JPS6148438B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a compressed layer of a printing blanket, particularly a compressible blanket. Printing blankets used in high speed offset printing have been provided with compressed layers of elastomeric polymers. Firstly, the compressed layer described above uniformly absorbs the bulge that occurs on the compressed surface of the blanket during printing pressure, thereby reducing deformation of the blanket surface and making it possible to obtain a clear image. Secondly, because of this compression layer, when the printing paper is folded and sent, or when two or more sheets are sent in piles, the compression layer compresses the printing paper cylinder. It can absorb and relieve the forces (other than printing pressure) applied to the blanket surface, and therefore the plate cylinder,
The lifetime of the blanket surface layer can be significantly improved.
Thirdly, when tailoring the torso, for ordinary blankets, the thickness must be adjusted very precisely, but by providing a compression layer, it is possible to make the torso slightly oversized than the standard torso tailoring. It has the advantage that it is possible to obtain clear printing, and that the body can be tailored regardless of the skill level of the operator. It is known to manufacture such compressed layers from foam. For example, a foaming agent is blended into synthetic rubber and heated and foamed during vulcanization of the rubber to form a compressed layer with countless closed cells, or a method of curing as disclosed in JP-A No. 48-97609. There is a method in which fine latex spongy rubber particles are dispersed in an elastic substrate to form a large number of non-interconnected cells (closed cells) in the substrate. Furthermore, a method (Japanese Patent Publication No. 7371/1983) is also known in which hollow microspheres are dispersed in an elastomer to form closed cells. However, printing blankets with compressed layers as described above do not fully achieve the effect of providing a compressed layer. That is, the compressed layer cannot sufficiently and uniformly absorb the bulge that occurs on the compressed surface of the blanket during printing pressure, making it difficult to obtain a sufficiently clear image. Furthermore, since the plate cylinder rotates at high speed during printing, the blanket is compressed at extremely high speed.
It is necessary to alleviate the compression strain with a response speed proportional to the compression speed, but the above-mentioned known example has the disadvantage that this response speed is slow. This is basically due to the fact that the compressed layer of the above-mentioned known blanket is a closed-cell foam. This is because in a closed cell system, the pores are independent, so there is no place for the air within the cells to escape due to compressive deformation, and the deformation due to compressive stress cannot be fully absorbed, and in addition, the relaxation rate of compressive strain is This is because it will be late. In the case of open cells, since the cells communicate with each other, air can circulate freely and can freely buffer against large compressive deformations, and the rate of relaxation of compressive strain is also remarkable. improve,
It becomes possible to obtain clear printing, and in addition, it becomes possible to improve the durability of the plate cylinder and blanket. As described above, it is desirable that the compressed layer of a printing blanket be made of a foam with a high open cell ratio, but as mentioned above, closed cell foam is mainly used because it has a high open cell ratio. Furthermore, it was extremely difficult to manufacture a foam having micropores, which is an essential factor for obtaining halftone dot reproducibility in printed matter. For example, in a rubber foam foamed with an organic blowing agent, it is difficult to provide uniform micropores of 100 μm or less, and the open cell ratio is extremely low at 50% or less. Figure 2 is a 75x micrograph of a foam produced by this method, and as is clear from the figure, the bubbles are non-uniform, ranging from large to small, and the open cell ratio is low. Furthermore, according to the method of mixing hollow microspheres into elastomer (Japanese Patent Publication No. 7371/1989), it is easy to adjust the size of the bubbles because the microspheres are mixed in in advance, but the microspheres mixed in are individual. Since it is an independent sphere, the bubbles are 100% closed cells. In addition, in the method of dispersing fine particles of cured latex spongy rubber in a substrate to form a compressed layer (Japanese Patent Application Laid-Open No. 1976-97609), it is possible to produce a foam with small bubbles; It takes a lot of work to do this, and it also has the disadvantage that it gets mixed into the rubber glue and clogs the doctor knife when applying the glue, resulting in poor production efficiency and poor open cell rate.
