Preparation method of micro-foamed materials

Abstract

This invention belongs to the field of plastic foaming technology, specifically relating to a method for preparing micro-foamed materials, comprising: a co-extrusion module, including a co-extrusion compounding device and a first screw extruder and a second screw extruder whose discharge ends are respectively sealed to the feed end of the co-extrusion compounding device; a layer multiplier, whose feed end is sealed to the discharge end of the co-extrusion compounding device; and a static mixer, whose feed end is sealed to the discharge end of the layer multiplier. Through this invention, a chemical foaming agent is carried by a low-melting-point carrier and melted and extruded with a high-melting-point main material through two screw extruders, then extruded into a sealed co-extrusion compounding device to form a first layered fluid. This fluid is then cut and layered by the layer multiplier, and finally mixed by the mixer. This method allows for a wider range of foaming agent selection, strong foaming controllability, and the actual bubble content is close to the theoretical value. Furthermore, the resulting plastic foamed material exhibits a more uniform bubble distribution.

Description

Technical Field

[0001] This invention belongs to the field of plastic foaming technology, specifically relating to a method for preparing micro-foamed materials. Background Technology

[0002] In existing technologies, plastic foaming processes based on chemical foaming agents mostly involve the decomposition of the plastic during melting in a screw extruder to generate gas, thereby achieving a foaming effect. However, this foaming process has the following technical drawbacks: First, the chemical foaming agent generally needs to match the melting temperature of the plastic raw material; otherwise, premature foaming may occur, severely limiting the selection of foaming agents. Second, during the plastic melting process, the chemical foaming agent decomposes and cannot form a sealed environment in the screw. The generated gas escapes along the gap between the screw and the molten material, affecting the gas generation and solubility in the melt, resulting in uncontrollable bubble size and a lower-than-theoretical gas generation content. Finally, relying solely on screw-driven agitation results in bubbles that are too large and have a wide range, with limited uniformity in bubble distribution, affecting the performance of the foamed board (e.g., mechanical properties, thermal insulation properties, and light diffusion uniformity). Summary of the Invention

[0003] In order to overcome the technical defects in the prior art, the present invention provides a method for preparing micro-foamed materials. Based on the system of the present invention, a wider range of foaming agents can be selected, the foaming is highly controllable, the actual bubble content is close to the theoretical value, and the bubble distribution in the formed plastic foamed material is more uniform.

[0004] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0005] A method for preparing a micro-foamed material, the apparatus comprising: a co-extrusion module, including a co-extrusion compounding device and a first screw extruder and a second screw extruder whose discharge ends are respectively sealed to the feed end of the co-extrusion compounding device; a layer multiplier, whose feed end is sealed to the discharge end of the co-extrusion compounding device; and a static mixer, whose feed end is sealed to the discharge end of the layer multiplier.

[0006] The preparation method includes: the main material and the carrier material mixed with a chemical foaming agent are melt-extruded by a first screw extruder and a second screw extruder, respectively, and extruded into a co-extrusion compounding device. In the co-extrusion compounding device, a first layered fluid composed of a main material layer and a carrier material layer is formed. The first layered fluid then enters a layer multiplier and is split and stacked to form a second layered fluid composed of at least four alternating main material layers and at least four carrier material layers, forming micro-mixing in the thickness direction. The second layered fluid then enters a static mixer and is fully stirred, sheared, and mixed to form a uniform micro-foamed material melt precursor. The foaming agent extruded by the second screw extruder is further heated and fully decomposed in the subsequent stacking and mixing process to form uniformly dispersed foam nuclei.

[0007] The main material and the carrier material are compatible, and the melting point of the carrier material is less than the decomposition temperature of the chemical foaming agent and less than the melting point of the main material.

[0008] It also includes an extrusion die. After the molten precursor of the micro-foamed material is extruded through the extrusion die, the pressure is quickly released, allowing the bubble nuclei to grow and eventually form a plastic micro-foamed material.

