Itaconic acid-based self-healing polyurethane containing dynamic disulfide bond, and preparation method and application thereof

Abstract

The application provides itaconic acid-based self-repairing polyurethane containing dynamic disulfide bonds, which is prepared from itaconic acid as a bio-based raw material through an esterification reaction-mercapto-ene click reaction-polymerization reaction in sequence. By using the technical scheme of the application, three hydroxyl groups are introduced at both ends and side chains of itaconic acid by using the conjugated structure of the carboxyl and double bond of itaconic acid, and then reacted with isocyanate and an amino compound containing a disulfide bond to form a crosslinked compound with a three-dimensional network structure; meanwhile, the disulfide bond with high exchange activity is introduced into the network structure, so that self-healing at a low temperature can be realized, and the polyurethane material is endowed with the functions of repeated processing and self-repairing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane materials, in particular to itaconic acid-based self-healing polyurethane containing dynamic disulfide bond and its preparation method and application. BACKGROUND

[0002] Polyurethane (PU), also known as polyurethane, is traditionally synthesized by polyaddition of polyisocyanate with short-chain and / or long-chain polyols, and then chain-extended with low molecular weight chain extender. Polyurethane materials have excellent elasticity, toughness, dimensional stability, and good resistance to oil, wear, low temperature, aging, and certain biocompatibility, and are widely used in furniture, transportation, automotive, electronic equipment, insulation, construction, adhesives and other fields. Because of the various applications of polyurethane in industry and daily life, its demand and output have grown rapidly in recent years.

[0003] Polyurethane can be divided into thermoplastic and thermoset according to whether there is a crosslinked network structure in the structure. Thermoset materials cannot be recycled / reprocessed due to permanent network structure. In order to solve these problems, dynamic reversible covalent bonds are introduced into polyurethane to create dynamic crosslinked networks. Dynamic covalent bond is a kind of covalent bond that can reversibly break and form under certain conditions, which can endow the crosslinked network with the characteristics of repeatable processing, self-healing, remoldability and recyclability. For example, Chinese invention patent CN113105607A discloses a self-healing polyurethane crosslinked network, which introduces UPy system with self-aggregation ability in the side chain, so that it can realize fast self-repairing at low temperature.

[0004] Dynamic covalent bond includes Diels-Alder bond, disulfide bond, borate bond, imine bond, carbamate bond, etc. Among them, disulfide bond is a dynamic chemical bond widely existing in living organisms. Compared with other dynamic covalent bonds, disulfide bond has higher exchange activity, so materials containing disulfide bond can realize self-healing at lower temperature, and it is one of the few covalent reversible chemical bonds that can exchange at room temperature. The introduction of dynamic disulfide bond into polyurethane material can endow it with self-repairing, shape memory, repeatable processing and other functions. For example, Chinese invention patent CN111423602A discloses a preparation method of self-healing polyurethane based on hydrogen bond and dynamic disulfide bond, which includes introducing multiple diisocyanate into low molecular weight unsaturated polyester to form hydroxyl-terminated unsaturated polyurethane; then grafting and introducing a prepolymer containing isocyanate group and dynamic disulfide bond on the hydroxyl group of the unsaturated polyurethane to form a polymer; the polymer is subjected to thiol-ene click reaction with a multi-thiol compound to obtain a self-healing polyurethane based on dynamic disulfide bond.

[0005] On the other hand, the polyols used in the prior art to prepare polyurethane are obtained from petroleum-based raw materials, and large-scale use will cause problems such as shortage of petrochemical resources, industrial environmental pollution, and overexploitation of resources, in order to solve these problems, it is necessary to develop environmentally friendly technologies and green, renewable biomass resources for the preparation of PU. Itaconic acid is a material produced by using Aspergillus terreus to ferment agricultural and sideline products such as starch, cane sugar, wood chips, and straw, it contains active carboxyl and double bond, both of which are in a conjugated relationship, and the properties are very active, and it is widely used in the chemical synthesis industry. At the same time, the annual output is huge, and the price is low, and it is selected by the US Department of Energy as one of the 12 potential bio-based platform chemicals. At present, itaconic acid is often used to prepare unsaturated polyester, polyamide and polyacrylate, etc. Using itaconic acid as a bio-based material to prepare bio-based polyurethane materials can reduce the cost of raw materials and provide a solution to renewable polyurethane materials, on the other hand, combining it with the self-repairing function, using itaconic acid as a raw material, using the conjugation properties of the carboxyl and double bond at both ends, bio-based polyurethane materials with self-repairing function can provide a certain idea for the development direction of bio-based polyurethane materials. SUMMARY

