CA2324113C - Polymeric desiccant articles and process for their manufacture - Google Patents
Polymeric desiccant articles and process for their manufacture Download PDFInfo
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- CA2324113C CA2324113C CA002324113A CA2324113A CA2324113C CA 2324113 C CA2324113 C CA 2324113C CA 002324113 A CA002324113 A CA 002324113A CA 2324113 A CA2324113 A CA 2324113A CA 2324113 C CA2324113 C CA 2324113C
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/26—Synthetic macromolecular compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/261—Drying gases or vapours by adsorption
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/28—Selection of materials for use as drying agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
- B01J20/3206—Organic carriers, supports or substrates
- B01J20/3208—Polymeric carriers, supports or substrates
- B01J20/3212—Polymeric carriers, supports or substrates consisting of a polymer obtained by reactions otherwise than involving only carbon to carbon unsaturated bonds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
- B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
- B01J20/3268—Macromolecular compounds
- B01J20/327—Polymers obtained by reactions involving only carbon to carbon unsaturated bonds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
- B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
- B01J20/3268—Macromolecular compounds
- B01J20/3272—Polymers obtained by reactions otherwise than involving only carbon to carbon unsaturated bonds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
- B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
- B01J20/3268—Macromolecular compounds
- B01J20/328—Polymers on the carrier being further modified
- B01J20/3282—Crosslinked polymers
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- Analytical Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Drying Of Gases (AREA)
Abstract
Articles comprising a substrate and a polymeric desiccant either impregnated therein or coated thereon are disclosed as well as processes for their manufacture. The invention also contemplates a process f or synthesizing a polymeric desiccant in particulate form for use as such or for use as a coating material for desiccant articles.
Description
POLYMERIC DESICCANT ARTICLES AND
PROCESS FOR THEIR MANUFACTURE
Technical Field The present invention concerns the manufacture of desiccant articles consisting of a substrate or other material onto which is synthesized a polymeric desiccant and, in particular, a desiccant article capable of multiple cycles of absorption and desorption of gases such as water vapour in the air or in any gaseous stream.
This article has possible applications in the field of air treatment, such as dehumidification, in systems for the transfer of moisture and heat between two air streams, in HVAC systems and in other applications involving moisture control and recovery.
Background Art The solid desiccants used in air treatment or liquid absorption systems are primarily inorganic (silica gel, molecular sieves, etc). They take the form of fine powders which must be bonded to a rigid substrate. There are a number of techniques for depositing these desiccants, some of which have been patented. Examples include patents filed in the United States under Nos.
3,338,034; 4,769,053; 5,052,188; 5,120,694; 5,496,397; and 5,542,968.
U.S. Patent No. 5,542,968 describes a method which involves mixing the desiccant powder with fibres in a solution containing a binder and fire retardants, among other ingredients. A
manufacturing process borrowed from the paper industry is then used to produce sheets of this compound. Canadian Patent No. 1,285,931 uses a technique which consists of coating a metallic substrate with a mixture consisting primarily of an inorganic desiccant and a heat-curable binder or adhesive in a solvent. The powder is then bonded to the substrate by heating the article. U. S. Patent No. 4,172,164 describes the use of a solvent to partially dissolve the thermoplastic substrate, leaving the polymer particles imbedded in it following evaporation of the solvent. These techniques have the disadvantage of inhibiting to some extent the absorption of water by the desiccant powder, which may deliquesce and become detached under conditions of actual use.
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PROCESS FOR THEIR MANUFACTURE
Technical Field The present invention concerns the manufacture of desiccant articles consisting of a substrate or other material onto which is synthesized a polymeric desiccant and, in particular, a desiccant article capable of multiple cycles of absorption and desorption of gases such as water vapour in the air or in any gaseous stream.
This article has possible applications in the field of air treatment, such as dehumidification, in systems for the transfer of moisture and heat between two air streams, in HVAC systems and in other applications involving moisture control and recovery.
Background Art The solid desiccants used in air treatment or liquid absorption systems are primarily inorganic (silica gel, molecular sieves, etc). They take the form of fine powders which must be bonded to a rigid substrate. There are a number of techniques for depositing these desiccants, some of which have been patented. Examples include patents filed in the United States under Nos.
3,338,034; 4,769,053; 5,052,188; 5,120,694; 5,496,397; and 5,542,968.
U.S. Patent No. 5,542,968 describes a method which involves mixing the desiccant powder with fibres in a solution containing a binder and fire retardants, among other ingredients. A
manufacturing process borrowed from the paper industry is then used to produce sheets of this compound. Canadian Patent No. 1,285,931 uses a technique which consists of coating a metallic substrate with a mixture consisting primarily of an inorganic desiccant and a heat-curable binder or adhesive in a solvent. The powder is then bonded to the substrate by heating the article. U. S. Patent No. 4,172,164 describes the use of a solvent to partially dissolve the thermoplastic substrate, leaving the polymer particles imbedded in it following evaporation of the solvent. These techniques have the disadvantage of inhibiting to some extent the absorption of water by the desiccant powder, which may deliquesce and become detached under conditions of actual use.
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Another category of articles relates to water absorption in diapers or sanitary napkins. The absorbent materials used in these applications arc polymers capable of absorbing up to hundreds of tunes their own weight in water and are hence referred to as superabsorbents. U.5. Patents Noa. 3,669,103 and S 3,810,468 describe a method which consists of spreading a copolymer of acrylic acid and acrylamide, in powder form, on a fibrous material. This material is exposed to steam to swell the particles of powder, then compressed and dried to bond the polymer to the fibres. One of the disadvantages of this method is the fact that tile polymer detaches from the fibres after absorbing the liquid and swelling. Another mothod described in U.S. Patent No. 3,005,456 consists of treating the fibres with chloroaeetic acid to permit the attachment of carboxymethyl groups for absorbency. This technique uses chloroacetic acid, a very expensive product, in a propanol solution. In addition, the absorptive capacity of the fibres is considered i5 insufficient. Finally, another method described in U.S. Patent No.
