Device for preparing expanded microspheres

Abstract

The invention relates to a method and a device for producing expanded microspheres.

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for producing expanded microspheres. Background Technology

[0002] Thermally expandable microspheres are known in the art and are described in detail, for example, in U.S. Patent No. 3,615,972. Various grades of expandable microspheres with different expansion temperatures are available from Nouryon under the trademark Expancel™, both as dry, free-flowing microspheres and as aqueous slurries of microspheres.

[0003] These expandable microspheres contain a foaming agent encapsulated within a thermoplastic shell. Upon heating, the foaming agent evaporates, increasing the internal pressure, while the shell softens, causing the microspheres to expand significantly, typically 2 to 5 times their diameter.

[0004] Thermoplastic microspheres can be used in a variety of applications in either unexpanded or pre-expanded states. Examples of products using dried (essentially anhydrous) pre-expanded microspheres include their use as sensitizers in emulsion explosives and as lightweight fillers in solvent-based paints and various thermosetting materials such as artificial marble, polyester putty, and artificial wood. Wet pre-expanded microspheres are used in many products such as water-based paints and coatings, thermal printing paper, porous ceramics, and emulsion explosives.

[0005] Transporting pre-expanded microspheres requires significant space, so unexpanded microspheres are typically transported to the end user who wants to use expanded microspheres and subsequently expanded on-site. The microspheres can then be expanded near the process where the final product is produced (e.g., any of the above) or directly within that process.

[0006] Various methods and devices have been developed to expand thermoplastic microspheres.

[0007] US 5484815 and US 7192989 disclose methods and apparatus suitable for expanding dry microspheres.

[0008] US 4513106 discloses a method and apparatus for expanding microspheres in an aqueous slurry, wherein steam is introduced into the slurry in an amount sufficient to heat the microspheres and cause them to expand at least partially in a pressure zone, and then the partially expanded microspheres are allowed to leave the pressure zone under a pressure drop, thereby causing the microspheres to expand further and accelerate into a flow with a velocity of at least 1 m / s.

[0009] WO2014198532 describes an expander for unexpanded, thermally expandable microspheres, wherein a slurry of microspheres in a suitable carrier is fed into a pressure zone and heated, the slurry not in direct contact with the heating medium. The heating zone can be, for example, a heat exchanger. Compared to steam expansion, the advantage of indirect heating is that it eliminates the need to introduce (additional) water into the slurry. Indirect heating also allows for the use of other heating media besides steam and water, thus providing greater flexibility in terms of temperature range.

[0010] The apparatus disclosed in WO2014198532 includes a heating zone capable of withstanding a pressure of at least 4 bar. The apparatus includes a pump for feeding a slurry of thermally expandable thermoplastic microspheres into the heating zone. The pump is capable of generating a pressure of at least 4 bar in the heating zone. The pressure within the heating zone is maintained such that the thermally expandable thermoplastic microspheres do not fully expand. The apparatus includes means for heating the slurry of the thermally expandable thermoplastic microspheres in the heating zone to a temperature of at least 60°C without direct contact between the slurry and any fluid heat transfer medium. After the microspheres are heated in the heating zone, the slurry is extracted from the heating zone and subjected to a pressure drop into a region with a sufficiently low pressure to allow the microspheres to begin expanding.

[0011] WO2016091847 describes further improvements to the expansion device. To reduce the potential agglomeration of expanding particles, the slurry is drawn from the heating zone through an outlet pipe. After leaving the heating zone where it has been pressurized and heated, the particles begin to expand in the outlet pipe. WO2016091847 describes that the outlet pipe (where the particles begin to expand) can be attached to a downstream distribution pipe (also called a “mixing zone”). The distribution pipe has an inlet for a cooling medium, and the outlet pipe is attached downstream of this inlet to the distribution pipe (or “mixing zone”) (between the inlet and outlet of the distribution pipe).

[0012] As an additional measure, to maintain sufficiently high pressure in the heating zone, WO2016091739 proposes fluidly communicating a back pressure generator with the heating zone. This back pressure generator increases the pressure in the heating zone, after which the particles experience a pressure drop and begin to expand (e.g., in the "expansion zone," which may take the shape of the outlet pipe described in WO2016091847). The back pressure generator can restrict and / or control the flow of fluid material through the heating zone (referred to as the "processing zone" in WO2016091739) to ensure that the temperature within the heating zone is sufficient to cause the expandable polymer microspheres to expand to the desired extent. The back pressure generator can provide increased pressure within the heating zone and may include, for example, flow control valves or flow limiting devices, such as orifice nozzles.

[0013] WO2019192936 describes further improvements to the expansion device. By changing the back pressure (counter-pressure) in the expansion zone, the final density of the particles can be affected, allowing the particles to continue expanding even at very low densities. The density of the microspheres obtained from this device is determined by sampling, drying the sample in the laboratory, and measuring it in a specific gravity bottle, which is both time-consuming and labor-intensive, thus complicating the quality control (QC) process for the expanded microspheres. Summary of the Invention

[0014] The purpose of this disclosure is to improve the expansion device of WO2019192936 by providing a method for automatically controlling the density of expanded microspheres. The overall goal is to automate product quality control, thereby significantly improving the overall effectiveness and efficiency of the expansion device. Attached Figure Description

[0015] Figure 1 A simplified schematic diagram of a preferred embodiment of the device disclosed herein is provided: 10 = tank containing slurry of unexpanded expandable microspheres; 12 = first pump; 14 = first flow sensor; 16 = heating zone; 18 = expansion zone; 20 = flow control device (second pump); 22 = second flow sensor; 24 = tank containing diluent; 26 = fluid metering device (third pump); 28 = third flow sensor; 30 = fluid inlet; 32 = controller.

