A modified polyurethane resin and a method for preparing the same

Abstract

The application relates to the field of polyurethane resins, in particular to a modified polyurethane resin and a preparation method thereof. The modified polyurethane resin comprises the following substances in mass fractions: diisocyanate 60-70 parts, tetraisocyanate 5-10 parts, polyether polyol 30-35 parts, polydimethylsiloxane 6-12 parts, dihydric alcohol 3-5 parts, tetrahydric alcohol 3-5 parts, polyamine 3-5 parts, N-ethyl morpholine 0.8-1 part, modified chitosan 2-5 parts, auxiliary agent 0-2 parts and solvent 0-150 parts. The preparation method comprises the following steps: S1, preparing a prepolymer; S2, chain extension reaction and secondary chain extension reaction; and S3, preparing the modified polyurethane resin. The modified polyurethane resin prepared by the application has good air permeability and antibacterial performance, and can be applied to the fields of artificial leather and the like.

Description

Technical Field

[0001] This invention relates to the field of polyurethane resins, specifically to a modified polyurethane resin and its preparation method. Background Technology

[0002] Polyurethane resin is a highly diverse polymer material produced by the reaction of diisocyanates and polyols, sometimes with the addition of chain extenders and other additives. It can exhibit a wide range of applications depending on its chemical structure and preparation conditions, from flexible foams to rigid plastics, and various elastomers in between.

[0003] Due to its excellent properties, polyurethane resin has a wide range of applications, among which its main applications in leather include:

[0004] 1. Finishing Agents: Polyurethane resins, used as leather finishing agents, provide excellent surface protection and aesthetic effects. They are categorized into several types, including repair agents, base coats, intermediate coats, and top coats, each with specific functions such as increasing gloss, improving abrasion resistance, and water resistance. Water-based polyurethane finishing agents are particularly popular due to their environmental friendliness and low VOC content.

[0005] 2. Retanning agents: In the leather tanning process, polyurethane retanning agents are used to improve the physical properties of leather, such as increasing softness, fullness and flexural strength, while also improving the feel and color uniformity of the leather.

[0006] 3. Filling resin: Used for filling treatment of leather, it can fill the micropores on the surface of leather, increase the firmness and smoothness of leather, and improve subsequent processing performance, such as the uniformity of coating and the physical and mechanical properties of leather.

[0007] 4. Footwear adhesives: Polyurethane resin, with its high bonding strength and weather resistance, has become an important adhesive material in the footwear industry. It is used to bond the upper and sole of the shoe, as well as to fix other parts, to ensure the durability of the shoes.

[0008] 5. Resins for Artificial Leather: Polyurethane synthetic leather is made using polyurethane resin as the main raw material through different processing techniques (such as wet and dry processes). It has an appearance and feel similar to natural leather and is widely used in clothing, bags, furniture, and other fields. The application of polyurethane resin in artificial leather is not limited to coatings but also includes the synthesis of substrates, thereby creating environmentally friendly and high-performance leather alternatives.

[0009] CN115894851B provides a method for preparing silicone-modified waterborne polyurethane for leather finishing, relating to the field of organic chemistry. The method includes: mixing 5-10 parts by weight of a dihydroxy polyether-modified siloxane and 20-30 parts by weight of a polyester diol, dehydrating, cooling, adding isoflurane diisocyanate, and dropwise adding stannous octoate, reacting at 65-75°C for 1.5-2.5 h; then adding 2-4 parts by weight of dimethylolpropionic acid, continuing the reaction at 65-75°C for 1-3 h to obtain a prepolymer; cooling to 40-50°C, adding 2-4 parts by weight of triethylamine, and adding 35-45 parts by weight of water and 1-3 parts by weight of ethylenediamine under stirring, reacting for 1-2 h to obtain a silicone-modified waterborne polyurethane emulsion. By introducing a dihydroxy polyether-modified siloxane structure into the polyurethane, the resulting silicone-modified waterborne polyurethane emulsion is stable, and the prepared film exhibits both low water absorption and excellent mechanical properties. However, its breathability is poor. Summary of the Invention

[0010] The purpose of this invention is to provide a modified polyurethane resin and its preparation method. The prepared polyurethane resin has good air permeability, the preparation method is simple, and it is easy to apply industrially, especially suitable for use in leather.