[0006] In view of the technical problems existing in the prior art, the present application discloses a kind of itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond and its preparation method and application, adopt itaconic acid as bio-based material, green and environmental protection, and cost is low, simple and easy to obtain.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme, a kind of itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond, structural formula is as follows:

[0008]

[0009] Among them, A is diisocyanate residue;B is aromatic or aliphatic functional group containing disulfide bond (-S-S-) or is the polymer residue formed after the polymerization of itaconic acid-based polyol, diisocyanate and amino compound with dynamic disulfide bond;N is a natural number greater than 0.

[0010] Preferably, A structural formula includes but is not limited to Any one of them.

[0011] B structural formula includes but is not limited to Any one of them.

[0012] Preferably, itaconic acid is used as a bio-based raw material, and the itaconic acid-based self-repairing polyurethane material containing dynamic disulfide bond is obtained by esterification reaction-mercapto-ene click reaction-polymerization in turn.

[0013] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0014] The structure of itaconic acid is as follows:

[0015] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0016] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0017] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0018] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0019] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0020] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0021] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0022] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0023] Preferably, the itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction using itaconic acid as raw material.

[0024] Preferably, the diisocyanate includes any one or a combination of two or more of diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate, and 4,4'-dicyclohexyl diisocyanate.

[0025] Preferably, the hydroxyl-containing mercapto compound includes one of mercaptoethanol, 6-mercapto-1-hexanol, 3-mercapto-1-propanol, and thioglycerol.

[0026] To achieve another object, the present application further provides another technical solution, a method for preparing the itaconic acid-based self-repairing polyurethane with dynamic disulfide bonds, and the specific steps include:

[0027] S1. Preparation of itaconic acid-based diol

[0028] A catalyst and a free radical inhibitor are added to itaconic acid and 1,6-hexanediol, and the reaction is carried out under a nitrogen atmosphere to obtain itaconic acid-based diol with hydroxyl groups at both ends; preferably, the reaction temperature is 130-140°C.

[0029] S2. Preparation of itaconic acid-based polyol

[0030] The itaconic acid-based diol and the hydroxyl-containing mercapto compound are added to a photoinitiator, and the itaconic acid-based polyol is obtained under ultraviolet conditions; preferably, the photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone; the ultraviolet conditions include an ultraviolet lamp power of 50W and a wavelength of 365nm.

[0031] S3. Preparation of itaconic acid-based self-repairing polyurethane with dynamic disulfide bonds

[0032] The itaconic acid-based polyol, the diisocyanate, and the amino compound with dynamic disulfide bonds are subjected to a curing reaction at 80°C to obtain a cured product; then the cured product is subjected to post-curing after being heated to 80-100°C to obtain the itaconic acid-based self-repairing polyurethane with dynamic disulfide bonds.

[0033] Preferably, the temperature of the curing reaction in S3 is 80-100°C, and the reaction time is 2-3h. The post-curing temperature is 100-120°C, and the reaction time is 2-3h.

[0034] In the prior art, the synthesis of polyurethane usually involves pre-polymerization of diol with excess diisocyanate, followed by chain extension or crosslinking. However, in the present application, itaconic acid is used as a raw material, and the carboxyl and double bond structures of itaconic acid are utilized to obtain itaconic acid-based polyol, which is then subjected to crosslinking reaction with diisocyanate and amino compound with dynamic disulfide bonds, thereby obtaining a three-dimensional crosslinking network structure.

