Multistage synergic covalent grafting type hydrolysis-resistant self-cleaning PET submarine cable monofilament and preparation method thereof

Abstract

The application discloses a kind of multistage synergic covalent grafting type hydrolysis-resistant self-cleaning PET submarine cable monofilament and preparation method, the monofilament includes three parts of core layer, skin layer and surface layer, the core layer is the high viscosity polyethylene terephthalate resin containing carbodiimide anti-hydrolysis agent;Skin layer is the modified PET resin of functional polysiloxane covalent grafting, wherein the functional polysiloxane has epoxy end group or isocyanate end group, and main chain has Si-H group;Surface layer is the fluorine-free low surface energy layer formed by polyvinyl long side chain alkane polysiloxane and residual Si-H group in skin layer through hydrosilylation reaction.The application significantly improves the durability of monofilament in humid heat environment, so that it is suitable for long-term humid heat service environment such as marine cable and industrial fabric, and can maintain stable mechanical strength and self-cleaning performance for a long time.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrolysis-resistant self-cleaning PET industrial monofilament for marine engineering, belonging to the field of industrial monofilaments. Background Technology

[0002] Polyethylene terephthalate (PET) is an important engineering thermoplastic polyester, widely used in marine engineering fields such as marine fisheries, marine cables, and deep-sea mooring due to its advantages of high strength, high modulus, and low cost. However, in complex environments such as seawater, high humidity, salt spray, and cyclic tension, ester bonds are easily induced to hydrolyze, resulting in problems such as strength reduction and shortened service life. In addition, PET has a high surface energy, making it easy for algae, oil, marine organisms, and other pollutants to adhere, leading to surface dulling, increased frictional resistance, and decreased antifouling properties.

[0003] The ester bonds in the PET backbone are prone to hydrolysis in high temperature, high humidity, and high salinity environments, as are the Cl- in seawater. － Mg 2+ Plasma promotes the formation of terminal carboxyl groups, accelerates chain segment breakage, and leads to a decrease in molecular weight and a decline in mechanical properties. Hydrolysis is often inhibited by adding carbodiimide (CDI)-type anti-hydrolysis agents to cap the carboxyl groups, thereby improving hygrothermal stability to some extent. However, these technologies are mostly based on "overall addition," which cannot avoid the water diffusion channels formed by water absorption on the material surface. Under long-term immersion conditions, the strength retention rate still declines rapidly. To improve the surface properties of PET in seawater, existing technologies employ various forms of hydrophobic coatings, such as fluoropolymer coatings, organosilicon coatings, and alkylsilane coatings. Although these have some effect, many problems remain: fluorinated materials are expensive, have limited interfacial bonding with PET, and suffer from poor environmental friendliness; coating technologies are mostly based on physical adsorption, making them prone to peeling off after stretching and abrasion; and they are insufficient to meet the durability requirements of submarine cables under hundreds of thousands of bending / friction cycles.

[0004] In summary, existing PET monofilaments still cannot meet the comprehensive requirements of marine engineering for hydrolysis resistance, fouling resistance, abrasion resistance, and service life. There is an urgent need for a new type of PET monofilament with integrated structure, controllable chemical reaction, and excellent surface durability. Summary of the Invention

[0005] To overcome the technical shortcomings of existing PET monofilaments in seawater, humid and hot environments, such as rapid hydrolytic degradation, severe surface contamination, and poor durability of the hydrophobic layer, this invention proposes a multi-level synergistic covalently grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament and its preparation method. This invention constructs a three-layer synergistic structure of "hydrolysis-resistant core layer + PDMS grafted sheath layer + hydrosilicified low surface energy surface layer," enabling the monofilament to maintain high strength, low surface energy, and excellent hydrolysis resistance during long-term marine service.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament comprises three parts: core layer, sheath layer, and outer layer.

[0008] The core layer is a high-viscosity PET resin containing carbodiimide anti-hydrolysis agents; the skin layer is a modified PET resin covalently grafted with functional polysiloxane, which has epoxy end groups or isocyanate end groups and Si-H groups on the main chain; the surface layer is a fluorine-free low surface energy layer formed by polyvinyl long side-chain alkane polysiloxane.

