CN112111044B - Polyisocyanate composition and preparation method and application thereof - Google Patents
Polyisocyanate composition and preparation method and application thereof Download PDFInfo
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
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Abstract
The invention belongs to the technical field of preparation of polyisocyanate compositions, and particularly relates to a polyisocyanate composition, and a preparation method and application thereof. The method comprises the following steps: the polyisocyanate composition is obtained by subjecting component A) to self-polymerization in the presence of the following components B) and C), and then terminating the reaction by adding a catalyst poison to the reaction system; wherein A) comprises a mixture of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate, B) a solvent, C) a polymerization catalyst; the content of dihaloimines in component A) is less than 30ppm by weight; the color number of the polyisocyanate composition is less than or equal to 40 Hazen. The method can obviously reduce the dosage of the catalyst in the reaction process, so that the obtained polyisocyanate composition has lower color number and better aging resistance when being applied to paint.
Description
Technical Field
The invention belongs to the technical field of preparation of polyisocyanate compositions, and particularly relates to a polyisocyanate composition, and a preparation method and application thereof.
Background
The preparation of polyisocyanate compositions based on the self-polymerization of isocyanates has been known for a long time in the art and is reported in numerous publications and patent documents, such as patent documents DE 4428107 a1, US 2993870A, DE 1201992B, DE 2452532 a1 and journal documents j.prakt.chem.336,185-200,1994.
Today, commercially common polyisocyanate composition products are prepared by the following methods: the desired product is finally obtained by self-polymerizing commercially available toluene diisocyanate on a large scale with a suitable organic solvent under the catalysis of a phenol catalyst containing dialkylaminomethyl groups (Mannich base) until almost complete conversion, and then deactivating the catalyst by addition of an acidic substance or by means of an alkylating agent.
With increasing sophistication of environmental regulations and emphasis on occupational health reasons, products of the trimer type are often prepared by controlling the trimerization reaction at correspondingly high conversions until the monomer is substantially converted to the more oligomeric isocyanurate. Corresponding solvent-containing products are prepared having<Monomeric TDI-content of 0.5% (e.g., Wannate)@TT350B, a sales product of wanhua chemistry).
However, the prior art processes for preparing polyisocyanates are subject to the common problem that, owing to the sequential introduction of catalysts and terminators during the preparation process, the higher amounts of both, especially of the catalyst, lead to more rapid yellowing and aging of the polyisocyanates and of the lacquers prepared therewith. The high catalyst incorporation and the resulting discoloration of the polyisocyanates and of the lacquers produced therewith are mainly due to: microscopic impurities were present in the starting toluene diisocyanate used.
There are therefore no attempts to provide TDI-grades which can be used to prepare aromatic polyisocyanates which are lighter in color and more stable to ageing. For example, in patent document EP 1413571 a process is disclosed which obtains a product fraction having a TDI-content of at least 99.5% and less than 200 ppm by weight of solvent and/or chlorinated aromatic hydrocarbons, less than 100 ppm by weight of hydrolysable chlorine and less than 40 ppm by weight of acid by preconcentrating the TDI-crude solution to a solvent content of < 20% and subsequent fractionation in a divided wall distillation column. In patent document US 6900348B 1 and in the corresponding EP 1187808 a1, it is disclosed that a lighter color of diphenylmethane-diisocyanate can be obtained by using phosgene having a bromine content of <50 ppm. EP 0816333 a1 claims a process for reducing the color of TDI by treating the crude solution with hydrogen before separating off the solvent.
Although TDI grades of higher purity and lighter color can be prepared by these methods as described above, the process is relatively complicated and no indication is given in the disclosure of which minor components have a discoloration effect on the polyisocyanate which is still not sufficiently prevented during its preparation. In addition, they do not indicate which minor components lead to an increased catalyst consumption and thus to discoloration of the lacquer prepared with the polyisocyanate, and how this discoloration can be adequately prevented. Thus, there is still a great need for light-colored, aging-stable aromatic paint polyisocyanates.
In patent document CN105026454 a process is described for the preparation of light-colored TDI-polyisocyanates by limiting the content of 2-chloro-6-isocyanato-methyl-cyclohexadiene in TDI. Although this patent has made some progress in the research of color-forming substances, the disclosed method is limited to TDI produced by a gas phase method, and most of the current commercial TDI is prepared by a liquid phase method, and thus, it does not have broad spectrum and cannot achieve sufficient prevention of discoloration. There is therefore still an urgent need to investigate the preparation of polyisocyanates in light-coloured aromatic paints.
