MULTILAYERED CONTAINER

Abstract

A multilayered container having an intermediate layer that contains a resin composition B obtained by blending a resin composition A that contains at least a resin (a) having a hydroxyl group with a carboxyl compound (b) of which the -carbon is quaternary and of which the carboxyl group is forming no metal salt, wherein a ratio (COOH/OH) of the amount of the carboxyl groups of the carboxyl compound (b) to the amount of the hydroxyl groups of the resin (a) in the resin composition A is not more than 0.4 The multilayered container maintains excellent anti-eluting property and flavor-retaining property even when it is subjected to the retort sterilization.

Claims

1. A multilayered container having an intermediate layer that contains a resin composition B obtained by blending a resin composition A that contains at least a resin (a) having a hydroxyl group with a carboxyl compound (b) of which the -carbon is quaternary and of which the carboxyl group is forming no metal salt, wherein a ratio (COOH/OH) of the amount of the carboxyl groups of the carboxyl compound (b) to the amount of the hydroxyl groups of the resin (a) in the resin composition A is not more than 0.4.

2. The multilayered container according to claim 1, wherein said carboxyl compound (b) is an ethylene-methacrylic acid copolymer.

3. The multilayered container according to claim 1, wherein the resin (a) is an ethylene-vinyl alcohol copolymer.

4. The multilayered container according to claim 1, wherein said resin composition A, further, contains an olefin resin.

5. The multilayered container according to claim 1, wherein the ratio (COOH/OH) of the amount of the carboxyl groups of said carboxyl compound (b) to the amount of the hydroxyl groups of the resin (a) in said resin composition A is 0.04 to 0.4.

6. The multilayered container according to claim 1, wherein said resin composition A, further, contains an oxidizing organic component and a transition metal compound, and a ratio (COOH/OH) of the amount of the carboxyl groups of said carboxyl compound (b) to the amount of the hydroxyl groups of the resin (a) in said resin composition A is not more than 0.04.

7. The multilayered container according to claim 1, wherein the total amount of the organic carbon eluted out after the retort sterilization is less than 3.0 ppm.

8. The multilayered container according to claim 1, wherein the amount of the acetaldehyde eluted out after the retort sterilization is less than 40 ppb.

9. The multilayered container according to claim 3, wherein a decomposition start temperature of the ethylene-vinyl alcohol copolymer in said resin composition B is 20 C. or more higher than a decomposition start temperature of the ethylene-vinyl alcohol copolymer in said resin composition A.

10. The multilayered container according to claim 1, wherein the multilayered container includes inner and outer layers comprising an olefin resin and an intermediate barrier layer comprising a barrier resin, and the intermediate layers that contain said resin composition B are interposed between any adjacent layers selected from the inner layer, the outer layer and the intermediate barrier layer.

11. The multilayered container according to claim 10, wherein said intermediate barrier layer has a multilayered structure comprising a barrier layer/an oxygen-absorbing layer/a barrier layer.

12. The multilayered container according to claim 10, wherein the layer constitution comprises a polypropylene inner layer/a regrind resin layer/an adhesive layer/a barrier layer/an oxygen-absorbing layer/a barrier layer/an adhesive layer/a regrind resin layer/a polypropylene outer layer in this order from the inner side, and said regrind resin layer contains said resin composition B.

13. The multilayered container according to claim 10, wherein a deodorizing component is contained in any layer that is positioned on the inner side of said oxygen-absorbing layer.

14. The multilayered container according to claim 13, wherein the layer constitution comprises a polypropylene inner layer/a deodorizing component-containing layer/as required, a regrind resin layer/an adhesive layer/a barrier layer/an oxygen-absorbing layer/a barrier layer/an adhesive layer/a regrind resin layer/a polypropylene outer layer in this order from the inner side, and said regrind resin layer contains said resin composition B.

Description

EXAMPLES

[0087] The present invention will be further described by way of the following Examples and Comparative Examples to which only, however, the invention is in no way limited.

[0088] In Examples and Comparative Examples, various kinds of measurements were taken by the methods described below.

