Low-temperature drying equipment and drying method for thermal expansion microspheres

Abstract

The invention relates to the technical field of thermal expansion microsphere drying and dehydration, in particular to a low-temperature drying device and method for thermal expansion microspheres, the drying device comprises a microsphere slurry pre-liquid-removing device, and the microsphere slurry pre-liquid-removing device is internally provided with a filter screen and a stirring blade; a feeding port of the single-screw drying and conveying device is communicated with a discharging port of the microsphere slurry pre-dewatering device, and the interior of the single-screw drying and conveying device is under a negative pressure heating condition; a discharge port of the single-screw drying and conveying device is communicated with a feed port of the pneumatic drying device, and an umbrella-shaped filtering assembly is arranged in the pneumatic drying device. According to the drying equipment and the drying method, energy consumption can be reduced, bonding in the microsphere drying process can be effectively prevented, the bad defects that particles have holes or pits or shrinkage or the like are overcome, the dried microspheres are good in appearance, and the dried thermal expansion microspheres can be continuously and rapidly obtained at a time.

Description

Technical Field

[0001] The present invention relates to a low-temperature drying device and a drying method for thermally expandable microspheres, belonging to the technical field of drying and dehydrating thermally expandable microspheres. Background Art

[0002] Thermally expandable microspheres are a kind of polymer material with a core-shell structure. The outer shell and the core material reach the glass transition temperature and boiling point respectively under heating conditions, and then soften and vaporize, finally realizing the expansion of the thermally expandable microspheres. The huge expansion ability of thermally expandable microspheres makes them have good applications in reducing the mass of products, changing the properties of products and saving the amount of materials used. In the aspect of coatings, the three-dimensional effect of wallpaper can be achieved and the effects of heat preservation and sound insulation can be realized. Thermally expandable microspheres can reduce the weight in the automotive field, and can also play a role in improving corrosion resistance and reducing noise. In addition, applying thermally expandable microspheres at the adhesive joint can achieve rapid destruction of the adhesive joint, so thermally expandable microspheres also have good applications in the field of thermally expandable tapes.

[0003] Thermally expandable microspheres need to remove moisture in many important application fields and be used as additives or fillers in a dry and free-flowing form. Many existing technologies have disclosed methods for drying expandable microspheres, but the currently disclosed drying methods all have certain defects and cannot ensure good drying effect, non-damage of microspheres and energy-saving effect during the microsphere drying process, and continuous drying cannot be achieved.

[0004] The patent application with the publication number CN102633936A discloses a method for preparing dry expandable microspheres by spray drying. However, this method requires a relatively high drying temperature, which is not conducive to the drying of expandable microspheres, especially low-temperature foaming microspheres, and is likely to cause the expansion of microspheres during the drying process. In addition, spray drying has disadvantages such as high energy consumption, high cost, product loss and serious environmental dust.

[0005] The patent application with the publication number CN1093830663A mentions a device using a twin-screw for solid-liquid separation. Since in most cases, a screw press can remove liquid as much as possible, it can simplify the subsequent drying and make the drying more economical. Due to the continuous stirring of the screw for the material, the situation where the material wraps moisture inside is largely avoided, making the dehydration more thorough. However, due to the easy agglomeration problem during the powder filtration, this device cannot solve the agglomeration problem during the dehydration of the slurry of expandable microspheres. At the same time, the strong shearing of the twin-screw on the thermally expandable microspheres will also cause a part of the microspheres to be lost and have a certain impact on the appearance.

[0006] Therefore, the existing microsphere drying methods still need to be further improved, and there is an urgent need for a drying method and a continuous preparation process that can solve the problems of microsphere agglomeration, reduce damage, and save energy. Summary of the Invention

[0007] In view of the deficiencies of the existing technology, the present invention provides a low-temperature drying device and a drying method for thermally expandable microspheres. The drying device and the drying method can reduce energy consumption, effectively prevent the adhesion of microspheres during the drying process, solve the problems of poor defects such as holes, depressions or shrinkage in the particles, the appearance of the dried microspheres is good, and the dried thermally expandable microspheres can be obtained continuously and quickly at one time.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: A low-temperature drying device for thermally expandable microspheres, the drying device includes:

[0009] A microsphere slurry pre-dehydration device, in which a filter screen and stirring blades are provided;

[0010] A single-screw drying and conveying device, the feed port of the single-screw drying and conveying device is connected to the discharge port of the microsphere slurry pre-dehydration device, and the inside of the single-screw drying and conveying device is under negative pressure heating conditions;

[0011] An air-flow drying device, the discharge port of the single-screw drying and conveying device is connected to the feed port of the air-flow drying device, and an umbrella-shaped filter assembly is provided inside the air-flow drying device.

