A kind of expanded polyolefin beads and preparation method thereof

Abstract

The present invention relates to a kind of foamed polyolefin beads and a preparation method thereof, wherein the foamed polyolefin beads at least include 50-85% of polybutene A, 15-50% of polybutene B, 0.01-1% of a cell nucleating agent, and 0.4-4% of an anti-aging agent. The preparation method of the foamed polyolefin beads of the present application comprises the following steps: S1, polybutene A, polybutene B, a cell nucleating agent, and other plastic additives are mixed uniformly according to a proportion, and then melt-granulated by an extruder to obtain microparticles; S2, the microparticles, a dispersant, and water are added to an autoclave together, CO2 is added after sealing, stirring continuously, the temperature of the reactor is increased to the foaming temperature, the pressure in the reactor is adjusted to the foaming pressure, the heat and pressure are maintained, and then the pressure is released to discharge the material into a normal pressure environment, and finally the foamed polyolefin beads are obtained. The present invention provides a kind of foamed polyolefin beads and its molded parts, and obtains foamed polyolefin beads that are easy to mold, and the molding energy consumption is low, the molded parts have excellent appearance, high compression strength, and excellent light aging resistance.

Description

Technical Field

[0001] The invention relates to the technical field of foaming materials, in particular to a foaming polyolefin bead and a molded product thereof. Background Art

[0002] Foamed polyolefin (mainly foamed polyethylene EPE and foamed polypropylene EPP) beads and their molded parts are light in weight and have diverse structural shapes. They are suitable for special-shaped structural parts such as weight reduction, energy absorption and cushioning, sound insulation, and heat insulation. They have been widely used in automotive parts, packaging materials, building insulation materials, sound insulation and noise reduction materials, and are a type of foam material with great potential.

[0003] With the increasing application of expanded polyolefin bead molding products, considering the energy consumption cost of the bead molding process and the use strength of the molded parts, the market demands for expanded polyolefin beads with low molding energy consumption and high compression strength and their molded parts; in addition, the expanded polyolefin bead molding products used in many occasions need to be directly exposed to the outdoor environment, which puts forward more requirements for the light aging resistance of the bead molding parts. However, due to the inherent physical property limitations of PE and PP resin materials, EPE materials have poor temperature resistance, and EPP materials have high molding energy consumption, poor toughness, and are prone to brittleness and light-oxidation aging.

[0004] Chinese patent CN115058081A uses the method of adding activated titanium dioxide to improve the anti-aging performance of EPP molded parts, but does not mention the energy-saving effect of the EPP bead molding process, and the color of EPP in this technology is milky white, and the color adjustable freedom is small. Chinese patent CN116376093A uses the method of adding mica powder and cross-linking to improve the weather resistance of EPP and inhibit the phenomenon of EPP being easy to pulverize under high temperature or ultraviolet irradiation environment, but the cross-linking agent and cross-linking auxiliary agent in the foaming process may remain in the wastewater, which is not conducive to environmental protection. Moreover, the EPP of this technology is a cross-linked product, which is not conducive to recycling. In addition, the high content of mica powder may reduce the foaming properties of the material.

[0005] Compared with PE and PP, polybutene-1 (PB-1) has good low temperature resistance, creep resistance, high toughness, weather resistance and excellent stress cracking resistance, and its bead foaming products have the characteristics of low molding energy consumption. Chinese patent CN115636971A discloses a method for preparing polybutene foaming beads and its application, including the following steps: (S1) melt blending a mixture containing polybutene, thermoplastic elastomer, nucleating agent, and antioxidant, adding supercritical carbon dioxide, depressurizing, cooling, pelletizing, and drying to obtain the polybutene blended particles; (S2) placing a mixture containing polybutene blended particles, dispersant and water in a closed container, adding supercritical carbon dioxide, foaming, depressurizing, and obtaining the polybutene foaming beads; although the molding steam pressure of the polybutene foaming beads in this technology is lower than 0.2MPa, it does not mention that the material has high compressive strength and excellent light aging resistance. Chinese patent CN117511070A discloses a polypropylene / polybutene-1 foam material with high elasticity and low molding pressure and its preparation method and application. The foam material comprises polypropylene and polybutene-1, and the content of polybutene-1 is 10-40 parts by weight relative to 100 parts by weight of the polypropylene. This technology obtains a polypropylene / polybutene-1 foam material with both elasticity and rigidity, but does not mention the light aging resistance of the foam material.

