Foaming device and foaming process of thermal expansion microspheres, expansion microspheres and application

Abstract

The invention discloses a foaming device and a foaming process of a thermal expansion microsphere, the thermal expansion microsphere and application, belongs to the technical field of foaming of the thermal expansion microsphere, and overcomes the defect of inconsistent foaming effect caused by non-uniform heating of the thermal expansion microsphere by a foaming device in the prior art. The foaming device for the thermal expansion microspheres comprises a stock bin, a feeder and an expansion chamber, the expansion chamber comprises a shell and a guide cylinder arranged in the shell, the shell and the outer wall of the guide cylinder form a first cavity with a closed upper end and an open lower end, and the shell and the inner wall of the guide cylinder form a second cavity; heating devices are arranged on the inner wall of the shell of the first cavity and the outer wall of the guide cylinder; the stock bin is connected with an inlet pipeline of the feeder, and an outlet pipeline of the feeder is tangentially connected with the first cavity. The foaming device is uniform in heating and does not need stirring.

Description

Technical Field

[0001] The invention belongs to the technical field of foaming of heat-expandable microspheres, and in particular relates to a foaming device, a foaming process, expanded microspheres and applications of heat-expandable microspheres. Background Art

[0002] Heat-expandable microspheres are polymer particles with a core-shell structure, with a thermoplastic polymer as the shell and a foaming agent (low-boiling-point alkane or other compound) as the core. When the microspheres are heated, the internal foaming agent vaporizes or decomposes to generate pressure, and the shell wall softens. If the thermoplasticity of the capsule wall polymer matches the pressure generated by the internal foaming agent properly, the microspheres can show good expansion performance. After cooling, the polymer shell does not shrink. After expansion, the volume can be expanded to dozens or even hundreds of times the original, and the density is reduced to 2.5% to 7.5% of the original. It can be used in printing and dyeing, printing and other industries to obtain three-dimensional effect products; it can be used as a foaming agent or lightweight filler, and is used in the extrusion or injection molding of thermoplastic materials; it can be used as an adhesive to improve the strength of the node; it can be used as a micro-etching liquid container, and is used in the electronic materials industry for chemical mechanical polishing.

[0003] However, the existing foaming devices have problems of uneven heating and inconsistent foaming effects for foaming heat-expandable microspheres. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that the foaming device heats the heat-expandable microspheres unevenly, resulting in inconsistent foaming effects, thereby providing a foaming device, foaming process, expanded microspheres and applications of heat-expandable microspheres.

[0005] To this end, the present invention provides the following technical solutions.

[0006] In a first aspect, the present invention provides a foaming device for heat-expandable microspheres, comprising a silo, a feeder, and an expansion chamber;

[0007] The expansion chamber comprises a shell and a guide tube arranged in the shell, wherein the shell and the outer wall of the guide tube form a first chamber with a closed upper end and an open lower end, and the shell and the inner wall of the guide tube form a second chamber;

[0008] A heating device is provided on the inner wall of the shell of the first chamber and the outer wall of the guide tube;

[0009] The silo is connected to an inlet pipe of the feeder, and an outlet pipe of the feeder is tangentially connected to the first chamber.

[0010] The outer wall of the guide tube is 0.3-1.5 m away from the inner wall of the expansion chamber; preferably, the distance is 0.65-1.26 m.

[0011] In a possible implementation manner, an ultrasonic vibration generator is provided on the housing;

[0012] In a possible implementation manner, a gas flow aid is provided at the bottom of the expansion chamber, and the gas flow aid introduces compressed gas into the expansion chamber;

[0013] In a possible implementation, the silo is provided with an air hammer, which impacts the silo intermittently to prevent the heat-expandable microspheres from bridging in the silo. Optionally, the air hammer is provided at the conical portion of the silo.

[0014] In a possible implementation manner, the feeder is a jet feeder; the material in the silo is pumped into the expansion chamber through the jet feeder.

