WO2022003248A1

WO2022003248A1 - Method for obtaining a heavy-duty coating, a heavy-duty coating obtained by the method and coating agent composition suitable for use in the method

Info

Publication number: WO2022003248A1
Application number: PCT/FI2021/050502
Authority: WO
Inventors: Mika Pettersson
Original assignee: Epu Coat Oy
Priority date: 2020-06-29
Filing date: 2021-06-29
Publication date: 2022-01-06
Also published as: FI129797B; FI20205690A1

Abstract

The object of the invention is a method for obtaining a heavy-duty coating. The coating process of the invention begins with pre-treatment of the surface to be coated. After this, a preparatory coating layer (7) is applied on a pre-treated surface of up to about one square meter at a time using a coating agent composition comprising organic solvents and at least one coating agent selected from a group consisting of polymeric coating agents and polymeric resins. Subsequently, a second coating layer (8) is applied on top of the preparatory coating layer using a similar coating agent composition, the coating agent composition being at a higher temperature than in the previous step. A finishing agent is applied on the dust-dry surface (10), after which it is left to dry and removed. The surface is polished to achieve the desired low-friction and high shine surface. After this, final hardening of the coating (11) takes place. Further objects of the invention are a heavy-duty coating obtained by the method, a coating agent composition suitable for use in the method as well as an article coated by such a heavy-duty coating.

Description

METHOD FOR OBTAINING A HEAVY-DUTY COATING, A HEAVY-DUTY COATING OBTAINED BY THE METHOD AND COATING AGENT COMPOSITION SUITABLE FOR USE IN THE METHOD

Object of the Invention

The object of the invention is a method for obtaining a heavy-duty coating, a heavy- duty coating obtainable by the method, a coating agent composition suitable for the heavy-duty coating as well as an article coated by such a heavy-duty coating.

Background of the Invention

Boats, ships, and other sea vessels are traditionally coated with heavy-duty paints or wax layers protecting the surface of the vessel. There are several agents and processes known to obtain such a coating, such as paints and waxes, giving the sur face a high gloss finish. Many of these dissolves or wear out over a relatively short period of time, increasing the need to reapply layers on a yearly basis and concur rently contributing to contamination of natural waters. This is especially the case for toxic paints, that are used to prevent biofilms and water organisms, such as barna cle, from sticking to the hulls of boats and ships.

Surface coatings, such as paint, wax and varnish are also commonly used in other indoors and outdoors applications. Alternatively, conventional polymeric or ceramic coatings are utilized. Such conventional or alternative coatings often show either a high surface porosity or vulnerability towards strong solvents, making cleaning of the coated surface very challenging. Ceramic coatings are also often very pressure- sensitive, limiting the use of these for coating of objects to be submerged under wa ter. In outdoor use, challenging weather conditions, such as sun, wind and temper ature changes, may damage the coatings, whereby colors of the surface fade and the surface structure may form cracks or peel off over time. Outdoor objects, such as bridges, walls, and electrical enclosures are also often exposed to graffiti paint ings. Cleaning of such surfaces is very demanding and expensive. The cleaning of ten also cause damage to the surface beneath.

Many of the coatings known in prior art show poor resistance to solvents and chal lenging whether conditions. There is a need to renew or clean the coated surface regularly, and especially for sea vessels there is a problem of biofilms and water or ganisms sticking to the sides or hulls of the sea vessel. The life span of surfaces ex posed to dirt or challenging conditions may be improved by high-duty coatings. There is also a need for alternative anti-fouling coatings, that does not have a nega tive impact on the environment.

Description of the Invention

The object of the invention is a method for obtaining a heavy-duty coating, a heavy- duty coating obtainable by the method, coating agent composition suitable for use in the method and an article coated by the heavy-duty coating according to the pre sent disclosure. By the term heavy-duty coating is herein meant a long-lasting coat ing that is resistant to a wide range of external stress. It maintains good surface properties over time and is also capable of to withstand at least some chemical and mechanical stress. The final coating obtained by the method of the invention is very durable and provides complete protection of the substrate. The glossy finish, dense structure and low-friction properties of the coating brings forth anti-fouling proper ties, making this very diverse and suitable for a wide range of applications.

