Blocked polyisocyanate composition and preparation method thereof

Abstract

The invention belongs to the field of isocyanate, and particularly relates to a blocked polyisocyanate composition and a preparation method thereof. The composition comprises blocked polyisocyanate, one or more alkali metal ions (A) and one or more halogen ions (B), wherein the blocked polyisocyanate is prepared by reacting polyisocyanate with a blocking agent; wherein the mass ratio (A / B) of the alkali metal ions (A) to the halogen ions (B) is 0.1-500. The curing temperature of the blocked polyisocyanate composition can be as low as 100 DEG C or below, and precipitates and crystals are not prone to being separated out in the low-temperature storage or long-term storage process.

Description

Technical Field

[0001] The invention belongs to the field of isocyanates, and in particular relates to a blocked polyisocyanate composition and a preparation method thereof. Background Art

[0002] Blocked isocyanates are mainly used in single-component coatings. Under high-temperature heating conditions, the blocking agent can be unblocked to release free NCO groups, which then react with the polyol component to cure. Known types of blocking agents for blocked polyisocyanates include oximes, alcohols, lactams, and phenols. Blocked polyisocyanates formed using these blocking agents usually require a heating temperature of more than 140°C, which results in high energy consumption costs.

[0003] Active methylene compounds, such as diethyl malonate, have long been known as isocyanate blockers. Their curing temperature can be as low as below 100°C, making them a relatively promising isocyanate blocker with a low deblocking temperature. However, their disadvantage is that polyisocyanates blocked with diethyl malonate tend to crystallize during storage, which in turn affects their use.

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

[0005] In view of the shortcomings of the existing methods, there is an urgent need in the art to develop a solvent-based blocked polyisocyanate composition with low curing temperature and stable storage. Summary of the invention

[0006] The object of the present invention is to provide a low-temperature curable and storage-stable blocked isocyanate composition and a preparation method thereof in view of the above problems existing in the existing methods for preparing blocked isocyanates. The blocked polyisocyanate composition of the present invention has a curing temperature as low as 100° C. or below; can be applied to plastic substrates with low heat resistance; and is not prone to precipitates and crystal precipitation during low-temperature storage or long-term storage.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, a blocked polyisocyanate composition is provided, comprising:

[0009] Blocked polyisocyanate prepared by the reaction of polyisocyanate and blocking agent,

[0010] 1 or more alkali metal ions (A),

[0011] 1 or more halogen ions (B);

[0012] Wherein, the mass ratio (A / B) of the alkali metal ion (A) to the halogen ion (B) is 0.1-500, for example, 0.2, 0.4, 0.5, 0.6, 0.8, 1, 2, 5, 10, 15, 20, 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, 480.

[0013] According to the blocked polyisocyanate composition provided by the present invention, in some embodiments, the halogen ion is selected from one or more of fluoride ion, chloride ion and bromide ion, preferably chloride ion. The source of the halogen ion is not limited, and can be a metal halide, ammonium ion halide, such as ammonium chloride, calcium chloride, etc.

[0014] In some embodiments, the alkali metal ion is selected from one or more of sodium ion, potassium ion and lithium ion, preferably sodium ion. The source of the alkali metal ion is not limited, and can be alkali metal carbonate, alkali metal sulfate, alkali metal nitrate, alkali metal carboxylate, etc., such as sodium carbonate, potassium sulfate, etc.

[0015] According to the blocked polyisocyanate composition provided by the present invention, in some embodiments, the blocking agent includes at least one or more malonic acid diester compounds.

[0016] In some embodiments, the malonic acid diester compound is selected from one or more of dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate and di-tert-butyl malonate, preferably diethyl malonate.

[0017] In some embodiments, the blocking agent further includes other types of blocking agents; the other types of blocking agents are selected from one or more of ethyl acetoacetate, diisopropylamine, 3,5-dimethylpyrazole, butanone oxime, caprolactam, methanol, ethanol, n-butanol, isobutanol and isopentanol, preferably diisopropylamine and ethyl acetoacetate.

[0018] The inventors conducted a systematic study on the problem of storage precipitation of polyisocyanate compositions blocked with malonic acid diester compounds and found that for polyisocyanate compositions blocked with malonic acid diester compounds, controlling the mass ratio of alkali metal ions / halogen ions within an appropriate range can significantly improve the storage stability of the isocyanate compositions.

