Methods for producing durable bronze pastes or bronze powders from them

Description

[0001] Method for producing durable bronze pastes or bronze powders therefrom. The invention relates to a method for producing durable, free from conventional color binders, buoyant, high-gloss bronze powder, especially containing aluminium bronze powder Pastes or bronze powders. from this.

[0002] The usual starting material for the preparation of ready-to-use bronze paints is the so-called bronze powder. This consists of As is well known, they consist of fine metal particles in the form of plates or scales, whose surface is covered with a membrane that gives them the so-called mirror or high gloss, and which is the reason that the particles on a liquid surface remain in the same state for a period of time. Wise people float like a greasy needle on water.

[0003] According to the older manufacturing process (cf. Edwards and Buschlinger, Aluminiumbronzepulver und Aluminiumfarben 1931), the Bronze powder, metal to be processed in pieces of suitable size together with a small fraction of one percent of a lubricant, such as tallow or olive oil, are placed in a mortar and pounded or pounded. When the particles are sufficiently fine, they are either continuously or periodically, using fine sieves or vertical mills, possibly in multiple repeated passes. After the After tamping and sifting, the powder enters a polishing drum or burnishing mill equipped with brushes. The brushes rub against the inner surface. Along the outer surface of the drum, they exert a polishing effect and distribute the stearic acid, which is added simultaneously with the powder or subsequently. The substance is added to the surface of the metal particles. After several hours of polishing, the duration of which varies depending on the conditions, the... The powder is stored and left to age. During this aging process, certain changes occur that enhance the high gloss. The exact The nature of the chemical reaction taking place is the subject of various theoretical considerations, which, however, are not sufficient for the full Understanding the present invention is not of direct importance. It suffices to point out that flotation or floating agents, e.g. B. stearic acid, and the conditions required for its effectiveness have been known at least empirically for a long time. Later, the grinding process was carried out in ball mills or vortex mills. This involved flattening the metal particles. either by means of spheres, or the effectiveness of gas vortices was used; in some cases, in addition, as well as In the stamping process, fats and oils are used as lubricants. However, the use of ball mills for this purpose proved to be extremely difficult. The area was dangerous due to the recurring and devastating explosions. These dust explosions were essentially caused by the » due to the regularly occurring oxidation of the aluminium dust (cf. Ritter, VDI-Zeitschrift 1930, p. 145ff.).

[0004] To reduce the possibility of explosion, it has been proposed to produce the bronze powders in the presence of an organic to add liquid while simultaneously excluding air from the mill, as described in American patent 1,569,484. The product was then completely dried.

[0005] The bronze powders produced by the various methods were then mixed, for example by means of a mixing liquid made of benzene or whose homologs, a resin and stearic acid, as specified in American patent 1 4I1673, are processed into bronze paint.

[0006] Although all previously known methods yielded highly lustrous, more or less buoyant bronze powders, they did not at all Products that permanently retained these properties.

[0007] The invention primarily relates to a method for producing highly lustrous, buoyant bronze pastes, in particular Aluminum bronze pastes that are durable and free of conventional paint binders. These pastes retain their buoyancy indefinitely. retained, represent a completely new product that can be easily mixed with the usual color binders.

[0008] According to the invention, the production of the mirror or the buoyancy of bronze powders can be achieved by completely bypassing the the aforementioned prolonged paling and aging process through treatment of pure, plate-shaped metal particles with a solution of a buoyancy agent in an organic liquid that does not impair the desired properties of the product. It is sufficient to use the pure to vigorously move platelet-shaped metal powders in such a solution; but the application of heat accelerates the process, whereby However, excessively high temperatures should be avoided. Favorable results can easily be achieved at temperatures near 50°C. It turned out that... Surprisingly, it turns out that in the case of aluminum, the presence of oxygen, e.g. air, is indispensable, whereas during processing it It does not appear to be harmful to other metals, at least.

