JPH0447918A - Manufacture of multi-layer plastic fuel tank - Google Patents

Abstract

PURPOSE:To make it possible to manufacture fuel tank, which is excellent in impact resistance and has high density polyethylene layer having the composition, which is prepared by finely and favorably dispersing polyamide in high density polyethylene, by a method wherein the high density polyethylene and flash and the like of multi-layer plastic fuel tank for reworking are kneaded with and extruder having a screw with specified structure. CONSTITUTION:The mixing ratio of reworked material (which is obtained from some part or the whole of multi-layer plastic fuel tank) to high density polyethylene is normally 20 - 200 pts. wt. of reworked material added to 100 pts. wt. of high density polyethylene. An extruder kneads said mixture at the feed zone 22 of a screw 21 and meters it at the metering zone 23. Further, the extruder performs the lateral mixing of resin flow, which tends to be insufficient at said respective zones, at a cross saw zone 24. In succession, the extruder performs the melting of unmolten resin at the high shearing zone 25. After that, the extruder delivers the resin by mixing longitudinally and laterally. Normally, the length of the screw 21 is set to be length/diameter ratio (L/D) of 20 or more. If L/D is below 20, enough kneading can not be performed.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a high-density polyethylene layer by recycling the material of a multilayer plastic fuel tank having a polyamide layer, a high-density polyethylene layer, and a modified high-density polyethylene layer. The present invention relates to a method for manufacturing a multilayer plastic fuel tank with excellent impact resistance.

[Prior art and problems to be solved by the invention] Polyolefin resins are inexpensive, have high strength, and have excellent weather resistance and chemical resistance, so they are widely used in the manufacture of various containers. However, polyolefin resins do not necessarily have sufficient gas barrier properties, making them inappropriate for use in gasoline or other fuel tanks in areas with strict regulations.

Therefore, various attempts have been made to blend polyamide resins such as nylon with excellent gas barrier properties with polyolefin resins to create thermoplastic resin compositions with excellent both mechanical strength and gas barrier properties. Showa 54-12
No. 3158, No. 59-232135, No. 62-158
No. 739, No. 62-241938, No. 62-2419
No. 41, etc.) Also, instead of blending the two, a so-called multilayer molded product has been proposed in which a polyamide resin layer is laminated on a polyolefin layer to improve gas barrier properties (
JP 54-113678, JP 55-91634,
55-121017, Special Publication No. 60-14695)
. In this case, since the adhesive force between the polyolefin layer and the polyamide layer is generally weak, a method is adopted in which a modified plastic layer, such as a polyolefin resin modified with an unsaturated carboxylic acid, is interposed between the two layers.

Such a multilayer molded product for a fuel tank is usually manufactured by blow molding after creating a parison by extrusion molding, but a large amount of parison and defective products are generated during blow molding. Therefore, it has been proposed to collect these particles and defective products and mix them with polyolefin for reuse (Japanese Patent Application Laid-open Nos. 54-113678 and 55-91634).

However, simply blending polyolefin with a multilayer molded product does not necessarily provide a thermoplastic resin composition with satisfactory adhesive strength and impact resistance. This is believed to be due to the low compatibility between polyolefin and polyamide. Since impact resistance is particularly important for fuel tanks and the like, a decrease in impact resistance will greatly impair commercial value. Furthermore, if the material is manufactured without recovering the paris, it is not possible to maintain the impact resistance or reduce the cost of raw materials, which is not preferable.

Therefore, an object of the present invention is to provide a high-density polyamide layer when the material of a multi-layer plastic fuel tank, which has a polyamide layer and a high-density polyethylene layer and has excellent impact resistance, is recycled as a resin for the high-density polyethylene layer. An object of the present invention is to provide a method for producing a multilayer plastic fuel tank having excellent impact resistance, in which a high-density polyethylene layer is made of a composition finely and well dispersed in high-density polyethylene.

