CN115490998A - Microcellular injection molding foaming molding polyester foam material and preparation method thereof - Google Patents
Microcellular injection molding foaming molding polyester foam material and preparation method thereof Download PDFInfo
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- CN115490998A CN115490998A CN202210175064.XA CN202210175064A CN115490998A CN 115490998 A CN115490998 A CN 115490998A CN 202210175064 A CN202210175064 A CN 202210175064A CN 115490998 A CN115490998 A CN 115490998A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—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
- 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
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/16—Dicarboxylic acids and dihydroxy compounds
- C08G63/20—Polyesters having been prepared in the presence of compounds having one reactive group or more than two reactive groups
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/06—CO2, N2 or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/08—Supercritical fluid
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08J2205/00—Foams characterised by their properties
- C08J2205/04—Foams characterised by their properties characterised by the foam pores
- C08J2205/044—Micropores, i.e. average diameter being between 0,1 micrometer and 0,1 millimeter
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
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Abstract
The invention relates to the field of polyester materials, and discloses a microcellular injection molding foaming molding polyester foam material and a preparation method thereof. The polyester foam material comprises the following raw materials: 100 parts of low-melting-point high-melt-strength polyester, 0.1 to 1.0 part of branching agent, 1.0 to 5.0 parts of nucleating agent, 0.1 to 1.0 part of antioxidant and 1.0 to 6.0 parts of foaming agent; the low-melting-point high-melt-strength polyester comprises the following raw materials: 100 portions of terephthalic acid, 30 to 60 portions of ethylene glycol, 10 to 40 portions of polyalcohol or polybasic acid (anhydride) comonomer, 0.01 to 1 portion of catalyst and 0.01 to 1 portion of stabilizer. The invention firstly prepares the low-melting-point high-melt-strength polyester which is suitable for microcellular injection molding foaming, and then carries out microcellular injection molding foaming at a lower temperature to prepare the polyester foam material with high foaming multiplying power, stable foam structure and excellent mechanical property.
Description
Technical Field
The invention relates to the field of polyester materials, in particular to a microcellular injection molding foaming molding polyester foam material and a preparation method thereof.
Background
Polyethylene terephthalate (PET) is widely used in the fields of fiber weaving, packaging and the like due to its excellent mechanical properties, high temperature resistance and aging resistance. With the increase of the production capacity and the technological innovation, new application fields of the polyester are developed, such as the foaming production of foam plates, sheets or beads by using fiber-grade, bottle-grade and recycling-grade polyester, and the application of the foam plates, sheets or beads in the fields of wind power, buildings, automobiles and the like.
Generally, polyester foaming mainly comprises extrusion foaming and kettle pressure foaming processes, the extrusion foaming process applied to industry in large scale at present belongs to a continuous foaming process, and plates and sheets with the foaming ratio of more than 10 times can be obtained. The kettle pressure foaming process belongs to a batch foaming process and is generally only used in laboratories or small-batch production. However, both of the kettle pressure foaming and the extrusion foaming can only produce the polyester foam with simple shape, and can not produce the high-precision polyester foam product with three-dimensional complex structure.
The microcellular injection molding foaming technology is provided by Trexel company, combines an injection molding process with the microcellular foaming technology, and has the characteristics of short molding period, raw material saving, low shrinkage rate of products, high dimensional stability and the like compared with the common injection molding process; compared with extrusion and kettle pressing processes, the microcellular injection molding can produce foam products with complex three-dimensional structures, and various places with certain appearance structure requirements on the finished parts can be produced without complex later processing. However, since the birth of microcellular injection molding, the foaming process is special, so that the foaming agent cannot be widely applied to various materials, further popularization of the foaming agent in the foaming technical industry is limited, and the foaming agent is only applied to production of a few polymer foams at present. Patent CN105504498A proposes a polypropylene foaming composite material formula suitable for foaming by microcellular injection molding, the formula uses micro-crosslinked polypropylene and polyethylene as modifiers, a toughening agent and talcum powder are added as auxiliary agents, the multiplying power of a product obtained by foaming is about 1.25 times, and the product has uniform cells and good mechanical properties. Patent 109501107A optimized technology proposes that high pressure full injection is used, and a core retreating mode is adopted in the demolding process, so that polystyrene, polyethylene, polylactic acid and other foams with the foaming multiplying power of 2-10 times are prepared, and the multiplying power is higher than that of foams obtained by a traditional injection molding mode.
From the above, the use of the microcellular injection molding foaming process expands the application range of materials such as polypropylene. However, in the course of previous research, we found that the microcellular injection molding foaming process is not well applicable to polyester foaming. This is due to the fact that the crystallization temperature of polyesters is higher compared to polymers such as polypropylene, resulting in a foaming process temperature in excess of 260 ℃. In the process of microcellular injection molding and foaming, if the temperature of the mold is too low, the polyester can be rapidly cooled and is difficult to foam after the mold is opened to generate a cellular structure; if the temperature is too high, the dimensional stability of the foam after the die opening is poor, and the requirement on equipment materials in a high-temperature environment is also high; in addition, the viscosity of the polyester after melting is drastically reduced, and it is difficult to stabilize the cell structure at high temperature. In conclusion, the polyester is rarely applied to microcellular injection molding foaming at present.