The coating obtainable by the method of the invention has been developed espe cially for the sides and bottoms of boats or other sea vessels. It forms a transpar ent, continuous, nanotechnical surface that is very smooth, durable, and easy-care. The surface friction of the coating obtained by this process is extremely low. This have been proven in use, since when employed as a coating for the hulls of boats, a reduction in fuel consumption of 18% has been experienced compared to uncoated surfaces. Another object of the invention is a heavy-duty coating obtainable by use of the method as well as a coating composition suitable for use in the method of the invention. The pressure resistance of the coating of the present invention is very high, making it suitable for objects to be submerged in water. This brings forth a clear benefit over ceramic surfaces.

The heavy-duty coating of the invention may be achieved by use of a composition comprising at least one coating agent and suitable solvents. Proportions of coating agent to solvent are chosen depending on the surface to be coated and the stage of the coating process. The concentration of coating agent in the composition may be in the range 1-85%. The coating agent is selected from a group consisting of poly meric coating agents or polymeric resins, preferably the coating agent is chosen from polysilazanes, polysiloxanes, acrylic resins, such as poly(acrylic acid), and iso cyanates. The composition may further contain activation and/or binding agents, such as (3-aminopropyl)triethoxysilane. The coating agent composition is prepared in a solution comprising organic solvents, which may include organic acids. The sol vents of the coating agent composition are preferably chosen based on the material to be coated, such that an activation of the surface to be treated is achieved, which ideally improves the interaction with the substrate. Examples of preferable solvents are propylene glycol butyl ether, propyl benzene, 1,3,5-trimethyl benzene, 1,2, 4-tri- methyl benzene, o-xylene, toluene, acetic acid and C7-C9 hydrocarbons. The compo sition may comprise an activation and/or binding agent, preferably in an amount of 1-50%, even more preferably in an amount of 1-30%. The binding agents may also be chosen from the above-mentioned coating agents.

Two different compositions have been found to be especially preferred for use in the method of the invention. The components of these compositions are presented in Table 1 and Table 2. Both compositions can be used for all of the above-men tioned applications, providing the desired properties of the coating of the invention, forming a technical, protective layer. Preferred embodiments for each composition are listed in connection with the tables.

The method of the invention comprises the following steps:

The surface to be coated is pretreated. Preferably the surface is thoroughly cleaned (1) by an acid treatment process. Most preferred is use of phosphoric acid. Also, other acids, such as oxalic acid may be employed. The acid treatment is initially per formed by use of a concentrated bulk solution ( e.g . 35-50 or 50-85%) and diluted to very low (a few percent to technically zero) concentration towards the end of the treatment. Special care should be taken not to let the acid dry at the surface. The acid treatment is continued until possible contamination, such as staining and wax, is completely removed. After the acid treatment, the surface is carefully cleaned (2) using warm water. Possible dust or loose material can be removed (3) at this stage. Once dry, the surface is further cleaned (5) by removing possible grease and other remaining contamination with a solvent, preferably xylene, and the surface is let to dry. Any loose matter or dust is also removed at this stage. For certain surfaces, such as most metal surfaces, a further neutralization step (6) is beneficial. For new surfaces, mechanical treatment of the surface might be sufficient, whereby there is no need for the acid treatment process. The pretreatment of the surface may also comprise washing using organic solvents.