Since it is not 100%, its performance as a compression layer is also not sufficient. The object of the present invention is to eliminate the above-mentioned drawbacks and provide a method for producing a foam having 100% open cells and micropores of 100 μm or less. Therefore, the method for manufacturing the compressed layer of a printing blanket according to the present invention is to add a polymer to a polymer solution prepared by dissolving the polymer in a solvent capable of dissolving the polymer at a polymer concentration of 2 to 70%. A composition containing one or more surfactants having at least one functional group or having an amine structure and/or a sufficient amount of silicone to exhibit an antifoaming effect is coated on the base fabric. It is characterized in that it is immersed in a gelling liquid at 50° C. to 100° C. that is soluble in the solvent but not in the polymer, dried, and optionally vulcanized. According to the present invention, it is possible to easily produce a compressed foam layer having micropores of 100 μm or less with a 100% open cell ratio,
The printing blanket provided with the compressed layer produced according to the present invention can evenly and reliably absorb the swelling of the blanket surface caused by printing pressure, making it possible to obtain clear images. In addition, the compression strain relaxation speed during high-speed printing becomes faster, which not only makes it possible to obtain clear printing, but also has the advantage of improving the durability of the plate cylinder or blanket. The present invention will be explained in more detail. The polymer used in the present invention is a general rubber, a thermoplastic resin, or a compound containing this rubber or this thermoplastic resin as a main component. It is preferable to use one that has strong resistance to the solvent used.
For example, it may be one or more of butadiene/acrylonitrile copolymer, polyvinyl chloride, chloroprene rubber, or a compound containing one or more of these as a main component. This compound is made of, for example, a main component such as rubber, a vulcanizing agent such as sulfur, a vulcanization accelerator, a reinforcing agent such as carbon black, etc.
It may be kneaded with addition of processing aids such as anti-aging agents and stearic acid. Next, as the solvent for dissolving this polymer, any solvent may be used as long as it can be dissolved in the gelling liquid. That is, since the gelling liquid gels the polymer solution by mutually diffusing with the solvent, the solvent must mutually diffuse with the gelling liquid, which has a stronger affinity than the polymer. . Therefore, this solvent varies depending on the type of gelling liquid, but generally it is one or a mixture of two or more of N,N'-dimethylformamide, diethylformamide, dimethylacetamide, dimethyl sulfoxide, etc. I can do it. The polymer is dissolved in this solvent, and the polymer concentration at this time is 2 to 70%. If it is outside this range, it will be difficult to apply glue and work efficiency will be reduced. By adjusting the polymer concentration, the density of the foam can be changed from a high-density open cell to a low-density open cell. For example, if the polymer concentration is 30%, a foam with a specific gravity of 0.35-0.40 can be obtained, and if it is 60%, a foam with a specific gravity of 0.65-0.75 can be obtained. This is because, as will be described later, the pores are formed by mutual diffusion of the solvent and the gelling solution, and therefore the density can be changed depending on the polymer concentration. In the present invention, the polymer solution contains a surfactant having at least one functional group selected from a sulfonic acid group, an ether group, and a hydroxyl group or having an amine structure, and/or a silicone material sufficient to have an antifoaming effect. Add. This group of substances is added to facilitate adjustment of the pore size of the compressed layer by varying the polymer concentration described above. This is particularly effective when it is desired to provide micropores of a desired size, ie, 10 μm or more. the polymer concentration mentioned above,
The size of the pores can be adjusted by changing the type and amount of the substance in this group. Examples of surfactants that are pore regulators include sodium dodecylbenzenesulfonate, sodium di-sulfosacinate,
Examples include one or more of polyoxyethylene oleate, polyoxyethyl lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene stearyl ether, dodecyldimethylamine, and octadecylamine.
As the silicone, SAG-471, SAG-100 (manufactured by Nippon Unicar Co., Ltd.), SH-193 (manufactured by Toray Silicon Co., Ltd.), etc. can be used, but the silicone is not basically limited to these. The amount added can be functionally varied depending on the desired pore size, polymer concentration, type of surfactant and/or silicone, but in order to provide ideal micropores of 100-10 μm, the surface active Preferably, the additive and/or silicone is added in an amount of 20% or less. If more than 20% is added, the pores will become too large. In particular, when one or more surfactants are added, it is preferably added in an amount of 0.1 to 15%, and in the case of silicone, it is preferably added in an amount of 0.1 to 20%. When surfactants and silicones are used in combination, the amounts functionally correspond to those mentioned above. In the case of silicone, it is generally added as a foam stabilizer, but when the amount added is increased, it begins to act as an antifoaming agent. For example, in the case of SH-193, when added in an amount of 5% or more, it has an antifoaming effect. Therefore, when adding silicone, it must be in an amount sufficient to have an antifoaming effect, and the amount of silicone added above must be
If it is less than 0.1%, it will not have a sufficient antifoaming effect. This composition is coated on the base fabric,
Examples of this base fabric include cotton, polyester,
It can be nylon or the like. This base fabric is basically not limited in the present invention, and the method of coating is not similarly limited. For example, as a coating method, a doctor knife, a roll coater, etc. may be used. Next, the base fabric coated with this composition is immersed in a gelling solution. The gelling liquid must be insoluble in the polymer and soluble in the solvent. As mentioned above, this is because the solvent is selectively eluted from this polymer solution, and therefore the affinity between the solvent and the gelling liquid is greater than the affinity between the solvent and the polymer. be.
