Amine curing agent and preparation method thereof

Abstract

The present invention provides an amine curing agent and a preparation method thereof, wherein the amine curing agent comprises a modified polyamide, wherein the modified polyamide comprises an aromatic active hydroxyl group derived from the modifier, thereby being able to improve the curing and cross-linking reaction activity and increase the curing speed while maintaining the good mechanical properties and durability of the long-chain polymer curing agent.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a curing agent commonly used for epoxy resins, and more particularly to an amine curing agent with improved curing rate and a preparation method thereof. Background Art

[0002] Reactive polyamide curing agent is mainly a yellow or brown viscous liquid formed by the reaction of monomer acid, dimer acid and polyamines such as diethylenetriamine, triethylenetetramine, pentaethylenehexamine at high temperature (180℃~280℃). The relative molecular mass is 500~6000. It has viscosity and adhesion due to the long aliphatic hydrocarbon carbon chain and polar amide group. The polyamide structure contains a large amount of unreacted active hydrogen, and it undergoes cross-linking reaction and hardens when used with epoxy resin. Compared with the general amines (polyethylene polyamines) of epoxy resin curing agent, it has the characteristics of wide ratio range, simple operation, low toxicity, strong bonding force, etc., especially its excellent flexibility makes it a good curing agent and toughening agent for epoxy resin. Because the cross-linked product after curing has good mechanical properties and chemical environment resistance, it is widely used in coatings, adhesives, composite materials and other fields.

[0003] Usually, epoxy resin and polyamide curing agent are two-component curing systems stored separately. When used, the two are mixed. During the mixing process, the active hydrogen in the polyamide structure cross-links with the epoxy groups in the epoxy resin to form a thermosetting resin. The active hydrogen in the polyamide comes from the primary amine and secondary amine that do not participate in the reaction. Although the use of polyamide instead of aliphatic polyamine can give epoxy resin cured products excellent flexibility and bonding effect, part of the active hydrogen is consumed in the process of synthesizing polyamide, resulting in the active hydrogen equivalent in polyamide being significantly higher than that of aliphatic polyamine, and the generated polyamide has a longer molecular chain segment, which increases the steric hindrance. The reaction of amine curing agent and epoxy resin mainly occurs between active hydrogen and epoxy groups. The structure of polyamide leads to a decrease in the amount of active hydrogen and an increase in steric hindrance, thereby increasing the difficulty of the reaction between polyamide and epoxy resin, which is manifested as a slow curing speed in the macroscopic sense, especially for polyamide with low amine value (amine value less than 220mgKOH / g). Low amine value polyamide has a long molecular chain, which gives the cured product good flexibility and adhesion. However, there are a large number of secondary amines with low reactivity in its structure, which leads to a slow curing speed of low amine value polyamide. This prolongs the operation cycle in actual application, reduces construction efficiency, and even causes the problem of failure to cure at low temperatures in winter. Therefore, improving the curing speed of polyamide curing agent is one of the key technologies to improve the performance of polyamide curing agent.

[0004] Reference 1 discloses a method for preparing a curing agent for epoxy resin adhesive with low cost, fast curing speed and good curing effect on wet surface and its application, wherein one or more of polyethylene polyamine, polyether amine or long-chain fatty amine is used, and then added with aldehyde with aromatic ring or heterocyclic ring, and then hydrophilic additives with hydroxyl group such as ethanolamine are added. The adhesive after bonding with epoxy resin has good affinity and permeability for wet board, high tolerance for water, can clean and drive away the water-rich board, and achieves the goal of no need to bake the board at room temperature and no need to heat the curing, which reduces the cost and improves the curing speed. However, the product in the invention has a small molecular weight, resulting in a brittle cured product, poor flexibility and bonding effect.

[0005] Reference 2 discloses a method for preparing a modified polyamide epoxy curing agent, wherein the prepared polyamide is first reacted with ketones and then modified by cardanol. The modified polyamide epoxy curing agent of the invention has strong viscosity and fast curing speed, and effectively improves the defect of incomplete low-temperature curing of existing polyamides, and has good low-temperature resistance, high-humidity resistance and solvent resistance. However, in the invention, cardanol is directly added, which not only deepens the color of the product, but also exists in a free form. It does not participate in the reaction during the curing process and finally still exists in a free state, which has a certain adverse effect on the performance of the cured product.

[0006] Reference 3 discloses a thiourea-modified polyamide epoxy curing agent and a preparation method thereof, which is made of polyamide and thiourea. First, polyamide is prepared, and then a thiourea-modified polyamide epoxy curing agent with excellent performance is prepared by polycondensation reaction with thiourea. The thiourea-modified polyamide epoxy curing agent prepared by the invention can make epoxy resin quickly cure at a low temperature of -10°C, and the film after the epoxy resin is cured has excellent toughness and adhesion, the surface is not easy to absorb moisture, and has good corrosion resistance and chemical resistance, which can meet the needs of epoxy heavy-duty anti-corrosion coatings in low temperature environments. However, the thiourea used in the patent has an unpleasant odor, has high biological toxicity, and is easy to decompose H2S and other gases at high temperatures, which is very harmful to operators and the environment. In addition, thiourea has a strong reducing property, and the product color will become darker after polyamide is modified with thiourea.

[0007] In addition, some researchers have added some small molecule promoters to the polyamide curing agent, such as DMP-30, phenol, etc., but the addition of these promoters has brought other problems, such as the unpleasant odor of the additives affecting the physical and mental health of the operator, the poor compatibility of the additives with the resin causing migration to the surface of the cured product, affecting the water resistance and solvent resistance of the cured product, etc.

[0008] It can be seen that although various types of curing agents for epoxy resins and the like have been studied in the art, it is still not sufficient to provide a curing agent with high curing efficiency and good curing performance.

