CA1317826C - Process for impregnating porous materials - Google Patents
Process for impregnating porous materialsInfo
- Publication number
- CA1317826C CA1317826C CA000572461A CA572461A CA1317826C CA 1317826 C CA1317826 C CA 1317826C CA 000572461 A CA000572461 A CA 000572461A CA 572461 A CA572461 A CA 572461A CA 1317826 C CA1317826 C CA 1317826C
- Authority
- CA
- Canada
- Prior art keywords
- porous material
- moisture
- temperature
- gaseous
- solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000011148 porous material Substances 0.000 title claims abstract description 156
- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000007788 liquid Substances 0.000 claims abstract description 76
- 238000000576 coating method Methods 0.000 claims abstract description 5
- 239000011248 coating agent Substances 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000009834 vaporization Methods 0.000 claims description 16
- 230000008016 vaporization Effects 0.000 claims description 16
- 238000009833 condensation Methods 0.000 claims description 14
- 230000005494 condensation Effects 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 9
- 230000001939 inductive effect Effects 0.000 claims description 6
- 239000012080 ambient air Substances 0.000 claims description 3
- 238000005470 impregnation Methods 0.000 abstract description 9
- 239000000126 substance Substances 0.000 abstract 1
- 239000000463 material Substances 0.000 description 27
- 230000006698 induction Effects 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 239000002023 wood Substances 0.000 description 4
- 238000001035 drying Methods 0.000 description 3
- 238000007654 immersion Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 239000000565 sealant Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- RZVAJINKPMORJF-UHFFFAOYSA-N Acetaminophen Chemical group CC(=O)NC1=CC=C(O)C=C1 RZVAJINKPMORJF-UHFFFAOYSA-N 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- -1 masonry Substances 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- 244000045947 parasite Species 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000010025 steaming Methods 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
- B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
- B05D3/0218—Pretreatment, e.g. heating the substrate
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
- B27K3/02—Processes; Apparatus
- B27K3/0207—Pretreatment of wood before impregnation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
- B27K3/02—Processes; Apparatus
- B27K3/0278—Processes; Apparatus involving an additional treatment during or after impregnation
- B27K3/0285—Processes; Apparatus involving an additional treatment during or after impregnation for improving the penetration of the impregnating fluid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
- B27K5/001—Heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
- B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00
- B27K5/003—Treating of wood not provided for in groups B27K1/00, B27K3/00 by using electromagnetic radiation or mechanical waves
- B27K5/0055—Radio-waves, e.g. microwaves
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A new method for the impregnation of porous materials by solutions, especially solutions which impart desirable physical, electrical, chemical and other properties to the porous material, is disclosed.
Microwave energy inductively heats the liquid moisture contained within the porous material for a prescribed time, in such a manner so as to rapidly convert the liquid moisture in the inner portion of the porous material to gaseous moisture. The gaseous moisture drives the remaining liquid moisture to the surface of the porous material. The porous material is quickly cooled and the desired solution applied to the surface of the porous material immersing or coating. The gaseous moisture contained in the outer portion of the porous material condenses to liquid moisture thereby creating a relative vacuum which induces the solution to impregnate the porous material.
A new method for the impregnation of porous materials by solutions, especially solutions which impart desirable physical, electrical, chemical and other properties to the porous material, is disclosed.
Microwave energy inductively heats the liquid moisture contained within the porous material for a prescribed time, in such a manner so as to rapidly convert the liquid moisture in the inner portion of the porous material to gaseous moisture. The gaseous moisture drives the remaining liquid moisture to the surface of the porous material. The porous material is quickly cooled and the desired solution applied to the surface of the porous material immersing or coating. The gaseous moisture contained in the outer portion of the porous material condenses to liquid moisture thereby creating a relative vacuum which induces the solution to impregnate the porous material.
Description
~3~7~2~
PROCESS FOR IMPREGNATING POROUS MATERIALS
1 BACKGROUND O_ THE INVENTION
This lnventlon relates to a method for impregnating selected solutions, such as sealants and antl-rot solutions, into porous materials, particularly wood.
In the past, many methods have been employed to mpregnate porous materials with solutions which would lmpart deslred qualltles to the materials. Generally, a two-step process has been employed comprising, ~irstly, a drylng step to reduce the material's moisture content to as little as possible, and secondly, an impregnation step in which the material is exposed to the solution and the solution penetrates into the materlal.
~d~
PROCESS FOR IMPREGNATING POROUS MATERIALS
1 BACKGROUND O_ THE INVENTION
This lnventlon relates to a method for impregnating selected solutions, such as sealants and antl-rot solutions, into porous materials, particularly wood.
In the past, many methods have been employed to mpregnate porous materials with solutions which would lmpart deslred qualltles to the materials. Generally, a two-step process has been employed comprising, ~irstly, a drylng step to reduce the material's moisture content to as little as possible, and secondly, an impregnation step in which the material is exposed to the solution and the solution penetrates into the materlal.
~d~
- 2 - ~3~7~26 1 In drying me~hods known in the prior art, the materlal lS conductlvely heated by an external means, such as ln a kiln, to evaporate tne molsture within the material. Such a method heats the surface of the material more rapidly than the interior of the material because of the insulative properties of porous materials. As a result, drying occurs more rapidly at the external portions oE the material than at the internal portions.
