Polyethylene composition and foam board thereof, and preparation method of foam board

Abstract

The invention relates to the technical field of compositions of high-molecular compounds, and particularly discloses a polyethylene composition, a foam board thereof and a preparation method of the foam board. The polyethylene composition is prepared from the following raw materials in parts by weight: 15 to 25 parts of high-density polyethylene, 25 to 35 parts of regenerated high-density polyethylene, 25 to 35 parts of regenerated low-density polyethylene, 5 to 15 parts of calcium carbonate master batch and 0.1 to 0.5 part of AC foaming agent. The polyethylene composition disclosed by the invention has the beneficial effects that the regenerated high-density polyethylene and the regenerated low-density polyethylene used in the polyethylene composition are both prepared by recovering waste polyethylene products; the material prepared from the polyethylene composition can meet the requirements of transportation packaging, advertisement display, temporary buildings and other use scenes where the requirements for the strength and flexibility of the polyethylene material are not very high, resource recycling is achieved, and resource waste and environmental pollution are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compound compositions, and in particular to a polyethylene composition and a foamed board thereof, and a method for preparing the foamed board. Background Art

[0002] High-density polyethylene foam board is a lightweight, high-strength board made of high-density polyethylene (HDPE) as the main raw material through physical or chemical foaming methods. HDPE itself has high rigidity and strength, but relatively low flexibility. When the HDPE content in the foam board is too high, the rigidity of the foam board may be enhanced, but the flexibility may decrease. Therefore, in order to meet the requirements for the flexibility of the foam board in some use environments, plasticizers are usually added to the high-density polyethylene foam board to improve the board performance.

[0003] Plasticizers are additives that can increase the softness, fluidity and processing properties of plastics. They are usually some high-boiling, non-volatile viscous liquids or low-melting solids, and usually do not react chemically with plastics. According to the chemical structure, plasticizers can be divided into many types, such as phthalates, fatty acid esters, phosphate esters, polyesters, epoxy esters and chlorine-containing compounds.

[0004] Foamed boards made from HDPE and plasticizers play an important role in industrial production, but their environmental protection and safety issues are also receiving increasing attention. Discarded HDPE foamed boards will occupy a large amount of land resources in landfill treatment, and due to their difficult-to-degrade properties, they will occupy landfill space for a long time; at the same time, discarded HDPE foamed boards may release plasticizers in the environment, which will be washed away by rainwater or directly discharged into the soil and water sources, causing pollution to the ecological environment. Some plasticizers are also believed to have environmental hormone effects and may cause potential harm to human health. Therefore, there is an urgent need for a reasonable reuse plan for discarded HDPE foamed boards to reduce their harm to the environment and human health. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a polyethylene composition, in which recycled high-density polyethylene and recycled low-density polyethylene are used, both of which are recycled materials obtained by recycling waste HDPE products and undergoing a series of processing. The material prepared by the polyethylene composition still maintains good strength and flexibility and can be suitable for some use environments.

[0006] The present invention is achieved through the following technical solutions: A polyethylene composition, whose raw material composition, measured by weight, comprises: 15-25 parts of high-density polyethylene, 25-35 parts of recycled high-density polyethylene, 25-35 parts of recycled low-density polyethylene, 5-15 parts of calcium carbonate masterbatch, and 0.1-0.5 parts of AC foaming agent.

[0007] As a further improvement of the present invention, the melt index of the high-density polyethylene is (0.23~0.25) g / 10min; the melt index of the recycled high-density polyethylene is (0.27~0.30) g / 10min; and the melt index of the recycled low-density polyethylene is (0.6~0.7) g / 10min.

[0008] As a further improvement of the present invention, the ash content of the recycled high-density polyethylene is 1-1.5%.

[0009] As a further improvement of the present invention, the calcium content of the calcium carbonate masterbatch is 50-55%.

[0010] As a further improvement of the present invention, the raw materials of the polyethylene composition further include: 1 to 4 parts of weather-resistant particles.

[0011] In a second aspect, the present invention provides a polyethylene foam board, which is prepared using any one of the polyethylene compositions described above.

[0012] In a third aspect, the present invention provides a method for preparing a polyethylene foam board, which is used to prepare the above-mentioned polyethylene foam board, and the specific steps include: S1. Raw material processing: vacuum low-temperature drying of each raw material; S2. Raw material mixing: The low-temperature dried raw materials are placed in a mixer according to the ratio for mixing; S3 extrusion foaming: the mixed mixture is transferred to a preheated extruder for extrusion; S4. Cooling and molding: Cooling and molding the extruded profile to obtain the polyethylene foam board.

