Poly(3-hydroxyalkanoate) foam particles and poly(3-hydroxyalkanoate) foam molded article

1. Poly(3-hydroxyalkanoate) foam particles having at least two melting peaks on a DSC curve obtained by differential scanning calorimetry, a melting calorie (X) on a high temperature side being 0.1 to 20 J/g, a gel fraction (Y) being 20 to 75% by weight, and the melting calorie (X) and the gel fraction (Y) satisfying the following formula (1):

X+Y≥ 30  (1),

wherein the poly(3-hydroxyalkanoate) foam particles are obtained by a process comprising foaming resin particles comprising a poly(3-hydroxyalkanoate) composition, where the resin particles contain no isocyanate compound or contain the isocyanate compound in an amount of less than 3 parts by weight based on 100 parts by weight of poly(3-hydroxyalkanoate).

2. The poly(3-hydroxyalkanoate) foam particles according to claim 1 , wherein poly(3-hydroxyalkanoate) is at least one selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

3. The poly(3-hydroxyalkanoate) foam particles according to claim 2 , wherein poly(3-hydroxyalkanoate) is a copolymer of 3-hydroxybutyrate and a comonomer, and a monomer ratio in the copolymer is 3-hydroxybutyrate/comonomer=99/1 to 80/20 (mol %/mol %).

4. The poly(3-hydroxyalkanoate) foam particles according to claim 1 , wherein the amount of the isocyanate compound is less than 0.1 parts by weight based on 100 parts by weight of poly(3-hydroxyalkanoate).

5. The poly(3-hydroxyalkanoate) foam particles according to claim 1 , wherein the poly(3-hydroxyalkanoate) foam particles comprise a crosslinked structure formed by bonding molecular chains of poly(3-hydroxyalkanoate) directly without a structure derived from a crosslinking agent.

6. The poly(3-hydroxyalkanoate) foam particles according to claim 1 , wherein the poly(3-hydroxyalkanoate) foam particles have an apparent density of 0.02 to 0.6 g/cm 3 .

7. The poly(3-hydroxyalkanoate) foam particles according to claim 1 , wherein the poly(3-hydroxyalkanoate) foam particles have an average cell diameter of 50 to 500 μm.

8. A process for producing the poly(3-hydroxyalkanoate) foam particles according to claim 1 , comprising:

introducing a blowing agent into a pressure-resistant vessel comprising a dispersion comprising the resin particles comprising the poly(3-hydroxyalkanoate) composition, water, a dispersant, and a crosslinking agent;

heating a content of the pressure-resistant vessel to a temperature equal to or higher than a softening temperature of the resin particles;

holding the content of the pressure-resistant vessel at around a foaming temperature for a certain period of time; and

releasing an end of the pressure-resistant vessel, and releasing the content into an atmosphere at a lower pressure than a pressure in the pressure-resistant vessel to foam the resin particles.

9. The process according to claim 8 , wherein the crosslinking agent is an organic peroxide.

10. The process according to claim 9 , wherein the organic peroxide is an diacyl peroxide.

11. The process according to claim 8 , wherein a foaming pressure is 2 to 5 MPa.

12. A poly(3-hydroxyalkanoate) foam molded article obtained by molding the foam particles according to claim 1 .

13. A process for producing a poly(3-hydroxyalkanoate) foam molded article, comprising:

producing the poly(3-hydroxyalkanoate) foam particles in accordance with the process of claim 8 ;

filling the poly(3-hydroxyalkanoate) foam particles in a mold; and

heating the poly(3-hydroxyalkanoate) foam particles with superheated steam.