JP2750329B2 - Barrier container and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrier container which is excellent in mechanical strength and is suitable for storing a substance requiring a barrier property and is obtained by a rotational molding method, and a method for producing the same.

[0002]

2. Description of the Related Art Polyolefin resins are inexpensive, have high strength, and are excellent in chemical resistance, and are therefore widely used alone in various container materials. However, the range is limited due to insufficient barrier properties against some industrial chemicals, especially hydrocarbon solvents, and containers made of composite materials have been developed. Accordingly, various multilayer blow-molded containers of, for example, a polyolefin-based resin and another engineering plastic have been manufactured.

[0003] However, blow molding requires a huge apparatus for producing a large container exceeding 200 liters, and is not economically feasible. In practice, the manufacture of large containers had to rely on rotational molding.

[0004] As rotational molding suitable for the production of large containers, a multilayered molded product having a foamed layer as an intermediate layer (Japanese Patent Publication No. 50-8110)
) And a multi-layer rotationally molded article (JP-A-3-216) in which a resin other than the innermost layer uses a resin having a melt tension greater than a certain level.

However, in rotational molding using a foamed layer as an intermediate layer, a layered structure made of a thermoplastic resin having low compatibility or a thermoplastic resin which is difficult to be heat-sealed has a low adhesive strength between layers and a sufficient practical strength. It has disadvantages that cannot be obtained. On the other hand, in the method using a resin whose melt tension is larger than a certain level, if the difference in apparent viscosity of each resin is large or the melting point is different, the layer structure will not have a constant thickness of each layer, or pinholes will occur. However, there is a disadvantage that it is difficult to exhibit sufficient barrier properties.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an adhesive layer even when an incompatible resin is used as a raw material in a barrier container obtained by rotational molding. It is an object of the present invention to provide a multilayer container having a stable interlayer adhesion strength, sufficient practical strength, a uniform thickness of each layer, and excellent solvent barrier properties. Another object of the present invention is to provide a method for producing such a multilayer container by rotational molding.

[0007]

Means for Solving the Problems As a result of intensive studies in view of the above object, as a resin forming each layer in a barrier container, the apparent viscosity in a predetermined temperature and a predetermined shearing region is within a certain range, If the difference in viscosity is small and the difference in melting point between each resin is small, and if it is rotationally molded sequentially from the outer layer, the thickness of each layer will be uniform,
The present inventors have found that a container having stable mechanical strength and stable high barrier properties can be obtained, and have led to the present invention.

In the barrier container of the present invention, the inner layer is made of a polyamide resin (a), the intermediate layer is made of a polyolefin resin (b) modified with an unsaturated carboxylic acid or a derivative thereof, and the outer layer is made of a polyolefin resin (c). In the barrier container, based on JIS K 7210 of each constituent resin (a), (b), (c),
Apparent viscosity η (a) in the shearing region at 220 ° C and 10 sec ^-1
η (b) and η (c) are in the range of 0.2 × 10 ^{4 to} 20 × 10 ⁴ poise, respectively, satisfying the viscosity condition of the following formula, and 0.10 ≦ η (a) / η (c) ≦ 10.0 0.10 .Ltoreq..eta. (B) /. Eta. (C) .ltoreq.10.0 and the resin has a melting point difference of less than 60.degree. C. Further, each of the constituent resins (a),
It is characterized in that a multilayer structure is formed by sequentially rotating and molding the powdery particles (b) and (c) from the outer layer.

The present invention will be described in detail below.

In the present invention, examples of the polyolefin resin used as the outer layer include a homopolymer of ethylene or propylene or a copolymer of ethylene or propylene with another α-olefin.

As the α-olefin copolymerized with ethylene or propylene, propylene, butene-1,4
-Methyl-pentene-1, hexene-1, octene-1
And the like, and these may be used as a mixture.

The content of α-olefin in the copolymer is 15
% Or less is preferable.

Specifically, homopolymers and copolymers such as polyethylene and polypropylene can be used, and further, blends of these can be used.

Of these, linear low-density polyethylene and a blend thereof with polyethylene, polypropylene and a copolymer thereof are particularly preferred.

