Alternating multilayer polymer foam material and preparation method thereof

Abstract

The invention discloses an alternating multilayer polymer foam material and a preparation method thereof. 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 50-500 microns, and the thickness of the polymethyl methacrylate layers is 50-500 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 first foam hole layer, the polymethyl methacrylate layer forms a second foam hole layer, and the alternate multi-layer polymer foam material is prepared.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to an alternating multilayer polymer foam material and its preparation method. Background Technology

[0002] The performance of polymer foam materials is closely related to their cell structure. In recent years, polymer foam materials with bimodal cell structures have attracted widespread attention. These materials contain two different cell sizes and exhibit excellent mechanical, sound insulation, damping, and thermal insulation properties, while also meeting the requirements for lightweighting.

[0003] The existing technology CN112300436A proposes a method for preparing multilayer polymer foam materials with different cell structures. This method utilizes the overlapping foaming temperature ranges of two different polymers, layering them to obtain a foam material with a high expansion ratio. However, this preparation method has significant limitations. The thickness of manually stacked samples is difficult to control precisely, leading to defects. Layer interface separation easily occurs during the foaming process, and the number of layers that can be prepared manually is limited. The fewer the layers, the easier it is for the layer interfaces to separate during foaming. Therefore, a compatibilizer layer or binder layer needs to be added between the layers to prevent delamination. However, the presence of a compatibilizer layer increases the preparation cost and also affects the material's performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to develop a novel alternating multilayer polymer foam material preparation process that suppresses delamination without the addition of a compatibilizer layer or binder layer, while ensuring that the foam material has a large expansion ratio.

[0005] To achieve the above objectives, the present invention provides a method for preparing alternating multilayer polymer foam materials, 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 layer is 50~500 μm and the thickness of the polymethyl methacrylate layer is 50~500 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 the first pore layer of the polystyrene layer and the second pore layer of the polymethyl methacrylate layer, thereby preparing an alternating multilayer polymer foam material.

[0006] This invention uses multilayer co-extrusion technology to prepare polymer sheets with alternating layered structures. It can precisely control the layer thickness, reduce internal defects, and control the thickness of the polymer single layer to be small, making the synergistic effect between layers more obvious and effectively suppressing the occurrence of delamination. This method can prepare foam materials with alternating regular arrangement of the first cell layer and the second cell layer without the use of compatibilizer layer or binder layer.

[0007] Furthermore, in step S2, the thickness of the polystyrene layer is less than or equal to the thickness of the polymethyl methacrylate layer. By controlling the thicknesses of the polystyrene layer and the polymethyl methacrylate layer, the impact of cell growth competition on polymethyl methacrylate foaming is reduced, ensuring a bimodal cell structure is obtained.

[0008] Furthermore, in step S2, the thickness of the polymer sheet obtained by multi-layer co-extrusion is 0.5~2mm. The large number of alternating layers in the polymer sheet makes the interlayer synergy more pronounced, ensuring that the layer interfaces do not separate during the foaming process.

[0009] Furthermore, in step S1, the polystyrene and polymethyl methacrylate are weighed in equal quantities to ensure the stability of each monolayer polymer component.

[0010] Furthermore, in step S3, the saturation pressure is 1~2.5 MPa.

[0011] Furthermore, in step S3, the saturation pressure and foaming temperature satisfy the following formula: ; In the formula, T is the foaming temperature (°C), and P is the foaming temperature. b The saturation pressure is (MPa), and A1 and A2 are constants, with A1 ranging from 145 to 155 and A2 ranging from 125 to 135.

[0012] Because polystyrene and polymethyl methacrylate have different foaming properties, they exhibit different cell structures under different saturation pressures and foaming temperatures. The above formula can be used to calculate the appropriate foaming temperature corresponding to different saturation pressures, ensuring that the preparation process can produce foam materials with alternating 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] This invention also provides a method for preparing an alternating multilayer polymer foam material. The foam material prepared by the above method has an expansion ratio greater than 4 times, with the first layer having a cell size of 30-70 μm and the second layer having a cell size of 8-50 μm. This invention combines multilayer co-extrusion technology with high-pressure heating foaming technology, employing a two-step method to prepare an alternating multilayer polymer foam material with a high expansion ratio. This foam material has a bimodal cell structure, endowing it with excellent mechanical, optical, barrier, and electromagnetic shielding properties.

