JP3251740B2 - Endless printing belt for rotating rubber stamps - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless printing belt for rotating rubber stamps.

2. Description of the Related Art Conventionally, an endless printing belt for a rotary rubber stamp has a vulcanizing agent, filler,
After accommodating a sheet made of unvulcanized rubber kneaded with additives and the like, a reinforcing cloth is placed on the upper surface, pressurized and heated, vulcanized, and then released from the mold. A plate-shaped vulcanized rubber formed on the surface is manufactured, and then, an unvulcanized rubber dissolved in a rubber solvent is applied to the adhesive portion A from which the rubber at one end is peeled off, and then the adhesive portion at the other end is applied. B is vulcanized and bonded to form an endless annular body, which is cut into a required width to obtain an annular band (see FIGS. 1 and 2). The rubber used is mainly natural rubber (NR), but acrylonitrile-butadiene rubber (NBR) generally showing excellent oil and solvent resistance is also used as an industrial / industrial rubber stamp. However, natural rubber is inferior in abrasion resistance, oil resistance and solvent resistance, and has a drawback that it cannot withstand long-term use or oil-based stamp ink. In that respect, NBR has excellent wear resistance,
It shows excellent oil and solvent resistance to mineral oils and hydrocarbon solvents, but the main solvents are glycol ethers such as ethylene glycol monoethyl ether, ellen glycol monobutyl ether, propylene glycol monoethyl ether, and benzyl alcohol. There is a disadvantage that the stamp ink using an aromatic alcohol swells and cannot withstand long-term use. Therefore, the applicant has filed an ethylene-propylene-diene rubber (EP
When DM) was used as a rubber stamp material, a rubber stamp having excellent abrasion resistance and excellent solvent resistance to glycol ether and benzyl alcohol could be obtained. But E
PDM has a disadvantage that adhesiveness is remarkably inferior, and since an adhesive portion peels off or a cloth peels off in a short period of time, it is very difficult to obtain an endless printing belt for rotating rubber stamps that can withstand long-term use. It was difficult. Particularly, since the bonding portion is in a special state in which the vulcanized rubber is fixed to the reinforcing cloth, the bonding portions may not even be bonded to each other. Therefore, as a rubber for improving the adhesiveness while maintaining the physical properties of EPDM, a blend rubber containing NBR or the like has been proposed (JP-A-49-89949, JP-A-54-1).
06554, JP-A-62-172043), the amount of NBR was too large, the physical properties of EPDM were reduced, and the EPDM swelled. On the other hand, if the blending amount of NBR is small, sufficient adhesive strength cannot be obtained, and an endless printing belt cannot be obtained. In addition, EP
Unlike the EPDM 100% rubber or the NBR 100% rubber, the DM-NBR blend rubber requires a large amount of sulfur and a vulcanization accelerator in order to obtain satisfactory physical properties, and has a drawback of discoloration to black. It was difficult to obtain rubber.

[0002]

SUMMARY OF THE INVENTION The present invention relates to an endless printing belt for a rotary rubber stamp which is excellent in abrasion resistance, does not swell in solvents such as glycol ether and benzyl alcohol, and can obtain various colors. I will provide a.

[0003]

Means for Solving the Problems In an endless printing belt for a rotary rubber stamp in which a convex character is formed on the surface of rubber and the back surface is reinforced with cloth, the endless printing belt is composed of 70 to 99 parts by weight of ethylene-propylene-diene rubber. Acrylonitrile-butadiene rubber: 1 to 30 parts by weight, for a total of 100 parts by weight, a rubber composition comprising 40 parts by weight or more of a filler containing 20 parts by weight or more of silicic acid is sulfur vulcanized. Endless printing belt for rotating rubber stamps.

