GB2179932A

GB2179932A - Settable plaster composition

Info

Publication number: GB2179932A
Application number: GB08620499A
Authority: GB
Inventors: Philip Pain
Original assignee: AECI Ltd
Current assignee: AECI Ltd
Priority date: 1985-09-05
Filing date: 1986-08-22
Publication date: 1987-03-18
Also published as: FR2588856A1; NO863542L; AU6176786A; NO863542D0; SE8603715L; SE8603715D0; DE3630182A1; GB8620499D0

Abstract

A set plaster- and resin-containing composition is made by mixing together an aqueous solution of a settable resin, for example an aminoplast resin such as a urea-formaldehyde resin, a calcium sulphate plaster which sets on contact with water, and a resin hardener. A resin modifier such as furfuryl alcohol or glycerol may advantageously be mixed into the composition, which may also include further additives such as dispersing agents, inert fillers, reinforcing fibres, thickeners, surfactants, foaming agents and plaster hardeners. The composition may advantageously be made from a kit comprising a resin component and a plaster component, the plaster component including the resin hardener. The composition may be used for strata consolidation in mining, as a roof bolt grouting composition in mining, for modelling statuettes, for the manufacture of prefabricated building panels, and other uses.

Description

SPECIFICATION Plastering composition THIS INVENTION relates to a method of making a set plaster- and resin-containing composition.

It also relates to a set plaster- and resin-containing composition, to a settable plaster- and resincontaining composition suitable for plastering, and to a kit for making such compositions.

According to the invention there is provided a method of making a set plaster- and resincontaining composition which comprises mixing together an aqueous solution of a settable resin, a plaster which sets on contact with water, and a resin hardener which causes the resin to set, and allowing the composition to set.

The resin may be an aminoplast resin, the plaster being a hemihydrate of calcium sulphate such as plaster of Paris. More particularly, the aminoplast resin may be a urea-formaldehyde resin, the plaster being the alpha hemihydrate of calcium sulphate. A suitable alpha hemihydrate of calcium sulphate is available as "Ludur 250 Carbonate Free" from Giulini Chemie GmbH, West Germany, or as "Herculite No.2" available from British Gypsum PLC, Great Britain. Instead, for applications where very high strength is not required, the plaster may comprise the beta hemihydrate of calcium sulphate, for example "Non Carbonated Standard Plaster" available from Gypsum Industries Limited, South Africa.

In accordance with the method the ratio between the plaster and the water in the solution on a mass basis may be between 1:0,15 and 1:1, preferably between 1:0,20 and 1:0,75. In the case of the alpha hemihydrate this ratio is preferably between 1:0,20 and 1:0,35, and in the case of the beta hemihydrate it is preferably between 1:0,45 and 1:0,75.

The ratio of resin solids to plaster on a mass basis may be between 10:90 and 50:50, preferably between 15:85 and 40:60.

The invention may include the step of mixing a dispersing agent into the mixture, for promoting even mixing of the constituents of the mixture and for promoting homogenuity of the mixture. The proportion of dispersing agent mixed into the mixture may be from 0,01-0,03% by mass.

The method may include the step of mixing reinforcing fibres into the mixture. The fibres may be chopped glass fibres less than 20 mm in length, the proportion thereof mixed into the mixture being from 0,5-5% by mass. Preferably, the fibres are from 5-10 mm in length and the proportion thereof is from 1-3% by mass.

The method may include the step of mixing a granular inert filler into the mixture. The granular inert filler may be crushed silica sand, the proportion thereof mixed into the mixture being at most 60% by mass. A suitable crushed silica sand for this purpose has been found to have the following typical particle size distribution: Mesh Size Proportion Retained (mm) (% mm) 0,6 1 max 0,425 4,5-4,7 0,300 18,4-18,8 0,212 30,5-30,9 0,150 24,1-24,5 0,106 14,8-15,2 Remainder-Fines 6,4 max As the above particle size distribution has been found to be suitable, other sands having similar particles size distributions will also be suitable, although the exact particle size distribution can vary, within limits, from that set out in tabular form above.

The invention may include the step of mixing a rubbery compound into the mixture. The rubbery compound may be a latex, and the proportion thereof mixed into the mixture may be at most 10% by mass. This rubbery compound or latex can act to improve tensile and flexural strengths and resistance to water penetration of the set product composition, and can act to improve the adhesive properties of the mixture before setting, ie in the unset product composition. Suitable latexes include styrene-butadiene latexes.

