CN109605708B - Thermoplastic polyester extrusion foaming forming method - Google Patents
Thermoplastic polyester extrusion foaming forming method Download PDFInfo
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- CN109605708B CN109605708B CN201811534002.3A CN201811534002A CN109605708B CN 109605708 B CN109605708 B CN 109605708B CN 201811534002 A CN201811534002 A CN 201811534002A CN 109605708 B CN109605708 B CN 109605708B
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- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/14—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
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- C08J2201/00—Foams characterised by the foaming process
- C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
- C08J2201/03—Extrusion of the foamable blend
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- C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
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- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/18—Binary blends of expanding agents
- C08J2203/182—Binary blends of expanding agents of physical blowing agents, e.g. acetone and butane
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- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
- C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
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Abstract
The invention provides a thermoplastic polyester extrusion foaming molding method, which comprises the following steps: adding thermoplastic polyester, a lubricant and a foaming auxiliary agent into a double-screw extruder for melting, wherein the outlet pressure of the double-screw extruder is 3-10 MPa; introducing a physical foaming agent into a thermoplastic polyester melt, mixing, and pumping the mixture into a single-screw extruder by a melt pump, wherein the inlet pressure of the single-screw extruder is 15-25 MPa; the temperature of the thermoplastic polyester melt containing the physical foaming agent is reduced through a single-screw extruder, and the thermoplastic polyester foamed product is obtained through extrusion foaming through an oral die, cooling and shaping. The method realizes efficient, stable and high-quality production of thermoplastic polyester foam molding by adding a high-temperature-resistant lubricant and regulating and controlling by adopting a melt pump.
Description
Technical Field
The invention relates to a polymer extrusion molding method, in particular to a thermoplastic polyester extrusion foaming molding method.
Background
The foam plastic is a composite material which takes plastic as a matrix and is filled with a large amount of bubbles, so the foam plastic has the excellent performances of light weight, material saving, high specific strength, low thermal conductivity, heat insulation and sound insulation, capability of absorbing impact load and the like, is widely used as a material for packaging, heat insulation, freezing prevention and heat preservation, buffering, vibration prevention and noise reduction, and is widely applied to the fields of building, transportation, daily living goods, packaging, aerospace, navigation, national defense and the like. Traditional polymer foams such as polyurethane foam (PU), polyethylene foam (PE), polystyrene foam (PS), etc., have certain disadvantages in material properties and processing methods. For example, in the preparation process of polyurethane foam, residues harmful to human bodies, such as isocyanate, are released, the foamed polyurethane is difficult to recycle, the polystyrene foam has certain limitations in the use field due to poor high-temperature resistance, and the polyethylene foam has the defects of poor mechanical properties, low heat resistance and the like. Therefore, efforts have been made to develop high-performance foams to broaden the application fields of the foamed materials and meet the increasing demands on the material properties in the social and technological development.
Compared with the traditional foam plastic, the thermoplastic polyester foam has the advantages of good dimensional stability at high temperature, excellent mechanical property and fatigue resistance, low smoke, flame retardance, no toxicity, low water absorption, good gas barrier property, recyclability and the like, and has wide application prospect in the fields of electronic industry, buffer packaging, building materials, transportation, wind power generation and the like.
