CN113025007A

CN113025007A - Polyester foam material and preparation method thereof

Info

Publication number: CN113025007A
Application number: CN202110292788.8A
Authority: CN
Inventors: 冉启迪; 曹堃; 王松林; 刘少帅; 李院院; 龚新超; 汪凯
Original assignee: Zhejiang University ZJU; Zhejiang Henglan Technology Co Ltd
Current assignee: Zhejiang University ZJU; Zhejiang Henglan Technology Co Ltd
Priority date: 2021-03-18
Filing date: 2021-03-18
Publication date: 2021-06-25

Abstract

The invention relates to the technical field of polyester modification processing, and discloses a polyester foam material and a preparation method thereof, aiming at the problems of difficult control of the polyester foaming processing process and poor foaming uniformity in the prior art, wherein the polyester foam material comprises the following components in parts by mass: 100 parts of polyester, 0.1-0.5 part of antioxidant, 0.1-0.5 part of branching agent, 0.1-0.5 part of chain extender, 1.0-5.0 parts of nucleating agent and 1.0-5.0 parts of foaming agent. Vacuum drying polyester and nucleating agent, and mixing with antioxidant, branching agent and chain extender; pouring the raw materials into an extruder, extruding the foam strips, and quickly reducing the pressure and the temperature at a neck mold to form foam holes. The invention introduces epoxy branching agent, adopts polymer as nucleating agent, omits the master batch preparation process; in addition, the selected epoxy branching agent can react with terminal carboxyl and terminal hydroxyl in PET at the same time, the activity is higher, the addition amount of the branching agent is reduced, the reaction time is shortened, the melt strength of the PET can be effectively improved, and a better foaming effect is achieved.

Description

Polyester foam material and preparation method thereof

Technical Field

The invention relates to the technical field of polyester modification processing, in particular to a polyester foam material and a preparation method thereof.

Background

At present, the main application of Polyester (PET) is in the fields of fiber, packaging, engineering plastics and the like, and with the continuous expansion and surplus of global productivity, other applications of PET gradually attract people's attention. The PET foam material is mainly applied to the fields of wind power, rail transit, automobiles, buildings and the like as a structural core material, and has a high additional value. PET foams on the market are made by adding physical blowing agents and chain extenders through an extrusion process. Extrusion foaming is greatly influenced by melt strength, and the foam is easy to break and escape due to too low strength, so that a foam structure is difficult to form; if the melt strength is too high, the cells are difficult to expand, and the foaming ratio is greatly influenced.

Conventional polyester molecules have a linear structure, and when the temperature is below the melting point, almost no fluidity occurs, and the apparent viscosity of the melt drops sharply after the melting point is reached. Therefore, the melt strength is low, the temperature range for foaming is narrow, and the characteristics are all unfavorable factors for foaming. The key to realize PET foaming is to improve the melt strength, namely to improve the molecular weight, widen the molecular weight distribution, introduce a branched structure and the like. The chain extension reaction of PET with the added branching agent is the most common method, and the branching structure is introduced while the molecular weight is increased, so that the melt strength can be effectively increased.

Japanese ponding chemistry originally proposed a process for making PET foam sheets (US5000991) and was used to produce meal boxes. Isopentane is used as a foaming agent, 0.05-5.0% of polyfunctional branching agent pyromellitic anhydride (PMDA) is added, and each molecule reacts with 4 PET end groups at most, so that a branching structure is introduced into the molecule and the molecular weight is effectively improved. Meanwhile, a small amount of metal salt is added for synergistic effect, so that the strength of the polyester melt can be greatly improved, and the highest foaming ratio of 15 times can be realized. WO90/10667 first proposed the use of PET regrind and supercritical carbon dioxide (scCO)₂) Extrusion foaming process to give a density of about 200kg/m³The polyfunctional branching agent used in the rigid PET foam of (1) is likewise PMDA, preferably in an amount of from 0.1 to 0.5% by weight. In addition, the talcum powder master batch taking polystyrene as a carrier is added as a nucleating agent, so that the foam holes are more uniform.

