High-resilience polyether type TPU (thermoplastic polyurethane) sheath material for robot joints, preparation method of high-resilience polyether type TPU sheath material and cable

Abstract

The invention belongs to the technical field of preparation of sheath materials and cables, and provides a high-resilience polyether type TPU sheath material for robot joints, a preparation method of the high-resilience polyether type TPU sheath material and a cable. The preparation method comprises the following steps: firstly, preparing branched polyester, and modifying the branched polyester by utilizing an isocyanate group functionalized end-capping reagent; meanwhile, the halloysite nanotubes are subjected to acid etching and amination treatment, diisocyanate is utilized, a segmented copolymer formed by polypropylene glycol monobutyl ether and caprolactone is chemically grafted to the surfaces of the halloysite nanotubes, and grafted halloysite is obtained; then, preparing a prepolymer, carrying out chain extension reaction in cooperation with branched polyester and di (2-ethoxyl) disulphide, and carrying out curing, melt extrusion and gradient cooling shaping; according to the invention, a branched structure, multiple hydrogen bonds and disulfide bonds are introduced to construct a dual dynamic network, and organic-inorganic hybrid interface enhancement is combined, so that the rebound resilience and fatigue resistance of the material are improved.

Description

Technical Field

[0001] This invention belongs to the field of sheath material and cable preparation technology, and relates to high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and cables. Background Technology

[0002] With the development of industrial automation, industrial robots are operating at increasingly higher frequencies and intensities in complex environments, placing extremely high performance demands on the cable sheath materials used in robot joints. As an outer barrier protecting the internal conductors and insulation layers, the cable sheath not only needs excellent wear resistance, oil resistance, and hydrolysis resistance, but also must maintain structural integrity during long-term, high-frequency bending, torsion, and stretching reciprocating motions of the joint. Thermoplastic polyurethane elastomers, especially polyether-based TPUs, have become the preferred matrix material for robot cable sheaths due to their excellent low-temperature resistance, hydrolysis resistance, and biocompatibility.

[0003] However, existing polyether-based TPU materials still face significant technical bottlenecks in high-end applications of robotic joints. Firstly, under long-term dynamic cyclic loading, traditional linear TPU molecular chains are prone to irreversible slippage, leading to substantial hysteresis loss. This energy loss translates into heat accumulation, accelerating material aging and fatigue failure, manifested as decreased resilience and increased permanent deformation. Secondly, to improve mechanical strength and wear resistance, inorganic nanofillers are often introduced. However, the inherent polarity difference between inorganic fillers and the organic polymer matrix results in poor interfacial compatibility. During repeated deformation, the fillers are prone to agglomeration or detachment from the matrix, forming microscopic cavities and stress concentration points, which become the source of crack initiation, severely weakening the material's flexural fatigue life. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a high-resilience polyether-based TPU sheath material for robot joints, its preparation method, and cables. The invention involves synthesizing branched polyesters modified with isocyanate groups, grafting block copolymers onto the surface of halloysite nanotubes using chemical bonding, then mixing polyether polyols with the grafted halloysite nanotubes and prepolymerizing with diisocyanate, followed by chain extension, and finally obtaining the finished product through melt extrusion and cooling. This invention solves the problems of high hysteresis loss and poor fatigue resistance in traditional materials by introducing a branched structure, multiple hydrogen bonds, and disulfide bonds to construct a dual dynamic network, thereby meeting the needs of practical production.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a high-resilience polyether-type TPU sheath material for robot joints, the preparation method comprising: S1, Trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid are mixed and reacted to obtain a branched polyester; S2, branched polyester, dibutyltin dilaurate and anhydrous dimethylacetamide are mixed, a capping agent is added dropwise and the reaction is continued until the infrared peak of isocyanate disappears, to obtain the additive; S3, acid-etched halloysite nanotubes are dispersed in an aqueous ethanol solution, and 3-aminopropyltriethoxysilane is added to react and obtain aminated halloysite. Aminated halloysite is dispersed in a first portion of anhydrous toluene, and 4,4'-diphenylmethane diisocyanate is added to react and obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface is redispersed in a second portion of anhydrous toluene, and block copolymer is added to react with dibutyltin dilaurate to obtain grafted halloysite. S4, polytetrahydrofuran ether diol is mixed with grafted halloysite, and 4,4'-diphenylmethane diisocyanate is added and stirred to react to obtain a prepolymer. 1,4-butanediol, additives and di(2-hydroxyethyl) disulfide are mixed and added to the prepolymer to react and mature. The mixture is then melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0006] Specifically, it includes: S1, trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid are mixed, nitrogen gas is introduced and the temperature is raised to the first temperature and stirred to react. Then the temperature is raised to the second temperature and the reaction is carried out under vacuum. When the acid value is lower than 5 mg KOH / g, the temperature is lowered to the third temperature, calcium oxide powder is added and stirred, and then filtered while hot. The filtrate is dehydrated under vacuum to obtain branched polyester. S2, branched polyester, dibutyltin dilaurate and anhydrous dimethylacetamide are mixed, heated to the fourth temperature under nitrogen atmosphere, end-capping agent is added dropwise and reacted until the infrared peak of isocyanate disappears, the reaction solution is poured into diethyl ether to precipitate, filtered and dried to obtain additive. S3, acid-etched halloysite nanotubes were dispersed in an ethanol-water solution, glacial acetic acid was added to adjust the pH to 4.5-5.5, 3-aminopropyltriethoxysilane was added, and the reaction was carried out under reflux at a fourth temperature. After washing and drying, aminated halloysite was obtained. Aminated halloysite was dispersed in a first portion of anhydrous toluene under a nitrogen atmosphere, 4,4'-diphenylmethane diisocyanate was added, and the reaction was carried out at a fifth temperature to obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface was redispersed in a second portion of anhydrous toluene, block copolymer and dibutyltin dilaurate were added, and the reaction was carried out at a fourth temperature. After the reaction, it was extracted with tetrahydrofuran by Soxhlet and dried to obtain grafted halloysite. S4, polytetrahydrofuran ether diol is mixed with grafted halloysite, and 4,4'-diphenylmethane diisocyanate is added at a fourth temperature and stirred to obtain a prepolymer. 1,4-butanediol, additives and di(2-hydroxyethyl) disulfide are mixed and added to the prepolymer for reaction and aging. The mixture is then melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0007] In the branched polyester preparation stage, trihydroxy polyols and carboxyl-containing dihydroxy acids undergo esterification polycondensation under an inert atmosphere. The carboxyl group undergoes a nucleophilic substitution addition-elimination process with the hydroxyl group to form an ester bond. Toluenesulfonic acid provides protic acid catalysis, enhancing the electronegativity of the carboxyl carbonyl group and promoting hydroxyl departure, thereby increasing the esterification rate. Water generated during the polycondensation process is continuously removed under reduced pressure, shifting the reaction equilibrium towards esterification. Subsequently, calcium oxide is added, primarily through acid-base neutralization, to consume residual toluenesulfonic acid and some free carboxylic acid, generating insoluble salts and reducing the acidity of the system, thus minimizing potential side reactions in the subsequent isocyanate reaction. After hot filtration to remove solid salts and insoluble matter, vacuum dehydration is performed to reduce the moisture and volatile small molecule content of the system, yielding a branched polyester with hydroxyl groups as the main end groups.

