JPH0680817A - Porous high polymer sheet and its production - Google Patents

Abstract

PURPOSE:To easily obtain the subject sheet having excellent water- impermeability, moisture-permeability and uniformity and useful as a clothing material, medical coating material, etc., without necessitating the treatment with a large amount of a solvent by forming a thin film from a solution of a high molecular material and contacting the film with fine droplets of a specific coagulation solvent. CONSTITUTION:A solution of a high molecular material such as polyurethane is formed in the form of a thin film and brought into contact with fine droplets of a coagulation solvent (e.g. water or methanol) unable to dissolve the high molecular material and compatible with a solvent (e.g. DMF) for the dissolution of the high molecular material. The objective sheet produced by this process has an average pore diameter of 0.5-30mum, a porosity of 40-70% and a moisture permeability of 50-5,000g/m<2>.24hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing a polymeric porous sheet by a wet method and a polymeric porous sheet which is particularly useful as a medical covering material, a water impermeable clothing material and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a polymer porous sheet, 1) kneading an inorganic salt powder or the like into a thermoplastic polymer,
Method of dissolving and extracting an inorganic salt with a solvent after molding into a thin film, 2) Method of physically forming small pores by stretching a thin film by kneading an inorganic salt or the like, 3) Dissolving in a solvent A method in which the polymer solution is made into a thin film, is compatible with the solvent, and is placed in another solvent that does not dissolve the polymer material, the original solvent is eluted, and the polymer material is aggregated by replacing the solvent, etc. Are known. However, the above 2
In one of the methods, the pore size is regulated by the size of powder such as an inorganic salt, so it is difficult to obtain a porous sheet having a fine pore size, and as a method for obtaining a fine porous sheet, the method of 3) is exclusively used. Is used.

In the method 3), however, the pore size is controlled by the rate of substitution of the two kinds of solvents, so that the pore size can be influenced by the concentration of the polymer, the treatment temperature, and the concentration of the dissolved solvent in the coagulating solvent. There are many factors, and strict control of these is necessary to obtain uniform pores. In particular, since there is a drawback that a huge amount of coagulation solvent is required for controlling the concentration of the dissolution solvent in the coagulation solvent, only water is used as the coagulation solvent, and water containing a small amount of the dissolution solvent is used. There is a drawback that the manufacturing cost becomes high, for example, enormous cost is required for the recovery of the solvent from the tank and the treatment of the waste water.

[0004]

SUMMARY OF THE INVENTION The present invention does not require strict control conditions for obtaining desired micropores, uses a small amount of solvent, has a good solvent recovery rate, and is economically high. An object is to provide a method for producing a molecular porous sheet.

The present invention also provides a novel porous polymer sheet having finer and more uniform porosity, which is widely required for medical covering materials, water-impermeable clothing materials and the like, and which has good physical properties. This is an issue.

[0006]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a thin film obtained from a melt of a polymer material is dissolved by contacting a coagulating solvent in a fine particle state. When a phase transition occurs due to the mixing of the solvent and the coagulating solvent, the polymer material solidifies by the coagulating solvent, and the solvent accumulates in the gap between the polymer materials that coagulates, causing the intermolecular cohesive force. A uniform spherical solvent layer (micropores) is formed on the polymer sheet, and as the micropores expand, they are replaced with air when the micropore diameter exceeds the capillary pressure of the solvent, so that the mixed solvent is removed from the sheet. Was eliminated by
It was found that the dissolving solvent can be recovered in a high concentration state.
Further, it has been found that the polymer porous sheet thus obtained has a large number of uniform micropores.

The present invention has been completed based on the above findings, and its gist is as follows. 1. It is characterized in that the solution of the polymer material is in the form of a thin film, and is in contact with the coagulation solvent that is compatible with the solvent for the solution and does not dissolve the polymer material in the fine particle state of the coagulation solvent. Method for producing polymer porous sheet and polymer porous sheet thus produced.

2. In the porous sheet, the average pore diameter is 0.5 to 30 μm, the porosity is 40 to 70%, and the water vapor permeability is 500.
A polymer porous sheet having a weight of up to 5000 g / m ² · 24 hrs.

In the present invention, the polymer material is dissolved in a single or mixed solvent for dissolution to prepare a solution of the polymer material. The dissolution concentration is appropriately selected depending on the pore diameter and thickness of the target porous sheet and the solution viscosity for ease of processing, but is generally 5 to 50%, preferably 10 to 30%. What is used.

As the polymer material, for example, polyurethane, ethylene vinyl acetate copolymer, EVOH (polyethylene vinyl hydroxide), polyacrylate, polystyrene, nylon, SIS (styrene isoprene copolymer), tetron, polyethylene, polypropylene, chloride Various thermoplastic resins such as vinyl, polyacetal, polyvinyl acetate, SBR (styrene butadiene rubber), NB
Polymer compounds such as R (nitrile rubber) and synthetic rubber such as polybutadiene are advantageously used, but polyurethane is particularly preferable.

The solvent is preferably a solvent which is compatible with the coagulating solvent to make the polymer substance insoluble, and examples thereof include hydrocarbons such as dimethylformamide, hexane, heptane, cyclohexane, cycloheptane, benzene, toluene and xylene. Although used, dimethylformamide is particularly preferred. These solvents may be used alone or as a mixed solvent.

Next, the polymer solution is formed into a thin film. As a molding method, a general method such as coating on a plastic film or coating on a stainless steel conveyor is used, but it may be coated, impregnated or sprayed on a non-woven fabric or other fibers. The thus obtained thin film-shaped molded product generally has a thickness of 10 to 500 μm, preferably 20 to 60 μm, and the molded product contains 50 to 95% (by weight) of solvent, preferably 70 to 90% (by weight). .

The molded sheet-like material is brought into contact with a coagulating solvent in a fine particle state. Such fine particles are those in a vapor state or atomized, and have a particle diameter of 0.5 mm or less, preferably 0.1 mm or less, and more preferably 0.01 mm or less. The contact is usually performed by passing a molded sheet-like material through a coagulation tank. Here, the particles of the coagulating solvent contact the sheet,
It is absorbed and diffusely mixed in the solvent in the sheet. The dissolved polymeric material begins to coagulate due to the mixing of the insoluble solvent, and the coagulation proceeds from the surface toward the inside. On the other hand, the dissolution solvent containing the coagulation solvent that has lost its place due to the coagulation of the polymer material accumulates in the gap between the coagulating polymer materials, and tends to become spherical due to the intermolecular cohesive force. This phenomenon starts from the surface layer and gradually progresses to the inside, so that spherical solvent layers are successively solidified in the polymer material. When the expansion pressure exceeds the surface tension of the solvent layer, the spherical solvent layer is repelled from a part thereof and communicates with the adjacent spherical solvent layer on the inner side of the sheet. In this way, the spherical solvent layers are connected and reach from the coagulation solvent contact side to the opposite side to complete coagulation and uniformly form fine pores. Due to this phenomenon, innumerable spherical micropores are connected to the solidified polymer sheet to be formed in a uniform state.

Examples of such coagulating solvent include water,
A polar solvent such as methanol, ethanol, propanol, ethylene glycol, or propylene glycol is appropriately selected from the relationship with the solvent for the polymer material solution.

The coagulation solvent is usually sprayed in the form of particles into the coagulation tank by an appropriate particle generator. The contact time and temperature conditions with the fine particles in the coagulation tank are appropriately selected depending on the type of coagulation solvent and the treatment temperature, but generally the contact time is
It is usually 1 to 10 minutes, preferably 5 to 6 minutes, and the treatment temperature is usually 10 to 80 ° C, preferably 20 to 40 ° C. The amount of the coagulation solvent used is usually 30 to 200%, preferably 30 to 50%, relative to the coating amount of the polymer solution per unit time. In addition, the coagulation solvent may be sprayed directly onto a sheet-like material directly molded in a fine particle state of 0.5 mm or less, preferably 0.01 mm or less, by appropriately controlling the particle size of the sprayed particles. .

The desired polymer porous sheet is obtained by drying the thus obtained film by a conventional method, for example, heat drying. The thickness is usually 10
It is 500 μm, preferably 20 to 60 μm.

In the present invention, it is particularly preferable that the polymer material is polyurethane, the dissolving solvent is dimethylformamide, and the coagulating solvent is water.

The thus obtained porous sheet of the present invention has a structure in which spherical fine pores are uniformly distributed and formed therein,
Its physical property value is an average pore diameter of 0.5 to 30 μm, preferably
1 to 10 μm, porosity 40 to 70%, preferably 50 to
60%, moisture permeability 500~5000g / m ² · 24hrs, preferably 2000g / m ² · 24hrs or more.

Such a porous sheet is excellent in various properties such as waterproofness, air permeability and mechanical strength, and is useful as a medical or clothing sheet.

[0020]

[Examples] The present invention will be specifically described below with reference to Examples and Experimental Examples, but the present invention is not limited thereto.

Example 1 100 ml of dimethylformamide was added to 200 ml of a polyurethane resin (polyurethane dimethylformamide solution manufactured by Nippon Polyurethane Industry Co., Ltd .; trade name: Nipolan 5111: solid content 30%) to prepare a 20% solution. This solution is applied on a polypropylene film to have a thickness of 70 μm, and then introduced into a steam tank. The inside of the steam tank is kept at a humidity of 80% or more and a temperature of 50 ° C. by a steam generator. The passing speed in the steam tank was 7 minutes. The sheet formed by passing through the steam tank was introduced into a drying tank, pre-dried at 60 ° C. for 20 minutes, and further dried at 100 ° C. for 20 minutes to obtain a porous urethane sheet. The apparatus used for the above operation has the structure shown in FIG.

