EPP foamed bead, preparation method thereof and molded part

Abstract

The invention relates to the technical field of foaming materials, in particular to EPP foamed beads, a preparation method thereof and a molded part, and the preparation method of the EPP foamed beads comprises the following steps: preparing polypropylene pre-foamed particles from a raw material containing a friction-resistant master batch; wherein the friction-resistant master batch is prepared from the following raw materials in parts by weight: 100 parts of polypropylene; 5-15 parts of an inorganic filler; 20 to 40 parts of ethylene bis stearamide; and preparing the EPP foamed beads by taking the polypropylene pre-foamed particles as a raw material and octadecanamide as an activating agent. The friction-resistant master batch is introduced into the raw materials, and the activator octadecanamide in the preparation process of the EPP foamed beads is further combined to induce the inorganic filler in the friction-resistant master batch to be arranged outside the EPP foamed beads, so that the friction resistance of the EPP foamed beads can be improved.

Description

Technical Field

[0001] This invention relates to the field of foamed materials technology, and in particular to an EPP foamed bead, its preparation method, and its molded parts. Background Technology

[0002] EPP (expanded polypropylene) possesses characteristics such as lightweight, impact resistance, heat resistance, chemical corrosion resistance, energy absorption and cushioning, and 100% recyclability, perfectly meeting the comprehensive requirements of energy storage batteries in scenarios such as in-plant turnover, cross-warehouse transportation, and export sea freight for "drop protection, shock resistance, heat insulation, weight reduction, and environmental protection." Compared with metal pallets, EPP pallets can significantly reduce weight, facilitating manual handling and automated loading and unloading; compared with wooden pallets, EPP is nail-free, shaving-free, recyclable, hygienic, and poses a lower risk of secondary damage to the battery casing and electrical connection points.

[0003] While foam pallets are experiencing rapid growth in the energy storage market, their inherent problems have increased the cost of use in certain situations. Due to the high coefficient of friction of EPP material, there will be friction between it and the products it contacts. This friction generates significant dust, which can contaminate the surface of the internal battery cells, causing dirt buildup and increasing the need for manual cleaning. In severe cases, it can even affect the subsequent assembly and use of the battery cells.

[0004] Commonly, manufacturers will spray lubricants (such as mold release agents, which are effective and significantly improve friction-induced powdering, but during transportation, they can migrate to the surface of the battery cell due to friction, producing oily substances that contaminate and corrode the battery cell) or perform heat coating on the surface of the molded parts, such as coating with non-woven fabric. Although this can completely eliminate friction-induced powdering, it greatly increases the labor and material costs of production. Moreover, since the process is a secondary processing step, the yield of the finished product also decreases, and the production cycle also increases.

[0005] Therefore, improving the friction resistance of EPP materials is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the problem of poor friction resistance of EPP materials in existing technologies, this invention provides a method for preparing EPP foamed beads. The EPP foamed beads prepared by this method do not require secondary processing and can improve friction resistance by utilizing their own properties, thus solving the problem of poor friction resistance of EPP materials in existing technologies.

[0007] The technical solution adopted by this invention to solve its technical problem is: A method for preparing EPP foamed beads includes the following steps: S1: Prepare polypropylene pre-foamed microparticles using raw materials containing abrasion-resistant masterbatch; The raw materials of the abrasion-resistant masterbatch, by weight, include the following components: 100 parts of polypropylene; 5-15 parts of inorganic filler; 20-40 parts of ethylene bis-stearamide; S2: Using the pre-foamed polypropylene microparticles as raw materials and stearamide as an activator, EPP foamed beads are prepared.

[0008] Optionally, the inorganic filler is talc.

[0009] Optionally, the talc powder is activated talc powder; the activated talc powder is prepared by the following method: heating the talc powder to 100-150℃, and spraying a maleic anhydride alcohol solution onto the heated talc powder under vibration conditions to obtain activated talc powder.

[0010] Optionally, the talc powder has a particle size of 5-10 μm.

[0011] Optionally, the mass concentration of maleic anhydride in the maleic anhydride alcohol solution is 1%.

[0012] Optionally, the amount of maleic anhydride alcohol solution sprayed is 5‰ of the mass of the talc powder.

[0013] Optionally, in step S2, during the preparation of EPP foamed beads, butter is used as an interfacial tension modifier, water as a dispersant, and kaolin powder as an anti-caking agent.

[0014] Optionally, in step S2, the mass ratio of the polypropylene pre-foamed microparticles, the water, the kaolin, the butter, and the stearamide is 100:300:1:1:(2-4).

