Method of producing fluoropolymer powdered materials

FIELD: chemistry.

SUBSTANCE: invention relates to production of fluoropolymer powdered materials. A modified fluoropolymer powdered material is obtained. A suspension of solid fluoropolymer particles from a group comprising a fluoroethylenepropylene polymer and a polymer of perfluoroalkoxy compounds together with PTFE particles in an aqueous liquid carrier is obtained. The aqueous suspension is frozen. The frozen carrier is removed by sublimation at pressure below atmospheric pressure to obtain dry fluoropolymer particles, which are modified by presence of PTFE modifier in powder form.

EFFECT: method of obtaining fluoropolymer powdered materials is disclosed.

14 cl, 3 dwg, 1 ex

 

This invention relates to a process for the preparation of fluoropolymer powdered materials.

Fluorocarbon polymers are long-chain polymers, including, mainly, linear ethylene structural units, in which some or all hydrogen atoms replaced by fluorine. Examples of fluoropolymers include polytetrafluoroethylene polymer performativeness ether (PPPSA), polymer theretransparent (PVC), plastic perforamce connections (APF), polytrifluorochloroethylene and polivinilhlorid. They are the most chemically inert of the polymers and have unusual resistance to acids, bases and solvents. They have an unusually low frictional properties and have the ability to withstand extreme temperatures. Accordingly, the fluoropolymers are used in a variety of applications that require resistance to extreme external conditions. Current applications include the formation of pipes and gasket materials for chemical plants, semiconductor equipment, automotive parts and structural lining.

There are some applications that require powder form of the polymer. The fluoropolymer can be applied to the surface by electrostatic spraying powder. Applications which may include a coating on the home cookware for better non-stick properties and increased wear resistance and coating on automotive parts to increase the resistance to fracture under the influence environmental influences.

Currently typically use two methods to obtain a powder form of the polymer. Methods of spray drying include pumping water dispersion of fluoropolymer starting material in the spray system, usually located in the upper part of the drying chamber. The liquid is sprayed into the stream of heated gas to evaporate the water and obtain a dry powder. This method has some limitations. The need for pumping water dispersion in the spray system limits the use of this method materials amenable to pumping by the pump, and the agglomerates obtained by spray drying, are strongly related to each other and difficult to follow deagglomeration. In addition, you can process only materials that are not capable of forming fibers, because spraying can lead to the formation of the fluoropolymer fibers, resulting in an intractable, zafiropoulo material with which it is difficult to apply.

An alternative method involves the coagulation of particles in aqueous dispersion. Coagulation ease by applying a large shear forces, adding acids or the addition of gel-forming substances and subsequent processing of the organic liquid that is not miscible with water. Coagulated particles can be separated from the adjusted liquid by filtration and then dried, usually using tray dryer, belt dryer or flash dryer evaporation. Coagulated pellets are usually subjected to surface hardening for convenience in handling. However, the formation of agglomerates leads to the fact that the particle size becomes too large for use in traditional methods of applying the powder coating. Grinding, which is traditionally used to regulate the distribution of particle sizes, can lead to the formation of fibers from the particles and to obtain a tenacious material with which it is difficult to apply. Surface-hardened material also forms a solid agglomerate, which is difficult to follow deagglomeration.

In both these methods, it is difficult to introduce a significant amount of modifier to improve the barrier properties of the fluoropolymer.

Thus, the aim of the present invention is the provision of a method of obtaining modified fluoropolymer powder material with high barrier properties.

In accordance with this invention provide a method of obtaining modified fluoropolymer material in powder form, which includes stages: formation of a suspension of the solid fluoropolymer particles together with particles of polytetrafluoroethylene (PTFE) as a modifier in liquid water the nose is the body; freezing water suspension and subsequent sublimation of the frozen water suspension to obtain dry particles of fluoropolymer modified by the presence of a modifier of the PTFE in powder form.

The method according to the invention allows to add to the polymer more modifier compared to the possible number using conventional technologies.

