阅读说明：本技术 一种高强度抗回缩微孔聚乙烯发泡珠粒(epe)的方法 (Method for preparing high-strength anti-retraction microcellular polyethylene (EPE) foam beads ) 是由 宫瑞英 孙德春 李朝旭 韩冲 杜庆霞 孙并臻 于 2019-08-22 设计创作，主要内容包括：本发明将常规适用于调控聚丙烯结晶行为的成核剂应用控制聚乙烯的结晶行为,公开了一种利用不同结晶行为控制组装,制备微孔聚乙烯发泡珠粒的方法：线性低密度聚乙烯作为主体树脂,用量20～95份；高密度聚乙烯或无规聚丙烯(熔点在130～150℃),用量10～45份；具有α结晶成核功能的无机成核剂、芳香羧酸盐类、山梨醇类等系列α结晶成核剂,总α结晶成核剂用量份0.05～5份；助剂1～15份。采用双螺杆挤出机挤出造粒。本发明生产时采用通过间歇式法,利用不同结晶成核剂协调层层组装结晶,将聚丙烯α结晶成核剂产生的增刚性变化、配合结晶的速度,结晶颗粒大小与发泡材料泡孔的成长固化过程进行灵活的结合,制备了性能良好抗回缩的微孔聚乙烯发泡珠粒。(The invention controls the crystallization behavior of polyethylene by applying a conventional nucleating agent which is suitable for regulating and controlling the crystallization behavior of polypropylene, and discloses a method for preparing microcellular polyethylene foamed beads by controlling and assembling different crystallization behaviors, which comprises the following steps: linear low-density polyethylene is used as main resin, and the using amount is 20-95 parts; 10-45 parts of high-density polyethylene or random polypropylene (the melting point is 130-150 ℃); inorganic nucleating agent with alpha crystal nucleation function, aromatic carboxylate, sorbitol and other series alpha crystal nucleating agents, wherein the dosage of the total alpha crystal nucleating agent is 0.05-5 parts; and 1-15 parts of an auxiliary agent. And extruding and granulating by adopting a double-screw extruder. In the production process, different crystallization nucleating agents are coordinated to assemble and crystallize layer by an intermittent method, and the rigidity increasing change generated by the polypropylene alpha crystallization nucleating agent is matched with the crystallization speed and the crystal particle size to be flexibly combined with the growth and solidification process of foam pores of a foaming material, so that the microporous polyethylene foamed beads with good performance and retraction resistance are prepared.)

1. A method of high strength anti-recoil microcellular polyethylene expanded beads (EPEs), comprising: the linear low-density polyethylene LDPE is used as main resin, and the using amount is 20-95 parts; 10-45 parts of high-density polyethylene (HDPE) or random polypropylene (melting point 130-150 ℃); the alpha crystal nucleating agent comprises 0.05-5 parts of inorganic nucleating agent with alpha crystal nucleating agent function, aromatic carboxylate of alpha crystal nucleating agent, sorbitol of alpha crystal nucleating agent and the like; and 1-15 parts of an auxiliary agent.

2. The linear low density polyethylene LDP, high density polyethylene HDPE melt flow index of claim 1 is from 0.3 to 10; the random polypropylene is a blend of one or more of binary or ternary copolymers of propylene, ethylene and 1-butene, the molecular weight distribution Mw/Mn of the copolymer is 2-20, and the melt flow index (190 ℃ and 2.16Kg) is 0.2-15 g/10 min.

3. The method of claim 1, wherein the alpha crystal nucleating agent comprises three or more of inorganic nucleating agents with alpha crystal nucleating function, aromatic carboxylates of alpha crystal nucleating agents, sorbitol alpha crystal nucleating agents, and the like, and the total amount of the alpha crystal nucleating agent is 0.05-5 parts.

4. The method of claim 1, wherein the method comprises the steps of: the auxiliary agent is one or more of a foaming nucleating agent, an antioxidant, an antistatic agent, a flame retardant, color master batch and a coupling agent. The dosage of the auxiliary agent is 1-15 parts.

