Device for producing a shear thickening fluid based on a dispersed phase and a method for producing a shear thickening fluid based on a dispersed phase associated thereto

Abstract

A device and method for producing a shear thickening liquid based on a dispersed phase, the device comprising a closable tank (11) having a bottom (13) for receiving a liquid matrix and mixing means 2 placed in the tank (11) for mixing the liquid, means (17) for supplying protective gas atmosphere to the matrix to supersaturate the matrix with the protective gas, means (3) for feeding protective gas to the tank, connected to the tank (11), means (5) for removing protective gas from the tank, connected to the tank (11), means (12) for providing mixing temperature, means (5) for feeding expanded solid phase, connected to the tank (11), means (1) for expanding solid phase during the feeding thereof.

Description

[0001] Device for producing a shear thickening fluid based on a dispersed phase and a method for producing a shear thickening fluid based on a dispersed phase associated thereto

[0002] DESCRIPTION BACKGROUND OF THE INVENTION

[0003] The invention relates to a device and method for producing shear thickening fluids (STF), i.e. non-Newtonian fluids. The invention is applicable to the production of liquids based on a dispersed phase, e.g. silica.

[0004] Shear thickening fluids (STF), obtained from a solid phase, i.e. silica and an organic matrix, are characterized by a non-linear increase in viscosity as a function of shear rate. The shear thickening effect is that as the mixing speed of the STF increases, the viscosity increases exponentially. Unfortunately, this effect translates into an increase in torque and current drawn by the mixing system drive system. The shear thickening phenomenon complicates the process of scaling up the production of shear thickening fluids. In addition, the phenomenon of shear thickening contributes to reduced service life of drive systems.

[0005] PRIOR ART

[0006] Methods of producing shear thickening fluids have been disclosed in the non-patent literature. Most of the solutions are based on the method of direct introduction of the solid phase into the liquid polymer matrix [Haiqing Liu, Kunkun Fu, Xiaoyu Cui, Huixin Zhu, Bin Yang, Shear Thickening Fluid and Its Application in Impact Protection: A Review; Polymers 2023, 15(10), 2238].

[0007] The most commonly used solid phase is various types of ceramic powders, e.g. irregular or spherical silica of various particle sizes, halloysite, kaolin, calcium carbonate and others [Chadwick M.D., Goodwin J.W., Vincent B., Lawson E.J., Mills P.D.A., Rheological behaviour of titanium dioxide (uncoated anatase) in ethylene glycol. Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 2002, 196, 235 - 245].

[0008] The polymer matrix may have chains of various lengths, e.g. polyethylene glycol) with an average molecular weight of 200-400 g / mol, polypropylene glycol) with an average molecular weight of 400-4000 g / mol. As the average molecular weight of the matrix increases, its viscosity increases.

[0009] At the beginning of the STF manufacturing process, no shear thickening effect is observed. Only in later stages, when the solid phase content increases, the unfavourable shear thickening effect occurs. This effect means that the viscosity of the mixture can increase exponentially even with a small increase in the agirator speed or a moderate addition of solid phase. Then the agitator rotation speed is reduced and the process is continued, which significantly extends the STF production process.

[0010] In order to reduce the effect of shear thickening, a diluent (ethanol, ethyl acetate, tetrahydrofuran, etc.) is added to reduce the viscosity of the mixture. After introducing the intended amount of ceramic powder, the diluent is removed [Neelanchali Asija, Hemant Chouhan, Shishay Amare Gebremeskel, Naresh Bhatnagar, Impact Response of Shear Thickening Fluid (STF) Treated High Strength Polymer Composites - Effect of STF Intercalation Method, Procedia Engineering 2017, 173, 655]. The process of removing the diluent requires appropriate equipment in the form of an evaporation system that operates at elevated temperature and reduced pressure. The process itself is difficult to implement due to high viscosity and foam formation during distillation. Additionally, the solvent vapours are flammable, which poses a risk of explosion.

[0011] Another, simpler, method known from the prior art to limit the shear thickening effect is to heat the STF to a temperature of 60-150°C and maintain this temperature during the period of addition of the solid phase. The relationship between decreasing viscosity of STF and increasing temperature is characteristic of all STFs.Therefore, the optimal solution seems to be to carry out the process at the highest possible temperature in order to avoid the thickening effect. This also results in faster production times.

[0012] However, during the tests it was observed that at temperatures of 90-150°C an unfavourable and irreversible phenomenon of degradation of the polymer matrix occurs. The rule is that the longer the manufacturing process is carried out and the higher the process temperature, the more of the matrix is decomposed. The matrix degrades in such a way that short chains are formed from long polymer chains. The degraded matrix then evaporates from the agitator as a low-molecular-weight product, disturbing the composition of the recipe (we do not know exactly how much of the matrix is decomposed and evaporated).

[0013] Additionally, the degradation process occurs throughout the entire volume of the matrix in such a way that long polymer chains are cut uncontrollably into smaller ones. So, for example, in the case of a polypropylene glycol) matrix with an average molecular weight of 4000 g / mol, as a result of degradation we get a mixture with a wide molecular weight distribution with the disappearance of chains with a molecular weight of 4000 g / mol. The difficult-to-control change of matrix properties during the process prevents the use of elevated temperature as a factor limiting the shear thickening effect.

