CN107236114A - A kind of watersoluble closed type polyisocyanate crosslinking agent of nano-silica-containing structure and preparation method thereof - Google Patents

Abstract

The invention discloses a water-based blocked polyisocyanate crosslinking agent containing a nano silicon dioxide structure and a preparation method thereof. The crosslinking agent reacts with the isocyanate group on the surface of the nano-silica to form a highly branched isocyanate group-terminated polymer skeleton, and then introduces ionic and non-ionic hydrophilic groups into the skeleton. Finally, the remaining active isocyanate groups are blocked with a blocking agent, and the ionic groups on the skeleton structure are neutralized with an organic base to obtain a water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure. The low surface tension and high flexibility of the Si-O-Si group endow the cured coating with better water resistance and scratch resistance, so this crosslinking agent has a wide application prospect in the field of water-based coating curing.

Description

A kind of water-based blocked polyisocyanate crosslinking agent containing nano silicon dioxide structure and its preparation method

technical field

The invention belongs to the technical field of macromolecular materials, and in particular relates to a water-based blocked polyisocyanate crosslinking agent containing a nano-silicon dioxide structure and a preparation method thereof.

Background technique

After water-based polyisocyanate crosslinking agent is added to the water-based coating system, the abrasion resistance, tear resistance and flex resistance of the cured coating will be significantly improved, but due to the defects in the molecular structure of the cross-linking agent, the water resistance of the coating There is still much room for improvement. Introducing silicon-oxygen bonds into the molecular chain can effectively solve this problem. The low-temperature flexibility and low surface tension of silicon-oxygen bonds make the silicon atoms migrate to the coating surface during the curing process, and the water contact angle on the coating surface becomes larger. , thereby improving the water resistance of the coating.

Zhang Zhiguo et al. (Journal of Jinan University, 2007, 21(3): 200) summarized the copolymerization improvement methods of organosilicon-modified polyurethane, which mainly include the following four methods: silanol modification method, alkoxysilane cross-linking modification method, Hydroxyalkyl polysiloxane modification method and aminoalkyl polysiloxane modification method. The key to silicone modification of polyurethane is to improve the compatibility between the two and avoid phase separation.

Nano-silica is a non-toxic, odorless white amorphous non-metallic material. Among many inorganic fillers, nano-silica is due to its low price, simple preparation process, stable performance, and its unique quantum size effect, The surface interface effect is currently the most widely used inorganic filler. Fangming et al. (Fine Chemical Raw Materials and Intermediates, 2011, (1): 19) introduced several preparation methods of nano-silica and its wide application in plastics, coatings, rubber, cosmetics, electronic metallurgy and other fields. Bauer F et al. (Progress in Organic Coatings, 2007, 60:121) found that inorganic nanoparticles can improve the defects of the cured film in application, so that the cured composite material has both the rigidity of inorganic matter and the toughness of organic matter .

Contents of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure and a preparation method thereof. The cross-linking agent combines nano-silica Introduced into the water-based blocked polyisocyanate crosslinking agent, the particles can be uniformly dispersed in it, which can play the role of crosslinking and branching, and at the same time can exert the excellent performance of the inorganic substance itself, effectively overcome the defects of the cured film, and improve the heat of the cured film. stability and mechanical properties. The products have high application value in leather retanning agent, paper strengthening agent, water-based wood varnish, silk fabric finishing agent, etc.

In order to solve the problems of the prior art, the technical scheme that the present invention takes is:

A water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure, which has the following structural formula

In the formula, R ₁ is _R2 is _R3 is _R4 is B for M for

The preparation method of the above-mentioned water-based blocked polyisocyanate cross-linking agent containing nano-silica structure, the whole process is carried out under the protection of nitrogen, stirring is carried out, and each component is weighed and added to the reaction system in parts by mass, which specifically includes the following steps : Step 1, adding 0.1 to 0.5 parts of dibutyltin dilaurate, 25.0 to 40.0 parts of N,N-dimethylacetamide and 20.0 to 35.0 parts of diisocyanate into a four-necked flask and stirring evenly, 4 Raise the temperature to 50-80°C within ~8 minutes to obtain component 1; step 2, add 0.2-1.0 parts of nano-silica to component 1, and keep warm for 0.5-1.5 hours to obtain component 2; step 3, in 10- Add 2.0-5.0 parts of ionic hydrophilic chain extender to component 2 within 15 minutes, adjust the temperature to 60-70°C, keep warm for 15-45 minutes to obtain component 3; step 4, add to component 3 within 10-15 minutes Add a mixed solution of 2.0-12.0 parts of non-ionic hydrophilic chain extender and 5.0-10.0 parts of N,N-dimethylacetamide, and keep warm at 60-70°C for 1.0-2.5 hours to obtain component 4; step 5, Add 8.0-20.0 parts of blocking agent to component 4, keep it warm at 60-90°C for 2.0-4.0 hours, then cool down to 30°C with 2.0-6.0 parts of organic base, and stir for 20-60 minutes.