[0008] In the end-capping reaction stage, the branched polyester is dissolved in an anhydrous polar solvent and heated under an inert atmosphere. After adding an organotin catalyst, the end-capping agent is added dropwise. The isocyanate groups in the end-capping agent undergo nucleophilic addition with the terminal hydroxyl groups of the branched polyester to form urethane bonds. During the reaction, the isocyanate groups are consumed until the infrared characteristic peak disappears, indicating that the main isocyanate reaction is complete, and a branched polyester containing ureidopyrimidinone groups is obtained. In addition to retaining some reactive hydroxyl groups, the ureidopyrimidinone groups can form reversible non-covalent association sites through multi-point hydrogen bond dimerization, thereby providing a physical association network in the polyurethane system.

[0009] In the halloysite grafting stage, acid etching helps remove impurities and increase surface hydroxyl sites. Subsequently, in an ethanol / water system, aminosilane is first hydrolyzed to generate silanol, which then condenses with the hydroxyl groups on the halloysite surface to form siloxane bonds and introduce terminal amino groups, giving the filler surface nucleophilic sites that can react with isocyanates. Next, the aminated halloysite reacts with diisocyanate, and the surface amino groups form urea bonds with the isocyanate groups, leaving unreacted isocyanate groups on the surface, thus obtaining halloysite with isocyanate groups on the surface. The block copolymer is prepared using a stannous octoate-catalyzed lactone ring-opening polymerization mechanism to obtain polyether-polyester block chains with terminal hydroxyl groups. These block chains then undergo addition with surface isocyanate groups to form urethane bonds. Soxhlet extraction is used to remove free polymers that are only physically adsorbed.