[0009] The core layer to the outer layer resin has a mass ratio of 1:9, and the monofilament diameter is 0.3-0.9 mm.

[0010] Preferably, the anti-hydrolysis agent is one of carbodiimide or polycarbodiimide, the anti-hydrolysis agent content is 0.5-2%, and the intrinsic viscosity of the high-viscosity PET resin is 0.95-1.2 dL / g.

[0011] Preferably, the functional polysiloxane has a viscosity of 100-500 cst at 25°C, a Si–H group content of 0.5-2.5 mol%, and its dosage is 2-5% of the PET resin; the intrinsic viscosity of the modified PET resin is 0.85-0.95 dL / g; and the intrinsic viscosity of the low-viscosity PET resin is 0.65-0.75 dL / g.

[0012] Preferably, the polyvinyl long-side-chain alkane polysiloxane has a viscosity of 50-500 cst at 25 °C, a vinyl content of 0.5-1.5 mol%, a long alkane side-chain unit content of 10-20 mol%, and the long alkane side chain has a carbon number of C. 12 -C 18 .

[0013] The present invention also provides a method for preparing the PET submarine cable monofilament, comprising the following steps:

[0014] Step 1: Preparation of premix

[0015] Low-viscosity PET resin was dried to a moisture content of less than 50 ppm, then melt-blended with functional polysiloxane and catalyst using a twin-screw extruder. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix. The temperature range of the twin-screw extruder was 270-285 °C.

[0016] Step 2: Preparation of modified PET resin

[0017] The premixed material was placed in a solid-phase thickening device and reacted at 210-225 °C under a vacuum of less than 200 Pa for 48-60 hours to obtain modified PET resin.

[0018] Step 3: Core-Sheath Composite Spinning

[0019] High-viscosity PET resin containing carbodiimide was used as the core layer material, and modified PET resin was used as the sheath material. The two materials were melted in a single-screw extruder and fed into a bicomponent spinning assembly. The sheath layer covered the core layer, and after cooling, hot stretching, and heat setting, PET composite monofilaments were obtained.

[0020] Step 4: Surface Treatment

[0021] The PET monofilaments obtained in step 3 are immersed in a solution of polyvinyl long side-chain alkane polysiloxane and Karstedt type platinum catalyst and reacted at 80-100 °C for 2-4 hours. After washing and drying, a low surface energy layer is formed on the surface of the monofilaments.

[0022] Preferably, the catalyst in step one is triphenylphosphine or stannous isooctanoate, and the amount of catalyst used is 0.05-0.12% of the PET resin.

[0023] Preferably, the hot stretching in step three is a two-stage stretching with a total stretching ratio of 4-7 times and a heat setting temperature of 160 ℃.

[0024] Preferably, the solution in step four uses xylene as a solvent, the mass fraction of polyvinyl long-chain alkane polysiloxane is 3-5%, the Karstedt type platinum catalyst is platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, and the amount of catalyst is 10-30 ppm of the total mass of the system.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) This invention introduces a carbodiimide-based anti-hydrolysis agent into the core layer of the monofilament, which can effectively capture the carboxyl end groups generated by PET in a humid and hot environment, inhibit ester bond depolymerization, and improve the hydrolysis resistance of the bulk phase. At the same time, the skin layer uses modified PET covalently grafted with functional polysiloxane, whose low polarity segments can reduce the diffusion of moisture from the interface to the core layer. Furthermore, the Si–H groups enriched in the skin layer form a stable Si–C bond hydrophobic surface layer with long-chain alkyl polysiloxane through hydrosilylation reaction, which significantly improves the water-blocking ability of the monofilament surface.

[0027] The synergy between the internal anti-hydrolysis structure and the external water-blocking structure effectively suppresses the diffusion rate and chain hydrolysis rate of water in the monofilament, thereby extending the material's service life. After immersion in artificial seawater at 85 ℃ for 500 h, the strength retention rate of the monofilament of this invention is still as high as about 90%, which is significantly better than the comparative sample with only CDI modification or the comparative sample without surface treatment, fully verifying the synergistic hydrolysis resistance effect of the three-layer structure of this invention.

