JP5501798B2 - Printing blanket - Google Patents

Description

  The present invention relates to a printing blanket used in a printing method such as an offset printing method.

In an offset printing method using a printing blanket, oil-based ink (oxidation polymerization type) or UV ink (ultraviolet curing type) is generally used as ink.
Of these, oil-based inks have been used for a long time, and are inexpensive and economical. On the other hand, since oil-based ink contains an organic solvent, it is necessary to pay sufficient attention to its handling in order to preserve the working environment.

  In addition, since oil-based inks require a relatively long time to cure, in order to prevent the ink of the lower printed matter from adhering to the back surface of the printed matter that has been stacked, It is necessary to spray the powder on either the front or back side of the printed material after printing. Therefore, sufficient care must be taken to prevent powder scattering in order to preserve the work environment.

On the other hand, UV ink is instantly cured by UV irradiation, so there is no need to spray powder when stacking, and it is basically superior to oil-based inks in terms of maintenance of the working environment because it does not contain organic solvents. Demand has been increasing in recent years.
As a printing blanket for oil-based inks, the amount of acrylonitrile is adjusted to about 31-35% for the surface rubber layer that constitutes the surface that comes into direct contact with the ink in consideration of swelling resistance to organic solvents and processability. The acrylonitrile-butadiene copolymer rubber (NBR), so-called medium-high nitrile rubber, is used alone, or is formed by blended rubber obtained by blending the medium-high nitrile rubber with other NBR having different acrylonitrile amount. A thing is generally used (refer patent document 1 grade | etc.,).

However, NBR has a problem that it swells excessively with respect to the acrylic monomer contained in the UV ink. If the surface of the surface rubber layer cannot swell to a certain extent, the transferability of the ink from the plate (inking property) will be insufficient and good printing will not be possible. Too much swelling.
When the printing is repeated, the surface rubber layer is excessively swollen by the UV ink, and when the thickness of the surface rubber layer is excessively increased and the hardness is greatly reduced, the surface rubber layer is easily deformed by an external force. Become.

As a result, when the ink is transferred from the plate to the surface rubber layer, or when the ink is retransferred from the surface rubber layer to the printing material, the amount of deformation of the surface rubber layer becomes too large and the print quality deteriorates. Cause problems.
Therefore, a printing blanket having a surface rubber layer formed of NBR such as medium-high nitrile rubber cannot be used for UV ink.

As a printing blanket for UV ink, a printing blanket in which a surface rubber layer is formed of a nonpolar rubber that does not swell excessively with respect to an acrylic monomer, particularly ethylene propylene diene rubber (EPDM), is preferably used.
In addition, in order to adjust the hardness of the surface rubber layer made of EPDM, the surface rubber layer has compatibility with the EPDM having a solubility parameter value (SP value) of 8 (cal / cm ³ ) ^1/2 , for example. In general, a process oil such as a paraffinic or naphthenic oil having an SP value of about 6 to 9 (cal / cm ³ ) ^1/2 is included.

In the offset printing method, the surface of the printing blanket is manually or automatically using a washing machine at the start or end of continuous printing, or at any time during printing to maintain print quality. Cleaning is performed (see Patent Document 2 and the like).
In the case of UV ink, as the cleaning liquid, glycol-based, ester-based, ether-based, etc. having good compatibility with an acrylic monomer having an SP value of about 12 (cal / cm ³ ) ^1/2 contained in the UV ink. The cleaning solution is preferably used. In particular, ester-based cleaning liquids are widely used as cleaning liquids for the UV ink because of their excellent ability to clean UV ink.

Japanese Patent Publication No. 7-17113 Japanese Patent Laid-Open No. 7-228071

However, according to the study by the inventors, the surface rubber layer made of EPDM and containing process oil such as paraffinic or naphthenic is easily swelled excessively by the ester-based cleaning liquid.
When the cleaning is repeated, the surface rubber layer is excessively swollen by the cleaning liquid, thereby excessively increasing the thickness of the surface rubber layer and drastically decreasing the hardness, so that the surface rubber layer is easily deformed by an external force. When the ink is transferred from the plate to the surface rubber layer, or when the ink is transferred again from the surface rubber layer to the printing material, the amount of deformation of the surface rubber layer becomes too large and the print quality is deteriorated. This causes a problem.

