JPH09309968A - Porous film or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porous film having an excellent air permeability by forming a film from a soln. comprising a polyurethane, a volatile org. solvent which can dissolve the polyurethane and is miscible with water, and water by casting. SOLUTION: A thermoplastic polyurethane is dissolved in an org. solvent (e.g. tetrahydrofuran) to give a soln, with a concn, of about 3-5wt.%. The soln, is added under stirring to a liq. mixture comprising water and a volatile org. solvent which is miscible with water and can dissolve a polyurethane (e.g. methanol), thus giving a polyurethane soln, comprising 1-5wt.% polyurethane, 62.5-96.5wt.% volatile org. solvent (or 45-49wt.% solvent for polyurethane and 17.5-47.5wt.% volatile org. solvent), and 2.5-32.5wt.% water. This soln. is cast on a flat plate (e.g. a glass plate). cooled to form a gel and to evaporate the solvent, and treated at about 100-120 deg.C to give a porous film having a water vapor permeability of 3,000-8,000g/m<2> /day.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous film or sheet which is useful as a wound dressing material, an outer layer material for diapers, a material for clothes, etc., which requires air permeability.

[0002]

2. Description of the Related Art Wound coverings for the purpose of protecting an affected area for treating wounds, outer layer materials such as diapers, materials for sports equipment, etc. Sheets are used. As the film or sheet, a film is known in which a synthetic resin added with an inorganic filler is formed into a film and then stretched to form fine slits [Specialty Chemicals, Vol. 15, No. 10, published by Technomart. (199
1), Separation / Transportation Functional Materials, edited by Japan Society of Polymer Science, published by Kyoritsu Shuppan (1991), Japanese Patent Publication No. 56-45773, Japanese Patent Publication No. 56-17216]. Also poly-γ-methyl-L
-Glutamate-based medical film [Japanese Patent Publication No. 51-4
No. 2878] or a wound dressing using a silicone film as a base material [Science, 215 , 174-].
176 (1982)] is also known. The water vapor permeability of the poly-γ-methyl-L-glutamate film or silicone film is about 1,000 (g / m ² / day) at a thickness of 20 μm. In addition, a polyurethane membrane used as a wound dressing has a water vapor permeability of 450 to 850 (g / m ^2).
/ Day), the segmented polyurethane membrane with the highest water vapor transmission rate has a value of 4,300 (g /
m ² / day) [Higata Journal, 1
0 , 165-180 (1990)]. A thin film of segmented polyurethane, in which the soft segment is a hydrophilic polyol, has a blocking property for the purpose of improving water vapor permeability. In particular, if blocking occurs in a thin film having a thickness of 50 μm or less, it is difficult to remove this blocking.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-blocking porous polyurethane film or sheet having excellent water vapor permeability.

[0004]

According to the present invention, a porous film or sheet obtained by casting a mixture of polyurethane, a volatile organic solvent capable of dissolving polyurethane and miscible with water, and water. Will be provided. Also, a porous film or sheet obtained by casting a polyurethane, an organic solvent that dissolves polyurethane, a volatile organic solvent that is compatible with an organic solvent that dissolves polyurethane and is miscible with water, and water is cast. Provided. Further, after mixing a polyurethane solution consisting of polyurethane and an organic solvent dissolving polyurethane and a solution consisting of water and a volatile organic solvent miscible with water and miscible with the organic solvent dissolving polyurethane, the mixture is cast. Provided is a porous film or sheet obtained by forming a film. Further, there is also provided a method for producing a porous film or sheet by casting a liquid mixture of polyurethane, a volatile organic solvent that dissolves polyurethane and is miscible with water, and water.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Polyurethanes usable in the present invention include polymers having a urethane bond in the molecular chain obtained by a polyaddition reaction of di- or polyisocyanates with diols. Of the polymer group, linear polyurethane is preferable, and a segment having a microphase-separated structure in which a domain with a hard segment in which a part of urea and urethane bonds is aggregated is dispersed in a continuous phase of a flexible soft segment such as polyalkylene glycol. Polyurethane is particularly preferred. These polyurethanes may be commercially available products or may be obtained by synthesis. As a commercially available segmented polyurethane, Biomer-S
B, -EB (manufactured by Ethicon), Pelletha
ne (Upjohn Chem), Tecofle
x (manufactured by Thermo Elec.), Angiofl
ex (manufactured by Abiomed), Estene 58245
(Manufactured by BFG), TM-1,3,5 (manufactured by Toyobo), K
P (made by Kanegafuchi Chemical Co., Ltd.) and the like.

