WO2020252807A1

WO2020252807A1 - Polyisocyanate composition, preparation method therefor and use thereof

Info

Publication number: WO2020252807A1
Application number: PCT/CN2019/093291
Authority: WO
Inventors: 王暖程; 尚永华; 石滨; 王玉启; 陈行; 王丹; 李文滨; 黎源
Original assignee: 万华化学集团股份有限公司; 万华化学（宁波）有限公司
Priority date: 2019-06-21
Filing date: 2019-06-27
Publication date: 2020-12-24
Also published as: CN112111044B; CN112111044A

Abstract

Disclosed is a method for preparing a polyisocyanate composition, comprising the following steps: subjecting component A) to a self-polymerization reaction in the presence of component B), a solvent, and component C), a polymerization catalyst; and then terminating the reaction by adding a catalyst poison to obtain a polyisocyanate composition, wherein component A) includes a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, the content of dihalide imide in component A) is less than 30 ppm by weight, and the color number of the polyisocyanate composition is ≤ 40 Hazen. According to the method, the amount of the catalyst can be significantly reduced, and the resulting polyisocyanate composition has a lower color number, and has a better aging resistance when applied to paints.

Description

Polyisocyanate composition and preparation method and application thereof

Technical field

The invention belongs to the technical field of polyisocyanate composition preparation, and in particular relates to a polyisocyanate composition and a preparation method and application thereof.

Background technique

In the field, the preparation of polyisocyanate compositions based on the self-polymerization of isocyanates has long been known, and has been reported in many publications and patent documents, such as patent documents DE 4428107 A1, US 2993870 A, DE 1201992 B, DE 2452532 A1 And the journal file J.prakt.Chem.336,185-200,1994.

Nowadays, the methods for preparing commercially common polyisocyanate composition products are as follows: by making toluene diisocyanate available on a large scale in industry and a suitable organic solvent in a phenolic catalyst containing dialkylaminomethyl (Mannich base) Under the catalysis of ), self-polymerization is carried out until almost complete conversion, and then the catalyst is deactivated by adding acidic substances or alkylating reagents, and finally the desired product is obtained.

With the improvement of environmental protection regulations and the emphasis on occupational hygiene, products of the trimer type are often controlled by the trimerization reaction at a correspondingly high conversion rate until the monomer is basically converted into a higher degree of oligomeric isocyanurea Acid ester to prepare. The obtained corresponding solvent-containing product has a monomer TDI-content of <0.5% (for example, Wannate ^@ TT350B, a product sold by Wanhua Chemical).

However, the existing technologies for preparing polyisocyanates all have to face a common problem, that is, the introduction of catalyst and terminator in the preparation process successively, and when the amount of the two, especially the introduction of the catalyst, is high, it will cause the polyisocyanate and the paint prepared therewith. Appears more rapid yellowing and aging. The main reason for the high introduction of the catalyst and the discoloration of the polyisocyanate and the paint prepared with it is mainly due to the presence of microscopic impurities in the raw material toluene diisocyanate.

Therefore, there is no shortage of attempts to provide TDI-grades that can be used to prepare lighter colored and more stable aromatic polyisocyanates against aging. For example, in the patent document EP 1413571, a method is disclosed, which obtains a TDI-content of at least 99.5% by pre-concentrating the crude TDI-solution to a solvent content of <20% and subsequent fractionation in a partitioned distillation column. The product fraction of less than 200 ppm by weight of solvents and/or chlorinated aromatics, less than 100 ppm by weight of hydrolyzable chlorine, and less than 40 ppm by weight of acid. In the patent document US 6900348 B1 and the corresponding EP 1187808 A1, it is disclosed that lighter diphenylmethane-diisocyanate can be obtained by using phosgene with a bromine content of <50 ppm. EP 0816333 A1 claims a method of reducing the color of TDI by treating a crude solution with hydrogen before separating off the solvent.

Although the above methods can be used to prepare TDI grades with higher purity and lighter color, the process is relatively very complicated, and the disclosure does not indicate which secondary components are still relevant to the polyisocyanate during the preparation process. Discoloration that cannot be prevented sufficiently. In addition, they did not indicate which secondary components would cause the increase in catalyst consumption and thus the discoloration of paints prepared with polyisocyanates, and how to prevent this discoloration sufficiently. Therefore, there is always an urgent need for light-colored, aging-stable aromatic paint polyisocyanates.