  An object of the present invention is to provide a novel printing blanket that does not swell excessively even after repeated washing using an ester-based cleaning solution suitable for UV ink cleaning, and that can always maintain good print quality. There is.

The present invention comprises at least a surface rubber layer, and the surface rubber layer uses ethylene propylene diene rubber alone as a rubber component , or uses ethylene propylene diene rubber and butyl rubber together, and per 100 parts by mass of the rubber component. A phthalate plasticizer and an adipate plasticizer each having a solubility parameter value of 10 (cal / cm ³ ) ^1/2 or more and 11 (cal / cm ³ ) ^1/2 or less, both of 10 parts by weight and 50 parts by weight agent, and a printing blanket which comprises at least one plasticizer which sebacate system selected from plasticizers or Ranaru group.

According to the inventor's investigation, all of the three types of plasticizers are contained in the surface rubber layer of a printing blanket made of EPDM, and the cleaning liquid such as ester is supplied to the surface of the surface rubber layer. When performing the cleaning operation, compared to conventional process oil, it has a characteristic that it is easily extracted from the surface rubber layer into the cleaning liquid.
Therefore, when the printing blanket is washed, the plasticizer is extracted from the surface rubber layer into the washing liquid instead of being swollen into the surface rubber layer, thereby suppressing excessive swelling of the surface rubber layer. As a result, the thickness of the surface rubber layer does not increase excessively and the hardness does not decrease significantly.

Therefore, the surface rubber layer can maintain an appropriate thickness, hardness and deformation amount suitable for printing, and can always maintain good print quality.
In addition, in this invention, it is based on the following reason that the content rate of the plasticizer per 100 mass parts of rubber parts is limited to 10 mass parts or more and 50 mass parts or less.
That is, when the content of the plasticizer is less than the above range, the surface rubber layer is caused to swell by being extracted from the surface rubber layer instead of the cleaning liquid at the time of cleaning, which is described above, by including the plasticizer. The suppression effect cannot be obtained.

On the other hand, not only the effect is not obtained even if the content ratio exceeds the above range, but an excess plasticizer bleeds to the surface of the surface rubber layer to change the wettability of the surface to UV ink. Or the surface roughness is increased, or it is transferred to a plate or a substrate to cause a problem that the printing quality is deteriorated.
In the present invention, the SP value of the plasticizer and other components is set to the Small molecular binding constant of Table 13-2 on page 287 of “Paint flow and pigment dispersion” (Kenji Ueki, published by Kyoritsu Shuppan Co., Ltd.). It shall be expressed by the value obtained based on it. The SP value of the mixture is expressed as a value obtained by arithmetically averaging the SP value of each component constituting the mixture in proportion to the molar fraction based on the description in Section 13.1.10 of the same page.

  According to the present invention, there is provided a novel printing blanket that can always maintain good print quality because it does not swell excessively even after repeated cleaning using an ester-based cleaning liquid suitable for UV ink cleaning. Can do.

The printing blanket of the present invention includes at least a surface rubber layer, and the surface rubber layer uses ethylene propylene diene rubber alone as a rubber component , or uses ethylene propylene diene rubber and butyl rubber in combination, and the rubber component 100 A phthalate plasticizer having a solubility parameter value of 8 (cal / cm ³ ) ^1/2 or more and 11 (cal / cm ³ ) ^1/2 or less, each of 10 parts by mass or more and 50 parts by mass or less per part by mass, adipate-based plasticizers, and is characterized in that it comprises at least one plasticizer which sebacate system selected from plasticizers or Ranaru group.

  Among them, EPDM is a copolymer of ethylene, propylene and diene, and the ratio of the three components is adjusted, the type of diene (ethylidene norbornene, dicyclopentadiene, etc.) is selected, or As described above, it does not swell excessively with respect to the acrylic monomer contained in the UV ink from among various types of EPDM having various properties synthesized by adding a new fourth component. Any of those having the original characteristics of EPDM as a nonpolar rubber can be used.

