WO2006066304A1

WO2006066304A1 - Contact body and method of producing fire proof contact body

Info

Publication number: WO2006066304A1
Application number: PCT/AU2004/001827
Authority: WO
Inventors: Jeremy Schreiber
Original assignee: Munters Pty Ltd
Current assignee: Munters Pty Ltd
Priority date: 2004-12-24
Filing date: 2004-12-24
Publication date: 2006-06-29
Anticipated expiration: 2007-06-24

Abstract

A method of producing a fire proof sheet comprising the steps of: passing a bonded web of fibrous material (42) through an impregnating solution, the impregnating solution (44) comprising 5-40% by weight of an organic resin binder, 5-40% by weight of a fire proofing agent and 20-80% by weight of an organic solvent, removing the excess impregnating solution, forming the impregnated sheets into corrugated sheets at a temperature to dry the sheets, and curing the sheets. A method of producing a contact body for use in cooling towers or evaporative coolers and contact bodies is also disclosed.

Description

Contact body and Method of producing fire proof contact body

Field of the invention

This invention relates to the production of air and water contact bodies for cooling towers and evaporative coolers and in particular to contact bodies formed from a plurality of sheets of impregnated fibrous webbing defining a plurality of channels or conduits in said contact body through which gas and liquid passes.

Background of the invention

Air and water contact bodies of the type used in cooling towers, humidifiers, evaporative coolers and the like equipment comprise interleaved corrugated layers of non-metallic materials. Corrugated sheets are placed adjacent one another with their ridges or crests contacting each other so that channels or passage ways are formed between the sheets. This provides continuously varying width passages in the sheets which result in the flow direction of the gas and liquid being repeatedly changed during passage through the body. In use water is sprayed over the contact body to effect heat and water vapour transfer between the water and the ambient air. Such contact bodies are generally formed from a range of fibrous non-metallic materials including Kraft paper, fibreglass, plastics and other materials generally impregnated with a resin to improve rigidity and wet strength.

Gas contact bodies of this type have distinct advantages in cooling towers and evaporative cooling apparatus and are generally produced to be non-flammable. While such materials will not easily catch fire, they will ignite when subjected to a fire over a prolonged period. In the case of the gas contact bodies being used in evaporative air cooling apparatus, these apparatus rely on air being withdrawn from a particular environment and cooled through evaporative contact with a cooling medium such as water. Thus there is continuously a forced draft into the evaporative cooler. If a fire breaks out near the intake of an evaporative cooler, the contact bodies will be exposed to fire for an extended period. Hence there is a need for the contact bodies to be able to be fire proof to withstand contact of this nature with a fire rather than being simply fire resistant or non flammable. Summary of the invention

Accordingly the invention provides a method of producing a fire proof sheet comprising the steps of

passing a bonded web of fibrous material through an impregnating solution, the solution comprising 5-40% by weight of an organic resin, 5-40% by weight of a fire proofing agent, and 20-80% by weight of an organic solvent,

removing the excess impregnating solution, forming the impregnated sheets into corrugated sheets at a temperature to dry the sheets, and

curing the sheets.

The fire proofing agent is preferably a clay and more preferably an alumino silicate clay such as Kaolin. The web of fibrous material is preferably a mineral glass fibre banded with a binder such as poly vinyl acetate binder.

The applicant has found that by increasing the solids content of the impregnating solution the solids impregnation into the web is increased. The content of the resin and fireproofing agent in the dried and cured fire proof sheet is in the range of 10-25 wt% and more preferably 12-19 wt%.

In a preferred form of the invention, prior to drying the web, the method further comprises the step of passing the impregnated web of fibrous material through at least a pair of squeeze rollers. This has been found to increase the solids impregnation into the fibrous material. This increased solids impregnation into the fibrous material improves the fire proofing characteristics of the impregnated fibrous web.

Preferably the organic resin is selected from the group of phenolic resins and melamin- formaldehyde resins and the drying step is at a temperature in excess of 100⁰C and may be in the range of 105^°C -140^°C. It is preferable that the step of forming the corrugated sheet is performed by a vacuuming forming operation and preferably at the drying temperature. Subjecting the wet corrugated sheet to these temperatures also enables the corrugated sheet to dry without curing the binder. The curing step is preferably carried out at a temperature in excess of 120^°C and less than 20CTC.

The web of impregnated fibrous material is then passed through to a second heating step where the binder solution is cured.

The formed cured impregnated sheet may then be shaped to produce a contact body.

In a second aspect of the invention, there is provided a method of producing a contact body comprising the steps of

applying an adhesive mixture to at least one side of an impregnated web of bonded fibrous material, the adhesive mixture comprising an alkaline metal silicate and a fire proofing agent,

shaping the sheets of impregnated bonded fibrous material, and

assembling the shaped sheets of fibrous material to form an assembled article and heating the assembled article to finally cure the adhesive.

