High-hardness and high-transparency weather-resistant TPU material and preparation method thereof

Abstract

The application discloses a kind of high hardness, high weather-resistant TPU material and preparation method thereof, the TPU material includes by weight fraction: 30~60 parts cyclohexane polyol, 30~60 parts cyclohexane diisocyanate, 0.3~2 parts antioxidant, 0.05~1 parts lubricant, 0.05~0.5 parts wax powder, 0.01~0.5 parts catalyst.The application adopts double symmetry cyclohexane aliphatic ring structure, molecular chain arrangement is neat, phase region size is less than visible light wavelength, with high hardness, high transmittance and low haze;Pure aliphatic ring structure eliminates yellowing from the source, and has excellent weather resistance and aging resistance;Double cyclohexane skeleton forms steric barrier, has outstanding hydrolysis resistance, acid and alkali resistance, fuel resistance, while high temperature mechanical retention rate, creep resistance and dimensional stability are excellent, and can be widely used in diesel filter oil cup, high temperature sealing element, outdoor transparent structural member and other high-end scenes.

Description

Technical Field

[0001] This invention relates to the field of TPU materials, and in particular to a high-hardness, high-transparency weather-resistant TPU material and its preparation method. Background Technology

[0002] Polyurethane rubber is a polymer material polymerized from diisocyanate and oligomeric polyols. It possesses excellent mechanical properties, as well as good resistance to chemical reagents, weathering, and water resistance, and is widely used in automobiles, electronics, precision components, filters, and other fields. With the upgrading of high-end application scenarios, multiple requirements are placed on materials, including high hardness, high transparency, weather resistance, anti-yellowing, chemical resistance, and dimensional stability. It is particularly suitable for applications such as diesel filter cups, high-temperature seals, and outdoor transparent structural components.

[0003] The following shortcomings are common in existing TPU materials: (1) Conventional aromatic TPU contains benzene ring structure and has high hardness, but it is easy to generate quinone chromophores under ultraviolet light and high temperature, that is, obvious yellowing and rapid decrease in transparency, which cannot meet the long-term weather resistance requirements. (2) Ordinary TPU has insufficient resistance to alkaline detergents, fuels and hydrolysis. Long-term use is prone to cracking, swelling and leakage, which affects the reliability of the device. (3) High hardness system is often accompanied by decreased toughness, poor bending resistance and obvious softening at high temperature. The Vicat softening temperature is too low and cannot be adapted to high temperature conditions such as engine compartment.

[0004] Therefore, this invention provides a high-hardness, high-transparency weather-resistant TPU material and its preparation method, solving the above-mentioned technical problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a TPU material that combines high hardness, high transparency, and weather resistance, enabling its application in the production of outdoor transparent structural products.

[0006] To achieve the above objectives, the present invention provides a high-hardness, high-transparency weather-resistant TPU material, comprising the following components by weight: 30-60 parts of cyclohexane polyol, 30-60 parts of cyclohexane diisocyanate, 0.3-2 parts of antioxidant, 0.05-1 part of lubricant, 0.05-0.5 parts of wax powder, and 0.01-0.5 parts of catalyst.

[0007] Preferably, the cyclohexane polyol is 1,4-dihydroxyalkylcyclohexane or 4,4'-dihydroxydicyclohexane; the cyclohexane diisocyanate is 1,4-cyclohexane diisocyanate, 1,4-cyclohexane dialkyl diisocyanate or dicyclohexylmethane-4,4'-diisocyanate.

[0008] Preferably, the molar ratio of the hydroxyl groups in the cyclohexane polyol to the isocyanate groups in the cyclohexane diisocyanate is 0.8~1.2:1.

[0009] Preferably, the hydroxyalkyl group of the 1,4-dihydroxyalkylcyclohexane has 1 to 4 carbon atoms, and the alkyl group of the 1,4-cyclohexane dialkyl diisocyanate has 1 to 4 carbon atoms.

[0010] Preferably, the lubricant is a saturated aliphatic amide, wherein the saturated aliphatic amide molecule has 12 to 25 carbon atoms.

[0011] Preferably, the wax powder is lignite wax.