  Specific examples of such EPDM include, for example, MITSUI EPT4045 manufactured by Mitsui Chemicals, Inc. (diene content: ethylidene norbornene, iodine value: ultra high, ethylene content: medium, Mooney viscosity: 45 ML (1 + 4) 100 ° C.), Sumitomo Chemical ( Esprene (registered trademark) 505A (ethylene content 50%, diene content 9.5%, Mooney viscosity: 47 ML (1 + 4) 100 ° C.), 501A (ethylene content 52%, diene content 4.0%, Mooney viscosity) : 44 ML (1 + 4) 100 ° C.], 505 [ethylene content 50%, diene content 10.0%, Mooney viscosity: 59 ML (1 + 4) 125 ° C.], 5754 [ethylene content 63%, diene content 7.0%, Mooney viscosity : 30 ML (1 + 4) 100 ° C.], JSR (registered trademark) EP33 manufactured by JSR Corporation (diene content: ethyl) Down norbornene, diene content 8.1 wt%, C2: 52%, Mooney viscosity: 28ML (1 + 4) 125 ℃] one or more of the like.

As the rubber component, only the EPDM may be used alone (including the case where two or more kinds of EPDM are used in combination, the same applies hereinafter), or the EPDM may be used in combination with butyl rubber .
When EPDM and butyl rubber are used in combination as a rubber component, the content ratio of EPDM is considered in view of maintaining the characteristics that do not swell excessively with respect to the acrylic monomer by using EDPM as the rubber component described above. Is preferably 50% by mass or more, more preferably 25% by mass or more, based on the total amount of rubber.

However, considering the above characteristics, it is preferable to use only EPDM alone as the rubber component.
The SP value of the plasticizer that forms the surface rubber layer together with the rubber component is limited to 8 (cal / cm ³ ) ^1/2 or more and 11 (cal / cm ³ ) ^1/2 or less for the following reason by.
That is, a plasticizer having an SP value less than the above range is less likely to be extracted from the surface rubber layer into the cleaning liquid during cleaning than a plasticizer having an SP value within the above range. Therefore, repeating the washing makes the surface rubber layer easily swell excessively, and as a result, good print quality cannot be maintained.

A plasticizer having an SP value exceeding the above range is likely to bleed on the surface of the surface rubber layer because of low compatibility with EPDM. For this reason, the bleed causes a problem that the wettability of the surface with respect to UV ink is changed, the surface roughness is increased, or the surface is transferred to a plate or a printing material to deteriorate the printing quality.
Of the three types of plasticizers, the phthalate plasticizer is a phthalate ester, and among various compounds that can function as the plasticizer of the EPDM, the SP value is 8 (cal / cm ³ ) ^1/2. As mentioned above, what is 11 (cal / cm < ³ >) < ^1/2 > or less can be used.

Examples of the phthalate plasticizer include di-n-butyl phthalate [DBP, SP value: 9.3 (cal / cm ³ ) ^1/2 ], diethyl phthalate [DEP, SP value: 10.0 (cal / Cm ³ ) ^1/2 ], dimethyl phthalate [DMP, SP value: 10.7 (cal / cm ³ ) ^1/2 ] and the like.
The adipate plasticizer is an adipate of aliphatic dibasic acid esters, and among various compounds that can function as the plasticizer of EPDM, the SP value is 8 (cal / cm ³ ) ^{1/2. What is 2} or more and 11 (cal / cm < ³ >) < ^1/2 > or less can be used.

Examples of the adipate plasticizer include dioctyl adipate [DOA, SP value: 8.7 (cal / cm ³ ) ^1/2 ], diisobutyl adipate [DIBA, SP value: 8.9 (cal / cm ³ ). ^1/2 ] and the like.
The sebacate-based plasticizer is a sebacic acid ester of the aliphatic dibasic acid ester, and among various compounds that can function as the plasticizer of the EPDM, the SP value is 8 (cal / cm ³ ) ^1/2. As mentioned above, what is 11 (cal / cm < ³ >) < ^1/2 > or less can be used.