Patent document CN105026454 describes a method for preparing light-colored TDI-polyisocyanate by limiting the content of 2-chloro-6-isocyanato-methyl-cyclohexadiene in TDI. Although the patent has made some progress in the research of color-causing substances, the disclosed method is limited to TDI produced by the gas phase method, and most of the current commercial TDI is produced by the liquid phase method, so it does not have broad spectrum. , Can not achieve a sufficient degree of prevention of discoloration. Therefore, there is still an urgent need to study the preparation of polyisocyanates in light-colored aromatic paints.

The purpose of the present invention is to find a method that can reduce the content of the catalyst used in the polyisocyanate, while being able to prepare lighter-colored and more aging resistant polyisocyanate compositions and paints.

Summary of the invention

The purpose of the present invention is to provide a method for preparing a polyisocyanate composition based on the self-polymerization reaction of toluene diisocyanate in view of the existing problems in the process of preparing a polyisocyanate composition, which can significantly reduce the amount of catalyst in the reaction process Therefore, the obtained polyisocyanate composition has a lower color number, and the polyisocyanate composition is applied to paint with better aging resistance.

In order to achieve the above objective, the technical solution of the present invention is as follows:

In one aspect of the present invention, a method for preparing a polyisocyanate composition based on the self-polymerization of toluene diisocyanate is provided, which includes the following steps:

The polyisocyanate composition is obtained by allowing the component A) to undergo self-polymerization in the presence of the following component B) and component C), and then terminating the reaction by adding a catalyst poison to the reaction system; wherein,

A) A mixture containing 2,4-toluene diisocyanate and 2,6-toluene diisocyanate,

B) Solvent,

C) Polymerization catalyst;

In the component A), the content of dihalogenimine is less than 30 wt ppm (for example, less than 25 wt ppm, less than 20 wt ppm, less than 15 wt ppm, less than 12 wt ppm, less than 8 wt ppm ppm, less than 5 ppm by weight).

The component A) described here is used as the starting diisocyanate raw material. Its main components (active ingredients) are 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, and may also contain various impurities. For example, it can be used TDI-65, TDI-80; the present invention controls the content of the impurity dihaloimine in component A). As the starting diisocyanate, toluene diisocyanate contains various impurities due to side reactions during the preparation process. For example, it may contain toluene monoisocyanate, chlorinated toluene monoisocyanate, carbamoyl chloride and phenyl diisocyanate, and may also contain Other side reaction products. The applicant found that when the content of the dihaloimine is controlled within a certain range, the consumption of the catalyst will be significantly reduced when the polyisocyanate composition is used to prepare the polyisocyanate composition, thereby obtaining a polyisocyanate composition with a lower color number and more resistant Aging paint.

Through the method of the present invention, a polyisocyanate composition with a lower color number can be prepared. In the context of this article, the meaning of "color number" can refer to the color number determination method in GB/T 3143-1982. In some examples, the low color number may refer to the color number of the polyisocyanate composition ≤ 40 Hazen, preferably ≤ 30 Hazen, more preferably ≤ 25 Hazen.

According to the method provided by the present invention, in some preferred embodiments, the content of dihaloimine in the component A) is less than 10 wt ppm, more preferably less than 1 wt ppm. For example, this grade of TDI (toluene diisocyanate) can be obtained by targeted distillation to reduce or remove dihalogenimines by means of rectification. In some examples in this context, the structure of the dihaloimine is one or more of the following compounds represented by Formula I or Formula II:

In the formula, each X is the same or different, and each is independently selected from Cl, Br or I.

The dihalogenimines are generated by side reactions in the photochemical process of TDI preparation, and the specific reaction process formula is as follows:

among them,

R is

The component A used in the present invention can be prepared by gas phase phosgenation. In the structure of the compound represented by Formula I or Formula II, the halogen represented by X is derived from phosgene. Since the preparation process of phosgene requires Cl ₂ , Cl ₂ is mainly derived from electrolytic NaCl. Therefore, the trace amounts of NaBr, MgBr, NaI, etc. will cause the introduction of bromine and iodine.

According to the method provided by the present invention, in some examples, the amount of component A) is 20-80wt% (for example, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 75wt%), and the group The amount of part B) is 20-80wt% (for example, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 75wt%). Here, the percentage of the amount of each component can be calculated based on the sum of the amounts of component A) and component B) in the system.

