Polystyrene processing method and system and application thereof

Abstract

The invention relates to the technical field of high-molecular polymers, in particular to a polystyrene processing method and system and application thereof, and discloses a polystyrene processing method and system and application thereof. The method comprises the following steps: S1, carrying out melt mixing on polystyrene, and cooling to obtain a polystyrene adhesive tape; s2, spraying an external lubricating aid on the surface of the polystyrene rubber strip to obtain a coated polystyrene rubber strip; wherein the viscosity of the external lubricating auxiliary agent at the temperature of 30 DEG C is 20 to 5000 mPa.s. According to the processing method, the external lubricating additive is sprayed on the surface of the melt-mixed polystyrene adhesive tape, the environmental problems such as dust flying can be avoided, meanwhile, the external lubricating additive with specific viscosity can further avoid additive precipitation, it is guaranteed that the polystyrene product has the excellent mechanical property, and the pressure drop in the material conveying process is further reduced.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, specifically to a polystyrene processing method and system and its application. Background Technology

[0002] During the melting, processing, and transportation of polymers, friction occurs between the polymer and the surfaces of processing machinery, as well as between polymers themselves. This friction can reduce the melt flow rate or cause the polymer product surface to become rough, uneven, or even cracked. To reduce the impact of friction on the polymer production process, additives that mitigate the negative effects of friction are typically added. Additives that reduce polymer melt friction are usually internal lubricants. Internal lubricants can reduce the cohesive forces between polymer molecules. Generally, internal lubricants have good compatibility with polymer molecules, can reduce internal frictional heat generation in the polymer, and can improve the polymer's flowability. Additives that reduce friction between the polymer and the processing surfaces of machinery are usually called external lubricants. External lubricants typically have poor compatibility with polymers and form an interface between the polymer and the processing machinery, thereby reducing direct contact friction between the polymer and the machinery surface. Generally, lubricants have both internal and external lubrication functions, with different emphases depending on the process conditions.

[0003] Polystyrene, a commonly used general-purpose plastic, also requires lubricants during its production process. Typically, lubricants for polystyrene are added during the granulation stage, specifically at the feed port of the screw extruder. They are added to the polystyrene granules through a series of steps including conveying, melting, extrusion, and pelletizing by the screw. Commonly used lubricants include stearylamine, stearates, stearates, and ethylene bis-stearamide. Traditional lubricants and their addition methods often have the following drawbacks: The addition of powdered materials inevitably leads to dust dispersion and environmental problems. Furthermore, after granulation by the screw extruder, some lubricant becomes encapsulated within the polymer, failing to function as an external lubricant and increasing production costs. In addition, lubricants often have poor compatibility with polystyrene; over time, the external lubricant may precipitate onto the polymer surface, affecting the polymer's appearance and properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems in the existing technology where the addition of external lubricants during the processing of polystyrene easily causes dust and additive precipitation, resulting in poor overall performance of polystyrene products. This invention provides a polystyrene processing method that sprays an external lubricant onto the surface of the melt-mixed polystyrene strip, thus avoiding environmental problems such as dust. Furthermore, the specific viscosity of the external lubricant further prevents additive precipitation, ensuring that the polystyrene product has excellent mechanical properties and further reducing pressure drop during material transport.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for processing polystyrene, wherein the method includes:

[0006] S1. Polystyrene is melt-blended and then cooled to obtain polystyrene strips;

[0007] S2. Spray the external lubricant onto the surface of the above polystyrene strip to obtain a coated polystyrene strip;

[0008] The viscosity of the external lubricant at 30°C is 20-5000 mPa·s.

[0009] A second aspect of the present invention provides a system for processing polystyrene, wherein the system comprises: a screw extruder, a conveying device, a container, a nozzle, a first conveying pump, and an additive storage tank;

[0010] The screw extruder, conveying device, and container are connected in sequence.

[0011] The container is equipped with a nozzle, and the additive storage tank is connected to the nozzle via a first delivery pump for spraying additives onto the surface of the polystyrene strip passing through the container.

[0012] Preferably, the bottom of the container is conical to collect excess external lubricant from the surface of the polystyrene strip.

[0013] The third aspect of the present invention provides the application of the method described in the first aspect or the system described in the second aspect of the present invention in the preparation of polystyrene products.

