RESIN ARTICLE HAVING EXCELLENT DISCOLORATION RESISTANCE

Abstract

An article represented by a container that is formed of a thermoplastic resin blended with a metal or a metal compound that can react with a corrosive gas or a volatile sulfur compound and give a color. The thermoplastic resin includes at least one metal selected from three metals of Zn, Sn and Mn or one metal compound thereof, and a metal or a metal compound that is not any of these three metals and that can react with the corrosive gas or the volatile sulfur compound and give a color. The metal selected from the three metals or the metal compound functions as a scavenger for the corrosive gas or the volatile sulfur compound.

Claims

1. An article formed of a thermoplastic resin including at least one metal selected from three metals of Zn, Sn and Mn or one metal compound of any of the three metals, and a metal or a metal compound other than the three metals and capable of reacting with a corrosive gas or a volatile sulfur compound so as to give a color, the metal selected from the three metals or the metal compound functions as a scavenger for the corrosive gas or the volatile sulfur compound.

2. The article according to claim 1, wherein the metal other than the three metals is derived from Co and/or Fe.

3. The article according to claim 1, wherein the corrosive gas is hydrogen sulfide.

4. The article according to claim 1, wherein the metal selected from the three metals or the metal compound is derived from zinc oxide or zinc stearate.

5. The article according to claim 1, wherein the article has a multilayer structure including a layer that contains the metal selected from the three metals or the metal compound and another layer that contains the metal or the metal compound other than the three metals.

6. The article according to claim 5, wherein the metal selected from the three metals or the metal compound is contained in a layer arranged inside the layer containing the metal or the metal compound other than the three metals.

7. The article according to claim 5, wherein the multilayer structure includes at least an inner layer, an intermediate layer, an oxygen-absorbing layer and an outer layer, the metal selected from the three metals or the metal compound is contained in the intermediate layer, and the metal or the metal compound other than the three metals includes a transition metal or a transition metal compound contained in the oxygen-absorbing layer.

8. The article according to claim 7, wherein the metal or the metal compound selected from the three metals in an amount of 0.1 to 5.0 wt % is contained in the article.

9. The article according to claim 7, wherein the article having the multilayer structure is a cup-shape container having a body with a haze of not more than 70%.

10. The article according to claim 9, which is a container to be filled with a content containing an amino acid including elemental sulfur.

Description

EXAMPLES

[Evaluation Method]

[0072] In the evaluation, Sample A is a multilayer container filled with water as a content that cannot cause blackening of the container at the time of the heat treatment. Sample B is a multilayer container filled with 0.5 wt % cysteine aqueous solution as a content that can cause blackening of the container at the time of the heat treatment. The Samples A and B for each Example were subjected to retort sterilization under the conditions of 115 C. for 60 minutes, then evaluated as described below.

[Discoloration Evaluation]

[0073] After discharging the contents from Samples A and B, the surfaces of the bodies of these Samples were cut out to obtain sample pieces. *L*a*b of these sample pieces were measured with a chroma meter (CR-400 manufactured by Konica Minolta Inc.), and *E was calculated from the following Equation (1).

*E={(*L.sub.B*L.sub.A).sup.2+(*a.sub.B*a.sub.A).sup.2+(*b.sub.B*b.sub.A).sup.2}.sup.0.5(1)

[0074] (*L.sub.A*a.sub.A*b.sub.A is the *L*a*b measured value of Sample A, and *L.sub.B*a.sub.B*b.sub.B is the *L*a*b measured value of Sample B)

[Transparency Evaluation]

[0075] A sample piece was obtained by cutting out the body surface of the Sample B after discharging the content. Liquid paraffin was applied on the sample piece, and the internal haze was measured with SM color computer (MODEL SM-4 manufactured by Suga Test Instruments Co., Ltd.)

Example 1

[0076] A multilayer sheet including eight layers of five kinds was produced from a polypropylene resin having 0.5 g/10 min of MFR, an adhesive resin, an ethylene vinyl alcohol copolymer resin (hereinafter EVOH), a pellet of an oxygen-absorbing barrier resin composition, a pellet of zinc-containing resin composition pellet.

