Anti-static and flame-retardant high-toughness TPU material and preparation method thereof

Abstract

The application discloses a kind of anti-static, flame-retardant high toughness TPU material and preparation method thereof, the TPU material includes by weight percentage: polyether polyol 15~30 parts, small molecule chain extender 1~5 parts, aromatic diisocyanate 7~15 parts, aromatic organic phosphorus flame retardant 5~15 parts, inorganic flame retardant 40~60 parts, synergistic flame retardant 1~5 parts, antistatic agent 0.5~1 part, antioxidant 0.1~1 part, ultraviolet absorber 0.1~1 part, catalyst 0.01~1 part.The anti-static, flame-retardant high toughness TPU material described in the application has excellent flame-retardant and antistatic synergistic effect, and uses halogen-free environmental protection flame-retardant system, low smoke and non-toxic when burning, while maintaining excellent toughness and bending resistance, can meet the long-term safe use demand of special scene such as mine.

Description

Technical Field

[0001] This invention relates to the field of TPU materials, and in particular to an antistatic, flame-retardant, high-toughness TPU material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane rubber (TPU) is a polymer material polymerized from diisocyanate, oligomeric polyols, and chain extenders, exhibiting a unique "soft-hard" multi-segment structure. Its properties fall between those of plastics and rubber; it displays rubber-like elasticity at room temperature, but undergoes secondary cross-linking and disintegration at high temperatures, exhibiting plasticity and facilitating molding and processing. It possesses excellent mechanical properties such as high strength, high elasticity, high abrasion resistance, and high flexibility, and is also oil and solvent resistant. It is widely used in construction, automotive manufacturing, shock-absorbing materials, paving materials, and leather tanning.

[0003] Because TPU has a certain degree of elasticity and hardness, it can be used in pipe products. However, in some special environments, there are high requirements for the physical and chemical properties of TPU. For example, in the environment of coal mines where there are explosive gases and combustible dust, TPU hoses used for underground water supply and drainage and cable protection must simultaneously have stable and efficient flame retardancy and antistatic properties. The antistatic property prevents the material from burning due to electric sparks, and it also needs high toughness to meet the needs of long-term bending and dragging.

[0004] Existing TPU materials generally suffer from the following shortcomings: 1. Adding antistatic agents alone to traditional TPU materials weakens the flame-retardant effect, while adding large amounts of flame retardants leads to increased surface resistance and failure of antistatic properties, failing to simultaneously meet the dual safety requirements for downhole applications. 2. Flame retardants and antistatic agents are mostly added through physical blending and secondary granulation. Large amounts of inorganic / organic fillers can damage the TPU molecular chain structure, resulting in decreased material toughness, brittleness, and poor bending resistance. Under frequent dragging conditions, this can easily lead to breakage and leakage, affecting the reliability of the water supply and drainage system.

[0005] In view of this, the present invention proposes an antistatic, flame-retardant, high-toughness TPU material and its preparation method to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a TPU material that synergistically combines excellent flame retardancy, antistatic properties, and high toughness, thereby solving the problems of antagonistic flame retardancy and antistatic properties, poor toughness, and brittleness in traditional TPU materials.

[0007] To achieve the above objectives, the present invention provides an antistatic and flame-retardant high-toughness TPU material, comprising the following raw materials in parts by weight: 15-30 parts of polyether polyol, 1-5 parts of small molecule chain extender, 7-15 parts of aromatic diisocyanate, 5-15 parts of aromatic organophosphorus flame retardant, 40-60 parts of inorganic flame retardant, 1-5 parts of synergistic flame retardant, 0.5-1 part of antistatic agent, 0.1-1 part of antioxidant, 0.1-1 part of ultraviolet absorber, and 0.01-1 part of catalyst.

[0008] Preferably, the mass ratio of the aromatic diisocyanate, the aromatic organophosphorus flame retardant, and the polyether polyol is 1:0.7~1:2~2.4.

[0009] Preferably, the aromatic diisocyanate is one or a mixture of several of diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and orthophthalic diisocyanate.

[0010] Preferably, the aromatic organophosphorus flame retardant is one or a combination of several of bisphenol A bis(diphenylphosphonate), triphenyl phosphate, isopropyl phenyl phosphate, and resorcinol bis(diphenyl phosphate).

