JP2021095430A - Antioxidant and resin composition containing the same - Google Patents

Abstract

To provide a novel antioxidant that enables the long-run molding of an oxygen barrier polymer such as a vinyl alcoholic resin and also can suppress the thermal degradation of a molded article, and a resin composition including the antioxidant.SOLUTION: An antioxidant includes a hindered phenol unit having a radical scavenging ability and an atomic group having a polar group, and has an SP value of 11 or more by the formula of Hoy. The antioxidant has excellent compatibility with a resin that is dissolved in a solvent with a high SP value and is not dissolved in a solvent with a low SP value and can exhibit effectively a radical scavenging ability to the resin.SELECTED DRAWING: None

Description

The present invention relates to a novel antioxidant, particularly an antioxidant effective for an oxygen barrier resin, and a resin composition containing the same.

Since plastics are originally not sufficiently stable against heat and light, they are easily oxidized and deteriorated by heat and ultraviolet light applied during molding and use, and have a drawback that the inherent properties of polymer materials are impaired.
Such drawbacks are generally addressed by the addition of additives such as antioxidants, light stabilizers, quenchers and the like.

For example, in Non-Patent Document 1 (Tomoyuki Kurumada "Recent Trends in Light Stabilizers" Color Materials, 62 [4] 215-222, 1989), light stabilizers (hindered amine light) are found in polyolefin molded products and various paints. Stabilizers: HALS) and hindered phenolic antioxidants have been described as effective.

Further, in Special Table 11-513676 (Patent Document 1), by blending a hindered phenol type antioxidant having a specific structure with an organic elastomer, the tensile strength and elongation at break point of the elastomer after the aging test can be increased. It has been shown to be improved.

Further, Patent No. 3533498 (Patent Document 2) proposes a novel liquid phenolic antioxidant that is stable against oxidative and / or photoinduced decomposition, and Patent No. 5925402 (Patent Document 3). Has proposed a novel compound obtained by chlorinating p-hydroxyphenylalkanol as a novel antioxidant capable of imparting excellent stability to a thermoplastic resin even when processed at a high temperature.

Further, as an antioxidant for polyamide, Japanese Patent Application Laid-Open No. 2004-535504 (Patent Document 4) proposes a novel antioxidant in which hindered phenol is linked by a special linking structure. It has been shown to be superior to conventional polyamide antioxidants (such as Irganox 1098) in discoloration and thermal and oxidative degradation.
In addition, there is also a proposal of a novel hindered phenol-based antioxidant capable of improving heat resistance of thermoplastic resins such as olefin-based resins that are easily oxidatively deteriorated (WO2016 / 021315: Patent Document 5).

On the other hand, vinyl alcohol-based resins known as oxygen barrier polymers are also exposed to high-temperature environments for a long period of time due to variations in the quality of the molded products when melt molding is continuously performed for a long time (long-run molding). It is known that the desired oxygen barrier property is impaired in the molded product for various purposes, and it is disclosed that the deterioration of the characteristics can be prevented by devising the additive.

For example, in Japanese Patent Application Laid-Open No. 2002-127135 (Patent Document 6), regarding the molding of a film by long-run molding of an ethylene-vinyl alcohol-based resin (hereinafter abbreviated as EVOH), an antioxidant (“Irganox 1098” manufactured by Ciba Geigy Co., Ltd.”: By adding 0.1 to 5% by weight of [N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide)]), the film to be molded It is disclosed that the variation in thickness is suppressed.

Further, in Japanese Patent Application Laid-Open No. 2000-102918 (Patent Document 7), a hot water circulation pipe (Example 8) using EVOH to which "Irganox 1098" manufactured by Ciba Geigy Co., Ltd. is added as an antioxidant as an outer layer, Ciba Geigy Co., Ltd. "Irganox 1010" ([Pentaerythrityl-tetrakis {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate}]] and Irgafos 168 ([Tris (2,4-di-t)] A fuel tank (Example 9) using an EVOH composition containing −butylphenyl) phosphite]) as an oxygen barrier layer and a high-density polyethylene layer as a surface layer can be used even after a long period of heat treatment. It is disclosed that no decrease in oxygen permeability was observed.

Special Table No. 11-513676 Japanese Patent No. 3533498 Japanese Patent No. 5925402 Special Table 2004-535504 WO2016 / 021315 Japanese Unexamined Patent Publication No. 2002-127135 Japanese Unexamined Patent Publication No. 2000-102918

Tomoyuki Kurumada, "Recent Trends in Light Stabilizers," Color Materials, 62 [4] pp. 215-222, 1989

In recent years, not only oxygen barrier properties but also durability of physical properties such as elongation at break have been required for hot water circulation pipes and fuel tanks as described above.
Further, with respect to food packaging films and other packaging films, since the appearance is emphasized, oxidative deterioration and yellowing due to heat treatment of the package have come to be regarded as problems.

The present invention has been made in view of the above circumstances, and an object of the present invention is a novel article capable of long-run molding of an oxygen barrier polymer such as a vinyl alcohol resin, and further suppressing thermal deterioration of a molded product. It is an object of the present invention to provide an antioxidant and a resin composition using the antioxidant.

