JPH0250878B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing printing blankets, and in particular to a method for manufacturing printing blankets having a compressed layer. Printing blankets used for high-speed offset printing and the like are provided with a compressed layer of elastic polymer. This compressed layer firstly absorbs uniformly the swelling that occurs on the compressed surface of the blanket during printing pressure, reducing deformation of the blanket surface;
Its function is to make it possible to obtain clear images. Second, the printing paper is sent folded,
When two or more sheets are stacked and sent, this compressed layer absorbs and relieves the force (force other than printing pressure) applied to the plate cylinder and blanket surface by compressing, and therefore the plate cylinder and blanket surface layer can significantly improve the service life of Third, when tailoring the body, for ordinary blankets, the thickness must be adjusted very precisely, but by providing a compressed layer, even if the body is tailored a little over the standard body style, clear printing can be achieved. This has the advantage that the torso can be tailored regardless of the skill level of the worker. As a method for manufacturing such a compressed layer, there is a method in which a foaming agent is mixed into a synthetic rubber compound, and the foaming agent is heated and foamed during rubber vulcanization to form a compressed layer having air bubbles. Alternatively, an elastomer is applied to a porous felt. A method of impregnation and a method of dispersing hollow microspheres in an elastomer to form closed cells to form a compressed layer are known. The compressed layer of a printing blanket needs to have the above-mentioned characteristics, namely, to uniformly absorb the swelling that occurs on the blanket surface, to relieve the force applied to the blanket surface, and to have a corresponding response speed when printing at high speeds. It is required to have various properties such as the need to recover from compressive strain and sufficient durability. In addition, printing blankets have different performance requirements depending on various printing methods, so the methods for manufacturing this compressed layer include:
It is desirable to have a method that easily satisfies these requirements. A compressed layer that satisfies these characteristics has a compressibility of 2.0 to 8.0 Kg/cm ² (compression speed of 1 mm/min, 0.15
mm compression stress (hereinafter the same), cohesive force must be 200 g/cm or more [peeling test (hereinafter the same)], etc. Especially in compressibility, due to differences in printing methods etc., various compression We need a blanket that has the properties of This is because the blanket pressurized by the impression cylinder will be subjected to shear stress due to this pressurization, but unless the cohesive force is at least 200 g/cm or more, it will not be able to withstand this shear stress. However, according to the conventional method, both
It has not been possible to produce blankets with high compressibility of less than Kg/cm ² and it has been impossible to produce printing blankets with versatility. The object of the present invention is to provide a method for producing a printing blanket free from such drawbacks, and more specifically, to provide a printing blanket having a compressibility in the range of 2.0 to 8.0 kg/cm ² and a cohesive force of 200 g/cm or more. It is an object of the present invention to provide a method for easily manufacturing printing blankets and for easily manufacturing printing blankets having various compressibility. Therefore, the compressibility according to the present invention is 2.0 to 8.0 kg/
cm ² and having a compressed layer with a peeling strength of 200 g/cm or more, the method for manufacturing a compressed layer of an offset printing blanket is characterized by including the following steps. a Rubber compound of oil-resistant polymer with an average particle size of 10~
A step of adding 70 to 200 parts by weight of a powder of 50 μm that is soluble in the eluate to 100 parts by weight of the formulation. b. Apply the formulation of item a to which this powder is added on the base fabric.
A process of laminating and vulcanizing at a rate of 300 to 1000 g/ ^m2 . c. A step of applying a tension of 10 to 100 Kg/m width to both ends of this laminate and immersing it in an eluent having a temperature range of 60 to 100°C. According to the method for manufacturing a printing blanket according to the present invention, the cohesive force is 200 g/cm or more and the compressibility is 2.0 to 2.0.
There is an advantage that a blanket exhibiting any compressibility in the range of 8.0 Kg/cm ² can be easily obtained by controlling the amount of powder added, the amount of the compound solution applied, elution conditions, etc. The present invention will be explained in more detail. According to the method for producing printing blankets according to the invention, a powder that can be eluted in an eluent is added to a rubber compound of an oil-resistant polymer. The rubber compound of oil-resistant polymer is the main body of the compressed layer, and since it is a printing blanket, it is required to be resistant to printing inks and solvents used when changing ink. It is necessary to use the following. The polymer used in such a formulation may be one or more of polyvinyl chloride, chloroprene rubber, nitrile rubber, polysulfide rubber, polyurethane, fluorine rubber, acrylic rubber, hydrin rubber, and the like. Such oil-resistant polymer formulations are made by adding vulcanizing agents such as sulfur, vulcanization accelerators, etc. to the main components such as rubber.
One or more of reinforcing agents such as carbon black, anti-aging agents, and processing agents such as stearic acid may be added. This polymer blend is usually used after being dissolved, and the solvent may basically be any solvent as long as it dissolves the polymer blend. For example, N-N'-dimethylformamide, diethylformamide, dimethylacetamide, dimethylsulfoxide, toluene, MEK,
