WO2004033567A1

WO2004033567A1 - Heat insulation coatings

Info

Publication number: WO2004033567A1
Application number: PCT/GB2003/004383
Authority: WO
Inventors: Mansoor Khorasani; Ali Kalantar
Original assignee: Mansoor Khorasani; Ali Kalantar
Priority date: 2002-10-10
Filing date: 2003-10-10
Publication date: 2004-04-22
Also published as: AU2003300173A1; GB0223471D0

Abstract

A thermal insulating material which can be used to prevent corrosion under insulation of a substrate, advantageously it also acts to prevent corrosion of the substrate and is fire retardant. The thermal insulating material is comprised of hollow particles, one or more resin binders and a fire retardant.

Description

Heat Insulation Coatings

The present invention relates to a material for use as an external coatings or encapsultant for structures such as pipes and pipelines, process equipment, vessels, valves, storage tanks, components, etc. The invention relates particularly to a material for use in preventing corrosion under insulation in areas where heat insulation is required but where there is a chance of chemical corrosion. The material is also fire retardant.

In the present Application references to a "substrate" are intended to encompass structures such as pipes and pipelines, valves, process equipment, vessels, storage tanks and components.

Currently, insulation of structures such as those mentioned above, is achieved using materials such as rockwool, glass fibre or fumed silica. These are typically contained in a protective outer layer in the form of a rigid or loose enclosures/wrappings/containers or similar. For example, it is common to lag pipes with rockwool, glass or a similar fragile material, which is then contained and supported in a removable enclosure or cladding made from aluminium. Pre-moulded sections of rockwool protected by foil or fabrics can be wrapped around a substrate such as pipes or valves .

Where heat insulation materials such as fumed silica are used, it is common to enclose the material in a protective layer to produce a "heat resistant pillow". In addition, at present where the surface layer of the substrate is at a temperature greater than 50 °C safety guarding is used to isolate the hot surface from the environment. Although it is well known to provide insulating layer or layers protected with the application of a protective outer layer such as plastic, aluminium foil or fluorinated coatings, these coatings are expensive and are hard to apply, maintain, inspect and repair.

A particular problem with these protective outer layers is that are prone to suffering from "internal condensation", as they are not fully sealed. The temperature difference between the internal surface of the substrate and the external ambient temperature is such that condensation is very likely to occur because of the relative humidity contained within the insulation medium. This condensation can contain highly corrosive chemicals from the process environment and will start to corrode the surface of the substrate. This "internal condensation" is an ideal environment for the creation of a severe corrosion cell.

Typically, in traditional insulating systems such as rockwool cladding, water vapour condenses within the insulation and falls onto the hot substrate. This then evaporates, leaving a concentrated chloride solution on the substrate that is highly corrosive to mild steel pipe-work and process equipment. This constant cycle of condensation and evaporation exposes the substrate to a highly corrosive environment and it is the creation of this "corrosion cell" that is primarily responsible for what is known as "corrosion under insulation".

As a result these protective outer layers have to be removed periodically so that the substrate can be inspected for corrosion. This requires the protective outer layer and insulation material to be cut away. However these materials are they are easily damaged and hard to reseal. Once the integrity of the outer layer and insulation material has been breached it is extremely difficult, if not impossible, to preserve the substrate as efficiently as before.

As rockwool does not burn, it is a safe heat insulation material and for this reason is most commonly used for lagging purposes. However it will be appreciated that rockwool is extremely difficult to repair. As a result the problem of condensation is never entirely solved and will increase as the insulation material ages, as these systems are easily damaged and hard to repair cost effectively.

Furthermore, these systems are prone to rainwater and other fluids leaking through the outer protective layer and collecting within the insulating layer or layers. This aids the "internal condensation" and helps to create a corrosion cell. Once damaged, these systems are poor at preventing liquids, vapours, water, rainwater or steam from getting into the insulating medium and thereby creating a corrosion cell.