[0009] References:

[0010] Reference 1: CN 108359398 A

[0011] Reference 2: CN 104497274 A

[0012] Reference 3: CN 106995525 A Summary of the invention

[0013] Problem that the invention aims to solve

[0014] As mentioned above, the existing curing agents in the field usually have the problem of not being able to balance the curing performance and curing efficiency. Specifically, when an amine curing agent with a certain chain length, such as polyamide, is used as a curing agent, it has better advantages in mechanical properties and durability of the cured product compared to a small molecule curing agent, but has the problem of a long curing operation cycle.

[0015] In view of the above-mentioned technical problems, the primary purpose of the present invention is to provide an amine-based curing agent with a certain chain length and a relatively high molecular weight. The cured product based on the curing agent not only has improved mechanical properties and durability of use, but also has an improved curing or cross-linking rate, thereby having a shortened operating cycle.

[0016] Furthermore, the present invention also aims to provide a method for preparing the above-mentioned amine curing agent, by which the amine curing agent of the present invention can be obtained in a convenient, low-consumption and low-toxic manner.

[0017] Solutions for solving problems

[0018] After long-term research, the inventors of the present invention found that the above technical problems can be solved by implementing the following technical solutions:

[0019] [1] An amine curing agent of the present invention, wherein the amine curing agent comprises a modified polyamide, and the modified polyamide comprises the following structure:

[0020] i) amine residues derived from secondary amine groups in the polyamide structure;

[0021] ii) derived from a modifier and connected to the amino residue described in i) is the following structural formula (I):

[0022]

[0023] Wherein, in the formula (I):

[0024] Ar represents a substituted or unsubstituted aromatic group;

[0025] n represents an integer from 1 to 10;

[0026] -(OH) n Directly bonded to the aromatic ring of the aromatic group of Ar;

[0027] * indicates the position where the structure of formula (I) is connected to the amine residue in i).

[0028] [2] The amine curing agent according to [1], wherein the modified polyamide includes amine residues derived from primary and secondary amine groups in the polyamide structure; and the amine residues are derived from the polyacid and / or polyamine forming the polyamide.

[0029] [3] The amine curing agent according to [1] or [2], wherein the Ar-(OH) n It has the structure of formula (II) or formula (III):

[0030]

[0031] in,

[0032] R, when it appears each time, is the same or different and independently represents one of hydrogen, an alkyl group, a halogen group, an alkoxy group, an aryloxy group, a carboxyl-containing group, an amino-containing group, an ester-containing group, and a keto-containing group;

[0033] a represents an integer from 0 to 4; n1 represents an integer from 1 to 5;

[0034] b represents an integer from 0 to 6; n2 represents an integer from 1 to 7.

[0035] [4] The amine curing agent according to any one of [1] to [3], wherein the Ar-(OH) n It has the structure of the following formula (II-1):

[0036]

[0037] Here, R represents hydrogen, an alkyl group, a halogen group, an alkoxy group or an aryloxy group.

[0038] [5] The amine curing agent according to any one of [1] to [4], wherein the molecular weight of the polyamide is 10,000 or less, preferably 6,000 or less.

[0039] [6] The amine curing agent according to any one of [1] to [5], wherein the amine value of the amine curing agent is 100 to 400 mgKOH / g.

[0040] [7]. Furthermore, the present invention also provides a method for preparing an amine curing agent according to any one of [1] to [6] above, wherein the method comprises:

[0041] a step of obtaining polyamide, and a step of modifying polyamide,

[0042] In the polyamide modification step, a modifier having the following formula (M) is used to react with the polyamide:

[0043]

[0044] Wherein, Ar, n, -(OH) in the formula (M) n and Ar-(OH) n The definition is the same as that in any one of claims 1 to 6.

[0045] [8] The method according to [7], wherein in the step of forming the polyamide, a polyacid and a polyamine are used for a condensation polymerization reaction, and the polyamine structure includes a secondary amine group.

[0046] [9] The method according to [7] or [8], wherein in the step of modifying the polyamide, the modifier includes benzaldehyde having a phenolic hydroxyl group.

[0047]

[10] . In addition, the present invention also provides a curing agent composition, wherein the curing agent composition comprises the amine curing agent according to any one of the above [1] to [6] or the amine curing agent obtained according to any one of the above methods [7] to [9].

[0048]

[11] . In addition, the present invention also provides a curable composition, wherein the curable composition comprises the curing agent composition according to the above

[10] , an epoxy component and optionally a catalyst.

[0049]

[12] . In addition, the present invention also provides a cured product, wherein the cured product is obtained by curing the curable composition described in

[11] above, and optionally, the curing includes photocuring and / or thermal curing.

[0050] Effects of the Invention

[0051] Through the implementation of the above technical solution, the present invention can obtain the following technical effects:

[0052] 1) The amine curing agent obtained by the present invention has a relatively fast curing speed and can be cured at room temperature, low temperature (even around 0°C) and humid environment, meeting the requirements of application under low temperature conditions;

[0053] 2) The amine curing agent obtained by the present invention has good compatibility with epoxy resin;

[0054] 3) The cured product (e.g., paint film) finally formed by the amine curing agent obtained by the present invention has high hardness, excellent flexibility, adhesion, and good durability;

[0055] 4) The amine curing agent obtained by the present invention can be obtained by modifying polyamide with an easily available small molecule modifier. In this process, no special purification treatment is required, the process is simple, and the cost is low;

[0056] 5) The amine curing agent obtained by the present invention has a suitable amine value, and can avoid being non-toxic and irritating while maintaining the reaction activity. During the use of the product, there will be no volatilization and overflow of small molecular amines, and no adverse effects such as irritation to the skin of the operator will be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 : Schematic diagram of the reaction process of the modifier and polyamide in a specific embodiment of the present invention DETAILED DESCRIPTION

[0058] The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0059] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0060] In the present specification, the use of “substantially” or “essentially” means that the standard deviation from a theoretical model or theoretical data is within a range of 5%, preferably 3%, and more preferably 1%.

[0061] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0062] In the present specification, the term "poly" as used in "polyacid" and "polyamine" refers to a number of two or more.

