This invention concerns aerylic/urethane UV drying system. 2-component (=2C) polyurethane paints are based on the reaction of two materials, polyisonate and polyol ( polyacrylate and/or polyester). This forms a polyurethane combination. This system is commonly in use throughout the world. Both components are saturated products, and consequently they will not react with UV-radiation. The initiator used does not directly influence in the saturated products, but in the minor OH-groups existing in them. These groups will start a reaction, which is not sufficient for a complete hardening. It only gives a surface hardness to a certain exten , by using drying. The drying is based on heat produced by air circulation or infrared radiation. Both of these require energy and time to a great extent. The drying of normal 2 component urethane paints lasts about 45 minutes with the temperature of 60 C and 25-30 minutes with the temperature of 80 C when painting a car- Drying times have been shortened to some extent with the help of UV-radiation, but according to the invention the drying time has really been managed to shorten, even so that a car is practically dry immediately when moved through the paint shop and drying unit. Drying of mud-guards will take about two minutes.

This has been achieved by addinα initiators and additional components to the paint. UV-initiator alone does not dry the paint thoroughly, but it needs additional components according to the invention. Regardless of the speed of drying any external heat will not be needed, but the painted surface stays approximately at the room tempera- ture, i.e. about 20-30 °C.

With the help of additional components the paint will get much oxygen, and plenty of OH-groups are formed. This speeds up the hardening process on the level as mentioned hereinabove . According to the invention the process will be carried

out by an UV-radiation on a certain frequency and at a suit¬ able distance. According to the invention the radiation on the frequency of 240-260 ,u is used. This will be focused to the surface to be dried from a distance of 60 cm at best. In practise the radiation is focused to the surface to be dried with the help of a computer and so the drying functions best by using the drying equipment.

As an example of the invention the following paint and its drying is presented: Type of paint: polyacrylate- and/or polyester. Hardener: isocyanate.

Thinner and/or additional components: initiator + DBTL + Dabco. Drying: UV-ray, frequency 240-260 ,u. Mixture: Polyacrylate 2 parts, 1 part of isocyanate + appr. 20 % UV-additional components. Resul : evaporation 5 minutes drying - ^' 1-2 minutes hardness close to final • polish good adhesiveness good grindability after 1/2 hour (with a machine) chemical durability good (does not dissolve in gasoline energy consumption whole coating 6 minutes/2kW (former appr. 16 kg oil heater)

Does not cause changes in plastics with heat. Chemical reaction:

Polyisonate Polyol (and/or polyester) includes includes combinations all versions

H

®- N - - 0 polyurethane -©

Reaction is the formation of a polyurethane binding with add¬ itional component. With this together with UV-light the reaction will b e accelerated to its end in a few minutes. Additional component:

Initiator the chemical formula is the form or derivate of

CH,

C C - OH

0 i ^υ o

DBTL = Dibutyltin dilaurate Dabco = Triethylenediamine UV-light herz 240-260 ,u

In connection with normal car painting the following relation- ship can be succesfully utilized:

2C paint 10 weight units hardener 5 " "

UV-thinner - 3 " " ^'

The thinner is, for example, as follows: - xyleπe 55 weight units

10 % DBTL xylene 2 " or dabco 10 % initiator 4 " "

BA (butylacetate) 39 " ^ 100 weight units

Xylene and butylacetate can be replaced by solvents suitable for polyurethane paints depending on various circumstances .

The invention is known in the frame of the following patent claims.

The basis to the reaction is the joint effect of the initiator and DBTL created by UV-lamps, with frequency of 240-275 u, and thus the UV-ray unites with the absorption curves on Initiator Darogur 1116 and Darogur 1173 as described in the charts.

If DBTL alone is used, the sprayability and the glance will deteriorate and "Pot Life" becomes impossible. There

will appear evaporation bubbles. The UV-initiator affects only irr the initial reaction as deep as the layer thickness allows (clear lacquer or pigment).

The joint effort of both components creates a reaction with the following results:

1. There are no damages caused by heat. The maximum temperature is 40 centigrades.

2. No change in the shades of colour.

3. Does not turn yellow. 4. No bubbles even in thicker layers.

5. Depending on the reactivity of Polyacrylate and Poly- isosyanate the paint coating can be polished after 30-40 minutes .

The optimum result will be achieved when the distance of the lamp is between 30-60 centimetres, and the drying time approx. 1-2 minutes. The lamp in question (description enclosed) is t.he only type of lamp suitable for the purpose so far. When using other lamp types there is no reaction at all. ^' The exact dosing of compunding agents in relation with the binding agent is a condition precedent for the hardening process as a whole. This is a result of long lasting experiments.

The suitability and hardening of clear laquers and pigmented paints under varying occasions, such as car painting and industrial coating, can be regulated with exact dosing of compunding agents.

The invention is based on the combined influence - not separately - with which a fast hardening of high glance products can be reached without deteriorating the glance or changing the characteristics of the paints. The energy consumption is next to nil. The radiation of the UV-lamps does not include IR-rays.