Epoxy modified isocyanate as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and provides epoxy modified isocyanate as well as a preparation method and application thereof. According to the epoxy modified isocyanate provided by the invention, the diisocyanate, the polyether polyol, the epoxy monomer, the sealing agent and the catalyst are adopted as main preparation raw materials, and the epoxy monomer is added, so that an epoxy group reacts with an-NCO group of the isocyanate to generate an oxazolidinone structure, and the rigidity of a molecular chain is enhanced; the prepared epoxy modified isocyanate can be used as a curing agent and is used for preparing a single-component polyurethane amino baking coating, the coating is barrier-free, the state of a construction liquid in 24 hours is normal, and the curing agent can be used as a curing agent for curing the single-component polyurethane amino baking coating, so that the curing agent can be used for curing the single-component polyurethane amino baking coating. The flexibility, the hardness, the adhesive force, the impact resistance, the heat stability and the solvent resistance of a paint film can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more specifically, to an epoxy-modified isocyanate and a preparation method and application thereof. Background Art

[0002] Polyurethane curing agent is a special curing agent widely used in furniture, decoration, metal, leather and plastic, etc. Blocked polyisocyanate curing agent has the advantage of long-term stable coexistence with resin components containing active hydrogen groups (hydroxyl, carboxyl, amino, etc.) at room temperature, so it can be made into a one-component polyurethane amino baking coating that is easy to use. After coating construction, at high temperature, the blocked groups lurking in the coating can be unblocked, thereby releasing -NCO active groups, which react chemically with hydroxyl, carboxyl, amino, etc. on the resin molecular chain to form a dense cross-linked structure, so that the paint film has excellent properties such as high adhesion, high strength, weather resistance and cooking resistance, but the defects are also obvious, such as brittle paint film, poor impact resistance, poor thermal stability and poor solvent resistance.

[0003] Therefore, there is an urgent need to provide a polyisocyanate curing agent with a blocking effect, which can be further used to prepare a one-component polyurethane amino baking coating, and the resulting paint film has the characteristics of good flexibility, impact resistance, high thermal stability and solvent resistance. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes an epoxy-modified isocyanate and a preparation method and application thereof. The epoxy-modified isocyanate provided by the present invention, with epoxy monomer added as the main raw material for preparation, can be further used as an epoxy-modified isocyanate curing agent for preparing a one-component polyurethane amino baking coating, has a sealing effect, and the normal stable state of the construction fluid can be maintained for at least 24 hours. The paint film prepared by the epoxy-modified isocyanate has the advantages of good flexibility (at least 8-10mm), high hardness (at least 2H), strong adhesion (at least 1 level), impact resistance (at least 40-50cm), high thermal stability (no change in the paint film after thermal stability test) and solvent resistance (at least 277-289 times of test).

[0005] A first aspect of the present invention provides an epoxy-modified isocyanate curing agent.

[0006] Specifically, an epoxy-modified isocyanate comprises the following preparation raw materials:

[0007] Diisocyanate, polyether polyol, epoxy monomer, blocking agent, catalyst.

[0008] The present invention adds epoxy monomers so that the epoxy group reacts with the -NCO group of isocyanate to generate an oxazolidinone structure, which enhances the rigidity of the molecular chain, reduces the number of weak bonds and hydroxyl groups on the main chain, and not only improves the flexibility of the prepared epoxy-modified isocyanate, but also helps to improve its thermal stability, impact resistance and solvent resistance. The epoxy-modified isocyanate can be used as a curing agent to further prepare a one-component polyurethane amino baking coating, and improve the flexibility, hardness, adhesion, impact resistance, thermal stability and solvent resistance of the paint film.

[0009] In the present invention, the -NCO value refers to the weight of isocyanate (-NCO) groups contained in 100 g of a sample, and the unit is %.

[0010] Preferably, the epoxy-modified isocyanate comprises the following preparation raw materials in parts by weight:

[0011] 15-30 parts of diisocyanate, 8-20 parts of polyether polyol, 5-20 parts of epoxy monomer, 5-20 parts of sealing agent, and 0.01-0.1 parts of catalyst.