In order to overcome the defects that the thermoplastic polyester has low melt strength, is difficult to maintain a cell structure, is easy to cause cell collapse and merging and the like, the prior art mainly adds a chain extender or a cross-linking agent to improve the viscosity of the polyester. For example, us patent us4981631 discloses polyethylene terephthalate (PET) foaming trays with a branching agent pyromellitic dianhydride (PMDA) to increase the viscoelasticity of the PET melt and with the addition of 1-6% of polyolefins (PP, PE) as nucleating agent with a maximum foaming ratio of 2 times. US3553157 discloses a process for increasing the melt viscosity of PET by mixing 0.5 to 1 wt% PMDA with PET and feeding to an extruder, but does not relate to foam production. Japanese patent 59-210955 (1984) discloses a PET foaming process in which PET is mixed with 0.01-2 mol% PMDA and 0.03-2.5 mol% of a polyfunctional epoxy compound to increase the melt strength of the PET. US5000991 and US5134028 discloses a process for preparing PET foams, which process is characterized in that a compound containing two or more anhydride groups, such as PMDA, is added to PET. Among them, the US5000991 patent discloses PMDA in an amount of 0.05 to 5.0 wt%, indicating that when the PMDA content exceeds 5%, gel formation will occur. The mixing method of PMDA and PET comprises the following steps: directly mixing and then adding into an extruder, or adding a master batch (taking PET or other polymers as a matrix) in advance, or adding PET firstly, melting and then adding PMDA, but the advantages and the disadvantages of the processes and the influence on PET foaming are not compared. In addition, the US5000991 patent discloses the addition of 0.05 to 5% sodium carbonate and shows that the addition of sodium carbonate results in a foamed material having higher tensile elongation and finer cells. US5958164 discloses a thermoplastic polyester extrusion foaming method, which adopts recycled and virgin PET as raw materials, directly extrudes and foams without drying, adopts PMDA and sodium carbonate as chain extenders, butane as foaming agents, and prepares a PET foamed sheet with the sheet density of 0.23-0.26g/cm3. EP2163577a1 discloses a process for preparing a chain extender master batch for foamed polyester, wherein the chain extender master batch comprises an acid anhydride compound, an antioxidant, an oxazoline compound and the like, and can balance pressure and torque fluctuation in a reaction extrusion process so that the reaction extrusion foaming process is carried out more stably.
The above patents all disclose that the foaming properties of PET resins are improved by increasing the viscosity of the PET resins with polyfunctional chain extenders. Typically the number of functional groups of the chain extender is greater than 2, preferably greater than 4 or more. During the extrusion chain extension reaction, the viscosity of the system is suddenly increased, so that the pressure in an extrusion system is increased, the torque is increased, the melt is difficult to transport to the downstream of a machine head, and the melt viscosity and the melt elasticity are too high, so that the melt is easy to have serious melt fracture phenomenon when passing through a small die gap of a foaming machine head, the surface of a product is rough, gas escapes, such as the phenomenon of sharkskin, and the qualified foamed product is difficult to obtain.
Disclosure of Invention
The invention provides a method for extrusion foaming molding of thermoplastic polyester, which aims to realize efficient, stable and high-quality production of foaming molding of thermoplastic polyester.
The invention provides a method for extrusion foaming molding of thermoplastic polyester, which comprises the following steps: adding thermoplastic polyester, a lubricant and a foaming auxiliary agent into a double-screw extruder for melting, wherein the outlet pressure of the double-screw extruder is 3-10 MPa; introducing a physical foaming agent into a thermoplastic polyester melt in a double-screw extruder, mixing, and pumping the mixture into a single-screw extruder by a melt pump, wherein the inlet pressure of the single-screw extruder is 15-25 MPa; the temperature of the thermoplastic polyester melt containing the physical foaming agent is reduced through a single-screw extruder, and the thermoplastic polyester foamed product is obtained through extrusion foaming through an oral die, cooling and shaping.
In the above method, the lubricant is preferably added in an amount of 0.5 to 5% by weight based on the total weight of the thermoplastic polyester.
In the above method, preferably, the thermal decomposition temperature of the lubricant is higher than 350 ℃, and the lubricant is selected from one or more of organic fatty acid ester, amide compound, low molecular weight polyethylene wax, low molecular weight oxidized polyethylene wax and polydimethylsiloxane.
In the above method, preferably, the lubricant is added in the form of a masterbatch, the masterbatch comprising 10% to 50% by weight of the lubricant.
In the method, preferably, the double-screw extruder and the single-screw extruder are connected through a melt pump, and the inlet pressure of the melt pump is 3MPa to 10MPa, and the outlet pressure of the melt pump is 15MPa to 20 MPa.
In the above method, preferably, the foaming aid includes a chain extender, a nucleating agent, an antioxidant and a heat stabilizer.
In the above method, preferably, the chain extender is an acid anhydride compound, and the addition amount is 0.2 to 1 percent of the total weight of the thermoplastic polyester.
