Preparation method of polyester-type ndi prepolymer and polyester-type ndi elastomer

Abstract

The application discloses a polyester NDI prepolymer preparation method and polyester NDI elastomer, and relates to the technical field of polyurethane elastomers. The polyester NDI prepolymer preparation method comprises the following steps: S10, mixing polyester polyol with deionized water, heating and reacting, removing the deionized water, and obtaining an intermediate product; wherein the polyester polyol is obtained by reacting adipic acid and small molecule diol under the catalysis of a titanate catalyst; S20, mixing the intermediate product with phosphoric acid to obtain a mixture; S30, heating the mixture, adding 1,5-naphthalene diisocyanate, mixing and reacting, and removing bubbles in a vacuum to obtain the polyester NDI prepolymer. By adding deionized water to the polyester polyol, the residual titanate catalyst in the polyester polyol is removed in the form of titanium dioxide by hydrolysis, so that the polyester NDI prepolymer with good stability is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane elastomer, in particular to a preparation method of polyester type NDI prepolymer and polyester type NDI elastomer. BACKGROUND

[0002] Polyurethane elastomer is a kind of high molecular synthetic material with performance between general rubber and plastic, which combines high elasticity of rubber and high hardness and high strength of plastic. Due to its unique micro-phase separation characteristics and a large number of hydrogen bonds between urethane groups, polyurethane elastomer has excellent mechanical properties, wear resistance and resilience, and is widely used in the fields of wheels, rubber rollers, seals and the like. In the production of polyurethane elastomer, diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) is used as raw material in a large amount in the isocyanate component, mainly because of low price, simple production process and meeting the requirements of most applications. However, in some high requirement applications, such as high speed or high load wheels, the polyurethane wheels made of MDI or TDI cannot usually meet the requirements due to poor dynamic performance and high internal heat.

[0003] 1,5-naphthalene diisocyanate (NDI) has excellent dynamic performance, extremely low internal heat, good mechanical properties and wear resistance, and high resilience due to the rigid naphthalene ring in the molecule, and can be applied to high dynamic load and heat resistant occasions which cannot be met by conventional MDI or TDI.

[0004] In the preparation of cyanate prepolymer, the reaction usually occurs between hydroxyl and isocyanate to form urethane, and the excess isocyanate in the prepolymer will not continue to react with urethane to cause viscosity rise. However, in NDI-based prepolymer, due to the extremely high isocyanate activity of NDI itself, it is easy to continue to react with urethane to form urethine, which causes the content of isocyanate (NCO, %) to decrease and the viscosity to rise. In addition to the high activity of NDI itself, the catalyst (titanate) used to synthesize polyester polyol also catalyzes the side reaction of 1,5-naphthalene diisocyanate and urethane to form urethine, causing the viscosity to rise. Therefore, the storage stability of the prepared NDI prepolymer is extremely poor (<1 day), which is manifested in that the NCO% will decrease and the viscosity will rise quickly during storage of the prepolymer, and even the viscosity is too high to be used, and the physical properties of the elastomer prepared therefrom decrease. SUMMARY

[0005] The main purpose of the present application is to provide a preparation method of polyester type NDI prepolymer and polyester type NDI elastomer, which aims to solve the problem of poor storage stability of polyester type NDI prepolymer prepared by the existing method.

[0006] To achieve the above objectives, the present invention proposes a method for preparing a polyester-type NDI prepolymer, the method comprising the following steps:

[0007] S10. The polyester polyol is mixed with deionized water, heated to react, and the deionized water is removed to obtain an intermediate product; wherein the polyester polyol is obtained by reacting adipic acid and a small molecule diol under the catalysis of a titanate catalyst.

[0008] S20. The intermediate product is mixed with phosphoric acid to obtain a mixture;

[0009] S30. The mixture is heated, 1,5-naphthalene diisocyanate is added and mixed and reacted, and the bubbles are removed under vacuum to obtain a polyester-type NDI prepolymer.

[0010] In one embodiment, in step S10, the mass ratio of the polyester polyol to deionized water is 100:(1-5).