[0015] In a possible implementation manner, the inner wall of the shell is provided with a non-stick coating. Optionally, the thickness of the non-stick coating is 10 to 50 μm.

[0016] In a possible implementation manner, the foaming device further includes a cooling device, and the material outlet of the expansion chamber is connected to the cooling device;

[0017] Optionally, the cooling device is a fluidized bed;

[0018] Optionally, the cooling device comprises a cold air distribution plate;

[0019] Optionally, the cooling device is provided with a dust collector;

[0020] Optionally, the dust collector is a bag dust collector; preferably, the precision of the bag dust collector is 100 to 500 meshes.

[0021] Optionally, the heating device is an infrared generator, and the infrared may be electric infrared or catalytic infrared.

[0022] In a second aspect, the present invention provides a foaming process for heat-expandable microspheres, using the foaming device, comprising:

[0023] The heat-expandable microspheres in the silo are tangentially fed into the first chamber through a feeder, rotate downward under the condition of heating in the first chamber, then enter the second chamber from the lower end opening of the first chamber, and then enter the cooling device for cooling to obtain expanded microspheres.

[0024] In a possible implementation, the feeder is a jet feeder, which feeds the heat-expandable microspheres tangentially into the first chamber through a power gas source;

[0025] Optionally, the power gas source is a protective gas, exemplarily nitrogen;

[0026] Optionally, the material flow rate fed into the first chamber is 15 to 25 m / s.

[0027] In a possible implementation, the heat-expandable microspheres enter the second chamber from the lower opening of the first chamber and are driven by the compressed gas to flow upward;

[0028] Optionally, the pressure of the pulsed compressed gas is 0.4-0.6MpaG;

[0029] Optionally, the compressed gas is a pulsed compressed gas, and the agglomerated microspheres are broken up by the pulsed compressed gas.

[0030] Optionally, the temperature of the compressed gas is below 80-200°C; preferably, the temperature of the compressed gas is 110-150°C;

[0031] Optionally, the temperature in the first chamber is 80-200° C.; preferably, the temperature in the first chamber is 110-140° C. After infrared heating in the first chamber, the heat-expandable microspheres soften their shells, increase their elasticity, and expand their volumes.

[0032] In a possible implementation, the power density of the ultrasonic vibration generator provided on the housing is 0.35 to 0.6 W / cm 2 , preferably 0.5 to 0.55 W / cm 2 .

[0033] In a possible implementation, the heat-expandable microspheres are cooled to below 80° C. in a cooling device;

[0034] In a possible implementation manner, the total amount of intake air of the cooling device is less than or equal to the total amount of exhaust air of the cooling device.

[0035] When the total amount of air intake of the cooling device is less than the total amount of exhaust of the cooling device, the cooling device performs a decompression operation. After the microsphere shell softens, the internal and external pressure difference can cause the sphere to expand secondary.

[0036] Optionally, cooling gas is introduced into the cooling device to cool the material introduced into the cooling device from the second chamber;

[0037] Optionally, the flow rate of the cooling gas entering the cooling device is 190-750 Nm 3 / h, total exhaust volume is 550~78500Nm 3 / h.

[0038] Optionally, the cooling gas is a protective gas, preferably nitrogen;

[0039] Optionally, the temperature of the cooling gas is below room temperature;

[0040] In a possible embodiment, the residence time of the heat-expandable microspheres in the expansion chamber is 1 to 5 minutes, preferably 2.1 to 4.2 minutes. The residence time in the expansion chamber refers to the total residence time in the first chamber and the second chamber. The residence time within the range defined in the present invention can avoid the microspheres from breaking, causing agglomeration and skinning.

[0041] In one possible embodiment, the bulk density of the heat-expandable microspheres is 0.4 to 0.6 g / cm 3 Preferably, the bulk density of the heat-expandable microspheres is 0.42 to 0.5 g / cm 3 .

