FI124997B - Surface coated wood material, its manufacturing process and use - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to a coated wood material. the method of manufacture of the material and the use of the material or its coating film. In particular, the invention relates to providing a resinous wood material with a resin-impermeable coating so that a sticky, poorly curing resin does not interfere with the use of the material, in particular the painting or varnishing of the surface of the material.

On wood surfaces to be painted, penetration of coniferous resin through the paint layer is particularly problematic at high pitch knots. Despite attempts, the paint industry has not found a solution to this problem. Therefore, coniferous wood cannot be used, for example, in high-quality furniture and interior materials. If knotty softwood material is used to make door or window frames, nowadays one has to resort to removing knots and expensive finger joints. This eats up the cost advantage that would otherwise be achieved by using cheaper knotty timber.

A solution to the resin problem is, according to the invention, provided with a knot-impermeable coating attached to the knotty softwood material.

It is known in the art to provide a heat-cured, resin-impregnated protective film for various fiber-based panels used as building materials. Such protected discs include e.g. plywood, particle board, fiber board, hardboard and OSB. The protective film is typically kraft paper or decor paper, which is impregnated with a phenolic or amino resin and affixed to the substrate at elevated pressure and temperature. The purpose of the protective film is to make the material resistant to mechanical stress, to resist moisture penetration and / or to remain unchanged in outdoor use. In addition, phenolic resin impregnated films are attached to building boards as a painting substrate to smooth out board surface irregularities and provide a good adhesive substrate for the paint. However, due to the paintability, the resin content of the paint bases is lower than that of the impregnated protective films and their outdoor use is limited to coating of good quality birch plywood.

As an example of said known sheet coating technique, Fl patent application 20050172, which discloses a coating for plywood or chipboard based on kraft paper impregnated with a resin alloy, may be mentioned. Specifically to solve the darkening problem associated with phenolic resin, the publication discloses pigmentation of resin alloy and kraft paper coloring with light, well-covering ink. The use of an impregnated film as a resin penetration barrier film is not disclosed in the publication, nor is it known to any other known technique in the applicant's knowledge. In addition, resin is not a problem in gluing and pressing boards made from chips or similar particulate material, such as chipboard or fibreboard, or in hardwood-based materials, where the chemical composition of the resin (extractives) is different. There is no mention of coniferous materials, and in particular coniferous conifers, where pitch is a problem, in FI-20050172.

According to the invention, a specific solution to the problem of the resin penetrating through the knots of coniferous branches is that the coniferous wood material containing knots or resinous knots of knots is provided with a resin-impermeable, fiber-based amino-resin impregnated insulating film with a heat seal.

The conifers affected by the resin problem are especially those of the genera Picea, Pinus, Larix and Pseudotsuga. Scandinavian examples of these are six (picea abies) and pine (Pinus sylvestris).

The coating according to the invention prevents the resin from seeping through the paint or varnish layer, not only from the knots but also from the resin pockets which are located outside the knots in the coniferous tree and from the core wood itself.

The invention is based on the finding that it is surprisingly possible to obtain insulation by means of a fiber-based film treated with an amino resin, through which coniferous resin cannot penetrate the surface of the material and thereby degrade the surface in door or window frames or the like. It is observed that phenolic resins commonly used in impregnated films lack the same property. The use of an amino resin per se in impregnated coatings for building boards is known, but as already mentioned, it is not known that this type of coating has previously been used as an insulator to prevent pitch penetration.

In addition to avoiding the pitch problem, other advantageous properties of the coated wood material according to the invention include good weather resistance and good mechanical resistance. The coating protects the wood surface from contamination and makes the surface easy to clean.

According to the invention, the resin insulating film is preferably impregnated with a softened amino resin. Suitable plasticizers which increase the flexibility of the impregnated film and which prevent cracking of the coating include caprolactam, ortho / paratoluenesulfonamide, acetoguanamine, monoethylene glycol, diethylene glycol, polyethylene glycol, polyvinyl alcohol, polyacrylamide, polyacrylamide.