[0014] A method for producing highly concentrated STFs with deliberate, controlled degradation of the lowconcentrated STF matrix is also known. The essence of the process is that previously produced STF with low solid phase content, easy to prepare, is kept at an elevated temperature with simultaneous access to air. Due to the gradual degradation of the matrix, the concentration of the solid phase increases to the volatile low-molecular fractions that evaporate [Materials 2022, 15(17), 5818; https: / / doi.org / 10.3390 / ma15175818]. Unfortunately, it was unexpectedly observed that three months after production, STF samples obtained by the gradual degradation method lose their properties. A decrease in the maximum viscosity value observed during the dilatation jump and a shift of the jump towards lower shear rate values were observed.

[0015] A system for producing shear thickening liquids, which comprises a reciprocating chamber, is also known from Polish patent application P.445847. However, these types of systems are suitable for producing small volumes of shear thickening fluids where the mixing tip's striking surface area is small enough that it can rotate at 300-3000 rpm without damaging the tip or overloading the motor. The problem with this type of design is the raising and lowering of the mixing chamber, because in the case of designs capable of producing several hundred to several thousand litres or more, the reciprocating motion will consume much more energy than the system will be able to save by using a tip with a small rake surface. Moreover, the chamber known from the application has an open structure for the purpose of filling bulk substances. This design, combined with the very fast rotation of the mixing tip, the movement of the tank and the high temperature, guarantees a turbulent air flow above the liquid surface, which causes constant exposure to atmospheric oxygen, which at this temperature can decompose the continuous phase of the produced fluid, causing a loss of control over the process product. PROBLEMS TO BE SOLVED

[0016] All known methods and devices for producing silica-based STF are mainly laboratory-scale production devices. The volume of liquid produced at one time does not exceed 250 mL. However, known methods and devices for larger-scale production are energy inefficient and do not ensure a controlled production process.

[0017] The object of the invention is therefore to provide a device and a method for producing STF liquids that do not have the above-mentioned disadvantages shown in the description of the prior art, in particular to provide a device that would enable the production of STF liquids on an industrial scale and in an efficient and controllable manner.

[0018] SUMMARY OF THE INVENTIONThe invention consists in that a device for producing a shear thickening liquid based on a dispersed phase comprises:

[0019] - a closed tank containing a bottom for receiving a liquid matrix and

[0020] - mixing means disposed in the tank for mixing the liquid,

[0021] - means for supplying protective gas atmosphere to the matrix to supersaturate the matrix with the protective gas,

[0022] - means for feeding protective gas to the tank, connected to the tank,

[0023] - means for removing protective gas from the tank, connected to the tank,

[0024] - means for ensuring mixing temperature,

[0025] - means for feeding the expanded solid phase, connected to the tank,

[0026] - means for expanding the solid phase during the feeding thereof.

[0027] Preferably, the mixing means is a mechanical agitator;

[0028] Preferably, the mixing means are two mechanical agitators connected to separate drive systems;

[0029] Preferably, at least one agitator is a horseshoe agitator.

[0030] Preferably, the means for feeding the expanded solid phase comprise a pipe conduit comprising a first section, the main axis of which is perpendicular to the bottom, and a second section, the main axis of which forms an angle a in the range of 90° to 180° with the main axis of the first section.

[0031] Thanks to the appropriate selection of parameters of the means for feeding the expanded solid phase, it is possible to control the degree of solid phase dosing, which makes it possible to obtain the optimum rate of solid phase penetration into the rotating matrix, and then into the matrix and solid phase mixture, thus minimizing the effect of a sudden increase in viscosity resulting in: damage to the engine; plastic deformation of the mixing tip; sudden uncontrolled increase in temperature, which may cause degradation of the continuous phase (polymer matrix) and disruption of the assumed ratio of components in the mixture, and consequently the functional properties of the manufactured product; inappropriate dosing may also cause the formation of a solid phase layer on the surface of the continuous phase mirror, which will not take part in the homogenization (conditioning) process, will separate new portions of the solid phase from the conditioned mixture, thus preventing the scaling up of production on an industrial scale.

[0032] Preferably, the means for supplying protective gas atmosphere into the matrix to supersaturate the matrix with the protective gas are bubbler nozzles.

[0033] By feeding the protective gas during production of a shear thickening liquid, an oxygen-free liquid is obtained on an ongoing basis, which prevents the polymer matrix, which constitutes the continuous phase of the product, from degrading during the manufacturing process.

[0034] Preferably, the feeding of the matrix during the matrix feeding period is performed while simultaneously mixing the matrix.

[0035] By forcing an appropriate circulation of the protective gas in the tank space, the impact of this circulation on the remaining key stages of the shear thickening fluid production process is minimized.

[0036] Thanks to the appropriately selected flow of the protective gas through the tank, a sufficient degree of oxygen removal from the matrix, and then from the mixture, is ensured, while minimizing the impact of the protective gas movement on the efficiency of solid phase feeding.

[0037] Preferably, the protective gas is selected from argon, nitrogen or carbon dioxide, or any mixture thereof. Preferably, the number of bubbler nozzles may be preferably from 1 to 3 pieces per 9.5 cm of the bottom diameter, preferably on average 1 piece per 3.3 cm of the bottom diameter.By using the bubbler technique to supersaturate the matrix, an effective method of removing oxygen from the matrix is achieved.

[0038] Preferably, the bubbler nozzle may preferably have a diameter in the range of 4 mm to 20 mm.

[0039] Preferably, the means for providing mixing temperature comprises heating means.