[0004] The endless printing belt of the present invention comprises EPDM and N
After kneading a rubber composition obtained by adding a filler containing 20 parts by weight or more of silicic acid to a blended rubber composed of BR and
It is obtained by sulfur vulcanization together with a reinforcing cloth. The blend rubber has an EPDM content of 70 to 99 parts by weight, preferably 80 to 99 parts by weight.
95 parts by weight, and 1 to 30 parts by weight of NBR, preferably 5 parts by weight.
And 20 parts by weight in total, that is, 100 parts by weight. EPDM and NBR used in the present invention may be generally commercially available. For example, JSR EP35,
EP37C, EP65, etc. (These are EP made by Nippon Synthetic Rubber Co., Ltd.)
DM), JSR N220S, N223L, N221H
(NBR manufactured by Nippon Synthetic Rubber Co., Ltd.) can be used. The filler is used in an amount of 40 parts by weight or more, preferably 65 to 75 parts by weight, based on 100 parts by weight of the blend rubber. Here, this filler is required to contain at least 20 parts by weight of silicic acid. Therefore, the filler may be composed of only silicic acid, or may be composed of 20 parts by weight of silicic acid and 20 parts by weight or more of other fillers. As the silicic acid used in the present invention, both commercially available hydrous silicic acid and anhydrous silicic acid can be used. ) And the like. As other fillers used as needed, commercially available fillers can be used, and examples thereof include magnesium silicate, calcium silicate, and calcium carbonate. When compounding carbon black,
Although a black endless printing belt having a uniform and non-uniformity can be obtained, a white / chromatic endless printing belt cannot be obtained, so that it is not used in the present invention. The reinforcing cloth is not particularly limited as long as it does not dissolve or shrink at the vulcanization temperature, and usually, cotton is used. The vulcanizing agent may be a commercially available sulfur vulcanizing agent, for example, sulfur, a compound containing sulfur can be used,
About 5 to 5 parts may be blended. When the rubber composition is sulfur-vulcanized, it becomes a cream-colored vulcanized rubber having a high whiteness. Therefore, when a coloring agent is blended, an endless printing belt having a clear color can be obtained.

[0005] The rubber composition of the present invention may optionally contain known coloring agents, vulcanization aids, vulcanization accelerators, softeners and the like. As the colorant, any commercially available pigment other than black can be used without particular limitation. Titanium oxide (white), lead chromate (yellow), iron oxide (red), phthalocyanine (blue) ) Etc. can be given. Since the rubber composition of the present invention has a cream color having a high whiteness without blackening even when sulfur is vulcanized, it is possible to provide an endless printing belt of various clear colors by adding a coloring agent, and to provide an excellent appearance. Often increase purchase motivation. Examples of the vulcanization aid include stearic acid and zinc white.
Examples of the vulcanization accelerator include thiazoles, thiurams, sulfenamides, dithiocarbamates and the like. Examples of the softening agent include paraffin-based process oil and naphthene-based process oil.

[0006] The endless printing belt of the present invention is obtained by kneading EPDM, NBR, silicic acid, a sulfur-based vulcanizing agent and, if necessary, other additives at the above-mentioned predetermined ratio, using a conventional rotary rubber stamp. Can be manufactured through the same manufacturing process as that of the endless printing belt.

Here, when the rubber composition used in the present invention deviates from the above-mentioned compounding, the following results are produced. If the amount of EPDM is less than 70 parts by weight, even if the filler is blended in a required ratio, the solvent resistance to a stamp ink containing glycol ether or benzyl alcohol as a main solvent is reduced, while 99 parts by weight is used. If it is larger than the part, the adhesiveness of the bonding part is deteriorated, and an endless printing belt cannot be manufactured. Even if the blended rubber is blended at a required ratio, if the amount of silicic acid is less than 20 parts by weight, it is not possible to obtain an endless printing belt that can withstand long-term use due to reduced adhesive strength, The color changes to black during sulfur vulcanization, and a clear color endless printing belt cannot be obtained.

