Containers of a multilayered structure

Abstract

A container of a multilayered structure comprising an inner layer and an outer layer of a low-density polyethylene, and an intermediate layer that includes a gas-barrier resin layer and adhesive layers, wherein the adhesive layers contain an acid-modified polyethylene and a propylene resin, the propylene resin being contained in an amount of 0.5 to 10% by weight in the adhesive layers. The container is obtained by using decreased amounts of resins without impairing properties of the containers.

Claims

1. A container of a multilayered structure comprising an inner layer and an outer layer of a low-density polyethylene, and an intermediate layer that includes a gas-barrier resin layer and adhesive layers, wherein said adhesive layers contain an acid-modified polyethylene and a propylene resin, said propylene resin being contained in an amount of 0.5 to 10% by weight in the adhesive layers and being one which has not been modified with acid.

2. The container of a multilayered structure according to claim 1, wherein said adhesive layers, further, contain a linear low-density polyethylene.

3. The container of a multilayered structure according to claim 1, wherein said acid-modified polyethylene is the one obtained by modifying a linear low-density polyethylene with an acid.

4. The container of a multilayered structure according to claim 1, wherein said acid-modified polyethylene has a density in a range of from 0.925 to 0.950 g/cm.sup.3.

5. The container of a multilayered structure according to claim 1, the container of the multilayered structure being obtained by the direct blow-forming.

6. The container of a multilayered structure according to claim 1, wherein said propylene resin is a homopolypropylene or a copolymer obtained by copolymerizing a propylene with another -olefin.

Description

EXAMPLES

(1) The invention will now be described by way of the following Examples.

(2) Properties of the containers and properties of the resins that were used were measured according to the methods described below.

(3) (1) Buckling Strength.

(4) The obtained multilayered container was set with its mouth portion facing upward into a compression tester, a load was exerted thereon in the longitudinal direction at a rate of 10 mm a minute, and the load (kgf) by which the container buckled was regarded to be a buckling strength. Five containers were measured to find an average value which was then evaluated on the following basis. The containers marked with , and were regarded to be in allowable ranges. : Not less than 5 kgf. : Not less than 4 kgf but less than 5 kgf. : Not less than 3 kgf but less than 4 kgf. X: Less than 3 kgf.
(2) Tensile Modulus of Elasticity.

(5) A test piece was cut out from a flat body wall of the obtained multilayered container in compliance with the JIS 7113, and was put to the tension test in the direction of height of the container to measure the tensile modulus of elasticity. Five test pieces were measured to find an average value which was then evaluated on the following basis. The containers marked with and were regarded to be in allowable ranges. : Not less than 800 MPa. : Not less than 700 MPa but less than 800 MPa. X: Less than 700 MPa.
(3) Shatter Strength.

(6) The obtained multilayered containers were each filled with 300 ml of tap water, stored in a refrigerator maintained at 5 C. for 24 hours, taken out therefrom, and were permitted to fall onto the concrete floor surface from a height of 1.5 meters in an upright attitude (bottoms of the containers down) in a number of 10 containers and in a sideways attitude (bottoms of the containers sideways) in a number of 10 containers. The number of the containers that were broken were counted and was regarded as the shatter strength, which was then evaluated on the following basis. The containers marked with and were regarded to be in allowable ranges. : No container was broken. : The containers were not broken but were locally delaminated. X: Some containers were broken.
(4) Shading in the Appearance.

(7) The body wall of the obtained multilayered container was observed with the eye to evaluate shading in the appearance. The clouded portions having low transparency were regarded to be shading in the appearance. Maximum shadings in ten containers were measured and were evaluated on the following basis. The containers marked with and were regarded to be in allowable ranges. : No shading. : Less than 30% of the surface areas of the containers was shaded. X: Not less than 30% of the surface areas of the containers was shaded.
(5) Close Adhesion.

(8) A flat portion of the body of the obtained multilayered container was cut out into a size of 4 cm6 cm, and was repetitively folded so as to form a line in the direction of height of the container to evaluate the close adhesion. Folding and unfolding were repeated 50 times so that the folded part became 0. Ten containers were used and evaluated on the following basis. The containers marked with and were regarded to be in allowable ranges. : No delamination occurred. : No delamination occurred up to 40 times but occurred on the way up to 50 times. X: Delamination occurred before 39 times.
(6) Overall Evaluation.

