High-wear-resistance long-chain nylon material for engineering pipeline and application thereof

Abstract

The invention discloses a high-wear-resistance long-chain nylon material for an engineering pipeline and application of the high-wear-resistance long-chain nylon material, and the long-chain nylon material is prepared from the following raw materials in percentage by weight: 68-90% of long-carbon-chain polyamide, 8-25% of a toughening agent, 1.0-5% of metal sulfide, 0.4-1.0% of a lubricant and 0.6-1.0% of an antioxidant. The long-chain nylon material disclosed by the invention has excellent wear resistance and self-lubricating performance, high melt strength and good long-term high temperature resistance and chemical corrosion resistance, and can be used for preparing engineering pipelines such as mortar conveying pipelines, concrete conveying pipelines, tailing conveying pipelines or cable sheaths and the like with the outer diameter Dn of 250mm.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis and processing of polymer materials, and relates to a highly wear-resistant long-chain nylon material for engineering pipelines and its applications. Background Art

[0002] At present, engineering pipelines such as sand transportation pipes and concrete transportation pipes are mainly made of materials such as steel pipes, polyethylene, and ultra-high molecular weight polyethylene. However, these materials have certain limitations in terms of mechanical strength, self-lubricity, corrosion resistance, and material forming and processing, resulting in short service life and high cost of mortar transportation pipes, which limits their application in the field of mortar transportation. Nylon is a polymer material with excellent mechanical strength, self-lubricity, corrosion resistance and other properties, and is widely used in fields such as automobiles, electronics, textiles, and aviation. However, due to problems such as its usually rough surface after wear resistance modification, low melt strength at processing temperature leading to difficulty in forming pipelines, and hydrolysis intolerance, its application in the field of mortar transportation is still relatively limited. In addition to the common advantages of nylon, long-chain nylon has natural advantages in water absorption, chemical stability, density, and low-temperature resistance.

[0003] Pipelines such as mortar transportation pipes and tailings transportation pipes usually have an outer diameter ranging from Dn110 - 250 mm, and have relatively high requirements for the melt strength of the material during the extrusion processing. In the processing temperature range of nylon materials, due to the dissociation of hydrogen bonds and the activation of molecular chains, the melt strength will drop significantly, resulting in serious melt sag phenomenon of the material after passing through the die, making it difficult to form large-diameter pipelines. At the same time, single-screw extrusion equipment with relatively weak shear ability often requires the material to have a certain fluidity, and problems such as excessive torque and too high melting temperature will occur when processing nylon materials containing a high grafting rate toughening agent. CN110982262 A developed a wear-resistant enhanced long-chain nylon PA1012 composite material, which effectively improved the wear resistance and low-temperature impact performance of nylon by blending long-chain nylon with glass fiber, wear-resistant additives, and toughening compatibilizers. However, due to the introduction of glass fiber, the surface of the material is rough and the internal defects of the material increase, making it impossible to extrude and form pipelines. CN102051043 A effectively improved the low-temperature resistance and wear resistance of nylon 66 by adding PTFE and toughening agents to nylon 66. However, due to the addition of macromolecular lubricants, the melt strength of the material is insufficient at the melting processing temperature, and it cannot meet the performance requirements for extruding pipelines with a diameter above Dn110mm. CN102757641 A used additives such as graphite to improve the wear resistance and surface smoothness of long-chain nylon materials, but limited by its poor toughness and low melt strength, its application in the field of engineering pipelines is restricted.

[0004] Existing methods for wear-resistant modification of long-chain nylon usually mainly use single or multiple wear-resistant fillers, such as polytetrafluoroethylene powder, ultra-high molecular weight polyethylene powder, graphite, erucic acid amide, silicone powder, etc. However, many of these materials are non-polar materials and have poor compatibility with the polyamide main chain, and will migrate in the material matrix, resulting in a decrease in the melt strength of the modified long-chain nylon material, and at the same time causing the material toughness to become worse, unable to meet the performance requirements for extrusion of pipes above Dn110mm; while the fiber wear-resistant modification methods such as filling glass fiber and aramid fiber will greatly increase the surface roughness of the extruded pipe and increase the internal defects, making it difficult to extrude and form.