[0063] In this specification, the term "normal temperature" refers to a room temperature of 23±2°C.

[0064] In the present specification, "optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes cases where the event occurs and cases where it does not occur.

[0065] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., 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 exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0066] The present invention mainly provides an amine curing agent with a certain molecular chain length mainly used for epoxy resin curing and a preparation method thereof. The present invention is mainly completed based on the following insights:

[0067] Amine curing agents with a certain molecular chain length usually have a relatively low amine value relative to small molecule amine curing agents due to their molecular length or molecular weight. And the curing or cross-linking reaction activity of such amine curing agents is usually relatively reduced relative to the low amine value. For example, when the amine curing agent is subjected to a curing reaction with an epoxy resin, there are disadvantages such as slow curing speed and long construction period. Further, when the amine curing agent reacts with the epoxy resin, if a phenolic hydroxyl structure is introduced, it can form a hydrogen bond with the oxygen atom of the epoxy group to promote ring opening, and the phenolic hydroxyl group is more likely to form such a hydrogen bond, so it has a better promotion effect. Based on this, the present invention believes that introducing a stable phenolic hydroxyl group into the amine curing agent structure with a certain molecular chain length can significantly increase its curing speed.

[0068] <First aspect>

[0069] In a first aspect of the present invention, an amine curing agent is provided, wherein the amine curing agent comprises a modified polyamide.

[0070] The modified polyamide in the present invention has a structure derived from the polyamide and a structure derived from the modifier. Further, the polyamide structure includes secondary amine groups and optionally primary amine groups. The modifier achieves modification of the polyamide by reacting with the secondary amine groups and the optionally present primary amine groups.

[0071] Specifically, the modified polyamide structure described in the present invention includes the following structure:

[0072] i) amine residues derived from secondary amine groups in the polyamide structure, and optionally amine residues derived from primary amine groups in the polyamide structure;

[0073] ii) derived from the following structural formula (I) connected to the amino residue described in i) by a modifier

[0074]

[0075] For the structural part i), the presence of an amine residue derived from a secondary amine group in the polyamide structure is important, which can be linked to the structure of the above formula (I) derived from the modifier, thereby introducing a phenolic hydroxyl reactive structure.

[0076] In addition, in the present invention, optionally, in the structure of i), an amine residue derived from a primary amine group in the polyamide structure may be further included, which may also be connected to the structure of the above formula (I) derived from the modifier, thereby introducing another phenolic hydroxyl active structure.

[0077] In some specific embodiments of the present invention, the secondary amine group and the primary amine group may be derived from polyacid molecules and monoacid molecules when synthesizing polyamide. In some other specific embodiments of the present invention, the secondary amine group and the primary amine group may be derived from polyamine molecules when synthesizing polyamide.

[0078] In some preferred embodiments of the present invention, the secondary amine groups and primary amine groups are derived from or mainly derived from polyamine molecules during the synthesis of polyamide.

[0079] Furthermore, the molecular weight of the polyamide is not particularly limited in principle in the present invention, and the molecular weight of the polyamide curing agent commonly used in the art can be selected. In some specific embodiments of the present invention, the molecular weight of the polyamide can be 10,000 or less, preferably 8,000 or less, and more preferably 6,000 or less; in addition, the lower limit of the molecular weight of the polyamide can be 500 or more, preferably 800 or more, and more preferably 1,000 or more.

[0080] The structural part ii) mentioned above can be obtained by reacting a modifier with the secondary amine group or the primary amine group in the polyamide structure described above.

[0081] Specifically, for structure (I):

[0082] Ar represents a substituted or unsubstituted aromatic group. In some specific embodiments, the aromatic group can be selected from phenyl, naphthyl, and the residue of an aromatic group containing heteroatoms. From the perspective of the convenience of obtaining raw materials and the reaction activity, it is preferred that Ar is a residue of phenyl or substituted phenyl in the present invention. In addition, there is no particular restriction in principle on the substituents that can be used, and preferably, the substituents present can be substituents that do not affect the activity of the aromatic structure to the hydroxyl group directly bonded thereto.

[0083] n represents an integer of 1 to 10, preferably, n represents an integer of 1 to 5, more preferably, n represents an integer of 1 to 3, and further preferably, n represents 1 or 2; the mark "*" represents the connection position between the structure of formula (I) and the amino residues derived from the secondary amino group and the primary amino group in the polyamide structure.

[0084] In addition, -(OH) n The hydroxyl group is directly bonded to the aromatic ring of the aromatic group of Ar, and the activation of the hydroxyl group can be effectively achieved by directly bonding the hydroxyl group to the aromatic ring structure of the aromatic group.

[0085] Further, in some specific embodiments of the present invention, Ar-(OH) in the structure of formula (I) n It has the following structure:

[0086]

[0087] in,

[0088] Each time R appears, it is the same or different and independently represents one of hydrogen, an alkyl group, a halogen group, an alkoxy group, an aryloxy group, a carboxyl-containing group, an amino-containing group, an ester-containing group, and a keto-containing group.

[0089] In some preferred embodiments, R appears each time, the same or different, and independently represents hydrogen, an alkyl group, a halogen group, an alkoxy group or an aryloxy group; more preferably, R appears each time, the same or different, and independently represents hydrogen, an alkyl group or an alkoxy group.

[0090] a represents an integer of 0 to 4; n1 represents an integer of 1 to 5. Preferably, a represents an integer of 0 to 2; n1 represents 1 or 2.

[0091] b represents an integer of 0 to 6; n2 represents an integer of 1 to 7. Preferably, b represents an integer of 0 to 2; n1 represents 1 or 2.

[0092] Further, in some specific embodiments of the present invention, the formula (II) has the structure of the following formula (II-1):

[0093]

[0094] Wherein, R represents hydrogen, an alkyl group, a halogen group, an alkoxy group or an aryloxy group. Preferably, R represents hydrogen, an alkyl group or an alkoxy group.

