JPH0325515B2 - - Google Patents
Info
- Publication number
- JPH0325515B2 JPH0325515B2 JP1137283A JP1137283A JPH0325515B2 JP H0325515 B2 JPH0325515 B2 JP H0325515B2 JP 1137283 A JP1137283 A JP 1137283A JP 1137283 A JP1137283 A JP 1137283A JP H0325515 B2 JPH0325515 B2 JP H0325515B2
- Authority
- JP
- Japan
- Prior art keywords
- water
- solution
- alkali metal
- silicate solution
- alkali
- 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
- 239000000243 solution Substances 0.000 claims description 41
- 238000000576 coating method Methods 0.000 claims description 25
- 229910052910 alkali metal silicate Inorganic materials 0.000 claims description 21
- 239000011248 coating agent Substances 0.000 claims description 21
- 239000011253 protective coating Substances 0.000 claims description 21
- 230000001681 protective effect Effects 0.000 claims description 18
- 239000003513 alkali Substances 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 14
- 239000002184 metal Substances 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 10
- 238000010306 acid treatment Methods 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 7
- 239000005871 repellent Substances 0.000 claims description 7
- 239000011259 mixed solution Substances 0.000 claims description 6
- 239000004111 Potassium silicate Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 229910052913 potassium silicate Inorganic materials 0.000 claims description 5
- 235000019353 potassium silicate Nutrition 0.000 claims description 5
- NNHHDJVEYQHLHG-UHFFFAOYSA-N potassium silicate Chemical compound [K+].[K+].[O-][Si]([O-])=O NNHHDJVEYQHLHG-UHFFFAOYSA-N 0.000 claims description 5
- GBPOWOIWSYUZMH-UHFFFAOYSA-N sodium;trihydroxy(methyl)silane Chemical group [Na+].C[Si](O)(O)O GBPOWOIWSYUZMH-UHFFFAOYSA-N 0.000 claims description 4
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 2
- 239000004115 Sodium Silicate Substances 0.000 claims 1
- 229910052700 potassium Inorganic materials 0.000 claims 1
- 239000011591 potassium Substances 0.000 claims 1
- 229910052911 sodium silicate Inorganic materials 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 33
- 230000007797 corrosion Effects 0.000 description 19
- 238000005260 corrosion Methods 0.000 description 19
- 238000000034 method Methods 0.000 description 17
- 239000000523 sample Substances 0.000 description 8
- 238000005299 abrasion Methods 0.000 description 6
- 229910001413 alkali metal ion Inorganic materials 0.000 description 6
- 239000011550 stock solution Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 239000000428 dust Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 2
