Preparation system and method of fumed silica plastic concentrate

Abstract

The present invention discloses a system and method for preparing fumed silica plastic concentrate, the system comprising a fumed silica feeding mechanism, a polymer feeding mechanism, a kneading mechanism, a forced feeding mechanism, and a screw extrusion mechanism; the kneading mechanism is provided with a plurality of kneading devices, each kneading device is sequentially connected to form a multi-stage kneading structure; the polymer feeding mechanism is connected to the first-stage kneading device; a plurality of fumed silica feeding mechanisms are provided, and the fumed silica feeding mechanisms correspond to the kneading devices one by one and are connected; the kneading device at the last stage is sequentially connected to the forced feeding mechanism and the screw extrusion mechanism. The technical solution provided by the system and method for preparing fumed silica plastic concentrate can obtain a high-concentration fumed silica plastic concentrate, and filling plastic with the fumed silica plastic concentrate can make the obtained product performance uniform, and effectively improve the performance of the modified plastic.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical preparation, and in particular relates to a system and method for preparing a fumed silica plastic concentrate. Background Art

[0002] Fumed silica is a nanostructured material with rich hydroxyl groups on its surface. Therefore, it can be used in silicone rubber, plastics, coatings, inks, adhesives and other fields to play the role of reinforcement, thickening, thixotropy, and anti-sedimentation. Fumed silica is a powder with a relatively low tap density, usually only 50 g / L. When it is used to modify plastics and dry-mix fumed silica powder with plastics, the fumed silica powder is very easy to float on the plastic particles, making it difficult to effectively mix the fumed silica powder with the plastic particles. In particular, when the amount of fumed silica powder added is greater than 1%, it is basically impossible to obtain the effect of uniform solid mixing of fumed silica powder and plastic, which leads to the modified plastic particles and the molded plastic products having large non-uniform performance when the modified plastic is melt-extruded, granulated and plasticized, which leads to the failure of the performance of the plastic modified by fumed silica powder. Summary of the invention

[0003] The object of the present invention is to provide a system for preparing a fumed silica plastic concentrate, by which a high-concentration fumed silica plastic concentrate can be prepared.

[0004] The above-mentioned purpose is achieved by the following technical solutions.

[0005] A fumed silica plastic concentrate preparation system, comprising a fumed silica feeding mechanism, a polymer feeding mechanism, a kneading mechanism, a forced feeding mechanism, and a screw extrusion mechanism;

[0006] The kneading mechanism is provided with a plurality of kneading devices, each of which is connected in sequence to form a multi-stage kneading structure, and the kneading device is used to mix and knead the material;

[0007] The polymer feeding mechanism is connected to the first-stage kneading device and is used to feed plastic particles into the first-stage kneading device;

[0008] The fumed silica feeding mechanism is provided with a plurality of fumed silica feeding mechanisms, and the fumed silica feeding mechanisms correspond to and are connected with the kneading devices one by one, and the fumed silica feeding mechanisms are used to feed fumed silica into the kneading devices at each level;

[0009] The kneading device located at the last stage is connected with the forced feeding mechanism and the screw extrusion mechanism in sequence.

[0010] In some of the embodiments, the fumed silica feeding mechanism includes a feeding tank, a stirring device and an automatic weighing device;

[0011] The feeding tank has a feeding cavity, the stirring device is rotatably connected to the feeding tank and accommodated in the feeding cavity, and the feeding cavity is controlled and communicated with the kneading device through the automatic weighing device.

[0012] In some embodiments, the kneading device includes a kneading tank and two kneading paddles; the kneading tank has a kneading cavity, the two kneading paddles are rotatably connected to the kneading tank and accommodated in the kneading cavity, and the two kneading paddles rotate towards each other.

[0013] In some embodiments, the kneading paddle has a ∑-shaped structure or a Z-shaped structure.

[0014] In some embodiments, the forced feeding mechanism includes a feeding trough body and two screw members rotatably disposed in the feeding trough body, and the two screw members rotate in opposite directions or in the same direction to convey materials.

