A low temperature curable coating and its preparation and use

Abstract

The application discloses a low-temperature curable paint and preparation and application thereof, which is a mixture of component A and component B with a mass ratio of 22:3.4-5.1; the component A comprises the following components in mass fractions: 88-96 parts of epoxy resin, 2.3-2.7 parts of butyronitrile rubber, 2.1-2.5 parts of aluminum silicate powder, 1.5-2.0 parts of a pH regulator, 1.2-1.8 parts of a dispersing agent, 0.8-1.0 parts of a leveling agent, 0.8-1.0 parts of a defoaming agent and 25-32 parts of an organic solvent; the component B comprises the following components in mass fractions: 10-18 parts of modified polyamine and 3.3-4.5 parts of NIPAAm modified boron nitride; the modified polyamine has a chemical formula of RNH-CS-NH2, wherein R represents any group; the epoxy resin paint can be cured at low temperature (-10 DEG C), and the curing is rapid; the mechanical properties of the cured film are stable, and the protection effect is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, in particular to a low-temperature curable coating and its preparation and application. BACKGROUND

[0002] In Xinjiang, Northeast China, Northwest China and other regions, the climate is harsh, and the diurnal temperature difference is large in winter, with the minimum temperature reaching minus 10-20 degrees Celsius, which brings great inconvenience to the construction of coatings.

[0003] In existing coatings, amine curing agents can only be cured at about 20℃, and cannot be cured at all at about -10℃. Although polythiol curing agents can be cured at -10℃, they have poor durability and short service life. Other types of coatings also have the problems of low-temperature curing or long curing time (≥10h), which results in that the mechanical properties of the paint film cannot meet the application requirements.

[0004] Therefore, a technical solution is needed to achieve rapid curing of the coating at low temperature and good protective performance of the cured coating. SUMMARY

[0005] Therefore, the present application provides a low-temperature curable coating and its preparation and application, which solves the technical problem of how to achieve rapid curing of the coating at low temperature and good protective performance of the coating after curing.

[0006] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a low-temperature curable coating, which is a mixture of component A and component B with a mass ratio of 22:3.4-5.1; component A includes the following components in mass fraction: 88-96 parts of epoxy resin, 2.3-2.7 parts of nitrile rubber, 2.1-2.5 parts of aluminum silicate powder, 1.5-2.0 parts of pH adjuster, 1.2-1.8 parts of dispersant, 0.8-1.0 parts of leveling agent, 0.8-1.0 parts of defoaming agent, and 25-32 parts of organic solvent; component B includes the following components in mass fraction: 10-18 parts of modified polyamine, 3.3-4.5 parts of NIPAAm modified boron nitride; the chemical formula of the modified polyamine is RNH-CS-NH2, wherein R represents any group.

[0008] Preferably, the preparation method of the modified polyamine is as follows: taking a polyamine containing primary amino group and thiourea as raw materials, heating in an oil bath at 100-130℃ to carry out polymerization reaction, and thus obtaining the modified polyamine.

[0009] Preferably, the polyamine containing primary amino group is one or more of triethylenetetramine, ethylenediamine and polyamide.

[0010] Preferably, the mass ratio of the polyamine containing primary amino group to thiourea is (1.2-1.8):1.

[0011] Preferably, the preparation method of the NIPAAm modified boron nitride is as follows:

[0012] K1. Dissolve boron nitride in hydrogen peroxide solution, heat and react to obtain activated boron nitride;

[0013] K2. Under N2 atmosphere, add NIPAAm and HMTETA to the DMF solution of the activated boron nitride, and stir to react to obtain the modified boron nitride.

[0014] Preferably, the temperature of the heating reaction is 120-130℃, and the reaction time is 3h.

[0015] Preferably, the mass ratio of boron nitride to NIPAAm is 100:70-90; and the mass ratio of boron nitride to HMTETA is 100:0.15-0.37.

[0016] Preferably, after the heating reaction in step K1 ends, the product is washed with deionized water to pH 6-7.

[0017] In the second aspect, the application provides a preparation method of a low-temperature curable coating, which comprises stirring and mixing component A and component B according to the ratio to obtain the low-temperature curable coating.

[0018] In the third aspect, the application provides the application of the low-temperature curable coating at-10-40℃.