Examples of the sebacate plasticizer include dioctyl sebacate [DOS, SP value: 8.6 (cal / cm ³ ) ^1/2 ] .

Content of the previous SL plasticizer, rubber per 100 parts by per 10 parts by mass or more, being limited to 50 parts by weight, due to the following reason.

That is, when the content of the plasticizer is less than the above range, the amount of the plasticizer that is extracted from the surface rubber layer instead of the cleaning liquid at the time of cleaning and functions to suppress the swelling of the surface rubber layer is insufficient. It will be. Therefore, repeating the washing makes the surface rubber layer easily swell excessively, and as a result, good print quality cannot be maintained.
On the other hand, not only the effect is not obtained even if the content ratio exceeds the above range, but an excess plasticizer bleeds to the surface of the surface rubber layer to change the wettability of the surface to UV ink. Or the surface roughness is increased, or it is transferred to a plate or a substrate to cause a problem that the printing quality is deteriorated.

In consideration of further effectively suppressing the swelling of the surface rubber layer when the washing is repeated, the content of the plasticizer per 100 parts by mass of the rubber component is 20 parts by mass or more even within the above range. Is preferred.
The printing blanket of the present invention can be constructed in the same manner as in the prior art except that the surface rubber layer is provided. That is, the printing blanket may be formed of the surface rubber layer alone or may be a laminated structure of the surface rubber layer and the support layer. Further, as the support layer, any one having an arbitrary structure in which a base fabric made of synthetic or natural fibers, a compressible layer having a porous structure, or the like is laminated in an appropriate number of layers and arrangement can be used.

In order to produce the printing blanket of the present invention, first, the predetermined plasticizer and, for example, a vulcanizing agent, a vulcanization accelerator, a vulcanization acceleration aid, a scorch prevention agent, an antiaging agent are added to the rubber component containing EPDM. A rubber paste for the surface rubber layer is prepared by blending various additives such as a reinforcing agent, a filler, and a colorant and adjusting the viscosity by adding a solvent.
Next, the rubber paste for the surface rubber layer is applied (glue) to a predetermined thickness on the support layer or its precursor (including the unvulcanized rubber component), and then, for example, continuously The surface rubber layer is formed by heating to a predetermined temperature using a vulcanizer or a vulcanizing can to vulcanize the rubber component in the rubber paste. At this time, the unvulcanized rubber component in the precursor of the support layer is also vulcanized almost simultaneously.

Thereafter, if necessary, the surface of the surface rubber layer is polished to have a predetermined surface roughness and thickness to produce a printing blanket.
Alternatively, a rubber compound in which the predetermined plasticizer and other additives are blended with the rubber component, a vulcanized adhesive for vulcanization adhesion, if necessary, on a support layer or a precursor thereof, After separating and laminating the primer rubber paste layer, the rubber layer in the rubber compound is vulcanized by heating to a predetermined temperature using a continuous vulcanizer or vulcanizing can in the same manner. Form. At this time, the unvulcanized rubber component in the precursor of the support layer is also vulcanized almost simultaneously.

Thereafter, if necessary, the surface of the surface rubber layer is polished to have a predetermined surface roughness and thickness to produce a printing blanket.
Among the additives, examples of the vulcanizing agent include one or more of sulfur, an organic sulfur-containing compound, an organic peroxide, and the like. Examples of the organic sulfur-containing compound include 4,4'-dithiodimorpholine, and examples of the organic peroxide include benzoyl peroxide and dicumyl peroxide.

  Examples of the vulcanization accelerator include thiuram vulcanization accelerators such as tetramethylthiuram disulfide and tetramethylthiuram monosulfide, and dithiocarbamic acids such as zinc dibutyldithiocarbamate, zinc diethyldithiocarbamate, sodium dimethyldithiocarbamate, and tellurium diethyldithiocarbamate. , Thiazoles such as dibenzothiazyl disulfide, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolesulfenamide, thioureas such as trimethylthiourea, N, N′-diethylthiourea, or slaked lime, magnesium oxide, One type or two or more types of inorganic promoters such as titanium oxide and risurge (PbO) can be used.

