A method for preparing an isocyanate composition

Abstract

The present invention relates to a method for preparing an isocyanate composition, in which an isocyanate monomer is reacted under the action of a quaternary phosphonium salt catalyst to obtain an isocyanate composition containing an iminooxadiazinedione group. In the mixed system of the quaternary phosphonium salt catalyst and an alcohol, the proportion of dissociable fluorine in the theoretical total fluorine amount is not less than 90%, preferably not less than 95%. The preparation method of the present invention can ensure the activity of the catalyst solution and realize the stability of the product process and product color number.

Description

Technical Field

[0001] The present invention relates to the technical field of isocyanate preparation, and particularly relates to an isocyanate composition containing an iminooxadiazinedione group. Background Art

[0002] Polyisocyanates prepared by polymerizing aliphatic diisocyanate monomers have been widely used in the polyurethane coating or adhesive industry.

[0003] Isocyanate monomers can polymerize by themselves to obtain structures such as uretidione, isocyanurate, iminooxadiazinedione, etc. Among them, polyisocyanates containing an iminooxadiazinedione group have the advantages of high functionality and low viscosity, and have become very useful raw materials in polyurethane plastics and coatings. Many patents have reported its preparation methods, and the catalysts used mainly include alkylphosphines, fluoroacid compounds, triazolium salts, polyfluorinated salts, etc. Among them, polyfluorinated salts are the most commonly used catalysts, and it is a well-known technical means to further dissolve and prepare a catalyst solution with an alcohol substance.

[0004] For example, the technical means of mixing a polyfluorophosphonium salt with a mixture of alcohols having a number average molecular weight of 32 - 250 has been disclosed in CN1140518C.

[0005] However, in the actual production process, since the reaction process is an intermittent operation, we have found that in the catalytic polymerization reaction of isocyanate monomers, even if the instant usage amounts of the quaternary phosphonium salt catalyst solutions prepared in the same batch are not very different during use, there are obvious differences in the color numbers of different batches of products, and at the same time, the safety risk in the reaction control process is also increased.

[0006] The applicant further studies and finds that in the reaction of preparing an isocyanate composition containing iminooxadiazinedione using a polyfluorophosphonium salt, the key role is played by the fluorine amount in the catalyst solution. And surprisingly, it is found that by controlling the fluorine amount of the quaternary phosphonium salt catalyst solution, the above-mentioned problem of poor batch stability can be solved, thus completing the present invention. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method of an isocyanate composition, by controlling the fluorine amount in the quaternary phosphonium salt catalyst solution, the stability of the product color number and the reaction process control between different batches can be ensured.

[0008] To achieve the above invention purpose, the present invention adopts the following technical solutions:

[0009] A method for preparing an isocyanate composition, wherein an isocyanate monomer is subjected to a polymerization reaction under the action of a quaternary phosphonium salt catalyst solution to obtain an isocyanate composition containing an iminooxadiazinedione group, and the proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution is not less than 90% of the theoretical total fluorine content.

[0010] In a preferred embodiment, the proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution is not less than 95% of the theoretical total fluorine content.

[0011] In a specific embodiment, the quaternary phosphonium salt catalyst solution is a mixed solution formed by dissolving a quaternary phosphonium salt catalyst in a solvent.

[0012] In a specific embodiment, the general structural formula of the quaternary phosphonium salt catalyst is shown as formula (I):

[0013]

[0014] wherein, R1, R2, R3, and R4 are the same or different and are each independently selected from linear or branched C1-C 15 alkyl, optionally substituted C7-C 15 aralkyl, or optionally substituted C6-C 12 aryl; Y is selected from polyfluoride ions (F - (HF) n ), where 0.1 < n < 20.

[0015] In a specific embodiment, the solvent is selected from linear or branched monohydric alcohols and / or dihydric alcohols containing 1 to 20 carbon atoms; preferably any one or a mixture of methanol, ethanol, 1- or 2-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-octanol, 2-ethyl-hexanol, heptanol, 2-ethyl-1,3-hexanediol, 1,3- or 1,4-butanediol, 1-methoxy-2-propanol; more preferably any one or a mixture of ethanol, n-butanol, hexanol, heptanol, or 2-ethyl-hexanol.

[0016] In a specific embodiment, the mass concentration of the quaternary phosphonium salt catalyst solution is 20 - 80 wt%, based on the total mass of the quaternary phosphonium salt catalyst solution, preferably 20 - 50 wt%.