[0042] In a third aspect, the present invention provides an expanded microsphere, which is produced by using the foaming device or foaming process;

[0043] Optionally, the bulk density of the expanded microspheres is 0.02 to 0.2 g / cm 3 .

[0044] In a fourth aspect, the present invention provides an application of expanded microspheres in the preparation of electronic materials.

[0045] The heat-expandable microspheres are a core-shell structure, the shell layer is composed of a thermoplastic polymer and the core is a foaming agent.

[0046] Optionally, the foaming agent is a low-boiling alkane or other compound, including one or more of propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, cyclohexane, petroleum ether, n-heptane, and isooctane.

[0047] The shell layer is composed of a thermoplastic polymer; illustratively, the monomer of the thermoplastic polymer contains N-hydroxyalkyl acrylamide or at least two different ethylenically unsaturated monomers and at least one metal comonomer or conjugated diene, or is modified with a hydrophilic substance.

[0048] Furthermore, the inner wall of the expansion chamber is provided with a non-stick coating; preferably, the thickness of the non-stick coating is 10-50 μm, preferably 30-40 μm. Optionally, the non-stick coating is made of PTFE (polytetrafluoroethylene) or its modified product.

[0049] The foaming device and method provided by the present invention can heat-expandable microspheres to soften the shell by heat through an infrared generator, and the gas in the shell expands by heat. The gas flow aid at the bottom of the expansion chamber emits compressed gas to further impact the microspheres and expand and dry by heat, and then cool and solidify through a fluidized bed, and then package them, so as to obtain expanded microspheres without using a rotating device (stirring structure) and without using additional additives.

[0050] The technical solution of the present invention has the following advantages:

[0051] 1. The foaming device of heat-expandable microspheres of the present invention comprises a silo, a feeder and an expansion chamber; the expansion chamber comprises a shell and a guide tube arranged in the shell, the shell and the outer wall of the guide tube form a first chamber with a closed upper end and an open lower end, and the shell and the inner wall of the guide tube form a second chamber; a heating device is provided on the inner wall of the shell and the outer wall of the guide tube of the first chamber; the silo is connected to the inlet pipe of the feeder, and the outlet pipe of the feeder is tangentially connected to the first chamber.

[0052] The shell and the outer wall of the guide tube form a first chamber with a closed upper end and an open lower end, and a heating device is provided on the inner wall of the shell and the outer wall of the guide tube of the first chamber. The spatial structure of the first chamber limits the heating space and shortens the heating distance, thereby avoiding the problem of large temperature difference between the center of the expansion chamber and the position close to the wall of the expansion chamber and uneven heating. The present invention can ensure the heating uniformity of the heat-expandable microspheres without providing an agitator, and can avoid the rupture of the microspheres caused by stirring.

[0053] The outlet pipe of the feeder is tangentially connected to the first chamber, that is, the heat-expandable microspheres enter the expansion chamber together with the gas that drives the heat-expandable microspheres into the expansion chamber. The movement paths of the gas and the heat-expandable microspheres are consistent, and they move tangentially along the wall surface used for heating, further improving the heating uniformity.

[0054] Furthermore, the device of the present invention can carry out continuous production of expanded microspheres with high production efficiency.

[0055] 2. The foaming process of the heat-expandable microspheres of the present invention adopts the foaming device, and the foaming process includes: the heat-expandable microspheres in the silo are tangentially fed into the first chamber through the power gas source of the jet feeder, the heat-expandable microspheres rotate downward under the condition of heating in the first chamber, and then enter the second chamber from the lower end opening of the first chamber, and then enter the cooling device for cooling to obtain expanded microspheres.

[0056] The device of the present invention can be used to perform dry foaming on heat-expandable microspheres, and no additives need to be introduced during the foaming process. The prepared expanded microspheres have high cleanliness and can be used in the preparation of electronic materials, for example, as micro-etching liquid containers in chemical mechanical polishing.

