JPH0447938A - Multilayer plastic fuel tank - Google Patents

Abstract

PURPOSE:To improve the drawdown resistance of a parison and to shorten a molding cycle by forming a polymaide layer from a copolymer of polyamide 6 and polyamide 66. CONSTITUTION:A multilayer plastic fuel tank is formed by laminating a high density polyethylene layer and a polyamide layer through a high density polyethylene layer modified with unsaturated carboxylic acid or a derivative thereof. Herein, the polyamide layer is composed of co-polyamide of polyamide 6 and polyamide 66 and the content of the repeating unit constituting polyamide 6 in co-polyamide is 60 - 90 wt.%, pref., 70 - 80 wt.% and the content of the repeating unit constituting polyamide 56 is 40 - 10 wt.%, pref., 30 - 20 wt.%.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a multilayer plastic fuel tank, and in particular, it has a high-density polyethylene layer, a polyamide layer, and a modified high-density polyethylene layer, and has good moldability at low temperatures. Regarding multi-layer plastic fuel tanks.

[Prior Art and Problems to be Solved by the Invention] Polyolefin resins are inexpensive, have high strength, and have excellent weather resistance, chemical resistance, etc., and are therefore widely used in the manufacture of various containers. However, its barrier properties are not necessarily sufficient, and it has not been possible to use it in fuel tanks such as gasoline in areas with strict regulations. Therefore, attempts have been made to use polyolefin as the main layer and polyamide as the barrier layer, but since the adhesive strength between the polyolefin layer and the polyamide layer is weak, polyolefin resin is used as an adhesive layer between these two layers using unsaturated carboxylic fermentation. Various methods have been proposed for laminating layers with a modified plastic layer interposed therebetween (Japanese Patent Laid-open Nos. 58-220738 and 62-110526).
No. etc.).

Furthermore, Japanese Patent Publication No. 60-34461 discloses that when manufacturing a multilayer blow container in which a polyolefin resin layer and a layer of nylon resin or saponified ethylene-vinyl acetate copolymer are laminated via an intermediate layer by blow molding, the intermediate layer is A modified ethylene copolymer obtained by graft-polymerizing 0.01 to 1% by weight of maleic anhydride to a copolymer of ethylene having a crystallinity of 2 to 30% and a secondary olefin having 3 or more carbon atoms is used. Disclosed is a method for manufacturing a multilayer blow-molded container characterized by the following.

On the other hand, JP-A No. 55-91634 discloses (a) a polyolefin resin layer, (b) a crystallinity of 1 to 35% and a melt index of 0. Polyamide system consisting of a molten mixture of a modified polymer in which maleic anhydride is grafted onto an olefin copolymer (maleic anhydride content 0.05 to 1% by weight) and nylon. The resin layer is made of (C) an ethylene/reactive olefin copolymer with a crystallinity of 2 to 30% and a melt index of 0.01 to 50 g/10 min, to which maleic anhydride is grafted (maleic anhydride content 0. This patent discloses a multilayer molded article which is laminated through modified polyolefin resin layers made of a modified polymer (01 to 1% by weight) and which exhibits little decrease in strength even when Paris is used as a raw material.

However, polyamide 6 is usually used for the polyamide layer of the above-mentioned multilayer molded product, and in this case, from the viewpoint of moldability of the polyamide layer, the resin temperature of the high-density polyethylene layer, which is the main layer, is controlled to be lower than that of the high-density polyethylene single layer. If it is necessary to set it higher than in the case of a plastic fuel tank, there is a problem that the drawdown resistance of the parison decreases.

In particular, when mixing paris generated during the production of multilayer plastic fuel tanks into the polyolefin side, the resin temperature must be set at 230-250°C to improve the dispersibility of the polyamide.
It is necessary to set the temperature to 0°C, and there is a remarkable tendency for the drawdown resistance of this parison to decrease.

