CORDOVA, Armando (Vanadisvägen 40, Stockholm, S-113 46, SE)
NADERI, Ali (Tullingebergsvägen 8B 2 tr, lgnr 60, Tullinge, S-146 45, SE)
CORDOVA, Armando (Vanadisvägen 40, Stockholm, S-113 46, SE)
| CLAIMS 1. A method of making a cellulosic material water-repellent, comprising: providing a solution of an acid of pKa <i.o in a C2-C4 alcohol optionally comprising water; providing an alkyltrialkoxyosilane; efficiently mixing the solution and the alkyltrialkoxysilane to produce a silanization composition; contacting the cellulosic material with the silanization composition; curing the cellulosic material contacted with the composition at a temperature of 100 °C or more until substantially dry; optionally rinsing the treated cellulosic material with a liquid media to remove the acid; and optionally drying the rinsed treated material. 2. The method of claim l, wherein the C2-C4 alcohol is selected from isopropanol and tert-butanol. 3. The method of claim 1 or 2, wherein the alkyltrialkoxysilane is of the general formula R1 (OR2)3Si, wherein R1 is straight, branched or cyclic, saturated or non-saturated C8-C22 alkyl, and R2 is methyl, ethyl, butyl, tert-butyl or isopropyl. 4. The method of claim 3, wherein R1 is straight or branched C12-C18 alkyl. 5. The method of claim 3, wherein R1 is straight or branched G4-Ci6 alkyl. 6. The method of claim 3, wherein the alkyltrialkoxysilane is hexadecyltrimethoxysilane. 7. The method of any of claims 1 to 6, wherein the acid is an organic sulfonic acid. 8. The method of claim 7, wherein the organic sulfonic acid is selected from the group consisting of benzenesulfonic acid, p-toluenesulfonic acid, m- toluenesulfonic acid, naphthalenesulfonic acid, camphor sulfonic acid, methanesulfonic acid. 9. The method of any of claims 1 to 8, wherein the curing temperature is from 120 °C or 150 °C to 200 °C. 10. The method of any of claims 1 to 9, wherein the water content of the silanization composition is 5.0 % by weight or less, in particular 0.5 % or less. 11. The method of any of claims 1 to 10, wherein the cellulosic material is a cellulosic textile. 12. A water-repellent cellulosic material obtained or obtainable by the method of any of claims 1 to 10. 13. A water-repellent cellulosic textile obtained or obtainable by the method of any of claims 1 to 11. 14. A cellulose material hydrophobization composition comprising or substantially consisting of an alkyltrialkoxysilane of the general formula R1 (OR2)3Si, wherein R1 is straight or branched, saturated or non-saturated C8-C22 alkyl, in particular Ci2 to C18 alkyl, and R2 is methyl, ethyl, butyl, tertbutyl or isopropyl; a C1-C4 alcohol; an organic sulfonic acid; optionally water. 15. The composition of claim 14, wherein the organic sulfonic acid is selected from the group consisting of benzenesulfonic acid, p-toluenesulfonic acid, m- toluenesulfonic acid, naphthalenesulfonic acid, camphor sulfonic acid, methanesulfonic acid. 16. The composition of any of claims 14 to 15 of a water content of 5 % by weight or less, in particular of 0.5 % or less. 17. The composition of any of claims 15 to 16, comprising from 2 % by weight to 10 % by weight, preferably from 2 % by weight to 5 % by weight of alkyltrialkoxysilane and from 0.05 % by weight to 1.0 % by weight, preferably from 0.1 % by weight to 0.5 % by weight of organic sulfonic acid. 18. The composition of any of claims 14 to 17 wherein the cellulosic material is a cellulosic textile. |
The invention relates to a method of making a cellulosic material such as paper, wood or textile water-repellent and to a cellulosic material made water-repellent by the method.
BACKGROUND OF THE INVENTION
A number of methods of making cellulosic materials water-repellent are known in the art. A cellulosic material has a substantially hydrophilic surface rich in hydroxy! groups which attract water molecules and bind them by hydrogen bonds. By transforming these hydroxyl groups into groups that do not attract water molecules or by barring access of water molecules to them a cellulosic material can be made water-repellent. Agents proposed for use in these methods include fluorinated hydrocarbons and organosilicon compounds of various kinds.
In many available technologies, cellulosic fibre webs, e.g. paper and cardboard, are made water-repellent by the physisorption of the hydrophobizing agent to the cellulosic material. The major draw-back of this methodology includes the readily removal of the hydrophobizing agent through e.g. prolonged exposure of the material to water and/or organic solvents, or through mechanical rubbing of the material.
This shortcoming becomes even more apparent with cellulosic textiles made water-repellent by most state-of-the-art methods , as evident from their poor washing stability, in particular when washed in household or laundry washing machines using alkaline washing media at elevated temperatures Ο25 °C). In order to achieve persistent water-repellency the formation of covalent bonds between the hydroxyl groups of the textile and the water-repellent coating is desired.
