Abstract: An objective of the present invention is to provide a mode conversion device capable of designing any coupling efficiency and full width at half maximum, and a design method therefor. According to the present invention, a mode conversion device includes a long period grating at a core of an optical fiber through which light is able to propagate in at least two propagation modes. The long period grating satisfies a relationship of Expression C1, where a full width at half maximum FWHM is a wavelength band in which the coupling efficiency is a half of coupling efficiency of mode conversion at a center wavelength, C is coupling efficiency, Lc is a complete coupling length, Lg is a grating length, ? is a grating pitch, and ?? is a propagation constant difference between the two propagation modes at the center wavelength of a mode conversion target. [ Math .

Abstract: Hot-melt-adhesive conjugate fibers consisting of a fiber-forming component and an adhesive component are provided, with at least one of the fiber-forming component and the adhesive component being a low-melting, modified polyester resin obtained by subjecting to polycondensation, a diol component consisting of 3 to 40 molar % of a 2,2-dialkyl-substituted-1,3-propanediol and 60 to 97 molar % of ethylene glycol and/or 1,4-butanediol, and an aromatic dicarboxylic acid, said low-melting, modified polyester resin having a melting point range between the melting point of polyethylene and a temperature at least 20.degree. C. lower than the melting point of highly crystalline polyethylene terephthalate.

Abstract: An improved woody fiber mat composed mainly of woody fibers, long fibers, thermoplastic fibers and a thermoset resin and moldable under heat and pressure into a product having a definite shape and very suitable to deep draw forming is provided, which mat is characterized in that the thermoplastic fibers are composite fibers composed of a plurality of components having different melting points; the fibers constituting the mat are entangled with each other and also subjected to melt adhesion and joining by a lower melting point component of the composite fibers; and the thermoset resin is in an uncured state.

Abstract: A process for producing side-by-side type composite fibers made of polypropylene-polyethylene which do not have hardly any crimp nor latent crimpability is provided. In said process, a composite spinning is carried out by melt-extrusion by using, as composite components of side by side type, crystalline polypropylene of an intrinsic viscosity (I.V.) of 1.45.about.2.15 and high density polyethylene of I.V. of 0.85.about.1.05 under a condition satisfying the relationship of 10,500.gtoreq.DX V.gtoreq.5,139 (V: take-up speed (m/min); D: denier of taken up unstretched fibers); and stretching the resulting filaments to 3.about.5 times the original length at a temperature of 90.degree. C. or higher.

Abstract: A method for producing a hollow-cylindrically shaped fibrous article stabilized by hot adhesion and an apparatus suitable to produce the same are provided. Said method comprises passing a web of gathered fiber layer carried on a conveyer belt through a heating zone, heating said web in such a way that a lower-melting component of composite fiber contained in the lower part of said web contacting the conveyer belt is not in the molten state and a lower-melting component contained in the upper part of said web is in the molten state, while separating said web from the conveyer belt, winding up said web on a take-up rod or tube in such a way that the upper surface thereof occupies the inner side of the winding, while heating the web further, cooling the wound up article and drawing out the take-up rod or tube from the shaped product.The production method of the present invention is simple and does not require complicated apparatus and the resultant product is useful for filtration.

Abstract: A method for producing a hollow-cylindrically shaped fibrous article stabilized by hot adhesion and an apparatus suitable to produce the same are provided. Said method comprises passing a web of gathered fiber layer carried on a conveyor belt through a heating zone, heating said web in such a way that a lower-melting component of composite fiber contained in the lower part of said web contacting the conveyor belt is not in the molten state and a lower-melting component contained in the upper part of said web is in the molten state, while separating said web from the conveyor belt, winding up said web on a take-up rod or tube in such a way that the upper surface thereof occupies the inner side of the winding, while heating the web further, cooling the wound up article and drawing out the take-up rod or tube from the shaped product.The production method of the present invention is simple and does not require complicated apparatus and the resultant product is useful for filtration.