[0012] Further, the microsphere slurry pre-dehydration device includes a cylindrical conical shell, a cylindrical conical filter screen is provided inside the shell, the filter screen is a Johnson screen, the stirring blades are conical spiral stirring blades, a differential pressure transmitter is installed between the upper part and the lower part of the microsphere slurry pre-dehydration device, and the differential pressure transmitter is associated with a regulating valve at the discharge port of the microsphere slurry pre-dehydration device.

[0013] Further, a single-screw is provided inside the single-screw drying and conveying device, and from the feed port to the discharge port of the single-screw drying and conveying device, the pitch of the single-screw gradually increases.

[0014] Further, the discharge port of the single-screw drying and conveying device is in a horn cone shape, and the angle of the horn cone shape is 55-65°; the horn cone-shaped discharge port is directly above the umbrella-shaped filter assembly.

[0015] Further, in the air-flow drying device, the top cone angle of the umbrella-shaped filter assembly is 40-50°, and the umbrella-shaped filter assembly is made of Johnson screen.

[0016] The present invention also discloses a drying method for thermally expandable microspheres. The thermally expandable microspheres are dried using the drying equipment of the present invention. The drying method is as follows:

[0017] The microsphere slurry is added into the microsphere slurry pre-dehydration device. Through the filter screen, part of the liquid in the microsphere slurry is removed, and then it enters the single-screw drying and conveying device. Under the condition of negative pressure heating, the microsphere slurry is dried again, and finally it enters the pneumatic drying device, where hot air drying is used to finally obtain the dried thermally expandable microspheres.

[0018] Further, when the microsphere slurry is added into the microsphere slurry pre-dehydration device, the water content is 70-80%, and the feeding speed is 15-50 kg / h.

[0019] The pressure difference between the inlet and outlet of the microsphere slurry pre-dehydration device is 0.1 MPa - 1 Mpa.

[0020] Further, when the microsphere slurry enters the single-screw drying and conveying device, the water content is 30-40%. In the single-screw drying and conveying device, the microsphere slurry is conveyed by a single screw, and the conveying speed is 0.1-0.3 m / s.

[0021] The heating temperature in the single-screw drying and conveying device is 70-90 °C, and the absolute vacuum pressure is 1-10×10 3 Pa.

[0022] Further, when the microsphere slurry enters the pneumatic drying device, the water content is 10-15%.

[0023] The hot air in the pneumatic drying device is heated and dried hot air, and the temperature of the hot air is 50-70 °C.

[0024] Further, both the microsphere slurry pre-dehydration device and the pneumatic drying device are provided with Johnson filter screens, and the gap of the Johnson filter screens is 100-200 meshes.

[0025] The beneficial effects of the present invention are as follows:

[0026] The drying method of the present invention realizes the continuous low-temperature drying of microspheres through the combination of filtration dehydration, screw conveying and vacuum heating drying, and pneumatic drying in sequence, which can effectively prevent the microspheres from sticking and deforming during the drying process, improve the production efficiency, and achieve the purpose of energy conservation and environmental protection at the same time.