[0015] In summary, 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 or interface compatibilizers. The foam material with alternating cell layers can be obtained by controlling the thickness of the single layer. Moreover, the polymer foam material has a high expansion ratio, which meets the requirements of material lightweighting.

[0016] (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 precisely control the thickness of a single layer polymer. When the layer thickness is small, the synergistic effect between layers is more obvious, which can effectively suppress the occurrence of delamination.

[0017] (3) The present invention designs a formula relating saturation pressure and foaming temperature, which can accurately control the structure of the first foaming layer and the second foaming layer by controlling the saturation pressure and foaming temperature, so as to realize the design of foam material structure as needed. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the polymer foam material prepared in Example 1 of the present invention.

[0019] Figure 2 This is a scanning electron microscope image of the polymer foam material prepared in Example 3 of the present invention.

[0020] Figure 3 This is a scanning electron microscope image of the polymer foam material prepared in Comparative Example 4 of the present invention.

[0021] Figure 4 This is a scanning electron microscope image of the polymer foam material prepared in Comparative Example 5 of the present invention. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The present invention provides an alternating multilayer polymer foam material and a method for preparing the same, the specific steps of which are as follows: S1. Weigh out polystyrene and polymethyl methacrylate. Preferably, the mass of polystyrene and polymethyl methacrylate is equal.

[0026] S2. Polystyrene and polymethyl methacrylate (PMMA) are processed into polymer sheets using a multi-layer 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 50–500 μm, the thickness of the PMMA layer is 50–500 μm, and the thickness of the polymer sheet is 0.5–2 mm. Preferably, the thickness of each polymer layer is 50–350 μm, and the thickness of the polystyrene layer is less than or equal to that of the PMMA layer, ensuring that the polystyrene and PMMA layers can be foamed simultaneously without delamination.

[0027] 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 the first cell layer and the polymethyl methacrylate layer forms the second cell layer, thus preparing an alternating multilayer polymer foam material.

[0028] The principle of forming a multilayer structure with alternating layers of two types of foam is as follows: a high-pressure saturant is introduced into the polymer sheet under saturation pressure, 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, and the supercritical fluid forms cell nuclei in the polystyrene layer, which continue to grow and stabilize, eventually forming an alternating multilayer foam material with alternating layers of foam.

[0029] In a specific embodiment, the saturant used is supercritical carbon dioxide or supercritical nitrogen, and the saturation pressure is 1~2.5 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 saturation pressure and foaming temperature satisfy the following formula: ; In the formula, T is the foaming temperature (°C), and P is the foaming temperature. b Let A1 be the saturation pressure (MPa), and A2 be constants, with A1 ranging from 145 to 155 and A2 ranging from 125 to 135. Based on this saturation pressure, a suitable foaming temperature can be calculated to ensure a regular alternating arrangement of the first and second cell layers.

[0030] The foam material prepared by the above method has an expansion ratio of more than 4 times, thereby achieving material lightweighting; wherein the cell size of the first cell layer is 30~70 μm and the cell size of the second cell layer is 8~50 μm. This foam material has excellent mechanical, optical, barrier and electromagnetic shielding properties.

[0031] The technical solution and effects of the present invention will be illustrated below with specific embodiments.

[0032] Example 1

[0033] 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 64 μm and each polymethyl methacrylate layer having a thickness of 64 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0034] 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 150 °C for 15 seconds to obtain a polymer foam material with alternating polystyrene and polymethyl methacrylate (PMMA) pore layers. Its cross-sectional structure is shown in the figure. Figure 1 As shown, the expansion ratio of the polymer foam material is 6 times. Its thermal conductivity at room temperature is 0.033 W / (m*K).

[0035] Example 2

[0036] 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 80 μm and each polymethyl methacrylate layer having a thickness of 100 μm. The overall thickness of the polymer sheets is approximately 1.5 mm.

[0037] Polymer sheets were placed in an autoclave and subjected to supercritical carbon dioxide 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 145 °C for 15 seconds to obtain a polymer foam material with alternating layers of polystyrene and polymethyl methacrylate (PMMA) cells. The expansion ratio of the polymer foam material was 9.5 times. Its thermal conductivity at room temperature was 0.030 W / (m*K).

[0038] Example 3

[0039] 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 64 μm and each polymethyl methacrylate layer having a thickness of 64 μm. The overall thickness of the polymer sheets is approximately 1 mm.