[0015] In some embodiments, the screw element has a conical structure, and a diameter of the first end of the screw element close to the screw extrusion mechanism is smaller than a diameter of the second end of the screw element close to the kneading device.

[0016] In some embodiments, the screw extrusion mechanism is a twin-screw extrusion mechanism, and a ratio of the length to the diameter of the screw of the twin-screw extrusion mechanism is greater than or equal to 42:1.

[0017] In some of the embodiments, the screw of the twin-screw extruder mechanism includes at least three forward kneading blocks and at least two reverse kneading blocks.

[0018] A method for preparing a fumed silica plastic concentrate is applied to the fumed silica plastic concentrate preparation system as described above, comprising the following steps:

[0019] The fumed silica powder is introduced into the first-stage kneading device through a fumed silica feeding mechanism, and the plastic particles are introduced into the first-stage kneading device through a polymer feeding mechanism for mixing and kneading;

[0020] The materials obtained after mixing and kneading are sequentially passed into the remaining kneading devices at various levels for multi-stage mixing and kneading, and the kneading devices at various levels continue to add fumed silica powder through the corresponding fumed silica feeding mechanism to mix and knead the materials to obtain a mixed material;

[0021] The obtained mixed material is passed into a forced feeding mechanism to be conveyed to a screw extrusion mechanism, and the screw extrusion mechanism extrudes and granulates the mixed material to obtain a fumed silica plastic concentrate;

[0022] Among them, the temperature of each kneading device is 150℃~250℃, and the kneading time of each kneading device is 5min~30min; the temperature of the forced feeding mechanism is 180℃~280℃, and the temperature of the screw extrusion mechanism is 180℃~300℃.

[0023] In some of the embodiments, the temperature of each kneading device is 180℃~230℃, and the kneading temperature of each kneading device increases successively; the temperature of the forced feeding mechanism is 180℃~240℃, and the temperature of the screw extrusion mechanism is 180℃~230℃.

[0024] The technical solution provided by the present invention has the following advantages and effects:

[0025] The fumed silica plastic concentrate preparation system can perform multi-stage kneading on the material by arranging a plurality of kneading devices arranged in sequence. A fumed silica feeding mechanism is correspondingly arranged through each kneading device. The first-stage kneading device is provided with a polymer feeding mechanism, so that the fumed silica powder to be added can be kneaded and mixed with the plastic particles in multiple times, so that the fumed silica powder and the plastic particles are fully mixed. After multi-stage melt kneading, the mixed material is further continuously conveyed to the screw extrusion mechanism by a forced feeding mechanism for melt mixing, extrusion and granulation to obtain a high-concentration fumed silica plastic concentrate. The fumed silica plastic concentrate is used to fill plastic to modify the plastic. When the plastic is modified, the stratification of plastic and powder during dry mixing and the dust problem during dry mixing can be effectively avoided, and the powder dispersion unevenness during melt extrusion mixing of the powder and plastic can be reduced, so that the plastic and the powder can be fully mixed and evenly dispersed, so that the performance of the obtained product is more uniform, thereby effectively improving the performance of the modified plastic. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a schematic structural diagram of a system for preparing fumed silica plastic concentrate according to an embodiment of the present invention;

[0027] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure at AA;

[0028] Figure 3 is a schematic structural diagram of a ∑-type kneading paddle according to an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the structure of the Z-type kneading paddle according to an embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 100. Preparation system of fumed silica plastic concentrate;

[0032] 1. Fumed silica feeding mechanism; 11. Feeding tank; 111. Feeding chamber; 12. Stirring device; 13. Automatic weighing device; 2. Polymer feeding mechanism; 3. Kneading mechanism; 31. Kneading device; 311. Kneading tank; 312. Kneading paddle; 4. Forced feeding mechanism; 41. Feeding trough; 42. Screw member; 5. Screw extrusion mechanism; 6. Buffer tank. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

[0034] Unless otherwise specified or defined, the "first, second..." used in this article is merely used to distinguish names and does not represent a specific quantity or order.

