JPH06889A - Porous material and production thereof - Google Patents

Abstract

PURPOSE:To obtain a porous material excellent in mechanical characteristics even when voids are increased and adapted to the production of an ink roll or pad rich in durability and increased in ink occuluding quantity. CONSTITUTION:Fine spheres 2 made of a porous polymer are bonded in a porous state by an adhesive. Two kinds of spaces of voids in fine spheres 2 and the gaps 3... between the fine spheres 2... are present.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous material used for printing ink rolls, ink pads, etc., having a myriad of minute spaces in which ink or the like can be filled, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a porous material forming such an ink roll or an ink pad, a polyvinyl chloride type, a polyurethane type or a nitrile rubber type is known. The polyvinyl chloride type is one in which salt powder is mixed with polyvinyl chloride, this mixture is molded into a predetermined shape, and then salt is dissolved and removed with warm water to form a large number of minute spaces inside. is there. Also, for polyurethane type, soft polyurethane foam is heated,
It is compressed to have a desired porosity.

The nitrile rubber-based porous material is prepared by mixing nitrile rubber with salt powder and evenly dispersing the salt powder in toluene or the like, then casting in a predetermined shape and then vaporizing the toluene. After solidification, the salt is dissolved and removed with warm water to form a minute space inside.

However, the polyvinyl chloride type porous material is not sufficient in oil resistance, cannot cope with various compositional changes accompanying the improvement of the function of the ink, and is also unsatisfactory in terms of mechanical durability. In addition, the polyurethane-based porous material is easily hydrolyzed by the ink component and is easily damaged. Further, in the nitrile rubber type porous material, there is a problem that the use of the organic solvent is being restricted in recent years from the viewpoint of environmental protection. Further, in any of polyvinyl chloride-based, urethane-based, and nitrile rubber-based materials, the mechanical strength is drastically reduced when the porosity is increased to 80% or more, which is not suitable for practical use.

[0005]

Therefore, the object of the present invention is to provide excellent oil resistance and durability, no reduction in mechanical strength even if the porosity is increased, and salt is used even in the production thereof. It is not necessary to do so, and it is to obtain a porous material and a method for producing the same that can reduce the consumption of the organic solvent.

[0006]

[Means for Solving the Problems] The problem is that porous polymer microspheres made of a crystalline polymer or an amorphous polymer having fine voids are manufactured in advance, and the microspheres are consolidated into a porous shape with an adhesive. It will be solved.

The present invention will be described in detail below. Figure 1
Shows schematically an example of the porous material of the present invention. In the figure, reference numeral 1 is the porous material of the present invention. The porous material 1 is a porous polymer microsphere (hereinafter referred to as a microsphere). Abbreviated.) ... are joined to each other by an adhesive 3 ... and are fixed integrally, and innumerable voids 4 are formed between these innumerable microspheres 2.

Therefore, the porous material 1 has two kinds of voids, that is, the voids (pores) existing in the microspheres 2 and the voids 4 existing between the microspheres 2 ... The porosity is in the range of 40 to 90%, preferably 55 to 80%.

Next, the microspheres 2 constituting the porous material 1 of the present invention will be described. FIG. 2 is a cross-sectional view schematically showing the microspheres 2 made of a crystalline polymer. In FIG. 2, (A) is a lamella crystal of the polymer, and the lamella crystal (A) is from the center of the sphere. It extends radially to form spherical particles. (B) is a hole formed between a plurality of lamella crystals (A), and extends radially from the center of the sphere. The width of each lamella crystal (A) is about 70 to 120Å. The opening diameter (B ₁ ) of the holes (B) varies depending on the diameter of the microspheres, but it is usually preferable to set it to about 150 to 200 Å.

The particle size, porosity, etc. of the microspheres differ depending on the application and cannot be determined unconditionally, but generally the particle size is 1
It is preferable that the average particle size is not more than 00 μm, that is, the particle size distribution width is as small as possible. The lower limit of the particle size is about 10 μm from the practical point of view. Especially preferred is a particle size of 20.
˜80 μm, especially 30 to 50 μm. When the Dp50 is 35 μm or more, the particle size distribution width is preferably within a range of ± 10 μm, especially ± 5 μm, centering on the Dp50 value.