The object of the present invention was to find a process which makes it possible to reduce the amount of catalyst used in the polyisocyanate and at the same time to prepare lighter-colored and more resistant-to-aging polyisocyanate compositions and paints.
Disclosure of Invention
The invention aims to provide a method for preparing a polyisocyanate composition based on the self-polymerization reaction of toluene diisocyanate, aiming at the problems in the existing preparation process of the polyisocyanate composition, and the method can obviously reduce the dosage of a catalyst in the reaction process, so that the obtained polyisocyanate composition has lower color number and better aging resistance when being applied to paint.
In order to achieve the purpose, the technical scheme of the invention is as follows:
in one aspect of the present invention, there is provided a method for preparing a polyisocyanate composition based on the self-polymerization of toluene diisocyanate, comprising the steps of:
the polyisocyanate composition is obtained by subjecting component A) to self-polymerization in the presence of the following components B) and C), and then terminating the reaction by adding a catalyst poison to the reaction system; wherein the content of the first and second substances,
A) comprising a mixture of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate,
B) a solvent, a water-soluble organic solvent,
C) a polymerization catalyst;
the content of dihaloimine in the component A) is less than 30ppm by weight (for example, less than 25ppm by weight, less than 20 ppm by weight, less than 15 ppm by weight, less than 12 ppm by weight, less than 8ppm by weight, less than 5ppm by weight).
The component A) described herein as a starting diisocyanate raw material contains 2, 4-tolylene diisocyanate and 2, 6-tolylene diisocyanate as main components (effective components) and may further contain various impurities, for example, TDI-65, TDI-80; the invention controls the content of the dihaloimine impurity in the component A). Toluene diisocyanate as the starting diisocyanate may contain various impurities due to side reactions during the preparation, for example, toluene monoisocyanate, chlorotoluene monoisocyanate, carbamoyl chloride and phenyl diisocyanate, and may contain other side reaction products. The Applicant has found that when the content of dihaloimine is controlled within a certain range, the use of the dihaloimine for the preparation of polyisocyanate compositions leads to a significant reduction in the consumption of catalyst, which in turn leads to polyisocyanate compositions of lower color number and to paints which are more resistant to ageing.
By the process of the present invention, polyisocyanate compositions of lower color numbers can be obtained. In this context, "color number" means that reference is made to the color number determination method in GB/T3143-1982. In some examples, a low color number may refer to a color number of the polyisocyanate composition of ≦ 40Hazen, preferably ≦ 30Hazen, and more preferably ≦ 25 Hazen.
According to the process provided by the present invention, in some preferred embodiments, the content of dihaloimine in said component a) is lower than 10 ppm by weight, more preferably lower than 1ppm by weight. This grade of TDI (toluene diisocyanate) can be obtained, for example, by targeted distillative reduction or removal of dihaloimines by means of rectification. In some examples herein and in the context thereof, the dihaloimine is structurally one or more of the compounds represented by formula I or formula II:
The dihaloimine is generated by side reaction in the process of the preparation of TDI by means of the photochemical reaction, and the specific reaction process is as follows:
r is
And/or
The component A used in the present invention may be prepared by gas phase phosgenation. In the structure of the compound represented by the formula I or the formula II, the halogen represented by X is derived from phosgene, and Cl is required in the preparation process of phosgene2，Cl2And the NaCl is mainly derived from electrolysis of NaCl, so trace amounts of NaBr, MgBr, NaI and the like in NaCl can cause the introduction of bromine and iodine elements.
In accordance with the methods provided herein, in some examples, component a) is used in an amount of 20 to 80wt% (e.g., 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 75 wt%), and component B) is used in an amount of 20 to 80wt% (e.g., 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 75 wt%). Here, the percentages of the amounts of the components may be based on the sum of the amounts of component A) and component B) in the system.
In some preferred examples, the 2, 4-toluene diisocyanate is present in an amount of 65 to 95wt% (e.g., 70 wt%, 75 wt%, 80wt%, 85 wt%, 90 wt%) and the 2, 6-toluene diisocyanate is present in an amount of 5 to 35wt% (10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%), based on the total weight of component a) taken as 100 wt%.