[0035] Unless specifically stated or defined otherwise, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] It should be noted that, in this document, “fixed to” or “connected to” may mean directly fixing or connecting to an element, or indirectly fixing or connecting to an element.

[0037] The present invention provides a system 100 for preparing fumed silica plastic concentrate, such as Figures 1 to 4 As shown, the fumed silica plastic concentrate preparation system 100 includes a fumed silica feeding mechanism 1 , a polymer feeding mechanism 2 , a kneading mechanism 3 , a forced feeding mechanism 4 , and a screw extrusion mechanism 5 .

[0038] The kneading mechanism 3 is provided with a plurality of kneading devices 31, and the kneading devices 31 are sequentially connected to form a multi-stage kneading structure;

[0039] The polymer feeding mechanism 2 is connected to the first-stage kneading device 31, and is used to feed plastic particles into the first-stage kneading device 31;

[0040] The fumed silica feeding mechanism 1 is provided with a plurality of fumed silica feeding mechanisms 1, and the fumed silica feeding mechanisms 1 correspond to and are connected with the kneading devices 31 one by one, and the fumed silica feeding mechanisms 1 are used to feed fumed silica into the kneading devices 31 at each level;

[0041] The kneading device 31 is used to knead and mix the plastic particles and the fumed silica;

[0042] The kneading device 31 at the last stage is connected to the forced feeding mechanism 4 and the screw extrusion mechanism 5 in sequence, and the mixed material output from the last stage kneading device 31 is transported to the screw extrusion mechanism 5 through the forced feeding mechanism 4 for extrusion and granulation to obtain a phase silica plastic concentrate.

[0043] Based on the above-mentioned fumed silica plastic concentrate preparation system 100, a method for preparing fumed silica plastic concentrate includes the following steps:

[0044] The fumed silica powder is introduced into the first-stage kneading device 31 through the fumed silica feeding mechanism 1, and the plastic particles are introduced into the first-stage kneading device 31 through the polymer feeding mechanism 2 for mixing and kneading;

[0045] The material obtained after mixing and kneading is sequentially passed into the remaining kneading devices 31 at each level for multi-stage mixing and kneading, and the fumed silica powder is continuously added to the material through the correspondingly connected fumed silica feeding mechanism 1 at each level of the kneading device 31 for mixing and kneading to obtain a mixed material;

[0046] The obtained mixed material is passed into the forced feeding mechanism 4 and transported to the screw extrusion mechanism 5, and the screw extrusion mechanism 5 extrude and granulate the mixed material to obtain the fumed silica plastic concentrate.

[0047] It should be noted that the above-mentioned fumed silica feeding mechanism 1 and kneading device 31, the polymer feeding mechanism 2 and kneading device 31, and the kneading device 31 and the forced feeding mechanism 4 are all connected through automatic switch valves, which automatically control the opening and closing of the switch valves through a control circuit.

[0048] As can be seen from the above, the fumed silica plastic concentrate preparation system 100 can perform multi-stage kneading on the material by setting a plurality of kneading devices 31 arranged in sequence. A fumed silica feeding mechanism 1 is correspondingly arranged through each kneading device 31, and the first-stage kneading device 31 is provided with a polymer feeding mechanism 2, so that the fumed silica powder to be added can be kneaded and mixed with the plastic particles in multiple times, so that the fumed silica powder and the plastic particles are fully mixed. After multi-stage melt kneading, the mixed material is further continuously conveyed to the screw extrusion mechanism 5 by the forced feeding mechanism 4 for melt mixing, extrusion and granulation to obtain a high-concentration fumed silica plastic concentrate. The fumed silica plastic concentrate is used to fill plastic to modify the plastic. When the plastic is modified, the stratification of plastic and powder during dry mixing and the dust problem during dry mixing can be effectively avoided, and the powder dispersion unevenness when the powder and plastic are melted, extruded and mixed can be reduced, so that the plastic and powder are fully mixed and evenly dispersed, so that the performance of the obtained product is more uniform, thereby effectively improving the performance of the modified plastic.