[0012] Further preferably, the epoxy-modified isocyanate comprises the following preparation raw materials in parts by weight:

[0013] 17-26 parts of diisocyanate, 10-16 parts of polyether polyol, 8-13 parts of epoxy monomer, 10-14 parts of sealing agent, and 0.01-0.05 parts of catalyst.

[0014] Preferably, the raw materials for preparing the epoxy-modified isocyanate further include an organic solvent.

[0015] Preferably, the raw materials for preparing the epoxy-modified isocyanate further include 30-50 parts of an organic solvent in parts by weight.

[0016] Further preferably, the raw materials for preparing the epoxy-modified isocyanate further include 35-45 parts of an organic solvent in parts by weight.

[0017] Preferably, the diisocyanate is at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and xylylene diisocyanate (XDI).

[0018] More preferably, the diisocyanate is toluene diisocyanate (TDI).

[0019] Preferably, the toluene diisocyanate is a mixture of 80% by mass of 2,4-toluene diisocyanate and 20% by mass of 2,6-toluene diisocyanate (ie, TDI-80).

[0020] Preferably, the polyether polyol is at least one of polyether N204, polyether N210, polyether N310, polyether DP400, polyether DP750E, polyether DE600, polyether DP1000M, and polyether GY1000.

[0021] Preferably, the epoxy monomer is at least one of 3-phenoxy-1,2-epoxypropylene, 3-o-tolyloxy-1,2-epoxypropylene, 3-benzyloxy-1,2-epoxypropylene, and 3-p-tert-butylphenoxy-1,2-epoxypropylene.

[0022] Preferably, the blocking agent is at least one of phenol, caprolactam, methyl ethyl ketone oxime and ethyl acetoacetate.

[0023] Preferably, the catalyst is at least one of dibutyltin dilaurate, monobutyltin oxide, bismuth neodecanoate and bismuth isooctanoate.

[0024] Preferably, the organic solvent is at least one of xylene, cyclohexanone, propylene glycol methyl ether propionate, and butyl acetate.

[0025] Preferably, the viscosity of the epoxy-modified isocyanate is 150-250 sec / coat-4 cup at 25° C., and / or the solid content of the epoxy-modified isocyanate is 60±3 wt %, and / or the -NCO value of the epoxy-modified isocyanate is ≤3%.

[0026] Further preferably, the viscosity of the epoxy-modified isocyanate is 180-230 seconds / coat-4 cup at 25°C, and / or the solid content of the epoxy-modified isocyanate is 60±2wt%, and / or the -NCO value of the epoxy-modified isocyanate is ≤2%.

[0027] A second aspect of the present invention provides a method for preparing epoxy-modified isocyanate.

[0028] A method for preparing epoxy-modified isocyanate comprises the following steps:

[0029] Firstly, diisocyanate and blocking agent are mixed, and then subjected to a first temperature rise reaction and a second temperature rise reaction in sequence to obtain an intermediate. Then, the intermediate is mixed with polyether polyol, epoxy monomer and catalyst, and then subjected to a third temperature rise reaction to obtain the epoxy-modified isocyanate.

[0030] The invention undergoes three temperature-raising reactions, and controls the three temperature-raising reactions to achieve the purpose of controlled polymerization. First, diisocyanate and a blocking agent are mixed and reacted to "block" the -NCO group at one end to obtain an intermediate, and then polyether polyol, epoxy monomer and catalyst are added to continue to react with the -NCO group at the other end. On the one hand, the structural segments in the product prepared by the invention are uniform, the molecular distribution is more uniform, and a controlled polymerization reaction is achieved; on the other hand, the product is further used as a curing agent to prepare a one-component polyurethane amino baking coating with a resin component containing an active hydrogen group such as an amino resin and a hydroxyl resin. Due to the presence of the blocking agent, the coating has a blocking effect, can coexist stably with the resin component for a long time, and the construction liquid is not gelled when placed for a long time. After coating construction, the blocking group is unblocked at high temperature, so that the -NCO group can be released and cross-linked with the active hydrogen group of the resin component to obtain a paint film with good flexibility, high hardness, high adhesion, impact resistance, high thermal stability and solvent resistance.