The present inventors have found that even resins having oxygen barrier properties such as EVOH and polyvinyl alcohol undergo oxidative deterioration during melt molding or in an environment exposed to high temperatures for a long period of time, and are physically caused by decomposition of polymer chains. It was considered that the target strength decreased and yellowing occurred. As a result of various studies on a novel antioxidant capable of effectively exerting a radical scavenging function even in an oxygen barrier resin such as a vinyl alcohol resin, a hindered phenol unit is contained as a structural unit exhibiting a radical scavenging ability, and We have devised an antioxidant of the present invention in which the SP value is increased by having a polar group.

That is, the antioxidant of the present invention has the structure of the following general formula (1) and has an SP value of 11 or more according to the Hoy formula.

In the formula, R ¹ and R ² are bulky electron-donating substituents, A is an alkylene group having 1 to 5 carbon atoms, L is a single bond or a bonding group, and α is an atomic group having a polar group. is there.

The polar group contained in the α is preferably a hydroxyl group, and the α is preferably an atomic group containing a plurality of hydroxyl groups, particularly an atomic group containing a condensate of a polyhydric alcohol.

The resin composition of the present invention is a resin composition containing the above-mentioned antioxidant of the present invention and at least one selected from vinyl alcohol-based resin, polyamide, polyvinylidene chloride, and polyacrylonitrile.

From another point of view, the resin composition of the present invention is insoluble in xylene as the above-mentioned antioxidant and resin component of the present invention, but is soluble in a 1: 1 (weight ratio) mixed solvent of water and methanol. Contains thermoplastic resin.

The SP (solubility parameter) value referred to in the present specification means an SP value calculated based on Hoy's formula unless otherwise specified.
The SP value calculated by Hoy's formula is δt calculated by the following formula.

式中、Ｆｔ_i、Ｖiは、置換基の化学構造に依拠する固有の値である。

In the formula, Ft _i and Vi are unique values depending on the chemical structure of the substituent.

The antioxidant of the present invention has an excellent phase for resins that do not dissolve in a solvent having a low SP value but dissolve in a solvent having a high SP value, such as vinyl alcohol-based resin, polyamide, polyvinylidene chloride, and polyacrylonitrile. It has solubility and is excellent as a radical trapping type antioxidant for these resins.

It is a figure for demonstrating the method of synthesizing the ester-bonded type antioxidant which is one Embodiment of this invention. It is a figure which shows the synthesis process of the antioxidant used in an Example. 6 is an NMR chart of the antioxidant AO-1 obtained in the examples.

〔Antioxidant〕
The antioxidant according to the present invention has the structure of the following general formula (1) and has an SP value of 11 or more according to the Hoy formula.

In the formula, R ¹ and R ² are bulky electron-donating substituents, and each of them independently includes a methyl group, an ethyl group, an isopropyl group, a tert-butyl group (tert-Bu), a methoxy group and the like. , Preferably a tert-butyl group. That is, the aromatic compound moiety represented by the formula (11) constitutes a hindered phenol unit.

The interposition group A is usually an alkylene group having a linear or branched carbon number of 1 to 5, preferably an alkylene group having 1 to 3 carbon atoms.

In the formula (1), L is a single bond or a bonding group. The bonding group L includes an ester bond (-COO-), an ether bond (-O-), an amide bond (-CONH-), a carbonyl bond (-CO-), a sulfide bond (-S-), or a carbonate bond (-S-). -O- (C = O) -O-) can be mentioned, and an ester bond is preferable from the viewpoint of ease of production. The case where L is a single bond corresponds to the case where the intervening group A and the atomic group α having a polar group are directly bonded.

In the formula (1), α is an atomic group having a polar group.
Examples of the polar group, a hydroxyl group (-OH), carboxyl group (-COOH), a sulfonyl group _(-SO 2), a sulfo group _(-SO 3 H), amino groups (-NH ₂₎ and the like, among these , Hydroxyl group is preferable.

The atomic group α having a polar group is preferably an atomic group containing at least one, preferably two or more polar groups. When a plurality of polar groups are contained, the polar groups may be the same or different.

The atomic group α preferably has polar groups linked by an alkylene chain (preferably an alkylene chain having 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms), an ether bond, or the like.

A preferable atomic group α is a residue obtained by desorbing one hydrogen or one hydroxyl group from a polyhydric alcohol containing a plurality of hydroxyl groups or a derivative thereof (referred to as “polyhydric alcohol-containing atomic group”). As the derivative of the polyhydric alcohol, the antioxidant having the structure finally represented by the formula (1) is a derivative having an SP value of 11 or more according to the Hoy formula.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butylene glycol, glycerin, pentaerythritol, sorbitol, sugar alcohol, and condensates thereof.
A preferable polyhydric alcohol-containing atomic group is, for example, an atomic group containing a derivative of the polyhydric alcohol condensate represented by the following formula (2).

In the formula, B may be a hydrogen, an alkyl group having a linear or branched carbon number of 1 to 6 or a hindered phenol unit-containing atomic group represented by the following formula (3). .. Preferably, it is a hindered phenol unit-containing atomic group represented by the formula (3) from the viewpoint of antioxidant ability.

In the formula (3), R ³ and R ^{4, which} are constituents of the hindered phenol unit, are bulky substituents having a high electron donating property, and are independently methyl group, ethyl group, isopropyl group, and tert-butyl group. (Tert-Bu), a methoxy group and the like can be mentioned, and a tert-butyl group is preferable.

