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CN114603889A - High-mechanical-strength and high-reflectivity polyester foamed sheet and preparation method thereof - Google Patents

High-mechanical-strength and high-reflectivity polyester foamed sheet and preparation method thereof Download PDF

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Publication number
CN114603889A
CN114603889A CN202210501214.1A CN202210501214A CN114603889A CN 114603889 A CN114603889 A CN 114603889A CN 202210501214 A CN202210501214 A CN 202210501214A CN 114603889 A CN114603889 A CN 114603889A
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China
Prior art keywords
polyester
layer
sheet
foamed sheet
foaming
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CN202210501214.1A
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Chinese (zh)
Inventor
刘欣然
赵红
周玉波
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Ningbo Solartron Technology Co Ltd
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Ningbo Solartron Technology Co Ltd
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Priority to CN202210501214.1A priority Critical patent/CN114603889A/en
Publication of CN114603889A publication Critical patent/CN114603889A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D7/00—Producing flat articles, e.g. films or sheets
    • B29D7/01—Films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
    • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2266/00—Composition of foam
    • B32B2266/02—Organic
    • B32B2266/0214—Materials belonging to B32B27/00
    • B32B2266/0264—Polyester
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/416—Reflective
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • 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
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K7/00—Use of ingredients characterised by shape
    • C08K7/22—Expanded, porous or hollow particles
    • C08K7/24—Expanded, porous or hollow particles inorganic
    • C08K7/26—Silicon- containing compounds

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Laminated Bodies (AREA)

Abstract

The invention relates to the technical field of layered products, and discloses a high-mechanical-strength and high-reflectivity polyester foamed sheet and a preparation method thereof, wherein the preparation method comprises the following steps: (1) the polyester sheet comprises outer layers on two outer sides and a core layer in the middle, wherein the raw materials of the outer layers comprise polyester and a nucleating agent, and the raw materials of the core layer comprise polyester; carrying out three-layer co-extrusion melt extrusion and quenching to obtain a polyester sheet; (2) and (3) placing the polyester sheet into a container filled with a physical foaming agent and having a pressure of 1-8 MPa, swelling and permeating for 2-24 h, then releasing the pressure, taking out, and heating and foaming to obtain the polyester foamed sheet. The polyester foamed sheet has smaller cell size and higher foaming density, so that the product has higher reflectivity and can meet higher mechanical strength requirement.

Description

High-mechanical-strength and high-reflectivity polyester foamed sheet and preparation method thereof
Technical Field
The invention relates to the technical field of layered products, in particular to a polyester foamed sheet with high mechanical strength and high reflectivity and a preparation method thereof.
Background
The polyester foamed sheet prepared by foaming polyethylene terephthalate (PET) resin can effectively reduce the density and the weight of the sheet, greatly reduce the dielectric constant, reduce the dielectric loss and the leakage current, and simultaneously improve the reflectivity of the polyester sheet, so that the polyester foamed sheet can be widely applied to the fields of manufacturing insulated cables, integrated circuits, liquid crystal display screen reflecting plates, packaging containers and the like.
The conventional polymer foaming method is generally classified into a physical foaming method and a chemical foaming method, based on whether or not a chemical change occurs when a foaming gas is generated. Although the application of the chemical foaming method is quite common, the requirements for environmental protection, post-consumption plastic recovery, product cost performance and the like are improved, and CO is used2、N2Physical foaming methods such as physical foaming agents are widely regarded. However, in general, the polyester foamed sheet obtained by physical foaming has a large cell size (>10 μm) and the product is thicker, and is mainly used for structural materials such as wind power blades, automobile doors and the like. At present, in order to obtain a high-reflectivity polyester foamed sheet with high mechanical strength in the industry, the following problems mainly exist: 1. when the thickness of the product is reduced, most light rays are often transmitted through the cells due to the large size of the cells, so that the diffusely reflected light rays are reduced, and the reflectivity is generally low; meanwhile, the density of the foam holes is reduced rapidly due to the larger size of the foam holes, and the wall of the foam hole is very thin, so that the material is more fragile when the whole thickness is thinned, and the use is influenced; 2. incompatible resin or inorganic filler is added into polyester resin, a biaxial stretching process is adopted, and phase separation is utilized to generate tiny cells, so that high reflectivity is obtained, but the cost is relatively high due to the addition of the filler and the resin, and the use requirement cannot be met in occasions with high mechanical strength requirements.
The Chinese patent with the publication number of CN113336997A discloses a polyester foamed sheet and a semi-continuous preparation method thereof, wherein the polyester foamed sheet comprises a non-foamed skin layer and a foamed core layer inside the non-foamed skin layer, the thickness of the non-foamed skin layer is 10-100 mu m, and the thickness of the foamed core layer is 0.2-2 mm. Although the core layer foaming structure of the polyester foaming sheet can ensure higher light reflectivity, the thickness of the non-foaming skin layer is thinner, so that the overall mechanical strength of the polyester foaming sheet is poorer.
Disclosure of Invention
In order to solve the problem that the high mechanical strength and the high reflectivity cannot be ensured simultaneously in the production process of the polyester foamed sheet, the invention provides the polyester foamed sheet with the high mechanical strength and the high reflectivity and the preparation method thereof.
The specific technical scheme of the invention is as follows:
in a first aspect, the present invention provides a method for preparing a polyester foamed sheet with high mechanical strength and high reflectivity, comprising the following steps:
(1) the polyester sheet comprises outer layers on two outer sides and a core layer in the middle, wherein the raw materials of the outer layers comprise polyester and a nucleating agent, and the raw materials of the core layer comprise polyester; carrying out three-layer co-extrusion melt extrusion and quenching to obtain a polyester sheet;
(2) and (3) placing the polyester sheet into a container filled with a physical foaming agent and having a pressure of 1-8 MPa, swelling and permeating for 2-24 h, then releasing the pressure, taking out, and heating and foaming to obtain the polyester foamed sheet.
The invention uses three-layer coextrusion casting equipment, and obtains a sheet with a certain thickness and a three-layer structure after melt extrusion, wherein the outer layer contains a nucleating agent, and the core layer is polyester without the nucleating agent. And (3) after the sheet is melted and extruded, rapidly immersing the sheet into normal-temperature water for quenching to obtain the transparent amorphous three-layer structure polyester sheet. The selective addition of nucleating agents to the outer layer enables the cells to form preferentially at the outer layer, which is beneficial to obtain a rigid core layer with the outer layer foamed and unfoamed in the middle. The nucleating agent can remarkably reduce the nucleation energy barrier and provide nucleation sites for foaming, is beneficial to reducing the size of cells, improving the density of the cells, enhancing the diffuse reflection effect of the cells on light rays and weakening transmission and specular reflection, thereby ensuring that the foamed sheet has higher reflectivity.
In the foaming process, most of the polyester material is not in a molten state, so that the addition of a chain extender is not needed to improve the melt strength, and the cost is saved; and the addition of the outer-layer nucleating agent can reduce the pressure required by kettle pressure foaming in the invention and shorten the saturation time of the physical foaming agent, thereby reducing energy consumption and improving productivity. By controlling reasonable saturation pressure and saturation time, the physical foaming agent is gradually diffused into the sheet from the edge, and a certain degree of concentration difference is formed: i.e. high concentration of the outer layer and low concentration of the core layer. And then quickly releasing the pressure, taking the sheet out of the high-pressure kettle, quickly heating to a certain temperature, and foaming at the temperature to quickly reduce the solubility of the physical foaming agent in the sheet, wherein the outer layer is quickly nucleated and foamed to grow into cells with a certain size due to the concentration difference of the physical foaming agent in the interlayer structure of the sheet and the addition of the outer-layer physical nucleating agent, and the core layer is difficult to nucleate and foam due to the fact that the physical foaming agent is less and the activation energy of homogeneous nucleation is higher, so that the polyester foamed sheet with the outer surface foamed structure and the core layer of a compact and unfoamed structure is finally obtained.
