JP4378563B2

JP4378563B2 - Metal container manufacturing method and metal container

Info

Publication number: JP4378563B2
Application number: JP2003171822A
Authority: JP
Inventors: 實竹腰; 正一朗赤根
Original assignee: Takeuchi Press Industries Co Ltd
Current assignee: Takeuchi Press Industries Co Ltd
Priority date: 2003-06-17
Filing date: 2003-06-17
Publication date: 2009-12-09
Anticipated expiration: 2023-06-17
Also published as: JP2005008166A

Description

【０００１】
【発明の属する技術分野】
本発明は、内面が樹脂組成物で塗装された金属容器の製造方法に関し、さらに詳しくは金属容器との密着性、耐食性及びフレーバー性を損なうことなく、耐加工性に優れると共に、特に耐レトルト性に優れた金属容器の製造方法に関する。
【０００２】
【従来の技術】
従来、炭酸飲料、コーヒー、紅茶、ビール、スポーツ飲料等を収納する金属容器の内面には、アルミニウム等の金属と内容物である飲料との直接的な接触を防止するために、樹脂組成物である内面塗料が塗装されている。このような内面塗料としては、特７−２３２７３７号公報に開示されたエポキシ樹脂とアクリル樹脂の共重合体と、ポリ塩化ビニルとフェノール樹脂から構成される樹脂組成物がある。又特開２００２−３６１７８４号には、主な含有樹脂組成物として、（ａ）エポキシ樹脂とアクリル樹脂の重量比が６５：３５〜８８：１２の範囲で共重合して形成され、（ｂ）フェノキシタイプの重量平均分子量３００００〜６５０００のエポキシ樹脂の含有量が５〜４５重量％で構成され、（ｃ）アクリル樹脂が、任意共重合モノマーを０〜２０重量％含有し、さらに、フェノール樹脂の添加量を、エポキシアクリル共重合体１００重量％に対して、１〜７重量％に限定した内面塗料がある。
【０００３】
【発明が解決しようとする課題】
しかしながら、このような金属容器の内面塗料は、前者のようにポリ塩化ビニルを含有するものにあっては、近年の脱塩化ビニルの環境意識の高まりに逆行する内面塗料であると共に、後者のような内面塗料にあっては、金属容器の製造工程において、内面塗装後における耐加工性、特にネッキング加工工程及びねじ加工工程後における容器本体の内面塗膜の耐加工性、耐レトルト性が著しく劣るという欠点がある。すなわちネッキング加工工程及びねじ加工工程後において、内面塗膜の通電値の測定値が悪く、内面塗膜の損傷が著しいという欠点があった。
【０００４】
この発明は、このような従来の課題に着目してなされたものであり、金属容器との密着性、耐食性及びフレーバー性を損なうことなく、特に耐加工性及び耐レトルト性に優れた金属容器の製造方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
この課題を解決するため、請求項１記載の発明に対応する手段は、金属製の板材を有底筒状に成形するカッピング工程、胴部をしごいて引き延ばすアイアニング工程、口部先端を切り揃えるトリミング工程、内面を洗浄・乾燥する洗浄・乾燥工程、容器本体の外面にベースコートを施す下地塗装工程およびその下地塗装の上に印刷を施す外面印刷工程をこの順に行うと共に、前記いずれかの工程の前または後において、金属製の容器本体の内面に、エポキシアクリル共重合体樹脂及びフェノール樹脂を含有する内面塗料を塗装する内面塗装工程を行い、前記外面印刷工程の後、または外面印刷工程の後に内面塗装工程を施す場合はその後に、ネッキングマシンに取付けられたダイによって容器本体の口部を複数回に亘って所望の外径まで絞り、テーパ状に成形するネッキング工程を行い、さらにそのネッキング工程の後、容器本体の口部内面に２回目の内面塗装工程を行い、前記内面塗装工程および２回目の内面塗装工程で用いる内面塗料が、（Ａ）エポキシ樹脂とアクリル樹脂の重量比が６７：３３〜８８：１２の範囲で共重合して形成され、（Ｂ）フェノキシタイプの重量平均分子量３００００〜６５０００のエポキシ樹脂の含有量が４６〜５５重量％で構成され、（Ｃ）アクリル樹脂が、メタクリル酸、スチレン及び任意共重合モノマーで構成され、任意共重合モノマーを２１〜５０重量％含有し、（Ｄ）フェノール樹脂が、エポキシアクリル共重合体１００重量％に対して、１〜５重量％を含有する塗料を、親水性溶媒中に溶解または分散させて均一としたものであり、前記内面塗装工程において内面塗料を塗布した後、加熱して硬化させることを特徴とする金属容器の製造方法である。