(1) Decomposition start temperature;

[0089] The decomposition start temperature was measured by using a thermal analyzer (TG/DTA7220 manufactured by Hitachi High Technologies Co.). Measurement was performed in a nitrogen stream by placing a measuring sample of about 2 to about 10 mg on an aluminum pan, and elevating the temperature to 40 to 550 C. at a rate of 20 C. per minute. The decomposition start temperature was found from a point where an extrapolation line of the TG curve in a steady state of before the decomposition takes place intersects an extrapolation line of a temperature at which a differential weight loss on heating (DTG) becomes a maximum in the initial weight loss observed near 200 to 400 C. on a curve of weight loss on heating (TG curve). A value found at the intersecting point was defined as the decomposition start temperature.

[0090] When the decomposition start temperature of the ethylene-vinyl alcohol copolymer (hereinafter EVOH) in the resin composition B was higher than the decomposition start temperature of the EVOH in the resin composition A by 20 C. or more, the decomposition start temperature was evaluated to be (good). The decomposition start temperature was evaluated to be (poor) if it was higher by less than 20 C.

(2) Total amount of elution of the organic carbon (TOC);

[0091] The total amount of the organic carbon eluted out was measured by using an instrument for measuring the total amount of elution of organic carbon (TOC-5000A manufactured by Shimadzu Corporation). When the TOC was not less than 1 ppm, there was a tendency that taste due to the eluted matter was perceived. Specifically, when the TOC was not less than 3 ppm, there was a tendency that taste was perceived strongly.

(3) Amount of elution of acetaldehyde (AA);

[0092] 1.0 Milliliter of sample water was picked up from the container, and 0.2 ml of a 2,4-dinitrophenyl hydrazinephosphoric acid solution of a concentration of 0.1% was added thereto. After 30 minutes, the solution was filtered through a 0.45-m membrane filter, and the filtrate was measured by using a high-speed liquid chromatography (Agilent 1200 Infinity manufactured by Agilent Technologies). A threshold value of taste of the acetaldehyde in water was less than 40 ppb.

(4) Evaluating the flavor-retaining property (sensory evaluation);

[0093] The sample water in the container after the retort treatment was evaluated for its flavor by three panelists. Water was evaluated to be (very good) when it had almost no taste, evaluated to be (good) when it had a slight degree of taste, evaluated to be (fair) when it had a taste, and (bad) when it had a strong taste.

Example 1

[0094] Pellets of polypropylene (hereinafter PP) (MFR 0.5 g/10 min, 230 C., load 2160 g), EVOH (ethylene content of 27 mol %, MFR 4.0 g/10 min, 210 C., load 2160 g) and adhesive resin (hereinafter AD) (MFR 5.7 g/10 min, 230 C., load 2160 g) were mixed together such that their weight ratio was PP/EVOH/AD=93/5/2. To 100 parts by weight of the above mixed pellets, there were added and mixed 3 parts by weight of a compatibilizing agent (GF31 produced by Kuraray Co. Ltd.) and 5 parts by weight of an ethylene-unsaturated carboxylic acid copolymer (hereinafter EMAA) (carboxylic acid content 3.1 mol %, MFR 8.0 g/10 min, 190 C., load 2160 g) . The mixture thereof was melt-kneaded by using a single axis extruder at a forming temperature of 250 C. to prepare pellets of the resin composition B.

[0095] Next, by using a multilayered film-forming machine, there was prepared a film comprising three layers of PP inner layer/resin composition B layer/PP outer layer. The PP used here possessed an MFR of 0.5 g/10 min (230 C., load 2160 g) , and the respective layers possessed thicknesses of 20/100/20 (m). The film was cut into a piece having a long side of 270 mm and a short side of 190 mm. A set of two pieces thereof was heat-sealed at the ends over a width of 1 cm to form a pouch. The thus prepared pouch was filled with 100 mL of ultrapure water of normal temperature, subjected to the retort treatment under the sterilizing conditions of 121 C. for 30 minutes, and water in the container after the retort treatment was evaluated for the elution of components. Table 1 shows the decomposition start temperature, total amount of the organic carbon eluted out, amount of the acetaldehyde eluted out and the results of the sensory evaluation.