[0012] Preferably, the antioxidant is a combination of a phosphite antioxidant and a hindered phenolic antioxidant, wherein the mass ratio of the phosphite antioxidant to the hindered phenolic antioxidant is 1:1 to 7.

[0013] Preferably, the catalyst is an organotin compound.

[0014] In view of the shortcomings of the prior art, the second objective of the present invention is to provide a preparation method that can produce a weather-resistant TPU material with high hardness and high transparency by mixing various substances.

[0015] A method for preparing a high-hardness, high-transparency weather-resistant TPU material includes the following steps:

[0016] (1) Vacuum dehydration of cyclohexane polyols and cyclohexane diisocyanates;

[0017] (2) Then, the antioxidant, lubricant, and wax powder are mixed and added to the cyclohexane polyol and cyclohexane diisocyanate in step (1), and mixed evenly.

[0018] (3) Add the mixture from step (2) into a high-speed stirred reactor. After the reaction, pour it into a block. Place the block in a drying room at 110-125℃ for 1-5 hours to obtain the final product.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The cyclohexane polyols and cyclohexane diisocyanates of the present invention serve as the main polymerization raw materials, thereby avoiding the yellowing defects caused by the benzene ring structure from the molecular root, while cyclohexane endows TPU with high hardness and chemical resistance.

[0021] 2. In this invention, 1,4-dihydroxyalkylcyclohexane or 4,4'-dihydroxydicyclohexane is preferably used as a cyclohexane polyol; the cyclohexane diisocyanate is 1,4-cyclohexane diisocyanate, 1,4-cyclohexane dialkyl diisocyanate, or dicyclohexylmethane-4,4'-diisocyanate, so that the polymerized molecular chain has a bicyclohexane symmetrical structure and the molecular chain arrangement is highly regular. This not only gives the TPU material high light transmittance, but also increases the cohesive energy density of the TPU material, significantly improving the material's hardness, heat resistance, and stability. Detailed Implementation

[0022] The following examples further illustrate the features and other related characteristics of the present invention to facilitate understanding by those skilled in the art:

[0023] The embodiments of the present invention provide a high-hardness, high-transparency weather-resistant TPU material, comprising the following parts by weight: 30-60 parts of cyclohexane polyol, 30-60 parts of cyclohexane diisocyanate, 0.3-2 parts of antioxidant, 0.05-1 part of lubricant, 0.05-0.5 parts of wax powder, and 0.01-0.5 parts of catalyst.

[0024] The hydroxyl groups of cyclohexane polyols can react with the isocyanate groups of cyclohexane diisocyanates to obtain TPU polymer materials. Using cyclohexane polyols and cyclohexane diisocyanates as the main polymerization raw materials avoids the yellowing defects caused by the benzene ring structure at the molecular level. Simultaneously, the cyclohexane structure is chemically stable, endowing TPU with excellent chemical resistance and high hardness. The TPU material of this invention is particularly suitable for high-end applications requiring stringent hardness, transparency, and weather resistance, such as diesel filter cups that need to be cleaned with alkaline reagents, seals that need to be used in high-temperature environments, and outdoor transparent structural components.

[0025] In some embodiments, the cyclohexane polyol is 1,4-dihydroxyalkylcyclohexane or 4,4'-dihydroxydicyclohexane. The cyclohexane diisocyanate is 1,4-cyclohexane diisocyanate, 1,4-cyclohexane dialkyl diisocyanate, or dicyclohexylmethane-4,4'-diisocyanate. Both the cyclohexane polyol and the cyclohexane diisocyanate have symmetrical structures. Under this preferred embodiment, the polymer obtained by polymerization has a dicyclohexane symmetrical structure, and the molecular chain arrangement is highly regular. This not only gives the TPU material high light transmittance but also increases the cohesive energy density within the molecules, significantly improving the material's hardness, heat resistance, and dimensional stability, making the material less prone to deformation.