For example, 20 to 80% by weight of a mixture comprising 65 to 95% by weight of 2, 4-tolylene diisocyanate and 5 to 35% by weight of 2, 6-tolylene diisocyanate, which is industrially available on a large scale and consists essentially of 2, 4-tolylene diisocyanate and 2, 6-tolylene diisocyanate, as a starting diisocyanate, is contacted with a polymerization catalyst and 20 to 80% by weight of a solvent to carry out a self-polymerization reaction, and then the reaction is terminated by adding a catalyst poison to the reaction system to obtain the polyisocyanate composition; wherein the content of dihaloimines in the starting diisocyanates is less than 30ppm by weight.
As the polymerization catalyst for initiating and accelerating the trimerization reaction, a catalyst commonly used in the art may be used. In some examples, the polymerization catalyst may be selected from (i) hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, etc., salts of organic weak acids such as acetic acid, capric acid, etc.; (ii) hydroxides of hydroxyalkylammonium such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, and triethylhydroxyethylammonium, and salts of organic weak acids such as acetic acid and capric acid; (iii) metal salts of alkyl carboxylic acids such as acetic acid, caproic acid, caprylic acid, and myristic acid such as tin, zinc, and lead; (iv) metal alkoxides of sodium, potassium, and the like; (v) a compound containing an aminosilyl group such as hexamethyldisilazane; (vi) mannich bases; (vii) mixtures of tertiary amines with epoxy compounds; (viii) phosphorus compounds such as tributylphosphine.
The Mannich base catalysts have N, N-dialkylaminomethyl and phenolic OH-groups bonded to aromatic compounds. Where "alkyl" refers to different or identical radicals each having up to 18 carbon atoms optionally separated by oxygen or sulfur, or to a bridging alkyl group in the form of an alkylene group having up to 18 carbon atoms optionally containing oxygen or sulfur. The N, N-dialkylaminomethyl and phenolic OH-groups may be distributed over a plurality of Mannich base molecules or on one or more benzene-based aromatic compounds. Preferably, Mannich bases containing both phenolic hydroxyl groups and dialkylaminomethyl groups in the molecule are used as catalyst systems for this reaction. Particular preference is given to using systems in which the dialkylaminomethyl group is in the ortho position relative to the aromatic hydroxyl group, where the alkyl groups are identical or different C1-to C3-alkyl groups.
The polymerization catalyst is preferably a mannich base-based catalyst. In some preferred embodiments, the Mannich base catalyst is prepared by reacting phenol, p-isononyl phenol, or bisphenol A with dimethylamine and formaldehyde, more preferably by reacting phenol or bisphenol A with dimethylamine and formaldehyde.
In this context, reference is made to the patent documents US3996223 and US4115373 for the mannich base catalysts and the preparation thereof which are suitable according to the invention.
The polymerization catalyst in the present invention may be used as a pure substance or optionally dissolved in the reaction system in a plurality of small portions or continuously. In some examples, the polymerization catalyst is added in an amount of 0.05 to 0.8wt%, e.g., 0.06 wt%, 0.08 wt%, 0.12 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.35 wt%, 0.45 wt%, 0.5wt%, 0.6 wt%, 0.7 wt%, preferably 0.1 to 0.4wt% of the amount of the component A).
The solvent used in the present invention may be a diluent and/or a solvent commonly used in the field of polyurethane chemistry. In some examples, the solvent is selected from one or more of toluene, xylene, cyclohexane, chlorobenzene, butyl acetate, ethyl glycol acetate, amyl acetate, hexyl acetate, methoxypropyl acetate, tetrahydrofuran, dioxane, acetone, N-methylpyrrolidone, methyl ethyl ketone, mineral spirits, highly substituted aromatic compounds, and plasticizers. Highly substituted aromatic compounds, for example, may be selected from one or more of heavy benzene, tetralin and decalin; the plasticizer may be, for example, a phthalate, benzoate, sulfonate or phosphate ester. In some preferred examples, the solvent is added in an amount of 40 to 60 wt%.
According to the method provided by the invention, in some examples, the content of unreacted monomeric toluene diisocyanate in the reaction system is less than 0.5 wt%.
