JP4101671B2 - Porous rubber print with open cells - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a porous rubber printing body having open cells, which is usually used for a rubber stamp of a built-in ink type. In particular, the present invention relates to a porous rubber print having open cells suitable for oil-based inks containing a volatile organic solvent as a main solvent.
[0002]
[Prior art]
A stamp that can be continuously printed without using a stamp stand each time it is used by using a porous rubber having countless open cells as a stamping material is widely used. JP-B-59-29606 is disclosed. Such a porous rubber printed body can contain a large amount of ink even if it is a pigment ink having a relatively high viscosity, and boasts a good ink discharge amount. The raw rubber used is natural rubber (NR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), etc. Among them, acrylonitrile-butadiene rubber which generally shows excellent oil resistance and solvent resistance is mainly used. It is used.
However, acrylonitrile-butadiene rubber is excellent in abrasion resistance and has excellent oil and solvent resistance against mineral oils and hydrocarbon solvents, but the main solvents are ethylene glycol monoethyl ether, erene glycol monobutyl ether, Stamp inks using glycol ethers such as propylene glycol monoethyl ether and aromatic alcohols such as benzyl alcohol swell and have a drawback that they cannot be used for a long time.
Therefore, when the applicant used ethylene-propylene-diene rubber (EPDM) as a raw material rubber, he was able to obtain a rubber print having excellent wear resistance and excellent solvent resistance to glycol ether and benzyl alcohol. The ethylene-propylene-diene rubber was found to shrink slightly due to the solvent. Moreover, since it does not flow uniformly when it is formed into a sheet shape with a calender roll or the like, there is a disadvantage that the thickness of the sheet is uneven or cracked.
Therefore, for the purpose of improving the physical properties of ethylene-propylene-diene rubber, blend rubbers in which acrylonitrile-butadiene rubber is blended with JP-A-49-89749, JP-A-54-106554, JP-A-62-172043, and the like are disclosed. Although it has been proposed, the amount of acrylonitrile-butadiene rubber is too large, and the physical properties of the ethylene-propylene-diene rubber are deteriorated, so that they are swollen with respect to the solvent. On the other hand, if the amount of acrylonitrile-butadiene rubber is reduced, sufficient physical properties could not be obtained. In addition, ethylene-propylene-diene rubber and acrylonitrile-butadiene rubber solid at room temperature have poor compatibility and are difficult to mix uniformly.
Further, a blend rubber of ethylene-propylene-diene rubber and acrylonitrile-butadiene rubber is different from 100% ethylene-propylene-diene rubber and 100% acrylonitrile-butadiene rubber, and a vulcanizing agent and a vulcanization accelerator are used to obtain satisfactory physical properties. It was necessary to add a large amount of. However, if a large amount of vulcanizing agent or vulcanization accelerator is blended, the rubber after vulcanization will turn black, making it difficult to obtain rubber other than black.
[0003]
[Patent Document 1]
JP 49-8949 A [Patent Document 2]
JP-A-54-106554 [Patent Document 3]
Japanese Patent Application Laid-Open No. Sho 62-172043
[Problems to be solved by the invention]
The present invention provides a porous rubber printed body having open cells that do not shrink or swell in solvents such as glycol ether and benzyl alcohol, and have excellent solvent resistance and wear resistance.
[0005]
[Means for Solving the Problems]
Raw rubber, a water soluble powder, a vulcanizing agent, after the filler has been vulcanized at least compounded formed by a rubber composition, met porous rubber printing material having open cells obtained by removing the water-soluble powder And
The proportion in 100 parts by weight of the raw rubber is 70 to 99 parts by weight of ethylene-propylene-diene rubber and 1 to 30 parts by weight of liquid acrylonitrile-butadiene rubber,
A porous rubber printed body in which a stamp ink containing at least one of glycol ether and benzyl alcohol as a solvent is occluded.
[0006]
Hereinafter, the present invention will be described in detail.
In order to obtain a porous rubber print having open cells of the present invention, at least ethylene-propylene-diene rubber, liquid acrylonyl-butadiene rubber, water-soluble fine powder, vulcanizing agent, and filler are used.
As the ethylene-propylene-diene rubber that can be used in the present invention, commercially available ones can be used. For example, JSR EP35, EP37C, EP65 and the like (the above, ethylene-propylene-diene rubber manufactured by Nippon Synthetic Rubber Co., Ltd.) are used. be able to.
