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
  • B41M5/132—Chemical colour-forming components; Additives or binders therefor
  • B41M5/155—Colour-developing components, e.g. acidic compounds; Additives or binders therefor; Layers containing such colour-developing components, additives or binders
  • B41M5/1555—Inorganic mineral developers, e.g. clays

Definitions

• the invention relates to color developers for carbonless papers which adhere to the paper base (base paper) without or with very little addition of binder.
• the main constituent of the color donor layer are dense-walled microcapsules made of gelatin, polyurethane, melamine formaldehyde and similar substances, which contain solutions of dyes in the so-called leuco form.
• Dye precursors predominantly from the class of di- or triphenylmethanes, thiazines, spiropyrans or fluorans, act as electron donors (Lewis bases) and can be converted into the dye form in a chemical reaction using electron acceptors (Lewis acids).
• Lewis acids of this type are in the dye receptor layer in the form of acidic phenolic resins, zinc salicylates or acid-activated clay minerals, for example acid-activated smectic layered silicates. If the walls of the microcapsules concerned are now destroyed when writing a carbonless copy due to the pen pressure, the capsule content - the dye solution - is released and developed on the Lewis acidic receiver layer, a copy being produced.
• Particularly suitable color developer pigments can be produced by acidic activation of clay minerals, such as attpulgites or preferably smectic layered silicates, such as bentonites.
• Calcium bentonite that is to say a layered silicate, the negative layer charges of which are compensated for by calcium ions at interlayer sites, is preferably used.
• the bentontite is chemically changed: firstly, the interlamellar-bound Ca2+ is replaced by 2H+ in an ion exchange step, secondly, the layer lamella is attacked from the edges and the central, octahedrally coordinated Al3+, Fe2+, Fe3+ and / or Mg2 + ions are more or less dissolved and washed out depending on the activation conditions.
• the resulting product can be described as a combination of residual layer silicate with voluminous, amorphous silica bound at the edges. It is characterized by very high specific surface areas of about 300 m2 / g (measured according to the BET method), a high adsorption capacity and pore volume, due to the presence of many acidic ones Centers (Brönstedt and Lewis acids), where the development of the dyes takes place catalytically, as well as lack of swelling capacity.
• EP-A-0 572 037 discloses a coating pigment for coating printing substrates, in particular paper and cardboard, which contains at least one swellable layered silicate which can be fixed on the print substrate essentially without a binder, the proportion of the swellable layered silicate being at least 30% by weight .-%, and the swelling volume of the coating pigment is 5 to 30 ml, based on a suspension of 2 g of coating pigment in 100 ml of water.
• Such a coating pigment can be used to produce an aqueous coating color with which a printing medium can be coated on one or both sides.
• color developers for carbonless papers can be developed on the basis of swellable layered silicates which, because of their inherent adhesion, are fixed on the paper backing without - or with only very little use of binder.
• the invention thus relates to a color developer for carbonless paper based on a swellable layered silicate, which is characterized in that the proportion of swellable layered silicate is 50 to 100 wt .-%, and that the layered silicate has a swelling volume of 5 to 30 ml, based on a suspension of 2 g in 100 ml of water, and has a specific surface area of ⁇ 140 m2 / g.
• the indicated swelling volume is very important. If the swelling volume is lower, i.e. ⁇ 5 ml / 2 g, the adhesive force is no longer sufficient for the coating pigment to be fixed on the base paper without binder. Higher swelling volumes of> 30 ml / 2 g cause very poor rheological behavior with very low coating colors.
• the specific surface area of ⁇ 140 m 2 / g turns out to be a further critical parameter for the color developers according to the invention, since color developers with higher surfaces can no longer be processed without a binder.
• the CF lines obtained with the color developers according to the invention can also be recycled much better than the conventional lines known to date. Furthermore, there is no or only a very small amount of waste acid, so that the ecological balance can be significantly improved.
• the proportion of the swellable layered silicate is preferably approximately 50 to 100% by weight, in particular approximately 70 to 90% by weight.
• the rest consists of impurities that cannot swell, such as feldspar, mica, kaolin, dolomite, etc. in very fine-particle form. These contaminants can generally no longer be removed with the coarse-grained contaminants (grit). They do not interfere, but rather contribute to reducing the swelling volume of the layered silicate to the claimed range, since certain layered silicates in pure form have a swelling volume greater than 30 ml.
