JPH04326932A - Polyester porous film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a porous film of a polyester copolymer having 3-hydroxybutyrate units (hereinafter referred to as 3HB component) and 4-hydroxybutyrate units (hereinafter referred to as 4HB component). It is something.

0002

[Prior Art] In recent years, research and development of porous membranes made of polymeric materials has been actively carried out, and porous membranes formed in the form of flat membranes and hollow fiber membranes are widely used in dialysis, filtration, gas exchange, etc. It is applied. In particular, in the medical field, their use as artificial organs, artificial livers, plasma exchange, artificial lungs, wound dressings, etc. is rapidly expanding. Compatible. Therefore, there is currently an urgent need to search for porous membranes using biocompatible materials.

On the other hand, biopolyester produced by microorganisms has attracted attention as an excellent biocompatible material, and recently, porous poly-3-hydroxybutyrate (hereinafter referred to as PHB), a typical biopolyester, has been attracting attention as an excellent biocompatible material. Research and development on membranes has been carried out, and is described, for example, in Japanese Patent Application Laid-Open Nos. 60-137402 and 61-8107, respectively.

[0004] The methods for producing porous membranes disclosed in these publications include eluting additives such as various organic polymers, oligomers, and inorganic salts with uniform particle size after molding, or stretching and opening pores after heating and melting.
A porous membrane of PHB is manufactured.

[0005] However, in these additive elution methods and heat melting and stretching pore opening methods, the pores are uniformly arranged in the membrane.
Furthermore, it is impossible to make the size and shape of the holes uniform. In addition, problems that are undesirable as medical materials arise, such as mixing of additives and polymer denaturation during heating.

[0006]

[Problems to be Solved by the Invention] From the above points of view, the present inventors have conducted intensive research to produce a biopolyester porous membrane made by microorganisms with excellent biocompatibility. We discovered a completely new fact that a polyester copolymer having a 4HB component can be easily produced into a porous membrane by adjusting the solvent scattering rate during casting film production, and based on this knowledge, we completed the present invention. I ended up doing it.

[0007]

[Means for Solving the Problems] That is, the present invention has three
- Polyester copolymer having hydroxybutyrate units and 4-hydroxybutyrate units (hereinafter referred to as 3HB-
The water vapor permeability produced by casting a solution of 4HB copolymer and adjusting the scattering speed of the solvent is 0.5 kg/m2.
The present invention relates to a polyester porous film that lasts for 24 hours or more.

The present invention will be explained in detail below. The 3HB-4HB copolymer, which is the raw material for the porous membrane of the present invention, is mainly produced using microorganisms, although it is not particularly limited. The microorganism to be used is not particularly limited as long as it has the ability to produce PHB, but in practical terms, for example, Alcaligenes faecalis
calis), Alcaligenes roulandii (Al
caligenes ruhlandii), Alcaligenes leitus (Alcaligenes l)
atus), Alcaligenes eutrophus (Al
microorganisms of the genus Alcaligenes such as Caligenes eutrophus).

[0009] These microorganisms can be used in the same manner as in conventional methods.
Mainly the first stage of culturing to proliferate the bacterial cells, and the nitrogen and/or
Alternatively, the copolymer used in the present invention is produced by culturing in the second stage of culture, which controls phosphorus and produces and accumulates the copolymer within the bacterial cells.

[0010] For the first-stage culture, a conventional culture method for culturing microorganisms can be applied. That is, it is sufficient to adopt a medium and culture conditions that allow the microorganisms used to proliferate.

[0011] There are no particular restrictions on the medium components as long as they can be assimilated by the microorganisms used, but in practical terms, carbon sources include synthetic carbon sources such as methanol, ethanol and acetic acid, carbon dioxide, etc. Inorganic carbon sources, natural products such as yeast extracts, molasses, peptones and meat extracts, sugars such as arabinose, glucose, mannose, fructose and galactose and nitrogen sources such as sorbitol, mannitol and inositol, such as ammonia, ammonium salts. , inorganic nitrogen compounds such as nitrates, or urea, corn steep liquor,
Examples of organic nitrogen-containing substances and inorganic components such as casein, peptone, yeast extract, and meat extract include calcium salts, magnesium salts, potassium salts, sodium salts,
The salts are selected from phosphates, manganese salts, zinc salts, iron salts, copper salts, molybdenum salts, cobalt salts, nickel salts, chromium salts, boron compounds, iodine compounds, and the like. Furthermore, vitamins and the like can also be used if necessary.

[0012] As for the culture conditions, the temperature is, for example, 20°C.
The temperature is about 40°C, preferably about 25 to 35°C, and the pH is, for example, about 6 to 10, preferably 6.
It is said to be about 5 to 9.5. Cultivate aerobically under these conditions. If culture is performed outside of these conditions, the growth of microorganisms will be relatively poor, but this is not particularly limited. The culture method may be either batch culture or continuous culture.