The inherent problem with existing insulating material lies in the fact that they do not provide corrosion resistance to protect the substrate from decomposition. To counter this the inner surface can be protected from corrosion with a protective layer or coating. A typical method would be with a thermal metal sprayed coating. However, this increases the cost of the procedure and requires the application of more than one coating or treatment to the vessel.

Similarly current chemical corrosions resistant (anti- corrosion) coatings do not offer substantial or significant thermal insulation properties. Current insulation systems do not have sufficient chemical resistance to prevent chemical corrosion. They are liable to "internal condensation" and leakage and are an ideal medium to create a corrosion cell.

The prior art teaches of materials which are effective at providing thermal insulation but which do not offer protection against corrosion under insulation, and which are not fire retardant. The prior art also teaches of materials which have effective anti-corrosion properties but which do not offer thermal insulation.

This invention not only offers similar chemical resistance to current anti-corrosion coatings, but also has significant thermal insulation properties. For example, a temperature drop of 60 °C can be achieved with a coating thickness of 10mm. Yet further the material is fire retardant, and therefore has the advantageous property that it does not burn.

A further advantage of the material present invention lies in the fact that it is easier to remove in section from the substrate, and therefore assists in the monitoring of the integrity of the substrate which is coated. In fact the material of the present invention can be used to patch repair sections of existing insulating material such as those described above which have been removed for this purpose, or which have become damaged.

The material is also suitable for cryogenic application. Existing materials used in cryogenics, such as foamglass are good insulators but do not prevent corrosion which often occurs on contact with moisture.

According to a first aspect of the present invention there is provided a thermal insulating material which can be applied to a substrate, wherein the thermal insulating material also prevents corrosion of the substrate and is fire retardant, the thermal insulating material comprising a plurality of hollow particles, one or more resin binders and a fire retardant.

Preferably the hollow particles contain a gas. The gas may be, but is not limited to, carbon dioxide, pentane, air, oxygen, an inert gas such as helium, neon, argon, krypton, xenon, radon, air or oxygen. The hollow particles may be manufactured from an organic or inorganic material.

The hollow particles may be manufactured from a polymer, expanded polystyrene, ceramics, glass, phenolic, Expansil, Dualite, cenosphere, finite, Garosphere, minoset, phenoset or Ethylene Vinyl Acetate (EVA) . The material may comprise a mixture of particles manufactured from different materials.

The hollow particles may be micro-particles having a diameter in the range of 0.01mm to 1.5mm.

The resin binder may be selected from the group consisting of; epoxy, vinyl ester, polyester, polyurethane, polyvinyl chloride, Acrylic, Silicons, Alkyds, Epoxy ester, polysilizane, polysiloxane, Nitril- rubber, Polytetrafluoroethylene, polyvinyl alcohol (PVA and PVA_L) , polyamide, polyurea, polysulphates, Polyfluoro Rein, Phenolic Resin, 2 pack Epoxy, 1 pack moisture curing polyurethane, 2 pack polyurethane systems, or 2 pack Epoxy Novolac systems.

Typically the choice of the resin binder is set by the anticipated corrosion and operating conditions.

The fire retardant may be tetramethylolmethane, ammonium polyphosphate, calcium sulphate, carbonyl diamide, ATH, antymony oxide, chrorinated paraffin, 2,6 ditertiary butyl-para cresol or ceepree.

Preferably the thermal insulating material also comprises one or more anti-corrosive pigments. These may be, but are not limited to Zinc phosphate, aluminium phosphate, Calcium phosphate, Heucophos ZPA, HeucophosZPIO, Zinc chromate, Zinc oxide, Iron Oxides, Zinc Chromate, Zinc Tetraoxichromate, Strontium Chromate, Chrome Phosphate, Barium Chromate, Zinc Molybdate and rendered organophilic oxyaminophosphate salt of magnesium, oxyaminophosphate salt of magnesium and calcium, oxyphosphate salt of magnesium and iron, Shieldex® AC 5, Shieldex® AC 3 or Shieldex® C 303.

