Method for treating a wood board

Abstract

The invention relates to a method for treating a wood board. According to the invention, a composition containing a hydrophobic agent is provided onto the surface of the wood board and coating agent is provided over it to form a coating layer.

Claims

1. A method for treating a plywood or an oriented strand board for use as a mold form for molding concrete, the method comprising: (a) providing a hydrophobic composition containing a hydrophobic agent in an amount of 60 to 100% by weight on a surface of the plywood or the oriented strand board; (b) coating the plywood or the oriented strand board with a coating agent to form a coating layer on the surface of the plywood or the oriented strand board treated with the hydrophobic composition to form a treated plywood or oriented strand board, wherein the hydrophobic agent comprises alkene ketene dimer, and wherein the hydrophobic composition and the coating layer are provided on the plywood or the oriented strand board by hot pressing sufficient to cause the hydrophobic agent to penetrate into wood grains in the plywood or the oriented strand board, and wherein the amount of hydrophobic composition provided on the surface of the plywood or the oriented strand board is 30-50 g/m.sup.2, and wherein the coating agent forms a film and comprises one or more resins selected from phenolic resin, amino resin, acrylate resin, urea resin, melamine resin, or urea melamine resin; and (c) molding concrete using the treated plywood or oriented strand board.

2. The method according to claim 1, wherein the hydrophobic composition is provided on the surface of the plywood or the strand board before coating with the coating agent.

3. The method according to claim 1, wherein the hydrophobic composition is provided on the surface of the plywood or the strand board with the coating layer.

4. The method according to claim 1, wherein the hydrophobic composition is provided in a carrier material from which it is conveyed to the surface of the plywood or the strand board.

5. The method according to claim 1, wherein the hydrophobic composition is provided as a layer separate from the coating layer.

6. The method according to claim 1, wherein the coating agent comprises phenol-formaldehyde resin.

7. The method according to claim 1, wherein the coating agent comprises melamine-formaldehyde resin.

8. The method according to claim 1, wherein the coating agent comprises phenolic and amino resins.

9. The method according to claim 1, wherein the hydrophobic composition is a solid form.

10. The method according to claim 1, wherein the coating layer is provided on the surface of the plywood or the oriented strand board at 220 g/m.sup.2.

11. The method according to claim 1, wherein the coating agent comprises phenolic resin.

12. The method according to claim 1, wherein the hydrophobic composition contains the hydrophobic agent in the amount of 100% by weight.

13. The method according to claim 1, wherein the hydrophobic composition comprises 100% by weight alkene ketene dimer.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In the following section, the invention will be described by means of detailed examples of its embodiments.

EXAMPLES

Example 1

(2) Preliminary tests were carried out to examine the spreading of water into the wood board and the top veneer through holes made in the coating, and the resulting problems as well as a solution to them.

(3) It was surprisingly discovered as a solution that the spreading of water through holes in the coating of the wood board and the swelling of the grains of the top veneer may be prevented by treating the surface of the wood board with a hydrophobic agent, such as e.g. paraffin wax. Wax can be easily applied over the surface of a wood board as a liquid or emulsion. In this case, the wax and the optional emulsifier or the like must be selected so as to not have any negative effect on the outcome. The wax may also be applied as molten or solid or it can be melted on the surface of the wood board. It is important that the selected wax does not prevent the coating of the wood board after the wax treatment. Instead of wax, also other hydrophobic chemicals exhibiting the same properties may be used.

(4) The wax may be applied over the surface of the wood board before the wood board is coated. It can be applied over the surface of the wood board e.g. in the liquid form or it may be absorbed in a separate carrier material from which it is conveyed onto the surface of the wood board before the wood board is coated. Alternatively, the wax may be brought onto the surface of the wood board together with the coating. This can be carried out in at least two alternatives: 1) Treatment of the coating film by wax on one side, e.g. in a 2-step production process whereby the wax is conveyed to the surface of the wood board in connection with the coating as a separate layer; or 2) By preparing a coating agent mixture which is rich in said wax, e.g. a 50/50 wax-resin mixture. The coating according to method 2 is possibly not suitable alone to provide sufficient coating on the wood board, but it may be used as a base film with other suitable coating.

