JPS6148435B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition for manufacturing a compressed layer of a printing blanket, particularly a compressible blanket, and a method for manufacturing a compressed layer of a compressible blanket using the composition. 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, due to the presence 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 and the surface of the blanket. 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 compressed layer, even if the body is tailored slightly over the standard torso design, it will still be sharp. This method has the advantage that it is possible to obtain accurate printing, and that the cylinder 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 pores (closed cells) that do not communicate with each other in the substrate. Furthermore, a method (Japanese Patent Publication No. 7371/1983) is 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 swelling that occurs on the compressed surface of the blanket during printing pressure, making it impossible to form a clear image. Furthermore, during printing, since the plate cylinder rotates at high speed, the blanket is compressed at an extremely high speed, and compression strain must be alleviated with a response speed proportional to this compression speed. The disadvantage of this is that the 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, the pores communicate with each other, so air can circulate freely and can freely buffer against large compressive deformations, and the relaxation rate of compressive strain is The printing quality is also significantly improved, making it possible to obtain clear printing, and in addition, it becomes possible to improve the durability of the plate cylinder and blanket. In this way, 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 foams are mainly used because they have a high open cell ratio. This is because it has been extremely difficult to manufacture a foam having micropores, which is an essential factor in obtaining halftone dot reproducibility in printed matter. For example, in a rubber foam foamed with an organic foaming 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. Second
The figure is a 75x photomicrograph of a foam produced by this method. As is clear from the figure, the bubbles are more non-uniform in the small size than the large ones, and the open cell ratio is low. Also, according to the method of mixing hollow microspheres into elastomer (Japanese Patent Publication No. 7371/1989),
Since pre-manufactured microspheres are mixed in, it is easy to adjust the size of the bubbles, but since the mixed microspheres are individual spheres, the bubbles are 100% closed cells. In addition, in the method of dispersing fine particles of cured latex spongy rubber in a substrate to generate a compressed layer (Japanese Patent Application Laid-open No. 1976-97609), it is possible to produce a foam with small bubbles and a relatively high open cell ratio. However, it is time-consuming to produce spongy rubber fine particles, and when mixing them into rubber glue for sizing,
It has the disadvantage of clogging the doctor knife, poor production efficiency, and the foaming rate is not 100%, so its performance as a compressed layer is not sufficient. The present invention eliminates the above-mentioned drawbacks and provides a composition for producing a foam with 100% open cells and micropores of 100 μm or less, and a method for producing a compressed layer of a printing blanket using the composition. The purpose is to Therefore, the composition for producing a compressed layer according to the present invention has at least one type of functional group selected from sulfonic acid groups, ether groups, and hydroxyl groups in a polymer solution prepared by dissolving a polymer in a solvent at a polymer concentration of 2 to 70%. or a surfactant having an amine structure and/or a sufficient amount of silicon to exhibit an antifoaming effect, and is soluble in the solvent,
and 20 to 95% of the amount necessary for the polymer solution to gel the gelling liquid that does not dissolve in the polymer.
It is characterized in that it basically consists of the following: In addition, the method for manufacturing the compressed layer of the printing blanket according to the present invention includes using a polymer in a solvent at a polymer concentration of 2.
