JPS6026028B2 - multilayer container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer container that burns low calories during incineration and has excellent mechanical properties.

Conventionally, containers made of polyethylene or polyvinyl chloride have been widely used as containers for liquid detergents, shampoos, and the like.

In particular, polyethylene containers have excellent processability and are inexpensive, so they are most commonly used as containers for liquid detergents, shampoos, and the like. When disposing of this type of polyethylene container by incineration, the high calorie combustion of the resin causes problems such as damage to the incinerator, and the disposal of this type of resin container has become a social problem. Various methods have been used to solve this problem by lowering the

For example, as shown in Hakama Kosho No. 47-6892,
It has been proposed to form a hollow container using a resin filled with a nonflammable inorganic material such as calcium carbonate or talc in polyolefin.

However, with polyolefin filled with such nonflammable inorganic materials, the burned calories decrease as the filling amount increases, but the environmental stress cracking resistance (hereinafter referred to as ESCR) and impact strength are lower than that of polyolefin single containers. It becomes inferior. For this reason, the amount of nonflammable inorganic material to be filled is naturally limited. Moreover, even if a polyolefin filled with a small amount of nonflammable inorganic material is used in a container containing liquid detergent, the ESCR is lower than that of a polyolefin not filled with nonflammable inorganic material, and the ESCR does not satisfy the practically desirable value. It was impenetrable. In order to improve this ESCR problem, a nonflammable inorganic filled polyolefin is used as an intermediate layer, and among the
A three-layer container using polyolefin for the outer layer was developed in 1991.
It is shown in Japanese Patent No.-26478.

ESCR
problem can be solved. However, since polyolefin is used as it is for the inner and outer layers, in order to reduce the calorie burn of the container, which is the main objective, it is necessary to increase the amount of nonflammable inorganic material filled into the polyolefin of the middle layer. Therefore, the filling amount is preferably 6% by weight or more, but such a high filling amount causes the disadvantage that the mechanical strength of the intermediate layer decreases.

Further, according to the findings of the present inventors, it has been found that mold reproducibility and dimensional accuracy are poor when the inner and outer layers are made of polyolefin that is not filled with a nonflammable inorganic material. These findings are specifically shown below as reference examples of the present invention.

First, the density is 0.951/earth, and the melt index is 0.3.
The mechanical properties of a material made by uniformly dispersing heavy calcium carbonate (average particle size 1.6 French) in high-density polyethylene for 10 minutes in the evening and a single-layer container (capacity 400 cm) made of this material were first evaluated. Shown in the table. The thickness of this single-layer container is constant, and the thickness of the second layer is constant.
It has the shape shown in the figure. Table 1 As shown, when the amount of calcium carbonate charged exceeds 5% by weight, the Wizodt impact strength and ESCR decrease rapidly, making it impossible to put it to practical use.

Therefore, if polyethylene filled with calcium carbonate is used as the intermediate layer, and inner and outer layers made of the same polyethylene not filled with calcium carbonate are provided on both sides, ES
CR has reached the desired value of 12 feeding hours or more, but
By providing the inner and outer layers, the filling amount of the intermediate layer must be increased, resulting in a disadvantage that the mechanical strength of the intermediate layer decreases.

The present inventors have conducted extensive research into polyolefin containers that can solve the above-mentioned problems, and as a result, have arrived at the present invention.

That is, as shown in FIG. 1, the present invention has an outer layer 1, an intermediate layer 2
and an inner layer 3.

The outer layer 1 is mainly made of polyolefin such as polyethylene, and contains 50% of nonflammable inorganic material such as calcium carbonate and talc.
It consists of a resin filled with ~2% by weight and necessary additives such as colorants, UV absorbers, antistatic agents, etc.

The intermediate layer 2 uses polyolefin such as polyethylene as the main material, and fills it with 30 to 5% by weight of nonflammable inorganic materials such as calcium carbonate and talc, and necessary additives such as colorants, ultraviolet absorbers, and antistatic agents. Made of resin.

The inner layer 3 is made of polyolefin such as polyethylene,
This is a resin that is not filled with nonflammable inorganic materials.

Here, the thickness of the outer layer, middle layer, and inner layer of the multilayer container of the present invention is 5 to 30% and 50 to 90% of the total thickness, respectively.
, 5 to 20% is suitable for the purpose of the present invention. The polyolefin used in the present invention includes low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, or polypropylene with polyethylene, polypropylene, ethylene-propylene copolymer,
It consists of a mixed resin containing 5 to 3% by weight of any one of ethylene ethyl acrylate copolymers.

This mixed resin is made by mixing polypropylene with other resins.
Since the rigidity of polypropylene can be used as is,
A container with better mechanical strength can be obtained. In addition, the nonflammable inorganic substances used in the present invention include calcium carbonate, talc,
Calcium sulfite, kaolin clay, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, basic magnesium carbonate, precipitated barium sulfate, gypsum, etc. are crushed, and the particle size is 0.5~50R and used as a filler for plastics. Any normal size that can be used will suffice.

