A polyisocyanate composition with low free monomer, high compatibility and good dilution stability and a preparation method thereof

Abstract

The invention discloses a polyisocyanate composition with low free monomer, high compatibility and good dilution stability; the integral area ratio of the polymer to the trimer of the polyisocyanate composition is 2-7. The polyisocyanate composition prepared by the method of the invention has the characteristics of low free monomer, high compatibility, low color number and good dilution storage stability.

Description

Technical Field

[0001] The present invention relates to a polyisocyanate composition with low free monomer, high compatibility and good dilution stability and a preparation method thereof. The present invention further relates to the use of the polyisocyanate composition as a curing agent for coatings and adhesives. Background Art

[0002] Polyisocyanate curing agents are widely used as paint raw materials and in the fields of polyurethane elastomers and polyurethane foams. Among them, toluene diisocyanate as a curing agent has fast curing speed, high hydrolysis resistance, corrosion resistance and thermal stability compared to other curing agents, and plays an important role in wood painting and in the field of adhesives. Toluene diisocyanate curing agents contain free monomers. The national standard GB1858-2009 "Limits of Harmful Substances in Solvent-based Wood Coatings for Interior Decoration and Renovation Materials" stipulates that the limit value of free toluene diisocyanate after painting should be ≤0.4%, which means that the content of free toluene diisocyanate monomers in the curing agent must be below 0.8% to meet the national standard. Therefore, curing agents with low free toluene diisocyanate content are very necessary. Commonly used methods are divided into physical methods and chemical methods.

[0003] The chemical reaction method mainly adds catalysts such as amines, quaternary ammonium bases, and metal soaps to make isocyanate self-polymerize and reduce the content of free TDI. The advantages of the chemical synthesis method are simple synthesis process, no need for additional separation operations, and low cost. However, the monomer content of the chemically prepared curing agent is 0.5-1.0wt%. To reduce the monomer content, it is necessary to increase the degree of reaction and change the formula, which will lead to an increase in product color number, a low NCO content, and poor miscibility with hydroxyl resins.

[0004] Chinese patent CN 103183808 A discloses a method for reducing free TDI of a non-toxic polyurethane curing agent by a chemical reaction method. In the reaction, 10-20% 2,4-TDI is added to reduce the monomer. Although the free TDI content of the prepared curing agent is not higher than 0.4%, the method of adding 2,4-TDI is costly and the operation is complicated.

[0005] Chinese patent publication CN 109863215 A discloses a low-viscosity polyisocyanate based on TDI with isocyanurate groups, having a weight average molecular weight of ≥350 to ≤800 g / mol and a polydispersity D of >1 to ≤1.5. However, the patent uses evaporation to remove monomers, resulting in high production costs.

[0006] During the use of isocyanate curing agent, solvents are generally added to dilute the curing agent. We call this process "dilution". The diluted isocyanate curing agent solution is sometimes stored for a period of time before use. During this storage process, the toluene diisocyanate curing agent solution will change from clear to blue and finally to turbid, thus affecting its use. Therefore, it is of great significance to prepare an isocyanate curing agent with low free monomer content, good compatibility with resin and good storage stability after dilution. Summary of the invention

[0007] The technical problem to be solved by the present invention is to prepare a polyisocyanate curing agent with low free monomer content and high compatibility while also having good dilution storage stability.

[0008] In the study, we surprisingly found that when preparing a polyisocyanate composition, adding alcohol modification and controlling the integral area ratio of the polymer to the trimer of the polyisocyanate composition to be 2-7, a polyisocyanate curing agent with low free monomer and high compatibility was obtained, and good storage stability was also shown in the dilution test.

[0009] To this end, the present invention provides a polyisocyanate composition, which comprises a plurality of isocyanate components, wherein the integrated area ratio of polymers to trimers is 2-7, preferably 3-6, as determined by gel permeation chromatography using polystyrene as a standard sample and tetrahydrofuran as an eluent according to GB / T27810-2011, and the polymer refers to components above nonamers.