[0014] Through the above technical solutions, the polystyrene processing method and system and their application provided by the present invention achieve the following beneficial effects: by spraying an external lubricant onto the surface of the melt-mixed polystyrene strip, environmental problems such as dust flying can be avoided. At the same time, the external lubricant of a specific viscosity can further prevent the precipitation of the additive, ensuring that the polystyrene product has excellent mechanical properties. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the polystyrene processing system in Example 1.

[0016] Explanation of reference numerals in the attached figures

[0017] 1. Screw extruder; 2. Conveying device; 3. Container; 4. Nozzle; 5. First conveying pump; 6. Additive storage tank; 7. Pelletizer; 8. Second conveying pump; 9. Silo; 10. Additive recovery storage tank; 11. Third conveying pump. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of this invention provides a method for processing polystyrene, wherein the method includes:

[0020] S1. Polystyrene is melt-blended and then cooled to obtain polystyrene strips;

[0021] S2. Spray the external lubricant onto the surface of the above polystyrene strip to obtain a coated polystyrene strip;

[0022] The viscosity of the external lubricant at 30°C is 20-5000 mPa·s.

[0023] In this invention, the viscosity of the external lubricant at 30°C meets the above-mentioned range, which can ensure that environmental problems caused by dust flying during addition are avoided, and can also ensure the excellent mechanical properties of polystyrene products.

[0024] According to some preferred embodiments of the present invention, the viscosity of the external lubricant at 30°C is 500-3000 mPa·s.

[0025] According to the present invention, the external lubricant is selected from high-carbon alkanes with 12-18 carbon atoms and / or compounds with the structure shown in Formula I;

[0026]

[0027] In Equation I, m ≥ 3;

[0028] R1, R2, R3, and R4 are each independently selected from C1-C6 alkyl groups.

[0029] In this invention, the inventors have discovered through extensive research that when the polystyrene processing method provided by this invention is combined with the external lubricant with the above-mentioned specific structure, the overall performance of polystyrene products can be further improved and the pressure drop during material transportation can be reduced.

[0030] According to some preferred embodiments of the present invention, in Formula I, m is 3-8, and R1, R2, R3, and R4 are each independently selected from methyl or ethyl compounds. Specific compounds may be, for example, methyl silicone oil or ethyl silicone oil.

[0031] According to some preferred embodiments of the present invention, when the viscosity of the high-carbon alkane at 30°C is 500-3000 mPa·s, it can be better matched with the processing method described in the present invention. At the same time, controlling the operating temperature of the high-carbon alkane at 30-60°C can further improve the overall performance of polyethylene products and reduce the pressure drop during material transportation.

[0032] According to the present invention, the mass content of the external lubricant is 300-1600 ppm, based on the total weight of the coated polystyrene strip.

[0033] Furthermore, in order to ensure that the polystyrene products have better mechanical properties, the content of the external lubricant is 500-1500 ppm.

[0034] According to the present invention, the method further includes: pelletizing the coated polystyrene strip.

[0035] According to the present invention, the method further includes recovering excess external lubricant from the surface of the polystyrene strip.

[0036] According to the present invention, in step S2, during the spraying process, the external lubricant is a droplet with an average particle size of 10-200 μm.

[0037] In this invention, when the average particle size of the external lubricating agent is controlled to meet the above requirements during the spraying process, the agent can be atomized and coated more evenly on the surface of the material.

[0038] Furthermore, the external lubricant is a droplet with an average particle size of 50-180 μm.

[0039] A second aspect of the present invention provides a system for processing polystyrene, such as Figure 1 As shown, the system includes: a screw extruder 1, a conveying device 2, a container 3, a nozzle 4, a first conveying pump 5, and an additive storage tank 6;

[0040] The screw extruder 1, the conveying device 2, and the container 3 are connected in sequence.

[0041] The container 3 is equipped with a nozzle 4, and the additive storage tank 6 is connected to the nozzle 4 via a first delivery pump 5 for spraying additives onto the surface of the polystyrene strip passing through the container 3.

[0042] In this invention, the screw extruder 1 is used for melt-blending polystyrene. Exemplarily, the screw extruder can be a twin-screw extruder with a screw length-to-diameter ratio of 20-60:1; the extruder speed is 300-500 rad / min; and it contains 6 temperature zones. The temperatures of each temperature zone are set as follows: Zone 1 to Zone 6 are 160-180℃, 180-200℃, 170-190℃, 190-210℃, 190-210℃, and 210-230℃, respectively, and the die temperature is 200-240℃.