[0027] In the drying equipment of the present invention, a conical spiral blade is built into the microsphere slurry pre-dehydration device. Under the combined action of the pressure difference and the conical spiral blade, the slurry on the surface of the Johnson screen is continuously updated, making it more convenient to filter out the water in the slurry. In the single-screw drying and conveying device, single-screw conveying can avoid the problems of excessive shear force and adhesion and agglomeration caused by double screws. Moreover, the pitch of the single screw is small at the front and large at the back. The small pitch at the front is convenient for dispersing the pre-dehydrated microsphere slurry, and the increased pitch at the back can reduce the shear force on the microsphere slurry, avoiding damage to the microspheres during drying and conveying, and can also achieve accurate conveying of the microsphere slurry. In the single-screw drying and conveying device, due to the continuous stirring of the screw on the material, the situation where the material wraps the water inside is largely avoided. In coordination with appropriate temperature and pressure conditions, the microspheres can be dehydrated more thoroughly. The slurry conveyed by the single screw is sprayed from the trumpet-shaped discharge port onto the umbrella surface of the umbrella-shaped filter assembly in the pneumatic drying device. The microsphere slurry slowly flows downward along the umbrella surface and falls after reaching the edge of the umbrella surface under the drying of the gas flowing upward on the umbrella surface, and convective heat transfer occurs with the hot air blown in from the bottom for further drying and then becomes a qualified product, obtaining the dried thermally expanded microspheres. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the low-temperature drying equipment for thermally expanded microspheres in the embodiment of the present invention;

[0029] Figure 2 It is a schematic structural diagram of the Johnson screen;

[0030] Figure 3 It is an SEM diagram of the thermally expanded microspheres obtained in Example 5;

[0031] In the figure, 1. Microsphere slurry pre-dehydration device; 2. Single-screw drying and conveying device; 3. Pneumatic drying device; 4. Housing; 5. Slurry inlet; 6. Filter screen; 7. Water outlet; 8. Conical spiral stirring blade; 9. Differential pressure transmitter; 10. Control valve; 11. Jacket; 12. Hot water inlet; 13. Hot water outlet; 14. Exhaust port; 15. Trumpet-shaped discharge port; 16. Umbrella-shaped filter assembly; 17. Inner cylinder of pneumatic drying; 18. Outer cylinder of pneumatic drying; 19. First hot air inlet; 20. Second hot air inlet; 21. Material outlet. Detailed Embodiments

[0032] The following makes a detailed description of the specific embodiments of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0034] As Figure 1 shown, a low-temperature drying device for thermal expansion microspheres, the drying device comprising:

[0035] A microsphere slurry pre-dehydration device 1, in which a filter screen 6 and stirring blades are provided;

[0036] A single-screw drying and conveying device 2, the feed port of the single-screw drying and conveying device 2 is connected to the discharge port of the microsphere slurry pre-dehydration device 1, and the inside of the single-screw drying and conveying device 2 is under negative pressure heating conditions;

[0037] An air-flow drying device 3, the discharge port of the single-screw drying and conveying device 2 is connected to the feed port of the air-flow drying device 3, and an umbrella-shaped filter assembly 16 is provided inside the air-flow drying device 3.

[0038] Specifically, the microsphere slurry pre-dehydration device 1 includes a cylindrical conical shell 4, a slurry inlet 5 is provided at the upper end of the shell 4, a cylindrical conical filter screen 6 is provided inside the shell 4, the filter screen 6 is a Johnson screen, and a certain annular gap is maintained between the shell 4 and the filter screen 6 to facilitate the removal of water in the microsphere slurry. A water outlet 7 is provided at the lower end of the shell 4, the stirring blades are conical spiral stirring blades 8, a differential pressure transmitter 9 is installed between the upper and lower parts of the microsphere slurry pre-dehydration device 1, and the differential pressure transmitter 9 is associated with a regulating valve 10 at the discharge port of the microsphere slurry pre-dehydration device 1.

[0039] Specifically, a single-screw is provided inside the single-screw drying and conveying device 2. From the feed port to the discharge port of the single-screw drying and conveying device 2, the pitch of the single-screw gradually increases from small to large.

[0040] Preferably, the pitch of the single-screw is 0.5 - 2.0 times the diameter of the screw, and the pitch gradually increases from small to large within this range. A smaller pitch at the front is convenient for dispersing the pre-dehydrated microsphere slurry, and a larger pitch at the rear can reduce the shear on the microsphere slurry and also achieve accurate conveying of the slurry.

[0041] More specifically, the single-screw drying and conveying device 2 is provided with an external jacket 11. The single-screw drying and conveying device 2 is heated by passing hot water into the jacket 11. A hot water inlet 12 is provided on the lower side of the jacket 11, and a hot water outlet 137 is provided on the upper side of the jacket 11. The jacket 11 is internally provided with spiral turbulators, which can enhance the drying effect of hot water on the microsphere slurry. An exhaust port 14 is provided on the inner cylinder of the single-screw drying and conveying device 2, and the exhaust ports 14 are equally spaced at the upper end of the single-screw drying and conveying device 2.

