High-density polyethylene resin for large hollow containers and trays and preparation method of high-density polyethylene resin

Abstract

The invention discloses high-density polyethylene resin for large hollow containers and trays and a preparation method of the high-density polyethylene resin. The resin comprises the following raw materials in parts by weight: 100 parts of ethylene-hexene copolymerized polyethylene base resin, 0.06-0.15 part of a main antioxidant and 0.05-0.11 part of an auxiliary antioxidant, the ethylene-hexene copolymerized polyethylene resin is obtained by uniformly mixing the components through a mixer, heating and melting the components through an extruder, and granulating the resin at a granulation unit template of the extruder. By adopting a double-ring pipe slurry method polyethylene production process technology, the diluent is easily removed from the resin, the stability of the polymerization reaction is improved, and the product quality is further improved; the ethylene-hexene copolymerized polyethylene resin prepared by the invention has good rigidity and toughness balance performance and also has good processability.

Description

Technical Field

[0001] The present invention relates to a high-density polyethylene resin and a preparation method thereof, and particularly to a high-density polyethylene resin for large hollow containers and pallets and a preparation method thereof, belonging to the technical field of blow molding resins. Background Art

[0002] Due to excellent low-temperature resistance, chemical stability, acid and alkali corrosion resistance, insolubility in common solvents at room temperature, low water absorption, and excellent electrical insulation performance, polyethylene resin has been widely used in plastic hollow products. In 1977, Mauser Company in Germany and BASF Company jointly developed the 220-liter L-ring plastic drum successfully, opening the door for the wide use of large hollow containers in the chemical industry. The 200-liter large hollow container drum produced by the extrusion blow molding process with high-density polyethylene as the raw material has excellent mechanical strength, excellent impact resistance, and good environmental stress cracking resistance, and is particularly suitable for the packaging and transportation of liquid hazardous chemical products. Therefore, 200-liter double L-ring drums are generally used internationally to package dangerous goods. Since the mid-1980s, when Sinopec Corporation introduced two sets of L-ring drum blow molding units from Germany, and with the promotion of the development trend of "replacing steel with plastic", 200-liter double L-ring drums have gradually been accepted by domestic chemical enterprises.

[0003] In recent years, with the rapid development of the logistics industry, new demands have emerged in aspects such as improving turnover efficiency, turnover convenience, and increasing turnover volume. Plastic pallets have responded to these demands and are becoming increasingly popular among users. Plastic pallets produced by the blow molding process with high-density polyethylene as the raw material have emerged, and the demand for pallet resins has increased year by year. Currently, blow molded pallets often use the same type of high-density polyethylene resin as blow molded large hollow containers to meet the processing performance and mechanical performance requirements of pallet products.

[0004] In Chinese Patent CN114292356A, a special-purpose polyethylene for blow molding large hollow containers was prepared using a main catalyst containing a titanium halide compound; among them, the environmental stress cracking resistance of the resin with 1-butene as the comonomer is weaker than that of the resin with 1-hexene as the comonomer; the polymerization medium used is hexane, and the removal of hexane from the resin is more difficult than isobutane. In Chinese Patent CN116063771A, the upper limit of the melt flow rate range of the prepared ethylene-hexene copolymerized polyethylene resin is relatively low. When the processing conditions are the same, a lower melt flow rate will affect the processing efficiency of the product to a certain extent. In Chinese Patent CN102942733A, the upper limit of the melt flow rate range of the prepared ethylene-hexene copolymerized polyethylene resin is relatively high, and a higher melt flow rate will affect the mechanical properties of the resin to a certain extent.

[0005] In the market, large and hollow resins have problems such as insufficient drop performance and stacking performance. Moreover, with the increasing demand for large and hollow containers and pallets, relevant product manufacturers have put forward high requirements for the processing performance, molding performance and processing efficiency of resin raw materials. Therefore, resins with good processing performance and a balance between rigidity and toughness have become the requirements and development trend for high-density polyethylene used in large and hollow containers and pallets. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-density polyethylene resin for large and hollow containers and pallets and its preparation method in view of the deficiencies in the prior art. The products of the present invention have both good processing performance and a balance between rigidity and toughness, so that when hollow products such as large and hollow containers and pallets meet the mechanical property requirements, the advantages of the resin in terms of processing performance and molding performance of complex structure products are reflected. In the preparation process of the high-density polyethylene resin described in the present invention, the double-loop slurry process for polyethylene production technology makes it easy to remove the diluent from the resin and improves the stability of the polymerization reaction, further improving the product quality.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] One object of the present invention is to provide a high-density polyethylene resin for large and hollow containers and pallets, comprising the following raw materials in parts by weight: 100 parts by weight of ethylene-hexene copolymerized polyethylene base resin, 0.06 - 0.15 parts by weight of a primary antioxidant, and 0.05 - 0.11 parts by weight of a secondary antioxidant.