[0035] Specifically, the two carboxyl groups of the end group of itaconic acid are reacted with 1,6-hexanediol by esterification to generate a diol, and the side group double bond of itaconic acid is relatively active, and a free radical inhibitor is used in the esterification reaction to prevent the double bonds from crosslinking with each other; then, the double bond of the side chain of itaconic acid is reacted with a hydroxyl-containing mercapto compound by a mercapto-ene click reaction, so as to introduce a hydroxyl group on the side chain of itaconic acid, and generate an itaconic acid-based polyol product with three hydroxyl groups; then, the product is reacted with diisocyanate and an amino compound containing a dynamic disulfide bond to prepare a polyurethane material. The introduced dynamic disulfide bond can endow the polyurethane material with a crosslinked network structure with the functions of remolding and self-repairing, and the strong hydrogen bond formed between the urea groups generated by the reaction of the amino group and the isocyanate group can also increase the mechanical properties and toughness of the polyurethane material. The raw material itaconic acid selected in the application is green and environmentally friendly, and is low in cost and easy to obtain, as compared with the traditional petroleum-based polyol raw material.

[0036] Since the self-repairing polyurethane prepared in the application has good mechanical strength and multiple self-repairing functions, it can be widely applied in the fields of adhesives, environmentally friendly coatings, biomimetic materials, aerospace and aviation materials or electronic components. In particular, as compared with the polyurethane with self-repairing function in the prior art, the application uses bio-based itaconic acid as a raw material, which can not only reduce the cost, but also provide certain ideas for the development direction of bio-based polyurethane materials.

[0037] Technical effects of the technical scheme of the application:

[0038] 1. By adopting the technical scheme of the application, three hydroxyl groups are introduced into the two ends and the side chain of itaconic acid by using the conjugated structure of the carboxyl group and the double bond of itaconic acid, and a crosslinked compound with a three-dimensional network structure is formed by the crosslinking action of the hydroxyl group and the amino group with diisocyanate; and a disulfide bond with high exchange activity is introduced into the network structure, so as to endow the polyurethane material with the functions of repeated processing and self-repairing.

[0039] 2. By adopting the technical scheme of the application, bio-based polyurethane material is prepared by using itaconic acid as a raw material, the raw material is derived from biomass, and is green, environmentally friendly and low in cost, so that the production cost of polyurethane is greatly reduced, and technical support is provided for the degradation and metabolism of polyurethane material.

[0040] 3. The polyurethane self-repairing material prepared by adopting the technical scheme of the application not only has high mechanical strength, but also realizes the functions of remolding and self-repairing by introducing a dynamic disulfide bond. Meanwhile, strong hydrogen bonds are formed between the urea groups generated by the reaction of the amino group and the isocyanate group, so as to increase the mechanical properties and toughness of the polyurethane material. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1This is a schematic diagram illustrating the synthesis principle of the itaconic acid-based self-healing polyurethane material containing dynamic disulfide bonds provided in Embodiment 1 of the present invention.

[0042] Figure 2 The infrared spectra of the polyurethane materials prepared in Examples 1-3 and Comparative Example 1 of this invention are shown.

[0043] Figure 3 The tensile property curves are for the polyurethane materials prepared in Examples 1-3 and Comparative Example 1 of this invention. Detailed Implementation

[0044] 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 are clearly and completely described. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0045] All patent and non-patent literature publications cited in this invention are incorporated herein by reference.

[0046] The terms “comprising,” “including,” “containing,” “covering,” “having,” “with,” or any other variations thereof, as used in this invention, are intended to cover non-exclusive inclusion. For example, a process, method, article of manufacture, or apparatus that includes a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to the process, method, article of manufacture, or apparatus. Furthermore, unless expressly stated otherwise, “or” means inclusive “or” rather than exclusive “or.” For example, condition A or B satisfies any of the following: A is real (or exists) and B is fictitious (or does not exist); A is fictitious (or does not exist) and B is real (or exists); and both A and B are real (or exist). The phrase “one or more” is intended to cover non-exclusive inclusion. For example, one or more A, B, and C means any of the following: A alone, B alone, C alone, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C.

[0047] Additionally, the terms "an" or "a" are used to describe the elements and components described herein. This is done solely for convenience and to provide a general meaning regarding the scope of the invention. This description should be understood to include one or at least one, one or at least one, and the singular includes the plural unless explicitly stated otherwise.

