Printing ink concentrate and corresponding production method

The invention relates to an offset printing ink concentrate and a process for its production.

Printing inks are usually prepared by combining the starting materials pigment, binders, auxiliaries and liquids and subsequent dispersing. The dispersing process serves to separate the pigment agglomerates to the required pigment particle size. As a result, the properties required for the printing ink, such as sufficient color strength and good printability, are achieved.

For a more economical and economical production of printing inks, it is also customary to produce an intermediate stage in the above-mentioned production process. This intermediate is a printing ink concentrate which differs from the customary printing ink in that the pigment concentration is significantly higher. As a result, the binder and liquid fraction is naturally lower. Printing ink concentrates serve both for the production of finished printing inks as well as for the enhancement of the colorant concentration of a printing ink of the same color tone as for the nuance of printing inks.

Binders and liquids are added to the printing ink concentrate for dilution and the final printing ink is prepared by a mixing process. A dispersing process is no longer required in the dilution stage, since the printing ink concentrate was produced by a dispersing step from the starting materials pigment, binders, auxiliaries and liquids.

Compressed-ink concentrates therefore differ substantially from pigment preparations in that the pigments are already present in dispersed form in a printing-ink concentrate.

Compressive color concentrates are usually prepared by mixing together solids such as coloring pigments and solid auxiliaries by means of dispersing aggregates such as three-roll mills, kneaders, extruders or agitator ball mills in binders and liquids in several stages or in a one-stage process as described in EP 0 807 670 A1, Can be dispersed.

This process produces viscous to highly viscous printing ink concentrates which have a tackiness.

The solids used are pigments, such as phthalocyanine (Cl 15), ruby ​​pigment (Cl 57: 1), diaryl yellow (Cl 12/13), as well as spot coloring pigments and further unbuntary solids, often referred to as fillers such as chalk, kaolin, butylhydroxytoluene or dispersants. These are used in the form of powders or granules. The binders used can be varnishes for printing inks produced by boil-up of printing ink resins, printing ink oils and alkyds. Alkyds, such as linseed oil alkyd, soybean oil alkyd, are also used as binders. Liquid oils used are special mineral oils for printing inks with a boiling range between 230-370 ° C, such as Printosol^® C 800, and vegetable oils, such as linseed oil, soybean oil.

A form of printing ink concentrates produced by other means are flush pastes. These are also viscous to highly viscous and have a tackiness. Also in flush pastes, the pigment is present in the frictional fineness required for application as a printing ink and no longer has to be dispersed or rubbed.

These printing ink concentrates are filled into transport containers, such as cans, buckets, drums, hobbocks or production containers, after manufacture. These are used for storing, transporting and removing the ink concentrates.

To produce a finished printing ink, one or more printing ink concentrates are removed, weighed and mixed, usually with the addition of auxiliaries, binders or liquid components, such as oils.

Weighing is usually effected by manual removal of the ink concentrates, for example with a spatula, and introduction into a weighing container. Another method is the use of so-called dosing stations, in which the dyestuff concentrates are present in storage containers such as hobbocks or drums and are conveyed by means of pumps or hydraulic presses and metered volumetrically or gravimetrically via metering valves. Such automatic systems are commercially available.

The weighed components are then mixed into the finished paint in mixers, such as dissolvers, kneaders, blade agitators or other mixing units, with the addition of auxiliaries, binders and oils. The mixing process is used to homogenize the product. Pigment dispersing is no longer required here since this has already taken place during the preparation of the printing ink concentrate.

One problem is the high viscosity and stickiness of the ink concentrates, especially as a function of the amount of pigment used. The higher the pigment content, ie the solids content of the concentrate, the more viscid the product is. Correspondingly, the handling, ie the manual extraction or the pumpability of the printing ink concentrates, becomes more difficult.

Manual removal is often no longer possible. Product removal can only be carried out with considerable technical effort, eg by means of high-pressure presses, frequently supported by heating the product.

While liquid printing inks can be pumped and conveyed and metered with relatively little effort, expensive and expensive suction pumps, such as spindle pumps or compressed-air piston pumps, must be used for pasty ink concentrates. The number of different shades required for the creation of special colors means that 20 to 60 pump units are usually required for an automatic mixing plant, which is a considerable expense.

At even higher viscosities of the printing ink concentrates, hydraulic presses must be used in order to achieve a sufficient conveying of the product. This high-pressure technology increases the investment expenditure by a multiple. A manual removal, for example, of such offset printing ink concentrates, is generally no longer possible at all.

The object of the present invention is to overcome the described disadvantages of the prior art and, at the same time, to provide an offset printing ink concentrate which can be easily transported and easily mixed with additional components.

The object is achieved by means of an offset printing ink concentrate in which the pigment is present in the frictional fineness required for the use of the offset printing inks in the form of coated non-sticky and / or non-coated non-sticky pellets.

For this purpose, it was assumed that the high viscosity of the offset printing ink concentrates was to be utilized and, despite their viscid and sticky properties, to be regarded as a solid body. For this purpose, the adhesive, highly viscous, original offset printing ink concentrate had to be changed to a new, non-sticky material by changing and adapting its properties.

