Peroxyester composition and polymerization initiator

Abstract

To provide a peroxy ester composition excellent in long-term storage stability.SOLUTION: The peroxy ester composition comprises a peroxy ester represented by the specified general formula (1) and an acid anhydride represented by the specified general formula (2), where the content of the acid anhydride is 0.005-5 pts.mass based on 100 pts.mass of the peroxy ester.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a peroxyester composition and a polymerization initiator. [Background technology]

[0002] Generally, organic peroxides generate radicals when heated, etc., and are very useful compounds as polymerization initiators, but on the other hand, there is a possibility that decomposition reactions may occur during storage or transportation. In particular, most peroxyesters are unstable at room temperature, so their stability cannot be maintained for long periods of time unless temperature control is performed, such as by freezing storage.

[0003] Conventionally, several stabilizers have been proposed to improve the storage stability of organic peroxides. For example, Non-Patent Document 1 discloses phenol derivatives, acetanilide, nitro compounds such as trinitrobenzene, or iodine as stabilizers for diisopropyl peroxydicarbonate.

[0004] Furthermore, Patent Document 1 discloses organic hydroperoxides such as 2-hydroperoxy-2,4,4-trimethylpentane and cumene hydroperoxide as stabilizers for peroxydicarbonates, while Patent Document 2 discloses halogenated ethylenes such as trichloroethylene and tetrachloroethylene as stabilizers for organic peroxides consisting of a carboxylic acid group having a tertiary hydrogen atom in the side chain.

[0005] Furthermore, Patent Document 3 discloses an unsaturated nitrile such as methacrylonitrile or an unsaturated acetylenic compound as a stabilizer for dialkyl peroxydicarbonate.

[0006] Patent Document 4 discloses phosphomolybdic acid as a stabilizer for peroxydicarbonates. Furthermore, Patent Document 5 discloses peracetic acid as a stabilizer for diacyl peroxides or peroxydicarbonates. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Journal of the American Chemical Society, Vol. 72, p. 1254 (1950) [Patent documents]

[0008] [Patent Document 1] Japanese Unexamined Patent Publication No. 62-106903 [Patent Document 2] Japanese Patent Application Publication No. 3-294263 [Patent Document 3] US Patent No. 5,548,046 [Patent Document 4] Japanese Patent Application Publication No. 10-59932 [Patent Document 5] JP 2001-151750 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, the compounds used as the stabilizers are intended to capture radicals generated during the decomposition of organic peroxides to suppress deterioration, and if the decomposition of the organic peroxides occurs in an amount greater than the amount of stabilizer added, the stabilizers will not be effective, and therefore the stabilizers cannot fully achieve their effect during long-term storage, resulting in the problem of deterioration of the organic peroxides.

[0010] Furthermore, the above-mentioned patent documents disclose examples of organic peroxides such as peroxydicarbonates, hydroperoxides, and diacyl peroxides, but have not reported anything related to peroxyesters.

[0011] The present invention has been made in view of the above-mentioned problems existing in the prior art, and an object of the present invention is to provide a peroxyester composition having excellent long-term storage stability. [Means for solving the problem]

[0012] That is, the present invention relates to a compound represented by the general formula (1): [ka] (In formula (1), R 1 represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms; R 2 represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.) and a peroxy ester represented by the general formula (2): [ka] (In formula (2), R 3 and R 4 each independently represents an alkyl group having 2 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms.), and the amount of the acid anhydride is 0.005 to 5 parts by mass per 100 parts by mass of the peroxyester.

[0013] The present invention also relates to a polymerization initiator comprising the peroxyester composition. Effect of the Invention

[0014] The peroxyester composition of the present invention can sufficiently improve its long-term storage stability by adding the above-mentioned acid anhydride to the above-mentioned peroxyester. The reason for this is presumed to be as follows. Usually, peroxyester contains a small amount of water of about 0.2% or less during the production process. On the other hand, the above-mentioned acid anhydride is hardly soluble in water, and therefore does not become an acid in the organic phase. However, since the above-mentioned acid anhydride has a polar distribution in the molecule, it is considered that the water in the peroxyester composition is captured near the acid anhydride molecule. Therefore, the presence of the acid anhydride suppresses hydrolysis of the peroxyester, and therefore the peroxyester composition of the present invention has excellent storage stability.

[0015] In particular, the peroxyester composition of the present invention has excellent storage stability even in a state where the peroxyester molecules are easily decomposed due to increased interactions between them (for example, a state where the peroxyester is in a liquid state or in a state where it has become a homogeneous liquid by dilution with an organic solvent, etc.) Furthermore, the peroxyester composition of the present invention is useful when used as a polymerization initiator for vinyl monomers because it does not adversely affect polymerization characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] <Peroxy ester> The peroxyester of the present invention is represented by the following general formula (1). [ka] (In formula (1), R 1 represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms; R 2 represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

[0017] In general formula (1), R 1 R is an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms, and among these, a methyl group, an ethyl group, a normal propyl group, a 2,2-dimethylpropyl group, and a phenyl group are preferable. 2 represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and among these, a methyl group, a t-butyl group, a 1-ethylpentyl group, a 2,4,4-trimethylpentyl group, a 1,1-dimethylheptyl group, an undecyl group, a phenyl group, an isopropoxy group, or a 2-ethylhexyloxy group is preferred.

[0018] Examples of the peroxy ester include t-butyl peroxyacetate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxyneodecanoate, t-butyl peroxylaurate, t-butyl peroxybenzoate, t-hexyl peroxypivalate, t-hexyl peroxyisopropyl monocarbonate, t-hexyl peroxy-2-ethylhexanoate, t-hexyl peroxyneodecanoate, t-hexyl peroxybenzoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, and cumyl peroxyneodecanoate.

[0019] The 10-hour half-life temperature of the peroxyester is preferably 20° C. to 110° C., and more preferably 30° C. to 105° C. The 10-hour half-life temperature means the decomposition temperature at which the half-life is 10 hours.

[0020] The peroxyester can be obtained by a known technique, for example, by reacting a hydroperoxide with a halogenated carboxylic acid or an acid anhydride in the presence of an alkali.

[0021] <Acid anhydride> The acid anhydride of the present invention is represented by the following general formula (2). [ka] (In formula (2), R 3 and R 4 each independently represents an alkyl group having 2 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms.)

[0022] In general formula (2), R 3 and R 4are each independently an alkyl group having 2 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, and among these, a t-butyl group, a 1-ethylpentyl group, a 2,4,4-trimethylpentyl group, a 1,1-dimethylheptyl group, an undecyl group, and a phenyl group are preferred.

[0023] Examples of the acid anhydride include propionic anhydride, butyric anhydride, pivalic anhydride, valeric acid, hexanoic anhydride, octylic anhydride, nonanoic anhydride, decanoic anhydride, undecanoic anhydride, neodecanoic anhydride, benzoic anhydride, etc. These may be used alone or in combination of two or more.

[0024] The acid anhydride can be obtained by dehydration condensation of the corresponding carboxylic acid, and a commercially available reagent may be used.

[0025] <Peroxyester Composition> The peroxyester composition of the present invention contains the peroxyester and the acid anhydride, and the amount of the acid anhydride is 0.005 to 5 parts by mass per 100 parts by mass of the peroxyester.

[0026] From the viewpoint of improving storage stability, the amount of the acid anhydride is preferably 0.008 parts by mass or more, more preferably 0.01 parts by mass or more, and is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, relative to 100 parts by mass of the peroxy ester.

[0027] The peroxyester composition of the present invention may contain an organic solvent as a diluent. Examples of the organic solvent include hydrocarbon solvents, aromatic hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, perfluorocarbon solvents, hydrochlorofluorocarbon solvents, hydrofluorocarbon solvents, hydrofluoroether solvents, and hydrofluoroolefin solvents. These may be used alone or in combination of two or more.

[0028] When using the organic solvent, the proportion of the organic solvent is preferably about 10% to 70% by mass, more preferably about 20% to 60% by mass, in the peroxyester composition.

[0029] The peroxyester composition is useful as a polymerization initiator for polymerizing or copolymerizing vinyl monomers. Examples of the polymerization or copolymerization method in that case include bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc.

[0030] As the vinyl monomer, any known one can be used, and examples include vinyl chloride, vinylidene chloride, vinylidene fluoride, ethylene, styrene, vinyl acetate, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, etc. Also, the addition amount of the peroxide is usually about 0.01 to 3 parts by mass with respect to 100 parts by mass of the vinyl monomer.

Examples

[0031] Next, the present invention will be specifically described by way of Examples, Comparative Examples and Reference Examples, but the present invention is not limited to the following Examples.

