CN110804146B - Storage-stable closed isocyanate composition and preparation method and application thereof - Google Patents
Storage-stable closed isocyanate composition and preparation method and application thereof Download PDFInfo
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- CN110804146B CN110804146B CN201911244172.2A CN201911244172A CN110804146B CN 110804146 B CN110804146 B CN 110804146B CN 201911244172 A CN201911244172 A CN 201911244172A CN 110804146 B CN110804146 B CN 110804146B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/2805—Compounds having only one group containing active hydrogen
- C08G18/285—Nitrogen containing compounds
- C08G18/286—Oximes
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/80—Masked polyisocyanates
- C08G18/8061—Masked polyisocyanates masked with compounds having only one group containing active hydrogen
- C08G18/807—Masked polyisocyanates masked with compounds having only one group containing active hydrogen with nitrogen containing compounds
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- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
- C09D175/04—Polyurethanes
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
- C09J175/04—Polyurethanes
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Abstract
The invention belongs to the technical field of isocyanate preparation, and particularly relates to a storage-stable closed isocyanate composition, a preparation method and an application thereof, wherein the preparation method comprises the following steps: (1) mixing polyisocyanate with an alkylating agent and heating to obtain alkylated polyisocyanate; (2) contacting the alkylated polyisocyanate with a blocking agent for reaction to obtain a blocked isocyanate composition; the blocking agent comprises at least one oxime compound. The preparation method can effectively improve the storage stability of the isocyanate product sealed by the oxime compound and ensure the low chroma of the product.
Description
Technical Field
The invention belongs to the technical field of isocyanate preparation, and particularly relates to a storage-stable closed isocyanate composition, and a preparation method and application thereof.
Background
Blocked isocyanates are formed by reacting isocyanates with blocking agents which form relatively weak chemical bonds with NCO and which can be deblocked under certain conditions to release free NCO. Blocked isocyanates are therefore widely used in one-component polyurethane coatings and adhesives, in particular in automotive coatings and coil coatings. There are many types of blocking agents that can be used for isocyanate groups, and currently, phenolic compounds, alcohol compounds, oxime compounds, β -dicarbonyl compounds, pyrazole compounds, amide compounds, and the like are commonly used.
The oxime compounds have a low deblocking temperature and are widely used as isocyanate blocking agents. However, blocked isocyanates blocked by oximes are prone to yellowing during storage, which affects the application of the products in clear paints and light-colored paints. For example, patent documents US5504178, US 561339, EP0829500 all disclose the use of substances with a partial hydrazinoacyl structure as stabilizers to improve the thermal yellowing problem that occurs during the application of the product. By utilizing the patent technology, although the color stability of the closed isocyanate product in the storage process can be improved to a certain extent, the problems that part of hydrazine acyl compounds are low in solubility and large in molecular weight, and a plurality of active hydrogens capable of reacting with isocyanate exist, so that the viscosity of the product is increased and the transparency is reduced easily occur.
Disclosure of Invention
The invention aims to provide a storage-stable blocked isocyanate composition and a preparation method thereof aiming at the problem of color instability of the existing blocked isocyanate in the storage process.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
in one aspect, there is provided a process for the preparation of a storage stable blocked isocyanate composition comprising the steps of:
(1) mixing polyisocyanate with an alkylating agent and heating to obtain alkylated polyisocyanate;
(2) contacting the alkylated polyisocyanate obtained in the step (1) with a blocking agent for reaction to obtain a blocked isocyanate composition;
the blocking agent comprises at least one oxime compound.
In order to improve the storage stability of polyisocyanate products, phenolic antioxidants are generally included or added to the products. Generally, the color stability of the product can be improved by adding hindered phenols into the isocyanate composition system. However, the applicant has found that in the course of research, when an oxime compound is used as a blocking agent to prepare a blocked isocyanate composition, the color stability of the blocked isocyanate composition is rather deteriorated due to the presence of a certain amount of a hindered phenol antioxidant. The applicant has found that the color storage stability of the blocked isocyanate composition obtained by treating the commercially available polyisocyanate with the alkylating agent and then reacting the treated polyisocyanate with the oxime blocking agent is obviously improved.