5,026,596 consists of producing a water absorbent polymer coated article which has excellent water adsorption and swelling properties. This~patent is the result of continual improvement of the techniques described in Japanese Patents Nos. 50-82143/1975, 55~84304/1980 and 58-$480411983. These ZO applications involve large quantities of polymer and, once it is swollen by the absorbed liquid, the structure of the article deteriorates and disintegrates.
Further patents relating to such highly absorbent materials (supcrabsorbents) include U.S. Patents Nos. 4,605,401; 4,948,659; 5,567,478 and S,OZ6,596.
Summary of the Inveotian 25 The article of the present invention is intended for the absorption of water in gaseous form (l.c. water vapour or humidity) and not water in liquid form, as is the case with superabsarbents. With superabsorbents, the theory is to attempt to maximize the water-absarpdve capacity of the polymer, which causes it to swell considerably. Absorptive capacities on the order of 30 several tens to several hundreds of times the dry weight of the material are thereby obta.incd. In order not to restrict swelling, the polymer is weakly AF~E1~D~D S!HEE~
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5,026,596 consists of producing a water absorbent polymer coated article which has excellent water adsorption and swelling properties. This~patent is the result of continual improvement of the techniques described in Japanese Patents Nos. 50-82143/1975, 55~84304/1980 and 58-$480411983. These ZO applications involve large quantities of polymer and, once it is swollen by the absorbed liquid, the structure of the article deteriorates and disintegrates.
Further patents relating to such highly absorbent materials (supcrabsorbents) include U.S. Patents Nos. 4,605,401; 4,948,659; 5,567,478 and S,OZ6,596.
Summary of the Inveotian 25 The article of the present invention is intended for the absorption of water in gaseous form (l.c. water vapour or humidity) and not water in liquid form, as is the case with superabsarbents. With superabsorbents, the theory is to attempt to maximize the water-absarpdve capacity of the polymer, which causes it to swell considerably. Absorptive capacities on the order of 30 several tens to several hundreds of times the dry weight of the material are thereby obta.incd. In order not to restrict swelling, the polymer is weakly AF~E1~D~D S!HEE~
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cross-linked. To that end, the cross-polymerizing agent (CPA) used during the synthesis to give a minimum of structure to the supcrabsorbent product is introduced in very small amounts. The proportion of CPA is typically on the order of 8.1% of the quantity of acrylic acid, Most cross-polymerizing agents dissolve readily in aqueous solution when usod in such proportions.
In the case of the present invention, however, it is necessary to control the swelling of the substrate when it absorbs water vapour or other gas and also to limit the absorption of liquid water. For this reason, the polymer of the present invention is strongly cross-linked. This is aehicved by using a I O greater quantity of cross linlong agent than in the case of the superabsorbent materials. The proportion of cross-linking agent is typically at least 0. I %
by weight, preferably 1% to 2%. For quantities of this magnitude, a solubility problem can ariso with ecrtain cross linking agents such as trimathlolpropane triacrylato. To solve this problem, it is necessary to use an organic solvent and as little water as possible, in which the cross Iinldng agent dissolves morn readily and more urufarmly. The presence of organic solvents thus makes it possible to obtain a polymeric gel that is uniform and three-dimensional. The maximum quantity of water permitted is 359~o by weight of the total solution. Another advantage of the use of compatible organic solvents is that they do not alter the structure of substrates such as cardboard or paper substrates containing a glue.
Thug, the present invention in its broadest aspect rotates to a pmcess for malting a desiccant article for repeated cycles of water vapour absorption and desorption. It comprises the steps of:
(a) preparing a polymcrizable organic solution containing a polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid in which up to 50% of the carboxyl groups are neutralized by treatlaent with a bast, a homolytic reaction initiator, at least 0.1% by weight of a cross-polymerization agent and an organic solvent, said polymerizable organic solution containing less than 35% by weight of water;
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In the case of the present invention, however, it is necessary to control the swelling of the substrate when it absorbs water vapour or other gas and also to limit the absorption of liquid water. For this reason, the polymer of the present invention is strongly cross-linked. This is aehicved by using a I O greater quantity of cross linlong agent than in the case of the superabsorbent materials. The proportion of cross-linking agent is typically at least 0. I %
by weight, preferably 1% to 2%. For quantities of this magnitude, a solubility problem can ariso with ecrtain cross linking agents such as trimathlolpropane triacrylato. To solve this problem, it is necessary to use an organic solvent and as little water as possible, in which the cross Iinldng agent dissolves morn readily and more urufarmly. The presence of organic solvents thus makes it possible to obtain a polymeric gel that is uniform and three-dimensional. The maximum quantity of water permitted is 359~o by weight of the total solution. Another advantage of the use of compatible organic solvents is that they do not alter the structure of substrates such as cardboard or paper substrates containing a glue.
Thug, the present invention in its broadest aspect rotates to a pmcess for malting a desiccant article for repeated cycles of water vapour absorption and desorption. It comprises the steps of:
(a) preparing a polymcrizable organic solution containing a polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid in which up to 50% of the carboxyl groups are neutralized by treatlaent with a bast, a homolytic reaction initiator, at least 0.1% by weight of a cross-polymerization agent and an organic solvent, said polymerizable organic solution containing less than 35% by weight of water;
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(b) i><tipregnating a cellulose fibre substrate with the solution defined in (a);
(c) heating the impregnated substrate in a substantially oxygen-Liee atmosphere to initiate polymerization of the monomer, S (d) treating the polymerized substrate in an alkaline solution to transform the polymer into a salt; and (e) drying the article.
