Multilayer system of at least three polyester layers, production thereof and use thereof

Abstract

The present invention relates to a multilayer system of at least 3 polyester layers, production thereof and use thereof for producing packaging, protective films, adhesive films, solar cells or medical materials and also solar cells produced therefrom.

Claims

1. A multilayer system of at least 3 polyester layers having the following construction: at least one polyester layer (I) containing at least one carbodiimide, at least one polyester layer (II) on the top of the polyester layer (I) and at least one polyester layer (III) on the bottom of the polyester layer (I), characterized in that at least one of these polyester layers (II) or (III) contains at least one epoxide, wherein the amount of carbodiimide in the polyester layer (I) is 0.2% to 3% by weight based on the polyester layer (I).

2. The multilayer system according to claim 1, characterized in that the carbodiimide is a compound of formula (I)
R.sup.1—R.sup.2—(—N═C═N—R.sup.2—).sub.n—R.sup.1  (I), where n represents an integer from 1 to 500, R.sup.1 represents a radical of the series —NCO, —NCNR.sup.3, —NHCONHR.sup.3, —NHCONR.sup.3R.sup.4 or —NHCOOR.sup.5, wherein R.sup.3 and R.sup.4 are identical or different and each independently represent a radical of the series C.sub.1-C.sub.12-alkyl, C.sub.6-C.sub.12-cycloalkyl, C.sub.7-C.sub.18-aralkyl or C.sub.6-C.sub.18-aryl and R.sup.5 represents a radical of the series C.sub.1-C.sub.22-alkyl, C.sub.6-C.sub.12-cycloalkyl, C.sub.6-C.sub.18-aryl or C.sub.7-C.sub.18-aralkyl, or an unsaturated alkyl radical having 2-22 carbon atoms or an alkoxypolyoxyalkylene radical, R.sup.2 represents C.sub.1-C.sub.12-alkyl-substituted C.sub.6-C.sub.18-arylenes, C.sub.7-C.sub.18-alkylaryl-substituted C.sub.6-C.sub.18-arylenes or optionally C.sub.1-C.sub.12-alkyl-substituted arylenes bridged via C.sub.1-C.sub.8-alkylene groups comprising a total of 7 to 30 carbon atoms or arylene.

3. The multilayer system according to claim 1, wherein the carbodiimides are compounds of formula (II), ##STR00006## where R.sup.1 is selected from the group of —NCO, —NHCONHR.sup.3, —NHCONR.sup.3R.sup.4 or —NHCOOR.sup.5, wherein R.sup.3 and R.sup.4 are identical or different and represent C.sub.1-C.sub.12-alkyl, C.sub.6-C.sub.12-cycloalkyl, C.sub.7-C.sub.18-aralkyl or C.sub.6-C.sub.18-aryl, R.sup.5 represents C.sub.1-C.sub.22-alkyl, C.sub.6-C.sub.12-cycloalkyl, C.sub.6-C.sub.18-aryl or C.sub.7-C.sub.18-aralkyl or an unsaturated alkyl radical having 2-22 carbon atoms, or an alkoxypolyoxyalkylene radical, and R.sup.6, R.sup.7 and R.sup.8 each independently of one another represent methyl or ethyl, wherein each benzene ring bears only one methyl group and n=1 to 20.

4. The multilayer system according to claim 1, wherein the polyester layer (I), (II) and/or (Ill) is thermoplastic polyester.

5. The multilayer system according to claim 1, wherein the polyester is selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutylene adipate terephthalate (PBAT), polytrimethylene terephthalate (PTT) and copolyesters, thermoplastic polyester elastomers (TPE E), ethylene vinyl acetate (EVA), polylactic acid (PLA) and/or PLA derivatives, polybutylene succinates (PBS), polyhydroxyalkanoates (PHA), and various blends and/or polyester-based thermoplastic polyurethanes.

6. The multilayer system according to claim 1, wherein the epoxides are compounds based on molecules having two or more epoxy groups per molecule.

7. The multilayer system according to claim 1, wherein the epoxides are a compound of formula (IV) ##STR00007## wherein R.sup.9, R.sup.10 each independently of one another represent H or C.sub.1-C.sub.8-alkyl, R.sup.11 represents C.sub.1-C.sub.8-alkyl, x and y independently of one another represent an average number of 1 to 20 and z represents an average number of 2 to 20, wherein the end groups R* independently of one another represent H or C.sub.1-C.sub.8-alkyl.