In the method, the chain extender is preferably a polyfunctional epoxy compound, and the addition amount of the polyfunctional epoxy compound is 0.5 to 3 percent of the total weight of the thermoplastic polyester.
In the above method, preferably, the chain extender is added in the form of a masterbatch, and the masterbatch comprises 8% to 30% of the chain extender by weight.
In the method, preferably, the physical foaming agent is one or more of carbon dioxide, nitrogen, isobutane, isopentane, cyclopentane, hexane, heptane and fluorine-containing compounds, and the total addition amount is 1-10% of the total weight of the thermoplastic polyester.
According to the method for extrusion foaming molding of the thermoplastic polyester, on one hand, the melt temperature in the processing process is effectively controlled by adding the high-temperature-resistant lubricant, and the surface quality of a product is improved; on the other hand, the melt pump is adopted for regulation and control, and the outlet pressure of the double-screw extruder and the inlet pressure of the single-screw extruder are controlled, so that the thermal decomposition of the thermoplastic polyester in the double-screw extruder is avoided, and the pressure of a machine head is ensured to meet the foaming requirement. Thereby realizing the high-efficiency, stable and high-quality production of thermoplastic polyester foam molding.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below.
Fig. 1 is a flow chart of a method of extrusion foam molding of thermoplastic polyester according to an embodiment of the present invention.
Fig. 2 is a schematic view of an apparatus for extrusion foaming of thermoplastic polyester according to an embodiment of the present invention.
Fig. 3 is a thermogravimetric plot of lubricant pentaerythritol stearate according to an embodiment of the present invention.
Detailed Description
As shown in figure 1, the invention discloses a method for extrusion foaming molding of thermoplastic polyester, which comprises the following steps:
s1 adding the thermoplastic polyester, the lubricant and the foaming auxiliary agent into a double-screw extruder for melting, wherein the outlet pressure of the double-screw extruder is 3 MPa-10 MPa. Wherein the foaming auxiliary agent comprises a chain extender, a nucleating agent, an antioxidant and a heat stabilizer
S2 introducing a physical foaming agent into the thermoplastic polyester melt in the double-screw extruder, mixing, and pumping the mixture into the single-screw extruder through the melt pump, wherein the inlet pressure of the single-screw extruder is 15-25 MPa. In this step, a physical blowing agent is introduced into the thermoplastic polyester melt in the twin-screw extruder and mixed with the screws of the twin-screw extruder to form a homogeneous solution.
S3 reduction of the temperature of a thermoplastic polyester melt containing a physical blowing agent to T, T by means of a single-screw extruderm-10℃≤T≤Tm+30 ℃ wherein, TmIs the melting point of the thermoplastic polyester. And extruding and foaming through an oral die, and cooling and shaping to obtain the thermoplastic polyester foamed product. In this step, when the thermoplastic polyester is PET, the temperature of the melt is reduced to 240 ℃ to 260 ℃ by means of a single-screw extruder. Extruding and foaming through a mouth die, cooling and molding the foamed product on a cooling and shaping device to obtain a thermoplastic polyester foamed product, wherein the density of the finally obtained thermoplastic polyester foamed product is 60kg/m3～300kg/m3。
The thermoplastic polyester is mainly aromatic polyester, specifically polymer obtained by polycondensation of aromatic dicarboxylic acid and dihydric alcohol, such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate and their copolymer, preferably polyethylene terephthalate (PET). Further, the thermoplastic polyester resin may contain a third component copolymer such as resorcinol and the like in addition to the aromatic dicarboxylic acid and the diol. The intrinsic viscosity of the aromatic polyester is between 0.6 and 0.85dl/g, and the intrinsic viscosity is tested according to the GB/T14190-2008 method (the solvent adopts phenol/tetrachloroethane (mass ratio 50/50))). Recycled thermoplastic polyesters, such as recycled PET, having an intrinsic viscosity of 0.6dl/g or more, may also be used as the starting material.
