JPH0380628B2 - - Google Patents
Info
- Publication number
- JPH0380628B2 JPH0380628B2 JP17264286A JP17264286A JPH0380628B2 JP H0380628 B2 JPH0380628 B2 JP H0380628B2 JP 17264286 A JP17264286 A JP 17264286A JP 17264286 A JP17264286 A JP 17264286A JP H0380628 B2 JPH0380628 B2 JP H0380628B2
- Authority
- JP
- Japan
- Prior art keywords
- layer
- polypropylene
- vinyl acetate
- acetate copolymer
- gas barrier
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004743 Polypropylene Substances 0.000 claims description 33
- -1 polypropylene Polymers 0.000 claims description 33
- 229920001155 polypropylene Polymers 0.000 claims description 32
- 239000005038 ethylene vinyl acetate Substances 0.000 claims description 26
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 claims description 26
- 229920001903 high density polyethylene Polymers 0.000 claims description 22
- 239000004700 high-density polyethylene Substances 0.000 claims description 22
- 239000000203 mixture Substances 0.000 claims description 9
- 229920003023 plastic Polymers 0.000 claims description 2
- 239000004033 plastic Substances 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 48
- 230000004888 barrier function Effects 0.000 description 27
- 230000001954 sterilising effect Effects 0.000 description 27
- 238000004659 sterilization and disinfection Methods 0.000 description 27
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 25
- 229910001882 dioxygen Inorganic materials 0.000 description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 23
- 230000035699 permeability Effects 0.000 description 13
- 238000000034 method Methods 0.000 description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 11
- 230000007423 decrease Effects 0.000 description 11
- 239000001301 oxygen Substances 0.000 description 11
- 229910052760 oxygen Inorganic materials 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 7
- 239000012790 adhesive layer Substances 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 229920001577 copolymer Polymers 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 4
- 239000005977 Ethylene Substances 0.000 description 4
- 238000001802 infusion Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000002274 desiccant Substances 0.000 description 3
- 235000013305 food Nutrition 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- FPIPGXGPPPQFEQ-UHFFFAOYSA-N 13-cis retinol Natural products OCC=C(C)C=CC=C(C)C=CC1=C(C)CCCC1(C)C FPIPGXGPPPQFEQ-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- FPIPGXGPPPQFEQ-BOOMUCAASA-N Vitamin A Natural products OC/C=C(/C)\C=C\C=C(\C)/C=C/C1=C(C)CCCC1(C)C FPIPGXGPPPQFEQ-BOOMUCAASA-N 0.000 description 2
- 239000004840 adhesive resin Substances 0.000 description 2
- 229920006223 adhesive resin Polymers 0.000 description 2
- FPIPGXGPPPQFEQ-OVSJKPMPSA-N all-trans-retinol Chemical compound OC\C=C(/C)\C=C\C=C(/C)\C=C\C1=C(C)CCCC1(C)C FPIPGXGPPPQFEQ-OVSJKPMPSA-N 0.000 description 2
- 150000001413 amino acids Chemical class 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 229920005674 ethylene-propylene random copolymer Polymers 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 229920001911 maleic anhydride grafted polypropylene Polymers 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000005022 packaging material Substances 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 238000007127 saponification reaction Methods 0.000 description 2
- 235000019155 vitamin A Nutrition 0.000 description 2
- 239000011719 vitamin A Substances 0.000 description 2
- 229940045997 vitamin a Drugs 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000000071 blow moulding Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000000796 flavoring agent Substances 0.000 description 1