[0040] Preferably, the means for providing mixing temperature comprises cooling means.

[0041] Preferably, the means for expanding solid phase during the feeding thereof is a mechanical vibrator.

[0042] By feeding the solid phase in an expanded form, a more uniform supply of the solid phase to the entire volume of the previously added matrix is achieved. In particular, the entire mirror surface of the matrix is used for the penetration of the solid phase into the matrix. As a consequence, the time required for effective homogenization of the suspension is minimized, thus enabling scale-up of production to an industrial scale. Preferably, the mechanical vibrator is mounted on the pipeline for feeding the expanded solid phase.

[0043] Preferably, the pipeline for feeding the expanded solid phase preferably has a diameter in the range of 1 .5 to 5 times the diameter of the pipeline for feeding the protective gas.

[0044] Preferably, the ratio of the diameter of the pipeline to the diameter of the bottom is 1 :6.

[0045] According to another embodiment, the subject of the invention is that a method of producing a shear thickening liquid based on a dispersed phase is carried out with the device according to the invention, comprising the steps of: activating mixing means, simultaneously feeding a matrix through matrix feeding means and supplying a protective gas atmosphere through bubbler nozzles, for a period of supersaturation of the matrix with the protective gas, to supersaturate the matrix with the protective gas, closing the bubbler nozzles and feeding the protective gas atmosphere through protective gas feeding means, activating expanding means and means for providing mixing temperature and simultaneously: reheating the matrix, feeding a solid phase through solid phase feeding means for a period of dosing the solid phase to dose the expanded dispersed phase, while simultaneously heating the mixture, and after the solid phase dosing period, deactivating the mechanical vibrator, mixing the mixture for a period of conditioning to condition it at an appropriate temperature, deactivating the agitator, pouring off the resulting liquid.

[0046] Thanks to the device and the associated method according to the invention, it is possible to obtain STF volumes on an industrial scale, of the order of at least 10 litres, with the possibility of obtaining up to 6,000 litres of liquid at a time at a reasonable energy expenditure.

[0047] BRIEF DESCRIPTION OF FIGURES

[0048] The device and the associated method for producing STF liquids according to the invention are described in detail in embodiments with reference to the attached Figures, in which:

[0049] Fig. 1 shows a flow diagram of a method that can be implemented in the device according to the invention;

[0050] Fig. 2 shows a side general view of the device for producing STF according to one embodiment of the invention;

[0051] Fig. 3 shows a longitudinal section of the device for producing STF according to one embodiment of the invention;

[0052] Fig. 4 shows a cross-section under the flange above the liquid surface of the STF production device according to one embodiment of the invention;

[0053] Fig. 5 shows a perspective cross-sectional view of the STF production device according to one embodiment of the invention;Fig. 6 shows another longitudinal section of the STF production device according to one embodiment of the invention;

[0054] Fig. 7 shows a bottom perspective view of the STF production device according to one embodiment of the invention;

[0055] Fig. 8 shows a bottom perspective view of the cover of the STF production device according to one embodiment of the invention;

[0056] Fig. 9 shows a general view of the cover of the STF production device according to one embodiment of the invention, comprising a double agitator;

[0057] The following understanding of terms should be adopted in this description:

[0058] 'STF / shear thickening fluid' - a fluid whose viscosity increases non-linearly with increasing shear rate, usually obtained by homogenization of a selected solid phase and a suitable organic matrix;

[0059] 'matrix' - dispersing medium in which the solid phase particles are suspended;

[0060] 'protective gas' - an inert gas / mixture of inert gases that does not react with the matrix;

[0061] 'solid phase' - dispersed medium that is suspended in the matrix, otherwise the STF component in the form of solid particles dispersed in the STF matrix;

[0062] 'additives' - a dispersed or dispersing medium that significantly changes the functional properties of the STF fluid, in particular these are optional STF components that change the properties of STF, including those influencing STF stability, STF density, STF viscosity jump, behaviour in different temperature ranges and others;

[0063] The device for producing a shear thickening liquid based on a dispersed phase, for example silica, according to the invention, comprises:

[0064] - a tank 11 and

[0065] - means 2 for mixing, disposed in the tank 11

[0066] - means 17 for supplying protective gas atmosphere to the matrix to supersaturate the matrix with the protective gas

[0067] - means 3 for feeding protective gas to the tank, connected to the tank 11

[0068] - means 5 for removing protective gas from the tank, connected to the tank 11

[0069] - means 12 for providing mixing temperature, i.e. heating / cooling means 12 for heating / cooling the contents of the tank 11

[0070] - means 5 for feeding expanded solid phase, connected to the tank 11

[0071] - means 1 for expanding solid phase during the feeding thereof, associated with means 5 for feeding the expanded solid phase.

[0072] Fig. 2 shows one possible embodiment of the device 100 according to the invention. The device 100 according to the invention comprises a tank 11 , substantially in the form of a hollow cylinder, closed at the bottom by a bottom 13. The tank has the function of storing, first, the matrix itself, then a mixture of the matrix and the fed solid phase (and / or additives), and finally a mixture of both components for conditioning purposes. The tank is made of a material that conducts heat and does not react chemically with the produced mixture. For example, it can be 304 or 316 stainless steel, and preferably duplex. In a preferred embodiment, the tank may be enameled. Appropriate selection of the material of the tank 11 also reduces the risk of abrasion of the walls of the tank 11 during the operation of the agitator 2, preventing contamination of the produced mixture. The thickness of the walls of the tank 11 is selected so that the tank 11 , depending on its volume, is sufficientlyrigid and resistant to deformation. The volume of the tank 11 of the device according to the invention may be from 100 mL to 6000 L, preferably from 1000 mL to 6000 L, even more preferably from 10 L to 6000 L.