Suitable amino resins include melamine formaldehyde resin and urea formaldehyde resin, and mixtures thereof. Melamine formaldehyde resin is preferred for outdoor use and urea formaldehyde resin for indoor use. The proportion of amino resin in the impregnating composition may be, for example, about 60-95% by weight and the amount of plasticizer about 5-40% by weight.

An amino-resin impregnated insulating film of the material of the invention may, as such, form a surface of the material which may be painted with water-borne paint or varnished. Particularly for a lacquer surface, a colorless translucent impregnate film is very suitable and the resin of the wood cannot penetrate through it to prevent the lacquer from drying. If desired, a pigment may be incorporated in the impregnation film or varnish to color the surface of the material.

On the other hand, in order to smooth the surface of the material and improve its paintability, an amino-resin impregnated coating can also be applied to the impregnated insulating film, whereby the coating of the material is two-layer. The resin concentrations of the layers may then be different; the resin content of the inner insulating layer may be higher to prevent resin penetration, while the resin content of the outer coating layer is lower to improve the surface paintability. The coating layers can be adhered to the wood material in a single hot-pressing step in which the inner layer impregnating resin acts as an adhesive for the outer layer. Thus, no separate adhesive layer is required between the resin impregnated coating layers.

According to yet another embodiment of the invention, the content of the impregnated amino resin in the coating film to be adhered to the wood material is low, whereby the film as such serves as a good painting base. Resin insulation is achieved by applying an additional amino resin to the surface of the film against the wood material prior to application of the film. At the same time, the brushed resin acts as a hot-cure adhesive to the wood material of the film. The result is thus a coating comprising a single fiber-based insulating film with a higher resin content at the inner interface and lower at the outer surface to be painted.

The wood material to be coated in accordance with the invention may be solid wood or glue-wood, the provision of which with a resin impregnated coating film is known to be unknown.

The wood material coated according to the invention may also be knotty, resinous coniferous plywood. Solid wood, glulam and plywood are typically spruce or pine in the invention. Spruce resin is a resole and pine resin is a phenolic acid, both of which are soluble in phenolic resins but not in amino resins.

The resin insulating film according to the invention is preferably an amino resin impregnated paper, such as bleached or unbleached paper made from a chemical, chemimechanical or mechanical pulp or a mixture of pulps. A preferred example is kraft paper of sulphate pulp. The film, preferably impregnated with the same amino resin, may be made of thicker Kraft Paper, which may be applied to the insulating film as a painting base.

Preferably, the weight of the paper to be used as the insulating film is 40-100 g / m 2 and the amount of amino resin impregnated therein is 70-170 g / m 2 preferably the weight of the base forming paper is 150-300 g / m 2 and 60-120 g / m 2. In the insulating film, the resin may represent more than 45% by weight, preferably more than 55% by weight, and less than 45%, preferably less than 35% by weight of the paint base, respectively.

The process of the invention for the production of the coated wood material described above is characterized in that the knotty coniferous resin-bearing material containing knots or pockets of knots is provided with a resin-impervious, fiber-based, amino-resin impregnated insulating film which is fixed to the wood material.

The various applications described above for the coated wood material according to the invention apply equally to the method of manufacturing the material according to the invention. The invention also encompasses painting or varnishing or painting and varnishing of a surface of a two-layered wood material with either a simple impregnated insulating film alone or an insulating film and an impregnated base.

The applications of the invention include the use of the coated birch material as described above, the use as a painted or to be painted building material or furniture material, and the use of material in which the resin is prevented from penetrating the outer surface of the material. The invention also includes the use of a fiber-based, amino-resin impregnated and heat-cured film as a coating of softwood material to prevent the resin from knots or pitch pockets from penetrating the outer surface of the material.

The invention will be illustrated by the following embodiments and related tests. The impregnating resin was in each case doped with a minor amount of plasticizer contained in said grams of resin.

Example 1 (Comparison)

The coniferous material to be coated was knotty plywood 9 mm thick. The plywood was provided with a two-layer coating with an inner layer of paper weighing 30 g / m 2 impregnated with 47 g / m 2 of phenolic resin and a thicker paper of 150 g / m 2 with an outer layer (base) impregnated with 64 g / m 2 of phenol resin. . The coating layers were fixed by hot pressing with a compression pressure of 15 bar, a compression temperature of 135 ° C and a compression time of 7 min.

