JP2014180790A - Porous rubber print body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous rubber print body capable of reducing a production cost, and capable of absorbing ink to rubber by natural impregnation without reducing rubber hardness and tensile strength without using a vacuum impregnation method for forcibly absorbing ink to rubber.SOLUTION: Rubber, a water-soluble compound, a vulcanizer, and a filler are mixed for forming a master batch. Then, the master batch is vulcanized and then the water-soluble compound is removed for obtaining the porous rubber print body. With respect to 100 pts.wt. of rubber, 0.5-5 pts.wt. of a silicone surfactant is added and mixed.

Description

  The present invention relates to a porous rubber printing body having open cells used for a penetrating ink of a built-in ink type.

  Patent Document 1 discloses a porous rubber used as a porous rubber printing body having countless open cells. The porous rubber printed body disclosed in Patent Document 1 is a master batch obtained by kneading a rubber composition, carbon black, a water-soluble compound, a vulcanizing agent, a filler, and additives as necessary. After vulcanizing the batch, the water-soluble compound is removed.

JP 2003-237205 A

However, the invention of Patent Document 1 disclosed by the present applicant can use additives and the like as required. Of these, the purpose of the lubricant is to improve processability during rubber production. There was room for improvement in terms of increasing the ink absorption time without lowering the hardness or tensile strength.
That is, when ink is absorbed by a porous rubber printed body, so-called natural impregnation that only uses capillary force requires a lot of time, so conventionally, a method of forcibly absorbing ink by rubber by a vacuum impregnation method has been employed. It was. The vacuum impregnation method is expensive because it requires a vacuum impregnation apparatus. Therefore, the development of rubber that can be absorbed by natural impregnation to reduce the production cost has been eagerly desired.
If the rubber hardness is lowered and softened, the printing surface of the printed body is distorted at the time of printing, resulting in a problem that the amount of ink adhesion increases and the imprinted image is blurred. Further, when the tensile strength is weakened, when the number of times of stamping increases, there arises a problem that the stamping surface is lost due to friction between the stamping surface and the paper surface.

The porous rubber print of the first invention completed to solve the above problems is a master batch obtained by kneading rubber, a water-soluble compound, a vulcanizing agent and a filler, and vulcanizing the master batch. A porous rubber print obtained by removing the water-soluble compound, wherein 0.5 to 5 parts by weight of a silicone surfactant is added and kneaded with respect to 100 parts by weight of the rubber.
The second invention is characterized by impregnating an ink containing at least a solvent containing a castor oil derivative, a colorant, and a resin soluble in the solvent, according to the first invention. It is a quality rubber print.

  According to the present invention, the ink absorption time can be increased without lowering the rubber hardness and tensile strength, and ink impregnation is possible by natural impregnation instead of the conventional vacuum impregnation method.

  Hereinafter, embodiments of the present invention will be described in detail.

  As the rubber, natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, polyurethane rubber, acrylic rubber, ethylene-propylene-diene rubber, dimethyl silicone rubber, methyl phenyl silicone rubber, methyl vinyl silicone rubber and the like can be used.