[0017] In a specific embodiment, the usage amount of the quaternary phosphonium salt catalyst solution is 0.001% - 1% of the mass of the organic isocyanate monomer, preferably 0.01% - 0.05%.

[0018] In a specific embodiment, the isocyanate monomer is selected from aliphatic diisocyanates, preferably one or more of hexamethylene diisocyanate (HDI), 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), and 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI), more preferably HDI.

[0019] In a specific embodiment, the reaction temperature of the isocyanate monomer polymerization reaction is 0°C to 250°C, preferably 10 - 100°C, more preferably 60 - 90°C; the reaction time is 1 - 12 h, preferably 1 - 6 h.

[0020] In a specific embodiment, when the NCO content of the reaction solution reaches 38% - 42% based on the weight of the reaction solution, a terminator is added to terminate the reaction; preferably, it further includes the step of removing unreacted isocyanate monomer from the reaction mixture to obtain an isocyanate composition with a monomer content of less than 0.3 wt% and an iminooxadiazinedione group content of not less than 30 mol%.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] Adopting the preparation method of the present invention is conducive to scientifically guiding and determining the content of the actually effective catalytic components in the quaternary phosphonium salt catalyst solution, which is particularly important in the industrial continuous production process. It can achieve precise control of the catalyst solution dosage, thereby realizing the stability of product color number and reaction process control in different batches or continuous production processes. Detailed Embodiments

[0023] To better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples and should also include any other well-known changes within the scope of the claims of the present invention.

[0024] A method for preparing an isocyanate composition, in which an isocyanate monomer is subjected to a polymerization reaction under the action of a quaternary phosphonium salt catalyst to obtain a polyisocyanate composition containing an iminooxadiazinedione group. Among them, the quaternary phosphonium salt catalyst is a quaternary phosphonium salt catalyst solution formed by mixing a quaternary phosphonium salt catalyst with an alcohol. The proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution system to the theoretical total fluorine amount is not less than 90%, for example, including but not limited to not less than 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, preferably not less than 95%. In fact, due to various reasons, the proportion of dissociable fluorine in the catalyst solution system to the theoretical total fluorine amount is always less than 100%, for example, including but not limited to less than 99.9%, 99.8%, 99.7%, 99.6%, 99.5%, and more preferably not less than 95% and not higher than 99.5%.

[0025] Among them, the theoretical total fluorine amount of the quaternary phosphonium salt catalyst solution is based on the structure of the polyfluorophosphonium salt, and the calculation method is as follows:

[0026] Theoretical total fluorine amount = (number of HF * molecular weight of F + molecular weight of F ion) / total molecular weight of quaternary phosphonium salt * concentration of catalyst solution; among them, the molecular weight of F ion can be regarded as equal to the molecular weight of F.

[0027] The content of dissociable fluorine is obtained through actual testing, and the specific detection method is as follows.

[0028] It can be understood that the theoretical fluorine content of the quaternary phosphonium salt catalyst solution is the maximum value, and theoretically it can be completely dissociated. However, due to the high activity of fluoride ions, many side reactions will occur during the process of forming a mixed system with alcohol, resulting in the actual dissociable fluorine content of the catalyst solution being lower than the theoretical value.

[0029] At the same time, the content of this actual dissociable fluorine can be controlled by many methods, and the control methods are often not unique. For example, controlling the chlorine and bromine content of the catalyst quaternary phosphonium salt, for example, controlling the chlorine and bromine content and unsaturated bond compound content (such as carbonyl compounds) in the alcohol, for example, controlling the temperature in the preparation process not to be higher than 50°C, more preferably not to be higher than 30°C, for example, using the method of standing at 10 - 30°C and then filtering, the standing time is recommended to be about 1 - 7 days, and for example, controlling the mixing time of the quaternary phosphonium salt catalyst and alcohol, or controlling the above means simultaneously, etc., can all achieve the control of the dissociable fluorine content in the catalyst. In the present invention, there are no restrictions on the control method of the dissociable fluorine content, as long as the proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution to the theoretical total fluorine amount can be within the scope of the present invention.