[0057] 3. The compressed gas drives the heated and expanded microspheres in the first chamber to flow upward, and at the same time has a certain impact and dispersion effect on the agglomerated microspheres. The use of hot compressed gas can make the microspheres further expand in the second chamber.

[0058] 4. An ultrasonic vibration generator is set on the shell, and the power density of the ultrasonic vibration generator is 0.35~0.6W / cm 2The ultrasonic vibration of the expansion chamber wall causes the heat-expandable microspheres to form a straight flow on the expansion chamber wall, preventing the microspheres from approaching the wall and adhering to it, thereby reducing the aggregation and adhesion of the polymer on the wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 A schematic diagram of a thermally expandable microsphere foaming device;

[0061] Figure 2 It is a schematic diagram of the tangential connection between the outlet pipe of the jet feeder and the first chamber.

[0062] Reference numerals:

[0063] 1- silo, 2- air hammer, 3- jet feeder, 4- expansion chamber, 401- shell; 402- guide tube; 5- heating device, 6- ultrasonic vibration generator, 7- gas flow aid, 8- cooling device, 9- cold air distribution plate, 10- bag dust collector, 11- fan, 12- packaging equipment, 13- first chamber; 14- second chamber. DETAILED DESCRIPTION

[0064] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0065] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0066] The heat expandable microspheres used in Examples 2 to 7 were prepared according to CN 117924788 A, and the bulk density of the heat expandable microspheres was 0.4 to 0.6 g / cm 3 .

[0067] Example 1

[0068] This embodiment provides a thermally expandable microsphere foaming device, such as Figure 1, Figure 2 As shown, it includes a silo 1, a jet feeder 3 and an expansion chamber 4; the expansion chamber 4 includes a shell 401 and a guide tube 402 arranged in the shell, the shell 401 and the outer wall of the guide tube 402 form a first chamber 13 with a closed upper end and an open lower end, and the shell 401 and the inner wall of the guide tube 402 form a second chamber 14; the inner wall of the shell 401 of the first chamber 13 and the outer wall of the guide tube 402 are both provided with a heating device 5; the silo 1 is connected to the inlet pipe of the jet feeder 3, and the outlet pipe of the jet feeder 3 is tangentially connected to the first chamber 13. In this embodiment, the heating device 5 is an infrared generator, and the infrared is electric infrared.

[0069] The shell 401 is provided with an ultrasonic vibration generator 6. The bottom of the expansion chamber 4 is provided with a gas flow aid 7, which introduces pulsed compressed gas into the expansion chamber 4; and the conical part of the silo 1 is provided with an air hammer 2.

[0070] The heat-expandable microsphere foaming device further comprises a cooling device 8, and the material outlet of the expansion chamber 4 is connected to the cooling device 8. Figure 1 As shown, in this embodiment, the material outlet of the expansion chamber 4 is arranged at the top of the second chamber 14. The cooling device 8 in this embodiment is a fluidized bed; the fluidized bed includes a cold air distribution plate 9 inside, and the cold air distribution plate 9 is arranged at the bottom of the fluidized bed.

[0071] The cooling device 8 is provided with a bag dust collector 10 . In this embodiment, the bag dust collector 10 is arranged on the top of the cooling device 8 .

[0072] The inner wall of the housing 401 is provided with a non-stick coating, and the thickness of the non-stick coating is 30 μm.

[0073] The heat-expandable microsphere foaming device also includes a fan 11 and a packaging device 12. The heat-expandable microspheres in the silo 1 are brought into the expansion chamber 4 by the protective gas through the jet feeder 3, and the rising airflow in the expansion chamber 4 (including the airflow from the jet feeder into the first chamber and the airflow from the gas flow aid 7 into the second chamber) is sent to the cooling device 8 through the pipeline, and the gas phase is sent out of the boundary area by the fan 11 after dust removal by the bag filter 10, and the airflow containing the expanded microspheres enters the packaging device 12 for gas-solid separation and packaging.

