JPH0149634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a porous printing material having a two-layer structure of a printing part and an ink storage part, and a method for manufacturing the same.

Conventionally, as a manufacturing method for porous stamp materials, a printed part made by sintering thermoplastic resin powder is heated to an ink storage part, which is a porous body that can be fused to the printed part and has already developed strength. There are known methods that fuse the
(See Publication No. 22962).

Such a manufacturing method has the following problems.

(i) Since the porous body constituting the ink storage part has thermoplastic properties, if a resin mold such as Bakelite is used as the molding mold, heating during heating and pressure molding → The resin master mold is warped and deformed by temperature cycles such as cooling, and as a result, the thickness of the porous stamp material after molding (particularly, the ink storage portion) tends to be non-uniform. As a result, when stamping is performed, certain stamping characteristics (for example, shading of the stamp) cannot be obtained. That is, when a plurality of stamps are molded using one parent mold, the stamping characteristics are not stable between each stamp material, and when one stamp material is molded using one parent mold, the stamping characteristics are not stable within one stamp material.
Therefore, conventionally, in the center of the master mold (intaglio),
Techniques that have been adopted include providing a spacer with the same thickness as the desired stamp material, or decreasing the molding area of the parent mold to release the warpage, but these methods increase the number of steps and increase the production time per press. There was a problem that there were restrictions on the number of stamp materials that could be made or the size of the stamp materials.

(ii) In addition, since the porous body constituting the ink storage part has thermoplasticity, the porous body fuses to the upper mold during pressurization and heating, and as a result, when the mold is disassembled, the printing area Since the ink absorbing portion and the ink storage portion tend to separate, a special mold release treatment had to be applied.

(iii) Furthermore, even if the master mold (intaglio) does not undergo "warping" deformation, the ink storage part is composed of thermoplastic foam, so dimensional shrinkage occurs due to the temperature cycle of heating → cooling. , it was not possible to mold to a predetermined thickness, and there was a tendency for large dimensional variations in thickness to occur within the same parent mold.

The present invention has been made in view of the above, and its main object is to provide a porous stamp material that is easy to manufacture and has excellent stamping properties, and a method for producing the same.

The porous stamp material of the present invention comprises a printed part made of a sintered foam of thermoplastic resin powder, and a crosslinked foam that maintains elasticity at the sintering temperature of the thermoplastic resin powder, and an ink having a larger porosity than the printed part. The printing part is formed by heat-sealing the ink-storage part to the ink-storage part, and the printing part further includes a thin layer part fused to the ink-storage part;
a first thermoplastic resin powder that forms the printed characters of the printed part has a particle size of 300 mesh or less, and a second thermoplastic resin powder that forms the thin layered part; The particle size of the second thermoplastic resin powder is 150 to 300 mesh, and the particle size of the second thermoplastic resin powder is larger than that of the first thermoplastic resin powder.

That is, as shown in FIG.
The printing part 2 and the ink storage part 3, which is thicker than the printing part 2, are heat-sealed to each other without impairing the ink circulation at the interface, and the printing part 2 is made of a thin layer. It is composed of a portion 2a and a type portion 2b protruding from the thin layer portion 2a. This thin layer portion 2a enhances the fusion property between the printing portion 2 and the ink storage portion 3.

The thermoplastic resin powder constituting the printing part 2 is one with good sintering properties, and the first thermoplastic resin powder with a particle size of 300 mesh or less is used in the character recesses of the parent die for stamping molding. A second thermoplastic resin powder having a particle size of 150 to 300 mesh and larger in particle size than the first thermoplastic resin powder is used in the character recesses and above the top surface of the parent mold. Specifically, for example, plasticized polyvinyl chloride resin powder, thermoplastic urethane elastomer powder, thermoplastic polyester elastomer powder, styrene-butadiene block copolymer elastomer powder, etc., can be used permanently under the molding conditions of the stamp material. The material is made of a material that causes almost no distortion, and is appropriately selected in relation to the porous body which is an elastic body used for the ink storage layer 3.