[0009] Furthermore, the extrusion die feed end is also connected to another co-extrusion module for forming a multilayer board structure, one of which is formed from a micro-foamed material molten precursor.

[0010] Furthermore, another co-extrusion module is connected to the feed end of the extrusion die. Another multiplier is provided between the co-extrusion module and the extrusion die to form a multi-layer plate structure with different structural layers alternating as needed. The multi-layer plate structure alternately contains micro-foamed layers formed by the molten precursor of micro-foamed material.

[0011] Furthermore, depending on the different application areas and usage requirements, the main material can be polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), polypropylene (PP), etc.

[0012] Furthermore, the carrier material can be any polymer in the field of plastic microfoam materials that is compatible with the host material and can meet the application performance requirements of plastic microfoam materials, such as ethylene-vinyl acetate copolymer (EVA).

[0013] Furthermore, depending on the application field and usage requirements, the main material may contain fillers, light diffusing agents, flame retardants, antioxidants, UV stabilizers, etc.

[0014] Compared with the prior art, the present invention has the following technical advantages: the chemical foaming agent is carried by a low-melting-point carrier and is melted and extruded with the high-melting-point main material through two screw extruders and extruded into a closed co-extrusion composite device to form a first layered fluid. Then, it is cut and stacked by a layer multiplier and finally mixed by a mixer. On the one hand, it avoids the premature decomposition of the foaming agent when the carrier material melts. After entering the stacked co-extrusion module, the chemical foaming agent is further heated and decomposed to form dispersed bubble nuclei. On the other hand, the layering and stacking action of the layer multiplier is combined with the mixing and shearing action of the static mixer to make the carrier material layer and the main material layer fully mixed, and the bubbles are sheared multiple times, thereby forming a micro-foamed board melt precursor with uniformly distributed microbubbles, which is conducive to improving the controllability of foaming and obtaining a micro-foamed board with uniformly distributed bubbles. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the preparation method of micro-foamed material in one embodiment of the present invention.

[0016] Figure 2 This is a schematic diagram of the structure of the first layered fluid, the second layered fluid, and the micro-foamed material melt precursor obtained by the preparation method of micro-foamed material in an embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of the preparation method of micro-foamed material according to another embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram of a cross-section of a typical multilayer board.

[0019] Figure 5 This is a schematic cross-sectional view of the multilayer plate before mixing in this application.

[0020] Figure 6 This is a cross-sectional schematic diagram of the foamed board prepared in the embodiments of this application. Figure 7 This is a cross-sectional schematic diagram of the foamed board prepared in the embodiments of this application.

[0021] The reference numerals in the figure are as follows: 1. First screw extruder, 2. Second screw extruder, 3. Co-extrusion compounding unit, 4. Layer multiplier, 5. Static mixer, 6. Extrusion die, 7. Third screw extruder, 8. Another co-extrusion compounding unit. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments:

[0023] One embodiment of the micro-foaming device is shown below. Figure 1 It includes a co-extrusion module, a layer multiplier 4, and a static mixer 5.

[0024] The co-extrusion module includes a co-extrusion compounding device 3 and a first screw extruder 1 and a second screw extruder 2, whose discharge ends are respectively hermetically connected to the feed end of the co-extrusion compounding device 3. Specifically, the co-extrusion compounding device 3 is provided with a first feed port and a second feed port. The first feed port of the co-extrusion compounding device 3 is hermetically connected to the discharge port of the first screw extruder 1, and the second feed port is hermetically connected to the discharge port of the second screw extruder 2.

[0025] The layer multiplier has its feed end sealed to the discharge end of the co-extrusion compounding unit 3; the static mixer 5 has its feed end sealed to the discharge end of the layer multiplier 4.