[0016] Figure 2 The set point, calculated density of expandable microspheres, and measured density of expandable microspheres (specific gravity bottle; points A, B, and C) of Example 2 were plotted. Detailed Implementation

[0017] This objective is achieved by the following apparatus and method. Therefore, in a first aspect, the present invention relates to an apparatus for expanding unexpanded, thermally expandable microspheres, comprising: - A heating zone having an inlet and an outlet, wherein the inlet is configured to receive a slurry of unexpanded, thermally expandable microspheres; - The first pump is located upstream of the heating zone inlet and is in fluid communication with the heating zone inlet; - An expansion zone having an inlet and an outlet, the inlet of the expansion zone being connected to the outlet of the heating zone, wherein the expansion zone is configured to be at a lower pressure than the heating zone; - A flow control device located downstream of the expansion zone outlet and in fluid communication with the expansion zone outlet; - Fluid inlet, located between the expansion zone outlet and the flow control device; - A fluid metering device configured to control the addition rate of a diluent introduced at the fluid inlet; and - A controller, wherein at least one of the first pump, the flow control device, and the fluid metering device is operatively connected to the controller, and wherein the controller is programmed to: It receives at least a first flow signal related to a first flow rate generated by a first pump, a second flow signal related to a second flow rate generated by a flow control device, and a third flow signal related to a third flow rate of the diluent. The density of the expanded microspheres was calculated by responding to at least the first, second, and third flow rates. The density of the expanded microspheres is controlled by controlling at least one of the first flow rate, the second flow rate, and / or the third flow rate.

[0018] In a second aspect, this disclosure relates to a method for expanding unexpanded, thermally expandable microspheres, the microspheres comprising a polymer encapsulating a blowing agent, wherein the blowing agent is a liquid with a boiling point not higher than the softening temperature of the polymer shell, the method comprising: - A slurry of unexpanded thermally expandable microspheres is fed into the heating zone using a first pump operating at a first pump speed to generate a first flow rate. - Heat the microspheres to a temperature above their softening temperature while applying sufficiently high pressure to ensure they do not expand completely; - By transferring the heated microspheres from the heating zone to the expansion zone, a pressure drop is created, resulting in a sufficiently low pressure in the expansion zone for the microspheres to expand. - Remove the expanded microspheres from the expansion zone and dilute them with a diluent introduced at the fluid inlet via a fluid metering device operating at a third flow rate to obtain the final slurry solids content value. - The diluted expanded microspheres are delivered to a flow control device operating at a second flow rate; The controller, which is operatively connected to at least one of the first pump, the flow control device, and the fluid metering device, calculates the density of the expanded microspheres in response to at least the first flow rate, the second flow rate, and the third flow rate, and controls the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.

[0019] In the apparatus of the first aspect and the method of the second aspect, an initial density value and an initial solids content value of the slurry of unexpanded thermally expandable microspheres can be determined, and the controller can be further programmed to receive the initial density value and / or the initial solids content value and, in response to a first flow rate, a second flow rate, a third flow rate, and one or both of the initial density value or the initial solids content value, calculate the density of the expanded microspheres. Therefore, in a preferred embodiment, the present invention relates to an apparatus for expanding unexpanded thermally expandable microspheres, comprising: - A heating zone having an inlet and an outlet, wherein the inlet is configured to receive a slurry of unexpanded, thermally expandable microspheres having an initial density value and an initial solids content value; - The first pump is located upstream of the heating zone inlet and is in fluid communication with the heating zone inlet; - An expansion zone having an inlet and an outlet, the inlet of the expansion zone being connected to the outlet of the heating zone, wherein the expansion zone is configured to be at a lower pressure than the heating zone; - A flow control device located downstream of the expansion zone outlet and in fluid communication with the expansion zone outlet; - Fluid inlet, located between the expansion zone outlet and the flow control device; - A fluid metering device configured to control the addition rate of a diluent introduced at the fluid inlet; and - A controller, wherein at least one of the first pump, the flow control device, and the fluid metering device is operatively connected to the controller (such that the operation of at least one of the first pump, the flow control device, and the fluid metering device can be controlled by the controller), and wherein said controller is programmed to: Receives a first flow signal related to a first flow rate generated by a first pump, a second flow signal related to a second flow rate generated by a flow control device, a third flow signal related to a third flow rate of the diluent, and one or both of an initial density value or an initial solids content value. The density of the expanded microspheres is calculated based on the first, second, and third flow rates, as well as one or both of the initial density or initial solids content value. The density of the expanded microspheres can be controlled by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.

[0020] In another preferred embodiment, this disclosure relates to a method comprising: - A slurry of unexpanded thermally expandable microspheres, having an initial density value and an initial solids content value, is fed into the heating zone using a first pump operating at a first pump speed to generate a first flow rate. - Heat the microspheres to a temperature above their softening temperature while applying sufficiently high pressure to ensure they do not expand completely; - By transferring the heated microspheres from the heating zone to the expansion zone, a pressure drop is created, resulting in a sufficiently low pressure in the expansion zone for the microspheres to expand. - Remove the expanded microspheres from the expansion zone and dilute them with a diluent introduced at the fluid inlet via a fluid metering device operating at a third flow rate to obtain the final slurry solids content value. - The diluted expanded microspheres are delivered to a flow control device operating at a second flow rate; The controller, which is operably connected to at least one of the first pump, the flow control device, and the fluid metering device (such that the operation of at least one of the first pump, the flow control device, and the fluid metering device can be controlled by the controller), calculates the density of the expanded microspheres in response to at least one or both of the first flow rate, the second flow rate, the third flow rate, the initial density value, and the initial solid content value, and controls the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.

[0021] The apparatus of the first aspect can be used in the method of the second aspect; therefore, the following description of the features of the apparatus is equally applicable to the method.