The polyolefin resin JI as described above
The apparent viscosity in the shear zone at 220 ° C. and 10 sec ^{−1 according} to SK 7210 is between 0.2 × 10 ^{4 and} 20 × 10 ⁴ poise.
When the apparent viscosity of the polyolefin resin is 0.2 × 10 ⁴ or less, dripping of the resin on the inner surface side increases, and when the apparent viscosity is 20 × 10 ⁴ or more, the resin does not turn uniformly or leaves bubbles. In any case, the smoothness of the inner surface is insufficient.

In the present invention, the modified polyolefin resin used as the intermediate layer is a modified polyolefin obtained by copolymerizing an unsaturated carboxylic acid or a derivative thereof. Examples of the unsaturated carboxylic acid for modification include acrylic acid, monocarboxylic acid such as methacrylic acid, maleic acid, dicarboxylic acid such as fumaric acid, and metal salts thereof, and unsaturated carboxylic acid derivatives such as amide , Imides, acid anhydrides and the like. Examples of the metal salt include potassium, sodium, lithium, zinc, calcium and the like.

The apparent viscosity of the modified polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof as described above in the shear range of 220 ° C. and 10 sec ⁻¹ based on JIS K 7210 is 0.2 × 10 ^{4 to} 20 × 10 ⁴ poise. It is. The apparent viscosity of the modified polyolefin resin used for the intermediate layer is 0.2 × 10 ⁴
In the following, the dripping of the resin on the inner surface side increases, and conversely, if the apparent viscosity is 20 × 10 ⁴ or more, the resin may not be able to uniformly turn around, or may be molded with bubbles remaining, and in any case, the inner surface Is insufficient in smoothness. Furthermore, when the ratio η (b) / η (c) relating to the apparent viscosity does not satisfy the following expression: 0.10 ≦ η (b) / η (c) ≦ 10.0, or when the melting point difference of each resin is 60 ° C. or more, The multilayer structure of the outer layer and the intermediate layer and / or the multilayer structure of the intermediate layer and the inner layer may be disturbed or the layers may be broken, resulting in poor adhesion.

In the present invention, the polyamide resin used as the inner layer is nylon 6, nylon 66, nylon 1
1, ordinary polyamide resin such as nylon 12, or copolymer polyamide resin such as nylon 6/66, nylon 6/11, nylon 66/11, nylon 6/12, nylon 66/12, or a blend thereof. Can be used. Preferred are nylon 6/11 and nylon 6/12 copolymerized polyamide resins.

JIS K 7 of polyamide resin as described above
The apparent viscosity in the shear zone at 220 ° C. and 10 sec ⁻¹ based on 210 is between 0.2 × 10 ^{4 and} 20 × 10 ⁴ poise. When the apparent viscosity of the resin is 0.2 × 10 ⁴ or less, dripping of the resin on the inner surface side increases, and when the apparent viscosity is 20 × 10 ⁴ or more, the resin does not uniformly turn or bubbles remain. Also in the case of the above, the smoothness of the inner surface is insufficient. Furthermore, when the ratio η (a) / η (c) regarding the apparent viscosity does not satisfy the following formula: 0.10 ≦ η (a) / η (c) ≦ 10.0, or when the melting point difference of each resin is 60 ° C. or more, The multilayer structure of the intermediate layer and the inner layer may be disturbed or the layers may be broken, thereby impairing the barrier function.

In the present invention, a filler, a colorant, a heat stabilizer, a light stabilizer, a flame retardant, an antistatic, and the like are added to the resin for each of the above-mentioned layers for the purpose of modifying the resin so as not to affect molding. An agent, a foaming agent, a nucleating agent and the like can be appropriately added.

Next, the method of the present invention for producing a large barrier container will be described.

The apparatus used for rotational molding is a direct heating method,
Regardless of the indirect heating method, a known rotary molding facility is used regardless of whether there is a single-axis rotation, a double-axis rotation, or a rocking motion.