- 235000019634 flavors Nutrition 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000003205 fragrance Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 229920001600 hydrophobic polymer Polymers 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920005606 polypropylene copolymer Polymers 0.000 description 1
- 229920005629 polypropylene homopolymer Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000007666 vacuum forming Methods 0.000 description 1
Landscapes
- Wrappers (AREA)
- Laminated Bodies (AREA)
Description
＜産業上の利用分野＞
本発明は、レトルト殺菌可能で、高度な耐気体
透過性を有し、さらにはレトルト殺菌後も高度な
耐気体透過性を保持することが出来る、透明又は
半透明な多層容器に関するもので、食品又は医薬
品を長期間にわたつて保存し得る包装材料として
使用される。
＜従来の技術及びその問題点＞
エチレン−酢酸ビニル共重合体ケン化物は優れ
たガスバリヤー性、保香性、透明性により、多層
容器等の包装材料のガスバリヤー層として使用す
ることにより、包装された食品又は医薬品の酸素
等による劣化を防ぎ、長期保存が可能となるた
め、多用されている。
しかしながら、エチレン−酢酸ビニル共重合体
は低湿度状態では優れた酸素ガスバリヤー性を示
すが、高湿度状態や含水率が高い場合には酸素ガ
スバリヤー性は大巾に低下する。その為、一般に
はポリエチレン、ポリプロピレン等の低透湿性の
疎水性高分子を両面に積層し使用される。
エチレン−酢酸ビニル共重合体ケン化物の酸素
ガスバリヤー性が優れている理由として、分子間
あるいは分子内水素結合が他の高分子に比べ強力
な点が挙げられる他に、分子鎖の対称性、極性な
どが相乗して寄与していることが挙げられる。こ
れに対し、エチレン−酢酸ビニル共重合体ケン化
物の含水率が高くなると、吸着された水分子はま
ず親水性のOH基に結合し、含水率の増加に伴つ
て吸着水は分子間の水素結合を破壊し、酸素分子
拡散の為に必要な分子運動を可能ならしめ、酸素
透過係数の増加をもたらすものと考えられてい
る。
この状態からさらに含水率が増大すれば、吸着
水の他に自由水が存在するようになつて、更に分
子間力は弱まり、分子運動に対する可塑化効果に
より、酸素透過係数は益々大きくなると考えられ
ている。
このようなエチレン−酢酸ビニル共重合体ケン
化物を透明なレトルト殺菌用多層容器として使用
する場合、レトルト殺菌における120℃程度の熱
水又は蒸気に対する耐熱性の点から、エチレン−
酢酸ビニル共重合体ケン化物の両側にポリプロピ
レンを積層するのが一般的である。
しかしながら、レトルト殺菌時の過熱加圧状態
では、ポリプロピレンの透湿度は常温時に比べ15
〜20倍増大する為、エチレン−酢酸ビニル共重合
体ケン化物層の含水率は急激に増加し、それとと
もに酸素ガスバリヤー性は大巾に低下する。
この様なレトルト殺菌により、酸素ガスバリヤ
ー性が大巾に低下した多層容器は、レトルト殺菌
後の保存により、序々にエチレン−酢酸ビニル共
重合体ケン化物層の水分が外部に放出されること
により、酸素ガスバリヤー性は回復するものの、
長期間を要し、その用途は比較的劣化に対する許
容酸素量の大きい内容物や、保存期間の短いもの
に限定されている。
これらの問題点の改良するために、主に３つの
方法が検討されており、その１はエチレン−酢酸
ビニル共重合体ケン化物自体に耐熱水性を付与す
る方法であり、その２は、エチレン−酢酸ビニル
共重合体が吸収した水の放出速度を早め、酸素ガ
スバリヤー性の回復を早める方法であり、その３
は、水の浸入を防ぐ保護層をエチレン−酢酸ビニ
ル共重合体層の両側に設け、酸素ガスバリヤー性
の低下を抑える方法である。
第１の方法については、エチレン−酢酸ビニル
共重合体ケン化物におけるエチレン含有率を増大
させることにより、耐水性、耐熱水性が向上する
が、それに伴つて本来の酸素ガスバリヤー性が大
巾に低下するため実用的ではない。また、第２の
方法としては、外層のポリプロピレン層の厚さを
内層のポリプロピレン層の厚さに比べ薄くするこ
とにより、レトルト殺菌後の保存時におけるエチ
レン−酢酸ビニル共重合体ケン化物が吸収した水
の外気への放出速度を早め、酸素ガスバリヤー性
の回復を早めるものである。しかし、この方法は
外層ポリプロピレンが薄いため、レトルト殺菌時
のエチレン−酢酸ビニル共重合体ケン化物層の吸
水量が多い。
その為、酸素ガスバリヤー性の低下度合が大き
く、その回復速度が速いとしても長期的に見て累
積透過酸素量が若干低減出来る程度であり、さら
に、レトルト殺菌後初期においては、逆に容器内
の酸素濃度が高くなるため、内容物によつては劣
化を助長する恐れがある。
第３の方法としては、特開昭57−170748公報に
より、エチレン−酢酸ビニル共重合体ケン化物層
の両側を乾燥剤を含む層で保護することにより、
レトルト殺菌時に浸入する水を補捉し、エチレン
−酢酸ビニル共重合体ケン化物層の含水率の増加
を低減化し、酸素ガスバリヤー性の低下を抑える
方法が提案されている。この方法では、レトルト
殺菌による酸素ガスバリヤー性の低下は抑えられ
るが、乾燥剤を含む（10〜20wt％）ことにより、
当然のことながら透明性は犠牲となり不透明な容
器となり、商品アピール効果が半減し、さらには
乾燥剤層を含む多層容器を製造することは装置的
にも技術的にも複雑となり、容器コストを押し上
げるという問題点があつた。
以上の通り、従来エチレン−酢酸ビニル共重合
体ケン化物を酸素ガスバリヤー層とするレトルト
殺菌可能な多層容器において、透明性を保持し、
かつレトルト殺菌による酸素ガスバリヤー性の低
下を防ぐことが出来、かつ従来と同様な加工方法
により安価に製造出来るものは得られておらず、
待望されていた。
＜問題点を解消するための手段＞
本発明は以上の事情に鑑み、種々検討の結果得
られたものである。
すなわち、本発明は少なくとも５層以上のプラ
スチツク多層容器において、外層及び内層がポリ
プロピレンと密度0.95ｇ／cm3以上の高密度ポリエ
チレンの混合物で、その混合比がポリプロピレ
ン／高密度ポリエチレン＝95／５〜60／40であ
り、中間層がエチレン−酢酸ビニル共重合体ケン
化物であり、さらにそれらを接着する層を含む透
明又は半透明なレトルト殺菌可能な多層容器であ
る。
すなわち、本発明は、外層及び内層としてポリ
プロピレンと高密度ポリエチレンの混合物を用い
ることにより、ポリプロピレン単体の場合に比
べ、レトルト殺菌による酸素ガスバリヤー性の低
下を大巾に抑えることが出来、かつ、高密度ポリ
エチレンの添加量が比較的少ない範囲において
も、顕著な効果があるため、内容物が目視出来る
程度の透明性を保持出来ることを見出したため提
案された。
以下本発明を図によつて詳細に説明する。
第１図は本発明による多層容器の断面を示す図
であり、外層及び内層がポリプロピレンと高密度
ポリエチレンの混合物１であり、中間層がエチレ
ン−酢酸ビニル共重合体ケン化物２、そしてそれ
らの接着層３より成る少なくとも５層以上の構成
である。
本発明で用いるポリプロピレンは、ホモポリプ
ロピレン、エチレン−プロピレンコポリマーであ
り、その中でも高密度ポリエチレンとの混合によ
り、透明性の低下度合の小さいエチレン−プロピ
レンランダムコポリマーが好ましい。
また、高密度ポリエチレンとしては密度0.95
ｇ／cm3以上のものを使用し、ポリプロピレンとの
混合比はポリプロピレン／高密度ポリエチレン＝
95／５〜60／40、好ましくは90／10〜70／30であ
る。
本発明の多層容器がレトルト殺菌によつても、
酸素ガスバリヤー性の低下が少ない基本的な理由
は、高密度ポリエチレンはポリプロピレンに比
べ、レトルト殺菌温度（110〜120℃）での透湿度
が1/3〜1/5と低く、高密度ポリエチレンとポリプ
ロピレンの混合物も、ポリプロピレンに比べ透湿
度が小さくなる為、レトルト殺菌中のエチレン−
酢酸ビニル共重合体ケン化物の含水率の増加が抑
えられ、容器としての酸素ガスバリヤー性の低下
を小さくすることが出来ると考えられる。
ここで、本発明の最も重要な点は、多層容器の
レトルト殺菌後の酸素ガスバリヤー性が、高密度
ポリエチレンの添加率に正比例の関係で向上する
のでなく、添加率が少ない範囲で急激に向上する
点である。レトルト殺菌条件での透湿度を測定す
ることは困難であるので、この様な現象の理論的
解析はなされていないが、ポリプロピレンと高密