[0022] Unexpanded thermally expandable microspheres Unexpanded thermoplastic microspheres typically comprise a thermoplastic polymer encapsulating a blowing agent, wherein the blowing agent is typically a liquid with a boiling point not exceeding the softening temperature of the thermoplastic polymer shell. The device according to this disclosure can be used with all types of thermoplastic microspheres. As used herein, "thermally expandable thermoplastic microspheres" refers to a thermoplastic polymer shell encapsulating a blowing agent. When heated and expanded, the thermoplastic microsphere is referred to as an expanded thermoplastic microsphere.

[0023] Thermoexpandable thermoplastic microspheres are those sold by Nouryon under the trademark Expancel™. Thermally expandable thermoplastic microspheres and their manufacturing methods are disclosed, for example, in US 3,615,972, US 3,945,956, US 4,287,308, US 5,536,756, US 6,235,800, US 6,235,394, US 6,509,384, US 6,617,363, US 6,984,347, US2004 / 0176486, EP 486080, EP 566367, EP 1067151, EP 1230975, EP 1288272, EP 1598405, EP 1811007, EP 1964903, WO 2002 / 096635, WO 2004 / 072160, WO The contents of 2007 / 091960, WO 2007 / 091961, WO 2007 / 142593, JP 1987-286534 and JP 2005-272633 are incorporated herein by reference.

[0024] The thermoplastic polymer shell can be made from polymers or copolymers polymerized from various olefinic unsaturated monomers. The olefinic unsaturated monomers can be nitrile monomers, such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaric acid, and crotonitrile; acrylates, such as methyl acrylate or ethyl acrylate; methacrylates, such as methyl methacrylate, isobornyl methacrylate, and ethyl methacrylate; vinyl halides, such as vinyl chloride; vinylidene halide, such as vinylidene chloride; vinylpyridine; vinyl esters, such as vinyl acetate; optionally substituted styrene, such as styrene, halostyrene, and α-methylstyrene; dienes, such as butadiene, isoprene, and chloroprene; and any mixtures thereof.

[0025] Unsaturated olefin monomers may also include cross-linked polyfunctional monomers. Cross-linked polyfunctional monomers include any of the following: divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ... Pentaerythritol hexa(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, triallyl formaldehyde tri(meth)acrylate, allyl methacrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane triacrylate, tributylene glycol di(meth)acrylate, PEG#200 di(meth)acrylate, PEG#400 di(meth)acrylate, PEG#600 di(meth)acrylate, 3-acryloyloxyethylene glycol monoacrylate, triacryloylformaldehyde or triallyl isocyanate, triallyl isocyanurate, or any mixture thereof. The crosslinked polyfunctional monomer accounts for 0.1 to 1% by weight, most preferably 0.2 to 0.5% by weight, of the total amount of olefinically unsaturated monomers in the thermoplastic polymer shell.

[0026] The thermoplastic polymer shell may also be made of biopolymers or biopolymers, such as, but not limited to, those described in EP3678768, EP3713664, EP3880744, EP4153347, EP4294557, EP4126333, EP4126334 and WO 2024 / 089208.

[0027] Preferably, the thermoplastic polymer shell accounts for 60 to 95% by weight, more preferably 75 to 85% by weight, of the thermally expandable thermoplastic microspheres.

[0028] The softening temperature of a thermoplastic polymer shell corresponds to its glass transition temperature (T). g ). T g Preferably, the temperature is in the range of 50 to 250°C, and more preferably in the range of 60 to 200°C.

[0029] The foaming agent in thermally expandable thermoplastic microspheres can have a boiling point (at room temperature and normal pressure) not higher than the glass transition temperature (T). g The foaming agent is a liquid. It can be at least one hydrocarbon or any mixture thereof. The hydrocarbon can be selected from n-pentane, isopentane, neopentane, butane, isobutane, hexane, isohexane, neohexane, heptane, isoheptane, octane, and isooctane. The hydrocarbon can also be petroleum ether, chlorinated hydrocarbon, or fluorinated hydrocarbon, such as chloromethane, dichloromethane, dichloroethane, dichloroethylene, trichloroethane, trichloroethylene, and trichlorofluoromethane. The foaming agent is preferably at least one selected from isobutane, isopentane, isohexane, cyclohexane, isooctane, isododecane, and any mixture thereof. The foaming agent is more preferably isobutane and isopentane.

[0030] The foaming agent is present in an amount of 5 to 40% by weight of the thermally expandable thermoplastic microspheres.

[0031] The boiling point of the foaming agent (at atmospheric pressure) is preferably between -20 and 200°C, more preferably between -20 and 150°C, and even more preferably between -20 and 100°C.

[0032] The temperature at which thermally expandable thermoplastic microspheres begin to expand under atmospheric pressure is called T. 起始 T 起始 The T-value depends on the type and combination of the thermoplastic polymer shell and the foaming agent. The thermally expandable thermoplastic microspheres used in this disclosure have a T-value that... 起始 Preferably between 0 and 230°C, more preferably between 60 and 180°C.

[0033] Unexpanded, thermally expandable thermoplastic microspheres will be referred to hereinafter as expandable microspheres. The particle size of expandable microspheres can vary over a wide range and can be selected according to the desired performance of the product in which they are used. In most cases, the preferred median particle size (determined by laser scattering of a wet sample using a Malvern Mastersizer Hydro 2000 SM instrument) is 1 µm to 1 mm, preferably 2 µm to 0.5 mm, and particularly 3 µm to 100 µm. The diameter of the microspheres increases upon expansion, for example, by a factor of 2 to 5.

