Rotational molding polypropylene composition easy to defoam and preparation method thereof

Abstract

The invention discloses an easy-to-defoam rotational molding polypropylene composition and a preparation method thereof, and belongs to the technical field of rotational molding processes. 0.2 to 0.6 part of an antioxidant; 0.02 to 0.1 part of an acid acceptor; 0.05 to 2 parts of a lubricant; and 0.2 to 0.8 part of hydrated alumina. Uniformly mixing the polypropylene, the antioxidant, the acid acceptor and the lubricant A; adding a lubricant B, hydrated alumina and a coupling agent into absolute ethyl alcohol, and uniformly mixing; uniformly mixing the rest polypropylene with the materials, melting and mixing in a co-rotating twin-screw extruder, and extruding and granulating; and grinding the granulated material into fine powder. According to the invention, multiple problems of resin grinding, oxidation resistance and bubble discharge during application of polypropylene in the field of rotational molding processing technology are solved, and the prepared rotational molding polypropylene composition has few bubbles and excellent mechanical properties; meanwhile, the preparation method has the advantages of being simple, reliable, easy to implement and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of roto-molding technology, and in particular relates to an easily defoaming roto-molding polypropylene composition and a preparation method thereof. Background Art

[0002] After half a century of development, the equipment and technology of roto-molding technology have been increasingly improved, and the molded products range from doll eyes to auto parts and tens of thousands of liters of storage tanks. In recent years, in the domestic market, more and more products are made by roto-molding technology, such as nuclear waste barrels, military supplies, one-time roto-molded car shells, inspection wells, telecommunications wells and other products will promote the continuous development of the domestic roto-molding industry. The demand for buried products such as inspection wells, septic tanks, and garbage cans is growing, which has spawned a large number of new manufacturers to invest in these industries. The rapid development of the roto-molding industry not only requires product design to be creative, functional and systematic, and processing equipment to be large-scale automated, precise and energy-saving, but also drives the development of roto-molding raw materials towards diversification and functionality.

[0003] Roto-molding process usually uses polyethylene as the main raw material for 90%. Polypropylene has excellent rigidity, heat resistance, chemical stability and good ESCR performance, and has great application potential in the field of roto-molding. It is suitable for preparing containers with high temperature resistance requirements, ventilation ducts and equipment shells with high rigidity requirements, and has broad application prospects in the fields of container storage tanks, automotive parts, etc.

[0004] In the field of rotational molding, eliminating bubbles is an important research direction. Since rotational molding is melt-molded under pressure-free conditions, bubbles are usually entrained in the powder. If the bubbles are not completely removed, the mechanical properties of the product will decrease, seriously affecting the service life of the product. It is easier to remove bubbles from polyethylene than from polypropylene. Therefore, it is more necessary to study the removal of bubbles from polypropylene.

[0005] In the prior art, sufficient time is provided for the bubbles to be discharged by increasing the melting time or melting temperature of the resin, but the long thermal history makes the material easy to age. In order to solve the aging problem, a large amount of antioxidants are usually added, but too much antioxidant will increase the cost and the product will turn yellow. In addition, the antioxidants commonly used in the industry will produce bubbles when used for rotational molding products, which will reduce the mechanical properties of the products. At the same time, in the rotational molding process, the raw materials need to be heated in the mold at 240-280℃ for at least 30-60 minutes, and the material's resistance to thermal oxidation aging is extremely high. Compared with polyethylene, the molecular structure of polypropylene makes it more susceptible to oxidation. The application of polypropylene in the field of rotational molding technology faces multiple pressures of resin grinding, anti-oxidation and bubble discharge, which makes the application of rotational molding polypropylene in my country still blank. Summary of the invention

[0006] In order to solve the multiple problems of resin grinding, anti-oxidation and bubble discharge faced by the application of polypropylene in the field of rotational molding process, the present invention provides a rotational molding polypropylene composition that is easy to defoam and a preparation method thereof. The rotational molding polypropylene composition prepared by the present invention has fewer bubbles and excellent mechanical properties; at the same time, the preparation method adopted by the present invention has the advantages of being simple, reliable and easy to operate.

[0007] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0008] The present invention provides an easily defoamable rotomolding polypropylene composition, which comprises the following components in parts by weight:

[0009]

[0010] Preferably, the antioxidant is a phosphite antioxidant.