The porosity is 40 to 75% by volume, especially 45 to
A range of 60% by volume is preferable. When the porosity is lower than the above range, the amount of the active ingredient that can be contained in the pores is small, so that the use is limited. If the porosity is higher than the above range, the mechanical strength decreases, which is not preferable. In the present invention, it is possible to easily obtain microspheres in which individual particles have a uniform porosity within the above range of porosity.

The polymer forming the microspheres is a crystalline polymer by hydrogen bonding, and a crystalline polymer capable of forming lamella crystals is preferably used. Usually, a crystalline thermoplastic polymer is used. Examples of such crystalline thermoplastic polymers include polyamides such as nylon 6 and nylon 66, polyesters such as polyethylene and polyethylene terephthalate, and polyvinyl alcohol.

Further hard segment (crystalline, hydrophobic)
Random or block copolymers composed of and soft segments (non-crystalline and hydrophilic) are mentioned. Soft segments mainly contribute to the formation of hydrogen bonds in these copolymers. Examples of combinations of hard segments and soft segments include those shown in Table 1.

[0014]

[Table 1]

In the above, examples of the polyacrylate include polyalkyl acrylate and polyalkyl methacrylate (wherein the alkyl group has 1 to 8 carbon atoms). Incidentally, polybutadiene is hydrophilic and hydrogen-bonding due to trace components contained at the time of polymerization together with itself.

Further, the polymer may have a semi-IPN structure. For example, in a combination of polyethylene and polyacrylate, the polyethylene segment may be non-crosslinked and the polyacrylate segment may be crosslinked.

The polymer used for the microspheres preferably has many hard segments and is regularly crystallized. The ratio of the hard segment to the soft segment is preferably 95 to 75 mol% of the former and 5 to 25 mol% of the latter. Is preferred. When each segment deviates from this range and the former is small and the latter is large, crystallization and porosity tend to be difficult. However, it can be used outside the above range by modifying it by adding a third component.

Although the polymer to be used varies depending on the kind, it is preferable that the molecular weight distribution width is narrow so that crystallization and desolvation molecule precipitation can be carried out uniformly and fine particle spheres having a particle size distribution width can be obtained.

As a method for producing such microspheres, the inventors of the present invention have previously proposed JP-A-3-26729, JP-A-3-140340, and JP-A-3-185.
The method described in Japanese Patent Application No. 028, etc. is used.

For example, in the production method described in JP-A-3-26729, a crystalline polymer by hydrogen bonding is dissolved in a first solvent (solvent A), and the obtained polymer solution is used as the first solvent. Are compatible with each other but are a poor solvent or a non-solvent for the above polymer, and are finely dispersed in a second solvent (solvent B) having a hydrogen bond index larger than that of the first solvent to obtain fine particles having a desired particle size. In addition, the second solvent is permeated into the fine particles, phase separation and crystallization of the polymer are performed in the fine particles to make them porous, and then the fine particles are separated from the solvent and dried. It is a microsphere.

Here, the solvent A is preferably one having a small hydrogen bond index, for example, a hydrogen bond index of 2 to.
7 range, dimethylformamide (6.4), acetone (5.7), isopropyl acetate (5.2), butyl acetate (5.4), methyl ethyl ketone (5.0), benzene (3.8) , Methanol (8.9), etc. are used alone or as a mixture.

As the solvent B, those having a hydrogen bond index larger than that of the solvent A are preferable, and the hydrogen bond index is 10 to 10.
20 units of ethylene glycol monomethyl ether (15.3), ethylene glycol monoethyl ether (15.3), ethylene glycol monobutyl ether (15.5), propylene glycol monomethyl ether (14.6), etc., alone or mixed, Used.

Further, as a means for dispersing the polymer solution in the second solvent (solvent B), it is preferable to use a means in which mechanical shearing force is first applied and then ultrasonic waves are applied to disperse the polymer solution.

Further, in the production method described in Japanese Patent Laid-Open No. 3-140340, a solution in which a crystalline polymer by hydrogen bond is dissolved in a first solvent is discharged from a spinneret to form ultrafine fibers, Is compatible with the first solvent, but is a poor solvent or non-solvent for the polymer,
In addition, by introducing the second solvent into the atmosphere composed of the second solvent having a hydrogen bond index larger than that of the first solvent, the second solvent is permeated into the ultrafine fibers to cause phase separation and crystallization of the polymer in the fibers. The porous crystal regions discontinuous along the length direction of the fibers are formed, and then the crystal regions are separated from each other to form isolated particles.

