Process for the preparation of a reinforced flame-retardant pbt / pet alloy stable to thermal distortion

Abstract

The application discloses a preparation method of a reinforced flame-retardant PBT / PET alloy with stable heat deformation temperature, and belongs to the technical field of high polymer materials. In the preparation method, a double-screw extruder with a feeding section, a melting section, a metering section and a machine head is used in sequence, a flame retardant is fed in the melting section, decomposition of the flame retardant can be prevented to the maximum extent, and the shearing and mixing force in the feeding section can be increased, so that the mutual dispersion, mixing, melting and reaction of PBT, PET and other additives are realized to the maximum extent. The nucleating agent is fed in the metering section, thermal decomposition of the organic nucleating agent caused by early addition of the nucleating agent can be avoided to the maximum extent, the efficiency of the organic nucleating agent in the PBT / PET alloy is maximized, the heat deformation temperature of the PBT / PET alloy is more stable, and the performance of the blended material is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a preparation method of a reinforced flame-retardant PBT / PET alloy with stable heat distortion temperature. BACKGROUND

[0002] Polybutylene terephthalate (PBT) is a thermoplastic, semi-crystalline saturated polyester, which has high strength, excellent aging resistance and heat resistance, good dimensional stability, extremely low water absorption (about 0.1%), good electrical insulation and many other advantages, so it has become the world's fifth largest general-purpose engineering plastic after polyamide (PA), polycarbonate (PC), polyformaldehyde (POM) and polyphenyl ether (MPPO), and has been widely used in the automotive industry, mechanical equipment, electronics and other industries.

[0003] As a polyethylene terephthalate (PET) with similar structure to PBT, it can effectively reduce the production cost of PBT material due to its low price, so it has been widely used in PBT modification in recent years, and has achieved fruitful results and wide application.

[0004] At present, there are many disclosed technologies about PET modified PBT, but the focus is on the improvement of mechanical properties and flame retardant properties, and few attention is paid to the improvement and stability of heat distortion temperature, which is the pain point of domestic PBT / PET alloy materials at present. The heat distortion temperature test difference of PBT / PET alloy produced by the same formula is more than 10℃, which is a common thing, and this is also the biggest difference between domestic PBT / PET alloy and similar materials in European and American countries.

[0005] For example, the patent application with the application number "CN2021103996160" and the name "PBT / PET alloy material and its preparation method" provides a technical solution with a temperature difference of 5.5℃, but this technical solution relies on the three-dimensional network structure formed by ultra-high molecular weight polyethylene, polyamide and acrylate, which is difficult to implement in specific implementation, and the cost is high, waste materials are difficult to recycle, and the universality is not high. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method of a reinforced flame-retardant PBT / PET alloy with stable heat distortion temperature, which can prepare a reinforced flame-retardant PBT / PET alloy with more stable heat distortion temperature, and the prepared reinforced flame-retardant PBT / PET alloy has better mechanical properties.

[0007] To solve the above technical problems, the technical scheme of the present application is: a preparation method of a reinforced flame-retardant PBT / PET alloy with stable hot deformation temperature, comprising a double-screw extruder for continuously shearing and mixing the material and then extruding, the double-screw extruder comprising a feeding section, a melting section, a metering section and a head arranged in sequence, a raw material feeding device being connected to the starting end of the feeding section, a glass fiber adding port being arranged at the starting end of the melting section, a flame retardant side feeding device being connected to the melting section downstream of the glass fiber adding port, a vacuum exhaust port being arranged at the starting end of the metering section, and a nucleating agent side feeding device being connected to the metering section downstream of the vacuum exhaust port.

[0008] In the preparation, the feeding section, the melting section, the metering section and the head are heated to a specified temperature and kept for 30 min; then the double-screw extruder is started, the raw material feeding device feeds the double-screw extruder with the weighed and mixed raw material composed of PBT, PET, antioxidant, lubricant, stabilizer, hydrolysis inhibitor and compatibilizer; the feeding section continuously shears and dispersively mixes the raw material, the raw material is initially melted and then enters the melting section; at the starting end of the melting section, glass fiber is added from the glass fiber adding port, the hot air wrapped by the material and the gas generated by the preliminary action of the hydrolysis inhibitor during the initial melting process form natural exhaust from the glass fiber adding port, the flame retardant is added when the material reaches the flame retardant side feeding device, the material with the added flame retardant is further sheared and mixed and further melted in the melting section and then enters the metering section; at the starting end of the metering section, the low molecular material generated by the reaction of the hydrolysis inhibitor with PBT and PET in the material is discharged from the vacuum exhaust port, the nucleating agent is added when the material reaches the nucleating agent side feeding device, and the material with the added nucleating agent is further sheared and mixed in the metering section to form a stable melt flow, and the melt flow is extruded into a strip-shaped material through the head.

[0009] As a preferred technical scheme, at the starting end of the melting section, when the gas discharged at the glass fiber adding port significantly increases, glass fiber is further added from the glass fiber adding port.

[0010] As a preferred technical scheme, the strip-shaped material is cooled in a cooling water tank and then cut into granular material by a granulator; the cooling method of the strip-shaped material in the cooling water tank is that the strip-shaped material enters the cooling water in the cooling water tank and is immediately pulled out of the water surface of the cooling water, and then passes through the cooling water tank in a manner of being suspended in the air above the cooling water.

[0011] As a preferred technical scheme, the feeding section comprises feeding area, I area, II area, III area and IV area arranged in sequence, the melting section comprises V area, VI area, VII area and VIII area arranged in sequence, and the metering section comprises IX area and X area arranged in sequence; the specified temperature required for heating of the feeding section, the melting section and the metering section is respectively 205-215℃ for I area, 225-235℃ for II area, 245-250℃ for III area, 245-250℃ for IV area, 235-245℃ for V area, 235-245℃ for VI area, 245-250℃ for VII area, 245-250℃ for VIII area, 235-245℃ for IX area and 235-240℃ for X area, and the specified temperature required for heating of the head is 240-245℃.

[0012] As a preferred technical scheme, the weighing of the components in the raw material is as follows: PBT 25-45 parts, PET 9-20 parts, antioxidant 0.3-0.5 parts, lubricant 0.15-0.3 parts, stabilizer 0.15-0.35 parts, anti-hydrolysis agent 0.15-0.3 parts, and compatibilizer 2-3 parts; the corresponding mass fraction of the glass fiber is 20-40 parts, the corresponding mass fraction of the flame retardant fed by the flame retardant side feeding device is 11-15 parts, and the corresponding mass fraction of the nucleating agent fed by the nucleating agent side feeding device is 0.3-0.5 parts.