Particle modifier effectively distributed between the particles of the fluoropolymer in the aqueous medium, thus giving increased barrier properties of the final powder material. Formed alloy PTFE/fluorocarbon polymer, which by its nature is more crystalline than the non-modified fluoropolymer. The subsequent grinding or irradiation dried by sublimation of the modified fluoropolymer material can also improve its suitability as a material for powder coating.

Preferably the fluoropolymer is a polymer performativeness ether (PPPSA). Preferably the particle size of the polymer is from 30 to 350 nm, preferably from 200 to 250 nm, for example approximately 230 nm. Preferably PTFE-modifier has a particle size of from 30 to 350 nm, preferably from 200 to 250 nm, and is present in a mixture of FMVE/PTFE in an amount up to 50 wt.%, preferably from 20 to 30 wt.%, for example, about 25% wt., in the ascete dry substance.

The method is especially suitable for processing of polymer performativeness ether (PPPSA), polymer theretransparent (FEP) and polymers of perforamce connections (PFA).

Preferably the particle size of the modified fluoropolymer powder material is quite small, allowing for the application of traditional methods of powder deposition. The resulting agglomerates (primary particle size of about 0.2 μm) can have an average diameter from 1 to 100 μm, more preferably from 20 to 30 μm,

Preferably, the suspension of the solid fluoropolymer particles in a liquid carrier freeze in freezer installed at temperatures below 0°C. More preferably, the suspension is frozen at a temperature of from -60°C to -20°C. Typically, the freezing perform within 6-24 hours.

Preferably before freezing the suspension of the solid fluoropolymer particles in a liquid medium, pour, scoop, or in any other way transferred to the pallet. Preferably the pallet containing a suspension of solid particles of fluoropolymer, then transferred into a freezer installation and freeze in the pan.

Preferably the aqueous medium is water, with surface-active substance or without it, with intermediate solvents (organic solvents used to promote dis is ergonovine/salvationarmy incremental resins) or without them. If you use an intermediate solvent, they must be present in sufficiently low concentrations, and their melting temperature should be high enough so that they do not slow freezing.

Preferably sublimation carried out using a pressure below atmospheric or vacuum. Using the low pressure causes the sublimation of the media from the frozen state directly to a gaseous state, bypassing the transition from solid to liquid and from liquid to gaseous. Preferably create a reduced pressure using a vacuum pump. Preferably the reduced pressure is from 1 kPa to 0.1 MPa (from 0.01 ATM to 0.99 ATM), more preferably from 4 kPa to 8.1 kPa (from 0.04 MPa to 0.08 MPa). Usually sublimation can be carried out within 12-48 hours

The method is preferably carried out at a temperature, which in practice is below the glass transition temperature of the fluoropolymer. The glass transition temperature of the polymer, Twithis the temperature at which it changes from a glassy form in kauchukopodobnoe form. The measured value of Twithdepends on the molecular weight of the polymer, its thermal history and shutter speed and the speed of heating and cooling. Typical values of glass transition temperature are: for PFMPE approximately 75°C, for the APF p is blithedale 75°C, for PVCs approximately -208°C for PVDF (polyvinylidene fluoride) is approximately -45°C.

To facilitate the process of sublimation and to avoid melting of the carrier liquid, regulate the temperature. Favorable coincidence is that this regulation also maintains a temperature below the values of Twithfor some of the listed substances. Thus, this method can be carried out at ambient temperature. Alternatively, this method can be carried out at a temperature which is above ambient temperature, to reduce the time required for the process.

Particles modified fluoropolymer can be processed after the implementation of sublimation or at any time during implementation of the method according to the present invention. Such processing may include crushing or irradiation of the fluoropolymer. Irradiation of polymer can usually be done after grinding, contributing to the regulation of the particle size. By crushing govern the distribution of the particles of the modified fluoropolymer in size, for example, reducing the average particle size to get a smaller powder. Typically, the grinding can be done the traditional way in a pin or a jet mill.

When the method further includes the irradiation of the particle m is definerowana fluoropolymer, usually irradiated powder or, alternatively, the suspension. By irradiation govern the characteristics of the melt of the modified fluoropolymer, such as lower melting point/glass transition and increase the melt flow index.

