JPH04163022A - Polyacetal resin gasoline tank - Google Patents

Abstract

PURPOSE:To obtain a gasoline tank, the formability of which is favorable and which has small transmittances with respect to gasoline and to methanol and favorable impact resistance by a method wherein polyacetal resin having a certain fixed melt index is formed by blow molding at a certain fixed extrusion temperature. CONSTITUTION:The polyacetal resin gasoline tank concerned is formed by blow-molding polyacetal resin having the melt index (MI) of 0.005-1.0 at the resin extrusion temperature of 180-260 deg.C. In this case, in order to improve the practical properties, polymeric substance for improving the impact resistance mainly consisting of vinyl polymer and elastomer is preferably blended or reacted with polyacetal for use. The resultant gasoline tank has very small transmission factors to gasoline and to methanol. The gasoline tank having arbitrary shape can be produced by blow molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a gasoline tank made of polyacetal resin molded by blow molding.

[Conventional technology]

Traditionally, gas tanks have been manufactured exclusively using metal. In recent years, gasoline tanks mainly made of high-density polyethylene have been put into practical use with the aim of reducing the weight of automobiles.

[Problems to be Solved by the Invention] However, high-density polyethylene has an essential drawback of high gasoline permeability.

In order to overcome this drawback, methods have been developed in which the inner surface of high-density polyethylene gasoline tanks is chemically treated, such as by fluorination or sulfonation. Alternatively, a method of laminating high-density polyethylene and polyamide has also been developed.

Chemical treatment methods not only complicate the manufacturing process but also have the disadvantage of non-uniformity of the chemical treatment.

In addition, the lamination method has the drawback that it cannot use recycled materials, so there is an extremely large loss of resin during molding. [Measures to Solve the Problems] In order to solve the above problems, the present inventors have proceeded with their studies, and as a result, they have developed a blow molding method using a polyacetal resin having a certain melt index at a certain extrusion temperature. It was discovered that a polyacetal gasoline tank with extremely excellent performance could be obtained by molding it using the following method.

That is, the present invention is a polyacetal resin gasoline tank formed by blow molding a polyacetal resin having a melt index of 0.005 to 1.0 at an extrusion resin temperature of 180 to 260°C.

The gasoline tank of the present invention has extremely low permeability for gasoline and methanol, and can be made into any shape by blow molding.

[Detailed Description of the Invention] In the present invention, the melt index (hereinafter abbreviated as IMI) is
A polyacetal resin in the range of 0.005 to 1.0 can be used as a raw material.

Here, MI in the present invention refers to a value measured according to ASTM D-1238 (E condition). (Unit: 8710 minutes) Ml is o,
If there is no oos groove, the blow moldability will be significantly poor. On the other hand, when Ml exceeds 1.0, the drawdown of the parison during blow molding is large and a good molded product (
gas tank).

Further, in the present invention, it is necessary that the extrusion temperature be in the range of 180 to 260°C. If the extrusion temperature is less than 180°C, a molded article with a good shape cannot be obtained.

On the other hand, if the extrusion temperature exceeds 260°C, silver streaks will run on the surface of the molded product, impairing its appearance.

The polyacecool resin of the present invention has an MI of 0.005 to
If it is a polyacetal in the range of 1.0, it can be linear, branched,
Any cross-linked molecular structure can be used.

Among these molecular structures, a branched or crosslinked molecular structure is more preferable from the viewpoint of the appearance of the molded article, that is, from the viewpoint of the surface finish of the molded article and from the viewpoint of preventing drawdown.

Here, polyacetal resin with a straight-line molecular structure is
It can be obtained by homopolymerizing formaldehyde or trioxane, or by copolymerizing formaldehyde or trioxane with a cyclic ether.

Polyacetal resins having a branched molecular structure can be produced by homopolymerizing formaldehyde or trioxane in the presence of a polyfunctional compound containing three or more functional groups such as hydroxyl, amino, or carboxyl groups in one molecule, or by homopolymerizing formaldehyde or trioxane. It can be obtained by copolymerizing honosymane or trioxane with a cyclic ether.