[0005] Therefore, in this field, it is desired to develop a long-chain nylon material with high melt strength, suitable fluidity and high wear resistance. Summary of the Invention

[0006] Aiming at the deficiencies in material technology in the field of engineering pipelines, the purpose of the present invention is to provide a high-wear-resistant nylon material for engineering pipelines and its applications. The long-chain nylon material of the present invention has high melt strength, suitable fluidity and high wear resistance, and is suitable for various pipe, sheath and other parts with large size requirements and wear resistance.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a high-wear-resistant long-chain nylon material for engineering pipelines, which is prepared from the following raw materials, calculated by weight percentage,

[0009]

[0010] In the present invention, the dosage of the long carbon chain polyamide can be 68%, 70%, 75%, 80%, 85%, 90%, etc.

[0011] In the present invention, the dosage of the toughening agent can be 8%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, etc.

[0012] In the present invention, the dosage of the metal sulfide can be 1%, 2%, 3%, 4%, 5%, etc.

[0013] In the present invention, the dosage of the lubricant can be 0.4%, 0.6%, 0.8%, 1.0%, etc.

[0014] In the present invention, the dosage of the antioxidant can be 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc.

[0015] In the present invention, long-chain nylon with the number of continuous methylene groups between 8 and 16 has a relatively low processing temperature, appropriate hydrogen bond density and melt fluidity, which is beneficial to the processing and forming of large-diameter pipes. At the same time, the long-chain nylon material will be in a working environment containing water, hydrocarbons, hydrogen sulfide, carbon dioxide, etc. at low temperature to normal temperature for a long time. Long-chain nylon with the number of continuous methylene groups between 8 and 16 has natural advantages in properties such as low-temperature stability, water absorption, and chemical stability resistance.

[0016] Preferably, the long-chain polyamide includes any one or a combination of at least two of PA11, PA12, PA1012, and PA1212.

[0017] In the present invention, the addition of a toughening agent effectively increases the molecular weight of the long-chain nylon material and improves the melt strength of the material to achieve the processing and forming of large-size pipes. Long-chain polyamide is a polar material, and the end-capping groups of the molecular chain are amino and carboxyl groups, which can undergo active reactions with other polar groups, such as maleic anhydride, glycidyl methacrylate, etc. However, a toughening agent with a too high grafting rate of polar groups will greatly increase the molecular weight of the long-chain nylon, making its fluidity poor and difficult to form pipes. A too low grafting rate of polar groups will result in insufficient melt strength of the long-chain nylon, leading to serious sagging of the material after passing through the die. Therefore, by optimizing the grafting rate of polar groups of the toughening agent, the fluidity of the material is ensured and its melt strength is improved. Preferably, the toughening agent is an EPDM-based matrix.

[0018] EPDM is usually a copolymer of ethylene, propylene and a small amount of non-conjugated diene. Its main chain is composed of saturated hydrocarbons, but it contains unsaturated double bonds in the side chain, which has a greater polarity compared with POE-based toughening agents and improves the compatibility with long-chain nylon. EPDM has excellent antioxidant properties, thermal stress resistance, and anti-aging properties. Grafted modified EPDM usually refers to grafting some monomers with special functional groups to make EPDM obtain polarity, thereby improving the bonding force between the EPDM and the nylon matrix interface, and thus enhancing the mechanical properties and performance stability of the material. The methods of grafting modified EPDM mainly include solution grafting method, electron beam radiation grafting, melt grafting method, and direct swelling grafting, etc. The glass transition temperature of POE-based toughening agents is usually higher than -50°C, and the molecular chain movement ability gradually becomes worse as the temperature decreases. As a result, at -30°C and even lower temperatures, the toughened long-chain nylon material is prone to change from tough to brittle, affecting the performance of large-diameter pipes buried underground in terms of resistance to geological settlement and external force damage.

[0019] The toughening agent has a grafting compatibilization modification with one or more of maleic anhydride and glycidyl methacrylate, and the grafting rate can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.2%, etc.