The process of the present invention may be carried out with 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 ℃ (e.g., 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃), preferably 50-70 ℃; the reaction time is 5 to 48 hours (e.g., 8 hours, 15 hours, 20 hours, 25 hours, 40 hours), preferably 10 to 30 hours.
For example, when the free TDI content of the reaction system mixture is less than 0.5wt%, the polymerization (or trimerization) may be terminated by adding a catalyst poison. As catalyst poisons, acidic reactive substances such as protic acids (e.g. dibutyl phosphate) or acylating and alkylating agents, for example, isophthalic acid dichloride or methyl tosylate, can be considered. In some examples, the catalyst poison is selected from one or more of a protic acid, an acylating agent and an alkylating agent, preferably from dibutyl phosphate and/or methyl tosylate.
It will be understood by those skilled in the art that different types of polymerization catalysts used in the reaction system, as well as different types of catalyst poisons selected, will result in different amounts of catalyst poisons. In the reaction system of the present invention, the catalyst poison is added in an amount such that the polymerization catalyst in the system loses activity.
In order to further achieve the purpose of the invention and improve the corresponding technical effect, the invention can also adopt the following technical scheme:
the method further comprises the following steps: when the content of unreacted monomer toluene diisocyanate in the mixture of the reaction system is less than 0.5wt%, adding 0.5-2.0wt% of cyclodextrin into the system, stirring for 5-20min, filtering, and adding catalyst poison into the reaction system to stop the self-polymerization reaction.
In some examples, 20 to 80% by weight of a commercially available mixture consisting essentially of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate comprising 65 to 95% by weight of 2, 4-toluene diisocyanate and 5 to 35% by weight of 2, 6-toluene diisocyanate as a starting diisocyanate is contacted with a polymerization catalyst and 20 to 80% by weight of a solvent to conduct a self-polymerization reaction; when the content of unreacted monomeric Toluene Diisocyanate (TDI) in the mixture of the reaction system is less than 0.5wt%, 0.5-2.0wt% (e.g., 0.8wt%, 1.0 wt%, 1.5 wt%) of cyclodextrin is added to the system and stirred for 5-20min (e.g., 8min, 10min, 15min), and after filtration, a catalyst poison is added to the reaction system to terminate the self-polymerization reaction. The amount of the cyclodextrin used is based on the weight (calculated as a theoretical value) of the polyisocyanate composition obtained by the reaction.
The cyclodextrin has the characteristics of hydrophilic outer edge and hydrophobic inner cavity, can selectively identify and combine with a polymerization catalyst in a reaction system to separate the catalyst from the reaction system, thereby greatly reducing the contents of the catalyst and catalyst poison remained in the polyisocyanate composition and achieving the purpose of reducing the color number of the polyisocyanate composition. In some preferred embodiments, the cyclodextrin is selected from one or more of alpha-cyclodextrin, beta-cyclodextrin and gamma-cyclodextrin, particularly preferably beta-cyclodextrin.
In a second aspect of the present invention, there is provided a polyisocyanate composition obtainable by a process as described above. The obtained polyisocyanate composition has the characteristic of low color number, and the color number is less than or equal to 40Hazen, preferably less than or equal to 30Hazen, and more preferably less than or equal to 25 Hazen.
In a third aspect of the present invention, there is provided a polyisocyanate composition obtainable by the process as described above for use as a polyisocyanate component in a polyurethane paint. Preferably, the polyisocyanate composition is applied as a cross-linking agent in a two-component polyurethane paint.
The polyisocyanate compositions prepared according to the process of the present invention are valuable raw materials which 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 polyisocyanate component in two-component polyurethane paints. In this preferred use, the other reaction raw materials which can be mixed and dosed with the polyisocyanate compositions of the invention can be selected from the polyhydroxy polyesters and polyhydroxy polyethers, polyhydroxy polyacrylates and optionally low molecular weight polyols which are well known in polyurethane paint technology.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
in the preparation method, the content of the dihaloimine in the initial diisocyanate is effectively controlled, so that the dosage of the catalyst in the reaction process can be obviously reduced, the obtained polyisocyanate composition has a lower color number (the color number is less than or equal to 40Hazen), and the polyisocyanate composition has better aging resistance when being applied to paint.
