EP0088466A1 - Desensitizing ink for emulsion lithographic printing - Google Patents

Abstract

In a desensitizing ink for the wet offset printing of a given area of the acceptor surface of a duplicating set containing an alkoxylated nucleophilic compound, preferably having a molecular weight lying in the range of from 2000 to 4000 and having a hydrophilic-lipophilic balance (HLB) of from 3 to 6, emulsified water is added to the mass of ink. This rapidly forms a fine stable emulsion of water in the ink which is favorable for continuous wet offset printing.

Description

The subject of the invention is a desensitizing ink for wet offset printing on an acceptor surface of a carbonless chemical assembly, comprising at least two superimposed sheets, the facing faces of which have an acceptor electrophilic coating and the other a coating nucleophile capable of producing a chromogenic reaction with said accepting electrophilic coating.

Carbonless assemblies are known which are obtained by a layer of microcapsules applied to the back of a 1st sheet, these microcapsules comprising a nucleophilic leuco-dye. The microcapsules burst under the impact of a typewriter or the pressure of a writing instrument on the front of the first sheet, and a colored reaction occurs between the nucleophilic leuco-dye and an electrophilic acceptor applied to the front of a second sheet. In this way, we obtain the reproduction on the second sheet of the writing made on the first sheet.

There are cases where it is desired to prevent such a reaction from taking place on certain parts of the surface of the second sheet. For this purpose, the desired parts of the acceptor surface are neutralized by printing a layer of fatty nucleophilic ink.

• Le procédé typographique utilise une matrice contenant des caractères d'imprimerie surélevés ou des surfaces surélevées. Cette surélévation permet de mettre en contact les caractères et surfaces devant être encrés, tout en évitant que les espaces non-surélevés soient enduits d'encre. Ainsi se différencient les parties imprimées et non imprimées d'une feuille et dans le cas de la neutralisation les parties neutralisées (non réactives au colorant de la microcapsule) et les parties non-neutralisées (réagissant avec les colorants, donc chromogéniques).

The main printing processes used to apply the neutralizing fatty ink on carbonless paper are as follows:

• The letterpress process uses a matrix containing raised block letters or raised areas. This elevation makes it possible to bring the characters and surfaces to be inked into contact, while preventing the non-raised spaces from being coated with ink. Thus, the printed and non-printed parts of a sheet are differentiated and in the case of neutralization the neutralized parts (not reactive to the dye of the microcapsule) and the non-neutralized parts (reacting with the dyes, therefore chromogenic).

Due to pressures of the order of several tens of atmospheres required by the typographic process, there is a risk of bursting the microcapsules on the CB face (back of the first sheet). This process is therefore not recommended for the application of the neutralizer.

The dry offset printing process uses an elastomer plate where the surfaces to be printed are raised. These surfaces are coated with ink which is transferred to a rubber blanket which in turn deposits the ink on the paper.

This process requires much less pressure to transfer the ink to the front of a sheet with microcapsules (CFB) on the back. Thus, the risk of bursting the microcapsules is considerably reduced.

The wet offset or lithographic offset printing process uses a metal plate where the areas to be printed are oleophilic and the areas which are not to be printed have a hydrophilic character. An inkwell followed by an inking train nourishes the oleophilic zones while a tank of dampening water and dampening rollers moisten the hydrophilic zones.

At the level of the plate, a balance of the ink and water supplies must be established in addition to the possible emulsion balance of the water in the ink and sometimes of the ink in water. These balances ensure the sharpness of im pressure and they are in physico-chemical relation with the hydrophilic-lipophilic balance (HLB).

During the wet offset printing, the oleophilic areas of the plate are coated with ink which is transferred onto a rubber blanket to finally be deposited on the acceptor surface (CF) of the carbonless.

