Special material for anti-sagging HDPE (high-density polyethylene) pipe as well as preparation method and application of special material and anti-sagging HDPE pipe

Abstract

The invention discloses a special material for an anti-sagging HDPE (High-Density Polyethylene) pipe, a preparation method and application of the special material and the anti-sagging HDPE pipe. The anti-sagging HDPE pipe special material comprises HDPE resin powder, cellulose-based hydrogel, an optional nucleating agent, an antioxidant, an acid acceptor and a processing aid. Compared with the traditional HDPE pipe resin, the special material for the anti-sag HDPE pipe has excellent sag resistance, excellent mechanical property and excellent processability, has very strong practicability, and is suitable for preparing the large-diameter high-wall-thickness anti-sag pipe.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and particularly relates to a special material for anti-sag HDPE pipes, a preparation method and application thereof, and anti-sag HDPE pipes. Background Art

[0002] High-density polyethylene has a linear structure with high regularity of the main chain and no long branched chains. Therefore, it has a high degree of crystallinity, resulting in greater strength, such as high mechanical properties in tension, compression, bending, etc. Moreover, HDPE pipe materials have strong corrosion resistance and good anti-creep performance, and are widely used in natural gas pipelines, water supply and drainage pipelines, and sewage pipes. Especially, the PE100 pipes that emerged in the 1980s have been widely used with their excellent performance and occupy a large market share.

[0003] In recent years, due to the excellent comprehensive performance of PE pipes, such as corrosion resistance, good flexibility, and good welding performance, large-diameter PE pipes have been applied in fields such as domestic water supply, nuclear power plant cooling systems, seawater aquaculture, seawater desalination projects, submarine waste discharge, transportation of corrosive media or slurries, corrosive soil environments, and used for lining method to repair old pipes. However, a major defect of traditional PE100 or PE80 pipes is that they are prone to the "sag" phenomenon during the extrusion process and cannot be used for the production and processing of large-diameter and high-wall-thickness pipes. During the extrusion of large-diameter pipes, due to the thick wall thickness, the cooling and solidification speed is slow, and the melt will sag under the action of gravity, resulting in a small wall thickness on the upper part and a large wall thickness on the lower part, that is, the "sag effect", making the obtained pipe wall unable to reach the required tolerance and unable to achieve compliant butt fusion welding. By adjusting the die gap, that is, increasing the upper gap and decreasing the lower gap, although it can be compensated to a certain extent, the effect of this compensation is also very limited. Summary of the Invention

[0004] Aiming at the above deficiencies of the existing products, the present invention first provides a special material for anti-sag HDPE pipes, which can effectively improve the "sag effect" when used for the processing of large-diameter pipes.

[0005] Another aspect of the present invention provides a preparation method of a special material for anti-sag HDPE pipes, and this method is simple and easy to implement.

[0006] Another aspect of the present invention lies in providing the application of this special material for anti-sag HDPE pipes and an anti-sag HDPE pipe.

[0007] To achieve the above object, the present invention is realized through the following technical solutions:

[0008] A special material for anti-sag HDPE pipes, the preparation raw materials include cellulose-based hydrogel.

[0009] In a preferred practical solution, the raw materials for preparation include 80-100 parts by mass of HDPE resin, such as 80, 81, 82, 83, 84, 82, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 parts by mass, preferably 85-90 parts by mass; 1-20 parts by mass of cellulose-based hydrogel, such as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts by mass, preferably 10-15 parts by mass.

[0010] In some specific implementation solutions, the cellulose-based hydrogel is prepared by the following steps:

[0011] 1) Weigh sodium hydroxide and urea and put them into a container, dissolve them in an appropriate amount of water to prepare an aqueous solution of sodium hydroxide and urea;

[0012] 2) Under stirring, slowly add cellulose and sodium carboxymethyl cellulose solution to the aqueous solution of sodium hydroxide and urea, and continue stirring;

[0013] 3) Under stirring, add an appropriate amount of polyethylene glycol diglycidyl ether, heat and stir for reaction. After the reaction is completed, wash the hydrogel, then dialyze, filter, and then dry the solid to obtain the cellulose-based hydrogel.