[0015] Optionally, the polypropylene pre-foamed microparticles have a core-shell structure, including a core layer and a skin layer covering the outside of the core layer; The raw material of the core layer comprises the following components in parts by weight: 100 parts of polypropylene; 1-2 parts of the abrasion-resistant masterbatch; 3-5 parts of dispersant masterbatch; The raw material of the leather layer comprises the following components in parts by weight: 100 parts of polypropylene; 30-50 parts of polyolefin elastomer; The abrasion-resistant masterbatch is 20-30 parts.

[0016] Optionally, the raw materials of the dispersant masterbatch, by weight, include the following components: 100 parts of polypropylene; 20-40 parts of ethylene bis-stearamide; Antioxidant 2-8 parts; 0.5-1.5 parts of anti-UV aging agent.

[0017] Optionally, the polypropylene has a melting point of 140-145°C and a melt index of 8-10 g / 10min.

[0018] Optionally, the melt index of the polyolefin elastomer is 2-5 g / 10min.

[0019] Optionally, the ethylene content in the polyolefin elastomer is 10-15% by mass.

[0020] Another object of the present invention is to provide an EPP foamed bead, which is prepared by the EPP foamed bead preparation method described above.

[0021] Another object of the present invention is to provide a molded part prepared by steam molding of EPP foam beads as described above.

[0022] The beneficial effects of this invention are: The method for preparing EPP foam beads provided by the present invention, through the introduction of abrasion-resistant masterbatch into the raw materials, and further combined with stearamide, an activator in the EPP foam bead preparation process, induces the inorganic fillers in the abrasion-resistant masterbatch to arrange to the outside of the EPP foam beads, thereby improving the abrasion resistance of the EPP foam beads. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Figure 1 This is a schematic diagram of the structure of the EPP foamed beads in this invention. Detailed Implementation

[0025] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] To address the problem of poor abrasion resistance of EPP materials in existing technologies, this invention provides a method for preparing EPP foamed beads, which includes the following steps: S1: Prepare polypropylene pre-foamed microparticles using raw materials containing abrasion-resistant masterbatch; Preferably, in this step, polypropylene pre-foamed microparticles are prepared by extrusion using raw materials containing abrasion-resistant masterbatch; to improve the abrasion resistance of the material, the present invention preferably includes the following components by weight parts: 100 parts of polypropylene; 5-15 parts of inorganic filler; 20-40 parts of ethylene bis-stearamide; Specifically, the preferred abrasion-resistant masterbatch of the present invention is prepared according to the following method: According to the formula, polypropylene, inorganic filler, and EBS (ethylene bis-stearamide) are blended by twin screw extruder (temperature 180-200℃), extruded and granulated to prepare abrasion-resistant masterbatch for polypropylene. The preferred granulation length is 5mm and the weight is 50mg. Furthermore, the raw materials of the preferred abrasion-resistant masterbatch of the present invention, by weight, comprise the following components: 100 parts of polypropylene; 10 parts of inorganic filler; 10 parts of ethylene bis-stearamide; Inorganic fillers are introduced into the friction-resistant masterbatch to improve the friction resistance of the material. S2: EPP foam beads are prepared using pre-foamed polypropylene microparticles as raw materials and stearamide as an activator. Preferably, this step uses a carbon dioxide autoclave foaming process to prepare EPP foamed beads, and further preferably, the heating temperature is 142-145℃, the foaming pressure is 2.0-2.9MPa, and the foaming density is 30-50g / L. In the preferred embodiment of the present invention, the melting point of stearamide in step S2 is 105-110℃.

[0027] In step S2, by using stearamide as an activator, the surface of the beads can be softened in advance during the heating process, inducing the inorganic filler to align outward, thereby improving the product's abrasion resistance.

[0028] The method for preparing EPP foam beads provided by the present invention, through the introduction of abrasion-resistant masterbatch into the raw materials, and further combined with stearamide, an activator in the EPP foam bead preparation process, induces the inorganic fillers in the abrasion-resistant masterbatch to arrange to the outside of the EPP foam beads, thereby improving the abrasion resistance of the EPP foam beads.

[0029] Furthermore, since stearamide is used as an activator in this invention, it can not only fix the inorganic filler inside the PP body and improve the product dispersion uniformity, thereby improving the product's friction resistance, but also help to reduce the amount of inorganic filler inside the material matrix while ensuring friction resistance, thereby improving its friction resistance without damaging the material's mechanical properties.

[0030] Furthermore, the inorganic filler preferred in this invention is talc powder.