[Means to solve the problem]

As a result of intensive research in view of the above problems, the present inventors have found that if high-density polyethylene is kneaded with Paris, etc. for multilayer plastic fuel tanks for recycling using an extruder with a screw of a specific structure, the composition The inventors have discovered that it is possible to reduce the dispersed particle size of polyamide in a product, and to improve the physical properties of a multilayer plastic fuel tank using this composition as a high-density polyethylene layer, and have conceived the present invention.

That is, the method of the present invention for producing a multilayer plastic fuel tank consisting of a high-density polyethylene layer/modified high-density polyethylene layer/polyamide layer/modified high-density polyethylene layer/high-density polyethylene layer includes 20 to 20 parts or all of the multilayer plastic fuel tank per 100 parts by weight of polyethylene
It is formed from a composition obtained by kneading 0 parts by weight as recycled material, and the kneading has an L/D of 20 or more, and includes a feed section, a metering section for measuring the extrusion amount, and a metering section for measuring the extrusion amount in order from the hopper side. Using an extruder with a single screw consisting of a cross-saw section that performs mixing by applying shear force in the lateral direction of the flow, a deep groove section that retains the resin, a high shear section, and an end section that has a mixing pin. The extrusion temperature is 200 to 250°C.

The present invention will be explained in detail below.

The multilayer plastic fuel tank used for regeneration consists of a high-density polyethylene layer, a polyamide layer, and a high-density polyethylene layer modified with an unsaturated carboxylic acid or its derivative.

The high-density polyethylene that forms the high-density polyethylene layer has a density of 0.935 g/cd or more, and its melt index (Ml 190°C, 2.16 kg load) takes into account drawdown resistance, moldability, and impact resistance. Then, 0
．． 003 to 2 g/10 minutes is preferable.

More preferably, it is 0.01-1 g/10 minutes. In addition, High Road Melt Index (HLMI, 19
0℃, 21, 6kg load), 70g710
It is preferably 1 to 20 g/10 minutes, more preferably 1 to 20 g/10 minutes.

Further, as the polyamide of the polyamide layer, hexamethylene diamine, decamethylene diamine, dodecamethylene diamine, 2.2.4- or 2.4.4. - aliphatic, cycloaliphatic or aromatic diamine,
Polyamide resins produced from aliphatic, alicyclic or aromatic dicarboxylic acids such as adipic acid, superric acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 6-aminocaproic acid, 11-aminoundecane acids, polyamide resins produced from aminocarboxylic acids such as 12-aminododecanoic acid, polyamide resins produced from lactams such as ε-caprolactam and ω-dodecalactam, and copolyamide resins consisting of these components, Or a mixture of these polyamide resins may be mentioned. Specifically, nylon 6, nylon 66, nylon 11. Examples include nylon 12 and copolymers thereof. Furthermore, these nylon resins 5
Copolymers of 0% by weight or more and other resins mentioned above can be used.

The molecular weight of the polyamide is preferably in the range of 3.000 to 200.000, particularly 10.000 to 100.00.
A range of 000 is preferred.

In addition, in order to improve impact resistance, ε-caprolactam, N-butylbenzenesulfonamide, octyl p-oxybenzoate, etc. are added to the above polyamide as a plasticizer.
It can be contained in an amount of up to 30% by weight. A more preferable plasticizer content is 10 to 20% by weight.

Furthermore, the modified high-density polyethylene forming the modified high-density polyethylene layer in the present invention is high-density polyethylene 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, high-density polyethylene modified with maleic anhydride or endic anhydride (himic anhydride) is particularly preferred.

Further, as the high-density polyethylene modified with an unsaturated carboxylic acid or its anhydride, the same high-density polyethylene as described above can be used.

The content of the unsaturated carboxylic acid or its anhydride in the modified polyolefin is preferably in the range of o, oos to 5% by weight. Specifically, when modifying with maleic anhydride, the content of maleic anhydride is 0.01 to 3% by weight, more preferably 0.1 to 1% by weight, and when using Himic anhydride, , its content is 0°015~
4% by weight, more preferably 0.15 to 1.5% 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 the amount exceeds the upper limit value, the modification will occur. The adhesion between the high-density polyethylene layer and the high-density polyethylene layer decreases.

