DE19917151A1 - Production of polymer coating for utensil baskets for dish washers comprises melt coating to yield rough or uneven surface - Google Patents

Abstract

In the polymer coating of a wire basket for dish washers uncoated basket or insert is first heated for a set duration and mixed with a polymer powder such that the powder melts when contacted with the wire and is then cooled. The surface of the basket wire (7) which is in contact with the goods to be washed has a coating (10) with a rough or uneven surface (11).

Description

The invention relates to a method for the plastic coating of a wire basket, in particular particular of a crockery basket or basket insert for dishwashers, the unbe layered basket or insert is first heated and then heated with powdered Plastic is provided, whereupon the powder mass adhering to the basket wires melted and the basket is cooled.

It is general in water-bearing household appliances, in particular in dishwashers I know the dishes that come into contact with the washing or cleaning liquid to verse baskets and / or their inserts made of wire material with a plastic coating hen. The material used for this is generally polyamide (see e.g. German Ge utility model DE 72 40 941 U1 and DE 70 01 337 U1). These measures serve on the one hand the corrosion protection and on the other hand protect the dishes or clothes placed in the basket stuck. The basket manufacturers try to encase the plastic, the plastic surfaces to produce even, smooth and shiny, so that water droplets can be drained well from the Baskets and the crockery or cutlery that has been placed in it. An improved one Water droplet drainage has a positive effect on the drying of dishes and is in terms of one low water and heating energy consumption advantageous.

The baskets are usually coated with plastic so that the curved, ge welded and cleaned wire baskets or basket inserts as so-called semi-finished products on a noble steel suspension wire to be hung on a device and first heated. According to the he The basket and / or the partial inserts are heated in a powder bath with which the subsequent Sheath-forming plastic is dipped. Depending on the dwell time in the powder bath, it adheres more or less powder mass on the cage wires and at the same time the wire experiences a little cooling. After taking it out of the bath, the basket wire still has so much heat energy stored so that the absorbed plastic powder layer is completely warmed through, melts and forms a closed outer skin. By quenching in a water bath this outer skin becomes particularly smooth and shiny as a sheathing of the basket wires.

However, the known covering of a crockery or cutlery basket with plastic can be a Accumulation of water droplets between the plastic surface and the dishes or cutlery on the Do not completely prevent the basket frame. Furthermore, stuck water droplets produce the Dishes dry unsightly water stains on crockery and cutlery.

To improve the dripping behavior of the coated crockery baskets, it is known that To provide baskets with additional droplet arresters, or the meshes and grids of the basket design racks in the profile with a cutting edge or sawtooth shape (see EP-PS 0 186 157). Such measures complicate and make the production of the Washware carriers and only partially avoid their disadvantages. Looking for a remedy to the known disadvantages was recognized that in a new crockery basket with smooth and glossy plastic coating initially a hydrophobic behavior of the plastic coating sets in the washing process, which, however, after a long period of use of the crockery basket in the washing processes into a hydrophilic behavior.

On the basis of a method of the type mentioned at the outset, the object of the invention is based on the dripping behavior of the com with the rinsing or cleaning liquid Menden plastic coating of the crockery baskets or the like. With a view to optimization the cleaning and drying performance as well as for an energy-saving dishwashing operation improve.

According to the invention, this object is achieved by the method specified in claim 1 rens steps solved. Claim 8 faces the problem with a different solution variant. Advantageous developments of the method result from the following Subclaims.

The advantages achieved with the invention are a substantial improvement in drainage behavior in the crockery baskets. The inventive treatment of the Basket coating or the plastic surface becomes a hydrophilic surface property generated by the basket coating, through which the contact angle of a drop at the loading agitation with items to be washed is very small or extremely flat. This makes wetting its own Shaft of the plastic surface increased. Drops of rinsing water can be flat and thin train so that a quick drainage of flushing liquid is concerned. With such behan The number of crockery baskets exposed to the washing-up liquid or cleaning liquid is reduced also the amount of residual water bound in the meshes and grids of the basket a crockery basket not treated according to the invention, so that the crockery also NEN carried out energy-saving and water marks or the like. On the cutlery, glasses and Plates and cups are avoided.

Using the example of the crockery baskets and cutlery drawers used in dishwashers or crockery racks for the baskets should be provided with the method used according to the invention advantageously achieved effect of improving the water dripping behavior is described in more detail will.

An embodiment of the invention is shown purely schematically in the drawings and is described in more detail below. It shows

Fig. 1 is a dishwasher for the household with the Ge dish baskets according to the invention in a perspective view and

Fig. 2 is a section through the coated wire basket of a crockery basket, in an enlarged representation ver.

A household dishwasher ( 1 ) shown in FIG. 1 has a washing compartment ( 2 ) which can be closed at the front via a hinged appliance door ( 3 ). Inside the washing compartment ( 2 ), crockery baskets ( 4 ) above and below assigned spray arms ( 5 ), in which the items to be cleaned are placed, are arranged in superimposed washing levels so that they can be removed from the washing area. As a rule, two crockery baskets (lower and upper basket) are always provided, with a cutlery drawer ( 6 ) also being arranged so that it can be pulled out of the washing container ( 2) in a third washing level above the upper basket.