The interposition group A'is usually a linear or branched alkylene group having 1 to 5 carbon atoms, and is preferably an alkylene group having 1 to 3 carbon atoms.

In the formula (3), L'is a single bond or a bonding group. The bonding group includes an ester bond (-COO-), an ether bond (-O-), an amide bond (-CONH-), a carbonyl bond (-CO-), a sulfide bond (-S-), or a carbonate bond (-S-). O- (C = O) -O-) can be mentioned, preferably an ester bond. The case where L'is a single bond is the same as the case where L is a single bond.

Therefore, a preferable antioxidant has a structure represented by the following formula (4).

In the formula (4), R ¹ , R ² , R ³ , and R ⁴ are bulky substituents having the same or different electron donating properties, and A and A'are carbon atoms which may be the same or different. It is an alkylene group of 1 to 5, and L and L'are bonding groups that may be the same or different. From the viewpoint of simplicity in the production method, it is preferable that the hindered phenol units are equal. That is, it is preferable that R ¹ , R ² , R ³ , and R ⁴ are the same, A and A'are the same, and L and L'are the same. Further, since a tert-butyl group is preferable as the bulky substituent, the preferable structure of the antioxidant represented by the general formula (4) appears in the following formula (5).

Among the antioxidants having the above structures, an example of a method for synthesizing an antioxidant having the structure of the formula (4), which is a preferable antioxidant and having an ester bond as a bonding group (L, L'), is described. This will be described with reference to FIG.

Dipentaerythritol is used as a condensate of a polyhydric alcohol as a starting material, and first, the hydroxyl group adjacent to the erythritol portion is protected by converting it into an acetal to obtain a dialcohol (alcoholic hydroxyl group protectant).
The obtained dialcohol is esterified with a carboxylic acid (carboxyl group-containing hindered phenol) as a hindered phenol unit, and the hindered phenol unit-containing atomic group and the polyhydric alcohol-containing atomic group are bonded by an ester bond. Let me.
In the obtained ester bond, the hydroxyl protecting group of the polyhydric alcohol may be removed and returned to the original hydroxyl group.

In the antioxidant having the above structure, the hindered phenol unit can capture radicals generated by oxidation of the target polymer chain to become phenoxy radicals, which can be stabilized as phenoxy radicals. On the other hand, the polymer chain having an olefin-bonded portion reacts with oxygen to generate a peroxy radical (ROO ·), and this radical abstracts hydrogen from RH to generate R ·, which itself is a hydroperoxide (ROOH). Therefore, it is considered that oxidative deterioration progresses due to this repetition. Therefore, the compound represented by the formula (1) can function as a radical scavenger type antioxidant that captures peroxy radicals generated from the polymer chain.

In the synthesis method shown in FIG. 1, dipentaerythritol was used as a polyhydric alcohol condensate, and hindered phenol units were linked by ester bonds, but oxo acids in which some hydroxyl groups in dipentaerythritol were replaced with carboxyl groups. May be reacted with an alcohol to which a hindered phenol group is bonded (alcoholic hydroxyl group-containing hindered phenol) to form an ester bond.

Depending on the type of bonding group (L), a compound used by converting the hydroxyl group of dipentaerythritol used as a starting material into a carboxyl group, amine, etc. is used as the starting material, and the terminal functional group of the hindered phenol unit is used. By converting to amines, hydroxyl groups, acid halides, etc., it is possible to synthesize compounds in which the linking group L is an amide bond, a carbonyl bond, an ether bond, or a carbonate bond.

The antioxidant of the present invention is an antioxidant having the above-mentioned structure, and has an SP value of 11 (cal / cm ³ ) ^1/2 or more calculated by Hoy's formula. In other words, the antioxidant according to the present invention includes ^{the types of bulky substituents (R 1} , R ² , R ³ , R ⁴ ), the types of intervening groups A and A', and the types of binding groups L and L'. Although it depends on the structure of the atomic group α having a polar group, it has a feature that the ^{SP value calculated by Hoy's formula is 11 (cal / cm 3} ) ^{1/2 or more.}

Here, Hoy's equation is expressed by the following equation, and δt is the SP value.

In the formula, Ft _i and Vi are unique values depending on the chemical structure of the substituent. Therefore, the SP value may be calculated by Hoy's formula based on the chemical structure, or may be calculated by using commercially available calculation software (for example, Hoy solubility parameter (Computer Chemistry Consultancy) or the like).

The antioxidant of the present invention usually has a molecular weight of 400 to 1500, preferably 500 to 1000.
Further, the antioxidant of the present invention usually has a melting point of 30 to 300 ° C, preferably 50 to 250 ° C.

Generally used phenolic antioxidants have an SP value of less than 11 calculated by Hoy's formula. Specifically, the SP value calculated by the Hoy formula of BHT (2,6-di-t-butyl-p-cresol), which is a hindered phenol-type antioxidant often used in the field of polyolefin molded products, is It is 9/11, and the SP value of Irganox 1098 used in Patent Document 1 is 9.89, and the SP value of Irganox 1010 used in Patent Document 2 is 9.93.
Therefore, the antioxidant of the present invention also has a feature that the SP value calculated by Hoy's formula is 11 (cal / cm ³ ) ^{1/2 or more.}

Based on these characteristics, the antioxidant of the present invention does not dissolve in a solvent having a low SP value (for example, xylene (SP value: 9.04)) such as a vinyl alcohol-based resin, and has a high SP value. (For example, a 1: 1 mixed solvent of water (SP value: 23.47) / methanol (SP value: 14.52)) is considered to exhibit excellent compatibility with a resin that is soluble. By enabling such excellent compatibility, the radical scavenging action of the hindered phenol unit is effectively exerted on the resin.

