WO1993014169A1

WO1993014169A1 - Curable aqueous phenolic resin coating composition

Info

Publication number: WO1993014169A1
Application number: PCT/GB1993/000002
Authority: WO
Inventors: Geoffrey Crompton
Original assignee: CROMPTON GARLAND Ltd
Current assignee: CROMPTON GARLAND Ltd
Priority date: 1992-01-21
Filing date: 1993-01-04
Publication date: 1993-07-22
Anticipated expiration: 1994-07-21
Also published as: AU3260893A

Abstract

A composition for use in coating substrates comprises a curable aqueous phenolic resin emulsion containing free phenol and free formaldehyde and a binder in liquid form, which binder imparts flexibility to the composition when the composition is cured, wherein the binder is a silicone resin emulsion.

Description

Title: CURABLE AQUEOUS PHENOLIC RESIN COATING COMPOSITION.

DESCRIPTION

This invention concerns emulsions, especially for producing fire resistant coatings and materials. Aqueous phenolic resin emulsions are known which contain unreacted phenol and formaldehyde. The emulsions are used to impregnate and/or coat various materials, including paper, glass fibre and asbestos. They may also be used as binders for various materials, including abrasives, refractories and other aggregates. When applied onto a substrate the solids remain isolated until heat is applied of upto about 135°C for curing, which results in a cohesive waterproof material with no free phenol or formaldehyde remaining. When the cured emulsion is subjected to fire it has, however, some disadvantages. Although the cured emulsion is classed as non-flammable, it is combustible and does burn with a yellow flame on its surface. Some smoke is also given off. Furthermore, resultant char is fragile and offers no protection to the substrate.

Furthermore, when such phenolic resin emulsions are aired, they lack flexibility and so are liable to cracking, particularly in situations where flexing and vibration occur. One object of this invention is to modify aqueous phenolic resin emulsions containing free phenol and formaldehyde to improve flexibility of the cured resin.

Another object of this invention is to modify aqueous phenolic resin emulsions containing free phenol and formaldehyde to improve fire resistant properties.

According to the invention there is provided a composition comprising a curable aqueous phenolic resin emulsion containing free phenol and free formaldehyde and a binder in liquid form which binder imparts flexibility to the composition when the composition is cured, wherein the binder is a silicone emulsion.

The present invention further provides a method of coating a substrate comprising the steps of mixing a curable aqueous phenolic resin emulsion containing free phenol and free formaldehyde with a binder in liσuid form to impart flexibility to the cured coating, applying said mixture to the substrate and curing the coating, wherein the binder is a silicone emulsion. The aqueous phenolic resin emulsions used in the invention ideally have one or more of the following properties:

1. Solvent free sprayable;

2. Adhere to steel and aluminum; 3. Non-corrosive to steel and, although binding to aluminum, non-corrosive thereafter; and 4. Curable within normal paint cycle and temperature.

When cured the composition of the invention ideally have one or more of the following properties:

1. Impervious to oil, petrol, hydraulic fluid and water;

2. High heat resistance;

3. Low smoke production - any smoke produced in a fire situation preferably being non-toxic;

4. Stone chip resistant; and

5. Retain adhesion under flex without cracking.

The aqueous phenolic resin emulsions used in the invention preferably have relatively low amounts of free phenol and free formaldehyde. Preferably free phenol is present in the emulsion in an amount of less than 5%, especially from 2 to 5% by weight and preferably free formaldehyde in an amount of less than 3%, especially from 1 to 3% by weight. The emulsions used in the invention preferably have a viscosity in the range of 5 to 20 poise, although viscosities above and below that range may be useful.

The specific gravity of the emulsion is preferably >1.0.

The silicone emulsion flexible binder may be added to the components of the invention in amounts of from 1 upto 20, preferably from 3 to 7, and especially about 5% by weight of the phenolic emulsion.