[0010] Polytetrahydrofuran ether glycol (PTFE) is mixed with grafted halloysite, and then diisocyanate is added to initiate a prepolymerization reaction. The diisocyanate reacts with the terminal hydroxyl groups of the soft segment glycol to form urethane bonds and a terminal isocyanate prepolymer. Hydroxyl groups that may be present on the surface of the grafted halloysite or at the end of the graft layer can also participate in the reaction, allowing the filler to connect with the polyurethane segments through chemical bonds. Subsequently, glycol chain extenders, additives, and disulfide-bonded glycol chain extenders are added to jointly extend the chain. In the system, isocyanate undergoes rapid addition with various hydroxyl groups to form urethane bonds. The branched polyester, due to its polyfunctional hydroxyl groups, introduces branching or local network connection points and distributes ureidopyrimidinone groups within the polyurethane segments. The disulfide-bonded glycol introduces disulfide bonds into the main chain or network points by forming disulfide-bonded urethane links. Under heat or stress, a reversible disulfide bond exchange reaction can occur, thereby changing the network connection mode and allowing segment rearrangement. The curing process brings the chain extension reaction of the prepolymer closer to completion and promotes the differentiation between the soft and hard segments. The hydrogen bonding between the urethane, urea and ureidopyrimidinone groups in the hard segments forms an aggregate structure. The grafted halloysite reduces the inorganic / organic interface mismatch and transfers the external load through interfacial covalent bonding with the polymer brush layer. Finally, the sheath material particles are obtained through melt processing. The subsequent cable forming mainly involves melt extrusion coating and structural layer assembly. The polyurethane sheath layer forms the outer protective structure through thermoplastic extrusion.

[0011] In a preferred embodiment of the present invention, in S1, the mass ratio of trimethylolpropane, 2,2-dimethylolpropionic acid, p-toluenesulfonic acid, and calcium oxide powder is (45-55):(540-660):(0.5-1.2):(0.1-0.25), for example, it can be (45, 46, 47, 48, 49, 50, 51, 52, 53, 54 or 55):(540, 552, 564, 576, 588, 600, 612). 624, 636, 648 or 660: (0.5, 0.57, 0.64, 0.71, 0.78, 0.85, 0.92, 0.99, 1.06, 1.13 or 1.2): (0.1, 0.115, 0.13, 0.145, 0.16, 0.175, 0.19, 0.205, 0.22, 0.235 or 0.25), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0012] In some alternative embodiments, the first temperature is 135-145°C, for example, it can be 135°C, 136°C, 137°C, 138°C, 139°C, 140°C, 141°C, 142°C, 143°C, 144°C or 145°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0013] In some optional embodiments, the stirring reaction time at the first temperature is 1.5-2.5 h, for example, it can be 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0014] In some alternative embodiments, the second temperature is 155-165°C, for example, it can be 155°C, 156°C, 157°C, 158°C, 159°C, 160°C, 161°C, 162°C, 163°C, 164°C or 165°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0015] In some alternative embodiments, the third temperature is 90-110°C, for example, it can be 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, 102°C, 104°C, 106°C, 108°C or 110°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] As a preferred embodiment of the present invention, in S2, the mass ratio of the branched polyester, dibutyltin dilaurate, anhydrous dimethylacetamide, and the capping agent is (120-180):(0.04-0.15):1000:(18-30), for example, it can be (120, 126, 132, 138, 144, 150, 156, 162, 168, 174 or 180):(0.04, 0.15, 1000, 18 ... 0.051, 0.062, 0.073, 0.084, 0.095, 0.106, 0.117, 0.128, 0.139 or 0.15): 1000: (18, 19.2, 20.4, 21.6, 22.8, 24, 25.2, 26.4, 27.6, 28.8 or 30), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0017] In some alternative embodiments, the fourth temperature is 75-85°C, for example, it can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C or 85°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] In some optional embodiments, the end-capping agent is prepared by mixing 6-methylisocytosine, hexamethylene diisocyanate and anhydrous dimethylacetamide, heating to a fourth temperature under a nitrogen atmosphere and stirring the reaction, and then distilling under reduced pressure after the reaction is completed to obtain the end-capping agent.

[0019] In some optional embodiments, the mass ratio of 6-methylisocytosine, hexamethylene diisocyanate, and anhydrous dimethylacetamide is (10-14):(60-85):200, for example, (10, 10.4, 10.8, 11.2, 11.6, 12.0, 12.4, 12.8, 13.2, 13.6, or 14):(60, 62.5, 65, 67.5, 70, 72.5, 75, 77.5, 80, 82.5, or 85):200, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the stirring reaction time at the fourth temperature is 4-6 hours, for example, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, or 6.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] As a preferred embodiment of the present invention, in S3, the mass ratio of the acid-etched halloysite nanotubes, the ethanol aqueous solution, and 3-aminopropyltriethoxysilane is (30-60):1000:(5-10), for example, it can be (30, 33, 36, 39, 42, 45, 48, 51, 54, 57 or 60):1000:(5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the acid etching of halloysite nanotubes involves immersing the nanotubes in a 1M hydrochloric acid solution for 0.5-1 hour, filtering, washing until the filtrate is nearly neutral, and then drying. For example, this could be immersing the nanotubes in a 1M hydrochloric acid solution for (0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1.0) hours, filtering, washing until the filtrate is nearly neutral, and then drying. However, this is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the mass ratio of anhydrous ethanol to deionized water in the aqueous ethanol solution is 10:1.