[0049] Furthermore, in order to prepare a high-concentration fumed silica plastic concentrate, appropriate kneading temperature, kneading time, forced feeding temperature and screw extrusion granulation temperature are critical to the mixing effect of the fumed silica powder and the plastic. The present invention controls the temperature of each stage of the kneading device 31 to 150°C to 250°C, and the kneading time of each stage of the kneading device 31 to 5min to 30min; the temperature of the forced feeding mechanism 4 is 180°C to 280°C, and the temperature of the screw extrusion mechanism 5 is 180°C to 300°C. Combined with other steps, the high-concentration fumed silica powder and the plastic can be fully mixed during dry mixing to obtain a high-concentration fumed silica plastic concentrate.

[0050] Preferably, the temperature of each stage of the kneading device 31 is 180℃~230℃, and the kneading temperature of each stage of the kneading device 31 increases successively; the temperature of the forced feeding mechanism 4 is 180℃~240℃, and the temperature of the screw extrusion mechanism 5 is 180℃~230℃.

[0051] In some embodiments, Figure 1 As shown, the fumed silica feeding mechanism 1 includes a feeding tank 11, a stirring device 12 and an automatic weighing device 13; the feeding tank 11 has a feeding cavity 111, the stirring device 12 is rotatably connected to the feeding tank 11 and accommodated in the feeding cavity 111, and the feeding cavity 111 is controlled to communicate with the kneading device 31 through the automatic weighing device 13. It can be understood that the stirring device 12 and the automatic weighing device 13 are arranged in the feeding tank 11, and the fumed silica powder in the feeding cavity 111 can be stirred by the stirring device 12 to break up the soft agglomerates in the fumed silica powder, which is beneficial to the homogenization of the fumed silica powder. After stirring and homogenizing, the fumed silica powder enters into the kneading devices 31 at each level respectively through the automatic weighing device 13 according to different formula ratios to accurately control the powder output and further mix and knead with the plastic particles. Specifically, the stirring device 12 can be an existing spiral stirrer with adjustable speed, and the automatic weighing device 13 can be an electronic scale, a mechanical scale, a weighing sensor, etc., and no special limitation is made here.

[0052] In some embodiments, Figure 1 , Figure 3 and Figure 4As shown, the kneading device 31 includes a kneading tank 311 and two kneading paddles 312; the kneading tank 311 has a kneading cavity, and the two kneading paddles 312 are both rotatably connected to the kneading tank 311 and accommodated in the kneading cavity, and the two kneading paddles 312 rotate in opposite directions. It can be understood that the mixture obtained by mixing the fumed silica and the plastic can be quickly sheared by the two kneading paddles 312 rotating in opposite directions, so that the materials are evenly mixed and kneaded into agglomerates to enhance the powder dispersion and plasticizing effect. Preferably, the kneading paddle 312 has a ∑-shaped structure or a Z-shaped structure, and can knead and rub the mixture at high speed to make the materials fully mixed and evenly mixed, so as to achieve good powder dispersion and plasticizing effect.

[0053] In some embodiments, Figure 1 and Figure 2 As shown, the forced feeding mechanism 4 includes a feeding trough body 41 and two screw members 42 rotatably arranged in the feeding trough body 41. The two screw members 42 rotate in opposite directions or in the same direction to convey materials, that is, the high-viscosity mixture is smoothly pushed forward to the screw extrusion mechanism 5 for extrusion granulation through the two rotating screw members 42.

[0054] In some embodiments, the screw member 42 is of a conical structure, and the diameter of the first end of the screw member 42 near the screw extruder mechanism 5 is smaller than the diameter of the second end near the kneading device 31. It can be understood that the diameter of the screw member 42 gradually decreases from the kneading device 31 to the screw extruder mechanism 5, which can prevent the mixed material from returning during the conveying process, and due to the high viscosity of the material, the gradual decrease in the diameter of the screw member 42 can form a certain compression ratio to smoothly force the material into the screw extruder 5. Preferably, the ratio of the diameter of the first end of the screw member 42 to the diameter of the second end is not higher than 1:1.5, preferably 1:1.3.