[0011] In one embodiment, in step S10, the heating reaction time is 1 h to 3 h; and / or,

[0012] In step S10, the temperature of the heating reaction is 90°C to 110°C; and / or,

[0013] In step S10, the moisture content of the intermediate product is less than 500 ppm.

[0014] In one embodiment, in step S20, the mass ratio of the intermediate product to phosphoric acid is 1000:(0.01 to 0.03).

[0015] In one embodiment, in step S30, the mixture is heated to 130°C to 135°C; and / or,

[0016] In step S30, the reaction temperature is 80℃~90℃.

[0017] In one embodiment, the isocyanate content in the obtained polyester-type NDI prepolymer is 2.7% to 5%.

[0018] In one embodiment, the small molecule diol includes at least one selected from ethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and propylene glycol.

[0019] The present invention also proposes a polyester-type NDI elastomer, which is prepared by the above-described method for preparing polyester-type NDI prepolymer and a chain extender.

[0020] In one embodiment, the chain extender is 1,4-butanediol; and / or,

[0021] The mass ratio of the polyester-type NDI prepolymer to the chain extender is 100:(2.8~5.1).

[0022] In one embodiment, the hardness of the polyester-type NDI elastomer is 90A to 97A.

[0023] The technical solution provided by this invention first removes residual titanate catalysts from the polyester polyol by adding deionized water and hydrolyzing them into titanium dioxide. Then, the added deionized water is removed under vacuum. Next, phosphoric acid is added to the polyester polyol to suppress the occurrence of side reactions, thereby obtaining a stable polyester-type NDI prepolymer. Therefore, the method for preparing polyester-type NDI prepolymer provided by this invention can produce polyester-type NDI prepolymers with good stability. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Polyurethane elastomers are high-molecular synthetic materials with properties between those of general rubber and plastics, combining the high elasticity of rubber with the high hardness and strength of plastics. Due to their unique microphase separation characteristics and the presence of numerous hydrogen bonds between urethane groups, polyurethane elastomers possess excellent mechanical properties, wear resistance, and resilience, making them widely used in the manufacture of wheels, rollers, and seals. In polyurethane elastomer production, diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI) are widely used as raw materials for the isocyanate component, primarily because they are inexpensive, have simple production processes, and can meet most application requirements. However, in some demanding applications, such as high-speed or high-load wheels, polyurethane wheels made with MDI or TDI often fail to meet requirements due to poor dynamic performance and high internal heat generation.

[0026] Due to the presence of a rigid naphthalene fused ring in its molecule, 1,5-naphthalene diisocyanate (NDI) produces polyurethane elastomers with excellent dynamic properties, extremely low internal heat generation, good mechanical properties and wear resistance, and high resilience. It can be used in high dynamic load and heat-resistant applications where conventional MDI or TDI cannot meet the requirements.

[0027] In the preparation of cyanate prepolymers, the usual reaction is the reaction of hydroxyl groups and isocyanates to form urethane. Excess isocyanate in the prepolymer does not continue to react with urethane to cause an increase in viscosity. However, in NDI-based prepolymers, due to the extremely high isocyanate reactivity of NDI itself, it easily continues to react with urethane to form urea, resulting in a decrease in isocyanate content (NCO, %) and an increase in viscosity. In addition to the high reactivity of NDI itself, the catalysts (titanium esters) used in the synthesis of polyester polyols also catalyze the side reaction of 1,5-naphthalene diisocyanate and urethane to form urea, causing an increase in viscosity. Therefore, the resulting NDI prepolymer has extremely poor storage stability (<1 day), manifested in a rapid decrease in NCO% and an increase in viscosity during storage, sometimes to the point of being unusable, and a decline in the physical properties of the resulting elastomer.

[0028] In view of this, the present invention proposes a method for preparing polyester-type NDI prepolymer and polyester-type NDI elastomer, which can effectively solve the problem of poor storage stability of polyester-type NDI prepolymers prepared by existing methods, thereby obtaining polyester-type NDI prepolymers that can be stored at room temperature for at least six months without significant viscosity increase.

[0029] The method for preparing polyester-type NDI prepolymer provided by the present invention includes the following steps:

[0030] S10. The polyester polyol is mixed with deionized water, heated to react, and the deionized water is removed to obtain an intermediate product; wherein the polyester polyol is obtained by reacting adipic acid and a small molecule diol under the catalysis of a titanate catalyst.