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

In addition, in the method of the present invention, for the purpose of modifying the resin for each of the above-mentioned shoes, fillers, heat stabilizers, light stabilizers, flame retardants, plasticizers, antistatic agents, mold release agents, Additives such as blowing agents and nucleating agents can be added.

A multilayer plastic fuel tank made of resin for each type of wear has a layered structure as shown in FIG. 1, for example.

Here, the multilayer molded product consists of a high-density polyethylene layer 1.1, a polyamide resin layer 2, and a modified high-density polyethylene layer 3.3 that adheres both layers. The layer thickness ratio of the multilayer plastic fuel tank is, for example, high density polyethylene: modified high density polyethylene: polyamide = 99 to 6.
0: 0°5 to 20: About 0.5 to 20 is preferable.

In the present invention, part or all of the multilayer plastic fuel tank as described above is recycled by mixing it with high-density polyethylene.

The mixing ratio of recycled material (obtained from part or all of the multilayer plastic fuel tank) and high density polyethylene is:
Generally, 20 to 200 parts by weight of recycled material is added to 100 parts by weight of high-density polyethylene, although it varies depending on the thickness of each layer of the multilayer molded product. The amount of recycled material added is 20
If the amount is less than 20 parts by weight, the regeneration efficiency will not be sufficient.
If it exceeds 0 parts by weight, the amount of polyamide in the composition for a high-density polyethylene layer becomes too large, and physical properties such as impact resistance deteriorate.

Next, a method of manufacturing a multilayer plastic fuel tank using such a mixture according to the method of the present invention will be described.

In the method for manufacturing a multilayer plastic fuel tank of the present invention, the screw of the extruder is connected in order from the hopper side to the feed section for the mixture, the metering section for measuring the extrusion amount, and the transverse direction (horizontal direction of resin flow). A structure consisting of a cross-saw section that performs mixing by applying shearing force, a deep groove section that retains the resin, a high shear section, and an end section that has a mixing pin is used.

FIG. 2 is a schematic diagram showing an example of a screw in an extruder that can be used in the method of the present invention.

In FIG. 2, the screw 21, which is rod-shaped and has a spiral protrusion, has a feed part 22, a metering part 23, a cross-saw part 24, a deep groove part 25, and
It consists of a high shear section 26 and a distal section 27 with a mixing pin.

The length of the screw is generally conveniently expressed as a length/diameter ratio (L/D), and L/D is preferably 20 or more. L/
If D is less than 20, sufficient kneading cannot be performed.

Although the upper limit of L/D is not particularly limited, it is approximately 40.

A single screw extruder having the above screw has a structure as shown in FIG. 3, for example.

In FIG. 3, the extruder 30 has a cylindrical cylinder 31.
a screw 32 that is rotatably fitted coaxially into the cylinder and has a spiral protrusion on its outer peripheral surface; a hopper 33 that supplies thermoplastic resin; and a hopper 33 located at the front end of the screw. It consists of a thermoplastic resin supply opening 34 provided in the cylinder and communicating with the hopper, and an extrusion molding mechanism 35 provided in the cylinder so as to be located at the rear end of the screw.

In such an extruder, a resin mixture mainly composed of high-density polyethylene supplied from a hopper 33 is sent from a thermoplastic resin supply opening 34 to a screw 32, melted and kneaded, and then sent to an extrusion molding mechanism 35. However, this melting and kneading can be carried out satisfactorily by the screw consisting of various parts as described above.

Below, the process by which a resin mixture mainly composed of high-density polyethylene is melt-kneaded in various parts of the screw will be explained along the flow of the resin composition.

(a) Feed section 22 In the feed section, a screw is provided with a spiral protrusion, and performs the first stage of melt-kneading and gradually compresses the resin mixture. The shape of the feed section is not particularly limited, and any commonly used shape can be used.

