Thermoplastic polyester, particularly, polyethylene terephthalate (PET) is excellent in a balance such as mechanical properties, heat resistance, moldability, chemical resistance, and is inexpensive, therefore, it has a significantly wide application use as molding and packaging material represented as fiber, film, and PET bottle. Further, in recent years, from the viewpoint of reuse of resources, polyester resin after use or polyester resin obtained from recovery of polyester waste generated in molding process, has been reused as a raw materials for fiber or PET bottle. However, in the increase of such demand, thermoplastic polyester has a weak point of easy combustibility, and further, in recent years, by increasing recognition for fire and environment, environmentally-friendly flameproofing technology alternative to halogen type flame retardant is strongly desired.
Heretofore, various trials for flameproofing the polyester fiber have been carried out, various methods such as a method of using copolymerized polyester obtained by copolymerization with flame retardant; a method of kneading flame retardant into polyester and spinning it; a method of flameproofing a recycled polyester; a method of flameproofing a textile product by after-processing, have been proposed. On the other hand, as for the flame retardant resin composition, various proposals are reported, however, it is reported that the expression of flame retardant performance is wide-ranging.
For example, Patent document 1 discloses the method of producing flame retardant recycle polyester fiber obtained by spinning, or spinning and stretching with using the raw material, mixed copolymerized polyester obtained by copolymerization of the organic phosphorus compound and recovered polyester.
In addition, Patent document 2 discloses flame retardant recycled spun-dyed polyester fiber obtained by melt blending and spinning fibrously the recycled polyester resin having 1.0 to 1.4 of intrinsic viscosity obtained from recovery in chip producing process and/or film producing process, and the polyester resin composition obtained by adding pigment to the polyester resin obtained by adding the organic phosphorus compound such as phosphine oxide, phosphonate and phosphinate to the polyester resin having 0.5 to 1.0 of intrinsic viscosity.
In addition, for example, Patent document 3 discloses flame retardant polyester fiber obtained by melt-spinning the resin composition having 0.2 to 15% by mass of inorganic red phosphorus or resin coated inorganic red phosphorus, and 0 to 5% by mass of carbon black.
Further, for example, Patent document 4 discloses the flame retardant recycle polyester fiber in which the recycled polyester obtained by adding organic phosphorus compound into low molecular weight substance obtained by depolymerization of the recycle polyester and by re-polymerizing it, subsequently is spun.
Furthermore, for example, Patent document 5 discloses the flame retardant textile product to which ammonium polyphosphate containing substances coated with thermoplastic resin was contained in treatment process after spinning.
In addition, for example, Patent document 6 discloses flame retardant for after-processing of polyester based synthetic fiber including polyphosphate compound which have no effect for dyeability of dye.
Furthermore, for example, Patent document 7 reports that, in flame retardant composition using inorganic red phosphorus and ammonium polyphospate in combination, when 10% by mass of ammonium polyphospate is added in the presence of 6% by mass of inorganic red phosphorus, synergy effect for flame proofing is recognized in polyether-ester resin. In addition, there are many reports on the resin composition using inorganic red phosphorus and inorganic phosphorus-nitrogen based compound such as ammonium polyphosphate in combination, however, there is no report that significantly effective flame retardant fiber can be obtained by kneading inorganic hybrid type flame retardant using them in combination, and subsequently by spinning.