The raw material resin used in the rotational molding is in the form of powder particles. Usually, resin pellets obtained by mechanical pulverization are used, but the resin powder obtained in the polymerization step may be used as it is. . Its average particle size is 3-100
A mesh mesh is used, and preferably 30 to 80 mesh. The use of a resin powder having such a mesh is preferable in that the thickness of each layer to be formed is made uniform and the melt molding time is shortened.

In the manufacture of the container, first, a predetermined amount of the polyolefin resin for the outer layer is charged into a mold for rotational molding. Heating the mold directly or indirectly while rotating the mold to melt and form the resin makes it possible to form the first outer layer.
Form a layer.

The temperature applied at this time must be higher than the melting point of the raw resin and lower than the decomposition temperature. In addition, it is necessary to heat until the thickness reaches a thickness in proportion to the amount of injected resin so that the unmelted resin does not remain. These temperatures and times are common to the following heating operations unless otherwise specified.

Next, a predetermined amount of a polyolefin resin modified with an unsaturated carboxylic acid or derivative for an intermediate layer is charged into the mold. As above, while rotating and heating again,
The second layer of the intermediate layer is formed by melting the raw material resin.

Further, a predetermined amount of the polyamide resin for the inner layer is charged into the mold. Similarly, the third layer of the inner layer is formed by melting the raw material resin while rotating and heating.

Depending on the required performance of the container product, the fourth and subsequent layers can be provided as inner and outer layers, and any number of layers can be formed in the same procedure.

After the formation of the layer structure of the necessary layers is completed, post-treatment for smoothing the inner surface is performed, if necessary, solidified by cooling, and released from the mold to obtain a product container. At this time, the cooling method may be any of leaving cooling and forced cooling, but it is desirable to combine both methods.

[0030]

Embodiments of the present invention will be described below. In addition, for the evaluation of the barrier properties, the containers of Example 2 and Comparative Examples 3 to 5 were subjected to a test liquid permeation enhancement test. The test method is as follows.

[Permeation Acceleration Test] To minimize the permeation of the test solution (xylene, primary reagent, density 0.87 g / cm ³ ), use an aluminum laminate film at the mouth of the container and heat seal with an iron. do. Therefore, it is necessary to cut out the aluminum laminate film to an appropriate size according to the shape of the mouth. First, prior to the test, a container adjusted for 24 hours or more and a film for sealing were added to a constant temperature room at 23 ° C., and the balance was weighed with a precision plate (manufactured by Sartorius, model MP8-1).
, And the weight is defined as the container weight (Wc).

Next, 20% (2 liters) of the test solution is placed in the container, and the aluminum laminate film is heat-sealed at the mouth with an iron. The weight is measured in the same manner, and this is defined as the initial weight (Wo).

The container filled with the test solution was placed in a thermostat (Tabayspeck, Model SPH-200) kept at 50 ° C.
Let stand for a day and conduct the penetration enhancement test. The weight of the container after completion of the test is measured, and this is defined as the weight (W ₁ ) after the test.

The barrier performance is represented by the following transmittance. Transmittance (%) = [(Wo-W ₁ ) / (Wo-Wc)] × 100 where Wc: container weight (g) Wo: initial weight (g) W ₁ : weight after test (g)

[Deformation of Container] Deformation of the container was evaluated by visually observing the container after the permeation enhancement test, by ○ when there was no deformation, and X when there was deformation.

The following examples are not intended to limit the present invention in any way, and can be widely used as a solvent, a solution containing the solvent, or a container such as an emulsion or dispersion in which a polymer substance or an inorganic substance is dispersed. It is.

[0037]

Example 1 As shown in Table 1, as the resin for the outer layer,
25 kg of linear low-density polyethylene (density 0.92 g / cm ³ ) powder
Was filled in a 1000-liter square mold, and heated while rotating the mold to melt and form the resin. Here, the molding was temporarily interrupted, the injection port of the mold was opened, and 6 kg of a maleic anhydride-modified polyethylene resin (density 0.93 g / cm ³ ) powder for the intermediate layer was charged into the mold and heated similarly. Heating the resin,
Melt formed. Further, the molding was interrupted again, the inlet of the mold was opened, and 8 kg of nylon 6/12 copolymer resin (density 1.04 g / cm ³ ) powder for the inner layer was charged into the mold and heated similarly. The resin was melt formed. After spin-molding the layer structure, it was cooled and solidified, and released from the mold to obtain a product having a three-layer structure as shown in FIG.