Therefore, an object of the present invention is to provide a multilayer plastic fuel tank having a high-density polyethylene layer and a polyamide layer, which has sufficient barrier properties and impact resistance, and has improved parison drawdown resistance. The goal is to provide the following.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventors found that if the polyamide layer is formed from copolymerized polyamide 6-66,
The present inventors have discovered that even if the resin temperature of the high-density polyethylene layer during extrusion molding is lowered, it is possible to manufacture a multilayer plastic fuel tank, thereby improving drawdown, etc., and have conceived the present invention.

In other words, the high-density polyethylene layer and the polyamide layer are
The multilayer plastic fuel tank of the present invention is constructed by laminating layers of high-density polyethylene modified with an unsaturated carboxylic acid or a derivative thereof. ,
(b) Repeating single positions 0 to 4 constituting polyamide 66
It is characterized by being made of copolymerized polyamide with 0% by weight.

The present invention will be explained in detail below.

In the present invention, the high density polyethylene forming the high density polyethylene layer has a density of 0.935 g/a1 or more,
In addition, its melt index (Ml 190℃, 2.1
6 kg load) is preferably 0.003 to 2 g/10 min in consideration of drawdown resistance, moldability, and impact resistance. More preferably, it is 0.01 to 1 g and 710 minutes. In addition, High Road Melt Index (HLMI,
190℃, 21.6kg load), 70g/
Preferably 10 minutes or less, more preferably 1 to 20 g/1
It is 0 minutes.

In the present invention, the resin for the high-density polyethylene layer is a mixture of 100 parts by weight of high-density polyethylene as described above and 20 to 200 parts by weight of recycled material obtained from part or all of the multilayer plastic fuel tank. The resulting compositions can also be used.

The polyamide layer is made of a copolymerized polyamide (polyamide 6-66) of (a) repeating units constituting polyamide 6 and (b) repeating units constituting polyamide 66.

In the present invention, the repeating units constituting polyamide 6 (a) are those represented by the following general formula (1): NH-(CHt)s-c-4-0..(11).

In addition, in the present invention, the repeating units constituting (b) polyamide 66 refer to the following general formula (2): % formula % The content ratio of the repeating units constituting (a) polyamide 6 in the above copolyamide is 60 to 90. % by weight, preferably 70 to 80% by weight, and the content of repeating units constituting (b) polyamide 66 is 40 to 10% by weight,
Preferably it is 30 to 20% by weight. (The unit of al is 6
If the unit (b) is less than 40% by weight, the gasoline barrier properties of the multilayer plastic fuel tank will deteriorate, while if the unit (a) exceeds 90% by weight (
If the unit (b) is less than 10% by weight, the impact resistance decreases.

The above polyamide 6-66 is produced by adding ε-caprolactam to a system of hexamethylene diamine and adipic acid, for example.
It can be obtained by forming it into a binary copolymer.

The relative viscosity of such polyamide 6-66 (JISK6
810) is usually 3 to 6.5, particularly preferably in the range of 4 to 6.

In addition, in order to improve impact resistance, the above polyamide 6-
66 may contain up to about 20% by weight of ε-caprolactam, N-butylbenzenesulfonamide, octyl oxybenzoate, etc. as plasticizers. A more preferable plasticizer content is 10% by weight or less.

In addition, in the present invention, as a resin for the polyamide layer,
A blend of the above polyamide 6-66 and a modified olefin elastomer can be used.

In the present invention, the modified olefin elastomer is an olefin elastomer modified with an unsaturated carboxylic acid or its anhydride. Examples of unsaturated carboxylic acids or their anhydrides include monocarboxylic acids such as acrylic acid and methacrylic acid, dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, maleic anhydride, itaconic anhydride, and endic acid anhydride (anhydrous dicarboxylic acid anhydrides such as hymic acid), and dicarboxylic acids and their anhydrides are particularly preferred. Specifically, olefin-based elastomers modified with maleic anhydride or endic anhydride (himic anhydride) are particularly preferred.

