Water-based blocked polyisocyanate cross-linking agent and preparation method thereof

Abstract

The preparation method comprises the following steps: adding diisocyanate, a first organic solvent and a first catalyst into a four-neck flask, and uniformly stirring to obtain a first component; sequentially adding a second organic solvent, a first end-capping reagent and a second catalyst into the first component to obtain a second component; adding a mixed solution of epoxy-terminated polyether silicone oil and formic acid into the second component, and carrying out heat preservation reaction to obtain a third component; and adding the second end-capping reagent into the third component again, and finally adding triethylamine. According to the water-based blocked polyisocyanate cross-linking agent adopting the structure and the preparation method thereof, the prepared cross-linking agent can be used in a coating, the reaction between active functional groups in a product and iron metal is avoided due to the absence of sulfonate radicals and carboxyl groups, the flash rust resistance of a coating film is improved, polyether with large molecular weight is introduced, and the water-based blocked polyisocyanate cross-linking agent can be applied to the coating. And the crosslinking agent is endowed with excellent hydrophilicity.

Description

Technical Field

[0001] This application relates to the field of crosslinking agent technology, specifically to an aqueous blocked polyisocyanate crosslinking agent and its preparation method. Background Technology

[0002] Isocyanates are a general term for various esters of isocyanate. Monoisocyanates are important intermediates in organic synthesis and can be used to produce a series of carbamate insecticides, fungicides, and herbicides. They are also used to improve the water resistance of plastics, fabrics, and leather. Isocyanates with difunctional groups or higher can be used to synthesize a series of high-performance polyurethane foams, rubber, elastic fibers, coatings, adhesives, synthetic leather, and artificial wood.

[0003] Methods for preparing water-based blocked isocyanate crosslinking agents include: reacting isocyanates with polyols and end-capping agents to introduce hydrophilic groups, such as carboxyl groups, sulfonic acid groups, and polyether groups. Currently, the most commonly used method is to introduce sulfonate groups to obtain water-based blocked isocyanates, as illustrated in invention patent CN200810246160.9, a method for preparing water-soluble blocked isocyanate monomers, which involves reacting sodium bisulfite with isocyanate groups to introduce sulfonate groups, thus making the blocked isocyanate water-soluble; and patent CN201210293106.6, a method for preparing water-soluble blocked isocyanate crosslinking agents, which introduces carboxyl groups and neutralizes them with amines to obtain water-soluble blocked isocyanates. Sulfonate groups and carboxyl groups readily react with iron on ferrous metal surfaces, making iron metals more prone to flash rust, especially cast iron parts. Summary of the Invention

[0004] To address the aforementioned deficiencies in this field, this application aims to provide a water-based blocked polyisocyanate crosslinking agent and its preparation method. The obtained crosslinking agent can be used in coatings. The absence of sulfonate and carboxyl groups avoids the reaction between the active functional groups in the product and iron metal, thereby increasing the anti-flash rust performance of the coating film. The introduction of high molecular weight polyether imparts excellent hydrophilicity to the crosslinking agent.

[0005] According to one aspect of this application, a method for preparing an aqueous blocked polyisocyanate crosslinking agent is provided, comprising the following steps:

[0006] (1) Mix diisocyanate, first organic solvent and first catalyst, and stir to react to obtain first component;

[0007] (2) Add the second organic solvent, the first capping agent and the second catalyst to the first component, mix them and heat them to carry out the reaction to obtain the second component;

[0008] (3) Add a mixed solution of terminal epoxy polyether silicone oil and formic acid to the second component and react to obtain the third component;

[0009] (4) Add the second capping agent and triethylamine to the third component, stir to react, and it is ready.

[0010] According to some embodiments of this application, the weight parts of diisocyanate, first organic solvent and first catalyst are: 20-35 parts diisocyanate, 15-30 parts first organic solvent and 0.1-0.5 parts first catalyst;

[0011] According to some embodiments of this application, the reaction temperature in step (1) is 40-70°C and the reaction time is 4-8 min.

