Solvent-free polyurea material based on activated carboxylic acid and preparation method thereof

Abstract

The invention discloses a solvent-free polyurea material based on activated carboxylic acid and a preparation method thereof, and the preparation method comprises the following steps: mixing an amino compound component with activated carboxylic acid, then adding an isocyanate component, uniformly mixing, and reacting to obtain the solvent-free polyurea material. According to the invention, the reaction of amino and isocyanate is inhibited by activating carboxylic acid, and amino is protonized by introducing carboxylic acid, so that the amino and isocyanate do not react during mixing so as to realize uniform mixing; under the mild heating condition, the activated carboxylic acid is decomposed under the action of alkalinity, namely an amino compound, carbon dioxide is generated and loses acidity, protonated amino is promoted to be dissociated to form active amino, and the active amino reacts with isocyanate; in the heating process, amido is not only a catalyst for catalyzing and activating carboxylic acid decomposition, but also a substrate for reacting with isocyanate; and after the decomposition of the activated carboxylic acid is completed, the protonated amido is thoroughly dissociated and reacts with isocyanate to form a polyurea material, so that solvent-free preparation is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurea materials, and in particular to a solvent-free polyurea material based on activated carboxylic acid and a preparation method thereof. Background Art

[0002] Polyurea and polyurethane (PU) have similar molecular structures, including polysiloxane-polyurea, polyurethane-polyurea, and polyamide-urea-polyurea. The difference is that polyurethane is prepared by the reaction of hydroxyl groups and isocyanates, while polyurea is prepared by the reaction of amine groups and isocyanates. Polyurea materials possess excellent elasticity, and the introduction of urea bonds imparts self-healing and reworkability, enabling reuse and recycling. Unlike polyurethane, the preparation of polyurea requires the use of large amounts of solvent. Amine groups, especially primary amines, are highly reactive with isocyanates, leading to rapid molecular chain growth and entanglement, resulting in gelation. The addition of solvents not only dilutes the reactant concentration and slows the reaction rate, but also rapidly releases heat, suppressing the temperature rise of the reaction system and slowing the self-accelerating reaction. It also disrupts the dense hydrogen bonds between urea bonds, preventing gel formation and achieving uniform material preparation. The use and removal of solvents, especially high-boiling-point solvents, during preparation raise environmental, energy, and cost issues, hindering the use of polyurea materials in transportation, consumer goods, and other fields. Therefore, achieving solvent-free preparation of polyurea materials is a pressing technical challenge that needs to be addressed.

[0003] One strategy involves capping isocyanates to prepare reactive blocked isocyanates. Heat is then used to control the dissociation of the isocyanate, releasing the isocyanate bond to react with active hydrogen. However, the use of reactive blocked isocyanates presents the following challenges: ① Removal of the blocking agent typically requires high temperatures, which can cause side reactions with functional groups in the system, such as furan and thiol, affecting the mechanical properties and processability of the material; ② The structure of the introduced amine group lacks tunability, such as by reacting isocyanates with water to produce amino groups; and ③ Complete removal of the blocking agent is difficult, especially considering ketoxime compounds, which require high-temperature removal.

[0004] Another strategy involves protecting the amine group, controlling its release under stimulation to regulate the reaction rate between isocyanate and amine groups. However, the following challenges exist: 1) The synthesis and, in particular, the separation of protected amines is cumbersome, requiring column separation and making large-scale production difficult; 2) Heating and removing the protecting group at high temperatures can easily cause side reactions; and 3) UV deprotection requires high transparency and thickness, limiting its application. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a solvent-free polyurea material based on activated carboxylic acid and a preparation method thereof.

[0006] The technical solutions of the present invention are as follows: In one aspect, a method for preparing a solvent-free polyurea material based on activated carboxylic acid is provided, comprising the following steps: The amino compound component and the activated carboxylic acid are mixed, and then the isocyanate component is added and mixed evenly, and heated for reaction to obtain the solvent-free polyurea material.

