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 0.3-2.5% by weight of a carbodiimide composition into biobased plastic based on polyester resin, wherein the carbodiimide composition consists of carbodiimides of the formula (II) ##STR00005##

2. 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.

3. The process as claimed in claim 2, wherein the biobased polyester resin is polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and/or polybutylene succinate terephthalate (PBST).

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

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

6. The process as claimed in claim 1, wherein the biobased plastic based on polyester resin further comprises nucleating agents, reinforcement fibers, impact modifiers, flow improvers, and/or UV stabilizers.

7. A method for increasing hydrolysis resistance of polylactic acid, the method comprising introducing 1 to 1.5% by weight of a carbodiimide composition into polylactic acid, wherein the carbodiimide composition consists of carbodiimides of the formula (II) ##STR00006##

8. The process as claimed in claim 7, wherein: the incorporating is done at 150 to 280 C., and the incorporating comprises mixing the carbodiimide composition into the polylactic acid by means of an extruder.

9. The process as claimed in claim 1, wherein the amount of carbodiimide composition incorporated into the plastic is 1 to 1.5% by weight, based on the total weight of the biobased plastic.

10. The process as claimed in claim 9, wherein the biobased plastic based on polyester resin is polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), and/or polybutylene succinate terephthalate (PBST).

11. The process as claimed in claim 10, wherein the incorporating is done at 150 to 280 C., and comprises mixing the carbodiimide composition into the plastic by means of an extruder.

Description

EXAMPLES

(1) Chemicals Used:

(2) CDI I: a carbodimide of formula (II) for the inventive example

(3) CDI II: bis-2,6-dilsopropylphenylcarbodlimide for the comparative example

(4) CDI III: polymeric carbodiimide based on triisopropylphenyl diisocyanate for the comparative example

(5) Commercially available polylactic acid (PLA) 3251 D from NatureWorks LLC

(6) Method:

(7) 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.

(8) The quantities used of carbodimide and the nature of the carbodimide used can be seen in table 1.

(9) The standard F3 test samples were produced in an Arburg Allrounder 320 S 150-500 injection molding machine.

(10) 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.

(11) 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

(12) 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.