Example 2

[0096] A resin composition B and a pouch thereof were prepared in the same manner as in Example 1 but adding 0.42 parts by weight of cobalt stearate (hereinafter StCo) (400 ppm calculated as cobalt) in addition to 3 parts by weight of the compatibilizing agent and 5 parts by weight of the EMAA that have been added per 100 parts by weight of the mixed pellets of PP/EVOH/AD.

[0097] Table 1 shows the results of evaluation.

Example 3

[0098] A resin composition B and a pouch thereof were prepared in the same manner as in Example 2 but using the EMAA containing 4.3 mol of acid (MFR 7.0 g/10 min, 190 C., load 2160 g). Table 1 shows the results of evaluation.

Example 4

[0099] A resin composition B and a pouch thereof were prepared in the same manner as in Example 2 but filling the pouch with ultrapure water of 80 C. and without conducting the retort treatment. Table 1 shows the results of evaluation.

Example 5

[0100] By using a machine for forming a multilayered sheet by co-extrusion, there was prepared a multilayered sheet of a constitution of PP inner layer/resin composition B layer/AD layer/EVOH layer/AD layer/PP outer layer. The resins used for the layers were the same as those of Example 1. The resin composition B used here was the one prepared by adding and mixing together the pellets of PP/EVOH/AD at a ratio of 95.8/3/1.2 and, further, adding and mixing 3 parts by weight of the compatibilizing agent (GF31 produced by Kuraray Co. Ltd.) and 3 parts by weight of the EMAA (carboxylic acid content of 3.1 mol %) per 100 parts by weight of the above mixed pellets. The forming temperatures were 190 to 230 C. for the PP layer, 180 to 200 C. for the resin composition B layer, 200 to 220 C. for the adhesive resin layer, and 180 to 200 C. for the EVOH layer. The obtained sheet possessed a thickness of 1.2 mm, the thicknesses of the layers being PP inner layer/resin composition B layer/AD layer/EVOH layer/AD layer/PP outer layer =110/450/45/90/45/450 (m).

[0101] Next, by using a compressed air/vacuum forming machine, a cup was formed from the above sheet. By using a heater, the surface of the sheet was heated to 185 C., and the cup was formed by the plug assist compressed air/vacuum forming.

[0102] The thus obtained cup was filled with 85 mL of ultrapure water of normal temperature, and was subjected to the retort treatment under the sterilizing conditions of 121 C. for 30 minutes. Table 1 shows the results of evaluation.

Example 6

[0103] A multilayered sheet and a cup thereof were formed and the elution was evaluated in the same manner as in Example 5 but using a sheet of a layer constitution of PP inner layer/resin composition B layer/AD layer/EVOH layer/oxygen absorber (hereinafter Sc) layer/EVOH layer/AD layer/PP outer layer, and using a resin composition B obtained by adding and mixing together the pellets of PP/EVOH/Sc/AD at a ratio of 93.4/3.6/1.8/1.2 and, further, adding and mixing 3 parts by weight of the compatibilizing agent and 5.4 parts by weight of the EMAA per 100 parts by weight of the above mixed pellets. The Sc used here was the one comprising chiefly EVOH and containing an oxidizing organic component and a transition metal catalyst, and was formed at a temperature of 180 to 200 C. The obtained sheet possessed a thickness of 1.2 mm, the thicknesses of the layers being PP inner layer/resin composition B layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/PP outer layer=110/380/45/60/60/60/45/440 (m).

[0104] The thus obtained cup was filled with 85 mL of ultrapure water of normal temperature, and was subjected to the retort treatment under the sterilizing conditions of 121 C. for 30 minutes. Table 1 shows the results of evaluation.