【０００６】
請求項２記載の発明に対応する手段は、前記２回目の内面塗装工程の後に、口部のねじ加工工程を行うことを特徴とする金属容器の製造方法である。
【０００７】
請求項３記載の発明に対応する手段は、前記２回目の内面塗装工程の後に、口部のフランジ加工工程を行うことを特徴とする金属容器の製造方法である。
【００１０】
請求項４記載の発明に対応する手段は、前記いずれかの製造方法で造られたことを特徴とする金属容器である。
【００１１】
【発明の実施の形態】
次にこの発明の実施の形態を説明する。
本発明に用いられる内面塗料３は、（Ａ）エポキシ樹脂とアクリル樹脂の重量比が６７：３３〜８８：１２の範囲で共重合して形成される。アクリル樹脂／エポキシ樹脂が１２／８８未満の場合、水性の分散媒中での樹脂の分散が不安定、塗装が不可能であるという欠点があり、又アクリル樹脂／エポキシ樹脂が３３／６７を超えると、塗膜の加工性、耐食性が低下するという欠点がある。この樹脂組成物は、親水性溶媒中に溶解又は分散させて均一とし、スプレー又はロールコーティング等公知の方法により金属容器内面に塗布し、その後加熱することにより硬化させ金属容器内面に塗膜を形成する。本発明の製造工程において用いられる内面塗料３の被覆は、図１及び図２に示すように、金属容器の容器本体２の内面、すなわち、内容物である飲料と接触する部位に内面塗料３を形成するものであり、容器本体２の口部、肩部及び胴部の内面に塗布されれば、本発明の効果は十分に得られる。前記金属容器の金属材料としては、アルミニウム、スチール、ブリキ等の金属材料が用いられる。
【００１２】
本発明に用いられる内面塗料３は、図１に示すねじ付金属容器、図５に示すＤＩ缶、図８及び図９に示すインパクト成形によって製造される、ねじ付き金属容器又は小型のエアゾール容器に適用でき、特に図中のＸの部位等の塑性変形が大きく、加工度が高い部位の内面塗料として有効である。図２（ａ）（ｂ）は、ねじ付き金属容器である図１のＡ部拡大断面を示しており、金属容器１の容器本体２の内面に、内面塗料３が塗装された状態を示す拡大断面図である。本発明者等は、本発明の製造工程で用いられる内面塗料３を、従来の内面塗料と比較して、エポキシアクリル共重合体におけるフェノキシタイプの重量平均分子量３００００〜６５０００のエポキシ樹脂の含有量を、４６〜５５重量％と多くすると共に、アクリル樹脂中の任意共重合モノマーを２１〜５０重量％と多くすることにより、耐食性及びフレーバー性を損なうことなく耐加工性に優れ、特に耐レトルト性に優れた金属容器を製造できることを見出したのである。
【００１３】
本発明の製造工程で用いられる内面塗料３におけるエポキシ樹脂は、平均分子量が１００００〜２００００のエポキシ樹脂と、平均分子量が３００００〜６５０００のフェノキシタイプのエポキシ樹脂が混合されたものである。平均分子量が１００００〜２００００のエポキシ樹脂の含有量は、２５〜３３重量％の範囲であり、平均分子量が３００００〜６５０００のフェノキシタイプのエポキシ樹脂の含有量が４６〜５５重量％の範囲とされ、好ましくは４８〜５２重量％である。平均分子量が３００００〜６５０００のフェノキシタイプのエポキシ樹脂が４６重量％未満では、加工性、レトルト性、耐食性が劣るという欠点があり、又５５重量％以上では、塗料製造時の粘度が高く、塗料の製造が困難になるという欠点がある。なお、フェノキシタイプのエポキシ樹脂は、高分子タイプのエポキシ樹脂とも呼ばれ、ビスフェノールＡタイプ、ビスフェノールＦタイプ、ビスフェノールＡタイプとビスフェノールＦタイプの混合タイプもある。
【００１４】
本発明に用いられるアクリル樹脂は、メタクリル酸が３０〜６０重量％、スチレンが２１〜５０重量％、任意共重合モノマーが２１〜５０重量％で構成されている。任意共重合モノマーとしては、例えば、共重合物、エチルアクリレート、メタクリ酸メチルの１種又は２種以上が用いられる。任意共重合モノマーが２１重量％未満の場合、加工による下地追随性が悪くなり、又レトルト処理において、塗膜剥離が生じ易くなるという欠点がある。又任意共重合モノマーが５０重量％を超える場合、香料が塗膜へ吸着し、フレーバー適性が劣るという欠点がある。
【００１５】
