JPH0224231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a porous stamp material.

(Prior Art) Conventionally, as a method for manufacturing porous stamp materials, thermoplastic resin powder is filled only in the character recesses of a parent die for stamping molding, or in the character recesses and above, and then the same powder as the above-mentioned powder is filled on top of the character recesses. A porous foam that is an elastic body that can be fused with the material or the above powder, has thermoplasticity at the molding temperature of the stamp material, and has sufficient physical properties to compress the powder in the character recesses during compression molding, and has already developed strength. The base materials made of fibers or fibrous network structures are piled up, and then, in a state where the base materials are compressed,
The powder is sintered by heating at a temperature near the melting point of the thermoplastic resin, and the sintered form of the powder is integrally thermally fused to the base material without impairing ink flowability at the interface. Things that cause this are known (see, for example, Japanese Patent Application Laid-Open No. 136080/1983).

(Problems to be Solved by the Invention) However, such a manufacturing method has the following problems.

(i) If the bulk specific gravity of the thermoplastic resin powder filled only in the character recesses of the parent mold for stamping molding or the character recesses and the upper side thereof is small, the filling density in the character recesses tends to be small. In order to obtain clear marking characteristics, it is necessary to increase the compressibility of the powder by the base material. However, when the compressibility of the powder is increased, the compressibility of the base material itself is inevitably increased, the porosity decreases, and the ink flowability also decreases.

(ii) Since the base material has thermoplasticity, if a resin mold such as Bakelite is used as a molding mold, the temperature cycle of heating → cooling during heating and pressure molding will cause the resin mold to The parent mold warps and deforms, which tends to result in uneven thickness of the porous stamp material (particularly the ink storage portion) after molding. As a result, it is not possible to obtain constant seal characteristics (for example, the shading of the seal impression).
In other words, when a plurality of stamp materials are molded in one master mold, the stamping characteristics differ between each stamp material, and when one stamp material is molded with one master mold, the stamping characteristics differ within one stamp material. It is not stable and constant. For this reason, conventional techniques have been adopted, such as providing a spacer with the same thickness as the predetermined stamp material in the center of the master mold (intaglio), or reducing the molding area of the master mold to eliminate the above-mentioned "warpage". However, there were problems in terms of productivity, such as an increase in the number of steps and restrictions on the number or size of stamp materials that can be manufactured per press.

(iii) In addition, even if the master mold (intaglio) does not undergo "warping" deformation, the ink storage section is made of thermoplastic foam, so dimensional shrinkage occurs due to the temperature cycle of heating → cooling. There was a tendency that it was not possible to mold to a predetermined thickness, and that large dimensional variations occurred in the thickness within the same parent mold.

The present invention has been made in view of these points, and an object of the present invention is to provide a method for manufacturing a porous stamp material that can produce a porous stamp material with excellent stamping properties with good productivity.

(Means for Solving the Problems) In order to achieve the above object, the present invention fills the character recesses of a parent die for stamping molding with thermoplastic resin powder, and then heat deforms the powder at the molding temperature and An upper porous body made of a crosslinked elastic foam that is not thermally deformed at the molding temperature and can be fused to the lower porous body is stacked via the lower porous body that can be fused with the powder, and then The lower porous body and the upper porous body are integrally heat-sealed by heating and pressurizing the lower porous body at a compression ratio sufficient to sufficiently compress the lower porous body. Note that the term "thermal deformation" means that the material is melted and compressed to some extent by heating and pressurizing, and the dimensions are set by cooling to the compressed state.

(Function) During compression molding, the upper porous body made of cross-linked elastic foam presses and thermally deforms the lower porous body while maintaining its porosity and maintaining its elasticity, thereby forming thermoplastic resin powder. will be pressurized almost uniformly.

As a result, the thermoplastic resin powder follows the character recesses of the parent mold, and the molded type becomes sharp.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The porous stamp material 1 manufactured by the manufacturing method of the present invention includes a printing part 2 and an ink storage part 3 thicker than the printing part 2, as shown in FIG.
are thermally fused to each other without impairing ink flowability at the interface. The printing part 2 is a thin layer part 2
a, and a type portion 2b protruding from the thin layer portion 2a.

