DE3146051C2 - - Google Patents

Description

The invention relates to a lubricant and its use for coating a tire vulcanization bladder.

Pneumatic rubber vehicle tires are used in a conventional manner by molding and vulcanizing a green or non-vulcanized or non-molded tire in one Forming press in which the green tire faces outwards a mold surface by means of a bubble which is marked by a inner fluid is expanded. In this way the green tire is molded from the outer mold surface, the tread pattern of the tire and the configuration forms the side walls. By allowing it to act the tire is vulcanized by heat. Generally speaking the bladder expands due to an internal pressure that a fluid is made available, for example by a hot gas, hot water and / or water vapor, this Fluids also on heat transfer for hardening or vulcanizing take part. The tire is then left in the mold cool down a bit, sometimes using cold or cool water is fed to the bladder. Then the mold is opened and the bladder collapse by releasing the internal pressure left, whereupon the tire is removed from the tire mold becomes. The use of tire vulcanization bladders is known.

There is a significant relative movement between the outer contacting surface of the bladder and the inner Surface of the tire during the expansion phase Bladder before fully curing the tire. Further there is a considerable relative movement between the outer contacting surface of the bladder and the vulcanized inner surface of the tire after molding and vulcanization of the tire during the collapse and peeling the bladder from the tire.  

Unless there is sufficient lubrication between the Bladder and the inner surface of the tire is taken care of the bladder tends to kink or wrinkle, which causes an undesirable deformation of the tire in the Shape as well as excessive wear and roughening of the Bladder surface itself conditional. The bubble surface also tends to stick to the inner surface of the Tire after vulcanization and during the Bladder collapse during the tire curing cycle. There may also be air bubbles between the bubble and the tire surfaces are trapped and tire vulcanization defects due to insufficient heat transfer condition.

For this reason, it is conventional practice, the inner one Surface of the green or unvulcanized tire with to apply a lubricant to provide lubrication between the outer bladder surface and the inner tire surface ensure during tire molding. Sometimes the lubricant is used as a liner (lining cement). In a conventional way the inner surface of the green tire, which in typical Way consists of a rubber material, simply in one ventilated spray chamber sprayed with a lubricant, which are based, for example, on a silicone polymer can. Other additives can also be used in a conventional manner used in a lubricant preparation, such as Mica, polymeric polyols, cellulose ether, clay, such as bentonite clay. Some lubricants are solvent based and others are water-based. Often aqueous soap solutions are used. Lots of lubricants are known for these purposes.

The conventional spray coating of the inner surface of the green tire with a lubricant requires one intense workload, which translates into a substantial Amounts to the cost of the tire.  

The tire must be transported into and from the spray chamber be transported away again, and it must also dry of the sprayed spray can be left standing.

There is therefore a need for an improved lubrication system for molding and vulcanizing green tires.

This object is achieved by the lubricant of the claim 1 solved.

DE-OS 24 55 377 describes release agent mixtures in the preamble of claim 1 genus described. Across from these known mixtures differ according to the invention Lubricant due to the fact that at least one of the polymethylsiloxanes (B) and (C), especially that Has polydimethylsiloxane (B), hydroxyl end groups.

As a result, the lubricant according to the invention comes without organic Solvent from what is significant economic as well limited physiological and ecological advantages. Also allow the lubricants according to the invention more vulcanization Cycles than the known.

The preparation for application to the bladder surface is an aqueous emulsion or dispersion of the ingredients. For example, the preparation to be applied can also (G) about 500 to about 1500, and preferably about Contain 600 to about 800 parts by weight of water after application to the bladder dried by evaporation becomes. You can also use more water, though however, a further dilution of the preparation's efficiency his assignment diminished.  

Component (D) preferably consists of polypropylene glycol with the specified molecular weight.

The invention provides an expandable rubber tire vulcanization bladder with a coating like the one above has been described, especially after removal of water, provided. The rubber for the Blister is typically a butyl or butyl type rubber (Copolymer of isoprene and isobutylene). Under the The term "butyl type" are various modified basic butyl rubbers understand how halogen-substituted Butyl rubbers, for example made of chlorobutyl rubber or bromobutyl rubber.  

In particular, there is a molding process a pneumatic or semi-pneumatic tire from the following levels:

• (A) Manufacturing or building a green tire with Components that its outer tread that the Contacted floor, two at a distance inextensible beads, side walls that are radial extend outward from the beads and extend with the Connect tread, a supporting carcass with reinforcing elements and an inner surface from one Will form rubber material;
• (B) Inserting the green tire into a tire molding press and positioning a tire vulcanization bladder coated in accordance with the present invention into the inside of the green tire, the bladder with an inner Section of the tire press is connected;
• (C) closing the tire mold and expanding the coated ones Tire vulcanization bladder heated by an inner one Fluid outwards against the inner rubber surface of the tire, causing the tire to go out under the action of heat and pressure is pressed, wherein the tire is molded and vulcanized;
• (D) opening the tire mold, collapsing the bladder and removing the vulcanized tire with an in general toroidal shape.