度ポリエチレンの混合比とレトルト殺菌１日後の
多層容器の酸素透過率及び透明性（ヘーズ：
JISK7105）の関係を実証的に確認した結果を第
２図に示す。第２図より高密度ポリエチレンの添
加率が０〜40％の範囲でレトルト殺菌後の酸素透
過率は急激に低下し、40％以上ではその減少率は
低く、逆に容器の透明性が悪くなり、内容物が目
視出来なくなることがわかる。
この様な結果より、レトルト殺菌後の酸素ガス
バリヤー性と透明性を共に満足するのは、ポリプ
ロピレンと高密度ポリエチレンの混合比がポリプ
ロピレン／高密度ポリエチレン＝95／５〜60／40
の範囲である。
また、高密度ポリエチレンの密度は透湿度に大
きく影響し、密度が0.95ｇ／cm3以下の場合、容器
としての透明性を保持出来る添加率40％以下で
は、実用上レトルト殺菌による容器の酸素ガスバ
リヤー性の低下を抑える効果が少なく適さない。
本発明で用いるエチレン−酢酸ビニル共重合体
ケン化物は、一般に市販されるエチレン含有率20
〜60モル％、ケン化度96モル％以上のものが従来
通り使用出来、接着層としては、市販のポリプロ
ピレン／エチレン酢酸ビニル共重合体ケン化物接
着用樹脂、例えば無水マレイン酸グラフトポリプ
ロピレン等が使用出来る。
以下本発明を実施例により説明する。
実施例 １
共押出し多層シート製造装置により、表−１に
示す樹脂を３台の押出機より同時押出しし、溶融
樹脂合流部にて合流後、Ｔダイよりシート状に押
出し冷却することにより、表−２に示す。ポリプ
ロピレンと高密度ポリエチレンの混合比率を変え
た、エチレン−酢酸ビニル共重合体ケン化物を酸
素ガスバリヤー層とする９種類の総厚520μの３
種５層シートを得た。
<Industrial Application Field> The present invention is directed to a transparent or translucent material that can be retort sterilized, has a high degree of gas permeation resistance, and can maintain a high degree of gas permeation resistance even after retort sterilization. It relates to multilayer containers, used as packaging materials that can preserve foods or medicines for long periods of time. <Prior art and its problems> Saponified ethylene-vinyl acetate copolymer has excellent gas barrier properties, fragrance retention properties, and transparency, and can be used as a gas barrier layer for packaging materials such as multilayer containers. It is widely used because it prevents food or medicine from deteriorating due to oxygen, etc., and allows long-term preservation. However, although the ethylene-vinyl acetate copolymer exhibits excellent oxygen gas barrier properties in low humidity conditions, the oxygen gas barrier properties are significantly reduced in high humidity conditions or when the water content is high. Therefore, it is generally used by laminating low moisture permeability hydrophobic polymers such as polyethylene and polypropylene on both sides. The reason why the saponified ethylene-vinyl acetate copolymer has excellent oxygen gas barrier properties is that the intermolecular and intramolecular hydrogen bonds are stronger than those of other polymers, as well as the symmetry of the molecular chain, One example is the synergistic contribution of factors such as polarity. On the other hand, when the water content of the saponified ethylene-vinyl acetate copolymer increases, the adsorbed water molecules first bond to the hydrophilic OH groups, and as the water content increases, the adsorbed water becomes intermolecular hydrogen. It is thought that it breaks bonds and enables the molecular movement necessary for oxygen molecule diffusion, leading to an increase in the oxygen permeability coefficient. If the water content increases further from this state, free water will exist in addition to adsorbed water, and the intermolecular force will further weaken, and the oxygen permeability coefficient will increase further due to the plasticizing effect on molecular motion. ing. When using such a saponified ethylene-vinyl acetate copolymer as a transparent multilayer container for retort sterilization, it is necessary to
It is common to laminate polypropylene on both sides of a saponified vinyl acetate copolymer. However, under superheated and pressurized conditions during retort sterilization, the moisture permeability of polypropylene is 15% higher than at room temperature.
Since the water content increases by ~20 times, the water content of the saponified ethylene-vinyl acetate copolymer layer increases rapidly, and the oxygen gas barrier property decreases significantly. Due to such retort sterilization, multi-layered containers whose oxygen gas barrier properties have been greatly reduced are stored after retort sterilization, as moisture in the saponified ethylene-vinyl acetate copolymer layer is gradually released to the outside. , although the oxygen gas barrier property recovered,
