A chemically cross-linked polyurea and its preparation method

Abstract

The present invention relates to a chemically cross-linked polyurea and a method for preparing the same. The chemically cross-linked polyurea is obtained by polymerization of a raw material composition comprising a polyaniline compound and an isocyanate compound. The polyaniline compound is a compound having two or more amino groups attached to a benzene ring and having a melting point below 110°C; the isocyanate compound has an average isocyanate group content of 2.5 or more. The polyurea can be molded using a solvent-free, catalyst-free casting method, exhibits excellent mechanical properties, and is recyclable and reprocessable with minimal performance degradation.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and in particular relates to a chemically cross-linked polyurea and a preparation method thereof. The chemically cross-linked polyurea can be formed by a solvent-free and catalyst-free casting method and is recyclable and reprocessable. Background Art

[0002] Polyurea is widely used in critical areas such as industrial and military protection due to its wear and corrosion resistance, strong mechanical properties, and VOC-free properties. Polyurea can be prepared and processed primarily through spraying and casting. Spraying polyurea is suitable for large-area coatings on irregular surfaces, while casting is suitable for mass production of standard parts. However, due to the rapid reaction between commonly used aliphatic amino groups and isocyanates, spraying is the only method available.

[0003] To improve the weather resistance of polyurea materials, multifunctional crosslinking agents are often added during the material preparation process, resulting in chemically crosslinked polyureas. However, chemically crosslinked polymers cannot be reprocessed once formed, hindering the preparation of complex parts and material recycling.

[0004] To make cross-linked polymer materials recyclable and reprocessable, dynamic covalent bonds can be introduced into the polymer, such as disulfide bonds, Diels-Alder bonds, and β-hydroxyester bonds. These dynamic covalent bonds can undergo exchange and recombination under thermal stimulation, thereby achieving rearrangement of the polymer cross-linked network structure and enabling plastic processing.

[0005] Patent Document 1 discloses a self-repairing, reprocessable polyurea material obtained by curing a mixture of a crosslinker, an amino-terminated polyetheramine, a diisocyanate, and a catalyst. The resulting polyurea elastomer exhibits dynamic exchange of fatty urea bonds under the action of an organometallic catalyst.

[0006] Patent Document 2 discloses a cross-linked polyurea elastomer with self-healing properties. The cross-linked polyurea elastomer is obtained by copolymerizing a diisocyanate monomer, an amino-terminated alkenyl ether monomer, a trifunctional or higher-functionality isocyanate, and a disulfide-containing monomer. The resulting cross-linked polyurea elastomer exhibits self-healing and reproducible processing capabilities. The disulfide bonds in the resulting polyurea elastomer undergo rapid dynamic exchange reactions at a certain temperature, thereby destroying and reforming the dynamic cross-linking points.

[0007] Patent Document 3 discloses a cross-linked polyurea-urethane based on stable borate bonds. This material is obtained by dissolving and mixing a cyclic borate compound with internal coordination of nitrogen and boron and an isocyanate compound in an organic solvent and curing the mixture. The dynamic borate bonds in the resulting material can undergo an exchange reaction at high temperatures.

[0008] References:

[0009] Patent Document 1: CN108559045A;

[0010] Patent document 2: CN108559052B;

[0011] Patent document 3: CN109897148B. Summary of the Invention

[0012] Problems to be solved by the invention

[0013] Patent Document 1 introduces an organometallic catalyst into a conventional aliphatic polyurea system to activate the dynamics of the urea bond. However, metal catalysts can cause problems such as precipitation in the polymer, accelerated aging, and environmental pollution. Furthermore, the reaction between aliphatic amino groups and isocyanates is too rapid, requiring the addition of large amounts of solvent for casting processing, which is environmentally unfavorable.

[0014] Patent Documents 2 and 3 use special compounds containing dynamic covalent bonds in polyureas, such as diaminodiphenyl sulfide and 4-hydroxyphenylboronic acid. However, these compounds are solid and require solvents to dissolve before mixing and reacting with other materials. Furthermore, the introduction of hybrid structures such as disulfide bonds and borate ester bonds may affect some of the properties of the polyurea itself.