The chain extender is a compound containing two or more compounds capable of reacting with the terminal hydroxyl or terminal carboxyl of the thermoplastic polyester, and comprises one or more combinations of anhydride compounds, epoxy compounds and/or oxazoline compounds. Acid anhydride compounds such as pyromellitic dianhydride (PMDA), naphthalenetetracarboxylic anhydride, pyromellitic dianhydride and cyclopentanetetracarboxylic anhydride, preferably pyromellitic dianhydride (PMDA). The epoxy compound includes a polyfunctional epoxy compound or an epoxy oligomer, such as those of the Pasteur company
ADR-4368, tetraglycidyl diaminodiphenylmethane (TGDDM), and the like. The oxazoline compound is a compound containing a nitrogen-oxygen five-membered heterocycle in the molecular structure, and can be mono oxazoline or bis oxazoline, preferably bis oxazoline, such as 1, 3-phenyl bis oxazoline or 1, 4-phenyl bis oxazoline. The addition amount of the acid anhydride chain extender is generally 0.2 to 1 percent, preferably 0.3 to 0.5 percent, based on the total weight of the thermoplastic polyester; the addition amount of the ADR epoxy compound chain extender is 0.5 to 3 percent of the total weight of the thermoplastic polyester, preferably 0.6 to 1.5 percent, and more preferably 0.8 to 1.2 percent; the addition amount of the oxazoline is 0.5 to 2 percent of the total weight of the thermoplastic polyester, and preferably 0.8 to 1.2 percent. In the present invention, the acid anhydride-based chain extender may be used together with the epoxy-based chain extender or together with the oxazoline-based chain extender. The chain extender is added in a manner of master batch, and specifically can be processed into master batch taking thermoplastic polyester as a matrix, wherein the master batch comprises 8-30% of the chain extender by weight, and preferably 10-20%.
The physical foaming agent is one or a combination of more of carbon dioxide, nitrogen, low molecular weight alkane, such as isobutane, isopentane, cyclopentane, hexane and heptane, fluorine-containing compounds, such as HCFC-142a, HCFC-22, HFC-134a, HFC-152a, HFO-1234ze, HFO-1233zd and 1, HCFO-1233zd, and the total addition amount is 1-10% of the total weight of the thermoplastic polyester.
The nucleating agent, namely the foam cell nucleating agent, can be an inorganic nucleating agent or an organic nucleating agent, the inorganic nucleating agent comprises talcum powder, calcium carbonate, nano-silica, nano-montmorillonite and the like, the organic nucleating agent is Azodicarbonamide (AC) and the like, and the addition amount of the nucleating agent is 0-5 percent of the total weight of the thermoplastic polyester, preferably 1-3 percent.
Wherein the antioxidant is hindered phenol antioxidant such as (tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid)]Pentaerythritol ester) (antioxidant 1010), (3- (1, 1-dimethylethyl) - β - [3- (1, 1-dimethylethyl) -4-hydroxyphenyl]-4-hydroxy- β -methylbenzoic acid-1, 2-ethylene ester) (antioxidant O3) β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecanoic carbonate (antioxidant 1076), hexanediol bis [3,5-di-tert-butyl-4-hydroxyphenyl]Acrylate (antioxidant 259) and (1,3,5 tri (3, 5-di-tert-butyl-4-hydroxybenzyl) -1,3, 5-triazine-2, 4,6(1H,3H,5H) -trione) (antioxidant 3114), wherein the addition amount of the antioxidant is 0.1-0.2 percent of the total weight of the thermoplastic polyester.
Wherein the heat stabilizer is phosphate ester compounds, such as triphenyl phosphate, triethyl phosphoryl acetate, (bis (2, 4-di-tert-butylphenyl) pentaerythritol phosphite), tetrakis (2, 4-di-tert-butylphenyl-4, 4' -biphenyl) bisphosphite, tris (2, 4-di-tert-butylphenyl) phosphite, and the amount of the heat stabilizer is 0.2 to 0.5% based on the total weight of the thermoplastic polyester. The antioxidant and the heat stabilizer are used independently or in a compound way. The antioxidant and/or the heat stabilizer can be processed into master batches taking the thermoplastic polyester as a matrix, and the master batches are added into the thermoplastic polyester.
