JPH0432758B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a compressible offset blanket, and more particularly to a method for manufacturing a compressible offset blanket having a compressible rubber layer made of porous rubber inside. . 2. Prior Art A known compressible offset blanket used in an offset printing process has an oil-resistant surface rubber layer 1 and a reinforcing fiber layer 2 on the lower surface of the surface rubber layer, or It is made up of a compressible layer 3 made of a porous material and a fiber backing layer 4 which are laminated one after another without intervening. In such a compressible offset blanket, as a means for forming the compressible layer 3, the method disclosed in German Patent No.
As described in Japanese Patent Publication No. 1165046, a method of constructing the material from a foamed rubber sponge, or a method of constructing it from a cytoplasmic material obtained by impregnating a nonwoven fabric with latex, as described in Japanese Patent Publication No. 37-13110, has been proposed. The constituent materials of the above-mentioned compressible offset blanket, especially the compressible layer made of non-woven fabric, have a weak elastic recovery force, which poses practical difficulties in transmitting the necessary printing pressure to the oil-resistant surface rubber layer. . Naturally, a compressible offset blanket having such a compressible layer faces a major obstacle in its practical application, since its printing properties deteriorate due to insufficient printing pressure. In addition, compressible offset blankets with a compressible layer made of foamed rubber sponge have a thickness of 0.1 mm to
Because it is difficult to form bubbles with a uniform diameter inside the ultra-thin compressible layer of approximately 1.0 mm, it is impossible to generate uniform printing pressure over the entire surface of the compressible offset blanket. Improvements are strongly desired. As a means to solve such problems,
Japanese Patent Publication No. 52-7371 discloses a compression offset layer in which the compressible layer is formed of a rubber elastic material containing microscopic hollow spheres (microcapsules) made from a soluble or crushable material such as thermoplastic plastic. A method of manufacturing the blanket is described. By adopting this method, the diameter of the pores formed inside the compressible rubber layer and the state of dispersion of the pores can be made fairly uniform, but the individual microcapsules may be slightly unevenly formed during vulcanization. Due to the expansion, the uniformity of pore distribution within the compressible rubber layer may be impaired. Alternatively, after vulcanizing and molding a rubber sheet made of a rubber composition containing an appropriate amount of salt, the sheet is immersed in water to extract the salt, and the sheet is compressed to contain a large number of continuous pores. Techniques for molding rubber layers are also known. However, compressible offset blankets having such a porous rubber layer are not easily molded into blankets in which the salt contained in the rubber glue initiates a doctor knife during the "sizing operation" during the manufacturing process. Corrosion occurs in equipment and instruments, so it is necessary to apply anti-corrosion treatment such as coating equipment and equipment components that come into contact with the rubber glue with expensive corrosion-resistant materials such as Teflon resin. Moreover, it causes inconveniences such as the need to frequently perform removal work and cleaning work to remove adhered rubber glue. Problems to be Solved by the Invention The present invention solves the non-uniformity of pore size and pore distribution in the method for producing a compressible layer using microcapsules, and also solves the problem of rust generation in the salt extraction method. Its primary objective is to provide a method of manufacturing a compressible offset blanket that is reversible. Means for Solving the Problems In view of the above object, the present invention provides a compressible offset rubber layer consisting of an oil-resistant surface rubber layer 11, a compressible rubber layer 12 and a fiber backing layer 13, which are sequentially laminated on the lower surface of the oil-resistant surface rubber layer 11. In the blanket manufacturing process,
As a material for forming the compressible rubber layer 12, 40 to 80% of a microencapsulated salt whose surface is coated with a thermoplastic resin insoluble in a solvent is added to 100 parts by weight of rubber.
Prepare a rubber composition in the proportion of parts by weight, mold the rubber composition into a sheet-like material of a predetermined thickness, vulcanize the sheet-like material, and simultaneously melt the microcapsules, The gist of this invention is a method for producing a compressible offset blanket, in which the obtained vulcanized rubber sheet is immersed in water to extract the salt, thereby forming a compressible rubber layer 12 having numerous continuous pores. Example When carrying out the present invention, it is necessary to select a thermoplastic resin that is insoluble in a solvent, such as polymethacrylic acid methacrylate or polyvinylidene chloride, and to encapsulate it in the microcapsule. As the salt, salts such as magnesium chloride and sodium chloride can be used. The particle size of the microencapsulated salt is preferably adjusted to a range of 10 to 100 μm in order to obtain an excellent printing effect with sharp halftone dots and no thickening, blank spots, or thick stitches. To explain the embodiment of the present invention in more detail, a rubber paste (main rubber is NBR) containing 40 to 80 parts by weight of microencapsulated salt per 100 parts by weight of rubber is used to form the fiber backing layer 13. After "sizing" the constituent plain woven fabric to a thickness of 0.1 to 1.0 mm, the obtained rubberized fabric is introduced into a known vulcanization device to vulcanize the rubber, and then At the same time, the microcapsules are melted. The vulcanized rubberized cloth is then immersed in a water bath to extract the salt.
The blending amount of the microencapsulated salt is determined so that continuous pores are formed in the obtained compressible rubber layer 12 based on salt extraction, and the impression given by the compressible rubber layer 12 to the oil-resistant surface rubber layer 11 is determined. In order to maintain the pressure at a predetermined level, it is necessary to adjust the amount within the range of 40 to 80 parts by weight based on 100 parts by weight of the rubber composition constituting the compressible rubber layer. After forming the compressible rubber layer 12 in this manner, as shown in FIG. A second fiber backing layer 15 made of plain woven fabric is laminated on the lower surface of the intermediate rubber layer 4. Further, on the upper surface of the compressible rubber layer 12, an oil-resistant surface rubber layer 11 functioning as a printing layer is laminated via a primer (adhesive layer, indicated by reference number 16) and a reinforcing cloth layer 17 made of plain woven cloth. An example of the composition of the compressible rubber layer 12 is shown in Table 1 below.

