US 3819471 A
A printing blanket, especially for offset printing, comprising a strength carrier layer, an intermediate layer, and an ink transfer layer comprising a polymer base, filler materials containing hydroxyl groups, and high molecular weight, surface active substances.
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Description (OCR text may contain errors)
United States Patent 1191 June 25, 1974 Sohnemann PRINTING BLANKET, ESPECIALLY FOR 161/401 OFFSET PRINTING  Inventor: Richard Sohnemann, Northeim,  References Cited Germany UNITED STATES PATENTS  Assignee: Continental Gummi-Werke 3,235,772 2/1966 Gurin 161/401 Aktiengesellschaft, Hannover, 3,676,282 7/1972 Volmer l6l/401 Germany 22 Filed; N0 2 1972 Primary Examiner\l Villiam J. Van Balen  A 1 NO 310 093 Attorney, Agent, or Fzrm-Walter Becker 0  ABSTRACT  Forelgn Application Pnomy Data A printing blanket, especially for offset printing, com- NOV. 29, 1971 Germany 2159085 p g a Strength carrier y an intermediate y and an ink transfer layer comprising a polymer base,  [1.8. CI 161/162, 161/401, 161/160, finer materials containing hydroxyl groups and-high 51 1 lm Cl i /i molecular weight, surface active substances.  Field of Search 161/160, 161, 162, 87, 7 Claims, 1 Drawing Figure O O O PRINTING BLANKET, ESPECIALLY FOR OFFSET PRINTING The present invention relates to printing blankets, especially for offset printing, with an essentially nonductile strength carrier layer, an if necessary volume compressible intermediate layer, and a dye or ink transmitting layer.
In the past, the quality of printing products in offset printing was considerably improved by means of constructive measures with the designing of the strength carrier layer and the intermediate layer of blankets. However, one of the main difficulties were encountered with regard to the coordination of the properties of the dye transmitting layer of the blanket, the printing ink, and the ink carriers to each other. Thus, frequently, with a change of the ink carrier to be printed upon and/or the ink, a herewith coordinated blanket must be mounted upon the printing cylinder of the machine.
A certain amount of improvement could be obtained by forming the upper surfaces of the blanket as smooth as possible to reduce the absorption of water. Thusit has been suggested, for example, to make the upper surfaces of the blanket water repellent by means of a lacquer coating and to obtain a largely smooth upper surface. These coating measures, however, are very sensitive to mechanical influences, so that the improvement of the printing style is obtained at the expense of a highly reduced life expectancy.
Three parameters may be considered critical for the behavior of the blanket during printing in relation to the upper surfaces, namely:
1. The critical upper surface tension, which is proportional to the wettability by ink and water,
2. The roughness of the upper surface, and
3. The electrical charge, which in addition to the upper surface movements can often be made responsible for the adhesion of the paper to the rubber blanket.
It is therefore an object of the present invention to produce an ink transmitting layer for blankets which are especially suitable for offset printing, and in which the dye transmitting layer in addition to having a good resistance against mechanical influences, will also have a smooth paper repelling upper surface, and will be able to maintain its critical upper surface tension as well as its upper surface conductivity over a long period of time.
These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing showing a section through a printing blanket according to the present invention.
As exemplary of the blanket according to the invention, the blanket shown in the drawing consists of an in necessary multi layer strength carrying layer 1 provided with an if necessary porous intermediate layer 2, which is coated with a dye or ink transmitting layer 3 constructed according to the invention.
The blanket according to the present invention is characterized primarily in that the ink transmitting layer is constructed upon a base of polymers which essentially correspond to those used in the intermediate layer or at least are excellently fusable with them. The mass or material made upon the base of this polymer and used to form the ink transmitting layer has a concentration between 50 and per cent by weight, with regard to the polymer portion of the material, of bright or transparent filler material containing hydroxyl groups. The material also preferably contains antistatic, high molecular, surface active substances in a proportion of between 1 and 15 per cent by weight, likewise with reference to the polymer content.
The selection of surface active substances is especially critical because materials are involved which separate from the mixture and are continuously removed from the surface during cleaning of the blanket as well as during the printing itself. Materials with too small a molecular weight permit only small doses, are very quickly bleached or washed out, and arrive, in this connection, in too large of a concentration in the damping solution as well as in the printing ink.
On the other hand, it is known that high surface activity need not always be combined with good conductivity. A number of materials, which are known as surface active and anti-static, show no long duration effects because they exhibit too high of an incompatability with the polymer and thereby too high of a migration velocity. It has been proven that for example polyethylene oxide, polyethylene oxide condensates, polyethylene glycol ethers and polyglycol esters, amines, amino polyethers, quaternary ammonium salts, sulfonated organic compounds, such as for example, sulfonated paraffin and the like, are only effective over a limited period of time.
