JPS5928193B2 - Sponge rubber printed material with open cells - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sponge rubber printed body having open cells and a method for producing the same.

Stamps that use sponge rubber having countless open cells as a stamp material and allow continuous stamping without using a stamp pad each time have recently become popular. Conventionally, the following methods are known for manufacturing sponge rubber bodies having numerous open cells that have been used for this type of stamp.

[1] A method in which raw rubber is foamed using only a foaming agent to form countless open cells.

[2] Easily water-soluble salt powder is mixed with a curing agent and filler in raw rubber without using a blowing agent, and heated and cured (see Figure 4), and then the easily water-soluble salt powder is removed by washing with water. ,
Method for forming open cells (see Figure 3) and [3
] A method in which easily water-soluble salt powder and a foaming agent are mixed with a curing agent and a filler in raw rubber, heated and cured, and then the easily water-soluble salt powder is removed by washing with water to form countless open cells (see Figure 5). However, according to the method [1], the formed open cells were non-uniform and the amount of ink occlusion was insufficient.

Another problem was that a bubble-free film layer was formed on the surface of the stamp formed by contact with the mold during curing. On the other hand
According to method 2], since the contact between the easily water-soluble salt powders mixed in the raw rubber is point contact or line contact,
As shown in FIG. 3, the connection path a of each bubble formed was narrow, making it impossible to use ink with high viscosity and containing pigment.

Another drawback is that a bubble-free film layer is formed on the surface of the stamp. Furthermore, according to the 0th method, a valve-shaped piece c is formed as shown in FIG. Therefore, the connection path b was narrowed, and there was a problem in that it was impossible to use an ink containing a highly viscous pigment.

Furthermore, there is also the problem that a bubble-free film layer is formed on the surface of the stamp. In addition, according to methods [2] and [3], if the ink used is low in viscosity and contains dye, clear printing can be maintained for a long time, but When a known general-purpose ink was used, the above-mentioned effects could not be obtained. For example, it is difficult to bleed,
Moreover, it is unsuitable when using a pigment-based ink with high viscosity and excellent water resistance and light resistance.

The present invention overcomes the above-mentioned drawbacks and has numerous open cells that can sufficiently occlude a highly viscous liquid ink composition and do not impede the fluidity of this liquid. The present invention relates to a sponge rubber body and a method for manufacturing the same.

An object of the present invention is to provide an open-cell sponge rubber printed body that can continue to print clearly for a long period of time. Another object of the present invention is to provide a sponge rubber body having countless open cells for printing, which allows use of high viscosity ink containing pigments by appropriately adjusting the cell diameter. That's true.

Another object of the present invention is to provide a method for producing sponge rubber that can be used for the above-mentioned purposes. Still another object of the present invention is to provide an open-cell sponge rubber body for printing bodies, which has a structure in which the bubble diameter is adjusted appropriately and is made by integrating two sponge rubber sheets with different bubble diameters. Another object of the present invention is to appropriately adjust the above-mentioned bubble diameter and to adjust the bubble diameter. To provide a method for manufacturing a sponge rubber body for a printed body, which is formed by integrating two sponge rubber sheets with different properties.

Further objects of the invention will become apparent from the following description and claims.

A feature of the present invention is the use of soluble starch having a suitable particle size, thereby eliminating the shortcomings of conventional sponge rubbers for printing bodies.

This solves the problem of low ink storage capacity which prevents the use of highly viscous pigment-containing inks due to narrow connection paths caused by point and line contact or the formation of valve-shaped pieces between easily water-soluble salt fine powders. be. First, various raw materials used in the present invention will be explained.

The raw material rubber J1 that can be used in the present invention is natural rubber or synthetic rubber with a molecular weight of approximately 10,000 to 100,000 (JlSK63OO viscosity = approximately 70 to 95). As synthetic rubber, butadiene-styrene copolymer,
Butadiene-acrylonitrile copolymer, chloroprene, polyurethane rubber, etc. can be used.

In particular, butadiene-acrylonitrile copolymer (nitrile content 31-42%) is suitable for obtaining products with excellent oil resistance, aging resistance, etc., and has excellent elasticity and toughness, so it is particularly suitable as a rubber stamp material. ing. Further, as the curing agent that can be used in the present invention, known curing agents such as sulfur, selenium, tellurium, and sulfur chloride can be used.