[0028] (2) The surface layer constructed by hydrosilylation forms a dense long-chain alkyl polysiloxane network with a stable Si–C bond structure, which has significantly higher bonding strength compared with the physical enrichment layer formed by traditional PDMS migration. This structure forms a durable low surface energy region on the monofilament surface, resulting in an initial water contact angle >130°, which remains ≥120° even after 10,000 friction cycles, far exceeding the durability level of physically coated hydrophobic layers.

[0029] This stable surface layer not only significantly reduces the water absorption rate of monofilaments, but also reduces the tendency of algae, silt, and biological adhesions to attach, thus significantly improving the antifouling ability in marine environments.

[0030] (3) The fluorine-free long-chain alkyl polysiloxane surface layer designed in this invention avoids the environmental risks of traditional fluorinated hydrophobic materials and has good compatibility with existing PET industrial yarn production equipment. At the same time, through the multi-level synergistic design of "core layer hydrolysis resistance + skin layer low polarity grafted segments + surface layer durable hydrophobicity", the monofilament can maintain good mechanical properties, low water absorption and surface self-cleaning ability under long-term seawater immersion, humid heat aging and wear conditions. Its comprehensive performance is significantly better than the existing single hydrolysis resistance or single hydrophobic modification scheme. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] A multi-level synergistic covalently grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament, with a monofilament diameter of 0.3-0.9 mm, comprises three parts: a core layer, a sheath layer, and a surface layer. The mass ratio of the core layer to the sheath layer resin is 1:9. The core layer is a high-viscosity polyethylene terephthalate (PET) resin containing a carbodiimide-based hydrolysis resistant agent. The sheath layer is a modified PET resin covalently grafted with functional polysiloxanes, wherein the functional polysiloxanes have epoxy end groups or isocyanate end groups, and the main chain carries Si-H groups. The surface layer is a fluorine-free, low surface energy layer formed by hydrosilylation of polyvinyl long-side-chain alkane polysiloxanes with residual Si-H groups in the sheath layer.

[0033] Specifically, the anti-hydrolysis agent is one of carbodiimide or polycarbodiimide, with an anti-hydrolysis agent content of 0.5-2%; the intrinsic viscosity of the high-viscosity PET resin is 0.95-1.2 dL / g; the functional polysiloxane has a viscosity of 100-500 cst at 25°C, a Si–H group content of 0.5-2.5 mol%, and its dosage is 2-5% of the PET resin; the intrinsic viscosity range of the modified PET resin is 0.85-0.95 dL / g; the intrinsic viscosity of the low-viscosity PET resin is 0.65-0.75 dL / g; the polyvinyl long-side-chain alkane polysiloxane has a viscosity of 50-500 cst at 25°C, a vinyl content of 0.5-1.5 mol%, a long alkane side-chain unit content of 10-20 mol%, and the long alkane side chain has a carbon number of C. 12 -C 18 .

[0034] Specifically, the present invention also provides a method for preparing the PET submarine cable monofilament, comprising the following steps:

[0035] Step 1: Preparation of premix

[0036] Low-viscosity PET resin was dried to a moisture content of less than 50 ppm, and then melt-blended with functional polysiloxane and catalysts triphenylphosphine or stannous isooctanoate using a twin-screw extruder. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix. The catalyst content was 0.05-0.12% of the PET resin, and the twin-screw extruder temperature range was 270-285 °C.

[0037] Step 2: Preparation of modified PET resin

[0038] The premixed material was placed in a solid-phase thickening device and reacted at 210-225 °C under a vacuum of less than 200 Pa for 48-60 hours to obtain modified PET resin.

