Thermoformed articles with improved ease of cutting and resistance to sticking

• US 5,102,943 A
• Filed: 12/04/1990
• Issued: 04/07/1992
• Est. Priority Date: 12/04/1990
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Logullo, Francis M.
• Primary Examiner(s): Michl, Paul R.
• Assistant Examiner(s): Cain, Edward J.
• Application Number:
  US07/622,420
• Time in Patent Office: 490 Days
• Field of Search: 524/275, 524/487, 524/604, 524/605, 524/539, 524/540
• US Class Current: 524/487
• CPC Class Codes: C08L 23/00 Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 67/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C08L67/06 takes precedence
• CPC Class Codes: C08L 91/06 Waxes

Abstract

Thermoformed trays prepared from a blend of 90 to 99.9 percent of polyethylene terephthalate resin, a small amount of sodium ion, and a small amount of wax exhibit effective crystallization rates and improved trimming and stacking properties.

Claims

1. A process for preparation of a thermoformed article, comprising the steps of

(a) blending together

(i) about 90 to about 99.9 percent of weight of a thermoplastic, crystallizable polyester resin;

(ii) an amount of sodium ion sufficient to function as an effective crystallization agent; and

(iii) about 0.05 to about 1.5 percent by weight of wax;

(b) extruding the blend into a sheet;

(c) thermoforming the sheet into an article; and

(d) trimming excess material from the periphery of the thermoformed article.

2. The process of claim 1 wherein the thermoplastic, crystallizable polyester resin is polyethylene terephthalate.

3. The process of claim 2 wherein the amount of sodium ion is about 60 to about 250 parts per million.

4. The process of claim 2 wherein the amount of sodium ion is about 100 to about 150 parts per million.

5. The process of claim 2 wherein the amount of wax is about 0.1 to about 0.6 percent by weight.

6. The process of claim 2 wherein the sodium ion is supplied by addition of about 3 to about 15 percent by weight of a concentrate of polyethylene terephthalate resin containing about 800 to about 4500 parts per million sodium ion.

7. The process of claim 6 wherein the concentrate is sodium carboxylate chain ended polyethylene terephthalate.

8. The process of claim 2 wherein the wax is low density polyethylene wax.

9. The process of claim 2 wherein the wax is oxidized high density polyethylene wax.