Extruded polystyrene foam using a multi-component blowing agent and method of making

Abstract

The application discloses an extruded polystyrene foam adopting multi-component foaming agents and a preparation method thereof. The foam is made of the following components by weight percentage: 85-90wt% polystyrene, 0.5-3wt% nucleating agent, 2.6-5wt% flame retardant and 5-10wt% foaming agent. The foaming agent adopts CO2 and pentane, and is matched with the fourth generation low global warming potential (GWP) hydrofluoroalkene series or / and alcohol. The synergistic effect among the components not only promotes the solubility of CO2 in the polymer, is beneficial to the nucleation of the foam cell, but also reduces the greenhouse gas emission, and is beneficial to meeting the development goal of carbon neutralization. The results show that by adjusting the ratio of different components of the foaming agent, the average cell size of the foam product is reduced by about 30%, from 130mu m to 90mu m, the compression strength of the extruded board is improved, and the long-term thermal conductivity is also reduced from 034 grade to 030 grade.

Description

Technical Field

[0001] This invention relates to a polystyrene foam, specifically to an extruded polystyrene foam using a multi-component foaming agent and its preparation method. Background Technology

[0002] Polystyrene (PS) is produced by the addition polymerization of styrene. Based on its application, it can be divided into general-purpose PS and high-impact PS (HIPS). Foamed plastic products can be made by introducing a foaming agent into PS. Common foamed PS products include expandable polystyrene (EPS) produced by compression molding and extruded polystyrene (XPS) produced by extrusion.

[0003] XPS boards are widely used in exterior wall and roof insulation, composite wall insulation, cold storage transportation, and underfloor heating insulation layers due to their durable thermal insulation performance, excellent dimensional stability, superior moisture and vapor permeability resistance, good compressive strength, and ultra-long service life. Unlike EPS produced by intermittent methods, XPS is generally produced by continuous extrusion. Its production process mainly includes: a twin-screw extruder (material blending): blending PS with nucleating agents and flame retardants; gas injection; multiphase dispersion mixing; a single-screw extruder (melt cooling): melt cooling; die lip extrusion foaming; shaping and post-processing (board forming): traction shaping; edge trimming; cross-cutting, stacking, and packaging; waste recycling. Depending on product requirements, a surface roughening machine (to roughen the XPS surface) or a grooving machine may be added before the cross-cutting equipment.

[0004] Thermal conductivity refers to a material's ability to conduct heat under stable heat transfer conditions. The lower the thermal conductivity, the worse the material's heat transfer capacity, and the better its insulation performance. Currently, XPS insulation boards used for underfloor heating are classified into three grades based on their thermal conductivity: 034 (≤0.034 W / (m·K)), 030 (≤0.030 W / (m·K)), and 024 (≤0.024 W / (m·K)). The mainstream XPS products for underfloor heating on the market are grade 034. Now, through adjustments to the foaming agent formula, the thermal conductivity grade has been lowered to 030. In underfloor heating applications, for insulation layers of the same thickness, provided the compressive strength meets usage requirements, a lower thermal conductivity helps maintain indoor heat, thereby improving the heat transfer efficiency of underfloor heating and saving energy.

[0005] Solid materials exhibit three modes of heat conduction: conduction, radiation, and convection. In foam materials, due to the small and closed cell structure, the gas trapped within the cells experiences almost no heat convection. Therefore, heat conduction in foam materials is primarily divided into conduction and radiation. Radiation is related to the material's Rothsland extinction coefficient, which is influenced by the formulation but not significantly by the cell structure. Heat conduction in foam materials is divided into solid-phase conduction and gas-phase conduction. Because the solid phase is relatively small in foam materials, heat is mainly conducted through the gas phase, accounting for approximately 60% of the total heat transfer.

[0006] Currently, the blowing agents used in XPS production are mainly alcohol + carbon dioxide + R152a or R134a. Although R152a and R134a do not damage the ozone layer, they have a high global warming potential (GWP, R152 has a GWP of 124, and R134a has a GWP of 1370). Therefore, in order to achieve the goals of energy conservation, emission reduction and carbon neutrality, it is necessary to find a blowing agent with low thermal conductivity and low GWP value. Summary of the Invention

[0007] The purpose of this invention is to provide an extruded polystyrene foam plastic using a multi-component foaming agent and its preparation method. The fourth-generation HFO series foaming agent is used to reduce greenhouse gas emissions while lowering the thermal conductivity of XPS, thereby achieving energy conservation and emission reduction and increasing the thermal insulation performance of XPS.