[0010] Preferably, according to the gel permeation chromatography method using polystyrene as a standard sample and tetrahydrofuran as an eluent in accordance with GB / T27810-2011, the integrated area of ​​the polymer is 40%-60%, and the integrated area of ​​the trimer is 8%-15%.

[0011] In the present invention, the prepared polyisocyanate composition contains multiple isocyanate components at the same time, and peaks appear at different retention times in gel chromatography analysis.

[0012] The present invention also provides a method for preparing a polyisocyanate composition with low free monomers and good dilution stability, the method comprising the following steps:

[0013] a) toluene diisocyanate, alcohol and solvent are mixed to react;

[0014] b) adding a catalyst during the reaction to carry out a catalytic reaction;

[0015] c) adding a terminator to terminate the reaction to obtain a polyisocyanate composition;

[0016] The integrated area ratio of the polymer to the trimer of the obtained polyisocyanate composition is 2-7.

[0017] In the present invention, the toluene diisocyanate in 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.

[0018] In the present invention, the general structural formula of the alcohol in step a) is R-(OH)n, wherein R is a C4-22 fatty chain or alicyclic chain, and n=1-3; the alcohol is preferably one or more of butanol, isobutanol, octanol, isooctyl alcohol, dodecanol, tetradecanol and octadecyl alcohol.

[0019] In the present invention, the solvent in step a) is one or more of ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and propylene glycol methyl ether acetate.

[0020] In the present invention, the catalyst in step b) is a Mannich base, a hydroxide of hydroxyalkylammonium, a phosphorus compound or a metal salt of an alkyl carboxylic acid, preferably a Mannich base; the hydroxide of the hydroxyalkylammonium is preferably trimethylhydroxypropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, triethylhydroxypropylammonium hydroxide, triethylhydroxyethylammonium hydroxide; the phosphorus compound is preferably tributylphosphine; the metal salt of the alkyl carboxylic acid is preferably a salt of a metal such as potassium acetate, tin octoate, zinc octoate and tin acetate;

[0021] The Mannich base catalyst preferably contains a hydroxyl group and a dialkylaminomethyl group in one molecule, and particularly preferably contains a dialkylaminomethyl group (alkyl group = C1 to C3 chain) in an ortho position relative to the aromatic hydroxyl group.

[0022] The amount of the catalyst used is ≥0.01%-1%, preferably 0.05%-0.5%, based on the total weight of toluene diisocyanate in step a.

[0023] In step c) of the present invention, 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 agent is preferably one or two of methyl p-toluenesulfonate and di-n-butyl phosphate. The terminator is used in an amount of 0.1-5.0 times the weight of the catalyst;

[0024] In the present invention, the amount of alcohol and toluene diisocyanate added is 1:10-30, preferably 1:15-25, based on the molar ratio of hydroxyl group to isocyanate group;

[0025] In a specific embodiment, the method for preparing the polyisocyanate comprises the following steps:

[0026] 1) adding alcohol to a mixed solution of toluene diisocyanate and a solvent at 40° C. to 90° C. for 0.5 to 12 hours to obtain a prepolymer reaction solution;

[0027] 2) adding a catalyst to the prepolymer reaction solution obtained in step 1) to continue the reaction;

[0028] 3) When the NCO solid content of step 2) is 11-14%, the reaction temperature is controlled at 10°C-20°C, and the reaction is continued until the NCO solid content is 7-8%;

[0029] 4) adding a terminator to obtain a polyisocyanate composition.

[0030] In the present invention, the integrated area ratio of the polymer to the trimer of the polyisocyanate composition obtained is 2-7, preferably 3-5.

[0031] In the present invention, the mass fraction of the solvent in step a) is 20-80% by weight, preferably 40-60%, and most preferably 50%.

