Blends of styrene butadiene copolymers with poly(lactic acid)

Abstract

The present invention relates to a polymer blend comprising 75-99.5% (w/w) of at least one polylactic acid) (PLA) and 0.5-25% (w/w) of at least one styrene butadiene copolymer containing at least 50% (w/w) styrene. The present invention further relates to the use of such polymer blend for producing products and to the resulting products. Moreover, an object of the present invention is the use of a styrene butadiene block copolymer having a dendrimer structure comprising 50-85% (w/w) styrene as an additive of polymer blends comprising at least 50% (w/w) of PLA and a method of producing the polymer blend according to the invention.

Claims

1. A polymer blend comprising: A) 0.5-10% (w/w), based on the total mass of the polymer blend, of at least one styrene butadiene copolymer comprising A1.) at least 50% (w/w), based on the total mass of the at least one styrene butadiene copolymer, of styrene moieties, A2.) at least 10% (w/w), based on the total mass of the at least one styrene butadiene copolymer, of butadiene moieties, and optionally A3.) one or more other comonomer moieties; B) 90-99.5% (w/w), based on the total mass of the polymer blend, of at least one poly(lactic acid) (PLA); and optionally C) 0 to 5% (w/w), based on the total mass of the polymer blend, of one or more additive(s).

2. The polymer blend according to claim 1, wherein the styrene butadiene copolymer is a block copolymer.

3. The polymer blend according to claim 1, wherein the styrene butadiene copolymer comprises: A1) 50-85% (w/w) styrene moieties; A2) 15-50% (w/w) butadiene moieties; and A3) 0-25% (w/w) other comonomer moieties.

4. The polymer blend according to claim 1, wherein the styrene butadiene copolymer is selected from the group consisting of a block copolymer having a branched structure, a block copolymer having a dendrimer structure, a block copolymer having a first generation dendrimer structure, and a block copolymer having a first generation dendrimer structure having four branches.

5. The polymer blend according to claim 1, wherein the styrene butadiene copolymer is an anionically produced block copolymer containing: (i) at least one block of styrene-containing hard phase with a glass transition temperature (Tg) >70° C.; and (ii) at least one block of butadiene-containing soft phase with Tg <0° C.

6. The polymer blend according to claim 1, wherein the styrene butadiene copolymer comprises at least one butadiene-containing soft-phase block, wherein said soft-phase block comprises styrene moieties in an amount of 1-45% (w/w), based on the total mass of the soft-phase block, and has an overall Tg <0° C.

7. The polymer blend according to claim 1 comprising: A) 0.5-10% (w/w) of at least one styrene butadiene copolymer; B) 90-99.4% (w/w) of at least one PLA; and C) 0.1 to 5% (w/w) of one or more additive(s).

8. The polymer blend according to claim 1 comprising: A) 1-5% (w/w) of at least one styrene butadiene copolymer; B) 94-98.5% (w/w) of at least one PLA; and C) 0.5 to 5% (w/w) of one or more additive(s).

9. The polymer blend according to claim 1 comprising: A) 1-5% (w/w) of at least one styrene butadiene block copolymer having a dendrimer structure; B) 94-99% (w/w) of at least one PLA, wherein the PLA has a melt flow index (MFI) of between 4 and 10 g/10 min (determined at a temperature of 210° C. and at a load of 2.16 kg according to ASTM procedure D1238); and optionally C) 0 to 5% (w/w) of one or more additive(s).

10. A product comprising the polymer blend according to claim 1, wherein said product is selected from the group consisting of: (i) film material, (ii) packing material, (iii) a plastics molding, (iv) fiber or yarn, (v) foam, (vi) a fabric or tissue, (vii) a composite (viii) micro- or nanobeads, and (ix) an implant, wherein said polymer blend constitutes for more than 50% (w/w) of said product.

11. The product according to claim 10, wherein the polymer blend constitutes for more than 60% (w/w) of said product.

12. A method of producing a polymer blend according to claim 1 comprising the steps of: (i) blending of at least one styrene butadiene copolymer and of at least one PLA and optionally one or more additive(s) under conditions at which the styrene butadiene copolymer(s) and the PLA(s) can be mixed; and (ii) hardening the blend obtained from step (i).

13. The method according to claim 12, wherein: step (i) comprises the heating of the at least one styrene butadiene copolymer and the at least one PLA above the glass transition temperatures (Tgs) of said at least one styrene butadiene copolymer and said at least one PLA; and step (ii) comprises the cooling of the blend below the glass transition temperature (Tg) of the blend.

14. A polymer blend comprising a styrene butadiene copolymer that is a block copolymer having a dendrimer structure, wherein said styrene butadiene copolymer comprises: A1) 50-85% (w/w) styrene moieties, A2) 15-50% (w/w) butadiene moieties, and A3) 0-25% (w/w) other comonomer moieties, wherein the polymer blend comprises at least 50% (w/w), based on the total mass of the polymer blends, of at least one PLA, and wherein said styrene butadiene copolymer is selected from the group consisting of a block copolymer having a first generation dendrimer structure.

