KR101304893B1 - Method of preparing and concentration the ptfe dispersion - Google Patents

Abstract

The present invention relates to the preparation of polytetrafluoroethylene nanoaqueous dispersions and their concentration. More specifically, the present invention is to prepare a polytetrafluoroethylene (PTFE) water dispersion having a solid content of 20 ~ 30wt.% By emulsion polymerization method, the particle size is 700 ~ 3,000㎛, the expansion coefficient (expansion coefficient , g / g, DI water (SAP: Super Absorbent Polymer), which is 100 ~ 1,000 times its own weight, is supported or supported on PTFE water dispersion, and the water is expanded by capillary or absorbent elastic expansion. It relates to a method for producing a PTFE water dispersion having a nano-size (100 ~ 500nm) having a solid content of more than 60wt.% By absorbing and removing.

Description

Preparation of PTFE Aqueous Dispersion and Method of Concentration {METHOD OF PREPARING AND CONCENTRATION THE PTFE DISPERSION}

The present invention relates generally to the preparation and concentration of polytetrafluoroethylene nanoaqueous dispersions. More specifically, the present invention is to prepare a polytetrafluoroethylene (PTFE) water dispersion having a solid content of 20 ~ 30wt.% By the emulsion polymerization method, poly (acrylic) is a super absorbent polymer (SAP) It relates to a method for producing a PTFE aqueous dispersion having a nano-size (100 ~ 500nm) having a solid content of 60wt.% Or more by supporting or contacting the rate-acrylamide) crosslinked copolymer.

PTFE of high molecular weight has a very high melt viscosity, and thus there is a limit to applying general molding processes such as injection and extrusion. A water dispersion concentrated to 60 wt.% Or more is required. As a part of this, evaporative concentration method, reduced pressure concentration method, freeze concentration method, electrodialysis method, ultrafiltration membrane method and decantation method using cloud point are applied to low concentration of PTFE water dispersion. The ultrafiltration membrane method and the decantation method are mainly used.

For example, U. S. Patent No. 6,153, 668 obtains 30 wt.% Of PTFE water dispersion, and then 70 wt.% Of PTFE water through a separate concentration step using the characteristics of the cloud point of the nonionic surfactant in the aqueous solution. Posting to get the body.

In addition, US Pat. No. 6,153,688 describes a technique for concentrating PTFE water dispersion having environmentally friendly properties up to 60 wt.% Using polyethylene alkyl ether as a nonionic surfactant.

In another example, U.S. Patent No. 6,136,933 discloses an aqueous dispersion having a solid content of 44.1 wt.% By performing a TFE emulsion polymerization in two stages of low temperature (55) and high temperature (80) using paraffin wax. Manufactured.

For example, US Pat. No. 60,638,296 describes a process for concentrating with removal of fluorine-based surfactants using ion exchange resins.

The PTFE water dispersion should be secured in high concentration with the formation of stable particles during emulsion polymerization. However, the above method has a limit in reducing the loss of PTFE particles in the process of removing the emulsion stabilizer along with an increase in the energy cost of the concentration process.

Methods of concentrating the aqueous dispersion of modified fluorine compounds including PTFE include evaporation concentration method, reduced pressure concentration method, freeze concentration method, electrodialysis method, ultrafiltration membrane method and decantation method using cloud point. The ultrafiltration membrane method using organic thin film and the decantation method which can perform a continuous process are mainly used because of the convenience of overworking.

However, the ultrafiltration membrane method using a thin film of natural or synthetic polymers such as chitosan, alginic acid, cellulose, cellulose acetate, polyacrylonitrile and polysulfone generally has low heat resistance. As a result, high energy costs are consumed.