[0015] Therefore, there is still an urgent need to develop a chemically cross-linked polyurea that can be molded by a solvent-free, catalyst-free casting method and has intrinsic dynamic covalent bonds (ie, urea bonds) to achieve recyclability.

[0016] Solutions for solving problems

[0017] To address these issues, the inventors conducted in-depth research and discovered that aniline-urea bonds (i.e., urea bonds attached to a benzene ring) exhibit the ability to undergo high-temperature, catalyst-free, dynamic exchange reactions at moderate reaction rates. Furthermore, a wide variety of liquid chemical raw materials containing aniline groups are particularly well-suited for reaction with isocyanate compounds to prepare castable, chemically cross-linked polyureas.

[0018] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0019] [1] A polyurea obtained by polymerization of a raw material composition comprising a polyaniline compound and an isocyanate compound,

[0020] The polyaniline compound is a compound having two or more amino groups connected to a benzene ring, and has a melting point of below 110°C.

[0021] The isocyanate compound has an average isocyanate group content of 2.5 or more.

[0022] [2] The polyurea according to [1], wherein the raw material composition does not contain a solvent and a catalyst.

[0023] [3] The polyurea according to [1] or [2], wherein, in the raw material composition, the ratio of polyaniline compound to isocyanate compound is 1:(0.5-1.5), preferably 1:(0.6-1), calculated on a molar basis.

[0024] [4] The polyurea according to [1] or [2], wherein the isocyanate compound comprises a compound having a structure represented by formula (I);

[0025]

[0026] Here, R' is a hydrocarbon group having 2 to 30 carbon atoms, and n is an integer of 2 or greater.

[0027] [5] The polyurea according to [4], wherein the isocyanate compound includes a compound having two isocyanate groups and a compound having three or more isocyanate groups,

[0028] The compound having two isocyanate groups is preferably one or more selected from aliphatic diisocyanates, more preferably one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, cyclohexyldimethylene diisocyanate, tetramethyl-m-xylylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and methylcyclohexyl diisocyanate;

[0029] The compound having three or more isocyanate groups is preferably a polymer of diisocyanate, more preferably a trimer, and further preferably comprises one or more selected from hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and dicyclohexylmethane diisocyanate trimer.

[0030] [6] The polyurea according to [1] or [2], wherein the polyaniline compound comprises a compound having a structure represented by formula (II) or formula (III):

[0031]

[0032] in,

[0033] A is an m-valent alkyl group, wherein one or more -CH2- groups are optionally replaced by -O-, and one or more H groups are optionally replaced by halogen;

[0034] B is a single bond, -CO-O-, -O-CO- or -O-;

[0035] L is an alkyl or alkoxy group having 1 to 5 carbon atoms, or a halogen substituent, preferably a methyl, ethyl, chlorine or fluorine group;

[0036] m is an integer from 2 to 8;

[0037] p is an integer from 0 to 4;

[0038]

[0039] in,

[0040] s is an integer from 2 to 4;

[0041] t is an integer from 0 to 4;

[0042] L' is a methylthio group, an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or a halogen substituent; preferably a methylthio group, a methyl group, an ethyl group, chlorine or fluorine.

[0043] [7] The polyurea according to [6], wherein

[0044] The polyaniline compound is one or more selected from p-aminobenzoate-terminated polytetrahydrofuran, dimethylthiotoluenediamine, diethyltoluenediamine, 4,4'-methylenebis(2-chloroaniline) and m-phenylenediamine.

[0045] [8] A method for preparing a polyurea according to any one of [1] to [7], comprising the following steps:

[0046] injecting the raw material composition into a mold;

[0047] The raw material composition is polymerized in the mold.

[0048] [9] The preparation method according to [8], wherein it is a casting or injection molding method.

[0049]

[10] The preparation method according to [8] or [9], wherein the polymerization reaction temperature is 40 to 110°C and the reaction time is 6 to 48 hours.

