JPH06263929A - Polyolefinic resin composition for automotive fuel tank and automotive fuel tank made thereof - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent gasoline resistance, heat-resistance, etc., and exhibiting extremely little lowering of various physical properties after immersing in fuel oil for a long period by compounding a polyolefine resin with a combination of three specific kinds of additives. CONSTITUTION:This resin composition is produced by compounding (A) 100 pts.wt. of a polyolefinic resin (preferably a high-density polyethylene having a weight-average molecular weight of 100,000-500,000) with 0.01-5 pts.wt. each of (B) a phenolic compound of formula I (A is residue obtained by removing n X hydroxyl groups from a mono to tetrahydric alcohol; (n) is 1-4) [e.g. stearyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], (C) a phosphite compound of formula II (R1 is 1-30C alkyl) [e.g. 2,2'-methylenebis(4,6-dirt- butylphenyl).methylphosphite] and (D) a compound containing 2,2,6,6- tetramethylpiperidyl group [preferably bis (2,2,6,6-tetramethyl-4-piperidinyl) terephthalate, etc.].

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyolefin resin composition for automobile fuel tanks containing a combination of optimum additives, and a molding process using the composition.
Further, the present invention relates to a polyolefin-based resin fuel tank which is less deteriorated during use and, in particular, does not deteriorate in physical properties for a long period of time even when immersed in automobile fuel such as gasoline.

[0002]

2. Description of the Related Art In recent years, the weight of vehicles has tended to increase in order to improve safety and equipment specifications, and to prevent noise.
On the other hand, from the viewpoint of protection of the global environment, along with the movement of tightening fuel consumption regulations against the background of the problem of reducing carbon dioxide emission, there is an increasing demand for achieving weight reduction of automobiles. For this reason, the use of plastics as a material for automobile parts is becoming more concrete. Currently, about 8% of the weight of automobiles is made of plastics, such as fuel tanks, bumpers, armrests, headrests, instrument panels, and seat leathers. It has reached the point of occupying. In particular, plastic fuel tanks have improved space efficiency due to the ease with which tanks of complicated shapes can be manufactured, can be lightened even if the fuel capacity is increased, have excellent impact resistance, methanol, ethanol, or methanol. Even when using an oxygen-containing fuel containing a mixture of Cheer Tertiary Butyl Ether (MTBE) and the like, there are merits such as no rust, and it is used in many vehicle types.

From the viewpoint of safety, such a plastic fuel tank is required to have excellent heat resistance, oil resistance, impact resistance, and the like, and to be free from permeation of fuel such as gasoline. Polyolefin resin such as high molecular weight high density polyethylene is used.

[0004]

However, most of the polyolefin resins usually used for producing a polyolefin resin fuel tank are high-molecular-weight high-density polyethylene having a molecular weight of about 200,000 or more. The processing temperature is about 230 ° C. or higher, which is extremely high, and the molding cycle also takes a long time. Therefore, the thermal history is remarkably severer than in the usual case. Moreover, since such a fuel tank is not only exposed to a high temperature during use but is also immersed in a fuel oil such as gazoline for a long period of time, the compounded additive is extracted by the fuel and the It is expected that even if the characteristics are deteriorated and if it is severe, a serious safety problem such as cracking occurs. Further, when manufacturing a fuel tank made of a polyolefin resin, usually 30-40% of molding burr is generated, but it is desired to reuse such a molding burr from the viewpoint of resource conservation. There is. As described above, the molding burr has been subjected to a severe heat history in the molding process, and recycling this molding burr causes a severe heat history twice, which causes a problem of deterioration in quality. .

When a polyolefin resin is processed, in order to prevent thermal oxidative deterioration at the processing temperature and oxidative deterioration in the working environment, a phenolic antioxidant, a thioether antioxidant, a phosphorus antioxidant, etc. Several kinds of various antioxidants are used together, and naturally these antioxidants are also used when molding plastic fuel tanks, but if these additive systems are used alone, It was difficult to prevent the decrease. Therefore, in JP-A-3-174459, a phenolic antioxidant, a phosphorus antioxidant and / or
Alternatively, it has been proposed to prevent deterioration of quality during molding and use by adding four components of a thioether antioxidant, a hindered amine light stabilizer, and carbon black. Even in this case, the effect is still insufficient, and it has been strongly desired to find a combination of higher performance additives.