[0034] The liquid medium (carrier liquid) of the slurry for expandable microspheres can be any liquid that is inert to the microspheres and capable of withstanding the heating temperature of the slurry. In many cases, water or an aqueous liquid is preferred, thus forming an aqueous slurry; however, depending on the intended use of the expandable microspheres, it may also be preferred to use a non-aqueous liquid to form the slurry, such as at least one of vegetable oil, mineral oil, and glycerol, which may be anhydrous. Since no steam or any other form of water needs to be added to the slurry in the method of this disclosure, anhydrous expandable microspheres that can be used directly in water-free applications can be prepared. Furthermore, since no other fluid medium needs to be added to the slurry, expandable microspheres with tightly controlled solids content can be prepared.

[0035] The slurry of unexpanded thermally expandable microspheres has an initial density value and an initial solids content value. "Initial density value" refers to the density of the slurry of unexpanded thermally expandable microspheres before it enters the apparatus of this disclosure. "Initial solids content value" refers to the solids content of the slurry of unexpanded thermally expandable microspheres before it enters the apparatus of this disclosure. Both values ​​are routine measurements for such slurries, and the determination of these values ​​is within the ordinary capabilities of those skilled in the art.

[0036] In most industrial methods for producing expandable microspheres, they are typically first obtained in an aqueous slurry, which, optionally after dilution or dehydration to the desired microsphere content, can be used directly in the methods of this disclosure. Alternatively, such an aqueous slurry can be dried to obtain substantially anhydrous microspheres that can be used to prepare slurries in non-aqueous liquids.

[0037] The content of expandable microspheres in the slurry depends on the requirements for the product obtained after expansion. The upper limit is limited by the pumpability of the slurry and its transport capacity through the heating zone. In most cases, the content of expandable microspheres is suitably 5 to 50% by weight, preferably 10 to 40% by weight, and most preferably 15 to 30% by weight.

[0038] Heating zone, first pump and expansion zone The slurry of expandable microspheres flows through a heating zone, which can be made of any container, pipe or tube having an inlet and an outlet and capable of withstanding the pressure maintained therein.

[0039] The heating zone in the device heats the slurry of expandable microspheres to a temperature above the softening temperature of the thermoplastic polymer in the specific medium (carrier fluid) used as a carrier. The slurry can be heated in the heating zone, for example, by a fluid heat transfer medium that is not in direct contact with the slurry, an electric heating element, or microwave heating. For example, the heating zone may include a heat exchanger comprising at least one conduit or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of expandable microspheres. The heat transfer medium can be any suitable fluid medium, such as hot water, steam, or oil. Alternatively, heat can be provided by an electric heating element, which may be located, for example, inside or outside the heating zone, within its walls, or any combination thereof. Alternatively, heat can be provided by electromagnetic radiation such as microwaves.

[0040] The container or at least one pipe or tube through which the expandable microsphere slurry flows in the heating zone is preferably made of a thermally conductive material such as steel or copper, especially when the slurry is heated by a fluid heat transfer medium or by an electric heating element. If heating is by electromagnetic radiation, the container or at least one pipe or tube is preferably made of a material that is permeable to such radiation, such as various polymer materials.

[0041] In a heat exchanger comprising at least one pipe or tube, the inner diameter of each of such at least one pipe or tube may be, for example, 5 to 20 mm, preferably 7 to 15 mm, and most preferably 9 to 12 mm. The wall thickness of the at least one pipe or tube is suitably 0.5 to 3 mm, preferably 0.7 to 1.5 mm.

[0042] If heating is achieved by an electric heating element, such an element may be disposed, for example, on the outside and / or inside of at least one pipe or tube (e.g., a single pipe or tube). The inner diameter of such a pipe or tube may be, for example, 20 to 80 mm or 35 to 65 mm. For instance, the electric heating element may be disposed at the center inside the pipe or tube, so that the slurry containing expandable microspheres flows in the gaps around the heating element. Such an electric heating element itself may be a pipe or tube with a main electric heating source inside, so that heat is transferred through the wall to the slurry flowing in the gaps. Preferably, the electric heating element is disposed both inside and outside the at least one pipe or tube.

[0043] The optimal size and capacity of the device for heating the slurry are determined by the slurry flow rate, slurry concentration, and inlet temperature, and should be sufficient to raise the slurry to a high enough temperature to allow the microspheres to expand as the pressure drops after passing through the heating zone outlet. This temperature is always higher than the volatilization temperature of the blowing agent for the specific microspheres.

[0044] The device is equipped with a first pump upstream of the heating zone for feeding a slurry of unexpanded expandable microspheres in a liquid medium (carrier liquid) into the inlet of the heating zone at a first flow rate. The pump is capable of generating sufficiently high pressure in the heating zone so that the microspheres in the slurry do not fully expand. Examples of suitable pumps include hydraulic diaphragm pumps, piston pumps, screw pumps (e.g., eccentric screw pumps), gear pumps, rotary pumps, centrifugal pumps, etc. Hydraulic diaphragm pumps are particularly preferred. The pump preferably also generates a force to convey the slurry through the heating zone to its outlet. The device may also be equipped with a conduit for conveying the slurry of expandable microspheres, for example, from a tank containing the slurry to the pump.

[0045] A signal indicating the first flow rate generated by the first pump can be directly transmitted from the first pump to a controller (described in more detail below), and / or the device may also be equipped with a first flow sensor disposed between the first pump and the heating zone inlet and communicatively connected to the controller, the first flow sensor being configured to provide the controller with a first flow signal (i.e., a signal indicating the first flow rate of the microsphere slurry generated by the first pump). It should be understood that alternative techniques for transmitting the first flow signal from the first pump to the controller are also within the scope of this disclosure.