- 239000010407 anodic oxide Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000002950 deficient Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 230000002940 repellent Effects 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000006482 condensation reaction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
- 229910001950 potassium oxide Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 125000005625 siliconate group Chemical group 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
Landscapes
- Application Of Or Painting With Fluid Materials (AREA)
- Chemical Treatment Of Metals (AREA)
Description
本発明は、アルミニウム反射鏡等の金属板の表
面にアルカリ金属ケイ酸塩溶液を用いて形成する
保護被膜の製造方法に関し、特に、耐食性に秀れ
ているばかりでなく保護被膜の表面に水分や塵埃
等が付着しにくく、仮に付着しても容易にふきと
ることができるばかりでなく、耐摩耗性や耐スク
ラツチ性も秀れている等の特長を備えた保護被膜
の製造方法に関する。
アルミニウム反射鏡等の金属板の表面にアルカ
リ金属ケイ酸塩溶液を用いて保護被膜を形成する
方法は既に公知であり、例えば特公昭56−30521
号公報等に詳細に記載されている。かかる方法に
より製造された保護被膜は、一般的にガラス状の
密着した透明な被膜であつて、化学的にも安定し
ており、従来の陽極酸化被膜などに比べて化学物
質や汚染物質による浸食に対して極めて大きな耐
性を有するという特長を有する。ところが、この
ような方法によつて製造された被膜の厚みは、通
常１〜2μ程度と極めて薄いため、耐摩耗性や耐
スクラツチ性に劣るという弱点があつた。このよ
うな弱点をカバーするために、例えば特許昭57−
43634号公報に記載されているような製造方法が
提案された。即ち、金属板の表面にアルカリ金属
ケイ酸塩溶液を塗布し乾燥させ高温で焼き付けて
第一の保護被膜を形成し、該被膜を酸処理して被
膜中のアリカリ金属イオンを抽出除去した後、同
じ工程を再度繰り返すことにより前記第一の保護
被膜の上に第二の保護被膜を強固に形成する方法
である。これにより被膜の耐摩耗性や耐スクラツ
チ性も改善され、アルカリ金属ケイ酸塩被膜の特
長を大いに生かすことができるようになつた。
ところが、上記のような方法により製造した保
護被膜を有する物体も、これを長年使用している
と、従来の陽極酸化被膜に比べれば著しく少ない
とはいうものの、徐々に腐食する現象があらわ
れ、特に水と塵埃や汚染物質が付着しやすい場所
で使用した場合にこの傾向が著しいことがわかつ
た。その原因を徹底的に追求した結果、腐食が生
ずるのは、主として保護被膜の表面に存在する欠
陥部分と、被膜表面が親水性であることに起因す
ることが判明した。即ち、保護被膜の表面はこれ
を微視的に見ると、製造条件や製造環境に起因す
ると考えられる「ピンホール」と称する小孔や
「クラツク」と称する微小亀裂等の欠陥が部分的
に存在している。一方、従来のアルカリ金属ケイ
酸塩被膜は、高温で焼き付けた後、「曇り」が発
生するのを防止するため酸で処理して被膜中のア
ルカリ金属イオンを抽出除去することに起因して
表面層に親水性の水酸基〔−OH〕が存在してお
り、全体として親水性の強い被膜となつている。
従つて、保護被膜の表面に水が付着すると被膜全
体が広く水で覆われることとなり、先に述べた被
膜の欠陥部分も水の侵入を受け、しかも親水性の
ために水が流れ落ちにくい状態となる。かかる状
態において水とともに塵埃や汚染物質が付着する
と化学反応が起り、被膜の欠陥部分から腐食が発
生し、孔食へと発展する。この孔食部から生成し
たアルミニウム水酸化物等は親水性の被膜に強固
に付着し、ふきとつても容易にとれず、腐食をま
すます進行させるのみならず金属板の表面外観を
著しく汚損させる。
このような問題を解決するためには、腐食の原
因となる水が付着しにくいように保護被膜の表面
に更に撥水性の被膜を形成するか、又は保護被膜
の膜厚を極めて厚くすることによりピンホールや
クラツクを通して水が基板と接触するのを防ぐこ
とが考えられる。前者の具体的手段としては、完
成した保護被膜の表面にシリコーンオイルやワニ
スを塗布する方法がある。ところが、かかる方法
によると、撥水性の被膜の密着性が悪く、耐久性
も低いうえ、光線透過率も低いので、反射鏡等に
適用した場合に反射率が低下するという大きな欠
点がある。又、前記後者の具体的手段としては、
同種の保護被膜を３回〜５回程度重ねて塗る方法
があるが、この方法によると、被膜の曇りによる
反射率の低下や熱的衝撃による被膜のひび割れが
発生しやすいという欠点がある。
本発明は、以上の点に鑑みてなされたもので、
従来のアルカリ金属ケイ酸塩被膜に比べて大きな
撥水性を有し、腐食される度合が極めて少なく、
腐食生成物が付着しても容易にふきとることがで
きるばかりでなく、耐摩耗性や耐スクラツチ性に
おいても優れている保護被膜の製造方法を提供す
ることを目的とする。
発明者（等）は先に述べたような腐食の問題を
根本的に解決するために種々実験検討を加えた結
果、アルカリ金属ケイ酸塩溶液中に水溶性シリコ
ーン、殊にアルカリメチルシリコネートを混合し
たものを使用して一定の処理を施すことにより耐
食性を大巾に向上しうることを確認した。即ち、
アルカリ金属ケイ酸塩とアルカリメチルシリコネ
ートの混合溶液を金属板に塗布し、乾燥させ、高
温で焼き付けた後に酸処理及び水洗いをすること
により、表面が撥水性に富んでおり、従つて水や
塵埃等がが付着しにくく、仮に付着しても水で容
易にふきとることができる保護被膜を得ることが
できた。なお、上記のアルカリメチルシリコネー
トとしては、例えば東レシリコン株式会社から
「ドライシールＥ」なる商品名で市販されている
ものを使用すればよい。
上記のような保護被膜は、先に述べたような、
溶液の塗布、乾燥、焼付、酸処理という一連の工
程をただ一回だけ行うことにより形成したもので
あつても、アルカリメチルシリコネートを添加し
