JPH05507489A - Stabilization method for unsaturated carboxylic acid esters - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Stabilization method for unsaturated carboxylic acid esters Background of the invention The present invention provides a mixture of specific N,N'-substituted paraphenylene diamines (PPDA). This article relates to a method for stabilizing unsaturated carboxylic acid esters. In particular, water and and the characteristic solubility in the aqueous phase containing esters. A specific mixture of N,N'-substituted paraphenylene diamines with methyl meth Introduced during the manufacturing process of acrylates or lower alkyl esters of acrylic acid. and a method for stabilizing the ester.

Alkyl esters of methacrylic acid and acrylic acid are used in textiles and plastics. It has a wide range of uses as a raw material. These compounds have reactive unsaturated bonds in their molecules. It easily polymerizes under appropriate conditions during manufacture or storage. This polymerization Occurs in the presence of heat, light, oxygen and other conditions. Therefore, methacrylic acid or Related esters of taacrylic acid esters have minimal tendency to polymerize during their manufacturing process It is most preferred to do so or eliminate the tendency. By removing the tendency to polymerize It is possible to keep the container or pipe that transfers the substance clean during production, and the height of the reaction tank can be kept clean. It is possible to eliminate the accumulation of viscous and high molecular weight polymeric substances. Methyl methacrylate ) (MMA) and other unsaturated carboxylic acids during the production of alkyl esters. loquinoline, or certain paraphenylenediamine or phenothiazine derivatives. It is common practice to add conductors as polymerization inhibitors.

In addition, the use of N,N'-substituted paraphenylene diamines containing certain substances Japanese Publication No. 49-43920 N'Phenyl-p-phenylenediamine N,N,N'-di(sec-heptyl)-p-phenylenediamine in the organic phase (or unsaturated carboxylic acids or their esters, such as ethyl Acrylate, 2-ethylhexyl acrylate, methyl acrylate, acrylic Used to stabilize acid, methacrylic acid. This publication contains methyl methacrylate. There is no description of the route and it has not been tested. Furthermore, the aqueous phase is stabilized. There has also been no evaluation of the significance of This publication is just paraphenylene. Diamine substances inhibit polymerization in the pure liquid (organic) phase of acids or their esters. It merely teaches that it exhibits effective activity as a drug.

The above describes the effectiveness of polymerization inhibition properties on a laboratory scale for pure organic monomer phases. However, in large-scale commercial production units worldwide, various types of containers are still , Decanter 1 Distillation tower, pipes, heat exchanger or boiler containing troublesome esters Or, acid polymers are formed and are a problem. This means that the polymerization inhibiting effect is still sufficient. Indicates that there is no The present invention provides esters (and their precursors) in both aqueous and organic phases. It was completed by realizing the protection of Understanding this problem Recognition of critical factors that are difficult to understand and result in the development of polymeric cross-agent systems that protect both phases. The students were encouraged to conduct research with great enthusiasm. Recognition of the second problem is related to various phenylenediamine compounds. The protection of the aqueous phase is highly dependent on the pH of the aqueous phase. Every phenomenon happened before was neither recognized nor proposed.

The aim of the present invention is to provide an effective stable package in organic and aqueous phases. It's there. Additionally, the present invention improves the acidity of the aqueous phase by various inorganic and organic acids. Low pH levels characteristic of harsh manufacturing conditions, dropping to 4, 3 or even 2 The purpose is to protect The present invention provides protection for both phases. Minimizes polymer build-up in manufacturing equipment, thus eliminating Eliminates the need to remove polymerization residue due to stopping various units in the manufacturing process, improving factory productivity. It is intended to improve the

mouth fI+ In one aspect of the invention, the present invention provides Concerning how to prohibit This process stream consists of water and unsaturated carboxylic esters. an aqueous phase having a pH in the range of about 1 to about 5 and containing a small amount of said ester; an organic phase comprising a major portion of the ester, wherein the process stream contains (a) water at a pH of 2; N,N alkyl- or phenyl-substituted baraf with a solubility of 50% or more in the phase and Cb) having a solubility in the aqueous phase of pH 2 of 20% or less. 2 N,N alkyl- or phenyl-substituted paraphenylenediamines It consists of adding a stabilizer mixture.

