Self-repairing halogen-free flame-retardant polyurethane material for robot cable and preparation method of self-repairing halogen-free flame-retardant polyurethane material

Abstract

The invention relates to the technical field of materials, and discloses a self-repairing halogen-free flame-retardant polyurethane material for a robot cable and a preparation method of the self-repairing halogen-free flame-retardant polyurethane material for the robot cable, the polyurethane material is prepared by taking a polyurethane matrix, carbon black, a filler and the like as raw materials through mixing and extrusion processes, the polyurethane material is prepared by taking binary isocyanate as a hard segment and carrying out polymerization reaction with a chain extender and a cross-linking agent under the action of a catalyst, and the cross-linking agent is a macromolecular substance containing a disulfide bond-cyclic ammonium phosphate block alternating structure and can improve the cross-linking density of a polyurethane molecular chain, so that the structural density of the polyurethane material is better; the existence of disulfide bonds can endow the polyurethane material with good intrinsic self-repairing performance, and the cyclic ammonium phosphate structure contains a gas source and an acid source, so that the flame retardant property of the polyurethane material can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a self-repairing halogen-free flame-retardant polyurethane material for robot cables and a preparation method thereof. Background Art

[0002] As core equipment in intelligent manufacturing, robots place stringent demands on cables through their motion systems. For example, the end effectors of industrial robots move at high speeds, and drag chain systems must withstand millions of reciprocating bends while maintaining stable performance across a wide temperature range of -40°C to 85°C. Traditional polyvinyl chloride or cross-linked polyethylene cable sheaths develop numerous microcracks during drag chain operation. These cracks gradually expand with increasing motion, leading to higher failure rates. Consequently, these cables have been gradually phased out in recent years.

[0003] Polyurethane (PU), due to its unique microphase separation structure, is an ideal base material for robotic cable sheathing. Its polyether polyol soft segment provides flexibility from -50°C to 60°C, while its isocyanate hard segment forms physical crosslinks through hydrogen bonding, enabling the material to maintain excellent mechanical strength even at high temperatures. Consequently, polyurethane has seen increasing application in robotic cables in recent years. However, the use of polyurethane in robotic cables currently faces two major technical bottlenecks: the lack of a self-repair mechanism, necessitating manual replacement after mechanical damage; and the poor flame retardancy of pure polyurethane, which is flammable and presents significant safety risks.

[0004] Based on this, the present invention provides a polyurethane material with good comprehensive properties, which can be directly used in the manufacture of robot cables. Summary of the Invention

[0005] (1) Technical problems solved In view of the deficiencies in the prior art, the present invention provides a self-repairing halogen-free flame-retardant polyurethane material for robot cables and a preparation method thereof.

[0006] (2) Technical solution A self-repairing halogen-free flame-retardant polyurethane material for robot cables is made of the following raw materials measured in parts by weight: 75-95 parts of polyurethane base material, 5-10 parts of carbon black, 4-8 parts of filler, 1-2 parts of lubricant, 0.5-1.5 parts of coupling agent; The preparation method of the polyurethane substrate comprises the following steps: Step 1: Dehydrate the polycarbonate diol in a temperature environment of 100-110°C for 10-20 minutes, then adjust the temperature to 40-50°C, add diisocyanate and tin catalyst, stir and mix, then adjust the temperature to 70-80°C, keep warm and polymerize for 2-4 hours to form a prepolymer; Step 2: Add chain extender and crosslinker to the prepolymer, continue stirring for 1-2 hours, stop heating, cool and discharge the material to obtain the polyurethane substrate; The preparation method of the cross-linking agent comprises the following steps: Step S1, adding cyclophosphamide, a catalyst, and 1,4-dioxane to a reactor filled with nitrogen, and mechanically stirring until a uniform mixture is formed. Then, glycidol is added to the reactor. After the addition is complete, heating is turned on and the temperature is raised to 60-70° C., and stirring is continued at this temperature for 2-4 hours. The solvent is evaporated and the product is collected. The product is purified to obtain an intermediate product; Step S2, adding the intermediate product, dithioglycolic acid and toluene to a polymerization kettle, stirring and mixing them uniformly, introducing nitrogen, exhausting the air, and then continuing to add a phase transfer catalyst to the polymerization kettle. After the addition is completed, the temperature is increased to 70-80° C. at a heating rate of 2-3° C. / min, and the temperature is maintained for 3-6 hours. The solvent is evaporated and the product is purified to obtain a cross-linking agent; The catalyst is sodium hydride; and the molar ratio of the catalyst to cyclophosphamide is 1.05-1.1:1.