[0032] In the present invention, the free monomer content of the isocyanate composition is ≤0.8 wt %, preferably ≤0.5 wt %; the free monomer refers to toluene diisocyanate monomer.

[0033] In the present invention, the prepared isocyanate composition has an isocyanate group content of 6%-9%, a color value of 5 Hazen-65 Hazen, and a viscosity of 80 Cp / 25°C-1200 Cp / 25°C.

[0034] Finally, the present invention also provides the use of the polyisocyanate composition as a curing agent in polyurethane paints and polyurethane adhesives. DETAILED DESCRIPTION

[0035] The following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention. The specific application of the present invention is not limited to the application mentioned in the examples, and those familiar with the art can make any modifications and further development within the scope of the claims of the present invention.

[0036] Dodecanol, Tianjin Guangfu Chemical Industry;

[0037] Octanol, Tianjin Guangfu Chemical;

[0038] Tetradecanol, Tianjin Guangfu Chemical;

[0039] Toluene diisocyanate, Wanhua Chemical;

[0040] Mannich base catalysts: (1) Mannich base based on bisphenol A / formalin / dimethylamine, synthesized by referring to lines 5-10 on page 6 of US 4115373; (2) Mannich base based on phenol / formalin / dimethylamine, synthesized by referring to lines 5-40 on page 8 of US 4115373.

[0041] Unless otherwise specified, other raw materials and reagents can be purchased through commercial channels.

[0042] NCO content test is in accordance with standard GB / T 12009.4;

[0043] The free isocyanate monomer content test adopts the national standard GB / T 18446-2009;

[0044] The dynamic viscosity was measured at 25 °C using a rotor viscometer (Brookfield DV-II);

[0045] The Hazen color value was determined using a colorimetric device (BYK LCS IV);

[0046] Solid content is tested according to GB / T2793-1995;

[0047] The xylene tolerance is tested by xylene titration, which is the ratio of the mass of xylene to the mass of the sample when turbid insoluble matter appears.

[0048] The components and number average molecular weight Mn of the polyisocyanate composition of the present invention can be obtained by GPC (gel chromatography) testing. The specific test conditions are as follows:

[0049] GPC equipment: Agilent1260

[0050] GPC columns: Pl1113-6520 and Pl113-6325 (Agilent)

[0051] Sample concentration: 3wt%

[0052] Mobile phase: tetrahydrofuran

[0053] Detection method: differential detector

[0054] Flow rate: 1ml / min

[0055] Column temperature: 35°C

[0056] The standard curve used polystyrene with a molecular weight range of 162-17900.

[0057] In the invention, the storage stability of the diluted sample is to mix Wannet@TL-75E, TDI trimer curing agent, butyl acetate and toluene in a mass ratio of 30:18:30:22, place it in a constant temperature and humidity chamber at 35°C and 80% for 2 days, and observe whether there is a bluing phenomenon. If the sample is clear, the storage stability is considered good, and if the sample is bluing, the storage stability is considered poor.

[0058] Example 1

[0059] 1000g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 1112.5g of butyl acetate were added to a reactor and stirred evenly. Then, 112.5g of dodecanol was added to the reactor. After reacting at 60°C for half an hour, 1g of catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate trimerization reaction. When the reaction NCO was 11%, the reaction temperature was controlled at 20°C to continue the reaction. When the reaction NCO was 7.4%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0060] Example 2

[0061] 900g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 1028.3g of butyl acetate were added to a reactor and stirred evenly. Then, 128.3g of dodecanol was added to the reactor. After reacting at 50°C for half an hour, 0.45g of a catalyst (Mannich base based on phenol / formalin / dimethylamine) was added to initiate a trimerization reaction. When the reaction NCO was 12%, the reaction temperature was controlled at 10°C to continue the reaction. When the reaction NCO was 7.8%, 2.25g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0062] Example 3

