| WO/2005/087356 | SEPARATION MEMBRANE |
| WO/2009/005745 | ZEOLITE MEMBRANE STRUCTURES AND METHODS OF MAKING ZEOLITE MEMBRANE STRUCTURES |
| WO/2010/024901 | METHODS OF MAKING INORGANIC MEMBRANES |
Hyun, Byung Nam (102-202 Hyoseung Apt. 742 Kongleung-dong Nowon-ku Seoul 139-240, KR)
Hyun, Byung Nam (102-202 Hyoseung Apt. 742 Kongleung-dong Nowon-ku Seoul 139-240, KR)
| 1. | A method for preparing a polymer membrane having waterproof and gas permeable properties, comprising the steps of: mixing polymer materials with granular inorganic ingredients soluble in acidic or alkaline solution; molding the mixture into a film form; and immersing the film mold in acidic or alkaline solution to dissolve out and thus remove the granular inorganic ingredients. |
| 2. | The method as defined in claim 1, wherein the molding step is carried out either by uniformly mixing a solution of the polymers in suitable solvent with granular inorganic ingredients, coating the mixture on substrates and then drying ; or by directly heatingmixing polymer materials with granular inorganic ingredients, and molding the heated mixture in a film form. |
| 3. | The method as defined in claim 1, wherein the granular inorganic ingredients having average grain size of 0.120 tm are used in the amount of 60 800 parts by weight, on the basis of 100 parts by weight of polymer. |
PRIOR ART In general, polymer membranes having water-proof and gas permeable properties are defined to those passing not liquid or solid substances, but only gaseous substances. Conventionally, such polymer membranes can be prepared in three manners: a porous membrane-forming method (A), a pore-forming method (B) and a pore-forming method (C). In the porous membrane forming method (A), polymers which are membrane materials are dissolved in polar solvent, added with DMF (N, N-dimethyl formamide), wet-molded in a film form, immersed in aqueous solution to extract the polar solvent contained in said film, to produce a porous membrane. The pore forming method (B) comprises mixing polymer materials having high elongation ratio with moisture-controlled inorganic fillers, extrusion-molding the mixture in a film form, and elongating the film. The pore forming method (C) is composed of mixing soluble inorganic salt or soluble polymer with the corresponding polymer materials, extrusion-molding the mixture to form n fi) m. and immersinp thf fi) m in water to dissolve out and remove said
However, the method (A) suffers from the disadvantages of limited selection of polymer materials because only those polymers which can be dissolved in polar solvents can be used, and it is difficult control of pore sizes and number. On the other hand, the method (B) is advantageous in terms of easy control of pore size, but disadvantageous in being unable to use polymers having high elongation ratio. In the method (C), usable inorganic salt is water-soluble so that it is reacted with water at room temperature, thus grains being coagulated, thereby lowering workability. Additionally, water-soluble polymers are swelled when dissolved in water within the polymer matrix, and thus a long period of time is required to extract the polymers.
Generally, steam permeability (Q) of polymer membrane having water- proof and gas permeable properties is proportional to surface area (A), permeation time (T), and difference of pressure (AP) of steam attributed to different temperature at the surface contacted with liquid, and is inverse proportion to thickness (L), as represented in the following equation: Q = K. A. T. AP/L Wherein, a proportionality constant K is a permeability constant, and shown as the sum of a diffusion constant showing mobility of gas-phase water molecules in polymer membrane and a solubility constant showing steam solubility in polymers, which determines gas permeability.
In order to prepare polymer membrane having excellent water-proof property, the diffusion constant should be increased. When the pore size is physically increased, the diffusion constant becomes larger. But, in the case of large pore size in the polymer membrane, osmotic phenomenon is caused by cohesive energy of water. Accordingly, the polymer membrane having water- proof and gas permeable properties should have a pore size limited within the range not causing osmotic phenomenon of water, and great numbers of pores.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of the present invention to alleviate said problems of the prior arts and to provide a novel method for preparing polymer membranes having water-proof and gas permeable properties, which has advantages of simplified preparation process and lowered preparation cost, whereby control of pore size and number in polymer membranes results in the preparation of polymer membrane having excellent water-proof and gas permeable properties.