The length of such a feed portion is preferably 10 or more in terms of L/D, particularly preferably 12 to 16. If L/D is less than 10, it becomes difficult to sufficiently melt and knead the resin mixture, and it is not preferable because the resin mixture cannot be compressed to obtain a resin having a sufficiently large apparent density.

(b) Metering section 23 Also here, the screw is provided with a spiral protrusion, which homogenizes the resin and determines the amount of resin fed from the feed section that is extruded per one rotation of the screw.

The shape of the metering section is not particularly limited, and any commonly used metering section can be used; however, since the outer diameter of the screw core is large, the spiral protrusion is smaller than that at the feed section. is preferable.

Moreover, the length of the metering part is preferably 4 or more in terms of L/D, particularly preferably 4 to 6. If L/D is less than 4, it becomes difficult to sufficiently fulfill the above-mentioned functions, which is not preferable.

(C) Cross-saw section 24 The cross-saw section is a section mainly for mixing in the lateral direction, since the mixing in the above-mentioned feed section and metering section does not sufficiently knead in the lateral direction. Therefore, the outer diameter of the screw core is slightly larger, and the shape is such that a bottle is provided in the groove between the spiral protrusions, or a shape in which the spiral protrusions are cut out. ing.

An example of the cross saw section is shown in FIG.

In FIG. 4, the screw has a shape with a spiral protrusion cut away. By having such a notch 41, the resin mixture has a more spiral shape than a normal spiral shape.
It will be subjected to much stronger kneading in the lateral direction.

By mixing in the lateral direction in this manner, it is possible to obtain a fine and good dispersion of the polyamide, a homogeneous composition, and a uniform temperature distribution.

The length of the cross saw part is preferably 1 or more in terms of L/D, particularly preferably 1 to 2. If L/D is less than 1, it becomes difficult to sufficiently fulfill the above-mentioned functions, which is not preferable.

(d) Deep groove section 25 The deep groove section temporarily stores the resin generated in the metering section and the cross saw section described above, and cools it by the barrel of the extruder. For this reason, the shaft diameter of the screw is reduced.

The length of the deep groove portion 25 is preferably 0.5 or more in terms of L/D, particularly preferably 1 to 2. If L/D is less than 0.5,
This is not preferable because it becomes difficult to fully fulfill the above-mentioned functions.

(e) High shear section 26 The high shear section 26 allows the resin that has passed through the feed section, metering section, cross saw section, and deep groove section to pass therethrough even if it contains unmelted material. This is the point where large shear is applied to the resin to melt the unmelted resin and make it homogeneous.

The shape of this high shear portion is not particularly limited, and conventionally used shapes such as a dam ring type, a tobead type, and a muddock type can be mentioned. Particularly preferred is the Madotsuku type. In addition, in order to apply large shear and a high amount of heat to the resin, the distance between the cylinder and the cylinder must be narrow, and the shaft diameter is larger than the above-mentioned parts.

An example of such a high shear section is shown in FIG.

In FIG. 5, the shaft diameter of the screw is increased, and several sets of vertical grooves 51.51' are arranged alternately in sets of two. The vertical grooves 51, 51' are communicated through a communication groove 52.

When the resin composition enters the vertical groove 51, it passes through the vertical groove 51° via the communication groove 52. At this time, since the screw diameter of the high shear section is large, a large shear and a high amount of heat are applied to the resin, and the unmelted resin is melted to form a homogeneous kneaded product.

The length of the high shear portion is preferably 2 or more in terms of L/D, particularly preferably 2 to 4. If L/D is less than 2, it becomes difficult to sufficiently fulfill the above-mentioned functions, which is not preferable.

(g) End part 27 having a mixing pin At the end part, unmelted resin is kneaded in a high shear part in the vertical and horizontal directions to make it homogeneous.

An example of the distal end is shown in FIG.

In FIG. 6, the screw has a spiral protrusion 61, and a mixing pin 62 is inserted into a groove formed by the protrusion. By having such a mixing pin 62, a resin mixture mainly composed of high-density polyethylene is subjected to stronger kneading in the lateral direction than when it has only ordinary spiral protrusions.