As an illustration, the maximum absorption capacity of the article of the present invention for deionized water is 7 times the weight of the polymer by itself or 2.5 times that of an article made of cardboard, for example, treated with 20% polymer by weight. A higher absorption csgacity has the effect of destroying the structure of the article, which would make it difficult to ootain a product that is sufRciently rigid for sonic applications such as a humidity exchanger. In addition, this article is designed to withstsud a very large number of absorptionldesotption or dehumidificatioalrcgcneration cycles, which is not the case with the superabsorbent materials. They arc generally designed for single-use applications (diapers, paper towels, toilet paper, etc.).
A further feature of the prosant invention is a high rate of absorption and dcsorption, so that the article reacts rapidly to a sudden variation in the concentration of water vapour or other gases in the flow of air in contact with the desiccant. Deposition of the polymer in a thin layer on the walls of the substrate makes it possible to obtain very rapid sorption kinetics, In general, the process of the present invention consists of impregnating a substrate of a given shape with a monomer solution in which up to 50% of the carboxyl groups are neutcall2ed by traattnent with s base and heating it to initiate polymerization. This process does not alter the deaiceant's absorptive properties. In addition, it givas the substrate a number of other interesting properties, including mechanical rigidity and fire resistance. Due .................................. A~aEr~t~ :::..::.
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to the thermal properties of the polymer, the desiccant article is also capable of transferring heat from a waxen air (gas) stream to a cool air (gas) stream within a recovery system. The bond obtained between the desiccant and the substrate is very strong and permits it to withstand a large number of 5 absorption and desorptioa cycles without any deterioration in absorptive properties or physical characteristics. A further advantage of this techaiQue is the fact that these properties eau be controlled by adjusting the composition and quantity of polymer. Most supports made from natural or synthetic cellulose fibres are permeable to air, which can pose a contamination pmblem in certain applications such as air Exchangers.
Treatment of this typo of support with the polymer makes it much more air-tight and also more rigid, oven using amounts of the polymer on the order of only 10°!o by weight. Cellulosi~based substrates are preferred due to their chemi~;al afg"tnity for polymer and low cost. Preferably, the support is made from corrugated cardboard or paper due to the high quality/price ratio.
However, other types of substrate made from natural or synthetic fibres, woven or non~woven, can be used. The polymer has also been successfully deposited on silica-gel powder in order to fix it by some other technique, such as gluing on to substrates made of metal or plastic material, Other inorganic powders (talc, etc.) or organic powders (skeletons of micm-organisms, et;..) can also be used.
The monomer solution consists prima.-ily of a member of the carboxylic acid family such as acrylic acid, methacrylic acid or itacoaic acid, a hemolytic reaction initiator such as peroxide and a cross-linking agent such as trimethylolpropane triaaylate, dissolved in an organic solvent, such as acetone.
Following impregnation with the solution, the substrate is heated in a chamber with low oxygen to a temperature of between 60°C and 80°C to effect polymerization.
The acidic polymer is then placed in contact with an alkaline solution of sodium, potassium or other hydroxide, to transform it into a salt. This :::>::.::.::.:::::....::.:::.:.........::.::...:.:..:.:::...::...:;._..-:::::::....;. ~ENt~:.-D S.j~E't' :::::
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(c) heating the impregnated substrate in a substantially oxygen-Liee atmosphere to initiate polymerization of the monomer, S (d) treating the polymerized substrate in an alkaline solution to transform the polymer into a salt; and (e) drying the article.
As an illustration, the maximum absorption capacity of the article of the present invention for deionized water is 7 times the weight of the polymer by itself or 2.5 times that of an article made of cardboard, for example, treated with 20% polymer by weight. A higher absorption csgacity has the effect of destroying the structure of the article, which would make it difficult to ootain a product that is sufRciently rigid for sonic applications such as a humidity exchanger. In addition, this article is designed to withstsud a very large number of absorptionldesotption or dehumidificatioalrcgcneration cycles, which is not the case with the superabsorbent materials. They arc generally designed for single-use applications (diapers, paper towels, toilet paper, etc.).
A further feature of the prosant invention is a high rate of absorption and dcsorption, so that the article reacts rapidly to a sudden variation in the concentration of water vapour or other gases in the flow of air in contact with the desiccant. Deposition of the polymer in a thin layer on the walls of the substrate makes it possible to obtain very rapid sorption kinetics, In general, the process of the present invention consists of impregnating a substrate of a given shape with a monomer solution in which up to 50% of the carboxyl groups are neutcall2ed by traattnent with s base and heating it to initiate polymerization. This process does not alter the deaiceant's absorptive properties. In addition, it givas the substrate a number of other interesting properties, including mechanical rigidity and fire resistance. Due .................................. A~aEr~t~ :::..::.
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to the thermal properties of the polymer, the desiccant article is also capable of transferring heat from a waxen air (gas) stream to a cool air (gas) stream within a recovery system. The bond obtained between the desiccant and the substrate is very strong and permits it to withstand a large number of 5 absorption and desorptioa cycles without any deterioration in absorptive properties or physical characteristics. A further advantage of this techaiQue is the fact that these properties eau be controlled by adjusting the composition and quantity of polymer. Most supports made from natural or synthetic cellulose fibres are permeable to air, which can pose a contamination pmblem in certain applications such as air Exchangers.
Treatment of this typo of support with the polymer makes it much more air-tight and also more rigid, oven using amounts of the polymer on the order of only 10°!o by weight. Cellulosi~based substrates are preferred due to their chemi~;al afg"tnity for polymer and low cost. Preferably, the support is made from corrugated cardboard or paper due to the high quality/price ratio.
However, other types of substrate made from natural or synthetic fibres, woven or non~woven, can be used. The polymer has also been successfully deposited on silica-gel powder in order to fix it by some other technique, such as gluing on to substrates made of metal or plastic material, Other inorganic powders (talc, etc.) or organic powders (skeletons of micm-organisms, et;..) can also be used.