A surfactant having at least one kind of functional group among a sulfonic acid group, an ether group, and a hydroxyl group and/or a sufficient amount of silicon to exhibit an antifoaming effect are added to a polymer solution dissolved at ~70%, and 20 to 95% of the amount necessary for gelling the polymer solution is added to a gelling liquid that is soluble in the solvent and insoluble in the polymer, and a composition that basically consists of this is coated on the base fabric. The method is characterized by immersing the gelling liquid, removing the solvent, drying, and optionally vulcanizing. According to the present invention, it is possible to easily produce a compressed foam layer having micropores of 100 μm or less with an open cell ratio of 100%, and therefore, the produced printing blanket has no swelling of the blanket surface under printing pressure. can be absorbed uniformly and reliably, making it possible to obtain clear prints. In addition, the relaxation rate of compressive strain during high-speed printing becomes faster, making it possible to obtain clearer printing, which has the advantage of improving the durability of the plate cylinder or blanket. The present invention will be explained in more detail. First, as the polymer used in the present invention, general rubber, thermoplastic resin, or a compound containing this rubber or this thermoplastic resin as a main component can be used. Preferably, the ink is resistant to ink and/or has strong resistance to solvents used during ink replacement. For example, it can be one or more of butadiene-acrylonitrile copolymer, polyvinyl chloride, and chloroprene rubber. It may also be a compound obtained by adding and kneading a vulcanizing agent such as sulfur, a vulcanization accelerator, a reinforcing agent such as carbon black, an anti-aging agent, and a processing aid such as stearic acid to the main component such as rubber. Next, as the solvent for dissolving this polymer, basically any solvent may be used as long as it can be dissolved in the gelling liquid. That is, since the gelling liquid is to be gelled by mutually diffusing with the solvent of the polymer solution, the solvent must be mutually diffusing 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 workability will be significantly 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%, the specific gravity is 0.35-0.40
A foam of 60% is obtained with a specific gravity of 0.65
A foam of ~0.75 can be obtained. This is because, as will become clear from the manufacturing method described below, 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, a surfactant having at least one functional group selected from sulfonic acid groups, ether groups, and hydroxyl groups or having an amine structure and/or silicone in an amount sufficient to have an antifoaming effect are added to the polymer solution. Added. This group of materials is added to facilitate pore size adjustment according to the polymer concentration described above. This is particularly effective when it is desired that the pores be of a desired size, that is, 10 μm or more. The pore size can be adjusted by changing the concentration of the above-mentioned polymer, the type of substance in this group, and the amount added. Examples of surfactants that are pore regulators include sodium dotesylbenzenesulfonate, Na di-alkyl sulfosinate, polyoxyethylene oleate, polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene oleate. One or more types of ethylene stearyl ether, dodecyl dimethylamine, octadecyl amine, etc. can be used, and silicones such as SAG
-471, SAG-100 (manufactured by Nippon Unicar Co., Ltd.),
SH-193 (manufactured by Toray Silicon Co., Ltd.) etc. can be used, but is not basically limited to these. The amount added can be functionally varied depending on pore size and polymer concentration, type of surfactant and/or silicone;
Generally, in order to provide pores of 100 to 10 μm, it is preferable to add 20% or less. If more than 20% is added, the pore size becomes too large. In general, in the case of an organic surfactant alone, preferably
Add 0.1-15%, 0.1-15% for silicone alone
It is recommended to add 15%. When surfactants and silicones are used in combination, it is preferred that the amounts 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 at 5% or more, it has an antifoaming effect. Therefore, when silicone is added, it must be in an amount sufficient to have an antifoaming effect, and if the amount of silicone added is less than 0.1%, the antifoaming effect will not be sufficient. Next, the gelling liquid added to this polymer solution needs to be a liquid that is insoluble in the polymer and soluble in the solvent. This is to selectively elute the solvent from this polymer solution as described above, and therefore the liquid is such that the affinity between the solvent and the gelling liquid is greater than the affinity between the solvent and the polymer. . Basically, there are no limitations as long as it is like this. For example, water, monools such as methanol and ethanol, glycerin,
It can be one kind or a mixture of two or more kinds of polyols such as ethylene glycol. The amount of this gelling solution added is 20 to 95% of the amount of gelling solution.
It is. Here, the amount of gelling liquid refers to the amount of gelling liquid required for the polymer solution to reach the gelling point. This gelling liquid is added to increase the elution rate of the solvent when forming a compressed layer, thereby increasing the film formation rate and generating pores with a fine cell structure. The amount of liquid