Examples of the vulcanization acceleration aid include one or more metal oxides such as zinc white (zinc oxide) and fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid.
Examples of the scorch inhibitor (vulcanization retarder) include aromatic organic acids such as salicylic acid, phthalic anhydride and benzoic acid, N-nitrosodiphenylamine, N-nitroso-2,2,4-trimethyl-1,2-di Examples thereof include one or more of nitroso compounds such as hydroquinone and N-nitrosophenyl-β-naphthylamine, and N-cyclohexylthiophthalimide.

  Examples of the antioxidant include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, and N-phenyl-N′-isopropyl-p-. One or two kinds of amines such as phenylenediamine, or phenols such as di-t-butyl-p-cresol, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), styrenated phenol The above is mentioned.

  Examples of the reinforcing agent include inorganic reinforcing agents such as silica-based or silicate-based white carbon, carbon black, zinc white, surface-treated precipitated calcium carbonate, magnesium carbonate, talc, clay, or coumarone indene resin, One type or two or more types of organic reinforcing agents such as phenol resin and high styrene resin (styrene-butadiene copolymer having a high styrene content) can be used.

Examples of the filler include inorganic fillers such as calcium carbonate, clay, barium sulfate, diatomaceous earth, mica, asbestos, graphite, and organic fillers such as recycled rubber, powder rubber, asphalt, styrene resin, and glue. Or 2 or more types are mentioned.
Further, examples of the colorant include pigments of various colors.
In addition to the above, for example, a tackifier, a dispersant and the like may be appropriately blended with the rubber paste for the surface rubber layer.

  The compressible layer contained in the support layer has an independent pore structure formed by blending various rubbers with a foaming agent and foaming together with vulcanization of the rubber, or blending hollow microparticles. And those having a continuous pore structure formed by dispersing particles such as salt in rubber and vulcanizing the rubber, and then dissolving and removing particles such as salt with hot water or the like.

The following examples and comparative printing blankets were manufactured, measured for properties, and tested in an environment of 23 ± 1 ° C. and 55 ± 1% relative humidity unless otherwise specified.
<Example 1>
(Preparation of primer rubber paste)
Each component shown in Table 1 below was blended with toluene twice the total amount (130 parts by mass) to prepare a primer rubber paste.

Each component in the table is as follows.
NBR: Medium-high nitrile rubber, N232S manufactured by JSR Corporation, 35% acrylonitrile content
Coumarone resin: Tackifier Zinc flower: Zinc oxide, Vulcanization accelerating agent Stearic acid: Vulcanization accelerating agent DOA: Dioctyl adipate, plasticizer Sulfur powder: Vulcanizing agent Noxeller (registered trademark) DM: Vulcanization acceleration Agent, dibenzothiazyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd. Noxeller TT: vulcanization accelerator, tetramethylthiuram disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd. (preparation of rubber paste for compressible layer)
Each component shown in Table 2 was mixed with twice the total amount (162 parts by mass) of toluene to prepare a rubber paste for a compressible layer.

Each component in the table is as follows.
NBR: NIPOL (registered trademark) DN202 manufactured by Nippon Zeon Co., Ltd., 31% acrylonitrile content
Carbon black HAF 40: Reinforcing agent Zinc white: Zinc oxide, Vulcanization accelerating agent Stearic acid: Vulcanization accelerating agent DOA: Dioctyl adipate, plasticizer Powdered sulfur: Vulcanizing agent Noxeller DM: Vulcanization accelerator, dibenzothia Nozeller TT: Vulcanization accelerator, Tetramethylthiuram disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd. Microballoon: Matsumoto Microsphere (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) Registered trademark) F50D
(Preparation of support layer precursor)
After applying the primer rubber paste on one surface of one cotton cloth, the operation of pasting another cotton cloth on the same is repeated, and two cotton cloths are laminated through the primer rubber glue to form a laminate A. did.