According to another aspect, the present invention has multiple process streams consisting of water and esters. The present invention relates to a method for producing an unsaturated carboxylic acid ester. This process flow at least an aqueous phase containing water and an ester, and at least one process The stream is essentially water-free organic phase of the ester. Inhibits polymerization of said ester The improved method for providing a structure comprising: (a) adding a structural a first N,N-substituted heterophenylenediamine of formula (r); and (b) a structural formula (n ) by adding a stabilizer mixture consisting of a second N,N-substituted disparate phenylene diamine. and.

R1 and iso are each independently phenyl or alkyl to G-; C4 alkyl, & is phenyl or C1-C4 alkyl.

In structural formula 11■, R1 is phenyl, Rs is Cs-Co alkyl, and the island is 01 to C4, and when Ryo is phenyl are preferred. More preferable combination As a combination, ゐ and 艮 are C3-C3 alkyl, R1 is phenyl, and R This is the case where 1 is α to C2 alkyl. In this specification, "alkyl" The term includes straight chain, branched and cyclic alkyl.

In yet another aspect, the invention provides that the stabilizer mixture consists essentially of (a) structural formula (1 ); (b) Structural formula (n); a second NSN-substituted paraphenylenediamine represented by; and (C)(a), (b) relates to a mixture consisting of alcohols soluble in

1's ' In the following discussion, MMA has been chosen as a typical example, and many unsatisfactory It is understood that any of the Japanese carboxylic acid esters can be substituted by appropriate modification by a person skilled in the art. You should understand. Esters of acrylic acid and methacrylic acid are stabilized by this method. It is a well-defined material. Methyl, ethyl, propyl, butyl, pentyl, Esters exemplified by hexyl, heptyl and octyl are preferred. most Preferred are methyl, ethyl, and propylene acrylic and methacrylic acids. It is a lower alkyl ester of Methyl methacrylate, the most preferred ester rate (hereinafter sometimes abbreviated as MMA) is discussed below by way of example only. , the scope of the invention should not be considered limited thereto.

Commercial methods for producing methyl methacrylate basically involve acetone, hydrogen cyanide, Uses methanol and sulfuric acid as raw materials. Acetone reacts with hydrogen cyanide to form acetone. form cyanohydrin.

The chemistry of the above production method involves reacting acetone cyanohydrin with an excess amount of concentrated sulfuric acid to produce methane. Including forming acrylamide sulfate. The methacrylamide sal The phase stream reacts with the methanol solution, resulting in a combined hydrolysis-esterification reaction. formed into methyl methacrylate in the reaction. Modification of the esterification process is Modified procedures for separation of methanol and methacrylic acid for recovery and recycling of alcohol This may take various forms. In addition, manufacturing conditions also vary depending on the method used to supply methacrylamide. By changing the feed ratio of tanol and water, reactor temperature and residence time. can be done.

In one variation, a methacrylamide sulfate stream (excess ethanol aqueous solution, and circulating flow into a steam-jacketed esterification reactor at 80-100°C. There are examples of continuous feeding and reaction with residence times of 2 to 4 hours (61).

The effluent from the reaction tank is distilled in an acid stripping tower to produce crude methyl methacrylate and methanol. and water. The crude ester washed with water is purified in a multi-stage distillation system, and the methanol The aqueous solution is distilled and methanol is recovered for recycling. Methyl methacrylate The yield is approximately 90% based on ACN, based on methanol, and depending on the reaction conditions and 80-90% depending on production and manufacturing planning.

As a variation of other esterification steps, the reaction can be run at 790 kPA (100 psig). Under a pressure of 100 to 150℃, the residence time is 1 hour or more depending on the reaction temperature. There are examples where it is within. The product may be recovered as described above, or the product may be collected with reactor effluent. Separate wax into machine phase and waste acid phase.