The method may include the step of mixing a thickener into the mixture. Such thickeners can act to improve the thixotropic nature of the mixture or unset product composition, and an example is carboxymethyl cellulose gum, the proportion thereof being mixed into the mixture being at most 1% by mass. Other thickeners will typically be mixed into the mixture in similar proportions.

The method may include the step of mixing a surfactant into the mixture. Thus, one or more surfactants may be employed, particularly if the mixture is intended for the production of moulded products.

The method may further include the step of foaming the mixture. Thus, a chemical foaming agent may be mixed into the mixture to effect the foaming, an example of a foaming agent being calcium carbonate and the proportion thereof mixed into the mixture being 0,5-5% by mass, preferably 1-3%. Instead, the mixture may be foamed mechanically. Typically the foaming and surfactants will be employed together, when the mixture is intended for producing foamed products. Naturally, if a coloured set product composition is desired, a suitable pigment may be mixed into the mixture, in suitable proportions.

The resin hardener may comprise at least one member of the group consisting in ammonium dihydrogen phosphate, citric acid, ammonium chloride, maleic anhydride, paratoluene sulphonic acid, and sodium pyrophosphate.

The method may include the step of mixing a resin modifier into the mixture. By a "resin modifier" is meant a substance, such as a copolymer for the resin, which upon hardening of the resin becomes incorporated into and polymerizes with the resin. The resin modifier may comprise at least one member of the group consisting in furfuryl alcohol and glycerol.

The method may include the step of mixing a plaster hardener into the mixture. The plaster hardener will act to accelerate plaster hardening, and may comprise at least one member of the group consisting in ammonium chloride, boric acid and sodium pyrophosphate.

The invention may further include the step of mixing a pH modifying agent into the mixture.

The pH modifying agent comprise at least one member of the group consisting in ammonium chloride, ammonium dihydrogen phosphate and boric acid.

From the aforegoing it will be appreciated that certain substances can act as resin hardeners, as plaster hardeners and/or as pH modifying agents, so that they fullfil more than one function.

The method may comprise a final mixing step in which two components are mixed together, namely a resin component containing the aqueous resin solution, and a plaster component containing the plaster component and the resin hardener. It follows that any constituents of the mixture which are chemically inert to the plaster and reactive to the resin may be incorporated into the plaster component prior to the final mixing step, any constituents of the mixture which are reactive to the plaster and chemically inert to the resin being incorporated in the resin component prior to the final mixing step, and any constituents which are chemically inert to both the resin and plaster optionally, as desired, being incorporated into either of said components, ie being incorporated into at least one of said components, prior to the final mixing step.

The method may include the step, after the mixing and prior to the setting, of coating the mixture on to a substrate. This coating may be by means of trowelling, or, particularly, by spraying. Thus, the coating may be by spraying the mixture on to rock surfaces, eg the surfaces of adjacent rock strata, in a mine as a screeding, to stabilize such strata.

Instead, the method may include the step, after the mixing and prior to the setting, of introducing the mixture into a cavity as grouting, eg by pouring or pumping it into a cavity or hole as a grouting material for grouting bolts into the cavity.

Instead, the method may include the step, after the mixing and prior to the setting, of moulding or casting the mixture, optionally followed by machining the composition after it has set, eg to make free-standing articles such as mouldings.

Other examples of use of the composition are use in the building industry as an exterior protective wall coating or for the manufacturing of prefabricated building panels; use in the interior decorating industry for textured wall coatings; and use in lining ducts, vessels and tunnels for industrial and civil engineering applications.

When foamed, for example with calcium carbonate as described above, the composition may be used in the mining industry as a thermally insulating wall screeding; in the building industry for the manufacture of thermally insulating prefabricated wall panels; or as a general insulating and/or cavity filling composition.

When cast and/or machined, the composition may be used in the industrial model making industry; in the sanitaryware industry; or as a model making composition for the hobbyist.

The invention extends to a set plaster- and resin-containing composition, when made according to the method described above.

The invention extends further to a settable plaster- and resin-containing composition which comprises, prior to its setting, the set composition as described above.

