A modified expanded bead that includes an expanded bead which includes a specific base polymer (β) and a coating layer which includes a specific base polymer (α). The coating layer covers at least part of an outer surface of the expanded bead. The melting point Tα of the base polymer (α) and the melting point Tβ of the base polymer (β) satisfy a relationship of 0≤Tα−Tβ≤20. When the modified expanded bead is cut into two halves along a cutting plane to form two half portions and thereafter one of the two half portions is cut along planes perpendicular to the cutting plane to form ten small pieces, outermost pieces among the ten small pieces have a xylene-insoluble content (B) which is less than a xylene-insoluble content (A) in the half portion and the xylene-insoluble content (A) is 10-80% by mass.

A process can be used for producing a thermoplastic polyurethane, where the process at least involves converting at least one isocyanate composition and a polyol composition, to obtain a prepolymer having isocyanate groups, and reacting the resulting prepolymer with at least one chain extender. The at least one isocyanate composition contains an isocyanate selected from naphthylene 1,5-diisocyanate (NDI), diphenylmethane 4,4′-diisocyanate (MDI), p-phenyl diisocyanate (PPDI), o-tolidine diisocyanate (TODI), ethylene diphenyl diisocyanate (EDI), or mixtures thereof. The polyol composition contains a polytetrahydrofuran or a derivative thereof. A thermoplastic polyurethane obtained or obtainable by such a process is useful, and a foamed pellet material can be produced containing such a thermoplastic polyurethane. The foamed pellet material of the invention can be used for production of a molded article.

This invention relates to monodisperse cross-linked polymer particles, comprising particles with a substantially smooth outer surface and an average diameter of less than 1 μm, wherein the particles are solid or porous, and wherein the coefficient of variation (CV) % of the particles, when measured by CPS disk centrifugation analysis, is less than 15%. These monodisperse cross-linked polymer particles may comprise magnetic material and are useful in various application. This invention also relates to monodisperse polymer particles for use as seed particles in the Ugelstad process.

The present invention relates to expanded thermoplastic polyurethane beads, a preparation method for same, and an application thereof. The expanded thermoplastic polyurethane beads consists of components of the following parts by weight: 100 parts of a thermoplastic polyurethane, 1-10 parts of a cell size stabilizer, and 1-35 parts of a melt viscosity modifier. The preparation method for the expanded thermoplastic polyurethane beads is also disclosed. The bead is produced by employing a volatile blowing agent to immerse the thermoplastic polyurethane, comprising the pore size stabilizer and the melt viscosity modifier, in an aqueous suspension, and is then followed by the foaming process. Utilization of the expanded thermoplastic polyurethane beads of the present invention allows for preparation of a foam product. The expanded thermoplastic polyurethane beads prepared per the present invention has uniform cell sizes and a high product yield. At the same time, the expanded thermoplastic polyurethane bead provides a great sintering performance even at a relatively low vapor pressure, a molded foam product has a small deformation, a low dimensional shrinkage ratio relative to a mold, great dimensional stability, and an aesthetically appealing appearance.

The present invention relates to expanded thermoplastic polyurethane beads, a preparation method for same, and an application thereof. The expanded thermoplastic polyurethane beads consists of components of the following parts by weight: 100 parts of a thermoplastic polyurethane, 1-10 parts of a cell size stabilizer, and 1-35 parts of a melt viscosity modifier. The preparation method for the expanded thermoplastic polyurethane beads is also disclosed. The bead is produced by employing a volatile blowing agent to immerse the thermoplastic polyurethane, comprising the pore size stabilizer and the melt viscosity modifier, in an aqueous suspension, and is then followed by the foaming process. Utilization of the expanded thermoplastic polyurethane beads of the present invention allows for preparation of a foam product. The expanded thermoplastic polyurethane beads prepared per the present invention has uniform cell sizes and a high product yield. At the same time, the expanded thermoplastic polyurethane bead provides a great sintering performance even at a relatively low vapor pressure, a molded foam product has a small deformation, a low dimensional shrinkage ratio relative to a mold, great dimensional stability, and an aesthetically appealing appearance.

An expanded polypropylene resin particle is obtained from a base material resin having a melting point of 140° C. to 150° C., wherein the base material resin includes a polypropylene resin A including 3 weight % to 15 weight % of 1-butene and having a melting point of 130° C. to 140° C.; and a polypropylene resin B having a melting point of 145° C. to 165° C., and wherein the expanded polypropylene resin particle has an average cell diameter of 100 μm to 340 μm.

An expanded polypropylene resin particle is obtained from a base material resin having a melting point of 140° C. to 150° C., wherein the base material resin includes a polypropylene resin A including 3 weight % to 15 weight % of 1-butene and having a melting point of 130° C. to 140° C.; and a polypropylene resin B having a melting point of 145° C. to 165° C., and wherein the expanded polypropylene resin particle has an average cell diameter of 100 μm to 340 μm.

An expanded bead having a tubular shape with a through hole and a method for producing the same are provided. The expanded bead includes a foamed core layer and a covering layer. A polyolefin-based resin included in the covering layer has a melting point lower than a melting point of a polypropylene-based resin included in the foamed core layer. An average hole diameter d of the through hole of the expanded bead is less than 1 mm, and a ratio d/D of the average hole diameter d to an average outer diameter D of the expanded bead is 0.4 or less. The polypropylene-based resin for the foamed core layer has a flexural modulus of 1,200 MPa or more and a melting point of 158° C. or lower.

An expanded bead having a tubular shape with a through hole and a method for producing the same are provided. The expanded bead includes a foamed core layer and a covering layer. A polyolefin-based resin included in the covering layer has a melting point lower than a melting point of a polypropylene-based resin included in the foamed core layer. An average hole diameter d of the through hole of the expanded bead is less than 1 mm, and a ratio d/D of the average hole diameter d to an average outer diameter D of the expanded bead is 0.4 or less. The polypropylene-based resin for the foamed core layer has a flexural modulus of 1,200 MPa or more and a melting point of 158° C. or lower.

In foamable polystyrene resin particles that are obtained by granulating a polystyrene resin containing a flame retardant and a foaming agent, the flame retardant has a bromine atom in a molecule, contains less than 70% by mass of bromine, has a benzene ring in a molecule, and has a 5% by mass decomposition temperature in a range of from 200° C. to 300° C. the flame retardant is the sole source of bromine in the foamable polystyrene resin particles, a ratio (B:A) between (A) a by mass of the flame retardant contained in the total foamable polystyrene resin particles and (B) a % by mass of the flame retardant contained in the surface of the resin particles is in a range of from 0.8:1 to 1.2:1, and the amount of the flame retardant added is in a range of from 0.5% by mass to 5.0% by mass, based on 100 parts by mass of the resin fraction in the foamable polystyrene resin particles.