[0048] As used herein, the term "biologically derived" is used interchangeably with "bio-based" or "derived from a biological source" and refers to chemical compounds, both monomeric and polymeric, obtained from any renewable resource, in whole or in any part, including but not limited to, plant, animal, marine, or forestry materials. The "bio-based content" of any such compound shall be understood to be the percentage of the carbon content of the compound that has been obtained or derived from such renewable resource.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the disclosed compositions, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including the definitions herein, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0050] The present application provides a itaconic acid-based self-healing polyurethane material containing disulfide bond, which is prepared by esterification reaction-mercapto-ene click reaction-polymerization reaction in sequence using itaconic acid as bio-based raw material. The structural formula of the obtained material is shown as formula (I).

[0051] As one of the preferred embodiments, itaconic acid is used as raw material, and itaconic acid-based diol with terminal hydroxyl group is obtained by the esterification reaction.

[0052] As one of the preferred embodiments, the esterification reaction comprises reacting itaconic acid with 1,6-hexanediol in the presence of a catalyst and a free radical inhibitor to obtain itaconic acid-based diol with two hydroxyl groups at the terminal.

[0053] As one of the preferred embodiments, the catalyst is p-toluenesulfonic acid; and the addition amount is 0.2-0.7% of the mass of itaconic acid.

[0054] As one of the preferred embodiments, the free radical inhibitor is 4-methoxyphenol; and the addition amount is 0.3-0.7% of the sum of the amounts of substance of itaconic acid and 1,6-hexanediol.

[0055] As one of the preferred embodiments, the itaconic acid-based diol is subjected to mercapto-ene click reaction to obtain itaconic acid-based polyol.

[0056] Preferably, the mercapto-ene click reaction utilizes the double bond structure contained in the itaconic acid-based diol to react with the mercapto group contained in the hydroxyl-containing mercapto compound, thereby introducing an additional hydroxyl group to the side chain of the itaconic acid-based diol to obtain itaconic acid-based polyol.

[0057] As one of the preferred embodiments, the hydroxyl-containing thiol compound includes one of mercaptoethanol, 6-mercapto-1-hexanol, 3-mercapto-1-propanol, and thioglycerol.

[0058] As one of the preferred embodiments, itaconic acid polyol is polymerized with diisocyanate and a compound containing dynamic disulfide bonds to obtain an itaconic acid self-healing polyurethane material containing dynamic disulfide bonds as shown in structural formula (I).

[0059] As one of the preferred embodiments, the amino compound containing dynamic disulfide bonds includes any one or both of 4,4'-dithiodiphenylamine and 2,2'-dithiodiphenylamine.

[0060] As one preferred embodiment, the diisocyanate includes any one or a combination of two or more of diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate and 4,4'-dicyclohexyl diisocyanate.

[0061] The technical solution, implementation process, and principle of the present invention will be further explained and illustrated below through specific embodiments. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. The described embodiments are merely some embodiments of the present invention, and not all embodiments. 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. Unless otherwise stated, the reagents and raw materials used in the following embodiments are commercially available, and the test methods without specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers. Furthermore, unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in the present invention all employ conventional techniques in this technical field. These techniques have been well described in existing literature.

[0062] Example 1

[0063] This embodiment provides a method for preparing a self-healing polyurethane material containing disulfide bonds based on itaconic acid. The synthesis steps of this method are described in [reference needed]. Figure 1 The following raw materials, itaconic acid, 1,6-hexanediol, and 6-mercapto-1-hexanol, were purchased from Aladdin, and 4,4'-dithiodiphenylamine was purchased from Anaiji.

[0064] like Figure 1As shown, itaconic acid reacts with 1,6-hexanediol to form itaconic acid-based diol; itaconic acid-based diol reacts with 6-mercapto-1-hexanol under UV to perform thiol-ene click reaction, and a hydroxyl group is introduced again in the side chain of itaconic acid to obtain itaconic acid-based polyol; itaconic acid-based polyol is subjected to curing reaction with 4,4'-dicyclohexyl methane diisocyanate and aromatic disulfide 4,4'-dithiodianiline; during the curing process, strong hydrogen bonds are formed between the urea groups generated by the reaction of amino groups and isocyanate groups, and a large number of crosslinking sites and exchangeable disulfide bonds are generated; after further post-curing, itaconic acid-based polyurethane material containing disulfide bonds is obtained. The disulfide bond has high exchange activity, and the covalent reversible exchange reaction can be realized at room temperature, so that the polyurethane material has self-healing function at low temperature.