Its usage ratio is about 2 to 5 parts, particularly preferably 3 to 4 parts, per 100 parts of raw rubber. Furthermore, fillers that can be used in the present invention include known carbon black, fine powder silicic acid, artificial silicates, calcium carbonate, etc. Carbon black in particular has a strong bond with the rubber used and has a reinforcing effect. preferable.

The usage ratio is about 40 to 6 parts per 100 parts of raw rubber.
0 parts, and a range of 45 to 55 parts is particularly preferred. The easily water-soluble compound (salt) used in the present invention is one that is easily pulverized, does not decompose and gasify at the rubber curing temperature (11°C to 160°C) (that is, withstands the curing temperature), Moreover, it is a crystalline inorganic compound that can be easily washed away with water even after heating.

Specifically, salts such as sodium chloride, sodium sulfate, and sodium nitrate are used. The diameter of the fine particles of the compound varies depending on the use.

Usually 32-350 mesh (0.044-0.498%
). The diameter approximately corresponds to the bubble diameter of the sponge rubber body. That is, the diameter is 0.498 to 0.14
It contributes to the formation of large bubbles b in the range of 9. Its usage ratio is approximately 200 to 1200 parts per 100 parts of raw rubber.
parts, preferably 800 to 1000 parts. As the soluble fine powder starch used in combination with the easily water-soluble salt fine powder that can be used in the present invention, zeta valley starch,
These include corn starch and rice starch.

As long as the particle size is selected, the source of the raw material does not matter. Valley starch is widely used because it has excellent solubility, powders with a uniform required particle size can be easily obtained, and it is inexpensive. The particle size is 150 mesh pass (
0.01 to 0.103) is used. Its usage ratio is about 100 to 300 parts, preferably 150 to 250 parts, per 100 parts of raw rubber. During curing, soluble starch swells under the influence of heat and generates a small amount of water contained therein as a gas, and this gas acts as a kind of blowing agent and produces good results in the formation of bubbles. Furthermore, soluble starch itself also tends to be decomposed and saccharified to some extent during the curing process, making it more soluble in water than before heating. In the present invention, the blending weight ratio of soluble starch and easily water-soluble salt is preferably about 1:9 to 1:3,
In particular, it is preferable to use them in a ratio of 1:4.

In the present invention, the reason why the blending weight ratio of soluble starch and easily water-soluble salt is set in this range is that if the amount of soluble starch is too large, water and carbon dioxide gas will be generated during heat curing. There is a risk that these will create too many bubbles, making the bubbles in the sponge rubber uneven, and that the decomposition of the soluble starch itself will progress too much, making it impossible to mold the mixture that should be cured in the mold. It is. On the other hand, if the amount of soluble starch is too small, the easily water-soluble salt will not be properly interposed between the fine powders, and the effect of adding soluble starch will not be fully exhibited.

In the present invention, it is also possible to use additives commonly used in the rubber industry. For example, reinforced amine-based anti-aging petrolatum, such as carbon black,
An effective amount of a softening agent such as a plasticizer, a curing accelerator such as a guanidine-based curing accelerator such as zinc white, etc. can be added.
Next, a method for manufacturing the open-cell sponge rubber printed body of the present invention will be explained.

a curing agent, a filler, a soluble starch, each having the above particle size;
The raw material rubber mixed with the easily water-soluble salt in the ratio within the above-mentioned range is put into a kneader and masticated and kneaded.

Next, put it in the mold and keep it at about 110℃~1 hour for 10 minutes~1 hour.
Heat and harden at a temperature of 6'C.