In an aspect of the present invention, there is provided a method for preparing polymer membranes comprising mixing polymers which are membrane materials, with suitable amounts of granular inorganic ingredients soluble in acidic or alkaline solution, molding the mixture in a film form, immersing the film mold in acidic or alkaline solution to dissolve out and thus remove the granular inorganic ingredients contained in polymer membranes.
BEST MODES FOR CARRYING OUT THE INVENTION In the present invention, granular inorganic ingredients, soluble in acidic or alkaline solution, are mixed with polymers which are membrane materials, molded in a film form, followed by immersing the film mold in acidic or alkaline solution and thus removing the granular inorganic ingredients by chemical reaction, thereby preparing a desired polymer membrane having water-proof and gas permeable properties. As such, any granular inorganic ingredients may be used, so long as they are soluble in acidic or alkaline solution, for example, including metal oxides, such as zinc oxide, magnesium oxide and so on; metal powders, such as iron powder, aluminum powder etc. ; calcium carbonate, magnesium carbonate and the like. In polymer materials, polymers which can be molded into film form can be used without need for differentiating thermoplastic or thermosetting materials.
The preparation methods of a polymer membrane with water-proof and gas permeable properties using granular inorganic ingredients are classified into two
manners : the first comprising uniformly mixing granular inorganic ingredients with a solution of polymers in suitable solvent, coating the mixture onto a substrate such as glass plate or stainless steel plate in suitable thickness, drying, peeling off, to form a membrane film, or directly coating the mixture on fiber or paper materials to be coated to polymer membrane and drying to form a membrane, which is immersed in acidic or alkaline solution to remove the granular inorganic ingredients; the second manner comprising heating-mixing thermoplastic polymer materials of pellet or powder phases with granular inorganic ingredients, molding the heated mixture into film form by extrusion or calendaring in the film form, and immersing the film in acidic or alkaline solution to remove the granular inorganic ingredients.
In the present invention, sizes and amounts of granular inorganic ingredients are important factors determining pore size and gas permeability of final products. The average grain size ranges, but is not limited to, 0.1-20 plu7 and the used amount is in the range of about 60-800 parts by weight on a basis of 100 parts by weight of polymers.
A better understanding of the present invention may be obtained in light of the following examples which are set forth to illustrate, but are not to be construed to limit the present invention.
EXAMPLE 1 A rubber composition comprising 100 parts by weight of natural rubber, 5 parts by weight of zinc oxide, 2.5 parts by weight of stearic acid, 2.5 parts by weight of sulfur for rubber, 2.5 parts by weight of dibenzothiazyl disulfide and 0.5 parts by weight of BZ (zinc di-n-butyldithiocarbamate), kneaded on an open roll, was dissolved in 500 parts by weight of toluene, and added with calcium carbonate (supplied from Yujin Industry Co., average grain size 6.05 jj. m) in various amounts as shown in Table I, below.
TABLE I Unit: part by weight No. 1 2 3 4 5 6 7 8 9 10 Dissolved Rubber 100 100 100 100 100 100 100 100 100 100 Composition CaCO3 20 40 60 80 100 120 140 160 180 200
Each of thusly mixed rubber compositions was dried and then applied to a stainless steel container having a diameter of 50 cm without a cover, to a thickness of about 2 mm, and let stand in a vacuum chamber under the condition of 750 mmHg x 40 °C for 2 days, to totally remove toluene.
The toluene-removed test pieces were introduced to an iron mold and vulcanized under the condition of 200 kg/cm2 # 150 °C for 10 minutes.
