Sulphur-free expanding, hot hardening shaped parts

Details Sulphur-free expanding, hot hardening shaped parts Sulphur-free expanding, hot hardening shaped parts

1999-04-29

2000-08-01

Foelak, Morton

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

264 451, 264 459, 264 463, 264 54, 521 82, 521 841, 521 87, 521 91, 521 92, 521 93, 521 94, 521 95, C08J 910, C08J 932, B01J 1302

Patent

active

060967919

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to heat-curing expanding mouldings based on solid polybutadiene rubbers and vulcanizing agents of which the vulcanizing agent is free from elemental sulfur. The invention also relates to a process for the production of these mouldings, to their use for bonding and/or sealing metal parts and to a process for the bonding of solid surfaces, more particularly metal parts for use in vehicle construction.
2. Discussion of the Related Art
The metal parts bonded and sealed in car manufacture, particularly in car bodies, are often untreated. The adhesives/sealants used are cured at a later stage in the paint drying ovens. Before this, the bonded and sealed parts pass through cleaning, phosphating and dip-priming stages. Under the effect of the treatment chemicals used in these stages, the adhesives or sealants can be removed from the joints. Various procedures have been developed to meet these requirements, including for example thermal/inductive precuring of low-viscosity paste-form adhesives/sealants, the use of adhesives in the form of solvent-containing compositions or hotmelts, as two-component products or even as mouldings which are generally applied by hand and which are surface-tacky at the time of application. These mouldings may be present in tape form or as round cords, stampings or profiles as any cross-section.
DE-A-34 45 325 describes surface-tacky mouldings, more particularly sealant profiles, which are produced from plastisols based on PVC and/or polymeric methacrylic acid esters and/or ethylene/vinyl acetate copolymers. However, these mouldings are in need of improvement. For example, they only adhere to EC-primed metal so that, for this reason alone, they cannot be used at the "white shell" stage, i.e. cannot be applied to the non-pretreated oil-covered metal panels. Since it is known that plastisol compositions retain their thermoplastic character, even after gelling, corresponding bonds or seals lose their mechanical strength on exposure to heat.
To overcome the last two technical problems, heat-curing mouldings based on rubber have been in use for several years. They generally consist of a mixture of liquid and optionally solid rubbers based on polyolefins, more particularly on diene homopolymers and copolymers. As their curing system, these rubber mouldings contain a vulcanization system based on elemental sulfur and optionally accelerating vulcanization auxiliaries. In principle, the composition of these mouldings is similar to that of the pumpable paste-form products described, for example, in JP-A-93059345 or in DE-A-38 35 740. Other examples of heat-curing, expanding and non-expanding adhesives based on sulfur-vulcanizing rubber adhesives in solvent-containing or solvent-free form are described in EP-A-476 224, EP-A-643 117 and in hitherto unpublished DE-A-195 18 673. JP-A49099643 describes readily extrudable vulcanizable rubber compositions which contain Li-catalyzed butadiene rubber, i.e. rubber with a high trans-1,4-content, and of which the vulcanization system consists of elemental sulfur and p-benzoquinone dioxime. In addition, these compositions have a very high content of carbon black. For these reasons, the rubber compositions in question are unsuitable for the production of the heat-curing expanding mouldings according to the present invention, i.e. are unsuitable as white shell adhesives and sealants in car production.
Heat-curing expanding mouldings based on solid and, in some cases, even liquid rubbers and vulcanizing agents containing elemental sulfur belong to the prior art although, as far as applicants are aware, they have not been published in patents. These known mouldings generally consist essentially of a mixture of solid butyl rubber, precrosslinked solid butyl rubber, solid natural rubber and extender oils, fillers, tackifying resins, pigment black, coupling resins and a vulcanization system based on elemental sulfur and optionally organic expanding agents.
Although the heat-curing moulding

REFERENCES:
patent: 5700845 (1997-12-01), Chang

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