Detailed Description
In order that the technical features and contents of the present invention can be understood in detail, preferred embodiments of the present invention will be described in more detail below. While the preferred embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
< sources of raw materials >
(1) Toluene diisocyanate (I) is added to the reaction mixture,
TDI, wanhua chemistry;
the chemical structures of the impurities dichloroimine, dibromoimine and chlorobromoimine appearing in the following examples are as follows:
1) the dichloroimine is represented by formula i or formula ii:
2) the dibromoimine is shown in formula iii or formula iv:
3) the chlorobromoimine is shown in a formula v or a formula vi:
the total content of the dihaloimine in the toluene diisocyanate is the sum of the contents of the dichloroimine, the dibromoimine and the chlorobromoimine.
(2) Butyl acetate, gold Yimeng;
methyl tosylate, sigma aldrich;
mannich bases based on bisphenol a/formalin (Fomalin)/dimethylamine, cf synthesis in US4115373, page six, lines 5-10;
mannich bases based on phenol/formalin (Fomalin)/dimethylamine, TMR-30, winning industry group;
beta-cyclodextrin, sigma aldrich;
polyol (matte varnish), HS-129, SAPICI;
< detection method >
All percentages referred to in the present invention are by weight unless otherwise specified.
The NCO content is measured according to the method of GB/T12009.4-1989.
The invention is based on the method of GB/T3143-1982, and the color number is measured in a 50mm disposable rectangular cuvette by using LICO 400 from HACH Lange.
The method is based on the method of GB/T18583-2008, and the content of residual monomers in a reaction system is determined by gas chromatography.
The invention is based on the method of GB/T1725-1979, and the solids content is determined under the test conditions described for isocyanates.
The kinetic viscosity referred to in the present invention is obtained with a Brookfield DV-I Prime viscometer, using S21 spindle at 25 ℃.
Drying (tack-free) test: GB/T1728;
matte glossiness test: GB/T9754;
ultraviolet aging resistance test: GB/T1865;
and (3) leveling property testing: preparing a paint film on the surface of the tinplate, placing the sample plate under the conditions of constant temperature and constant humidity (30 ℃, 35-40% relative humidity), and observing the time required for the painted surface to reach a uniform, smooth and wrinkle-free (no orange peel or goose skin) state; whether the painted surface is in a uniform, smooth, non-wrinkled (orange peel or goose skin free) state is acceptable or not is related to the user's standard regulation for different products;
and (3) hardness testing: GB/T1730;
and (4) testing the adhesive force grade: GB/T9286.
Example 1
800g of toluene diisocyanate as a 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 a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 25ppm, a dibromoimine content of 2ppm, a chlorobromoimine content of 1ppm, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 28 ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. The trimerization reaction was initiated by dropwise addition of 10g of a solution of the polymerization catalyst in butyl acetate as a Mannich base at a concentration of 20% by weight based on bisphenol A/formalin (Fomalin)/dimethylamine. After 8 hours of reaction, 6g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 7.98 wt%). To safely stop the trimerization reaction, 1.5g (i.e., an amount 1.15 times the molar amount of the polymerization catalyst) of methyl tosylate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was stirred at 60 ℃ for 1 hour. The polyisocyanate composition 1 containing solvent and isocyanurate groups thus obtained had the following characteristic values:
NCO content 7.98 wt%,
the viscosity was 1300mPa s/25 c,
the residual monomer content is 0.23 wt%,
the solid content is 50.8 wt%,
color number 35 Hazen.
Example 2
800g of toluene diisocyanate together with 800g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture; wherein the tolylene diisocyanate had a 2, 4-tolylene diisocyanate content of 80% by weight and a dichloroimine content of 8ppm, a chlorobromoimine content of 1ppm, a dibromoimine content below the detection limit (i.e., the minimum detection concentration by gas chromatography detection), i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 9 ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. The trimerization reaction was initiated by dropwise addition of 8g of a solution of the polymerization catalyst in butyl acetate as a Mannich base at a concentration of 20% by weight based on bisphenol A/formalin (Fomalin)/dimethylamine. After 8 hours of reaction, 4g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 7.99 wt%). To safely stop the trimerization reaction, 1.2g (i.e., 1.15 times the molar amount of the polymerization catalyst) of methyl tosylate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was stirred at 60 ℃ for 1 hour. The polyisocyanate composition 2 containing solvent and isocyanurate groups thus obtained had the following characteristic values:
NCO content 7.99 wt%,
the viscosity is 1200 mPas/25 ℃,
the residual monomer content is 0.15 wt%,
the solid content is 50.7 wt%,
color number 25 Hazen.
