JP4462722B2 - Polyester laminate for metal plate surface coating - Google Patents

Description

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２０】
【化２】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２１】
【化３】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２２】
【化４】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２３】
【化５】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２４】
【化６】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３、Ｒ４はアルキレン基であり、Ｒ１〜Ｒ４の炭素数の合計が２４〜３６の範囲にある。）
【００２５】
【化７】

（ここで、Ｒ１、Ｒ２はアルキル基、Ｒ３はアルキレン基であり、Ｒ１〜Ｒ３の炭素数の合計が２４〜３６の範囲にある。）
【００２６】
好ましい具体例としては、ユニケマ社製のＰＲＩＰＯＬ１００８（炭素数３６で、芳香族タイプ／脂環族タイプ／脂肪族タイプ＝９／５４／３７（モル％）の水添ダイマー酸）、ＰＲＩＰＯＬ１００９（炭素数３６で、芳香族タイプ／脂環族タイプ／脂肪族タイプ＝１３／６４／２３（モル％）の水添ダイマー酸）、ＰＲＩＰＯＬ１０９８（炭素数３６で、芳香族タイプ／脂環族タイプ／脂肪族タイプ＝１３／６４／２３（モル％）の未水添ダイマー酸）、さらにエステル形成性誘導体としてユニケマ社製のＰＲＩＰＬＡＳＴ３００８（ＰＲＩＰＯＬ１００８のジメチルエステル）が挙げられる。
【００２７】
［組成物］
本発明の接着層に用いられるポリエステル樹脂組成物は、エチレンテレフタレートを主体としたポリエステル樹脂（Ａ）を３０〜９０重量％、好ましくは３５〜７０重量％、特に好ましくは４０〜６０重量％、およびブチレンテレフタレートを主体とし、脂環族ダイマー酸および／または芳香族ダイマー酸を構成成分として含む共重合ポリエステル樹脂（Ｂ）が７０〜１０重量％、好ましくは６５〜３０重量％、特に好ましくは６０〜４０重量％からなるポリエステル樹脂組成物である。ポリエステル樹脂（Ａ）が３０重量％未満の場合は耐熱性とフレーバー性が不十分であり、９０重量％を超える場合は耐衝撃性と接着性が不足する。
【００２８】
［添加剤］
また本発明の接着層に用いられるポリエステル樹脂組成物には、必要に応じて他のポリマーまたは各種添加剤を添加してもよい。例えば、易滑性を向上させる無機滑剤及び有機滑剤として、カオリン、クレー、炭酸カルシウム、酸化ケイ素、テレフタル酸カルシウム、酸化アルミニウム、酸化チタン、硫酸バリウム、リン酸カルシウム、フッ化リチウム等の公知の不活性外部粒子、ポリエステル樹脂よりも高融点の有機化合物、および架橋ポリマー、さらにアルカリ金属化合物触媒等のポリマー内部に形成される内部粒子等がある。また、その他の添加剤として酸化防止剤、帯電防止剤、着色剤、耐候剤なとが挙げられる。
【００２９】
ここで、酸化防止剤は製缶工程での乾燥、印刷焼き付け等の加熱処理における樹脂組成物の熱劣化を防止し、耐衝撃性を維持するため添加することが望ましい。有用な酸化防止剤としては、ヒンダードフェノール系の有機化合物が好ましく、かかる化合物の具体例としては（化８）が例示できる。酸化防止剤の添加量は、ポリエステル樹脂組成物に対して０．０１〜０．５重量％である。添加量が０．０１重量％未満の場合、樹脂組成物の熱劣化を防止する効果がなく、また０．５重量％を超える場合、効果は上がらずフィルムの白濁が激しくなる。酸化防止剤の添加時期は、ポリエステル樹脂組成物製造工程のいずれの段階でも構わないが、ポリエステル組成物中に均一に分散されるためには、ポリエステル樹脂（Ａ）及び／またはポリエステル樹脂（Ｂ）の重合工程において添加することが好ましい。
【００３０】
【化８】