In contrast, the decantation method using the cloud point of the nonionic surfactant is added by adding a certain amount of the nonionic surfactant to the aqueous dispersion of the modified fluorine compound containing 20-30 wt.% PTFE, and then warming to 70-90 ° C. It is the concentration method that induces the separation of reaction products. However, the use of such a method not only leads to a decrease in the quality of the non-ionic surfactant added, but also to an increase in the energy cost by repeating the heating-cooling-heating process, as well as the precipitation and separation processes in the concentration process. The loss of modified fluorine-containing nanoparticles, including PTFE, generated in the process and the prolonged operating time remain a challenge.

Thus, the present invention provides a TFE monomer; And monomers selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene in an aqueous dispersion medium. By law, a water dispersion of a modified fluorine compound containing PTFE having a solid content of 20-30 wt.% Is prepared, and a nano-size (200-500) having a solid content of 60 wt. It was confirmed that the modified fluorine compound containing the PTFE aqueous dispersion of (nm) can be obtained, and the present invention was completed.

In a first aspect, the present invention provides a water-phase in which a water-soluble initiator is dissolved in a continuous phase, and tetrafluoroethylene (TFE) which is a gaseous olefin monomer; And dispersion-phase monomers selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene. ) To provide an aqueous dispersion of a modified fluorine compound including PTFE having a nano-size prepared by emulsion polymerization.

In a second aspect, the present invention provides a method for producing an aqueous dispersion of a modified fluorine compound containing PTFE as described above.

a) tetrafluoroethylene (TFE) by emulsion polymerization; And solidifying by polymerizing a gaseous monomer selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene. Preparing a nanowater dispersion of a modified fluorine compound including PTFE having a content of 20-30 wt.%;

b) cooling the reaction product to below the melting point of the paraffin wax using a cooling device, and then removing the solidified paraffin wax of the upper layer:

c) supporting or contacting the superabsorbent polymer in the reaction product from which the paraffin wax has been removed;

d) separating the superabsorbent polymer carrying or absorbing water from the reaction product; And

e) repeating steps c) and d) provides a method for preparing an aqueous dispersion of a modified fluorine compound containing a desired concentration of PTFE.

Methods for producing modified fluorine compounds including PTFE include solution polymerization, suspension polymerization and emulsion polymerization or dispersion polymerization. In the case of solution polymerization The use of environmentally friendly solvents has continued as the Montreal Protocol limits the use of solvents such as chlorofluorocarbons and perfluorocarbons. As a part of these, hydrofluoroether and hydrofluorocabon have been adopted as alternative solvents, but they do not overcome the limitations in commercial application and cost. In the suspension polymerization method, the modified fluorine compound including PTFE is obtained in the form of granules. In this polymerization process, since the surfactant is not used, it is directly filtered without the coagluation or washing process accompanying the emulsion polymerization process. It has the advantage of being available. However, modified fluorine compounds including PTFE prepared by this method have a broad particle size distribution and have many limitations in forming a copolymer for modification of a formulation. On the other hand, the emulsion polymerization method is capable of synthesizing high molecular weight fluorine compounds by controlling chain transfer during growth reaction of modified fluorine compounds including PTFE by using fluorine-based surfactants and controlling particle size distribution. It has the advantage of being easy. However, the water dispersion of the modified fluorine compound containing a low concentration of PTFE has a disadvantage that the concentration process is complicated and requires a high energy cost. Therefore, the present invention excludes the decantation method by the addition of nonionic surfactant (using cloud point characteristics) which is most commonly used for the water dispersion of modified fluorine compound including PTFE prepared at low concentration, and has high absorbency without additional equipment. The present invention provides a technique for producing an aqueous dispersion of a modified fluorine compound containing a high concentration of PTFE by a single process as well as reducing energy costs by performing a concentration step by adding a resin.

1 is a 500 ~ 4000 cm ^{- 1} region of a resolution of 2 cm ^-1 , the number of scans (4) using the Midac FT-IR spectrometer of the PTFE water dispersion prepared in Example 1 The result of measuring the spectrum.
2 is a quantitative and qualitative analysis result of the PTFE nanoparticles prepared by Example 1 by EDS.
3 shows the surface morphology of PTFE nanoparticles prepared by Example 1. FIG.
Figure 4 shows the particle size distribution of the PTFE water dispersion prepared in Example 1.