The monomer solution consists prima.-ily of a member of the carboxylic acid family such as acrylic acid, methacrylic acid or itacoaic acid, a hemolytic reaction initiator such as peroxide and a cross-linking agent such as trimethylolpropane triaaylate, dissolved in an organic solvent, such as acetone.
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operation gives the polymer its absorptive properties, the catioas being linked to the polymer chain in as ionic manner.
Best Mode for Carrying Out the Invention The technique first presented here consists of manufacturing a desiccant article from a cellulose-based substrate and a polymorizable monomer solution, to pcnnit the absorption of gaseous products such as water vapour.
The product must retain its physical structure and sorptive properties even after repeated use. Polymer-based desiccants have the advantage of being readily modified to obtain the desired absorptive properties, as well as other properrr<es of interest for certain applications. They can also be obtained in a number of geometric forms. Some have a certain affinity for structural products used as substrates, which can facilitate bonding.
One particularly preferred embodiment of the invention comprises a potassium salt of polyacrylic acid polymerized on a paper or cardboard subssrate. The water vapour absorption properties of the desiccant aro in no way affected by the presence of the substrate, even when the proportion of polymer by mass is relatively low. In addition, the article possesses good fire resistance and acceptable mechanical strength, The process consists of preparing a monomer solution with a base of acrylic, methacrylic or itaconic acid or a mixture thereof. The concentration of the basC monomer in the BOlutioa Can be adjusted on the basis Of the desired proportion of desiccant by mass to be obtained. rn the prefeaed embodiment, acrylic acid is used. The quantity of acrylic acid should be between 2.5M and 4.0M; at 1CBB than 2.5M, the gel obtained will be insufficiently rigid, and above 4.0M, there is a risk of the reaction being too violent (exotherrnic~ and thus di~cult to control. Up to 50%, preferably 20% to 50% of the carboxyl groups must be initially neutralized by the addition of potassium hydroxide (KOI~ or another base, The total quantity of water in the final solution must not exceed 35% of the overall volume. A
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Best Mode for Carrying Out the Invention The technique first presented here consists of manufacturing a desiccant article from a cellulose-based substrate and a polymorizable monomer solution, to pcnnit the absorption of gaseous products such as water vapour.
The product must retain its physical structure and sorptive properties even after repeated use. Polymer-based desiccants have the advantage of being readily modified to obtain the desired absorptive properties, as well as other properrr<es of interest for certain applications. They can also be obtained in a number of geometric forms. Some have a certain affinity for structural products used as substrates, which can facilitate bonding.
One particularly preferred embodiment of the invention comprises a potassium salt of polyacrylic acid polymerized on a paper or cardboard subssrate. The water vapour absorption properties of the desiccant aro in no way affected by the presence of the substrate, even when the proportion of polymer by mass is relatively low. In addition, the article possesses good fire resistance and acceptable mechanical strength, The process consists of preparing a monomer solution with a base of acrylic, methacrylic or itaconic acid or a mixture thereof. The concentration of the basC monomer in the BOlutioa Can be adjusted on the basis Of the desired proportion of desiccant by mass to be obtained. rn the prefeaed embodiment, acrylic acid is used. The quantity of acrylic acid should be between 2.5M and 4.0M; at 1CBB than 2.5M, the gel obtained will be insufficiently rigid, and above 4.0M, there is a risk of the reaction being too violent (exotherrnic~ and thus di~cult to control. Up to 50%, preferably 20% to 50% of the carboxyl groups must be initially neutralized by the addition of potassium hydroxide (KOI~ or another base, The total quantity of water in the final solution must not exceed 35% of the overall volume. A
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fibre support and would limit the maximum quantity of dissolved cross-polymcrizittg agent.
The monomer is then mixed with a sufFtcient quantity of a hemolytic reaction initiator such as a peroxide, azabisisobutyronitrile or other initiator, in an organic solvent, preferably acetone. The amount of reaction-initiating , agent must be suflxeient to start the reaction, that is, about 1% of the total, although as excess of this substance would .have no impact an the polymerized product.
A emss-linking agent such as trimethylolprogane ethoxylate triacrylate, divinylbenzcne or other cross-polymerization agent is added to the solution in a quantity corresponding to the desired density of cross-linkages to be obtained in the polymer. To obtain an article capable of absorbing enough water vapour without excessive swelling, it is necessary to use at least 0.1%, preferably about 0.1% to 2.0% by weight of the cross-linking agent, The increase in volume (or swelling) of the desiccant material as a result of the absorption of water vapour can be controlled by the proportion of cross-linking agent used to synthesize the polymer.
A quantity of organic solvents f acetone, for example) must be added to bring about complem solution. Other solvents may be used or mixed with 2Q the acetone. In order to minimize toss of acrylic acid during the heating phase, it is possible to use propylene glycol, ethylene glycol or other solvents compatible with acetone and having a high boiling point.
The solution is well mixed, then applied to the cellulose-based substrate.
The article, impregnated with the solution, is placed is a closed chamber substantially free of oxygen and heated to a temperature sufficient to initiate palymerization. The polymerization reaction thus initiated should be completed within a few minutes, depending on the rate of thermal exchange in the chamber. Since polymerization is a radical reaction which is blocked in the presence of oxygen, it is therefore preferable to minimize the amount of oxygen in the solution is order to avoid the fon~nation of short-chain ~~wF~IGVD ~1?E~
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molecules or a poor polymerization yield. The presence of minute quantities of oxygen should have no perceptible effect on the quality of polymerization. In practice, purging with a flow of nitrogen or argon is usually su~eient to displace any oxygen dissolved in the solution or present in the dead apace amend the article.
Heating temperature moat be sufficient to initiate polymerisation, but must not lead to excessive evaporation of the acrylic acid. A temperature of 80°C
to 120°C is suggested. Preferably, the heating equipment will be sufficiently powerful to minimize the heating tiiae.