[0012] According to some embodiments of this application, the weight parts of the second organic solvent, the end-capping agent, and the second catalyst are: 5-10 parts of the second organic solvent, 0.5-6.5 parts of the first end-capping agent, and 0.1-0.5 parts of the second catalyst;

[0013] According to some embodiments of this application, the reaction temperature in step (2) is 60-70°C and the reaction time is 1.0-2.5h.

[0014] According to some embodiments of this application, the mixed solution comprises 5-15 parts of terminal epoxy polyether silicone oil and 0.3-0.5 parts of formic acid;

[0015] According to some embodiments of this application, step (3) involves reacting at 60-70°C for 0.5-1.5 hours and then cooling down to 50°C.

[0016] According to some embodiments of this application, the weight parts of the second capping agent and triethylamine are: 0.5-6.5 parts of the second capping agent and 1.0-5.0 parts of triethylamine;

[0017] According to some embodiments of this application, step (4) involves adding the capping agent to the third component again, reacting at 60-90°C for 3.0-4.0 hours, cooling to 30°C, adding triethylamine, and stirring for 20-60 minutes to obtain the final product.

[0018] According to some embodiments of this application, the diisocyanate is selected from one or more of the following: isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0019] According to some embodiments of this application, the first organic solvent and the second organic solvent are selected from one or more of ethyl acetate, acetone, N,N-dimethylformamide, N-methylpyrrolidone, isophorone, butyl acetate, toluene, and xylene.

[0020] According to some embodiments of this application, the first catalyst is stannous octoate and the second catalyst is triethylenediamine.

[0021] According to some embodiments of this application, the first capping agent and the second capping agent are selected from one or more of 2-hydroxypyridine, 3-hydroxypyridine and 8-hydroxypyridine.

[0022] According to another aspect of this application, an aqueous blocked polyisocyanate crosslinking agent prepared by the above preparation method is provided.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] This application provides a water-based blocked polyisocyanate crosslinking agent and its preparation method. In the preparation method of this application, diisocyanate reacts with terminal epoxy polyether silicone oil. By introducing a high molecular weight polyether, the crosslinking agent has excellent hydrophilicity. The absence of sulfonate and carboxyl groups in the chain segments avoids the reaction between the active functional groups in the product and iron metal, thereby increasing the anti-flash rust performance of the coating film.

[0025] The waterborne blocked polyisocyanate crosslinking agent of this application introduces a Si-O-Si structure into the chain segment. During the coating curing process, due to the low surface tension and strong chain segment flexibility of siloxane, silicon atoms spontaneously accumulate to the coating surface, effectively improving the water resistance, stain resistance, high temperature resistance and mechanical properties of the waterborne coating after curing. Therefore, it can be widely used in leather, textiles, wood products, steel coils and other fields.

[0026] The preparation method of this application also uses pyridine phenols as end-capping agents. Due to the presence of amino groups, the decapping temperature is further reduced. Pyridine phenol-blocked isocyanates have a faster curing temperature and can be cured into hydroxyl acrylic resin at 110°C for 20 minutes.

[0027] This application employs a synergistic effect of catalysts, using stannous octoate and triethylenediamine in combination to enhance catalytic activity. Attached Figure Description

[0028] Figure 1 This is an example of the rusting condition of the tinplate sheet in a typical embodiment of this application.

[0029] Figure 2 This shows the rusting status of the tinplate sheet in the blank control group of the experimental examples in this application. Detailed Implementation

[0030] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] It should be particularly noted that similar substitutions and modifications made to this application are obvious to those skilled in the art, and they are all considered to be included in this application. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0032] Unless otherwise specified, this application shall be made in accordance with conventional conditions or conditions recommended by the manufacturer. The raw materials or excipients used, as well as the reagents or instruments used, whose manufacturers are not specified, are all conventional products that can be obtained commercially.

[0033] The following is a detailed description of this application.

[0034] The method for preparing the waterborne blocked polyisocyanate crosslinking agent of this application includes the following steps:

[0035] (1) Add 20-35 parts of diisocyanate, 15-30 parts of the first organic solvent and 0.1-0.5 parts of the first catalyst into a four-necked flask and stir evenly. Stir for 4-8 minutes under water bath heating temperature of 40-70℃ to obtain the first component.