[0024] In some optional embodiments, the fourth temperature reflux reaction time is 4-6 hours, for example, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, or 6.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the mass ratio of the aminated halloysite, the first part of anhydrous toluene, 4,4'-diphenylmethane diisocyanate, the second part of anhydrous toluene, the block copolymer, and dibutyltin dilaurate is (20-40):1000:(10-20):1000:(60-80):(0.01-0.1), for example, it can be (20, 22, 24, 26, 28, 30, 32, 34, 36, 38 or 40):1000:(10, 1 1, 12, 13, 14, 15, 16, 17, 18, 19 or 20): 1000: (60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 80): (0.01, 0.019, 0.028, 0.037, 0.046, 0.055, 0.064, 0.073, 0.082, 0.091 or 0.1), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0026] In some optional embodiments, the block copolymer is prepared by mixing polypropylene glycol monobutyl ether with ε-caprolactone under a nitrogen atmosphere, heating to 105-125°C, adding stannous octoate and reacting, pouring the reaction solution into cold methanol to precipitate, filtering and drying to obtain the block copolymer.

[0027] In some optional embodiments, the mass ratio of polypropylene glycol monobutyl ether, ε-caprolactone, and stannous octoate is (180-320):(60-180):(0.1-0.6), for example, (180, 194, 208, 222, 236, 250, 264, 278, 292, 306, or 320):(60, 72, 84, 96, 108, 120, 132, 144, 156, 168, or 180):(0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, or 0.6), but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the reaction time after the addition of stannous octoate is 12-15 h, for example, it can be 12.0 h, 12.3 h, 12.6 h, 12.9 h, 13.2 h, 13.5 h, 13.8 h, 14.1 h, 14.4 h, 14.7 h or 15.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] As a preferred embodiment of the present invention, in S4, the mass ratio of polytetrahydrofuran ether diol, grafted halloysite, and 4,4'-diphenylmethane diisocyanate is (800-1200):(40-60):(180-360), for example, it can be (800, 840, 880, 920, 960, 1000, 1040, 1080, 1120, 1160 or 1200):(40, 42, 44, 46, 48, 50, 52, 54, 56, 58 or 60):(180, 198, 216, 234, 252, 270, 288, 306, 324, 342 or 360), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the stirring reaction time is 60-120 min, for example, 60 min, 66 min, 72 min, 78 min, 84 min, 90 min, 96 min, 102 min, 108 min, 114 min or 120 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the mass ratio of 1,4-butanediol, additive, and di(2-hydroxyethyl)disulfide is (60-140):(30-50):(4-6), for example, (60, 68, 76, 84, 92, 100, 108, 116, 124, 132, or 140):(30, 32, 34, 36, 38, 40, 42, 44, 46, 48, or 50):(4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, or 6.0), but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the reaction time for adding the prepolymer is 20-60 s, for example, 20 s, 24 s, 28 s, 32 s, 36 s, 40 s, 44 s, 48 ​​s, 52 s, 56 s or 60 s, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the curing temperature is 105-115°C and the time is 16-24 hours. For example, the temperature can be (105, 106, 107, 108, 109, 110, 111, 112, 113, 114 or 115)°C and the time can be (16, 16.8, 17.6, 18.4, 19.2, 20, 20.8, 21.6, 22.4, 23.2 or 24) hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] In a second aspect, the present invention provides a high-resilience polyether-type TPU sheath material for robot joints prepared by the preparation method described in the first aspect.

[0035] Thirdly, the present invention provides a cable comprising a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed of the high-resilience polyether-type TPU sheath material for robot joints.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The additive prepared by the present invention utilizes terminal ureidopyrimidinone groups to form high-strength quadruple hydrogen bonds, constructing a reversible physical cross-linking network. Under external force, it preferentially breaks to dissipate energy and rapidly recombines, giving the material excellent resilience and extremely low hysteresis loss, effectively reducing dynamic heat generation. Secondly, a chemical grafting strategy is adopted, using diisocyanate to bond block copolymers to the surface of halloysite nanotubes, improving interfacial compatibility. The grafted segments physically entangle with the matrix, enhancing interfacial bonding force, effectively inhibiting filler agglomeration and peeling, and improving wear resistance and flexural fatigue life. In addition, the synergistic effect of disulfide bonds and hydrogen bonds endows the material with microscopic self-healing ability, enabling it to meet the stringent requirements of high-frequency reciprocating motion of robot joints. Detailed Implementation