The actual coating composition is applied (7) by spreading the coating agent com position over a limited surface using a spreading device. Depending on the object to be coated, this can be for example a sponge, pad, cloth, or roller. In case of uneven surfaces or smaller spaces that are hard to access thoroughly, even a spraying de vice can be used. For easily accessible surfaces, preferably an area of about 1 m² at a time is processed, optionally by leaving an agent reserve at the joint region. When no more of the coating agent composition is absorbed, meaning that the surface is saturated such that there is no more uptake of coating agent composition, the sur face agent composition is spread over the surface by parallel, continuous strokes, making sure that the thickness of the film is constant and that no sagging is allowed to take place. The temperature of the coating agent composition is of high im portance at this preparatory coating stage. The coating is performed using a compo sition that has been cooled down, such that is has a temperature from -15°C to 0, especially preferred is a temperature of about -5°C or -4°C. A guideline is that for a more porous surface, a colder composition should be used. In some applications, it is preferred to cool down the surface to be coated as well.

Subsequently, a second layer of the coating agent composition is immediately ap plied (8) on the obtained preparatory or base layer of coating agent composition us ing a significantly warmer mixture. This step should be performed immediately after the previous step of preparatory coating. For this second layer, the temperature of the coating agent composition used is preferably in the range of 1 to 40°C. Thereby, the temperature difference of the two coating layer compositions can be for exam ple 40°C when applied, such that the temperature is quickly raised from -10°C to +30°C or from -5°C to +35°C. This liquid coating agent composition also functions as an activator as well as a binder in the final coating. The coating is then left to dry (9) until surface dry. It is important that it reaches a stage where it is dry to the touch without being completely dry. At this point it might be just slightly clammy, i.e. dust-dry.

The coating process is finished (10) using a finishing agent, for which the concen trations of the components in the coating agent composition are altered. Like the coating composition, the finishing agent comprises different solvents and may also comprise a smaller amount of coating agent. The purpose of this step is to remove friction and possible small edges or bevels that might have been formed during the preparation of the surface. The finishing agent is worked into the surface using strong circular motion and a thin spreading cloth or pad. After this, the surface is left to dry for 10-20 minutes after which the layer is removed by use of, for exam ple, a soft microfiber cloth. Thus, the removal of the finishing agent herein includes partial or complete removal of the finishing agent as well as the finishing agent be ing worked into the surface. The surface coating is finalized by use of, for example, a polishing cloth, pad or wool.

The coating agent composition of the invention may be modified to be thicker than normal with respect to the worksurface. For this purpose, one can optionally add at least one activator in an amount of preferably 10-30% and/or at least one binder in an amount of preferably 10-30%, such that for example a newly painted surface is not to absorb or take up too much coating agent. Higher amounts can also be used depending on the substrate. The purpose of the activator is to provide a thicker so lution, as well as to speed up the drying of the surface, whereby the uppermost nanotechnical layer of surface agent is stabilized on the surface of the coated mate rial and thereby guarantee an essentially 100% tightness, such that the surface is completely sealed. For example, catalysts, initiators, cross-linking agents and poly meric resins may function as activator or binder in the composition. Thus, also a higher amount of coating agent may be utilized to achieve a thicker composition.

During the final drying (11), the temperature or ventilation in the space might be raised. Depending on the circumstances, full drying, i.e. hardening, of the surface will take from 24 to 48 hours, after which the ultrathin layer formed still settles into its complete strength and polished, high gloss finish. The coating and the method of the invention is suitable for coating of metal sur faces ( e.g . steel, aluminum and zinc), painted surfaces (polyurethane, epoxy, pow der, alkyd, acryl, zinc, acid and etch primers or paints), gelcoat surfaces, concrete surfaces, cement surfaces, stone surfaces, glass fiber surfaces, plastic surfaces, laminate surfaces (e.g. water-protected wood panels or plywood boards), polymeric surfaces (e.g. polystyrene), composite surfaces, ceramic surfaces and rubber, not being limited thereto.

