Low-sag high-density polyethylene thick-wall pipe resin and preparation method thereof

Abstract

The invention relates to the technical field of high-molecular polymer resin, in particular to low-sag high-density polyethylene thick-wall pipe resin and a preparation method thereof. The polyethylene thick-wall pipe resin is prepared from the following raw materials in parts by weight: 100 parts of ethylene / 1-butene copolymer powder, 0.30 to 0.50 part of antioxidant, 0.10 to 0.20 part of acid remover and 0.01 to 0.05 part of fluorine-containing polymer processing aid. The low-sag high-density polyethylene thick-wall pipe resin prepared by the invention has excellent processability and excellent sag resistance, is suitable for manufacturing pressure pipes, and is particularly suitable for manufacturing large-diameter thick-wall sag-resistant pipes.

Description

Technical field:

[0001] The invention relates to the technical field of high molecular polymer resins, and in particular to a low sag high density polyethylene thick wall pipe resin and a preparation method thereof. Background technology:

[0002] Polyethylene (PE) pipe materials have outstanding chemical corrosion resistance, good welding performance, no pollution to the conveying medium, long service life, low manufacturing and installation costs, etc., and are widely used in municipal engineering construction, agricultural production, petrochemical and other fields. At home and abroad, because PE pipes have the advantages of hygiene, corrosion resistance and convenient and fast laying compared with traditional ductile iron, the application of low-sag large-diameter PE pipes in my country has also increased year by year, and is used in the fields of reclaimed water pipelines and drinking water transportation, sea discharge pipelines, etc.

[0003] During the extrusion process of large-diameter pipes, due to the thick pipe wall and slow cooling and solidification, the melt will sag under the action of gravity, resulting in a small wall thickness on the top and a large wall thickness on the bottom, which is the "sag effect". The resulting pipe wall cannot meet the required tolerance and cannot achieve the required butt fusion welding. Although compensation can be made to a certain extent by adjusting the die gap, that is, increasing the upper gap and reducing the lower gap, the effect of this compensation is also very limited. The research results show that the anti-"sag" performance of high-density polyethylene pipes is related to the zero shear viscosity. The greater the zero shear viscosity, the better the anti-"sag" performance. The resin raw materials used to produce large-diameter PE pipe materials should have excellent anti-sag performance.

[0004] Chinese patent CN111100362A "A bimodal polyethylene resin for large-diameter, thick-walled, low-sag pipes and its preparation method". Provides a bimodal polyethylene resin for large-diameter, thick-walled, low-sag pipes and its preparation method. The resin comprises a high molecular weight portion and a low molecular weight portion, the mass ratio of the low molecular weight portion to the high molecular weight portion is 3:7-7:3; its number average molecular weight Mn is 2000-10000, the weight average molecular weight Mw is 100000-400000, Mw / Mn is 10-200, the melt flow rate MFR is 0.2-1.0g / 10min, and the resin density is 0.945-0.960g / cm 3 The provided bimodal polyethylene resin can be prepared by a reactor consisting of a loop reactor and a fluidized bed reactor connected in series. The bimodal polyethylene resin has improved mechanical properties, excellent processing properties, and excellent strength and anti-sag properties, and is suitable for preparing large-diameter, thick-walled, low-sag pipes.

[0005] Chinese patent CN113930008A discloses a special resin for high-density polyethylene pipes with sag resistance and a production method thereof; a production method for a special resin for high-density polyethylene pipes with high sag resistance is produced on an Innovene S process double-loop high-density polyethylene device using a high-activity Ziegler-Natta catalyst. The special resin components for high-density polyethylene pipes with sag resistance include high-density polyethylene pipe resin powder, antioxidant, halogen absorber and fluorine-containing polymer processing aid; the prepared high-density polyethylene pipe resin has an oxidation induction time t≥65min (210°C), a melt strength ≥0.35N (230°C); a melt index of 0.18-0.25g / 10min at a temperature of 190°C and a load of 5kg; and an impact strength ≥40kJ / m 2 The bimodal polyethylene resin has excellent mechanical properties, excellent processing properties and anti-sag properties, and is suitable for the preparation of large-diameter thick-walled anti-sag pipes.

