Transparent barrier coatings exhibiting reduced thin film interference

• US 6,051,296 A
• Filed: 09/24/1998
• Issued: 04/18/2000
• Est. Priority Date: 06/12/1996
• Status: Expired due to Fees

• Current Assignee: Hoechst Trespaphan GmbH
• Original Assignee: Hoechst Trespaphan GmbH
• Inventors: Hubbard, Michael A., McCaulley, James A.
• Primary Examiner(s): Michl, Paul R.
• Application Number:
  US09/160,763
• Time in Patent Office: 572 Days
• Field of Search: 428/35.7, 428/446
• US Class Current: 428/35.7
• 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 7/048 Forming gas barrier coatings
• CPC Class Codes: C08J 7/06 with compositions not containing macromolecular substances
• CPC Class Codes: C09D 1/02 alkali metal silicates
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]

Abstract

A vapor barrier coating solution for poly(ethylene terephthalate) (PET) polymeric articles contains a metal polysilicate and transparent nanocrystalline titanium dioxide. The coating reduces interference between light reflected from the top surface of a coated PET polymeric article and the interface between the dried coating and said PET polymeric article. The coated articles are also provided.

Claims

1. A gas, vapor and aroma barrier coating solution for polymeric substrates consisting of:

(a) an aqueous metal polysilicate solution;

(b) nanocrystalline titanium dioxide having an average particle size of less than about 100 nm; and

(c) up to about 1% by weight of an organic surfactant;

wherein said coating solution has an inorganic solids content of from about 2 to 20% by weight, and wherein the nanocrystalline titanium dioxide is present in said coating solution at about 9% or less bv weight of said inorganic solids content.

2. The solution according to claim 1 wherein said metal polysilicate is selected from the group consisting of lithium polysilicate, sodium polysilicate, potassium polysilicate and copolysilicate blends thereof.

3. The solution according to claim 1 wherein said metal polysilicate is a copolysilicate of lithium and potassium of the formula (Li₂ O)_x (K₂ O)_1-x (SiO₂)_y wherein x is between 0 and 1 and y is between 1 and 10.

4. The solution according to claim 1, which yields a dried coating that is substantially transparent at a thickness of less than 500 nm.

5. The solution according to claim 1 wherein said nanocrystalline TiO₂ has an average particle size of less than about 100 nm.

6. The solution according to claim 1 wherein said nanocrystalline TiO₂ has an average particle size of less than about 50 nm.

7. The solution according to claim 1 wherein said nanocrystalline TiO₂ is rutile.

8. The solution according to claim 1 wherein said nanocrystalline TiO₂ is anatase.

9. The solution according to claim 1 wherein said nanocrystalline TiO₂ is up to 25 percent by weight of total inorganic solids in said solution.

10. The solution according to claim 3, wherein x is between 0.5 and 1 and y is between 4.6 and 10.

11. The coating solution according to claim 1, wherein the surfactant is nonionic and possesses a critical micelle concentration sufficiently low to ensure a dried coating uncompromised by residual surfactant.

12. The coating solution according to claim 11, wherein the surfactant is selected from the group consisting of acetylenic diols and alkyl ethoxylates.

13. A method of making a coating solution for poly(ethylene terephthalate) articles consisting of the steps of:

adding to an aqueous alkali metal polysilicate solution, nanocrystalline TiO₂ and an organic surfactant, wherein said coating solution has a total inorganic solids content of from about 2 to 20% by weight, and said nanocrystalline TiO₂ is added in an amount of up to 9 weight percent of said total inorganic solids, and said surfactant is added at up to approximately 1% by weight of said coating solution.