[0032] <Synthesis Example 1> <Synthesis of t-butyl peroxypivalate> 92.6 g of 70% t-butyl hydroperoxide and 111.0 g of 25% sodium hydroxide solution were added to a 300 mL four-necked round-bottom flask. While further stirring the mixed solution with a stir bar, 64.3 g of pivalic acid chloride was added dropwise at 25 °C over 60 minutes, and then reacted at 27 °C for 70 minutes. After completion of the reaction, the oil phase and the aqueous phase were separated using a 300 mL separatory funnel. The obtained oil phase was washed once with 5% aqueous sodium hydroxide solution equal in amount to the chemical solution, then once with a buffer washing solution (a mixed solution of 10% sodium sulfite, 5% glacial acetic acid, and 85% water) equal in amount to the chemical solution, and then twice with water equal in amount to the chemical solution. After dehydration using a dehydrating agent, suction filtration was performed to obtain 92.1 g of t-butyl peroxypivalate. The active oxygen content of the obtained solution was 9.01%, the purity was 98.1%, and it contained 0.2 mass% or less of water.

[0033] <Synthesis Example 2> <Synthesis of t-butylperoxy-2-ethylhexanoate> t-Butylperoxy-2-ethylhexanoate with a purity of 98.0% was obtained by the same procedure as in Synthesis Example 1, except that 75.6 g of octanoic acid chloride was used instead of 64.3 g of pivalic acid chloride in Synthesis Example 1.

[0034] <Synthesis Example 3> <Synthesis of t-butylperoxylaurate> t-Butylperoxylaurate with a purity of 98.3% was obtained by the same procedure as in Synthesis Example 1, except that 80.2 g of lauric acid chloride was used instead of 64.3 g of pivalic acid chloride in Synthesis Example 1.

[0035] <Synthesis Example 4> <Synthesis of t-butylperoxybenzoate> t-Butylperoxybenzoate with a purity of 97.9% was obtained by the same procedure as in Synthesis Example 1, except that 82.4 g of benzoyl chloride was used instead of 64.3 g of pivalic acid chloride in Synthesis Example 1.

[0036] <Synthesis Example 5> <Synthesis of t-Hexyl Peroxy-2-ethylhexanoate> t-Hexyl hydroperoxide (76.4 g) was used instead of 92.6 g of t-butyl hydroperoxide in Synthesis Example 1, and octanoic acid chloride (64.6 g) was used instead of 64.3 g of pivalic acid chloride. Otherwise, the same procedure as in Synthesis Example 1 was carried out to obtain t-hexyl peroxy-2-ethylhexanoate with a purity of 93.0%.

[0037] <Synthesis Example 6> <Synthesis of 1,1,3,3-Tetramethylbutyl Peroxy-2-ethylhexanoate> 1,1,3,3-Tetramethylbutyl hydroperoxide (85.3 g) was used instead of 92.6 g of t-butyl hydroperoxide in Synthesis Example 1, and octanoic acid chloride (79.3 g) was used instead of 64.3 g of pivalic acid chloride. Otherwise, the same procedure as in Synthesis Example 1 was carried out to obtain 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate with a purity of 94.3%.

[0038] <Synthesis Example 7> <Synthesis of Cumyl Peroxyneodecanoate> Cumyl hydroperoxide (64.3 g) was used instead of 92.6 g of t-butyl hydroperoxide in Synthesis Example 1, and neodecanoic acid chloride (59.8 g) was used instead of 64.3 g of pivalic acid chloride. Otherwise, the same procedure as in Synthesis Example 1 was carried out to obtain cumyl peroxyneodecanoate with a purity of 86.6%.

[0039] <Example 1> <Preparation of Peroxyester Composition> 0.01 g of pivalic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to 100 g of t-butyl peroxypivalate and mixed to obtain a peroxyester composition. The following evaluations were performed on the obtained peroxyester composition. The results are shown in Table 3.

[0040] <Storage Stability Test> The peroxyester composition prepared above was stored in a sealed glass container maintained at a specified temperature, and the purity retention rate was measured after 90 days and 180 days to evaluate storage stability. The purity retention rate is an index for measuring deterioration relative to the initial purity, and was calculated using the following formula. The purity was calculated from the theoretical amount of active oxygen by measuring the amount of active oxygen.

number

[0041] <Measurement of active oxygen> 50mL of isopropanol, 5mL of glacial acetic acid, and 5mL of saturated potassium iodide solution were placed in a 300mL flask. 0.3g of sample was then weighed out and placed in the flask, a reflux condenser was attached, and the mixture was boiled for 3 minutes. After that, the mixture was titrated with 1 / 10N sodium thiosulfate solution until the color disappeared, and the amount of active oxygen (Act.O) was calculated.

[0042] <Examples 2 to 13 and Comparative Examples 1 to 5> Peroxyester compositions of Examples 2 to 13 and Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that peroxyester and acid anhydride or additives were used in the composition ratios shown in Table 1. The obtained peroxyester compositions were evaluated as described above. The results are shown in Table 3.

