JPS5843415B2 - Katoseibikou Sheet Oyobi Sonoseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible microporous sheet having uniformly distributed continuous micropores and a method for manufacturing the same.

Conventionally, a typical manufacturing method for microporous sheets involves mixing a pore-forming agent into a polymeric substance and extracting the pore-forming agent after film formation, but this requires a considerably long extraction time. It has many drawbacks, such as difficulty in extracting completely, and difficulty in obtaining continuous pores unless a considerable amount of pore-forming agent is used.

The second method is to heat and sinter a group of particles of a polymer material, but this method requires extremely severe manufacturing conditions, is not flexible and has low strength, is difficult to obtain a thin material, and is difficult to produce a thin material. There were many disadvantages such as relatively large pore size.

Thirdly, there is a method in which a solution of a polymeric substance in a solvent is formed into a sheet and then coagulated into a film using a non-solvent, or as a modification of this method, a composition consisting of a polymeric substance, a solvent, and a non-solvent is formed into a sheet and dried. Although there are colloidal precipitation methods, these methods have problems in terms of workability and economy, such as being limited to polymeric substances and not being versatile, and using organic solvents, which poses the risk of fire and explosion. .

In view of these points, the inventor of the present invention conducted extensive research with the aim of embedding fine powder of thermoplastic resin in the surface voids of a flexible substrate without forming rough pores, and found that during insolubilization, Fine thermoplastic resin powder (hereinafter referred to as "jelly polymer") is added to a dilute aqueous solution of a limited number of water-soluble polymers (hereinafter referred to as jelly polymers), such as carboxyalkyl cellulose salts, alginate, and pectin, which form a transparent jelly. After applying a viscous composition prepared by mixing and dispersing a fine powder) to a substrate, an aqueous solution of a selected polyvalent metal salt, etc. (hereinafter referred to as
By treating the composition with a jelly-forming agent), the entire aqueous phase of the composition is instantly jelly-ized while uniformly containing the fine powder without forming coarse pores, and finally, by drying, continuous fine pores are formed. This led to the development of a method for generating .

That is, in the present invention, a viscous composition in which fine thermoplastic resin powder is mixed and dispersed in an aqueous solution of a water-soluble polymer that becomes jelly-like upon insolubilization is applied and buried in a thin film in the voids on the surface of a substrate, and then The composition is characterized by instantaneously turning the composition into a jelly, followed by drying and heat treatment to fuse at least a portion of the fine powder group to the substrate. The present invention provides a flexible microporous sheet using an economically efficient method.

The water-soluble polymer jelly used in the present invention is a solid substance containing 97 to 99% water, such as agar, which is known as a food.

In the present invention, dilute aqueous solutions of limited water-soluble polymer electrolytes, such as soda salts and ammonium salts of alginates, are mixed with acid aqueous solutions such as sulfuric acid and hydrochloric acid, or polyelectrolytes such as calcium chloride, zinc sulfate, aluminum sulfate, and ferric chloride. Transparent jelly (hereinafter referred to as polymer jelly) that is insoluble in water and organic solvents can be instantly and easily produced by dipping or spraying with a jelly-forming agent such as an aqueous solution of a valent metal salt.

Furthermore, polymer jelly dried as is is called polymer xerogel.

) can be obtained. As a special example, in the case of an alginate aqueous solution, a polymer jelly is produced simply by contacting it with hydrochloric acid vapor.

Similarly, in the case of carboxyalkylcellulose soda salt, it is preferable to use mainly polyvalent metal salts such as aluminum sulfate, aluminum nitrate, ferric chloride, etc. as the gelling agent, and in the case of pectin, lead acetate is preferably used.

These jelly-forming reactions are all cation exchange reactions of metal ions in carboxyl groups, and the polymer becomes three-dimensional when it comes into contact with hydrogen ions or polyvalent metal ions in the above-mentioned aqueous polymer solution. It is thought that water is trapped within the three-dimensional network molecules and becomes solid phase water (jelly).

By utilizing such polymer jelly and polymer xerogel in the present invention, the following characteristics are exhibited.

The first feature is that such a viscous composition, which is made by uniformly mixing and dispersing fine powder in an aqueous solution of a jelly-forming polymer, is applied so as to fill the voids on the surface of the substrate, and then instantly turned into a jelly by a jelly-forming agent. The aqueous phase of the applied composition becomes solid phase water without being dehydrated, and therefore the composition is Since no shrinkage occurs, the composition filled in the voids of the substrate can be formed into a film without forming coarse pores, and a sheet with extremely high airtightness is finally obtained.

However, the jelly formation mechanism of the present invention and the coagulation method of other water-soluble polymers, which are completely different, such as Glauber's sulfate coagulation of polyvinyl alcohol, Glauber's sulfate coagulation of alkali viscose, acid coagulation of hydroxyethylcellulose, or polyacrylic It is impossible to use trivalent metal salt coagulation of acid soda to fix the fine powder of the present invention.

