JP2003182257A - Printing blanket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing blanket which suppresses the generation of static electricity even in waterless printing of a direct plate making type printing machine, and has a surface printing layer with no fear that a printing plate may be broken. <P>SOLUTION: In this (exemplified) printing blanket 10 having the surface printing layer 11 and a support layer 12, the printing layer 11 is composed of a rubber composition including an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer (ZSN) and other rubber materials; and preferably, the ZSN occupies 5-35 pts.wt. when the total amount of the ZSN and the other rubber materials is set at 100 pts.wt. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to offset printing,
In particular, it relates to a printing blanket that can be advantageously used in waterless printing in a direct plate-making printing machine.

[0002]

2. Description of the Related Art Offset printing is a printing method in which an ink image on a printing plate is transferred through a printing blanket and reproduced on a printing material such as printing paper. The offset printing unit section mainly includes a plate cylinder, a blanket cylinder, and an impression cylinder. The printing plate mounted on the plate cylinder has water which requires the supply of dampening water to the non-image area, and the printing plate which does not require supply of dampening water to the non-image area. There are two types of printing plates. In the printing method using these two types of printing plates, the waterless printing method does not require management and adjustment of dampening water, and thus the waterless printing method has been gradually increasing in recent years.

In particular, recently, a type of printing machine having a plate-making machine in the printing machine itself has been commercially available. The plate used therefor is a laminated body of silicon / metal / PET, and the silicon / metal layer is blown by a laser to perform image formation. In order to perform such a printing machine with good printability and workability, a printing blanket suitable for printing is required, but at present, various improvements are left. One of the improvements to be made is that in the case of a blanket made mainly of oil-resistant nitrile butadiene rubber (NBR), static electricity is generated in the absence of fountain solution to destroy the printing plate. Heretofore, carbon black has been blended as a conductive substance in a conductive roller in order to blend a conductive rubber for the purpose of reducing static electricity.

However, in the case of a printing blanket, when carbon black is blended to such an extent that conductivity can be exhibited and the surface printing layer is polished by a conventional method, the surface roughness becomes fine and the paper at the time of printing is printed. There is a problem that the distance becomes worse. This decrease in the paper separation property is a serious problem since high-speed printing has been emphasized in recent years.

[0005]

As described above, generation of static electricity when performing waterless printing in a direct plate-making type printing machine is solved by simply adding an ordinary conductive substance to the rubber component of the printing blanket. It is not a problem of being caused, and it is also necessary to improve so as not to cause a decrease in printing performance and durability. The purpose of the present invention is to
It is intended to provide such a printing blanket.

[0006]

Accordingly, the present inventors have conducted various studies on the rubber composition constituting the surface printing layer of the printing blanket from the viewpoint of accomplishing the above-mentioned object, and as a result, have found that it is known as a water-swellable polymer substance. By using the known ethylene oxide-propylene oxide-allyl glycidyl ether copolymer (hereinafter sometimes abbreviated as ZSN) in combination with another rubber material, it is effective in preventing the generation of static electricity, and unexpectedly. It was found that even when contacting with printing ink, the degree of swelling was small and the flexibility was not different from that of the conventional one, and based on this knowledge, further studies were conducted to complete the present invention.

That is, the present invention is: 1) In a printing blanket having a surface printing layer and a support layer, the surface printing layer is composed of a rubber composition containing an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer. 2) In the rubber composition, when the total amount of the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer and the rubber material is 100 parts by weight, the copolymer The printing blanket according to the above item 1), wherein the proportion of the polymer is from 5 to 35 parts by weight, and 3) the blanket for waterless printing in a direct plate-making printing machine, according to the item 1) or 2) above. A printing blanket.

The printing blanket of the present invention is extremely unlikely to damage the printing plate because static electricity is suppressed even when continuously used for waterless printing in a direct plate making type printing machine. Moreover, the degree of swelling by immersion in ink is small, and it has the flexibility required for transfer. Specifically, the surface resistance value of the printing blanket of the present invention is 7th power or less, and can be suppressed to at least 2/3 or less as compared with the case where the ZSN is not added.