[0009] For example, a given weight of pure plate-shaped aluminum is heated in the presence of air under strong Stir with five times the weight of a 2% solution of stearic acid in white spirit to 50°C. The excess liquid is... removed. The resulting paste, as well as any bronze powder produced from it, floats in lacquer or white spirit.

[0010] Furthermore, according to the invention, the production of the high gloss or the buoyancy can also be carried out simultaneously with the The metal is pulverized in a ball mill, thus completing the process in a single, relatively simple step and in a relatively short time. high-quality products can be obtained in a short time. Furthermore, it is no longer necessary to exclude air from the ball mill. Since the liquid prevents the formation of explosive mixtures of metal dust with air. When crushing metal dust in this way... As already mentioned, the presence of oxygen, e.g., air, is necessary for aluminium to give the metal the desired buoyancy. This contrasts with the technical rules of previously known processes, which required great care to maintain the atmosphere in the To regulate the ball mill in order to avoid the formation of explosive mixtures.

[0011] The grinding of aluminium in a ball mill according to the invention can be carried out in such a way that a marketable, homogeneous, a stable paste is obtained. When stearic acid is used as a float, aluminum stearic acid forms in sufficient quantities to act as Dispersing agent to act so that when the liquid content is reduced to the desired level, a paste with approximately 60% is obtained. Aluminum is achieved.

[0012] It is known that various mechanical conditions play an extremely important role in the grinding of these metals. For example, For example, when working in a ball mill, the size of the mill and the balls, impact force and rotational speed all depend on Influence on the quality of the product.

[0013] For example, when platelet and membrane production is carried out jointly, The grinding should be done by impact and not by rubbing and abrasion; furthermore, care must be taken not to over-process the metal. to claim. This means that there is a maximum force of the impact directed at the metal particle and that with further increase of the The result leaves much to be desired due to the force applied. The temperature at which the work process is carried out must also be regulated. This will be necessary because there is also a maximum value for this working condition. Furthermore, a relationship must be established between the amount of metal and the size. the metal particles, the amount of stearic acid and aluminum stearic acid, the amount and type of organic liquid used, The conditions depend on the atmosphere in which one works and the temperature. However, these conditions cannot be calculated but must be determined. can be determined based on experience.

[0014] Since it is more convenient to perform the plate and high-gloss production simultaneously, this is the procedure used in practice. While grinding can be carried out in various grinding devices that employ an impact action, a Ball mills, whose balls primarily exert a striking effect on the metal particles, are preferred.

[0015] Good results were obtained when 0.45 kg of aluminium powder, the particle size of which was tested on a sieve with 1600 meshes per square centimeter corresponds to (see paragraphs A and B below), 0.45 kg of white spirit (see paragraph C), 3% stearic acid (see paragraphs D and E), i% aluminum stearic acid (see paragraph E) and 9.1% spheres (see paragraphs F urid J) were taken and when for 7 hours. long (see paragraph G) in a ball mill with a diameter of 40 cm x a length of 15 cm (see paragraph H), which uses balls with a diameter of 9.5 mm (see paragraph I) runs at a speed of 65 rpm (see paragraph J), with a feed of 135 g of aluminium (see paragraph K) at a temperature ground at 50°C (see paragraph L) in an atmospheric environment (see paragraph D) or in a ball mill measuring 60 cm in diameter x 15 cm in length, which uses 6.35 mm diameter balls and runs at a speed of 54 revolutions / min, loaded with 2180 g of aluminum. is.

[0016] A. Aluminium is chosen as an example because it is the most widely used and excellent representative of bronze powders.

[0017] B. A sieve with 1600 meshes per square centimeter is expressly specified because it has proven advantageous to filter the metal to grind down to this degree of fineness before proceeding to the production of the plate shape and the creation of the high gloss.