ないアルカリ金属ケイ酸塩溶液を用いて形成した
保護被膜に比べると秀れた耐食性を有するが、被
膜の厚みは１〜2μ程度であるため、耐摩耗性及
び耐スクラツチ性の点においては必ずしも満足で
きるものではない。この問題を解決するために
は、従来方法と同様、上記工程を最低二回繰り返
せばよいが、それを実施してみたところ、第一回
目の工程で形成された被膜が撥水性であるため、
第二回目の工程で前記被膜のうえに溶液が全く付
着しないという新たな問題が生じた。発明者
（等）は、アルカリメチルシリコネートを添加し
ない従来の保護被膜が親水性であるという点に着
目して、第一回目の工程ではアルカリメチルシリ
コネートを添加しない溶液を用いて保護被膜を形
成し、第２回目の工程でアルカリメチルシリコネ
ートを添加した溶液を用いて保護被膜を形成した
ところ、極めて満足できる結果を得ることができ
た。
以下、本発明に係る保護被膜の製造方法を工程
に基づいて説明する。
先ず、アルカリ金属ケイ酸塩溶液の原液を用意
し、これを水で薄めて浸漬用溶液とする。実験に
用いたアルカリ金属ケイ酸塩溶液はカリウムケイ
酸塩溶液で、その原液は重量％においておおむね
次のような組成を有する。
カリウム酸化物 K2O 8.3％
シリカ SiO2 20.8％
水 70.9％
また希釈用の水との混合比は次のとおりであ
る。
カリウムケイ酸塩溶液原液 26％
水 74％
上記のような溶液を用意したらその中にアルミ
ニウム反射鏡等の金属板をデイプし、その表面に
溶液を十分に付着させた後、金属板を引き上げて
これを乾燥室で約32℃の温度で10分間乾燥させ
る。
次に、上記金属板を加熱炉に入れて250〜320℃
の温度で10分間加熱して被膜中の水分をほぼ完全
に取り除き被膜を硬化させる。
次いで、加熱を終えた金属板を取り出して、約
70℃の３％硝酸液に３分間浸漬して酸処理を施
す。この酸処理によつて曇りの原因となる被膜中
のアルカリ金属イオンが抽出除去される。
酸処理を終えたら、次に被膜表面を水洗いし乾
燥させて第一回目の工程を終了する。なお、この
工程は必要に応じて複数回繰り返してもよい。
次に、第二回目の工程に移るわけであるが、今
度は、アルカリ金属ケイ酸塩溶液原液に所定量の
水とアルカリメチルシリコネートを加えた溶液を
用意する。
実験に用いたアルカリメチルシリコネートはナ
トリウムメチルシリコネートで、これは先にも述
べたように、「ドライシールＥ」なる商品名で市
販されているものである。その一般的特性は次の
とおりである。
外 観 淡黄色透明
比重（25℃） 1.26〜1.27
固形分（％） 30
PH 13
また、カリウムケイ酸塩溶液の原液と水とナト
リウムシリコネートの混合比は容量％において次
のとおりである。
カリウムケイ酸塩溶液原液 26％
水 73％
ナトリウムメチルシリコネート １％
この場合、ナトリウムメチルシリコネートの混
合比は、0.5〜10重量％の範囲内であれば適宜選
択することができる。もし、この下限値より少な
いと十分な撥水性をうることができなくなり、逆
に上限値より多いと被膜の透明度が低下する。
また、本発明で注意しなければならないのは、
上記混合液のPHを10以上に維持しなければならな
いことである。これは、PHが10未満、特に８〜９
以下になると、アルカリ金属ケイ酸塩溶液が重合
又は縮合反応を起し、これによつて生じた遊離ケ
イ酸の沈殿及びゲル化によつて溶液が不透明とな
り、被膜を構成できなくなるからである。
上記のような混合液を用意したら、これに第一
回目の工程を終えた金属板をデイプしてその表面
に溶液を付着させる。この後は第一回目の工程と
同じ条件で、乾燥、焼付及び酸処理を行ない、水
洗に並に乾燥をして第二回目の工程を終了する。
先にも述べたように、アルカリ金属ケイ酸塩溶液
のみを用いて形成した被膜中から酸処理によつて
アルカリ金属イオンを抽出除去すると被膜表面は
強い親水性となるにもかかわらず、アルカリメチ
ルシリコネートを添加した混合溶液を用いて形成
した被膜中からアルカリ金属イオンを抽出除去し
ても何ら悪影響が見られないばかりでなく、被膜
表面は強い撥水性を示す。これは被膜表面に撥水
性をもたらすメチル基をもつたメチルシリコネー
トが存在するためであると考えられる。そして、
この撥水性のために金属板の表面には腐食の原因
となる水や塵埃などがたまりにくくなる。のみな
らず、メチルシリコネートのメチル基は不活性
で、腐食生成物たるアルミニウムの水酸化物に対
して非粘着性であるため、保護被膜の表面には腐
食生成物が付着しにくく、仮に付着しても水など
で容易にふきとることができるのである。また、
親水性の被膜の水酸基〔−OH〕は、金属板との
密着性を良くし、さらに撥水性の被膜との密着性
をもよくするプライマー効果を有するので被膜全
体の機械的強度が高まるという大きな利点もあ
る。
なお、アルカリ金属ケイ酸塩溶液とアルカリメ
チルシリコネートの混合溶液を用いて保護被膜を
形成した場合、前記のごとき酸処理によつて被膜
中のアルカリ金属を抽出除去しないと、短期間の
うちに被膜に曇りが発生することは勿論、被膜中
の残留アルカリ金属イオンと水分とが化合して水
酸化カリウムや水酸化ナトリウム等の腐食性溶液
となり、これが被膜中のシロキサン結合を破壊
し、撥水性をもたらすメチル基をも侵す原因とな
る。
最後に、本発明の効果を実験データによつて示
す。
実験は、アルカリメチルシリコネートを添加し
ないアルカリ金属ケイ酸塩溶液を用いて、これを
アルミニウム反射鏡の表面に塗布し、乾燥させ、
焼き付けた後、酸処理及び水洗いする工程をただ
一回だけ行うことによつて形成した保護被膜（試
料１）と、アルカリメチルシリコネートを添加し
た溶液を用いて上記工程を一回だけ行つて形成し
た保護被膜（試料２）と、アルカリメチルシリコ
ネートを添加しない溶液のみを用いて前記工程を
二回繰り返すことにより得られた保護被膜（試料
３）と、第一回目の工程ではアルカリメチルシリ
コネートを添加しない溶液を用い、第二回目の工
程ではそれを添加した溶液を用いた本発明に係る
保護被膜（試料４）とを、それぞれキヤス耐食試
験（JIS H8681）により試験し、レイテイングナ
ンバー（R.N.）による耐食度、孔食の程度、試
験後の外観、腐食部分の水のふきとり性、及び反
射鏡の反射率について調べてみた。また、耐摩耗
性、耐スクラツチ性及び耐沸酸性についてもそれ