The thermal insulating material may also comprise one or more additives such as UV absorbent additives (titanium dioxide), adhesion promoters (A187), rheological additives (bentonite, fumed silica, acrylics, PUD, fumed silica) , extenders, solvent carriers, co-solvents, light stabilisers, hydrophobizing additives, colour pigments, antioxidants and heat stabilisers.

The thermal insulating material can be applied as a one layer coating to the substrate.

Preferably the thermal insulating material can be patch repaired in the event of damage.

Preferably the thermal insulating material can be used to patch repair existing insulating materials in the event of damage.

The thermal insulating material may be provided in the form of a spray. Alternatively the thermal insulating material may be provided as a liquid, solid or putty-like material. The thermal insulating material can be applied to the substrate by spray application, brush, trowel or roller application, dipping, immersion, encapsulation or any other suitable means.

The thermal insulating material may also be applied to the substrate as a pre-mould. In this embodiment an adhesive or primer can be used to adhere the pre-mould to the substrate. Alternatively a non-moulded version of the thermal insulating material itself may be used to adhere the pre-mould to the substrate.

The thermal insulating material may also be applied to the substrate by in situ moulding. In this event a mould will be placed around the substrate prior to pouring, pumping or injecting the thermal insulating material into the mould.

The thermal insulating material disclosed in the present invention is comprised essentially of hollow particles, one or more resin binders, fire retardant, diluent and additives. The thermal insulating material is used to prevent and reduce the occurrence of corrosion under insulation occurring on structures such as pipes and pipelines, process equipment, vessels, valves, storage tanks, components, etc.

The material is also fire retardant. It will be appreciated that this is an inherently advantageous property over existing insulation materials (with the exception of rockwool) which are generally not fire or flame retardant and which can catch fire. As a result the structures on which these materials can be used is limited as at high levels of heat the materials may propagate fires.

More specifically a blend of particles or micro-particles are used to control heat transfer rate across a layer or multiple layers. In this way, each layer can be set to match the individual requirements of the heat insulation requirements, process condition and the characteristics of the micro-particles, additives and resin binder at that point within the coating.

The micro-particles range in diameter from 0.01mm to 1.5mm and are filled with gases such as carbon dioxide, pentane, air, oxygen an inert gas such as helium, neon, argon, krypton, xenon, radon or air or oxygen.

The hollow particles may be manufactured from an organic or inorganic material, typically a polymer, expanded polystyrene, ceramics, glass, phenolic, Expansil, Dualite, cenosphere, finite, Garosphere, minoset, phenoset or Ethylene Vinyl Acetate (EVA) . The material may comprise a mixture of different particles manufactured from a selection of these materials. The hollow particles act to insulate the substrate on which the material is used. Blends of various sizes of particles may also be used. This level of selectivity allows control of the thermal conductivity and temperature gradient across the coating, as well as the chemical and thermal stability of the formula.

The hollow particles may be of any geometric shape, fibrous or honeycombed in structure. For example the hollow micro-particles may take the form of being spherical or substantially spherical, cuboid or substantially cuboid, cylindrical or substantially cylindrical, or rhomboid in shape, although this list is not intended to be exclusive. In all cases the particles contain a gas in an impermeable or semi-permeable layer.

The choice of the resin binder is set by the anticipated corrosion and operating conditions. The resin binder may be selected from the group consisting of; epoxy, vinyl ester, polyester, polyurethane, polyvinyl chloride, Acrylic, Silicons, Alkyds, Epoxy ester, polysilizane, polysiloxane, Nitril-rubber, Polytetrafluoroethylene, polyvinyl alcohol (PVA and PVA_L) , polyamide, polyurea, polysulphates, Polyfluoro Rein, Phenolic Resin, 2 pack Epoxy, 1 pack moisture curing polyurethane, 2 pack polyurethane systems, or 2 pack Epoxy Novolac systems.