[0042] Specifically, the discharge port of the single-screw drying and conveying device 2 is in a horn cone shape, and the angle of the horn cone is 55 - 65°; the horn cone-shaped discharge port 15 is directly above the umbrella-shaped filter assembly 16.

[0043] Specifically, in the pneumatic drying device 3, the top cone angle of the umbrella-shaped filter assembly 16 is 40 - 50°, and the umbrella-shaped filter assembly 16 is made of Johnson screen.

[0044] More specifically, if the angle of the horn cone-shaped discharge port 15 is A and the top cone angle of the umbrella-shaped filter assembly 16 is B, then B = b ± 1, where b = -60ln(A) + 290. When the angle relationship between the horn cone-shaped discharge port 15 and the umbrella-shaped filter assembly 16 meets this condition, it is more conducive to achieving efficient drying of the thermally expanded microspheres and avoiding damage to the thermally expanded microspheres during the drying process.

[0045] More specifically, the pneumatic drying device 3 includes a pneumatic drying inner cylinder 17 and a pneumatic drying outer cylinder 18. The umbrella-shaped filter assembly 16 is provided at the upper end of the pneumatic drying inner cylinder 17. A first hot air inlet 19 is provided at the lower end of the pneumatic drying inner cylinder 17. A second hot air inlet 20 is provided on one side of the pneumatic drying outer cylinder 18, and a material outlet 21 for the dried thermally expanded microspheres is provided on the other side of the pneumatic drying outer cylinder 18.

[0046] A drying method for thermally expanded microspheres, using the drying equipment to dry the thermally expanded microspheres. The drying method is as follows:

[0047] The microsphere slurry is added to the microsphere slurry pre-dehydration device 1. Part of the liquid in the microsphere slurry is removed through the filter screen 6, and then it enters the single-screw drying and conveying device 2. Under the condition of negative pressure heating, the microsphere slurry is dried again, and finally it enters the pneumatic drying device 3, where hot air drying is used to finally obtain the dried thermally expanded microspheres.

[0048] Specifically, when the microsphere slurry is added to the microsphere slurry pre-dehydration device 1, the water content (the water here refers to the components to be dried and removed in the microsphere slurry, and may also contain a small amount of other solvents besides water) is 70-80% (mass content, the same below), and the feeding speed is 15-50 kg / h;

[0049] The pressure difference between the inlet and outlet of the microsphere slurry pre-dehydration device 1 is 0.1 MPa - 1 Mpa.

[0050] Specifically, when the microsphere slurry enters the single-screw drying and conveying device 2, the water content is 30-40%; in the single-screw drying and conveying device 2, the microsphere slurry is conveyed by a single screw, and the conveying speed is 0.1-0.3 m / s;

[0051] The heating temperature in the single-screw drying and conveying device 2 is 70-90 °C, and the absolute vacuum pressure is 1-10×103 Pa.

[0052] Specifically, when the microsphere slurry enters the pneumatic drying device 3, the water content is 10-15%;

[0053] The hot air in the pneumatic drying device 3 is heated and dried hot air, and the temperature of the hot air is 50-70 °C.

[0054] The microsphere slurry conveyed by the single screw is sprayed from the horn-shaped conical outlet onto the umbrella surface in the pneumatic drying device 3. The slurry flows downward along the umbrella surface and is dried by the hot air flowing from bottom to top on the umbrella surface. When it reaches the edge of the umbrella surface, the water content of the microsphere slurry is 3-5%. It conducts convective heat transfer with the hot air blown from the bottom and is further dried to become a qualified product, obtaining dried thermally expandable microspheres.

[0055] Specifically, both the microsphere slurry pre-dehydration device 1 and the pneumatic drying device 3 are provided with Johnson filters 6, and the gap of the Johnson filters 6 is 100-200 mesh.

[0056] The gaps of the Johnson net are not easily deformed and will not cause thermally expandable microspheres with a size of more than 100-200 mesh to be filtered out. However, part of the water in the slurry will pass through the gaps of the Johnson net and be removed; most of the water is pre-removed through the firmness of the Johnson net and its accurate filtration accuracy, with low energy consumption and strong economy; moreover, the filter 6 uses a Johnson net, which has a high porosity and precise gap size, and the service life of the Johnson net is relatively long.