Example 7

[0105] By using the machine for forming a multilayered sheet by co-extrusion, there was prepared a multilayered sheet of a constitution of PP inner layer/resin composition B layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/PP outer layer. The resins used for the layers were the same as those of Example 1. The resin composition B used here was prepared by mixing the pellets of PP/EVOH/Sc/AD at a weight ratio of 78/12/6/4 and kneading them and forming them into pellets thereof by using a biaxial extruder. The pellets were then mixed with the PP at a weight ratio of 30/70, and to which the EMAA (carboxylic acid content of 3.1 mol %) was added in an amount of 3 parts by weight per 100 parts by weight of the mixture thereof.

[0106] The obtained sheet possessed a thickness of 1.2 mm, the thicknesses of the layers being PP inner layer/resin composition B layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/PP outer layer=150/360/20/65/60/75/30/440 (m).

[0107] Next, a cup was formed from the above sheet by the plug assist compressed air/vacuum forming by using the compressed air/vacuum forming machine. The obtained cup possessed a mouth diameter of 76 mm and a volume of 110 mL. Table 1 shows the results of evaluation.

Example 8

[0108] A multilayered sheet and a cup thereof were formed in the same manner as in Example 7 but changing the amount of the EMAA in the resin composition B to 5 parts by weight, and the elution was evaluated (COOH/OH=0.04). Table 1 shows the results of evaluation.

Example 9

[0109] By using the machine for forming a multilayered sheet by co-extrusion, there was prepared a multilayered sheet of a constitution of PP inner layer/deodorizing component-containing (OE) layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/PP outer layer. The resins used for the layers were the same as those of Example 8. The OE layer was the one comprising chiefly the polypropylene and containing a synthetic zeolite. The thicknesses of the layers were PP inner layer/OE layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/PP outer layer=360/140/20/70/65/60/25/460 (82 m).

[0110] Next, the multilayered sheet that was pulverized and recovered and the PP were mixed together at a weight ratio of 50/50. To 100 parts by weight of the mixture thereof, the EMAA (carboxylic acid content of 3.1 mol %) was added in an amount of 3 parts by weight to prepare a resin composition B, and from which a sheet was formed (COOH/OH=0.01). The obtained sheet was a multilayered sheet of a layer constitution of PP inner layer/OE layer/AD layer/EVOH layer/Sc layer/EVOH layer/AD layer/resin composition B layer/PP outer layer. The thicknesses of the layers were, from the inner layer, 360/140/20/70/65/60/25/350/110 (m).

[0111] Next, a cup was formed by the plug assist compressed air/vacuum forming by using the compressed air/vacuum forming machine. Table 1 shows the results of evaluation.

Example 10

[0112] A multilayered sheet and a cup thereof were formed in the same manner as in Example 9 but changing the amount of the EMAA in the resin composition B to 5 parts by weight, and the elution was evaluated (COOH/OH=0.02). Table 1 shows the results of evaluation.

Comparative Example 1

[0113] A resin composition A and a pouch thereof were prepared in the same manner as in Example 1 but without adding the EMAA. Table 1 shows the results of evaluation.

Comparative Example 2

[0114] A resin composition A and a pouch thereof were prepared in the same manner as in Example 2 but without adding the EMAA. Table 1 shows the results of evaluation.

Comparative Example 3

[0115] A resin composition A and a pouch thereof were prepared in the same manner as in Example 2 but using a maleic anhydride-modified polypropylene (hereinafter MAR) (maleic anhydride content of 0.26 mol %, MFR 9.1 g/10 min, 230 C., load 2160 g) instead of the EMAA. Table 1 shows the results of evaluation.

Comparative Example 4

[0116] A resin composition B and a pouch thereof were prepared in the same manner as in Example 2 but adding the EMAA in an amount of 50 parts by weight. Despite the EMAA was added in an amount of 50 parts by weight, the formability was favorable. Table 1 shows the results of evaluation.

[0117] (Comparative Example 5)

[0118] A resin composition A and a pouch thereof were prepared in the same manner as in Comparative Example 2 but filling the pouch with ultrapure water of 80 C. without conducting the retort treatment. Table 1 shows the results of evaluation.