[0073] In the embodiment shown in Fig. 2, the device 100 is composed of a tank 11 and a cover 7. As a rule, the gases used in the method according to the invention, which form the protective atmosphere, have a density greater than or comparable to air, so the cover 7 does not fulfil in this context the key role of isolating the interior of the tank 11 from the external environment. On the other hand, the closure of tank 11 is necessary due to the degradation processes of the tank contents as a result of the action of visible light. In addition, however, during the process in the device 100 there are forced convective movements which could cause solid phase to escape from the device, and therefore it is ultimately desirable to close the container.

[0074] The tank 11 is preferably covered by a removable cover 7, but other tank designs are possible which allow it to be closed while still allowing cleaning and maintenance. According to the discussed embodiment, the tank 11 may preferably have in its upper part a collar 10 intended for releasably attaching to the collar 9 of the cover 7. A seal (not shown) is preferably provided between the flange 10 of the tank 11 and the flange 9 of the cover 7. Preferably, the seal may be located in a suitable recess provided in the flange of the tank or the flange of the cover. For example, the seal may take the form of a gasket made of rubber, natural rubber or silicone. Depending on the solid phase expanding system, the seal may additionally function as a vibration dampening element from the solid phase expanding system. In other words, impact operation of the entire device 100 becomes possible. The flange 10 of the tank 11 and the flange of the cover 7 can be connected by connecting means 8 in the form of screw connections 8. In the bottom 13 there is a drainage opening passing into the drainage pipeline 14, in particular a drain stub-pipe 14. A suitable shut-off valve is provided in the discharge pipeline 14 (not shown). Preferably this may be a ball valve. The ball valve is opened after the STF conditioning phase is completed.

[0075] Within the volume of the tank 11 there are arranged means 2 for mixing the contents of the tank. The means 2 for mixing the contents of the tank 11 is at least one mechanical agitator 2. The agitator 2 is preferably arranged so that it does not come into contact with the walls of the tank 11 during rotation. The purpose of agitator 2 is to introduce into the swirling motion both the matrix itself and, at later stages, the matrix together with the fed solid phase (including additives), as well as the mixture of both components for the purpose of conditioning. The agitator 2 essentially consists of a blade part 2a and a main shaft 2b which is attached at one end to a drive system (not shown).

[0076] The agitator 2 is preferably made of metal, for example stainless steel. As shown in Fig. 7, the blade part 2b of the agitator 2 may be in the form of at least two L-shaped arms extending from the main shaft 2a. In another variant, the blade part 2b of the agitator 2 may be in the form of a ribbon, a helix or a half-ring.

[0077] Due to the high forces applied to the mixing means 2, the agitator 2 must be suitably stiff. Furthermore, the skilled person will appreciate that the shape and dimensions of the blade portion 2b of the agitator 2 ultimately influence the swirling movements in the tank 11 .

[0078] The authors unexpectedly observed that at a sufficiently high mixing speed, the Weissenberg effect normally observed when mixing STF disappears. Namely, in typical situations the fluid climbs up the agitator shaft forming a zone of high yield point fluid which solidifies on shaft 2a and ceases to participate in the homogenization process. Meanwhile, at a sufficiently high mixing speed (for example for a linear mixing speed of 1 m / s, where the limiting mixing speed depends on the temperature, in this case the process was carried out at a temperature of 150°C), the STF not only does not climb faster up the shaft 2a of the agitator 2, but itstops climbing up the shaft 2a of the agitator. This does not form an STF zone with a high yield point, which does not solidify on shaft 2a of agitator 2.

[0079] The inventors have further observed that, in view of this phenomenon, it is advantageous for two or more agitators 2 to be provided in the tank, wherein their main shafts 2a may preferably be coaxial, and each of the agitators 2 may be connected to a separate drive system (not shown).

[0080] For a sufficiently large volume, when a single agitator is working quickly, due to the long arm, in its blade part 2b, typically in the shape of an anchor part, such large moments occur at the agitator wall that the steel can plastically deform. It is then not possible to quickly mix the entire volume with one agitator because the paddle part will be damaged.

[0081] However, if the agitator is a double or multiple agitator, the middle agitator, i.e. the inner one, closest to the tank axis, can safely rotate at high speed because its paddle part has a short arm. Then it is possible to eliminate the Weissenberg phenomenon. However, it can be removed slowly from the STF walls because the Weissenberg effect occurs only in the shaft axis. In the case of an external horseshoe agitator, the blade part, i.e. the mixing tip, is located significantly away from the shaft axis. Moreover, in the case of an external horseshoe agitator, the low angular velocity on the long arm translates into a relatively high linear velocity. Therefore, as shown in Fig. 9, it is advantageous for the internal agitator 2", preferably ribbon-type, to mix at a high speed, many times greater than the external agitator 2', preferably of a horseshoe-type.

[0082] Consequently, a double or multiple agitator 2 enables effective homogenization throughout the volume, further contributing to the scalability of the method of the invention.