Subsequently, the vulcanized test pieces were cut into sheets of width 5 cm x length 5 cm x thickness 2 mm, immersed in 5 % diluted hydrochloric acid solution at ambient temperature for 24 hours, followed by washing and drying the test pieces. Then, weights before and after immersion in hydrochloric acid of the samples were measured to observe formation of pores according to the amounts of the mixed calcium carbonate. The results are shown in Table 2, below.
TABLE 2 Unit: g No. 1234 5 678 9 10 Sample Weight before 7.35 8.6 9.4 9.95 10. 35 10. 7 10. 9 11. 1 11. 25 11. 4 immersion Sample Weight after 7. 15 7.9 4. 2 2.36 2 1. 52 1. 37 1. 23 1.13 1. 04 immersion From the above results and observation by the naked eye, it can be confirmed that, in the samples of Nos. 1 and 2, only calcium carbonate present in the surface of the membrane is dissolved out; in the sample of No. 3, at least half
of calcium carbonate is dissolved out ; and in the samples of Nos. 4-10, almost or all calcium carbonate is dissolved out.
EXAMPLE 2 A rubber composition comprising 100 parts by weight of Neoprene AD, 8 parts by weight of MgO, 5 parts by weight of ZnO, and 40 parts by weight of phenol resin was dissolved in toluene to have a solid content of 10 wt%, and added with 70 parts by weight of calcium carbonate, to yield a uniformly dispersed mixture. Thereafter, the mixture was applied to a fabric cloth woven with nylon fibers by use of a knife coater in the amount of 20 g/m27 dried at ambient temperature for 10 minutes, and then vulcanized under hot atmosphere of 150 °C.
The vulcanized samples were immersed in 5 % hydrochloric acid solution at room temperature for 10 minutes, thereby thoroughly dissolving out the calcium carbonate. After washing and drying, a polymer membrane having water-proof and gas permeable properties was laminated on nylon fabric cloth.
The moisture permeability of thusly obtained polymer membrane was measured as 9800 glum2 24 hrs by use of JISL-1099 (A-l) method.
EXAMPLE 3 The present experiment was performed in the same manner as described in the example 2, except that metal aluminum powder and 30 % caustic soda solution were substituted for calcium carbonate and 5 % hydrochloric acid solution, respectively. So, a polymer membrane with water-proof and gas permeable properties was layered on nylon fabric cloth, after which the membrane moisture permeability was measured in the same method as in the example 2, and found to be 8700 g/nr-24 hrs.
EXAMPLE 4
Urethane prepolymer (L-83, suppled from Uniroyal Chemical Corporation, USA) was dissolved in MEK to make a 20 % solution, and MOCA (4,4'- methylene-bis-ortho-chloro aniline) was dissolved in MEK to prepare a 20 % solution as a curing agent. An admixture of 100 parts by weight of said prepolymer solution and 3 parts by weight of the curing agent was added with 70 parts by weight of calcium carbonate and thus uniformly dispersed. The dispersed mixture was coated onto nylon fabric cloth using a knife coater in the amount of 28 glum2, dried at room temperature for 10 minutes and then cured for 10 hours under hot atmosphere of 120 °C. The samples were immersed in 5 % hydrochloric acid solution at room temperature for 15 minutes, taken out of the solution and then washed and dried, to obtain a polymer membrane having water- proof and gas permeable properties, which was layered on nylon fabric cloth.
The moisture permeability test of the obtained polymer membrane was performed in the same manner as in the above example 2. The moisture permeability was 9100 glm2 24 hrs.
INDUSTRIAL APPLICABILITY As stated above, the polymer membrane prepared according to the method of the present invention is advantageous in terms of excellent water-proof and gas permeable effect, simplified preparation process, and decreased preparation cost.
Therefore, the present polymer membranes in the form directly laminated onto film or fiber can be applied to the fields of feminine hygiene products, infant diapers, outdoor and camping equipment and so on.
The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.