[0026] In some embodiments, the hydroxyalkyl carbon number of the 1,4-dihydroxyalkylcyclohexane is 1 to 4, and the alkyl carbon number of the 1,4-cyclohexanedialkyl diisocyanate is 1 to 4. The fewer the carbon numbers of the hydroxyalkyl and alkyl groups, the higher the content of the polymeric cyclohexane and the greater the hardness. One of 1,4-cyclohexanediethanol, 1,4-cyclohexanediethanol, 1,4-cyclohexanedipropanol, 1,4-cyclohexanedibutanol, and 4,4'-dihydroxydicyclohexane can be selected as the 1,4-dihydroxyalkylcyclohexane, depending on the required hardness. One of 1,4-cyclohexanediisocyanate, 1,4-cyclohexanedimethyl diisocyanate, 1,4-cyclohexanediethyl diisocyanate, 1,4-cyclohexanedipropyl diisocyanate, 1,4-cyclohexanedibutyl diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate can be selected as the cyclohexane-based diisocyanate.

[0027] In some embodiments, the molar ratio of the hydroxyl groups in the cyclohexane polyol to the isocyanate groups in the cyclohexane diisocyanate is 0.8:1, 0.9:1, 1:1, 1.1:1, or 1.2:1, to ensure that the molar number of hydroxyl groups and isocyanate groups are similar, thus ensuring that the cyclohexane polyol can fully react with the cyclohexane diisocyanate.

[0028] In some embodiments, the lubricant is a saturated aliphatic amide with 15-25 carbon atoms. The amide groups in the saturated aliphatic amide have good affinity with the urethane groups of the TPU molecular chain, providing internal lubrication during polymerization and processing, reducing melt viscosity, and improving material flowability. Its long-chain alkyl groups provide external lubrication, reducing melt adhesion to the metal wall, which is beneficial for demolding and surface finish during injection molding. Simultaneously, this type of lubricant has a refractive index similar to cyclohexane-based TPUs, and will not affect the material's high transparency even at extremely low addition levels. The saturated aliphatic amide can be ethylene bis-stearamide or stearamide.

[0029] In some embodiments, the wax powder is lignite wax. Lignite wax is a natural mineral wax, mainly composed of long-chain fatty acid esters, fatty alcohols, and resin acids, and has a high melting point and good thermal stability. In this system, lignite wax works synergistically with saturated aliphatic amides: lignite wax acts as an external lubricant to enhance the release effect and improve the dryness of the material surface. The amount of lignite wax added is controlled at 0.05~0.5 parts to ensure its lubricating effect on the TPU material without affecting the high transparency of the TPU material.

[0030] In some embodiments, the antioxidant is a combination of a phosphite antioxidant and a hindered phenolic antioxidant. The hindered phenolic antioxidant can rapidly capture peroxide free radicals and alkyl free radicals generated under heat, oxygen, and ultraviolet conditions, terminating the oxidation chain reaction and inhibiting molecular chain degradation and yellowing at the source. The phosphite antioxidant can interrupt the generation of free radicals during the oxidation process, and the combination of the two enhances the antioxidant effect.

[0031] In some embodiments, the mass ratio of phosphite antioxidant to hindered phenolic antioxidant is 1:1 to 7.

[0032] In some embodiments, the hindered phenolic antioxidant may be antioxidant 1010 or antioxidant 1076. The phosphite antioxidant may be antioxidant 626, antioxidant 168, or tridecyl phosphite.

[0033] In some embodiments, the catalyst is an organotin compound, which may be one or a combination of several of dimethyltin, dioctyltin, tetraphenyltin, and dibutyltin dilaurate. The organotin compound can catalyze the reaction of cyclohexane polyols with cyclohexane diisocyanates.

[0034] A method for preparing a high-hardness, high-transparency weather-resistant TPU material includes the following steps:

[0035] (1) Vacuum dehydrate cyclohexane polyols and cyclohexane diisocyanates to avoid water reacting with isocyanates.

[0036] (2) Then, the antioxidant, lubricant and wax powder are mixed and added to the cyclohexane polyol and cyclohexane diisocyanate in step (1), and the mixture is stirred and mixed evenly so that each auxiliary agent is uniformly dispersed at the molecular level before the reaction.

[0037] (3) The mixture from step (2) is added to a high-speed stirring reactor, and after reaction, it is poured into a block shape to obtain the TPU material.