[0013] As a preferred technical scheme, the glass fiber is non-silane impregnated flat alkali-free glass fiber with a wire diameter of 13-14μm.

[0014] As a preferred technical scheme, the flame retardant is compounded from a main flame retardant and an auxiliary flame retardant at a compounding mass ratio of 3:1; the main flame retardant is one of brominated epoxy resin, brominated polystyrene, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, phenoxy tetra-bromobisphenol A carbonate oligomer, 1,2,4,5-tetrabromo-3,6-di(pentabromophenoxy)benzene, 1,2-bis(tetrabromophthalimide)ethane, and polypropylene acid pentabromobenzyl ester; and the auxiliary flame retardant is one of antimony trioxide and zinc borate.

[0015] As a preferred technical scheme, the nucleating agent is one of dibenzyl sorbitol, 1,3-2,4-di(α-ethyl) benzyl sorbitol, sodium benzoate, methylene bis(2,4-di-t-butylphenoxy) sodium phosphate, and bis[2,2'-methylene bis(4,6-di-t-butylphenyl) phosphate]hydroxy aluminum.

[0016] As a preferred technical scheme, the double screw extruder comprises a barrel, a screw rotatably installed in the barrel, and a screw driving device connected to the screw and extending out of the barrel; the screw is provided with a feeding thread combination, a melting thread combination and a metering thread combination corresponding to the feeding section, the melting section and the metering section respectively.

[0017] As a preferred technical scheme, the feeding thread combination comprises a feeding initial conveying combination corresponding to the raw material feeding device, and the feeding initial conveying combination is provided with a feeding shearing mixing combination and a feeding subsequent conveying combination arranged alternately in sequence after the feeding initial conveying combination, and a feeding reverse thread block is arranged after the feeding subsequent conveying combination at the end.

[0018] The melting thread combination comprises a melting initial conveying combination corresponding to the glass fiber feeding port and the flame retardant side feeding device respectively, and the melting initial conveying combination is provided with a melting shearing mixing combination and a melting subsequent conveying combination arranged alternately in sequence after the melting initial conveying combination, and a melting reverse thread block is arranged after the melting subsequent conveying combination at the end.

[0019] The metering thread combination comprises a metering initial conveying combination corresponding to the vacuum exhaust port and the nucleating agent side feeding device respectively, and the metering initial conveying combination is provided with a metering shearing mixing combination and a metering subsequent conveying combination arranged alternately in sequence after the metering initial conveying combination.

[0020] Due to the above technical scheme, the flame retardant is fed in the melting section, which can prevent the decomposition of the flame retardant to the maximum extent, ensure the flame retardation performance of the alloy, and facilitate the increase of the shearing mixing force in the shearing mixing process in the feeding section due to the absence of the flame retardant in the raw material, so as to maximize the dispersion, mixing, melting and reaction of PBT, PET and other additives, so that the prepared PBT / PET alloy has better mechanical properties. The nucleating agent is fed in the metering section, which can avoid the thermal decomposition of the organic nucleating agent caused by the early addition of the nucleating agent to the maximum extent, thereby effectively avoiding the failure or partial failure of the organic nucleating agent, maximizing the efficiency of the organic nucleating agent in the PBT / PET alloy, avoiding the influence of the failure problem or the agglomeration problem caused by the inorganic nucleating agent on the thermal deformation temperature stability, i.e. making the thermal deformation temperature of the PBT / PET alloy more stable. At the same time, the nucleating effect of the nucleating agent can further improve the performance of the blended material. BRIEF DESCRIPTION OF DRAWINGS

[0021] The following drawings are only intended to illustrate and explain the present application and do not limit the scope of the present application. Among them:

[0022] Figure 1 is a structural schematic view of the double screw extruder of the embodiment of the present application;

[0023] Figure 2 is a structural schematic diagram of the screw of the embodiment of the present application;

[0024] Figure 3 is a structural schematic diagram of the screw of Comparative Examples 1 to 3;

[0025] Figure 4 is a structural schematic diagram of the screw of Comparative Examples 4 to 6.

[0026] In the figure: 1 - twin-screw extruder; 11 - barrel; 12 - screw; 13 - screw driving device;

[0027] 2 - feeding section; 21 - feeding zone; 22 - Zone I; 23 - Zone II; 24 - Zone III; 25 - Zone IV; 26 - raw material feeding device;

[0028] 3 - melting section; 31 - Zone V; 32 - Zone VI; 33 - Zone VII; 34 - Zone VIII; 35 - glass fiber feeding port; 36 - flame retardant side feeding device;

[0029] 4 - metering section; 41 - Zone IX; 42 - Zone X; 43 - vacuum vent; 44 - nucleating agent side feeding device;

[0030] 5 - head;

[0031] 6 - feeding thread combination; 61 - feeding initial conveying combination; 62 - feeding shearing mixing combination; 621 - feeding shearing mixing combination one; 622 - feeding shearing mixing combination two; 623 - feeding shearing mixing combination three; 624 - feeding shearing mixing combination four; 625 - feeding shearing mixing combination five; 63 - feeding successive conveying combination; 631 - feeding successive conveying combination one; 632 - feeding successive conveying combination two; 633 - feeding successive conveying combination three; 634 - feeding successive conveying combination four; 635 - feeding successive conveying combination five; 64 - feeding reverse thread block; 65 - feeding successive conveying combination six;

[0032] 7 - melting thread combination; 71 - melting initial conveying combination; 711 - melting initial conveying combination one; 712 - melting initial conveying combination two; 72 - melting shearing mixing combination; 721 - melting shearing mixing combination one; 722 - melting shearing mixing combination two; 723 - melting shearing mixing combination three; 724 - melting shearing mixing combination four; 73 - melting successive conveying combination; 731 - melting successive conveying combination one; 732 - melting successive conveying combination two; 733 - melting successive conveying combination three; 734 - melting successive conveying combination four; 74 - melting reverse thread block;

[0033] 8 - metering thread combination; 81 - metering initial conveying combination; 811 - metering initial conveying combination one; 812 - metering initial conveying combination two; 82 - metering shearing mixing combination; 83 - metering successive conveying combination; 84 - metering extruding combination. DETAILED DESCRIPTION

[0034] The application will be further described below in connection with examples. In the following detailed description of the application, exemplary embodiments of the application are described in terms of procedures, materials, and examples. It is understood that the examples described are not intended to limit the scope of the application, but rather to provide exemplary embodiments of the application. It is also understood that the examples described herein can be modified in various ways without departing from the spirit or scope of the application.