However, it has been found that a number of these materials in mixtures, which, as filler material contain magnesium silicate containing hydroxyl groups and additional polyglycols with molecular weights between 5,000 and 20,000, migrate at a considerably slower rate and in addition thereto can be incorporated into the mixture in larger amounts so that they can remain effective over a considerably greater period of time and thereby can increase the life expectancy of the blanket.
It can be taken for granted that the magnesium silicates which contain hydroxyl groups and/or high molecular polyglycols improve the compatability of the mixture for the surface active substances and increase their conductivity.
The thickness of the layer of the ink transmitting layer constructed according to the invention should amount to at least 0.01 to 0.02 millimeters, preferably 0.05 millimeters, in order to produce in the layer a suf ficient deposit of slowly migrating surface active substance and to assure a better elimination of the electrostatic charges.
Butadiene-acrylonitrile mixed polymerizates are preferred as polymers. To obtain the surface smoothness, the polymers contain an admixture of thermoplastic synthetic materials, such as for example polyvinyl chloride, chlorinated polyethylenes, polyamides or the like. To improve the hydrophile, or affinity for water, the polymers contain fatty acid modified, constantly swelling factices (rubber substitutes) upon a castor oil base.
The selection of the filler material shows greater influences than can be at first expected. Bright or transparent filler materials, especially silicates, have shown themselves superior to carbon black. Especially favorable is the insertion of a magnesium silicate containing hydroxyl groups (a vapor talc known under the trade mark Mistron).
The combined use of filler materials containing hydroxyl groups and polyglycols with molecular weights between 5,000 and 20,000 permits a high dose of surface active substances and apparently also a control of their migration velocity, so that even with a layer thickness of only 0.01 to 0.02 mm, a sufficient deposit of surface active substances may be formed, which remains throughout the life of the blanket.
The coating measures formed according to the invention may be manufactured in a customary manner and applied to the surface of the blanket.
The mixture formed according to the invention may be made in a customary manner and applied. The invention will be further illustrated by the following examples:
EXAMPLE 1 In an internal mixer at a temperature between 140 and 150 C, a blend is made of 100 parts by weight butadiene-acrylonitrile mixed polymerizates (28 to 38 percent acrylonitrile) with 30 parts by weight of polyvinyl chloride in the form of a polymerizate suspension. After cooling to about 90 C, 50 parts by weight of a fatty acid modified factice upon a Castor oil base and 25 parts by weight of a polyglycol ester of fatty acids of average chain length are mixed in. After a further cooling to about 70 to 80 C, 3 parts by weight of a polyglycol having a molecular weight of 5,000 to 20,000, one part by weight of paraffin wax and seven parts by weight of sulfonated paraffin, one part by weight of stearic acid and one part by weight of a phenol age resistor as well as five parts by weight of zinc oxide are mixed in, whereupon at the same temperature 85 parts by weight of a magnesium silicate containing hydroxyl groups (Mistron vapor talc) are mixed in. Finally, at a temperature between 50 to 60, 1.5 parts by weight sulfur as well as three parts by weight of accelerators or catalysts of the mercaptoand thiuram classes are mixed in. The mixture obtained is worked into a brushable paste through the addition as solvent of ethyl acetate toluene (1:3). The resulting mixture is applied to the prepared blanket foundation in a layer having a thickness of about 0.02 mm, and the thus obtained product is vulcanized.
EXAMPLE 2 A rubber mixture is made according to the procedure described in detail in example 1, and consists of the following:
Parts by Weight Butadienc-acrylonitrile mixed polymerizate -Continued Parts by Weight sulfonated castor oil 1 l thiuram sulfide classes 3 Sulfur Vulcanizates of this mixture show the following physical properties:
Strength (DIN 53504) kp/cm Expansion (DIN 53504) 600% Shore hardness A 70 upper surface resistance 10*0- cm current-flow resistance Electrical conductivity (DIN 53596) It is, of course, to be understood that the present invention is by no means limited to the specific showing in the drawings or in the examples, but also comprises any modifications within the scope of the appended claims.
What I claim is:
1. A printing blanket, especially for offset printing, which comprises a strength carrier layer, an intermediate layer, and an ink transfer layer, said ink transfer layer comprising a polymer base, bright filler material containing hydroxyl groups, and surface active substances having high molecular weights.
2. A blanket according to claim 1, in which said filler material is present at the rate of from 50 to per cent by weight in relation to said polymer content.
3. A blanket according to claim 1, in which said surface active substances are present at the rate of from 1 to 15 per cent by weight in relation to said polymer content.
4. A blanket according to claim 1, in which said sub stances are polyglycols having molecular weights ranging between 5,000 and 20,000.
5. A blanket according to claim 1, in which said filler material is magnesium silicate.
6. A blanket according to claim 1, in which said surface active substances are anti-static.
7.'A blanket according to claim 6, in which said substances are sulfonated paraffin, sulfonated castor oil,
and ethylene oxide condensates.