[0031] S20. The intermediate product is mixed with phosphoric acid to obtain a mixture;

[0032] S30. The mixture is heated, 1,5-naphthalene diisocyanate (NDI) is added and mixed and reacted, and the bubbles are removed under vacuum to obtain a polyester-type NDI prepolymer.

[0033] The technical solution provided by this invention first removes residual titanate catalysts from the polyester polyol by adding deionized water and hydrolyzing them into titanium dioxide. Then, the added deionized water is removed under vacuum. Next, phosphoric acid is added to the polyester polyol to suppress the occurrence of side reactions, thereby obtaining a stable polyester-type NDI prepolymer. Therefore, the method for preparing polyester-type NDI prepolymer provided by this invention can produce polyester-type NDI prepolymers with good stability.

[0034] It should be noted that in the synthesis of polyester polyols, adipic acid and small-molecule diols are typically reacted under the catalysis of titanate catalysts. The polyester polyols have a molecular weight of 1000 g / mol to 2000 g / mol, and the small-molecule diols include at least one selected from ethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and propylene glycol. Preferably, the small-molecule diols include ethylene glycol and 1,4-butanediol, or 1,4-butanediol and 1,6-hexanediol.

[0035] The titanate catalyst can be tetrabutyl titanate, isopentyl titanate, diethylene titanate, etc. Adding titanate catalysts during the synthesis of polyester polyols can solve the problems of difficulty in reducing the reaction acid value, long esterification reaction time, and high energy consumption, thereby improving production efficiency.

[0036] In the preparation of isocyanate prepolymers, the usual reaction is the reaction between hydroxyl groups and isocyanate to form urethane. Excess isocyanate in the prepolymer does not continue to react with urethane, thus preventing an increase in viscosity. However, in NDI-based prepolymers, due to the extremely high isocyanate reactivity of NDI itself, it easily continues to react with urethane to form urea, causing a decrease in NCO% and an increase in viscosity. At this point, the residual titanate catalyst in the polyester polyol further catalyzes the side reaction of NDI and urethane to form urea, resulting in an increase in viscosity.

[0037] Therefore, in this application, deionized water is added to the polyester polyol to remove the residual titanate catalyst in the polyester polyol by hydrolyzing it into titanium dioxide. Phosphoric acid is added during the synthesis of the prepolymer to block the side reaction, thus preparing a stable polyester-type NDI prepolymer with a storage time of up to six months.

[0038] In step S10, the mass ratio of the polyester polyol to deionized water is 100:(1-5). Specifically, the mass ratio of the polyester polyol to deionized water can be 100:1, 100:1.5, 100:3, 100:5, etc. If too little deionized water is added, the titanate catalyst will not be completely hydrolyzed; if too much deionized water is added, the polyester polyol will also be easily hydrolyzed, and the water will be difficult to remove after the reaction. Preferably, when the mass ratio of the polyester polyol to deionized water is 100:1.5, the resulting polyester-type NDI prepolymer can have better stability.

[0039] Besides the amount of deionized water affecting the hydrolysis effect of titanate catalysts, the temperature and time of the hydrolysis reaction also influence the hydrolysis effect. Therefore, in some embodiments, the heating reaction time is 1-3 hours, and the heating reaction temperature is 90°C-110°C; specifically, the heating reaction time can be 1 hour, 2 hours, 3 hours, etc., and the heating reaction temperature can be 90°C, 100°C, 110°C, etc. If the reaction temperature is too low or the reaction time is too short, the hydrolysis reaction cannot proceed completely; if the reaction temperature is too high or the reaction time is too long, the ester bonds in the polyester polyol will also hydrolyze into hydroxyl and carboxyl groups. Preferably, the heating reaction time is 1.5 hours, and the heating reaction temperature is 100°C or 110°C, which can achieve better hydrolysis and catalyst removal without affecting the effect of the polyester polyol. That is, in step S10, the polyester polyol is mixed with deionized water and heated at 90°C-110°C for 1-3 hours to remove the deionized water, obtaining an intermediate product.