[0037] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0038] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0039] Example 1 This embodiment provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and a cable. The preparation method specifically includes the following steps: S1, 45g of trimethylolpropane, 660g of 2,2-dimethylolpropionic acid and 0.5g of p-toluenesulfonic acid were mixed, nitrogen gas was introduced and the mixture was heated to 145℃ and stirred for 2.5h. Then the mixture was heated to 155℃ and vacuumed. When the acid value was lower than 5mg KOH / g, the mixture was cooled to 110℃, 0.10g of calcium oxide powder was added and stirred. The mixture was then filtered while hot, and the filtrate was dehydrated under vacuum to obtain branched polyester. S2, 120g of branched polyester, 0.15g of dibutyltin dilaurate and 1000g of anhydrous dimethylacetamide are mixed, heated to 75°C under a nitrogen atmosphere, 30g of end-capping agent is added dropwise and reacted until the infrared peak of isocyanate disappears. The reaction solution is poured into diethyl ether to precipitate, filtered and dried to obtain the additive. The preparation method of the end-capping agent is as follows: 10g of 6-methylisocytosine, 80g of hexamethylene diisocyanate and 200g of anhydrous dimethylacetamide are mixed, heated to 85°C under a nitrogen atmosphere and stirred to react. After the reaction is completed, the mixture is distilled under reduced pressure to obtain the end-capping agent. S3, 60g of acid-etched halloysite nanotubes were dispersed in 1000g of an ethanol-water solution, wherein the mass ratio of anhydrous ethanol to deionized water in the ethanol-water solution was 10:1. Glacial acetic acid was added to adjust the pH to 4.5, and 10g of 3-aminopropyltriethoxysilane was added. The mixture was refluxed at 75°C for 6 hours, washed, and dried to obtain aminated halloysite. The acid-etched halloysite nanotubes were immersed in 1M hydrochloric acid solution for 0.5 hours, filtered, washed until the filtrate was nearly neutral, and then dried. 40g of aminated halloysite was dispersed in 1000g of anhydrous toluene under a nitrogen atmosphere, and 10g of... 4,4'-diphenylmethane diisocyanate was reacted at 60°C for 1 h to obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface was redispersed in 1000 g of fresh anhydrous toluene, and 80 g of block copolymer and 0.01 g of dibutyltin dilaurate were added. The mixture was reacted at 85°C for 16 h. After the reaction, it was extracted with tetrahydrofuran by Soxhlet extraction and dried to obtain grafted halloysite. The block copolymer was prepared by mixing 320 g of polypropylene glycol monobutyl ether and 60 g of ε-caprolactone under a nitrogen atmosphere and heating to 125°C. 0.10 g of stannous octoate was added and the mixture was reacted for 15 h. The reaction solution was poured into cold methanol to precipitate, filtered, and dried to obtain the block copolymer. S4, 800g of polytetrahydrofuran ether diol and 60g of grafted halloysite were mixed, and 360g of 4,4'-diphenylmethane diisocyanate was added at 75°C and stirred for 60min to obtain a prepolymer. 140g of 1,4-butanediol, 30g of additives and 6g of di(2-hydroxyethyl) disulfide were mixed and added to the prepolymer and reacted for 60s. The mixture was then cured at 115°C for 16h and melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0040] The cable for robot joints includes a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed from the high-resilience polyether-type TPU sheath material for robot joints prepared in Example 1.

[0041] Example 2 This embodiment provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and a cable. The preparation method specifically includes the following steps: S1, 55g of trimethylolpropane, 540g of 2,2-dimethylolpropionic acid and 1.2g of p-toluenesulfonic acid were mixed, nitrogen gas was introduced and the mixture was heated to 135℃ and stirred for 1.5h. Then the mixture was heated to 165℃ and vacuumed. When the acid value was lower than 5mg KOH / g, the temperature was lowered to 90℃, 0.25g of calcium oxide powder was added and stirred. The mixture was then filtered while hot, and the filtrate was dehydrated under vacuum to obtain branched polyester. S2, 180g of branched polyester, 0.04g of dibutyltin dilaurate and 1000g of anhydrous dimethylacetamide are mixed, heated to 85°C under a nitrogen atmosphere, 18g of end-capping agent is added dropwise and reacted until the infrared peak of isocyanate disappears. The reaction solution is poured into diethyl ether to precipitate, filtered and dried to obtain the additive. The preparation method of the end-capping agent is as follows: 14g of 6-methylisocytosine, 65g of hexamethylene diisocyanate and 200g of anhydrous dimethylacetamide are mixed, heated to 75°C under a nitrogen atmosphere and stirred to react. After the reaction is completed, the mixture is distilled under reduced pressure to obtain the end-capping agent. S3, 30g of acid-etched halloysite nanotubes were dispersed in 1000g of an ethanol-water solution, wherein the mass ratio of anhydrous ethanol to deionized water in the ethanol-water solution was 10:1. Glacial acetic acid was added to adjust the pH to 5.5, and 5g of 3-aminopropyltriethoxysilane was added. The mixture was refluxed at 85°C for 4 hours, washed, and dried to obtain aminated halloysite. The acid-etched halloysite nanotubes were immersed in 1M hydrochloric acid solution for 1 hour, filtered, washed until the filtrate was nearly neutral, and then dried. 20g of aminated halloysite was dispersed in 1000g of anhydrous toluene under a nitrogen atmosphere, and 20g of... 4,4'-Diphenylmethane diisocyanate was reacted at 45°C for 3 h to obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface was redispersed in 1000 g of fresh anhydrous toluene, 60 g of block copolymer and 0.10 g of dibutyltin dilaurate were added, and the mixture was reacted at 75°C for 28 h. After the reaction, the mixture was extracted with tetrahydrofuran by Soxhlet extraction and dried to obtain grafted halloysite. The block copolymer was prepared by mixing 180 g of polypropylene glycol monobutyl ether and 180 g of ε-caprolactone under a nitrogen atmosphere and heating to 105°C. 0.60 g of stannous octoate was added and the mixture was reacted for 12 h. The reaction solution was poured into cold methanol to precipitate, filtered, and dried to obtain the block copolymer. S4, 1200g of polytetrahydrofuran ether diol and 40g of grafted halloysite were mixed, and 180g of 4,4'-diphenylmethane diisocyanate was added at 85°C and stirred for 120min to obtain a prepolymer. 60g of 1,4-butanediol, 50g of additives and 4g of di(2-hydroxyethyl) disulfide were mixed and added to the prepolymer and reacted for 20s. The mixture was then cured at 105°C for 24h and melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0042] The cable for robot joints includes a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed from the high-resilience polyether-type TPU sheath material for robot joints prepared in Example 2.