PMDA is the most commonly used branching agent for PET extrusion foaming at present, but the PMDA has the defects that anhydride is very easy to absorb water, and the chain extension effect is seriously influenced by hydrolysis inactivation, so that the preparation and addition processes of master batches are strictly dried, and the cost and the instability are increased. The talcum powder is a common foaming nucleating agent, but the powder particles are extremely fine, so that the safety risk and dust-proof cost of a workshop are increased, the harm to a human body is also increased, and in addition, the dispersibility and compatibility of the inorganic nucleating agent in PET are also in disadvantage.

Disclosure of Invention

The invention provides a polyester foaming material and a preparation method thereof, aiming at solving the problems that the existing polyester foaming processing process is difficult to control and the foaming uniformity is poor. The invention introduces the epoxy branching agent which is insensitive to moisture, the selected epoxy branching agent can react with terminal carboxyl and terminal hydroxyl in PET at the same time, the activity is higher, the addition amount of the branching agent can be reduced, the reaction time is shortened, the melt strength is effectively improved, and a better foaming effect is achieved. In addition, the polymer is used as the nucleating agent, so that the preparation process of mother particles of the nucleating agent is omitted, and the preparation work of raw materials is greatly facilitated.

In order to achieve the purpose, the invention adopts the following technical scheme:

the polyester foam material comprises the following components in parts by mass:

the specific content of the invention is that polyfunctional branching agent and bifunctional chain extender are added in the extrusion foaming process, so that the molecular weight of linear PET raw material is increased, a long branched chain structure is formed, the regularity of molecules is reduced, and the crystallinity is reduced. In the research process, the applicant finds that the epoxy branching agent has high reaction activity, the tackifying performance of the epoxy branching agent is not easily influenced by trace moisture, and the introduction of the epoxy branching agent can not only shorten the reaction time, but also save the addition cost of the branching agent. However, branching agents of this type have the disadvantage that the speed of reaction is very sensitive to the amount added. If the addition amount is too low, the reaction is still insufficient within the retention time of the extruder, and the melt strength cannot meet the foaming requirement; if the amount is too high, the reaction proceeds too quickly, a crosslinked structure is likely to be formed in a very short time, and foaming is also disadvantageous, so that the concentration range is narrow. In order to solve the problem, the invention adopts two chain extenders to compound, namely, the branching agent with more than three functional groups is compounded with the bifunctional chain extender, and the bifunctional chain extender replaces part of the branching agent to slow and control the reaction rate, and simultaneously ensure that the melt strength meets the foaming requirement, thereby not only effectively controlling the reaction time and widening the operation range, but also avoiding the generation of a cross-linked structure while improving the melt strength and achieving the stable foaming effect.

The anhydride branching agent PMDA used in the traditional PET extrusion foaming is reacted with the polyester terminal hydroxyl to generate ester bonds and terminal carboxyl, and two anhydride functional groups are opened to form two ester bonds and two terminal carboxyl. In the actual reaction, the terminal carboxyl group cannot react with the other two polyester terminal hydroxyl groups to form a complete branched structure of four ester bonds due to the influence of steric hindrance, so the PMDA actually has the effect of chain extension rather than branching, the reaction is mild, a cross-linked structure is not easily formed, and the addition amount is high. The steric hindrance between the functional groups of the epoxy branching agent adopted by the invention is reduced, and the epoxy group can simultaneously react with the hydroxyl-terminated group and the carboxyl-terminated group of the polyester to form a long branched chain structure, so that the reaction rate is improved, and the addition amount of the branching agent is obviously lower than that of PMDA. In order to control the reaction rate not to be too fast, a bifunctional chain extender is added to dilute the concentration of the epoxy branching agent, so that the reaction rate is stably increased while the foaming effect is ensured.

Meanwhile, the polymer nucleating agent with the melting point below the extrusion temperature and the crystallization rate higher than that of PET is added, the polymer nucleating agent has better compatibility with a polyester matrix in a molten state, the uniform dispersion and the rapid crystallization of the nucleating agent can be realized, and a crystal nucleus interface is used as a nucleation point, so that the prepared sample has more uniform foam pores and the extrusion foaming process is stable.

