CN115490998B - Microporous injection foaming formed polyester foam material and preparation method thereof - Google Patents
Microporous injection foaming formed polyester foam material and preparation method thereof Download PDFInfo
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- CN115490998B CN115490998B CN202210175064.XA CN202210175064A CN115490998B CN 115490998 B CN115490998 B CN 115490998B CN 202210175064 A CN202210175064 A CN 202210175064A CN 115490998 B CN115490998 B CN 115490998B
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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
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- 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
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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Abstract
The invention relates to the field of polyester materials, and discloses a microporous injection molding foaming molded 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, 0.1-1.0 part of branching agent, 1.0-5.0 parts of nucleating agent, 0.1-1.0 parts of antioxidant and 1.0-6.0 parts of foaming agent; the low melting point high melt strength polyester comprises the following raw materials: 100 parts of terephthalic acid, 30-60 parts of glycol, 10-40 parts of polyalcohol or polybasic acid (anhydride) comonomer, 0.01-1 part of catalyst and 0.01-1 part of stabilizer. The invention firstly prepares the low-melting point high-melt strength polyester which can be suitable for microcellular injection foaming, and then carries out microcellular injection 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 microporous injection foaming 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 and high temperature resistance and aging resistance. With the increase of productivity and the technological innovation, new application fields of polyester are developed, such as foaming production of foam boards, sheets or beads by using fiber grade, bottle grade and recovery grade polyester, and the polyester is applied to the fields of wind power, construction, automobiles and the like.
The polyester foaming mainly comprises extrusion foaming and kettle pressure foaming processes, and the extrusion foaming process applied in large scale in industry at present belongs to continuous foaming processes, and can obtain plates and sheets with the foaming multiplying power of more than 10 times. The autoclave foaming process belongs to a batch foaming process and is generally only used in laboratories or in small-batch production. However, both autoclave foaming and extrusion foaming can produce polyester foam with simple shape, and cannot produce high-precision polyester foam products with three-dimensional complex structures.
The microporous injection molding foaming technology is proposed by Trexel company, combines an injection molding process with a microporous foaming technology, and has the characteristics of short molding period, raw material saving, low product shrinkage, high dimensional stability and the like compared with the common injection molding process; compared with extrusion and kettle pressure processes, the microporous injection molding can produce foam products with complex three-dimensional structures, and places with certain appearance structure requirements on various products can be produced without post-complex processing. However, since microcellular injection molding is carried out, the microcellular injection molding cannot be widely applied to various materials due to the special foaming process, further popularization in the foaming technology industry is limited, and the microcellular injection molding is only applied to few polymer foam production at present. Patent CN105504498A proposes a polypropylene foaming composite material formula suitable for foaming by micro-porous injection molding, wherein the formula uses micro-crosslinked polypropylene and polyethylene as a modifier, and a toughening agent and talcum powder as auxiliary agents are added, so that the product obtained by foaming has the advantages of about 1.25 times of multiplying power, uniform foam holes and good mechanical property. The patent 109501107A optimizes the process, proposes to use high-pressure full injection and adopts a core retreating mode in the mould withdrawing process to prepare foams of polystyrene, polyethylene, polylactic acid and the like with the foaming multiplying power of 2 to 10 times, and the multiplying power is higher than that of foams obtained by the traditional injection molding mode.
From the above, the application range of materials such as polypropylene is widened by using the microcellular injection foaming process. However, in the previous research process, the microcellular injection foaming process is not well applicable to polyester foaming. This is due to the fact that the crystallization temperature of polyesters is higher than that of polymers such as polypropylene, resulting in a foaming process temperature exceeding 260 ℃. In the process of microcellular injection molding foaming, if the temperature of the mold is too low, polyester can be rapidly cooled and is difficult to foam after mold opening to generate a cell structure; if the temperature is too high, the dimensional stability of the foam after mold opening is poor, and the requirement on equipment materials in a high-temperature environment is high; in addition, the viscosity of the polyester drops sharply after melting, and it is difficult to stabilize the cell structure at high temperatures. To sum up, the polyester has a bright application in microcellular injection foaming at present.