Comparative Example 6

[0119] A resin composition A and a pouch thereof were prepared in the same manner as in Comparative Example 2 but adding the StCo in an amount of 0.24 parts by weight. Table 1 shows the results of evaluation.

Comparative Example 7

[0120] A resin composition A and a pouch thereof were prepared in the same manner as in Comparative Example 6 but adding the calcium stearate (StCa) instead of the StCo. Table 1 shows the results of evaluation.

Comparative Example 8

[0121] A multilayered sheet and a cup thereof were prepared in the same manner as in Example 5 but without adding the EMAA. Table 1 shows the results of evaluation.

Comparative Example 9

[0122] A multilayered sheet and a cup thereof were prepared in the same manner as in Example 6 but without adding the EMAA. Table 1 shows the results of evaluation.

Comparative Example 10

[0123] A multilayered sheet and a cup thereof were prepared in the same manner as in Example 7 but without adding the EMAA. Table 1 shows the results of evaluation.

Comparative Example 11

[0124] A multilayered sheet and a cup thereof were prepared and the elution was evaluated (COOH+COOM/OH=0.04) in the same manner as in Example 7 but using an ethylene-methacrylic acid copolymer neutralized with a metal (carboxylic acid content of 5.4 mol %, degree of neutralization with Na of 50%, MFR 0.9g/10 min (190 C., load 2160 g)) instead of using the EMAA. Table 1 shows the results of evaluation.

Comparative Example 12

[0125] A multilayered sheet and a cup thereof were prepared and the elution was evaluated (COOH+COOM/OH =0.02) in the same manner as in Comparative Example 11 but using the ethylene-methacrylic acid copolymer neutralized with the metal in an amount of 1.5 parts by weight. Table 1 shows the results of evaluation.

Comparative Example 13

[0126] A multilayered sheet and a cup thereof were prepared and the elution was evaluated in the same manner as in Example 7 but using the compatibilizing agent (GF31 produced by Kuraray Co. Ltd.) in an amount of 3 parts by weight instead of using the EMAA. Table 1 shows the results of evaluation.

TABLE-US-00001 TABLE 1 Composition of the reground resin PP EVOH Sc AD *1 StCo StCa EMAA MAH Metal No. wt % wt % wt % wt % phr phr phr phr *2 mol % phr salt Example 1 93 5 2 3 5 3.1 Example 2 93 5 2 3 0.42 5 3.1 Example 3 93 5 2 3 0.42 5 4.3 Example 4 93 5 2 3 0.42 5 3.1 Example 5 95.8 3 1.2 3 3 3.1 Example 6 93.4 3.6 1.8 1.2 3 5.4 3.1 Example 7 93.4 3.6 1.8 1.2 3 3.1 Example 8 93.4 3.6 1.8 1.2 5 3.1 Example 9 89 6 3 2 3 3.1 Example 10 89 6 3 2 5 3.1 Comp. Ex. 1 93 5 2 3 Comp. Ex. 2 93 5 2 3 0.42 Comp. Ex. 3 93 5 2 3 0.42 5 Comp. Ex. 4 93 5 2 3 0.42 50 3.1 Comp. Ex. 5 93 5 2 3 0.42 Comp. Ex. 6 93 5 2 3 0.24 Comp. Ex. 7 93 5 2 3 0.24 Comp. Ex. 8 95.8 3 1.2 3 Comp. Ex. 9 93.4 3.6 1.8 1.2 3 Comp. Ex. 10 93.4 3.6 1.8 1.2 Comp. Ex. 11 93.4 3.6 1.8 1.2 3 5.4 Na Comp. Ex. 12 93.4 3.6 1.8 1.2 1.5 5.4 Na Comp. Ex. 13 89 6 3 2 3 Results Decomposition start Mol ratio of temperature COOH to OH Shape of Filling Difference from TOC AA Sensory No. COOH/OH container condition C. the reference ppm ppb evaluation Example 1 0.04 pouch retort 377 89 0.6 N.D. Example 2 0.04 pouch retort 348 72 0.9 N.D. Example 3 0.06 pouch retort 357 81 0.8 N.D. Example 4 0.04 pouch hot pack 348 72 0.2 N.D. Example 5 0.04 cup retort 364 70 0.7 18 Example 6 0.04 cup retort 382 80 0.9 30 Example 7 0.02 cup retort 372 45 0.5 32 Example 8 0.04 cup retort 384 57 0.7 28 Example 9 0.01 cup retort 396 69 0.4 30 Example 10 0.02 cup retort 394 67 0.4 29 Comp. Ex. 1 pouch retort 288 0 2.0 58 X Comp. Ex. 2 pouch retort 276 0 9.7 163 X Comp. Ex. 3 0.01 pouch retort 284 8 5.2 38 X Comp. Ex. 4 0.43 pouch retort 373 97 2.5 32 X Comp. Ex. 5 pouch hot pack 276 0 0.5 8 Comp. Ex. 6 pouch retort 280 0 8.2 368 X Comp. Ex. 7 pouch retort 292 0 2.5 188 X Comp. Ex. 8 cup retort 294 0 0.9 73 X Comp. Ex. 9 cup retort 302 0 1.0 75 X Comp. Ex. 10 cup retort 327 0 2.0 136 X Comp. Ex. 11 0.04 cup retort 375 48 0.5 33 Comp. Ex. 12 0.02 cup retort 360 33 0.6 50 X Comp. Ex. 13 cup retort 295 32 0.5 64 X *1: Compatibilizer, *2: Acid content