[Resin composition]
In the resin composition of the present invention, the antioxidant according to the present invention is at least one selected from vinyl alcohol-based resin, polyamide, polyvinylidene chloride, and polyacrylonitrile, or a solvent having a low SP value (for example, xylene (SP)). Value: 9.04), etc.) and in a solvent with a high SP value (for example, a 1: 1 mixed solvent of water (SP value: 23.47) / methanol (SP value: 14.52)) Is a resin composition containing a soluble resin as a base resin.

(A) Base resin The base resin is a resin that serves as a matrix for the composition, and is 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more of the resin component. It is a resin contained.

The vinyl alcohol-based resin refers to polyvinyl alcohol (PVA), ethylene / vinyl alcohol copolymer (EVOH), and modified products thereof. Here, EVOH is a vinyl alcohol-based resin containing 10 to 60 mol%, preferably 20 to 50 mol% of ethylene units.

The vinyl alcohol-based resin contains the following vinyl alcohol unit (formula (a)) as an essential component as a structural unit, and further contains an ethylene unit (formula (b)) in the case of EVOH.

Such a vinyl alcohol-based resin is usually synthesized by saponifying a vinyl ester polymer. Therefore, when the saponification degree is less than 100 mol%, the vinyl ester unit (as an unsaponified portion) ( The formula (c)) is also included.

The vinyl ester unit is derived from the vinyl ester-based monomer used in the synthesis of the polymer. Examples of the vinyl ester compound used as the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, and stearic acid. Examples thereof include vinyl, vinyl benzoate, vinyl versaticate, and the like, of which vinyl acetate is preferably used. Therefore, in the formula (c), R ¹¹ is an alkyl group having 1 to 18 carbon atoms, preferably a methyl group.

As a modified vinyl alcohol resin, a part of the vinyl ester monomer can be copolymerized with the following compound as long as the gas barrier property is not impaired (usually less than 10 mol%, preferably 5 mol% or less). Examples thereof include copolymers obtained by copolymerization. Examples of the copolymerizable monomer include active methylene-containing vinyl monomers such as vinyl acetoacetate, acetoacetoxyalkyl (meth) acrylate, and diacetoneacrylamide; ethylene (excluding EVOH), propylene, isobutylene, and α-octene. , Α-dodecene, α-octadecene and other olefins; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, undecylene acid, salts thereof, monoesters, or dialkyl esters; Nitrites such as acrylonitrile and metaacrylonitrile; amides such as acrylamide and methacrylicamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof; alkyl vinyl ethers; dimethyl allyl vinyl ketone, N- Vinyl compounds such as vinylpyrrolidone, vinyl chloride, vinylethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerin monoallyl ether; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate , Vinylidene Chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, vinylene carbonate; allyl alcohol, 3-butene-1-ol, 4-pentene-1-ol, 5-hexene Monohydroxyalkyl group-containing monomers such as -1-ol and 6-hepten-1-ol; disubstituted diol monomers such as 2-methylene-1,3-propanediol and 2-methylene-1,3-propanediol; 3 , 4-diol-1-butene, 4,5-diol-1-pentene, 4,5-diol-3-methyl-1-pentene, 4,5-diol-3-methyl-1-pentene, 5,6 1,2-diol group-containing monomer such as −diol-1-hexene; hydroxymethylvinylidene diacetate may be mentioned, and one or more of these may be contained.

Further, the modified form of the vinyl alcohol-based resin may contain various binding chains such as an ether bond (-O-).
The bonding chain is not particularly limited, but in addition to hydrocarbon chains such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbons may be substituted with halogens such as fluorine, chlorine, and bromine), and the like. Structures containing ether binding sites such as −O−, − (CH ₂ O) m−, − (OCH ₂ ) m−, − (CH ₂ O) mCH _{2 −; −CO−, −COCO−, −CO (} CH ₂ ) Structure containing carbonyl groups such as mCO-, -CO (C ₆ H ₄ ) CO-; Structure containing sulfur atoms such as _{-S-, -CS-, -SO-, -SO 2-; -NR} -, - CONR -, - NRCO -, - CSNR -, - NRCS -, - structures including NRNR- such as nitrogen atoms; -HPO ₄ -, etc. structure containing a hetero atom such as structures containing phosphorus atoms; -Si _{(OR) 2 -, - OSi} (OR) 2 -, - OSi (OR) structure containing 2 O- such as silicon _{atoms; -Ti (OR) 2 -,} - OTi (OR) 2 -, - OTi (OR ) ₂ Structures containing titanium atoms such as O-; Structures containing metal atoms such as structures containing aluminum atoms such as -Al (OR)-, -OAl (OR)-, and -OAl (OR) O-. (R is an independent substituent, preferably a hydrogen atom or an alkyl group, and m is a natural number, usually 1 to 30, preferably 1 to 15, and even more preferably 1 to 10. ). Among them, an ether bond (-O-) and a hydrocarbon chain having 1 to 10 carbon atoms are preferable from the viewpoint of stability during production or use, and further, an ether bond (-O-) and a hydrocarbon chain having 1 to 6 carbon atoms are preferable. It is preferably a hydrocarbon chain.

