JP2794868B2 - Reactive antioxidant and polymer composition containing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an antioxidant having a double bond crosslinkable with a polymer in a molecule, and a polymer composition containing the same.

[Prior Art] Antioxidants such as amine-based and phenol-based antioxidants have been conventionally used to prevent deterioration of polymer materials due to oxidation. Most of amine-based antioxidants are contaminants, so their applications are limited. Recently, phenol-based antioxidants have been widely used.

Examples of phenolic antioxidants include n-octadecyl-3- (4'-hydroxy-3 ', 5'-di-
t-butylphenyl) propionate (trade name: Irganox 1076, manufactured by Ciba Geigy) or tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] Methane (trade name: Irganox 1010, manufactured by Ciba-Geigy) or the like is used.

However, these antioxidants are merely physically mixed into the formulation by a kneading operation,
Therefore, when the compound comes into contact with an organic solvent or water, the antioxidant is easily extracted, and its effect is extremely reduced. Also,
During use for a long period of time, the antioxidant precipitates on the product surface, so-called blooming occurs, which has the disadvantage that the antioxidant effect is reduced and the surroundings are contaminated.

In order to solve these problems, recently, a reactive antioxidant having a double bond capable of crosslinking with a polymer in a molecule has been used. Typical examples of such antioxidants are
For example, the formula: Or the formula: It is a compound shown by these. ("Antioxidant Handbook", 1st edition, pp. 3-4, Taiseisha) In addition, Japanese Patent Application No. 1-238132 discloses a reactive antioxidant comprising a phenolic compound. JP-A-54-153896 discloses a method for producing a copolymer containing a phenolic reactive aging inhibitor.

[Problems to be Solved by the Invention] Reactive antioxidants exhibit a feature that they are excellent in extraction resistance and do not cause blooming only after reacting with a polymer. Therefore, simply kneading the reactive antioxidant does not improve the extraction resistance, and the reactive antioxidant is added to the polymer by heating or irradiating with a chemical crosslinking agent. It is necessary to react with. However, if the time from molding or extracting the composition in which the reactive antioxidant is kneaded to reacting the reactive antioxidant is long, the reactive antioxidant blooms during that time. Occurs. Further, the reactive antioxidant has a disadvantage that the antioxidant function is inferior to the non-reactive antioxidant.

An object of the present invention is to provide an antioxidant which has a sufficient antioxidant effect and is excellent in extraction resistance and blooming resistance, and a polymer composition containing the same.

[Means for Solving the Problems] The above-mentioned problems are achieved by formulating a polydiene having a hydroxyl group in a molecule by the formula: [In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group having 1 to 4 carbon atoms, and 1 represents a number of 0 to 3. Can be solved by using a reactive antioxidant obtained by reacting the ester compound represented by the following formula:

Examples of polydienes include polybutadiene, polypentadiene, and polyhexadiene. The polydiene is not particularly limited as long as it has a hydroxyl group in the molecule. The position of the hydroxyl group may be inside the molecule or at the end of the molecule. The preferred molecular weight of the polydinene is from 500 to 10,000.

The alkyl groups R ₁ and R ₂ in the ester compound are, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl group and the like, preferably a t-butyl group, and a t-butyl group. Ester compounds having a hydroxyl group on both sides, for example, compounds having a 3,5-di-t-butyl-4-hydroxyphenyl group are preferred. Examples of such ester compounds include methyl-
Examples thereof include 3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate and methyl-1- (3,5-t-butyl-4-hydroxyphenyl carbonate).

Polybutadiene having a hydroxyl group in the molecule has the formula: [In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group having 1 to 4 carbon atoms, and 1 represents a number of 0 to 3. Is reacted with an ester compound represented by the formula: [Wherein, R ₁ , R ₂ , R ₃ and 1 have the same meanings as described above, and n represents a natural number. ] The reactive antioxidant shown by these is obtained. The above equation is
It is an example of a reactive antioxidant obtained by synthesis. In addition, those obtained by transesterification of all the hydroxyl groups present in the polydiene with the ester compound or those synthesized from a polydiene having a double bond in the side chain may be used. The reaction can be performed by a method known per se and commonly used, and does not require a special device or the like.

The reactive antioxidant thus obtained is blended with the polymer material in an amount of 0.1 to 20% by weight, preferably 0.5 to 10% by weight, based on the polymer material to obtain a polymer composition. The type of the polymer material is not particularly limited, and may be any polymer that can react with the reactive antioxidant. Representative examples include polyolefins, polyester elastomers,
Examples thereof include polyolefin elastomers, polyurethanes, and ethylene propylene rubbers. Further, such a polymer composition may contain an appropriate amount of a compounding agent that is usually compounded, for example, a stabilizer, a lubricant, a filler, a reinforcing agent, a flame retardant, and the like.

