DE3200858A1 - Process for applying a dye coating to an article - Google Patents

Abstract

The invention relates to a process for applying a dye coating to articles, in particular to spectacle frames, onto which a coating of resin-containing polymer powder has been applied. The article is fired, the polymer powder melting to form a coating. The article is subsequently immersed in a hot dye solution and, after removal from the dye bath, is heated up, the dye diffusing deeply into the polymer coating. The dye coating is therefore particularly abrasion-resistant and substantially resistant to solvents.

Description

R. Engelhardt Nominees Pty. Ltd. A 37 287 / raxu 15 Lindsay Avenue iq Ι, _Ί ~ 'gA9

Edwardstown / Australia ' ^Vl * "" ·· ^l " ^0L

Process for applying a paint coating to an object

The invention relates to a method for applying a color coating to an object according to Preamble of claim 1. The method is for a A large number of objects can be used, e.g. also on small items such as glasses frames.

In a known method for producing a spectacle frame or a frame for sunglasses the ring frames for the glasses, the temples and frame parts are manufactured separately and then put together. The frame is then provided with a noble metal coating for corrosion protection.

Due to fashion trends, colored metal frames or gold or silver-coated frames are often used demands.

In the case of known colored spectacle frames, a large number of problems arise with the final color coating. Some of these problems are:

a) poor adhesion of the plastic coating on the Metal substrate,

b) the coating is extremely thin and wears out very quickly due to its low abrasion resistance,

c) the paint application is not resistant to strong solvents.

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The invention is based on the object of applying the paint to objects, in particular spectacle frames, in such a way that that it is resistant to solvents and abrasion resistant.

The object is achieved according to the invention by the characterizing Features of claim 1 solved. In the method according to the invention, the plastic coating is through the color to penetrated to a considerable depth so that the finished product z. B. placed in acetone or paint thinner without loosening the paint coating or seriously damaging the external appearance.

Usually this is used to apply the plastic coating (Polyester cover) on a spectacle frame this carried by a holder, the plastic powder is applied by an electrostatic field to the frame by means of a spray gun. The frame will then heated. One of the problems encountered with eyeglass frames has been that the polyester or other plastic material fell off the very thin frame, leaving the coating uneven or incomplete became. According to the method of the invention, the polyester (or epoxy) coating can be substantial can be kept thicker by keeping the rack above ambient temperature is heated and the plastic powder is only applied when the frame is heated. Surprisingly It has been shown that the particle adhesion is considerably better here than when it is applied to a cold one Metal surface, so that the thickness of the coating is made much stronger.

If a metal frame is simply painted, the applied paint is often dull and lifeless. To an improved

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To achieve appearance along with improved adhesion of the paint coating, the metal frame comes first sandblasted with a granular material (e.g. silicon carbide), which creates small indentations in the metal will. These indentations or depressions increase the adhesion and form small reflective ones Surfaces between the plastic coating or the melting glaze, so that a strong gloss in the overall appearance is achieved. The small depressions surprisingly eliminate unevenness in the plastic surface, so z. B. an otherwise occurring ripple is reduced.

Another problem when coating eyeglass frames are undesirable accumulations of material, which are particularly strong when coating a frame with lacquer or a polyester resin in the area of the hinges between the Ironing and the glass frames and also occur in the areas of the flexible mounting of the nose bridges. In a development of the method according to the invention are after the application of a certain plastic material on the metal surface of the spectacle frame in the areas of the relative movements of frame sections the applied plastic particles are removed again in a targeted manner by means of a vacuum suction line. Retroactively a relatively thin layer of the plastic powder used is then applied again. That way will the "welding" of the relatively movable parts by the plastic (polyester) avoided. Yet a uniform appearance of the frame is achieved in this way.

An embodiment of the invention is shown in the drawings and is described in more detail below. It demonstrate;

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Fig. 1 schematically shows a first step of the invention Method for applying a color coating to a spectacle frame,

FIGS. 2 to 13 continuously show the 2nd to 13th process step ,

14 shows the final step of the method according to the invention.

The spectacle frame 10 shown in FIG. 1 to be worn by a person has frame sections 11 for the. Glasses, nose bridge sections 12 and foldable temples 13 open. The frame 10 is first with a maximum 180-grain silicon carbide powder 14 dry-sandblasted. This process becomes the required amount of time consuming Manual polishing and the likelihood of rejects due to machining errors.

The size of the carbide grains, as well as the air pressure to be used, can vary. With a silicon carbide powder with a maximum grain size of 180 grit applied under a pressure of 0.703 kp / cm ^a (10 psi), a very good final surface reflection can be achieved. The length of the treatment time can be adapted to the respective conditions, but in most cases it will be sufficient to provide a relatively short treatment time. Once the necessary surface cleanliness and deformation have been achieved, only slightly better results can be achieved by further sandblasting. Sandblasting creates local indentations on the metal surface which create a series of closely spaced "valleys" in the metal surface, resulting in brilliant reflections of light and an excellent surface for coatings that adhere firmly.