The method according to the present invention does not lead to strong agglomeration of the particles, but instead leads to the formation of fine powder which is suitable for use in extrusion, the conventional methods of powder deposition or re-dispersion in aqueous or organic media. Fragile powder can easily grind to change the size of the particles.

The method according to this invention can be performed at a temperature lower than the glass transition temperature of the fluoropolymer, in contrast to known methods, including spray drying and coagulation, which require temperatures much larger than 100°C. Application temperature environment can improve energy efficiency, although to increase the speed at which sublimation occurs, you can apply a temperature above ambient temperature but below the glass transition temperature. Temperature above the ambient temperature, can also be used to facilitate secondary drying to remove any traces of remaining fluid is th media.

The method according to this invention can be applied to obtain the modified fluoropolymer powder material, regardless, does the fluoropolymer or the tendency to form fibers. Capable of forming fibers, the polymer is a polymer that forms a fiber under the action of shear forces. Known methods, which include spray drying and coagulation, is subjected to solid particles of fluoropolymer influence of shear forces, which can lead to the formation of a tenacious material. The present invention does not include the application of shear forces at any stage and therefore suitable for application to capable of forming fibers of the fluoropolymer,

The method according to the invention can be applied for the preparation of modified fluoropolymer powder material of the curable pumping of the pump or of a non-pumping pump suspension of the solid fluoropolymer particles in a liquid carrier. Suspension may not be pumping the pump due to high viscosity or sensitivity to shear. This method does not include any stage at which it is necessary to pump pump suspension. Instead, the suspension can be poured or scooped into the tray for freezing and frozen solid block PE emeset in a vacuum chamber.

The invention may be put into practice in various ways, and in the example below describes some embodiments of the invention with reference to the accompanying drawings, where:

Figure 1 represents a curve of differential scanning calorimetry (DSC) for PFMPE;

Figure 2 is a DSC curve for PTFE and

Figure 3 is a DSC curve for PPPSA, modified PTFE, in accordance with this invention.

Example 1

Experiment with PTFE, used as a modifier for PFMPE

The aqueous dispersion of PTFE SFN-DN, stable 0,6% D6483 (100% polysiloxane) per dry PTFE was added to the dispersion of PFMPE 6202-1, receiving of the content of solids PTFE:FMVA 25:75. The dispersion was mixed with slow stirring. The mixture was frozen and sublimated. The obtained dry powder was applied using a spray gun for electrostatic spraying of powder on top of the primer Xylan 4018/G0916, in turn deposited on a sandblasted aluminum panel. The panel was treated at 150°C for 5 min and utverjdali at 400°C for 20 minutes, the Powder was melted with the formation of a solid film.

Figure 1-3 shows three sets of data obtained by DSC. Comparing the shift of the melting temperature at the transition from the pure polymer is (1 - PFMPE and 2 - PTFE) to the alloy (PTFE 25, 75 PPPSA) shows that the polymers form a true alloy and crystallize together. The heat of crystallization of PFMPE is 21 j/g, while for the alloy it is 30 j/g, which indicates that the degree of crystallinity increases by 30%. A similar phenomenon was discovered and heat of fusion (second melting curve).

Obtained in this method a mixture of PFMPE/PTFE has obvious advantages. Consideration of the heat of melting point according to DSC shows the increase of crystallinity of the polymer PFMPE. A polymer with a high degree of crystallinity has better barrier properties. In addition, the process of freeze-drying provides a homogeneous mixture of PTFE and PFMPE. Mixing at the nanoscale and freeze drying retains the polymer particles in the same state; macroaggregate polymers does not occur.

1. The method of obtaining modified fluoropolymer material in powder form selected from the group consisting of a polymer theretransparent (FEP) and polymers of perftorgeksilsilanami (APF), which includes the following stages: formation of a suspension of the solid fluoropolymer particles together with particles of polytetrafluoroethylene (PTFE) as a modifier in an aqueous liquid medium;
freezing water suspension and subsequent sublimation of the frosting is its aqueous suspension to obtain dry particles of fluoropolymer, modified by the presence of a modifier of the PTFE in powder form.