• 1. d'amener la quantité d'encre requise sur les parties à neutraliser de la surface acceptrice (CF)
• 2. d'assurer l'impression d'un film d'encre uniforme avec netteté de contour
• 3. de saturer la surface acceptrice (CF) avec une quantité d'encre suffisante pour assurer la neutralisation complète de l'accepteur avec des quantités d'encre inférieures à celles nécessaires en typographie ou en offset sec. En effet, la neutralisation complète de la surface acceptrice (CF) est en rapport avec le volume d'encre nécessaire pour saturer la couche acceptrice. Ce volume tient compte d'une proportion d'eau émulsionnée dans sa masse qui participe à l'augmentation du volume total.
• 4. d'assurer une meilleure pénétration de l'encre neutralisante dans la couche acceptrice (d'où une meilleure performance neutralisante, car la formation d'un voile coloré ou de points colorés se situe dans les zones profondes de la couche acceptrice). En effet, la présence d'une émulsion d'eau dans l'encre engendre une diminution de la viscosité et cette diminution est d'autant plus grande que la quantité d'eau émulsionnée dans l'encre est importante.
• 5. de considérablement baisser le risque d'éclatement des microcapsules d'une feuille (CFB) lors de l'impression du recto de la feuille à des pressions moindres que dans le procédé typographique.

The wet offset process thus allows

• 1. bring the required quantity of ink to the parts to be neutralized on the acceptor surface (CF)
• 2. ensure the printing of a uniform ink film with sharpness of outline
• 3. to saturate the acceptor surface (CF) with a sufficient quantity of ink to ensure complete neutralization of the acceptor with less quantities of ink than those required in letterpress or dry offset. Indeed, the complete neutralization of the acceptor surface (CF) is related to the volume of ink necessary to saturate the acceptor layer. This volume takes into account a proportion of water emulsified in its mass which contributes to the increase in the total volume.
• 4. ensure better penetration of the neutralizing ink into the acceptor layer (hence a better neutralizing performance, since the formation of a colored veil or of colored dots is located in the deep areas of the acceptor layer). Indeed, the presence of a water emulsion in the ink causes a decrease in viscosity and this decrease is all the greater the greater the quantity of water emulsified in the ink.
• 5. considerably lower the risk of bursting of the microcapsules of a sheet (CFB) when printing the front of the sheet at lower pressures than in the typographic process.

Among the wetting devices used in offset-wet printing, it is necessary to consider direct or conventional wetting according to which the plate is moistened by a wetting roller soaked in wetting water. The plate is then brought into contact with the ink rollers which deposit the ink only on the oleophilic surfaces, since the hydrophilic zones have been moistened. These two operations are performed at each turn of the plate, therefore in a normal print run at a rate of 4,000 to 10,000 times per hour.

The speed of these two successive operations always brings a certain amount of water into the ink, hence the need for the ink to have a propensity to emulsify water, the amount of water acceptance being limited (relationship with the HLB). The reverse emulsion, that is to say the emulsification of ink in water, is an exceptional phenomenon which leads to the undesirable phenomenon of "fogging".

On the other hand, consider indirect wetting, also called "Dahlgren", where the first ink roller is in contact with the wetting roller. This first ink roller is responsible for most of the water supply to nourish the hydrophilic areas of the plate. The wetting water is in an incomplete emulsion state. This state of emulsion is facilitated by adding an alcohol or a polyol to the wetting water, in order to lower the surface tension of the water. According to this wetting process, precise equilibria preside over the water and ink supplies (linked to the HLB).

In US patent 3,952,117, a desensitizing ink containing a polypropylene glycol (PPG) with an average molecular weight of 400-5,000 is described, intended for printing in letterpress or dry offset.

According to DE OS 2.526.592, adducts of ethylene oxide and / or propylene oxide are used on aliphatic amines, for example adducts of propylene oxide on triethylenetetramine, tetraethylene pentamine or tetrapropylene pentamine which are subsequently esterified or etherified. These products have a molecular weight of less than 1,000 and are intended for printing in letterpress and dry offset.

According to US Pat. No. 4,101,690, neutralizing adducts are used which are block copolymers of ethylene oxide and propylene oxide on polyethylene polyamines which cannot be used in wet offset.

In German patent DE PS 21 45 641, the neutralizing activity is based on adducts of propylene oxide on alkylene diamines. These products also do not lead to obtaining inks usable in wet offset.

