Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-01-04
2003-09-02
Shusho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S270000, C524S271000, C524S318000, C525S149000
Reexamination Certificate
active
06613813
ABSTRACT:
The invention relates to a low migration, odor and swelling sheet-fed offset printing ink which is suitable for the production of food wrapping.
On the one hand, sheet-fed offset printing inks are known in the prior art which can be described as low as to odor and flavor. These inks contain low odor components such as hard resins, hydrogenated mineral oil cuts, synthetic aromatic oils, alkyd resins, in particular such with a low iodine number of ≦30 g J2/100 g, and dialkyl ether such as di-n-dodecyl ether, di-n-undecyl ether, allyl-n-octyl ether, n-hexyl-n-undecyl ether as a vehicle.
However, mass transfers of these inks to the filling material can occur, the mass transfers being assessable according to the law of diffusion. However, the German food law prohibits any mass transfer, except for components which are safe with regard to health, odor and flavor and which are technically unavoidable. Migration of the liquid components in inks of the prior art can occur, however, which can further cause the unwanted aspect of the so-called swelling. As a result of migration, in particular thin packing films, i.e. films under 30 &mgr;m, can be affected by warping of the film in form of wrinkling and waves. These warps are irreversible and optically and technically non-acceptable.
Furthermore, so-called anti-swelling inks are known in the prior art which have a vehicle composition free of mineral oil. The serious disadvantage of these inks is, however, that the low-viscous vehicle components can have considerable migration potentials. Therefore, it is possible that mass transfers occur in primary packing which can disadvantageously change the odor and flavor of the filling material, in particular of the food. Such transfers are treated, for example, according to Swiss law as impurities (“Decree on Food Additives and Ingredients”—Fremd- und Inhaltsstoffe-verordnung, FIV—of Jun. 26, 1996). According to the German food law, too, it is applicable to the wrapping of food and semiluxuries that changes in odor and flavor of the filling material by the wrapping are to be avoided (§31 LMBG, section 1).
Therefore, it was an object of the invention to provide sheet-fed offset printing inks which are low in migration and odor as well as low in swelling, and which, therefore, do not cause any unwanted changes in odor and flavor of the wrapping and which obey the migration values stipulated by law, respectively.
Changes in odor and flavor of the wrapped goods caused by printing inks are tested according to DIN 10955, testing of packaging and wrapping material for food. In this connection, the values must be smaller than 2 in order to meet the requirements mentioned.
The object of the invention is solved by an offset printing ink which comprises a colophony-modified phenolic resin (A) and/or a maleic resin (B) and/or a modified hydrocarbon resin (C) and/or a colophony resin ester (D),which is characterized in that it comprises one or more water-insoluble fatty acid ester(s) of multivalent alcohols with a high steric spatial requirement and/or of ethinols as a solvent for the resin(s).
Spatial requirement is to be understood as the three-dimensional steric measurement of molecules. In this connection, the steric measurements of the esters being employed as a solvent can amount to l
max
of from 2.0 to 7.0 nm in diameter and to a V
mean
of from 1.0 to 21.0 nm
3
in volume, the indicated values referring to the maximum length of the molecules.
Furthermore, in a preferred embodiment, the offset printing ink according to the invention comprises multifunctional allyl esters of multivalent organic acids. These allyl esters are capable of oxidative drying and during the drying process they do not produce any fragments which cause sensory impairments of the wrapped food. In the oxidative drying process, a cross-linking takes place and this results in a stable printing ink film. This process of oxidative cross-linking of the printed ink is caused by the salts of organic acids of cobalt and/or manganese in concentrations of 0.05-0.2% which are contained therein.
Preference is given to allyl esters of multivalent organic acids with an acid number of 2-20 mg KOH/g (DIN 55 936), a iodine number of 50-120 g J
2
/100 g (DIN 55 936) and a viscosity of 0.5-300 mPa·s measured at 20° C. and 50 l/s as well as with a molecular weight M
w
of 300-10000.
Furthermore, an offset printing ink is preferred which comprises a polyallyl ether, additionally. Its function basically corresponds to the one of the multifunctional allyl esters.
With the addition of multifunctional allyl esters and polyallyl ethers, respectively, it is possible to achieve the mechanical resistance which is required in the technical application for the wrapping of food and semiluxuries and which has so far been achieved in a majority of cases only by coating, so that this can be dropped.
Furthermore, an offset printing ink according to the invention is preferred which is free of mineral oil.
These inks are free of substances with a high migration potential. The resins and special fatty acid esters with their high steric spatial requirements contained in the vehicles of the inks and/or the fatty acid esters of ethinols are coordinated so that, also in the case of primary packing, the mass transfer to the food is so much reduced that it distinctly remains under the limit values stipulated by law. Moreover, in the case of direct contact between the printed ink and, for example, a polypropylene packing film there is almost no change in the dimension due to the prevention of a mass transfer according to the invention. This was hitherto caused by a migration to the polymer matrix which is called swelling of films.
Therefore, with the inks according to the invention it is the first time that the advantageous properties low in odor, migration and swelling have been achieved simultaneously in sheet-fed offset printing inks. Therefore, these inks are particularly suited for the production of food wrappings under employment of, for example, cardboard and paper.
Moreover, a very substantial advantage of the offset printing ink according to the invention is the fact that it is based on renewable raw materials.
Furthermore, an offset printing ink according to the invention is particularly preferred in which the fatty acids of the fatty acid esters comprise a carbon chain of 6-26, in particular of 8-26, carbon atoms. The fatty acids can be saturated or unsaturated fatty acids. The following fatty acids are given as examples: octadecene acid, linolic acid, linolenic acid, elaeostearic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, arachic acid, dodecanoic acid, hexanoic acid, octanoic acid, decanoic acid, and docosenoic acid. These fatty acids can be purified by means of distillation before esterifying them.
An offset printing ink according to the invention is preferred in which the multivalent alcohols are selected from trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol and 2-butyl-2-ethyl-1,3-propanediol. Furthermore, an offset printing ink according to the invention is preferred in which the fatty acid esters of multivalent alcohols have an acid number between 5 and 20 mg KOH/g (DIN 53402), a iodine number between 0 and 150 g J
2
/100 g (DIN 55936) and a viscosity between 20 and 500 mPa·s (DIN 53229). The multivalent alcohols are polyesterified or completely esterified.
Examples for water-insoluble fatty acid esters which are employed according to the invention are: pentaerythritol tetracaprate, dipentaerythritol hexacaprate, pentaerythritol tetradocoseate, and dipentaerythritol hexadocoseate.
The employment of natural vegetable oils, i.e. of the corresponding triglycerides, cannot solve the problem posed. With the employment of the specified offset printing ink according to the invention it was unexpectedly possible to solve the problem for the first time.
Furthermore, an offset printing ink according to the invention is preferred which is characterized in that that the resins have a molecular weight M
w
of 5000-120000, an acid nu
Borgmann Ursula
Fuss Thomas
Hanke Klaus
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