[0011] Preferably, the phosphite antioxidant is tris(2,4-di-tert-butylphenyl)phosphite.

[0012] Preferably, the acid absorber is calcium stearate or zinc stearate.

[0013] Preferably, the lubricants are lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1-1:2.

[0014] Preferably, the lubricant A is didodecyl phthalate.

[0015] Preferably, the lubricant B is Hyper c100.

[0016] Preferably, the hydrated alumina is pseudo-boehmite with a particle size of 10-60 nm.

[0017] Preferably, the easily defoamable rotomolding polypropylene composition provided by the present invention comprises the following components in parts by weight:

[0018]

[0019] The present invention provides a method for preparing a rotomolded polypropylene composition that is easy to defoam, which mainly comprises the following steps:

[0020] (1) Add one-half of polypropylene, antioxidant, acid absorbent and lubricant A into a high-speed mixer, stir at 50-90° C. and 1000-1500 r / min to mix evenly; after high-speed stirring in a heated state, lubricant A penetrates into the polypropylene molecules;

[0021] (2) adding lubricant B, hydrated alumina and coupling agent to anhydrous ethanol and mixing them evenly in an ultrasonic mixer, wherein the amount of coupling agent added is 6-10 times that of hydrated alumina;

[0022] (3) adding the remaining half of the polypropylene and the material obtained in step (2) into a high-speed mixer, stirring at 300-800 r / min to mix evenly;

[0023] (4) melt-mixing the materials obtained in step (1) and step (3) in a co-rotating twin-screw extruder, and extruding and granulating the mixture;

[0024] (5) Grind the granulated material into fine powder on a grinder.

[0025] Preferably, the highest section temperature of the co-rotating twin-screw extruder is 190-230° C., the main engine speed is 150-230 r / min, and the feeding speed is 30-50 r / min.

[0026] Preferably, among the fine powder, powders with a size of 40-100 meshes account for 70-85%; among the powders with a size of 40-100 meshes, powders with a size of 40-80 meshes account for 25-60%.

[0027] The beneficial effects of the present invention are:

[0028] The present invention adds lubricant to polypropylene to reduce friction, increase the fluidity of resin, and is more conducive to processing. However, there is no processing shear for the rotational molding process, so the type and amount of lubricant are different from other processes. Some lubricants plasticize the resin too early, and the material is in a melting time that is too long and is easy to thermally degrade, especially heat-sensitive materials such as polypropylene, which have higher requirements for heating time and heating temperature. Therefore, the lubricant A used in the present invention takes effect in the early stage of polypropylene plasticization, and the lubricant B is resistant to high temperature and takes effect in the late stage of polypropylene plasticization. The synergistic effect of lubricant A and lubricant B realizes molecular internal lubrication and external lubrication, which can shorten the plasticization time, resist the material degradation caused by overheating oxidation of polypropylene, and improve the problem of fast aging of resin. In addition, the two lubricants have different onset times, which are beneficial to the melt plasticization of resin. At the same time, the two lubricants have antistatic effects, reduce the occurrence of dust absorption, electrostatic discharge and other phenomena of the rotational molding process products, and improve the impact resistance of rotational molding polypropylene.

[0029] Since an excessive amount of acid absorber may cause yellowing of the product after rotational molding, in the present invention, the amount of acid absorber added should be strictly controlled. Specifically, in the rotational molding process of the present invention, the amount of acid absorber added in the rotational molding polypropylene should be reduced by 30-40% to prevent the product from yellowing.

[0030] Since the smaller the bubbles formed in the roto-molding process, the harder it is to discharge, there are tiny cavities inside the product after it is formed and cooled, which leads to a decrease in the mechanical properties of the product. Therefore, in the present invention, the hydrated alumina is specifically selected from pseudo-boehmite, which slowly releases crystal water when the temperature exceeds 200°C during roto-molding, which is conducive to the surrounding bubbles combining with it, and larger bubbles are easier to discharge. DETAILED DESCRIPTION

[0031] The present invention provides an easily defoamable rotomolding polypropylene composition, which comprises the following components in parts by weight:

[0032]

[0033] Preferably, the easily defoamable rotomolding polypropylene composition provided by the present invention comprises the following components in parts by weight:

[0034]

[0035] The polypropylene is preferably copolymerized polypropylene, and ethylene as a copolymer gives the material good toughness. The ethylene mass content is preferably 4-11%, more preferably 7.8-10.3%; the number average molecular weight is preferably 42,000-47,000, and the distribution width is preferably 5.1-6.3.