As the water-soluble compound, fine powders such as salt and sugar can be used.
The salt here refers to an inorganic compound that is easily finely powdered, does not decompose and gasify at the rubber vulcanization temperature (about 110 ° C. to about 160 ° C.), and can be easily removed by water after heating. Specific examples thereof include metal salts such as sodium chloride, sodium sulfate, and sodium nitrate. These can be used alone or in combination.
In addition, the sugar referred to here swells under the influence of heat during vulcanization and generates a trace amount of moisture as a gas. This gas acts as a kind of foaming agent and has a good effect on bubble formation. Preferred examples include monosaccharides such as pentose and hexose, disaccharides such as saccharose and maltose, polysaccharides such as starch and glycogen, and these can be used alone, It can also be used together. In particular, starch is preferably used as the sugar. This is because starch is excellent in solubility, and a powder having a uniform required particle size can be easily obtained and is inexpensive.
As the water-soluble compound, a salt and a sugar may be used alone, or these may be used in combination. Whether to use a salt and a sugar alone or to use them together can be selected depending on the application. When these are used in combination, the blending weight ratio of the salt and sugar is preferably about 9: 1 to about 3: 1, particularly preferably about 4: 1.
By setting such a blending weight ratio, it is possible to prevent generation of a large amount of moisture and carbon dioxide during vulcanization due to an excessive amount of sugar. The moisture or the like makes it difficult to control the bubbles in the rubber, and the bubbles may become non-uniform, so it is necessary to avoid them. In addition, if the amount of sugar is too large, the decomposition of the sugar itself proceeds so much that the mixture may not be molded in the mold. On the other hand, if the amount of sugar is too small, the sugar particles do not intervene properly between the salt particles, and the effect of adding the sugar cannot be sufficiently exhibited.
Although the size of the metal salt depends on the type, it is usually preferable to use a metal salt of about 32 mesh to about 350 mesh (about 0.044 mm to about 0.498 mm). Further, the metal salt may be used in an amount of about 200 parts to about 1200 parts, preferably about 400 parts to about 600 parts, relative to 100 parts of rubber.
On the other hand, although the size of the sugar depends on the type, it is usually preferable to use a sugar of about 150 mesh path (about 0.010 mm to about 0.103 mm). Moreover, the ratio of sugar used may be about 50 parts to about 300 parts, preferably about 100 parts to about 200 parts, with respect to 100 parts of rubber.

  Examples of the vulcanizing agent (crosslinking agent) include sulfur-based vulcanizing agents such as precipitated sulfur, sulfur, selenium, tellurium and sulfur chloride, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5. Examples thereof include peroxides such as -di- (t-butylperoxy) hexane and 1,3-bis (t-butylperoxy-i-propyl) benzene. Any of these can be used alone or in combination of two or more. The use ratio of the vulcanizing agent may be about 2 parts to about 5 parts with respect to 100 parts of rubber, and preferably about 3 parts to about 4 parts.

  As the filler, clay, talc, silica, mica, silicic acid, magnesium silicate, calcium silicate, calcium carbonate, magnesium carbonate, titanium dioxide, silicon oxide, antimony oxide, tin oxide, black iron oxide, red iron oxide, etc. Examples thereof include a coated metal oxide-coated mica. Any of these can also be used alone or in combination of two or more. The use ratio of the filler may be about 0.1 part to about 60 parts with respect to 100 parts of rubber.

  Furthermore, in this embodiment, various additives can also be used as needed. For example, an effective amount of an amine-based antioxidant, a softener such as petrolatum or a plasticizer, a vulcanization aid such as zinc white, or a guanidine-based vulcanization accelerator can be added. Any of these can also be used alone or in combination of two or more.

  Further, an appropriate amount of organic synthetic fiber can be added. 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 about 0.2 mm to about 2 mm are used. Any of these can also be used alone or in combination of two or more. Further, it is preferable to use those organic synthetic fibers having a fineness of 0.1d to 100d.

