JP3085784B2 - Multi-layer laminated structural material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer laminated structural material having at least three and three layers having an adhesive layer interposed therebetween. More specifically, the present invention relates to a multilayer laminated structural material that can be non-destructively detected by ultrasonic waves for the presence or absence of an adhesive layer constituting the structural material, and is particularly suitable for a fuel oil container (tank) of an automobile.

[0002]

2. Description of the Related Art If a fuel oil tank is used as an example of a multi-layer laminated structure, a metal oil tank was used before, but the tank is lighter, the degree of freedom and the shape of the tank are increased, the rust resistance, etc. However, tanks made of high-density polyethylene resin only have a problem in terms of barrier properties against gas-liquid permeation of fuel oil. As a countermeasure, a fuel oil tank consisting of multiple layers using high-density polyethylene resin, modified polyethylene resin, polyamide resin, etc. as the material for each layer has been proposed [Kurihara et al., "SEE Technical Paper Series ( SAE Technical Paper Series) NO.8703
04 (February 23-27, 1978), Fukuhara "Plastic Age"
35, No. 3, p. 129 (1989)].

In this multi-layer structure, a high-density polyethylene resin is used for the outer layer, a modified polyethylene resin having adhesiveness for the intermediate layer, a three-layer structure using polyamide for the inner layer, a high-density polyethylene resin for the innermost and outermost layers, and an intermediate layer. The structure of a fuel oil tank having a fuel oil permeation preventing property is extremely promising, for example, a three-layer five-layer structure in which an adhesive resin layer is provided between the innermost and outermost layers and the intermediate layer.
Further, as a similar technique, a multilayer container having at least a structure of a modified polyolefin resin layer / a polyamide resin layer, which is composed of, for example, a combination of a polyamide resin and a modified polyolefin resin having an adhesive property is disclosed. Further, as a barrier material for gasoline containing alcohol such as methyl alcohol or ethyl alcohol, ethylene vinyl acetate saponified (EVOH) resin or nitrile resin is considered to be promising instead of polyamide resin.

[0004] By the way, in such a container having a multilayer structure, a main material layer contributing to the shape retention and mechanical properties of the container and a barrier material function such as a polyamide resin, an EVOH resin and a nitrile resin are provided. It is extremely important to confirm the presence of an adhesive layer between the intermediate layer and the intermediate layer, as described later.
According to Japanese Patent No. 60417, a detection object such as iron powder or glass fiber is mixed into a predetermined layer of a multilayer parison, and bonded using a magnetic sensor in the case of iron powder or an ultrasonic head in the case of glass fiber. A method for detecting the presence or absence of a material layer has been proposed.

[0005]

A fuel oil tank mounted on an automobile is regarded as one of the important security parts, and an extremely strict and high level of performance is required. Therefore, the same applies to a multi-layer fuel oil tank provided with fuel oil permeation prevention performance, such as a high-density polyethylene resin as a main material layer used in the tank, a modified polyethylene resin as an adhesive, and a polyamide as a barrier material. Needless to say, resin and other materials are required to have more stringent performance as materials for tanks, but in particular, the modified polyethylene resin as the adhesive layer has high adhesiveness between polyethylene resin and polyamide resin and under various environments. Not only have excellent long-term durability, but also have excellent mechanical, thermal and chemical properties, and have good moldability. However, since the reliable presence of the adhesive layer in the product (fuel oil tank) is a major premise for exhibiting these characteristics, establishing a method for confirming its existence is an important issue.

In other words, in the multi-layer liquid fuel oil tank, if there is a part where the adhesive layer located in the middle is partially or completely missing for some reason, not only will mechanical properties such as impact resistance deteriorate, but also the like. In the long-term durability, fuel oil or the like stays in the missing portion, permeates from the portion, or invades between layers to significantly reduce the physical properties of the tank, causing a serious problem. Become. Therefore, in a product such as a multi-layer fuel oil tank as described above, it is an important production control item to confirm the presence of an intermediate adhesive layer reliably. However, without destruction of a product having such a multilayer structure, and without mixing materials such as iron powder and glass fiber which are unnecessary as a container material as described above, it is confirmed that the adhesive layer exists. There is no known technique to confirm.