In this way, by intensively mixing in the vertical and horizontal directions, the melt can be made homogeneous and can be sent to the extrusion molding mechanism 35 with a uniform temperature distribution.

The length of the end portion having the mixing pin is preferably 1 or more in terms of L/D, and particularly preferably 1 to 2. If L/D is less than 1, it becomes difficult to sufficiently fulfill the above-mentioned functions, which is not preferable.

The extrusion molding mechanism 35 normally communicates with a blow molding machine, but in the present invention, it is preferably communicated with a blow molding machine having a mandrel for producing a parison for a multilayer molded article by co-injection molding.

In the screw having such a configuration, the cylinder temperature may be appropriately controlled within the range of 170 to 250°C. Specifically, the feed part 22 is heated to 170 to 200°C, the metering part 23 is heated to 170 to 200°C, the cross saw part 24 is heated to 170 to 200°C, and the deep groove part 25 is heated to 170 to 200°C.
The high shear portion 26 may be heated at 170-200°C, and the end portion 27 having the mixing pin may be heated at 200-240°C.

Also, the amount of resin discharged during kneading with such an extruder is set appropriately depending on the size of the extruder.
For example, in the case of an extruder with a cylinder diameter of 90 mmφ, 150 to
It is about 200 kg/hr. If the amount of resin discharged is too large, the residence time in the extruder becomes short, making it difficult to sufficiently knead, which is not preferable.

By using the extruder as described above, it is possible to make the dispersed particles of polyamide in the composition for a high-density polyethylene layer obtained by kneading extremely fine particle sizes of 10 particles or less.

The multilayer plastic fuel tank of the present invention, in which the resin composition obtained by kneading in this manner is used for the high density polyethylene layer, has a layered structure as shown in FIG. 1, as described above. Such a multilayer molded product is produced by, for example, extruding each required resin from each extruder, molding a cylindrical parison having the above-mentioned layer structure by coextrusion molding, etc., and molding this parison into a cavity having a desired shape. It can be manufactured by blow molding after placing it in a mold. At this time, in the present invention, as described above, part or all of the multilayer plastic fuel tank such as Paris produced in this manufacturing process can be recovered and mixed with the high-density polyethylene that forms the resin layer 1.1. .

The thus obtained multilayer plastic fuel tank of the present invention exhibits very little deterioration of various physical properties such as impact resistance even if paris generated during the manufacture of the multilayer plastic fuel tank is mixed with the high-density polyethylene side.

[For production]

In the present invention, part or all of a multilayer plastic fuel tank is mixed with high-density polyethylene, melted and kneaded using an extruder having a specific screw structure, and recycled as resin for the high-density polyethylene layer of a multilayer plastic fuel tank. We are using.

Therefore, physical properties such as impact resistance of the multilayer plastic fuel tank obtained using this recycled product do not deteriorate.

This is because the extruder used in the present invention kneads a mixture of high-density polyethylene and part or all of the multilayer plastic fuel tank in the feed section, weighs it in the metering section, and then The resin flow, which tends to be insufficient, is mixed in the lateral direction in the cross-saw section, then the unmelted resin is melted in the high-shear section, and then mixed in the longitudinal and lateral directions before being sent out. This is thought to be because the polyamide in the composition for the high-density polyethylene layer can be finely and well dispersed due to the synergistic effect of the functions of the various parts.

〔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, and polyamide.

[1] High density polyethylene HDPE: (melt index (Ml 190℃
, 2.16kg load) 0.03g/10min, High Road Melt Index (HLMI 190℃, 21.6
kg load) 5.5g/10 minutes, density 0.945g/al
, weight average molecular weight (~) 2 (1xlO') [21 modified high density polyethylene CMPE: (MI (190℃・, 2.16kg
Load) 0.3g 710 minutes, maleic anhydride addition rate 0°4% by weight, density 0.953g/cnf, weight average molecular weight (12XlO') [3] Polyamide PA-1: (nylon-6, relative viscosity 4.2] PA-2
: (Nylon-6, relative viscosity 6.0) The following was used as an extruder for resin containing high-density polyethylene as a main component.