[0057] More specifically, the collection method of the finished product after the drying process also includes a cyclone separator + and a bag filter.

[0058] The thermally expandable microsphere slurry used in the embodiments of the present invention is a microsphere slurry with a water content of 70-80% obtained by suspension polymerization, and the thermally expandable microspheres therein are low-temperature microspheres (thermal expansion temperature < 100°C).

[0059] Example 1

[0060] A drying method for thermally expandable microspheres, using the drying equipment to dry the thermally expandable microspheres, the drying method is as follows:

[0061] (1) First, add the microsphere slurry with a water content of 80% into the microsphere slurry pre-dehydration device, the feeding speed is 45 kg / h, keep the pressure difference between the inlet and outlet at 0.2 Mpa, and the void size of the Johnson screen is 100 mesh.

[0062] (2) The pre-dehydrated microsphere slurry enters the single-screw drying and conveying device, wherein the conveying speed of the single-screw is 0.1 m / s, the vacuum pressure is 10×10 3 Pa (absolute pressure), and the heating temperature is 90°C.

[0063] (3) The microsphere slurry processed by the single-screw drying and conveying device passes through the trumpet-shaped discharge port. The trumpet-shaped discharge port is 60°. The microsphere slurry is sprayed from the trumpet-shaped discharge port onto the umbrella surface of the umbrella-shaped filter component in the pneumatic drying device. The umbrella-shaped filter component is made of Johnson screen, the void size of the Johnson screen is 100 mesh, and the top cone angle of the umbrella-shaped filter component is 45°. The medium temperature of the hot air is 70°C. After fluidized drying, vacuum drying, and air convection, finally, thermally expandable microspheres with good appearance, unexpanded and good dispersibility are obtained.

[0064] Example 2

[0065] The process flow of Example 2 is basically the same as that of Example 1, and the specific differences are as follows:

[0066] In step (1), add the microsphere slurry with a water content of 80% into the microsphere slurry pre-dehydration device, the feeding speed is 45 kg / h, and keep the pressure difference between the inlet and outlet at 0.3 MPa.

[0067] In step (2), the conveying speed of the single-screw remains unchanged, the medium temperature of the hot water heating remains unchanged, and the vacuum pressure remains unchanged.

[0068] In step (3), the medium temperature of the hot air remains unchanged

[0069] Finally, microspheres with good appearance, unexpanded and good dispersibility are obtained.

[0070] Example 3

[0071] The process flow of Example 3 is basically the same as that of Example 1, and the specific differences are as follows:

[0072] In step (1), microsphere slurry with a water content of 80% is added into the microsphere slurry pre-dehydration device at a feeding speed of 45 kg / h, and the pressure difference between the inlet and outlet is maintained at 0.2 MPa.

[0073] In step (2), the conveying speed of the single screw remains unchanged, and the vacuum pressure becomes 5×10 3 Pa.

[0074] In step (3), the medium temperature of the hot air remains unchanged.

[0075] Finally, microspheres with good appearance, no swelling and good dispersibility are obtained.

[0076] Example 4

[0077] The process flow of Example 4 is basically the same as that of Example 1, and the specific differences are as follows:

[0078] In step (1), microsphere slurry with a water content of 80% is added into the microsphere slurry pre-dehydration device at a feeding speed of 45 kg / h, and the pressure difference between the inlet and outlet is maintained at 0.2 MPa.

[0079] In step (2), the conveying speed of the single screw is 0.2 m / s, and the vacuum pressure is 5×10 3 Pa.

[0080] In step (3), the medium temperature of the hot air remains unchanged.

[0081] Finally, microspheres with good appearance, no swelling and good dispersibility are obtained.

[0082] Example 5

[0083] The process flow of Example 5 is basically the same as that of Example 1, and the specific differences are as follows:

[0084] In step (1), microsphere slurry with a water content of 70% is added into the microsphere slurry pre-dehydration device at a feeding speed of 45 kg / h, and the pressure difference between the inlet and outlet is maintained at 0.2 MPa.