本発明に用いられるフェノール樹脂は、平均分子量が３００〜１０００の大きさのものが用いられる。フェノール樹脂の添加量は、エポキシアクリル共重合体１００重量％に対して１〜５重量％である。１〜５重量％に限定した理由は、
１重量％未満では、硬化性及び耐食性が劣る。又５重量％を超えて添加した場合は、塗膜の硬化が進み、加工による下地追随性が悪くなるという欠点がある。その他、本発明に用いられる内面塗料には、その他ブチルセロソルブ等の溶剤、添加剤が含有されてもよい。
【００１６】
次に、本発明に係る内面塗料を塗装する塗装工程を含む、一連のねじ付金属容器の製造工程を説明する。図３はこの発明外の製造工程の一例を示す図面である。図３は、ねじ付金属容器の製造工程を示す図面であり、図３（ａ）は、アルミニウムの板材を、有底筒状に成形するカッピング工程から、胴部をしごいて引き延ばすアイアニング工程を示す図面である。図３（ｂ）は、口部先端を切り揃えるトリミング工程、図３（ｃ）は洗浄・乾燥工程を経た後、容器本体２の外面にホワイトコート又はサイズコート等のベースコートを施す下地塗装工程である。この下地塗装を行う場合、製造ラインには、下地塗装機（ベースコーター）が一台組み込まれ、この下地塗装機の一対のアプリケーターローラ及びメータリングローラにより、下地塗装が施されている。図３（ｄ）は下地塗装の上に印刷を施す外面印刷工程、図３（ｅ）は容器本体２の内面に、ノズル４により内面塗料３をスプレー塗装する内面塗装工程である。図３（ｆ）（ｇ）は、ネッキング工程であり、通常ネッキングマシンに取付けられたダイによって、容器本体２の口部を、複数回に亘って所望の外径まで絞るものである。図３（ｈ）はねじ加工工程である。この第１実施の形態の特徴は、ネッキング工程の前工程である図３（ｅ）に示す内面塗装工程において、この内面塗料３が、（Ａ）エポキシ樹脂とアクリル樹脂の重量比が６７：３３〜８８：１２の範囲で共重合して形成され、（Ｂ）フェノキシタイプの重量平均分子量３００００〜６５０００のエポキシ樹脂の含有量が４６〜５５重量％で構成され、（Ｃ）アクリル樹脂が、メタクリル酸、スチレン及び任意共重合モノマーで構成され、任意共重合モノマーを２１〜５０重量％含有し、（Ｄ）フェノール樹脂が、エポキシアクリル共重合体１００重量％に対して、１〜５重量％を含有する塗料であり、この内面塗料３をスプレー塗装するものである。なお、ネッキング工程以外の他の工程前に内面塗装が行われてもよい。
【００１７】
図４はこの発明に係る製造方法の実施の形態を示す図面である。この製造方法の特徴は、図３の製造方法と異なり、内面塗装工程が全製造工程中において、少なくとも２回行われる点である。すなわち、図４（ｉ）のねじ加工工程の前に、再度内面塗装工程を有する金属容器の製造方法である。図４（ｆ）〜図４（ｇ）におけるネッキング加工工程が終了した容器本体２の口部に対して、内面塗膜の修復を目的として、洗浄後に再塗装を行うものである。この２回の内面塗装により、容器本体２の内面塗装は完全化される。そして、内面塗膜が修復され通電値も一層低下する。その他の製造工程は、図３の製造方法と同様である。
【００１８】
図５はこの発明に係る製造方法で製造された金属容器を示す図面であり、通常のＤＩ缶を示す図面である。図５において、Ｘの部位の加工性が高く、本発明等は特にＸの部分の多段ネッキング加工工程における内面塗料１３の耐加工性及び耐レトルト性の向上を図ったものである。図７（ａ）は、アルミニウムの板材を、有底筒状に成形するカッピング工程から、胴部をしごいて引き延ばすアイアニング工程を示す図面である。図７（ｂ）は、口部先端を切り揃えるトリミング工程、図７（ｃ）は洗浄・乾燥工程を経た後の容器本体１２に、ホワイトコート又はサイズコート等のベースコートを施す下地塗装工程、図７（ｄ）は下地塗装の上に印刷を施す外面印刷工程、図７（ｅ）は、容器本体１２の内面に塗装を施す内面塗装工程である。図７（ｆ）（ｇ）はネッキング工程であり、通常ネッキングマシンに取り付けられたダイによって、容器本体の口部を複数回に亘って所望の外径まで絞る工程である。図７（ｈ）はフランジ加工工程である。この製造方法の特徴は、ネッキング工程前の図７（ｅ）の内面塗装工程において、ノズル１４から内面塗料１３をスプレー塗装することにより行われる。内面塗料１３は、（Ａ）エポキシ樹脂とアクリル樹脂の重量比が６７：３３〜８８：１２の範囲で共重合して形成され、（Ｂ）フェノキシタイプの重量平均分子量３００００〜６５０００のエポキシ樹脂の含有量が４６〜５５重量％で構成され、（Ｃ）アクリル樹脂が、メタクリル酸、スチレン及び任意共重合モノマーで構成され、任意共重合モノマーを２１〜５０重量％含有し、（Ｄ）フェノール樹脂が、エポキシアクリル共重合体１００重量％に対して、１〜５重量％を含有する塗料である。なお、ネッキング工程以外の他の工程前において、内面塗装が行われてもよく、又全製造工程中において、少なくとも２回以上内面塗装が行われる。