[0040] It should be noted that deionized water can be removed by vacuuming or other methods. This invention does not impose any restrictions on these methods, as long as the water content in the intermediate product obtained is less than 500 ppm.

[0041] Mixing the intermediate product with phosphoric acid before adding NDI can suppress side reactions in the polyurethane prepolymer. Adding phosphoric acid before the reaction of the polyester polyol with NDI can reduce the branching reaction of urethane esters, thereby significantly improving the stability of the obtained polyester-type NDI prepolymer. The mass ratio of the intermediate product to phosphoric acid is 1000:(0.01–0.03). Specifically, the mass ratio of the intermediate product to phosphoric acid can be 1000:0.01, 1000:0.02, 1000:0.03, etc. Adding a small amount of phosphoric acid can suppress branching side reactions, resulting in a stable polyester-type NDI prepolymer.

[0042] After mixing the intermediate product with phosphoric acid, 1,5-naphthalene diisocyanate (NDI) is added to the mixture for further reaction. Further, the mixture is heated to 130°C–135°C before adding NDI. Specifically, the mixture can be heated to 130°C, 132°C, 135°C, etc. Adding NDI to the polyol at a lower temperature (below 127°C) will result in a higher viscosity product. This is because NDI dissolves slowly at low temperatures, gradually entering the reaction system, which can easily lead to a lower NCO:OH ratio in the initial stage of the reaction, resulting in the formation of high molecular weight components in the product. These high molecular weight components are prone to gelation during storage, leading to instability of the prepolymer.

[0043] However, after adding NDI, the aforementioned high temperature cannot be maintained for the reaction. This is because at high temperatures, 1,5-naphthalene diisocyanate reacts with urethane to form urethane, causing a sharp drop in NCO value and an increase in viscosity. Simultaneously, the branched products generated by this side reaction act as multifunctional crosslinking agents in the prepolymer, significantly increasing the likelihood of gelation during product storage. Therefore, in step S30, the reaction temperature for adding naphthalene diisocyanate and mixing is set to 80°C–90°C to further improve the stability of the obtained polyester-type NDI prepolymer.

[0044] Specifically, in step S30, the mixture can be heated to slightly above the melting point of NDI (127°C), NDI is added, and after the NDI melts, the temperature is rapidly reduced to 90°C. After 10 minutes, vacuum degassing is performed to obtain a polyester-type NDI prepolymer. The isocyanate content in the obtained polyester-type NDI prepolymer is 2.7% to 5%.

[0045] This invention also proposes a polyester-type NDI elastomer, which is prepared from a polyester-type NDI prepolymer obtained by the above-described method for preparing polyester-type NDI prepolymer and a chain extender. Specifically, the polyester-type NDI prepolymer and the chain extender are mixed and reacted at 90–100°C, then poured into a mold at 100–120°C. After demolding, the mixture is vulcanized at 100–120°C for 20–50 hours to obtain a polyester-type NDI elastomer with a hardness of 90A–97A.

[0046] Furthermore, the chain extender is 1,4-butanediol; the mass ratio of the polyester-type NDI prepolymer to the chain extender is 100:(2.8-5.1). Using 1,4-butanediol as a chain extender not only improves the wear resistance and heat resistance of the polyester-type NDI elastomer, but also enhances its mechanical properties and low-temperature flexibility. It also promotes chemical crosslinking, improves oil resistance, and reduces internal heat generation, thereby improving the overall performance of the polyester-type NDI elastomer in multiple aspects.

[0047] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0048] The raw materials used in the examples are as follows:

[0049] PEBA2000: Purchased from Asahikawa Chemical, Mn = 2000 g / mol, a polyol prepared from adipic acid, ethylene glycol, and 1,4-butanediol under the action of titanate catalyst, wherein the molar ratio of ethylene glycol to 1,4-butanediol is 6:4.

[0050] PBHA1500: Purchased from Huafeng Group, Mn = 1500 g / mol, a polyol produced by adipic acid, 1,4-butanediol, and 1,6-hexanediol under the action of titanate catalyst, wherein the molar ratio of 1,4-butanediol and 1,6-hexanediol is 5:5.