[0043] In this invention, the conveying device 2 can be a water-cooled traction device or an air-cooled traction device. The length of the cooling conveying device is 2-6m, and the temperature of the cooling medium is 10-45℃. The cooling medium can be water.

[0044] In this invention, the container 3 has a channel for the polystyrene strip to enter and exit, and the nozzle 4 is positioned above and below the polystyrene strip to facilitate the all-round coating of the external lubricant onto the surface of the polystyrene strip.

[0045] In this invention, the bottom of the container 3 is conical, which is used to collect excess external lubricant from the surface of the polystyrene strip, deposit it at the bottom of the container 3, and flow into the additive recovery storage tank 10.

[0046] According to the present invention, the inventors have discovered that when the cone angle at the bottom of the container 3 is 30-60°, it is possible to better collect uncoated additives and facilitate the return of the additives to the recycling tank.

[0047] Furthermore, the cone angle at the bottom of the container 3 is 35-55°.

[0048] According to the present invention, the metering flow rate of the first delivery pump 5 is 0.04%-0.2% of the output of the screw extruder 1.

[0049] Furthermore, the metering flow rate of the first delivery pump 5 is 0.05-0.18% of the output of the screw extruder 1.

[0050] According to some specific embodiments of the present invention, the extrusion output of the screw extruder 1 is 45-125 kg / h.

[0051] According to some specific embodiments of the present invention, the conveying flow rate of the first conveying pump 5 is 0.03-0.2 kg / h.

[0052] In this invention, it should be noted that while the output of the screw extruder 1 and the conveying flow rate of the first conveying pump 5 meet the above-mentioned ranges, the relationship that "the metering flow rate of the first conveying pump 5 is 0.04%-0.2% of the output of the screw extruder 1" must also be met.

[0053] According to some specific embodiments of the present invention, when the external lubricant is sprayed onto the surface of the polystyrene strip, the spraying rate is the same as the conveying flow rate of the first delivery pump 5.

[0054] According to the present invention, the system further includes a pelletizer 7, a second conveying pump 8, a silo 9, an additive recovery storage tank 10, and a third conveying pump 11.

[0055] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene strips coated with the spraying agent.

[0056] The hopper 9 is connected to the pelletizer 7 via a third conveying pump 11, and is used to collect the polystyrene strips of the spraying additive after pelletizing.

[0057] The auxiliary agent recovery storage tank 10 is connected to the bottom outlet of the container 3 and is used to recover excess external lubricating agent.

[0058] The auxiliary agent storage tank 6 is connected to the auxiliary agent recovery storage tank 10 via a second transfer pump 8, and is used to recycle the external lubricating agent collected in the auxiliary agent recovery storage tank 10.

[0059] The third aspect of the present invention provides the application of the method described in the first aspect or the system described in the second aspect of the present invention in the preparation of polystyrene products.

[0060] In this invention, the polystyrene granules obtained by the method of this invention have excellent mechanical properties. Specifically, the tensile strength is not less than 24 MPa, preferably not less than 27 MPa, and the notched cantilever beam impact strength is not less than 9.5 kJ / m. 2 Preferably, it should be no less than 12.5 kJ / m 2 Furthermore, the process is smooth, the material conveying is good, and the pressure drop generated during the process from the pelletizer 7 to the hopper 9 is no higher than 125 kPa, preferably no higher than 60 kPa.

[0061] Combination Figure 1 The present invention describes a method for processing polystyrene, comprising:

[0062] Polystyrene is fed into a screw extruder 1 for melt mixing. The screw extruder 1, conveying device 2, and container 3 are connected in sequence. After melt mixing, the polystyrene is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The container 3 has channels for the polystyrene strips to enter and exit. The container 3 is equipped with nozzles 4, which are connected to the auxiliary agent storage tank 6 via a first conveying pump 5. The auxiliary agent storage tank 6 contains external lubricating agent. The nozzles 4 are positioned above and below the polystyrene strips in the container 3, atomizing the external lubricating agent into droplets with an average particle size of 10-200 μm, so that the external lubricating agent can be coated all around the surface of the polystyrene strip. The bottom of the container 3 is conical with an angle of 30-60° to collect excess external lubricating agent from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery storage tank 10 is connected to the bottom of the container 3, and the outlet of the auxiliary agent recovery storage tank 10 is connected to the auxiliary agent storage tank 6 via a second conveying pump 8, for recycling the collected excess external lubricating agent.

[0063] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 through the third conveying pump 11 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive.