Further, the thin layer portion 2a and the type portion 2b constituting the printing portion 2 are made of powder with different particle sizes, and the type portion 2b
The particle size of the thermoplastic resin powder forming the thin layer portion 2a
From the viewpoint of ink flowability, it is desirable that the particle size be smaller than the particle size of the thermoplastic resin powder forming the ink (for example, the former is 300 mesh or less, the latter is 150 to 300 mesh). In this way, in the porous stamp material 1 after being integrated, the pore diameter (capillary diameter) is
The ink storage part 3, the thin layer part 2a, and the type part 2b are made smaller in this order, which allows for smooth ink transfer due to capillary action, and improves the smoothness and denseness of the type surface of the type part 2b after molding the printing material. It has the advantage of being superior.

As the porous body constituting the ink storage section 3, a crosslinked foam without thermoplasticity is used. As the crosslinked foam, crosslinked urethane foam, crosslinked NBR foam, etc. are preferable because they are less swellable with oil-based ink. Note that there is no problem in practical use as long as the ink storage portion 3 has a permanent deformation of 5% or less after molding.

The first method for manufacturing a porous stamp material according to the present invention includes:
A first thermoplastic resin powder with a particle size of 300 mesh or less is filled into the character recess of the parent mold for stamping molding, and a powder with a grain size of 150 mesh is further filled in the character recess and the upper side of the top surface of the parent mold.
A second thermoplastic resin powder having a particle size larger than that of the first thermoplastic resin powder is filled in ~300 meshes, and the first and second thermoplastic resin powders are heated and pressed or non-heated and pressed, and then The first and second thermoplastic resin powders are sintered by stacking base materials made of crosslinked foam that maintains elasticity at the sintering temperature of the first and second thermoplastic resin powders and heating and pressurizing them. A sintered form having a printing surface having a shape that follows the character recesses is formed by sintering, and the base material is integrally heat-sealed onto the sintered form without impairing ink flowability at the interface. Characterized by urging.

The thermoplastic resin powder is 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.

Furthermore, the first manufacturing method will be described in detail with reference to FIGS. 2 to 6.

(Step 1) As shown in FIG. 2, the parent mold 11 for stamping molding is placed in the lower mold 12, and the thermoplastic resin powder 13 is uniformly distributed in the character concave portion 11a of the parent mold 11. Fill it with. This powder 13 is usually 300 mesh or less.

(Step 2) Next, as shown in FIG. 3, the top surface side of the parent mold 11 is filled with thermoplastic resin powder 14 of the same quality as the powder 13 used in (Step 1) to a uniform thickness. to form a thin layer of the powder 14. The powder 14 used in this step has a larger particle size than the powder 13 used in (step 1), and is 150 to 300 mesh.

(Step 3) As shown in FIG. 4, the upper mold 15 is attached to the lower mold 12, thereby pressurizing the thin layer of powder 14 formed in (step 2). ,
(performed with or without heating). This pressure compresses the thin layer of powder 14.

In addition, this pressure determines the thickness of the printed part 2 in the case of heating and pressing, but in the case of non-heating and pressing, the thickness is restored even if it is compressed once, so it is possible to print large characters. The former is preferable when applied to a device having a type portion 2b. Note that instead of applying pressure without heating, pressure may be applied in a slightly cooled state.

(Step 4) As shown in FIG. 5, the upper mold 15 is removed from the lower mold 12, and the ink storage part 3 (sheet-like porous material) made of crosslinked foam is placed on the compressed thin layer. ). This process is (Process 3)
If it is carried out in a heated state, it is carried out in a cooled state, and if it is carried out in an unheated state, it is carried out in a non-cooled state. Incidentally, the ink storage section 3 contains the powder 13, 1.
At the sintering temperature of No. 4, it exhibits elasticity.

(Step 5) As shown in FIG. 6, the upper mold 15 is mounted on the lower mold 12 via the ear frame 17 having a predetermined height h, and heated and pressurized. Here, the height h of the ear frame 17
is set so that the ink storage section 3 is compressed (preferably at a compression ratio of 10 to 30%).

In this way, the porous stamp material 1 shown in FIG. 1 is formed.

According to this first manufacturing method, in (step 3), a flat surface that is fused and bonded to the ink storage section 3 is formed on the printing section 2 (thin layer section 2a).
Even when the printing part 2 and the ink storage part 3 are stably joined and the printing part 2b is large, the printing part 2b
It does not deform and can be molded easily and in a short time.

