Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/165—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components characterised by the use of microcapsules; Special solvents for incorporating the ingredients
  • B41M5/1655—Solvents

Definitions

• the present invention relates to microcapsules useful in particular for making carbonless pressure-sensitive paper, containing an organic solution of a hydrophobic dye, the solvent of which is at least partly of vegetable origin.
• the invention also relates to pressure-sensitive paper coated on one side with a layer of such microcapsules and to the bundle of pressure-sensitive paper comprising at least one paper according to the invention.
• the invention relates generally to CB, CFB and autonomous sheets.
• the operating principle of carbonless pressure-sensitive paper consists in bursting the microcapsules under the pressure of a pen or under the shock caused by a typewriter strike or by the needles of a dot-matrix printer or more generally by all the so-called "impact" printing processes.
• the internal phase contained in the microcapsules thus released flows on the CF receiving layer and the chromogenic agents react with the developer to form the colored image.
• solvents are most often mixed with diluents such as kerosene, light mineral oils or alkylbenzenes (for example dodecylbenzene) etc.
• solvents of natural origin such as vegetable oils (soya, rapeseed, olive, peanut, palm kernel, corn, sunflower, copra, sesame, castor, palm, babassu, jojoba, etc. ) in particular in American patents No. 2,712,507, 2,730,457, 3,016,308, 4,783,196, 4,923,641 and European patent applications No. 86,636, 155,593, 262,569.
• microcapsules according to the invention make it possible to overcome the drawbacks mentioned above and are characterized in that the solvent for the hydrophobic chromogenic agent comprises an ester obtained by transesterification of a vegetable oil.
• microcapsules advantageously, but not exclusively, those formed from a wall of crosslinked gelatin.
• esters is generally meant the mixture obtained by transesterification, comprising at least 95% fatty acid esters of natural origin.
• Transesterification is the chemical operation which consists in exchanging glycerol in an acidic or basic medium with a monoalcohol, generally with a short chain, which leads to the formation of an ester, then eliminating the glycerol.
• the solvent must contain sufficient ester obtained by transesterification of a vegetable oil to meet the conditions set out above.
• oils can be used alone or as a mixture.
• the alcohol part of the ester resulting from the transesterification is a lower linear or branched alcohol residue, that is to say of which the carbon number ranges from C1 to C10.
• the alcohol residue is a C en to C8 residue.
• alcohol residues mention may be made of the residues of the following alcohols: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 2-ethylhexanol.
• phthalic type derivatives such as 3,3-bis (4-dimethylaminophenyl) -6-dimethylamino-phthalide (CVL) and 3,3-bis (1-octyl- 2-methylindole-3-yl) phthalide or fluorane derivatives such as 2-anilino-3 methyl-6 dialkylamino -2 '- (N'-eryth-N-phenylamino-4'-methylfluorane) or 2'-anilino-3' methyl-6 diethylamino fluorane, 6'-dimethylamino-2 '- (N-ethyl-N-phenylamino-4'-methylfluorane), 3'-chloro-6'-cyclohexylaminofluorane or 3,7-bis (dimethylamino) -10-benzoylphenotiazine (BLMB ) and bisarylcarbazo
• the solution of chromogenic agent in the solvent is around 5% by weight.
• the solvent comprises at least 30% by weight of ester obtained by transesterification of a vegetable oil.
• the solvent may contain mineral oils.
• mineral oils which it is possible to use in combination with the esters, mention may be made, for example, of kerosene, paraffinic or naphthenic oil.
• Preferably light naphthenic or paraffinic oils are used.
• the alcohol part of these esters is most of the time chosen from the alcohol residues already mentioned above for the esters obtained by transesterification of a vegetable oil.
• mineral oils are preferred.
• the invention also relates to a process for the preparation of such microcapsules.
• an emulsion of a hydrophobic phase consisting of an organic solution as described previously of a chromogenic substance, in a basic aqueous phase comprising several colloids including gelatin and one or more other anionic colloids among which mention may be made of carboxymethylcellulose (CMC) and a maleic anhydride copolymer such as a copolymer of l 'ethyl ethervinyl and maleic anhydride (PVMMA) or a copolymer of ethylene and maleic anhydride (EMA).
• CMC carboxymethylcellulose
• PVMMA copolymer of l 'ethyl ethervinyl and maleic anhydride
• EMA copolymer of ethylene and maleic anhydride
• the temperature is then raised and the emulsion is coacerved by adding an appropriate acid, in particular acetic acid, in order to adjust the pH to around 4.
• an appropriate acid in particular acetic acid
• Liquid-walled microcapsules are thus formed by formation of the coacervate around the droplets of emulsified oil. Cooling the mixture to about 10 ° C causes the walls of liquid coacervate to solidify.