The chemical constitution of the neutralizing products or of the examples of inks cited in these patents, does not allow their use in wet offset, given the delicate water / ink balance required for printing in wet offset, which has not been took into consideration.

US Patent 4,078,493 mentions the impossibility of formulating a desensitizing ink for conventional wet offset (or lithography) and proposes the use of special lithographic plates whose printing areas are hydrophilic and non-printing areas are lyophilic. This is therefore an inverted lithographic process.

In patent US Pat. No. 4,287,234, desensitizing inks containing alkanoxylated derivatives having equilibrium have been described. hydrophilic-lipophilic (HLB) required to suit wet offset printing. Are mentioned as alkanoxylated derivatives having neutralizing properties, ethylene oxide adducts on octyl or nonylphenol. polypropylene glycol and copolymer blocks of ethylene oxide and propylene oxide.

In order to ensure a continuous transfer of the ink from the ink rollers to the hydrophobic areas and a simultaneous supply of water to the hydrophilic areas of an offset printing plate, the ink according to the invention is characterized in that 'It comprises an alkanoxylated nucleophilic compound and water emulsified in the ink mass.

If a second supply of water is required to ensure optimal water saturation of the hydrophilic areas of the offset plate, the water emulsified in the ink and that coming from the wetting device of the offset press allow more adjustment faster and easier stabilization of ink flow and water-ink balance, especially when printing a thick film of ink.

In the case where the ink contains sufficient water emulsified in the ink to ensure optimum water saturation of the hydrophilic areas of the offset plate, no addition of water from the wetting device of the offset press is required. Indeed, the microemulsification of water in oil forms droplets of the order of 0.1 to 1 micron.

The microemulsion thus obtained causes an increase in viscosity and thus improves the drawing of the ink.

As soon as the concentration of emulsified water in the ink exceeds 20%, it is possible to print without the addition of dampening water by the dampening system. Obviously, the relationship between the oleophilic zones (ink) and the hydrophilic zones (water) must be taken into account.

When this ratio is favorable, that is to say that the zones to be neutralized represent at least 20% of the total surface, the addition of water contained in the ink is sufficient to moisten the non-printing zones of the plate.

The alkanoxylated nucleophilic liquid must have a molecular weight (PM) greater than 700, because the propoxylated derivatives of PM less than 700 are partially soluble in water and could have a desensitizing action, on the entire surface of the printed sheet in contact with humidification water from the plate. The PM of the alkanoxylated nucleophilic liquid is between 700 and 10,000 and, more precisely, between 2,000 and 4,000.

When the limitations described above are taken into account, printing on an offset printing machine without using the dampening system gives good results and the printing is started up quickly.

The ink contains an alkanoxylated nucleophilic compound having a water / ink equilibrium value (HLB) from 0 to 8 and, more precisely, from 3 to 6.

Details on the HLB will be given later. The presence of emulsified water in the ink mass does not change the HLB value since the HLB tests are carried out in the presence of an excess of water. On the other hand, the speed of emulsification and the prevention of the shock created by the mixture of two liquids which are sparingly soluble with respect to each other are favorably influenced by the presence of water already emulsified in the ink.

• - un homopolymère de l'oxyde de propylène (p.e. polypropylène-glycol 4000 (PM)
• - ou un bloc copolymère d'oxyde de propylène et de l'oxyde d'éthylène, où la fraction éthylénique n'excède pas les 20 % du copolymère (p.e. bloc copolymère 90 % d'oxyde de popylène, 10 % d'oxyde d'éthylène (PM 2500))
• - ou un alkylphenol polyalcanoxylé ou préférablement polypropoxylé (p.e. nonylphénolpolypropoxylé)
• - ou un acide gras saturé ou non, substitué ou non, polyalcanoxylé ou préférablement polypropoxylé (p.e. acide gras en C ₁₂ propoxylé)
• - ou un adduct d'une amine primaire ou secondaire d'une polyamine alkylène ou polyalkylène, d'une polyimine, avec un mélange d'oxyde d'alkylène ou préférablement avec de l'oxvde de propylène (p.e. éthylènediamine propoxylé PM 3500 diéthylènetriamine propoxylé PM 4000).
• - ou un dérivé organique polyalcanoxylé ou préférablement polypropoxylé.