As an improvement, the diisocyanate in step 1 is one of hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate or dicyclohexylmethane diisocyanate.

As an improvement, the ionic hydrophilic chain extender in step 3 is 2,2-dimethylol propionic acid or 2,2-dimethylol butyric acid.

As an improvement, the non-ionic hydrophilic chain extender in step 4 is polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polytetrahydrofuran Alcohol 200, polytetrahydrofuran diol 400, polytetrahydrofuran diol 600, polytetrahydrofuran diol 800, polytetrahydrofuran diol 1000, polycaprolactone diol 400, polycaprolactone diol 600, polycaprolactone diol 800 or polycaprolactone diol 1000.

As an improvement, the blocking agent in step 5 is 3,5-dimethylpyrazole, triazole, butanone oxime, imidazole or caprolactam; the organic base is selected from triethylamine, triethanolamine or N-methyldiethanolamine .

The reaction equation of the present invention is:

Beneficial effect

The present invention is a water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure and a preparation method thereof. The isocyanate group-blocked polyisocyanate group with a higher degree of branching is formed through the reaction of the silicon hydroxyl group on the surface of the nano-silica and the isocyanate group. Then, introduce ionic and non-ionic hydrophilic groups on the backbone, and finally block the residual active isocyanate groups with a blocking agent, and use an organic base to neutralize the ionic groups on the backbone structure , to obtain a water-based blocked polyisocyanate crosslinking agent containing nano-silica structure, the low surface tension and high flexibility of the Si-O-Si group, endowing the cured coating with better water resistance and scratch resistance , so this crosslinking agent has a broad application prospect in the field of water-based coating curing.

Description of drawings

Fig. 1 is the infrared spectrum of a kind of water-based blocked polyisocyanate cross-linking agent containing nano silicon dioxide structure that embodiment 1 makes.

Fig. 2 is the infrared spectrum of a kind of water-based blocked polyisocyanate crosslinking agent containing nano silicon dioxide structure that embodiment 2 makes.

detailed description

The present invention can be better understood from the following examples. However, those skilled in the art can easily understand that the content described in the embodiments is only for illustrating the present invention, and should not and will not limit the present invention described in the claims.

Example 1

The preparation method of the above-mentioned water-based blocked polyisocyanate cross-linking agent containing nano-silica structure, the whole process is carried out under the protection of nitrogen, stirring is carried out, and each component is weighed and added to the reaction system in parts by mass, which specifically includes the following steps : Step 1, add 0.3 parts of dibutyltin dilaurate, 40.0 parts of N,N-dimethylformamide and 30.0 parts of hexamethylene diisocyanate into a four-necked flask and stir evenly, heat up within 4min to 65°C to obtain component 1; step 2, add 0.5 parts of nano-silica to component 1, and keep warm for 1.0 hours to obtain component 2; step 3, add 4.0 parts of 2 to component 2 within 10 minutes, 2-Dimethylolbutyric acid, adjust the temperature to 65°C, keep warm for 25 minutes to obtain component three; step 4, add 8.0 parts of polyethylene glycol 600 and 10.0 parts of N,N-dimethyl to component three within 10 minutes Mixed solution of methyl formamide, react at 65°C for 1.5h to obtain component 4; step 5, add 15.0 parts of 3,5-dimethylpyrazole to component 4, react at 65°C for 3.0h, then cool down 3.0 parts of organic base at 30°C, stir for 30 minutes, then

Example 1 obtained a water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure; the storage time at room temperature exceeded 6 months, the solid content was 53.5%, and the isocyanate content was 7.6%; FT-IR (KBr, ^{cm- 1} ): 3346(NH), 2937(- CH ₃ ,-CH ₂ -), 1726(C=O), 1548(CN), 1099(Si-O-Si); Figure 1 is prepared in Example 1 Infrared spectrum of a water-based blocked polyisocyanate crosslinking agent containing nano-silica structure.