As the heating means, any known heating means can be used. For example, electric heating or steam heating can be used. The thus cured product is taken out from the mold. Next, the easily water-soluble salts and soluble starch are washed out by repeatedly compressing and expanding and restoring using cold or hot water. These two substances are first washed away from the surface, then water enters the countless bubbles formed by washing the surface, and the easily water-soluble salts and fine powder of soluble starch inside are washed away. The easily water-soluble salt and the fine powder of soluble starch can be completely washed away in the same manner as water infiltrates deep into the tank and the fine powder inside is washed away. Although water at 20 to 3°C may be used for washing, using warm water at 45 to 55°C will further improve the washing out of soluble starch and shorten the time required for washing. Note that when curing is carried out at a low temperature for a relatively long time, for example at 110° C. for 60 minutes, hot water of 70° C. or higher is required to wash out the soluble starch. This is considered to be because the water solubility of the soluble starch did not increase significantly due to insufficient thermal decomposition of the soluble starch. Thus the diameter is about 0.01-0.103
Small bubbles a within the range of % and diameter approximately 0.149~0
．． Total volume % of large bubbles b within 498%
is within the range of 60% to 85 volume (:f) (sponge rubber standard), and the bubbles A and b communicate with each other, and their communication connection path is wide. A sponge rubber body is obtained that does not contain the valve-like pieces that obstruct the passages found in the manufactured sponge body.

Preferably, the relative volume percentage of the small bubbles a and large bubbles b is 5 to 60% by volume for the small bubbles a (same below the sponge rubber standard), while 40% for the large bubbles b.
It is preferable that the proportion of small bubbles a is 5 to 40%, while the proportion of large bubbles b is 50% to 75%. Most preferred is 5-20% of small bubbles a and 60%-75% of large bubbles b. As another embodiment of the present invention, when obtaining a sponge rubber printed body in which the properties of the open cells formed in the upper layer (ink holding part) and the lower layer (printing part) are different, the raw material rubber, curing agent, filler, and soluble starch used are Fine powder, easily water-soluble salt fine powder,
The curing conditions, washing conditions, etc. are the same or almost the same as those described above.

However, separate sheets are made in which only the particle sizes of the easily water-soluble salt and soluble starch fine powder differ, and then the two sheets are overlapped and heated to harden and integrate. Note that the particle sizes of the easily water-soluble salt and soluble starch fine powder used in both sheets are not particularly limited, but especially when used as a stamp material using relatively high viscosity ink containing pigments. The easily water-soluble salt added to the layer sheet used for printing has a particle size of 200 to 350 mesh (0.044 to 0.0
．． 074%), and the soluble starch has a particle size of 2.
00 mesh pass (0.01 to 0.074%), and the particle size of the easily water-soluble salt added to the layer sheet used for ink retention is 32 to 100 mesh (0.01 to 0.074%).
．． 149-0.498X), and the particle size of soluble starch is 150-250 mesh (0.062-0.103
%). Such limitations regarding particle size are such that if the particle size is too large, the formed bubbles will become coarse and the desired goal of fine and uniform bubbles cannot be obtained, and conversely, if the particle size is too small, the resulting bubbles will become coarse. This is based on the fact that the flowability of viscous ink, etc. is impaired. In any case, what is unique about the present invention is the new use of ζ-soluble starch, and especially the use of this in combination with the easily water-soluble salt that has been used in the past.

The effect of using this soluble starch in combination with an easily water-soluble salt is to prevent the fine powder of the easily water-soluble salt from aggregating and becoming large, and to facilitate release from the mold immediately after hardening. This finely powdered soluble starch adheres around the easily water-soluble salt and substantially increases the surface area of the easily water-soluble salt, making it easier to flow inks with higher viscosity than conventional sponge rubber with the same volumetric porosity. It gets a lot better.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. first,
The conventional technology will be explained. FIG. 4 is a longitudinal cross-sectional view of a sponge body manufactured according to a prior art method in the hardened stage before washing with water. In this conventional method, a readily water-soluble salt powder is used, and the salt is crystalline inorganic material particles 41. In addition, such particles have high hardness and are suitable for raw rubber 42
If both are mixed, the mutual contact will be point contact or line contact. Therefore, the connecting path 31 formed after the particles 41 are washed away becomes narrower as shown in FIG. FIG. 5 shows an example in which the method is almost the same as that shown in FIG. 4, but a blowing agent is further mixed in the raw rubber.