Because porous materials are generally poor conductors of heat, a large amount of heat may be required to suf iciently heat, to the point of evaporation, the moisture contained in the interior of the material. This gives rise to potentially hazardous effects such as heat damage to the exposed surfaces of the material.
On the other hand, at temperatures where there is little risk of such hazards, another disadvantage of the prior art methods arises. In particula{, liquid moisture within the material may not be sufficiently heated to the point of evaporation, thereby trapping liquid moisture within the material. The presence of the dense water molecules within the material may provide an undesired barrier to the full and/or uniform penetration of the impregnating solution. During the subsequent impregnation step of the prior art methods, unsatisfactory results may be achieved where residual moisture remains in _ 3 _ ~3~7~2~
1 the interior portions of the mater1al.
Passive lmpregnation methods/ wherein the SOlUtlOn lS applied by lmmersion, brushing, spraying or other such method, at standard atmospherlc pressuret may be slow. This is because the internal pressure within the material lS the same as the pressure of the ambient air, so no driving pressure diEferential exists to assist in the lmpregnation process. To overcome this disadvantage, prior art methods have often employed the expensive addltlonal step of providing an external pressurization means to increase the rate of impregnation.
S~MMARY_OF THE INVENTION
Accordingly, it is in object of this invention to overcome at least some of the disadvantages of the prior art by providing an efficient and economical alternatlve process for impregnating porous materlal with solutions capable of imparting desired qualities to the material.
It is another object of this invention to provlde an impregnation method for porous materials includlng a drying stage which min1mizes the risk of heat damage to the material, while effectively removing liquld moisture from the material.
It is another object of this invention to - 4 ~ 1 3 ~7 ~26 1 provlde a method of lmpregnating a porous material which provides rapid removal of liquid moisture ~rom the porous material by creating a pressure differential between the pressure within the material and the external pressure of tne amblent environment.
It is a further object of this invention to provide a method of lmpregnating a porous material which provides for rapid impregnation of porous materials by creating a pressure differential between the internal pressure within the material and the external pressure of the ambient environment.
With these and other objects in mind, in one of its broad aspects this lnvention resides in providing a process for impregnating a solution into a porous material comprising heating the porous material by microwave energy for a prescribed time, applying the solutlon to the porous material after the prescribed time, and cooling the porous material for a further prescribed time.
In another of its broad aspects the invention resides in providing a process for impregnating a solution into a porous material wherein the porous material is surrounded by an ambient environment having a pressure and the porous material contains liquid moisture having a temperature of vaporization and a pressure; the process comprising heating the liquid moisture by microwave energy - 5 - ~ 3 1 7 ~ 6 1 ~o a temperature at least as great as the temperature of vaporlzation so as to conver~ the liquid moisture to gaseous moisture having a temperature of condensation and having a pressure greater than the pressure o~ the liquld moisture and greater than the pressure of the ambient environment; applying the solution to the porous material;
coollng the gaseous moisture to a temperature less than the temperature of condensation so as to convert the gaseous moisture to liquid moisture having a pressure less than the pressure of the solution, thereby inducing entry of the solution into the porous material.
In another of its broad aspects the invention resides in providing a process for impregnating a solution into a porous material, the porous material having an outer surEace, an outer portion and an lnner portion, and the porous material containing at least a prescribed amount of liquid moisture; the process comprising a first step of heating the porous material by microwave energy for a prescribed time, wherein the outer surface of the porous material is ln substantial contact with ambient air having a temperature less than a temperature of vaporization of the liquid moisture contained within the porous material; whereln liquld moisture in the inner portion of the porous material having a volume is heated more rapidly than liquid moisture in the outer portion of - 6 - ~31782~
1 the porous material to a temperature at least as great as the temperature of vaporization of the liquid moisture;
converting the liquid moisture in the inner portion to gaseous moisture having a volume greater than the previous volume of the liquid moisture in the inner portion of the porous material; driving liquid moisture in the outer portion of the porous material to the outer surface of the porous material; the first step continuing until an acceptable amount of the liquid moisture contained within the porous material has been replaced by gaseous moisture and then followed by a second step of applying the solution to the outer surface of the porous material;
cooling the gaseous moisture in the outer portion of the porous material to a temperature less than the temperature of condensation of the gaseous moisture; converting the gaseous moisture in the outer portion oE the porous material to liquid moisture having a volume less than the previous volume of the gaseous moisture in the outer portion. thereby creating a relative vacuum in the outer portion of the porous material; inducing the solution to impregnate the outer portion of the porous material by the relatlve vacuum in the outer portion of the porous material; and preferably further comprising cooling the gaseous moisture in the inner portion of the porous 25 material to a temperature less than the temperature of ~ 7 ~ ~3~26 1 condensatlon of the gaseous moisture; converting the gaseous moisture in the inner portion of the porous material to ll~uid moisture having a volume less than tne volume of the gaseous molsture; creating a relative vacuum in the lnner portlon of the porous material; and inducing the solution to impregnate the lnner portion of the porous material by the relative vacuum in the inner portion of the porous material.
