Preparation method of high-strength and high-transparency MDI-based polyurethane elastomer
By regulating the type and amount of polyols, MDI-based polyurethane elastomers with branched and cross-linked structures were prepared, which solved the problem of low transmittance of aromatic-based polyurethane elastomers and achieved synergistic optimization of high strength and high transparency.
Patent Information
- Application Number
- CN202510901927.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-01
- Publication Date
- 2025-09-16
AI Technical Summary
Existing aromatic-based polyurethane elastomers have low light transmittance and are difficult to meet application scenarios requiring high transparency.
By regulating the type and amount of polyols, MDI-based polyurethane elastomers with branched and cross-linked structures are prepared, and the hard segment phase crystal size is controlled by the type and amount of chain extenders to improve the optical and mechanical properties of the material.
The synergistic optimization of high strength and high transparency is achieved. The transmittance of the polyurethane elastomer reaches 88~96%, the refractive index is 1.54~1.65, the tensile strength is 30.3~45MPa, and the tear strength is 55~125.2kN/m.
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Figure CN120647883A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of preparation of aromatic transparent polyurethane elastomers, and in particular to a method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer. Background Art
[0002] Transparent polyurethane elastomers are typically synthesized by reacting oligomeric polyols, diisocyanates, and alcohol chain extenders. They possess excellent optical properties, mechanical strength, hydrophobicity, and weather resistance, demonstrating significant application potential across multiple fields and becoming a key material driving industrial upgrading and technological innovation. Microscopically, polyurethane elastomers are segmented polymers composed of alternating flexible soft segments and rigid hard segments. The soft segments are typically composed of small-molecule polyols, which are soft in aggregate and have a low tendency to crystallize. The hard segments, composed of isocyanates and small-molecule chain extenders, readily form an ordered arrangement and crystallize under the influence of strong polar urethane groups, hydrogen bonds, and intermolecular forces, becoming dispersed within the soft segment phase. Microphase separation occurs due to the thermodynamic incompatibility between the soft and hard segments, causing light transmitted through the polyurethane material to refract at the phase separation interface, resulting in opacity. Aliphatic isocyanates, such as hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), generally do not contain benzene rings in their structures, making them suitable for the preparation of highly transparent polyurethanes. Transparent polyurethane elastomers prepared with aromatic diisocyanates easily generate quinone structures under ultraviolet light because they contain aromatic diurea bridge bonds, causing the material to turn yellow and reduce transparency. Therefore, aromatic isocyanates are mostly used in situations where transparency is not required, and transparent polyurethanes mostly use aliphatic isocyanates. Xiang et al. used bisphenol A (BPA) as a chain extender to react with HDI and polytetramethylene glycol (PTMG) to prepare polyurethane elastomers containing aromatic carbamates. As the hard segment content increases, the visible light transmittance can reach more than 94%. (Xiang C, Chen H, Wang W, et al. Transparency-tunable and moderate-temperature healable thermoplastic polyurethane elastomer based on bisphenolA chain-extender[J]. Journal of Applied Polymer Science, 2021, 138(6), p.49794.) Summary of the Invention
[0003] In order to solve the problem of low light transmittance of current aromatic-based polyurethane elastomers, the present invention provides a method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer.
[0004] The present invention is achieved through the following technical solution: a method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer, comprising the following steps: Add any one of the following raw materials (a), (b), and (c) to a reaction vessel, and stir at 80-130° C. for 2-5 hours to prepare a prepolymer; degas the prepolymer for 200-600 seconds under heat preservation conditions, add a chain extender and stir after degassing, degas the prepolymer for another 200-600 seconds, pour the prepolymer into a prepared mold, hot-press at 80-130° C. for 30-60 minutes, cold-press at room temperature until it reaches room temperature, and then demold the prepolymer; and finally, let it stand at room temperature for 5-7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. Wherein (a): macromolecular diol and diphenylmethane diisocyanate; (b): macromolecular diols, small molecule polyols and diphenylmethane diisocyanate; (c): Macromolecular diols, macromolecular polyols and diphenylmethane diisocyanate.