The liquid acrylonitrile-butadiene rubber that can be used in the present invention is an acrylonitrile-butadiene rubber having a nitrile content of 20 to 40% that is a liquid at room temperature, and commercially available ones can be used. N280 or the like (above, acrylonitrile-butadiene rubber manufactured by Nippon Synthetic Rubber Co., Ltd.) can be used.
In the present invention, ethylene-propylene-diene rubber and liquid acrylonitrile-butadiene rubber are blended and used as raw rubber. The proportion of the blend rubber in 100 parts by weight is such that ethylene-propylene-diene rubber is 70 to 99 parts by weight (preferably 80 to 95 parts by weight), and liquid acrylonitrile-butadiene rubber is 1 to 30 parts by weight (preferably 5 to 20 parts by weight). Part) is used.
[0007]
As the water-soluble fine powder that can be used in the present invention, fine powders such as salts and sugars can be used. The salt is an inorganic compound that is easily pulverized, does not decompose and gasify at the rubber curing temperature (110 ° C. to 160 ° C.), and can be easily removed by water after heating. Specifically, sodium chloride, sulfuric acid Salts such as sodium and sodium nitrate are used. The diameter is usually 32 to 350 mesh (0.044 to 0.498 mm), and the use ratio is about 200 to 1200 parts, particularly preferably 400 to 600 parts, based on 100 parts of the raw rubber. . As the sugar, any of monosaccharides such as pentose and hexose, disaccharides such as saccharose and maltose, and polysaccharides such as starch and glycogen can be used, and these can be used in combination. The particle diameter is usually 150 mesh pass (0.010 to 0.103 mm). Among them, potato starch is particularly preferable because it is excellent in solubility, and a powder having a uniform required particle size can be easily obtained and is inexpensive. The use ratio is about 50 to 300 parts, preferably 100 to 200 parts, with respect to 100 parts of the raw rubber. Upon curing, these sugars swell under the influence of heat and generate a trace amount of moisture as a gas. This gas acts as a kind of foaming agent and gives a good result for bubble formation. In the present invention, the water-soluble fine powder may be used in combination with a salt and a sugar, or may be used in combination, and may be appropriately selected depending on the application. When used in combination, the blending weight ratio of the salt and sugar is preferably about 9: 1 to 3: 1, particularly preferably 4: 1. In the present invention, the reason why the blending weight ratio of the salt and the sugar is in such a range is that if the amount of the sugar is too large, the generation of moisture and carbon dioxide gas increases during the heat curing, and these excessively create bubbles. This is because the bubbles of the porous rubber may become non-uniform, and the decomposition of the saccharide itself may proceed so that the mixture to be cured in the mold may not be molded. On the other hand, if the amount of sugar is too small, the sugar particles are not properly interposed between the salt particles, and the effect of the sugar cannot be sufficiently exhibited.
[0008]
As the vulcanizing agent that can be used in the present invention, known vulcanizing agents such as sulfur, selenium, tellurium, sulfur chloride and the like can be used, and the use ratio thereof is 0.5 to 5 with respect to 100 parts of the raw rubber. About one part may be blended.
[0009]
As the filler that can be used in the present invention, fillers commercially available for rubber such as carbon black, hydrous silicic acid, anhydrous silicic acid, magnesium silicate, calcium silicate, calcium carbonate and the like can be used. 40 parts by weight or more, preferably 65 to 75 parts by weight with respect to parts.
When it is desired to obtain a black rubber print, a rubber print with stable physical properties can be obtained by adding carbon black to the filler.
When it is desired to obtain a rubber printing body other than black, such as white or chromatic color, carbon black is not used, but another filler is used. In this case, it is preferable that 20 parts by weight or more of the filler is hydrous silicic acid and / or anhydrous silicic acid. In this way, a black rubber print with high whiteness is obtained without being blackened even when vulcanized. Since the base color is cream color, rubber prints of various clear colors can be obtained when a necessary amount of a colorant described later is blended.
[0010]
Furthermore, the rubber composition of the present invention may be blended with additives commonly used in rubber production such as known colorants, vulcanization aids, vulcanization accelerators, softeners, etc., if necessary. it can.
In order to obtain a black rubber print, carbon black (black) is mainly used as a colorant. Carbon black also serves as a filler as described above. Carbon black is not used to obtain rubber prints other than black such as white and chromatic colors, and titanium oxide (white), lead chromate (yellow), iron oxide (red), phthalocyanine (blue), etc. are commercially available. Pigment other than black is used without particular limitation.