Further aspects of the invention will become apparent upon reviewing the following detailed description and drawings, which illustrate the invention and embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which illustrate embodiments of the inventlon:
Fiy. 1 is a schematic perspective view oE one embodlment of the heating stage of the inventlon;
Flg 2 is a cross-sectional view along the line II-II of Figure l;
Flg 3 is a cross-sectional vlew of one embodlment of the invention; and Fig ~ lS a cross-sectional view of another embodiment of the process.
~3~78~
l DETAILED DESCRIPTION OF THE INVENTION
AND PREFERRED EMBODIMENTS THEREOF
_ Tne lmpregnation process of this invention is applicable to any material of a porous or semi-porous nature. The phrase "porous material" includes all materials of porous or semi-porous nature, and materials having porous characteristics. Wood is particularly well-suited to the process. However, other materials such as stone, masonry, ceramics, textiles and paper can be used in the invention.
A porous material 10 is shown is Figure 1. The dimensions, shape and configuration illustrated in Figure 1, and all other Figures, are not actual characteristics, but are shown only for the purpose of illustration.
As shown is Figure 2, the porous material 10 has an inner portion 16, an outer portion 18 and an outer surface 20. Tne outer surface 20 of the porous material 10 comprises the exposed ex~erior of the porous material 10. The outer portion 18 is the interior part of the porous material 10 which is relatively proximal to the outer surface 20. The inner portion 16 is that part of 1 3 t rJ~
1 the interior of the porous material 10 relatively less proximal to the outer surface 20 than tne outer portion 18.
When porous material 10 contains little or no water, or other liquids, a preliminary step of this process may be necessary. The added step is to add sufficient liquid moisture 22 to the porous material 10 by soaking, steaming or suitable other method. The liquid moisture 22 present or added to the porous material 10 is preferably water, but any other liquid capable of vaporization by induction heating can be employed.
In Figure 2, liquid moisture 22 is shown schematically in only a portion of the porous material 10. It should be understood, however, that liquid moisture 22 is preferably, and in the case of wood most likely, distributed throughout the entire interior of the porous material lOo The liquid moisture 22 may be in uniform or varying concentrations throughout the porous material 10.
Prior to the impregnation stage, the porous material 10 is subjected to a neating stage to remove from the porous material 10 some or all of the liquid moisture 22.
The process uses high frequency induction heating, more commonly called microwave heating, to heat - lo - ~ 31 7 ~2 ~
1 the porous materlal 10. In Figure 1, m1crowaYeS are schematically lndicated as 14. The transmitter of the mlcrowaves (not shown) and the manner of transmission of the microwaves are not features of the lnvention.
Preferably however, the microwaves 14 have a frequency of about 2450 MHz.
The heating process takes place in an ambient environment 26, preferably an area filled with ordinary atmospheric air at ordinary "room" temperature.
The ambient environment 26 could also be an inert gas, such as argon, or other gas. Also, it could be a liquid such as the impregnation solution. Such liquid, however, must have a temperature of vaporization higher than the temperature o vaporization of the liquid moisture 22 within the porous material 10. The temperature of the ambient environment 26 is lower than the temperature of vaporization of the liquid moisture 22.
The porous material 10 is subjected to induction heating by microwave energy 14 at such a rate and quality that the liquid moisture 22 contained within the porous material is rapidly converted into gaseous moisture 24.
Having more proximal contact with the cooler ambient environment 26, the outer portion 18 of the poro~s material loses heat energy to a greater extent than does the inner portion 16 of the porous material 10. As a `` - ll - ~317~26 1 result,the liquid moisture 30 in the inner portion 16 heats up more rapidly to the temperature of vaporization of the moisture 22 than does the liquid moisture 34 ln the outer portion 18. ~ccordingly the liquid moisture 30 in the inner portion 16 is converted to gaseous moisture 32 more quickly than the liquid moisture 34 in the outer portion 18 is converted to gaseous moisture 36.
As vaporization of the liquid moisture 30 into gaseous moisture 32 takes place, there is a corresponding increase in the molecular activity of the moisture 30, thereby causing a corresponding increase in pressure or volume, or both, of the moisture 30 in the inner portion 16. An increase in the pressure of the gaseous moisture 32 in the inner portion 16 of the porous material 10 results in expansion of the gaseous moisture 32 outwards in the direction of the outer surface 20 of the porous material 10.
The liquid moisture 34 in the outer portion 18 of the porous material ln is displaced by the expanding gaseous moisture 32 from the inner portion 16.
Accordinglyl at least some of the liquid moisture 34 is driven out of the porous material 10 to the outer surface 20. Preferably, the heating stage continues until the porous material 10 is substantially saturated by gaseous moisture 24 and contains minimal liquid moisture 22.
- 12 - ~3~782~
1 However, the heating need only continue for a prescribed time such that a suitable amount of gaseous moisture 24 is Eormed ln the porous material 10 so as to create a sultable pressure difference as described below.
At this point in the process, the vapour-filled porous material 10 is subjected to a quenching stage, wnerein the porous material 10 is cooled and the selected solution 12 is impregnated into the porous material 10.
