METHOD FOR COLORING HOLLOW GLASS OBJECTS

Description

[0001] The present invention relates to a method of molecular change with vitrifiable colors, and in particular to a method for the permanent coloring of hollow glass objects, such as bottles and containers of different types. Still in particular, the present invention relates to a method for the permanent coloring of glass objects, obtained by means of a mixture of colored powder and a medium (for example, oil), diluted with water.

[0002] Patent No. IT-B-0001359872 in the name of the applicant is known, which describes a method for the permanent coloring of glass objects, which consists in the electrostatic application of a layer of colored glass powders on the objects and subsequent melting of said powders with consequent partial incorporation in the liminal layer of the external surface of the objects themselves.

[0003] This known method for coloring glass objects has the problem that requires the vaporization and polarization of the glass objects to be colored.

[0004] Object of the present invention is solving the aforementioned prior art problems by providing a faster and more flexible method of molecular change with vitrifiable colors, which does not require the vaporization and polarization of the glass objects to be colored and allows carrying out several coloring steps at the same time, coloring and obtaining greater coverage, partial colors, shades, using more colors on the same object, creating both visually and tactile special effects. Document WO2004035499 discloses a method of colouring hollow glass, similar to the method of the present invention.

[0005] The above and other objects and advantages of the invention, as will emerge from the following description, are achieved with a method of molecular change with vitrifiable colors such as claimed in the main claim. Preferred embodiments and non-trivial variants of the present invention are the subject matter of the dependent claims.

[0006] It is understood that all attached claims form an integral part of the present description.

[0007] The present invention will be better described by a preferred embodiment thereof, provided by way of non-limiting example, with reference to the attached drawings, in which the only Figure 1 shows a schematic view of a plant that can be used for the method according to the present invention.

[0008] Referring to the Figure, the molecular change method with vitrifiable colors, in particular the method for coloring hollow glass objects, according to the invention includes the following steps: a step of transporting the hollow glass objects to be colored, for example bottles, to a coloring booth 2A, 2B, 2C by means of a transport system 1 comprising means for locking the objects, for example configured food silicone expansion mandrels to go down inside the mouth of the glass object to be transported; a step of moving the objects into the coloring booth 2A, 2B, 2C by means of handling means K, for example a chain with spindles; a step of coloring, preferably with vitrifiable colors, said hollow glass objects by means of a reciprocator 3 which allows the application on their external surface of a pasty mixture of glass powder and a binder ("medium"), for example an oil, diluted in water, for example with spray application; a step of leaving the hollow glass objects from the coloring booth 2A, 2B, 2C by means of first advancement means 4, for example a conveyor belt 4, and for transferring said objects by means of transferring 5, preferably a robot 5, in a cooking oven 6; a step of fixing the color to the surface of the hollow glass objects by melting inside the cooking oven 6, performed by heating the objects to a temperature of about 600 °C, preferably at a temperature between 570 °C and 650 °C, in such a way that the applied colored pasty mixture and the glass surface of the objects merge with each other and the colored mixture remains partially incorporated in the external surface of the hollow glass objects; a step of gradually cooling the hollow glass objects, subsequent to the melting step in the firing oven 6, by means of a calibrated descent, maintaining a constant descent temperature in a cooling zone 6A, in order to avoid the tensioning of the glass, so as to bring said objects to an internal temperature between 60 °C and 40 °C.

[0009] The glass powders used in the method for coloring hollow glass objects according to the invention have a dilatometric coefficient having a value between 75x10 -7< and 95x10 -7< , and must be free from lead, lithium and cadmium.

[0010] The red and yellow shades and their derivatives can only be obtained through the use of cadmium.

[0011] To comply with the main regulations, in particular "Proposition 65", one embodiment of the method according to the invention envisages the use of red, yellow and color derived glass powders, containing encapsulated cadmium (not harmful to those who uses it) which are applied, mixed with the binder, in a first layer on the surface of the glass objects to be colored; in a subsequent step, a second layer of colored pasty mixture is applied over the first layer, using glass powders free from lead, lithium and cadmium. The first layer of yellow and red glass powders containing encapsulated cadmium is thus incorporated between two layers free from unwanted materials, allowing to comply with the regulations.