[0019] The application has the following beneficial effects: the modified polyamine and the NIPAAm modified boron nitride are used in cooperation to realize the curability of the epoxy resin coating at low temperature (-10℃), and the coating is quickly cured, and the mechanical properties of the cured film are stable, and the protection effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The turbidity-time change curve of the modified boron nitride and the ungrafted NIPAAm boron nitride (active boron nitride);

[0021] Figure 2 The coating temperature change of the mixture of components A and B. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0023] The application provides a low-temperature curable coating, which is a mixture of component A and component B in a mass ratio of 22:3.4-5.1; component A comprises the following components in a mass fraction: 88-96 parts of an epoxy resin, 2.3-2.7 parts of a butyronitrile rubber, 2.1-2.5 parts of an aluminum silicate powder, 1.5-2.0 parts of a pH regulator, 1.2-1.8 parts of a dispersant, 0.8-1.0 parts of a leveling agent, 0.8-1.0 parts of an antifoaming agent, and 25-32 parts of an organic solvent; and component B comprises the following components in a mass fraction: 10-18 parts of a modified polyamine, and 3.3-4.5 parts of NIPAAm modified boron nitride; the modified polyamine has a chemical formula of RNH-CS-NH2, wherein R represents any group.

[0024] The application adopts a two-component curing mode to form the low-temperature curable coating. In component B, the modified polyamine has a faster and more active reaction rate with the epoxy group in the epoxy resin than the unmodified polyamine, so that the curing time can be significantly shortened. Meanwhile, the active hydrogen atoms in the primary amine and the secondary amine of the modified polyamine can open the epoxy group at a low temperature, for example, -10 ℃, to occur cross-linking and curing, so as to realize the curing at a low temperature. On the other hand, the NIPAAm modified boron nitride in component B introduces NIPAAm (N-isopropyl acrylamide). The application utilizes the temperature responsiveness of NIPAAm, which has the property of a low critical transition temperature. When the critical transition temperature is reached, NIPAAm collapses from the solution to form a spherical shape. Boron nitride is a ceramic material with excellent thermal conductivity. The NIPAAm modified boron nitride can also have temperature responsiveness. When the temperature rises to a certain value (for example, 42 ℃), the NIPAAm modified boron nitride occurs self-assembly to form a gel state under the action of electrostatic force and hydrophobic force. The self-assembly process accelerates the movement of molecules in the coating, thereby accelerating the curing speed of the coating and shortening the curing time. After the self-assembly is completed, a large number of amino groups on the side chain are exposed, which improves the compatibility of the NIPAAm modified boron nitride with the coating and effectively improves the film-forming property of the epoxy resin at a low temperature after curing.

[0025] It is worth noting that the NIPAAm modified boron nitride in the application can only occur self-assembly reaction when the modified polyamine in the application and the epoxy resin exist at the same time. The reason is that the active hydrogen atoms in the primary amine and the secondary amine of the modified polyamine can open the epoxy group to occur cross-linking and curing. This process is accompanied by a violent exothermic process and the exothermic speed is extremely fast. The heat released reaches the response temperature of the NIPAAm modified boron nitride, which provides conditions for the self-assembly process of the NIPAAm modified boron nitride.

[0026] In addition, the exothermic reaction process of the modified polyamine and the epoxy resin is fast and the heat is large, which is easy to cause the epoxy resin to be brittle and have poor thermal conductivity in a low temperature state after curing. The regularly arranged boron nitride after self-assembly solves this problem due to its excellent thermal conductivity, which effectively improves the toughness and thermal conductivity of the epoxy resin in a low temperature state after curing. Since the self-assembly process is a process of first absorbing heat and then releasing heat, the exothermic process can be effectively delayed, so that the entire coating continuously releases heat for a period of time, thereby realizing rapid curing in a low temperature environment. Finally, the NIPAAm modified boron nitride and the modified polyamine cooperate to realize rapid curing in a low temperature environment (-10°C), and the mechanical properties of the coating are good.

[0027] In some embodiments, the epoxy resin is one or more of BDR 6100, E-12, E-44, E-51; the butyronitrile rubber is 2255F, wherein the content of butadiene is greater than or equal to 78%; the aluminum silicate powder is CAS12141; and the dispersant is one or both of CP5, 731A or D346.

[0028] The preparation method of the modified polyamine is as follows: taking a polyamine containing a primary amino group and thiourea as raw materials, heating in an oil bath at 100-130°C to carry out a polymerization reaction, obtaining a brownish viscous liquid, and cooling to room temperature to obtain the modified polyamine.