[0055] In some embodiments, Figure 1 and Figure 2 As shown, the forced feeding mechanism 4 and the spiral extrusion mechanism 5 are arranged perpendicular to each other. Specifically, in the three-dimensional coordinate system, the forced feeding mechanism 4 is arranged horizontally below the last-stage kneading device 31 along the X-axis direction, and the spiral extrusion mechanism 5 is arranged vertically at the conveying end of the forced feeding mechanism 4 along the Y-axis direction. The perpendicular arrangement between the two is beneficial to the processing of the equipment, reduces costs, and facilitates the transportation of materials.

[0056] In some embodiments, Figure 1As shown, the screw extrusion mechanism 5 is a twin-screw extrusion mechanism, the two screws rotate in opposite directions or in the same direction, and the ratio of the length to the diameter of the screw of the screw extrusion mechanism 5 is greater than or equal to 42:1, and the ratio of the length to the diameter of the screw of the screw extrusion mechanism 5 is preferably 45-50:1. A higher aspect ratio is conducive to the melting and dispersion of the powder, and can enable the fumed silica to be fully dispersed for a longer time under strong shear.

[0057] In some embodiments, the screw of the screw extrusion mechanism 5 includes at least three forward kneading blocks and at least two reverse kneading blocks to further enhance the powder dispersion effect, so that the fumed silica plastic concentrate obtained by extrusion granulation has better shape and performance.

[0058] In some embodiments, Figure 1 As shown, the last stage kneading device 31 and the forced feeding mechanism 4 may also be provided with a buffer tank 6, and the buffer tank 6 is used to initially store the mixed material coming out of the last stage kneading device 31, and then enter the forced feeding mechanism 4 for conveying operation, so as to form a buffer for the conveying process of the mixed material.

[0059] The present invention is further described in detail below with reference to specific embodiments.

[0060] Example 1

[0061] The fumed silica plastic concentrate preparation system 100 includes a fumed silica feeding mechanism 1, a polymer feeding mechanism 2, a kneading mechanism 3, a forced feeding mechanism 4, and a screw extrusion mechanism 5; wherein the kneading mechanism 3 includes three kneading devices 31 to form a three-stage kneading structure, and each kneading device 31 is equipped with a ∑-type kneading paddle 312; the screw member 42 of the forced feeding mechanism 4 adopts a conical twin screw, and the ratio of the diameter of the first end to the diameter of the second end of the screw member 42 is 1:1.3; the screw extrusion mechanism 5 is an opposite twin screw extruder, equipped with a three-stage forward kneading block and a two-stage reverse kneading block. The temperatures of the three kneading devices 31 are set to 195°C, 200°C, and 205°C respectively, the temperature of the forced feeding mechanism 4 is set to 220°C, and the temperature of the screw extrusion mechanism 5 is controlled between 180°C and 230°C.

[0062] Take 20 parts of fumed silica and 80 parts of polypropylene plastic particles for later use;

[0063] 80 parts of polypropylene plastic particles and 10 parts of fumed silica are added to the first-stage kneading device 31 through the polymer feeding mechanism 2 and the fumed silica feeding mechanism 1 respectively, and the kneading is carried out in the first-stage kneading device 31 for 15 minutes, and then the mixed materials enter the second-stage kneading device 31; 6 parts of fumed silica are added to the second-stage kneading device 31 through the fumed silica feeding mechanism 1, and the kneading is carried out in the second-stage kneading device 31 for 15 minutes, and then the mixed materials enter the third-stage kneading device 31; the remaining 4 parts of fumed silica are added to the third-stage kneading device 31 through the fumed silica feeding mechanism 1, and the mixture is kneaded in the third-stage kneading device 31 for 10 minutes to obtain the mixture, and then the mixture enters the forced feeding mechanism 4.

[0064] The forced feeding mechanism 4 feeds the molten material into the screw extrusion mechanism 5 from the side. After shearing, kneading, compression and conveying by the screw extrusion mechanism 5, the molten material is extruded through the die head, and after underwater pelletization, it is dried to become a fumed silica polypropylene concentrate.