The crockery baskets (4 ) are made in a known manner from bent basket wires ( 7 ) and each form a basket base frame ( 8 ), in which one or more shelves or basket inserts ( 9 ) for cups, plates, depending on the type of associated washing , Pots etc. are detachably inserted if necessary. The metal wires of the baskets, which are bent towards the base frame (8 ) or towards the basket inserts, are coated with a plastic jacket ( 10 ) for reasons of corrosion and hygiene. According to known basket manufacturing processes, the baskets or their basket wires ( 7 ) are first bent, welded and cleaned. The uncoated baskets or inserts are then hung on stainless steel suspension wires in a device and initially heated over a predetermined period of time. When heated, the entire basket (or basket inserts) is immersed in a plastic powder bath. Depending on the dwell time in the bath, more or less plastic powder or sintered mass adheres to the wires. By absorbing the plastic, the basket wires ( 7 ) experience a certain cooling. After removing the basket and / or using it from the plastic powder bath, the wire has still stored enough residual heat that the applied powder layer is completely warmed through and forms a closed outer skin in the sintering process. Sudden quenching in a water bath can make the outer skin particularly smooth and shiny. This is the general state of the art, and according to the usual opinion, the smooth coating is synonymous with a rapid drainage of residual water after washing the dishes, so that this allegedly promotes the dripping behavior of washing liquid.

The applicant has found that in a particularly smooth and shiny art fabric surface, as it has a new crockery basket, creates a hydrophobic effect. the very smooth surfaces lead to droplets at the points of contact with the items to be washed struggles. But it was also found that a long time already be in the flushing mode the basket used exhibits such behavior less, i.e. through an "aging process" sets in behavior more hydrophilic.

The standard baskets according to the state of the art are usually made of polyamide 11 or Po lyamid 12. As a plastic, known vortex sintering powder made from these materials is advantageous usable. Polyesters, polyethylene copolymers and polyurethanes can also be used are set.

These polyamide 11/12 materials combine the properties of polyamides: <PA 6 <;<PA 6.6 <and polyethylene <PE <due to their chemical structure.

The physical and chemical properties depend on the stoichiometric ratio of the "methylene groups (-CH ₂ -)" and "amide groups (CONH)" in the macromolecule:

PA6 and PA6.6 Ratio 5 PA11 Ratio 10 PA12 Ratio 11 PE has only methyl groups

Continuous use temperature

PA6 80 to 100 ° C depending on the type PA6.6 85 to 120 ° C depending on the type PA11 and PA12 70 ° C to 80 ° C PE approx. 60 ° C

The oil resistance falls as the ratio of the methylene group increases.

Water absorption

PA6 8.5 to 11% depending on the type PA6.6 7.5 to 10% depending on the type PA11 1.8 to 2.2% depending on the type PA12 1.5 to 2.2% depending on the type PE 0.0%

As a result, however, there is a certain negative sensitivity to hydrolysis:
The higher the proportion of amide groups, the higher the water absorption, the more susceptible to hydrolytic degradation of the molecular chain. Depolymerization.

This is still catalyzed by strong acids and alkalis, which are forced into the rinsing liquor circulation are in season.

The aging process can thus be seen as a process of the above-mentioned effects, which is still through the soiling of the items to be washed can be viewed. That old man tion process should be artificially preferred by the method described, namely by thermo-oxidative processes on the surface of the substrate. This takes place at the Amide group undergoes depolymerization by hydrolysis. On the methylene groups takes place after a radical formation by carboxylation a depolymerization, which then leads to a better Water wettability leads. The same process can also occur after the radical formation via a Hydroperoxide formation take place. The preceding is a desired physical pre-damage by swelling of the substrate through water absorption and thus a surface enlargement change and / or a change in the crystalline structure.

Using this knowledge, the invention proposes that the Korbdräh te ( 7 ) be provided with a coating ( 10 ) of a rough or uneven surface ( 11 ), as shown in more detail in FIG.

According to the invention, the rough or uneven surface ( 11 ) of the coating ( 10 ) is produced by temperature and time changes in the coating process and / or by plastic powder materials of different grain sizes. This can be achieved in that the melting of the plastic powder mass on the basket wires is interrupted and the powder mass carried on is cooled prematurely. As a result of changes in temperature and time within the manufacturing process, the melting process is therefore not completely completed, so that a completely smooth formation of the surface is prevented.

A rough or uneven coating surface is specifically larger than the smooth surface che. Between the tips of the rough surface, a mass of drops pulls through capillary effect to form a larger surface (has a hydrophilic effect) and can therefore do better evaporate. In contrast, the smooth surface binds according to the prior art Technology is no longer water, but in a different way, namely in the form of a ball-like drop (hydrophobic surface). This leads to the fact that at the contact points with the items to be washed larger drop mass is retained, which then be a lot of energy to evaporate compels.

