Foamed thermoplastic resin particles and method of producing the foamed particles
View Patent ↗It is intended to provide resin foamed particles having a high environmental compatibility. Furthermore, it is intended to provide an economical and easy-to-use method of producing resin foamed particles having biodegradability without using a crosslinking agent, which should be handled with care, in the step of producing foamed resin particles. It is also intended to provide a molded article made of foamed particles having an extremely high heat insulating property and a biodegradability. Thermoplastic polyester-type resin foamed particles, in which the ratio of cells with diameter of 50 μm or less amounts to 20% or more in an arbitrary two-dimensional section of a thermoplastic polyester-type resin foamed particles, are first produced and then a molded article is produced with the use of these resin foamed particles.
1. A thermoplastic polyester-based resin foamed particle having an occupancy rate of the cell diameter of equal to or less than 50 μm in an arbitrary two-dimensional cross section of the thermoplastic polyester-based resin foamed particle being equal to or greater than 20%.
2. The thermoplastic polyester-based resin foamed particle according to claim 1 wherein the thermoplastic polyester-based resin comprises a copolymer poly(3-hydroxyalkanoate) having a repeating monomer unit represented by the general formula (1):
[—CHR—CH 2 —CO—O—] (1)
wherein, R is an alkyl group represented by C n H 2n+1 ; and n is an integer of 1 to 15, produced from a microorganism.
3. The thermoplastic polyester-based resin foamed particle according to claim 2 wherein the poly(3-hydroxyalkanoate) is poly(3-hydroxybutyrate)-co-3-hydroxyhexanoate).
4. The thermoplastic polyester-based resin foamed particle according to claim 3 wherein the composition ratio of the copolymerizing components of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is poly(3-hydroxybutyrate)/poly(3-hydroxyhexanoate) in a molar ratio=99/1 to 80/20.
5. A molded product of the foamed particles obtained by heat molding of the thermoplastic polyester-based resin foamed particles according to claim 1 .
6. The molded product of the foamed particles according to claim 5 wherein the molded product of the foamed particles has a thermal conductivity of equal to or less than 0.040 W/mK.
7. The molded product of the foamed particles according to claim 6 wherein the molded product of the foamed particles has a thermal conductivity of equal to or less than 0.034 W/mK.
8. The thermoplastic polyester-based resin foamed particle according to claim 1 wherein the thermoplastic polyester-based resin is a thermoplastic polyester-based resin (X) predominantly comprising a copolymer (x) comprising a compound (a) containing an alkane carboxylic acid and/or an ester-forming derivative of the alkane carboxylic acid, a compound (b) containing an aromatic carboxylic acid and/or an ester-forming derivative of the aromatic carboxylic acid and an alkane diol compound (c).
9. The thermoplastic polyester-based resin foamed particle according to claim 8 wherein the compound (a) is adipic acid and/or an ester-forming derivative of adipic acid, the compound (b) is terephthalic acid and/or an ester-forming derivative of terephthalic acid, and the compound (c) is butanediol.
10. The thermoplastic polyester-based resin foamed particle according to claim 8 wherein the copolymer (x) is a thermoplastic polyester-based resin obtained by allowing a monomer (x1) that imparts a branched structure and/or a chain extender (x2) to react.
11. The thermoplastic polyester-based resin foamed particle according to claim 1 having an occupancy rate of the cell diameter of equal to or less than 50 μm in an arbitrary two-dimensional cross section of the thermoplastic polyester-based resin foamed particle being equal to or greater than 50%.
12. A method of producing the thermoplastic polyester-based resin foamed particles according to claim 1 comprising: a step of dispersing thermoplastic polyester-based resin particles in a water-based dispersion medium in an airtight vessel together with a dispersant; a step of feeding a foaming agent into the airtight vessel after the dispersion, followed by heating the resin particles to not lower than the softening temperature thereof; and a step of opening one end of the airtight vessel after the heating so as to release the resin particles and the water-based dispersion medium to an atmosphere with a pressure lower than the pressure in the airtight vessel.