If it is less than 20%, there will be a mixture of large and small pores, and if it exceeds 95%, the polymer solution will partially gel, making sizing impossible. This composition will be used to manufacture the compressed layer of a printing blanket, and the manufacturing method will be explained. First, the above-described composition is coated on a woven fabric such as cotton, polyester, or nylon. 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 in this case may be the same as the gelling liquid contained in the composition, or may be different. For example, the gelling liquid contained in the composition can be alcohol and the gelling liquid in the immersion bath can be water, or vice versa, but considering economics etc., it is possible to use an immersion bath. It is preferable to use inexpensive water as the gelling liquid. Furthermore, the gelling liquid contained in the composition and the gelling liquid in the immersion bath may be the same. For example, both the gelling liquid in the composition and the gelling liquid in the immersion bath may be water. When the base fabric is immersed in the gelling liquid in this way, the solvent in the composition and the gelling liquid mutually diffuse and gel. This is because the affinity between the gelling liquid and the solvent is greater than the affinity between the polymer and the solvent, so the polymer is in an undissolved state rather than a dissolved state, and the polymers coagulate and aggregate together. At this time, spaces are created in areas other than the agglomerated and aggregated polymer parts. This becomes micropores, and since the pores generated in this way are caused by the mutual diffusion of the polymer solvent and the gelling liquid, they are considered to be 100% continuous pores. Furthermore, although it is clear that such micropores are generated at the gel point, unless the composition contains 20 to 95% of the amount of gelling liquid, it will not be possible to immerse it in the solvent. Because the gelled liquid in the bath does not quickly diffuse into each other and remains in a semi-gel state for a long time, the formed film becomes weak during the pore generation process, the pore walls become easy to tear, and the stability of the pores decreases. As the size of the hole becomes larger, the size of the hole becomes less constant. According to the present invention, since the composition contains a gelling liquid in advance (that is, it contains a gelling liquid close to gelling), it quickly gels when immersed in the gelling liquid, and the walls of the pores become gelled. Strength increases in a short time. In other words, fine pores with stable dimensions can be formed. This gelling solution for immersion may be at room temperature, but
It may be heated to further accelerate the gelation rate. For example, add this gelling solution to 50~
It may be kept at about 100°C. In this case, the pores become even finer. The gelled material is deliquified and, for example,
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 required, so it may be dried for about 30 minutes at a temperature of 150° C. or lower, for example. Of course, the drying method, drying time, drying temperature, etc. are not limited in the present invention. It can be determined functionally by considering the type of composition and the like. A necessary number of base fabrics and a surface rubber layer are provided on the foamed layer thus produced by a conventional method to obtain a printing blanket. Examples of the present invention will be described below. Example 1 Composition of composition Group A butadiene/acrylonitrile copolymer
100 parts by weight (Hiker 1042; manufactured by Nippon Zeon Co., Ltd.) Zinc white 5 parts by weight Stearic acid 1.0 〃 Carbon black (SRF) 50 〃 Anti-aging agent 1.0 〃 Total 157 〃 Group B antifoaming agent (Silicone; SAG-471; Japan Unicar Co., Ltd.) 1.0 parts by weight Group C Sulfur 1.5 parts by weight Vulcanization accelerator 3.0 Total 4.5 Group D Dimethylformamide; Gelling liquid (water) = 1:
1 {weight ratio) When compounding agents of group A are kneaded with a roll and dissolved in dimethyl formaldehyde to a rubber content of 40%, a rubber paste with a viscosity of 450 poise is obtained. Add group B antifoaming agent and silica to this, stir thoroughly, add group C vulcanizing agent and vulcanization accelerator, and then add 100 g of dimethylformamide:water = 1:1 solution.
8.0 g of the sample was added to the sample while stirring thoroughly. This composition was coated with a doctor knife to a thickness of 0.35 mm onto a cotton fabric having a thickness of 0.41 mm and a number of strokes of 61 lines/inch. This was immersed in water at 18°C for 20 minutes, dehydrated, and dried in a dryer at 150°C for 20 minutes, at the same time completing the vulcanization of the rubber. A cross-sectional photograph of this foam is shown in FIG. FIG. 1 is a 75x micrograph of a compressed layer produced 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 the photo, most of the compressed layer according to the present invention consists of micropores of 50 μm or less, and the open cell ratio is 100%, whereas the conventional one has micropores of 100 μm or less.
It is difficult to form uniform pores with the following micropores, the pores have non-uniform dimensions and large dimensions, and the open cell rate is low. Next, from the composition according to the present invention, an antifoaming agent (group B)
A compressed layer was similarly produced using the composition except for. A 75x microscopic photograph of the cross section of the compressed layer is shown in Figure 3. As is clear from FIG. 3, when group B is not included, the number of micropores of 10 μm or less increases. Example 2 A compressed layer manufactured by the method of the present invention according to the composition shown in the table below, a compressed layer manufactured using an organic blowing agent, and a compressed layer manufactured by mixing hollow microspheres into an elastomer (Japanese Patent Publication No. 52 - No. 7371) using a printing blanket manufactured using compressive stress -
A strain curve test was conducted. The results were as shown in Figure 4.

【table】

[Table] As is clear from Fig. 4, the blankets C ₁ , C ₂ , C ₃ , and C ₄ of the present invention are the conventional blanket A, which has a compressed layer in which micro hollow spheres are mixed into an elastomer, and the blanket A, which has a compressed layer in which micro hollow spheres are mixed into an elastomer. Blanket B manufactured using
showed an extremely superior stress-strain curve. When we conducted a printing test using these blankets, we found that they had excellent halftone dot reproducibility and had durability that was comparable to A above.