[0018] C. Lacquer naphtha is chosen as the grinding liquid because it is a common lacquer component and furthermore because its boiling limits, approximately 150 to 100°, such that neither excessive loss through evaporation occurs, nor is there a great risk of fire. Nevertheless, the liquid can be If a dry product is desired, it can be easily removed by evaporation. Turpentine oil can also be used instead of white spirit. Use benzene or naphtha. However, it does not necessarily follow that the metal particles will float in this liquid. For example, if you grind... Aluminum in paint benzine floats in this liquid and also in the final paint binder with which the painter mixes it. If aluminum is ground in naphtha, it doesn't float in the naphtha itself, but it does float in the pigment binder. The amount used will selected so that it provides the desired dispersion (see paragraph E).

[0019] D. There are clear indications that a chemical reaction takes place between the aluminium and the stearic acid, when Oxygen plays a role. As the milling process progresses, the amount of stearic acid in the solution decreases, and a mixture is formed. a compound, probably aluminum stearic acid. If grinding is carried out in a tightly sealed mill, a characteristic appears. This results in a negative pressure for oxygen absorption, provided that this is not caused by the increasing pressure resulting from the temperature increase. The vapor pressure of the liquid is balanced. Furthermore, when using an oxygen-free gas, e.g., hydrogen, no negative pressure occurs. The buoyancy or mirror effect is still developing. The additive can be added at the beginning or towards the end of the process. Substances such as palmitic acid can also be used instead of stearic acid, which is listed as a skin-forming agent.

[0020] E. In a ball mill there are different zones of action (see J), ​​and it is necessary to remove the metal as much as possible into to have the impact zone treated. To prevent the metal from penetrating the gaps and spaces between the individual balls. Since the metal particles migrate through and primarily reach the friction and grinding zone, it is necessary to create a foam that carries the metal particles. which has sufficient mass and adhesive strength to coat the spheres and adhere to them to migrate through the impact zone, but allowing the particles sufficient mobility to enable them to move upon contact with adjacent spheres and with the mill walls, turn their flat sides towards the same. Stearic acid and aluminum stearic acid are for This purpose is stated, however, numerous other substances can also be used, e.g. palm oil, oleic acid; olive oil, palmitic acid.

[0021] F. A weight ratio of 20:T between spheres and aluminium resulted in effective grinding and satisfactory results with regard to the production of plate-shaped bronze powder with a high gloss finish.

[0022] G. The time required for grinding is influenced by practically all of the conditions mentioned so far and depends on the desired fineness grades of the product.

[0023] H. The capacity and performance of the mill depend on its length and diameter, and the choice of size is a question of economic efficiency.

[0024] I. In the mill described, balls with a diameter of 9.5 mm were used, but the amount of force required depends on This naturally depends on the physical properties of the metal and the particle size of the ground material, and this in turn influences the ball size. or the diameter of the mill, or both. Furthermore, it is clear that the specific gravity of the metal depends on the ratio of metal to other materials. Conditions affect the process. If one intends to treat waste film or sheet metal directly, these are first cut into pieces of approximately 3 to 13 mm. ° cut. For* foil from -0.05- to 0.1 mm thickness, grinding can advantageously be carried out in two stages: - firstly with balls of i9 mm diameter in, a 40 cm mill and finish as above, secondly, for sheet metal of 1.6 mm, it is advantageous to start with balls of 5 to Use 7.5 mm.

[0025] J. The speed of the ball mill determines whether the grinding is carried out by rubbing and grinding or predominantly by impact. This occurs when the mill is set in motion. The balls are carried upwards laterally, but tend to slide back down. The latter is delayed by the addition of internal ribs. After reaching a certain height, which depends on the feed rate, the Balls in the upper layers descend below a certain speed, while the layers in contact with the drum wall... The spheres are carried upwards together with the spheres orbiting around non-oriented axes. At the points of contact, a rubbing movement, and therefore a scraping effect occurs, which in the lower layers is caused by the weight of what rests on them. The formation of spheres is further intensified. This is not conducive to the production of platelets, but rather results in an excessive amount of sludge while simultaneously... Destruction of the highly glossy membrane. With decreasing sphere size and increasing number of contact points, the effect is less pronounced. pronounced. When the mill is filled with the correct amount of balls, i.e., when it is about 2] full, and at the correct speed of rotation, the balls – by the combination of centrifugal force and gravity – are lifted to a point where they are separated from the drum wall and the balls moving in an upward direction are flung away, falling freely to the opposite side of the drum and The balls that have fallen previously are struck, producing the desired tiles. From the point of impact, the... The direction of rotation creates a zone of friction and abrasion, but the main comminution of the particles occurs through impact. To achieve the For most effective grinding, the metal particles must lie between the contacting surfaces, and this is precisely what the aforementioned [function] achieves. Foam. The force of the impact is naturally determined by the ball size and the drum diameter of the mill. An impact that is too forceful destroys the platelet and the surface skin, and these two parameters together with the resistance of the metal particles determine the Ratio of drum diameter to ball size.

