BIODEGRADABLE COPOLYESTERS

Abstract

The present invention relates to biodegradable copolyesters with molecular weight Mn from 10 000 to 100 000 measured by GPC, obtainable via reaction of i) from 51 to 84% by weight, based on the copolyester, of a branched polyester middle block produced from aliphatic or aliphatic and aromatic dicarboxylic acids and from aliphatic dihydroxy compounds with molecular weight Mn from 5000 to 25 000 measured by .sup.1H NMR with from 15.9 to 48.9% by weight, based on the copolyester, of a lactide in the presence of a catalyst, and then the resultant polyester triblock with molecular weight Mn measured by .sup.1H NMR from 5800 to 49 500 with ii) from 0.1 to 3% by weight, based on the copolyester, of a diisocyanate.

The present invention further relates to a process for the production of, and to the use of, the abovementioned biodegradable copolyesters.

Claims

1.-8. (canceled)

9. A process for the continuous production of biodegradable copolyesters, which comprises i-1) mixing a mixture of the aliphatic dihydroxy compounds and the aliphatic and aromatic dicarboxylic acids to give a paste, optionally without addition of a catalyst, or alternatively the dihydroxy compound and the liquid esters of the dicarboxylic acids, and optionally other comonomers are fed into the system, optionally without addition of a catalyst, and in a first stage this mixture is continuously esterified or, respectively, transesterified together with optionally the entire quantity or a partial quantity of the catalyst; i-2) in a second stage, the transesterification or esterification product obtained according to i-1) is continuously precondensed until intrinsic viscosity in accordance with DIN 53728 reaches from 20 to 70 cm.sup.3/g; i-3) in a third stage, the product obtainable from i-2) is continuously polycondensed until intrinsic viscosity in accordance with DIN 53728 reaches from 50 to 180 cm.sup.3/g, where the ratio of hydroxy number to (hydroxy number+acid number) in the middle blocks is more than 85% and the molecular weight Mn of the middle blocks is from 5000 to 25 000 measured by .sup.1H NMR, ii) from 51 to 84% by weight, based on the copolyester, of the polyester middle block obtainable from i-3) is then continuously reacted with from 15.9 to 48.9% by weight, based on the copolyester, of a lactide in the presence of tin dioctanate, and iii) in a fifth stage, the polyester triblock obtainable from ii) with molecular weight Mn from 5800 to 49 500 measured by .sup.1H NMR is continuously reacted in a polyaddition reaction with from 0.1 to 3% by weight, based on the copolyester, of a diisocyanate until intrinsic viscosity in accordance with DIN 53728 reaches from 100 to 320 cm/g.

10. The process according to claim 9, wherein the molecular weight Mn of the polyester middle block i is from 5000 to 25 000 measured by .sup.1H NMR and said middle block i is composed of: A) an acid component: a1) from 45 to 100 mol %, based on the acid component A, of at least one aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, azelaic acid, sebacic acid, and brassylic acid, and ester-forming derivatives thereof, and mixtures thereof a2) from 0 to 55 mol %, based on the acid component A, of a terephthalic acid or a furan-2,5-dicarboxylic acid, or ester-forming derivatives thereof; and B) an alcohol component: b1) from 98 to 99.99 mol %, based on the alcohol component B, of a C.sub.2- to C.sub.12-alkanediol, or a mixture thereof; and b2) from 0.01 to 2 mol %, based on the alcohol component B, of a polyol selected from the group consisting of trimethylolpropane, trimethylolethane, pentaerythritol, polyethertriol, and glycerol.

11. The process according to claim 10, wherein the molecular weight Mn of the polyester middle block i is from 10 000 to 25 000 measured by .sup.1H NMR and said middle block i is composed of: A) an acid component: a1) from 50 to 80 mol %, based on the acid component A, of at least one aliphatic dicarboxylic acid selected from the group consisting of succinic acid, adipic acid, and sebacic acid, and ester-forming derivatives thereof, and mixtures thereof a2) from 20 to 50 mol %, based on the acid component A, of a terephthalic acid or ester-forming derivative thereof; and B) an alcohol component: b1) from 98 to 99.99 mol %, based on the alcohol component B, of 1,4-butanediol or 1,3-propanediol, or a mixture thereof; and b2) from 0.01 to 2 mol %, based on the alcohol component B, of a polyol selected from the group consisting of trimethylolpropane, pentaerythritol, and glycerol.

12. The process according to claim 9, wherein more than 90% of the quantity of the lactide ii) used is composed of L-lactide.

13. The process according to claim 11, wherein more than 90% of the quantity of the lactide ii) used is composed of L-lactide.

14. The process according to claim 9, wherein hexamethylene diisocyanate is used as diisocyanate iii).

15. The process according to claim 13, wherein hexamethylene diisocyanate is used as diisocyanate iii).

Description

EXAMPLES

Comparative Example 1

[0079] A mixture of 68% by weight of Ecoflex® F1300 (polybutylene terephthalate-co-adipate from BASF SE) and 32% of Ingeo® 4043 D (polylactic acid from NatureWorks) were compounded in a Coperion MC 40 extruder. The discharge temperatures were set to 250° C. The extrudate was then pelletized under water.

