A multilayer coextruded thermoplastic elastomer foam film and a method of making the same

Abstract

The application discloses a kind of multilayer co-extrusion thermoplastic elastomer foamed film and preparation method thereof, and relates to the technical field of foamed material.A kind of multilayer co-extrusion thermoplastic elastomer foamed film includes top layer, middle layer, bottom layer, and the middle layer includes the following components: thermoplastic elastomer; Nucleating agent; Chain extender; Antioxidant.A kind of preparation method of multilayer co-extrusion thermoplastic elastomer foamed film includes the following steps: after the components of middle layer are mixed uniformly, then in top layer extruder and bottom layer extruder, compatible agent and polyethylene are added; Physical foaming agent is added to middle layer extruder, then it is co-extruded through co-extrusion die, after being cooled quickly by flow roller, air knife, traction, winding, multilayer co-extrusion thermoplastic elastomer foamed film is obtained.The application solves the problems of low melt strength of existing thermoplastic elastomer, too fast gas escape, low foaming ratio, uneven cell and easy cell rupture.

Description

Technical Field

[0001] This invention relates to the technical field of foamed materials, and in particular to a multilayer co-extruded thermoplastic elastomer foam film and its preparation method. Background Technology

[0002] Thermoplastic elastomers possess the excellent properties of traditional cross-linked vulcanized rubber, such as high elasticity, aging resistance, and oil resistance, while also having the advantages of easy processing and wide range of processing methods found in ordinary plastics. Lightweight polymer foam materials produced by foaming thermoplastic elastomers have wide applications in aerospace, defense, energy, transportation, packaging, electrical appliances, and sporting goods.

[0003] However, existing thermoplastic elastomer foam materials are prone to problems such as low foaming ratio of the foam layer due to rapid gas escape during the production process, and easy rupture of the cell walls and difficulty in cell formation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multilayer co-extruded thermoplastic elastomer foam film and its preparation method. The method of this invention solves the problems of low melt strength, excessive gas escape, low foaming ratio, uneven cell structure, and easy cell rupture in existing thermoplastic elastomers.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a multilayer co-extruded thermoplastic elastomer foam film, comprising a top layer, an intermediate layer, and a bottom layer, wherein the thickness of the top layer and the bottom layer are both 0.05-1 mm, and the average size of the pores in the intermediate layer is 10-150 μm.

[0007] The intermediate layer comprises the following components in parts by weight:

[0008] 90-100 parts thermoplastic elastomer; 0.1-6 parts nucleating agent; 0.1-0.8 parts chain extender; 0-0.5 parts antioxidant.

[0009] This invention relates to a multilayer co-extruded thermoplastic elastomer foam film comprising a top layer (solid layer), an intermediate layer (foamed layer), and a bottom layer (solid layer), forming a three-layer "skin-core-skin" structure. This structure utilizes non-foaming, rapidly crystallizing polyethylene (PE) solid layers (skin layers) on both the top and bottom sides of the thermoplastic elastomer to further prevent rapid gas escape, thereby rapidly increasing the foaming ratio of the thermoplastic elastomer foam film. The addition of chain extenders effectively improves the melt strength of the thermoplastic elastomer and further enhances the ability of the thermoplastic elastomer matrix to restrict rapid gas escape. The addition of nucleating agents effectively lowers the heterogeneous nucleation barrier of the cells, further improving the cell nucleation efficiency, thus achieving the goal of refining the cells and increasing the cell density. The multilayer co-extruded thermoplastic elastomer foam film prepared by this invention exhibits a smooth surface, good flatness, uniform cell size, and high foaming ratio.

[0010] Preferably, the overall density of the multilayer co-extruded thermoplastic elastomer foam film is 0.1 g / cm³. 3 The thickness is 2.5-4.5mm and the width is 50-55cm.

[0011] Preferably, the thermoplastic elastomer has a melting point of 140-160℃ and a hardness of 85-98A.

[0012] This invention controls the melting point and hardness of thermoplastic elastomers, which is beneficial for improving cell uniformity and foaming ratio.