[11 Single screw extruder (cylinder diameter 90mmφ) (a):
(L/D=30, special screw with the structure shown in Figure 2) (b): (L/D=32, special screw with the structure shown in Figure 2) (C1: (L/D=24, second screw) Special screw with the structure shown in the figure] (d): CL/D=28, special screw with the structure shown in Fig. 2] (e): (L/D=24, full flight screw): (L/D =28, full flight screw] high density polyethylene, modified high density polyethylene,
Polyamide and multilayer blow molding machine (NB made by Japan Steel Works)
-60G) to create a multilayer plastic fuel tank (capacity 401) with three types and five layers having the layer and wall thickness configurations shown in Table 1.

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

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

Table 1 Using the extruder of the type shown in Table 2, the resin mixture described above was processed at the resin temperature shown in Table 2, and the resin discharge amount was 90 kg/H.
r and 180 kg/Hr to prepare a parison.

The particle diameter of the polyamide in the parison thus obtained was examined, and the maximum discharge amount at which the particle diameter of the polyamide was 0 or less was defined as the maximum discharge amount at which the polyamide was well dispersed. Furthermore, the dispersion rate is 0.180 kg when the polyamide particle size is less than 1 Oum at a discharge rate of 180 kg/Hr.
A case where the particle diameter of polyamide exceeded 1 Oun at a discharge rate of /Hr was evaluated as ×.

The results are shown in Table 2 together with the type of polyamide used.

In addition, the maximum discharge amount axis aX with good dispersion of the polyamide
A parison was prepared with a discharge amount of 1/2 max (1/2 max discharge), and the tensile elongation and tensile impact strength of the parison were measured.

These values were compared with those of a parison made of virgin material prepared under similar conditions by a tensile test at -40°C and a tensile impact test.

The tensile elongation is the value measured by tensile test ASTM D638, and the tensile impact strength is the value measured by tensile impact test ASTM D638.
This is a value measured by DL822.

The results are also shown in Table 2.

From Table 2, the resin composition for high density polyethylene layer produced by the production method of the present invention has a resin discharge rate of 90 kg/Hr and 18 kg/Hr.
In any case of 0 kg/Hr, the dispersed particle size of polyamide is 1- or less, and it can be seen that there is no deterioration in tensile elongation and tensile impact strength compared to virgin material.

In addition, in the case of Comparative Examples 1 to 4 using a normal single-screw extruder, the resin composition for the high-density polyethylene layer had a resin discharge rate of 90 k
Up to 180 kg/Hr, the polyamide dispersion particle size was 10 or less, but at 180 kg/Hr, the particle size was 50 to 200.
It became coarse and coarse, and deterioration of tensile elongation and tensile impact strength was observed.

Evaluation The Paris obtained in the above evaluation of the extrusion dispersibility of polyamide and the virgin high-density polyethylene material were triblended at a weight ratio of 50=50, and this was multilayer blown at the melting temperature of the resin shown in Table 3. (b) as the main extruder of the molding machine;
(Using C1, (e), melt and knead, and create a high-density polyethylene: modified high-density polyethylene with the same layer structure as in "Creation of a mixture of multilayer plastic fuel tank and high-density polyethylene" described above. Polyamide = 91:3:
3 thick configuration (3300 prisoners: 100 tan: 1
00 Ia) multilayer plastic fuel tank (capacity 40
A', weight 6 kg) was created.

At this time, the moldability of the fuel tank was evaluated.

Also, using the obtained fuel tank, low temperature (-40"C)
) and a gasoline permeability test at 40°C.

The results are shown in Table 3 along with the wall thickness composition ratio of the fuel tank.

Example 13 In Example 11, the thickness ratio of high-density polyethylene:modified high-density polyethylene lipolyamide was 60:2.
A multilayer plastic fuel tank was prepared as 0:20, and subjected to a drop impact test and 40°C in the same manner as in Example 11.
A gasoline permeability test was conducted.

The results are also shown in Table 3.