[0043] <Example 14> A peroxyester composition was obtained by mixing 75 g of the peroxyester composition of Example 1 with 25 g of Merveille 30 (manufactured by Showa Cell Sekiyu Co., Ltd.) as an organic solvent. The obtained peroxyester composition was subjected to the above evaluations. The results are shown in Table 3.

[0044] <Examples 15 to 20> The peroxyester compositions of Examples 15 to 20 were obtained in the same manner as in Example 14, except that the peroxyester composition and the organic solvent were used in the composition ratios shown in Table 2. The obtained peroxyester compositions were evaluated as described above. The results are shown in Table 3.

[0045] [Table 1]

[0046] [Table 2]

[0047] The organic solvents in Table 2 are Merveille 30: Hydrocarbon solvent manufactured by Showa Cell Sekiyu Co., Ltd.; Asahiklin AE-3000: AGC Corporation, hydrofluoroether solvent;

[0048] [Table 3]

[0049] From the results in Table 3, good storage stability was shown in all of Examples 1 to 13. Furthermore, in Examples 14 to 20, in which a certain amount of organic solvent was mixed, no significant difference due to the dilution solvent was observed, and good storage stability was also shown.

[0050] In Comparative Example 1, which did not contain acid anhydride, the retention rate fell below 95% after 180 days. In Comparative Example 2, which contained a larger amount of acid anhydride, the retention rate fell below 95% after 180 days. It is believed that the addition of an excess of acid anhydride promoted polarization in the solution, destabilizing the peroxyester.

[0051] Even in Comparative Example 3, in which an acid anhydride with a long alkyl side chain was used, the retention rate fell below 95% after 180 days. This is thought to be because the alkyl chain of the acid anhydride surrounds the polar carbonyl group, and the steric hindrance prevents water capture.

[0052] In Comparative Example 4, which used aniline as an additive, the retention rate fell below 95% after 90 days, and further fell below 90% after 180 days. Aniline is a weakly basic organic substance, so it easily donates electrons to other substances in the vicinity, leading to the decomposition of peroxyester. This is thought to be the reason for the significant drop in retention rate and the decrease in storage stability.

[0053] In Comparative Example 5, which uses peracetic acid as described in Patent Document 5, the retention rate after 180 days was below 95%, and no improvement in long-term storage stability was observed. This is because peracetic acid captures radicals generated when peroxyester decomposes, and when more peroxyester than the added peracetic acid decomposes, the decomposition proceeds in a chain reaction without being able to capture all the radicals.

[0054] <Reference example> <Synthesis of copolymer 1> Using a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube and a cooling tube, 250 parts by mass of t-amyl alcohol as an organic solvent was heated to 80° C. while blowing in nitrogen gas. The following solution (a) (a solution in which 50 parts by mass of methyl methacrylate, 40 parts by mass of butyl acrylate, and 10 parts by mass of 2-hydroxyacrylate were mixed) and solution (b) (a solution in which 0.4 parts by mass of the peroxyester composition (radical polymerization initiator) shown in Example 1 was dissolved in 20 parts by mass of t-amyl alcohol) were dropped into this reaction vessel over 2 hours. After dropping, the mixture was stirred for 1 hour to obtain a solution of copolymer (A). The polymerization conversion rate of the charged monomer of copolymer (A) measured by gas chromatography was 95%. The weight average molecular weight of the copolymer measured by gel permeation chromatography was 95,000.

[0055] <Synthesis of copolymer 2> A solution of copolymer (B) was obtained by the same procedure as in copolymer synthesis 1, except that solution (b) was changed to solution (b') (a solution obtained by dissolving 0.4 parts by mass of the peroxyester composition (radical polymerization initiator) shown in Comparative Example 2 in 20 parts by mass of t-amyl alcohol). The polymerization conversion rate of the charged monomers of copolymer (B) measured by gas chromatography was 75%. In addition, the weight average molecular weight of copolymer (B) measured by gel permeation chromatography was 40,000. It can be seen that when the peroxyester composition contains more than a certain amount of acid anhydride as in Comparative Example 2, the ion concentration in the polymerization system changes, causing a hindrance to the polymerization reaction.

Claims

1. General formula (1): 【Chemistry 1】 (In formula (1), R １ represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms; R ２ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms; General formula (2): 【Chemistry 2】 (In formula (2), R ３ and R ４ each independently represents an alkyl group having 2 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms; A peroxyester composition, characterized in that the acid anhydride is contained in an amount of 0.005 to 5 parts by mass per 100 parts by mass of the peroxyester.

2. 2. The peroxyester composition of claim 1, further comprising an organic solvent.

3. A polymerization initiator comprising the peroxyester composition according to claim 1 or 2.

Images