[0095] In some preferred embodiments of the present invention, the formula (II-1) has the following structures of formula (II-1a) to formula (II-1c):

[0096]

[0097] The mark "*" indicates the position of these structures in the structure of formula (I).

[0098] For the modified polyamide of the present invention, due to the introduction of the structure of the above formula (I) derived from the modifier, hydrogen atoms derived from the secondary amine groups and primary amine groups in the polyamide structure are consumed at the same time. In some specific embodiments, based on the total amount of all secondary amine groups and primary amine groups in the polyamide structure, the amount of secondary amine groups and primary amine groups connected to the above structural formula (I) is less than 10% of the total amount of all secondary amine groups and primary amine groups in the polyamide structure, preferably less than 8%, more preferably less than 7%, and is more than 0.1%, preferably more than 0.5%, more preferably more than 1%.

[0099] Although the introduction of an appropriate number of structures of formula (I) consumes the active hydrogen atoms on the secondary amines and primary amines in the polyamide, it also introduces more active hydroxyl groups directly connected to the aromatic structure, thus generally improving the curing or cross-linking reactivity of the polyamide as a curing agent. At the same time, the introduction of too many structures of formula (I) may cause certain difficulties in the modification reaction, and in some cases, although more active hydroxyl groups are introduced, the cross-linking activity of the main chain of the polyamide molecular structure is excessively inhibited, so the expected optimal curing efficiency may not be obtained, or in some extreme cases, uneven curing may occur.

[0100] Further, for the amine curing agent containing the modified polyamide in the present invention, in some specific embodiments of the present invention, from the perspective of ease of use, it can have a viscosity of 200,000 mPa·s or less (40°C), preferably a viscosity of 150,000 mPa·s or less, more preferably a viscosity of 100,000 mPa·s or less, more preferably a viscosity of 60,000 mPa·s or less, and even more preferably a viscosity of 50,000 mPa·s or less. In addition, the amine value of the amine curing agent of the present invention can generally be 100 to 400 mgKOH / g, preferably 110 to 350 mgKOH / g, more preferably 120 to 300 mgKOH / g, for example, 130 to 350 mgKOH / g or 150 to 350 mgKOH / g, etc. If the amine value is too high, there may be concerns that the small molecule amine component in the polyamide is too high, and the small molecule amine reacts preferentially with the modifier such as p-hydroxybenzaldehyde, resulting in a lower degree of reaction between the modifier and the polyamide. If the amine value is too low, there may be concerns about insufficient curing activity or catalytic activity in the subsequent curing reaction with the epoxy resin.

[0101] <Second Aspect>

[0102] In the second aspect of the present invention, a method for preparing the amine curing agent described in <the first aspect> is provided.

[0103] Specifically, the preparation method of the present invention comprises:

[0104] (A) a step of obtaining polyamide, and (B) a step of modifying polyamide,

[0105] In the polyamide modification step, a modifier having the following formula (M) is used to react with the polyamide:

[0106]

[0107] (A) Step of obtaining polyamide

[0108] In step (A) of the present invention, the polyamide is prepared or obtained to carry out the modification reaction of the subsequent step (B).

[0109] In principle, the present invention has no particular limitation on the steps of obtaining polyamide, and the polyamide can be obtained by directly purchasing commercially available polyamide. Such polyamide has secondary amine groups and optionally primary amine groups. Moreover, such polyamide also has a suitable molecular weight, for example, the molecular weight can be 10,000 or less, preferably 8,000 or less, and more preferably 6,000 or less; in addition, the lower limit of the molecular weight of the polyamide can be 500 or more, preferably 800 or more, and more preferably 1,000 or more.

[0110] In some specific embodiments of the present invention, in step (A), the compound can be synthesized by a conventional polycondensation method. Specifically, the compound can be obtained by polycondensation of a carboxylic acid compound and an amine compound through an amidation reaction.

[0111] There is no particular limitation on the carboxylic acid compound, and one or more polyacids commonly used in the synthesis of polyamides in the art can be used. For example, the polyacid can be one or more aliphatic, alicyclic or aromatic polyacids having a carbon number of 4 to 60. Preferably, the polyacid of the present invention is a dicarboxylic acid compound.

[0112] In some specific embodiments of the present invention, polyacids include fatty acids with carbon atoms of 4 to 15 such as adipic acid, azelaic acid, succinic acid, dodecanedioic acid, glutaric acid, suberic acid, maleic acid, pimelic acid, sebacic acid, and undecanedioic acid; or aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, and isophthalic acid.

[0113] In some other specific embodiments of the present invention, polymerized fatty acids are also suitable. Polymerized fatty acids are also referred to as "polyacids" in the present invention. Usually, such "polyacids" can exist or be used in the form of "dimer acids" or "trimer acids".

[0114] In the present invention, the fatty acids forming these "polyacids" can be unsaturated fatty acids having more than 10 carbon atoms, preferably, unsaturated fatty acids having 12 to 30 carbon atoms. Typically, the fatty acids that can form polyacids suitable for the present invention are selected from various oleic acids (linoleic acid, cotton oleic acid, rapeseed oleic acid, soybean oleic acid, palmitoleic acid, tall oil acid, etc.), linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosapentaenoic acid or docosahexaenoic acid, etc.

[0115] In addition, in some specific embodiments of the present invention, a mixture of polymerized fatty acids can also be used. A mixture of polymerized fatty acids can be obtained, for example, from the polymerization of tall oil fatty acids or commercially available. These polymerized fatty acids preferably have the following typical composition: based on the total weight of the polyacid, containing about 0 to 10% by weight of C18 monoacid (monomer), 60 to 95% by weight, sometimes up to about 98% by weight of C36 diacid (dimer), and about 1 to 35% by weight of C54 and higher polyacids (trimers). In the polymerized fatty acids, the relative proportions of monomers, dimers and trimers depend on the nature of the starting materials, the conditions of polymerization and the degree of purification. A purer grade of polymerized fatty acids can be obtained by distillation and contain at least 70% by weight, preferably 80% by weight and usually up to 95% by weight or even 98% by weight of dimerized fatty acids. In addition, these polymerized fatty acids or their mixtures can also be unhydrogenated or hydrogenated.