Example 2

The preparation method of the above-mentioned water-based blocked polyisocyanate cross-linking agent containing nano-silica structure, the whole process is carried out under the protection of nitrogen, stirring is carried out, and each component is weighed and added to the reaction system in parts by mass, which specifically includes the following steps : Step 1, add 0.5 parts of dibutyltin dilaurate, 40.0 parts of N,N-dimethylformamide and 30.0 parts of isophorone diisocyanate into a four-necked flask and stir evenly, heat up within 4min to 70°C to obtain component 1; step 2, add 0.3 parts of nano-silica to component 1, and keep warm for 1.0 hours to obtain component 2; step 3, add 3.0 parts of 2 to component 2 within 10 minutes, 2-Dimethylolpropionic acid, adjust the temperature to 65°C, keep warm for 25 minutes to obtain component three; step 4, add 9.0 parts of polytetrahydrofuran diol and 10.0 parts of N,N-dimethylformaldehyde to component three within 15 minutes Mixed solution of amide, heat preservation reaction at 65°C for 1.0h to obtain component 4; Step 5, add 12.0 parts of triazole to component 4, after heat preservation reaction at 65°C for 3.0h, cool to 30°C when 3.0 parts of triazole Ethanolamine, stir for 30min, then

Example 2 obtains a water-based blocked polyisocyanate crosslinking agent containing nano-silica structure; the storage time at room temperature exceeds 6 months, the solid content is 52.1%, and the isocyanate content is 7.8%. FT-IR (KBr, cm ^-1 ): 3326(NH), 2923(-CH ₃ ,-CH ₂ -), 1730(C=O), 1546(CN), 1103(Si-O-Si); Fig. 2 is the infrared spectrum of a kind of water-based blocked polyisocyanate crosslinking agent containing nano silicon dioxide structure that embodiment 2 makes.

Claims (6)

1. A water-based blocked polyisocyanate crosslinking agent containing a nano-silica structure, characterized in that it has the following structural formula In the formula, R ₁ is _R2 is _R3 is _R4 is B for M for 2. the preparation method based on a kind of water-based blocked polyisocyanate crosslinking agent containing nano silicon dioxide structure according to claim 1, is characterized in that, under nitrogen protection, stirring is carried out in the whole process, and each component is by mass parts Weighing and adding to the reaction system by counting, specifically including the following steps: Step 1, adding 0.1 to 0.5 parts of dibutyltin dilaurate, 25.0 to 40.0 parts of N,N-dimethylacetamide and 20.0 to 35.0 parts of Add diisocyanate into the four-necked flask and stir evenly, and heat up to 50-80°C within 4-8 minutes to obtain component 1; step 2, add 0.2-1.0 parts of nano-silica to component 1, and keep warm for 0.5-1.5 h to obtain component 2; step 3, add 2.0 to 5.0 parts of ionic hydrophilic chain extender to component 2 within 10 to 15 minutes, adjust the temperature to 60 to 70°C, and keep warm for 15 to 45 minutes to obtain component 3; Step 4: Add a mixed solution of 2.0 to 12.0 parts of non-ionic hydrophilic chain extender and 5.0 to 10.0 parts of N,N-dimethylacetamide to component three within 10 to 15 minutes, and keep warm at 60 to 70°C for reaction 1.0～2.5h to get component 4; step 5, add 8.0～20.0 parts of sealing agent to component 4, keep warm at 60～90°C for 2.0～4.0h, cool down to 30°C 2.0～6.0 parts of organic base , and stir for 20-60 minutes. 3. the preparation method of a kind of water-based blocked polyisocyanate crosslinking agent containing nano-silica structure according to claim 2, is characterized in that, in step 1, diisocyanate is hexamethylene diisocyanate, toluene diisocyanate , isophorone diisocyanate or dicyclohexylmethane diisocyanate. 4. the preparation method of a kind of water-based blocked polyisocyanate crosslinking agent containing nano-silica structure according to claim 2, is characterized in that, in step 3, ionic hydrophilic chain extender is 2,2-di Methylolpropionic acid or 2,2-dimethylolbutyric acid. 5. the preparation method of a kind of water-based blocked polyisocyanate crosslinking agent containing nano-silica structure according to claim 2, is characterized in that, in step 4, non-ionic hydrophilic chain extender is Polyethylene Glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polytetrahydrofuran diol 200, polytetrahydrofuran diol 400, polytetrahydrofuran diol 600, polytetrahydrofuran diol 800, Polytetrahydrofuran diol 1000, polycaprolactone diol 400, polycaprolactone diol 600, polycaprolactone diol 800 or polycaprolactone diol 1000. 6. the preparation method of a kind of water-based blocked polyisocyanate crosslinking agent containing nano silicon dioxide structure according to claim 2, is characterized in that, in step 5, blocking agent is 3,5-dimethylpyrazole, Triazole, butanone oxime, imidazole or caprolactam; the organic base is selected from triethylamine, triethanolamine or N-methyldiethanolamine.