[0085] In step (2), the conveying speed of the single screw remains unchanged, and the vacuum pressure becomes 5×10 3 Pa.

[0086] Finally, microspheres with good appearance, no swelling and good dispersibility are obtained.

[0087] Example 6

[0088] A drying method for thermally expandable microspheres, using the drying equipment to dry the thermally expandable microspheres, and the drying method is as follows:

[0089] (1) First, add microsphere slurry with a water content of 80% into the microsphere slurry pre-dehydration device at a feeding speed of 15 kg / h, maintain the pressure difference between the inlet and outlet at 0.1 Mpa, and the pore size of the Johnson screen is 100 mesh.

[0090] (2) The pre-dehydrated microsphere slurry enters the single-screw drying and conveying device, where the conveying speed of the single screw is 0.3 m / s, and the vacuum pressure is 1×10 3 Pa (absolute pressure), and the heating temperature is 70 °C.

[0091] (3) The microsphere slurry processed by the single-screw drying and conveying device passes through the horn-shaped discharge port. The horn-shaped discharge port is 65°, and the microsphere slurry is sprayed from the horn-shaped discharge port onto the umbrella surface of the umbrella-shaped filter component in the pneumatic drying device. The umbrella-shaped filter component is made of Johnson screen, the pore size of the Johnson screen is 100 mesh, and the top cone angle of the umbrella-shaped filter component is 40°. The medium temperature of the hot air is 50 °C. After fluidized drying, vacuum drying, and air convection, finally, thermally expandable microspheres with good appearance, no swelling, and good dispersibility are obtained.

[0092] Example 7

[0093] A drying method for thermally expandable microspheres, using the said drying equipment to dry the thermally expandable microspheres. The drying method is as follows:

[0094] (1) First, add microsphere slurry with a water content of 80% into the microsphere slurry pre-dehydration device at a feeding speed of 50 kg / h, maintain the pressure difference between the inlet and outlet at 1 Mpa, and the pore size of the Johnson screen is 100 mesh.

[0095] (2) The pre-dehydrated microsphere slurry enters the single-screw drying and conveying device, where the conveying speed of the single screw is 0.3 m / s, and the vacuum pressure is 5×10 3 Pa (absolute pressure), and the heating temperature is 80 °C.

[0096] (3) The microsphere slurry processed by the single-screw drying and conveying device passes through the horn-shaped discharge port. The horn-shaped discharge port is 55°, and the microsphere slurry is sprayed from the horn-shaped discharge port onto the umbrella surface of the umbrella-shaped filter component in the pneumatic drying device. The umbrella-shaped filter component is made of Johnson screen, the pore size of the Johnson screen is 100 mesh, and the top cone angle of the umbrella-shaped filter component is 50°. The medium temperature of the hot air is 60 °C. After fluidized drying, vacuum drying, and air convection, finally, thermally expandable microspheres with good appearance, no swelling, and good dispersibility are obtained.

[0097] Example 8

[0098] The process flow of Example 8 is basically the same as that of Example 1. The specific differences are as follows:

[0099] In Example 8, the horn-shaped conical discharge port is 60°, and the top cone angle of the umbrella-shaped filter component is 50°. Finally, thermally expandable microspheres with good appearance, no swelling, and good dispersibility are obtained.

[0100] Example 9

[0101] The process flow of Example 9 is basically the same as that of Example 1, and the specific differences are as follows:

[0102] In Example 9, the horn-shaped conical discharge port is 55°, and the top cone angle of the umbrella-shaped filter component is 45°. Finally, thermally expandable microspheres with good appearance, no swelling, and good dispersibility are obtained.

[0103] Comparative Example 1

[0104] Drying is carried out using the same process method as in Example 1, except that: in this Comparative Example 1, the pitch of the single screw is evenly distributed, and the pitch is 0.5 times the diameter of the screw.

[0105] Comparative Example 2

[0106] Drying is carried out using the same process method as in Example 1, except that: in this Comparative Example 2, the pitch of the single screw is evenly distributed, and the pitch is 1.5 times the diameter of the screw.

[0107] Comparative Example 3

[0108] Drying is carried out using the same process method as in Example 1, except that: in this Comparative Example 3, the discharge port of the single-screw drying and conveying device is not a horn-shaped conical discharge port, but just an ordinary tubular outlet.