2. The method according to claim 1, characterized in that the fluoropolymer of perforamce connection (APF) is a polymer performativeness ether (PPPSA).

3. The method according to claim 1, characterized in that the particle size of the polymer is from 30 to 350 nm.

4. The method according to claim 1, characterized in that the particle size of the modifier PTFE is from 30 to 350 nm.

5. The method according to claim 1, characterized in that the PTFE is present in the mixture of PFMPE/ PTFE in an amount up to 50 wt.%, based on the weight of dry matter.

6. The method according to claim 1, characterized in that the sublimation is achieved through the pressure below atmospheric.

7. The method according to claim 6, wherein the reduced pressure is from 1 kPa to 0.1 MPa (from 0.01 to 0.99 ATM).

8. The method according to claim 1, characterized in that the sublimation is carried out at a temperature below the glass transition temperature of the fluoropolymer.

9. The method according to claim 8, characterized in that the sublimation is carried out at ambient temperature.

10. The method according to claim 8, characterized in that the sublimation is carried out at a temperature in the range from ambient temperature to the glass transition temperature of the fluoropolymer.

11. The method according to claim 1, characterized in that a suspension of solid particles in aqueous media is frozen at a temperature of from -60°C. to -20°C.

12. The method according to claim 1, characterized in that when spengiu solid particles in aqueous media freeze in the trays.

13. The method according to claim 1, characterized in that it comprises the additional step of grinding and/or radiation particles modified fluoropolymer.

14. The method according to any of the preceding claims 1 to 13, characterized in that the polymer capable of forming fibers and/or not amenable to pumping by the pump.



 

Same patents:

FIELD: food industry.

SUBSTANCE: one first performs the sections preliminary vacuum treatment using an ejector vacuum pump till residual pressure is equal to 610 Pa, then one cools the external surface of the profile drum acting as the desublimator with electric current supplied onto the groups of thermoelectric modules placed on the internal surface of the profile drum which creates the required temperature gradient for vapours movement to the desublimator surface; then one supplies heat energy to the product using heaters, as a result moisture evaporation takes place at a residual pressure lower than 610 Pa; part of the moisture evaporated from the product is removed from the chamber via the ejector vacuum pump, the other part is adsorbed by the desublimator surface represented by a nanomaterial layer; release of evaporated moisture molecules takes place after the desublimator turning due to the thermoelectric modules connection polarity changing. In the vacuum-and-sublimation drier using nanomaterials and thermoelectric modules, including a drying chamber consisting of sections equipped with a nipple with a locking valve installed with the possibility to connect to a vacuum pump, the vacuum pump, the desublimator placed between the sections and a heater. The drying chamber is made of two sealed sections connected to the vacuum pump and separated with a plate wherein a profile drum representing the desublimator is horizontally installed so that to enable rotation; a nanomaterial layer is applied onto the drum external surface while independent groups of thermoelectric modules are installed on the internal surface.

EFFECT: evaporated moisture vapours capture effectiveness is enhanced; desublimation surface regeneration is ensured during the drier operation in a continuous mode; workload onto the vacuum pump is reduced due to depressurisation in the vacuum-and-sublimation chamber.

2 cl, 1 dwg

FIELD: chemistry.

SUBSTANCE: method for freeze drying an erythrocyte diagnosticum involves deep freezing the preparation, putting into a freeze drying chamber and further sublimation thereof in vacuum conditions with subsequent formation of a lyophilisate. At the preparatory step after deposition by centrifuging, separations of the supernatant fluid of erythrocytes are diluted in ratio of 1:9 by a drying medium consisting of a solution of 15 wt % rheopolyglucin and 7.5 wt % saccharose in distilled water, and shelf temperature and pressure in the sublimation chamber is not changed for the first 8 hours and maintained at -15°C and 30 Pa, respectively, and then for the next 14 hours, gradually varied at a rate of (2.6±0.4)°C/h and (2±0.1) Pa/h to 22°C and 3 Pa, respectively, and said parameters are maintained for at least 3 hours.