[0065] 5 parts of the fumed silica polypropylene concentrate were mixed with 95 parts of polypropylene in a mixer at room temperature, and then melt-extruded to obtain sample 1#.

[0066] Example 2

[0067] The fumed silica plastic concentrate preparation system 100 includes a fumed silica feeding mechanism 1, a polymer feeding mechanism 2, a kneading mechanism 3, a forced feeding mechanism 4, and a screw extrusion mechanism 5; wherein the kneading mechanism 3 includes four kneading devices 31 to form a four-stage kneading structure, and each kneading device 31 is equipped with a ∑-type kneading paddle 312; the screw member 42 of the forced feeding mechanism 4 adopts a conical twin screw, and the ratio of the diameter of the first end to the diameter of the second end of the screw member 42 is 1:1.3; the screw extrusion mechanism 5 adopts an opposite twin screw extruder, and is equipped with a four-stage forward kneading block and a three-stage reverse kneading block. The temperatures of the four kneading devices 31 are set to 190°C, 195°C, 200°C, and 200°C respectively, the temperature of the forced feeding mechanism 4 is set to 210°C, and the temperature of the screw extrusion mechanism 5 is controlled between 180-220°C.

[0068] Take 25 parts of fumed silica and 75 parts of high-pressure polyethylene plastic particles for later use;

[0069] 70 parts of high-pressure polyethylene plastic particles and 10 parts of fumed silica are added to the first-stage kneading device 31 through the polymer feeding mechanism 2 and the fumed silica feeding mechanism 1 respectively, and the materials are mixed and kneaded in the first-stage kneading device 31 for 15 minutes, and then the mixed materials enter the second-stage kneading device 31; 8 parts of fumed silica are added to the second-stage kneading device 31 through the fumed silica feeding mechanism 1, and the materials are mixed and kneaded in the second-stage kneading device 31 for 15 minutes, and then the mixed materials enter the third-stage kneading device 31; 6 parts of fumed silica are added to the third-stage kneading device 31 through the fumed silica feeding mechanism 1, and the materials are mixed and kneaded in the third-stage kneading device 31 for 10 minutes, and then 6 parts of fumed silica are added to the fourth-stage kneading device 31 through the fumed silica feeding mechanism 1 after mixing, and the materials are mixed and kneaded in the fourth-stage kneading device 31 for 10 minutes to obtain a mixture, and then the mixture enters the forced feeding mechanism 4.

[0070] The forced feeding mechanism 4 feeds the molten material into the screw extrusion mechanism 5 from the side. After shearing, kneading, compression and conveying by the screw extrusion mechanism 5, the molten material is extruded through the die head, and after underwater pelletization, it is dried to become a fumed silica high-pressure polyethylene concentrate.

[0071] Example 3

[0072] The fumed silica plastic concentrate preparation system 100 includes a fumed silica feeding mechanism 1, a polymer feeding mechanism 2, a kneading mechanism 3, a forced feeding mechanism 4, and a screw extrusion mechanism 5; wherein the kneading mechanism 3 includes three kneading devices 31 to form a three-stage kneading structure, and each kneading device 31 is equipped with a Z-type kneading paddle 312; the screw member 42 of the forced feeding mechanism 4 adopts a conical twin screw, and the ratio of the diameter of the first end to the diameter of the second end of the screw member 42 is 1:1.3; the screw extrusion mechanism 5 adopts an opposite twin screw extruder, and is equipped with a four-stage forward kneading block and a three-stage reverse kneading block. The temperatures of the three kneading devices 31 are set to 200°C, 210°C, and 220°C respectively, the temperature of the forced feeding mechanism 4 is set to 210°C, and the temperature of the screw extrusion mechanism 5 is controlled between 200-230°C.