Disclosure of Invention
In order to enable the microcellular injection molding foaming process to be better applied to the polyester foaming industry, the invention provides a microcellular injection molding foaming molded polyester foam material and a preparation method thereof. The invention firstly prepares the low-melting-point high-melt-strength polyester which is suitable for microcellular injection foaming, and then microcellular injection foaming is carried out on the polyester at a lower temperature, so that the polyester foam material with high foaming multiplying power, stable foam structure and excellent mechanical property can be prepared.
The specific technical scheme of the invention is as follows:
in a first aspect, the present invention provides a microcellular injection-molded foam polyester material having a foam density of 100 to 800kg/m 3 The average diameter of the cells is 20-100 μm, and the compressive strength is 3.5-5.0MPa.
The polyester foam material comprises the following raw materials in parts by weight: 100 parts of low-melting-point high-melt-strength polyester with the intrinsic viscosity of 0.80-1.00dl/g, the melting index range of 190 ℃ of 60-80g/10min and the melting point of 170-180 ℃, 0.1-1.0 part of branching agent, 1.0-5.0 parts of nucleating agent, 0.1-1.0 part of antioxidant and 1.0-6.0 parts of foaming agent.
The low-melting-point high-melt-strength polyester comprises the following raw materials in parts by weight: 100 portions of terephthalic acid, 30 to 60 portions of ethylene glycol, 10 to 40 portions of polyalcohol or polybasic acid (anhydride) comonomer, 0.01 to 1 portion of catalyst and 0.01 to 1 portion of stabilizer.
The invention adopts an in-situ copolymerization method to directly prepare the polyester with low melting point and high melt strength. Wherein the polyester is modified by the addition of a polyol or polyacid (anhydride) comonomer, which functions to: on one hand, the original regularity of the polyester can be broken, and the crystallization is broken to reduce the crystallization temperature of the polyester, so that the processing temperature is reduced; on the other hand, because the polyester has three or more polyfunctional groups, a branched structure can be generated after the polyester is introduced into the polyester so as to increase the molecular weight of chain segments and improve the melt strength of the polyester at high temperature, thereby enabling cells to be more stable in the foaming process. It should be noted that the addition amount of the polyol or polyacid (anhydride) comonomer needs to be controlled within a specific reasonable range, if the content is too low, the modification effect is not obvious, and the injection molding foaming is difficult to be stable at a lower temperature; if the content is too high, the foam properties are affected.
After the low-melting-point high-melt-strength polyester is prepared, the polyester is fully mixed with auxiliary agents such as a branching agent, a nucleating agent, an antioxidant and the like, and then the mixture is added into an injection molding machine for foaming. The reason for adding the branching agent is that we have found that the branching effect of the polyol or polyacid (anhydride) comonomer during the polyester synthesis process is not sufficient to ensure that the melt can form a stable cell structure during the foaming process, and the addition of the branching agent during the foaming process can further increase the melt strength, prevent cells from foaming and collapsing during the foaming process, and improve the stability of the cell structure. The addition of the nucleating agent is beneficial to increasing the nucleation points of bubbles and increasing the density of the bubbles. Antioxidants are used to mitigate thermal oxidative degradation of polyesters during injection molding.
Preferably, the polyol or polyacid (anhydride) comonomer is one or more of pentaerythritol, 1,2,4,5-pyromellitic dianhydride (PMDA), glycerol, trimellitic anhydride, 1,2,4-butanetriol.
Further preferably, the polyol or polyacid (anhydride) comonomer is one or more of pentaerythritol and 1,2,4-butanetriol.
According to the invention, researches show that not any polyol or polyacid (anhydride) comonomer can obtain ideal technical effects, but pentaerythritol and 1,2,4-butanetriol have the best effects in comprehensive consideration, and the branching effects are better and the crystallinity can be obviously reduced compared with glycerol and trimellitic anhydride. Compared with PMDA, the carboxyl in PMDA is in an ortho position, the steric hindrance is large, and the adjacent carboxyl can not completely participate in the reaction, so that the branching effect in the polymerization reaction is not large, the melt index (MFR) of the obtained polyester chip is higher, the cell structure is not stable enough during microcellular injection foaming, and finally abnormal cell shapes such as large cells, cell collapse and the like are shown, and the final mechanical property is influenced.
Preferably, the branching agent is a trifunctional or higher epoxy branching agent with an actual epoxy equivalent weight of 100 to 150.
The epoxy branching agent can simultaneously react the epoxy group with the terminal carboxyl group and the terminal hydroxyl group in the polyester to form a cross-linked structure. An excessively high epoxy equivalent means a small amount of epoxy groups, low reactivity and poor crosslinking effect; if the epoxy equivalent is too low, the crosslinking effect is good, but gel is easily generated to influence the foam uniformity.
As a further preference, the branching agent is selected from triglycidyl isocyanurate (TGIC), 4,4' -diaminodiphenylmethane tetraglycidyl amine.
Preferably, the antioxidant is selected from at least one of phenolic antioxidants and phosphite antioxidants; the antioxidant is further preferably selected from the group consisting of antioxidants 1010.
Preferably, the nucleating agent is one selected from talc, calcium carbonate and titanium dioxide.