[0029] During the preparation process, the polyamine and the thiourea undergo an addition reaction:

[0030] RNH2+H2N-CS-NH2=RNH-CS-NH2+NH3.

[0031] The reactivity of the amino group on the thiourea and the primary amino group on the polyamine is very high, and a polymerization reaction can occur under heating conditions to release one molecule of ammonia. The activity of the addition product is higher than that of the polyamine, so the modified polyamine has a faster curing speed and a lower curing temperature at low temperatures.

[0032] The polyamine containing a primary amino group is one or more of triethylenetetramine, ethylenediamine, and polyamide.

[0033] The mass ratio of the polyamine containing a primary amino group to the thiourea is (1.2-1.8):1. If the amount of thiourea is too high, the amount of by-products will also increase, which will affect the mechanical properties of the coating after curing. Excessive thiourea will first greatly shorten the curing time, but it is likely that the coating will be cured in the bucket before it can be applied to the wall, so the curing time is not the shorter the better. Secondly, excessive amount will increase the reaction rate and release more heat. A high temperature will produce many by-products, which will affect the mechanical properties of the film after curing.

[0034] The preparation method of the NIPAAm modified boron nitride is as follows:

[0035] K1. Dissolve boron nitride in hydrogen peroxide solution, heat and react to obtain activated boron nitride;

[0036] K2. Under N2 atmosphere, add NIPAAm and HMTETA to the DMF solution of activated boron nitride, and stir to react, to obtain modified boron nitride.

[0037] Preferably, the temperature for heating and reacting is 120-130℃, and the reaction time is 3h.

[0038] Preferably, the mass ratio of boron nitride to NIPAAm is 100:70-90, and the mass ratio of boron nitride to HMTETA is 100:0.15-0.37. A low ratio may result in a low grafting rate, and a high ratio may result in ineffective exposure of grafting sites, leading to a decrease in grafting rate and waste of raw materials.

[0039] Preferably, after the heating and reaction in step K1, the product is washed with deionized water to a pH of 6-7.

[0040] Specifically, the preparation process of NIPAAm modified boron nitride is as follows: after stirring boron nitride in 30% hydrogen peroxide for 24h, place it in a reaction kettle and react at 120℃ for 3h. After cooling, filter out the boron nitride with a 0.45mm microporous filter membrane, wash with deionized water to a pH of 6, and dry in a drying oven at 80℃ for standby use. Mix the treated boron nitride with dimethylformamide (DMF) according to a mass ratio of 8:(23.4-32.6) for ultrasonic mixing for 2h. Then, introduce high-purity nitrogen into the boron nitride solution for 10min, and sequentially add N-isopropyl acrylamide (NIPAAm) accounting for 70-90% of the mass of boron nitride and hexamethyl triethylene tetramine (HMTETA) accounting for 0.15-0.37% of the mass of boron nitride into the oxygen-free boron nitride solution, and stir for 24h. Then, transfer the reaction liquid to a 14000Da dialysis bag and dialyze to a pH of 7 to obtain NIPAAm modified boron nitride.

[0041] In a second aspect, the application provides a preparation method of a low-temperature curable coating. Components A and B are mixed according to the ratio and stirred at a speed of 800r / min-1000r / min for 10min to obtain a low-temperature curable coating.

[0042] In a third aspect, the application provides an application of a low-temperature curable coating at-10-40℃, especially at-10℃-0℃, to achieve rapid curing (less than or equal to 3h) in this temperature range.

[0043] The present application is further described below through specific embodiments.

[0044] Raw material preparation

[0045] NIPAAm modified boron nitride: the boron nitride was placed in 30% hydrogen peroxide for stirring for 24 h, then placed in a reaction kettle for reaction at 120℃ for 3 h, after cooling, the boron nitide was filtered out with a 0.45 mm microporous filter membrane, washed with deionized water until pH 6, and dried in a drying oven at 80℃ for standby, to obtain active boron nitride, the active boron nitride was ultrasonically mixed with dimethylformamide (DMF) according to a mass ratio of 8:26.7 for 2 h for standby. High-purity nitrogen was passed into the boron nitride solution for 10 min, N-isopropyl acrylamide (NIPAAm) with a mass of 78% of the boron nitride and hexamethyltriethylenetetramine (HMTETA) with a mass of 0.28% of the boron nitride were sequentially added into the boron nitride solution in an oxygen-free system, stirred for 24 h, and then the reaction solution was transferred to a 14000 Da dialysis bag for dialysis until pH 7, to obtain NIPAAm modified boron nitride.