(1) A parison with little drawdown and moldability was evaluated as ○, and a case with large drawdown and poor wall thickness distribution of the parison was evaluated as ×.

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

(3) In accordance with BCE34, measure the permeation amount of gasoline, and if the permeation amount is 20 g/day or less, it is 0.120 g/d.
Those exceeding ay were evaluated as ×.

As is clear from Table 3, the multilayer plastic fuel tank with a high-density polyethylene layer made of the resin composition produced by the manufacturing method of the present invention has good moldability, as well as good impact strength and gasoline barrier properties. Ta.

This is thought to be because, according to the production method of the present invention, even if polyamide is present in high-density polyethylene, it is well dispersed, so that the physical properties of the high-density polyethylene layer do not deteriorate. .

On the other hand, the multilayer plastic fuel tank manufactured by the manufacturing method of Comparative Example 5.6 was destroyed due to insufficient impact strength.

〔Effect of the invention〕

As detailed above, according to the method for manufacturing a multilayer plastic fuel tank of the present invention, a part or all of the multilayer plastic fuel tank is regenerated using an extruder having a screw of a specific structure. The high-density polyethylene layer is made of a composition in which the dispersed particle size of the polyamide in the resin composition is reduced by kneading it with a virgin material of high-density polyethylene, so even though the high-density polyethylene contains polyamide, There is almost no deterioration in physical properties such as impact resistance.

Therefore, the multilayer plastic fuel tank manufactured by the manufacturing method of the present invention is economically advantageous because it is possible to reuse the paris produced by the manufacturing process by mixing it into the high-density polyethylene side. be.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing an example of the layered structure of the multilayer plastic fuel tank of the present invention, and FIG. 2 is a diagram of the screw of the extruder used for kneading the resin for the high-density polyethylene layer in the manufacturing method of the present invention. FIG. 3 is a partially cutaway schematic diagram showing an example of an extruder used for kneading the resin for the high-density polyethylene layer in the manufacturing method of the present invention; FIG. 5 is a schematic diagram illustrating an example of a high shear section; FIG. 6 is a schematic diagram illustrating an example of an end section with a mixing pin; FIG. l ・ ・ 2 ・ 3 ・ 21.32 22 ・ 23 ... High shear section 27 ... End section 30 with mixing pin ... Extruder 31 ... Cylinder 32 ... Screw 33 ... Hopper 34 ... Thermoplastic resin supply opening 35 ... Extrusion molding mechanism applicant

Claims (3)

[Claims] (1) In a method for manufacturing a multilayer plastic fuel tank consisting of a layer of high density polyethylene/modified high density polyethylene layer/polyamide layer/modified high density polyethylene layer/high density polyethylene, the high density polyethylene layer is made of high density polyethylene 100. It is formed from a composition obtained by kneading 20 to 200 parts by weight of part or all of the multilayer plastic fuel tank as recycled material, and the kneading has an L/D of 20 or more, and the hopper side In this order, a feed section, a metering section that measures the amount of extrusion, a cross-saw section that performs mixing by applying shear force in the transverse direction of the resin flow, a deep groove section that retains the resin, and a high shear section. Using an extruder with a single screw consisting of an end with a mixing pin, the extrusion temperature is 200~
A method for manufacturing a multilayer plastic fuel tank characterized by carrying out the process at 250°C. (2) In the method according to claim 1, the multilayer structure of the multilayer plastic fuel tank has a wall thickness ratio of high density polyethylene:modified high density polyethylene lipolyamide=9.
9-60: 0.5-20: A method for manufacturing a multilayer plastic fuel tank, characterized in that the ratio is 0.5-20. (3) In the method according to claim 1 or 2, the feed section of the extruder has an L/D of 10 or more, the metering section has an L/D of 4 or more, and the cross saw section has an L/D of 4 or more. D is 1 or more, L/D of the deep groove part is 0.5 or more, L/D of the high shear part is 2 or more, and L/D of the end portion having the mixing pin is 1 or more. A method for manufacturing a multilayer plastic fuel tank, characterized in that: