CN115651162A

CN115651162A - Polyisocyanate composition with low free monomer, high compatibility and good open-dilution stability and preparation method thereof

Info

Publication number: CN115651162A
Application number: CN202211005807.5A
Authority: CN
Inventors: 张晓鹏; 王玉启; 尚永华; 石滨; 陈立樟; 李明杰; 杨洗; 吴元波; 黎源
Original assignee: Wanhua Chemical Group Co Ltd
Current assignee: Wanhua Chemical Group Co Ltd
Priority date: 2022-08-22
Filing date: 2022-08-22
Publication date: 2023-01-31

Abstract

The invention discloses a polyisocyanate composition with low free monomer, high compatibility and good thinning stability; the polyisocyanate composition has an integrated area ratio of multimers to trimers of 2 to 7. The polyisocyanate composition prepared by the method has the characteristics of low free monomer, high compatibility, low color number and good dilution and storage stability.

Description

Polyisocyanate composition with low free monomer, high compatibility and good open-dilution stability and preparation method thereof

Technical Field

The invention relates to a polyisocyanate composition with low free monomer, high compatibility and good dilution stability and a preparation method thereof. The invention further relates to the use of the polyisocyanate composition as a curing agent for coatings and adhesives.

Background

Polyisocyanate curing agents are widely used as raw materials for paints and in the field of polyurethane elastomers and polyurethane foams. The toluene diisocyanate is used as a curing agent, has high curing speed, high hydrolysis resistance, corrosion resistance and thermal stability compared with other curing agents, and plays an important role in wood painting and in the field of adhesives. The toluene diisocyanate curing agent contains free monomers, and the limit value of free toluene diisocyanate after paint preparation is less than or equal to 0.4% specified in national standard GB1858-2009 harmful substance limit in solvent type wood lacquer coating for interior decoration materials, which indicates that the content of the free toluene diisocyanate monomer in the curing agent must be less than 0.8% to reach the national standard, so the curing agent with low content of free toluene diisocyanate is very needed, and the common methods are divided into physical methods and chemical methods.

The chemical reaction method mainly adds catalysts such as amine, quaternary ammonium base, metal soap and the like to enable isocyanate to be self-polymerized to reduce the content of free TDI, and has the advantages of simple synthesis process, no need of additional separation operation and low cost, but the content of the monomer of the curing agent prepared by the chemical method is 0.5-1.0wt%, and the reduction of the monomer needs to depend on the increase of reaction degree and the change of a formula, so that the color number of a product is increased, the content of NCO is lower, and the miscibility with hydroxy resin is poor.

Chinese patent publication No. CN 103183808A discloses a method for reducing free TDI of non-toxic polyurethane curing agent by chemical reaction, wherein 10-20% of 2,4-TDI is added in the reaction to reduce monomer, and although the content of the prepared curing agent is not higher than 0.4%, the mode of supplementing 2,4-TDI has high cost and complex operation ratio.

Chinese published patent CN 109863215A discloses TDI-based low-viscosity polyisocyanates having isocyanurate groups, a weight average molecular weight of 350 to 800g/mol or more and a polydispersity D of 1 to 1.5 or less, but the removal of the monomers by evaporation is used in the patent, which is expensive to produce.

During the use of the isocyanate curing agent, a solvent is generally added to dilute the curing agent, and the process is called 'dilution'. The diluted isocyanate curing agent solution is stored for a period of time for use, and the toluene diisocyanate curing agent solution is clear, blue and turbid finally during the storage process, so that the use is influenced. Therefore, the preparation of the isocyanate curing agent which has low free monomer content, good compatibility with resin and good open-dilution storage stability is of great significance.

Disclosure of Invention

The technical problem to be solved by the invention is that the polyisocyanate curing agent with low free monomer content and high compatibility has good open-diluent storage stability.

In the course of the research, we have surprisingly found that the addition of an alcohol modification and the control of the integral area ratio of multimers to trimers of the polyisocyanate compositions obtained in question to be between 2 and 7, when preparing polyisocyanate compositions, gives polyisocyanate curing agents of low free monomers, high compatibility and, at the same time, also show good storage stability in open evaluations.

To this end, the present invention provides a polyisocyanate composition comprising a plurality of isocyanate components, wherein the ratio of the integrated area of multimers to trimers, which refers to components above nonamers, is in the range of 2 to 7, preferably 3 to 6, as determined by gel permeation chromatography using polystyrene as standard and tetrahydrofuran as eluent according to GB/T27810-2011.

