ES2844176T3 - Method for applying nanoparticles - Google Patents

Abstract

Method for manufacturing a sheet comprising photocatalytic nanoparticles, the method comprising the steps of: - impregnating (41, 42) a sheet (10) of paper with a polymeric resin, comprising wear resistant particles; - drying the polymeric resin; - spraying (43, 40) the paper sheet (10) with the dried polymeric resin with an impregnating fluid composition comprising dispersed photocatalytic nanoparticles; - drying and / or curing (44, 45) at least partially said impregnated paper sheet comprising the polymeric resin and the impregnation fluid, wherein the photocatalytic nanoparticles comprise photocatalytically active TiO2 nanoparticles, wherein said nanoparticles have a size of primary particle <50 nm, where the concentration of said photocatalytic nanoparticle impregnation fluid is> 1% by weight, and where the amount of impregnation fluid composition per square meter of the applied surface is in the range of 1- 200 ml / m2.

Description

DESCRIPTION

Method for applying nanoparticles

Technical field

The description generally refers to methods of applying nanoparticles to a surface to create a layer with integrated photocatalytic nanoparticles. Furthermore, the invention relates to a method for achieving a homogeneous distribution of nanoparticles in the upper layer of boards and panels.

Background

It is known to produce laminated building panels with a surface comprising laminated paper sheets. Also known is a new type of panel called Wood Fiber Floor (WFF) which is described in document WO2009 / 065769, which shows both products and methods for producing said product also using nanoparticles. Furthermore, the application of nanoparticles on a laminated surface or on a covering paper is shown in document WO2009 / 062516. The following documents describe various ways to treat impregnated papers or papers before final oven and before using the paper on laminated panels.

US-2009 / 0208646A1 describes a wet-wet application of a coating to an impregnated deck via a coating inlet. The control of the thickness of the layer is obtained by means of cloths that wipe off the excess of coating. The document shows a method for producing a cover, in particular for laminates, which involves impregnating a paper with the following method steps:

1) Unroll a cover base paper from a roller in order to obtain a paper web (10);

2) Moisten the paper web (10) on one side with an impregnation medium (14);

3) Impregnate the paper band (10) with an impregnation medium (18)

4) Wet apply a dispersion (27) of coarse corundum and resin on one side on the paper web (10) 5) Apply wet wet on the opposite side a coating substance (29), in the form of resin and corundum thin, on the paper band (10);

6) A dosage of the coating substance (29) applied by means of a cloth (32), at the desired application weight;

7) Dry the paper web (10) using a drying duct.

Document US-3798111 describes the incorporation of particles to the paper machine where the particles can be found in the whole of the paper, entangled by the fibers.

Document WO2007144718 describes a suspension of hard nanoparticles applied to the carrier sheet previously treated with resin. The method claims that the suspension comprises resin. The method comprises adding the suspension via a wire distributor roll and / or a texturizing roll or other methods comprising rolls and / or blades. Also air blades.

Summary of the invention

Embodiments of the invention relate to a method of applying nanoparticles on a surface to create a sheet or a surface layer with photocatalytic nanoparticles.

The objective is to improve the effect of the photocatalytic nanoparticles when the particles are integrated in the sheet or in the surface layer, that is, keeping the level of activity at a high level and maintaining the desired properties of the sheet or layer with the particles. integrated.

The use of photocatalytic nanoparticles in a surface layer to enhance eg WO2009 / 062516A2 is shown in document WO2009 / 062516A2. eg, cleaning ability. Furthermore, a method for applying the nanoparticles is described. The method according to embodiments of the invention provides improved transparency, long shelf life and improved nanoparticle distribution.

A first aspect of the invention is a method for manufacturing a sheet comprising photocatalytic nanoparticles, the method comprising the steps of:

• impregnating a sheet with a polymeric resin, preferably comprising wear resistant particles;

• spraying the sheet, freshly impregnated with the polymeric resin in an uncured and wet state, with an impregnating fluid composition comprising dispersed photocatalytic nanoparticles;

• drying and / or at least partially curing said impregnated sheet comprising the polymeric resin and the impregnating fluid,

wherein the photocatalytic nanoparticles comprise photocatalytically active TO2 nanoparticles, wherein said nanoparticles have a primary particle size <50 nm,

wherein the concentration of said photocatalytic nanoparticle impregnation fluid is> 1% by weight, and

wherein the amount of impregnating fluid composition per square meter of the applied surface is in the range of 1-200 ml / m2.

