Foam material with thin film layer / foam hole layer alternate multi-layer structure and preparation method of foam material

Abstract

The invention discloses a foam material with a thin film layer / foam hole layer alternate multi-layer structure and a preparation method of the foam material. The preparation method comprises the following steps: S1, weighing polystyrene and polymethyl methacrylate; s2, polystyrene and polymethyl methacrylate are prepared into a polymer sheet through multi-layer co-extrusion equipment, the polymer sheet comprises polystyrene layers and polymethyl methacrylate layers which are alternately stacked, the thickness of the polystyrene layers is 5-25 microns, and the thickness of the polymethyl methacrylate layers is 5-25 microns; s3, the polymer sheet is placed in a high-pressure kettle for saturation, after full saturation, a sample is taken out of the high-pressure kettle, foaming is conducted at the foaming temperature, the polystyrene layer forms a foam hole layer, the polymethyl methacrylate layer forms a thin film layer, and the foam material of the thin film layer / foam hole layer alternate multi-layer structure is prepared.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a foam material with an alternating multilayer structure of thin film layers / cell layers and its preparation method. Background Technology

[0002] The various properties of polymer foam materials are closely related to the cell structure. Studies have found that inserting a solid film layer into the foam material can combine the advantages of the film layer and the cell layer. The film layer acts as a "skeleton" to support the cell layer and enhance the mechanical properties of the material; while the cell layer has high thermal insulation, sound insulation and damping properties.

[0003] Currently, the preparation of multilayer polymer foam materials with alternating film / cell layers typically involves adding a chemical foaming agent to the foaming layer, and then using a multilayer co-extrusion device to obtain the alternating film / cell layer material. However, foam samples prepared using chemical foaming agents have a smaller expansion ratio, which fails to meet the requirements for lightweight materials, and also have a higher thermal conductivity, poor thermal insulation performance, and many internal defects.

[0004] Existing technology CN112300436A proposes a method for preparing a multilayer polymer foam material with alternating thin film layers and foam layers. The polymer materials in the alternating layers are of the same monomer, and nanoparticles are added to one of the polymers to provide nucleation sites during foaming. Since the substrates of adjacent layers are the same polymer, significant interfacial mixing occurs during co-extrusion, resulting in a thinner pure polymer layer and a thicker nanocomposite layer. The pure polymer layer is too thin to foam, thus remaining a thin film layer. The foam cells in the nanocomposite layer easily grow and foam, becoming a foamed layer. The foam material prepared by this method has a large expansion ratio, but due to the difficulty in controlling interfacial mixing, the thickness of the thin film layer and the foamed layer cannot be accurately designed, and the pure polymer layer is prone to foaming as well, making it impossible to obtain a thin film layer / foam layer alternating structure. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a foam material that can control the thickness of the film layer and the foam layer and has a high expansion ratio.

[0006] To achieve the above objectives, the present invention provides a method for preparing a foam material with an alternating multilayer structure of thin film layers / cell layers, comprising the following steps: S1. Weigh out polystyrene and polymethyl methacrylate; S2. Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion device. The polymer sheets include alternating layers of polystyrene and polymethyl methacrylate, wherein the thickness of the polystyrene layers is 5-25 μm and the thickness of the polymethyl methacrylate layers is 5-25 μm. S3. The polymer sheet is placed in an autoclave for saturation. After full saturation, the sample is taken out of the autoclave and foamed at the foaming temperature to form a cell layer from the polystyrene layer and a thin film layer from the polymethyl methacrylate layer, thus preparing a foam material with an alternating multilayer structure of thin film layer / cell layer.

[0007] This invention selects polystyrene and polymethyl methacrylate (PMMA) as raw materials and utilizes the partially overlapping foaming temperature windows of the two polymers to prepare high expansion ratio foam materials using an autoclave heating foaming method. During the co-extrusion process of polystyrene and PMMA, interfacial mixing is minimal, allowing for precise control of the thickness of the polystyrene and PMMA layers. When the single-layer thickness is small, the cell growth rate of the polystyrene layer is much greater than that of the PMMA layer. The competition between the two polymers in cell growth prevents the PMMA layer from growing, ultimately forming a thin film layer, while the polystyrene layer forms a cell layer. Therefore, this invention can produce foam materials with a regular alternating arrangement of thin film layers and cell layers.

[0008] Furthermore, in step S2, the thickness of the polystyrene layer is greater than or equal to that of the polymethyl methacrylate layer. By controlling the thickness relationship between the polystyrene layer and the polymethyl methacrylate layer, the difference in cell growth rate between the polystyrene layer and the polymethyl methacrylate layer is ensured to be sufficiently large, preventing the polymethyl methacrylate layer from growing and ultimately forming a thin film layer.