[0036] The melt mass flow rate of polypropylene is preferably 6-20 g / 10 min, more preferably 10.0-16.0 g / 10 min, and the test conditions are preferably 230° C. and 2.16 kg.

[0037] Among them, the antioxidant is preferably a phosphite antioxidant.

[0038] Among them, the phosphite antioxidant is preferably tris(2,4-di-tert-butylphenyl)phosphite.

[0039] Among them, the acid absorber is preferably calcium stearate or zinc stearate.

[0040] The lubricants are lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1-1:2; lubricant A is preferably didodecyl phthalate, lubricant B is preferably Hyper c100, and the density of Hyper c100 is preferably 1.1 g / cm 3 .

[0041] Among them, the hydrated alumina is preferably pseudo-boehmite, and the particle size is preferably 10-60nm.

[0042] The present invention provides a method for preparing a rotomolded polypropylene composition that is easy to defoam, which mainly comprises the following steps:

[0043] (1) Add half of polypropylene (50 parts), antioxidant, acid absorbent and lubricant A into a high-speed mixer, stir for 5 minutes at 50-90°C and 1000-1500 r / min, and mix them evenly; after high-speed stirring under heating, lubricant A penetrates into the polypropylene molecules, effectively reducing the interaction between molecular chains, reducing friction, and promoting the plasticization of polypropylene.

[0044] (2) Lubricant B, hydrated alumina, and coupling agent are added to anhydrous ethanol and mixed evenly in an ultrasonic mixer for 10 minutes, wherein the amount of coupling agent added is 6-10 times that of hydrated alumina. The amount of anhydrous ethanol added is not specifically limited and is only used for dilution. It will evaporate during the subsequent high-speed stirring process.

[0045] Among them, the hydrated alumina specifically uses pseudo-boehmite. The powder of pseudo-boehmite with small particle size is easy to agglomerate. Under the action of coupling agent and anhydrous ethanol, the pseudo-boehmite is well dispersed. Its high porosity can efficiently adsorb lubricant B.

[0046] (3) adding the remaining half of the polypropylene (50 parts) and the material obtained in step (2) into a high-speed mixer, stirring at 300-800 r / min for 2-3 min to mix evenly;

[0047] (4) melt-mixing the materials obtained in step (1) and step (3) in a co-rotating twin-screw extruder, and extruding and granulating the mixture;

[0048] Preferably, the highest section temperature of the co-rotating twin-screw extruder is 190-230°C, the main engine speed is 150-230r / min, and the feed speed is 30-50r / min.

[0049] (5) Grind the granulated material into fine powder on a grinder.

[0050] Preferably, among the fine powder, powders with a size of 40-100 meshes account for 70-85%; among the powders with a size of 40-100 meshes, powders with a size of 40-80 meshes account for 25-60%.

[0051] In the present invention, the grinding machine can specifically be a grinding machine for polyethylene grinding. Usually, when polypropylene is ground, since polypropylene is a poor conductor of heat, the shear heat is difficult to remove, and the powder is prone to tailing. The tailing powder has poor fluidity when the product is formed by the rotational molding process, and the surface of the product is uneven. The powder with a bad shape will also cause bubbles inside the product. The present invention solves the problems of anti-oxidation and bubbles when the polypropylene rotational molding process is used to form products, and the high tolerance of the grinding machine allows downstream manufacturers to carry out the polypropylene rotational molding process without improving the grinding equipment, which solves the problem of costly equipment updates and makes the promotion of rotational molding polypropylene more convenient.

[0052] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] Example 1

[0054] A method for preparing a rotomolded polypropylene composition that is easy to defoam comprises the following steps:

[0055] (1) 50 parts of polypropylene (melt mass flow rate 10 g / 10 min (230° C., 2.16 kg), ethylene mass content 8%), 0.2 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.04 parts of calcium stearate and 0.03 parts of didodecyl phthalate were added to a high-speed mixer and stirred at 60° C. and 1000 r / min for 5 min to mix well.