Another solution provides a so-called two-layer coating. The basket wires ( 7 ) are provided with coarse-grained plastic powder in a first coating process. Then, in a second operation, a coating of fine-grained plastic powder mass is applied to or melted onto the irregular, possibly already firm, uneven surface coating, which follows the rough surface. With this method, a significantly smaller amount of coarse-grained powder is sintered or adhered to the cage wires compared to the "one-layer process". The remaining amount of plastic from the very fine-grained material applied in the second step covers the coarse surface and follows the resulting troughs and peaks in the material, the peaks being rounded like an "orange peel".

There is also the possibility of coating the basket wires (7 ), which were provided with coarse-grained plastic powder in the first coating step, with a colored lacquer in the subsequent second step, which also follows the rough surface (11 ) of the solid powder mass, with the character of the uneven "rough" surface is preserved.

According to a further variant of a two-layer coating, the basket wires can be used in an ers th coating process can also be coated with fine-grained plastic powder. To then the powder is applied to the plasticized fine plastic surface mass a coarse-grained plastic powder embedded.

Most of the fine-grained powder is first sintered on and then returned to the plasti Fified mass is coarse-grained sintering powder on the same polymer basis, z. B. polyamide 11 and / or 12, or coarse-grained sintering powder made from another base polymer, e.g. B. Polyester, Embedded in polyethylene copolymer or polyurethane. Replasticizing is also conceivable embed crystallites of minerals such as titanium oxide, magnesium oxide, silicon dioxide or mixed crystallites.

A formulation of the plastic or sinter powder is also possible, with which in just one Operation can be coated. The suitable recipe for this preferably has 60% -95% plastic fine grain proportions and 5% -40% plastic coarse grain proportions.

Another method could be that one manufactures according to the state of the art th series baskets retains the smooth and glossy plastic coating and subsequently the surface coating of the basket wires of the baskets or inserts is roughened. This can can be achieved, for example, that the coated baskets or inserts with sand, Steel prisms, steel balls or similar. be stolen.

Under certain circumstances, it can be advantageous to treat only the "functional inserts" of the crockery or cutlery baskets or cutlery drawers ( 4 , 6 , 9 ) according to the aforementioned method. The basic basket environment could be left in the optically high-quality gloss standard. Depending on the manufacturing process, areas of the baskets or inserts that are in contact with the items to be washed could also be slightly melted down in order to achieve the rough surface. The other areas (e.g. grip areas, basket frames or the like) could be heavily re-melted in order to achieve the shiny surface.

Claims (9)

1. A method for the plastic coating of a wire basket, in particular a crockery basket or basket insert for dishwashers, the uncoated basket or insert being initially heated over a predetermined period of time and then provided with powdered plastic in the heated state, whereupon the powder mass adhering to the basket wires is melted and afterwards the basket is cooled, characterized in that at least the basket wires (7 ) which come into contact with the items to be washed are provided with a coating device ( 10 ) with a rough or uneven surface ( 11 ). 2. The method according to claim 1, characterized in that the rough or uneven surface ( 11 ) of the coating ( 10 ) is generated by temperature and time changes in the coating process and / or by plastic powder materials of different powder grain sizes. 3. The method according to claim 1 and 2, characterized in that the melting of the plastic powder mass on the basket wires ( 7 ) is interrupted and the applied powder mass is cooled prematurely. 4. The method according to claim 1 and 2, characterized in that the basket wires ( 7 ) are provided in a first coating step with coarse-grained plastic powder, and that then in a second step on the un regular, possibly already firm uneven surface coating a coating from feinkörni ger plastic powder mass or from a paint or melted or aufgetra conditions, which follows the rough surface (11 ). 5. The method according to claim 4, characterized in that the provided in the first coating step with coarse-grained plastic powder mass cage wires ( 7 ) are coated in the subsequent second step with a colored lacquer which follows the rough surface (11 ) of the solid powder mass. 6. The method according to claim 1 and 2, characterized in that the basket wires ( 7 ) are coated in a first coating process with fine-grain plastic powder, and that then in the plasticized fine plastic surface of the powder mass applied a coarse plastic powder or crystallites of minerals , such as titanium oxide, magnesium oxide, silicon dioxide or mixed crystallites are embedded. 7. The method according to claim 1 and 2, characterized in that the basket wires ( 7 ) are coated with plastic or sintered powder, the Re recipe preferably has 60% -95% plastic fine-grain fractions and 5% -40% plastic coarse-grain fractions. 8. A method for the plastic coating of a wire basket, in particular a crockery basket or basket insert for dishwashers, the uncoated basket or insert being first heated over a predetermined period of time and then provided with powdered plastic in the heated state, whereupon the powder mass adhering to the basket wires is melted and afterwards the basket is cooled, characterized in that the surface coating ( 10 ) of the basket wires ( 7 ) of the baskets ( 4 , 6 ) or inserts ( 9 ) is roughened. 9. The method according to claim 8, characterized, that the coated baskets or inserts with sand, steel prisms, steel balls or the like. be stolen.