EFFECT: owing to the disclosed method of drying labile erythrocyte diagnosticums in maximally gentle conditions, activity thereof virtually does not change after prolonged storage and rehydration.

1 tbl, 2 dwg

FIELD: chemistry.

SUBSTANCE: method of obtaining a lyophilisate of a pharmaceutical preparation involves immersing a cellular carrier into the solution of the pharmaceutical preparation to form films of the solution in cells of the carrier, putting the carrier into a freezing zone and then into a heating zone where the solution is dried, with subsequent removal of the lyophilisate of the pharmaceutical preparation, wherein moisture content is controlled in each cell in the heating zone by positioning a fibre-optic sample of a transmission-type spectrophotometer operating in the near-infrared range or which detects Raman shift.

EFFECT: simple process of production, high output of the end product, enabling automation of the process, low cost of the product, enabling inspection of moisture of the end product, high quality of the end product.

8 cl

FIELD: food industry.

SUBSTANCE: cryogenic vacuum-and sublimation installation with complex usage of inert gas includes a device for preliminary freezing of the product, a vacuum-and sublimation drier with a sealed drying chamber wherein a perforated drum and a heating element are positioned; the element is designed in the form of a coil installed in the bottom zone of the drum, its cross-section having the form of a segment; the heating element is the cooling agent cooler and is designed with the spacing between the tubes amounting to no more than 15 mm; the element inlet nipple is connected to the pump line of the desublimator cooling machine while the outlet nipple is connected to the low-pressure line of the cooling agent feed into the cooling machine; the drier chamber is connected to the vacuum-pumping system via the desublimator; the novelty is in the following: the device for preliminary freezing of the product is represented by a tunnel-type cryogenic fast-freezing aggregate (its frozen product feeding conveyor connected to the vacuum-and-sublimation drier doser, the drier heating element made of a material with high heat-conduction coefficient or a semi-permeable material) while the desublimator cooling machine is represented by a gas liquefaction machine working according to the Stirling reverse cycle principle; the machine nipple for feeding liquefied gas is connected to the desublimator represented by a nitrogen trap and to the fast-freezing aggregate nozzles; the nitrogen trap is installed between the vacuum-and- sublimation drier chamber and the vacuum pump; the exhaust gas outlet nipple of the cryogenic fast-freezing aggregate and the outlet nipple of the vacuum pump are connected to the inlet nipple of a membrane apparatus while its outlet nipple for inert gas cleared of impurities is connected to the automatic packaging device.

EFFECT: product fast freezing with cells preservation taking place within the whole bulk, enhancement of the sublimation process intensity due to ensuring highly efficient combined energy input to the product by varied methods.

2 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: suspension of solid particles of a fluorine-containing polymer in a liquid carrier, preferably water, is frozen and the frozen carrier is then removed via sublimation at subatmospheric pressure to obtain dry powder of fluorine-containing polymer particles.

EFFECT: method enables to obtain powdered materials from a liquid suspension of solid particles of a fluorine-containing polymer which, at normal conditions, cannot be pumped by a pump due to fibrillation capacity.

13 cl

FIELD: medicine.

SUBSTANCE: glass reservoirs with flat bottom, containing biopreparations, are placed into tray with low-temperature medium. Low-temperature layer in tray is, as minimum, twice as thick as layer of frozen biopreparation in reservoir. As medium water solution of calcium chloride is used. Freezing and further sublimation drying are carried out.

EFFECT: reduction of time for process carrying out and obtaining product with developed capillary-porous structure.

2 tbl, 4 ex, 1 dwg

FIELD: food industry.

SUBSTANCE: installation contains a cryogenic freezing chamber, a separation chamber containing a device for cleaning fruits of crystalline hydrates and a device for cleaning inert gas of crystalline hydrates, a drying chamber with an US radiation source and an inert gas inlet, a gas chilling machine with a vertical tube. The cryogenic freezing chamber, the separation chamber and the drying chamber are tightly connected and included into one main with the compressor.