(9) Overall evaluation was rendered as follows from the results of evaluating the buckling strength, tensile modulus of elasticity, shatter strength, shading in the appearance and close adhesion. : Evaluated to be or in all respects. : Evaluated to be in any or some respects but evaluated to be X in none of the respects. X: Evaluated to be X in at least one respect.
(Properties of the Resins that were Used).

(10) The resins used for forming the layers were measured for their MFR's in compliance with the ASTM D123 (190 C.) and were measured for their densities in compliance with the ASTM D792.

(11) (Resins and Lubricant that were Used).

(12) The following resins and lubricant were used for forming the layers.

(13) [Resins for Forming the Inner and Outer Layers]

(14) Low-density polyethylene (LDPE) MFR; 1.1 g/10 min., density; 0.92 g/cm.sup.3 (as a lubricant, oleic acid amide was contained in an amount of 300 ppm)
[Resin for Forming the Gas-Barrier Layer] Ethylene-vinyl alcohol copolymer (EVOH) density; 1.19 g/cm.sup.3, MFR (190 C.); 1.3 g/10 min.
[Resins for Forming the Adhesive Layers] a) Maleic anhydride-modified linear low-density polyethylene-A. (Acid-modified LLDPE-A in Table 1) (used in an amount of 15% by weight) MFR; 2.7 g/10 min. Density; 0.946 g/cm.sup.3 b) Maleic anhydride-modified linear low-density polyethylene-B. (Acid-modified LLDPE-B in Table 1) (used in an amount of 98% by weight) MFR; 0.8 g/10 min. Density; 0.930 g/cm.sup.3 c) Maleic anhydride-modified low-density polyethylene-A. (Acid-modified LDPE-A in Table 1) (used in an amount of 98% by weight) MFR; 1.0 g/10 min. Density; 0.930 g/cm.sup.3 d) Homopolypropylene (homoPP in Table). MFR; 0.5 g/10 min. Density; 0.900 g/cm.sup.3 e) Block-copolymerized polypropylene (copolymerized PP in Table). MFR; 0.6 g/10 min. Density; 0.900 g/cm.sup.3 f) Linear low-density polyethylene (LLDPE in Table). MFR; 1.0 g/10 min. Density; 0.916 g/cm.sup.3
[Lubricant Master Batch]

(15) The low-density polyethylene as a base material and the oleic acid amide as a lubricant were thrown into separate feeders, and were extruded by using a biaxial extruder to prepare a master batch containing the oleic acid amid in an amount of 3% by weight.

(16) [Preparation of Pellets for Forming Adhesive Layers]

(17) The pellets thrown into the adhesive layers were those obtained by dry-blending the pellets of the propylene resin, acid-modified polyethylene and linear low-density polyethylene that were weighed into predetermined amounts in percent by weight by using a tumbler.

Example 1

(18) Resin pellets obtained by dry-blending the low-density polyethylene with 1.0% by weight of the lubricant master batch were fed into a 50-mm extruder to form the outer layer, a resin shown in Table 1 was fed into a 40-mm sub-extruder A to form the adhesive layer, an ethylene-vinyl alcohol copolymer was fed into a 40-mm sub-extruder B to form the gas-barrier layer, and resin pellets obtained by dry-blending the low-density polyethylene with 1.0% by weight of the lubricant master batch were fed into a 40-mm sub-extruder C to form the inner layer. These resins were extruded through a multi-layer die head heated at 210 C. to form a molten parison which was then melt-blow-formed in a customary manner into a tubular multilayered container of a three-kind-five-layer structure for containing ketchup having a diameter of nozzle 025 mm, a volume of 300 ml and a weight of 11.8 g.

(19) The body wall of the container possessed the layer constitution which on the average was as follows:
Outer layer 15.0% (67.5 m)/adhesive layer 1.0% (4.5 m)/gas-barrier layer 6.30% (28.4 m)/adhesive layer 1.0% (4.5 m)/inner layer 76.7% (345.2 m).

(20) The adhesive layers of the container possessed the resin constitution as described below.

(21) 2% By weight of mono PP as the PP resin, 15% by weight of acid-modified LLDPE-A as the acid-modified PE resin, and 83% by weight of LLDPE.

(22) The container prepared above was evaluated for its buckling strength, tensile modulus of elasticity, shatter strength, shade in the appearance and close adhesion. The specifications of the container and the evaluated results were as shown in Table 1.

