JPS6362728A - Resin-aluminum composite material having excellent cold moldability - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a resin film that is used as a material for storage containers for foods, cosmetics, electronic parts, etc., in which an aluminum foil and a resin film are laminated together. aluminum composite,
In particular, it relates to composite materials with excellent cold-opening formability.

Conventional technology Aluminum foil is used as a material for storage containers for foods, cosmetics, electronic parts, etc. because it has excellent moisture, gas, and light blocking properties and fragrance retention, and has a moderate amount of rigidity. There is. As such an aluminum foil container,
Deep drawing of a relatively thick foil with a thickness of around 100 μm has been used, but it has the drawback of lacking elasticity.

Therefore, it has been proposed to use a resin/aluminum composite material as a container material, which is made by laminating thermoplastic resin films containing stretched films on both sides of aluminum foil (for example, Utility Model Publications No. 60-28582, No. 61-14430, No. 6
1-14431). Such composite materials have advantages such as excellent cold-opening moldability, especially stretch moldability, allowing the rigidity of the container to be designed over a wide range by selecting the resin film, and excellent productivity.

Problems to be Solved by the Invention However, in the above-mentioned composite material, even when the same type of resin film is attached to the aluminum foil with the same thickness, there is a large difference in the formability of the composite material, which does not meet the user's requirements. The inventors' research has revealed that this is not necessarily satisfactory.

The present invention was made based on such a technical background, and an object of the present invention is to provide a resin/aluminum composite material that can stably achieve high moldability.

Means for Solving the Problems For the above purpose, the inventors have conducted various experiments and research, and have found that in order to obtain high formability of composite materials, aluminum foil and stretched film must have certain characteristics. We have come to the knowledge that this is necessary, and have completed this invention based on this knowledge.

That is, in this invention, one or more stretched films made of thermoplastic resin are laminated on both sides of an aluminum foil, and the aluminum foil has a thickness of 20 to 70 μm and a work hardening index (n). value) is specified to be 0.2 or more, and the average crystal grain size is specified to be 60 μm or less, while the stretched film has fexp ( n) In the nominal strain range of −11 to 0°8, and when the nominal strain is 0. For those that break at (e1) before reaching 8, in the nominal strain range from (exp (n) -11 to e1), the composite value of the tensile load increase of each film is 1 m + 0. A resin with excellent cold-opening moldability characterized by a 18~1° OK.
The focus is on aluminum composite materials.

The reason for laminating stretched films on both sides of aluminum foil is as follows. That is, during tensile deformation of aluminum foil, the surface roughness increases as the deformation progresses, stress concentration occurs due to non-uniform deformation, and the tensile elongation appears low. As the thickness of the foil becomes thinner, these effects become more dominant and the elongation at break becomes smaller. For this reason, by laminating stretched films on both sides of the aluminum foil, the surface of the aluminum foil is restrained to suppress surface roughness, and the aluminum foil is uniformly deformed to suppress stress concentration. Stretched film (2)
As shown in Figure 1, one layer may be laminated on each side of the aluminum foil (1), or two or more layers may be laminated on either both sides or only one side (though not shown). It's okay to have something like that.

However, in either case, the adhesion between the aluminum foil and the stretched film must be sufficient.

The material for the stretched film is polypropylene (PP).
, polyester (PET), nylon, and the like.

The reason why the thickness of the aluminum foil (1) is specified to be in the range of 20 to 70 μm is that if it is less than 20 μm, pinholes will occur as deformation progresses during molding, and as a result, the molding height cannot be increased; If it exceeds 70 μm, the container after molding will lack elasticity, and the stretched film will need to be thick to achieve sufficient elongation, resulting in high cost.

A desirable thickness of the aluminum foil is 30 to 50 μm. Further, the work hardening index (n value) of the aluminum foil is 0.
The reason why it is specified to be 2 or more is because if it is less than 0.2, the moldability will be poor.

The higher the n value, the better the moldability, and it is preferably 0.23 or more. Furthermore, the average crystal grain size of aluminum foil is specified to be 60 μm or less.
This is because if the thickness exceeds 0 μm, the moldability will be poor. The thickness is desirably 30 μm or less.

Generally speaking, the tensile load-nominal strain characteristics during tensile deformation of a stretched film are as shown in Figure 2, where the tensile load increases parabolically in the initial stage, and then gradually increases almost in proportion to the strain on the high strain side. It is represented by a curve that looks like this. In the present invention, regarding this stretched film, if the nominal strain (e) shown on the horizontal axis extends to 0.8 or more, {exp(n)-
In the nominal strain range of 11 to 0.8, and with a nominal strain of 0
．． For those that break at (e1) before reaching 8 (the break point is indicated by an X mark), (exp (n)-1} ~ e
In the nominal strain range of 1, the composite value of the tensile load increase of each stretched film is 0.18 to 1°0 Ny per 1 m width for the strain amount 1 (hereinafter 0.18 to 1.0 Kg/unit strain, in the layer) ). Here, the composite value refers to the sum of the tensile load increases in the above-mentioned nominal strain range of each stretched film. Combined value is 0.18Kg/
If the unit strain is less than the middle of the layer, the effect of improving formability is poor, and on the other hand, if the IK'l/unit strain exceeds 1 width, the springback will increase and the shape retention will be poor or the film will be thick. This results in drawbacks such as poor economic efficiency. The preferable tensile load increase amount is 0.2 to 0.5 Nf
/unit strain amount, in between.