[0014] Specifically, the cellulose-based hydrogel is prepared, for example, by the following steps:

[0015] 1) Weigh an appropriate amount of sodium hydroxide and urea and put them into a beaker, dissolve them in an appropriate amount of water, and perform ultrasonic dissolution to prepare a sodium hydroxide and urea solution;

[0016] 2) Under stirring, slowly add cellulose and sodium carboxymethyl cellulose solution to the beaker containing the solution, and continue stirring;

[0017] 3) Under stirring, add an appropriate amount of polyethylene glycol diglycidyl ether, heat and stir for reaction. After the reaction is completed, wash the hydrogel with deionized water and absolute ethanol, then dialyze, filter, and then put the solid into an oven to dry to obtain the cellulose-based hydrogel sample.

[0018] In some specific embodiments, the mass concentration of sodium hydroxide in the aqueous solution in step 1) is 2-8 wt%, such as 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, etc., preferably 3-5 wt%; the mass concentration of urea is 1-5 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc., preferably 2-4 wt%; the mass ratio of the solutes of sodium hydroxide to urea in the solution is 1:1-2, preferably 1:2; preferably, ultrasonic assistance is used for dissolution, the ultrasonic frequency is 20-80 KHZ, such as 20, 30, 40, 50, 60, 70, 80 KHZ, etc., preferably 30-60 KHZ, and the ultrasonic time is 10-60 minutes, such as 10, 20, 30, 40, 50, 60 minutes, etc., preferably 20-40 minutes.

[0019] In some specific embodiments, the mass concentration of the cellulose solution in step 2) is 1-6 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, etc., preferably 2-4 wt%; the mass concentration of the sodium carboxymethyl cellulose solution is 1-6 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, etc., preferably 3-5 wt%; the mass ratio of cellulose to sodium carboxymethyl cellulose in the solution is 1-3:1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., preferably 1.5:1; preferably, the stirring is carried out in an ice-water mixed bath, and the stirring time is 10-60 minutes, such as 10, 20, 30, 40, 50, 60 minutes, etc., preferably 20-40 minutes.

[0020] In some specific embodiments, the mass concentration of polyethylene glycol diglycidyl ether in the mixed solution in step 3) is 1-10 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc., preferably 3-6 wt%; the heating temperature for the heating and stirring is 40-80 °C, such as 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, etc., preferably 50-70 °C; the reaction time is 5-10 hours, preferably 6-8 hours; the polyethylene glycol diglycidyl ether is added continuously, preferably dropwise addition, and the addition time is 3-15 minutes, preferably 5-10 minutes, and the addition time is included in the reaction time.

[0021] In a preferred embodiment, the raw materials for preparing the anti-drooping HDPE pipe special material further include at least one of an antioxidant, a nucleating agent, an acid absorbent, and a processing aid; preferably, the antioxidant is 0.1-1 part by mass, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 part by mass, preferably 0.2-0.5 part by mass; the nucleating agent is 0.1-0.5 part, such as 0.1, 0.2, 0.3, 0.4, 0.5 part by mass, preferably 0.3-0.4 part; the acid absorbent is 0.1-0.5 part by mass, such as 0.1, 0.2, 0.3, 0.4, 0.5 part by mass, preferably 0.2-0.4 part; the processing aid is 0.01-0.1 part by mass, such as 0.01, 0.03, 0.05, 0.08, 0.1 part by mass, preferably 0.03-0.05 part.

[0022] In some specific embodiments, the HDPE resin of the present invention is high-density polyethylene, and the high-density polyethylene is selected from high-density polyethylene with a melt index (5 kg weight) of 0.1-0.5 g / 10 min, preferably a PE 100 grade pipe product.

[0023] In some specific embodiments, the antioxidant is a compound antioxidant, preferably two or more of a hindered phenol antioxidant, a hindered amine antioxidant, a phosphite antioxidant, an anti-hydrolysis agent, and a benzotriazole ultraviolet absorber. Preferably, for example, the main antioxidant is at least one of 1010, 3114, and 1330, the auxiliary antioxidant is 168 and / or 626, and the mass ratio of the main antioxidant to the auxiliary antioxidant is 0.25-2:1, such as 0.25:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, etc.

[0024] In some specific embodiments, the nucleating agent is at least one of p-tert-butylbenzoate, sodium benzoate, cyclohexanedicarboxylate, and phosphate.

[0025] In some specific embodiments, the acid absorbent is a stearate, preferably zinc stearate and / or calcium stearate.

[0026] In some specific embodiments, the processing aid is a kind of fluororubber, such as a polymer of 1,1,2,3,3,3-hexafluoro-1-propene and 1,1-difluoroethylene.