Note that in order for the printing part 2 and the ink storage part 3 to be effectively thermally fused without impairing ink circulation, it is necessary to melt the printing part 2 (sintered part) both partially and completely. (Step 3)
compressed by heating or non-heating pressure,
It goes without saying that the heating during heating and pressurization in (Step 5) needs to be within an allowable range.

The second method for manufacturing a porous stamp material according to the present invention includes:
A first thermoplastic resin powder with a grain size of 300 mesh or less is filled into the character recesses of the parent mold for stamping molding, and a powder with a grain size of 150 mesh is further filled in the character recesses and the upper side of the top surface of the parent mold.
After filling a second thermoplastic resin powder with a particle size larger than the first thermoplastic resin powder in ~300 meshes, a second thermoplastic resin powder that maintains elasticity at the sintering temperature of the first and second thermoplastic resin powders is placed thereon. By stacking base materials made of cross-linked foam and applying heat and pressure, the first and second thermoplastic resin powders are sintered to form a sintered foam having a printing surface shaped along the character recesses. In addition, the base material is integrally heat-sealed onto the sintered foam without impairing ink flowability at the interface.

In other words, in the second manufacturing method, molding is completed in one cycle of heating and pressurizing→cooling and depressurizing.

According to the second manufacturing method, the bonding force is slightly inferior when the ink storage section 3 (porous body) is thicker than the first manufacturing method, but the bonding force is slightly inferior when the ink storage section 3 is thicker. There is almost no difference when it is thin.

Next, the configuration of the present invention will be specifically described with reference to embodiments.

(Example 1) First, an adipic acid ester thermoplastic urethane resin (E-185 manufactured by Nippon Elastolan Co., Ltd.) was used as the thermoplastic urethane resin constituting the printed part.
It was buffed using a grinder and thereby powdered. Next, the powder obtained in this way is sieved to 150 mesh or more (A),
It was classified into three types: those with 150 to 300 meshes (B) and those with less than 300 meshes (C). Among these, the average bulk specific gravity of the powders is 0.153 for powder (B) and 0.153 for powder C.
is 0.128. Note that powder (A) is not used.

A pre-formed Bakelite master mold (e.g. with an effective area of 150 mm x 200 mm and a 20 mm x 60
The powder (C) was then filled into the character recesses of the parent mold (in this case, the type molded in the character recesses (Set so that the porosity of the part is 35%). Furthermore, approximately 2.5% of the powder (B) is added on top of it.
Laminated in layers with a thickness of mm.

Next, the upper plate was attached, the powder (B) was compressed until the thin layer became approximately 0.6 mm thick, and the temperature was 150°C.
But it was heated for about 3 minutes. Incidentally, during the heating and pressing, a polyester film (about 1 mm thick) is interposed between the thin layer of powder B and the upper plate to facilitate release from the mold.

After that, press it in a cooling press for about 5 minutes.
Cool under pressure.

On a thin layer of powder B compressed in this way,
A porous body made of cross-linked urethane foam (Bridgestone Co., Ltd., Scott Felt PH-20, density 0.29 g/cm ³ , porosity 76%) with a thickness of about 2.5 mm is laminated, and the thickness of the porous body is Saga 2.5mm→2.0
mm, that is, the compressibility is 20%, and heated at a temperature of 150°C for 6 minutes, thereby completely sintering the powder, and
The printed portion formed by the sintering was thermally fused to the ink storage portion.

Thereafter, the mold was cooled under pressure for about 5 minutes using a cooling press, and then the mold was disassembled and cut to a predetermined size to obtain a desired stamp material.

When we measured the thickness of the 18 stamp materials obtained in this way, the maximum value was 3.05 mm, the minimum value was 2.90 mm, and the average value =
It was 2.87 mm, and the variation was extremely small, with a standard deviation σ = 0.045.

(Example 2) In this example, the thickness of Scotstofel PH-20 (ink storage part), which is the porous body in Example 1, was
9.5mm, and the thickness of the porous body is 9.5mm→
A stamp material was obtained by heating at a temperature of 150° C. for about 6 minutes in a compressed state of 6.5 mm, that is, a compression ratio of about 32%. Note that the other configurations are the same as in the first embodiment.