【００１９】
図８は、本発明の金属容器の実施の形態を示す図面である。図８に示す金属容器は、インパクト成形により製造されるねじ付金属容器２２である。又図９は本発明のさらに他の実施の形態を示す図面である。小型のエアゾール容器２３であり、いずれも本発明の製造工程で用いられる内面塗料を被覆した金属容器である。インパクト成形後に行われるＸの部位の塑性変形が大きいので、内面塗装工程で内面塗料として用いることで、同様に耐加工性及び耐レトルト性の向上に効果的である。本実施の形態において、同様に全製造工程中において、内面塗装が少なくとも２回以上行われる。
【００２０】
【実施例】
本発明に係る樹脂組成物で構成された内面塗料を塗装したねじ付金属容器の製造方法と、従来のねじ付金属容器の製造方法によって製造されたねじ付金属容器について、各々通電値とフレーバー性を比較した。
＜試験条件＞
▲１▼加工性通電値ｍａｘ；ボトル缶のねじ部まで１％食塩水を入れ、ＤＣ６．３Ｖ３秒後を測定。
▲２▼レトルト性１通電値；キャッピングをして、水に浸漬し、１２５℃×３０分処理後のねじ部の通電値を測定。
▲３▼レトルト性２通電値；市販のコーヒー飲料をホットパック＋ＬＮ２充填＋キャッピングをして、１２５℃×３０分処理後のねじ部の通電値を測定。
▲４▼耐食性メタカリ通電値；メタ重亜硫酸カリウム３００ｐｐｍ・クエン酸１重量％・塩化ナトリウム６００ｍｇ／Ｌ・エタノール１０重量％の調整水を１００ｍｌ、ボトル缶に入れ、キャッピングし、倒立にて、４０℃×３日保存後のねじ部の通電値を測定。
▲５▼フレーバー性ＫＭｎＯ４；ボトル缶に４００ｍｌの精製水を入れ、１２５℃×３０分処理後の抽出液の過マンガン酸カリウム消費量。
※参考
通電値が小さい場合は、下地金属の露出が少なく、塗膜の割れ、剥離、ダメージが少ない状態であり、加工性やレトルト性及び耐食性が良好である。又過マンガン酸消費量が小さい場合、塗膜からの有機物の抽出が少ない。
【表１】

＜試験結果＞
耐レトルト性・耐加工性の試験結果から、本発明に係る製造方法によれば、ネッキング加工、ねじ加工後の金属容器の内面塗膜の通電値が低くなり、特に大きな遡性変形を伴う加工後のレトルト処理においても、内面塗膜の損傷が著しく少ないという結果が得られた。又フレーバー性の試験結果において、過マンガン酸の流出量が著しく小さいという試験結果が得られた。
【００２１】
【発明の効果】
この発明は、このような従来の課題に着目してなされたものであり、金属容器との密着性、耐食性及びフレーバー性を損なうことなく耐加工性に優れ、特に耐レトルト性に優れるという効果を有する。
【図面の簡単な説明】
【図１】この発明に係る実施の形態の製造方法で製造される、ねじ付金属容器を示した断面図。
【図２】図１のＡ矢視部の拡大断面図。
【図３】この発明外の製造方法における各製造工程を示す図面。
【図４】この発明に係る製造方法における各製造工程の実施の形態を示す図面。
【図５】この発明に係る製造方法で製造されるＤＩ缶を示した断面図。
【図６】図５のＢ矢視部の拡大断面図。
【図７】この発明外の製造方法における各製造工程を示す図面。
【図８】この発明に係る製造方法で製造される、ねじ付金属容器を示した断面図。
【図９】この発明に係る製造方法で製造される、エアゾール容器を示した断面図。
【符号の説明】
１１１金属容器
２１２容器本体
３１３内面塗料
４１４ノズル
２２ねじ付金属容器
２３小型のエアゾール容器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a metal container whose inner surface is coated with a resin composition. More specifically, the present invention is excellent in workability without impairing adhesion, corrosion resistance and flavor properties with a metal container, and particularly retort resistance. It is related with the manufacturing method of the metal container excellent in.