Disclosure of Invention
In order to better apply the microcellular injection foaming technology in the polyester foaming industry, the invention provides a microcellular injection foaming polyester foam material and a preparation method thereof. The invention firstly prepares the low-melting point high-melt strength polyester which can be suitable for microcellular injection foaming, and then carries out microcellular injection foaming at a lower temperature to prepare the polyester foam material with high foaming multiplying power, stable foam structure and excellent mechanical property.
The specific technical scheme of the invention is as follows:
in a first aspect, the present invention provides a microcellular injection-molded foam polyester foam 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 melt index range of 60-80g/10min at 190 ℃ 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 parts of terephthalic acid, 30-60 parts of glycol, 10-40 parts of polyalcohol or polybasic acid (anhydride) comonomer, 0.01-1 part of catalyst and 0.01-1 part of stabilizer.
The invention adopts an in-situ copolymerization method to directly prepare the low-melting-point high-melt-strength polyester. Wherein the polyester is modified by the addition of a polyol or a polyacid (anhydride) comonomer, which functions in that: on one hand, the original regularity of the polyester can be broken, and the crystallization is broken to lower the crystallization temperature of the polyester so as to lower the processing temperature; on the other hand, since they have three or more multifunctional groups, a branched structure can be generated after being introduced into the polyester to increase the molecular weight of the segment, and the melt strength of the polyester at high temperature can be improved, so that cells can be more stable during foaming. It should be noted that the addition amount of the polyhydric alcohol or polybasic acid (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 stable injection molding foaming at a lower temperature is difficult; 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 branching agent, nucleating agent, antioxidant and the like, and then added into an injection molding machine for foaming. The reason for adding the branching agent is that the branching effect of the polyol or the polybasic acid (anhydride) comonomer in the polyester synthesis process is not enough to ensure that a stable cell structure can be formed in the melt in the foaming process, and the branching agent can further increase the melt strength in the foaming process, prevent cells from being combined and foamed and collapsed in the foaming process and improve the stability of the cell structure. The addition of the nucleating agent is beneficial to increasing the nucleation point of bubbles and increasing the density of cells. The antioxidant is used for relieving thermal oxidative degradation of the polyester in the injection molding process.
Preferably, the polyol 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 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 polybasic acid (anhydride) comonomer can obtain ideal technical effects, and the effects of pentaerythritol and 1,2, 4-butanetriol are optimal in comprehensive consideration, so that compared with glycerol and trimellitic anhydride, the branched effects are better, and meanwhile, the crystallinity can be remarkably reduced. Compared with PMDA, the carboxyl in the PMDA is in an ortho position, the steric hindrance is large, and the adjacent carboxyl cannot 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, so that the cell structure is not stable enough during microcellular injection foaming, and finally, the cell structure is in abnormal cell forms such as large cells and cell collapse, and the final mechanical property is influenced.
Preferably, the branching agent is an epoxy branching agent with three functional groups and above, and the actual epoxy equivalent is between 100 and 150.
The epoxy branching agent has epoxy group capable of reacting with terminal carboxyl and terminal hydroxyl in polyester to form cross-linking structure. An excessively high epoxy equivalent weight means fewer epoxy groups, low reactivity and poor crosslinking effect; if the epoxy equivalent is too low, the crosslinking effect is good, but gel is easy to generate to influence the uniformity of foam.
As a further preferred option, the branching agent is selected from triglycidyl isocyanurate (TGIC), 4' -diaminodiphenylmethane tetraglycidyl amine.
Preferably, the antioxidant is at least one selected from phenolic antioxidants and phosphite antioxidants; the antioxidant is further preferably selected from the group consisting of antioxidants 1010.
Preferably, the nucleating agent is selected from one of talcum powder, calcium carbonate and titanium dioxide.
Preferably, the foaming agent is supercritical carbon dioxide.
Preferably, the catalyst is one of 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 invention provides a method for preparing a microporous injection foam-molded polyester foam material, comprising the following steps:
(1) Adding the low-melting-point high-melt-strength polyester raw materials except the stabilizing agent 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 stabilizing agent and stirring uniformly.