[0083] The means 2 for mixing the contents of the tank must be suitably mounted both to the drive system and to the upper part of the tank 11 . As shown in Fig. 5 the main shaft 2a of the agitator 2 passes through the cover 7. Hole 7a in the cover has sufficient clearance to allow the shaft to rotate but prevent the agitator from buckling. Additionally, the hole through which the main shaft 2a of the agitator 2 passes is appropriately sealed. The seal 7b of the opening 7a is in the form of a stuffing box. In the event that the solid-phase expanding system comprises vibrating means, the seal of the opening 7a additionally acts as a shock absorber, reducing the transfer of vibrations between the components of the device 100, in particular towards the drive system. The apparatus 100 of the invention also comprises means 17 for feeding protective gas atmosphere into the matrix to supersaturate the matrix with the protective gas. In the simplest case, the means 17 may be any tube (not shown) immersed in the matrix with the reservoir 11 open before the solid phase is fed thereto. Tank 11 is filled with the appropriate amount of matrix at an earlier stage. The protective gas is fed directly to the matrix via a tube connected to a protective gas source (not shown) to supersaturate it with the protective gas. The matrix may or may not rotate while being saturated with the protective gas.

[0084] The protective gas applicable in the method of producing STF based on a dispersed phase, including silica, according to the invention may be argon or nitrogen or carbon dioxide or any mixture thereof.

[0085] As shown in Fig. 6, in one embodiment the means 17 for feeding protective gas atmosphere to the matrix to supersaturate the matrix with the protective gas may be bubbler nozzles 17 located in the bottom 13. The number of bubbler nozzles can be selected according to the bottom diameter 13. The number of bubbler nozzles may preferably be from 1 to 3 pieces per 9.5 cm of the bottom diameter, on average 1 nozzle per 3.3 cm of the bottom. The bubbler nozzle 17 may preferably have a diameter in the range from 4 mm to 20 mm. The use of one or more bubbler nozzles 17 in the bottom 13 enables the protective gas to be injected directly into the rotating matrix located in the tank 11. By injecting the protective gas into the matrix, the matrix is supersaturated with the protective atmosphere while simultaneously removing traces of oxygen. Simultaneousmixing of the matrix increases the efficiency of protective gas saturation. Residual oxygen causes degradation of the polymer matrix.

[0086] Since it is advantageous to supply the protective gas until all of the solid phase has been supplied to the tank, the device 100 according to the invention must have separate means 3 for supplying the protective gas to the tank 11 above the surface of the shear thickening fluid that is being mixed. The means 3 may be any tube positioned above the surface of the shear thickening fluid that is being mixed, and shaped at its end so as to permit the introduction of the protective gas at an appropriate angle to both the wall 11 a of the tank 11 and the surface 18 of the shear thickening fluid that is being mixed. As a rule, the outlet position of means 3 should not be such that the main axis of the outlet intersects the surface of the shear thickening fluid that is being mixed. On the other hand, the position of the outlet of means 3 should be such that the introduced gas does not cause the blowing out of the introduced solid phase.

[0087] As shown in Fig. 5 and Fig. 2, in a preferred embodiment, the means 3 for feeding protective gas to the tank 11 is a tube 3 passing into the tank through the cover 7, ending with a suitable stub-pipe above the surface of the cover 7. Tube 3 has a pipe-shaped ending under the cover. Fig. 5 and Fig. 4 show the corresponding cross-sections passing through the main axis of the outlet opening of the pipe-shaped tube 3. The main axis of the outlet opening of the means 3 for feeding protective gas to the tank 11 forms an angle © in the range of 120-180° with the wall 11a of the tank 11 . On the other hand, the main axis of the outlet opening of the means 3 for feeding the protective gas to the tank 11 forms an angle p in the range of -30°, +30° with the surface of the shear thickening fluid that is being mixed. The larger the angle ©, the more laminar the gas flow in the chamber becomes. On the other hand, the closer the angle p is to 0°, the more laminar the gas flow in the chamber becomes.

[0088] Preferably, the end section of the means 3 for feeding protective gas to the tank 11 itself may be shaped in such a way that it is bent into a radius of the tank, while the angular relationships previously defined in the plane of the outlet opening of the means 3 for feeding protective gas to the tank 11 still hold true. The person skilled in the art will know that in the case where the means for supplying the protective gas also function as the means for supplying glycol (matrix, liquid phase), the configuration of these means 3 for conducting the protective gas should not cause local stopping of the flow of the matrix. This can happen when angle p is in the range from +5° to +30°.

[0089] The device 100 according to the invention also comprises means 5 for discharging protective gas from the tank 11 . In the example embodiment shown in Fig. 2 the means 5 for discharging protective gas from the tank 11 is a pipeline 5. The protective gas is discharged from the tank by gravity buoyancy. This means that there is no pressure in pipeline 5 higher than the supply pressure. The means 5 for discharging protective gas from the tank 11 should generally have a larger cross-section than the means 3 for feeding protective gas to the tank, in order to enable laminar discharge of the gas from the tank. The conduit 5 may be a pipeline made from a material such as 304 stainless steel or 306 stainless steel, and more preferably duplex stainless steel. In another embodiment, the pipeline 5 may be made of a transparent material such as polycarbonate. The protective gas from the tank 11 is conveyed via the protective gas discharge means / system 5 to the hopper (i.e. the tank in which the solid phase is stored) (not shown) and then by gentle exhaust to the atmosphere. Furthermore, the device 100 for producing a shear thickening liquid based on a dispersed phase, for example silica, according to the invention comprises means 5 for feeding expanded solid phase at an appropriate rate. As shown in Fig. 2 the means 5 for feeding the expanded solid phase may be, at least in part, means 5 for removing protective gas from the tank 11 . Experiments have shown that both the matrix and the solid phaseshould be fed and mixed with each other in the constant presence of the protective gas. This means that the protective gas should also fill the entire pipeline through which the solid phase is supplied. Due to the forced flow of the protective gas through the device 100 according to the invention, it becomes logical to use the means 5 for feeding the expanded solid phase also as a means 5 for removing the protective gas at least in the section from the tank 11 to the place where the unexpanded solid phase is stored.