It can be one or more types such as MIBK. As mentioned above, the powder added to the polymer formulation may be any powder as long as it can be eluted into the eluent. For example, inorganic salts such as sodium carbonate, sodium bicarbonate, potassium bicarbonate, sodium chloride, sodium nitrate, calcium nitrate, water-soluble organic substances such as sugar starch, organic acids such as phenol, sulfosalicylic acid, tartaric acid, etc., or one of these salts. It can be more than that. The average particle size of this powder is 10 to 50 μm. 50μ
If the pores are larger than m, the pores become large and a compressed layer with a uniform and strong cohesive force cannot be formed.If the diameter is smaller than 10 μm, a long extraction time is required, and due to poor dispersion, it is difficult to form a uniform compressed layer, making it difficult to maintain the compressed layer. sea bream. In addition, the amount of powder added is 100%
It is 70 to 200 parts by weight. If it is less than 70 parts by weight, the compressive stress will exceed 4.0 Kg/cm ² , and if it is more than 200 parts by weight, it will be less than 2.0 Kg/cm ² . The pressure required for ink transfer during printing cannot be obtained and cohesive force is insufficient, causing peeling development due to shearing force during printing. The method of adding this powder to the polymer formulation is essentially not limited. For example, an open-type mixing roll or a closed-type mixer (Banbury mixer, pressure kneader, etc.) can be used, and when a polymer blend is made into a solution, a stirring mixer can be used to dissolve the polymer blend. Distribute uniformly. This powder-added polymer blend is laminated onto a base fabric, and this base fabric may basically be of any type. For example, it can be cotton cloth, rayon cloth, polyester cloth, etc. The method of laminating the powder-added polymer blend on such a base fabric is not limited, and may be laminated by calendering, or extruded film may be laminated. When used as a solution, it can be coated and laminated using a knife coater, roll coater, or the like. The ratio of this lamination is 300 to 1000 g/cm ² . 300
If it is less than g/m ² , the compressibility will not be less than 4.0 Kg/cm ² . Moreover, if it exceeds 1000 g/cm ² , the required thickness of the surface rubber layer and reinforcing base fabric layer cannot be secured due to restrictions on the product thickness of the blanket. After optionally vulcanizing such a laminate, it is immersed in an eluent. At this time, the temperature of the eluate is 60 to 100.
It is ℃. If the temperature is lower than room temperature, it will take too long for the powder to dissolve, which may result in loss of rubber properties, and if it exceeds 100°C, extraction of the compound will also occur, which will affect the durability of the product. Moreover, the immersion time is 3 minutes to 6 hours. If the time is less than 3 minutes, the powder will not be sufficiently eluted and a blanket with the desired compressive stress cannot be obtained; if it is more than 6 hours, the properties of the base fabric will change and the rubber compound will be extracted. . Examples of eluents include water, monools such as methanol and ethanol, and polyols such as glycerin and ethylene glycol.
More than one species is used. When immersing in this eluate, both ends of the laminate 1 are wound around the rolls 2, 2' (wound through guide rolls 4, 4), and the rolls 2, 2' are rotated in forward and reverse directions while applying tension. Preferably, it is immersed in water 3 (FIG. 1). The tension applied to this laminate is 10
~100 (Kgm/width m) is preferable. If the width is smaller than 10Kg/m, the squeezing effect will be less and 100 (Kgm/m)
Width) larger than this will lead to a decrease in the strength of the base fabric. This squeezing effect destroys the microcells in the compressed layer and increases the number of communicating pores, making it easier for powder and water to replace each other.
Since the rolls 2, 2' rotate in forward and reverse directions, which allows rapid dissolution and no risk of impairing the properties of the compressed layer, the laminate is squeezed as it is wound around the rolls 2, 2'. Since dehydration is facilitated, the elution of the powder is accelerated.
That is, the added powder can be reliably removed, and compressibility can be easily controlled. Rubber paste is applied onto the compressed layer thus produced, a reinforcing cloth is laminated thereon, and a surface rubber layer etc. are provided thereon to obtain a printing blanket. Examples will be described below. Example 1 A nitrile rubber compound kneaded in a conventional manner is dissolved in toluene, and 2 parts of surfactant and 150 parts of common salt with an average particle size of 20 μm are added to the compound.
of the mixture and stirred well to ensure uniform dispersion. Apply this onto cotton cloth using a knife coater,
g/m ² , dried the solvent, vulcanized, and then immersed in water at 80° C. for 4 hours. This was made into a printing blanket in the same manner as in Example 1. The compressive stress of this blanket is 2.5Kg/cm ²
It was hot. The compressive stress at this time and the compressive stress of the blanket manufactured by the conventional method are shown in a table.

[Table] As explained above, according to the printing blanket manufacturing method of the present invention, the cohesive force is 200g/
A wide variety of blankets can be produced with a compressive stress of 2.0 to 8.0 Kg/cm ² . In particular, it has the advantage of being able to manufacture a blanket with a high degree of compressibility of less than 4.0 kg/cm ² , which was previously impossible to manufacture, and providing a blanket with good printing reproducibility such as halftone dots and tone reproducibility. .

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the dipping process of the present invention. 1...Laminated body, 2...Roll, 3...Water.

Claims (1)

[Scope of Claims] 1. A method for producing a compressed layer for an offset printing blanket, the method comprising the following steps: a Rubber compound of oil-resistant polymer with an average particle size of 10~
A step of adding 70 to 200 parts by weight of a powder of 50 μm that is soluble in the eluate to 100 parts by weight of the formulation. b. Apply the formulation of item a to which this powder is added on the base fabric.
A process of laminating and vulcanizing at a rate of 300 to 1000 g/ ^m2 . c. A step of applying a tension of 10 to 100 Kg/m width to both ends of this laminate and immersing it in an eluent having a temperature range of 60 to 100°C.