【発明の詳細な説明】[Detailed description of the invention]
本発明は密着性の優れた金属用クリヤー焼付塗
料に関する。罐詰容器王冠、キヤツプ、玩具、家
電製品等の金属製品は、その装飾と表面保護の目
的で、熱硬化性樹脂によるクリヤー焼付塗料を施
す場合が多い。これらの製品で最も必要な性能は
塗膜表面の傷付に対する性能である。塗膜の耐熱
傷付性を向上させるために、一般的に塗料樹脂の
組成を調整し、塗膜の表面硬度を高くする方法が
とられている。ところが、塗膜と金属の鋭利な部
分との衡突が起る場合、例えば、ガラスびんに王
冠を打栓する際のホツパー中での王冠塗膜と王冠
エツヂ部の衡突、あるいは罐詰容器の輸送の際の
罐胴塗膜とフランジ部との衝突のような場合に
は、塗膜の表面硬度にかかわらず、傷付は起り、
むしろ硬い塗膜では傷付いた部分の塗膜が剥離し
やすく、外観上の問題と共に剥離した塗膜が容器
中に混入する等の問題がある。このような問題を
解決するためには従来は、剥離しにくいように塗
膜硬度を下げる方法がとられていたが、この方法
では製品使用中の傷付性が悪く、また耐汚染性が
悪くなるという欠点があり、塗膜硬度、耐汚染
性、金属の鋭利な部分との衡突による塗膜の剥離
性を備えた塗料の開発が要望されていた。
本発明者等はこれらの問題を解決するための研
究を重ねた結果、塗膜硬度、耐汚染性の優れた金
属用焼付塗料に有機酸を配合することにより塗膜
−金属間の密着性を著しく向上し、金属の鋭利な
部分との衡突による塗膜の剥離が極めて起こりに
くくなることを見出した。
即ち本発明は金属用クリヤー焼付塗料におい
て、熱硬化性樹脂100重量部に対し、焼付温度以
上の沸点を有する有機酸0.05〜3.0重量部を配合
することを特徴とする金属用焼付塗料組成物
本発明において金属用焼付塗料は（変性）アル
キツド樹脂−アミノ樹脂系塗料、（変性）エポキ
シエステル樹脂−アミノ樹脂系塗料、アクリル樹
脂−アミノ樹脂系塗料、エポキシ樹脂−アミノ樹
脂系塗料、エポキシ樹脂−フエノール樹脂系塗料
等公知の熱硬化性樹脂からなる金属用焼付塗料が
用いられ、これら塗料は有機溶剤に溶解あるいは
分散していてもよく、また、水−有機溶剤系に溶
解、分散していてもよい。
本発明の重要な特徴である有機酸は、安息香
酸、セバシン酸無水マレイン酸、無水フタル酸、
テレフタル酸、イタコン酸、フマール酸、アジピ
ン酸等、脂肪族、芳香族、あるいは、飽和酸、不
飽和酸、一塩基酸、多塩基酸を使用することがで
きる。これらの有機酸は、塗装、焼付によつて塗
膜−金属界面に吸着することにより、密着性を向
上させることが考えられる。又、一部は塗膜表面
にも吸着され、塗膜表面の流れ、光沢をも向上さ
せる。有機酸の配合量は、熱硬化性塗料樹脂100
重量部に対して0.05重量部以下では著しい効果は
みられず、また３重量部以上では、耐水性等他の
物に悪影響を与えると共に、密着性も除々に低下
していくので0.05〜3.0重量部の範囲が望ましい
が特に望ましい配合は、0.2〜0.8重量部である。
またこれら有機酸と共にエポキシ樹脂を前記塗料
樹脂100重量部に対して２〜10重量部併用すると
密着性はさらに向上し、金属の鋭利な部分と衡突
した時の塗膜の剥離に特に有効である。尚、本発
明に係わる塗料は、常法により塗装することがで
き、焼付温度が140〜240℃ぐらいの範囲にある。
かくして本発明は、塗膜と金属の鋭利な部分と
の衡突の起りやすい、王冠、罐詰容器、玩具、家
電製品等の塗料として特に有用であると共に、表
面硬度と密着性の優れた性質を利用して、建材用
鋼板、自動車等他の金属用塗装材料としても有用
である。
以上本発明を比較例、実施例で具体的に説明す
る、例中部は重量部を示す。
比較例 １
表１に示す配合でアルキツド：メラミンが50：
50のアルキツド−メラミン塗料を作成した。固形
分53％粘度（25℃＃４フオードカツプ）70秒であ
つた。この塗料をブリキ板（＃50ET）上にロー
ルコートで塗膜量80mg/dm2に塗装し、180℃で10
分間焼付けた。得られた塗装板について光沢（60
゜鏡面反射率）、密着性（ごばん目テスト、セロ
ハンテープはくり）、汚染性（赤マジツク、ブタ
ノール拭き）鉛筆硬さ（三菱ユニ）金属の鋭利な
部分との衡突、による塗膜の剥離（以下衡突塗膜
剥離性とする。５×５cmの塗装板を円筒状に丸め
た試料20個と打抜直後の王冠シエル100個を直径
20cm 長さ40cmの円筒内に入れ、200回左右に振
つた後の塗膜の減量）について試験を行つた。結
果は表２に示す。
比較例 ２
表１に示す配合で アルキツド：メラミンが
70：30のアルキツド−メラミン塗料を作成した。
固形分50％粘度72秒であつた。この塗料を比較例
１と同様に塗装、焼付を行い試験をした。結果は
表２に示す通り比較例１にくらべ、衡突塗膜剥離
性は向上しているが、鉛筆硬さ、汚染性は悪い。
実施例 １
表１に示す配合で アルキツド：メラミンが
50：50で無水マレイン酸を配合したアルキツド−
メラミン塗料を作成した。固形分54％粘度70秒で
あつた。比較例１と同様に塗装、焼付および試験
を行つた。結果は表２に示す通り、比較例１にく
らべ、光沢密着性衡突塗膜剥離性が向上し、他は
同等である。
比較例 ３
表１に示す配合で、アクリル：メラミンが50：
50のアクリル−メラミン塗料を作成した。固形分
46％、粘度70秒であつた。比較例１と同様に塗
装、焼付および試験を行つた。結果は表２に示
す。
比較例 ４
表１に示す配合で、アクリル：メラミンが70：
30のアクリル−メラミン塗料を作成した。固形分
42％粘度72秒であつた。比較例１と同様に塗装、
焼付および試験を行つた。結果は表２に示すよう
に比較例３にくらべて衡突塗膜剥離性、密着性は
向上しているが鉛筆硬度、汚染性が劣つている。
実施例 ２
表１の配合でアクリル：メラミンが50：50のア
ジピン酸を配合したアクリル−メラミン塗料を作
成した。固形分46％粘度70秒であつた。比較例１
と同様に塗装、焼付および試験を行つた。結果は
表２に示す通り、比較例３に比べ衡突塗膜剥離
性、密着性が向上し、他の物性は変らない。
実施例 ３
表１の配合で、実施例３にエポキシ樹脂を５％
添加した塗料を作成し、比較例１と同様に塗装、
焼付および試験を行つた。結果は表２に示す通
り、実施例２よりもさらに衡突塗膜剥離性に優れ
ている。