The first solvent and the second solvent in this method are the same as those used in the previous manufacturing method. Also, the ultrafine fibers are first exposed to a steam bath of a second solvent,
It is then preferably exposed to a droplet bath and then introduced into a liquid bath for crystallization of the polymer and phase separation.

Furthermore, in the production method described in Japanese Patent Laid-Open No. 185028/1993, a crystalline polymer by hydrogen bonding is used as the first method.
A solution of a second solvent which is compatible with the first solvent but is substantially non-solvent to the polymer and has a hydrogen bond index larger than that of the first solvent. In the form of a thin film, the second solvent is allowed to penetrate into the thin film to cause phase separation and crystallization of the polymer in the thin film, and the spherical porous crystalline region is discontinuous in both directions of the thin film. And then the crystal regions are separated from each other to form isolated particles.

Also in this manufacturing method, as the first solvent and the second solvent, those similar to those described in the previous example are used. Further, it is preferable to carry out phase separation and crystallization while supporting and moving the thin film with a supporting member.

The porous polymer microspheres used in the present invention may be those obtained from an amorphous polymer. For example, an acrylic resin or a thermoplastic polyurethane resin is dissolved in a first solvent to form a resin solution, and a second resin which does not dissolve the resin in the resin solution and is compatible with the first solvent is used. It can also be produced by a method in which a solvent is added and agitated rapidly to form the microspheres of the resin solution, and at the same time, the microspheres of the porous polymer are precipitated by the second solvent.

As the adhesive used in the present invention, various ones such as one made of a thermoplastic resin and one made of a thermosetting resin can be used. The size and ratio of the voids in the porous material 1 are used. A powdery hot-melt type adhesive is preferable from the viewpoint of controlling the temperature, for example, a diameter of 10 to 100.
Synthetic fibers such as nylon and acrylic with a length of μm 2
It is preferable to use curled short fibers or the like having a thickness of 0 to 100 μm. Further, it is necessary to select the adhesive whose melting point or melting start temperature is lower than that of the crystalline polymer forming the microspheres by 10 to 30 ° C.

Such an adhesive is used for microspheres, No. 4
After adding about 10% (weight ratio) and mixing uniformly with a mixer, this mixture is filled in the cavity of a mold having a cavity of a desired shape and heated to melt the adhesive and By adhering the spheres to each other, the porous material of the present invention can be manufactured. Further, hot air can be used as a heating source.

At this time, by using a thermosetting adhesive such as a short fiber of a fiber obtained by mixing a thermoplastic with a crosslinking agent, an accelerator, etc. as an adhesive, high adhesive strength, heat resistance and resistance are obtained. A porous material having good chemical properties can be obtained. In addition, when the mixture is heated excessively during heating, a mixture having almost no voids can be obtained, so it is necessary to pay sufficient attention to the pressurization. Furthermore, in the case of using a powdery adhesive, if the particle size is increased, the size of the individual voids is increased, and a porous material with a high void ratio is obtained. On the contrary, if the particle size is reduced, a porous material having a small porosity can be obtained. The porosity of the porous material thus obtained is 40 to 90%, preferably 55.
The range is -80%. If it is less than 40%, the storage amount of ink or the like will be insufficient, and if it exceeds 90%, the mechanical strength will be insufficient.

In such a porous material, since the microspheres constituting the porous material are porous materials having a porosity of 40 to 60%, even if the total porosity is increased to about 80%, It has excellent mechanical properties with almost no reduction in mechanical strength.

For example, if a microsphere itself having a porosity of 50% is used to manufacture a porous material having a total porosity of 80%, it is sufficient to secondarily secure a porosity of 30%.
A sufficient volume occupied by the microspheres can be secured. On the other hand, in the case of a porous material produced by one ordinary behavior, when the total porosity is 80%, the volume occupied by the polymer particles is only 20%, so the mechanical strength of the porous material is extremely low. Will be things.

Specific examples will be shown below. Reference Examples 1 to 3 and Production Example of Microspheres Table 2 shows the polymer and solvent A shown in Table 2 in a large-sized dispenser (improved so that Twinflow VR50 manufactured by Tomita Engineering Co., Ltd. can be continuously discharged). It was supplied at a ratio to dissolve the polymer to obtain a polymer solution. Supply to the large-scale dispenser was carried out continuously using an air pressure feeding tank. The polymer was dissolved at room temperature in Reference Example 1 and at about 50 ° C. in Reference Examples 2 to 3.