[0011] Preferably, the polyether polyol is one or a combination of several of the following: polytetrahydrofuran ether diol, propylene glycol polyether, trimethylolpropane polyether, polypropylene oxide diol, and polypropylene oxide diol.

[0012] Preferably, the inorganic flame retardant is one or both of aluminum hydroxide and magnesium hydroxide, with a particle size of 180-12500 mesh.

[0013] Preferably, the antistatic agent is one or a combination of lithium salt ionic antistatic agents and polyether block polyamides.

[0014] Preferably, the antioxidant is one or a combination of several of the following: hindered phenolic antioxidants, phosphite antioxidants, thioester antioxidants, and aromatic amine antioxidants.

[0015] Preferably, the small molecule chain extender is a diol with 2-6 carbon atoms.

[0016] To address the shortcomings of existing technologies, a second objective of this invention is to provide a preparation method that enables the mixing of various substances to produce an antistatic, flame-retardant, high-toughness TPU material.

[0017] A method for preparing an antistatic, flame-retardant, high-toughness TPU material includes the following steps:

[0018] (1) Add polyether polyol, aromatic diisocyanate, small molecule chain extender, catalyst, aromatic organophosphorus flame retardant, synergistic flame retardant, antistatic agent, ultraviolet absorber and some antioxidant to a casting machine, heat to 80-95℃, continuously mix and polymerize in a vacuum environment of -0.08~-0.1 MPa to obtain a semi-flame retardant and antistatic high-strength TPU matrix;

[0019] (2) The obtained TPU matrix is ​​mixed evenly with inorganic flame retardant and the remaining antioxidant, and then melt-blended, extruded, cooled and granulated by an extruder under normal pressure to obtain antistatic and flame-retardant high-toughness TPU material.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention preferably uses aromatic diisocyanate as a curing agent. Its aromatic ring structure is highly compatible with the structure of aromatic organophosphorus flame retardants, enabling in-situ uniform blending of the two during the TPU polymerization stage. This significantly improves the dispersion stability and interfacial compatibility of the flame retardant in the matrix, ensuring uniform, durable, and non-attenuating overall flame retardant performance of the material. Simultaneously, the aromatic ring structure is not easily damaged, compensating for the decrease in material strength and toughness caused by the addition of large amounts of inorganic flame retardants.

[0022] 2. The inorganic hydroxide of this invention serves as the main flame retardant system. It decomposes upon heating, absorbs heat, and releases water vapor, achieving a triple effect of cooling, dilution, and oxygen isolation. It is low in smoke, non-toxic, and meets safety requirements. Combined with aromatic phosphorus flame retardants and synergistic flame retardants, it forms a ternary synergistic system with higher flame retardant efficiency and a flame retardant rating of up to UL94 V-0.

[0023] 3. The antistatic agent is one or a combination of lithium salt ionic antistatic agents and polyether block polyamides. It has good compatibility with TPU and does not interfere with char formation or weaken flame retardancy. Detailed Implementation

[0024] The following examples further illustrate the features and other related characteristics of the present invention in detail, to facilitate understanding by those skilled in the art:

[0025] The embodiments of the present invention provide an antistatic, flame-retardant, high-toughness TPU material, comprising the following raw materials in parts by weight: 15-30 parts of polyether polyol, 1-5 parts of small molecule chain extender, 7-15 parts of aromatic diisocyanate, 5-15 parts of aromatic organophosphorus flame retardant, 40-60 parts of inorganic flame retardant, 1-5 parts of synergistic flame retardant, 0.5-1 part of antistatic agent, 0.1-1 part of antioxidant, 0.1-1 part of ultraviolet absorber, and 0.01-1 part of catalyst.

[0026] The antistatic and flame-retardant high-toughness TPU material described in this invention has excellent synergistic effects of flame retardancy and antistatic properties. It uses a halogen-free environmentally friendly flame-retardant system, produces low smoke and is non-toxic when burning, while maintaining excellent toughness and bending resistance, which can meet the long-term safe use requirements of special scenarios such as mines.