The term "pneumatic tires" means tires which is an internal fluid, such as Air, under pressure in its tire cavity for how it works operate if they are mounted on a rim while under the term "semi-pneumatic tires" tires too that have an internal fluid, like air, in their  Cavity included, but not completely open the pressure of this fluid when mounted on a rim have to leave for their functioning.

Various lubricant mixtures or preparations have already been studied as coatings for tire bladders.

For example, lubricants that have been investigated Contain silicone compounds in organic solvents. However, difficulties were identified that were obvious are due to the fact that the organic Solvent in the preparation the rubber surface the bladder itself is destroyed or deteriorated. The organic Solvent itself is flammable and toxicity dangerous. Beyond that found that the coating compositions examined organic solvent-based only about 4 to 6 tire vulcanization cycles outlasted until it was required was considered to re-coat the bladder surface. Such frequency of re-coating is economically disadvantageous, especially taking into account the associated dangers.

To carry out the invention in practice, the aqueous Emulsion or dispersion of the lubricant preparation be conveniently made by a method which consists of the following levels:

• (A) Under high shear mixing conditions, 10 to 40 and preferably 25 to 35 parts by weight of bentonite clay with a particle size such that the particles through sieves with sieve openings between 0.03 mm and 0.15 mm and in particular 0.04 mm and 0.07 mm pass through, with 500 to 1500 and preferably 600 to 800 parts by weight of water a temperature between 20 and 95 ° C, the water preferably at 50 to 85 ° C is preheated, mixed until the mixture  seems to have thickened.
• (B) Then under high shear mixing conditions 15 to 45 and preferably 25 to 35 parts by weight of a polydimethylsiloxane a viscosity between 15 and 25 Million mm² / s at 25 ° C and 3 to 25 parts by weight of a surfactant for the polydimethylsiloxane,
• (C) then 15 to 45 and preferably 25 to 35 parts by weight of a polydimethylsiloxane with a viscosity between 40,000 to 120,000 and preferably 50,000 to 70,000 mm² / s at 25 ° C, 12 to 36 and preferably 20 to 30 parts by weight of polyethylene glycol and / or propylene glycol with a molecular weight between 1500 and 2500 and preferably 1800 and 2200 as well 4 to 10 parts by weight of a surfactant Agent for polydimethylsiloxane and poly (alkylene glycol) added, at least one of the polydimethylsiloxanes (B) and (C), especially the polydimethylsiloxane (B) has hydroxyl end groups.
• (D) If necessary, 2 to 10 parts by weight another surfactant for reduced friction between blisters and tires added;
• (E) optionally 2 to 8 parts by weight admixed with a corrosion inhibitor;
• (F) optionally 0.2 to 1.0 part by weight added a defoaming agent; and
• (G) optionally 2 to 10 parts by weight a stabilizing agent mixed.

Various known defoaming agents as well as various Stabilizing agents can be used to carry out the Invention are used.  

The aqueous emulsion or dispersion is simply applied to the Bubble applied, for example by spray coating, and by evaporation at a temperature of, for example about 20 to about 110 ° C. Preferably the bladder is about 80 to about 150% of its tire vulcanization expansion state for this coating purpose before (i.e. it did not collapse) where however, this is not considered necessary and also Bubbles successfully in something collapsed Condition have been successfully coated.

Various aqueous emulsions or dispersions the basis of silicones or siloxane have so far been considered Vulcanization bubble coatings formulated and examined. Such preparations have so far been made with the viscous Polydimethylsiloxanfluid (C) used. The experience has shown, however, that when a blister with a coating made therefrom was used only approximately 6 to 9 tires are molded using such a bladder could be (6 to 9 tire hardening cycles) because then excessive adhesion between the outer surface the bladder and the inner surface of the tire it was determined what could be seen from the fact that the bladder after the tire vulcanization when collapsing adhered excessively to the tire. After Add the viscous organopolysiloxane polymer to the mixture it was found that about 10 to about 15 tires with the bladder (10 to 15 cycles) are molded could before excessive adhesion (sticking) between the surfaces was found.

An essential feature of the lubricant preparation is of course the presence of both types of the polydimethylsiloxane polymers (B and C) which are both a highly viscous polymer as well as a somewhat viscous fluid. A coating however, something is greasy from these materials, if not The bentonite clay is used, which is not just the greasy one  Removed appearance of the coated bubble surface, but also noticeably trapped air from the surface pushes out. An additional one if necessary Soap or a surfactant can be beneficial since it is obviously the slippery between bladder and Tires increased.

The optionally added defoaming agent can be from a dimethylpolysiloxane emulsion in water and prevents or suppresses foaming during the Mixing.

The following example illustrates the invention. Unless otherwise stated, refer all parts and percentages are by weight.

Example 1

A lubricant preparation is made according to the approach in Table I below.