The intrinsic viscosity of the foaming polyester prepared by the invention reaches more than 0.80dl/g, and the foam density range is 60-250kg/m³The average diameter of the cells is 50-300 μm.

Preferably, the polyester is selected from fiber grade, bottle grade or recycled chip.

Preferably, the antioxidant is at least one selected from the group consisting of phenolic antioxidants and phosphite antioxidants.

The antioxidant is further preferably selected from the group consisting of an antioxidant 1010, an antioxidant 168, and triphenyl phosphite.

Preferably, the branching agent is selected from trifunctional and higher epoxy.

The actual epoxy equivalent weight of the branching agent is between 100-150, and includes triglycidyl isocyanurate, 4' -diaminodiphenylmethane tetraglycidyl amine, and other low molecular weight polyglycidyl ethers.

Preferably, the chain extender is selected from difunctional isocyanates. Including diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane diisocyanate, and the like. In the experimental process, compared with the anhydride chain extender, the isocyanate chain extender has the advantages that the reaction activity is not easily influenced by trace moisture, and the chain extension effect is better.

Preferably, the nucleating agent is selected from nylon 6, nylon 66 and isotactic polypropylene.

The processing temperature of the high polymer material selected by the nucleating agent is close to the PET foaming temperature, the melt strength cannot be obviously reduced, the high polymer material is not easy to decompose, and the nucleating agent is crystallized before PET in the cooling process, so that a nucleating interface can be effectively formed.

Preferably, the blowing agent is supercritical carbon dioxide.

The preparation method of the polyester foaming material comprises the following steps:

(1) vacuum drying polyester and nucleating agent, and mixing with antioxidant, branching agent and chain extender;

(2) pouring the raw materials into a hopper of an extruder, and adopting a phi 20m double-screw extruder with a foaming agent injection pump to perform continuous extrusion foaming;

(3) and (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes.

Preferably, in the step (1), vacuum drying is carried out for 10-12h at 80-100 ℃.

Preferably, in the step (2), the temperature of the feeding end of the extruder is set to 250-.

The specific content of the invention is that polyfunctional branching agent and bifunctional chain extender are added in the extrusion foaming process, so that the molecular weight of linear PET raw material is increased, a long branched chain structure is formed, the regularity of molecules is reduced, and the crystallinity is reduced. The amount of the branching agent/chain extender added is adjusted according to the intrinsic viscosity of the raw material polyester, and the amount of the branching agent added is reduced by 50% at most compared with PMDA. Meanwhile, the polymer nucleating agent with the melting point below the extrusion temperature and the crystallization rate higher than that of PET is added, so that the uniform dispersion and the rapid crystallization of the nucleating agent are realized, a crystal nucleus interface is used as a nucleation point, the sample cell holes are more uniform, and the extrusion foaming process is stable.

The invention has the following beneficial effects:

(1) carbon dioxide is used as a foaming agent, and polymer chips are used as a nucleating agent, so that the experiment is safer and more environment-friendly. Meanwhile, compared with an inorganic nucleating agent, the polymer nucleating agent can be more uniformly dispersed in the polyester melt under the high shear and melting state, so that inner and outer layer cells are more uniform;

(2) by compounding the bifunctional chain extender and the polyfunctional branching agent, the reaction rate and the intrinsic viscosity of the product can be more finely controlled, the reaction is milder, excessive gel is avoided, and the process stability and the product performance are favorably improved;

(3) the foaming process of the invention obviously reduces the cost of the branching agent, shortens the reaction time, produces no by-product, prepares high-performance foaming products, and has simple and high-efficiency operation process.

Detailed Description

The invention is further described with reference to specific embodiments.

Intrinsic viscosity test method: a quantity of the sample was dissolved in phenol: in a mixed solvent of tetrachloroethane in a mass ratio of 3:2, the intrinsic viscosity of the sample was measured at room temperature using an Ubbelohde viscometer.