Preferably, the polymer has an integrated area of 40% to 60% and the trimer has an integrated area of 8% to 15% as determined by gel permeation chromatography according to GB/T27810-2011 using polystyrene as a standard and tetrahydrofuran as an eluent

In the present invention, the polyisocyanate composition prepared in the presence of a plurality of isocyanate components simultaneously exhibits peaks at different retention times in gel chromatography analysis.

The invention also provides a preparation method of the polyisocyanate composition with low free monomer and good open-end dilution stability, which comprises the following steps:

a) Mixing toluene diisocyanate, alcohol and a solvent for reaction;

b) Adding a catalyst in the reaction process to perform catalytic reaction;

c) Adding a terminator to terminate the reaction to obtain a polyisocyanate composition;

the resulting polyisocyanate composition has an integrated multimer to trimer area ratio of 2 to 7.

In the present invention, the toluene diisocyanate of step a) is selected from 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, or a mixture of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate.

In the invention, the structural general formula of the alcohol in the step a) is R- (OH) n, wherein R is a C4-22 aliphatic chain or alicyclic chain, and n =1-3; the alcohol is preferably one or more of butanol, isobutanol, octanol, isooctanol, dodecanol, tetradecanol, and octadecanol.

In the invention, the solvent in the step a) is one or more of ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and propylene glycol monomethyl ether acetate.

In the invention, the catalyst in the step b) is a Mannich base, hydroxide of hydroxyalkyl ammonium, a phosphorus compound or metal salt of alkyl carboxylic acid, preferably a Mannich base; the hydroxide of the hydroxyalkyl ammonium is preferably trimethyl hydroxypropyl ammonium hydroxide, trimethyl hydroxyethyl ammonium hydroxide, triethyl hydroxypropyl ammonium hydroxide or triethyl hydroxyethyl ammonium hydroxide; the phosphorus-based compound is preferably tributylphosphine; the metal salt of the alkyl carboxylic acid is preferably a salt of a metal such as potassium acetate, tin octylate, zinc octylate, or tin acetate;

the mannich base catalyst is preferably a catalyst containing a hydroxyl group and a dialkylaminomethyl group in one molecule, and particularly preferably a catalyst whose dialkylaminomethyl group (alkyl = C1 to C3 chain) is located at an ortho position with respect to the aromatic hydroxyl group;

the amount of the catalyst is more than or equal to 0.01-1%, preferably 0.05-0.5% based on the total weight of the toluene diisocyanate in the step a.

The reaction terminator in the step c) of the invention is a protonic acid, an acylation reagent or an alkylation reagent; the protonic acid is preferably one or more of phosphoric acid, hydrochloric acid and sulfuric acid; the acylating agent is preferably benzoyl chloride; the alkylating agent is preferably one or two of methyl p-toluenesulfonate and di-n-butyl phosphate. The dosage of the terminator is 0.1 to 5.0 times of the weight of the catalyst;

in the present invention, the amount of the alcohol and toluene diisocyanate added is 1:15-25;

in a specific embodiment, the preparation method of the polyisocyanate comprises the following steps:

1) Adding alcohol into the mixed solution of toluene diisocyanate and solvent at 40-90 ℃ to carry out an ammonia esterification reaction for 0.5-12 hours to obtain a prepolymer reaction solution;

2) Adding a catalyst into the prepolymer reaction liquid obtained in the step 1) to continue reaction;

3) When the solid content of NCO in the reaction in the step 2) is 11-14%, controlling the reaction temperature at 10-20 ℃, and continuing the reaction until the solid content of NCO is 7-8%;

4) Adding a terminating agent to obtain the polyisocyanate composition.

In the present invention, the obtained polyisocyanate composition has an integrated area ratio of multimer to trimer of 2 to 7, preferably 3 to 5.

In the present invention, the mass fraction of the solvent in step a) is 20 to 80% by weight, preferably 40 to 60%, most preferably 50%.

In the present invention, the isocyanate composition is prepared with a free monomer content of 0.8% by weight or less, preferably 0.5% by weight or less; the free monomer refers to toluene diisocyanate monomer.

In the invention, the isocyanate composition prepared has 6 to 9 percent of isocyanate group content; color number 5Hazen-65Hazen; viscosity 80Cp/25 ℃ to 1200Cp/25 ℃.

