Organic peroxide, polymerizable composition, and (meth)acrylate polymer

Abstract

To provide an organic peroxide capable of forming a (meth)acrylic acid ester polymer excellent in heat resistance.SOLUTION: The organic peroxide is represented by the general formula (1) in the figure, where m represents an integer from 1 to 5, and n represents an integer from 1 to 3.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an organic peroxide, a polymerizable composition, and a (meth)acrylate polymer.

Background Art

[0002] (Meth)acrylate polymers are widely used in the fields of automobiles, building materials, household appliances, and optical materials because they have excellent transparency and weather resistance, and a good balance of various physical properties such as mechanical strength, heat resistance, and color development properties. For example, in the automotive field, they are used for automotive parts such as meter covers and tail lamps, as well as decorative films for automotive interior materials, and are required to be compatible with various molding methods.

[0003] For the polymerization of (meth)acrylate polymers, organic peroxides and azo compounds are used as polymerization initiators. In Patent Document 1, a method for producing a methacrylate resin having a high heat resistance temperature is proposed by using a specific peroxyester as a polymerization initiator, since the weight loss at 230 ° C is 2% or less.

[0004] In Patent Document 2, a method for producing a methacrylate resin having excellent heat-induced foaming suppression properties is proposed by using a specific peroxyester as a polymerization initiator, since it has a specific weight average molecular weight and the DTG value at 220 ° C measured by differential thermogravimetric analysis (DTG) is 0.015% / ° C or less.

[0005] In Patent Document 3, a method for producing a (meth)acrylate resin having a low yellowness index even at a temperature up to 150 ° C is proposed by using a peroxyketal having a cyclic structure as a polymerization initiator.

[0006] In Patent Document 4, a method for producing a methacrylate-based material having excellent heat resistance and not generating cracks on the surface even in a use environment of 200 ° C is proposed by using an azo compound having an acyclic hydrocarbon group as a polymerization initiator.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] Generally, the molding temperature of a (meth)acrylate polymer is 160 to 260°C, and for further expansion of the field of use, heat resistance in this temperature range is required. Therefore, in the production methods of the (meth)acrylate-based resins disclosed in the above patent documents, there is room for improvement regarding the heat resistance of the (meth)acrylate polymer.

[0009] An object of the present invention is to provide an organic peroxide from which a (meth)acrylate polymer excellent in heat resistance can be obtained.

Means for Solving the Problems

[0010] That is, the present invention relates to an organic peroxide represented by the general formula (1):

Chemical Formula

[0011] Further, the present invention relates to a polymerizable composition containing the organic peroxide and a (meth)acrylate. Furthermore, the present invention relates to a (meth)acrylate polymer obtained from the polymerizable composition.

Effects of the Invention

[0012] The organic peroxide represented by the general formula (1) of the present invention has a cyclic hydrocarbon group at the molecular terminal. Therefore, in the (meth)acrylate polymer obtained by using this, a cyclic hydrocarbon group derived from the organic peroxide can be introduced at the terminal of the polymer, so that the heat resistance can be further improved compared with the conventional (meth)acrylate polymer. Although the reason for the improvement in the heat resistance of the (meth)acrylate polymer is not clear, it is presumed that the thermal decomposition of the (meth)acrylate polymer is reduced because the thermal motility at the terminal of the (meth)acrylate polymer is suppressed in the heating state. Further, since the organic peroxide has a diacyl structure, it is presumed that the above effect can be obtained because the polymer has a bulky cyclic hydrocarbon group at the terminal.

Embodiments for Carrying Out the Invention

[0013] <Organic Peroxide> The organic peroxide of the present invention is represented by the following general formula (1).

