WO2024120052A1

WO2024120052A1 - Blocked polyisocyanate composition, and preparation method therefor and use thereof

Info

Publication number: WO2024120052A1
Application number: PCT/CN2023/127470
Authority: WO
Inventors: 林成栋; 刘伟; 王丹; 张现锋; 辛光震; 俞涛; 石滨; 尚永华; 黎源
Original assignee: 万华化学集团股份有限公司
Priority date: 2022-12-09
Filing date: 2023-10-30
Publication date: 2024-06-13
Also published as: CN118165228A

Abstract

Disclosed herein are a blocked polyisocyanate composition, and a preparation method therefor and the use thereof. The composition comprises the following two structures, wherein the amount of formula (I) is 0.05-1.5 wt%, preferably 0.1-1 wt%, based on formula (II), and R is formula (A). The blocked polyisocyanate composition has a viscosity of 1000-3000 cP (25ºC), and has good adhesion when used in the field of single-component coatings.

Description

A blocked polyisocyanate composition and its preparation method and use

Technical Field

The embodiments of the present application relate to the technical field of polyisocyanates, for example, a blocked polyisocyanate composition and a preparation method and application thereof.

Background technique

Blocked isocyanate is generated by the reaction of isocyanate and blocking agent. The chemical bond formed by blocking agent and NCO is relatively weak, and free NCO can be released under certain conditions. Blocked isocyanate is widely used in adhesives, coatings, elastomers and sealants. Commonly used isocyanate blocking agents include caprolactam, phenols, acetylacetone, sodium bisulfate, butanone oxime, etc. Among them, caprolactam is a common raw material for isocyanate blocking agents because its raw materials are cheap and easy to obtain. In addition, caprolactam blocked isocyanate is also widely used as a curing agent for powder coatings.

US4302351 records that IPDI forms IPDI trimer under the action of trimerization catalyst, and the monomer is removed by thin film evaporation at 150-160°C to obtain IPDI trimer. Caprolactam is added at 150°C and reacted for 2h to obtain closed IPDI trimer.

CN114276520A introduces a method for preparing a blocked isocyanate composition, which obtains a blocked IPDI trimer with color number thermal stability by adjusting the content of n-valeramide and caprolactam blocking compounds.

However, the blocked polyisocyanates described in the above related art have the problem of poor product adhesion during downstream use.

Summary of the invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

In order to solve the above technical problems, the present invention provides a blocked polyisocyanate composition and a preparation method and use thereof. The blocked polyisocyanate composition has a viscosity of 1000 to 3000 cP (25°C). It also has good adhesion when used in one-component coatings.

The technical solutions adopted in the embodiments of this application are as follows:

A blocked polyisocyanate composition comprises the following two structures, wherein the content of formula I is 0.05-1.5wt%, preferably 0.1-1wt%, based on formula II,

R is

In the present application, when the blocked polyisocyanate composition of formula I structure/formula II is controlled at 0.05wt%-1.5wt%, such as 0.1wt%, 0.5wt%, 1wt%, etc., the polyisocyanate composition has a lower viscosity at 25°C. At the same time, due to the presence of hydrogen bonds in the formula I structure, the adhesion of the paint film is further improved, and the adhesion of the product during the application of the single-component coating is significantly improved.

In this embodiment, the blocked polyisocyanate composition is diluted by an aromatic hydrocarbon solvent.

The blocked polyisocyanate composition described in the present application has a viscosity of 1000-3000 mPa·s at 25° C., preferably 1500-2500 mPa·s.

In the blocked polyisocyanate composition described in the present application, the content of free caprolactam accounts for 0.1%-2% of the total amount of the blocked polyisocyanate composition, and more preferably 0.5%-1.5%.

A method for preparing the blocked polyisocyanate composition comprises the following steps:

(1) in the presence of a trimerization catalyst, isophorone diisocyanate undergoes a polymerization reaction, wherein the polymerization reaction is terminated when the NCO content in the system is 20% to 26%;

(2) removing isophorone diisocyanate monomer from the product of step (1) to reduce the content of unreacted isophorone diisocyanate monomer to less than 1 wt %, preferably less than 0.5 wt %, and more preferably less than 0.3 wt %;

(3) adding caprolactam dropwise to the product of step (2) to carry out reaction until the free NCO in the system is less than 0.2 wt %, adding water to continue the reaction to obtain a blocked polyisocyanate composition.