[0006] Chinese patent CN114426718A discloses a polyethylene resin with anti-sag performance and its preparation and application, and provides a polyethylene resin with anti-sag performance and its preparation and application. The polyethylene resin includes a low molecular weight ethylene homopolymer part and a high molecular weight α-olefin copolymer part, the molecular weight is bimodal distribution, and the mass ratio of the low molecular weight part to the high molecular weight part is 4:6-6:4; its weight average molecular weight Mw is 200000-240000, and the molecular weight distribution is 8-20; the melt flow rate MFR5 is 0.20-0.32g / 10min, and the resin density is 0.945-0.952g / cm 3 .

[0007] Although the above patented product is a bimodal product, the double loop process and the series process of loop reactor and fluidized bed reactor cannot effectively remove low molecular weight wax during the production process. The presence of a large amount of low molecular weight wax will affect the zero shear viscosity of the product, thereby affecting the anti-sag performance of the pipe resin. Summary of the invention:

[0008] The technical problem to be solved by the present invention is to provide a low-sag high-density polyethylene thick-wall pipe resin and a preparation method thereof. The low-sag high-density polyethylene thick-wall pipe resin has excellent processing performance and excellent anti-sag performance, is suitable for manufacturing pressure pipes, and is particularly suitable for manufacturing large-diameter thick-wall anti-sag pipes.

[0009] The technical solution adopted by the present invention is: a low-sag high-density polyethylene thick-wall pipe resin, which contains the following raw materials in parts by weight: ethylene / 1-butene copolymer powder: 100 parts, antioxidant: 0.30-0.50 parts, acid scavenger: 0.10-0.20 parts, and fluorine-containing polymer processing aid: 0.01-0.05 parts.

[0010] Furthermore, the antioxidant is a mixture of a primary antioxidant and an auxiliary antioxidant in a mass ratio of 1:1, the primary antioxidant is antioxidant 1010, and the auxiliary antioxidant is antioxidant 168.

[0011] Furthermore, the acid scavenger is a mixture of calcium stearate and zinc stearate in a mass ratio of 1:1.

[0012] Furthermore, the fluorine-containing polymer processing aid is One of PPA9000E or DA-810X.

[0013] Furthermore, the preparation method of the ethylene / 1-butene copolymer powder is as follows:

[0014] Step 1, adding ethylene at a feed rate of 12.0-14.0 t / h, Z501 catalyst hexane solution at a feed rate of 36.5-42.5 kg / h, triethylaluminum and hydrogen into a first autoclave reactor, controlling the Al / Ti molar ratio to be 20-30, the hydrogen to ethylene molar ratio to be 3:1-4:1, and the melt index of the first autoclave reactor to be controlled at 600-700 g / 10 min, to carry out a polymerization reaction;

[0015] Step 2: sending the polymer slurry from the first kettle reactor to a dehydrogenation flash tank, controlling the pressure of the dehydrogenation flash tank at 0.04-0.06 MPa, and sending the polymer slurry after flash dehydrogenation to a second kettle reactor;

[0016] Step 3: Add ethylene at a feed rate of 13.0-15.8 t / h and 1-butene at a feed rate of 350-420 kg / h into the second batch reactor at the same time, and carry out polymerization reaction under the condition that the percentage of ethylene feed amount of the second batch reactor to the total feed amount of the first batch reactor and the second batch reactor is controlled at 52%-53%, and obtain ethylene / 1-butene copolymer powder by polymerization.

[0017] A method for preparing a low sag high-density polyethylene thick-wall pipe resin, the method comprising the following steps:

[0018] Step 1, adding ethylene / 1-butene copolymer powder, antioxidant, acid scavenger, and fluorine-containing polymer processing aid into a high-speed mixer and mixing them thoroughly;

[0019] Step 2: adding the fully mixed materials into a twin-screw extruder for granulation;

[0020] Step 3: Dry the pellets extruded in step 2 to obtain low sag high-density polyethylene thick-wall pipe resin.