Although it is convenient for descriptive purposes only to consider the heating and quenching stages as two distinct steps within the invention, it should be understood that the two stages are intimately interconnected and should be thought of as two aspects, a forward aspect and a reverse aspect, of one another.
The quenching stage is initiated by the termlnation of induction heating by the microwaves 14 and ~he introduction of the solution 12. Preferably, these two events are substantially coincidental such that the solution 12 is applied to the porous material 10 before the porous materlal 10 has an opportunity to cool below the temperature of condensation of the gaseous moisture 24 contained therein. Alternatively, the quenching stage could take place some time after the termination of heating, if a means to maintain the vapour condition of porous material 10 was provided for the intervening period 13~7~2~
1 before the solution 12 was applied to the porous material 10 .
The solution 12 to be impregnated into porous material 10 is preferably one which will impart advantageous physical, electrical, chemlcal and/or other properties to the porous material 10. Wood, for example, may be impregnated with solutions 12 such as a strengthener, a sealant against moisture or rot, a fire retardant, a parasite retardant, a colouring pigment or 1~ other such solutionsO
In a preferred embodiment, the solution 12 is applied to the porous material 10 at a temperature below the temperature at which the gaseous moisture 24 will condense into liquid moisture 22.
The selected solution 12 may be applied to the porous material 10 ln a variety of ways. Preferably, the material 10 is immersed in the solution 12 (see Fig. 3) providing complete exposure of the outer surface 20 to the porous material 10 to the solution 12.
In a second embodiment, a coating 28 of the solution 12 is applied to the material 10 by spraying (see Fig. 4), brus~ing or other suitable means, other than immersion. Preferably, a coating method would take place in an ambient environment 26 having a temperature less than the temperature of condensation of the gaseous - 14 - ~ 3 ~ 7 8 2 ~
I moisture 24 and at standard atmospheric pressure.
Preferably, the application of the solution 12 is concurrent with the conductive cooling of the porous material 10. Preferably, it is the cooler solution 12, in the case of an immersion application, and the cooler solution 12 and the cooler ambient environment 26 in the case of a non-immersion or coating method, that cools the porous material 10 and the gaseous moisture 24 within the porous material 10.
When the porous material 10 is cooled, the gaseous moisture 24 in the porous material 10 that is closest to the outer surface in 20 of the porous material 10 is condensed and converted to liquid moisture 22. This creates a reduced pressure at the region where the newly-condensed moisture 22 is located in comparison to the pressure prior to condensation. The pressure in this area is less than the pressure of the ambient enviroment.
Accordingly, the ambient environment 26 forces the impregnating solution 12 into the material 10.
Preferably, the cooling takes place quickly so as to ensure that there is sufficient pressure difference between the ambient environment 26 and/or the solution 12 and the interior of the porous material 10 so as to cause impregnation of the solution 12.
As the porous material 10 is progressively - 15 - 1 3~82~
1 cooled towards its inner portion 16, gaseous moisture 2~
further from the surface 20 is progressively converted to liquid moisture 22, and the impregnating solution 12 is progressively penetrated further into the porous material 10 such that penetration of the solution 12 to all areas of the porous material 10 is possible, if desired, depending on the length of time the porous material 10 is allowed to cool quickly.
The residual heat from the heating process is generally sufficient to dry the impregnating solution 12.
Although the disclosure describes and illustrates certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. The invention includes all embodiments which are functional, mechanical or electrical equivalents to the embodiments disclosed and illustrated nerein.
~0
Because porous materials are generally poor conductors of heat, a large amount of heat may be required to suf iciently heat, to the point of evaporation, the moisture contained in the interior of the material. This gives rise to potentially hazardous effects such as heat damage to the exposed surfaces of the material.
On the other hand, at temperatures where there is little risk of such hazards, another disadvantage of the prior art methods arises. In particula{, liquid moisture within the material may not be sufficiently heated to the point of evaporation, thereby trapping liquid moisture within the material. The presence of the dense water molecules within the material may provide an undesired barrier to the full and/or uniform penetration of the impregnating solution. During the subsequent impregnation step of the prior art methods, unsatisfactory results may be achieved where residual moisture remains in _ 3 _ ~3~7~2~
1 the interior portions of the mater1al.
Passive lmpregnation methods/ wherein the SOlUtlOn lS applied by lmmersion, brushing, spraying or other such method, at standard atmospherlc pressuret may be slow. This is because the internal pressure within the material lS the same as the pressure of the ambient air, so no driving pressure diEferential exists to assist in the lmpregnation process. To overcome this disadvantage, prior art methods have often employed the expensive addltlonal step of providing an external pressurization means to increase the rate of impregnation.
S~MMARY_OF THE INVENTION
Accordingly, it is in object of this invention to overcome at least some of the disadvantages of the prior art by providing an efficient and economical alternatlve process for impregnating porous materlal with solutions capable of imparting desired qualities to the material.
It is another object of this invention to provlde an impregnation method for porous materials includlng a drying stage which min1mizes the risk of heat damage to the material, while effectively removing liquld moisture from the material.
It is another object of this invention to - 4 ~ 1 3 ~7 ~26 1 provlde a method of lmpregnating a porous material which provides rapid removal of liquid moisture ~rom the porous material by creating a pressure differential between the pressure within the material and the external pressure of tne amblent environment.