[0019] In a second aspect, a method for preparing the blocked polyisocyanate composition as described above is provided, comprising the following steps:

[0020] In the presence of an alkaline catalyst, a polyisocyanate is contacted with a blocking agent and reacted, and a regulator is added to the resulting reaction solution to adjust the mass ratio of the alkali metal ion (A) to the halogen ion (B) in the resulting blocked polyisocyanate composition to be in the range of 0.1-500 (e.g., 0.2, 0.4, 0.5, 0.6, 0.8, 1, 2, 5, 10, 15, 20, 30, 50, 100, 150, 200, 250, 300, 350, 400, 450, 480).

[0021] In the present invention, the malonic acid diester compound accounts for 30-90mol% (e.g., 32mol%, 35mol%, 40mol%, 45mol%, 50mol%, 55mol%, 60mol%, 65mol%, 70mol%, 75mol%, 80mol%, 85mol%) of the total molar amount of the blocking agent, and other types of blocking agents account for 10-70mol% of the total molar amount of the blocking agent. The molar amount of the blocking agent is 0.90-1.3 equivalents, preferably 0.95-1.1 equivalents, relative to the isocyanate group of the polyisocyanate.

[0022] According to the preparation method provided by the present invention, in some embodiments, the polyisocyanate and the blocking agent are subjected to blocking reaction in the presence or absence of an organic solvent. Whether to add an organic solvent can be determined based on the viscosity of the product; generally, it can be considered to add an organic solvent to the system before the reaction to reduce the viscosity of the system during the reaction.

[0023] In some embodiments, the organic solvent is selected from one or more of aromatic hydrocarbon solvents (such as toluene, xylene), ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, 3-methoxybutyl acetate, acetone, butanone, 4-methyl-2-pentanone and cyclohexanone.

[0024] When adding an organic solvent to the system, in some embodiments, the amount of the organic solvent added accounts for 10-70wt% (e.g., 12wt%, 14wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%) of the mass of the blocked isocyanate composition.

[0025] In some embodiments, the temperature for reacting the polyisocyanate with the blocking agent is 30-120°C (e.g., 35°C, 45°C, 50°C, 60°C, 70°C, 75°C, 90°C, 100°C, 110°C), preferably 40-80°C.

[0026] According to the preparation method provided by the present invention, in some embodiments, the alkaline catalyst is selected from alkali metal alkoxides; hydroxides, acetates, octanoates, myristates or benzoates of tetraalkylammonium (such as tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.); alkali metal salts of alkyl carboxylic acids; tin metal salts, zinc metal salts or lead metal salts of alkyl carboxylic acids; compounds containing aminosilyl groups; and one or more of alkali metal hydroxides;

[0027] In some embodiments, the basic catalyst is an alkali metal alkoxide, preferably sodium methoxide.

[0028] In some embodiments, the basic catalyst is a hydroxide of tetraalkylammonium (such as tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.).

[0029] In the present invention, the amount of the alkaline catalyst added is 0.005wt%-5wt% (for example, 0.008wt%, 0.01wt%, 0.05wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt%) relative to the mass of the polyisocyanate, preferably 0.1wt%-2wt%.

[0030] In some embodiments, the regulator is selected from alkali-free halide salts and / or halogen-free alkali metal salts. Examples of alkali-free halide salts include, but are not limited to, ammonium chloride, calcium chloride, etc.; examples of halogen-free alkali metal salts include, but are not limited to, sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, etc.

[0031] According to the preparation method of the present invention, when the alkaline catalyst is a compound containing alkali metal ions, the regulator is mainly a halide salt (such as ammonium chloride, calcium chloride) that does not contain alkali metals; the alkaline catalyst described here is a compound containing alkali metal ions, for example, it can be an alkali metal alcohol salt, an alkali metal salt of an alkyl carboxylic acid, an alkali metal hydroxide, etc.