The blocked isocyanate composition has a dynamic equilibrium of blocking and unblocking of the blocking agent and NCO in the isocyanate during storage. Presumably, the yellowing mechanism of the product is that free oxime compounds are easy to form a highly conjugated structure and a chromogen group such as nitroso with certain content of hindered phenolic substances in the product. After mixing with an alkylating agent and heat treatment, the phenolic hydroxyl group of the hindered phenol substance contained in the polyisocyanate is alkylated to block the formation of a coloring group such as a highly conjugated structure or a nitroso group.
According to the production method provided by the present invention, it is preferable that the content of the phenolic compound in the blocked isocyanate composition is 50ppm or less (for example, the content of the phenolic compound is 10ppm, 20ppm, 30ppm, 40ppm, 45 ppm). In the closed isocyanate composition, the content of the phenolic compound is controlled within a certain range, so that the color number stability of the blocked isocyanate composition in the storage process can be ensured. For example, the difference in color numbers of the products before and after storage is small. The "color number difference" as used herein refers to the absolute value of the difference between the color number of the blocked isocyanate composition after storage for a period of time and the color number of the blocked isocyanate composition before storage.
In some examples, the phenolic compound is a hindered phenolic antioxidant, preferably selected from the group consisting of 2, 6-di-tert-butyl-4-methylphenol (antioxidant BHT), N-octadecyl- β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate (antioxidant 1076), pentaerythritol tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] (antioxidant 1010), N '-bis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine (antioxidant 1024), 2-oxamido-bis- [ ethyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) ] propionate (antioxidant 697), N' -hexylene-1, 6-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ] (antioxidant 1098, also known as N, N' -1, 6-hexylene-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ]), 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid (antioxidant 3114), diethylene glycol bis [ beta- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ] (antioxidant 245), isooctyl 3, 5-di-tert-butyl-4-hydroxyphenylpropionate (antioxidant 1135), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene (antioxidant 330) and 1, one or more of 3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) -1,3, 5-triazine-2, 4,6- (1H,3H,5H) -trione (antioxidant 1790).
According to the preparation method provided by the invention, in a preferred embodiment, the alkylating reagent is selected from one or more of methyl p-toluenesulfonate, ethyl p-toluenesulfonate, dimethyl carbonate, diethyl carbonate and dimethyl sulfate.
According to the preparation method provided by the invention, in a preferred embodiment, the oxime compound is selected from one or more of butanone oxime, acetone oxime, formaldehyde oxime, acetaldehyde oxime and cyclohexanone oxime, and more preferably butanone oxime.
In some examples, the oxime compound is present in a molar amount of 80 mol% or more (e.g., 85 mol%, 88 mol%, 90 mol%, 95 mol%, 100 mol%) of the total molar amount of the blocking agent.
According to the preparation method provided by the invention, in some examples, the blocking agent further comprises one or more of an alcohol compound, a lactam compound, a pyrazole compound and a beta-dicarbonyl compound; preferably, the blocking agent further comprises epsilon-caprolactam and/or 3, 5-dimethylpyrazole.
In some examples, the alcohol compound may be selected from one or more of methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol; the lactam compound can be selected from one or more of epsilon-caprolactam, delta-valerolactam and gamma-butyrolactam; the pyrazole compound can be selected from one or more of pyrazole, 3-methylpyrazole and 3, 5-dimethylpyrazole; the beta-dicarbonyl compound may be selected from one or more of dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, and diisobutyl malonate.