In order to improve the foaming performance of the thermoplastic polyester, a chain extender or a branching agent is added into a double-screw extruder, and a chain extension reaction occurs in the extrusion process, so that the viscoelasticity of the thermoplastic polyester melt is obviously improved. However, the viscoelasticity of the thermoplastic polyester melt is remarkably improved, so that the shearing heat generation in the extrusion process is serious, the polyester is easily subjected to thermal degradation, the product quality is influenced, and on the other hand, the melt fracture phenomenon is easily generated in a high-shear area of a foaming machine head, so that the surface of a product is rough, even the surface of the foamed product is cracked, and the like.
In order to overcome the defects in the polyester extrusion foaming process, the lubricant is added in the extrusion process, so that the interaction between polyester macromolecular chains is reduced, the shearing heat is reduced, the friction between a melt and the inner metal walls of a machine barrel and a machine head is reduced, and the surface quality of a product is obviously improved. The thermal decomposition temperature of the lubricant is higher than 350 ℃, and the lubricant is selected from one or more of organic fatty acid ester, amide compound, low molecular weight polyethylene wax, low molecular weight oxidized polyethylene wax and polydimethylsiloxane. For example, pentaerythritol stearate, modified ethylene bisstearamide, EBS, and the like. The amount of the lubricant added is 0.5 to 5%, preferably 1 to 5%, more preferably 1 to 3% of the total weight of the thermoplastic polyester. The lubricant can be added into the thermoplastic polyester extrusion foaming process by way of master batch, preferably the thermoplastic polyester is used as a master batch carrier, such as polyethylene terephthalate and polybutylene terephthalate, wherein, the master batch comprises 10-50% of the lubricant by weight.
The device for thermoplastic polyester foaming molding of the invention adopts a two-stage extruder series system, the first stage is a co-rotating twin-screw extruder, the second stage is a single-screw extruder, the two extruders are connected in series by a melt pump, figure 2 is a preferred embodiment of the device for thermoplastic polyester foaming molding, and figure 2 is marked as follows: 1-double screw feeder 2-double screw extruder 3-back pressure valve 4-gas metering pump 5-stop valve 6-gas source 7-test point 8-melt pump 9-test point 10-single screw extruder 11-foaming machine head.
As shown in the attached figure 2, the device comprises a co-rotating double-screw extruder 2 (screw diameter is 65mm, L/D is 32; Nanjing Chuangbo mechanical equipment Limited company), a melt pump 8(ZB-C300, Zhengzhou Batt melt pump Limited company), a set of vacuum system, a single-screw extruder 10 (diameter is 150mm, length-diameter ratio is 23), a static mixer, a foaming machine head 11 (fish tail type plate machine head) and a cooling and shaping device arranged at the downstream of the outlet of the foaming machine head 11, wherein the vacuum system is connected with an exhaust port of the double-screw extruder 2, the melt pump 8 is connected with the outlet of the double-screw extruder and the inlet of the single-screw extruder in series, namely, the outlet of the double-screw extruder is connected with the inlet of the melt pump, the outlet of the single-screw extruder is connected with the foaming machine head 11, the cooling and shaping device is arranged at the downstream of the foaming machine head 11, the outlet pressure P1 of the double-screw extruder and the inlet pressure P2 of the single-screw extruder can be respectively monitored by pressure sensors arranged at a test point 7 and a gas injection system 6, a backpressure valve 5 is used for injecting a foaming agent into the foaming machine through the gas injection system and a gas injection system in the foaming process.
In the foaming process of the thermoplastic polyester, on one hand, the resistance of the material in the double screws is easily increased due to the overhigh pressure of the head of the double screw extruder, the foaming agent is difficult to inject, and in addition, the shearing heat generation of the material in the double screws is increased, so that the material is easily degraded; too low a pressure causes difficulties in dissolving the blowing agent in the polyester melt, on the other hand, a sufficiently high head pressure is generally required in order to increase the nucleation density of the foamed article, while the second single screw is primarily intended to lower the melt temperature, so that the melt conveying capacity is poor, in particular for low-temperature, high-viscosity melts. In order to solve the problems, the melt pump and the single-screw rotating speed are controlled in the invention, so that the melt pressure P1 at the outlet of the double screws is lower than 10MPa, even lower than 5MPa, and the inlet pressure P2 of the single-screw extruder is higher than 12MPa, preferably higher than 15 MPa. For example, according to a preferred embodiment of the invention, the pressure P1 is maintained at any set value between 3MPa and 10MPa, preferably between 3MPa and 8MPa, more preferably between 5MPa and 8 MPa. The melt pump is controlled so that the single screw inlet pressure P2 is equal to or greater than 15MPa, preferably equal to or greater than 18 MPa.