The sheet can comprise cellulose fibers.

Preferably, the impregnating fluid composition comprises a solvent comprising water.

The method may comprise a stage between the impregnation stage and the spraying stage, in which stage the polymeric resin is partially dried.

By applying the photocatalytic nanoparticles to a wet surface, the particle distribution is especially improved.

The composition of the impregnating fluid can comprise photocatalytic nanoparticles and a solvent, said solvent being selected from water, ethylene glycol, butyl ether, linear, branched or cyclic aliphatic alcohols or aromatic-aliphatic alcohol mixtures such as methanol, ethanol, propanol, isopropanol, butanol. , isobutanol, benzyl alcohol or methoxypropanol or combinations thereof.

A second aspect of the invention is a method of producing a laminated board or panel by laying the sheet produced according to the first aspect on a core, preferably a HDF panel, and applying heat and pressure.

A third aspect of the invention is a method for manufacturing a sheet comprising photocatalytic nanoparticles, the method comprising the steps of:

• mixing the photocatalytic nanoparticles in a polymeric resin to obtain an impregnation mixture;

• apply the impregnation mixture to a sheet, preferably by spraying.

A fourth aspect of the invention is a method of producing a paper sheet comprising photocatalytic nanoparticles in the paper mill, preferably prior to lamination of the paper.

A fifth aspect of the invention is a method for producing a WFF panel comprising photocatalytic nanoparticles, the method comprising the step of:

1) Disperse a dry mix comprising wood fibers, a thermosetting resin, preferably melamine resin, and wear resistant particles on a core;

2) Apply an organic solvent to the mixture on the core;

3) Spraying an impregnating fluid composition comprising dispersed photocatalytic nanoparticles, preferably dispersed in water;

4) Apply heat and pressure.

Steps 2 and 3 of the method can be applied in any of the methods described in WO2009 / 065769 and WO2009 / 124704 for the production of WFF panels.

The method is preferably performed in the order numbered 1-4.

The organic solvent preferably comprises ketone, such as acetone and methyl ethyl ketone and / or alcohol, such as ethanol, propanol and methanol and / or acetate, such as butyl acetate, ethyl acetate. In a preferred embodiment, the organic solvent is ethanol.

In another embodiment, the method comprises the step of applying, preferably before step 2, a fluid with a wetting agent on the mixture, preferably in the form of water containing 1% by weight content of BYK-348 from BYK Chemie. The fluid with the wetting agent and the organic solvent can also be applied together.

It is well known that a nanomaterial is not just a nanomaterial and the characteristics of the embedded nanoparticles are important for their behavior and, p. For example, the properties of that board or panel. In an especially preferred embodiment of any of the aspects, the integrated nanoparticles have a primary particle size or a crystal size of <50 nm, such as <30 nm, preferably a primary particle or a crystal size <20 nm. In this way, the efficacy of the nanoparticles is improved and / or fewer nanoparticles are required to obtain a specific effect.

Primary particles are rarely present as individual primary particles, but in a more or less aggregated form. Effective control of agglomerate and / or group size is highly preferred. Thus, in preferred embodiments, the integrated nanoparticles have a cluster or aggregate size of <100 nm, such as <80 nm, preferably a cluster or aggregate size of <60 nm, such as <40 nm, and even more preferably a group or aggregate size of <30 nm, such as <20 nm. In this way, said nanoparticles can be more easily dispersed homogeneously in said cover layer, and said layer becomes optically more transparent.

In any embodiment of the present invention, the concentration of said nanoparticles in said impregnating fluid can be> 1% by weight,> such as 5% by weight, preferably a concentration of said nanoparticles> 10% by weight, such as> 15 % by weight and even more preferably a concentration of said nanoparticles> 20% by weight, such as> 25% by weight.

Furthermore, in any embodiments, the nanoparticles of said impregnating fluid composition have a cluster or aggregate size of <100 nm, such as <80 nm, preferably a cluster or aggregate size of <60 nm, such as <40 nm. , and even more preferably a group or aggregate size of <30 nm, such as <20 nm.

In all aspects of the invention, the amount of impregnating fluid composition per square meter of cover sheet or sheets may be in the range of 1-200 ml / m2, such as in the range of 5 100 ml / m2 and , preferably in the range of 10-50 ml / m2, such as 20-40 ml / m2, of said impregnating fluid composition per square meter of sheet or sheets to be impregnated.