[0002]
[Prior art]
Conventionally, on the inner surface of a metal container for storing carbonated beverages, coffee, tea, beer, sports beverages, etc., in order to prevent direct contact between a metal such as aluminum and the beverage as a content, a resin composition is used. Some internal paint is painted. As such an inner surface coating material, there is a resin composition composed of a copolymer of an epoxy resin and an acrylic resin, polyvinyl chloride and a phenol resin disclosed in Japanese Patent Publication No. 7-232737. In JP-A-2002-361784, as a main resin composition, (a) a weight ratio of epoxy resin and acrylic resin is copolymerized in the range of 65:35 to 88:12, and (b) The content of an epoxy resin having a weight average molecular weight of 30000-65000 of phenoxy type is 5 to 45% by weight, (c) the acrylic resin contains 0 to 20% by weight of an optional copolymerization monomer, There is an internal coating whose addition amount is limited to 1 to 7% by weight with respect to 100% by weight of the epoxy acrylic copolymer.
[0003]
[Problems to be solved by the invention]
However, such an inner surface paint for a metal container is an inner surface paint that counteracts the recent increase in environmental awareness of dechlorinated vinyl, if it contains polyvinyl chloride as in the former, and the latter. In the inner surface coating process, in the metal container manufacturing process, the processing resistance after the inner surface coating, particularly the processing resistance and retort resistance of the inner surface coating of the container body after the necking process and the screw processing process are remarkably inferior. There is a drawback. That is, after the necking process and the threading process, the measured value of the energization value of the inner surface coating film was poor and the inner surface coating film was significantly damaged.
[0004]
The present invention has been made by paying attention to such a conventional problem, and does not impair adhesion, corrosion resistance, and flavor properties with a metal container, and in particular, a metal container excellent in workability and retort resistance. An object is to provide a manufacturing method.
[0005]
[Means for Solving the Problems]
In order to solve this problem, the means corresponding to the first aspect of the invention includes a cupping step of forming a metal plate into a bottomed cylindrical shape, an ironing step of squeezing and stretching the body portion, and aligning the tip of the mouth portion. The trimming process, the cleaning / drying process for cleaning / drying the inner surface, the base coating process for applying the base coat to the outer surface of the container body, and the outer surface printing process for printing on the base coating are performed in this order. before or after, the inner surface of the metal container main body, performs internal surface painting process of painting an interior paint containing epoxy acrylic copolymer resins and phenolic resins, after the outer surface printing process, or after the outer surface printing process When applying the inner surface painting process, the mouth of the container body is then squeezed several times to the desired outer diameter by a die attached to the necking machine. Performed necking step of forming a tapered, further after the necking process, the mouth portion inner face of the container body a second time inside surface painting process, the inner surface coating used in the inner surface painting process, and the second inner surface painting process, (A) The weight ratio of the epoxy resin to the acrylic resin is formed by copolymerization in the range of 67:33 to 88:12, and the content of the epoxy resin having a weight average molecular weight of 30000 to 65000 of (B) phenoxy type is 46 to (C) acrylic resin is composed of methacrylic acid, styrene and an optional copolymerization monomer, contains 21 to 50 wt% of the optional copolymerization monomer, and (D) the phenol resin is an epoxy acrylic copolymer. respect polymer 100 wt%, which a paint containing 1 to 5% by weight to obtain a uniform dissolved or dispersed in a hydrophilic solvent, before After application of the inner surface coating on the inner surface painting process, a method for producing a metal container wherein the curing by heating.
[0006]
According to a second aspect of the present invention, there is provided a metal container manufacturing method characterized in that a mouth threading step is performed after the second inner surface coating step.
[0007]
According to a third aspect of the present invention, there is provided a metal container manufacturing method characterized in that after the second inner surface coating step, a mouth flange processing step is performed .
[0010]
According to a fourth aspect of the present invention, there is provided a metal container characterized in that it is manufactured by any one of the manufacturing methods.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
The inner surface coating material 3 used in the present invention is formed by copolymerization in a weight ratio of (A) epoxy resin and acrylic resin in the range of 67:33 to 88:12. When the acrylic resin / epoxy resin is less than 12/88, there are disadvantages that the dispersion of the resin in the aqueous dispersion medium is unstable and the coating is impossible, and the acrylic resin / epoxy resin exceeds 33/67. And there exists a fault that the workability and corrosion resistance of a coating film fall. This resin composition is dissolved or dispersed in a hydrophilic solvent to make it uniform, and is applied to the inner surface of the metal container by a known method such as spraying or roll coating, and then cured by heating to form a coating film on the inner surface of the metal container. To do. As shown in FIGS. 1 and 2, the inner surface paint 3 used in the manufacturing process of the present invention is coated on the inner surface of the container main body 2 of the metal container, that is, on the portion that comes into contact with the beverage as the contents. If it is formed and applied to the inner surface of the mouth, shoulder and trunk of the container body 2, the effect of the present invention can be obtained sufficiently. As the metal material of the metal container, a metal material such as aluminum, steel, or tinplate is used.