[0011] This invention provides a modified polyurethane resin, comprising the following substances in parts by weight:

[0012] 60-70 parts of diisocyanate

[0013] 5-10 parts of tetraisocyanate

[0014] 30-35 parts of polyether polyol

[0015] 6-12 parts of polydimethylsiloxane

[0016] 3-5 parts of diol

[0017] 3-5 parts tetrahydric alcohol

[0018] 3-5 parts of polyamines

[0019] 0.8-1 part of N-ethylmorpholine

[0020] 2-5 parts modified chitosan

[0021] 0-2 parts of auxiliary agent

[0022] Solvent: 0-150 parts.

[0023] The formulation of this invention introduces tetraisocyanate and tetraol, which can form chain structures in both the longitudinal and transverse directions, and may also form ring structures. The gaps in the middle of the rings and the interlaced gaps can serve as air pores to increase air permeability.

[0024] Furthermore, the diisocyanate is dimer diisocyanate (DDI) or dicyclohexylmethane diisocyanate (HMDI), and the tetraisocyanate is 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate. The tetraisocyanate has more functional groups, a higher proportion of hard segments, and increased air permeability of the prepared product.

[0025] Furthermore, the polyether polyol is a mixture of polyether 220 and polyether 330, with a mass ratio of polyether 220 to polyether 330 of 1:1.

[0026] Furthermore, the diol is a mixture of 3-fluoro-1,2-propanediol and 1,4-butanediol, with a mass ratio of 3-fluoro-1,2-propanediol to 1,4-butanediol of (0~1):1. Increasing the number of fluorine atoms can improve product performance. The tetraol is pentaerythritol, which contains more hydroxyl groups, increasing the hydrophilic components and improving breathability.

[0027] Further, the polyamine is 1,4-butanediamine or 1,5-pentanediamine.

[0028] Furthermore, the additive is modified ammonium nitrate or ammonium bicarbonate. The modified ammonium nitrate is modified ammonium nitrate for automotive airbags. The additive can decompose during heating and form micropores inside the material, increasing the air permeability of the product. When using modified ammonium nitrate for automotive airbags, it is more effective than ordinary ammonium nitrate because ordinary ammonium nitrate is prone to absorbing water, has poor performance, and affects its use.

[0029] Furthermore, the solvent is ethyl acetate.

[0030] The present invention also provides a method for preparing the modified polyurethane resin, comprising the following steps:

[0031] S1: Add solvent to reaction vessel, then add diisocyanate, tetraisocyanate, polyether polyol, polydimethylsiloxane and N-ethylmorpholine, mix and react, the reaction temperature is 80~120℃, the reaction time is 2~4h, and the prepolymer is obtained.

[0032] S2: After the additives and modified chitosan are pulverized and mixed evenly, they are added to the prepolymer obtained in S1. Then, diol and tetraol are added to carry out chain extension reaction. Then, polyamine is added to carry out secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 90~140℃ and the reaction time is 1~2h. The secondary chain extension reaction temperature is 100~150℃ and the reaction time is 1~2h. The additives and modified chitosan must be pulverized and mixed evenly before being added. This is to ensure that they are evenly dispersed inside the prepolymer. If they are added after chain extension, it will cause large pores inside the product, resulting in decreased performance and uneven pore formation.

[0033] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 150°C. After drying for 2 to 3 hours, it is then bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1 to 0.2°C / min.

[0034] Furthermore, the modified polyurethane resin requires further processing. The processing procedure involves heating the prepared modified polyurethane resin to 150°C, then rapidly cooling it to 10°C, and then heating the cooled modified polyurethane resin back to 150°C, followed by rapid cooling to 10°C, to obtain the processed modified polyurethane resin. The cooling rate is 10~15°C / min. Heating increases the internal pore size of the prepared product, and further cooling causes shrinkage. Because the cooling is rapid, the enlarged pores do not return to their original size, further increasing the internal air permeability of the product and enhancing its air permeability.