As long as it is such, the type of gelling liquid is basically not limited in the present invention. for example,
Water, monools such as methanol and ethanol,
It may be a mixed solution of one or more polyols such as glycerin and ethylene glycol. Considering economic efficiency, water (hot water) is preferable. The temperature of this gelling liquid is 50 to 100°C. The purpose of heating the gelling solution in this manner is to remove the solvent as quickly as possible, shorten the semi-gel state, and form fine pores. In this case, if the gelling solution is at room temperature, the semi-gel state will continue for a long time.
The pores gradually become larger as they aggregate and break. If the temperature of the gelling liquid is lower than 50°C, the result will be the same as simply immersing the gelling liquid in a gelling liquid at room temperature, resulting in a state in which pores ranging from large pores of 200 μm or more to minute pores of 20 μm or less coexist. Moreover, if the temperature is 100°C or higher, the pores become too fine, resulting in the disadvantage that the material cannot withstand use. Preferably the temperature is 60°C or higher. This is because fine pores are formed quickly and reliably. In the present invention, as described above, the solvent and the gelling liquid are mutually diffused to form a gel. That is, since the affinity between the gelling liquid and the solvent is greater than the affinity between the polymer and the solvent, the polymer is in an undissolved state rather than a dissolved state, and the polymers aggregate together. At this time, spaces are created in areas other than the agglomerated and aggregated polymer parts. This becomes pores, and since the pores created in this way are the result of mutual diffusion of the polymer solvent and gelling liquid, they are 100% continuous pores. After being immersed in the gelling solution in this way, e.g.
Dry for 20 minutes or more in a hot air dryer at 100-160℃,
Vulcanize at the same time. In the case of a thermoplastic elastomer, vulcanization is not necessary, so it may be dried for about 30 minutes at a temperature of 150° C. or lower, for example. Of course, the drying time, drying temperature, and drying method are not limited in the present invention. It can be determined functionally by considering the type of polymer solution, etc. Examples of the present invention will be described below. Example 1 Composition A Group butadiene/acrylonitrile copolymer
70 parts by weight (Hiker 1041; manufactured by Zeon Corporation) Polyvinyl chloride (degree of polymerization 1100) 30 〃 Zinc white 3.5 〃 Stearic acid 1.0 〃 Carbon black (MT) 60 〃 Anti-aging agent 1.0 〃 Plasticizer (DOP) 5 〃 Total 170.5 〃 Group B Sulfur Yellow 1.5 parts by weight Vulcanization accelerator 3.0 〃 Total 4.5 〃 Group C Sodium dodecylbenzenesulfonate
3 parts by weight The compounding ingredients of Group A were kneaded with a roll and dissolved in N,N'-dimethylformamide to a polymer concentration of 45%, to obtain a solution with a viscosity of 500 poise. To this was added the surfactant of group C with sufficient stirring. Next, a group B vulcanizing agent, etc. was added, and this polymer solution was shot at a rate of 70 pieces/inch.
Using a doctor knife on a cotton cloth with a thickness of 0.38 mm,
It was coated to a thickness of 0.37 mm. This was immersed in hot water at 80°C, taken out for 40 minutes, and sent directly to a drying chamber at 140°C to be vulcanized and dried. A micrograph of this compressed layer is shown in FIG. 1st
The figure is a 75x micrograph of a compressed layer produced by the method according to the invention. For comparison, a 75x micrograph of a compressed layer made using a conventional organic blowing agent is shown in Figure 2.
As is clear from these photographs, the compressed layer manufactured by the method of the present invention mostly consists of micropores of 50 μm or less and has an open cell ratio of 100%, whereas the compressed layer manufactured by the conventional method has Small-sized pores are more non-uniform than large-sized ones of 100 μm or more, and the open cell rate is also lower. Next, a compressed layer was manufactured in the same manner using the above composition except that Group C (surfactant) was removed. A 75x micrograph of this compressed layer is shown in Figure 3.