[0013] The microbial cells are separated and recovered from the culture solution obtained in the first-stage culture by ordinary solid-liquid separation means such as filtration and centrifugation, and these cells are subjected to the second-stage culture, or This can also be done by substantially depleting nitrogen and/or phosphorus in the first-stage culture and transferring this culture solution to the second-stage culture without separating and recovering the bacterial cells.

[0014] In this latter stage of culturing, the medium or culture solution is substantially free of nitrogen and/or phosphorus, but contains a carbon source that will serve as a substrate for the polyester. As substrates, butyric acid derivatives such as 4-hydroxybutyric acid, 4-chlorobutyric acid, and 4-bromobutyric acid, and their respective sodium salts, potassium salts, magnesium salts, calcium salts, aluminum salts, etc., and γ-butyrolactone and the general formula HO(CH2)nOH (n=2, 4, 6, 8, 10, 1
2) When cultured using diol etc., -OCH(CH3)CH2 becomes the material of the polyester porous film of the present invention.
CO- unit (3HB) and -OCH2CH2CH2CO-
A polyester copolymer having units (4HB) is obtained.

[0015] As for the culture conditions in the latter stage, the pH is 6 to 10.
, preferably 7 to 8, and the dissolved oxygen concentration is 0.5
-40 ppm, preferably 5-20 ppm. When culturing under these conditions, the polyester content produced and accumulated within the dried bacterial cells becomes extremely low, making it ineffective for industrial production. The culture temperature is 20
The temperature is about 40°C, preferably about 25 to 35°C.

On the other hand, if the culture substrate is a saccharide such as glucose or fructose and an even number carboxylic acid such as acetic acid or butyric acid, PHB can be obtained, and if the culture substrate is an odd number carboxylic acid such as propionic acid or valeric acid, 3HB units can be obtained. A copolymer (hereinafter referred to as 3HB-3HV copolymer) consisting of 3-hydroxyvalerate (3HV) is produced.

However, even if the scattering speed of the solvent is adjusted in the process of producing a cast film of such a polymer having a similar polymer structure, it is not possible to obtain a porous film as in the present invention.

That is, the present invention provides an image that can be obtained for the first time through the synergistic effect of the combination of the 3HB-4HB polyester copolymer, which is the material of the porous film, and the adjustment of the scattering speed of the solvent in the process of manufacturing the cast film. This is a revolutionary porous film. The copolymer used is 4HB
The component content is 3 to 90%, preferably 5 to 60%, more preferably 7 to 40%.

The microorganisms cultured as described above are separated from the culture solution by centrifugation, washed and dried, extracted with chloroform, acetone, etc., and the extract is poured into a poor solvent such as n-hexane. The copolymer used in the invention is obtained as a white precipitate.

The copolymer thus obtained is dissolved in a solvent to produce a uniform cast film. Any method can be used to produce the cast film, but a simple method is to pour a solution in which the copolymer is dissolved into a glass petri dish, etc., and dry it naturally while adjusting the scattering speed of the solvent using any method. There is a way to do it.

The scattering rate of the solvent can be adjusted so that the water vapor permeability of the present invention is 0.5 kg/m2/24 hr or more, preferably 1.0 kg/m2/24 hr, and more preferably 3.
Any method that can produce a polyester porous film of 0 kg/m2/24 hr or more can be used, but a simple method is to place a lid on a petri dish filled with the above copolymer solution. . In particular, if the solvent scattering rate immediately after the polyester begins to precipitate is fast, a film without pores will be produced, but if it is slow, a porous film will be obtained, and the slower the rate, the lower the water vapor permeability. A highly porous film can be obtained. Immediately before polyester starts to precipitate, it varies depending on the conditions, but for example, the polyester concentration is about 60%, preferably,
Refers to a condition of 70% or more.

For example, a petri dish about 9 cm in diameter containing a 3-5 W/V% 3HB-4HB copolymer solution dissolved in an organic solvent such as chloroform is covered with a lid, and the mixture is heated at room temperature for two days or more. Splash the solvent. The scattering time is adjusted by the external temperature, and when carried out on a large scale, preliminary experiments are required to obtain the desired porous film.

The solvent used in the production of the polyester porous film of the present invention is an organic solvent such as chloroform, dichloromethane or acetone, but is not particularly limited as long as it dissolves the polyester. From the viewpoint of solvent recovery, a single solvent is preferable, but a mixed solvent may be used.