In addition, olefin elastomers modified with unsaturated carboxylic acids or their anhydrides include ethylene, propylene,
It means a copolymer rubber of two or more kinds of olefins such as 1-butene, 1-hexene, 4-methyl-pentene, etc., especially ethylene-propylene copolymer rubber (EPR).
and ethylene-butene copolymer rubber (EBR) are preferred.

The ethylene-propylene copolymer (EPR) rubber used in the present invention has a content of repeating units derived from ethylene of 10 to 90 mol% and a content of repeating units derived from propylene of 90 to 10 mol%. It is preferable that A more preferable range is 20 to 80 mol% of the ethylene repeating unit and 80 to 20 mol% of the propylene repeating unit.

In addition, Mooney viscosity ML++a (100°C) of EPR
is preferably in the range of 1 to 120, more preferably 5 to 100.

In the present invention, ethylene-butene copolymer rubber (EB
R) is a block copolymer with a butene-1 content of 10 to 90% by weight, particularly a butene-1 content of 20 to 90% by weight.
80% by weight is preferred.

Mooney viscosity ML of the above ethylene-butene copolymer rubber,
. , (100°C) is preferably in the range of 1 to 120, more preferably 5 to 100.

In addition, in the present invention, ethylene-propylene copolymer (
EPR) and ethylene-butene copolymer rubber (EBR)
basically consists of the above repeating units,
Copolymers containing other resin components can also be used within a range that does not impair the properties of these copolymers.

The content of unsaturated carboxylic acid or its anhydride in the modified olefin elastomer is 1.0X10-' to 6
．． OXl0-'5nol/g, favorable t L < 4:!
2. OX10-'~5, OXl0-'■ol/g. For example, in the case of modification with maleic anhydride, the content of maleic anhydride is o, oos ~ 5% by weight,
Preferably, the content is 0.01 to 3% by weight, and when Himic acid anhydride is used, the content is 0.015 to 4% by weight.
, preferably 0.15 to 1.5% by weight. unsaturated,
If the amount of modification by carboxylic acid or its anhydride is less than the above lower limit, the modified olefin elastomer will not be sufficiently compatible with the polyamide, and if it exceeds the upper limit, the modified olefin elastomer will not be uniformly distributed in the polyamide. Difficult to disperse.

The modified olefin elastomer can be produced by either a solution method or a melt mixing method.

The blending ratio of such modified olefin elastomer is 100 polyamide 6-66 olefin elastomer.
00% by weight is preferably 30% by weight or less. If the olefin elastomer content exceeds 30% by weight, the gasoline barrier properties of the multilayer plastic fuel tank will deteriorate, which is not preferable.

In the present invention, a modified high-density polyethylene layer is formed (
C) Modified high density polyethylene is high density polyethylene modified with an unsaturated carboxylic acid or its anhydride.

As the unsaturated carboxylic acid or its anhydride, those similar to those of the above-mentioned modified olefin elastomer can be used.

Further, as the high-density polyethylene modified with an unsaturated carboxylic acid or its anhydride, the same high-density polyethylene as the above-mentioned high-density polyethylene for the high-density polyethylene layer (A) can be used.

The content of unsaturated carboxylic acid or its anhydride in the modified polyolefin is preferably within the range of 0.005 to 5% by weight. Specifically, when modified with maleic anhydride, The content of maleic anhydride is 0.01 to 3% by weight, more preferably 0.1 to 1% by weight.
When using Himic acid anhydride, the content is 0.015 to 4% by weight, more preferably 0.15 to 1% by weight.
．． The amount shall be 5% by weight. If the amount of modification by maleic anhydride and himic anhydride is less than the lower limit values above, there will be no sufficient effect in improving the adhesion between the modified high-density polyethylene layer and the polyamide layer (and if it exceeds the upper limit value, the The adhesiveness between the modified high-density polyethylene layer and the high-density polyethylene layer decreases.

Such modified high-density polyethylene can be produced by either a solution method or a melt-kneading method.