In addition, the polyacetal resin that develops the crosslinking molecular structure is produced by homopolymerizing formaldehyde or trioxane in the presence of a polyfunctional glycidyl ether containing three or more epoxy groups in one molecule, or by polymerizing formaldehyde or trioxane with a cyclic ether. It can be obtained by copolymerizing with.

Further, in the present invention, a composition obtained by blending or reacting a polymer for improving impact resistance with straight-set, branched, or cross-linked polyacetal may be used as a raw material, or a composition obtained by blending these polymers may be used. Alternatively, polyacetal alone may be used as a raw material without reacting.

However, from the viewpoint of improving the practical performance of a gasoline tank, it is preferable to blend or react with polyacetal a polymer for improving impact resistance, the main component of which is a vinyl polymer or an elastomer.

Here, the polymer for improving impact resistance is 125 to 80
It is a vinyl polymer or/and elastomer having a glass transition temperature of °C.

Here, the vinyl polymer will be specifically explained.

The first group of vinyl polymers includes low density polyethylene (LD), high density polyethylene (HD), linear low density polyethylene (LL), low density polyethylene/styrene graft copolymer, and low density polyethylene/acrylonitrile styrene graft copolymer. Polyethylene polymers such as copolymers and modified low-density polyethylene (hydroxyl modified).

The second group of vinyl polymers are ethylene-propylene copolymers, ethylene-propylene-diene copolymers,
Modified ethylene/propylene/diene copolymer (hydroxyl group modified), ethylene/acrylic acid copolymer, ethylene/methacrylic acid/2-hydroxylethyl methacrylic acid copolymer, modified ethylene/vinyl acetate copolymer (hydroxyl group modified) It is an ethylene polymer such as

The third group of vinyl polymers are butadiene-based polymers such as polybutadiene, modified hydrogenated polybutadiene (hydroxyl modified), and isoprene-butadiene copolymers.

In addition to these vinyl polymers, glass transition temperatures of 112
It is also possible to use vinyl polymers between 5 and 80°C.

Next, the elastomer will be specifically explained.

The elastomer referred to in the present invention is a thermoplastic polymer, consisting of an amorphous segment with a low glass transition temperature (soft segment) and a segment with a high glass transition temperature (hard segment) that creates a thermoreversible crosslinking/bonding structure. )
It is a copolymer of

In the present invention, it is possible to use an elastomer whose soft segment and hard segment have a glass transition temperature between -125 and 80°C.

The first group of elastomers are polystyrene-based elastomers, which have polystyrene as the hard segment. Soft segments to be combined with polystyrene include diene types such as polybutadiene and polyisoprene, and hydrogenated diene types such as hydrogenated polybutadiene and hydrogenated polyisoprene. Among these polystyrene elastomers, polystyrene-polybutadiene block copolymers and polystyrene-hydrogenated polybutadiene block copolymers are particularly preferred.

The second group of elastomers are polyester elastomers, which have hard segments of polyester such as polyethylene terephthalate, polybutylene terephthalate, modified polyethylene terephthalate, and polyethylene butylene terephthalate. Soft segments to be combined with polyesters include polyethers such as polypropylene glycol, polytetramethylene glycol, and the like.

Among these polyester elastomers, polybutylene terephthalate-polytetramethylene glycol block copolymer and polyethylene-butylene terephthalate-polytetramethylene glycol block copolymer are particularly preferred.

The third group of elastomer portions are polyamide elastomers, which have polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12 as hard segments. Soft segments to be combined with polyamides include polyethers such as polypropylene glycol, polytetramethylene glycol, and polyesters such as polyethylene adipate and polybutylene succinate. Among these polyamide elastomers, nylon 6-polypropylene glycol block copolymer and nylon 6-polytetramethylene glycol block copolymer are particularly preferred.

The fourth group of elastomers are polyurethane elastomers, which have urethane as the hard segment. [Here, urethane is obtained by reacting a diisocyanate such as 4,4'-diphenylmethane diisocyanate or 4,4'-dicyclohexylmethane diisocyanate with a glycol such as ethylene glycol or tetramethylene glycol.

