JPH1086156A - Bladder consisting of rubber for vulcanizing tire or air spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high temperature expandible material consisting of rubber to one layer bladder and thereby reduce flaws causing excessive expansion during a mold release process by forming a bladder of at least two different layers made up of rubber. SOLUTION: By closing the vulcanizing mold 1, at least, a rubber mixture B is set within a vulcanizing mold 1 in order to reach the upper mold half 2 or lower mold half 3 and the wall of a metal core 4, in which a rubber mixture B' about 0.05mm in thickness is adhered to the wall. An A' layer is interposed by another pressing process between the layer B' being in the inner radial direction and the layer B' being in the outer radial direction, and the A' layer indicates a rubber mixture of a non-vulcanized bladder raw material. At first, the rubber mixture B set within a hollow chamber of the vulcanizing mold 1 forms the B' layer being in the inner radial direction having characteristics of a good expansibility and an anti-sulfur property, and the layer A' is one having good tension and compressive deformation characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bladder made of rubber and a method for manufacturing a bladder made of rubber. The bladder is used during vulcanization to contain a pressure medium, for example hot water or steam, and to transmit pressure and temperature onto the inner wall of the object to be vulcanized for its shaping. To be able to fulfill this feature as long and as well as possible,
Certain conditions are imposed on the quality of the bladder. Bladder generally must withstand high tensile stresses at very high vulcanization temperatures (above 200 ° C.).

[0002]

BACKGROUND OF THE INVENTION In the past, bladders have generally been made from a single butyl rubber mixture. Butyl-based rubber mixtures are
Any conditions to which the bladder is exposed (extensibility at vulcanization temperature,
Pressure resistance, heat resistance and heating steam resistance, tear resistance). However, a single butyl rubber mixture cannot meet all these requirements, thus limiting the life of the bladder.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a bladder having good characteristics.

[0004]

According to the invention, this object is achieved by the bladder being composed of at least two different layers of rubber. The desired effect on the bladder properties can be achieved via the layered configuration of the bladder.

During the bladder molding process, ie during the demolding step, a layered construction has proven advantageous. In the demolding process, the bladder generally must be separated from the metal core required for molding the bladder. The narrow opening of the bladder is then stretched so that the opening fits the large diameter of the metal core. Since conventional bladders generally consist of only a single vulcanized butyl rubber mixture and the butyl rubber mixture only allows a certain amount of elongation in the vulcanized state, the finished bladder has cracks in the bead area and tears are separated. It causes overextension during the molding process. This tear represents a quality loss in the production of the bladder.

[0006] It is therefore particularly advantageous if the bladder is composed of different layers of rubber in the region of the bladder opening and in the central region. An embodiment in which the upper half and the lower half of the bladder (parallel to the bladder opening) consist of two different layers of rubber is also technically suitable.
In this case, it is also possible for one of the bladders to be provided with a high-temperature extensible material made of rubber in at least one bead area (in the area of the bladder opening) of the bladder half, so that during the demolding process, the overstretching takes place The bladder deficiencies with respect to scratches that cause blemishes are reduced.

As a second layer, conventional rubbers, which are already customary in bladders, can be used. Bladders are arranged from top to bottom or alternate in the radial direction,
It is, of course, also possible to constitute a plurality of layers of different or repeated layer materials. It is also advantageous for the bladder to be composed of at least two different layers which alternate in the radial direction.

[0008] The bladder thus constructed has proven to be suitable for vulcanizing tires or air springs.
That is, for example, the outer layer of the bladder in the radial direction
Because it can be made from rubber that is sulfur resistant and / or more sulfur impermeable than conventional bladder materials. In butyl rubber, which was previously used and could not be used during tire vulcanization, sulfur diffused into the bladder and thereby caused premature aging of the bladder. Sulfur-resistant bladder materials are effective, especially in the sulfur-resistant radially outer layer of the bladder, because the outer layer generally comes into contact with the object to be vulcanized (tire, air spring). is there.

Due to the radially inner layer of the bladder according to the invention, which comes into direct contact with the pressure medium (steam, water), the radially inner layer is heat-resistant and water- and / or steam-proof. It is advantageous if it has permeability and / or water resistance and / or steam resistance. Furthermore, the objects (tires,
This bladder layer has good hot stretchability to ensure good molding of the (air spring).

It is most preferred in terms of process technology if the radially inner layer and the radially outer layer consist of a rubber mixture. The dimensions of the bladder raw material composed of layers are small. In addition, the vulcanizing mold walls (lower and upper mold and metal core walls), which determine the outer dimensions of the bladder from the flow properties of the rubber mixture, are first coated with the bladder raw material introduced. Thus, in the simplest way, it is obtained that the inner and outer walls of the finished bladder consist of the same rubber mixture.