In addition, in the present invention, fillers, heat stabilizers, light stabilizers, flame retardants, plasticizers, antistatic agents, mold release agents, blowing agents, Additives such as nucleating agents can be added as appropriate.

The multilayer plastic fuel tank of the present invention, which is composed of each layer as described above, has a layered structure as shown in FIG. 1, for example. In FIG. 1, the multilayer molded body consists of a high-density polyethylene layer 1.1, a polyamide layer 2, and a modified high-density polyethylene 3.3 that adheres both layers.

The thickness of each layer may be set appropriately depending on the impact resistance and barrier properties required for the fuel tank, but for example, when used for a gasoline tank, the high density polyethylene layer may be 1.5 to 5 mm thick. polyamide layer for 20~500μs
, the modified high-density polyethylene layer may have a thickness of 20 to 500 un.

Such multilayer plastic fuel tanks are basically made by molding a cylindrical parison having the above-mentioned layered structure using the usual coextrusion method, and then placing this parison in a mold having a cavity of the desired shape. After that, it may be manufactured by blow molding.

In addition, in the present invention, during extrusion of the parison in the above-mentioned manufacturing process, the extrusion temperature of the resin for the high-density polyethylene layer, which is the main layer, is set lower than conventionally. The extrusion temperature of the high-density polyethylene layer is appropriately set within the temperature range of 200 to 230°C depending on the melting point of polyamide 6-66, which will become the polyamide layer.

For example, (a) repeating unit constituting polyamide 6:
(b) When the weight ratio of the repeating units constituting polyamide 66 is 90:10, the resin for the high-density polyethylene layer may be extruded at 220 to 230°C, and (a): (b
)=70:30, 210-220℃, (a):
(b) = 60: In the case of 40, the temperature may be set at 200 to 210°C.

This has the effect of improving the drawdown resistance of the parison and shortening the molding cycle.

In addition, even if the recycled materials collected from parison and defective products generated when blow molding the parison of multilayer plastic/stick fuel tanks are mixed with the resin for the high-density polyethylene layer, the melting point of polyamide 6-66 is polyamide 6
Since the polyamide is lower, it is possible to disperse the polyamide well in the high-density polyethylene matrix even when melt-kneading is performed at a lower temperature than conventionally as described above. Therefore, even if a resin in which recycled material obtained from part or all of the multilayer plastic fuel tank of the present invention is mixed with high-density polyethylene as the resin for the high-density polyethylene layer, the impact resistance of the resulting multilayer plastic fuel tank can be improved. No decrease was observed.

[For production]

In the present invention, since the polyamide layer of the multilayer plastic fuel tank is formed of polyamide 6-66, the resin temperature of the high-density polyethylene layer during extrusion molding of the parison can be lowered than before. Therefore, the drawdown properties of the parison are improved.

The reason why such an effect is obtained is not necessarily clear, but by using polyamide 6-66 as the polyamide layer, melting point, crystallinity, heat resistance, moldability, etc. are improved compared to the case of polyamide 6 homopolymer. This is thought to be because coextrusion molding with , high-density polyethylene, and modified high-density polyethylene becomes possible even at lower temperatures than before.

〔Example〕

The present invention will be explained in further detail by the following examples.

The following materials were used as high-density polyethylene, modified high-density polyethylene, modified olefin elastomer, and polyamide as raw materials for each layer.