[0116] In some specific embodiments of the present invention, the above-mentioned fatty acids that can form "polyacids" are derived from animal fats or plant fats, preferably from plant fats.

[0117] Furthermore, the amine compound in the present invention is not particularly limited, and one or more polyamine monomers commonly used in the synthesis of polyamide in the art can be used.

[0118] The polyamine of the present invention can be selected from diamine, triamine or more amines, where the number of amines refers to the sum of primary amine groups, secondary amine groups and tertiary amine groups. In addition, as necessary raw materials, the present invention uses at least those polyamines having secondary amine groups.

[0119] In some specific embodiments of the present invention, as the diamine that can be used, one or more aliphatic, alicyclic or aromatic diamines can be used.

[0120] The aliphatic diamine having two primary amine groups that can be used in the present invention can be a diamine having a linear structure or a branched structure. More preferably, diamines having an even number of carbon atoms and primary amine groups at both ends can be used. In the present invention, the aliphatic diamine can contain 2 to 30 carbon atoms, preferably 2 to 26 carbon atoms, and more preferably 4 to 20 carbon atoms.

[0121] In addition, the alicyclic diamine that can be used in the present invention may be a diamine having one or more alicyclic rings in the structure, and these alicyclic rings may have common atoms.

[0122] The aromatic diamine that can be used in the present invention may be a diamine having one or more aromatic rings, preferably one or more benzene rings, in its structure.

[0123] More specifically, the diamines that can be cited in the present invention can be selected from ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, methylpentanediamine, 1,6-hexanediamine, 1,4-cyclohexanediamine, isophoronediamine, 4,4'-diamino-dicyclohexylmethane, norbornanediamine, trimethylhexanediamine, 2-methylpentanediamine, 1,8-diaminooctane, neopentyldiamine, 1,12-diaminododecane, diaminodipropylmethylamine, p-phenylenediamine and m-phenylenediamine, etc.

[0124] In addition, the diamine of the present invention may comprise a polyoxyalkylene diamine (polyether diamine), such as polyethylene diamine, polyoxypropylene diamine or bis-(diaminopropyl)-polytetrahydrofuran. Polyoxyalkylene diamines are commercially available under the trade name "Jeffamines" (Huntsman Co.).

[0125] In addition, triamines or more polyamines can be used for the present invention, which can be selected from one or more aliphatic, alicyclic or aromatic polyamines. In some preferred embodiments, various polyalkylene polyamines can be selected for these polyamines, and more preferably, such polyalkylene polyamines have two primary amine groups and one or more secondary amine groups. Typically, the polyalkylene polyamines can be selected from one or more of diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, etc. By the use of these triamines or more polyamines, one or more secondary amine groups can be conveniently introduced into the final polyamide structure.

[0126] In addition, there is no particular limitation on the ratio of polyacid to polyamine in the polycondensation reaction, and it can be adjusted according to the desired molecular weight and amine value. In some preferred embodiments, the polycondensation reaction is carried out in an excess amount of polyamine equivalent.

[0127] Furthermore, in some specific embodiments, in addition to the above-mentioned polyacids and polyamines, one or more monoacids and monoamines commonly used in the art may be used for the purpose of end-capping or controlling molecular weight.

[0128] Furthermore, there is no particular limitation on the synthesis method of the polyamide of the present invention, and the polyamide can be obtained by heating and dehydration polycondensation under common polycondensation conditions in the art. Optionally, the polycondensation reaction can be carried out under an inert gas atmosphere such as nitrogen.

[0129] The obtained polyamide is generally a viscous liquid with a color ranging from light yellow to yellow to brownish yellow at room temperature.

[0130] (B) Polyamide modification steps

[0131] In step (B) of the present invention, the modified polyamide in the amine-based curing agent of the present invention is obtained by reacting the modifier with the polyamide obtained in step (A).

[0132] The above-mentioned modifier of the present invention has the structure of the following formula (M):

[0133]

[0134] Wherein, Ar, n, -(OH) in the formula (M) n and Ar-(OH) n The definition of is the same as the description or definition of <first aspect> of the present invention.

[0135] In some specific embodiments, the formula (M) has the structure of the following formula (M-1) or formula (M-2):

[0136]

[0137] The definitions of R, a, b, n1, and n2 are the same as those described or defined in the <first aspect> of the present invention.

[0138] Further, in some preferred embodiments of the present invention, the modifier has the following structures of formula (M-1a) to formula (M-1c):

[0139]

[0140] Among them, R is preferably hydrogen, an alkyl group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms.

[0141] Typically, the modifier that can be used in the present invention may be hydroxybenzaldehyde or vanillin molecules.

[0142] The modification reaction between the modifier and the polyamide is mainly completed by the addition reaction between the active hydrogen of the secondary amine group on the polyamide and the aldehyde structure of the modifier. In some specific embodiments of the present invention, the amount of the modifier is 0.5% to 10% by mass, preferably 2% to 8% by mass, based on the mass of the polyamide.

[0143] In some specific embodiments, the typical reaction process can be found in Figure 1 The process shown.

[0144] There is no particular restriction on the conditions of the modification reaction. The above reaction can be carried out by mixing the modifier and polyamide at 40-100°C, preferably 50-90°C. If necessary, an organic solvent can be used. For example, when using the modifier, an organic solvent such as alcohol can be used to assist in dissolving the modifier.