The adjustment is achieved by reducing the stickiness of the concentrate by increasing the solids content of the concentrate. The flowability and deformability of the offset printing ink concentrate is reduced by the combination of a high proportion of pigment and a low proportion of binder. The offset printing ink concentrates obtained therefrom and the pellets obtained therefrom can still have a low residual tack which can be reduced or excluded by a subsequent coating or coating. The pigment content in the offset printing ink concentrate in the pellets according to the invention is usually 45-65%. The pigment concentration is thus significantly higher than in the case of customary offset printing ink concentrates.

The shape of the pellets is typically spherical. However, they may also have other symmetrical and unsymmetrical shapes.

The size of the pellets is ideally adapted to the following dosing process. The specific density of the offset printing ink concentrate is generally 0.9-2.0 g / cm 3³. With a precision of +/- 1 g, a pellet has a volume of approx. 0.5-1.0 cm³. Depending on the sequence processes used, the volume can also be selected individually.

The offset printing ink concentrate according to the invention in the form of coated non-sticky and / or non-coated non-sticky pellets has a number of essential advantages.

This can be treated as a bulk material. Thus, each pellet can be individually removed and metered. A manual removal is now possible not only in the case of offset printing ink concentrates, but also in a particularly simple manner.

The offset printing ink concentrate according to the invention can thus be easily dosed and is thus accessible to use in standard solids dosing systems, as a result of which automation of the weighing and dosing process becomes possible.

The pellets, like a solid, are easy to transport and thus easily refillable. They can also be filled and transported in a simple manner like a free-flowing solid. Since the pellets have no stickiness, sticking and caking of the particles is excluded.

In the offset printing ink concentrates of the prior art, there is a great contamination of all parts in contact with the product, which entails a high cleaning effort, as well as a disposal problem of the residual quantities and the packaging. Contrary to this, fouling can now be prevented by staining the surface of offset printing ink concentrates. The contamination of the parts in contact with the product is minimal so that the cleaning effort is very low. During emptying, no residues and thus no waste are generated, which for environmental reasons must be regarded as particularly advantageous. In addition, there is no material loss and simpler packaging can be used.

After being weighed, the coated pellets are mixed in conventional mixing units. These include, for example, dissolvers, kneaders, vibration mixers, wobble mixers. Postdispersion or post-dispersion is not required.

The optionally used coating material is a constituent of the printing ink produced therefrom as a component of the offset printing ink concentrate. The coating material thus does not have to be removed before further processing.

There is also provided a process for preparing a printing ink using the offset printing ink concentrate according to the invention.

In this way, for example, UV printing inks, flexographic printing inks based on water, toluene gravure inks, solvent-containing printing inks, for example based on ethanol and ethyl acetate, nitrocellulose printing inks, screen printing inks, artist paints or tampon printing inks.

In a preferred embodiment of the invention, an offset printing ink concentrate is provided in which the coating consists of powdery solids, wax or liquid substances. Here, the liquid substance can be an oil.

The respective coating material can thus be optimally adapted to the particular application.

Solid and liquid materials which are compatible with the printing ink can be used as the coating material. Suitable solid materials are, for example, pulverulent substances, such as chalk, kaolin, paraffinic waxes, PE waxes, Fischer-Tropsch waxes or talcum. The pulverulent substances have an average grain size of maximally 25 μm, in the ideal case the grain size being less than 5 μm. Although average grain sizes of more than 25 μm can also be used, however, in the application of the end product, printing ink leads to problems, such as for example on the printing plate.

Due to the coating, the surface of the pellets has virtually no sticky properties.

In a further preferred embodiment of the invention, the coating of the offset printing ink concentrate is a solid sheath. Such a complete solid enclosure can be, for example, a wax cover.

The present invention further provides a process for the production of the offset printing ink concentrate, which is characterized in that the offset printing ink concentrate is comminuted and coated. The pellets can be produced separately, but can also be connected directly to the production of the offset printing ink concentrate.

For pelletization, known processes, such as are used, for example, in food or feed production, can be used.

In this case, either a portioned discharge from a nozzle or a metering valve or the production of an offset printing ink concentrate strand in a die can be carried out with subsequent division. In an extreme case, an offset printing ink concentrate strand or thread is produced, which is only cut off during the subsequent processing step of the dosage.

In a preferred embodiment of the process according to the invention, the coating is carried out by directly applying the pulverulent solid to the offset printing ink concentrate.

The application of the pulverulent substance can be effected, for example, by direct spraying of the pellets or rolling of the pellets in the respective coating material.

In a further preferred embodiment of the process according to the invention, the pulverulent solids are applied indirectly via a liquid carrier, which subsequently evaporates.

Suitable carriers are liquids and solvents in which the coating material can be suspended or dissolved. The application can be carried out by spraying or dipping into the suspension or solution. Subsequent drying removes the carrier liquid or solvent and leaves the coated pellet back.

In a further preferred embodiment of the process according to the invention, the solid shell is produced by applying a molten substance or by applying a dissolved substance which is suitable for coating, the solvent subsequently evaporating.