[0035] As shown in Figure 1 and Figure 2 The preparation method of the heat distortion temperature stable reinforced flame-retardant PBT / PET alloy comprises a double-screw extruder 1 for continuously shearing and mixing the materials and then extruding. Conventionally, the double-screw extruder 1 comprises a barrel 11, a screw 12 rotatably installed in the barrel 11, and a screw driving device 13 connected to the screw 12 extending out of the barrel 11.

[0036] The double-screw extruder 1 comprises a feeding section 2, a melting section 3, a metering section 4, and a head 5 arranged in sequence. The feeding section 2 is connected with a raw material feeding device 26 at the starting end thereof, which is used to feed the mixed raw materials into the feeding section 2. The screw 12 feeding and the like can be used for active feeding, which is a common technology known to those skilled in the art, and the specific structure and principle will not be described here.

[0037] The melting section 3 is provided with a glass fiber adding port 35 at the starting end thereof. The melting section 3 is connected with a flame retardant side feeding device 36 downstream of the glass fiber adding port 35, which is used to add flame retardant to the melting section 3. The screw 12 feeding and the like can be used for active feeding, and preferably the hopper of the flame retardant adopts a loss-in-weight scale to realize uniform metering and continuous feeding of the flame retardant. The loss-in-weight scale feeding method is also a common technology known to those skilled in the art, and will not be described here.

[0038] The metering section 4 is provided with a vacuum exhaust port 43 at the starting end thereof. The metering section 4 is connected with a nucleating agent side feeding device 44 downstream of the vacuum exhaust port 43, which is used to add nucleating agent to the metering section 4. The screw 12 feeding and the like can be used for active feeding, and the hopper of the nucleating agent also preferably adopts a loss-in-weight scale to realize uniform metering and continuous feeding.

[0039] In the preparation, the feeding section 2, the melting section 3, the metering section 4 and the head 5 are heated to the specified temperature and kept for 30 minutes. Then the twin-screw extruder 1 is started, and the raw material feeding device 26 feeds the weighed and mixed raw material composed of PBT, PET, antioxidant, lubricant, stabilizer, anti-hydrolysis agent and compatibilizer to the twin-screw extruder 1. The feeding section 2 continuously shears and dispersively mixes the raw material, and the raw material is initially melted and enters the melting section 3. At the starting end of the melting section 3, the glass fiber is added from the glass fiber adding port 35, and the hot air wrapped by the material and the gas generated by the preliminary action of the anti-hydrolysis agent during the initial melting process form natural exhaust from the glass fiber adding port 35. The material reaches the flame retardant side feeding device 36, and the flame retardant is added to the material. The material with the added flame retardant is further sheared and mixed and further melted in the melting section 3, and then enters the metering section 4. At the starting end of the metering section 4, the low molecular material generated by the reaction of the anti-hydrolysis agent with PBT and PET in the material is discharged from the vacuum exhaust port 43, and the nucleating agent is added to the material when it reaches the nucleating agent side feeding device 44. The material with the added nucleating agent is further sheared and mixed in the metering section 4 to form a stable melt flow, and the melt flow is extruded into a strip-shaped material through the head 5.

[0040] The gas discharged from the glass fiber adding port 35 is mainly the gas generated by the preliminary reaction of the anti-hydrolysis agent with PBT and PET, and the preliminary reaction is based on shearing and mixing and temperature supply. Therefore, preferably, when the gas discharged from the glass fiber adding port 35 significantly increases at the starting end of the melting section 3, the glass fiber is added from the glass fiber adding port 35 again to ensure that the added glass fiber is not easily chemically reacted with the anti-hydrolysis agent under the condition that the preliminary reaction of the anti-hydrolysis agent with PBT and PET produces harmless anti-degradation harmless products, thereby reducing the influence of the glass fiber on the action of the anti-hydrolysis agent.

[0041] Preferably, the strip-shaped material is cooled in a cooling water tank and then cut into granular material by a granulator. The cooling method of the strip-shaped material in the cooling water tank is that the strip-shaped material enters the cooling water in the cooling water tank and is immediately pulled out of the water surface of the cooling water, and then passes through the cooling water tank in a way of being suspended in the air above the cooling water. This cooling method in the way of a dragonfly landing on water can ensure that the strip-shaped material still maintains a high temperature when it reaches the granulator, thereby avoiding the situation that the strip-shaped material becomes hard and increases the burden of the granulator. Of course, after granulation, the granular material can be packaged and output after being screened by a vibrating screen.

[0042] The flame retardant is fed at the beginning of the melting section 3, which can prevent the decomposition of the flame retardant to the maximum extent, ensure the flame retardation of the alloy, and on the other hand, since there is no flame retardant inside when the raw material is added, the shearing and mixing force can be increased during the shearing and mixing process in the feeding section, so that the mutual dispersion, mixing, melting and reaction of PBT, PET and other additives are maximized, so that the prepared PBT / PET alloy has better mechanical properties. The nucleating agent is fed at the beginning of the metering section 4, which can avoid the thermal decomposition of the organic nucleating agent caused by the premature addition of the nucleating agent to the maximum extent, thereby effectively avoiding the failure or partial failure of the organic nucleating agent, thereby maximizing the effectiveness of the organic nucleating agent in the PBT / PET alloy, avoiding the influence of the agglomeration problem caused by the inorganic nucleating agent on the thermal deformation temperature stability, that is, making the thermal deformation temperature of the PBT / PET alloy more stable. At the same time, the nucleation of the nucleating agent can further improve the performance of the blended material.

[0043] Based on the segmented arrangement of the double-screw extruder 1 and the shearing and mixing effect on each section, the screw 12 is provided with a feeding thread combination 6, a melting thread combination 7 and a metering thread combination 8 corresponding to the feeding section 2, the melting section 3 and the metering section 4 respectively.