[0020] In the present invention, metal sulfide can effectively improve wear resistance. It is usually a binary compound formed by sulfur and metal, or formed by the reaction of hydrogen sulfide (or hydrosulfuric acid) with metal oxide or hydroxide. During the preparation process, 0.1-0.6 mol% of free acid usually remains. The content of free acid can be increased to 0.7-0.9 mol% by acidifying pretreatment of the metal sulfide. This part of free acid will activate polar groups such as maleic anhydride and glycidyl methacrylate in the toughening agent during the twin-screw granulation process, and produce a synergistic effect with the toughening agent with a grafting rate of polar groups between 0.5 and 1.2, which can effectively improve the melt strength of the long-chain nylon material. When the content of free acid is lower than 0.6 mol%, no obvious synergistic effect can be achieved. When the content of free acid is higher than 0.9%, on the one hand, the free acid will cause the degradation of the long-chain carbon nylon material as a catalyst at high temperature, and on the other hand, it will cause excessive activation and too high melt strength, resulting in an increase in torque during the twin-screw granulation and single-screw pipe extrusion processes, making it difficult to extrude.

[0021] Preferably, the content of free acid in the metal sulfide is 0.7-0.9 mol%.

[0022] Preferably, the metal sulfide is any one or a combination of at least two of molybdenum disulfide, tin disulfide or tungsten disulfide.

[0023] Preferably, the lubricant includes one or more of erucamide, silicone, zinc stearate, magnesium stearate, calcium stearate or titanate.

[0024] Preferably, the antioxidant includes any one or a combination of at least two of hindered phenol, hindered amine, phosphite, potassium iodide-copper iodide inorganic stabilizer or aromatic amine.

[0025] In the second aspect, the present invention provides the application of the high wear-resistant long-chain nylon material for engineering pipelines described in the first aspect in wear-resistant pipelines and cable sheaths. The long-chain nylon material for mortar conveying pipelines described in the first aspect can be used for extrusion or injection molding.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] (1) In the present invention, the reaction of long-chain carbon nylon with a continuous methylene number between 8 and 16 and a toughening agent with a grafting rate of polar groups between 0.5 and 1.2 can greatly improve the melt strength of the material while ensuring a certain fluidity. When the grafting rate is lower than 0.5, it is difficult to form a micro-crosslinked structure with long-chain carbon nylon, and the melt strength is not enough to form large-diameter pipes, resulting in serious melt sag. When the grafting rate is higher than 1.2, the crosslinking degree of the blend material is too high and the fluidity is poor, resulting in too large torque of the single-screw extrusion equipment and difficulty in forming pipes.

[0028] (2) In the present invention, in the metal sulfide containing 0.7 - 0.9 mol% free acid, polar groups such as maleic anhydride and glycidyl methacrylate in the toughening agent will be activated during the twin-screw granulation process, and produce a synergistic effect with the toughening agent with a grafting rate of polar groups between 0.5 - 1.2. It can effectively reduce the ring-opening activation energy of acid anhydride and glycidyl methacrylate, enhance their reaction activity with the end groups of long-chain nylon, so as to increase the melt strength of the long-chain nylon material to more than 0.03 N at 240 °C, achieve the balance of low-temperature resistance, chemical corrosion resistance, wear resistance and processing performance of the long-chain nylon material, and can form an SDR 11 engineering pipeline with a smooth surface and a Dn250 mm caliber. Detailed implementation manners

[0029] The technical solutions of the present invention will be further described below through specific implementation manners. Those skilled in the art should clearly understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0030] The raw material grades and supplier information used in the preparation examples and implementation examples of the present invention are shown in Table 1 below:

[0031] Table 1 Raw material sources

[0032]

[0033] Preparation Example 1

[0034] In this preparation example, an acidified metal sulfide is provided, and the metal sulfide is prepared by the following method:

[0035] Take a certain mass of metal sulfide and soak it in a 0.1000 mol / L oxalic acid solution, with a solid-liquid mass ratio of 1:10 (Kg:L). After stirring for 2 h, filter, and dry the filter cake in an oven at 60 °C to obtain the acidified metal sulfide (acidified SLS22F-1), and titrate to test its free acid content.

[0036] Preparation Example 2

[0037] In this preparation example, a metal sulfide with a higher degree of acidification is provided, and the metal sulfide is prepared by the following method:

[0038] Take a certain mass of metal sulfide and soak it in a 0.5000 mol / L oxalic acid solution, with a solid-liquid mass ratio of 1:10 (Kg:L). After stirring for 2 h, filter, and dry the filter cake in an oven at 60 °C to obtain the metal sulfide with a higher degree of acidification (acidified SLS22F-2), and titrate to test its free acid content.

