A polymerization inhibitor for inhibiting the polycondensation of high carbon aldehydes and a preparation method thereof

Abstract

The application discloses a polymerization inhibitor for inhibiting high-carbon aldehyde condensation polymerization and a preparation method thereof, and belongs to the technical field of high-carbon aldehyde production. The polymerization inhibitor is prepared by the following steps: a mercaptophenol compound containing a tertiary butyl hindered group is reacted with 4,7-diaza-1,9-decadiene to obtain an intermediate A; the intermediate A is reacted with 5-chloropentanal to introduce a dialdehyde group; and the intermediate B is condensed with an aminopropyl end-capped polydimethylsiloxane to obtain the product by end-capping with 5-amino-2,4-di-tert-butyl-phenol containing a tertiary butyl hindered group. The polymerization inhibitor contains a hindered phenol structure and an organic silicon chain segment, can inhibit the condensation polymerization of high-carbon aldehyde during storage or transportation, improves the activity of a phenolic hydroxyl group due to an alkylthio group, inhibits the start of the condensation polymerization due to a large spatial volume of a tertiary butyl group, has good chemical stability due to the combination of the intermediate B and the aminopropyl end-capped polydimethylsiloxane through a Schiff base reaction, and can improve the polymerization inhibition effect and prolong the effective period of the polymerization inhibition due to the good compatibility of the polydimethylsiloxane chain segment with the high-carbon aldehyde.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-carbon aldehyde production, and particularly relates to a polymerization inhibitor for inhibiting the polymerization of high-carbon aldehyde and a preparation method thereof. BACKGROUND

[0002] High-carbon aldehyde is a class of aldehyde compounds containing aldehyde groups in the molecule and having a carbon chain length of usually C8 and above, and its general structure can be represented as R-CHO (wherein R is an alkyl group of C7 and above or a hydrocarbon group containing an unsaturated bond). Common high-carbon aldehydes include octanal (C8), nonanal (C9), decanal (C10), undecanal (C11), dodecanal (lauryl aldehyde, C12), undecylenic aldehyde (C11 aldehyde containing an unsaturated double bond), etc. Such compounds have an important position in the chemical industry, and they are widely sourced, either by extraction of natural products or by large-scale industrial synthesis.

[0003] The application scenarios of high-carbon aldehyde are very diverse: in the perfume industry, they are key components of many natural perfumes or intermediates of synthetic perfumes, for example, nonanal can impart a rose, citrus-like aroma to products, and lauryl aldehyde is often used to blend floral and fruity fragrances; in the pharmaceutical field, high-carbon aldehyde can be used as an intermediate for the synthesis of antibacterial drugs, vitamin derivatives, etc.; in the pesticide industry, its derivatives are often used as precursors of insecticides and fungicides; in addition, in the fields of plastic additives, surfactants, cosmetic raw materials, etc., high-carbon aldehyde also plays an irreplaceable role.

[0004] However, high-carbon aldehyde has poor chemical stability, and in the process of storage, transportation and processing, it is prone to spontaneous polycondensation due to the influence of external conditions, and the most important reaction type is aldol condensation. The occurrence of polycondensation reaction will bring a series of negative effects to the application of high-carbon aldehyde: first, the decrease of monomer concentration leads to the decrease of effective ingredients, which directly affects the yield and economic benefits of the product; second, the generated oligomers or solid precipitates will cause the high-carbon aldehyde product to appear viscous, turbid or even layered, which seriously damages its appearance quality; in addition, the polycondensation products will also change the chemical properties of high-carbon aldehyde, for example, in perfumes, it will cause the aroma to weaken and produce an odor, in chemical synthesis, it will reduce the reaction activity and increase the generation of by-products, thereby affecting the efficiency of subsequent processing and the quality of the final product.

[0005] To solve the problem of polycondensation of high-carbon aldehyde, the method of adding a polymerization inhibitor is often used in industry to inhibit or delay its polycondensation reaction. A polymerization inhibitor is a chemical substance that can inhibit polymerization by combining with reactive centers or by steric hindrance effect to prevent active molecules from colliding. At present, the commonly used polymerization inhibitors for aldehyde compounds mainly include: phenolic polymerization inhibitors (such as hydroquinone, 2,6-di-tert-butyl-p-cresol), quinone polymerization inhibitors (such as p-benzoquinone), amine polymerization inhibitors (such as N,N-dimethylaniline, triethylamine), inorganic polymerization inhibitors (such as sodium sulfite, sodium thiosulfate).