The invention extends further to a kit for making a set composition or settable composition as described above, which kit comprises a resin component including an aqueous solution of a settable resin, and a plaster component which includes a plaster which sets on contact with water and a resin hardener for causing the resin of the resin component to set, the resin component being mixable with the plaster component to form at least part of a composition as described above.

The kit may be a two-component kit in which any constituents of the composition which are chemically inert to the plaster and reactive to the resin are included in the plaster component, any constituents of the composition which are chemically inert to the resin and reactive to the plaster are included in the resin component, and any constituents of the composition which are inert to both the resin and the plaster are included in at least one of the components.

Naturally, in deciding which component of a two-component kit any constituent will form part of, it should be borne in mind that that constituent should be not incompatible with the resin and water on the one hand and if it is to be included in the resin component, or with the plaster and resin hardener on the other hand, if it is to be included in the plaster component, and if several additional constituents are included in any component, they should not be incompatible with one another in the environment of that component. Similar considerations apply if the kit has three or more components. In certain cases, it may be preferably to have a three component kit, comprising a resin component containing an aqueous solution of a settable resin, a plaster component containing a plaster, and a hardener component containing the hardener for the resin.

Typically for a two-component kit, the resin component will include the water necessary to cure the plaster, and the plaster component will contain the other constituents for the mixture to be formed, although naturally as suggested above, some components can be included in the resin component, eg reinforcing fibres, if not incompatible therewith.

The components of the kit may be as described above in connection with the method of the present invention. Thus, the resin may be an aminoplast resin, the plaster being a hemihydrate of calcium sulphate, the resin preferably being a urea-formaldehyde resin. In particular, the plaster component may comprise plaster in the form of the alpha hemihydrate of calcium sulphate, the resin hardener being a hardener for causing a urea-formaldehyde resin to set.

This kit may be provided in a two-component pack with the resin component and the plaster component contained in separate containers, and the relative amounts of the resin component and plaster component in their respective containers may be selected so that mixing the entire contents of the two containers together, without any measuring, automatically gives a composition in accordance with the present invention having its constituents in the appropriate proportions. For a three component kit, this may naturally be supplied in three containers, namely a container for the resin component, a container for the plaster component and a container for the hardener. In this case some of the water required to cure the plaster may be included with the hardener in its container, if not incompatible therewith.

Further according to the invention a plaster component for a kit as described above, comprises a plaster which sets on contact with water, and a resin hardener for causing a resin to set.

The plaster component may include other components, as described above, with reference to the method, which are not incompatible with the plaster and resin hardener, or with one another.

The plaster of the plaster component may be a hemihydrate of calcium sulphate, the resin hardener being a hardener for causing an aminoplast resin to set. In particular, the plaster may be the alpha hemihydrate of calcium sulphate, the resin hardener being a hardener for causing a urea-formaldehyde resin to set. The resin hardener may thus comprise at least one member of the group consisting in ammonium dihydrogen phosphate, citric acid, ammonium chloride, maleic anhydride, paratoluene sulphonic acid and sodium pyrophosphate.