It is a further object of this invention to provide a method of lmpregnating a porous material which provides for rapid impregnation of porous materials by creating a pressure differential between the internal pressure within the material and the external pressure of the ambient environment.
With these and other objects in mind, in one of its broad aspects this lnvention resides in providing a process for impregnating a solution into a porous material comprising heating the porous material by microwave energy for a prescribed time, applying the solutlon to the porous material after the prescribed time, and cooling the porous material for a further prescribed time.
In another of its broad aspects the invention resides in providing a process for impregnating a solution into a porous material wherein the porous material is surrounded by an ambient environment having a pressure and the porous material contains liquid moisture having a temperature of vaporization and a pressure; the process comprising heating the liquid moisture by microwave energy - 5 - ~ 3 1 7 ~ 6 1 ~o a temperature at least as great as the temperature of vaporlzation so as to conver~ the liquid moisture to gaseous moisture having a temperature of condensation and having a pressure greater than the pressure o~ the liquld moisture and greater than the pressure of the ambient environment; applying the solution to the porous material;
coollng the gaseous moisture to a temperature less than the temperature of condensation so as to convert the gaseous moisture to liquid moisture having a pressure less than the pressure of the solution, thereby inducing entry of the solution into the porous material.
In another of its broad aspects the invention resides in providing a process for impregnating a solution into a porous material, the porous material having an outer surEace, an outer portion and an lnner portion, and the porous material containing at least a prescribed amount of liquid moisture; the process comprising a first step of heating the porous material by microwave energy for a prescribed time, wherein the outer surface of the porous material is ln substantial contact with ambient air having a temperature less than a temperature of vaporization of the liquid moisture contained within the porous material; whereln liquld moisture in the inner portion of the porous material having a volume is heated more rapidly than liquid moisture in the outer portion of - 6 - ~31782~
1 the porous material to a temperature at least as great as the temperature of vaporization of the liquid moisture;
converting the liquid moisture in the inner portion to gaseous moisture having a volume greater than the previous volume of the liquid moisture in the inner portion of the porous material; driving liquid moisture in the outer portion of the porous material to the outer surface of the porous material; the first step continuing until an acceptable amount of the liquid moisture contained within the porous material has been replaced by gaseous moisture and then followed by a second step of applying the solution to the outer surface of the porous material;
cooling the gaseous moisture in the outer portion of the porous material to a temperature less than the temperature of condensation of the gaseous moisture; converting the gaseous moisture in the outer portion oE the porous material to liquid moisture having a volume less than the previous volume of the gaseous moisture in the outer portion. thereby creating a relative vacuum in the outer portion of the porous material; inducing the solution to impregnate the outer portion of the porous material by the relatlve vacuum in the outer portion of the porous material; and preferably further comprising cooling the gaseous moisture in the inner portion of the porous 25 material to a temperature less than the temperature of ~ 7 ~ ~3~26 1 condensatlon of the gaseous moisture; converting the gaseous moisture in the inner portion of the porous material to ll~uid moisture having a volume less than tne volume of the gaseous molsture; creating a relative vacuum in the lnner portlon of the porous material; and inducing the solution to impregnate the lnner portion of the porous material by the relative vacuum in the inner portion of the porous material.
Further aspects of the invention will become apparent upon reviewing the following detailed description and drawings, which illustrate the invention and embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which illustrate embodiments of the inventlon:
Fiy. 1 is a schematic perspective view oE one embodlment of the heating stage of the inventlon;
Flg 2 is a cross-sectional view along the line II-II of Figure l;
Flg 3 is a cross-sectional vlew of one embodlment of the invention; and Fig ~ lS a cross-sectional view of another embodiment of the process.
~3~78~
l DETAILED DESCRIPTION OF THE INVENTION
AND PREFERRED EMBODIMENTS THEREOF
_ Tne lmpregnation process of this invention is applicable to any material of a porous or semi-porous nature. The phrase "porous material" includes all materials of porous or semi-porous nature, and materials having porous characteristics. Wood is particularly well-suited to the process. However, other materials such as stone, masonry, ceramics, textiles and paper can be used in the invention.
A porous material 10 is shown is Figure 1. The dimensions, shape and configuration illustrated in Figure 1, and all other Figures, are not actual characteristics, but are shown only for the purpose of illustration.
As shown is Figure 2, the porous material 10 has an inner portion 16, an outer portion 18 and an outer surface 20. Tne outer surface 20 of the porous material 10 comprises the exposed ex~erior of the porous material 10. The outer portion 18 is the interior part of the porous material 10 which is relatively proximal to the outer surface 20. The inner portion 16 is that part of 1 3 t rJ~
1 the interior of the porous material 10 relatively less proximal to the outer surface 20 than tne outer portion 18.
When porous material 10 contains little or no water, or other liquids, a preliminary step of this process may be necessary. The added step is to add sufficient liquid moisture 22 to the porous material 10 by soaking, steaming or suitable other method. The liquid moisture 22 present or added to the porous material 10 is preferably water, but any other liquid capable of vaporization by induction heating can be employed.