[0006]

In view of the above situation, the present inventors have conducted diligent studies to find a combination of additives suitable for the production of a polyolefin-based resin fuel tank, and as a result, have identified a specific phenol-based compound. In addition to the combination of an antioxidant and a 2,2,6,6-tetramethylpiperidine compound, a polyolefin resin composition using an antioxidant composed of a specific phosphite compound is used at the time of heat molding processing and used. Not only the deterioration of the physical properties of the resin due to thermal oxidative deterioration at the time is significantly prevented, but also the physical properties are not significantly deteriorated even when immersed in the fuel oil for a long time, and it is extremely suitable as a polyolefin resin composition for automobile fuel tanks. That is, the present invention has been reached.

That is, the present invention relates to a polyolefin resin and 100 parts by weight of the polyolefin resin,
(A) The following general formula

[Chemical 3] (In the formula, A represents a residue obtained by removing n hydroxyl groups from a monohydric to tetrahydric alcohol, and n represents 1 to 4.) 0.01 to 5 weight of at least one phenol compound represented by Part, (b) the following general formula

[Chemical 4] (In the formula, R ₁ represents an alkyl group having 1 to 30 carbon atoms.) 0.01 to 5 parts by weight of at least one kind of phosphite compound and (c) 2, 2, 6, 6 -A polyolefin resin composition for automobile fuel containing 0.01 to 5 parts by weight of at least one compound having a tetramethylpiperidyl group, and a single layer comprising the composition or an inner layer comprising the composition. The present invention relates to an automobile fuel tank formed of a laminated structure having an outer layer.

The polyolefin resin used in the present invention includes high density polyethylene, low density polyethylene,
Linear low density polyethylene, polypropylene, propylene and a small proportion of ethylene, butene-1, pentene-1, 4,
-Random or block copolymers with other olefins such as methylpentene-1, polybutene-1, butene-1
With a small proportion of other olefins or a blend of these polyolefin resins with a small proportion of ethylene-propylene copolymer rubber, ethylene-propylene-butadiene copolymer rubber, ethylene-propylene-ethylidene norbornene and other thermoplastic elastomers. Examples of the polyolefin resin include high-density polyethylene and modified products thereof. Particularly, a weight average molecular weight of 100,000 to 50 is preferable. High molecular weight high density polyethylene is preferred.

In the phenol compound represented by the above [Chemical formula 3] of the present invention, the monohydric alcohol which gives the residue represented by A is methanol, ethanol, butanol, octanol, 2-ethylhexanol, Monohydric alcohols such as decanol, dodecanol, tridecanol, isotridecanol, tetradecanol, hexadecanol, octadecanol, eicosanol, docosanol, triacontanol, ethylene glycol,
Diethylene glycol, triethylene glycol, thiodiethanol, propylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol, 1,10-decanediol, 2,2-bis (4-
(2-hydroxyethoxy) phenyl) propane, 3,
9-bis (1,1-dimethyl-2-hydroxyethyl)
Dihydric alcohols such as -2,4,8,10-tetraoxaspiro [5,5] undecane, trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, tris (2-hydroxyethyl) isocyanurate, penta Erythritol, ditrimethylolethane,
Examples thereof include tetrahydric alcohols such as ditrimethylolpropane and diglycerin.

Therefore, specific examples of the phenol compound represented by [Chemical Formula 3] include stearyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and hexamethylenebis-3- (3 , 5-Ditert-butyl-4-hydroxyphenyl) propionate, thiodiethylenebis (3- (3,5-ditert-butyl-4-hydroxyphenyl) propionate), 2,2-bis (4-
(2- (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy) ethyl) phenyl) propane, tris (2- (3- (3,5-di-tert-butyl-
4-hydroxyphenyl) propionyloxy) ethyl) isocyanurate, tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl) methane and the like can be mentioned.

The amount of these phenol compounds added is 0.01 to 5 relative to 100 parts by weight of the polyolefin resin.
Parts by weight, more preferably 0.05 to 3 parts by weight, and if the addition amount is less than 0.01 parts by weight, the effect of preventing thermal oxidation deterioration during molding is insufficient, and 5 parts by weight is added. Even if it is contained in excess, no further improvement in stabilizing effect is observed.

In the phosphite compound represented by the chemical formula 4 used in the present invention, the alkyl group having 1 to 30 carbon atoms represented by R ₁ is methyl, ethyl, propyl, isopropyl, butyl or isobutyl. , Tert-butyl, tert-butyl, amyl, hexyl, heptyl, isoheptyl, octyl, isooctyl, 2-ethylhexyl, nonyl, decyl, isodecyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, heneicosyl, docosyl, tetracosyl, hexacosyl,
Examples thereof include linear and branched alkyl groups such as triacontyl.