When the cross section of the obtained product was confirmed with a microscope, the inner layer 1 had a thickness of 1.5 mm, the intermediate layer 2 had a thickness of 1 mm, and the outer layer 3 had a thickness of 4 mm. As shown in FIG. The product is obtained. In addition, the three-layer molded product had a sufficient interlayer adhesive strength. The cross section of the product is confirmed by a microscope, and the same shall be followed unless otherwise specified.

[0039]

Example 2 The same raw materials as in Example 1 are used. First,
Linear low-density polyethylene (density 0.92 g / cm ³ ) powder 1100
g was charged into a 10-liter mold, and the mold was heated while rotating to form a resin in a molten state. Here, the molding is temporarily stopped, the injection port of the mold is opened, and maleic anhydride-modified polyethylene resin (density 0.93 g / cm ³ ) powder for the intermediate layer is used.
g was placed in a mold and heated in the same manner to melt the resin and spin-formed. Further, the molding was interrupted again, the inlet of the mold was opened, and a nylon 6/12 copolymer resin for the inner layer (density 1.
04 g / cm ³ ) 340 g of the powder was similarly heated in a mold to melt and form the resin. After completing the formation of the layer structure, it was cooled and solidified, released from the mold, and a small three-layer container for testing the barrier performance was prepared.

The cross section of the obtained product was 1.5 mm in the inner layer 1, 1 mm in the intermediate layer 2 and 4 mm in the outer layer 3, and was a good container having a uniform thickness as in Example 1. In addition, this three-layer molded product had sufficient interlayer adhesion strength between the inner layer and the intermediate layer and between the intermediate layer and the outer layer.

In order to evaluate the solvent barrier property of the molded container, the above-mentioned permeation acceleration test was carried out. The results are shown in Table 2. The product obtained in Example 2 had no deformation of the container and the transmittance was as very small as 0.01%, indicating good barrier performance.

[0042]

Comparative Example 1 A molding was performed in the same manner as in Example 1 except that the nylon 6/12 copolymer resin for the inner layer in Example 1 was changed to nylon 6 (density: 1.14 g / cm ³ ). It took a long time to melt and form the inner layer, and the cross section of the product was confirmed.
As shown in Table 2, the thickness of each layer was not uniform, bubbles and pinholes were observed, and the product was defective.

[0043]

Comparative Example 2 A molding was performed in the same manner as in Example 1 except that the nylon 6/12 copolymer resin for the inner layer in Example 1 was changed to nylon 12 (density: 1.02 g / cm ³ ). When the cross section of this product was confirmed, as shown in FIG. 4, the thickness of each layer was uneven, and the inner layer was broken and the product was defective.

[0044]

Comparative Example 3 1700 g of the same linear low-density polyethylene (density: 0.92 g / cm ³ ) powder as the resin for the outer layer of Example 1 was charged into a 10-liter circular mold, and the mold was heated while rotating. Then, the resin was melted and rotationally molded. This is cooled and solidified,
The mold was released from the mold, and a small single-layered container for testing the solvent barrier performance was prepared.

When the cross section of the obtained product was confirmed, the product had a thickness of 6.5 mm and was a good container having a uniform thickness.

In order to evaluate the solvent barrier property of the molded container, the above-mentioned permeation acceleration test was carried out. The results are shown in Table 2. The deformation of the container is large, and the solvent permeability is as large as 20.0%. That is, it has poor solvent barrier performance and is not suitable as a solvent container.

[0047]

Comparative Example 4 From the nylon 6/12 copolymer resin for the inner layer in Example 2, the same nylon 6 (density 1.14) as in Comparative Example 1 was used.
g / cm ³ ), except that the molding was performed in the same manner as in Example 2.
It took a long time to melt and form the inner layer, and the cross section of the container was uneven in thickness of each layer, and bubbles and pinholes were observed.