5. A method of high strength anti-retraction cellular polyethylene expanded beads (EPEs) according to claim 1, characterized in that: the foaming nucleating agent in the auxiliary agent of claim 4 is at least one of talcum powder, mica, glass beads, silicon dioxide, calcium carbonate, montmorillonite, kaolin, alumina, barium sulfate, zinc oxide, zinc stearate and calcium stearate; the antioxidant is at least one of antioxidants 168, 1010, 1076 and 626; the antistatic agent is alkyl imidazoline, quaternary phosphonium salt, quaternary sulfur salt, quaternary ammonium salt, alkyl sulfonate or phosphate; the flame retardant is one or more of magnesium hydroxide, aluminum hydroxide, zinc borate and intumescent flame retardant DTPB; the coupling agent is one or more of silane coupling agent, titanate coupling agent and aluminate coupling agent.

6. A method of high strength anti-retraction cellular polyethylene expanded beads (EPE) according to any of claims 1 to 5, characterized in that: the method comprises the following steps:

(1) 20-95 parts of linear Low Density Polyethylene (LDPE); 10-45 parts of high-density polyethylene (HDPE) or random polypropylene (melting point 130-150 ℃); the alpha crystal nucleating agent comprises 0.05-5 parts of inorganic nucleating agent with alpha crystal nucleating agent function, aromatic carboxylate of alpha crystal nucleating agent, sorbitol of alpha crystal nucleating agent and the like; and 1-15 parts of an auxiliary agent. Fully compounding by a high-speed mixer, extruding, water-cooling, bracing and granulating by a double screw to obtain modified polyethylene small particles with the length of 1-2 mm and the diameter of 0.5-2 mm; ,

(2) putting polyethylene particles, a dispersing agent and water into an autoclave, injecting a physical foaming agent into the autoclave under a stirring condition, simultaneously raising the temperature of the autoclave to 95-130 ℃, raising the pressure to 2.0-5.0 MPa, and keeping for 20-60 min after the set temperature and pressure are reached so that the foaming agent permeates into the polyethylene particles;

(3) the pressure of the high-pressure kettle can be controlled to be released, and the polyethylene particle-high-pressure water dispersion mixed material is sprayed into a cold water cooling system to obtain foamed beads with the foaming ratio of 2-30 times; in order to obtain polypropylene expanded beads with higher expansion ratio, the primarily obtained expanded beads need to be subjected to pressure release in a secondary foaming device under the condition of controlling the pressure of 0.1-1.5 MPa for 5-60 s in a steam atmosphere, so as to further obtain expanded beads with higher expansion ratio, wherein the expansion ratio is 15-60 times.

(4) And drying the prepared polyethylene foamed beads for 10-48 hours in an environment of 30-60 ℃, injecting the dried polyethylene foamed beads into steam compression molding equipment, heating by steam, and cooling to obtain a polyethylene foamed bead molding body.

7. The method of claim 6, wherein the dispersant is one or more of kaolin, sodium dodecylbenzenesulfonate, aluminum sulfate, calcium carbonate, barium sulfate, and aluminosilicate.

8. The method of claim 6, wherein the physical blowing agent is one or both of carbon dioxide and nitrogen.

9. The method according to claim 6, wherein in the step (4), the pressure release rate of the autoclave is 0.3 to 2.0MPa/s, and the cooling rate of the polypropylene particle-water dispersion mixture is 20 to 40 ℃/s.

Technical Field

The invention relates to a method for preparing high-strength anti-retraction microporous polyethylene expanded beads (EPE), which belongs to the field of high polymer modification processing. According to the invention, different crystallization nucleating agents are coordinated to assemble and crystallize layer by layer through an intermittent or continuous physical foaming method, the rigidity increasing variation generated by the polypropylene alpha crystallization nucleating agent is matched with the crystallization speed, the crystal particle size is flexibly combined with the growth and solidification process of foam material cells, the cell structure of the generated polyethylene expanded beads (EPE) is uniformly distributed, the cell size of the prepared material is 20-50 mu m, and the microporous polyethylene expanded beads with excellent performance are prepared.