ぞれ試験をしてみた。耐摩耗性試験は、試料を
45゜の角度で設置しその上に230mm上方より定量の
砂を落下させた後、表面をプローブで電流の導通
度をあたつた。耐スクラツプ性は約３Kgの荷重の
表面にガーゼをあて、その部分で試料の表面をこ
すつて表面状態を目視判定した。さらに耐沸酸試
験は１％沸酸溶液を試料の表面に滴下し規定時間
放置して侵食されるまでの時間をはかつた。これ
らの試験の結果を第１表に示す。これらの結果か
ら本発明に係る製造方法により製造した保護被膜
は、耐食性、耐摩耗性、耐スクラチ性の何れにお
いても、従来の保護被膜より秀れていることは容
易に判断できるであろう。
The present invention relates to a method for manufacturing a protective coating formed on the surface of a metal plate such as an aluminum reflector using an alkali metal silicate solution, and in particular, it not only has excellent corrosion resistance but also prevents moisture from forming on the surface of the protective coating. The present invention relates to a method for producing a protective coating which has features such that it is difficult to attract dust and the like, and even if it does, it can be easily wiped off, as well as having excellent abrasion resistance and scratch resistance. A method of forming a protective film on the surface of a metal plate such as an aluminum reflector using an alkali metal silicate solution is already known, for example, as disclosed in Japanese Patent Publication No. 56-30521.
It is described in detail in the publication number etc. The protective coating produced by this method is generally a glass-like, adhesive, transparent coating that is chemically stable and less susceptible to erosion by chemicals and pollutants than conventional anodic oxide coatings. It has the feature of extremely high resistance to However, the thickness of the coating produced by such a method is usually very thin, about 1 to 2 microns, and therefore has the disadvantage of poor abrasion resistance and scratch resistance. In order to cover such weaknesses, for example, the patent
A manufacturing method as described in Publication No. 43634 was proposed. That is, a first protective film is formed by applying an alkali metal silicate solution to the surface of a metal plate, drying it and baking it at a high temperature, and then treating the film with an acid to extract and remove alkali metal ions in the film. This is a method of strongly forming a second protective film on the first protective film by repeating the same process again. This improved the abrasion resistance and scratch resistance of the coating, making it possible to take full advantage of the features of the alkali metal silicate coating. However, when objects with protective coatings manufactured by the above-mentioned method are used for many years, the phenomenon of gradual corrosion appears, although it is significantly less than with conventional anodic oxide coatings. This tendency was found to be more pronounced when used in locations where water, dust, and other pollutants tend to adhere. As a result of thorough investigation into the cause, it