In Figure 2, liquid moisture 22 is shown schematically in only a portion of the porous material 10. It should be understood, however, that liquid moisture 22 is preferably, and in the case of wood most likely, distributed throughout the entire interior of the porous material lOo The liquid moisture 22 may be in uniform or varying concentrations throughout the porous material 10.
Prior to the impregnation stage, the porous material 10 is subjected to a neating stage to remove from the porous material 10 some or all of the liquid moisture 22.
The process uses high frequency induction heating, more commonly called microwave heating, to heat - lo - ~ 31 7 ~2 ~
1 the porous materlal 10. In Figure 1, m1crowaYeS are schematically lndicated as 14. The transmitter of the mlcrowaves (not shown) and the manner of transmission of the microwaves are not features of the lnvention.
Preferably however, the microwaves 14 have a frequency of about 2450 MHz.
The heating process takes place in an ambient environment 26, preferably an area filled with ordinary atmospheric air at ordinary "room" temperature.
The ambient environment 26 could also be an inert gas, such as argon, or other gas. Also, it could be a liquid such as the impregnation solution. Such liquid, however, must have a temperature of vaporization higher than the temperature o vaporization of the liquid moisture 22 within the porous material 10. The temperature of the ambient environment 26 is lower than the temperature of vaporization of the liquid moisture 22.
The porous material 10 is subjected to induction heating by microwave energy 14 at such a rate and quality that the liquid moisture 22 contained within the porous material is rapidly converted into gaseous moisture 24.
Having more proximal contact with the cooler ambient environment 26, the outer portion 18 of the poro~s material loses heat energy to a greater extent than does the inner portion 16 of the porous material 10. As a `` - ll - ~317~26 1 result,the liquid moisture 30 in the inner portion 16 heats up more rapidly to the temperature of vaporization of the moisture 22 than does the liquid moisture 34 ln the outer portion 18. ~ccordingly the liquid moisture 30 in the inner portion 16 is converted to gaseous moisture 32 more quickly than the liquid moisture 34 in the outer portion 18 is converted to gaseous moisture 36.
As vaporization of the liquid moisture 30 into gaseous moisture 32 takes place, there is a corresponding increase in the molecular activity of the moisture 30, thereby causing a corresponding increase in pressure or volume, or both, of the moisture 30 in the inner portion 16. An increase in the pressure of the gaseous moisture 32 in the inner portion 16 of the porous material 10 results in expansion of the gaseous moisture 32 outwards in the direction of the outer surface 20 of the porous material 10.
The liquid moisture 34 in the outer portion 18 of the porous material ln is displaced by the expanding gaseous moisture 32 from the inner portion 16.
Accordinglyl at least some of the liquid moisture 34 is driven out of the porous material 10 to the outer surface 20. Preferably, the heating stage continues until the porous material 10 is substantially saturated by gaseous moisture 24 and contains minimal liquid moisture 22.
- 12 - ~3~782~
1 However, the heating need only continue for a prescribed time such that a suitable amount of gaseous moisture 24 is Eormed ln the porous material 10 so as to create a sultable pressure difference as described below.
At this point in the process, the vapour-filled porous material 10 is subjected to a quenching stage, wnerein the porous material 10 is cooled and the selected solution 12 is impregnated into the porous material 10.
Although it is convenient for descriptive purposes only to consider the heating and quenching stages as two distinct steps within the invention, it should be understood that the two stages are intimately interconnected and should be thought of as two aspects, a forward aspect and a reverse aspect, of one another.
The quenching stage is initiated by the termlnation of induction heating by the microwaves 14 and ~he introduction of the solution 12. Preferably, these two events are substantially coincidental such that the solution 12 is applied to the porous material 10 before the porous materlal 10 has an opportunity to cool below the temperature of condensation of the gaseous moisture 24 contained therein. Alternatively, the quenching stage could take place some time after the termination of heating, if a means to maintain the vapour condition of porous material 10 was provided for the intervening period 13~7~2~
1 before the solution 12 was applied to the porous material 10 .
The solution 12 to be impregnated into porous material 10 is preferably one which will impart advantageous physical, electrical, chemlcal and/or other properties to the porous material 10. Wood, for example, may be impregnated with solutions 12 such as a strengthener, a sealant against moisture or rot, a fire retardant, a parasite retardant, a colouring pigment or 1~ other such solutionsO
In a preferred embodiment, the solution 12 is applied to the porous material 10 at a temperature below the temperature at which the gaseous moisture 24 will condense into liquid moisture 22.
The selected solution 12 may be applied to the porous material 10 ln a variety of ways. Preferably, the material 10 is immersed in the solution 12 (see Fig. 3) providing complete exposure of the outer surface 20 to the porous material 10 to the solution 12.
In a second embodiment, a coating 28 of the solution 12 is applied to the material 10 by spraying (see Fig. 4), brus~ing or other suitable means, other than immersion. Preferably, a coating method would take place in an ambient environment 26 having a temperature less than the temperature of condensation of the gaseous - 14 - ~ 3 ~ 7 8 2 ~
I moisture 24 and at standard atmospheric pressure.
Preferably, the application of the solution 12 is concurrent with the conductive cooling of the porous material 10. Preferably, it is the cooler solution 12, in the case of an immersion application, and the cooler solution 12 and the cooler ambient environment 26 in the case of a non-immersion or coating method, that cools the porous material 10 and the gaseous moisture 24 within the porous material 10.