Silicone surfactants according to the present embodiment include polyether-modified polydimethylsiloxane (for example, BYK-302, BYK-333, BYK-378), polyether-modified polymethylalkylsiloxane (for example, BYK-320), poly Ether-modified siloxane (for example, BYK-345, BYK-346), polyether-modified hydroxyl group-containing polydimethylsiloxane (for example, BYK-377), polyester-modified polydimethylsiloxane (for example, BYK-310, BYK-313), polyester-modified hydroxyl group Containing polydimethylsiloxane (for example, BYK-370), aralkyl-modified polymethylalkylsiloxane (for example, BYK-322, BYK-323), acrylic group-containing polyether-modified polydimethylsiloxane (for example, BYK-U) It can be any of the silicone-based surfactant of 3500).
In order to speed up only the ink absorption time without reducing other properties (moldability, hardness, tensile strength, laser workability, ink consumption), among the above-mentioned silicone surfactants, polyether-modified polydimethyl is particularly preferred. Siloxane (for example, BYK-302, BYK-333, BYK-378), aralkyl-modified polymethylalkylsiloxane (for example, BYK-322, BYK-323), polyether-modified hydroxyl group-containing polydimethylsiloxane (for example, BYK-377), It is preferable to use any silicone surfactant of acrylic group-containing polyether-modified polydimethylsiloxane (for example, BYK-UV3500).
Here, the BYK series is manufactured by Big Chemie Co., Ltd., and the silicone surfactant may be used alone or in combination of a plurality of types.
When the silicone surfactant of the present embodiment is employed, the ink absorption time is shortened, and so-called natural impregnation utilizing capillary force is possible. If natural impregnation is possible, there is an advantage that the capital investment such as a vacuum impregnation apparatus becomes unnecessary and the production cost can be reduced.

Here, as the porous rubber printed body, there is a single layer that does not distinguish between a two-layered one having a top layer that has innumerable fine bubbles and the engraving surface of which is engraved, and a base layer located on the back surface thereof. There are some layers. The porous rubber printed body of this embodiment can be applied to both single-layer and double-layer porous rubber printed bodies, and in the case of two layers, it can be applied to both the top layer and the base layer. it can. This is because the porous rubber printed body of the present embodiment can be suitably used for the top layer from the surface of laser processing as described later, and can be suitably used for the base layer from the surface of its hardness. by.
In the case of a two-layer porous rubber printed body having a top layer and a base layer, the cell diameter of the base layer may be designed to be larger than the cell diameter of the top layer. This is because a stable ink supply from the base layer to the top layer becomes possible by capillary action. Further, the base layer and the top layer may be simply overlapped, or may be overlapped and vulcanized and integrated at an unvulcanized stage.

Next, the above raw materials are put into a kneader and kneaded to obtain a master batch. Next, the shape is adjusted with a calendar roll or a press to produce an unvulcanized sheet.
Then, the sheeted master batch is put into a mold and heated and vulcanized at a temperature of about 80 ° C. to 160 ° C. for about 10 minutes to about 2 hours. As the heating means, for example, electric heating or steam heating can be used.
Next, the vulcanized product is taken out from the mold, and the water-soluble compound is washed out while repeatedly compressing and expanding using cold water or hot water. Thereby, a porous rubber sheet having open cells is obtained. If this porous rubber sheet is cut into an appropriate size, a porous rubber printed body can be obtained.

Next, when the porous rubber printed body is used for the top layer, the printed surface may be engraved with a carbon dioxide gas laser processing machine or a YAG laser processing machine and then cut into an appropriate size. On the other hand, when the porous rubber printed body is used for the base layer, it may be used after being cut into an appropriate size.
In the case of a two-layer porous rubber printed body having a base layer and a top layer, the base layer and the top layer, which are overlapped at the unvulcanized stage, are vulcanized and integrated, and then the top layer side Then, the stamping surface is engraved using a carbon dioxide gas laser processing machine or a YAG laser processing machine and then cut into an appropriate size for use.

The ink contains at least a solvent containing a castor oil derivative, a colorant, and a resin soluble in the solvent.
The castor oil derivative is selected from a castor oil polyhydric alcohol ether obtained by modifying castor oil with an alkylene oxide such as propylene oxide or ethylene oxide, or a castor oil fatty acid alkyl ester obtained by modifying castor oil with an alcohol such as methanol, ethanol, propanol, or butanol. The fatty acid is selected from ricinoleic acid, oleic acid, palmitic acid, stearic acid, linoleic acid, linolenic acid and the like.
Moreover, glycol ether can be mixed as needed. As glycol ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, 2-methoxypropanol, 3-methoxybutanol, 3-methoxy-3-methylbutanol, ethylene glycol monohexyl Ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether Diethylene glycol monohexyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol mono 2-ethylhexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether, propylene glycol Monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono n-butyl ether, triethylene glycol dimethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl Ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol monopropyl ether, polyethylene glycol monobutyl ether, Examples thereof include poly (oxyethyleneoxypropylene) monomethyl ether and poly (oxyethyleneoxypropylene) monoethyl ether.

