Extruded microfoamed high density polyethylene and method and apparatus for making same

Abstract

The present application relates to the technical field of foamed material, and discloses an extruded micro-foamed high-density polyethylene and a preparation method and device thereof, and the preparation comprises the following steps: step 1, mixing raw materials containing high-density polyethylene, expanded microspheres, fillers and interfacial compatibilizers to obtain a premix; and step 2, drying the premix, melt blending and extruding, and obtaining through high-temperature steam assisted foaming. In the present application, the expanded microspheres are used as a foaming agent, and through the mode of melt blending and extruding and high-temperature steam assisted foaming, the expanded microspheres are micro-foamed during melt extrusion, and then further foamed twice through high-temperature steam, so that the expanded microspheres fully play the role of lightweight fillers and foaming agents, a highly controllable and stable foaming effect is achieved, a fine and uniform cell structure is obtained in the material, and a polyethylene foamed material with high mechanical properties and foaming ratio is prepared.

Description

Technical Field

[0001] This invention relates to the field of foamed materials technology, specifically to an extruded micro-foamed high-density polyethylene and its preparation method and apparatus. Background Technology

[0002] High-density polyethylene (HDPE) has a predominantly linear molecular structure with high crystallinity, resulting in high operating temperature, mechanical strength, and chemical resistance. It can be used to produce products in fields such as pipes and furniture. In the context of carbon neutrality, to achieve carbon reduction and weight reduction, microporous structures are often introduced into HDPE to reduce material costs, improve the performance of polyethylene foam materials, and broaden their application areas.

[0003] Chinese invention patent CN102229708A discloses a high-expansion-ratio high-density polyethylene microporous foamed profile and its preparation method. The characteristic of this foamed profile is that it is directly prepared from high-density polyethylene raw materials using a physical gas foaming method in the presence of a physical gas foaming agent, and its foam density is 0.032-0.20 g / cm³. 3 With a foaming ratio of 5-30 times, an average pore size of 10-120 μm, and uniform pore distribution, 95% of the pore diameter deviation does not exceed 15% of the average pore size. It has no skin structure and can be made into materials of any shape. This high-expansion-ratio high-density polyethylene microporous foam material features high mechanical strength, good resilience, good heat resistance, good chemical corrosion resistance, and recyclability, thus overcoming the shortcomings of existing foam materials.

[0004] Chinese invention patent CN103554626A discloses a micro-foamed polyethylene-based wood-plastic composite material and its preparation method. This micro-foamed polyethylene-based wood-plastic composite material is prepared by stirring and heating a matrix polyethylene resin, modified wollastonite powder and talc powder, a crosslinking agent, a lubricant, a heat-balanced foaming agent, an antioxidant, a UV stabilizer, pigments, and modified plant fibers until uniformly mixed, cooled, and discharged to obtain a premix. The modified plant fibers are selected from one or more of wood flour, bamboo flour, and rice husk powder in any proportion. The premix is ​​then granulated, extruded, foamed, and cooled to set in an extruder. A density of 0.81~0.91 g / cm³ is obtained by adding highly filled plant fibers during extrusion. 3 Microfoamed polyethylene-based wood-plastic composite material with a flexural strength of 16.56~17.54MPa.

[0005] Maintaining high strength while reducing density is a common challenge for foamed materials. As the number of pores within the foam increases, the gas content also increases, leading to a gradual decrease in density. However, the point of application also decreases, resulting in a reduction in mechanical strength. Furthermore, adding highly filler-rich materials to the polymer matrix presents problems of poor compatibility and difficulty in foaming, affecting the foaming and mechanical properties of microporous foamed materials and limiting their application range. Summary of the Invention

[0006] This invention addresses the problem that foaming performance and mechanical properties cannot be simultaneously achieved in micro-foamed resins. It provides a method for preparing extruded micro-foamed high-density polyethylene. By combining extrusion with high-temperature steam-assisted foaming, a polyethylene foam material with both mechanical properties and high foaming density can be obtained with low foaming filler content.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing extruded micro-foamed high-density polyethylene includes the following steps: Step 1: Mix the raw materials containing high-density polyethylene, expanded microspheres, fillers, and interfacial compatibilizers to obtain a premix; Step 2: After drying the premix, it is melt-blended and extruded. The molten mixture leaving the die is foamed with the aid of high-temperature steam, cooled and shaped, dried and cut to obtain the extruded micro-foamed high-density polyethylene. The raw materials, by weight, include: 65-95 parts high-density polyethylene, 3-15 parts expanded microspheres, 1-15 parts filler, and 1-3 parts interface compatibilizer.