Preferably, the blowing agent is supercritical carbon dioxide.
Preferably, the catalyst is one selected from ethylene glycol antimony, antimony trioxide and antimony acetate.
Preferably, the stabilizer is triphenyl phosphite.
The stabilizer can effectively prevent degradation caused by high temperature in the synthesis process.
In a second aspect, the present invention provides a method for preparing microcellular injection foam-molded polyester foam material, comprising the following steps:
(1) Adding the low-melting-point high-melt-strength polyester raw materials except the stabilizer into a preheated reactor, stirring and mixing uniformly, pressurizing and heating under the protection of inert gas for esterification reaction, stirring and collecting condensed water until water outlet is finished, and adding the stabilizer and stirring uniformly.
(2) Heating and vacuumizing simultaneously, carrying out pre-polycondensation reaction and final polycondensation reaction in sequence, discharging and granulating after the reaction is finished, and obtaining the polyester chip with low melting point and high melt strength.
(3) The low-melting point high-melt strength polyester chips and the nucleating agent are dried in vacuum and then are evenly mixed with the antioxidant and the branching agent.
(4) Transferring the mixture obtained in the step (3) to an injection molding machine, wherein the mixture is fully melted in the injection molding machine and subjected to a branching reaction, and the viscosity is increased; the blowing agent is then homogeneously mixed into the resulting molten polymer to provide a single homogeneous polymer melt.
(5) When the temperature of a nozzle of an injection molding machine reaches 195-205 ℃ and the temperature of a mold reaches 120-140 ℃, 5-10MPa of carbon dioxide is filled into the mold in advance, then the polymer melt is injected into the mold at the injection pressure of 90-160MPa and the injection speed of 100-200mm/s, and after the mold is completely filled, a screw continuously maintains the original shape to maintain the pressure, so as to ensure that pores generated in the injection molding process are completely filled.
(6) After 20-40s, the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 20-40MPa for 10-30min and cooled to be in a high elastic state.
(7) And after the pressure maintaining is finished, using circulating cooling water to quickly reduce the temperature of the surface of the die by 8-12 ℃, opening the die within 2-8s after the temperature of the die is stabilized for 5-15s, foaming and quickly cooling the polymer to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
The invention firstly adopts an in-situ copolymerization method to directly prepare the low-melting-point high-melt-strength polyester, and after obtaining polyester slices, the polyester slices are fully mixed with auxiliary agents such as branching agent, nucleating agent, antioxidant and the like and then are added into an injection molding machine for microcellular injection molding foaming. The pre-filling of carbon dioxide before foaming has the functions of removing the original air and increasing the dissolved amount of carbon dioxide. The temperature of the mould in the foaming process is lower and is 120-140 ℃, and the polyester can be smoothly foamed to generate a cell structure after the mould is opened at the temperature; meanwhile, the branching agent is added at a lower temperature in a matching way, so that the technical problem of low melt strength caused by rapid reduction of viscosity after the conventional polyester is melted can be avoided, and the cell structure is stable and is not easy to collapse during microcellular injection molding foaming. In addition, a step of quickly cooling the mould is added before the mould opening in the step (7), and the mould opening after quick cooling can slightly solidify the skin layer, so that the rate insufficiency caused by excessive gas leakage during pressure relief is reduced.
Preferably, in the step (1), the preheating temperature of the reactor is 50-160 ℃, the esterification reaction temperature is 190-250 ℃, and the pressure is 0.1-0.45MPa.
Preferably, in the step (2), the vacuum is pumped for 60-120min until the absolute pressure is below 1000Pa, the pre-polycondensation reaction temperature is 250-290 ℃, the final polycondensation reaction temperature is 245-290 ℃, the pressure is 0-500Pa, and the reaction time is 60-120min.
Preferably, in the step (3), the vacuum drying temperature is 60-130 ℃ and the time is 10-12h.
Preferably, in the step (4), the temperature of the feeding section of the screw of the injection molding machine is 160-200 ℃, the temperature of the reaction section is 210-240 ℃, the temperature from the gas injection port to the head is 215-240 ℃, the back pressure in the screw is 12-20MPa, and the injection pressure of the foaming agent is 15-25MPa.
Compared with the prior art, the invention has the following technical effects:
(1) The invention prepares low-melting-point high-melt-strength polyester suitable for microcellular injection molding foaming, and specifically, polyol or polyacid (anhydride) comonomer with specific content is added in the polyester synthesis process. On the one hand, the crystallization temperature of the polyester can be reduced, thereby reducing the processing temperature; on the other hand, a branched structure may be generated to increase the molecular weight of the polyester segment and improve the melt strength of the polyester at high temperature, thereby making the cells more stable during foaming. The polyester with low melting point and high melt strength obtained by the invention has the intrinsic viscosity of 0.80-1.00dl/g and the melting point of 170-180 ℃.
(2) The invention fully mixes the low-melting point high-melt strength polyester with the branching agent, the nucleating agent, the antioxidant and other auxiliary agents, and then adds the mixture into an injection molding machine for foaming. Wherein, the branching agent can further increase the melt strength, prevent the foam cells from foaming and collapsing in the foaming process and improve the structural stability of the foam cells. The foam density of the polyester foam material obtained by the invention is 100-800kg/m 3 The average diameter of the cells is 20-100 μm, and the compressive strength range is 3.5-5.0MPa.
