A supercritical foaming method using nanomaterials as foaming medium

Abstract

The present invention relates to the technical field of foaming materials, and in particular to a supercritical foaming method using nanomaterials as foaming media. A supercritical foaming method using nanomaterials as foaming media comprises the following steps: taking nanoparticles and coating them on the surface of a polymer sheet to be foamed after injection molding, and adjusting the coating thickness; after coating is completed, placing the polymer sheet at the center of a mold cavity, closing the mold cavity, introducing gas into the mold cavity, adjusting the flow rate of the gas introduced into the mold cavity, and after the introduction of gas is completed, increasing the temperature and maintaining the pressure, and quickly releasing the pressure to normal pressure, thereby preparing a foaming material. The technical solution of the present application changes the foaming medium during supercritical foaming to ensure that the polymer material is heated evenly during the pressure relief process, and the foaming ratio of each part is consistent, thereby ensuring that the surface of the polymer foam material is smooth and further improving the overall performance of the foaming material.

Description

Technical Field

[0001] The invention relates to the technical field of foaming materials, in particular to a supercritical foaming method using nanometer materials as foaming medium. Background Art

[0002] Supercritical foaming is the process of supercritical fluid dissolving and diffusing in a polymer matrix at a certain temperature and pressure, eventually forming a homogeneous system. In this process, the foaming temperature, foaming pressure and immersion time of the foaming system play a key role; the thermodynamic instability in the homogeneous system causes the polymer and gas in the supersaturated system to separate and drive the nucleation of the pores, and the plasticization of the supercritical fluid on the polymer will also enhance the fluidity of the polymer, thereby reducing the energy barrier of pore nucleation. Thermodynamic instability is caused by a sudden increase in temperature or a sudden drop in pressure. The growth of the pores is closely related to the physicochemical parameters of the foaming system (such as the type, solubility and diffusion rate of the foaming agent) and the process parameters (such as the foaming temperature, foaming pressure and pressure relief rate); after the pores are nucleated, the gas will diffuse into the nucleus, and the diffusion of the gas will cause the pore nucleus to expand. When the diffusion of the gas continues for a certain period of time, the foaming agent is consumed to a point where it is insufficient to maintain the growth of the pores, and the driving force for the growth of the pores disappears. In addition, the supercritical foaming process of polymers is closely related to factors such as gas diffusion rate, polymer viscoelasticity and crystallization behavior.

[0003] At present, polymer materials (sheet materials) are placed in a mold cavity for supercritical foaming. During the foaming process, the lower surface of the polymer is in direct contact with the mold, and the upper surface of the polymer is exposed in the mold and directly in contact with the supercritical fluid. When the gas reaches a dissolution equilibrium in the polymer material, the pressure is quickly released to complete the foaming of the polymer material.

[0004] However, during the heat absorption process of rapid pressure release, the temperatures of the upper and lower surfaces of the polymer material are inconsistent, resulting in uneven heating of the polymer material and inconsistent foaming ratios of the upper and lower surfaces, causing the polymer foam material to bend and deform, affecting the surface flatness and performance of the polymer foam material. Summary of the invention

[0005] Based on the technical problems existing in the above-mentioned prior art, the present invention provides a supercritical foaming method using nanomaterials as foaming medium.

[0006] A supercritical foaming method using nanomaterials as foaming medium comprises the following steps: Taking nanoparticles and coating them on the surface of the injection-molded polymer sheet to be foamed, and adjusting the coating thickness; After the coating is completed, the polymer sheet is placed in the center of the mold cavity, and the mold cavity is closed and gas is introduced into the mold cavity. The flow rate of the gas introduced into the mold cavity is adjusted. After the gas is introduced, the temperature is increased, the pressure is maintained, and the foaming process is performed. The pressure is quickly released to prepare the foamed material.

[0007] Through the above technical scheme, the technical scheme of the present application changes the foaming medium during supercritical foaming to ensure that the polymer material is heated evenly during the pressure relief process, thereby ensuring that the surface of the polymer foam material is smooth and further improving the overall performance of the foaming material.

[0008] Furthermore, the nanoparticles include nano inorganic non-metallic particles.

[0009] Through the above technical scheme, the technical scheme of the present application selects inorganic non-metallic particles. This type of material has good chemical stability and thermal stability, is cheap and easy to obtain, can be used as a foaming medium, and has no negative impact on the foaming process of the foaming material.