[0021] Furthermore, the ethylene / 1-butene copolymer powder in step 1 is added to a high-speed mixer and fully mixed with an antioxidant, an acid scavenger, and a fluorine-containing polymer processing aid, first at a speed of 500 r / min for 1-2 minutes, and then at a speed of 1200 r / min for 0.5-1 minute.

[0022] Furthermore, various parameters of the extruder in the granulation process in step 2 are set to 180-220°C.

[0023] Furthermore, the drying conditions in step three are: drying at 70-80° C. for 1-1.5 hours.

[0024] The beneficial effects of the present invention are: by controlling the concentration of hydrogen in the second reactor, the weight average molecular weight of the polyethylene product is further increased, the amount of the comonomer 1-butene added is controlled, the branching degree of the product is increased, and the purpose of increasing the degree of entanglement between molecular chains is achieved, and at the same time, the low molecular weight wax content in the product is effectively controlled by optimizing the production process. The low sag high-density polyethylene thick-wall pipe resin obtained by the above method has excellent processing performance and excellent anti-sag performance, and is suitable for manufacturing pressure pipes, especially suitable for manufacturing large-diameter thick-wall anti-sag pipes. Description of the drawings:

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 This is a schematic diagram of the preparation process of ethylene / 1-butene copolymer powder. Specific implementation method:

[0027] Example 1

[0028] Ethylene at a feed rate of 12.0 t / h, Z501 catalyst hexane solution at a feed rate of 36.5 kg / h, triethylaluminum and hydrogen were added to the first reactor, the Al / Ti molar ratio was controlled to be 20, the molar ratio of hydrogen to ethylene was 3:1, and the melt index of the first reactor was controlled to be 610 g / 10 min, and a polymerization reaction was carried out; the polymer slurry from the first reactor was sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank was controlled to be 0.06 MPa, and the polymer slurry after flash dehydrogenation was sent to a second reactor; ethylene at a feed rate of 13 t / h and 1-butene at a feed rate of 350 kg / h were simultaneously added to the second reactor, and a melt index of 0.25 g / 10 min and a density of 0.950 g / cm were obtained by polymerization. 3 Ethylene / 1-butene copolymer powder. Add ethylene / 1-butene copolymer powder and composite additives into a high-speed mixer and mix thoroughly. First, mix at 500r / min for 1 minute, then mix at 1200r / min for 1 minute. The ethylene / 1-butene copolymer powder has 100 parts by mass, antioxidant 1010 has 0.15 parts by mass, antioxidant 168 has 0.15 parts by mass, zinc stearate has 0.05 parts by mass, calcium stearate has 0.05 parts by mass, and fluorine-containing polymer processing aid has 0.05 parts by mass. The mass fraction of PPA9000E is 0.01 parts; the fully mixed ethylene / 1-butene copolymer powder and the composite additive are added into a twin-screw extruder for granulation, and the various parameters of the extruder are set to 180-220°C during the granulation process; the extruded pellets are dried at 70-80°C for 1 hour to obtain a low-sag high-density polyethylene thick-wall pipe resin.

[0029] Example 2

[0030] Ethylene at a feed rate of 14.0 t / h, Z501 catalyst hexane solution at a feed rate of 42.5 kg / h, triethylaluminum and hydrogen were added to the first reactor, the Al / Ti molar ratio was controlled to be 30, the molar ratio of hydrogen to ethylene was 4:1, and the melt index of the first reactor was controlled to be 700 g / 10 min, and a polymerization reaction was carried out; the polymer slurry from the first reactor was sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank was controlled to be 0.04 MPa, and the polymer slurry after flash dehydrogenation was sent to a second reactor; ethylene at a feed rate of 15.8 t / h and 1-butene at a feed rate of 420 kg / h were simultaneously added to the second reactor, and a melt index of 0.22 g / 10 min and a density of 0.946 g / cm were obtained by polymerization. 3Ethylene / 1-butene copolymer powder. The ethylene / 1-butene copolymer powder and the composite additive are added to a high-speed mixer and fully mixed, first at a speed of 500r / min for 2 minutes, and then at a speed of 1200r / min for 0.5 minutes, wherein the ethylene / 1-butene copolymer powder has 100 parts by mass, the antioxidant 1010 has 0.20 parts by mass, the antioxidant 168 has 0.20 parts by mass, the zinc stearate has 0.08 parts by mass, the calcium stearate has 0.08 parts by mass, and the fluorine-containing polymer processing aid DA-810X has 0.02 parts by mass; the fully mixed ethylene / 1-butene copolymer powder and the composite additive are added to a twin-screw extruder for granulation, and the various parameters of the extruder during the granulation process are set to 180-220°C; the extruded pellets are dried at 70-80°C for 1.5 hours to obtain a low-sag high-density polyethylene thick-wall pipe resin.