8. The multilayer system according to claim 1, wherein the amount of carbodiimide in the polyester layer (I) is 0.5% to 1.5% by weight based on the polyester layer (I).

9. The multilayer system according to claim 1, wherein the amount of epoxides in at least one of the polyester layers (II) or (III) is 0.1% to 6% by weight based on the polyester layer (II) or (III).

10. The multilayer system according to claim 1, wherein the weight fraction of the carbodiimide-containing polyester layer (I) is 70% by weight to 90% by weight based on the total weight of the multilayer system.

11. Process for producing a multilayer system according to claim 1, comprising coextruding the carbodiimide-containing polyester layer (I) and the polyester layers (II) and (III) to afford a multilayer system.

12. The process according to claim 11, wherein the polyester layer (I) is extruded and the polyester layers (II) and (III) are extruded around this polyester layer (I) by coextrusion.

13. (canceled)

14. A solar cell comprising at least one multilayer system according to claim 1.

15. The multilayer system according to claim 2, wherein n in formula (I) represents an integer from 3 to 20.

16. The multilayer system according to claim 2, wherein R.sup.2 represents ##STR00008## wherein R.sup.6, R.sup.7 and R.sup.8 each independently of one another represent methyl or ethyl, wherein each benzene ring bears only one methyl group.

17. The multilayer system according to claim 3, wherein R.sup.5 represents an unsaturated alkyl radical having 12-20 carbon atoms.

Description

EXAMPLES

Example 1

[0072] Tests were carried out on: [0073] 1) Carbodiimide A: a polymeric carbodiimide having an NCN content of about 11.8% by weight, D=about 1.8 and Mw=2300 g/mol of formula (II) where n=about 3-4, R.sup.6, R.sup.7, R.sup.8 each independently represent methyl or ethyl, wherein each benzene ring bears only one methyl group and R.sup.1=—NHCOOR.sup.5 and R.sup.5=cyclohexyl. [0074] 2) Carbodiimide masterbatch B: Polyethylene terephthalate (PET) obtainable from Invista Deutschland GmbH having an intrinsic viscosity of 0.8 which is admixed with 10% by weight of carbodiimide A and extruded. [0075] 3) Stabilizer C: Epoxide of formula (III) where n=in the range of 2-3 having an epoxide equivalent weight (DIN 16945) of 500 to 700 g/eq and a softening point (Mettler, DIN 51920) between 75° C. and 90° C. [CAS No 25068-38-6]. [0076] 4) Polyethylene terephthalate (PET) obtainable from Invista Deutschland GmbH having an intrinsic viscosity of 0.8.

[0077] The multilayer systems recited in table 1 were produced using an extruder for the inner polyester layer (I) and a co-extruder for the outer polyester layers (II) and (III) using polyethylene terephthalate as the polyester. An air extraction means was attached to the slot die. Table 1 summarizes the usage amounts and also the results of the qualitative emissions measurement in the stretching region using standardized indicator tubes for isocyanates (measurement duration about 30 min.) and the hydrolysis stability of the PET multilayer films.

Measurement of Hydrolysis Stability

[0078] For the hydrolysis test the layers were stored in steam at a temperature of 120° C. for 24 hours and their breaking elongation is measured after 0 and 24 hours.

[0079] The values for hydrolysis stability reported in table 1 derive from the following calculation: Breaking elongation [%]=(breaking elongation after 24 hours/breaking elongation after 0 hours)×100.

TABLE-US-00001 TABLE 1 Hydrolysis Composition stability Composition of polyester Isocy- (breaking of polyester layer (II) anate elongation layer (I) and (III) test in %) Comparative 100% by wt. 100% by wt. negative 38 example PET PET Comparative 15% by wt. 15% by wt. positive 95 example carbodiimide carbodiimide analogous to masterbatch B/ masterbatch B/ EP0838500 85% by wt. PET 85% by wt. PET Comparative 4% by weight 4% by weight negative 36 example stabilizer C, stabilizer C, analogous to 96% by wt. PET 96% by wt. PET EP1634914 Inventive 15% by wt. 0.5% by wt. negative 91 example carbodiimide stabilizer C, masterbatch B/ 99.5% by wt. 85% by wt. PET PET Comparative 15% by wt. 100% by wt. positive test values example carbodiimide PET highly masterbatch B/ scattered. 85% by wt. PET

[0080] The inventive example demonstrates the positive effect of the multilayer system according to the invention since said system shows no outgassing of isocyanate whatsoever coupled with good hydrolysis stability.