[0064] The present invention will be described in detail below through embodiments. In the following embodiments, the tensile strength was measured according to the method of GB / T1042.2-2006;

[0065] The notched impact strength of the cantilever beam was measured according to the method in GB / T1843-2008.

[0066] Test method for external lubricant content:

[0067] 1. When the external lubricant is a high-carbon alkane, polystyrene products are immersed in hexane-ethanol (V / V=1) and then measured using gas chromatography.

[0068] 2. When the external lubricant is a compound with the structure shown in Formula I, the polystyrene product is immersed in 4-methyl-2-pentanone and then measured by atomic absorption spectrometry.

[0069] The polystyrene used in the examples and comparative examples was purchased from New Sino-American Chemical Co., Ltd., and its brand name was HIPPS-990.

[0070] No. 68 white oil, purchased from Maoming Petrochemical.

[0071] Example 1

[0072] HIPS-990 polystyrene is melt-blended in a screw extruder 1. The screw extruder 1 is a twin-screw extruder with a screw length-to-diameter ratio of 60:1 and an extruder speed of 500 rad / min. It contains 6 temperature zones, and the temperatures of each temperature zone are set as follows: 180℃, 190℃, 190℃, 200℃, 210℃, and 220℃, respectively. The die temperature is 220℃.

[0073] The screw extruder 1, conveying device 2 and container 3 are connected in sequence. The polystyrene after molten compounding is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The conveying device 2 is a water tank type cooling conveying device with a water tank length of 6m, a cooling water temperature of 25℃, and a polystyrene strip extrusion output of 125kg / h.

[0074] Container 3 has a channel for the inlet and outlet of polystyrene adhesive strips. A nozzle 4 is installed in container 3, and the nozzle 4 is connected to the auxiliary agent storage tank 6 via a first delivery pump 5. The auxiliary agent storage tank 6 contains a compound with the structure shown in Formula I as an external lubricant (viscosity of 5000 mPa·s at 30°C, R1, R2, R3, and R4 are all ethyl, m is 8), with an operating temperature of 30°C. The nozzle 4 is positioned above and below the polystyrene adhesive strips passing through container 3, atomizing the external lubricant into droplets with an average particle size of 120-200 μm. To ensure that the external lubricant is fully coated onto the surface of the polystyrene strip, the nozzle 4 sprays at a rate of 0.125 kg / h, and the first delivery pump 5 delivers at a flow rate of 0.125 kg / h. The bottom of the container 3 is a cone with an angle of 60°, used to collect excess external lubricant from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery tank 10 is connected to the bottom of the container 3, and the outlet of the auxiliary agent recovery tank 10 is connected to the auxiliary agent storage tank 6 via the second delivery pump 8, used to recycle the collected excess external lubricant.

[0075] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive to obtain polystyrene granules.

[0076] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0077] Example 2

[0078] The method is the same as in Example 1, except that the external lubricant is n-hexadecane.

[0079] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0080] Example 3

[0081] HIPS-990 polystyrene is melt-blended in a screw extruder 1. The screw extruder 1 is a twin-screw extruder with a screw length-to-diameter ratio of 48:1 and an extruder speed of 420 rad / min. It contains 6 temperature zones, and the temperatures of each temperature zone are set as follows: 170℃, 190℃, 180℃, 200℃, 200℃, and 220℃, respectively. The die temperature is 220℃.

[0082] The screw extruder 1, conveying device 2 and container 3 are connected in sequence. The polystyrene after molten compounding is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The conveying device 2 is a water tank type cooling conveying device with a water tank length of 4m and a cooling water temperature of 20℃. The extrusion output of the polystyrene strips is 100kg / h.

[0083] Container 3 has a channel for the inlet and outlet of polystyrene adhesive strips. A nozzle 4 is installed in container 3, and the nozzle 4 is connected to the auxiliary agent storage tank 6 via a first delivery pump 5. The auxiliary agent storage tank 6 contains a compound with the structure shown in Formula I as an external lubricant (viscosity of 3000 mPa·s at 30°C, R1 and R2 are methyl, R3 and R4 are ethyl, m is 7), and the temperature is 30°C. The nozzle 4 is positioned above and below the polystyrene adhesive strips passing through container 3, and atomizes the external lubricant into droplets with an average particle size of 100-180 μm. This facilitates the all-around coating of the external lubricant onto the surface of the polystyrene strip. The nozzle 4 sprays at a rate of 0.2 kg / h, and the first delivery pump 5 delivers at a flow rate of 0.2 kg / h. The bottom of the container 3 is a cone with an angle of 45°, used to collect excess external lubricant from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery tank 10 is connected to the bottom of the container 3, and the outlet of the auxiliary agent recovery tank 10 is connected to the auxiliary agent storage tank 6 via the second delivery pump 8, used to recycle the collected excess external lubricant.