[0065] Specifically, the synthesis steps include:

[0066] (1) Preparation of itaconic acid-based diol

[0067] Itaconic acid and 1,6-hexanediol are added into a 250ml three-necked flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet according to a molar ratio of 1:2. p-Toluenesulfonic acid (0.5% relative to the mass of itaconic acid) and 4-methoxyphenol (0.5% relative to the total amount of substance of itaconic acid and 1,6-hexanediol) are added into the flask as catalyst and free radical inhibitor, respectively. The mixture is stirred under a nitrogen atmosphere at 140°C, the reaction time is 3h, and after the reaction is completed, vacuum is applied at 90°C for 1h to remove water to obtain itaconic acid-based diol with hydroxyl groups at the end.

[0068] (2) Preparation of itaconic acid-based polyol

[0069] Itaconic acid-based diol and 6-mercapto-1-hexanol are added into a beaker according to a molar ratio of 1:1, and a photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173 photoinitiator) is added, the mass of which is 0.2% of the total mass of itaconic acid-based diol and 6-mercapto-1-hexanol. After stirring under the condition of a 50W 365nm ultraviolet lamp for 2h, itaconic acid-based polyol is obtained.

[0070] (3) Preparation of itaconic acid-based self-repairing polyurethane material containing disulfide bonds

[0071] This step includes primary curing and secondary curing, and the specific steps include:

[0072] a. Primary curing

[0073] Into a 20ml sample bottle, 4,4'-dicyclohexylmethane diisocyanate, itaconic acid based polyol and aromatic disulfide 4,4'-dithiodianiline (dissolved with N,N-dimethylformamide) were added according to the molar ratio of 15:9:1.5 (-OH:-NH2=9:1), a catalyst dibutyltin dilaurate was added, stirred uniformly, and then cured at 80°C for 3h to obtain a cured product.

[0074] b. Secondary curing

[0075] The cured product obtained by the first curing was placed in a vacuum oven for secondary curing at 100°C for 3h to obtain an itaconic acid based self-healing polyurethane material containing disulfide bond.

[0076] The polyurethane material sample was cut into dumbbell-shaped tensile samples, and tensile test was performed at room temperature according to international standard ISO 527-1:2012. It was found that the tensile strength of the material was 3.6MPa, the elongation at break was 72.3%, and the Young's modulus was 43.9MPa.

[0077] Example 2

[0078] The difference between this example and Example 1 is that in step (3), the molar ratio of 4,4'-dicyclohexylmethane diisocyanate, itaconic acid based polyol and 4,4'-dithiodianiline is 15:8:3 (-OH:-NH2=8:2), and the other steps are the same as Example 1. The tensile strength of the material is 5.4MPa, the elongation at break is 60.9%, and the Young's modulus is 105.1MPa.

[0079] Example 3

[0080] The difference between this example and Example 1 is that in step (3), the molar ratio of 4,4'-dicyclohexylmethane diisocyanate, itaconic acid based polyol and 4,4'-dithiodianiline is 15:7:4.5 (-OH:-NH2=7:3), and the other steps are the same as Example 1. The tensile strength of the material is 12.9MPa, the elongation at break is 39%, and the Young's modulus is 347.7MPa.

[0081] Example 4

[0082] The difference between this example and Example 1 is that in step (3), the molar ratio of 4,4'-dicyclohexylmethane diisocyanate, itaconic acid based polyol and 4,4'-dithiodianiline is 15:6:6 (-OH:-NH2=6:4), and the other steps are the same as Example 1. The tensile strength of the material is 17.2MPa, the elongation at break is 6.4%, and the Young's modulus is 549.4MPa.

[0083] Example 5

[0084] The difference between this example and Example 1 is that in step (3), the polymerization temperature of 80°C is replaced by 100°C, and the other steps are the same as those of Example 1.

[0085] The sample is cut into dumbbell-shaped tensile samples, and it is found through testing on a universal material testing machine that the tensile strength of the material is 3.5 MPa, the elongation at break is 70.1%, and the Young's modulus is 41.5 MPa.

[0086] Example 6

[0087] The difference between this example and Example 1 is that in step (2), the mercapto compound 6-mercapto-1-hexanol is replaced by mercaptoethanol, and the other steps are the same as those of Example 1.