Further Materials that may be added to the aqueous phenolic resin emulsion may be selected from substances that give off water on heating, reinforcement, insulation materials, fire resistant additives, flexible binders and substances to improve adhesion. Examples of substances that give off water on heating include alumina trihydrate and hydrated magnesium calcium carbonate. Reinforcement may be any suitable form, examples only of which are fibres, powders and flakes. Suitable fibrous reinforcement may be flexible or non-flexible. Examples of flexible fibrous reinforcement include ceramic fibres and basalt fibres. Another suitable form of reinforcement may be flakes, such as of glass, for example, borosilicate glass (C glass), which can be used to reinforce, to prevent moisture ingress and to increase fire resistance. Preferred flakes are in fine plate form having a thickness of about 4 microns. Insulation materials that may be included in the compositions of the invention include expanded fire clay grog powder, poraver (expanded porous glass beads) and vermiculite. Fire resistant materials that may be included in the compositions of the invention include combinations of frits, such as sold under the trade name CEEPREE. Suitable substances to improve adhesion include, for example, starch.

A rheological control agent, such as clay, may be added to the compositions of the invention in order to render them thixotropic. The compositions of the invention are preferably used to provide a coating on a substrate. The emulsion composition may be applied to the substrate in any suitable way, although spraying is preferred. Prior to spraying the additives are preferably vigorously mixed with the phenolic resin emulsion. Then heat is applied say up to about 135°C to cure the coating to leave a cohesive coating.

The compositions of the invention may be used on a variety of substrates and may be modified accordingly. For example compositions according to the invention may be used for underbody protection for motor vehicles and trains, for coating aluminium, for coating structural steel work both on and off shore and for coating panels of various types. One typical emulsion composition may contain expanded fire clay grog, hydrated magnesium calcium carbonate, Ceepree, silicone emulsion, poraver and vermiculite. The expanded fire clay grog, vermiculite and poraver act as heat insulation materials and the Ceepree is to binds char in the case of a fire. The hydrated magnesium calcium carbonate gives off water vapour at high temperatures. The silicone emulsion cures and bonds with the phenolic resin to give flexibility.

For steel work preferably poraver of particle size from 0.5 to 4.0mm and both micronised and 5.0mm size vermiculite may be used in the composition to provide a quick build coating which is sprayable. The sprayed coatings may be oven cured.

The compositions of the invention may also be formulated to provide waterproof coatings -for use in areas coated with intumescent paints, which ordinarily would suffer from moisture degradation.

An emulsion composition containing a substance to give off water on heating and a frit mixture (Ceepree) may be used as a precured gel coat in phenolic resin lay-up work.

A^* gel coat for use in glass reinforced phenolic and polyester mouldings can be produced according to the invention. Optionally, addition of an amount of water tillable polyester resin to the phenolic emulsion can make the gel more compatible with polyester mouldings.

Compositions of the invention may be used for forming a filling between metal sheets, such as of steel or aluminum, to form a laminate. Such compositions preferably contain insulation materials, such as poraver

(expanded porous glass beads) and optionally vermiculite, optionally a substance that gives off water on heating especially hydrated magnesium calcium carbonate, and fire resistant materials, such as mixtures of frit. The preferred laminates are produced by sandwiching the composition of the invention between the metal sheets with a porous spacer between the sheets around the periphery thereof. Pressure may then be applied and heat may be applied simultaneously or later for curing. Possibly heat may be applied during a subsequent paint spraying treatment for the laminate. The porous spacer allows water from the filling to escape as water vapour during curing.

The laminates with a filling having a flexible binder may be of use in forming panels for use in situations subject to vibration, such as in motor vehicles and machinery.

Compositions of the invention may be coloured, for example, using powdered cement/concrete colourings. The invention will now be further described by means of the following Examples.

Example 1 An aqueous phenolic resin emulsion composition was prepared by mixing the following ingredients in the amounts stated in parts by weight:

Aqueous phenolic resin emulsion (containing <2% by weight free phenol and <1% by weight free formaldehyde - viscosity 5-20 poise, specific gravity >1.0) 200 Expanded fire clay grog 20

Ultracarb (hydrated magnesium calcium carbonate) 30

Ceepree (optional) 20

Silicone emulsion (aqueous) 20 Poraver (0.5mm diameter) 15

Poraver (1.0mm diameter) 15

Expanded micronised vermiculite 30

The ingredients were mixed together with vigorous beating immediately prior to spraying onto a substrate. Heating the sprayed material to about 135°C effected curing to form a cohesive waterproof coating on the substrate.