The control of the foaming process conditions enables the dense unfoamed structure in the polyester foamed sheet to meet the requirement of high mechanical strength of the reflector plate. Because the polyester foamed sheet is of a three-layer co-extrusion structure, the bonding property and stability of an interlayer structure are easily influenced in the foaming process, the control of the saturation pressure and the saturation time can ensure that the foamed layer is positioned in the range of the outer layer, and the unfoamed part tightly combined with the core layer is reserved on the outer layer. Otherwise, if the foaming layer is just located at the interlayer joint of the outer layer and the core layer, or the foaming layer extends to the core layer, the interlayer joint performance is easily reduced due to foaming cells, and the mechanical property is also reduced. Therefore, the foaming conditions in the present invention need to be strictly controlled to obtain a polyester foamed sheet having excellent mechanical properties and reflectivity.
Preferably, in the step (1), the outer layer includes 100 parts by weight of the polyester resin and 0.1 to 10 parts by weight of the nucleating agent.
The addition ratio of the nucleating agent can affect the foaming effect and the nucleating effect after the nucleating agent is added. Insufficient addition of the nucleating agent can result in low nucleation density and large cell size, and results in low reflectivity and poor mechanical properties; on the contrary, the addition of the nucleating agent too much can cause the agglomeration of the nucleating agent and influence the nucleation, and simultaneously, the material density is increased, the whole material becomes brittle, and interlayer defects can be caused.
Preferably, in the step (1), the nucleating agent is one or a combination of more of fumed silica, calcium carbonate, titanium dioxide, calcium oxide and magnesium oxide.
Preferably, in the step (1), the outer layer further comprises 0.01-2 parts by weight of an antioxidant.
Preferably, in the step (1), the thickness ratio of the outer layer to the core layer is 1: 1-10; the thickness of the obtained polyester sheet is 30-2000 mu m.
The proportion of the outer layer and the core layer is related to the mechanical property of the polyester foaming material, and the sheet material in the proportion range can maintain higher mechanical strength. However, the foaming performance of the outer layer is affected by the ratio of the outer layer being too low, so that the overall reflectivity is affected by the number of the foam holes being too low.
Preferably, in the step (2), the physical foaming agent is one or a combination of carbon dioxide, nitrogen, butane and pentane; the heating foaming comprises the following steps: heating to 70-180 ℃ for foaming for 3-120 s.
The density and size of foamed cells are influenced in the heating foaming process, compact micropores can be formed by rapid foaming in the temperature range, and the reflectivity of the polyester foamed sheet is higher. If the temperature is too high or the foaming time is too long, cells grow excessively, the size is too large, and even light is transmitted, so that the reflectivity is low. If the temperature is too low or the foaming time is too short, insufficient foaming and too low cell density may result, and a high reflectance may not be obtained.
Preferably, in the step (2), the temperature in the container is 0-65 ℃.
Preferably, in the step (2), the pressure relief speed is 0.1-2 MPa/s; the temperature rise rate is 20-200 ℃/s, and more preferably 100-200 ℃/s.
The rapid pressure relief and rapid temperature rise can reduce the escape of the physical foaming agent dissolved on the outer layer of the sheet, simultaneously, the solubility of the physical foaming agent in the sheet is rapidly reduced to form core, the foaming foam hole does not influence the interlayer structure, and the high mechanical strength and the high reflectivity can be ensured.
In a second aspect, the invention also provides a polyester foamed sheet prepared by the preparation method, wherein the polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer.
Preferably, the thickness of the foaming layer is 28-1 mm, the diameter of each foam pore is 50-10 μm, and the density of each foam pore is 105~1015 cell/cm3(ii) a The thickness of the unfoamed layer is 2 mu m-1 mm.
Compared with the prior art, the invention has the following advantages:
(1) in the three-layer co-extruded polyester sheet, the addition of the nucleating agent provides a nucleation site for foaming, so that the foaming nucleation energy barrier is reduced, and the size of foam cells is reduced and the density of the foam cells is improved; high foaming density of>105cell/cm3) Small size of (A), (B)<10 mu m) of the foam holes can diffuse light better, so that the product has higher reflectivity>95%）；
(2) Meanwhile, the foaming process conditions are controlled, so that the interior of the sheet material is kept in an unfoamed hard amorphous state, and the foamed polyester sheet material still has high mechanical strength even if the thickness of the foamed polyester sheet material is very thin, and can meet the requirement of high mechanical strength;
(3) most of the polyester materials are not in a molten state in the foaming process, so that the addition of a chain extender is not needed to improve the melt strength, and the cost is saved; and the foaming process condition does not need higher pressure and saturation time, so that the energy consumption can be reduced, and the production efficiency can be improved.