[0109] Comparative Example 4

[0110] Drying is carried out using the same process method as in Example 1, except that: in this Comparative Example 4, the pneumatic dryer containing the umbrella-shaped filter component is replaced with a cyclone pneumatic dryer of the same volume and operated for the same time.

[0111] Comparative Example 5

[0112] Drying is carried out using the same process method as in Example 1, except that: in this Comparative Example 5, the medium temperature of the hot air in step (3) is 90 °C (higher than the temperature condition defined in the present invention).

[0113] The water content of the thermally expandable microspheres after drying in the above examples and comparative examples is tested, and the specific test results are shown in Table 1 below. The method for measuring the water content of the thermally expandable microspheres is as follows:

[0114] Take 100 g of the dried thermally expandable microsphere powder, place it in an oven at 50 °C, and weigh it every 0.5 h until the mass of the thermally expandable microspheres no longer changes. The formula for calculating the water content is as follows:

[0115] Among them, is the moisture content, m0 is the mass of the thermally expandable microspheres before being put into the oven, and m1 is the mass of the thermally expandable microspheres that no longer changes after being put into the oven.

[0116] Table 1 Drying conditions of thermally expandable microspheres

[0117]

[0118] The drying equipment described in the present invention includes a microsphere slurry pre-dehydration device, a single-screw vacuum heating and drying conveying device, and a pneumatic drying device. The microsphere slurry synthesized by suspension is pressurized and added to the microsphere slurry pre-dehydration device. Under the condition of maintaining the pressure difference between the inlet and the outlet, part of the water in the slurry is removed through the Johnson screen gap; the treated slurry enters the single-screw vacuum heating and drying conveying device. During the single-screw conveying process, under the vacuum and heating systems and the dispersion effect of the single screw, part of the water in the microsphere slurry is further removed; then it enters the pneumatic drying device, and after the slurry passing through the bell mouth is dispersed, fluidized heating and drying by the umbrella-shaped filter assembly and pneumatic drying by the bottom hot air, finally qualified products are obtained and collected. It can be seen from the data in the above table that: the moisture content of the thermally expandable microspheres obtained by using the drying equipment and drying method described in the present invention in Examples 1-9 is not higher than 1%, the drying effect is good, and the obtained thermally expandable microspheres have good appearance, are not expanded, and have good dispersibility. Especially in Examples 1-7, the angle of the trumpet-shaped discharge port and the angle of the top cone of the umbrella-shaped filter assembly cooperate with each other, and the moisture content of the thermally expandable microspheres after drying is lower and the drying effect is better.

[0119] In addition, SEM photographs were taken of the thermally expandable microspheres after drying in Example 5, and the photos are shown in Figure 3 , and it can be seen from Figure 3 that the dried thermally expandable microspheres are evenly dispersed, indicating that thermally expandable microspheres with good dispersibility can be obtained by the drying method described in the present invention. The present invention can reduce energy consumption, effectively prevent the adhesion during the drying process of microspheres, solve the problems of poor defects such as holes, depressions or shrinkage on the particles, the obtained microspheres have good appearance, and dry solid materials can be obtained quickly at one time.

[0120] From the comparison of the drying results of Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that the structural setting of the single-screw pitch changing from small to large is more conducive to obtaining good drying effect, and the thermally expandable microspheres have good appearance, are not expanded and have good dispersibility. The small pitch at the front is convenient for breaking up the pre-dehydrated microsphere slurry, and the increased pitch at the rear can reduce the shear force on the microsphere slurry and also achieve accurate transportation of the slurry.

[0121] From the comparison of the drying results of Comparative Example 3 and Example 1, it can be seen that if the discharge port of the single-screw drying and conveying device is not a trumpet-shaped conical discharge port, the drying effect will be affected.

[0122] From the comparison of the drying results of Comparative Example 4 and Example 1, it can be seen that if the pneumatic dryer containing the umbrella-shaped filter component is replaced with a cyclone pneumatic dryer of the same volume, the drying effect of the thermally expandable microspheres is poor. Using the pneumatic dryer described in the present invention is more conducive to obtaining thermally expandable microspheres with better drying effect and lower energy consumption.