[0010] Furthermore, the nano inorganic non-metallic particles include at least one of silicon dioxide, titanium dioxide or talc.

[0011] Furthermore, the gas is at least one of nitrogen or carbon dioxide. Furthermore, the flow rate of the gas is 2 MPa / s.

[0012] Further, the heating and foaming treatment is performed at 120-200°C for 6000-9000 seconds. Furthermore, the introducing of gas comprises the following steps: Carbon dioxide is filled into the mold cavity at a rate of 2 MPa / s for 3 seconds to replace the gas inside the mold cavity. After the replacement is completed, the pressure relief valve is closed and carbon dioxide is filled again until the pressure inside the mold cavity is 15-20 MPa.

[0013] Through the above technical solution, the technical solution of the present application adjusts the ratio of the mixed gas (carbon dioxide and nitrogen) to adjust the pores of the foaming material and improve the performance of the foaming material. The density and performance of the foaming material can also be improved by adjusting the foaming temperature.

[0014] In summary, this application has the following beneficial effects: First, the technical solution of the present application changes the foaming medium during supercritical foaming to ensure that the polymer material is heated evenly during the pressure relief process, thereby ensuring that the surface of the polymer foam material is flat and further improving the overall performance of the foam material.

[0015] Second, the technical solution of the present application uses inorganic non-metallic particles. This type of material has good chemical stability and thermal stability. It is cheap and easy to obtain. It can be used as a foaming medium and has no negative impact on the foaming process of the foaming material.

[0016] Third, the technical solution of this application adjusts the ratio of the mixed gas (carbon dioxide and nitrogen) to adjust the pores of the foaming material and improve the performance of the foaming material. It can also improve the density and performance of the foaming material by adjusting the foaming temperature. DETAILED DESCRIPTION

[0017] The present application is further described in detail below in conjunction with embodiments.

[0018] In the examples of the present application, the raw materials and instruments used are as follows, but not limited thereto. Raw materials not otherwise specified are of analytical grade.

[0019] Example 1 Evenly coat the silicon dioxide, titanium dioxide and talc powder mixed in a mass ratio of 1:1:1 on the surface of the injection-molded TPU (BASF polyester thermoplastic polyurethane S85A) sheet, and adjust the coating thickness to 1-2 mm; After the coating is completed, it is placed in the center of the mold cavity, and carbon dioxide gas is first introduced at a flow rate of 2 MPa / s to replace the gas inside the mold cavity. The replacement time is 3 s, and then the pressure relief valve is closed, and foaming gas is introduced at a flow rate of 2 MPa / s. The gas pressure in the foaming cavity is controlled to be 15-20 MPa, the foaming temperature is 120-200℃, and the foaming time is 6000-9000s. After the foaming is completed, the pressure is quickly released to obtain the TPU foaming material. The pressure relief time is controlled at 3-4 s to prepare the TPU foaming material.

[0020] Example 2 Silicon dioxide, titanium dioxide and talc mixed in a mass ratio of 1:1:1 are evenly coated on the surface of the injection-molded TPEE (Hytrel 3078 of DuPont Co., USA) sheet, and the coating thickness is adjusted to 1-2 mm; After the coating is completed, it is placed in the center of the mold cavity, and carbon dioxide gas is first introduced at a flow rate of 2 MPa / s to replace the gas inside the mold cavity. The replacement time is 3 s, and then the pressure relief valve is closed, and foaming gas is introduced at a flow rate of 2 MPa / s. The gas pressure in the foaming cavity is controlled to be 15-20 MPa, the foaming temperature is 120-200℃, and the foaming time is 6000-9000s. After the foaming is completed, the pressure is quickly released to obtain TPU foaming material. The pressure relief time is controlled at 3-4 s to prepare TPEE foaming material.

[0021] Example 3 Silica, titanium dioxide and talc mixed in a mass ratio of 1:1:1 were evenly coated on the surface of the injection-molded TPA (Pebax 3533 from Arkema, France) sheet, and the coating thickness was adjusted to 1-2 mm.

[0022] After the coating is completed, it is placed in the center of the mold cavity, and carbon dioxide gas is first introduced at a flow rate of 2 MPa / s to replace the gas inside the mold cavity. The replacement time is 3 s, and then the pressure relief valve is closed, and foaming gas is introduced at a flow rate of 2 MPa / s. The gas pressure in the foaming cavity is controlled to be 15-20 MPa, the foaming temperature is 120-200℃, and the foaming time is 6000-9000s. After the foaming is completed, the pressure is quickly released to obtain TPU foaming material. The pressure relief time is controlled at 3-4 s to prepare TPA foaming material.