The coating was not bubbling and was not interlayered, nor did the plywood become Pals. However, pitch came through the branches.

Example 2 (comparison)

The coniferous material to be coated was a 9 mm thick spruce plywood according to Example 1. The plywood was provided with a two-layer coating with an inner layer of paper weighing 30 g / m 2 impregnated with 47 g / m 2 phenol resin and a 245 g / m 2 impregnated melamine resin impregnated paper with a thicker paper weight of 245 g / m 2. The coating layers were fixed by hot pressing with a pressure of 15 bar, a compression temperature of 135 ° C and a compression time of 8.5 min.

The coating did not bubble up or split between layers, and neither did the plywood. However, pitch came through the branches.

Example 3

The coniferous material to be coated was a 9 mm thick spruce plywood according to Example 1. The plywood was provided with a two-layer coating with an inner layer of paper weighing 42 g / m 2 impregnated with 75 g / m 2 of amino resin and a thicker paper of 245 g / m 2 impregnated with 178 g / m 2 of melamine resin. The coating layers were fixed by a hot press with a compression pressure of 18 bar, a compression temperature of 135 ° C and a compression time of 8.5 min.

The coating was not bubbling and was not interlayered, nor did the plywood become Pals. The pitch did not come through the branches. The coating is opaque and the material is well suited for use when painted.

Example 4

The coniferous material to be coated was a 9 mm thick spruce plywood according to Example 1. The plywood was provided with a single coating layer of paper having a weight of 42 g / m2 impregnated with 73 g / m2 of amino resin. The coating was fixed by hot pressing with a compression pressure of 15 bar, a compression temperature of 135 ° C and a compression time of 7.5 min.

The coating did not bubble up or split between layers, and neither did the plywood. The pitch did not come through the branches. The coating is transparent, leaving the structure of the wood visible and the material well suited for use as varnished or as such.

Example 5 (Comparison)

The softwood material to be coated was a knotty log panel planed from pine. The panel was provided with a two-layer coating with an inner layer of paper 30 g / m 2 coated with phenol resin impregnated 47 g / m 2 and an outer layer (base) weight 150 g / m 2 impregnated with phenol resin 64 g / m 2. A series of tests were performed in which the coating layers were fixed by hot pressing with a pressing pressure of 14 bar each, a pressing temperature ranging from 110 to 180 ° C and a pressing time ranging from 20 s to 28 min. The conditions for Experiments 1-8 are as follows:

table 1

The coating did not bubble or split between layers. However, in all experiments in the series, the pitch came through the knots.

Further, a series of tests were carried out at a compression pressure of 14 bar, a compression temperature of 130 ° C and a compression time of 7 min, the outer coating layer (painting base) as above, but the inner coating layer was varied so that paper / resin amounts were 30/47 g. / m2, 40/80 g / m2, 60/107 g / m2 and 80/140 g / m2 Also in this series, the pitch came through the knots in each experiment. As the thickness of the inner film increased, the pitch of the resin decreased, but in the last experiment the phenolic resin began to come through the paint base.

Example 6

A series of four experiments were carried out using coniferous glulam pine (Experiment 1) and a planed pine log panel (Experiment 2-4) of pine as the coating material. In Experiment 1, the single-layer coating consisted of paper weighing 150 g / m2 impregnated with 160 g / m2 amino resin. In Experiments 2-4, the inner layer of the two-layer coating was impregnated coating paper according to Experiment 1 and the outer layer paper weighing 60 or 100 g / m 2 and impregnated with amino resin 114 or 170 g / m 2. The coating layers were fixed by hot pressing with a compression pressure of 14 bar each, a compression temperature of 130 ° C each, a compression time of Experiment 1 of 7.5 min and a compression time of Experiments 2 and 3 of 9.5 min. The test conditions are summarized in the following table:

Table 2

The coating did not bubble or split between layers. In Experiment 1, the resin leaked slightly through the knot site. Experiments 2-4 did not pass through the resin. The materials of Experiments 2-4 are particularly suitable for use as such, although it is also possible to varnish or paint them.