It is preferable that the fire proofing agent is an alumino silicate, and in a preferred form of the invention the alumino silicate is a clay such as kaolin. The alkaline metal silicate is preferably a high grade, high viscosity liquid sodium silicate which is able to absorb onto the impregnated web of bonded fibrous material. The fibrous material is preferably a glass fibre veil bonded together by a suitable binder such as polyvinyl acetate. The final curing step for the assembled article preferably occurs at a temperature of 250- 300⁰C to solidify the adhesive. Prior to the final cure, the front and rear edges of the assembled article may be coated with the adhesive mixture. The impregnated web of fibrous material is preferably produced by the method of the first aspect of the invention.

The invention further provides in the third aspect an impregnated web of fibrous material comprising a bonded web of fibrous material and 10-25wt% of a resin and a fire proofing agent. The resin is preferably selected from the group of a plenolic resin or a melamine- formaldeyde resin and the fireproofing agent is an alumino-silicate such as Kaolin clay. The fibrous material is preferably a bonded glass fibre matting or kraft paper.

In an embodiment of this aspect of the invention the fire proofing agent and binder is present in the cured impregnated web in a total amount of 12-19 wt% and preferably 14- 16 wt%. The impregnated web of fibrous material is preferably produced by the method of the first aspect of the invention.

In a fourth aspect of the invention, there is provided a contact body for use in a gas and liquid contact apparatus in which gas and liquid flow in cross flow relationship, the body comprising at least first and second sets of corrugated sheets, the sheets including a bonded web of fibrous material having impregnated therein an organic resin and a fireproofing agent.

In a preferred form of this aspect, the organic resin is a phenolic resin or a melamine formaldehyde resin and content of the fireproofing agent which may be an aluminosilicate such as kaolin and resin is within the range of 10-25 wt% of the total sheet, preferably 12-19 wt%.

In a fifth aspect the invention provides an apparatus for producing a fire proof sheet, comprising:

a vessel for contacting a web of fibrous material through an impregnating solution; at least a pair of squeeze rollers through which the impregnated web passes,

an oven having a first stage for drying the impregnated web and a second stage for curing the impregnating solution on the web; and

a shape former for forming corrugations in the dried impregnated sheets prior to curing. The shape former of this aspect of the invention is preferably a vacuum former.

Further features objects and advantages of the present invention will become apparent from the preferred embodiment and accompanying drawings. Brief description of the drawings

Figure 1 is a sectional view of an evaporative cooling tower which uses contact bodies in accordance with the invention;

Figure 2 is a perspective view of a contact body; and

Figure 3 is a schematic diagram showing the production of a contact body in accordance with the invention.

Detailed description of the embodiments

Referring to the drawings, a cooling tower 10 includes the casing 12 in which one or more contact bodies 22 constructed in accordance with the present invention are mounted. The base of casing 12 is formed into a sump 23 having a float 24 and drainage line 25. Gas such as air, enters the channels or ducts within the contact bodies of the air inlet edge portion 26 thereof and is drawn upwardly within the apparatus to an outlet 29 equipped with a farm 30 and motor 31. Liquid such as water is introduced into the evaporative cooling apparatus or cooling tower through a liquid supply line 27 and escapes from the line through perforations or nozzles 28. The liquid escaping from the supply line 28 passes through a distribution pad 32 of conventional construction in the top of the contact bodies 22.

Figure 2 shows a contact body which can be formed from the impregnated sheets in accordance with the invention. The contact body comprises a plurality of corrugated sheets 33, 34, 35, 36 with the corrugations in adjacent sheets such as 33 and 34 being disposed at an angle to each other and the corrugations in alternate sheets such as 33 and 35 or 34 and 36 being disposed in parallel, whereby a plurality of crossing channels is formed within the contact body. When the contact body is mounted in a cooling tower or evaporative cooling unit, the corrugations are generally at an angle relative to the horizontal so as to permit the gravity flow of liquid there through. The angle at which the adjacent corrugated sheets are disposed is not critical and as is evident from Figure 1, the angular disposition of the alternate sheets as suggested by the crossing solid and dash lines in contact bodies 11 and 22 in Figure 1 may vary from apparatus to apparatus depending on the particular construction or particular function to be performed.

The corrugations in the corrugated sheets of contact bodies like those shown in Figure 2 are generally from 5 to 40 millimetres in height from trough to peak and are usually 10 to 30 millimetres wide.

The method of producing impregnated sheets in accordance with the invention for forming contact bodies will now be described with reference to Figures 3 and 4. The method of forming the contact bodies will also be described.