The present invention relates to a clear baking paint for metals with excellent adhesion. Metal products such as canned container crowns, caps, toys, and home appliances are often coated with clear baking paint made from thermosetting resin for the purpose of decoration and surface protection. The most important performance for these products is resistance to scratches on the coating surface. In order to improve the heat damage resistance of a paint film, a method is generally used in which the composition of the paint resin is adjusted to increase the surface hardness of the paint film. However, if collision occurs between the coating film and a sharp metal part, for example, collision between the crown coating film and the edge of the crown in the hopper when capping a glass bottle, or the collision of the crown coating with the edge of the crown when capping a glass bottle. In cases such as a collision between the can body coating and the flange during transportation, damage may occur regardless of the surface hardness of the coating.
On the contrary, if the paint film is hard, the paint film is likely to peel off in the damaged area, causing problems such as not only the appearance but also the peeled paint film getting mixed into the container. In order to solve this problem, conventional methods have been used to reduce the hardness of the paint film to make it less likely to peel off, but this method results in poor scratch resistance during product use and poor stain resistance. There has been a need to develop a paint that has hardness, stain resistance, and removability when it comes into contact with sharp metal parts. As a result of repeated research to solve these problems, the inventors of the present invention have improved the adhesion between the coating film and the metal by blending an organic acid into a baking paint for metals that has excellent coating hardness and stain resistance. It has been found that the coating film is significantly improved, and peeling of the coating film due to collision with sharp metal parts becomes extremely difficult to occur. That is, the present invention provides a clear baking paint composition for metals, characterized in that 0.05 to 3.0 parts by weight of an organic acid having a boiling point higher than the baking temperature is blended with 100 parts by weight of a thermosetting resin. In the invention, baking paints for metals include (modified) alkyd resin-amino resin paints, (modified) epoxy ester resin-amino resin paints, acrylic resin-amino resin paints, epoxy resin-amino resin paints, and epoxy resin-phenol paints. Metal baking paints made of known thermosetting resins such as resin paints are used, and these paints may be dissolved or dispersed in an organic solvent, or may be dissolved or dispersed in a water-organic solvent system. good. The organic acids that are important features of the present invention include benzoic acid, sebacic acid, maleic anhydride, phthalic anhydride,
Aliphatic, aromatic, saturated, unsaturated, monobasic, and polybasic acids such as terephthalic acid, itaconic acid, fumaric acid, and adipic acid can be used. It is thought that these organic acids improve adhesion by adsorbing to the coating film-metal interface during painting and baking. A part of it is also adsorbed on the surface of the coating film, improving the flow and gloss of the coating surface. The amount of organic acid blended is 100% of the thermosetting paint resin.