[0044] The feeding thread combination 6 includes a feeding initial conveying combination 61 corresponding to the raw material feeding device 26, and the feeding initial conveying combination 61 is provided with a feeding shearing and mixing combination 62 and a feeding subsequent conveying combination 63 arranged alternately in sequence, and the feeding subsequent conveying combination 63 at the end is provided with a feeding reverse thread block 64. The input raw material is initially conveyed through the feeding initial conveying combination 61, and the raw material is continuously sheared and dispersed mixed through the feeding shearing and mixing combination 62, and in this process, the feeding subsequent conveying combination 63 arranged at intervals maintains the conveying effect; finally, at the end of the feeding section 2, the blocking effect of the feeding reverse thread block 64 causes the conveyed raw material to form a pressure zone at this position, which on the one hand can make the internal hot air and the initially reacted gas of the raw material easily reverse from the raw material feeding position by pressure polymerization, and on the other hand can facilitate the raw material to be concentrated at the bottom position of the screw 12 after passing through the pressure zone due to the release of pressure and the reduction of volume, which is convenient for the subsequent addition of components such as glass fibers, and also facilitates the internal hot air and the initially reacted gas of the raw material to be further discharged from the glass fiber feeding port 35.

[0045] The greater shearing mixing force effect of the feeding section 2 generated based on the post-adding of the flame retardant can be achieved, five feeding shearing mixing combinations 62 are arranged in the feeding screw thread combination 6 of the application, and correspondingly, five feeding continuous conveying combinations 63 are arranged. The five feeding shearing mixing combinations 62 and the five feeding continuous conveying combinations 63 arranged alternately are sequentially defined as feeding shearing mixing combination one 621, feeding continuous conveying combination one 631, feeding shearing mixing combination two 622, feeding continuous conveying combination two 632, feeding shearing mixing combination three 623, feeding continuous conveying combination three 633, feeding shearing mixing combination four 624, feeding continuous conveying combination four 634, feeding shearing mixing combination five 625 and feeding continuous conveying combination five 635.

[0046] More specifically, the feeding initial conveying combination 61 is composed of a middle lead positive conveying thread, a large lead positive conveying thread and a middle lead positive conveying thread, the feeding shearing mixing combination one 621 is composed of a 30° stagger angle kneading block and a 45° stagger angle kneading block, the feeding continuous conveying combination one 631 is composed of a middle lead positive conveying thread and a small lead positive conveying thread, the feeding shearing mixing combination two 622, the feeding shearing mixing combination three 623, the feeding shearing mixing combination four 624 and the feeding shearing mixing combination five 625 are each composed of a 45° stagger angle kneading block, the feeding continuous conveying combination two 632 is composed of a middle lead positive conveying thread and a small lead positive conveying thread, the feeding continuous conveying combination three 633, the feeding continuous conveying combination four 634 and the feeding continuous conveying combination five 635 are each composed of a small lead positive conveying thread, and the feeding reverse thread block 64 is composed of a half lead small lead reverse conveying thread.

[0047] In the thread elements, the stagger angle kneading block has shearing mixing effect, with the increase of the stagger angle, the shearing effect will be stronger and stronger, the dispersion mixing effect will be weaker and weaker, and the distribution mixing effect will be stronger and stronger. When the stagger angle is 45°, the shearing effect is moderate, and the dispersion mixing and the distribution mixing reach balance. For this filling process, the non-fiber filling is mainly dispersion mixing, and the fiber filling is mainly distribution mixing. Therefore, the 30° and 45° stagger angle kneading blocks are mainly arranged for shearing mixing in the feeding section 2 of the application, the moderate shearing effect and the relatively balanced dispersion mixing effect can be achieved, multiple groups of kneading blocks are simultaneously used in the feeding section 2 to strengthen the shearing and dispersion mixing of the raw materials, the uniform dispersion and melting of PBT, PET and other additives can be promoted as soon as possible, and the reaction process of the hydrolysis-resistant agent and PBT, PET can be accelerated.

[0048] The melt thread combination 7 comprises melt start conveying combinations 71 corresponding to the glass fiber feeding port 35 and the flame retardant side feeder 36 respectively, and is followed by melt shear mixing combinations 72 and melt continuation conveying combinations 73 arranged alternately, and the melt continuation conveying combination 73 at the end is followed by a melt reverse thread block 74. The raw materials with added glass fiber and flame retardant are continuously conveyed through the melt start conveying combination 71, and the materials formed by the glass fiber, flame retardant and raw materials are continuously sheared and mixed through the melt shear mixing combination 72, and in this process, the melt continuation conveying combination 73 arranged at intervals maintains the conveying function; finally, at the end of the melt section 3, the melt reverse thread block 74 also hinders the conveying of the materials to form a pressure zone, which is also conducive to the exhaust and the subsequent addition of components such as nucleating agents.

[0049] The melt thread combination 7 comprises melt start conveying combinations 71 corresponding to the glass fiber feeding port 35 and the flame retardant side feeder 36 respectively, and is followed by melt shear mixing combinations 72 and melt continuation conveying combinations 73 arranged alternately, and the melt continuation conveying combination 73 at the end is followed by a melt reverse thread block 74. The raw materials with added glass fiber and flame retardant are continuously conveyed through the melt start conveying combination 71, and the materials formed by the glass fiber, flame retardant and raw materials are continuously sheared and mixed through the melt shear mixing combination 72, and in this process, the melt continuation conveying combination 73 arranged at intervals maintains the conveying function; finally, at the end of the melt section 3, the melt reverse thread block 74 also hinders the conveying of the materials to form a pressure zone, which is also conducive to the exhaust and the subsequent addition of components such as nucleating agents.

[0050] More specifically, the melt start conveying combination one 711 is composed of a large lead positive conveying thread, a medium lead positive conveying thread and a small lead positive conveying thread, the melt start conveying combination two 712 is composed of a large lead positive conveying thread and a medium lead positive conveying thread, the melt shear mixing combination one 721 is composed of a 45° stagger angle kneading block and a 60° stagger angle kneading block, the melt continuation conveying combination one 731 is composed of a medium lead positive conveying thread, the melt shear mixing combination two 722 is composed of a 45° stagger angle kneading block, the melt continuation conveying combination two 732 is composed of a small lead positive conveying thread, the melt shear mixing combination three 723 is composed of a 45° stagger angle kneading block and a 60° stagger angle kneading block, the melt continuation conveying combination three 733 is composed of a small lead positive conveying thread, the melt shear mixing combination four 724 is composed of a 45° stagger angle kneading block, the melt continuation conveying combination four 734 is composed of a half lead small lead positive conveying thread, and the melt reverse thread block 74 is composed of a half lead small lead reverse conveying thread.