As the vulcanization aid, stearic acid, zinc white or the like can be blended.
As the vulcanization accelerator, thiazoles, thylliums, sulfenamides, dithiocarbamates, guanidines and the like can be blended in an effective amount.
As the softening agent, paraffinic process oil, naphthenic process oil, petrolatum, plasticizer and the like can be blended.
In addition, an appropriate amount of an amine-based anti-aging agent or organic synthetic fiber can be blended. Organic synthetic fibers include polyethylene terephthalate fibers, polyacrylonitrile fibers, acrylic fibers, aliphatic polyamide fibers such as nylon 6, nylon 6/6, nylon 4/6, nylon 6/10, nylon 11, etc., polypropylene fibers, polyethylene Fiber, polyvinyl alcohol fiber, polyvinyl chloride fiber, polyvinylidene chloride fiber, polyurethane fiber, polyalkyl paraoxybenzoate fiber, polytetrafluoroethylene fiber, aramid fiber, wholly aromatic polyester fiber, poly-p-phenylenebenzobisthiazole fiber, Poly-p-phenylenebenzbisoxazole fiber, polybenzimidazole fiber, polyoxymethylene fiber, and the like can be used, and staples having a fiber length of 0.2 to 2 mm are used. Further, those organic synthetic fibers having a fineness of 0.1 to 100d are particularly preferably used.
[0011]
Next, the manufacturing method of the porous rubber printed body of the present invention will be described.
The above-mentioned ethylene-propylene-diene rubber, liquid acrylonyl-butadiene rubber, water-soluble fine powder, vulcanizing agent, filler, and additives as necessary are kneaded in a kneader to prepare a rubber composition. Next, after the rubber composition is formed into a sheet with a calender roll or the like, the sheet is placed in a mold and cured by heating at a temperature of about 110 ° C. to 160 ° C. for 10 minutes to 1 hour. As the heating means, known means such as electric heating or steam heating can be used. Next, the said sheet | seat is taken out from a metal mold | die, and a porous rubber sheet is obtained by washing out water-soluble fine powder, repeating compression and expansion restoration using cold water or warm water. Next, the porous rubber sheet is engraved with a carbon dioxide gas laser processing machine, a YAG laser processing machine, etc., and a required porous rubber printed body is manufactured.
The porous rubber printing body of the present invention is not only a single-layer rubber printing body but also an upper layer (ink holding part) and / or a lower layer (ink holding part) composed of two layers of an upper layer (ink holding part) and a lower layer (printing body) ( It can also be used as a printed body. However, the water-soluble fine powder for the upper layer is slightly larger than the water-soluble fine powder for the lower layer. This is because the bubble diameter of the upper layer becomes larger than the bubble diameter of the lower layer, and when ink is impregnated, stable ink supply to the lower layer is possible due to capillary action.
[0012]
Here, the porous rubber printed body of the present invention is not deformed by a solvent such as glycol ether or benzyl alcohol. This seems to be due to the fact that the ethylene-propylene-diene rubber slightly shrinks with respect to the solvent and the liquid acrylonitrile-butadiene rubber swells with respect to the solvent. As a result, the blended rubber is not affected at all by the solvent. Therefore, it is possible to obtain a porous rubber printed body that retains a fixed impression semipermanently.
In addition, since the compatibility of the ethylene-propylene-diene rubber and the liquid acrylonitrile-butadiene rubber is excellent, a porous rubber printed body in which the respective components are uniformly kneaded is obtained, and rubber chipping and rubber peeling do not occur. Furthermore, both ethylene-propylene-diene rubber and liquid acrylonitrile-butadiene rubber are excellent in wear resistance, and in the present invention, they can be colored in various colors other than black. The font can be obtained.
[0013]
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. “Parts” are all parts by weight. Example 1
90 parts of ethylene-propylene-diene rubber, 10 parts of liquid acrylonitrile-butadiene rubber, 5 parts of sulfur, 50 parts of silicic acid, 5 parts of titanium oxide, 5 parts of zinc oxide, 5 parts of hardening accelerator, 30 parts of softener consisting of petroleum jelly, aging 2 parts of an inhibitor, 800 parts of 80-100 mesh (0.149-0.176 mm) sodium chloride, and 200 parts of 150-250 mesh (0.062-0.103 mm) potato starch are kneaded and rubber composition This was a flat sheet having a thickness of 7 mm.