[0013] As a further improvement of the present invention, in S1, the vacuum low-temperature drying temperature is 35-40°C and the duration is 4.5-5.5h.

[0014] As a further improvement of the present invention, in S2, the mixing speed is 60-70 r / min, and the mixing duration is 10-15 min.

[0015] As a further improvement of the present invention, in the extruder of S3, the barrel temperature is 175-180°C, the flange temperature is 170-175°C, and the mold temperature is 180-185°C.

[0016] The beneficial effects of the present invention include: (1) The recycled high-density polyethylene and recycled low-density polyethylene used in the polyethylene composition of the present invention are both made by recycling waste polyethylene products. The material prepared by using the polyethylene composition of the present invention can meet the needs of use scenarios such as transportation packaging, advertising display, and temporary buildings that do not require particularly high strength and flexibility of polyethylene materials, thereby achieving resource recycling and reducing resource waste and environmental pollution. (2) High-density polyethylene is a thermoplastic with good recyclability. It can be recycled by melt regeneration and reprocessed into new plastic products. This feature allows high-density polyethylene containing plasticizers to retain some plasticizers during the recycling process. Therefore, in the polyethylene foam board of the present invention, the plasticizers retained in the recycled high-density polyethylene can be reused.

[0017] At the same time, plasticizers such as DOP (dioctyl phthalate) may not be completely combined with the plastic matrix during the original high-density polyethylene material processing, but exist in a free state or microcapsule form, that is, some plasticizers are ineffective excess added components in the original high-density polyethylene material and are not fully utilized. However, under the material ratio of the present invention, such plasticizers can be reused, which makes it unnecessary to add additional plasticizers in the solution of the present invention to improve the flexibility of the material prepared from the polyethylene composition, thereby making the product itself and the production process more environmentally friendly; (3) The calcium carbonate filler masterbatch in the raw material of the present invention can play a lubricating role because the addition of calcium carbonate masterbatch can increase the hardness and rigidity of the material, improve the dimensional stability and surface finish of the product, and the improvement of the above performance also indirectly promotes the smooth extrusion of the sheet during the processing, thereby achieving a lubricating effect; (4) The raw materials of the present invention preferably also include weather-resistant particles. Specifically, the weather-resistant particles can be selected from ultraviolet absorbers, light stabilizers, antioxidants, etc., so that the composition obtained by the present invention can be applied to some fields that do not have high requirements for board strength and flexibility, but have requirements for anti-oxidation, yellowing resistance and other properties, thereby further improving the scope of application of the composition of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below based on implementation cases.

[0019] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in combination with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In this embodiment, the recycled high-density polyethylene and recycled low-density polyethylene are obtained by the following steps: S1. Collecting various types of waste polyethylene materials, such as plastic bottles, plastic bags, plastic pipes, etc.; S2. Classifying the collected waste polyethylene materials according to the type of polyethylene. Specifically, the raw materials used in this embodiment need to screen out waste materials in which high-density polyethylene and low-density polyethylene exist alone, and the classified waste materials are cleaned; S3. The classified and cleaned waste polyethylene are crushed separately to obtain corresponding recycled high-density polyethylene materials and recycled low-density polyethylene materials.

[0021] Embodiment 1: The present embodiment provides a polyethylene foam board, which uses a polyethylene composition prepared from the following raw materials in the following weight ratio: 15 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, and 0.5 parts of azodicarbonamide (AC foaming agent).

[0022] In this embodiment, the performance parameters of the recycled high-density polyethylene and recycled low-density polyethylene are required to meet the following requirements: the melt index of high-density polyethylene is 0.23g / 10min, the melt index of recycled high-density polyethylene is 0.27g / 10min, and the melt index of recycled low-density polyethylene is 0.7g / 10min; the ash content of high-density polyethylene is 0, and the ash content of recycled high-density polyethylene is 1.5%. At the same time, the calcium content of the calcium carbonate masterbatch used in this embodiment is 54%, and the gas evolution of the AC foaming agent is 150-170mL / g.