1 a High-frequency or microwave ovens ace especially recommended, but a suf3ficiently powerful conventional oven can be used effectively and can reduce manufacturing costs.
The extent of cross-linkage is fixed by the amount of cross-linking agent which has actually reacted during the polymerization. To that end, it is important to ensure that it is uniformly and completely diesolvad in the monomer solution. In the present case, where the prcfemd agent is trimetbylolpropane triacrylate whivh has limited aqueous solubility, it is necessary to use organic solvents such as acetone or propylene glycol. The organic solvents promote improved solubility of the cross-polymerizing 24 agent, which makes it possible to obtain a polymeric gel with a three-dimcnaional structure. Tt is necessary to limit the volume of water to 35% of the total volume of monomer solution.
Once the polymerized solution is bonded to the substrate, the polymer is placed in contact with an alkaline solution, such as a hydroxide solution of sodium, potassium, lithium or ammonium, The polymer is transformed into a salt of the cation corresponding to the alkaline solution used to give the polymer its absorptive properties, In the preferred embodiment, the acrylic acid based polymer is converted to a polyacrylic acid salt by wetting the article with a aelution of potassium hydroxide or sodium hydroxide ...:..:.:.....::::::..:::.::.::.::::.:::::<:.::::;:>:;:::...:.:;:..::....;..:.
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dissolved in methanol, Potassium hydroude is preferred as ii gives the polymer better absorptive properties.
The substrate and the desiccant may then be dried or allowed to dry, if necessary, td form a rigid arrficlc.
It has also hecn found that the polymeric desiccant can, in general, be similarly spthesized onto other materials or particles such as silica gel or oth« organic and inorganic powders, Finely powdered silica gel, for example can be added to a mixture containing the hemolytic reaction initiator solution and the a.,~rylic acid solution. T'he mixture is then 1p permitted to polymerize under suitable temperature sad atmospheric (low oxygen) conditions. The resultant acidic polymer containing the silica gel is ground into small particles aad then transformed into its salt by wetting with a suitable alkaline solution to give the polymer its absorptive properties.
This maurial is dried and may then be further crushed or pulverized to obtain a desiccant powd«. This desiccant powder may t#ten be used as such or may be applied ,~ ~ nl:~ . ......
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using known techniques, such as with adhesive, to a variety of substrates like metals and plastics.
Illustrations of the principles of the present invention are provided by way of the following examples which are not to be considered as limiting. The production methods may be modified and other chemicals may be used in various quantities as will be understood by those skilled in the art.
Ezample 1: POLYACRYLIC ACID POTASSIUM SALT ON CELLULOSE
The desiccant polymer is synthesized directly on a cellulose support in a series of steps. An IVEX corrugated cardboard is provided to be used as a support for the samples.
First of all, the support is moistened with an aqueous hemolytic reaction initiator solution (solution A1) mixed with an acrylic acid solution (solution B1) in ratios of 1/10 and 9/10 respectively. The wetted cardboard is then purged with argon and heated in the drying oven to 80°C to permit polymerization. Finally, the acid polymer is transformed into a potassium salt by immersion in a solution of potassium hydroxide. After drying in the drying oven, the product resembles plasticized cardboard.
EXPERIMENTAL PROTOCOL
1) Substrate IVEX corrugated cardboard 2) Aqueous hemolytic reaction initiator solution (solution Al) 5 grams of sodium persulphate are dissolved in 100mQ of deionized water.
3) Acrylic acid solution (solution B) 274mQ of acrylic acid (4 M) and 275mQ of 1,2-propanediol are placed in a 2Q
flask mounted with a septum and a bubbler. The acrylic acid solution is cooled to under 10°C in an ice and water bath. 1328 of potassium hydroxide (85%, 2M) are transferred into a SOOmp beaker together with enough deionized water to make 250m1. The heat released by the KOH
as it dissolves is dissipated by placing the beaker in an ice and water bath.
This solution is then added slowly to the acrylic acid solution; the temperature of the mixture should not exceed 30°C. Following this addition, 27mQ of trimethylolpropane ethoxylate triacrylate (7/3}
The monomer is then mixed with a sufFtcient quantity of a hemolytic reaction initiator such as a peroxide, azabisisobutyronitrile or other initiator, in an organic solvent, preferably acetone. The amount of reaction-initiating , agent must be suflxeient to start the reaction, that is, about 1% of the total, although as excess of this substance would .have no impact an the polymerized product.
A emss-linking agent such as trimethylolprogane ethoxylate triacrylate, divinylbenzcne or other cross-polymerization agent is added to the solution in a quantity corresponding to the desired density of cross-linkages to be obtained in the polymer. To obtain an article capable of absorbing enough water vapour without excessive swelling, it is necessary to use at least 0.1%, preferably about 0.1% to 2.0% by weight of the cross-linking agent, The increase in volume (or swelling) of the desiccant material as a result of the absorption of water vapour can be controlled by the proportion of cross-linking agent used to synthesize the polymer.
A quantity of organic solvents f acetone, for example) must be added to bring about complem solution. Other solvents may be used or mixed with 2Q the acetone. In order to minimize toss of acrylic acid during the heating phase, it is possible to use propylene glycol, ethylene glycol or other solvents compatible with acetone and having a high boiling point.
The solution is well mixed, then applied to the cellulose-based substrate.
The article, impregnated with the solution, is placed is a closed chamber substantially free of oxygen and heated to a temperature sufficient to initiate palymerization. The polymerization reaction thus initiated should be completed within a few minutes, depending on the rate of thermal exchange in the chamber. Since polymerization is a radical reaction which is blocked in the presence of oxygen, it is therefore preferable to minimize the amount of oxygen in the solution is order to avoid the fon~nation of short-chain ~~wF~IGVD ~1?E~
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molecules or a poor polymerization yield. The presence of minute quantities of oxygen should have no perceptible effect on the quality of polymerization. In practice, purging with a flow of nitrogen or argon is usually su~eient to displace any oxygen dissolved in the solution or present in the dead apace amend the article.