[0012]
The inner surface coating 3 used in the present invention is applied to a threaded metal container shown in FIG. 1, a DI can shown in FIG. 5, a threaded metal container or a small aerosol container manufactured by impact molding shown in FIGS. application can, in particular 塑 deformation is large site such as the X in the figure, it is effective as an inner surface coating of a high degree of processing sites. 2 (a) and 2 (b) show an A-section enlarged cross section of FIG. 1 which is a threaded metal container, and an enlarged view showing a state in which the inner surface coating 3 is coated on the inner surface of the container main body 2 of the metal container 1. It is sectional drawing. The inventors have compared the content of the epoxy resin having a weight average molecular weight of 30,000 to 65,000 of the phenoxy type in the epoxy acrylic copolymer by comparing the inner surface paint 3 used in the production process of the present invention with a conventional inner surface paint. , 46-55% by weight, and by increasing the optional copolymerization monomer in the acrylic resin to 21-50% by weight, it is excellent in processing resistance without impairing corrosion resistance and flavor, especially in retort resistance. It was found that an excellent metal container can be manufactured.
[0013]
The epoxy resin in the inner surface coating 3 used in the production process of the present invention is a mixture of an epoxy resin having an average molecular weight of 10,000 to 20,000 and a phenoxy type epoxy resin having an average molecular weight of 30,000 to 65,000. The content of the epoxy resin having an average molecular weight of 10,000 to 20,000 is in the range of 25 to 33% by weight, and the content of the phenoxy type epoxy resin having an average molecular weight of 30,000 to 65,000 is in the range of 46 to 55% by weight. Preferably it is 48 to 52 weight%. If the phenoxy type epoxy resin having an average molecular weight of 30000 to 65000 is less than 46% by weight, there is a disadvantage that the processability, retortability and corrosion resistance are inferior, and if it is 55% by weight or more, the viscosity during the production of the paint is high. There is a drawback that it is difficult to manufacture. The phenoxy type epoxy resin is also called a polymer type epoxy resin, and there are bisphenol A type, bisphenol F type, and mixed type of bisphenol A type and bisphenol F type.
[0014]
The acrylic resin used in the present invention is composed of 30 to 60% by weight of methacrylic acid, 21 to 50% by weight of styrene, and 21 to 50% by weight of an optional copolymerization monomer. As an arbitrary copolymerization monomer, the 1 type (s) or 2 or more types of a copolymer, ethyl acrylate, and methyl methacrylate are used, for example. When the arbitrary copolymerization monomer is less than 21% by weight, there are disadvantages that the followability of the groundwork due to processing is deteriorated, and coating film peeling is liable to occur in the retort treatment. Further, when the optional copolymerization monomer exceeds 50% by weight, there is a disadvantage that the fragrance is adsorbed to the coating film and the flavor suitability is inferior.
[0015]
The phenol resin used in the present invention has a mean molecular weight of 300 to 1,000. The addition amount of the phenol resin is 1 to 5% by weight with respect to 100% by weight of the epoxy acrylic copolymer. The reason for limiting to 1 to 5% by weight is
If it is less than 1% by weight, curability and corrosion resistance are inferior. Moreover, when adding exceeding 5 weight%, there exists a fault that hardening of a coating film progresses and the base following property by processing worsens. In addition, the inner coating material used in the present invention may contain other solvents such as butyl cellosolve and additives.
[0016]
Next, a series of manufacturing processes of the metal container with a screw including the painting process of painting the inner surface paint according to the present invention will be described. FIG. 3 is a drawing showing an example of a manufacturing process outside the present invention. FIG. 3 is a drawing showing a manufacturing process of a threaded metal container, and FIG. 3 (a) shows an ironing process in which an aluminum plate is formed into a bottomed cylindrical shape, and an ironing process is performed by squeezing and stretching the trunk. FIG. FIG. 3B is a trimming process for trimming the front end of the mouth, and FIG. 3C is a base coating process in which a base coat such as a white coat or a size coat is applied to the outer surface of the container body 2 after a cleaning / drying process. is there. When this base coating is performed, one base coating machine (base coater) is incorporated in the production line, and the base coating is performed by a pair of applicator rollers and metering rollers of the base coating machine. FIG. 3D shows an outer surface printing process in which printing is performed on the base coating, and FIG. 3E shows an inner surface coating process in which the inner surface coating 3 is spray-coated on the inner surface of the container body 2 by the nozzle 4. 3 (f) and 3 (g) show a necking process, in which the mouth of the container body 2 is squeezed to a desired outer diameter a plurality of times by a die attached to a normal necking machine. FIG. 3 (h) shows a threading process. The feature of the first embodiment is that, in the inner surface coating process shown in FIG. 3 (e), which is the previous process of the necking process, the inner surface paint 3 has a weight ratio of (A) epoxy resin and acrylic resin of 67:33. The content of the epoxy resin having a weight average molecular weight of 30000-65000 of (B) phenoxy type is 46 to 55% by weight, and (C) the acrylic resin is methacrylic. It is composed of an acid, styrene and an optional copolymerization monomer, contains 21 to 50% by weight of the optional copolymerization monomer, and (D) the phenol resin is 1 to 5% by weight with respect to 100% by weight of the epoxy acrylic copolymer. It is a paint to contain, and this inner surface paint 3 is spray-coated. It should be noted that the inner surface coating may be performed before other steps other than the necking step.