[0063] 1000g of about 80% toluene-2,4-diisocyanate and about 20% toluene-2,6-diisocyanate and 1085.5g of butyl acetate were added to a reactor and stirred evenly. Then, 85.5g of dodecanol was added to the reactor. After reacting at 75°C for half an hour, 0.5g of a catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate a trimerization reaction. When the reaction NCO% was 13.2%, the reaction temperature was controlled at 5°C to continue the reaction. When NCO%=7.1%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0064] Example 4

[0065] 800g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 859.8g of butyl acetate were added to the reactor and stirred evenly. Then 59.8g of octanol was added to the reactor. After reacting at 40°C for half an hour, 4g of trimethylhydroxypropylammonium hydroxide was added to initiate trimerization. When the reaction NCO was 14, the reaction temperature was controlled at 15°C to continue the reaction. When the reaction NCO was 7.3%, 4g of methyl p-toluenesulfonate was added to terminate the reaction to obtain a polyisocyanate composition.

[0066] Example 5

[0067] 800 g of 100% toluene-2,4-diisocyanate and 909.3 g of butyl acetate were added to a reactor and stirred evenly. Then, 109.3 g of tetradecanol was added to the reactor. After reacting at 85° C. for half an hour, 1.6 g of zinc octoate was added to initiate trimerization. When NCO%=11%, the reaction temperature was controlled at 20° C. to continue the reaction. When NCO%=7.2%, 2 g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0068] Example 6

[0069] 1000g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 1042.6g of butyl acetate were added to a reactor and stirred evenly. Then 42.6g of butanol was added to the reactor. After reacting at 60°C for half an hour, 1g of catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate a trimerization reaction. When the reaction NCO was 11%, the reaction temperature was controlled at 20°C to continue the reaction. When the reaction NCO was 7.7%, 3g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0070] Comparative Example 1

[0071] 1000g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 1112.5g of butyl acetate were added to a reactor and stirred evenly. Then 112.5g of dodecanol was added to the reactor. After reacting at 90°C for half an hour, 1g of catalyst (Mannich base of bisphenol A / formalin / dimethylamine) was added to initiate trimerization. When the reaction NCO was 7.1%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0072] Comparative Example 2

[0073] 1000g of about 80% toluene-2,4-diisocyanate, about 20% toluene-2,6-diisocyanate and 1112.5g of butyl acetate were added to a reactor and stirred evenly. Then, 112.5g of dodecanol was added to the reactor. After reacting at 60°C for half an hour, 1g of a catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate a trimerization reaction. When the reaction NCO was 15%, the reaction temperature was controlled at 20°C to continue the reaction. When the reaction NCO was 8.5%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0074] Comparative Example 3

[0075] 1000g of about 80% toluene-2,4-diisocyanate and about 20% toluene-2,6-diisocyanate and 1112.5g of butyl acetate were added to a reactor and stirred evenly. Then, 112.5g of dodecanol was added to the reactor. After reacting at 60°C for half an hour, 5g of catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate trimerization. When the reaction NCO was 9.0%, the reaction temperature was controlled at 20°C to continue the reaction. When the reaction NCO was 6.8%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0076] Comparative Example 4

[0077] 1000g of about 80% toluene-2,4-diisocyanate and about 20% toluene-2,6-diisocyanate and 1000 butyl acetate were added into a reactor and stirred evenly. Then, after reacting at 60°C for half an hour, 5g of catalyst (Mannich base based on bisphenol A / formalin / dimethylamine) was added to initiate trimerization reaction. When the reaction NCO was 12%, the reaction temperature was controlled at 20°C to continue the reaction. When the reaction NCO was 6.8%, 2g of dibutyl phosphate was added to terminate the reaction to obtain a polyisocyanate composition.

