Method of providing a polycarbonate article with a uniform and durable silica filled organopolysiloxane coating

• US 4,242,381 A
• Filed: 04/18/1979
• Issued: 12/30/1980
• Est. Priority Date: 04/18/1979
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Olson, Daniel R., Goossens, John C.
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): Buffalow, E. Rollins
• Application Number:
  US06/031,127
• Time in Patent Office: 622 Days
• Field of Search: 428/412, 428/447, 427/387, 427/412.1
• US Class Current: 427/387
• CPC Class Codes: B05D 2601/22 Silica
• CPC Class Codes: B05D 7/02 to macromolecular substances, e.g. rubber treatment or coating of shaped articles made of macromolecular substances C08J7/00
• CPC Class Codes: B05D 7/04 to surfaces of films or sheets producing layered products by applying coatings of pasty or pulverulent plastics B29C41/00
• CPC Class Codes: B05D 7/536 each layer being cured, at least partially, separately
• CPC Class Codes: B29D 11/00865 Applying coatings; tinting; colouring printing, marking or copying processes B41M; identification in general G09F3/00; producing decorative effects in general B44C; positioning or marking of lenses B24B13/0055
• CPC Class Codes: C08J 2369/00 Characterised by the use of polycarbonates; Derivatives of polycarbonates
• CPC Class Codes: C08J 2433/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C08J 2483/04 Polysiloxanes
• CPC Class Codes: C08J 7/042 with two or more layers, where at least one layer of a composition contains a polymer binder
• CPC Class Codes: C08J 7/043 Improving the adhesiveness of the coatings per se, e.g. forming primers adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50
• CPC Class Codes: C08J 7/046 Forming abrasion-resistant coatings; Forming surface-hardening coatings
• CPC Class Codes: Y10T 428/31507 Of polycarbonate
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

A process for providing a protective coating on a polycarbonate substrate comprising (i) applying onto said polycarbonate substrate a priming emulsion composition containing (a) a thermosettable acrylic polymer, (b) an ultraviolet light absorber selected from the benzylidene malonates and cyanoacrylates, (c) water, and (d) a hydroxy ether or an alkanol; (ii) curing the thermosettable acrylic polymer thereby forming a primer layer containing a thermoset acrylic and an ultraviolet light screener on said substrate; (iii) applying a top coat composition containing colloidal silica and a further curable organopolysiloxane; and (iv) curing said further curable organopolysiloxane thereby obtaining a silica filled thermoset organopolysiloxane top coat.

Claims

1. A method for producing a polycarbonate article having improved mar, abrasion, scratch and chemical solvent resistance and possessing enhanced ultraviolet light stability comprising:

(i) applying onto a polycarbonate substrate a primer emulsion composition consisting essentially of a thermosettable acrylic polymer, (b) at least one ultraviolet light screening compound selected from the class consisting of benzylidene malonates and cyanoacrylates, (c) from about 20 to about 40 weight percent of a hydroxy ether or alkanol containing from 1 to 4 carbon atoms, and (d) water;

(ii) evaporating off a substantial portion of said water and hydroxy ether or alkanol from said primer emulsion composition thereby forming a layer of comprised of said thermosettable acrylic polymer and at least one of said ultraviolet light screening compounds;

(iii) applying heat to said layer at a temperature and for a period of time effective to cure said thermosettable acrylic polymer;

(iv) applying onto said cured primer layer a top coat composition containing a colloidal silica filled further curable organopolysiloxane comprising a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol of the formula R⁶ Si(OH)₃ wherein R⁶ is an alkyl radical containing 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of said silanol being CH₃ Si(OH)₃, said composition containing sufficient acid to provide a pH in the range of 3.0 to 6.0;

(v) evaporating off a substantial portion of the volatile solvents from said top coat composition thereby forming a layer comprised of a colloidal silica filled partial condensate of said silanol; and

,

(vi) thermally curing said colloidal silica filled partial condensate of said silanol.

2. The method of claim 1 wherein said hydroxy ether is represented by the general formula

3. The method of claim 2 wherein said hydroxy ether is butoxy ethanol.

4. The method of claim 1 wherein said cured primer layer has a thickness of from about 0.01 to about 0.1 mil.

5. The method of claim 1 wherein said benzylidene malonates are represented by the general formula ##STR5## wherein x is selected from hydrogen, OH, halogen radicals, alkyl radicals, and alkoxy radicals, and R³ and R⁴ are independently selected from alkyl radicals, substituted alkyl radicals, aryl radicals, substituted aryl radicals, alkaryl radicals, and aralkyl radicals.