[0013] Preferably, the intermediate layer comprises the following components in parts by weight:

[0014] 95-100 parts thermoplastic elastomer; 3-5 parts nucleating agent; 0.1-0.5 parts chain extender; 0.2-0.3 parts antioxidant.

[0015] Preferably, both the top and bottom layers comprise 1-5 parts of a compatibilizer and 100 parts of polyethylene.

[0016] Preferably, the compatibilizer is at least one of polyethylene wax and maleic anhydride.

[0017] Preferably, the thermoplastic elastomer is at least one of thermoplastic polyurethane (TPU), TPEE, and TPAE.

[0018] Preferably, the nucleating agent includes organic nucleating agents and inorganic nucleating agents.

[0019] More preferably, the organic nucleating agent includes at least one of EVA, POE, OBC, SBES, and EPDM; and the inorganic nucleating agent includes at least one of calcium carbonate, talc, mica, and glass microspheres.

[0020] Preferably, the chain extender comprises at least one of a difunctional acid derivative, an isocyanate, an acid anhydride, and an epoxide.

[0021] Preferably, the antioxidant includes at least one of amine antioxidants and phosphorus antioxidants.

[0022] Preferably, the processing equipment for the multilayer co-extruded thermoplastic elastomer foam film includes a top layer extruder, an intermediate layer extruder, a bottom layer extruder, a co-extrusion die, an air knife, and a casting roller.

[0023] Preferably, the top layer extruder, the middle layer extruder, and the bottom layer extruder are all single screw extruders, and the single screw extruder includes an air inlet.

[0024] Secondly, the present invention also provides a method for preparing a multilayer co-extruded thermoplastic elastomer foam film, comprising the following steps:

[0025] (1) First, the thermoplastic elastomer is mixed with nucleating agent, chain extender and antioxidant to obtain premix. Then, the premix is ​​added to the intermediate layer extruder. Compatibilizer and polyethylene are added to both the top layer extruder and the bottom layer extruder.

[0026] (2) Add the physical foaming agent to the intermediate layer extruder, and then extrude the materials extruded by the intermediate layer extruder, the top layer extruder and the bottom layer extruder through the co-extrusion die, and then quickly cool them through the casting roller and air knife. Finally, after the cooled and shaped multilayer film is pulled and wound up, the multilayer co-extruded thermoplastic elastomer foam film is obtained.

[0027] This invention utilizes a multi-layer co-extrusion foaming process. Thermoplastic elastomer raw materials and additives are pre-mixed and added to the extruder corresponding to the intermediate foaming layer. Polyethylene and a compatibilizer are then added to the extruders corresponding to the top and bottom layers, respectively. After all three layers are stably extruded, a physical foaming agent is injected into the air inlet of the extruder corresponding to the intermediate foaming layer. Subsequently, after the multi-layer co-extruded foam film is extruded from the die, the material is rapidly drawn to a casting roller and rapidly cooled by an air knife. The top layer is the roller-attached surface and is rapidly cooled by the casting roller, while the bottom layer is rapidly cooled by the air knife. Finally, after rapid cooling and shaping by the air knife and low-temperature casting roller, the material is drawn to a winding roller to obtain a multi-layer co-extruded thermoplastic elastomer foam film.

[0028] The preparation method described in this invention has the advantages of being continuous and efficient, overcoming the problems of easy gas escape, easy rupture of cell walls, and low foaming ratio in the TPU melt foaming process.

[0029] Preferably, the physical foaming agent in step (2) is at least one of CO2, N2, methane, propane, butane, and Freon.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention relates to a processing method for multi-layer co-extrusion foaming, which uses two extruders and an extrusion foaming machine in parallel. By providing solid layers with fast crystallization rates on both sides of the foamed layer, and adding chain extenders and nucleating agents to the TPU matrix, the method simultaneously improves the melt strength of the matrix and the efficiency of heterogeneous nucleation of the cells. This avoids the low foaming ratio of the foamed layer caused by rapid gas escape, and solves the technical problems of easy cell wall rupture and difficult cell formation caused by low melt strength of TPU. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the processing of the multilayer co-extruded thermoplastic elastomer foam film described in this invention.