[0073] Take 40 parts of fumed silica and 60 parts of thermoplastic polyacrylonitrile-butadiene-styrene plastic particles for later use;

[0074] 60 parts of thermoplastic polystyrene-butadiene elastomer plastic particles and 15 parts of fumed silica are added to the first-stage kneading device 31 through the polymer feeding mechanism 2 and the fumed silica feeding mechanism 1 respectively, and the kneading is carried out in the first-stage kneading device 31 for 10 minutes, and then the mixed material enters the second-stage kneading device 31; 15 parts of fumed silica are added to the second-stage kneading device 31 through the fumed silica feeding mechanism 1, and the kneading is carried out in the second-stage kneading device 31 for 10 minutes, and then the mixed material enters the third-stage kneading device 31; and then 10 parts of fumed silica are added to the third-stage kneading device 31 through the fumed silica feeding mechanism 1, and the kneading is carried out in the third-stage kneading device 31 for 5 minutes to obtain a mixture, and then the mixture enters the forced feeding mechanism 4.

[0075] The forced feeding mechanism 4 feeds the molten material into the screw extrusion mechanism 5 from the side. After shearing, kneading, compression and conveying by the screw extrusion mechanism 5, the molten material is extruded through the die head, and after underwater pelletization, it is dried to become a gas phase silica polyacrylonitrile-butadiene-styrene plastic concentrate.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that there is no kneading mechanism, and 1 part of fumed silica and 99 parts of room temperature mixture of polypropylene are directly added to the forced feeding mechanism 4, and the molten material is fed into the screw extrusion mechanism 5 through the side of the forced feeding mechanism 4. After shearing, kneading, compression and transportation by the screw extrusion mechanism 5, the molten material is extruded through the die head, pelletized, dried and melt-extruded to prepare fumed silica modified polypropylene sample 2#. This comparative example has the same fumed silica content as sample 1#.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the kneading mechanism 3 includes a kneading device 31 to form a primary kneading structure.

[0080] The temperature of the kneading device 31 was set to 205°C.

[0081] 80 parts of polypropylene plastic particles and 20 parts of fumed silica are added to the primary kneading device 31 through the polymer feeding mechanism 2 and the fumed silica feeding mechanism 1 respectively, and the mixture is kneaded in the kneading device 31 for 15 minutes to obtain a mixed material, and then the mixed material enters the forced feeding mechanism 4.

[0082] The forced feeding mechanism 4 feeds the molten material into the screw extrusion mechanism 5 from the side. After shearing, kneading, compression and conveying by the screw extrusion mechanism 5, the molten material is extruded through the die head, pelletized and dried to become a fumed silica polypropylene concentrate.

[0083] 5 parts of fumed silica polypropylene concentrate were mixed with 95 parts of polypropylene plastic in a mixer at room temperature, and then melt-extruded to obtain sample 3#, which had the same fumed silica content as sample 1#.

[0084] The samples obtained in the above examples and comparative examples were prepared by injection molding process into I-type tensile specimens in accordance with the national standard GB1040-92 and subjected to tensile property test at a speed of 50 mm / min, with a blank polypropylene sample without adding fumed silica as a control example. The test results are shown in Table 1.

[0085] Table 1 Tensile properties of samples

[0086] Sample No. Tensile strength MPa Elongation at break % Polypropylene blank sample 22.7 245.3 1# 21.3 835.5 2# 21.5 198.1 3# 21.4 326.2

[0087] From the results in the above table, it can be seen that sample 1# is prepared by adding fumed silica polypropylene concentrate to polypropylene. While basically maintaining the strength of polypropylene, sample 1# can increase the elongation at break of the sample, which is beneficial to alleviate the fracture of the sample under medium strain conditions.

[0088] Comparative Example 1 did not prepare fumed silica polypropylene concentrate, but directly added fumed silica to polypropylene to prepare sample 2#, whose elongation at break was not improved but decreased, and the toughening effect of fumed silica on the polymer could not be achieved.

[0089] Comparative Example 2 adopts a one-stage kneading structure to prepare sample 3#. By comparison, it can be seen that the different levels of kneading structure set for sample 1# have a significant effect on the elongation at break relative to sample 3#. The elongation at break of sample 1# is significantly improved, reflecting its significant tensile toughening effect.