The modified product may be one in which the hydroxyl group of the vinyl alcohol-based resin is "post-modified" such as urethanization, acetalization, cyanoethylation, oxyalkyleneization, acetylation, and acetoacetylation.

Among such modified vinyl alcohol-based resins, a structural unit having a primary hydroxyl group in the side chain is preferably used. In particular, a modified vinyl alcohol-based resin containing the following structural unit having a 1,2-diol structure in the side chain is preferably used as a modified vinyl alcohol-based resin having excellent melt moldability.

The average degree of polymerization of the vinyl alcohol-based resin used in the present invention (according to JIS K6726) is usually 200 to 3000, particularly preferably 300 to 2500, and more preferably 500 to 2300.
The saponification degree is usually 80 to 100 mol%, preferably 85 to 100 mol%, and more preferably 90 to 100 mol%. The saponification degree is an amount obtained from the amount of alkali consumed for hydrolysis of the residual acetate group in the resin, and is measured based on JIS K6726.

As the base resin of the resin composition of the present invention, in addition to the vinyl alcohol-based resin, a solvent that is insoluble in a solvent having a low SP value (for example, xylene (SP value: 9.04)) and has a high SP value (for example). , A resin that is soluble in water (SP value: 23.47) / methanol (SP value: 14.52) 1: 1 mixed solvent, etc.), for example, polyamide, polyvinylidene chloride, polyacrylonitrile, or a combination thereof is used. You can also do it.

A combination of a polyvinyl alcohol-based resin and at least one selected from the group consisting of polyamide, polyvinylidene chloride, and polyacrylonitrile may be used as the base resin.

(B) Other resin If the resin component is 30% by weight or less, preferably 28% by weight or less, more preferably 25% by weight or less, a solvent having a high SP value (for example, water (SP value: 23.47)) / A resin that does not correspond to a soluble resin may be contained in methanol (such as a 1: 1 mixed solvent of SP value: 14.52). For example, polyolefins such as polyethylene and polypropylene; polystyrene; rubbers such as fluororubber, polyisobutylene, isoprene rubber and styrene-butadiene rubber; polyvinyl acetate, polyethylene terephthalate, polymethyl methacrylate and the like can be mentioned.

(C) Other Additives In the resin composition of the present invention, a conventionally used antioxidant may be used in combination with the antioxidant of the present invention as an antioxidant.
Antioxidants that can be used in combination include phenol-based antioxidants and aromatic amine-based antioxidants that are classified as radical-capturing antioxidants, as well as sulfur-based antioxidants and phosphorus-based antioxidants. Examples thereof include peroxidation-decomposition type antioxidants having a substance-decomposing action.

Examples of the phenolic antioxidant include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis- (6-t-butylphenol), and 2 , 2'-Methylene-bis (4-methyl-6-t-butylphenol), tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, N , N'-hexamethylene-bis (3,5-di-t-butyl-4'-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6 tris (3,5-di) -T-Butyl-4-hydroxybenzyl) benzene, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, triethylene glycol-bis [3- (3-t) -Butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis -(N-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di) -T-Butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 3,5-di-t-butyl-4-hydroxy-benzyl Phosphonate-diethyl ester, bis (3,5-di-t-butyl-4-hydroxybenzylphosphonate ethyl) calcium, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanu Late, 2,4-bis [(octylthio) methyl] -O-cresol, isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, n-octadecyl-3- (3,5) -Di-t-Butyl-4-hydroxyphenyl) propionate, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate, 2- [1- (2-Hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 4 , 4'-thiobis (3-methyl-6-t-butylphenol), 3,9-bis [2- [3- (3) -T-Butyl-4-hydroxy-5-methylphenyl) -propioniloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro (5.5) undecane and the like.

Examples of the aromatic amine-based antioxidant include dimethyl 1- (2-hydroxyethyl) succinate-4-hydroxy-2,2,6,6-tetramethylpepyridine polycondensate and poly [[6- (1). , 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl) imino] hexamethylene [( 2,2,6,6-tetramethyl-4-piperidyl) imino]], N, N'-bis (3-aminopropyl) ethylenediamine, 2,4-bis [N-butyl-N- (1,2,2, 2,6,6-pentamethyl-4 piperidyl) amino] -6-chloro-1,3,5-triazine condensate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1) , 2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalate bis (1,2,2) , 6,6-Pentamethyl-4-piperidyl) and the like.

Phenyl-based antioxidants include triarylphosphite such as triphenylphosphite, tris (p-nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite; monoalkyldiphenylphosphite. Alkylaryl phosphites such as (eg, diphenylisooctylphosphite, diphenylisodecylphosphite), dialkylmonophenylphosphite (eg, phenyldiisooctylphosphite, phenyldiisodecylphosphite); triisooctylphosphite, tristearylphos. Trialkyl phosphite such as phyto; bis (2,4-di-t-butylphenyl) pentaerythritol-di-phosphite and the like can be mentioned.