[0078] Table 1: Basic indicators of polyisocyanate composition

[0079]

[0080] Table 2: Storage stability test of polyisocyanate composition

[0081] Storage time 1 day 2 days Embodiment 1 (present invention) clarify clarify Embodiment 2 (present invention) clarify clarify Embodiment 3 (present invention) clarify clarify Embodiment 4 (present invention) clarify clarify Embodiment 5 (present invention) clarify clarify Embodiment 6 (present invention) clarify clarify Comparative Example 1 clarify Bluing Comparative Example 2 clarify clarify Comparative Example 3 clarify Bluing Comparative Example 4 clarify clarify

[0082] From the table, it can be seen that when the peak area ratio of the polymer to the trimer of the polyisocyanate composition is controlled at 2-7, a polyisocyanate with low free monomer, high xylene tolerance and good storage stability can be prepared.

Claims

1. A polyisocyanate composition, comprising a plurality of isocyanate components, wherein the integrated area ratio of polymers to trimers is 2-7 as measured by gel permeation chromatography using polystyrene as a standard sample and tetrahydrofuran as an eluent according to GB / T27810-2011, wherein the polymer refers to a component of nonamer or above; and a method for preparing the polyisocyanate composition comprises the following steps: a) toluene diisocyanate, alcohol and solvent are mixed to react; b) adding a catalyst during the reaction to carry out a catalytic reaction; c) adding a terminator to terminate the reaction to obtain a polyisocyanate composition.

2. The polyisocyanate composition according to claim 1, characterized in that According to the gel permeation chromatography method using polystyrene as a standard sample and tetrahydrofuran as an eluent in accordance with GB / T27810-2011, the integrated area of ​​the polymer is 40%-60%, and the integrated area of ​​the trimer is 8%-15%.

3. The polyisocyanate composition according to claim 1, characterized in that The integrated area ratio of polymers to trimers is 3-6.

4. The polyisocyanate composition according to claim 3, characterized in that In step a), the toluene diisocyanate is selected from 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.

5. The polyisocyanate composition according to any one of claims 1 to 4, characterized in that The general structural formula of the alcohol in step a) is R-(OH)n, wherein R is a C4-22 aliphatic chain or alicyclic chain, n＝1-3。 6. The polyisocyanate composition according to claim 5, characterized in that The alcohol is one or more of butanol, isobutanol, octanol, isooctyl alcohol, dodecanol, tetradecanol and octadecyl alcohol.

7. The polyisocyanate composition according to any one of claims 1 to 4, characterized in that The solvent in step a) is one or more of ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate and propylene glycol methyl ether acetate.

8. The polyisocyanate composition according to any one of claims 1 to 4, characterized in that The catalyst in step b) is a Mannich base, a hydroxide of hydroxyalkylammonium, a phosphorus compound or a metal salt of an alkyl carboxylic acid; the amount of the catalyst used is 0.01%-1% based on the total weight of the toluene diisocyanate in step a.

9. The polyisocyanate composition according to claim 8, characterized in that The hydroxide of the hydroxyalkylammonium is trimethylhydroxypropylammonium hydroxide, trimethylhydroxyethylammonium hydroxide, triethylhydroxypropylammonium hydroxide, and triethylhydroxyethylammonium hydroxide; the phosphorus compound is tributylphosphine; the metal salt of the alkyl carboxylic acid is potassium acetate, tin octoate, zinc octoate, and salt of tin acetate metal; the Mannich base catalyst uses a catalyst containing a hydroxyl group and a dialkylaminomethyl group in one molecule.

10. The polyisocyanate composition according to any one of claims 1 to 4, characterized in that The terminator is a proton acid, an acylating agent or an alkylating agent; the proton acid is one or more of phosphoric acid, hydrochloric acid and sulfuric acid; the acylating agent is benzoyl chloride; the alkylating agent is one or both of methyl p-toluenesulfonate and di-n-butyl phosphate; and / or the terminator is used in an amount of 0.1-5.0 times the weight of the catalyst.

11. Use of the polyisocyanate composition according to any one of claims 1 to 10 as a curing agent in polyurethane paints and polyurethane adhesives.

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