[0005] As a further improvement of the technical solution of the present invention, the weight proportion of the macromolecular diol used is 42-300 parts, the weight proportion of the small molecule polyol used is 0-2.68 parts, the weight proportion of the macromolecular polyol used is 0-18 parts, and the weight proportion of diphenylmethane diisocyanate used is 50-125 parts; the chain extender is a diol chain extender, and the weight proportion of the diol chain extender used is 7.6-103.4 parts.
[0006] As a further improvement of the technical solution of the present invention, the small molecule polyol is glycerol or trimethylolpropane.
[0007] As a further improvement of the technical solution of the present invention, the macromolecular polyol is any one of polyoxypropylene triol, polyoxypropylene tetraol, polycaprolactone triol or polycaprolactone tetraol having a number average molecular weight of 300-1000.
[0008] As a further improvement to the technical solution of the present invention, the macromolecular diol is a mixture of one or more of polyethylene adipate diol, polybutylene adipate diol, polyhexane adipate diol, polyethylene adipate diol, polyethylene succinate diol, polybutylene succinate diol, polycaprolactone diol, polyoxypropylene diol, polyethylene glycol and polytetramethylene ether diol with a number average molecular weight of 600-3000, mixed in any proportion.
[0009] As a further improvement of the technical solution of the present invention, the diol chain extender is any one of 1,2-propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, 1,2-tridecanediol, 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol.
[0010] The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer provided by the present invention has the following advantages compared with the prior art: 1. The present invention achieves synergistic optimization of the optical and mechanical properties of the material by regulating the type and amount of polyols to obtain branched and cross-linked polyurethanes, and then controlling the hard segment crystal size by adjusting the type and amount of chain extenders. In particular, by introducing specific branched or cross-linked structures, an MDI-based polyurethane elastomer with excellent optical transparency and mechanical strength was successfully prepared. Test results show that the polyurethane elastomer of the present invention has the following outstanding properties: light transmittance of 88-96%, refractive index of 1.54-1.65, tensile strength of 30.3-45 MPa, tear strength of 55-125.2 kN / m, and Shore A hardness of 69-97.5 HA.
[0011] 2. Raw materials are cheap and easily available, and no special equipment is required, which greatly reduces equipment investment and production costs. The process is simple and efficient, significantly shortening the production cycle and improving production efficiency. 3. Completely eliminating the solvent system, this method avoids the environmental pollution, residue, and post-processing challenges associated with traditional solvent-based methods. Using a catalytic-free polymerization technique, the product achieves high purity, meeting the requirements of green chemistry and sustainable development. These technical features give this invention broad application prospects in high-end fields such as optical devices, flexible displays, and specialty packaging. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0014] Figure 1 This is a sample picture of the polyurethane elastomer obtained in Comparative Example 1. It can be seen from the picture that the transparency of the polyurethane elastomer is not high.
[0015] Figure 2 This is a sample picture of the polyurethane elastomer obtained in Comparative Example 2. It can be seen from the picture that the transparency of the polyurethane elastomer is not high.
[0016] Figure 3 This is a sample picture of the high-strength and high-transparency MDI-based polyurethane elastomer prepared in Example 1 of the present invention. It can be seen from the picture that the polyurethane elastomer has high transparency.
[0017] Figure 4 The following is a comparison of the UV transmittance curves of the polyurethane elastomers obtained in Comparative Examples 1, 2, and Example 1. As can be clearly seen from the figure, the high-strength, high-transparency MDI-based polyurethane elastomer obtained in Example 1 has a significantly higher transmittance than the polyurethane elastomer in Comparative Example 1, reaching 93.0% (at 800 nm). The transmittance for Comparative Example 1 is 54%, while that for Comparative Example 2 is 62%.
[0018] Figure 5 3 is a comparison diagram of the XRD curves of the polyurethane elastomers obtained in Comparative Example 1, Comparative Example 2 and Example 1. It can be seen from the figure that the peak intensity of Comparative Example 2 is higher than that of Example 1, indicating that the crystallization performance of the polyurethane obtained in Comparative Example is stronger than that in Example 1. DETAILED DESCRIPTION
[0019] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.
[0020] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.