[0026] In the preparation of microfoamed materials, the main material and the carrier material mixed with a chemical foaming agent are melt-extruded through a first screw extruder 1 and a second screw extruder 2, respectively, and then enter a co-extrusion compounding unit 3. Within the co-extrusion compounding unit 3, a first layered fluid consisting of a main material layer and a carrier material layer is formed. Figure 2As shown in Figure 2a, the first layered fluid then enters the layer multiplier 4, where it is segmented and stacked to form a second layered fluid consisting of alternating layers of host material (at least 4 layers) and carrier material (at least 4 layers). Of course, the more alternating layers there are, the more uniform the bubble distribution will be in the later stages. Figure 2 As shown in Figure 2b (taking a two-layer example), the second layer of fluid then enters the static mixer 5, where it comes into contact with, rubs against, shears, and is thoroughly mixed with the hot surface of the static mixer 5 to form a uniform micro-foamed material melt precursor (see Figure 2b). Figure 2 As shown in 2c); after being extruded by the second screw extruder 2, the foaming agent is further heated and fully decomposed in the subsequent process to form uniformly dispersed foam nuclei.

[0027] Specifically, the foaming agent can be thermally decomposed based on the thermal conduction of the molten bulk material, and / or thermally decomposed based on the heating devices installed in the co-extrusion compounding unit 3, the multiplier and / or the static mixer 5.

[0028] The main material and the carrier material are compatible, and the melting point of the carrier material is less than the decomposition temperature of the chemical foaming agent and less than the melting point of the main material.

[0029] It also includes an extrusion die 6. After the molten precursor of the microfoamed material is extruded through the extrusion die 6, the pressure is quickly released, allowing the bubble nuclei to grow and ultimately form a plastic microfoamed material (see...). Figure 6 and Figure 7 The diagram shows the cell structure and distribution of foam boards made of two different materials with varying degrees of softness. Figure 6 The major axis dimension of the bubble at the marked location is 476.04 micrometers, and the minor axis is 115.09 micrometers. Figure 7 The major axis dimension of the bubble at the marked location is 951.93 micrometers, and the minor axis dimension is 189.35 micrometers.

[0030] In another embodiment, the feed end of the extrusion die 6 is also connected to another co-extrusion module for forming a multilayer board structure, one layer of which is formed from a micro-foamed material molten precursor. For example, for forming a multilayer board structure consisting of a non-foamed layer and a foamed layer, the other co-extrusion module consists of a third screw extruder 7 and another co-extrusion composite device 8, see [link to documentation]. Figure 3 As shown.

[0031] In another embodiment, the feed end of the extrusion die 6 is also connected to another co-extrusion module. This other co-extrusion module and the extrusion die 6 are further provided with another multiplier 4, used to form a multilayer board structure with alternating layers of different structural structures as needed. The multilayer board structure alternately contains micro-foamed layers formed from molten precursors of micro-foamed materials. For example, it can be used to form a multilayer board structure composed of alternating layers of non-foamed layers and layers of foamed layers. Of course, depending on the number of feed ports of the co-extrusion compounding device 3 in the other extrusion module and the configuration of the screw extruder matching the number of feed ports of the co-extrusion compounding device 3, a multilayer board structure containing multiple structural layers can be achieved.

[0032] Furthermore, depending on the different application areas and usage requirements, the main material can be polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), polypropylene (PP), etc.

[0033] Furthermore, the carrier material can be any polymer in the field of plastic microfoam materials that is compatible with the host material and can meet the application performance requirements of plastic microfoam materials, such as ethylene-vinyl acetate copolymer (EVA).

[0034] Furthermore, depending on the application field and usage requirements, the main material may contain fillers, nucleating agents (such as any one or more of calcium carbonate, talc, titanium dioxide, magnesium aluminum hydrotalcite, polydimethylsiloxane, etc.), light diffusing agents, flame retardants, antioxidants, UV stabilizers, etc.