[0006] But the traditional polymerization inhibitor for high carbon aldehyde aldol condensation reaction inhibition is not strong, especially at higher temperature, the polymerization inhibition effect is greatly reduced, it is difficult to meet the long-term stability requirements, some polymerization inhibitors may even with high carbon aldehyde new reaction, generate new impurities, rather than affect the product purity, or with high carbon aldehyde compatibility is poor, easy to appear stratification, precipitation phenomenon, resulting in uneven dispersion of polymerization inhibitor, local area will still occur condensation reaction, therefore, according to the structure characteristics and condensation reaction mechanism of high carbon aldehyde, development of a new type of special polymerization inhibitor with high efficiency, long-acting, good compatibility, no secondary pollution etc, become the key to solve the high carbon aldehyde storage, transportation and application stability problem, has important industrial value and application prospect. SUMMARY

[0007] In view of the above situation, in order to overcome the defects of the prior art, the polymerization inhibitor disclosed by the application is obtained by reacting the mercaptophenol compound containing a tertiary butyl hindered group with 4,7-diaza-1,9-decadiene, then introducing dialdehyde group by reacting the obtained intermediate A with 5-chloropentanal, and then condensing the intermediate B with aminopropyl end-capped polydimethylsiloxane, and finally obtaining the end product polymerization inhibitor by end-capping with 5-amino-2,4-di-tert-butyl-phenol which also contains a tertiary butyl hindered group. The polymerization inhibitor contains hindered phenol structure and silicone chain segment in the structure, and can inhibit the condensation reaction of high carbon aldehyde during storage or transportation.

[0008] In order to achieve the above purpose, the following technical scheme is adopted: on the one hand, the application provides a polymerization inhibitor for inhibiting high carbon aldehyde condensation, which has the following structure:

[0009] .

[0010] On the other hand, the application also provides a preparation method of the polymerization inhibitor for inhibiting high carbon aldehyde condensation, comprising the following steps:

[0011] S1, in a reaction vessel protected by nitrogen, 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene are added, then tetrahydrofuran is added, followed by adding azo initiator, the reaction system is heated to 60-70 DEG C, and stirred for 4-6 h. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain intermediate A;

[0012] S2, 5-chloropentanal is added to the reaction vessel containing intermediate A, N,N-dimethylformamide is added, then triethylamine is added, the temperature of the reaction system is controlled at 30-40 DEG C, and stirred for 8-10 h. After the reaction is completed, the generated impurities are removed by filtration, and the solvent is removed by distillation under reduced pressure to obtain intermediate B;

[0013] S3, under the protection of nitrogen, intermediate B and aminopropyl terminated polydimethylsiloxane are added into a reaction vessel, toluene is added, the reaction system is warmed to 80-90 DEG C, stirring for 6-10 h, then 5-amino-2, 4-di-tert-butyl-phenol is added, and stirring is continued at 80-90 DEG C for 3-4 h. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain the polymerization inhibitor.

[0014] The synthesis reaction formula of the polymerization inhibitor is as follows:

[0015] .

[0016] Further, the molar ratio of 2, 6-di-tert-butyl-4-mercaptophenol and 4, 7-diaza-1, 9-decadiene in step S1 is 1: 1.0-1.2, and the amount of tetrahydrofuran is 3-5 times the total mass of the two reactants.

[0017] Further, the azo initiator is one of azobisisobutyronitrile, azobisisoheptyl nitrile and dimethyl azobis isobutyrate.

[0018] Further, the amount of the azo initiator is 0.5%-1% of the mass of 2, 6-di-tert-butyl-4-mercaptophenol.

[0019] Further, the molar ratio of intermediate A, 5-chloropentanal and triethylamine in step S2 is 1: 1.1-1.3: 1.5-1.8, and the amount of N, N-dimethylformamide is 4-6 times the total mass of the two reactants.

[0020] Further, the molar ratio of intermediate B and aminopropyl terminated polydimethylsiloxane in step S3 is 1: 0.8-1.0, and the amount of toluene is 2-3 times the total mass of the two reactants.

[0021] Further, the average molecular weight of the aminopropyl terminated polydimethylsiloxane is 2000.

[0022] Further, the amount of 5-amino-2, 4-di-tert-butyl-phenol is 30%-50% of the mass of intermediate B.