As a preferred solution, in a specific polymerization reaction process, isophorone diisocyanate (abbreviated as IPDI) can be first added into a round-bottom flask equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen inlet, and then the system is heated to 70-90° C., and then 5-100 ppm of a methanol solution of tetrabutylammonium hydroxide (30%) is added dropwise thereto to carry out the polymerization reaction. As is well known to those skilled in the art, the specific operation sequence of the polymerization reaction is common knowledge in the art and will not be described in detail herein.

In some specific embodiments, when the above polymerization reaction is carried out to the NCO value in the system of 20%-26%, a terminator can be used to terminate the reaction, and the amount of the terminator is 0.8-1 times the molar amount of the catalyst. The terminator is an acid compound, preferably at least one of dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, 2-ethylhexyl phosphate, phosphoric acid, hydrochloric acid, benzenesulfonic acid, p-toluenesulfonic acid, benzoyl chloride, and acetyl chloride. In some other embodiments, the above polymerization reaction can also be stopped for a period of time by heating. In the specific implementation process, the system can be heated to 100-120°C and left for 30-60 minutes.

In some preferred embodiments, in step (2) described in the present application, thin film evaporation can be used to remove unreacted isophorone diisocyanate monomers in the polymerization reaction system; in some specific embodiments, a thin film evaporator can be used to remove unreacted monomers in the reaction system at 140-170°C (e.g., 150°C, 160°C) and 10-200Pa (e.g., 50Pa, 100Pa, 150Pa). The unreacted isophorone diisocyanate monomer in the product of step (1) is evaporated and removed by a film evaporator at a temperature of 170° C. and an absolute pressure of 100 Pa.

In some specific embodiments, preferably, the trimerization catalyst is selected from tetraalkylammonium hydroxides and organic acid salts thereof, more preferably, the amount of the trimerization catalyst is 5-100ppm, preferably 10-90ppm, based on the mass of the diisocyanate monomer; the above-mentioned tetraalkylammonium hydroxides are, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc., and the organic acid salts of tetraalkylammonium are, for example, acetates, butyrates, decanoates, etc. of tetramethylammonium and tetraethylammonium.

The trimerization catalyst used in the present application can be used without solvent or dissolved in solvent. The solvent mainly includes a linear or branched monohydric alcohol or dihydric alcohol with 1-20 carbon atoms. Examples of solvents for dissolving the catalyst include methanol, ethanol, n-butanol, isobutanol, tert-butanol, n-octanol, isooctyl alcohol, and heptanol, preferably methanol, ethanol, n-butanol, and heptanol.

When the trimerization catalyst of the present application is used in the form of a solution, the concentration of the trimerization catalyst is 5-50%, preferably 10-30%, based on the catalyst solution.

As a preferred solution, in the step (3), the product of step (2) is heated to 80-120° C., caprolactam is added dropwise thereto, and the free NCO content is monitored during the reaction. When the free NCO content is lower than 0.2wt%, water is added thereto, and the temperature is raised to 120-140° C., and the reaction is continued for 60-120 min to obtain a blocked polyisocyanate composition.

In step (3) described in the present application, the material feed ratio is calculated by molar amount, caprolactam/NCO=0.95-1.1:1, preferably 1-1.05:1.

In step (3) described in the present application, it is preferred that the mass of water added is 5-120 ppm relative to the total amount of caprolactam and the product of step (2).

The blocked polyisocyanate composition described in the present application is mainly used in one-component polyurethane coatings or adhesives, and is preferably used in coil and can coatings.

The above-mentioned technical scheme has the following technical effects: the blocked isocyanate composition provided in the embodiment of the present application controls the content of formula I relative to formula II, so that the blocked polyisocyanate composition has a viscosity of 1000 to 3000 cP (25°C) and improves the adhesion during product application.

Still other aspects will be apparent upon reading and understanding the detailed description.

Detailed ways

The method provided in the present application will be further illustrated by the following examples, but the present application is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present application.