The light end (low boiling fraction) is removed from the organic phase of the flash column. Next, crude espresso Wash the cellulose with water or ammonia to remove methanol and some methacrylic acid. leave Aqueous raffinate is esterified Recirculated to the reactor. The washed crude ester is purified using a three-column distillation system. . In the first stage column, water and methanol are taken out from the head and sent to the esterification reaction tank. Recirculated. The final product is removed from the head of the product column. product column The bottoms are stripped to recover compounds for recycling and the residue is incinerated.

Table 1 Form with methyl metarelate Pressure Boiling point Ester U]　-2　” Wednesday 101 83 86 27 49 88.4 Methanol 101 84.2 15.5 Ethanol 27 34.5 18 Table 2 Methyl methacrylate and ′ Methyl methacrylate in water methyl methacrylate one temperature relate, g/100g rel. Waterworks under construction mass production 0 1.85 0.85 10 1.72 0.99 20 1.59 1.15 30 1.50 1.34 40 1.43 1.56 50 1.43 1.80 60 1.49 2.07 70 1.60 2.38 80 1.80 2.74 The present invention uses MMA that exhibits high solubility in water and easily forms an azeotrope with water. Based on the recognition that (or its ester) needs to be protected in the aqueous phase It is. Tables 1 and 2 detail their solubility. Next to carrying out the invention The necessary steps are to ensure that the given stabilizer/blocker is soluble in the aquarium at the required pH level. It is necessary to evaluate the The following test summaries will be utilized to make said decision: .

Water solubility test method extraction test general description 1 infusion: Determining the polymerization inhibitor to be distributed in the MMA and water composition with a specific pH.

1 match: 1. Preparation of a standard sample of pure MMA containing approximately 11,000 pp of each inhibitor.

2. Preparation of aqueous solution by prescription: MMA 1.5% 3. Adjust the aqueous solution sample to any pH level with sulfuric acid! l! I[,ta.

4. 100 g of each MMA solution was extracted with 100 g of an aqueous solution at an arbitrary pH.

a) Place the solution in a 16 oz. mechanical shaker bottle and mix the solution at low speed for 16 hours. It was over time.

b) The layers were separated. If emulsion occurs, carefully heat with a heat gun. Destroyed.

5. Each layer is tested by PPDA standards to determine the level of inhibitor in each phase. It was submitted to a chemical property laboratory for analysis.

P.P.D.A. The side layer method is based on oxidation/coupling of quinoline and paraphenylenediamine. Based on the formation of a dark colored solution. The standard is equipped with 1 cm or 0.5 cm cells. Determine colorimetrically using a spectrophotometer in the visible range.

Standard solutions of phenylene diamine and p-benzoquinone were each added to 100 ml of acetic acid. Make up exactly 0.1 weight of reagent.

Calibration is performed as follows. That is, (1) Pipette weigh 10 ml of MMA and Pour into a 50ml flask, add 25ml of acetic acid and 1ml of p-benzoquinone solution. Prepare a reagent blank by adding distilled water, then fill the 50ml flask with distilled water. Add with . (2) L 2 and 3 ml of appropriate para-phenylenediamine standard solution was added to a 50 ml labeled flask and then pipetted into 10 ml of MMA. (from the reagent blank side layer) and add enough acetic acid to bring the total volume to 25ml. Then, quickly add distilled water to bring the total volume to 50ml, mix this, and add water for 5 minutes. Measure the spectrum of the solution after 15 minutes.

Analysis of test samples other than the 10 ml analytical MMA solution is performed using the calibration recipe. . The calibration curve calibrates the microgram amount of paraphenylenediamine in each sample. used for. The amount of conversion to ppm para-phenylenediamine is per 10ml. Divide into microgram amounts (9.34g/10ml) determined by the weight of MMA. This is done by

As mentioned above, methyl methacrylate is shown only as a representative sample; Other esters within the clear range are also evaluated by the complete analytical method. Other than MMA If the ester is to be protected, the above method can be carried out with different weights with appropriate modifications. Must be.