[0031] Preferably, the temperature of the first temperature-raising reaction is 40-90° C., and / or the time of the first temperature-raising reaction is 120-240 min.

[0032] Further preferably, the temperature of the first temperature-raising reaction is 50-80° C., and / or the time of the first temperature-raising reaction is 150-210 min.

[0033] Preferably, the temperature of the second temperature-raising reaction is 80-110° C., and / or the second temperature-raising reaction is terminated by controlling the -NCO value to 2 / 3 or less of the value before the reaction.

[0034] Further preferably, the temperature of the second temperature-raising reaction is 90-102° C., and / or the second temperature-raising reaction is terminated by controlling the -NCO value to 1 / 2 or less of the value before the reaction.

[0035] Preferably, the temperature of the third temperature-raising reaction is 90-100° C., and / or the third temperature-raising reaction is terminated when the -NCO value of the epoxy-modified isocyanate is controlled to be less than or equal to 4%.

[0036] Further preferably, the temperature of the third temperature-raising reaction is 90-95° C., and / or the third temperature-raising reaction is terminated when the -NCO value of the epoxy-modified isocyanate is controlled to be less than or equal to 2%.

[0037] Preferably, the preparation method of the epoxy-modified isocyanate specifically comprises the following steps:

[0038] Firstly, a blocking agent is dissolved in an organic solvent to obtain a blocking agent solution, and a diisocyanate is dissolved in an organic solvent, a protective gas is introduced, and the temperature is raised to a temperature required for a first temperature-raising reaction at a rate of 10-15°C / h, and then the blocking agent solution is dropped to carry out a first temperature-raising reaction; then the temperature is raised to a temperature required for a second temperature-raising reaction, and the temperature is kept until the -NCO value of the reaction system reaches 2 / 3 or less of that before the reaction, the blocking reaction is completed, and the temperature is lowered to 40-60°C to obtain an intermediate; the intermediate is mixed with a polyether polyol, an epoxy monomer, and a catalyst, and the temperature is raised to a temperature required for a third temperature-raising reaction at a rate of 10-15°C / h, and the temperature is kept, and when the -NCO value of the epoxy-modified isocyanate is less than or equal to 4%, the temperature is lowered to obtain the epoxy-modified isocyanate.

[0039] Preferably, the protective gas is nitrogen and / or carbon dioxide.

[0040] Preferably, the polyether polyol, epoxy monomer and catalyst are all pre-treated by dehydration before use.

[0041] Preferably, the stirring temperature is 30-50°C.

[0042] More preferably, the stirring temperature is 40-45°C.

[0043] The third aspect of the present invention provides an application of epoxy-modified isocyanate.

[0044] The invention discloses an application of epoxy modified isocyanate in the preparation of curing agent, coating, adhesive and foam material.

[0045] A fourth aspect of the present invention provides a curing agent.

[0046] A curing agent, the raw material components of the curing agent include the epoxy-modified isocyanate.

[0047] Preferably, the curing agent is a curing agent for polyurethane coatings.

[0048] A fifth aspect of the present invention provides a one-component polyurethane amino baking coating.

[0049] A one-component polyurethane amino baking coating comprises the following raw material components:

[0050] The curing agent, hydroxyl resin, amino resin, solvent and auxiliary agent.

[0051] Preferably, the one-component polyurethane amino baking coating comprises the following raw material components calculated by weight:

[0052] The curing agent is 5-15 parts, the hydroxy resin is 40-60 parts, the amino resin is 10-30 parts, the acid catalyst is 1-3 parts, the auxiliary agent is 0.5-1.5 parts, and the solvent is 15-20 parts.

[0053] Further preferably, the one-component polyurethane amino baking coating comprises the following raw material components calculated by weight:

[0054] The curing agent comprises 10-13 parts, hydroxyl resin 50-55 parts, amino resin 20-25 parts, acid catalyst 2-3 parts, auxiliary agent 1-1.5 parts, and solvent 17-20 parts.