• a curing agent such as formalin or glutaraldehyde is then added in order to crosslink said solid walls of coacervate and to obtain the desired microcapsules.
• the emulsions obtained were more stable and had a narrower particle size distribution than the emulsions prepared with solvents based on virgin oil.
• the emulsion obtained is of the oil in water type and comprises droplets of the hydrophobic phase whose diameter is between 1 and 12 micrometers (preferably 3 to 8 micrometers).
• microcapsules obtained are mixed with starch binders or latexes, a spacer, generally calibrated wheat starch and various additives such as optical brightener, water retention etc.
• the subject of the invention is also a pressure-sensitive paper coated on one side with a layer of microcapsules as described above.
• This paper support constituting the transmitting sheet, called CB, with a grammage generally between 40 to 90 g / m 2 was coated by coating the suspension of microcapsules, then these microcapsules were dried to obtain the paper according to the invention.
• the method of coating and the formulation of the coating bath are not critical to the invention.
• the invention also relates to a bundle of pressure-sensitive paper comprising, as has been described in the preamble to the present description, a transmitting sheet and a receiving sheet, and optionally one or more intermediate sheets (CFB) and also so-called autonomous sheets obtained by coating the front of a mixture of microcapsules and receiving layers.
• a bundle of pressure-sensitive paper comprising, as has been described in the preamble to the present description, a transmitting sheet and a receiving sheet, and optionally one or more intermediate sheets (CFB) and also so-called autonomous sheets obtained by coating the front of a mixture of microcapsules and receiving layers.
• CFRB intermediate sheets
• the CF receiving paper associated with the CB sheet is preferably of the "activated clay" type as described in French patents 2,581,350 or US 4,422,670, but it is also possible to use a phenolic type CF such as those described in US Patents 4,559,242 or 4,769,305, or a CF of the zinc salycilate type.
• the use of the solvent according to the invention makes it possible to improve, in addition to the viscosity and the quality of the emulsion, the degree of encapsulation in a completely surprising manner but also the intensity and the light fastness of the 'writing.
• the organic phase and the aqueous phase are mixed with stirring and emulsified using an Ultra-TURRAX type apparatus until particles having an average diameter between 5 and 6 ⁇ m are obtained (the diameter is measured using a Coulter LS 100 laser granulometer).
• Carboxymethylcellulose has a degree of substitution of the order of 0.8 and a viscosity in 3% aqueous solution at 20 ° C of between 60 and 100 mPas measured using a Haake VT 181 viscometer with MVI coaxial cylinders at 180 rpm.
• the temperature is raised to 60 ° C and acetic acid is added over 30 minutes to adjust the pH to 4.3.
• the coacervate is cooled to 8 ° C. and this temperature is maintained for 10 hours.
• Example 1 is reproduced by replacing the rapeseed methyl ester obtained by transesterification produced by Novamont with the same type of product produced by the company Robbe under the brand Estorob or Lubrirob 926.
• Example 2 is repeated but with the methyl ester of rapeseed produced by the company Henkel.
• Example 1 is reproduced by replacing the rapeseed methyl ester with an isopropyl soy ester obtained by transesterification manufactured by the company Stéarinerie Dubois et Fils.
• Example 4 is reproduced by replacing the soybean oil with a "tall oil” (product manufactured by the company Stéarinerie Dubois et Fils) from wood.
• Example 1 is repeated, replacing the solvent mixture with 400 g of Novamont rapeseed methyl ester + 445 g of purified isopropyl palmitate (Kessco IPP brand from Akzo).
• Example 1 is repeated, replacing the solvent mixture with 400 g of Novamont rapeseed methyl ester + 445 g of purified methyl stearate (brand Edenol W750 from Henkel).
• Example 1 is reproduced by replacing the rapeseed methyl ester with refined virgin rapeseed oil (produced by the company CEREOL).
• the loss of reactivity of the CB is measured by crushing with the calender before and after aging.
• the loss of whiteness of the CF due to the migration of part of the chromogenic agents present in the microcapsules is measured compared to a blank test on the same CF.

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• Color Printing (AREA)
• Manufacturing Of Micro-Capsules (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

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Family Applications (1)

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Cited By (3)

Citations (28)

• 1994
  • 1994-07-26 FR FR9409220A patent/FR2723032B1/fr not_active Expired - Lifetime
• 1995
  • 1995-07-24 DE DE1995604612 patent/DE69504612T2/de not_active Expired - Lifetime
  • 1995-07-24 EP EP19950401746 patent/EP0697293B1/de not_active Expired - Lifetime

Patent Citations (29)

Non-Patent Citations (1)

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