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In the next process step according to FIG. 2, the spectacle frame is nickel-plated in an electroplating bath 15. The nickel coating forms a basic protection against corrosion for the starting metal and envelops each one small particles of silicon carbide that may become part of the parent metal embedded, the wavy surface that reflects the light (scattered light) is still so more reflective, so that the gloss is increased.

To further increase the shine and to achieve good protection against sweat for the areas of the frame that not protected with a plastic cover (e.g. nose bridge protector or base metal) will be in one further electroplating bath 16 a thin chrome or rhodium coating upset. This coating is also advantageous in order to ensure a uniform color for the reflection of the starting metal to achieve. The chrome or rhodium plating also reduces the likelihood of that in the nickel plating occurring impurities a yellow color penetrating into the subsequently applied polyester coating generated.

The next step in the process is to prepare the Plastic powder coating frame.

It is important that the inner surfaces of the frame portions 11 for the spectacle lenses are not affected by the powdery polyester resin can be added. This would create great difficulties when inserting the optical glasses entail.

To avoid this, the inner surfaces are covered by loops 17 of masking tape, so that the powdery polyester resin cannot penetrate into the grooves of the socket (Fig. 4).

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If the glasses are fitted, they can go up ground to very tight tolerances (usually by - 0.1 mm), whereby by avoiding plastic powder accumulations a correspondingly narrow tolerance can be achieved in the grooves of the socket sections 11.

In the next process step, the spectacle frame is preheated before the plastic powder coating is applied.

The spectacle frame is heated to a temperature of about 80 ° C. in an oven 18 for about 2 minutes (FIG. 5). It has been shown that under these conditions a considerably thicker plastic coating is applied to the frame than is possible under ambient temperature conditions. Furthermore, the thickness of the the frame applied coating over all areas much more evenly, which leads to an end product, which is provided with a very even coating.

The next step in the process is to select the powder and apply the powder to the rack.

The powder used in the exemplary embodiment is a clear, powdery polyester or epoxy with a grain size between 30 microns and 150 microns. The powder 19 is Applied by an electrostatic spray gun 20 in a known manner, the powder particles being an electrostatic Pass through a field in which the particles are charged, causing them to be attracted to the metal surface (Fig. 6).

Before the powder finally hits the metal surface is melted, the loops 17 are made of masking tape removed from the socket sections 11 of the frame (Fig. 7). A vacuum suction tube 21 is close to the movable

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Parts of the frame attached to the applied powder from the two hinges of the bracket 13, the two To remove nose bridges 12 and the two edge attachment sections. At these points a very narrow one becomes Powder application reapplied, which is so thin that it does not interfere with the function of the glasses frame causes.

The frame is in an oven at a temperature between about 170 ° and 250 ° C, in the present embodiment Fired at 200 ° C to fuse the powder, creating a continuous film of the powdery polyester or epoxy is formed. The frame is shown in FIG. 9 with its brackets perpendicular to the ground and arranged with its socket section 1 parallel to the floor in the oven. The free ends of the Bracket 13 to the floor. This differs from known methods that work in a different way. Through this suspension the powder melts into a uniform, even coating with fewer small waves in the plastic surface than is possible with a frame suspended in a known manner.

At this stage of the process, the racks are covered with an even, finished polyester coating greater thickness than it is possible by the known method. In the next step of the invention In the process, the applied plastic coating is colored.

The plastic coating is made by immersing the frame 10 in a bath 22 of hot, caustic sodium solution for prepared for the application of paint for about a minute (Fig. 10). This softens the surface of the plastic coating, so that the paint can penetrate more easily and

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the risk of staining is reduced.

The rack is removed from the etching bath 22 and then used for held at a temperature of about 85 ° C (between 75 ° C and 95 ° C) for a predetermined period of time Dipped dye bath 23 (Fig. 11). The time span is determined according to the desired color gradation. A darker one Color gradation results from a deeper penetration of the color into the polyester layer, while lighter color gradations can be achieved by a superficial penetration into the polyester layer. The color gradation is a function of immersion time, temperature and the selected dye bath. A paint that can be used for dyeing polyester is known under the trademark "Dylon".

After such coloring of the plastic coating, it is desirable to treat the surface so that certain solvents cannot damage the paint application. For this purpose, the frame for a given Period of time placed in an oven 24 (FIG. 12) heated to about 200 ° C., the period of time being determined in this way is that the upper layer of the polyester at least partially melts. An applicable period of time is approximately 90 seconds. The melting of the top layer (this occurs when the top layer of the plastic coating has a Temperature between about 150 ° C and 170 ° C) causes the formation of a thin upper part in the dyed polyester part Protective layer that is essentially resistant to known solvents that otherwise attack the surface is. When it is heated up, the paint diffuses deeper into the polyester, damaging the upper Color layer are essentially only superficially visible.

Although the polyester coating exhibits excellent resistance to most chemicals with which it may come into contact, the polyester coating can still be attacked by certain products, especially those with a high pH value. So z. B. of diesel oil, caustic and pickling agents, certain oils and aromatic substances and certain amino acids. As shown in FIG. 13, a wet spray of polyurethane, which forms a layer approximately 20 microns thick, is additionally applied to the frame or product. The frame is then fired in an oven 26 (Fig. 14) at a temperature between about 69 ° C and 80 ⁰ C for about 30 minutes. It is important not to overheat the colored polyester resin layer underneath, as this can cause a color change.