Main raw material sources:

Polyisocyanate, Wannate IPDI, Wanhua Chemical;

No. 100 aromatic solvent oil, Jiangsu Hualun Chemical Co., Ltd.;

Caprolactam, Sinopec Shijiazhuang Refining;

Tetrabutylammonium hydroxide, Sigma-Aldrich, 95%

Dibutyl phosphate, Sigma-Aldrich, 97%;

Di(2-ethylhexyl) phosphate, Sigma-Aldrich, 96%;

Diethyl phosphate, Sigma-Aldrich, 98%.

The following examples are tested using the following methods:

(1) Test method for the content of monomers in polyisocyanate compositions: GB/T18446-2009;

(2) Viscosity test: Brookfield CAP2000+ rotational viscometer, test temperature 25°C, speed set to 50 rpm;

(3) Determination of NCO content: The isocyanate groups in the test sample were neutralized with an excess of 2 mol/L di-n-butylamine and then back-titrated with 1 mol/L hydrochloric acid.

(4) The content of the structure of formula 1 is determined by liquid chromatography-mass spectrometry, and the determination method is as follows:

①LC (liquid chromatograph): device: Agilent 1100 series; chromatographic column: Phenomenex, Kinetex 2.6μXB-C18 100A, (inner diameter 2.1mm, length 50mm); column temperature: 40℃; detection: 205nm; flow rate: 0.3mL/min; mobile phase: gradient of A and B liquids, where A liquid is water (0.05% formic acid) and B liquid is acetonitrile (0.05% formic acid); injection volume: 1μL;

②MS (mass spectrometer): Device: Thermo Electron, LCQ; Ionization: ESI; Mode: positive ion (Positive); Scanning range: m/z100～2000.

The target solution was scanned, and the quantitative ratio of the compounds represented by formula II and formula I was taken as the mass ratio of the two compounds; the retention time of the structure represented by formula I was 12.1 min, and it was detected by the detection ion (m/z) 1761.2; the retention time of the structure represented by formula II was 8.5 min, and it was detected by the detection ion (m/z) 1006.7; (5) The test method for adhesion of polyisocyanate application products refers to: GB/T 9286-2021 Paint and varnish cross-cut test.

Preparation Example 1

Place 20,000 g of IPDI in a round-bottom flask equipped with a reflux condenser, a stirrer, a thermometer and a nitrogen inlet; heat the reaction system to 80°C, then add 2.66 g of a methanol solution of tetrabutylammonium hydroxide (30 wt%) dropwise into the reaction system with stirring, and carry out polymerization reaction by controlling the reaction temperature between 80 and 90°C. When the NCO content of the reaction liquid system is 25.5%, add dibutyl phosphate in an amount equimolar to tetrabutylammonium hydroxide to terminate the reaction to obtain a polymerization reaction liquid.

The unreacted isophorone diisocyanate monomer in the polymerization reaction liquid was evaporated and removed using a thin film evaporator at a temperature of 170° C. and an absolute pressure of 100 Pa to a content of 0.34 wt %, thereby obtaining a polyisocyanate composition 1.

Example 1

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.1wt%, add 5ppm of water, heat it to 120°C and continue to react for 2h. After the reaction is completed, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 1.

Example 2

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.1wt%, add 10ppm of water, heat it to 120°C and continue the reaction for 2h. After the reaction is completed, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 2.

Example 3

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.12wt%, add 50ppm of water, heat it to 120°C and continue the reaction for 2h. After the reaction is completed, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 3.

Example 4

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.15wt%, add 120ppm of water, heat it to 120°C and continue the reaction for 2h. After the reaction is completed, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 4.

Comparative Example 1

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.1wt%, heat it to 120°C and continue the reaction for 2h. After the reaction, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 5.

Comparative Example 2

Take 2000g of polyisocyanate composition 1 and heat it to 100°C. The amount of the blocking agent is added according to caprolactam/NCO=1.02. When the remaining free NCO is 0.15wt%, add 200ppm of water, heat it to 120°C and continue to react for 2h. After the reaction is completed, add an aromatic solvent to dilute it to 60% solid content to obtain a blocked polyisocyanate composition 6.

Example 5

A varnish was prepared based on the blocked polyisocyanate and polyester resin (Evonik resin DYNAPOL 915) prepared in Examples 1-4 and Comparative Examples 1-2, with NCO/OH=1 and a solid content of 50% (the dilution solvent was butyl acetate), and 0.5wt% (calculated based on the solid content of the varnish) of dibutyltin dilaurate was added to the coating.