[0090] In one of the embodiments shown in Fig. 2 the means 5 for feeding the expanded solid phase are in the form of a pipeline 5 extending from the device 100, preferably extending from the cover 7. As shown in Fig. 9, the pipeline 5 is perpendicular to the surface of the mixed liquid in the first section 5a. The second section 5b of the pipeline 5 is inclined relative to the main axis of the tank 11 at an angle a ranging from 90° to 180°. This range was experimentally determined as ensuring the effect of appropriate administration of the expanded solid phase. The person skilled in the art will appreciate that the means 5 for feeding the expanded phase to the tank 11 may be designed in other ways. For example, the means 5 for feeding the expanded solid phase in the form of a pipeline may extend from the vessel wall above the target level 18 of the shear thickening liquid that is being mixed. In this case, the final last section of the means 5 for feeding the expanded solid phase is also preferably inclined at a suitable, experimentally selected angle in relation to the wall of the tank 11. In order to ensure an appropriate rate of feeding of the solid phase (silica), the pipe 5 preferably has a diameter in the range of 1 .5 to 5 times of the diameter of the pipe 3 through which the protective atmosphere is supplied. The diameter of the pipeline should be in an appropriate ratio to the diameter of the bottom, namely it should be 1 :6.

[0091] The device 100 according to the invention also comprises means 12 for providing mixing temperature for the period of mixing of the contents of the tank. As will be explained later, the means 12 can supply thermal energy and / or receive thermal energy. In one embodiment, the means 12 for providing mixing temperature are heating means 12 and are in the form of a heating jacket 12. The heating jacket 12 may, as shown in Fig. 2, surround the tank along the entire height of the tank walls 11 . In another example, the heating jacket 12 may surround the tank 11 only over a portion of the height of the walls of the tank 11 . The heating jacket 12 may have a single section or be divided into at least two sections (not shown). In another embodiment, the sections of the heating jacket 12 may not be in contact with each other.

[0092] As shown in Fig. 2, the heating means 12 are necessary to heat the contents of the tank and supply thermal energy from outside. The person skilled in the art will appreciate that it is also possible to provide heating means 12 which provide thermal energy in another way, e.g. from the inside, for example in the form of heating means arranged in the mixing means 2.

[0093] The heating means 12, for example the heating jacket 12, may be an electric mat, a tube or a jacket exchanger. In the case of large installations, it may be advantageous to use a glycol system.

[0094] The heating jacket 12 may, but does not have to, be insulated from the outside. The inventors unexpectedly discovered during experiments that the process occurring in tank 11 during the production of silica-based shear thickening fluid becomes exothermic. This phenomenon becomes noticeable when at least 70% by mass of ceramic powder is introduced, i.e. the solid phase, specified in the recipe. The value at which this phenomenon can be observed will depend on the recipe. Accordingly, in order to better control the temperature of the mixture in the tank 11 , in yet another embodiment, sections of the heating jacket 12 may be adjacent to sections of the means 12 for providing mixing temperature, which is in the form of a cooling system for the tank 11 (not shown). In another embodiment, the given sections may perform both functions interchangeably, i.e. when the processinside the tank 11 becomes exothermic, they may, instead of supplying heat to the tank 11 , receive heat from the tank 11 , so that the mixture inside is within the appropriate temperature range.

[0095] Furthermore, the device 100 for producing a shear thickening liquid based on a dispersed phase according to the invention comprises means 1 for expanding solid phase during the feeding thereof. According to one embodiment, the means 1 for expanding solid phase are in the form of a mechanical vibrator 1 . The mechanical vibrator 1 may in one embodiment be arranged on the solid phase feeding pipeline 5 (see Fig. 2). In another embodiment, the mechanical vibrator 1 may be structurally spaced from the tank 11. For example, it may be disposed on a structurally separate solid phase distributor connected to the tank 11 by a suitable pipeline 5 (not shown).

[0096] The mechanical vibrator 1 is designed to provide both transverse and longitudinal vibrations to the solid-state feeding system. Appropriate vibrations cause the silica to expand into dust, which significantly facilitates the feeding process and more uniform penetration of silica particles into the shear thickening liquid mixed in the tank 11 .

[0097] A person skilled in the art will know that the silica expanding process can be performed by other technical means, for example using a diaphragm pump, an industrial shaker, or a vibrating sieve system. The skilled person will know that expanding systems with other technical means will have a different structure than that described above. Preferably, only the last pipeline section 5 of the system, through which the expanded solid phase is fed into the interior of the tank, may, but does not have to, be similar in all systems.

[0098] At least one sight glass 4 can be used in the device 100 according to the invention to observe the course of the method according to the invention. As shown in Fig. 2, the sight glass 4 may be located in the cover 7. The person skilled in the art will recognize that the sight glass 4 may also be located in the wall or floor of the tank 11.