【００３１】
［ポリエステル樹脂組成物の粘度］
本発明のポリエステル樹脂組成物は、混合物として測定した極限粘度（以下ＩＶと記す）が、０．７０〜１．２ｄｌ／ｇの範囲にあることが、優れた耐衝撃性と良好なフィルム製膜性が得られるために好ましく、更に０．８〜１．０ｄｌ／ｇが特に好ましい。ＩＶが０．７０未満となる場合は、フィルム製膜性が劣り、かつ耐衝撃性が劣る。ＩＶが１．２を超える場合は、樹脂溶融押出機のトルクが上昇し、スクリューへの負荷が過大となる。
【００３２】
［ポリエステル樹脂（Ａ）、（Ｂ）の粘度］
また、上記混合物が前記範囲のＩＶを有するためには、ポリエステル樹脂（Ａ）のＩＶは０．６〜１．０ｄｌ／ｇ、更に好ましくは０．７〜０．８５ｄｌ／ｇ、ポリエステル樹脂（Ｂ）のＩＶは０．７〜２．０ｄｌ／ｇ、更に好ましくは０．８〜１．２ｄｌ／ｇの範囲とすることが好ましい。一方の樹脂のみが極端に高ＩＶであれば、混合物としてのバランスが崩れてフィルム製膜性の悪化につながるためである。
【００３３】
［製造方法］
［ポリエステルの重合方法］
本発明で用いるポリエステルは、例えばテレフタル酸、エチレングリコール（または１，４−ブタンジオール）及び共重合成分をエステル化反応させ、次いで得られる反応生成物を重縮合させてポリエステルとする方法、あるいはジメチルテレフタレート、エチレングリコール（または１，４−ブタンジオール）及び共重合成分をエステル交換反応させ、次いで得られる反応生成物を重縮合させてポリエステルとする方法等を用いて重合することができる。
【００３４】
［組成物の製造方法］
本発明の接着層に使用するポリエステル樹脂組成物の製造方法としては、従来公知の任意の方法を採用することができる。例えば、乾燥したポリエステル樹脂（Ａ）及びポリエステル樹脂（Ｂ）のチップをタンブラー等で混合し、通常の一軸または二軸押出し機を用いて溶融混合する方法、２種類の樹脂をチップの状態で混合し、これを後述する溶融押出機に供給する方法等によって製造することができる。 尚、本発明の範囲内であれば、各々２種類以上のポリエステル樹脂（Ａ）及びポリエステル樹脂（Ｂ）を用いて良いことは言うまでもない。
【００３５】
［金属板表面被覆用ポリエステル積層体］
［金属板への被覆］
本発明の金属板表面被覆用ポリエステル積層体は、ポリエステル樹脂基材層（Ｉ）とポリエステル樹脂組成物接着層（ＩＩ）とを積層した構造を有している。かかる積層構造の被覆積層体は、例えば各々の層を構成するポリエステル樹脂とポリエステル樹脂組成物を金属板上に直接溶融押出しラミネートする方法、各々の層を構成するポリエステル樹脂とポリエステル樹脂組成物を別々に溶融して、共押出し、固化前に積層融着させた積層フィルムを未延伸または延伸させた状態で金属板と貼り合わせる方法、または前記各層ポリエステル樹脂を別に溶融、押出してフィルム化し、未延伸または延伸させた状態で両者を積層融着させた後に金属板と貼り合わせる方法等により製造することが出来る。しかしながら、工程の簡略化が図れることから、金属板上に被覆積層体を直接溶融押出しラミネートする方法が好ましい。
【００３６】
［被覆層厚み］
本発明の金属板被覆用ポリエステル積層体は、好ましくは厚みが５〜６０μｍである。特に１０〜５０μｍであることが好ましい。
【００３７】
接着層の厚みは金属板の表面粗度によって異なるが、通常の滑らかな表面の場合には、安定した接着力を得るために、５μｍ以上で十分である。特に耐レトルト性や防錆性等を重視すると、１０μｍ以上が好ましい。従って基材層の厚みＴＡと接着層の厚みＴＢとの比（ＴＡ／ＴＢ）は０．２〜１．０程度が好ましく、特に好ましくは０．２５〜０．７である。具体的には、例えば被覆層の厚みが２５μｍの場合、接着層の厚みを６．２５〜１７．５μｍとすることが好ましい。
【００３８】
［金属板］
本発明のポリエステル積層体が被覆される金属板には、一般的に金属缶に使用される公知の錫メッキ鋼板（ブリキ）、錫なし鋼板（電解クロム酸処理鋼板）、アルミニウムまたはアルミニウム合金板などを用いることができる。被覆材との接着性向上のために、極性基やキレート構造を有する有機物処理やリン酸塩およびクロム酸塩処理を施しても良い。
【００３９】
［金属缶］
本発明のポリエステル積層体を被覆した金属板は、飲料用の金属缶に用いることができる。具体的には、接着ないし溶接により筒状とした缶胴に蓋と底をつけた３ピース缶、深絞り成形や絞りしごき成形によって得られる２ピース缶のいずれでも良いが、本発明のポリエステル積層体から得られるポリエステル積層体被覆金属板は、延展性や金属と被覆層の接着性が優れていることから特に２ピース缶に利用することが好ましい。
【００４０】
このようにして得られた金属缶は、優れた接着性、耐熱性、耐衝撃性、成形加工性、フレーバー性を有するためコーヒー、紅茶、ジュース、ビール等の各種飲料用の缶として好ましく使用することができる。
【００４１】
【実施例】