[0031] Example 3

[0032] Ethylene at a feed rate of 13.0 t / h, Z501 catalyst hexane solution at a feed rate of 39.3 kg / h, triethylaluminum and hydrogen were added to the first reactor, the Al / Ti molar ratio was controlled to be 25, the molar ratio of hydrogen to ethylene was controlled to be 3.5:1, and the melt index of the first reactor was controlled to be 630 g / 10 min, and a polymerization reaction was carried out; the polymer slurry from the first reactor was sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank was controlled to be 0.05 MPa, and the polymer slurry after flash dehydrogenation was sent to a second reactor; ethylene at a feed rate of 14.4 t / h t / h and 1-butene at a feed rate of 400 kg / h were simultaneously added to the second reactor, and a melt index of 0.23 g / 10 min and a density of 0.949 g / cm were obtained by polymerization. 3 Ethylene / 1-butene copolymer powder. The ethylene / 1-butene copolymer powder and the composite additive are added to a high-speed mixer and fully mixed, first at a speed of 500r / min for 1 minute, and then at a speed of 1200r / min for 0.5 minute, wherein the ethylene / 1-butene copolymer powder has 100 parts by mass, the antioxidant 1010 has 0.25 parts by mass, the antioxidant 168 has 0.25 parts by mass, the zinc stearate has 0.08 parts by mass, the calcium stearate has 0.08 parts by mass, and the fluorine-containing polymer processing aid DA-810X has 0.02 parts by mass; the fully mixed ethylene / 1-butene copolymer powder and the composite additive are added to a twin-screw extruder for granulation, and the various parameters of the extruder during the granulation process are set to 180-220°C; the extruded pellets are dried at 70-80°C for 1.5 hours to obtain a low-sag high-density polyethylene thick-wall pipe resin.

[0033] Example 4

[0034] Ethylene at a feed rate of 14.0 t / h, Z501 catalyst hexane solution at a feed rate of 38.0 kg / h, triethylaluminum and hydrogen were added to the first reactor, the Al / Ti molar ratio was controlled to be 20, the molar ratio of hydrogen to ethylene was controlled to be 3:1, and the melt index of the first reactor was controlled to be 600 g / 10 min, and a polymerization reaction was carried out; the polymer slurry from the first reactor was sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank was controlled to be 0.04 MPa, and the polymer slurry after flash dehydrogenation was sent to a second reactor; ethylene at a feed rate of 15.2 t / h and 1-butene at a feed rate of 410 kg / h were simultaneously added to the second reactor, and a melt index of 0.20 g / 10 min and a density of 0.947 g / cm were obtained by polymerization. 3 Ethylene / 1-butene copolymer powder. The ethylene / 1-butene copolymer powder and the composite additive are added to a high-speed mixer and fully mixed, first at a speed of 500r / min for 1 minute, and then at a speed of 1200r / min for 0.5 minute, wherein the ethylene / 1-butene copolymer powder has 100 parts by mass, the antioxidant 1010 has 0.25 parts by mass, the antioxidant 168 has 0.25 parts by mass, the zinc stearate has 0.08 parts by mass, the calcium stearate has 0.08 parts by mass, and the fluorine-containing polymer processing aid DA-810X has 0.05 parts by mass; the fully mixed ethylene / 1-butene copolymer powder and the composite additive are added to a twin-screw extruder for granulation, and the various parameters of the extruder during the granulation process are set to 180-220°C; the extruded pellets are dried at 70-80°C for 1.5 hours to obtain a low-sag high-density polyethylene thick-wall pipe resin.