was found that corrosion occurs mainly due to defects existing on the surface of the protective coating and the fact that the coating surface is hydrophilic. In other words, when looking microscopically at the surface of the protective coating, it can be seen that there are some defects such as small holes called "pinholes" and microcracks called "cracks" that are thought to be caused by manufacturing conditions or the manufacturing environment. are doing. On the other hand, conventional alkali metal silicate coatings are baked at high temperatures and then treated with acid to extract and remove alkali metal ions in the coating to prevent clouding. Hydrophilic hydroxyl groups [-OH] are present in the layer, resulting in a highly hydrophilic coating as a whole.
Therefore, if water adheres to the surface of the protective film, the entire film will be extensively covered with water, and the aforementioned defective areas of the film will also be subject to water intrusion, and due to its hydrophilic nature, it will be difficult for water to run off. Become. Under such conditions, when dust and contaminants adhere to the surface along with water, a chemical reaction occurs, causing corrosion from the defective portions of the coating, which develops into pitting corrosion. Aluminum hydroxide, etc. generated from this pitting corrosion firmly adheres to the hydrophilic film and cannot be easily removed even if wiped off, which not only further progresses corrosion but also significantly stains the surface appearance of the metal plate. . In order to solve this problem, it is necessary to form an additional water-repellent film on the surface of the protective film to prevent water that causes corrosion from adhering to it, or to make the protective film extremely thick. It is possible to prevent water from coming into contact with the substrate through pinholes or cracks. A specific example of the former method is to apply silicone oil or varnish to the surface of the completed protective film. However, according to this method, the adhesion of the water-repellent coating is poor, the durability is low, and the light transmittance is also low, so there is a major drawback that the reflectance decreases when applied to a reflecting mirror or the like. Moreover, as a specific means for the latter,
There is a method in which the same type of protective coating is applied three to five times, but this method has the drawbacks that the reflectance decreases due to fogging of the coating and cracking of the coating is likely to occur due to thermal shock. The present invention has been made in view of the above points, and
It has greater water repellency than conventional alkali metal silicate coatings, and is extremely less susceptible to corrosion.