[0030] Specifically, the structural general formula of the quaternary phosphonium salt catalyst is shown in formula (I):

[0031]

[0032] Wherein, R1, R2, R3, and R4 are the same or different and are independently selected from a linear or branched C1-C 15 Alkyl, optionally substituted C7-C 15 Arylalkyl or optionally substituted C6-C 12 Y is selected from polyfluoride ion (F - (HF) n ), where 0.1 <n<20。例如,季膦盐催化剂为四烷基季膦盐,还可以为本领域常用的其它季膦盐催化剂。另外,本领域技术人员可以理解的是,本发明的关键在于控制季膦盐催化剂溶液中可解离氟占理论总氟量的比例在本发明的范围内即可,对季膦盐催化剂没有特别的限制,只要本领域异氰酸酯单体聚合常用的、符合上述通式(I)结构的季膦盐催化剂均可。

[0033] In the present invention, the quaternary phosphonium salt catalyst is dissolved in a solvent and used in the form of a solution, and the solvent is selected from a straight-chain or branched monohydric alcohol and / or dihydric alcohol containing 1 to 20 carbon atoms; the solvent is preferably methanol, ethanol, 1- or 2-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-octanol, 2-ethylhexanol, heptanol, 2-ethyl-1,3-hexanediol, 1,3- or 1,4-butanediol, 1-methoxy-2-propanol, and more preferably any one or a mixture of ethanol, n-butanol, hexanol, heptanol or 2-ethylhexanol.

[0034] When the catalyst is used in the form of a solution, the mass concentration of the catalyst solution is 20-80wt%, based on the total mass of the catalyst solution, for example, including but not limited to 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, preferably 20-50wt%. The catalyst solution can be added all at once or continuously by dropwise addition, for example, by using a pump for dropwise addition control. In combination with actual production operations, it is recommended to control the dropwise addition within 10-30min.

[0035] In the present invention, the isocyanate monomer is selected from aliphatic diisocyanates, preferably one or more of hexamethylene diisocyanate (HDI), 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), and 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI), more preferably HDI.

[0036] In the method for preparing the isocyanate composition of the present invention, the reaction temperature for the self-polymerization reaction of the isocyanate monomer is 0°C to 250°C, for example, including but not limited to 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 150°C, 175°C, 200°C, 230°C, 250°C, preferably 10 - 100°C, more preferably 60 - 90°C; the reaction time is 1 - 12 h, for example, including but not limited to 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, preferably 1 - 6 h.

[0037] In the polymerization reaction of the above isocyanate monomer, the usage amount of the quaternary phosphonium salt catalyst solution is, based on the quaternary phosphonium salt catalyst, 0.001% - 1% of the mass of the organic isocyanate monomer, for example, including but not limited to 0.001%, 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.25%, 0.5%, 0.75%, 1%, preferably 0.01% - 0.05%.

[0038] For the polymerization reaction of the above isocyanate monomer, when the NCO content of the reaction solution reaches 38% - 42% based on the weight of the reaction solution, it is terminated by adding a terminator. Among them, the NCO content of the reaction solution can be detected by common detection methods in the art without any limitation. The terminator can also be a terminator commonly used in the art, for example, selected from one or more of benzoyl chloride, dibutyl phosphate, phosphoric acid, and dodecylbenzenesulfonic acid, but not limited thereto.

[0039] Furthermore, the preparation method of the present invention further includes the step of removing unreacted monomers from the reaction mixture after terminating the reaction, and finally obtaining a polyisocyanate composition with a monomer content of less than 0.3 wt% and an iminooxadiazinedione group content of not less than 30 mol%. Among them, the process for removing unreacted isocyanate monomers is not particularly limited, and any conventional process in the art can be adopted, such as vacuum rectification, thin-film evaporation, extraction or distillation.

[0040] The isocyanate composition prepared by the method of the present invention can be used after being dissolved in a solvent, and the solvent includes conventional benzene-based or ester-based solvents, such as one or two of butyl acetate, ethyl acetate, propylene glycol methyl ether acetate, xylene, toluene, S100 solvent oil, etc.

[0041] The present invention will be further described below in conjunction with examples. It should be noted that the examples do not constitute a limitation on the scope of protection required by the present invention.

[0042] The main raw material sources of the examples and comparative examples are as follows:

[0043] Hexamethylene diisocyanate: Wanhua Chemical, wannate HDI, 99%;

[0044] Methanol: sigma-Aldrich, 99%;

[0045] n-Butanol: sigma-Aldrich, 99%;

[0046] 2-Ethyl-1,3-hexanediol: sigma-Aldrich, 98%;

[0047] Tetrabutylphosphonium chloride, sigma-Aldrich, 96%;

[0048] Benzyltrimethylphosphonium chloride,

[0049] Potassium fluoride, TCI, 98%;

[0050] Anhydrous hydrogen fluoride, Yantai Zhongrui, 99%;

[0051] Dodecylbenzenesulfonic acid, sigma-aldrich, 95%.