Accordingly, as a specific example of the phosphite compound represented by the chemical formula 4, 2,2'-methylenebis (4,6-ditertiarybutylphenyl) .methylphosphite (R ₁ = methyl compound ), 2,2 'methylenebis (4,6-di-tert-butylphenyl) butyl phosphite (R ₁ = compound of butyl), 2,2'-methylenebis (4,6-di-tert-butylphenyl) octyl Phosphite (R ₁ = octyl compound), 2,2′-methylenebis (4,6-di-tert-butylphenyl) .2-ethylhexyl phosphite (R ₁ = 2-ethylhexyl compound), 2,2′- methylenebis (4,6-di-tert-butylphenyl) dodecyl phosphite (compound of R ₁ = dodecyl), 2,2'-methylenebis (4,6-di-tert-butylphenyl) octa Etc. Sil phosphite (Compound of R ₁ = octadecyl) and the like.

The amount of these phosphite compounds added is
0.01 to 100 parts by weight of polyolefin resin
5 parts by weight, more preferably 0.05 to 3 parts by weight. If the addition amount is less than 0.01 parts by weight, the effect of preventing thermal oxidative deterioration during molding is insufficient. Even if it is contained in excess, no further improvement in stabilizing effect is observed.

The compound having a 2,2,6,6-tetramethylpiperidyl group used in the present invention is 1-substituted or unsubstituted-2,2,6,6-tetramethyl-4-.
Ester compound of piperidinol and organic carboxylic acid or inorganic oxygen acid or 1-substituted or unsubstituted-2,
Examples thereof include amides of 2,6,6-tetramethyl-4-piperidylamines and organic carboxylic acids, condensates of cyanuric chloride, and condensates of organic dihalides. In addition, these compounds are 1-substituted or unsubstituted-
2,2,6,6-Tetramethyl-4-piperidinol and mixtures with other monohydric or polyhydric alcohols and 1
May be a mixed ester compound with a tetravalent carboxylic acid, 1-substituted or unsubstituted-2,2,6,6-tetramethyl-4-piperidylamine and other monovalent or polyvalent amine compounds It may be a condensate of a mixture of and cyanuric chloride.

1-substituted or unsubstituted-2,2,6,6-
Examples of the substituent at the 1-position in tetramethyl-4-piperidinol or 1-substituted or unsubstituted-2,2,6,6-tetramethyl-4-piperidylamines include an alkyl group, an alkoxy group and an acyl group. As the alkyl group, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, amyl, hexyl, octyl, isooctyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl and the like having 1 to 10 carbon atoms. 12 alkyl groups, the alkoxy groups include alkoxy groups derived from the above alkyl groups, and the acyl groups include formyl, acetyl, propionyl, butyroyl, acryloyl, methacryloyl, benzoyl and the like.

The carboxylic acid having a valence of 1 to 4 used to derive the compound having a 2,2,6,6-tetramethylpiperidyl group used in the present invention includes acetic acid, propionic acid, acrylic acid and methacrylic acid. , Monocarboxylic acids such as butyric acid, octylic acid, isooctylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, montanic acid, benzoic acid, toluic acid, salicylic acid, oxalic acid, malon Acid, succinic acid,
Glutaric acid, adipic acid, azelaic acid, sebacic acid,
Dodecanedioic acid, maleic acid, fumaric acid, itaconic acid,
Divalent carboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid, trivalent carboxylic acids such as tricarballylic acid, butanetricarboxylic acid, butenetricarboxylic acid and trimellitic acid, and tetravalent carboxylic acids such as butanetetracarboxylic acid and pyromellitic acid. The acid is given.

As described above, the compound having a 2,2,6,6-tetramethylpiperidyl group used in the present invention is a mixture of a piperidinol compound and another monohydric or polyhydric alcohol. Although it may be an ester compound, as the other alcohol used in this case, an alcohol which gives a residue represented by A in [Chemical Formula 3] can be used.