It is an object of the present invention to provide a method for producing a protective coating that not only can be easily wiped off even if corrosion products adhere to it, but also has excellent wear resistance and scratch resistance. In order to fundamentally solve the corrosion problem mentioned above, the inventors (and others) conducted various experimental studies and found that water-soluble silicone, especially alkali methyl siliconate, was added to the alkali metal silicate solution. It was confirmed that corrosion resistance could be greatly improved by using a mixture and subjecting it to certain treatments. That is,
By applying a mixed solution of alkali metal silicate and alkali methyl siliconate to a metal plate, drying it, baking it at high temperature, and then treating it with acid and washing it with water, the surface becomes highly water-repellent and therefore resistant to water and water. It was possible to obtain a protective film to which dust and the like do not easily adhere, and even if they do adhere, they can be easily wiped off with water. As the above alkali methyl siliconate, for example, one commercially available from Toray Silicon Co., Ltd. under the trade name "Dry Seal E" may be used. The above protective coating is, as mentioned earlier,
Protective coatings formed using alkali metal silicate solutions without the addition of alkali methyl siliconates, even if formed by a single series of steps of solution application, drying, baking, and acid treatment. However, since the thickness of the coating is about 1 to 2 μm, it is not necessarily satisfactory in terms of wear resistance and scratch resistance. In order to solve this problem, the above steps should be repeated at least twice as in the conventional method, but when we tried this, we found that the film formed in the first step was water repellent.
A new problem arose in that no solution adhered to the coating in the second step. The inventors (and others) focused on the fact that the conventional protective coating without the addition of alkali methyl siliconate was hydrophilic, and in the first step, they created a protective coating using a solution without the addition of alkali methyl siliconate. When a protective coating was formed using a solution to which alkali methyl siliconate was added in a second step, very satisfactory results were obtained. Hereinafter, the method for manufacturing a protective film according to the present invention will be explained based on the steps. First, a stock solution of alkali metal silicate solution is prepared and diluted with water to obtain a dipping solution. The alkali metal silicate solution used in the experiment was a potassium silicate solution, and the stock solution had the following composition in terms of weight percent. Potassium oxide K 2 O 8.3% Silica SiO 2 20.8% Water 70.9% The mixing ratio with water for dilution is as follows. Potassium silicate solution stock solution 26% Water 74% After preparing the above solution, dip a metal plate such as an aluminum reflector in it, and after the solution has sufficiently adhered to the surface, pull up the metal plate. This is dried in a drying room at a temperature of approximately 32°C for 10 minutes. Next, put the above metal plate into a heating furnace at 250-320℃.
Heat for 10 minutes at a temperature of 100 to remove almost all moisture in the film and harden the film. Next, take out the heated metal plate and heat it to approx.