[0052] The present invention tests the product color number according to the method of GB / T 3143-1982.

[0053] Detection method for dissociable fluorine:

[0054] Weigh approximately 10 g of the catalyst solution sample in a 20-ml screw-thread transparent vial, add 10 mL of 5% sodium hydroxide solution, shake it on a shaker for 3 min at a time, repeat 3 times, then let it stand at room temperature for 24 h and separate into layers. Take the lower aqueous phase sample, then adjust the pH value to 5 - 5.5 with 1% sodium hydroxide solution, and finally test it using a conventional fluoride ion selective electrode.

[0055] Preparation of Catalyst I:

[0056] Dissolve tetrabutylphosphonium chloride (10 g) in a methanol solution, add potassium fluoride (3.94 g) according to a molar ratio of 1:2, continuously stir at 50 °C for 48 h, filter to obtain the filtrate, then add the same mass of potassium fluoride as last time (3.94 g), stir for 48 h, and filter to obtain the filtrate; introduce anhydrous hydrogen fluoride equimolar to tetrabutylphosphonium chloride, and finally rotary evaporate to remove methanol at 45 °C and 500 Pa until constant weight to obtain the target tetrabutyldifluorophosphine catalyst, dissolve it in n-butanol to prepare a catalyst solution with a mass content of 50%, which is catalyst solution 1-d, store it at room temperature for 4 days, 9 days, and 10 days respectively, corresponding to catalyst solutions 1-c, 1-b, and 1-a.

[0057] Preparation of Catalyst II:

[0058] Dissolve benzyltriphenylphosphonium chloride (10 g) in a methanol solution, add potassium fluoride (3.74 g) according to a molar ratio of 1:2.5, continuously stir at 45 °C for 48 h, filter to obtain the filtrate, then add the same mass of potassium fluoride as last time (3.74 g), stir for 48 h, and filter to obtain the filtrate; introduce anhydrous hydrogen fluoride with a molar amount twice that of benzyltriphenylphosphonium chloride, and finally rotary evaporate to remove methanol at 40 °C and 300 Pa until constant weight to obtain the target benzyltrimethyltrifluorophosphine catalyst, dissolve it in 2-ethyl-1,3-hexanediol to prepare a catalyst solution with a mass content of 30%, which is catalyst 2-d, store this catalyst solution at room temperature for 3 days, 6 days, and 7 days respectively, which are catalyst solutions 2-c, 2-b, and 2-a.

[0059] The relevant catalyst solutions and related indicators are as follows in the table:

[0060] Table 1 Catalyst Solution System and Corresponding Indicators

[0061]

[0062] Example 1:

[0063] Under the conditions of 60 °C / 1 mbar, 1000 g of HDI was degassed for 10 min. Under nitrogen protection, the treated HDI was preheated to 60 °C, and the corresponding catalyst solution 1-b was added dropwise. The system temperature was controlled at 60-62 °C. The change of NCO% was monitored during the reaction. When the NCO% value dropped to 38%, dodecylbenzenesulfonic acid in an equimolar amount to the catalyst was added to terminate the reaction. The reaction solution was subjected to thin-film evaporation to remove the remaining monomers to obtain a low-viscosity polyisocyanate composition product. The key indicators are shown in Table 1 below.

[0064] The operations of Examples 2 and 3 were the same as those of Example 1, except that the catalysts were changed to 1-c and 1-d.

[0065] The operation of Comparative Example 1 was also the same as that of Example 1, and the catalyst was 1-a.

[0066] The operations of Comparative Example 2 and Examples 4-6 were the same as those of Example 1, except that the corresponding catalyst solution systems were 2-a, 2-b, 2-c, and 2-d.

[0067] The corresponding isocyanate compositions and process parameters obtained are shown in Table 2 below.

[0068] Table 2 Comparison of the products of Examples 1-6 and Comparative Examples 1 and 2 is shown in the table below

[0069] Project Catalyst Number Catalyst Dosage / % Product Color Number / Hazen Comparative Example 1 1-a 0.025 35 Example 1 1-b 0.025 27 Example 2 1-c 0.024 26 Example 3 1-d 0.024 26 Comparative Example 2 2-a 0.026 39 Example 4 2-b 0.027 26 Example 5 2-c 0.025 25 Example 6 2-d 0.025 25

[0070] It can be found from the experimental data in the above table that when the same catalyst solution was used and the ratio of the dissociable fluorine content to the theoretical fluorine content of the catalyst solution was controlled to be not less than 90%, the catalyst dosage and the product color number could be stabilized; on the contrary, in Comparative Examples 1 and 2, the ratio of the dissociable fluorine content to the theoretical fluorine content of the catalyst solution was lower than 90%, and the catalyst dosage and the product color number fluctuated greatly.