[0051] NDI: Naphthalene diisocyanate purchased from Chongshun Co., Ltd.

[0052] BDO: 1,4-Butanediol purchased from BASF.

[0053] Phosphoric acid solution: purchased from Sigma-Aldrich, with a phosphoric acid mass fraction >85%.

[0054] The standards, methods, or instruments used for testing in the examples are as follows:

[0055] Hardness: GB / T 531.2-2009

[0056] Tensile strength: GB / T 528-2009

[0057] Elongation at break: GB / T 528-2009

[0058] Tear strength: GB / T 529-2009

[0059] Resilience: GB / T 1681-2009

[0060] Abrasion resistance: GB / T 9867-2008

[0061] Compression set: GB / T 7759-2015

[0062] Moisture content: Karl-Fischer micromoisture analyzer (Wantong)

[0063] NCO content: ASTM D2572-97

[0064] Viscosity: Rotational viscometer

[0065] Example 1

[0066] The polyester-type NDI prepolymer was prepared using the following method:

[0067] S10. Add 660g of PEBA2000 and 9.9g of deionized water to a container equipped with a stirrer, thermometer and vacuum interface, mix, heat to 100℃ and react for 1.5h, then vacuum until the moisture content is less than 500ppm to obtain the intermediate product.

[0068] S20. Add 0.016 g of phosphoric acid to the intermediate product to obtain a mixture;

[0069] S30. Heat the mixture to 130°C, add 138.6g of NDI, and after the NDI has completely melted, quickly cool it to 90°C using an ice-water bath. After 10 minutes, remove the bubbles under vacuum to obtain a polyester-type NDI prepolymer.

[0070] Example 2

[0071] The polyester-type NDI prepolymer was prepared using the following method:

[0072] S10. Add 660g of PBHA1500 and 9.75g of deionized water to a container equipped with a stirrer, thermometer and vacuum interface, mix, heat to 100℃ and react for 1.5h, then vacuum until the moisture content is less than 500ppm to obtain the intermediate product.

[0073] S20. Add 0.016 g of phosphoric acid to the intermediate product to obtain a mixture;

[0074] S30. Heat the mixture to 130°C, add 182g of NDI, and after the NDI has completely melted, quickly cool it to 90°C using an ice-water bath. After 10 minutes, remove the bubbles under vacuum to obtain a polyester-type NDI prepolymer.

[0075] Example 3

[0076] The polyester-type NDI prepolymer was prepared using the following method:

[0077] S10. Add 660g of PEBA2000 and 9.9g of deionized water to a container equipped with a stirrer, thermometer and vacuum interface, mix, heat to 100℃ and react for 5h, then vacuum until the moisture content is less than 500ppm to obtain the intermediate product.

[0078] S20. Add 0.016 g of phosphoric acid to the intermediate product to obtain a mixture;

[0079] S30. Heat the mixture to 130°C, add 138.6g of NDI, and after the NDI has completely melted, quickly cool it to 90°C using an ice-water bath. After 10 minutes, remove the bubbles under vacuum to obtain a polyester-type NDI prepolymer.

[0080] Example 4

[0081] The polyester-type NDI prepolymer was prepared using the following method:

[0082] S10. Add 660g of PEBA2000 and 9.9g of deionized water to a container equipped with a stirrer, thermometer and vacuum interface, mix, heat to 130℃ and react for 1.5h, then vacuum until the moisture content is less than 500ppm to obtain the intermediate product.

[0083] S20. Add 0.016 g of phosphoric acid to the intermediate product to obtain a mixture;

[0084] S30. Heat the mixture to 130°C, add 138.6g of NDI, and after the NDI has completely melted, quickly cool it to 90°C using an ice-water bath. After 10 minutes, remove the bubbles under vacuum to obtain a polyester-type NDI prepolymer.

[0085] Comparative Example 1

[0086] Except for step S10, which is changed to:

[0087] "Add 660g of PEBA2000 to a container equipped with a stirrer, thermometer, and vacuum interface, heat to 100℃, and then evacuate until the moisture content is less than 500ppm to obtain the intermediate product."

[0088] The other steps are the same as in Example 1.