The present invention prepares an aqueous dispersion of a modified fluorine compound containing a low concentration of PTFE of 20 ~ 30wt.% By emulsion polymerization, and then continuously using a superabsorbent polymer to perform the absorption concentration process without any special heating or the like It is a manufacturing technology for obtaining an aqueous dispersion of a modified fluorine compound containing a high concentration of PTFE having a solid content of 60 wt.% Or more.

In the present invention, in order to obtain a nano water dispersion of the modified fluorine compound containing a high concentration of PTFE in the water system, tetrafluoroethylene (TFE) in the gas (gas); And emulsion polymerization of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and monomers selected from the group consisting of chlorotrifluoroethylene and ethylene. Thereafter, a nano-water dispersion of a modified fluorine compound containing 20-30 wt.% PTFE was obtained, and then the superabsorbent polymer was continuously used to perform an absorption concentration process without any special heating or the like, so that the solid content was 60 wt. It is a manufacturing technology to obtain nano water dispersion of modified fluorine compound containing high concentration of PTFE.

In an embodiment, the emulsion polymerization is polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkylvinylether including PTFE Copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE) and the like are produced.

In order to achieve the above object,

a) gaseous tetrafluoroethylene (TFE) with shear stress applied to the continuous phase (aqueous phase) in which the fluorine-based surfactant, paraffin wax and water-soluble initiator are dissolved; And a gaseous monomer (dispersed phase) selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene. Preparing an aqueous dispersion of a modified fluorine compound containing 20-30 wt.% Of low concentration PTFE by injection;

b) cooling the reaction product prepared in step a) to room temperature to remove the upper solidified paraffin wax; And

c) providing a preparation method comprising the step of absorbing and removing water by concentrating the superabsorbent polymer on or in contact with the reaction product prepared in step b).

Specifically, the present invention relates to

a) tetrafluoroethylene (TFE) with shear stress applied to a continuous phase (aqueous phase) in which fluorine-based surfactant, paraffin wax and water-soluble initiator are dissolved in deionized water; And a gaseous monomer (dispersed phase) selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene. Preparing an aqueous dispersion of a modified fluorine compound containing 20 to 30 wt.% Of a low concentration of PTFE by performing emulsion polymerization;

b) cooling the reaction product prepared in step a) to room temperature to remove the upper solidified paraffin wax;

c) concentrating by absorbing and removing water by supporting or contacting the superabsorbent polymer in the reaction product prepared in step b);

d) separating the superabsorbent polymer carrying or absorbing water from the reaction product; And

e) repeating steps c) and d) to obtain an aqueous dispersion of the modified fluorine compound containing a high concentration of PTFE, wherein the aqueous dispersion of the modified fluorine compound containing a high concentration of PTFE of 60 to 80% by weight is prepared. It provides a method of manufacturing.

In an embodiment of the present invention, the compound which may be prepared from a fluorine-based polymer includes PTFE, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), tetra Fluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene Copolymer (ECTFE) and the like.

Ammonium perfluorocarboxylate, ammonium perfluorocaprylate and ammonium perfluorooctanoate as ammonium perfluorocarboxylate added to the aqueous phase which is the continuous phase of the present invention. ) May be used alone or in a mixture of two or more thereof. Double ammonium perfluorocarboxylates are suitable.

The amount of the fluorine-based surfactant may be determined in consideration of reaction rate, molecular weight, monomer content, and the like, and may be used in an amount of 0.02 to 1.0 wt.% Based on the content of the modified fluorine compound including the prepared PTFE. Preferably from 0.1 wt% to 0.8 wt% is suitable, more preferably from 0.2 wt% to 0.6 wt%. If it is less than 0.02 wt.%, The particles do not have sufficient emulsification stability and coagulation occurs between the particles. If it exceeds 1.0 wt.%, The particle size distribution becomes impossible to control.