The prepared varnish was sprayed on clean tinplate and baked at 200°C for 15 minutes to obtain a 50 μm film, and then the adhesion of the film was tested by the 100-grid method. The evaluation was performed according to the grading method in Table 1, and the test results are shown in Table 2 below.

Table 1 Classification method

Table 1 Test results

As can be seen from the above table, the blocked isocyanate products prepared in Examples 1-4 have significantly better adhesion than the product of Comparative Example 1 that does not contain the compound of Formula 1, and the viscosity of Examples 1-4 is significantly lower than the viscosity of Comparative Example 2. Therefore, the blocked polyisocyanate prepared in the present application has a viscosity of 1000 to 3000 cP (25° C.) and has better product adhesion when used in the process of using a single-component coating.

Claims

A blocked polyisocyanate composition comprising the following two structures, wherein the content of formula I is 0.05-1.5wt%, preferably 0.1-1wt%, based on formula II,

Among them, R is
The blocked polyisocyanate composition according to claim 1, wherein the viscosity at 25°C is 1000-3000 mPa·s, preferably 1500-2500 mPa·s.
The blocked polyisocyanate composition according to claim 1 or 2, wherein the content of free caprolactam accounts for 0.1-2wt% of the blocked isocyanate composition, more preferably 0.5-1.5wt%.
A method for preparing a blocked polyisocyanate composition according to any one of claims 1 to 3, comprising the following steps:

(1) in the presence of a trimerization catalyst, isophorone diisocyanate undergoes a polymerization reaction, wherein the polymerization reaction is terminated when the NCO content in the system is 20% to 26%;

(2) removing isophorone diisocyanate monomer from the product of step (1) to reduce the content of unreacted isophorone diisocyanate monomer to less than 1 wt %;

(3) adding caprolactam to the product of step (2) to carry out the reaction until the free NCO in the system is less than When the content of polyisocyanate is 0.2 wt%, water is added to continue the reaction to obtain a blocked polyisocyanate composition.
The method according to claim 4, wherein the amount of the trimerization catalyst is 5-100 ppm, preferably 10-90 ppm, of the mass of the isophorone diisocyanate monomer; and/or the trimerization catalyst is selected from one or more of tetraalkylammonium hydroxides and organic acid salts thereof;

Preferably, the hydroxide of tetraalkylammonium is selected from one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide, and the organic acid salt of tetraalkylammonium is selected from one or more of acetate, butyrate, and decanoate of tetramethylammonium and tetraethylammonium.
The method according to claim 4 or 5, wherein in step (1), the reaction is terminated by using a terminator or by staying at 100 to 120° C. for 30 to 60 minutes;

Preferably, the terminator is selected from one or more of dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, 2-ethylhexyl phosphate, phosphoric acid, hydrochloric acid, benzenesulfonic acid, p-toluenesulfonic acid, benzoyl chloride, and acetyl chloride.
The method according to any one of claims 4 to 6, wherein in the step (2), the content of unreacted isophorone diisocyanate monomer is less than 0.5 wt%, preferably less than 0.3 wt%.
The method according to any one of claims 4 to 7, wherein in the step (3), the product of step (2) is heated to 80-120° C., caprolactam is added dropwise thereto, and the free NCO content is monitored during the reaction. When the free NCO content is lower than 0.2 wt %, water is added thereto, and the temperature is raised to 120-140° C., and the reaction is continued for 60-120 min to obtain a blocked polyisocyanate composition.
The method according to any one of claims 4 to 8, wherein in the step (3), the material feed ratio, calculated by molar amount, is caprolactam/NCO=0.95-1.1:1, preferably 1-1.05:1.
The method according to any one of claims 4 to 9, wherein in step (3), the mass of water added is 5 to 120 ppm relative to the total amount of caprolactam and the product of step (2).
The blocked polyisocyanate composition according to any one of claims 1 to 3 or according to any one of claims 4 to 9 The use of the blocked polyisocyanate composition prepared by any of the methods described above, wherein the composition is used for one-component polyurethane coatings or adhesives, preferably for coil or can coatings.