However, it is known that the ultrasonic reflection method can be used to detect the presence of a polyamide resin layer in a multilayer structure container using a polyamide resin as a barrier material without destroying the container. The presence of the modified polyethylene resin layer in the multilayer multilayer structure having at least the structure of the high-density polyethylene resin layer / modified polyethylene resin layer / polyamide resin layer as in the present invention can be achieved without destroying the container. It is difficult to detect this, and an example of an attempt was made by the inventors in Japanese Patent Application No. 2-30.
5801 and Japanese Patent Application No. 2-315484. The two inventions are characterized in that the acoustic impedance of the adhesive layer is lower than that of the main material layer. The fact that the acoustic impedance of the adhesive layer is higher than that of the main material layer is characterized in that it generally has a lower impact resistance than a material having a low acoustic impedance, but gives a large reflected wave because the sound wave is less attenuated. From the above, the present invention provides a multilayer laminated structure material in which a modified polyethylene resin is surely present as an adhesive layer by enabling detection of the presence of a modified polyethylene which has not been subjected to a detection method so far. The purpose is to do so.

[0008]

SUMMARY OF THE INVENTION As a result of intensive studies to solve this problem, the present invention takes into account the difference in acoustic impedance caused by ultrasonic waves between the main material layer and the adhesive layer having a special composition. The present invention has been completed. That is, the gist of the present invention is that a main material layer mainly composed of a polyethylene resin and a resin layer selected from a polyamide resin, an EVOH resin and a nitrile resin are laminated on the outside with an adhesive layer interposed therebetween. A multilayer laminated structural material having a layer structure comprising: an adhesive layer having a density of 0.950 g / cm
³ above, MFR0.01g / 10 min or more, the main chain C number 1000 per short chain branches having 20 or fewer high-density polyethylene resin of,
A density of at least 0.950 g / cm ² comprising a resin containing at least 0.1% by weight of a modified high-density polyethylene resin selected from the high-density polyethylene resin graft-modified with an unsaturated carboxylic acid and / or a derivative thereof; / Or derivative content 0.001 to 5.0
A multilayer laminated structure made of a resin composition whose acoustic impedance by ultrasonic waves of 20 to 25 MHz by weight is higher than that of the main material by 8.5 × 10 ⁻³ g / cm ² · μsec or more.
Hereinafter, the present invention will be described specifically. The multilayer laminated structural material according to the present invention has a layer structure in which a main material layer mainly composed of polyethylene resin is laminated on an outer layer via an adhesive layer, and a barrier resin layer such as polyamide resin is laminated on the inner side. doing.

(A) Main Material Layer Examples of the polyethylene resin used as a component of the main material layer in the present invention include an ethylene homopolymer and a copolymer of ethylene and an α-olefin. The α-olefin generally has 3 to 12 carbon atoms (preferably 3 to 12 carbon atoms).
８8) olefins. Representative α-olefins include propylene, butene-1, hexene-1, octene-1 and 4-methylpentene-1.

Among the polyethylene resins, preferred are those having a density of 0.950 g / cm ³ or more (preferably,
0.960 g / cm ³ or more) and an ethylene-based polymer selected from a copolymer of ethylene and an α-olefin. Further, these ethylene homopolymers and copolymers of ethylene and α-olefin have a density of less than 0.950 g / cm ³ and copolymers of monomers other than α-olefins, propylene homopolymers and propylene and ethylene. Or a copolymer with another α-olefin or the like, and the density of the obtained ethylene copolymer composition is 0.950 g / cm ³ or more (preferably,
0.960 g / cm ³ or more) can also be preferably used. Among these ethylene polymers, polyethylene having a density of 0.950 g / cm ³ or more and high density polyethylene are particularly preferable.

[0011] The MFR of the polyethylene resin is not particularly limited.
It is 0.005 g / 10 min or more, preferably 0.01 g / 10 min or more, and particularly preferably 0.020 g / 10 min or more. In the present invention, a filler generally added may be added to the polyethylene resin. Examples of the filler include calcium carbonate, talc, mica, glass fiber, carbon fiber, metal fiber, and other inorganic and organic polymer fibers (for example, polyester fiber and polyamide fiber). In the present invention, when an elastomer, another synthetic resin and / or a filler are blended with the polyethylene resin, the composition ratio thereof preferably does not exceed about 5% by weight in total.