[0008]

Although it is not clear why the rubber composition used in the present invention imparts adhesiveness and suppresses discoloration when the above composition is used, it is estimated as follows from the results obtained when the composition deviates from this composition. it can. By adding a small amount of NBR having high chemical reactivity to EPDM, EPDM is somewhat modified, and the chemical reactivity of EPDM is activated by silicic acid, thereby improving the adhesiveness. In the case of a blended rubber, it is considered that the uncrosslinked free sulfur flows out due to the difference in the vulcanization rate between NBR and EPDM, and the color changes to black. However, the discoloration is suppressed because the silicic acid adsorbs this unreacted free sulfur. Can be even. Therefore, all disadvantages can be overcome only when the rubber composition has the above-mentioned composition.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples. "Parts" means parts by weight. Pigments used in Examples and Comparative Examples were white: titanium oxide (manufactured by Shiraishi Calcium Co.), red: Seika Fast Red 8040 (manufactured by Dainichi Seika), blue: Seika Fast Blue 4920 (manufactured by Dainichi Seika), yellow:
Seika First Yellow 2200 (manufactured by Dainichi Seika). The vulcanization aid used was a mixture of zinc white and stearic acid = 1: 1. The vulcanization accelerator is Noxeller TOT
-N: Noxeller CZ: Noxeller TS = 8: 1: 1
(Above, manufactured by Ouchi Shinko Chemical Co., Ltd.). As the softening agent, a process oil (manufactured by Idemitsu Kosan Co., Ltd.) was used.

[0010]

[Table 1]

After kneading each component in the upper column of Table 1 with a kneading rubber roller, the rubber composition sheeted out by a calender roll is accommodated in a mold having a concave character, and a reinforcing material is placed on the upper surface thereof. At a temperature of 160 ° C and a pressure of 150kg /
After vulcanization for 10 to 15 minutes in cm ² , the rubber at one end of the plate-shaped vulcanized rubber obtained by releasing the mold was peeled off, and the peeled off portion (adhered portion) was dissolved in a rubber solvent. After applying the unvulcanized rubber of the same component, the adhesive at the other end and temperature 170
An endless annular body was obtained by vulcanizing and bonding at 4 ° C. and a pressure of 4 kg / cm ² , and this was cut into a required width to obtain an endless printing belt. The width of the endless printing belt was unified to 3 mm for the test. Table 1
The lower column shows the results. Hardness and tensile strength are JIS
-Measured based on K6301. The adhesive strength was measured by an autograph. The swelling rate was 50 days for each solvent for 7 days.
After immersion at ℃, the dimensional change was measured. The degree of discoloration is
It was relatively visually evaluated. (◎ ... not black. △…
It becomes slightly black. ×: Blackened. )

From the above results, the endless printing belt of the embodiment was excellent in all of the adhesive strength, the swelling ratio, and the degree of discoloration. At the same time, I could not be satisfied.

[0013]

The present invention does not impair the abrasion resistance of EPDM and the solvent resistance to glycol ether and benzyl alcohol. Even if the adhesive portion is in a state in which the vulcanized rubber is fixed to the reinforcing cloth, Since the parts can be firmly adhered to each other, the endless printing belt for rotating rubber stamps having various clear colors can be obtained because the adhered parts do not peel off even when used for a long period of time and do not discolor by sulfur vulcanization. .

[0014]

[Brief description of the drawings]

FIG. 1 is a perspective view of a vulcanized rubber plate.

FIG. 2 is an annular body having an adhesive portion bonded thereto.

[Explanation of symbols]

 1 Adhesion A 2 Adhesion B

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41K 1/02 B41K 1/10 B41K 1/50 B41N 1/12

Claims (1)

(57) [Claims] 1. An endless printing belt for a rotary rubber stamp, wherein a convex character is formed on the surface of rubber and the back surface is reinforced with cloth, wherein the endless printing belt is made of ethylene-propylene-diene rubber.
0 to 99 parts by weight and acrylonitrile-butadiene rubber 1
20 parts by weight of silicic acid to 100 parts by weight
An endless printing belt for rotary rubber stamps, characterized in that a rubber composition comprising 40 parts by weight or more of a filler containing at least 40 parts by weight is sulfur-vulcanized.