WO1999022879A1 - A coating material and application methods therefor - Google Patents

Abstract

A coating material of a modified, climate resistant wax substance, which is applicable in melted condition, has been found to be perfectly applicable not only from an already melted wax bath, but still better if it is used in the form of a powder that can be injected into a blowlamp flame or a flow of hot air. A possible technique for making the powder is disclosed. Smaller articles may be 'wax painted' by receiving, in heated condition, a surface layer of the powder.

Description

A coating material and application methods therefor

The present invention relates to novel applications of a special wax material, viz. the material disclosed in WO 97/41175. Compared to ordinary paraffin wax this wax is characteristic m being much harder and m having a noticeably higher softening and melting point, and also m being wear resistant and totally environment friendly. Moreover, the wax is resistant to chemicals and, in suitably heated condition, very well suited for application as a protective coating on a wide variety of surfaces such as metal or wood, with good adhesion and impregnation properties. The wax can be coloured and will thus be highly suited for use as "paint".

A highly efficient painting of articles can be obtained simply by dipping the articles m a bath of the melted wax, or the melted wax can be applied to fixed surfaces by some spraying or brushing technique.

According to the present invention, however, it has been found that there is no need for developing special applica- tion techniques for the hot wax, inasfar as it has been realized that instead of departing from a "wax bath" made e.g. of melted pieces of wax, it is m fact possible to depart from the solid wax, viz. with the "hard wax" m a granular condition thereof and make use of already well known methods and equipment for converting granules or powder of more conventional thermoplastic materials into "paint" or "a coating". As a first step it was realized that it would be possible to dip an article into a powder or granular mass of the hard wax m order to obtain a sticky adhesion of the material to the article surface and then subject the thus coated article to a heating treatment m order to make the wax particle coating flowing together into a contmuos paint layer. Such an adhesion could be provided for by making the wax particles slightly adhering in incorporating m the wax material a cer- tain amount of an oily constituent. A similar result will be achievable by coating the article with some sticky substance prior to its being dipped into the particulate wax material. A following step was to realize that the particulate wax material could perhaps be applied to the article surface by the "electrostatic method" as used m connection with powder coating, using opposite high voltages on the article and on a flow of wax particles sent against the article, respectively. At this stage, expert consultants could not predict what would happen, but following experiments demonstrated that the method worked perfectly. In this way the articles could be moved through an application zone m which they, in a more or less heated condition, were exposed to a blast of the particulate wax material, whereby there was no need to arrange for a mechanical attraction as by means of adhesives. The particle-coated article could still afterwards be subjected to heat m orαer to make the particulate coating flowing to- gether into a continuous "paint layer" .

Later on it was realized that the granular wax material may m fact be applied m basically the same manner as conventionally used m connection with various types of plastic coating based on the use of granular plastics. Thus, for ex- ample, it is possible to arrange for spray painting in causing a flow of small wax granules to pass through a heater unit from a storage container for further delivery of the now melted wax to a discharge spray nozzle. A major breakthrough arose when it was found that, as mentioned below, it is pos- sible to effectively convert the granular material into "powder" , whereby it was found that even already existing spraying equipments for applying melted plastic as a surface coating could be perfectly usable m the present connection as mobile or portable units. This implies that the powder is currently injected into a blowlamp flame or a flow of hot air directed against the surface to be treated, and it is envisaged that m particular m connection with a protective surface treatment of large, stationary outdoor structures such as building surfaces, roads and runways, bridges, historical monuments and inner details thereof, etc., it will be possible to use the equipment m such a controlled manner that a surface portion being treated is initially subjected merely to the heating action of the flame or the flow of hot air, so as to be preheated for evaporation of moisture prior to a following initiation of the said powder injection. The powder may become a paint when coloured as desired, or a visually and environmentally neutral, highly, protective coating or impregnation, addressing all structures and not least all of the climatically endangered, ancient monuments throughout the world. The same interest, of course, is to be paid to any modern "monument", be it a gravestone, a building surface or a sewer pipe among extremely many other possibilities. A fully corresponding application technique may be used in connection with the treatment of minor articles, e.g. in connection with car painting or undercarriage rust protection.

To the extent it is desirable to fill out cavities m surfaces being treated it will be possible to currently inject also sand or other particulate matter m the flame or hot air flow, whereby such a filler, without further precautions, will act as a self adhering filler. Glass granules may be incorporated for rendering the resulting surface light re- fleeting.

Another possibility is to use, for smaller articles, the "whirl sintering" method, according to which a heated article is lowered into an air fluidized whirling mass of plastic powder or granules, such that the hot article surface will "catch" the particles hitting it, resulting m a rapidly obtained full coating of the article.

For the use of the wax as a raw material for the spray application m connection with already known and applicable techniques it is important that the raw material is a "pow- der" . A natural state of the produced material is in the form of larger granules, which do not amount to a "powder", preferably with a grain size of only some 100-400 μm. A coarse granular material may well be milled into a powder, but normally with a resulting temperature rise, which m the present connection would be liable to result in a "baking together" of the powder, rendering the powder useless in practice.

According to the invention, however, for an industrial production of the powder it has been found possible to solve this problem, not m prescribing some new milling technique, but rather m prescribing that the raw material prior to the milling tnereof is suojected to such an efficient cooling, preferably even to a cryogenic cooling to below - 100°c, that the processing heat added by the following milling operation will not bring up the temperature of the processed material to the sticking point thereof.

This is a very important aspect of the present invention, inasfar as it seems to be a key to the practical application of the wax to all sorts of surfaces, be it as paint or as an invisible protective impregnation of surfaces in general, e.g. various wooden or metal or concrete surfaces, including surfaces of ancient stone structures of historic importance. It is aforeseen that relevant wax coatings may be used and even especially developed or modified for a long row of specialized applications. As an important example among many others, reference can be made to an exterior treatment of ship and boat hulls, where the hard wax is perfectly applicable not only as a protective coating, but also as an environ- mentally totally neutral coating having pronounced an lfouling properties which, of course, may be further enhanced by addition of special antl -growth agents m the wax itself. The coating, being cheap and both wear and climate resistant, is even likely to lower the degree of friction between the hull and the water.

In sailing boat marinas it could be practiceable to arrange for a service station m which the boats could be passed through for a cleaning and waxing treatment almost as in car washing machines, though here with the wax in a heated condition.

The low friction property of the wax material may be relevant even with respect to air friction on aeroplanes and windmill wings. In this connection, another relevant property is that an ice formation on a wax coating will not stick very firmly to the coated surface, such that when icing occurs, the ice is likely to get loosened by a r pressure or centrifugal forces. Still, the hard wax will be fully usable for such purposes because it is fully climate resistant even during warm periods .

The indicated low- friction characteristic of the wax may be advantageous also in other respects, e.g. in connection with slip properties of various types of shaping moulds.

The "hard wax" does not contain water or solvents for later disappearance in a moulded structure, and the hot and melted wax is very effectively sticking to any surface to which it is supplied. It has been realized that these facts will account for another important application of the material, viz. as a joining or pointing material between interspaced solid items such as paving stones or tiles. In this connection the wax, with or without a filler material, may be used as a joining material, e.g. based on a granular material being swept into the interspaces between the laid out items and then activated by heating by means of an air heater or a blowlamp. Inasfar as no shrinking will occur, the stones or tiles will thereafter be intimately connected by way of a hard and non-corroding material, which is resistant also to mechanical sweeping and to the impact of high pressure cleaning water jets. A wax coated sand material will be perfect for this application.

For the same reason the non-shrinking wax material will be highly applicable for the filling out of moulding cavi- ties, e.g. in connection with a moulding out of holes in a concrete floor or stair steps for a firm anchoring of the bottom end of railing poles therein. Any visible surface of the wax material, with or without a filler material, may be smoothened out by means of a heated smoothening blade on a relevant hand tool.

The material will be perfectly suited as a repair mass in general, e.g. for floors in wet rooms.

Instead of sand, also other granular materials may be used as a carrier for the wax, and it is worth mentioning that rice grains have proved to be particularly advantageous. Basically, the wax material is a poor heat conductor, whereby it is well applicable in various skin touching products such as toilet seats. On the other hand, it can be made heat con- ductive if it is mixed e.g. with 10-30% of aluminium powder or another heat conducting material.