[0056] (2) Add 0.06 parts of Hyper c100, 0.3 parts of pseudo-boehmite (particle size of 10 nm), and 2.4 parts of aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 minutes.

[0057] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 500 r / min for 3 minutes, and mix well.

[0058] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 200 r / min, and the feed speed is 30 r / min.

[0059] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 85%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 50%.

[0060] Example 2

[0061] A method for preparing a rotomolded polypropylene composition that is easy to defoam comprises the following steps:

[0062] (1) 50 parts of polypropylene (melt mass flow rate 14 g / 10 min (230° C., 2.16 kg), ethylene mass content 8.6%), 0.3 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.05 parts of calcium stearate and 0.05 parts of didodecyl phthalate were added into a high-speed mixer and stirred at 50° C. and 1000 r / min for 5 min to mix well.

[0063] (2) 0.08 parts of Hyper c100, 0.5 parts of pseudo-boehmite (particle size of 30 nm), and 4.0 parts of aluminate coupling agent were added to anhydrous ethanol and mixed uniformly in an ultrasonic mixer for 10 minutes.

[0064] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 300 r / min for 3 minutes, and mix well.

[0065] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 200° C., the main engine speed is 190 r / min, and the feed speed is 40 r / min.

[0066] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 85%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 60%.

[0067] Example 3

[0068] A method for preparing a rotomolded polypropylene composition that is easy to defoam comprises the following steps:

[0069] (1) 50 parts of polypropylene (melt mass flow rate 9 g / 10 min (230° C., 2.16 kg), ethylene mass content 10.3%), 0.25 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.03 parts of zinc stearate and 0.1 parts of didodecyl phthalate were added into a high-speed mixer and stirred at 50° C. and 1500 r / min for 5 min to mix well.

[0070] (2) Add 0.1 parts of Hyper c100, 0.2 parts of pseudo-boehmite (particle size of 30 nm), and 1.6 parts of aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 minutes.

[0071] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 500 r / min for 3 minutes, and mix well.

[0072] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 190 r / min, and the feed speed is 50 r / min.

[0073] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 72%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 55%.

[0074] Example 4

[0075] A method for preparing a rotomolded polypropylene composition that is easy to defoam comprises the following steps:

[0076] (1) 50 parts of polypropylene (melt mass flow rate 15 g / 10 min (230° C., 2.16 kg), ethylene mass content 7.8%), 0.4 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.02 parts of calcium stearate and 0.8 parts of didodecyl phthalate were added into a high-speed mixer and stirred at 90° C. and 1300 r / min for 5 min to mix well.

[0077] (2) 0.9 parts of Hyper c100, 0.8 parts of pseudo-boehmite (particle size 60 nm), and 6.4 parts of aluminate coupling agent were added to anhydrous ethanol and mixed uniformly in an ultrasonic mixer for 10 minutes.

[0078] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 300 r / min for 3 minutes, and mix well.

[0079] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 180 r / min, and the feed speed is 50 r / min.

[0080] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 83%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 55%.

[0081] Comparative Example 1

[0082] A method for preparing a rotomolded polypropylene composition comprises the following steps:

[0083] (1) 50 parts of polypropylene (melt mass flow rate 12 g / 10 min (230° C., 2.16 kg), ethylene mass content 8%), 0.2 parts of pentaerythritol tetrakis[β(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant), 0.04 parts of calcium stearate and 0.03 parts of didodecyl phthalate were added into a high-speed stirrer and stirred at 60° C. and 1000 r / min for 5 min to mix well.

[0084] (2) 0.06 parts of Hyper c100, 0.3 parts of pseudo-boehmite (particle size of 20 nm), and 2.4 parts of aluminate coupling agent were added to anhydrous ethanol and mixed in an ultrasonic mixer for 10 minutes.

[0085] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 400 r / min for 3 min, and mix well.

[0086] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 180 r / min, and the feed speed is 30 r / min.

[0087] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 80%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 55%.

[0088] Since the antioxidant used in Comparative Example 1 is hindered phenol antioxidant 1010, and the other components are the same as those in Example 1, the final antioxidant performance of the material is slightly poor, the yellow index of the product after rotational molding is relatively large, and the density of the rotational molded product becomes smaller, indicating that there are more bubbles inside.

