Coating processes – Electrical product produced – Metallic compound coating
Reexamination Certificate
2001-06-26
2003-10-14
Dawson, Robert (Department: 1712)
Coating processes
Electrical product produced
Metallic compound coating
C106S031130, C106S031920, C523S309000, C525S186000, C525S189000, C427S058000, C101S483000
Reexamination Certificate
active
06632472
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a redispersible or soluble product obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
BACKGROUND OF THE INVENTION
The preparation of polythiophenes and dispersions thereof for use in antistatic coatings has been described in the literature e.g. ‘Handbook of Organic Conductive Molecules and Polymers’, ed. H. S. Nalwa, J. Wiley & Sons, 1997. Polythiophenes have conductive properties which can be controlled, for example, by the degree of doping.
FR-A-88 7976 discloses a process for the preparation or electrically conducting polymers based on polythiophenes by chemical polymerization of thiophene in a reaction medium comprising a ferric salt, an alkyl halide and water.
U.S. Pat. No. 5,254,648 discloses a process for the preparation of electrically conductive, doped polythiophene, the process comprising: unsubstituted thiophene, a ferric salt which is effective as a doping agent and as an agent inducing polymerization and which is added to the reaction medium as an anhydrous ferric salt, an alkyl halide present in an amount of less than 0.04 liter per gram thiophene, and water, wherein the water is introduced in an amount ranging between 0.009 and 900% by weight of the alkyl halide, and wherein the water and the anhydrous ferric salt are present in a molar ratio ranging between 0.01 and 6.
WO A-99 25753 describes a method for the preparation of polyanilines, polythiophenes and polypyrroles. EP-A 0 440 957 discloses dispersions of polythiophenes, constructed from structural units of formula (I):
in which R
1
and R
2
independently of one another represent hydrogen or a C
1-4
-alkyl group or together form an optionally substituted C
1-4
-alkylene residue, in the presence of polyanions.
EP-A-0 686 662 discloses mixtures of A) neutral polythiophenes with the repeating structural unit of formula (I),
in which R
1
and R
2
independently of one another represent hydrogen or a C
1-4
-alkyl group or together represent an optionally substituted C
1-4
-alkylene residue, preferably an optionally with alkyl group substituted methylene, an optionally with C
1-12
-alkyl or phenyl group substituted 1,2-ethylene residue or a 1,2-cyclohexene residue, and B) a di- or polyhydroxy- and/or carboxy groups or amide or lactam group containing organic compound; and conductive coatings therefrom which are tempered to increase their resistance preferably to <300 ohm/square.
EP-A 1 081 549 discloses a coating composition comprising a solution of a substituted or unsubstituted thiophene-containing-conductive polymer, a film-forming binder; and an organic solvent media; the media having a water content of less than 37 weight percent. Percentages by weight of poly(3,4-ethylenedioxythiophene) of 0.1% in the coating solution are exemplified.
EP-A 1 081 546 discloses a coating composition of an electrically-conductive polymer (ECP) and an organic solvent media wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent. Percentages by weight of ECP of 0.02 to 0.18% in the coating solution are exemplified.
EP-A 1 081 548 discloses a coating composition comprising a substituted or unsubstituted thiophene-containing electrically-conductive polymer and an organic solvent media; the media having a water content of less than 12 weight percent. Percentages by weight of poly(3,4-ethylenedioxythiophene) of 0.02 to 0.1% in the coating dispersion are exemplified.
In large scale methods for preparing aqueous dispersions of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene the solids content is limited to only a few percent, due to production reasons such as the need for ultrafiltration, the viscosity of the dispersion etc. It should be noted that such dispersions are often erroneously referred to, even in patent texts, as solutions due to their very small particle size, 20 to 50 nm, of the polythiophene/polyanion latex. Shipment of such dilute dispersions is expensive and cumbersome in view of the high volume and weight associated therewith.
Freeze drying has been developed as a method of preserving and increasing the transportability, e.g. in space travel, expeditions and military campaigns, of perishable organic materials such as food, flavours, aroma's, blood products and pharmaceutical formulations. Since the 1960's it has been applied to upwards of 400 foods from meat to fruits and vegetables. This background is reflected in a definition of freeze drying (or lyophilization process) given by T. A. Jennings and H. Duan in 1995 in the Journal of Parenteral Science and Technology, volume 49, no. 6 pp. 272-282, as ‘a stabilising process in which a substance is first frozen and then the quantity of solvent is reduced, first by sublimation and then by desorption to values that will no longer support biological activity or chemical reactions’.
It is an object of the present invention to provide a highly concentrated latex of a substituted or unsubstituted polythiophene.
A further aspect of the present invention is the provision of a method of making an antistatic or electroconductive layer.
A still further aspect of the present invention is the provision of a coating solution or dispersion of a latex from a highly concentrated dispersion latex of a polythiophene.
Another aspect of the present invention is the provision of a printing ink from a highly concentrated dispersion latex of a polythiophene.
Further objects and advantages of the present invention will become apparent from the description hereinafter.
BRIEF SUMMARY OF THE INVENTION
Efforts aimed at obtaining concentrated products from a dispersion or solution of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene provides solids or films using conventional techniques such as evaporating aqueous dispersions or precipitation produced compositions have shown that, if redispersible in water or organic solvents, redispersion required considerable investment of time and thermal and/or mechanical energy.
Surprisingly it has been found that if freeze-drying, an unconventional concentration technique, is applied to an aqueous dispersion of a latex comprising a polyanion and a copolymer or polymer of a substituted or unsubstituted thiophene, a sponge-like or wool-like powder is produced, which can be rapidly redispersed or dissolved without expenditure of thermal and/or mechanical energy in water or an organic solvent so as to obtain a coating dispersion or solution (optionally adding other ingredients) without leaving a coarse fraction behind. The resulting coating dispersion or solution can be applied to any object, for example a support.
A redispersible or soluble product is provided by the present invention obtainable by freeze drying an aqueous dispersion of a latex comprising a polyanion and a polymer or copolymer of a substituted or unsubstituted thiophene.
A method for making an antistatic or electroconductive layer or pattern is further provided by the present invention comprising the steps of redispersing or diluting the above-mentioned product by adding water or an organic solvent so as to obtain a solution or dispersion; optionally adding other ingredients to the solution or dispersion; and—applying the solution or dispersion to an object.
A coating solution or dispersion is also provided according to the present invention comprising the above-mentioned redispersible or soluble product.
Use of the above-mentioned coating solution or dispersion is also provided by the present invention for preparing an antistatic or electroconductive layer.
A printing ink is also provided according to the present invention comprising the above-mentioned redispersible or soluble product.
Use of the above-mentioned printing ink is also provided by the present invention
Louwet Frank
Samijn Raf
Agfa-Gevaert
Dawson Robert
Leydig , Voit & Mayer, Ltd.
Zimmer Marc S
LandOfFree
Redispersable latex comprising a polythiophene does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Redispersable latex comprising a polythiophene, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Redispersable latex comprising a polythiophene will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3167072