The invention will now be described, by way of non-limiting illustration, with reference to the following Examples, in which, unless otherwise specified, the constituents are as follows: Tradenaze or Designation Nature or Function Source Ludur 250 alpha hemihydrate Guilini Chemie of calcium sulphate GmbH, West Germany Herculite No. 2 alpha hemihydrate British Gypsum of calcium sulphate PLC, Great Britain Non-Carbonated Standard beta hydrate of Gypsum Industries Plaster calcium sulphate Limited, South Africa FUF 009 Resin resin Resinkem (Proprietary) Limited, South Africa UF Resin 285 resin Resinkem (Proprietary) Limited, South Africa UF Resin 385 resin Resinkem (Proprietary) Limited, South Africa Norilose 7062 NP thickening agent Noricel (Proprietary) Limited, South Africa A6 grade crushed silica sand Lancaster Sand and (having the Transport particle size (Proprietary) distribution Limited, South specified in the Africa Table hereinabove) Alcosperse AR671D dispersing agent Revertex (South Africa) (Proprietary) Limited Grrm Chopped glass fibres Acoustical Fibreglass Insulation (Proprietary) Limited, South Africa EXAMPLE 1 Ingredients Quantity (by mass) Ludur 250 561,20 UF Resin 285 376,00 Water 32,10 Ammonium chloride 16,80 Ammonium dihydrogen phosphate 9,60 Boric acid 4,30 1 000,00 EXAMPLE 2 Ingredients Quantity (by mass) Ludur 250 529,65 FUF 009 Resin 402,77 Alcosperse AR671D 0,07 Glass fibres (6mm length) 38,41 Ammonium chloride 15,95 Ammonium dihydrogen phosphate 9,08 Boric acid 4,07 1 000,00 EXAMPLE 3 Ingredients Quantity (by mass) Ludur 250 679,80 A6 Sand 67,98 Maleic anhydride 0,68 Ammonium chloride 2,72 UF Resin 385 183,55 Water 64,72 Norilose 7062 NP 0,41 Alcosperse AR671D 0,14 1 000,00 EXAMPLE 4 Ingredients Quantity (by mass) Ludur 250 556,73 A6 Sand 175,3 Ammonium chloride 13,36 Citric acid 8,91 UF Resin 385 155,88 Norilose 7062 NP 0,67 Water 89,08 1 000,00 EXAMPLE 5 Ingredients Quantity (by mass) Non-Carbonated Standard Plaster 446,45 A6 Sand 195,82 Citric acid 5,87 Ammonium chloride 19,58 UF Resin 385 211,47 Water 119,44 Norilose 7062 NP 1,37 1 000,00 EXAMPLE 6 Ingredients Quantity (by mass) Non-Carbonated Standard Plaster 508,59 A6 Sand 223,06 Citric acid 6,69 Ammonium chloride 11,15 p-Toluene sulphonic acid 4,46 UF Resin 385 156,15 Water 89,23 Norilose 7062 NP 0,67 1 000,00 EXAMPLE 7 Ingredients Quantity (by mass) Herculite No. 2 661,59 A6 Sand 66,16 FUF 009 Resin 208,20 Ammonium chloride 2,65 Norilose 7062 NP 0,40 Alcosperse AR671D 0,14 Water 60,87 1 000,00 EXAMPLE 8 Ingredients Quantity (by mass) Non-Carbonated Standard Plaster 222,51 A6 Sand 507,34 UF Resin 385 137,96 Norilose 7062 NP 0,89 Water 117,94 Ammonium Chloride 11,13 p-Toluene sulphonic acid 2,23 1 000,00 EXAMPLE 9 Ingredients Quantity (by mass) Non-Carbonated Standard Plaster 622,34 p-Toluene sulphonic acid 4,67 Ammonium chloride 9,34 UF Resin 385 231,83 Norilose 7062 NP 0,50 Water 131,32 1 000,00 Setting times were measured at various temperatures together with compressive strength after various periods for the various Examples.These setting times are as follows: EXAMPLE SEITING Ssr1ING COMPRESSIVE STRENGTH AFTER TD E TEMPERATURE (Minutes) ( C) 4 HOURS 24 HOURS 48 HOURS (MPa) (MPa) ~ (MPa) 1 50 35 - 44 2 75 35 - - 45 3 70 35 - 53 61 4 35 35 * - 46 5 60 18 15 20 24 6 40 18 13 24 7 90 35 - 26 36 8 120 20 - 11 9 35 18 - 15 The compositions described in Examples 2 and 4 were successfully applied, in a mining environment, to the surfaces of rock strata for the purpose of strata consolidation.

The composition of Example 5 has been successfully applied, also in a mining environment, as a roof bolt grouting composition for the purpose of rock consolidation.

The composition of Example 9 has been used successfully for modelling statuettes.

In all the above Examples, it was found that the unset compositions, when appropriately mixed, could be pumped using eg a positive displacement pump say of the piston type, typically used for slurries or plaster-based grouting materials. Suitable equipment for this purpose is available from Spedel Engineering (Proprietary) Limited, South Africa. Furthermore, the compositions could be poured and cast, as desired.

When compared with particulate compositions which comprise essentially plaster, chopped glass fibre and an aminoplastic resins selected from urea-formaldehyde or melamine-formaldehyde resins, which are sprayed on to rock faces to form coatings which harden, or are poured or pumped into holes for the purpose of rock consolidation, the Examples of the present invention appear to have a number of advantages. These advantages include improved absolute compressive strengths (up to 77% better); a reduced tendency to cracking or crazing; an improved resistance to water; a higher green strength; a faster rate of attainment of ultimate strength; a reduced level of formaldehyde emission upon curing: and improved adherance to certain rock types.