[0084] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive to obtain polystyrene granules.

[0085] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0086] Example 4

[0087] The method is the same as in Example 3, except that the external lubricant is n-octadecane.

[0088] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0089] Example 5

[0090] HIPS-990 polystyrene is melt-blended in a screw extruder 1. The screw extruder 1 is a twin-screw extruder with a screw length-to-diameter ratio of 28:1 and an extruder speed of 330 rad / min. It contains 6 temperature zones, and the temperatures of each temperature zone are set as follows: 180℃, 190℃, 190℃, 200℃, 190℃, 200℃, and the die temperature is 210℃.

[0091] The screw extruder 1, conveying device 2 and container 3 are connected in sequence. The polystyrene after molten compounding is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The conveying device 2 is a water tank type cooling conveying device with a water tank length of 4m and a cooling water temperature of 20℃. The extrusion output of the polystyrene strips is 45kg / h.

[0092] Container 3 has channels for the inlet and outlet of polystyrene adhesive strips. A nozzle 4 is installed in container 3, and the nozzle 4 is connected to the auxiliary agent storage tank 6 via a first delivery pump 5. The auxiliary agent storage tank 6 contains a compound with the structure shown in Formula I as an external lubricant (viscosity of 1000 mPa·s at 30°C, R1, R2, and R3 are methyl, R4 is ethyl, and m is 6), at a temperature of 30°C. The nozzle 4 is positioned above and below the polystyrene adhesive strips passing through container 3, atomizing the external lubricant into droplets with an average particle size of 80-150 μm. To facilitate the all-around coating of the external lubricant onto the surface of the polystyrene strip, the nozzle 4 has a spray rate of 0.03 kg / h, and the first delivery pump 5 has a delivery flow rate of 0.3 kg / h. The bottom of the container 3 is a cone with an angle of 30°, used to collect excess external lubricant from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery storage tank 10 is connected to the bottom of the container 3, and the outlet of the auxiliary agent recovery storage tank 10 is connected to the auxiliary agent storage tank 6 through the second delivery pump 8, used to recycle the collected excess external lubricant.

[0093] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive to obtain polystyrene granules.

[0094] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0095] Example 6

[0096] The method is the same as in Example 5, except that the external lubricant is No. 68 white oil.

[0097] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0098] Example 7

[0099] HIPS-990 polystyrene is melt-blended in a screw extruder 1. The screw extruder 1 is a twin-screw extruder with a screw length-to-diameter ratio of 58:1 and an extruder speed of 480 rad / min. It contains 6 temperature zones, and the temperatures of each temperature zone are set as follows: 180℃, 190℃, 190℃, 200℃, 210℃, and 220℃, respectively. The die temperature is 220℃.

[0100] The screw extruder 1, conveying device 2 and container 3 are connected in sequence. The polystyrene after molten compounding is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The conveying device 2 is a water tank type cooling conveying device with a water tank length of 6m and a cooling water temperature of 30℃. The extrusion output of the polystyrene strips is 90kg / h.

[0101] Container 3 has channels for the inlet and outlet of polystyrene adhesive strips. A nozzle 4 is installed in container 3, and the nozzle 4 is connected to the auxiliary agent storage tank 6 via a first delivery pump 5. The auxiliary agent storage tank 6 contains a compound with the structure shown in Formula I as an external lubricant (viscosity of 500 mPa·s at 30°C, R1, R2, R3, and R4 are all methyl groups, m is 4), and the temperature is 30°C. The nozzle 4 is positioned above and below the polystyrene adhesive strip in container 3, atomizing the external lubricant into droplets with an average particle size of 50-120 μm, facilitating... External lubricant is applied to the surface of the polystyrene strip in all directions. The spray rate of nozzle 4 is 0.045 kg / h, and the delivery flow rate of the first delivery pump 5 is 0.045 kg / h. The bottom of container 3 is conical with an angle of 50° to collect excess external lubricant from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery tank 10 is connected to the bottom of container 3, and the outlet of the auxiliary agent recovery tank 10 is connected to the auxiliary agent storage tank 6 through the second delivery pump 8 to recycle the collected excess external lubricant.

