An agent for inhibiting the generation of black particles in a polyethylene pelletizing process and a method for preparing the same
By adding additives made from vinylidene fluoride and hexafluoropropylene during the polyethylene granulation process, the problem of black particles caused by the screw material was solved, thereby improving product quality and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-12-05
- Publication Date
- 2026-06-05
AI Technical Summary
Black particles are generated during the polyethylene granulation process due to screw material issues, affecting product quality and economic benefits.
An additive using vinylidene fluoride and hexafluoropropylene as the main components is prepared into an oily substance through emulsion or free radical solution polymerization and then added to polyethylene resin to suppress the generation of black particles.
It effectively reduces the generation of black particles, improves the light transmittance and tensile strength of polyethylene products, reduces production costs and energy consumption, and improves product quality.
Smart Images
Figure CN122145691A_ABST
Abstract
Description
Technical fields:
[0001] This invention relates to the field of polyethylene production technology, and in particular to an additive for inhibiting the generation of black particles during the polyethylene granulation process and its preparation method. Background technology:
[0002] During the melt granulation process, polyethylene resin is subjected to intense extrusion and shearing in the mixing extruder. This process raises the resin temperature, making it susceptible to the effects of oxygen, catalyst residues, and light, negatively impacting the performance and economic benefits of polyethylene products. Therefore, different types of additives need to be added during the melt granulation process to enhance the degradation resistance of polyethylene products and improve their performance and efficiency.
[0003] In the industrial production of polyethylene, antioxidants, slip agents, and plasticizers are generally added during granulation. Antioxidants mainly prevent free radicals and growing chains in polyethylene resin from reacting with oxygen in the air, leading to deterioration and increasing the induction time of oxidative degradation. Slip agents can reduce the friction between polymer molecules, making the polyethylene resin shear more uniform and flow more smoothly, which is beneficial to improving the surface quality of the product. Plasticizers can increase the flexibility and cold resistance of polyethylene products, lower their glass transition temperature, melting point, and viscosity, and increase their flow properties, thereby improving the elongation and impact resistance of polyethylene film products.
[0004] During the polyethylene melt granulation process, when the screw surface of the granulator is uniformly chrome-plated, smooth, and highly clean, the resulting polyethylene granules are uniform in size and have a certain gloss. However, when the screw surface is not chrome-plated, or when materials and costs are saved, the screw surface becomes rough. Polyethylene resin easily adheres to the grooves on the screw surface, and if it does not flow in time, it will carbonize at high temperatures. Excessive accumulation will cause it to fall off and enter the normal granules, resulting in black particles in the product that cannot be removed, ultimately affecting product quality. Summary of the Invention:
[0005] The technical problem to be solved by the present invention is to provide an additive for inhibiting the generation of black particles in the polyethylene granulation process and its preparation method. The additive effectively reduces the number of black particles generated in the polyethylene granulation process, can improve the tensile strength and light transmittance of film products, delay melt fracture, improve energy utilization efficiency, and reduce production costs, energy consumption, and material consumption.
[0006] The technical solution adopted in this invention is: an additive for inhibiting the generation of black particles during the polyethylene granulation process, the additive comprising the following components: vinylidene fluoride and hexafluoropropylene; the fluorine content in the additive, by mass fraction, is 30-60%.
[0007] Furthermore, the additive, under normal temperature and pressure, appears as a white, free-flowing powder free of mechanical impurities, with a bulk density of 0.6–0.8 g / cm³. 3 Volatile matter 0.5-2 wt%, ash 3-8 wt%, residue on 30-mesh sieve 0-3 wt%, residue on 20-mesh sieve 0 wt%.
[0008] A method for preparing an additive to inhibit the generation of black particles during the granulation process of polyethylene includes the following steps: taking vinylidene fluoride and hexafluoropropylene materials, and preparing an oily substance by emulsion polymerization or free radical solution polymerization, washing the oily substance with pentane, and drying it until the mass is constant to obtain the additive.
[0009] Furthermore, the drying temperature is 80–90°C.
[0010] Further, the emulsion polymerization method comprises the following steps: under vacuum conditions, vinylidene fluoride, hexafluoropropylene, and polyethylene glycol are added to deionized water, and under the combined action of fluorocarbon emulsifier, initiator, and regulator, the emulsion polymerization reaction is carried out for 9 to 11 hours at 105–115°C and 1.5–1.8 MPa by continuous stirring.
[0011] Furthermore, the fluorocarbon emulsifier includes H(CF2CF2). n COOK, n = 3, 4, 5 or one or more of CF2Cl(CFClCF2)3COOK.