(B) Adhesive layer The adhesive layer in the present invention has a density of 0.955 g / cm ³ or more, MFR of 0.01 g / 10 min or more, and a short chain branch number of 20 or less per 1000 main chain C atoms. Selected from the above-mentioned high-density polyethylene resins graft-modified with high-density polyethylene resins and unsaturated carboxylic acids and / or derivatives thereof;
The first requirement is that the resin selected contains at least 0.1% by weight or more of the graft-modified high-density polyethylene resin in the adhesive layer, and the grafted acid and / or Derivative in adhesive layer
Second requirement to contain 0.001 to 5.0% by weight, 20 to 25M
A third requirement is that the resin composition be such that the acoustic impedance of the adhesive layer by ultrasonic waves of Hz is higher than that of the main material layer by 8.5 × 10 ⁻³ g / cm ² μsec or more.

(B-1) Regarding the First Requirement The adhesive layer of the present invention comprises only a modified high-density polyethylene resin or a composition of an unmodified high-density polyethylene resin and a modified high-density polyethylene resin. In the following, “modified” refers to a substance to which an unsaturated carboxylic acid and / or a derivative thereof is grafted, and “unmodified” refers to
Refers to those that are not grafted.

Hereinafter, each of the components and the method for producing them will be described in detail. (B-1-1) High-density polyethylene resin The high-density polyethylene resin used in the adhesive layer of the present invention and the high-density polyethylene resin used for the production of the modified high-density polyethylene resin described below are all ethylene alone or ethylene. And an α-olefin having 3 to 12 (preferably 3 to 8) carbon atoms by homopolymerization or copolymerization in the presence of a so-called Phillips catalyst or Ziegler catalyst,
In general, it is produced at normal pressure to a pressure of about 100 kg / cm ² (medium to low pressure polymerization). Preferred examples of the α-olefin include propylene, butene-1,
Hexene-1, 4-methylpentene-1 and octene-
One is given. At most 6.5% by weight
Or less, and particularly preferably 6.0% by weight or less. The number of short-chain branches per 1000 carbon atoms in the main chain of this high-density polyethylene resin is at most 20.

The density is at least 0.950 g / cm ³ , preferably at least 0.958 g / cm ^3, more preferably at least 0.960 g / cm ^3.
cm ³ or more is preferred. When a polyethylene resin having a density of less than 0.950 g / cm ³ is used, a product molded using the obtained composition is inferior in ultrasonic detection performance and the like. Further, the MFR is 0.01 g / 10 min or more, preferably 0.015 g / 10 min or more, and particularly preferably 0.02 g / 10 min or more. If the MFR is less than 0.01 g / 10 minutes, the molding process is not good. The upper limit is not particularly limited, but is usually 50
g / 10 minutes, and particularly preferably 35 g / 10 minutes or less.

Particularly, in the modified high-density polyethylene resin described below, the MFR of the raw material high-density polyethylene resin is 0.01 g / 10
If it is less than 10 minutes, the MFR of the resulting grafted high-density polyethylene resin is generally the MFR of the high-density polyethylene resin used for grafting, depending on the graft modification conditions.
And the processability is reduced, and the compatibility when producing a mixture with a non-grafted high-density polyethylene resin is significantly reduced, so that a uniform composition cannot be obtained. M of this modified polyethylene resin
Generally, FR is preferably 0.05 g / 10 minutes or more,
In particular, 0.1 g / 10 min or more is preferable. Each of these high-density polyethylene resins may be used alone,
Two or more types may be combined.

(B-1-2) Modified high-density polyethylene resin The modified high-density polyethylene resin used in the present invention is obtained by adding an unsaturated carboxylic acid and / or a derivative thereof described later to the high-density polyethylene resin as a radical initiator. It can be obtained by treating in the presence. At this time, a synthetic resin or an elastomer (rubber) described later, which has an affinity for the high-density polyethylene resin to be grafted, may be present. Examples of the unsaturated carboxylic acids and derivatives thereof used in the grafting treatment include monobasic unsaturated carboxylic acids and dibasic unsaturated carboxylic acids, and metal salts, amides, imides, esters and anhydrides thereof. Among them, the monobasic unsaturated carboxylic acid generally has at most 20 (preferably 15 or less) carbon atoms. Further, the derivative usually has at most 20 (preferably 15 or less) carbon atoms. Further, the carbon number of the dibasic unsaturated carboxylic acid is generally at most 30 (preferably 25 or less).