(2) Heating, vacuumizing, pre-condensing and final condensing, discharging and granulating to obtain the low-melting-point high-melt-strength polyester chip.
(3) And (3) vacuum drying the low-melting-point high-melt-strength polyester chip and the nucleating agent, and uniformly mixing with the antioxidant and the branching agent.
(4) Transferring the mixture obtained in the step (3) into an injection molding machine, fully melting the mixture in the injection molding machine, carrying out branching reaction, and raising viscosity; the blowing agent is then homogeneously mixed into the resulting molten polymer to give a single homogeneous polymer melt.
(5) After the temperature of the nozzle of the injection molding machine reaches 195-205 ℃ and the temperature of the mold reaches 120-140 ℃, 5-10MPa of carbon dioxide is filled into the mold in advance, then 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, the screw rod continuously maintains the original pressure, so that the pores generated in the injection molding process are ensured to be completely filled.
(6) After 20-40s, after the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained for 10-30min under 20-40MPa and cooled to be in a high-elastic state.
(7) After the pressure maintaining is finished, the surface of the die is quickly cooled by using circulating cooling water to 8-12 ℃, the die is opened within 2-8s after the temperature of the die is stabilized for 5-15s, and the polymer is foamed and quickly cooled to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
The invention adopts an in-situ copolymerization method to directly prepare low-melting-point high-melt-strength polyester, and after polyester chips are obtained, the polyester chips are fully mixed with branching agents, nucleating agents, antioxidants and other auxiliary agents, and then the mixture is added into an injection molding machine to carry out micropore injection molding foaming. The pre-charging of carbon dioxide before foaming has the effect of removing original air and increasing the dissolution 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 foam cell structure after the mould is opened at the temperature; meanwhile, the technical problem that the melt strength is too low due to the fact that the viscosity is rapidly reduced after the conventional polyester is melted can be avoided by matching with the branching agent at a lower temperature, so that the cell structure is stable and is not easy to collapse during microcellular injection foaming. In addition, a rapid cooling step of the die is added before the die opening in the step (7), the die is opened after rapid cooling, the cortex can be slightly solidified in advance, and the rate deficiency caused by excessive leakage of gas 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), vacuum is applied for 60-120min to absolute pressure 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 a screw feeding section of the 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 is kept in the screw and 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 provides a low-melting point high-melt strength polyester suitable for microcellular injection foaming, which is prepared by adding a polyol or a polybasic acid (anhydride) comonomer with specific content in the synthetic process of the polyester. On the one hand, the crystallization temperature of the polyester can be reduced so as to reduce the processing temperature; on the other hand, branched structures can be created to increase the molecular weight of the polyester segment and increase the melt strength of the polyester at high temperatures, thereby making the cells more stable during foaming. The intrinsic viscosity of the low-melting-point high-melt-strength polyester obtained by the invention is 0.80-1.00dl/g, and the melting point is 170-180 ℃.
(2) The invention fully mixes the low-melting-point high-melt-strength polyester, 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 being combined and collapsed 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 is 3.5-5.0MPa.
(3) Pentaerythritol and 1,2, 4-butanetriol are preferred as branching agents according to the invention, which have a better branching effect than glycerol and trimellitic anhydride and at the same time significantly reduce the crystallinity. Compared with PMDA, the carboxyl in the PMDA is in an ortho position, the steric hindrance is larger, and the adjacent carboxyl cannot fully 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 invention adopts carbon dioxide to pre-fill the mould, which not only can remove the original air in the mould cavity to prevent the melt from oxidizing, but also can increase the solubility of the carbon dioxide in the melt so as to increase the foaming multiplying power; meanwhile, a novel rapid cooling technology for the surface of the die is adopted before die opening, the surface of the blank body can be partially solidified in advance before foaming, the structure of the workpiece is stabilized, shrinkage collapse is prevented, and the stability of the whole structure is ensured.
Detailed Description
The invention is further described below with reference to examples.