[0027] In some embodiments, the mass ratio of aromatic diisocyanate to polyether polyol is 1:2 to 2.4. At this ratio, the functional group ratio of isocyanate to polyol is moderate, resulting in a more complete and thorough prepolymerization reaction. The system contains no excess free isocyanate, making it less prone to post-curing, foaming, yellowing, or chain segment degradation, thus ensuring material structural stability. Simultaneously, the polyether polyol, as the main component of the TPU soft segment, provides excellent elasticity and flexibility; the aromatic diisocyanate, as the hard segment component, provides high strength, high modulus, and thermal stability. At the above ratio, suitable hardness, elasticity, and flexibility can be achieved.

[0028] The mass ratio of aromatic organophosphorus flame retardant to polyether polyol is 1:0.7~1. Under this ratio, the benzene ring structure of the aromatic organophosphorus flame retardant has excellent compatibility with the aromatic organophosphorus flame retardant, which can promote the uniform dispersion and stable binding of the flame retardant, while compensating for the chain segment degradation caused by the additives and maintaining the mechanical properties of the material.

[0029] In some embodiments, the aromatic diisocyanate is one or a mixture of several of diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and o-phthalic diisocyanate. Under the action of a catalyst, it reacts with polyether polyols to form benzene rings on the molecular chain, thereby improving the hardness, heat resistance, and water resistance of the TPU material. Simultaneously, the benzene ring is inert, not easily oxidized, and unlikely to react chemically with other chemical agents without a catalyst, thus improving the oxidation resistance and solvent resistance of the TPU material.

[0030] In some embodiments, the aromatic organophosphorus flame retardant is one or a combination of several of bisphenol A bis(diphenylphosphonate), triphenyl phosphate, isopropyl phenyl phosphate, and resorcinol bis(diphenyl phosphate). All of these molecules contain a benzene ring, enabling the phosphorus-based flame retardant to be compatible with the TPU material interface, effectively reducing the damage to the TPU molecular chain structure and mechanical properties caused by the addition of the flame retardant, allowing the material to maintain excellent toughness and mechanical stability while achieving high flame retardancy. Simultaneously, the benzene ring has a highly conjugated stable structure, readily undergoing dehydrogenation cyclization, cross-linking, and graphitization at high temperatures, thereby forming a dense and stable char layer on the polymer surface. This char layer can isolate oxygen, prevent the escape of combustible gases, and reduce heat feedback, effectively inhibiting the spread of combustion. The phosphate ester structure in the aromatic organophosphorus flame retardant can block reactions during material combustion and produce strongly dehydrating phosphoric acid under high-temperature combustion, promoting material carbonization. The char layer covering the material surface provides heat insulation and oxygen barrier functions.

[0031] In some embodiments, the polyether polyol is one or a combination of several of polytetrahydrofuran ether diol, propylene glycol polyether, trimethylolpropane polyether, polypropylene oxide diol, and polypropylene oxide diol, and the polyether segments can improve the flexibility of the material.

[0032] In some embodiments, the inorganic flame retardant is one or both of aluminum hydroxide and magnesium hydroxide. Upon heating, it decomposes, absorbs heat, cools, and releases water vapor to dilute flammable gases, generating metal oxides to form a dense insulating layer. This results in high safety and low cost. The inorganic flame retardant has a particle size ranging from 180 to 12500 mesh, which helps to uniformly mix a large amount of inorganic flame retardant within the organic matrix of the material, making it easier to form an insulating layer during combustion. Simultaneously, it ensures that adding a large amount of inorganic flame retardant to the organic matrix does not result in surface roughness.

[0033] In some embodiments, the antistatic agent is one or a combination of lithium salt ionic antistatic agents and polyether block polyamides. Specifically, the lithium salt ionic antistatic agent can be LiTFSI or LiFSI, which forms uniform and continuous ionic conductive channels inside the TPU, enabling rapid conduction of static charges accumulated on the material surface and preventing the accumulation of static electricity that could generate electric sparks. Polyether block polyamides exhibit good compatibility with TPU, do not migrate, do not precipitate, and do not antagonize flame-retardant systems.

[0034] In some embodiments, the antioxidant is one or a combination of several of hindered phenolic antioxidants, phosphite antioxidants, thioester antioxidants, and aromatic amine antioxidants. For example, at least one of antioxidants 1010, 405, 168, DNP, DLTP, CA, and 1076. Antioxidants can slow down TPU oxidation and improve the service life of TPU materials.