Representative examples of these unsaturated carboxylic acids and their derivatives are described in JP-A-62-10107.
Among these unsaturated carboxylic acids and derivatives thereof, acrylic acid, methacrylic acid, maleic acid and anhydride thereof, 5-norbornene-2,3-dicarboxylic acid and anhydride thereof, and glycidyl methacrylate are preferred, and maleic anhydride is particularly preferred. Acids and 5-norbornene anhydride are preferred. Further, the radical initiator used for the graft modification usually has a decomposition temperature with a one-minute half-life of 100 ° C. or higher, preferably 103 ° C. or higher, and more preferably 105 ° C. or higher. Suitable radical initiators include dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2 And organic peroxides such as, 5-dimethyl-2,5-di (tert-butylperoxy) hexane-3-lauroyl peroxide and tert-butylperoxybenzoate.

The synthetic resins and elastomers that can coexist during the graft reaction will be described. As synthetic resin, high-pressure low-density polyethylene resin,
Copolymers of ethylene with other vinyl monomers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer Polymers.

Further, as the elastomer, ethylene-
Ethylene-α-olefin copolymer rubbers such as propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, ethylene-butene-1 copolymer rubber, polyisobutylene rubber, polyurethane rubber, styrene-butadiene copolymer rubber And synthetic rubber such as polybutadiene rubber and natural rubber. The proportion of these synthetic resins and elastomers in the high-density polyethylene resin is generally at most 5% by weight, and particularly preferably 3% by weight or less. If the total amount of the synthetic resin and / or elastomer in the total amount of the high-density polyethylene resin exceeds 5% by weight, the basic characteristics of the high-density polyethylene resin may be impaired.

In producing the modified polyethylene resin used in the present invention, the ratio of the unsaturated carboxylic acid and / or its derivative and the radical initiator used to 100 parts by weight of the high-density polyethylene resin to be grafted is as follows. It is on the street. The total amount of unsaturated carboxylic acids and / or derivatives thereof is generally 0.01 to 5.0 parts by weight, preferably 0.01 to 3.0 parts by weight, particularly preferably 0.02 to 2.0 parts by weight. The proportion of unsaturated carboxylic acids and their derivatives as their total amount
If the amount is less than 0.01 part by weight, the graft modification becomes insufficient, and there is a problem in the affinity or adhesiveness aimed at by the present invention. On the other hand, if it exceeds 5.0 parts by weight, the resulting graft-modified high-density polyethylene resin gels,
There is a risk of causing coloring, deterioration, and the like, and no improvement in the performance of the object of the present invention is recognized.

The ratio of the radical initiator is usually 0.0
01 to 1.0 part by weight, preferably 0.05 to 1.0 part by weight,
Particularly, 0.005 to 0.5 part by weight is suitable. When the ratio of the radical initiator is less than 0.001 part by weight, the effect of the graft modification is poor, and not only a long time is required to complete the graft modification, but also unreacted substances are mixed. On the other hand, if it exceeds 1.0 part by weight, excessive decomposition or crosslinking reaction is caused, which is not preferable.

The modified high-density polyethylene resin of the present invention comprises the above-mentioned high-density polyethylene resin (optionally in the presence of another synthetic resin and / or elastomer), an unsaturated carboxylic acid and / or a derivative thereof, and a radical initiator. Can be produced by processing within the range of the ratio. The processing method is described in JP-A-62-10107.
A well-known method described in JP-A-61-132345 or JP-A-61-132345 may be employed. Specifically, a method of kneading a high-density polyethylene resin or the like in a molten state using an extruder, a Banbury mixer, a kneader, or the like, a solution method in which a polymer such as a high-density polyethylene resin is dissolved in an appropriate solvent, a high-density polyethylene A slurry method in which particles of a polymer such as a resin are suspended, or a so-called gas phase grafting method is used.

The treatment temperature is appropriately selected in consideration of the deterioration of the polymer such as the high-density polyethylene resin, the decomposition of the unsaturated carboxylic acid or its derivative, the decomposition temperature of the radical initiator used, and the like. For example, the method of kneading in a state is usually 100 to 350 ° C, 150 to 300 ° C.
C. is desirable, and particularly preferably 180 to 300.degree. Of course, to produce the modified high-density polyethylene resin of the present invention in this way, for the purpose of improving its performance,
As described in JP-A-62-10107, a method known in the art, such as a method of treating with an epoxy compound or a polyfunctional compound containing an amino group or a hydroxyl group at the time of graft modification or after graft modification, and further heating or washing, etc. A method of removing unreacted monomers (unsaturated carboxylic acids and their derivatives) and by-product components can be employed.

