Hydrophobisation composition, method for hydrophobisation and substrate

Abstract

A hydrophobisation composition, which includes a hydrophobisation extract obtained by extracting outer bark of birch in an organic and/or polar solvent and which includes at least 30 weight-% betulinol. Also disclosed is a method for hydrophobisation of a surface, which includes steps of applying a layer of hydrophobisation composition containing betulinol on a surface of a substrate, and drying and heat-treating the layer of hydrophobisation composition. A substrate having a surface which is hydrophobised by using the method is also disclosed.

Claims

1. Method for hydrophobisation of a surface, comprising steps of applying a layer of hydrophobisation composition comprising betulinol on a surface of a substrate, and drying and heat-treating the layer of hydrophobisation composition.

2. Method according to claim 1, characterised in applying the hydrophobisation composition on the surface of the substrate by dipping, coating, painting or spraying.

3. Method according to claim 1, characterised in forming a uniform composition layer on the surface of the substrate, providing a full coverage of the surface.

4. Method according to claim 1, characterised in repeating the application step of the hydrophobisation composition on the surface a plurality of times.

5. Method according to claim 1, characterised in performing the heat-treatment at a temperature of at least 70 C.

6. Method according to claim 5, characterised in performing the heat-treatment simultaneously with the drying of the surface of the substrate.

7. Method according to claim 5, characterised in that the duration of the heat-treatment is in the range of 3-60 min.

8. Substrate comprising fibers and having a surface which is hydrophobised by using a method according to claim 1, the substrate surface having a contact angle with water of at least 90 degrees.

9. Substrate according to claim 8, characterised in that the substrate is a member of the group consisting of paper, paperboard, textile, wood, plywood and leather.

10. Substrate according to claim 8, characterised in that substrate surface has a contact angle with water at least 100 degrees.

11. The method of claim 1, wherein said hydrophobisation composition comprises a hydrophobisation extract, which is obtained by extracting outer bark of birch in an organic and/or polar solvent and which comprises at least 30 weight-% betulinol.

12. The method of claim 11, wherein said organic solvent of the hydrophobisation extract is selected from ethanol, methanol, acetone, hexane, and isopropanol.

13. The method of claim 11, wherein said polar solvent of the hydrophobisation extract is supercritical CO.sub.2.

14. The method of claim 11, wherein said extract comprises at least 50 weight-% betulinol.

15. The method of claim 11, wherein the extract comprises 30-97 weight-% betulinol.

16. The method of claim 11, wherein said outer bark of birch is obtained as a by-product from industrial wood processing.

17. The method of claim 11, wherein the composition further comprises additives, which are selected from preservatives, dispersing agents, anti-crystallization agents, colorants and binders.

18. The method of claim 17, wherein the binder is a latex selected from the group consisting of acrylate latex, styrene butadiene latex, linseed oil, tung oil and an alkyd binder.

19. The method of claim 11, wherein said extract further comprises betulinol in particle form.

20. The method of claim 11, wherein said composition comprises water in an amount up to 20 weight-%.

Description

EXPERIMENTAL

Example 1

(1) Preparation of Birch Bark Suitable for Extraction

(2) 100 kg of birch bark from a plywood mill was dried to air dryness. The bark was ground with a hammer mill. The bark was screened with a rotary sieve with a sieve with 3 mm wire mesh. The bark not passing though the screen (>3 mm, 28 kg) included 98% outer bark based on both chemical analysis and manual sorting. The material passing though the screen comprised primarily inner bark and other impurities.

Example 2

(3) Preparation of a Hydrophobisation Extract

(4) 25 g of air dry birch outer bark prepared according to Example 1 was refluxed in 1000 ml 99% ethanol for 1 h in a 2 L round-bottom flask. The extract was recovered by filtering the solution through a filter paper. The extract contained 7.49 g of dry solids corresponding to yield of 29.9% on extracted bark. The composition of the dried extract comprised 70% betulinol, 6% lupeol, 3% betulinic acid as well a smaller amounts of triterpenoids and other birch bark extractives. The concentration of the hydrophobisation extract was 0.75% weight dry solids.

Example 3

(5) The Temperature and Time Dependence on Hydrophobicity of Treated Filter Paper

(6) A series of pieces of filter paper, 4 cm1 cm, were dipped in a hydrophobisation extract prepared in accordance with Example 2. The treated pieces of filter paper were dried in an oven for various lengths of time and temperature. To achieve the same level of relative hydrophobicity, as determined by placing a drop of water on the paper surface and noting that the drop had not absorbed onto the substrate in 1 h, the following temperatures and times were observed. The concentration of applied dry hydrophobisation extract was 0.5% of the weight of the paper substrate.

(7) 25 C.several weeks

(8) 70 C.24h

(9) 85 C.30 min

(10) 120 C.15 min

(11) 150 C.3 min

(12) From these results we can clearly see that the drying temperature has an effect on the reaction time needed for obtaining a hydrophobic substrate.

Example 4

(13) Application of Hydrophobisation Extract on Filter Paper

(14) A piece of filter paper, 4 cm1 cm, was dipped in a hydrophobisation extract prepared in accordance with Example 2. The treated piece of filter paper was dried in an oven for 24 h at 105 C. The hydrophobic property was evaluated by measuring the contact angle of a 3 l drop of water with a contact angle measurement device. The contact angle was 126 degrees at 3 seconds after contact and the angle decreased to 118 degrees at 3 minutes. Except for the hydrophobic property the filter paper retained other typical characteristics of an untreated piece of filter paper. SEM imaging of hydrophobic filter paper revealed a thin layer of crystalline material coating the surface, shown in FIG. 1. In addition nodules of crystal a few m in diameter can be seen.

Example 5

(15) Application of Hydrophobisation Extract on Cotton Cloth

(16) A piece of cotton cloth, 4 cm1 cm, cut from a white T-shirt was dipped in a hydrophobisation extract prepared in accordance with Example 2. The treated piece of cloth was dried in an oven for 24 h at 105 C. The hydrophobic property was evaluated by measuring the contact angle of a 3 l drop of water with a contact angle measurement device. The contact angle was 135 degrees at 3 seconds after contact and the angle decreased to 130 at 3 minutes. Except for the hydrophobic property the cotton cloth retained other typical characteristics of an untreated piece of cotton cloth.

(17) Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.