Example 2

(5) Two test series were carried out, the first including five reference tests and eight tests and the second including one reference test and five tests. The tests were carried out to examine the effect of the waxing of plywood on anti-rippling, i.e. prevention of the swelling of the wood grains on a broken surface.

(6) Samples of plywood were formed for the test series with birch used as the starting material. The samples of plywood were treated with wax and/or coated by a film at 120 and 220 g/m.sup.2. The waxed and/or coated samples of plywood were tested in a rippling test.

(7) The wax used in the tests was a hydrophobic Bekophob P60 paraffin wax emulsion. The wax was applied over the surface of the plywood in an amount of about 30 g/m.sup.2.

(8) The coating was carried out with Dynea film coatings based on phenolic resin at 120 g/m.sup.2 or 220 g/m.sup.2 in normal pressure conditions (about 18 kg/cm.sup.2/6 min/130 C.).

(9) Samples of birch plywood which had not been subjected to a wax treatment and in which the above-mentioned coating films were used as the coating were employed as the reference.

(10) In the rippling tests, a hole was made in the coating and a wet piece of paper/cloth was placed over the hole for 1 h and 3 h. The top veneer should not swell around the hole.

(11) The first set of tests was carried out to study the effect of waxing of the plywood surface, or the effect of the wax-layered coating film provided on the surface, on rippling, i.e. swelling of the wood grains, as compared with the reference samples of plywood. The reference samples of plywood were formed from untreated plywood and different surface and/or base films. The tested samples of plywood were formed from either a) waxed plywood and different surface films or b) plywood and a base film, one side of which was provided with a wax layer at 40 g/m.sup.2, and/or a surface film. The wax layer of the base film in the tested samples of plywood b was provided against the surface of the plywood.

(12) Table 1 presents the test arrangements of the first test for treating and/or coating the samples of plywood, and the results obtained from the tests.

(13) The results were evaluated by measuring the swelling around the hole in millimeters: (diameter of the swelling areadiameter of the hole) divided by two=swelling result. A smaller result, mm, indicates smaller swelling of the wood grains due to the provided hole.

(14) In this context, surface structure refers to the thickness of the total coating on the surface of the plywood.

(15) TABLE-US-00001 TABLE 1 Surface structure, Swelling, Swelling Test Treatment g/m2 mm, 1 h mm, 3 h ref1 Untreated plywood + Light surface film 120 20 25 ref2 Untreated plywood + Heavy surface film 220 47 60 ref3 Untreated plywood + Light base film + 220 29 31 Light surface film ref4 Untreated plywood + Light base film + 340 42 49 Heavy surface film ref5 Untreated plywood + Heavy base film + 340 19 25 Light surface film 1 Waxed plywood + Light surface film 120 3 5 2 Waxed plywood + Heavy surface film 220 19 25 3 Plywood + 1 wax-layered Light base film 120 8 10 4 Plywood + 1 wax-layered Heavy base film 220 12 16 5 Plywood + 1 wax-layered Light base film + 220 18 21 Light surface film 6 Plywood + 1 wax-layered Light base film + 340 9 13 Heavy surface film 7 Plywood + 1 wax-layered Heavy base film + 340 5 9 Light surface film 8 Plywood + 1 wax-layered Heavy base film + 440 10 14 Heavy surface film

(16) The second set of tests was also carried out to study the effect of the waxing of the plywood surface, or the effect of the wax-layered coating film provided on the surface, on rippling, i.e. swelling of the wood grains, as compared with the reference plywood. The reference plywood was formed from untreated plywood and a surface film. The tested samples of plywood were formed from either a) waxed plywood and a surface film, b) plywood and a base film, one side of which was provided with a wax layer at 40 g/m.sup.2, and/or a surface film, or c) plywood and a base film, both sides of which were provided with a wax layer at 40 g/m.sup.2, and/or a surface film. The wax layer of the base film in tested samples of plywood b and c was provided against the surface of the plywood.

(17) Table 2 presents the test arrangements of the second test for treating and/or coating the samples of plywood, and the results obtained from the tests.

