EP1760535A2 - Method for fixing toner in a document printing or reproducing device and compositions that can be used in this method - Google Patents

Abstract

Composition comprises a hydrofluorocarbon having 3-6 carbon atoms and a co-solvent such as organic compounds, miscible with the hydrofluorocarbon, in a weight ratio of 1:100 to 1:1.

Description

The present invention relates to a method for fixing a toner in a printing apparatus or to reproducing documents and to compositions that can be used in this process.

It is known to use halogenated hydrocarbons, alone or mixed with other organic compounds, in the gaseous state, as chemical fixing agents for a toner to a recording medium in printing or reproduction apparatus. documents, apparatus in which the toner has been previously deposited on the recording medium, for example electrostatically. It is clear that the fixing agent used must absolutely not have a flash point under the temperature and pressure conditions prevailing in the printing or reproduction apparatus. A conventional fixing agent consists of a azeotropic mixture of 1,1,2-trichlorotrifluoroethane (CFC-113) and acetone, as proposed in US Pat. US Patent 4311723 . However, since CFC-113 is suspected of having a negative impact on the stratospheric ozone layer, international regulations ultimately prohibit its use. Alternative fixing agents have already been proposed, including 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) or 1,1-dichloro-1-fluoroethane (HCFC-141b) ( WO-A-93/10485 ), compositions based on perfluorinated compounds ( EP-A-0465037 ), as well as HCFC-141b-based compositions ( EP-A-0605128 ). These compositions are, however, not entirely satisfactory, in particular because of their toxicity (HCFC-123), their nonzero ozone depletion potential (HCFC-123 and HCFC-141b) and / or their long duration of inactivity. atmospheric life (perfluorinated compounds).

It is an object of the present invention to provide a method for fixing a toner in a printing or copying apparatus which no longer has the disadvantages of known methods.

The invention therefore relates to a method for fixing a toner to a recording medium in a printing or reproducing apparatus by contacting the recording medium on which the toner is deposited with an agent. chemical fixer in the gaseous state, which is characterized in that the fixing agent contains a C3-C6 hydrofluorocarbon.

By C3-C6 hydrofluorocarbon is meant saturated hydrocarbons, aliphatic or alicyclic, consisting solely of carbon, fluorine and hydrogen, comprising from 3 to 6 carbon atoms, at least one fluorine atom and at least one atom hydrogen. In particular, hydrofluorocarbons which can be used as fixing agent in the process according to the invention are hydrofluoroalkanes of general formula C _a H _b F _c , in which a is an integer of 3 to 5, b is an integer of 1 to a + 2) and c is an integer from a to (2a + 1). Hydrofluoroalkanes as defined above, containing 4 carbon atoms are preferred. By way of example, the hydrofluoroalkane of the fixing agent used in the process according to the invention may be selected from compounds of the formula C ₃ H ₃ F ₅ , C ₄ H ₅ F ₅ , C ₄ H ₄ F ₆ and C ₅ H ₂ F ₁₀ , such as 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,2,2,3-pentafluoropropane (HFC-245ca), 1,1,1,3,3-pentafluoropropane , 1,3,3-pentafluorobutane (HFC-365mfc), 2-methyl-1,1,1,3,3-pentafluoropropane (HFC-365mps), 1,1,1,4,4,4-hexafluorobutane (HFC-356mff), 1,1,1,2,2,4-hexafluorobutane (HFC-356mcf) and 1,1,1,2,2,3,4,6,6,6-decafluoropentane (HFC -4310mee). 1,1,1,3,3-Pentafluorobutane is very suitable. The fixing agent may alternatively comprise a mixture of C3-C6 hydrofluorocarbons as defined above.

Preferably, the fixing agent also contains a cosolvent. By co-solvent is meant an organic compound, or a mixture of several organic compounds, miscible with the hydrofluorocarbon C3-C6 in weight proportions of 1: 100 to 1: 1.

Co-solvents which can be used in the fixing agents used in the process according to the invention include C 1 -C 3 alcohols (for example methanol, ethanol, propanol and isopropanol); C3-C6 ketones (for example acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone and diethyl ketone); C2-C8 esters, formed from a carboxylic acid, such as formic acid, acetic acid, propionic acid or butyric acid, and an alcohol such as methanol, ethanol or propanol; and C1-C3 chlorinated hydrocarbons (for example dichloromethane, 1,2-dichloroethylene-trans and 1,2-dichloroethylene-cis).

Ketones and esters are preferred cosolvents. Esters are the most preferred cosolvents. Among the ketones, acetone is particularly preferred. Among the esters, ethyl acetate, methyl acetate, formate ethyl and methyl formate are preferred. Ethyl acetate is especially preferred.

The content of C3-C6 hydrofluorocarbon in the fixing agent is advantageously at least 50%, preferably at least 60%, of the total weight of the fixing agent composition. The fixing agent may consist solely of C3-C6 hydrofluorocarbon. Preferably, the content of C3-C6 hydrofluorocarbon does not exceed 98%, particularly preferably 96% and most preferably 90% of the total weight of the fixing agent composition.

The content of co-solvent in the fixing agent used in the process according to the invention is advantageously at least 2%, preferably at least 4%, and particularly preferably at least 10%. of the total weight of the fixing agent composition. The cosolvent content does not generally exceed 40%, preferably 30%, and most preferably 20%, of the total weight of the fixing agent composition.

The fixing agent used in the process according to the invention may contain, in addition to the hydrofluorocarbon and the co-solvent, additives making it possible to improve the performance of the fixing process, in particular stabilizers, such as nitroalkanes (eg nitromethane or nitroethane) and epoxides (eg propylene oxide or butylene oxide).