Soft segments to be combined with urethane include polyester diols such as polyethylene adipate and polybutylene adipate, and polyether diols such as polypropylene glycol and polytetramethylene glycol.

Among these polyurethane elastomers, 4.
Polyurethanes synthesized from 4'-diphenylmethane diisocyanate, tetramethylene glycol and polytetramethylene glycol are preferred.

In addition to these elastomers, glass transition temperatures of -112
It is also possible to use elastomers with temperatures between 5 and 80°C.

Vinyl polymers and elastomers are used by being oriented with linear, branched, or crosslinked polyacetals, or by reacting with polyacetals using a binder such as diisocyanate.

The blending or reaction amount of the polymer for improving impact resistance, which mainly consists of vinyl polymers and elastomers, is preferably in the range of 0.5 to 50 parts per 100 parts of polyacetal. If the blending and reaction amount of the polymer is less than 0.5 part, no effect of improving the impact resistance of the gasoline tank will be observed. On the other hand, if the blending and reaction amount of the positive polymer exceeds 50 parts, the amount of permeation of gasoline and methanol increases, which may pose a practical problem.

After antioxidants, heat stabilizers, flame retardants, etc. are added to the polyacetal resin of the present invention, it is shaped into a gasoline tank by blow molding. The gasoline tank of the present invention is used as a storage tank for gasoline, hydrocarbons such as kerosene, and alcohols such as methanol and ethanol.

Hereinafter, the present invention will be specifically explained using examples. The meanings of the terms used in the examples are as follows.

MI: Melting index at 190°C and 2.16 kg standard load (ASTM D-1238E conditions) Antioxidant: 2,2
-Methylenebis(4-methyl-6-t-butylphenol) Heat stabilizer: Nylon 3 Izot impact value: A polyacetal resin is made into a flat plate using an injection molding machine, and a test piece is made from this flat plate according to ASTM D-256. measurement.

Example 1 (1) Production method of polyacetal resin (branched) Anhydrous formaldehyde was blown into cyclohexane containing glycerin as a branching agent and tetrabutylammonium acetate as a polymerization catalyst, and polymerization was carried out in a 50'' C4 oven.

After the polymer was separated from the cyclohexane by filtration, the ends of the polymer were stabilized using acetic anhydride.

For 100 parts of the stabilized polymer, polyurethane elastomer, (synthesized from 4,4'-diphenylmethane diisocyanate, tetramethylene glycol, polytetramethylene glycol, glass transition temperature -48°C)
and 15°C), 0.5 part of an antioxidant, and 0.3 part of a heat stabilizer were blended and melt-mixed in a 65-cylinder φ twin-screw extruder to form pellets. The Ml of this pellet was 0.08.

(2) Manufacturing method of gasoline tank Using this pellet, the internal volume is 55% by extrusion resin temperature of 215°C using a large blow molding machine with a 90mmφ single-screw extruder.
1 gasoline tank was molded. The moldability is good;
Compared to the case of using high-density polyethylene, the molding time could be considerably shortened.

Moreover, the appearance of the gasoline tank was shiny and had a good finish.

(3) Gasoline tank performance The gasoline permeability of the polyacetal resin of this example at 25°C is 0.23 g, -mII]/m' ・day
The methanol permeability is 0.72 g-proof/m2·day, which is a very low permeability. In addition, the Izot impact value was 15 kg-cm/cm, which was a good value. The pinch-off strength of the bottom of the gasoline tank was also good.

Example 2 (4) Production of polyacetal resin (crosslinking) 1,4-butanediol diglycidyl ether as a crosslinking agent and boron trifluoride butyl etherate as a polymerization catalyst were added to trioxane and ethylene oxide in a twin-screw kneader. 85
Polymerization was carried out at ℃. Triethylamine and water were added to the polymer and stabilized in a 65 mmφ twin screw extruder. Next, to 100 parts of this polymer, a polyester elastomer (terephthalic acid, adipic acid, isophthalic acid, 1,
Synthesized from 4-butanediol, glass transition temperature -18℃
), 0.4 part of antioxidant, and 0.3 part of heat stabilizer were blended and melt-mixed in a 65-m screw extruder to form pellets. The MI of this pellet was 0.2.