[0077] A pellet of an oxygen-absorbing barrier resin composition was prepared from, EVOH, cobalt neodecanoate, and maleic acid-modified polybutadiene, where the content of the cobalt neodecanoate was 0.23 parts by weight and the content of the maleic acid-modified polybutadiene was 5.00 parts by weight with respect to 94.77 parts by weight of the EVOH. A pellet of zinc-containing resin composition was prepared by adding 5 parts by weight of zinc stearate to 95 parts by weight of polypropylene resin having 0.5 g/10 min of MFR (zinc compound concentration: 5 wt %).

[0078] The layer constitution and the weight rate when viewed from the outside were as follows.

[0079] polypropylene layer (39 wt %)

[0080] adhesive resin layer (2 wt %)

[0081] EVOH layer (6 wt %)

[0082] oxygen-absorbing barrier resin composition layer (6 wt %)

[0083] EVOH layer (6 wt %)

[0084] adhesive resin layer (2 wt %)

[0085] zinc-containing resin composition layer (10 wt %)

[0086] polypropylene layer (29 wt %)

The total thickness was 1200 m.

[0087] Here, the concentration of the zinc compound in the zinc-containing resin composition layer (hereinafter, in-layer zinc compound concentration) was 5 wt %, the concentration of the zinc compound in the multilayer sheet (hereinafter, total zinc compound concentration) was 0.5 wt %, or 0.052 wt % in terms of metal (zinc).

[0088] The multilayer sheet was shaped as a cup by use of plug-assist vacuum pressure forming machine, thereby producing multilayer containers. The multilayer containers were subjected to retort treatment with reference to the evaluation method, thereby producing Samples A and B to conduct evaluations on the discoloration and transparency. The evaluation results are shown in Table 1.

Example 2

[0089] A multilayer sheet, a multilayer container, Sample A and Sample B were produced and subjected to a discoloration evaluation and a transparency evaluation in the same manner as in Example 1, except that the zinc-containing resin composition layer was formed of the zinc-containing resin composition pellet (zinc compound concentration: 5 wt %) and a polypropylene resin having 0.5 g/10 min of MFR, and the in-layer zinc compound concentration and the total zinc compound concentration were determined as 1 wt % and 0.1 wt %, respectively. The evaluation results are shown in Table 1.

Example 3

[0090] A multilayer sheet, a multilayer container, Sample A and Sample B were produced and subjected to a discoloration evaluation and a transparency evaluation in the same manner as in Example 1, except that the weight rate of the zinc-containing resin composition layer was set to 20 wt %, the weight rate of the polypropylene layer at the inner layer side was set to 19 wt %, the zinc-containing resin composition layer was composed of the zinc-containing resin composition pellet (zinc compound concentration: 5 wt %) and a polypropylene resin containing 0.5 g/10 min of MFR, the in-layer zinc compound concentration was set to 2 wt %, and the total zinc compound concentration was set to 0.4 wt %. The evaluation results are shown in Table 1.

Example 4

[0091] The layer constitution and the weight rates when viewed from the outside were as follows.

[0092] polypropylene layer (15 wt %)

[0093] regrind layer (23 wt %)

[0094] adhesive resin layer (2 wt %)

[0095] EVOH layer (6 wt %)

[0096] oxygen-absorbing barrier resin composition layer (6 wt %)

[0097] EVOH layer (6 wt %)

[0098] adhesive resin layer (2 wt %)

[0099] zinc-containing resin composition layer (10 wt %)

[0100] adsorbent layer (10 wt %)

[0101] polypropylene layer (20 wt %)

The adsorbent layer included Na type ZSM5 Zeolite as adsorbent and a polypropylene resin comprising 0.5 g/10 min of MFR as base resin so that the adsorbent concentration in the layer would be 2 wt %. The zinc-containing resin composition layer was formed of the zinc-containing resin composition pellet and polypropylene resin comprising 0.5 g/10 min of MFR so that the in-layer zinc compound concentration would be 2 wt % and the total zinc compound concentration would be 0.2 wt %. The evaluation results are shown in Table 1.

Example 5

[0102] A multilayer sheet, a multilayer container, Sample A and Sample B were produced and subjected to a discoloration evaluation and a transparency evaluation in the same manner as in Example 1, except that the zinc-containing resin composition layer was replaced by a mixture layer of a zinc-containing resin composition and an adsorbent. The mixture layer was formed of the zinc-containing resin composition pellet (zinc compound concentration: 5 wt %) and Na type ZSM5 Zeolite as the adsorbent, and an adjacent layer was formed of a propylene resin comprising 0.5 g/10 min of MFR, where the concentration of the in-layer adsorbent was set to be 2 wt %, the in-layer zinc compound concentration was set to be 2 wt %, and the total zinc compound concentration was set to be 0.2 wt %. The evaluation results are shown in Table 1.