General examples
A microporous injection-foaming polyester foam material with 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 melt index range of 60-80g/10min at 190 ℃ 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 at least one selected from phenolic antioxidants and phosphite antioxidants; the antioxidant is further preferably selected from the group consisting of antioxidants 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 parts of terephthalic acid, 30-60 parts of glycol, 10-40 parts of polyalcohol or polybasic acid (anhydride) comonomer, 0.01-1 part of catalyst and 0.01-1 part of stabilizer.
Wherein the polyalcohol or polybasic acid (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 an epoxy branching agent with three functional groups and above, and the actual epoxy equivalent is between 100 and 150. Further preferred are triglycidyl isocyanurate (TGIC), 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 microporous injection foaming polyester foam material comprises the following steps:
(1) Adding the low-melting point high-melt strength polyester raw materials except the stabilizer into a preheated reactor 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 reaction, stirring and collecting condensed water until water outlet is finished, adding the stabilizer and stirring uniformly.
(2) Heating and vacuumizing for 60-120min to absolute pressure below 1000Pa, performing pre-polycondensation reaction at 250-290 ℃ and 0-500Pa, performing final polycondensation reaction at 245-290 ℃ and 0-500Pa for 60-120min, discharging and granulating after the reaction is finished, and obtaining the low-melting-point high-melt-strength polyester chip.
(3) Vacuum drying low-melting point high-melt strength polyester slice and nucleating agent at 60-130 ℃ for 10-12h, and then uniformly mixing with antioxidant and 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 ℃, and the mixture is fully melted and subjected to branching reaction in the injection molding machine, so that the viscosity is increased; and then uniformly mixing the 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 is kept at 12-20Mpa in a screw, and the injection pressure of the foaming agent is 15-25Mpa. A single homogeneous polymer melt is obtained.
(5) After the nozzle temperature of the injection molding machine reaches 195-205 ℃ and the mold temperature 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, the screw rod continuously maintains the original pressure.
(6) After 20-40s, after the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained for 10-30min under 20-40MPa and cooled to be in a high-elastic state.
(7) After the pressure maintaining is finished, the surface of the die is quickly cooled by using circulating cooling water to 8-12 ℃, the die is opened within 2-8s after the temperature of the die is stabilized for 5-15s, and the polymer is foamed and quickly cooled to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
Example 1
16.6kg of terephthalic acid, 6.5kg of ethylene glycol, 3.6kg of pentaerythritol and 6.68g of ethylene glycol antimony are added into a 50L reaction kettle, stirred for 10min at 150 ℃ and then N is introduced 2 The esterification reaction was started at 225℃and 0.3 MPa. After the water outlet is finished, 10g of triphenyl phosphite is added and stirred uniformly, the low vacuum is pumped for 90min, and the kettle temperature is set to 280 ℃. And after the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque indication is recorded, and the reaction is started for 70 minutes from the rising of the torque. Stopping the reaction, discharging and granulating. The viscosity, melting point and melt index of the chips were measured.
Vacuum drying 100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder at 80 ℃ for 10 hours, and mixing with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) for 2-5min by using a high-speed mixer; the raw materials are poured into a hopper of an injection molding machine, the temperature of a screw rod 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 of a gas injection port to a machine head is 210 ℃ and 205 ℃ in a fourth area. Back pressure is kept at 15Mpa in the screw, supercritical CO 2 The injection pressure was 20MPa and the amount was 2 parts. After the nozzle temperature reached 205℃and the mold temperature reached 140℃the mold was pre-filled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure at an injection pressure of 100MPa and an injection rate of 200mm/s. The screw continues to remain intact after the mold is completely filled to maintain pressure. After 30s, the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained at 25MPa for 10min and cooled to be in a high-elastic state. And after the pressure maintaining is finished, rapidly cooling the die to reduce the temperature to 10 ℃, and opening the die within 3s after the temperature is maintained for 10s to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
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 are added into a 50L reaction kettle, stirred for 10min at 150 ℃ and then introduced with N 2 The esterification reaction was started at 225℃and 0.3 MPa. After the water outlet is finished, 10g of triphenyl phosphite is added and stirred uniformly, the low vacuum is pumped for 90min, and the kettle temperature is set to 280 ℃. And after the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque indication is recorded, and the reaction is started for 70 minutes from the rising of the torque. Stopping the reaction, discharging and granulating. The viscosity, melting point and melt index of the chips were measured.