[0021] The present invention provides a specific embodiment of a method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer, comprising the following steps: Add any one of the following raw materials (a), (b), and (c) to a reaction vessel, and stir at 80-130° C. for 2-5 hours to prepare a prepolymer; degas the prepolymer for 200-600 seconds under heat preservation conditions, add a chain extender and stir after degassing, degas the prepolymer for another 200-600 seconds, pour the prepolymer into a prepared mold, hot-press at 80-130° C. for 30-60 minutes, cold-press at room temperature until it reaches room temperature, and then demold the prepolymer; and finally, let it stand at room temperature for 5-7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. Wherein (a): macromolecular diol and diphenylmethane diisocyanate; (b): macromolecular diols, small molecule polyols and diphenylmethane diisocyanate; (c): Macromolecular diols, macromolecular polyols and diphenylmethane diisocyanate.
[0022] Among them, the weight proportion of the macromolecular diol used is 42-300 parts, the weight proportion of the small molecule polyol used is 0-2.68 parts, the weight proportion of the macromolecular polyol used is 0-18 parts, and the weight proportion of diphenylmethane diisocyanate used is 50-125 parts; the chain extender is a diol chain extender, and the weight proportion of the diol chain extender used is 7.6-103.4 parts.
[0023] In different embodiments, the heating temperature for preparing the prepolymer is maintained at precisely or approximately 80°C, 90°C, 100°C, 110°C, 120°C or 130°C; or a heating temperature within the range defined by any two of the aforementioned example values, for example, 80-100°C, 80-110°C, 90-120°C, 100-130°C, 80-120°C, 100-130°C.
[0024] In various embodiments, the heating time for preparing the prepolymer is maintained at precisely or approximately 2 h, 3 h, 4 h, or 5 h; or a heating time within a range defined by any two of the aforementioned exemplary values, such as 2-4 h, 3-5 h, or 4-5 h.
[0025] In different embodiments, the preparation hot pressing temperature is maintained at precisely, approximately 80°C, 90°C, 100°C, 110°C, 120°C or 130°C; or a heating temperature within the range defined by any two of the aforementioned example values, for example, 80-100°C, 80-110°C, 90-120°C, 100-130°C, 80-120°C, 100-130°C.
[0026] In various embodiments, the hot pressing is maintained for precisely, approximately, 30 min, 40 min, 50 min, 60 min; or a heating time within a range defined by any two of the aforementioned example values, such as 30-40 min, 30-50 min, 50-60 min.
[0027] As used herein, the term "about" generally means within a range of ±0.5%, 1%, 2%, 5%, or up to ±10% of the indicated value.
[0028] It should be noted that the present invention utilizes relatively low amounts of large and small molecule polyols to avoid excessive cross-linking reactions, enabling efficient and controllable synthesis of branched polyurethanes. High amounts of large and small molecule polyols enable efficient and controllable synthesis of cross-linked polyurethanes, both of which enhance the mechanical properties of polyurethane elastomers. Using 1,2-octanediol as a chain extender for elastomers can reduce the crystallinity of polyurethane elastomers and enhance the degree of phase separation, thereby yielding high-strength and highly transparent MDI-based polyurethane elastomers.
[0029] The polyols of the small molecule polyols and macromolecular polyols involved in the present invention refer to alcohols with three or more hydroxyl groups. For example, the small molecule polyol is glycerol or trimethylolpropane. The macromolecular polyol is any one of polyoxypropylene triol, polyoxypropylene tetraol, polycaprolactone triol, or polycaprolactone tetraol having a number average molecular weight of 300-1000.
[0030] In an example provided by the present invention, the macromolecular diol is a mixture of one or more of polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyethylene adipate diol, polyethylene succinate diol, polybutylene succinate diol, polycaprolactone diol, polyoxypropylene diol, polyethylene glycol and polytetramethylene ether diol with a number average molecular weight of 600-3000, mixed in any proportion.
[0031] In another example provided by the present invention, the diol chain extender is any one of 1,2-propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, 1,2-tridecanediol, 1,2-tetradecanediol, 1,2-pentadecanediol, and 1,2-hexadecanediol.
[0032] The specific embodiments of the present invention are described in detail below.
