 hours (vulcanization cycles) before it is necessary to re-coat the bladder with the composition. lubricant.

In general, it is considered necessary to re-coat when the bladder excessively sticks to the internal surface of the pre-vulcanized envelope when the expanded bladder is deflated or deflates after the vulcanization operation.

• * It is recognized that the internal surface of the casing 10 is typically a mixture of gum which may consist of various rubbers or their mixtures, such as natural rubber, cis-1,4-polyisoprene, cis-1 , 4-polybutadiene, butadiene-styrene copolymers, butyl rubber, halobutyl rubbers such as chlorobutyl and bromobutyl and EPDM (ethylene-propylene terpolymer, low amount of diene).

We have chosen here as an example the manufacture of an envelope with a radial carcass. Although the invention may sometimes be considered more adaptable to the production of radial carcass envelopes than of diagonal carcass envelopes, since the bladders generally have to expand more during the vulcanization cycle of an envelope with a diagonal carcass, thus stretching the surface coating of the bladder, it is considered that, in general, the invention is easily adaptable to the manufacture of envelopes with a diagonal carcass. _

It is important to note that the envelope of this example was made by expanding the coated bladder directly against the inner gum mixture surface of the envelope to press the envelope outward when hot and ^ under pressure to shape and vulcanize the envelope. Thus, the coated bladder effectively made it possible to manufacture an envelope without applying a coating of lubricant or of a lining cement, on the internal face of the raw envelope. j 4 11 ·

This is considered important because it is thus demonstrated that the coated bladder of the invention provides adequate lubrication for a series of successive cycles of vulcanization of the envelopes under conditions of heat and pressure, expansion and contraction, without 1 * conventional prior application of a jacket lining cement or of a lubricant on the internal face of the envelope. It is reasonable to assume that this will lead to considerable savings in labor and material in the manufacture of the pneumatic casings. Although a pre-coating of lubricant can be applied, if desired, to the internal face of the raw shell, in combination with the coated bladder, it is considered important that this example shows that this is not necessary.

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Claims (14)

12 1. Lubricating composition, characterized in that it comprises: - (A) from 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 having a viscosity of about 40,000 to about 120,000 centistokes at 25 ° C. 10 (C) approximately 12 to approximately 36 parts by weight of poly (ethylene glycol and / or propylene glycol) characterized in that it has a molecular mass of between approximately 1500 and approximately 2500 d (D) approximately 10 to approximately 25 parts by weight of active ingredient (s) for the polydimethylsiloxanes and the poly (alkylene glycol); (E) if desired, about 4 to about 12 parts by weight of a stabilizer. 2. Lubricating composition according to claim 20 1, characterized in that the polydimethylsiloxane of (B) has hydroxyl end groups. 3. Lubricating composition according to claim 1, characterized in that it is an aqueous emulsion containing about 500 to. about 1500 parts of water by weight. 25. 4 - Lubricating composition according to claim 2, characterized in that it is an aqueous emulsion containing about 500 to about 1500 parts of water by weight. 5. Vulcanizing bladder for envelopes or bandages, made of vulcanized rubber, expandable, characterized in that it carries a coating of the composition according to claim 1 on its exposed external face. 6. Vulcanizing bladder for envelopes of vulcanized rubber of the butyl type, expandable, of toroxdale shape, for pneumatic or semi-pneumatic tires, characterized, Jr 13 in that it carries on its external face a coating of the. A composition according to claim 2. 7. A process for preparing the composition according to any one of claims 1 and 2, characterized in that: (A) about 10 to about 40 parts by weight of a bentonite clay having high shear conditions is mixed. a particle size of between about 0.149 and about 0.03 mm with about 500 to about 1500 10 parts of water at a temperature of about 20 ° C to about 90 ° C until the mixture appears to be thickened; (B) mixing with the previous mixture, while maintaining the mixture at a temperature of from about 20 ° C to about 95 ° C, about 10 to about 45 parts by weight of a polydimethylsiloxane characterized in that it has a viscosity of about 40,000 to about 120,000 centistokes at 25 ° C, about 12 to about 36 parts by weight of poly (ethylene glycol and / or propylene glycol) characterized in that it has a molecular weight comprised between about 1500 and about 2500, and a surfactant for polydimethylsiloxane and poly (alkylene glycol); (C) optionally mixing with the preceding mixture approximately 2 to approximately 10 parts by weight of an additional surfactant; * 25 (D) optionally mixed with the preceding mixture approximately 2 to approximately 8 parts by weight of a corrosion inhibitor; <E) optionally mixed with the preceding mixture approximately 0.2 k approximately 1 part by weight of anti-foaming agent; (F) optionally about 2 to about 10 parts by weight of stabilizer is mixed with the preceding mixture. 8. Method for treating a vulcanization bladder of pneumatic envelopes, of vulcanized rubber, expandable, of toroidal shape, for a pneumatic or: - .. / 14 semi-pneumatic envelope, characterized in that the face is coated ex-. dull exposure of the bladder, to about 80 to about 150% of its expanded tire vulcanization state, of the composition of claim 3 and in drying this composition. 9. Method according to claim 8, characterized in that the bladder is of butyl rubber. 10. The method of claim 9, characterized in that the polydimethylsiloxane has hydroxyl end groups. 11. A method of molding a pneumatic or semi-pneumatic casing, characterized in that (A) a raw casing is obtained or manufactured comprising elements intended to form its external tread which will be in contact with the ground , two separate inextensible heels, flanks extending radially outward from the heels to join the tread, a support carcass comprising reinforcing elements, and an internal face of rubber compound; 20 (B) the green envelope is introduced into an envelope molding press and there is a coated envelope vulcanization bladder according to claim 5, inside the green envelope, the bladder being fixed to an internal part the envelope press; (C) the envelope mold is closed and the vulcanized coated bladder of the envelopes is expanded, by means of a heated internal fluid, outwardly against the internal gum mixture surface of the envelope to press the envelope towards the outside when hot and under pressure, so as to shape and vulcanize the envelope; and (D) the envelope mold is opened, the bladder is deflated and the vulcanized envelope having a generally toroidal shape is removed. 12. The method of claim 11, characterized in that the bladder is made of butyl rubber of the bu-tyle type. - 13. The method of claim 12, characterized in that the polydimethylsiloxane of the coating composition has hydroxyl end groups. 14. Method according to any one of claims 12 and 13, characterized in that the bladder is dilated, said coating being pressed directly against the internal surface * of the envelope "t \ s · ~ 4 if '% /