Examples of the volatile organic solvent which dissolves polyurethane and is miscible with water include ketone solvents such as methyl ethyl ketone, acetone and cyclohexanone, and ether solvents such as tetrahydrofuran and dioxane, and methyl ethyl ketone, acetone and tetrahydrofuran are preferable. These solvents can be used alone or as a mixture.

Examples of the organic solvent for dissolving polyurethane include ketone solvents such as methyl ethyl ketone, acetone and cyclohexanone, ether solvents such as tetrahydrofuran and dioxane, aromatic solvents such as toluene and xylene, acetic acid such as ethyl acetate and butyl acetate. Ester solvents,
Examples thereof include dimethylformamide, dimethylacetamide, dimethylsulfoxide, and the like, with preference given to ketone solvents such as methylethylketone, acetone and cyclohexanone, and ether solvents such as tetrahydrofuran and dioxane. These solvents can be used alone or as a mixture.

The volatile organic solvent that is compatible with the organic solvent that dissolves polyurethane and that is miscible with water has a carbon number of 1
To alcohols, acetone, methyl ethyl ketone, tetrahydrofuran and the like. Among the organic solvents, alcohols such as methyl alcohol, ethyl alcohol, n-propanol and isopropanol are more preferable, and ethyl alcohol is particularly preferable. These solvents are
They can be used alone or as a mixture.

As the water, tap water can be used, but ion-exchanged water is preferably used. The mixing ratio of the liquid mixture of polyurethane, a volatile organic solvent that dissolves polyurethane and is miscible with water, and water is polyurethane 1 to 5
% By weight, 62.5-96.5% by weight of volatile organic solvents which dissolve polyurethane and are miscible with water and 2.5-3 of water
It is preferably a 2.5 wt% mixed solution. Further, the mixing ratio of the liquid mixture of polyurethane, an organic solvent that dissolves polyurethane, a volatile organic solvent that is compatible with an organic solvent that dissolves polyurethane and is miscible with water, and water,
1-5% by weight of polyurethane, 45-49% by weight of organic solvent for dissolving polyurethane, volatile organic solvent 17.5 compatible with organic solvent for dissolving polyurethane and miscible with water 17.5
It is preferably a mixed solution of ˜47.5% by weight and water 2.5 to 32.5% by weight.

Further, in preparing the mixed solution,
It is preferable that a polyurethane solution consisting of polyurethane and an organic solvent capable of dissolving polyurethane and a solution containing a water-soluble organic solvent and water are separately prepared in advance and then mixed. The polyurethane concentration of the polyurethane solution composed of polyurethane and an organic solvent capable of dissolving polyurethane may be appropriately increased or decreased in consideration of the type of polyurethane, molecular weight, film forming conditions and the like and the concentration of polyurethane after mixing. -10% by weight, preferably 3-8
%, Particularly preferably 3 to 5% by weight is used.

It is preferable to use a solution containing a volatile organic solvent that is compatible with an organic solvent that dissolves polyurethane and that is miscible with water, and has a water concentration of 5 to 65% by weight, preferably 10 to 60% by weight. . In preparing the mixed solution, it is preferable to mix 30 parts by weight of a solution containing polyurethane and an organic solvent capable of dissolving polyurethane, and 1 to 40 parts by weight of a solution containing a water-soluble organic solvent and water.

When a mixed solution is prepared, polyurethane may precipitate and become cloudy depending on the addition ratio. In this case, white turbidity of the mixed liquid can be prevented by raising the liquid temperature and increasing the solubility of polyurethane. The temperature varies depending on the solvent used, but is preferably 20 to 60 ° C. when using tetrahydrofuran, for example. Each of the above-mentioned mixed liquids may optionally contain an antibacterial agent, an organic or inorganic filler, a pigment, a dye or the like.

The casting film formation is a film formation method in which the mixed solution is cast in a mold or on a flat plate such as a glass plate and then the solvent is allowed to escape to solidify to form a film or sheet. In order to prepare a large amount of the same film in a short time, the method using a casting knife is practical and preferable. An example of the method for producing the porous film or sheet of the present invention is shown below. Polyurethane, a mixture of water and a volatile organic solvent that dissolves polyurethane and is miscible with water, or polyurethane, an organic solvent that dissolves polyurethane, and a volatile organic solvent that is compatible with and is miscible with water. A porous film or sheet can be produced by pouring the mixed solution of water and water onto a flat plate such as a petri dish and then allowing the solution to escape.