[0050] Effects of the Invention

[0051] The chemically cross-linked polyurea of ​​the present invention can be formed by a solvent-free and catalyst-free casting method, has excellent mechanical properties, can be recycled and reprocessed, and has almost no performance impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 (a) and (b) are experimental photos of the polyurea sheet obtained in Example 1 before and after recycling;

[0053] Figure 21 is the tensile stress-strain curve of the polyurea sheet obtained in Example 1 before and after recycling, wherein the solid line is before recycling and the dotted line is after recycling;

[0054] Figure 3 : The tensile stress-strain curves of the polyurea sheet obtained in Example 2 before and after recycling, wherein the solid line is before recycling and the dotted line is after recycling;

[0055] Figure 4 3 is the tensile stress-strain curve of the polyurea sheet obtained in Example 3 before and after recycling, wherein the solid line is before recycling and the dotted line is after recycling. DETAILED DESCRIPTION

[0056] The following describes the technical features of the present invention in detail. The technical features described below are described based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0057] <Terms and Definitions>

[0058] As used herein, a "dynamic crosslinked structure" refers to a structure in which the chemical bonds forming the crosslinks between polymer chains can be dynamically broken and re-formed as external conditions change. For example, under one condition, the polymer chains are chemically connected to form a crosslinked structure. Under a second condition, the connecting bonds break. When the first condition is restored, the broken bonds reform.

[0059] In this specification, the term "hydrocarbon group" includes linear, branched or cyclic alkyl groups, unless otherwise specifically stated.

[0060] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.

[0061] In this specification, the numerical range expressed using "above" or "below" means a numerical range including the number.

[0062] In this specification, the use of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0063] In this specification, "optionally" or "optional" is used to indicate that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0064] In this specification, the unit names used are all international standard unit names, and unless otherwise stated, the "%" used means weight or mass percentage.

[0065] In this specification, references to "preferred embodiments," "embodiments," and the like mean that the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein and may or may not be present in other embodiments. In addition, it should be understood that the elements may be combined in any suitable manner in the various embodiments.

[0066] <Polyurea>

[0067] An object of the present invention is to provide a polyurea obtained by a polymerization reaction of a raw material composition comprising a polyaniline compound and an isocyanate compound, wherein the polyaniline compound is a compound having two or more amino groups connected to a benzene ring and having a melting point of below 110°C; and the isocyanate compound has an average isocyanate group content of above 2.5.

[0068] a. Isocyanate compounds

[0069] In the present invention, the average isocyanate group content of the isocyanate compound contained in the raw material composition is 2.5 or more, wherein the "average isocyanate group content" refers to the average number of isocyanate groups per molecule of the isocyanate compound.

[0070] In one embodiment, the isocyanate compound comprises one or more compounds having a structure represented by formula (I):

[0071]

[0072] in,

[0073] R' is a hydrocarbon group having 2 to 30 carbon atoms;

[0074] n is an integer greater than or equal to 2, for example, 2, 3, 4, 5, 6, 7 or 8.

[0075] In a specific embodiment, the isocyanate compound includes a compound having two isocyanate groups and a compound having three or more isocyanate groups.

[0076] In a preferred embodiment, the compound having two isocyanate groups (hereinafter also referred to as "diisocyanate compound") is one or more selected from aliphatic diisocyanates, preferably one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, cyclohexyldimethylene diisocyanate, tetramethyl-m-xylylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and methylcyclohexyl diisocyanate.

[0077] In a preferred embodiment, the compound having three or more isocyanate groups (hereinafter also referred to as a "polyisocyanate compound") is a polymer of diisocyanate, preferably a trimer, and more preferably comprises one or more selected from hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and dicyclohexylmethane diisocyanate trimer.

