JPH0515710B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing polycarboxylic acid anhydride. [Prior art] Polycarboxylic acid anhydrides, represented by unsaturated alicyclic 1,2-dicarboxylic acid anhydrides, are widely used industrially as raw materials for epoxy resin curing agents and polyester resins. It is well known that it is produced industrially by the Diels-Ander reaction between an acid and a diene component. Here, the diene component, which is one of the raw materials, is generally obtained as a component of a hydrocarbon mixture such as naphtha, kerosene, gas oil, etc., and there are some that can be separated and purified industrially, but there are generally various types. paraffins,
It is used as a hydrocarbon mixture consisting of olefins and dienes. During the reaction process, polymers from these non-active ingredients were produced as by-products, resulting in lower product yield and increased viscosity, and in some cases, the acid anhydride produced was denatured and colored by heat. . When acid anhydrides containing polymers are used as raw materials for polyester or as curing agents for epoxy resins, insoluble components may precipitate, the desired product may be colored, viscosity may increase, etc., which may cause problems in product design. This is undesirable as it causes various defects and deterioration of characteristics. Therefore, in order to add a phenolic polymerization inhibitor or to carry out the Diels-Ander reaction at a lower temperature, conventional techniques have been used to add benzene, toluene, etc., which can dissolve both maleic anhydride and acid anhydride, as a third component. , a method using a solvent such as xylene, and a method using a combination of other cyclic acid anhydrides (Japanese Unexamined Patent Publication No. 39082/1982) have been proposed. [Problems to be Solved by the Invention] However, even in these methods, polymer formation cannot be prevented unless the temperature is accurately controlled, and when a solvent is used, it cannot be used after the Diers-Ander reaction is completed. This method requires a step of removing and recovering the solvent, which is industrially expensive, and is therefore not a fully satisfactory method, and the color tone of the product is also unsatisfactory. [Means for Solving the Problems] The present inventors have discovered that when industrially producing polycarboxylic acid anhydrides, the formation of polymers was observed even at higher temperatures without using the above-mentioned solvents. As a result of intensive study on a method that would not cause the polymer to be oxidized, give a good color, and be easy to control the temperature, the desired objective was achieved by carrying out a Diels-Ander reaction in the coexistence of a phenolic radical polymerization inhibitor and a specific compound. Based on this finding, we have completed the present invention. That is, the present invention is characterized in that when producing a polycarboxylic acid anhydride by subjecting maleic anhydride and a diene component to a Diels-Ander reaction, the reaction is carried out in the coexistence of a phenolic radical polymerization inhibitor and an organic sulfur compound. It is an object of the present invention to provide a novel method for producing polycarboxylic acid anhydride with good yield and no polymer component and excellent hue. In the present invention, the product is an unsaturated alicyclic 1,
Examples of the 2-dicarboxylic anhydride include tedrahydrophthalic anhydride, its alkyl substituted product having 1 to 8 carbon atoms, and the above-mentioned acid anhydride having an endomethylene group. Specifically, Δ ⁴ -tetrahydrophthalic anhydride Acid, 4-methyl- ^Δ4 -tetrahydrophthalic anhydride, 3-methyl- ^Δ4 -tetrahydrophthalic anhydride, 3-ethyl- ^Δ4 -tetrahydrophthalic anhydride, 3,6-dimethyl- ^Δ4 -tetrahydrophthalic anhydride Acid, 4,5-dimethyl-Δ ⁴ -tetrahydrophthalic anhydride, 3,4-dimethyl-Δ ⁴
-Tetrahydrophthalic anhydride, nadicic anhydride, and their alkyl-substituted products, as well as
Related anhydrides derived from the typical Diels-Ander reaction or similar effective reactions are mentioned. Therefore, the diene component according to the present invention is a diene that can produce the above polycarboxylic acid anhydride, and specifically, butadiene, isoprene, trans-1,3-pentadiene, cyclopentadiene, methylcyclopentadiene. , myrcene, alloocymene and the like. Specific examples of the phenolic radical polymerization inhibitor according to the present invention include 2,6-di-tert-butyl-4-methylphenol, 2,6-dicyclopentyl-4-methylphenol, 2,2'- Methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-methylenebis(2,6-di-tert
-butylphenol), 4,4'-thiobis(3-
Methyl-6-tert-butylphenol), hydroquinone, 3,5-di-tert-butylhydroxytoluene, p-tert-butylcatechol, butylhydroxyanisole, and the like. The organic ionic compounds according to the present invention are various compounds that fall into the following categories. (1) General formula, R ¹ -SX-R ² (wherein R ¹ and R ² are alkyl groups having 1 to 20 carbon atoms,
A hydroxycarbonylalkyl group having 1 to 20 carbon atoms, an alkyl ester thereof having 1 to 20 carbon atoms, an allyl group or an aralkyl group which may have a substituent, and x represents an integer of 1 to 3. ) (2) General formula, R ³ CH ₂ C (CH ₂ R ⁵ ) * * (CH ₂ R ⁶ ) (CH ₂ R ⁷ ) (wherein, R ³ is −OCO(CH ₂ )nSR ⁴ , R ⁵ , ^R6 ,