(B-2) Regarding the second requirement The composition ratio of the modified polyethylene resin in the adhesive layer is at least 0.1% by weight, and the grafted unsaturated carboxylic acid and / or the unsaturated carboxylic acid in the adhesive layer is contained in the adhesive layer. The proportions of the derivatives are 0.001 to 5.0% by weight as their total amount. In general, when a polymer (in the case of the present invention, a high-density polyethylene resin) is graft-modified with a monomer (in the case of the present invention, an unsaturated carboxylic acid or a derivative thereof),
It is difficult to graft a monomer to all polymers, and some of the polymers are not grafted. In the present invention, the ungrafted high-density polyethylene resin may be used as it is without separation. Further, a high-density polyethylene resin that has not been subjected to a grafting treatment may be further added.

In any of the above cases, the proportion of the grafted monomer in the adhesive layer of the present invention in the total amount is 0.001 to 5.0% by weight, preferably 0.01 to 2.0% by weight, more preferably 0.02 to 1.0% by weight. % By weight is preferred. If the proportion of the grafted monomer in the adhesive layer is less than 0.001% by weight in total, the various effects of the present invention cannot be sufficiently exerted. 5.0
Even if it exceeds the weight percentage, the effects of the present invention cannot be further improved.

In producing the resin composition used in the present invention, antioxidants, heat stabilizers, and ultraviolet absorbers generally used in the field of polyolefin resins within a range that does not substantially impair the effect of the composition. Additives such as agents, lubricants, antistatic agents, and pigments (colorants) can be blended. As a mixing method for producing the composition, various mixing methods generally performed in the field of synthetic resins, that is, a method of dry blending using a mixer such as a tumbler or a Henschel mixer, an extruder,
Any method of melt-kneading using a kneader such as a kneader, a Banbury mixer and a roll can be employed. At this time, a more uniform composition can be obtained by performing two or more of these mixing methods (for example, a method of dry blending in advance and further melting and kneading the resulting mixture).

The density of the adhesive layer obtained as described above needs to be 0.955 g / cm ³ or more, especially 0.958 g / cm ^3.
cm ³ or more is desirable. The density of the adhesive layer is 0.955g / c
is less than m ^3, not good ultrasonic detectability. This density 0.95
In order to obtain 5 g / cm ³ or more, the mixing ratio can be easily determined in consideration of each density of the modified or unmodified high-density polyethylene resin.

[0029] (B-3) for the acoustic impedance of the main material layer described above in the present invention (Z ₀₎ is the third requirement, Z ₀ as measured using ultrasound 20~25MHz
Is preferably about 2.28 × 10 ⁻¹ g / cm ² · μsec or less,
2.20 × 10 ⁻¹ g / cm ² μsec or less is more preferable.
The lower limit is about 2.00 × 10 ⁻¹ g / cm ² μsec.
The acoustic impedance (Z ₁ ) of the adhesive layer is 2.08 × 10
^-1 g / cm ² · μsec or more, preferably 2.28 × 10 ^-1 g /
cm ² · μsec is more preferred. Its upper limit is 2.60 × 10
^-1 g / cm ² · μsec. In the present invention, Z ₁
Is higher than Z ₀ , but the difference Z ₁ −Z _{0 from} the acoustic impedance (Z ₁ ) of the adhesive layer is 8.5 × 10 ^{− in} order to be able to detect the presence or absence of the adhesive layer by a non-destructive method. ³ g / cm ²
· .Mu.sec or more, preferably ^{9.0 × 10 -3 g / cm 2} · μse
c, more preferably 9.5 × 10 ⁻³ g / cm ² · μsec or more. Therefore, a combination of materials is used so that such a difference in acoustic impedance is obtained from the above-mentioned main material layer and adhesive material layer. If the difference in acoustic impedance is less than 8.5 × 10 ⁻³ g / cm ² · μsec, it becomes extremely difficult to detect the presence or absence of the adhesive layer inside the main material layer.

(B-4) Production of Resin for Adhesive Layer In the case of melt-kneading to produce this resin, it must be carried out at a temperature at which various polyethylene resins, other synthetic resins or elastomers melt. However, when carried out at elevated temperatures, they can thermally decompose. For the above reasons, generally 170-300 ° C. (preferably 190 ° C.
280 ° C.).

