JP2852488B2 - Rubber stamp material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber stamp material, and more particularly to a rubber stamp material suitably used for laser engraving.

[0002]

2. Description of the Related Art Conventionally, as a rubber stamp material such as a name stamp, a company name stamp, an address stamp, and a rotary stamp using an endless printing belt, for example, a number ring, a date stamp, etc., a continuous bubble which can penetrate ink so that continuous printing can be performed. Molded foam rubber slabs or porous plastics are commonly used.
As a means for producing such open-cell foamed rubber slabs, a particle coagulation method or a salt extraction method is known. The former coagulation method involves putting thermoplastic elastomer particles into a mold, compressing and heating them to thermally fuse the particles together, and forming voids in pores.The latter salt extraction method uses inorganic salt added to crosslinked rubber. Water-soluble particles such as are mixed, rubber is crosslinked, and salts are dissolved and extracted, and this extraction path is used as pores.

[0003]

In the conventional open-cell foam rubber, the former cannot increase the pressing pressure to secure pores between particles, and the latter cannot maintain a certain amount or more to secure an extraction path. The addition of salt is required, and therefore the foaming rate must be high, making it difficult to obtain an elastic modulus and hardness suitable for the imprinting pressure.When used as a stamping material, ink bleeding and character There is a drawback that deformation occurs and printing characteristics are inferior. In addition, the above-mentioned manufacturing methods have a problem that all of them require many steps and the productivity is poor. In view of these problems, closed-cell foam rubber or foam plastic, whose elasticity and hardness can be easily adjusted, may be used as the rubber stamp material, but in this case, continuous stamping is possible because the ink permeability of the stamp material is lost. Not suitable for imprint materials.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a rubber stamp material having a proper ink permeability, elasticity, and hardness while being a closed-cell foam rubber, and a method of manufacturing the same. It was made for the purpose of.

[0005]

That is, the first invention relates to a rubber stamp material, which is a closed-cell foam rubber having a volume expansion rate of 50 to 180%.
5 to 80 parts by weight of a hydrophilic polymer incompatible with the crosslinkable rubber is uniformly dispersed with respect to 00 parts by weight.

The second invention relates to a method for producing the rubber stamp material, wherein 5 to 80 parts by weight of a hydrophilic polymer incompatible with the crosslinkable rubber and 100 parts by weight of a crosslinkable rubber and a foaming agent and other necessary additives are added to 100 parts by weight of the crosslinkable rubber. A foaming agent is added to the foaming agent so that the foaming agent has a volume expansion ratio of 50 to 180%. The third invention relates to the improvement of the rubber stamp material and the manufacturing method. Wherein the hydrophilic polymer incompatible with the bridging rubber is water-soluble and thermoplastic.

The crosslinkable rubber used in the present invention includes natural rubber, SBR, BR, NBR, CR, EP
Synthetic rubber such as M or EPDM or a mixture thereof can be arbitrarily used. As the hydrophilic polymer incompatible with the crosslinkable rubber, acrylic acid-based, vinyl alcohol-based, polyethylene glycol-based, HEAM-based resin or fiber, amide-based, acrylic-based fiber surface graft,
Fibers subjected to hydrophilic treatment by hydrolysis or the like are used. As the thermoplastic hydrophilic polymer incompatible with the crosslinkable rubber, the above-mentioned polyethylene glycol resins are preferably used.

[0008] Further, as in the prior art, other additives for the crosslinkable rubber include reinforcing agents such as carbon black, silica and calcium carbonate, fillers, crosslinking agents such as sulfur and peroxide, and accelerators thereof. Activators, co-crosslinking agents, foaming agents and auxiliaries, tackifiers, processing aids such as lubricants, and other general rubber compounding agents are appropriately added as conventionally known.

[0009]

In the present invention, the hydrophilic polymer incompatible with the crosslinkable rubber is 5 to 80 parts by weight based on 100 parts by weight of the crosslinkable rubber.
The reason for adding the parts by weight is to allow the aqueous ink to penetrate through the hydrophilic polymer uniformly dispersed in the foamed rubber matrix and to impart ink permeability to the foamed rubber while being a closed cell type. If the amount of the hydrophilic polymer is less than 5 parts by weight with respect to 100 parts by weight of the crosslinkable rubber, sufficient permeability cannot be obtained. If the amount is more than 80 parts by weight, excessive osmosis causes "bleeding" and the like. That is, the same problem as the conventional coagulation method or salt extraction method occurs.

The reason why the volume expansion ratio is set to 50 to 180% is to make the elasticity and hardness of the rubber stamp material appropriate values.
In particular, it is for obtaining a foaming ratio suitable for the laser irradiation engraving method. That is, if the volume expansion rate is lower than 50%, the elasticity of the rubber stamp material is small and the hardness is too high, in combination with the reinforcing effect of the added polymer. Therefore, sufficient compressive deformation at the time of imprinting cannot be obtained, and the permeation of the penetrated ink to the surface is not smooth, which causes "fading". Also, the engraving efficiency (engraving depth / required energy) of the laser is reduced.
On the other hand, if it is more than 180%, the ink permeability becomes too high to cause "bleeding". In addition, when laser engraving is performed, the problem of the “smearing” when the mark is used repeatedly becomes remarkable due to the correlation with the shape of the edge of the protruding mark portion that appears characteristically.