[0074] Example 2

[0075] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, comprising:

[0076] The heat-expandable microspheres in the buffer silo are fed into the first chamber of the expansion chamber through a jet feeder with nitrogen as the power source. The flow rate of the material (including the power source and the heat-expandable microspheres) is 15m / s. The power of the infrared generator is adjusted to make the temperature of the first chamber 140℃, and the power density of the ultrasonic vibration generator is 0.5W / cm2 . The shell of the heat-expandable microspheres softens and expands under the action of infrared heating. When the material flows to the bottom of the first chamber and enters the second chamber, the high-temperature pulse compressed gas emitted by the gas flow aid at the bottom further expands and dries the microspheres. The temperature of the high-temperature pulse compressed gas is 145°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 3.5min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The expanded material is cooled to 80°C in the fluidized bed to solidify the shell of the expanded microspheres. Then it is sent to the packaging equipment to obtain the final product. The gas volume of the expanded material (including expanded microspheres and gas) is 355Nm 3 / h, cooling gas volume 400Nm 3 / h, the exhaust volume of the cooling device is 755Nm 3 / h.

[0077] The bulk density of the expanded microspheres obtained in this example is 0.022 g / cm 3 , particle size 37.3 μm, product yield 73%. Product yield = mass of expanded microsphere product / mass of heat-expandable microspheres entering the foaming device.

[0078] Example 3

[0079] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, including:

[0080] The material in the buffer silo is fed into the expansion chamber through a jet feeder with nitrogen as the power source, and the material flow rate is 15m / s. The power of the infrared generator is adjusted so that the temperature of the first chamber is 135℃, and the power density of the ultrasonic vibration generator is 0.5W / cm 2 , the heat-expandable microspheres produce a straight flow on the wall, reducing the adhesion of the polymer on the shell wall. The shell of the heat-expandable microspheres softens and expands under the action of infrared. When the material flows to the bottom, the high-temperature pulse compressed gas emitted by the gas flow aid at the bottom causes the microspheres to further expand and dry. The temperature of the pulse compressed gas is controlled at 140°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 4.2min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The expanded material is cooled to 80°C in the fluidized bed to solidify the microsphere shell. Then it is sent to the packaging equipment to obtain the final product. The gas volume of the expanded material (including expanded microspheres and gas) is 295Nm 3 / h, cooling gas volume 307Nm 3 / h, the exhaust volume of the cooling device is 602Nm 3 / h.

[0081] The density of the expanded microspheres was 0.030 g / cm 3, particle size 36.5μm, product yield 78%.

[0082] Example 4

[0083] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, comprising:

[0084] The material in the buffer silo is fed into the expansion chamber through a jet feeder with nitrogen as the power source, and the material flow rate is 15m / s. The power of the infrared generator is adjusted so that the temperature of the first chamber is 140℃, and the power density of the ultrasonic vibration generator is 0.5W / cm 2 , the heat-expandable microspheres produce a straight flow on the shell wall, reducing the adhesion of the polymer on the wall. The shell of the heat-expandable microspheres softens and expands under the action of infrared. When the material flows to the bottom, the high-temperature compressed gas emitted by the gas flow aid at the bottom causes the microspheres to further expand and dry. The temperature of the pulsed compressed gas is controlled at 145°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 2.5min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The expanded material is cooled to 80°C in the fluidized bed to solidify the microsphere shell. Then it is sent to the packaging equipment to obtain the final product. The gas volume of the expanded material (including expanded microspheres and gas) is 494Nm 3 / h, cooling gas volume 561Nm 3 / h, the exhaust volume of the cooling device is 1055Nm 3 / h.

[0085] The density of the expanded microspheres was 0.034 g / cm 3 , particle size 31.8μm, product yield 85%.