[0035] Furthermore, the preparation of the modified chitosan includes the following steps:

[0036] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, then filter and dry.

[0037] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, then filter and dry.

[0038] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan. The ultrasonic frequency is 25kHz. The modified chitosan has more active groups, which enhances the antibacterial properties of the product. At the same time, it can also act as a nucleating agent to improve the air permeability of the product.

[0039] The modified polyurethane resin prepared using this invention has good air permeability and antibacterial properties, making it suitable for a wide range of applications, including industries such as artificial leather. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1

[0042] A modified polyurethane resin, comprising the following substances in parts by weight:

[0043] 60kg of dimeric acid diisocyanate

[0044] 5 kg of 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate

[0045] Polyether 220 15kg and Polyether 330 15kg

[0046] 6kg of polydimethylsiloxane

[0047] 1.5 kg of 3-fluoro-1,2-propanediol and 1.5 kg of 1,4-butanediol

[0048] Pentaerythritol 3kg

[0049] 3 kg of 1,4-Butanediamine

[0050] N-ethylmorpholine 0.8kg

[0051] 3kg of modified chitosan

[0052] 1 kg of ammonium bicarbonate

[0053] 80 kg of ethyl acetate.

[0054] The preparation of the modified chitosan includes the following steps:

[0055] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, filter, and dry. The mass of the 3wt% hydrogen peroxide solution is five times the mass of the chitosan.

[0056] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, filter, and dry. The mass of the 0.2wt% sodium hydroxide solution is 4 times the mass of the dried chitosan.

[0057] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

[0058] The preparation method of the above-mentioned modified polyurethane resin includes the following steps:

[0059] S1: Add ethyl acetate to the reactor, then add dimer diisocyanate, 2,2′-dimethyl-3,3′,5,5′-triphenylmethane, polyether 220, polyether 330, polydimethylsiloxane and N-ethylmorpholine, mix and react at 80~100℃ for 3h to obtain the prepolymer;

[0060] S2: After the ammonium bicarbonate and modified chitosan are pulverized and mixed evenly, they are added to the prepolymer obtained in S1. Then, 3-fluoro-1,2-propanediol, 1,4-butanediol, and pentaerythritol are added to carry out a chain extension reaction. Then, 1,4-butanediamine is added to carry out a secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 100~120℃ and the reaction time is 2h. The secondary chain extension reaction temperature is 120~140℃ and the reaction time is 2h.

[0061] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 130°C. After drying for 2 hours, it is bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1°C / min.

[0062] The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 12°C / min.

[0063] Example 2

[0064] A modified polyurethane resin, comprising the following substances in parts by weight:

[0065] 70 kg of dicyclohexylmethane diisocyanate

[0066] 8 kg of 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate

[0067] Polyether 220 15kg and Polyether 330 15kg

[0068] 10kg of polydimethylsiloxane

[0069] 2 kg of 3-fluoro-1,2-propanediol, 2 kg of 1,4-butanediol

[0070] Pentaerythritol 3kg

[0071] 1,5-Pentanediamine 4kg

[0072] N-ethylmorpholine 0.8kg

[0073] 3kg of modified chitosan

[0074] 1 kg of modified ammonium nitrate for automotive airbags

[0075] 100 kg of ethyl acetate.

[0076] The preparation of the modified chitosan includes the following steps:

[0077] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, filter, and dry. The mass of the 3wt% hydrogen peroxide solution is five times the mass of the chitosan.

[0078] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, filter, and dry. The mass of the 0.2wt% sodium hydroxide solution is 4 times the mass of the dried chitosan.

[0079] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

[0080] The preparation method of the above-mentioned modified polyurethane resin includes the following steps:

[0081] S1: Add ethyl acetate to the reactor, then add dicyclohexylmethane diisocyanate, 2,2′-dimethyl-3,3′,5,5′-triphenylmethane, polyether 220, polyether 330, polydimethylsiloxane and N-ethylmorpholine, mix and react at 100~120℃ for 3h to obtain the prepolymer;

[0082] S2: The modified ammonium nitrate and modified chitosan of the car airbag are pulverized and mixed evenly and then added to the prepolymer obtained in S1. Then, 3-fluoro-1,2-propanediol, 1,4-butanediol and pentaerythritol are added to carry out a chain extension reaction. Then, 1,5-pentanediamine is added to carry out a secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 130~150℃ and the reaction time is 2h. The secondary chain extension reaction temperature is 120~140℃ and the reaction time is 2h.

[0083] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 130 and 150°C. After drying for 2 hours, it is bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1°C / min.

[0084] The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 12°C / min.

[0085] Example 3

[0086] A modified polyurethane resin, comprising the following substances in parts by weight:

[0087] 60kg of dicyclohexylmethane diisocyanate

[0088] 5 kg of 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate

[0089] Polyether 220 15kg and Polyether 330 15kg

[0090] 8kg of polydimethylsiloxane

[0091] 1.5 kg of 3-fluoro-1,2-propanediol and 1.5 kg of 1,4-butanediol

[0092] Pentaerythritol 3kg

[0093] 3 kg of 1,4-Butanediamine

[0094] N-ethylmorpholine 0.8kg

[0095] 3kg of modified chitosan

[0096] 1 kg of ammonium bicarbonate

[0097] 100 kg of ethyl acetate.

[0098] The preparation of the modified chitosan includes the following steps:

[0099] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, filter, and dry. The mass of the 3wt% hydrogen peroxide solution is five times the mass of the chitosan.

[0100] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, filter, and dry. The mass of the 0.2wt% sodium hydroxide solution is 4 times the mass of the dried chitosan.

[0101] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

[0102] The preparation method of the above-mentioned modified polyurethane resin includes the following steps:

[0103] S1: Add ethyl acetate to the reactor, then add dicyclohexylmethane diisocyanate, 2,2′-dimethyl-3,3′,5,5′-triphenylmethane, polyether 220, polyether 330, polydimethylsiloxane and N-ethylmorpholine, mix and react at 80~100℃ for 3h to obtain the prepolymer;

[0104] S2: After the ammonium bicarbonate and modified chitosan are pulverized and mixed evenly, they are added to the prepolymer obtained in S1. Then, 3-fluoro-1,2-propanediol, 1,4-butanediol, and pentaerythritol are added to carry out a chain extension reaction. Then, 1,4-butanediamine is added to carry out a secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 100~120℃ and the reaction time is 2h. The secondary chain extension reaction temperature is 120~140℃ and the reaction time is 2h.

[0105] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 130°C. After drying for 2 hours, it is bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1°C / min.

[0106] The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 12°C / min.

[0107] Example 4

[0108] A modified polyurethane resin, comprising the following substances in parts by weight:

[0109] 60kg of dimeric acid diisocyanate

[0110] 5 kg of 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate

[0111] Polyether 220 15kg and Polyether 330 15kg

[0112] 6kg of polydimethylsiloxane

[0113] 3 kg of 1,4-Butanediol

[0114] Pentaerythritol 3kg

[0115] 3 kg of 1,4-Butanediamine

[0116] N-ethylmorpholine 0.8kg

[0117] 3kg of modified chitosan

[0118] 80 kg of ethyl acetate.

[0119] The preparation of the modified chitosan includes the following steps:

[0120] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, filter, and dry. The mass of the 3wt% hydrogen peroxide solution is five times the mass of the chitosan.

[0121] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, filter, and dry. The mass of the 0.2wt% sodium hydroxide solution is 4 times the mass of the dried chitosan.