In the case of industrially forming a film, the mixed solution can be formed into a film by using, for example, a doctor blade, and a porous film or sheet can be produced. As a method for escaping the solvent, the mixed solution may be cast on a flat plate such as a petri dish and allowed to stand at room temperature to allow the solvent to escape, but after pouring the mixed solution onto the flat plate,
The plate is rapidly cooled from the surroundings and the liquid temperature is 0 to 25 ° C, preferably 0.
A method in which the solvent is allowed to escape by keeping it in a non-flowing gel state by keeping at -15 ° C, or 25-60 ° C, preferably 25-4
A method of escaping the solvent in a fluid state at 0 ° C may be used. The atmosphere in which the solvent is allowed to escape may be a normal working environment, but it is preferably performed in a nitrogen gas atmosphere in order to reduce changes in environmental conditions. The rate of solvent escape depends on the type of solvent, concentration, temperature, and other conditions. After the film or sheet is formed, if necessary, 80 to 13
The solvent can be more completely removed by heat treatment at 0 ° C., preferably at 100 to 120 ° C., for 1 to 3 hours.

The film thickness of the film or sheet can be adjusted by, for example, the concentration of polyurethane in the mixed solution used for casting film formation or the amount of solution to be cast. The film thickness is not particularly limited, but is preferably 1 to 500 μm, more preferably 3 to 150 μm. In particular, as a wound dressing material, 20 to 80 μm
Is highly preferred. In the present invention, the film thickness is 200 μm.
The following are called films, and those exceeding 200 μm are called sheets.

The porosity which affects the water vapor permeability can be adjusted by adjusting the polyurethane concentration or water concentration. Water vapor permeability is 3,000-
It is 8,000 (g / m ² / day). The known film or sheet obtained by casting only a solution containing polyurethane and an organic solvent that dissolves polyurethane is non-porous. On the other hand, the film or sheet obtained by the present invention is porous with distorted cavities having a diameter of 0.1 to 100 μm. Moreover, the adjacent cavities in the film or sheet may be partially continuous, but have an independent structure partitioned by an ultrathin film, and the front and back surfaces form an integral skin layer, and the front and back surfaces are formed. Is in a sealed state.

Further, while a non-porous film of 50 μm obtained by directly casting a solution of polyurethane and an organic solvent which dissolves polyurethane in a film is found to have strong blocking, the porous film of the present invention is Also, even a film having a film thickness of 40 μm or less or 10 to 20 μm does not cause blocking at all. The texture is similar to that of microfiber fabric. In addition, the cast surface forms a very fine matte surface.

The water vapor permeability of the polymer film or sheet depends on the film thickness, and the thinner the film, the greater the permeability. In addition, segmented polyurethane is known to have excellent water vapor permeability due to its molecular structure. Therefore, the porous film or sheet of the present invention is porous and has an extremely thin cell thickness, so that the water vapor permeability thereof is significantly improved as compared with the conventionally known ones. In addition, since the cross section of the membrane is independent and porous and the front and back sides are covered with the skin layer, it is suitable as a wound dressing capable of preventing the invasion of bacteria.

The skin has both a respiratory function such as skin respiration and water vapor transmission and a barrier function such as prevention of invasion of bacteria and retention of body fluid, and it is preferable that the wound covering material to be applied to an affected area such as a burn has both of these functions. The amount of water disperse on the skin is about 4,300 g / m ² / m in II degree burn wounds.
Day, about from granulating wound 5,100 g / m ² / day, it is said that from Tokawa wounds than about 3,600g / m ² / day.
Therefore, the water vapor permeability of the wound dressing is preferably higher than this. The porous film of the present invention satisfies this condition and is particularly useful as a wound dressing material.

Further, the porous film or sheet of the present invention has a higher water vapor permeability than a known cast film obtained by a conventional method, and also has a high gas permeability, and particularly a high carbon dioxide selective permeability.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples. Physical properties shown in Examples and Comparative Examples were measured or observed by the following methods.

(1) Water vapor transmission rate Water vapor transmission rate tester (L80-4000 type, Switzerland
Dr. (Manufactured by LYSSY) and used at a measurement temperature of 40 ° C. and a relative humidity of 90% RH. And 19 μm as a standard sample
The PET film (25 g / m ² / day) was used for the measurement using a 10-hole holder.

