WOOD-PLASTIC COMPOSITE MATERIAL

Abstract

Described is a wood-plastic composite material for structural components of transport pallet, said structural components being capable of being nailed together, having a matrix foamed by means of a blowing agent, wood meal fibres and an adhesion promoter. To create a wood-plastic composite material of this kind which enables a cost-efficient production of transport pallets with a wood-like appearance and constitutes a reliable replacement for the soft wood materials used up until now, at least with regard to weight and mechanical strength properties, it is proposed that the matrix, which comprises a long chain-branched polyolefin, has a mass fraction of 30-95%, the wood meal fibres have a mass fraction of 5-50% and the adhesion promoter has a mass fraction of up to 10% of the wood-plastic composite material, the composite material density being less than 0.3 g/cm.sup.3.

Claims

1. Wood-plastic composite material for structural components of transport pallets that can be nailed together, said composite material comprising: a matrix, wood meal fibres and an adhesion promoter, wherein the matrix is foamed by means of a blowing agent; wherein the matrix comprises a long-chain branched polyolefin and has a mass fraction of 30-95%, the wood meal fibres have a mass fraction of 5-50%, and the adhesion promoter has a mass fraction of up to 10% of the wood-plastic composite material; and wherein the composite material has a density that is less than 0.3 g/cm.sup.3.

2. The wood-plastic composite material according to claim 1, wherein the long-chain branched polyolefin is a polyethylene or a polypropylene.

3. The wood-plastic composite material according to claim 1, wherein the composite material has a modulus of elasticity of 500 to 1000 MPa.

4. The wood-plastic composite material according to claim 1, wherein the wood meal fibres have a mass fraction of 20-40% and the adhesion promoter has a mass fraction of 1-5%.

5. The wood-plastic composite material according to claim 1, wherein the matrix is a polymer blend of a polyolefin that has a processing temperature and at least one thermoplastic polymer, wherein the mass fraction of the at least one thermoplastic polymer is 5-50% of the polymer blend, and wherein the at least one thermoplastic polymer has a melting temperature that is 20-70° C. above the processing temperature of the polyolefin and/or has a glass transition temperature that is up to 40° C. below the processing temperature of the polyolefin.

6. The wood-plastic composite material according to claim 5, wherein the at least one thermoplastic polymer is a thermoplastic polycondensate.

7. The wood-plastic composite material according to claim 6, wherein the polycondensate is a polyamide and/or a thermoplastic polyester.

8. The wood-plastic composite material according to claim 6, wherein the polycondensate is a polyamide 6, a polycarbonate, a polyethylene terephthalate and/or a polybutylene terephthalate.

9. A method for producing a wood-plastic composite material according to claim 1 using a two-stage screw extrusion process, said method comprising: in a first step, mixing a matrix melt, the wood meal fibres and the adhesion promoter so as to form a composite melt; and then in a second step, homogenizing and extruding the composite melt at a melt temperature between 170 and 200° C. and at a mass throughput of 5 to 15 kg/hour; wherein the method further comprises feeding a blowing agent to the composite melt upstream of an extruder mixing zone via a gas metering device.

10. A transport pallet comprising structural components made of a wood-plastic composite material according to claim 1, wherein the structural components are at least partially nailed together.

11. The wood-plastic composite material according to claim 2, wherein the wood meal fibres have a mass fraction of 20-40% and the adhesion promoter has a mass fraction of 1-5%.

12. The wood-plastic composite material according to claim 2, wherein the matrix is a polymer blend of a polyolefin that has a processing temperature and at least one thermoplastic polymer, wherein the mass fraction of the at least one thermoplastic polymer is 5-50% of the polymer blend, and wherein the at least one thermoplastic polymer has a melting temperature that is 20-70° C. above the processing temperature of the polyolefin and/or has a glass transition temperature that is up to 40° C. below the processing temperature of the polyolefin.

13. The wood-plastic composite material according to claim 3, wherein the matrix is a polymer blend of a polyolefin that has a processing temperature and at least one thermoplastic polymer, wherein the mass fraction of the at least one thermoplastic polymer is 5-50% of the polymer blend, and wherein the at least one thermoplastic polymer has a melting temperature that is 20-70° C. above the processing temperature of the polyolefin and/or has a glass transition temperature that is up to 40° C. below the processing temperature of the polyolefin.

14. The wood-plastic composite material according to claim 7, wherein the polycondensate is a polyamide 6, a polycarbonate, a polyethylene terephthalate and/or a polybutylene terephthalate.

15. The wood-plastic composite material according to claim 12, wherein the at least one thermoplastic polymer is a thermoplastic polycondensate.

16. The wood-plastic composite material according to claim 15, wherein the polycondensate is a polyamide and/or a thermoplastic polyester.

17. The wood-plastic composite material according to claim 15, wherein the polycondensate is a polyamide 6, a polycarbonate, a polyethylene terephthalate and/or a polybutylene terephthalate.

18. The wood-plastic composite material according to claim 13, wherein the at least one thermoplastic polymer is a thermoplastic polycondensate.

19. The wood-plastic composite material according to claim 18, wherein the polycondensate is a polyamide and/or a thermoplastic polyester.

20. The wood-plastic composite material according to claim 19, wherein the polycondensate is a polyamide 6, a polycarbonate, a polyethylene terephthalate and/or a polybutylene terephthalate.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary Embodiment 1

[0012] A wood-plastic composite material according to the invention comprises a long-chain branched polypropylene (WB140HMS) as matrix with a mass fraction of 67%, wood meal fibres (Lignocel C120) with a mass fraction of 30%, and an adhesion promoter (Scona TPPP 8112) with a mass fraction of 3%.

[0013] For example, a single-screw extruder (50 mm diameter) equipped with a core-progressive screw with an additional mixing section is used to produce the wood-plastic composite material. The melt is charged with the blowing gas carbon dioxide via a gas metering station, wherein the blowing gas is fed to the melt upstream of the mixing section with respect to the conveying direction. The melt temperatures along the screw are set in the range of 175 to 195° C., the melt throughput is about 10 kg/hour. The extrudate is extruded through a profile nozzle and subsequently cooled and drawn off.

[0014] The wood-plastic composite has a composite density of 0.06 g/cm.sup.3. The modulus of elasticity was determined by means of an ISO 178 bending test at room temperature and a test speed of 1 mm/s and amounts to 800 MPa. The bending strength achieved is 16 MPa.

Exemplary Embodiment 2

[0015] A wood-plastic composite material according to the invention comprises a polymer blend as matrix with a mass fraction of 67%, wood meal fibres (Lignocel C120) with a mass fraction of 30%, and an adhesion promoter (Scona TPPE 5002 GALL) with a mass fraction of 3%. The polymer blend itself comprises a low-density polyethylene (PE-LD recyclate) with a mass fraction of 70% of the polymer blend and a polyamide 6 with a mass fraction of 30% of the polymer blend. The polyamide 6 used has a melting temperature of 215° C.

[0016] The production can be carried out in the same way as in the exemplary embodiment 1. At a processing temperature in the range of 175 to 195° C., the melting temperature of the polyamide 6 used is therefore 20 to 40° C. above the processing temperature.

[0017] The wood-plastic composite has a composite density of 0.08 g/cm.sup.3. The modulus of elasticity was determined by means of an ISO 178 bending test at room temperature and a test speed of 1 mm/s and amounts to 620 MPa. The bending strength achieved is 7 MPa.