[0012] Preferably, the step of transporting the objects into the coloring booth 2A, 2B, 2C is preceded by the following steps: a step of loading the hollow glass objects to be colored, for example bottles, on second feeding means 7, for example a conveyor belt 7; a step of flaming the hollow glass objects by means of a flaming cabin 8 configured to eliminate excess impurities and comprising at its inlet third advancement means 7A, for example a first screw 7A, configured to divide and time the incoming objects in the flaming booth 8. Said flaming booth 8 preferably comprises at least one first, second, third, fourth, fifth and sixth flaming unit, said first and second flaming units being positioned respectively at the entrance and exit of the flame 8, and the third, fourth, fifth and sixth flaming units being oriented towards the pursuit of objects; a step of cooling the hollow glass objects subsequent to the flaming step, by means of a cooling station 9 configured to decrease the temperature of the objects; a step of cadenced advancement of the hollow glass objects by means of fourth advancement means 1A, for example a second auger 1A, configured to separate said objects from each other for the purpose of entering the coloring booth 2A, 2B, 2C.

[0013] Preferably the step of gradual cooling of the objects, subsequent to the melting step in the baking oven 6, is followed by the following steps: a step of unloading the hollow glass objects onto a handling line 10, for example by means of a stacker or compactor 11, a step of conveying the objects in a palletizing robot 12.

[0014] The method of molecular change with vitrifiable colors according to the invention allows obtaining numerous advantages: it does not require to vaporize the objects to be colored, and to polarize the line; it allows greater speed in changing the size of the object to be colored; it allows greater speed in the application of colored powders; it allows carrying out several coloring steps at the same time and obtaining a greater coverage; it allows obtaining partial colors, even faded ones; it allows coloring the same glass object with more colors; it allows creating special effects, both visually and tactile.

Claims

1. A method for coloring hollow glass objects, preferably in an upright or inverted position, comprising the following steps: - a step of transporting the hollow glass objects to be colored to a coloring booth (2A, 2B, 2C) by means of a transport system (1) comprising means for locking the objects, - a step of handling the objects in the coloring booth (2A, 2B, 2C) by means of handling means (K), - a step of coloring, with vitrifiable colors, said hollow glass objects by applying on their external surface a pasty mixture of glass powder and a binder, in the coloring step the use being provided of glass powders in red, yellow and derived colors, containing encapsulated cadmium which are applied, mixed with the binder, in a first layer on the surface of the glass objects to be colored, while, in a subsequent step, a second layer of colored pasty mixture is applied above the first layer, using glass powders free of lead, lithium and cadmium in order to incorporate the first layer of yellow and red glass powders containing cadmium encapsulated between two layers free of lead, lithium and cadmium, - a step of exiting the hollow glass objects from the coloring booth by means of first advancement means (4) and transferring said objects (5) into a baking oven (6) through transferring means, - a step of fixing the color to the surface of the hollow glass objects by melting inside the cooking oven (6) so that the applied colored pasty mixture and the glass surface of the objects merge with each other and the colored mixture remains partially incorporated in the external surface of the hollow glass objects, the melting inside the cooking oven (6) being performed by heating the objects to a temperature between 570 °C and 650 °C, and - a step of gradually cooling the hollow glass objects, following the melting step in the cooking oven (6), in a cooling zone (6A).

2. Method according to claim 1, characterized in that the melting inside the cooking oven (6) is performed by heating the objects to a temperature of about 600 °C.

3. Method according to any one of the preceding claims, characterized in that the cooling step is carried out in such a way as to bring said objects to a temperature between 60 °C and 40 °C.

4. Method according to any one of the preceding claims, characterized in that the glass powders used have a dilatometric coefficient having a value ranging from 75x10-7 to 95x10-7.

5. Method according to any one of the preceding claims, characterized in that the step of transporting the objects into the coloring booth is preceded by the following steps: - a step of loading the hollow glass objects to be colored on second advancing means (7), - a step of flaming of the hollow glass objects by means of a flaming booth (8) configured to eliminate excess impurities and including at its entrance third advancement means (7A) configured to divide and time the objects entering the flaming booth, - a cooling step of the hollow glass objects following the flaming step, by means of a cooling station (9) configured to decrease the temperature of the objects, - a step of cadenced advancement of the hollow glass objects by means of fourth advancement means (1A) configured to separate said objects from each other for the purpose of entering the coloring booth (2A, 2B, 2C).

6. Method according to claim 5, characterized in that said flaming booth (8) comprises at least one first, second, third, fourth, fifth and sixth flaming device, said first and second flaming devices being positioned respectively at the inlet and outlet of the flaming booth (8), and the third, fourth, fifth and sixth flaming devices being oriented to the pursuit of objects.

7. Method according to any one of the preceding claims, characterized in that the step of gradually cooling of the objects, subsequent to the step of melting in the cooking oven, is followed by the following steps: - a step of unloading the hollow glass objects on a handling line (10), - a step of conveying the objects in a palletizing robot (12).