[0007] As a further embodiment of the present invention, the filler is any one of talc, calcium carbonate or titanium dioxide; the lubricant is polyethylene wax; and the coupling agent is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0008] As a further embodiment of the present invention, the mass ratio of the polycarbonate diol, diisocyanate, tin catalyst, chain extender and cross-linking agent is 35-45:15-30:0.3-0.5:1-2:1-3.

[0009] As a further embodiment of the present invention, the diisocyanate is any one of diphenylmethane diisocyanate, toluene diisocyanate or isophorone diisocyanate; the tin catalyst is any one of dibutyltin dilaurate, stannous octoate, methyl tin mercaptan or octyl tin mercaptan; and the chain extender is ethylene glycol or ethylenediamine.

[0010] As a further embodiment of the present invention, the molar ratio of cyclophosphamide to glycidol is 1:2.

[0011] As a further embodiment of the present invention, the molar ratio of the intermediate product to dithioglycolic acid is 1:1-1.2.

[0012] As a further embodiment of the present invention, the phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetramethylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide or triethylamine.

[0013] Specifically, first, under the action of a catalyst, the halogen substituent in the cyclophosphamide structure can undergo a substitution reaction with the active hydroxyl substituent in the glycidol structure. By controlling the dosage ratio of the two, a cyclophosphamide derivative containing two equivalent epoxy substituents in the structure, i.e., an intermediate product, can be obtained. Then, under the action of a phase transfer catalyst, the two equivalent epoxy substituents in its structure can undergo a continuous ring-opening esterification reaction with the carboxyl substituent in the dithioglycolic acid structure to obtain a macromolecular substance with alternating disulfide bonds and cyclophosphamide blocks. Since additional active hydroxyl functional groups are generated during the ring-opening esterification reaction, they can act as a crosslinking agent in the chain extension process of the polyurethane, i.e., a crosslinking agent.

[0014] A method for preparing a self-repairing halogen-free flame-retardant polyurethane material for robot cables comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into an open mill, control the temperature to 70-80°C, stir and mix for 20-30 minutes, and then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

[0015] (3) Beneficial technical effects The present invention prepares a macromolecular substance with alternating disulfide bonds and cyclic phosphate amine blocks as a crosslinking agent to participate in the chain extension and crosslinking of polyurethane. First, the presence of the crosslinking agent can increase the crosslinking density of the prepared polyurethane molecular chain, and the resulting polyurethane material has a better structural density, which is beneficial to improving the mechanical strength of the polyurethane material. Second, the crosslinking agent structure contains reversible dynamic disulfide bonds with a relatively fast reversible exchange rate, thereby endowing the polyurethane material with good intrinsic self-healing properties. Finally, the crosslinking agent structure also contains a cyclic phosphate amine structure, which contains a gas source and an acid source. When the material burns, it can quickly catalyze the formation of a dense carbon layer on the surface of the material, while reducing the surrounding oxygen concentration, thereby preventing continued combustion and significantly improving the flame retardant properties of the polyurethane material. DETAILED DESCRIPTION