Detailed Description
The present invention will be further described with reference to the following examples.
General examples
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) the polyester sheet comprises outer layers on two outer sides and a core layer in the middle, and the thickness ratio of the outer layers to the core layer is 1: 1-10; the outer layer comprises 100 parts of polyester resin and 0.1-10 parts of nucleating agent by weight, or comprises 100 parts of polyester resin, 0.1-10 parts of nucleating agent and 0.01-2 parts of antioxidant by weight; the raw materials of the core layer comprise polyester, or the core layer comprises 100 parts of polyester resin and 0.01-2 parts of antioxidant; adopting three-layer co-extrusion casting equipment, and quickly immersing the polyester sheet into normal-temperature water for quenching after melt extrusion to obtain a transparent amorphous three-layer structure polyester sheet, wherein the thickness of the sheet is 30-2000 mu m;
wherein, the nucleating agent is one or a combination of more of fumed silica, calcium carbonate, titanium dioxide, calcium oxide and magnesium oxide;
(2) placing the polyester sheet in an autoclave with the temperature of 0-65 ℃ and the pressure of 1-8 MPa, wherein the autoclave is filled with a physical foaming agent which is one or a combination of carbon dioxide, nitrogen, butane and pentane; swelling and permeating a physical foaming agent in the polyester sheet for 2-24 hours; and then rapidly releasing the pressure at the speed of 0.1-2 MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 20-200 ℃/s, and heating to 70-180 ℃ for foaming for 3-120 s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 28-1 mm, the diameter of the foam hole is 50-10 μm, and the density of the foam hole is 105~1015 cell/cm3(ii) a The thickness of the unfoamed layer is 2 mu m-1 mm; the expansion ratio of the polyester foamed sheet is 1-5 times.
Example 1
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a film with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 7: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then quickly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, quickly heating at the speed of 150 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 300 mu m, the diameter of the foam cells is 7 mu m, and the density of the foam cells is 1012cell/cm3The thickness of the unfoamed layer was 1.6 mm.
Example 2
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 8 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a mixture with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 5: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 40 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 18 hours; and then quickly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, quickly heating at the speed of 200 ℃/s, and heating to 100 ℃ for foaming for 50s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; foaming layerHas a thickness of 400 μm, a cell diameter of 8 μm and a cell density of 1011cell/cm3The thickness of the unfoamed layer was 1.4 mm.
Example 3
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 5 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a mixture with a total thickness of 1mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 3: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 25 ℃ and the pressure of 3MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 12 hours; and then quickly releasing the pressure at the speed of 0.5MPa/s, taking the polyester sheet out of the kettle, quickly heating at the speed of 100 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 500 μm, the diameter of the foam cells is 5 μm, and the density of the foam cells is 1010cell/cm3The thickness of the unfoamed layer was 600. mu.m.
Comparative example 1
The difference from example 1 is that: the polyester sheet is of a single-layer structure.
The method comprises the following steps:
(1) melting and plasticizing 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant in an extruder and protecting the PET resin, the nucleating agent fumed silica and the antioxidant with nitrogen to prevent the PET from thermal degradation; the total thickness of the obtained product is 2mm after melt extrusion, and the obtained product is quickly immersed in normal temperature water for quenching after melt extrusion to obtain a transparent amorphous polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 150 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The obtained polyester foamed sheet was entirely foamed, and after foaming, the thickness was 3.2. mu.m, the cell diameter was 12 μm, and the cell density was 103cell/cm3。
Comparative example 2
The difference from example 1 is that: the polyester sheet was placed in an autoclave with a pressure of 12MPa for swelling and permeation for 48 hours.