It requires a long period of time, and its use is limited to contents that have a relatively large amount of oxygen that can be tolerated against deterioration, and those that have a short shelf life. In order to improve these problems, three main methods are being considered.The first method is to impart hot water resistance to the saponified ethylene-vinyl acetate copolymer itself; This is a method that accelerates the release rate of water absorbed by vinyl acetate copolymer and accelerates the recovery of oxygen gas barrier properties. Part 3
This method involves providing a protective layer on both sides of an ethylene-vinyl acetate copolymer layer to prevent water from entering, thereby suppressing a decrease in oxygen gas barrier properties. Regarding the first method, water resistance and hot water resistance are improved by increasing the ethylene content in the saponified ethylene-vinyl acetate copolymer, but the original oxygen gas barrier property is also significantly reduced. Therefore, it is not practical. In addition, as a second method, by making the thickness of the outer polypropylene layer thinner than the thickness of the inner polypropylene layer, the saponified ethylene-vinyl acetate copolymer is absorbed during storage after retort sterilization. This speeds up the release of water into the outside air and speeds up the recovery of oxygen gas barrier properties. However, in this method, since the outer polypropylene layer is thin, the saponified ethylene-vinyl acetate copolymer layer absorbs a large amount of water during retort sterilization. Therefore, the degree of decrease in oxygen gas barrier properties is large, and even if the rate of recovery is fast, the cumulative amount of permeated oxygen can only be slightly reduced in the long term.Furthermore, in the early stage after retort sterilization, The oxygen concentration in the container increases, which may accelerate deterioration depending on the contents. As a third method, according to JP-A-57-170748, by protecting both sides of the saponified ethylene-vinyl acetate copolymer layer with a layer containing a desiccant,
A method has been proposed in which water that enters during retort sterilization is captured, the increase in water content of the saponified ethylene-vinyl acetate copolymer layer is reduced, and the deterioration of oxygen gas barrier properties is suppressed. This method suppresses the deterioration of oxygen gas barrier properties due to retort sterilization, but by including a desiccant (10 to 20 wt%),
Naturally, transparency is sacrificed, resulting in an opaque container, which reduces the product's appeal by half.Furthermore, manufacturing a multilayer container that includes a desiccant layer is both equipment and technologically complex, increasing container costs. There was a problem. As mentioned above, in a multilayer container that can be retorted and sterilized using a saponified ethylene-vinyl acetate copolymer as an oxygen gas barrier layer, transparency can be maintained,
There is no product that can prevent the deterioration of oxygen gas barrier properties due to retort sterilization and can be manufactured at low cost using the same processing method as before.
It was long awaited. <Means for solving the problems> The present invention was achieved as a result of various studies in view of the above circumstances. That is, the present invention provides a plastic multilayer container having at least five layers, in which the outer layer and the inner layer are a mixture of polypropylene and high-density polyethylene having a density of 0.95 g/cm 3 or more, and the mixing ratio is polypropylene/high-density polyethylene = 95/5 or more. It is a transparent or semi-transparent multi-layer container that can be sterilized by retort and