Consideration

[0127] The anti-eluting property is a factor that affects the flavor-retaining property. That is, if the anti-eluting property is poor, components may elute out much and the flavor-retaining property may become poor. If the anti-eluting property is excellent, components may elute out little and the flavor-retaining property may become excellent. However, there is no perfect correlation between the amounts of components eluted out and the flavor-retaining property. A sensory evaluation by actual tasting is suitable for evaluating flavor-retaining property of the content.

[0128] In Comparative Examples 1 to 3, 5 to 10 and 13 in which no EMAA is contained in the resin composition A layer, the decomposition starts at low temperatures close to a region of forming temperatures (near 250 C.). It is, therefore, considered that low-molecular components were much generated and eluted out. In Comparative Example 4, the decomposition start temperature is high but the EMAA having a melting point of about 100 C. is much contained. It is, therefore, considered that the resin composition B was plasticized during the retort treatment, and a decomposition product formed in small amounts has diffused easily and eluted out. In Comparative Examples 11 and 12 in which the ethylene-methacrylic acid copolymer neutralized with a metal is added, the elution of components is suppressed but part of the ethylene-methacrylic acid copolymer that is used forms a metal salt. It is, therefore, considered that the interaction with the transition metal catalyst was weaker than that of the ethylene-methacrylic acid copolymer (EMAA) that was forming no metal salt. Accordingly, the action of accelerating the deterioration was not suppressed despite of using the transition metal catalyst, and the results of sensory evaluation became poor.

INDUSTRIAL APPLICABILITY

[0129] In the present invention, the EVOH copolymer is effectively suppressed from being thermally decomposed even when the multilayered container uses the scrap resin that contains the EVOH copolymer and the like or even when the multilayered container, further, uses oxidizing organic components and transition metal catalysts. Even when subjected to the retort sterilization, therefore, it is made possible to prevent a decrease in the anti-eluting property and flavor-retaining property. The multilayered containers can, therefore, be favorably used in such fields where economy and retention of taste and flavor are required. By utilizing such properties, the multilayered container can be effectively used for storing beverages such as beer, wine, fruit juice, and carbonated soft drinks,, as well as fruits, nuts, vegetables, meat products, infant foods, coffee, jam, mayonnaise, ketchup, edible oil, dressing, sauces, tsukudani (food boiled down in soy sauce) , dairy products, processed fish products, pet food and the like. By providing an oxygen-barrier layer, further, the multilayered container can be very favorably used for containing a variety of contents such as medicines, cosmetics, gasoline, etc. that may be deteriorated in the presence of oxygen.