As a layer between the radially inner layer and the radially outer layer of the bladder, a rubber mixture which has good compression and tensile deformation properties with minimal fatigue phenomena is suitable. In principle, it is of course also possible for the radially outer layer and the radially inner layer of the bladder to consist of different rubber mixtures. To make this possible, the walls of the vulcanizing mold (for example the walls of the metal core) are particularly roughened and the other walls (the walls of the upper and lower mold halves) are particularly smooth. Conceivable. This results in the bladder green material, which is first pushed into the vulcanization mold by the closing force, adheres only to the walls of the metal core, because the bladder green material is of the upper and lower halves. This is because they slide along the wall. The bladder raw material layer to be inserted next is superimposed on the layer adhering to the wall of the metal core in the vulcanization mold, and the vulcanization-type cavity is formed up to the upper mold half and the lower mold half. Fill. This results in a bladder having different radially inner and radially outer rubber layers. The properties of both these layers can be adapted to the conditions of use of the bladder.

The same properties are obtained by the layered construction of the bladder according to the invention. In contrast to conventional bladders which attempt to compensate for the disadvantages of the properties by increasing the material thickness of the rubber, the layer structure according to the invention achieves a precise property optimization in the bladder and thereby the rubber or rubber material Usage decreased. To enable a bladder layered structure, it is necessary to select a suitable layer combination based on its chemical and physical properties. In that case,
The layers must be fluid and mutually "harmonic",
That is, in the bladder production, a vulcanization step must usually result in a layered composite.

[0013] Furthermore, the construction type of the bladder production type or the method used for the production of the bladder plays a role. In principle, all known methods for the production of bladders constructed in layers are suitable for the bladder raw material, which is first inserted into the vulcanization mold, to adhere to the walls of the vulcanization mold. . A possibility for keeping the adhesion to the vulcanization mold can be, for example, its wall roughness.

To obtain the configuration of the bladder according to the invention,
The transfer-casting method can be used in an advantageous manner. For this purpose, a pre-laminated bladder green material composed of at least two different rubber mixture layers, which is obtained, for example, by an extrusion process, facing the vulcanizing mold wall of the pre-fabricated bladder green material Side) is pressed against the vulcanization mold wall, resulting in an almost uniform coating of the vulcanization mold wall with the initially pressed parts of the bladder green material.
First, an almost uniform coating of the vulcanization mold wall with the pressed bladder raw material is performed, in which the vulcanization mold cavity is first inserted in the immediate vicinity of the bladder raw material at the beginning of the pressing process. This layer is moved along the vulcanizing mold (the wall of the metal core and the walls of the upper or lower mold half) in the subsequent step of the pressing step and the final step. This layer is coated. First, the inserted bladder green material proved advantageous with a wall coating thickness of at least 0.05 mm. Furthermore, each inserted bladder green material is stratified as a substantially uniform layer on the layer formed by the previously installed bladder green material.

By selecting the composition of the rubber mixture (bladder raw material) into the pre-fabricated bladder raw material,
A bladder of the intended configuration can be manufactured, the characteristics of which can be predetermined. The following describes in the examples two mixtures of butyl rubber bases which are particularly suitable for the radial layer structure for the bladders according to the invention. Mixture composition (pphr) Mixture A Mixture B Butyl rubber Double bond content 0.7 mol-% 95-Butyl rubber Double bond content 1.6 mol-%-95 Neoprene rubber 55 HAF-carbon black 50 50 Castor oil 55 Zinc Hua 55 Vulcanized resin 10 10 Mooney viscosity ML 1 + 3 100 ° C 72 89 Rheometer 190 ° C [min] t5 2.7.2.4 t50 11.4.9.4 t90 29.4 26.9 26.9 Physical data (60 min) 7.3 bar) Mixture A Mixture B Density [g / cm] 1.12 1.12 Tensile strength [N / mm] 9.3 10.7 Elongation at break [%] 790 730 Elasticity 300% [N / mm 3.1 4.4 Hardness [° ShA] 61 60 Tensile deformation [%] Room temperature 117 70 ° C 20 11 100 ° C 30 19 butyl rubber Mixture commensurate with different double bond content with different characteristics (e.g., flow characteristics). Mixture A has good flow properties. Such mixtures are particularly suitable for the radially inner and / or outer layers of the bladder. It is clear that the properties of the rubber mixture already described during the vulcanization process during the production of the bladder allow mixture A to form the radially inner and outer layers of the bladder. Due to the good extensibility of the mixture, the bladder green material is accurately pressed into a tire vulcanizing mold, for example, during vulcanization of the tire, and the tire is thus shaped well. As a radially inner layer, the mixture can optimally contain a pressure medium, since the mixture is particularly extensible at the vulcanization temperature and therefore the pressure applied during vulcanization is well utilized. This has economic benefits. Furthermore, mixture A has a lower double bond content than mixture B and therefore reacts only slightly with sulfur, which is particularly suitable in the radially outer layer of the bladder. Sulfur that diffuses during the vulcanization of the tire or air spring is therefore not absorbed by the bladder, thus preventing premature aging of the bladder. Layer B is suitable as a layer between the radially inner layer and the radially outer layer, since layer B has good pressure and tension deformation properties.

In order to produce bladders with as precise properties as possible, the specified dimensions of the rubber mixture (layer width)
It is necessary to prepare a bladder raw material. In the following embodiments, the principle of the bladder manufacturing of the present invention will be described in detail with reference to the drawings.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vulcanizing mold 1 has an upper half 2, a lower half 3 and a metal core 4. FIG. 1 shows a bladder raw material 5 composed of a rubber mixture (bladder raw material) A and B manufactured by a press molding method, and the bladder raw material is a vulcanization mold 1 as a string having a rectangular cross section. Is set on the lower half of the.

