METHOD FOR STABILIZING POLYESTER-RESIN-BASED BIOPLASTICS

Abstract

The object of the invention is a method for stabilizing polyester-resin-based bioplastics by means of specific carbodiimides.

Claims

1. A process for the stabilization of biobased plastic based on polyester resin, the process comprising incorporating carbodiimides of the formula (I) ##STR00005## where p is 0 to 50, into the biobased plastic.

2. The process as claimed in claim 1, wherein the carbodiimide is a compound of the formula (II) ##STR00006##

3. The process as claimed in claim 1, further comprising incorporating 0.3-2.5% by weight, of the carbodiimide of the formula (I) into the biobased plastic.

4. The process as claimed in claim 1, wherein the biobased plastic based on polyester resin is at least one of: an aliphatic polyester resin produced by polymerization of monomers obtained by fermentation, an aliphatic polyester resin of polymers obtained by fermentation from starch, from sugar, from carbohydrates, from fats, or from vegetable oil, an aliphatic-aromatic polyester resin based on a biogenically produced diol component, and a biopolyamide in which the acid component is obtained from naturally occurring substances.

5. The process as claimed in claim 4, wherein the biobased polyester resin is polylactic acid (PL), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and/or polybutylene succinate terephthalate (PBST), preferably polylactic acid (PLA).

6. The process as claimed in claim 1, wherein the incorporation is achieved by means of an extruder.

7. The process as claimed in claim 1, wherein the incorporation is done at a temperature of 150 to 280 C.

8. The process as claimed in claim 1, further comprising additionally incorporating nucleating agents, reinforcement fibers, impact modifiers, flow improvers, and/or UV stabilizers as further additives into the biobased plastic.

9. A method for protecting biobased plastics from hydrolysis, the method comprising introducing carbodiimides of the formula (I) ##STR00007## where p=0 to 50, and/or of the formula (II) ##STR00008## into the biobased plastic.

10. The process as claimed in claim 1, further comprising incorporating 1 to 1.5% by weight, based on the total weight of the plastic, of the carbodiimide of the formula (I) into the biobased plastic.

11. The process as claimed in claim 10, wherein the biobased polyester resin is polylactic acid (PL), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and/or polybutylene succinate terephthalate (PBST).

12. The process as claimed in claim 11, wherein the incorporating is done at 150 to 280 C., and comprises mixing the carbodiimide into the plastic by means of an extruder.

13. The process as claimed in claim 2, further comprising incorporating 0.3-2.5% by weight, based on the total weight of the plastic, of the carbodiimide of the formula (II) into the biobased plastic.

14. The process as claimed in claim 13, further comprising incorporating 1 to 1.5% by weight, based on the total weight of the plastic, of the carbodiimide of the formula (II) into the biobased plastic.

15. The process as claimed in claim 14, wherein the biobased polyester resin is polylactic acid (PL), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and/or polybutylene succinate terephthalate (PBST).

16. The process as claimed in claim 15, wherein the incorporating is done at 150 to 280 C., and comprises mixing the carbodiimide into the plastic by means of an extruder.

Description

EXAMPLES

[0035] Chemicals Used:

[0036] CDI I: a carbodimide of formula (II) for the Inventive example

[0037] CDI II: bis-2,6-dilsopropylphenylcarbodlimide for the comparative example

[0038] CDI III: polymeric carbodiimide based on triisopropylphenyl diisocyanate for the comparative example

[0039] Commercially available polylactic acid (PLA) 3251 D from NatureWorks LLC

[0040] Method:

[0041] The respective carbodiimides were incorporated into the polylactic acid by means of a 10 ZSK 25 laboratory twin-screw extruder from Werner & Pfleiderer at a temperature of 190 C.

[0042] The quantities used of carbodimide and the nature of the carbodimide used can be seen in table 1.

[0043] The standard F3 test samples were produced in an Arburg Allrounder 320 S 150-500 injection molding machine.

[0044] For the polylactic acid (PLA) hydrolysis test, the standard F3 test samples were stored at a temperature of 65 C. in water, and tensile strength was checked after various time intervals. Hydrolysis resistance was tested by determining the number of days that have expired before the tensile strength value is less than 5 MPa. Comparative example 1 is polylactic acid (PLA) without carbodiimide.

TABLE-US-00001 TABLE 1 Hydrolysis resistance Duration of protection Example CDI Concentration of CDI from hydrolysis [days] 1 (C) 4 2 (I) CDI I 1% 10 3 (I) CDI I 1.5% 16 4 (C) CDI II 1% 7 5 (C) CDI II 1.5% 11 6 (C) CDI III 1% 8 7 (C) CDI III 1.5% 11

[0045] It can be seen from the table that, even at low carbodiimide concentration, the process of the invention can achieve the hydrolysis resistance that the carbodiimides known in the prior art achieve only at markedly higher concentrations.