Next, the manufacturing method of the present invention will be explained as shown in FIGS. 2 to 4.
This will be explained in detail along the drawings.

(Step 1) As shown in FIG.
Thermoplastic resin powder 13 is uniformly filled in 1a. This powder 13 is typically 350 mesh or less.

(Step 2) Subsequently, as shown in FIG. 3, another sheet-shaped upper porous body 15 is stacked on the top surface side of the parent mold 11 via the sheet-shaped lower porous body 14. . The lower porous body 14 is thermally deformed at the molding temperature and can be fused to the powder 13. On the other hand, the upper porous body 15 is an elastic crosslinked foam that does not undergo thermal deformation at the molding temperature and can be fused to the lower porous body 14 . Therefore, at the sintering temperature of the powder 13, the upper porous body 15
Porosity is maintained and elasticity is not compromised.

Further, the upper porous body 15 and the lower porous body 14 may be laminated and integrated in advance, or may simply be stacked one on top of the other as long as they can be thermally fused during compression molding.

(Step 3) As shown in FIG. 4, the upper mold 17 is mounted on the lower mold 12 via the ear frame 16 of a predetermined height h, and heated and pressurized. Here, the height h of the ear frame 16 is set so that both the porous bodies 14 and 15 are compressed at a predetermined compression rate.

During compression molding, the upper porous body 15 is hardly deformed, and the lower porous body 14 is thermally deformed, and a part of it enters into the character recess 11a.
The powder in a is compressed and the state is sintered.
Thus, an integrated porous stamp material 1 as shown in FIG. 1 is obtained.

The porous stamp material 1 thus obtained has a pore diameter (capillary diameter) in the ink storage part 3 and the thin layer part 2.
The size decreases in the order of a and type portion 2b, which allows for smooth ink transfer due to capillary action, and provides excellent smoothness and denseness of the type surface of type portion 2b after molding of the printing material.

In addition, as the thermoplastic resin powder 13,
A material with good sintering properties and a small particle size (50 μm as a powder to fill in the recessed parts of letters)
(preferably 30μ or less). Specifically, for example, thermoplastic urethane resin powder, plasticized polyvinyl chloride resin powder, mixture of plasticized polyvinyl chloride resin powder and nitrile rubber (NBR) powder, ethylene-vinyl acetate copolymer powder, etc. It is. Further, the powder can be obtained by grinding a thermoplastic resin of a predetermined material with a grinder, or by foaming it chemically or physically, and then freezing and grinding it, for example.

The lower porous body 14 is desirably made of a thermoplastic resin of the same material as the powder, from the viewpoint of thermal fusion with the powder (printed portion).

The upper porous body 15 is not thermoplastic,
An elastic crosslinked foam, such as polyurethane, which has a melting point higher than that of the lower porous body 14, mainly distorts the lower porous body during compression molding, and is a material that can be fused to the lower porous body. A crosslinked form is preferred.

Next, specific examples of the present invention will be described.

First, adipic acid polyester thermoplastic urethane resin (E-185 manufactured by Nippon Elastolan) was freeze-pulverized in liquid nitrogen (temperature -150°C), and the powder thus obtained was sieved to a size of 350 mesh or less. It is classified to obtain thermoplastic resin powder that constitutes the printed part. The average bulk specific gravity of this powder is 0.20
It is.

Subsequently, the powder was uniformly filled into an aluminum alloy mold (depth 4.5 mm), and a continuous porous cross-linked urethane foam with a thickness of 2.5 mm was placed on top of it as the upper porous body. (Bridgestone Scott Felt PH-20, 70% vacancy) were piled up and heated at 150°C for 3 minutes in a slightly compressed state.
As a result, a laminate of the crosslinked urethane foam and the sintered foam (lower porous body) of the thermoplastic urethane resin is obtained. In this laminate, the thickness of the cross-linked urethane foam is 2.5 mm, and the thickness of the sintered foam is 2.0 mm.
mm, and the apparent density of the sintered foam is 0.25
g/ ^cm3 .