EFFECT: invention enables production of a high quality product.

1 dwg, 1 tbl

FIELD: medicine.

SUBSTANCE: method for preparing a frozen-dried material involves the use of a container enclosed by a capsule, has a permeable area, and contains a dispersed material in a carrier fluid, and said capsule having the permeable area is permeated with a penetrator to form a channel through the capsule to connect an internal part and an external part of the container when the penetrator has passed through the permeable area, evaporation of the carrier fluid from the container through said channel and removal of the penetrator from the permeable area. The penetrator contains an integrally tapered element with a hole adjacent to its top, an open base or a hole adjacent to its base, and with a channel passing through the penetrator, connecting these two holes so that the top of the penetrator can pass through the permeable area, and the carrier fluid vapour can be supplied into the top, pass through the hollow internal part of the taper and escape. Said method is implemented inside a sterile cover which temperature can be changed between ambient temperature and temperature whereat the carrier fluid freezes, and which atmospheric pressure can be changed between environment pressure and lowered atmospheric pressure.

EFFECT: simplification of the method.

21 cl, 27 dwg

FIELD: heating.

SUBSTANCE: during vacuum-sublimation drying process the product is pre-frozen in trays with transverse partitions for increasing the heat exchange surface, at double bottoms of which made from material with high heat conductivity coefficient there installed are thermoelectric modules the operating principle of which is based on Peltier effect. Trays in lower part have finning serving for desublimation of steam of below located cascade. Heat generated with hot ends of thermoelectric modules is used for supply of energy to the product. Drying chamber (sublimator) has cylindrical shape with the flap cover made in the form of semi-cylinder with inspection hole. Along the perimeter of inner surface of sublimator there installed is desublimator for additional condensation (desublimation) of steam.

EFFECT: reduction of specific energy consumption, improvement of product quality, simplifying the drier design, multi-cascade location of trays on the support allows increasing the volume of loaded product.

4 dwg

FIELD: heating systems.

SUBSTANCE: device meant for low-temperature vacuum material dehydration and drying includes vacuum process chamber in which there are process heat exchangers-evaporators with tubular channels for heat carrier, vacuum pumping assembly, assembly of charging original material to vacuum process chamber, assembly of discharging dehydrated end product, condensate collection and drain assembly, heat carrier supply assembly and heat pump. At that, vacuum process chamber is made in the form of individual units of pre-heating, pre-dehydration and final drying, cavities of each of which are connected to vacuum pumping assembly; at that, unit of final drying is made in the form of a tube with screw mechanism located in it and made in the form of blades which are fixed on the shaft and have pitch changing throughout the shaft; at that, one end of tube is connected to unit of pre-dehydration, and the other end - to finished product capacity; at that, blades from the side of finished product capacity are needle-shaped; shaft cavity is connected to heat carrier supply system; evaporation circuit of heat pump is connected to condensate collection assembly, and condenser circuit of heat pump is connected to final drying unit.

EFFECT: improving dehydration and drying efficiency of original materials, reducing energy consumption.

2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing fine polytetrafluoroethylene powder, as well as fine powder obtained using said method. The method of producing fine polytetrafluoroethylene powder involves emulsion polymerisation of tetrafluoroethylene in the presence of an aqueous medium, a fluorinated surfactant and a radical polymerisation initiator to obtain an aqueous emulsion of polytetrafluoroethylene and coagulation thereof in the presence of at least one apparent density-reducing compound selected from a group consisting of ammonia, an ammonium salt and urea, in amount ranging from 0.4 to 10 pts.wt per 100 pts.wt polytetrafluoroethylene. The fine polytetrafluoroethylene powder obtained using said method has standard specific mass from 2.140 to 2.180 and paste extrusion pressure from 10 to 25 MPa.

EFFECT: method of obtaining fine polytetrafluoroethylene powder which is capable of paste extrusion at low pressure using a simple method.