[0027] On the other hand, a method for preparing an anti-drooping HDPE pipe special material includes the following steps:

[0028] S1: Add HDPE resin, cellulose-based hydrogel, optional antioxidant, optional nucleating agent, optional acid absorbent, and optional processing aid to a mixer according to the ratio and stir evenly to obtain a preliminary mixture;

[0029] S2: Transfer the preliminary mixture obtained in step S1 to a twin-screw extruder, extrude and pelletize to obtain the special material for anti-drooping HDPE pipes.

[0030] Specifically, take the dried HDPE resin, cellulose hydrogel, optional antioxidant, optional nucleating agent, optional acid absorbent, and optional processing aid and place them together in a high-speed mixer to mix evenly;

[0031] Extrude and pelletize the evenly mixed material in a twin-screw extruder, and obtain the special material for anti-drooping HDPE pipes after cooling, pelletizing, and drying.

[0032] In some specific embodiments, the heating and melting temperature in the twin-screw extruder is 170 - 230 °C, such as 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, etc., the extrusion temperature is 190 - 220 °C, such as 190 °C, 200 °C, 210 °C, 220 °C, etc., and the screw speed is 200 - 350 r / min, such as 200 r / min, 250 r / min, 300 r / min, 350 r / min, etc.

[0033] On the other hand, the special material for anti-drooping HDPE pipes of the present invention is mainly used for large-diameter water conveyance pipes, pipes for the seawater cooling circulation system of nuclear power plants, municipal engineering pipes, etc.

[0034] On another aspect, an anti-drooping HDPE pipe is made of the aforementioned special material for anti-drooping HDPE pipes or the special material for anti-drooping HDPE pipes prepared by the aforementioned preparation method. Its preparation method has no special limitation, for example, common melting extrusion in the art is used.

[0035] Compared with the prior art, the positive effects of the present invention are as follows:

[0036] 1. The "drooping effect" of the pipe is that during the extrusion process of the pipe, the melt will sag under the action of gravity, resulting in a thin upper wall and a thick lower wall, so that the obtained pipe wall cannot reach the required tolerance. By adding a cellulose-based hydrogel to the raw materials in the present invention, the binding ability between the hydrogel and the HDPE matrix can be increased, and the HDPE branches can form a three-dimensional network structure with the hydrogel, improving the zero-shear viscosity of the pipe, and further improving the melt strength of the pipe.

[0037] 2. By preferably adding a nucleating agent in the present invention, larger spherulites will be formed during the cooling process, promoting abnormal nucleation of the crystals, improving the crystallization rate, enabling the HDPE pipe resin to cool and form faster under the same processing conditions, and improving the "drooping" defect. Detailed Embodiments

[0038] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these embodiments.

[0039] In the various embodiments and comparative examples of the present invention, the sources of the main raw materials are as follows. Unless otherwise specified, other raw materials and reagents are purchased through common commercial channels:

[0040] HDPE powder: Wanhua 23050;

[0041] Sodium hydroxide: Aladdin;

[0042] Urea: Aladdin;

[0043] Cellulose: Anergy;

[0044] Sodium methylcellulose: Anaiji;

[0045] Polyethylene glycol diglycidyl ether: Anaiji;

[0046] Antioxidant (compound of 1010 and 168, mass ratio 2:1): Sanfeng Chemical;

[0047] Nucleating agent NAP 50: present and;

[0048] Acid absorbent calcium stearate: Sanfeng Chemical;

[0049] Processing aid fluoroelastomer: M9000E, Luju Chemical.

[0050] The main performance of the embodiments of the present invention is tested by the following methods:

[0051] Melt index: MI40 melt index meter, temperature 230℃.

[0052] Tensile strength: CMT 6014 universal testing machine, test rate 100 mm·min-1.

[0053] Crystallization rate: DSC.

[0054] Shear viscosity: MCR301 polymer rheometer.

[0055] Melt strength: MCR301 polymer rheometer.

[0056] Example 1

[0057] Preparation of cellulose hydrogel, the steps are:

[0058] 1) Take 20g of 3wt% urea solution and add it into a beaker containing 10g of 3wt% NaOH aqueous solution. Place the beaker in an ultrasonic cleaner with an ultrasonic frequency of 50HZ for 30min to mix the components.