(18) TABLE-US-00002 TABLE 2 Surface structure, Swelling, Swelling, Test Treatment g/m2 mm, 1 h mm, 3h ref6 Untreated plywood + Heavy surface film 220 31 41 9 Waxed plywood + Heavy surface film 220 4 5 10 Plywood + 1 wax-layered Heavy base film 220 9 15 11 Plywood + 2 wax-layered Heavy base film 220 1 3 12 Plywood + 1 wax-layered Heavy base film + 340 2 5 Light surface film 13 Plywood + 2 wax-layered Heavy base film + 340 1 2 Light surface film

(19) It was discovered that in tests 1 to 13, samples of plywood were provided in which the swelling of the wood grains in the event of breaking of the surface was considerably smaller as compared with the reference samples of plywood. It was discovered that the waxing of the plywood surface as well as the wax-layered base films, both used in the tested samples of plywood, provided reduction in swelling of the wood grains. In addition, it was discovered that mixing the wax with the coating improved anti-rippling, i.e. prevention of local swelling.

(20) By the tests it could be observed that a suitable hydrophobic wax which prevented swelling of the wood grains was discovered. Also, it was found that the coating was made to persist well on the surface of waxed plywood.

(21) By the method according to the invention, it is also possible to reduce cracking of the coating because stretching and contracting of the top veneer is substantially reduced. This may permit easier coating of softwood plywood with light phenolic coatings and coating of plywood with melamine coatings.

Example 3

(22) This set of tests was carried out to study, according to Example 2, the effect of different hydrophobic agents on rippling on both laboratory and pilot scale. In the tests, birch plywood was used and the surface was hydrophobized (Test 3: 30 g/m.sup.2 and Test 4: 30/50 g/m.sup.2) with a selected hydrophobizing agent before coating the plywood surface with the coating film at 220 g/m.sup.2. The surface of the reference plywood was not treated before coating. The test results are presented in Tables 3 (laboratory tests) and 4 (laboratory and pilot tests).

(23) TABLE-US-00003 TABLE 3 Surface structure, Swelling, Swelling, Test Treatment g/m2 mm, 1 h mm, 3 h ref7 Untreated plywood + Heavy surface film 220 74 111 14 Waxed plywood (paraffin 4110) + Heavy surface film 220 6 14 15 Waxed plywood (paraffin C80) + Heavy surface film 220 9 23 16 Waxed plywood (AKD, type K) + Heavy surface film 220 7 13 17 Waxed plywood (AKD, type C) + Heavy surface film 220 10 21 18 Waxed plywood (silicone oil) + Heavy surface film 220 7 17 19 Waxed plywood (polyglycol P1200) + Heavy surface film 220 33 39

(24) TABLE-US-00004 TABLE 4 Surface structure, Swelling, Swelling, Test Treatment g/m2 mm, 1 h mm, 3 h ref8 Untreated plywood + Heavy surface film/ 220 59 69 laboratory test ref9 Untreated plywood + Heavy surface film/ 220 59 69 pilot test 20 Waxed plywood (paraffin 5205, 50 g/m.sup.2) + 220 5 10 Heavy surface film/laboratory test 21 Waxed plywood (paraffin 5205, 30 g/m.sup.2) + 220 10 21 Heavy surface film/pilot test 22 Waxed plywood (paraffin 5205, 50 g/m.sup.2) + 220 6 14 Heavy surface film/pilot test

(25) It was discovered that e.g. different paraffins, AKD (alkene ketene dimer) and silicones are particularly effective in preventing rippling, i.e. swelling of the wood grains, in plywood. The tests indicated that hydrophobizing the surface before coating improves the properties. In addition, it was found in the tests that plywood may be easily coated after the hydrophobization treatment of the surface if suitable hydrophobizing agents, such as paraffins, AKD or silicone oil, are used.

(26) The method according to the invention is suitable in different embodiments for treating various materials, e.g. plywood, chipboard and other wood board products.

(27) The embodiments of the invention are not limited merely to the examples referred to above; instead, many variations are possible within the scope of the accompanying claims.