WO1992008767A1

WO1992008767A1 - Ice-preventive covering

Info

Publication number: WO1992008767A1
Application number: PCT/SE1991/000776
Authority: WO
Inventors: Sture Persson; Lars-Olof Andersson
Original assignee: Skega Ab
Priority date: 1990-11-15
Filing date: 1991-11-15
Publication date: 1992-05-29
Also published as: SE467411B; SE9003655D0; FI923184A0; FI923184A; SE9003655L; CA2069951A1; NO922755D0; JPH05503734A; RU2086601C1; FI100335B; NO922755L; NO300379B1

Abstract

An anti-icing surface covering comprising at least one polymeric material which itself is comprised of polyolefins or polydienes, i.e. hydrocarbon rubber material. For the purpose of obtaining an extraordinary anti-icing covering, the polymeric material is comprised of a polymeric hydrocarbon material or a mixture of polymeric hydrocarbon materials, and each polymeric hydrocarbon material present lacks polar groups but is polymerized and vulcanized with the aid of a vulcanizing agent comprised peroxides, sulphur, sulphur derivate or metal oxides or combination of sulphur and sulphur derivate.

Description

ICE-PREVENTIVE COVERING

The present invention relates to an anti-icing device in the form of a covering applied to that or those surfaces to be protected against ice formation, said covering comprising one or more polymeric materials comprised of polyolefins, polydienes, i.e. a hydrocarbon rubber mate¬ rial.

Icing is a problem which has not hitherto been solved successfully in a satisfactory manner from one or all aspects, despite the large number of materials which, over past years, have been said to present extremely low adherence to ice, snow and other crystalline forms of frozen water. Subseguent to having been used over a given period of time and exposed to outdoor environ¬ ments, the adherence of all of these materials to ice is found to increase, thereby reducing the efficiency of such materials as anti-icing devices.

In other words, it is known that certain materials are able to provide relatively good protection against icing over a relatively short period of time, but that these materials do not afford durable protection capable of preventing ice, snow or other forms of frozen water from depositing on and freezing to the protected surface over a period of several years. Accordingly, there is always an uncertainty as to just how effective the prevailing protected afforded by an anti-icing device is at a given moment in time, i.e. there is an uncertainty as to whether the ability of the protective covering to pre¬ vent icing has dissipated completely or whether this protection is still sufficient for one or two years further use. In this uncertainty also lies a serious drawback of known materials and material combinations hitherto used and still used at present as anti-icing devices.

The problems caused by icing are well known to people who live in arctic and subarctic regions, these problems ranging from what can be characterized as serious prob¬ lems to minor irritations, for instance such as frozen windscreen wipers and door seals of private automobiles, trucks and other automotive vehicles, to life-threaten- ing conditions, such as the build-up of ice on aircraft wings, helicopter blades, water craft, radio masts, other forms of mast, power cables and the like.

Another example where the build-up of ice can result in high costs and serious risk of destruction is the growth of ice on the intake gates of hydropower plants, where the growth of ice can quickly cause the power plant to be closed down completely with the resultant loss of electrical power. A further example is the growth of ice on subaqueous cables and on the pipes of heat pumps used in lakes and waterways as a heat magazine. In these latter cases, the ice coatings may cause the cables or hoses, pipes, to float to the surface of the water with the obvious risk of damage to watercraft traffic in the area.

Investigations have shown that the adherence or the freeze-bond between ice and substrate is undoubtedly material-dependent, and it has also been found that the surface energy of the material concerned plays a certain part in the occurrence of such adherence. For example, polymer materials, irrespective of type, have a much lower adherence to ice than metals. It has also been established that low surface energy materials can pres- ent a lower adherence to ice than materials which have a high surface energy. Notwithstanding this, however, the internal (bulk) strength of the materials is coupled directly to the surface energy, and more specifically the surface energy can be said to be a sequence of, and therewith dependent on, the internal bonding forces and strength of the material concerned. A mechanically strong material will thus have a higher surface energy than a mechanically weak material, and with knowledge of these facts it has also been said that materials having a low surface energy should be preferred to materials having high surface energies when used as an anti-icing device and similar surface coverings.

The adherence of ice or its ability to freeze solid on surfaces, however, is not inversely proportional to the surface energy of a material other than to a given lowest level. It has been found that beneath this level, the force with which-ice adheres is practically constant at surface energy values beneath this lowest level. Similar observations have also been made in the case of adhesion - surface energy enhancing treatment of polyethylene has shown that this adhesion increases drastically above a given level. This fact that the ability of ice to freeze or adhere firmly to a surface is not inversely proportional to the surface energy of the material at all surface energy levels has also been given as a reason why known surface coverings comprised of material which has a low surface energy have unac- ceptably short useful lives with regard to their func¬ tion as anti-icing devices.