Kei ``Niisen'' Shimote Good Lord A LL! il I N-(1,4 dimethylpentyl)-No-phenylparaphenylenediamine Mixture of and N-(1 methylpentyl)-No-phenylbara phenylene diamine thing 2 N-(1,4 dimethylpentyl)-No-phenylbara phenylenediamine 3 N,N'-di(isopropyl)paraphenylenediamine 4 N-(isopropyl)-No-phenylvara phenylenediamine 5 N, N'-di(1,4 dimethylpentyl) paraphenylenediamine The compounds shown in Table 3 have the general formula R-NH-(Cs)L)-NH-L11enyl Ct Ht- 2 phenyl C,) (+11 2, 3 9”r, 73 Cm Ht Q Ht 97, 2 2.

4 7 Knee 1-/L/QHy’k 90. 10.0 Note) * indicates meth in the aqueous phase. Contains nool.

As can be easily seen from the data in Table 3, some phenylenediamines have low pH Easily partitions into the aqueous phase at normal levels. It can be said that it is a candidate for an aqueous phase inhibitor that achieves the purpose of the present invention. In order to Alternatively, 50% must be distributed in the aqueous phase with a pH 2 test method. Compound 3.4 is It will be understood that it is such a substance. At least one lower alkyl (C, ~ N,N'-substituted phenylenediamines having C,) substituents are the inhibitor systems of the present invention. It is a preferred compound as an aqueous phase component.

Isopropyl-substituted phenylenediamine compound 3.4 is present in the aqueous phase, especially in highly acidic Provides particularly high protection for MMA monomers present under conditions. This condition is usually manufacturing conditions or temporary during an abnormal manufacturing period. . Without the high protection of the present invention, substantially undesirable polymerization occurs under highly acidic conditions. This will cause dust and contaminate the equipment. and the need for downtime for cleaning. Both cause a decrease in heat exchange efficiency.

The compound of structural formula (1) does not pass the water solubility test and the compound of structural formula (II) Products that also fail this test are considered soluble in the aqueous phase.

If a candidate substance meets the water solubility criteria, it proves that it has adequate polymerization inhibition properties. . Aqueous phase inhibitors are used in conjunction with highly active organic phase inhibitors, so these substances It should be recognized that there is no need to demonstrate maximum or optimal activity. Also, typical In a manufacturing process flow, a relatively small amount of ester is present in the aqueous phase compared to the organic phase. This must also be taken into consideration. The degree of protection required for this is greater than that of the organic phase. (essentially all MMA or other esters), the following polymerization test procedure: The candidate substances evaluated by the water solubility test method are evaluated according to the steps in step 1.

Mu's 1. Distill the MMA to remove all storage inhibitors.

2. Stock solution of 0.1% test inhibitor in MMA prepare.

3. A solution containing 10 ppm test inhibitor is prepared from the raw solution and placed in a test tube.

4. Place the test tube with internal oil tube and thermocouple in a constant temperature oil bath at 80°C.

5. Read the graph recorder and determine the first sign of exotherm as the beginning of polymerization expressed in time. Ru.

Table 4 凰””L-expansion j-nie Methyl methacrylate Condition 2 80° Inhibitor time "Uni-Ko" Run #1 Run #2 Target test A None 4.75 4.75 Target test B Phenothiazine 12.7 5 14.25 Subject Test C Hydroquinone 19.25 19.50 Compound 1 83°50 103.00 Compound 2 68.75 96.00 Compound 4 136.50 143.50 Compound 5 60.00 42.00 As seen in the data in Table 4, paraphenylenediamine compounds of structural formulas I and ■ are Shows remarkable long-term polymerization inhibition effect. Target exams A, B and C are within 20 hours. Alkyl-substituted para-phenylene diamines have 60 to 140 Show protection of time.

