Patent Application
20190135981
The present invention relates to a polyarylene sulfide resin composition which is excellent in hydrolysis resistance and thus suitable for parts of an automobile coolant system.
Currently, a demand for polyarylene sulfide (also, referred to as “PAS”), a representative engineering plastic, has increased in various electronic goods and products used in high temperatures and corrosive environments due to its high thermal resistance, chemical resistance, flame resistance and electric insulation.
Polyphenylene sulfide (also, referred to as “PPS”) is the only commercially available polyarylene sulfide. PPS is widely used for housing or major parts of automobile equipment, electric or electronic devices due to its excellent mechanical, electrical and thermal properties, and chemical resistance.
The process widely used for the commercial production of PPS is a solution polymerization of p-dichlorobenzene (hereinafter, referred to as ‘pDCB’) and sodium sulfide in a polar organic solvent such as N-methyl pyrrolidone, which is known as the Macallum process.
When PPS is produced by the Macallum process, however, the solution polymerization process using sodium sulfide, etc. may produce by-products in a salt form (e.g., NaCl). Since such by-products in a salt form may deteriorate the performance of electronic parts, additional washing or drying processes, etc. are required to remove the by-products and residual organic solvents (see U.S. Pat. Nos. 2,513,188 and 2,583,941).
In order to resolve the above problems, a process of preparing PAS by melt polymerization of reactants containing diiodide aromatic compounds and elemental sulfur has been suggested. As such process neither produces by-products in a salt form during the preparation of PAS nor uses organic solvents, it does not require any separate processes for removing such by-products or organic solvents (see Korean Laid-Open Patent Publication No. 2011-0102226).
Meanwhile, PPS exhibits excellent chemical resistance, particularly durability against solution immersion, and thus, it is used for engine parts, particularly coolant, oil pump parts, etc. However, since the parts of the automobile engine are related with the safety of a driver, the improvement of their durability is essential. Particularly, since an engine coolant part is in direct contact with the coolant, the improvement of its long-term durability is needed.
Accordingly, an object of the present invention is to provide a PAS resin composition which is excellent in hydrolysis resistance and can confer long-term durability to automobile coolant (antifreeze solution) system and the like.
Another object of the present invention is to provide a molded article manufactured by molding the PAS resin composition.
To achieve the above objects, the present invention provides a resin composition which comprises: a polyarylene sulfide having a chlorine content of 300 ppm or less; a mercapto silane coupling agent; a hydrolysis resistant additive; and a filler.
In addition, the present invention provides a molded article manufactured by molding the above-described resin composition.
The resin composition according to the present invention exhibits an improved working life in water contact environment in comparison with conventional PAS, without compromising excellent mechanical and thermal properties unique to PAS. Thus, it can be widely used in various fields requiring durability and high temperature hydrolysis resistance.
The present invention provides a resin composition comprising a polyarylene sulfide, a mercapto silane coupling agent, a hydrolysis resistant additive and a filler.
The polyarylene sulfide has a chlorine content of 300 ppm or less. Specifically, the polyarylene sulfide may have a chlorine content of 200 ppm or less, 100 ppm or less, or 50 ppm or less.
The polyarylene sulfide may be comprised in the resin composition in an amount of 15 to 70 wt %, specifically 20 to 65 wt %, based on the total weight of the composition. If the polyarylene sulfide is comprised in an amount of 15 wt % or more, the mechanical strength of the manufactured product such as tensile strength does not decrease, and when it is comprised in an amount of 70 wt % or less, the mechanical strength of the manufactured product becomes excellent.
The polyarylene sulfide comprises an arylene sulfide repeating unit and an arylene disulfide repeating unit, and for example, the weight ratio of arylene sulfide repeating unit to arylene disulfide repeating unit may range from 1:0.0001 to 1:0.05, or from 1:0.001 to 1:0.01. Since the polyarylene sulfide used in the present invention comprise an arylene disulfide repeating unit as described above, it may have a lower melting point than that of a polyarylene sulfide having the same molecular weight and consisting of an arylene sulfide repeating unit only, and, thus, the processing temperature can be lowered and the physical properties of the finally manufactured polyarylene sulfide can be improved.