Thereafter, the pre-formed Bakelite master mold is installed in an aluminum alloy mold, the character recesses of the master mold are filled with the powder, and on top of that,
The laminates are stacked with the sintered foam layer on the bottom. Then, heat and pressure is applied at a temperature of 150° C. for 5 minutes at a compression rate such that the final stamp material has a thickness of 3.0 mm (for example, using the edge frame 16 with a height of 2.7 mm), thereby compressing the inside of the character recess. The powder is completely sintered, and the type formed by the sintering is heat-sealed to the sintered foam layer.

In the stamp material obtained in this way, the thickness of the crosslinked urethane foam is 2.4 mm, which is almost unchanged, but the thickness of the sintered foam layer is 0.6 mm.
It will be quite compressed. Therefore,
The total thickness of the stamp material excluding the type part is 3.0 mm.

Further, the type portion is formed sharply, and the total thickness of the stamp material is uniform throughout. That is, the total thickness is
It is 3.0±0.05mm.

When impregnated with ink of 1000 cps viscosity and printed, the ink flowability was excellent, continuous printing characteristics were good, and the printing quality was uniform and clear.

(Effects of the Invention) As described above, in the present invention, since the elastic crosslinked foam is used for the upper porous body, the porosity of the upper porous body is maintained during compression molding, and the elasticity is not impaired. Instead, the upper porous body presses the thermoplastic resin powder almost uniformly, and the powder follows the character concave portions of the parent mold, making the type portion sharp. Therefore, a stamp material with a sharp impression can be obtained.

In addition, since the upper porous body that serves as the ink storage area does not undergo thermal deformation at the molding temperature, by setting the porosity of the upper porous body in advance, the ink storage area can be enlarged and the stamping life can be increased. Excellent printing material can be obtained.

Furthermore, since it is only necessary to fill the powder into the character recesses of the parent mold and sinter only the parts that will become the type, even if the parent mold is used to mold multiple pieces, the upper and lower porous bodies can be made to an appropriate size. Although it is necessary to cut the stamp material, 1
It is also possible to mold only individual pieces. Moreover, since only the type portions need to be sintered, the volume of the sintered portions is small, and therefore, the sinterability is good, and a stamp material with excellent strength can be stably produced in a short time.

Therefore, according to the production method of the present invention, a porous stamp material with excellent stamping properties can be produced with good productivity.

[Brief explanation of drawings]

The drawings show examples of the present invention, and FIG. 1 is an explanatory diagram of a porous stamp material manufactured by the manufacturing method of the present invention, and FIGS. 2 to 4 are schematic diagrams showing the manufacturing process of the porous stamp material. It is an explanatory diagram. 1... Porous stamp material, 11... Master mold for stamp molding,
11a...Character depressions, 13...Thermoplastic resin powder, 14...Lower porous body, 15...Upper porous body.

Claims (1)

[Scope of Claims] 1. Thermoplastic resin powder is filled into the character recesses of a master mold for stamping molding, and a lower porous body that is thermally deformed at the molding temperature and can be fused with the powder is placed on top of it. Then, an upper porous body made of a crosslinked elastic foam that does not undergo thermal deformation at the molding temperature and can be fused to the lower porous body is stacked, and then the lower porous body is sufficiently compressed. A method for manufacturing a porous stamp material, comprising integrally heat-sealing the lower porous body and the upper porous body by heating and pressurizing at a sufficient compression rate. 2. The method for manufacturing a porous stamp material according to claim 1, wherein the lower porous body is integrally heat-sealed to the upper porous body in advance. 3 The upper porous body made of crosslinked elastic foam is
A method for producing a porous stamp material according to claim 1, wherein the porous stamp material is a polyurethane crosslinked elastic foam. 4. The method for manufacturing a porous stamp material according to claim 1, wherein the thermoplastic resin powder is a thermoplastic urethane resin powder. 5. The method for producing a porous stamp material according to claim 4, wherein the particle size of the powder is 350 mesh or less. 6. The method of manufacturing a porous stamp material according to claim 1, wherein the lower porous body is made of a sintered foam of thermoplastic urethane resin powder.