[0006] Therefore, the present technology provides a method for preparing foamed polyolefin beads and molded parts thereof, thereby obtaining foamed polyolefin beads that are easy to mold, have low molding energy consumption, excellent molded parts appearance, high compression strength, and excellent light aging resistance. Summary of the invention

[0007] The object of the present invention is to provide a foamed polyolefin bead and a molded product thereof, so as to obtain a foamed polyolefin bead which is easy to mold, has low molding energy consumption, has excellent molded product appearance, high compression strength, and excellent light aging resistance.

[0008] To achieve the above object, the present invention provides a foamed polyolefin bead, and the preparation method thereof comprises the following steps:

[0009] S1, polybutene A, polybutene B, cell nucleating agent, anti-aging agent and other plastic additives are uniformly mixed in proportion, melt-blended in an extruder, and then cooled, drawn into strips and pelletized to obtain microparticles; the length of the microparticles is preferably 1.0-3.0 mm, and the unit weight is 0.5-2.0 mg.

[0010] S2, add the microparticles, dispersant and water into the autoclave, seal it and add CO 2 , stirring continuously, raising the temperature of the reactor to the foaming temperature, adjusting the pressure in the reactor to the foaming pressure, maintaining the temperature and pressure, and then releasing the pressure to discharge the material into a normal pressure environment, to finally obtain foamed polyolefin beads.

[0011] Preferably, in step S1, polybutene A is random copolymer polybutene-1, with a melt index of 0.2-5 g / 10 min and a melting point of 105-120° C.;

[0012] Polybutene B is isotactic polybutene-1, with a melt index of 0.2-5 g / 10 min and a melting point of 125-138°C;

[0013] Preferably, in step S1, the weight ratio of polybutene A, polybutene B, cell nucleating agent, and anti-aging agent is: 50-85: 15-50: 0.01-1: 0.4-4;

[0014] Preferably, in step S1, the cell nucleating agent is one or more of silicon dioxide, zinc borate, talc, and calcium carbonate, and the particle size range is 1-15 microns;

[0015] The anti-aging agent is a mixture of a light stabilizer and an antioxidant; the light stabilizer is one or more of benzophenones, benzotriazoles and hindered amines, accounting for 0.2-2% by weight in the particles; the antioxidant is one or more of hindered phenol compounds, phosphite compounds, and thioester compounds, accounting for 0.2-2% by weight in the particles.

[0016] The microparticles also include other plastic additives, which are at least one of lubricants, antistatic agents, and colorants; the lubricant is at least one of erucamide, oleamide, monostearate glyceryl, polyethylene wax, and polypropylene wax; the weight proportion of other plastic additives in the microparticles is 0-5%.

[0017] Preferably, in step S2, the weight ratio of microparticles: dispersant: water = 1: (0.002-0.015): (1.5-2.5), and the dispersant includes kaolin and sodium dodecylbenzene sulfonate, wherein the weight ratio is kaolin: sodium dodecylbenzene sulfonate = (4-20): 1.

[0018] Preferably, in step S2, the foaming temperature is 108°C-138°C, the foaming pressure is 2.2-4.0MPa, and the heat preservation and pressure holding time is 10-60min;

[0019] The present invention provides a foamed polyolefin bead, wherein the melting peak endothermic enthalpy value (high-temperature melting peak endothermic enthalpy value) higher than the intrinsic melting point in the first DSC melting curve is 5-15 J / g.

[0020] The present invention provides a foamed polyolefin molded part and a preparation method thereof, wherein foamed polyolefin beads are subjected to air pressure treatment in a pressure tank, molded by water vapor, and dried to obtain a molded part. The molding pressure of the molded part is lower than 1.8 bar, and the molded part has excellent appearance, that is, there are no or few gaps and pits; the density of the molded part is 60-65 g / L, the compression stress of the molded part at 10% strain is not lower than 100 kpa, and the light aging resistance is excellent.