[0031] To improve the compatibility of talc in the system, the present invention preferably uses activated talc; more preferably, the activated talc is prepared by the following method: heating the talc to 100-150°C, preferably to 120°C, and spraying a maleic anhydride (PP-g-MAH) alcohol solution onto the heated talc under vibration conditions to obtain activated talc.

[0032] The talc powder preferred in this invention is ultrafine talc powder, specifically, the particle size of the talc powder is preferably 5-10 μm.

[0033] The preferred form of the maleic anhydride alcohol solution of the present invention is a methanol or ethanol solution of maleic anhydride (PP-g-MAH); specifically, the mass concentration of maleic anhydride in the maleic anhydride alcohol solution is preferably 1%.

[0034] The present invention further preferably uses a spraying amount of maleic anhydride alcohol solution of 5‰ of the mass of talc powder.

[0035] Specifically, the activated talc powder in this invention can be prepared according to the following method: According to the formula, heat the talc powder to 100-150℃, preferably to 120℃, and spray it with a 1% (w / w) alcohol (ethanol or methanol) solution of maleic anhydride (PP-g-MAH) while it is being vibrated uniformly through a powder vibrating screen. The spraying amount is 5‰ of the pretreated powder mass. After spraying, vibrate continuously for 20 minutes to complete the activation treatment of the powder, and store it in a waterproof and light-proof place.

[0036] In a further preferred embodiment of the present invention, during the preparation of EPP foamed beads in step S2, butter is used as an interfacial tension regulator, water as a dispersant, and kaolin powder as an anti-caking agent. In step S2, the mass ratio of polypropylene pre-foamed microparticles, water, kaolin, butter, and stearamide is preferably 100:300:1:1:(2-4).

[0037] Specifically, step S2 in this invention can be performed as follows: EPP foamed beads were prepared using a carbon dioxide autoclaving process, with pre-foamed polypropylene microparticles as raw material, water as dispersant, kaolin powder as anti-caking agent, butter as interfacial tension modifier, and stearamide (melting point 105-110℃) as surface activator. The heating temperature was 142-145℃, the foaming pressure was 2.0-2.9MPa, and the foaming density was 30-50g / L.

[0038] To balance the friction resistance and mechanical properties of EPP material, this invention preferably uses pre-foamed polypropylene microparticles with a core-shell structure, including a core layer and a skin layer covering the outside of the core layer. The core layer material comprises the following components by weight: 100 parts of polypropylene; 1-2 parts of abrasion-resistant masterbatch; 3-5 parts of dispersant masterbatch; By weight, the raw material of the hide layer includes the following components: 100 parts of polypropylene; 30-50 parts of polyolefin elastomer; 20-30 parts of abrasion-resistant masterbatch.

[0039] The core-shell structured polypropylene pre-foamed microparticles in this invention can be prepared according to the following method: A co-extrusion process was used to prepare abrasion-resistant polypropylene pre-foamed microparticles with a core-shell structure, wherein the skin layer accounts for 10-20% of the mass and the core layer accounts for 80-90% of the mass, and the extrusion temperature is controlled at 200-230℃; the pre-foamed microparticles are prepared with a granulation length of 2mm and a weight of 1.2mg.

[0040] Specifically, the raw materials of the dispersant masterbatch preferably include the following components by weight: 100 parts of polypropylene; 20-40 parts of ethylene bis-stearamide; Antioxidant 2-8 parts; 0.5-1.5 parts of anti-UV aging agent.

[0041] The antioxidant preferred in this invention is antioxidant 1010, and the UV aging resistant agent is UV 326; and more preferably, the raw materials of the dispersant masterbatch, by weight, include the following components: 100 parts of polypropylene; 30 parts of ethylene bis-stearamide; 5 parts antioxidant; One part of anti-UV aging agent.

[0042] The dispersant masterbatch in this invention can be prepared according to the following method: According to the formula, polypropylene, EBS (ethylene bis-stearamide), antioxidant 1010, and UV aging resistant agent UV326 are blended by twin screw extruder (temperature 180-200℃), extruded and granulated to prepare dispersant masterbatch with a granulation length of 5mm and a weight of 50mg.

[0043] In this invention, it is preferred that all polypropylene types selected herein are the same, and specifically preferred that the polypropylene has a melting point of 140-145℃ and a melt index of 8-10 g / 10min (test conditions: 230℃ / 2.16kg).

[0044] This invention designs pre-foamed polypropylene microparticles with a core-shell structure and introduces a polyolefin elastomer into the skin layer. In step S2, during the preparation of EPP foamed beads, stearamide softens the bead skin layer in advance during the heating process. See [link to relevant documentation]. Figure 1 As shown, while inducing inorganic talc to align outwards, it also helps promote the formation of a certain "sea-island" structure between the polyolefin elastomer and talc on the outer side of the skin, thereby comprehensively improving the product's friction resistance.

