Blocked polyisocyanate composition with stable storage as well as preparation method and application of blocked polyisocyanate composition

Abstract

The invention discloses a closed type polyisocyanate composition with stable storage and a preparation method and application thereof, the closed type polyisocyanate composition comprises a structure I, a structure II, a structure III and a structure IV, A represents a gel chromatography (GPC) integral area percentage of the structure I; b represents the gel chromatography test GPC integral area percentage of the structure II, C represents the gel chromatography test GPC integral area percentage of the structure III, and D represents the gel chromatography test GPC integral area percentage of the structure IV; wherein A / (A + B + C + D) = 0.15-0.25, and B / (A + B + C + D) = 0.30-0.45. The water-based polyurethane adhesive contains terminated polyisocyanate which is obtained by carrying out a reaction on a hexamethylene diisocyanate polymer, diethyl malonate and diisopropylamine. The composition is clear and transparent after being stored for 12 months at normal temperature.

Description

Technical Field

[0001] The present invention belongs to the field of isocyanates, and particularly relates to a storage-stable blocked polyisocyanate composition, a preparation method thereof, and an application thereof. Background Art

[0002] Blocked isocyanates are mainly used in one-component coatings. Free isocyanate groups can be released by high-temperature heating, and thus react with polyol components to cure. As blocking agents for blocked polyisocyanates, oximes, phenols, alcohols, and lactams are known. The blocked polyisocyanates formed using these blocking agents usually require a temperature above 140°C, resulting in high energy consumption costs.

[0003] Diethyl malonate has long been known as an isocyanate blocking agent, and the curing temperature can be as low as within 100°C. It is a relatively promising isocyanate blocking agent. The disadvantage is that the blocked polyisocyanate with diethyl malonate has a tendency to crystallize during storage, affecting its use. Diisopropylamine is used as an isocyanate blocking agent, and the curing temperature can also be as low as about 100°C. The disadvantage is also that there is a tendency to crystallize during storage. The HDI trimer with diisopropylamine blocking agent is prone to become a white wax-like substance during storage.

[0004] Patent US5350825 discloses a blocked polyisocyanate blocked by a mixture of diisopropylamine, active methylene compounds, and 1,2,4-triazole, which improves the problem of storage crystallization in a solvent system to a certain extent, but there is still a problem of partial crystallization precipitation during long-term storage.

[0005] In view of the deficiencies of the existing methods, it is urgent to develop a solvent-based blocked polyisocyanate composition with a low curing temperature and high storage stability in the art, so that the product is clear and transparent after long-term storage. Summary of the Invention

[0006] The purpose of the present invention is to provide a blocked polyisocyanate composition. Diethyl malonate and diisopropylamine are used together as blocking agents, and the obtained blocked polyisocyanate composition has high product stability, and the product is still clear and transparent after long-term storage.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] A blocked isocyanate composition contains Structure I, Structure II, Structure III, and Structure IV. A represents the GPC integral area percentage of Structure I; B represents the GPC integral area percentage of Structure II, C represents the GPC integral area percentage of Structure III, and D represents the GPC integral area percentage of Structure IV.

[0009] Among them, A / (A + B + C + D) = 0.15 - 0.25, and B / (A + B + C + D) = 0.30 - 0.45.

[0010]

[0011]

[0012] Preferably, the blocked isocyanate composition is obtained by reacting a hexamethylene diisocyanate polymer with a blocking agent. The blocking agent includes diethyl malonate and diisopropylamine. Through research on the hexamethylene diisocyanate polymer blocked by the mixture of diethyl malonate and diisopropylamine, it is found that although the crystallization precipitation stability of the solvent-based blocked polyisocyanate composition can be improved by this mixture of two blocking agents, during the storage of the product, partial crystallization precipitation still occurs, affecting the use of the product.