[0038] Example 1 of the present invention provides a method for preparing TPU material, comprising the following steps:

[0039] (1) Place cyclohexane polyols and cyclohexane diisocyanates in a vacuum drying oven and dehydrate them for 2 hours at a temperature of 100~120℃ and a vacuum degree of ≤-0.095MPa.

[0040] (2) Mix the antioxidant, lubricant and wax powder evenly at room temperature, and add the resulting mixture to the cyclohexane polyol and cyclohexane diisocyanate in step (1). Stir at 60~80℃ for 30 minutes to achieve uniform molecular dispersion of each additive before polymerization reaction.

[0041] (3) The uniformly mixed material is fed into a high-speed mixing head, the reaction temperature is controlled at 60~90℃, and the reaction is stirred for 2 hours to allow the polyol and isocyanate to fully undergo addition polymerization to form a polyurethane molecular chain with a dicyclohexane symmetrical structure. After the reaction, it is cast into a block material to obtain the TPU material.

[0042] 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.

[0043] Table 1 shows the formulations of Examples 1-5 and Comparative Examples 1-4.

[0044]

[0045] Performance testing

[0046] The TPU materials prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests according to the following standards, as detailed below:

[0047] (1) Shore hardness: The Shore D hardness of the sample was tested according to GB / T 2411-2008, and the average value of 5 points was taken as the result.

[0048] (2) Transmittance / haze: The transmittance and haze of the sample were tested according to GB / T 2410-2008, and the average value was taken after three parallel tests.

[0049] (3) Weather resistance and yellowing resistance: The TPU material was placed in an ultraviolet aging chamber with a wavelength of 340nm, an irradiation intensity of 0.51W / (m²·nm), and a black panel temperature of 60℃ for 72 hours of continuous aging. The yellowing index of the samples was tested with a colorimeter before and after aging, and ΔYI=YI(after aging)−YI(before aging) was calculated. The smaller ΔYI is, the better the yellowing resistance.

[0050] (4) Hydrolysis resistance: The TPU material was placed in an 80℃ constant temperature hot water tank and soaked for 3000h. The tensile strength was tested according to GB / T 528-2009. The strength retention rate was calculated as (strength after aging / strength before aging) × 100%.

[0051] (5) Acid and alkali resistance and solvent resistance: The TPU material was immersed in 5% NaOH solution, 5% HCl solution, low sulfur diesel and E10 ethanol gasoline at room temperature for 720h respectively. The appearance, swelling and cracking were observed according to GB / T 1690-2010.

[0052] (6) Resistance to fuel swelling: The TPU material was immersed in low sulfur diesel at 80℃ for 1000h. The volume change was tested and the swelling rate was calculated according to GB / T1690-2010.

[0053] (7) Compression set: The compression set was tested according to GB / T 7759-2015 under the conditions of 70℃×22h and compression rate of 25%.

[0054] (8) High temperature creep resistance: The TPU material was kept at 80℃ and 0.5MPa static load for 24h, and the dimensional change rate was tested according to GB / T11546-2008.

[0055] Table 2 shows the test results of Examples 1-5 and Comparative Examples 1-4.

[0056]

[0057] The performance test results of Examples 1-5 show that the TPU material prepared using the components and proportions described in this invention has high hardness, high transparency, weather resistance and anti-yellowing properties, chemical resistance, and high-temperature dimensional stability.

[0058] In Examples 1-3 and 4, 1,4-cyclohexanediethanol and 1,4-cyclohexane diisocyanate were selected as a compound. Both are bisymmetrical cyclohexane alicyclic structures, forming highly regular hard segment microregions during the polymerization stage. The cohesive energy density and steric hindrance of TPU are significantly higher than those of conventional linear systems, giving the TPU material high hardness, high-temperature mechanical retention, and creep resistance. Simultaneously, the pure saturated alicyclic structure does not contain aromatic benzene rings, eliminating the risk of yellowing from quinone chromophores generated by thermo-oxidative and UV aging at the molecular level. Combined with the steric hindrance barrier formed by the bicyclohexane hydrophobic framework, it effectively blocks the corrosion of water molecules, acids, alkalis, fuels, and other media, achieving extreme weather resistance, hydrolysis resistance, and chemical stability. Furthermore, the regular symmetrical structure makes the phase region size much smaller than the visible light wavelength, resulting in high light transmittance and extremely low haze, while also maintaining a highly transparent appearance.