以下、実施例によって本発明を詳細に説明する。各物性の測定及び評価は下記の方法に従った。
【００４２】
（１）融点（Ｔｍ）
ポリエステル樹脂を結晶化させた後、示差走査熱量計（パーキン・エルマー社製ＤＳＣ−７型）により、１０℃／分の昇温速度で測定した。
【００４３】
（２）極限粘度（ＩＶ）
ポリエステル樹脂または被覆用ポリエステル積層体をフエノール／テトラクロロエタン＝６０／４０の混合溶液に溶かし、２０℃にて測定した。
【００４４】
（３）押出しラミネート性
基材層、接着層を構成するポリエステル樹脂を別々の押出し機に供給して溶融し、スリット厚み１ｍｍ、幅方向長さ３００ｍｍのＴ型ダイス内で２層化したポリエステル積層体を、予め予熱したアルミニウム板上に押出した後急冷することにより、厚さ３０〜５０μｍのポリエステル積層体層を有する被覆金属板を生産する。同様にして両面被覆金属板を作成した。得られた被覆金属板におけるポリエステル積層体層部分の幅方向長さおよび耳部揺れの有無により評価した。
◎：幅方向長さ２５０ｍｍ以上、耳部の揺れなし
○：幅方向長さ２５０ｍｍ以上、耳部の揺れややあり
△：幅方向長さ２５０ｍｍ以上、耳部の揺れあり
×：幅方向長さ２５０ｍｍ未満
【００４５】
（４）耐レトルト性
前述の被覆金属板を１３０℃で３０分間レトルト後、９０℃の水中で２週間放置した前後において被覆用ポリエステル積層体の粘度を測定し、下記式に示した粘度保持率から評価した。
粘度保持率（％）＝（処理後粘度／処理前粘度）×１００
◎：粘度保持率７０％以上
○：粘度保持率６０％以上、７０％未満
△：粘度保持率５０％以上、６０％未満
×：粘度保持率５０％未満
【００４６】
（５）成形加工性
前述の被覆金属板を直径１５０ｍｍの円板状に切り取り、絞りダイスとポンチを用いて４段階で深絞り加工し、直径６０ｍｍ、深さ７５ｍｍのツーピース缶を製造した。加工後の缶の被覆材部分について亀裂や剥離等の欠陥を観察した。
○：亀裂や剥離等の欠陥が見られない
△：一部に気泡、シワによる剥離が見られる
×：一部に破断による亀裂が見られる
【００４７】
（６）耐衝撃性（耐熱性）
成形が良好な缶について、２２０℃、６分間熱処理を行い室温まで冷却する。次いで胴部に高さ１０ｃｍから０．５ｋｇの鋼球を落とした後、被覆割れによる金属露出を電流試験により行った。
◎：０．０５ｍＡ未満
○：０．０５以上０．１ｍＡ未満
△：０．１以上１ｍＡ未満
×：１ｍＡ以上
【００４８】
（７）味特性
成形が良好な缶について、２２０℃、６分間熱処理を行い室温まで冷却する。次いでミネラルウオーターを１０缶ずつ充填して密封し、レトルト殺菌後４０℃、３ヶ月保持した。開封後、香り・味の変化を官能検査した。
○：香り・味の変化はなかった
△：香り・味が若干変化しているものが２〜３本あった
×：香り・味の変化が５本以上認められた
【００４９】
実施例１〜１４、比較例１〜８
ポリエステル樹脂（ポリエステル樹脂（Ａ））の製造方法
ステンレス製オートクレーブに、テレフタル酸ジメチルエステル及びイソフタル酸ジメチルエステルとエチレングリコールをジオール成分が酸成分に対してモル比２．０となる量を仕込み、次いでエステル交換触媒として酢酸カルシウムを添加して２３０℃にてエステル交換反応を行った。メタノールの留出が完了した後、重合触媒として三酸化アンチモンと熱安定剤としてトリメチルリン酸を加え、２８０℃減圧下で重縮合反応を行いポリエステル樹脂（ポリエステル樹脂（Ａ））を得た。
【００５０】
ポリエステル樹脂（Ｂ）の製造方法
上記のポリステル樹脂（Ａ）の場合と同様の装置を用い、脂環族ダイマー酸および／または芳香族ダイマー酸と１，４−ブタンジオールをジオール成分が酸成分に対してモル比１．４となる量を仕込み、次いでエステル交換触媒としてチタン原子換算値で３５ｐｐｍのテトラブチルチタネートを添加して２１０℃にてエステル交換反応を行った。メタノールの留出が完了した後、先ほどと同量のテトラブチルチタネートを重合触媒として、２４５℃、減圧下で重縮合反応を行い、ポリエステル樹脂（Ｂ）を得た。
【００５１】
ポリエステル積層体被覆金属板製造
表１に示すポリエステル樹脂（Ａ）と表２に示すポリエステル樹脂（Ｂ）、及び酸化防止剤としてチバガイギ社製イルガノックス１０１０を０．２重量％のブレンドよりなるポリエステル樹脂組成物が接着層に、表１に示すポリエステル樹脂が基材層となるように、それぞれを別々に乾燥して押出し機に供給して溶融し、スリット厚み１ｍｍ、幅方向長さ３００ｍｍのＴ型ダイス内で２層化した後、予め予熱したアルミニウム金属板上に押出し急冷することにより、表３および表４に示すポリエステル樹脂層厚さ２５μｍのポリエステル積層体を両面に被覆した金属板（基材層および接着層の厚みは、それぞれ１０μｍ及び１５μｍ）を製造した。こうして得られたポリエステル積層体被覆金属板を用いて、前述の評価を実施した。評価結果を表５、表６に示す。
【００５２】
【表１】

