DE60102240T2 - Process for producing a resin-containing wood - Google Patents

Abstract

The invention relates to a method for treatment of resin-containing wood substrate which method comprises the step of hardening at least a part of the resin in said wood substrate.

Description

at Components that are made of wood, it is required that the wood an aesthetic nice looking surface and of course has high strength and durability. That's in the field particularly relevant to the production of wooden window frames and doors. In such applications, it is particularly important that the wood of defects essentially free and completely free of cracks and knots. However as much wood as possible to use without any defects To repair, a series of small cracks and small branches are usually in purchase taken.

however even small cracks and small branches are critical, because it finds always some degree of resin exudation through these cracks and branches in the wood instead. It therefore remain sticky in the wood on the surface, the difficulties due to differences in liability to lead, if paint or other surface coating agents on the surface can be applied, and further, the resin sites for discoloration of the Lead wood.

in the Over time, this stickiness decreases or disappears, due to exposure ordinary Daylight and temperature conditions shrink the resin as however, such normally, i. it retains its dimensional stability and / or dimensional accuracy not at. This phenomenon usually leads to unstable branches or even too completely loose branches, the finally fall out of the wood, i. leave a hole in the wood surface, and what cracks, especially those that are filled with resin, As far as the phenomenon is concerned after all also for the formation of holes and depressions. As a result, the treatment and maintenance of the wood surface, i. by Painting, even more difficult. Repairing or replacing the damaged piece of wood would be one Possibility, however, this situation is extremely undesirable.

The The problem is further compounded by modern forestry where Trees that all year round, inclusive while of spring, if Turgescence strongest is, like become. Furthermore you can Storage methods to exacerbate the exudation of the resin, since Storage often involves the use of organic solvents containing the Release resin and make it even more fluid.

Several Methods to prevent the exudation of resin from resin-containing wood to put an end to it, are known. One of them is the sealing the surface with different sealants. The disadvantage of these methods However, it is that they do not complete the exudation of resin, but rather only temporarily, as long as the active part of the sealant is working.

Examples the above mentioned Methods are the application of primer / wax systems or Shellac on the surface of the wood.

In DE-A-3 914 421 discloses a process for treating a resin containing Wood substrate discloses which method the steps of applying a coating of a fast-curing compound on the surfaces for preventing the resin from sweating out.

In Japanese Patent Application No. JP3166905A discloses a method in which wood is impregnated with a melamine-based resin, followed by drying by high frequency heating (microwaves).

One another method is immersing the wood in hot water, followed by immersion in an impregnating solution which immobilizes the resin power.

Other Known methods are lamination by coating the wood with paper or HDF plates.

The known methods are all through the use of an active Sealing or coating agent to prevent exudation characterized by resin from the wood. On the application of the sealing or coating agent usually followed by an aftertreatment it is often a heat treatment is.

The known methods all involve the application of at least one Means on the surface of the wood. It is a step in the manufacturing line, which is expensive and extra Time is required. Furthermore The known methods are often based on the use of chemical Means that are not environmentally friendly and cause difficulties can, if the wood is to be removed as waste.

The Sealing of the wooden surface loses its effectiveness when the seal, which is relatively thin, destroyed becomes. This allows the resin to pass through the broken Squeeze through parts of the seal.

Due to the shortcomings of the known methods, there is a need for a method of treating wood containing resin that is simple and requires the application of sealing or loading coating agent not required.

The The object of the present invention is a method to treat wood containing resin that provides a permanent seal at least a part of the surface of the wood to prevent the exudation of resin offers.

A Another object of the present invention is a method for treating a resin-containing wood substrate, which is cost effective and time-saving to execute.

A Another object of the present invention is a method to provide for the treatment of resin-containing wood, the application a sealing or a coating agent is not required.

These and other objects are all achieved by the method according to the invention, as stated in the claims is defined, fulfilled ,

The Invention is based on the amazing result that it is possible to cure the resin in a resin-containing wood substrate. In growing trees that is natural This resin is usually under pressure and sweat from the Wood through small openings in the bark of the trees out. When the trees like and for industrial purposes are debarked, many openings in the form of corridors, Cracks and branches exposed. This obviously makes the natural tendency of the wood, Resin to the surface to sweat out of the wood, greatly increased, causing sticky spots on the surface remain. Hardens over time the natural one Resin and tackiness disappear, but the natural cure of the resin is a process that continues for several years. The cured resin has a smooth, relatively hard surface, like that of one synthetic hard plastic.

at the course present resins in the wood is a relatively complex Mixture of various substances, including terpenes. The natural resin in wood usually includes oleoresins such as monoterpenoids, diterpenoids, and triterpenoids and steroids comprising parenchymal resin. Furthermore can the resins a mixture non-volatile, partially unsaturated Compounds including Esters and free acids include. As mentioned above, The resin forms a very sticky Rubber that is able to undergo a certain slow cure, when exposed to the air.