[0086] Example 5

[0087] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, comprising:

[0088] The material in the buffer silo is fed into the expansion chamber through a jet feeder with nitrogen as the power source, and the material flow rate is 15m / s. The power of the infrared generator is adjusted so that the temperature of the first chamber is 110℃, and the power density of the ultrasonic vibration generator is 0.5W / cm 2, the heat-expandable microspheres produce a straight flow on the wall, reducing the adhesion of the polymer on the wall. The shell of the heat-expandable microspheres softens and expands under the action of infrared. When the material flows to the bottom, the high-temperature compressed gas emitted by the gas flow aid at the bottom causes the microspheres to further expand and dry. The temperature of the pulsed compressed gas is controlled at 150°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 4.2min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The expanded material is cooled to 80°C in the fluidized bed to solidify the microsphere shell. Then it is sent to the packaging equipment to obtain the final product. The gas volume of the expanded material (including expanded microspheres and gas) is 295Nm 3 / h, cooling gas volume 266Nm 3 / h, the exhaust volume of the cooling device is 561Nm 3 / h.

[0089] The density of the expanded microspheres was 0.035 g / cm 3 , particle size 31.5μm, product yield 75%.

[0090] Example 6

[0091] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, including:

[0092] The material in the buffer silo is fed into the expansion chamber through a jet feeder with nitrogen as the power source, and the material flow rate is 15m / s. The power of the infrared generator is adjusted so that the temperature of the first chamber is 110℃, and the power density of the ultrasonic vibration generator is 0.5W / cm 2 The heat-expandable microspheres produce a straight flow on the wall, reducing the adhesion of the polymer on the wall. The shell of the heat-expandable microspheres softens and expands under the action of infrared. When the material flows to the bottom, the high-temperature compressed gas emitted by the gas flow aid at the bottom causes the microspheres to further expand and dry. The temperature of the pulsed compressed gas is controlled at 120°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 4.2min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The gas volume of the expanded material (including expanded microspheres and gas) is 295Nm 3 / h, cooling gas volume 187Nm 3 / h, the exhaust volume of the cooling device is 28375Nm 3 / h, reduce the fluidized bed pressure to produce a 3 bar pressure difference, the microspheres further expand under the internal and external pressure difference, and the expanded material is cooled to 80°C in the fluidized bed to solidify the microsphere shell. Then it is sent to the packaging equipment to obtain the final product.

[0093] The density of the expanded microspheres was 0.038 g / cm 3, particle size 34.8μm, product yield 77%.

[0094] Example 7

[0095] This embodiment provides a thermally expandable microsphere foaming process, using the device of embodiment 1, including:

[0096] The material in the buffer silo is fed into the expansion chamber through a jet feeder with nitrogen as the power source, and the material flow rate is 15m / s. The power of the infrared generator is adjusted so that the temperature of the first chamber is 140℃, and the power density of the ultrasonic vibration generator is 0.25W / cm 2 , the heat-expandable microspheres produce a straight flow on the wall, reducing the adhesion of the polymer on the wall. The shell of the heat-expandable microspheres softens and expands under the action of infrared. When the material flows to the bottom, the high-temperature compressed gas emitted by the gas flow aid at the bottom causes the microspheres to further expand and dry. The temperature of the pulsed compressed gas is controlled at 145°C and the pressure is 0.4MPaG. The residence time of the microspheres in the expansion chamber is controlled at 3.5min. The expanded material enters the fluidized bed, and cooling gas nitrogen is introduced into the fluidized bed. The expanded material is cooled to 80°C in the fluidized bed to solidify the microsphere shell. Then it is sent to the packaging equipment to obtain the final product. The gas volume of the expanded material (including expanded microspheres and gas) is 353Nm 3 / h, cooling gas volume 401Nm 3 / h, the exhaust volume of the cooling device is 754Nm 3 / h.

[0097] The density of the expanded microspheres was 0.039 g / cm 3 , particle size 40.1μm, product yield 55%.

[0098] Compared with Example 2, the product yield decreased, the ultrasonic power density was reduced, the straight flow effect of the microspheres was significantly reduced, and the microsphere shell softened and adhered to the inner wall of the expansion chamber during the flow process, affecting heat transfer and thus affecting the expansion of the microspheres.