The chemical nature of the alkanoxylated nucleophilic derivative, having the neutralizing power, consists of:

• - a homopolymer of propylene oxide (eg polypropylene glycol 4000 (PM)
• - or a copolymer block of propylene oxide and ethylene oxide, where the ethylenic fraction does not exceed 20% of the copolymer (eg copolymer block 90% popylene oxide, 10% d oxide '' ethylene (PM 2500))
• - or a polyalkanoxylated or preferably polypropoxylated alkylphenol (eg nonylphenolpolypropoxylated)
• - or a saturated or unsaturated, substituted or unsubstituted, polyalkanoxylated or preferably polypropoxylated fatty acid (eg propoxylated C ₁₂ fatty acid)
• - or an adduct of a primary or secondary amine of an alkylene or polyalkylene polyamine, of a polyimine, with a mixture of alkylene oxide or preferably with propylene oxide (eg propoxylated ethylenediamine PM 3500 propoxylated diethylenetriamine PM 4000).
• - or a polyalkanoxylated or preferably polypropoxylated organic derivative.

Thanks to the presence of amino or imino groups in the propoxylated adduct, the product has a greater neutralizing effect compared to propylene oxide homopolymers or block copolymers of ethylene oxide and propylene oxide mentioned in US Patent 4,287,234.

Comparative tests carried out with different CB (coated back = surface coated with microcapsules) on different CF (coated front = surface coated with acceptor) have shown that in a large number of cases, the neutralization carried out with the neutralizing ink based on non-amino or non-imaged products, was incomplete and there was a visible haze.

These products have a neutralizing effect greater than that of non-amino propoxylated compounds, and therefore a greater affinity for the electrophilic acceptor, which makes it possible to obtain a stronger bond between the acceptor and the neutralizer than with non-amino compounds.

This neutralizing force can be achieved by using polypropylene glycol to which, during the preparation of the varnish, an amino derivative or a heterocyclic nitrogen or solid or liquid derivative is added. This additive must have little or no water solubility. As an example, we can mention 2 (2 '-hydroxy-3', 5 'di-ter-butylphenyl) - benzotriazol in a proportion of 1 to 10 parts of the total amount of ink.

• - En plus du liquide nucléophile alcanoxyle neutralisant, le liant de l'encre désensibilisante contient des résines insolubles dans l'eau mais soluble dans le liquide nucléophile alcanoxylé, en général par solubilisation à chaud.

The alkanoxylated nucleophilic derivative represents 10 to 60% of the neutralizing ink.

• - In addition to the neutralizing alkanoxylated nucleophilic liquid, the binder of the desensitizing ink contains water-insoluble resins but soluble in the alkanoxylated nucleophilic liquid, generally by hot solubilization.

• a) La colophane et ses dérivés sous toutes leurs formes, par exemple la colophane hydratée, dimérisée ou polymérisée, estérifiée avec des monoalcools ou des polyalcools, avec des formateurs de résines, tels que l'acide acrylique et le butyne- diol ou l'acide maléique et le pentaérythrite, la résine de colophane modifiée, des sels de calcium ou de zinc de la colophane, l'acide abiétique et ses esters; les résines à base de composés acryliques, ainsi que d'autres résines naturelles telles que des modifications de l'huile de lin ou la gomme- laque;
• b) Les résines maléiques, les résines alkydes exemptes d'huile, les résines alkydes styrolisées, les résines alkydes modifiées au vinyltoluène, les résines alkydes à acides gras synthétiques, les résines alkydes à l'huile de lin, les résines alkydes à l'huile de soja, les résines alkydes à l'huile de coco, les résines alkydes à l'huile de tall et à l'huile de table et les résines alkydes acrylées;
• c) Les résines terpéniques;
• d) Les résines phénoliques;

The preferred resins are as follows:

• a) Rosin and its derivatives in all their forms, for example hydrated rosin, dimerized or polymerized, esterified with monoalcohols or polyalcohols, with resin formers, such as acrylic acid and butydiol or maleic acid and pentaerythritis, modified rosin resin, calcium or zinc salts of rosin, abietic acid and its esters; resins based on acrylic compounds, as well as other natural resins such as modifications of linseed oil or shellac;
• b) Maleic resins, oil-free alkyd resins, styrolized alkyd resins, vinyltoluene modified alkyd resins, alkyd resins with synthetic fatty acids, alkyd resins with linseed oil, alkyd resins with soybean oil, coconut oil alkyd resins, tall oil and edible oil alkyd resins and acrylated alkyd resins;
• c) Terpene resins;
• d) Phenolic resins;

In addition, the desensitizing ink may contain conventional pigments such as titanium dioxide, barium sulfate, magnesium carbonate, basic magnesium carbonate, magnesium hydroxide, calcium carbonate, barium carbonate , bentonite or talc, these can also be coated with a resin or a wax.

• - Les encres désensibilisantes ainsi obtenues sont imprimées suivant le procédé offset humide, sur la surface enduite d'accepteur de la feuille, et ceci avec ou sans apport d'eau de mouillage.

The desensitizing ink may also contain a solvent that is insoluble or poorly soluble in water, compatible with the neutralizer and the resin.

• - The desensitizing inks thus obtained are printed according to the wet offset process, on the coated surface of the sheet acceptor, and this with or without the addition of wetting water.

The acceptor surface (CF) contains the usual electrophilic acceptors. These include, for example, clays such as acid clays, activated clays, attapulgite, zeolite, kaolin, montmorillonite, pyrophylite, or phenolic resins, in particular phenolaldehyde resins, polymers as well as organic acids, especially acids. aromatic carboxylic or polymeric organic acids and their metal salts, in particular the zinc salts of organic acids.

The other sheet of the carbonless assembly (CB) contains a nucleophilic compound, also called a color generator or chromogen, which is dissolved in a liquid and contained in microcapsules.

As chromogens, the usual leuco derivatives are used, such as triarylmethane compounds, diphenylmethane, xanthene derivatives, thiazine, spiropyran or the like.

The appropriate chromogen concentration can be in the range of about 1 to 10% by weight, preferably 1 to 3% by weight. The solution obtained in this way is then encapsulated.

• - Adduct tensio-actif d'oxyde d'éthylène Dr. Niklaus Schônfeld. Wissenschaftliche Verlags GmbH, Stuttgart (1976), p. 209-218;
• - Le système Atlas-HLB, méthode moderne de travail pour l'étude de systèmes émulsionnants appropriés Atlas Chemie GmbH - 43 Essen 1 - Allemagne (1971).

Since the HLB value of the desensitizing ink according to the invention plays a decisive role, an explanation should be provided here. The HLB value specifies the balance between the hydrophilic and lipophilic groups of a substance. The scale ranges from 0 (fully lipophilic substance) to 20 (fully hydrophilic substance). For the determination of the HLB value, reference is made to known bibliographic references, for example:

• - Ethylene oxide surfactant adduct Dr. Niklaus Schônfeld. Wissenschaftliche Verlags GmbH, Stuttgart (1976), p. 209-218;
• - The Atlas-HLB system, modern working method for the study of suitable emulsifying systems Atlas Chemie GmbH - 43 Essen 1 - Germany (1971).

• - L'équilibre hydrophile-lipophile (HLB) (Griffin J. Soc. Cosmetic Chemists 1, 311 (1949));
• - L'indice hydrophile-lipophile (HL) (V.R. Huebner, Anal. Chem. ₃₄, 488 (1962));
• - L'indice de polarité (PI) (V.R. Anebner, Anl. Chem. 34, 488 (1962))

et constatent que le système le plus utile est le système HLB qui offre l'avantage de l'additivité lors de mélanges.In "Rumànische Chemische Revue" 22, 8. 117-1123 (1975), Leca and others compare

• - The hydrophilic-lipophilic balance (HLB) (Griffin J. Soc. Cosmetic Chemists 1, 311 (1949));
• - The hydrophilic-lipophilic index (HL) (VR Huebner, Anal. Chem. ₃₄ , 488 (1962));
• - The polarity index (PI) (VR Anebner, Anl. Chem. 34, 488 (1962))

and find that the most useful system is the HLB system which offers the advantage of additivity when mixing.