In addition, in the case of paraffin wax, a saturated stabilizer that prevents coagulation between particles during emulsion polymerization may be used as a saturated hydrocarbon that exists in a solid phase at room temperature and causes a phased change to a liquid phase at a polymerization temperature. Normal saturated hydrocarbons with a melting point (mp: melting point) of 40 to 85 ° C. are most suitable, and saturated hydrocarbons having a melting point of 50 to 65 ° C. are most suitable. If it is less than 40, the polymerization rate is significantly lowered and the paraffin wax is not efficiently removed. In addition, if it exceeds 85 ℃, there is a problem that the dispersion stability is significantly lower.

The amount of paraffin wax may be determined in consideration of the viscosity and molecular weight of the reaction product, but usually 0.1-12 wt.% May be used with respect to the aqueous solvent. Preferably it is suitable to use 2 ~ 8wt.%, More preferably 4 ~ 6wt.% Is most suitable. If it is less than 0.1 wt.%, It is difficult to give efficient dispersion stability due to the decrease of relative specific surface area for the modified fluorine compound nanoparticles including PTFE produced. Dropping problem occurs.

Ammonium persulfate or potassium persulfate may be used as the water-soluble radical initiator used in the emulsion polymerization of the present invention, and permanganate salts may be used as an initiator to reduce the half-life of the persulfate system. A mixture of potassium permangnate and oxalic acid, ammonium bisulfite, and sodium metabisulfite may be used alone or in the form of two or more mixed compounds.

As for the usage-amount of the said polymerization initiator, 0.1-1,000 ppm is suitable with respect to the modified fluorine compound containing PTFE produced, Preferably 0.5-500 ppm is suitable. More preferably, 100-300 ppm is suitable. In order to produce a modified fluorine compound containing a high molecular weight PTFE by reducing the half-life can be used by mixing the above initiator. If the amount of the initiator is less than 0.1 ppm, it is difficult to facilitate the polymerization, and if it exceeds 1,000 ppm, it may cause coagulation between particles.

In preparing the nanowater dispersion of the modified fluorine compound including PTFE by the emulsion polymerization of the present invention, the polymerization reaction temperature is preferably in the range of 40 ° C to 80 ° C, and the polymerization reaction time is in the range of 1 to 12 hours. Preferably the polymerization reaction proceeds at 60 ° C. for 2 hours. If the polymerization reaction temperature is less than 40 ° C, the polymerization reaction may not proceed completely. If the polymerization reaction temperature is higher than 80 ° C, the system tends to be unstable due to rapid polymerization, which is not preferable.

The nanowater dispersion of the modified fluorine compound including PTFE obtained by the emulsion polymerization method preferably has a particle size in the range of 100 nanometers to 500 nanometers. If the particle size is less than 100 nanometers, there is a problem in that the amount of various additives must be increased by increasing the specific surface area, and if the particle size is larger than 500 nanometers, the modified fluorine compound particles including PTFE may be unstable due to external stress.

In another embodiment, the present invention obtains a modified fluorine compound nanoaqueous dispersion containing 20-30 wt.% PTFE by emulsion polymerization, and then supported or contacted with an aqueous dispersion of a modified fluorine compound including PTFE using a super absorbent polymer. The purpose of this invention is to provide a condensation method of obtaining a nano-water dispersion of a modified fluorine compound containing a high concentration of PTFE having a solid content of 60 wt.% Or more by absorbing and removing water by elastic expansion of a capillary tube or an absorber.

In general, the superabsorbent polymer is a polymer exhibiting the absorption of fluid due to the introduction of hydrophilic groups in a three-dimensional network or a single chain structure through crosslinking between polymer chains, and exists in the form of white powder or beads. On the other hand, it is a substance that absorbs water and swells and gels instantly when it is supported or contacted with an aqueous dispersion.