In some preferred examples, based on the total weight of the component A) being 100 wt%, the content of the 2,4-toluene diisocyanate is 65-95 wt% (for example, 70 wt%, 75 wt%, 80 wt%, 85 wt% %, 90wt%), the content of the 2,6-toluene diisocyanate is 5-35wt% (10wt%, 15wt%, 20wt%, 25wt%, 30wt%).

For example, 20-80wt% of industrially available large-scale basically composed of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate contains 65-95wt% of 2,4-toluene diisocyanate and 5 A mixture of -35wt% of 2,6-toluene diisocyanate as the starting diisocyanate is contacted with a polymerization catalyst and 20-80wt% of a solvent for self-polymerization, and then the reaction is terminated by adding a catalyst poison to the reaction system to obtain the Polyisocyanate composition; wherein the content of dihaloimine in the starting diisocyanate is less than 30 ppm by weight.

As a polymerization catalyst for initiating and accelerating the trimerization reaction, a catalyst commonly used in the art can be used. In some examples, the polymerization catalyst may be selected from (i) tetraalkylammonium hydroxides such as tetramethylammonium and tetraethylammonium, and weak organic acid salts such as acetic acid and capric acid; (ii) trimethyl Hydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and other hydroxyalkylammonium hydroxides, acetic acid, capric acid and other organic weak acid salts; iii) Metal salts of tin, zinc, lead and the like of alkyl carboxylic acids such as acetic acid, caproic acid, caprylic acid, and myristic acid; (iv) metal alkoxides such as sodium and potassium; (v) hexamethyldisilazane Compounds containing aminosilyl groups such as alkanes; (vi) Mannich bases; (vii) mixtures of tertiary amines and epoxy compounds; (viii) phosphorus compounds such as tributylphosphine.

The Mannich base catalyst has an N,N-dialkylaminomethyl group and a phenolic OH- group bonded to an aromatic compound. Wherein, "alkyl" refers to different or the same groups each having up to 18 carbon atoms optionally separated by oxygen or sulfur, or refers to groups having up to 18 carbon atoms optionally containing oxygen or sulfur. A bridged alkyl group in the form of an alkylene group of atoms. The N,N-dialkylaminomethyl and phenolic OH- groups can be distributed on multiple Mannich base molecules or on one or more benzene-based aromatic compounds. Preferably, a Mannich base containing both a phenolic hydroxyl group and a dialkylaminomethyl group in the molecule is used as the catalyst system for this reaction. It is particularly preferred to use such a system in which the dialkylaminomethyl group is located at the ortho position relative to the aromatic hydroxyl group, where the alkyl group refers to the same or different C1- to C3-alkyl groups.

The polymerization catalyst is preferably a Mannich base catalyst. In some preferred embodiments, the Mannich base catalyst is prepared by reacting phenol, p-isononylphenol or bisphenol A with dimethylamine and formaldehyde, more preferably by reacting phenol or bisphenol A with It is prepared by reacting dimethylamine and formaldehyde.

In this context, the Mannich base catalyst suitable for the present invention and its preparation process can be referred to patent documents US3996223 and US4115373.

The polymerization catalyst in the present invention can be used as a pure substance or optionally dissolved in a plurality of small portions or continuous form in the reaction system. In some examples, the added amount of the polymerization catalyst is 0.05-0.8 wt% of the amount of the component A), for example, 0.06 wt%, 0.08 wt%, 0.12 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt% %, 0.35wt%, 0.45wt%, 0.5wt%, 0.6wt%, 0.7wt%, preferably 0.1-0.4wt%.

The solvent used in the present invention may be a diluent and/or solvent commonly used in the field of polyurethane chemistry. In some examples, the solvent is selected from toluene, xylene, cyclohexane, chlorobenzene, butyl acetate, ethyl acetate, ethyl glycol acetate, amyl acetate, hexyl acetate, methoxy acetate One or more of methyl propyl ester, tetrahydrofuran, dioxane, acetone, N-methylpyrrolidone, methyl ethyl ketone, mineral spirits, highly substituted aromatic compounds and plasticizers. Highly substituted aromatic compounds, for example, can be selected from one or more of heavy benzene, tetralin and decalin; plasticizers, for example, can be phthalate, benzoate, sulfonate Or phosphate ester. In some preferred examples, the added amount of the solvent is 40-60 wt%.