[0033] Figure 2 This is a schematic diagram of the structure of the multilayer co-extruded thermoplastic elastomer foam film described in this invention. Detailed Implementation

[0034] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0035] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0036] Example 1

[0037] A multilayer co-extruded thermoplastic elastomer foam film comprises a three-layer structure: a top layer, a middle layer, and a bottom layer, such as... Figure 2 As shown; the processing equipment for the multilayer co-extruded thermoplastic elastomer foam film of the present invention includes a top layer extruder, a middle layer extruder, a bottom layer extruder, a co-extrusion die, an air knife, and a casting roller, as shown. Figure 1 As shown.

[0038] The intermediate layer described in this embodiment comprises the following components in parts by weight:

[0039] 100 parts thermoplastic elastomer; 5 parts nucleating agent; 0.3 parts chain extender; 0.3 parts antioxidant;

[0040] The thermoplastic elastomer is TPU, with a melting point of 140°C and a hardness of 85A; the nucleating agent is calcium carbonate, the chain extender is a multifunctional epoxy chain extender, and the antioxidant is an amine antioxidant.

[0041] A method for preparing a multilayer co-extruded thermoplastic elastomer foam film includes the following steps:

[0042] (1) Feeding the intermediate layer extruder: TPU, nucleating agent, chain extender and antioxidant are premixed to obtain a premix. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone reaches 128℃ (feeding zone)-178℃-178℃-145℃-113℃-115℃-135℃ (die head)-145℃ (screen changer), the blend is put into the intermediate layer extruder for melt extrusion. The screw speed is 60 rpm.

[0043] (2) Feeding the top / bottom extruder: Premix 100 parts of PE with 5 parts of compatibilizer. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone is 100℃ (feeding zone)-110℃-120℃-130℃-140℃-140℃-120℃ (die head), the blend is added to the top / bottom extruder for melt extrusion. The screw speed is 20 rpm.

[0044] (3) After the material co-extrusion is stable, open the air inlet valve of the middle layer extruder and introduce physical foaming agent (10MPa). The physical foaming agent is butane. Then observe the air inlet pressure valve and the die pressure valve. After the pressure is stable, pull the multi-layer co-extruded foam film to the casting roller and turn on the air knife. After rapid cooling and shaping, it is wound into a film by the take-up roller.

[0045] The TPU foam film prepared in this embodiment has a smooth and clean surface and an overall density of 0.1 g / cm³. 3 The thickness is 3±0.2mm and the width is 50cm. The foam layer has uniform pores with an average pore size of about 100μm. The foam layer has good adhesion to the surface layer (top / bottom layer).

[0046] Example 2

[0047] A multilayer co-extruded thermoplastic elastomer foam film comprises a three-layer structure: a top layer, a middle layer, and a bottom layer, such as... Figure 2 As shown; the processing equipment for the multilayer co-extruded thermoplastic elastomer foam film of the present invention includes a top layer extruder, a middle layer extruder, a bottom layer extruder, a co-extrusion die, an air knife, and a casting roller, as shown. Figure 1 As shown.

[0048] The intermediate layer described in this embodiment comprises the following components in parts by weight:

[0049] 100 parts thermoplastic elastomer; 5 parts nucleating agent; 0.3 parts chain extender; 0.3 parts antioxidant;

[0050] The thermoplastic elastomer is TPU, with a melting point of 160°C and a hardness of 98A; the nucleating agent is calcium carbonate, the chain extender is a multifunctional epoxy chain extender, and the antioxidant is an amine antioxidant.

[0051] A method for preparing a multilayer co-extruded thermoplastic elastomer foam film includes the following steps:

[0052] (1) Feeding the intermediate layer extruder: TPU, nucleating agent, chain extender and antioxidant are premixed to obtain a premix. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone reaches 128℃ (feeding zone)-178℃-178℃-145℃-113℃-115℃-135℃ (die head)-145℃ (screen changer), the blend is put into the intermediate layer extruder for melt extrusion. The screw speed is 60 rpm.