[0008] This invention uses expanded microspheres as a foaming agent. Through melt blending extrusion and high-temperature steam-assisted foaming, the expanded microspheres undergo micro-foaming during melt extrusion, followed by secondary foaming with high-temperature steam. This fully utilizes the expanded microspheres as a lightweight filler and foaming agent, achieving a highly controllable and stable foaming effect, resulting in a fine and uniform cell structure within the material. It eliminates the need for excessive amounts of chemical foaming agents and complex physical foaming techniques such as N2 or CO2, producing polyethylene foam materials with high mechanical properties and high expansion ratios.

[0009] The high-temperature steam-assisted foaming in this invention involves foaming a molten mixture by passing it through an extrusion channel continuously supplied with high-temperature steam. The high-temperature steam is saturated water vapor with a temperature of 85-230 ℃ and an absolute pressure of 57.88-2798.59 kPa.

[0010] Preferably, the temperature of the high-temperature steam is not lower than the expansion temperature of the expanded microspheres.

[0011] The expanded microspheres are at least one of dry unexpanded microspheres, dry expanded microspheres, wet unexpanded microspheres, and wet expanded microspheres.

[0012] The expanded microspheres are Norinon's Expanded Microspheres Expansionl, such as any one or more models including 920 DU20, 950 DU80, 044 DU40, 980 DU100, and 031 DU40.

[0013] The filler includes at least one of the following: talc, attapulgite, calcium carbonate, modified wollastonite, carbon black, silica, boron nitride, aluminum nitride, alumina, diatomaceous earth, zirconium phosphate, montmorillonite, activated clay, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, kaolin, silicon dioxide, glass powder, and silica.

[0014] The high-density polyethylene includes at least one of high-density polyethylene powder, high-density polyethylene granules, or recycled high-density polyethylene.

[0015] The raw materials also include one or more additives selected from pigments, UV stabilizers, and antioxidants, with each additive used in amounts of 0.1-5 parts. Other additives can be added to the raw materials according to the actual application scenario to improve the material's antioxidant and anti-aging properties.

[0016] The pigment includes at least one of masterbatch, carbon black, titanium dioxide, iron oxide red, or iron oxide yellow; The interface compatibilizer includes at least one of maleic anhydride-grafted polyethylene, acrylic compound-grafted polyethylene, or acrylic compound-grafted metallocene ethylene-1-octene copolymer. The UV stabilizer includes 2-hydroxy-4-n-octyloxybenzophenone UV531; The antioxidant includes at least one of hindered phenolic antioxidant 1010 and phosphite antioxidant 168.

[0017] The temperature of the melt blending is 110-160℃; the die for the melt blending extrusion is one of a strip die, a T-die, a round die, or a tubular die.

[0018] The present invention also provides extruded microcellular high-density polyethylene prepared by the aforementioned method, wherein the density of the extruded microcellular high-density polyethylene is 0.50~0.80 g / cm³. 3 The static bending strength is above 9.5 MPa.

[0019] The present invention also provides an apparatus for extruding micro-foamed high-density polyethylene, including a screw extrusion device and a steam-assisted foaming device; the steam-assisted foaming device is connected to the extrusion die of the screw extrusion device and is provided with a steam inlet and a steam outlet.

[0020] The screw extrusion device includes a single-screw or twin-screw extrusion device.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of the present invention uses an extruder with high temperature steam-assisted foaming. The foam structure can be customized by controlling the decomposition temperature of the expanded microspheres. The product has a uniform foam structure and high material mechanical strength.

[0022] (2) The extruded micro-foamed high-density polyethylene material of the present invention uses a series of expanded microspheres, without the need to add chemical foaming agents or modify equipment to implement physical foaming technology such as N2 or CO2, and has a wider range of applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the equipment structure for extruding micro-foamed high-density polyethylene according to the present invention, wherein 1 is a screw extrusion device, 2 is a feeding port, 3 is an extrusion screw, 4 is a mixture, 5 is an extrusion die, 6 is a steam-assisted foaming device, and 7 is the extruded micro-foamed high-density polyethylene material.