[0088] The sample is cut into dumbbell-shaped tensile samples, and it is found through testing on a universal material testing machine that the tensile strength of the material is 3.3 MPa, the elongation at break is 56%, and the Young's modulus is 63.4 MPa.

[0089] Example 7

[0090] The difference between this example and Example 1 is that in step (3), the para-disulfide 4,4'-dithiodianiline is replaced by the ortho-disulfide 2,2'-dithiodianiline, and the other steps are the same as those of Example 1.

[0091] The sample is cut into dumbbell-shaped tensile samples, and it is found through testing on a universal material testing machine that the tensile strength of the material is 3.5 MPa, the elongation at break is 69.3%, and the Young's modulus is 45.7 MPa.

[0092] Example 8

[0093] The difference between this example and Example 1 is that in step (3), 4,4'-dicyclohexylmethane diisocyanate is replaced by hexamethylene diisocyanate, and the other steps are the same as those of Example 1.

[0094] The sample is cut into dumbbell-shaped tensile samples, and it is found through testing on a universal material testing machine that the tensile strength of the material is 2.8 MPa, the elongation at break is 80.1%, and the Young's modulus is 23.9 MPa.

[0095] Example 9

[0096] The difference between this example and Example 1 is that in step (3), 4,4'-dicyclohexylmethane diisocyanate is replaced by diphenylmethane diisocyanate, and the other steps are the same as those of Example 1.

[0097] The sample was cut into dumbbell-shaped tensile sample, and it was found by testing on the universal material testing machine that the tensile strength of the material was 4.2 MPa, the elongation at break was 65.1%, and the Young's modulus was 63.6 MPa.

[0098] Comparative Example 1

[0099] The difference between the present comparative example and Example 1 is that in step (3), only itaconic acid-based polyol and 4,4'-dicyclohexylmethane diisocyanate are added, the molar ratio is 1:1.5, and 4,4'-dithiodianiline is not added, and the other steps are the same as those of Example 1.

[0100] The sample was cut into dumbbell-shaped tensile sample, and it was found by testing on the universal material testing machine that the tensile strength of the material was 2.54 MPa, the elongation at break was 79%, and the Young's modulus was 21.6 MPa.

[0101] Comparative Example 2

[0102] The difference between the present comparative example and Example 1 is that in step (3), itaconic acid polyol is replaced by itaconic acid diol prepared in step (1), and the other steps and parameters are the same as those of Example 1. It is found that the material prepared in the present comparative example is too soft and basically has no mechanical properties. The reason is analyzed: it is possible that the carbon chain of diol is short and no cross-linking structure is formed, resulting in low molecular weight.

[0103] Table 1 Comparison of mechanical properties of examples and comparative examples

[0104] Tensile strength / MPa Elongation at break / % Young's modulus / MPa Self-repairing efficiency (%) Example 1 3.6 72.3 43.9 68.3 Example 2 5.4 60.9 105.1 72.1 Example 3 12.9 39.4 347.7 79.0 Example 4 17.2 6.4 549.4 82.4 Example 5 3.5 70.1 41.5 70.1 Example 6 3.3 56.3 63.4 66.5 Example 7 3.5 63.9 45.7 67.2 Example 8 2.8 80.1 39.0 70.0 Example 9 4.2 65.1 63.6 67.2 Comparative Example 1 2.5 79.2 21.6 /

[0105] Referring to Table 1, the mechanical properties and self-repairing properties of Examples 1-9 and Comparative Examples 1-2 of the present application are compared.

[0106] Among them, the self-repairing effect is the self-healing efficiency The self-repairing property of the material is represented. Among them, σ0 is the tensile strength of the original material, σ h is the tensile strength of the material after repair (80℃, 12h).

[0107] As can be seen from Table 1, Examples 1-4 are polyurethane materials prepared under the condition that the molar ratio of -OH:-NH2 in itaconic acid-based polyol and 4,4'-dithiodianiline is 9:1, 8:2, 7:3 and 6:4 respectively. As can be seen from the results in Table 1, with the increase of the proportion of -NH2, the content of benzene ring also increases, the tensile strength and Young's modulus gradually increase, and the elongation at break gradually decreases.

