WO2002079571A1

WO2002079571A1 - Paper for producing panels and paper-making method

Info

Publication number: WO2002079571A1
Application number: PCT/EP2001/003661
Authority: WO
Inventors: Dieter DÖHRING; Josef Stutz
Original assignee: Kronospan Technical Company Ltd.
Priority date: 2001-03-30
Filing date: 2001-03-30
Publication date: 2002-10-10
Also published as: US20030138600A1; CN1358247A; PL357213A1; EP1272707A1; CN100342080C

Abstract

The invention relates to a method for making paper, which is characterized in that the paper is impregnated with an acrylate-containing dispersion or mixture and the acrylate-containing dispersion or mixture is forced into the paper. The paper so produced can be used to produce boards, especially floor panels even if said panels have only a mass per unit area of 15 to 35 g/m2, thereby reducing the costs of production of such panels.

Description

Paper for the manufacture of panels and processes for the manufacture of paper

The invention relates to a method for producing paper for plates and to a paper produced in accordance with the method. The invention further relates to plates, in the manufacture of which paper is used, and to an associated manufacturing process.

A panel according to the invention can be processed into a panel. A panel, for example known from the document EP 090 6994 AI, is a generally elongated, thin plate which can be connected to other panels laterally, that is to say * on the longitudinal and transverse sides, for example via grooves and tongues. Panels connected in this way are used in particular as flooring or as wall cladding.

A plate is u. a. manufactured as follows. A resin-soaked paper, which is called "backing paper" is provided. Above the backing paper, a carrier plate is arranged. Another, soaked paper with resin is arranged above the plate. The two papers are with the plate at temperatures around 200 ° C pressed together to form the plate.

The paper arranged above the plate is regularly provided with a decor that determines the appearance of the plate from the top. SiC particles or corundum grains can be rolled on the side with the decor before pressing in order to obtain a plate with a particularly resistant surface. A layer of cellulose is additionally applied to the side with the SiC particles or the corundum.

The paper with the printed decor is called decorative paper. The cellulose layer is referred to as an "overlay".

The decorative paper is placed with the overlay above the carrier plate. The decorative paper is then between the carrier plate and the overlay. Then the backing paper, backing plate,

Decor paper and overlay pressed together at a temperature of the order of 200 ° C. If the layer system leaves the press, there is a plate with a decor with a particularly hard surface on one side.

Sawing and milling can be used to produce panels with the desired dimensions, tongue and groove on the side. The panels are used in particular as floor coverings.

The carrier plate gives the panel mechanical stability. The decor on the decor paper determines the appearance of the later wall or floor surface. The layer made of corundum or SiC ₂ ensures good resistance to abrasion and the like. The backing paper counteracts warping of the carrier plate. The overlay protects a surface of the Press in front of the otherwise protruding hard SiC ₂ or corundum grains.

The papers used in the prior art generally have a weight of more than 70 g per square meter. If the value falls below the above value, the paper is not tearproof enough to be able to withstand the mechanical loads during plate production. The paper 10 also becomes so thin that it becomes too transparent to be used as decorative paper.

However, a high paper weight has the disadvantage that the material consumption is correspondingly high.

L5 Not only the actual paper weight has to be taken into account, but also the resin with which the paper is soaked so that it can be used in the manufacture of a plate. The higher the paper weight, the more resin is used to impregnate the

.0 paper required. Accordingly, paper production becomes more expensive.

In order to obtain thin, tear-resistant paper, a plastic mixture is placed on pre-impregnated paper

25 spread. This plastic insulation does not penetrate the paper, but represents an additional layer that is adjacent to the paper. The other side of the paper is regularly provided with a self-adhesive layer. The paper so produced is under

50 known as the "finish film" and can be glued to plates. The object of the invention is the manufacture and provision of a paper which is substantially more tear-resistant and, in one embodiment, optically more opaque in color compared to the prior art mentioned at the beginning. The object of the invention is the manufacture and provision of inexpensive plates in which the paper according to the invention is used.

According to the process, the paper is impregnated with an acrylate-containing dispersion or mixture. Compared to an impregnation that is only carried out with a resin, the paper impregnated according to the process is considerably more tear-resistant. The paper can have a weight per unit area of, for example, 30 g / m ² and is nevertheless able to withstand the mechanical loads in the production of a plate in the manner mentioned at the beginning. Tests have even shown that the mechanical strength of the paper according to the invention is so high that the

Impregnation speed in the resin impregnation provided for the plate production can be increased from currently 40 to 60 m / min to 120 m / min. The consumption of the paper material and the impregnating agent is correspondingly low - compared to the prior art mentioned at the beginning.