[0090] The above embodiments are not exhaustive enumerations of the present invention, and there may be multiple other implementations not listed. Any replacement and improvement made without violating the concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A system for preparing fumed silica plastic concentrate, characterized in that: It includes a fumed silica feeding mechanism, a polymer feeding mechanism, a kneading mechanism, a forced feeding mechanism, and a screw extrusion mechanism; The kneading mechanism is provided with a plurality of kneading devices, each of which is connected in sequence to form a multi-stage kneading structure, and the kneading device is used to mix and knead the material; The polymer feeding mechanism is connected to the first-stage kneading device and is used to feed plastic particles into the first-stage kneading device; The fumed silica feeding mechanism is provided with a plurality of fumed silica feeding mechanisms, and the fumed silica feeding mechanisms correspond to and are connected with the kneading devices one by one, and the fumed silica feeding mechanisms are used to feed fumed silica into the kneading devices at each level; The kneading device at the last stage is connected with the forced feeding mechanism and the screw extrusion mechanism in sequence; The kneading device comprises a kneading tank and two kneading paddles; the kneading tank has a kneading cavity, the two kneading paddles are rotatably connected to the kneading tank and accommodated in the kneading cavity, and the two kneading paddles rotate in opposite directions; The fumed silica feeding mechanism comprises a feeding tank, a stirring device and an automatic weighing device; The feeding tank has a feeding cavity, the stirring device is rotatably connected to the feeding tank and accommodated in the feeding cavity, and the feeding cavity is controlled and communicated with the kneading device through the automatic weighing device; The forced feeding mechanism comprises a feeding trough body and two screw members rotatably arranged in the feeding trough body, and the two screw members rotate in opposite directions or in the same direction to convey materials; The screw element has a conical structure, and the diameter of the first end of the screw element close to the screw extrusion mechanism is smaller than the diameter of the second end of the screw element close to the kneading device.

2. The system for preparing fumed silica plastic concentrate according to claim 1, characterized in that: The kneading paddle has a ∑-shaped structure or a Z-shaped structure.

3. The system for preparing fumed silica plastic concentrate according to claim 1, characterized in that: The screw extrusion mechanism is a twin-screw extrusion mechanism, and the ratio of the length to the diameter of the screw of the twin-screw extrusion mechanism is greater than or equal to 42:

1.

4. The system for preparing fumed silica plastic concentrate according to claim 3, characterized in that: The ratio of the length to the diameter of the screw of the twin-screw extruder mechanism is 45 to 50:

1.

5. The system for preparing fumed silica plastic concentrate according to claim 3, characterized in that: The screw of the twin-screw extruder mechanism includes at least three forward kneading blocks and at least two reverse kneading blocks.

6. A method for preparing fumed silica plastic concentrate, characterized in that: The system for preparing fumed silica plastic concentrate as claimed in any one of claims 1 to 5 comprises the following steps: The fumed silica powder is introduced into the first-stage kneading device through a fumed silica feeding mechanism, and the plastic particles are introduced into the first-stage kneading device through a polymer feeding mechanism for mixing and kneading; The materials obtained after mixing and kneading are sequentially passed into the remaining kneading devices at various levels for multi-stage mixing and kneading, and the kneading devices at various levels continue to add fumed silica powder through the corresponding fumed silica feeding mechanism to mix and knead the materials to obtain a mixed material; The obtained mixed material is passed into a forced feeding mechanism to be conveyed to a screw extrusion mechanism, and the screw extrusion mechanism extrudes and granulates the mixed material to obtain a fumed silica plastic concentrate; Among them, the temperature of each kneading device is 150℃~250℃, and the kneading time of each kneading device is 5min~30min; the temperature of the forced feeding mechanism is 180℃~280℃, and the temperature of the screw extrusion mechanism is 180℃~300℃.

7. The method for preparing fumed silica plastic concentrate according to claim 6, characterized in that: The temperature of each kneading device is 180℃~230℃, and the kneading temperature of each kneading device increases successively; the temperature of the forced feeding mechanism is 180℃~240℃, and the temperature of the screw extrusion mechanism is 180℃~230℃.

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