[0007] Preferably, the isocyanate component is a diisocyanate monomer, a polyisocyanate monomer or an isocyanate-terminated prepolymer.

[0008] Preferably, the diisocyanate monomer is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0009] Preferably, the isocyanate-terminated prepolymer is a prepolymer of isocyanate and polyol or polyamine.

[0010] Preferably, the activated carboxylic acid is any one or more of 2-phenyl-2-cyanopropionic acid, 2-(4-chlorophenyl)-2-cyanopropionic acid, 2-(4-tolyl)-2-cyanopropionic acid, 2-(4-methoxyphenyl)-2-cyanopropionic acid, trichloroacetic acid, tribromoacetic acid, and nitroacetic acid.

[0011] Preferably, the amino compound component is a chain extender containing an amine group.

[0012] Preferably, the chain extender containing an amine group is any one or more of hydrazide, primary amine, and secondary amine.

[0013] Preferably, the molar ratio of the amino group in the amino compound component, the carboxyl group in the activated carboxylic acid, and the isocyanate component is 1:0.1-1:1.

[0014] Preferably, the heating reaction is carried out at 45-120° C. for 12-48 hours.

[0015] On the other hand, a solvent-free polyurea material based on activated carboxylic acid is also provided, which is prepared by any of the above methods for preparing a solvent-free polyurea material based on activated carboxylic acid.

[0016] The beneficial effects of the present invention are: The present invention does not require additional synthesis and purification steps to protect isocyanate or amino groups, and only requires the addition of activated carboxylic acid for protonation. The activation of the amino group is catalyzed by the presence of a substrate amine under mild heating conditions without the use of an additional catalyst. The acid decomposes to produce carbon dioxide and low-boiling-point hydrocarbons, and no by-products remain in the material system, which does not affect the performance of the final material. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of infrared spectra of polyurea materials of Example 1, Example 2 and Comparative Example 2; Figure 2 is the tensile stress-strain curve of polysiloxane-polyurea of ​​Example 1; Figure 3 is the tensile stress-strain curve of polyetheramine-polyurea of ​​Example 2; Figure 4 This is the tensile stress-strain curve of polyetheramine-polyurea of ​​comparative example 2. DETAILED DESCRIPTION

[0019] The present invention is further described below with reference to the accompanying drawings and examples. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0020] On the one hand, the present invention provides a method for preparing a solvent-free polyurea material based on activated carboxylic acid, comprising the following steps: mixing an amino compound component with an activated carboxylic acid, then adding an isocyanate component and mixing them evenly, and heating the reaction to obtain the solvent-free polyurea material.

[0021] In the present invention, an activated carboxylic acid is used to inhibit the reaction between amine groups and isocyanates. The introduction of the carboxylic acid protonates the amino groups, preventing them from reacting during mixing and achieving uniform mixing. A unique feature is that under mild heating conditions, the activated carboxylic acid decomposes under the action of an alkaline amino compound, producing carbon dioxide, which loses its acidity. This promotes the dissociation of the protonated amino groups into active amine groups, which then react with the isocyanate. During the heating process, the amine groups act as both a catalyst for the decomposition of the activated carboxylic acid and a substrate for the reaction with the isocyanate. Following the completion of decomposition of the activated carboxylic acid, the protonated amine groups completely dissociate and react with the isocyanate to form a polyurea material, enabling solvent-free preparation.

[0022] In addition, it should be noted that if the isocyanate component used has good acid resistance, the isocyanate component can be mixed with the activated carboxylic acid first, and then the amino compound component can be mixed.

[0023] In a specific embodiment, the isocyanate component is a diisocyanate monomer, a polyisocyanate monomer, or an isocyanate-terminated prepolymer. Optionally, the diisocyanate monomer is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; and the isocyanate-terminated prepolymer is a prepolymer of an isocyanate and a polyol or a polyamine.