As is clear from these photographs, the compressed layer produced by the method of the present invention has ideal pores of 10 μm or more and 100 μm or less, whereas the compressed layer produced without using a surfactant has micropores of 10 μm or less. It is understood that too many holes were obtained. Example 2 A compressed layer according to the present invention manufactured with a composition according to the table below and a compressed layer manufactured using an organic blowing agent, as well as a compressed layer manufactured by incorporating hollow microspheres into an elastomer (Tokuko Showa) A compressive stress-strain curve test was conducted using a blanket manufactured using the same method (No. 52-7371). The results are shown in FIG.

【table】

[Table] As is clear from FIG. 4, the blanket of the present invention (curves C ₁ , C ₂ , C ₃ , C ₄ ) is different from the conventional blanket having a compressed layer in which micro hollow spheres are mixed in an elastomer (curve A ) showed a significantly better stress-strain curve than the blanket made with organic blowing agent (curve B). When printing tests were carried out using these blankets, the dot reproducibility was excellent and the durability was 2 to 3 times higher than that of the blankets with compressed layers manufactured using the hollow microspheres. This is thought to be because the strain rate is much larger for the same compressive force compared to conventional blankets (curves A and B), so the compressed layer can sufficiently cope with the deformation load.

[Brief explanation of the drawing]

FIG. 1 is a 75x micrograph of a printing blanket compressed layer according to an embodiment of the present invention, and FIG. 2 is a 75x micrograph of a conventional compressed layer using an organic blowing agent. FIG. 3 is a 75x micrograph of a compressed layer prepared in the same manner as the composition used in the present invention except that the surfactant was removed. FIG. 4 is a stress-strain graph of a printing blanket with a compressed layer produced by the method according to the invention and a conventional printing blanket with a compressed layer. A...Stress-strain curve of a printing blanket having a compressed layer manufactured by mixing micro hollow spheres in an elastomer. B... Stress of a printing blanket with a compressed layer manufactured using an organic blowing agent
Strain rate curve, C ₁ , C ₂ , C ₃ , C ₄ ... Stress-strain rate curve of a printing blanket with a compressed layer produced by the method according to the invention.

Claims (1)

[Claims] 1. Polymer in a solvent with a polymer concentration of 2 to 70%
(wt%, same hereinafter) One or more surfactants having at least one functional group among sulfonic acid, ether group, and hydroxyl group or having an amine structure and/or Alternatively, a sufficient amount of silicone to exhibit an antifoaming effect is added and the basic composition is coated on a base fabric to form a gel at 50 to 100°C that is soluble in the solvent but not in the polymer. 1. A method for producing a compressed layer of a printing blanket, which comprises immersing it in a chemical solution, drying it, and optionally vulcanizing it. 2. The method for producing a compressed layer of a printing blanket according to claim 1, wherein the polymer is a rubber or a thermoplastic resin, or a compound containing the rubber or the thermoplastic resin as a main component. 3. A method for producing a compressed layer of a printing blanket according to claim 2, characterized in that the polymer is resistant to printing inks and/or solvents used during ink changes. 4. The polymer is a compound whose main component is one or more of butadiene/acrylonitrile copolymer, polyvinyl chloride, and chloroprene rubber, or one or more of butadiene/acrylonitrile copolymer, polyvinyl chloride, and chloroprene rubber. A method for producing a compressed layer of a printing blanket according to claim 3, characterized in that: 5. The solvent is selected from N,N'-dimethylformamide, diethylformamide, dimethylacetamide and dimethyl sulfoxide.
A method for producing a compressed layer of a printing blanket according to any one of claims 1 to 4, characterized in that it is a species or a mixture of two or more species. 6. The method for producing a compressed layer of a printing blanket according to any one of claims 1 to 5, characterized in that 20% or less of the surfactant and/or the silicone is added. 7. The method for producing a compressed layer of a printing blanket according to claim 6, wherein when one or more of the surfactants is added alone, the amount added is 0.1 to 15%. 8. The method for producing a compressed layer of a printing blanket according to claim 6, wherein when the silicone is added alone, the amount added is 0.1 to 20%. 9. Claims 1 to 8, wherein the gelling liquid is one or a mixture of two or more selected from the group consisting of water, monools, and polyols.
A method for producing a compressed layer of any of the printing blankets. 10. The method for manufacturing a printing blanket according to claim 9, wherein the gelling liquid is hot water.