[0078] In one embodiment, the molar ratio of the diisocyanate compound to the polyisocyanate compound in the raw material composition is (0-4):1, preferably (0.5-3.8):1, more preferably (1-3.7):1, even more preferably (2-3.6):1, and further more preferably (2.5-3.5):1. A too low ratio of polyisocyanate compounds will result in weak chemical crosslinking and poor mechanical properties of the material. A too high ratio of polyisocyanate compounds will cause a secondary reaction between urea bonds and excess isocyanate, forming a large amount of additional permanent crosslinks, which will reduce the toughness and reproducibility of the material.

[0079] b. Polyaniline compounds

[0080] The two or more amino groups in the polyaniline compound used in the present invention may be connected to the same benzene ring or to different benzene rings.

[0081] In one embodiment, the polyaniline compound used in the present invention has a structure shown in formula (II):

[0082]

[0083] in,

[0084] A is an m-valent alkyl group, wherein one or more -CH2- groups are optionally replaced by -O-, and one or more H groups are optionally replaced by halogen;

[0085] B is a single bond, -CO-O-, -O-CO- or -O-;

[0086] L is an alkyl or alkoxy group having 1 to 5 carbon atoms, or a halogen substituent, preferably a methyl, ethyl, chlorine or fluorine group;

[0087] m is an integer from 2 to 8, for example, 2, 3, 4, 5, 6, 7 or 8;

[0088] p is an integer from 0 to 4.

[0089] In one embodiment, m is 2, and A is a segment having repeating oxyalkylene units, or an alkylene group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms, which is optionally substituted with one or more halogen groups.

[0090] The oxyalkylene group may be oxyethylene, oxypropylene, oxybutylene, etc., and the number of repeating units may be 1 to 30 (e.g., 2 to 25, 3 to 20, 4 to 15). Specifically, A may be a polyethylene glycol segment, a polypropylene oxide segment, a polyoxetane segment, or a polytetrahydrofuran segment.

[0091] The alkylene group may be methylene, ethylene, propylene, butylene, pentylene, or the like.

[0092] In one embodiment, the polyaniline compound used in the present invention has a structure shown in formula (III):

[0093]

[0094] in,

[0095] s is an integer from 2 to 4, for example, 2, 3 or 4;

[0096] t is an integer from 0 to 4, for example, 0, 1, 2, 3 or 4;

[0097] L' is a methylthio group, an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or a halogen substituent; preferably a methylthio group, a methyl group, an ethyl group, chlorine or fluorine.

[0098] In a specific embodiment, the polyaniline compound is one or more selected from p-aminobenzoate-terminated polytetrahydrofuran, dimethylthiotoluenediamine, diethyltoluenediamine, 4,4'-methylenebis(2-chloroaniline) and m-phenylenediamine.

[0099] In one embodiment, the raw material composition has a molar ratio of polyaniline compound to isocyanate compound of 1:(0.5-2), preferably 1:(0.6-1), and more preferably 1:(0.8-0.95). A ratio of polyaniline compound to isocyanate compound within the above range allows for complete polymerization reaction, thereby forming a high molecular weight polymer.

[0100] In one embodiment, from the perspective of obtaining a high molecular weight polymer, in the raw material composition, the molar ratio of the total molar number of aniline groups contained in the polyaniline compound to the isocyanate groups contained in the isocyanate compound is 1:(0.950~1.050), preferably 1:(0.980~1.035).

[0101] The present inventors have discovered that the aniline-urea bond formed by the reaction of an aniline group with an isocyanate group exhibits high-temperature dynamic exchange reaction capability without a catalyst and at a moderate reaction rate. Therefore, in a preferred embodiment, the raw material composition does not contain a catalyst. Furthermore, because the reaction raw materials are liquid at the polymerization reaction temperature, in a preferred embodiment, the raw material composition does not contain a solvent.

[0102] In this specification, "does not contain a catalyst" means that the content of the catalyst is less than 0.1 mass% (for example, less than 0.01 mass%, less than 0.001 mass%, or even completely free of catalyst). The catalyst referred to here is a catalyst commonly used to activate the dynamic properties of urea bonds, including but not limited to organic metal catalysts, amine catalysts, acid catalysts, etc.