[0023] The beneficial effects of the present application are: the polymerization inhibitor disclosed in the present application is obtained by reacting a mercaptophenol compound containing a tert-butyl hindered group with 4, 7-diaza-1, 9-decadiene, then introducing a dialdehyde group by reacting intermediate A with 5-chloropentanal, and then condensing intermediate B with aminopropyl terminated polydimethylsiloxane, and finally capped with 5-amino-2, 4-di-tert-butyl-phenol which also contains a tert-butyl hindered group. The polymerization inhibitor contains a hindered phenol structure and a silicone chain segment in its structure, and can inhibit the polycondensation reaction of high-carbon aldehyde during storage or transportation.

[0024] The alkylthio group generated at the hydroxyl para-position of 2,6-di-tert-butyl-4-mercaptophenol is a strong electron-donating group, which can push the electron cloud to the benzene ring through resonance effect or induction effect, the increase of the electron cloud density will delocalize to the oxygen atom of the phenolic hydroxyl group, so as to increase the electron cloud density of the oxygen atom, thereby improving the activity of the phenolic hydroxyl group, the tert-butyl groups introduced in multiple places in the molecular structure are typical steric hindering groups, which have large spatial volume, and can physically hinder the approach and collision of the active aldehyde group in the high-carbon aldehyde molecule through steric hindering effect, and the double steric hindering protection formed by the two end tert-butyl groups further strengthens the polymerization inhibition effect on the high-carbon aldehyde.

[0025] The intermediate B is combined with the aminopropyl-terminated polydimethylsiloxane through Schiff base reaction, the imine bond has good chemical stability and is not easy to be oxidized or hydrolyzed, thereby avoiding the problem that the polymerization inhibitor itself is invalid due to structural decomposition, and the introduced polydimethylsiloxane segment is a nonpolar flexible chain, which has good compatibility with the high-carbon aldehyde, so that the polymerization inhibitor can be uniformly dispersed in the high-carbon aldehyde system, the polymerization inhibition effect is improved, and the effective period of the polymerization inhibition is prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The infrared spectrum of the polymerization inhibitor prepared for the embodiment 3 of the present application;

[0027] Figure 2 The monomer retention rate of various polymerization inhibitors of the present application at room temperature (25℃);

[0028] Figure 3 The monomer retention rate of various polymerization inhibitors of the present application at medium temperature (40℃);

[0029] Figure 4 The monomer retention rate of various polymerization inhibitors of the present application at high temperature (60℃).

[0030] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, which together with the embodiments of the present application, serve to explain the present application, and do not constitute a limitation of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application are described below clearly and completely, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments, based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the present application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of the present application. The preferred materials and methods are described herein, although any method and material similar or equivalent to those described herein can be used. The materials described or

[0033] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all commercially available unless otherwise specified. In all examples of the present application, the average molecular weight of the aminopropyl-terminated polydimethylsiloxane is 2000.

[0034] Example 1: A method for preparing a polymerization inhibitor for inhibiting the polycondensation of high-carbon aldehydes, comprising the following steps:

[0035] S1, in a reaction vessel under nitrogen protection, 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene were added, followed by the addition of tetrahydrofuran, and then the addition of an azo initiator azobisisobutyronitrile. The reaction system was heated to 60°C, and stirred for 4h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain intermediate A;

[0036] The molar ratio of 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene was 1:1.0, the amount of tetrahydrofuran was 3 times the total mass of the two reactants, and the amount of azo initiator was 0.5% of the mass of 2,6-di-tert-butyl-4-mercaptophenol;

[0037] S2, 5-chloropentanal was added to the reaction vessel containing intermediate A, followed by the addition of N,N-dimethylformamide and triethylamine. The temperature of the reaction system was controlled at 30°C, and stirred for 8h. After the reaction was completed, the generated impurities were removed by filtration, and the solvent was removed by distillation under reduced pressure to obtain intermediate B;

[0038] The molar ratio of intermediate A, 5-chloropentanal and triethylamine was 1:1.1:1.5, and the amount of N,N-dimethylformamide was 4 times the total mass of the two reactants;

[0039] S3, under nitrogen protection, intermediate B and aminopropyl-terminated polydimethylsiloxane were added to the reaction vessel, and toluene was added. The reaction system was heated to 80°C, and stirred for 6h. Then 5-amino-2,4-di-tert-butyl-phenol was added, and the stirring was continued at 80°C for 3h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain the polymerization inhibitor;

[0040] The feeding molar ratio of the intermediate B and the aminopropyl-terminated polydimethylsiloxane is 1:0.8, the amount of toluene is 2 times of the total mass of the two reactants, and the amount of 5-amino-2,4-di-tert-butyl-phenol is 30% of the mass of the intermediate B.