During the development of the method and coating of the invention it has been found that the coating functions exceptionally well also as an anti-fouling or anti graffiti coating. The nanotechnical surface of the coating obtained by the method of the invention is so smooth and dense, that pressure cleaning with water is enough to remove 95-98% of spray paints from coated surfaces. Since it, once completely dried, is very resistant to different solvents, the use of these may remove graffiti completely without damaging the surface beneath. Another benefit of the coating of the present invention is that it functions at least partially as a blocker of ultraviolet (UV) radiation, thereby protecting the colors and material of the coated surface. The coating also protects the substrate from oxidizing, functioning as an anticorrosion agent. Thus, the coating is suitable for both outdoors and indoors use to increase the life span of surfaces exposed to dirt or challenging weather conditions. Espe cially the life span of the painting on bridges, towers and other constructions that are hard to reach might be greatly improved by protecting the colors from fading or the material beneath from corrosion etc. Bridges, walls, and electrical enclosures are examples of places often exposed to graffiti, thereby natural objects to protect by the coating obtainable by the method of the invention.

Another benefit of the coating obtainable by the method of the invention is that it shows anti fouling properties, whereby it as such can be used to prevent fouling of ship's bottoms and other surfaces that are in contact with sea or lake water for a prolonged time. The coating of the present invention is thereby a pro-environmental alternative to toxic paints that currently are widely used for this purpose and a long- lasting alternative to other traditional coatings. The high gloss surface of the coating as such protects the material beneath com pletely, as it seals the material from the surroundings. It also prevents dirt and dust from attaching to the surface, making the coating obtained by the method of the present invention highly beneficial for use in spaces requiring a high hygiene level, such as institutional kitchens, hospitals and sanitary facilities. It also makes the cleaning of common buildings or places easier, such as (unmanned) train stations and petrol stations.

Construction parts that are difficult to reach, such as pipe sections or wiring ducts are also suitable objects for the coating of the invention. Likewise, heavy-duty ma chinery, such as snow ploughs, construction machines and power tools may be coated to protect parts from wearing.

Once the coating of the present invention is completely dry and have settled into full strength, the surface can withstand a wide range of stress. For instance, chal lenging weather conditions, such as sun, wind and temperature changes does not damage the coating noticeably. Likewise, the coating is not noticeably affected by solvents, such as petrol, diesel, and ethanol, making it very easy to clean. It is also very stable over a broad pH range, such that both acidic and alkaline solutions may be used. The nanotechnical surface of the coating withstands contact with water for a prolonged time, whereby it can be used in preventing biofilms and water organ isms from sticking to the hulls of boats and ships. For example, it has been shown to prevent barnacle from attaching to the hulls of boats. Thus, it is a pro-environ mental alternative to toxic paints that currently are widely used for this purpose and a long-lasting alternative to other traditional coatings. The coating obtained by the method of the invention is very smooth, providing low-friction properties compared to the surface structure of conventional coatings.

The novel coating obtainable by the method of the present invention is found to be very stable over time. In normal use, it has been proven to last at least five times longer than conventional coatings, such as wax coatings, without showing any signs of wearing. The properties of the coating are expected to remain essentially un changed for at least ten years, probably longer, without the need of maintenance other than normal washing. Summary of the Invention

An object of the invention is a method for obtaining a heavy-duty coating, wherein the coating process begins with pre-treatment of the surface to be coated. After this, a preparatory coating layer (7) is applied on the pre-treated surface, up to about one square meter at a time, by use of a coating agent composition compris ing organic solvents and at least one coating agent selected from a group consisting of polymeric coating agents and polymeric resins. Subsequently, a second coating layer (8) is applied on top of the preparatory coating layer using a coating agent composition comprising organic solvents and at least one coating agent selected from a group consisting of polymeric coating agents and polymeric resins, the coat ing agent being at a higher temperature than in the previous step. After this, the surface is left to dry until dust-dry (9). A finishing agent is then applied on the dust- dry surface (10) and allowed to dry. The finishing agent is then removed, after which the surface is polished to achieve the desired low-friction and high shine sur face. After this, final hardening of the coating (11) takes place.