Heating temperature moat be sufficient to initiate polymerisation, but must not lead to excessive evaporation of the acrylic acid. A temperature of 80°C
to 120°C is suggested. Preferably, the heating equipment will be sufficiently powerful to minimize the heating tiiae.
1 a High-frequency or microwave ovens ace especially recommended, but a suf3ficiently powerful conventional oven can be used effectively and can reduce manufacturing costs.
The extent of cross-linkage is fixed by the amount of cross-linking agent which has actually reacted during the polymerization. To that end, it is important to ensure that it is uniformly and completely diesolvad in the monomer solution. In the present case, where the prcfemd agent is trimetbylolpropane triacrylate whivh has limited aqueous solubility, it is necessary to use organic solvents such as acetone or propylene glycol. The organic solvents promote improved solubility of the cross-polymerizing 24 agent, which makes it possible to obtain a polymeric gel with a three-dimcnaional structure. Tt is necessary to limit the volume of water to 35% of the total volume of monomer solution.
Once the polymerized solution is bonded to the substrate, the polymer is placed in contact with an alkaline solution, such as a hydroxide solution of sodium, potassium, lithium or ammonium, The polymer is transformed into a salt of the cation corresponding to the alkaline solution used to give the polymer its absorptive properties, In the preferred embodiment, the acrylic acid based polymer is converted to a polyacrylic acid salt by wetting the article with a aelution of potassium hydroxide or sodium hydroxide ...:..:.:.....::::::..:::.::.::.::::.:::::<:.::::;:>:;:::...:.:;:..::....;..:.
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dissolved in methanol, Potassium hydroude is preferred as ii gives the polymer better absorptive properties.
The substrate and the desiccant may then be dried or allowed to dry, if necessary, td form a rigid arrficlc.
It has also hecn found that the polymeric desiccant can, in general, be similarly spthesized onto other materials or particles such as silica gel or oth« organic and inorganic powders, Finely powdered silica gel, for example can be added to a mixture containing the hemolytic reaction initiator solution and the a.,~rylic acid solution. T'he mixture is then 1p permitted to polymerize under suitable temperature sad atmospheric (low oxygen) conditions. The resultant acidic polymer containing the silica gel is ground into small particles aad then transformed into its salt by wetting with a suitable alkaline solution to give the polymer its absorptive properties.
This maurial is dried and may then be further crushed or pulverized to obtain a desiccant powd«. This desiccant powder may t#ten be used as such or may be applied ,~ ~ nl:~ . ......
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using known techniques, such as with adhesive, to a variety of substrates like metals and plastics.
Illustrations of the principles of the present invention are provided by way of the following examples which are not to be considered as limiting. The production methods may be modified and other chemicals may be used in various quantities as will be understood by those skilled in the art.
Ezample 1: POLYACRYLIC ACID POTASSIUM SALT ON CELLULOSE
The desiccant polymer is synthesized directly on a cellulose support in a series of steps. An IVEX corrugated cardboard is provided to be used as a support for the samples.
First of all, the support is moistened with an aqueous hemolytic reaction initiator solution (solution A1) mixed with an acrylic acid solution (solution B1) in ratios of 1/10 and 9/10 respectively. The wetted cardboard is then purged with argon and heated in the drying oven to 80°C to permit polymerization. Finally, the acid polymer is transformed into a potassium salt by immersion in a solution of potassium hydroxide. After drying in the drying oven, the product resembles plasticized cardboard.
EXPERIMENTAL PROTOCOL
1) Substrate IVEX corrugated cardboard 2) Aqueous hemolytic reaction initiator solution (solution Al) 5 grams of sodium persulphate are dissolved in 100mQ of deionized water.
3) Acrylic acid solution (solution B) 274mQ of acrylic acid (4 M) and 275mQ of 1,2-propanediol are placed in a 2Q
flask mounted with a septum and a bubbler. The acrylic acid solution is cooled to under 10°C in an ice and water bath. 1328 of potassium hydroxide (85%, 2M) are transferred into a SOOmp beaker together with enough deionized water to make 250m1. The heat released by the KOH
as it dissolves is dissipated by placing the beaker in an ice and water bath.
This solution is then added slowly to the acrylic acid solution; the temperature of the mixture should not exceed 30°C. Following this addition, 27mQ of trimethylolpropane ethoxylate triacrylate (7/3}
and 200mQ of acetone are added. The solution is stirred with a magnetic stir bar for one hour at room temperature. This produces 1 litre of a polymerizable solution containing a 4M
concentration of acrylic acid, half of which has been neutralized as a potassium salt.
4} The corrugated cardboard is immersed in the acrylic acid solution mixed with the aqueous solution in ratios of 9/10 and 1/10 respectively. The excess solution is removed by means of a paper towel. The cardboard is then placed in a glass desiccator. A
mechanical pump is used to create a vacuum in the desiccator, and argon is then introduced into the desiccator to establish atmospheric pressure. The purging operation is repeated to remove as much oxygen as possible from the acrylic acid solution and the desiccator. The desiccator is then placed in the drying oven at 70 to 80°C for two hours to permit polymerization.
5) Finally, the corrugated cardboard is immersed in a solution of potassium hydroxide (KOI-~ for approximately twenty minutes. The solution is prepared by adding S.Og to I OOmQ
of methanol and SOmQ of deionized water. The cardboard is then dried in the drying oven. The initial weight of the IVEX corrugated cardboard was 0.758g. After synthesis of the desiccant polymer, its weight is 0.953g, a difference of O.I95g, representing the quantity of polymer deposited on the cardboard, or 20% by weight of polymer deposited on the IVEX
corrugated cardboard. It is then washed again with methanol and dried to ensure quantitative polymerization. Microgravimetric measurements have given the following absorption capacities (percentage dry mass of polymer) as a function of the relative humidity of the air:
Relative humidi of the 30 60 90 air %
Abso tion ca aci % ' 35 45 90 Table 1 The product is fire resistant as well and does not support the development of airborne bacteria.