(3) Pentaerythritol and 1,2,4-butanetriol are preferred branching agents for the present invention, which are more effective in branching than glycerol and trimellitic anhydride, while having significantly reduced crystallinity. Compared with PMDA, the carboxyl in the PMDA is in the ortho position, the steric hindrance is large, and the adjacent carboxyl can not completely participate in the reaction, so that the branching effect in the polymerization reaction is not large, and the melt index (MFR) of the obtained polyester chip is higher.
(4) The carbon dioxide is adopted to fill the mold in advance, so that the original air in the mold cavity can be removed to prevent the melt from being oxidized, and the solubility of the carbon dioxide in the melt can be increased to increase the foaming ratio; meanwhile, a novel rapid cooling technology for the surface of the mold is adopted before mold opening, so that the surface of the blank can be partially solidified in advance before foaming, the structure of a product is stabilized, shrinkage and collapse are prevented, and the stability of the whole structure is ensured.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
The microcellular injection-molded foaming polyester foam material has a foam density of 100-800kg/m 3 The average diameter of the cells is 20-100 μm, and the compressive strength is 3.5-5.0MPa.
The polyester foam material comprises the following raw materials in parts by weight: 100 parts of low-melting-point high-melt-strength polyester with the intrinsic viscosity of 0.80-1.00dl/g, the melting index range of 190 ℃ of 60-80g/10min and the melting point of 170-180 ℃, 0.1-1.0 part of branching agent, 1.0-5.0 parts of nucleating agent, 0.1-1.0 part of antioxidant and 1.0-6.0 parts of foaming agent.
Wherein the antioxidant is selected from at least one of phenolic antioxidant and phosphite antioxidant; the antioxidant is further preferably selected from the group consisting of antioxidant 1010. The nucleating agent is selected from one of talcum powder, calcium carbonate and titanium dioxide. The foaming agent is supercritical carbon dioxide.
The low-melting-point high-melt-strength polyester comprises the following raw materials in parts by weight: 100 portions of terephthalic acid, 30 to 60 portions of ethylene glycol, 10 to 40 portions of polyalcohol or polybasic acid (anhydride) comonomer, 0.01 to 1 portion of catalyst and 0.01 to 1 portion of stabilizer.
Wherein the polyalcohol or polyacid (anhydride) comonomer is one or more of pentaerythritol, 1,2,4,5-pyromellitic dianhydride (PMDA), glycerol, trimellitic anhydride and 1,2,4-butanetriol. Further preferred are one or more of pentaerythritol and 1,2,4-butanetriol. The branching agent is epoxy branching agent with three or more functional groups, and the actual epoxy equivalent weight is between 100 and 150. More preferably triglycidyl isocyanurate (TGIC), 4,4' -diaminodiphenylmethane tetraglycidyl amine. The catalyst is one of ethylene glycol antimony, antimony trioxide and antimony acetate. The stabilizer is triphenyl phosphite.
A preparation method of a microcellular injection molding foaming molded polyester foam material comprises the following steps:
(1) Adding the low-melting-point high-melt-strength polyester raw materials except the stabilizer into a reactor preheated at 50-160 ℃, stirring and mixing uniformly, pressurizing to 0.1-0.45MPa under the protection of inert gas, heating to 190-250 ℃ for esterification, stirring and collecting condensed water until water outlet is finished, adding the stabilizer, and stirring uniformly.
(2) Heating and vacuumizing for 60-120min to below 1000Pa, pre-polycondensing at 250-290 deg.c and 0-500Pa, final polycondensing at 245-290 deg.c and 0-500Pa for 60-120min, discharging and pelletizing to obtain low-melting-point high-melt-strength polyester chip.
(3) The low-melting point high-melt strength polyester chips and the nucleating agent are dried in vacuum at the temperature of 60-130 ℃ for 10-12h and then are evenly mixed with the antioxidant and the branching agent.
(4) Transferring the mixture obtained in the step (3) into an injection molding machine, wherein the temperature of a screw feeding section of the injection molding machine is 160-200 ℃, the temperature of a reaction section is 210-240 ℃, the mixture is fully melted in the injection molding machine and undergoes a branching reaction, and the viscosity is increased; and then, uniformly mixing a foaming agent into the obtained molten polymer, wherein the temperature from a gas injection port to a machine head is 215-240 ℃, the back pressure in a screw is 12-20Mpa, and the injection pressure of the foaming agent is 15-25Mpa. A single homogeneous polymer melt is obtained.
(5) When the nozzle temperature of the injection molding machine reaches 195-205 ℃ and the mold temperature reaches 120-140 ℃, the mold is pre-filled with 5-10MPa carbon dioxide, then the polymer melt is injected into the mold at the injection pressure of 90-160MPa and the injection speed of 100-200mm/s, and the screw continuously maintains the original shape and maintains the pressure after the mold is completely filled.
(6) After 20-40s, the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 20-40MPa for 10-30min and cooled to be in a high elastic state.