[0041] Example 2: A preparation method of a polymerization inhibitor for inhibiting the polycondensation of high-carbon aldehydes, comprising the following steps:

[0042] S1, in a reaction vessel under nitrogen protection, 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene are added, followed by the addition of tetrahydrofuran, and then an azo initiator azobisisoheptane nitrile is added, the reaction system is heated to 70℃, and stirred for 6h, after the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain intermediate A;

[0043] The feeding molar ratio of the 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene is 1:1.2, the amount of tetrahydrofuran is 5 times of the total mass of the two reactants, and the amount of the azo initiator is 1% of the mass of 2,6-di-tert-butyl-4-mercaptophenol;

[0044] S2, 5-chloropentanal, N,N-dimethylformamide, and triethylamine are added to the reaction vessel containing intermediate A, the temperature of the reaction system is controlled at 40℃, and stirred for 10h, after the reaction is completed, the generated impurities are removed by filtration, and the solvent is removed by distillation under reduced pressure to obtain intermediate B;

[0045] The feeding molar ratio of the intermediate A, 5-chloropentanal, and triethylamine is 1:1.3:1.8, and the amount of N,N-dimethylformamide is 6 times of the total mass of the two reactants;

[0046] S3, under nitrogen protection, intermediate B and aminopropyl-terminated polydimethylsiloxane are added to the reaction vessel, toluene is added, the reaction system is heated to 90℃, and stirred for 10h, then 5-amino-2,4-di-tert-butyl-phenol is added, and the stirring is continued at 90℃ for 4h. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain the polymerization inhibitor;

[0047] The feeding molar ratio of the intermediate B and the aminopropyl-terminated polydimethylsiloxane is 1:1.0, the amount of toluene is 3 times of the total mass of the two reactants, and the amount of 5-amino-2,4-di-tert-butyl-phenol is 50% of the mass of the intermediate B.

[0048] Example 3: A preparation method of a polymerization inhibitor for inhibiting the polycondensation of high-carbon aldehydes, comprising the following steps:

[0049] S1, in a reaction vessel under nitrogen protection, 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene were added, followed by the addition of tetrahydrofuran, and then an azo initiator dimethyl azobis-2-methylpropionate was added, the reaction system was heated to 65℃, and stirred for 5h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain intermediate A;

[0050] The molar ratio of 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene was 1:1.1, the amount of tetrahydrofuran was 4 times the total mass of the two reactants, and the amount of the azo initiator was 0.75% of the mass of 2,6-di-tert-butyl-4-mercaptophenol;

[0051] S2, 5-chloropentanal, N,N-dimethylformamide, and triethylamine were added to the reaction vessel containing intermediate A, the temperature of the reaction system was controlled at 35℃, and stirred for 9h. After the reaction was completed, the generated impurities were removed by filtration, and the solvent was removed by distillation under reduced pressure to obtain intermediate B;

[0052] The molar ratio of intermediate A, 5-chloropentanal, and triethylamine was 1:1.2:1.65, and the amount of N,N-dimethylformamide was 5 times the total mass of the two reactants;

[0053] S3, under nitrogen protection, intermediate B and aminopropyl-terminated polydimethylsiloxane were added to the reaction vessel, toluene was added, the reaction system was heated to 85℃, and stirred for 8h. Then 5-amino-2,4-di-tert-butyl-phenol was added, and the stirring was continued at 85℃ for 3.5h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain the polymerization inhibitor;

[0054] The molar ratio of intermediate B and aminopropyl-terminated polydimethylsiloxane was 1:0.9, the amount of toluene was 2.5 times the total mass of the two reactants, and the amount of 5-amino-2,4-di-tert-butyl-phenol was 40% of the mass of intermediate B.

[0055] Result analysis

[0056] Figure 1 The infrared spectrum of the polymerization inhibitor prepared in Example 3 of the present application is shown in the figure, wherein 3364cm -1 is the O-H stretching vibration peak, 2850cm -1 is the C-H asymmetric stretching peak dominated by tert-butyl methyl, 1566cm -1 is the C=N stretching vibration peak, 1116cm -1 is the symmetric bending peak of Si-CH3, 959cm -1 is the stretching vibration peak of Si-O-Si, and 2550-2600cm -12700-2800cm -1 The absence of characteristic peaks for -SH and aldehyde CH indicates that the present invention has successfully prepared the polymerization inhibitor for the target product.