Example 6

[0103] A multilayer sheet, a multilayer container, Sample A and Sample B were produced and subjected to a discoloration evaluation and a transparency evaluation in the same manner as in Example 5, except that the zinc-containing resin composition pellet (zinc compound concentration: 5 wt %) contained zinc oxide in place of zinc stearate. The evaluation results are shown in Table 1.

Comparative Example 1

[0104] A multilayer sheet, a multilayer container, Sample A and Sample B were produced and subjected to a discoloration evaluation and a transparency evaluation in the same manner as in Example 4, except that the layer constitution and the weight rates of the multilayer sheet when viewed from the outside were as follows.

[0105] polypropylene layer (10 wt %)

[0106] regrind layer (29 wt %)

[0107] adhesive resin layer (2 wt %)

[0108] EVOH layer (6 wt %)

[0109] oxygen-absorbing barrier resin composition layer (6 wt %)

[0110] EVOH layer (6 wt %)

[0111] adhesive resin layer (2 wt %)

[0112] adsorbent layer (10 wt %)

[0113] polypropylene layer (29 wt %)

The evaluation results are shown in Table 1.

TABLE-US-00001 TABLE 1 Layer constitution Ex. 1 Polypro- Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Polypro- pylene resin layer absorbing layer resin layer containing pylene layer layer barrier resin layer resin compound composition layer layer 39.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 29.0 wt % Ex. 2 Polypro- Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Polypro- pylene resin layer absorbing layer resin layer containing pylene layer layer barrier resin layer resin compound composition layer layer 39.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 29.0 wt % Ex. 3 Polypro- Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Polypro- pylene resin layer absorbing layer resin layer containing pylene layer layer barrier resin layer resin compound composition layer layer 39.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 20.0 wt % 19.0 wt % Ex. 4 Polypro- Regrind Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Adsorbent Polypro- pylene layer resin layer absorbing layer resin containing layer pylene layer layer barrier layer resin layer resin compound composition layer layer 15.0 wt % 23.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 10.0 wt % 20.0 wt % Layer constitution Ex. 5 Polypro- Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Polypro- pylene resin layer absorbing layer resin adsorbent pylene layer layer barrier layer mixture layer resin layer composition layer 39.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 29.0 wt % Ex. 6 Polypro- Adhesive EVOH Oxygen- EVOH Adhesive Zinc- Polypro- pylene resin layer absorbing layer resin adsorbent pylene layer layer barrier layer mixture layer resin layer composition layer 39.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 29.0 wt % Com. Polypro- Regrind Adhesive EVOH Oxygen- EVOH Adhesive Adsorbent Polypro- Ex. 1 pylene layer resin layer absorbing layer resin layer pylene layer layer barrier layer layer resin composition layer 10.0 wt % 29.0 wt % 2.0 wt % 6.0 wt % 6.0 wt % 6.0 wt % 2.0 wt % 10.0 wt % 29.0 wt % In-layer zinc In-laminate zinc Discoloration Transparency compound compound Zinc compound evaluation evaluation concentration concentration type E Internal haze Ex. 1 5.0 wt % 0.5 wt % Zinc stearate 1.6 54.3 Ex. 2 1.0 wt % 0.1 wt % Zinc stearate 5.2 52 Ex. 3 2.0 wt % 0.4 wt % Zinc stearate 1.2 56.3 Ex. 4 2.0 wt % 0.2 wt % Zinc stearate 0.3 43.8 Ex. 5 5.0 wt % 0.5 wt % Zinc stearate 1.6 62.9 Ex. 6 5.0 wt % 0.5 wt % Zinc oxide 1.6 87 Com. 0.0 wt % 0.0 wt % 6.7 62.6 Ex. 1 *Ex.: Example Com. Ex.: Comparative Example Ex.: Example

[0114] Table 1 illustrates that the present invention serves to decrease blackening of a container even when the content in the container is a sample that can cause blackening of the container. In addition, transparency is also improved in some Examples.

INDUSTRIAL APPLICABILITY

[0115] The article of the present invention can be used preferably for a container to be filled with meat or seafood containing sulfur-containing amino acids that may generate a corrosive gas or a volatile sulfur compound after being subjected to retort sterilization or the like.