[0016] To facilitate understanding of the present invention, the present invention will be described in more detail below. Preferred embodiments of the present invention are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0017] Preparation Example Preparation of polyurethane substrate: Step A: Dehydrate 38 g of polycarbonate diol having a number average molecular weight of 2000 at 100° C. for 15 min, then adjust the temperature to 45° C., add 16 g of diphenylmethane diisocyanate and 0.4 g of dibutyltin dilaurate, and stir and mix. Then adjust the temperature to 75° C. and heat for 3 h to form a prepolymer. Step B, 0.5 g of cyclophosphamide, 0.05 g of sodium hydride and 30 mL of 1,4-dioxane were added to a reactor filled with nitrogen. After the addition was completed, mechanical stirring was performed to form a uniform mixture. Then, 0.28 g of glycidol was added to the reactor. After the addition was completed, heating was turned on and the temperature was raised to 65 ° C. After continuous stirring for 3 hours, the solvent was evaporated and removed, the product was collected, and the intermediate product was obtained through a purification process; Step C, adding 0.8 g of the intermediate product, 0.45 g of dithioglycolic acid and 50 mL of toluene to a polymerization kettle, stirring and mixing, introducing nitrogen, exhausting the air, and then continuing to add 0.01 g of tetrabutylammonium bromide to the polymerization kettle. After the addition is completed, the temperature is raised to 80° C. at a heating rate of 2° C. / min, and the temperature is maintained for 4 hours. The solvent is evaporated and the product is purified to obtain a crosslinking agent; Step D: Add 1.5 g of ethylene glycol and 2.5 g of a cross-linking agent to the prepolymer. After the addition is complete, continue stirring for 2 h, stop heating, cool and discharge the material to obtain a polyurethane substrate.

[0018] Example 1 A self-repairing halogen-free flame-retardant polyurethane material for robot cables is made of the following raw materials measured in parts by weight: 75 parts of polyurethane base material, 5 parts of carbon black, 4 parts of filler talc, 1 part of lubricant polyethylene wax, 0.5 parts of coupling agent 3-aminopropyltrimethoxysilane; The preparation method of the polyurethane material comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into an open mill, control the temperature to 70°C, stir and mix for 30 minutes, and then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

[0019] The preparation method of the polyurethane substrate is shown in the preparation example, and the same applies to the following.

[0020] Example 2 A self-repairing halogen-free flame-retardant polyurethane material for robot cables is made of the following raw materials measured in parts by weight: 90 parts of polyurethane base material, 6 parts of carbon black, 6 parts of filler calcium carbonate, 1.5 parts of lubricant polyethylene wax, 1 part of coupling agent 3-aminopropyltriethoxysilane; The preparation method of the polyurethane material comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into the open mill, control the temperature to 72°C, stir and mix for 30 minutes, then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

[0021] Example 3 A self-repairing halogen-free flame-retardant polyurethane material for robot cables is made of the following raw materials measured in parts by weight: 95 parts of polyurethane base material, 10 parts of carbon black, 8 parts of filler calcium carbonate, 2 parts of lubricant polyethylene wax, 1.5 parts of coupling agent 3-aminopropyltriethoxysilane; The preparation method of the polyurethane material comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into an open mill, control the temperature to 80°C, stir and mix for 20 minutes, and then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

[0022] Comparative Example 1 A self-repairing halogen-free flame-retardant polyurethane material for robot cables is made of the following raw materials measured in parts by weight: 90 parts of polyurethane base material, 6 parts of carbon black, 6 parts of filler calcium carbonate, 1.5 parts of lubricant polyethylene wax, 1 part of coupling agent 3-aminopropyltriethoxysilane; The preparation method of the polyurethane material comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into the open mill, control the temperature to 72°C, stir and mix for 30 minutes, then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

[0023] The preparation method of the polyurethane substrate is different from that of the preparation example in that no cross-linking agent is added, and the rest are the same.

[0024] Test Case According to the standard GB / T 1040.2-2022, the tensile rate was controlled at 50 mm / min and the mechanical properties test was carried out; Conduct flame retardant performance test according to standard GB / T 2406.2-2009; The polyurethane materials in the examples and comparative examples were made into test samples with a size of 10 cm × 10 cm × 5 mm. A scratch with a depth of 1 mm was then made on the surface of the sample. The sample was then placed in an oven at 60°C. The time it took for the scratch to disappear was recorded to evaluate the self-healing performance of the polyurethane material. The test results are recorded in the following table: Table 1 - Test results

[0025] Analysis and test results show that the polyurethane material prepared with the addition of a cross-linker has excellent mechanical properties, flame retardant properties and self-healing effects. After removing the cross-linker, the structural density of the polyurethane material decreases, and the molecular chain does not contain cyclic phosphate amines and dynamic disulfide bonds, resulting in a significant decrease in the performance of the material.