(7) And after the pressure maintaining is finished, using circulating cooling water to quickly reduce the temperature of the surface of the die by 8-12 ℃, opening the die within 2-8s after the temperature of the die is stabilized for 5-15s, foaming and quickly cooling the polymer to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
Example 1
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 3.6kg of pentaerythritol and 6.68g of ethylene glycol antimony were put into a 50L reactor, stirred at 150 ℃ for 10min and N was introduced 2 The esterification reaction was started at 225 ℃ and 0.3 MPa. After the end of the water discharge, 10g of triphenyl phosphite were added and stirred well, and a low vacuum was applied for 90min while the kettle temperature was set to 280 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70min. Stopping the reaction, discharging and granulating. The slices were subjected to viscosity, melting point and melt index measurements.
100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder are dried in vacuum at 80 ℃ for 10 hours, and then are mixed with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) by a high-speed mixer for 2-5min; pouring the raw materials into hopper and screw of injection molding machineThe rod temperature from the inlet port was 180 ℃ in the first zone, 200 ℃ in the second zone, 210 ℃ in the third zone, 210 ℃ from the inlet port to the head, and 205 ℃ in the fourth zone. The back pressure in the screw is kept at 15Mpa, and the supercritical CO is kept 2 The injection pressure is 20Mpa, and the dosage is 2 parts. And after the temperature of the nozzle reaches 205 ℃ and the temperature of the mold reaches 140 ℃, pre-filling the mold with 10MPa carbon dioxide gas, and then injecting the polymer melt into the mold at high pressure of 100MPa and at the injection speed of 200mm/s. The screw continues to remain intact to maintain the pressure after the mold is completely filled. After 30s, when the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 25MPa for 10min and cooled to be in a high elastic state. And after the pressure maintaining is finished, rapidly cooling the mold to 10 ℃, keeping the temperature for 10s, and opening the mold within 3s to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
The polyester foam was subjected to density testing, compressive strength testing and microscopic characterization.
Example 2
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 5.8kg of 1,2,4, 5-pyromellitic dianhydride (PMDA), and 6.68g of ethylene glycol antimony were put into a 50L reactor, stirred at 150 ℃ for 10 minutes, and then N was introduced thereinto 2 The esterification reaction was started at 225 ℃ and 0.3 MPa. After the water discharge was completed, 10g of triphenyl phosphite was added and stirred uniformly, and a low vacuum was applied for 90min while the pot temperature was set to 280 ℃. After the vacuum meter reaches-102 kPa, high vacuum is pumped, torque readings are recorded, and the reaction is carried out for 70min from the moment of torque rise. Stopping the reaction, discharging and pelletizing. The slices were subjected to viscosity, melting point and melt index measurements.
100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder are dried in vacuum at 80 ℃ for 10 hours, and then are mixed with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) by a high-speed mixer for 2-5min; pouring the raw materials into a hopper of an injection molding machine, wherein the temperature of a screw of the injection molding machine from a feed inlet is 180 ℃ in a first area, 190 ℃ in a second area, 200 ℃ in a third area, and the temperature from a gas inlet to a machine head is 200 ℃ in a fourth area and 200 ℃. The back pressure in the screw is kept at 15Mpa, and the supercritical CO is kept 2 The injection pressure is 20Mpa, and the dosage is 2 parts. When the temperature of the nozzle reaches 200 ℃, the temperature of the die is controlledAfter reaching 130 ℃, the mold was prefilled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure, injection pressure 100MPa, injection speed 200mm/s. The screw continues to hold pressure after the mold is completely filled. After 30s, when the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 25MPa for 10min and cooled to be in a high elastic state. And after the pressure maintaining is finished, rapidly cooling the mould to reduce the temperature by 10 ℃, keeping the temperature for 10s, and opening the mould within 3s to obtain the polyester foam material with the solid skin layer and the foam core layer.
The polyester foam was subjected to density testing, compressive strength testing and microscopic characterization.
Example 3
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 2.8kg of 1,2, 4-butanetriol and 6.68g of ethylene glycol antimony were put into a 50L reactor, stirred at 150 ℃ for 10 minutes and then N was introduced thereinto 2 The esterification reaction was started at 225 ℃ and 0.3 MPa. After the water discharge was completed, 10g of triphenyl phosphite was added and stirred uniformly, and a low vacuum was applied for 90min while the pot temperature was set to 280 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70min. Stopping the reaction, discharging and pelletizing. The slices were subjected to viscosity, melting point and melt index measurements.
100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder are dried in vacuum at 80 ℃ for 10 hours, and then are mixed with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) by a high-speed mixer for 2-5min; pouring the raw materials into a hopper of an injection molding machine, wherein the temperature of a screw of the injection molding machine from a feed inlet is 190 ℃ in a first area, 200 ℃ in a second area, 210 ℃ in a third area, and the temperature from a gas inlet to a machine head is 210 ℃ and 200 ℃ in a fourth area. The back pressure in the screw is kept at 15Mpa, and the supercritical CO is kept 2 The injection pressure is 20Mpa, and the dosage is 2 parts. And when the temperature of the nozzle reaches 200 ℃ and the temperature of the mold reaches 140 ℃, pre-filling the mold with 10MPa carbon dioxide gas, and then injecting the polymer melt into the mold at high pressure of 100MPa and at the injection speed of 200mm/s. The screw continues to hold pressure after the mold is completely filled. After 30s, when the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is meltedMaintaining the pressure for 10min at 25MPa and cooling to obtain high elastic state. And after the pressure maintaining is finished, rapidly cooling the mold to 10 ℃, keeping the temperature for 10s, and opening the mold within 3s to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
The polyester foam was subjected to density testing, compressive strength testing and microscopic characterization.