Example 7

The coniferous material to be coated was pine glue used for window frames. The glulam was provided with a two-layer coating of paper with an inner layer of paper weighing 42 g / m 2 impregnated with 75 g / m 2 of amino resin and a 245 g / m 2 impregnated melamine resin impregnated with 245 g / m 2 of impregnated paper. The coating layers were fixed by a hot press with a pressure of 15 bar, a compression temperature of 135 ° C and a compression time of 8.5 min.

The coating did not bubble or split between layers. The pitch did not come through the branches.

Halkeilutesti

The coated glued wood sample of Example 7 was kept in an oven at 80 ° C for one week. The sample was then immersed in water at room temperature for 24 hours. Finally, the sample was re-stored in the oven for one week at 80 ° C. No cracks were formed in the sample during the test.

painting Tests

The coated glulam according to Example 7 was painted on both sides once with water-borne paint (Aquatop 2600, marketed by Teknos Oy). The adhesion of the paint to the wood was found to be good.

The painted wood was subjected to a cold check with the following cycle: (a) 6 hours immersion in water at 23 ° C, (b) 16 hours in a freezer at -18 ° C, and (c) 24 hours in an oven at 60 ° C. The cycle (steps a-c) was repeated for the test sample 10 times. The paint remained well attached to the wood during the test and did not otherwise detect any appreciable damage to the wood.

The painted wood was further subjected to a 1000 h refrigerator test, repeating cycles of: (a) 102 min heating with a 0.40 W / m2 sunlight spectrum simulating lamp, exposed by irradiation to surface temperature of 60 ° C, air temperature 40 ° C, relative humidity 65%; (b) 18 minutes of spraying with cold tap water, (c) air blowing at 50 ° C, (d) returning to step (a). The 1000 h refrigerator test is estimated to be equivalent to approximately 5 years of actual weather exposure except during frost. The paint remained well attached to the wood during the test and did not otherwise detect any appreciable damage to the wood.

According to the tests, the coated glulam according to the invention, when painted, can withstand the stresses and weathering of the weather.

Claims (17)

Coated wood material, characterized in that the wood material is knotty, cone-like resin or resinous pocket coniferous wood and is provided with a resin-impervious, fiber-based, amino-resin impregnated insulating film which is heat-bonded to the surface of the material. Wood material according to claim 1, characterized in that the insulating film is impregnated with a plasticized amino resin. Wood material according to claim 1 or 2, characterized in that the amino resin is a melamine-formaldehyde resin or a urea-formaldehyde resin or a mixture thereof. Wood material according to one of the preceding claims, characterized in that the surface of the insulating film is painted with water-borne paint or varnished. Wood material according to one of the preceding claims, characterized in that the resin content at the wood-side interface of the insulating film is higher than that of the outer surface to be painted or painted. Wood material according to one of Claims 1 to 3, characterized in that an amino-resin impregnated base is attached to the insulating film impregnated with an amino resin. Wood material according to one of the preceding claims, characterized in that it is coated solid wood or glued wood. Wood material according to one of Claims 1 to 6, characterized in that it is a coated softwood plywood. Wood material according to any one of the preceding claims, characterized in that the insulating film is made of paper or nonwoven impregnated with an amino resin. Process for producing a coated wood material according to any one of the preceding claims, characterized in that the knotty coniferous resinous knot-containing, resin-impregnated insulating film is applied to the surface of the wood material. The method according to claim 10, characterized in that the insulating film is impregnated with a plasticized amino resin. Method according to Claim 10 or 11, characterized in that the surface of the insulating film is painted with water-borne paint or varnished. Method according to claim 10 or 11, characterized in that an amino-resin impregnated primer is applied to the insulating film. Method according to Claim 13, characterized in that the insulating film and the painting base are fixed to the wood material by hot pressing in one step. Use of a coated coniferous material according to any one of claims 1 to 9 as a building material or furniture material. Use of a coated softwood material according to claim 15 as a painted or varnished building material or furniture material. 17. Use of a fiber-based, amino-resin impregnated and heat-cured film as a coating of coniferous material to prevent the resin penetration of knots or pitch pockets from the outer surface of the material.