According to one embodiment, a brief description of the concentration technique by the superabsorbent polymer 1) The superabsorbent polymer containing a carboxyl group neutralized by sodium hydroxide (NaOH) is in contact with water when in contact with an aqueous solution. After hydration due to the strong affinity, 2) the swelling gel is formed by the mutual repulsion of carboxyl groups with the same charge, and 3) the polymer chain expands and, as a result, of the hydrophilic groups with charge in the polymer In proportion to the increase, the expansion of the polymer chains together with the larger amount of water can be accommodated.

The superabsorbent polymer applicable to the present invention includes starch and carboxy copolymerized with starch and monomers such as acrylonitrile, acrylic acid, acrylamide, methacrylate, and the like. Cellulose-based and polyvinyl alcohol-methacrylic acid block copolymers copolymerized with the above monomers in methyl cellulose (CMC), styrene (maleic anhydride) copolymer, polyacrylamide Any compound may be used as long as it is a substance capable of absorbing water to form a hydrogel such as a synthetic resin system including polyacryl amide and polyoxyethylene.

In the present invention, the particle size is 700 ~ 3,000㎛, "HISOBEAD" of 100 to 250 times the weight (expansion coefficient, g / g, D.I. water) of its own weight was purchased from Aekyung Fine Chemical Co., Ltd. was used. The compound has a property of quickly absorbing water in the range of 0 ~ 100 ℃ and does not easily release water by external pressure or the like even after the swelling gel. After absorbing water, the superabsorbent polymer in solid form can be easily recovered and reused by a simple operation such as blowing or heating.

The amount of the superabsorbent polymer may be differently applied according to the concentration of the reaction product. In the present invention, 0.05 to 1.0 wt.% Is suitable for 100 parts by weight of the modified fluorine compound aqueous dispersion including PTFE from which paraffin wax is removed. Preferably, 0.2 to 0.8 wt.% Is suitable. More preferably, 0.5 to 0.7 wt.% Is most suitable.

Hereinafter, the present invention will be exemplified in order to make the present invention easier to understand, but the present invention is not limited to these examples.

PTFE Of nano water dispersion Manufacturing example  One

In a 1,000 ml high-pressure glass reactor, 500 ml of deionized water and 0.7 g of ammonium perfluorocarboxylate, a fluorine-based surfactant, 0.03 g of ammonium persulfate (APS), an initiator, and ammonium bisulfite (initiator) Bisulfite) was added 0.0025g, 25g paraffin wax (mp: 50.6) and dissolved uniformly to prepare a continuous phase, purge the nitrogen for 10 minutes to completely remove the oxygen present in the reactor. Subsequently, the temperature of the reactor was raised to 60 ° C. under a stirring speed of 700 rpm, and the gaseous TFE monomer was injected to perform emulsion polymerization for 2 hours, and then the reaction product was cooled to room temperature to remove solidified paraffin wax of the upper layer. The infrared spectrum (Midac FT-IR spectrometer) was recovered by recovering the PTFE aqueous dispersion prepared in this example, and the stretching vibration of the -CF2- group was observed around 1,000 to 1,400 cm ^-1 , and the carbon double bond of TFE was also observed. The stretching vibration by C = C bond by disappeared at 1,900 cm ^-1 , indicating that PTFE was synthesized by radical polymerization. In addition, these results are pure PTFE polymer composed of 77.96% F (fluorine) and 22.04% C (carbon), as can be seen from the results of component analysis by EDS (Energy Dispersive X-ray Spectroscopy) after recovering PTFE nanoparticles. Confirmed. In addition, when the surface of the reaction product using the scanning electron microscope VEGA TESCAN confirmed the surface morphology, it was confirmed that the spherical particles of 232.7 was synthesized, the solid content of PTFE FD-610 (purchased from Kett, Japan) of infrared moisture meter As a result of using, it showed 25wt.%. (See FIGS. 1, 2, 3 and 4)