The acrylate-containing dispersion or mixture contains water in which acrylate particles are dispersed. Suitable acrylates are therefore those that are well dispersing. In an advantageous embodiment of the invention, the acrylate-containing dispersion or mixture is pressed into the paper for the purpose of impregnation. For this purpose, for example, the paper is passed through rollers that are pressed against each other. The acrylate-containing dispersion or mixture is applied continuously to a roller. When the paper leaves the roller, the dispersion or mixture has been pressed into the paper.

It is essential that the dispersed acrylate or the mixture is not only spread onto the paper, since then the dispersed acrylate or the mixture would not or only insufficiently penetrate into the paper. Pressing ensures that the dispersion or mixture penetrates the paper and the paper thus achieves the desired improved strength. In addition, the paper is then provided with the dispersion or the mixture in such a way that additional resin which is used during the further processing into a plate does not penetrate into the paper, or at least only relatively slightly.

In an advantageous embodiment of the method, the paper is pressed in before the acrylate-containing dispersion or mixture is pressed in

/ Impregnation vented. For this purpose, the paper is impregnated with the dispersion or mixture containing acrylate, in particular on one side. The air in the paper is so through the dispersion or

Mix replaced. In one embodiment of the invention, a resin-acrylate mixture or dispersion, in particular an amino resin-acrylate mixture, is used for the impregnation. With such a mixture or dispersion, paper weights up to one

Realize the lower limit of approx. 15 g per square meter. Papers produced in this way are sufficiently tear-resistant with a suitable mixing ratio in order to be used, for example, as printing base paper in the manufacture of plates. It can be left to the person skilled in the art to find suitable mixing ratios by a few experiments.

The paper should not exceed an upper limit of 60 g / m ² , preferably 40 g / m ² , in order to achieve sufficiently high cost advantages. Optimal values are currently between 25 to 35 g / m ² .

In an advantageous embodiment of the invention, color pigments, for example aluminum silicate, calcium carbonate, Ti0 ₂ , Al ₂ 0 ₃ or magnesium silicate, are added to the mixture. This greatly reduces light transmission.

The impregnated using color pigments

Paper can be used very well as decorative paper due to its opacity and high opacity.

In a preferred embodiment of the invention, the acrylate-containing dispersion or mixture is pressed into deaerated paper from both sides. It has been shown that the paper then moves away from the Top up with the dispersion or mixture containing acrylate. Paper impregnated in this way is particularly suitable for the plate production mentioned at the outset.

The paper produced according to the method differs from the finish foils in particular in that the acrylate is in the paper and not only wholly or predominantly on the surface. The splitting strength is considerably greater than that of the finish foils mentioned at the outset, as a steam test shows. The water vapor test exposes paper to water vapor for two hours. In conventional paper, in contrast to the invention, cleavage occurs.

ua-SD αutopj-u hgemielle paper can then be used as backing paper or decorative paper in the manufacture of a plate in the manner mentioned above.

In one embodiment of the method, decorative paper is not only provided with abrasion-resistant particles such as silicon carbide or corundum particles on one side, but also with fibers and / or balls. In comparison to the abrasion-resistant particles, the fibers or balls consist of soft materials such as polyester, polyamide or glass. The fibers and / or balls protect a press belt from damage during the pressing of a layer system which comprises the decorative paper. It is not necessary to provide an overlay above a layer with abrasion-resistant particles. This saves approx. 1/3 of the costs for impregnating the decorative paper and bring a layer with the overlay incurred in the prior art.

The impregnation of the decorative paper comprises in particular the following steps. The decorative paper is impregnated with resin, in particular an amino resin, and abrasion-resistant particles are applied to one side with the decor. The fibers and / or balls are then applied to this. The result is that the fibers and / balls form a protective cover layer above the abrasion-resistant particles in a pressing device.

Before the fibers or balls are applied, the method can be configured as follows.

A layer of an amino resin with abrasion-resistant particles in a special dispersion is also sprayed onto the decorative paper, the final basis weight - based on the dry weight of the base paper - being 100% to 250%. Spraying on the dispersion has proven to be advantageous, as can be seen from the publication WO 00/44984. In the following, it is expedient to ensure smoothing and uniform distribution of the sprayed-in dispersion by means of rollers.