As the colorant, conventionally known organic pigments and inorganic pigments and conventionally known oil-soluble dyes can be used without any particular limitation.
Examples of the pigment include organic pigments such as condensed azo-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-thioindigo-based, verinone-berylene-based, isoindolenone-based, azomethyleneazo-based, diketopyrrolopyrrole-based pigment, etc. Inorganic pigments such as carbon black, mica, titanium white, pearl pigments, metal pigments such as iron oxide, aluminum powder, and brass can be used. These pigments are usually kneaded in known resins such as nitrocellulose, ethyl cellulose, vinyl chloride / vinyl acetate copolymer, rosin ester, etc., and are conveniently processed pigments because they disperse easily when mixed with a solvent. . Further, as commercially available processed pigments in which a pigment is already kneaded in a dispersant, MICROLIT Black SC, MICROLIT Yellow RA, MICROLIT Yellow 2R-A, MICROLIT Red 4C-K, MICROLIT Blue Blue 4G-T Or Ciba Specialty Chemicals Co., Ltd.) may be used. These pigments can be used singly or in combination while taking the hue into consideration, and a pigment content of 1 to 30% by weight based on the total amount of ink can be used.
Examples of the dye include monoazo series, disazo series, metal complex type monoazo series, anthraquinone series, phthalocyanine series, and triallylmethane series. These oil-soluble dyes can be used singly or in combination while considering the hue, and can be used in an amount of 1 to 30% by weight based on the total amount of ink.

  As the resin, a resin that dissolves in the solvent can be selected and used in the range of 1 to 30% by weight based on the total amount of the ink. Specific examples include alkyd resins, maleic resins, styrene maleic resins, rosin resins, rosin maleic resins, ethyl cellulose resins, nitrocellulose resins, polyvinyl butyral resins, vinyl chloride / vinyl acetate copolymers, and the like.

The above solvents can be used by arbitrarily mixing them in consideration of the viscosity, the dissolving power of other substances, the intended use, the properties of the target stamped object, the erosion of the ink occlusion body, containers, etc. It is preferable to use 30 to 99% by weight of the total amount of ink and 40 to 95% by weight of castor oil derivative based on the total amount of ink.
The ink of the present invention is produced by selecting an appropriate amount of the above substances, and mixing and dispersing the mixture with a stirrer at room temperature to 100 ° C. for about 2 hours. The viscosity can be freely set, but in the present invention, it is particularly preferable to use an ink of 100 to 1000 mPa · s (25 ° C.). This is because it takes too much time for the seal impression to dry above this range, and it is difficult to prevent bleeding below this range.

  Hereinafter, the porous rubber printed body of the example of the present invention will be described in more detail. However, it should be noted that the present invention is not limited to these examples.

  About 100 parts by weight of synthetic rubber (NBR), about 3.5 parts by weight of sulfur, about 5 parts by weight of zinc white, about 5 parts by weight of vulcanization accelerator, liquid rubber (low polymerized NBR molecular weight), petroleum jelly, DBP About 30 parts by weight of a softening agent comprising, etc., about 0.5 parts by weight of a polyether-modified polydimethylsiloxane (BYK-333), about 28 parts by weight of silica, about 2 parts by weight of an anti-aging agent, about 200 mesh to about After adding about 800 parts by weight of 350 mesh (about 0.044 mm to about 0.074 mm) sodium chloride and about 200 parts by weight of about 150 to about 250 mesh (about 0.062 mm to about 0.103 mm) starch, These were kneaded to produce a master batch (Example 1).

