Thermoforming process for polyalkylene terephthalate polyester resins

Claim 2

A process for thermoforming to a draw ratio in excess of about 3 of a polyalkylene terephthalate resin sheet is substantially unoriented, has a half-time for crystallization at 410° F. below about 5 minutes, is at an average temperature in the range of about 210°-300° F., and has an initial thermally induced average crystallinity in the range of about 0% to 18%, said process comprising: (a) contacting said sheet with a deep-draw mold which is at a temperature in the range of about 240°-350° F.; (b) applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold; (c) allowing said thermoformed sheet to remain in contact with said mold until an average crystallinity of at least about 20% is achieved; and (d) removing said thermoformed sheet from said mold; whereby a thermoformed sheet is made which has both a draw ratio in excess of about 3 and superior uniformity in wall thickness.

Claim 3

The process of claim 1, wherein said mold is at a temperature in the range of about 270°-310° F.

Claim 4

The process of claim 2, wherein said sheet is at a temperature in the range of about 225°-270° F.

Claim 5

The process of claim 3, wherein said initial thermally induced average crystallinity is in the range of about 5% to 15%.

Claim 6

The process of claim 3, wherein said differential in applied pressure is in the range of up to about 5 atmospheres.

Claim 7

The process of claim 3, wherein said differential in applied pressure is about 1 atmosphere.

Claim 8

The process of claim 3, wherein said resin is polyethylene terephthalate.

Claim 9

The process of claim 7, wherein said half-time for crystallization is below about 3 minutes.

Claim 10

A low pressure process for thermoforming a sheet consisting essentially of about 100 parts by weight of polyalkylene terephthalate resin and up to about 1 part by weight of a crystallization initiator, which sheet is substantially unoriented, has a half-time for crystallization at 410° F. below about 5 minutes, is at an average temperature in the range of about 210°-300° F., and has an initial thermally induced average crystallinity in the range of about 0% to about 18%, said process comprising: (1) contacting said sheet with a mold which is at a temperature in the range of about 240°-350° F.; (2) applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold, whereby a thermoformed sheet is made; (3) allowing said thermoformed sheet to remain in contact with said mold until an average crystallinity of at least about 20% is achieved; and (4) removing said thermoformed sheet from said mold.

Claim 11

A low pressure process for thermoforming a sheet consisting essentially of about 100 parts by weight of polyalkylene terephthalate resin and up to about 1 part by weight of a crystallization initiator, which sheet is substantially unoriented, has a half-time for crystallization at 410° F. below about 5 minutes, is at an average temperature in the range of about 210°-300° F., and has an initial thermally induced average crystallinity in the range of about 0% to about 18%, said process comprising: (1) contacting said sheet with a mold which is at a temperature in the range of about 240°-350° F.; (2) applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold, whereby a thermoformed sheet is made; (3) allowing said thermoformed sheet to remain in contact with said mold until an average crystallinity of at least about 20% is achieved; and (4) removing said thermoformed sheet from said mold.

Claim 12

A process for thermoforming a sheet consisting essentially of about 100 parts by weight of a polyalkylene terephthalate resin and up to 1 part by weight of a crystallization initiator comprising: (1) forming said sheet so that it is substantially unoriented and has a thermally induced average crystallinity in the range of about 0-10%, and has a half-time for crystallization at 410° F. below about 5 minutes; (2) heating said sheet an average temperature in the range of about 210°-300° F. at a rate so that by the time that said sheet has reached said average temperature, the average crystallinity of said sheet has increased to a value in the range of about 0% to about 18%; (3) thermoforming said sheet by: (a) contacting the sheet of Step (2) before there is either substantial cooling or a substantial change in the average crystallinity therein with a mold which is at a temperature in the range of about 240°-350° F.; (b) applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold, whereby a thermoformed sheet is made; (4) allowing said thermoformed sheet to remain in contact with said mold until an average crystallinity of at least about 20% is achieved; and (5) removing said thermoformed sheet from said mold and allowing said thermoformed sheet to cool.

Claim 13

A process for thermoforming a sheet consisting essentially of about 100 parts by weight of a polyalkylene terephthalate resin and up to 1 part by weight of a crystallization initiator comprising: (1) forming said sheet so that it is substantially unoriented and has a thermally induced average crystallinity in the range of about 0-10%, and has a half-time for crystallization at 410° F. below about 5 minutes; (2) heating said sheet an average temperature in the range of about 210°-300° F. at a rate so that by the time that said sheet has reached said average temperature, the average crystallinity of said sheet has increased to a value in the range of about 0% to about 18%; (3) thermoforming said sheet by: (a) contacting the sheet of Step (2) before there is either substantial cooling or a substantial change in the average crystallinity therein with a mold which is at a temperature in the range of about 240°-350° F.; (b) applying forces comprising a differential in applied pressure to said sheet so as to make said sheet conform to said mold, whereby a thermoformed sheet is made; (4) allowing said thermoformed sheet to remain in contact with said mold until an average crystallinity of at least about 20% is achieved; and (5) removing said thermoformed sheet from said mold and allowing said thermoformed sheet to cool.

Claim 14

The process of claim 10, wherein said mold is at a temperature in the range of about 270°-310° F.

Claim 15

The process of claim 11, wherein the sheet in step (3) (a) is at a temperature in the range of 225°-270° F.

Claim 16

The process of claim 12, wherein said resin is polyethylene terephthalate.

Claim 17

The process of claim 13, wherein said sheet has a half-time for crystallization at 410° F. below about 3 minutes.

Claim 18

The process of claim 12, wherein the average crystallinity of the sheet in Step (3) (a) is in the range of about 5% to about 15%.

Claim 19

The process of claim 12, wherein said differential in applied pressure is in the range of up to about 5 atmospheres.

Claim 20

The process of claim 12, wherein said differential in applied pressure is about 1 atmosphere.