According to the method provided by the present invention, in some examples, the unreacted monomer toluene diisocyanate content in the reaction system is less than 0.5 wt%.

The method of the present invention can be implemented by toluene diisocyanate in the presence of a solvent and a polymerization catalyst. In some examples, the reaction temperature of the self-polymerization reaction is 40-120°C (for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C), preferably 50-70°C; The reaction time is 5-48 hours (for example, 8 hours, 15 hours, 20 hours, 25 hours, 40 hours), preferably 10-30 hours.

For example, when the free TDI content in the mixture of the reaction system is less than 0.5 wt%, the polymerization reaction (or trimerization reaction) can be terminated by adding a catalyst poison. As catalyst poisons, acidic reactive substances such as protic acid (for example, dibutyl phosphate), or acylating and alkylating agents such as isophthalic acid dichloride or methyl toluenesulfonate can be considered. In some examples, the catalyst poison is selected from one or more of protonic acid, acylating agent and alkylating agent, preferably selected from dibutyl phosphate and/or methyl tosylate.

Those skilled in the art can understand that different types of polymerization catalysts used in the reaction system and different types of selected catalyst poisons will lead to different amounts of catalyst poisons. In the reaction system of the present invention, the added amount of the catalyst poison is based on the deactivation of the polymerization catalyst in the system.

In order to further achieve the purpose of the present invention and improve the corresponding technical effects, the present invention may also adopt the following technical solutions:

The method also includes: when the unreacted monomer toluene diisocyanate content in the mixture of the reaction system is less than 0.5wt%, adding 0.5-2.0wt% cyclodextrin to the system and stirring for 5-20min, and then filtering A catalyst poison is added to the reaction system to terminate the self-polymerization reaction.

In some examples, 20-80wt% of industrially available large-scale substantially composed of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate contains 65-95wt% of 2,4-toluene diisocyanate The mixture of isocyanate and 5-35wt% of 2,6-toluene diisocyanate is used as the starting diisocyanate, which is contacted with the polymerization catalyst and 20-80wt% of the solvent to carry out the self-polymerization reaction; when the unreacted monomer toluene in the mixture of the reaction system When the diisocyanate (TDI) content is less than 0.5wt%, add 0.5-2.0wt% (for example, 0.8wt%, 1.0wt%, 1.5wt%) of cyclodextrin to the system and stir for 5-20min (for example, 8min , 10min, 15min), after filtering, add catalyst poison to the reaction system to stop the self-polymerization reaction. The amount of the cyclodextrin is based on the weight (calculated value of the theoretical value) of the polyisocyanate composition obtained by the reaction.

The cyclodextrin used has the characteristics of hydrophilic outer edge and hydrophobic inner cavity. It can selectively identify and combine the polymerization catalyst in the reaction system to separate the catalyst from the reaction system, thereby greatly reducing the residue in the polyisocyanate composition. The catalyst and the catalyst poison content can achieve the purpose of reducing the color number of the polyisocyanate composition. In some preferred embodiments, the cyclodextrin is selected from one or more of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, particularly preferably β-cyclodextrin.

In the second aspect of the present invention, there is provided a polyisocyanate composition prepared by the method described above. The prepared polyisocyanate composition has the characteristic of low color number, and its color number is less than or equal to 40 Hazen, preferably less than or equal to 30 Hazen, more preferably less than or equal to 25 Hazen.

In the third aspect of the present invention, a polyisocyanate composition prepared by the method described above is provided as a polyisocyanate component and used in a polyurethane paint. Preferably, the polyisocyanate composition is used as a crosslinking agent in a two-component polyurethane paint.

The polyisocyanate composition prepared according to the method of the present invention is a valuable raw material that can be used in one-component and two-component polyurethane paints. A particularly preferred field of application of these polyisocyanate compositions is their use as a polyisocyanate component in two-component polyurethane paints. In this preferred application, other reaction materials that can be mixed and compounded with the polyisocyanate composition of the present invention can be selected from polyhydroxy polyesters, polyhydroxy polyethers, polyhydroxy polyacrylates, and optional Of low molecular weight polyols.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

In the preparation method of the present invention, by effectively controlling the content of dihalogenimine in the starting diisocyanate, the amount of catalyst in the reaction process can be significantly reduced, so that the obtained polyisocyanate composition has a lower color number (color number≤40Hazen ), and the polyisocyanate composition used in paint has better aging resistance.