[0033] It is worth noting that: 1) the mass fractions of each material in the following examples and comparative examples are all parts by mass. 2) the materials used in the following examples and comparative examples were all dried to remove water. Example 1
[0034] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 100 parts of polycaprolactone diol (number-average molecular weight: 1000) and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, while maintaining the prepolymer at 80°C, add 25.1 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 88%, the transmittance in the haze meter test was 94%, the refractive index in the refractometer test was 1.54, the tensile strength was 36.3 MPa, the tear strength was 55.0 kN / m, and the hardness was 77 HA. Example 2
[0035] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 70 parts of polycaprolactone diol (number-average molecular weight: 1000), 6 parts of polyoxypropylene triol (number-average molecular weight: 300), and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and degas for 600 seconds in a planetary mixer at 1000 rpm. Then, maintain the prepolymer at 80°C and add 26.4 parts of 1,2-heptanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 91%, the transmittance in the haze meter test was 90%, the refractive index in the refractometer test was 1.62, the tensile strength was 39.6 MPa, the tear strength was 125.2 kN / m, and the hardness was 81HA. Example 3
[0036] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 95.5 parts of polytetrahydrofuran diol (number-average molecular weight: 1000), 0.9 parts of polyoxypropylene triol (number-average molecular weight: 300), and 75 parts of MDI. Slowly heat to 90°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 90°C and add 32 parts of 1,2-nonanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 50 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 92%, the transmittance in the haze meter test was 94%, the refractive index in the refractometer test was 1.59, the tensile strength was 37.3 MPa, the tear strength was 79.4 kN / m, and the hardness was 82HA. Example 4
[0037] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 51.6 parts of polybutylene adipate (number-average molecular weight 600), 2.98 parts of polyoxypropylene tetraol (number-average molecular weight 426), and 125 parts of MDI. Slowly heat to 90°C and stir for 4 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 90°C and add 103.2 parts of 1,2-hexadecanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 30 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 93%, the transmittance in the haze meter test was 95%, the refractive index in the refractometer test was 1.62, the tensile strength was 35.6 MPa, the tear strength was 62.3 kN / m, and the hardness was 84 HA. Example 5
[0038] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 191 parts of polyethylene glycol adipate (number-average molecular weight 2000), 0.276 parts of glycerol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150 g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 80°C and add 10.1 parts of 1,2-butanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 60 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 91%, the transmittance in the haze meter test was 94%, the refractive index in the refractometer test was 1.58, the tensile strength was 37.2 MPa, the tear strength was 65.6 kN / m, and the hardness was 80 HA. Example 6
[0039] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 188 parts of polypropylene glycol (number-average molecular weight 2000), 1.278 parts of polyoxypropylene tetraol (number-average molecular weight 1000), and 75 parts of MDI. Slowly heat to 90°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 90°C and add 34.8 parts of 1,2-decanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 90%, the transmittance in the haze meter test was 93%, the refractive index in the refractometer test was 1.60, the tensile strength was 39.4 MPa, the tear strength was 77.2 kN / m, and the hardness was 85 HA. Example 7
[0040] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 59.6 parts of polybutylene succinate (600 number-average molecular weight), 0.46 parts of trimethylolpropane, and 75 parts of MDI. Slowly heat to 110°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, while maintaining the prepolymer at 110°C, add 17.5 parts of 1,2-hexanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 60 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 92%, the transmittance in the haze meter test was 94%, the refractive index in the refractometer test was 1.58, the tensile strength was 30.3 MPa, the tear strength was 74.6 kN / m, and the hardness was 76 HA. Example 8
[0041] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 98.5 parts of polypropylene glycol (1000 number-average molecular weight), 0.9 parts of polycaprolactone triol (900 number-average molecular weight), and 50 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 80°C and add 7.6 parts of 1,2-propylene glycol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 90%, the transmittance in the haze meter test was 91%, the refractive index in the refractometer test was 1.55, the tensile strength was 33.8 MPa, the tear strength was 69.3 kN / m, and the hardness was 69 HA. Example 9