In the present invention, the polyisocyanate may be prepared by using diisocyanate as a reactive monomer. In some examples, the polyisocyanate has an NCO functionality of 2.5 or more, for example, an NCO functionality of 3, 4, 5; the NCO content is from 5 to 40% by weight, for example 8%, 10%, 12%, 15%, 20%, 25%, 30%, 35%.
In some examples, examples of isocyanate raw materials for preparing the polyisocyanate include, but are not limited to, aliphatic isocyanates and/or cycloaliphatic isocyanates. A suitable isocyanate starting material is a diisocyanate. In some preferred embodiments, the polyisocyanate is prepared by reacting a diisocyanate as a monomer; the diisocyanate is preferably an aliphatic diisocyanate having 4 to 20 carbon atoms and/or a cycloaliphatic diisocyanate having 4 to 20 carbon atoms.
In some examples, the diisocyanate is selected from the group consisting of tetramethylene diisocyanate, Hexamethylene Diisocyanate (HDI), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate, 2,4 '-or 4, 4' -dicyclohexyl diisocyanateMethane diisocyanate (H)12MDI having two isomers, typically a mixture, of 2,4 and 4,4 and one or two or more of isophorone diisocyanate (IPDI), preferably selected from Hexamethylene Diisocyanate (HDI), 2,4 'or 4, 4' -dicyclohexylmethane diisocyanate (H)12MDI) and isophorone diisocyanate (IPDI).
In some examples, the low-architecture groups contained in the polyisocyanate are selected from one or more of isocyanurate groups, uretdione groups, biuret groups, urethane groups, allophanate groups, iminooxadiazinedione groups and carbodiimide groups.
In some preferred embodiments, the polyisocyanate is selected from isocyanurates and/or biurets.
According to the preparation method provided by the invention, preferably, in the step (1), the alkylating agent is used in an amount of 0.01 wt% to 0.1 wt% of the mass of the polyisocyanate, for example, 0.015 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.08 wt%, 0.09 wt%.
Preferably, in step (2), the ratio of the amount of NCO material to the amount of blocking agent material in the polyisocyanate is from 0.9 to 1.1:1 (e.g., 0.95:1, 0.97:1, 0.99:1, 1:1, 1.05: 1). For example, n (NCO group in polyisocyanate): n (blocking agent) is 0.95:1, 0.97:1, 0.99:1, 1:1 or 1.05: 1.
According to the preparation method provided by the invention, in some examples, the process conditions of the heating treatment in the step (1) include: the reaction temperature is 30-150 deg.C (e.g., 40 deg.C, 50 deg.C, 80 deg.C, 100 deg.C, 120 deg.C), and the reaction time is 1-5h (1.5h, 2h, 3h, 4.5 h).
In some examples, the process conditions for the reaction of step (2) include: the reaction temperature is 30 to 120 deg.C (e.g., 40 deg.C, 60 deg.C, 80 deg.C, 100 deg.C, 110 deg.C). The reaction time in this step is not particularly limited, and for example, the reaction is carried out under stirring until the NCO characteristic absorption peak is not detected by infrared spectroscopy, to obtain a blocked isocyanate composition.
According to the production method provided by the present invention, in some examples, a solvent which is inert to the reaction of NCO groups is added to the reaction system in the step (2).
In some examples, the solvent is selected from one or more of ethyl acetate, butyl acetate, 1-methoxy-2-propyl acetate, n-butyl 3-methoxyacetate, acetone, butanone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, and S100 mineral spirits, preferably from one or more of S100 mineral spirits, n-butyl acetate, and 1-methoxy-2-propyl acetate. The amount of the solvent to be added here is, for example, such that the polyisocyanate and the blocking agent in the reaction system are completely dissolved.
According to the preparation method provided by the invention, in order to further reduce the chroma of the blocked polyisocyanate composition product, inert gas can be used for protection in the reaction process. The inert gas includes but is not limited to N2、CO2One or more of CO, He and Ar, preferably N2。
According to the preparation method provided by the invention, in some examples, a hindered amine stabilizer and/or a phosphite stabilizer can be added. The hindered amine stabilizer and/or phosphite ester stabilizer can be added in the reaction process or after the reaction is finished.