In the process according to the invention, the contacting of the recording medium on which the toner is deposited with the gaseous chemical fixing agent can be carried out in any device driving the recording medium comprising the toner to be fixed in a chamber. containing vapors of the fixing agent. Such devices are described for example in the patent US Patent 4311723 and in the patent application EP-A-605128 . Conventionally, the recording medium comprising the image formed by the toner passes through a fixing chamber whose atmosphere is saturated with vapors of the fixing agent, at a temperature of 50 to 100 ° C. The fixing agent used causes a very fast fixing of the toner to the recording medium, which allows a high printing or reproduction rate. Typically, the recording medium comprising the toner to be fixed is contacted with the fixing agent for a period of 0.5 to 3 seconds.

The toners which can be fixed by the process according to the invention consist of finely divided, free-flowing particles based on colored or pigmented thermoplastic resins, for example carbon black, as described in particular in Kirk-Othmer - Encyclopedia of Chemical Technology, 4th Ed., Vol. 9, pp. 270-271 , in the chapter on electrophotography. The process according to the invention is particularly applicable to the fixing of powder toners consisting essentially of a polymeric matrix, such as for example a matrix based on polystyrene or polyester, and a pigment. The method according to the invention in which the fixing agent contains a co-solvent is particularly well suited to fixing toners comprising a polyester-based polymeric matrix.

The method according to the invention makes it possible to fix a toner to a large number of recording media, in particular paper, transparent sheets of polymeric synthetic material and natural or synthetic fabrics. The fixing agent used in the process according to the invention generally does not alter the recording media usually used in printing or reproduction processes using powder toners.

The invention also relates to compositions containing a C3-C6 hydrofluorocarbon and a C2-C8 ester, corresponding to the fixing agents preferably used in the fixing process according to the invention.

The following nonlimiting examples are given for illustrative purposes.

Example 1

In a flask with a capacity of 11, surmounted by a condenser, was placed 3 ml of a fixing agent consisting of 80% by weight of 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and 20% by weight of ethyl acetate, then the flask was immersed in a thermostatic bath maintained at 95 ° C, so as to completely vaporize the fixing agent in the flask. A paper tongue was then introduced into the flask for 2 seconds, on which toner containing a polyester polymer matrix (type A2.5 - S26312-F497 from Siemens-Nixdorf) had previously been placed. After this treatment, the toner was firmly attached to the paper.

Examples 2-8

Example 1 was repeated replacing the fixer agent with others. The nature of the fixing agents used and the degree of fixing obtained are reported in Table I below. <u> Table I </ u> Example Fixative agent (% weight) Degree of fixing * 2 HFC-365mfc / acetone (80/20) + + + 3 HFC-365mfc / ethanol (80/20) + + 4 HFC-365mfc / trans-1,2-dichloroethylene (70/30) + 5 HFC-365mfc / ethyl acetate (90/10) + + + 6 HFC-365mfc / methyl formate (80/20) + + + 7 HFC-365mfc / ethyl formate (80/20) + + + 8 HFC-365mfc / methyl acetate (80/20) + + + *: + + + = excellent; + + = very good; + = good

Examples 9-11

For the fixing agents listed in Table II, the existence of a closed-cup flash point (Pensky-Martens) according to the ASTM D93-90 standard was sought. Although co-solvents such as acetone or ethyl acetate are highly flammable, none of the fixatives tested has a flash point. HFC-365mfc therefore has a very pronounced inerting effect on the flammability of these co-solvents. <u> Table II </ u> Example Fixative agent (% weight) 9 HFC-365mfc / ethyl acetate (80/20) no flash point between -38 and 35 ° C 10 HFC-365mfc / acetone (80/20) no flash point between -38 and 35 ° C 11 HFC-365mfc / trans-1,2-dichloroethylene (70/30) no flash point between -30 and 40 ° C

Claims (11)

Compositions containing a C3-C6 hydrofluorocarbon and a co-solvent which is an organic compound, or a mixture of several organic compounds, miscible with C3-C6 hydrofluorocarbon in weight proportions of 1: 100 to 1: 1. Compositions according to claim 1, in which the cosolvent is chosen from C1-C3 alcohols, C3-C6 ketones and C2-C8 esters, formed from a carboxylic acid, such as formic acid. , acetic acid, propionic acid or butyric acid, and an alcohol such as methanol, ethanol or propanol, and chlorinated hydrocarbons C1-C3. Compositions according to claim 2, wherein the co-solvent is selected from methanol, ethanol, propanol, and isopropanol. Compositions according to claim 2, wherein the co-solvent is selected from acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone and diethyl ketone. Compositions according to claim 2, wherein the co-solvent is selected from dichloromethane, 1,2-dichloroethylene-trans and 1,2-dichloroethylene-cis. Compositions according to any one of Claims 1 to 4, in which the hydrofluoroalkane is selected from compounds of the formula C ₃ H ₃ F ₅ , C ₄ H ₅ F ₅ , C ₄ H ₄ F ₆ and C ₅ H ₂ F ₁₀ . Compositions according to claim 5, wherein the hydrofluoroalkane is 1,1,1,3,3-pentafluoropropane (HFC-245fa). Compositions according to claim 5, wherein the hydrofluoroalkane is 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC-43 10mee). Compositions according to any one of claims 1 to 7, wherein the content of C3-C6 hydrofluorocarbon is 50 to 98% by weight. Compositions according to any one of claims 1 to 8, wherein the co-solvent content is 2 to 40% by weight. Compositions containing a C3-C6 hydrofluorocarbon and a C2-C8 ester.