By Application of the method according to the invention occurs curing of the resin, in particular of the resin in the surface of the Wood, essentially immediately on. In fact, that is required for curing Time reduced to seconds or a few minutes. The procedure provides wood with a dry and relatively hard surface without loose branches, depressions or holes, the excellent properties for further processing, such as the application of paint or other coating materials possesses.

The Invention provides a method for treating resin-containing Wood substrate, which method comprises the following steps:

• - Identify of resin gullies and / or cracks and / or branches in the pieces of wood and
• - selective Harden at least a portion of the resin in at least a portion of the identified resin ducts and / or cracks and / or branches Crosslinking of the monomers and polymers in the resin.

The Resin that cured that is natural resin present in the wood substrate. Hardening of the resin prevents that the resin sweats out of the wood substrate, and thereby becomes the Formation of sticky resin spots on the surface of the wood substrate prevented. The term wood substrate designates a substrate for the curing process, which is a typically shaped wood article, lumber, Timber, posts, etc., but also includes material that shredded wood such as wood chips and building boards, etc.

at an embodiment the method according to the invention the resin is cured in a layer extending from the surface of the Wooden substrates and at least to a certain depth in the wood extends, wherein the layer preferably has a thickness of 0.001 - 5.0 cm, even more preferably has a thickness of 0.01-1.0 cm.

Of the mentioned above embodiment Accordingly, the resin is cured in a layer that from the surface of the wood substrate to at least a certain depth into the wood substrate extends into it. This ensures that at least one surface layer of wood substrate hardened Resin includes. As a result, the surface coating seals the surface and does not prevent hardened Resin within the wood substrate from it, to the surface of the Auszuschwitzen wood substrates.

In an alternative preferred embodiment of the method according to the invention substantially all of the resin present in the wood substrate is cured. This method is advantageous when the wood substrate of another Be such as trimming or drilling. Although such treatments reveal new surfaces of the wood substrate, no resin sweats on these surfaces.

at a preferred embodiment the method according to the invention will that be in aisles and / or Cracks and / or branches Hardened resin present in the wood substrate. The natural present Resin flows in the wood in aisles or resin gullies, from those from it in the unhardened Condition to the surface of the wood substrate, e.g. through cracks or branches in the wood substrate, penetrate can. Because the exudation of resin mainly from corridors, cracks and branches occurs, it is preferred to cure the resin present therein.

at an embodiment the method according to the invention the resin is prepared by crosslinking monomers and / or polymers in the resin by application of UV radiation, IR radiation, high-frequency heating, laser radiation, Corona treatment, plasma treatment and / or heat treatment in a fluidized bed hardened. Preferably, the resins are crosslinked at elevated temperatures.

UV light can with wavelengths be applied within the range of 250 to 400 nm and 300 to 600 WPI lamps are of use.

The Treatment of the surface disclosed above may be used in conjunction with or followed by a treatment of the surface with a suitable gas, e.g. Oxygen or ozone, take place.

Around agreement for that too obtained which of the above Erhärtungsmethoden, i.e. which curing method could be successfully applied Several tests are done and in the following section are the observations that in this regard have been mentioned.

A Wood surface, through the curing process can be treated almost any surface configuration exhibit. As a result, not all of the treatments mentioned above in all cases can be recommended. Indicates the wood surface for example height differences on, that is the laser radiation (the laser could be Nd: Yag or Argon lasers act) a better choice than the UV radiation, IR radiation or the microwave treatment. Tests have shown that the strength of cured by laser Binding (the cross-linking) does not decrease with increasing distance seems while for the other types at a distance of more than 0.5 mm one measurable decrease seems to take place.

typically, becomes the surface to be treated longitudinal at a rate of 0.5 m per minute up to for example more than 30 m / min. emotional. The amount, size and location of the branches will be recorded using a standard wood detection device, that with a standard image processing and assessment facility equipped is. Are those in the wood surface identified branches or cracks of the potentially dangerous type, i.e. of sticky or sweaty type, so will a signal sent to the treatment station (radiation, "beam" or similar source) further downstream. At this point will be a calculated measure (depending on a number of factors the exposure time, size and intensity of the "beam"), while the Wood sample at the source passes in the station (it could of course several different and / or individually attached sources).

at the beam can be different types such as UV radiation (UV light), a laser or IR or a microwave type act. The requirement It is the possibility has, the natural Binding (crosslinking), that in the natural Resin takes place when exposed to normal weathering conditions, i. Daylight and air, is exposed to accelerate. This effect becomes main through the local heating process caused by the resin, causing the natural aging processes within the surface of the resin, which is the exterior of the Wood profile of the resin forms, be accelerated.