[0009] Furthermore, in step S2, the thickness of the polymer sheet obtained by multilayer co-extrusion is 0.5~2mm. The polymer sheet has a large number of alternating layers to ensure the competitive effect of cell growth between the two polymers, so that the polymethyl methacrylate layer forms a thin film layer.

[0010] Furthermore, in step S1, the polystyrene and polymethyl methacrylate are weighed in equal quantities to ensure the stability of each monolayer polymer component.

[0011] Furthermore, in step S3, the saturation pressure is 1~3 MPa.

[0012] Further, in step S3, the saturation pressure and foaming temperature satisfy the following relationship: when the saturation pressure is 1 MPa, the foaming temperature is 130~150 ℃; when the saturation pressure is 1.5 MPa, the foaming temperature is 125~155 ℃; when the saturation pressure is 2 MPa, the foaming temperature is 115~145 ℃; when the saturation pressure is 2.5 MPa, the foaming temperature is 125~135 ℃; and when the saturation pressure is 3 MPa, the foaming temperature is 125~130 ℃. Since polystyrene and polymethyl methacrylate have different foaming characteristics, they exhibit different cell structures at different saturation pressures and foaming temperatures. Selecting a suitable foaming temperature at different saturation pressures ensures the successful preparation of a multilayer structure alternating between thin film layers and cell layers.

[0013] Furthermore, in step S3, the saturating agent used is supercritical carbon dioxide or supercritical nitrogen. Using supercritical fluid as a foaming agent results in good foaming effect and a high expansion ratio of the foam material.

[0014] The present invention also provides a foam material with an alternating multilayer structure of thin film layer / cell layer, which is prepared by the above preparation method. The expansion ratio of the foam material is greater than 4 times, and the cell size of the cell layer is greater than 70 μm; wherein the thickness of the thin film layer is less than 10 μm, and the thickness of the cell layer is greater than 70 μm.

[0015] This invention combines multilayer co-extrusion technology with high-pressure heating foaming technology, and uses a two-step method to prepare high expansion ratio film layer / cell layer alternating multilayer polymer foam material, thereby achieving material lightweighting. This foam material has excellent mechanical, optical, barrier and electromagnetic shielding properties.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention selects two incompatible polymers with similar foaming temperatures as raw materials. The preparation process does not require chemical foaming agents, and only requires controlling the thickness of a single layer to obtain an alternating structure of film layer / cell layer. Moreover, the alternating multilayer polymer foam material has a high expansion ratio, which meets the requirements of material lightweighting.

[0017] (2) This invention combines multilayer co-extrusion preparation technology with high-pressure heating foaming technology, and uses a two-step method to prepare foam materials with high expansion ratio. The co-extrusion process can accurately control the thickness of single-layer polymer, and achieve low thermal conductivity and high heat insulation performance while ensuring barrier performance.

[0018] (3) By controlling the saturation pressure, foaming temperature and number of sample layers, the present invention can accurately control the thickness of the foam layer, the average diameter of the cells, the cell density and the expansion ratio, so that the performance of the foam material meets the design requirements. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the polymer foam material prepared in Example 1 of the present invention.

[0020] Figure 2 This is a scanning electron microscope image of the polymer foam material prepared in Example 2 of the present invention.

[0021] Figure 3 This is a scanning electron microscope image of the polymer foam material prepared in Comparative Example 1 of the present invention.

[0022] Figure 4 This is a scanning electron microscope image of the polymer foam material prepared in Comparative Example 2 of the present invention.

[0023] Figure 5 This is a scanning electron microscope image of the polymer foam material prepared in Comparative Example 3 of the present invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art.

[0027] The present invention provides a foam material with an alternating multilayer structure of thin film layers / cell layers and a method for preparing the same. The specific steps of the preparation method are as follows: S1. Weigh out polystyrene and polymethyl methacrylate. Preferably, the mass of polystyrene and polymethyl methacrylate is equal.

[0028] S2. Polystyrene and polymethyl methacrylate (PMMA) are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets comprise alternating layers of polystyrene and PMMA. The thickness of each polymer layer and the polymer sheet is controlled, wherein the thickness of the polystyrene layer is 5–25 μm, the thickness of the PMMA layer is 5–25 μm, and the thickness of the polymer sheet is 0.5–2 mm. Preferably, the thickness of each polymer layer is 5–15 μm, and the thickness of the polystyrene layer is greater than or equal to that of the PMMA layer.

[0029] S3. The polymer sheet is placed in an autoclave for saturation. After full saturation, the sample is taken out of the autoclave and foamed at the foaming temperature. Since the two polymers have different foaming characteristics, they exhibit different cell structures under different saturation pressures and foaming temperatures. By controlling the saturation pressure and foaming temperature, the polystyrene layer forms a cell layer and the polymethyl methacrylate layer forms a film layer, thus preparing a foam material with an alternating film layer / cell layer multilayer structure.