It has not hitherto been known to add a water-swelling substance such as ZSN as a component of the surface printing layer, but the surface printing layer consisting of a very thin rubber layer is based on an oil resistant rubber material. From the viewpoint of swelling property, it has been recognized that coexistence of a water-swelling substance should be avoided. Thus, from a conventional perspective,
It can be said that the above-mentioned effects of the present invention are extremely unexpected and beyond the range of prediction. Incidentally, Japanese Patent No. 3111510 discloses a ZSN water-swellable vulcanizate, but there is no disclosure of using this together with another rubber material, and no mention is made of its specific use. . on the other hand,
JP-A-2001-115005 discloses a crosslinkable rubber composition prepared by using, as a rubber material, a polyether copolymer having a specific property, alone or in combination with an ethylenically unsaturated nitrile-conjugated diene copolymer rubber. Is disclosed to be used for a rubber roll, but it is mainly intended to be used for a rubber roll for OA equipment.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. As an example of the configuration of the printing blanket, FIG.
As illustrated in, the surface printing layer 11 is provided on the support layer 12 composed of the compressive layer 14 and the reinforcing layer (consisting of the base cloth layers 13a, 13b, and 13c in this example) via the upper cloth 13d. An example is a flat-plate printing blanket 10 that is laminated in this order. This type of blanket is integrally molded by vulcanization and is used by mounting it on the cylinder of a printing machine.

Further, a printing blanket having a replaceable surface printing layer, for example, a reinforcing layer as disclosed in JP-A-6-344682, a base layer optionally provided with a compression layer, and a further surface In a printing blanket provided with a layer, in the printing blanket provided with an adhesive layer on any one or both of the base layer and the surface layer,
It is also possible to apply the surface printing layer in the present invention to the surface printing layer. On the other hand, a printing blanket to be applied to a printing apparatus (for example, Japanese Patent Application Laid-Open No. 11-309937) having a supply roll around which a long blanket is wound and a recovery roll thereof, the surface printing layer and the support layer ( Type (including a compressible layer).

The printing blanket of the present invention may be composed of a surface printing layer and a support layer for supporting the surface printing layer, and the surface printing layer is composed of a rubber composition containing ZSN. It is characterized by The ZSN
Is a polyalkylene oxide copolymerized with allyl glycidyl ether as a cross-linking point, for example, 40 to 90 mol% of ethylene oxide, 10 to 60 mol% of propylene oxide, and 1 to 1 of allyl glycidyl ether.
A copolymer of 5 mol% is used. If the copolymerization ratio of ethylene oxide does not reach this range, the effect of reducing the electric resistance becomes small, which is not preferable.

The surface printing layer in the printing blanket of the present invention is formed as a vulcanizate having a desired shape by preparing a rubber composition using the above ZSN together with other rubber materials. As the other rubber material here, rubber having little ink swelling property and oil resistance is used, and examples thereof include NBR, chloroprene rubber, polyurethane rubber,
Synthetic rubber such as polysulfide rubber can be used. Among these, NBR can be particularly preferably used.

In the rubber composition, the ZSN is preferably blended so that the ratio thereof is 5 to 35 parts by weight when the total amount of the ZSN and the rubber material is 100 parts by weight. If it is less than this mixing ratio, the effect of lowering the surface electric resistance value is small, and it is not possible to sufficiently suppress the generation of static electricity during use in printing, and if it is more than this ratio, the ink swelling property becomes too great or the blanket becomes soft. It is not preferable because it lacks sex.

In the production of the surface-printed layer, an organic solvent (eg, toluene) is added to unvulcanized rubber containing ZSN, and a predetermined amount of a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid, and a vulcanization accelerator are added thereto. Sulfur retarder and, if necessary, anti-aging agent, reinforcing agent, filler,
A rubber paste is prepared by adding various additives such as a softening agent and a plasticizer. Then, the obtained rubber paste may be formed by coating the support layer with a suitable coating means such as a blade coating method and drying to form an unvulcanized rubber layer, followed by vulcanization. . Alternatively, an unvulcanized rubber sheet made of rubber pound may be laminated on the base fabric and vulcanized to form the surface printing layer.