Example 3
800g of toluene diisocyanate together with 800g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture; wherein the toluene diisocyanate had a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 5ppm, a dibromoimine content below the detection limit (i.e., the minimum detection concentration detected by gas chromatography), a chlorobromoimine content, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 5ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. 6g of a solution of the polymerization catalyst in butyl acetate as Mannich base with a concentration of 20% by weight of Mannich base based on bisphenol A/formalin (Fomalin)/dimethylamine are added dropwise to initiate the trimerization. After 8 hours of reaction, 3g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 8.00 wt%). To safely stop the trimerization reaction, 0.85g (i.e., 1.15 times the molar amount of the polymerization catalyst) of methyl tosylate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was stirred at 60 ℃ for 1 hour. The polyisocyanate composition 3 containing solvent and isocyanurate groups thus obtained had the following characteristic values:
the NCO content was 8.00 wt%,
viscosity 1150 mPas/25 ℃,
residual monomer content is 0.08 wt%,
the solid content is 50.8 wt%,
color number 19 Hazen.
Example 4
800g of toluene diisocyanate together with 800g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture; wherein the toluene diisocyanate had a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 5ppm, a dibromoimine content below the detection limit (i.e., the minimum detection concentration detected by gas chromatography), a chlorobromoimine content, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 5ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. 6g of a solution of the polymerization catalyst in butyl acetate as Mannich base, 20% by weight based on phenol/formalin (Fomalin)/dimethylamine, were added dropwise to initiate the trimerization. After 8 hours of reaction, 4g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 7.99 wt%). To safely stop the trimerization reaction, 2.4g (i.e., 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 stirred at 60 ℃ for 0.5 hour. The polyisocyanate compositions containing solvent and isocyanurate groups thus obtained had the following characteristic values:
NCO content 7.99 wt%,
viscosity 1150 mPas/25 ℃,
the residual monomer content is 0.09 wt%,
the solid content is 51.0wt percent,
color number 20 Hazen.
Example 5
800g of toluene diisocyanate together with 800g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture; wherein the toluene diisocyanate had a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 5ppm, a dibromoimine content below the detection limit (i.e., the minimum detection concentration detected by gas chromatography), a chlorobromoimine content, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 5ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. 6g of a solution of the polymerization catalyst in butyl acetate as Mannich base, 20% by weight based on phenol/formalin (Fomalin)/dimethylamine, were added dropwise to initiate the trimerization. After 8 hours of reaction, 4g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 8.01 wt%). 16g of beta-cyclodextrin was added to the system and stirred for 10min, and after filtration, 2.4g (i.e., the amount added was 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 stirred at 60 ℃ for 0.5 hour. The polyisocyanate composition 5 containing solvent and isocyanurate groups thus obtained had the following characteristic values:
the NCO content was 8.01% by weight,
the viscosity is 1200 mPas/25 ℃,
residual monomer content is 0.10 wt%,
the solid content is 51.2 wt%,
color number 15 Hazen.
Example 6
800g of toluene diisocyanate together with 800g of butyl acetate were placed in a 2L reaction vessel purged with nitrogen in advance and mixed to obtain a reaction mixture; wherein the toluene diisocyanate had a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 5ppm, a dibromoimine content below the detection limit (i.e., the minimum detection concentration detected by gas chromatography), a chlorobromoimine content, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 5ppm by weight, and the impurity content was controlled by the operation of rectification. The reaction mixture was heated to the desired reaction temperature of 60 ℃. 6g of a solution of the polymerization catalyst in butyl acetate as Mannich base, 20% by weight based on phenol/formalin (Fomalin)/dimethylamine, were added dropwise to initiate the trimerization. After 8 hours of reaction, 4g of the polymerization catalyst solution was added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 7.99 wt%). 8g of beta-cyclodextrin was added to the system and stirred for 10min, and after filtration, 2.4g (i.e., the amount added was 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 stirred at 60 ℃ for 0.5 hour. The polyisocyanate composition 6 containing solvent and isocyanurate groups thus obtained had the following characteristic values:
NCO content 7.99 wt%,
viscosity 1230 mPas/25 ℃,
residual monomer content is 0.10 wt%,
the solid content is 51.3 wt%,
color number 17 Hazen.