Accordingly, the object of the present invention is to provide an anti-icing device in the form of a covering which can be applied to surfaces and which has a long useful life and prolonged effectiveness as an anti-icing device, and which accordingly has a low adhesion to ice, snow or other forms of frozen water and which, at the same time, is environmentally tolerant and has an opti¬ mum strength with regard at least to scratch resistance, and to its resistance to adhesion and abrasive wear, impacts and the like.

In order to achieve the object of the present invention, namely to provide an anti-icing device which will remain effective over long periods of time, the inventive anti- icing covering comprises a hydrocarbon rubber material or a mixture of two or more such materials, wherein the actual material itself or the material mixture shall also be optimum with regard to the demands placed there¬ on with respect to low adhesion to ice, snow or other forms of frozen water and also to high wear strength and therewith long useful life. The inventive covering includes a wear-resistant material or a wear-resistant material combination which will not be degraded by sunlight, ultraviolet radiation, etc., and which will resist erosion by ice particles, sand and the like carried by the wind. The material or material mixture shall also be insensitive to the low small pH-values which often occur when acids are precipitated in the regions where icing is a real problem.

The types of material primarily concerned with the present invention are those types of hydrocarbons which lack polar groups. Examples of such hydrocarbon rubber materials are: 1) natural rubber (NR), 2) synthetic natural rubber, e.g. isoprene rubber (IR), ethylene- propylene rubber (EPT, EPM, EPDM), butadiene rubber (BR) and butyl rubber (IIR).

For the purpose of providing an effective preventative against ice, snow or other forms of frozen water fasten- ing to a substrate of any kind of material whatsoever, it is proposed in accordance with this invention that the substrate is provided with a surface covering con¬ sisting of a material or a material mixture which includes polymeric hydrocarbons of the type which com¬ pletely lack polar groups and which are polymerized to form a rubber material which includes one or more of the following flexible materials, namely: natural rubber (NR) , synthetic rubber (SR), isoprene rubber (IR), ethylene-propylene rubber (EPT, EPM, EPDM), butadiene rubber (BR), butyl rubber (IIR), isobutene-isoprene rubber. This rubber material or this mixture of rubber materials is/are vulcanized with the aid of a vulcaniz¬ ing system or vulcanizing agent in the form of perox¬ ides, sulphur, sulphur derivate or metal oxides or sulphur and sulphur derivate.

In accordance with the invention, the rubber material may include carbon black of a non-reinforcing kind and in quantities ranging from 0 to 100 phr (parts per hundred parts of rubber). This carbon black may be replaced completely or partially with silica.

The inventive covering may also include a substance which will lower the freezing point, such as glycerol or glycol for instance.

Because the surface covering is comprised of a rubber material, it will have good flexibility even at tempera¬ tures as low as -40 to -90^βC, depending on the choice of polymer. The inventive surface covering will also generate high frictional forces, which makes the cover¬ ing highly suitable for use on surfaces intended for pedestrian traffic, with or without vehicles.

The covering is joined to the surface or surfaces to be protected against icing, by gluing, vulcanizing or in some other chemical or mechanical fashion. With the intention of reducing the extent to which ice adheres, e.g., to the leading edge of aircraft wings or mainplanes, propeller blades, etc. , tests carried out on the inventive surface covering have shown a threefold improvement in each of these cases in comparison with known surface covering materials used for the same purpos .

Compared with conventional paints and, to some extent, also other surface coatings, vulcanized rubber material can be applied in thicker, flexible layers which afford greater possibility of crack initiation and crack propa¬ gation with a covering of good strength. The flexible material is also able to yield against impact from particles and to dampen the force of such impact, where¬ with mechanical wear on the covering is reduced and is commensurately very low, thereby extending the useful life of the covering.

Claims

1. An anti-icing surface covering comprising at least one polymeric material comprised of polyolefins or polydienes, i.e. a hydrocarbon rubber material, c h a r a c t e r i z e d in that the polymeric materi¬ al is comprised of a polymeric hydrocarbon material or a mixture of polymeric hydrocarbon materials; and in that each polymeric hydrocarbon material included in the covering lacks polar groups but is polymerized and vulcanized with the aid of a vulcanizing agent comprised of peroxides, sulphur, sulphur derivate or metal oxides or a combination of sulphur and sulphur derivate.

2. A coating according to Claim 1, c h a r a c ¬ t e r i z e d by one or more of the following flexible materials, natural rubber (NR) , synthetic rubber (SR), isoprene rubber (IR), ethylene propylene rubber (EPT, EPM, EPDM), butadiene rubber (BR), butyl rubber (IIR).

3. A coating according to Claim 1 or 2, c h a r a c ¬ t e r i z e d in that it includes carbon black.

4. A coating according to Claim 3, c h a r a c ¬ t e r i z e d in that the carbon black is of the non- reinforcing type.

5. A coating according to Claim 3 or 4, c h a r a c ¬ t e r i z e d in that carbon black is present in an amount ranging from 0 to 100 phr.