According to this method, in addition to a narrow connecting path as shown at 51, a valve-like piece as shown at 52 is produced. These, in turn, impede the movement of the used ink. Particularly when the ink used has a high viscosity, its movement is significantly hindered. On the other hand, in the present invention, as shown in Fig. 2, soft soluble starch fine powder made of an organic substance is interposed between the easily water-soluble salt fine powder 1 mixed in the raw rubber 2, and it deforms as if it were a rubber ball. do.

That is, the easily water-soluble salt fine powder 1 and the soluble starch fine powder come in surface contact. Therefore, when the easily water-soluble salt fine powder 1 and the soluble starch fine powder 5 are washed away, the first
As shown in the figure, the continuous cell 3 becomes a valveless product in which the cells A and B are connected through a sufficiently wide connection path 4.

Furthermore, due to the good contact between the fine powders, the time required for washing out is significantly shortened.

FIG. 7 does not show an example of a gripping body having a sponge rubber printed body consisting of two layers A and B.

The highly viscous pigment-containing ink that can be used for the sponge rubber printing body of the present invention is a mixed vehicle of castor oil polyhydric alcohol ether obtained by modifying castor oil with alkylene oxide and castor oil fatty acid alkyl ester obtained by modifying castor oil with alcohol. An ink in which pigment particles whose particle surfaces are encapsulated with ethyl cellulose is dispersed in a medium or a single vehicle, for example, an ink in which the above-mentioned alkylene oxide is propylene oxide, and an ink in which the castor oil fatty acid alkyl ester is castor oil fatty acid methyl ester, etc. are used. . The pigment used in the above-mentioned high viscosity pigment-containing ink has a particle size of 0.1
The following materials in the range of microns to 0.01 microns are used. In other words, it is a pigment powder (manufactured by Microlisu Suisse Cibagaigi Co., Ltd.) in which the surface of pigment particles is encapsulated with ethyl cellulose, and the colors are as shown below. In addition to being used for the above-mentioned stamps using relatively high viscosity pigment-based ink, the sponge rubber printing body according to the present invention can also be used for stamp pads, ink pads, rollers, etc. to ensure sufficient ink absorption and prevent bleeding. Clear stamping without blurring is possible. However, the sponge rubber body of the present invention is not limited to such uses, but has an extremely wide range of uses such as cushioning materials, filtering materials, and sanitary materials. Hereinafter, the present invention will be explained in more detail with reference to Examples.

However, the present invention is not limited to these Examples in any way. Example 1 Sulfur was 3.5% by weight per 100% of synthetic rubber (NBR),
Zinc white 5, curing accelerator 5 and liquid rubber (low polymerized NBR
Molecular weight) Softener 301 consisting of petrolatum, DBP, etc. Carbon black 50, Anti-aging agent 2, 80-100 mesh (0.149-0.176%) of sodium chloride or sodium sulfate or sodium nitrate fine powder 800, 15
A kneaded product was prepared by adding 0 to 250 mesh (0.062 to 0.103%) of soluble potato starch fine powder (200) and masticating it.

Fill this into a roll molding mold and press it between hot plates.
After curing by heating at 150°C for 15 minutes, the mold is released, and the sodium chloride, sodium sulfate, or sodium nitrate and soluble potato starch are thoroughly washed with water to completely make the 8tsu! ，
:±: Wash, dehydrate and dry to obtain an inking roller?
2000 to 40 to the thus obtained inking roller.
When a highly viscous pigmented ink of approximately 00cp/25℃ was used in a ticket vending machine, the ink storage capacity was sufficient and it was possible to print clear stamps over a long period of time without bleeding or fading. did it.

Examples 2 to 4 In the same manner as in Example 1, a stamp pad, an ink pad for a check writer, and a cushioning material were prepared using the formulations shown in Table 1, and all showed extremely good performance.

As described above, the sponge rubber body according to the present invention has an extremely wide range of uses. FIG. 6 shows an example in which the ink pad manufactured according to this embodiment is used as an ink pad for mimeograph paper.

In the symbols in FIG. 6, 61 is a grip, 62 is a cover body 63 is a spring, 64 is a printing body storage case, X is an ink pad manufactured in this example, 65 is a mimeograph paper, and 66 is a mimeograph paper presser frame. There is.