has a 60/40 ratio, with an intermediate layer made of a saponified ethylene-vinyl acetate copolymer, and a layer that adheres them. That is, by using a mixture of polypropylene and high-density polyethylene as the outer layer and the inner layer, the present invention can greatly suppress the decrease in oxygen gas barrier properties due to retort sterilization compared to the case of polypropylene alone. It was proposed because it was discovered that even when the amount of density polyethylene added is relatively small, it has a remarkable effect and can maintain transparency to the extent that the contents can be visually observed. Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a multilayer container according to the present invention, in which the outer and inner layers are a mixture 1 of polypropylene and high-density polyethylene, the middle layer is a saponified ethylene-vinyl acetate copolymer 2, and their adhesion. It has a structure of at least five layers consisting of layer 3. The polypropylene used in the present invention is a homopolypropylene or an ethylene-propylene copolymer, and among these, an ethylene-propylene random copolymer is preferable because the degree of decrease in transparency is small when mixed with high-density polyethylene. In addition, the density of high-density polyethylene is 0.95.
g/cm 3 or more, and the mixing ratio with polypropylene is polypropylene/high-density polyethylene =
The ratio is 95/5 to 60/40, preferably 90/10 to 70/30. Even when the multilayer container of the present invention is subjected to retort sterilization,
The basic reason for the small decrease in oxygen gas barrier properties is that high-density polyethylene has a lower moisture permeability than polypropylene at 1/3 to 1/5 at the retort sterilization temperature (110 to 120 degrees Celsius). Polypropylene mixtures also have lower moisture permeability than polypropylene, so ethylene-
It is thought that an increase in the water content of the saponified vinyl acetate copolymer can be suppressed, and a decrease in the oxygen gas barrier properties of the container can be minimized. The most important point of the present invention is that the oxygen gas barrier properties of multilayer containers after retort sterilization do not improve in direct proportion to the addition rate of high-density polyethylene, but rapidly improve within a small range of addition rates. This is the point. Since it is difficult to measure moisture permeability under retort sterilization conditions, a theoretical analysis of this phenomenon has not been conducted. rate and transparency (haze:
Figure 2 shows the results of empirically confirming the relationship of JISK7105). Figure 2 shows that when the addition rate of high-density polyethylene is in the range of 0 to 40%, the oxygen permeability after retort sterilization decreases rapidly, and when it exceeds 40%, the rate of decrease is low, and on the contrary, the transparency of the container deteriorates. , it can be seen that the contents are no longer visible. From these results, it is found that the mixing ratio of polypropylene and high-density polyethylene is 95/5 to 60/40 to satisfy both oxygen gas barrier properties and transparency after retort sterilization.
is within the range of In addition, the density of high-density polyethylene has a large effect on moisture permeability, and if the density is 0.95 g/cm 3 or less, it is practical to use oxygen gas in the container by retort sterilization at an addition rate of 40% or less, which can maintain transparency as a container. It is not suitable as it has little effect in suppressing the deterioration of barrier properties. The saponified ethylene-vinyl acetate copolymer used in the present invention is a commercially available saponified product with an ethylene content of 20%.