The use of fluorinated hydrocarbons has been proven effective to achieve water- repellency, but is highly undesired due to its negative impact on the
environment and on human health.
The use of non-fluorinated organosilicon compounds is advantageous from an environmental and public health point of view. A problem with the
organosilanes is that they are reactive and prone to undergo condensation reactions that lead to polymeric structures and gel formation of the coating compositions. The polymerization reaction leads to a decrease in the number of available silanol (Si-OH) groups that can be used for covalent attachment of the silanes to the cellulosic surface. Also, the washing stability of textiles achieved with methods utilizing non-fluorinated compounds has so far not been satisfactory. U.S. 4,339,479 discloses a process to render paper water-repellency by subjecting the material to vapors of lower alkyl silicon halides.
U.S. 5,073,195 discloses an aqueous composition of a water soluble silane coupling agent and an alkylalkoxysilane. After applying the composition, the material is dried for prolonged times to achieve water-repellency.
U.S. 2009/0206296 Al discloses an organosilane composition comprising an organosilane, an acid catalyst, a solvent, and water and its use in a method for making a cotton fabric water-repellent. The method comprises applying the composition to the fabric and drying the fabric in an automatic laundering and drying system, such as at a temperature of 135 °F (57 °C), or at ambient temperature. The pH of the composition is disclosed to be 1.5 or higher.
EP 1400 625 A2 discloses a process of treating the surface of a cellulosic material, comprising contacting the material with an organosilane of the general formula
(X) 4 -n— Si— R n , wherein R is a hydrocarbon chain of from C 7 to C 2 o and X is a Ci to C 4 alkoxy group. The treatment is carried out in an aqueous or alcoholic environment. The treated material is cured at a temperature of from 40 °C to 150 °C.
OBJECTS OF THE INVENTION
An objective of this invention is to provide a method for rendering water- repellency to cellulosic materials.
Another object of the invention is to provide a method of making a cellulosic textile permanently water-repellent so that it can be washed in household or laundry washing machines.
Another object of the invention is to provide method of this kind, which is attractive from an economic and environmental standpoint.
Another object of the invention is to provide a method of this kind, which is suitable and advantageous for industrial scale treatment of cellulosic materials.
Still another object of the invention is to provide a water-repellent cellulosic textile.
An additional object of the invention is to provide a silanization composition for cellulosic materials, rendering them excellent water-repellency and washing- stability properties
Further objects of the invention will become evident from the following short description of the invention and preferred embodiments thereof as well as from the appended claims. SUMMARY OF THE INVENTION
According to the present invention is disclosed a method of making a cellulosic materials e.g. paper, cardboard and textiles (made of for example cotton) water-repellent. The method comprises providing a solution of an acid of a < l. o in a C 2 -C 4 alcohol optionally comprising water; providing an
alkyltrialkoxysilane; efficiently mixing the solution and the allyltrialkoxysilane to produce a silanization composition; contacting the cellulosic material with the silanization composition; curing the material contacted with the
composition at a temperature of 100 °C or more until substantially dry;
optionally rinse the treated material with a liquid suitable to remove the non- reacted chemicals; and optionally drying the rinsed treated textile.
The cellulosic material can be contacted with the silanization composition in any suitable manner, such as by dipping, padding application by roller or brush, coating and spraying. The silanization composition can be brought in contact with the material in a manner so as to substantially fully wet (soak) the material or only wet the material to a desired depth from the face of the material to which it is applied.
The method of the invention can be incorporated in many production processes used industrially to treat cellulosic materials, e.g. by using a standard padding process, impregnation process, spraying process, size press process and coating process.
Most preferred Ci-C 4 alcohols of the invention are isopropanol and tert-butanol and their mixtures. Ethanol, n-propanol, butanol-l and/or butanol-2 are also preferred.
It is preferred for the alkyltrialkoxysilane of the invention to be of the general formula R 1 (OR 2 ) 3 Si, wherein R 1 is straight, branched or cyclic, saturated or unsaturated C8-C 22 alkyl. R 2 is methyl, ethyl, butyl, tert-butyl or. R 1 is preferably straight and saturated to allow better packing of the chains at the cellulostic material interface, but branched, cyclic and/or non-saturated chains are also conceivable. More preferred is an alkyltrialkoxysilane wherein R 1 is straight or branched C 12 -Ci8 alkyl. Most preferred is alkyltrialkoxysilane wherein R 1 is straight or branched Ci 4 -C l6 alkyl, in particular hexadecyltrimethoxysilane.