[0017]
Figure 4 is a view illustrating a form of implementation of the engagement Ru manufacturing method of this invention. Features of the method for manufacturing this, unlike the manufacturing method of FIG. 3, during the internal surface painting process is entire manufacturing process is that performed at least twice. That is, this is a method of manufacturing a metal container having an inner surface painting process again before the screw machining process of FIG. For the purpose of repairing the inner surface coating film, recoating is performed on the mouth portion of the container body 2 after the necking process in FIGS. 4F to 4G is completed. The inner surface coating of the container body 2 is completed by the two inner surface coatings. And an inner surface coating film is restored | repaired and an electricity supply value falls further. Other manufacturing steps are the same as those in the manufacturing method of FIG.
[0018]
FIG. 5 is a drawing showing a metal container manufactured by the manufacturing method according to the present invention, and is a drawing showing a normal DI can . In FIG. 5, the processability of the portion X is high, and the present invention and the like are intended to improve the workability and retort resistance of the inner surface coating 13 particularly in the multi-stage necking process of the portion X. FIG. 7A is a drawing showing an ironing process in which a body portion is squeezed and stretched from a cupping process in which an aluminum plate is formed into a bottomed cylindrical shape. FIG. 7B is a trimming process for trimming the front end of the mouth, and FIG. 7C is a base coating process for applying a base coat such as a white coat or a size coat to the container body 12 after the cleaning and drying process. 7 (d) is an outer surface printing step for printing on the base coating, and FIG. 7 (e) is an inner surface coating step for coating the inner surface of the container body 12. FIGS. 7F and 7G show a necking process, which is a process of narrowing the mouth of the container body to a desired outer diameter a plurality of times with a die attached to a normal necking machine. FIG. 7 (h) shows the flange processing step. This manufacturing method is characterized by spray coating the inner surface coating 13 from the nozzle 14 in the inner surface coating step of FIG. 7 (e) before the necking step. The inner surface coating 13 is formed by copolymerization in a weight ratio of (A) epoxy resin and acrylic resin in the range of 67:33 to 88:12, and (B) a phenoxy type epoxy resin having a weight average molecular weight of 30,000 to 65,000. The content is composed of 46 to 55% by weight, (C) the acrylic resin is composed of methacrylic acid, styrene and an optional copolymerization monomer, and contains 21 to 50% by weight of the optional copolymerization monomer, (D) a phenol resin However, it is a coating material containing 1 to 5% by weight with respect to 100% by weight of the epoxy acrylic copolymer. Incidentally, before other steps other than the necking process may be performed inside surface coating, also during the entire manufacturing process, the inner surface coating is carried out at least twice.
[0019]
Figure 8 illustrates the implementation in the form of a metal container of the present invention. The metal container shown in FIG. 8 is a threaded metal container 22 manufactured by impact molding. Matazu 9 is a view showing still another form of implementation of the present invention. These are small aerosol containers 23, both of which are metal containers coated with an internal coating used in the production process of the present invention. Since the site of 塑 of X which is performed after impact molding deformation is large, by using as the inner surface coating on the inner surface painting process, is equally effective in improving the resistance to workability and retort resistance. In this embodiment, similarly during the entire manufacturing process, the inner surface coating is Ru performed at least twice.
[0020]
【Example】
About the manufacturing method of the threaded metal container which coated the inner surface paint comprised with the resin composition concerning this invention, and the threaded metal container manufactured by the manufacturing method of the conventional threaded metal container, respectively, electricity value and flavor property Compared.
<Test conditions>
(1) Workability energization value max: 1% saline solution was put into the screw part of the bottle can and measured after DC 6.3 V for 3 seconds.
{Circle around (2)} Retort 1 energization value: capped, immersed in water, and measured the energization value of the threaded portion after treatment at 125 ° C. for 30 minutes.