[0089] Comparative Example 2

[0090] Except for step S10, which is changed to:

[0091] "Add 660g of PBHA1500 to a container equipped with a stirrer, thermometer, and vacuum interface, heat to 100℃, and then evacuate until the moisture content is less than 500ppm to obtain the intermediate product."

[0092] The other steps are the same as in Example 2.

[0093] Performance testing

[0094] 1) The polyester-type NDI prepolymers obtained in Examples 1-2 and Comparative Examples 1-2 were stored in nitrogen-sealed containers. The isocyanate content and viscosity were measured 1 hour after production and every month. The results are shown in Tables 1-4 below.

[0095] Table 1. Isocyanate content and viscosity of the polyester-type NDI prepolymer obtained in Example 1

[0096] NCO % Viscosity (cps, 90°C) 1 hour after production 3.51 2109 1 month 3.49 2130 2 months 3.46 2142 3 months 3.44 2150 4 months 3.42 2167 5 months 3.42 2170 6 months 3.40 2200

[0097] Table 2. Isocyanate content and viscosity of the polyester-type NDI prepolymer obtained in Example 2

[0098] NCO % Viscosity (cps, 90°C) 1 hour after production 4.41 1520 1 month 4.39 1540 2 months 4.38 1558 3 months 4.35 1570 4 months 4.35 1576 5 months 4.32 1600 6 months 4.30 1603

[0099] Table 3 shows the isocyanate content and viscosity of the polyester-type NDI prepolymer obtained in Comparative Example 1.

[0100]

[0101]

[0102] Table 4 shows the isocyanate content and viscosity of the polyester-type NDI prepolymer obtained in Comparative Example 2.

[0103] NCO % Viscosity (cps, 90°C) 1 hour after production 4.39 2210 1 month Gel, not testable Gel, not testable 2 months Gel, not testable Gel, not testable 3 months Gel, not testable Gel, not testable 4 months Gel, not testable Gel, not testable 5 months Gel, not testable Gel, not testable 6 months Gel, not testable Gel, not testable

[0104] As can be seen from Tables 1 to 4, the isocyanate content and viscosity of the polyester NDI prepolymers obtained in Examples 1 to 2 in Tables 1 and 2 did not change significantly within 6 months after production. However, the polyester NDI prepolymers obtained in Comparative Examples 1 to 2 in Tables 3 and 4 showed gelation after 1 month after production. This indicates that the preparation method of polyester NDI prepolymers provided by the present invention can produce polyester NDI prepolymers with good stability.

[0105] 2) After storing the polyester-type NDI prepolymer obtained in Example 1 for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months and 6 months, the polyester-type NDI prepolymer and 1,4-butanediol were mixed at a mass ratio of 100:3 and reacted at 95°C. The mixture was then poured into a mold at 110°C and demolded. After demolding, the mixture was vulcanized at 120°C for 45 hours to obtain polyester-type NDI elastomers.

[0106] The polyester-type NDI prepolymer obtained in Example 2 was stored for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months. Then, the polyester-type NDI prepolymer and 1,4-butanediol were mixed at a mass ratio of 100:3 and reacted at 95°C. The mixture was then poured into a mold at 110°C and demolded. After demolding, the mixture was vulcanized at 120°C for 45 hours to obtain polyester-type NDI elastomers.

[0107] The polyester-type NDI prepolymer obtained in Example 3 was stored for 1 hour. The polyester-type NDI prepolymer and 1,4-butanediol were mixed at a mass ratio of 100:3 and reacted at 95°C. The mixture was then poured into a mold at 110°C. After demolding, it was vulcanized at 120°C for 45 hours to obtain the polyester-type NDI elastomer.

[0108] The polyester-type NDI prepolymer obtained in Example 4 was stored for 1 hour. The polyester-type NDI prepolymer and 1,4-butanediol were mixed at a mass ratio of 100:3 and reacted at 95°C. The mixture was then poured into a mold at 110°C. After demolding, it was vulcanized at 120°C for 45 hours to obtain the polyester-type NDI elastomer.

[0109] The polyester NDI elastomers prepared from the polyester NDI prepolymer obtained in Example 1 above were subjected to hardness, tensile strength, elongation at break, tear strength, resilience, abrasion resistance and compression set tests after being placed for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months and 6 months. The results are shown in Table 5.