Chemical Formula

[0014] Examples of the organic peroxide represented by the general formula (1) include di(cyclopropylacetyl)peroxide (m = 1, n = 1), di(cyclobutylacetyl)peroxide (m = 2, n = 1), di(cyclopentylacetyl)peroxide (m = 3, n = 1), di(cyclohexylacetyl)peroxide (m = 4, n = 1), di(cycloheptylacetyl)peroxide (m = 5, n = 1), di(3-cyclopropylpropionyl)peroxide (m = 1, n = 2), di(3-cyclobutylpropionyl)peroxide (m = 2, n = 2), di(3-cyclopentylpropionyl)peroxide (m = 3, n = 2), di(3-cyclohexylpropionyl)peroxide (m = 4, n = 2), di(3-cycloheptylpropionyl)peroxide (m = 5, n = 2), di(4-cyclopropylbutanoyl)peroxide (m = 1, n = 3), di(4-cyclobutylbutanoyl)peroxide (m = 2, n = 3), di(4-cyclopentylbutanoyl)peroxide (m = 3, n = 3), di(4-cyclohexylbutanoyl)peroxide (m = 4, n = 3), di(4-cycloheptylbutanoyl)peroxide (m = 5, n = 3). Among these, it is preferable that m is from 3 to 4 and n is from 1 to 3, and it is particularly preferable that m is 4 and n is 2.

[0015] <Method for producing organic peroxide> Examples of the method for producing the organic peroxide include reacting a peroxide with an acid chloride having a cyclic hydrocarbon group (such as 3-cyclohexylpropionyl chloride, 4-cyclohexylbutyryl chloride, etc.) in the presence of an alkali. Also, from the viewpoint of safety, the reaction may be carried out in the presence of an organic solvent. Note that after the reaction, a purification step may be included.

[0016] The peroxide is hydrogen peroxide, sodium peroxide, potassium peroxide, etc., and preferably hydrogen peroxide. The concentration of the hydrogen peroxide solution is not particularly limited, and it is preferably in the range of 20 to 65%.

[0017] As the alkali, an aqueous solution of an alkali metal hydroxide can be used. Sodium hydroxide and potassium hydroxide are preferred, and sodium hydroxide is more preferred. The concentration of the alkali is preferably 6% to 16%, and more preferably 8% to 14%.

[0018] The usage amounts of the peroxide and the alkali with respect to the acid chloride are preferably, for example, in the range of 0.5 to 1.5 mol of the peroxide and 1.0 to 3.0 mol of the alkali per 1 mol of the acid chloride.

[0019] As the organic solvent, hydrocarbon solvents such as benzene, toluene, chlorobenzene, o-dichlorobenzene, nitrobenzene, methanol, hexane, cyclohexane, and isoparaffin can be used. The organic solvent may be added after the reaction to improve safety.

[0020] In the above reaction, from the viewpoint of increasing the yield of the target product, the reaction temperature is preferably from -20°C to 40°C, and more preferably from 10°C to 30°C. The reaction time varies depending on the raw materials, reaction temperature, etc. and cannot be determined unconditionally. Usually, from the viewpoint of increasing the yield of the target product, it is preferably from 5 minutes to 180 minutes, and more preferably from 30 minutes to 120 minutes.

[0021] The purification step of the above reaction includes, for example, a step of washing with ion-exchanged water or an aqueous sodium chloride solution to remove excess raw materials and by-products and purify the target product. In addition, for the organic peroxide represented by the general formula (1), the content (active oxygen amount) of the peroxide group can be determined by measuring the active oxygen by iodometry.

[0022] <Polymerizable composition> The polymerizable composition of the present invention contains the organic peroxide represented by the general formula (1) and a (meth)acrylate ester.

[0023] The above (meth)acrylic acid ester is used as a monomer. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol (meth)acrylate, hydroxyphenyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, ethylene oxide adduct of (meth)acrylic acid, etc. may be mentioned. Preferably, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate having an alkyl group structure, more preferably methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate having an alkyl group structure with 4 or less carbon atoms, and even more preferably methyl (meth)acrylate. The (meth)acrylic acid ester may be used alone or in combination of two or more. Note that "(meth)acrylic acid ester" means at least one selected from "acrylic acid ester" and "methacrylic acid ester".

[0024] The organic peroxide represented by the general formula (1) is preferably 0.03 to 20 parts by mass, more preferably 0.1 to 10 parts by mass in terms of pure product based on 100 parts by mass of the (meth)acrylic acid ester.