The article allows very little air permeability. Note that the concentration of acrylic acid (2.5M
in this example) may be increased to obtain a larger deposit of polymer and would thus absorb more water vapour or other gases; for example, a 4M concentration of acrylic acid would produce a deposit of approximately 32% by weight.
concentration of acrylic acid, half of which has been neutralized as a potassium salt.
4} The corrugated cardboard is immersed in the acrylic acid solution mixed with the aqueous solution in ratios of 9/10 and 1/10 respectively. The excess solution is removed by means of a paper towel. The cardboard is then placed in a glass desiccator. A
mechanical pump is used to create a vacuum in the desiccator, and argon is then introduced into the desiccator to establish atmospheric pressure. The purging operation is repeated to remove as much oxygen as possible from the acrylic acid solution and the desiccator. The desiccator is then placed in the drying oven at 70 to 80°C for two hours to permit polymerization.
5) Finally, the corrugated cardboard is immersed in a solution of potassium hydroxide (KOI-~ for approximately twenty minutes. The solution is prepared by adding S.Og to I OOmQ
of methanol and SOmQ of deionized water. The cardboard is then dried in the drying oven. The initial weight of the IVEX corrugated cardboard was 0.758g. After synthesis of the desiccant polymer, its weight is 0.953g, a difference of O.I95g, representing the quantity of polymer deposited on the cardboard, or 20% by weight of polymer deposited on the IVEX
corrugated cardboard. It is then washed again with methanol and dried to ensure quantitative polymerization. Microgravimetric measurements have given the following absorption capacities (percentage dry mass of polymer) as a function of the relative humidity of the air:
Relative humidi of the 30 60 90 air %
Abso tion ca aci % ' 35 45 90 Table 1 The product is fire resistant as well and does not support the development of airborne bacteria.
The article allows very little air permeability. Note that the concentration of acrylic acid (2.5M
in this example) may be increased to obtain a larger deposit of polymer and would thus absorb more water vapour or other gases; for example, a 4M concentration of acrylic acid would produce a deposit of approximately 32% by weight.
WO 99/4?241 PCTlCA99/00234 Example 2: POWDERED POLYACRYLIC ACID POTASSIUM SALT
ON SILICA GEL
A desiccant powder is obtained when acrylic acid is polymerized on silica gel.
Synthesis is performed by mixing the acrylic acid solution (solution B2) with the homolytic reaction initiator solution (solution A2) and adding this mixture to finely powdered silica gel. The mixture is then purged with argon and polymerized by heating in the drying oven. The acid polymer is ground into small particles and transformed into a potassium salt by immersion in a solution of potassium carbonate. The material is then dried and crushed to a fine powder.
EXPERIMENTAL PROTOCOL
1) Base Material Aldrich silica gel (5.0g, 2-25 ,um, SOOmz/g).
2) Aqueous homolytic reaction initiator solution (solution A2) 200mg of sodium persulphite dissolved in 1 OmQ of water.
3) Acrylic acid solution (solution B) Same as solution B in Example 1 4) The Aldrich silica gel is transferred into a 250mQ flask mounted with a vacuum head and septum. The silica gel is purged twice with argon. One millilitre of the initiator solution (solution A2) is aspirated into a 1 OmQ syringe, then 9mQ of the acrylic acid solution is aspirated into the same syringe and mixed with the initiator solution. The resulting solution is then added to the silica gel and the system is purged twice more with argon. The silica gel/aqueous solution mixture is heated in the drying oven for 2 hours at 60°C. The product recovered after heating resembles a flexible plastic completely enveloping the silica gel.
5) This product is ground into small particles and dispersed in a water-methanol solution (50mQ of each) containing S.Og of potassium carbonate. It is allowed to stand for two hours in suspension in the alkaline solution; the particles are then filtered and dried in the drying oven. The white product recovered after drying is crushed into a fine powder using a mortar and pestle. The weight of the white product is 7.97g. This material consists of S.Og of silica gel together with a deposit of 2.978 of desiccant polymer. This procedure is merely an example of a deposit performed; the protocol is not necessarily optimal and certain chemicals may be replaced by other compatible products.
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n Indastrfal Appiicab~ity The desiccant article in accordance with this inv ention has possible applications in the field of 2~ir treatment, such as dehumidification, in syst"-ins for the transfer of moisture and heat between two air strcarns, in Ht~
AC systems aad is other applications involving moisture control and recovery.
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ON SILICA GEL
A desiccant powder is obtained when acrylic acid is polymerized on silica gel.
Synthesis is performed by mixing the acrylic acid solution (solution B2) with the homolytic reaction initiator solution (solution A2) and adding this mixture to finely powdered silica gel. The mixture is then purged with argon and polymerized by heating in the drying oven. The acid polymer is ground into small particles and transformed into a potassium salt by immersion in a solution of potassium carbonate. The material is then dried and crushed to a fine powder.
EXPERIMENTAL PROTOCOL
1) Base Material Aldrich silica gel (5.0g, 2-25 ,um, SOOmz/g).
2) Aqueous homolytic reaction initiator solution (solution A2) 200mg of sodium persulphite dissolved in 1 OmQ of water.
3) Acrylic acid solution (solution B) Same as solution B in Example 1 4) The Aldrich silica gel is transferred into a 250mQ flask mounted with a vacuum head and septum. The silica gel is purged twice with argon. One millilitre of the initiator solution (solution A2) is aspirated into a 1 OmQ syringe, then 9mQ of the acrylic acid solution is aspirated into the same syringe and mixed with the initiator solution. The resulting solution is then added to the silica gel and the system is purged twice more with argon. The silica gel/aqueous solution mixture is heated in the drying oven for 2 hours at 60°C. The product recovered after heating resembles a flexible plastic completely enveloping the silica gel.