Concentration of PTFE Nanoaqueous Dispersion According to the Present Invention

Example  One

 0.8 kg of a superabsorbent polymer "HISOBEAD" was added to 100 kg of 25 wt.% PTFE nanoaqueous dispersion having an average particle size of 232.7 nm obtained by Preparation Example 1, and then left at room temperature for 2 hours. Subsequently, the swelling gel absorbing water was separated using a 80-mesh polarizer, and the solid content was measured using the FD-610 equipped with an infrared lamp. The result was 62.5 wt.%.

Example 2

The same procedure as in Example 1 was conducted except that 1.0 kg of the superabsorbent polymer "HISOBEAD" was used. As a result, the solid content was 76.4 wt.%.

Example 3

Concentration was carried out in the same manner as in Example 1, but was carried out for 5 hours with respect to the PTFE aqueous dispersion. At this time, the solid content was 74.6wt.%.

Example  4

In Example 1, after absorbing water to dry the superabsorbent polymer swelling gel at 110 ℃ for 12 hours, the solid superabsorbent polymer was recovered and applied to the PTFE water dispersion obtained in Preparation Example 1, the solid content was 61.4 wt.%.

Claims (9)

a) tetrafluoroethylene (TFE) with shear stress applied to a continuous phase (aqueous phase) in which fluorine-based surfactant, paraffin wax and water-soluble initiator are dissolved in deionized water; And a gaseous monomer (dispersed phase) selected from the group consisting of vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, perfluoroalkyl vinyl ether, hexafluoropropylene, ethylene, and chlorotrifluoroethylene and ethylene. Preparing an aqueous dispersion of a modified fluorine compound containing 20 to 30 wt.% Of a low concentration of PTFE by performing emulsion polymerization;
b) cooling the reaction product prepared in step a) to room temperature to remove the upper solidified paraffin wax;
c) concentrating by absorbing and removing water by supporting or contacting the superabsorbent polymer in the reaction product prepared in step b);
d) separating the superabsorbent polymer carrying or absorbing water from the reaction product; And
e) repeating steps c) and d) to obtain an aqueous dispersion of the modified fluorine compound containing a high concentration of PTFE, wherein the aqueous dispersion of the modified fluorine compound containing a high concentration of PTFE of 60 to 80% by weight is prepared. As a manufacturing method,
The superabsorbent polymer is a starch-based polymer in which starch is copolymerized with monomers of acrylonitrile, acrylic acid, acrylamide, or methacrylate, carboxymethylcellulose (CMC). A cellulose polymer copolymerized with the above monomers, or a polyvinyl alcohol-methacrylic acid block copolymer, a styrene-maleic anhydride copolymer, or a polyacrylamide series amide) or a synthetic resin polymer including polyoxyethylene.
The process according to claim 1, wherein the emulsion polymerization is carried out at 40 ° C to 85 ° C.
The method of claim 1, wherein the fluorine-based surfactant is ammonium perfluorocarboxylate, ammonium perfluorocaprylate, ammonium perfluorooctanoate and two kinds The method selected from the group consisting of the above mixtures thereof.
4. The method of claim 3 wherein the fluorine-based surfactant is ammonium perfluorocarboxylate.
The method of claim 1 wherein the water soluble initiator is ammonium persulfate or potassium persulfate.
The process of claim 1, wherein in step a) a mixture of potassium permangnate and oxalic acid, ammonium bisulfite, sodium metabisulfite and Wherein an initiator is selected from the group consisting of two or more mixtures thereof.
delete The method of claim 1 wherein the superabsorbent polymer is a poly (acrylate-acrylamide) crosslinked copolymer. The modified fluorine compound according to claim 1, wherein the modified fluorine compound is polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), or chlorotrifluoroethylene-ethylene copolymer (ECTFE).

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