While the invention will now be described with reference to the using of fibre glass matting, other types of fibrous material such as kraft paper may be used. In the embodiment of the invention, the starting material for producing the impregnated matting is a fibre glass matting which is generally provided in reel form. The fibre glass matting is produced by combining fine fibre glass veil and polyvinyl acetate (PVA) fibre binder and adding a PVA powder binder to the surface of the combined fibres. The matting and the binder are then cured together in an oven and stored in reel form 40.

The bonded fibre glass matting 42 is then passed through an impregnation solution which is a combination of an organic resin which in the preferred embodiment is a phenolic resin, or melamine-formaldeyde resin or both, a fire proofing agent and a solvent. A typical solution has the composition given below.

It is important that the impregnation solution has a high solids content from say 10-40% and has appropriate rheological properties to enable coverage and impregnation into the bonded matting. The phenolic resin binder binds the fire proofing agent into the bonded matting.

In order to prepare the impregnating solution, Resinox® IL2132, a phenolic resin binder supplied by Orica Australia Pty Ltd, is added to a mixing vessel and water added to the mixing vessel while stirring the solution at 80 rpm for 10 minutes. Methanol is then stirred into the mixture for a further 10 minutes to maintain adequate rheological properties. The fire proofing agent (Eckalite 1 ) is then added to the mixture. Once the Eckalite has been completely added to the mixture, the mixture is stirred for a further 30 minutes at 135 rpm.

The bonded fibre glass matting is passed through the impregnating solution to coat and impregnate the bonded fibre matting with the solution. The coated matting 45 is then passed through at least one pair of squeeze rollers 46 which are a metal roller paired with a rubber roller to further impregnate the matting with the solid from the dipping solution. Due to the nature of the matting, the solid within the solution will generally not easily penetrate the matting. Hence the squeeze rollers are highly desirable to physically impregnate the solid in the dipping solution into the matting. In this way the solids content of the final cured matting can be greatly increased.

The excess dipping solution is then removed from the coated and impregnated matting before the matting progresses to the forming and curing stage of the process. The forming and curing stage of the process comprises at least two sequential ovens which initially complete drying of the matting and then cure the phenolic resin. The impregnated sheeting is transported by conveyor 51 initially formed into corrugated sheets by a suitable operation such as a vacuum forming 54 operation within the first oven. The first oven is operated preferably at a maximum temperature of 140^°C principally to dry the impregnated matting. The oven is heated by infra red heating 52 from beneath the matting as it progresses through the oven.

The dried corrugated impregnated matting 59 is then passed to a second oven 60 where the phenolic resin is cured. In order to cure the phenolic resin, the oven which is also heated by infra red heaters 62 operates at a temperature above 120⁰C and preferably heats the matting to a temperature of 150⁰C. In order to avoid discolouration of the cured phenolic resin, it is preferable that the matting does not reach a temperature in excess of 200^°C. Hence it is preferable for the oven to operate at a temperature of less that 200^°C.

The cured web of impregnated material is then passed by belt 64 to a cutting station 66 and in turn the cut sheets are passed to a stacker 68. The resulting corrugated impregnated sheets have excellent fire proofing characteristics and do not produce smoke or flame when subjected to fire conditions.

The corrugated impregnated fibre glass sheets then undergo a assembly process in order to produce contact bodies suitable for use in evaporative coolers and cooling towers as shown in Figure 1. The impregnated sheets have a solids content of fire proofing agent which in the case of the above example is Eckalite 1 , (a kaolin clay) of between 10 and 25 wt %, typically 12 to 19 wt % and preferably between 14 and 16 wt %.

In order to produce contact bodies which have the same fire proofing qualities or characteristics, it is essential that the corrugated sheets are glued together with an adhesive which will not only bind to and cross link with the resin coating on the sheets but also exhibit fire proofing characteristics

In order to produce the contact bodies the sheets initially pass over adhesive coating rollers in order to coat one side of the sheet. The adhesive is formed from an alkali metal silicate in combination with a fire proofing agent which can be the same as that used in the impregnation solution or another suitable fire proofing agent. The adhesive contains up to 50% of a fire proofing agent and preferably less than 40 wt % to ensure adequate rheological properties. Other suitable fire proofing agents are metal oxides or clays. The preferred fire proofing agent is Eckalite 1. The Eckalite 1 is a hydrated aluminium silicate supplied by EEC Australia Pty Ltd.

The preferred alkali metal silicate is a liquid sodium silicate "O" grade supplied by PQ Australia Pty Limited.

The adhesive mixtures is formed by adding the liquid sodium silicate to a drum and stirring the mixture at 80 rpm. The Eckalite 1 is then slowly added to the liquid sodium silicate and the stirring increased as the mixture thickens. Water is then added to control the viscosity and the formula stirred for a further 45 minutes at 135 rpm.