【００５３】
【表２】

【００５４】
【表３】

【００５５】
【表４】

【００５６】
【表５】

【００５７】
【表６】

【００５８】
【発明の効果】
本発明に係わる金属板被覆用ポリエステル積層体は、金属板との接着性、金属缶への成形加工性に優れ、かかるポリエステル積層体を被覆したラミネート鋼板からなる金属缶は耐レトルト性、耐衝撃性、味特性に優れ、コーヒー、紅茶、ジュース、ビール等の各種飲料用途に使用するのに好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester laminate for coating a metal plate surface that is excellent in retort resistance, heat resistance, impact resistance, molding processability, and flavor properties, and is suitable for a metal can for beverages produced by molding process. .
[0002]
[Prior art]
Conventionally, for the coating of the inner and outer surfaces of a metal can, a method of applying various thermosetting resin paints such as epoxy type and phenol type in order to prevent corrosion and metal elution to the contents is generally used. However, such a method of applying a thermosetting resin requires a long time for drying the thermosetting resin paint, and a squeezed iron can requires a water washing step with a large amount of water, resulting in a decrease in productivity. However, there are problems such as carbon dioxide emission due to exhaustion of a large amount of organic solvent.
[0003]
As a method for solving these problems, there has been proposed a method of manufacturing a metal can by laminating a pre-manufactured polyester film on a steel plate, an aluminum plate, or a metal plate subjected to plating treatment, and then forming the metal film. . For example, a copolymer polyester film having a specific density and plane orientation coefficient (Japanese Patent Laid-Open No. 64-22530), a copolymer polyester film having a specific crystallinity (Japanese Patent Laid-Open No. 2-57339), and the like can be used in a metal can. A method of bonding is disclosed. However, since these methods use a single-layer polyester film, when thermally bonded to a metal plate at a temperature equal to or higher than the melting point of the polyester resin constituting the film, the film is broken (cracked) by impact during can manufacturing. appear. Moreover, when thermally bonded at a temperature below the melting point, the occurrence of cracks due to impact during canning is suppressed, but the adhesion to the metal plate is insufficient and the film peels off.
[0004]
In order to solve such problems, a method of laminating a composite film composed of two layers of a base layer made of polyester having a high melting point and an adhesive layer made of polyester having a low melting point (Japanese Patent Laid-Open No. 2-81630, JP-A-7-1693, JP-A-7-47650, JP-A-9-150492) are disclosed. According to these methods, a satisfactory evaluation has been obtained for the corrosion resistance as a beverage can, but it is still possible to further improve the adhesion of the film to the metal substrate and to handle the high-speed can. There is a need for further improvement. In order to further improve the preservability of the contents to be filled, after retort sterilization, improvement of high temperature and humidity resistance to withstand aging, improvement of impact resistance after retort sterilization, after retort sterilization and impact Improvement of corrosion resistance is an important technical issue.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the prior art, and is excellent in retort resistance, heat resistance, impact resistance, molding processability and flavor properties, and suitable for a metal can for beverages produced by molding process. Another object of the present invention is to provide a polyester laminate for covering a metal plate surface.
[0006]
[Means for Solving the Problems]
The purpose is to form a base layer (I) made of polyester mainly composed of ethylene terephthalate, 30 to 90% by weight of polyester (A) mainly composed of ethylene terephthalate, and alicyclic dimer mainly composed of butylene terephthalate as a structural unit. It is characterized by comprising an adhesive layer (II) comprising a polyester composition comprising 70 to 10% by weight of a copolyester (B) containing 3 to 8 mol% of an acid and / or aromatic dimer acid component. This is achieved by a polyester film for coating a metal plate surface.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
[Polyester resin]
The polyester resin used in the substrate layer in the present invention is a saturated polyester resin composed of a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol, and has a melting point of 220 ° C. or higher from the viewpoint of heat resistance. It is preferable that A melting point of 220 ° C. or higher is preferable because it can sufficiently withstand the heat treatment during printing and baking in the can making process and is excellent in impact resistance.
[0008]
Examples of dicarboxylic acid components other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and cyclohexanedicarboxylic acid. An alicyclic dicarboxylic acid can be illustrated. Examples of the diol component other than ethylene glycol include aliphatic diols such as propanediol and butanediol, neopentyl glycol, cyclohexanedimethanol, polyalkylene glycol, bisphenol A or bisphenol S diethoxy compound. These can be used alone or in combination of two or more.
[0009]
Among these, as a preferable polyester resin, a polyethylene terephthalate resin composed of terephthalic acid and ethylene glycol, and a copolymerized polyethylene terephthalate resin to which isophthalic acid is added as a third component are preferably used, and the polymerization reaction is easy to proceed at low cost. This is preferable. When isophthalic acid is used as the third component, the copolymerization ratio is preferably 15 mol% or less in order to satisfy the melting point range described above.
[0010]
Further, when the intrinsic viscosity (hereinafter referred to as IV) of the polyester resin is in the range of 0.6 to 1.2 dl / g, the film-forming property of the coated polyester laminate (film) excellent in impact resistance can be obtained. Therefore, 0.7 to 0.8 dl / g is particularly preferable. When IV is less than 0.6, the film-forming property is inferior, and when it exceeds 1.2, the torque during film formation increases and the screw load becomes excessive.