~60 mol%, saponification degree of 96 mol% or more can be used as usual, and commercially available polypropylene/ethylene vinyl acetate copolymer saponified adhesive resins, such as maleic anhydride grafted polypropylene, can be used as the adhesive layer. I can do it. The present invention will be explained below with reference to Examples. Example 1 Using a coextrusion multilayer sheet manufacturing apparatus, the resins shown in Table 1 were simultaneously extruded from three extruders, and after merging at the molten resin confluence section, the resins were extruded into a sheet form from a T-die and cooled. -2. 3 types of 9 types with a total thickness of 520μ with oxygen gas barrier layers made of saponified ethylene-vinyl acetate copolymer with different mixing ratios of polypropylene and high-density polyethylene.
A five-layer seed sheet was obtained.
【表】【table】
【表】
得られた多層シートの各層厚さは全て同等で以
下の通りであつた。
外層（200μ）／接着層（40μ）／エチレン−酢
酸ビニル共重合体ケン化物層（40μ）／接着層
（40μ）／内層（200μ）。
次に各多層シートをプラグアシスト真空成形法
により、絞り比（深さ／開口径）0.2のトレー容
器に成形し、内容物として水を充填後、二軸延伸
ポリエステル（12μ）／アルミ箔（9μ）／ポリプ
ロピレン（50μ）構成の蓋材をヒートシールし密
封した。
さらに、それら充填密封された多層容器を、レ
トルト殺菌装置により、120℃−30分間の熱水式
レトルト殺菌を行つた。
以上の様にして得られたレトルト殺菌された多
層容器のレトルト殺菌１日後の酸素透過率及び容
器側面部の透明性をヘーズ（曇価：JISK7105）
とし側定し表−３に示し、その結果を第２図に示
す。またレトルト殺菌された水が充填密封された
状態の各多層容器を20℃−65％RHで１カ月間保
存後酸素透過率を測定した結果を同様に表−３に
示す。[Table] The thickness of each layer of the obtained multilayer sheet was all the same and was as follows. Outer layer (200μ) / Adhesive layer (40μ) / Saponified ethylene-vinyl acetate copolymer layer (40μ) / Adhesive layer (40μ) / Inner layer (200μ). Next, each multilayer sheet was formed into a tray container with a drawing ratio (depth/opening diameter) of 0.2 using the plug-assisted vacuum forming method, and after filling with water, biaxially oriented polyester (12μ)/aluminum foil (9μ )/polypropylene (50μ) was heat-sealed and sealed. Furthermore, the filled and sealed multilayer containers were subjected to hot water retort sterilization at 120°C for 30 minutes using a retort sterilizer. The oxygen permeability and transparency of the side surface of the retort sterilized multilayer container obtained as described above one day after retort sterilization were measured using haze (haze value: JISK7105).
The results are shown in Table 3 and the results are shown in Figure 2. Table 3 also shows the results of measuring the oxygen permeability of each multilayer container filled with retort-sterilized water and stored for one month at 20° C. and 65% RH.
【表】
表−３の結果より、エチレン−酢酸ビニル共重
合体ケン化物をガスバリヤー層とするレトルト殺
菌用多層容器として、外層及び内層にポリプロピ
レンを使用したもの（試料No.１）に比べ、本発明
の外層及び内層にポリプロピレンと高密度ポリエ
チレンの混合物を使用したもの（試料No.２〜No.
５）は、レトルト殺菌による酸素ガスバリヤー性
の低下度合いが小さく、また、内容物を目視出来
る透過性を保持することが出来る。
実施例 ２
実施例１で得た多層容器のうち、試料No.１（外
層及び内層はポリプロピレン）、試料No.２（外層及
び内層はポリプロピレン／高密度ポリエチレン＝
90／10）、及び試料No.５（外層及び内層はポリプロ
ピレン／高密度ポリエチレン＝60／40）に内容物
として中華料理の八宝菜と充填密封し、120℃−
30分間のレトルト殺菌を行ない、20℃−65％RH
及び37℃−75％RHで保存し、経時により外観及
び味を評価した。その結果を表−４に示す。[Table] From the results in Table 3, compared to a multilayer container for retort sterilization that uses saponified ethylene-vinyl acetate copolymer as a gas barrier layer and uses polypropylene for the outer and inner layers (Sample No. 1), Products using a mixture of polypropylene and high-density polyethylene for the outer and inner layers of the present invention (Samples No. 2 to No.