[0071] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. Those skilled in the art can understand that under the teaching of this specification, some modifications or adjustments can be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing an isocyanate composition, wherein an isocyanate monomer is subjected to a polymerization reaction under the action of a quaternary phosphonium salt catalyst solution to obtain an isocyanate composition containing an iminooxadiazinedione group, characterized in that, The proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution is not less than 90% of the theoretical total fluorine content; The general structural formula of the quaternary phosphonium salt catalyst is shown in formula (I): Among them, R1, R2, R3, and R4 are the same or different and are each independently selected from linear or branched C1-C 15 alkyl, optionally substituted C7-C 15 aralkyl, or optionally substituted C6-C 12 aryl; Y is selected from polyfluoride ion F - (HF) n , where 0.1 < n < 20.

2. The preparation method according to claim 1, wherein The proportion of dissociable fluorine in the quaternary phosphonium salt catalyst solution is not less than 95% of the theoretical total fluorine content.

3. The preparation method according to claim 1 or 2, characterized in that, The quaternary phosphonium salt catalyst solution is a mixed solution formed by dissolving the quaternary phosphonium salt catalyst in a solvent.

4. The preparation method according to claim 3, characterized in that, The solvent is selected from straight-chain or branched-chain monohydric alcohols and / or dihydric alcohols containing 1 to 20 carbon atoms.

5. The preparation method according to claim 4, characterized in that, The solvent is selected from any one or a mixture of methanol, ethanol, 1- or 2-propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-octanol, 2-ethyl-hexanol, heptanol, 2-ethyl-1,3-hexanediol, 1,3- or 1,4-butanediol, 1-methoxy-2-propanol.

6. The preparation method according to claim 5, characterized in that, The solvent is selected from any one or a mixture of ethanol, n-butanol, hexanol, heptanol or 2-ethyl-hexanol.

7. The preparation method according to claim 3, characterized in that, The mass concentration of the quaternary phosphonium salt catalyst solution is 20 - 80 wt%, based on the total mass of the quaternary phosphonium salt catalyst solution.

8. The preparation method according to claim 7, wherein The mass concentration of the quaternary phosphonium salt catalyst solution is 20 - 50 wt%, based on the total mass of the quaternary phosphonium salt catalyst solution.

9. The preparation method according to claim 1, wherein, The usage amount of the quaternary phosphonium salt catalyst solution is 0.001% - 1% of the mass of the organic isocyanate monomer, calculated based on the quaternary phosphonium salt catalyst.

10. The preparation method according to claim 9, characterized in that, The usage amount of the quaternary phosphonium salt catalyst solution is 0.01% - 0.05% of the mass of the organic isocyanate monomer, calculated based on the quaternary phosphonium salt catalyst.

11. The preparation method according to claim 1, characterized in that, The isocyanate monomer is selected from aliphatic diisocyanates.

12. The preparation method according to claim 11, wherein The isocyanate monomer is selected from one or more of hexamethylene diisocyanate (HDI), 2-methylpentane-1,5-diisocyanate, 2,4,4-trimethyl-1,6-hexane diisocyanate, 2,2,4-trimethyl-1,6-hexane diisocyanate, 4-isocyanatomethyl-1,8-octane diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), and 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI).

13. The preparation method according to claim 12, characterized in that, The isocyanate monomer is hexamethylene diisocyanate.

14. The preparation method according to claim 1, characterized in that, The reaction temperature for the polymerization reaction of the isocyanate monomer is 0 °C to 250 °C; the reaction time is 1 - 12 h.

15. The preparation method according to claim 14, wherein, The reaction temperature for the polymerization reaction of the isocyanate monomer is 10 - 100 °C; the reaction time is 1 - 6 h.

16. The preparation method according to claim 15, characterized in that, The reaction temperature for the polymerization reaction of the isocyanate monomer is 60 - 90 °C.

17. The preparation method according to claim 1, characterized in that, When the NCO content of the reaction solution reaches 38% - 42% based on the weight of the reaction solution, a terminator is added to terminate the reaction.

18. The preparation method according to claim 17, wherein, It also includes the step of removing the unreacted isocyanate monomer from the reaction mixture to obtain an isocyanate composition with a monomer content of less than 0.3 wt% and an iminooxadiazinedione group content of not less than 30 mol%.

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