A fire retardant is also present in the material, for example, tetramethylolmethane, ammonium polyphosphate, calcium sulphate, carbonyl diamide, ATH, antymony oxide, chrorinated paraffin, 2,6 ditertiary butyl-para cresol or ceepree. The material also comprises one or more pigments. These may be, but are not limited to Zinc phosphate, aluminium phosphate, Calcium phosphate, Heucophos ZPA, HeucophosZPIO, Zinc chromate, Zinc oxide, Iron Oxides, Zinc Chromate, Zinc Tetraoxichromate, Strontium Chromate, Chrome Phosphate, Barium Chromate, Zinc Molybdate and rendered organophilic oxyaminophosphate salt of magnesium, oxyaminophosphate salt of magnesium and calcium, oxyphosphate salt of magnesium and iron, Shieldex® AC 5, Shieldex® AC 3 or Shieldex® C 303. Examples of additives which may be added to the thermal insulating material are provided in Table 1:

TABLE 1 EXAMPLE ADDITIVES

Additive Quantity Examples

Rheology 0.1-10% bentonite, fumed silica, acrylics, additives PUD, Heat 0.1-10% dibutyl tin, phosphite, calcium stabiliser palmitate, calcium stearate, Tin organimetalic compounds,

Antioxidant 0.1-10% phenol 2, 4-bis (1, 1-dimethyl ether) , -phosphite, Alvinox 100,Alvinox p, irganoxlOlO colour 0.1-10% organic pigments, inorganic pigments, organometalic pigments, heat-stable pigments

Adhesion 0.1-10% Silanes, titanates, zirconate and promotors aluminate coupling agents, amidoamines,

UV absorber 0.1-10% benzotriazols and derivatives, benzophenone and derivatives,

Light 0.1-10% piperidinyl esters, triazine stabiliser compounds, uvasorb

HA29, tinuvin292, tinuvinll30, uvasorb 3C,

Hydrophibizing 0.1-10% Silanes, titanates, hydrohobic Additive fumed silicas, precipitated silicas, Aerogels

Solvent 2.0 - 50 % MEK, Acetone, Toluene, IPA, Water Carriers Co-Solvents 0.1- 10% Butyl Sellosolve, Texanol, N-MP Re-enforcing 0.5 - 40% Silicas, Carbon Black, Aerogel, Aides Calcium Carbonate, Fumed Alumina Extenders 3-40% reactive diluents, calcim caronate, talc, fumed silica, bentonite,

More than one layer of coating can be applied to the substrate to provide the ideal temperature gradient for the compound and the structure coated.

The composition of each layer, as well as the number, of layers and the thickness of each layer, is determined by considering:

• the temperature difference between the substrate's surface and the external ambient temperature.

• the anticipated process conditions. The number of layers will also be determined by the temperature gradient required across the coating as a whole.

The additives are primarily used to help with corrosion resistance, inter-coat and substrate adhesion and application properties.

An important aspect of the present invention lies in the fact that the material is applied to a substrate as a coating, which forms a continuous surface between the substrate and the external environment. As a result it is far less prone to leakage than other insulation coatings, and as a result offers far better corrosion resistance. The coating produced by the material, once dried or fully cured, is continuous from the inner layer to the outer layer, in contrast to existing materials such as rockwool. This greatly hinders the ingress of fluids and the occurrence of internal condensation.

The integrity of this insulation coating is maintained far longer than standard systems, and thereby provides higher efficiency thermal insulation and chemical resistance for longer periods of time than traditional systems. The material prevents the occurrence of "internal condensation" and is more resistant to damage and wear and tear. This prevents the creation of corrosion cell.

A further important advantage of the present invention lies in the fact that it can be easily repaired. It will be appreciated that from time to time it will be necessary to inspect or obtain access to the substrate, which is coated with the material. This necessitates the coating to be removed from the substrate in some fashion, for example by cutting. With existing materials this results in necessary damage and breaching of the integrity of the insulating material. Once the integrity of any outer layer and insulation material has been breached it is extremely difficult, if not impossible to preserve the substrate as efficiently as before, as they are easily damaged and hard to reseal.