In the above, if the hydrophilic polymer incompatible with the crosslinkable rubber is made to be water-soluble, it is eluted with water after molding the foamed rubber, so that the foamed rubber having continuous pores can be formed similarly to the salt extraction method. can do.

Next, an embodiment of the present invention will be described. [Examples 1 to 8] In comparison with the composition shown in Table 1 as a composition of a crosslinkable rubber as a base material, a hydrophilic polymer (a water-absorbing resin manufactured by Kuraray Co., Ltd., trade name "KI gel", Sumitomo Chemical Co., Ltd.) Water-absorbent resin, trade name "Sumikagel S520", Toyobo Co., Ltd. surface-hydrophilic treated acrylic short fiber trade name "Lanseal F"), kneading with a roll, sheeting, primary vulcanization at 140 ° C x 13 minutes Then, secondary vulcanization was carried out by press vulcanization under the condition of 160 ° C. × 10 minutes to obtain a 10 mm thick independent foamed rubber slab. The foamed rubber slab had a volume expansion ratio of 70 to 140% and an Asker C hardness of 50 to 70 degrees. In Table 1, PHR indicates the number of parts by weight added to 100 parts by weight of rubber.

Next, one side of the independent foamed rubber slab was irradiated with a laser to engrave a striped pattern having a width of 1 mm and a depth of 1 mm at intervals of 2 mm. Next, 0.5 cc of ink was dropped on the surface of the engraved rubber slab obtained above, and the permeation end time was measured.
The results were as shown in the lower column of Table 2. In Table 2, the comparative example containing no hydrophilic polymer did not penetrate the ink at all, whereas the inks of Examples 1 to 8 all showed permeability and were proportional to the amount of the hydrophilic polymer added. It was confirmed that the permeability improved.

[0014]

[Table 1]

[0015]

[Table 2] * 1 The permeation time is indicated by “minute-second”. * 2 No ink penetration.

Examples 9 to 11 Next, as shown in Table 3, a water-soluble thermoplastic resin (PAOGEN, trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the hydrophilic polymer in the same manner as in Example 1. Thus, a closed-cell foamed rubber was produced and stamped. As is clear from Table 3, it was found that the permeation time could be shortened.

[0017]

[Table 3]

Examples 12 to 14 Next, the closed-cell foamed rubber slabs obtained in Examples 9 to 11 were sliced to a half thickness and immersed in water for about 5 hours to extract a water-soluble hydrophilic polymer. Later dried. Thereafter, the same mark as in Example 1 was engraved on the surface opposite to the slice surface by a laser irradiation method, and the same permeability evaluation as in Example 1 was performed. The results are as shown in the right column of Table 3. It has been found that when the water-soluble hydrophilic polymer is extracted with water, the permeability is further improved. Example 9
Also, the volume expansion ratio of 70 to 140%,
Hardness was 50-70 degrees.

[0019]

As described above, the rubber stamp material of the present invention is a closed-cell foamed rubber whose elastic modulus and hardness can be easily adjusted, but has a penetrability capable of penetrating aqueous ink by adding a hydrophilic polymer. It has the effect of functioning as a stamping material. Further, if a thermoplastic polymer is used as the hydrophilic polymer, the penetration speed is significantly increased without sacrificing the elasticity and hardness of the rubber stamp material, and the stamp material has excellent performance. In addition, if a water-soluble hydrophilic polymer is used as the hydrophilic polymer and water is extracted therefrom, it is possible to exhibit even better permeability. It is possible to do. Further, according to the production method of the present invention, it is possible to produce a permeable foamed rubber simply by blending the materials, and it is not necessary to perform an extraction step, a compression step, and the like as in the production of a conventional continuous-porous foamed rubber. It has effects such as facilitating the production of foamed rubber.

Claims (3)

(57) [Claims] 1. A closed-cell foamed rubber having a volume expansion rate of 50 to 180%, wherein a crosslinkable rubber is contained in the rubber matrix.
A rubber stamp material characterized in that 5 to 80 parts by weight of a hydrophilic polymer incompatible with the crosslinkable rubber is uniformly dispersed in 100 parts by weight. 2. A foaming agent is foamed by adding 5 to 80 parts by weight of a hydrophilic polymer incompatible with the crosslinkable rubber and a foaming agent and other necessary additives to 100 parts by weight of the crosslinkable rubber. A method for producing a rubber stamp material, wherein the volume expansion ratio is 50 to 180%. 3. The hydrophilic polymer incompatible with the crosslinkable rubber is water-soluble and thermoplastic.
The method for producing a rubber stamp according to claim 2 or the rubber stamp according to claim 2.