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Polyurethane curing agent with low free isocyanate monomer and preparation method thereof

A polyurethane curing agent, isocyanate technology, applied in the direction of polyurea/polyurethane coatings, coatings, etc., can solve the problems of unfavorable polyurethane curing agent use, poor molecular weight distribution of products, low prepolymer NCO content, etc., to achieve excellent coating properties , Excellent resistance to yellowing, and the effect of improving leveling

Inactive Publication Date: 2013-07-31
HUBEI TRASION CHEM IND CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, in the process of preparing hexamethylene diisocyanate curing agent, there are the following problems: 1. Since the two isocyanate groups of HDI have the same activity, it is very easy to form deep polymer or gelation, and the production process requires high requirements. Difficult to operate; 2. Excessive heat release during the trimerization reaction makes it difficult to control the reaction process, resulting in poor product molecular weight distribution; 3. In order to avoid side reactions, it is often necessary to use excessive HDI feed ratio
Although this method reduces the free isocyanate monomer through the excess of polyol hydroxyl groups, the excessive hydroxyl value reduces the free NCO and also makes the NCO content of the prepolymer low and the viscosity increases, which is not conducive to use as a polyurethane curing agent.

Method used

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  • Polyurethane curing agent with low free isocyanate monomer and preparation method thereof
  • Polyurethane curing agent with low free isocyanate monomer and preparation method thereof
  • Polyurethane curing agent with low free isocyanate monomer and preparation method thereof

Examples

Experimental program
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Effect test

Embodiment 1

[0043] Under the protection of nitrogen, first put 168g of hexamethylene diisocyanate monomer into the reaction vessel and stir evenly, raise the temperature to 55°C, and then melt 22g of 2-ethyl-2-butyl 1,3-propanediol (BEPD) Then slowly add it dropwise into the reaction vessel under stirring condition, the dropwise time is 1 hour, after the dropwise addition is completed, keep it warm at 55°C for 2 hours, add 0.57g tri-n-butyltin oxide at one time, heat up to 70°C and continue Stir and react for 4 hours, when the NCO group content is reduced to 17.8 wt%, add 0.19g of phosphoric acid, keep warm at 70°C for 1 hour, cool and discharge to obtain a water-white viscous liquid polyurethane curing agent.

Embodiment 2

[0045] Under the protection of nitrogen, put 168g of hexamethylene diisocyanate monomer into the reaction vessel and stir evenly, raise the temperature to 65°C, then melt 42g of 1,4-cyclohexanedimethanol and slowly add it dropwise under stirring condition Into the reaction container, the dropwise addition time is 1.5 hours. After the dropwise addition, keep the temperature at 65°C for 4 hours, add 1g of quaternary ammonium salt (trade name DABCO TMR) at one time, raise the temperature to 80°C and continue stirring for 1 hour. The content of NCO groups was reduced to 22.5 wt%, and 0.5 g of benzoyl chloride was added, kept for 2 hours, cooled and discharged to obtain a water-white viscous liquid polyurethane curing agent.

Embodiment 3

[0047] Under the protection of nitrogen, put 168g of hexamethylene diisocyanate monomer into the reaction vessel and stir evenly, raise the temperature to 85°C, then melt 23g of 1,4-cyclohexanedimethanol and slowly add it dropwise under stirring condition Into the reaction vessel, the dropwise addition time is 1.5 hours. After the dropwise addition is completed, it is kept at 85°C for 4 hours, and 0.8g of 2,4,6-tris(dimethylaminomethyl)phenol (trade name DABCO) is added at one time. TMR-30), lower the temperature to 70°C and continue to stir and react for 4 hours. When the NCO group content is reduced to 23.8 wt%, add 0.5g phosphoric acid, keep warm for 1 hour, cool and discharge, and obtain a water-white viscous liquid polyurethane curing agent.

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Abstract

The present invention relates to a polyurethane curing agent with low free isocyanate monomer and a preparation method thereof. The polyurethane curing agent comprises the raw materials in weight percentage as following: 80 - 88 parts of hexamethylene diisocyanate monomer; 12 - 20 parts of polyhydric alcohol; 0.1-0.5 part of catalyst; and 0.1-1.0 part of terminating agent. The invention adopts a two-step chemical conversion reaction, namely, adds one step of polymerization reaction based on one-step addition reaction to remove free isocyanate monomer by a trimer method so as to obtain the 100% solid content, wherein the NCO content is between 21 and 22 %, and the free HDI content is between 0.1 and 1.0 %. According to the present invention, the preparation process of polyurethane curing agent is simplified without post-processing . The polyurethane curing agent of the invention is matched with hydroxyl acrylic resin and polyester resin etc., and the paint film will not be yellowed, and has excellent light resistance, weathering resistance, chemical resistance and gorgeous gloss.

Description

technical field [0001] The invention relates to a polyurethane curing agent, in particular to a preparation method of a polyurethane curing agent with a free isocyanate monomer content of less than 1.0%. Background technique [0002] Polyisocyanate curing agent is an important part of polyurethane coatings and adhesives. Its composition and chemical structure directly determine the physical and mechanical properties, dryness, medium resistance and weather resistance of polyurethane coating films. At present, the polyisocyanate curing agent produced and used in China is mainly derivatives of toluene diisocyanate (TDI), such as TDI-TMP (trimethylolpropane) adduct and TDI trimer. The benzene ring in the TDI polyisocyanate curing agent changes into a colored quinone structure under conditions such as light, which can cause the varnish to yellow under long-term outdoor sunlight, and the luster of the paint will gradually disappear. Therefore, it is mostly used for medium and low-...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08G18/73C08G18/32C08G18/08C09D7/12C09D175/04
Inventor 何春全于郭王瑞莲王继成
Owner HUBEI TRASION CHEM IND CO LTD
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