[0042] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 98.5 parts of polycaprolactone diol (number-average molecular weight: 1000), 0.3 parts of polyether triol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and degas for 600 seconds in a planetary mixer at 1000 rpm. Then, control the prepolymer to 80°C and add 25.3 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 93%, the transmittance in the haze meter test was 95%, the refractive index in the refractometer test was 1.54, the tensile strength was 43.8 MPa, the tear strength was 70.6 kN / m, and the hardness was 80 HA. Example 10
[0043] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 95.5 parts of polycaprolactone diol (number-average molecular weight: 1000), 0.9 parts of polyether triol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and degas for 600 seconds in a planetary mixer at 1000 rpm. Then, control the prepolymer to 80°C and add 25.6 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 92%, the transmittance in the haze meter test was 95%, the refractive index in the refractometer test was 1.55, the tensile strength was 45.0 MPa, the tear strength was 75.1 kN / m, and the hardness was 85 HA. Example 11
[0044] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 92.5 parts of polycaprolactone diol (number-average molecular weight: 1000), 1.5 parts of polyether triol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and degas for 600 seconds in a planetary mixer at 1000 rpm. Then, maintain the prepolymer at 80°C and add 26.0 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 91%, the transmittance in the haze meter test was 93%, the refractive index in the refractometer test was 1.54, the tensile strength was 37.8 MPa, the tear strength was 71.4 kN / m, and the hardness was 91HA. Example 12
[0045] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 89.5 parts of polycaprolactone diol (number-average molecular weight 1000), 2.1 parts of polyether triol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer to 80°C and add 26.3 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 93%, the transmittance in the haze meter test was 96%, the refractive index in the refractometer test was 1.65, the tensile strength was 38.4 MPa, the tear strength was 79.7 kN / m, and the hardness was 94 HA. Example 13
[0046] A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer comprises the following steps: To a three-necked flask, add 85 parts of polycaprolactone diol (number-average molecular weight: 1000), 3.0 parts of polyether triol, and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and degas for 600 seconds in a planetary mixer at 1000 rpm. Then, control the prepolymer to 80°C and add 26.9 parts of 1,2-octanediol while stirring. Stir for 10 minutes and then degas for 400 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 92%, the transmittance in the haze meter test was 94%, the refractive index in the refractometer test was 1.65, the tensile strength was 39.9 MPa, the tear strength was 115.0 kN / m, and the hardness was 97.5 HA. Comparative Example 1
[0047] A method for preparing a polyurethane elastomer comprises the following steps: To a three-necked flask, add 100 parts of polycaprolactone diol (number-average molecular weight: 1000) and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer temperature to 80-85°C and add 10.6 parts of ethylene glycol while stirring. Stir for 10 minutes and then degas for 200 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain an MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 41%, the transmittance in the haze meter test was 54%, the refractive index in the refractometer test was 1.59, the tensile strength was 28.8 MPa, the tear strength was 114.0 kN / m, and the hardness was 94 HA.
[0048] Supplementary explanation: In Comparative Example 1, ethylene glycol was added, stirred for 10 minutes, and then degassing was performed for 200 seconds. This is because the reaction activity of ethylene glycol and MDI is relatively high, so the degassing time is relatively short. Comparative Example 2
[0049] A method for preparing a polyurethane elastomer comprises the following steps: To a three-necked flask, add 100 parts of polycaprolactone diol (number-average molecular weight: 1000) and 75 parts of MDI. Slowly heat to 80°C and stir for 2 hours to prepare a prepolymer. Pour 150g of the prepolymer into a degassing box and place it in a planetary mixer at 1000 rpm for 600 seconds to degas. Then, control the prepolymer temperature to 80-85°C and add 25.1 parts of 1,8-octanediol while stirring. Stir for 10 minutes and then degas for 200 seconds to ensure uniform mixing and no bubbles. Finally, the mixture was poured into a preheated mold coated with a release agent. The mixture was hot-pressed at 120°C for 40 minutes in a flat-plate vulcanizer, then cold-pressed to room temperature and demolded. The sample was aged at room temperature for 7 days to obtain an MDI-based polyurethane elastomer. The transmittance of the polymer elastomer in the UV test was 52%, the transmittance in the haze meter test was 62%, the refractive index in the refractometer test was 1.64, the tensile strength was 38.4 MPa, the tear strength was 135.0 kN / m, and the hardness was 96 HA.
[0050] Supplementary explanation: In Comparative Example 1, ethylene glycol was added, stirred for 10 minutes, and then degassing was performed for 200 seconds. This is because the reaction activity of ethylene glycol and MDI is relatively high, so the degassing time is relatively short.