[0011]
[Polyester resin (A)]
The polyester resin (A) used for the adhesive layer in the present invention is a polyester resin mainly composed of terephthalic acid and ethylene glycol, and preferably has a melting point of 220 ° C. or higher. A melting point of 220 ° C. or higher is preferable because it can withstand the heat treatment during drying and printing baking in the can-making process.
[0012]
The polyester resin (A) of the present invention may be a homopolymer, but a copolymer component may be used depending on the purpose. Specific examples of compounds that can be used include dicarboxylic acids such as adipic acid, oxalic acid, malonic acid, succinic acid, azelaic acid, sebacic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, cyclohexanedicarboxylic acid, and dimer acid. Examples include acids and diol components such as butanediol, neopentyl glycol, propylene glycol, hexamethylene glycol, cyclohexanedimethanol, polyalkylene glycol, bisphenol A or bisphenol S diethoxy compounds.
[0013]
Among these, preferred copolymer components include aromatic dicarboxylic acid components such as isophthalic acid, naphthalene dicarboxylic acid, and diphenyl carboxylic acid, and are preferably used because of excellent thermal stability and flavor properties. Particularly, among these aromatic dicarboxylic acid components, isophthalic acid is preferably used, and it is preferable because it is inexpensive and the polymerization reaction easily proceeds. When isophthalic acid is used, the copolymerization ratio is preferably 15 mol% or less in order to satisfy the aforementioned melting point range.
[0014]
[Crosslinking agent]
Furthermore, in the polyester resin (A) of the present invention, in order to improve the film forming property of the polyester laminate (film) for coating a metal plate surface, three ester bond-forming functional groups per molecule or It is more preferable to add 4 polyfunctional compounds (hereinafter referred to as polyfunctional compounds). A polyfunctional compound is a compound that reacts with a carboxyl group and a hydroxyl group in a polyester molecular chain to form an ester bond, and is a compound having a carboxyl group, a hydroxyl group, a methyl ester group, and an ethyl ester group. By adding a compound containing 3 to 4 such functional groups, a crosslinked structure is formed in the polyester molecular chain, and the film-forming property is improved.
[0015]
Specific examples of polyfunctional compounds include trimellitic acid, trimesic acid, pyromellitic acid and their anhydrides, polyfunctional acids such as trimethylolpropane, pentaerythritol, alcohols, and the like. From the viewpoint of the effect of improving film formability, the content is preferably 0.1 to 2.0 mol%, more preferably 0.2 to 0.5 mol%, based on the total amount of the polymer.
[0016]
[Copolymerized polyester resin (B)]
The copolymer polyester resin (B) used for the adhesive layer in the present invention comprises terephthalic acid and 1,4-butanediol as main constituent components, and alicyclic dimer acid and / or aromatic dimer acid as a copolymer component. It is a polyester resin containing 3 to 8 mol% with respect to the acid component. If the copolymerization ratio of the alicyclic dimer acid and / or aromatic dimer acid is less than 3 mol%, the polyester laminate (film) for coating the surface of the metal plate will be poor in flexibility, so that good impact resistance and Workability cannot be obtained. On the other hand, if it exceeds 8 mol%, the heat resistance becomes insufficient, and troubles such as adhesion of the resin to the cooling roll during film formation tend to occur. Further, the copolymer polyester resin (B) containing an alicyclic dimer acid and / or an aromatic dimer acid component is excellent in hydrolysis resistance, and a polyester laminate for coating a metal plate excellent in retort resistance can be obtained. .
[0017]
The copolymer polyester resin (B) containing the alicyclic dimer acid and / or aromatic dimer acid component of the present invention preferably has a melting point of 200 ° C. or higher and 220 ° C. or lower, and 210 ° C. or higher and 220 ° C. or lower. Is more preferable. A melting point within this range is preferable because it has sufficient heat resistance, less trouble occurs during film formation, and adhesion between the polyester laminate and the metal plate is improved.
[0018]
The alicyclic dimer acid and / or aromatic dimer acid used as a copolymerization component of the copolymer polyester resin (B) used in the present invention is trimer acid by separation from a low polymer of unsaturated fatty acid using a clay catalyst. Obtained after removing by-products such as monomeric acids. The dimer acid obtained by such a method includes an alicyclic dimer acid represented by (Chemical Formula 1), (Chemical Formula 2), (Chemical Formula 3), and (Chemical Formula 4), and an aroma represented by (Chemical Formula 5). In addition to the group dimer acid, the aliphatic dimer acid represented by (Chemical Formula 6) and (Chemical Formula 7) is also included, but the content is preferably less than 50 mol% of the total dimer acid, and 30 mol More preferably, it is less than%. When the content of the aliphatic dimer acid is 50 mol% or more, the hydrolysis resistance of the obtained polyester laminate for covering a metal plate surface is lowered.
[0019]
[Chemical 1]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0020]
[Chemical formula 2]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0021]
[Chemical 3]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0022]
[Formula 4]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0023]
[Chemical formula 5]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0024]
[Chemical 6]