Examples of the above-mentioned vulcanizing agent include sulfur, organic sulfur-containing compounds, organic peroxides and the like. Among these, examples of the organic sulfur-containing compounds include N, N'-dithiobismorpholine and the like. Examples of the organic peroxide include benzoyl oxide and dicumyl peroxide. Examples of the above-mentioned vulcanization accelerator include thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide and tetramethylthiuram monosulfide; zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, tellurium dibutyldithiocarbamate, etc. Dithiocarbamic acids; thiazoles such as 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazole sulfenamide; organic accelerators such as thioureas such as trimethylthiourea and N, N'-diethylthiourea; and slaked lime Inorganic accelerators such as magnesium oxide, titanium oxide, and litharge (PbO).

Examples of the vulcanization accelerator aid include metal oxides such as zinc white, and fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid. Examples of the vulcanization retarder include aromatic organic acids such as salicylic acid, phthalic anhydride, and benzoic acid; N-nitrosodiphenylamine, N
Examples include nitroso compounds such as -nitroso-2,2,4-trimethyl-1,2-dihydroquinone and N-nitrosophenyl-β-naphthylamine.

Examples of the above-mentioned antiaging agents include imidazoles such as 2-mercaptobenzimidazole; amines such as phenyl-α-naphthylamine, N, N'-di-β-naphthyl-p-phenylenediamine; di-t. -Butyl-p-cresol; phenols such as styrenated phenol and the like can be mentioned. As the above-mentioned reinforcing agent, carbon black is used in a relatively small amount, and inorganic reinforcing agents such as silica-based or silicate-based white carbon, zinc white, surface-precipitating calcium carbonate, magnesium carbonate, talc, and clay, Alternatively, an organic reinforcing agent such as coumarone indene resin, phenol resin, high styrene resin (styrene-butadiene copolymer having a high styrene content) can be used.

Examples of the above-mentioned fillers include inorganic fillers such as calcium carbonate, clay, barium sulfate, diatomaceous earth, mica, asbestos and graphite, or organic fillers such as recycled rubber, asphalt, styrene resin and glue. Is mentioned. Examples of the softening agent include various plant-based, mineral oil-based, and synthetic softening agents such as fatty acids (stearic acid, lauric acid, etc.), cottonseed oil, tall oil, asphalt substances, paraffin wax, and the like.

Examples of the above-mentioned plasticizer include various plasticizers such as dibutyl phthalate, dioctyl phthalate and tricresyl phosphate. In addition to the above additives, for example, a tackifier, a dispersant, a solvent and the like may be appropriately blended. The thickness of the surface printing layer is usually 0.1 to 0.
It is preferably in the range of 4 mm. If it is less than this range, the solid portion may be deteriorated due to deterioration of the solid inking property, and if it exceeds this range, the surface printing layer on the vulcanization side in the rotation direction of the printing blanket during printing may have Since the deviation becomes large and the rate of change in circumference becomes large accordingly, the printed image may become unclear and the print quality may be deteriorated. Within the above range, especially 0.1 to
0.3 mm is preferable, and 0.15-0.3 mm
Is more preferable.

The surface of the surface printing layer formed as described above is usually finished by polishing to have a predetermined surface roughness and a predetermined thickness as described above. Surface roughness is closely related to printing accuracy, but usually 10-point average roughness (R
z), the range is 1 to 10 μm, more preferably 2 to 8 μm, and further preferably 3 to 6
It is in the range of μm. The flexibility of the surface-printed layer may be the same as conventional one, but generally, the tan δ value is 0.08 to 0.
It is preferably in the range of 12. If the hardness of the surface printing layer is less than the above range, an appropriate printing pressure cannot be obtained, and if it exceeds this range, the flexibility becomes insufficient.
That is, tan δ when dynamic change stress (distance between chucks 20 mm, measurement temperature 40 ° C., initial strain 2 mm, amplitude 50 mm, frequency 10 Hz) is applied is 0.08 to 0.1.
The range is 2. Here, the tan δ is a viscoelastic property observed when a dynamically changing stress such as a sine wave vibration is applied to the rubber composition, and a complex elastic modulus E ^* [the following formula (1)] Elastic modulus E'and loss elastic modulus E ''
Is expressed by the ratio [Equation (2) below].