In a preferred embodiment of the invention, at least one coating agent is selected from a group consisting of polysilazanes, polysiloxanes, acrylic resins and isocya nates. Preferably, the coating agent composition used in the preparatory coating step is initially at a temperature of -15-0°C and that the coating composition used in the subsequent step is at a temperature of 1-40°C. In a further embodiment of the invention, the surface to be coated is cooled down before the step of the pre paratory coating (7). The subsequent, or second coating layer may be applied (8) in vertical direction with respect to the surface to be coated. In one preferred embodi ment, the surface is neutralized (6) prior to coating, preferably by use of a composi tion containing acetic acid.

A further object of the invention is a heavy-duty coating obtainable by the above method. The coating obtained is very thin and dense, providing a durable and low- friction protective surface. Preferably, the heavy-duty coating obtained by the method of the invention is transparent and/or of nanoscale thickness. Furthermore, the coating may completely seal the coated surface from the surroundings. The properties of the coating obtained by the method of the invention makes it suitable as an anti-fouling and/or anti-graffiti coating. The coating obtained is resistant to a wide range of solvents. A first especially preferred coating agent composition for a heavy-duty coating ac cording to the invention comprises propylene glycol butyl ether, propyl benzene, acrylic resin, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, s-xylene and at least one C7-C9 hydrocarbon. A second especially preferred coating agent composition for a heavy-duty coating according to the invention comprises butyl acetate, at least one polysilazane com pound, (3-aminopropyl)triethoxysilane, toluene, acetic acid and at least one C7-C9 hydrocarbon.

The above-mentioned compositions may further comprise an activator and/or bind- ing agent in an amount of 1-50%, preferably in an amount of 1-30%.

A further object of the invention is an article coated by a heavy-duty coating obtain able by the method of the invention.

Drawings Figure 1: Flowchart presenting preferred steps in the method of the invention.

Detailed Description of the Invention

The heavy-duty coating of the invention may be achieved by use of a composition comprising at least one polymeric coating agent or polymeric resin and suitable sol- vents. The polymeric coating agent may be a polymeric compound, that is capable of forming a solid coating upon curing. Proportions of coating agent to solvent are chosen depending on the properties of the article, such as alignment and size of the surfaces, structural properties of the surface to be coated and the stage of the coat ing process.

The coating process of the invention includes a pre-treatment step and two subse quent coating steps. The pretreatment may include washing with an acidic solution or with solvent, mechanical treatment, or a combination of these. The first coating step is being performed with a cold coating agent composition. The second, subse- quent coating step is performed with a warmer coating agent composition. A finish ing agent is then applied to a dust dry surface of the coating, and after it has dried, it is removed, and the surface is polished prior to final curing of the coating. The coating process is carried out using a coating agent composition comprising at least one coating agent and different solvents. The coating agent is preferably se lected from a group consisting of polymeric coating agents and polymeric resins, even more preferably the coating agent is selected from a group consisting of pol- ysilazanes, polysiloxanes, acrylic resins and isocyanates. The composition may fur ther contain activation and/or binding agents, such as, catalysts, initiators or cross- linking agents.

The coating agent composition is prepared in a mixture of organic solvents, which may include acids. The coating agent and solvents of the coating agent composition are preferably chosen based on the material to be coated, such that an activation of the surface to be treated, and thereby increased interaction with the coating agent, is achieved. Examples of preferable solvents are propylene glycol butyl ether, propyl benzene, 1,3,5-trimethylbenzene, 1,2,4-trimethyl benzene, s-xylene, toluene, acetic acid and C7-C9 hydrocarbons. In one embodiment, the composition comprises (3- aminopropyl)triethoxysilane. The amount of activation and/or binding agent in the composition is preferably 1-50%, more preferably 1-30% and even more preferably 10-30%. The above-mentioned coating agents may also function as binder in the composition.