In order to evaluate the solvent barrier property of the molded container, the above-mentioned permeation acceleration test was carried out. The results are shown in Table 2. The container is deformed, and the transmittance is as large as 1.5%. That is, it has poor barrier performance and is not suitable as a solvent container.

[0049]

Comparative Example 5 From the nylon 6/12 copolymer resin for the inner layer in Example 1, the same nylon 12 (density 1.02
g / cm ³ ), except that the molding was performed in the same manner as in Example 2.
In the cross section of this container, the thickness of each layer was not uniform, and the inner layer was broken, and the container was defective.

In order to evaluate the barrier property of the molded container, the above-mentioned permeation enhancement test was carried out. The results are shown in Table 2. Deformation of the container was observed, and the transmittance was as large as 3.2%. That is, it has poor barrier performance and is not suitable as a solvent container.

The measured values of the apparent viscosities and melting points of the raw materials of the respective Examples 1 and Comparative Examples 1 and 2 are shown in Table 1, and the results of the barrier performance tests of Example 2 and Comparative Examples 3 to 5 are shown in Table 1. It is shown in Table 2.

[0052]

As described in detail above, the container of the present invention can provide a large-sized barrier container having uniform thickness of each layer and excellent mechanical strength. Therefore, it is suitable as a container for industrial chemicals, agricultural chemicals, paints, various processing agents, and the like.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a three-layer molded container molded in Example 1 of the present invention and Comparative Examples 1 and 2.

FIG. 2 shows a corner portion (A) of the container obtained in Example 1.
And an enlarged sectional view of a side wall portion (B).

FIG. 3 shows a corner portion (A) of the container obtained in Comparative Example 1.
And an enlarged sectional view of a side wall portion (B).

FIG. 4 shows a corner portion (A) of the container obtained in Comparative Example 2.
And an enlarged sectional view of a side wall portion (B).

[Explanation of symbols]

 1: inner layer 2: middle layer 3: outer layer 4: air bubble 5: pinhole 6: broken part of layer

[Table 1]

[Table 2]

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/34 B32B 27/34 // B29K 23:00 77:00 B29L 22:00

Claims (2)

(57) [Claims] 1. A barrier container comprising an inner layer comprising a polyamide resin (a), an intermediate layer comprising a polyolefin resin (b) modified with an unsaturated carboxylic acid or a derivative thereof, and an outer layer comprising a polyolefin resin (c). Based on JIS K 7210 for each component resin (a), (b), (c), 22
0 ° C, apparent viscosity η (a), η in shear range of 10 sec ^-1
(b) and η (c) are in the range of 0.2 × 10 ^{4 to} 20 × 10 ⁴ poise, respectively. The viscosity condition of the following formula is satisfied, and 0.10 ≦ η (a) / η (c) ≦ 10.0 0.10 ≦ η (b) / η (c) ≦ 10.0 c. A barrier container having a multilayer structure, wherein the container has a melting point difference of less than 60 ° C. between the resins. 2. A method for producing a barrier container comprising an inner layer comprising a polyamide resin (a), an intermediate layer comprising a polyolefin resin (b) modified with an unsaturated carboxylic acid or a derivative thereof, and an outer layer comprising a polyolefin resin (c). (1) a. Apparent viscosity η in the shearing region of 220 ° C. and 10 sec ⁻¹ based on JIS K 7210 of each constituent resin (a), (b) and (c)
(a), η (b) and η (c) are in the range of 0.2 × 10 ^{4 to} 20 × 10 ⁴ poise, respectively. Satisfies the viscosity of the following formula, and 0.10 ≦ η (a) / η (c) ≦ 10.0 0.10 ≦ η (b) / η (c) ≦ 10.0 c. In addition, a resin having a melting point difference of less than 60 ° C. between the resins is used. (2) The powdery particles of each of the constituent resins (a), (b), and (c) are sequentially rotated from the outer layer resin (c). A method for producing a barrier container, comprising forming a container having a multilayer structure of an outer layer, an intermediate layer and an inner layer by molding.