[0012] Furthermore, the regulator includes one or more of acetonitrile, acetone, ethyl acetate, and glacial acetic acid.
[0013] Further, the free radical solution polymerization method is carried out in the following steps: the process is carried out intermittently in a borosilicate Carius tube, the initiator and acetonitrile are first added to vinylidene fluoride and hexafluoropropylene, and then oxygen is removed by vacuuming or rinsing and replacing with rare gas. The tube is then sealed and placed in a vibrating furnace, and the polymerization reaction is carried out at 115-125°C for 8-12 hours.
[0014] Furthermore, the initiator includes one or more of di-tert-butyl peroxide, dicumyl peroxide, diisopropyl peroxide, and tert-butyl hydroperoxide.
[0015] Furthermore, when the additive is used as a polyethylene granulation additive, if it is used to produce film material, it needs to be added periodically, with an addition amount of 15-30 kg every half month; if it is used to produce pipe material, the addition amount, i.e., the unit consumption, is 0.050-0.070 kg / t.
[0016] The beneficial effects of this invention are:
[0017] Beneficial effect 1: This invention provides a fluorinated polyethylene granulation process aid that can effectively reduce the number of black particles caused by screw material issues;
[0018] Beneficial effect 2: The additives prepared by this invention have good dispersibility and are less prone to coking at the template during long-term application in polyethylene melt extrusion.
[0019] Beneficial effect 3: The additives obtained by this invention can improve the impact strength and improve the quality of the product when added to polyethylene resin.
[0020] Beneficial effect 4: The additives obtained by this invention can reduce mechanical wear and lower the overall cost of film processing after being added to polyethylene resin;
[0021] Beneficial Effect 5: The additives obtained by this invention can effectively improve production efficiency when added to polyethylene resin and are easy to implement in continuous industrial production processes. Attached image description:
[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0023] Figure 1 This is a schematic diagram of the screw surface of an extrusion granulation unit without the additives of this invention.
[0024] Figure 2 This is a schematic diagram of the screw surface of an extrusion granulator after the addition of the additives of this invention. Detailed implementation method:
[0025] An additive for inhibiting the generation of black particles during the polyethylene granulation process, the additive comprising the following components: vinylidene fluoride and hexafluoropropylene; the fluorine content in the additive, by mass fraction, is 30-60%.
[0026] The additive, under normal temperature and pressure, appears as a white, free-flowing powder free of mechanical impurities, with a bulk density of 0.6–0.8 g / cm³. 3 Volatile matter 0.5-2 wt%, ash 3-8 wt%, residue on 30-mesh sieve 0-3 wt%, residue on 20-mesh sieve 0 wt%.
[0027] A method for preparing an additive to inhibit the generation of black particles during the polyethylene granulation process includes the following steps: taking vinylidene fluoride and hexafluoropropylene materials, and preparing an oily substance by emulsion polymerization or free radical solution polymerization, washing the oily substance with pentane, and drying it at 80-90°C until the mass is constant to obtain the additive.
[0028] The emulsion polymerization method comprises the following steps: under vacuum conditions, vinylidene fluoride, hexafluoropropylene, and polyethylene glycol are added to deionized water. Under the combined action of fluorocarbon emulsifier, initiator, and regulator, the emulsion polymerization reaction is carried out for 9–11 hours at 105–115°C and 1.5–1.8 MPa with continuous stirring.
[0029] The fluorocarbon emulsifier includes H(CF2CF2). n COOK, n = 3, 4, 5 or one or more of CF2Cl(CFClCF2)3COOK.
[0030] The regulator includes one or more of acetonitrile, acetone, ethyl acetate, and glacial acetic acid.
[0031] The free radical solution polymerization method is as follows: the process is carried out intermittently in a borosilicate Carius tube. First, the initiator and acetonitrile are added to vinylidene fluoride and hexafluoropropylene. Then, oxygen is removed by vacuuming or rinsing and replacing with rare gas. The tube is then sealed and placed in a vibrating furnace for polymerization reaction at 115-125°C for 8-12 hours.
[0032] The initiator includes one or more of di-tert-butyl peroxide, dicumyl peroxide, diisopropyl peroxide, and tert-butyl hydroperoxide.
[0033] The process of using the additive prepared in this invention is as follows: the additive is added to the granulator through the feeding port, mixed evenly with polyethylene resin, and then extruded and melted on the surface of the screw. The additive is then conveyed to the underwater pelletizer for pelletizing by the transmission action of the screw.
[0034] The present invention will be further illustrated below by means of embodiments. These embodiments are only used to explain the present invention and do not constitute any limitation on the present invention.