Detailed ways

In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the examples, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

(1) Toluene diisocyanate,

TDI, Wanhua Chemical;

The chemical structures of the impurities dichloroimine, dibromoimine and chlorobromoimine appearing in the following examples are as follows:

1) Dichloroimines are shown in formula i or formula ii:

2) Dibromoimine is represented by formula iii or formula iv:

3) Chlorobromoimine is represented by formula v or formula vi:

The total content of dihaloimine in toluene diisocyanate is the sum of the content of dichloroimine, dibromoimine and chlorobromoimine.

(2) Butyl acetate, Jin Yimeng;

Methyl toluenesulfonate, Sigma-Aldrich;

Mannich base based on bisphenol A/formalin (Fomalin)/dimethylamine, synthesized with reference to lines 5-10 on page 6 of US4115373;

Mannich base based on phenol/Fomalin/dimethylamine, TMR-30, Evonik Industries;

β-Cyclodextrin, Sigma-Aldrich;

Polyol (matt varnish), HS-129, SAPICI;

TL75E (commonly known as TDI-TMP addition in this field), Wanhua Chemical.

All the percentages involved in the present invention are mass percentages unless otherwise specified.

The present invention determines the NCO content according to the method of GB/T 12009.4-1989.

The present invention is based on the method of GB/T 3143-1982 using HACH Lange's LICO 400 to measure the color number in a 50mm disposable rectangular cuvette.

The present invention is based on the method of GB/T18583-2008, and the residual monomer content in the reaction system is determined by gas chromatography.

The present invention is based on the method of GB/T1725-1979, and the solid content is determined under the test conditions described for isocyanate.

The dynamic viscosity involved in the present invention is obtained using BrookField DV-I Prime viscometer and S21 rotor at 25°C.

Dryness (surface dryness) test: GB/T 1728;

Matte gloss test: GB/T 9754;

UV resistance test: GB/T 1865;

Leveling test: prepare a paint film on the surface of the tinplate, place the sample under constant temperature and humidity (30℃, 35%-40% relative humidity), observe that the painted surface is uniform, smooth and wrinkle-free (no The time required for the state of orange peel or goose skin; whether the painted surface is uniform, smooth, and wrinkle-free (no orange peel or goose skin) is related to the user's standard requirements for different products;

Hardness test: GB/T 1730;

Adhesion level test: GB/T 9286.

Example 1

800g of toluene diisocyanate was used as the starting diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen and mixed to obtain a reaction mixture; wherein the toluene diisocyanate had 80wt% of 2,4- Toluene diisocyanate content and 25ppm dichloroimine content, 2ppm dibromoimine content, 1ppm chlorobromoimine content, that is, the total content of the impurity dihalogenimine in the starting diisocyanate is 28 wtppm, which is through rectification The operation controls the impurity content. The reaction mixture was heated to the desired reaction temperature of 60°C. 10g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on bisphenol A/Fomalin/dimethylamine is 20wt%) to initiate three Poly reaction. After the reaction was carried out for 8 hours, 6 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60° C. until the desired NCO content (NCO content = 7.98 wt%) was reached. In order to safely stop the trimerization reaction, 1.5 g (that is, the amount of methyl toluenesulfonate added is 1.15 times the molar amount of the polymerization catalyst) was added to the reaction mixture to terminate the polymerization reaction. After that, the reaction product was continuously stirred at 60°C for 1 hour. The polyisocyanate composition 1 containing solvent and isocyanurate groups thus obtained has the following characteristic values:

NCO content=7.98wt%,

Viscosity = 1300mPa*s/25℃,

Residual bill content = 0.23wt%,

Solid content = 50.8wt%,

Color number = 35Hazen.

Example 2

800g of toluene diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen for mixing to obtain a reaction mixture; wherein the toluene diisocyanate has 80wt% of 2,4-toluene diisocyanate content and 8ppm dichloroimine content, 1ppm chlorobromoimine content, dibromoimine content below the detection limit (ie, the minimum detection concentration detected by gas chromatography), which is the impurity dihalide in the starting diisocyanate The total content of imine is 9 wtppm, and the impurity content is controlled through the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60°C. 8g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on bisphenol A/Fomalin/dimethylamine is 20wt%) to initiate three Poly reaction. After the reaction was carried out for 8 hours, 4 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60°C until the desired NCO content (NCO content = 7.99 wt%) was reached. In order to safely stop the trimerization reaction, 1.2 g (that is, the amount of methyl toluenesulfonate added is 1.15 times the molar amount of the polymerization catalyst) was added to the reaction mixture to terminate the polymerization reaction. After that, the reaction product was continuously stirred at 60°C for 1 hour. The polyisocyanate composition 2 containing solvent and isocyanurate groups thus obtained has the following characteristic values:

NCO content=7.99wt%,

Viscosity = 1200mPa*s/25℃,

Residual bill content = 0.15wt%,

Solid content = 50.7wt%,

Color number = 25Hazen.