Background

The low-density polyethylene foam material has excellent physical, chemical and mechanical properties. It is tough, flexible, wear resistant, electrically insulating, heat insulating and chemical resistant, and may be used widely in packing, chemical industry, building and other fields. The polyethylene expanded beads prepared by the supercritical fluid have high expansion ratio (more than 30 times), can be prepared into various expanded products by a molding process, is an effective means for obtaining polyethylene expanded products with complex shapes, and is breakthrough development of a polymer foaming technology. However, the existing low-density polyethylene foam material has the defects of low strength, poor rebound resilience, uneven foam holes and the like, and the existing polyethylene foam bead products (pearl wool) sold in the market mostly adopt organic foaming agents, are flammable and explosive, have low production efficiency and high energy consumption, have poor plasticity for special-shaped products, are easy to collapse in the foam holes in the preparation process, and cause complex preparation process, high rejection rate in the production process and large material loss. In addition, for the existing EPE beads, the shrinkage phenomenon is very serious in the foaming process, when the foaming multiplying factor of the particles is less than 20 times, the shrinkage rate of a common EPE product is close to about 5%, and for high-multiplying factor EPE, the shrinkage of a molded product can reach more than 8%. Aiming at overcoming the defects of the materials, related patent researches are few, and a non-tin-containing light material (CN 105037912B) discloses a low-shrinkage high-resilience EPE bead prepared from non-metallocene-catalyzed LLDPE resin, 5-20 parts of HDPE resin, an antistatic agent and an auxiliary agent. The invention discloses a Rongmao plastic packaging material (CN 109593246A) in Anhui, and provides a method for producing high-foaming EPE pearl cotton by using a carbon dioxide foaming agent, which can ensure that the pearl cotton has good elasticity, thermal stability and mechanical property, and improve the tensile strength and the tearing strength of the pearl cotton.

Disclosure of Invention

The invention aims to provide a method for producing high-foaming EPE by adopting a kettle type supercritical fluid process, wherein a nucleating agent suitable for controlling polypropylene crystallization form is applied to control polyethylene crystallization behavior, and the new idea of shortening the molding period, improving the product transparency, surface gloss, tensile strength, rigidity, heat deformation temperature, impact resistance, creep resistance and other physical and mechanical properties is achieved by changing the crystallization behavior of resin, increasing the crystallization density and promoting the grain size to be micronized, so as to solve the defects of the application of the existing EPE material in the background art.

1. A method for preparing high-strength anti-retraction microcellular polyethylene expanded beads (EPE) comprises the following specific formula: the dosage of the linear low density polyethylene LDPE is 20-95 parts; 10-45 parts of high-density polyethylene (HDPE) or random polypropylene (melting point 130-150 ℃); the alpha crystal nucleating agent comprises 0.05-5 parts of inorganic nucleating agent with alpha crystal nucleating agent function, aromatic carboxylate of alpha crystal nucleating agent, sorbitol of alpha crystal nucleating agent and the like; and 1-15 parts of an auxiliary agent.

2. The linear low density polyethylene LDPE and the high density polyethylene HDPE according to claim 1, both having a melt flow index of 0.3 to 10; the random polypropylene is a blend of one or more of binary or ternary copolymers of propylene, ethylene and 1-butene, the molecular weight distribution Mw/Mn of the copolymer is 2-20, and the melt flow index (190 ℃ and 2.16Kg) is 0.2-15 g/10 min. Preferably the resin is a combination of linear low density polyethylene and atactic polypropylene.