[0102] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive to obtain polystyrene granules.

[0103] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0104] Example 8

[0105] HIPS-990 polystyrene is melt-blended in a screw extruder 1. The screw extruder 1 is a twin-screw extruder with a screw length-to-diameter ratio of 30:1 and an extruder speed of 300 rad / min. It contains 6 temperature zones, and the temperatures of each temperature zone are set as follows: 170℃, 190℃, 190℃, 200℃, 210℃, and 220℃, respectively. The die temperature is 220℃.

[0106] The screw extruder 1, conveying device 2 and container 3 are connected in sequence. The polystyrene after molten compounding is cooled by the conveying device 2 to form polystyrene strips, which are then conveyed to the container 3. The conveying device 2 is a water tank type cooling conveying device with a water tank length of 6m, a cooling water temperature of 45℃, and an extrusion output of 75kg / h for polystyrene strips.

[0107] Container 3 has a channel for the inlet and outlet of polystyrene adhesive strips. A nozzle 4 is installed in container 3, and the nozzle 4 is connected to the auxiliary agent storage tank 6 via a first delivery pump 5. The auxiliary agent storage tank 6 contains a compound with the structure shown in Formula I as an external lubricant (viscosity of 1000 mPa·s at 30°C, R1, R2, and R3 are methyl, R4 is ethyl, and m is 5), at a temperature of 30°C. The nozzle 4 is positioned above and below the polystyrene adhesive strips passing through container 3, atomizing the external lubricant into droplets with an average particle size of 80-150 μm. To ensure that the external lubricant is fully coated onto the surface of the polystyrene strip, the nozzle 4 sprays at a rate of 0.045 kg / h, and the first delivery pump 5 delivers at a flow rate of 0.045 kg / h. The bottom of the container 3 is a cone with an angle of 60°, used to collect excess external lubricant from the surface of the polystyrene strip. The inlet of the auxiliary agent recovery tank 10 is connected to the bottom of the container 3, and the outlet of the auxiliary agent recovery tank 10 is connected to the auxiliary agent storage tank 6 via the second delivery pump 8, used to recycle the collected excess external lubricant.

[0108] The pelletizer 7 is connected to the outlet of the container 3 and is used to pelletize the polystyrene adhesive strips of the spraying additive. The hopper 9 is connected to the outlet of the pelletizer 7 and is used to collect the pelletized polystyrene adhesive strips of the spraying additive to obtain polystyrene granules.

[0109] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0110] Example 9

[0111] The method is the same as in Example 8, except that the external lubricant is n-dodecane.

[0112] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0113] Example 10

[0114] The method is the same as in Example 1, except that the external lubricant used is polyethylene wax.

[0115] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0116] Example 11

[0117] The method is the same as in Example 1, except that the compound with the structure shown in Formula I is used as the external lubricant (viscosity of 5000 mPa·s at 30°C, R1, R2, R3, and R4 are all ethyl, m is 8), the temperature is 30°C, the nozzle 4 is set above and below the polystyrene strip in the container 3, and atomizes the external lubricant into droplets with an average particle size of 120-200 μm, so that the external lubricant can be coated all around the surface of the polystyrene strip. The spraying rate of the nozzle 4 is 0.625 kg / h, and the delivery flow rate of the first delivery pump 5 is 0.625 kg / h.

[0118] The production capacity of polystyrene adhesive strips is 125 kg / h.

[0119] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0120] Example 12

[0121] The method is the same as in Example 1, except that the compound with the structure shown in Formula I is used as the external lubricant (viscosity of 5000 mPa·s at 30°C, R1, R2, R3, and R4 are all ethyl, m is 8), the temperature is 30°C, the nozzle 4 is set above and below the polystyrene strip in the container 3, and atomizes the external lubricant into droplets with an average particle size of 120-200 μm, so that the external lubricant can be coated all around the surface of the polystyrene strip. The spraying rate of the nozzle 4 is 0.05 kg / h, and the delivery flow rate of the first delivery pump 5 is 0.05 kg / h.

[0122] The production capacity of styrene adhesive strips is 250 kg / h.

[0123] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0124] Comparative Example 1

[0125] The method is the same as in Example 1, except that no external lubricant is added.

[0126] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1 and the content of external lubricating agents in the polystyrene granules are shown in Table 1.

