Biodegradable multi-layer film

A multi-layer polymer film comprising:

• at least one middle layer A, the polymeric constituents of which are soluble in aqueous solution;
• at least one covering layer B that is water-impermeable so as to withstand a column of water of at least 20 mm in accordance with DIN EN 20811:1992;
• and
• at least one covering layer C that water-impermeable so as to withstand a column of water of at least 20 mm in accordance with DIN EN 20811:1992,
• wherein the middle layer A is arranged between the layer B and the layer C, the layer B being arranged above or below the middle layer A and the layer C being correspondingly arranged below or above the middle layer A,
• wherein the middle layer A and the layer C, independently of each other and independently of layer B, in each case comprise at least one thermoplastic polymer,
• wherein the layer B, independently of middle layer A and layer C, comprises:
• component (i), which includes at least one polyhydroxyalkanoate in an amount of 20 wt. % to 95 wt. % based on a total weight of the layer B,
• component (ii), which includes at least one additional thermoplastic polymer, and
• component (iii), which includes destructured starch, wherein a total amount of the destructured starch in the layer B is 0.5 to less than 10 wt. % based on the total weight of the layer B or wherein a total amount of the destructured starch of component (iii) in the layer B is 10 to 50 wt. % based on the total weight of the layer B,
• wherein the layer B includes 95 wt. % to 100 wt. % by combined weight of the component (i), the component (ii), and the component (iii) based on the total weight of the layer B,
• wherein the at least one polyhydroxyalkanoate of the component (i) of the layer B includes at least one of poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), or poly-4-hydroxybutyrate,
• wherein the at least one additional thermoplastic polymer of the component (ii) of the layer B includes at least one of thermoplastic starch, starch-containing thermoplastics, polyvinyl alcohol, thermoplastic polyvinyl alcohol, polyvinyl acetate, poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxy-valerate), poly(3-hydroxy-butyrate-co-3-hydroxyhexanoate), polylactic acid, polycaprolactone, polybutylene succinate, poly(butylene adipate-co-succinate), aromatic-aliphatic copolyester, poly(butylene adipate-co-terephthalate), or poly(butylene sebacate-co-terephthalate), wherein the thermoplastic starch and the starch-containing thermoplastics, if included in component (ii) are an additional starch component or components distinct from the component (iii), which includes the destructured starch, and
• wherein the polyhydroxyalkanoate of the component (i) of the layer B, through post-crystallization, causes or allows the layer B to disintegrate in aqueous solution within at most 14 days into parts having (i) a surface area of at most 60% of the total surface area of the multi-layer polymer film and/or (ii) a surface area of at most 100 cm2.

A process for producing a multi-layer polymer film, the process comprising:

• (a) providing a polymer composition of a first covering layer B which comprises
• component (i), which includes at least one polyhydroxyalkanoate in an amount of 20 wt. % to 95 wt. % based on a total weight of the first covering layer B,
• component (ii), which includes at least one additional thermoplastic polymer, and
• component (iii), which includes destructured starch, wherein a total amount of the starch in the layer B is 0.5 to less than 10 wt. % based on the total weight of the layer B or wherein a total amount of the destructured starch of component (iii) in the layer B is 10 to 50 wt. % based on the total weight of the layer B,
• wherein the first covering layer B includes 70 wt. % to 100 wt. % by combined weight the component (i), the component (ii), and the component (iii) based on the total weight of the first covering layer B,
• (b) forming the first covering layer B from the polymer composition in (a),
• (c) providing at least one thermoplastic polymer of a middle layer A,
• (d) forming the middle layer A from the at least one thermoplastic polymer of (c),
• (e) providing a polymer composition of a second covering layer C, and
• (f) forming the second covering layer C from the polymer composition in (e) so that the middle layer A is between first covering layer B and second covering layer C,
• wherein the at least one polyhydroxyalkanoate of the component (i) of the first covering layer B includes at least one of poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), or poly-4-hydroxybutyrate,
• wherein the at least one additional thermoplastic polymer of the component (ii) of the first covering layer B includes at least one of thermoplastic starch, starch-containing thermoplastics, polyvinyl alcohol, thermoplastic polyvinyl alcohol, polyvinyl acetate, poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxy-valerate), poly(3-hydroxy-butyrate-co-3-hydroxyhexanoate), polylactic acid, polycaprolactone, polybutylene succinate, poly(butylene adipate-co-succinate), aromatic-aliphatic copolyester, poly(butylene adipate-co-terephthalate), or poly(butylene sebacate-co-terephthalate), wherein the thermoplastic starch and the starch-containing thermoplastics, if included in the component (ii) are an additional starch component or components distinct from the component (iii), which includes the destructured starch, and
• wherein the polyhydroxyalkanoate of the component (i) of the first covering layer B, through post-crystallization, causes or allows the layer B to disintegrate in aqueous solution within at most 14 days into parts having (i) a surface area of at most 60% of the total surface area of the multi-layer polymer film and/or (ii) a surface area of at most 100 cm2.