[0145] By introducing active phenolic hydroxyl groups into the polyamide structure, after being blended with the epoxy component, the ring-opening curing of the epoxy structure at low temperature can be promoted, so that the amine curing agent of the present invention can be cured at room temperature, low temperature (even around 0°C), and humid environment. The effect of lowering the temperature on the polyamide curing agent decreases with the increase in the amount of polyamide resin added. In addition, a benzene ring structure is introduced into the polyamide structure to improve the rigidity and heat deformation temperature of the subsequent epoxy resin cured product, so that the cured product has both flexibility and rigidity. At the same time, the introduction of the aromatic structure in the modifier can also improve the compatibility of the polyamide curing agent with the epoxy resin, so that the performance of the subsequent epoxy resin cured product is more outstanding.

[0146] <Third Aspect>

[0147] In a third aspect of the present invention, a curing agent composition comprising the amine curing agent of the present invention is provided.

[0148] In addition to the above-mentioned amine curing agent of the present invention, the curing agent composition may also use other types of epoxy curing agents in the art for any purpose, and these curing agents include but are not limited to: phenolic substances, phenolic resins, polyisocyanates, polyamides, alcohol compounds (including small molecule alcohol compounds and polymer alcohols such as polyether polyols), amine compounds (monoamines or polyamines), and carboxyl-containing compounds.

[0149] In some preferred embodiments of the present invention, the curing agent composition may be a mixture of the amine curing agent of the present invention and one or more of a phenolic resin and a polyamide.

[0150] In addition to the various curing agents disclosed above, the curing agent composition of the present invention may also include an accelerator for epoxy curing. The curing accelerator is selected from any one of imidazole compounds, tertiary amine compounds, dicyandiamide, quaternary ammonium salts, organic phosphorus compounds, pyridine compounds and DBU (diazabicyclo); preferably, the imidazole compound is selected from any one of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-phenylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole and trimellitic acid 1-cyanoethyl-2-undecylimidazole salt or a combination of at least two; preferably, the tertiary amine compound is selected from any one of triethanolamine, tetramethylguanidine, triethylenediamine, benzyldimethylamine or N,N-dimethylpiperazine or a combination of at least two; preferably, the organic phosphorus compound is triphenylphosphine and its derivatives.

[0151] In some preferred embodiments of the present invention, the curing agent composition contains at least 50% by mass of the amine curing agent of the present invention, preferably at least 60% by mass, and more preferably at least 70% by mass or at least 80% by mass.

[0152] <Fourth Aspect>

[0153] In a fourth aspect of the present invention, a curable composition comprising the above curing agent composition is provided.

[0154] In some specific embodiments, the curable composition of the present invention includes an epoxy component and the curing agent composition.

[0155] The epoxy component is not particularly limited and may be an epoxy resin commonly used in the art, in particular, an epoxy resin that can be used to form a coating or a film.

[0156] Generally, such epoxy components may include glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, alicyclic epoxy resins, and silicone-modified epoxy resins.

[0157] The glycidyl ether epoxy resin can be bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, o-cresol epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, tetramethyl biphenyl epoxy resin, biphenyl phenol epoxy resin, dicyclopentadiphenol epoxy resin.

[0158] The glycidyl ester epoxy resin can be diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl terephthalate, diglycidyl isophthalate, diglycidyl tetrahydrophthalate, diglycidyl methyltetrahydrophthalate, diglycidyl endomethyltetrahydrophthalate, and diglycidyl adipic acid.

[0159] The glycidylamine epoxy resin can be triglycidyl isocyanurate, triglycidyl p-aminophenol, tetraglycidyl diaminodiphenylmethane, diisopropylphenylene tetraglycidylamine, tetramethylisopropylphenylene tetraglycidylamine, N,N,N',N'-tetraepoxypropyl-4,4-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether tetraglycidylamine.

[0160] The alicyclic epoxy resin can be 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, bis((3,4-epoxycyclohexyl)methyl)adipate, 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 4-vinyl-1-cyclohexene diepoxide, dicyclopentadiene diepoxide, 1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexanecarboxylate).

[0161] The organosilicon-modified epoxy resin includes a modified epoxy resin in which an organosilicon structure is introduced into epoxy molecules to increase toughness.

[0162] In some preferred embodiments of the present invention, the epoxy resin is selected from one or more of bisphenol A epoxy resin, o-cresol epoxy resin, tetramethyl biphenyl epoxy resin, dicyclopentadiphenol epoxy resin and triglycidyl isocyanurate. More typically, for example, E51 epoxy resin can be used.

[0163] There is no particular limitation on other components in the above composition, and optionally, the composition may include any one or a combination of at least two of diluents, flame retardants, solid fillers, defoamers, antistatic agents, leveling agents, coupling agents, anti-aging agents, anti-settling agents, wetting and dispersing agents or toughening agents.

[0164] As for the diluent, active or inactive diluents can be used to adjust the viscosity of the system, such diluents include but are not limited to: C 12 ~C 14One or more of alkyl glycidyl ether, butyl glycidyl ether, benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,2-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, benzyl alcohol, phenylethyl alcohol, nonylphenol, propylene carbonate, trimethylolpropane triacrylate, diisopropyl alcohol methyl ether, toluene and xylene.

[0165] As the flame retardant, for example, a phosphorus-based flame retardant containing an aromatic group and a fluorine-based flame retardant can be used.

[0166] For the solid filler, it can be selected from any one or a combination of at least two of white carbon black, titanium dioxide, aluminum hydroxide, carbon black, zinc stearate, talc, calcium carbonate, barium sulfate, montmorillonite, diatomaceous earth, kaolin, gypsum, mica, magnesium hydroxide or conductive materials (carbon nanotubes, graphene, conductive metal particles).

[0167] Furthermore, the curable composition of the present invention can be applied to adhesives and coatings. In some specific embodiments, the curable composition of the present invention can be adjusted to a liquid coatable state at a suitable temperature, and coated on a substrate by roller coating or other spreading methods, and further cured by applying a certain temperature and humidity to obtain a cured coating or film layer.