[0021] The present invention has the following beneficial effects:

[0022] A mixed system of random copolymerized polybutene A and isotactic polybutene B is used, wherein random copolymerized polybutene A gives the material easy foaming and excellent molding expansion, and isotactic polybutene B improves the material's compressive strength, making it easy to mold the foamed beads, and the molded parts have excellent appearance and mechanical properties. If the isotactic polybutene B content is higher than 50%, the foaming properties of the material deteriorate, the molding energy consumption is high during the molding process, and the apparent quality of the parts is poor; if the isotactic polybutene B content is lower than 15%, the compressive strength of the foamed bead molded parts is reduced. In addition, polybutene-1 with excellent weather resistance is added with a specific component anti-aging agent to give the molded parts excellent light aging resistance, which is suitable for outdoor applications with various color requirements. DETAILED DESCRIPTION

[0023] Example

[0024] The technical solution of the present invention is further illustrated by the following examples.

[0025] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0026] Preparation Example of Expanded Polyolefin Beads:

[0027] Preparation of microparticles: polybutene A, polybutene B, cell nucleating agent, anti-aging agent and other plastic additives are uniformly mixed in proportion, melt-blended in a single extruder, and then cooled, drawn into strips and pelletized to obtain microparticles; the length of the microparticles is preferably 2.0 mm and the single weight is 1.2 mg; the temperature of the heating section of the extruder is 200°C.

[0028] Preparation of expanded polyolefin beads: Add microparticles, kaolin, sodium dodecylbenzene sulfonate, and water in a weight ratio of 1:0.011:0.001:2 into an autoclave, seal it, and add CO 2 , stirring continuously, raising the temperature of the reactor to the foaming temperature, adjusting the pressure in the reactor to the foaming pressure, maintaining the temperature and pressure for 20 minutes, then releasing the pressure to discharge the material into a normal pressure environment to obtain foamed polyolefin beads. The products of Examples 1-6 and Comparative Examples 1-8 were prepared according to the above preparation method.

[0029] Table 1 Information on the main raw materials used in this application

[0030]

[0031] Table 2 Formulation parameters of microparticles S1-S6 and D1-D8

[0032]

[0033] Table 3 Parameters of the foamed beads and properties of the molded parts in Examples 1-6 and Comparative Examples 1-8

[0034]

[0035]

[0036] Preparation examples of molded parts:

[0037] The foamed polyolefin beads were filled into a mold with a cuboid cavity (length 450 mm, width 350 mm, thickness 60 mm) after being carried by 0.5 MPa of air for 6 h, and then molded by steam.

[0038] Among them, the lowest molding pressure: the lowest steam sintering pressure required for the proportion of particles with damaged cell walls at the fracture surface of the foamed bead molded parts to be more than 95%.

[0039] Measurement of the performance parameters of the molded parts:

[0040] Appearance quality of the parts: “■” indicates较多 pits or cracks on the surface of the part; “□” indicates少量 pits or cracks on the surface of the part; “○” indicates no or极少 or极小 pits or cracks on the surface of the part.

[0041] The compression stress at 10% strain of the molded parts was tested in accordance with GB / T 8813-2020.

[0042] In accordance with GB / T 16422.2-2014, the xenon lamp was used to simulate the light aging test to test the light aging resistance of each molded part: judged by the appearance of powdering on the surface of the molded part, “A” indicates that the simulated light aging time is longer than 6 years, “B” indicates that the simulated light aging time is longer than 5 years (shorter than 6 years), and “C” indicates that the simulated light aging time is longer than 3 years (shorter than 5 years).

[0043] Examples 1-6 are all within the technical requirements range, showing excellent molding formability, high compressive strength, excellent appearance quality and light aging resistance.