[0123] From the comparison of the drying results of Comparative Example 5 and Example 1, it can be seen that if the temperature of the hot air in the pneumatic dryer is higher than the problem conditions defined in the present invention, the thermally expandable microspheres are prone to expansion. Therefore, the combination of the pneumatic dryer containing the umbrella-shaped filter component and the appropriate hot air temperature in the present invention is more conducive to realizing the drying of the thermally expandable microspheres.

[0124] The technical features of the above-mentioned embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above-mentioned embodiments are not exhausted. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0125] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A low temperature drying device for heat-expandable microspheres, characterized in that: The drying equipment comprises: A microsphere slurry pre-dehydration device, wherein the microsphere slurry pre-dehydration device is provided with a filter screen and a stirring blade; A single screw drying and conveying device, wherein the feed port of the single screw drying and conveying device is connected to the discharge port of the microsphere slurry pre-deliquidation device, and the single screw drying and conveying device is under negative pressure heating conditions; The airflow drying device is provided with an umbrella-shaped filter assembly inside the airflow drying device. The discharge port of the single-screw drying and conveying device is connected to the feed port of the airflow drying device.

2. The low-temperature drying device for heat-expandable microspheres according to claim 1, characterized in that: The microsphere slurry pre-deliquidation device includes a cylindrical-conical shell, a cylindrical-conical filter screen is arranged in the shell, the filter screen is a Johnson screen, the stirring blade is a conical spiral stirring blade, and a differential pressure transmitter is installed between the upper and lower parts of the microsphere slurry pre-deliquidation device, and the differential pressure transmitter is associated with a regulating valve at the discharge port of the microsphere slurry pre-deliquidation device.

3. The low-temperature drying device for heat-expandable microspheres according to claim 1, characterized in that: A single screw is arranged in the single screw drying and conveying device, and the pitch of the single screw increases from a feed port to a discharge port of the single screw drying and conveying device.

4. The low-temperature drying device for heat-expandable microspheres according to claim 1, characterized in that: The discharge port of the single-screw drying and conveying device is in a trumpet-cone shape, and the angle of the trumpet-cone is 55-65°; the trumpet-cone-shaped discharge port is directly above the umbrella-shaped filtering component.

5. The low-temperature drying device for heat-expandable microspheres according to claim 1, characterized in that: In the airflow drying device, the top cone angle of the umbrella-shaped filter assembly is 40-50°, and the umbrella-shaped filter assembly is made of Johnson net.

6. A method for drying heat-expandable microspheres, characterized in that: The heat-expandable microspheres are dried using the drying device described in any one of claims 1 to 5, wherein the drying method is: The microsphere slurry is added into the microsphere slurry pre-deliquidation device, and part of the liquid in the microsphere slurry is removed through the filter screen, and then enters the single-screw drying and conveying device, and the microsphere slurry is dried again under negative pressure heating conditions, and finally enters the airflow drying device, and is dried with hot air to finally obtain dried thermal expansion microspheres.

7. A method for drying heat-expandable microspheres according to claim 6, characterized in that: When the microsphere slurry is added to the microsphere slurry pre-deliquidation device, the water content is 70-80% and the feeding speed is 15-50 kg / h; The pressure difference between the feed port and the discharge port of the microsphere slurry pre-deliquidation device is 0.1 MPa to 1 MPa.

8. A method for drying heat-expandable microspheres according to claim 6, characterized in that: When the microsphere slurry enters the single-screw drying and conveying device, the water content is 30-40%; in the single-screw drying and conveying device, the microsphere slurry is conveyed by the single screw at a conveying speed of 0.1-0.3 m / s; The heating temperature in the single screw drying and conveying device is 70-90°C, and the vacuum absolute pressure is 1-10×10 3 Pa.

9. A method for drying heat-expandable microspheres according to claim 6, characterized in that: When the microsphere slurry enters the airflow drying device, the water content is 10-15%; The hot air in the airflow drying device is heated and dried hot air, and the temperature of the hot air is 50-70°C.

10. A method for drying heat-expandable microspheres according to claim 6, characterized in that: The microsphere slurry pre-deliquidation device and the airflow drying device are both provided with a Johnson filter, and the gap of the Johnson filter is 100-200 meshes.

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