The thickness of the 18 stamp materials thus obtained was an average value of 9.85 mm and a standard deviation σ = 0.065.

(Example 3) In this example, instead of Scotstofel PH-20 in Example 2, Scotstofel PF-20 (density 0.13 g/cm ³ , porosity 90
%), the thickness of the porous body is 9.5 mm → 8.0 mm,
That is, a stamp material was obtained by heating at a temperature of 150° C. for about 8 minutes in a compressed state with a compression rate of about 15.8%.
Note that the other configurations are the same as in the second embodiment.

When the thickness of the obtained stamp material was measured, the average value =
The diameter was 9.8 mm, and the standard deviation σ was 0.051.

(Example 4) In this example, after filling thermoplastic resin powder (C) into the character recesses of the parent mold in Example 1 and layering powder B on top of it, a porous body was immediately prepared. Scotstofel PH-20 (same as Example 1) was laminated thereon, and as in Example 1, the compressibility
A stamp material was obtained by pressurizing at 20% compression for about 8 minutes at a temperature of 150°C. That is, a stamp material was obtained by heating and pressing only once.

As a result, as in Example 1, a stamp material with small variation in thickness was obtained. That is, the average thickness of the stamp material was 2.85 mm, and the standard deviation σ was 0.062.

In all of the above Examples 1 to 4, the printing part (sintered foam) and the ink storage part (crosslinked urethane foam)
The adhesion force between the two was sufficient, and when attempting to separate the two, the printed portion suffered cohesive failure.

In addition, the typed portion of the printed portion was sharp because it was in close contact with the character recessed portion of the parent mold.

Furthermore, when the stamp materials of Examples 2 and 3 were made to absorb oil-based dye ink (ink viscosity: 3,000 cps) and a continuous stamp test was conducted, the results were as follows: 50,000 times and 8 times, respectively.
It was possible to make ten thousand clear stamps.

Next, each of the above embodiments will be discussed based on comparative examples.

(Comparative example) In this example, the thermoplastic urethane resin powder (B) used in Example 1 was uniformly filled into an aluminum alloy mold (with a thickness of 3.0 mm and a density of
The powder filling amount was adjusted to 0.25 g/cm ³ ), and the resulting thermoplastic urethane foam was heated at 150° C. for about 3 minutes.

A stamp material was produced in the same manner as in Example 1, using the above thermoplastic urethane foam instead of Scott Felt PH-20. However, when applying heat and pressure, the thickness of the thermoplastic urethane foam is 3.0 mm.
→This was done in a compressed state of 2.5mm.

The resulting 18 stamps had a thickness of 3.0 mm.
-2.55 mm, and the amount of variation is approximately three times that of Example 1. That is, average value = 2.78
mm, and the standard deviation σ = 0.15. The reason for this large amount of variation is that due to the thermoplasticity of the porous material that serves as the ink storage section, the dimensions are set through the cycle of temperature changes from heating to cooling, and the dimensions of the porous material that becomes the ink storage section are set due to the temperature change cycle of heating → cooling. This is thought to be because the warpage of the character recesses and the shrinkage of the porous body remain in the thickness of the stamp material even after molding is completed.

In the present invention, as described above, the crosslinked foam that becomes the ink storage part maintains elasticity at the sintering temperature of the thermoplastic resin powder that forms the printing part, so even if heated and pressurized during stamp molding, After cooling and depressurizing, the original thickness is restored and a stamp material with good dimensional accuracy is obtained.

In addition, since such a crosslinked foam is used, during molding (sintering the thermoplastic resin powder), the thermoplastic resin powder is in a compressed state, which means that the printing area and the ink storage are in a compressed state. In addition, the powder in the character recesses of the parent mold is pressurized and sintered so that it comes into close contact with the character recesses, and the type part is accurately sharp and the printing characteristics are improved. Excellent printing material can be obtained.

The only part to be sintered is the printed part close to the surface of the character concave part of the parent mold, and since its volume is small, the sintering property is good, and a stamp material with excellent strength can be obtained stably in a short time.