Vacuum drying 100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder at 80 ℃ for 10 hours, and mixing with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) for 2-5min by using a high-speed mixer; the raw materials are poured into a hopper of an injection molding machine, the temperature of a screw rod 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 of a gas injection port to a machine head is set to be 200 ℃ in a fourth area. Back pressure is kept at 15Mpa in the screw, supercritical CO 2 The injection pressure was 20MPa and the amount was 2 parts. After the nozzle temperature reached 200℃and the mold temperature reached 130℃the mold was pre-filled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure at an injection pressure of 100MPa and an injection rate of 200mm/s. The screw continues to remain intact after the mold is completely filled to maintain pressure. After 30s, the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained at 25MPa for 10min and cooled to be in a high-elastic state. And after the pressure maintaining is finished, rapidly cooling the die to reduce the temperature to 10 ℃, and opening the die within 3s after the temperature is maintained for 10s to obtain the polyester foam material with the solid skin layer and the foam holes on the 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 are added into a 50L reaction kettle, stirred for 10min at 150 ℃ and then introducedIn N 2 The esterification reaction was started at 225℃and 0.3 MPa. After the water outlet is finished, 10g of triphenyl phosphite is added and stirred uniformly, the low vacuum is pumped for 90min, and the kettle temperature is set to 280 ℃. And after the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque indication is recorded, and the reaction is started for 70 minutes from the rising of the torque. Stopping the reaction, discharging and granulating. The viscosity, melting point and melt index of the chips were measured.
Vacuum drying 100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder at 80 ℃ for 10 hours, and mixing with 2 parts of antioxidant 1010 and 1 part of branching agent triglycidyl isocyanurate (TGIC) for 2-5min by using a high-speed mixer; the raw materials are poured into a hopper of an injection molding machine, the temperature of a screw rod 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 of a gas injection port to a machine head is set to be 210 ℃ in a fourth area, 200 ℃. Back pressure is kept at 15Mpa in the screw, supercritical CO 2 The injection pressure was 20MPa and the amount was 2 parts. After the nozzle temperature reached 200℃and the mold temperature reached 140℃the mold was pre-filled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure at an injection pressure of 100MPa and an injection rate of 200mm/s. The screw continues to remain intact after the mold is completely filled to maintain pressure. After 30s, the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained at 25MPa for 10min and cooled to be in a high-elastic state. And after the pressure maintaining is finished, rapidly cooling the die to reduce the temperature to 10 ℃, and opening the die within 3s after the temperature is maintained for 10s to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
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 are added into a 50L reaction kettle, stirred for 10min at 150 ℃ and then N is introduced 2 The esterification reaction was started at 225℃and 0.3 MPa. After the water outlet is finished, 10g of triphenyl phosphite is added and stirred uniformly, the low vacuum is pumped for 90min, and the kettle temperature is set to 280 ℃. And after the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque indication is recorded, and the reaction is started for 70 minutes from the rising of the torque. The reaction was stopped and the reaction was stopped,discharging and granulating. The viscosity, melting point and melt index of the chips were measured.