In the method of the invention the acid component acts as a catalyst. While acid catalysis can be provided, in principle, by a wide range of inorganic and organic acids, a catalyst acid of a pKa of <1.5, in particular of <i.o, which is substantially non-volatile at ambient pressure and temperatures up to 200 °C, is preferred. Organic sulfonic acids meet this requirement and have been found to be particularly useful in the method of the invention. A preferred acid of the invention thus is an organic sulfonic acid, in particular one selected from the group consisting of benzenesulfonic acid, p-toluenesulfonic acid, m- toluenesulfonic acid, naphthalenesulfonic acid, camphor sulfonic acid, and methanesulfonic acid. An important feature of the method of the invention is the curing temperature, which is at least 100 °C, preferably at least 120 °C, more preferred at least 140 °C or 150 °C, and even up to 200 °C. The curing time is about inversely proportional to the curing temperature. Thus, curing at higher temperatures can be carried out in a correspondingly shorter time, such as in a few minutes or in about from 1 min to 3 min in a pre-heated oven at a temperature of from 150 °C to 200 °C. A person skilled in the art will realize that air convection during drying, the thickness and density of the cellulosic material, and other physical parameters of the material, will influence the curing time at a given drying temperature.. According to the method of the invention, the curing is continued until the fabric is substantially dry, that is, has a content of solvent below 5 % by weight and even below 2 % by weight. In this application, "drying" includes evaporation of solvent other than water; "substantially dry" means substantially devoid of water and/or solvent.
According to a preferred aspect of the invention the water content of the silanization composition is 5.0 % by weight or less, in particular 0.5 % or less. A low water content will promote the reaction of the alkyltrialkoxysilane with cellulose hydroxyl groups on the fabric.
One embodiment of the invention comprises the following steps in applying the method of the invention in the context of a standard industrial application process such as a padding process, impregnation process, a spraying process, a coating process or an exhaust process. First, the acid catalyst of the invention and the solvent of the invention are mixed until complete dissolution of the catalyst. Then the alkyltrialkoxysilane component of the invention is blended into the solution of the catalyst. The composition is applied onto the cellulosic material. The material is then passed through a curing station, such as an oven kept at a temperature of 150 °C to 200 °C for approximately 1-3 minutes.
According to another preferred aspect of the invention, the silanization composition of the invention is prepared immediately prior to its application, in particular by blending a premixed solution of the acid, catalyst of the invention in the solvent of the invention with the alkyltrialkoxysilane of the invention immediately prior to application. Such blending and application are preferably carried out in a continuous manner.
According to the present invention a water-repellent cellulosic material obtained or obtainable by the method of the invention is also disclosed.
According to the present invention a water-repellent cellulosic textile obtained or obtainable by the method of the invention is also disclosed.
According to a further preferred aspect of the invention a cellulose material hydrophobization composition comprising or substantially consisting of an alkyltrialkoxysilane of the general formula R 1 (OR 2 ) 3 Si, wherein R 1 is straight or branched, saturated or unsaturated C8-C 22 alkyl, in particular C 12 to C18 alkyl, and R 2 is methyl, ethyl, butyl, tertbutyl or isopropyl; a C2-C4 alcohol; an organic sulfonic acid; optionally water is disclosed. It is preferred for the organic sulfonic acid to be selected from the group consisting of benzenesulfonic acid, p- toluenesulfonic acid, m-toluenesulfonic acid, naphthalenesulfonic acid, camphor sulfonic acid, or methanesulfonic acid. A water content of 5 % by weight or less, in particular of 0.5 % or less is preferred.
Also preferred for the composition is to comprise from 2 % by weight to 10 % by weight, more preferred from 2 % by weight to 5 % by weight of
all yltriall oxysilane, and from 0.05 % by weight to 1.0 % by weight, more preferred from 0.1 % by weight to 0.5 % by weight, of organic sulfonic acid.
According to the present invention a composition of the invention wherein the cellulosic material is a cellulosic textile is also disclosed.
The invention will now be described in more detail by reference to a number of preferred embodiments, which are given as an exemplification of the invention but should not be understood as limiting the scope of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Materials
Ethanol 99.5 %, Kemetyl AB
2-Propanol, Sigma Aldrich
2-Methyl-2-propanol, Sigma Aldrich
Benzenesulfonic acid, Sigma Aldrich
p-Toluenesulfonic acid, Sigma Aldrich
Oxalic acid, Sigma Aldrich
Camphorsulfonic acid, Sigma Aldrich
Hexadecyltrimethoxysilane, Evonik Degussa Chemicals
Determination of resistance to surface wetting (spray test) of fabrics
European Standard EN 24 920 (ISO 4920:1981). Principle: A specified amount of water is sprayed on a textile specimen mounted on a ring. The specimen is disposed at an angle of 45 0 in respect to the nozzle. The centre of the
standardized nozzle is disposed at a given distance above the centre of the specimen. A given amount of water is filled in a reservoir disposed above the nozzle and in communication with it. The spray rating is determined visually and/or photographically. The five-step spray rating scale of ISO 5 - ISO 1 corresponds to 100 %, 90 %, 80 %, 70 %, and 50 %, respectively, of the specimen having withstood wetting.