Finally, the invention also provides the use of the polyisocyanate composition as a curing agent in polyurethane paints, polyurethane adhesives.

Detailed Description

The following examples will further illustrate the process provided by the present invention but the invention is not limited to the examples set out and encompasses any other known variations within the scope of the claims appended hereto, the specific application of the invention is not limited to the examples set out herein and any modifications and further applications within the scope of the claims appended hereto may be made by those skilled in the art.

Dodecanol, tianjin optical compound chemical;

octanol, tianjin light complex chemical engineering;

tetradecanol, tianjin light complex chemical;

toluene diisocyanate, wanhua chemistry;

mannich base catalyst: (1) Mannich bases based on bisphenol a/formalin (Fomalin)/dimethylamine, cf synthesis in US 4115373, page six, lines 5-10; (2) Mannich bases based on phenol/formalin (Fomalin)/dimethylamine are synthesized according to US 4115373 on page eight, lines 5-40.

Other raw materials and reagents may be commercially available unless otherwise specified.

Testing the NCO content according to the standard GB/T12009.4;

the content test of the free isocyanate monomer adopts the national standard GB/T18446-2009;

dynamic viscosity was measured at 25 ℃ using a spindle viscometer (Brookfield DV-II);

hazen colour number was determined using a colour number measuring device (BYK LCS IV);

solids content was tested according to GB/T2793-1995;

and the xylene tolerance is measured by xylene titration, namely the ratio of the mass of the xylene to the mass of the sample when turbid and insoluble substances appear.

The components and the number average molecular weight Mn of the polyisocyanate composition in the present invention can be determined by GPC (molecular gel chromatography) measurement. The specific test conditions were as follows:

GPC apparatus: agilent1260

GPC column: pl1113-6520 and Pl113-6325 (Agilent)

Sample concentration: 3 wt.%

Mobile phase: tetrahydrofuran (THF)

The detection method comprises the following steps: differential detector

Flow rate: 1ml/min

Column temperature: 35 deg.C

The standard curve used polystyrene with a molecular weight of 162-17900.

In the invention, the diluent storage stability is that Wannet @ TL-75E, TDI tripolymer curing agent, butyl acetate and toluene are mixed according to the weight ratio of 30:18:30:22, placing the mixture in a constant temperature and humidity box at 35 ℃ and 80 percent for 2 days, and observing whether the bluing phenomenon exists or not. The storage stability was considered good if the sample was clear, and poor if the sample had bluing.

Example 1

1000g of about 80% of toluene-2, 4-diisocyanate, about 20% of toluene-2, 6-diisocyanate and 1112.5g of butyl acetate were added to a reaction vessel and stirred uniformly, 112.5g of dodecanol was then added to the reaction vessel, 1g of a catalyst (of which Mannich base based on bisphenol A/formalin/dimethylamine) was added after reacting at 60 ℃ for half an hour to initiate trimerization, the reaction was continued while controlling the reaction temperature at 20 ℃ when the reaction NCO was 11%, and the reaction was terminated by adding 2g of dibutyl phosphate when the reaction NCO was 7.4%, to obtain a polyisocyanate composition.

Example 2

900g of about 80% of toluene-2, 4-diisocyanate, about 20% of toluene-2, 6-diisocyanate and 1028.3g of butyl acetate were added to a reaction kettle, the mixture was stirred uniformly, then 128.3g of dodecanol was added to the reaction kettle, 0.45g of a catalyst based on phenol/formalin/dimethylamine Mannich base) was added after reacting for half an hour at 50 ℃ to initiate trimerization, the reaction temperature was controlled at 10 ℃ to continue the reaction when the reaction NCO was 12%, and 2.25g of dibutyl phosphate was added to terminate the reaction when the reaction NCO was 7.8%, to obtain a polyisocyanate composition.

Example 3

1000g of about 80% toluene-2, 4-diisocyanate, about 20% toluene-2, 6-diisocyanate and 1085.5g of butyl acetate were added to a reaction vessel, stirred uniformly, 85.5g of dodecanol was then added to the reaction vessel, 0.5g of a catalyst based on Mannich base of bisphenol A/formalin/dimethylamine) was added after reacting at 75 ℃ for half an hour to initiate trimerization, the reaction was continued while controlling the reaction temperature at 5 ℃ when NCO% was 13.2%, and the reaction was terminated by adding 2g of dibutyl phosphate when NCO% =7.1%, to obtain a polyisocyanate composition.