The foam density was determined by drainage.

And characterizing the diameter of the cells by adopting a scanning electron microscope.

General examples

A preparation method of a polyester foaming material comprises the following steps:

(1) 100 parts of polyester (selected from fiber grade, bottle grade or recycled chips), 1.0-5.0 parts of nucleating agent (nylon 6, nylon 66 or isotactic polypropylene) are dried in vacuum at 80-100 ℃ for 10-12h, and then are uniformly mixed with 0.1-0.5 part of antioxidant (at least one of phenol antioxidant and phosphite antioxidant), 0.1-0.5 part of branching agent (trifunctional and above epoxy), and 0.1-0.5 part of chain extender (bifunctional isocyanate);

(2) pouring the raw materials into a hopper of a double-screw extruder, injecting 1.0-5.0 parts of foaming agent (supercritical carbon dioxide) for continuous extrusion foaming, wherein the temperature of the feed end of the extruder is 250-;

Example 1

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 3 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Example 2 (different from example 1 in that isotactic polypropylene was used as a nucleating agent)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 3 parts of nucleating agent isotactic polypropylene chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Example 3

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 1 part of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, taken out and uniformly mixed with 0.5 part of antioxidant 1010, 0.5 part of branching agent 4, 4' -diaminodiphenylmethane tetraglycidyl amine (TGDDM) and 0.5 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical gas injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 200rpm, and the injection amount of carbon dioxide of a foaming agent is 1 percent of the raw materials. The extruded foam strip is quickly decompressed and cooled at the position of the neck mould to promote the formation of bubble nuclei and the expansion of foam holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Example 4

100 parts of bottle grade polyester chip (intrinsic viscosity 0.80dl/g) and 5 parts of nucleating agent nylon 6 chip are dried in vacuum at 85 ℃ for 12 hours, and then taken out to be uniformly mixed with 0.1 part of antioxidant 1010, 0.1 part of branching agent triglycidyl isocyanurate (TGIC) and 0.1 part of chain extender diphenylmethane diisocyanate (MDI). Adopting a double-screw extruder with a supercritical gas injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 245 ℃, the rotating speed of the extruder is 200rpm, and the injection amount of carbon dioxide of a foaming agent is 5 percent of the raw materials. The extruded foam strip is rapidly cooled and decompressed at the position of a neck mould to promote the formation of bubble nuclei and the expansion of foam holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Example 5 (different from example 1 in that a bottle grade chip having a higher intrinsic viscosity was used as a starting material.)

100 parts of bottle grade polyester chips (intrinsic viscosity 0.80dl/g) and 3 parts of nucleating agent nylon 66 chips are dried in vacuum at 85 ℃ for 12 hours, and then are uniformly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 1 (difference from example 1 in that the chain extender IPDI was replaced with an equal mass of the branching agent TGIC.) 100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g), 3 parts of nucleating agent nylon 66 chip were vacuum dried at 100 ℃ for 12h and then homogeneously mixed with 0.3 part of antioxidant 1010, 0.6 part of the branching agent triglycidyl isocyanurate (TGIC). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 2 (distinguished from example 1 by the absence of addition of the chain extender IPDI.)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 3 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010 and 0.3 part of branching agent triglycidyl isocyanurate (TGIC). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 3 (differing from example 1 in that no branching agent TGIC was added.)

100 parts of fiber grade polyester chip (intrinsic viscosity is 0.65dl/g) and 3 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010 and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 4 (different from example 1 in that nylon 66, a nucleating agent, was not added.)

100 parts of fiber grade polyester chips (intrinsic viscosity 0.65dl/g) are dried in vacuum at 100 ℃ for 12h, and then are uniformly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 5 (different from example 1 in that calcium carbonate powder was used as a nucleating agent)

100 parts of fiber-grade polyester chips (intrinsic viscosity of 0.65dl/g) and 3 parts of nucleating agent calcium carbonate powder are dried in vacuum at 100 ℃ for 12 hours, and then are uniformly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 6 (different from example 1 in that maleic anhydride was used as the chain extender)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 3 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender maleic anhydride. Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 7 (differing from example 1 in that the branching agent used was PMDA.)

