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Method for producing writing pencil or coloring pencil by triple extrusion, and writing pencil or coloring pencil having intermediate protective layer
Method for producing writing pencil or coloring pencil by triple extrusion, and writing pencil or coloring pencil having intermediate protective layer
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机译:通过三重挤压生产书写笔或着色笔的方法,以及具有中间保护层的书写笔或着色笔
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摘要
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.
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