[0013] The applicant further studies and finds that in the composition, the trimers in the hexamethylene diisocyanate polymer blocked by diethyl malonate and diisopropylamine are relatively easy to precipitate during storage; while the polymers with more than three molecules in the hexamethylene diisocyanate polymer blocked by diethyl malonate and diisopropylamine have relatively good crystallization precipitation stability during storage. Further discovery shows that by controlling the ratio of the two components in which all 3 NCO groups in the hexamethylene diisocyanate trimer are blocked by diethyl malonate (Structure I) and all 3 NCO groups are blocked by diisopropylamine (Structure II), the problem of long-term crystallization precipitation of the composition can be effectively prolonged.

[0014] For the blocked isocyanate composition described above, the component contents of Structures I, II, III, and IV are tested by gel permeation chromatography (GPC), and the component contents are the integral percentages of the gel chromatography peak areas.

[0015] A represents the integral area percentage of Structure I in GPC; B represents the integral area percentage of Structure II in GPC, C represents the integral area percentage of Structure III in GPC, and D represents the integral area percentage of Structure IV in GPC. Among them, A / (A + B + C + D) = 0.15 - 0.25, and B / (A + B + C + D) = 0.30 - 0.45.

[0016] The present invention also provides a method for preparing the blocked isocyanate composition, which involves reacting a polyisocyanate containing a hexamethylene diisocyanate polymer with a blocking agent. The blocking agent includes diethyl malonate and diisopropylamine. In the hexamethylene diisocyanate polymer, the mass content of the HDI trimer component is 45-75%. In the present invention, the blocking agent further includes other blocking agents, which are selected from ethanol, methanol, isooctanol, isobutanol, isopentanol, 3,5-dimethylpyrazole, and ethyl acetoacetate. The molar proportion of the other blocking agents is less than 10% of the total molar amount of the blocking agent.

[0017] Diethyl malonate accounts for 30-70% (molar amount) of the total amount of the blocking agent, and diisopropylamine accounts for 30-70% (molar amount) of the total amount of the blocking agent. The amount of the blocking agent used is 0.90-1.3 equivalents, preferably 0.95-1.1 equivalents, relative to the isocyanate groups of the polyisocyanate.

[0018] In the present invention, the reaction of the polyisocyanate with the blocking agent can be carried out under solvent or solvent-free conditions, mainly determined by the viscosity of the product. Generally, a solvent is added before the reaction to reduce the viscosity of the system during the reaction.

[0019] In the present invention, the solvent can be a conventional solvent for paints, such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, n-butyl 3-methoxyacetate, acetone, methyl ethyl ketone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, aromatic solvent oil, etc. The amount of the solvent added here accounts for 10-60% of the mass of the blocked isocyanate composition.

[0020] In the present invention, the reaction temperature of the polyisocyanate with the blocking agent is 30-120 °C, preferably 40-80 °C.

[0021] In the present invention, the blocking reaction of the polyisocyanate is carried out under the condition of an alkaline catalyst. Examples include metal alkoxides such as sodium methoxide, sodium ethoxide, sodium phenoxide, and potassium methoxide; hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and their organic weak acid salts such as acetates, octanoates, myristates, and benzoates; alkali metal salts of alkyl carboxylic acids such as acetic acid, hexanoic acid, octanoic acid, and myristic acid; metal salts of alkyl carboxylic acids such as acetic acid, hexanoic acid, octanoic acid, and myristic acid with metals such as tin, zinc, and lead; compounds containing silylamino groups such as hexamethyl disilazane; hydroxides of alkali metals such as lithium, sodium, and potassium. Alkali metal alkoxides are preferred, and sodium methoxide is further preferred.

[0022] To achieve the control of the component ratio content and improve the storage stability, in some preferred embodiments of the present invention, diethyl malonate, a basic catalyst, and diisopropylamine are simultaneously added to the reaction system for reaction, and the addition time of diethyl malonate, the basic catalyst, and diisopropylamine is 1 - 6 h. If the addition time is less than 1 h, the content of the isocyanate trimer blocked by ethyl malonate and the content of the isocyanate trimer blocked by diisopropylamine are likely to be too high; if the dropping time is greater than 6 h, the content of the isocyanate trimer blocked by ethyl malonate is likely to be too low, and the viscosity is likely to be too large.