[0035] In some embodiments, the small molecule chain extender is a diol with 2-6 carbon atoms, such as one or a combination of butanediol, hexanediol, ethylene glycol, and pentanediol, which can improve the bonding density, mechanical strength, and wear resistance of TPU, giving the material both rigidity and toughness.

[0036] In some embodiments, the ultraviolet absorber may be one or more of 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-(2′-hydroxy-3′,5′-tributylphenyl)-5-chlorobenzotriazole, and 2-(2′-hydroxy-5′-methylphenyl)benzotriazole, which can absorb ultraviolet light, inhibit photo-oxidative aging, improve the weather resistance and yellowing resistance of materials, and extend their service life in outdoor and underground light environments.

[0037] In some embodiments, the catalyst may be an organotin compound, or a combination of one or more of dimethyltin, dioctyltin, tetraphenyltin, and dibutyltin dilaurate.

[0038] In some embodiments, the synergistic flame retardant is a modified epoxy resin, such as at least one of phosphorus-containing epoxy resin, DOPO type epoxy resin, and o-crestoform type epoxy resin.

[0039] Example 1 of the present invention provides a method for preparing TPU material, comprising the following steps:

[0040] (1) Add polyether polyol, aromatic diisocyanate, small molecule chain extender, catalyst, aromatic organophosphorus flame retardant, synergistic flame retardant, antistatic agent, ultraviolet absorber, and part of antioxidant to the casting machine, heat to 80-95℃, and continuously mix in a vacuum environment of -0.08~-0.1 MPa.

[0041] (2) The obtained TPU matrix is ​​mixed evenly with inorganic flame retardant and the remaining antioxidant, and then melt-blended, extruded, cooled and granulated by an extruder under normal pressure to obtain antistatic and flame-retardant high-toughness TPU material.

[0042] The antioxidants added in steps (1) and (2) have a mass ratio of 4:1.

[0043] The raw material components of TPU materials in Examples 1-5 and Comparative Examples 1-4 are shown in Table 1. All raw material quantities are parts by mass. Based on Table 1, the raw material formulations were modified, and the preparation methods of Example 1 were followed to prepare Examples 2-5 and Comparative Examples 1-4.

[0044] Table 1 shows the formulations of Examples 1-5 and Comparative Examples 1-4.

[0045] Performance testing

[0046] The TPU materials prepared in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests according to national standards, as detailed below:

[0047] (1) Tensile strength and elongation at break: GB / T528-2009

[0048] (2) Tear strength: GB / T529-2008

[0049] (3) Flame retardant performance: UL94 vertical burning test

[0050] (4) Surface resistivity: GB / T1410-2018

[0051] (5) Bending resistance: The TPU material is made into a 35 (mm) 2 Test the cable sheath of the wire number by bending it 180° 1000 times and observe whether it cracks.

[0052] (6) Precipitation performance: After being placed at room temperature for 30 days, observe whether any substance is precipitated on the surface.

[0053] Table 2 shows the test results of Examples 1-5 and Comparative Examples 1-4.

[0054] The performance test results of Examples 1-5 show that the TPU material prepared using the components and proportions described in this invention can achieve a synergistic improvement in antistatic properties, flame retardancy, and high toughness. The core difference in performance stems from the differences in the matching of raw material structures, interfacial compatibility, and molecular chain integrity.

[0055] In Examples 1-2 and 4, aromatic diisocyanates and aromatic organophosphorus flame retardants were selected for blending. The benzene ring structures of the two are highly matched, achieving in-situ uniform blending during the TPU polymerization stage. This significantly improves the dispersion stability and interfacial compatibility of the flame retardant in the matrix, effectively compensating for the damage to the material's mechanical properties caused by the addition of large amounts of inorganic flame retardants. This allows the material to maintain high tensile strength, elongation at break, and tear strength, as well as excellent bending resistance. Using aluminum hydroxide as the main flame retardant, combined with aromatic organophosphorus flame retardants and synergistic flame retardants, a ternary synergistic system is formed. Upon heating, the system decomposes and absorbs heat, releasing water vapor to achieve cooling, dilution, and oxygen isolation. At high temperatures, a dense char layer is formed to block the flame, achieving a flame retardant rating of UL94 V-0.