[0035] Example 1: Add 20 grams of the additive A of the present invention to a twin-screw granulator for extrusion granulation at a speed of 1415 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles, after analysis, have a light transmittance of 88.31%.
[0036] Example 2: Add 50 grams of the additive A of the present invention to a twin-screw granulator for extrusion granulation at a speed of 1415 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles, after analysis, have a light transmittance of 92.53%.
[0037] Example 3: 100 grams of additive A of the present invention were added and fed into a twin-screw granulator for extrusion granulation at a speed of 1415 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles, after analysis, had a light transmittance of 93.31%.
[0038] Example 4: Add 50 grams of the additive A of the present invention, and put it into a twin-screw granulator for extrusion granulation at a speed of 1500 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles were analyzed and found to have a light transmittance of 91.77%.
[0039] Example 5: Add 50 grams of the additive A of the present invention, and put it into a twin-screw granulator for extrusion granulation at a speed of 1400 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles were analyzed and found to have a light transmittance of 92.64%.
[0040] The invention will be further illustrated below with comparative examples.
[0041] Comparative Example 1: Without adding the additives of this invention, the pellets were extruded and granulated in a twin-screw granulator at a speed of 1415 r / min, a barrel temperature of 180-250℃, and a pressure of 2.5 MPa. The resulting particles, after analysis, had a light transmittance of 85.96%.
[0042]
[0043] Table 1. Specific production conditions and performance indicators of the polyethylene products prepared in Examples 1-5 and Comparative Example 1.
[0044] Table 1 shows that, under the condition that other factors remain unchanged, increasing the amount of the additive prepared by this invention within a certain range will improve the light transmittance of the polyethylene product. (See Table 1.) Figure 1 , Figure 2 As shown, compared to the case without the additives of this invention, tests have proven that the additives and their preparation methods involved in this patent have a positive impact on the surface finish and quality of the product.
[0045] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.
Claims
1. An additive for inhibiting the generation of black particles during the polyethylene granulation process, characterized in that: The additive comprises the following components: vinylidene fluoride and hexafluoropropylene; the fluorine content in the additive, by mass fraction, is 30-60%.
2. The additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 1, characterized in that: The additive, under normal temperature and pressure, appears as a white, free-flowing powder free of mechanical impurities, with a bulk density of 0.6–0.8 g / cm³. 3 Volatile matter 0.5-2 wt%, ash 3-8 wt%, residue on 30-mesh sieve 0-3 wt%, residue on 20-mesh sieve 0 wt%.
3. A method for preparing an additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 1, characterized in that: The method involves the following steps: taking vinylidene fluoride and hexafluoropropylene materials, and preparing an oily substance through emulsion polymerization or free radical solution polymerization. The oily substance is then cleaned with pentane and dried until its mass is constant to obtain the additive.
4. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 3, characterized in that: The drying temperature is 80-90℃.
5. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 3, characterized in that: The emulsion polymerization method comprises the following steps: under vacuum conditions, vinylidene fluoride, hexafluoropropylene, and polyethylene glycol are added to deionized water. Under the combined action of fluorocarbon emulsifier, initiator, and regulator, the emulsion polymerization reaction is carried out for 9–11 hours at 105–115°C and 1.5–1.8 MPa with continuous stirring.
6. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 5, characterized in that: The fluorocarbon emulsifier includes H(CF2CF2). n COOK, n = 3, 4, 5 or one or more of CF2Cl(CFClCF2)3COOK.
7. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 5, characterized in that: The regulator includes one or more of acetonitrile, acetone, ethyl acetate, and glacial acetic acid.
8. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 3, characterized in that: The free radical solution polymerization method is as follows: the process is carried out intermittently in a borosilicate Carius tube. First, the initiator and acetonitrile are added to vinylidene fluoride and hexafluoropropylene. Then, oxygen is removed by vacuuming or rinsing and replacing with rare gas. The tube is then sealed and placed in a vibrating furnace for polymerization reaction at 115-125°C for 8-12 hours.
9. The method for preparing the additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 8, characterized in that: The initiator includes one or more of di-tert-butyl peroxide, dicumyl peroxide, diisopropyl peroxide, and tert-butyl hydroperoxide.
10. The additive for inhibiting the generation of black particles during the polyethylene granulation process according to claim 1, characterized in that: When the additive is used as a polyethylene granulation additive, if it is used to produce film material, it needs to be added periodically, with an addition amount of 15-30 kg every half month; if it is used to produce pipe material, the addition amount, i.e., the unit consumption, is 0.050-0.070 kg / t.