[0039] Step 3: Core-Sheath Composite Spinning

[0040] High-viscosity PET resin containing carbodiimide was used as the core layer material, and modified PET resin was used as the sheath material. Both were melted separately using a single-screw extruder and then fed into a bicomponent spinning assembly. The sheath layer coated the core layer, and after cooling, two-stage hot stretching, and heat setting, PET composite monofilaments were obtained. The total stretch ratio was 4-7 times, and the heat setting temperature was 160 ℃.

[0041] Step 4: Surface Treatment

[0042] The PET monofilaments obtained in step three were immersed in a xylene solution of polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, and reacted at 80-100 °C for 2-4 hours. After washing and drying, a low surface energy layer was formed on the surface of the monofilaments. The mass fraction of the polyvinyl long-chain alkane polysiloxane was 3-5%, and the amount of catalyst was 10-30 ppm of the total mass of the system.

[0043] The initial strength of the monofilament was tested using a monofilament tensile tester, and the strength retention rate of the monofilament was measured after 168 hours and 500 hours in an artificial seawater environment at 85°C. The initial surface contact angle of the monofilament and the contact angle after 10,000 cycles of friction were measured using a water contact angle meter.

[0044] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0045] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available. Example 1

[0046] Step 1: Preparation of premix

[0047] Low-viscosity PET resin with an intrinsic viscosity of 0.75 dL / g was selected. 97 parts of the low-viscosity PET resin were dried to a water content of 50 ppm. Then, it was melt-blended with 3 parts of functional polysiloxane with a viscosity of 100 cst, a Si-H group content of 2.5 mol%, and an epoxy-terminated group, and 0.1% of triphenylphosphine relative to the total system using a twin-screw extruder at 270-285 °C. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix.

[0048] Step 2: Preparation of modified PET resin

[0049] The premix was placed in a solid-phase thickening device and reacted at 210 °C and a vacuum of 200 Pa for 48 hours to obtain a modified PET resin with an intrinsic viscosity of 0.91 dL / g.

[0050] Step 3: Core-Sheath Composite Spinning

[0051] High-viscosity PET resin with a viscosity of 1.05 dL / g was selected. High-viscosity PET resin containing 1.0% carbodiimide was used as the core layer material, and modified PET resin was used as the sheath layer material. Both were melted in a single-screw extruder and fed into a bicomponent spinning assembly. The sheath layer coated the core layer. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.3 mm were obtained. The monofilament draw ratio was 7 times.

[0052] Step 4: Surface Treatment

[0053] A polyvinyl long-chain alkane polysiloxane with a viscosity of 150 cst, a vinyl content of 1 mol%, a long alkane side chain unit content of 20 mol%, and a long side chain carbon number of C12 was selected. The polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane were dissolved in xylene to prepare a 5% (w / w) solution with a catalyst content of 30 ppm. The PET monofilament obtained in step three was immersed in the solution and reacted at 80 °C for 3 hours. After washing and drying, PET submarine cable monofilaments were obtained. Example 2

[0054] Step 1: Preparation of premix

[0055] Low-viscosity PET resin with an intrinsic viscosity of 0.75 dL / g was selected. 98 parts of the low-viscosity PET resin were dried to a water content of 50 ppm. Then, it was melt-blended with 2 parts of functional polysiloxane with a viscosity of 500 cst, a Si-H group content of 1.5 mol%, and an epoxy-terminated group, and 0.1% of triphenylphosphine relative to the total system using a twin-screw extruder at 270-285 °C. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix.

[0056] Step 2: Preparation of modified PET resin

[0057] The premix was placed in a solid-phase thickening device and reacted at 225 °C and a vacuum of 100 Pa for 60 hours to obtain a modified PET resin with an intrinsic viscosity of 0.95 dL / g.

[0058] Step 3: Core-Sheath Composite Spinning

[0059] High-viscosity PET resin with a viscosity of 1.0 dL / g was selected. High-viscosity PET resin containing 1.5% carbodiimide was used as the core layer material, and modified PET resin was used as the sheath layer material. Both were melted in a single-screw extruder and fed into a bicomponent spinning assembly. The sheath layer coated the core layer. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.3 mm were obtained. The monofilament draw ratio was 7 times.