Example 4
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 3.6kg of pentaerythritol and 6.68g of ethylene glycol antimony were put into a 50L reactor, stirred at 150 ℃ for 10min and then N was introduced 2 The esterification reaction was started at 225 ℃ and 0.3 MPa. After the water discharge was completed, 10g of triphenyl phosphite was added and stirred uniformly, and a low vacuum was applied for 90min while the pot temperature was set to 280 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70min. Stopping the reaction, discharging and pelletizing. The slices were subjected to viscosity, melting point and melt index measurements.
100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder are dried in vacuum at 80 ℃ for 10 hours, and then are mixed with 2 parts of antioxidant 1010 and 1 part of branching agent 4,4-diaminodiphenyl methane tetraglycidyl amine (TGDDM) by a high-speed mixer for 2-5 minutes; pouring the raw materials into a hopper of an injection molding machine, wherein the temperature of a screw of the injection molding machine from a feed inlet is 180 ℃ in a first area, 200 ℃ in a second area, 210 ℃ in a third area, and the temperature from a gas inlet to a machine head is 210 ℃ and 205 ℃ in a fourth area. The back pressure in the screw is kept at 15Mpa, and the supercritical CO is kept 2 The injection pressure is 20Mpa, and the dosage is 2 parts. And after the temperature of the nozzle reaches 205 ℃ and the temperature of the mold reaches 140 ℃, pre-filling the mold with 10MPa carbon dioxide gas, and then injecting the polymer melt into the mold at high pressure of 100MPa and at the injection speed of 200mm/s. The screw continues to hold pressure after the mold is completely filled. After 30s, when the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 25MPa for 10min and cooled to be in a high elastic state. And after the pressure maintaining is finished, rapidly cooling the mold to 10 ℃, keeping the temperature for 10s, and opening the mold within 3s to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
The polyester foam was subjected to density testing, compressive strength testing and microscopic characterization.
Example 5
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 1.4kg of 1,2, 4-butanetriol, 1.8kg of pentaerythritol and 6.68g of ethylene glycol antimony were put into a 50L reactor, stirred at 150 ℃ for 10 minutes and then N was introduced thereinto 2 The esterification reaction was started at 225 ℃ and 0.3 MPa. After the water discharge was completed, 10g of triphenyl phosphite was added and stirred uniformly, and a low vacuum was applied for 90min while the pot temperature was set to 280 ℃. After the vacuum meter reached-102 kPa, the vacuum was pulled high, and the torque reading was recorded, starting from the torque rise, and the reaction was carried out for 70min. Stopping the reaction, discharging and granulating. The slices were subjected to viscosity, melting point and melt index measurements.
100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder are dried in vacuum at 80 ℃ for 10 hours, and then are mixed with 2 parts of antioxidant 1010 and 1 part of branching agent 4,4-diaminodiphenyl methane tetraglycidyl amine (TGDDM) by a high-speed mixer for 2-5 minutes; pouring the raw materials into a hopper of an injection molding machine, wherein the temperature of a screw of the injection molding machine from a feed inlet is 190 ℃ in a first area, 200 ℃ in a second area, 210 ℃ in a third area, and the temperature from a gas inlet to a machine head is 210 ℃ and 200 ℃ in a fourth area. The back pressure in the screw is kept at 15Mpa, and the supercritical CO is kept 2 The injection pressure is 20Mpa, and the dosage is 2 parts. And when the temperature of the nozzle reaches 200 ℃ and the temperature of the mold reaches 140 ℃, pre-filling the mold with 10MPa carbon dioxide gas, and then injecting the polymer melt into the mold at high pressure of 100MPa and at the injection speed of 200mm/s. The screw continues to hold pressure after the mold is completely filled. After 30s, when the inner cavity of the mold is completely filled, the screw rod is retracted, and the polymer melt is kept at 25MPa for 10min and cooled to be in a high elastic state. And after the pressure maintaining is finished, rapidly cooling the mold to 10 ℃, keeping the temperature for 10s, and opening the mold within 3s to obtain the polyester foam material with the skin layer solid and the core layer provided with the foam holes.
The polyester foam was subjected to density testing, compressive strength testing and microscopic characterization.
The following are comparative examples, the injection molding machine temperatures were all adjusted according to actual operation:
comparative example 1 (formulation difference from example 1 in that no modified monomeric pentaerythritol and no branching agent were added during polyester synthesis and injection molding).
Comparative example 2 (a formulation different from example 1 in that no pentaerythritol was added during the polyester synthesis).
Comparative example 3 (differing from the formulation of example 1 in that 8.3kg parts of pentaerythritol were added during the polyester synthesis for modification) comparative example 4 (differing from the formulation of example 1 in that the same parts of neopentyl glycol were used instead of pentaerythritol during the polyester synthesis).
