ITMI961728A1 - METHOD FOR HOT AIR APPLICATION OF THERMOFUSABLE POLYMER POWDER COMPOSITIONS - Google Patents

Description

Title: "METHOD FOR HOT AIR APPLICATION OF THERMOFUSABLE POLYMER POWDER COMPOSITIONS"

TEXT OF THE DESCRIPTION

Powder coatings are currently used almost exclusively in industrial plants as they require static and bulky systems such as cooking ovens and application booths.

To overcome these limitations, flame guns have recently been patented that allow the application of thermoplastic powder paints in an open atmosphere in the middle of a ring flame that melts the projected powder paint which is deposited melted on a support, however the presence flame limits their use only to thermoplastic and high molecular weight paints and furthermore to avoid the combustion of the deposited and melted paint it is necessary to continuously and rapidly move the flame projection point.

To apply "hot-melt" glues, heat guns are used which contain glue sticks compressed against a heated nozzle that melts them and only allows them to be spread.

There are also commercially available hot air blowers that are used for packaging with shrink film.

The use of hot air generating devices for the application of hot melt powder compounds is currently not known.

We found that the flame for the too much heat supplied charred the powder paint already in the nozzle, we thought that by replacing the flame with a flow of hot air it was perhaps possible to melt and harden the paint and therefore we deposited the paint with a normal electrostatic gun. powder on some aluminum panels, then using a normal variable temperature hot air blower used for the shrink wrapping we projected the hot air into the surface covered with powder paint but the first panels were not acceptable because the flow rate air was too strong and much of the paint was blown away.

But then we tried to decrease the air flow by partially covering the air intake and surprisingly found that by adjusting the air intake not only can the paint melt and harden without blowing it off but it is also possible once. melted make it dilate and expand it as you do with a brush.

Having found that the idea of using hot air instead of the flame was valid, we then put together the powder projection gun and the hot air blower, making sure that the hot air coming out wrapped the nozzle of the gun and in this way the powder was going to settle partially melted, then we increased the temperature of the dryer until the projected powder was deposited in the molten state and then by suspending the delivery of the powder it was possible to make it reticulate.

Subsequently we tried to apply it in the molten state on non-conductive supports and we found that precisely because it was deposited when melted it adhered perfectly to wood, plastic, paper, fabrics etc ... and if applied in the molten state even on metal supports it is no longer necessary that the gun is either tribo-loading or electrostatic.

Therefore, according to the method invented by us, which consists of the way of using one or more appliances composed of one or more guns for spraying the paint or glue or powder compound and of one or more hair dryers that can deliver hot air to Variable temperature and air flow rate, possibly with a single nozzle for which the gun and the hairdryer can be used simultaneously or alternatively according to the needs, it is possible to apply any compound or polymer in thermofusible plastic or hardening powder on the most varied supports or surfaces.

These devices are practically without limitations because the powder product to be applied can be projected into powder from an adjustable close distance and can be deposited on a surface in a molten or powdered state and, subsequently or simultaneously, using the fon part, melt it and / or heat cross-link it. , or by using the hair dryer first, you can preheat the surface on which to apply the polymer powder with the gun and melt it during or after application.

Furthermore, being a compact device, it can be used alone or in series, it can be mobile or fixed and with it you can paint static or bulky surfaces or it is possible to paint small surfaces even for retouching by applying the molten paint at a temperature lower than the cross-linking temperature. to make it dilate and then by increasing the temperature of the delivered air, make it reticulate.

With the same technique, thermosensitive supports can also be painted or a photo-curable powder paint can be applied, melting it and subjecting the applied film to UV irradiation while still hot or after cooling, or it can be painted with thermosetting powder paints by melting them and making them dilate by checking that are perfectly extended and without defects and subsequently can be thermoset when you want and with any heat source such as hot air, flame, IR ovens, EB etc ...

In order to better illustrate our invention, we give below some practical and non-limiting examples of the invention itself.

Example 1 Using at the same time the gun and the hairdryer with hot air emission at the speed of 2200 feet minute and at the temperature of 250 ° C a hybrid Polyester-Epoxy powder paint composed of:

Alftalat AN 783 390

Epoxy resin (EEW 700-900) 180

Additol XL 496 30

Degassing agent 5

Solid white 105

Ti02. 290

was sprayed melted on a steel sheet having the dimensions of 6 x 15 cm covering it uniformly with a thickness of -60 μ then interrupting the spraying and at the same time raising the air temperature to ~ 500 ° C only hot air was projected for 2 minutes to make it reticulate.

The sheet was then subjected to analysis tests by comparing it with a sheet painted in the traditional way and hardened in an oven at 180 ° C for 20 minutes and the comparison resulted equal to the standard.

Then just to highlight the goodness of our discovery, that you can use hot air to melt and harden a thermosetting powder paint, we applied this same paint with only the gun part on a plate and then using the hair dryer part with flow rate of hot air lowered to 500 feet / minute, reducing the opening of the air intake to prevent the deposited dust from being removed and with the temperature set at 200 ° C we made the deposited paint melt and expand and after melting we raised the flow at 2000 feet / minute and the temperature at 400 ° C and held this condition for 3 minutes.

This sheet was also hardened like the one hardened in the oven at 180 ° C for 20 minutes.