[0059] 2) Take 15 g of a cellulose solution with a concentration of 3 wt% and add it to a beaker containing 10 g of a methylcellulose solution with a concentration of 3 wt%. Place it in an ice-water bath and stir with a magnetic stirrer for 60 min until completely dissolved.

[0060] 3) Add NaOH and urea solution to the cellulose and methylcellulose solution, heat and stir. The heating temperature is 60 °C. Use a sterile syringe to extract 10 g of a polyethylene glycol diglycidyl ether solution with a concentration of 20 wt%, and continuously drip it into the mixed solution using a micro-injection pump at an injection rate of 1 ml / min, and continue to react for 6 h. After the reaction is completed, wash the hydrogel 3 times with deionized water and anhydrous ethanol respectively, then dialyze and filter. Place the solid in an oven and dry it at a temperature of 50 °C for 4 h to obtain a cellulose-based hydrogel sample.

[0061] To prepare a special material for HDPE anti-drooping pipes, the raw material formula composition is as follows by weight parts:

[0062] 89 parts of HDPE (WH-23050), 10 parts of the prepared cellulose-based hydrogel, 0.2 parts of antioxidant (a compound of 1010 and 168 with a mass ratio of 2:1), 0.4 parts of nucleating agent NAP50, 0.3 parts of acid absorbent calcium stearate, and 0.1 part of processing aid MA9000E. Mix in a high-speed mixer for 5 minutes, and granulate the uniformly mixed material in a twin-screw extruder. The temperature settings of the extruder are: Zone I 190 °C, Zone II 200 °C, Zone III 210 °C, Zone IV 220 °C, Zone V 230 °C, Zone VI 230 °C, and the head is 220 °C. The screw speed is 300 r / min. After the material is extruded, it is cooled, pelletized, and dried, and then corresponding performance tests are carried out. The test results are shown in Table 1-1.

[0063] Example 2

[0064] To prepare a cellulose hydrogel, the steps are as follows:

[0065] 1) Take 20 g of a urea solution with a concentration of 1 wt% and add it to a beaker containing 10 g of an NaOH aqueous solution with a concentration of 2 wt%. Place the beaker in an ultrasonic cleaner with an ultrasonic frequency of 50 HZ and ultrasonicate for 30 min to mix the components evenly.

[0066] 2) Take 10 g of a cellulose solution with a concentration of 6 wt% and add it to a beaker containing 10 g of a methylcellulose solution with a concentration of 3 wt%. Place it in an ice-water bath and stir with a magnetic stirrer for 60 min until completely dissolved.

[0067] 3) Add the NaOH and urea solutions to the cellulose and methylcellulose solutions, heat and stir at a heating temperature of 60 °C. Use a sterile syringe to extract 10 g of polyethylene glycol diglycidyl ether with a concentration of 20 wt%, and continuously drip it into the mixed solution using a micro-injection pump at an injection rate of 1 ml / min, and continue the reaction for 6 h. After the reaction is completed, wash the hydrogel with deionized water and absolute ethanol three times respectively, then dialyze and filter. Place the solid in an oven to dry at a temperature of 50 °C for 4 h to obtain a cellulose-based hydrogel sample.

[0068] Prepare a special material for HDPE anti-drooping pipes. The raw material formula composition is as follows by weight parts:

[0069] 89 parts of HDPE (WH-23050), 10 parts of the prepared cellulose-based hydrogel, 0.2 parts of antioxidant (a compound of 1010 and 168 with a mass ratio of 2:1), 0 parts of nucleating agent NAP50, 0.3 parts of acid absorbent calcium stearate, and 0.1 parts of processing aid MA9000E. Mix in a high-speed mixer for 5 minutes, and granulate the uniformly mixed material in a twin-screw extruder. The temperature settings of the extruder are: Zone I 190 °C, Zone II 200 °C, Zone III 210 °C, Zone IV 220 °C, Zone V 230 °C, Zone VI 230 °C, and the head is 220 °C. The screw speed is 300 r / min. After the material is extruded, it is cooled, pelletized, and dried, and then corresponding performance tests are carried out. The test results are shown in Table 1-1.

[0070] Example 3

[0071] Prepare a cellulose hydrogel. The steps are as follows:

[0072] 1) Take 10 g of a urea solution with a concentration of 4.5 wt% and add it to a beaker containing 10 g of an NaOH aqueous solution with a concentration of 1.5 wt%. Place the beaker in an ultrasonic cleaner with an ultrasonic frequency of 50 HZ and ultrasonicate for 30 min to mix the components evenly.