Vacuum drying 100 parts of low-melting-point high-melt-strength polyester chips and 1 part of 10000-mesh talcum powder at 80 ℃ for 10 hours, and mixing with 2 parts of antioxidant 1010 and 1 part of branching agent 4, 4-diaminodiphenylmethane tetraglycidyl amine (TGDDM) for 2-5 minutes by using a high-speed mixer; the raw materials are poured into a hopper of an injection molding machine, the temperature of a screw rod 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 of a gas injection port to a machine head is 210 ℃ and 205 ℃ in a fourth area. Back pressure is kept at 15Mpa in the screw, supercritical CO 2 The injection pressure was 20MPa and the amount was 2 parts. After the nozzle temperature reached 205℃and the mold temperature reached 140℃the mold was pre-filled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure at an injection pressure of 100MPa and an injection rate of 200mm/s. The screw continues to remain intact after the mold is completely filled to maintain pressure. After 30s, the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained at 25MPa for 10min and cooled to be in a high-elastic state. And after the pressure maintaining is finished, rapidly cooling the die to reduce the temperature to 10 ℃, and opening the die within 3s after the temperature is maintained for 10s to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
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 are added into a 50L reaction kettle, stirred for 10min at 150 ℃ and then introduced with N 2 The esterification reaction was started at 225℃and 0.3 MPa. After the water outlet is finished, 10g of triphenyl phosphite is added and stirred uniformly, the low vacuum is pumped for 90min, and the kettle temperature is set to 280 ℃. And after the vacuum instrument reaches-102 kPa, high vacuum is pumped, torque indication is recorded, and the reaction is started for 70 minutes from the rising of the torque. Stopping the reaction, discharging and granulating. The viscosity, melting point and melt index of the chips were measured.
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 agent4, 4-diaminodiphenylmethane tetraglycidyl amine (TGDDM) was mixed for 2-5min using a high speed mixer; the raw materials are poured into a hopper of an injection molding machine, the temperature of a screw rod 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 of a gas injection port to a machine head is set to be 210 ℃ in a fourth area, 200 ℃. Back pressure is kept at 15Mpa in the screw, supercritical CO 2 The injection pressure was 20MPa and the amount was 2 parts. After the nozzle temperature reached 200℃and the mold temperature reached 140℃the mold was pre-filled with 10MPa carbon dioxide gas, and then the polymer melt was injected into the mold using high pressure at an injection pressure of 100MPa and an injection rate of 200mm/s. The screw continues to remain intact after the mold is completely filled to maintain pressure. After 30s, the inner cavity of the die is completely filled, the screw rod is retracted, and the polymer melt is maintained at 25MPa for 10min and cooled to be in a high-elastic state. And after the pressure maintaining is finished, rapidly cooling the die to reduce the temperature to 10 ℃, and opening the die within 3s after the temperature is maintained for 10s to obtain the polyester foam material with the solid skin layer and the foam holes on the core layer.
The polyester foam was subjected to density testing, compressive strength testing, and microscopic characterization.
The following are comparative examples, and the temperature of the injection molding machine is adjusted according to actual operation:
comparative example 1 (the formulation of example 1 differs in that the modified monomer pentaerythritol and branching agent were not added during the synthesis and injection molding of the polyester).
Comparative example 2 (the difference from the formulation of example 1 is that pentaerythritol was not added during the polyester synthesis).
Comparative example 3 (differing from the formulation of example 1 in the modification of 8.3kg parts of pentaerythritol added during the polyester synthesis) comparative example 4 (differing from the formulation of example 1 in the substitution of the same parts of neopentyl glycol for pentaerythritol during the polyester synthesis).
Comparative example 5 (the difference from the formulation of example 1 is that no branching agent is added during injection molding)
Comparative example 6 (the difference from the formulation of example 1 is that 5 parts of branching agent are added during injection molding)
Comparative example 7 (the process of example 1 differs in that the mold was not prefilled with carbon dioxide during injection molding).
Comparative example 8 (the process of example 1 differs in that no rapid cooling technique of the mold was used before the injection mold was opened).
Performance testing
The polyester and polyester foam materials obtained in each example and comparative example were subjected to performance tests, each of which was as follows: (1) intrinsic viscosity: the polyester sample was dissolved in phenol: mass ratio of tetrachloroethane 3:2, and measuring the intrinsic viscosity of the sample at room temperature by using an Ubbelohde viscometer.
(2) Melting point: the sample was scanned with a differential scanning calorimeter for 3 cycles of temperature rise and fall between 30 and 280℃to determine the melting point of the polymer.
(3) Foam density: the actual density of the foam beads was determined by drainage and an average of 3 samples was taken.
(4) Cell diameter: 100 points were observed with a scanning electron microscope and averaged.