Therefore, 2, 2, 6 used in the present invention
Examples of the ester compound having a 6-tetramethylpiperidyl group include 2,2,6,6-tetramethyl-4-
Piperidyl benzoate, 2,2,6,6-tetramethyl-4-piperidyl acrylate, 1,2,2,6,6
-Pentamethyl-4-piperidyl acrylate, 2,
2,6,6-Tetramethyl-4-piperidyl stearate, 1,2,2,6,6-pentamethyl-4-piperidyl stearate, bis (2,2,6,6-tetramethyl-4-piperidyl) Succinate, bis (2, 2, 6,
6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (1-octoxy-2,2,6,6)
6-tetramethyl-4-piperidyl) sebacate, bis (1-acetyl-2,2,6,6-pentamethyl-4-)
Piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) terephthalate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl)
-1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tris (2,2 2,6,6-tetramethyl-4-
Piperidyl) -mono (tridecyl) -1,2,3,4-
Butane tetracarboxylate, Tris (1, 2, 2,
6,6-Pentamethyl-4-piperidyl) -mono (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) -di (tridecyl) ) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,6,6-
Pentamethyl-4-piperidyl) -di (tridecyl)-
1,2,3,4-butane tetracarboxylate, 3,
9-bis (1,1-dimethyl-2- (tris (2,2,
6,6-Tetramethyl-4-piperidyloxycarbonyl) butylcarboxy) ethyl) -2,4,8,10-
Tetraoxaspiro [5,5] undecane, 3,9-bis (1,1-dimethyl-2- (tris (1,2,2,
6,6-Pentamethyl-4-piperidyloxycarbonyl) butylcarboxy) ethyl) -2,4,8,10-
Tetraoxaspiro [5,5] undecane and the like can be mentioned.

Further, 1-substituted or unsubstituted-2,2
Examples of derivatives of 6,6-tetramethylpiperidylamines include 2,4,6-tris (2,2,6,6-
Tetramethyl-4-piperidylamino) -1,3,5-
Triazine, 2,4,6-tris (N-butyl-N-)
2,2,6,6-Tetramethyl-4-piperidylamino) -1,3,5-triazine, 1,5,8,12-tetrakis (4,6-bis (N-butyl-N-2,2) ，
6,6-Tetramethyl-4-piperidylamino) -1,
3,5-triazin-2-yl) -1,5,8,12-
Tetraazadodecane, 1,5,8,12-tetrakis (4,6-bis (N-butyl-N-1,2,2,6,6)
-Pentamethyl-4-piperidylamino) -1,3,5
-Triazin-2-yl) -1,5,8,12-tetraazadodecane, 1,5,12-tris (4,6-bis (N-butyl-N-2,2,6,6-tetramethyl) -4
-Piperidylamino) -1,3,5-triazine-2-
Ill) -1,5,8,12-tetraazadodecane, 1,
5,12-Tris (4,6-bis (N-butyl-N-
1,2,2,6,6-pentamethyl-4-piperidylamino) -1,3,5-triazin-2-yl) -1,
5,8,12-Tetraazadodecane, 1,6,11-tris (4,6-bis (N-butyl-N-2,2,6,6)
-Tetramethyl-4-piperidylamino) -1,3,5
-Triazin-2-ylamino) undecane, 1,6
11-tris (4,6-bis (N-butyl-N-1,
2,2,6,6-Pentamethyl-4-piperidylamino) -1,3,5-triazin-2-ylamino) undecane, 1,6-bis (2,2,6,6-tetramethyl-4-piperidyl Amino) hexane / 2-tert-octylamino-4,6, -dichloro-1,3,5-triazine condensate, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) Examples include hexane / dibromoethane condensate.

Among these compounds having a 2,2,6,6-tetramethylpiperidyl group, a compound having two or more 2,2,6,6-tetramethylpiperidyl groups in one molecule is particularly preferable. Great effect and preferable.

The compound having 2,2,6,6-tetramethylpiperidyl group is 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight based on 100 parts by weight of the recycled polyolefin resin. If added in an amount of less than 0.01 part by weight, the effect of preventing thermal oxidative deterioration during molding is insufficient, and if more than 5 parts by weight is contained, it is more stable. No improvement in effect is observed.

The polyolefin-based resin composition of the present invention is also effective for recycling the molding burrs of a polyolefin-based automobile fuel tank as described above, but the collected polyolefin-based resin automobile is further used. It is also effective when manufacturing a polyolefin resin fuel tank using recycled fuel tank materials. The stabilizing effect of the additive combination of the present invention is remarkably large, and it is possible to manufacture an automobile fuel tank made of a polyolefin resin with extremely little deterioration in physical properties even when a polyolefin resin deteriorated to some extent by such heat history is used. it can.