[0044] Compared with Example 1, Comparative Example 1 does not contain isotactic polybutene B, lacks reinforcement, and a small number of collapsed pits appear on the appearance of the molded part due to the action of high-temperature steam, and the compressive stress of the part is reduced; Compared with Example 3, Comparative Example 2 contains too much isotactic polybutene B, which affects the molding expansion, resulting in an increase in molding pressure, and more gaps and a small number of pits appear on the surface of the part. In addition, the increase in molding pressure is not conducive to the closed-cell structure of the material, and the compressive stress of the part is reduced; Compared with Example 2, the antioxidant content of Comparative Example 3 is lower than the technical requirement, and the light aging resistance of the molded part is reduced. low; compared with Example 2, the light stabilizer content of Comparative Example 4 is lower than the technical requirement, and the light aging resistance of the molded parts is reduced; compared with Example 4, the antioxidant content of Comparative Example 5 is lower than the technical requirement, and the light aging resistance of the molded parts is reduced; compared with Example 4, the light stabilizer content of Comparative Example 6 is lower than the technical requirement, and the light aging resistance of the molded parts is reduced; compared with Example 6, Comparative Example 7 does not contain antioxidants, and the light aging resistance of the molded parts is reduced; compared with Example 3, Comparative Example 8 does not contain light stabilizers, and the light aging resistance of the molded parts is reduced.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A foamed polyolefin bead, characterized in that: The beads are prepared by high temperature and high pressure autoclave foaming method. The microparticles at least include by weight: 50-85% polybutene A, 15-50% polybutene B, 0.01-1% cell nucleating agent, 0.4-4% anti-aging agent; the polybutene A is a random copolymer polybutene-1, with a melt index of 0.2-5g / 10min and a melting point of 105-120°C; the polybutene B is an isotactic polybutene-1, with a melt index of 0.2-5g / 10min and a melting point of 125-138°C; The test conditions of the melt index are 190°C and 2.16kg.

2. The expanded polyolefin beads according to claim 1, characterized in that The random copolymer polybutene-1 has a melt index of 0.5-4 g / 10 min and a melting point of 106-118° C.

3. The expanded polyolefin beads according to claim 1, characterized in that: The isotactic polybutene-1 has a melt index of 0.5-4 g / 10 min and a melting point of 126-137° C.

4. The expanded polyolefin beads according to claim 1, characterized in that The cell nucleating agent is silicon dioxide, One or more of zinc borate, talc, and calcium carbonate, with a particle size ranging from 1 to 15 microns.

5. The expanded polyolefin beads according to claim 1, characterized in that: The anti-aging agent is a mixture of a light stabilizer and an antioxidant; the light stabilizer is one or more of benzophenones, benzotriazoles and hindered amines, accounting for 0.2-2% by weight in the microparticles; the antioxidant is one or more of hindered phenol compounds, phosphite compounds and thioester compounds, accounting for 0.2-2% by weight in the microparticles.

6. The expanded polyolefin beads according to claim 1, characterized in that The particles also include other plastic additives The other plastic additives are at least one of lubricants, antistatic agents, and colorants; the lubricant is at least one of erucamide, oleamide, monostearate glyceryl, polyethylene wax, and polypropylene wax; the weight proportion of other plastic additives in the particles is 0-5%.

7. The method for preparing foamed polyolefin beads according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, polybutene A, polybutene B, cell nucleating agent, anti-aging agent and other plastic additives are mixed evenly in proportion, melt-blended in an extruder, and then cooled, drawn into strips, and pelletized to obtain microparticles; S2. Add the microparticles, dispersant and water into the autoclave together, seal it, add CO2, stir continuously, raise the temperature of the autoclave to the foaming temperature, adjust the pressure in the autoclave to the foaming pressure, keep the temperature and pressure, then release the pressure to discharge the material into a normal pressure environment to obtain foamed polyolefin beads.

8. The method for preparing foamed polyolefin beads according to claim 7, characterized in that: In step S2, the weight ratio of each component is microparticle: dispersant: water = 1: (0.002-0.015): (1.5-2.5), and the dispersant includes kaolin and sodium dodecylbenzene sulfonate, wherein the weight ratio is kaolin: sodium dodecylbenzene sulfonate = (4-20):

1.

9. The method for preparing foamed polyolefin beads according to claim 7, characterized in that: In step S2, the foaming temperature is 108°C-138°C, the foaming pressure is 2.2-4.0MPa, and the heat preservation and pressure holding time is 10-60min.

10. A molded article of expanded polyolefin beads, characterized in that: The foamed polyolefin beads according to any one of claims 1 to 9 are obtained by steam sintering, and the specific steps are: the foamed polyolefin beads are pressurized by air and then steam molded; the molding pressure of the molded parts is lower than 1.8 bar.

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