[0024] Figure 2 This is a schematic diagram of the cross-sectional structure of the high-temperature steam-assisted foaming device of the present invention.

[0025] Figure 3 The image shows the microporous structure of the extruded microfoamed high-density polyethylene prepared in Example 1 using SEM.

[0026] Figure 4 The image shows the microporous structure of the extruded microfoamed high-density polyethylene prepared for Comparative Example 1, as shown in the SEM image. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0028] The raw materials used in the following specific embodiments are all purchased from the market. Specifically, the high-density polyethylene is high-density polyethylene material produced by Yanshan Petrochemical and Saudi Basic Industries Corporation. The expanded microspheres are expanded microspheres of the Expansionl series produced by Noryon. The interface compatibilizer is maleic anhydride-grafted polyethylene PE-g-MAH series, acrylic compound-grafted polyethylene PAA-g-PE series, or acrylic compound-grafted metallocene ethylene-1-octene copolymer PAA-g-MAH series. The hindered phenolic antioxidant 1010 or phosphite antioxidant 168 is used. The UV stabilizer includes 2-hydroxy-4-n-octyloxybenzophenone UV531.

[0029] The apparatus and basic preparation process of extruded micro-foamed high-density polyethylene are as follows: An apparatus for extruding micro-foamed high-density polyethylene, such as Figure 1 As shown, it includes a screw extrusion unit 1 and a steam-assisted foaming unit 6; the cross-section of the steam-assisted foaming unit 6 is shown in the figure. Figure 2 As shown, it is connected to the extrusion die 5 of the screw extrusion device and is equipped with a steam inlet A1 and a steam outlet A2.

[0030] In the preparation of micro-foamed high-density polyethylene, the mixture 4 enters the extrusion screw 3 from the feed port 2, is melt-mixed and extruded from the extrusion die 5, and is immersed in the steam-assisted foaming device. High-temperature steam enters from the steam inlet A1 and leaves through the steam outlet A2, acting on the molten mixture to promote secondary foaming and obtain the extruded micro-foamed high-density polyethylene material 7.

[0031] Example 1 Step 1: Weigh 60 parts by weight of high-density polyethylene powder, 20 parts by weight of recycled high-density polyethylene, 10 parts by weight of dry unexpanded microspheres Expansionl 950 DU80, 6 parts by weight of attapulgite clay, 1 part by weight of color masterbatch, 2 parts by weight of interface compatibilizer (PAA-g-PE), 0.5 parts by weight of antioxidant 1010, and 0.5 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a T-type extrusion die with a width of 20 cm and a thickness of 3 cm, and control the melt temperature in the extruder to around 130°C to extrude and obtain a molten mixture; after the molten mixture leaving the die is foamed with 180°C high-temperature steam, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0032] The microstructure of the extruded microfoamed high-density polyethylene material prepared in this embodiment is shown in the SEM image. Figure 3 As shown, the bubbles are uniform, and the material density is 0.68 g / cm³. 3The static bending strength was tested according to GB / T 9341-2008 and was 11.6 MPa.

[0033] Example 2 Step 1: Weigh approximately 85 parts by weight of high-density polyethylene granules, 5 parts by weight of wet-type unexpanded microspheres Expansionl921 WE40, 5 parts by weight of calcium carbonate, 2 parts by weight of color masterbatch, 2 parts by weight of interface compatibilizer (PE-g-MAH), 0.4 parts by weight of antioxidant 168, and 0.6 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a round extrusion die with a diameter of 1cm, control the melt temperature in the extruder to around 115℃ for extrusion processing to obtain a molten mixture, and then subject the molten mixture leaving the die to 200℃ high-temperature steam-assisted foaming, cool and shape, dry, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0034] The extruded microfoamed high-density polyethylene prepared in this embodiment has a density of 0.74 g / cm³. 3 Its static bending strength is 14.8 MPa.

