GB2444617A

GB2444617A - Powder coating material

Info

Publication number: GB2444617A
Application number: GB0723530A
Authority: GB
Inventors: Dale Windridge
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-12-06
Filing date: 2007-11-30
Publication date: 2008-06-11
Anticipated expiration: 2027-11-30
Also published as: GB2444617B; GB0723530D0; WO2008068464A1

Abstract

A powder coating material has a powder (epoxy, polyester, etc.) in which is bonded hollow glass or ceramic micro spheres having a melting point in excess of 200{C. The micro spheres typically have a size in the range 10 - 40 microns. The ratio of powder to micro spheres may be 5:1 by weight. Such a powder coating material has thermal insulation properties as well as anti-condensation properties. The material may be mixed with an infra red reflecting substance to provide the coating material with infra-red reflecting properties.

Description

* 2444617

POWDER COATING MATERIAL

This invention relates to a powder coating material.

Powder coatings have been applied to objects on an industrial scale since the 1970s and the global average annual growth for powder coatings is thought to have been approximately 7 -9%. Thermoplastic resins were initially employed to coat objects usually by heating the component and immersing in a fluidised bed of the thermoplastic resin. Thermosetting powders have been developed for wider fields of use, since such powders have many advantages including that they are easier to apply using electrostatic attraction. Such powder is produced by IGP IG Pulvertechnik AG of Kirchberg, Switzerland. The powder is usually placed in a fluidised bed and passed through a gun where an electrostatic charge is introduced. This means much larger and complicated shapes can be coated. l'here is less powder required during the application process; superior cured film properties, as well as being able to apply powders with a lower thickness than with thermoplastic resins.

Powder coatings are particularly, although not exclusively, used for architectural objects where it is required to coat, for example, steel railings, balustrades, stairways or staircases, fire escapes, security gates and shop fittings.

There is in the UK, Building Regulation Part M2004 which requires handrails and door handles, to be not cold to touch, i.e. they are to be warm to the touch. Such warm to touch handrails are needed where there are flights of stairs, ramps and landings, so that people are not deterred from using the rails because they are unpleasantly cold to hold on to. It is also desirable for the handrail to be slip-resistant and hard wearing.

It is known to produce a liquid paint containing a ceramic additive of high strength ceramic micro spheres to provide the liquid paint with a radiant heat reflecting, insulating, thermal barrier coating and such a paint is produced by Fly-Tech, P.O. Box 216, Melbourne, Florida 32902, U.S.A. Hitherto, however, it has not been thought possible to provide a thermo setting powder coating material with high thermal insulation properties.

According to, this invention there is provided a powder coating material including a powder having hollow elements formed therein, said hollow elements having a melting point in excess of 200 C.

Advantageously, the hollow elements have a size in the range 10 -40j.im.

Conveniently the hollow elements are one of glass or ceramic micro spheres.

Advantageously, the hollow elements are substantially evacuated, preferably to 10% or less atmospheric pressure.

Alternatively, the hollow elements are filled with a gas, which may be air or an inert gas.

Advantageously, the ratio of powder to hollow elements is in the range 90% to 60% by weight, and, preferably, approximately 5:1 by weight. Any addition of micro spheres or material that has a higher insulation value than the powder could be advantageous, in some circumstances.

Conveniently, the powder is a resin made of one of, or a combination of or a modified epoxy, polyester, polyurethane, acrylic or PVDF.

According to a feature of this invention, there is provided a method of making a powder coating material including the steps of producing a powder having a desired colour and formulation, grinding the powder to a desired size, and bonding hollow elements having a melting point in excess of 200 C to the ground powder.

Advantageously, the hollow elements have a size in the range 10 -40j.im.

Conveniently, the hollow elements are one of glass or ceramic micro spheres.

Advantageously, the hollow elements are substantially evacuated.

Prefi.rably, the ratio of powder to hollow elements is 5:1 by weight.

Such bonding is necessary because the powder is much denser than the hollow micro spheres. If the two components are mixed and not bonded, the micro spheres will float to the surface when the mixture is used in a fluidised bed for spraying, resulting in an uneven distribution of micro spheres with the powder when sprayed on to a work surface. Further, it has been found that if the micro spheres are added to the powder and the combination is then ground, the micro spheres become crushed.

Bonding is a process of adhering (bonding) the micro spheres to the powder.

When the powder has been manufactured to the desired colour and formulation, it is mixed at a ratio of approximately 5:1 with the micro spheres. The combined formulation is then stirred until an even distribution has been achieved. It is gently heated until the powder becomes tacky. The micro spheres then stick to the powder particles.

In one embodiment, graphite is added to provide the material with infra-red reflecting properties.

The evacuated glass micro spheres provide the powder coating material with improved thermal resistance by the spheres substantially reducing internal thermal conductivity. The problem in cold weather of known powder coatings having poor thermal insulation properties, where for example prolonged contact of a hand with a cold metal rail, absorbs heat from the hand, is then overcome by the use of the present invention. Thus, by increasing the thermal insulation properties of the paint coating, the heat transfer between a user's hand and a handrail, for example, is reduced making the handrail more comfortable to a user.