[0103] In this specification, "does not contain solvent" means that the content of solvent is 1% by mass or less (for example, 0.1% by mass or less, 0.01% by mass or less, or even no solvent at all). The solvent here refers to a solvent commonly used in the preparation of polyurea, including but not limited to ethers, amides, chlorinated hydrocarbons, sulfoxide solvents, etc. Specific examples thereof include but are not limited to tetrahydrofuran, N,N'-dimethylformamide, N,N'-dimethylacetamide, 1,4-dioxane, dichloromethane, chloroform, dimethyl sulfoxide, etc.

[0104] In a preferred embodiment, the raw material composition consists of a polyaniline compound and an isocyanate compound.

[0105] The polyurea of ​​the present invention has excellent mechanical properties, with a tensile strength of 5 MPa or more, preferably 7 MPa or more, for example 30 MPa or more; and an elongation at break of 50% or more, for example 300% or more.

[0106] The polyurea of ​​the present invention can be recycled and reprocessed, and the secondary processed polyurea obtained by reprocessing can substantially maintain the mechanical properties of the original polyurea (i.e., the polyurea obtained by polymerizing the raw material composition). Specifically, the tensile strength of the secondary processed polyurea is 80-120%, for example, 90-110%, of the original polyurea, and the elongation at break of the secondary processed polyurea is 80-120%, for example, 85-110%, of the original polyurea.

[0107] <Preparation method>

[0108] An object of the present invention is to provide a method for preparing the polyurea of ​​the present invention, which comprises the following steps:

[0109] injecting the raw material composition as described above and below into a mold;

[0110] The raw material composition is polymerized in the mold.

[0111] In a specific embodiment, the raw material composition can be injected into the mold by casting or injection, that is, the preparation method of the present invention is a casting or injection molding method.

[0112] In one embodiment, the polymerization temperature is 40 to 110°C, preferably 60 to 105°C.

[0113] In one embodiment, the polymerization reaction time is 6 to 48 hours, preferably 8 to 24 hours.

[0114] The preparation method of the present invention has no particular limitation on the mold, which can have any shape and size as needed, and can be made of metal or polytetrafluoroethylene.

[0115] In one embodiment, the preparation method of the present invention is a method for preparing a polyurea profile. As used herein, "polyurea profile" refers to an object composed of polyurea having a specific geometric shape. The present invention does not particularly limit the specific shape and size, and those skilled in the art may select an appropriate shape based on actual needs.

[0116] <Recycling and Reprocessing>

[0117] The polyurea profile of the present invention can be recycled and reprocessed. The present invention has no particular limitation on the recycling method, which can be any known recycling method for polymer materials (such as plastics) in the art, preferably a hot pressing method.

[0118] In one embodiment, the present invention accordingly provides a method for recycling and reprocessing polyurea, comprising the following steps:

[0119] The recycled polyurea of ​​the present invention (eg, polyurea profile) is placed in a mold and hot pressed.

[0120] In one embodiment, the reprocessing method of the present invention further comprises a step of crushing the recovered polyurea before placing it in the mold, for example, crushing it into relatively small blocks or particles by cutting, grinding, etc.

[0121] In one embodiment, the temperature of hot pressing is 120 to 250°C, such as 150 to 200°C.

[0122] By selecting a suitable hot pressing mold, the reprocessing method of the present invention can directly form the recycled polyurea of ​​the present invention into a desired shape.

[0123] Example

[0124] The present invention will be further described by enumerating specific embodiments below. It should be understood that these embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that, after reading the content described in the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms fall within the scope of the present invention.

[0125] Among the reagents used in the following examples: p-aminobenzoate-terminated polytetrahydrofuran (molecular weight 1238, 888, 488) was produced by Air Product; hexamethylene diisocyanate trimer was produced by Wanhua Chemical Company, product model HT100; isophorone diisocyanate trimer was produced by Evonik, product model Vestanat T1890E; dimethylthiotoluenediamine, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate were purchased from Aladdin Reagent.