[0055] Preferably, the hydroxy resin is at least one of hydroxy alkyd resin, hydroxy acrylic resin and hydroxy polyester resin, such as H146-70 and H32-70F from Beixin Carpoly Paint Company.

[0056] Preferably, the amino resin is at least one of butylated amino resin (such as 582-2 and 582-2A of Sanmu Chemical), methylated amino resin and mixed etherified amino resin.

[0057] Preferably, the acid catalyst is dinonylnaphthalenesulfonic acid.

[0058] Preferably, the auxiliary agent is at least one of a defoaming agent, a leveling agent, an antifreeze agent, an antibacterial agent, an anti-ultraviolet agent, and a viscosity stabilizer.

[0059] Preferably, the solvent is at least one of an alcohol solvent (such as n-butanol, isobutanol, isopropanol), a lipid solvent (such as butyl acetate, ethyl acetate, propylene glycol methyl ether acetate, dimethyl carbonate), a ketone solvent (such as cyclohexanone, acetone, methyl isobutyl ketone), and an aromatic hydrocarbon solvent (such as toluene, xylene).

[0060] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0061] The epoxy-modified isocyanate provided by the present invention adopts diisocyanate, polyether polyol, epoxy monomer, sealing agent and catalyst as main raw materials for preparation, and by adding epoxy monomer, epoxy group and -NCO group of isocyanate are reacted to generate oxazolidone structure, thereby enhancing the rigidity of molecular chain, improving the flexibility, thermal stability, impact resistance and solvent resistance of the prepared epoxy-modified isocyanate, and further the epoxy-modified isocyanate provided by the present invention can be used as curing agent and used to prepare single-component polyurethane amino baking coating, which has no obstacle in application, and the construction liquid state is normal for 24 hours, and can improve the flexibility (at least 8-10mm), hardness (at least 2H), adhesion (at least 1 level), impact resistance (at least 40-50cm), thermal stability (the paint film has no change after thermal stability test) and solvent resistance (at least 277-289 times of test resistance) of the paint film. DETAILED DESCRIPTION

[0062] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0063] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0064] Example 1

[0065] An epoxy-modified isocyanate, comprising the following raw materials in parts by weight:

[0066]

[0067] A method for preparing epoxy-modified isocyanate comprises the following steps:

[0068] Dissolve phenol in 2 / 5 of cyclohexanone and pump it into the high-level tank. Put TDI-80 and the remaining 2 / 5 of cyclohexanone into the reactor, pass the protective gas, start stirring, heat up to 50°C at a rate of 10°C / h, and start dripping the phenol solution. The reaction is exothermic, and the dripping speed is strictly controlled. The dripping is completed in 190 minutes and the temperature reaches 83°C. Then maintain the temperature at 98°C, and start detecting the -NCO value after 1h. When the -NCO value reaches less than 1 / 2 of the value before the reaction, the blocking reaction is completed, and the temperature is lowered to 50°C to prepare the intermediate for use. Put the dehydrated polyether polyol, epoxy monomer, catalyst and the remaining 1 / 5 of cyclohexanone into the above intermediate, and heat up to 93°C at a rate of 12°C / h to maintain the temperature. After 4h of heat preservation, measure the -NCO value. When it is less than 2%, cool down, adjust the solid content so that the solid content of the final product is between 60.0±2.0%, stir evenly and filter to obtain epoxy-modified isocyanate.

[0069] Example 2

[0070] An epoxy-modified isocyanate, comprising the following raw materials in parts by weight:

[0071]

[0072]

[0073] A method for preparing epoxy-modified isocyanate comprises the following steps:

[0074] Dissolve caprolactam in 2 / 5 of xylene and cyclohexanone, pump into the high-level tank, put TDI-80 and the remaining 2 / 5 of xylene and cyclohexanone into the reactor, pass the protective gas, start stirring, heat up to 50°C at a rate of 12°C / h and start dripping caprolactam solution. The reaction is exothermic, and the dripping speed is strictly controlled. The dripping is completed in 200 minutes and the temperature reaches 85°C. Then maintain the temperature at 96°C, and start to detect the -NCO value after 1h. When the -NCO value reaches less than 1 / 2 of the value before the reaction, the closed reaction is completed and the temperature is lowered to 50°C for use in the intermediate. The dehydrated polyether DP400, 3-benzyloxy-1,2-propylene oxide, bismuth neodecanoate and the remaining 1 / 5 of xylene and cyclohexanone are put into the above intermediate, and the temperature is raised to 95°C at a rate of 11°C / h to maintain the temperature. After keeping the temperature for 4 hours, measure the -NCO value. When it is lower than 2%, cool down and adjust the solid content so that the solid content of the final product is between 60.0±2.0%. Stir evenly and filter to obtain epoxy-modified isocyanate.

[0075] Example 3

[0076] An epoxy-modified isocyanate, comprising the following raw materials in parts by weight:

[0077]

[0078] A method for preparing epoxy-modified isocyanate comprises the following steps:

[0079] Dissolve methyl ethyl ketone oxime in 2 / 5 of propylene glycol methyl ether propionate, pump into the high-level tank, TDI-80 and the remaining 2 / 5 of propylene glycol methyl ether propionate are put into the reactor, pass the protective gas, start stirring, heat up to 50°C at a rate of 13°C / h, and start dripping methyl ethyl ketone oxime solution. The reaction is exothermic, and the dripping speed is strictly controlled. The dripping is completed in 180 minutes and the temperature reaches 81°C. Then maintain the temperature at 99°C, and start to detect the -NCO value after 1h. When the -NCO value reaches less than 1 / 2 of the value before the reaction, the closed reaction is completed, and the temperature is lowered to 50°C for use in the intermediate. The dehydrated polyether DP1000M, 3-o-tolyloxy-1,2-propylene oxide, bismuth isooctanoate and the remaining 1 / 5 of propylene glycol methyl ether propionate are put into the above intermediate, and the temperature is raised to 94°C at a rate of 12°C / h to maintain the temperature. After keeping the temperature for 4 hours, measure the -NCO value. When it is lower than 2%, cool down and adjust the solid content so that the solid content of the final product is between 60.0±2.0%. Stir evenly and filter to obtain epoxy-modified isocyanate.

[0080] Example 4

[0081] An epoxy modified isocyanate, comprising the following raw material components in parts by weight:

[0082]

[0083] A method for preparing epoxy-modified isocyanate comprises the following steps:

[0084] Ethyl acetoacetate was added to 2 / 5 of the amount of propylene glycol methyl ether propionate and butyl acetate, and pumped into the high-level tank. TDI-80 and the remaining 2 / 5 of propylene glycol methyl ether propionate and butyl acetate were put into the reactor, and the protective gas was passed. Stirring was started, and the temperature was raised to 50°C at a rate of 13°C / h to start dripping the ethyl acetoacetate solution. The reaction was exothermic, and the dripping speed was strictly controlled. The dripping was completed in 180 minutes and the temperature reached 81°C. Then the temperature was maintained at 99°C, and the -NCO value was detected after 1h. When the -NCO value reached less than 1 / 2 of the value before the reaction, the closed reaction was completed and the temperature was lowered to 50°C for use in the intermediate. The dehydrated polyether DP1000M, 3-o-tolyloxy-1,2-propylene oxide, bismuth isooctanoate and the remaining 1 / 5 of propylene glycol methyl ether propionate and butyl acetate were put into the above intermediate, and the temperature was raised to 91°C at a rate of 12°C / h to maintain insulation. After keeping the temperature for 4 hours, measure the -NCO value. When it is lower than 2%, cool down and adjust the solid content so that the solid content of the final product is between 60.0±2.0%. Stir evenly and filter to obtain epoxy-modified isocyanate.

[0085] Comparative Example 1

[0086] An isocyanate compound, which differs from Example 1 in that 3-phenoxy-1,2-propylene oxide (epoxy monomer) is replaced by an equal weight portion of polyether N310 (polyether polyol).