[0073] 2) Take 10 g of a cellulose solution with a concentration of 6 wt% and add it to a beaker containing 10 g of a methylcellulose solution with a concentration of 2 wt%. Place it in an ice-water bath and stir with a magnetic stirrer for 60 min until completely dissolved.

[0074] 3) Add NaOH and urea solution to the cellulose and methylcellulose solution, heat and stir at a heating temperature of 60 °C. Use a sterile syringe to extract 10 g of polyethylene glycol diglycidyl ether with a concentration of 30 wt%, and continuously add it dropwise to the mixed solution using a micro-injection pump at an injection rate of 1 ml / min. Continue the reaction for 6 h. After the reaction is completed, wash the hydrogel with deionized water and absolute ethanol three times respectively, then dialyze and filter. Put the solid into an oven and dry it at a temperature of 50 °C for 4 h to obtain a cellulose-based hydrogel sample.

[0075] Prepare a special material for HDPE anti-drooping pipes. The raw material formula composition is as follows by weight parts:

[0076] 89 parts of HDPE (WH-23050), 10 parts of the prepared cellulose-based hydrogel, 0.2 parts of antioxidant (a compound of 1010 and 168 with a mass ratio of 2:1), 0.4 parts of nucleating agent NAP50, 0.3 parts of acid absorbent calcium stearate, and 0.1 parts of processing aid MA9000E. Mix in a high-speed mixer for 5 minutes, and granulate the uniformly mixed material in a twin-screw extruder. The temperature settings of the extruder are: Zone I 190 °C, Zone II 200 °C, Zone III 210 °C, Zone IV 220 °C, Zone V 230 °C, Zone VI 230 °C, and the die head is 220 °C. The screw speed is 300 r / min. After the material is extruded, it is cooled, pelletized, and dried, and then corresponding performance tests are carried out. The test results are shown in Table 1-1.

[0077] Example 4

[0078] Prepare a cellulose hydrogel. The steps are as follows:

[0079] 1) Take 20 g of a 3 wt% urea solution and add it to a beaker containing 10 g of a 3 wt% NaOH aqueous solution. Place the beaker in an ultrasonic cleaner with an ultrasonic frequency of 50 HZ and ultrasonicate for 30 min to mix the components evenly.

[0080] 2) Take 15 g of a 4 wt% cellulose solution and add it to a beaker containing 10 g of a 4 wt% methylcellulose solution. Place it in an ice-water bath and stir with a magnetic stirrer for 60 min until completely dissolved.

[0081] 3) Add NaOH and urea solution to cellulose and methyl cellulose solution, heat and stir, heating temperature 60°C, extract 10g of 20wt% polyethylene glycol diglycidyl ether with a sterile syringe, use a microinjection pump to continuously drip into the mixed solution, injection speed 1ml / min, continue to react for 6h. After the reaction is completed, wash the hydrogel with deionized water and anhydrous ethanol three times, then dialyze and filter, put the solid into an oven to dry, temperature 50°C, drying time 4h, to obtain a cellulose-based hydrogel sample.

[0082] To prepare special material for HDPE anti-sag pipe, the raw material formula composition is calculated by weight:

[0083] 88 parts of HDPE (WH-23050), 10 parts of prepared cellulose-based hydrogel, 0.5 parts of antioxidant, 0.9 parts of nucleating agent, 0.5 parts of acid absorbent, and 0.1 parts of processing aid. Mix in a high-speed mixer for 5 minutes, and granulate the evenly mixed materials in a twin-screw extruder. The extruder temperature is set to: 190°C in zone I, 200°C in zone II, 210°C in zone III, 220°C in zone IV, 230°C in zone V, and 230°C in zone VI, the die is 220°C, and the screw speed is 300r / min. After the material is extruded, it is cooled, pelletized, and dried before the corresponding performance test. The test results are shown in Table 1-1.

[0084] Example 5

[0085] Preparation of cellulose hydrogel, the steps are:

[0086] 1) Take 20g of 3wt% urea solution and add it into a beaker containing 10g of 3wt% NaOH aqueous solution. Place the beaker in an ultrasonic cleaner with an ultrasonic frequency of 50HZ for 30min to mix the components.