[0168] Example

[0169] The technical solution of the present invention will be specifically described below through embodiments:

[0170] (raw material)

[0171] The dimer acid and oleic acid used were purchased from Wilmar Surfactant Materials (Lianyungang) Co., Ltd.;

[0172] Diethylenetriamine, triethylenetetramine, and tetraethylenepentamine were purchased from Tosoh Corporation;

[0173] p-Hydroxybenzaldehyde and vanillin were purchased from Shanghai Titan Technology Co., Ltd.

[0174] (Test Method)

[0175] The detection methods used in the following embodiments and comparative examples are as follows:

[0176] (1) Amine value: Accurately weigh an appropriate amount of polyamide sample, place it in a 250 mL conical flask, add about 50 mL of acetic acid, and shake until it is completely dissolved. If the sample is difficult to dissolve, slightly heat it until it is completely dissolved, then cool it to room temperature. After the sample is completely dissolved, add 5 to 6 drops of bromophenol blue indicator, shake well, and titrate with a hydrochloric acid-ethanol standard solution with c(HCl)=0.1 mol / L. The end point is when the solution changes from blue to yellow.

[0177] (2) Viscosity: The viscosity test is mainly carried out using a BROOKFIELD DV-S digital viscometer. After the digital viscometer is turned on, turn on the constant temperature water bath, set the temperature to the required temperature (40°C), weigh a certain amount of polyamide sample and place it in the small sample adapter 13R (9.0 mL for the 31# rotor sample and 9.4 mL for the 34# rotor sample), then place the sample cup in the insulation jacket, select the appropriate rotor model and speed, press the power button to start the test, and end the test after the data reads a stable value.

[0178] (3) Gel time and curing time: Weigh a total of 100 g of the curing agent and epoxy resin (E51) at room temperature in proportion, mix them evenly, and place them at room temperature for observation. When the sample begins to release heat and can be drawn with a glass rod but is not easy to apply, the time from the time the sample is stirred evenly to the time it is drawn and not easy to apply is the gel time; when the surface of the sample reaches a Shore hardness (D meter) of more than 60 HD, and the sample in the paper cup is evenly cured from top to bottom, the time from the time the sample is stirred evenly to the time the Shore hardness (D meter) is more than 60 HD is the curing time.

[0179] (4) Surface drying time and actual drying time: Surface drying time refers to the time it takes for the coating surface to form a film, and actual drying time refers to the time it takes for the coating to form a solid coating. Use BGD 262 BGD intelligent linear drying time recorder to test surface drying time and actual drying time.

[0180] At room temperature, the curing agent and epoxy resin are mixed evenly in proportion and then evenly applied on a glass test plate (329×24×3mm) with a specific film applicator. The coating thickness is set to 150μm, and then the test plate is placed on the instrument bracket and fixed. The drying speed test is carried out under the test temperature and relative humidity of 50±5%. During the test, the stylus will be drawn on the glass test plate at a uniform speed. At different drying stages, the stylus leaves different tracks on the sample surface. When the stylus leaves a scratch mark on the sample surface, the time used is the surface drying time; when the stylus cannot leave a mark on the sample surface, the time used is the actual drying time.

[0181] (5) Mechanical properties: The tensile strength and flexural strength samples were prepared and tested in accordance with the national standard "GBT 2567-2008 Test method for properties of resin castings"; the shear strength samples were prepared and tested in accordance with the national standard "GBT 7124-2008 Determination of tensile shear strength of adhesives (rigid material to rigid material)".

[0182] Test sample preparation process: Heat the curing agent and epoxy resin in an oven at 80°C for 1.5 hours, then mix them evenly in proportion and pour them into the mold. Cure them at room temperature for 18 to 20 hours, then heat and cure them in an oven at 80°C for 3 hours. After high-temperature curing, take out the mold and take out the prepared specimen from the mold after it returns to room temperature.

[0183] Example 1

[0184] The raw materials are 495 parts of dimer acid, 240 parts of oleic acid, 108 parts of diethylenetriamine, 157 parts of pentaethylenehexamine, and 200 parts of p-hydroxybenzaldehyde-methanol solution (p-hydroxybenzaldehyde mass concentration is 25%). The specific implementation steps are as follows:

[0185] Add dimer acid, oleic acid, diethylenetriamine and pentaethylenehexamine into a four-mouth reaction kettle in sequence, introduce nitrogen after stirring evenly, raise the temperature to 250°C, keep the temperature for reaction for 3 hours, then cool to 200°C, reduce pressure and evacuate for 1 hour to discharge the water generated by the reaction.

[0186] After the reaction is completed, the mixture is cooled to below 50° C., a p-hydroxybenzaldehyde-methanol solution (p-hydroxybenzaldehyde mass concentration is 25%) is added, and the mixture is kept warm at 50° C. for 1 hour, then the temperature is raised to 80° C. and kept warm for 2 hours. After the reaction is completed, the mixture is decompressed and vacuumed for 1 hour to remove the methanol, and the mixture is filtered to obtain the final product.

[0187] Comparative Example 1

[0188] The raw materials are 506 parts of dimer acid, 259 parts of oleic acid, 98 parts of diethylenetriamine, and 157 parts of pentaethylenehexamine. The specific implementation steps are as follows:

[0189] Add dimer acid, oleic acid, diethylenetriamine and pentaethylenehexamine into a four-mouth reaction kettle in order, stir evenly, introduce nitrogen and heat to 250°C, keep the temperature for 3 hours, then cool to 200°C, reduce pressure and vacuum for 1 hour to discharge the water generated by the reaction. After the reaction is completed, cool to 80°C and filter to obtain the final product.

[0190] Table 1 Comparison of physical and chemical indicators and curing speed

[0191]

[0192] Example 2

[0193] The raw materials are 612 parts of dimer acid, 117 parts of oleic acid, 271 parts of triethylenetetramine, and 300 parts of vanillin-methanol solution (the mass concentration of vanillin is 20%). The specific implementation steps are as follows:

[0194] Add dimer acid, oleic acid and triethylenetetramine into a four-mouth reaction kettle in sequence, introduce nitrogen after stirring evenly, raise the temperature to 260°C, keep the temperature for reaction for 3 hours, then cool to 200°C, reduce pressure and evacuate for 1 hour to discharge the water generated by the reaction.