[0087] Comparative Example 2

[0088] An isocyanate compound, which differs from Example 2 in that caprolactam (blocking agent) is replaced by an equal weight portion of polyether GY1000 (polyether polyol).

[0089] Comparative Example 3 (conventional curing agent)

[0090] An isocyanate compound, which differs from Example 3 in that methyl ethyl ketone oxime (blocking agent) is replaced by an equal weight portion of polyether DP750E (polyether polyol), and 3-o-tolyloxy-1,2-propylene oxide (epoxy monomer) is replaced by an equal weight portion of polyether N210 (polyether polyol).

[0091] Comparative Example 4

[0092] An isocyanate compound, which differs from Example 4 in that the preparation process is different. Comparative Example 4 uses a one-step synthesis method, and the formula is exactly the same as that of Example 4. The specific preparation steps are as follows:

[0093] Put all the prepared raw materials into the reaction kettle, mix them, introduce protective gas, stir, heat up to 95°C at a rate of 13°C / h and maintain heat preservation. After keeping warm for 5 hours, measure the -NCO value. When it is lower than 2%, cool down, adjust the solid content, stir evenly and filter to obtain the product of Comparative Example 4.

[0094] Product effect testing

[0095] 1. Basic performance test

[0096] The epoxy-modified isocyanates prepared in the above Examples 1-4 and the isocyanate compounds prepared in Comparative Examples 1-4 were tested for basic properties, and the test results are as follows:

[0097] Table 1 Basic performance test results of the products obtained in each embodiment and comparative example

[0098]

[0099] As can be seen from the above table, the epoxy-modified isocyanate prepared in Examples 1-4 of the present invention is transparent in appearance and free of mechanical impurities, has a viscosity of 185-220 seconds / coat-4 cup (25° C.), a solid content of 60.3-61.6%, and an -NCO value of 1.8-2.0%.

[0100] 2. Performance testing of paint film

[0101] The products prepared in the above embodiments and comparative examples are respectively used as isocyanate curing agents to prepare a one-component polyurethane amino baking coating. The preparation method of the one-component polyurethane amino baking coating is as follows: 10 parts of curing agent, 50 parts of hydroxyl resin (H146-70 product of Beixin Jiabaoli Coating Company), 20 parts of amino resin (butylated amino resin, 582-2 product of Sanmu Chemical), 2 parts of acid catalyst (dinonylnaphthalenesulfonic acid), 0.5 parts of viscosity stabilizer (DVP product of Hemmings Deqian Company), 0.2 parts of organosilicon defoamer (141 product of BYK Company), 0.3 parts of leveling agent (polydimethylsiloxane, 306 product of YK Company), 5 parts of xylene, 10 parts of toluene, and 2 parts of n-butanol are added into a reaction kettle and mixed and dispersed for 10 minutes to obtain a one-component polyurethane amino baking coating; the above parts are parts by weight.

[0102] Then, the above-mentioned single-component polyurethane amino baking coatings were applied by manual spraying and curing conditions of 130°C*20min. After curing, a paint film was formed. The performance test results of the paint film are shown in Table 2 below.

[0103] Table 2 Performance test results of the paint films obtained from each single-component polyurethane amino baking coating

[0104]

[0105] Among them, the flexibility value in Table 2 is the diameter of the wire rod, in mm, and the smaller the value, the better the flexibility. The impact resistance value represents the height distance, in cm, and the larger the value, the better the impact resistance. Solvent resistance is the number of times the bottom is not exposed after wiping with a solvent, and the larger the value, the better the solvent resistance.

[0106] It can be seen from the above table that the one-component polyurethane amino baking coating prepared by the epoxy-modified isocyanate curing agent in Examples 1-4 of the present invention can be applied without obstacles, the normal stable state of the construction fluid can be maintained for at least 24 hours, the paint film has good flexibility (8-10mm), the impact resistance test reaches 40-50cm, the adhesion reaches level 1, the hardness is 2H, the paint film does not change before and after the thermal stability test, and the solvent resistance test can reach 277-289 times, indicating that the paint film has the advantages of good flexibility, high hardness, high adhesion, high thermal stability, impact resistance and solvent resistance.