Sulfur-based antioxidants include pentaerythritol-tetrakis- (β-laurylthiopropionate), tetrakis [methylene-3- (dodecylthio) propionate] methane, and bis [2-methyl-4- [3-n-alkylthionate). Propionyloxy] -5-t-butylphenyl] sulfide, dilauryl-3,3'-thiodipropionate, dimystylyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, Examples thereof include pentaerythryl-tetrakis (3-laurylthiopropionate), ditridecyl-3,3'-thiodipropionate, 2-mercaptobenzimidazole and the like.

The resin composition of the present invention further contains, if necessary, an additive generally blended with a thermoplastic resin within a range that does not impair the effects of the present invention (usually 5% by weight or less in the resin composition). May be good.

Examples of the additives include heat stabilizers, antistatic agents, colorants, ultraviolet absorbers, lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, and cross-linking agents. Examples thereof include agents, hardeners, foaming agents, crystal nucleating agents, antifogging agents, biodegradation additives, silane coupling agents, oxygen absorbers and the like.

The resin composition having the above composition has excellent oxidative deterioration resistance. In particular, it has excellent resistance to oxidative deterioration due to heating of melt-molded products. Specifically, even if the molded product is exposed to a heated state for a long period of time, yellowing of the molded product is suppressed, and a decrease in strength such as breaking strength is also suppressed.
Since the antioxidant of the present invention has an SP value of 11 or more according to Hoy's formula, it does not dissolve in a solvent having a low SP value and has an excellent affinity with a base resin that dissolves in a solvent having a high SP value. It is considered that it can be finely dispersed in the matrix composed of the base resin. In particular, it is considered that the finely dispersed state is maintained even under the condition that the base resin is softened by heating. Therefore, it is considered that the oxidative deterioration is suppressed even when exposed to the heating state.

In the resin composition having the above composition, the content of the antioxidant of the present invention is usually 0.001 to 5% by weight, preferably 0.01 to 1% by weight, and more preferably 0.05 to 0. It is 5.5% by weight. The active group equivalent to the resin component is usually 2.6 × 10 ^{-5 to} 1.3 × 10 ^-1 eq / kg of resin, preferably 2.6 × 10 ^{-4 to} 2.6 × 10 ^-2 eq /. The resin kg, more preferably 1.3 × 10 ^{−3 to} 1.3 × 10 ⁻² eq / resin kg.
Since the antioxidant of the present invention has an excellent ability to prevent oxidative deterioration due to heat per active group equivalent ^{, even at about 2.1 × 10 -3} eq / kg of resin, oxidation is equal to or higher than that of conventional antioxidants. Preventive ability can be imparted.

〔Antioxidant〕
(1) AO-1
The polyhydric alcohol-type hindered phenolic antioxidant according to the embodiment of the present invention was synthesized through the steps shown in FIG.

Step 1: Synthesis of alcoholic hydroxyl-protecting body Under an argon atmosphere, dimethylformamide (DMF: 3.2L) is poured into a 10L four-necked flask, and dipentaerythritol (400g) is stirred with a stirring blade and a mechanical stirrer. , 1.57 mol), benzaldehyde dimethyl acetal (598.5 g, 3.93 mol) was added slowly. After adding 29.9 g (0.16 mol) of p-toluenesulfonic acid (p-TsOH · H ₂ O), the mixture was heated to 100 ° C. After heating and stirring at 100 ° C. for 2 hours, the mixture was naturally allowed to cool to room temperature.
The obtained reaction solution was concentrated with a 10 L evaporator (water bath 60 ° C.) to obtain 831.4 g of pale yellow oil (crude material). The crude product was dissolved in toluene / ethyl acetate = 1/1 (2.0 L) and then purified by silica gel column chromatography.
When the fraction containing the target compound was recovered and concentrated, a white solid was precipitated. A white solid was obtained by filtration under reduced pressure, washed with heptane, and then dried under reduced pressure at 50 ° C. to obtain an alcoholic hydroxyl group-protected body (white solid, 263.3 g).

Step 2: Synthesis of carboxyl group-containing hindered phenol Acetone (2.0 L) is poured into a 10 L four-necked flask under an argon atmosphere, and 3- (3,5-) is stirred with a stirring blade and a mechanical stirrer. Stearyl propionate (650 g, 1.22 mol) was added slowly, followed by washing with acetone (1.3 L).
Aqueous sodium hydroxide solution was slowly added to the above solution and heated to 55 ° C. Hydrolysis was carried out by heating and stirring at 55 ° C. for 9 hours. After allowing to cool naturally to room temperature, the hydrolyzate was filtered under reduced pressure, and the precipitated solid (pale yellow) was filtered off. The solid was washed with acetone (3.3 L).

The filtrate of the hydrolyzate and the washing filtrate were combined, and the concentrated solution obtained by concentration was diluted with ion-exchanged water (3.8 L).
When concentrated hydrochloric acid was added little by little to the obtained diluted solution, when 130 ml was added, it became acidic and the amount of precipitates increased.