[0023] Comparative Example 1 Place the injection-molded TPU at the center of the mold cavity, first introduce carbon dioxide gas at a flow rate of 2 MPa / s to replace the gas inside the mold cavity, and the replacement time is 3 s. Then close the pressure relief valve and introduce foaming gas at a flow rate of 2 MPa / s. Control the gas pressure in the foaming cavity to 15-20 MPa, the foaming temperature to 120-200℃, and the foaming time to 6000-9000 s. After the foaming is completed, quickly release the pressure to obtain the TPU foaming material, and the pressure relief time is controlled at 3-4s.

[0024] Comparative Example 2 The injection-molded TPEE (Hytrel 3078 from DuPont, USA) sheet was placed in the mold cavity. Carbon dioxide gas was first introduced at a flow rate of 2 MPa / s to replace the gas inside the mold cavity. The replacement time was 3 s. The pressure relief valve was then closed and foaming gas was introduced at a flow rate of 2 MPa / s. The gas pressure in the foaming cavity was controlled to be 15-20 MPa. The temperature in the foaming cavity was heated to 120-200°C. The foaming time was 6000-9000 s. After the foaming was completed, the pressure was quickly released to obtain the TPEE foaming material.

[0025] Comparative Example 3 The injection-molded TPA (Pebax 3533 from Arkema, France) sheet was placed in the mold cavity. Carbon dioxide gas was first introduced at a flow rate of 2 MPa / s to replace the gas inside the mold cavity. The replacement time was 3 s. The pressure relief valve was then closed and foaming gas was introduced at a flow rate of 2 MPa / s. The gas pressure in the foaming cavity was controlled to be 15-20 MPa. The temperature was raised to 120-200°C in the foaming cavity. The foaming time was 6000-9000 s. After the foaming was completed, the pressure was quickly released to obtain the TPA foaming material.

[0026] Performance Testing The foaming materials prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests: The testing standards are:

[0027] The results are shown in Table 1 below: Table 1 Performance test table

[0028] From the above examples 1-3 and comparative examples 1-3, combined with the test results in Table 1, it can be found that: The technical solution of this application changes the foaming medium during supercritical foaming to ensure that the polymer material is heated evenly during the pressure relief process, thereby ensuring that the surface of the polymer foam material is flat and further improving the overall performance of the foam material The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0029] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0030] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0031] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A supercritical foaming method using nanomaterials as foaming medium, characterized in that: The following steps are involved: Taking nanoparticles and coating them on the surface of the injection-molded polymer sheet to be foamed, and adjusting the coating thickness; After the coating is completed, the polymer sheet is placed in the center of the mold cavity, and the mold cavity is closed and gas is introduced into the mold cavity. The flow rate of the gas introduced into the mold cavity is adjusted. After the gas is introduced, the temperature is increased, the pressure is maintained, and the foaming process is performed. The pressure is quickly released to prepare the foamed material.

2. The supercritical foaming method using nanomaterials as foaming medium according to claim 1, characterized in that: The nanoparticles include nano inorganic non-metallic particles.

3. A supercritical foaming method using nanomaterials as foaming medium according to claim 2, characterized in that: The nano inorganic non-metallic particles include at least one of silicon dioxide, titanium dioxide or talc.

4. The supercritical foaming method using nanomaterials as foaming medium according to claim 1, characterized in that: The gas includes at least one of nitrogen or carbon dioxide.

5. The supercritical foaming method using nanomaterials as foaming medium according to claim 1, characterized in that: The flow rate of the gas is 2 MPa / s.

6. The supercritical foaming method using nanomaterials as foaming medium according to claim 1, characterized in that: The heating and foaming treatment is carried out at 120-200° C. for 6000-9000 seconds.

7. The supercritical foaming method using nanomaterials as foaming medium according to claim 1, characterized in that: The introduction of gas comprises the following steps: Carbon dioxide is filled into the mold cavity at a rate of 2 MPa / s for 3 seconds to replace the gas inside the mold cavity. After the replacement is completed, the pressure relief valve is closed and carbon dioxide is filled again until the pressure inside the mold cavity is 15-20 MPa.

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