[0046] In one embodiment, the first pump is operatively connected to a controller, meaning the first pump can be controlled by the controller, for example, the pump speed and the first flow rate generated by the first pump can be controlled by the controller. Any suitable arrangement can be used. For example, the first pump can be directly controlled by the controller (i.e., the controller can be directly connected to the first pump and the speed of the first pump can be directly controlled). Alternatively, the first pump can be controlled by a first flow sensor, and the first flow sensor can be controlled by the controller (i.e., the first pump can still be operatively connected to the controller, albeit indirectly). Thus, the first pump and / or the first flow sensor can be operatively connected to the controller (i.e., one or both of the first pump and the first flow sensor can be controlled by the controller).

[0047] The exact pressure required in the heating zone depends on the temperature and the type of microspheres, and generally corresponds to the vapor pressure of the blowing agent of the expandable microspheres. The pressure maintained in the heating zone is preferably at least 10 bar, most preferably at least 20 bar, or at least 30 bar. Upper limits are determined by practical considerations, for example, up to 40 bar or 50 bar. Therefore, the heating zone should be able to withstand such pressure.

[0048] The temperature of the expandable microspheres in the heating zone is typically substantially the same as the temperature of the slurry therein. The exact temperature for heating the slurry depends on the microsphere grade. For most grades of microspheres, the temperature is preferably in the range of 60 to 160°C or 70 to 150°C, although some grades of microspheres may require higher temperatures, such as 200°C or even 250°C or higher. Therefore, the apparatus for heating the slurry is preferably capable of heating the slurry to such temperatures.

[0049] In the heating zone, a slurry flow of expandable microspheres is conveyed from the inlet to the outlet and heated under pressure to a sufficiently high temperature so that the microspheres expand as the pressure drops at the outlet of the heating zone and enter the heating zone at a sufficiently low pressure. The average residence time of the microspheres in the heating zone is preferably long enough to ensure that the slurry reaches and maintains a sufficiently high temperature for subsequent expansion. To ensure the production of high-quality and consistently high-quality products, the apparatus may optionally be equipped with a pulsation damper to stabilize the slurry flow.

[0050] Due to the increased pressure in the heating zone, the thermally expandable thermoplastic microspheres do not fully expand when heated in the heating zone. Upon leaving the heating zone, the microparticles enter the expansion zone. The inlet of the expansion zone is connected to the outlet of the heating zone. To maintain a sufficiently high pressure in the heating zone, the slurry of the expandable microspheres is discharged through its outlet, which can be configured with any suitable device for generating a pressure drop corresponding to the pressure difference between the interior of the heating zone and the expansion zone, preferably a flow area limiting device, such as a valve, nozzle, or any other type of narrow channel. The outlet of the heating zone can, for example, be an insulated conduit or tube with a flow area limiting at its end, such as an opening with a diameter of 0.5 to 0.05 times, preferably 0.3 to 0.1 times, the inner diameter of the conduit or tube. Such a conduit or tube can be rigid or flexible, in the latter case, in which it can be easily guided to the desired outlet point of the microspheres without moving the entire device.

[0051] After leaving the heating zone, the particles expand in the "expansion zone." The pressure in the expansion zone is low enough after the pressure drop to allow the thermoplastic microspheres to expand. Typically, the pressure in the expansion zone is essentially atmospheric pressure, but can be maintained at higher (or lower) pressures depending on the desired microsphere density. To maintain the high temperature, the pipes can be insulated.

[0052] When expansion begins under this pressure drop, the flow of the microspheres also accelerates significantly. To optimize microsphere disintegration and avoid agglomeration, it is preferable that the pressure drop occurs over the shortest possible distance in the flow direction.

[0053] The expansion zone may contain a tube or pipe with a diameter at least twice that of the tube in the heating zone. When in the form of a flexible tube, this facilitates the guidance of the expanded thermoplastic microspheres to their end-use application.

[0054] Flow control device, fluid inlet and fluid metering device A flow control device is positioned downstream of the expansion zone outlet and in fluid communication with the expansion zone outlet. The function of the flow control device is to control the flow rate of the slurry downstream of the expansion zone (expandable microspheres), which in turn affects the pressure within the expansion zone. For example, the flow control device could be an electrically controlled flow limiter positioned downstream of the expansion zone outlet and in fluid communication with the expansion zone outlet. The restricted flow area will reduce the "volume flow rate per unit pressure drop," thereby increasing the pressure within the expansion zone (higher pressure in the expansion zone corresponds to higher density of the expanded particles, and vice versa).

[0055] In a preferred embodiment, the flow control device includes or comprises a second pump. Examples of suitable pumps include hydraulic diaphragm pumps, piston pumps, screw pumps (e.g., eccentric screw pumps), gear pumps, rotary pumps, centrifugal pumps, etc. Screw pumps are particularly preferred. If the second pump operates at a high speed (thus producing a higher second flow rate), the pressure in the expansion zone is lower; if the second pump operates at a low speed (thus producing a lower second flow rate), the pressure in the expansion zone is higher.

[0056] A signal indicating the second flow rate generated by the flow control device can be directly transmitted from the flow control device to the controller (described in more detail below), and / or the device may also be equipped with a second flow sensor disposed downstream of the flow control device and communicatively connected to the controller, the second flow sensor being configured to provide the controller with a second flow signal (i.e., a signal indicating the second flow rate of the microsphere slurry generated by the flow control device). It should be understood that alternative techniques for transmitting the second flow signal from the flow control device to the controller are conceivable and also fall within the scope of this disclosure.

[0057] In one implementation, the flow control device is operatively connected to the controller, i.e., the flow control device can be controlled by the controller, thereby allowing the controller to control the second flow generated by the flow control device. Any suitable arrangement can be used. For example, if the flow control device is a (variable speed) second pump, the second flow generated by the second pump can be directly controlled by the controller (i.e., the speed of the second pump can be directly controlled by the controller directly connected to the second pump, thereby directly controlling the second flow). Alternatively, the flow control device can be controlled by a second flow sensor, and the second flow sensor can be controlled by the controller (i.e., the flow control device is still operatively connected to the controller, albeit indirectly). Therefore, the flow control device and / or the second flow sensor can be operatively connected to the controller (i.e., one or both can be controlled by the controller).