In other words, since all of these solidifications are caused by dehydration and solidification, the composition filled in the voids of the substrate and the dehydration contraction effect of these polymers during solidification move and adhere to the intersection points and surfaces of the substrate filaments. As a result, coarse pores are formed in the voids of the base, and no effect of filling the fine powder can be obtained.

Furthermore, the fine powder retention power of these ordinary polymer coagulates is much smaller than that of polymer jelly, which does not allow water to flow out, so most of the fine powder is flowed out of the substrate along with water due to its dehydration effect during solidification. Put it away.

That is, these conventional polymer coagulation methods have extremely low covering ability and retention ability compared to the polymer serification method of the present invention, and cannot achieve the object of the present invention at all.

The second feature, which is the most important in the present invention, is that the polymer jelly, which is a composition that uniformly contains fine powder and is made into a jelly, is dried by heating to remove moisture. As the volume drastically decreases, it transforms into a three-dimensional network-like polymeric xerogel in which fine powders are interconnected.

Therefore, extremely fine continuous pores of several microns or less are formed in the gap between the fine powder and the microreticulated polymer xerogel.

However, it should be noted here that the polymer xerogel obtained by drying only the polymer jelly that does not contain fine powder does not have continuous micropores, and due to the presence of fine powder in the polymer jelly, The synergistic effect appears and forms micropores.

Now, the third characteristic is that when the polymer jelly of the above-mentioned composition is dried to form a polymer xerogel, the film shrinks, so a smooth product cannot be obtained, and the obtained product is extremely brittle. Therefore, in the present invention, a porous substrate having a certain degree of strength and flexibility is used to apply the composition to the surface of this substrate to prevent shrinkage during drying and form a smooth sheet. Furthermore, after drying, the fine powder is fused to this substrate through the micro network of the polymer xerogel, thereby preventing the fine powder group from easily falling off and obtaining a microporous sheet with excellent strength and flexibility. It is.

Based on the above-mentioned reasons, the present invention provides a sheet having extremely small and uniform pores due to the mutual effect of the thermoplastic resin fine powder, the polymer xerogel, and the substrate.

In the drawings, FIG. 1 is a sectional view of a microporous sheet showing an embodiment of the present invention, and FIG. 2 is an enlarged plan view of the microporous sheet, showing a fine thermoplastic resin powder 2 fused to a base 1. Micropores 4 are observed in the gaps between the three-dimensional network-like polymer xerogel 3.

Next, the present invention will be explained step by step.

In the coating composition, the gelatinized polymer is present in an amount of 1% to 5%.
It is used as a concentrated aqueous solution.

Next, the fine powder is uniformly mixed and dispersed in the viscous aqueous solution of the gelatinized polymer.

Examples of the thermoplastic resin fine powder mixed here include polyethylene, polypropylene, ethylene-propylene copolymer, polyvinyl acetate polyvinyl chloride, and ethylene-propylene copolymer.
Vinyl acetate copolymer, ethylene-vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, vinyl chloride vinyldene chloride copolymer, polystyrene,
A wide variety of thermoplastic resins can be used, such as polycarbonate, polyacrylonitrile copolymers, polyamide copolymers, polyester copolymers, or mixtures thereof.
These have chemical resistance, light resistance, flexibility, heat sealability,
It should be selected depending on required properties such as weldability and electrical properties.

These shapes are fine spheres, hollow spheres, flocks, or fibrils, with an average diameter of 1 to 2 microns.
00 microns, preferably 100 microfron to 100 microfka.

If the particle size is less than 1 micron, it will form an airtight sheet, but it will be difficult to form micropores, and if it is more than 200 microns, it will be difficult to uniformly apply the composition to a substrate.

The mixing ratio of the fine powder is generally 100% of the jelly-formed polymer aqueous solution.
The range is preferably from 20 parts to 150 parts by weight,
It depends on the porosity of the substrate, the particle size, shape, amount of application, etc. of the fine powder, and is not limited thereto.

In addition to this, the composition also contains an emulsifying dispersant, an antifoaming agent, a water repellent,
It is also possible to mix softeners, fillers, colorants, or fine droplets that are incompatible with water.

Finally, these compositions are mixed and dispersed using a stirrer or the like, and applied at a rate of 1000 cps to 10
It is adjusted appropriately so that the viscosity is about 000 cps,
At this time, care should be taken not to introduce coarse air bubbles, and defoaming treatment should be performed before application.

The viscous composition thus prepared is coated and buried in the voids on the surface of the substrate by means such as knife coating or reverse roll coating.

The substrates to be used here include synthetic resin nets,
Porous materials such as sponge or coarse paper, woven fabric, and nonwoven fabric made of fibers are preferred.

Next, by treating the coated substrate with the jelly-forming agent, the coating composition is instantaneously jelly-formed and fixed in the voids of the substrate.

The jelly-forming agent is generally an aqueous solution of the acid or polyvalent metal salt mentioned above with a concentration of 2% to 10%, and these are applied to the substrate by means such as spraying or dipping.

The jelly-formed sheet is squeezed with a mangle or the like and thoroughly washed with water to remove excess jelly-forming agent.

Even in this case, since the coating composition is a strong polymer jelly, it is very stable against mechanical tensile and compressive stress, and the fine powder never falls off from the substrate.