  Further, with respect to the polyether-modified polydimethylsiloxane (BYK-333) in Example 1, instead of the addition amount of about 0.5 parts by weight, the addition amounts of about 1 part by weight, about 3 parts by weight, and about 5 parts by weight. As other conditions, the master batch was manufactured in the same manner as in Example 1 (Examples 2, 3, and 4).

In addition, as a comparative example, with respect to polyether-modified polydimethylsiloxane (BYK-333), instead of an addition amount of about 0.5 parts by weight, 0 part by weight (not added), an addition amount of about 7 parts by weight, etc. A master batch was produced in the same manner as in Example 1 (Comparative Examples 1 and 2).
Further, as a comparative example, instead of polyether-modified polydimethylsiloxane (BYK-333), the addition amount of about 5 parts by weight of PEG and about 5 parts by weight of PPG was used, and other conditions were the same as in the case of Example 1. A master batch was manufactured (Comparative Examples 3 and 4).

Subsequently, the master batch according to each example was formed into a flat sheet having a thickness of about 5 mm using a calendar roll. Next, the sheets were accommodated in a smooth mold. Next, a pressure of about 200 kg / cm 2 was applied to sandwich between the hot plates, and vulcanized at a temperature of about 100 ° C. for about 60 minutes.
Thereafter, after each vulcanization, each was released from mold, washed thoroughly with water until sodium chloride and starch were completely removed, and then dehydrated and dried to produce a liquid absorbent rubber. Then, in order to check the suitability as the top layer, the liquid absorbing rubber is cut into an appropriate size after performing a desired engraving with a YAG laser processing machine, and engraved in order to see the suitability as a base layer. It cut | disconnected to the appropriate size, without performing.

  Table 1 is a table showing evaluation results of molding processability, hardness, tensile strength, laser processability, ink consumption, and ink absorption time for each of Examples 1 to 4. Comparative examples 1 to 4 are also included for reference. For easy understanding, the contents of silicone surfactant, PEG, and PPG with respect to rubber are also shown.

  As shown in Table 1, when comparing the porous rubber printed bodies of Examples 1 to 4 and the porous rubber printed bodies of Comparative Examples 1 to 4 with respect to molding processability, Examples 1 to 4 and Comparative Examples 1 and 2, No. 4 had good kneadability. On the other hand, in Comparative Example 3, the solvent was bleed and the molding processability was poor.

Next, regarding the hardness, when the porous rubber printed bodies of Examples 1 to 4 and the porous rubber printed bodies of Comparative Examples 1 to 4 are compared, it can be seen that the hardness is substantially the same except for Comparative Example 2. Since it is recommended that the top layer of the porous rubber printed body has a hardness of about 40 to 50, the porous rubber printed bodies of Examples 1 to 4 and Comparative Examples 1, 3, and 4 are, among other things, the top layer. As can be seen from FIG. When the hardness is softer than 40, the printing surface of the printed body is distorted at the time of printing, resulting in a problem that the amount of ink adhesion increases and the imprint of the printing is blurred.
For the measurement of hardness, place the porous rubber print body to be tested on a hard, rigid flat surface and hold the E-type hardness meter so that the push needle is perpendicular to the measurement surface of the porous rubber print body. Then, the measurement was performed by bringing the scale into close contact with the test piece measurement surface as quickly as possible so that no impact was applied to the pressure surface. This measuring method is based on JIS K 6253.

Next, regarding the tensile strength, when the porous rubber printed bodies of Examples 1 to 4 and the porous rubber printed bodies of Comparative Examples 1 to 4 are compared, it can be seen that the tensile strength is 1.30 Mpa or more except for Comparative Example 2. Since it is recommended that the top layer of the porous rubber printed body has a tensile strength of about 1.30 Mpa to 1.60 Mpa, the porous rubber printed bodies of Examples 1 to 4 and Comparative Examples 1, 3, and 4 are In particular, it can be seen that it can be suitably used as a top layer. When the tensile strength is weaker than 1.30 MPa, there is a problem that the stamp surface is lost due to friction between the stamp surface and the paper surface when the number of times of stamping is increased.
The tensile strength was measured in accordance with the vulcanized rubber tensile test method JIS6251 and the size of the test piece was dumbbell-shaped No. 2.