The polyarylene sulfide may have a number average molecular weight of 3,000 to 1,000,000, or 10,000 to 100,000, and a polydispersity, defined as a ratio of a weight average molecular weight with respect to the number average molecular weight, may be 2.0 to 4.0, which indicates a relatively narrow dispersion.
The polyarylene sulfide may have a melting point ranging from 270 to 290° C., specifically from 275 to 285° C., and more specifically about 280° C. In addition, the melt viscosity of the polyarylene sulfide measured by a rotational disk-type viscometer at a temperature of a melting point of +20° C. may be from 100 to 5,000 poises, specifically from 500 to 3,000 poises, and more specifically about 2,000 poises.
The polyarylene sulfide is not particularly limited as long as it satisfies the physical properties described above. For example, the polyarylene sulfide may be manufactured by a melt polymerization method. In addition, the polyarylene sulfide satisfying the physical properties described above may improve the hydrolysis resistance of a resin composition.
Specifically, the polyarylene sulfide may be manufactured by the manufacturing method disclosed in Korean Laid-open Patent Publication No. 2011-0102226, which may comprise the steps of: (a) polymerizing reactants comprising diiodo aromatic compound and a sulfur compound; and (b) further adding 0.1 to 20 parts by weight of a sulfur compound based on 100 parts by weight of the sulfur compound contained in the reactants during the polymerizing step.
The diiodo aromatic compound may be, for example, selected from the group consisting of diiodobenzene, diiodonaphthalene, diiodobiphenyl, diiodobisphenol, diiodobenzophenone, and a combination thereof, but is not limited thereto.
The polymerization reaction condition in step (a) is not particularly limited as long as the polymerization of the reactants comprising the diiodo aromatic compound and the sulfur compound can be initiated. For example, step (a) may be carried out under elevated temperature and reduced pressure conditions. Specifically, the temperature elevation and pressure reduction is performed by changing the initial reaction condition of a temperature of 180 to 250° C. and a pressure of 50 to 450 torr to a final reaction condition of 270 to 350° C. and 0.001 to 20 torr. The reaction may be carried out for 1 to 30 hours.
The reactants comprising a diiodo aromatic compound and a sulfur compound may be subjected to a melt blending step prior to the polymerization step. The diiodo aromatic compound may be used in an amount of 1,000 to 2,000 parts, or 1,000 to 17,000 parts by weight based on 100 parts by weight of the sulfur compound introduced before the polymerization.
In the above method, a sulfur compound may be further added during the polymerization reaction as in step (b) to form a disulfide-type bond in the polymer. Such disulfide-type bond may continuously participate in a sulfur exchange reactions, a type of an equilibrium reaction, with the polymer chains included in a polyarylene sulfide, thereby rendering uniform the molecular weights of the polymer chains included in the polyarylene sulfide. Particularly, due to the sulfur exchange reaction, the equilibrium reaction, the degree of polymerization of the polyarylene sulfide may be uniform, and, thus, the formation of polyarylene sulfide polymer chains having excessively large or small molecular weights may be suppressed.
In step (b), 1 to 30 parts by weight of a polymerization terminator may be further added based on 100 parts by weight of the sulfur compound comprised in the reactants. The polymerization terminator is not particularly limited as long as it can terminate the polymerization by removing iodine groups contained in the polymer to be manufactured. Specifically, the polymerization terminator may be selected from the group consisting of diphenyl sulfide, diphenyl ether, biphenyls (or diphenyls), benzophenone, dibenzothiazyl disulfide, monoiodoaryl compounds, benzothiazoles, benzothiazolesulfen amides, thiurams, dithiocarbamates, diphenyl disulfide, and a combination thereof.
The mercapto silane coupling agent may improve the tensile strength and hydrolysis resistance of the resin composition. Specifically, the mercapto silane coupling agent may be selected from the group consisting of 2-mercaptoethyl trimethoxy silane, 3-mercaptopropyl trimethoxy silane, 3-mercaptopropyl triethoxy silane, 2-mercaptoethyl tripropoxy silane, 2-mercaptoethyl tributoxy silane, 2-mercaptoethyl tri sec. butoxy silane, 3-mercaptopropyl triisopropoxy silane, 3-mercaptopropyl trioctoxy silane, 2-mercaptoethyl tri 2′-ethylhexoxy silane, 2-mercaptoethyl dimethoxy ethoxy silane, 3-mercaptopropyl dimethoxy methyl silane, 3-mercaptopropyl methoxy dimethyl silane, 3-mercaptopropyl dimethoxy methylmercapto silane, 3-mercaptopropyl methoxy di(methylmercapto) silane, 3-mercaptopropyl methoxy methyl methylmercapto silane, 2-mercaptoethyl tris(methylmercapto) silane, 2-mercaptoethyl tris(isopropylmercapto) silane, 3-mercaptopropyl tributylmercapto silane, 3-mercaptopropyl tris(octylmercapto) silane, 3-mercaptopropyl cyclohexoxy dimethyl silane, 4-mercaptobutyl trimethoxy silane, 3-mercaptocyclohexyl trimethoxy silane, 3-mercaptocyclohexyl triethoxy silane, 12-mercaptododecyl trimethoxy silane, 18-mercaptooctadecyl trimethoxy silane, 18-mercaptooctadecyl methoxy dimethylsilane, 2-mercaptoethyl tripropoxy silane, 3-mercaptopropyl tripropoxy silane, 4-mercaptobutyl tripropoxy silane, 3-mercaptopropyl dimethoxy silane, 3-mercaptopropyl diethoxy silane and a combination thereof. Specifically, the mercapto silane coupling agent may be selected from the group consisting of 3-mercaptopropyl trimethoxy silane, 3-mercaptopropyl triethoxy silane, 3-mercaptocyclohexyl trimethoxy silane, 3-mercaptocyclohexyl triethoxy silane, 3-mercaptopropyl dimethoxy silane, 3-mercaptopropyl diethoxy silane, and a combination thereof. More specifically, the mercapto silane coupling agent may be selected from the group consisting of 3-mercaptopropyl trimethoxy silane, 3-mercaptopropyl triethoxy silane, and a combination thereof.
The mercapto silane coupling agent may be added in an amount of 0.01 to 5 wt %, specifically 0.1 to 3 wt %, based on the total weight of the resin composition. If the mercapto silane coupling agent is contained within the above range, the effects of increasing mechanical strength and improving hydrolysis resistance may be achieved.
The hydrolysis resistant additive may be selected from the group consisting of functionalized epoxy resin, polycarbodiimide, para-phenylene-diisocyanate and a combination thereof.
In addition, the hydrolysis resistant additive may be added in an amount of 0.01 to 5 wt %, specifically 0.1 to 3 wt %, based on the total weight of the resin composition. If the hydrolysis resistant additive is comprised within the above range, the effect of prolonging the working life of the resin composition may be obtained by extending the property-retention period even in a high temperature and high humidity environment.
The resin composition may comprise 15 to 70 wt % of a polyarylene sulfide, 0.01 to 5 wt % of a mercapto silane coupling agent, 0.01 to 5 wt % of a hydrolysis resistant additive, and 25 to 80 wt % of a filler. Specifically, the resin composition may comprise 20 to 65 wt % of a polyarylene sulfide, 0.1 to 3 wt % of a mercapto silane coupling agent, 0.1 to 1 wt % of a hydrolysis resistant additive, and 45 to 75 wt % of a filler.
The filler may be selected from the group consisting of a glass fiber, a carbon fiber, a boron fiber, a glass bead, a glass flake, talc, calcium carbonate, a pigment, and a combination thereof. Specifically, the filler may be selected from the group consisting of a glass fiber, calcium carbonate, a pigment, and a combination thereof.
The glass fiber may be added to improve the mechanical strength and durability of the resin composition. The average diameter of the glass fiber may be 6 to 13 μm, specifically 9 to 11 μm. In addition, the average length of the glass fiber may be 1 to 6 mm, specifically 3 to 5 mm. The glass fiber may be selected from the group consisting of a glass fiber surface-treated with an urethane/epoxy silane, a glass fiber surface-treated with an urethane/amino silane, and a combination thereof. The urethane/epoxy silane refers to a water-soluble urethane resin containing an epoxy silane, and the urethane/amino silane refers to a water-soluble urethane resin which containing an amino silane. Commercially available glass fibers include OCV910 manufactured by Owens Corning and FT523 manufactured by Owens Corning, etc.
The calcium carbonate may be added to improve the modulus characteristic of the resin composition and may have an average particle diameter of 0.8 to 20 μm, specifically 1.0 to 10 μm.
As the pigment, various conventional organic or inorganic pigments known in the art may be used. For example, the pigment may be selected from the group consisting of titanium dioxide (TiO2), carbon black, and a combination thereof, and specifically, it may be carbon black.
In addition, the filler may include 20 to 65 wt % of a glass fiber, 10 to 45 wt % of calcium carbonate, and 0.01 to 5 wt % of a pigment based on the total weight of the resin composition. Specifically, the filler may include 30 to 60 wt % of a glass fiber, 15 to 40 wt % of calcium carbonate, and 0.1 to 3 wt % of a pigment based on the total weight of the resin composition. More specifically, the filler may include 35 to 55 wt % of a glass fiber, 15 to 30 wt % of calcium carbonate, and 0.1 to 1 wt % of a pigment based on the total weight of the resin composition.
The resin composition of the present invention may further comprise a component selected from the group consisting of a lubricant, a stabilizer, a plasticizer and a combination thereof.
The lubricant may be added to improve moldability. In particular, a hydrocarbon-based lubricant may be used to prevent friction between the resin and the mold metal, and to confer releasability from the mold. The hydrocarbon-based lubricant may be selected from the group consisting of montanic acid, a metal salt (e.g., one having calcium, magnesium, zinc, etc.), an ester, stearic amide, a polyethylene wax and a combination thereof. In addition, the lubricant may be added to the resin composition in an amount of 0.1 to 3.0 parts by weight, specifically 0.1 to 1.0 part by weight based on 100 parts by weight of the composition.
The stabilizer may be selected from the group consisting of antioxidants, photo stabilizers, UV stabilizers, and a combination thereof. The stabilizer may be added to the resin composition in an amount of 0.1 to 3.0 parts by weight, specifically 0.1 to 1.0 part by weight based on 100 parts by weight of the composition.
The antioxidant is not particularly limited as long as it can sustain high heat resistance and thermal stability of the resin composition, and examples thereof include phenolic antioxidants, amine antioxidants, sulfur antioxidants and phosphorus antioxidants. As the phenolic antioxidant, hindered phenolic compounds may be used. Specific examples thereof include tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], and so on.
Examples of the phosphorus antioxidants may include tris(2,4-di-tert-butylphenyl)phosphate, O,O′-dioctadecylpentaerythritol bis(phosphite), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxy-3,9-diphospaspiro[5.5]undecane, and so on.
The photo stabilizer and the UV stabilizer are not particularly limited as long as they can prevent the discoloration of the resin composition and provide light (UV) stability. Examples of the light stabilizer and UV stabilizer may include benzotriazoles, benzophenones, and hindered amine compounds, etc.
The resin composition may have a tensile strength value of 50 to 200 MPa, 60 to 200 MPa, 70 to 180 MPa or 100 to 180 MPa, as measured according to ASTM D 638.
Meanwhile, the present invention provides a molded article manufactured from the resin composition. Specifically, the resin composition may be manufactured into a molded article having an excellent hydrolysis resistance and durability and applicable to various uses, by molding the resin composition by a method known in the art such as biaxial extrusion.
The molded article may be in various forms such as a film, a sheet, or a fiber, and the molded article may be an injection molded article, an extrusion molded article, or a blow molded article. For example, in the case of injection molding the temperature of the mold may be about 130° C. or higher in consideration of crystallization. In case that the molded articles are in film or sheet forms, they may be manufactured as various films or sheets by a non-orientation method, a uniaxial orientation method, biaxial orientation method, or the like. In case that the molded articles are fibers, they may be various kinds of fibers such as a non-drawn fiber, a drawn fiber, or an ultra-drawn fiber, etc., and may be used as a fabric, knitted goods, a non-woven fabric (spunbond, meltblow, or staple), a rope, or a net. The above molded articles may be used as electric/electronic parts, building materials, automobile parts, machine parts, or basic commodities, as well as coatings of an area in contact with chemicals or an industrial fiber with chemical resistance. They are particularly useful as parts of automobile coolant (antifreeze solution) systems.
Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are intended to further illustrate the present invention without limiting its scope.
40 kg of p-diiodobenzene, 3.4 kg of sulfur, and 150 g of 1,3-diiodo-4-nitrobenzene as a catalyst were put into a reactor and melt blended at 180° C. A polymerization reaction was carried out while raising the temperature of the mixed reactants from 180° C. to 340° C. and reducing the pressure from the atmospheric pressure to 10 torr. After 5 hours from the initiation of the polymerization, 150 g of sulfur and 100 g of diphenyl sulfide as a polymerization terminator were added thereto, and the reaction was further performed for 3 hours to obtain PPS resins. Each of the PPS resins prepared was injected with an injection speed of 50 mm/s, an injection pressure of 120 MPa, and an injection temperature of 310° C. using 80 ton Engel injection machine, to prepare injection specimens.
Melt viscosity (MV), melting point (Tm), number average molecular weight (Mn), polydispersity index (PDI), weight ratio of arylene sulfide repeating unit to arylene disulfide repeating unit, chlorine content and iodine content of the resulting PPS resins were measured by the following method. As a result, the PPS resin had MV of 2,000 poises, a Tm of 280° C., Mn of 15,000, PDI of 2.8, the chlorine content of 0 ppm, a weight ratio of arylene sulfide repeating unit to arylene disulfide repeating unit of 1:0.003, and the iodine content of 1,000 ppm.
Melt Viscosity (MV)
Melt viscosity was measured at 300° C. using a rotating disk viscometer. In the frequency sweep method, the angular frequency was measured from 0.6 to 500 rad/s, and the viscosity at 1.84 rad/s was defined as melt viscosity (MV).
Melting Point
Using a differential scanning calorimeter (DSC), the melting point was measured while the temperature was raised from 30° C. to 320° C. at a rate of 10° C./minute, cooled to 30° C., and then raised from 30° C. to 320° C. at a rate of 10° C./minute.
Number Average Molecular Weight (Mn) and Polydispersity Index (PDI)
A sample was prepared by dissolving the PPS resin in 1-chloronaphthalene to obtain the PPS concentration of 0.4 wt % and stirred at 250° C. for 25 minutes. Then, the sample was introduced at a flow rate of 1 mL/min in the column of a high temperature gel permeation chromatography (GPC) system (210° C.), polyarylene sulfides having different molecular weights were sequentially separated, and the intensities corresponding to the molecular weight of the separated polyarylene sulfide was measured using an RI detector. After determining a calibration curve with a standard specimen (polystyrene) whose molecular weight was known, the number average molecular weight (Mn) and polydispersity index (PDI) of the PPS resin were calculated.
Chlorine (Cl) Content
50 mg of the injection specimen was heated at 1,000° C. using AQF (Auto Quick Furnace) to completely incinerate any organic substances and the combustion gas was entrapped in an absorption solution (900 ppm of hydrogen peroxide solution) and auto-injected into Ion chromatography (Auto Quick Furnace) to measure the chlorine (Cl) content.
Iodine (I) Content
50 mg of the injection specimen was heated at 1,000° C. using AQF (Auto Quick Furnace) to completely incinerate any organic substances and the combustion gas was entrapped in an absorption solution (900 ppm of hydrogen peroxide solution, and 900 ppm of hydrazine) and auto-injected into Ion chromatography (Auto Quick Furnace) to measure the iodine (I) content.
Arylene Disulfide Weight Analysis Method
After incinerating a small amount (about 2 mg) of a sample at 1,000° C. using AQF (Automatic Quick Furnace), the sulfuric acid gas was collected in an absorbing solution (hydrogen peroxide solution) and ionized, and then sulfur ion was separated in the column using IC (Ion Chromatography) measurement method. The sulfur content was quantified by the sulfur ion standard material (K2SO4), and the difference between the measured sulfur content and the theoretical sulfur content was calculated as the amount of disulfide.