[0025] <Other organic peroxides> For the purpose of improving productivity and the like, the polymerizable composition of the present invention can use organic peroxides other than the organic peroxide represented by the general formula (1). Other organic peroxides are not particularly limited, and those generally used in this field can be used, but an oil-soluble polymerization initiator that can be dissolved in the polymerizable composition is preferred.

[0026] Examples of the other organic peroxides include peroxydicarbonates such as bis-(4-t-butylcyclohexyl) peroxydicarbonate, diacyl peroxides such as di(3,5,5-trimethylhexanoyl) peroxide, peroxyesters such as t-butyl peroxy-2-ethylhexanoate and 1-cyclohexyl-1-methylethyl peroxyneodecanoate, peroxymonocarbonates such as t-butyl peroxy 2-ethylhexyl monocarbonate, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane, dialkyl peroxides such as α,α'-bis(t-butylperoxy)diisopropylbenzene, hydroperoxides such as cumene hydroperoxide, and azo compounds such as 2,2'-azobis(2-methylbutyronitrile). The other described organic peroxides can be used alone or in combination of two or more. The amount of the other organic peroxide used is not particularly limited, but it is less than the amount of the organic peroxide represented by the general formula (1) and can be used within a range that does not impair the effects of the present invention.

[0027] <Other Components> The polymerizable composition of the present invention can contain components other than organic peroxides as other components. Examples of other components include chain transfer agents (such as n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate, etc.), antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, mold release agents (mold release agents such as alcohols, esters of alcohols and fatty acids, esters of alcohols and dicarboxylic acids, silicone oils, etc.), dyes (such as nitroso dyes, nitro dyes, azo dyes, stilbene azo dyes, ketoimine dyes, triphenylmethane dyes, xanthene dyes, acridine dyes, quinoline dyes, etc.), pigments (organic pigments, inorganic pigments, etc.), fillers (such as glass fibers, carbon fibers, glass beads, calcium carbonate, talc, etc.), dispersants, and the like. The other components can be used alone or in combination of two or more. The amount of the other components used is not particularly limited, but can be used within a range that does not impair the effects of the present invention, and is usually about 5 parts by mass or less with respect to 100 parts by mass of the (meth)acrylate.

[0028] <Method for producing polymerizable composition> The polymerizable composition of the present invention can be produced by mixing the above components. The mixing method is not particularly limited, and all components can be mixed simultaneously, or each component can be dissolved sequentially. The order of dissolution and working conditions are not particularly limited, and it can be produced by a known method.

[0029] <(Meth)acrylate polymer> The (meth)acrylate polymer of the present invention is obtained by heating and polymerizing the above polymerizable composition.

[0030] The (meth)acrylate polymer of the present invention preferably has a 5% weight loss temperature measured at a heating rate of 10 °C / min of 240 °C or higher, more preferably 250 °C or higher, as an index of thermal stability for withstanding heating during injection molding.

[0031] Any of the known polymerization methods can be used for the above polymerization, and examples thereof include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and the like. Further, as one of the methods for producing a (meth)acrylic acid ester polymer, a method for producing an acrylic syrup in which a part of the (meth)acrylic acid ester is polymerized is known. The acrylic syrup is obtained by polymerizing a part of the polymerizable raw material, and the polymer content in the acrylic syrup is in the range of 15 to 60%. Supplying the polymerizable raw material in the form of an acrylic syrup to a mold can shorten the polymerization time and improve productivity, which is preferable. Further, since it has viscosity, workability and operability are good. As a method for obtaining an acrylic syrup, from the viewpoint of productivity, a bulk polymerization method using a radical polymerization method is suitable.

[0032] The above polymerization temperature is set according to the 1-hour half-life temperature of the organic peroxide represented by the general formula (1), and is usually appropriately set in the range of 10 to 150°C. The polymerization time is usually 0.5 to 24 hours, preferably 0.5 to 12 hours.

[0033] The weight average molecular weight (Mw) of the (meth)acrylic acid ester polymer is usually 2,000 to 2 million, preferably 7,000 to 1 million. When the weight average molecular weight of the (meth)acrylic acid ester polymer is within the above range, it becomes easy to heat and dissolve the (meth)acrylic acid ester polymer and process it into a film or the like, and the heat resistance of the (meth)acrylic acid ester polymer is also good.