[0059] The TPU in Example 5 showed a slight decrease in transparency, hardness, and resistance to media, which may be due to the asymmetric structure of 1,2-cyclohexanediethanol and the resulting decrease in molecular chain regularity.

[0060] Comparative Example 1 uses aromatic diphenylmethane diisocyanate instead of alicyclic diisocyanate. The molecular chain contains a benzene ring structure, which easily generates quinone chromophores under ultraviolet light and thermo-oxidative environments, resulting in a sharp increase in the yellowing index. Furthermore, the transparency of TPU decreases, and its resistance to hydrolysis and acids and alkalis deteriorates. At the same time, the hard segments are prone to softening and dissociation at high temperatures, and the compression set and creep resistance are reduced. This is because the chemical stability of the benzene ring structure is lower than that of cyclohexane. The benzene ring structure in the curing agent is different from the cyclohexane structure of the polyol, which leads to the decline in TPU performance.

[0061] The absence of antioxidants in Comparative Examples 2 and 3 reduced the material's resistance to aging, yellowing, chemical reagents, and weathering.

[0062] Comparative Example 4: Without the addition of lubricant, the system's processing compatibility and interfacial bonding strength decreased, resulting in a slight reduction in material toughness, dimensional stability, and transparency, as well as a deterioration in compression set and creep resistance.

[0063] 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-hardness, high-transparency weather-resistant TPU material, characterized in that, It comprises the following components by weight: 30-60 parts cyclohexane polyol, 30-60 parts cyclohexane diisocyanate, 0.3-2 parts antioxidant, 0.05-1 part lubricant, 0.05-0.5 parts wax powder, and 0.01-0.5 parts catalyst.

2. The high-hardness, high-transparency weather-resistant TPU material according to claim 1, characterized in that, The cyclohexane polyol is 1,4-dihydroxyalkylcyclohexane or 4,4'-dihydroxydicyclohexane; the cyclohexane diisocyanate is 1,4-cyclohexane diisocyanate, 1,4-cyclohexane dialkyl diisocyanate or dicyclohexylmethane-4,4'-diisocyanate.

3. The high-hardness, high-transparency weather-resistant TPU material according to claim 2, characterized in that, The molar ratio of the hydroxyl groups in the cyclohexane polyol to the isocyanate groups in the cyclohexane diisocyanate is 0.8~1.2:

1.

4. The high-hardness, high-transparency weather-resistant TPU material according to claim 2, characterized in that, The hydroxyalkyl group of the 1,4-dihydroxyalkylcyclohexane has 1 to 4 carbon atoms, and the alkyl group of the 1,4-cyclohexane dialkyl diisocyanate has 1 to 4 carbon atoms.

5. The high-hardness, high-transparency weather-resistant TPU material according to claim 1, characterized in that, The lubricant is a saturated aliphatic amide, and the saturated aliphatic amide molecule has 12 to 25 carbon atoms.

6. The high-hardness, high-transparency weather-resistant TPU material according to claim 5, characterized in that, The total mass ratio of the cyclohexane polyols and cyclohexane diisocyanates to the saturated aliphatic amides is 1:130-350.

7. The high-hardness, high-transparency weather-resistant TPU material according to claim 1, characterized in that, The wax powder is lignite wax.

8. The high-hardness, high-transparency weather-resistant TPU material according to claim 1 is characterized in that, The antioxidant is a combination of a phosphite antioxidant and a hindered phenolic antioxidant, wherein the mass ratio of the phosphite antioxidant to the hindered phenolic antioxidant is 1:1 to 7.

9. The high-hardness, high-transparency weather-resistant TPU material according to claim 1, characterized in that, The catalyst is an organotin compound.

10. A method for preparing a high-hardness, high-transparency weather-resistant TPU material as described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) First, dehydrate cyclohexane polyols and cyclohexane diisocyanates under vacuum; (2) Add the antioxidant, lubricant, and wax powder to the mixture from step (1) and mix well; (3) Add the mixed material from step (2) to the high-speed mixing head, pour it into a block, and place the block in the drying room at 110-125℃ for 1-5 hours to obtain the final product.

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