[0039] The free acid content of the metal sulfide is tested according to the following method:

[0040] Take 1 g of metal sulfide, soak it in 20 mL of deionized water and stir for 24 h. After standing for precipitation for 6 h, titrate the supernatant with a standard NaOH solution of 0.1000 mol / L, using phenolphthalein or thymolphthalein as the titration indicator. The titration results are shown in Table 2:

[0041] Table 2 Free acid content of metal sulfide

[0042] Metal sulfide Free acid content (mol%) SLS 22F 0.2 Acidified SLS 22F-1 0.8 Acidified SLS 22F-2 1.5

[0043] Example 1

[0044] In this example, a long-chain nylon material for mortar conveying pipelines is provided. The raw materials for preparing the long-chain nylon material for mortar conveying pipelines, calculated by weight percentage, mainly include the following components:

[0045]

[0046] Among them, the long carbon chain polyamide is polyamide 12 resin (grade L3000); the toughening agent is N416; the metal sulfide is acidified SLS22F-1; the lubricants are calcium stearate (0.2%) and erucamide (0.2%); the antioxidants are 1098 (0.4%) and 168 (0.2%).

[0047] The high wear-resistant long-chain nylon material particles for engineering pipelines are prepared through the following steps:

[0048] Mix a certain amount of long carbon chain polyamide, toughening agent, lubricant, antioxidant and other additives evenly according to the ratio using a low mixer, with a rotation speed of 100 rpm, a mixing time of 10 min, an extrusion temperature of 250 °C, a screw rotation speed of 500 - 700 rpm, a production capacity of 35 Kg / h, and a vacuum degree of -0.05 MPa.

[0049] Example 2

[0050] The difference between this example and Example 1 is only that 10% acidified metal sulfide (acidified SLS22F-1) is added; at the same time, the proportion of long carbon chain polyamide is adjusted to 79%, and the preparation method is the same.

[0051] Example 3

[0052] The difference between this example and Example 1 is only that the toughening agent with a polar group grafting rate of 0.5% (grade N416) is replaced with a toughening agent with a polar group grafting rate of 1.1% (grade VA1803), and other conditions are the same as those in Example 1.

[0053] Example 4

[0054] The difference between this embodiment and Embodiment 1 is only that the addition ratio of the polar group graft toughening agent (grade N416) is adjusted to 15%, and at the same time the ratio of the long carbon chain polyamide is adjusted to 79%, and other conditions are the same as those in Embodiment 1.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Embodiment 1 is only that polyamide 12 (grade L3000) is replaced with polyamide 6 (grade 1030B), and other conditions are the same as those in Embodiment 1.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Embodiment 1 is only that the acidified metal sulfide (grade acidified SLS22F-1) is replaced with the non-acidified metal sulfide (grade SLS22F), and other conditions are the same as those in Embodiment 1.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Embodiment 1 is only that the acidified metal sulfide (grade acidified SLS 22F-1) is replaced with the metal sulfide with a higher degree of acidification (grade acidified SLS22F-2), and other conditions are the same as those in Embodiment 1.

[0061] Comparative Example 4

[0062] The difference between this comparative example and Embodiment 1 is only that the toughening agent with a polar group grafting rate of 0.5% (grade N416) is replaced with a non-grafted toughening agent (grade 3072EM), and other conditions are the same as those in Embodiment 1.

[0063] Comparative Example 5

[0064] The difference between this comparative example and Embodiment 1 is only that the toughening agent with a polar group grafting rate of 0.5% (grade N416) is replaced with a toughening agent with a polar group grafting rate of 1.6% (grade ROYALTUF 527), and other conditions are the same as those in Embodiment 1.