Perform acid treatment by immersing in 3% nitric acid solution at 70°C for 3 minutes. This acid treatment extracts and removes alkali metal ions in the coating that cause clouding. After completing the acid treatment, the surface of the coating is washed with water and dried to complete the first process. Note that this step may be repeated multiple times as necessary. Next, the process moves to the second step, and this time, a solution is prepared by adding a predetermined amount of water and alkali methyl siliconate to the alkali metal silicate solution stock solution. The alkali methyl siliconate used in the experiment was sodium methyl siliconate, which, as mentioned above, is commercially available under the trade name "Dry Seal E." Its general characteristics are as follows. Appearance Pale yellow and transparent Specific gravity (25°C) 1.26 to 1.27 Solid content (%) 30 PH 13 The mixing ratio of the stock solution of potassium silicate solution, water and sodium siliconate in volume % is as follows. Potassium silicate solution stock solution 26% Water 73% Sodium methyl siliconate 1% In this case, the mixing ratio of sodium methyl siliconate can be appropriately selected within the range of 0.5 to 10% by weight. If the amount is less than this lower limit, sufficient water repellency cannot be obtained, and on the other hand, if it is more than the upper limit, the transparency of the coating will decrease. In addition, what must be noted in the present invention is that
The pH of the above mixture must be maintained at 10 or higher. This means that the pH is less than 10, especially between 8 and 9.
If the concentration is below, the alkali metal silicate solution will undergo a polymerization or condensation reaction, and the resulting precipitation and gelation of free silicic acid will make the solution opaque, making it impossible to form a film. Once the above-mentioned mixed solution is prepared, the metal plate that has undergone the first step is dipped in it, and the solution is adhered to the surface of the metal plate. After this, drying, baking, and acid treatment are performed under the same conditions as the first step, followed by washing with water and drying to complete the second step.
As mentioned earlier, when alkali metal ions are extracted and removed from a film formed using only an alkali metal silicate solution by acid treatment, the surface of the film becomes strongly hydrophilic. Even when alkali metal ions are extracted and removed from a film formed using a mixed solution containing siliconate, not only is no adverse effect observed, but the surface of the film exhibits strong water repellency. This is thought to be due to the presence of methyl siliconate having a methyl group on the surface of the coating that provides water repellency. and,
This water repellency makes it difficult for water and dust, which can cause corrosion, to accumulate on the surface of the metal plate. In addition, the methyl group of methyl siliconate is inactive and non-adhesive to aluminum hydroxide, which is a corrosion product, so corrosion products are difficult to adhere to the surface of the protective film, and even if they do However, it can be easily wiped off with water. Also,
The hydroxyl group [-OH] in the hydrophilic coating has a primer effect that improves the adhesion to the metal plate and also improves the adhesion to the water-repellent coating, which has the effect of increasing the mechanical strength of the entire coating. There are also advantages. Note that when a protective film is formed using a mixed solution of an alkali metal silicate solution and an alkali methyl siliconate, unless the alkali metal in the film is extracted and removed by the acid treatment described above, it will deteriorate in a short period of time. Not only will the film become cloudy, but the residual alkali metal ions in the film will combine with water to form corrosive solutions such as potassium hydroxide and sodium hydroxide, which will destroy the siloxane bonds in the film and make it water repellent. It also causes damage to the methyl groups that lead to Finally, the effects of the present invention will be demonstrated using experimental data. In the experiment, an alkali metal silicate solution without the addition of alkali methyl siliconate was applied to the surface of an aluminum reflector, dried, and
A protective film (sample 1) formed by performing the acid treatment and water washing process only once after baking, and a protective film formed by performing the above process only once using a solution containing alkali methyl siliconate. (Sample 2), a protective coating obtained by repeating the above process twice using only a solution to which no alkali methyl siliconate was added (Sample 3), and a protective coating obtained by repeating the above process twice using only a solution to which no alkali methyl siliconate was added (Sample 3). A protective coating according to the present invention (sample 4) using a solution without the addition of the same in the second step, and a solution with the same added in the second step were tested by the cast corrosion resistance test (JIS H8681), and the rating number ( RN), the degree of pitting corrosion, the appearance after the test, the ability to wipe away water from the corroded area, and the reflectance of the reflector. We also conducted tests for abrasion resistance, scratch resistance, and boiling acid resistance. Abrasion resistance test
After installing it at a 45° angle and dropping a fixed amount of sand from 230 mm above, the surface was tested for current conductivity using a probe. Scrap resistance was determined by applying gauze to the surface under a load of approximately 3 kg, rubbing the surface of the sample with the gauze, and visually evaluating the surface condition. Furthermore, in the boiling acid resistance test, a 1% boiling acid solution was dropped on the surface of the sample and left for a specified period of time to determine the time until corrosion occurred. The results of these tests are shown in Table 1. From these results, it can be easily determined that the protective coating produced by the production method according to the present invention is superior to conventional protective coatings in terms of corrosion resistance, abrasion resistance, and scratch resistance.