[0030] The principle of forming a multilayer structure of alternating thin film layers and foam layers is as follows: Under saturation pressure, a high-pressure saturant is introduced into the polymer sheet, and the supercritical fluid continuously dissolves in the two polymer layers. As the saturation time increases, the dissolution eventually stabilizes, forming a homogeneous system of supercritical fluid / foam layer. After reaching the saturation time, the temperature is raised to foam. The supercritical fluid forms cell nuclei in the polystyrene layer, which continue to grow and stabilize, thus eventually forming a foam layer. However, due to the competitive effect, the polymethyl methacrylate layer is too thin to meet the nucleation requirements and cannot foam, thus ultimately forming a thin film layer.

[0031] In specific embodiments, the saturant used is supercritical carbon dioxide or supercritical nitrogen, and the saturation pressure is 1~3 MPa. By controlling the saturation pressure and foaming temperature, parameters such as the thickness of the foamed layer, the average diameter of the cells, the cell density, and the expansion ratio can be adjusted. The preferred relationship between saturation pressure and foaming temperature is as follows: when the saturation pressure is 1 MPa, the foaming temperature is 130~150℃; when the saturation pressure is 1.5 MPa, the foaming temperature is 125~155℃; when the saturation pressure is 2 MPa, the foaming temperature is 115~145℃; when the saturation pressure is 2.5 MPa, the foaming temperature is 125~135℃; and when the saturation pressure is 3 MPa, the foaming temperature is 125~130℃. Selecting an appropriate foaming temperature under different saturation pressures ensures the achievement of a multilayer structure with alternating thin film layers and cell layers.

[0032] The foam material prepared by the above method has an alternating multilayer structure of thin film layer / cell layer, and the expansion ratio of the foam material is more than 4 times, thereby achieving material lightweighting; wherein the thickness of the thin film layer is less than 10 μm, the thickness of the cell layer is greater than 70 μm, and the cell size is greater than 70 μm. This foam material has excellent mechanical, optical, barrier and electromagnetic shielding properties.

[0033] The technical solution and effects of the present invention will be illustrated below with specific embodiments.

[0034] Example 1

[0035] This embodiment prepares polymer foam material using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, each polystyrene layer having a thickness of 10 μm and each polymethyl methacrylate layer having a thickness of 10 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0036] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced at a saturation pressure of 1.0 MPa for 48 h. The sample was then removed from the autoclave and foamed in a silicone oil bath at 130 °C for 15 s to obtain a polymer foam material with alternating layers of polymethyl methacrylate film and polystyrene cells. Its cross-sectional structure is shown in the figure. Figure 1 As shown, the expansion ratio of the polymer foam material is 7 times. Its thermal conductivity at room temperature is 0.032 W / (m*K).

[0037] Example 2

[0038] This embodiment prepares polymer foam material using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, with each polystyrene layer having a thickness of 10 μm and each polymethyl methacrylate layer having a thickness of 5 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0039] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced at a saturation pressure of 1.5 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 130 °C for 15 seconds to obtain a polymer foam material with alternating layers of polymethyl methacrylate film and polystyrene cells. Its cross-sectional structure is shown in the figure. Figure 2 As shown, the expansion ratio of the polymer foam material is 10 times. Its thermal conductivity at room temperature is 0.031 W / (m*K).

[0040] Example 3

[0041] This embodiment prepares polymer foam material using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, with each polystyrene layer having a thickness of 15 μm and each polymethyl methacrylate layer having a thickness of 10 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0042] Polymer sheets were placed in an autoclave and subjected to supercritical carbon dioxide at a saturation pressure of 2.0 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 130 °C for 15 seconds to obtain a polymer foam material with alternating layers of polymethyl methacrylate film and polystyrene cells. The expansion ratio of the polymer foam material was 13 times. Its thermal conductivity at room temperature was 0.030 W / (m*K).

[0043] Example 4

[0044] This embodiment prepares polymer foam material using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, with each polystyrene layer having a thickness of 20 μm and each polymethyl methacrylate layer having a thickness of 15 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0045] Polymer sheets were placed in an autoclave and subjected to supercritical carbon dioxide at a saturation pressure of 2.5 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 130 °C for 15 seconds to obtain a polymer foam material with alternating layers of polymethyl methacrylate film and polystyrene cells. The expansion ratio of the polymer foam material was 20 times. Its thermal conductivity at room temperature was 0.028 W / (m*K).