[0099] The device according to the invention also comprises a suitable measurement system (not shown) enabling measurement of the most important parameters of the method for producing a silica-based STF according to the invention.

[0100] As shown in Fig. 1 , in one embodiment, a method of producing a silica-based shear thickening fluid, employing the device 100 of Fig. 2, may comprise:

[0101] - activating the agitator 2,

[0102] simultaneously

[0103] - feeding a matrix— polypropylene glycol), through the stub-pipe 3,

[0104] - supplying the protective gas atmosphere through bubbler nozzles for the period of supersaturation of the matrix with the protective gas in order to supersaturate the matrix with the protective gas,

[0105] - closing the bubbler nozzles and feeding the protective gas atmosphere through the stub-pipe 3, - activating the heating means 12 (for providing a mixing temperature) and the mechanical vibrator 1 and simultaneously

[0106] - matrix reheating,

[0107] - feeding a solid phase through pipeline 5 for the period of dosing the solid phase to dose the expanded dispersed phase (for example silica, supersaturated with the protective atmosphere exiting through the pipeline, fed through the stub-pipe 3) with simultaneous heating of the mixture, - deactivating the mechanical vibrator

[0108] - mixing the mixture for a conditioning period to condition it at the appropriate temperature- deactivating the agitator 2,

[0109] - pouring off the resulting shear thickening liquid.

[0110] As mentioned earlier, mixing is preferably done with a double agitator. The fact that each agitator is connected to a separate drive allows for additional options for controlling the mixing process for better homogenization of the mixture, i.e. STF conditioning. The internal agitator, i.e. the agitator whose blade portion (mixing tip) is closer to the shaft axis of the agitator set, may mix at a speed 1 .5 to 10 times faster than the second agitator in order to avoid the formation of a zone of shear thickening fluid with a high yield point that is not subject to homogenization. An external agitator, whose mixing tip is closer to the agitator walls, can mix at a correspondingly slower speed. This makes it possible to avoid plastic deformation associated with the occurrence of a large moment due to the large distance from the axis of rotation. At the same time, such control of the speed of the external agitator prevents the formation of a zone at the boundary of the side walls of the device where homogenization does not occur.

[0111] Preferably, in the case of a split mixing system, i.e. a double agitator 2, the external agitator 2' should mix in the range of 0.1 to 30 rpm - depending on the diameter of the tank 11 (the larger the tank, the slower the rotation). The internal agitator 2" should rotate at a speed ranging from 25 to even 120 rpm. This speed actually depends on the attack surface of the mixing tip, i.e. the blade part 2b of the agitator 2. The smaller the rake surface, the faster the internal agitator 2” can spin without fear of damage. The creators predict that for a properly selected rake surface, even speeds of up to 400 rpm can be achieved.

[0112] It should be mentioned here that the mechanical agitator 2 is connected to a drive system that provides the appropriate power. Experiments have shown that, for example, to carry out the process to produce STF with a volume of 10 litres, the minimum required instantaneous engine power is 3 kW. In the case of multiple drive systems used, this power can be multiplied. It should also be mentioned that the relationship between the volume of mixed fluid and the engine power requirement is not linear. For example, for a system with a 4 L tank, a 0.75 kW motor is sufficient. The inventors noted that the engine power requirement for a given volume of mixed shear thickened liquid depends on the attack surface of the mixing tip (blade part 2b) and the distance at which the shear thickening effect of the produced STF is transferred from the mixing tip (blade part 2b) -i.e. how much STF in litres is subject to the mixing process by a given mixing tip - and this will depend on the formulation and type of fluid used.

[0113] It should be added here that a poorly conducted process with incomplete use of the device according to the invention may lead to degradation of the matrix, which is an irreversible process. A degraded matrix can be recognized by the inappropriate smell and colour of the mixture.

[0114] EXAMPLES

[0115] Example 1

[0116] 5.8 kg of polypropylene glycol) with a molar mass of 1000 g / mol was introduced into the tank (11 ) through the stub-pipe (3) while stirring and with a flow of 450 dm3 / h of argon atmosphere supplied by bubbler nozzles (17). After 20 minutes of saturating the liquid with argon, the supply of protective atmosphere was switched from the nozzles (17) to the stub-pipe (3). Then, within 30 minutes, the liquid matrix was heated to a temperature of 60°C while 4.2 kg of Aerosil 200 silica (manufacturer: Evonik; specific surface area: 200 m2 / g) was dosed through a pipe (5, with an inclination angle of a=95°) while vibrating. The solid phase was dosed into the liquid phase at such a rate that the solid phase could become supersaturated with the emerging protective atmosphere. The silica dosing process was carried out for 16 h at a continuous flow of 40-60 dm3 / h argon atmosphere. After dosing the ceramic powder, the vibrator was turned off and the mixture was conditioned bystirring under a continuous flow of protective atmosphere for 4 h. The contents of the agitator were then poured. The suspension thus obtained was homogeneous throughout its entire volume. FT-IR analysis of the obtained mixture excluded degradation of the polymer matrix. 9.9 kg of transparent, odourless liquid was obtained. Example 2 NEGATIVE

[0117] 6.4 kg of polypropylene glycol) with a molar mass of 1000 g / mol was introduced into the tank (11 ) through the stub-pipe (3) and the matrix was heated to 60°C while stirring. Then, 4.7 kg of Aerosil 300 silica (manufacturer Evonik; specific surface area 300 m2 / g) was introduced through the pipe (5, with an inclination angle of a=145°) within 8 h. The silica dosing process was carried out without a protective atmosphere and without vibration of the supplied solid phase. Due to the presence of an undispersed solid phase after the dosing was completed, the contents of the tank (11) were stirred at 110°C for 12 h. After this time, the contents of the agitator were poured. The suspension thus obtained was non-homogeneous throughout its volume. FT-IR analysis of the obtained mixture showed degradation of the polymer matrix. 11 kg of opalescent liquid with a pungent, irritating odour was obtained.

