Method for making a writing or coloring pencil by triple extrusion and writing or coloring pencil comprising an intermediate protective layer
US6572295B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 25, 2002 |
| Grant date | Jun 3, 2003 |
| Priority date | — |
| Expiry date | Jul 27, 2022 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/31928
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
The method of continuously manufacturing pencils or crayons consists in coextruding a filled first thermoplastic material referred to as “lead” material, and around it both an intermediate “protective” layer of a thermoplastic material having no expanding agent and a second thermoplastic material containing an expanding agent and referred to as “wood” material, and in cooling said coextruded thermoplastic materials. According to the invention, the thermoplastic material constituting the protective layer is determined so that during cooling it remains deformable while the lead material shrinks. The pencil is constituted by superposing a core of a filled first thermoplastic material referred to as “lead” material, a protective layer of a non-expanded thermoplastic material, and a layer of an expanded second thermoplastic material referred to as “wood” material. According to the invention, the thermoplastic material constituting the protective layer has a solidification point which is lower than that of the thermoplastic material constituting the lead material.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.