Example 2

(23) A multilayered container was produced in the same manner as in Example 1 but changing the content of the homo PP into 0.5% by weight and the content of the LLDPE into 84.5% by weight in the adhesive layers. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Example 3

(24) A multilayered container was produced in the same manner as in Example 1 but changing the content of the homo PP into 10% by weight and the content of the LLDPE into 75% by weight in the adhesive layers. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Example 4

(25) A multilayered container was produced in the same manner as in Example 1 but using a block-copolymerized PP as the PP resin in the adhesive layers. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Example 5

(26) A multilayered container was produced in the same manner as in Example 1 but using 98% by weight of the acid-modified LLDPE-B as the acid-modified PE in the adhesive layers and using no LLDPE. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Example 6

(27) A multilayered container was produced in the same manner as in Example 1 but using 98% by weight of the acid-modified LDPE-A as the acid-modified PE in the adhesive layers and using no LLDPE. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Example 7

(28) A multilayered container was produced in the same manner as in Example 1 but constituting the layers of the multilayered container as described below. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.
Outer layer 15.0% (67.5 m)/adhesive layer 3.0% (13.5 m)/gas-barrier layer 6.30% (28.4 m)/adhesive layer 3.0% (13.5 m)/inner layer 72.7% (327.2 m)

Comparative Example 1

(29) A multilayered container was produced in the same manner as in Example 1 but using 100% by weight of the acid-modified LLDPE-B as the acid-modified PE in the adhesive layers and using neither the PP resin nor the LLDPE. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Comparative Example 2

(30) A multilayered container was produced in the same manner as in Example 1 but changing the content of the homo PP into 0.3% by weight and the content of the LLDPE into 84.7% by weight in the adhesive layers. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

Comparative Example 3

(31) A multilayered container was produced in the same manner as in Example 1 but changing the content of the homo PP into 15% by weight and the content of the LLDPE into 70% by weight in the adhesive layers. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.

(32) <Control Example>

(33) A multilayered container was produced in the same manner as in Example 1 but selecting the weight of the multilayered container to be 12.8 g, constituting the layers of the multilayered container as described below, using 100% by weight of the acid-modified LDPE-A in the adhesive layers and using neither the PP resin nor the LLDPE. The thus produced container was evaluated in the same manner as in Example 1. The specifications of the container and the evaluated results were as shown in Table 1.
Outer layer 15.0% (73.5 m)/adhesive layer 0.65% (3.2 m)/gas-barrier layer 6.30% (30.9 m)/adhesive layer 0.65% (3.2 m)/inner layer 77.4% (379.3 m)

(34) TABLE-US-00001 TABLE 1 Weight .Math. layer constitution Adhesive layers (note) PP resin (%) Acid-modified PE (%) LLDPE (%) Ex. 1 layer 1 homoPP (2) acid-modified LLDPE-A(15) LLDPE(83) 2 layer 1 homoPP (0.5) LLDPE(84.5) 3 layer 1 homoPP (10) LLDPE(75) 4 layer 1 copolymerizedPP (2) LLDPE(83) 5 layer 1 homoPP (2) acid-modified LLDPE-B(98) none 6 layer 1 homoPP (2) acid-modified LDPE-A(98) none 7 layer 2 homoPP (2) acid-modified LLDPE-A(15) LLDPE(83) Comp. layer 1 none acid-modified LLDPE-B(100) none Ex. 1 2 layer 1 homoPP (0.3) acid-modified LLDPE-A(15) LLDPE(84.7) 3 layer 1 homoPP (15) acid-modified LLDPE-A(15) LLDPE(70) Control layer 3 none acid-modified LDPE-A(100) none Ex. (Note) {circle around (1)} Layer 1 (weight 11.8 g, outer layer LDPE 15.0%, adhesive layer 1.0%, gas-barrier layer 6.30%, adhesive layer 1.0%, inner layer LDPE 76.7%). {circle around (2)} Layer 2 (weight 11.8 g, outer layer LDPE 15.0%, adhesive layer 3.0%, gas-barrier layer 6.30%, adhesive layer 3.0%, inner layer LDPE 72.7%). {circle around (3)} Layer 3 (weight 12.8 g, outer layer LDPE 15.0%, adhesive layer 0.65%, gas-barrier layer 6.30%, adhesive layer 0.65%, inner layer LDPE 77.4%) large weight. Evaluation Tensile Buckling modulus of Shatter Shade in Close Overall Strength elasticity strength appearance adhesion evaluation Ex. 1 2 3 4 5 6 7 Comp. X X X Ex. 1 2 X X X 3 X X Control Ex.