The aforementioned dispersion preferably consists of 100 parts of an amino resin, 20 to 95 parts of an abrasive, ie abrasion-resistant substance, 0.5 to 2.5 parts of a silane coupling agent, 5 to 25 parts of a flow aid, 0.1 to 0.4 parts of one Wetting agent, 0.05 to 0.4 parts of a release agent and an amino resin hardener. A melamine resin is used in particular as an amino resin, as a flow aid for example polyglycol ether, ε-caprolactam or butanediol and as an abrasive substance for example silicon carbide with an average grain size of 60 to 160 μm or aluminum oxide in the form of corundum or from the melt with a grain size of 60 to 160 μm used. Any mixture of silicon carbide and aluminum oxide can also be provided.

The subsequent application of fibers and / or balls is advantageously carried out as follows. A mixture of a resin, the fibers or the balls is produced and the mixture on the above

Wise treated decorative paper applied. The provision of a mixture further improves protection in a pressing device, since the additional resin then also contributes to the protection.

The thickness of the fibers or the diameter of the balls should preferably be chosen such that the corundum or silicon carbide particles are kept away from the corresponding surface of the press during the pressing of a corresponding layer system for the production of plates. This prevents damage due to hard silicon carbide or corundum particles.

The average diameter of the balls is preferably larger than the average diameter of the fibers if both fibers and balls are used. The balls then provide the desired protective distance between the abrasion-resistant particles and, for example, a press belt. The fibers in particular ensure that resin is fixed and counteract crack formation.

The affected surface of a press is protected by the invention in an improved and particularly inexpensive manner against damage by abrasion-resistant particles, for example hard corundum or silicon carbide particles. The processing of the affected surfaces in a press - for example a press belt of a so-called double belt laminating system - takes place at correspondingly larger intervals, so that the costs associated with the processing and production downtimes are reduced. Overall, there are considerable cost savings.

Typical fiber lengths are at least 0.5 mm, but preferably at least a few millimeters, for example 2 mm, 4 mm or 5 mm. The longer the fiber, the better it is able to protect the surface of a plate from cracking. An upper limit of the fiber length is given in particular by the associated increase in viscosity. If the viscosity of a resin-fiber mixture is too high, it can no longer be processed. The diameter of the fibers is, for example, a few 10 μm or even 100 μm and more.

A typical diameter of the balls is 30 to 200 μm. On the one hand, the desired distance between the corundum or silicon carbide particles is thereby no guarantee of the corresponding surface in a press. On the other hand, the balls are small enough

; ι in order not to be noticed with the naked eye.

The optical impression is not adversely affected by the fibers or balls if they have the aforementioned dimensions and are embedded in the resin.

The fibers or balls preferably consist of polyester, polyamide or glass. These materials fulfill the properties that are required during production and after production. They are sufficiently stable during production. Polyester, polyamide or glass are sufficiently soft materials in the sense of the invention to avoid damage to a pressing device. In the case of a finished panel, the aforementioned materials create sufficient transparency so that the visual impression of the decor is not adversely affected. The materials advantageously enable relatively large, processable fiber lengths which significantly exceed the length of fibers made of cellulose and used according to the invention. The increase in viscosity with increasing fiber length of artificial polymers such as polyester, polyamide fibers or glass fibers is namely small in comparison to the increasing fiber length of cellulose fibers.

Sufficient fibers can therefore be inserted, so that a press is better protected against damage

Compared to short cellulose fibers. This is particularly the case when the fibers are in Form of a fleece, as will be explained below.

The fibers and / or balls can consist of different materials. For example, polyester fibers, polyamide fibers and glass fibers can be used at the same time.

Fibers should be preferred over spheres, as this avoids the formation of cracks in the surface. Balls are therefore preferably used in addition. Hollow balls made of glass are therefore preferably added as balls to reinforce the protective effect, which in particular have a diameter of 30 to 200 μm for the aforementioned reasons.

The decorative paper as claimed preferably has a solids mass of 25 to 35 g / m ² . The fiber content is then in particular 5 to 100 g / m ² . In addition, up to 80 g / m ² balls, in particular hollow micro glass balls, are advantageously provided for reinforcement.

In a further advantageous embodiment, the fibers are in the form of a fleece. The fibers are woven together, so to speak. A fleece reinforces and protects in a particularly good way. The risk of crack formation is further reduced and thus the risk of damage to the upper part concerned in each case.

/ area. With the application of a resin-fiber mixture, the resin fixes the resin particularly well during pressing. The resin then contributes particularly well to protection in a pressing device. If a fleece is provided, the protective effect is further improved by introducing balls.

The invention is illustrated by the following example:

Paper with a weight of 30 g / m ² is moistened on one side with an acrylate-containing dispersion. The dispersion contains the following constituents: 770 g of a commercially available acrylate dispersion with a solids content of 50% by weight, 225 g of a commercially available urea-formaldehyde impregnating resin with a solids content of 50% by weight and 5 g of a urea resin hardener. The mixture is mixed finely stirred and applied.