The material of the present invention can be manufactured in the form of a spray, pre-mould, liquid or as a putty- like material. Advantageously the material of the present invention, once cured or dried, can be easily cut, to allow access to the substrate underneath and then patch repaired quickly and efficiently. This may be done for example by applying the material in its putty-like form to the area of the substrate where the original material/coating was removed. Protection of the substrate will therefore be maintained. The material is also suitable for patch repairing areas, which have become damaged.

Yet further, the material is compatible with existing insulating materials such as rockwool and can therefore be used to patch repair sections of existing insulation on substrates that have been damaged, either intentionally or accidentally.

The material can be applied to the substrate by spray application, brush, trowel or roller application, dipping, immersion, encapsulation or any other suitable means. The material may also be applied to the substrate as a pre-mould. For example small moulds may be used to manufacture "wet" slabs of the material which are laid on the substrate. Pre-casts of regular process equipment to be coated can also be manufactured. When moulds are manufactured, an adhesive or primer can be used to adhere the pre-mould to the substrate. Alternatively a virgin version of the material may be used to adhere the pre- mould to the substrate.

In any pre-cast or offsite moulding, a high temperature glue, or primer, or an adhesive version of the material itself can be used to adhere the mould to the substrate. Joints between moulds and gaps can be filled using putties, pastes and fillers. The surface of the material can also be sealed to protect against vapour or moisture. A standard sealing coat such as silane or a silicone based coat is preferably used. Moulds can also be made around the substrate to be coated into which the material can be pumped, injected or poured. The moulds can then be removed once the material has cured.

The material can be manufactured from a simple blending process. However where a hydrophilic powder form of the heat insulation fillers, extenders, fire retardant, heat stabilisers, antioxidants, adhesions promoters, UV absorbers, and light stabilisers are used, these must be hydrophobised before addition - using silicone or poly- siloxane oils for example. Alternatively hydrophobic free flow aids such as Nippon Aerosil RY 200 S or Wacker HDK 2000 and be used to coat the powder particles - typically at levels of 0.5 - 10 % by weight of the dry fillers. The powders are therefore premixed and then mixed with the resin and then a hardener.

When preparing moulds, mixing of the Resin binder and hardeners can be carried out just at the point of mould injection or casting.

Alternatively the fillers could be added to the hardener instead of the resin and then mixed as before when the mould or coating is to be applied. In addition the fillers could be added to both the filler and the resin parts prior to mixing.

Various modifications may be made to the invention herein described without departing from the scope thereof.

Claims

1. A thermal insulating material which can be applied to a substrate, wherein the thermal insulating material also prevents corrosion of the substrate and is fire retardant, the thermal insulating material comprising a plurality of hollow particles, one or more resin binders and a fire retardant.

2. A thermal insulating material as claimed in Claim 1, wherein the hollow particles contain a gas.

3. A thermal insulating material as claimed in Claim 2, wherein the gas is selected from the group consisting of carbon dioxide, pentane, air, oxygen, helium, neon, argon, krypton, xenon, radon, air and oxygen.

4. A thermal insulating material as claimed in any one of the preceding Claims, wherein the hollow particles are manufactured from an organic material.

5. A thermal insulating material as claimed in any one of Claims 1 to 3, wherein the hollow particles are manufactured from an inorganic material.

6. A thermal insulating material as claimed in any one of the preceding Claims, wherein the hollow particles are manufactured from a material selected from the group consisting of polymer, expanded polystyrene, ceramics, glass, phenolic, Expansil, Dualite, cenosphere, fillite, Garosphere, minoset, phenoset or Ethylene Vinyl Acetate (EVA) .

7. A thermal insulating material as claimed in any one of the preceding Claims, wherein the hollow particles are micro-particles having a diameter in the range of 0.01mm to 1.5mm.