In another aspect, there is provided a blocked isocyanate composition obtained by the production method as described above, wherein the content of the phenolic compound in the blocked isocyanate composition is 50ppm or less.
In a further aspect, the blocked isocyanate composition prepared by the preparation method or the application of the blocked isocyanate composition in one-component polyurethane coating or adhesive is provided. Preferably, the one-component polyurethane coating is an automobile coating or a coil coating.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the invention firstly mixes polyisocyanate as raw material with alkylating agent and heats them, which can alkylate phenolic hydroxyl of phenolic compound in them, thus blocking the formation of certain amount of chromogen group such as high conjugated structure and nitroso; therefore, the present invention strictly controls the content of the phenolic compound (50 ppm or less) in the blocked isocyanate composition obtained. The resulting blocked isocyanate composition has low color and a stable color number (e.g., a color number difference of 10Hazen or less) after storage for a long period of time (e.g., 3 months at 50 ℃).
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.
The main raw material sources in the first, various examples and comparative examples are as follows:
polyisocyanate:
selecting commercial products Desmodur N3300 (Colesine HDI tripolymer, NCO content is 22 wt%) and Desmodur N100 (Colesine HDI biuret, NCO content is 22 wt%);
methyl p-toluenesulfonate, available from carbofuran;
dimethyl carbonate, purchased from Shidazhenhua;
butanone oxime, available from the chemical industry in Hubei Xiangliang;
acetoxime, available from the Hubei Xiangliang chemical industry;
butyl acetate, available from au-yimeng;
s100 solvent oil, purchased from exxonmobil chemical;
epsilon-caprolactam, available from Shanxi chemical industry.
Second, test methods related to the respective examples and comparative examples:
1. the color number of the blocked isocyanate composition was measured using a BYK colorimeter.
2. The content of the phenolic compound in the closed isocyanate composition is tested by adopting a high performance liquid chromatography external standard quantitative method, and the specific test conditions are as follows:
shimadzu Nexera, chromatographic column ODS-SP (Inertsil) column, PDA detector,
the detection wavelength is 220nm, the mobile phase is acetonitrile/water, the flow rate is 1.0mL/min, and the elution gradient is shown in the following table 1:
| time/min | Ultra pure water/%) | Acetonitrile/%) |
| 0.01 | 10 | 90 |
| 5 | 10 | 90 |
| 6 | 0 | 100 |
| 25 | 0 | 100 |
| 26 | 10 | 90 |
| 32 | 10 | 90 |
Example 1
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.15g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 11ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 2
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.20g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 9ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 3
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.02g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 43ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 4
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.10g of dimethyl carbonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 83g of butanone oxime and 10g of 3, 5-dimethylpyrazole into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 25ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Comparative example 1
(1) Adding 200g of polyisocyanate Desmodur N3300 and 97.5g of Mofu S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃, treating for 2 hours, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 73ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Comparative example 2
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.01g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 78g of acetone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peak can not be detected by infrared spectrum to obtain a closed isocyanate composition product; the product has a chroma of 18Hazen by testing; the product was tested for a phenolic compound content of 70ppm by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 5
(1) Adding 200g of polyisocyanate Desmodur N100, 0.15g of methyl p-toluenesulfonate and 97.5g of butyl acetate into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 13Hazen by testing; the product was tested for 16ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 6
(1) Adding 200g of polyisocyanate Desmodur N100, 0.10g of methyl p-toluenesulfonate and 97.5g of butyl acetate into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 83g of butanone oxime and 11.9g of epsilon-caprolactam into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, thereby obtaining a closed isocyanate composition product; the product has the chroma of 13Hazen by testing; the product was tested for 27ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 7