The composition of the present invention may also contain other additives such as other phenolic antioxidants, other phosphite-based or phosphonite-based antioxidants, and thioether-based antioxidants to be added to the polyolefin-based polymer material. Antioxidants, benzophenone-based or benzotriazole-based UV absorbers, nucleating agents, antistatic agents, lubricants, processing aids, acid neutralizers,
Pigments, fillers and the like can be added.

Further, the polyolefin resin automobile fuel tank produced from the composition of the present invention can be produced by a usual blow molding method, and the polyolefin resin automobile fuel tank can be produced by the above-mentioned polyolefin resin. It may be formed of a single resin layer, or may have a multi-layer structure in which a polyamide resin layer such as polycaprolactam is included in a polyolefin resin layer in order to improve barrier properties.

[0026]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following examples.

Example 1 and Comparative Example 1 High-density polyethylene having a weight average molecular weight of 250,000 and a density of 0.945 g / cm ³ (manufactured by Tonen Kagaku KK: B-5742X)
100 parts by weight, tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl) methane 0.05 parts by weight, tetrakis (2,2,6,
6-Tetramethyl-4-piperidyl) -1,2,3,4
-Butane tetracarboxylate 0.1 parts by weight and Table 1
0.2 parts by weight of each of the sample compounds shown in 1 above are mixed by a Henschel mixer, and extruded at 230 ° C. by a single-screw extruder to prepare pellets, and each pellet is pressed, and is stipulated in JIS K 7113. No. 2 test piece was prepared.

Each of these test pieces was placed in a pressure-resistant stainless steel container having a volume of 500 mL and containing gazoline, and
It was kept at ℃ and stored for 9 months. Then, heat at 110 ° C for 28 days in a gear oven to determine the tensile elongation at break according to JIS.
It was measured according to K 7113, and the retention rate with respect to the tensile elongation at break of the test piece before immersion was shown as a percentage.

Also, a test piece was prepared in the same manner by using a pellet obtained by repeating the extrusion process 5 times, and the tensile fracture elongation of this test piece was measured according to JIS K 7113, and the test piece was prepared from the pellet of the extrusion process once. The retention rate with respect to the tensile elongation at break of the test piece was shown as a percentage. The results obtained are shown in Table 1.

[0030]

[Table 1]

Example 2 and Comparative Example 2 High-density polyethylene having a weight average molecular weight of 250,000 and a density of 0.945 g / cm ³ (Tonen Kagaku KK: B-5742X)
100 parts by weight, tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxymethyl) methane 0.05 parts by weight, 2,2'-methylenebis (4,6-di-tert-butylphenyl) 0.2 parts by weight of 2-ethylhexyl phosphite and 0.1 parts by weight of the sample compound shown in Table 2 were mixed with a Henschel mixer and extruded at 230 ° C. with a single screw extruder to prepare pellets.

Using these pellets, test pieces were prepared in the same manner as in Example 1, and the same tests as in Example 1 were conducted. Further, a test piece was prepared from a pellet obtained by repeating extrusion processing 5 times by the same operation, and the same test as in Example 1 was performed. The results obtained are shown in Table 2.

[0033]

[Table 2]

Example 3 and Comparative Example 3 100 parts by weight of high-density polyethylene (HIZEX 8200B manufactured by Mitsui Petrochemical Co., Ltd.) having an average molecular weight of 240,000, a density of 0.956 g / cm ³ , and a melt flow index of 0.03, tetrakis (3- (3,5-di-tert-butyl-4-
Hydroxyphenyl) propionyloxymethyl) methane 0.1 part by weight, 1,6,11-tris (4,6-bis (N-butyl-N-1,2,2,6,6-pentamethyl-4-piperidylamino) ) -1,3,5-triazine-
0.2 parts by weight of 2-ylamino) undecane and 0.1 parts by weight of the sample compound shown in Table 3 were mixed with a Henschel mixer and extruded at 230 ° C. with a single screw extruder to prepare pellets.

The high density polyethylene pellets obtained,
Polycaprolactam and an adhesive resin (Admer-GT-3 manufactured by Mitsui Petrochemical Co., Ltd.) are formed into a polyethylene layer-adhesive resin layer-polycaprolactam layer-adhesive resin layer-polyethylene layer in three types and five layers. 3 extruders, 5
Using a blow molding machine having two ring-shaped plungers and an accumulator head, the accumulator head temperature was processed at 230 ° C., and 6 types of gasoline tanks having an average wall thickness of 6 mm were manufactured.