10 cl, 1 tbl, 10 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a novel aqueous polytetrafluoroethylene emulsion obtained using a special fluorinated emulsifying agent, and to fine polytetrafluoroethylene powder and porous material produced from said powder. Described is a porous material produced from polytetrafluoroethylene via extrusion of a paste of fine polytetrafluoroethylene powder which is obtained through coagulation of aqueous polytetrafluoroethylene emulsion obtained during emulsion polymeristion of tetrafluoroethylene in an aqueous medium using a fluorinated emulsifying agent of formula (I): CF3CF2OCF2CF2OCF2COOA, in which A is an alkali metal atom or an NH4 group taken in amount of 1500-20000 parts per million relative the final output of polytetrafluoroethylene, followed by stretching.

EFFECT: obtaining porous material with excellent various characteristics, made from polytetrafluoroethylene, having excellent processability during extrusion of the paste.

5 cl, 3 ex, 1 tbl, 1 dwg

FIELD: chemistry.

SUBSTANCE: method is realised through granulation by stirring in water in the presence of a liquid organic solvent which is partially soluble in water. A polytetrafluoroethylene emulsion is added, as well as a coagulant for coagulation of the polytetrafluoroethylene emulsion in form of a surface layer of polytetrafluoroethylene granules containing filler.

EFFECT: obtaining granules with high looseness with low separation of filler, which prevents release of the polytetrafluoroethylene emulsion into liquid wastes.

12 cl, 1 tbl, 5 ex

FIELD: chemistry.

SUBSTANCE: invention relates to processes of separating polydisperse systems through vibroacoustic effect. The method of separating polydisperse solution of distillery stillage involves coagulation of colloidal and dissolved substances of a dispersed phase and subsequent separation of the solid fraction of the formed product from the solution with separation of the liquid fraction of the dispersed medium. The dispersed phase is coagulated in two steps by applying energy of acoustic vibrations on the solution in at least two spectra in the 1-18 kHz range, providing weakening of surface tension of colloidal and dissolved substances, and in the 80-400 Hz range, increasing their amplitude of vibration. Before coagulation of the dispersed phase from the solution through evacuation, volatile aromatic substances are separated in form of a condensate, and before the second step for applying energy of acoustic vibrations the solution is dehydrated by 20-50% in vacuum drying conditions with extraction of the water condensate.

EFFECT: invention provides environmentally safe non-waste technology of processing distillery stillage and widens the range of processed products.

FIELD: chemistry.

SUBSTANCE: described is a fluoropolymer latex which contains a fluoropolymer and fluorine-containing emulsifier of formula (1): F(CF2)4OCF2CF2OCF2COOA, where A is a hydrogen atom, alkali metal or NH4. A method is also described for producing such latex, and a fluoropolymer, which is obtained by coagulating fluoropolymer latex. The fluoropolymer latex can be used as an agent for coating different materials, such as metallic substrates, inorganic oxide substrates, polymer substrates, synthetic fibre, glass fibre, carbon fibre or natural fibre.

EFFECT: fluoropolymer is useful as material with excellent heat resistance, oil resistance, chemical resistance, weather resistance, non-stickiness, anti-overgrowth properties, water-repellent properties, oil-repellent properties, solvent-repellent properties.

7 cl, 2 tbl, 14 ex

FIELD: chemistry.

SUBSTANCE: scope of invention covers stabilized water dispersions of curing agent suitable for coating preparation. Dispersion dispersed in water contains the following components: A1) at least one organic polyisocyanate with isocyanate groups connected in aliphatic, cycloaliphatic, araliphatic and/or aromatic manner, A2) ionic or potentially ionic and/or non-ionic substance, A3) blocking agent, B) stabilizer containing a) at least one amine with structural element of common formula (I) without any hydrazide group, b) substance with formula (IV) .

EFFECT: resistance to thermal yellowing increases.

6 cl, 5 tbl, 11 ex

FIELD: polymer production.