(C) Barrier Material Layer (C-1) Polyamide Resin The polyamide resin used for the barrier material layer in the present invention includes nylon 6, a copolymer of nylon 6, modified nylon 6, nylon 11, and nylon 12. And nylon 6-6. Among them, those having a melting point of 265 ° C. or less when absolutely dry are preferred, and those having a melting point of 230 ° C. or less are particularly preferred. These polyamide resins may be used alone or as a mixture of two or more. Particularly, a nylon 6-based polyamide resin is preferable. Relative viscosity [ηr] of the resin
Is preferably from 2 to 7, and particularly preferably from 2.5 to 7.

(C-2) EVOH Resin Similarly, EVOH resins include those having an ethylene content of 25% or more and 40% or less. Above all, more than 25% 35
% Or less, and more preferably 25% or more and 32% or less.

(C-3) Nitrile resin Further, as the nitrile resin, acrylonitrile is 60%
Among the resins contained above, copolymers of acrylic acid esters, methacrylic acid esters, butadiene, styrene and the like are preferable. Because of its polar nitrile group, it is difficult to transmit oxygen and carbon dioxide gas, and is known as a gas barrier resin. These may be a mixture or copolymer of two or more.

(D) Method for Producing a Multi-Layered Structure In order to produce the multi-layer laminated structure of the present invention, a molding machine for co-extruding an adhesive layer between a main material layer and a barrier material layer. A typical example is a method of performing blow molding using a multilayer blow molding machine having a multilayer die (concentric) and having a multilayer die. Regarding the blow molding method, see JP-A-62-104.
No. 707, "Polymer Digest", March 1988 (Vol. 40, No. 3, pp. 33-42) and "Plastic Age", March 1989, pp. 129-136. ing. In the thus obtained multilayer laminated structure of the present invention, the thickness of the adhesive layer, the polyamide resin layer and the like are practically 25 μm to 3 mm, and particularly preferably 40 μm to 2 mm. The thickness of the main material layer is
It is 0.5 to 10 mm, especially 0.5 to 7 mm.

The structure of the multilayer laminated structure of the present invention is as follows.
Examples typical configuration is described in detail in JP 64-38233 and the 64 ^-3 No. 8232 each publication. Assuming that the main material layer is A, the adhesive layer is B, and the barrier resin layer is C, A / B / C, A /
If B / C / B, A / B / C / B / A, or a repetition of these configurations, and the regenerated material layer is D, A
Between layer and layer B, or D / A / B / C or A / B / C
A D layer may be provided outside of A and B as in / B / D.
Of course, these combinations (eg, D / A / D / B
/ C). Burrs generated during the production of the thus obtained multilayer laminated structure may be finely pulverized and mixed with the main material layer.

[0036]

The present invention will be described in more detail with reference to the following examples. In the embodiment, the EVOH resin is used as the barrier layer. However, the same applies to the polyamide resin and the nitrile resin. Here, a fuel oil container (tank) was formed as a multilayer laminated structural material and tested. In Examples and Comparative Examples, the density was measured according to the method A of JIS K7112. The acoustic impedance (Z) was measured using an ultrasonic thickness gauge equipped with a vertical probe using a piezoelectric element as a diaphragm (Model 5215, manufactured by Nippon Panametrics, Inc.).
The speed of sound when ultrasonic waves (frequency: 20 MHz) were incident on each of the obtained multilayer laminated structures in the thickness direction was determined, and the density was calculated by the above-mentioned density and the following equation. Z = ρ × c ρ: density, c: sound velocity