Comparative example 1
The preparation was carried out as in example 1, with the following differences: the toluene diisocyanate used had a 2, 4-toluene diisocyanate content of 80% by weight and a dichloroimine content of 55ppm, a dibromoimine content of 3ppm, a chlorobromoimine content of 5ppm, i.e., the total content of dihaloimines as impurities in the starting diisocyanate was 63 ppm by weight, the impurity content being controlled by the operation of rectification.
800g of the above toluene diisocyanate was placed in a 2L reaction vessel purged with nitrogen together with 800g of butyl acetate in advance and mixed to obtain a reaction mixture. The reaction mixture was heated to the desired reaction temperature of 60 ℃. 20g of a solution of the polymerization catalyst in butyl acetate as Mannich base, with a concentration of 20% by weight of Mannich base based on bisphenol A/formalin (Fomalin)/dimethylamine, were added dropwise to initiate the trimerization. After 8 hours of reaction, 10g of the polymerization catalyst solution were added and stirring was continued at a reaction temperature of 60 ℃ for 12 hours until the desired NCO content was reached (NCO content 7.97 wt%). To safely stop the trimerization reaction, 2.8g (i.e., an amount 1.15 times the molar amount of the polymerization catalyst) of methyl tosylate was added to the reaction mixture to terminate the polymerization reaction. Thereafter, the reaction product was stirred at 60 ℃ for 1 hour. The polyisocyanate composition 1' containing solvent and isocyanurate groups thus obtained had the following characteristic values:
NCO content 7.97 wt%,
viscosity 1430 mPas/25 ℃,
the residual monomer content is 0.30 wt%,
the solid content is 51.5 wt%,
color number 65 Hazen.
It can be seen from the above examples 1 to 4 that, when toluene diisocyanate having a dihaloimine content of < 30ppm is used, light-colored polyisocyanates having a colour number of <40Hazen can be obtained; furthermore, as the content of dihaloimine as an impurity in the starting diisocyanate decreases, the amount of catalyst used in the reaction system tends to decrease. It can be seen from examples 5 and 6 that the color number of the resulting polyisocyanate composition can be further reduced after addition of cyclodextrin to the system. While the toluene diisocyanate used in comparative example 1 had a dihaloimine content exceeding 30ppm, the amount of catalyst to be added was significantly increased, and finally, a light-colored polyisocyanate having a color number of <40Hazen could not be obtained.
Example 7 (use example)
Polyisocyanate compositions 2, 3 and 1' obtained in examples 2, 3 and 1, respectively, were mixed with Wanhua
TL75E is mixed according to the mass ratio of 1:2 to prepare a curing agent mixture, the obtained mixture is mixed with a commercially common polyol (matt varnish, HS-129) according to the NCO/OH molar ratio of 1:1 respectively, and a mixed solvent of butyl acetate/dimethylbenzene (equal mass mixture of the curing agent and the butyl acetate/dimethylbenzene) is added for dilution (wherein the content of the curing agent in a solution formed by the curing agent and the butyl acetate/dimethylbenzene is 40wt percent), and finally the paint is prepared. The paints prepared by adding polyisocyanate composition 2 and polyisocyanate composition 3 are denoted as paint 2 and paint 3, and the paint prepared by adding polyisocyanate composition 1 'is denoted as paint 1'. The results of the performance tests on the paint in terms of uv aging resistance, adhesion and the like are shown in table 1.
Table 1 paint performance test results
As can be seen from the performance test results in Table 1, the paint prepared by adding the polyisocyanate composition with low color number has better ultraviolet aging resistance than the paint prepared by adding the polyisocyanate composition with high color number under the condition of ensuring that other performances are all excellent.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (21)
1. A process for preparing polyisocyanate compositions based on the self-polymerization of toluene diisocyanate, characterized in that it comprises the following steps:
the polyisocyanate composition is obtained by subjecting component A) to self-polymerization in the presence of the following components B) and C), and then terminating the reaction by adding a catalyst poison to the reaction system; wherein the content of the first and second substances,
A) comprising a mixture of 2, 4-toluene diisocyanate and 2, 6-toluene diisocyanate,
B) a solvent, a water-soluble organic solvent,
C) a polymerization catalyst;
the content of dihaloimine in component A) is less than 30ppm by weight;
the dihaloimine is of the formula
Or formula
One or more of the compounds represented:
2. The process of claim 1, wherein the polyisocyanate composition has a color number of 40Hazen or less.
3. The process according to claim 1, characterized in that the content of dihaloimine in component A) is less than 10 ppm by weight.