[0108] The embodiments 1 and 5 are the embodiments of different polymerization temperatures, and it can be seen from Table 1 that the polymerization temperature is increased, and the influence on the tensile strength, elongation at break and Young's modulus is not large, and the temperature increase only influences the reaction rate and does not cause influence on the performance of the material.

[0109] The difference between the embodiment 1 and the embodiment 6 is only that the hydroxyl-containing mercapto compounds with different carbon numbers are replaced, and it is shown from the results that the elongation at break is reduced by using different hydroxyl-containing mercapto compounds, because the chain segment activity is limited by using the mercapto compounds with shorter carbon chains.

[0110] The difference between the embodiment 1 and the embodiment 7 is only that different diphenylamine compounds are replaced, and similarly, it is shown from the results that the influence on the tensile strength and elongation at break is not large by using different positions of the diamino diphenylamine compounds, and it is indicated that the substitution position of the amino group has little influence on the performance of the material.

[0111] The difference between the embodiment 1 and the embodiments 8-9 is only that different diisocyanates are replaced, the diisocyanate with a fatty chain used in the embodiment 8 can reduce the tensile strength and Young's modulus, increase the elongation at break and the self-repairing efficiency; and the diisocyanate containing a benzene ring used in the embodiment 9 can increase the tensile strength and Young's modulus, but reduce the elongation at break, and accordingly, the self-repairing efficiency is slightly reduced.

[0112] Further, it can be seen from the self-repairing rate results in Table 1 that the self-repairing rate of the polyurethane material prepared by using the technical solutions in the embodiments 1-7 can be more than 67%, and the self-repairing efficiency is increased with the increase of the disulfide bond content. Especially, the self-repairing rate of the embodiment 4 is greater than 82%, and obviously, the itaconic acid-based polyurethane material with self-repairing property is prepared by using the technical solutions of the application.

[0113] Referring to Figure 2 , the infrared spectrum of the embodiments 1-3 and the comparative example 1 of the application, it can be seen from the figure that the characteristic peak of -NCO at 2270 cm -1 disappears, the characteristic peak of -NH- in the urethane appears at 3380 cm -1 and 1530 cm -1 , and the peak intensity of the urea group -NH-CO-NH- at 1600 cm -1 is increased with the increase of the amount of -NH2, which proves the successful synthesis of the material.

[0114] Referring to Figure 3 , the tensile property curve of the embodiments 1-3 and the comparative example 1 of the application, with the increase of the proportion of -NH2, the content of the benzene ring is also increased, the tensile strength and Young's modulus are gradually increased, and the elongation at break is gradually reduced.

[0115] In summary, the polyurethane with dynamic self-repairing function can be prepared by using the bio-based itaconic acid as raw material according to the technical scheme of the application, and the cost of the dynamic self-repairing polyurethane material can be greatly reduced.

[0116] From the performance analysis, the conjugated performance characteristics of the special carboxyl and double bond at both ends of itaconic acid are utilized, itaconic acid polyol (itaconic acid triol) is obtained by esterification and alkyne click reaction, and then the itaconic acid polyol can be polymerized with diisocyanate to obtain a polymer macromolecule with cross-linking and stereonetwork structure, and an amino compound with a dynamic disulfide bond is introduced to endow the network structure with self-repairing function, so that the obtained polyurethane material can realize repeated processing and utilization. Especially, the amino compound with a dynamic disulfide bond also includes a benzene ring structure, which provides rigid support for the polyurethane material, and as the amount of the amino compound with a dynamic disulfide bond increases, the tensile strength and Young's modulus also gradually increase, so that the polyurethane material has good mechanical strength and multiple self-repairing functions, thereby further expanding the application field of the polyurethane material, and the polyurethane material can be applied in the fields of adhesives, environmentally friendly coatings, biomimetic materials, aerospace and aviation materials, or electronic components, etc.

[0117] The above is only the preferred embodiment of the present application, and does not limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and variations. Any change, modification, replacement, integration and parameter change of the embodiments within the spirit and principles of the present application, which can realize the same function without departing from the principles and spirit of the present application, falls within the protection scope of the present application.