E ^* = E ′ + i × E ″ (1) tan δ = E ′ / E ″ (2) [In the formula, i represents an imaginary number, and the following formula (3): i = (− 1) It is represented by ^1/2 (3). Next, the support layer constituting the printing blanket of the present invention has a function of supporting the surface printing layer when it is mounted on the cylinder of the printing machine and absorbing the vibration of the printing machine. This support layer is variously divided according to the intended function of the printing blanket, but is not particularly limited in the present invention. For example, in FIG. 1, the compressible layer 12 and the reinforcing layer (in this example, the base cloth layers 13 a, 1
3b and 13c). The support layer may be prepared by a conventional method, an example of which is as follows.

When the support layer has a base cloth layer, examples of the material thereof include woven cloth or non-woven cloth made of various fibers such as cotton, polyester and rayon. When the support layer has a compressible layer, the material thereof is an elastomer and is usually formed into a porous shape having excellent vibration absorption. Generally, the porous structure of the compressible layer is mainly divided into those having an independent pore structure in which the voids in the layer are independent, and those having a continuous pore structure in which the voids in the layer are connected. In the invention, a compressible layer having an independent pore structure is preferably used. The reason is that the compressible layer having an independent pore structure is generally durable and is less likely to cause settling even during printing for a long time.

The above-mentioned compressible layer is a rubber paste mixed with microballoons (hollow microspheres), such as base cloth, incompressible rubber layer (rubber layer not containing microballoons), PET film or the like. It is formed by coating on a support for forming, drying and vulcanizing. In the compressive layer, the porosity indicating the ratio of voids having an independent pore structure is preferably 15 to 80%. If the porosity of the compressible layer is less than the above range, the compressive layer may not exhibit sufficient impact absorption, and conversely, if the porosity exceeds the above range, the strength of the compressible layer Of the printing blanket is likely to occur, and the life of the printing blanket may be shortened. Even within the above range, the porosity of the compressible layer is more preferably 20 to 60%.

As the elastomer constituting the compressible layer, a material having excellent oil resistance is preferably used, and specific examples thereof include various synthetic rubbers and thermoplastic elastomers, and particularly vibration and impact loads. It is preferable to use an elastomer that has an excellent effect of absorbing the vibration and has a high damping property against vibration. Further, the elastomer is preferably excellent in oil resistance in consideration of resistance to printing ink and the like. Specific examples of such an elastomer include vulcanized rubbers such as acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR) and urethane rubber (U).

The compressive layer having an independent pore structure is formed by using unexpanded or expanded microballoons as described above. For example, a foaming agent which decomposes by heating to generate a gas is introduced into the matrix rubber. It is possible to employ a method in which the dispersed material is formed into a layer and the foaming agent is foamed simultaneously with the vulcanization of the rubber by heating during vulcanization. Moreover,
An independent pore structure may be formed by using a microballoon in which a gas is enclosed in a spherical shell made of a thermoplastic resin. Microballoons are disclosed in, for example, U.S. Pat. No. 4,770,928, JP-A-3-244595, and JP-A-7-505341.
Any of various conventionally known microballoons in which the shell body is formed of a thermoplastic resin can be used.

Among them, considering the oil resistance to printing inks, homopolymers of polymerizable monomers such as vinylidene chloride and (meth) acrylonitrile,
A co-aggregate containing these monomers or a ternary or higher multi-component copolymer containing these monomers is preferable. The particle size of the microballoons is not particularly limited, but in order to form a uniform independent pore structure and impart good compression characteristics to the compressible layer of the printing blanket for metal cans, the average particle size of the microballoons is approximately It is preferably about 10 to 200 μm. In the case of unfoamed microballoons described below, the particle size is the particle size after heating and foaming.

Specific examples of the above microballoons include:
Examples include the Expansell series microballoons manufactured by Nobel, and the microballoons manufactured by Matsumoto Yushi-Seiyaku Co., Ltd. Each of these microballoons is an unfoamed one in which the organic solvent that forms the voids is enclosed in the shell of the thermoplastic resin, and the above organic solvent is vaporized by heating, and the inside of the shell is It has been supplied with foamed ones having voids formed therein, and in the present invention,
Any of these can be used.

The support layer can be prepared, for example, by laminating a desired number of base fabrics and providing a compressive layer at a desired position in the usual manner. On the base cloth, a layer of a rubber composition for a compressible layer, in which microballoons are uniformly dispersed in an unvulcanized matrix rubber, is formed. The blending ratio of the microballoons is appropriately adjusted so that the porosity of the compressible layer is within the above range. Further, in the rubber composition, in addition to the above-mentioned both components, a rubber such as a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid, a vulcanization retarder and the like, as in the preparation of the surface printing layer. In addition to the components for vulcanizing, various additives such as an antiaging agent, a reinforcing agent, a filler, a softening agent and a plasticizer are added as necessary. The amount of these additives to be added may be similar to the conventional amount.