[0126] Example 1

[0127] Preparation of Dynamically Cross-linked Polyurea H-1000

[0128] A raw material composition was prepared by mixing para-aminobenzoate-terminated polytetrahydrofuran (molecular weight 1238), dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate trimer in a molar ratio of 1.5:1:1 / 3. This raw material composition was poured into a 100 mm x 100 mm x 10 mm square polytetrafluoroethylene mold and polymerized at 80°C for 12 hours to produce a 2 mm thick sheet of dynamically cross-linked polyurea H-1000.

[0129] Example 2

[0130] Preparation of Dynamically Cross-linked Polyurea M-650

[0131] A raw material composition was prepared by mixing para-aminobenzoate-terminated polytetrahydrofuran (molecular weight 888), dimethylthiotoluenediamine, hexamethylene diisocyanate, and hexamethylene diisocyanate trimer in a molar ratio of 1.05:0.45:1.05:1 / 3. The raw material composition was poured into a 100 mm*100 mm*10 mm square polytetrafluoroethylene mold and polymerized at 100°C for 16 hours to produce a 2 mm thick sheet of dynamically cross-linked polyurea M-650.

[0132] Example 3

[0133] Preparation of Dynamically Cross-linked Polyurea M-250

[0134] A raw material composition was prepared by mixing para-aminobenzoate-terminated polytetrahydrofuran (molecular weight 1238), para-aminobenzoate-terminated polytetrahydrofuran (molecular weight 488), isophorone diisocyanate, and isophorone diisocyanate trimer in a molar ratio of 0.15:1.35:0.98:1 / 3. The raw material composition was poured into a 100 mm*100 mm*10 mm square polytetrafluoroethylene mold and polymerized at 90°C for 15 hours to obtain a 2 mm thick sheet of dynamically cross-linked polyurea M-250.

[0135] <Mechanical Properties Evaluation>

[0136] 1. Tensile performance test before recycling

[0137] Tensile properties of the dynamically cross-linked polyureas H-1000, M-650, and M-250 obtained in Examples 1 to 3 were tested using a UTM-1432 electronic universal testing machine (Chengde Jinjian) according to GB / T 528-1998. The tensile speed was 50 mm / min. The tensile specimens had a marking spacing of 20.0 ± 0.2 mm, a width of 4.0 ± 0.1 mm, and a standard thickness of 2.0 ± 0.2 mm. The tensile specimens were cut from polyurea sheets using a strip cutter.

[0138] The tensile strength and elongation at break are shown in Table 1. The tensile stress-strain curves of the dynamically cross-linked polyureas H-1000, M-650, and M-250 of Examples 1 to 3 are shown in Table 1. Figures 2-4 As shown by the solid line in .

[0139] 2. Tensile performance test after recycling

[0140] The sheets of dynamically cross-linked polyurea H-1000, M-650, and M-250 obtained in Examples 1 to 3 were cut into pieces, and then placed in a mold. The pieces were hot-pressed at 180°C for 30 minutes using a small laboratory vacuum hot press, and then fully cooled to room temperature and demolded. Figure 1 The tensile properties of the recycled polyurea sheets were tested again in the same manner as before recycling. The tensile strength and elongation at break are shown in Table 1. The tensile stress-strain curves of the recycled dynamically cross-linked polyureas H-1000, M-650, and M-250 of Examples 1 to 3 are shown in Table 1. Figures 2-4 As shown by the dotted line in .

[0141] Table 1

[0142]

[0143] The results in Table 1 show that the dynamically cross-linked polyurea prepared by the present invention has excellent mechanical properties and can be adjusted from hard plastic to soft elastomer, thus being suitable for many applications such as protective coatings, gaskets, seals, plates, etc. Moreover, after recycling, the mechanical properties are maintained or only slightly reduced. Figures 2-4 It can be seen that the tensile stress-strain curves of the dynamically cross-linked polyurea of ​​Examples 1 to 3 before and after recycling are almost identical, which indicates that the dynamically cross-linked polyurea of ​​the present invention can be almost completely recycled and reprocessed.