In cases where price is a consideration or where very good thermal insulation is not required, or where colour is unimportant, ceramic spheres which are less expensive than glass spheres may he used.

it will be understood that conversely from providing heat insulation properties to the powder coating material, the introduction of hollow elements will also provide protection from excess heat, for example from the sun. The powder coating material may also be used as an anti-condensation coating. In a development of the powder coating material, graphite is introduced to provide the material with infra-red reflecting capabilities.

The invention will now be described, by way of example.

it is known for powder coating material to be a powder of one of, or a combination of, or modification of epoxy, polyester, polyurethane, acrylic or PVDF.

Polyester, polyurethane, acrylic and PVDF are generally used for outside use; epoxy is used for internal objects, as it is not UV stable but is used as a primer, since it has good waterproof properties. It is currently expected that in this invention polyester powder coatings will he most commonly used, although the invention is not intended to be so limited.

Either, thermoplastic or thermosetting powders, known per Se, may be used in dependence upon requirement. Typically, the powder is ground to a size of about 120 microns.

The powder is mixed with hollow spheres, sometimes referred to as micro spheres or bubbles, in the ratio of five parts powder coating material to one part glass or ceramic spheres by weight until the spheres are substantially evenly distributed in the powder coating material. The glass spheres may be 3MTM ScotchliteTM glass bubbles S22, produced by 3MTM Company of St. Paul, Minneapolis, U.S.A., but it is to be understood that suitable micro spheres from other manufacturers may be used.

Glass is preferred because it does not have a pigment which means it can be used in a topcoat without alfecting its colour. Thus, glass having a very good transparency is preferred. However, if ceramics are used, the desired thermal insulation could he achieved in, for example, a primer.

The combination of powder and micro spheres are gently heated until the powder becomes tacky, whereupon the micro spheres adhere to the powder particles.

It is desired that the micro spheres have a size in the range 10 -40.tm, since otherwise the spheres will produce a roughened coarse surface when applied to an object, although in some circumstances this may be desired. The spheres may he glass or ceramic in dependence upon requirements and the spheres may be 1 5 substantially evacuated, preferably to 10% or less atmospheric pressure.

Alternatively, the spheres may be filled with a gas, such as air, or an inert gas at a pressure, which may be at, above or below atmospheric pressure in dependence upon requirements.

The ratio of powder coating material to spheres is dependent upon requirements; the more micro spheres the better the insulation, but the maximum amount of spheres that can be used will depend on the strength of the bonding agents within the paint. For example, if the paint ratio has too much glass it will become brittle and crack, or, taking it to the extreme, end up as an aggregate. Also, it is believed that if the concentration of spheres is too great, then the resistance of the resultant powder coating material to chipping will be reduced.

It will be appreciated that, as well as providing objects to which the powder coating material of this invention is used with thermal insulation, the spheres facilitate enhanced grip and reduced wear capabilities. Moreover, the material will have anti-condensation properties.

In a further embodiment, a material such as graphite is added to the powder and micro sphere combination to provide a coating material having infra-red reflecting properties. The graphite may be added prior to bonding the micro spheres or at the bonding step.

Claims

CLAiMS: 1. A powder coating material including a powder having hollow

elements formed therein, said hollow elements having a melting point in excess of 200 C.
2. A material as claimed in claim 1, wherein the hollow elements have a size in the range l0-401.tm.
3. A material as claimed in claim I or 2, wherein the hollow elements are one of glass or ceramic micro spheres.
4. A material as claimed in any preceding claim, wherein the hollow elements are substantially evacuated.
5. A material as claimed in claim 4, wherein the hollow elements are substantially evacuated to 10% or less atmospheric pressure.
6. A material as claimed in any of claims I to 3, wherein the hollow elements are filled with a gas.
7. A material as claimed in claim 6, wherein the gas is one of air or an inert gas.
8. A material as claimed in any preceding claim, wherein the ratio of powder to hollow elements is in the range 90% to 60% by weight.
9. A material as claimed in any preceding claim, wherein the powder is a resin made of one of, or a combination of, or a modified epoxy, polyester, polyurethane, acrylic or PVDF.
10. A material as claimed in any preceding claim, wherein graphite is added to provide the material with infra-red reflecting properties.
11. A method of making a powder coating material including the steps of producing a powder having a desired colour and fbrmulation, grinding the powder to a desired size, and bonding hollow elements having a melting point in excess of 200 C to the ground powder.
12. A method as claimed in claim 11, wherein the hollow elements have a size in the range 10 -40tm.
13. A method as claimed in claim II or 12, wherein the hollow elements are one of glass or ceramic micro spheres.
14. A method as claimed in any of claims 11 to 13, wherein the hollow elements are substantially evacuated.
15. A method as claimed in any of claims 11 to 13, wherein the hollow elements are filled with a gas.
16. A method as claimed in any of claims 11 to 15, wherein the ratio of powder to hollow elements is 5:1 by weight.
17. A powder coating material substantially as herein described.
18. A method of making a powder coating material substantially as herein described.