Further, in order to determine the detectability of the adhesive layer, the apparatus used for measuring the acoustic impedance was used, and ultrasonic waves (frequency: 20 MHz) were subjected to three types and five layers of a multilayer laminated structural material (thickness: main material). Layer 3mm, adhesive layer 0.15mm, EVOH layer 0.10m
m, the adhesive layer 0.15 mm, the main material layer 3 mm), and the pulse wave reflected at each interface is output by a waveform observation oscilloscope equipped with a polaroid camera for recording, and the pulse waveform is recorded by the camera. did. A model of this recording is shown in FIG. FIG. 1 shows the intensity of the reflected wave, and the horizontal axis shows the distance in the thickness direction from the surface of the container. The pulse input from the left side of FIG. 1 shows the reflected wave intensity peak indicated by “a” on the main material layer surface, and then a part of the pulse enters the container wall, and the peak “a” and the peak “b” And passes through the thickness of the main material layer corresponding to the distance between them, and reflects at the adhesive material surface (interface with the main material layer) to show a peak “b”. In the case of this example (FIG.), The peaks “a” and “b” indicate the same direction because the acoustic impedance (Z ₀ ) of the main material layer and that of the adhesive material layer (Z ₀ ).
_This indicates that the value of ₁ ) is high (Z ₀ <Z ₁ ). If Z ₁ <Z ₀ , the peak height in the opposite direction is shown. Next, a further part of the pulse is reflected at the interface between the adhesive layer and the EVOH resin layer after passing through the thickness of the adhesive layer (the distance between the peak “b” and the peak “c”). EVO
After passing through the H resin layer (the distance between the peak “C” and the peak “D”), reflection is made as the peak “D”. When taking this measurement method, the difference between the peak at the interface between the adhesive layer and the main material layer h1, also the difference in the interfacial peak of the adhesive layer and the EVOH layer is h _2,
If h ₁ / h ₂ is less than 0.08, “no detectability” is determined and h ₁
/ H ₂ determines that "there is a sense of" is 0.08 or more. The reason is that when h ₁ / h ₂ is less than 0.08, it is extremely difficult to distinguish (identify) the peak “b” and the disturbance of the waveform due to noise.

The adhesive strength was measured by cutting a 10 mm wide and 150 mm long section from the flat surface of each container and measuring the adhesive strength between the adhesive and the EVOH layer by a T-type tensile test using a T-type peeling method. The measurement was performed with a peeling speed of 50 mm / min using a machine. Various polyethylene resins used for the adhesive layer in Examples and Comparative Examples were produced as follows.

The density is 0.960 g / cm ³ and the MFR is
0.80 g / 10 minutes high-density polyethylene resin [hereinafter "H
[DPE (1)]], 100 parts by weight of powder, 0.01 part by weight of 2,5-dimethyl-2,5-tert-butylperoxyhexane was added, and dry blending was performed using a Henschel mixer for 2 minutes. Was. Then, 0.35 parts by weight of maleic anhydride (hereinafter referred to as [MAH]) was added, and dry blending was further performed for 2 minutes. The resulting mixture was melt-kneaded with an extruder at a resin temperature of 260 ° C. to produce pellets. The grafted MAH amount of the obtained modified high-density polyethylene resin [pellet, hereinafter referred to as “modified HDPE (a)”) was 0.32% by weight. Modified HDP
In place of HDPE (1) used in producing E (a), the density was 0.950 g / cm ³ and the MFR was 0.12.
g / 10 minutes of high-density polyethylene resin [HDP
E (2) "], but modified HDPE
(A) Dry-blending and melt-kneading were carried out in the same manner as in the production to produce a modified high-density polyethylene resin [hereinafter referred to as “modified HDPE (b)”.
The amount of MAH grafted in (b) was 0.30% by weight.

The unmodified linear low-density polyethylene resin used for the adhesive layer has a density of 0.924 g / cm.
^A linear low density having an MFR of 0.8 g / 10 min, a melting point of 120 ° C., and the number of ethyl groups (branches) per 1000 carbon atoms in the main chain (hereinafter referred to as “branch number”) of 10 A polyethylene resin [hereinafter referred to as "L-LDPE (1)"] was used.
Dry blending of a modified high density [hereinafter referred to as “g-PE”] and an unmodified high density or linear low density polyethylene resin whose type and amount are shown in Table 1 for 5 minutes using a Henschel mixer in advance Was performed. Each of the obtained mixtures was kneaded while being melted using an extruder (diameter: 50 mm) at a resin temperature of 210 ° C. to produce pellets (composition). The MAH content, density, and acoustic impedance of the obtained composition (adhesive layer) were measured. They are shown in Table 1. Table 1 shows the abbreviations of the obtained adhesive layers.

[0041]

[Table 1]

As a main material layer, high-load MFR (JIS K7
According to 210, the conditions in Table 1 were measured at 7), but 5.0 g /
10 minutes, the density is 0.945 g / cm ³ , and the acoustic impedance is 2.23 × 10 ^-1 g / cm ² · μsec
High-density polyethylene resin [HDPE
(A) ”] and the MFR is 0.5 g / 10 min.
A high-density polyethylene resin [hereinafter referred to as “HDPE (B)”] having a density of 0.948 g / cm ³ and an acoustic impedance of 2.25 × 10 ⁻¹ g / cm ² μsec was used. Furthermore, the EVOH resin has a relative viscosity of 4.2 and an ethylene content of 30% by weight.