[1] High density polyethylene HDPE: (melt index (Ml 190°C1
2,16kg load) 0.03g/10min, High Road Melt Index (HLMI 190℃, 21.6k
g load) 5.5 g/10 min, density 0.945 g/a
I! , weight average molecular weight (~) 20X10') [21 modified high density polyethylene CMPE: (MI (190°C, 2.16kg load) 0.3g/10min, maleic anhydride addition rate 0°4
Weight%, density 0.953 g/cd, weight average molecular weight (
~) 12X10') [31 Modified olefin elastomer modified ethylene-propylene copolymer rubber CMEBR:
(Ethylene-butene copolymer rubber (ethylene content 5
0% by weight) with 0.4% by weight of maleic anhydride added. Ml (190℃, 2.16kg load) 0.3 g
/10 minutes] [41 Polyamide (PA) ■Polyamide 6 PA-1: (Polyamide 6, relative viscosity 4) ■Polyamide 6-66 CPA-1: (Boryamide 6: Polyamide 66=
90:10, relative viscosity 4] CPA-2: (Boryamide 6: Polyamide 66 = 7
0:30, relative viscosity 4] CPA-3: (Boryamide 6: Polyamide 66 = 5
0:50, relative viscosity 4] CPA-4: (Boryamide 6: Polyamide 66=
96:4, relative viscosity 4] ■Polyamide 6-12 CPA-5: (Boryamide 6: Polyamide 12 = 7
0:30, relative viscosity 4] ■Polyamide 6-66/modified olefin elasmer CPA blend-1: (Blend with CPA-2CMEBR (CPA-2: CMEBR=90:1
0) CPA blend-2: (CPA-2 and CMEB
Blend with R (CPA-2: CMEBR=70
: 30) ) Examples 1 to 4 and Comparative Examples 1 to 4 High-density polyethylene, modified high-density polyethylene, and various polyamides shown in Table 2 were molded using a multilayer blow molding machine (NB-60G manufactured by Japan Steel Works, Ltd.). The resin was molded at the temperature shown in Table 2, and a multilayer plastic fuel tank (capacity: 401) with three types and five layers having the layer and standard wall thickness configurations shown in Table 1 was created.

At this time, the drawdown properties during parison molding, the wall thickness distribution (minimum wall thickness) of the multilayer plastic fuel tank, and the low temperature (
A drop impact test at -40°C), gasoline permeability at 40°C and cycle time were measured.

The results are also shown in Table 2.

(1) ○: After extruding the parison, the drawdown at mold closing is 5 cm or less.

△: After extruding the parison, the drawdown at mold closing is 5 (2
) larger and 10an or less.

×: After extruding the parison, the drawdown after closing the mold is Loa.
greater than n.

It was evaluated as

(2) Fill the gasoline tank with a full amount of a mixed solution of water and ethylene glycol (weight equivalent to gasoline), and -4
It was dropped from a height of 6 m at 0° C., and those that did not break were evaluated as ◯, and those that did break were evaluated as ×.

(3) In accordance with ECE34, measure the permeation amount of gasoline, and if the permeation amount is 20 g/day or less, mark it as ○ or 20 g.
/day was evaluated as ×.

As is clear from Table 2, the multilayer plastic fuel tanks of Examples 1 to 5, in which the polyamide layer was formed of polyamide 6-66 with a specific composition, had good parison drawdown resistance and a large minimum wall thickness. , impact resistance, and gasoline barrier properties were also good.

On the other hand, the multilayer plastic fuel tanks of Comparative Example 11, in which the polyamide layer was formed of polyamide 6, and Comparative Example 4, in which the polyamide layer was formed of polyamide 6-12, had poor drawdown resistance.

Furthermore, the multilayer plastic fuel tank of Comparative Example 2 did not have sufficient gasoline barrier properties, and the multilayer plastic fuel tank of Comparative Example 3 did not have sufficient impact resistance.

Note that the minimum wall thickness is a value indicating that the larger the value, the less drawdown, etc., and the better the moldability.

High-density polyethylene, modified high-density polyethylene, and polyamide of the types shown in Table 3 are molded using a multilayer blow molding machine (NB-60G manufactured by Japan Steel Works, Ltd.) in the temperature range shown in Table 3. Multi-layer plastic fuel tank with three types and five layers (capacity 40
j7) was created.

This multilayer plastic fuel tank was crushed using a crusher with a punching plate hole diameter of 8 mm.

This pulverized product of the multilayer plastic fuel tank and a virgin high-density polyethylene material were triblended at a weight ratio of 50:50 to prepare a resin mixture.