(Here, R1 and R2 are alkyl groups, R3 and R4 are alkylene groups, and the total number of carbon atoms of R1 to R4 is in the range of 24 to 36.)
[0025]
[Chemical 7]

(Here, R1 and R2 are alkyl groups, R3 is an alkylene group, and the total number of carbon atoms of R1 to R3 is in the range of 24 to 36.)
[0026]
Preferred examples include PRIPOL 1008 (hydrogenated dimer acid having 36 carbon atoms, aromatic type / alicyclic type / aliphatic type = 9/54/37 (mol%)), PRIPOL 1009 (carbon number). 36, aromatic type / alicyclic type / aliphatic type = hydrogenated dimer acid of 13/64/23 (mol%)), PRIPOL 1098 (C36, aromatic type / alicyclic type / aliphatic) Type = 13/64/23 (mol%) non-hydrogenated dimer acid), and as an ester-forming derivative, PRIKLAST 3008 (dimethyl ester of PRIPOL 1008) manufactured by Unikema Corporation may be mentioned.
[0027]
[Composition]
The polyester resin composition used for the adhesive layer of the present invention comprises 30 to 90% by weight, preferably 35 to 70% by weight, particularly preferably 40 to 60% by weight, of the polyester resin (A) mainly composed of ethylene terephthalate, and The copolymer polyester resin (B) mainly composed of butylene terephthalate and containing alicyclic dimer acid and / or aromatic dimer acid as a constituent component is 70 to 10% by weight, preferably 65 to 30% by weight, particularly preferably 60 to 60%. This is a polyester resin composition comprising 40% by weight. When the polyester resin (A) is less than 30% by weight, the heat resistance and flavor properties are insufficient, and when it exceeds 90% by weight, the impact resistance and adhesion are insufficient.
[0028]
[Additive]
Moreover, you may add another polymer or various additives to the polyester resin composition used for the contact bonding layer of this invention as needed. For example, as inorganic lubricants and organic lubricants that improve easy lubrication, known inert external materials such as kaolin, clay, calcium carbonate, silicon oxide, calcium terephthalate, aluminum oxide, titanium oxide, barium sulfate, calcium phosphate, lithium fluoride, etc. There are particles, organic compounds having a higher melting point than the polyester resin, cross-linked polymers, and internal particles formed inside a polymer such as an alkali metal compound catalyst. Other additives include antioxidants, antistatic agents, colorants, weathering agents and the like.
[0029]
Here, it is desirable to add the antioxidant in order to prevent thermal deterioration of the resin composition in the heat treatment such as drying and printing baking in the can making process and to maintain impact resistance. As a useful antioxidant, a hindered phenol-based organic compound is preferable, and a specific example of such a compound is (Chemical Formula 8). The addition amount of antioxidant is 0.01 to 0.5 weight% with respect to the polyester resin composition. When the addition amount is less than 0.01% by weight, there is no effect of preventing thermal deterioration of the resin composition, and when it exceeds 0.5% by weight, the effect does not increase and the film becomes turbid. The antioxidant may be added at any stage in the production process of the polyester resin composition, but in order to be uniformly dispersed in the polyester composition, the polyester resin (A) and / or the polyester resin (B) It is preferable to add in the polymerization step.
[0030]
[Chemical 8]