[0060] Step 4: Surface Treatment

[0061] A polyvinyl long-chain alkane polysiloxane with a viscosity of 50 cst, a vinyl content of 1.5 mol%, a long alkane side chain unit content of 10 mol%, and a long side chain carbon number of C18 was selected. The polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane were dissolved in xylene to prepare a 5% (w / w) solution with a catalyst content of 30 ppm. The PET monofilament obtained in step three was immersed in the solution and reacted at 100 °C for 4 hours. After washing and drying, PET submarine cable monofilaments were obtained. Example 3

[0062] Step 1: Preparation of premix

[0063] Low-viscosity PET resin with an intrinsic viscosity of 0.65 dL / g was selected. 95 parts of the low-viscosity PET resin were dried to a water content of 50 ppm. Then, it was melt-blended with 5 parts of functional polysiloxane with a viscosity of 200 cst, a Si–H group content of 1.0 mol%, and an epoxy-terminated group, and 0.12% of triphenylphosphine relative to the total system using a twin-screw extruder at 270-285 °C. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix.

[0064] Step 2: Preparation of modified PET resin

[0065] The premix was placed in a solid-phase thickening device and reacted at 225 °C and a vacuum of 150 Pa for 48 hours to obtain a modified PET resin with an intrinsic viscosity of 0.85 dL / g.

[0066] Step 3: Core-Sheath Composite Spinning

[0067] High-viscosity PET resin with a viscosity of 0.95 dL / g was selected. High-viscosity PET resin containing 1% carbodiimide was used as the core layer material, and modified PET resin was used as the sheath layer material. Both were melted separately using a single-screw extruder and then fed into a bicomponent spinning assembly. The sheath layer coated the core layer. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.3 mm were obtained. The monofilament draw ratio was 5 times.

[0068] Step 4: Surface Treatment

[0069] A polyvinyl long-chain alkane polysiloxane with a viscosity of 200 cst, a vinyl content of 0.5 mol%, a long alkane side chain unit content of 10 mol%, and a long side chain carbon number of C12 was selected. The polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane were dissolved in xylene to prepare a 5% (w / w) solution with a catalyst content of 30 ppm. The PET monofilament obtained in step three was immersed in the solution and reacted at 90 °C for 2 hours. After washing and drying, PET submarine cable monofilaments were obtained. Example 4

[0070] Step 1: Preparation of premix

[0071] Low-viscosity PET resin with an intrinsic viscosity of 0.75 dL / g was selected. 95 parts of the low-viscosity PET resin were dried to a water content of 30 ppm. Then, it was melt-blended with 5 parts of functional polysiloxane with a viscosity of 150 cst, a Si–H group content of 2.0 mol%, and isocyanate end groups, and 0.05% of stannous isooctanoate relative to the total system using a twin-screw extruder at 270-285 °C. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix.

[0072] Step 2: Preparation of modified PET resin

[0073] The premix was placed in a solid-phase thickening device and reacted at 215 °C and a vacuum of 100 Pa for 54 hours to obtain a modified PET resin with an intrinsic viscosity of 0.93 dL / g.

[0074] Step 3: Core-Sheath Composite Spinning

[0075] High-viscosity PET resin with a viscosity of 1.2 dL / g was selected. High-viscosity PET resin containing 2% polycarbodiimide was used as the core layer material, and modified PET resin was used as the sheath material. Both were melted in a single-screw extruder and fed into a bicomponent spinning assembly. The sheath layer coated the core layer. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.9 mm were obtained. The monofilament draw ratio was 5 times.