[0043] Example 3 This embodiment provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and a cable. The preparation method specifically includes the following steps: S1, 50g of trimethylolpropane, 600g of 2,2-dimethylolpropionic acid and 0.8g of p-toluenesulfonic acid were mixed, nitrogen gas was introduced and the mixture was heated to 140℃ and stirred for 2.0h. Then the mixture was heated to 160℃ and vacuumed. When the acid value was lower than 5mg KOH / g, the mixture was cooled to 100℃, 0.18g of calcium oxide powder was added and stirred. The mixture was then filtered while hot, and the filtrate was dehydrated under vacuum to obtain branched polyester. S2, 150g of branched polyester, 0.10g of dibutyltin dilaurate and 1000g of anhydrous dimethylacetamide are mixed, heated to 80°C under a nitrogen atmosphere, 25g of end-capping agent is added dropwise and reacted until the infrared peak of isocyanate disappears. The reaction solution is poured into diethyl ether to precipitate, filtered and dried to obtain the additive. The preparation method of the end-capping agent is as follows: 12g of 6-methylisocytosine, 70g of hexamethylene diisocyanate and 200g of anhydrous dimethylacetamide are mixed, heated to 80°C under a nitrogen atmosphere and stirred to react. After the reaction is completed, the mixture is distilled under reduced pressure to obtain the end-capping agent. S3, 45g of acid-etched halloysite nanotubes were dispersed in 1000g of an ethanol aqueous solution, wherein the mass ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution was 10:1. Glacial acetic acid was added to adjust the pH to 5.0, and 8g of 3-aminopropyltriethoxysilane was added. The mixture was refluxed at 80℃ for 5h, washed, and dried to obtain aminated halloysite. The acid-etched halloysite nanotubes were immersed in 1M hydrochloric acid solution for 0.8h, filtered, washed until the filtrate was nearly neutral, and then dried. 30g of aminated halloysite was dispersed in 1000g of anhydrous toluene under a nitrogen atmosphere, and 15g of... 4,4'-diphenylmethane diisocyanate was reacted at 50°C for 2 h to obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface was redispersed in 1000 g of fresh anhydrous toluene, 70 g of block copolymer and 0.05 g of dibutyltin dilaurate were added, and the mixture was reacted at 80°C for 20 h. After the reaction, it was extracted with tetrahydrofuran by Soxhlet extraction and dried to obtain grafted halloysite. The block copolymer was prepared by mixing 250 g of polypropylene glycol monobutyl ether and 120 g of ε-caprolactone under a nitrogen atmosphere, heating to 115°C, adding 0.30 g of stannous octoate, and reacting for 13 h. The reaction solution was poured into cold methanol to precipitate, filtered, and dried to obtain the block copolymer. S4, 1000g of polytetrahydrofuran ether diol and 50g of grafted halloysite were mixed, and 250g of 4,4'-diphenylmethane diisocyanate was added at 80℃ and stirred for 90min to obtain a prepolymer. 100g of 1,4-butanediol, 40g of additives and 5g of di(2-hydroxyethyl) disulfide were mixed and added to the prepolymer and reacted for 40s. The mixture was then cured at 110℃ for 20h and melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0044] The cable for robot joints includes a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed from the high-resilience polyether-type TPU sheath material for robot joints prepared in Example 3.