[0026] "K. For the correct filling of a ball mill with a diameter of 40 cm and a length of 15 cm, 1135 g of aluminum and 22.7 kg of balls are needed. Reducing the amount of metal increases the fineness of the product, while conversely, increasing the amount of metal makes the product coarser. Provided that everything else remains the same.

[0027] A working temperature of 50°C yields satisfactory results. As the operating temperature rises above 50°C, the tendency to... to lose its high gloss, and at ioo° it has already suffered considerably.

[0028] After removal of some of the liquid, the material coming from the mill constitutes a finished, paste-like product which requires no further treatment and can be stored for any length of time without losing its mirror color or its ability to float.

[0029] It has now also been found that this durable, buoyant, high-gloss paste containing bronze powder also dry products, i.e., the bronze powder itself can be obtained without the latter losing its high gloss. or lose their buoyancy in the process. According to the invention, this is achieved by evaporating the liquid under carefully controlled conditions. Temperature conditions and in a properly chosen atmosphere.

[0030] In the absence of oxygen, i.e. in a non-oxidizing atmosphere, e.g. in illuminating gas, the drying temperature for the Allow the paste to reach approximately 200°C without destroying its high gloss or buoyancy. It can also be dried in a vacuum; however, this will... The permissible temperature is reduced compared to that applicable when drying in a gas atmosphere.

[0031] In the presence of oxygen, e.g., air, heating the paste to 50°C provides safety. If the temperature rises considerably higher, there is a risk of contamination. Tendency to lose its high gloss or buoyancy, and if heated to 100°C until completely dry, the high gloss will be restored. or rather, their buoyancy in the presence of oxygen, e.g., air, is more or less completely destroyed. Therefore, temperatures below 100°C are possible. necessary.

[0032] The method according to the invention applies generally to the production of bronze pastes or bronze powders therefrom, while the Details concern aluminium bronzes, and it is not claimed that these guidelines given for aluminium are directly equivalent to aluminium. Success can be transferred to other metals. Since each metal, both physically and chemically, has different properties. Given its specific characteristics, the individual conditions must be tailored to the respective features. However, it has been determined that That durable pastes can be made from copper, zinc and tin, just as from aluminum, which give these metals a high-gloss, buoyant finish. The form can be produced by grinding under the generally described conditions, and there is no reason to Assumption that alloys of these metals behave differently.

Claims

[0033] PATENT CLAIMS: i. Method for producing durable, free from conventional color binders, buoyant, high-gloss Bronze powder, in particular aluminum bronze powder, pastes containing or consisting of bronze powders, characterized in that the Metal during or after its comminution and conversion into platelet form in the presence of oxygen, e.g. air, with a solution of treated with a floating agent, e.g. stearic or palmitic acid, in a paint or varnish thinner, e.g. gasoline, turpentine oil or benzene and then the thinning agent is partially or completely removed.

2. Method according to claim i, characterized in that the pastes are used to obtain the The diluent is removed by evaporation in the absence of oxygen at any temperature below approximately 20°C.

3. Method according to claim 2, characterized in that the diluent is extracted from the pastes at temperatures below 100°, preferably at 50°, in The presence of oxygen, e.g. from air, is removed by evaporation.