4. The process according to claim 3, characterized in that the content of dihaloimine in component A) is less than 1ppm by weight.
5. The process according to any one of claims 1 to 4, wherein the component A) is used in an amount of 20 to 80% by weight and the component B) is used in an amount of 20 to 80% by weight, based on the sum of the amounts of the component A) and the component B) in the reaction system.
6. The process of claim 5, wherein said 2, 4-toluene diisocyanate is present in an amount of 65 to 95 wt.% and said 2, 6-toluene diisocyanate is present in an amount of 5 to 35 wt.%, based on 100 wt.% of the total weight of component A).
7. The method of claim 1, wherein the polymerization catalyst is a mannich base catalyst.
8. The method of claim 7 wherein the Mannich base catalyst is prepared by reacting phenol, p-isononyl phenol, or bisphenol A with dimethylamine and formaldehyde.
9. The method of claim 8, wherein the Mannich base catalyst is prepared by reacting phenol or bisphenol A with dimethylamine and formaldehyde.
10. The process according to any of claims 1 to 4, 7 to 9, characterized in that the polymerization catalyst is added in an amount of 0.05 to 0.8wt% of the amount of component a).
11. The process according to claim 10, wherein the polymerization catalyst is added in an amount of 0.1 to 0.4wt% based on the amount of component A).
12. The method of claim 1, wherein the solvent is selected from one or more of toluene, xylene, cyclohexane, chlorobenzene, butyl acetate, ethyl glycol acetate, amyl acetate, hexyl acetate, methoxypropyl acetate, tetrahydrofuran, dioxane, acetone, N-methylpyrrolidone, methyl ethyl ketone, mineral spirits, highly substituted aromatics, phthalates, benzoates, sulfonates, or phosphates; wherein the highly substituted aromatic compound is selected from one or more of heavy benzene, tetralin, and decalin.
13. The method according to any one of claims 1 to 4, 7 to 9 and 11 to 12, wherein the content of unreacted monomeric toluene diisocyanate in the reaction system is less than 0.5 wt%; and/or
The reaction temperature of the self-polymerization reaction is 40-120 ℃.
14. The method of claim 13, wherein the self-polymerization reaction is carried out at a reaction temperature of 50-70 ℃.
15. The method of claim 1, further comprising: when the content of unreacted monomer toluene diisocyanate in the reaction system is less than 0.5wt%, adding 0.5-2.0wt% of cyclodextrin into the system, stirring for 5-20min, filtering, and adding the catalyst poison into the reaction system to stop the self-polymerization reaction.
16. The method of claim 15, wherein the cyclodextrin is selected from one or more of the group consisting of alpha-cyclodextrin, beta-cyclodextrin, and gamma-cyclodextrin.
17. The process of any one of claims 1-4, 7-9, 11-12, 15-16, wherein the catalyst poison is selected from one or more of a protic acid, an acylating agent, and an alkylating agent.
18. The method of claim 17, wherein the catalyst poison is selected from dibutyl phosphate and/or methyl tosylate.
19. A polyisocyanate composition obtainable by the process of any one of claims 1 to 18 having a colour number of 40 Hazen.
20. A polyisocyanate composition obtainable by a process according to any one of claims 1 to 18 for use as a polyisocyanate component in polyurethane paints.
21. Use according to claim 20, of the polyisocyanate composition as a cross-linking agent in a two-component polyurethane paint.
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| EP0816333A1 (en) * | 1996-06-26 | 1998-01-07 | Basf Aktiengesellschaft | Process for the preparation of solutions containing one or more isocyanates which do not contain significant proportions of colour-forming components as well as the use of the prepared isocyanates |
| DE19928741A1 (en) * | 1999-06-23 | 2000-12-28 | Basf Ag | Preparation of isocyanates, useful for production of urethane compounds, comprises reaction of amine with phosgene having specified bromine and/or iodine content |
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| US7863440B2 (en) * | 2006-12-28 | 2011-01-04 | Great Eastern Resins Industrial Co., Ltd. | Macrocyclic carbodiimides (MC-CDI) and their derivatives, syntheses and applications of the same |
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