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a film with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 7: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 12MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 48 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 150 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foaming sheet comprises two outer foaming layers and a middle partial foaming layer; the thickness of the foaming layer is 1mm, the diameter of the cells of the outer foaming layer is 12 mu m, and the cell density is 106cell/cm3The diameter of the cells of the middle foaming layer is 30 μm, and the cell density is 103cell/cm3The thickness of the unfoamed layer was 1 mm.
Comparative example 3
The difference from example 1 is that: the outer layer includes 100 parts of a polyester resin and 20 parts of a nucleating agent.
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 20 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a mixture with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 7: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 150 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 1mm, the diameter of the foam hole is 8 mu m, and the density of the foam hole is 1010cell/cm3The thickness of the unfoamed layer was 1 mm.
Comparative example 4
The difference from example 1 is that: the proportion of the three-layer structure (outer layer: core layer: outer layer) is 2: 1: 2.
a preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to give a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 2: 1: 2, after melt extrusion, rapidly immersing the polyester sheet into normal-temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 150 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 1.5mm, the diameter of the foam hole is 8 mu m, and the density of the foam hole is 1010cell/cm3The thickness of the unfoamed layer was 600. mu.m.
Comparative example 5
The difference from example 1 is that: the rate of temperature rise was 20 ℃/s.
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a mixture with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 7: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 20 ℃/s, and heating to 120 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The obtained polyester foamed sheet comprises two outer foamed layersAnd an intermediate unfoamed layer; the thickness of the foaming layer is 500 μm, the diameter of the foam cells is 25 μm, and the density of the foam cells is 106cell/cm3The thickness of the unfoamed layer was 1.6 mm.
Comparative example 6
The difference from example 1 is that: the polyester sheet was foamed for 20s by raising the temperature to 230 ℃.
A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity comprises the following steps:
(1) using three-layer co-extrusion casting equipment, adding 100 parts of dried PET resin, 9 parts of nucleating agent fumed silica and 1 part of antioxidant into an outer-layer extruder, adding 100 parts of dried PET resin and 1 part of antioxidant into an extruder corresponding to a core layer, melting and plasticizing materials in the extruder, and protecting the materials with nitrogen to prevent PET from thermal degradation; melt-extruding to obtain a film with a total thickness of 2mm and a three-layer thickness ratio (outer layer: core layer: outer layer) of 1: 7: 1, after melt extrusion, rapidly immersing into normal temperature water for quenching to obtain a transparent amorphous three-layer structure polyester sheet;
(2) placing the polyester sheet in a high-pressure kettle with the temperature of 50 ℃ and the pressure of 4MPa, and filling carbon dioxide in the kettle to swell and permeate the carbon dioxide in the polyester sheet for 14 hours; and then rapidly releasing the pressure at the speed of 1MPa/s, taking the polyester sheet out of the kettle, rapidly heating at the speed of 150 ℃/s, and heating to 230 ℃ for foaming for 20s to obtain the polyester foamed sheet.
The polyester foamed sheet comprises two outer foamed layers and a middle unfoamed layer; the thickness of the foaming layer is 800 μm, the diameter of the foam cells is 20 μm, and the density of the foam cells is 106cell/cm3The thickness of the unfoamed layer was 1.2 mm.
Performance testing
Reflectance ratio: testing by a reflectivity tester designed according to GB/T13452.3-92, GB/T9270-88 and GB/T5211.17-88 standards;
tensile strength and elongation at break: tested according to GB/T13542.2-2009 standard.
TABLE 1 Performance test results of polyester foamed sheets
Figure DEST_PATH_IMAGE002
As shown in Table 1, the three-layer polyester foamed sheet of the present invention has a smaller cell size<10 μm) and has high foaming density>105cell/cm3) Can make better diffuse reflection to make the product have higher reflectivity>95%); the polyester foamed sheet has the advantages that the unfoamed hard amorphous state is reserved inside the polyester foamed sheet, so that the polyester foamed sheet still has high mechanical strength and can meet the requirement of high mechanical strength. Combining example 1 and comparative example 1, under the same foaming process conditions, a single-layer polyester foamed sheet has lower cell density and larger cell size due to cells distributed throughout the sheet, so that the mechanical properties are remarkably reduced while the reflectivity is reduced.
