Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1992-11-24
1994-02-22
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
525123, 528 53, 528 58, 528 745, 427 58, 427117, 4273855, C08L 7504
Patent
active
052887960
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to friable sealing compounds of a polyol component and an isocyanate component, for example for sealing cable joint boxes.
In many fields of industry, a housing, a tube or similar articles have to be sealed at their open end(s) so that moisture or water is unable to penetrate.
This applies in particular to cables for the transmission of information, for example in the communications field. These cables are normally laid underground where they are exposed to the effects of their surroundings, for example fluctuating temperatures or fluctuating moisture conditions. When the cables are laid, it is important to ensure that the moisture conditions prevailing inside the cable will not change at some later stage, as might happen through the possible penetration of water or moisture.
BACKGROUND OF THE INVENTION
Communications cables consist of a plurality of electrically conductive wires which are bunched together, several such bunches being accommodated in an outer protective sheath. To join two such cables or even to join cables of different construction to one another, these bunches of wires have to be fanned out and joined to the wires of the other cable. The individual wires thus joined have to be insulated from one another, so that, in some cases, a much more bulky structure is formed. Since the insulation of the individual wires was opened, this structure has to be protected against the penetration of moisture or water. This is done by so-called cable fittings in the form of connectors consisting of a joint box and a plastics material accommodated therein.
The plastics materials used for hermetically sealing hollow articles, particularly cables, have to satisfy a number of requirements:
1. Their viscosity during processing should be low enough to enable the plastics material to penetrate readily between the bunches of wires and between the interconnected wires, even at low temperatures.
2. The self-curing of the material should take place quickly; the so-called pot life in the particular processing temperature range should be at least about 5 minutes.
3. The plastics material must show good self-curing properties at temperatures in the range from -10.degree. to 15.degree. C. so that the cables can be laid at any time of year.
4. The elasticity of the cured plastics material should be high to compensate temperature-induced changes in volume of the metal parts.
5. The adhesive properties of the sealing compound, i.e. its ability to adhere firmly to the constituent material of the joint box, to the insulating material of the individual wires and to the insulating material of the wires joined to one another, should be good.
6. High resistance to moisture and impermeability to water are also important requirements.
7. The cured plastics material should show high notch sensitivity, i.e. should crumble, so that, when the cable joint consisting for example of two joined half shells is opened, the plastic filling can readily be moved by hand without any need for tools.
8. In the cured state, the plastics material should show a high insulation resistance of more than 10.sup.11 cm on exposure to at least 1 kV/mm. The need for a high insulation resistance also applies after storage of the materials in water and various chemicals. The dielectric constant and the loss angle should be as low as possible. If the material comes into contact with acidic or alkaline liquids, it should remain serviceable for at least 36 hours at 38.degree. C. Finally, the plastics material should be resistant to the effect of diesel oil, fungi and microbes.
Hitherto known filling compounds based on various plastics materials, such as polyurethane for example, do not meet these requirements satisfactorily, if at all.
BRIEF SUMMARY OF THE INVENTION
The problem addressed by the present invention was to provide a friable sealing compound, more particularly for sealing cables or cable joints, which satisfactorily meets the requirements stated above.
The problem addressed by the invention is solve
REFERENCES:
patent: 4029626 (1977-06-01), Gillemot et al.
patent: 4680203 (1987-07-01), Maki et al.
Daute Peter
Gruetzmacher Roland
Hoefer Rainer
Stoll Gerhard
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Ortiz Daniel S.
Szoke Ernest G.
Welsh Maurice J.
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