[0035] Example 5

[0036] Ethylene at a feed rate of 12.5 t / h, Z501 catalyst hexane solution at a feed rate of 40.0 kg / h, triethylaluminum and hydrogen were added to the first reactor, the Al / Ti molar ratio was controlled to be 20, the molar ratio of hydrogen to ethylene was 4:1, and the melt index of the first reactor was controlled to be 630 g / 10 min, and a polymerization reaction was carried out; the polymer slurry from the first reactor was sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank was controlled to be 0.06 MPa, and the polymer slurry after flash dehydrogenation was sent to a second reactor; ethylene at a feed rate of 13.5 t / h t / h and 1-butene at a feed rate of 420 kg / h were simultaneously added to the second reactor, and a melt index of 0.30 g / 10 min and a density of 0.948 g / cm were obtained by polymerization. 3Ethylene / 1-butene copolymer powder. Add ethylene / 1-butene copolymer powder and composite additives into a high-speed mixer and mix thoroughly. First, mix at a speed of 500r / min for 1 minute, and then mix at a speed of 1200r / min for 0.5 minute. The ethylene / 1-butene copolymer powder has 100 parts by mass, antioxidant 1010 has 0.25 parts by mass, antioxidant 168 has 0.25 parts by mass, zinc stearate has 0.08 parts by mass, calcium stearate has 0.08 parts by mass, and fluorine-containing polymer processing aid has 0. The mass fraction of PPA9000E is 0.05 parts; the fully mixed ethylene / 1-butene copolymer powder and the composite additive are added into a twin-screw extruder for granulation, and the various parameters of the extruder are set to 180-220°C during the granulation process; the extruded pellets are dried at 70-80°C for 1.5 hours to obtain a low-sag high-density polyethylene thick-wall pipe resin.

[0037] Comparative Example 1

[0038] Ethylene at a feed rate of 12.0 t / h, Z501 catalyst hexane solution at a feed rate of 40.0 kg / h, triethylaluminum and hydrogen are added to the first reactor, the Al / Ti molar ratio is controlled to be 20, the molar ratio of hydrogen to ethylene is 4:1, and the melt index of the first reactor is controlled to be 630 g / 10 min, and a polymerization reaction is carried out; the polymer slurry from the first reactor is sent to a dehydrogenation flash tank, the pressure of the dehydrogenation flash tank is controlled to be 0.1 MPa, and the polymer slurry after flash dehydrogenation is sent to a second reactor; ethylene at a feed rate of 13.0 t / h t / h and 1-butene at a feed rate of 4000 kg / h are simultaneously added to the second reactor, and a melt index of 0.35 g / 10 min and a density of 0.948 g / cm are obtained by polymerization. 3 Ethylene / 1-butene copolymer powder. Add ethylene / 1-butene copolymer powder and composite additives into a high-speed mixer and mix thoroughly. First, mix at a speed of 500r / min for 1 minute, and then mix at a speed of 1200r / min for 0.5 minute. The ethylene / 1-butene copolymer powder has 100 parts by mass, antioxidant 1010 has 0.25 parts by mass, antioxidant 168 has 0.25 parts by mass, zinc stearate has 0.08 parts by mass, calcium stearate has 0.08 parts by mass, and fluorine-containing polymer processing aid has 0. The mass fraction of PPA9000E is 0.05 parts; the fully mixed ethylene / 1-butene copolymer powder and the composite additives are added into a twin-screw extruder for granulation, and the various parameters of the extruder are set to 180-220°C during the granulation process; the extruded pellets are dried at 70-80°C for 1.5 hours to obtain a high-density polyethylene resin.