[0008] To achieve the above objectives, the present invention provides an extruded polystyrene foam using a multi-component blowing agent, the foam being made of the following components by weight percentage: 85-90 wt% polystyrene, 0.5-3 wt% nucleating agent, 2.6-5 wt% flame retardant, and 5-10 wt% blowing agent; wherein the blowing agent is selected from liquid carbon dioxide and a combination of pentane with alcohol and / or hydrofluoroolefin (HFO); the pentane is selected from one or more of n-pentane, isopentane, and cyclopentane; and the global warming potential (GWP) of the HFO is ≤6.

[0009] The extruded polystyrene foam of the present invention uses polystyrene as raw material. The nucleating agent increases the number of nucleation sites, reduces the cell size, and increases the number of cells per unit volume during the foaming process. The more nucleating agent, the more cells there are. The flame retardant is used to improve the flame retardant rating of the foam. The foaming agent is the driving force in the foam growth process. The more foaming agent, the greater the foam growth driving force. However, the foaming agent has a solubility limit in polystyrene and cannot be used in excess, otherwise it will not dissolve, resulting in pre-foaming.

[0010] Preferably, the foam is made of the following components in weight percentage: 87.2-90 wt% polystyrene, 0.9-1.8 wt% nucleating agent, 2.6-2.7 wt% flame retardant and 6.5-8.3 wt% foaming agent.

[0011] Preferably, the foaming agent is composed of the following components in parts by weight: a combination of 3.5 to 7.5 parts liquid carbon dioxide and 0.5 to 3.5 parts pentane with 0 to 2 parts alcohol and 0 to 2.5 parts hydrofluoroolefin (HFO), wherein the weight parts of alcohol and HFO cannot both be 0.

[0012] Preferably, the foaming agent is composed of the following components in parts by weight: a combination of 3.5-5.5 parts liquid carbon dioxide and 0.6-3.5 parts pentane, 0-1 parts alcohol, and 0-2.5 parts hydrofluoroolefin (HFO), wherein the weight percentages of alcohol and HFO cannot both be 0. The introduction of alcohol helps to improve the solubility of carbon dioxide in PS, reducing the average pore size from 130 μm to 90 μm.

[0013] Preferably, the hydrofluoroolefin HFO is selected from trans-1-chloro-3,3,3-trifluoropropene (HFO-1233zd) or trans-1,3,3,3-tetrafluoropropene (HFO-1234ze).

[0014] Preferably, the polystyrene is selected from general-purpose polystyrene (GPPS); the nucleating agent is selected from talc; and the flame retardant is selected from methyl octabromoether.

[0015] Another object of the present invention is to provide a method for preparing extruded polystyrene foam using a multi-component foaming agent, the method comprising the following steps:

[0016] (1) 85~90wt% polystyrene, 0.5~3wt% nucleating agent and 2.6~5wt% flame retardant are added to a twin-screw extruder in proportion. The twin-screw extruder is divided into 1-10 zones from the input end to the output end. Polystyrene, nucleating agent and flame retardant are added from zone 1. The temperature of zone 1 is 200℃. The temperature of zones 2 to 4 is increased from 200℃ to 220℃. The temperature of zones 4 to 7 is decreased from 220℃ to 205℃. The temperature of zone 8 is increased to 220℃. The temperature of zones 9 and 10 is decreased to 190℃. The polystyrene, nucleating agent and flame retardant are fully dispersed and mixed by the twin-screw extruder to form a homogeneous melt.

[0017] (2) At the point where polystyrene, nucleating agent, and flame retardant are uniformly mixed, the components of the foaming agent are injected into the twin-screw extruder in liquid form through a pressurizing pump and a metering pump from zone 4 to zone 5. Before injection, pressure should be applied to prevent backflow of gas in the foaming agent. The outer wall of the screw at the foaming agent injection point in the twin-screw extruder has several protrusions. These protrusions are used to prevent the formation of liquid pools and to promote the rapid and uniform dispersion of gas in the foaming agent in the melt. Moreover, at the foaming agent injection point in the twin-screw extruder, after the foaming agent is injected into the twin-screw extruder, the plasticization of the melt by the foaming agent leads to a decrease in melt strength. Therefore, the barrel of the twin-screw extruder at this point should be cooled down.