Example 3

800g of toluene diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen for mixing to obtain a reaction mixture; wherein the toluene diisocyanate has 80wt% of 2,4-toluene diisocyanate content and Dichloroimine content of 5 ppm, dibromoimine content below the detection limit (ie, the minimum detection concentration detected by gas chromatography), and chlorobromoimine content, that is, the impurity dihaloimine in the starting diisocyanate The total content of is 5 ppm by weight, and the impurity content is controlled through the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60°C. 6g of polymerization catalyst solution (this solution is a solution of Mannich base in butyl acetate, in which the concentration of Mannich base based on bisphenol A/Fomalin/dimethylamine is 20wt%) to initiate three Poly reaction. After the reaction was carried out for 8 hours, 3 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60° C. until the desired NCO content (NCO content = 8.00 wt%) was reached. In order to safely stop the trimerization reaction, 0.85 g (that is, the added amount of methyl toluenesulfonate is 1.15 times the molar amount of the polymerization catalyst) was added to the reaction mixture to terminate the polymerization reaction. After that, the reaction product was continuously stirred at 60°C for 1 hour. The polyisocyanate composition 3 containing solvent and isocyanurate groups thus obtained has the following characteristic values:

NCO content = 8.00wt%,

Viscosity=1150mPa*s/25℃,

Residual bill content = 0.08wt%,

Solid content = 50.8wt%,

Color number = 19Hazen.

Example 4

800g of toluene diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen for mixing to obtain a reaction mixture; wherein the toluene diisocyanate has 80wt% of 2,4-toluene diisocyanate content and Dichloroimine content of 5 ppm, dibromoimine content below the detection limit (ie, the minimum detection concentration detected by gas chromatography), and chlorobromoimine content, that is, the impurity dihaloimine in the starting diisocyanate The total content of is 5 ppm by weight, and the impurity content is controlled through the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60°C. 6g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on phenol/Fomalin/dimethylamine is 20wt%) to initiate the trimerization reaction . After the reaction proceeded for 8 hours, 4 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60°C until the desired NCO content (NCO content = 7.99 wt%) was reached. In order to safely stop the trimerization reaction, 2.4 g (that is, 1.5 times the molar amount of the polymerization catalyst) of dibutyl phosphate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was continuously stirred at 60°C for 0.5 hour. The polyisocyanate composition containing solvent and isocyanurate group thus obtained has the following characteristic values:

NCO content=7.99wt%,

Viscosity=1150mPa*s/25℃,

Residual bill content = 0.09wt%,

Solid content = 51.0wt%,

Color number = 20Hazen.

Example 5

800g of toluene diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen for mixing to obtain a reaction mixture; wherein the toluene diisocyanate has 80wt% of 2,4-toluene diisocyanate content and Dichloroimine content of 5 ppm, dibromoimine content below the detection limit (ie, the minimum detection concentration detected by gas chromatography), and chlorobromoimine content, that is, the impurity dihaloimine in the starting diisocyanate The total content of is 5 ppm by weight, and the impurity content is controlled through the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60°C. 6g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on phenol/Fomalin/dimethylamine is 20wt%) to initiate the trimerization reaction . After the reaction proceeded for 8 hours, 4 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60° C. until the desired NCO content (NCO content = 8.01 wt%) was reached. 16 g of β-cyclodextrin was added to the system and stirred for 10 min. After filtration, 2.4 g (that is, the addition amount of 1.5 times the molar amount of the polymerization catalyst) dibutyl phosphate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was continuously stirred at 60°C for 0.5 hour. The thus obtained polyisocyanate composition 5 containing solvent and isocyanurate groups has the following characteristic values:

NCO content = 8.01wt%,

Viscosity = 1200mPa*s/25℃,

Residual bill content = 0.10wt%,

Solid content = 51.2wt%,

Color number = 15Hazen.