[0032] According to the preparation method of the present invention, when the alkaline catalyst is a compound containing no alkali metal ions, the regulator is mainly a halogen-free alkali metal salt (such as sodium carbonate, potassium carbonate, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate), and a halide salt containing no alkali metal can also be optionally added, and the mass ratio of the alkali metal ion (A) to the halide ion (B) in the blocked polyisocyanate composition obtained in the system is determined in the range of 0.1-500; the alkaline catalyst described here is a compound containing no alkali metal ions, for example, it can be a hydroxide, acetate, octanoate, myristate or benzoate of tetraalkylammonium (such as tetramethylammonium, tetraethylammonium, tetrabutylammonium, etc.); a tin metal salt, a zinc metal salt or a lead metal salt of an alkyl carboxylic acid; a compound containing an aminosilyl group, etc.

[0033] In the present invention, the amount of the regulator added or the formula ratio can be determined based on making the mass ratio of the alkali metal ion (A) to the halogen ion (B) in the blocked polyisocyanate composition obtained in the system within the range of 0.1-500.

[0034] In some embodiments, the polyisocyanate is selected from the group consisting of a self-polymerization product of a diisocyanate and an isocyanate modified by the reaction of a diisocyanate with a polyol.

[0035] Herein, phosgene is used in the preparation process for obtaining the polyisocyanate, and trace amounts of chlorine may be present.

[0036] Herein, the polyisocyanate comprises one or more of isocyanurate, uretdione, biuret, carbamate, allophanate, iminooxadiazinedione and carbodiimide structures, preferably comprises isocyanurate and biuret structures.

[0037] Herein, the diisocyanate is one or more aliphatic and / or alicyclic diisocyanates containing 4 to 30 carbon atoms in addition to the NCO group in the carbon skeleton; for example, it can be selected from 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate (HDI), 1,3-bis(isocyanatomethyl)cyclohexane and 4,4'-dicyclohexylmethane diisocyanate, preferably 1,6-hexamethylene diisocyanate (HDI).

[0038] The polyol that reacts with diisocyanate to prepare polyisocyanate may be, for example, glycerol, trimethylolpropane, pentaerythritol, polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, and the like.

[0039] In some embodiments, the polyisocyanate has an NCO functionality of 2.5-10 (e.g., 3, 4, 5, 6, 7, 8, 9);

[0040] In some embodiments, the isocyanate group content of the polyisocyanate is 5-40wt% (calculated without solvent); for example, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%.

[0041] In the present invention, an antioxidant may be added to the blocked polyisocyanate composition to further improve the storage stability of the product. The antioxidant may include, for example, hindered phenol antioxidants, hindered amine antioxidants, and phosphite antioxidants.

[0042] In the present invention, the blocked polyisocyanate composition is particularly suitable for preparing a single-component coating or adhesive system.

[0043] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0044] (1) By controlling the mass ratio of alkali metal ions / halogen ions contained in the blocked polyisocyanate composition, the storage precipitation stability of the composition is improved;

[0045] (2) The method of the present invention controls the mass ratio of metal ions / halogen ions contained in the blocked polyisocyanate composition, is simple to operate, and has readily available raw materials, and is easy to realize industrialization. DETAILED DESCRIPTION

[0046] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. For those who do not specify specific conditions in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer.

[0047] Main raw material sources:

[0048] Wannate HT-100 (HDI polymer), NCO content 22.0%, Wanhua Chemical;

[0049] Wannate HB-100 (HDI polymer), NCO content 22.0%, Wanhua Chemical;

[0050] Diethyl malonate, Aladdin reagent;

[0051] Ethyl acetoacetate, Aladdin reagent;

[0052] Diisopropylamine, Aladdin reagent;

[0053] Ammonium chloride, Aladdin reagent;

[0054] Sodium carbonate, Aladdin reagent;

[0055] A methanol solution containing 30 wt% sodium methoxide, Aladdin reagent;

[0056] A methanol solution containing 25% tetramethylammonium hydroxide, Aladdin's reagent;

[0057] Propylene glycol methyl ether acetate, Jiangsu Hualun Chemical Co., Ltd.;

[0058] Butyl acetate, Jin Yimeng Group.

[0059] Test method:

[0060] Product storage stability test: The sample to be tested was placed in a 125 ml glass bottle under a nitrogen atmosphere and stored in a -18°C refrigerator for 3 weeks. Then it was taken out and returned to room temperature, and the appearance of the product was observed.

[0061] Test for the content of halogen ions and alkali metal ions: 50 g of the sample to be tested and 20 g of deionized water were stirred and mixed at 50°C for 2 h, allowed to stand for 24 h, the aqueous phase was taken, and the content was tested using ion chromatography.