Examples

[0034] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[0035] The abbreviations of the organic peroxides or polymerization initiators used in the examples mean the following compounds. c-HPPO: Di(3-cyclohexylpropionyl)peroxide (concentration 54%, diluted with a hydrocarbon solvent) c-HBPO: Di(4-cyclohexylbutanoyl)peroxide (concentration 52%, diluted with a hydrocarbon solvent) c-PAPO: Di(cyclopentylacetyl) peroxide (concentration 50%, diluted with hydrocarbon solvent) 355: Di(3,5,5-trimethylhexanoyl) peroxide (concentration 75%, diluted with hydrocarbon solvent, product name: Peroyl 355 / manufactured by NOF Corporation) BPO: Dibenzoyl peroxide (concentration 75%, water-containing product, product name: Nippo BW / manufactured by NOF Corporation) BND: t-Butyl peroxyneodecanoate (concentration 75%, diluted with hydrocarbon solvent, product name: Perbutyl ND / manufactured by NOF Corporation) OcO: 1,1,3,3-Tetramethylbutyl peroxy-2-ethylhexanoate (concentration 95% product, product name: Perocta O / manufactured by NOF Corporation) TCP: Di(4-t-butylcyclohexyl) peroxydicarbonate (concentration 96% product, product name: Peroyl TCP / manufactured by NOF Corporation) HxC: 1,1-Di(t-butylperoxy) cyclohexane (concentration 80%, diluted with hydrocarbon solvent, product name: Perhexa C / manufactured by NOF Corporation) ADVN: 2,2′-Azobis-2,4-dimethylvaleronitrile (concentration 95% product, product name: V-65 / manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0036] <Synthesis of Organic Peroxides> <Synthesis Example 1: Synthesis of c-HPPO> Into a 100 mL three-necked flask, 50.6 g (0.13 mol) of 10% NaOH and 14.0 g of toluene were added. While maintaining the liquid temperature at 15 °C under stirring, 3.1 g (0.050 mol) of 60% H2O2 was added. Further, while maintaining the liquid temperature at 15 °C under stirring, 17.5 g (0.10 mol) of 3-cyclohexylpropionyl chloride was added dropwise over 30 minutes. After continuing stirring for 1.5 hours while maintaining the liquid temperature at 15 °C, the aqueous phase was separated, and the organic phase was washed three times with 28 g of 3.3% aqueous sodium chloride solution. This solution (organic phase) was dehydrated with anhydrous sodium sulfate and anhydrous magnesium sulfate to obtain 19.3 g of c-HPPO. The active oxygen content was 2.76%, and the c-HPPO concentration was 54% by calculation. 1H-NMR (400 Hz, CDCl3): δ = 2.43 (t, 4H), 1.54 - 1.72 (m, 14H), 1.12 - 1.30 (m, 8H), 0.86 - 0.94 (m, 4H).

[0037] <Synthesis Example 2: Synthesis of c-HBPO> Into a 100 mL three-necked flask, 50.6 g (0.13 mol) of 10% NaOH and 15.1 g of toluene were added. While maintaining the liquid temperature at 15 °C with stirring, 3.08 g (0.050 mol) of 60% H2O2 was added. Further, while maintaining the liquid temperature at 15 °C with stirring, 18.9 g (0.10 mol) of 4-cyclohexylbutanoyl chloride was added dropwise over 30 minutes. After continuing stirring for 1.5 hours while maintaining the liquid temperature at 15 °C, the aqueous phase was separated, and the organic phase was washed three times with 28 g of a 3.3% aqueous sodium chloride solution. This solution (organic phase) was dehydrated with sodium sulfate and magnesium sulfate to obtain 18.2 g of c-HBPO. The active oxygen content was 2.47%, and the concentration was 52% by calculation. 1 H-NMR (400 Hz, CDCl3): δ = 2.32 (t, 4H), 1.60 - 1.75 (m, 14H), 1.10 - 1.30 (m, 12H), 0.85 - 0.94 (m, 4H).