  Next, regarding the processability with a YAG laser, each of the porous rubber printed bodies of Examples 1 to 4 and Comparative Examples 1 to 4 was excellent. Also, the processing speed with the YAG laser was almost the same. Therefore, for laser processing for engraving, it can be said that there is no significant difference between the porous rubber printed bodies of Examples 1 to 4 and the porous rubber printed bodies of Comparative Examples 1 to 4, and both are suitable for the top layer. Can be used.

Next, when the porous rubber printed bodies of Examples 1 to 4 and the porous rubber printed bodies of Comparative Examples 1 to 4 are compared with respect to the ink consumption, the porous rubber printed bodies of Examples 1 to 4 are all substantially omitted. A large amount of ink consumption exceeding 300 mg was confirmed. On the other hand, about the porous rubber printing body of the comparative example, comparative examples 1, 2, and 4 were able to confirm a large amount of ink consumption comparable to the case of Examples 1-4, but comparative example 3 was a small amount of ink. Only consumption was confirmed.
The ink consumption was measured as follows. First, the porous rubber printed body to be measured was a cylindrical shape having a thickness of 5 mm and a diameter of 9.5 mm. In this case, the area under the printing surface is about 25 mm ² . The ink used is an oil pigment vermilion ink containing at least a castor oil derivative and having a viscosity of about 700 mPa · s. After saturated impregnation of the porous rubber printing body, the ink consumption is continuously printed on fine paper 5000 times. The amount was measured. It can be considered that the greater the ink consumption, the more ink is ejected per stamping, and the higher the foamability. If the ink consumption is 300 mg or more, it can be determined that the continuous foaming property is good.

Next, the ink absorption time was measured. Here, after placing a pad impregnated with ink (ink occluding body) in a petri dish filled with ink and placing the porous rubber printed body on the pad, the entire porous rubber printed body is impregnated with ink. Was measured.
In each example and each comparative example, the porous rubber printed body is a cylindrical one having a thickness of 5 mm and a diameter of 9.5 mm. The ink contains at least a castor oil derivative and has a viscosity of about 700 mPa · s. An oil pigment vermilion ink was used, and a sintered body (porous body) made of a formalin condensate of polyvinyl alcohol was used as a pad (ink occlusion body). This measurement was performed five times at a temperature of about 20 ° C. and a humidity of about 65%, and Table 1 shows the average values.
In the case of the porous rubber printed bodies of Comparative Examples 1 and 4, the completion of ink absorption could not be confirmed even after 165 hours. On the other hand, in the case of the porous rubber printed bodies of Examples 1 to 4 and Comparative Example 2, the completion of ink absorption could be confirmed in 6 to 12 hours. In the case of the porous rubber printed body of Comparative Example 3, the completion of ink absorption could be confirmed in 46 hours. From this, it can be said that when the polyether-modified polydimethylsiloxane is added, the ink absorption can be shortened.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein, It should be understood that a porous rubber printed body with such changes can be appropriately changed without departing from the scope and spirit of the invention that can be read from the entire scope and specification, and that the porous rubber printed body with such changes is also included in the technical scope.

Claims (2)

A porous rubber print obtained by kneading rubber, a water-soluble compound, a vulcanizing agent, and a filler to form a master batch, vulcanizing the master batch, and then removing the water-soluble compound. A porous rubber printed body characterized by adding and kneading 0.5 to 5 parts by weight of a silicone surfactant to 100 parts by weight. The porous rubber printed body according to claim 1, which is impregnated with an ink containing at least a solvent containing a castor oil derivative, a colorant, and a resin soluble in the solvent.