The polyurethane itself can advantageously be pigmented. A usable polyurethane is made by the company Dulux Australia Limited, McNaughton Road, Clayton, Victoria sold under the name "DULUX ACRAN". It has shown, that a polyurethane layer not only increases the resistance to chemicals, but also the flexibility of the frame or product is improved and is resistant to hairline cracks.

With the method according to the invention, a product can be created are far superior in their properties to the products produced by previously known processes is.

The sandblasting results in a diffusing light effect that increases the shine of the frame, with the coating with Nickel and then with chromium or rhodium not only increase the resistance to corrosion, but also the polish or the gloss of the product is also significantly improved.

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The application of a polyester coating on days of high air humidity has so far led to a wavy surface condition. By preheating the frame and the possible application of a thicker plastic coating a uniform surface quality is achieved even on days of high humidity.

Covering the socket notches and removing excess powder using a vacuum results in a seamless high quality frame.

Because the plastic is remelted after the paint has been applied, the surface quality is maintained achieved, which is significantly better than that which was previously achievable by known methods.

In the exemplary embodiment shown, the method was based on an eyeglass frame that is considered difficult to color. The method according to the invention is _. can still be used on a wide variety of products, which are considerably easier to use with a colored or plastic coating can be provided as spectacle frames.

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Claims (10)

R. Engelhardt Nominees Pty. Ltd, A 37 287 / beu Lindsay Avenue 1 Jan. 3 I3d2 Edwardstown / Australia Expectations Λ
(ii Method of applying a paint coating to an object that is coated with a resin-based plastic powder, characterized in that the object (10) is fired at a temperature which fuses the plastic powder is that the plastic-coated article for a a predetermined period of time is immersed in a dye bath (23) kept above ambient temperature, the depth of penetration The color in the plastic coating is determined by the length of time that the plastic coated Object (10) taken from the dye bath (23) and then is heated to a temperature at which the color diffuses into the plastic coating. 2. The method according to claim 1, characterized in that prior to the application of a coating of plastic powder, the surface of the object abraded by sandblasting (Fig. 1) and then with a reflective metal coating (Fig. 2, Fig. 3) is provided, 3. The method according to claim 1 or 2, characterized in that the object (10) is preheated and is then subjected to overpressure while the coating is made of resin-containing plastic powder is applied. JZ U U Ö O ö 4. Process for applying a color coating to a spectacle frame,
characterized by the following process steps: a) the frame (10) is covered with silicon carbide sand sandblasted (Fig. 1), b) the frame (10) is provided with a reflective metal coating (Fig. 2, Fig. 3), c) the frame (10) is preheated (Fig. 5), d) the heated frame (10) becomes electrostatic coated with a resin-based plastic powder (Fig. 6), e) at least partial amounts of the plastic powder are removed in the area of the moving frame parts (Fig. 8), f) the frame (10) is fired at such a temperature that the powder melts and one the frame (10) forms an enveloping coating (Fig. 12), g) the plastic-coated frame (10) is in one on one over for a predeterminable period of time 0 ambient temperature held dye bath (23) is immersed, the length of the period of time being the depth of penetration the color in the plastic coating is determined, h) the plastic-coated frame (10) is made of the Color bath taken, i) the plastic-coated frame (10) is on a Temperature heated above ambient temperature, at which a diffusion of the color into the plastic coating is effected. 5. The method according to claim 4, characterized in that the resin-based plastic powder is a polyester powder, that the frame (10) is heated to a temperature of about 80 ° in process step c), that in process step f) the frame is heated to a temperature of about 170 ° C to 250 ° C is fired, that the frame in process step g) is immersed in the dye bath (23) at a temperature of about 75 ° C to 95 ° C and that the frame (10) in process step i) for a period of time at a temperature such is heated so that the plastic ^{coating assumes a temperature of about 150 0} C to 170 t. 6. The method according to claim 4 or 5, characterized in that the inner surfaces the glass frame sections (11) of the frame (10) prior to the electrostatic application of the plastic powder according to method step d) are covered with a mask (17), and that the masks before firing the Frame can be removed according to process step f). 7. The method according to any one of claims 4 to 6, characterized in that in a further process step the areas from which the plastic powder was removed according to process step e), be coated again with the resin-containing plastic powder in such a way that a coating can be formed, the thickness of which is less than the coating formed according to process step d). 8. The method according to any one of claims 4 to 7, characterized in that after the firing of the frame (10) according to process step f) the plastic ./4 coated rack (10) in a hot, caustic sodium * - solution (22) is immersed before it is immersed in a dye bath (23) according to method step g). 9. The method according to any one of claims 4 to 8, characterized in that after heating according to Process step i) the frame (10) is sprayed with polyurethane in a further process step (Fig. 13). 10. The method according to claim 9, characterized in that the plastic-coated frame (10) sprayed in with polyurethane at one Firing at a temperature of about 60 to 80 ° C.