For example, a wax cover can be produced by melting the wax and then wetting the surface of the offset printing ink concentrate. Suitable waxes are, for example, paraffin wax, PE wax and Fischer-Tropsch wax.

Suitable substances for covering the offset printing ink concentrate are, for example, fats such as Palmin^®, Or gelatin.

The substance suitable for the coating can be dissolved in a carrier liquid which is removed by evaporation after application to the uncoated offset printing ink pellets. By repeating this process, the layer thickness of the covering can be made as large as desired.

By using high solids parts of pigment in the offset printing ink concentrate of more than 50%, the residual tack of the product can be reduced such that a protective coating in the form of a coating is no longer required.

This results in further advantages such as, for example, the omission of the coating process and the omission of the additional components for the coating.

The invention is explained in more detail with reference to the examples for the production of coated and uncoated pellets.

example 1

In a laboratory extruder, an offset printing ink concentrate was prepared by filling it with 45% by weight of Pigment Yellow (CI 13) and 55% by weight of offset binder Grinding Base 100S from Lawter, and removing the offset printing ink concentrates from the extruder in the form of a rod. After cooling to room temperature the product has only a low residual tack and no significant deformability.

The offset printing ink concentrate was mechanically cut into pellets of about 1 g per piece.

The pellets were then immersed in a molten wax paste consisting of 37.5% by weight of PE wax with a melting range around 115 ° C. and 62.5% by weight of linseed oil. The pellets were then sieved and cooled.

The coated pellets thus obtained practically have no stickiness.

Example 2

An offset printing ink concentrate prepared according to Example 1 was placed in a heated container. When a product temperature of about 70 ° C. was reached, the offset printing ink concentrate was pressed with the aid of a gear pump through a die with a bore of 4 mm diameter. The resulting 4 mm thick color strand was cut into 10 mm long pellets and then rolled in a powder of talcum to give a coating of the powder material. The excess powder was removed by sieving.

The coated pellets thus obtained practically have no stickiness.

Example 3

Uncoated offset printing ink pellets according to Example 2 were prepared and these were immersed in an aqueous wax emulsion, then sieved and dried in a hot air stream.

The coated pellets thus obtained practically have no stickiness.

Example 4

Uncoated offset printing ink pellets according to Example 2 were prepared and dipped in a silicone emulsion, then sieved and dried in a stream of hot air.

The coated pellets thus obtained practically have no stickiness.

Example 5

A standard flush paste (Pigment Yellow Cl 12) was heated in a container. When 60 ° C. was reached, the flush paste was pressed with the aid of a pump through a die with a hole diameter of 4 mm. The resulting printing ink concentrate strand was cut into 10 mm long pellets. These were coated according to Example 1.

The coated pellets obtained in this way have practically no stickiness, but are still slightly deformable.

Example 6

Uncoated pellets according to Example 5 were prepared. These were coated according to Example 2.

The coated pellets thus obtained practically have no stickiness.

Example 7

Uncoated pellets according to Example 5 were prepared. These were coated according to Example 3.

The coated pellets thus obtained practically have no stickiness.

Example 8

Uncoated pellets according to Example 5 were prepared. These were coated according to Example 4.

The coated pellets thus obtained practically have no stickiness.

Example 9

An offset printing ink concentrate according to Example 1 was fed with a squeeze cylinder of a stencil. The obtained offset printing ink concentrate strand was sprayed with talcum powder swirled in air and a fine layer was applied to the strand surface. The coated strand was wound up or drained into a container. When the ready-for-printing-ink recipe was weighed in, the strand was simply cut or pelletized.

The coated strand of offset printing ink concentrate has practically no stickiness.

Example 10

An offset printing ink concentrate according to Example 1 was conveyed into a metering valve. One part of the offset printing ink concentrate was ejected per metering stroke.

The pellets of offset ink concentrate concentrated in this way fell into a fluidized bed which had air nozzles arranged in the soil so that the pellets were held in suspension together with an enveloping pulverulent pulverulent separating powder.

The coated pellets thus obtained practically have no stickiness.

Example 11

An offset printing ink concentrate prepared according to Example 1 was fed into a tube at the outlet of the extruder. The concentrates in partial strands at about 100 ° C exited through 25 holes laterally in the tube. The partial strands were placed on a cooling belt next to each other and transported away. The tape was powdered with talcum to avoid the adhesion of the concentrate, and the concentrate strands were also powdered.

After the concentrate had cooled to 25 ° C., the concentrate strands were cut into pieces of 20 mm length in a rotating cutter. Excess talcum powder was separated in a shaker sieve.

The pellets thus obtained practically have no stickiness.

Example 12

In a laboratory extruder, an offset printing ink concentrate was prepared by filling it with 63% by weight of pigment blue (CI 15: 3), for example Lutetia cyanine J 505 Micropearl, and 37% by weight of offset binder Grinding Base 100S from Lawter; The offset printing ink concentrating from the extruder in bar form.

After cooling to room temperature, the product has no stickiness and is converted into pellets of approx. 1 cm³ Volume cut.