[0023] In the present invention, the hexamethylene diisocyanate polymer further contains isocyanurate groups, uretdione groups, and iminooxadiazinedione groups; the NCO functionality of the polyisocyanate is 2.5 - 10, and the isocyanate group content is 5 - 40 wt%.

[0024] In addition, the blocked isocyanate composition may further include antioxidants, such as hindered phenol antioxidants, hindered amine antioxidants, and phosphite antioxidants, to improve the storage stability of the product.

[0025] The blocked isocyanate composition in the present invention is particularly suitable for preparing one-component coatings or adhesive systems.

[0026] Compared with the prior art, the present invention has the following beneficial effects: By optimizing the component ratio of substances, the storage stability of the diethyl malonate and diisopropylamine mixed blocked isocyanate composition is further improved. Detailed Embodiments

[0027] The method provided by the present invention will be further illustrated by the following examples, but the present invention is not limited to the listed examples and should also include any other known changes within the scope of the claims of the present invention.

[0028] Sources of main raw materials:

[0029] Wannate HT-100 (HDI polymer), NCO content 22.0%, trimer content 53%, Wanhua Chemical;

[0030] Wannate HT-600 (HDI polymer), NCO content 22.0%, trimer content 70%, Wanhua Chemical; diethyl malonate, Aladdin reagent

[0031] Diisopropylamine, Zhejiang Xinhu Chemical Co., Ltd.

[0032] 30% methanol solution of sodium methoxide, Aladdin reagent

[0033] Propylene glycol methyl ether acetate, Jiangsu Hualun Chemical Co., Ltd.;

[0034] Butyl Acetate, Jinyimeng Group

[0035] Component Ratio Test: Using gel chromatography technology (LC-20AD / RID-10A, the chromatographic column is MZ-Gel SDplus10E3A, 5μm (8.0*300mm), MZ-Gel SDplus 500A 5μm (8.0*300mm), MZ-Gel SDplus100A5μm (8.0*300mm) in series, Shimadzu, mobile phase: tetrahydrofuran; flow rate: 1.0 mL / min; analysis time: 40 min, column temperature: 35°C), using a differential detector for determination, and determining by area normalization method. Using standard molecular weight polystyrene in the molecular weight range of 200-20000, establish a molecular weight standard curve; the molecular weights of substances I, II, III, and IV are 985, 808, 926, and 867 respectively; according to the molecular weight, perform area normalization integration on the corresponding peaks. During the GPC test, collect the GPC test effluent of the peaks corresponding to molecular weights of 985, 808, 926, and 867 respectively, concentrate it, and then perform 13C-NMR nuclear magnetic resonance method test. The instrument used is a Bruker 400MHz instrument, dissolved in CDCl3, and the test conditions are 100MHz. The carbonyl carbon formed by the reaction of the NCO group with diethyl malonate has a nuclear magnetic spectrum signal near 165.3 ppm; the carbonyl carbon formed by the reaction of the NCO group with diisopropylamine has a nuclear magnetic spectrum signal near 156.9 ppm. There is no signal near 156.9 ppm in the nuclear magnetic spectrum of Structure I; there is no signal near 165.3 ppm in the nuclear magnetic spectrum of Structure II; the integral value at 165.3 ppm in the nuclear magnetic spectrum of Structure III is twice the integral value at 156.9 ppm; the integral value at 156.9 ppm in the nuclear magnetic spectrum of Structure IV is twice the integral value at 165.3 ppm.

[0036] Example 1

[0037] Create a nitrogen environment in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, add 500 g of polyisocyanate Wannate HT-100 and 378 g of butyl acetate, and heat to 70°C. Simultaneously drip the following three materials into the reaction flask: 278 g of diethyl malonate (2.3 g / min), 106 g of diisopropylamine (0.8 g / min), and 4.0 g of 30% sodium methoxide solution (0.03 g / min). After the addition of the materials is completed, continue the reaction at 70°C until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0038] Example 2