Further, after applying the rubber paste for the compressible layer to one surface of a separately prepared cotton cloth, the rubber paste for the compressible layer is vulcanized and bonded to the cotton cloth through a continuous vulcanizer. Thus, a laminate B of a compressible layer having an independent pore structure originating from the microballoon and a cotton cloth was formed. The vulcanization conditions were a pressure of 19.6 kPa, a temperature of 140 ° C., and a vulcanization time of 30 minutes.
Next, the primer rubber paste is applied to the surface of the exposed cotton cloth on one side of the previously formed laminate A, and then the laminate B is placed on the primer rubber paste so that the compressible layer contacts the primer rubber paste on the laminate A. A precursor of a support layer having a four-layer structure of cotton cloth (upper base cloth) / compressible layer / cotton cloth (lower base cloth) / cotton cloth (lower base cloth) / cotton cloth (lower base cloth) was prepared. .

(Preparation of rubber paste for surface rubber layer)
100 parts by mass of EPDM [MITSUI EPT4045 manufactured by Mitsui Chemicals, Inc.] and 20 parts by mass of dioctyl sebacate [DOS, SP value: 8.6 (cal / cm ³ ) ^1/2 ] as a plasticizer, Table 3 The rubber paste for the surface rubber layer was prepared by blending each component shown in the above with twice the total amount (163.3 parts by mass) of toluene.

Each component in the table is as follows.
Silica: Nipsil (registered trademark) VN3 manufactured by Tosoh Silica Corporation
NOCRACK (registered trademark) NS-6: anti-aging agent, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), manufactured by Ouchi Shinsei Chemical Co., Ltd. Epsilon Blue: pigment Zinc Hua No. 1: oxidation Zinc, vulcanization accelerating agent Stearic acid: Vulcanization accelerating agent Powdered sulfur: Vulcanizing agent Noxeller DM: Vulcanization accelerator, dibenzothiazyl disulfide, manufactured by Ouchi Shinsei Chemical Co., Ltd. Noxeller TT: Vulcanization accelerator , Tetramethylthiuram disulfide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. Barnock (registered trademark) R: vulcanizing agent, 4,4'-dithiodimorpholine, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. retarder CTP: scorch inhibitor , N-cyclohexylthiophthalimide, manufactured by Toray Industries, Inc. (Manufacture of printing blankets)
The rubber paste for the surface rubber layer is applied to the surface of the cotton fabric as the upper base fabric among the precursors of the support layer prepared previously, and the rubber paste for the surface rubber layer is added through a continuous vulcanizer. The surface rubber layer is formed by vulcanization, and the primer rubber paste contained in the precursor is vulcanized to vulcanize and bond the surface rubber layer, each cotton cloth, and the compressible layer to be integrated with the surface rubber layer. Then, the surface of the surface rubber layer is polished, and the surface rubber layer / cotton cloth (upper base cloth) / compressible layer / cotton cloth (lower base cloth) / cotton cloth (lower base cloth) 5 A printing blanket having a layer structure was produced.

The vulcanization conditions were a pressure of 19.6 kPa, a temperature of 150 ° C., and a vulcanization time of 30 minutes.
The thickness of each layer is as follows: the surface rubber layer is 0.4 mm, the compressible layer is 0.5 mm, two cotton cloths as the lower layer base cloth, and one cotton cloth as the upper layer base cloth are both 0.3 mm, The primer rubber glue layer between the two cotton cloths as the lower base cloth and the primer rubber glue layer between the uppermost cotton cloth and the compressible layer of the two sheets were each 0.05 mm.

<Example 2>
Surface rubber in the same manner as in Example 1 except that 20 parts by mass of dioctyl adipate [DOA, SP value: 8.7 (cal / cm ³ ) ^1/2 ] was used as the plasticizer instead of dioctyl sebacate. A layered rubber paste was prepared, and a printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that the surface rubber layer rubber paste was used.