[0127] Comparative Example 2

[0128] According to existing methods, the external lubricant is replaced with an equal amount of calcium stearate.

[0129] The percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1, and the content of calcium stearate in the polystyrene granules are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] Note: a refers to the percentage of the metering flow rate of the first delivery pump 5 to the output of the screw extruder 1;

[0134] b refers to the mass content of external lubricants or calcium stearate in the polystyrene granules.

[0135] Test case

[0136] The polystyrene granule samples prepared in the examples and comparative examples were subjected to mechanical property tests and material conveying tests. The results are shown in Table 2.

[0137] The material conveying status is judged by the pressure drop generated during the process from the pelletizer 7 to the silo 9. The greater the pressure drop, the more difficult the conveying is.

[0138] Table 2

[0139]

[0140]

[0141] As can be seen from the results in Table 1, Examples 1-12 achieved better technical results. Compared with Comparative Example 1, the mechanical properties of Examples 1-12 did not decrease significantly after the addition of external lubricating agents, with tensile strength not less than 24.3 MPa and cantilever beam notched impact strength not less than 9.5 kJ / m. 2 Furthermore, the pressure drop generated during the process from the pelletizer 7 to the silo 9 does not exceed 130 kPa, indicating good conveying performance.

[0142] In Example 11, the mechanical properties decreased due to excessive additive content. In Example 12, the material conveying was difficult because the metering flow rate of the first conveying pump 5 accounted for only 0.02% of the output of the screw extruder 1.

[0143] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for processing polystyrene, characterized in that, The method includes: S1. Polystyrene is melt-blended and then cooled to obtain polystyrene strips; S2. Spray the external lubricant onto the surface of the above polystyrene strip to obtain a coated polystyrene strip; The viscosity of the external lubricant at 30°C is 20-5000 mPa·s.

2. The method according to claim 1, wherein, The viscosity of the external lubricant at 30°C is 500-3000 mPa·s; Preferably, the external lubricant is selected from high-carbon alkanes with 12-18 carbon atoms and / or compounds with the structure shown in Formula I; In Equation I, m ≥ 3; R1, R2, R3, and R4 are each independently selected from C1-C6 alkyl groups.

3. The method according to claim 2, wherein, In Equation I, m is 3-8; Preferably, R1, R2, R3, and R4 are each independently selected from methyl or ethyl.

4. The method according to any one of claims 1-3, wherein, Based on the total weight of the coated polystyrene strip, the content of the external lubricant is 300-1600 ppm, preferably 500-1500 ppm.

5. The method according to any one of claims 1-4, wherein, The method further includes: cutting the coated polystyrene strip into pellets; Preferably, the method further includes recovering excess external lubricant from the surface of the polystyrene strip.

6. The method according to any one of claims 1-5, wherein, In step S2, during the spraying process, the external lubricant is a droplet with an average particle size of 30-200 μm, preferably a droplet with an average particle size of 50-180 μm.

7. A system for processing polystyrene, characterized in that, The system includes: a screw extruder, a conveying device, a container, a nozzle, a first conveying pump, and an additive storage tank; The screw extruder, conveying device, and container are connected in sequence. The container is equipped with a nozzle, and the additive storage tank is connected to the nozzle via a first delivery pump for spraying additives onto the surface of the polystyrene strip passing through the container. Preferably, the bottom of the container is conical to collect excess additives from the surface of the polystyrene strip.

8. The system according to claim 7, wherein, The cone angle at the bottom of the container is 30-60°, preferably 35-55°; Preferably, the metering flow rate of the first delivery pump is 0.04%-0.2% of the output of the screw extruder, and more preferably 0.05%-0.18%.

9. The system according to claim 7 or 8, wherein, The system also includes a pelletizer, a second conveying pump, a silo, and an additive recovery storage tank; The pelletizer is connected to the outlet of the container and is used to pelletize the polystyrene strips coated with the spraying agent. The hopper is connected to the pelletizer and is used to collect the polystyrene strips of the spraying additive after pelletizing. The auxiliary agent recovery storage tank is connected to the bottom outlet of the container and is used to recover excess auxiliary agents; The auxiliary agent storage tank is connected to the auxiliary agent recovery storage tank via a second transfer pump, which is used to recycle the auxiliary agents collected in the auxiliary agent recovery storage tank.

10. The use of the method according to any one of claims 1-6 or the system according to any one of claims 7-9 in the preparation of polystyrene articles.

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