When the porous material 10 is cooled, the gaseous moisture 24 in the porous material 10 that is closest to the outer surface in 20 of the porous material 10 is condensed and converted to liquid moisture 22. This creates a reduced pressure at the region where the newly-condensed moisture 22 is located in comparison to the pressure prior to condensation. The pressure in this area is less than the pressure of the ambient enviroment.
Accordingly, the ambient environment 26 forces the impregnating solution 12 into the material 10.
Preferably, the cooling takes place quickly so as to ensure that there is sufficient pressure difference between the ambient environment 26 and/or the solution 12 and the interior of the porous material 10 so as to cause impregnation of the solution 12.
As the porous material 10 is progressively - 15 - 1 3~82~
1 cooled towards its inner portion 16, gaseous moisture 2~
further from the surface 20 is progressively converted to liquid moisture 22, and the impregnating solution 12 is progressively penetrated further into the porous material 10 such that penetration of the solution 12 to all areas of the porous material 10 is possible, if desired, depending on the length of time the porous material 10 is allowed to cool quickly.
The residual heat from the heating process is generally sufficient to dry the impregnating solution 12.
Although the disclosure describes and illustrates certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. The invention includes all embodiments which are functional, mechanical or electrical equivalents to the embodiments disclosed and illustrated nerein.
~0
Claims (16)
1. A process for impregnating a solution into a porous material comprising:
heating the porous material by microwave energy for a first prescribed time;
applying the solution to the porous material after the first prescribed time; and quickly cooling the porous material for a second prescribed time.
heating the porous material by microwave energy for a first prescribed time;
applying the solution to the porous material after the first prescribed time; and quickly cooling the porous material for a second prescribed time.
2. The process as claimed in claim 1 wherein the porous material has an outer surface, an outer portion and an inner portion; wherein prior to being heated the porous material contains liquid moisture having a temperature of vaporization, wherein the outer surface of the porous material is in substantial contact with an ambient environment at least while being heated; and wherein the ambient environment has a temperature less than the temperature of vaporization of the liquid moisture contained within the porous material.
3. The process as claimed in claim 2 wherein the microwave energy heats liquid moisture contained within the inner portion of the porous material more rapidly than liquid moisture contained within the outer portion to a temperature at least as great as the temperature of vaporization of the liquid moisture such that the liquid moisture contained within the inner portion of the porous material is converted to gaseous moisture before liquid moisture contained within the outer portion of the porous material is converted to gaseous moisture.
4. The process as claimed in claim 3 wherein the gaseous moisture in the inner portion of the porous material has a pressure greater than a pressure of the liquid moisture in the outer portion and greater than a pressure of the ambient environment, thereby forcing the liquid moisture from the porous material to the outer surface of the porous material.
5. The process as claimed in claim 4 wherein heating the porous material by microwave energy continues until a suitable amount of the liquid moisture contained within the porous material has been converted to gaseous moisture.
6. The process as claimed in claim 5 wherein heating the porous material by microwave energy continues until substantially all of the liquid moisture contained within the porous material has been removed from the porous material.
7. The process as claimed in claim 5 wherein a coating of the solution is applied to the outer surface of the porous material.
8. The process as claimed in claim 7 wherein gaseous moisture most proximal to the outer surface of the porous material is quickly cooled to a temperature less than a temperature of condensation of the gaseous moisture before gaseous moisture less proximal to the outer surface is cooled to a temperature less than the temperature of condensation of the gaseous moisture, thereby converting the gaseous moisture most proximal to the surface of the porous material to a second liquid moisture having a pressure less than the pressure of the ambient environment.
9. The process as claimed in claim 8 wherein the relative pressure difference between the ambient environment and the second liquid moisture induces the solution to impregnate the porous material.
10. The process as claimed in claim 5 wherein the solution is applied to the porous material by immersing the porous material in the solution, said solution having a pressure.
11. The process as claimed in claim 10 where gaseous moisture most proximal to the outer surface of the porous material is quickly cooled to a temperature less than a temperature of condensation of the gaseous moisture before gaseous moisture less proximal to the outer surface is cooled to a temperature less than the temperature of condensation of the gaseous moisture, thereby converting the gaseous moisture most proximal to the outer surface of the porous material to a second liquid moisture having a pressure less than the pressure of the solution.
12. The process as claimed in claim 11 wherein the relative pressure difference between the solution and the second liquid moisture induces the solution to impregnate the porous material.