[0039] Table 1 Pipe performance test results

[0040]

[0041] When producing large-diameter thick-walled pipe materials, the extrusion speed is relatively slow. In a state close to equilibrium, the viscosity of the material is mainly affected by the molecular chain with a long relaxation time. The longer the molecular chain or the more long branched chain content, the higher the degree of entanglement between the chains, which hinders the movement of the chain segments and makes the zero shear viscosity higher. The greater the zero shear viscosity, the greater the effect of the polymer melt on resisting gravity, and the better the anti-sag effect during processing. As shown in Table 1, the low-sag high-density polyethylene thick-walled pipe resin prepared by the present invention has excellent processing performance and excellent anti-sag performance.

[0042] It can be understood that the above specific description of the present invention is only used to illustrate 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 the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A low sag high density polyethylene thick wall pipe resin, Features: The polyethylene thick-wall pipe resin comprises the following raw materials in parts by weight: 100 parts of ethylene / 1-butene copolymer powder, 0.30-0.50 parts of antioxidant, 0.10-0.20 parts of acid scavenger, and 0.01-0.05 parts of fluorine-containing polymer processing aid.

2. The low sag high density polyethylene thick wall pipe resin according to claim 1, Features: The antioxidant is a mixture of a primary antioxidant and an auxiliary antioxidant in a mass ratio of 1:

1. The primary antioxidant is antioxidant 1010, and the auxiliary antioxidant is antioxidant 168.

3. The low sag high density polyethylene thick wall pipe resin according to claim 1, Features: The acid scavenger is a mixture of calcium stearate and zinc stearate in a mass ratio of 1:

1.

4. The low sag high density polyethylene thick wall pipe resin according to claim 1, Features: The fluorine-containing polymer processing aid is One of PPA9000E or DA-810X.

5. The low sag high density polyethylene thick wall pipe resin according to claim 1, Features: The preparation method of the ethylene / 1-butene copolymer powder is as follows: Step 1, adding ethylene at a feed rate of 12.0-14.0 t / h, Z501 catalyst hexane solution at a feed rate of 36.5-42.5 kg / h, triethylaluminum and hydrogen into a first autoclave reactor, controlling the Al / Ti molar ratio to be 20-30, the hydrogen to ethylene molar ratio to be 3:1-4:1, and the melt index of the first autoclave reactor to be controlled at 600-700 g / 10 min, to carry out a polymerization reaction; Step 2: sending the polymer slurry from the first kettle reactor to a dehydrogenation flash tank, controlling the pressure of the dehydrogenation flash tank at 0.04-0.06 MPa, and sending the polymer slurry after flash dehydrogenation to a second kettle reactor; Step 3: Add ethylene at a feed rate of 13.0-15.8 t / h and 1-butene at a feed rate of 350-420 kg / h into the second batch reactor at the same time, and carry out polymerization reaction under the condition that the percentage of ethylene feed amount of the second batch reactor to the total feed amount of the first batch reactor and the second batch reactor is controlled at 52%-53%, and obtain ethylene / 1-butene copolymer powder by polymerization.

6. A method for preparing the low sag high density polyethylene thick wall pipe resin according to claim 1, Features: The method comprises the following steps: Step 1, adding ethylene / 1-butene copolymer powder, antioxidant, acid scavenger, and fluorine-containing polymer processing aid into a high-speed mixer and mixing them thoroughly; Step 2: adding the fully mixed materials into a twin-screw extruder for granulation; Step 3: Dry the pellets extruded in step 2 to obtain low sag high-density polyethylene thick-wall pipe resin.

7. The method for preparing the low sag high density polyethylene thick wall pipe resin according to claim 6, Features: In the step 1, the ethylene / 1-butene copolymer powder, antioxidant, acid scavenger and fluorine-containing polymer processing aid are added to a high-speed mixer and fully mixed, first at a speed of 500 r / min for 1-2 minutes, and then at a speed of 1200 r / min for 0.5-1 minute.

8. The method for preparing the low sag high density polyethylene thick wall pipe resin according to claim 6, Features: In the step 2, various parameters of the extruder during the granulation process are set at 180-220°C.

9. The method for preparing the low sag high density polyethylene thick wall pipe resin according to claim 6, Features: The drying condition in step 3 is: drying at 70-80° C. for 1-1.5 hours.

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