The present invention provides an aqueous phase inhibitor (a) poorly labeled as a compound of structural formula I. and the organic phase inhibitor (b), which is insufficiently displayed as a compound of structural formula ■. Utilize a fixative mixture. The stabilizer mixture has a polymerization inhibiting effect at any level. Preferably may be present from 50 to 10,000 ppm based on the weight of the stabilizing ester. . More preferably 100 to 2000 ppm, most preferably 200 to 11 000pp used for stabilization of esters and their precursors during ester production be done. The ratio of components (a) and (b) is roughly in the range of 5/95 to 9515, More preferably 30/70 to 70/30, and most preferably 40/6 The range is 0 to 60/40. Regarding structural formula 1 and ■, R.

is phenyl, R3 is C, ~Q alkyl, turtle is 01-C4 alkyl, and & is preferably phenyl. The most desirable combination is Shima, Ryo is 0. 1-C4 alkyl, R is phenyl, and R2 is Q-C1 alkyl . In this specification and claims, the term "alkyl" refers to straight chain branched, branched and cyclic alkyl.

The present invention enables even substances that are outside the range of the structural formula limitations of (1) and (II) to be It is believed to be effective as long as the laphenylene diamine is soluble in the aqueous phase. This totalization The following reciprocal formula (alte native formulation) is a solution for selecting useful compounds. Solving test method can be used. The stabilizer mixture is (a) 50% or more soluble in the aqueous phase at pH 2; N indicates resolution.

N-alkyl- or phenyl-substituted para-phenylenediamine; and (b) at pH 2 a second N,N alkyl- or phenyl-substituted substance having a solubility of 20% or less in the aqueous phase; It is rose phenylenediamine.

Craftsmanship and madness Global scale for producing esters of the present invention, more specifically methyl methacrylate Variables in the various vessels and process stream conditions in the plant were investigated in small-scale laboratory experiments. cannot be fully expressed in experiments. Therefore, we package experimental inhibitors in long-term tests. packaging shows truly improved performance. this test During the test, the accumulation of polymerized MMA on various actual manufacturing containers, pipes, heat exchangers, etc. is prohibited. You can decide to eliminate it, or at least minimize it, with drugs. This way The test involves a run using a 50150 mixture of compounds of formula 1 and formula evening. The interior of the manufacturing tower, which normally needs to be shut down and cleaned every two to three months, has been improved. By using a polymerization inhibitor, the plant was able to operate for nine months without cleaning. in other departments Also showed significantly improved cleaning intervals. Where water and organic phases are present , the present invention provides an unexpected improvement in Good results were obtained.

Another aspect of the invention is the creation of new and previously unknown useful stabilizer packages. It is a form. It is the alcohol that is compatible with the inhibitor compound in the ester manufacturing process. is used to ensure that the compound of structural formula I is completely soluble in solid substances and in liquid form. can do. In particular, essentially the following stabilizer formulations are disclosed: (a) First N,N-substituted paraphenylene diamine represented by structural formula (1): (b) a second N,N-substituted paraphenylenediamine represented by structural formula (II); and; (C) Alcohol soluble in (a) and (b) Alcohol is (a) + (b ) can be present in proportions up to 75% by weight. When using methyl methacrylate Methanol is most suitable. The ratio of (a) to (b) is the same as the above stabilizer mixture (immediately 5/95 to 9515).

Many changes and modifications may be made without departing from the principles of the invention, and these Reference should be made to the additional claims to understand the scope of protection of the invention.

abstract The present invention relates to the polymerization of unsaturated carboxylic esters in a process stream consisting of water and esters. A method for inhibiting said process stream from containing (a)p)(2) a first water-soluble N,N-substituted paraphenylenediamine: and (b) a second insoluble in water at pH 2. consisting of adding a stabilizer mixture consisting of N,N-substituted paraphenylene diamines Regarding the method. A preferable one of the N,N substituents in (a) is C, -c4 alkyl more preferably (a) a compound of structural formula (I) and (b) a compound of structural formula (n) It is a compound of

R and R2 are each independently selected from phenyl or 6-C, alkyl; Bird is alkyl of c1-c4\& is phenyl or alkyl of 01-Cs .

