Agitating – Having interrelated feed and discharge means – Including means to monitor or control operation
Reexamination Certificate
1999-10-07
2002-12-17
Cooley, Charles E. (Department: 1723)
Agitating
Having interrelated feed and discharge means
Including means to monitor or control operation
C366S134000, C366S136000, C366S138000, C366S140000, C366S152100, C366S153100, C366S160300
Reexamination Certificate
active
06494608
ABSTRACT:
BACKGROUND OF THE INVENTION
This concerns the development of a process which assures color uniformity, texture and viscosity in the production of paints specially for painting of metal objects, more specifically, car bodies.
Presently, the manufacture of paint by the conventional method involves a quite complex process and is formed by the following phases: weighing of the raw material, preparation, adjustment of color, coverage, adjustment of viscosity, quality control, canning and packaging. The raw materials which are necessary to produce a given color of paint are weighed in the quantities mentioned in a formula, placed on a pallet and taken, by the lifting truck, to the paint manufacturing plant which is awaiting the starting of the production. The raw materials, either solid or liquid, are weighed in different places, far from the production line, and we should point out that the accuracy of such weighed quantities depends upon the scales used which, in turn, should constantly be gauged so that precise results may be achieved in the weighing operations. Some raw material, which are added in large quantities (such as resins and solvents), are taken at the plant preparation area.
All raw materials which arrive at the preparation area are kept in tanks located in dikes. Each tank has its own pump which is driven by the respective feeding valve for raw materials and which is located in the piping which reach the plan, and in said piping system there is coupled a single flow meter which controls the quantity of the raw materials which have to be added to the mixing tank.
Initially, the operator connects one end of a hose to the pipe of the product which is to be added while the other end of the hose is placed against the mouth of the mixing tank, in such a way that in order to unload the raw material, the operator marks in the meter the quantity in weight (Kg) of the product and opens the feeding valve; the valve sends an electric signal to the pump (located in the dike) turning it on and transferring the product from the outside storage tank to the mixing tank, located at the plant and, in this manner, as soon as the quantity marked in the flow meter is reached the pump is automatically turned off.
The preparation phase consists of the addition, one by one, of the raw materials, following a given order and starting always with the products of larger quantity, followed by those of small quantity, with the resin being the first product to be added in the mixing tank, without stirring. It should be noted that if the resin is stored in drums, the operator should use a drum tumbler, which is kept in an appropriate place, taking it next to the mixing tank in order to proceed with the unloading of the resin and, if said resin is taken directly from the pipe system existing in the plant, the procedure is practically the same for the weighing or, if there is a pipe system feeding the plant, the addition process through the flow meter, as mentioned above.
Other products (additives) are added also by hand and under stirring, using pails and cans.
The whole addition work described above takes approximately 4 hours.
The dying or color adjustment process is performed by the manual addition, with use of pails, of the dying additives, with the color technician weighing first the empty pails where the dyes are placed and weighing the pails again when full, in order to identify the volume of concentrate materials which are placed in the tank under stirring, until reaching the appropriate color, with the pails being weighted once again in order to define the exact quantity which was added.
Then a small sample of the paint is taken to the quality control laboratory, which paints a small plate at the painting cabin, with said plate being dried, in open air, for 5 to 30 minutes, and than in a stove, at 60 to 180° C. for 10 to 30 minutes, waiting the cooling down of the plate and comparing it with a standard sample, either visually or through instruments. If the color is not within the required standards, the color technician makes the necessary adjustments and repeats the procedure in order to adjust the color until the paint is within the referred standards. Normally, in order to adjust the color, the color technician repeats from 3 to 4 times the above mentioned process and this takes, on average, 4 hours. It should be pointed out that if the color technician adds the wrong dye or in an exaggerated amount, it is impossible to adjust the color and, therefore, the whole lot is lost.
After the adjustment of the color a sample is taken and sent to the quality control department for the adjustment of viscosity and tests. The viscosity adjustment is made on the sample and performed through the identification of the volume of solvent contained in said sample, when the total volume of solvent to be added to the mixing tank is computed.
In this phase, the operator should bring the solvent to adjust the viscosity, weighing the solvent in pails, cans or drums (depending upon the quantity of solvent to be added) and pouring it into the mixing tank. If the use of drums is necessary, a drum tumbler equipment should be used, which is kept in an appropriate place, taking it next to the mixing tank in order to proceed with the unloading of the solvent.
In order to wash the tank or bowl, the operator fills a can with cleaning solvent, taken from the closest solvent pipe, pours it by hand and cleans the walls with a brush. After this starting work, the operator pours more solvent in order to rinse, and this dirty solvent, which comes from the tank or bowl, is drained through a draining cock into a drum, which is taken to the shipping platform of the plant in order to be removed to the so called “solvent recuperating” plant, which distills and recovers the solvent, which is returned to the plant through a pipe system, to be used again.
When the paint is ready, a sample is taken and sent to the quality control department, where the following tests are performed: color, coverage, solids, specific weight and viscosity. Presently, these tests are performed as follows:
Color: is the determination of differences in shade between a film and its respective standard, when looked under natural light and in which a sample is taken out, the viscosity is adjusted and the paint is applied on a steel plate, awaiting for 15 minutes to evaporate the light solvents and, after said period of time, the sample is placed on a stove under 60° C. for 30 minutes. The average time for the test is of 1 (one) hour, but in the case of white synthetic enamel, the color technician needs
16
hours for the drying of the paint in open air, and it may take up to 5 days in order to adjust the color and to finish the tests.
Specific weight: used for the determination of the specific mass of liquid paints, solutions and dispersions, the result of which is expressed in g/cm
1
, being traditionally referred to as density: the method is based upon the relationship between mass of a substance and its volume.
For this, a container, the volume of which is known, is filled with a sample at 25° C., the container is weighed obtaining the specific weight, with the average time spent to perform the test being approximately 10 minutes.
Solids: is the percentage of solid material existing in a paint. The content of non volatile material in a product is not an absolute quantity, but depends upon the temperature and time of heating used; the recommended temperature and time is 120° C. for 1 hour of stove, and, in this method a fixed quantity of the product is weighed, spread in a container and taken to a stove for 1 hour, after said period, the sample does to the drying oven for 30 minutes and then is weighed in a laboratory scale in order to obtain the percentage of solid material; the average time for said tests is 2 hours. If the percentile value of solids is out of the specified standards, the adjustment is made with the addition of resin or dyes and if during said addition a larger quantity is used, the whole lot is rejected.
Viscosity: in a quite empirical w
Auad Rogerio Batista
Retamal Antonio
Cooley Charles E.
Ostrolenk Faber Gerb & Soffen, LLP
Renner du Pont Tintas Automotives e Industriais S/A
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