[0053] (2) Feeding the top / bottom extruder: Premix 100 parts of PE with 5 parts of compatibilizer. After the extruder temperature reaches the preset temperature, that is, the temperature of each zone is 100℃ (feeding zone)-110℃-120℃-130℃-140℃-140℃-120℃ (die head), add the blend into the top / bottom extruder for melt extrusion. The screw speed is 30 rpm.

[0054] (3) After the material co-extrusion is stable, open the air inlet valve of the middle layer extruder and introduce physical foaming agent (12MPa). The physical foaming agent is butane. Then observe the air inlet pressure valve and the die pressure valve. After the pressure is stable, pull the multi-layer co-extruded foamed film to the casting roller and turn on the air knife. After rapid cooling and shaping, it is wound into a film by the take-up roller.

[0055] The TPU foam film prepared in this embodiment has a smooth and clean surface and an overall density of 0.1 g / cm³. 3 The thickness is 4±0.2mm and the width is 55cm. The foam layer has uniform pores with an average pore size of about 130μm. The foam layer has good adhesion to the surface layer (top / bottom layer).

[0056] Comparative Example 1

[0057] The difference from Example 1 is that the screw speed in step (2) is 10 rpm, while the other steps are the same as in Example 1.

[0058] The density of the TPU foam film prepared in this comparative example is 0.08 g / cm³. 3 The thickness is 3±0.1mm.

[0059] Compared with the product obtained in Example 1, it can be seen that due to the reduced extrusion amount of the surface layer (top / bottom solid layer), the surface layer's ability to restrict the rapid escape of gas decreases. Although the product density is reduced, the product surface is not smooth and is accompanied by surface cracks and wrinkles, affecting the product's appearance.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that no chain extender was added in step (1) and no compatibilizer was added in step (2), while the other steps are the same as in Example 1.

[0062] The density of the TPU foam film prepared in this comparative example is 0.8 g / cm³. 3 The thickness is 1.3±0.1mm.

[0063] Compared with the product obtained in Example 1, it can be seen that because no chain extender was added during the TPU extrusion process, the melt strength of the TPU matrix was too low. This made it extremely prone to cell wall rupture when the physical foaming agent was injected, resulting in a large amount of gas escape and cell aggregation, with a density of only 0.8 g / cm³. 3 Left and right. Furthermore, since no compatibilizer is added to the solid PE layer, the interfacial adhesion between the surface layer and the foam layer is poor, and the interface is smooth and easy to peel off.

[0064] Comparative Example 3

[0065] The difference from Example 1 is that no nucleating agent was added in step (1), while the other steps are the same as in Example 1.

[0066] The density of the TPU foam film prepared in this comparative example is 0.7 g / cm³. 3 The thickness is 1±0.1mm.

[0067] Compared with the product obtained in Example 1, it can be seen that because no nucleating agent was added during the TPU extrusion process, the TPU matrix's ability to prevent rapid gas escape and its ability to nucleate cells were reduced. When the physical foaming agent was injected, large cells were easily generated, further inducing cell wall rupture, thus causing a large amount of gas to escape, resulting in a density of only 0.7 g / cm³. 3 .

[0068] Comparative Example 4

[0069] The difference from Example 1 is that in step (2), TPU of equal mass is used instead of PE and no compatibilizer is added. All other steps are the same as in Example 1.

[0070] The density of the TPU foam film prepared in this comparative example is 0.3 g / cm³. 3 The thickness is 1.3±0.1mm.

[0071] Compared with the product obtained in Example 1, it can be seen that although the surface material (top / bottom solid layer) was replaced with TPU, the TPU crystallization rate is relatively slow during rapid cooling, which makes it easy for high-pressure fluid to break through the surface layer, ultimately resulting in the surface layer becoming uneven due to cracking.

[0072] Comparative Example 5

[0073] The difference from Example 1 is that the amount of nucleating agent used in step (1) is 7 parts, while the other steps are the same as in Example 1.

[0074] The density of the TPU foam film prepared in this comparative example is 0.3 g / cm³. 3 The thickness is 1.3±0.1mm.