Example 6

800g of toluene diisocyanate and 800g of butyl acetate were placed in advance in a 2L reaction vessel purged with nitrogen for mixing to obtain a reaction mixture; wherein the toluene diisocyanate has 80wt% of 2,4-toluene diisocyanate content and Dichloroimine content of 5 ppm, dibromoimine content below the detection limit (ie, the minimum detection concentration detected by gas chromatography), and chlorobromoimine content, that is, the impurity dihaloimine in the starting diisocyanate The total content of is 5 ppm by weight, and the impurity content is controlled through the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60°C. 6g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on phenol/Fomalin/dimethylamine is 20wt%) to initiate the trimerization reaction . After the reaction was carried out for 8 hours, 4 g of the polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60°C until the desired NCO content (NCO content = 7.99 wt%) was reached. 8 g of β-cyclodextrin was added to the system and stirred for 10 min. After filtration, 2.4 g of dibutyl phosphate (that is, 1.5 times the molar amount of the polymerization catalyst) was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was continuously stirred at 60°C for 0.5 hour. The polyisocyanate composition 6 containing solvent and isocyanurate groups thus obtained has the following characteristic values:

NCO content=7.99wt%,

Viscosity = 1230mPa*s/25℃,

Residual bill content = 0.10wt%,

Solid content = 51.3wt%,

Color number = 17Hazen.

Comparative Example 1

The preparation method is carried out with reference to Example 1, but the difference is that the toluene diisocyanate used has 80wt% 2,4-toluene diisocyanate content and 55ppm dichloroimine content, 3ppm dibromoimine content, 5ppm chlorine The bromine imine content, that is, the total content of the impurity dihalogen imine in the initial diisocyanate is 63 wt ppm, and the impurity content is controlled through the operation of rectification.

800 g of the toluene diisocyanate and 800 g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture. The reaction mixture was heated to the desired reaction temperature of 60°C. 20g of polymerization catalyst solution (this solution is a Mannich base in butyl acetate solution, wherein the concentration of Mannich base based on bisphenol A/Fomalin/dimethylamine is 20wt%) to initiate three Poly reaction. After the reaction was carried out for 8 hours, 10 g of polymerization catalyst solution was added, and stirring was continued for 12 hours at a reaction temperature of 60° C. until the desired NCO content (NCO content = 7.97 wt%) was reached. In order to safely stop the trimerization reaction, 2.8 g (that is, the amount added is 1.15 times the molar amount of the polymerization catalyst) of methyl toluenesulfonate was added to the reaction mixture to terminate the polymerization reaction. After that, the reaction product was continuously stirred at 60°C for 1 hour. The polyisocyanate composition 1'containing solvent and isocyanurate groups thus obtained has the following characteristic values:

NCO content = 7.97wt%,

Viscosity = 1430mPa*s/25℃,

Residual bill content = 0.30wt%,

Solid content = 51.5wt%,

Color number = 65Hazen.

It can be seen from the above examples 1-4 that when using toluene diisocyanate with a dihalogen content of <30 ppm, a light-colored polyisocyanate with a color number of <40 Hazen can be obtained; and with the impurities in the starting diisocyanate As the content of dihaloimine decreases, the amount of catalyst used in the reaction system also shows a downward trend. It can be seen from Examples 5 and 6 that after adding cyclodextrin to the system, the color number of the obtained polyisocyanate composition can be further reduced. However, the content of dihalogen imine in the toluene diisocyanate used in Comparative Example 1 exceeded 30 ppm, and the content of the catalyst to be added was significantly increased, and finally a light-colored polyisocyanate with a color number of <40 Hazen could not be obtained.

Example 7 (Use Example)

The polyisocyanate composition 2, polyisocyanate composition 3 and polyisocyanate composition 1'prepared in Example 2, Example 3 and Comparative Example 1 were combined with Wanhua respectively.

TL75E is mixed at a mass ratio of 1:2 to prepare a curing agent mixture, and then the obtained mixture is mixed with a commercial polyol (matt varnish, HS-129) at a NCO/OH molar ratio of 1:1, and then butyl acetate is added The mixed solvent of ester/xylene (the two are mixed with equal mass) is diluted (the content of the curing agent in the solution formed by the curing agent and butyl acetate/xylene is 40 wt%), and finally the paint is prepared. The paint prepared by adding the polyisocyanate composition 2 and the polyisocyanate composition 3 is denoted as paint 2 and paint 3, and the paint prepared by adding the polyisocyanate composition 1'is denoted as paint 1'. Table 1 shows the performance test results of various paints in terms of UV aging resistance and adhesion.