[0122] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

[0123] The preparation method of the above-mentioned modified polyurethane resin includes the following steps:

[0124] S1: Add ethyl acetate to the reactor, then add dimer diisocyanate, 2,2′-dimethyl-3,3′,5,5′-triphenylmethane, polyether 220, polyether 330, polydimethylsiloxane and N-ethylmorpholine, mix and react at 80~100℃ for 3h to obtain the prepolymer;

[0125] S2: After the modified chitosan is pulverized and mixed evenly, it is added to the prepolymer obtained in S1. Then, 3-fluoro-1,2-propanediol, 1,4-butanediol, and pentaerythritol are added to carry out a chain extension reaction. Then, 1,4-butanediamine is added to carry out a secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 100~120℃ and the reaction time is 2h. The secondary chain extension reaction temperature is 120~140℃ and the reaction time is 2h.

[0126] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 130°C. After drying for 2 hours, it is bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1°C / min.

[0127] The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 12°C / min.

[0128] Example 5

[0129] A modified polyurethane resin, comprising the following substances in parts by weight:

[0130] 60kg of dimeric acid diisocyanate

[0131] 5 kg of 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate

[0132] Polyether 220 15kg and Polyether 330 15kg

[0133] 6kg of polydimethylsiloxane

[0134] 1.5 kg of 3-fluoro-1,2-propanediol and 1.5 kg of 1,4-butanediol

[0135] Pentaerythritol 3kg

[0136] 3 kg of 1,4-Butanediamine

[0137] N-ethylmorpholine 0.8kg

[0138] 3kg of modified chitosan

[0139] 1 kg of ammonium bicarbonate.

[0140] The preparation of the modified chitosan includes the following steps:

[0141] S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, filter, and dry. The mass of the 3wt% hydrogen peroxide solution is five times the mass of the chitosan.

[0142] S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, filter, and dry. The mass of the 0.2wt% sodium hydroxide solution is 4 times the mass of the dried chitosan.

[0143] S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

[0144] The preparation method of the above-mentioned modified polyurethane resin includes the following steps:

[0145] S1: Diisocyanate dimer, 2,2′-dimethyl-3,3′,5,5′-triphenylmethane, polyether 220, polyether 330, polydimethylsiloxane and N-ethylmorpholine are added to the reaction vessel, mixed and reacted at a temperature of 80~100℃ for 3h to obtain the prepolymer.

[0146] S2: After the ammonium bicarbonate and modified chitosan are pulverized and mixed evenly, they are added to the prepolymer obtained in S1. Then, 3-fluoro-1,2-propanediol, 1,4-butanediol, and pentaerythritol are added to carry out a chain extension reaction. Then, 1,4-butanediamine is added to carry out a secondary chain extension reaction, and a mixture is obtained. The chain extension reaction temperature is 100~120℃ and the reaction time is 2h. The secondary chain extension reaction temperature is 120~140℃ and the reaction time is 2h.

[0147] S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 130°C. After drying for 2 hours, it is bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1°C / min.

[0148] The heating method in steps S1, S2, and S3 above is microwave heating.

[0149] The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 12°C / min.

[0150] Comparative Example 1

[0151] The modified chitosan component in Example 1 was removed, and everything else was the same as in Example 1, so it will not be repeated here.

[0152] Comparative Example 2

[0153] The further processing steps of the modified polyurethane resin in Example 1 are removed, and the rest is the same as in Example 1, so they will not be repeated here.

[0154] Comparative Example 3

[0155] Instead of adding the additives and modified chitosan after crushing and mixing them evenly in step S2 of Example 1 before the chain extension reaction, it is now added directly after chain extension without pre-crushing and mixing. The rest is the same as in Example 1, and will not be repeated here.

[0156] The modified polyurethane resins prepared in the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0157] Table 1 Performance Test Results

[0158]

[0159] Table 1 shows that the modified polyurethanes prepared in Examples 1-5 all exhibited good air permeability, water vapor permeability, elongation at break, and antibacterial rate. Example 4, with its reduced additives, showed decreased air permeability and water vapor permeability. Example 5, even under solvent-free and microwave heating conditions, still yielded a product with slightly reduced performance. Comparative Example 1 indicates that the modified chitosan powder exhibited good antibacterial properties. Comparative Example 2 shows that further processing of the polyurethane resin can improve the product's air permeability. Comparative Example 3 shows that the method and timing of adding additives and modified chitosan can significantly affect product performance.