The expanded fire clay grog, poraver and vermiculite act as high heat insulation and the Ceepree, when present, binds char in the case of a fire. The Ultracarb gives off water vapour over a high temperature range. The silicone cures and bonds with the emulsion to give flexibility.

Example 2 Aqueous phenolic resin emulsions contain solids which remain isolated from each other until heated. The addition of suitable compatible substances can result in a chemical combination of all the components when heat is applied. For the purpose of illustration, a semi- flexible coloured coating was produced from a composition comprising the following ingredients in the amounts stated: parts by weight Aqueous phenolic resin emulsion 100 (containing <2% by weight free phonel and <1% by weight free formaldehyde - viscosity 5-20 poise, specific gravity >1.0)

Ceepree (a frit mixture) 30 Ammonium Polyphosphate 20

Silicone Emulsion 20

Colour 5

A small amount of water can be added without affecting the cured product. Curing of the composition can be effected by heat- typically 130°C for 7 to 10 minutes depending on the thickness, or in some cases by phosphoric acid being mixed with the resin prior to the introduction of the alkaline additives into the spray, to avoid neutralisation.

It has been found that it can be advantageous to cure with acid, and subsequently heat to final cure. The length of time needed to cure in this case is reduced, and is particularly useful in the case of gel coating phenolic and glass lay-up.

The same formula, with the addition of vermiculite dust or expanded particles, and expanded glass beads, for example Poraver, can increase the insulation, as can the addition of glass flake.

Various paint-like coating compositions were produced from the following compositions.

Example 3 parts by weight Aqueous phenolic resin emulsion (containing <2% by weight free phenol and <1% by weight free- formaldehyde - viscosity 5-20 poise, specific gravity >1.0) 100

Aqueous silicone emulsion 1-20

(depending on devised flexibility of cured composition)

Ceepree 20 Mica 10

Ammonium Polyphosphate 5-7

Example 4 parts by weight Aqueous phenolic resin emulsion (containing <2% by weight free phenol and <1% by weight free formaldehyde - viscosity 5-20 poise, specific

gravity >1.0) 100

Aqueous silicone emulsion 1-20

(depending on devised flexibility of cured composition) Ceepree 20

Ultracarb 20

Mica 10

Example 5 parts by weight Aqueous phenolic resin emulsion

(containing <2% by weight free phenol and <1% by weight free formaldehyde - viscosity 5-20 poise, specific gravity >1.0) 200 Aqueous silicone emulsion 1-20

(depending on devised flexibility of cured composition)

Ceepree 20 Mica 10

Thixotropic agent - Pangel or Volclay 6

Claims

1. A coating composition comprising a curable aqueous phenolic resin emulsion containing free phenol and free formaldehyde and a binder in liquid form which binder imparts flexibility to the composition when the composition is cured, wherein the binder is a silicone emulsion.

2. A composition as claimed in claim 1, wherein free phenol is present in the phenolic emulsion in an amount of less than 5% by weight.

3. A composition as claimed in claim 2, wherein free phenol is present in the phenolic emulsion in an amount of from 2 to 5% by weight.

4. A composition as claimed in claim 1, 2 or 3, wherein free formaldehyde is present in the phenolic emulsion in an amount of less than 3% by weight.

5. A composition as claimed in claim 4, wherein free formaldehyde is present in the phenolic emulsion in an amount of from 1 to 3% by weight.

6. A composition as claimed in any one of claims 1 to 5, wherein the phenolic resin emulsion has a viscosity in the range of 5 to 20 poise.

7. A composition as claimed in any one of claims 1 to 6, wherein the phenolic resin emulsion has a specific gravity >1.0.

8. A composition as claimed in any one of claims 1 to 7, wherein the silicone emulsion is present in an amount of from 1 to 20% by weight of the phenolic resin emulsion.

9. A composition as claimed in claim 8, wherein the silicone emulsion is present in an amount of from 3 to 7% by weight of the phenolic resin emulsion.

10. A composition as claimed in claim 8 or 9, wherein the silicone emulsion is present in an amount of about 5% by weight of the phenolic resin emulsion.

11. A composition as claimed in claim 1 further comprising one or more of the following: substances to give off water when heated, reinforcements, insulation materials, fire resistant additives, substances to improve adhesion, thixotropic agents and colourants.