[0075] Compared with the product obtained in Example 1, it can be seen that when the nucleating agent content is increased to 7 parts, the nucleating agent begins to agglomerate, and the nucleation sites of the foam cells are more concentrated. Therefore, a large number of large foam cells with a size greater than 150 μm appear in the foaming layer, and the product is easy to compress and collapse.

[0076] Comparative Example 6

[0077] The difference from Example 1 is that the chain extender in step (1) is 0.9 parts, and the other steps are the same as in Example 1.

[0078] The density of the TPU foam film prepared in this comparative example is 0.8 g / cm³. 3 The thickness is 1±0.1mm.

[0079] Compared with the product obtained in Example 1, it can be seen that when the chain extender content is increased to 0.9 parts, the molecular chains have shown slight cross-linking and fiberization. The foamed layer has almost no uniform pores and has a large number of defects similar to phase separation behavior.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multilayer co-extruded thermoplastic elastomer foam film, characterized in that, The multilayer co-extruded thermoplastic elastomer foam film includes a top layer, an intermediate layer, and a bottom layer. The thickness of the top layer and the bottom layer is 1 mm. The average size of the cells in the intermediate layer is 10-150 μm. The thickness of the multilayer co-extruded thermoplastic elastomer foam film is 2.5-4.5 mm. The intermediate layer comprises the following components in parts by weight: 90-100 parts thermoplastic elastomer; 0.1-6 parts nucleating agent; 0.1-0.8 parts chain extender; 0-0.5 parts antioxidant; The thermoplastic elastomer is TPU; Both the top and bottom layers comprise 1-5 parts of a compatibilizer and 100 parts of polyethylene; the compatibilizer is polyethylene wax.

2. The multilayer co-extruded thermoplastic elastomer foam film as described in claim 1, characterized in that, The thermoplastic elastomer has a melting point of 140-160℃ and a hardness of 85-98A.

3. The multilayer co-extruded thermoplastic elastomer foam film as described in claim 1, characterized in that, The intermediate layer comprises the following components in parts by weight: 95-100 parts thermoplastic elastomer; 3-5 parts nucleating agent; 0.1-0.5 parts chain extender; 0.2-0.3 parts antioxidant.

4. The multilayer co-extruded thermoplastic elastomer foam film as described in claim 1, characterized in that, Includes at least one of the following: The nucleating agent includes organic nucleating agents and inorganic nucleating agents; The organic nucleating agent includes at least one of EVA, POE, OBC, SBES, and EPDM; the inorganic nucleating agent includes at least one of calcium carbonate, talc, mica, and glass microspheres. The chain extender includes at least one of difunctional acid derivatives, isocyanates, acid anhydrides, and epoxides; The antioxidants include at least one of amine antioxidants and phosphorus antioxidants.

5. The multilayer co-extruded thermoplastic elastomer foam film as described in claim 1, characterized in that, The processing equipment for the multilayer co-extruded thermoplastic elastomer foam film includes a top layer extruder, an intermediate layer extruder, a bottom layer extruder, a co-extrusion die, an air knife, and a casting roller.

6. The method for preparing the multilayer co-extruded thermoplastic elastomer foam film according to any one of claims 1-5, characterized in that, Includes the following steps: (1) First, the thermoplastic elastomer is mixed with nucleating agent, chain extender and antioxidant to obtain premix. Then the premix is ​​added to the intermediate layer extruder. Compatibilizer and polyethylene are added to both the top layer extruder and the bottom layer extruder. (2) Add the physical foaming agent to the intermediate layer extruder, and then extrude the materials extruded by the intermediate layer extruder, the top layer extruder and the bottom layer extruder through the co-extrusion die, and then quickly cool them through the casting roller and the air knife. Finally, after the cooled and shaped multilayer film is pulled and wound up, the multilayer co-extruded thermoplastic elastomer foam film is obtained.

7. The method for preparing the multilayer co-extruded thermoplastic elastomer foam film as described in claim 6, characterized in that, The physical foaming agent in step (2) is at least one of CO2, N2, methane, propane, butane, and Freon.

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