{Circle around (3)} Retort 2 energization value: A commercial coffee drink was hot-packed + filled with LN2 + capped, and the energization value of the screw part after treatment at 125 ° C. for 30 minutes was measured.
(4) Corrosion resistance Metakali energization value: Potassium metabisulfite 300ppm · Citric acid 1wt% · Sodium chloride 600mg / L · Ethanol 10wt% adjusted water 100ml, put into a bottle can, capped and inverted at 40 ° C × Measure the energization value of the screw part after storage for 3 days.
(5) Flavored KMnO4: Potassium permanganate consumption of the extract after adding 400 ml of purified water to a bottle can and treating at 125 ° C. for 30 minutes.
* When the reference energization value is small, there is little exposure of the underlying metal, and there is little cracking, peeling and damage of the coating film, and workability, retortability and corrosion resistance are good. In addition, when the permanganate consumption is small, there is little extraction of organic matter from the coating film.
[Table 1]

<Test results>
From the test results of retort resistance and work resistance, according to the manufacturing method according to the present invention, the energization value of the inner surface coating of the metal container after necking and screw processing is lowered, and particularly processing with large retroactive deformation. In the subsequent retort treatment, the result that the damage of the inner surface coating film was remarkably reduced was obtained. Further, in the flavor test results, a test result that the outflow amount of permanganic acid was remarkably small was obtained.
[0021]
【The invention's effect】
The present invention has been made by paying attention to such a conventional problem, and has an effect of being excellent in processing resistance without impairing adhesion, corrosion resistance and flavor properties with a metal container, and particularly excellent in retort resistance. Have.
[Brief description of the drawings]
[1] This invention produced by the production method of implementation in the form engaging Ru, cross-sectional view showing a metal container with a screw.
FIG. 2 is an enlarged cross-sectional view taken along the arrow A in FIG.
[3] The manufacturing steps shown to FIG surface in the present invention outside of the manufacturing process.
FIG. 4 is a drawing showing an embodiment of each manufacturing process in the manufacturing method according to the present invention.
FIG. 5 is a cross-sectional view showing a DI can manufactured by the manufacturing method according to the present invention.
6 is an enlarged cross-sectional view taken along the arrow B in FIG.
[7] The manufacturing steps shown to FIG surface in the present invention outside of the manufacturing process.
[8] The present invention is produced by engagement Ru Manufacturing method, cross-sectional view showing a metal container with a screw.
[Figure 9] is produced by the engagement Ru Manufacturing method of this invention, cross-sectional view illustrating the aerosol container.
[Explanation of symbols]
1 11 Metal container 2 12 Container body 3 13 Inner surface paint 4 14 Nozzle 22 Threaded metal container 23 Small aerosol container

Claims

A cupping process for forming a metal plate into a bottomed cylindrical shape,
Ironing process to squeeze and stretch the torso,
Trimming process to cut the front end of the mouth,
Cleaning / drying process for cleaning and drying the inner surface,
Basecoat step and applying a base coat to the exterior surface of the container body
While performing the outer surface printing process to print on the base coating in this order,
Before or after the one step, the inner surface of the metal container main body, performs internal surface painting process of painting an interior paint containing epoxy acrylic copolymer resins and phenolic resins,
After the outer surface printing step or when the inner surface coating step is performed after the outer surface printing step, the mouth of the container body is squeezed to a desired outer diameter several times by a die attached to the necking machine, and then tapered. Necking process to form
Furthermore, after the necking process, a second inner surface painting process is performed on the inner surface of the mouth of the container body.
The inner surface coating used in the inner surface coating step and the second inner surface coating step ,
(A) The epoxy resin and the acrylic resin are formed by copolymerization in a weight ratio of 67:33 to 88:12;
(B) The content of an epoxy resin having a weight average molecular weight of 30000-65000 of phenoxy type is comprised of 46-55% by weight,
(C) The acrylic resin is composed of methacrylic acid, styrene and an optional copolymerization monomer, and contains 21 to 50% by weight of the optional copolymerization monomer,
(D) A paint in which the phenol resin contains 1 to 5% by weight with respect to 100% by weight of the epoxy acrylic copolymer ,
It is made uniform by dissolving or dispersing in a hydrophilic solvent,
A method for producing a metal container, comprising applying an inner surface coating in the inner surface coating step and then heating to cure .

The method of manufacturing a metal container according to claim 1, wherein a screw processing step of the mouth portion is performed after the second inner surface coating step.

The method of manufacturing a metal container according to claim 1, wherein a flange processing step of the mouth portion is performed after the second inner surface coating step.

Metal container, characterized in that said prepared in claims 1-3 or of the manufacturing method according.