Comparative Example 2—(PLA)-(Polybutylene Terephthalate-Co-Adipate)-(PLA)

[0080] 140.0 g of polybutylene terephthalate-co-adipate (MB1; terephthalic acid:adipic acid=47:53) were used as initial charge in a 500 mL four-necked flask, and the apparatus was flushed with nitrogen. The mixture was heated until the internal temperature was 185° C., and 35.0 g of L-lactide and 0.51 mL of tin(II) bis(2-ethylhexanoate) (10% solution in toluene) were added. After 50 min and after 60 min 0.9 mL of hexamethylene diisocyanate was in each case added, and after a further 5 min the mixture was cooled to room temperature.

IV=153 ml/g; Mn=25 900 g/mol; PDI=4.8

Inventive Example 3—(PLA)-(Polybutylene Terephthalate-Co-Adipate)-(PLA)

[0081] 150.0 g of polybutylene terephthalate-co-adipate (MB1; terephthalic acid:adipic acid=47:53) were used as initial charge in a 500 mL four-necked flask, and the apparatus was flushed with nitrogen. The mixture was heated until the internal temperature was 185° C., and 75.0 g of L-lactide and 1.09 mL of tin(III) bis(2-ethylhexanoate) (10% solution in toluene) were added. After 60 min and after 75 min 0.96 mL of hexamethylene diisocyanate was in each case added, and after a further 5 min the mixture was cooled to room temperature.

IV=185 mL/g; Mn=34 900 g/mol; PDI=4.3

Inventive Example 4—(PLA)-(Polybutylene Terephthalate-Co-Adipate)-PLA)

[0082] 82.5 g of polybutylene terephthalate-co-adipate (MB1; terephthalic acid:adipic acid=47:53) were used as initial charge in a 500 mL four-necked flask, and the apparatus was flushed with nitrogen. The mixture was heated until the internal temperature was 185° C., and 55.0 g of L-lactide and 0.78 mL of tin(II) bis(2-ethylhexanoate) (10% solution in toluene) were added. After 55 min, 0.53 mL of hexamethylene diisocyanate was added, and after a further 5 min the mixture was cooled to room temperature.

IV=160 mug; Mn=33 300 g/mol; PDI=3.5

Inventive Example 5—(PLA)-(Polybutylene Terephthalate-Co-Adipate)-(PLA)

[0083] 65.0 g of polybutylene terephthalate-co-adipate (MB1; terephthalic acid:adipic acid=47:53) were used as initial charge in a 500 mL four-necked flask, and the apparatus was flushed with nitrogen. The mixture was heated until the internal temperature was 185° C., and 65.0 g of L-lactide and 0.92 mL of tin(II) bis(2-ethylhexanoate) (10% solution in toluene) were added. After 55 min, 0.41 mL of hexamethylene diisocyanate was added, and after a further 5 min the mixture was cooled to room temperature.

IV=122 mL/g; Mn=26 800 g/mol; PDI=2.9

Inventive Example 6—(PLA)-(Polybutylene Terephthalate-Co-Adipate)-(PLA)

[0084] 300.0 g of polybutylene terephthalate-co-adipate (MB2; terephthalic acid:adipic acid=47:53) were used as initial charge in a 1 mL four-necked flask, and the apparatus was flushed with nitrogen. The mixture was heated until the Internal temperature was 185° C., and 150.0 g of L-lactide and 2.18 mL of tin(II) bis(2-ethylhexanoate) (10% solution in toluene) were added. After 55 min and after 68 min 1.71 mL of hexamethylene diisocyanate were in each case added, and after a further 7 min the mixture was cooled to room temperature.

IV=126 mL/g; Mn=44 100 g/mol; PDI=7.2

TABLE-US-00001 TABLE 1 Mechanical data (tensile test in accordance with ISO 527 on pressed films of the thickness stated in the table) Proportion Proportion Thick- Modulus of PBAT of PLA ness of elasticity ε.sub.γ σ.sub.γ ε.sub.M σ.sub.M ε.sub.B σ.sub.B a.sub.B Example % % μm MPa % MPa % MPa % MPa J/cm.sup.3 CE1 68 32 136 221 — — 378 28 386 26 45 compound CE2 85 15 119 70 32  8 589 33 592 32 49 IE3 71 29 134 95 32 10 489 42 489 41 50.5 IE4 64 36 81 263 18 18 503 39 505 39 66 IE5 53 47 106 612  7 27 388 42 390 41 61 ε.sub.γ tensile strain at yield stress (tensile strain at yield) σ.sub.γ yield stress ε.sub.M tensile strain on determination of tensile strength σ.sub.M tensile strength ε.sub.B tensile strain at break σ.sub.B tensile stress at break a.sub.B fracture energy

[0085] The inventive copolyesters IE3 to IE5 exhibited optimized tensile strain at break/tensile stress at break performance in comparison with a mixture of the two individual components (CE1) and in comparison with films made of copolyesters with an excessively low proportion of PLA (15%, CE2). CE2 moreover exhibited a very low modulus of elasticity, and poor tensile stress at break performance. Copolyesters with a proportion of PLA greater than 49% exhibited high viscosity even before addition of the diisocyanate, and problems therefore occurred with the mixing procedure. Films produced from copolyesters of that type moreover lacked acceptable tensile strain performance.

TABLE-US-00002 TABLE 2 Disintegration test result Degradation Proportion of Proportion of after 12 weeks PBAT PLA Thickness by analogy with Example % % μm standard 16929 CE1 68 32 280 incomplete compound IE6 68 32 280 complete