Example 4

800g of about 80 percent of toluene-2, 4-diisocyanate, about 20 percent of toluene-2, 6-diisocyanate and 859.8g of butyl acetate are added into a reaction kettle and stirred uniformly, then 59.8g of octanol is added into the reaction kettle, 4g of trimethyl hydroxypropyl ammonium hydroxide is added after reaction for half an hour at 40 ℃ to initiate trimerization reaction, when the reaction NCO is 14, the reaction temperature is controlled at 15 ℃ to continue the reaction, and when the reaction NCO is 7.3 percent, 4g of methyl p-toluenesulfonate is added to terminate the reaction, so that the polyisocyanate composition is obtained.

Example 5

800g of 100% toluene-2, 4-diisocyanate and 909.3g of butyl acetate are added into a reaction kettle, the mixture is stirred uniformly, 109.3g of tetradecanol is added into the reaction kettle, 1.6g of zinc octoate is added after the reaction is carried out for half an hour at 85 ℃ to initiate trimerization, the reaction temperature is controlled to be 20 ℃ when NCO% =11% for continuous reaction, and 2g of dibutyl phosphate is added when NCO% =7.2% for terminating the reaction, so that the polyisocyanate composition is obtained.

Example 6

1000g of about 80% toluene-2, 4-diisocyanate, about 20% toluene-2, 6-diisocyanate and 1042.6g of butyl acetate were added to a reaction kettle, stirred to homogeneity, 42.6g of butanol was then added to the reaction kettle, 1g of a catalyst (among which Mannich base based on bisphenol A/formalin/dimethylamine) was added after reaction for half an hour at 60 ℃ to initiate trimerization, the reaction was continued while controlling the reaction temperature at 20 ℃ when the reaction NCO was 11%, and the reaction was terminated by adding 3g of dibutyl phosphate when the reaction NCO was 7.7%, to obtain a polyisocyanate composition.

Comparative example 1

1000g of about 80% toluene-2, 4-diisocyanate, about 20% toluene-2, 6-diisocyanate and 1112.5g of butyl acetate were added to the reaction vessel, stirred uniformly, 112.5g of dodecanol was then added to the reaction vessel, 1g of bisphenol A/formalin/dimethylamine Mannich base as a catalyst was added after reacting for half an hour at 90 ℃ to initiate trimerization, and when the reaction NCO was 7.1%, 2g of dibutyl phosphate was added to terminate the reaction, to give a polyisocyanate composition.

Comparative example 2

1000g of toluene-2, 4-diisocyanate (80%) and toluene-2, 6-diisocyanate (20%) and butyl acetate (1112.5 g) were added to a reaction vessel and stirred uniformly, 112.5g of dodecanol was then added to the reaction vessel, 1g of a catalyst based on bisphenol A/formalin/dimethylamine Mannich base) was added after reacting at 60 ℃ for half an hour to initiate trimerization, the reaction temperature was controlled at 20 ℃ when the reaction NCO was 15%, and the reaction was continued when the reaction NCO was 8.5%, and 2g of dibutyl phosphate was added to terminate the reaction, to obtain a polyisocyanate composition.

Comparative example 3

1000g of toluene-2, 4-diisocyanate (80%) and toluene-2, 6-diisocyanate (20%) and butyl acetate (1112.5 g) were added to a reaction vessel, stirred uniformly, 112.5g of dodecanol was then added to the reaction vessel, 5g of a catalyst based on bisphenol A/formalin/dimethylamine Mannich base) was added after reacting at 60 ℃ for half an hour to initiate trimerization, the reaction temperature was controlled at 20 ℃ when the NCO content was 9.0%, and the reaction was continued when the NCO content was 6.8%, and 2g of dibutyl phosphate was added to terminate the reaction, to obtain a polyisocyanate composition.

Comparative example 4

1000g of about 80% toluene-2, 4-diisocyanate, about 20% toluene-2, 6-diisocyanate and 1000g of butyl acetate were added to a reaction vessel, stirred to homogeneity, 5g of a catalyst (Mannich base based on bisphenol A/formalin/dimethylamine) were added after reaction for half an hour at 60 ℃ to initiate trimerization, the reaction was continued while controlling the reaction temperature at 20 ℃ when the reaction NCO was 12%, and the reaction was terminated by adding 2g of dibutyl phosphate when the reaction NCO was 6.8%, to obtain a polyisocyanate composition.