Controlling the inlet pressure of the melt pump to be 3 MPa-10 MPa, preferably 3 MPa-8 MPa, and more preferably 5 MPa-8 MPa; controlling the outlet pressure of the melt pump to be more than or equal to 15MPa, preferably more than or equal to 18MPa, and more preferably 15MPa to 20 MPa.
If pressure sensors are respectively arranged at the melt connection position of the melt outlet of the melt pump to monitor the outlet pressure P1 of the double-screw extruder and the inlet pressure P2 of the single-screw extruder, a double-closed-loop control system is adopted, the double-screw inlet pressure P1 and the single-screw outlet pressure P2 are taken as control targets, the melt pump rotating speed and the single-screw rotating speed are regulated and controlled through a P L C program to realize double-closed-loop automatic feedback control, so that the P1 is maintained at any set value between 3MPa and 10MPa, preferably at any set value between 3MPa and 8MPa, more preferably at any set value between 5MPa and 8MPa, and the P2 is maintained at any set value between 15MPa and 20MPa, the specific embodiment is as follows:
example 1:
raw materials: polyethylene terephthalate (PET), BG80, China petrochemical chemical fiber GmbH, intrinsic viscosity 0.8 dl/g;
chain extenders, pyromellitic dianhydride (PMDA), national pharmaceutical group chemicals limited;
nucleating agent: talc powder, 1000 mesh;
the antioxidant is pentaerythritol tetrakis (β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate) (antioxidant 1010), Nanjing Hualiming chemical Co., Ltd;
lubricant: pentaerythritol stearate PETs, Jiangsu Xingtai Thailand photochemical assistant Co., Ltd, and the thermal decomposition temperature is 400 ℃. The decomposition temperature was measured with a thermogravimetric analyzer, the temperature rise rate was 10 ℃/min, the atmosphere was nitrogen, and the temperature at which the thermogravimetric loss rate on the TG temperature curve was the maximum was defined as the thermal decomposition temperature. Fig. 3 is a thermogravimetric plot of pentaerythritol stearate.
The foaming process comprises the following steps: preheating the whole extrusion system, and drying the PET; after the extrusion system reaches the set temperature, starting a single-screw extruder, then sequentially starting a melt pump, a double-screw extruder and a feeding system, uniformly mixing 100kg of dried PET, 0.3kg of chain extender PMDA, 0.1kg of antioxidant 1010, 1kg of talcum powder and 0.5kg of lubricant pentaerythritol stearate PETs, adding the mixture from a feed inlet of a double-screw feeder 1 (shown in figure 2), then injecting a physical foaming agent cyclopentane into the PET melt in the double screws through a gas injection system, wherein the additive amount is 2 wt% of the total additive amount of the PET, reducing the temperature of each section of the single-screw extruder after the machine head extrudes gas-containing materials, and controlling the rotating speed of the melt pump and the rotating speed of the single screw so that the pressure P1 at the outlet of the double-screw extruder and the pressure P2 at the inlet of the single-screw extruder are controlled at set values, wherein the specific process parameters are shown in Table 1. And (5) obtaining the PET foamed sheet under the machine head pressure of 10 MPa. The density of the PET foamed sheets was tested according to GB/T6343-2009 with results as shown in table 1.
Example 2
The raw materials and the process are the same as example 1, except that lubricant pentaerythritol stearate is added in the form of master batch, the master batch concentration is 50 wt%, the master batch matrix is PET, the addition amount is 6% of the total weight of the PET, and the addition amount of the total pentaerythritol stearate is 3 wt% of the total weight of the PET.