Examples 1 to 4 and Comparative Examples 1 to 4 The main material layer and the adhesive material layer of each type shown in Table 1 and the EVOH resin having a relative viscosity of 4.2 were mixed with the main material layer / adhesive material layer. The thickness of the EVOH resin layer / adhesive layer / main material layer is 3.0mm / 0.15mm / 0.10mm / 0.15mm / 3.0mm respectively
Blow molding using a multi-layer blow molding machine equipped with a multi-layer die (concentric) equipped with a co-extrusion machine at 232 ° C, has a capacity of 45 cm ³ and a total weight of 6.5 kg for automobiles A fuel tank was manufactured. The difference in h ₁ / h ₂ , the adhesive strength before and after the treatment and the acoustic impedance of the obtained tank were measured. Table 2 shows the results.

[0044]

[Table 2]

Example 5 The tank obtained in Example 1 was pulverized using a crusher, and the obtained mixture was kneaded at 265 ° C. using a coaxial twin-screw extruder to produce pellets. Observation of the dispersed particle size of EVOH in the obtained pellets using an optical microscope revealed that the average particle size was 45 μm (up to 70 μm). 30% by weight of the pellets and a density of 0.945 g / c
m is ^3, and (subject to JIS K7210, condition measured at 7) Melt flow rate was produced by dry blending a mixture consisting of 70 wt% high molecular weight high density polyethylene resin is 4.8 g / 10 min. Except that this was used as a main material layer, a tank (multilayer laminated structural material) was used in the same manner as in Example 1.
Was manufactured. When the detectability of the obtained tank was determined in the same manner as above, h ₁ / h ₂ was 0.12, and detection was possible.

[0046]

The multilayer laminated structure of the present invention exhibits the following effects. (1) Since it is configured using an adhesive layer having extremely excellent adhesiveness and various durability, it has excellent functions and performance even in a severe environment. (2) The most excellent point is that it is possible to detect the adhesive layer in the structure without destroying it by using the ultrasonic reflection method, which is a technique which has not been practically known at all. It is. (3) Therefore, by using this specific material and the multilayer laminated structural material combined with the specific material, it is possible to check the deterioration of the function and performance due to the defect of the adhesive layer before the final product, and to check the quality. In addition, in the process control, it is possible to confirm the deterioration of the function or performance due to the lack before the final product (fuel oil container). The multilayer laminated structural material of the present invention can be used in various fields as a multilayer laminated structural material having the above structure in order to exhibit the above effects. Representative applications are shown below. (1) Containers for fuel oil such as gasoline (including gasohol) (2) Various industrial cans

[Brief description of the drawings]

FIG. 1 shows a pulse waveform in which ultrasonic waves are incident from the outside of a container of three types and five layers, and reflected pulses at each interface are output by an oscilloscope for waveform observation.

[Explanation of symbols]

Lee main member layer surface peak B Base material layer - Peak Ha adhesive layer of the adhesive layer surface (front side) - peak two barrier layers of the barrier layer interface - adhesive layer peak h ₁ of (inner side) interface, h ₂ Peak difference

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-38791 (JP, A) JP-A-5-38790 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B60K 15/02

Claims (1)

(57) [Claims] 1. A main material layer mainly composed of a polyethylene resin and a resin layer selected from a polyamide resin, an ethylene vinyl acetate saponified resin and a nitrile resin are laminated on the outside with an adhesive layer interposed therebetween. A multilayer laminated structural material having a layered structure, wherein the adhesive layer has a density of 0.950 g / cm.
³ or more, MFR 0.01 g / 10 minutes or more, from the high-density polyethylene resin having a number of branches of 20 or less per 1000 C atoms in the main chain, and the high-density polyethylene resin graft-modified with an unsaturated carboxylic acid and / or a derivative thereof. Density of at least 0.950 g / cm ³ comprising a resin containing at least 0.1% by weight of modified high-density polyethylene resin selected, content of the grafted acid and / or derivative thereof 0.001 to 5.0
Weight%, the acoustic impedance due to ultrasonic waves of 20 to 25 MHz is 8.5 × 10 ⁻³ g / cm ² μsec with respect to that of the main material layer.
A multilayer laminated structural material comprising the resin composition raised above.