[0118] List of reference numerals:

[0119] 100 - device for producing a silica-based STF

[0120] 1 - mechanical vibrator (pneumatic or electric)

[0121] 2 - mechanical agitator

[0122] 2a - agitator shaft

[0123] 2b - blade part

[0124] 3 - stub-pipe for feeding continuous phase (polyglycol) and protective atmosphere

[0125] 4 - sight glass

[0126] 5 - pipe supplying the solid phase (silica) and removing the protective atmosphere

[0127] 5a - the first section of pipe 5, perpendicular to the surface of the mixed liquid.

[0128] 5b - the second section of the pipe 5 inclined in relation to the main axis of the tank 11

[0129] 6 - mounting and flexible sealing of the stub-pipe 5

[0130] 7 - upper cover of the tank

[0131] 7a - hole in the cover for the pipe for supplying the solid phase

[0132] 7b - sealing the opening for the solid phase supply pipe

[0133] 8 - screws securing the flange to the cover

[0134] 9 - cover flange

[0135] 10 - tank flange

[0136] 11 - tank

[0137] 12 - heating jacket

[0138] 13 - tank bottom

[0139] 14 - drain stub-pipe

[0140] 15 - sealing of the cover flange with the tank flange

[0141] 17 - bubbler nozzles supplying protective atmosphere

[0142] 18 - surface of the mixed liquid

Claims

CLAIMS1. A device for producing a shear thickening fluid based on a dispersed phase, the device comprising:- a closed tank (11) containing a bottom (13) for receiving a liquid matrix and- mixing means (2) disposed in the tank (11 ) for mixing an STF,- means (17) for supplying protective gas atmosphere to the matrix to supersaturate the matrix with the protective gas,- means (3) for feeding protective gas to the tank, connected to the tank (11 ),- means (5) for removing protective gas from the tank, connected to the tank (11), - means (12) for providing mixing temperature,- means (5) for feeding expanded solid phase, connected to the tank (11),- means (1) for expanding solid phase during the feeding thereof.

2. The device according to claim 1 , characterized in that the mixing means (2) is a mechanical agitator (2);3. The device according to claim 1 , characterized in that the mixing means (2) are two mechanical agitators (2) connected to separate drive systems;4. The device according to claim 1 or 2, characterized in that at least one agitator (2) is a horseshoe agitator.5 The device according to claim 1 , characterized in that the means (5) for feeding the expanded solid phase comprise a pipe (5) comprising a first section (5a) whose main axis is perpendicular to the bottom, and a second section (5b) whose main axis forms an angle a in the range of 90° to 180° with the main axis of the first section (5a).

6. The device according to claim 1 , characterized in that the means (17) for supplying protective gas atmosphere into the matrix to supersaturate the matrix with the protective gas are bubbler nozzles.

7. The device according to claim 6, characterized in that the number of bubbler nozzles (17) may be preferably from 1 to 3 pieces per 9.5 cm of the bottom diameter (11), preferably on average 1 piece per 3.3 cm of the bottom diameter (11 ).

8. The device according to claim 6 or 7, characterized in that the bubbler nozzle (17) may preferably have a diameter in the range of 4 mm to 20 mm.

9. The device according to claim 1 , characterized in that the means (12) for providing mixing temperature include heating means (12).

10. The device according to claim 1 , characterized in that the means (12) for providing mixing temperature include cooling means (12).

11. The device according to claim 1 , characterized in that the means (1) for expanding solid phase during the feeding thereof are a mechanical vibrator (1).

12. The device according to claim 1 , characterized in that a mechanical vibrator (1) is mounted on a pipeline (5) for feeding the expanded solid phase.

13. The device according to claim 5, characterized in that the pipe (5) preferably has a diameter in the range of 1.5 to 5 times the diameter of the pipeline (3) through which the protective atmosphere is supplied.

14. The device according to claim 5, characterized in that the ratio of the diameter of the pipeline (5) to the diameter of the bottom (11 ) is 1 :6.

15. A method of producing a shear thickening liquid based on a dispersed phase performed with a device according to claim 1 , comprising the steps of:- activating mixing means (2),and simultaneously- feeding a matrix by means (3) for feeding the matrix,- supplying the protective gas atmosphere with bubbler nozzles for the period of saturation of the matrix with the protective gas in order to supersaturate the matrix with the protective gas, - closing the bubbler nozzles and feeding the protective gas atmosphere through means (3) for feeding the protective gas,- activating expanding means (1) and means (12) for providing mixing temperature and simultaneously:- reheating the matrix,- feeding a solid phase through solid phase feeding means (5) for a solid phase dosing period to dose the expanded dispersed phase, while simultaneously heating the mixture, and - after the solid phase dosing period, deactivating the mechanical vibrator (1),- mixing the mixture for a conditioning period to condition it at the appropriate temperature, - deactivating the agitator (2),- pouring the resulting STF.

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