The thickness of each layer was the same as in Example 1.
<Example 3>
Example 1 except that 20 parts by mass of di-n-butyl phthalate [DBP, SP value: 9.3 (cal / cm ³ ) ^1/2 ] was used in place of dioctyl sebacate as a plasticizer. A rubber blank for the surface rubber layer was prepared as described above, and a printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that the rubber paste for the surface rubber layer was used.

The thickness of each layer was the same as in Example 1.
<Example 4>
As a rubber component, 75 parts by mass of the EPDM and 25 parts by mass of butyl rubber are used in combination, and as a plasticizer, diethyl phthalate [DEP, SP value: 10.0 (cal / cm ³ ) ^1/2 instead of dioctyl sebacate. A printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that 20 parts by mass and 25 parts by mass of silica were used.

The thickness of each layer was the same as in Example 1.
<Example 5>
Other than using 20 parts by mass of dimethyl phthalate [DMP, SP value: 10.7 (cal / cm ³ ) ^1/2 ] instead of dioctyl sebacate as the plasticizer, and the amount of silica being 25 parts by mass Produced a printing blanket having a five-layer structure in the same manner as in Example 1.

The thickness of each layer was the same as in Example 1.
<Comparative example 1>
Except for using 20 parts by mass of naphthenic process oil [process R200 manufactured by Japan Energy, SP value: 6.7 (cal / cm ³ ) ^1/2 ] instead of dioctyl sebacate as a plasticizer. A rubber paste for the surface rubber layer was prepared in the same manner as in Example 1, and a printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that the rubber paste for the surface rubber layer was used.

The thickness of each layer was the same as in Example 1.
<Comparative example 2>
Other than using 20 parts by mass of paraffinic process oil [Fujikosan Co., Ltd. process oil P200, SP value: 7.2 (cal / cm ³ ) ^1/2 ] instead of dioctyl sebacate as a plasticizer. Prepared a rubber paste for the surface rubber layer in the same manner as in Example 1, and a printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that the rubber paste for the surface rubber layer was used.

The thickness of each layer was the same as in Example 1.
<Comparative Example 3>
Surface rubber in the same manner as in Example 1 except that 20 parts by mass of dioctyl phthalate [DOP, SP value: 7.9 (cal / cm ³ ) ^1/2 ] was used instead of dioctyl sebacate as a plasticizer. A layered rubber paste was prepared, and a printing blanket having a five-layer structure was produced in the same manner as in Example 1 except that the surface rubber layer rubber paste was used.

The thickness of each layer was the same as in Example 1.
<Comparative example 4>
As a plasticizer, instead of dioctyl sebacate, a polyester plasticizer [Rio & Haas Japan Co., Ltd. thiocol TP90B, SP value: 12.6 (cal / cm ³ ) ^1/2 ] 20 parts by mass A rubber paste for the surface rubber layer was prepared in the same manner as in Example 1 except that it was used, and a printing blanket having a five-layer structure was prepared in the same manner as in Example 1 except that the rubber paste for surface rubber layer was used. Manufactured.

The thickness of each layer was the same as in Example 1.
<Measurement of swelling ratio for cleaning liquid>
The printing blanket manufactured by the Example and the comparative example was sliced, and the surface rubber layer (thickness 0.3 mm as mentioned above) was taken out.
Next, the surface rubber layer was immersed in an ester cleaning solution (ester cleaning agent used in a wet cleaning cloth for UV ink “Prepack” manufactured by Nippon Baldwin Co., Ltd.) maintained at a liquid temperature of 23 ± 1 ° C. After leaving still for 24 hours, it pulled up and measured the volume, and change rate (DELTA) V% with respect to the volume before immersion was calculated | required as a swelling rate of the said surface rubber layer.

The smaller the swelling ratio is, the more the surface rubber layer does not swell excessively when washing with a washing liquid is repeated, and a good print quality can always be maintained. Specifically, those having a swelling ratio of 50% or less were evaluated as good, and those exceeding 50% were evaluated as defective.
<Bleed observation>
The printing blankets produced in the examples and comparative examples were allowed to stand at 25 ° C. for 168 hours, and then the surface of the surface rubber layer was observed to evaluate the presence or absence of bleeding. It is necessary that no bleeding occurs on the surface of the surface rubber layer.