If it is less than 0.05 parts by weight, no significant effect will be seen, and if it is more than 3 parts by weight, it will have a negative effect on other things such as water resistance, and the adhesion will gradually decrease. A particularly preferred formulation is 0.2 to 0.8 parts by weight.
In addition, when 2 to 10 parts by weight of epoxy resin is used in combination with these organic acids based on 100 parts by weight of the paint resin, the adhesion is further improved and is particularly effective for peeling off the paint film when it collides with sharp parts of metal. be. The paint according to the present invention can be applied by a conventional method, and has a baking temperature in the range of about 140 to 240°C. Thus, the present invention is particularly useful as a paint for crowns, canned containers, toys, home appliances, etc., where collisions between the paint film and sharp metal parts are likely to occur, and the present invention has excellent surface hardness and adhesion properties. It is also useful as a coating material for other metals such as steel plates for building materials and automobiles. The present invention will be specifically explained using comparative examples and examples. The middle part of each example indicates parts by weight. Comparative Example 1 In the formulation shown in Table 1, alkyd: melamine was 50:
50 alkyd-melamine paints were made. The solid content was 53% and the viscosity was 70 seconds (25°C #4 food cup). This paint was roll-coated onto a tin plate (#50ET) to a coating amount of 80mg/ dm2 , and heated at 180℃ for 10 minutes.
Bake for a minute. About the resulting painted board gloss (60
゜Specular reflectance), adhesion (eye test, cellophane tape peeling), contamination (red marker, butanol wiping), pencil hardness (Mitsubishi Uni), coating film due to collision with sharp metal parts. Peeling (hereinafter referred to as "balanced coating peelability").20 samples made by rolling 5 x 5 cm painted plates into cylindrical shapes and 100 crown shells immediately after punching.
A test was conducted on the weight loss of the coating film after placing it in a cylinder with a length of 20 cm and a length of 40 cm and shaking it from side to side 200 times. The results are shown in Table 2. Comparative Example 2 In the formulation shown in Table 1, alkyd: melamine was
A 70:30 alkyd-melamine paint was created.
The solid content was 50% and the viscosity was 72 seconds. This paint was painted and baked in the same manner as in Comparative Example 1, and tested. The results are shown in Table 2, as compared to Comparative Example 1, the uniform coating removability was improved, but the pencil hardness and staining properties were poor. Example 1 In the formulation shown in Table 1, alkyd: melamine was
Alkyd with 50:50 maleic anhydride
Created melamine paint. The solid content was 54% and the viscosity was 70 seconds. Painting, baking and testing were carried out in the same manner as in Comparative Example 1. The results are shown in Table 2, as compared to Comparative Example 1, the gloss adhesion, uniform coating removability were improved, and other things were the same. Comparative Example 3 With the formulation shown in Table 1, acrylic: melamine was 50:
Fifty acrylic-melamine paints were created. Solid content
46%, viscosity 70 seconds. Painting, baking and testing were carried out in the same manner as in Comparative Example 1. The results are shown in Table 2. Comparative Example 4 With the formulation shown in Table 1, acrylic: melamine was 70:
Thirty acrylic-melamine paints were created. Solid content
The 42% viscosity was 72 seconds. Painted in the same manner as Comparative Example 1,
Baked and tested. The results are shown in Table 2. Compared to Comparative Example 3, the uniform coating removability and adhesion were improved, but the pencil hardness and staining properties were inferior. Example 2 An acrylic-melamine paint containing adipic acid in a ratio of acrylic to melamine of 50:50 was prepared as shown in Table 1. The solid content was 46% and the viscosity was 70 seconds. Comparative example 1
Painting, baking and testing were carried out in the same manner as above. The results are shown in Table 2, as compared to Comparative Example 3, the uniform peelability and adhesion of the coating film were improved, and the other physical properties remained unchanged. Example 3 With the formulation shown in Table 1, 5% epoxy resin was added to Example 3.
A paint containing the additive was prepared and painted in the same manner as in Comparative Example 1.
Baked and tested. As shown in Table 2, the results are even better than in Example 2 in terms of balanced coating removability.
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