[0009] In the above technical solution, the high-density polyethylene resin for large and hollow containers and pallets preferably comprises the following raw materials in parts by weight: 100 parts by weight of ethylene-hexene copolymerized polyethylene base resin, 0.11 - 0.15 parts by weight of a primary antioxidant, and 0.05 - 0.11 parts by weight of a secondary antioxidant.

[0010] In the above technical solution, the ethylene-hexene copolymerized polyethylene base resin is prepared by using the INNOVENE S double-loop slurry process of INEOS: Add the diluent isobutane to the double-loop reactor, and make the isobutane in a forced circulation state through the axial flow pump of the double-loop reactor. Add ethylene, 1-hexene and a catalyst to the first loop reactor of the double-loop reactor. The slurry formed after the reaction in the first loop reactor enters the second loop reactor, and at the same time, add ethylene and 1-hexene to the second loop reactor. Ethylene and 1-hexene continue to react in the second loop reactor. Control the temperature in the double-loop reactor to be 96 - 103 °C, and the polyethylene base resin copolymerized with ethylene and hexene is obtained.

[0011] In the present invention, the diluent is isobutane, and the dosage of isobutane is 30 - 40 t / h. The isobutane preferably has the following specifications: purity ≥ 95.00% (wt), water content ≤ 5 mg / kg, CO content ≤ 1.0 mg / kg, CO2 content ≤ 5.0 mg / kg, O2 content ≤ 5 mg / kg, C5 and heavier components content ≤ 600.0 mg / kg, 1-butene content ≤ 97 mg / kg, butadiene content ≤ 3 mg / kg, acetylene content ≤ 0.5 mg / kg, total carbonyl content ≤ 2.5 mg / kg, total alcohol content ≤ 6 mg / kg, total sulfur content ≤

[0012] 1 mg / kg, chlorine content ≤ 1 mg / kg, ammonia content ≤ 1 mg / kg.

[0013] In the present invention, the mass ratio of 1-hexene to ethylene in the first loop reactor and the second loop reactor is 2.5 - 4 kg:1 t; the ethylene preferably has the following specifications: purity ≥ 99.90% (v), water content ≤ 1 mg / kg, CO content ≤ 1 mL / m 3 , CO2 content ≤ 2.0 mL / m 3 , acetylene content ≤ 5 mL / m 3 , allene content ≤ 2 mL / m 3 , propyne content ≤ 2 mL / m 3 , oxygen content ≤ 2 mL / m 3 , methanol content ≤ 1 mL / m 3 , oxide content ≤ 20 mL / m 3 , total sulfur ≤ 1 mg / kg. The 1-hexene preferably has the following specifications: purity ≥ 99.00% (wt), water content ≤ 1 mg / kg, (methanol + ethanol) content ≤ 10.0 mg / kg, 1,3-hexadiene content ≤ 10 mg / kg, total sulfur content ≤ 1 mg / kg, total chlorine content ≤ 1 mg / kg, oxygen content ≤ 1 mg / kg, benzene content ≤ 1.0 mg / kg, aromatic hydrocarbon content ≤ 1.0 mg / kg.

[0014] In the present invention, the catalyst is any one of HA30WFL or NTR-931TD, and the dosage of the catalyst is added according to the mass ratio of 0.15 - 0.35 kg:1 t of the catalyst to the total ethylene in the double loop reaction (the total amount of ethylene in the first loop reactor and the second loop reactor).

[0015] In the above technical solution, the main antioxidant is a phenolic antioxidant, preferably pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0016] In the above technical solution, the auxiliary antioxidant is an organic phosphite antioxidant, preferably bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite.

[0017] A second object of the present invention is to provide a method for preparing a high-density polyethylene resin for large hollow containers and pallets, comprising the following steps: Mixing 100 parts by weight of an ethylene-hexene copolymer polyethylene base resin, 0.06 to 0.15 parts by weight of a main antioxidant and 0.05 to 0.11 parts by weight of an auxiliary antioxidant in a continuous conveying mixer, heating and melting the mixture by an extruder, and granulating the resin at the die of the granulating unit of the extruder to obtain an ethylene-hexene copolymer polyethylene resin with a melt flow rate of 1.70 to 3.00 g / 10 min and a density of 0.9500 to 0.9580 g / cm 3 3.