[0046] Modified polyamine-1: triethylenetetramine and thiourea were added into a three-necked flask according to a mass ratio of 1.6:1, heated in an oil bath at 120℃ for 2 h to obtain a brownish sticky liquid, which was cooled to room temperature to obtain the modified polyamine.

[0047] Modified polyamine-2: triethylenetetramine and thiourea were added into a three-necked flask according to a mass ratio of 2:1, heated in an oil bath at 120℃ for 2 h to obtain a brownish sticky liquid, which was cooled to room temperature to obtain the modified polyamine.

[0048] Example 1

[0049] A low-temperature curable coating, which is a mixture of component A and component B according to a mass ratio of 22:3.6; component A includes ingredients in mass fractions as follows: 45 parts of epoxy resin E-12 and 45 parts of E-44 epoxy resin, 2.4 parts of butyronitrile rubber 2255F, 2.4 parts of aluminum silicate powder, 1.7 parts of pH adjuster, 1.5 parts of dispersant BYK, 1.0 part of leveling agent BYK399, 1.0 part of defoaming agent BYK8801, 26 parts of organic solvent PMA; component B includes ingredients in mass fractions as follows: 11 parts of modified polyamine-1, 3.7 parts of NIPAAm modified boron nitride.

[0050] Example 2

[0051] A low-temperature curable coating, which is the same as example 1 except that it includes 18 parts of modified polyamine-1.

[0052] Example 3

[0053] A low-temperature curable coating, which is the same as example 1 except that it includes 15 parts of modified polyamine-1.

[0054] Example 4

[0055] A low temperature curable coating, otherwise identical to Example 1, except that 4.5 parts of NIPAAm modified boron nitride was included.

[0056] Comparative Example 1

[0057] A low temperature curable coating, otherwise identical to Example 1, except that NIPAAm modified boron nitride was replaced by boron nitride.

[0058] Comparative Example 2

[0059] A low temperature curable coating, otherwise identical to Example 1, except that NIPAAm modified boron nitride was replaced by active boron nitride.

[0060] Comparative Example 3

[0061] A low temperature curable coating, otherwise identical to Example 1, except that NIPAAm modified boron nitride was not included.

[0062] Comparative Example 4

[0063] A low temperature curable coating, otherwise identical to Example 1, except that modified polyamine-1 was replaced by triethylenetetramine.

[0064] Comparative Example 5

[0065] A low temperature curable coating, otherwise identical to Example 1, except that modified polyamine-1 was replaced by modified polyamine-2.

[0066] Comparative Example 6

[0067] A low temperature curable coating, otherwise identical to Example 1, except that 20 parts of modified polyamine-1 was included.

[0068] Comparative Example 7

[0069] A low temperature curable coating, otherwise identical to Example 1, except that 6 parts of NIPAAm modified boron nitride was included.

[0070] Testing and Evaluation

[0071] Self-assembly effect of NIPAAm modified boron nitride: The turbidity-time curves of modified boron nitride and ungrafted NIPAAm boron nitride (active boron nitride) were monitored by UV spectrophotometer at 45°C (as shown in Figure 1 The turbidity-time curve of BN(NIPAAm) showed a typical "S" type self-assembly kinetic curve, and the whole process included three stages of lag phase, growth phase and plateau phase, successfully proving that the modified boron nitride grafted NIPAAm had self-assembly ability under certain temperature conditions.

[0072] The temperature change of the paint obtained after mixing components A and B in Example 1, Comparative Example 2 and Comparative Example 3 over time is shown in Figure 1. Figure 2 In Comparative Example 3, the components A and B were mixed uniformly, and the paint released a large amount of heat in a short time, and the heat release speed was extremely fast. The temperature returned to room temperature in about 40 minutes, and the paint was difficult to stir. In Comparative Example 2, the ungrafted modified boron nitride (active boron nitride) was added. Due to the excellent thermal conductivity of boron nitride, the temperature drop speed was slightly improved, but there was no obvious difference. If there is no nipaa grafted, the whole process is rapid heating and then rapid cooling. In Example 1, the heat provided by the heat release provides conditions for the self-assembly of the modified boron nitride, and the self-assembly process absorbs heat first and then releases heat, so the heat release speed slows down, and a constant temperature plateau appears, which allows the curing agent to react and then solidify. The paint can be rapidly solidified at this temperature (42°C), and the whole solidification time is within 2-3 hours. It is worth noting that low-temperature curing does not mean that the faster the curing speed is, the better. Too fast curing speed may cause defects such as pinholes and small holes on the surface of the paint film, and too short curing time may cause problems such as difficult construction. In addition, the large temperature difference caused by the violent heat release during the curing process and the extremely low construction environment temperature will result in poor mechanical properties of the coating, and may cause cracking, peeling and other phenomena. Therefore, the curing time is preferably controlled within 2-3 hours, which can ensure the construction efficiency and the mechanical properties and adaptability of the paint after coating.