[0030]

EXAMPLES Next, the present invention will be described more specifically with reference to Comparative Examples and Examples. Examples 1 to 3 and Comparative Examples 1 and 2 The rubber composition for surface printing layer having each composition shown in Table 1 was dissolved in toluene and molded into a shape of 100 mm × 200 mm × 0.5 mm, and at 160 ° C. for 30 minutes. A vulcanized molded product was obtained by heating. Numerical units in the table represent parts by weight.

The following materials were used as the materials shown in Table 1. NBR uses "N232S" made by JSR, and ZS
N is "ZNS8030" manufactured by Nippon Zeon Co., Ltd., and polysulfide rubber is "Thiocor ST" manufactured by Toray Thiokol Co., Ltd.
The silica is "Nipsil R" manufactured by Nippon Silica Industry Co., Ltd.
S150 ", the silane coupling agent is" Si-69 "manufactured by Degussa, the pigment is" Titanium oxide A-100 "manufactured by Fuji Titanium, and the antiaging agent is manufactured by Ouchi Shinko Chemical Co., Ltd. "Nocrac NS-6", the vulcanization activator is "Zinc Oxide # 3" manufactured by Mitsui Mining & Smelting Co., Ltd., and the vulcanization agent is "Salfax PS" manufactured by Tsurumi Chemical Industry Co., Ltd. Used respectively.

[0032]

[Table 1]

For each of the vulcanizates obtained above, the surface resistance value, the weight change rate when immersed in toluene, and the tan
The results of measuring δ are shown in Table 2. [Test method] -Surface resistance value: R8340 manufactured by Advantest,
According to JIS K 6723, the surface resistance value (Ω) was measured at a voltage of 1000V. Weight change rate during immersion in toluene: The weight change rate (%) after immersion in toluene at 40 ° C. for 24 hours was measured. This measured value is related to the ink swelling property when used as a blanket and is preferably in the range of 90 to 110%. Tan δ: using DVE-V4 FT Rheospectler manufactured by Rheology, at room temperature, between chucks: 20 mm,
Initial strain: 2 mm, amplitude: 50 μm, measured at 10 Hz. This measured value represents the flexibility of the blanket and is 0.
It is preferably in the range of 08 to 0.12.

[0034]

[Table 2]

As a result of Table 2, ZSN in Examples 1 to 3
The molded product for the surface printing layer prepared by blending the above-mentioned compound has a much smaller surface resistance value than that of the comparative example 1 without ZSN addition, and therefore, less static electricity is generated, and when immersed in toluene. It can be seen that the rate of change in weight is small, the ink swellability is within the allowable range, and the value of tan δ shows that the flexibility is appropriate. On the other hand, like Comparative Example 2, when 40 parts by weight of ZSN is added to 100 parts by weight of the rubber content, it is shown that at least this system is not suitable in terms of the rate of weight change and tan δ.

[0036]

As described above, the printing blanket of the present invention is characterized in that the rubber composition constituting the surface printing layer contains ZSN, which reduces the surface resistance value. Even if it is continuously used for waterless printing, the generation of static electricity is extremely small. Therefore, there is no risk of the printing plate being destroyed by static electricity. In addition, the volume change rate due to ink immersion is small and the elasticity required for transfer is provided.

[Brief description of drawings]

FIG. 1 shows an example of a printing blanket configuration.

[Explanation of symbols]

10 blanket 11 Surface printing layer 12 Support layer 13a to 13c Base cloth layer 14 Compressible layer

Claims (3)

[Claims] 1. A printing blanket having a surface printing layer and a support layer, wherein the surface printing layer is composed of a rubber composition containing an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer. A blanket for printing. 2. In the rubber composition, when the total amount of the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer and the rubber material is 100 parts by weight, the ratio of the copolymer is 5 to 35 parts by weight. The printing blanket according to claim 1, which is a part. 3. The printing blanket according to claim 1, which is a blanket for waterless printing in a direct plate making type printing machine.