Finally, by drying and heat treatment, at least a portion of the fine powder group is fused to the substrate through the formed micromesh of the polymeric xerogel.

Fusion methods include heat calendering by passing the dry sheet between steel rolls heated to a temperature above the softening point of the fine powder, or heating the sheet in a heating furnace to a temperature above the softening point of the fine powder and then immediately applying it. There are methods such as applying pressure between cold rolls.

In addition to this, embossing using a textured roll is also possible.

As a result, most of the fine powder group is fused to the substrate, but at this time, adjacent fine powder particles are sintered through the micro network of the polymer xerogel.

However, in this case, because the highly heat-resistant polymer xerogel network is present, the fine powder does not flow excessively even when heated and melted, and therefore the micropores can be closed even without strict heat treatment conditions. (This point is much more advantageous than the conventional resin sintering method.

As described above, the present invention provides a microporous sheet with excellent strength and flexibility by an extremely easy method using water as a medium, and the sheet obtained thereby has extremely uniform micropores. Of course, due to the presence of polymeric xerogel, it has extremely high hygroscopicity and moisture permeability, as well as liquid absorption properties such as water absorption and oil absorption, and liquid retention properties, making it a high-grade printing material. It can be used in a wide range of applications such as paper tape base materials, various filter materials, battery diaphragms, synthetic leather base materials, and construction materials.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example 1 After adding a small amount of antifoaming agent to a 3% aqueous solution of sodium alginate, polystyrene fine particles with an average diameter of 30 microns and a filler were mixed, stirred at low speed, and then defoamed to form a uniform solution with a viscosity of 4000 cps. The following composition was prepared.

Composition-1 Sodium alginate 3% aqueous solution...
60 parts polystyrene fine particles ・・・・・・・・・
...20 parts filler (titanium oxide) ...
・・・・・・ 5 parts antifoaming agent ・・・
・・・・・・・・・ 5 parts water
・・・・・・・・・10 parts then weight 30? /
i. On both surfaces of the 0.071m thick polyester nonwoven fabric,
The above composition was applied while strongly pressing with a round knife, and the coating amount was adjusted to 302/7 r/'' in terms of solid content.

This was immediately immersed in an 8% zinc sulfate aqueous solution for about 30 seconds to complete jelly formation, then washed with water and dried at 80°C.

This was passed through a steel roll calender at 150°C to fuse the polystyrene fine particles to the substrate, resulting in a micropore diameter of approximately 0.
．． 5 micron, air permeability 250 seconds/10 by Gurley method
A paper-like flexible microporous sheet of 0 cc was obtained.

This was suitable as a high-quality paper with good printability.

Example 2 After adding a small amount of antifoaming agent to a 2% aqueous solution of carboxymethyl cellulose soda, ethylene-vinyl acetate copolymer fine powder with an average particle size of 70 microns, calcium carbonate as a filler, and a coloring agent were mixed. Distributed in the same manner as in Example 1,
Defoaming was performed to obtain the following composition having a viscosity of 2500 cps.

Composition-2 "/L/yJ-"#'y)l fiv-+
,ny O-containing...60 parts 2% aqueous solution ethylene-vinyl acetate copolymer fine powder 000.2100111.
2. Sound filler (calcium carbonate)・・・・・・・・・・・・
5 parts Colorant ・・・・・・・・・・・・
・・5 parts antifoaming agent ・・・・・・・
...5 parts Next, the above composition was applied so as to embed it on one surface of a nylon non-woven fabric with a weight of 140 f/77+2 and a thickness of 0.7, and the amount of the coating was 40 cm in terms of solid content. 7.1
I set it to 11.

Immediately spray the applied surface with a 5% aluminum nitrate aqueous solution to turn the composition into a jelly, squeeze it with a mangle,
Washing with water and drying were performed.

Next, this sheet was heated in a heating furnace at 110° C. for 2 minutes, and then immediately passed through a grain-like embossing roll at room temperature to perform embossing.

The obtained sheet was a microporous sheet with moisture permeability and moisture absorption properties and excellent surface strength, and could be used as synthetic leather for lining leather.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a microporous sheet showing an embodiment of the present invention;
FIG. 2 is an enlarged plan view of such a microporous sheet. In addition, 1 is a base body, 2 is a thermoplastic resin fine powder, 3 is a polymer xerogel, and 4 is a micropore.

Claims (1)

[Scope of Claims] 1 Thermoplastic resin fine powders are buried in the voids on the surface of the substrate in a form that is mutually bonded by a three-dimensional network polymer xerogel, and at least one of the fine powders is 1. A flexible microporous sheet, characterized in that a portion of the sheet is fused to the substrate. 2. A viscous composition prepared by mixing and dispersing a thermoplastic resin powder into an aqueous solution of a water-soluble polymer that becomes jelly-like upon insolubilization is applied and buried in the voids on the surface of the substrate, and then the composition is made into a jelly. A method for producing a flexible microporous sheet, characterized in that at least a portion of the fine powder group is fused to the substrate by drying and heat treatment.