Example 2 With the same procedure of Example N. 1 a Polyester - Polyurethane powder paint composed of:

Alftalat AN 745 456 Additol XL 432 114 Additol XL 496 30 Degassing agent 5

TÌO2. 395

Example 3 With the same procedure of Example N. 1 a transparent acrylic paint in powder form composed of:

was sprayed melted on 2 steel sheets.

Then a sheet was subjected to analysis tests by comparing it with a sheet painted in the traditional way and hardened in an oven at 180 ° C for 20 minutes and the comparison resulted equal to the standard.

Then from the second sheet painted and hardened with a steel brush we abraded a part of the deposited paint and then with the same procedure reapplied the paint on the abraded part and then interrupting the spray with hot air maintained at the same temperature and increasing the speed. we dilated the paint applied in the molten state so that the retouching was uniform.

Then by reducing the emission speed and increasing the air temperature to 500 ° C, the paint was crosslinked in 2 minutes.

The second retouched sheet was also similar to the standard.

Example 4 A UV curable clear coat consisting of

was projected in the molten state onto 2 wooden boards covering them with a thickness of ~ 100 μ, then one was subjected again with the melted varnish to UV irradiation for 30 seconds while the other was left to cool and after a few days this too it was subjected to the same irradiation with the cold applied paint for a period of 1 minute and to our surprise also the second tablet subjected to the acetone test with the cotton swab passed 100 back and forth passes.

Example 5 A thermoplastic powder paint for road signs consisting of 600 parts of Mowilith 35-73 (a vinyl acetate-maleate copolymer from Hoechst) and 300 parts of fixed white and 100 parts of titanium dioxide was applied to asphalt in the state cast using a special device equipped with a gun and hairdryer with a projection nozzle positioned 5-10 cm from the ground and mounted on a mobile trolley equipped with a compressor and generator.

The flow of hot air from the hairdryer was increased to 2200 feet / minute and at a temperature of 700 ° C and the speed of the trolley was kept at 7-10 Km / h.

Five minutes after applying it and letting it cool, it was subjected to adhesion and abrasion resistance tests resulting in perfectly adherent and wear-resistant.

Claims (8)

CLAIMS 1. Method for simultaneous or subsequent application and / or thermofusion with possible simultaneous or subsequent thermosetting of polymers or powder compounds that are thermofusible through the use of devices composed of one or more guns to project and apply the powder products and by one or more generators and hot air convectors at variable temperature, speed and flow rate and using the two parts of the appliance simultaneously or individually to possibly preheat the surface to be coated and / or to apply and / or melt and / or possibly harden the product applied. 2. Method according to claim 1, in which the two component parts of the appliances can have a single nozzle for the projection of both the powder product and the hot air or they can be mounted separately and / or in series with the possibility that the hot air convector, if mounted in series, is placed first to preheat the surface on which to apply and / or after the gun part, to melt and / or harden the applied product. Method according to claim 1 wherein the gun part for projecting the powder product can be electrostatic or triboelectric or only projecting the powder product. 4. Method according to claim 1 wherein the part of the hot air generator and convector appliances is composed of electric resistances or other sources which generate heat at adjustable temperatures and of an adjustable air intake which conveys it with variable flow rate and speed crossing the heat source on the surface to be treated with preheating and / or melting and / or terraohardening. Method according to claim 1 wherein the hot-melt powder polymers can be paints, glues, insulating and protective layers and so on. The method according to claim 1 wherein the hot-melt powder polymers can be thermosetting or thermoplastic. 7. Method according to claims 5-6 wherein the hot-melt and thermosetting powder polymers can be selected from the following groups: A) Epoxy or glycidyl compounds in combination with di or polyamines, or substituted dicyandiamides and / or dicyandiamides, or carboxylated saturated and unsaturated polyesters, carboxylated acrylics or polyanhydride or polycarboxylic compounds. B) Hydroxylated compounds such as saturated and unsaturated polysts, acrylics and the like, in combination with polyanhydrides, or blocked polyisocyanates, or polyidions. C) Carboxylated compounds such as polysts or acrylics in combination with hydroxyalkylamides. D) Unsaturated polyesters and / or acrylic acrylates and the like, in combination with photoinitiators and subsequent use of UV lamps or in combination with dialkyl or diacyl peroxides, or peroxyesters or peroxyketals thermoactivated at temperatures above the melting point. E) Mixtures of A-B-C-D. 8. Method according to claims 5-6 wherein the thermoplastic powder polymers can be selected from the following groups: A) Poly (meth) acrylates such as for example polymethacrylate, polycyclohexyl (meth) acrylate, polyisobornyl (meth) acrylate, polytrifluoroisopropyl methacrylate and the like. B) Polyesters such as polyethylene terephthalate, polybutylene ether phthalate, polypropylen terephthalate, polyethylene isophthalate and the like. C) Polyolefins and polyol-olefins such as polyethylene, polypropylene, pot, acrylcarboxylated polyethylene copolymer and the like. D) Polystyrene, polystyrene oxide, ABS and polyhydroxy oxides. E) Vinyl and / or vinylidene polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, polyvinyl chloride (PVC), polyvinyl formal, polyvinylcarbazole and the like. F) Polyamides such as Nylon and the like. G) Polycarbonates. H) Cellulosic derivatives such as vinegar butyrate, vinegar propionate, triacetate and the like. I) Thermoplastic petroleum resins. J) Indenic, coumaronic, cycloparaffinic and similar resins.