• the layered silicate is preferably bentonite, beidellite, nontronite, saponite, hectorite or a mixture thereof. These layered silicates can be largely dispersed in the individual lamellae in aqueous suspension under the action of shear. Because of their ability to form numerous hydrogen bonds and because of their platelet-like structure, these have a high degree of adhesion to paper fibers, so that they can be fixed in order quantities of about 0.5 to 3 g / m 2 without binder on a paper support, such as coating base paper. Due to the platelet-like structure, they continue to form a barrier on the surface that largely prevents the leuco dye from penetrating the paper. It is particularly preferred to start from calcium bentonites, the swellability of which has been improved by treatment with alkali compounds, in particular with sodium compounds (ion exchange Ca2+ 2Na+).
• the ion exchange can be carried out in the usual way with soda.
• the activation is preferably carried out with a mixture of soda and magnesium hydroxide, with sodium aluminate and / or with water glass. With the help of these substances, the color development capacity is surprisingly increased.
• Lewis acids doping when activated with Lewis acids in amounts of about 5 to 100 mmol / 100 g has a very positive effect on the color reactivity.
• salts of alkaline earths, zinc, cadmium, aluminum, zircon, titanium and silicon are used as Lewis acids.
• the preferred Lewis acids are salts with the cations Mg2+, Zn2+, Al3+, Zr4+ and mixtures thereof.
• the color developer according to the invention is preferably blended in proportions of 1 to 50% by weight, in particular 5 to 30% by weight, with amorphous silica and / or amorphous silicates, such as calcium silicate, calcium hydrosilicate, magnesium silicate or sodium aluminum silicate.
• amorphous silica and / or amorphous silicates such as calcium silicate, calcium hydrosilicate, magnesium silicate or sodium aluminum silicate.
• binders such as styrene-butadiene latex
• binders such as styrene-butadiene latex
• the running properties and the dispersibility of the color developer according to the invention can be further improved if he uses hydrocolloids, e.g. of polyvinyl alcohol or guar, in amounts of 0.5 to 5% by weight, preferably 0.5 to 3% by weight.
• hydrocolloids e.g. of polyvinyl alcohol or guar
• the color developer according to the invention can be used in a ratio of 5 to 50% by weight, preferably 10 to 30 % By weight, blended with conventional, acid-activated layered silicates.
• the binder content of the color developers can be greatly reduced even in the case of relatively highly acid-activated layered silicates.
• the color developers according to the invention can also be blended with known coating pigments, such as kaolin or CaCO3. These blends can be applied from aqueous suspensions with solids contents of 10 to 50% by weight, preferably 15 to 35% by weight, to coating units, such as the gravure coater or to film presses. It is of course also possible to order blade coaters. Spray technology can also be used.
• the former coating units are preferred for low-gram lines of 1 to 3 g / m2, while the blade coater can be used for higher orders of 4 to 8 g / m2.
• the color developers according to the invention can be completely or partially cationically charged by reaction with a cationizing agent.
• the cationizing agent is preferably a quaternary, monomeric, oligomeric or polymeric organic ammonium compound, such as a dicyandiamide formaldehyde condensate or polydate mac (poly-diallyldimethylammonium chloride).
• the invention further relates to an aqueous coating color comprising the color developer defined above, the solids content being between about 5 and 50% by weight, preferably between about 15 and 35% by weight.
• the pH of the aqueous coating slip is preferably about 6.5 to 9.5, in particular 7 to 8.
• the invention further relates to a paper which is coated with a color developer or a coating color, as defined above.
• the application weight of the color developer is preferably 0.5 to 3 g / m2.
• the color developer is preferably with an application weight of 1 to 3 g / m2 applied to wood-free, wood-containing or waste paper-containing coating base paper.
• the color developer according to the invention which was activated only with soda, according to Example 1d, was additionally mixed with the activation of 50 mmol / 100 g of the chlorides of Zn2+, Al 3+ and Zr4+ and activated and worked up as above.
• Table I shows that the doped products have an increased color reactivity.
• the treatment gave the pigments a positive zeta potential (measured in 0.1% aqueous suspension at pH 8 on the 501 Lazer Zee Meter from Pankem).
• the cationized pigments 6a-c were coated with the addition of 3 parts HICAT 115® (a cationic potato starch from Roquette) at an application weight of approx. 3 g / m2.
• the paper was checked with an acidic, anionic permanent dye.
• the papers were printed on a laboratory gravure printing device (well depth 1.2 ⁇ m) with a 0.2% aqueous solution of Pigmosol black X58®, an anionic dye from BASF.
• the contrasts were: example Contrast% 1 a 68.5 6 a 74.5 6 b 78 6 c 78

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• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Color Printing (AREA)
• Paper (AREA)

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• 1994
  • 1994-04-20 DE DE19944413672 patent/DE4413672A1/de not_active Withdrawn
• 1995
  • 1995-03-21 EP EP95104149A patent/EP0678399A1/fr not_active Withdrawn
  • 1995-04-19 CA CA 2147326 patent/CA2147326A1/fr not_active Abandoned

Patent Citations (3)

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