Example 3
The raw materials and the process are the same as example 1, except that the chain extender adopts an epoxy chain extender, ADR4368 of BASF company, and the addition amount is 1 wt%; the lubricant is modified ethylene bis stearamide EBS, the thermal decomposition temperature is 300 ℃, the lubricant is added in the form of 50 percent of master batch concentration, the addition amount of the master batch is 10 percent of the total weight of PET, and the foaming agent is CO2And cyclopentane, injected from two sets of pumping systems and two gas injection ports respectively, CO2The injection amount of (A) is 1 wt% of the total weight of PET, and the injection amount of cyclopentane is 2 wt% of the total weight of PET.
Example 4
The raw materials and the process are the same as example 1, except that the lubricant is polyethylene wax oxide, the lubricant is added in the form of master batch, the concentration of the master batch is 20 wt%, the matrix is PET, the addition amount of the master batch is 10 wt% of the total weight of the PET, the total polydimethylsiloxane content is 2 wt% of the total weight of the PET, and the heat stabilizer tetrakis (2, 4-di-tert-butylphenyl-4, 4' -biphenyl) bisphosphite is added, the addition amount is 0.2 wt% of the total weight of the PET.
Example 5
The raw materials and process were the same as in example 1 except that carbon dioxide was used as a blowing agent, and the amount of blowing agent injected was 1 wt% based on the total weight of PET.
Comparative example 1
The raw materials are the same as example 3 except that no lubricant is added, an extrusion system is a double-screw extruder and single-screw extruder which are connected in series, the diameter and the length-diameter ratio of the screw are the same as those of example 1, but no melt pump is arranged between the double screw and the single screw, when PET is extruded and foamed, the pressure between the double-screw extruder and the single-screw extruder is unstable and fluctuates periodically, the maximum pressure can reach 20MPa, the pressure can be reduced to 3MPa by adjusting the rotating speed of the single screw, and as a result, the machine head pressure and the discharging fluctuation are large, normal production cannot be realized, and the surface of the obtained PET foamed product is rough.
Comparative example 2
The raw materials are the same as example 2 except that no lubricant is added, the temperature of each curve section of the extruder is set to be the same as that of example 2 in the extrusion foaming process, and as a result, the temperature of PET melt at an outlet is high, the surface of an extruded product is rough, obvious melt fracture phenomenon is caused, gas escapes, and the apparent density of the obtained PET foamed sheet is 350kg/m3。
According to the thermoplastic polyester extrusion foaming molding method provided by the invention, the high-temperature-resistant lubricant is added in the foaming process, so that the friction among polyester macromolecules after chain extension and between the polyester melt and the inner wall of the extruder and the inner wall of a mold is reduced, on one hand, the shearing heat generation in the extrusion process can be reduced, and the melt temperature can be effectively controlled; on the other hand, the critical shear rate of the melt fracture can be increased, the melt fracture is avoided, and the surface quality of the product is improved. The melt pump is adopted to regulate and control the outlet pressure of the double-screw extruder and the inlet pressure of the single-screw extruder, so that on one hand, the relatively lower melt pressure of the outlet of the double-screw extruder is kept to be lower than 5MPa, the smooth injection of a foaming agent is facilitated, the shearing heat generation of the double-screw extruder is reduced, the thermal decomposition of the thermoplastic polyester in the double-screw extruder is avoided, and a foundation is laid for stable extrusion; on the other hand, the high inlet pressure of the single-screw extruder provides power for conveying the high-viscosity polyester melt after chain extension, and the pressure of a machine head can meet the foaming requirement. The high-efficiency, stable and high-quality production of the thermoplastic polyester extrusion foaming molding is realized by the thermoplastic polyester extrusion foaming molding method provided by the invention.
Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (7)
1. A thermoplastic aromatic polyester extrusion foaming molding method is characterized by comprising the following steps:
adding a thermoplastic aromatic polyester, a lubricant and a foaming auxiliary agent into a double-screw extruder for melting, wherein the outlet pressure of the double-screw extruder is 3-10 MPa, the foaming auxiliary agent comprises a chain extender, the addition amount of the lubricant is 0.5-5% of the total weight of the thermoplastic aromatic polyester, the thermal decomposition temperature of the lubricant is higher than 350 ℃, and the lubricant is selected from one or more of organic fatty acid ester, amide compound, low molecular weight polyethylene wax, low molecular weight oxidized polyethylene wax and polydimethylsiloxane;
introducing a physical foaming agent into a thermoplastic aromatic polyester melt in the double-screw extruder, mixing, and pumping the mixture into a single-screw extruder through a melt pump, wherein the inlet pressure of the single-screw extruder is 15-25 MPa, the double-screw extruder and the single-screw extruder are connected through the melt pump, the inlet pressure of the melt pump is 3-10 MPa, and the outlet pressure of the melt pump is 15-20 MPa;
and reducing the temperature of the thermoplastic aromatic polyester melt containing the physical foaming agent through the single-screw extruder, extruding and foaming through an oral die, cooling and shaping to obtain the thermoplastic aromatic polyester foamed product.
2. The method of claim 1, wherein the lubricant is added as a masterbatch comprising 10% to 50% by weight of the lubricant.
3. The method of claim 1, wherein the foaming aid comprises a nucleating agent, an antioxidant, and a thermal stabilizer.
4. The method as claimed in claim 3, wherein the chain extender is an acid anhydride compound and is added in an amount of 0.2-1% by weight based on the total weight of the thermoplastic aromatic polyester.
5. The method according to claim 3, wherein the chain extender is a polyfunctional epoxy compound and is added in an amount of 0.5-3% by weight based on the total weight of the thermoplastic aromatic polyester.
6. The method according to any one of claims 3 to 5, wherein the chain extender is added in the form of master batch, and the master batch contains 8 to 30 percent of the chain extender by weight.
7. The method according to claim 3, wherein the physical blowing agent is one or more of carbon dioxide, nitrogen, isobutane, isopentane, cyclopentane, hexane, heptane, and fluorine-containing compounds in a total amount of 1-10% of the total weight of the thermoplastic aromatic polyester.
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| CN110204771A (en) * | 2019-06-11 | 2019-09-06 | 宁波邦泰汽车配件有限公司 | A kind of compound TPE foam shaping by extrusion technique |
| CN110561676B (en) * | 2019-09-18 | 2020-08-14 | 北京李尔现代坦迪斯汽车***有限公司 | Automatic foaming detection equipment |
| CN110624225B (en) * | 2019-09-24 | 2022-03-01 | 江苏正和体育用品有限公司 | Racket |
| CN113121949B (en) * | 2021-03-18 | 2022-11-15 | 浙江恒逸石化研究院有限公司 | Master batch for polyester extrusion foaming and application thereof |
| CN114196173B (en) * | 2021-12-29 | 2023-06-09 | 丹江口东筌新材料有限公司 | PET (polyethylene terephthalate) foaming material and manufacturing method thereof |
| CN114921066A (en) * | 2022-03-29 | 2022-08-19 | 浙江天振科技股份有限公司 | Foamed PET composite board and preparation method thereof |
| CN115124834B (en) * | 2022-07-13 | 2023-03-17 | 北京化工大学 | Thermoplastic polyamide elastomer blending foaming material and preparation method thereof |
| CN115286903A (en) * | 2022-07-29 | 2022-11-04 | 维赛(江苏)复合材料科技有限公司 | Fiber-reinforced high-performance high-rate PET foam material and preparation method thereof |
| CN115181319B (en) * | 2022-08-09 | 2023-03-21 | 北京化工大学 | Preparation method of polyphenyl ether foamable particles |
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| DE19800166A1 (en) * | 1998-01-05 | 1999-07-08 | Buehler Ag | Closed cell polyester foam production by reactive extrusion without granulation |
| DE10000712A1 (en) * | 2000-01-11 | 2001-07-12 | Buehler Ag | Modified thermoplastic polyester resin suitable for use in foam production are obtained by mixing and kneading a polyester with a preferably reactive chain-breaker and an elasticity-increasing additive |
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| CN108864662B (en) * | 2018-07-25 | 2020-10-13 | 南通德亿新材料有限公司 | Thermoplastic polyether ester elastomer foam material and preparation method thereof |
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