[0031]
[Viscosity of polyester resin composition]
The polyester resin composition of the present invention has excellent impact resistance and good film formation that the intrinsic viscosity (hereinafter referred to as IV) measured as a mixture is in the range of 0.70 to 1.2 dl / g. In view of obtaining good properties, 0.8 to 1.0 dl / g is particularly preferable. When IV is less than 0.70, the film-forming property is inferior and the impact resistance is inferior. When IV exceeds 1.2, the torque of the resin melt extruder increases and the load on the screw becomes excessive.
[0032]
[Viscosity of polyester resins (A) and (B)]
Moreover, in order for the said mixture to have IV of the said range, IV of polyester resin (A) is 0.6-1.0 dl / g, More preferably, 0.7-0.85 dl / g, polyester resin (B ) In the range of 0.7 to 2.0 dl / g, more preferably 0.8 to 1.2 dl / g. This is because if only one resin is extremely high IV, the balance as a mixture is lost and the film-forming property is deteriorated.
[0033]
[Production method]
[Polyester polymerization method]
The polyester used in the present invention is, for example, a method in which terephthalic acid, ethylene glycol (or 1,4-butanediol) and a copolymer component are esterified and then the resulting reaction product is polycondensed to form a polyester, or dimethyl Polymerization can be carried out by a method of transesterifying terephthalate, ethylene glycol (or 1,4-butanediol) and a copolymer component, and then polycondensing the resulting reaction product to obtain a polyester.
[0034]
[Method for producing composition]
Any conventionally known method can be employed as a method for producing the polyester resin composition used in the adhesive layer of the present invention. For example, a method of mixing dried polyester resin (A) and polyester resin (B) chips with a tumbler, etc., and melt-mixing them using a normal single-screw or twin-screw extruder, and mixing two kinds of resins in the form of chips And it can manufacture by the method etc. which supply this to the melt extruder mentioned later. Needless to say, two or more kinds of polyester resins (A) and polyester resins (B) may be used within the scope of the present invention.
[0035]
[Polyester laminate for metal plate surface coating]
[Coating on metal plate]
The polyester laminate for covering a metal plate surface of the present invention has a structure in which a polyester resin substrate layer (I) and a polyester resin composition adhesive layer (II) are laminated. For example, a coated laminate having such a laminated structure is obtained by, for example, directly melting and laminating a polyester resin and a polyester resin composition constituting each layer on a metal plate, and separately forming the polyester resin and the polyester resin composition constituting each layer. A method of laminating and co-extrusion, laminating and laminating the laminated film before solidification and bonding it to a metal plate in an unstretched or stretched state, or by separately melting and extruding each layer polyester resin to form a film and unstretched Alternatively, it can be produced by a method of laminating and fusing both in the stretched state and then bonding them to a metal plate. However, since the process can be simplified, a method in which the coated laminate is directly melt-extruded and laminated on a metal plate is preferable.
[0036]
[Coating layer thickness]
The polyester laminate for covering a metal plate of the present invention preferably has a thickness of 5 to 60 μm. In particular, the thickness is preferably 10 to 50 μm.
[0037]
The thickness of the adhesive layer varies depending on the surface roughness of the metal plate, but in the case of a normal smooth surface, 5 μm or more is sufficient to obtain a stable adhesive force. In particular, when the emphasis is on retort resistance and rust prevention, 10 μm or more is preferable. Therefore, the ratio (TA / TB) of the thickness TA of the base material layer to the thickness TB of the adhesive layer is preferably about 0.2 to 1.0, and particularly preferably 0.25 to 0.7. Specifically, for example, when the thickness of the coating layer is 25 μm, the thickness of the adhesive layer is preferably 6.25 to 17.5 μm.
[0038]
[Metal plate]
Examples of the metal plate coated with the polyester laminate of the present invention include known tin-plated steel plates (tinplates), tin-free steel plates (electrochromated steel plates), aluminum or aluminum alloy plates that are generally used for metal cans. Can be used. In order to improve adhesiveness with the coating material, treatment with an organic substance having a polar group or a chelate structure, or treatment with phosphate and chromate may be performed.
[0039]
[Metal can]
The metal plate which coat | covered the polyester laminated body of this invention can be used for the metal can for drinks. Specifically, it may be either a three-piece can with a lid and bottom attached to a cylindrical can body by bonding or welding, or a two-piece can obtained by deep drawing molding or drawing ironing. The polyester laminate-coated metal plate obtained from the body is particularly preferably used for a two-piece can because of its excellent spreadability and adhesion between the metal and the coating layer.
[0040]
The metal can thus obtained is preferably used as a can for various beverages such as coffee, tea, juice and beer because it has excellent adhesiveness, heat resistance, impact resistance, molding processability and flavor properties. be able to.
[0041]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. The measurement and evaluation of each physical property followed the following method.
[0042]
(1) Melting point (Tm)
After the polyester resin was crystallized, the polyester resin was measured with a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer Co.) at a heating rate of 10 ° C./min.
[0043]
(2) Intrinsic viscosity (IV)
The polyester resin or the polyester laminate for coating was dissolved in a mixed solution of phenol / tetrachloroethane = 60/40 and measured at 20 ° C.
[0044]