Example 5 100% of synthetic rubber (NBR), 3.5% of sulfur, 5% of zinc white, 5% of curing accelerator, and liquid rubber (low polymerized NBR),
Softener 301 consisting of petrolatum, DBP, etc. Carbon black 50, anti-aging agent 2, 200-350 mesh (0
．． 044-0.074%) of sodium chloride, sodium sulfate, or sodium nitrate 800, 200 mesh paste (0.01-0.074%) of soluble potato starch 200 is added, masticated and kneaded to form a thin flat A sheet 2.
I made X thickness.

Separately, 32 to 1
00 mesh (0.149-0.498X) of sodium chloride or sodium sulfate or sodium nitrate 80
0, 150-250 mesh (0.062-0.103
%) of potato starch 200 was added and masticated to make a slightly thick flat B sheet (5% thickness), and this B sheet was overlaid on the A sheet to form uneven characters on the inner bottom surface. It was housed inside. Next, a pressure of about 200 Kf/Crli was applied, and the A sheet was pressed between hot platens in a state in which it was in contact with the uneven characters, and was cured at a temperature of 150° C. for 15 minutes. After curing, the mold was released and thoroughly washed with water until sodium chloride, sodium sulfate, or sodium nitrate and soluble starch were completely removed, and dehydrated and dried to form a rubber stamp. The rubber stamp thus manufactured consists of sheet A and sheet B.
The sheets are integrated into a single printed body X, which is attached to a gripping body (see Figure 7) that has a structure that can accommodate ink inside, with the stamp side of characters or figures facing down. Keep it, 2000~4000cp/25
If pigment-based ink with a high viscosity of about °C is infiltrated from the B sheet side, which is the upper layer of the rubber stamp, the upper layer, which was the B sheet, will have a structure in which a wide variety of complex and fine open cells are interconnected. Because it is a type of paper, it stores a large amount of ink, and this stored ink gradually permeates into the stamp surface of the lower layer (A sheet side), so that the stamp can be stamped by lightly pressing the stamp surface against the paper surface or the like.

At this time, as mentioned above, the part that forms the stamp surface has countless fine air bubbles formed around it, and these air bubbles are delicate and communicated by wide connecting paths, so By pressing, a small amount of high viscosity ink necessary for stamping is leached out evenly, and delicate characters or figures are clearly stamped. In addition, the ink always infiltrates from the upper layer (B sheet side) and is occluded in countless open cells connected by wide connecting channels to the extent that it does not become excessive, so this rubber stamp can be used for a long time without replenishing ink. Can be used.
This is because the air bubbles are connected through a relatively wide connection path, so capillary action occurs even in relatively high viscosity ink that uses pigments, resulting in good ink leaching. it is conceivable that. Note that the characters, figures, etc. on the printed surface may be formed by engraving instead of being formed in a mold.

In the symbols in FIG. 7, 71 is a grip, 72 is a cover, 73 is a spring, 74 is a print holder, 75 is an ink absorber, X is the above-mentioned print body, 76 is a rod-shaped body that reinforces the print body This is a frame that prevents the printed body X from falling off. Example 6-P
7 In the same manner as in Example 5, ink pads for stamp pads and check writers were made using the compounding ratios shown in Tables 2 and 3, and both showed extremely good performance.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an example of a sponge rubber body obtained by the method of the present invention. a: Small bubbles, b: Large bubbles. FIG. 2 is a longitudinal cross-sectional view of a sponge rubber body in a cured stage before washing with water, produced by the method of the present invention.

Claims (1)

[Claims] 1. The void portion contains: a, 5 to 20% by volume of small air bubbles a having a diameter of approximately 0.01 mm to 0.103 mm (based on sponge rubber);
b, diameter approximately 0. , large bubbles B within the range of 149 mm to 0.498 mm are made up of 40 to 75% by volume (based on sponge rubber), and the total volume of the small bubbles A and large bubbles B is made up of 60% to 85% (sponge rubber). Open-cell foam is characterized in that both of them communicate with each other, and that the communication path between them is wide and does not contain valve-like pieces that obstruct the path, and that they are uniformly mixed in the rubber base portion. Sponge rubber printed body with