[0144] Industrial applicability

[0145] The dynamically cross-linked polyurea of ​​the present invention can be widely used in protective materials, structural materials and the like, including the fields of plastics and elastomers.

Claims

1. A polyurea, characterized in that: The invention is obtained by polymerization reaction of a raw material composition comprising a polyaniline compound and an isocyanate compound. The polyaniline compound is a compound having two or more amino groups connected to a benzene ring, and has a melting point of below 110°C. The average isocyanate group content of the isocyanate compound is greater than 2.5, wherein the "average isocyanate group content" refers to the average number of isocyanate groups per molecule of the isocyanate compound; The raw material composition does not contain solvent and catalyst; The isocyanate compound includes a compound having a structure shown in formula (I); wherein R' is a hydrocarbon group having 2 to 30 carbon atoms, and n is an integer greater than 2; The polyaniline compound includes a compound having a structure shown in formula (II): in, A is an m-valent alkyl group, wherein one or more -CH2- groups are optionally replaced by -O-, and one or more H groups are optionally replaced by halogen; B is a single bond, -CO-O-, -O-CO- or -O-; L is an alkyl group or alkoxy group having 1 to 5 carbon atoms, or a halogen substituent; m is an integer from 2 to 8; p is an integer from 0 to 4.

2. The polyurea according to claim 1, characterized in that In terms of moles, in the raw material composition, the ratio of polyaniline compound to isocyanate compound is 1:(0.5-1.5).

3. The polyurea according to claim 1 or 2, characterized in that In terms of moles, in the raw material composition, the ratio of polyaniline compound to isocyanate compound is 1:(0.6-1).

4. The polyurea according to claim 1 or 2, characterized in that The isocyanate compounds include compounds having two isocyanate groups and compounds having three or more isocyanate groups.

5. The polyurea according to claim 4, characterized in that The compound having two isocyanate groups is one or more selected from aliphatic diisocyanates; The compound having three or more isocyanate groups is a polymer of diisocyanate.

6. The polyurea according to claim 4, characterized in that The compound having two isocyanate groups is one or more selected from hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, cyclohexyldimethylene diisocyanate, tetramethyl-m-xylylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and methylcyclohexyl diisocyanate; The compound having three or more isocyanate groups is a trimer of diisocyanate.

7. The polyurea according to claim 4, characterized in that The compound having three or more isocyanate groups includes one or more selected from the group consisting of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and dicyclohexylmethane diisocyanate trimer.

8. The polyurea according to claim 1 or 2, characterized in that The polyaniline compound includes a compound having a structure shown in formula (III): in, s is an integer from 2 to 4; t is an integer from 0 to 4; L' is a methylthio group, an alkyl group or alkoxy group having 1 to 5 carbon atoms, or a halogen substituent.

9. The polyurea according to claim 1 or 2, characterized in that L in formula (II) is methyl, ethyl, chlorine or fluorine.

10. The polyurea according to claim 8, characterized in that L' in formula (III) is methylthio, methyl, ethyl, chlorine or fluorine.

11. The polyurea according to claim 1 or 2, characterized in that The compound having the structure represented by formula (II) is one or two selected from polytetrahydrofuran terminated with p-aminobenzoate and 4,4'-methylenebis(2-chloroaniline).

12. The polyurea according to claim 8, characterized in that The compound having the structure represented by formula (III) is one or more selected from dimethylthiotoluenediamine, diethyltoluenediamine and metaphenylenediamine.

13. A method for preparing polyurea according to any one of claims 1 to 12, characterized in that: The following steps are involved: injecting the raw material composition into a mold; The raw material composition is polymerized in the mold.

14. The preparation method according to claim 13, characterized in that It is a casting or injection molding method.

15. The preparation method according to claim 13 or 14, characterized in that: The polymerization reaction temperature is 40 to 110° C., and the reaction time is 6 to 48 hours.

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