[0039] Create a nitrogen environment in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-100 and 386 g of propylene glycol methyl ether acetate, and heat to 60 °C. Simultaneously add the following three materials dropwise into the reaction flask: 323 g of diethyl malonate (1.3 g / min), 79 g of diisopropylamine (0.33 g / min), and 4.0 g of a 30% sodium methoxide solution (0.02 g / min). After the addition of the materials is complete, continue the reaction at 70 °C until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0040] (0.02 g / min). After the addition of the materials is complete, continue the reaction at 70 °C until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0041] Example 3

[0042] Create a nitrogen environment in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-600 and 359 g of propylene glycol methyl ether acetate, and heat to 70 °C. Simultaneously add the following three materials dropwise into the reaction flask: 145 g of diethyl malonate (0.8 g / min), 194 g of diisopropylamine (1.08 g / min), and 3.0 g of a 30% sodium methoxide solution (0.02 g / min). After the addition of the materials is complete, continue the reaction at 70 °C until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0043] Example 4

[0044] Create a nitrogen environment in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-100 and 370 g of propylene glycol methyl ether acetate, and heat to 70 °C. Simultaneously add the following three materials dropwise into the reaction flask: 230 g of diethyl malonate (2.55 g / min), 132 g of diisopropylamine (0.88 g / min), and 3.5 g of a 30% sodium methoxide solution (0.02 g / min). After the addition of the materials is complete, continue the reaction at 70 °C until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0045] Example 5

[0046] Create a nitrogen environment in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-100 and 614 g of butyl acetate, and heat to 70 °C. Simultaneously dropwise add the following three materials into the reaction flask: 338 g of diethyl malonate (1.03 g / min), 83 g of diisopropylamine (0.25 g / min), and 5.0 g of a 30% sodium methoxide solution (0.015 g / min). After the addition of the materials is completed, continue the reaction at 70 °C until free NCO groups are undetectable by infrared spectroscopy to obtain a blocked isocyanate composition.

[0047] Comparative Example 1

[0048] Create a nitrogen environment in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-100 and 378 g of butyl acetate, and heat to 70 °C. Simultaneously dropwise add the following three materials into the reaction flask: 278 g of diethyl malonate (9.3 g / min), 106 g of diisopropylamine (3.53 g / min), and 4.0 g of a 30% sodium methoxide solution (0.13 g / min). After the addition of the materials is completed, continue the reaction at 70 °C until free NCO groups are undetectable by infrared spectroscopy to obtain a blocked isocyanate composition.

[0049] Comparative Example 2

[0050] Create a nitrogen environment in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. Add 500 g of polyisocyanate Wannate HT-100 and 386 g of propylene glycol methyl ether acetate, and heat to 40 °C. Dropwise add 79 g of diisopropylamine (0.33 g / min). After the addition is completed, continue the reaction for 30 min, then raise the temperature to 60 °C, and then simultaneously add 323 g of diethyl malonate (1.3 g / min) and 4.0 g of a 30% sodium methoxide solution (0.02 g / min). After the addition of the materials is completed, continue the reaction at 70 °C until free NCO groups are undetectable by infrared spectroscopy to obtain a blocked isocyanate composition.

[0051] Comparative Example 3

[0052] A nitrogen environment is formed in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube. 500 g of polyisocyanate Wannate HT-600 and 359 g of propylene glycol methyl ether acetate are added and heated to 70 °C. 145 g (0.8 g / min) of diethyl malonate and 3.0 g (0.02 g / min) of a 30% sodium methoxide solution are simultaneously added to the reaction flask. After the addition is complete, 194 g (1.08 g / min) of diisopropylamine is added, and the reaction proceeds until no free NCO groups are detected by infrared spectroscopy to obtain a blocked isocyanate composition.

[0053] Stability test of the blocked isocyanate composition.

[0054] Table 1 Experimental results of the stability test

[0055]

[0056] As can be seen from the above table, the blocked isocyanates prepared in Examples 1-5 were clear and transparent after being stored at room temperature for 12 months, while the blocked isocyanates prepared in Comparative Examples 1-3 were clear and transparent after being stored at room temperature for 6 months, but some white solid flocs appeared after being stored for 12 months. Therefore, the blocked isocyanate composition prepared by the present invention has better storage stability.