[0089] Comparative Example 2

[0090] A method for preparing a rotomolded polypropylene composition comprises the following steps:

[0091] (1) Mixing: Add 50 parts of polypropylene (melt mass flow rate 14 g / 10 min (230° C., 2.16 kg), ethylene mass content 9%), 0.3 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.03 parts of calcium stearate and 0.07 parts of propylene glycol monostearate (lubricant) into a high-speed mixer and stir at 1500 r / min for 3 min to mix well.

[0092] (2) Extrusion granulation: The uniformly mixed materials are added into a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest section temperature of the co-rotating twin-screw extruder is 210°C, the main engine speed is 200r / min, and the feed speed is 40r / min.

[0093] Since the present comparative example 2 does not select the combination of the two lubricants A and B and hydrated aluminum oxide, the yellow index of the material after rotational molding is large, there are many bubbles, and the mechanical properties are poor.

[0094] Comparative Example 3

[0095] A method for preparing a rotomolded polypropylene composition comprises the following steps:

[0096] (1) 50 parts of polypropylene (melt mass flow rate 12 g / 10 min (230° C., 2.16 kg), ethylene mass content 10.0%), 0.25 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.05 parts of calcium stearate and 0.02 parts of didodecyl phthalate were added to a high-speed mixer and stirred at 50° C. and 1500 r / min for 5 min to mix well.

[0097] (2) Add 0.01 parts of Hyper c100, 0.2 parts of pseudo-boehmite (particle size of 30 nm), and 1.6 parts of aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 minutes.

[0098] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 500 r / min for 3 minutes, and mix well.

[0099] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 190 r / min, and the feed speed is 50 r / min.

[0100] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 72%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 55%.

[0101] In this comparative example 3, since the ratio of the two lubricants A and B is not 1:1-1:2 and the total amount is smaller than that of the present invention, the material has many bubbles.

[0102] Comparative Example 4

[0103] A method for preparing a rotomolded polypropylene composition comprises the following steps:

[0104] (1) 50 parts of polypropylene (melt mass flow rate 16 g / 10 min (230° C., 2.16 kg), ethylene mass content 10.0%), 0.3 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.03 parts of calcium stearate and 1 part of didodecyl phthalate were added into a high-speed mixer and stirred at 50° C. and 1500 r / min for 5 min to mix well.

[0105] (2) Add 1.5 parts of Hyper c100, 0.5 parts of pseudo-boehmite (particle size of 50 nm), and 4.0 parts of aluminate coupling agent to anhydrous ethanol and mix them evenly in an ultrasonic mixer for 10 minutes.

[0106] (3) Add the remaining 50 parts of polypropylene and the material obtained in step (2) into a high-speed mixer, stir at 500 r / min for 3 minutes, and mix well.

[0107] (4) The materials obtained in step (1) and step (3) are melt-mixed in a co-rotating twin-screw extruder, and extruded into granules; the highest section temperature of the co-rotating twin-screw extruder is 230° C., the main engine speed is 190 r / min, and the feed speed is 50 r / min.

[0108] (5) Grind the granulated material into fine powder on a grinder. Among the fine powder, 40-100 mesh powder accounts for 72%; among the 40-100 mesh powder, 40-80 mesh powder accounts for 55%.

[0109] In this comparative example 4, since the ratio of the two lubricants A and B is not in the range of 1:1-1:2 and the total amount is greater than that of the present invention, the impact strength of the material is deteriorated.

[0110] Comparative Example 5

[0111] A method for preparing a rotomolded polypropylene composition comprises the following steps:

[0112] (1) Mixing: 50 parts of polypropylene (melt mass flow rate 14 g / 10 min (230° C., 2.16 kg), ethylene mass content 8.6%), 0.4 parts of tris(2,4-di-tert-butylphenyl)phosphite, 0.05 parts of calcium stearate, 0.1 parts of didodecyl phthalate, 0.1 parts of Hyper c100 and 0.2 parts of pseudo-boehmite (particle size 30 nm) were added into a high-speed mixer and stirred at 1000 r / min for 3 min to mix well.

[0113] (2) Extrusion granulation: The uniformly mixed materials are added into a co-rotating twin-screw extruder for melt mixing and extrusion granulation. The highest section temperature of the co-rotating twin-screw extruder is 230°C, the main engine speed is 200r / min, and the feed speed is 40r / min.