[0051] The melt thread combination 7 includes the melt feeding combination one 711 and the melt feeding combination two 712, both of which adopt the way of large lead positive conveying thread cooperating with medium lead positive conveying thread, which can effectively reduce the melt height of the mixed melt material at this position, and is beneficial to the addition of glass fiber and flame retardant and natural exhaust. The melt section 3 includes four kneading blocks with staggered angles of 45° to balance the dispersion and mixing of the flame retardant and the distribution and mixing of the glass fiber, and two kneading blocks with staggered angles of 60° to enhance the distribution and mixing of the glass fiber, so that the melt section 3 realizes the dispersion and mixing of the flame retardant and the blend material, and also realizes the efficient distribution and mixing of the glass fiber. In addition, the shearing action of the multiple kneading blocks is also beneficial to the sufficient reaction of the hydrolysis-resistant agent and PBT and PET.

[0052] The metering thread combination 8 includes a metering initial conveying combination 81 corresponding to the vacuum exhaust port 43 and the nucleating agent side feeding device 44, respectively, and is provided with a metering shearing mixing combination 82 and a metering consecutive conveying combination 83 arranged alternately in sequence after the metering initial conveying combination 81. The material added with the nucleating agent is continuously conveyed through the metering initial conveying combination 81, the shearing and mixing of the material are carried out through the metering shearing mixing combination 82, and the shearing and mixing material is also conveyed through the metering consecutive conveying combination 83, so as to finally realize the extrusion at the head 5.

[0053] The metering thread combination 8 in the application only includes one metering shearing mixing combination 82 and one metering consecutive conveying combination 83 to realize the uniform dispersion of the nucleating agent. The metering initial conveying combination 81 includes a metering feeding combination one 811 corresponding to the vacuum exhaust port 43 and a metering feeding combination two 812 corresponding to the nucleating agent side feeding device 44.

[0054] More specifically, the metering feeding combination one 811 and the metering feeding combination two 812 are both composed of two sections of large lead positive conveying thread and medium lead positive conveying thread, which can also effectively reduce the melt height of the mixed melt material at this position, and is beneficial to the vacuum exhaust and the addition of the nucleating agent. The metering shearing mixing combination 82 is composed of a section of 45° staggered angle kneading block, and the metering consecutive conveying combination 83 is composed of a section of small lead positive conveying thread.

[0055] The above is the implementation of the screw 12 cooperating with the segmented feeding in the application, and the implementation of the specified temperature required for heating in each section of the double-screw extruder 1 in the temperature cooperation is as follows.

[0056] The feeding section 2 comprises feeding zone 21, zone 22, zone 23, zone 24 and zone 25 in turn, the melting section 3 comprises zone 31, zone 32, zone 33 and zone 34 in turn, the metering section 4 comprises zone 41 and zone 42 in turn; the required heating temperature of the feeding section 2, the melting section 3 and the metering section 4 is respectively zone 22 205-215℃, zone 23 225-235℃, zone 24 245-250℃, zone 25 245-250℃, zone 31 235-245℃, zone 32 235-245℃, zone 33 245-250℃, zone 34 245-250℃, zone 41 235-245℃, zone 42 235-240℃, and the required heating temperature of the head 5 is 240-245℃.

[0057] The required heating temperature above changes in a wave shape, wherein zone 22-zone 24 gradually increases, and the highest temperature is maintained in zone 24 and zone 25, then the temperature of zone 31 and zone 32 decreases, the temperature of zone 33 and zone 34 restores to the highest temperature, the temperature of zone 41 and zone 42 gradually decreases again, and finally the temperature of the head 5 increases again. In this temperature change, the lower temperature of zone 31, zone 32, zone 41 and zone 42 can make the viscosity of the material relatively large, which is beneficial to the addition of glass fiber, flame retardant and nucleating agent, and natural or vacuum exhaust.

[0058] The above is the equipment and method for preparing PBT / PET alloy, and the implementation of the material components for preparing PBT / PET alloy is as follows.

[0059] The weighing of each component in the raw material is as follows: PBT 25-45 parts, PET 9-20 parts, antioxidant 0.3-0.5 parts, lubricant 0.15-0.3 parts, stabilizer 0.15-0.35 parts, anti-hydrolysis agent 0.15-0.3 parts, and compatible agent 2-3 parts; the corresponding mass fraction of the added glass fiber is 20-40 parts, the corresponding mass fraction of the flame retardant fed by the flame retardant side feeding device 36 is 11-15 parts, and the corresponding mass fraction of the nucleating agent fed by the nucleating agent side feeding device 44 is 0.3-0.5 parts.

[0060] Among them, the intrinsic viscosity of PBT is 0.70-0.82 dl / g, and the intrinsic viscosity of PET is 0.75-0.85 dl / g.

[0061] The antioxidant is a compound of one of the following: octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, and 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and one of the following: tris(2,4-di-tert-butylphenyl) phosphite, dilauryl thiodipropionate, distearate thiodipropionate, and dioctadecyl pentaerythritol diphosphite, in a mass ratio of 1:1. Preferably, it is a compound of octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and tris(2,4-di-tert-butylphenyl) phosphite.

[0062] The lubricant is one of pentaerythritol stearate, vinyl bis-stearamide, and oxidized polyethylene wax, preferably pentaerythritol stearate.

[0063] The stabilizer is one of calcium stearate or zinc stearate.

[0064] The anti-hydrolysis agent is one of carbodiimide, bis(di-oxazoline), or tetra(phenylglycidyl)ethane. The mechanism of action of the anti-hydrolysis agent is as follows: all anti-hydrolysis agents contain highly reactive groups, such as the cumulative double bond structure on carbodiimide and the double bond structure on bis(di-oxazoline). On tetra(phenylglycidyl)ethane Both PBT and PET contain easily hydrolyzed hydroxyl groups (-OH). After adding an anti-hydrolysis agent, the active groups on the anti-hydrolysis agent react with the hydroxyl groups generated during the hydrolysis of PBT and PET to generate stable and harmless products, which can effectively prevent further degradation and chain breakage.

[0065] The compatibilizer is one of SEBS-g-MAH, EPDM-g-MAH, and SEBS-g-GMA.

[0066] The glass fiber is a non-silane impregnated flat, alkali-free glass fiber with a diameter of 13-14 μm. Because flat glass fibers have an elliptical cross-sectional structure, this structure is more conducive to improving the mechanical properties of the blend and reducing the warpage of the modified material. Simultaneously, the non-silane impregnation of the glass fiber avoids the potential chemical reaction between the silane impregnation material and the anti-hydrolysis agent in the blend system, thereby effectively reducing the influence of the glass fiber on the anti-hydrolysis agent in this invention.