(5) Melt flow: MFR was measured using a melt index meter, thereby reflecting melt strength.
(6) Compressive strength: the ISO 844 standard test was used.
The data for the measurements of examples 1-5 and comparative examples 1-6 are shown in Table 1.
Table 1 sample parameter comparison tables for examples and comparative examples
Note that: by/is meant foam failure, polyester intrinsic viscosity is meant intrinsic viscosity without the addition of branching agents
From the above table data, it can be seen that:
the data for comparative example 1 and comparative examples 1 and 5 shows that comparative example 5 significantly lower the melting point of the polyester compared to comparative example 1 using pentaerythritol modified polyester. Meanwhile, the four hydroxyl groups of pentaerythritol can promote the generation of branched structures, and the molecular weight is increased, so that the melt strength is improved. However, comparative example 5 was limited in the increase of melt strength by adding pentaerythritol alone, and the cells could not be filled with gas, so that injection foaming could not be performed. In example 1, pentaerythritol and a branching agent are added in the processes of polyester synthesis and microcellular injection foaming respectively, so that the melting point of the polyester can be obviously reduced, the molecular weight can be further increased, the melt strength is improved, and the compression strength of the obtained polyester foam material is close to that of the existing basic rigid foam product on the market.
Comparative examples 1 and 2 show that the comparative examples can achieve the effect of post-branching chain extension by adding only branching agent, but the process temperature is too high during foaming due to the higher melting point of the polyester, which is unfavorable for injection foaming.
Comparative examples 1, 3 and 6 show that the addition of excessive pentaerythritol in comparative example 3 causes the melting point of the polyester to disappear to become an amorphous polymer, but the melt fluidity is too poor to facilitate filling of the mold, resulting in failure of injection molding; comparative example 6 the addition of an excessive amount of branching agent resulted in a melt viscosity that was too high to be advantageous for injection molding.
Comparative examples 1 and 4 show that comparative example 4 modified polyester with glycol, while glycol can also lower the melting point of polyester, it lacks branching effect, has too high melt index, lower melt strength, and foam formation during the foaming process is seen from the larger cells of the later foaming, and the resulting foam has lower compressive strength.
Comparative examples 1,2, 3 employed three modifying monomers, respectively. Although the melting point of the polyester can be effectively reduced by all three modified monomers, the PMDA effect adopted in the embodiment 2 is not as good as that of the other two modified monomers, because the carboxyl of the PMDA is in the ortho position, the steric hindrance is large, and the adjacent carboxyl cannot fully participate in the reaction, so that the branching effect in the polymerization reaction is not large, the obtained slice melt index (MFR) is also higher, and therefore, when the microporous injection foaming is carried out, the melt strength is insufficient, the phenomena of hole breaking and foaming are easy to occur, the number of large cells is large, the cell morphology is relatively poor, and the compression strength is not as good as that of the other two groups of embodiments.
Comparative examples 1, 7 and 8 show that pre-filling the mold with carbon dioxide under a certain pressure helps to increase the expansion ratio while slightly improving the mechanical strength of the article, because the filled carbon dioxide protects the article from air oxidation, and also increases the solubility of carbon dioxide in the melt, and the expansion ratio increases due to more nucleation sites of gas generated during the foaming process; the rapid cooling technology of the mold can stabilize the structure of the workpiece, prevent the surface of the workpiece from collapsing, and reduce the surface defects so as to obtain better mechanical properties. This illustrates that the improvement in the process increases the applicability of the polyester material in microcellular foaming.
In summary, it is known that only in the preferred scope of the claims of the present invention, it is possible to obtain an injection-foamable low-melting modified polyester with a low melting point and a high melt strength and a polyester foam material with a stable cell structure and excellent mechanical properties. And the corresponding negative effects are brought to the change of the proportion and the replacement/addition of the raw materials.
The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent transformation of the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.