5) This product is ground into small particles and dispersed in a water-methanol solution (50mQ of each) containing S.Og of potassium carbonate. It is allowed to stand for two hours in suspension in the alkaline solution; the particles are then filtered and dried in the drying oven. The white product recovered after drying is crushed into a fine powder using a mortar and pestle. The weight of the white product is 7.97g. This material consists of S.Og of silica gel together with a deposit of 2.978 of desiccant polymer. This procedure is merely an example of a deposit performed; the protocol is not necessarily optimal and certain chemicals may be replaced by other compatible products.
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n Indastrfal Appiicab~ity The desiccant article in accordance with this inv ention has possible applications in the field of 2~ir treatment, such as dehumidification, in syst"-ins for the transfer of moisture and heat between two air strcarns, in Ht~
AC systems aad is other applications involving moisture control and recovery.
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Claims (13)
1. A process for making a desiccant article for repeated cycles of water vapour absorption and desorption comprising the steps of:
(a) preparing a polymerizable organic solution containing a polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid in which up to 50% of the carboxyl groups are neutralized by treatment with a base, a homolytic reaction initiator, at least 0.1 % by weight of a cross-polymerization agent and an organic solvent, said polymerizable organic solution containing less than 35%
by weight of water;
(b) impregnating a cellulose fibre substrate with the solution defined in (a);
(c) heating the impregnated substrate in a substantially oxygen-free atmosphere to initiate polymerization of the monomer;
(d) treating the polymerized substrate in an alkaline solution to transform the polymer into a salt; and (e) drying the article.
(a) preparing a polymerizable organic solution containing a polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid and itaconic acid in which up to 50% of the carboxyl groups are neutralized by treatment with a base, a homolytic reaction initiator, at least 0.1 % by weight of a cross-polymerization agent and an organic solvent, said polymerizable organic solution containing less than 35%
by weight of water;
(b) impregnating a cellulose fibre substrate with the solution defined in (a);
(c) heating the impregnated substrate in a substantially oxygen-free atmosphere to initiate polymerization of the monomer;
(d) treating the polymerized substrate in an alkaline solution to transform the polymer into a salt; and (e) drying the article.
2. A process as claimed in claim 1 wherein the organic solvent is acetone or a glycol.
3. A process as claimed in claim 1 wherein the organic solvent is ethylene glycol or propylene glycol.
4. The process of claim 2 wherein the monomer is acrylic acid which is present in the solution in a concentration between 2.5M to 4.0M.
5. The process as claimed in claim 2 wherein the homolytic reaction initiator is peroxide, sodium persulphate or azabisisobutyronitrile.
6. The process as claimed in any one of claims 1 to 5 wherein the amount of cross-polymerization agent in the solution is between 0.1% to 2% by weight.
7. The process as claimed in any one of claims 1 to 6 wherein the cross-polymerization agent is trimethylolpropane ethoxylate triacrylate or divinylbenzene.
8. A process as claimed in any one of claims 1 to 7 wherein the impregnated substrate is rapidly heated to a temperature of from 60°C to 80°C to initiate polymerization of the polymerizable solution.
9. A process as claimed in any one of claims 1 to 8 wherein about 20% to 50%
of the carboxyl groups in the monomer are neutralized.
of the carboxyl groups in the monomer are neutralized.
10. A process as claimed in any one of claims 1 to 9 wherein the alkaline solution used to treat the polymerized substrate is sodium, potassium, lithium or ammonium hydroxide.
11. A process as claimed in any one of claims 1 to 10 wherein the cellulose fibre substrate is paper or cardboard.
12. A process as claimed in claim 11 wherein the cardboard is corrugated.
13. A desiccant article suitable for repeated cycles of water vapour absorption and desorption whenever produced by a process as claimed in any one of claims 1 to 12.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/039,409 US6110533A (en) | 1998-03-16 | 1998-03-16 | Polymeric desiccant articles and process for their manufacture |
| US09/039,409 | 1998-03-16 | ||
| PCT/CA1999/000234 WO1999047241A1 (en) | 1998-03-16 | 1999-03-15 | Polymeric desiccant articles and process for their manufacture |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2324113A1 CA2324113A1 (en) | 1999-09-23 |
| CA2324113C true CA2324113C (en) | 2004-02-10 |
Family
ID=21905298
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002324113A Expired - Lifetime CA2324113C (en) | 1998-03-16 | 1999-03-15 | Polymeric desiccant articles and process for their manufacture |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US6110533A (en) |
| AU (1) | AU2709399A (en) |
| CA (1) | CA2324113C (en) |
| WO (1) | WO1999047241A1 (en) |
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| US7811948B2 (en) * | 2003-12-19 | 2010-10-12 | Kimberly-Clark Worldwide, Inc. | Tissue sheets containing multiple polysiloxanes and having regions of varying hydrophobicity |
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| US7619131B2 (en) | 2005-12-02 | 2009-11-17 | Kimberly-Clark Worldwide, Inc. | Articles comprising transparent/translucent polymer composition |
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-
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- 1998-03-16 US US09/039,409 patent/US6110533A/en not_active Expired - Lifetime
-
1999
- 1999-03-15 AU AU27093/99A patent/AU2709399A/en not_active Abandoned
- 1999-03-15 CA CA002324113A patent/CA2324113C/en not_active Expired - Lifetime
- 1999-03-15 WO PCT/CA1999/000234 patent/WO1999047241A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO1999047241A1 (en) | 1999-09-23 |
| CA2324113A1 (en) | 1999-09-23 |
| US6110533A (en) | 2000-08-29 |
| AU2709399A (en) | 1999-10-11 |
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