[0018] (3) After the melt that has been mixed uniformly in step (2) is filtered to remove impurities by the screen changer of the twin-screw extruder, it is transported to the second-stage single-screw extruder through a pipeline without screws. The single-screw extruder cools down the homogeneous melt whose melt strength has dropped significantly after plasticization by the foaming agent. The single-screw extruder is divided into 1-6 zones from the input end to the output end. Each zone is cooled in stages, and the temperature of each zone is independently set to 85~160℃ in order to improve the melt strength, support the growth of cells, and achieve the melt strength range required for the molded product. Moreover, the speed of the single-screw extruder is controlled at 6~8 rpm to prevent the shear heat of the screw from heating the melt. A static mixer or melt pump is installed in front of the die head of the single-screw extruder to control and maintain the melt pressure ≥7.39MPa to prevent the melt from depressurizing too early and causing pre-foaming. The temperature of the static mixer is increased to 105~120℃ to prevent the melt from forming a dead zone where the flow stops.

[0019] (4) After being cooled by the single-screw extruder, the homogeneous melt passes through the die head and die lip of the single-screw extruder in sequence. Due to the rapid pressure relief, the thermodynamic steady state is broken, and the foaming agent gas escapes rapidly from the polymer, causing the melt volume to expand and forming a closed cell structure. Then, the extruded polystyrene is sized by the sizing template, leveling machine and traction roller. Among them, the pressure drop distribution in each zone of the die of the sizing template is considered and calculated under the premise of controlling the total melt pressure drop from the die head of the single-screw extruder to atmospheric pressure. The speed of the traction roller should be matched with the melt extrusion amount at the die orifice of the single-screw extruder to ensure that the tensile force on the sheet is consistent in the transverse direction.

[0020] Another object of the present invention is to provide a foaming agent for extruded polystyrene foam, said foaming agent being selected from liquid carbon dioxide and pentane with alcohol and / or hydrofluoroolefins (HFO);

[0021] The pentane is selected from one or more of n-pentane, isopentane and cyclopentane;

[0022] The global warming potential (GWP) of the hydrofluoroolefin (HFO) is ≤6.

[0023] Preferably, the foaming agent is composed of the following components in parts by weight: a combination of 3.5 to 7.5 parts liquid carbon dioxide and 0.5 to 3.5 parts pentane with 0 to 2 parts alcohol and 0 to 2.5 parts hydrofluoroolefin (HFO), wherein the weight parts of alcohol and HFO cannot both be 0.

[0024] Preferably, the foaming agent is composed of the following components in parts by weight: a combination of 3.5 to 5.5 parts liquid carbon dioxide and 0.6 to 3.5 parts pentane with 0 to 1 parts alcohol and 0 to 2.5 parts hydrofluoroolefin (HFO), wherein the weight parts of alcohol and HFO cannot both be 0.

[0025] Preferably, the hydrofluoroolefin HFO is selected from trans-1-chloro-3,3,3-trifluoropropene or trans-1,3,3,3-tetrafluoropropene.

[0026] The present invention relates to extruded polystyrene foam using a multi-component foaming agent and its preparation method, which solves the problems of pollution and heat transfer efficiency of existing XPS materials, and has the following advantages:

[0027] (1) The extruded polystyrene foam of the present invention uses a multi-component foaming agent. The synergistic effect between the foaming agent components promotes the solubility of CO2 in the polymer, which is beneficial to the nucleation of the cells. The cell size of the foam product is reduced by about 30%, and the compressive strength of XPS is improved.

[0028] (2) The extruded polystyrene foam of the present invention has a reduced thermal conductivity under the premise of constant XPS thickness, which is conducive to heat retention and achieves the purpose of energy saving and environmental protection;

[0029] (3) The extruded polystyrene foam of the present invention uses a multi-component foaming agent, which, compared with the original alcohol + carbon dioxide foaming system, reduces the dimensional shrinkage of XPS boards and increases dimensional stability and mechanical properties.