This was found to be a 2-3 times increase over the standard blanket. This is thought to be because the strain rate is much higher for the same compression force than the conventional blankets A and B, and the compression layer has the ability to 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 printing blanket layer prepared from a composition according to the invention without the antifoaming agent. FIG. 4 is a graph showing the stress-strain ratio of the printing blanket of the present invention and the conventional printing blanket. A... A stress-strain graph of a printing blanket with a compressed layer manufactured by mixing micro hollow spheres in an elastomer. B...Stress-strain rate graph of a printing blanket with a compressed layer manufactured using an organic blowing agent. C ₁ , C ₂ , C ₃ , C ₄ ... Stress-strain rate graph of a printing blanket provided with a compressed layer manufactured according to the present invention.

Claims (1)

[Claims] 1. Polymer in a solvent with a polymer concentration of 2 to 70%
(The same applies below weight percent) A surfactant having at least one functional group selected from sulfonic acid groups, ether groups, and hydroxyl groups or having an amine structure and/or sufficient to exhibit antifoaming action in the dissolved polymer solution. The method basically consists of adding an amount of silicone and adding a gelling liquid that is soluble in the solvent and insoluble in the polymer in an amount of 20 to 95% of the amount necessary for gelling the polymer solution. A composition for producing a compressed layer of a printing blanket. 2. The composition 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 thermoplastic resin as a main component. 3. The composition for producing a compressed layer of a printing blanket according to claim 2, wherein the polymer is resistant to printing ink and/or solvents used during ink change. 4 The polymer is butadiene. A patent claim characterized in that it is a compound containing as a main component one or more of acrylonitrile copolymer, polyvinyl chloride, and chloroprene rubber, or one or more of these butadiene-acrylonitrile copolymers, polyvinyl chloride, and chloroprene rubber. A composition for producing a compressed layer of a printing blanket according to Scope 3. 5. The solvent is selected from N,N'-dimethylformamide, diethylformamide, dimethylacetamide and dimethylsulfoxide.
The composition 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 composition 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 composition 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 composition 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. The printing blanket according to claim 1, wherein the gelling liquid is one or a mixture of two or more selected from the group consisting of water, monools, and polyols. A composition for producing a compressed layer. 10. The composition for producing a compressed layer of a printing blanket according to claim 9, wherein the gelling liquid is water. 11 A polymer solution prepared by dissolving the polymer in a solvent capable of dissolving the polymer at a polymer concentration of 2 to 70% has at least one functional group selected from sulfonic acid groups, ether groups, and hydroxyl groups, or has an amine structure. In addition to adding a surfactant and/or silicone in an amount sufficient to exhibit an antifoaming effect, a gelling liquid that is soluble in the solvent and insoluble in the polymer is added in an amount necessary for the polymer solution to gel. The composition for producing a compressed layer of a printing blanket, which basically consists of adding 20 to 95% of the amount, is coated on a base fabric, immersed in a gelling solution, solvent removed, dried, and optionally vulcanized. A method for producing a compressed layer of a printing blanket, characterized in that: 12. The method for producing a compressed layer of a printing blanket according to claim 11, wherein the polymer is a rubber or a thermoplastic resin, or a compound containing the rubber or thermoplastic resin as a main component. 13. A method for producing a compressed layer of a printing blanket according to claim 12, characterized in that the polymer is resistant to printing inks and/or solvents used during ink replacement. 14. The polymer is one or more of butadiene/acrylonitrile copolymer, polyvinyl chloride, and chloroprene rubber, or a compound containing one or more of these butadiene/acrylonitrile copolymers, polyvinyl chloride, and chloroprene rubber as a main component. A method for manufacturing a compressed layer of a printing blanket according to claim 13, characterized in that: 15 The solvent is 1 selected from N,N' dimethylformamide, diethylformamide, dimethylacetamide and dimethylsulfoxide.
A method for producing a compressed layer of a printing blanket according to any one of claims 11 to 14, characterized in that it is a species or a mixture of two or more species. 16. The method for producing a compressed layer of a printing blanket according to any one of claims 11 to 15, characterized in that the surfactant and/or the silicone is added in an amount of 20% or less. 17. The method for producing a compressed layer of a printing blanket according to claim 16, wherein when the surfactant is added alone, the amount added is 0.1 to 15%. 18. The method for producing a compressed layer of a printing blanket according to claim 16, wherein when the silicone is added alone, the amount added is 0.1 to 20%. 19. The printing blanket according to claim 11, wherein the gelling liquid is one or a mixture of two or more selected from the group consisting of water, monools, and polyols. Production method of compression method. 20. The method for producing a compressed layer of a printing blanket according to claim 19, characterized in that the gelling liquid contained in the composition and/or the gelling liquid in the immersion bath is water.