[0057] Lauraldehyde was used as the experimental sample, and the samples were grouped according to the following components:

[0058] Blank control group: lauraldehyde samples without added polymerization inhibitor;

[0059] Positive control group: Commonly used traditional polymerization inhibitors were added to lauraldehyde samples according to the following mass percentages: 0.1% hydroquinone, 0.1% BHT, and 0.1% sodium sulfite;

[0060] Example group: The polymerization inhibitor prepared in the example of the present invention was added to the lauraldehyde sample at a mass percentage of 0.2%.

[0061] Storage experiments were conducted at room temperature (25℃), medium temperature (40℃), and high temperature (60℃).

[0062] Samples were taken at 7, 14, 30, and 60 days, and monomer retention rates (%) were calculated by titration using the hydroxylamine method. The results are shown below. Figures 2-4 , Figure 2 , Figure 3 , Figure 4 The monomer retention rates for each group are as follows: at room temperature (25℃), medium temperature (40℃), and high temperature (60℃).

[0063] from Figures 2-4 It can be seen that at all temperatures, the monomer retention rate of the example group was significantly higher than that of other groups. Even at 60°C, the retention rate of the polymerization inhibitors in each example was still over 80% after 60 days, indicating that the polymerization inhibitors prepared in this invention have a long-term effective polymerization inhibition effect on high carbon aldehydes.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0065] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A process for the preparation of a polymerization inhibitor for inhibiting the polymerization of higher aldehydes, characterized by: It comprises the following steps: S1, in a reaction vessel under nitrogen protection, 2,6-di-tert-butyl-4-mercaptophenol and 4,7-diaza-1,9-decadiene are added, followed by the addition of tetrahydrofuran, and then an azo initiator is added. The reaction system is heated to 60-70℃, and stirred for 4-6h. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain intermediate A; S2, 5-chloropentanal, N,N-dimethylformamide, and triethylamine are added to the reaction vessel containing intermediate A, and the temperature of the reaction system is controlled at 30-40℃. After stirring for 8-10h, the generated impurities are removed by filtration, and the solvent is removed by distillation under reduced pressure to obtain intermediate B; S3, under nitrogen protection, intermediate B and aminopropyl-terminated polydimethylsiloxane are added to the reaction vessel, toluene is added, and the reaction system is heated to 80-90℃. After stirring for 6-10h, 5-amino-2,4-di-tert-butyl-phenol is added, and the reaction is continued at 80-90℃ for 3-4h. After the reaction is completed, the solvent is removed by distillation under reduced pressure to obtain the polymerization inhibitor. The polymerization inhibitor has the following structure: 。 2. The method for preparing the polymerization inhibitor for inhibiting high-carbon aldehyde polycondensation according to claim 1, characterized in that: In step S1, the molar ratio of 2,6-di-tert-butyl-4-mercaptophenol to 4,7-diaza-1,9-decadiene is 1:1.0-1.2, and the amount of tetrahydrofuran is 3-5 times the total mass of the two reactants.

3. The method for preparing the polymerization inhibitor for inhibiting high-carbon aldehyde condensation according to claim 2, characterized in that: The azo initiator is one of azobisisobutyronitrile, azobisisoheptyl nitrile, and dimethyl azobisbutyrate.

4. The method for preparing the polymerization inhibitor for inhibiting high-carbon aldehyde condensation according to claim 3, characterized in that: The amount of the azo initiator is 0.5%-1% of the mass of 2,6-di-tert-butyl-4-mercaptophenol.

5. The method for preparing the polymerization inhibitor for inhibiting high-carbon aldehyde polycondensation according to claim 4, characterized in that: In step S2, the molar ratio of intermediate A, 5-chloropentanal, and triethylamine is 1:1.1-1.3:1.5-1.8, and the amount of N,N-dimethylformamide is 4-6 times the total mass of the two reactants.

6. The method for preparing the polymerization inhibitor for inhibiting high-carbon aldehyde polycondensation according to claim 5, characterized in that: In step S3, the molar ratio of intermediate B to aminopropyl-terminated polydimethylsiloxane is 1:0.8-1.0, and the amount of toluene is 2-3 times the total mass of the two reactants.

7. The method of claim 6, wherein the method is characterized by: The average molecular weight of the aminopropyl-terminated polydimethylsiloxane is 2000.

8. The method of claim 7, wherein the method is characterized by: The amount of 5-amino-2,4-di-tert-butyl-phenol is 30%-50% of the mass of intermediate B.

9. A polymerization inhibitor for inhibiting the polymerization of a high carbon aldehyde, characterized by: The polymerization inhibitor for inhibiting the polycondensation of high-carbon aldehydes is prepared according to the method of any one of claims 1-8.

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