[0018] In the above technical solution, the extruder is an extruder of the LCM-450 model of KOBELCO. When the extruder is kneading, the temperature of the gate valve of the extruder barrel is 240 to 280 °C, the temperature of the pelletizing cooling water is 58 to 68 °C, and the flow rate of the pelletizing cooling water is 600 to 670 m 3 3 / h.

[0019] In the present invention, the melt flow rate of the ethylene-hexene copolymer polyethylene resin is preferably 2.00 to 2.80 g / 10 min, more preferably 2.20 to 2.65 g / 10 min, and the density of the ethylene-hexene copolymer polyethylene resin is preferably 0.9510 to 0.9540 g / cm 3 3. The melt flow rate of the resin of the present invention is measured according to the measurement method of GB / T 3682.1-2018 and tested under the conditions of 190 °C and a 21.6 kg weight pressure, and the density is tested according to the measurement method of GB / T 1033.2-2010. The ethylene-hexene copolymer polyethylene base resin prepared by the present invention has good processing performance and a balance of rigidity and toughness.

[0020] A third object of the present invention is to provide an application of the high-density polyethylene resin in the field of hollow blow molding technology, and the field of hollow blow molding technology is preferably the field of large hollow container and pallet blow molding technology; at the same time, the high-density polyethylene resin can be used as a blend formulation component and applied to the field of hollow container blow molding technology.

[0021] Compared with the prior art, it has the following characteristics:

[0022] (1) The present invention uses ethylene and 1-hexene as polymerization monomers and conducts a polymerization reaction under the action of a catalyst. By adjusting at least one of the catalyst type and its addition amount, the addition ratio of the polymerization monomers, the reaction temperature of the reactor, and the resin formulation, the high-density polyethylene resin is controlled to have a reasonable melt flow rate and density, and a high-density polyethylene resin with good processing performance and a balance between rigidity and toughness is obtained, which can meet the high requirements of product manufacturers for high-density polyethylene resins used in hollow blow molding products such as large hollow containers and pallets in terms of mechanical properties, processing performance, processing efficiency, etc.

[0023] (2) The present invention adopts a double-loop slurry process technology for polyethylene production. The slurry in the double-loop reactor is stirred by an axial flow pump installed at the bottom elbow of the circulation loop, so that the reactant slurry has good fluidity, excellent heat transfer ability and a large heat transfer area; the particle dynamic performance in the reactor is remarkable, and product grade conversion is easy.

[0024] (3) The double-loop reactor uses isobutane as a diluent. The diluent circulation system has a simple design, high working efficiency, easy removal of the diluent and low energy consumption, ensuring the stability of the process conditions in the reactor, thus ensuring product quality. The produced polymer powder has better mechanical properties and allows the production of high-concentration polymers.

[0025] Other advantages, objectives and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Detailed Description of the Invention

[0026] The following describes in detail the specific embodiments of the technical solution of the present invention, but the present invention is not limited to the following description:

[0027] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention, but do not constitute any limitation to the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

[0028] Melt Flow Rate

[0029] The melt flow rate is measured according to GB / T 3682.1-2018 under the test conditions of 190 °C and a weight pressure of 21.6 kg, and the unit is g / 10 min.

[0030] Density

[0031] The density is measured according to GB / T 1033.2-2010, and the unit is g / cm 3 .

[0032] Tensile Yield Stress

[0033] Measure the tensile yield stress according to GB / T 1040.2-2006, unit MPa.

[0034] Notched impact strength of simply supported beam

[0035] Measure the notched impact strength of simply supported beam according to GB / T 1043.1-2008, the test temperature is 23 °C, unit kJ / m 2 。

[0036] Flexural modulus

[0037] Measure the flexural modulus according to GB / T 9341-2008, unit MPa.

[0038] Example 1:

[0039] A high-density polyethylene resin for large hollow containers and pallets is obtained by the following method:

[0040] (1) Preparation method of ethylene-hexene copolymerized polyethylene base resin:

[0041] The ethylene-hexene copolymerized polyethylene base resin is prepared by using the INNOVENE S double-loop slurry process of INEOS company: Add diluent isobutane to the double-loop reactor, make isobutane in a forced circulation state through the axial flow pump of the double-loop reactor, add ethylene, 1-hexene and catalyst HA30WFL to the first loop reactor of the double-loop reactor, the slurry formed by the reaction in the first loop reactor enters the second loop reactor, add ethylene, 1-hexene to the second loop reactor, and ethylene and 1-hexene continue to react in the second loop reactor. Control the temperature in the double-loop reactor at 99.5-101.5 °C to obtain the polyethylene base resin copolymerized by ethylene and hexene.