Two different compositions have been found to be especially preferred for use in the method of the invention, depending on the quality of the surface and the in tended use. The alternative compositions of these coating agent compositions are presented in Table 1 and Table 2. These are suitable for a wide range of applica tions. Some especially preferred embodiments of the coating of the invention are presented in Example 1 and Example 2 below, although not being limited thereto. The composition of Table 1 can be used in an embodiment and method according to Example 2, and the composition of Table 2 can be used in an embodiment and method according to Example 1. The coating agent compositions and the finishing agent are prepared out of these components in different proportions and/or compo sitions depending on the surface to be coated and the phase of the coating process. Naturally, the desirable viscosity of the coating agent composition also depends on the article to be coated, the alignment of the surfaces to be coated, and the spread ing device used. As a general rule, the coating agent composition is thicker in the beginning of the coating process, partially due to the lower temperature of the coat ing agent composition. The finishing agent is preferably prepared out of at least partially the same components as the coating agent composition. It is generally of lower viscosity and applied only as a very thin layer. The finishing agent is left to dry and then at least partially removed or worked into the surface.

In order to obtain optimal result, the surface to be coated should always be pre treated to ensure the coating agent composition to be absorbed as completely as possible. By absorbing is herein meant all kind of uptake of the coating agent com- position, both by chemical interaction and by physical inclusion into a porous sur face structure. The aim is to achieve a saturated surface, such that no more uptake of coating agent composition is observed. For old surfaces, acid treatment is prefer able to achieve a good result in the pretreatment step. Most preferred is use of phosphoric acid, but also other acids, such as oxalic acid, may be used. For new surfaces, the heavy acid treatment step might be left out. In these cases, mechani cal treatment is often sufficient.

Example 1:

Method 1: Coating of rubber, plastic, glass fiber and polystyrene surfaces as well as water-protected wood panels or plywood boards

Table 1: Components used in the coating of Method 1

The surface to be coated is pre-treated according to the following steps:

Firstly, any impurities are removed (1), for example by use of an 85% solution of phosphoric acid, which during the step is diluted to 0%. In the final phase of this cleaning step, the solution is preferably applied in the lengthwise direction of the area to be coated. Special care is to be taken not to let the surface dry during this step. The acid treatment is repeated until possible impurities, stains, rust, scale, or wax is removed. Alternatively, a new surface may be pre-treated by mechanically activating the surface.

After this, the surface is washed (2) with warm water and mechanically cleaned us ing a cloth. This is repeated until no loose material or color variation is detected.

The deep cleaning is finished by removing (3) any loose material from the surface. The cleaning is performed by use of a lint-free cloth, such that the water used in the cleaning process is completely clear and one can be certain no loose matter re main. The surface is then dried (4) or left to dry completely.

Once the surface is completely dry, the surface to be coated is carefully wiped (5) with solvent, such that no impurities or grease are left on the surface. Preferably, xylene is used for this step.

The saturation or preparatory coating (7) is performed for a surface of up to about one square meter at a time by use of a spreading device, such as a sponge or pad, and a composition of coating agents presented in Table 1. The surface to be coated should be completely saturated, such that all pores or possible scratches are com pletely filled with the coating agent. This step is performed until no more agent is absorbed by the surface, i.e. until no more uptake of coating agent is observed. Usually a time of 3-15 minutes is required. The acid treatment in the previous step opens or activates the surface, such that the surface can be saturated with coating agent and ensured that the coating agent is evenly and thoroughly absorbed into or taken up by the material to be treated. In the first step of the coating process, the temperature of the coating composition is -15-0°C. The more porous the material to be coated is, the colder the solution is to be used.

The actual coating layer is applied (8) on top of the preparatory coating immedi ately. The temperature of the coating agent is rapidly raised to 1-40°C, providing a liquid composition functioning partially as an activator and partially as a binder for the final coating. Optionally, ethyl benzene (1-50%) and/or diluted polymer (1- 50%) can be added.