[0065] The materials of Embodiments 1-4 and Comparative Examples 1-5 were tested according to the following methods:

[0066] (1) Melt volume rate MVR: Tested according to ISO 1133 standard, and the test conditions are 5Kg + 275°C;

[0067] (2) Taber abrasion: Tested according to ISO 5470 standard;

[0068] (3) Melt strength: Tested according to ISO 16790 standard, and the test conditions are 240°C;

[0069] (4) Maximum extrusion pipe diameter: Use a WELICAN 75 pipe extruder to extrude pipes with diameters of Dn16, 32, 63, 110, 160, 200, 250, and 315 mm in SDR11 specification. By adjusting the extrusion temperature, die temperature, extrusion and traction speed, ensure that the outer diameter and wall thickness of the extruded pipe meet the tolerance requirements of the corresponding specifications, so as to test the maximum diameter of the SDR11 series that can be extruded from this material.

[0070] The test results are shown in Table 3:

[0071] Table 3 Test Results

[0072]

[0073] As can be seen from Table 3, for the high wear-resistant long-chain nylon materials for engineering pipes prepared in Examples 1-5 of the present invention, their melt index and melt strength are matched with the extrusion process of large-diameter pipes. The MVR is between 10-20 ml / min, and the melt strength is greater than 0.025 N, which can meet the extrusion process of pipes with diameters of Dn110-250 mm. Its Taber abrasion can simulate the wear degree during mortar transportation, and its abrasion is lower than 5 mg / 1000r, showing excellent wear resistance. Compared with the performance of the comparative example, the addition of metal sulfide effectively reduces the abrasion of the long-chain nylon material; the addition of a polar graft compatibilizing toughening agent activated by free acid improves the compatibility and reactivity between the toughening agent and the long carbon chain long-chain nylon, making the melt index of the long-chain nylon material at 275°C + 5 Kg between 11 and 20 ml / 10 min or less, improving the extrusion molding performance of pipes with diameters above Dn110. At the same time, the problem of poor low-temperature toughness caused by the addition of wear-resistant additives is solved. The low-temperature resistance, chemical corrosion resistance, wear resistance, and processing performance of the long-chain nylon material are balanced.

[0074] In the present invention, 0.7-0.9 mol% of free acid remaining in the metal sulfide will activate polar groups such as maleic anhydride and glycidyl methacrylate in the toughening agent during the twin-screw granulation process, producing a synergistic effect with a toughening agent with a grafting rate of polar groups between 0.5 and 1.2. Reacting with a long carbon chain polyamide with the number of continuous methylene groups between 8 and 16 can greatly improve the melt strength of the material, while ensuring a certain fluidity, and can form an engineering pipe with a smooth outer diameter of Dn250mm, realizing the balance of low-temperature resistance, chemical corrosion resistance, wear resistance, and processing performance of the long-chain nylon material.

[0075] The applicant declares that the present invention uses the above embodiments to illustrate the high wear-resistant long-chain nylon material for engineering pipelines, its preparation method and application, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the products of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A highly wear-resistant long-chain nylon material for engineering pipelines, which is prepared from the following raw materials, by weight percentage, 2. The nylon material according to claim 1, characterized in that, The long carbon chain polyamide includes one or more of PA1010, PA11, PA12, PA1012, and PA1212.

3. The nylon material according to claim 1 or 2, characterized in that, The polar groups grafted on the toughening agent include maleic anhydride and glycidyl methacrylate; the grafting rate is 0.7% to 1.0%.

4. The nylon material according to any one of claims 1 to 3, characterized in that, The toughening agent is an EPDM-based polymer modified by grafting polar groups.

5. The nylon material according to any one of claims 1-4, characterized in that, The metal sulfide includes one or more of molybdenum disulfide, tin disulfide, zinc sulfide, or tungsten disulfide.

6. The nylon material according to any one of claims 1-5, characterized in that, The lubricant includes one or more of erucamide, silicone, zinc stearate, magnesium stearate, calcium stearate, or titanate.

7. The nylon material according to any one of claims 1-6, characterized in that, The antioxidant includes one or more of hindered phenols, hindered amines, phosphite esters, potassium iodide-copper iodide.

8. The nylon material according to any one of claims 1-7, characterized in that, The metal sulfide is prepared by acidification treatment.

9. The application of the nylon material according to any one of claims 1-8 in wear-resistant pipelines and cable sheaths, the melt strength thereof at 240 °C is greater than 0.03 N, and large-diameter pipelines with an outer diameter Dn of 110-250 mm can be prepared.

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