A distinction is made between HLB of an "oil in water" emulsion (HLB O / W) and HLB of a "water in oil" emulsion (HLB W / O). The latter plays a role mainly for printing inks in the wet offset process, where the problem of the formation and the stability of a "water in oil" emulsion comes into play; in this case, W represents the fountain water protecting the unprinted surfaces, and O denotes the printing ink supplying the ink for the surfaces to be printed.

An ink which is printed by the wet offset process must have on the one hand a highly lipophilic behavior and on the other hand a tendency sufficiently hydrophilic to emulsify a certain quantity. of water, that is to say present an adapted HLB (W / O) value.

This HLB (W / O) value is between 0 and 8, preferably between 3 and 6.

• On agite pendant quelques minutes dans un becher 80 parties d'huile (O) 20 parties d'eau (W) 5 parties d'émulsionnant
• On désigne ici par "huile" un produit lipophile tel que : - l'acide linoléique - l'huile de lin blanchie - une huile minérale raffinée, ou - du dioctylphtalate.

The test carried out to determine the suitability of the emulsion of water in oil is as follows:

• The mixture is stirred for a few minutes in a beaker 80 parts of oil (O) 20 parts of water (W) 5 parts of emulsifier
• The term “oil” denotes a lipophilic product such as: - linoleic acid - bleached linseed oil - a refined mineral oil, or - dioctylphthalate.

The whole is left to stand for a few hours and the emulsion of the oily phase (O) is observed.

• - composé propoxylé (liquide) - vernis de base de l'encre (liquide très visqueux) - encre neutralisante

After having tested the known emulsifiers to determine the HLB (W / O) scale, the HLB (W / O) value of the products used for the manufacture of the neutralizing ink at the various stages of semi-finished products is sought, such as :

• - propoxylated compound (liquid) - base varnish of ink (very viscous liquid) - neutralizing ink

HLB W / O value of different products

HLB W / 0 value of different products

If an offset ink has a too high HLB (W / O) value, there is too much water emulsified in the ink, or even a tendency of the ink to emulsify in water and sometimes reaching values justifying an HLB (O / W) hence the phenomenon of the "veil".

The examples below explain the process for preparing the ink according to the invention. The proportions indicated are expressed in parts by weight.

Example 1: Varnish A

40 parts of an acidic phenolic resin are dissolved hot in 60 parts of polypropylene glycol (molecular weight 4000).

Desensitizing ink A:

73 parts of varnish A are mixed on a three-cylinder grinder with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink 7 parts of water are added which are emulsified by stirring. The HLB value of the ink rises to 3 (+1). This ink has a rheology suitable for printing in wet offset. The water / ink balance is quickly and easily established with the addition of fountain water from the fountain train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Example 2 / Varnish B

30 parts of an acidic phenolic resin are dissolved hot in 70 parts of propoxylated diethylenetriamine (molecular weight 4000).

Desensitizing ink B:

56 parts of varnish B are mixed on a three-cylinder mill with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink 24 parts of water are added which are emulsified by stirring.

The HLB value of the ink is 4 (+1). This ink has a rheology suitable for printing in wet offset. The water / ink balance is quickly and easily established without the need for additional wetting water from the wetting train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Example 3 / Varnish C

30 parts of an acidic phenolic resin are dissolved hot in 70 parts of propoxylated triethylenetetramine (molecular weight 4000).

Desensitizing ink C

64 parts of varnish C are mixed on a three-cylinder mill with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink is added 16 parts of water which is emulsified by stirring.

The HLB value of the ink is 6 ( ₊ 1). This ink has a rheology suitable for printing in wet offset. The water / ink balance is quickly and easily established with the addition of fountain water from the fountain train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Example 4 / Desensitizing ink D:

64 parts of varnish B are mixed on a three-cylinder mill with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink is added 16 parts of water which is emulsified by stirring. This water contains 2% of carboxy methylcellulose dissolved beforehand.

