Transparent wood and a method for its preparation

1. Transparent wood comprising a wood substrate and at least one polymer, wherein said transparent wood has an optical transmittance of at least 60% at a wavelength in the electromagnetic spectrum of wavelengths from 400 to 1000 nm, and wherein the wood substrate comprises more than 15% lignin, measured as Klason lignin.

2. The transparent wood according to claim 1 , further having a haze of at least 60% at a wavelength in the electromagnetic spectrum of wavelengths from 400 to 1000 nm.

3. The transparent wood according to claim 1 , wherein the optical transmittance is at least 70%.

4. The transparent wood according to claim 1 , having a thickness of at least 0.3 mm.

5. The transparent wood according to claim 1 , wherein the polymer has a refractive index from 1.3 to 1.7.

6. A method for preparing transparent wood, comprising the steps of

a) Providing at least one piece of wood substrate;

b) Adding a bleaching liquor to inactivate chromophores in the wood substrate, thereby obtaining a bleached wood substrate comprising at least 15% lignin;

c) Impregnating the bleached wood substrate obtained in (b) with a solution comprising pre-polymers, or monomers, or a combination thereof,

d) Polymerizing the impregnating pre-polymers, or monomers, or combination thereof, to obtain a transparent wood comprising a wood substrate and at least one polymer.

7. The method according to claim 6 , wherein the bleaching liquor comprises a peroxide system.

8. The method according to claim 7 , wherein the peroxide system comprises hydrogen peroxide.

9. The method according to claim 6 , wherein the method further comprises a step of removing metal ions from the piece of wood.

10. The method according to claim 9 , wherein removing metal ions from the piece of wood comprises adding DTPA before adding the bleaching liquor.

11. The method according to claim 6 , wherein bleaching of the wood in step (b) is performed until the wood substrate has a brightness of at least 70%.

12. The method according to claim 6 , wherein the bleaching liquor in step (b) further comprises stabilizers and chelating agents.

13. The method according to claim 6 , wherein the method further comprises a step of solvent exchange after having obtained the bleached wood in step (b).

14. The method according to claim 6 , wherein the polymer obtained in step (d) has a refractive index of from 1.3 to 1.7.

15. Transparent wood obtained by the method according to claim 6 , wherein the wood substrate comprises more than 15% lignin, measured as Klason lignin.