[0056] In Examples 3 and 5, due to the slight adjustment of the ratio of inorganic flame retardant to organic phosphorus flame retardant, the char formation and oxygen barrier effects were slightly reduced, and the flame retardant rating was UL94 V-1.

[0057] The use of lithium salt-based ionic antistatic agents ensures good compatibility with the TPU matrix, preventing migration and precipitation. It allows for the construction of continuous ionic conductive channels within the material, resulting in a stable surface resistivity of 10 Ω·cm. 8 On the order of Ω.

[0058] Comparative Example 1 uses aliphatic isocyanate instead of aromatic diisocyanate. It lacks the aromatic ring structure that matches the phosphorus-based flame retardant. The flame retardant is unevenly dispersed and has weak interfacial bonding, which seriously damages the continuity of the TPU molecular chain. This results in a significant decrease in the tensile strength, elongation at break, and tear strength of the material. It cracks after 1000 flexural cycles and cannot meet the requirements for high toughness and long-term dragging use.

[0059] Comparative Example 3: Replacing aromatic organophosphorus flame retardants with non-aromatic phosphorus flame retardants resulted in a decrease in flame retardant efficiency and a flame retardant rating of V-1. At the same time, the compatibility between the flame retardant and the matrix deteriorated, the molecular chains were more prone to breakage under stress, the elongation at break decreased, microcracks appeared in the bending resistance, and the mechanical stability was significantly reduced.

[0060] Comparative Example 4: Excessive addition of synergistic flame retardant leads to an imbalance in the ratio of soft and hard segments in TPU, resulting in increased material rigidity, decreased flexibility, reduced elongation at break and tear strength, and poorer bending resistance. Excessive synergist disrupts the continuity of the molecular chain, making it difficult to achieve a balance between flame retardancy and high toughness.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-toughness TPU material that is antistatic and flame-retardant, characterized in that, The raw materials include the following parts by weight: 15-30 parts of polyether polyol, 1-5 parts of small molecule chain extender, 7-15 parts of aromatic diisocyanate, 5-15 parts of aromatic organophosphorus flame retardant, 40-60 parts of inorganic flame retardant, 1-5 parts of synergistic flame retardant, 0.5-1 part of antistatic agent, 0.1-1 part of antioxidant, 0.1-1 part of ultraviolet absorber, and 0.01-1 part of catalyst.

2. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The mass ratio of the aromatic diisocyanate, aromatic organophosphorus flame retardant, and polyether polyol is 1:0.7~1:2~2.

4.

3. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The aromatic diisocyanate is one or a mixture of several of diphenylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and orthophthalic diisocyanate.

4. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The aromatic organophosphorus flame retardant is one or a combination of several of bisphenol A bis(diphenylphosphonate), triphenyl phosphate, isopropyl phenyl phosphate, and resorcinol bis(diphenyl phosphate).

5. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The polyether polyol is one or a combination of several of the following: polytetrahydrofuran ether diol, propylene glycol polyether, trimethylolpropane polyether, polyoxypropylene diol, and polyoxypropylene diol.

6. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The inorganic flame retardant is one or both of aluminum hydroxide and magnesium hydroxide, with a particle size of 180~12500 mesh.

7. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The antistatic agent is one or a combination of lithium salt ionic antistatic agents and polyether block polyamides.

8. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The antioxidant is one or a combination of several of the following: hindered phenolic antioxidants, phosphite antioxidants, thioester antioxidants, and aromatic amine antioxidants.

9. The antistatic, flame-retardant, high-toughness TPU material according to claim 1, characterized in that, The small molecule chain extender is a diol with 2-6 carbon atoms.

10. A method for preparing an antistatic, flame-retardant, high-toughness TPU material as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Add polyether polyol, aromatic diisocyanate, small molecule chain extender, catalyst, aromatic organophosphorus flame retardant, synergistic flame retardant, antistatic agent, ultraviolet absorber and some antioxidant to a casting machine, heat to 80-95℃, continuously mix and polymerize in a vacuum environment of -0.08~-0.1 MPa to obtain a semi-flame-retardant TPU matrix; (2) The obtained TPU matrix is ​​mixed evenly with inorganic flame retardant and the remaining antioxidant, and then melt-blended, extruded, cooled and granulated by an extruder under normal pressure to obtain antistatic and flame-retardant high-toughness TPU material.

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