After stirring at room temperature for 1 hour, the precipitated solid was collected by filtration under reduced pressure filtration and dried on a filter. The solid was recovered and dried under reduced pressure at 50 ° C. for 12 hours to obtain a crude body of carboxyl group-containing hindered phenol. The weight of the crude product after drying was 640.8 g.
This crude product (640.8 g) was dissolved in chloroform (2.0 L) and then purified by silica gel chromatography (developing solvent: CHCl ₃ / MeOH = 30/1).
The fraction containing the target compound was concentrated, and the white solid was collected by filtration through vacuum filtration. After washing with heptane, it was dried under reduced pressure at 50 ° C. (yield 306.7 g).

Step 3: Connection by Ester Bonding Under an argon atmosphere, chloroform (2.0 L) is poured into a 10 L four-necked flask, and the carboxyl group-containing hindered obtained in Step 2 is stirred with a stirring blade and a mechanical stirrer. The phenolic compound (300 g, 0.92 mol) and the alcoholic hydroxyl-protected compound (198.2 g, 0.46 mol) obtained in step 1 were slowly added and reacted. The obtained reaction solution was cooled to 5 ° C. or lower in a salt ice bath, and N, N'-dicyclohexylcarbodiimide (DCC) (285.1 g, 1.38 mol) was divided into two portions at 5 ° C. Added.
In addition, N, N'-dimethyl-4-aminopyridine (DMAP) (16.9 g, 0.14 mol) was added slowly. After the addition, the temperature of the mixture had risen to 8.0 ° C. After the heat generation had subsided, the mixture was removed from the ice bath and stirred at room temperature for 12 hours. As a result of confirmation by TLC, it was confirmed that the carboxyl group-containing hindered phenol disappeared and a conjugate was formed by an ester bond.

The product solution of the white suspension was filtered under reduced pressure, the white solid was filtered off, and washed with chloroform (1.0 L).
The filtrate and the washing liquid were combined and concentrated with an evaporator to obtain 596.5 g of yellow oil (crude material). The crude product (596.5 g) was dissolved in chloroform and purified by silica gel chromatography (developing solvent: ethyl acetate / toluene = 1/30).
The fraction containing the target compound was recovered, concentrated on an evaporator, and then dried under reduced pressure at 50 ° C. for 12 hours to obtain an ester conjugate (white solid, 231.3 g).

Step 4: Synthesis of AO-1 Ethyl acetate (1.2 L) was poured into a 3 L four-necked flask under an argon atmosphere, and the ester bond obtained in Step 3 was stirred with a stirring blade and a mechanical stirrer. (120 g, 0.12 mol) was added slowly. The ester conjugate was dissolved to give a clear, colorless solution.
After adding Pd / C (12.0 g, ASCA-2 (water content) (manufactured by NE Chemcat) into the reaction solution, the mixture was stirred at room temperature for 12 hours while bubbling hydrogen (10 ml / min). When the reaction solution was sampled and added onto TLC, it was confirmed that a compound having the structure of the following formula (5) was formed with the protective group removed.

The reaction solution was filtered through a filter lined with Celite (560 g), and the obtained filtrate was concentrated under reduced pressure to obtain a crude product (167.0 g) of the above structural compound. This crude product (167.0 g) was dissolved in chloroform (1.0 L) and purified by silica gel chromatography (developing solvent: CHCl ₃ / methanol = 9/1).

The fraction containing the target compound was recovered, concentrated with an evaporator, and heptane was added during the concentration to precipitate white crystals. The white solid was collected by filtration under reduced pressure and dried under reduced pressure at 50 ° C. for 12 hours. The target compound, which is a white solid, was obtained (144.0 g).
Further, it was dissolved in chloroform and poured into hexane for reprecipitation to obtain a white solid having a residual solvent (hexane) concentration of 0.25% by weight. ^{A 1} H-NMR (300 MHz, CDCl ₃ ) chart of such a white solid (deuterated alcohol-linked hindered phenol) is shown in FIG. This was used as AO-1 (molecular weight: 774, melting point: 100 to 120 ° C.).

AO-1 is dD8.11, dP6.43, dH4.35, and the SP value based on Hoy's equation is 11.23.

(2) AO-2
Irganox 1076 manufactured by BASF Japan was used. It has the following chemical structure, and the SP value calculated by Hoy's formula is 8.69.

(3) AO-3
Irganox 1010 manufactured by BASF Japan was used. This is ([pentaerythrityl-tetrakis {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate}] (see structural formula below). DD7.95, dP4.98, dH3. It is .26, and the SP value based on Hoy's formula is 9.93.

[Preparation of resin composition]
EVOH (ethylene content: 29 mol%, saponification degree: 99.7%) was used as the base resin. AO-1, AO-2, and AO-3 were added to the EVOH at the ratios shown in Table 1, and the resin composition No. 1 to 4 were prepared.
Reference example No. As No. 5, a composition containing no antioxidant was used.

Resin composition No. prepared above. 1 to 5 were extruded under the conditions shown below to produce an EVOH film having a thickness of 100 μm. Manufactured film No. Heat aging resistance was measured and evaluated for 1 to 5 based on the evaluation method described later. The results are also shown in Table 1.
In addition, the film No. With respect to 2 to 5, the tensile breaking strength was measured and evaluated based on the evaluation method described later. The results are also shown in Table 2.