[0067] The flame retardant is compounded by a main flame retardant and an auxiliary flame retardant in a compounding mass ratio of 3:1. The main flame retardant is one of brominated epoxy resin, brominated polystyrene, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, phenoxy tetra-bromobisphenol A carbonate oligomer, 1,2,4,5-tetrabromo-3,6-bis(pentabromophenoxy) benzene, 1,2-bis(tetrabromophthalimide) ethane, and polyacrylic acid pentabromobenzyl ester; and the auxiliary flame retardant is one of antimony trioxide and zinc borate.

[0068] The nucleating agent is one of dibenzyl sorbitol, 1,3-2,4-di(α-ethyl) benzyl sorbitol, sodium benzoate, methylene bis(2,4-di-tert-butylphenoxy) sodium phosphate, and bis[2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphoric acid] hydroxy aluminum.

[0069] The nucleation mechanism of the nucleating agent is that the crystal nucleus of PBT and PET is formed by the molecular movement of PBT and PET melt, so that the nucleation rate is slow, the number of formed crystal nucleus is small, the size of finally formed spherulite is large, and the performance of PBT and PET is relatively poor. The nucleating agent acts as a heterogeneous nucleation in the crystallization process of PBT and PET, the non-polar part of the nucleating agent forms a notch on the surface, accommodates the molecular chains of the bulk material and makes them arrange neatly, and promotes nucleation. Due to the existence of a large number of heterogeneous nucleation, the spherulite of PBT and PET collides with other spherulites before it grows up, so that the size of PBT and PET spherulite is greatly reduced, thereby the performance of the blended material can be improved.

[0070] The following is further described by examples and comparative examples.

[0071] Example 1: PBT 36.8 parts, PET 9.2 parts, glass fiber 40 parts, flame retardant 11 parts (brominated epoxy resin: antimony trioxide = 3:1), nucleating agent (1,3-2,4-di(α-ethyl) benzyl sorbitol) 0.3 parts, antioxidant 0.35 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) octadecyl propionate: tris(2,4-di-tert-butylphenyl) phosphite = 1:1), lubricant (pentaerythritol stearate) 0.3 parts, stabilizer (zinc stearate) 0.15 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.18 parts, and compatibilizer (SEBS-g-MAH) 3 parts.

[0072] Example 2: PBT 32.2 parts, PET 13.8 parts, glass fiber 40 parts, flame retardant 11 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-di(α-ethyl)benzyl sorbitol) 0.4 parts, antioxidant 0.4 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.2 parts, stabilizer (zinc stearate) 0.2 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.2 parts, compatibilizer (SEBS-g-MAH) 3 parts.

[0073] Example 3: PBT 27.6 parts, PET 18.4 parts, glass fiber 40 parts, flame retardant 11 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-di(α-ethyl)benzyl sorbitol) 0.5 parts, antioxidant 0.5 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.15 parts, stabilizer (zinc stearate) 0.3 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.3 parts, compatibilizer (SEBS-g-MAH) 3 parts.

[0074] Example 4: PBT 38.5 parts, PET 16.5 parts, glass fiber 30 parts, flame retardant 12 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-di(α-ethyl)benzyl sorbitol) 0.4 parts, antioxidant 0.4 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.2 parts, stabilizer (zinc stearate) 0.2 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.2 parts, compatibilizer (SEBS-g-MAH) 3 parts.

[0075] Example 5: PBT 44.8 parts, PET 19.2 parts, glass fiber 20 parts, flame retardant 13 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-di(α-ethyl)benzyl sorbitol) 0.4 parts, antioxidant 0.4 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.2 parts, stabilizer (zinc stearate) 0.2 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.2 parts, compatibilizer (SEBS-g-MAH) 3 parts.

[0076] Example 6: PBT 38.9 parts, PET 16.6 parts, glass fiber 30 parts, flame retardant 12 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-bis(p-ethyl) benzyl sorbitol) 0.4 parts, antioxidant 0.4 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.2 parts, stabilizer (zinc stearate) 0.2 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.2 parts, compatibilizer (SEBS-g-MAH) 2.5 parts.

[0077] Example 7: PBT 39.2 parts, PET 16.8 parts, glass fiber 30 parts, flame retardant 12 parts (brominated epoxy resin : antimony trioxide = 3 : 1), nucleating agent (1,3-2,4-bis(p-ethyl) benzyl sorbitol) 0.4 parts, antioxidant 0.4 parts (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (pentaerythritol stearate) 0.2 parts, stabilizer (zinc stearate) 0.2 parts, anti-hydrolysis agent (tetra(phenyl glycidyl ether) ethane) 0.2 parts, compatibilizer (SEBS-g-MAH) 2 parts.

[0078] Example 8: PBT 38.5 parts, PET 16.5 parts, glass fiber 30 parts, flame retardant 12 parts (brominated polystyrene : antimony trioxide = 3 : 1), nucleating agent (bis[2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphoric acid]hydroxyaluminum) 0.4 parts, antioxidant 0.4 parts (tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester : tris(2,4-di-tert-butylphenyl) phosphite = 1 : 1), lubricant (vinyl bis-stearamide) 0.2 parts, stabilizer (calcium stearate) 0.2 parts, anti-hydrolysis agent (carbodiimide) 0.2 parts, compatibilizer (SEBS-g-GMA) 3 parts.

[0079] Example 9: PBT 38.5 parts, PET 16.5 parts, glass fiber 30 parts, flame retardant 12 parts (poly(pentabromobenzyl acrylate) : zinc borate = 3 : 1), nucleating agent (bis[2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphoric acid]hydroxyaluminum) 0.4 parts, antioxidant 0.4 parts (1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane : distearyl thiodipropionate = 1 : 1), lubricant (oxidized polyethylene wax) 0.2 parts, stabilizer (calcium stearate) 0.2 parts, anti-hydrolysis agent (bis-bisoxazoline) 0.2 parts, compatibilizer (EPDM-g-MAH) 3 parts.