Claims

1. A modified polyurethane resin, characterized in that, The substance includes the following parts by weight: 60-70 parts of diisocyanate 5-10 parts of tetraisocyanate 30-35 parts of polyether polyol 6-12 parts of polydimethylsiloxane 3-5 parts of diol 3-5 parts tetrahydric alcohol 3-5 parts of polyamines 0.8-1 part of N-ethylmorpholine 2-5 parts modified chitosan 0-2 parts of auxiliary agent Solvent: 0-150 parts; The diol is a mixture of 3-fluoro-1,2-propanediol and 1,4-butanediol, with a mass ratio of 3-fluoro-1,2-propanediol to 1,4-butanediol of (0~1):1, and the tetraol is pentaerythritol; The additive is modified ammonium nitrate or ammonium bicarbonate, wherein the modified ammonium nitrate is modified ammonium nitrate for use in automotive airbags.

2. The modified polyurethane resin according to claim 1, characterized in that, The diisocyanate is a dimeric acid diisocyanate or a dicyclohexylmethane diisocyanate, and the tetraisocyanate is 2,2′-dimethyl-3,3′,5,5′-triphenylmethane tetraisocyanate.

3. The modified polyurethane resin according to claim 1, characterized in that, The polyether polyol is a mixture of polyether 220 and polyether 330, with a mass ratio of 1:1 between the two.

4. The modified polyurethane resin according to claim 1, characterized in that, The polyamine is 1,4-butanediamine or 1,5-pentanediamine.

5. The modified polyurethane resin according to claim 1, characterized in that, The solvent is ethyl acetate.

6. The modified polyurethane resin according to claim 1, characterized in that, The preparation of the modified chitosan includes the following steps: S21: Soak chitosan in a 3wt% hydrogen peroxide solution for 30 minutes, then filter and dry. S22: Soak the dried chitosan from step S21 in a 0.2wt% sodium hydroxide solution for 30 minutes, then filter and dry. S23: The chitosan dried in step S22 is subjected to ultrasonic treatment for 1 hour to obtain modified chitosan, wherein the ultrasonic frequency is 25 kHz.

7. A method for preparing a modified polyurethane resin according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Add solvent to reaction vessel, then add diisocyanate, tetraisocyanate, polyether polyol, polydimethylsiloxane and N-ethylmorpholine, mix and react, the reaction temperature is 80~120℃, the reaction time is 2~4h, and the prepolymer is obtained. S2: After the additives and modified chitosan are pulverized and mixed evenly, they are added to the prepolymer obtained in S1. Then, diol and tetraol are added to carry out chain extension reaction. Then, polyamine is added to carry out secondary chain extension reaction to obtain a mixture. The chain extension reaction temperature is 90~140℃ and the reaction time is 1~2h. The secondary chain extension reaction temperature is 100~150℃ and the reaction time is 1~2h. S3: The mixture obtained in step S2 is uniformly coated onto the velvet release paper, and the temperature is maintained between 120 and 150°C. After drying for 2 to 3 hours, it is then bonded to the nonwoven fabric base and dried for another hour. After slowly cooling to room temperature, it is peeled off to obtain the modified polyurethane resin. The cooling rate during the slow cooling process is 0.1 to 0.2°C / min.

8. The method for preparing the modified polyurethane resin according to claim 7, characterized in that, The modified polyurethane resin requires further processing. The processing procedure is as follows: the prepared modified polyurethane resin is heated to 150°C, then rapidly cooled to 10°C, and then the cooled modified polyurethane resin is heated to 150°C again, and then rapidly cooled to 10°C to obtain the processed modified polyurethane resin. The cooling rate is 10~15°C / min.

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