Each of the gasoline tanks was filled with 50% by volume of gasoline, allowed to stand at 40 ° C. for 8 weeks, and then heated in a gear oven at 110 ° C. for 4 weeks. After repeating this cycle twice, the test piece was cut out and stretched at tensile rupture. The tensile strength was measured and the retention rate (percentage) with respect to the tensile elongation at break of the test piece cut out from the gasoline tank before the test was determined.

The burrs produced when the above-mentioned three-kind five-layer gasoline tanks were manufactured were finely pulverized so that the average particle diameter of polyamide was 5 μm or less, and extruded again at 230 ° C. using these. To produce recycled pellets, and these recycled pellets are used to blow 230
A single-layer gasoline tank was manufactured at ℃.

A test piece was cut out from this gasoline tank, and the retention rate (percentage) with respect to the tensile elongation at break of the test piece cut out from the high-density polyethylene single-layer gasoline tank produced from the initial pellets was obtained. The results are shown in Table 3.
Shown in.

[0039]

[Table 3]

As shown in each example, the polyolefin resin composition for automobile fuel tanks containing the specific additive according to the present invention in combination is molded when heated after immersion in gasoline and under severe conditions. Even when the processing is repeated, the physical properties are not significantly deteriorated, and it is clear that the automobile fuel tank produced from these compositions has excellent gasoline resistance and heat resistance.

On the other hand, in the case of not using the phosphite compound or in the case of the comparative example using a phosphite compound different from that used in the present invention, the physical properties are deteriorated after the gasoline immersion and the molding process are repeated. Remarkably, this is because although the phosphite compound has a large effect of retaining the physical properties, phosphite compounds other than those specified in the present invention may be extracted into gasoline, or decomposed or volatilized under severe molding and processing conditions. It is thought that this is because the effect is lost.

Further, the tetramethylpiperidine compound is
Although it is generally known to be a light stabilizer that prevents deterioration of polyolefin due to ultraviolet irradiation, the composition of the present invention containing a tetramethylpiperidine compound unexpectedly unexpectedly undergoes heat treatment under severe molding and processing conditions. It shows an excellent stabilizing effect against oxidative deterioration. On the other hand, benzophenone-based compounds and benzotriazole-based compounds, which are known as light stabilizers for polyolefin-based resins like the tetramethylpiperidine compound, show almost no such effect, and the effect of the combination of the present invention is extremely specific. It is obvious that this is the case.

[0043]

As described above, in the present invention, by blending a polyolefin resin with a specific phenolic antioxidant, a specific phosphite compound and a tetraalkylpiperidine compound, gasoline resistance, It is possible to obtain a polyolefin-based resin composition having excellent heat resistance and suitable for manufacturing a polyolefin-based resin automobile fuel tank.

Front page continuation (72) Inventor Kaoru Asagawa 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Takayuki Fukui 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd.

Claims (3)

[Claims] 1. A polyolefin resin and 100 parts by weight of the polyolefin resin, (a) the following general formula: (In the formula, A represents a residue obtained by removing n hydroxyl groups from a monohydric to tetrahydric alcohol, and n represents 1 to 4.) 0.01 to 5 weight of at least one phenol compound represented by Part, (b) the following general formula: (In the formula, R ₁ represents an alkyl group having 1 to 30 carbon atoms.) 0.01 to 5 parts by weight of at least one kind of phosphite compound and (c) 2, 2, 6, 6 -A polyolefin resin composition for an automobile fuel tank, which contains 0.01 to 5 parts by weight of at least one compound having a tetramethylpiperidyl group. 2. The composition according to claim 1, wherein the polyolefin resin is high density polyethylene. 3. A polyolefin resin and 0.01 to 5 of at least one phenol compound represented by (a) [Chemical Formula 1] per 100 parts by weight of the polyolefin resin.
Parts by weight, 0.01 to 5 parts by weight of (b) at least one of the phosphite compounds represented by [Chemical Formula 2], and (c)
A single layer made of a polyolefin resin composition containing 0.01 to 5 parts by weight of at least one compound having a 2,2,6,6-tetramethylpiperidyl group, or an inner layer made of the composition; A vehicle fuel tank made of a polyolefin resin, characterized by being formed of a laminated structure having an outer layer.