In addition, the foaming process conditions in the present invention need to be strictly controlled, which is mainly influenced by the interlayer bonding properties of the three-layer structure. By combining the example 1 and the comparative example 2, the foaming agent can penetrate into the core layer more due to long-time swelling and permeation under high pressure, a foaming structure can be formed even if the core layer does not contain a nucleating agent, too much foaming is caused, interlayer delamination is easy to form, and the mechanical strength of the sheet is not improved. With the combination of example 1 and comparative example 3, the addition of too much nucleating agent in the outer layer would form interlayer defects instead due to the thin thickness of the polyester sheet, which is not favorable for improving the mechanical strength of the sheet. In the case of combining example 1 and comparative example 4, the ratio of the outer layer structure was too large, the intermediate hard amorphous portion was too small, the mechanical strength was lowered, and the foaming density was lowered and the reflectance was also lowered under the same conditions. Combining example 1 and comparative examples 5-6, too slow temperature rise rate or foaming at higher temperature is not beneficial to rapid decrease of the solubility of the physical foaming agent in the sheet, and also results in foaming of the core layer and reduction of mechanical strength.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modifications, alterations and equivalent changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (10)

1. A preparation method of a polyester foamed sheet with high mechanical strength and high reflectivity is characterized by comprising the following steps:
(1) the polyester sheet comprises outer layers on two outer sides and a core layer in the middle, wherein the raw materials of the outer layers comprise polyester and a nucleating agent, and the raw materials of the core layer comprise polyester; carrying out three-layer co-extrusion melt extrusion and quenching to obtain a polyester sheet;
(2) and (3) placing the polyester sheet into a container filled with a physical foaming agent and having a pressure of 1-8 MPa, swelling and permeating for 2-24 h, then releasing the pressure, taking out, and heating and foaming to obtain the polyester foamed sheet.
2. The method for preparing a high mechanical strength and high reflectivity polyester foamed sheet according to claim 1, wherein in the step (1), the outer layer comprises 100 parts by weight of the polyester resin and 0.1 to 10 parts by weight of the nucleating agent.
3. The method for preparing high mechanical strength and high reflectivity polyester foamed sheet according to claim 1 or 2, wherein in the step (1), the nucleating agent is one or more of fumed silica, calcium carbonate, titanium dioxide, calcium oxide and magnesium oxide.
4. The method for preparing the polyester foamed sheet with high mechanical strength and high reflectivity according to claim 2, wherein in the step (1), the outer layer further comprises 0.01 to 2 parts by weight of an antioxidant.
5. The method for preparing a high mechanical strength and high reflectance polyester foamed sheet according to claim 1, wherein in the step (1), the ratio of the thicknesses of the outer layer and the core layer is 1: 1-10; the thickness of the obtained polyester sheet is 30-2000 mu m.
6. The method for preparing the polyester foamed sheet with high mechanical strength and high reflectivity according to claim 1, wherein in the step (2), the physical foaming agent is one or a combination of carbon dioxide, nitrogen, butane and pentane; the heating foaming comprises the following steps: heating to 70-180 ℃ for foaming for 3-120 s.
7. The method for preparing the polyester foamed sheet with high mechanical strength and high reflectivity according to claim 1 or 6, wherein in the step (2), the temperature in the container is 0-65 ℃.
8. The method for preparing a high mechanical strength and high reflectivity polyester foamed sheet according to claim 1 or 6, wherein in the step (2), the pressure relief speed is 0.1-2 MPa/s; the temperature rising rate is 20-200 ℃/s.
9. A polyester foamed sheet obtained by the production method as claimed in any one of claims 1 to 8, wherein the polyester foamed sheet comprises two outer foamed layers and an intermediate unfoamed layer.
10. The polyester foamed sheet according to claim 9, wherein the foamed layer has a thickness of 28 to 1mm, a cell diameter of 50 to 10 μm, and a cell density of 105~1015 cell/cm3(ii) a The thickness of the unfoamed layer is 2 mu m-1 mm.
CN202210501214.1A 2022-05-10 2022-05-10 High-mechanical-strength and high-reflectivity polyester foamed sheet and preparation method thereof Pending CN114603889A (en)

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