13. A process for impregnating a solution into a porous material surrounded by an ambient environment having a pressure, wherein the porous material contains in an inner portion and an outer portion liquid moisture having a temperature of vaporization and a pressure;
comprising:
converting the liquid moisture in the inner portion to a gaseous moisture having a temperature of condensation and having a pressure greater than the pressure of the liquid moisture and greater than the pressure of the ambient environment by heating the liquid moisture by microwave energy to a temperature at least as great as the temperature of vaporization;
applying the solution to an outer surface of the porous material;
cooling first the gaseous moisture closer to the outer surface of the porous material to a temperature less than the temperature of condensation of the gaseous moisture, thereby converting the gaseous moisture closer to the outer surface to liquid moisture having a pressure less than a pressure of the solution and less than the pressure of the ambient environment, thereby inducing movement of the solution into the porous material.
comprising:
converting the liquid moisture in the inner portion to a gaseous moisture having a temperature of condensation and having a pressure greater than the pressure of the liquid moisture and greater than the pressure of the ambient environment by heating the liquid moisture by microwave energy to a temperature at least as great as the temperature of vaporization;
applying the solution to an outer surface of the porous material;
cooling first the gaseous moisture closer to the outer surface of the porous material to a temperature less than the temperature of condensation of the gaseous moisture, thereby converting the gaseous moisture closer to the outer surface to liquid moisture having a pressure less than a pressure of the solution and less than the pressure of the ambient environment, thereby inducing movement of the solution into the porous material.
14. A process for impregnating a solution into a porous material, the porous material having an outer surface, an outer portion and an inner portion, and the porous material containing at least a prescribed amount of liquid moisture; comprising:
a first step of heating the porous material by microwave energy for a prescribed time, wherein the outer surface of the porous material is in substantial contact with ambient air having a temperature less than a temperature of vaporization of the liquid moisture contained within the porous material; wherein liquid moisture in the inner portion of the porous material having a volume is heated more rapidly than liquid moisture in the outer portion of the porous material to a temperature at least as great as the temperature of vaporization of the liquid moisture; converting the liquid moisture in the inner portion to gaseous moisture having a volume greater than the volume previously occupied by the liquid moisture in the inner portion of the porous material; driving liquid moisture in the outer portion of the porous material to the outer surface of the porous material; the first step continuing until an acceptable amount of the liquid moisture contained within the porous material has been replaced by gaseous moisture; followed by a second step of applying the solution to the outer surface of the porous material; cooling the gaseous moisture in the outer portion of the porous material to a temperature less than the temperature of condensation of the gaseous moisture; converting the gaseous moisture in the outer portion of the porous material to liquid moisture having a volume less than the volume previously occupied by the gaseous moisture in the outer portion, thereby creating a relative vacuum in the outer portion of the porous material; and inducing the solution to impregnate the outer portion of the porous material by the relative vacuum in the outer portion of the porous material.
a first step of heating the porous material by microwave energy for a prescribed time, wherein the outer surface of the porous material is in substantial contact with ambient air having a temperature less than a temperature of vaporization of the liquid moisture contained within the porous material; wherein liquid moisture in the inner portion of the porous material having a volume is heated more rapidly than liquid moisture in the outer portion of the porous material to a temperature at least as great as the temperature of vaporization of the liquid moisture; converting the liquid moisture in the inner portion to gaseous moisture having a volume greater than the volume previously occupied by the liquid moisture in the inner portion of the porous material; driving liquid moisture in the outer portion of the porous material to the outer surface of the porous material; the first step continuing until an acceptable amount of the liquid moisture contained within the porous material has been replaced by gaseous moisture; followed by a second step of applying the solution to the outer surface of the porous material; cooling the gaseous moisture in the outer portion of the porous material to a temperature less than the temperature of condensation of the gaseous moisture; converting the gaseous moisture in the outer portion of the porous material to liquid moisture having a volume less than the volume previously occupied by the gaseous moisture in the outer portion, thereby creating a relative vacuum in the outer portion of the porous material; and inducing the solution to impregnate the outer portion of the porous material by the relative vacuum in the outer portion of the porous material.
15. A process as claimed in claim 14 further including cooling the gaseous moisture in the inner portion of the porous material to a temperature less than the temperature of condensation of the gaseous moisture;
converting the gaseous moisture in the inner portion of the porous material to liquid moisture having a volume less than the volume of the gaseous moisture; creating a relative vacuum in the inner portion of the porous material; inducing the solution to impregnate the inner portion of the porous material by the relative vacuum in the inner portion of the porous material.
converting the gaseous moisture in the inner portion of the porous material to liquid moisture having a volume less than the volume of the gaseous moisture; creating a relative vacuum in the inner portion of the porous material; inducing the solution to impregnate the inner portion of the porous material by the relative vacuum in the inner portion of the porous material.
16. A process as claimed in claim 1, 13 or 14 wherein a preliminary step of providing at least a prescribed amount of liquid moisture to the porous material is carried out prior to heating the porous material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000572461A CA1317826C (en) | 1988-07-19 | 1988-07-19 | Process for impregnating porous materials |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000572461A CA1317826C (en) | 1988-07-19 | 1988-07-19 | Process for impregnating porous materials |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1317826C true CA1317826C (en) | 1993-05-18 |
Family
ID=4138404
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000572461A Expired - Fee Related CA1317826C (en) | 1988-07-19 | 1988-07-19 | Process for impregnating porous materials |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1317826C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6296939B1 (en) | 1996-06-07 | 2001-10-02 | Basf Coatings Ag | Heat-sensitive material coated with powder paint |
-
1988
- 1988-07-19 CA CA000572461A patent/CA1317826C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6296939B1 (en) | 1996-06-07 | 2001-10-02 | Basf Coatings Ag | Heat-sensitive material coated with powder paint |
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