The HLB value of the ink is 5 (+1). This ink has a rheology suitable for printing in wet offset. The water / ink balance is quickly and easily established with the addition of fountain water from the fountain train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Example 5 / Varnish E

45 parts of a neutral esterified rosin resin are hot dissolved in 55 parts of polypropylene glycol (molecular weight 2500).

Desensitizing ink:

73 parts of varnish E are mixed on a three-cylinder mill with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink 7 parts of water are added which are emulsified by stirring.

The HLB value of the ink is 3 (_1). This ink has a rheology suitable for wet offset printing. The water / ink balance is quickly and easily established with the addition of fountain water from the fountain train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Example 6 / V varnish:

30 parts of an acidic phenolic resin are dissolved hot in 60 parts of polypropylene glycol (molecular weight 4000), then 10 parts of the benzotriazol derivative are added hot.

Neutralizing ink F:

70 parts of varnish F are mixed on a three-cylinder grinder with 11 parts of titanium dioxide, 3 parts of silicon oxide and 6 parts of calcium carbonate. To this ground ink, 10 parts of water are added which are emulsified by stirring.

The HLB value of the ink is 4 (+ 1). This ink has a rheology suitable for wet offset printing. The water / ink balance is quickly and easily established with the addition of fountain water from the fountain train. The print shows clear printing edges and the amount of neutralizing ink applied allows complete neutralization of the printed surface of the carbonless acceptor layer (CF or CFB).

Claims (16)

1. Desensitizing ink for wet offset printing on an acceptor surface of a chemical carbonless assembly, comprising at least two superimposed sheets, the facing faces of which have an acceptor electrophilic coating and the other a nucleophilic coating capable of producing a chromogenic reaction with said accepting electrophilic coating, characterized in that it comprises an alkanoxylated nucleophilic compound and water emulsified in the ink mass. 2. Ink according to claim 1, characterized in that the amount of water emulsified in the ink mass is sufficient to partially moisten the hydrophilic areas of an offset printing plate. 3. Ink according to claim 1, characterized in that the quantity of water emulsified in the ink mass is sufficient to ensure optimal saturation of the hydrophilic areas of an offset printing plate. 4. Ink according to one of claims 1 to 3, characterized in that the alkanoxylated nucleophilic compound which it possesses gives it a water / ink equilibrium value (HLB) from 0 to 8. 5. Ink according to one of claims 1 to 3 characterized in that the alkanoxylated nucleophilic compound which it possesses gives it a water / ink equilibrium value (HLB) of 3 to 6. 6. Ink according to one of claims 1 to 3 characterized in that the alkanoxylated nucleophilic compound has a molecular weight of 700 to 10,000 ". 7. Ink according to one of claims 1 to 3 characterized in that the alkanoxylated nucleophilic compound has a molecular weight of 2,000 to 4,000. 8. Ink according to one of claims 1 to 3 characterized in that the nucleophilic compound which it contains is an polypropoxylated organic derivative. 9. Ink according to one of claims 1 to 3 characterized in that the nucleophilic compound which it contains is an adduct of a primary or secondary amine, of an alkylene or polyalkylene polyamine or of a polyimine with the oxide of propylene or a mixture of alkylene oxide. 10. Ink according to one of claims 1 to 3 characterized in that it contains an aqueous solution of protective colloid emulsified in the ink mass. 11. Ink according to claim 10, characterized in that the protective colloid is a water-soluble cellulose derivative such as carboxy methylcellulose. 12. Ink according to claim 11, characterized in that the protective colloid is carboxy-methylcellulose. 13. Ink according to claim 11 or 12, characterized in that the water and protective colloid content is between 1 and 40% of the total weight of the ink. 14. Ink according to one of claims 1 to 3, characterized in that in addition to the alkanoxylated nucleophilic compound, the ink contains an amino additive or a heterocyclic nitrogen derivative sparingly or not soluble in water. 15. Ink according to claim 14, characterized in that it contains as an additive from 0.1 to 15% of a benzotriazole derivative. 16. Ink according to claim 15, characterized in that it contains as an additive 0.1 to 15% of 2 (2 '-hydroxy-3', 5 'di-butylphenyl) -benzotriazol.