A photograph of the cut surface of the polymer porous sheet thus produced is shown in FIG. The amount of the dimethylformamide aqueous solution recovered in the solvent recovery tank after applying 300 g of the polymer solution was about 320 ml, the concentration was 47%, and the dimethylformamide recovery rate was about 54% at this stage.

The polymer porous sheet obtained by the production method of the present invention has a pore size distribution of fine pores of 9 to 13 μm, an average pore size of 11 μm, a porosity of 58%, and a water vapor transmission rate of 4500 g / m ² · 24 hr.
s, breaking strength was 1.8 kg / cm 2 width.

Comparative Example 1 The polyurethane solution shown in the example was similarly coated on a polypropylene film, introduced into water at 15 ° C., passed through the water at a passage speed of 5 minutes, and dried as in the example. A similar porous urethane film was obtained. A photograph of the cut surface is shown in FIG. The temperature of the water tank is set to 15 ° C. because, when the temperature is high, the rate of solvent replacement is too fast and the size of the pores formed is too large.

The capacity of the water tank used in the comparative example was 12 liters, and when 1 kg of the polymer solution coating was passed, the water was continuously exchanged, and the total amount of water used was 65.
It becomes liter, and its dimethylformamide concentration is 0.
Since it was 8%, recovery by distillation was completely impossible.

Example 2 A polyurethane DMFA solution having the composition shown in Example 1 was
It was coated on a non-woven fabric so as to have a thickness of 50 μm and treated in the same manner as in Example 1 to obtain a porous urethane sheet. This sheet has a pore size distribution of fine pores of ^{2 to} 18 μm, an average pore size of 12 μm, a porosity of 55%, a moisture permeability of 4600 g / m ² · 24 hrs, and a breaking strength of 3.
The width was 5 kg / cm.

Example 3 100 g of EVA (ethylene vinyl acetate copolymer, vinyl acetate concentration 32%) resin was dissolved in toluene to obtain a solid content of 2
It was adjusted to 0%. This solution was applied on a polyester film to a thickness of 60 μm, introduced into a coagulation tank filled with ethyl alcohol vapor, and allowed to pass through the vapor tank. The passing speed of the steam tank was set to 12 minutes and the temperature was set to 35 ° C. After passing 15 minutes at 70 ℃, porous EVA
Got the sheet. This porous sheet has a fine pore size distribution of 0.
8 to 3 μm, average pore diameter 2.1 μm, porosity 47%, moisture permeability 1800 g / m ² · 24 hrs, breaking strength 1.6
The width was kg / cm.

[0028]

EFFECTS OF THE INVENTION The present invention does not require a large amount of solvent treatment as in the conventional method and does not require strict control conditions, and is fine and homogeneous, which is widely required for medical covering materials, water-impermeable clothing materials and the like. Thus, it becomes possible to easily and economically manufacture a porous polymer sheet having good physical properties.

Further, if various polymer materials which have not been used as porous materials in the past are soluble in a solvent, they can be made porous by this method and can be applied to a wide range of materials.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a manufacturing apparatus used in an example.

FIG. 2 is a cross-sectional photograph of the porous sheet obtained in the example (1
2,000 times).

[Fig. 3] Cross-sectional photograph of a porous sheet of a comparative example (12,000 times)
Is.

[Explanation of symbols]

 1 Polypropylene film 2 Coating device 3 Steam tank 4 Solvent recovery tank 5 Polymer solution 6 Drying device 7 Product winding device

[Procedure amendment]

[Submission date] August 25, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

FIG. 2 shows the thin film structure of the porous sheet obtained in the example.
It is a cross-sectional photograph (12,000 times) shown .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a cross-sectional photograph (12,000 times) showing a thin film structure of a porous sheet of a comparative example.

Claims (3)

[Claims] 1. A coagulation solvent in which a polymer material melt is formed into a thin film, is compatible with a solvent for dissolving the polymer material, and does not dissolve the polymer material, and in a fine particle state of the coagulation solvent, A method for producing a polymer porous sheet, which comprises contacting. 2. A polymer porous sheet obtained by the method according to claim 1. 3. An average pore diameter of 0.5 to 30 μm and a porosity of 40.
The polymer porous sheet according to claim ² , which has a water vapor permeability of 500% to 70% and a water vapor permeability of 500 to 5000 g / m ² · 24 hrs.