Extrusion molding conditions Molding equipment: Single-screw extruder with a diameter of 40 mm Screw: Full flight (compression ratio 3.4)
Die: T die screw rotation speed: 40 rpm
Screen mesh: 90/120/90
Roll temperature: 80 ° C
Temperature: C1 / C2 / C3 / C4 / H / D = 190/210/230/230/230/230 ° C

〔Evaluation method〕
(1) Heat aging resistance (YI value)
The prepared film (thickness 100 μm, 10 cm × 10 cm) was left in an oven at 140 ° C. for 24 hours, 48 hours, and 96 hours in an air atmosphere, and then the yellowness (YI value) of the film was measured by a spectrocolorimeter. (SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used to measure the spectral reflectance. The higher the YI value, the higher the degree of yellowing.

(2) Tensile breaking strength A strip-shaped film sample (thickness 100 μm, 1.5 cm × 15 cm) was prepared from the manufactured film, and the sample was placed in an oven set at an internal temperature of 140 ° C. in an air atmosphere. I left it for a while. After heating, the film was humidity-controlled for 1 week under the conditions of 23 ° C. and 50% relative humidity, and a tensile fracture test was conducted.
The tensile fracture test was performed using an autograph AGS-X manufactured by SHIMAZU. The tensile conditions are a distance between chucks of 50 mm and a tensile speed of 50 mm / min.

The retention ratio (%) of the breaking elongation with respect to 100% of the breaking elongation of the film before heating was calculated by the following formula. The higher the retention rate, the less the strength deterioration due to heat.
Retention rate = (breaking elongation after heating test) / (breaking elongation before heating test) x 100

As can be seen from Table 1, the degree of yellowing increases as the heating time increases.
Composition No. In each of 2 to 4, the amount of active group equivalent of the added antioxidant is the same. Therefore, the radical scavenging ability is considered to be equal. Before heating, the antioxidant of the present invention (No. 2) was not significantly superior, but as the heating time became longer, when the antioxidant was not contained (No. 5), the conventional method was used. Compared with the antioxidants (No. 3 and 4), the antioxidant (No. 2) of the present invention was significantly suppressed in increasing the degree of yellowing.

No. 1 and No. In case 2, the amount of the antioxidant is different and the amount of active group equivalent is different. The higher the content of the antioxidant (No. 1), the lower the degree of yellowing, but as the heating time became longer, the difference in the degree of yellowing due to the difference in the content became smaller. It is considered that the effect of suppressing the degree of yellowing is greater depending on the type of antioxidant than the increase in the content of the antioxidant.

As for the tensile elongation at break after heating, as shown in Table 2, when the antioxidant of the present invention is used even though it has the same active group equivalent (No. 2), It was the best.
Therefore, it can be seen that the antioxidant of the present invention has an excellent effect of preventing thermal deterioration with respect to the EVOH resin.

The antioxidant of the present invention does not dissolve in a gas barrier resin typified by a vinyl alcohol resin or a solvent having a low SP value, but dissolves in a solvent having a high SP value (polyamide, polyvinylidene chloride, poly). It is useful as an antioxidant to prevent oxidative deterioration of acrylonitrile). The resin composition containing the antioxidant of the present invention has excellent durability against oxidative deterioration at high temperatures, and is therefore useful as a molded article material for applications exposed to high temperatures for a long period of time.

Claims (9)

An antioxidant having the structure of the following general formula (1) and having an SP value of 11 or more according to the Hoy formula.

In the formula, R ¹ and R ² are bulky electron-donating substituents, A is an alkylene group having 1 to 5 carbon atoms, L is a single bond or a bonding group, and α is an atomic group having a polar group. is there. The antioxidant according to claim 2, wherein in the formula (1), R ¹ and R ² are t-butyl groups, A is an alkylene group having 1 to 5 carbon atoms, and L is an ester bond. The antioxidant according to claim 1 or 2, wherein the polar group contained in α is a hydroxyl group. The antioxidant according to any one of claims 1 to 3, wherein α is an atomic group containing a plurality of hydroxyl groups. The antioxidant according to claim 4, wherein the atomic group containing a plurality of hydroxyl groups is an atomic group containing a polyhydric alcohol or a condensate thereof. The antioxidant according to claim 5, wherein the atomic group containing the condensate of the polyhydric alcohol is an atomic group represented by the following general formula (2).

In the formula, B is a hydrocarbon, an alkyl group having a linear or branched carbon number of 1 to 6 or a phenolic compound-containing atomic group represented by the following formula (3), and is R ^{3 in the formula (3).} , R ⁴ is an electron-donating bulky substituent, a 'represents an alkylene group having 1 to 5 carbon atoms, L' represents a single bond or a linking group.

The antioxidant according to claim 6, which is represented by the following general formula (4).

In the formula, R ¹ , R ² , R ³ , and R ⁴ are bulky substituents having an electron donating property that may be the same or different, and A and A'are carbon atoms 1 to 5 that may be the same or different. L, L'is a bonding group that may be the same or different. A resin composition containing the antioxidant according to any one of claims 1 to 7, and at least one selected from vinyl alcohol-based resins, polyamides, polyvinylidene chloride, and polyacrylonitrile. A resin composition containing a thermoplastic resin that is insoluble in the antioxidant according to any one of claims 1 to 7 and xylene, but is soluble in a 1: 1 (weight ratio) mixed solvent of water and methanol. Stuff.

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