6. The method of claim 5 wherein x is an alkoxy radical, and R³ and R⁴ are independently selected from alkyl radicals.

7. The method of claim 6 wherein x is a methoxy radical.

8. The method of claim 7 wherein said methoxy radical is in the para position.

9. The method of claim 8 wherein R³ and R⁴ are both ethyl radicals.

10. The method of claim 8 wherein R³ and R⁴ are both methyl radicals.

11. The method of claim 1 wherein said cyanoacrylates are represented by the general formula ##STR6## wherein R⁵ is selected from alkyl radicals, substituted alkyl radicals, aryl radicals, substituted aryl radicals, alkaryl radicals and aralkyl radicals.

12. The method of claim 11 wherein R⁵ is an alkyl radical.

13. The method of claim 12 wherein said alkyl radical is octyl.

14. The method of claim 12 wherein said alkyl radical is ethyl.

15. A method for providing a uniform and durably adhered mar, scratch, abrasion and chemical solvent resistant colloidal silica filled organopolysiloxane coating on a polycarbonate article which comprises:

(i) applying onto the surface of a polycarbonate substrate a primer emulsion composition consisting essentially of, in percent by weight, (a) from about 1 to about 10 percent of a thermosettable acrylic polymer, (b) from about 1 to about 10 percent of at least one ultraviolet light screening compound selected from the class consisting of benzylidene malonates and cyanoacrylates, (c) from 20 to about 40 percent of a hydroxy ether or an alkanol containing from 1 to 4 carbon atoms, and (d) from about 40 to about 78 percent water;

(ii) evaporating off a substantial portion of said water and hydroxy ether or alkanol from said primer emulsion composition thereby forming a layer comprised of said thermosettable acrylic polymer and at least one of said ultraviolet light screening compounds;

(iii) applying heat to said layer at a temperature and for a period of time effective to cure said thermosettable acrylic polymer;

(iv) applying onto said cured primer layer a colloidal silica filled further curable organopolysiloxane top coat composition comprising a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH)₃ wherein R is an alkyl radical containing 1 to 3 carbon atoms, the vinyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical and the gamma-methacryloxypropyl radical, at least 70 weight percent of said silanol being CH₃ Si(OH)₃, said composition containing sufficient acid to provide a pH in the range of 3.0 to 6.0;

(v) evaporating off a substantial portion of the volatile solvents from said top coat composition thereby forming a layer comprised of a colloidal silica filled partial condensate of said silanol; and

,

(vi) thermally curing said colloidal silica filled partial condensate of said silanol.

16. The method of claim 15 wherein said hydroxy ether is represented by the general formula

17. The method of claim 16 wherein said hydroxy ether is butoxy ethanol.

18. The method of claim 15 wherein said cured primer layer has a thickness of from about 0.01 to about 0.1 mil.

19. The method of claim 15 wherein said benzylidene malonates are represented by the general formula ##STR7## wherein x is selected from hydrogen, OH, halogen radicals, alkyl radicals, and alkoxy radicals, and R³ and R⁴ are independently selected from alkyl radicals, substituted alkyl radicals, aryl radicals, substituted aryl radicals, alkaryl radicals, and aralkyl radicals.

20. The method of claim 19 wherein x is an alkoxy radical, and R³ and R⁴ are independently selected from alkyl radicals.

21. The method of claim 20 wherein x is a methoxy radical.

22. The method of claim 21 wherein said methoxy radical is in the para position.

23. The method of claim 22 wherein R³ and R⁴ are both ethyl radicals.

24. The method of claim 22 wherein R³ and R⁴ are both methyl radicals.

25. The method of claim 15 wherein said cyanoacrylates are represented by the general formula ##STR8## wherein R⁵ is selected from alkyl radicals, substituted alkyl radicals, aryl radicals, substituted aryl radicals, alkaryl radicals and aralkyl radicals.

26. The method of claim 25 wherein R⁵ is an alkyl radical.

27. The method of claim 26 wherein said alkyl radical is octyl.

28. The method of claim 26 wherein said alkyl radical is ethyl.