Table 1 Performance test results of paint

From the performance test results in Table 1, it can be seen that the paint obtained by adding the low-color polyisocyanate composition can effectively improve the UV aging resistance under the condition of ensuring that the other properties are excellent. It is better than adding the high-color polyisocyanate composition The resulting paint has excellent UV aging resistance.

The various embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to those of ordinary skill in the art.

Claims

A method for preparing a polyisocyanate composition based on the self-polymerization of toluene diisocyanate, which is characterized in that it comprises the following steps:

The polyisocyanate composition is obtained by allowing the component A) to undergo self-polymerization in the presence of the following component B) and component C), and then terminating the reaction by adding a catalyst poison to the reaction system; wherein,

A) A mixture containing 2,4-toluene diisocyanate and 2,6-toluene diisocyanate,

B) Solvent,

C) Polymerization catalyst;

In the component A), the content of dihaloimine is less than 30 wt ppm;

Preferably, the color number of the polyisocyanate composition is ≤40 Hazen, more preferably ≤30 Hazen, and further preferably ≤25 Hazen.
The method according to claim 1, characterized in that, in the component A), the content of dihaloimine is less than 10 ppm by weight, preferably less than 1 ppm by weight.
The method according to claim 1 or 2, wherein the dihaloimine is one or more of the following compounds represented by formula I or formula II:

In the formula, each X is the same or different, and each is independently selected from Cl, Br or I.
The method according to any one of claims 1 to 3, wherein the amount of the component A) is 20-80% by weight, and the amount of the component B) is 20-80% by weight. The sum of the amount of component A) and component B) is the basis;

Preferably, based on the total weight of the component A) being 100% by weight, the content of the 2,4-toluene diisocyanate is 65-95% by weight, and the content of the 2,6-toluene diisocyanate is 5-35% by weight %.
The method according to any one of claims 1 to 4, characterized in that the polymerization catalyst is a Mannich base catalyst, preferably, the Mannich base catalyst is made of phenol, p-isonon The base phenol or bisphenol A is prepared by reacting with dimethylamine and formaldehyde, and it is more preferably prepared by reacting phenol or bisphenol A with dimethylamine and formaldehyde.
The method according to any one of claims 1 to 5, wherein the added amount of the polymerization catalyst is 0.05-0.8 wt% of the amount of the component A), preferably 0.1-0.4 wt%.
The method according to any one of claims 1-6, wherein the solvent is selected from toluene, xylene, cyclohexane, chlorobenzene, butyl acetate, ethyl acetate, ethyl glycol ethyl Among the esters, amyl acetate, hexyl acetate, methoxypropyl acetate, tetrahydrofuran, dioxane, acetone, N-methylpyrrolidone, methyl ethyl ketone, mineral spirits, highly substituted aromatic compounds and plasticizers One or more; wherein, the highly substituted aromatic compound is selected from one or more of heavy benzene, tetralin and decalin.
The method according to any one of claims 1-7, wherein the unreacted monomer toluene diisocyanate content in the reaction system is less than 0.5% by weight; and/or

The reaction temperature of the self-polymerization reaction is 40-120°C, preferably 50-70°C.
The method according to any one of claims 1-8, characterized in that the method further comprises: when the unreacted monomer toluene diisocyanate content in the mixture of the reaction system is less than 0.5wt%, adding to the system Add 0.5-2.0wt% cyclodextrin and stir for 5-20min, and then add the catalyst poison to the reaction system after filtration to terminate the self-polymerization reaction;

Preferably, the cyclodextrin is selected from one or more of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, more preferably β-cyclodextrin.
The method according to any one of claims 1-9, wherein the catalyst poison is selected from one or more of protonic acid, acylating agent and alkylating agent, preferably selected from dibutyl phosphate Ester and/or methyl tosylate.
A polyisocyanate composition prepared by the method of any one of claims 1-10, and its color number is less than or equal to 40 Hazen.
The polyisocyanate composition prepared by the method according to any one of claims 1-10 is used as a polyisocyanate component in polyurethane paint; preferably, the polyisocyanate composition is used as a crosslinking agent in a two-component Parts of polyurethane paint.