In 5), the degree of decrease in oxygen gas barrier properties due to retort sterilization is small, and the permeability that allows the contents to be visually observed can be maintained. Example 2 Among the multilayer containers obtained in Example 1, sample No. 1 (outer layer and inner layer are polypropylene) and sample No. 2 (outer layer and inner layer are polypropylene/high-density polyethylene =
90/10), and sample No. 5 (outer and inner layers are polypropylene/high-density polyethylene = 60/40) were filled with Chinese food Happo na as the contents, sealed, and heated at 120°C.
Perform retort sterilization for 30 minutes at 20℃-65%RH
The samples were stored at 37°C and 75% RH, and their appearance and taste were evaluated over time. The results are shown in Table-4.
【表】
従来品としての試料No.１の多層容器では、１カ
月後に内容物の若干の濁りが認められ、酸化によ
ると考えられるフレーバー変化が見られ、この時
点で商品性が無いと判断された。さらに継続して
保存したところ、６カ月後には、さらに酸化臭が
強くなり、１年後には極度の酸化劣化が認められ
た。
これに対し本発明の多層容器試料No.２及び試料
No.５では、１年後において試料No.２で内容物の若
干の濁りが認められたものの味の変化はなく、実
用上問題のない長期保存性を示した。
実施例 ３
外層及び内層にポリプロピレン（エチレン−プ
ロピレンランダムコポリマー）と高密度ポリエチ
レン（密度0.958ｇ／cm3）の混合物で、その混合
比がポリプロピレン／高密度ポリエチレン＝85／
15、中間層にエチレン含有率38モル％、ケン化度
99モル％のエチレン−酢酸ビニル共重合体ケン化
物、接着層に無水マレイン酸グラフトポリプロピ
レンを使用し、５層の1000ml容量の輸液容器を共
押出しブロー成形法により成形した。得られた輸
送容器の胴部の厚さは総厚400μであり、各層厚
さは外層（155μ）／接着層（30μ）／エチレン−
酢酸ビニル共重合体ケン化物（30μ）／接着層
（30μ）／内層（155μ）であつた。
この中に下記処方の輸液を1000ml充填密封し、
110℃−60分間のレトルト殺菌を行なつた。
グルコース 200ｇ／
Na 40ｍEq／
Ｋ 20ｍEq／
Mg ５ｍEq／
アミノ酸 30ｇ／
ビタミンＡ 15ｇ／
その後20℃−65％HRで保存したところ、従来
のポリプロピレンを外層及び内層とした多層輸液
容器では、レトルト殺菌後３週間でアミノ酸及び
ビタミンＡが酸化分解し半減したのに対し、本発
明の輸液容器では１カ月後においてもほぼ初期の
濃度が保持され、その高い保存性が確認された。
＜発明の効果＞
(1) 本発明の多層容器は、レトルト殺菌によるエ
チレン−酢酸ビニル共重合体ケン化物の酸素ガ
スバリヤー性の低下度合いが、従来の多層容器
に比べ非常に少なく、その結果容器を通して内
容物に浸入する累積酸素透過量が低減化され、
内容物の保存性を大巾に向上出来る。
(2) 本発明の多層容器は、内容物を目視可能な透
明性を保持しており、商品効果が高い。
(3) 本発明の多層容器は、従来の多層容器製造装
置及び工程をそのまま使用出来、かつ材料コス
トもほぼ同等であるので、製造コストを上げ得
ることなく容器性能を大巾に向上出来る。[Table] In sample No. 1 multilayer container, which is a conventional product, the contents became slightly cloudy after one month, and a flavor change thought to be due to oxidation was observed, and at this point it was determined that it was not commercially viable. Ta. When stored further, the oxidized odor became even stronger after 6 months, and extreme oxidative deterioration was observed after 1 year. In contrast, multilayer container sample No. 2 and sample of the present invention
In sample No. 5, although some turbidity of the contents was observed in sample No. 2 after one year, there was no change in taste, and the sample showed long-term storage stability with no practical problems. Example 3 The outer layer and the inner layer are a mixture of polypropylene (ethylene-propylene random copolymer) and high-density polyethylene (density 0.958 g/cm 3 ), and the mixing ratio is polypropylene/high-density polyethylene = 85/
15, ethylene content in the middle layer is 38 mol%, saponification degree
Using a 99 mol% saponified ethylene-vinyl acetate copolymer and maleic anhydride grafted polypropylene for the adhesive layer, a five-layer infusion container with a capacity of 1000 ml was molded by coextrusion blow molding. The total thickness of the body of the resulting transport container was 400μ, and the thickness of each layer was outer layer (155μ) / adhesive layer (30μ) / ethylene layer.