[0062] Example 1

[0063] In a four-necked flask, 500 g of polyisocyanate Wannate HB-100, 336 g of diethyl malonate, 68 g of ethyl acetoacetate, and 602 g of butyl acetate were added, and the mixture was stirred and heated to 60° C. under nitrogen protection, and 5 g of a methanol solution containing 30 wt % of sodium methoxide was added. The reaction temperature was controlled at 60-80° C. and the reaction was continued until the free NCO content in the system was lower than 0.2 wt %, and 0.1 g of ammonium chloride was added. The mixture was stirred for 2 hours. The reaction solution was filtered using a 1-micron filter cloth to obtain a blocked polyisocyanate composition.

[0064] Example 2

[0065] In a four-necked flask, 500g of polyisocyanate Wannate HT-100, 230g of diethyl malonate, and 386g of propylene glycol methyl ether acetate were added, and the mixture was stirred and heated to 40°C under nitrogen protection. 170g of diisopropylamine was added in batches, and the reaction temperature was controlled to be lower than 80°C during the process. After the addition of diisopropylamine was completed, the reaction was continued for 30min. The system temperature was adjusted to 70°C, 3.5g of a methanol solution containing 30wt% of sodium methoxide was added, and the reaction temperature was controlled to be between 70-80°C. When the free NCO content in the system was lower than 0.2wt%, 0.2g of ammonium chloride was added, and stirring was continued for 2 hours. The obtained reaction solution was filtered using a 1-micron filter cloth to obtain a blocked polyisocyanate composition.

[0066] Example 3

[0067] In a four-necked flask, 500 g of polyisocyanate Wannate HT-100, 378 g of diethyl malonate, 34 g of ethyl acetoacetate, and 490 g of butyl acetate were added, and the mixture was heated to 60° C. under nitrogen protection, and 3 g of a methanol solution containing 25 wt % of tetramethylammonium hydroxide was added. The reaction temperature was controlled at 60-80° C. and the reaction was continued until the free NCO content in the system was less than 0.2 wt %, and then 0.1 g of sodium carbonate and 0.001 g of ammonium chloride were added, and stirring was continued for 2 hours. The obtained reaction solution was filtered using a 1-micron filter cloth to obtain a blocked polyisocyanate composition.

[0068] Comparative Example 1

[0069] In a four-necked flask, 500 g of polyisocyanate Wannate HB-100, 336 g of diethyl malonate, 68 g of ethyl acetoacetate, and 602 g of butyl acetate were added, and the mixture was heated to 60° C. under nitrogen protection, and 5 g of a methanol solution containing 30 wt % of sodium methoxide was added. The reaction temperature was controlled at 60-80° C., and the mixture was reacted until the free NCO content in the system was less than 0.2 wt %, and stirring was continued for 2 hours. The mixture was filtered using a 1 μm filter cloth to obtain a blocked polyisocyanate composition.

[0070] Comparative Example 2

[0071] In a four-necked flask, 500g of polyisocyanate Wannate HT-100, 230g of diethyl malonate, and 386g of propylene glycol methyl ether acetate were added, and the mixture was stirred and heated to 40°C under nitrogen protection. 170g of diisopropylamine was added in batches, and the reaction temperature was controlled to be lower than 80°C during the process. After the addition of diisopropylamine was completed, the reaction was continued for 30min. The system temperature was adjusted to 70°C, 3.5g of a methanol solution containing 30wt% of sodium methoxide was added, and the reaction temperature was controlled to be between 70-80°C. The reaction was continued until the free NCO content in the system was lower than 0.2wt%, and stirring was continued for 2 hours. The obtained reaction solution was filtered using a 1-micron filter cloth to obtain a blocked polyisocyanate composition.

[0072] Comparative Example 3

[0073] In a four-necked flask, 500 g of polyisocyanate Wannate HT-100, 378 g of diethyl malonate, 34 g of ethyl acetoacetate, and 490 g of butyl acetate were added, and the mixture was heated to 60° C. under nitrogen protection, and 3 g of a methanol solution containing 25 wt % of tetramethylammonium hydroxide was added. The reaction temperature was controlled at 60-80° C. and the reaction was continued until the free NCO content in the system was less than 0.2 wt %, and then 0.01 g of sodium carbonate and 0.1 g of ammonium chloride were added, and the mixture was stirred for 2 hours; and the mixture was filtered using a 1 μm filter cloth to obtain a blocked polyisocyanate composition.

[0074] The stability of the blocked polyisocyanate compositions prepared in the above examples and comparative examples was tested. The test results are shown in Table 1.

[0075] Table 1 Stability test results of blocked polyisocyanate compositions

[0076]

[0077] From the results in Table 1, it can be seen that in the blocked isocyanate compositions prepared in Examples 1-3, the mass ratio (A / B) of the alkali metal ion (A) to the halogen ion (B) is controlled within an appropriate range, and the composition product not only has a low curing temperature, but also remains clear and bright after storage at low temperatures. In the blocked isocyanate compositions prepared in Comparative Examples 1-3, the mass ratio (A / B) of the alkali metal ion (A) to the halogen ion (B) is less than 0.1 or greater than 500, which results in the appearance of white floccules in the compositions after storage at low temperatures.

[0078] Therefore, the blocked isocyanate composition prepared by the present invention has better storage stability.

[0079] The embodiments of the present invention 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 skilled in the art without departing from the spirit of the present invention.

Claims

1. A blocked polyisocyanate composition, characterized in that: It includes: Blocked polyisocyanate prepared by the reaction of polyisocyanate and blocking agent, 1 or more alkali metal ions (A), 1 or more halogen ions (B); Wherein, the mass ratio (A / B) of the alkali metal ion (A) to the halogen ion (B) is 0.1-500.

2. The blocked polyisocyanate composition according to claim 1, characterized in that: The halogen ion is selected from one or more of fluoride ion, chloride ion and bromide ion, preferably chloride ion.

3. The blocked polyisocyanate composition according to claim 1 or 2, characterized in that: The alkali metal ion is selected from one or more of sodium ion, potassium ion and lithium ion, preferably sodium ion.

4. The blocked polyisocyanate composition according to any one of claims 1 to 3, characterized in that: The blocking agent includes at least one or more malonic acid diester compounds; Preferably, the malonic acid diester compound is selected from one or more of dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate and di-tert-butyl malonate, preferably diethyl malonate; Preferably, the blocking agent also includes other types of blocking agents; the other types of blocking agents are selected from one or more of ethyl acetoacetate, diisopropylamine, 3,5-dimethylpyrazole, butanone oxime, caprolactam, methanol, ethanol, n-butanol, isobutanol and isopentanol, more preferably diisopropylamine and ethyl acetoacetate.

5. The method for preparing a blocked polyisocyanate composition according to any one of claims 1 to 4, characterized in that: The steps include: In the presence of an alkaline catalyst, a polyisocyanate is contacted with a blocking agent and reacted, and then a regulator is added to the obtained reaction solution to adjust the mass ratio of the alkali metal ion (A) to the halogen ion (B) in the obtained blocked polyisocyanate composition to be in the range of 0.1-500.

6. The preparation method according to claim 5, characterized in that: The polyisocyanate and the blocking agent undergo a blocking reaction in the presence or absence of an organic solvent; Preferably, the organic solvent is selected from one or more of aromatic hydrocarbon solvents, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, 3-methoxybutyl acetate, acetone, butanone, 4-methyl-2-pentanone and cyclohexanone.

7. The preparation method according to claim 5 or 6, characterized in that: The temperature for the reaction of polyisocyanate and blocking agent is 30-120°C, preferably 40-80°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The alkaline catalyst is selected from one or more of alkali metal alkoxides; hydroxides, acetates, octanoates, myristates or benzoates of tetraalkylammonium; alkali metal salts of alkyl carboxylic acids; tin metal salts, zinc metal salts or lead metal salts of alkyl carboxylic acids; compounds containing aminosilyl groups; and alkali metal hydroxides; Preferably, the alkaline catalyst is an alkali metal alkoxide, more preferably sodium methoxide.

9. The preparation method according to any one of claims 5 to 8, characterized in that: The regulator is selected from alkali-free halide salts and / or halogen-free alkali metal salts.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The polyisocyanate is selected from the self-polymerization product of diisocyanate and the isocyanate modified by the reaction of diisocyanate and polyol; The NCO functionality of the polyisocyanate is 2.5-10; The isocyanate group content of the polyisocyanate is 5-40 wt %.

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