[0035] Example 3 Step 1: Weigh approximately 70 parts by weight of recycled high-density polyethylene, 15 parts by weight of dry expanded microspheres Expansionl 920DU 40, 10 parts by weight of barium carbonate, 1 part by weight of color masterbatch, 1 part by weight of interface compatibilizer (PAA-g-POE), 1 part by weight of antioxidant 1010, and 2 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 3: Add the premix to the extruder, using a T-shaped extrusion die with a width of 50 cm and a thickness of 10 cm. Control the melt temperature in the extruder to around 160°C for extrusion processing to obtain a molten mixture. After the molten mixture leaving the die is foamed with 160°C high-temperature steam-assisted foaming, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0036] The extruded microfoamed high-density polyethylene prepared in this embodiment has a density of 0.75 g / cm³. 3 The static bending strength is 12.5 MPa.

[0037] Example 4 Step 1: Weigh approximately 68 parts by weight of recycled high-density polyethylene, 10 parts by weight of high-density polyethylene powder, 12 parts by weight of dry expanded microspheres Expansionl 920 DU 120, 7 parts by weight of barium carbonate, 1 part by weight of color masterbatch, 1 part by weight of interface compatibilizer (PAA-g-PE), 0.5 parts by weight of antioxidant 168, and 0.5 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, using a T-shaped extrusion die with a width of 10 cm and a thickness of 2 cm. Control the melt temperature in the extruder to around 135°C for extrusion processing to obtain a molten mixture. After the molten mixture leaving the die is foamed with 200°C high-temperature steam-assisted foaming, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0038] The extruded microfoamed high-density polyethylene prepared in this embodiment has a density of 0.65 g / cm³. 3 Its static bending strength is 11.9 MPa.

[0039] Comparative Example 1 Step 1: Weigh approximately 70 parts by weight of high-density polyethylene powder, 20 parts by weight of recycled high-density polyethylene, 6 parts by weight of attapulgite, 1 part by weight of color masterbatch, 2 parts by weight of interface compatibilizer (PAA-g-PE), 0.5 parts by weight of antioxidant 1010, and 0.5 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a T-type extrusion die with a width of 20 cm and a thickness of 3 cm, and control the melt temperature in the extruder to around 130°C to extrude and obtain a molten mixture; after the molten mixture leaving the die is foamed with 180°C high-temperature steam, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0040] The extruded microfoamed high-density polyethylene prepared in this embodiment has no obvious pores, and its microstructure is as follows: Figure 4 It has a high density, and since no expanded microspheres were added, there was no significant weight reduction effect; the density is 0.92 g / cm³. 3 Its static bending strength is 13.8 MPa.

[0041] Comparative Example 2 Step 1: Weigh approximately 60 parts by weight of high-density polyethylene powder, 20 parts by weight of recycled high-density polyethylene, 10 parts by weight of dry unexpanded microspheres Expansion 950 DU80, 6 parts by weight of attapulgite clay, 1 part by weight of color masterbatch, 2 parts by weight of interface compatibilizer (PAA-g-PE), 0.5 parts by weight of antioxidant 1010, and 0.5 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a T-type extrusion die with a width of 20 cm and a thickness of 3 cm, and control the melt temperature in the extruder to around 130°C to extrude and obtain a molten mixture; the molten mixture leaves the die and foams freely, cools and solidifies, and is cut to obtain extruded micro-foamed high-density polyethylene material.

[0042] The extruded micro-foamed high-density polyethylene prepared in this embodiment has uniform cell structure, but since it did not undergo high-temperature steam-assisted foaming, its density remains relatively high, and the foaming effect is not significant, with a density of 0.88 g / cm³. 3 There was no significant weight reduction effect, and the static bending strength was 13.1 MPa.

[0043] Comparative Example 3 Step 1: Weigh approximately 66 parts by weight of high-density polyethylene powder, 20 parts by weight of recycled high-density polyethylene, 10 parts by weight of dry unexpanded microspheres Expansion 950 DU80, 1 part by weight of color masterbatch, 2 parts by weight of interface compatibilizer, 0.5 parts by weight of antioxidant, and 0.5 parts by weight of UV stabilizer, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a T-type extrusion die with a width of 20 cm and a thickness of 3 cm, and control the melt temperature in the extruder to around 130°C to extrude and obtain a molten mixture; after the molten mixture leaving the die is foamed with 180°C high-temperature steam, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0044] The extruded microfoamed high-density polyethylene prepared in this embodiment has uniform cell structure and a density of 0.62 g / cm³. 3 The static bending strength is 8.2 MPa, but without the addition of filler, the mechanical strength is relatively low.