[0024] In a specific embodiment, the activated carboxylic acid is any one or more of 2-phenyl-2-cyanopropionic acid, 2-(4-chlorophenyl)-2-cyanopropionic acid, 2-(4-tolyl)-2-cyanopropionic acid, 2-(4-methoxyphenyl)-2-cyanopropionic acid, trichloroacetic acid, tribromoacetic acid, and nitroacetic acid.

[0025] In a specific embodiment, the amino compound component is an amine-containing chain extender. Optionally, the amine-containing chain extender is any one or more of hydrazide, primary amine, and secondary amine.

[0026] In a specific embodiment, the molar ratio of the amine group in the amino compound component, the carboxyl group in the activated carboxylic acid, and the isocyanate component is 1:0.1-1:1.

[0027] In a specific embodiment, the heating reaction is carried out at 45-120° C. for 12-48 hours.

[0028] On the other hand, the present invention further provides a solvent-free polyurea material based on activated carboxylic acid, which is prepared by any of the above methods for preparing a solvent-free polyurea material based on activated carboxylic acid.

[0029] Example 1 A solvent-free polyurea material based on activated carboxylic acid is prepared by the following steps: adding trichloroacetic acid (3.912 g, 0.024 mol, 1 eq.) to isocyanate-terminated propyl polyethylene glycol-terminated polydimethylsiloxane C15 with a molecular weight of 1000 g / mol (prepolymerized by prepolymerizing isophorone diisocyanate (5.334 g, 0.024 mol, 1 eq) and propyl polyethylene glycol-terminated polydimethylsiloxane (12 g, 0.012 mol, 2 eq)), adding N-methyl-1,3-propylenediamine (1.06 g, 0.012 mol, 1 eq) while stirring, stirring evenly, and then placing the mixture in an 80°C oven for reaction for 48 hours to obtain the solvent-free polyurea material.

[0030] Example 2 A solvent-free polyurea material based on activated carboxylic acid is prepared by the following steps: adding trichloroacetic acid (3.26 g, 0.02 mol, 2 eq) to a mixed solution of polyetheramine ED600 (6 g, 0.01 mol, 2 eq) with a molecular weight of 600 g / mol and N-methyl-1,3-propylenediamine (0.8815 g, 0.01 mol, 2 eq), stirring the mixture until uniform, then adding a mixed solution of isophorone diisocyanate (4 g, 0.018 mol, 1.8 eq) and hexamethylene diisocyanate isocyanurate trimer (0.672 g, 0.0013 mol, 0.13 eq), stirring the mixture until uniform, and then placing the mixture in an 80°C oven for reaction for 48 hours to obtain the solvent-free polyurea material.

[0031] It should be noted that the above embodiments are only some embodiments of the present invention. The polyurea material can also be prepared by using other activated carboxylic acids (such as 2-phenyl-2-cyanopropionic acid, 2-(4-chlorophenyl)-2-cyanopropionic acid, 2-(4-tolyl)-2-cyanopropionic acid, 2-(4-methoxyphenyl)-2-cyanopropionic acid, tribromoacetic acid, nitroacetic acid or a mixture thereof), other isocyanate components, other amino compound components, and changing parameters such as heating temperature and time.

[0032] Comparative Example 1 The difference from Example 2 is that in this comparative example, acetic acid, which also contains a carboxyl group, is not activated carboxylic acid.

[0033] In this comparative example, no polyurea material could be obtained using this method.

[0034] Comparative Example 2 A polyurea material is prepared by a solvent method, specifically comprising the following steps: adding 6 g of polyetheramine ED600 (0.01 mol, 2 eq) with a molecular weight of 600 g / mol and N-methyl-1,3-propylenediamine (0.8815 g, 0.01 mol, 2 eq) to 18 ml of tetrahydrofuran (THF); stirring the mixture uniformly; then slowly adding dropwise a mixed solution of isophorone diisocyanate (4 g, 0.018 mol, 1.8 eq) and hexamethylene diisocyanate isocyanurate trimer (0.672 g, 0.0013 mol, 0.13 eq); stirring the mixture uniformly; reacting the mixture at room temperature for 6-8 hours; then pouring the mixture into a mold to form a film; and placing the film in an 80°C oven for 24 hours to remove the THF solvent, thereby obtaining the polyurea material.