[0038] <Synthesis Example 3: Synthesis of c-PAPO> Into a 100 mL three-necked flask, 50.6 g (0.13 mol) of 10% NaOH and 11.7 g of toluene were added. While maintaining the liquid temperature at 15 °C with stirring, 3.1 g (0.050 mol) of 60% H2O2 was added. Further, while maintaining the liquid temperature at 15 °C with stirring, 14.7 g (0.10 mol) of cyclopentylacetyl chloride was added dropwise over 30 minutes. After continuing stirring for 1.5 hours while maintaining the liquid temperature at 15 °C, the aqueous phase was separated, and the organic phase was washed three times with 28 g of a 3.3% aqueous sodium chloride solution. This solution (organic phase) was dehydrated with sodium sulfate and magnesium sulfate to obtain 17.5 g of c-PAPO. The active oxygen content was 3.15%, and the concentration was 50% by calculation. 1H-NMR (400 Hz, CDCl3): δ = 2.36 (t, 4H), 2.21 - 2.24 (m, 2H), 1.81 - 1.86 (m, 4H), 1.54 - 1.65 (m, 8H), 1.15 - 1.20 (m, 4H).

[0039] <Example 1> Using a test tube with a capacity of 6 ml, 3.0 g of methyl methacrylate (manufactured by Kuraray Co., Ltd., methyl methacrylate purity 99.8%) was put in, and as an organic peroxide, 0.06 g of c-HPPO (Synthesis Example 1) was charged to prepare a polymerizable composition. The inside of the test tube was purged with nitrogen to create a nitrogen atmosphere. The temperature inside the test tube was raised to 70°C and reacted for 1 hour to obtain a polymer. Next, 2.0 g of the pulverized polymer (polymer containing residual monomers) and 10 ml of tetrahydrofuran were put in and dissolved. The dissolved polymer was dropped into 300 ml of stirred hexane. It was separated by filtration from hexane and dried in a vacuum dryer at 60°C for 3 hours to obtain a polymer powder (polymer from which residual monomers were removed).

[0040] <Examples 2 - 3, Comparative Examples 1 - 6> In each of the examples and comparative examples, polymerization was carried out in the same manner as in Example 1 except that the organic peroxide used in the polymerization in Example 1, its addition amount, polymerization temperature, and polymerization time were changed as described in Table 1, and pulverized polymers (polymers containing residual monomers) and polymer powders (polymers from which residual monomers were removed) were obtained.

[0041] <Evaluation Method> The evaluation in each of the examples and comparative examples was carried out by the following method. The results are shown in Table 1.

[0042] <Polymerization Conversion Rate> To confirm that the target polymerization reaction was achieved, the polymerization conversion rate was calculated. If the polymerization conversion rate is 90 or higher, it can be determined that the target polymerization reaction was achieved. Specifically, 0.1 g of the pulverized polymer obtained above was added with 2 mL of tetrahydrofuran (manufactured by FUJIFILM Wako Pure Chemical Corporation) and 0.01 g of cumene (manufactured by FUJIFILM Wako Pure Chemical Corporation) as an internal standard substance, and then dissolved. 10 mL of hexane (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added to the dissolved solution, and the supernatant was filtered through a membrane filter (0.45 μm). The filtrate was measured by gas chromatography (GC-2014, manufactured by Shimadzu Corporation), and the polymerization conversion rate was calculated from the amount of residual monomer.

[0043] <Weight-average molecular weight> To confirm that the target polymer was obtained, the polymerization average molecular weight was measured. If the weight-average molecular weight is between 2,000 and 2 million, it was considered the target polymer. Specifically, 10 mg of the polymer powder obtained above was dissolved in 5.0 g of tetrahydrofuran, filtered through a 0.45-μm membrane filter, and a sample solution was obtained. For the obtained sample solution, the weight-average molecular weight was measured using gel permeation chromatography. <Measurement of weight-average molecular weight> Column: Two TSKgel SuperMultipore HZ-M columns connected in series Column size: 4.6 mm I.D. × 15 cm Eluent: Tetrahydrofuran Flow rate: 1.0 mL / min Detector: Differential refractometer (RI) Column temperature: 40 °C Standard sample: Polystyrene

[0044] <5% weight loss temperature> As an index of the heat resistance of the polymer, the 5% weight loss temperature was calculated. Specifically, using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA6200, manufactured by Hitachi High-Tech Science Corporation), the thermogravimetric reduction curve in the temperature range from 40°C to 450°C was measured at a heating rate of 10°C / min in a nitrogen atmosphere (200 ml / min), and the temperature at which 5 mg of the polymer powder obtained above lost 5% of its weight was calculated. A value of 240°C or higher was taken as the passing criterion.