[Table] Effects of the Invention As can be understood from the above explanation, in the method of the present invention, a solid microencapsulated salt is used as a material for forming the compressible rubber layer, so that it is not possible to use known hollow microcapsules. It is possible to prevent the pore diameter from becoming non-uniform due to thermal expansion as observed in the above. Therefore, in the offset printing process, halftone dots (blurred contours), thickening (increase in diameter), and blank spots (occurrence of thin spots) due to uneven printing pressure.
These obstacles can be effectively eliminated. The compressible rubber layer with continuous pores according to the present invention also functions as a pressure absorbing part for the oil-resistant surface rubber layer, so that the blanket cannot absorb "backlash" caused by the gear clearance of the printing drum. It is possible to eliminate the risk of creating striped shading patterns, so-called "shock marks" on the printed surface. Furthermore, since the salt added to the compressible rubber layer is covered with a capsule made of a thermoplastic resin that is insoluble in solvents, there is no risk of the capsule being dissolved by the solvent in the rubber glue. After the compressible rubber layer is vulcanized and molded, the salt is reliably prevented from oozing into the rubber paste until it is immersed in water. Therefore, there is no need to apply anti-rust treatment to the glue pulling equipment and instruments.
It can also have a remarkable effect on reducing capital investment and increasing the service life of manufacturing equipment.

[Brief explanation of drawings]

FIG. 1 is an enlarged longitudinal cross-sectional view of a compressible offset blanket according to the present invention, and FIG. 2 is an enlarged longitudinal cross-sectional view of a conventional offset blanket. 11...Oil-resistant surface rubber layer, 12...Compressible rubber layer, 13...Fibre backing layer.

Claims (1)

[Claims] 1. In the manufacturing process of a compressible offset blanket consisting of an oil-resistant surface rubber layer, a compressible rubber layer and a fiber backing layer laminated in sequence on the lower surface thereof, a solvent-insoluble material is used as the material for forming the compressible rubber layer. 40 to 100 parts of rubber per 100 parts by weight of microencapsulated salt coated with a thermoplastic resin.
A rubber composition containing 80 parts by weight is prepared, the rubber composition is molded into a sheet-like material of a predetermined thickness, the sheet-like material is vulcanized, and at the same time the microcapsules are melted. . A method for producing a compressible offset blanket, which comprises immersing the obtained vulcanized rubber sheet in water to extract the salt and form a compressible rubber layer.