[0035] The materials obtained in each embodiment and comparative example 2 were subjected to infrared spectrum test, and the results were as follows: Figure 1 As shown. Figure 1It can be seen that Example 1 successfully prepared a polysiloxane-polyurea material, and Example 2 and Comparative Example 2 successfully prepared a polyetheramine-polyurea material.

[0036] The tensile properties of the materials obtained in each embodiment and comparative example 2 were tested, and the results are as follows: Figure 2-4 As shown. Figure 2-4 It can be seen that the strength of the polysiloxane-polyurea material of Example 1 can reach 2.2 MPa, and the elongation at break can reach 450%; the strength of the polyetheramine-polyurea material of Example 2 can reach 18.8 MPa, and the elongation at break can reach 337%; while the elongation at break of the polyetheramine-polyurea material of Comparative Example 2 can reach 600%, but the strength is only 10 MPa.

[0037] Comparing the performance of the materials of Example 2 and Comparative Example 2, it can be seen that the polyurea material prepared without solvent in the present invention not only has excellent elongation at break performance, but also has better strength than the polyurea material prepared by the solvent method.

[0038] It should be noted that the above test examples are only test results of some embodiments of the present invention. By changing the specific reagents of the isocyanate component, activated carboxylic acid, and amino compound component, as well as parameters such as temperature and time, polyurea materials can also be prepared under solvent-free conditions, and they all have similar properties, can maintain excellent elongation at break, and have higher strength than the solvent method.

[0039] In summary, the present invention can utilize activated carboxylic acid to prepare polyurea materials with excellent performance under solvent-free conditions. Compared with the prior art, the present invention is a significant improvement.

[0040] The above description is merely a representative embodiment of the present invention and does not constitute any form of limitation to the present invention. Any technical personnel familiar with the present invention who, without departing from the scope of the technical solution of the present invention, makes slight changes or modifications to the embodiments disclosed above using the technical contents disclosed above are equivalent embodiments of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a solvent-free polyurea material based on activated carboxylic acid, characterized in that: The following steps are involved: The amino compound component and the activated carboxylic acid are mixed, and then the isocyanate component is added and mixed evenly, and heated for reaction to obtain the solvent-free polyurea material.

2. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 1, characterized in that: The isocyanate component is a diisocyanate monomer, a polyisocyanate monomer or an isocyanate-terminated prepolymer.

3. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 2, characterized in that: The diisocyanate monomer is any one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

4. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 2, characterized in that: The isocyanate-terminated prepolymer is a prepolymer of isocyanate and polyol or polyamine.

5. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 1, characterized in that: The activated carboxylic acid is any one or more of 2-phenyl-2-cyanopropionic acid, 2-(4-chlorophenyl)-2-cyanopropionic acid, 2-(4-tolyl)-2-cyanopropionic acid, 2-(4-methoxyphenyl)-2-cyanopropionic acid, trichloroacetic acid, tribromoacetic acid, and nitroacetic acid.

6. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 1, characterized in that: The amino compound component is a chain extender containing an amine group.

7. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to claim 6, characterized in that: The chain extender containing an amine group is any one or more of hydrazide, primary amine and secondary amine.

8. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to any one of claims 1 to 7, characterized in that: The molar ratio of the amino group in the amino compound component, the carboxyl group in the activated carboxylic acid and the isocyanate component is 1:0.1-1:

1.

9. The method for preparing a solvent-free polyurea material based on activated carboxylic acid according to any one of claims 1 to 7, characterized in that: When heating the reaction, the reaction is carried out at 45-120°C for 12-48 hours.

10. A solvent-free polyurea material based on activated carboxylic acid, characterized in that: The polyurea is prepared by the method for preparing a solvent-free polyurea material based on activated carboxylic acid according to any one of claims 1 to 9.

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