[0076] Step 4: Surface Treatment

[0077] A polyvinyl long-chain alkane polysiloxane with a viscosity of 500 cst, a vinyl content of 1.5 mol%, a long alkane side chain unit content of 15 mol%, and a long side chain carbon number of C18 was selected. The polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane were dissolved in xylene to prepare a 5% (w / w) solution with a catalyst content of 30 ppm. The PET monofilament obtained in step three was immersed in the solution and reacted at 100 °C for 4 hours. After washing and drying, PET submarine cable monofilaments were obtained. Example 5

[0078] Step 1: Preparation of premix

[0079] Low-viscosity PET resin with an intrinsic viscosity of 0.7 dL / g was selected. 98 parts of the low-viscosity PET resin were dried to a water content of 50 ppm. Then, it was melt-blended with 2 parts of functional polysiloxane with a viscosity of 100 cst, a Si-H group content of 0.5 mol%, and an epoxy-terminated group, and 0.08% of triphenylphosphine relative to the total system using a twin-screw extruder at 270-285 °C. After extrusion granulation, the mixture was pre-crystallized at 160 °C for 30 minutes to obtain a premix.

[0080] Step 2: Preparation of modified PET resin

[0081] The premix was placed in a solid-phase thickening device and reacted at 215 °C and a vacuum of 100 Pa for 60 hours to obtain a modified PET resin with an intrinsic viscosity of 0.88 dL / g.

[0082] Step 3: Core-Sheath Composite Spinning

[0083] High-viscosity PET resin with a viscosity of 1.1 dL / g was selected. High-viscosity PET resin containing 0.5% polycarbodiimide was used as the core layer material, and modified PET resin was used as the sheath layer material. Both were melted in a single-screw extruder and fed into a bicomponent spinning assembly. The sheath layer coated the core layer. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.65 mm were obtained. The monofilament draw ratio was 5 times.

[0084] Step 4: Surface Treatment

[0085] A polyvinyl long-chain alkane polysiloxane with a viscosity of 50 cst, a vinyl content of 0.5 mol%, a long alkane side chain unit content of 10 mol%, and a long side chain carbon number of C12 was selected. The polyvinyl long-chain alkane polysiloxane and platinum(O)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane were dissolved in xylene to prepare a 3% (w / w) solution with a catalyst content of 10 ppm. The PET monofilament obtained in step three was immersed in the solution and reacted at 80 °C for 2 hours. After washing and drying, PET submarine cable monofilaments were obtained.

[0086] Comparative Example 1

[0087] High-viscosity PET resin with a viscosity of 1.05 dL / g was selected. The high-viscosity PET resin containing 1.0% carbodiimide was directly melted and spun using a single-screw extruder. After cooling, two-stage hot stretching, and heat setting at 160 ℃, PET composite monofilaments with a diameter of 0.3 mm were obtained. The monofilament stretch ratio was 7 times.

[0088] Comparative Example 2

[0089] Everything else is the same as in Example 1, except that no anti-hydrolysis agent is added to the PET resin in step 3.

[0090] Comparative Example 3

[0091] Everything else is the same as in Example 1, except that there is no fourth step of surface treatment.

[0092] Monofilament performance table

[0093]

[0094] Comparing Example 1 and Comparative Example 1, it can be seen that the monofilament with only the anti-hydrolysis agent added has no skin layer or surface water-blocking structure, allowing moisture to quickly penetrate from the surface. Therefore, the strength decreases significantly after 500 hours, and the surface has no hydrophobicity or abrasion resistance. Comparing Example 1 and Comparative Example 2, it can be seen that the monofilament with a surface hydrophobic layer has the lowest retention rate because the PET bulk phase still undergoes hydrolysis due to the lack of an anti-hydrolysis agent. However, due to the covalent bonding between the surface low-energy layer and the monofilament, it still maintains good hydrophobicity and abrasion resistance after friction. Comparing Example 1 and Comparative Example 3, it can be seen that because the functional polysiloxane structure blended with PET does not contain long alkyl side chains, its hydrophobicity is limited. Under long-term water immersion conditions, the skin layer has limited water-blocking ability, and the mechanical properties still decrease significantly over time. Moreover, the surface low-energy layer is only enriched by the internal polysiloxane, resulting in a low content and a large degree of corner chipping after friction.