[0045] Example 4 This embodiment provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and a cable. The preparation method specifically includes the following steps: S1, 48g of trimethylolpropane, 580g of 2,2-dimethylolpropionic acid and 1.0g of p-toluenesulfonic acid were mixed, nitrogen gas was introduced and the mixture was heated to 142℃ and stirred for 2.2h. Then the mixture was heated to 162℃ and vacuumed. When the acid value was lower than 5mg KOH / g, the mixture was cooled to 105℃, 0.20g of calcium oxide powder was added and stirred. The mixture was then filtered while hot, and the filtrate was dehydrated under vacuum to obtain branched polyester. S2, 160g of branched polyester, 0.08g of dibutyltin dilaurate and 1000g of anhydrous dimethylacetamide are mixed, heated to 82°C under a nitrogen atmosphere, 22g of end-capping agent is added dropwise and reacted until the infrared peak of isocyanate disappears. The reaction solution is poured into diethyl ether to precipitate, filtered and dried to obtain the additive. The preparation method of the end-capping agent is as follows: 11g of 6-methylisocytosine, 75g of hexamethylene diisocyanate and 200g of anhydrous dimethylacetamide are mixed, heated to 82°C under a nitrogen atmosphere and stirred to react. After the reaction is completed, the mixture is distilled under reduced pressure to obtain the end-capping agent. S3, 35g of acid-etched halloysite nanotubes were dispersed in 1000g of an ethanol-water solution, wherein the mass ratio of anhydrous ethanol to deionized water in the ethanol-water solution was 10:1. Glacial acetic acid was added to adjust the pH to 5.2, and 6g of 3-aminopropyltriethoxysilane was added. The mixture was refluxed at 82℃ for 4.5h, washed, and dried to obtain aminated halloysite. The acid-etched halloysite nanotubes were immersed in 1M hydrochloric acid solution for 0.6h, filtered, washed until the filtrate was nearly neutral, and then dried. 25g of aminated halloysite was dispersed in 1000g of anhydrous toluene under a nitrogen atmosphere, and 18g of... 4,4'-diphenylmethane diisocyanate was reacted at 55°C for 2.5 h to obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface was redispersed in 1000 g of fresh anhydrous toluene, 65 g of block copolymer and 0.08 g of dibutyltin dilaurate were added, and the mixture was reacted at 82°C for 24 h. After the reaction, the mixture was extracted with tetrahydrofuran by Soxhlet extraction and dried to obtain grafted halloysite. The block copolymer was prepared by mixing 220 g of polypropylene glycol monobutyl ether and 150 g of ε-caprolactone under a nitrogen atmosphere, heating to 120°C, adding 0.50 g of stannous octoate, and reacting for 14 h. The reaction solution was poured into cold methanol to precipitate, filtered, and dried to obtain the block copolymer. S4, 900g of polytetrahydrofuran ether diol and 45g of grafted halloysite were mixed, and 300g of 4,4'-diphenylmethane diisocyanate was added at 82℃ and stirred for 80min to obtain a prepolymer. 80g of 1,4-butanediol, 45g of additives and 4.5g of di(2-hydroxyethyl) disulfide were mixed and added to the prepolymer and reacted for 30s. The mixture was then cured at 112℃ for 18h and melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

[0046] The cable for robot joints includes a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed from the high-resilience polyether-type TPU sheath material for robot joints prepared in Example 4.

[0047] Comparative Example 1 This comparative example provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and cables. The difference between this example and Example 1 is that the mass of the end-capping agent in S2 is 0, and an equal mass of phenyl isocyanate is added instead. Other process parameters and operating conditions are exactly the same as in Example 1.

[0048] Comparative Example 2 This comparative example provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and cables. The difference between this example and Example 1 is that the step of "reacting halloysite with isocyanate groups on the surface with block copolymer and obtaining grafted halloysite by Soxhlet extraction" is not performed in S3. Instead, the aminated halloysite obtained in S3 is directly added to S4 as a filler, and the grafted halloysite in Scheme-1 is replaced with an equal mass of aminated halloysite. Other process parameters and operating conditions are exactly the same as in Example 1.

[0049] Comparative Example 3 This comparative example provides a high-resilience polyether-type TPU sheath material for robot joints, its preparation method, and cables. The difference between this example and Example 1 is that the mass of di(2-hydroxyethyl) disulfide in S4 is 0, and it is replaced by an equal mass of 1,6-hexanediol. Other process parameters and operating conditions are exactly the same as in Example 1.

[0050] The springback test method is DIN 53512; the flexural fatigue test method is ISO 132; and the compression set test method is ISO 815-1. Specimen preparation: The obtained sheath material granules are melt-plasticized and pressed into sheets or injection molded into standard specimen plates. After cooling and setting, they are conditioned in a specified environment, and then cut or punched according to the corresponding standards to obtain springback, flexural fatigue, and compression set specimens. Springback and compression set specimens are made from flat, bubble-free sheets / strips, while flexural fatigue specimens are obtained by punching from sheets according to the flexural standard.

[0051] The test results are shown in Table 1.