(2) Gas permeability gas permeability tester (GPM-500 type, Swiss D
r. (Manufactured by LYSSY) and a mixed gas of O ₂ , N ₂ and CO ₂ (DRY gas) as a test gas, and the measurement was performed in accordance with Japanese Industrial Standard (JIS) K7129 (1992).

(3) Film Observation Using a scanning electron microscope (S-510 type, manufactured by Hitachi), the fracture surface and front and back surfaces of the film were observed.

Example 1 Thermoplastic Polyurethane (Estene 58245, BF
(Manufactured by Company G) was dissolved in a tetrahydrofuran solvent to prepare a 3% by weight polyurethane solution. The polyurethane solution 54
g in a 100 ml glass beaker, and while stirring with a magnetic stirrer, slowly add 46 g of a mixed solution of 10 parts by weight of ion-exchanged water and 90 parts by weight of ethanol,
After sufficiently stirring and mixing, the mixture was poured into a flat petri dish, the petri dish was rapidly cooled from the surroundings, and the liquid temperature was set to 15 ° C or lower to give a gel state. Then, the solvent was allowed to escape under a nitrogen gas atmosphere at 17 ° C. or lower to obtain a cast film. Further, it is left in an air bath at 120 ° C. for 2 hours to form a non-blocking porous film 1
I got

The porous film 1 was observed with an electron microscope.
As a result, the film thickness is about 10.9 μm, which is several μm.
A distorted cavity with a diameter was formed. Each cavity is partial
Is continuous, but separated by an ultra-thin film
It was a different structure. In addition, the front and back of the film are thin
Because it is covered with an inner layer, it is a closed porous film.
I confirmed that there is. Water vapor permeability of the porous film
Was measured to be 6,100 g / m^Two/ Day.
Also, when the gas permeability was measured,_Two, N _Two, CO
_TwoMeasurement limit value (O_Two
For 10,000 ml / m^Two/ Day, N_TwoAnd CO
_TwoAbout tens of thousands ml / m^TwoPer day)
showed that.

Example 2 In Example 1, 48 g of a polyurethane solution and ionic
Mixed liquid 52 of 10 parts by weight of exchanged water and 90 parts by weight of ethanol
In the same manner as in Example 1 except that g was used,
A porous film 2 having a king property was obtained. The porous film
2 was observed with an electron microscope, and the thickness was 30.4 μm.
And is a sealed porous film similar to Film 1.
Was. The water vapor permeability of the porous film 2 is 4,300 g.
/ M^Two/ Day. Also, the gas permeability was measured.
R, O_TwoIs 4,500 ml / m^Two/ Day, N_TwoIs 1,50
0ml / m^Two/ Day, CO _TwoIs 55,000 ml / m^Two/
It was a day.

Example 3 In Example 1, a mixed solution of polyurethane solution and ethanol water was poured into a flat petri dish, and the solvent was allowed to escape under a nitrogen gas atmosphere at room temperature to obtain a non-blocking porous film 3. When the porous film 3 was observed with an electron microscope, it had a thickness of 13.4 μm and
It was a porous film that was closed in the same manner as in. The water vapor permeability of the porous film was 5,700 g / m ² / day.

Example 4 Thermoplastic polyurethane Estene 5 in Example 1
8245 (manufactured by BFG) in Pellethan (Up
A non-blocking porous film 4 was obtained in the same manner as in Example 1 except that it was manufactured by John Chem. When the porous film 4 was observed with an electron microscope, the thickness of the film was about 9.5 μm, and it was confirmed that the film was a closed porous film similar to the film 1.
The water vapor permeability of the porous film 4 is 6,500 g / m ²
/ Day.

Comparative Example 1 The 3 wt% polyurethane solution used in Example 1 was poured into a flat petri dish and the solvent was allowed to escape at room temperature under a nitrogen gas atmosphere to obtain a cast film. Further, it was left in an air bath at 120 ° C. for 2 hours to obtain a cast film a. When the cast film a was observed with an electron microscope, the film thickness was 85 μm, there were no cavities in the cross section, and the front and back surfaces were smooth. The water vapor permeability of the cast film a is 2,000.
It was 0 g / m ² / day. Further, when the gas permeability was measured, O ₂ was 1,200 ml / m ² / day and N ₂ was 40.
0 ml / m ² / day, CO ₂ is 18,000 ml / m ² /
It was a day.