The composition was saponified vinyl acetate copolymer (30μ)/adhesive layer (30μ)/inner layer (155μ). Fill this with 1000ml of the following prescription infusion and seal it.
Retort sterilization was performed at 110°C for 60 minutes. Glucose 200g / Na 40mEq / K 20mEq / Mg 5mEq / Amino acid 30g / Vitamin A 15g / After that, when stored at 20℃ - 65% HR, conventional multilayer infusion containers with polypropylene outer and inner layers were used for 3 weeks after retort sterilization. While the amino acids and vitamin A were oxidatively decomposed and reduced by half, the infusion container of the present invention maintained almost the initial concentration even after one month, confirming its high preservability. <Effects of the Invention> (1) In the multilayer container of the present invention, the degree of decrease in oxygen gas barrier properties of saponified ethylene-vinyl acetate copolymer due to retort sterilization is extremely small compared to conventional multilayer containers. The cumulative amount of oxygen that permeates into the contents through the
The shelf life of the contents can be greatly improved. (2) The multilayer container of the present invention maintains transparency that allows the contents to be viewed visually, and is highly effective as a product. (3) The multilayer container of the present invention can use conventional multilayer container manufacturing equipment and processes as is, and the material cost is almost the same, so the container performance can be greatly improved without increasing the manufacturing cost.
図面は本発明の実施例を示すもので、第１図は
本発明の多層容器の断面図を示すものであり、第
２図はポリプロピレンと高密度ポリエチレンの混
合比と、容器の酸素透過率及びヘーズの関係を示
すグラフである。
１……ポリプロピレンと高密度ポリエチレンの
混合物、２……エチレン−酢酸ビニル共重合体ケ
ン化物、３……接着樹脂。
The drawings show examples of the present invention, and FIG. 1 shows a cross-sectional view of a multilayer container of the present invention, and FIG. 2 shows the mixing ratio of polypropylene and high-density polyethylene, the oxygen permeability of the container, and It is a graph showing the relationship between haze. 1...Mixture of polypropylene and high density polyethylene, 2...Saponified ethylene-vinyl acetate copolymer, 3...Adhesive resin.
Claims (1)
において、外層及び内層が、ポリプロピレンと密
度0.95ｇ／cm3以上の高密度ポリエチレンの混合物
で、その混合比がポリプロピレン／高密度ポリエ
チレン＝95／５〜60／40であり、中間層がエチレ
ン−酢酸ビニル共重合体ケン化物であり、さらに
それらを接着する層を含む、透明又は半透明なレ
トルト殺菌可能な多層容器。1 In a plastic multilayer container with at least 5 layers, the outer and inner layers are a mixture of polypropylene and high-density polyethylene with a density of 0.95 g/cm 3 or more, and the mixing ratio is polypropylene/high-density polyethylene = 95/5 to 60/40. A transparent or translucent multilayer container that can be sterilized by retort, wherein the intermediate layer is a saponified ethylene-vinyl acetate copolymer and further includes a layer for adhering them.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17264286A JPS6328642A (en) | 1986-07-22 | 1986-07-22 | Multilayer vessel for retort sterilization |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17264286A JPS6328642A (en) | 1986-07-22 | 1986-07-22 | Multilayer vessel for retort sterilization |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6328642A JPS6328642A (en) | 1988-02-06 |
| JPH0380628B2 true JPH0380628B2 (en) | 1991-12-25 |
Family
ID=15945664
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17264286A Granted JPS6328642A (en) | 1986-07-22 | 1986-07-22 | Multilayer vessel for retort sterilization |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6328642A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0839743A (en) * | 1994-05-27 | 1996-02-13 | Kureha Plast Kk | Multilayer hollow plastic container |
| US7185780B2 (en) * | 2003-12-15 | 2007-03-06 | Sonoco Develpoment, Inc. | Container overcap with drying agent layer |
| JP7059648B2 (en) * | 2018-01-24 | 2022-04-26 | 住友ベークライト株式会社 | Multi-layer sheets, trays and packaging |
-
1986
- 1986-07-22 JP JP17264286A patent/JPS6328642A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6328642A (en) | 1988-02-06 |
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