Method for producing transparent plastic molded articles and thermoforming apparatus therefor
US4140457A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 4, 1977 |
| Grant date | Feb 20, 1979 |
| Priority date | — |
| Expiry date | Aug 4, 1997 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S425/235
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
This invention provides a simple and advantageous method for producing plastic moldings with good surface gloss, very excellent transparency and high stiffness from crystalline polypropylene sheets manufactured by a generally employed industrial method without adversely affecting mechanical strength, shape retention at high temperatures and other properties according to a thermoforming process. This invention, more specifically, concerns a method for producing transparent polypropylene molded articles, characterized by heating a polypropylene sheet at a temperature higher than the melting point thereof, stretching it by more than 5%, rapidly cooling it to a temperature of not more than 120.degree. C., and then subjecting the thus treated sheet to thermoforming at a temperature below the melting point of the sheet.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.