100 parts of fiber grade polyester chips (with the intrinsic viscosity of 0.65dl/g) and 3 parts of nucleating agent nylon 66 chips are dried in vacuum at 100 ℃ for 12 hours, and then are uniformly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent pyromellitic dianhydride (PMDA) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 8 (differing from example 1 in that an excess of branching agent TGIC was added.)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 3 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010, 0.6 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 9 (different from example 1 in that an excessive amount of nucleating agent nylon 66 was added.)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 8 parts of nucleating agent nylon 66 chip are dried in vacuum at 100 ℃ for 12 hours, and then are evenly mixed with 0.3 part of antioxidant 1010, 0.3 part of branching agent triglycidyl isocyanurate (TGIC) and 0.3 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical carbon dioxide injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 250rpm, and the injection amount of the foaming agent is 2 percent of the raw materials. And (3) rapidly reducing the pressure and the temperature of the extruded foam strip at the position of the neck mould to normal pressure and normal temperature to promote the formation of bubble nuclei and the expansion of bubble holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

Comparative example 10 (different from example 3 in that the nucleating agent nylon 66 was replaced with talc)

100 parts of fiber grade polyester chip (intrinsic viscosity 0.65dl/g) and 1 part of nucleating agent talcum powder are dried in vacuum at 100 ℃ for 12h, taken out and uniformly mixed with 0.5 part of antioxidant 1010, 0.5 part of branching agent 4, 4' -diaminodiphenylmethane tetraglycidyl amine (TGDDM) and 0.5 part of chain extender isophorone diisocyanate (IPDI). Adopting a double-screw extruder with a supercritical gas injection pump to carry out continuous extrusion foaming, wherein the diameter of the screw is 20mm, and the length-diameter ratio L/D is 40. The raw materials are poured into a hopper of an extruder, the temperature of a machine head is 260 ℃, the rotating speed of the extruder is 200rpm, and the injection amount of carbon dioxide of a foaming agent is 1 percent of the raw materials. The extruded foam strip is quickly decompressed and cooled at the position of the neck mould to promote the formation of bubble nuclei and the expansion of foam holes. Foam samples were collected, density testing and morphology observation were performed on the materials, and the experimental formulation and test results are shown in table 1.

TABLE 1 comparison of sample parameters for each example and comparative example

And (4) conclusion: in Table 1 above, the higher the intrinsic viscosity, the higher the melt strength, which is advantageous for foaming; the lower the density, the better the foaming effect. The polyester foam material obtained within the preparation process parameter range has high intrinsic viscosity and low density, the polyester foam material has more uniform foam pores, the extrusion foaming process is stable, and the foaming effect is better.

From the results of the example 1 and the comparative example 1, the addition of the compound chain extender can effectively prevent the melt from gelling, and meanwhile, the melt strength can meet the foaming requirement and the foaming ratio is higher. Example 1 and comparative example 2 show that the melt strength is not as good as that of the compound with the chain extender, the foam density is increased, the foaming ratio is reduced, and the effect of auxiliary tackifying is achieved by adding the chain extender under the condition of only adding the branching agent. Example 1 and comparative example 3 illustrate that the difunctional chain extender has a limited effect on increasing melt strength and does not achieve the foaming requirements alone, necessitating the use of a branching agent as the primary tackifying means. In example 1, compared with comparative example 4, the supercritical gas carbon dioxide can also perform the nucleation effect without adding the nucleating agent, but the cell diameter is smaller, and the cell is not fully expanded, thereby influencing the foaming ratio. Examples 1 and 2 select different nucleating agents, the intrinsic viscosity of which is not significantly different from the foam density, but the cell diameter is directly influenced by the type of nucleating agent. Example 3 increased the concentrations of branching agent and chain extender, further increased melt strength, reduced foam density, and increased foaming ratio. In example 4, since bottle grade polyester having a higher intrinsic viscosity was used as a raw material, the amounts of the branching agent and the chain extender to be added were reduced. Examples 1 and 5 show that higher foaming ratios can be achieved by selecting bottle grade polyester raw materials, and the higher the molecular weight of the raw materials, the easier the product can achieve higher melt strength. In example 5, the amounts of the branching agent and the chain extender added are increased based on example 4, and the foaming effect is better.