[0040] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced 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 140 °C for 15 seconds to obtain a polymer foam material with alternating polystyrene and polymethyl methacrylate (PMMA) pore layers. Its cross-sectional structure is shown in the figure. Figure 2 As shown, the expansion ratio of the polymer foam material is 22 times. Its thermal conductivity at room temperature is 0.028 W / (m*K).

[0041] Example 4

[0042] 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 120 μm and each polymethyl methacrylate layer having a thickness of 120 μm. The overall thickness of the polymer sheets is approximately 2 mm.

[0043] 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 polystyrene and polymethyl methacrylate cells. The expansion ratio of the polymer foam material was 20 times. Its thermal conductivity at room temperature was 0.028 W / (m*K).

[0044] 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 64 μm and each polymethyl methacrylate layer having a thickness of 64 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 1.0 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 100 °C for 15 seconds to obtain a polymer foam material with alternating layers of polystyrene and polymethyl methacrylate. The expansion ratio of the polymer foam material was 2 times. Its thermal conductivity at room temperature was 0.055 W / (m*K).

[0046] 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 80 μm and each polymethyl methacrylate layer having a thickness of 100 μm. The overall thickness of the polymer sheets is approximately 1.5 mm.

[0047] Polymer sheets were placed in an autoclave and subjected to supercritical carbon dioxide 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 100 °C for 15 seconds to obtain a polymer foam material with alternating layers of polystyrene and polymethyl methacrylate (PMMA) cells. The expansion ratio of the polymer foam material was 2.5 times. Its thermal conductivity at room temperature was 0.046 W / (m*K).

[0048] 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, each polystyrene layer having a thickness of 120 μm and each polymethyl methacrylate layer having a thickness of 120 μm. The overall thickness of the polymer sheets is approximately 2 mm.

[0049] 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 100 °C for 15 seconds to obtain a polymer foam material with alternating layers of polystyrene and polymethyl methacrylate. The expansion ratio of the polymer foam material was 3 times. Its thermal conductivity at room temperature was 0.044 W / (m*K).

[0050] 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 64 μm and each polymethyl methacrylate layer having a thickness of 64 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 2.5 MPa for 48 hours. The sample was then removed from the autoclave and foamed in a silicone oil bath at 100 °C for 15 seconds to obtain a polymer foam material. The cross-sectional structure of this foam material is shown below. Figure 3 As shown, the sample exhibits obvious stratification.

[0052] Comparative Example 5 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 15 μm and each polymethyl methacrylate layer having a thickness of 15 μm, with the overall thickness of the polymer sheets being 1 mm.

[0053] Polymer sheets were placed in an autoclave, and supercritical carbon dioxide was introduced 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 polystyrene cell layers and polymethyl methacrylate film layers. Its cross-sectional structure is shown in the figure. Figure 4 As shown, the expansion ratio of the polymer foam material is 5 times. Its thermal conductivity at room temperature is 0.038 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 an alternating multilayer polymer foam material, 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 layer is 50~500 μm and the thickness of the polymethyl methacrylate layer is 50~500 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 the first pore layer of the polystyrene layer and the second pore layer of the polymethyl methacrylate layer, thereby preparing an alternating multilayer polymer foam material.

2. The method for preparing alternating multilayer polymer foam material according to claim 1, characterized in that, In step S2, the thickness of the polystyrene layer is less than or equal to the thickness of the polymethyl methacrylate layer.

3. The method for preparing alternating multilayer polymer foam material 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 alternating multilayer polymer foam material 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 alternating multilayer polymer foam material according to claim 1, characterized in that, In step S3, the saturation pressure is 1~2.5 MPa.

6. The method for preparing alternating multilayer polymer foam material according to claim 5, characterized in that, In step S3, the saturation pressure and foaming temperature satisfy the following formula: ； In the formula, T is the foaming temperature (°C), and P is the foaming temperature. b The saturation pressure is (MPa), and A1 and A2 are constants, with A1 ranging from 145 to 155 and A2 ranging from 125 to 135.

7. The alternating multilayer polymer foam material according to claim 1, characterized in that, In step S3, the saturating agent used is supercritical carbon dioxide or supercritical nitrogen.

8. A method for preparing an alternating multilayer polymer foam material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The alternating multilayer polymer foam material according to claim 8, characterized in that, The expansion ratio of the foam material is greater than 4 times.

10. The alternating multilayer polymer foam material according to claim 8, characterized in that, The pore size of the first pore layer is 30~70 μm, and the pore size of the second pore layer is 8~50 μm.

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