[0080] Example 10: PBT 38.5 parts, PET 16.5 parts, glass fiber 30 parts, flame retardant 12 parts (phenoxy tetra-bromobisphenol A carbonate oligomer: antimony trioxide = 3:1), nucleating agent (bis[2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate]aluminum hydroxide) 0.4 parts, antioxidant 0.4 parts (1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane: distearyl thiodipropionate = 1:1), lubricant (oxidized polyethylene wax) 0.2 parts, stabilizer (calcium stearate) 0.2 parts, anti-hydrolysis agent (bis-bis-oxazoline) 0.2 parts, compatibilizer (EPDM-g-MAH) 3 parts.

[0081] Example 11: PBT 36.4 parts, PET 15.6 parts, glass fiber 30 parts, flame retardant 15 parts (2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine: antimony trioxide = 3:1), nucleating agent (bis[2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate]aluminum hydroxide) 0.4 parts, antioxidant 0.4 parts (1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane: distearyl thiodipropionate = 1:1), lubricant (oxidized polyethylene wax) 0.2 parts, stabilizer (calcium stearate) 0.2 parts, anti-hydrolysis agent (bis-bis-oxazoline) 0.2 parts, compatibilizer (EPDM-g-MAH) 3 parts.

[0082] The components and the respective component ratio of Comparative Example 1, Comparative Example 2 and Comparative Example 3 are the same as those of Example 3, Example 4 and Example 5 respectively, but Comparative Example 1, Comparative Example 2 and Comparative Example 3 all use the preparation method of mixing the flame retardant and the nucleating agent together in the raw materials and then adding them into the feeding section 2, which is defined as Comparative Preparation Method 1. The structure of the screw 12 of Comparative Preparation Method 1 is shown in Figure 3 Thus, the melt conveying combination two 712 corresponding to the flame retardant side feeding device 36, the metering conveying combination two 812 corresponding to the nucleating agent side feeding device 44 and the metering shearing mixing combination 82 for shearing and dispersing the later added nucleating agent do not exist in the screw 12 naturally. At the same time, because the flame retardant is added first, one feeding shearing mixing combination 62, such as the fourth feeding shearing mixing combination 624, is also reduced in the feeding thread combination 6.

[0083] In the above reduced thread combination: one, in the feeding thread combination 6, the feeding continuation combination three 633 and the feeding continuation combination four 634 automatically form a continuous continuation conveying combination, which is named as feeding continuation combination six 65 here, the feeding continuation combination six 65 is composed of two sections of middle lead positive conveying thread and small lead positive conveying thread; two, the melt feeding combination one 711 is extended to the length equal to the total length of the original melt feeding combination one 711 and the melt feeding combination two 712; three, the metering thread combination 8 as a whole forms a conveying combination, which is defined as metering extrusion combination 84 here, the metering extrusion combination 84 is composed of three sections of large lead positive conveying thread, middle lead positive conveying thread and small lead positive conveying thread.

[0084] The components and the proportion of each component of the comparative example 4, the comparative example 5 and the comparative example 6 are also respectively the same as those of the example 3, the example 4 and the example 5, but the comparative example 4, the comparative example 5 and the comparative example 6 all adopt the preparation method of mixing the nucleating agent with the flame retardant and then adding the mixture into the melt section 3 through the flame retardant side feeding device 36, which is defined as comparative preparation method two here, the screw 12 structure of the comparative preparation method two is shown in Figure 4 Therefore, the metering feeding combination two 812 corresponding to the nucleating agent side feeding device 44 and the metering shear mixing combination 82 for shearing and dispersing the added nucleating agent do not exist in the screw 12 naturally. Similarly, the metering thread combination 8 as a whole forms a conveying combination, which is also defined as metering extrusion combination 84 here, the metering extrusion combination 84 is also composed of three sections of large lead positive conveying thread, middle lead positive conveying thread and small lead positive conveying thread.

[0085] The components and the proportion of each component of the comparative example 7 are the same as those of the example 4, and the comparative example 7 adopts the same preparation method and screw 12 conveyor structure as the example 4, and the only difference is that the glass fiber of the comparative example 7 is selected as common non-silane impregnated alkali-free glass fiber.

[0086] The tensile strength, impact strength, bending strength, bending modulus and flame retardancy of the injection molded samples of the example 1 to the example 11 and the comparative example 1 to the comparative example 7 are tested, five times of formula granulation are carried out for each example and comparative example, three sample strips are taken from each time of formula granulation injection molded sample for heat distortion temperature test under 0.45 MPa, and the standard deviation is calculated according to the following formula.

[0087]

[0088] In the formula, S is the standard deviation, x i is the measured value, is the average value of x i , and N is the number of measurements.

[0089] Table 1 is the performance test results, and Table 2 is the heat distortion temperature test results.

[0090] Table 1, Examples 1-11 and Comparative Examples 1-7 Performance Comparison

[0091]

[0092] Table 2, Examples 1-11 and Comparative Examples 1-7 Heat Distortion Temperature Comparison

[0093]

[0094] Table 2 (continued Table 1), Examples 1-11 and Comparative Examples 1-7 Heat Distortion Temperature Comparison

[0095]

[0096] Table 2 (continued Table 2), Examples 1-11 and Comparative Examples 1-7 Heat Distortion Temperature Comparison

[0097]

[0098] As can be seen from Table 1, under the condition of achieving V-O grade flame retardation, the mechanical properties of the reinforced flame-retardant PBT / PET alloy prepared by the preparation method of the present application are higher than those of the reinforced flame-retardant PBT / PET alloys prepared by the comparative preparation method one and the comparative preparation method two. As can be seen from Table 2, the heat distortion temperature of the reinforced flame-retardant PBT / PET alloy prepared by the preparation method of the present application is significantly higher than that of the reinforced flame-retardant PBT / PET alloys prepared by the comparative preparation method one and the comparative preparation method two, and the highest temperature difference of the heat distortion temperature of the reinforced flame-retardant PBT / PET alloy of each of Examples 1-11 prepared by the preparation method of the present application is only 3.8℃, and the highest standard deviation is only 0.2℃, while the lowest temperature difference of the heat distortion temperature of the reinforced flame-retardant PBT / PET alloy of each of Comparative Examples 1-3 and Comparative Examples 4-6 prepared by the latter two methods is 21.2℃ and 13℃, and the lowest standard deviation is 1.14℃ and 1.60℃, which also shows that the heat distortion temperature stability of the reinforced flame-retardant PBT / PET alloy material prepared by the preparation method of the present application is significantly higher than that of the latter two. In addition, as can be seen from Example 4 and Comparative Example 7, the mechanical properties of the flat glass fiber are higher than those of the ordinary glass fiber, but the heat distortion temperature is not much different.