[0058] A fluid inlet is positioned between the expansion zone outlet and the flow control device. Diluent is added through this fluid inlet to the slurry of the expanded microspheres that has flowed from the expansion zone outlet to the flow control device. The rate at which the diluent is introduced at the fluid inlet is controlled by a fluid metering device. Any suitable fluid metering device can be used, such as a third pump, for example a hydraulic diaphragm pump, piston pump, screw pump (e.g., eccentric screw pump), gear pump, rotary pump, centrifugal pump, etc. The apparatus of this disclosure may also include a conduit for conveying the diluent, for example, from a tank containing the diluent to the fluid metering device. In one embodiment, the liquid medium (carrier liquid) of the slurry of the expandable microspheres is substantially the same as the diluent introduced at the fluid inlet.

[0059] A fluid metering device generates a third flow rate (of the diluent), thereby controlling the rate at which the diluent is introduced into the fluid inlet. The flow rate of the diluent is controlled to obtain the desired final solids content in the expanded slurry. A signal indicating the third flow rate generated by the fluid metering device can be directly transmitted to a controller (described in more detail below), and / or the device may also be equipped with a third flow sensor communicatively coupled to the controller, configured to provide a third flow signal (i.e., a signal indicating the third flow rate of the diluent generated by the fluid metering device) to the controller. Typically, the third flow sensor is located between the fluid metering device and the fluid inlet. It should be understood that alternative techniques for transmitting the third flow signal from the fluid metering device to the controller are conceivable and also fall within the scope of this disclosure.

[0060] In one implementation, the fluid metering device is operatively connected to a controller, i.e., the fluid metering device can be controlled by the controller, thereby allowing the controller to control the third flow rate generated by the fluid metering device. Any suitable arrangement can be used. For example, if the fluid metering device is a (variable speed) third pump, the third flow rate generated by the third pump can be directly controlled by the controller (i.e., the speed of the third pump can be directly controlled by the controller directly connected to the third pump, thereby directly controlling the third flow rate). Alternatively, the fluid metering device can be controlled by a third flow sensor, and the third flow sensor can be controlled by the controller (i.e., the fluid metering device is still operatively connected to the controller, albeit indirectly). Therefore, the fluid metering device and / or the third flow sensor can be operatively connected to the controller (i.e., one or both can be controlled by the controller).

[0061] The diluent introduced at the fluid inlet is not particularly limited. For the avoidance of ambiguity, "liquid" as used herein refers to a composition of substances that are liquid at 25°C and atmospheric pressure (i.e., 1 atmosphere). Preferably, the diluent is water or an aqueous liquid, or an organic liquid (e.g., organic oils, organic solvents, or plasticizers, such as, but not limited to, diisononyl phthalate (DINP) or diisononyl cyclohexanedicarboxylate (DINCH)) or an inorganic liquid (e.g., silicone oil), preferably an aqueous composition (i.e., an aqueous composition). Non-limiting examples of aqueous compositions that can be used as diluents include those containing biocides, thickeners, and combinations thereof. Preferred aqueous compositions are those containing water, one or more biocides, and one or more thickeners.

[0062] The apparatus according to this disclosure is preferably equipped with a distribution pipe that connects the expansion zone outlet to the flow control device, wherein the fluid inlet is located in the distribution pipe between the expansion zone outlet and the flow control device. Of course, within the scope of this disclosure, any suitable arrangement of the apparatus elements capable of achieving the same total material flow rate within the apparatus of this disclosure is considered.

[0063] The apparatus according to the invention may further include one or more mixing elements, such as a static mixer, downstream of the flow control device. If the apparatus of this disclosure includes such a mixing element, a second flow sensor may be disposed downstream of the mixing element, or may be disposed between the flow control device and the mixing element.

[0064] controller The apparatus according to this disclosure includes a controller operatively connected to at least one of a first pump (first flow rate), a flow control device (second flow rate), and a fluid metering device (third flow rate), wherein the controller calculates the density of the expanded microspheres in response to an initial density value, an initial solid content value, the first flow rate, the second flow rate, and the third flow rate, and wherein the controller controls the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.

[0065] Preferably, at least the flow control device is operatively connected to the controller. Preferably, the flow control device and the fluid metering device are operatively connected to the controller. Preferably, the flow control device, the fluid metering device, and the first pump are operatively connected to the controller. The operative connection can be direct (i.e., a direct connection between the controller and the corresponding pump or device) or indirect (e.g., via a flow sensor).

[0066] In a preferred embodiment, the controller is communicatively connected to at least the first pump, the flow control device, and the fluid metering device. More preferably, the controller is communicatively connected to at least the first pump, the flow control device, the fluid metering device, the first flow sensor, the second flow sensor, and the third flow sensor. For the avoidance of doubt, the term "communicative connection" as used herein refers to the ability to transmit data between the connected devices, while the term "operably connected" as used herein refers to the ability to be controlled; that is, "the controller is at least operably connected to the flow control device" means that the flow control device can be controlled by the controller.

[0067] As used herein, the term “controller” means any hardware, software, firmware, electronic control components, processing logic, and / or processor device that provides the desired functionality, alone or in any combination, including but not limited to: application-specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated, or aggregated) and memory that executes one or more software or firmware programs, combinational logic circuits, and / or other suitable components that provide the described functionality.