  The above results are shown in Tables 4 and 5.

From the results of Comparative Examples 1 and 2 in Table 4, it was found that the process oil was not extracted into the cleaning liquid, and as a result, the surface rubber layer was excessively swollen with a swelling rate exceeding 50%.
Further, from the results of Comparative Example 3, when a plasticizer having an SP value of less than 8 (cal / cm ³ ) ^1/2 is used, the plasticizer is difficult to be extracted into the cleaning liquid. Was found to cause excessive swelling with a swelling ratio exceeding 50%.

From the results of Comparative Example 4 in Table 5, when a plasticizer having an SP value exceeding 11 (cal / cm ³ ) ^1/2 is used, the surface of the plasticizer is low because the plasticizer has low compatibility with EPDM. It was also found that the rubber layer surface tends to bleed.
On the other hand, from the results of Examples 1 to 5 in Tables 4 and 5, phthalate plasticizers, adipate plasticizers, and sebacate plastics having SP values of 8 to 11 (cal / cm ³ ) ^1/2. In the case where an agent or a phosphate plasticizer is used, these plasticizers are extracted well into the cleaning liquid as the cleaning liquid swells. It was found that swelling can be suppressed. It has also been found that these plasticizers are excellent in compatibility with EPDM and do not bleed on the surface of the surface rubber layer.

<Examples 6 to 9, Comparative Examples 5 and 6>
The content ratio of dioctyl adipate [DOA, SP value: 8.7 (cal / cm ³ ) ^1/2 ] as a plasticizer is 5 parts by mass per 100 parts by mass of rubber (Comparative Example 5), 10 parts by mass ( Example 6), except that it was 30 parts by mass (Example 7), 40 parts by mass (Example 8), 50 parts by mass (Example 9), and 60 parts by mass (Comparative Example 6). Similarly, a rubber paste for the surface rubber layer was prepared, and a printing blanket having a five-layer structure was produced in the same manner as in Example 2 except that the rubber paste for the surface rubber layer was used.

The thickness of each layer was the same as in Example 2.
The printing blanket produced in each of the above Examples and Comparative Examples was subjected to the measurement of the swelling rate with respect to the previous cleaning liquid and the observation of bleed. The results are shown in Table 6 together with the results of Example 2.

From the results of Comparative Example 5 in Table 6, even when a plasticizer having an SP value of 8 to 11 (cal / cm ³ ) ^1/2 is used, the content ratio is less than 10 parts by mass per 100 parts by mass of rubber. Then, since the effect which suppresses the swelling by containing the said plasticizer is not acquired, it turned out that the surface rubber layer produces the excessive swelling exceeding 50% of swelling ratio.
From the results of Comparative Example 6, it was also found that when the content of the plasticizer exceeds 50 parts by mass per 100 parts by mass of rubber, excess plasticizer bleeds to the surface of the surface rubber layer.

On the other hand, from the results of Example 2 and Examples 6 to 9, the content of the plasticizer is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component, so that the surface rubber layer has a surface ratio. It was found that excessive swelling can be suppressed by preventing swelling of the surface rubber layer by making the swelling ratio of the surface rubber layer less than 50% while preventing bleeding.
In addition, from the results of each example, considering that the swelling of the surface rubber layer is more effectively suppressed, the content of the plasticizer per 100 parts by mass of the rubber component is 20 parts by mass or more even within the above range. Was found to be preferable.

Claims (1)

At least a surface rubber layer is provided, and the surface rubber layer uses ethylene propylene diene rubber alone as a rubber component , or a combination of ethylene propylene diene rubber and butyl rubber, and 10 parts by mass or more per 100 parts by mass of the rubber component. Phthalate plasticizer, adipate plasticizer, and sebacate having a solubility parameter value of 8 (cal / cm ³ ) ^1/2 or more and 11 (cal / cm ³ ) ^1/2 or less. printing blanket, characterized in that it comprises at least one plasticizer selected from systems plasticizer or Ranaru group.