Claims

1. A blocked isocyanate composition, characterized in that It includes Structure I, Structure II, Structure III, and Structure IV. A represents the percentage of the GPC integration area of the gel permeation chromatography test of Structure I; B represents the percentage of the GPC integration area of the gel permeation chromatography test of Structure II, C represents the percentage of the GPC integration area of the gel permeation chromatography test of Structure III, and D represents the percentage of the GPC integration area of the gel permeation chromatography test of Structure IV; Among them, A / (A + B + C + D) = 0.15 - 0.25, and B / (A + B + C + D) = 0.30 - 0.

45.

2. The blocked isocyanate composition according to claim 1, characterized in that, The blocked isocyanate composition is obtained by reacting a hexamethylene diisocyanate polymer with a blocking agent, and the blocking agent includes diethyl malonate and diisopropylamine.

3. A method for preparing the closed isocyanate composition according to claim 1 or 2, characterized in that, React a polyisocyanate containing a hexamethylene diisocyanate polymer with a blocking agent, and the blocking agent includes diethyl malonate and diisopropylamine; Preferably, in the hexamethylene diisocyanate polymer, the mass content of the HDI trimer component is 45 - 75%.

4. The preparation method according to claim 3, characterized in that, The blocking agent also includes other blocking agents, and it is characterized in that the other blocking agents are selected from ethanol, methanol, isooctanol, isobutanol, isopentanol, 3,5 - dimethylpyrazole, and ethyl acetoacetate; Preferably, the molar ratio of the other blocking agent is 10% or less of the total molar amount of the blocking agent; Preferably, the molar amount of diethyl malonate accounts for 30 - 70% of the total molar amount of the blocking agent, and the molar amount of diisopropylamine accounts for 30 - 70% of the total molar amount of the blocking agent; Preferably, relative to the isocyanate groups of the polyisocyanate, the amount of the blocking agent used is 0.90 - 1.3 equivalents, preferably 0.95 - 1.1 equivalents.

5. The preparation method according to claim 3, characterized in that, The polyisocyanate reacts with the blocking agent, and the blocking reaction is carried out under solvent or solvent - free conditions. Preferably, the amount of the solvent added accounts for 10 - 60% of the amount of the blocked isocyanate composition in terms of the amount of substance; Preferably, the reaction temperature of the polyisocyanate and the blocking agent is 30 - 120 °C, preferably 40 - 80 °C for the reaction.

6. The preparation method according to claim 3, characterized in that The blocking reaction of the polyisocyanate is carried out under the condition of an alkaline catalyst, Preferably, the alkaline catalyst is selected from one or more of metal alkoxides, hydroxides of tetraalkylammonium, acetates, octanoates, myristates, or benzoates; alkali metal salts of alkyl carboxylic acids; tin, zinc, or lead metal salts of alkyl carboxylic acids; compounds containing silylamino groups; hydroxides of alkali metals; preferably metal alkoxides, and more preferably sodium methoxide.

7. The preparation method according to claim 3, characterized in that Add diethyl malonate, the alkaline catalyst, and diisopropylamine to the reaction system simultaneously for reaction, and the addition time of diethyl malonate, the alkaline catalyst, and diisopropylamine is 1 - 6 h.

8. The preparation method according to claim 3, characterized in that, The hexamethylene diisocyanate polymer also contains one or more of isocyanurate groups, uretdione groups, and iminooxadiazinedione groups; Preferably, the NCO functionality of the polyisocyanate is 2.5 - 10, and the content of isocyanate groups is 5 - 40 wt%.

9. The preparation method according to claim 3, wherein The blocked isocyanate composition also includes an antioxidant, and the antioxidant includes hindered phenol antioxidants, hindered amine antioxidants, and phosphite antioxidants.

10. Use of the blocked isocyanate composition according to claim 1 or 2, or the blocked isocyanate composition prepared by the preparation method according to any one of claims 3 - 9, for preparing a one-component coating or an adhesive system.

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