R ⁷ is hydrogen, an alkyl group having 1 to 2 carbon atoms, or -
OCO(CH ₂ ) nSR ⁴ , R ⁴ is hydrogen or has 1 or more carbon atoms
20 alkyl groups, and n represents an integer of 1 to 5. ) (3) cyclic thioethers, (4) trialkyl (1 to 20 carbon atoms) trithiophosphite (5) tetraalkyl (1 to 4 carbon atoms) mono- or polysulfide, specifically dimethyldithiodipropionate, dithiodipropionic acid, alkylthioacetic acid and its esters, alkylthiopropionic acids,
p-aminophenylmercaptoacetic acid, benzylthioacetic acid, butylthiobenzoate, dibenzyl sulfide, dicetylthiodipropionate, N,
N′-diuralylthiodipropionate amide, dilaurylthiodipropionate, dimethylthiodipropionate, diphenyl sulfide, distearylthiodipropionate, didodecylthiodipropionate, methylenebisthioacetic acid, methylene Bispropionic acid, thioanisole, thiodipropionate polyesters, thiodipropionic acid, thiodiacetic acid, dithiodiacetic acid, thiophene,
Examples include 1,4-dithiodiene, among which thiodipropionic acid diester, especially carbon number 4-18
Diesters of aliphatic higher alcohols are preferred. The amounts of these phenolic radical polymerization inhibitors and organic sulfur compounds to be used are not particularly limited, but are usually in the range of 10 to 2000 ppm, preferably 30 to 1000 ppm, respectively, based on the theoretical production amount of acid anhydride. Generally, both are used together in approximately equivalent amounts, but they do not necessarily have to be in equivalent amounts, and the weight ratio of the phenolic radical polymerization inhibitor to the organic sulfur compound can be arbitrarily used within the range of 1:9 to 9:1. In the present invention, usually after melting maleic anhydride, a phenolic radical polymerization inhibitor and an organic sulfur compound are added, and then the amount is at least equimolar to maleic anhydride, preferably 1.0 to 1.0 molar.
This is carried out by adding 1.0 times the molar amount of the diene component. The reaction temperature is 30-150℃, preferably
The reaction is carried out at 40 to 120°C for 0.5 to 20 hours, preferably 0.5 to 10 hours. The diene component used in the present invention may be charged into maleic anhydride as a liquid or gasified. Although it is more industrially preferable to collect and remove non-reactive components and unreacted components continuously during the reaction, there is no problem in carrying out a step in which the entire amount is collected after the reaction is completed. A general implementation method of the present invention is shown below. A predetermined amount of raw materials, a phenolic antioxidant, and an organic sulfur compound are placed in a reactor equipped with a stirrer, a thermometer, a reflux condenser, and an inert gas inlet, and the mixture is heated preferably under an inert gas atmosphere such as nitrogen gas for 30 minutes. ~150
The reaction is carried out at a temperature of preferably 40 to 110°C for 0.5 to 20 hours to obtain the desired product. The polycarboxylic acid anhydride according to the present invention is excellent as an acid component of polyester, and as a curing agent for epoxy resins used as an insulating material for sealing electronic parts, casting electric parts, and impregnating varnish for motor coils. It has the following characteristics. [Example] The present invention will be explained below with reference to Examples and Comparative Examples. Examples 1 to 5 0.2 mol of maleic anhydride was charged into a 100 ml four-necked flask equipped with a stirrer, a thermometer, and a condenser, and a reaction was carried out according to the reaction conditions shown in Table 1. After the reaction was completed, the remaining diene component or unreacted component was removed under reduced pressure to obtain the desired polycarboxylic acid anhydride. The yield in each example and the degree of formation of the polymer component in the resulting polycarboxylic anhydride were determined by visually observing the appearance when dissolved in isopropanol, and the hue when melted was also measured. The obtained results are listed in Table 1. Comparative Examples 1 to 3 A reaction was carried out using a system in which only a radical polymerization inhibitor was added in the same manner as in the example and compared with the example. [Effect of the invention] By using a phenolic radical polymerization inhibitor and an organic sulfur compound together, the organic sulfur compound participates in the phenolic radical polymerization inhibitor as a cocatalyst, resulting in a good color hue and less polymerization. Polycarboxylic acid anhydride can be produced with good yield.

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Claims (1)

[Scope of Claims] 1. When producing a polycarboxylic acid anhydride by subjecting maleic anhydride and a diene component to a Diels-Ander reaction, the reaction is carried out in the coexistence of a phenolic radical polymerization inhibitor and an organic sulfur compound. A method for producing a polycarboxylic acid anhydride, characterized by: 2. Claim 1, wherein the diene component is trans-1,3-pentadiene.
A method for producing a polycarboxylic acid anhydride as described in Section 1.