[0099] The description of the application is presented for purposes of illustration and description, and is not intended to limit the application to the form described. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to provide the best illustration of the principles of the application and its practical application, and to enable others skilled in the art to understand the application for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

1. Process for the preparation of a heat distortion temperature stable reinforced flame retardant PBT / PET alloy, characterized in that: The invention includes a twin-screw extruder for continuously shearing and mixing materials before extrusion. The twin-screw extruder comprises a feeding section, a melting section, a metering section, and a die head arranged sequentially. A raw material feeding device is connected to the starting end of the feeding section. A glass fiber inlet is provided at the starting end of the melting section. A flame retardant side feeding device is connected to the melting section downstream of the glass fiber inlet. A vacuum exhaust port is provided at the starting end of the metering section. A nucleating agent side feeding device is connected to the metering section downstream of the vacuum exhaust port. During preparation, the feeding section, melting section, metering section, and die head are first heated to a specified temperature and held for 30 minutes. Then, the twin-screw extruder is started, and the raw material feeding device feeds the weighed and mixed raw material, consisting of PBT, PET, antioxidant, lubricant, stabilizer, anti-hydrolysis agent, and compatibilizer, into the twin-screw extruder. The feeding section continuously shears and disperses the raw material, and after initial melting, the raw material enters the melting section. At the beginning of the melting section, glass fiber is added through the glass fiber inlet. During the initial melting process, the hot air and anti-hydrolysis agent encapsulated in the material... The gas generated during the initial action forms natural exhaust from the glass fiber inlet. When the material reaches the flame retardant side feeding device, flame retardant is added. The material with added flame retardant undergoes further shearing, mixing, and melting in the melting section before entering the metering section. At the beginning of the metering section, low-molecular-weight substances generated by the reaction of the anti-hydrolysis agent in the material with PBT and PET are discharged from the vacuum exhaust port. When the material reaches the nucleating agent side feeding device, nucleating agent is added. The material with added nucleating agent undergoes further shearing and mixing in the metering section to form a stable melt flow. The melt flow is extruded into strip-shaped material through the die head.

2. The process for the preparation of heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1, wherein: At the beginning of the melting section, when the gas discharged from the glass fiber inlet increases significantly, glass fiber is then added from the glass fiber inlet.

3. The process for the preparation of heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The strip-shaped material is cooled in a cooling water tank and then cut into granules by a pelletizer. The cooling method of the strip-shaped material in the cooling water tank is as follows: after the strip-shaped material enters the cooling water in the cooling water tank, it is immediately pulled out of the water surface and then passes through the cooling water tank in a way that it is suspended above the cooling water.

4. The process for preparing heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The feeding section includes feeding zone, zone I, zone II, zone III, and zone IV arranged in sequence; the melting section includes zone V, zone VI, zone VII, and zone VIII arranged in sequence; and the metering section includes zone IX and zone X arranged in sequence. The specified heating temperatures required for the feeding section, the melting section, and the metering section are respectively: zone I 205–215℃, zone II 225–235℃, zone III 245–250℃, zone IV 245–250℃, zone V 235–245℃, zone VI 235–245℃, zone VII 245–250℃, zone VIII 245–250℃, zone IX 235–245℃, and zone X 235–240℃. The specified heating temperature required for the die head is 240–245℃.

5. The process for preparing heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The weighing of each component in the raw material is in the following mass fraction ratio: PBT 25-45 parts, PET 9-20 parts, antioxidant 0.3-0.5 parts, lubricant 0.15-0.3 parts, stabilizer 0.15-0.35 parts, anti-hydrolysis agent 0.15-0.3 parts, and compatible agent 2-3 parts; the corresponding mass fraction ratio of the glass fiber added is 20-40 parts, the corresponding mass fraction ratio of the flame retardant fed by the flame retardant side feeding device is 11-15 parts, and the corresponding mass fraction ratio of the nucleating agent fed by the nucleating agent side feeding device is 0.3-0.5 parts.

6. The process for preparing heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The glass fiber is non-silane impregnated flat alkali-free glass fiber with a wire diameter of 13-14 μm.

7. The process for preparing heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The flame retardant is compounded by a main flame retardant and an auxiliary flame retardant at a compound mass ratio of 3:1; the main flame retardant is one of brominated epoxy resin, brominated polystyrene, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, phenoxy tetra-bromobisphenol A carbonate oligomer, 1,2,4,5-tetrabromo-3,6-bis(pentabromophenoxy) benzene, 1,2-bis(tetrabromophthalimide) ethane, and polypropylene acid pentabromobenzyl ester; the auxiliary flame retardant is one of antimony trioxide and zinc borate.

8. The process for preparing heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 1 wherein: The nucleating agent is one of dibenzyl sorbitol, 1,3-2,4-di(α-ethyl) benzyl sorbitol, sodium benzoate, methylene bis(2,4-di-tert-butyl phenoxy) sodium phosphate, and bis[2,2'-methylene bis(4,6-di-tert-butyl phenyl) phosphoric acid] hydroxy aluminum.

9. Process for the production of heat distortion temperature stabilised reinforced flame retardant PBT / PET alloys according to any one of claims 1 to 8, characterized in that: The double-screw extruder comprises a barrel, a screw rotatably installed in the barrel, and a screw driving device connected to the screw and extending out of the barrel; the screw is provided with a feeding thread combination, a melting thread combination, and a metering thread combination corresponding to the feeding section, the melting section, and the metering section, respectively.

10. The process for the preparation of heat distortion temperature stabilized reinforced flame retardant PBT / PET alloy as claimed in claim 9 wherein: The feeding thread combination comprises a feeding initial conveying combination corresponding to the raw material feeding device, a feeding shearing mixing combination, and a feeding successive conveying combination arranged alternately behind the feeding initial conveying combination, and a feeding reverse thread block behind the last feeding successive conveying combination. The melting thread combination comprises a melting initial conveying combination corresponding to the glass fiber adding port and the flame retardant side feeding device, a melting shearing mixing combination, and a melting successive conveying combination arranged alternately behind the melting initial conveying combination, and a melting reverse thread block behind the last melting successive conveying combination. The metering thread combination comprises a metering initial conveying combination corresponding to the vacuum exhaust port and the nucleating agent side feeding device, a metering shearing mixing combination, and a metering successive conveying combination arranged alternately behind the metering initial conveying combination.

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