Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1995-06-07
2001-07-24
Morris, Terrel (Department: 1771)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S054420, C527S602000, C523S161000, C106S031340, C106S031350
Reexamination Certificate
active
06265481
ABSTRACT:
The invention relates to printing inks which contain, as the binder, phenolic resin-modified rosin in a proportion of 60 to 90% by weight and an alkyd resin in a proportion of 10 to 40% by weight, the sum of phenolic resin-modified rosin and alkyd resin giving 100% by weight. The alkyd resin has been prepared from
a) an unsaturated fatty acid having 6 to 12 carbon atoms or a mixture of such acids or their triglycerides,
b) a polyol and
c) a dicarboxylic acid.
The printing inks also contain pigments, if appropriate further binders and further conventional constituents, such as lubricants, solvents, thickeners and thixotropic agents.
German Patent Specification 3,023,118 has disclosed paper printing inks of this type for graphical purposes. These consist of pigments, an alkyd resin binder which has been modified by long-chain fatty acids having an iodine number of less than 20 (determined according to DIN 53,241) and which has an acid number of preferably 6 to 12 and an hydroxyl number of preferably greater than 15 (determined according to DIN 53,241), in particular from 20 to 35, and, if appropriate, further conventional constituents, such as lubricants, solvents and a viscosity control agent.
Depending on the field of application, printing inks must meet a large number of requirements. For example, printing inks should have a high abrasion resistance and, in many cases, good re-release properties. As far as possible, they should also be free from yellowing, have a neutral odor and be fast-drying. To prepare the printing ink, the various resins are first dissolved at an elevated temperature in mineral oil, and the pigments are then introduced. Subsequently, the printing inks of the composition described above cure by oxidation.
When the printing inks described in German Patent Specification 3,023,118 and also other printing inks are used for sheet-fed offset printing, the problem of setting off arises, i.e. printing inks which are well compatible with mineral oil release the latter only slowly, and consequently the prints remain wet and therefore require powdering. The powder serves as a spacer for the wet prints and also allows better access of oxygen for the oxidative drying. However, powdering has an adverse effect on the quality of the prints and the further processing steps.
The disadvantages of powdering comprise poor abrasion resistance of the prints, complications in downstream processes, such as varnishing and cellophaning, and contamination of the machine.
A review of the disadvantages of powdering in offset printing is given by W. Walenski in “Der Polygraph”, volume 5, 1984, pages 435-36. This review demonstrates the urgency of the demand for a rapidly absorbed printing ink.
The object of the invention is therefore to avoid these disadvantages of the state of the art and to provide a printing ink which is rapidly absorbed and therefore does not require powdering.
Surprisingly, it has been found that this object is achieved by a printing ink which, as the binder, contains an alkyd resin having a high hydroxyl number, a low acid number and a high iodine number of the fatty acids, in combination with a phenol resin-modified rosin. The invention therefore relates to a printing ink of the type described at the outset, wherein the unsaturated fatty acids have an iodine number of 120 to 190 [g of I
2
/100 g] and the alkyd resin has an acid number of less than 11 and a hydroxyl number of 40 to 260 [mg of KOH/g of resin].
In contrast to German Patent Specification 3,023,118, a type of fast-drying oils or fatty acids, which are distinguished by a high iodine number, are used for modifying the alkyd resin. The oxidative drying via the double bonds of the highly unsaturated fatty acids or oils is responsible for the chemical drying of the printing ink. Good chemical drying is supplemented by physical drying of the printing ink, which can be determined by the absorption properties. Good physical drying is obtained by the printing ink according to the invention. The alkyd resins used as the binders have hydroxyl numbers which are in the range from 40 to 260. These hydroxyl numbers, which are high in comparison with German Patent Specification 3,023,118, cause an increased polarity of the alkyd resin binders. These polar alkyd resins have only a limited solubility in mineral oils, which has the result that printing inks containing polar alkyd resins and mineral oil show good absorption. Hydroxyl numbers of at least 40 are necessary in order to obtain the polarity required for rapid absorption; the OH number range from 110 to 180 can be indicated as particularly advantageous for the absorption properties. If an alkyd resin OH number of 260 is exceeded, the polar alkyd resin is then hardly soluble in the mineral oil which is the conventional solvent for printing inks.
Refined linseed oil, soya oil or dehydrated castor oil have proved suitable as the unsaturated fatty acids or oils. Trimethylolpropane, glycerol and/or pentaerythritol are particularly suitable as the polyol components. The preferred dicarboxylic acids are phthalic acid, isophthalic acid, adipic acid or tetrahydrophthalic acid, their anhydrides being employed in practice, where these exist.
The invention also relates to a process for preparing a printing ink.
A fatty acid-modified alkyd resin is first prepared from
a) an unsaturated fatty acid having 6 to 20 carbon atoms or a mixture of such acids or their triglycerides,
b) a polyol and
c) a dicarboxlyic acid.
This resin is combined with phenolic resin-modified rosin and a mineral oil to give a binder mixture, the proportion of alkyd resin being 10 to 40% by weight and that of the modified rosin being 60 to 90% by weight, based on the total weight of alkyd resin and rosin. This binder mixture is dispersed, together with pigments, if appropriate further binders and further conventional constituents, such as lubricants, thickeners and thixotropic agents, by means of a dispersing device, for example a three-roll mill, a sand mill or a ball mill. The distinctive feature here is that the unsaturated fatty acids have an iodine number from 120 to 190 and the alkyd resins have a hydroxyl number from 40 to 260 and an acid number of less than 11.
Refined linseed oil, soya oil or dehydrated castor oil can advantageously be used for modifying the alkyd resins. Suitable polyol components are trimethylolpropane, glycerol and/or pentaerythritol, and phthalic acid, isophthalic acid, adipic acid or tetrahydrophthalic acid or their anhydrides, where these exist, can be used as the dicarboxylic acid component.
The printing inks according to the invention can be used for the sheet-fed offset printing process, in which the print is set down first on a rubber blanket and from the latter to the paper or another printing substrate. In the sheet-fed offset printing process, cut sheets are printed.
Since the printing inks according to the invention also show good physical drying, in addition to the oxidative drying, in other words are rapidly absorbed, the otherwise required powdering can be omitted. This is a great advantage, since the powder adversely affects the quality of the prints and makes the further processing steps more difficult.
With respect to the printing inks according to the invention, the combination of good chemical and physical drying as the result of suitable iodine numbers and hydroxyl numbers can be regarded as novel and advantageous.
Measurements of the absorption properties show that the printing inks according to the invention are absorbed more rapidly than the printing inks described in German Patent Specification 3,023,118.
The invention is described in more detail below by reference to illustrative examples.
REFERENCES:
patent: 3772171 (1973-11-01), Savageau et al.
patent: 4139500 (1979-02-01), Ruldolphy
patent: 4148767 (1979-04-01), Spicer et al.
patent: 4383860 (1983-05-01), Uhlemayr et al.
Dobbelstein Arnold
Fries Werner
Klemm Karl-Wilhelm
Sobitzkat Horst
BASF Lacke & Farben Aktiengesellschaft
Guarriello John J.
Kenyon & Kenyon
Morris Terrel
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