12. A composition as claimed in claim 11, wherein the substance that gives off water on heating is selected from alumina trihydrate and hydrated magnesium calcium carbonate.

13. A composition as claimed in claims 11 or 12, wherein reinforcement is selected from fibres, powders and flakes.

14. A composition as claimed in claim 13, wherein reinforcement is flexible or non-flexible.

15. A composition as claimed in claim 14 wherein flexible fibrous reinforcement is selected from ceramic fibres and basalt fibres.

16. A composition as claimed in claim 13 or 14 wherein reinforcement is in the form of glass flakes.

17. A composition as claimed in claim 16, wherein the glass flakes are in fine plate form having a thickness of about 4 microns.

18. A composition as claimed in any one of claims 11 to 17, wherein insulation materials are selected from expanded fire clay grog powder, poraver (expanded povous glass beads) and vermiculite.

19. A composition a claimed in any one of claims 11 to 18, wherein fire resistant materials are selected from combinations of frits.

20. A composition as claimed in any one of claims 11 to 19, wherein the adhesion improver is starch.

21. A composition as claimed in any one of claims 11 to 20, wherein the thixotropic agent is a clay.

22. A method of coating a substrate comprising the steps of mixing a curable aqueous phenolic resin emulsion containing free phenol and free formaldehyde with a binder in liquid form to impart flexibility to the cured coating applying said mixture to the substrate and curing the coating, wherein the binder is a silicone emulsion.

23. A method as claimed in claim 22, wherein free phenol is present in the emulsion in an amount of less than 5% by weight.

24. A method as claimed in claim 23, wherein free phenol is present in the emulsion in an amount of from 2 to 5% by weight.

25. A method as claimed in claim 22, 23 or 24, wherein free formaldehyde is present in the emulsion in an amount of less than 1 to 3% by weight.

26. A method as claimed in claim 25, wherein free formaldehyde is present in the emulsion in an amount of from 1 to 3% by weight.

27. A method as claimed in any one of claims 22 to

26, wherein the phenolic resin emulsion has a viscosity in the range of 5 to 20 poise.

28. A method as claimed in any one of claims 22 to

27, wherein the phenolic resin emulsion has a specific gravity >1.0.

29. A method as claimed in any one of claims 22 to

28, wherein the silicone emulsion is present in an amount of from 1 to 20% by weight of the phenolic resin emulsion.

30. A method as claimed in claim 29, wherein the silicone emulsion is present in an amount of from 3 to 7% by weight of the phenolic resin emulsion.

31. A method as claimed in claim 29 or 30, wherein the silicone emulsion is present in an amount of about 5% by weight of the phenolic resin emulsion.

32. A method as claimed in any one of claims 22 to 31 further comprising the step of adding to the mixture one or more of the following: substances to give off water when heated, reinforcements, insulation materials, fire resistant additives, substances to improve adhesion, thixotropic agents and colourants.

33. A method as claimed in claim 32, wherein the substance that gives off water or heating is selected from alumina trihydrate and hydrated magnesium calcium carbonate.

34. A composition as claimed in claim 32 or 33, wherein reinforcement is selected from fibres, powders and flakes.

35. A composition as claimed in claim 34, wherein reinforcement is flexible or non-flexible.

36. A composition as claimed in claim 35, wherein flexible fibrous reinforcement is selected from ceramic fibres and basalt fibres.

37. A composition as claimed in claim 34 or 35, wherein reinforcement is in the form of glass flakes.

38. A composition as claimed in claim 37, wherein the glass flakes are in fine plate form having a thickness of about 4 microns.

39. A composition as claimed in any one of claims 32 to 27, wherein insulation materials are selected from expanded fire clay grog powder, poraver (expanded povous glass beads) and vermiculite).

40. A composition as claimed in any one of claims 32 to 39, wherein fire resistant materials are selected from combinations of frits.

41. A composition as claimed in any one of claims 32 to 40, wherein the adhesion improver is starch.

42. A method as claimed in any one of claims 32 to 41, wherein the thixotropic agent is a clay.

43. A composition as claimed in claim 1 and substantially as hereinbefore devised with reference to any one of the foregoing Examples.

44. A method as claimed in claim 19 and substantially as hereinbefore described with reference to any one of the foregoing Examples.