[0045] Comparative Example 4 Step 1: Weigh 60 parts by weight of high-density polyethylene powder, 20 parts by weight of recycled high-density polyethylene, 10 parts by weight of dry unexpanded microspheres Expansionl 950 DU80 (expansion temperature of this series of products is 136-200℃), 6 parts by weight of attapulgite, 1 part by weight of color masterbatch, 2 parts by weight of interface compatibilizer (PAA-g-PE), 0.5 parts by weight of antioxidant 1010, and 0.5 parts by weight of UV stabilizer UV531, and mix them evenly to obtain a premix. Step 2: Add the premix to the extruder, select a T-type extrusion die with a width of 20 cm and a thickness of 3 cm, and control the melt temperature in the extruder to around 130°C to extrude and obtain a molten mixture; after the molten mixture leaving the die is foamed with 80°C high-temperature steam, it is cooled, shaped, dried, and cut to obtain extruded micro-foamed high-density polyethylene material.

[0046] Because the steam temperature is lower than the expansion temperature of the microspheres, the extruded microfoamed high-density polyethylene material prepared in this embodiment has no obvious cell structure and a material density of 0.90 g / cm³. 3 The static bending strength is 13.1 MPa.

[0047] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing extruded micro-foamed high-density polyethylene, characterized in that, Including the following steps: Step 1: Mix the raw materials containing high-density polyethylene, expanded microspheres, fillers, and interfacial compatibilizers to obtain a premix; Step 2: After drying the premix, it is melt-blended and extruded. The molten mixture leaving the die is foamed with the aid of high-temperature steam, cooled and shaped, dried and cut to obtain the extruded micro-foamed high-density polyethylene. The raw materials, by weight, include: 65-95 parts high-density polyethylene, 3-15 parts expanded microspheres, 1-15 parts filler, and 1-3 parts interface compatibilizer; The high-temperature steam-assisted foaming process involves foaming a molten mixture by passing it through an extrusion channel continuously supplied with high-temperature steam. The high-temperature steam is saturated water vapor with a temperature of 85-230 ℃ and an absolute pressure of 57.88-2798.59 kPa.

2. The method for preparing extruded micro-foamed high-density polyethylene according to claim 1, characterized in that, The expanded microspheres are at least one of the following: dry unexpanded microspheres, dry expanded microspheres, wet unexpanded microspheres, and wet expanded microspheres.

3. The method for preparing extruded micro-foamed high-density polyethylene according to claim 1, characterized in that, The expanded microspheres are Norinon's Expanded Microspheres Expansionl.

4. The method for preparing extruded micro-foamed high-density polyethylene according to claim 1, characterized in that, The filler includes at least one of the following: talc, attapulgite, calcium carbonate, modified wollastonite, carbon black, boron nitride, aluminum nitride, alumina, diatomaceous earth, zirconium phosphate, montmorillonite, activated clay, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, kaolin, glass powder, and silicon dioxide. The interface compatibilizer includes at least one of maleic anhydride-grafted polyethylene, acrylic compound-grafted polyethylene, or acrylic compound-grafted metallocene ethylene-1-octene copolymer.

5. The method for preparing extruded micro-foamed high-density polyethylene according to claim 1, characterized in that, The raw materials also include one or more additives selected from pigments, UV stabilizers, and antioxidants, with each additive used in an amount of 0.1-5 parts.

6. The method for preparing extruded micro-foamed high-density polyethylene according to claim 5, characterized in that, The pigment includes at least one of masterbatch, carbon black, titanium dioxide, iron oxide red, or iron oxide yellow; The UV stabilizer includes 2-hydroxy-4-n-octyloxybenzophenone UV531; The antioxidant includes at least one of hindered phenolic antioxidant 1010 and phosphite antioxidant 168.

7. The method for preparing extruded microfoamed high-density polyethylene according to claim 1, characterized in that, The temperature of the melt blending is 110-160℃; the die for the melt blending extrusion is one of a strip die, a T-die, a round die, or a tubular die.

8. The extruded microfoamed high-density polyethylene prepared by the preparation method according to any one of claims 1-7, characterized in that, The density of the extruded micro-foamed high-density polyethylene is 0.50~0.80 g / cm³. 3 The static bending strength is above 9.5 MPa.

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