[0107] The isocyanate curing agent of Comparative Example 1 is not modified with epoxy monomers. Since the oxazolidinone structure cannot be formed, and the reactant structure tends to be branched, lacking a straight-chain epoxy monomer, the flexibility and impact resistance of the paint film deteriorate, and the changes are obvious in the thermal stability test, and the solvent resistance times are reduced.

[0108] The isocyanate curing agent of Comparative Example 2 did not add a sealing agent. Since one -NCO group of the diisocyanate was still active, the construction fluid easily reacted with moisture in the air, causing the construction fluid to gel after 24 hours, and the impact resistance, solvent resistance and thermal stability of the paint film were all reduced.

[0109] Comparative Example 3 provides a common isocyanate curing agent, which contains neither epoxy monomer nor blocking agent. Since the structure lacks not only a straight-chain epoxy monomer but also one -NCO group of the diisocyanate is still active, the construction fluid is easy to react with moisture in the air, which not only causes the construction fluid to gel within 24 hours, but also deteriorates the flexibility of the paint film, and the impact resistance, solvent resistance and thermal stability are also significantly deteriorated.

[0110] The isocyanate curing agent of Comparative Example 4 is prepared by a one-pot method. Since the materials that can react with diisocyanate are sufficient during the one-step reaction, polyether DE600 and 3-tert-butylphenoxy-1,2-propylene oxide will react preferentially during the heating process. In this way, the remaining -NCO group of diisocyanate cannot completely react with the blocking agent due to the steric hindrance effect. The final product will have some residual -NCO active groups. The construction fluid is easy to react with moisture in the air, resulting in gelation of the construction fluid within 24 hours, and the flexibility, thermal stability and solvent resistance of the paint film are seriously reduced, and the impact resistance is also deteriorated.

Claims

1. An epoxy-modified isocyanate, characterized in that: The preparation includes the following raw materials: Diisocyanate, polyether polyol, epoxy monomer, blocking agent, catalyst.

2. The epoxy-modified isocyanate according to claim 1, characterized in that The epoxy-modified isocyanate comprises the following preparation raw materials in parts by weight: 15-30 parts of diisocyanate, 8-20 parts of polyether polyol, 5-20 parts of epoxy monomer, 5-20 parts of sealing agent, and 0.01-0.1 parts of catalyst.

3. The epoxy-modified isocyanate according to claim 1, characterized in that The diisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and xylylene diisocyanate.

4. The epoxy-modified isocyanate according to claim 1, characterized in that The polyether polyol is at least one of polyether N204, polyether N210, polyether N310, polyether DP400, polyether DP750E, polyether DE600, polyether DP1000M and polyether GY1000.

5. The epoxy-modified isocyanate according to claim 1, characterized in that: The epoxy monomer is at least one of 3-phenoxy-1,2-epoxypropylene, 3-o-tolyloxy-1,2-epoxypropylene, 3-benzyloxy-1,2-epoxypropylene, and 3-p-tert-butylphenoxy-1,2-epoxypropylene.

6. The epoxy-modified isocyanate according to claim 1, characterized in that The blocking agent is at least one of phenol, caprolactam, methyl ethyl ketone oxime and ethyl acetoacetate.

7. The method for preparing the epoxy-modified isocyanate according to any one of claims 1 to 6, characterized in that: The steps include: Firstly, diisocyanate and blocking agent are mixed, and then subjected to a first temperature rise reaction and a second temperature rise reaction in sequence to obtain an intermediate. Then, the intermediate is mixed with polyether polyol, epoxy monomer and catalyst, and then subjected to a third temperature rise reaction to obtain the epoxy-modified isocyanate.

8. Use of the epoxy-modified isocyanate according to any one of claims 1 to 6 in the preparation of curing agents, coatings, adhesives and foam materials.

9. A curing agent, characterized in that The raw material components of the curing agent include the epoxy-modified isocyanate according to any one of claims 1 to 6.

10. A one-component polyurethane amino baking coating, characterized in that: The raw material components include: The curing agent, hydroxy resin, amino resin, solvent and additives as described in claim 9.

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