[0045] Specifically, the melt index of the polyolefin elastomer in this invention is preferably 2-5 g / 10min (test conditions: 230°C / 2.16kg), and the mass content of ethylene in the polyolefin elastomer is preferably 10-15%.

[0046] Another object of the present invention is to provide an EPP foamed bead prepared by the EPP foamed bead preparation method described above.

[0047] The EPP foam beads provided by this invention do not require additional processing when molding energy storage turnover pallets. Due to their inherent characteristics, the product can greatly reduce friction during transportation, thereby increasing the transportation distance and overall service life of the product.

[0048] Another object of the present invention is to provide a molded part prepared by steam molding of EPP foamed beads as described above.

[0049] Specifically, the molded part can be prepared according to the following process: The EPP foamed beads prepared above are fully cured, dehydrated, and replaced with air. They are then pre-compressed in a pressure tank (the compressed gas is air, the pre-compression pressure is 0.2-0.35 MPa, and the pre-compression time is 8-15 h). The beads are then molded in an EPP steam molding machine, and the molded parts are baked to set their shape.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0051] Unless otherwise specified, the polypropylene in all embodiments and comparative examples of this invention has a melting point of 142°C and a melt index of 8 g / 10 min (test conditions: 230°C / 2.16 kg); the polyolefin elastomer has a melt index of 5 g / 10 min (test conditions: 230°C / 2.16 kg) and an ethylene content of 15%; and the stearamide has a melting point of 110°C.

[0052] Unless otherwise specified, the abrasion-resistant masterbatches in the embodiments and comparative examples of this invention are prepared according to the following method: Based on the weight percentages, 100 parts of polypropylene, 10 parts of activated talc, and 10 parts of EBS (ethylene bis-stearamide) were selected and blended by twin-screw extrusion (temperature 190℃) and granulated to prepare a friction-resistant masterbatch with a granulation length of 5 mm and a weight of 50 mg. The activated talc powder is prepared according to the following method: Ultrafine talc powder (particle size 5-10μm) was selected, heated to 120℃, and sprayed with a 1% maleic anhydride (PP-g-MAH) ethanol solution while being uniformly vibrated through a powder vibrating screen. The spraying amount was 5‰ of the pretreated powder mass. After spraying, the powder was continuously vibrated for 20 minutes to complete the activation treatment, and then stored in a waterproof and light-proof environment to obtain activated talc powder.

[0053] Unless otherwise specified, the dispersant masterbatch in each embodiment and comparative example of the present invention was prepared according to the following method: Based on the weight percentages, 100 parts of polypropylene, 30 parts of EBS (ethylene bis-stearamide), 5 parts of antioxidant 1010, and 1 part of UV aging resistant agent UV326 were selected and mixed by twin-screw extrusion (temperature 190℃) and granulated to prepare a dispersant masterbatch with a granulation length of 5 mm and a weight of 50 mg.

[0054] Unless otherwise specified, the molded parts in the embodiments and comparative examples of this invention are prepared according to the following method: S1: Preparation of polypropylene pre-foamed microparticles: Polypropylene pre-foamed microparticles with a core-shell structure were prepared by co-extrusion process. The raw materials of the core layer and the proportion of the skin layer are shown in Table 1. The extrusion temperature was controlled at 200-230℃. The granulation length was 2 mm and the weight was 1.2 mg. S2: Preparation of EPP foamed beads: The beads were prepared by carbon dioxide autoclaving process using polypropylene pre-foamed microparticles as raw material, water as dispersant, kaolin powder as anti-caking agent, butter as interfacial tension modifier, and stearamide as bead skin activator. The amount of polypropylene pre-foamed microparticles added was 100 parts by weight, water was 300 parts, kaolin was 1 part, and butter was 1 part. The amount of skin activator added, foaming temperature, foaming pressure, and foaming density are shown in Table 1. S3: Preparation of surface abrasion resistant polypropylene foamed molded parts: The EPP foamed beads prepared above are fully cured, dehydrated and replaced with air, and then pre-pressed in a pressure tank (the compressed gas is air, the pre-pressing pressure is shown in Table 1, and the pre-pressing time is 8-15 hours). The parts are then molded by an EPP steam molding machine. After baking and shaping, the molded parts are obtained.

[0055] The properties of the prepared molded parts were tested using the following methods: Product shrinkage rate: Product shrinkage rate = (mold size - drying size) / mold size * 100%.