Correspondingly, the wax material is basically electrically insulating, but it can be made conducting with a suffi- cient addition of conductive material . This implies that it is possible to build up electronic substructures that are totally harmless when they are later on destructed, this otherwise being a marked problem.

The wax material, whether alone or with an included filler material, has been found to have a noise damping effect on whichever surface it is applied. Thus, in many instances it can be relevant to apply the material to plate structures of machines etc., and there is reason to believe that the material can be further modified for this purpose, e.g. by selection of suitable filler components.

The wax is well usable as a thin protective coating on different types of surfaces. In the building sector it can serve as a mechanical protection on finished surface areas, for protection against damage during the remaining finishing work in the building. In the metal industry and particularly in regions with high air humidity, the wax is usable for corrosion protection even of raw materials and intermediate products; many working operations may be done despite the presence of a thin surface film. The wax or "wax concrete" is well suited in connection with details pertaining to roads liable to be salted during winter, as it is resistant to salt water. Moreover, a mixture of wax coated sand and salt particles seems to have good an- tiicing properties when used as a stabilized surface layer, e.g. on stair steps such as in fire escape stairs.

In connection with sand or other granular material used as filler material or in coated condition, some 20-30% (by volume) of wax will often be suitable.

The wax, despite its character of a highly rigid and cli- mate resistant material, will still be a combustible material, usable e.g. in kindling briquettes and torches and as a binder in straw briquettes and the like. In particular owing to its food grade status it is perfectly usable as a packag- ing material, either by itself e.g. as carrier plates or trays for foodstuff articles or as a coating on other packaging materials, and in both cases it will end up in the refuse system, in which it is directly usef l, because in the asso- ciated refuse disposal plants it will represent a high thermal value when actively burnt, already because it cannot possibly be soaked by water. The same will hold true for other carrier plates or trays, e.g. of cardboard, when these have been sprayed with or dipped into the wax, as even the edges there of will then also be wax coated and thus be impervious to intrusion of water. This will apply e.g. to carrier boards for sliced salmon and the like.

It should be mentioned as an extreme possibility that the wax can be usable for a resistant film coverage of bulk waste in order to enable the latter to be disposed of at unprotected dumping grounds. Also, in firework articles, the wax may be used to form a carrier substrate that is broken down in a well-controlled manner during the process of development of the pyrotechnical effects of the firework article.

Claims

C L A I M S :

1. A method of applying a wax coating on article surfaces, characterized in using the wax in a granular form thereof, causing the granular wax to be heated and to be applied to the article surface in a manner such that the wax forms a coherent coating thereon.

2. A method according to claim 1, characterized in using wax granules having adhesive properties, causing the granules to be distributed on the article surface, preferably with the latter preheated to 40┬░C or more, and then applying heat to melt the granules sticking to said surface.

3. A method according to claim 1, characterized in applying the granules to the article surface by the use of the electrostatic attraction principle, and then heating the surface.

4. A method according to claim 1, characterized in applying the granules in a non-sticky condition to the article surface with the latter in such a preheated condition that granules hitting the surface become sticking thereto by the associated heating of the granules.

5. A method according to claim 1, characterized in that the wax granules are caused to be conveyed through a heating zone, such as a blowlamp flame or a flow of hot air, in which they are melted, and from which the melted wax material with or without a filler material e.g. of sand is currently sprayed onto the surface to be coated.

6. A method according to any of the claims 1-5 characterized in that the wax granules are "powder articles" with a preferred grain size in the range of 50-500 ╬╝ .

7. A method according to any of the claims 1-6, characterized in that the wax, whether pigmented or not and optionally suitably modified, e.g. with a content of an antifouling or anti-icing agent is applied to the surface of a boat hull, a windmill wing or an aircraft or other moving or stationary objects.

8. A method according to any of the claims 1-6, characterized in that the wax is applied to large stationary struc- tures such as buildings, bridges, monuments, antique buildings and details therein.

9. A method of converting a granular wax material into a powder material for use in accordance with any of the claims 1-7, characterized in that the granular material is cooled, preferably by a cryogene cooling technique, prior to its being conveyed to a comminution mill .

10. An application of wax coated sand or other granular material as a pointing material e.g. between paving stones, the material being filled loosely into the relevant gap or gaps and then melted by application of heat, e.g. by a blowlamp or a hot air generator.