'
Determination of resistance to water penetration - Hydrostatic pressure test
International Standard ISO 811-1981. Principle: The textile specimen is subjected to a steadily increasing pressure of water on one face until penetration occurs in three places. The pressure at which the water penetrates the fabric at the third place is noted. A high penetration pressure value thus signifies a high resistance to water penetration. Determination of the water uptake of paper
International Standard ISO 535:1991 (E). The water absorbency of paper (Cobb- value) is defined as the amount of water adsorbed per unit area of the material for a specified time, when the paper specimen is horizontally placed under 1 cm of water. Principle: A test piece is weighted immediately before and immediately after exposure for a specified time of one surface to water, followed by blotting. The result of the increase in mass is expressed in grams per square metre (g/m 2 ).
Silanization procedure of cotton textile
To the alcohol (e.g. isopropanol 94.65 g) in a 250 ml glass beaker 0.35 g of the organic acid catalyst (e.g. benzenesulfonic acid) was added. The catalyst was dissolved by stirring the solvent for 5 min. Into the clear solution of the catalyst in the alcohol 5.0 g of hexadecyltrimethoxysilane was injected under stirring to form the liquid silanization composition. Stirring was continued for the time period indicated in Table 1 (Textile Contact Delay: 30 sec, 180 sec or 1800 sec). A 2 g piece of dyed cotton textile was immersed in the silanization composition for 10 sec and dried in a preheated oven at the temperature and for the time given in Table 1.
The water-repellency properties of the treated textile before and after washing with an aqueous solution of a household detergent (Skona®, pH > 10) were evaluated (washing temperature 60 °C) by testing the textile with the
standardized tests SS-EN 24 920 and ISO 811-1981. The results are summarized in Ex. 1-14 in Table 1 below.
Water Repellency Test EN 24920; **Water Penetration Resistance Test ISO 811
Use of hydrochloric acid as a catalyst
A silanization procedure was carried out as above, but instead of organic acid catalyst either 0.04 M or 12 M hydrochloric acid (HQ) was used. Aqueous HC1 catalyst solution as indicated in Table 2 was dissolved in 94.9 g isopropanol and blended with 5.0 g of hexadecyltrimethoxysilane for 2 minutes. A 2 g piece of dyed cotton textile was immersed in the silanization composition for 10-20 sec and dried in a preheated oven at 150 °C for 3 minutes. The water-repellency properties of the treated textile before and after washing with an aqueous solution of a household detergent (Skona®, pH > 10) were evaluated (washing temperature 60 °C) by testing the textile with the standardized tests SS-EN 24 920 and ISO 811. The results are summarised in Ex. 15-17 in the Table 2 below.
Table 2
* Water Repellency Test EN 24920; **Water Penetration Resistance Test ISO 811
Silanization procedure of filter paper To the alcohol (89.3 g isopropanol) in a 250 ml glass beaker 0.7 g of the organic acid catalyst (benzenesulfonic acid) was added. The catalyst was dissolved by stirring the solvent. Into the clear solution of the catalyst in the alcohol was injected 10 g of hexadecyltrimethoxysilane under stirring to form the liquid silanization composition.
A 2 g piece of filter paper was immersed in the silanization composition for 10 sec and then dried for 5 minutes in a preheated oven at 150 0 C.
The water-repellency properties of the treated filter paper were investigated before and after subjecting the paper to Soxhlet extraction for 1 h with Toluene. The water-repellency properties were evaluated by testing the treated paper with the standardized tests SS-EN 24 920 and ISO 535:1991 (Cobb method). The results are summarized in the Table 3.
Table
• The property was measured by subjecting the specimen to water during 60 seconds.
Silanization procedure of bleached kraft paper To the alcohol (89.3 g isopropanol) in a 250 ml glass beaker 0.7 g of the organic acid catalyst
(benzenesulfonic acid) was added. The catalyst was dissolved by stirring the solvent. Into the clear solution of the catalyst in the alcohol 10 g of
hexadecyltrimethoxysilane was injected under stirring to form the liquid silanization composition. A 2 g piece of paper sheet made of totally chlorine-free (TCF) chemical kraft softwood pulp was immersed in the silanization composition for 10 sec and then dried for 5 minutes in a preheated oven at 150 0 C.
The water-repellency properties of the treated paper were investigated before and after subjecting the paper to Soxhlet extraction for l h with Toluene. The water-repellency properties were evaluated by testing the treated paper with the standardized tests SS-EN 24 920 and ISO 535:1991 (Cobb method). The results are summarized in the Table 4.
• T e property was measure y su ect ng t e spec men to water ur ng 0 secon s.
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