[0036] (2) Add 5-10 parts of the second organic solvent, 0.5-6.5 parts of the first capping agent and 0.1-0.5 parts of the second catalyst to the first component in sequence, adjust the temperature to 60-70℃, and keep it at the temperature for 1.0-2.5h to obtain the second component;

[0037] Step (2) Reaction formula: This step is the reaction of part of the NCO with the hydroxyl groups on the capping agent.

[0038]

[0039] (3) Add 5-15 parts of terminal epoxy polyether silicone oil and 0.3-0.5 parts of formic acid to the second component, keep it at 60-70℃ for 0.5-1.5h, and then cool it down by 50℃ to obtain the third component;

[0040] Step (3) Reaction: This step involves the reaction of the remaining NCO with the epoxy groups on the terminal epoxy polyether silicone oil to form oxazolidinone. From a molar perspective, NCO is still in excess.

[0041]

[0042] Where R is CH2CH2O, and n and m are integers from 1 to 15.

[0043] (4) Add the second capping agent to the third component again, keep the reaction at 60-90℃ for 3.0-4.0h, then cool down to 30℃ and add 1.0-5.0 parts of triethylamine, stir for 20-60min, and it is ready.

[0044] Step (4) Reaction formula: This step mainly involves the reaction of the remaining NCO with the blocking agent, ensuring that all NCO reacts completely.

[0045]

[0046] Optionally, the diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0047] Optionally, the first organic solvent and the second organic solvent are selected from one or more of ethyl acetate, acetone, N,N-dimethylformamide, N-methylpyrrolidone, isophorone, butyl acetate, toluene, and xylene.

[0048] Optionally, the first catalyst is stannous octoate, and the second catalyst is triethylenediamine.

[0049] Optionally, the first and second capping agents are selected from one or more of 2-hydroxypyridine, 3-hydroxypyridine, and 8-hydroxypyridine.

[0050] Example 1

[0051] 30 parts hexamethylene diisocyanate, 30 parts N-methylpyrrolidone, and 0.3 parts stannous octoate were added to a four-necked flask and stirred until homogeneous. The mixture was then stirred for 6 minutes in a water bath at 40°C to obtain the first component. 6 parts N-methylpyrrolidone, 0.5 parts 2-hydroxypyridine, and 0.3 parts triethylenediamine were added to the first component, and the temperature was adjusted to 60°C. After holding at this temperature for 2.0 hours, the second component was obtained. A mixed solution of 5 parts terminal epoxy polyether silicone oil and 0.3 parts formic acid was added to the second component, and the mixture was reacted at 60°C for 1.5 hours. The temperature was then lowered by 50°C to obtain the third component. 0.5 parts 2-hydroxypyridine were added to the third component again, and the mixture was reacted at 60°C for 4.0 hours. The temperature was then lowered to 30°C, and 1.0 part triethylamine was added. The mixture was stirred for 30 minutes to obtain the final product.

[0052] Example 2

[0053] 30 parts hexamethylene diisocyanate, 30 parts N-methylpyrrolidone, and 0.3 parts stannous octoate were added to a four-necked flask and stirred until homogeneous. The mixture was then stirred for 6 minutes in a water bath at 40°C to obtain the first component. 6 parts N-methylpyrrolidone, 3.0 parts 2-hydroxypyridine, and 0.3 parts triethylenediamine were added to the first component, and the temperature was adjusted to 60°C. After holding at this temperature for 2.0 hours, the second component was obtained. A mixed solution of 5 parts terminal epoxy polyether silicone oil and 0.3 parts formic acid was added to the second component, and the mixture was reacted at 60°C for 1.5 hours. The temperature was then lowered by 50°C to obtain the third component. 3.0 parts 2-hydroxypyridine were added to the third component again, and the mixture was reacted at 60°C for 4.0 hours. The temperature was then lowered to 30°C, and 1.0 part triethylamine was added. The mixture was stirred for 30 minutes to obtain the final product.