[0099] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A foaming device for heat-expandable microspheres, characterized in that: It includes a silo, a feeder and an expansion chamber; The expansion chamber comprises a shell and a guide tube arranged in the shell, wherein the shell and the outer wall of the guide tube form a first chamber with a closed upper end and an open lower end, and the shell and the inner wall of the guide tube form a second chamber; A heating device is provided on the inner wall of the shell of the first chamber and the outer wall of the guide tube; The silo is connected to an inlet pipe of the feeder, and an outlet pipe of the feeder is tangentially connected to the first chamber.

2. The foaming device of heat-expandable microspheres according to claim 1, characterized in that: At least one of the following conditions is met: (1) An ultrasonic vibration generator is provided on the housing; (2) A gas flow aid is provided at the bottom of the expansion chamber, and the gas flow aid introduces compressed gas into the expansion chamber; (3) The silo is provided with a pneumatic hammer; (4) The feeder is a jet feeder; (5) The inner wall of the shell is provided with a non-stick coating. Optionally, the thickness of the non-stick coating is 10 to 50 μm.

3. The foaming device of heat-expandable microspheres according to claim 1, characterized in that: The foaming device further comprises a cooling device, and the material outlet of the expansion chamber is connected to the cooling device; Optionally, the cooling device is a fluidized bed; Optionally, the cooling device comprises a cold air distribution plate; Optionally, the cooling device is provided with a dust collector; Optionally, the dust collector is a bag dust collector; Optionally, the heating device is an infrared generator.

4. A foaming process for heat-expandable microspheres, characterized in that: The foaming device according to any one of claims 1 to 3 comprises: The heat-expandable microspheres in the silo are tangentially fed into the first chamber through a feeder, rotate downward under the condition of heating in the first chamber, then enter the second chamber from the lower end opening of the first chamber, and then enter the cooling device for cooling to obtain expanded microspheres.

5. The foaming process of heat-expandable microspheres according to claim 4, characterized in that: The feeder is a jet feeder, which feeds the heat-expandable microspheres tangentially into the first chamber through a power gas source; Optionally, the power gas source is a protective gas, preferably nitrogen; Optionally, the material flow rate fed into the first chamber is 15 to 25 m / s.

6. The foaming process of heat-expandable microspheres according to claim 4 or 5, characterized in that: After the heat-expandable microspheres enter the second chamber from the lower opening of the first chamber, they are driven by the compressed gas to flow upward; Optionally, the pressure of the compressed gas is 0.4-0.6MpaG; Optionally, the temperature of the compressed gas is below 80-200°C; preferably, the temperature of the compressed gas is 110-150°C; Optionally, the temperature in the first chamber is 80-200°C; preferably, the temperature in the first chamber is 110-140°C.

7. The foaming process of heat-expandable microspheres according to claim 4 or 5, characterized in that: The power density of the ultrasonic vibration generator installed on the shell is 0.35~0.6W / cm 2 .

8. The foaming process of heat-expandable microspheres according to claim 4 or 5, characterized in that: At least one of the following conditions is met: (1) The heat-expandable microspheres are cooled to below 80° C. in a cooling device; (2) The total amount of air intake of the cooling device is less than or equal to the total amount of exhaust of the cooling device; (3) The residence time of the heat-expandable microspheres in the expansion chamber is 1 to 5 minutes; (4) The bulk density of the heat-expandable microspheres is 0.4 to 0.6 g / cm 3 Preferably, the bulk density of the heat-expandable microspheres is 0.42 to 0.5 g / cm 3 .

9. An expanded microsphere, characterized in that: Made by using the foaming device described in any one of claims 1 to 3 or the foaming process described in any one of claims 4 to 8; Optionally, the bulk density of the expanded microspheres is 0.02 to 0.2 g / cm 3 .

10. Use of the expanded microspheres according to claim 9 in the preparation of electronic materials.

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