Each component constituting the composition was added to a biaxial screw extruder in a compositional amount corresponding to 35 wt % of PPS obtained in the above preparation Example, 40 wt % of urethane/amino silane-treated glass fiber (OCV-910, Owens Corning), 24 wt % of calcium carbonate (Omiya 1HB), 0.5 wt % of 3-mercaptopropyl trimethoxy silane (Momentive, Silquest A-189) and 0.5 wt % of a hydrolysis resistant additive (epoxy resin, BASF, ADR 4370S), and then 0.5 part by weight of carbon black (Orion Engineering Carbon Co., Ltd., Hiblck® 50L) based on 100 parts by weight of the composition was further added to prepare a resin composition.
The biaxial screw extruder manufactured by SM platek had a diameter of 40 mm and an L/D of 44. The process conditions were a screw speed of 250 rpm, a feed rate of 40 kg/hr, a barrel temperature of 280° C. to 300° C., and a torque of 60%. Three feeders were used to inject the raw materials. The first feeder was used to feed the PPS resin, carbon black, a mercapto silane coupling agent and a hydrolysis resistant additive; the second feeder to feed calcium carbonate, and the third feeder to feed a glass fiber, for preparing a PPS resin composition.
A PPS resin composition was prepared by the same method as in Example 1, except that the components and their contents shown in Table 2 were used.
A resin composition was prepared by the same method as in Example 1, except that the components and their contents shown in Tables 2 and 3 were used and neither calcium carbonate nor glass fibers was added.
The components used in Examples 1 to 4 and Comparative Examples 1 to 11 are shown in Table 1 below.
The properties of the resin compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 11 were measured as described below and the measurement results are shown in Tables 2 to 4.
First, the resin compositions prepared in Examples 1 to 4 and Comparative Examples 1 to 11 were respectively injected at 310° C. to prepare injection specimens.
(1) Measurement of Moisture Absorption Rate
Using Karl Fisher Moisture Meter (Mitsubishi, VA-100 solid-phase method), 5 g of the injection specimen (in a pellet form) was tested under the following conditions, and the moisture content was measured by heating at 230° C. for 1 hour after the surface moisture was removed.
Constant temperature/constant humidity test: 80° C. and 80% humidity
Sample: 5 g of pellet
Immersion time: 3 days
Absorption rate measurement equipment: Karl Fisher Moisture Meter
(2) Tensile Strength
The tensile strength of the injection specimen was measured according to ASTM D 638.
(3) Water Immersion Test
The flexural strength specimens (ASTM D 740) were immersed in distilled water at 60° C. for 1,000 hours. After 500 hours and 1,000 hours of immersion, the flexural strength specimens were taken out and the flexural strength was measured by the same method as described above, and the flexural strength values before and after immersion were compared, to evaluate the property retention ratio (Retention %, RT %).
(4) Long Life Coolant Test (LLC Test)
The tensile strength specimens (ASTM D 638) were immersed at 140° C. for 3,000 hours. After 1,000 hours and 3,000 hours of immersion, the injection specimens were taken out and the tensile strength was measured by the same method as described above, and the tensile strength values before and after immersion were compared, to evaluate the property retention ratio (Retention %, RT %).
As shown in Tables 2 and 3, the resin compositions of Examples 1 to 4 of the present invention showed long term hydrolysis resistant property-retention rate of 75% or more in the LLC test for 3,000 hours, which was substantially higher than those of Comparative Examples 1 to 11. In particular, the compositions of Comparative Examples 9 to 11 containing PPA or PA instead of PPS showed long term hydrolysis resistant property-retention rate of 20% or less, which is unsuitable for use as automobile coolant parts requiring a long working life.
In addition, the compositions of Examples 1 to 4 containing a mercapto silane coupling agent and a hydrolysis resistant additive showed increased long term hydrolysis resistant property-retention rate when compared with the composition of Comparative Example 1 containing neither mercapto silane coupling agent nor hydrolysis resistant additive and the composition of Comparative Example 3 containing a mercapto silane coupling agent only.
As shown in Table 4, the specimen of Comparative Example 2 containing the PPS prepared by melt polymerization method showed lower moisture absorption rate than the specimens of Comparative Examples 5 and 7 containing solution polymerization PPS. This may be due to no existence of residual salts that affect the moisture absorption.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2016-0051080 | Apr 2016 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2017/003130 | 3/23/2017 | WO | 00 |