8. A thermal insulating material as claimed in any one of the preceding Claims, wherein the resin binder is selected from the group consisting of; epoxy, vinyl ester, polyester, polyurethane, polyvinyl chloride, Acrylic, Silicons, Alkyds, Epoxy ester, polysilizane, polysiloxane, Nitril-rubber, Polytetrafluoroethylene, polyvinyl alcohol (PVA and PVA_L) , polyamide, polyurea, polysulphates, Polyfluoro Rein, Phenolic Resin, 2 pack Epoxy, 1 pack moisture curing polyurethane, 2 pack polyurethane systems, or 2 pack Epoxy Novolac systems.

9. A thermal insulating material as claimed in any one of the preceding Claims, wherein the fire retardant is selected from the group consisting of tetramethylolmethane, ammonium polyphosphate, calcium sulphate, carbonyl diamide, ATH, antymony oxide, chrorinated paraffin, 2,6 ditertiary butyl- para cresol or ceepree.

10. A thermal insulating material as claimed in any one of the preceding Claims, containing one or anti- corrosive more pigments.

11. A thermal insulating material as claimed in Claim 10, wherein the anti-corrosive pigments are selected from the group consisting of Zinc phosphate, aluminium phosphate, Calcium phosphate, Heucophos ZPA, HeucophosZPIO, Zinc chromate, Zinc oxide, Iron Oxides, Zinc Chromate, Zinc Tetraoxichromate, Strontium Chromate, Chrome Phosphate, Barium Chromate, Zinc Molybdate and rendered organophilic oxyaminophosphate salt of magnesium, oxyaminophosphate salt of magnesium and calcium, oxyphosphate salt of magnesium and iron, Shieldex® AC 5, Shieldex® AC 3 or Shieldex® C 303.

12. A thermal insulating material as claimed in any one of the preceding Claims comprising one or more additives.

13. A thermal insulating material as claimed in any one of the preceding Claims, containing UV absorbent additives .

14. A thermal insulating material as claimed in any one of the preceding Claims, containing adhesion promoters.

15. A thermal insulating material as claimed in any one of the preceding Claims, containing rheological additives.

16. A thermal insulating material as claimed in any one of the preceding Claims, containing extenders.

17. A thermal insulating material as claimed in any one of the preceding Claims, containing solvent carriers.

18. A thermal insulating material as claimed in any one of the preceding Claims, containing co-solvents.

19. A thermal insulating material as claimed in any one of the preceding Claims, containing light stabilisers.

20. A thermal insulating material as claimed in any one of the preceding Claims, containing hydrophobizing additives.

21. A thermal insulating material as claimed in any one of the preceding Claims, containing colour pigments.

22. A thermal insulating material as claimed in any one of the preceding Claims, containing antioxidants .

23. A thermal insulating material as claimed in any one of the preceding Claims, containing heat stabilisers.

24. A thermal insulating material as claimed in any one of the preceding Claims which is applied as a one layer coating to the substrate.

25. A thermal insulating material as claimed in any one of the preceding Claims which can be patch repaired in the event of damage.

26. A thermal insulating material as claimed in any one of the preceding Claims, which can be used to patch repair existing insulating materials in the event of damage.

27. A thermal insulating material as claimed in any one of the preceding Claims provided in the form of a spray.

28. A thermal insulating material as claimed in any one of Claims 1 to 26, provided in the form of a liquid.

29. A thermal insulating material as claimed in any one of Claims 1 to 26, provided in the form of solid.

30. A thermal insulating material as claimed in any one of Claims 1 to 26, provided in the form of a putty- like material.

31. A thermal insulating material as claimed in any one of Claims 1 to 28, which can be applied to the substrate by spray application.

32. A thermal insulating material as claimed in any one of Claims 1 to 30, which can be applied to the substrate as a pre-mould.

33. A thermal insulating material as claimed in Claim 32, wherein the pre-mould is adhered to the substrate by an adhesive or primer.

34. A thermal insulating material as claimed in Claim 32, wherein the pre-mould is adhered to the substrate by a non-moulded version of the thermal insulating material.

5. A thermal insulating material as claimed in any one of Claims 1 to 30, which can be applied to the substrate by in situ moulding.