In the present invention, it is important that the resin used for the outer layer is filled with the above-mentioned nonflammable inorganic material, and in order to obtain a multilayer container with low burn calories and excellent mechanical strength,
The filling amount of the outer layer is 5 to 2% by weight, and the filling amount of the middle layer is 30% by weight.
~5% by weight is required. If the filling amount of the outer layer is less than 5% by weight, surface gloss, ink and label adhesion will be poor, the molding cycle will be long, and mold reproducibility and dimensional stability will be poor.

Further, if the amount exceeds 2% by weight, surface stains become noticeable, and whitening occurs when mechanical force is applied due to violent movements, which is undesirable.

If the filling amount of the middle layer is less than 3% by weight, the calorie burn of the entire container will be high, and the initial purpose will not be achieved.

Also, if it exceeds 5% by weight, the calories burned will be lower, but
Mechanical strength decreases, which is not preferable.

Furthermore, it is clear that the effect becomes more pronounced as the total amount of nonflammable inorganic substances is increased in order to reduce the amount of calories burned during incineration of the container, which is the main objective. EXAMPLES The present invention will be explained in detail by showing Examples and Comparative Examples below.

High-density polyethylene (density 0.
951 multi/ground, MIO. 3 evenings/1 minute), using raw calcium carbonate (average particle size 1.6 grains) as a non-flammable inorganic material, wall thickness 0.7 skin, layer ratio 20:70:1 Filling of the middle layer By coextrusion method, the filling amount of the inner layer was set to 4% by weight, the filling amount of the inner layer was set to 0% by weight, and the filling amount of the outer layer was varied within the range of 0 to 3% by weight.
0' multilayer containers were molded. The mechanical strength of the product is the second
Shown in the table. The measurement results of production efficiency and dimensional stability are shown in Figure 3, and the measurement values of mold reproducibility are shown in Figure 4. Table 2 *4 Passed Container/Test Container *5 Sides A, B, and C are the positions that indicate the second worst K.

J, L, N, P are the same as those shown in Table 3. As shown in Table 2, if the amount of calcium carbonate filled in the polyethylene of the outer layer exceeds 2% by weight, the stain resistance of the container surface will deteriorate. and become susceptible to contamination.

Furthermore, if the cumulative cargo test, drop strength, and turbulence test taken into account during transportation exceeds 2% by weight, white streaks will appear on the surface of the container due to deformation and bending, a so-called whitening phenomenon. Therefore, not only the appearance deteriorates but also the mechanical strength decreases. Furthermore, as is clear from FIGS. 3 and 4, the production efficiency improves as the amount of calcium carbonate in the outer layer increases.

Furthermore, when the filling amount is 5% by weight or more, the change in the content of the container is small and a container with excellent dimensional stability can be obtained. In comparison, a three-layer container in which the outer layer was not filled with calcium carbonate had a large thermal shrinkage rate and lacked dimensional stability. For reference, among the various effects of the present invention, the results of measurements regarding surface gloss and label adhesion are shown below. First, the changes in surface glossiness are shown in Table 3.

Table 3 *1 Glossiness is measured according to JIS-Z-8741K As described above, as the amount of calcium carbonate charged increases, the surface glossiness decreases when it becomes 5% by weight or more.

This is particularly noticeable when the amount exceeds 1% by weight. When the surface becomes matte, the container as a whole becomes less glaring and has a softer appearance. Furthermore, the outer surface of the container is printed or labeled for advertising, decoration, etc. The test results of the surface adhesion are shown in Table 4 and FIG. Table 4 *2 Room temperature 24 years *3 40℃ 3 points By using this material, the adhesive properties of the label and printing ink are excellent, and there is no risk that the label will peel off or the printed pattern will disappear during transportation or use.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the container of the present invention, Figure 2 is an explanatory diagram showing the test points of the container in the drop test, Figure 3 is a graph showing dimensional stability with changes in filling amount, and Figure 4 is , a graph showing mold reproducibility with changes in filling amount, and FIG. 5 a graph showing label adhesiveness. 1...outer layer, 2...middle layer, 3...
・Inner layer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1 The outer layer is a polyolefin filled with a nonflammable inorganic material and necessary additives, the middle layer is a polyolefin filled with a nonflammable inorganic material in a larger amount than the outer layer and the necessary additives, and the inner layer is a polyolefin filled with a nonflammable inorganic material. Multi-layer container made of no polyolefin. 2 The thickness of the outer layer, middle layer, and inner layer is 5 to 50% of the total wall thickness.
30%, 50-90%, and 5-20% of the multilayer container according to claim 1. 3 Polyolefin in which the filling amount of nonflammable inorganic material in the outer layer is 5 to 20% by weight, and the filling amount of nonflammable inorganic material in the middle layer is 3
A multilayer container according to claim 1 or 2, comprising 0 to 50% by weight of polyolefin.