[0023] The polyethylene foam board is prepared by the following specific steps: S1. Raw material processing: high-density polyethylene, recycled high-density polyethylene, recycled low-density polyethylene, calcium carbonate masterbatch, AC foaming agent, and weather-resistant masterbatch are sent to a vacuum drying equipment for vacuum low-temperature drying at a temperature of 40°C and a duration of 5 hours; S2. Raw material mixing: put the low-temperature dried raw materials into a mixer for mixing, the mixing speed is 60 r / min, and the mixing time is 10min; S3. Extrusion foaming: The mixed raw materials are added to the preheated extruder for extrusion, the extruder barrel temperature is 175°C, the flange temperature is 170°C, and the mold temperature is 180°C; S4. Cooling and molding: The extruded profile is cooled and shaped by passing cooling water to obtain a polyethylene foam board.

[0024] Embodiment 2: The difference between this embodiment and embodiment 1 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 20 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, and 0.5 parts of azodicarbonamide (AC foaming agent).

[0025] Embodiment 3: The difference between this embodiment and embodiment 1 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 25 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, and 0.5 parts of azodicarbonamide (AC foaming agent).

[0026] Embodiment 4: The difference between this embodiment and Embodiment 1 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 25 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, 0.5 parts of azodicarbonamide (AC foaming agent), and 1 part of weather-resistant particles.

[0027] The weather-resistant particles used in this embodiment are nano-silicon dioxide, which can enhance the surface hardness and wear resistance of the polyethylene foam board and improve its anti-aging ability.

[0028] The weather-resistant particles are vacuum-dried at low temperatures in S1 together with other raw materials, and the remaining subsequent steps remain unchanged.

[0029] Embodiment 5: The difference between this embodiment and embodiment 4 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 25 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, 0.5 parts of azodicarbonamide (AC foaming agent), and 2 parts of weather-resistant particles.

[0030] Embodiment 6: The difference between this embodiment and embodiment 4 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 25 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, 0.5 parts of azodicarbonamide (AC foaming agent), and 3 parts of weather-resistant particles.

[0031] Embodiment 7: The difference between this embodiment and embodiment 4 is that this embodiment provides a polyethylene foam board, and the polyethylene composition used in the board is prepared from the following raw materials in the following weight ratio: 25 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, 0.5 parts of azodicarbonamide (AC foaming agent), and 4 parts of weather-resistant particles.

[0032] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example provides a polyethylene foam board, and the polyethylene composition used in the comparative example is prepared from the following raw materials in the following weight ratio: 10 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, and 0.5 parts of azodicarbonamide (AC foaming agent).

[0033] Comparative Example 2: The difference between the comparative example and Example 1 is that the comparative example provides a polyethylene foam board, and the polyethylene composition used in the comparative example is prepared from the following raw materials in the following weight ratio: 30 parts of high-density polyethylene, 30 parts of recycled high-density polyethylene, 30 parts of recycled low-density polyethylene, 10 parts of calcium carbonate masterbatch, and 0.5 parts of azodicarbonamide (AC foaming agent).

[0034] Comparative Example 3: This comparative example provides a foamed board prepared from brand-new high-density polyethylene, wherein the raw materials mainly include 80 parts of high-density polyethylene, 0.3 parts of azodicarbonamide (AC foaming agent), 1.5 parts of DOP (dioctyl phthalate) plasticizer, and 5 parts of weather-resistant particles.

[0035] Performance testing: The foamed boards in Examples 1 to 7 and Comparative Examples 1 to 3 were tested for performance parameters such as density, static bending strength, elastic modulus, minimum concentrated load, and aging resistance. The test steps for density, static bending strength, elastic modulus, and minimum concentrated load were performed in accordance with the steps described in "Wood Plastic Flooring" (GB / T 24508-2020), and the aging resistance test was performed using a 3000h xenon lamp aging test. The specific steps were performed in accordance with the steps described in "Plastics-Methods of exposure to laboratory lightsources Part 1: General guidance" (ISO 4892-1-2016). The test results are shown in Table 1: Table 1 Summary of foam board performance test results Among them, as shown in Table 1, the performance parameters of the high-density polyethylene foam board provided by Comparative Example 3 are the best. It has sufficient strength by using a large amount of high-density polyethylene material, and the high-density polyethylene foam board is finally able to achieve a balance between strength and flexibility by adding a plasticizer to modify the high-density polyethylene material, and thus has better static bending strength, elastic modulus and other properties.