3. The alpha crystal nucleating agent comprises three or more than three of inorganic nucleating agents with alpha crystal nucleating function, alpha crystal nucleating agent aromatic carboxylate, alpha crystal nucleating agent sorbitol and other series alpha crystal nucleating agents, and the using amount of the total alpha crystal nucleating agent is 0.05-5 parts. Further preferably 0.1 to 2 parts of total alpha crystal nucleating agent. The polypropylene alpha crystal nucleating agent is a very effective method for modifying the high rigidity of polypropylene, and the similar effect can be realized by expanding the application to linear low-density polyethylene. Different alpha crystallization nucleating agents have different influences on the crystallization speed, the crystallization temperature and the crystal form refining degree, and some crystallization nucleating agents can be assembled into a network structure in resin, so that the crystallization speed, the crystallization temperature and the bubble nucleus growth process can be properly matched by completely utilizing the layer-by-layer crystallization assembly control of the crystallization nucleating agents, and the high-strength shrinkage-resistant polyethylene foam beads are developed.

4. The auxiliary agent is one or more of a foaming nucleating agent, an antioxidant, an antistatic agent, a flame retardant, color master batches and a coupling agent. The dosage of the auxiliary agent is 1-15 parts. More preferably 3 to 10 parts.

5. The foaming nucleating agent in the auxiliary agent is at least one of talcum powder, mica, glass beads, silicon dioxide, calcium carbonate, montmorillonite, kaolin, aluminum oxide, barium sulfate, zinc oxide, zinc stearate and calcium stearate; the antioxidant is at least one of antioxidants 168, 1010, 1076 and 626; the antistatic agent is alkyl imidazoline, quaternary phosphonium salt, quaternary sulfur salt, quaternary ammonium salt, alkyl sulfonate or phosphate; the flame retardant is one or more of magnesium hydroxide, aluminum hydroxide, zinc borate and intumescent flame retardant DTPB; the coupling agent is one or more of silane coupling agent, titanate coupling agent and aluminate coupling agent.

6. The method for preparing the high-strength anti-retraction microcellular polyethylene expanded beads (EPE) specifically comprises the following steps:

1) 20-95 parts of linear Low Density Polyethylene (LDPE); 10-45 parts of high-density polyethylene (HDPE) or random polypropylene (melting point 130-150 ℃); the alpha crystal nucleating agent comprises 0.05-5 parts of inorganic nucleating agent with alpha crystal nucleating agent function, aromatic carboxylate of alpha crystal nucleating agent, sorbitol of alpha crystal nucleating agent and the like; and 1-15 parts of an auxiliary agent. Fully compounding by a high-speed mixer, extruding, water-cooling, bracing and granulating by a double screw to obtain modified polyethylene small particles with the length of 1-2 mm and the diameter of 0.5-2 mm; ,

(2) putting polyethylene particles, a dispersing agent and water into an autoclave, injecting a physical foaming agent into the autoclave under a stirring condition, simultaneously raising the temperature of the autoclave to 95-130 ℃, raising the pressure to 2.0-5.0 MPa, and keeping for 20-60 min after the set temperature and pressure are reached so that the foaming agent permeates into the polyethylene particles;

(3) the pressure of the high-pressure kettle can be controlled to be released, and the polyethylene particle-high-pressure water dispersion mixed material is sprayed into a cold water cooling system to obtain foamed beads with the foaming ratio of 2-30 times; in order to obtain polypropylene expanded beads with higher expansion ratio, the primarily obtained expanded beads need to be subjected to pressure release in a secondary foaming device under the condition of controlling the pressure of 0.1-1.5 MPa for 5-60 s in a steam atmosphere, so as to further obtain expanded beads with higher expansion ratio, wherein the expansion ratio is 15-60 times.

(4) And drying the prepared polyethylene foamed beads for 10-48 hours in an environment of 30-60 ℃, injecting the dried polyethylene foamed beads into steam compression molding equipment, heating by steam, and cooling to obtain a polyethylene foamed bead molding body.

7. The dispersant is one or more than two of kaolin, sodium dodecyl sulfonate, aluminum sulfate, calcium carbonate, barium sulfate and aluminosilicate.

8. The physical foaming agent is one or two of carbon dioxide and nitrogen. Carbon dioxide is further preferred.

9. The pressure release rate of the autoclave is 0.3-2.0 MPa/s, and the cooling rate of the polypropylene particle-water dispersion system mixture is 20-40 ℃/s.

Detailed Description