The rubber mixtures A and B are mutually horizontal and pressed into the cavity of the vulcanizing mold 1 by the closing pressure applied on the bladder raw material 5 during the lowering of the upper vulcanizing mold half 2. You. Depending on the pressure acting on the plastic rubber mixtures A and B, the temperature and the time, the rubber mixture becomes a rubber elastic layer (layer A 'and layer B'). The layer A 'is divided along the wall of the metal core 4 and the wall of the upper mold half 2 of the vulcanizing mold 1 and adheres to this wall, and the layer B' is correspondingly the lower half of the vulcanizing mold 1 3, the layer B 'is divided along the wall of the metal core 4 and the wall of the lower mold half 3. As a result, the vulcanized bladder is composed of two layers A 'and B' which are arranged from top to bottom, with layer A 'being the upper bead region 6 and layer B' being vulcanized. The lower bead region 7 of the bladder is formed. Mixture A 'is a vulcanized butyl rubber mixture of conventional properties, and mixture B' has significant hot extensibility, whereby the vulcanized bladder during the demolding process damages the bead area Without being able to be pulled out of the vulcanization mold via the metal core.

FIG. 2 differs from FIG. 1 in that prefabricated bladder raw material 5 is produced from plastic rubber mixtures (bladder raw material) A and B, which are positioned vertically and parallel to one another. Differs in that By closing the vulcanizing mold, the rubber mixture B is first set in the vulcanizing mold 1 and reaches the upper half or lower half (2 or 3) and the wall of the metal core 4, where the wall is approximately 0.1 mm. A rubber mixture B 'having a thickness of 05 mm is deposited. The precise adjustment of the manufacturing conditions, such as the width, pressure, temperature and mechanical and chemical pre-treatment of the vulcanized mold wall of the pre-fabricated bladder raw material, allows the thickness of the rubber coating on the vulcanized mold wall to be increased. It is possible to change the height and the area. Between the radially inner layer B ′ and the radially outer layer B ′ another layer A ′ is applied by means of another pressing step, the layer A ′ being a rubber mixture of uncured bladder raw material 5. A is shown. First, the rubber mixture B set in the hollow chamber of the vulcanizing mold 1
Forms a radially inward and radially outward layer B '(mixture plasticity see mixture A) having good stretchability and sulfur resistance properties in the manufactured bladder, and layer A '(Mixture plasticity see mixture B) is a layer which lies between the radially inner and outer layers B' and has good tensile and compressive deformation properties.

[Brief description of the drawings]

FIG. 1 is a radial cross-sectional view of a vulcanization mold on which a bladder raw material is set.

FIG. 2 is a radial cross-sectional view of a vulcanizing mold on which a bladder raw material is set.

[Description of sign]

 Reference Signs List 1 vulcanization type 2 type upper half 3 type lower half 4 metal core 5 bladder raw material A rubber mixture B rubber mixture A 'rubber elastic layer B' rubber elastic layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Peter Entmile, Germany, 30938 Burgwedel, Am Bollberg, 2 (72) Inventor Helmut Behring, Germany, 30453 Hannover, Sonnenweg, 11 (72) Inventor Ud Kampmann, Germany, 30823 Garbsen, Otto-Erhard-Strase, 21 (72) Inventor Ernst-Fuelkening, Germany, 31683 Obernki Lüyen, Ferener-Strasse, 42

Claims (8)

[Claims] 1. A bladder made of rubber for vulcanizing tires or air springs, the bladder being composed of at least two different layers of rubber. 2. The bladder upper and lower halves are composed of two different layers of rubber.
The bladder described. 3. The bladder, in at least the region of the bead of the bladder half, comprises a layer of hot-extensible rubber,
The bladder according to claim 1. 4. The bladder according to claim 1, wherein the different layers are arranged alternately in the radial direction. 5. The radially inner layer and / or the radially outer layer is a high-temperature extensible rubber and / or heat-resistant and / or water- and / or steam-impermeable or water-resistant and / or steam-resistant and / or sulfur-resistant. 5. The bladder according to claim 4, wherein the bladder is made of an elastic rubber. 6. A bladder according to claim 5, wherein the layer between the radially inner layer and the radially outer layer comprises rubber having good tensile and compressive deformation properties. 7. The method for producing a rubber bladder for vulcanizing tires or air springs according to claim 1, wherein the bladder raw material is made in layers from at least two different rubber mixtures. The working material is set in a ring shape in the vulcanizing mold, after which the vulcanizing mold is closed, whereby the bladder raw material is pressed into the vulcanizing mold cavity based on the closing force and the metal core and Or substantially abutting the walls of the mold halves, thereby forming a layered configuration of the bladder, followed by vulcanization of the bladder. 8. The wall of the vulcanized metal core and / or mold half is at least 0.1% by means of a bladder raw material introduced first.
The method according to claim 7, which is coated to a thickness of 05 mm.