[0035]

[Table 2]

The second large-scale dispenser (Twinflow VR100 manufactured by Tomita Engineering Co., Ltd.) can be continuously discharged at the ratio of the discharge liquid (polymer solution) from the large-scale dispenser and the solvent B shown in Table 2 in the ratio shown in Table 2. The polymer particles were continuously supplied and uniformly dispersed to obtain a primary dispersion liquid, which was then allowed to stand to precipitate fine polymer particles. Then, this product (primary dispersion) was applied to an ultrasonic disperser [Nissei Plant Unit 1, manufactured by Nippon Seiki Co., Ltd.].
Oscillation frequency 20 kHz, high frequency output 3 kW (600 W x
5 units)] and ultrasonically dispersed continuously to obtain a secondary dispersion liquid.

The secondary dispersion liquid discharged from the ultrasonic disperser was dehydrated with a vacuum suction type drum dryer (Kanebo PC separator A-1 type manufactured by Kanebo Co., Ltd.) to obtain a water content of about 1
0 wt% cake was obtained. This cake was dehydrated and dried by a medium fluidized drying device manufactured by Nara Machinery Co., Ltd. Super absorbent polymer particles with an average particle size of 100 μm as a fluid medium (Mitsubishi Yuka
An easily moldable water-absorbent resin plaweet G260H (made by KK) having a spherical shape was used, and the operation of contacting the cake at room temperature while transferring fluid and dehydrating and drying at room temperature was repeated 5 times. Thus, porous polymer microspheres having the characteristic values shown in Table 3 were obtained.

[0038]

[Table 3]

(Examples 1 to 3, Production Example of Porous Material) A fibrous adhesive (acrylic fiber curl type) was added to each of the three types of microspheres obtained in Reference Examples 1 to 3 at a weight ratio of 5% by weight. Cutting waste, length 5-10 mm, outer diameter 5-10 μm),
Mix well with a stirrer. This mixture is filled in a mold and heated under the conditions of a temperature of 150 ° C., a pressure of 0.5 kg / cm ² , and a time of 15 minutes to melt the adhesive and bond the microspheres to obtain a target having a thickness of 15 mm. Three types of porous materials were obtained. These 3
The porosity, compressive strength, and tensile strength of each kind of porous material were determined. The results are shown in Table 4. The compression strength and the tensile strength were measured according to JIS-K-6767 (polyethylene foam test method).

[0040]

[Table 4]

Table 4 also shows the characteristics of a conventional nitrile rubber type porous material (porosity 60%) for comparison. As is clear from the results in Table 4, it is understood that the porous material of the present invention exhibits excellent mechanical properties despite the high porosity.

Further, an ink roll was prepared using the porous material shown in Example 1 of Table 4, and the ink was enclosed in the voids of the ink roll to perform actual printing. Printing was possible with the same sharpness as the first.

[0043]

As described above, the porous material of the present invention is formed by adhering porous polymer microspheres with an adhesive, so that even if it has a high porosity, The characteristics are excellent. Therefore, an ink roll or an ink pad made of this porous material has an effect that the amount of stored ink can be increased and the durability becomes excellent. In addition, various polymers can be used as the polymer forming the porous polymer microspheres, and thus can be applied to a wide range of applications. In addition, it is not necessary to use salt or the like when manufacturing this, the amount of the organic solvent used is small, and the work is easy.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing the structure of a porous material of the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure of microspheres used in the present invention.

[Explanation of symbols]

 1 Porous Material 2 Microsphere 3 Adhesive 4 Void A Lamella Crystal B Void

Claims (7)

[Claims] 1. A porous material obtained by fixing porous polymer microspheres with an adhesive. 2. The porosity of the porous polymer microspheres is 25 to.
The porous material according to claim 1, which is 75%. 3. The porous material according to claim 1, which has a porosity of 55 to 80%. 4. The diameter of the porous polymer microspheres is 15 to 50.
The porous material according to claim 1, which has a thickness of μm. 5. A method for producing a porous material, which comprises adding an adhesive to and mixing the porous polymer microspheres and then solidifying the adhesive. 6. The method for producing a porous material according to claim 5, wherein a hot-melt adhesive is used as the adhesive, and the melt bonding is performed with hot air. 7. The method for producing a porous material according to claim 5, wherein the adhesive is a curled short fiber of synthetic fiber.