[0045] <Haze value> As an index of transparency, the haze value (%) of a test piece (thickness: 0.3 mm) was measured in accordance with JIS K 7136 using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.). Those with a haze value of 0.3% or less were considered qualified (evaluation ○), and those exceeding 0.3% were considered unqualified (evaluation ×). The test pieces used for measuring the haze value were prepared as follows. <Preparation of test piece> The polymer powder obtained above was molded using a compression molding machine to create a test piece that was 50 mm × 50 mm square and 0.3 mm thick. For the pressing process, a press machine at 210°C (NSF-100 type single-action compression molding machine, manufactured by Kando Metal Works, Ltd.) was used. First, it was heated for 5 minutes as preheating, and then held under a pressure of approximately 2 Mpa for 3 minutes. Subsequently, it was held under a pressure of approximately 13 Mpa for 1 minute. Furthermore, the molded sheet was removed from the press machine while being sandwiched between iron plates, and the sheet was cooled on a cooling plate for 5 minutes to obtain the test piece.

[0046]

Table 1

[0047] In Examples 1 to 3, since the 5% weight loss temperature was high, it was revealed that the (meth)acrylate polymer had high heat resistance.

[0048] In Comparative Example 1, when a diacyl peroxide (355) having an acyclic hydrocarbon group, which has the same number of carbon atoms as c-HPPO in Example 1, was used, the resulting (meth)acrylate polymer had poor heat resistance.

[0049] In Comparative Example 2, although a diacyl peroxide having a hydrocarbon group with a cyclic structure was used, when a diacyl peroxide (BPO) having an aromatic group was used, the obtained (meth)acrylate polymer had poor heat resistance. Also, a part of the (meth)acrylate polymer generated monomers by thermal decomposition, and the monomers became gas components, causing the resin to turn white and impairing the transparency.

[0050] In Comparative Examples 3 and 4, when peroxyesters (BND and OcO) having a hydrocarbon group with an acyclic structure were used, the obtained (meth)acrylate polymer had poor heat resistance. Also, a part of the (meth)acrylate polymer generated monomers by thermal decomposition, and the monomers became gas components, causing the resin to turn white and impairing the transparency.

[0051] In Comparative Example 5, since the bonding form of the fragment of the polymerization initiator introduced at the end of the polymer was different from that of the organic peroxide represented by the general formula (1), the obtained (meth)acrylate polymer had poor heat resistance.

[0052] In Comparative Example 6, when the peroxide bond of the peroxyketal decomposed during polymerization, the cyclic structure was ring-opened by β-cleavage and the cyclic structure was not introduced at the end of the polymer. Therefore, the obtained (meth)acrylate polymer had poor heat resistance.

[0053] In Comparative Example 7, when an azo compound having a hydrocarbon group with an acyclic structure was used, the obtained (meth)acrylate polymer had poor heat resistance.

Claims

**Claim 1** General formula (1): 【Chemical 1】 (In formula (1), m represents an integer of 4 or 5, and n represents an integer of 1 to 3.) An organic peroxide characterized by being represented by the formula. **Claim 2** A polymerizable composition comprising the organic peroxide according to Claim 1 and a (meth)acrylic acid ester. **Claim 3** General formula (1): 【Chemical 2】 (In formula (1), m represents an integer of 3, and n represents an integer of 1 to 3.) A polymerizable composition comprising an organic peroxide represented by the formula and a (meth)acrylic acid ester. **Claim 4** The polymerizable composition according to Claim 2 or 3, wherein the (meth)acrylic acid ester is methyl acrylate and / or methyl methacrylate. **Claim 5** A (meth)acrylic acid ester polymer obtained from the polymerizable composition according to any one of Claims 2 to 4.

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