By adjusting the scattering speed of the 3HB-4HB copolymer solution in this way, a membrane with a porous structure can be obtained, the diameter of these pores can be adjusted by the scattering speed of the solvent, and these characteristics can be improved. It is a finding obtained for the first time by the present invention that a porous membrane having the above-mentioned structure can be manufactured with extremely good reproducibility.

The porous film of the present invention, which is obtained by a manufacturing method completely unknown heretofore, is a useful material suitable for medical materials, since it is free from mixing of additives and denaturation of the polymer material due to heating.

[0026]

EXAMPLES The present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Production of 3HB-4HB copolymer for porous film material First, the 3HB-4HB copolymer used in the present invention was added to the bacterial cells of Alcaligenes eutrophus (AT).
CC17699). First, in order to culture the bacterial cells to proliferate (pre-stage culture), 200 ml of a medium having the following composition was placed in a 2-liter Sakaguchi flask, cultured at 28°C for 24 hours, and then centrifuged (8
000r. p. m. 15 minutes) to separate the bacterial cells.

[0028] First stage culture medium composition (in 1 liter) Yeast extract 10g Polypeptone 10g
Meat extract 5g (NH4)2SO4 5g Dissolve these in 1 liter of deionized water and adjust the pH to 7.0.

[0029] The bacterial cells obtained in the above-mentioned first stage culture were added to a copolymer production medium having the following composition at a concentration of 4 per liter.
It was suspended in a proportion of g. Pour a predetermined amount of this suspension into a 2 liter or 500 ml Sakaguchi flask, and store at 28°C for 48 hours.
After culturing for several hours, the resulting culture solution was centrifuged to obtain bacterial cells.

Composition of copolymer production medium (in 1 liter)
Na2HPO4 4.4g KH2PO4 1.2g MgSO4 0.2g Sodium 4-hydroxybutyrate 15.0g Sodium citrate was used in the amount shown in Table 1 (unit: g/l), and the above ingredients were mixed with 1 liter of deionized water. Dissolved in pH 7
．． Adjust to 0.

[0031] Next, as a bacterial cell treatment, the obtained bacterial cells were
The cells were washed with distilled water and dried under reduced pressure to obtain dry bacterial cells. The copolymer was extracted from the dried bacterial cells thus obtained with hot chloroform, and this extract was concentrated and precipitated dropwise into a large amount of hexane.The precipitate was collected by filtration and dried to separate the copolymer. . 3HB-4 used in the present invention obtained above
Table 1 shows the HB copolymers.

[0032]

[Table 1] Copolymer citrate Na medium amount
Polymer yield Composition ratio (mol%) No.
(g/l) (ml)
(g/l) 3HB:4HB------
−−−−−−−−−−−−−−−−−−−−−−−−−
--- 1 0
500 1.53
90:10------------
−−−−−−−−−−−−−−−−−−−− 2
0 400
1.41 77:23
−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−− 3
0 50
1.21 54:46---------
−−−−−−−−−−−−−−−−−−−−−−−−−
-- 4 5
50 1.10
19:81------------
−−−−−−−−−−−−−−−−−− Copolymer 1
and 2 used a 2000 ml Sakaguchi flask, and copolymer numbers 3 and 4 used a 500 ml Sakaguchi flask.

[0033] In addition, the PHB used in the comparative example is a medium using n-butyric acid as a substrate and without adding Na citrate.
Obtained in the same manner as above. As the 3HB-3HV copolymer, a copolymer having a 3HV content of 20 mol % manufactured by Aldrich was used in a comparative example.

Preparation of porous film and measurement of water vapor transmission rate The above polymer was dissolved in chloroform and poured into a glass petri dish with a diameter of 9 cm, and the scattering rate of the solvent (air drying rate) was determined depending on the temperature and the degree of sealing of the lid of the glass petri dish. Adjusted and air dried. The produced film was peeled off from the Petri dish, vacuum dried at room temperature for 24 hours, and then cut into appropriate sizes to obtain test pieces for use in measuring water vapor permeability.

The water vapor permeability was measured using a sample bottle with a water vapor permeable portion having a diameter of 12 cm.
℃, in a constant temperature and humidity chamber at 75% humidity, ASTM E96
-Measured by the method of 80 procedure A. The specific measurement procedure is as follows. ■Punch out the test film to a diameter of 20mm. ■Put about 10 g of calcium chloride in a sample bottle (diameter 12) for measuring water vapor permeability, and set the test sample with the wound side facing up. ■Weigh to two decimal places (W0 g). ■ Place in an incubator at 40°C and 75%. (2) After 24 hours, reweigh (W24 g) and determine water vapor permeability according to the formula below. Water vapor permeability (Kg/m2/
24hr)=(W24-W0)×1000/(62×π
)

The above results are shown in Tables 2, 3, 4 and 5.