[0026] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that are not substantially different from the literal description of the claims, then these other embodiments should also be included in the scope of the claims.

[0027] Based on the ideal embodiments of the present invention, and with reference to the above description, relevant personnel can make various changes and modifications without departing from the technical scope of the present invention. The technical scope of the present invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A self-repairing halogen-free flame-retardant polyurethane material for robot cables, characterized in that: The composition is prepared by using the following raw materials measured in parts by weight: 75-95 parts of polyurethane base material, 5-10 parts of carbon black, 4-8 parts of filler, 1-2 parts of lubricant, 0.5-1.5 parts of coupling agent; The preparation method of the polyurethane substrate comprises the following steps: Step 1: Dehydrate the polycarbonate diol in a temperature environment of 100-110°C for 10-20 minutes, then adjust the temperature to 40-50°C, add diisocyanate and tin catalyst, stir and mix, then adjust the temperature to 70-80°C, keep warm and polymerize for 2-4 hours to form a prepolymer; Step 2: Add chain extender and crosslinker to the prepolymer, continue stirring for 1-2 hours, stop heating, cool and discharge the material to obtain the polyurethane substrate; The preparation method of the cross-linking agent comprises the following steps: Step S1, adding cyclophosphamide, a catalyst, and 1,4-dioxane to a reactor filled with nitrogen, and mechanically stirring until a uniform mixture is formed. Then, glycidol is added to the reactor. After the addition is complete, heating is turned on and the temperature is raised to 60-70° C., and stirring is continued at this temperature for 2-4 hours. The solvent is evaporated and the product is collected. The product is purified to obtain an intermediate product; Step S2, adding the intermediate product, dithioglycolic acid and toluene to a polymerization kettle, stirring and mixing them uniformly, introducing nitrogen, exhausting the air, and then continuing to add a phase transfer catalyst to the polymerization kettle. After the addition is completed, the temperature is increased to 70-80° C. at a heating rate of 2-3° C. / min, and the temperature is maintained for 3-6 hours. The solvent is evaporated and the product is purified to obtain a cross-linking agent; The catalyst is sodium hydride; and the molar ratio of the catalyst to cyclophosphamide is 1.05-1.1:

1.

2. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The filler is any one of talc, calcium carbonate or titanium dioxide; the lubricant is polyethylene wax; and the coupling agent is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

3. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The mass ratio of the polycarbonate diol, diisocyanate, tin catalyst, chain extender and crosslinking agent is 35-45:15-30:0.3-0.5:1-2:1-3.

4. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The diisocyanate is any one of diphenylmethane diisocyanate, toluene diisocyanate or isophorone diisocyanate; the tin catalyst is any one of dibutyltin dilaurate, stannous octoate, methyl tin mercaptan or octyl tin mercaptan; and the chain extender is ethylene glycol or ethylenediamine.

5. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The molar ratio of cyclophosphamide to glycidol is 1:

2.

6. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The molar ratio of the intermediate product to dithioglycolic acid is 1:1-1.

2.

7. The self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The phase transfer catalyst is any one of tetrabutylammonium hydrogen sulfate, tetramethylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide or triethylamine.

8. A method for preparing the self-repairing halogen-free flame-retardant polyurethane material for robot cables according to claim 1, characterized in that: The following steps are involved: The first step is to weigh and prepare all the raw materials according to their weight; The second step is to add all the raw materials into an open mill, control the temperature to 70-80°C, stir and mix for 20-30 minutes, and then transfer the formed mixture into a twin-screw extruder for melt extrusion, and then pull, cool and dry.

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