[0110] The polyester-type NDI elastomers prepared from the polyester-type NDI prepolymer obtained in Example 2 above were subjected to hardness, tensile strength, elongation at break, tear strength, resilience, abrasion resistance and compression set tests after being placed for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months and 6 months. The results are shown in Table 6.

[0111] The polyester NDI elastomers prepared by placing the polyester NDI prepolymers obtained in Examples 3 and 4 for 1 hour were subjected to tests for hardness, tensile strength, elongation at break, tear strength, resilience, abrasion resistance, and compression set. The results are shown in Table 7.

[0112] Table 5. Performance results of polyester NDI elastomers prepared from the polyester NDI prepolymer obtained in Example 1 after 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months of storage.

[0113]

[0114] Table 6 shows the performance results of the polyester-type NDI elastomers prepared from the polyester-type NDI prepolymer obtained in Example 2 after being placed for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months.

[0115]

[0116]

[0117] Table 7 shows the performance results of the polyester NDI elastomers prepared after the polyester NDI prepolymers obtained in Examples 3 and 4 were left to stand for 1 hour.

[0118]

[0119] As can be seen from Tables 5 and 6, the polyester-type NDI prepolymers prepared by the technical solution provided by the present invention exhibit similar and excellent properties after being placed for 1 hour, 1 month, 2 months, 3 months, 4 months, 5 months, and 6 months. Therefore, the preparation method of polyester-type NDI prepolymers provided by the present invention can produce polyester-type NDI prepolymers with good stability.

[0120] As can be seen from Table 7, in Example 3, the reaction time was too long when water was added to the polyester polyol for deactivation, resulting in hydrolysis of the polyester polyol. Therefore, the tensile strength, tear strength, abrasion resistance, and compression set of the polyester NDI elastomer obtained after 1 hour of storage were all worse than those in Example 1. In Example 4, the reaction temperature was too high when water was added to the polyester polyol for deactivation, resulting in hydrolysis of the polyester polyol. Therefore, the tensile strength, tear strength, abrasion resistance, and compression set of the polyester NDI elastomer obtained after 1 hour of storage were all worse than those in Example 1.

[0121] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a polyester-type NDI prepolymer, characterized in that, Includes the following steps: S10. The polyester polyol is mixed with deionized water, heated to react, and the deionized water is removed to obtain an intermediate product; wherein the polyester polyol is obtained by reacting adipic acid and a small molecule diol under the catalysis of a titanate catalyst. S20. The intermediate product is mixed with phosphoric acid to obtain a mixture; S30. Heat the mixture, add 1,5-naphthalene diisocyanate, mix and react, remove bubbles under vacuum to obtain polyester-type NDI prepolymer; In step S10, the mass ratio of the polyester polyol to deionized water is 100:(1-5); In step S10, the heating reaction takes 1.5 hours and the heating reaction temperature is 100°C. Furthermore, in step S10, the moisture content of the intermediate product is less than 500 ppm; In step S20, the mass ratio of the intermediate product to phosphoric acid is 1000:(0.01~0.03); in step S30, the mixture is heated to 130°C. Furthermore, in step S30, the reaction temperature is 90°C.

2. The method for preparing the polyester-type NDI prepolymer as described in claim 1, characterized in that, The isocyanate content in the obtained polyester-type NDI prepolymer is 2.7% to 5%.

3. The method for preparing the polyester-type NDI prepolymer as described in claim 1, characterized in that, The small molecule diols include at least one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and propylene glycol.

4. A polyester-type NDI elastomer, characterized in that, The polyester-type NDI elastomer is prepared from the polyester-type NDI prepolymer obtained by the preparation method of the polyester-type NDI prepolymer according to any one of claims 1 to 3 and a chain extender.

5. The polyester-type NDI elastomer as described in claim 4, characterized in that, The chain extender is 1,4-butanediol; and / or, The mass ratio of the polyester-type NDI prepolymer to the chain extender is 100:(2.8~5.1).

6. The polyester-type NDI elastomer as described in claim 4, characterized in that, The hardness of the polyester-type NDI elastomer is 90A to 97A.

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