Comparative example 5 (differing from the formulation of example 1 in that no branching agent was added during injection molding)
Comparative example 6 (difference from the formulation of example 1 in that 5 parts of branching agent were added during injection moulding)
Comparative example 7 (a difference from the process of example 1 in that no carbon dioxide pre-charge mold was used during injection molding).
Comparative example 8 (the difference from the process of example 1 is that no mold rapid cooling technique was used before the injection mold was opened).
Performance testing
The polyester and polyester foam materials obtained in the examples and comparative examples were subjected to performance tests, the performance test methods were as follows: (1) intrinsic viscosity: polyester samples were dissolved in phenol: the mass ratio of tetrachloroethane is 3:2, the intrinsic viscosity of the sample was measured at room temperature using an Ubbelohde viscometer.
(2) Melting point: and (3) adopting a differential scanning calorimeter to scan the sample at 30-280 ℃ for heating and cooling cycles, and determining the melting point of the polymer.
(3) Foam density: the actual density of the foam beads was measured by draining and the average of 3 samples was taken.
(4) Cell diameter: the 100 points were observed with a scanning electron microscope and averaged.
(5) Melt flowability: MFR was measured using a melt indexer, thereby reflecting melt strength.
(6) Compressive strength: tested using the ISO 844 standard.
The indexes of the test data of examples 1 to 5 and comparative examples 1 to 6 are shown in Table 1.
TABLE 1 comparison of sample parameters for each example and comparative example
Note: the intrinsic viscosity of the polyester means the intrinsic viscosity without the addition of branching agent
From the above table data:
comparing the data of example 1 and comparative examples 1 and 5, it can be seen that comparative example 5 significantly reduces the melting point of the polyester compared to comparative example 1, which uses pentaerythritol modified polyester. Meanwhile, the four hydroxyl groups of the pentaerythritol can also promote the generation of a branched structure, and the molecular weight is improved, so that the melt strength is improved. However, comparative example 5 has a limited increase in melt strength with only pentaerythritol addition, and cells cannot encapsulate gas and thus injection molding foaming is impossible. In example 1, pentaerythritol and a branching agent were added during polyester synthesis and microcellular injection molding foaming, respectively, which not only significantly reduced the melting point of the polyester, but also further increased the molecular weight, thereby improving the melt strength, and the compressive strength of the resulting polyester foam material was close to the existing basic rigid foam product on the market.
Comparative example 1 and comparative example 2 show that the comparative example only adds the branching agent to achieve the effect of late branching and chain extension, but the melting point of the polyester is higher, so the process temperature is too high during foaming, which is not favorable for injection molding foaming.
As can be seen from comparison of example 1, comparative example 3 and comparative example 6, the addition of an excessive amount of pentaerythritol in comparative example 3 causes the melting point of the polyester to disappear and becomes amorphous, but the melt fluidity is too poor to facilitate the filling of the mold, resulting in the failure of injection molding; comparative example 6 the addition of an excess amount of branching agent resulted in a melt viscosity that was too high to be advantageous for injection molding.
Comparing example 1 with comparative example 4, it can be seen that comparative example 4 uses dihydric alcohol to modify polyester, although the dihydric alcohol can also lower the melting point of polyester, it lacks branching effect, has too high melt index, lower melt strength, and the foam combination during the foaming process can be seen from the larger cells in the later stage, and the compressive strength of the obtained foam is lower.
Comparative examples 1,2 and 3, each of which uses three modifying monomers. Although the three modifying monomers can effectively reduce the melting point of the polyester, the effect of using PMDA in example 2 is inferior to that of using the other two modifying monomers, because the carboxyl of PMDA is in the ortho position, the steric hindrance is large, the adjacent carboxyl can not completely participate in the reaction, the branching effect in the polymerization reaction is not large, and the melt index (MFR) of the obtained slices is also higher, so that the melt strength is not enough to easily generate the phenomena of hole breaking and foaming when the microcellular injection foaming is carried out, the number of large foam holes is large, the foam hole shape is relatively poor, and the compression strength is inferior to that of the other two modifying monomers.
As can be seen from comparison of example 1 and comparative examples 7 and 8, pre-charging carbon dioxide into the mold at a certain pressure helps to increase the expansion ratio while slightly improving the mechanical strength of the article, because the charged carbon dioxide protects the article from oxidation by air and also increases the solubility of carbon dioxide in the melt, and the expansion ratio is increased by more nucleation sites generated during the foaming process; and the adoption of the mold rapid cooling technology can stabilize the product structure, prevent the surface of the product from collapsing, and reduce the surface defects so as to obtain better mechanical properties. This demonstrates that process improvements improve the applicability of polyester materials for microcellular foaming.
In conclusion, the injection-moldable low-melting-point modified polyester with low melting point and high melt strength and the polyester foaming material with stable cell structure and excellent mechanical property can be obtained only by the scheme in the preferable scope of the claims of the invention. While the change of the proportion and the replacement/addition/subtraction of the raw materials bring corresponding negative effects.
The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modifications, alterations and equivalent changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.