Comparative Example 2 Using the 3 wt% polyurethane solution used in Example 1,
A cast film having a thickness of about 20 μm was formed. An attempt was made to peel it from the flat petri dish, but self-adhesion occurred and it was impossible to release the blocking. Similarly, about 40 μm
An attempt was also made to peel off the cast film of No. 1, but self-adhesion occurred and a flat film could not be obtained.

[0032]

EFFECTS OF THE INVENTION The present invention provides a non-blocking porous film or sheet excellent in water vapor permeability.

Claims (19)

[Claims] 1. A porous film or sheet obtained by casting a liquid mixture of polyurethane, a volatile organic solvent that dissolves polyurethane and is miscible with water, and water. 2. The mixed solution comprises 1 to 5% by weight of polyurethane,
The porous film or sheet according to claim 1, which is a mixed solution of 62.5 to 96.5% by weight of a volatile organic solvent which dissolves polyurethane and is miscible with water, and 2.5 to 32.5% by weight of water. 3. The porous film or sheet according to claim 1, wherein the volatile organic solvent which dissolves polyurethane and is miscible with water is at least one solvent selected from methyl ethyl ketone, acetone and tetrahydrofuran. 4. A porous film obtained by casting a film of polyurethane, an organic solvent capable of dissolving polyurethane, a volatile organic solvent compatible with an organic solvent capable of dissolving polyurethane and miscible with water, and water. Or sheet. 5. The porous film or sheet according to claim 4, wherein the organic solvent that dissolves the polyurethane is at least one solvent selected from methyl ethyl ketone, acetone, cyclohexanone, tetrahydrofuran and dioxane. 6. The volatile organic solvent which is compatible with an organic solvent that dissolves polyurethane and is miscible with water is one or more solvents selected from methyl alcohol, ethyl alcohol, n-propanol and isopropanol. Porous film or sheet. 7. A mixture of a polyurethane solution comprising polyurethane and an organic solvent capable of dissolving polyurethane and a solution comprising a volatile organic solvent miscible with water and compatible with an organic solvent capable of dissolving polyurethane and water. The porous film or sheet according to claim 4, which is the obtained mixed liquid. 8. A mixed solution comprising 30 parts by weight of a polyurethane solution composed of polyurethane and an organic solvent capable of dissolving polyurethane, a solution 1 composed of a volatile organic solvent compatible with an organic solvent capable of dissolving polyurethane and miscible with water, and water. ~ 40
The porous film or sheet according to claim 7, which is composed of parts by weight. 9. The porous film or sheet according to claim 7 or 8, wherein a polyurethane solution containing polyurethane and an organic solvent capable of dissolving polyurethane has a polyurethane concentration of 2 to 10% by weight. 10. The porous film according to claim 7, wherein the concentration of water in the solution consisting of water and a volatile organic solvent which is compatible with the organic solvent capable of dissolving polyurethane and is miscible with water is 5 to 65% by weight. Or sheet. 11. The volatile organic solvent that is compatible with the organic solvent that dissolves polyurethane and that is miscible with water is one or more solvents selected from methanol, ethanol, n-propanol and isopropanol. Porous film or sheet. 12. The porous film or sheet according to claim 7, wherein the solvent that dissolves the polyurethane is at least one solvent selected from methyl ethyl ketone, acetone, cyclohexanone, tetrahydrofuran and dioxane. 13. The porous film or sheet according to claim 1, 4 or 7, wherein the polyurethane is a segmented polyurethane. 14. The non-blocking property according to claim 1, 4.
Or the porous film or sheet according to 7. 15. A water vapor transmission rate of 3,000 to 8,000.
The porous film or sheet according to claim 1, 4 or 7, which has a concentration of 0 (g / m ² / day). 16. The porous film according to claim 1, 4 or 7 having a film thickness of 3 to 150 μm. 17. A method for producing a porous film or sheet by casting a mixed solution of polyurethane, a volatile organic solvent that dissolves polyurethane and is miscible with water, and water. 18. A porous film or sheet prepared by casting a mixture of polyurethane, an organic solvent capable of dissolving polyurethane, a volatile organic solvent compatible with an organic solvent capable of dissolving polyurethane and miscible with water, and water. A method of manufacturing. 19. A mixed solution comprising a polyurethane solution composed of polyurethane and an organic solvent capable of dissolving polyurethane, and a solution composed of a volatile organic solvent compatible with water and miscible with water, and a solution comprising water. The production method according to claim 18, which is the obtained mixed liquid.