[0087] 2) 15 g of 3 wt % cellulose solution was added to a beaker containing 10 g of 3 wt % methyl cellulose solution, placed in an ice water bath, and stirred with a magnetic stirrer for 60 min until all dissolved.

[0088] 3) Add NaOH and urea solution to cellulose and methyl cellulose solution, heat and stir, heating temperature 60°C, extract 10g of 20wt% polyethylene glycol diglycidyl ether with a sterile syringe, use a microinjection pump to continuously drip into the mixed solution, injection speed 1ml / min, continue to react for 6h. After the reaction is completed, wash the hydrogel with deionized water and anhydrous ethanol three times, then dialyze and filter, put the solid into an oven to dry, temperature 50°C, drying time 4h, to obtain a cellulose-based hydrogel sample.

[0089] To prepare special material for HDPE anti-sag pipe, the raw material formula composition is calculated by weight:

[0090] 79 parts of HDPE (WH-23050), 20 parts of prepared cellulose-based hydrogel, 0.2 parts of antioxidant, 0.4 parts of nucleating agent, 0.3 parts of acid absorbent, and 0.1 parts of processing aid. Mix in a high-speed mixer for 5 minutes, and granulate the uniformly mixed materials in a twin-screw extruder. The extruder temperature is set to: 190°C in zone I, 200°C in zone II, 210°C in zone III, 220°C in zone IV, 230°C in zone V, 230°C in zone VI, 220°C in die head, and 300r / min in screw speed. After the material is extruded, it is cooled, pelletized, and dried before the corresponding performance test. The test results are shown in Table 1.

[0091] Comparative Example 1

[0092] The anti-sag HDPE pipe material was prepared by referring to the method of Example 1, except that no cellulose-based hydrogel was added to the raw material formula. Other operations were the same as in Example 1 to prepare the anti-sag HDPE pipe material. The performance test results are shown in Table 1.

[0093] Comparative Example 2

[0094] The anti-sag HDPE pipe material was prepared by referring to the method of Example 1, except that methyl cellulose was directly used instead of cellulose-based hydrogel. Other operations were the same as in Example 1 to prepare the anti-sag HDPE pipe material. The performance test results are shown in Table 1.

[0095] Comparative Example 3

[0096] The anti-sag HDPE pipe material was prepared by referring to the method of Example 1, except that commercially available cellulose was directly used instead of cellulose-based hydrogel. Other operations were the same as in Example 1 to prepare the anti-sag HDPE pipe material. The performance test results are shown in Table 1.

[0097] The performance comparison test of the special materials for anti-sag HDPE pipes obtained in Examples 1-5 and Comparative Examples 1-3 is conducted, and the results are shown in Table 1.

[0098] Table 1 Performance test results

[0099]

[0100] The above results prove that:

[0101] 1) By comparing the examples with comparative examples 1-3, it can be seen that the use of cellulose-based hydrogel can effectively improve the zero shear viscosity and melt strength performance of the HDPE matrix resin, alleviate the "sag effect", and significantly improve the anti-sag performance of the product.

[0102] 2) It can be seen from the comparison between Example 1 and Example 2 that adding a nucleating agent can further reduce the semi-crystallization time of the HDPE resin, promote the rapid formation of co-crystallization in the HDPE matrix, and improve the crystallization efficiency.

Claims

1. A special material for anti - sagging HDPE pipes, characterized in that, The preparation raw materials include cellulose-based hydrogel.

2. The special material for anti - sagging HDPE pipes according to claim 1, characterized in that, The preparation raw materials include 80 - 100 parts by mass of HDPE resin, preferably 85 - 90 parts by mass; 1 - 20 parts by mass of cellulose-based hydrogel, preferably 10 - 15 parts by mass.

3. The special material for anti - sagging HDPE pipes according to claim 1 or 2, characterized in that, The cellulose-based hydrogel is prepared by the following steps: 1) Weigh sodium hydroxide and urea and put them into a container, dissolve them in an appropriate amount of water to prepare an aqueous solution of sodium hydroxide and urea; 2) Under stirring, slowly add cellulose and sodium carboxymethyl cellulose solution to the aqueous solution of sodium hydroxide and urea, and continue stirring; 3) Under stirring, add an appropriate amount of polyethylene glycol diglycidyl ether, heat and stir for reaction. After the reaction is completed, wash the hydrogel, then dialyze, filter, and dry the solid to obtain the cellulose-based hydrogel.