Claims (10)
1. The microcellular injection molding foaming molding polyester foam material is characterized in that: the foam density is 100-800kg/m 3 The average diameter of the cells is 20-100 μm, and the compression strength range is 3.5-5.0MPa;
the polyester foam material comprises the following raw materials in parts by weight: 100 parts of low-melting-point high-melt-strength polyester with the intrinsic viscosity of 0.80-1.00dl/g, the melting index range of 60-80g/10min at 190 ℃, the melting point of 170-180 ℃, 0.1-1.0 part of branching agent, 1.0-5.0 parts of nucleating agent, 0.1-1.0 part of antioxidant and 1.0-6.0 parts of foaming agent;
the low-melting-point high-melt-strength polyester comprises the following raw materials in parts by weight: 100 portions of terephthalic acid, 30 to 60 portions of ethylene glycol, 10 to 40 portions of polyalcohol or polybasic acid (anhydride) comonomer, 0.01 to 1 portion of catalyst and 0.01 to 1 portion of stabilizer.
2. The polyester foam of claim 1, wherein: the polyalcohol or polyacid (anhydride) comonomer is one or more of pentaerythritol, 1,2,4,5-pyromellitic dianhydride, glycerol, trimellitic anhydride and 1,2,4-butanetriol.
3. The polyester foam material of claim 2, wherein: the polyalcohol or polyacid (anhydride) comonomer is one or more of pentaerythritol and 1,2,4-butanetriol.
4. The polyester foam of claim 1, wherein: the branching agent is epoxy branching agent with three or more functional groups, and the actual epoxy equivalent weight is between 100 and 150.
5. The polyester foam of claim 4, wherein: the branching agent is selected from triglycidyl isocyanurate, 4,4' -diaminodiphenylmethane tetraglycidyl amine.
6. The polyester foam of claim 1, wherein:
the antioxidant is selected from at least one of phenolic antioxidant and phosphite antioxidant;
the nucleating agent is selected from one of talcum powder, calcium carbonate and titanium dioxide;
the foaming agent is supercritical carbon dioxide;
the catalyst is one of ethylene glycol antimony, antimony trioxide and antimony acetate;
the stabilizer is triphenyl phosphite.
7. A process for preparing microcellular foam injection-molded polyester foam according to any one of claims 1 to 6, which comprises the steps of:
(1) Adding polyester raw materials with low melting point and high melt strength except for a stabilizer into a preheated reactor, stirring and mixing uniformly, pressurizing and heating under the protection of inert gas to perform esterification reaction, stirring and collecting condensed water until water outlet is finished, adding the stabilizer and stirring uniformly;
(2) Heating and vacuumizing simultaneously, carrying out pre-polycondensation reaction and final polycondensation reaction in sequence, discharging and granulating after the reaction is finished, and preparing polyester chips with low melting point and high melt strength;
(3) Vacuum drying low-melting-point high-melt-strength polyester chips and nucleating agents, and then uniformly mixing the chips, the nucleating agents, the antioxidants and the branching agents;
(4) Transferring the mixture obtained in the step (3) to an injection molding machine, wherein the mixture is fully melted in the injection molding machine and subjected to a branching reaction, and the viscosity is increased; then, uniformly mixing a foaming agent into the obtained molten polymer to obtain a single homogeneous polymer melt;
(5) When the temperature of a nozzle of an injection molding machine reaches 195-205 ℃ and the temperature of a mold reaches 120-140 ℃, pre-charging 5-10MPa carbon dioxide into the mold, then injecting the polymer melt into the mold at the injection pressure of 90-160MPa and the injection speed of 100-200mm/s, and after the mold is completely filled, continuously maintaining the original shape of the screw to keep the pressure;
(6) After 20-40s, completely filling the inner cavity of the mold, retreating the screw, maintaining the pressure of the polymer melt at 20-40MPa for 10-30min, and cooling to form a high elastic state;
(7) After the pressure maintaining is finished, circulating cooling water is used for enabling the surface of the die to be rapidly cooled for 8-12 ℃, the die is opened in 2-8s after the temperature of the die is stabilized for 5-15s, and the polymer blank is foamed and rapidly cooled to obtain the polyester foam material with the solid skin layer and the foam hole in the core layer.
8. The method of claim 7, wherein:
in the step (1), the preheating temperature of the reactor is 50-160 ℃, the esterification reaction temperature is 190-250 ℃, and the pressure is 0.1-0.45MPa;
in the step (2), the vacuum is pumped for 60-120min until the absolute pressure is below 1000Pa, the pre-polycondensation reaction temperature is 250-290 ℃, the final polycondensation reaction temperature is 245-290 ℃, the pressure is 0-500Pa, and the reaction time is 60-120min.
9. The method of claim 7, wherein: in the step (3), the vacuum drying temperature is 60-130 ℃, and the time is 10-12h.
10. The method of claim 7, wherein: in the step (4), the temperature of a screw feeding section of an injection molding machine is 160-200 ℃, the temperature of a reaction section is 210-240 ℃, the temperature from a gas injection port to a machine head is 215-240 ℃, the back pressure in the screw is 12-20Mpa, and the injection pressure of a foaming agent is 15-25Mpa.
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| CN102492123A (en) * | 2011-11-11 | 2012-06-13 | 华东理工大学 | Method for preparing polyester with high melt strength for foaming CO2 by polyprotic acid in-situ modification and application thereof |
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