[0035] The chemical foaming agent is any one of the following: 2,2'-azobisisobutyronitrile nitroso compound, N,N'-dimethyl-N,N'-dinitrosoterephthaloyl, p-toluenesulfonyl hydrazine, 4,4'-oxobis(benzenesulfonyl hydrazine), 3,3'-disulfonyl hydrazine diphenyl sulfone, 1,3-benzenedisulfonyl hydrazine, p-toluenesulfonamide, 4,4'-oxobis(benzenesulfonamide), trihydrazine triazine, and 5-phenyltetrazole.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention. In the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0037] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A method for preparing a micro-foamed material, characterized in that: The equipment used includes: a co-extrusion module, including a co-extrusion compound device (3) and a first screw extruder (1) and a second screw extruder (2) whose discharge ends are respectively sealed to the feed end of the co-extrusion compound device (3); a layer multiplier (4), whose feed end is sealed to the discharge end of the co-extrusion compound device (3); and a static mixer (5), whose feed end is sealed to the discharge end of the layer multiplier (4). The preparation method includes: the main material and the carrier material mixed with the chemical foaming agent are melt-extruded by the first screw extruder (1) and the second screw extruder (2), respectively, and extruded into the co-extrusion compounding device (3). In the co-extrusion compounding device (3), a first layered fluid composed of a main material layer and a carrier material layer is formed. The first layered fluid then enters the layer multiplier (4) and is split and stacked to form a second layered fluid composed of at least four alternating main material layers and at least four carrier material layers. The second layered fluid then enters the static mixer (5) and is fully stirred, sheared and mixed to form a uniform micro-foamed material melt precursor. After being extruded by the second screw extruder (2), the foaming agent is further heated and fully decomposed in the subsequent process to form uniformly dispersed foam nuclei. The host material is compatible with the carrier material, and the melting point of the carrier material is less than the decomposition temperature of the chemical foaming agent and less than the melting point of the host material; the carrier material is a high molecular polymer that is compatible with the host material and can meet the application performance requirements of plastic microfoaming materials in the technical field of plastic microfoaming materials. The device also includes an extrusion die (6). After the molten precursor of the micro-foamed material is extruded through the extrusion die (6), the pressure is quickly released, and the bubble nuclei grow and are finally formed into plastic micro-foamed material.

2. The method for preparing micro-foamed materials according to claim 1, characterized in that: The extrusion die (6) feed end is also connected to another co-extrusion module for forming a multilayer board structure, one of which is formed by a micro-foamed material molten precursor.

3. The method for preparing micro-foamed materials according to claim 1, characterized in that: The feed end of the extrusion die (6) is also connected to another co-extrusion module. Another multiplier is provided between the other co-extrusion module and the extrusion die (6) for preparing a multilayer plate structure with different structural layers alternating in sequence. The multilayer plate structure contains alternating micro-foamed layers formed by the molten precursor of micro-foamed material.

4. The method for preparing microcellular foamed material according to claim 1, characterized in that: The main material is any one of polystyrene, polycarbonate, polymethyl methacrylate, polypropylene, polyethylene, and PET.

5. The method for preparing microcellular foamed material according to claim 1, characterized in that: The carrier material is an ethylene-vinyl acetate copolymer.

6. The method for preparing micro-foamed materials according to claim 1, characterized in that: The main material contains any one or more of the following: filler, nucleating agent, light diffusing agent, flame retardant, antioxidant, and UV stabilizer.

7. The method for preparing micro-foamed materials according to claim 1, characterized in that: The chemical foaming agent is any one of the following: 2,2'-azobisisobutyronitrile nitroso compound, N,N'-dimethyl-N,N'-dinitrosoterephthaloyl, p-toluenesulfonyl hydrazine, 4,4'-oxobis(benzenesulfonyl hydrazine), 3,3'-disulfonyl hydrazine diphenyl sulfone, 1,3-benzenedisulfonyl hydrazine, p-toluenesulfonamide, 4,4'-oxobis(benzenesulfonamide), trihydrazine triazine, and 5-phenyltetrazole.

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