Claims
- 1. In a method of making a clear blown article by blow molding a blowable plastic shape consisting essentially of polyethylene terephthalate, which tends to develop a haze of stress whitening when rapidly blown at a temperature conducive to molecular orientation, the steps of:
- closing the sections of a blow mold around a blowable plastic shape consisting essentially of polyethylene terephthalate;
- injecting blow fluid under pressure into the blowable shape while said shape is at a temperature conducive to molecular orientation within the range of about 165.degree. to about 200.degree. F., the blow fluid being (a) at a pressure of between about 400 and about 500 psi and (b) at a temperature between about 150 degrees F. and about 400 degrees F. when injected into the blowable shape prior to any adiabatic expansion, and the injecting step being performed in less than about three seconds; and
- removing the blown article from the blow mold.
- 2. The method of claim 1, further including the step of axially stretching the blowable shape prior to the injecting step, in order to biaxially orient the polyethylene terephthalate material of the blown article.
- 3. The method as defined in claim 1, further characterized by the blow fluid being at a temperature within the range of from about 165.degree. to about 300.degree. F. when injected into the blowable shape prior to any adiabatic expansion.
- 4. The method as defined in claim 1, further including the steps of:
- storing the heated blowing fluid under pressure within a plenum prior to its injection into the blowable plastic shape; and
- supplying the fluid under pressure to the plenum from a compressor through a flow line which bypasses an after-cooler that normally cools the blow fluid prior to its injection into a blowable plastic shape.
- 5. A method of making a clear blown bottle of polyethylene terephthalate which is essentially free of any haze caused by stress whitening and which is biaxially oriented, comprising the steps of:
- closing the sections of a blow mold around a blowable plastic shape consisting essentially of polyethylene terephthalate;
- axially stretching the blowable shape while the polyethylene terephthalate material is at a temperature conducive to molecular orientation in the range of from about 165.degree. F. to about 200.degree. F.;
- injecting blow fluid under pressure into the stretched blowable shape while said material is still at a temperature conducive to molecular orientation in said temperature range, the blow fluid being at a pressure of between about 400 and about 500 psi and at a temperature between about 150.degree. F. and about 400.degree. F. when injected into the blowable shape prior to any adiabatic expansion;
- during the streching and blowing steps, molecularly orienting the polyethylene material without developing a haze of stress whitening; and
- removing the blown article from the blow mold as a biaxially oriented, clear article.
CROSS REFERENCE TO RELATED APPLICATIONS
This patent application is a continuation-in-part application of U.S. Ser. No. 659,621 filed on Feb. 20, 1976, now abandoned.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1339479 |
Aug 1963 |
FRX |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
659621 |
Feb 1976 |
|