[0195] After the reaction is completed, the mixture is cooled to below 50°C, and a vanillin-methanol solution (with a p-hydroxybenzaldehyde mass concentration of 20%) is added. The mixture is kept at 50°C for 1 hour, and then the temperature is raised to 80°C and kept for 2 hours. After the reaction is completed, the mixture is decompressed and vacuumed for 1 hour to remove the methanol, and the mixture is filtered to obtain the final product.

[0196] Comparative Example 2

[0197] The raw materials are 627 parts of dimer acid, 122 parts of oleic acid, and 251 parts of triethylenetetramine. The specific implementation steps are as follows:

[0198] Add dimer acid, oleic acid and triethylenetetramine into a four-mouth reaction kettle in sequence, stir evenly, introduce nitrogen and heat to 260°C, keep the temperature for 3 hours, then cool to 200°C, reduce pressure and vacuum for 1 hour to discharge the water generated by the reaction. After the reaction is completed, cool to 80°C and filter to obtain the final product.

[0199] Table 2 Comparison of physical and chemical indicators and curing speed

[0200]

[0201] Example 3

[0202] The raw materials are 588 parts of dimer acid, 64 parts of oleic acid, 119 parts of diethylenetriamine, 229 parts of pentaethylenehexamine, and 200 parts of p-hydroxybenzaldehyde-methanol solution (p-hydroxybenzaldehyde mass concentration is 25%). The specific implementation steps are as follows:

[0203] Add dimer acid, oleic acid, diethylenetriamine and pentaethylenehexamine in sequence into a four-mouth reaction kettle, stir evenly, introduce nitrogen and heat to 245°C, keep the temperature for 3 hours, then cool to 200°C, reduce pressure and evacuate for 1 hour to discharge the water generated by the reaction. After the reaction is completed, cool to below 50°C, add p-hydroxybenzaldehyde-methanol solution (p-hydroxybenzaldehyde mass concentration is 25%), keep the temperature at 50°C for 1 hour, then heat to 80°C and keep the temperature for 2 hours, after the reaction is completed, reduce pressure and evacuate for 1 hour to discharge the methanol, filter and obtain the final product.

[0204] Comparative Example 3

[0205] The raw materials are 597 parts of dimer acid, 75 parts of oleic acid, 105 parts of diethylenetriamine, and 223 parts of pentaethylenehexamine. The specific implementation steps are as follows:

[0206] Add dimer acid, oleic acid, diethylenetriamine and pentaethylenehexamine into a four-mouth reaction kettle in order, stir evenly, introduce nitrogen and heat to 245°C, keep the temperature for 3 hours, then cool to 200°C, reduce pressure and vacuum for 1 hour to discharge the water generated by the reaction. After the reaction is completed, cool to 80°C and filter to obtain the final product.

[0207] Table 3 Comparison of physical and chemical indicators and curing speed

[0208]

[0209] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present disclosure should not be limited thereto.

[0210] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0211] Industrial Applicability

[0212] The amine curing agent of the present invention can be industrially prepared and used for curing epoxy resins.

Claims

1. An amine curing agent, characterized in that The amine curing agent includes a modified polyamide, and the modified polyamide includes the following structure: i) amine residues derived from secondary amine groups in the polyamide structure; ii) derived from the following structural formula (I) connected to the amino residue described in i) by a modifier Wherein, in the formula (I): Ar represents a substituted or unsubstituted aromatic group; n represents an integer from 1 to 10; -(OH) n Directly bonded to the aromatic ring of the aromatic group of Ar; * represents the position where the structure of formula (I) is connected to the amino residue in i), wherein the modified polyamide includes amino residues derived from primary and secondary amino groups in the polyamide structure; the amino residues are derived from the polyacid and / or polyamine forming the polyamide, The polyamide is obtained by polycondensation reaction of a polyacid and a polyamine, and the polyacid includes a dimer acid.

2. The amine curing agent according to claim 1, characterized in that The Ar-(OH) n It has the following structure: in, R, when it appears each time, is the same or different and independently represents one of hydrogen, an alkyl group, a halogen group, an alkoxy group, an aryloxy group, a carboxyl-containing group, an amino-containing group, an ester-containing group, and a keto-containing group; a represents an integer from 0 to 4; n1 represents an integer from 1 to 5; b represents an integer from 0 to 6; n2 represents an integer from 1 to 7.

3. The amine curing agent according to claim 1 or 2, characterized in that The Ar-(OH) n It has the structure of the following formula (II-1): Here, R represents hydrogen, an alkyl group, a halogen group, an alkoxy group or an aryloxy group.

4. The amine curing agent according to claim 1 or 2, characterized in that The molecular weight of the polyamide is less than 10,000, or the amine value of the amine curing agent is 100 to 400 mgKOH / g.

5. A method for preparing an amine curing agent according to any one of claims 1 to 4, characterized in that: The method comprises: a step of obtaining polyamide, and a step of modifying polyamide, In the polyamide modification step, a modifier having the following formula (M) is used to react with the polyamide: Wherein, Ar, n, -(OH) in the formula (M) n and Ar-(OH) n The definition is the same as that in any one of claims 1 to 4.

6. The method according to claim 5, characterized in that The polyamine structure includes secondary amine groups.

7. The method according to claim 5 or 6, characterized in that: In the step of modifying the polyamide, the modifier includes benzaldehyde having a phenolic hydroxyl group.

8. A curing agent composition, characterized in that The composition comprises the amine curing agent according to any one of claims 1 to 4 or the amine curing agent obtained by the method according to any one of claims 5 to 7.

9. A curable composition, characterized in that The curable composition comprises the curing agent composition according to claim 8, an epoxy component and optionally further comprises a catalyst.

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