Table I

The aqueous emulsion dispersion is made according to the following method produced:

• (A) The water is heated to a temperature of approximately 60 ° C heated and the clay added. In a Cowles mixer is mixed at 2500 rpm for about 2 to 5 minutes until the mixture is in an obviously thickened state has reached.
• (B) Under a shear (2500 rpm) the organopolysiloxane polymer blend to obtain a water emulsion admitted.
• (C) Under high shear mixing conditions, the viscous fluid mixture of organopolysiloxane and polyglycol added.
• (D) Further surfactant is added.
• (E) The rust inhibitor is used to protect the application device admitted.  
• (F) The silicone defoamer is added.
• (G) The stabilizing agent is used in an amount of 10%, based on the total amount of the siloxane polymer and the siloxane concentrate (B and C).

The mixture is applied to the outer surface of the rubber tire vulcanization bladder sprayed on in expanded state. The coating is allowed to dry at approximately 65 ° C. Then the coating is applied again after about 4 tire vulcanization cycles applied, with a maximum of approximately Spread 4 h between coats.

The coating is left on the hot (65 ° C) for about 1 min. Bubble surface dried, creating a lubricant coating is formed.

The bladder itself is made of a butyl rubber type material with a generally toroidal shape with a Expanded diameter of approximately 975 mm and a diameter of approximately 250 mm. The surface is by washing with a hydrocarbon solvent and then drying to remove oils been pretreated.

A radial tire with a dimension of 11 R 22.5 is produced.

The tire is inserted into a tire molding press and the coated blister that is attached to the mold inserted inside the tire. The shape will then closed and the bladder using steam with a Temperature of about 190 ° C expands, causing them is pressed against the inner surface of the tire and pressing the outer surface of the tire onto the mold the tire in the desired shape is molded and vulcanized.  

The mold is then opened, the bladder relaxed and the Tire removed. Using this method, approximately 10 to about 15 tires using the bladder during a period of approximately 8 to 13 hours (hardening cycles) be blown before the bladder becomes necessary to be coated with the lubricant.

Generally, re-coating is considered necessary considered if the bladder is excessively strong on the inner Surface of the vulcanized tire when collapsing adheres after vulcanization.

The inner surface of the tire is typically made of a mixed rubber material made of different Rubbers or mixtures thereof can consist, for example Natural rubber, cis-1,4-polyisoprene, cis-1,4- Polybutadiene, butadiene / styrene copolymers, butyl rubber, Halobutyl rubber, such as chlorobutyl and bromobutyl rubber, and EPDT (ethylene / propylene / diene terpolymer, with the diene in a smaller amount).

The present example was in connection with the manufacture of a radial tire explained. The invention is although more suitable for the manufacture of radial tires than for the production of diagonal tires because of the bubbles generally during the production of diagonal tires during of the vulcanization cycle are expanded more need so that the surface coatings of the bubbles exposed to greater tension, yet the However, the invention also applies to the production of diagonal tires applicable.

The tire manufactured according to the example described was generated by directly coating the bladder was pressed against the inner rubber surface of the tire,  whereby the tire is exposed to the outside Heat and pressure to shape and vulcanize the tire was pressed. The coated bladder therefore enables the manufacture of the tire without the use of a lubricating coating or lining agent on the inner surface of the green tire. This is an essential fact since it is clearly demonstrated in this way that the invention coated bladder adequate lubrication during a series of tire vulcanization cycles the action of heat and pressure as well as an expansion and contraction without a conventional tire liner (liner cement) or lubricant enables that is previously applied to the surface of the tire. This requires considerable labor and material savings in the manufacture of a pneumatic tire. Yet you can apply a lubricant precoat on the inside Surface of the green tire if desired provide with the coated bladder, however the present example has shown that this is not necessary.

Claims (5)

1. Lubricant out

• (A) 10 to 40 parts by weight of bentonite clay, the particles of which pass through sieves with sieve openings between 0.03 and 0.15 mm,
• (B) 15 to 45 parts by weight of polydimethylsiloxane with a viscosity between 15 and 25 million mm² / s at 25 ° C,
• (C) 15 to 45 parts by weight of a polydimethylsiloxane with a viscosity between 40,000 to 120,000 mm² / s at 25 ° C,
• (D) 12 to 31 parts by weight of poly (ethylene glycol) and / or propylene glycol with a molecular weight between 1500 and 2500,
• (E) 10 to 25 parts by weight of surfactants for the polydimethylsiloxanes and the poly (alkylene glycol), and
• (F) optionally 4 to 12 parts by weight of a stabilizing agent,

in which at least one of the polydimethylsiloxanes (B) and (C), Has hydroxyl end groups. 2. Lubricant according to claim 1, wherein it is in the form an aqueous emulsion is present, the 500 to 1500 parts by weight Contains water.   3. Lubricant according to one of the preceding claims 1 to 2, in which the bentonite clay particles by sieves pass through with sieve openings between 0.04 and 0.07 mm. 4. Use of a lubricant according to claims 1 to 3 for coating a tire vulcanization bladder.