Claims (9)
1. A microporous injection foaming polyester foam material is characterized in that: foam density of 100-800kg/m 3 The average diameter of the cells is 20-100 mu m, 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 melt index range of 60-80g/10min at 190 ℃ 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 supercritical carbon dioxide foaming agent;
the low-melting-point high-melt-strength polyester comprises the following raw materials in parts by weight: 100 parts of terephthalic acid, 30-60 parts of glycol, 10-40 parts of polyalcohol or polybasic acid anhydride comonomer, 0.01-1 part of catalyst and 0.01-1 part of stabilizer;
the preparation method of the microporous injection foaming polyester foam material comprises the following steps:
(1) Adding the low-melting-point high-melt-strength polyester raw materials except the stabilizing agent 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 stabilizing agent and stirring uniformly;
(2) Heating, vacuumizing simultaneously, sequentially carrying out pre-polycondensation reaction and final polycondensation reaction, discharging and granulating after the reaction is finished, and obtaining the low-melting-point high-melt-strength polyester chip;
(3) Vacuum drying the low-melting-point high-melt-strength polyester chip and the nucleating agent, and uniformly mixing with the antioxidant and the branching agent;
(4) Transferring the mixture obtained in the step (3) into an injection molding machine, fully melting the mixture in the injection molding machine, carrying out branching reaction, and raising viscosity; uniformly mixing a foaming agent into the obtained molten polymer to obtain a single homogeneous polymer melt;
(5) After the nozzle temperature of the injection molding machine reaches 195-205 ℃ and the mold temperature reaches 120-140 ℃, 5-10MPa of carbon dioxide is filled into the mold in advance, then 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, the screw rod continuously maintains the original pressure;
(6) After 20-40s, after the inner cavity of the die is completely filled, the screw rod retreats, and the polymer melt is maintained for 10-30min under 20-40MPa and cooled to a high-elasticity state;
(7) After the pressure maintaining is finished, the surface of the die is quickly cooled by using circulating cooling water to 8-12 ℃, the die is opened within 2-8s after the temperature of the die is stabilized for 5-15s, and the polymer embryo is foamed and quickly cooled to obtain the polyester foam material with the solid skin layer and the foam cells in the core layer.
2. The polyester foam material of claim 1, wherein: the polyalcohol or polybasic acid 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 polyol or polyacid or polyanhydride comonomer is one or more of pentaerythritol and 1,2, 4-butanetriol.
4. The polyester foam material of claim 1, wherein: the branching agent is an epoxy branching agent with three functional groups and above, and the actual epoxy equivalent is between 100 and 150.
5. The polyester foam material of claim 4, wherein: the branching agent is selected from triglycidyl isocyanurate, 4' -diaminodiphenylmethane tetraglycidyl amine.
6. The polyester foam material of claim 1, wherein:
the antioxidant is at least one selected from phenolic antioxidants and phosphite antioxidants;
the nucleating agent is selected from one of talcum powder, calcium carbonate and titanium dioxide; the catalyst is one of ethylene glycol antimony, antimony trioxide and antimony acetate;
the stabilizer is triphenyl phosphite.
7. The polyester foam material of claim 1, 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), vacuumizing is carried out for 60-120min to the absolute pressure 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.
8. The polyester foam material of claim 1, wherein: in the step (3), the vacuum drying temperature is 60-130 ℃ and the time is 10-12h.
9. The polyester foam material of claim 1, wherein: in the step (4), 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 temperature from a gas injection port to a machine head is 215-240 ℃, the back pressure in the screw is kept at 12-20Mpa, and the injection pressure of a foaming agent is 15-25Mpa.
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| CN1903554A (en) * | 2005-07-26 | 2007-01-31 | 黄建庭 | Process for injection formation of foam plastic |
| 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 |
| CN105131538A (en) * | 2014-05-28 | 2015-12-09 | 华东理工大学 | PET foam product and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1903554A (en) * | 2005-07-26 | 2007-01-31 | 黄建庭 | Process for injection formation of foam plastic |
| 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 |
| CN105131538A (en) * | 2014-05-28 | 2015-12-09 | 华东理工大学 | PET foam product and preparation method thereof |
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| 微孔注塑成型研究进展;张华等;《塑料科技》;第38卷(第1期);97-102 * |
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