[0030] (4) The present invention uses a novel HFO series foaming agent, which has a low GWP value and a low thermal conductivity, which is beneficial to reducing greenhouse gas emissions and achieving the corresponding carbon neutrality goal. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the apparatus used to prepare extruded polystyrene foam according to the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] An extruded polystyrene foam is made from the following components in parts by weight: 100 parts (89.9 wt%) of polystyrene (using general-purpose polystyrene GPPS), 1 part (0.9 wt%) of talc (as a nucleating agent), 3 parts (2.7 wt%) of flame retardant (using methyl octabromoether), and 7.2 parts (6.5 wt%) of blowing agent. The blowing agent is composed of the following components in parts by weight: 1.1 parts of alcohol, 5.5 parts of liquid carbon dioxide, and 0.6 parts of pentane.

[0035] The preparation process of the above-mentioned extruded polystyrene foam is as follows:

[0036] (1) 100 parts of polystyrene, 1 part of nucleating agent and 3 parts of flame retardant are added to a twin-screw extruder in proportion. The twin-screw extruder is divided into 1-10 zones from the input end to the output end. Polystyrene, nucleating agent and flame retardant are added from zone 1. The temperature of zone 1 is 200°C. The temperature of zones 2 to 4 is increased from 200°C to 220°C. The temperature of zones 4 to 7 is decreased from 220°C to 205°C. The temperature of zone 8 is increased to 220°C. The temperature of zones 9 and 10 is decreased to 190°C. The polystyrene, nucleating agent and flame retardant are fully dispersed and mixed by the twin-screw extruder to form a homogeneous melt. In this process, the temperature in zone 1 should not be too high, otherwise the polystyrene will melt and stick to the feed inlet, clogging it and affecting feeding. The temperature in zones 2-4 increases, and under the action of screw shear force and barrel temperature, the polystyrene melts and plasticizes, mixing evenly with talc and flame retardant. The foaming agent is injected from zones 4-5 of the twin-screw extruder. Because the foaming agent has a strong plasticizing effect on the material, the melt strength of the material decreases significantly. The temperature in zones 5-7 begins to decrease to slightly increase the melt strength. A screen changer is set between zones 7 and 8 as a filter to filter out unmelted impurities in the material, such as iron filings. The temperature in this area should be higher to promote the material to pass through the filter quickly.

[0037] (2) At the point where polystyrene, nucleating agent and flame retardant are uniformly mixed, the components of the foaming agent are injected into the twin-screw extruder in liquid form through a pressurizing pump and a metering pump between zones 4 and 5. Before injection, pressure should be applied to prevent backflow of gas in the foaming agent. The outer wall of the screw at the foaming agent injection point in the twin-screw extruder has several protrusions. These protrusions are used to prevent the formation of liquid pools and to promote the rapid and uniform dispersion of gas in the foaming agent in the melt. Moreover, at the foaming agent injection point in the twin-screw extruder, after the foaming agent is injected into the twin-screw extruder, the plasticization of the melt by the foaming agent leads to a decrease in melt strength. Therefore, the barrel of the twin-screw extruder should be cooled down.

[0038] (3) After the melt that has been uniformly mixed in step (2) is filtered to remove impurities by the screen changer of the twin-screw extruder, it is transported to the second-stage single-screw extruder through a pipeline without a screw. The single-screw extruder cools down the homogeneous melt whose melt strength has dropped significantly after plasticization by the foaming agent. The single-screw extruder is divided into 1-6 zones from the input end to the output end, and each zone is cooled in stages. The temperature of each zone is independently set to 85~160℃ in order to improve the melt strength, support cell growth, and achieve the melt strength range required for the molded product. In addition, the rotation speed of the single-screw extruder is controlled at 6~8 The rpm is adjusted to prevent the screw shear heat from overheating the melt. A static mixer or melt pump should be installed before the die head of the single-screw extruder to control and maintain the melt pressure ≥7.39MPa, preventing premature pressure release and pre-foaming. The temperature of the static mixer is increased to 105~120℃ to prevent dead zones where the melt flow stagnates. The temperature drop in zones 1-2 of the single-screw extruder should not be too large to prevent material accumulation at the front end, which could lead to excessive screw pressure; the temperature should be 140~160℃. Zones 3-6 then cool the material to 85~100℃. The static mixer, installed inside the single-screw extruder, stabilizes the melt pressure and prevents pre-foaming. Appropriate heating is required in the static mixer to prevent material blockage.

