Abstract: The present invention provides a method for producing a mulching sheet which easy to biodegrade and can be produced at a low cost. A cotton waste sheet is prepared with randomly accumulated cotton waste and impurities selected from a group consisting of cottonseeds, stems, leaves and calyxes of cotton tree. Water is sprayed to the cotton waste sheet. Thereafter, the cotton waste sheet is passed between a pair of calender rolls each taking a form of a Japanese drum, while being heated, to press the cotton waste sheet in the thickness direction. The cotton waste is thereby closed, and the obtained mulching sheet has a high tensile strength. Furthermore, the impurities in the cotton waste sheet are crushed or flatted. The mulching sheet is a mixture of parts made of flatted impurities and parts made of cotton waste.

Abstract: The invention provides a bleaching method of natural fibers. By the invention, it is possible to bleach raw cotton fibers without dewaxing. The method of the invention is to bring the natural fibers on each of which wax adhere, into contact with water solution containing hydroxy percarboxilic acid for bleaching. The natural fibers may be raw cotton fibers. The hydroxy percarboxilic acid may be perlactic acid. The water solution may contain hydroxy carboxilic acid, hydrogen peroxide and alkali agent with hydroxy percarboxilic acid.