The above resin mixture was melt-kneaded at the resin temperature shown in Table 3 to create a single-layer parison.

The dispersed particle size of the polyamide in the parison thus obtained was examined. Also, based on this value, the degree of dispersion of polyamide is determined as follows:
, those exceeding 10 were evaluated as ×.

The results are shown in Table 3 along with the type of polyamide used.

Furthermore, the tensile elongation and tensile impact strength of the above parison were measured, and how these values compared with those of a parison made of virgin material prepared under similar conditions was compared by a tensile test and a tensile impact test.

Note that the tensile elongation is a value measured according to ASTM D638, and the tensile impact strength is a value measured according to ASTM D1822.

The results are also shown in Table 3.

Preparation of multilayer plastic fuel tank The resin mixtures of Examples 5 to 8 were used as the resin for the high density polyethylene layer, and the resin mixtures were used in a multilayer blow molding machine (Japan Steel Works ■) together with modified high density polyethylene and various polyamides shown in Table 4.
NB-60G), the resin temperature is set to the temperature shown in Table 4, and a multilayer plastic fuel tank (capacity 4
01) was created.

At this time, drawdown properties during multilayer parison molding, wall thickness distribution (minimum wall thickness) of a multilayer plastic fuel tank, drop impact test at low temperature (-40°C), and gasoline permeability at 40°C were measured.

The cycle time during manufacturing was also measured.

The results are also shown in Table 4.

From Table 3, it can be seen that when the pulverized product of the multilayer plastic fuel tank of the present invention is mixed into a virgin high-density polyethylene material, its dispersibility is good even when kneaded at a low resin temperature. Therefore, the tensile properties do not deteriorate compared to virgin materials.

In addition, the multilayer plastic fuel tanks of Examples 9 to 12, in which the mixture of the above-mentioned pulverized material and high-density polyethylene was used as the resin for the high-density polyethylene layer, had excellent drawdown properties, wall thickness distribution, impact resistance, and gasoline permeability. All showed good values, and since the molding temperature was low, the cycle time was short at about 3 minutes.

From the above results, it was shown that the multilayer plastic fuel tank of the present invention can be reused by mixing recycled materials such as Paris into the high-density polyethylene layer side.

〔Effect of the invention〕

As detailed above, in the multilayer plastic fuel tank of the present invention, since the polyamide layer is formed of polyamide 6-66, it is possible to lower the resin temperature of the high density polyethylene layer when extruding the parison. I can do it.

Therefore, the drawdown resistance of the parison is improved, and the molding cycle can be shortened.

In addition, this multilayer plastic fuel tank has a high-density polyethylene layer made of a resin mixed with recycled materials, and even if the extrusion temperature of the high-density polyethylene layer is low, the polyamide is uniformly and finely dispersed. There is almost no decrease in physical properties such as impact resistance.

Thus, the multilayer plastic fuel tank of the present invention
It is also economically advantageous because it is possible to mix Paris and the like by-produced during its production into the high-density polyethylene and reuse it.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an example of the layered structure of the multilayer plastic fuel tank of the present invention. 1...High-density polyethylene layer 2...Polyamide resin layer 3...Modified polyolefin layer

Claims (2)

[Claims] (1) A multilayer plastic fuel tank in which a high-density polyethylene layer and a polyamide layer are laminated via a high-density polyethylene layer modified with an unsaturated carboxylic acid or a derivative thereof, wherein the polyamide layer is (a) polyamide 6 90 to 60% by weight of repeating units constituting (b
) A multilayer plastic fuel tank comprising a polyamide copolymerized with 0 to 40% by weight of a repeating single position constituting polyamide 66. (2) The multi-layer plastic fuel tank according to claim 1, wherein the resin for the high-density polyethylene layer includes 100 parts by weight of high-density polyethylene and 20 to 20 parts by weight of recycled material obtained from part or all of the multi-layer plastic fuel tank. 20
A multilayer plastic fuel tank comprising 0 parts by weight.