[0039] (4) After being cooled by the single-screw extruder, the homogeneous melt passes through the die head (the temperature of the die head mold is 100~105℃) and the die lip of the single-screw extruder in sequence. Due to the rapid pressure relief, the thermodynamic steady state is broken, and the foaming agent gas escapes from the polymer rapidly, causing the melt volume to expand and forming a closed cell structure. Then, the extruded polystyrene is sized by the sizing template, the leveling machine and the traction roller. Among them, the pressure drop distribution in each zone of the die of the sizing template is considered and calculated under the premise of controlling the total melt pressure drop from the die head of the single-screw extruder to atmospheric pressure. The speed of the traction roller should be matched with the melt extrusion amount at the die orifice of the single-screw extruder to ensure that the tensile force on the sheet is consistent in the transverse direction.

[0040] Example 2

[0041] An extruded polystyrene foam is essentially the same as in Example 1, except that it is made from the following components in parts by weight: 100 parts (89.5 wt%) of polystyrene (using general-purpose polystyrene GPPS), 1 part (0.9 wt%) of talc (as a nucleating agent), 3 parts (2.7 wt%) of flame retardant (using methyl octabromoether), and 7.7 parts (6.9 wt%) of blowing agent. The blowing agent is composed of the following components in parts by weight: 5.5 parts of liquid carbon dioxide, 1 part of alcohol, 0.6 parts of pentane, and 0.6 parts of HFO.

[0042] The preparation process of this extruded polystyrene foam is basically the same as that in Example 1, except that the components in this example are used as raw materials for preparation.

[0043] Example 3

[0044] An extruded polystyrene foam is essentially the same as in Example 1, except that the plastic is made from the following components in parts by weight: 100 parts (89 wt%) of polystyrene (using general-purpose polystyrene GPPS), 1 part (0.9 wt%) of talc (as a nucleating agent), 3 parts (2.7 wt%) of flame retardant (using methyl octabromoether), and 8.3 parts (7.4 wt%) of blowing agent. The blowing agent consists of the following components in parts by weight: 5.5 parts of liquid carbon dioxide, 1.2 parts of HFO-1233zd, and 1.6 parts of pentane.

[0045] The preparation process of this extruded polystyrene foam is basically the same as that in Example 1, except that the components in this example are used as raw materials for preparation.

[0046] Example 4

[0047] An extruded polystyrene foam is essentially the same as in Example 1, except that the plastic is made from the following components in parts by weight: 100 parts (87.33 wt%) of polystyrene (using general-purpose polystyrene GPPS), 2 parts (1.75 wt%) of talc (as a nucleating agent), 3 parts (2.62 wt%) of flame retardant (using methyl octabromoether), and 9.5 parts (8.3 wt%) of blowing agent. The blowing agent consists of the following components in parts by weight: 3.5 parts of liquid carbon dioxide, 2.5 parts of HFO-1233zd, and 3.5 parts of pentane.

[0048] The preparation process of this extruded polystyrene foam is basically the same as that in Example 1, except that the components in this example are used as raw materials for preparation.

[0049] Comparative Example 1

[0050] An extruded polystyrene foam is essentially the same as in Example 1, except that the plastic is made from the following components in parts by weight: 100 parts (90 wt%) of polystyrene (using general-purpose polystyrene GPPS), 1 part (0.9 wt%) of talc (as a nucleating agent), 3 parts (2.7 wt%) of flame retardant (using methyl octabromoether), and 7.1 parts (6.4 wt%) of blowing agent. The blowing agent consists of the following components in parts by weight: 1.6 parts of alcohol and 5.5 parts of liquid carbon dioxide.

[0051] The preparation process of this extruded polystyrene foam is basically the same as that in Example 1, except that the components in this example are used as raw materials for preparation.

[0052] Experimental examples of XPS sample performance testing

[0053] The compressive strength and thermal conductivity of the stabilized XPS foam products were measured using a universal testing machine and a thermal conductivity meter. The results are shown in Table 2.

[0054] As can be seen from Tables 1 and 2, the novel foaming agent used in this invention, after introducing HFO and pentane, can significantly reduce the thermal conductivity of XPS and improve the compressive strength. Furthermore, the thermal conductivity decreases with increasing amounts of pentane and HFO-1233zd. Therefore, the novel foaming agent used in this invention can achieve the goal of improving product performance and reducing energy consumption.

[0055] Table 1. Composition and content of XPS samples in each example

[0056]

[0057] Note: The polystyrene in the table is general-purpose polystyrene (GPPS); the flame retardant is methyl octabromoether.

