GB2130193A

GB2130193A - Coating composition

Info

Publication number: GB2130193A
Application number: GB08232475A
Authority: GB
Inventors: Anthony Hemmens
Original assignee: TANAT BUILDING PRODUCTS LIMITE
Current assignee: TANAT BUILDING PRODUCTS LIMITE
Priority date: 1982-11-13
Filing date: 1982-11-13
Publication date: 1984-05-31

Abstract

Textured coating composition comprises starch calcium carbonate (e.g. whiting), gypsum plaster and binder (e.g. gelatin), the amount of the starch being at least 0.5% by weight based on the total composition. The starch is used as a replacement for asbestos as it gives rise to similar rheological properties. The composition may also contain e.g. an extender such as talc, and other ingredients such as mica, a colouring agent or a fungicide.

Description

SPECIFICATION Textured coatings The present invention concerns textured coatings.

Textured paints first became popular in the period between the wars, because of their pleasing aesthetic appearance. After the second world war, there was a temendous demand for new housing and various steps were taken to speed up building and replace traditional "wet" trades, with more efficient and economical "dry" trades. One of the more significant changes, was the increasing use of plasterboard to replace traditional plastering. Existing texture finishes were developed for use on plasterboard, to provide a speedy and economic jointing and finishing system. The system was indeed found to be both economical and efficient and is now in general use.

Although there are many commercially available texture finishes on the market, the composition of the majority of products is very similar.

The bulk of the product is calcium carbonate, which is very cheap and readily available as whiting. Gypsum plaster is added because its chemical reaction with water helps prevent shrinkage. Mica is present because it gives a degree of structure in the mixed product and its plate-like properties improve the ease of application. Asbestos fibre is also included because it has a very high water absorption and the "interacting mesh like" effect of the fibres provides the rheological properties necessary for a good texture. These minerals are bound together with gelatine in the form of animal glue and small additions of various materials may be included, for example, to provide colour or fungicidal properties.

A typical formulation would be as follows:- % by weight Whiting 63.45 Plaster 11 Mica 7 Asbestos Fibre 4 Glue 4 White Pigment 0.5 Fungicide 0.5 This type of material has proved very successful commercially, but in recent years, investigation has shown that asbestors fibre can be a health hazard. Consequently, there is a great interest in finding a safe alternative.

Starch has been used for many years in textured coatings but only in very small amounts and for the purpose of identifying the product of a given manufacturer.

We have now found that starch can be used as a replacement for asbestos since it has a similar water demand and gives rise to similar rheological properties.

According to the present invention therefore a textured coating composition is provided which comprises starch, calcium carbonate, gypsum plaster and binder, the amount of the starch being at least 0.5% by weight based on the total composition.

The amount of the starch is preferably from 0.5% to 5%, especially from 2.5% to 5.0%, by weight.

The preferred starch is a viscosity modified potato starch such as, for example, an etherified starch modified by mineral acid and having a viscosity in 5% aqueous solution of 20,000 to 30,000 centipoises.

The calcium carbonate is suitably in the form of whiting and the binder may be, for example, gelatin in the form of animal glue.

In addition to the ingredients mentioned above the compositions of this invention may contain, for example, mica, a colouring agent or a fungicide.

They may also contain, for example, an extender e.g. talc which has an oil absorption in excess of 30. We have found that a composition containing 2.5% by weight of talc has improved properties as compared to a composition not containing the talc. If the composition contains 8% by weight of talc then the amount of starch can be as low as 0.5% by weight.

The amount of the calcium carbonate, gypsum plaster and mica taken together is suitably 93.5% by weight and the amount of the binder is suitably from 3.0 to 4.5% by weight of the composition.

A typical formulation for a textured coating composition according to the invention is: % by weight Whiting 67.6 Gypsum Plaster 24.3 Mica 1.6 Animal Glue 3.0 Starch 1.0 Talc 2.5 Arising out of the fact that the textured coating compositions of the invention contain no asbestos there are numerous advantages, as follows::- - it costs less to manufacture, - the actual manufacturing is easier, as asbestos linked safety apparatus is not needed, - insurance costs are lessened, ordering raw material is easier as there are no regulations attached to the haulage and some drivers can be wary of a potentiaily dangerous load, it is easier to get men in the factory to work in an asbestos-free atmosphere, - the material is easier to store since there are no regulations attached to how and where it should be stored, - the material is easier to mix on site, - less men are needed for the supervision of the new material as no hazards are involved, - the material is easier to mix and apply because it is less sticky than asbestos containing material and this is a distinct advantage for an inexperienced user, - the grey colour of asbestos is absent and the material has a cleaner, whiter appearance, and - the material has a greater covering capacity than asbestos-containing material.

Claims

1. Textured coating composition comprising starch, calcium carbonate, gypsum plaster and binder, the amount of the starch being at least 0.5% by weight based on the total composition.

2. Composition as claimed in claim 1 in which the amount of the starch is from 0.5% to 5% by weight based on the total composition.

3. Composition as claimed in claim 1 or 2 in which the amount of starch is from 2.5% to 5.0% by weight of the total composition.

4. Composition as claimed in claim 1, 2 or 3 in which the starch is a viscosity modified potato starch.

5. Composition as claimed in any of claims 1 to 4 in which the calcium carbonate is in the form of whiting.

6. Composition as claimed in any of claims 1 to 5 in which the binder is gelatin.

7. Composition as claimed in any of claims 1 to 6 which also contains mica, a colouring agent or a fungicide.

8. Composition as claimed in any of claims 1 to 6 which also contains mica, the amount of calcium carbonate, gypsum plaster and mica taken together is 93.5% by weight of the total composition.

9. Composition as claimed in any of claims 1 to 8 in which the amount of the binder is from 3.0 /0 to 4.5% by weight of the total composition.

10. Composition as claimed in any of claims 1 to 9 which also contains an extender.

11. Composition as claimed in claim 10 in which the extender is talc having an oil absorption in excess of 30.

12. Composition as claimed in claim 11 in which the amount of talc is 2.5% by weight of the total composition.

13. Composition as claimed in claim 11 or 12 in which the amount of talc is 8% by weight of the total composition.

14. Textured coating composition substantially as herein described.