# US 5,707,691 A · Coating hollow containers by in-situ polymerization of monomers in bi-axially orientated form

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- Number: US 5,707,691 A
- Document ID: US5707691A
- Status: Granted
- Kind: A
- Application number: 08/703,465
- Filed: 1996-08-27
- Granted: 1998-01-13
- Earliest claimed: 1996-08-27
- Assignees: The Coca-Cola Company
- Inventors: George Plester; Stijn Vandekerckhove
- Web page: https://patentgrep.com/patent/US5707691A

## CPC

- B05D 3/207: {post-treatment by magnetic fields}
- B05D 7/227: {of containers, cans or the like}
- C08J 7/18: using wave energy or particle radiation
- B05D 3/08: by flames
- B05D 3/144: {of polymeric substrates}
- B05D: PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL (conveying articles or workpieces through baths of liquid B65G, e.g. B65G49/02)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)

## Abstract

Methods for providing a low permeability coating on the interior of a refillable plastic container, such as a PET beverage bottle, include coating of a liquid crystal polymer (LCP) by depositing LCP monomers on the interior surface of the container and bi-axially orienting the monomers continuously while reacting the monomers to produce the polymer. The interior surface of the container may be pre-treated to produce free radicals which enhance the attachment of the monomers to the surface. Also, the surface may be post-treated to eliminate unsaturated radicals or free monomers. The application of the monomers to the interior surface of the container can be effected by condensing a gas blend of monomers, by spraying liquid monomers or by filling with liquid monomers and then emptying to leave a residual coating. The monomers are reacted by preheating them or by subjecting them to a heated inert gas. To achieve the bi-axial orientation of the monomers, the interiorly coated container may be alternately subjected to longitudinal and circumferential magnetic fields while supported for incremental end-to-end rotation and rotation about its axis. Another technique for achieving the bi-axial orientation comprises subjecting the container to alternately applied longitudinal and circumferential electrostatic fields.

## Claims

### Claim 1

A method of coating a surface of a plastic container by in-situ polymerization of monomers in biaxially oriented form, comprising the steps of:
coating the container surface with the monomers;
applying a magnetically or electrically generated field to the monomers in at least two generally perpendicular directions to biaxially orient the monomers; and
curing the monomers to form a biaxially oriented polymer coating on the surface of the container.

### Claim 2 (depends on 1)

The method of claim 1 including the further step of pre-treating the surface of the container to produce free radicals which aid the attachment of the monomers to the surface after the step of pretreating.

### Claim 3 (depends on 2)

The method of claim 2 including the further step of post-treating the polymer coating to remove free radicals and unpolymerized monomers.

### Claim 4 (depends on 1)

The method of claim 1 wherein the coating of monomers is applied to the surface by spraying.

### Claim 5 (depends on 1)

The method of claim 1 wherein the coating of monomers is applied by condensing gaseous monomers onto the surface.

### Claim 6 (depends on 1)

The method of claim 1 wherein the coating of monomers is applied to the interior surface of the container by filling the container with liquid monomers and emptying the liquid leaving a residual coating.

### Claim 7 (depends on 1)

The method of claim 1 wherein the field is applied along a longitudinal axis of the container and orthogonally thereto.

### Claim 8 (depends on 7)

The method of claim 7 wherein the field is from a magnetic source.

### Claim 9 (depends on 7)

The method of claim 7 wherein the field is from an electric source.

### Claim 10 (depends on 1)

The method of claim 1 wherein the polymer coating is a liquid crystal polymer.