[0056] 10% compressive strength: Tested in accordance with GB / T 8813-2020 "Rigid Foamed Plastics - Determination of Compressive Properties".

[0057] Surface hardness: Press test was performed using a Shore hardness tester.

[0058] Friction Test Method: Using 2000-grit standard sandpaper, the surface of the EPP sample is rubbed back and forth under dry conditions. A fixed load (1200g weight) is applied during friction, and the number of rubs and speed must be standardized (e.g., 43.1 times per minute, 57.2 mm stroke). After the test, the grade is assessed by visually comparing the staining on the rubbing cloth or by measuring the area of ​​ink fading using a colorimeter. The grades are divided into four levels: A: No dust or powder appears on the sandpaper surface, and the friction surface of the part is not broken; B: Slight dust or powder appears on the sandpaper surface, and the friction surface of the part is not broken; C: Obvious dust or powder appears on the sandpaper surface, but the surface of the part is not severely broken; D: A lot of dust appears on the sandpaper surface, and the surface of the part is severely damaged by friction and cannot be used again.

[0059] The test results are shown in Table 1.

[0060] Table 1 Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing EPP foamed beads, characterized in that, Includes the following steps: S1: Prepare polypropylene pre-foamed microparticles using raw materials containing abrasion-resistant masterbatch; The raw materials of the abrasion-resistant masterbatch, by weight, include the following components: 100 parts of polypropylene; 5-15 parts of inorganic filler; 20-40 parts of ethylene bis-stearamide; S2: Using the pre-foamed polypropylene microparticles as raw materials and stearamide as an activator, EPP foamed beads are prepared.

2. The method for preparing EPP foamed beads as described in claim 1, characterized in that, The inorganic filler is talc.

3. The method for preparing EPP foamed beads as described in claim 2, characterized in that, The talc powder is activated talc powder; the activated talc powder is prepared by the following method: heating the talc powder to 100-150℃, and spraying maleic anhydride alcohol solution onto the heated talc powder under vibration conditions to obtain activated talc powder.

4. The method for preparing EPP foamed beads as described in claim 3, characterized in that, The talc powder has a particle size of 5-10 μm.

5. The method for preparing EPP foamed beads as described in claim 3, characterized in that, The maleic anhydride alcohol solution has a maleic anhydride mass concentration of 1%.

6. The method for preparing EPP foamed beads as described in claim 3, characterized in that, The amount of maleic anhydride alcohol solution sprayed is 5‰ of the mass of the talc powder.

7. The method for preparing EPP foamed beads as described in claim 1, characterized in that, In step S2, during the preparation of EPP foamed beads, butter was used as an interfacial tension regulator, water as a dispersant, and kaolin powder as an anti-caking agent.

8. The method for preparing EPP foamed beads as described in claim 7, characterized in that, In step S2, the mass ratio of the polypropylene pre-foamed microparticles, the water, the kaolin, the butter, and the stearamide is 100:300:1:1:(2-4).

9. The method for preparing EPP foamed beads according to any one of claims 1-8, characterized in that, The polypropylene pre-foamed microparticles have a core-shell structure, including a core layer and a skin layer covering the outside of the core layer. The raw material of the core layer comprises the following components in parts by weight: 100 parts of polypropylene; 1-2 parts of the abrasion-resistant masterbatch; 3-5 parts of dispersant masterbatch; The raw material of the leather layer comprises the following components in parts by weight: 100 parts of polypropylene; 30-50 parts of polyolefin elastomer; The abrasion-resistant masterbatch is 20-30 parts.

10. The method for preparing EPP foamed beads as described in claim 9, characterized in that, The raw materials of the dispersant masterbatch, by weight, include the following components: 100 parts of polypropylene; 20-40 parts of ethylene bis-stearamide; Antioxidant 2-8 parts; 0.5-1.5 parts of anti-UV aging agent.

11. The method for preparing EPP foamed beads as described in claim 10, characterized in that, The polypropylene has a melting point of 140-145℃ and a melt index of 8-10 g / 10min.

12. The method for preparing EPP foamed beads as described in claim 9, characterized in that, The melt index of the polyolefin elastomer is 2-5 g / 10min.

13. The method for preparing EPP foamed beads as described in claim 9, characterized in that, The polyolefin elastomer contains 10-15% ethylene by mass.

14. An EPP foamed bead, characterized in that, The EPP foamed beads are prepared by the method described in any one of claims 1-13.

15. A molded part, characterized in that, It is prepared by steam molding of EPP foamed beads as described in any one of claims 1-13.

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