Here, the starting point of the nominal strain region that defines the amount of increase in tensile load is (
exp (n)-1) is used because the tensile deformation characteristics of aluminum foil are such that, as shown in the load-nominal strain curve in Figure 2, the tensile load of aluminum foil is such that the nominal strain (e) is l.
It reaches its maximum when e x p (n)-1), and (exp
This is because the nominal strain range of less than (n)-11 is a range where the aluminum foil uniformly deforms due to increased load and does not pose a problem. On the other hand, the reason why the end point of the nominal strain range is set to 0.8 for a stretched film with good elongation is that in a region where the nominal strain exceeds 0.8, it approaches the breaking limit of the stretched film itself. This is because it is sufficient. This (e
x p (n) −11 to 0. 8 or (exp (
n) In the nominal strain range of -11 to e1, the tensile load of the stretched film gradually increases almost in proportion to the strain, so there is no problem in evaluating the amount of increase in the tensile load based on the average value over the entire nominal range. The above conditions regarding the amount of increase in tensile load on stretched film should be satisfied in all directions of the film because the final container will be formed by stretching, etc., and in practice, it should be satisfied in all directions of the film. It is necessary to check in a total of 4 directions: 0@, 90°, and 45" (2 directions). It is desirable that the total thickness of the stretched film is about 15 to 40 μm. The above tensile load increase Stretched film that satisfies the condition of quantity has the effect of suppressing the stress concentration of aluminum foil in the high strain range and uniformly deforming it in the composite material laminated with aluminum foil, and as a result, the aluminum foil does not break. The composite material becomes capable of large deformation.In such a composite material, the load on the aluminum foil itself decreases in the high strain region.

This is because dislocation cross-slip occurs within the aluminum foil. In addition, in the tensile load-nominal strain curve of aluminum foil shown in Fig. 2, the broken line portion is Ho1l.
on+on formula σ−Fε (σ: true stress, F: constant, ε
: true strain, n: work hardening index). In addition, point X in the same curve indicates the breaking point in tensile deformation of the aluminum foil alone.

Effects of the Invention As mentioned above, the composite material according to the present invention has a stretched film made of a thermoplastic resin attached to both sides of the aluminum foil, and the aluminum foil have defined characteristics, so that the composite material can be stably and large. Cold-opening moldability, especially stretch moldability, can be obtained. For this reason, it is suitable for use as a material for storage containers for foods, cosmetics, etc.

Example Next, this invention will be explained in detail.

In producing a resin/aluminum composite material in which one layer of stretched film was laminated on both sides of aluminum foil, the following aluminum foil and stretched film were prepared.

(Aluminum foil) Aluminum foil with a thickness of 40 pm, neo, 25, and an average crystal grain size of 20 μm.

(Stretched Film) Four types of films shown in Table 1 were prepared. Here, the tensile test to determine the amount of increase in tensile load ΔP over a predetermined nominal range uses strip specimens with a width of 10, in order of gauge distance 100,
0', in the coil length direction at a tensile speed of 100 shoes/min.
The measurement was carried out in a total of four directions: 90' and ±45°. And ΔP is t in the load-nominal strain curve obtained from the recording paper.
exp (0,25)-11 to 0.8 or 0.28
The average value over the nominal range of ~0.8 is the unit strain amount, lim
Converted to per width.

[See the margins below.Next, stretch films were laminated on both sides of the aluminum foil in the combinations shown in Table 2 below to form a three-layer resin structure.
Made of aluminum composite material.

Each composite material was then subjected to a tensile test and stretched to examine its formability. The tensile test was conducted under the same conditions as the tensile test of the stretched film, and the average tensile elongation in the four directions of Oo, 90°, and ±45@ was determined. Also, the overhang processing is 50m in outer diameter.
The molding height was determined by using a Teflon punch (+) and a die having an inner diameter of 57#III at a punch speed of 75 M/min. In addition, the same sample was subjected to a stretching test 20 times, and the direction in which the largest number of fractures occurred was determined. those results as a second
It is also shown in the table.

[Margins below] As is clear from the above results, it was confirmed that the products of the present invention were elongated, had a large molding height, and had excellent moldability.

[Brief Description of the Drawings] Figure 1 is an enlarged sectional view showing a three-layer composite material as an example of the present invention, and Figure 2 shows the tensile load-nominal strain characteristics of the composite material, aluminum foil, and stretched film. FIG. (1)...Aluminum foil, (2)...Stretched film. Above Figure 1 Publication 1(e) Figure 2

Claims (1)

[Claims] One or more layers of stretched films (2) made of thermoplastic resin are laminated on both sides of the aluminum foil (1), and the aluminum foil (1) is processed to a thickness of 20 to 70 μm. Hardening index (n value) is 0.2
As described above, while the average crystal grain size is specified to be 60 μm or less, the stretched film has a tensile load-nominal strain characteristic in which the nominal strain extends to 0.8 or more, {exp(n)-1} In the nominal strain range of ~0.8,
In addition, for films that break at (e_1) before the nominal strain reaches 0.8, in the nominal strain range from {exp(n)-1} to e_1, the combined value of the tensile load increase of each film is the strain amount 1 A resin with excellent cold formability characterized by a regulated weight of 0.18 to 1.0 kg per 1 mm width.
Aluminum composite.