TABLE 1 basic specifications for polyisocyanate compositions

TABLE 2 storage stability test of polyisocyanate compositions

Storage time	1 day	2 days
			Example 1 (inventive)	Clarification	Clarification
Example 2 (inventive)	Clarification	Clarification
			Example 3 (inventive)	Clarification	Clarification
Example 4 (inventive)	Clarification	Clarification
			Example 5 (inventive)	Clarification	Clarification
Example 6 (inventive)	Clarification	Clarification
			Comparative example 1	Clarification	Bluing
Comparative example 2	Clarification	Clarification
			Comparative example 3	Clarification	Bluing
Comparative example 4	Clarification	Clarification

From the table, when the peak area ratio of the polymer to the trimer of the polyisocyanate composition is controlled to be 2-7, the prepared low-free monomer has high tolerance of xylene and good dilution storage stability.

Claims

1. A polyisocyanate composition comprising a plurality of isocyanate components wherein the integrated area ratio of multimers to trimers, which are components above nonamers, is in the range of 2 to 7, preferably 3 to 6, as determined by gel permeation chromatography according to GB/T27810-2011 using polystyrene as standard and tetrahydrofuran as eluent.

2. The polyisocyanate composition of claim 1 wherein the polymer has an integrated area of 40% to 60% and the trimer has an integrated area of 8% to 15% as determined by gel permeation chromatography according to GB/T27810-2011 using polystyrene as a standard and tetrahydrofuran as an eluent.

3. A process for preparing an isocyanate composition according to claim 1 or 2, said process comprising the steps of:

a) Mixing toluene diisocyanate, alcohol and a solvent for reaction;

b) Adding a catalyst in the reaction process to perform catalytic reaction;

c) Adding a terminator to terminate the reaction to obtain the polyisocyanate composition.

4. The method of claim 3, wherein the toluene diisocyanate of step a) is selected from the group consisting of 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, and a mixture of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate.

5. The process according to claim 3 or 4, wherein the alcohol of step a) has the general structural formula R- (OH) n, wherein R is a C4-22 aliphatic or alicyclic chain, and n =1-3; the alcohol is preferably one or more of butanol, isobutanol, octanol, isooctanol, dodecanol, tetradecanol and octadecanol.

6. The method according to any one of claims 3 to 5, wherein the solvent of step a) is one or more of ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and propylene glycol methyl ether acetate.

7. The process according to any one of claims 3 to 6, wherein the catalyst of step b) is a Mannich base, a hydroxide of a hydroxyalkylammonium, a phosphorus-based compound or a metal salt of an alkylcarboxylic acid, preferably a Mannich base; the amount of the catalyst is more than or equal to 0.01-1 percent, preferably 0.05-0.5 percent based on the total weight of the toluene diisocyanate in the step a.

8. The method according to claim 7, wherein the hydroxide of a hydroxyalkylammonium is preferably trimethyl hydroxypropyl ammonium hydroxide, trimethyl hydroxyethyl ammonium hydroxide, triethyl hydroxypropyl ammonium hydroxide, triethyl hydroxyethyl ammonium hydroxide; the phosphorus compound is preferably tributyl phosphine; the metal salt of the alkyl carboxylic acid is preferably a salt of a metal such as potassium acetate, tin octylate, zinc octylate, or tin acetate; the mannich base catalyst preferably uses a catalyst containing a hydroxyl group and a dialkylaminomethyl group in one molecule, and particularly preferably uses a catalyst whose dialkylaminomethyl group (alkyl = C1 to C3 chain) is located at an ortho position with respect to the aromatic hydroxyl group.

9. The production method according to any one of claims 3 to 8, wherein the reaction terminator is a protonic acid, an acylating agent or an alkylating agent; the protonic acid is preferably one or more of phosphoric acid, hydrochloric acid and sulfuric acid; the acylating agent is preferably benzoyl chloride; the alkylating reagent is preferably one or two of methyl p-toluenesulfonate and di-n-butyl phosphate; and/or the amount of the terminator is 0.1 to 5.0 times of the weight of the catalyst.

10. Use of the polyisocyanate composition according to any one of claims 1 to 2 or prepared by the process according to any one of claims 2 to 9 as a curing agent in polyurethane paints, polyurethane adhesives.