[0068] Preferably, the controller includes at least one processor and a computer-readable storage device or medium. The processor can be any custom or commercially available processor, central processing unit (CPU), graphics processing unit (GPU), semiconductor-based microprocessor (in the form of a microchip or chipset), macroprocessor, or any combination thereof, or generally any device for executing instructions. The computer-readable storage device or medium can include volatile and non-volatile memory, such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). The computer-readable storage device or medium can be implemented using any of a number of known storage devices, such as PROM (programmable read-only memory), EPROM (electrically programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), flash memory, or any other electrical, magnetic, optical, or combined storage device capable of storing data, some of which represents executable instructions for the controller to control the density of the expanded microspheres. The instructions can include one or more separate programs, each containing an ordered list of executable instructions for implementing logical functions. When these instructions are executed by the processor, the instructions receive and process a first flow signal associated with a first flow rate generated by a first pump, a second flow signal associated with a second flow rate generated by a flow control device, a third flow signal associated with a third flow rate of the diluent, and one or both of an optional initial density value and / or initial solid content value, and perform logic, calculations, methods, and / or algorithms for automatically controlling the density of the expanded microspheres.

[0069] The controller may optionally include a user interface (e.g., a GUI) to allow users to interact directly with the device disclosed herein, such as inputting initial density values ​​and initial solid content values ​​and / or controlling a first flow rate, a second flow rate, and / or a third flow rate.

[0070] In an exemplary embodiment, the controller can be programmed to control the dry density (kg / m³) of the expanded microspheres according to the following formula. 3 (“User input” refers to a predetermined value in the user input controller): Act_MS_dens= Dens_corr (MFT_FI01) / (FI02- MF_liquid_total / Dens_liquid) 1000 in: Act_MS_dens = Density of dried expanded microspheres (kg / m³) 3 ); -This article is also referred to as "density of setpoint expanded microspheres" (user input); MFT_FI01 = Dry mass flow rate of slurry (kg / min); FI02 = Volumetric flow rate of the outflowing expanded slurry ( Second flow (L / minute); MF_liquid_total = Mass flow rate of liquid flowing out of the slurry (kg / min); Dens_liquid = liquid density (constant; user input); Dens_corr = Correction factor [The correction factor compensates for the foaming agent lost by the microspheres during expansion, determined by dividing a calculated value by an empirically determined [specific gravity bottle method] value; user input].

[0071] The dry mass flow rate (MFT_FI01) of the slurry is determined by the following formula: MFT_FI01 = (SC_slurry_in / 100) FI01 Dens_slurry_in in: SC_slurry_in = Solid content of unexpanded slurry ( Initial solid content ; weight% (user input); Dens_slurry_in = density of the unexpanded slurry ( initial density value (kg / L; user input); FI01 = Volumetric flow rate of unexpanded slurry ( First Traffic (L / min).

[0072] The mass flow rate (MF_liquid_total) of the liquid flowing out of the slurry is determined by the following formula: MF_liquid_total =MFT_FI01 / (SC_slurry_out / 100)- MFT_FI01 in: SC_slurry_out = Setpoint solids content of expanded slurry (%); User input.

[0073] To achieve the set point solids content (SC_slurry_out) of the expanded slurry, the set point (i.e., the predetermined point) is... Third-rate quantity (SP_FC03; L / minute) is determined by the following formula: SP_FC03 = (MF_liquid_total -MF_liquid_slurry_in) / Dens_liquid in: MF_liquid_slurry_in = FI01 Dens_slurry_in - MFT_FI01.

[0074] In another exemplary embodiment, the controller can be programmed to control the wet density (kg / L) of the expanded microspheres according to the following formula: Dens_slurry_out = MF_tot / FI02 in: Dens_slurry_out = density of the expanded slurry (kg / L); MF_tot = FC03 Dens_liquid+ FI01 Dens_slurry_in; Dens_liquid = the density of the liquid (constant; user input); Dens_slurry_in = density of the unexpanded slurry ( initial density value (kg / L; user input); FI01= First Traffic (Preferably measured by a first flow sensor); FI02= Second flow (Preferably measured by a second flow sensor); FC03= Third traffic (Preferably measured by a third flow sensor, but can also correspond to the third flow at the set point, SP_FC03).

[0075] In both exemplary embodiments, for any given slurry, the liquid density, initial solids content, and initial density are constant values, so the density of the expanded slurry can be controlled by controlling the first, second, and / or third flow rates. However, in practice, the first flow rate is often limited (to maintain the preferred pressure in the heating zone), as is the third flow rate (because for practical purposes, the final solids content (% by weight) is typically kept within a reasonably narrow range). Therefore, the density of the expanded microspheres is usually controlled by controlling the second flow rate. This is especially true when the flow control device is a second pump, where the density of the expanded microspheres can be controlled by controlling the pump speed.

[0076] It is worth noting that the various elements of this disclosure (including, but not limited to, preferred ranges of various parameters) can be combined unless they are mutually exclusive.

[0077] Example This disclosure will be illustrated by the following embodiments, but is not limited thereto or thereby limited.

[0078] Example 1 To evaluate the effectiveness of the apparatus of this disclosure, a series of tests were conducted, in which the expanded microspheres obtained from the apparatus of this disclosure were evaluated using a specific gravity bottle (density calculation). The table below compares the density (Act_MS_dens) of the expanded microspheres at the set point automatically determined by the apparatus of this disclosure with the density of the expanded microspheres determined by the specific gravity bottle method (using the apparatus of WO2019192936).

[0079]

[0080] The calculated density (Act_MS_dens) correlates well with the experimentally measured density (specific gravity bottle).

[0081] Example 2 In this embodiment, the device of this disclosure is operated at the densities (“Act_MS_dens”) of the expanded microspheres at three different set points: 36, 32, and 44 kg / m³. 3 At each set point, the expanded microsphere sample was recovered from the device and the expanded density was determined experimentally (by the specific gravity bottle method).