After the coated sheets pass over the adhesive rollers, the sheets are assembled into pads and cut to size. The front and rear surfaces of the pads are then coated with a coating to seal in the loose fibres exposed by the cutting stage. The coating is preferably the same formulation as the adhesive and the coated pads then pass through an oven where the matting is heated to a minimum of 100°C in order to precure the adhesive on the impregnated sheets.

The assembled contact body is then passed through a further oven where the contact body is heated to a temperature of 250^° to 300^° C to fully cure and solidify the adhesive and make the contact body waterproof.

The produced contact bodies were then tested and found to withstand flame temperatures in excess of 1000^°C without producing flame or smoke.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

It will also be understood that the term "comprises" (or its grammatical variants) as used in this specification is equivalent to the term "includes" and should not be taken as excluding the presence of other elements or features.

Claims

The Claims defining the invention are as follows:

1. A method of producing a fire proof sheet comprising the steps of:

passing a bonded web of fibrous material through an impregnating solution, the impregnating solution comprising 5-40% by weight of an organic resin binder, 5-40% by weight of a fire proofing agent and 20-80% by weight of an organic solvent,

removing the excess impregnating solution,

forming the impregnated sheets into corrugated sheets at a temperature to dry the sheets, and

curing the sheets.

2. The method of claim 1 further comprising the step of passing the impregnated web of fibrous material through at least a pair of squeeze rollers prior to the drying stage to impregnate the solids into the web of fibrous materials.

3. The method of claim 1 wherein the fibrous material is a mineral glass fibre and the organic resin binder is selected from the group of a phenolic resin, a melamine formaldehyde resin or combinations thereof.

4. The method of claim 3 wherein the fire proofing agent is an alumino silicate.

5. The method of claim 3 wherein the organic resin binder is a phenolic resin.

6. The method of claimi wherein the drying step is carried out at a temperature in excess of 100^°C.

7. The method of claim 1 wherein the drying step is conducted at a temperature in the range of 105⁰C - 140⁰C.

8. The method of claim 1 wherein the curing step is carried out at a temperature in the range of 120^°C - 200^°C.

9. A method of producing a contact body comprising the steps of

applying an adhesive mixture to at least one side of an impregnated web of bonded fibrous material, the adhesive mixture comprising a liquid alkaline metal silicate and fire proofing agent,

shaping the sheets of impregnated bonded fibrous material, and assembling the shaped sheets of fibrous material to form an assembled article, and

heating the assembled article to finally cure the adhesive and bind the material.

10. The method of claim 9 wherein the alkaline metal silicate is a high grade high viscosity liquid sodium silicate which is absorbable onto the impregnated web of fibrous material.

11. The method of claim 9 or 10 wherein the web of fibrous material is glass fibre veil bonded together by a polyvinyl acetate binder.

12. The method of claim 9 wherein the step of shaping the sheets is a vacuum forming operation which forms corrugations in the surface of the sheet.

13. The method of claim 9 wherein the final curing step is conducted at a temperature of 250^° - 300^°C.

14. The method of claim 9 wherein the impregnated web of bonded fibrous materials is produced by the method of any one of claims 1 to 8.

15. An impregnated web of fibrous material comprising a bonded web of fibrous matting, and 10-25wt% of a cured resin binder and a fire proofing agent.

16. The fibrous material of claim 15 wherein the resinous binder is a phenolic resin binder and the fire proofing agent is an alumino silicate.

17. The fibrous material of claim 15 wherein the fire proofing agent and cured resin is present in the cured impregnated web in an amount of 12 to 19% by weight.

18. A contact body for use in a gas and liquid contact apparatus in which gas and liquid flow in close flow relationship, the body comprising at least first and second sets of corrugated sheets, the sheets including a bonded web of fibrous matting having impregnated therein an organic resin and a fire proofing agent.

19. The contact body of claims 18 wherein the organic resin is a phenolic resin and the fire proofing agent is an alumino silicate.

20. The contact body of claim 18 wherein the solids content of the fire proofing agent is within the range of 20 to 25% of the total dryer weight.

21. The contact body of claim 18 wherein the solids content of the fire proofing agent is within the range of 12 to 19%.

22. A contact body for use in a gas and liquid contacting apparatus in which gas and liquid flow in a cross flow relationship, the body comprising at least first and second sets of corrugated sheets, the sheets including bonded glass matting having impregnated therein an organic binder and a fire proofing agent the sheets being formed by the method of claim 1.

23. An apparatus for producing a fire proof sheet, comprising:

an oven having a first stage for drying the impregnated web and a second stage for curing the impregnating solution on the web; and a shape former for forming corrugations in the dried impregnated sheets prior to curing.

24. The apparatus of claim 23 wherein the shape former is a vacuum former.