A known method for the polymer composition thus obtained,
For example, the reactive antioxidant is reacted with the polymer by irradiation with radiation or a chemical crosslinking agent or a combination of both.
This operation can be carried out by methods and devices known per se and commonly used. Radiation dose is 0.1-100Mrad (1-1000KGy), preferably 1-5
It is 0Mrad (10-500KGy). As the chemical crosslinking agent, a known crosslinking agent usually used for crosslinking a polymer may be used in a usual amount. For example, crosslinking agents such as organic peroxides, polyamines, sulfurs, and oximes can be used.

[Function] In the phenolic antioxidant, the one having an antioxidant function is a hydroxyl group bonded to a benzene ring, and a radical generated by oxidation is captured by the hydroxyl group and stabilized, thereby exhibiting an antioxidant effect. Also in the reactive antioxidant of the present invention, a hydroxyl group bonded to a benzene ring has an antioxidant function. On the other hand, the reactive antioxidant of the present invention for extraction resistance and blooming resistance,
Bloom is less likely to occur even if it does not react with the polymer by irradiation or a chemical crosslinking agent. this is,
It is considered that the high molecular weight polydiene moiety is physically entangled with the polymer. Therefore, if the reactive antioxidant of the present invention is used, during the period from molding the polymer composition to reacting the reactive antioxidant,
Bloom of the antioxidant can be significantly reduced.

In addition, this reactive antioxidant has a double bond in the molecule, and the double bond reacts with the polymer by a known crosslinking method, for example, irradiation or a chemical crosslinking agent, so that the reactive antioxidant is bonded. After that, it is further excellent in extraction resistance and blooming resistance.

[Examples] The present invention will be described more specifically by the following examples. Note that these examples do not limit the present invention.

Preparation of Reactive Antioxidant (a) Methyl-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate 20 was placed in a reaction vessel.
g, 20 g of polybutadiene having both hydroxyl groups (number average molecular weight: 1200), 0.4 g of hydroquinone monomethyl ether and 0.4 g of p-toluenesulfonic acid.
Allowed to react for hours. The resulting reaction product was converted into a chloroform solution, washed with an aqueous sodium hydroxide solution and water, and then reprecipitated with methanol to obtain 15 g of a reactive antioxidant A.

(B) Methyl-2- according to the procedure described in (a) above.
20 g of (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) carbonate, 42 g of polybutadiene having both hydroxyl groups (number average molecular weight: 2500), 0.4 g of hydroquinone monomethyl ether and 0.4 g of p-toluenesulfonic acid g
The reaction was carried out at 100 ° C. for 10 hours to obtain 12 g of a reactive antioxidant B.

Example 1 Low-density polyethylene (melt index: 1,5) 100
5 parts by weight of the previously obtained reactive antioxidant A was blended with 5 parts by weight, and the mixture was roll-kneaded at 120 ° C. to prepare a polyethylene compound. The obtained mixture was pressed under the conditions of 130 ° C. × 10 minutes to produce a sheet having a thickness of 1 mm. Bande with an acceleration voltage of 1 MeV
The polyethylene formulation was crosslinked using a graph-type electron beam accelerator. The electron beam irradiation amount was 12 Mrad. The following test was performed using the obtained sample.

Example 2 Ethylene-vinyl acetate copolymer (EVA, vinyl acetate: 15
% By weight, melt index: 0.7) 100 parts by weight of reactive antioxidant B was mixed with 5 parts by weight, and the mixture was roll-kneaded at 120 ° C.
A VA formulation was prepared. The obtained mixture was pressed under the conditions of 130 ° C. × 10 minutes to produce a sheet having a thickness of 1 mm. Acceleration voltage 1
This formulation was crosslinked using a MeV Bande-Graft electron beam accelerator. The amount of electron beam irradiation was 24 Mrad. The following test was performed using the obtained sample.

Example 3 Ethylene-ethyl acrylate copolymer (EEA, ethyl acrylate: 20% by weight, melt index: 2.0) 100
3 parts by weight of a reactive antioxidant A and 2 parts by weight of dicumyl peroxide as a cross-linking agent were blended into 1 part by weight, and the mixture was roll-kneaded at 120 ° C. to prepare an EEA blend. The EEA formulation was crosslinked using a press at 160 ° C. for 30 minutes. The following test was performed using the obtained sample.

Example 4 A polyethylene compound was prepared by repeating Example 1 except that 3 parts by weight of the reactive antioxidant A was used, and the compound obtained by electron beam irradiation was crosslinked. The amount of electron beam irradiation was 24 Mrad. The following test was performed using the obtained sample.