[0082] like Figure 2 As shown, the calculated values ​​(based on sensor input) reflect the set values, indicating that the controller reliably controls the density of the expanded microspheres, and the calculated values ​​also match the experimentally determined values ​​(specific gravity bottle method; A = 38.9 kg / m³). 3 B = 33.9 kg / m 3 C = 43.8 kg / m 3The strong correlation between the data and the data confirms the reliability of the automated equipment.

[0083] It is anticipated that the automated control of the density of these expanded microspheres will automate the quality control (QC) process, which will lead to substantial improvements in terms of cost and time savings.

[0084] In this specification, unless otherwise expressly stated, the word “or” refers to the operator that returns a truth value when one or both of the stated conditions are met, and not the operator “exclusive OR” that only one of the conditions is met. The word “includes” means “includes”, not “consisting of”. All prior teachings acknowledged above are incorporated herein by reference. Any acknowledgment of any prior publication herein should not be construed as an acknowledgment or statement that its teachings were common general knowledge in Europe or elsewhere as of the date of this application.

Claims

1. An apparatus for expanding unexpanded thermally expandable microspheres, comprising: - A heating zone having an inlet and an outlet, wherein the inlet is configured to receive a slurry of unexpanded, thermally expandable microspheres; - The first pump is located upstream of the heating zone inlet and is in fluid communication with the heating zone inlet; - An expansion zone having an inlet and an outlet, the inlet of the expansion zone being connected to the outlet of the heating zone, wherein the expansion zone is configured to be at a lower pressure than the heating zone; - A flow control device located downstream of the expansion zone outlet and in fluid communication with the expansion zone outlet; - A fluid inlet, which is located between the expansion zone outlet and the flow control device; - A fluid metering device configured to control the addition rate of a diluent introduced at the fluid inlet; and - A controller, wherein at least one of the first pump, the flow control device, and the fluid metering device is operatively connected to the controller, and wherein the controller is programmed to: It receives at least a first flow signal related to a first flow rate generated by the first pump, a second flow signal related to a second flow rate generated by the flow control device, and a third flow signal related to a third flow rate of the diluent. The density of the expanded microspheres was calculated by responding to at least the first, second, and third flow rates. The density of the expanded microspheres is controlled by controlling at least one of the first flow rate, the second flow rate, and / or the third flow rate.

2. The apparatus of claim 1, wherein the apparatus further comprises a first flow sensor disposed between the first pump and the inlet of the heating zone and communicatively coupled to the controller, the first flow sensor being configured to provide a first flow signal to the controller.

3. The apparatus according to claim 1 or 2, wherein the apparatus further comprises a second flow sensor disposed downstream of the flow control device and communicatively connected to the controller, the second flow sensor being configured to provide a second flow signal to the controller.

4. The apparatus according to any one of claims 1 to 3, wherein the apparatus further comprises a third flow sensor communicatively coupled to the fluid metering device and the controller, the third flow sensor being configured to provide a third flow signal to the controller.

5. The apparatus according to any one of claims 1 to 4, wherein the flow control device is a second pump or a flow regulator, preferably a second pump.

6. The apparatus according to any one of claims 1 to 5, wherein the fluid metering device is a third pump.

7. The apparatus according to any one of claims 1 to 6, wherein the apparatus further comprises a static mixer disposed downstream of the flow control device.

8. The apparatus according to any one of claims 1 to 7, wherein the flow control device is operatively connected to the controller, and wherein the controller is programmed to control the density of the expanded microspheres by controlling the second flow rate.

9. The apparatus of claim 8, wherein the fluid metering device is operatively connected to the controller, and wherein the controller is programmed to control the density of the expanded microspheres by controlling the second flow rate and the third flow rate.

10. A method for expanding unexpanded, thermally expandable microspheres, the microspheres comprising a polymer encapsulating a blowing agent, wherein the blowing agent is a liquid with a boiling point not higher than the softening temperature of the polymer shell, the method comprising: - A slurry of unexpanded thermally expandable microspheres is fed into the heating zone using a first pump operating at a first pump speed to generate a first flow rate. - Heat the microspheres to a temperature above their softening temperature while applying sufficiently high pressure to ensure they do not expand completely; - The microspheres, thus heated, are conveyed from the heating zone to the expansion zone, creating a pressure drop that results in a sufficiently low pressure in the expansion zone for the microspheres to expand. - Remove the expanded microspheres from the expansion zone and dilute them with a diluent introduced at the fluid inlet via a fluid metering device operating at a third flow rate to obtain the final slurry solids content value, and - The diluted expanded microspheres are delivered to a flow control device operating at a second flow rate; The controller, operably connected to at least one of the first pump, the flow control device, and the fluid metering device, calculates the density of the expanded microspheres in response to at least the first flow rate, the second flow rate, and the third flow rate, and controls the density of the expanded microspheres by controlling at least one of the first flow rate, the second flow rate, and the third flow rate.

11. The method of claim 10, wherein the first flow rate is determined by a first flow sensor disposed between the inlet of the first pump and the heating zone and communicatively connected to the controller, wherein the second flow rate is determined by a second flow sensor disposed downstream of the flow control device and communicatively connected to the controller, and wherein the third flow rate is determined by a third flow sensor communicatively connected to the fluid metering device and the controller.

12. The method of claim 10 or 11, wherein the flow control device is a second pump operating at a second pump speed to generate a second flow rate.

13. The method according to any one of claims 10-12, wherein the diluent is water or an aqueous composition.

14. The method according to any one of claims 10 to 13, wherein the controller controls the density of the expanded microspheres by controlling at least a second flow rate.

15. The apparatus according to any one of claims 1-9 or the method according to any one of claims 10-14, wherein the controller is further programmed to receive an initial density value and / or an initial solids content value of the slurry of unexpanded thermally expandable microspheres, and to calculate the density of the expanded microspheres in response to at least a first flow rate, a second flow rate, a third flow rate, and one or both of the initial density value or the initial solids content value.

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