[0051] Table 1 is a comparison table of the ultraviolet transmittance, haze transmittance and refractive index of the polyurethane elastomers obtained in Comparative Example 1, Comparative Example 2, Example 1, Example 9, Example 10, Example 11, Example 12 and Example 13.
[0052] Table 1
[0053] Note: Transmittance a Data measured by UV test, transmittance b Data measured by the haze meter As can be clearly seen from the table, the high-strength, high-transparency MDI-based polyurethane elastomer obtained in Example 1 has a significantly higher UV transmittance than the polyurethane elastomer in Comparative Example 1, reaching 88.0% (at 800 nm), compared to 41% for Comparative Example 1 and 52% for Comparative Example 2. The high-strength, high-transparency MDI-based polyurethane elastomer obtained in Example 1 also has a significantly higher haze transmittance than the polyurethane elastomer in Comparative Example 1, reaching 94%, compared to 54% for Comparative Example 1 and 62% for Comparative Example 2.
[0054] Table 2 is a comparison table of the mechanical properties of the polyurethane elastomers obtained in Comparative Example 1, Comparative Example 2, Example 1, Example 9, Example 10, Example 11, Example 12, and Example 13.
[0055] Table 2
[0056] It can be clearly seen from the table that the tensile strength of the high-strength and high-transparency MDI-based polyurethane elastomer obtained in Example 10 is significantly higher than that of the polyurethane elastomer in Comparative Example 1, reaching 45.0 MPa, while that of Comparative Example 1 is 28.8 MPa and that of Comparative Example 2 is 38.4 MPa. The tear strength is also significantly improved, and the hardness gradually increases.
[0057] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments, and they should all be included in the scope of protection of the claims.
Claims
1. A method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer, characterized in that: The steps include: Add any one of the following raw materials (a), (b), and (c) to a reaction vessel, and stir at 80-130° C. for 2-5 hours to prepare a prepolymer; degas the prepolymer for 200-600 seconds under heat preservation conditions, add a chain extender and stir after degassing, degas the prepolymer for another 200-600 seconds, pour the prepolymer into a prepared mold, hot-press at 80-130° C. for 30-60 minutes, cold-press at room temperature until it reaches room temperature, and then demold the prepolymer; and finally, let it stand at room temperature for 5-7 days to obtain a high-strength and high-transparency MDI-based polyurethane elastomer. Wherein (a): macromolecular diol and diphenylmethane diisocyanate; (b): macromolecular diols, small molecule polyols and diphenylmethane diisocyanate; (c): Macromolecular diols, macromolecular polyols and diphenylmethane diisocyanate.
2. The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer according to claim 1, characterized in that: The weight proportion of the macromolecular diol is 42-300 parts, the weight proportion of the small molecule polyol is 0-2.68 parts, the weight proportion of the macromolecular polyol is 0-18 parts, and the weight proportion of diphenylmethane diisocyanate is 50-125 parts; the chain extender is a diol chain extender, and the weight proportion of the diol chain extender is 7.6-103.4 parts.
3. The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer according to claim 1 or 2, characterized in that: The small molecule polyol is glycerol or trimethylolpropane.
4. The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer according to claim 1 or 2, characterized in that: The macromolecular polyol is any one of polyoxypropylene triol, polyoxypropylene tetraol, polycaprolactone triol or polycaprolactone tetraol having a number average molecular weight of 300-1000.
5. The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer according to claim 1 or 2, characterized in that: The macromolecular diol is a mixture of one or more of polyethylene adipate diol, polybutylene adipate diol, polyhexane adipate diol, polydiethylene adipate diol, polyethylene succinate diol, polybutylene succinate diol, polycaprolactone diol, polyoxypropylene diol, polyethylene glycol and polytetramethylene ether diol with a number average molecular weight of 600-3000, mixed in any proportion.
6. The method for preparing a high-strength and high-transparency MDI-based polyurethane elastomer according to claim 2, characterized in that: The diol chain extender is any one of 1,2-propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, 1,2-tridecanediol, 1,2-tetradecanediol, 1,2-pentadecanediol and 1,2-hexadecanediol.