[0042] Among them, the ethylene feed rate of the first loop reactor is 14.5 t / h, the ethylene feed rate of the second loop reactor is 13.5 t / h, the dosage ratio of 1-hexene to ethylene in the first loop reactor and the second loop reactor is 3.5 kg:1 t, the catalyst feed rate is 5.2 kg / h, and the dosage of isobutane is 35 t / h.

[0043] (2) Preparation method of ethylene-hexene copolymerized polyethylene resin:

[0044] Mix 100 parts by weight of ethylene - hexene copolymer polyethylene base resin, 0.11 part by weight of the primary antioxidant pentaerythritol tetrakis [β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate], and 0.08 part by weight of the secondary antioxidant bis(2,4 - di - tert - butylphenyl) pentaerythritol diphosphite in a continuous conveying mixer. After mixing evenly, heat and melt them in an extruder, and granulate the resin at the die of the granulation unit of the extruder to obtain an ethylene - hexene copolymer polyethylene resin with a melt flow rate of 2.38 g / 10 min and a density of 0.9518 g / cm 3 3.

[0045] The extruder is an extruder of the LCM - 450 model of KOBELCO. The temperature of the gate valve of the extruder barrel is 270 °C, the temperature of the pelletizing cooling water is adjusted to 65 °C, and the flow rate of the pelletizing cooling water is 620 m 3 / h.

[0046] Example 2:

[0047] A high - density polyethylene resin for large hollow containers and pallets is obtained by the following method: The operation method of this example is basically the same as that of Example 1, except that: control the temperature in the double - loop reactor to be 100 - 102 °C, the ethylene feed rate of the first loop reactor is 14.5 t / h, the ethylene feed rate of the second loop reactor is 13.5 t / h, the usage ratio of 1 - hexene to ethylene in both the first loop reactor and the second loop reactor is 3.5 kg:1 t, the catalyst feed rate is 4.9 kg / h, and the usage amount of isobutane is 37 t / h.

[0048] Obtain an ethylene - hexene copolymer polyethylene resin with a melt flow rate of 2.60 g / 10 min and a density of 0.9517 g / cm 3 3.

[0049] Example 3:

[0050] A high - density polyethylene resin for large hollow containers and pallets is obtained by the following method: The operation method of this example is basically the same as that of Example 1, except that: control the temperature in the double - loop reactor to be 98 - 100 °C, the ethylene feed rate of the first loop reactor is 14.5 t / h, the ethylene feed rate of the second loop reactor is 13.5 t / h, the usage ratio of 1 - hexene to ethylene in both the first loop reactor and the second loop reactor is 3.6 kg:1 t, the catalyst feed rate is 5.3 kg / h, and the usage amount of isobutane is 37 t / h.

[0051] Obtain an ethylene - hexene copolymer polyethylene resin with a melt flow rate of 2.38 g / 10 min and a density of 0.9520 g / cm 3 3.

[0052] Example 4:

[0053] A high-density polyethylene resin for large hollow containers and trays is obtained by the following method:

[0054] (1) Preparation method of ethylene-hexene copolymerized polyethylene base resin:

[0055] This step is basically the same as that in Example 1, except that the catalyst used is NTR-931TD, the temperature in the double-loop reactor is controlled at 96.5 - 98.5 °C, the ethylene feed rate in the first loop reactor is 14.5 t / h, the ethylene feed rate in the second loop reactor is 13.5 t / h, the dosage ratio of 1-hexene to ethylene in both the first loop reactor and the second loop reactor is 3.6 kg:1 t, the catalyst feed rate is 7.8 kg / h, and the dosage of isobutane is 37 t / h.

[0056] An ethylene-hexene copolymerized polyethylene resin with a melt flow rate of 2.50 g / 10 min and a density of 0.9515 g / cm 3 is obtained.

[0057] Verification examples:

[0058] Measure the melt mass flow rate, density, tensile yield stress, notched Izod impact strength, and flexural modulus of the ethylene-hexene copolymerized polyethylene resins obtained in Examples 1 - 4 and the products of Comparative Examples 1 - 2; among them, the resin products prepared in Examples 1 - 3 use the catalyst HA30WFL, the product in Example 4 uses the catalyst NTR-931TD, and the products of Comparative Examples 1 and 2 are commercially available polyethylene resin products (grade 1158P, grade HD5420GA, abbreviated as Comparative Example 1 and Comparative Example 2 respectively). Table 1 shows the properties of the ethylene-hexene copolymerized polyethylene resins in Examples 1 - 4 and the polyethylene resins in Comparative Examples 1 - 2.