This second coating layer is applied using a spreading pad or sponge. This step should be performed using vertical, continuous strokes. Special care should be taken to apply an even layer while avoiding any sagging. The layer formed is a very thin nanolayer that seals the surface beneath completely and guarantee a dense and shiny surface.

The coating is then left to dry (9) until surface dry. It is important that it reaches a stage where it is dry to the touch without being completely dry. At this point it might be just slightly clammy, i.e. dust-dry.

As a last step (10), a finishing agent is rubbed into the coated surface. The purpose of this step is to remove friction and possible small edges or bevels that might have been formed during the preparation of the coated surface. The finishing agent is worked into the surface using strong circular motion and a thin spreading cloth or pad. After this, the surface is left to dry for 10-20 minutes after which the layer is removed by use of, for example, a soft microfiber cloth. The surface coating is final ized by use of, for example, a polishing cloth, pad or wool.

During the final drying (11) of the coating, the temperature and/or ventilation in the space might be raised. Depending on the circumstances, full drying, i.e. hardening, of the surface will take from 24 to 48 hours, during which time the coating still set tles into its complete strength and high gloss, polished finish. Example 2:

Coating of metal surfaces, zinc coated surfaces as well as stone and concrete sur faces Table 2: Components of the coating of Method 2

The surface to be coated is pre-treated in according to the following steps: Firstly, any impurities are removed (1), for example by use of an 85% solution of phosphoric acid, which during the step is diluted to 0%. The direction of the final acid treatment is preferably a lengthwise direction with respect to the area to be coated. Special care is to be taken not to let the surface dry during this step. The acid treatment is repeated until possible impurities, stains, rust, scale, or wax is re- moved. Alternatively, a new surface may be treated only by mechanically activating the surface.

After this, the surface is washed (2) with warm water and mechanically cleaned us ing a cloth. This is repeated until no color variation is detected.

The deep cleaning is finished by removing (3) any loose material from the surface. The cleaning is performed by use of a lint-free cloth, such that the water used in the cleaning process is completely clear and one can be certain no loose matter re main. The surface is then dried (4) or left to dry completely. Once the surface is completely dry, the surface to be coated is carefully wiped (5) with solvent, such that no impurities or grease are left on the surface. Preferably, xylene is used for this step.

As the first step of the actual coating process, the surface is neutralized (6) using a neutralizing agent containing acetic acid and other components of the coting agent composition. This pre-treatment is preferable, especially for steel surfaces, as it acti vates the material providing a uniform surface with improved binding properties.

The preparatory coating (7), i.e. base coat, is performed for a surface of up to about one square meter at a time by use of a spreading device, such as a sponge or pad. The composition of the coating agent used in this process is presented in Table 2. Any pores or scratches of the surface have to be completely filled with the coat ing agent. This step is performed until no more agent is absorbed into the surface, i.e. no more uptake of coating agent composition is observed. Usually a time of 2- 15 minutes is required. The acid treatment in the previous step activates the sur face, such that the coating agent can be absorbed deeper into the material to be coated.

In the first step of the coating process, the temperature of the coating composition is -15-0°C. The more porous the material to be coated, the colder is the solution to be used.

The actual (second) coating layer is applied (8) on top of the preparatory coating immediately by use of the composition in Table 2. The temperature of the coating agent is raised to 1-40°C, providing a liquid composition functioning partially as an activator and partially as a binder for the final coating. Optionally, ethyl benzene (1- 50%) can be added.