[0036] As shown in Table 1, the density, static bending strength, elastic modulus and minimum concentrated load of the polyethylene foam board prepared according to the ratio and method described in Examples 1 to 7 are weaker than the performance parameters of the high-density polyethylene in Comparative Example 3, so that the various performance parameters of the foam board have reached the conventional physical performance requirements of the wood plastic floor recorded in the "Wood Plastic Floor" (GB / T 24508-2020), that is, the board density is ≥0.75g / cm 3 , static bending strength ≥ 14MPa, elastic modulus ≥ 2000MPa, minimum concentrated load ≥ 2200N. This shows that the polyethylene foam board uses a large amount of high-density polyethylene material but does not add plasticizer, and still achieves a certain balance between strength and flexibility, so that its performance can meet people's conventional use needs in some fields. Therefore, the inventor speculates that during the preparation process of the polyethylene foam board in Examples 1 to 7, the plasticizer that has been combined with the high-density polyethylene in the recycled high-density polyethylene and the plasticizer that exists in the form of free state are used here, so that the board not only meets the requirements in terms of strength, but also still has good performance in terms of flexibility.

[0037] However, it can be seen from the results of Comparative Examples 1 to 2 that the amount of new high-density polyethylene is also required. For Comparative Example 1, the inventor speculates that too little new high-density polyethylene is used, which leads to the failure of the static bending strength, i.e., the strength of the sheet, to meet the requirements. The test results of Comparative Example 2 show that too much new high-density polyethylene is used, which improves the static bending strength of the polyethylene foam board but reduces its elastic modulus. Therefore, the inventor speculates that after adding an excessive amount of new high-density polyethylene, the original plasticizer and low-density polyethylene can no longer play a good role and improve the flexibility of the foam board, that is, the balance between the strength and flexibility of the foam board is broken, which makes it difficult for the foam board to meet the corresponding use requirements.

[0038] At the same time, by comparing the xenon lamp aging ΔE values ​​of the polyethylene foam sheets in Examples 1 to 7, it can be found that after adding weather-resistant particles, the anti-aging ability of the polyethylene foam sheet material is significantly improved. Therefore, after adding relevant weather-resistant particles, some specific properties of the polyethylene foam sheet can be significantly improved, so that the foam sheet can be used in some specific fields, expanding the application range of the polyethylene foam sheet.

[0039] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A polyethylene composition, characterized in that The raw material composition thereof comprises, by weight, 15 to 25 parts of high-density polyethylene, 25 to 35 parts of recycled high-density polyethylene, 25 to 35 parts of recycled low-density polyethylene, 5 to 15 parts of calcium carbonate masterbatch, and 0.1 to 0.5 parts of AC foaming agent.

2. A polyethylene composition according to claim 1, characterized in that: The melt index of the high-density polyethylene is (0.23-0.25) g / 10min; the melt index of the recycled high-density polyethylene is (0.27-0.30) g / 10min; and the melt index of the recycled low-density polyethylene is (0.6-0.7) g / 10min.

3. A polyethylene composition according to claim 2, characterized in that: The ash content of recycled high-density polyethylene is 1~1.5%.

4. A polyethylene composition according to claim 1, characterized in that: The calcium content of the calcium carbonate masterbatch is 50-55%.

5. A polyethylene composition according to claim 1, characterized in that: The raw materials of the polyethylene composition also include: 1 to 4 parts of weather-resistant particles.

6. A polyethylene foam board, characterized in that: The polyethylene composition is prepared by using any one of claims 1 to 5.

7. A method for preparing a polyethylene foam board, characterized in that: For preparing a polyethylene foam board as claimed in claim 6, the specific steps include: S1. Raw material processing: vacuum low-temperature drying of each raw material; S2. Raw material mixing: The low-temperature dried raw materials are placed in a mixer according to the ratio for mixing; S3 extrusion foaming: the mixed mixture is transferred to a preheated extruder for extrusion; S4. Cooling and molding: cooling and molding the extruded profile to obtain the polyethylene composition.

8. The method for preparing a polyethylene foam board according to claim 7, characterized in that: In S1, the vacuum low-temperature drying temperature is 35-40°C and the duration is 4.5-5.5 h.

9. The method for preparing a polyethylene foam board according to claim 7, characterized in that: In S2, the mixing speed is 60~70 r / min, and the mixing duration is 10~15min.

10. The method for preparing a polyethylene foam board according to claim 7, characterized in that: In the extruder of S3, the barrel temperature is 175-180°C, the flange temperature is 170-175°C, and the mold temperature is 180-185°C.

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