【表】【table】
Claims (1)
塗布し乾燥させ高温で焼き付けて親水性の保護被
膜を形成した後、該保護被膜の表面にアルカリ金
属ケイ酸塩溶液とアルカリメチルシリコネートの
混合溶液を塗布し乾燥させ高温で焼き付けてから
酸処理することにより撥水性の保護被膜を形成す
ることを特徴とする保護被膜の製造方法。 ２ アルカリ金属ケイ酸塩溶液がカリウムケイ酸
塩溶液又はナトリウムケイ酸塩溶液もしくはこれ
らの混合溶液であり、アルカリメチルシリコネー
トがナトリウムメチルシリコネート又はカリウム
メチルシリコネートもしくはこれらの混合体であ
ることを特徴とする特許請求の範囲第１項記載の
保護被膜の製造方法。 ３ アルカリ金属ケイ酸塩溶液を塗布し乾燥させ
高温で焼き付けた段階と、アルカリ金属ケイ酸塩
溶液とアルカリメチルシリコネートの混合溶液を
塗布し乾燥させ高温で焼き付けた段階とに分けて
酸処理を施すことを特徴とする特許請求の範囲第
１項記載の保護被膜の製造方法。[Claims] 1. After coating the surface of a metal plate with an alkali metal silicate solution, drying and baking at high temperature to form a hydrophilic protective film, the surface of the protective film is coated with an alkali metal silicate solution. A method for producing a protective film, which comprises forming a water-repellent protective film by applying a mixed solution of alkali methyl siliconate, drying it, baking it at high temperature, and then treating it with an acid. 2. The alkali metal silicate solution is a potassium silicate solution, a sodium silicate solution, or a mixture thereof, and the alkali methyl siliconate is sodium methyl siliconate, potassium methyl siliconate, or a mixture thereof. A method for producing a protective coating according to claim 1. 3 Acid treatment is carried out in two stages: applying an alkali metal silicate solution, drying, and baking at a high temperature; and applying a mixed solution of an alkali metal silicate solution and alkali methyl siliconate, drying, and baking at a high temperature. A method for producing a protective coating according to claim 1, characterized in that:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1137283A JPS59139969A (en) | 1983-01-28 | 1983-01-28 | Manufacture of protective coating film |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1137283A JPS59139969A (en) | 1983-01-28 | 1983-01-28 | Manufacture of protective coating film |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59139969A JPS59139969A (en) | 1984-08-11 |
| JPH0325515B2 true JPH0325515B2 (en) | 1991-04-08 |
Family
ID=11776180
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1137283A Granted JPS59139969A (en) | 1983-01-28 | 1983-01-28 | Manufacture of protective coating film |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59139969A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107674231A (en) * | 2017-10-20 | 2018-02-09 | 南京工程学院 | A kind of hydrophobic oleophobic high molecular composite microsphere and preparation method thereof |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8021004B2 (en) | 2007-01-13 | 2011-09-20 | Jacek Helenowski | Mirrored element |
-
1983
- 1983-01-28 JP JP1137283A patent/JPS59139969A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107674231A (en) * | 2017-10-20 | 2018-02-09 | 南京工程学院 | A kind of hydrophobic oleophobic high molecular composite microsphere and preparation method thereof |
| CN107674231B (en) * | 2017-10-20 | 2021-04-20 | 南京工程学院 | A kind of hydrophobic and oleophobic polymer composite microsphere and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59139969A (en) | 1984-08-11 |
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