(3) Polyester laminate in which the polyester resin constituting the extrusion laminating base material layer and the adhesive layer is supplied to separate extruders and melted to form two layers in a T-shaped die having a slit thickness of 1 mm and a width direction length of 300 mm. The body is extruded onto a pre-heated aluminum plate and then rapidly cooled to produce a coated metal plate having a polyester laminate layer with a thickness of 30-50 μm. Similarly, a double-sided coated metal plate was prepared. It evaluated by the width direction length of the polyester laminated body layer part in the obtained covering metal plate, and the presence or absence of the ear | edge part shaking.
◎: width direction length 250 mm or more, no ear part shake ○: width direction length 250 mm or more, ear part shake slightly Δ: width direction length 250 mm or more, ear part shake x: width direction length 250 mm Less than [0045]
(4) Retort resistance After the above-mentioned coated metal plate was retorted at 130 ° C. for 30 minutes, the viscosity of the coated polyester laminate was measured before and after being left in 90 ° C. water for 2 weeks. It was evaluated from.
Viscosity retention (%) = (viscosity after treatment / viscosity before treatment) × 100
A: Viscosity retention 70% or more B: Viscosity retention 60% or more, less than 70% Δ: Viscosity retention 50% or more, less than 60% ×: Viscosity retention 50% or less
(5) Formability The above-mentioned coated metal plate was cut into a disk shape having a diameter of 150 mm and deep-drawn in four stages using a drawing die and a punch to produce a two-piece can having a diameter of 60 mm and a depth of 75 mm. Defects such as cracks and delamination were observed on the covering portion of the can after processing.
○: Defects such as cracks and delamination are not observed Δ: Partial delamination due to bubbles and wrinkles is observed X: Partial cracks due to fracture are observed
(6) Impact resistance (heat resistance)
A can with good molding is heat-treated at 220 ° C. for 6 minutes and cooled to room temperature. Next, a steel ball having a height of 10 cm to 0.5 kg was dropped on the body, and then metal exposure by coating cracking was performed by a current test.
◎: Less than 0.05 mA ○: 0.05 or more and less than 0.1 mA Δ: 0.1 or more and less than 1 mA x: 1 mA or more
(7) A can with good taste characteristic molding is heat-treated at 220 ° C. for 6 minutes and cooled to room temperature. Then, 10 cans of mineral water were filled and sealed, and kept at 40 ° C. for 3 months after retort sterilization. After opening, sensory inspection was performed for changes in aroma and taste.
○: There was no change in fragrance and taste. △: There were 2-3 fragrances and tastes slightly changed. X: Five or more fragrance and taste changes were observed.
Examples 1-14, Comparative Examples 1-8
Method for producing polyester resin (polyester resin (A)) In a stainless steel autoclave, dimethyl terephthalate and dimethyl isophthalate and ethylene glycol were charged in an amount such that the diol component had a molar ratio of 2.0 to the acid component, Calcium acetate was added as a transesterification catalyst, and a transesterification reaction was performed at 230 ° C. After the distillation of methanol was completed, antimony trioxide as a polymerization catalyst and trimethyl phosphoric acid as a heat stabilizer were added, and a polycondensation reaction was performed at 280 ° C. under reduced pressure to obtain a polyester resin (polyester resin (A)).
[0050]
Method for producing polyester resin (B) Using the same apparatus as in the case of the polyester resin (A), the diol component is an alicyclic dimer acid and / or aromatic dimer acid and 1,4-butanediol as the acid component. In contrast, an amount of a molar ratio of 1.4 was charged, and 35 ppm of tetrabutyl titanate in terms of titanium atom was added as a transesterification catalyst, and a transesterification reaction was performed at 210 ° C. After the distillation of methanol was completed, a polycondensation reaction was performed at 245 ° C. under reduced pressure using the same amount of tetrabutyl titanate as the polymerization catalyst to obtain a polyester resin (B).
[0051]
Polyester laminate-coated metal sheet production Polyester resin comprising a blend of 0.2% by weight of polyester resin (A) shown in Table 1 and polyester resin (B) shown in Table 2 and Irganox 1010 manufactured by Ciba-Gigi Co., Ltd. as an antioxidant. The composition is applied to the adhesive layer, and the polyester resin shown in Table 1 is used as the base material layer. Each is dried separately, supplied to an extruder and melted, and is T-shaped having a slit thickness of 1 mm and a width direction length of 300 mm. After forming two layers in a die, a metal plate (base material) coated on both sides with a polyester laminate having a polyester resin layer thickness of 25 μm shown in Table 3 and Table 4 by extrusion and quenching on a preheated aluminum metal plate. The thickness of the layer and the adhesive layer was 10 μm and 15 μm, respectively. The above-described evaluation was carried out using the polyester laminate-coated metal plate thus obtained. The evaluation results are shown in Tables 5 and 6.
[0052]
[Table 1]

[0053]
[Table 2]

[0054]
[Table 3]

[0055]
[Table 4]

[0056]
[Table 5]

[0057]
[Table 6]

[0058]
【The invention's effect】
The polyester laminate for coating a metal plate according to the present invention is excellent in adhesion to a metal plate and moldability into a metal can, and a metal can comprising a laminated steel plate coated with such a polyester laminate is resistant to retort and impact. It has excellent properties and taste characteristics and is suitable for use in various beverage applications such as coffee, tea, juice and beer.

Claims (2)

  A base layer (I) made of a polyester resin mainly composed of ethylene terephthalate, 30 to 90% by weight of a polyester resin (A) mainly composed of ethylene terephthalate, and an alicyclic dimer acid as a structural unit mainly composed of butylene terephthalate and And / or an adhesive layer (II) comprising a polyester resin composition containing 70 to 10% by weight of a copolyester resin (B) containing 3 to 8 mol% of an aromatic dimer acid component. A polyester laminate for covering a metal plate surface. The metal according to claim 1, wherein the polyester resin (A) is a polyester resin containing 0.1 to 2.0 mol% of a compound having 3 or 4 ester bond-forming functional groups and mainly composed of ethylene terephthalate. Polyester laminate for board surface coating.