[0059] Table 1: Properties of the polyethylene resins in Examples 1 - 4 and Comparative Examples 1 - 2

[0060]

[0061]

[0062] As can be seen from Table 1, the notched Izod impact strength (23 °C) of the ethylene-hexene copolymerized polyethylene resin prepared by the present invention ranges from 53.0 to 69.0 kJ / m 2, higher than the notched Izod impact strength (23 °C) of the comparative example, a high impact strength indicates that the product has good toughness; the flexural modulus ranges from 1120 to 1180 MPa, higher than that of the comparative example, and a high flexural modulus indicates that the product has good rigidity; the melt mass flow rate (21.6 kg, 190 °C) ranges from 2.30 to 2.60 g / 10 min, higher than that of the control example, and a high melt mass flow rate indicates good fluidity of the resin during processing, thus enabling good resin processing performance and playing a positive role in energy conservation, consumption reduction and improving processing efficiency during the processing. It can be seen that the ethylene - hexene copolymerized polyethylene resin prepared by the present invention has good rigid - tough balance performance and also good processing performance at the same time.

[0063] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Any minor modifications, equivalent changes and modifications made to the above embodiments based on the substantial technology of the present invention all fall within the scope of the technical solution of the present invention.

Claims

1. A high-density polyethylene resin for large hollow containers and pallets, characterized in that, It comprises the following raw materials in parts by weight: 100 parts by weight of ethylene - hexene copolymerized polyethylene base resin, 0.06 - 0.15 parts by weight of a primary antioxidant, and 0.05 - 0.11 parts by weight of a secondary antioxidant.

2. The high-density polyethylene resin for large hollow containers and pallets according to claim 1, characterized in that, The ethylene - hexene copolymerized polyethylene base resin is prepared by a double - loop slurry process: Isobutane as a diluent is added to the double - loop reactor, and the isobutane is in a forced - circulation state through the axial - flow pump of the double - loop reactor. Ethylene, 1 - hexene, and a catalyst are added to the first loop reactor of the double - loop reactor. The slurry formed after the reaction in the first loop reactor enters the second loop reactor, and at the same time, ethylene and 1 - hexene are added to the second loop reactor. Ethylene and 1 - hexene continue to react in the second loop reactor. The temperature in the double - loop reactor is controlled at 96 - 103 °C to obtain the polyethylene base resin copolymerized from ethylene and hexene.

3. The high-density polyethylene resin for large hollow containers and pallets according to claim 2, characterized in that, The diluent is isobutane, and the dosage of isobutane is 30 - 40 t / h; the mass ratio of 1 - hexene to ethylene in both the first loop reactor and the second loop reactor is 2.5 - 4 kg:1 t.

4. The high-density polyethylene resin for large hollow containers and pallets according to claim 2, characterized in that, The catalyst is any one of HA30WFL or NTR - 931TD, and the dosage of the catalyst is added according to the mass ratio of the catalyst to the total ethylene in the double - loop reactor of 0.15 - 0.35 kg:1 t.

5. The high-density polyethylene resin for large hollow containers and pallets according to claim 1, characterized in that, The primary antioxidant is a phenolic antioxidant, and the secondary antioxidant is an organic phosphite antioxidant.

6. The high-density polyethylene resin for large hollow containers and pallets according to claim 5, characterized in that, The primary antioxidant is pentaerythritol tetrakis [β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate], and the secondary antioxidant is bis(2,4 - di - tert - butylphenyl) pentaerythritol diphosphite.

7. A method for preparing the high-density polyethylene resin for large hollow containers and pallets according to any one of claims 1-6, characterized in that, It includes the following steps: Mix 100 parts by weight of ethylene-1-hexene copolymer polyethylene base resin, 0.06 to 0.15 parts by weight of a primary antioxidant, and 0.05 to 0.11 parts by weight of a secondary antioxidant in a continuous conveying mixer, then heat and melt them through an extruder, and pelletize the resin at the die of the pelletizing unit of the extruder to obtain an ethylene-1-hexene copolymer polyethylene resin with a melt flow rate of 1.70 to 3.00 g / 10 min and a density of 0.9500 to 0.9580 g / cm 3 .

8. The preparation method according to claim 7, characterized in that, The extruder used is the LCM-450 model extruder of KOBELCO. When the extruder is mixing, the temperature of the gate valve of the extruder barrel is 240-280°C, the temperature of the pelletizing cooling water is 58-68°C, and the flow rate of the pelletizing cooling water is 600-670 m 3 / h.

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