Comparative example 5 shows that the excessive calcium carbonate acts as a lubricant, so that the melt strength is reduced, the expansion ratio is reduced, and the diameter of the formed cells is larger. The reason why the high molecular organic nucleating agent is more favorable for cell uniformity is that: on one hand, the selected polymer nucleating agent has better dispersibility in the melt; on the other hand, inorganic nucleating agent powder is easy to block in the feeding process of a single-feeding-port extruder to cause uneven feeding, and the feeding error of a metering pump is easy to be large due to the small addition amount of the inorganic nucleating agent powder in a multi-feeding-port extruder, so that the using condition is severer than that of the high-molecular nucleating agent, and the foaming effect is unstable. The comparative example 6 selects maleic anhydride as a chain extender, which has poor tackifying effect, and the melt strength does not meet the foaming requirement, probably because the maleic anhydride absorbs trace moisture and is inactivated in the mixing and extruding processes; comparative example 7, which used PMDA of equal mass instead of TGIC as a branching agent, significantly deteriorated the adhesion promotion effect, greatly reduced the intrinsic viscosity of the reactants, and failed to foam because PMDA had lower reactivity than TGIC and thus required a higher amount of addition; comparative example 8 the reaction rate was too fast with the addition of excess branching agent to form a gel; comparative example 9 excessive polymer nucleating agent is added, so that the melt strength is reduced, the intrinsic viscosity of the reactant is reduced, and foaming cannot be carried out; comparative example 10, in which talc was used as a nucleating agent and the amount of the inorganic nucleating agent added was reduced compared with comparative example 5 to avoid lubrication, it can be seen that the addition of a small amount of talc still reduced the melt strength, and the intrinsic viscosity was reduced and the expansion ratio was reduced compared with example 3.

As can be seen from the data of examples 1 to 5 and comparative examples 1 to 10, the above requirements can be satisfied in all aspects only by the scheme within the scope of the claims of the present invention, and the optimum effect can be obtained, and the optimum foaming performance can be obtained under the condition that the polyester foaming product is ensured to have the same intrinsic viscosity. The change of the mixture ratio and the replacement/addition/subtraction of the raw materials can 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 all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. The polyester foam material is characterized by comprising the following components in parts by mass:

polyester 100 parts

0.1 to 0.5 part of a branching agent

0.1-0.5 part of chain extender

1.0-5.0 parts of nucleating agent

0.1-0.5 part of antioxidant

1.0-5.0 parts of foaming agent.

2. The polyester foam material as claimed in claim 1, wherein the polyester is selected from fiber grade, bottle grade or recycled chip.

3. The polyester foam material as claimed in claim 1, wherein the antioxidant is at least one selected from phenolic antioxidants and phosphite antioxidants.

4. The foamed polyester material as claimed in claim 1, wherein the branching agent is selected from trifunctional and higher epoxy group.

5. The polyester foam according to claim 1, wherein the chain extender is selected from the group consisting of difunctional isocyanates.

6. The polyester foam material as claimed in claim 1, wherein the nucleating agent is selected from nylon 6, nylon 66 and isotactic polypropylene.

7. The polyester foam according to claim 1, wherein the blowing agent is supercritical carbon dioxide.

8. A process for the preparation of a polyester foam according to any of claims 1 to 7, comprising the steps of:

(2) pouring the raw materials into a hopper of an extruder, and adopting a double-screw extruder with a foaming agent injection pump to perform continuous extrusion foaming;

9. The method according to claim 8, wherein the drying is carried out at 80-100 ℃ for 10-12 hours under vacuum in step (1).

10. The method as claimed in claim 8, wherein in the step (2), the temperature of the feeding end of the extruder is 270 ℃ at 250-.