(1) Adding 200g of polyisocyanate Desmodur N100, 0.20g of dimethyl carbonate and 97.5g of butyl acetate into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, thereby obtaining a closed isocyanate composition product; the product has the chroma of 13Hazen by testing; the product was tested for 5ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Comparative example 3
(1) Adding 200g of polyisocyanate Desmodur N100, 0.01g of dimethyl carbonate and 97.5g of butyl acetate into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 13Hazen by testing; the product was tested for 92ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 8
(1) Adding 200g of polyisocyanate Desmodur N100, 0.15g of methyl p-toluenesulfonate and 97.5g of butyl acetate into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 77.2g of acetone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, stirring and reacting until NCO characteristic absorption peak can not be detected by infrared spectrum, and obtaining a closed isocyanate composition product; the product has the chroma of 13Hazen by testing; the product was tested for 16ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 9
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.15g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) adding 86.7g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until an NCO characteristic absorption peak cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 11ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Example 10
(1) Adding 200g of polyisocyanate Desmodur N3300, 0.15g of methyl p-toluenesulfonate and 97.5g of Mobil S100 solvent oil into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃ for treatment for 2 hours to obtain alkylated polyisocyanate, and then cooling to 60 ℃;
(2) then adding 100.4g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until an NCO characteristic absorption peak cannot be detected by infrared spectrum, thus obtaining a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for 11ppm phenolic compound by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
Comparative example 4
(1) Adding 200g of polyisocyanate Desmodur N3300, 97.5g of Mobil S100 solvent oil and 0.3g of BHT (2, 6-di-tert-butyl-4-methylphenol) into a four-neck flask, stirring uniformly under the protection of nitrogen, heating to 90 ℃, treating for 2 hours, and then cooling to 60 ℃;
(2) adding 92g of butanone oxime into a four-neck flask, controlling the reaction temperature to be 60-70 ℃, and stirring for reaction until NCO characteristic absorption peaks cannot be detected by infrared spectroscopy, so as to obtain a closed isocyanate composition product; the product has the chroma of 14Hazen by testing; the product was tested for a phenolic compound content of 135ppm by HPLC analysis.
The resulting blocked isocyanate composition product was stored at 50 ℃ for 3 months, and the hue value of the product was measured as shown in Table 2.
TABLE 2 storage stability of blocked isocyanate compositions obtained in examples and comparative examples
As can be seen from table 2: after 0.01-0.1% of alkylating agent is added into commercially available polyisocyanate for heating treatment, oxime compounds are used for blocking, phenolic substances in the prepared blocked isocyanate product are obviously reduced, and the color stability of the blocked isocyanate product in the storage process is good. Therefore, in the process of preparing the blocked isocyanate composition by using the oxime compound-containing blocking agent, the content of the phenolic compound is controlled within a certain range (less than or equal to 50ppm), and the color storage stability of the product can be effectively improved. While comparative example 1 did not undergo alkylation treatment and comparative examples 2-3 did not have a high degree of alkylation treatment, and the resulting blocked isocyanate product had poor color stability during storage. In addition, in comparative example 4, a hindered phenolic compound which is commonly used to stabilize the color number of isocyanate was added, rather, the color instability of the resulting isocyanate composition during storage was exacerbated.
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 the preparation of a storage stable blocked isocyanate composition comprising the steps of:
(1) mixing polyisocyanate with an alkylating agent and heating to obtain alkylated polyisocyanate; the alkylating reagent is selected from one or more of methyl p-toluenesulfonate, ethyl p-toluenesulfonate, dimethyl carbonate, diethyl carbonate and dimethyl sulfate; the amount of the alkylating agent is 0.01-0.1 wt% of the mass of the polyisocyanate;
(2) contacting the alkylated polyisocyanate obtained in the step (1) with a blocking agent for reaction to obtain a blocked isocyanate composition;
the blocking agent comprises at least one oxime compound;
the content of the phenolic compound in the blocked isocyanate composition is less than or equal to 50 ppm.