[0073] The paint in the examples and comparative examples was tested for curing performance, curing time, and mechanical properties at -10°C, and the results are shown in Table 1.

[0074] Table 1 Test Results

[0075]

[0076]

[0077] From the results, boron nitride cannot be dissolved in the solvent without modification, which seriously affects the adhesion and mechanical properties of the coating after film formation; the modified boron nitride without grafted NIPAAm has good compatibility with the coating, but has no promoting effect on the low-temperature curing of the coating, and the coating is cured in a very short time, resulting in brittle coating, which is prone to cracking and peeling under external force; the polyamine cannot react with the epoxy resin at low temperature without modification, the coating is difficult to dry, and the self-assembly of the modified boron nitride cannot be provided, and the mechanical properties of the coating cannot meet the application; the dosage of thiourea is too high, although the drying time is shortened, but the service time of the curing agent is also shortened, and the decomposition of thiourea and triethylenetetramine occurs before the reaction at a high temperature, and the by-products also increase, which affects the mechanical properties of the coating after curing and film formation; the modified polyamine is excessive, the curing time is shortened, the coating is brittle, and the peeling and cracking phenomenon is easy to occur; the modified boron nitride is excessive, more heat is absorbed and released during self-assembly, the temperature change trend is too large, and the mechanical properties of the coating after film formation are decreased.

[0078] It should be noted that each of the above embodiments belongs to the same inventive concept, and the description of each embodiment has its own emphasis. If not fully described in an individual embodiment, reference can be made to the description in other embodiments.

[0079] The above embodiments only express the implementation of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A low temperature curable coating characterized in that, It is a mixture of component A and component B with a mass ratio of 22:3.4-5.1; the component A comprises ingredients with mass fractions as follows: 88-96 parts of epoxy resin, 2.3-2.7 parts of nitrile rubber, 2.1-2.5 parts of aluminum silicate powder, 1.5-2.0 parts of pH regulator, 1.2-1.8 parts of dispersant, 0.8-1.0 parts of leveling agent, 0.8-1.0 parts of defoaming agent, 25-32 parts of organic solvent; the component B comprises ingredients with mass fractions as follows: 10-18 parts of modified polyamine, 3.3-4.5 parts of NIPAAm modified boron nitride; The modified polyamine has a chemical formula of RNH-CS-NH2, wherein R represents any group; the modified polyamine is prepared by using a polyamine containing primary amino group and thiourea as raw materials, heating in an oil bath at 100-130℃ to perform a polymerization reaction, and obtaining the modified polyamine; the polyamine containing primary amino group is one or several of triethylenetetramine, ethylenediamine, and polyamide; the mass ratio of the polyamine containing primary amino group to thiourea is (1.2-1.8):1; and the NIPAAm modified boron nitride is prepared as follows: K1. Dissolving boron nitride in hydrogen peroxide solution and heating to react to obtain activated boron nitride; K2. Under N2 atmosphere, adding NIPAAm and HMTETA into a DMF solution of the activated boron nitride, stirring to react, and obtaining the modified boron nitride; The mass ratio of the boron nitride to the NIPAAm is 100:70-90; and the mass ratio of the boron nitride to the HMTETA is 100:0.15-0.

37.

2. The low temperature curable coating of claim 1, wherein, The heating reaction is performed at a temperature of 120-130℃ for 3h.

3. The low temperature curable coating of claim 1, wherein, After the heating reaction in step K1, the product is further washed with deionized water until the pH is 6-7.

4. A process for the preparation of a low temperature curable coating as claimed in any one of claims 1 to 3, characterised in that, Mixing component A and component B according to the ratio to obtain the low-temperature curable coating.

5. Application of the low-temperature curable coating according to any one of claims 1-3 at -10-40℃.

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