[0095] The above results indicate that the core layer anti-hydrolysis agent provides bulk anti-hydrolysis capability, the polysiloxane graft structure in the skin layer reduces the rate of water centripetal diffusion, and the long-chain alkyl low surface energy layer constructed by hydrosilicification on the surface further blocks water. The three elements work together effectively to significantly improve the long-term mechanical and other property retention level of the monofilament in a humid and hot seawater environment.

Claims

1. A multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament, characterized in that: The monofilament consists of three parts: the core layer, the sheath layer, and the outer layer. The core layer is a high-viscosity polyethylene terephthalate resin containing carbodiimide anti-hydrolysis agents; The skin layer is a modified PET resin covalently grafted with functional polysiloxane, wherein the functional polysiloxane has epoxy end groups or isocyanate end groups and the main chain has Si-H groups. The surface layer is a fluorine-free low surface energy layer formed by hydrosilylation of polyvinyl long side chain alkane polysiloxane and residual Si-H groups in the skin layer. The core layer to the outer layer resin has a mass ratio of 1:9, and the monofilament diameter is 0.3-0.9 mm.

2. The multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 1, characterized in that, The anti-hydrolysis agent is one of carbodiimide or polycarbodiimide, and the content of the anti-hydrolysis agent in the high-viscosity PET resin is 0.5-2%, and the intrinsic viscosity of the high-viscosity PET resin is 0.95-1.2 dL / g.

3. The multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 1, characterized in that, The functional polysiloxane has a viscosity of 100-500 cst at 25°C, a Si–H group content of 0.5-2.5 mol%, and its dosage is 2-5% of the PET resin; the intrinsic viscosity range of the modified PET resin is 0.85-0.95 dL / g; and the intrinsic viscosity of the low-viscosity PET resin is 0.65-0.75 dL / g.

4. The multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 1, characterized in that, The polyvinyl long-side-chain alkane polysiloxane has a viscosity of 50-500 cSt at 25°C, a vinyl content of 0.5-1.5 mol%, a long alkane side-chain unit content of 10-20 mol%, and the long alkane side chain has a carbon number of C. 12 -C 18 .

5. A method for preparing the multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of premix Low-viscosity PET resin was dried to a moisture content of less than 50 ppm, and then melt-blended with functional polysiloxane and catalyst using a twin-screw extruder. After extrusion granulation, the mixture was pre-crystallized at 160°C for 30 minutes to obtain a premix. The temperature range of the twin-screw extruder was 270-285°C. Step 2: Preparation of modified PET resin The premixed material was placed in a solid-phase thickening device and reacted at 210-225℃ and a vacuum degree of less than 200 Pa for 48-60 hours to obtain modified PET resin. Step 3: Core-Sheath Composite Spinning High-viscosity PET resin containing carbodiimide was used as the core layer material, and modified PET resin was used as the skin layer material. They were melted in a single-screw extruder and then fed into a two-component spinning assembly. The skin layer covered the core layer, and after cooling, hot stretching, and heat setting, PET composite monofilaments were obtained. Step 4: Surface Treatment The PET monofilaments obtained in step 3 are immersed in a solution of polyvinyl long-side-chain alkane polysiloxane and Karstedt-type platinum catalyst and reacted at 80-100℃ for 2-4 hours. After washing and drying, a low surface energy layer is formed on the surface of the monofilaments.

6. The method for preparing multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 5, characterized in that, The catalyst mentioned in step one is triphenylphosphine or stannous isooctanoate, and the amount of catalyst used is 0.05-0.12% of the PET resin.

7. The method for preparing multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 5, characterized in that, In step three, the hot stretching is a two-stage stretching with a total stretching ratio of 4-7 times and a heat setting temperature of 160℃.

8. The method for preparing multi-level synergistic covalent grafted hydrolysis-resistant self-cleaning PET submarine cable monofilament according to claim 5, characterized in that, The solution in step four uses xylene as solvent, the mass fraction of polyvinyl long-chain alkane polysiloxane is 3-5%, the Karstedt type platinum catalyst is platinum(0)-1,3-diethylene-1,1,3,3-tetramethyldisiloxane, and the amount of catalyst is 10-30 ppm of the total mass of the system.

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