2. The method according to claim 1, wherein the oxime compound is one or more selected from the group consisting of butanone oxime, acetone oxime, formaldehyde oxime, acetaldehyde oxime and cyclohexanone oxime.
3. The process according to claim 2, wherein the oxime compound is butanone oxime.
4. The process according to any one of claims 1 to 3, wherein the oxime compound is contained in an amount of 80 mol% or more based on the total molar amount of the blocking agent.
5. The method according to any one of claims 1 to 3, wherein the blocking agent further comprises one or more of an alcohol compound, a lactam compound, a pyrazole compound and a β -dicarbonyl compound.
6. The method of claim 5, wherein the blocking agent further comprises epsilon-caprolactam and/or 3, 5-dimethylpyrazole.
7. The process according to any one of claims 1 to 3 and 6, wherein the polyisocyanate has an NCO functionality of 2.5 or more and an NCO content of 5 to 40% by weight.
8. The method according to claim 7, wherein the polyisocyanate is prepared by reacting a diisocyanate as a monomer.
9. The method according to claim 8, wherein the diisocyanate is an aliphatic diisocyanate having 4 to 20 carbon atoms and/or a cycloaliphatic diisocyanate having 4 to 20 carbon atoms.
10. The method according to claim 8, wherein the low-aggregation group contained in the polyisocyanate is one or more selected from the group consisting of an isocyanurate group, a uretdione group, a biuret group, a urethane group, an allophanate group, an iminooxadiazinedione group and a carbodiimide group.
11. The process according to any one of claims 1 to 3, 6 and 8 to 10, wherein in step (2), the ratio of the amount of NCO in the polyisocyanate to the amount of blocking agent is from 0.9 to 1.1: 1.
12. the production method according to any one of claims 1 to 3, 6 and 8 to 10,
the process conditions of the heat treatment in the step (1) comprise: the reaction temperature is 30-150 ℃, and the reaction time is 1-5 h;
the reaction process conditions in the step (2) comprise: the reaction temperature is 30-120 ℃.
13. The production method according to any one of claims 1 to 3, 6 and 8 to 10, wherein a solvent which is inert to NCO groups is added to the reaction system in the step (2).
14. The method of claim 13, wherein the solvent is selected from one or more of ethyl acetate, butyl acetate, 1-methoxy-2-propyl acetate, n-butyl 3-methoxyacetate, acetone, butanone, 4-methyl-2-pentanone, cyclohexanone, toluene, xylene, and S100 mineral spirits.
15. The method of claim 14, wherein the solvent is selected from one or more of S100 mineral spirits, n-butyl acetate, and 1-methoxy-2-propyl acetate.
16. The method according to claim 13, wherein a hindered amine stabilizer and/or a phosphite stabilizer is added during the reaction or after the reaction is completed.
17. The method according to any one of claims 1 to 3, 6, 8 to 10, and 14 to 16, wherein the phenolic compound is a hindered phenolic antioxidant.
18. The process according to claim 17, wherein the phenolic compound is selected from the group consisting of 2, 6-di-tert-butyl-4-methylphenol, N-octadecyl- β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythritol-tetrakis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], N '-bis [ β - (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, 2-oxamido-bis- [ ethyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) ] propionate, N' -hexylene-1, 6-bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], (ii) phenol, 1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid, diethylene glycol bis [ beta- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ], isooctyl 3, 5-di-tert-butyl-4-hydroxyphenylpropionate, 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, and 1,3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) -1,3, 5-triazine-2, 4,6- (1H,3H,5H) -trione.
19. A blocked isocyanate composition according to any one of claims 1 to 18, wherein the blocked isocyanate composition contains a phenolic compound in an amount of 50ppm or less.
20. Use of the blocked isocyanate composition obtained by the process according to any one of claims 1 to 18 in one-component polyurethane coatings or adhesives.
21. The use according to claim 20, wherein the one-component polyurethane coating is an automotive coating or a coil coating.
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