(5) Manufacturing method of gasoline tank Using the pellets, a gasoline tank with an internal capacity of 4M was molded at an extrusion resin temperature of 240° C. in a large blow molding machine equipped with a 120 mmφ single-screw extruder.

The moldability was good, and no parison drawdown was observed. Furthermore, compared to high-density polyethylene, it was possible to shorten the molding time. The exterior of the gas tank was also shiny.

(6) Performance of gasoline tank The gasoline permeability of the polyacetal resin of this example at 25°C is 0.28 g-mm/m'-day, and the methanol permeability is good at 0.68 g-mm/m'-day. It was a great value. In addition, the Izotsu impact value is 12kg-C.
It showed a good value of m/Cm. The pinch-off strength of the bottom surface of the gasoline tank in this example was also excellent.

Example 3 (7) Production method of polyacetal resin Trifluoromethanesulfonic acid was added as a polymerization catalyst to trioxane, 1, 3-dioxolane, and polymerized at 90°C in a twin-screw kneader. Tributylamine and water were added to this polymer, and it was stabilized in a 65-φ twin screw extruder. Next, 0 parts of antioxidant was added to 100 parts of this polymer.
．． 3 parts and 0.25 parts of a heat stabilizer were blended, and the mixture was melt-mixed in a 65 mmφ twin-screw extruder to form pellets. The MI of this pellet was 0.65.

(8) Method for manufacturing a gasoline tank Using this pellet, 12. A gasoline tank with an internal capacity of 35 Il was molded at an extrusion resin temperature of 190° C. using a large blow molding machine equipped with an Oanφ single-screw extruder.

The moldability was good and the molding time could be shortened.

(9) Performance of gasoline tank The gasoline permeability of the polyacetal resin of this example at 40"C is 0.30 g-mm/rd-day, and the methanol permeability is good at 3.5 g-mm/day. The Izod impact value was 9.0kg-Cm.
/ It was CM. The pinch-off strength of the bottom surface of the gasoline tank in this example was excellent.

Example 4 Preparation of polyacetal resin Trioxane and 1,3-dioxolane were added as a polymerization catalyst and trifluoromethanesulfonic acid was polymerized in a twin-screw kneader at 90°C. Triethylamine and water were added to this polymer, and it was stabilized in a 45 mIDφ twin screw extruder. To this polymer 100, 15 parts of polyester elastomer (synthesized from terephthalic acid, adipic acid, 1,4-butanediol, polytetramethylene glycol, glass transition temperature -68°C and 45°C), '4.4'-
Add 1 part of dicyclohexylmethane diisocyanate,
The reaction was carried out in a 65 mmφ extruder. Plus 0 antioxidants
．． 5 parts and 0.3 parts of a heat stabilizer were added, and pellets were made using a 50 mmφ single screw extruder. The MI of this pellet is 0.
It was 36.

(6) Method for manufacturing a gasoline tank Using the pellets, a gasoline tank with an internal capacity of 80 f was molded using a large blow molding machine equipped with a 90-hole single-screw extruder at an extrusion resin temperature of 230°C. The moldability was good.

Performance of beaten gasoline tank The gasoline permeability of the polyacetal resin of this example at 25°C is 0.24 g-mm/m'-day, and the methanol permeability is 0.70 g-mm/m'-day.
The transmittance was extremely low. In addition, the Izot impact value was good at 23 kg-cm/cm, and the pinch-off strength at the bottom of the tank was also good.

Comparative Example 1 (Example of other resins) 0 Manufacturing method of high-density polyethylene gasoline tank M I
Using high-density polyethylene of 0.02 (ASTM D-1239E conditions), the inner volume was 55I at an extrusion resin temperature of 200℃ using a large blow molding machine with a 90mmφ single-screw extruder.
2 gasoline tanks were molded. The molding time was longer than when polyacetal resin was used, and the appearance of the gasoline tank was lackluster and the finish was not necessarily good.