It It has also been observed that to achieve good dimensional stability and dimensional accuracy of the resin, i. of the one that surrounds a branch or in one Riss lies, a treatment with microwaves compared with IR radiation, UV radiation is to be preferred.

Similarly It has been observed that a shorter cure time through use of laser curing compared to UV radiation, i. up to 8 times faster without significant decrease in peel bond strength under shear stress.

The curing of the resin can be enhanced by subjecting the monomers and / or polymers in the resin to a treatment that significantly increases the number of free radicals. This makes it possible to significantly reduce the time required for the curing of the resin. For most wood-based resins, the base monomer is isoprene, such as in natural rubber; for this reason, the various polymers contain double bonds that may form the basis for derivatization in the form of oxidation, linking, attachment of other groups, and so on NEN. As with natural rubber, the isoprene type double formations provide the basis for crosslinking and curing of the resin.

at an alternative preferred embodiment of the invention the resin by crosslinking of monomers and / or polymers in the resin Apply a responsive Chemical which is preferably sulfur, sulfur trioxide, peroxide, Nitrogen oxides, phosphorus, halogens or ozone is selected, hardened. The reactive is preferred Chemical in gaseous form or vaporous Condition applied.

Of Further, it is preferable that the resin-containing wood substrate after application of the reactive chemical, a heat treatment step is subjected. In the heat treatment it can be heating by IR light, Microwaves or by superheated steam, e.g. under pressure, acting.

at The alternative preferred embodiment is crosslinking by reactive chemicals fires whereby the resin vulcanizes to provide a smooth and hard surface becomes.

at a preferred embodiment the method according to the invention The resin will continue even further with the naturally occurring cellulose crosslinked in the wood substrate. In this embodiment of the invention will caused a double vulcanization, since the resin with resin and cellulose of the wood substrate is crosslinked. The bonds can be through Double bonds in the resin and free OH groups of the cellulose formed become. It is possible, strong To achieve bonds between resin and cellulose and it can effective sealing of the surface be achieved. The crosslinking process can be caused by UV light, high frequency heating, reactive chemicals etc., as described above.

By Applying the method according to the invention Is it possible, the wood substrate in a very economical and cost effective way to treat. As explained above, the natural present resin flows in Wood in corridors or resin courses, from which it breaks through cracks or branches, the weak spots in the wood substrate, to the surface of the Wood substrate can penetrate. For this reason, the sweating occurs of resin essentially out of passages, Cracks and branches, it is usually sufficient to cure the resin present therein.

The sunsets, Cracks and knots can with the help of a well-known wood sorting system like WoodEye of the company Innovative Vision AB, Sweden, to be identified. As soon as the sunsets, Cracks and branches identified if the resin present therein is e.g. by submitting the sunsets, Cracks or knots of a UV light treatment or high-frequency heating are cured, whereby the crosslinking and curing process of the resin is triggered. The process can be controlled by a computer become and run automatically.

Prefers finds the curing by networking the course in the corridors, Cracks or branches present resin by application of UV radiation instead.

For some Purposes comprises a preferred embodiment of the method according to the invention further comprising the step of coating the resin Wood substrate with a coating material, e.g. Shellac or Paint.

At the Two step process, the first step comprises curing the Naturally in the wood substrate present resin. Thereupon the surface of the Wood substrate coated with a coating material, the man Harden or let it dry.

at the one-step process, the resin-containing wood substrate with a coating material coated, the resin in the wood substrate hardened and the coating material is simultaneously cured and dried.

The Wood substrate can be coated as a whole or the coating can go to the corridors, Cracks and / or branches be limited in the wood substrate.

The Coating of the wood substrate may be advantageous if the wood substrate for the use in wet environments with variable temperatures is.

The Invention also relates to a wood-containing wood substrate, in which at least a part of the resin corresponds to the method described above hardened becomes.

The The invention further relates to the use of a like method described above in the treatment of a molded Wood articles, timber, wood, posts and crushed wood Wood like wood shavings and building boards.

at In another embodiment, the invention relates to a Apparatus for the treatment of a resin-containing wood substrate, which apparatus Includes

• - An identification unit for identification resin gullies and / or cracks and / or branches in the wood substrate
• - downstream of the identification unit a unit for selective curing at least a portion of the resin in at least a portion of the identified Resin canal.

at a preferred embodiment the apparatus comprises an automatic transmission device of signals from the identification unit to the unit for the selective Curing, wherein the signals provide information regarding the position of the resin ducts and / or Cracks and / or branches. The identification unit preferably consists of a known one Wood sorting system.