Example 5 Reactive antioxidant B3 was added to 100 parts by weight of low-density polyethylene.
Parts by weight and 1 part by weight of dicumyl peroxide as a cross-linking agent were blended and roll-kneaded at 120 ° C. to prepare a polyethylene blend. The polyethylene blend was crosslinked using a press at 160 ° C. for 30 minutes. The following test was performed using the obtained sample.

Comparative Examples 1 to 4 As comparative examples, N-phenyl-N '-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine (trade name: Nocrack G-1, manufactured by Ouchi Shinko Chemical Co., Ltd.) Reactive antioxidants), (3,5-di-t-
Butyl-4-hydroxybenzyl) acrylate and n-octadecyl-3- (4'-hydroxy-3 ', 5'
-Di-t-butylphenyl) propionate (trade name:
Irganox 1076, Ciba-Geigy)
Each composition was prepared by roll milling according to the compounding amounts shown in Table 1. In Comparative Examples 1, 2 and 4, electron beam irradiation was performed according to the procedure shown in Example 1 to crosslink the obtained compound (electron beam irradiation amount: 12 to 24 Mrad). Also,
In Comparative Example 3, the obtained compound was crosslinked using a press at 160 ° C. for 30 minutes. The following test was carried out using the sample thus obtained.

Test 1. Aging test To evaluate the effect of the antioxidant contained in the sample, an aging test was performed according to JISK7212. From each sample
A JIS No. 2 test piece having a thickness of 1 mm specified in JISK7113 was used as a punching test sample. The tensile strength and elongation of the sample before aging at a tensile speed of 500 mm / min using a tensile tester and the sample after aging by heating at 160 ° C. for 168 hours using a hot oven were measured.

In Table 1, the tensile strength and elongation after aging are represented by the formula: Xa / Xo × 100 (%) [where Xa represents the tensile strength or elongation after aging, and Xo represents the tensile strength or elongation before aging. ], And the retention rate against tensile strength and elongation before aging.

2. Bloom test A Bloom test was performed to evaluate the blooming property of the polymer composition. In order to determine the presence or absence of the bloom of the antioxidant, 2 parts of carbon black was added to prepare a black sheet, which was left at room temperature for one month. The state of bloom of the antioxidant was visually evaluated.

3. Measurement of extraction rate In order to evaluate the extraction resistance of the antioxidant, the extraction rate was measured using acetone. The obtained sample was extracted with acetone for 8 hours using a Soxhlet extractor. The weight of the sample before and after extraction was measured, and the extraction rate was calculated from the following equation.

The results are shown in Table 1.

As can be seen from Table 1, the polymer composition obtained by crosslinking the reactive antioxidant of the present invention shows good aging resistance, does not cause bloom, and has excellent extraction resistance.

[Effects of the Invention] Since the reactive antioxidant synthesized from the polydiene and the ester compound according to the present invention has a high molecular weight by itself, it has excellent bloom resistance even without being reacted by a method such as irradiation or chemical crosslinking. Has extraction resistance. For this reason, bloom does not occur for a long period of time from the production of the molded article to the reaction of the reactive antioxidant. In addition, since the polydiene in the molecule has a plurality of double bonds, the amount of electron beam irradiation required for the reaction can be reduced, and chemical crosslinking can be performed under mild conditions.

In general, a reactive antioxidant is inferior to an ordinary antioxidant in antioxidant effect, but the reactive antioxidant of the present invention has an effect equivalent to that of an ordinary antioxidant. Further, the reactive antioxidant of the present invention has an advantage that it is phenol-based antioxidant and therefore has no pollution and therefore has a wide variety of uses such as being able to be used for blending of a colored substance and a light-colored substance.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriko Matoba 3-10-4 Nishi-Nagasu-Higashidori, Amagasaki-shi, Hyogo Nard Research Institute, Inc. (58) Field surveyed (Int.Cl. ⁶ , DB name) C09K 15/08 C08F 8/14 C08L 101/00 REGISTRY (STN) CA (STN)

Claims (3)

(57) [Claims] 1. A polydiene having a hydroxyl group in the molecule has the formula: [In the formula, R ₁ , R ₂ and R ₃ represent an alkyl group having 1 to 4 carbon atoms, and 1 represents a number of 0 to 3. ] The reactive antioxidant obtained by reacting the ester compound shown by these. 2. The reactive antioxidant according to claim 1, wherein said ester compound is a 3,5-di-t-butyl-4-hydroxyphenyl ester compound. 3. The reactive antioxidant of claim 1 in an amount of 0.1 to 2
A polymer composition comprising 0% by weight, wherein the reactive antioxidant is crosslinked with a polymer.