This second coating layer is applied using a spreading pad or sponge with vertical, continuous strokes. Special care should be taken to apply an even layer while avoid ing any sagging. The layer formed is a very thin layer that seals the surface beneath completely and guarantee a dense and shiny surface. The coating is left to dry (9) until surface dry. It is important that it reaches a stage where it is dry to the touch without being completely dry. At this point it might be just slightly clammy, i.e. dust-dry. As a last step, a finishing agent is rubbed (10) into the coated surface. The purpose of this step is to remove friction and possible small edges or bevels that might have been formed during the preparation of the surface. The finishing agent is worked into the surface using strong circular motion and a thin spreading cloth or pad. The surface is then left to dry for 10-20 minutes after which the layer is removed by use of, for example, a soft microfiber cloth. The coating is finalized by use of a polishing cloth, pad or wool. The uppermost, finishing layer is thus of nanoscale thickness.

During the final drying (11) of the coating, the temperature or ventilation in the space might be raised. Depending on the circumstances, full drying, i.e. hardening, of the surface will take from 24 to 48 hours, during which time the coating settles into its complete strength and high gloss, polished finish.

Claims

1. Method for obtaining a heavy-duty coating, characterized in that the coating process comprises the following steps:

- pre-treatment of the surface to be coated,

- applying a preparatory coating layer (7) on a pre-treated surface of up to about one square meter at a time using a coating agent composition comprising organic solvents and at least one coating agent selected from a group consisting of poly meric coating agents and polymeric resins,

- subsequently applying a second coating layer (8) on top of the preparatory coating layer using a coating agent composition comprising organic solvents and at least one coating agent selected from a group consisting of polymeric coating agents and polymeric resins, the coating agent composition being at a higher temperature than in the previous step,

- letting the surface dry until dust-dry (9),

- applying finishing agent on the dust-dry surface (10), after which it is left to dry,

- removal of the finishing agent, after which the surface is polished to achieve the desired low-friction and high shine surface,

- final hardening of the coating (11).

2. Method according to claim 1 for obtaining a heavy-duty coating, characterized in that said at least one coating agent is selected from a group consisting of polysi- lazanes, polysiloxanes, acrylic resins and isocyanates.

3. Method according to claim 1 or 2 for obtaining a heavy-duty coating, characterized in that the coating agent composition used in the preparatory coating step is initially at a temperature of -15-0°C and that the coating composition used in the subsequent step is at a temperature of 1-40°C.

4. Method according to any one of claims 1 to 3 for obtaining a heavy-duty coating, characterized in that the surface to be coated is cooled down before the step of the preparatory coating (7).

5. Method according to any one of claims 1 to 4 for obtaining a heavy-duty coating, characterized in that the subsequent coating layer is applied (8) in vertical direc tion with respect to the surface to be coated.

6. Method according to any one of claims 1 to 5 for obtaining a heavy-duty coating, characterized in that the surface is neutralized (6) prior to coating, preferably by use of a composition containing acetic acid.

7. Heavy-duty coating obtainable by the method of any one of claims 1 to 6.

8. A heavy-duty coating according to claim 7, characterized in that the coating is a transparent and of nanoscale thickness.

9. A heavy-duty coating according to claim 7 or 8, characterized in that the coat ing completely seals the coated surface from the surroundings.

10. A heavy-duty coating according to any one of claim 7 to 9, characterized in that the coating is an anti-fouling and/or anti-graffiti coating.

11. A heavy-duty coating according to any of claims 7 to 10, characterized in that the coating is solvent resistant.

12. A coating agent composition for a heavy-duty coating according to any one of claims 7-11, characterized in that the coating agent composition comprises pro pylene glycol butyl ether, propyl benzene, acrylic resin, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, s-xylene and at least one C7-C9 hydrocarbon.

13. A coating agent composition for a heavy-duty coating according to any one of claims 7-11, characterized in that the coating agent composition comprises butyl acetate, at least one polysilazane compound, (3-aminopropyl)triethoxysilane, tolu ene, acetic acid and at least one C7-C9 hydrocarbon.

14. A coating agent composition for a heavy-duty coating according to claim 12 or 13, characterized in that the composition further comprises an activator and/or binding agent in an amount of 1-50%, preferably in an amount of 1-30%.

15. Article coated by a heavy-duty coating according to any one of claims 7-11.