In particular, we take into account not only the porosity of the printing part and the ink storage part, but also the particle size of the thermoplastic resin powder that forms the type part and thin layer part of the printing part, so that the pore diameter (capillary diameter) The storage part, the thin layer part, and the type part become smaller in this order, which allows for smooth ink transfer due to capillary action, and also provides excellent smoothness and denseness of the type surface of the type part after molding of the printing material.

The cross-linked foam constituting the ink storage section can be of any thickness, and the porosity of the printing section is determined by the amount of powder filled into the character recesses of the parent mold and the pressing force applied to the powder (of the cross-linked foam). On the other hand, by changing the compression ratio), the ink storage section
By changing the porosity (density) of the crosslinked foam, the ink consumption can be adjusted and the ink consumption can be controlled, making it possible to create a variety of designs depending on usage conditions such as the size of the printing material and the pressure during printing. be.

Furthermore, since the ink storage part is formed of a cross-linked foam that maintains elasticity at the sintering temperature of the thermoplastic resin powder that makes up the printing part, it does not stick to the mold during molding, and therefore can be easily removed during the mold release process. is also unnecessary.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, and FIG. 1 is a sectional view of a porous stamp material, and FIGS. 2 to 6 are schematic process diagrams showing the manufacturing process of the porous stamp material. DESCRIPTION OF SYMBOLS 1... Porous stamp material, 2... Printing part, 2a... Thin layer part, 2b... Character part, 3... Ink storage part, 1
1... Master mold for stamping molding, 12... Lower mold, 11
a...Character recess, 13, 14...Thermoplastic resin powder, 15...Upper mold, 17...Ear frame.

Claims (1)

[Scope of Claims] 1. A printed part made of a sintered foam of thermoplastic resin powder, and an ink storage part made of a crosslinked foam that maintains elasticity at the sintering temperature of the thermoplastic resin powder and has a higher porosity than the printed part. Further, the printing part includes a thin layer part fused to the ink storage part and a type part protruding from the thin layer part, and the type part of the printing part The particle size of the first thermoplastic resin powder forming the thin layer portion is 300 mesh or less, the particle size of the second thermoplastic resin powder forming the thin layer portion is 150 to 300 mesh, and the particle size of the second thermoplastic resin powder is 300 mesh or less. A porous stamp material characterized by a particle size larger than that of thermoplastic resin powder. 2. The porous stamp material according to claim 1, wherein the crosslinked foam is a polyurethane crosslinked foam. 3 The first thermoplastic resin powder with a particle size of 300 mesh or less is filled into the character recesses of the parent mold for stamping molding, and the particle size is further added to the upper side of the character recesses and the top surface of the parent mold.
After filling a second thermoplastic resin powder with a particle size of 150 to 300 meshes and having a particle size larger than that of the first thermoplastic resin powder, and heating and pressing the first and second thermoplastic resin powders or pressing them without heating, On top of that, a base material made of a crosslinked foam that maintains elasticity at the sintering temperature of the first and second thermoplastic resin powders is stacked and heated and pressurized.
sintering the thermoplastic resin powder to form a sintered form having a printing surface shaped along the character recesses, and placing the base material on the sintered form without impairing ink flowability at the interface; A method for producing a porous stamp material characterized by integrally heat-sealing it. 4. The method for producing a porous stamp material according to claim 3, wherein the crosslinked foam is a polyurethane crosslinked foam. 5 Fill the character recesses of the parent mold for stamping molding with a first thermoplastic resin powder with a particle size of 300 mesh or less, and then fill the character recesses and the upper side of the top surface of the parent mold with a particle size of 300 mesh or less.
After filling a second thermoplastic resin powder with a particle size larger than that of the first thermoplastic resin powder at 150 to 300 meshes, a second thermoplastic resin powder that maintains elasticity at the sintering temperature of the first and second thermoplastic resin powders is placed thereon. By stacking base materials made of cross-linked foams and heating and pressurizing them, the first and second thermoplastic resin powders are sintered to form a sintered foam having a printed surface shaped along the character recesses. A method for producing a porous stamp material, characterized in that the base material is integrally heat-sealed onto the sintered foam without impairing ink flowability at the interface. 6. The method for producing a porous stamp material according to claim 5, wherein the crosslinked foam is a polyurethane crosslinked foam.