As regards preparing and handling of the composition of the present invention, it should be noted that the composition will set after the elapse of a predetermined time interval from mixing, depending on its composition. This means that the composition must usually be mixed more or less in situ, usually by the ultimate user or on his premises, and must be used (sprayed, poured, cast, etc) before any appreciable setting has taken place which can adversely affect its intended use.

Finally it should be noted that the composition of the present invention can be prepared in a number of ways. Thus, most of the dry constituents can be premixed into the plaster component, and the thickener, if used, can be pre-blended into the resin component, together with other compatible liquid and/or solid constituents. Pre-blending, as described, before the final mixing of the resin and plaster components, may be effected in any convenient fashion, until adequately homogeneous.

Claims

1. A method of making a set plaster- and resin-containing composition which comprises mixing together an aqueous solution of a settable resin, a plaster which sets on contact with water, and a resin hardener which causes the resin to set, and allowing the composition to set.

2. A method as claimed in Claim 1, in which the resin is an aminoplast resin and in which the plaster is a hemihydrate of calcium sulphate.

3. A method as claimed in Claim 2, in which the aminoplast resin is a urea-formaldehyde resin and the plaster is the alpha hemihydrate of calcium sulphate.

4. A method as claimed in Claim 2 or Claim 3, in which the ratio between the plaster and the water in the solution on a mass basis is between 1:0,15 and 1:1.

5. A method as claimed in Claim 4, in which the ratio is between 1:0,20 and 1:0,75.

6. A method as claimed in any one of the preceding claims, in which the ratio of resin solids.

to plaster on a mass basis is between 10:90 and 50:50.

7. A method as claimed in Claim 6, in which the ratio is between 15:85 and 40:60.

8. A method as claimed in any one of the preceding claims, which includes the step of mixing a dispersing agent into the mixture, for promoting even mixing of the constituents of the mixture and for promoting homogeneity of the mixture.

9. A method as claimed in Claim 8, in which the proportion of dispersing agent mixed into the mixture is from 0,01-0,03% by mass.

10. A method as claimed in any one of the preceding claims, which includes the step of mixing reinforcing fibres into the mixture.

11. A method acclaimed in Claim 10, in which the fibres are chopped glass fibres less than 20 mm in length, the proportion thereof mixed into the mixture being from 0,5-5% by mass.

12. A method as claimed in Claim 11, in which the fibres are from 5-10 mm in length and the proportion is from 1-3% by mass.

13. A method as claimed in any one of the preceding claims, which includes the step of mixing a granular inert filler into the mixture.

14. A method as claimed in Claim 13, in which the granular inert filler is crushed silica sand and the proportion thereof mixed into the mixture is at most 60% by mass.

15. A method as claimed in any one of the preceding claims, which includes the step of mixing a rubbery compound into the mixture.

16. A method as claimed in Claim 15, in which the rubbery compound is a latex and the proportion thereof mixed into the mixture is at most 10% by mass.

17. A method as claimed in any one of the preceding claims, which includes the step of mixing a thickener into the mixture.

18. A method as claimed in Claim 17, in which the thickener is carboxymethyl cellulose gum and the proportion thereof mixed into the mixture is at most 1 % by mass.

19. A method as claimed in any one of the preceding claims, which includes the step of mixing a surfactant into the mixture.

20. A method as claimed in any one of the preceding claims, which includes the step of foaming the mixture.

21. A method as claimed in Claim 20, in which a chemical foaming agent is mixed into the mixture to effect the foaming.

22. A method as claimed in Claim 22, in which the foaming agent is calcium carbonate and the proportion thereof mixed into the mixture is 0,5-5% by mass.

23. A method as claimed in Claim 21, in which the mixture is foamed mechanically.

24. A method as claimed in any one of the preceding claims, in which the resin hardener comprises at least one member of the group consisting in ammonium dihydrogen phosphate, citric acid, ammonium chloride, maleic anhydride, paratoluene sulphonic acid and sodium pyrophosphate.

25. A method as claimed in any one of the preceding claims, which includes the step of mixing a resin modifier into the mixture.

26. A method as claimed in claim 25, in which the resin modifier comprises at least one member of the group consisting in furfuryl alcohol and glycerol.

27. A method as claimed in any of the preceding claims, which includes the step of mixing a plaster hardener into the mixture.