[0037]

[Table 2] Example Polymer concentration Injection amount Air drying days Film thickness Water vapor permeability
W/V% ml day
μm Kg/m2/24hr -----
−−−−−−−−−−−−−−−−−−−−−−−−−
----------- 1 3
45 3 280
2.50 -----------
−−−−−−−−−−−−−−−−−−−−−−−−−
--- 2 3 45
4 352
3.49 −−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−−−
3 3 45
5 390
3.67 −−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−− 4
3 45
6 438 3.8
1 −−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−− 5
3 45 12
440 3.92
−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−Comparative example −−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−− 1 3
45 1
170 0.18 -----
−−−−−−−−−−−−−−−−−−−−−−−−−
----------- 2 3
45 3 218
0.05 -----------
−−−−−−−−−−−−−−−−−−−−−−−−−
--- 3 3 45
6 220
0.04 -------------
−−−−−−−−−−−−−−−−−−−−−−−−
4 3 45
3 188
0.04 −−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−− 5
3 45
6 190 0.0
3−−−−−−−−−−−−−−−−−−−−−−−−
-------------Examples 1 to 5 and Comparative Example 1 used Copolymer 2 in Table 1, the films of Comparative Examples 2 and 3 used PHB, and the films of Comparative Examples 4 and 5 is a film made of 3HB-3HV copolymer.

[0038]

[Table 3] Example Polymer concentration Injection amount Air drying days Film thickness Water vapor permeability comparative example W/
V% ml day
μm Kg/m2/24hr------
−−−−−−−−−−−−−−−−−−−−−−−−−
--Example 6 3 45
4 330
3.05 Comparative example 6 3 45
1 183
0.22 −−−−−−−−−−−−−−
--------------------------A film was produced using Copolymer 1 shown in Table 1.

[0039]

[Table 4] Example Polymer concentration Injection amount Air drying days Film thickness Water vapor permeability comparative example W/
V% ml day
μm Kg/m2/24hr------
−−−−−−−−−−−−−−−−−−−−−−−−−
--Example 7 3 13
7 56
1.01 Comparative example 7 3 13
1 45
0.07 −−−−−−−−−−−−−
--------------------------A film was produced using Copolymer 3 in Table 1.

[0040]

[Table 5] Example Polymer concentration Injection amount Air drying days Film thickness Water vapor permeability comparative example W/
V% ml day
μm Kg/m2/24hr------
−−−−−−−−−−−−−−−−−−−−−−−−−
--Example 8 2 20
8 63
0.70 Comparative example 8 2 20
1 51
0.03 −−−−−−−−−−−−−−−
--------------------------A film was produced using Copolymer 4 in Table 1.

The following points can be understood from the above examples and comparative examples. According to the results of the examples and comparative examples shown in Table 2,
Even if the solvent scattering speed is the same, only the film made using the 3HB-4HB copolymer is the porous film of the present invention, and the films made using other polymers have the same water vapor permeability as the present invention. It can be understood that this does not result in a porous film having properties.

According to the results of Examples and Comparative Examples shown in Tables 3, 4, and 5, even if the film was made using the 3HB-4HB copolymer, if the number of air-drying days was 1, the porous film of the present invention It can be understood that the porous film of the present invention can be obtained when the porous film is air-dried for two or more days.

Furthermore, by changing the copolymerization composition of the 3HB-4HB copolymer, the solution concentration, and the solvent scattering conditions expressed by the number of air-drying days, the water vapor permeability of the porous film can be controlled, and the water vapor permeability of the porous film can be controlled to a specified level. A porous film having water vapor permeability can be obtained.

[0044] When the cross section of the porous film of the present invention is observed using an electron micrograph, it can be seen that the porous state is very well expressed.

[0045]

Effects of the Invention As described above, a film having a porous structure obtained by adjusting the scattering speed of a 3HB-4HB copolymer solution has been developed as a result of intensive research by the present inventors, and is completely new to the present invention. This is a novel porous film obtained based on previously unknown knowledge, and is a useful material suitable for medical materials without mixing in additives or denaturing the polymer material due to heating.

[Brief explanation of the drawing]

FIG. 1 is an electron micrograph (500x magnification) of a cross section of the porous film of Example 3 showing the structure of the porous state.

FIG. 2 is an electron micrograph (2000x magnification) of a cross section of the porous film of Example 3, showing the structure of the porous state.

Claims (1)

[Claims] [Claim 1] 3-hydroxybutyrate unit and 4-
A polyester porous film having a water vapor permeability of 0.5 kg/m2/24 hr or more, manufactured by casting a solution of a polyester copolymer having hydroxybutyrate units and adjusting the scattering speed of the solvent.