The moistened paper is passed through rollers pressed against each other. The rollers have a surface made of hard rubber. The aforementioned dispersion is applied evenly to the rollers and distributed evenly on the roller surface with the aid of doctor blades.

Inside the paper leaving the rollers is the mixture containing acrylate. This

Paper is dried and can then be used in the manufacture of boards.

Color pigments are added to the dispersion for the production of decorative paper, namely 250 g

Titanium dioxide slurry with a solids content of 70 wt .-% and 50 g of magnesium silicate added. The paper is then at least as opaque as conventionally produced paper with a weight of 70 g / m ² .

The plates produced with the papers in the manner mentioned at the outset were tested in accordance with EN 438. All standard values were surely met. In particular, the water vapor test was successfully passed.

The decorative paper is preferably used in the manufacture of a plate as follows. A mixture of amino resin and corundum particles is evenly sprayed onto the top of the decoration. 15 g / m ² corundum is used. The now wet paper web is fed to a floating dryer. The temperature in the dryer is 170 ° C. A mixture of a commercially available amino resin and polyester fibers is metered onto the top of the decor onto the web treated in this way. The solids mass of the order is 70 g / m ² . The fiber content in the mixture is 30

Dimensions-%. The average length of the fibers is 5 mm. The average diameter is 80 μm. A second drying step is then carried out at 160 ° C until the residual moisture is 7%. The decorative paper impregnated in this way becomes one in the manner mentioned at the beginning

Plate, especially processed into a panel for floors. Paper according to the invention is also used as backing paper. In this way, 150 g / m ^{2 of} resin can be saved in comparison with the prior art. However, the paper according to the invention also offers advantages over the prior art when the paper weight is very high, for example up to 150 g / m ² .

Claims

Expectations

1. A process for producing a paper, characterized in that the paper is impregnated with an acrylate-containing dispersion or mixture.

2. The method according to claim 1, characterized in that the acrylate-containing dispersion or mixture is pressed into the paper.

3. The method according to any one of the preceding claims, characterized in that the acrylate-containing dispersion or mixture of water, in which acrylate particles are dispersed, and preferably contains resin, in particular an amino resin.

4. The method according to any one of the preceding claims, characterized in that color pigments such as aluminum silicate, calcium carbonate, Ti0 ₂ , Al ₂ 0 ₃ or magnesium silicate are added to the acrylate-containing mixture or dispersion.

5. The method according to any one of the preceding claims, characterized in that the paper is passed through rollers which are pressed against one another, with at least one

Roll the acrylate-containing dispersion or mixture is applied continuously and is preferably distributed on the roll with a doctor blade.

6. The method according to any one of the preceding claims, characterized in that the paper is deaerated before the acrylate-containing dispersion or mixture is pressed in and for this purpose is impregnated in particular on one side with the acrylate-containing dispersion or mixture.

7. The method according to any one of the preceding claims, characterized in that the paper weight is at least 15 grams per square meter and / or does not exceed an upper limit of 60 g / m ² , preferably 40 g / m ² .

8. A method for producing a plate, in which paper is impregnated according to one of the preceding claims and a layer system comprising the paper and a carrier plate is pressed with the application of heat.

9. A method for producing a plate according to the preceding claim, in which the layer system comprises a decorative paper, to which a mixture of amino resin and abrasion-resistant particles is applied, preferably by spraying, before being pressed.

10. A method for producing a plate according to the preceding claim, in which fibers made of polyester, polyamide or glass and / or balls on the abrasion-resistant particles before

Pressing can be applied.

11.. Paper, characterized by acrylate, which is at least predominantly inside the paper.

12. Paper after the previous one

Device claim, producible according to one of the preceding method claims.

13. Paper according to one of the preceding device claims, characterized by a

Paper weight from 15 to 60 g / m ² , preferably up to 40 g / m ² .

14. Paper according to one of the preceding device claims, characterized by

Color pigments that are inside the paper.

15. Paper according to one of the preceding device claims, characterized in that it shows no cleavage following the implementation of a standardized water vapor test in which the paper is exposed to water vapor for two hours.

16. Plate in which paper is used according to one of the preceding device claims.

17. Plate according to the preceding claim, in which a surface of the plate with abrasion-resistant particles such as corundum or silicon carbide particles and preferably with polyester, polyamide or Glass existing fibers and / or balls is provided.

18. Plate according to one of the two previous

Claims, characterized in that the plate is a floor panel.