[0054] Example 3

[0055] 30 parts hexamethylene diisocyanate, 30 parts N-methylpyrrolidone, and 0.3 parts stannous octoate were added to a four-necked flask and stirred until homogeneous. The mixture was then stirred for 6 minutes in a water bath at 40°C to obtain the first component. 6 parts N-methylpyrrolidone, 6.5 parts 2-hydroxypyridine, and 0.3 parts triethylenediamine were added to the first component, and the temperature was adjusted to 60°C. After holding at this temperature for 2.0 hours, the second component was obtained. A mixed solution of 5 parts terminal epoxy polyether silicone oil and 0.3 parts formic acid was added to the second component, and the mixture was reacted at 60°C for 1.5 hours. The temperature was then lowered by 50°C to obtain the third component. 6.5 parts 2-hydroxypyridine were added to the third component again, and the mixture was reacted at 60°C for 4.0 hours. The temperature was then lowered to 30°C, and 1.0 part triethylamine was added. The mixture was stirred for 30 minutes to obtain the final product.

[0056] Example 4

[0057] 30 parts hexamethylene diisocyanate, 30 parts N-methylpyrrolidone, and 0.3 parts stannous octoate were added to a four-necked flask and stirred until homogeneous. The mixture was then stirred for 6 minutes in a water bath at 40°C to obtain the first component. 6 parts N-methylpyrrolidone, 3.0 parts 2-hydroxypyridine, and 0.3 parts triethylenediamine were added to the first component, and the temperature was adjusted to 60°C. After holding at this temperature for 2.0 hours, the second component was obtained. A mixed solution of 10 parts terminal epoxy polyether silicone oil and 0.4 parts formic acid was added to the second component, and the mixture was reacted at 60°C for 1.5 hours. The temperature was then lowered by 50°C to obtain the third component. 3.0 parts 2-hydroxypyridine were added to the third component again, and the mixture was reacted at 60°C for 4.0 hours. The temperature was then lowered to 30°C, and 1.0 part triethylamine was added. The mixture was stirred for 30 minutes to obtain the final product.

[0058] Example 5

[0059] 30 parts hexamethylene diisocyanate, 30 parts N-methylpyrrolidone, and 0.3 parts stannous octoate were added to a four-necked flask and stirred until homogeneous. The mixture was then stirred for 6 minutes in a water bath at 40°C to obtain the first component. 6 parts N-methylpyrrolidone, 3.0 parts 2-hydroxypyridine, and 0.3 parts triethylenediamine were added to the first component, and the temperature was adjusted to 60°C. After holding at this temperature for 2.0 hours, the second component was obtained. A mixed solution of 15 parts terminal epoxy polyether silicone oil and 0.5 parts formic acid was added to the second component, and the mixture was reacted at 60°C for 1.5 hours. The temperature was then lowered by 50°C to obtain the third component. 3.0 parts 2-hydroxypyridine were added to the third component again, and the mixture was reacted at 60°C for 4.0 hours. The temperature was then lowered to 30°C, and 1.0 part triethylamine was added. The mixture was stirred for 30 minutes to obtain the final product.

[0060] Experimental Example

[0061] Performance tests were conducted on the crosslinking agents of the embodiments of this application:

[0062] 1. Solid content and storage time test

[0063] The crosslinking agents prepared in Examples 1-5 were stored at room temperature, and their storage time was calculated. The solid content of the hydrophilic isocyanate crosslinking agent was determined by the di-n-butylamine method. The results are shown in Table 1.

[0064] Table 1 Storage time of water-based blocked polyisocyanate crosslinking agents

[0065]

[0066] The waterborne blocked polyisocyanate crosslinking agent prepared in this application has good storage stability.

[0067] 2. The crosslinking agents prepared in Examples 1-5 were dispersed in 10 times their weight of water, and all of them could be quickly dispersed by manual stirring.

[0068] 3. The crosslinking agent prepared in Examples 1-5 was added to commercially available paint at a ratio of 3% to prepare a coating. The coating was then evenly applied to a tinplate sheet. A blank control group was set up: the crosslinking agent from the examples was not added, and the commercially available paint was directly and evenly applied to the tinplate sheet. At the same time, the water contact angle of the coating applied to the tinplate sheet was measured using an SZ-CAMC13 water contact angle tester, and the results are recorded in the table below.

[0069] The rusting of the tinplate sheets was observed, and the results are shown in Table 2.

[0070] Table 2 Rusting of Waterborne Blocked Polyisocyanate Crosslinking Agents

[0071]

[0072] For details on the rust condition of the tinplate sheets in Examples 1-5, please refer to... Figure 1 For details on the rusting of the tinplate sheets in the blank control group, please refer to [link / reference]. Figure 2 .

[0073] 4. The water-based blocked polyisocyanate crosslinking agent prepared in this case contains epoxy polyether silicone oil (containing organosilicon hydrophobic groups), which increases the hydrophobicity of the coating surface. When the organosilicon hydrophobic groups occupy the metal surface, the contact between water molecules and metal atoms is reduced, thus achieving good flash rust prevention. The water contact angle of the coating increases with the higher the content of epoxy polyether silicone oil, indicating a better rust prevention effect.

[0074] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of this application. It should be noted that, for those skilled in the art, several improvements and modifications can be made to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for preparing an aqueous blocked polyisocyanate crosslinking agent, characterized in that, Includes the following steps: (1) Mix diisocyanate, first organic solvent and first catalyst, and stir to react to obtain first component; (2) Add a second organic solvent, a first capping agent and a second catalyst to the first component, mix them and heat them to carry out the reaction to obtain the second component; (3) Add a mixed solution of terminal epoxy polyether silicone oil and formic acid to the second component and react to obtain the third component; (4) Add the second end-capping agent and triethylamine to the third component, stir and react to obtain the water-based blocked polyisocyanate crosslinking agent.

2. The preparation method according to claim 1, characterized in that, The weight parts of the diisocyanate, the first organic solvent, and the first catalyst are: 20-35 parts diisocyanate, 15-30 parts first organic solvent, and 0.1-0.5 parts first catalyst; Optionally, the reaction temperature in step (1) is 40-70℃ and the reaction time is 4-8 min.

3. The preparation method according to claim 1, characterized in that, The weight parts of the second organic solvent, the first capping agent, and the second catalyst are: 5-10 parts of the second organic solvent, 0.5-6.5 parts of the first capping agent, and 0.1-0.5 parts of the second catalyst; Optionally, the reaction temperature in step (2) is 60-70℃ and the reaction time is 1.0-2.5h.

4. The preparation method according to claim 1, characterized in that, The mixed solution consists of 5-15 parts of terminal epoxy polyether silicone oil and 0.3-0.5 parts of formic acid; Optionally, step (3) involves reacting at 60-70°C for 0.5-1.5 hours and then cooling to 50°C.

5. The preparation method according to claim 1, characterized in that, The second capping agent and the triethylamine are present in the following weight proportions: 0.5-6.5 parts of the second capping agent and 1.0-5.0 parts of triethylamine. Optionally, step (4) involves adding a capping agent to the third component again, reacting at 60-90°C for 3.0-4.0 hours, then cooling to 30°C and adding triethylamine, stirring for 20-60 minutes to obtain the final product.

6. The preparation method according to claim 1, characterized in that, The diisocyanate is selected from one or more of the following: isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

7. The preparation method according to claim 1, characterized in that, The first organic solvent and the second organic solvent are selected from one or more of ethyl acetate, acetone, N,N-dimethylformamide, N-methylpyrrolidone, isophorone, butyl acetate, toluene, and xylene.

8. The preparation method according to claim 1, characterized in that, The first catalyst is stannous octoate, and the second catalyst is triethylenediamine.

9. The preparation method according to claim 1, characterized in that, The first capping agent and the second capping agent are selected from one or more of 2-hydroxypyridine, 3-hydroxypyridine and 8-hydroxypyridine.

10. A water-based blocked polyisocyanate crosslinking agent, characterized in that, It is prepared by the method described in any one of claims 1 to 9 for the preparation of an aqueous blocked polyisocyanate crosslinking agent.

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