SUBSTANCE: invention relates to production of polymeric binders for toner and can be used for copying appliances and printers. Process comprises separate preparation via emulsion polymerization of (i) low-molecule weight copolymer of styrene (α-methylstyrene), 2-ethylhexyl acrylate (or butyl acrylate) and methacrylic acid at monomer weight ratio (88-91.5):(8-11):(0.5-1.0) with intrinsic viscosity in toluene 0.08-1.2 dL/g and (ii) high-molecule weight copolymer of styrene (α-methylstyrene) and 2-ethylhexyl acrylate (or butyl acrylate) at monomer weight ratio (88-92):(8-12) with intrinsic viscosity in toluene 1.0-1.28 dL/g. In both cases, polymerization is carried out at 60-70% to monomer conversion close to 100%. Resulting latexes of low- and high-molecule weight copolymers are supplemented by stopper and antioxidant and then mixed with each other at "dry" weight ratio between 70:30 and 75:25 and coagulated intrinsic viscosity in toluene 1.0-1.28 dL/g. with electrolyte solutions to form polymer characterized by intrinsic viscosity in toluene 0.4-0.45 dL/g and polydispersity Mw/Mn, which ensures bimodal molecular weight distribution of copolymer. The latter has melting (spreading) point 125-137°C and softening temperature 70-75°C.

EFFECT: improved quality of electrographic printing.

2 cl, 1 tbl, 4 ex

FIELD: polymers, chemical technology.

SUBSTANCE: invention relates to the continuous method for preparing polytetrafluoroethylene (PTFE) or modified PTFE finely divided powders. The continuous method for preparing PTFE or modified PTFE finely divided powders involves the following steps: (a1) dilution of PTFE-latex of modified PTFE-latex prepared in polymerization in the dispersion-emulsion to the concentration from 5 to 25 wt.-% of PTFE or modified PTFE with possible filtration of the prepared diluted latex; (b1) molding latex with inert gas to the relative pressure with respect to atmosphere pressure in the range 3-40 kg/cm2 (0.3-4 MPa); (c1) addition of acid electrolyte solution to latex in the line-flow mixer at pH value 1-4; (d1) feeding the latex flow from the mixer through capillary tube under condition of turbulent current with the Reynolds number above 3000; (e1) gel prepared at step (d1) is coagulated onto granules at mechanical stirring with the specific power 1.5-10 kWt/m3 and stirring is maintained up to flotation of finely divided powder; (f1) below water is separated from the finely divided powder. PTFE of modified PTFE finely divided powders that can't be processed by thermal method prepared by abovementioned method show the following indices: apparent density is ≥ 470 g/l; average diameter of particles (D50) is above 200 mcm; distribution of particles by diameter determined as ratio between particles mass with diameter from 0.7 to 1.3 times with respect to average particles diameter and the total particles mass above 50%. Invention provides preparing powders without using the complex and expensive equipment, and powders possess the improved fluidity and show the apparent density and narrow distribution of particles by the diameter index.

EFFECT: improved preparing method.

9 cl, 1 tbl, 1 dwg, 6 ex

The invention relates to powder rubbers containing other components to obtain vulcanizate rubber compound and method of production thereof

The invention relates to the production of emulsion rubbers in powdered form and can be used in the synthetic rubber industry

FIELD: process engineering.

SUBSTANCE: method of making immediately PET granules with degree of polymerisation varying from 132 to 165 whereat melt after cutting in hot state is subjected to preliminary drying and drying/degassing. Cutting in hot state is performed at water temperature of 70-95°C and water-to-granule ratio making 8:1 to 12:1. Note here that fluid is completely retained unless entering pre-drier while circulation water in the latter is separated for faster than 10 s. Besides, this invention relates to PET pellets thus produced with degree of polycondensation not more than 2% lower than that polycondensation of heavy melt. Melt feature degree of polymerisation varying from 132 to 165. Degree of crystallisation of PET pellets makes smaller than 38% (method of density measurement). Besides, invention covers the device for making above described pellets.

EFFECT: ruled out decrease in degree of polycondensation.

19 cl, 2 dwg, 3 ex

Up!