Performance of gasoline tank made of high-density polyethylene The gasoline permeability of the high-density polyethylene of this comparative example at 40° C. was 95 g-mm/m'·day, which was poor. Furthermore, the methanol permeability was 2.8 g-mm/m''·day. The Izod impact value was 15 kg-C [[17 cm], and the pinch-off strength at the bottom of the tank was also at a level that caused no problems.

Examples 5 to 10 From polyacecool having a linear, branched, or crosslinked structure shown in Table 1, a polymer for improving impact resistance shown in Table 1, an antioxidant, and a heat stabilizer, the A 55β gasoline tank was molded at the extrusion resin temperature shown. The moldability and finish of the gasoline tank were both good.

Furthermore, the gasoline permeability, methanol permeability, and Izodt impact value of the polyacetal resins of each example were all good, and the gasoline tanks molded from these polyacetal resins all had excellent performance.

Comparative Example 2 (Extrusion resin temperature example) The polyacetal resin used in Example 1 was
An attempt was made to perform blow molding at an extrusion resin temperature of 178° C. using a large blow molding machine with a 0 mmφ single screw extruder, but the shape of the gasoline tank was incomplete and a good molded product could not be obtained.

Although molding was attempted by raising the extrusion resin temperature to 263° C., numerous silver streaks were observed on the surface of the gasoline tank, and the appearance quality was extremely poor.

Comparative Example 3 (Example of Ml) Anhydrous formaldehyde was polymerized to synthesize a polyacetal having a straight-line structure with an MI of 1.5.

An antioxidant and a heat stabilizer were added to this polyacetal to obtain a polyacetal resin. Using this polyacetal resin, blow molding was attempted using a large blow molding machine equipped with a 90 mm diameter single screw extruder. However, the drawdown of the parison was severe, making blow molding impossible.

On the other hand, a polyacetal having a branched structure having an MI of 0.004 was synthesized using anhydrous formaldehyde and glycerin as a branching agent. An antioxidant and a heat stabilizer were added to this polyacetal to obtain a polyacetal resin.

Blow molding was attempted using this polyacetal resin in a large blow molding machine equipped with a 90 mm diameter single screw extruder, but due to the lack of fluidity of the resin, it was not possible to obtain a gasoline tank.

Example 11 The reaction amount of the modified ethylene-propylene-diene copolymer used in Example 10 (the amount of the ethylene-propylene-diene copolymer subjected to the coupling reaction using methylene diisocyanate) was increased to 55 parts. The same polyacetal as in Example 10 was used, and the same imitation as in Example Work 0 was carried out.

The MI of the polyacetal resin was 0.17.

When blow molding was performed using this polyacetal resin, the moldability of the gasoline tank was good, but it was observed that the gasoline permeability tended to increase to 35 g-mm/m'day. Further, a gasoline tank was formed by reducing the amount of the modified ethylene-propylene-diene copolymer to 0.4 parts. M of polyacetal resin
I was 0.13, and moldability was good. Also, the gasoline tank permeability is 0.25 g -mm/m' -
Good condition and impact value of 9 kg-c.
It was slightly low at m/cm.

The Izot impact value of the polyacetal resin to which the modified ethylene-propylene-diene copolymer was not added (therefore unreacted) was 9 kg-cm/cm.

〔Effect of the invention〕

The gasoline tank made of polyacetal judo of the present invention has good moldability during blow molding, and has low gasoline permeability and
The methanol permeability is also extremely low.

Furthermore, a gasoline tank made of polyacetal resin, which is obtained by blending or reacting a polymer for improving impact resistance with polyacetal, has good impact resistance.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. A gasoline tank made of polyacetal resin, characterized in that it is molded by blow molding a polyacetal resin having a melt index of 0.005 to 1.0 at an extrusion resin temperature of 180 to 260°C. . 2. The gasoline tank according to claim 1, wherein the polyacetal resin is a polyacetal having a branched or crosslinked molecular structure. 3. The polyacetal resin is a vinyl polymer having a glass transition temperature of -125 to 80°C, or 0.5 to 50 parts of a polymer for improving impact resistance, the main component of which is 1 and an elastomer, per 100 parts of polyacetal. The gasoline tank according to claim 1, which is a composition obtained by blending or reacting parts.