In The following examples will now illustrate embodiments of the invention illustrated.

example 1

One Resin-containing wood substrate made of a pinewood strip that is the measurements 4 × 8 × 50 cm is subjected to a manual examination, in which openings of resin gullies and / or cracks and / or branches be identified visually and marked with red ink.

The identified resin ducts and / or cracks and / or branches are subjected to treatment with UV light.

The marked areas on the surface The wood will be treated with UV light from a medium pressure mercury vapor lamp (300 WPI, about 365 nm) from a distance of 10 to 15 cm 20 to Subjected for 40 seconds.

you observed that, of course occurring resin is cured at the treated sites in a thickness, extending from the surface extends to 0, 2 mm to 0, 8 mm into the wood.

Example 2

One Resin-containing wood substrate made of a pinewood strip that is the measurements 4 × 8 × 50 cm has, is on a surface a treatment with UV light subjected.

The treated surface has dimensions of 8 × 50 cm on.

The surface becomes longitudinal at a speed of approx. 0.5 m / min. moves and UV light exposed from a fixed UV lamp. When the UV lamp acts it is a medium pressure mercury vapor lamp (300 WPI, approx. 365 nm) at a distance of about 10 cm above the treated, moving surface is positioned.

you observed that, of course occurring resin in the surface cured in a thickness that will be different from the surface to a depth of 0, 1 mm to 0, 3 mm into the wood hineinerstreckt.

Example 3A

A wood substrate consisting of a pinewood bar with a resin-filled crack measuring 4 × 2 mm was subjected to treatment with a UV radiation source. The intensity level was 500 mW / cm ² at 450 +/- 25 nm and the exposure time 40 seconds and the distance between the source and the substrate 1.5 mm. This sample had a measured average peel bond strength under shear stress of 12.3 MPa.

Example 3B

A wood substrate consisting of a pinewood bar with a resin-filled crack measuring 4 × 2 mm was subjected to treatment with an argon laser source. The intensity level was 500 mW / cm ² , the exposure time 5 seconds and the distance between the source and the substrate 1, 5 mm. This sample had a measured average peel bond strength under shear of 11.8 MPa.

Out the above mentioned Examples 3A and 3B show that a 5 second long Laseraushärtung with the help of an argon laser causes stress leading to failure of the binding, which are comparable to those after 40 seconds long curing be obtained by UV radiation. It did not become significant Loss of bond strength observed, however, a drastic decrease in curing time (in order a factor of 8).

Claims (15)

Process for treating a resin containing Wood substrate, which method comprises the following steps: - Identify of resin gullies and / or cracks and / or branches in the wood substrate and - selective Harden at least a portion of the resin in at least a portion of the identified resin grafts and / or Cracks and / or branches by crosslinking the monomers and polymers in the resin. The method of claim 1, wherein the resin is formed by crosslinking monomers and polymers in the resin by application of UV radiation, IR radiation, high frequency heating laser radiation, corona treatment, plasma treatment and / or heat treatment is selectively cured. The method of claim 2, wherein the curing by UV radiation takes place. The method of claim 1, wherein the resin is crosslinked of monomers and polymers in the resin by applying a reactive chemical hardened becomes. The method of claim 4, wherein the reactive chemical sulfur, sulfur trioxide, hydrogen peroxide, nitrogen oxides, Phosphorus, halogens or ozone is selected. The method of claim 5, wherein the reactive chemical in gaseous form or vaporous Condition is applied. A method according to any one of claims 4 to 6, wherein the resin containing Wood substrate a heat treatment step is subjected after the reactive chemical is applied has been. Method according to one of claims 1-7, further comprising the step coating the resin-containing wood substrate with a coating material includes. The method of claim 8, wherein the coating material is selected from the group, which consists of shellac, paints and polymer material. Method according to one of claims 8 - 9, wherein the coating material in the liquid Condition is applied and you put it on the surface of the Wood substrates can be hard or dry. Resin-containing wood substrate, wherein at least a portion of the resin is cured by the method of any one of claims 1-10. Application of a method according to one of claims 1 - 10 at the treatment of shaped wood articles, lumber, timber, Posts and shredded wood such as wood shavings and building boards. Apparatus for treating resinous wood substrate, which apparatus comprises - an identification unit for the Identify resin ducts and / or cracks and / or branches in the wood substrate, - of the Identification unit downstream of a unit for the selective Harden at least a portion of the resin in at least a portion of the identified Resin ducts. Apparatus according to claim 13, comprising a device for the automatic transfer of signals from the identification unit to the unit for the selective Harden the signals that provide information regarding the position of the resin ducts and / or Cracks and / or branches. Apparatus according to claim 14, wherein the identification unit consists of a known wood sorting system.