[0046] Comparative Example 1 This comparative example prepared polymer foam materials using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, each polystyrene layer having a thickness of 10 μm and each polymethyl methacrylate layer having a thickness of 10 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0047] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced at a saturation pressure of 1.0 MPa for 48 h. The sample was then removed from the autoclave and foamed in a silicone oil bath at 100 °C for 15 s to obtain a polymer foam material with alternating layers of polymethyl methacrylate film and polystyrene cells. Its cross-sectional structure is shown in the figure. Figure 3 As shown, the expansion ratio of the polymer foam material is 1.5 times. Its thermal conductivity at room temperature is 0.045 W / (m*K).

[0048] Comparative Example 2 This comparative example prepared polymer foam materials using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, with each polystyrene layer having a thickness of 10 μm and each polymethyl methacrylate layer having a thickness of 5 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0049] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced at a saturation pressure of 3.0 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 135 °C for 15 seconds to obtain a polymer foam material. The cross-sectional structure of this foam material is shown below. Figure 4 As shown, the sample exhibits obvious stratification.

[0050] Comparative Example 3 This comparative example prepared polymer foam materials using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, with each polystyrene layer having a thickness of 1 μm and each polymethyl methacrylate layer having a thickness of 1 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0051] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced at a saturation pressure of 1.0 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 135 °C for 15 seconds to obtain a polymer foam material. The cross-sectional structure of this foam material is shown below. Figure 5 As shown, the pores of the sample are arranged randomly. Its thermal conductivity at room temperature is 0.033 W / (m*K).

[0052] Comparative Example 4 This comparative example prepared polymer foam materials using the following method: Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion apparatus. The polymer sheets consist of alternating layers of polystyrene and polymethyl methacrylate, each polystyrene layer having a thickness of 50 μm and each polymethyl methacrylate layer having a thickness of 50 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0053] Polymer sheets were placed in an autoclave and subjected to supercritical carbon dioxide at a saturation pressure of 1.0 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 135 °C for 15 seconds to obtain a polymer foam material with alternating layers of polymethyl methacrylate and polystyrene cells. The expansion ratio of the polymer foam material was 6 times. Its thermal conductivity at room temperature was 0.033 W / (m*K).

[0054] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A method for preparing a multilayer foam material with alternating thin film layers and pore layers, characterized in that, Includes the following steps: S1. Weigh out polystyrene and polymethyl methacrylate; S2. Polystyrene and polymethyl methacrylate are processed into polymer sheets using a multilayer co-extrusion device. The polymer sheets include alternating layers of polystyrene and polymethyl methacrylate, wherein the thickness of the polystyrene layers is 5-25 μm and the thickness of the polymethyl methacrylate layers is 5-25 μm. S3. The polymer sheet is placed in an autoclave for saturation. After full saturation, the sample is taken out of the autoclave and foamed at the foaming temperature to form a cell layer from the polystyrene layer and a thin film layer from the polymethyl methacrylate layer, thus preparing a foam material with an alternating multilayer structure of thin film layer / cell layer.

2. The method for preparing a multilayer foam material with alternating thin film layers and pore layers according to claim 1, characterized in that, In step S2, the thickness of the polystyrene layer is greater than or equal to that of the polymethyl methacrylate layer.

3. The method for preparing a foam material with alternating thin film layers and cell layers according to claim 1 or 2, characterized in that, In step S2, the thickness of the polymer sheet obtained by multilayer co-extrusion is 0.5~2mm.

4. The method for preparing a multilayer foam material with alternating thin film layers and pore layers according to claim 1, characterized in that, Its features are, In step S1, the polystyrene and polymethyl methacrylate weighed are of equal mass.

5. The method for preparing a multilayer foam material with alternating thin film layers and pore layers according to claim 1, characterized in that, In step S3, the saturation pressure is 1~3MPa.

6. The method for preparing a foam material with alternating thin film layers and cell layers according to claim 5, characterized in that, In step S3, the saturation pressure and foaming temperature satisfy the following relationship: when the saturation pressure is 1 MPa, the foaming temperature is 130~150 ℃; when the saturation pressure is 1.5 MPa, the foaming temperature is 125~155 ℃; when the saturation pressure is 2 MPa, the foaming temperature is 115~145 ℃; when the saturation pressure is 2.5 MPa, the foaming temperature is 125~135 ℃; and when the saturation pressure is 3 MPa, the foaming temperature is 125~130 ℃.

7. The method for preparing a multilayer foam material with alternating thin film layers and pore layers according to claim 1, characterized in that, In step S3, the saturating agent used is supercritical carbon dioxide or supercritical nitrogen.

8. A foam material with an alternating multilayer structure of thin film layers / cell layers, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The foam material with alternating thin film layers and cell layers according to claim 8, characterized in that, The expansion ratio of the foam material is greater than 4 times, and the cell size of the foam layer is greater than 70 μm.

10. The foam material with alternating thin film layers / cell layers according to claim 8, characterized in that, The thickness of the thin film layer is less than 10 μm, and the thickness of the pore layer is greater than 70 μm.

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