Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
2000-02-14
2002-01-29
Dawson, Robert (Department: 1712)
Coating processes
Coating by vapor, gas, or smoke
C427S255600, C427S377000, C427S378000, C106S013000, C428S410000
Reexamination Certificate
active
06342268
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a method for treating a solid material of which the chemical structure defines reactive hydrophillic functions accessible to gases, with a view to the covalent grafting of hydrophobic groups in order to make the material hydrophobic and/or lipophilic.
BACKGROUND OF THE INVENTION
It has known been for a long time (FR-707688); “Breathable, Permanent Water-Repellent Treatment of Cotton”, Rudolph D. DEANIN et al., Textile Research Journal, Vol. 40, Nov. 11, 1970, pp 970), that it is possible to treat cellulosic textile materials by esterification in a liquid medium and in the absence of air with the aid of higher fatty acid derivatives in order to render these materials hydrophobic. To this end, a fabric is placed in at least one bath of a liquid solution comprising esterification reagents and a non-polar solvent which is neutral to the textile material, heated to a temperature of between 80° and 120° C. for fifteen or thirty minutes, and the fabric is washed and dried. FR-707688 states in addition that it is preferable to carry out esterification in the absence of air or oxygen.
This treatment in a heterogeneous liquid medium requires in practice several baths, a period of at least 15 min, washing and drying. It is therefore long, complex and costly and is reserved for laboratory use and cannot be exploited under satisfactorily profitable conditions on the industrial scale and for low cost materials.
Moreover, this treatment in a heterogeneous liquid medium cannot be considered for fragile materials such as non-wovens, agglomerates, paper, etc and/or those sensitive to solvents, such as cellulose acetates.
Similarly, FR-693 803 describes a method in which the textile material is immersed in a solution or an emulsion of a fatty acid anhydride in a solvent, is pressed and dried by heating, and is then subjected to a temperature above 35° C., preferably between 70 and 100° C. for approximately six hours.
Here again, the method is extremely long and costly and is not applicable to materials other than textiles.
In all cases, with these known methods in a liquid phase, if fatty acid chlorides are used as reagents, it is in practice necessary to neutralize the hydrochloric acid formed by adding a base in order to prevent acid hydrolysis of the cellulose fibres leading to total degradation of their mechanical properties. In addition, if fatty acid anhydrides are used as reagents, the presence of a catalyst such as pyridine or dimethyformamide is necessary for accelerating the reaction.
Consideration has already been given to attempts to make a cellulose material hydrophobic by acylation from organohalogenosilane vapors, such as methyl chlorosilanes having a sufficiently low molecular weight so that they can be vaporized at temperatures compatible with the cellulosic material to be treated (U.S. Pat. Nos. 2,306,222; 2,824,778; 4,339,479; 4,007,050 etc.). In order to form and contain the vapors and to put them in contact with the material to be treated, a chamber must be provided for confining the vapors. Moreover, the hydrophobic character produced is slight and not very resistant and a subsequent neutralization treatment must be provided.
In particular, U.S. Pat. No. 2,824,778 describes a method in which a fabric is passed into a U-shaped conduit closed on itself, in which a gaseous mixture of a saturating low molecular weight silane vapor and an inert gas is maintained by means of equipment injecting silane in an atomized form into the conduit. This vapor phase method calls for a closed recirculation circuit to prevent silane vapors escaping, taking in account their low boiling point. It does not enable non-porous materials to be treated. It is moreover necessary subsequently to provide treatment in a neutralization bath.
U.S. Pat. No. 4,107,426 also describes a method for treating a cellulosic material by putting it into contact with aliphatic acid chloride vapors formed by heating a liquid aliphatic acid chloride in a confinement chamber so as to create in this chamber, kept at atmospheric pressure, a partial pressure of the vapors of between 10 mm Hg (1333 Pa) and 20 mm Hg (2666 Pa), with a dilution gas such as nitrogen which is introduced into the chamber. The gaseous mixture in the chamber is extracted via a condenser which makes it possible to extract the HCl gas formed and to recover the acid chlorides escaping from the chamber.
This method is complex to put into practice since it is necessary to put the solid material into, or in contact with, a sealed confinement chamber. It is indeed only really effective with grafting reagents containing 8 to 14 carbons and having a sufficient vapor pressure at temperatures lower than 150° C., the temperature at which cellulose starts to decompose, to be able to form a sufficient vapor pressure in the chamber. Accordingly, a temperature of 150° C. is recommended with lauric acid chloride and 180° C. with myristic acid chloride. No precise example is given for grafting hydrophobic groups having more than 14 carbons.
Moreover, the grafting reaction does not in practice have satisfactory kinetics and yield.
Accordingly, although the principle of making a solid material hydrophobic by esterification with the aid of fatty acid derivatives has been known for a long time, and in spite of various research projects carried out on this subject since 1930, no practical exploitation based on this principle has as yet been possible on an industrial scale.
It should be noted that with all the solutions proposed up to now for making solid materials hydrophobic by covalent grafting of hydrophobic groups, the yield and kinetics of the grafting reaction increase with temperature, and with the concentration of the grafting reagent in contact with the solid material (concentration in the bath in the liquid phase or vapor pressures in the vapor phase), and decrease with the number of carbons of the grafting reagent, namely with its hydrophobic character.
OBJECT OF THE INVENTION
The invention thus aims at overcoming these disadvantages and providing an extremely simple, rapid and low-cost treatment method which can be exploited in practice on the industrial scale, enabling a solid material to be made hydrophobic and/or lipophilic.
The object of the invention is in particular to provide a treatment method of which the yield and kinetics are sufficiently improved to be compatible with profitability on the industrial scale. The object of the invention is also to provide a method with which the consumption of grafting reagent is reduced and which does not create toxic effluents or residues in a substantial quantity.
The invention moreover aims more particularly at providing such a method which does not require the use of catalysts, nor of compounds for trapping or neutralizing the acids formed, nor subsequent washing.
The object of the invention is also to provide a treatment method applicable to many solid materials and, in a general manner, any solid material having reactive hydrophillic functions on its specific area accessible to gases. The object of the invention is thus not only to enable cellulosic materials to be treated but also other materials, in particular materials with an inorganic structure such as glass. The object of the invention is in particular to enable fragile materials to be treated and/or those sensitive to solvents (materials which crumble). The object of the invention is thus to provide novel hydrophobic and/or lipophilic materials obtained by such a treatment in order to open up the field of applications which can be envisaged with such materials, in particular with fragile materials and/or materials which crumble such as paper.
The object of the invention is also to provide a treatment for obtaining a very pronounced hydrophobic or lipophilic character by covalent grafting of hydrophobic groups which can contain 18 or more carbons, which resist external attack and which are stable with time over a period very much longer than a day, in particular of the order of several months or several years
Dawson Robert
Young & Thompson
Zimmer Mare S.
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