Claims (15)

[Claims] 1. Inhibits polymerization of unsaturated carboxylic esters in process streams consisting of water and esters. In the method of (a) having an organic phase consisting of a large number of the esters, the process stream having the structural formula ( I) a first N,N-substituted paraphenylenediamine; and (b) structure A stable compound consisting of a second N,N-substituted paraphenylenediamine represented by formula (II) How to add the agent mixture. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)▲There are mathematical formulas, chemical formulas, tables, etc.▼( II) R1 and R2 are each independently selected from phenyl or C8-C9 alkyl; selected, R3 is C1-C4 alkyl, R4 is phenyl or C1-C9 alkyl. It's a kill. 2. 2. The method of claim 1, wherein the unsaturated carboxylic acid is acrylic acid or methacrylic acid. lylic acid and said ester is a lower alkyl ester thereof. 3. 3. The method of claim 2, wherein the unsaturated carboxylic acid is methacrylic acid; A method in which the ester is a methyl ester. 4. 2. The method of claim 1, wherein the stabilizer mixture has a molecular weight of about 50 to about 1 on an ester basis. A method containing 0,000 ppm. 5. 2. The method of claim 1, wherein the stabilizer mixture has a ratio of component (a) to component (b). 5/95 to about 95/5. 6. The method of claim 1, wherein the stabilizer formulation comprises a ratio of component (a) to component (b). A method containing a ratio of about 30/70 to about 70/30. 7. 2. The method of claim 1, wherein said stabilizer mixture comprises about 200% of said stabilizer mixture. ~2000 ppm. 8. 8. The method of claim 7, wherein from about 100 to about 1000 ppm of (a) and (b) ) of about 100 to about 1000 ppm. 9. The method of claim 1, wherein R1 is phenyl and R2 is C6-C9 alkyl. How to be a kill. 10. 10. The method of claim 9, wherein R3 is C1-C4 alkyl and R4 is fluorine. How to be an enyl. 11. The method of claim 1, wherein R3 and R4 are C3-C4 alkyl. . 12. The method of claim 9, wherein R1 is phenyl and R2 is a C6-C7 atom. How to be Lukiru. 13. Polymerization of unsaturated carboxylic esters in a process stream consisting of water and esters In the prohibited method, said process stream contains a small amount of said ester at a pH of about the process stream has an aqueous phase of 1 to about 5 and an organic phase consisting of a majority of the ester; (a) N,N alkyl- having a solubility of 30% or more in the aqueous phase at pH 2; or phenyl-substituted paraphenylene diamine; and (b) water at pH 2. a second N,N alkyl- or phenyl-substituted with a solubility of 20% or less in the phase; A method comprising adding a stabilizer mixture consisting of para-phenylenediamine. 14. a first N,N-substituted paraphenylenediamine substantially of structural formula (I); (b ) a second N,N-substituted paraphenylenediamine of structural formula (II); and (c) ( A stabilizer mixture consisting of alcohols soluble in a) and (b). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)▲There are mathematical formulas, chemical formulas, tables, etc.▼( II) R1 and R2 are each independently selected from phenyl or alkyl of G8 to G9; selected, R3 is C1-C4 alkyl, R4 is phenyl or C1-C9 alkyl. It's a kill. 15. In a method for producing unsaturated carboxylic acid esters having multiple process streams , at least one of the process streams has an aqueous phase containing water and an ester; An improved method for inhibiting the polymerization of esters, comprising: a first N,N-substituted paraphenylenediamine of structural formula (I); (b) a first N,N-substituted paraphenylenediamine of structural formula (II); ) of adding a second N,N-substituted paraphenylene diamine. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)▲There are mathematical formulas, chemical formulas, tables, etc.▼( II) R1 and R2 are each independently selected from phenyl or C6-C9 alkyl; selected, R8 is C1-C4 alkyl, R4 is phenyl or C1-C9 alkyl. It's a kill.