28. A method as claimed in Claim 27, in which the plaster hardener comprises at least one member of the group consisting in ammonium chloride, boric acid and sodium pyrophosphate.

29. A method as claimed in any one of the preceding claims, which comprises a final mixing step in which two components are mixed together, namely a resin component containing the aqueous resin solution, and a plaster component containing the plaster component and the resin hardener.

30. A method as claimed in Claim 29, in which any constituents of the mixture which are chemically inert to the plaster and reactive to the resin are incorporated into the plaster component prior to the final mixing step, any constituents of the mixture which are reactive to the plaster and chemically inert to the resin being incorporated in the resin component prior to the final mixing step, and any constituents which are chemically inert to both the resin and plaster being incorporated into at least one of said components prior to the final mixing step.

31. A method as claimed in any one of the preceding claims, which includes the step, after the mixing and prior to the setting, of coating the mixture on to a substrate.

32. A method as claimed in Claim 31, in which the coating is by means of trowelling or spraying.

33. A method as claimed in Claim 30 or Claim 31, in which the coating is by spraying the mixture on to rock surfaces in a mine as a screeding.

34. A method as claimed in any one of Claims 1 to 30 inclusive, which includes the step, after the mixing and prior to the setting, of introducing the mixture into a cavity as grouting.

35. A method as claimed in any one of Claims 1 to 30 inclusive, which includes the step, after the mixing and prior to the setting, of moulding or casting the mixture.

36. A method as claimed in Claim 35, which includes machining the composition after it has set.

37. A method of making a set plaster- and resin-containing composition, substantially as described herein.

38. A set plaster- and resin-containing composition, whenever made according to a method as claimed in any one of the preceding claims.

39. A set plaster- and resin-containing composition, substantially as described herein.

40. A settable plaster- and resin-containing composition which comprises, prior to its setting, a composition as claimed in Claim 38.

41. A settable plaster- and resin-containing composition, substantially as described herein.

42. A kit for making a composition as claimed in Claim 38 or Claim 40, which kit comprises a resin component including an aqueous solution of a settable resin, and a plaster component which includes a plaster which sets on contact with water and a resin hardener for causing the resin of the resin component to set, the resin component being mixable with the plaster component to form at least part of a composition as claimed in Claim 38 or Claim 40.

43. A kit as claimed in Claim 42, which is a two-component kit in which any constituents of the composition which are chemically inert to the plaster and reactive to the resin are included in the plaster component, any constituents of the composition which are chemically inert to the resin and reactive to the plaster are included in the resin component and any constituents of the composition which are inert to both the resin and the plaster being included in at least one of the components.

44. A kit as claimed in Claim 42 or Claim 43, in which the resin is an aminoplast resin and in which the plaster is a hemihydrate of calcium sulphate.

45. A kit as claimed in Claim 44, in which the resin is a urea-formaldehyde resin.

46. A kit as claimed in Claim 44 or Claim 45, in which the plaster component is as claimed in Claim 50.

47. A kit for making a composition as claimed in Claim 38 or Claim 40, substantially as described herein.

48. A plaster component for a kit as claimed in Claim 42, which component comprises a plaster which sets on contact with water, and a resin hardener for causing a resin to set.

49. A component as claimed in Claim 48, in which the plaster is a hemihydrate of calcium sulphate and the resin hardener is a hardener for causing an aminoplast resin to set.

50. A component as claimed in Claim 49, in which the plaster is the alpha hemihydrate of calcium sulphate and the resin hardener is a hardener for causing a urea-formaldehyde resin to set.

51. A component as claimed in any one of Claims 48 to 50, in which the resin hardener comprises at least one member of the group consisting in ammonium dihydrogen phosphate, citric acid, ammonium chloride, maleic anhydride, paratoluene sulphonic acid and sodium pyrophosphate.

52. A plaster component for a kit as claimed in Claim 42, substantially as described herein.

53. The use of a composition as claimed in any one of claims 38 to 41, for the coating of substrates, for the filling of cavities or for casting or moulding articles

54. The use as claimed in claim 53, in which the coating is as screeding on rock surfaces, the filling of cavities is grouting and the casting or moulding is of constructional elements, sanitaryware or models.

55. The use of a composition as claimed in any one of claims 38 to 41, substantially as described herein.