Claims

1. Itaconic acid based self-healing polyurethane containing dynamic disulfide bonds, characterized by, The structural formula (I) is as follows: A is a diisocyanate residue; B is a polymer residue formed by polymerization of itaconic acid-based polyol, diisocyanate and amino compound containing dynamic disulfide bond; n is a natural number greater than 0; The itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond is prepared by using itaconic acid as a bio-based raw material, and sequentially performing esterification reaction-mercapto-ene click reaction-polymerization reaction. The esterification reaction includes introducing a hydroxyl group by performing esterification reaction of the terminal carboxyl group of itaconic acid with 1,6-hexanediol, to obtain itaconic acid-based diol with terminal hydroxyl group. The mercapto-ene click reaction uses the double bond structure contained in the itaconic acid-based diol to react with the mercapto group in the hydroxyl-containing mercapto compound, to introduce another hydroxyl group in the side chain of the itaconic acid-based diol, and obtain itaconic acid-based polyol. The itaconic acid-based polyol is polymerized with diisocyanate and compound containing dynamic disulfide bond to obtain itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond as shown in structural formula (I). The hydroxyl-containing mercapto compound is 6-mercapto-1-hexanol.

2. The itaconic acid based self-healing polyurethane containing dynamic disulfide bonds according to claim 1, wherein, The esterification reaction includes reacting the itaconic acid with 1,6-hexanediol in the presence of a catalyst and a free radical inhibitor to obtain itaconic acid-based diol with two terminal hydroxyl groups.

3. The itaconic acid based self-healing polyurethane containing dynamic disulfide bonds according to claim 2, wherein, The catalyst includes p-toluenesulfonic acid; the addition amount is 0.2-0.7% of the mass of the itaconic acid.

4. The itaconic acid based self-healing polyurethane containing dynamic disulfide bonds according to claim 2, wherein, The free radical inhibitor includes 4-methoxyphenol; the addition amount is 0.3-0.7% of the sum of the amounts of substances of the itaconic acid and 1,6-hexanediol.

5. The itaconic acid based self-healing polyurethane containing dynamic disulfide bonds according to claim 2, wherein, The molar ratio of the itaconic acid to 1,6-hexanediol is 1:2-1:2.

2.

6. The itaconic acid based self-healing polyurethane containing dynamic disulfide linkages of claim 1, wherein, In the polymerization reaction, the amount of isocyanate (-NCO) fixed, and the molar ratio of amino group in the amino compound containing dynamic disulfide bond to amino group and hydroxyl group in the polyol is 9:1-6:

4.

7. The itaconic acid based self-healing polyurethane containing dynamic disulfide linkages of claim 1 wherein, The diisocyanate includes any one or a combination of two or more of diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate and 4,4'-dicyclohexyl diisocyanate.

8. The itaconic acid based self-healing polyurethane containing dynamic disulfide bonds according to claim 1, wherein, The amino compound containing dynamic disulfide bond is dithiodiphenylamine.

9. A process for the preparation of itaconic acid based self-healing polyurethanes containing dynamic disulfide bonds as claimed in any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1. Preparation of itaconic acid-based diol A catalyst and a free radical inhibitor are added to itaconic acid and 1,6-hexanediol, and the mixture is reacted under a nitrogen atmosphere to obtain itaconic acid-based diol with two terminal hydroxyl groups; S2. Preparation of itaconic acid-based polyol The itaconic acid-based diol and a hydroxyl-containing mercapto compound are added to a photoinitiator, and the mixture is subjected to ultraviolet treatment to obtain itaconic acid-based polyol; S3. Preparation of itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond The itaconic acid-based polyol, diisocyanate and amino compound containing dynamic disulfide bond are subjected to curing reaction to obtain a cured product; after heating, post-curing is continued to obtain itaconic acid-based self-repairing polyurethane containing dynamic disulfide bond as shown in structural formula (I).

10. The method for preparing itaconic acid-based self-healing polyurethane containing dynamic disulfide bond according to claim 9, characterized in that, In S3, the curing reaction includes primary curing reaction and secondary curing reaction; The temperature of the primary curing reaction is 80-100℃, and the reaction time is 2-3h; And / or, the temperature of the secondary curing reaction is 100-120℃, and the reaction time is 2-3h.

11. Use of the dynamic disulfide bond-containing itaconic acid-based self-healing polyurethane according to any one of claims 1-8, or prepared by the method according to claim 9 or 10, in adhesives, environmentally friendly coatings, electronic devices or aerospace.

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