4. The special material for anti - sagging HDPE pipes according to claim 3, characterized in that: In the aqueous solution of step 1), the mass concentration of sodium hydroxide is 2 - 8 wt%, preferably 3 - 5 wt%; the mass concentration of urea is 1 - 5 wt%, preferably 2 - 4 wt%; the mass ratio of sodium hydroxide to urea is 1:1 - 3, preferably 1:2; preferably, ultrasonic assistance is used for dissolution, the ultrasonic frequency is 20 - 80 KHZ, preferably 30 - 60 KHZ, and the ultrasonic time is 10 - 60 minutes, preferably 20 - 40 minutes; and / or In step 2), the mass concentration of the cellulose solution is 1 - 6 wt%, preferably 2 - 4 wt%; the mass concentration of the sodium carboxymethyl cellulose solution is 1 - 6 wt%, preferably 3 - 5 wt%; the mass ratio of cellulose to sodium carboxymethyl cellulose is 1 - 3:1, preferably 1.5:1; preferably, the stirring is carried out in an ice-water mixed bath; the stirring time is 10 - 60 minutes, preferably 20 - 40 minutes; and / or In step 3), the mass concentration of the polyethylene glycol diglycidyl ether is 1 - 10 wt%, preferably 3 - 6 wt%; the heating temperature for heating and stirring is 40 - 80 °C, preferably 50 - 70 °C; the reaction time is 5 - 10 hours, preferably 6 - 8 hours; the polyethylene glycol diglycidyl ether is added in a continuous feeding manner, preferably dropwise addition, and the feeding time is 3 - 15 minutes, preferably 5 - 10 minutes, and the feeding time is included in the reaction time.

5. The special material for anti - sagging HDPE pipes according to any one of claims 1 - 4, characterized in that, The preparation raw materials further include at least one of an antioxidant, a nucleating agent, an acid absorbent, and a processing aid; preferably, the antioxidant is 0.1 - 1 part by mass, preferably 0.3 - 0.5 part by mass; the nucleating agent is 0.1 - 0.5 part, preferably 0.3 - 0.4 part; the acid absorbent is 0.1 - 0.5 part by mass, preferably 0.2 - 0.4 part by mass; the processing aid is 0.01 - 0.1 part by mass, preferably 0.03 - 0.05 part by mass.

6. The special material for anti - sagging HDPE pipes according to claim 5, characterized in that, The antioxidant is a compound antioxidant, preferably at least two of a hindered phenol antioxidant, a hindered amine antioxidant, a phosphite antioxidant, a hydrolysis inhibitor, and a benzotriazole ultraviolet absorber; preferably, the main antioxidant is at least one of 1010, 3114, and 1330, the auxiliary antioxidant is 168 and / or 626, and the mass ratio of the main antioxidant to the auxiliary antioxidant is 0.25 - 2:1; and / or The nucleating agent is at least one of p-tert-butyl benzoate, sodium benzoate, cyclohexyl dicarboxylate, and phosphate salt; and / or The acid absorbent is a stearate, preferably zinc stearate and / or calcium stearate; and / or The processing aid is a fluororubber.

7. A preparation method of the special material for anti - sagging HDPE pipes according to any one of claims 1 - 6, characterized in that, It includes the following steps: S1: Add HDPE resin, cellulose-based hydrogel, optional antioxidant, optional nucleating agent, optional acid absorbent, and optional processing aid to a mixer according to the ratio and stir evenly to obtain a preliminary mixture; S2: Transfer the preliminary mixture prepared in step S1 to a twin-screw extruder, extrude and pelletize to obtain the special material for anti-drooping HDPE pipes.

8. The preparation method according to claim 7, characterized in that, In the twin-screw extruder, the heating and melting temperature is 170 - 230 °C, the extrusion temperature is 190 - 220 °C, and the screw speed is 200 - 350 r / min.

9. The application of the special material for anti - sagging HDPE pipes according to any one of claims 1 - 6 or the special material for anti - sagging HDPE pipes prepared by the preparation method according to claim 7 or 8 in large - diameter water - conveying pipes, pipes in the seawater cooling circulation system of nuclear power plants, and municipal engineering pipes.

10. An anti - sagging HDPE pipe, characterized in that, It is made of the special material for anti-drooping HDPE pipes described in any one of claims 1 - 6 or the special material for anti-drooping HDPE pipes prepared by the preparation method described in claim 7 or 8.

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