[0058] Table 2 Test data of each group of XPS samples after performance stabilization.

[0059]

[0060] By adjusting the proportions of different foaming agents, the average cell size of the foam product was reduced by about 30%, from 130μm to 90μm, and the compressive strength of the extruded board was improved. The long-term thermal conductivity was also reduced from grade 0.34 to grade 0.30.

[0061] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An extruded polystyrene foam employing a multi-component blowing agent, characterized in that, The foamed plastic is made of the following components by weight percentage: 85~90wt% polystyrene, 0.5~3wt% nucleating agent, 2.6~5wt% flame retardant and 5~10wt% foaming agent; the polystyrene is selected from general purpose polystyrene GPPS; the nucleating agent is selected from talcum powder; the flame retardant is selected from methyl octabromo ether; Wherein, the foaming agent is selected from the combination of liquid carbon dioxide and pentane and hydrofluoroolefin HFO; The pentane is selected from one or more of n-pentane, iso-pentane and cyclopentane; The global warming potential GWP of the hydrofluoroolefin HFO is ≤6, and the hydrofluoroolefin HFO is selected from trans-1-chloro-3,3,3-trifluoropropene; The foaming agent is composed of the following components by weight percentage: 3.5~5.5 parts of liquid carbon dioxide and 1.6~3.5 parts of the combination of pentane and 1.2~2.5 parts of hydrofluoroolefin HFO.

2. A process for the production of extruded polystyrene foam using a multicomponent blowing agent as claimed in claim 1, characterized in that, The method comprises the following steps: (1) 85~90wt% polystyrene, 0.5~3wt% nucleating agent and 2.6~5wt% flame retardant are added into a double-screw extruder in proportion, the double-screw extruder is divided into 1-10 zones from the input end to the output end, the polystyrene, the nucleating agent and the flame retardant are added from zone 1, the temperature of zone 1 is 200℃, the temperature is increased from 200℃ to 220℃ from zone 2 to zone 4, the temperature is decreased from 220℃ to 205℃ from zone 4 to zone 7, the temperature of zone 8 is increased to 220℃, the temperature of zone 9 and zone 10 is decreased to 190℃, the polystyrene, the nucleating agent and the flame retardant are fully dispersed and mixed by the double-screw extruder to form a homogeneous melt; (2) When the polystyrene, the nucleating agent and the flame retardant are uniformly mixed, each component of the foaming agent is injected into the double-screw extruder in liquid state through a pressure pump and a metering pump between zone 4 and zone 5 of the double-screw extruder, the gas in the foaming agent should be pressurized before injection to prevent backflow; wherein, the outer wall of the screw of the position where the foaming agent is injected in the double-screw extruder has a plurality of protrusions, which are used to prevent the formation of a liquid pool and promote the rapid dispersion of the gas in the foaming agent in the melt; (3) After the melt mixed uniformly in step (2) is filtered to remove impurities by a screen changer of the double-screw extruder, it is conveyed to a two-stage single-screw extruder through a pipeline without screw, the single-screw extruder cools the homogeneous melt whose melt strength is greatly reduced after plasticizing by the foaming agent, the single-screw extruder is divided into 1-6 zones from the input end to the output end, each zone is independently set to 85~160℃ for temperature gradient cooling, so as to improve the melt strength, support cell growth and achieve the required melt strength range of the formed product; moreover, the rotating speed of the single-screw extruder is controlled at 6~8 rpm to prevent the screw from shearing and heating the melt; a static mixer or a melt pump is arranged before the head of the single-screw extruder to control and maintain the pressure of the melt ≥7.39 MPa, prevent the melt from prematurely decompressing and causing pre-foaming, and increase the temperature of the static mixer to 105~120℃ to prevent the melt from flowing in the dead zone; (4) the homogeneous melt after temperature reduction by the single screw extruder is sequentially passed through the head of the single screw extruder and a die lip, and the thermodynamic steady state is broken due to rapid pressure relief, the blowing agent gas rapidly escapes from the polymer, the melt volume expands, a closed cell structure is formed, and then the extruded polystyrene is sized by a sizing mold, a leveling machine and a traction roller; wherein the speed of the traction roller should match the melt extrusion amount of the die port of the head of the single screw extruder, so as to ensure that the stretching force received by the plate in the transverse direction is consistent.

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