Next, the sheet was accommodated in a smooth mold, and then a pressure of about 200 kg / cm ² was applied to sandwich the sheet between hot plates and vulcanized at a temperature of 120 ° C. for 60 minutes. After vulcanization, the mold was released, washed thoroughly with water until sodium chloride and potato starch were completely removed, dehydrated and dried to obtain a white porous rubber sheet.
The porous rubber sheet thus obtained was engraved with a YAG laser processing machine, and then cut into a required size to obtain a white porous rubber printed body.
When the porous rubber printing body is imprinted with a high viscosity pigment-based ink of 500 to 2000 mPa · s (25 ° C.) and imprinted, the ink occlusion amount is sufficient and a clear imprinting without bleeding or blurring is performed over a long period of time. I was able to. In addition, no change with time such as deformation of the porous rubber printed body due to the solvent was observed, and a porous rubber printed body that maintained a semi-permanent impression was obtained.
[0014]
(Example 2)
95 parts of ethylene-propylene-diene rubber, 5 parts of liquid acrylonitrile-butadiene rubber, 5 parts of sulfur, 50 parts of carbon black, 5 parts of zinc oxide, 5 parts of curing accelerator, 30 parts of softener comprising petrolatum, 2 parts of anti-aging agent 400 parts of sodium chloride of 200 to 350 mesh (0.044 to 0.074 mm), 100 parts of potato starch of 200 mesh (0.010 to 0.074 mm), aramid fiber having a fiber length of 0.9 mm and a diameter of 0.011 mm Two parts were kneaded to obtain a rubber composition A, which was a flat sheet A having a thickness of 2 mm.
Separately, 100 parts of synthetic rubber (acrylonitrile-butadiene rubber), 5 parts of sulfur, 5 parts of zinc oxide, 5 parts of vulcanization accelerator, 30 parts of softener composed of petroleum jelly / DBP, 50 parts of carbon black, anti-aging 2 parts of an agent, 800 parts of sodium chloride of 32 to 100 mesh (0.149 to 0.498 mm), 150 parts of potato starch of 200 mesh (0.010 to 0.074 mm), and kneaded to give rubber composition B, This was designated as a flat sheet B having a thickness of 5 mm.
Next, the sheet B is overlaid on the sheet A and accommodated in a smooth mold, and then a pressure of about 200 kg / cm ² is applied to sandwich it between the heating plates, and the sheet is heated at 120 ° C. for 60 minutes. Sulfurated. After vulcanization, the mold was released, washed thoroughly with water until sodium chloride and potato starch were completely removed, dehydrated and dried to obtain a black porous rubber sheet. The porous rubber sheet produced in this way becomes a single multilayer sheet in which the sheet A and the sheet B are integrated, and after engraving with a carbon dioxide laser processing machine from the sheet A side, when cut into a required size, The sheet B portion formed an ink holding portion that occludes a large amount of ink, and the sheet A portion was able to obtain a black porous rubber printed body forming a printing portion on which a printing surface was formed.
When the porous rubber printing body is imprinted with a high viscosity pigment-based ink of 500 to 2000 mPa · s (25 ° C.) and imprinted, the ink occlusion amount is sufficient and a clear imprinting without bleeding or blurring is performed over a long period of time. I was able to. In addition, no change with time such as deformation of the porous rubber printed body due to the solvent was observed, and a porous rubber printed body that maintained a semi-permanent impression was obtained.
[0015]
【effect】
The present invention mutually utilizes the phenomenon in which ethylene-propylene-diene rubber slightly shrinks with respect to solvents such as glycol ether and benzyl alcohol and the phenomenon in which liquid acrylonitrile-butadiene rubber swells with respect to the solvent. As a result, the blend rubber mixed with is not changed at all with respect to the solvent. Accordingly, it is possible to obtain a porous rubber printed body that is excellent in solvent resistance and abrasion resistance, does not undergo changes such as shrinkage and swelling even when used for a long period of time, and retains a fixed impression semipermanently.

Claims (1)

Raw rubber, a water soluble powder, a vulcanizing agent, after the filler has been vulcanized at least compounded formed by a rubber composition, met porous rubber printing material having open cells obtained by removing the water-soluble powder And
The proportion in 100 parts by weight of the raw rubber is 70 to 99 parts by weight of ethylene-propylene-diene rubber and 1 to 30 parts by weight of liquid acrylonitrile-butadiene rubber,
A porous rubber printed body in which a stamp ink containing at least one of glycol ether and benzyl alcohol as a solvent is occluded.