[0114] Comparative Example 5 did not adopt the preparation method of the present invention, but only used general mixing and granulation, resulting in many bubbles in the material after rotational molding and a large yellow index.

[0115] Test Example 1

[0116] The products obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to the following standards:

[0117] Melt flow rate (MFR): According to GB / T 3682.1-2018, the test temperature is 230°C and the load is 2.16kg;

[0118] The simply supported beam notched impact strength is tested according to GB / T 1043-2008;

[0119] The tensile properties are tested according to GB / T1040.2-2006, type I spline, and the tensile speed is 50mm / min;

[0120] Bending properties are tested according to GB / T 9341-2008;

[0121] Oxidation induction time (OIT): carried out according to GB / T19466.6-2009, heating rate 20°C / min, temperature 200°C.

[0122] Yellowness index: tested in accordance with ASTM E313-2010. The sample used to test the yellowness index is a 2mm thick square piece, and the injection molding temperature is 200℃.

[0123] The rotomolded products in the embodiments and comparative examples are made by the following rotomolding process:

[0124] Heating temperature: 240°C Heating time: 1200 seconds

[0125] Cooling time: 900 seconds Cooling method: air cooling

[0126] Table 1 Amount of each component used in the examples and performance data of the examples

[0127]

[0128]

[0129] Table 2 The dosage of each component of the comparative example and the comparative example performance data

[0130]

[0131] In summary, according to the analysis of the above test results, the easy-to-defoam roto-molded polypropylene composition of the present invention is superior to the prior art in terms of tensile yield stress, nominal strain at break, simply supported beam notched impact strength, bending elastic modulus, oxidation induction time, yellow index of the composition, yellow index of the roto-molded product, density of the composition, and density of the roto-molded product.

[0132] The present invention discloses a rotomolded polypropylene composition that is easy to defoam and a preparation method thereof. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the same. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The product of the present invention has been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the product described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

Claims

1. A rotomolding polypropylene composition that is easy to defoam, characterized in that: The following components are included in parts by weight:

2. The easily defoamable rotomolding polypropylene composition according to claim 1, characterized in that: The antioxidant is a phosphite antioxidant.

3. The easily defoamable rotomolding polypropylene composition according to claim 2, characterized in that: The phosphite antioxidant is tris(2,4-di-tert-butylphenyl)phosphite.

4. The easily defoamable rotomolding polypropylene composition according to claim 1, characterized in that: The acid absorber is calcium stearate or zinc stearate.

5. The easily defoamable rotomolding polypropylene composition according to claim 1, characterized in that: The lubricants are lubricant A and lubricant B; the mass ratio of lubricant A to lubricant B is 1:1-1:2; the lubricant A is didodecyl phthalate, and the lubricant B is Hyper c100.

6. The easily defoamable rotomolding polypropylene composition according to claim 1, characterized in that: The hydrated alumina is pseudo-boehmite with a particle size of 10-60 nm.

7. The easily defoamable rotomolding polypropylene composition according to claim 1, characterized in that: The following components are included in parts by weight:

8. The method for preparing the easily defoaming rotomolding polypropylene composition according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Add one-half of polypropylene, antioxidant, acid absorbent and lubricant A into a high-speed mixer, stir at 50-90° C. and 1000-1500 r / min to mix evenly; after high-speed stirring in a heated state, lubricant A penetrates into the polypropylene molecules; (2) adding lubricant B, hydrated alumina and coupling agent to anhydrous ethanol and mixing them evenly in an ultrasonic mixer, wherein the amount of coupling agent added is 6-10 times that of hydrated alumina; (3) adding the remaining half of the polypropylene and the material obtained in step (2) into a high-speed mixer, stirring at 300-800 r / min to mix evenly; (4) melt-mixing the materials obtained in step (1) and step (3) in a co-rotating twin-screw extruder, and extruding and granulating the mixture; (5) Grind the granulated material into fine powder on a grinder.

9. The preparation method according to claim 8, characterized in that: The highest section temperature of the co-rotating twin-screw extruder is 190-230° C., the main engine speed is 150-230 r / min, and the feeding speed is 30-50 r / min.

10. The preparation method according to claim 8, characterized in that: Among the fine powder, powder with a mesh size of 40-100 accounts for 70-85%; among the powder with a mesh size of 40-100, powder with a mesh size of 40-80 accounts for 25-60%.

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