Description

EXAMPLES

(1) Preparing Blends of Styrene Butadiene Copolymers with Poly(Lactic Acid)

(2) Polylactic acid (commercial product Ingeo 2002D (NatureWorks LLC, Minnetonka, Minn., USA)) was compounded with an impact modifier using a twin-screw extruder with a melt temperature of from 180 to 210° C. The melt was passed through a die plate to form strands roughly 3 mm in diameter. Polymer strands were passed through a water bath to cool them and then the cooled polymer was cut into pellets roughly 3 mm in length.

(3) Pellets of the compounded polymer blend were injection molded at from 160 to 180° C. into Type I tensile bar specimen. The specimens were tested for ductility and toughness by stressing the specimen in tension according to ASTM procedure D638.

(4) The PLA materials were obtained from NatureWorks LLC as general purpose extrusion grade products Ingeo 2002D and Ingeo Biopolymer 2003D (both NatureWorks LLC, Minnetonka, Minn., USA)). The impact modifier is provided by Styrolution, LLC as Styroflex 2G66 (Styrolution Group GmbH, Frankfurt, Germany).

Example I

(5) Improvement of Poly(lactic acid) Ingeo 2002D by blending it with the styrene butadiene block copolymer (Styroflex 2G66)

(6) The styrene butadiene block copolymer (SBC) Styroflex 2G66 was blended with poly(lactic acid). The effect of admixing 20% (w/w) on energy to break and tensile strain at break (see DIN EN ISO 527) is shown in Table 1 below.

(7) TABLE-US-00001 TABLE 1 Blend of Poly(lactic acid) Ingeo 2002D with Styroflex 2G66 Test Units PA.1 QA.20 2002D CL Ingeo % 100 80 Styroflex 2G66 % 0 20 Tensile stress at break Psi 9478 3791 Tensile strain at break % 3.5 38.7 Energy to break in-lbf 53 389

(8) The above data clearly show that the tensile strain at break is increased from 3.5% for pure PLA to more than 38% for a blend comprising 20% (w/w) of the styrene butadiene block copolymer. Likewise, the energy to break is increased from 53 to 389 in-lbf. Therefore, the blend is significantly improved with respect to toughness and elasticity.

Example II Improvement of Poly(lactic acid) Ingeo Biopolymer 2003D by blending it with the styrene butadiene block copolymer (Styroflex 2G66)

(9) Various amounts of the styrene butadiene block copolymer (SBC) Styroflex 2G66 were blended with poly(lactic acid). The effect of admixing amounts of from 5 to 20% (w/w) on energy to break and tensile strain at break is shown in Table 2 below.

(10) TABLE-US-00002 TABLE 2 Blend of Poly(lactic acid) Ingeo Biopolymer 2003D with Styroflex 2G66 Test Units P.1 Q.5 Q.10 Q.15 Q.20 Ingeo Bio- % 100 95 90 85 80 polymer 2003D Styroflex 2G66 % 0 5 10 15 20 Tensile stress psi 3787 4060 4253 3863 4794 at break Tensile strain % 14 159 146 84 212 at break Energy to break in-lbf 154 1612 1452 860 2127

(11) The above data clearly show that, already at a content of the styrene butadiene block copolymer of only 5% (w/w), the tensile strain at break is increased from 14% for pure PLA to more than 159%. Likewise, the energy to break is increased from 154 to 1612 in-bf. Therefore, the blend is significantly improved with respect to toughness and elasticity.

(12) At contents of the styrene butadiene block copolymer of 10% (w/w) and 20% (w/w), respectively, the determined toughness and elasticity decreased and raised at a content of 20% (w/w). Nevertheless, in the entire range of between 0 and 20% (w/w), the values determined for the tensile strain at break and the energy at break are dramatically higher in comparison to PLA alone.

Example III

(13) Improvement of Poly(lactic acid) Ingeo Biopolymer 2003D by blending it with two different styrene butadiene block copolymers (Styrolux 6481 and Styrolux 3G55, both of Styrolution Group GmbH, Frankfurt, Germany).

(14) Various amounts of two styrene butadiene block copolymers (SBC) were blended with poly(lactic acid). The effect of admixing on energy to break and tensile strain at break is shown in Table 3 below.

(15) Styrolux 6481 is a styrene butadiene copolymer with an overall butadiene content of 36% and containing one block with a random arrangement of butadiene and styrene. Styrolux 3G55 is likewise a similar styrene butadiene copolymer, however, containing an overall butadiene content of only 25%.

(16) TABLE-US-00003 TABLE 3 Blends of Poly(lactic acid) Ingeo Biopolymer 2003D with two styrene butadiene copolymers. Test Units QB.10 QB.20 QC.15 QC.25 Ingeo Biopolymer 2003D % 90 80 85 70 Styrolux 6481 % 10 20 Styrolux 3G55 % 15 30 Tensile stress at break Psi 4296 3552 4382 5242 Tensile strain at break % 99 112 111 282 Energy to break in-lbf 1029 1062 1154 2863

(17) As noted above, addition of the styrene butadiene copolymer results in a significant improvement in material toughness as evidenced by the large increase in tensile strain at break and energy to break in comparison to the PLA alone (Sample P.1 from Table 2 in this case).

(18) From the Tables 2 and 3, it will be noted that already at a content of 10% (w/w) or even lower of styrene butadiene copolymer a significant increase in energy to break, tensile stress at break and tensile strain at break of the blends is achieved.