[0052] Table 1. Test results of Examples 1-4 and Comparative Examples 1-3. As shown in Table 1, compared to Example 1, Comparative Example 1 showed a decrease in springback, an increase in compression set, and a decrease in the number of cycles; Comparative Example 2 showed a decrease in springback, an increase in compression set, and a decrease in the number of cycles; and Comparative Example 3 showed a decrease in springback, an increase in compression set, and a decrease in the number of cycles. This is because, in Comparative Example 1, after the end-capping agent was changed to phenyl isocyanate, additive A lost its ureidopyrimidinone association point, resulting in reduced physical cross-linking, decreased springback, increased compression set, and faster flexural crack propagation. In Comparative Example 2, without grafting, only the amino-modified halloysite had weak interfacial bonding with the matrix and was prone to agglomeration, leading to increased interfacial slip and micropore defects, making it difficult to effectively transfer load and inducing stress concentration. At the same time, the accumulated wear heat was higher, resulting in poorer springback and deformation recovery, and a reduced flexural fatigue life. In Comparative Example 3, after replacing the disulfide-bonded diol with 1,6-hexanediol, the dynamic disulfide bond exchange and stress release pathway disappeared, the chain segment rearrangement under cyclic loading was restricted, damage accumulation accelerated, compression set increased, flexural life decreased, and springback decreased.

[0053] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-resilience polyether-type TPU sheath material for robot joints, characterized in that, The preparation method includes: S1, Trimethylolpropane, 2,2-dimethylolpropionic acid and p-toluenesulfonic acid are mixed and reacted to obtain a branched polyester; S2, branched polyester, dibutyltin dilaurate and anhydrous dimethylacetamide are mixed, a capping agent is added dropwise and the reaction is carried out until the infrared peak of isocyanate disappears, and an additive is obtained; S3, acid-etched halloysite nanotubes are dispersed in an aqueous ethanol solution, and 3-aminopropyltriethoxysilane is added to react and obtain aminated halloysite. Aminated halloysite is dispersed in a first portion of anhydrous toluene, and 4,4'-diphenylmethane diisocyanate is added to react and obtain halloysite with isocyanate groups on the surface. The obtained halloysite with isocyanate groups on the surface is redispersed in a second portion of anhydrous toluene, and block copolymer is added to react with dibutyltin dilaurate to obtain grafted halloysite. S4, polytetrahydrofuran ether diol is mixed with grafted halloysite, and 4,4'-diphenylmethane diisocyanate is added and stirred to react to obtain a prepolymer. 1,4-butanediol, additives and di(2-hydroxyethyl) disulfide are mixed and added to the prepolymer to react and mature. The mixture is then melt-extruded and granulated to obtain a high-resilience polyether-type TPU sheath material for robot joints.

2. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S1: The mass ratio of trimethylolpropane, 2,2-dimethylolpropionic acid, p-toluenesulfonic acid and calcium oxide powder is (45-55):(540-660):(0.5-1.2):(0.1-0.25).

3. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S2: The mass ratio of the branched polyester, dibutyltin dilaurate, anhydrous dimethylacetamide and the capping agent is (120-180):(0.04-0.15):1000:(18-30).

4. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S2: The method for preparing the capping agent is as follows: 6-methylisocytosine, hexamethylene diisocyanate and anhydrous dimethylacetamide are mixed, and the mixture is heated under a nitrogen atmosphere. After the reaction is completed, the mixture is distilled under reduced pressure to obtain the capping agent. The mass ratio of 6-methylisocytosine, hexamethylene diisocyanate and anhydrous dimethylacetamide is (10-14):(60-85):(200).

5. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S3: The mass ratio of the acid-etched halloysite nanotubes, the ethanol aqueous solution, and 3-aminopropyltriethoxysilane is (30-60):1000:(5-10).

6. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S3: The mass ratio of the aminated halloysite, the first part of anhydrous toluene, 4,4'-diphenylmethane diisocyanate, the second part of anhydrous toluene, the block copolymer and dibutyltin dilaurate is (20-40):1000:(10-20):1000:(60-80):(0.01-0.1).

7. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S3: The block copolymer is prepared by mixing polypropylene glycol monobutyl ether and ε-caprolactone under a nitrogen atmosphere, adding stannous octoate and reacting to obtain the block copolymer. The mass ratio of polypropylene glycol monobutyl ether, ε-caprolactone and stannous octoate is (180-320):(60-180):(0.1-0.6).

8. The method for preparing the high-resilience polyether-type TPU sheath material for robot joints according to claim 1, characterized in that, In S4: The mass ratio of the polytetrahydrofuran ether diol, grafted halloysite and 4,4'-diphenylmethane diisocyanate is (800-1200):(40-60):(180-360). The mass ratio of the 1,4-butanediol, the additive, and the di(2-hydroxyethyl) disulfide is (60-140):(30-50):(4-6).

9. A high-resilience polyether-type TPU sheath material for robot joints is obtained by the preparation method according to any one of claims 1-8.

10. A cable for robot joints, characterized in that, It includes a tinned copper stranded conductor, a cross-linked polyethylene insulation layer, a metal shielding layer, and a sheath layer, wherein the sheath layer is formed of the high-resilience polyether-type TPU sheath material for robot joints as described in claim 9.

Images