The polymeric resin used for said polymeric resin composition comprising nanoparticles can be selected from the group comprising melamine formaldehyde resin, phenol formaldehyde resin, urea formaldehyde resin, urea formaldehyde melamine resin, acrylamide resins, urethane resins, epoxy resins. , silicon resins, acrylic resins, vinyl resins or mixtures thereof.

In embodiments of the invention, the photocatalytic nanoparticles of said nanoparticle polymer resin composition can be introduced as a dry powder, as a paste or as a suspension and then dispersed in the polymer resin.

In embodiments of the invention, a solvent of said suspension of photocatalytic nanoparticles to be dispersed in the polymeric resin composition is selected from water, ethylene glycol, butyl ether, linear, branched or cyclic aliphatic alcohols or aromatic-aliphatic alcohol mixtures such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, benzyl alcohol or methoxypropanol or combinations thereof.

Embodiments of the invention can, in a sixth aspect, be obtained by a method of manufacturing a board or a panel; understanding the method

- providing the top surface of an assembled base or laminate board or panel with a coating applying a coating fluid composition comprising photocatalytic nanoparticles; Y

- drying and / or curing said base or laminate board or panel, after said coating step.

In any of the above aspects, the coating fluid can be applied to said material surface by spraying, dipping, rolling, brushing, or by other conventional application methods. The amount of coating fluid composition per square meter of said material surface may be in the range of 1-200 ml / m2, such as in the range of 5-100 ml / m2, and preferably in the range of 10- 50 ml / m2, such as 15-25 ml, of said coating fluid composition per square meter of said material surface.

Various combinations of the ingredients can be made into fully functional products. Three examples are provided below in order to show three functional realizations of the innovation.

Brief description of the drawings

The description will now be described with reference to preferred embodiments and, in greater detail, to the accompanying illustrative drawing, wherein

Fig. 1 illustrates a production line for producing a cover paper.

Fig. 2 illustrates a production line for producing a cover paper comprising a spraying unit.

Detailed description of the realizations

The present invention relates to the manufacture of a cover or boards or panels, such as laminated boards or panels, which comprise different types of photocatalytic nanoparticles, which make the manufactured products photocatalytically active. Each layer and the process step can be preferred over the others, e.g. eg depending on the price of laminated boards and panels (low cost / high cost product) and the facilities available from laminate manufacturers.

Laminate boards and panels are typically manufactured with a fiberboard base (mainly HDF high density fibreboard) and 3 or more sheets: a decorative sheet, a cover cellulose sheet on top, and one or more sheets backing pads located on the opposite side of the fiberboard to balance the board and prevent sagging. Other sheets are often placed between the fibreboard and the decorative sheet. The decorative foil could have monochrome or patterned decoration to have a p-like look. ex. made of wood, cork, stone, tile or a more abstract pattern. The cover sheet typically contains wear resistant particles, usually a certain amount of alumina oxide (Al2O3), to provide the laminate with increased resistance against abrasion. In addition, the cover sheet is impregnated with a polymeric resin, typically melamine formaldehyde resin. The other sheets, very often sheets of paper, are also impregnated with resin. The decorative sheet is typically impregnated with melamine-formaldehyde resin while phenol-formaldehyde resin is frequently used in the core of the laminate. The laminated board or panel is assembled by applying heat and pressure, causing the resin to polymerize in a thermosetting reaction. After lamination, the polymerized cover sheet and decorative paper constitute the top layer of the laminated board or panel and therefore must be optically transparent directly from the top surface of the laminate through the decorative printing of the decorative paper.

In an embodiment of the invention (Fig. 2) the photocatalytic nanoparticles are applied as a coating (43, 40) by wet spraying to the upper and / or lower surface of the paper (10), after a first (42) and / or a second (41) impregnation of the paper (10) with a wear resistant resin and particles, preferably aluminum oxide. The paper can dry (44, 45) after each impregnation. Preferably, the photocatalytic nanoparticles are applied after the impregnation step, but before the drying step. In one embodiment, the paper (10) is in a first stage (46) wetted with a resin and / or impregnated with a resin in its entirety. This method for spraying the photocatalytic nanoparticles can be incorporated into any production line to produce a cover or decorative paper, also in the line shown in Fig. 1 and previously described in document US-2009/0208646. Spraying of the photocatalytic nanoparticles can be carried out, along the line of Fig. 1, at any stage after wetting (14) of the paper web (10).

A suitable type of spray nozzle for spray coating photocatalytic nanoparticles is an electronically controlled Autojet Pulsejet B10000jjau.

The preferred spray speed of the cover or decorative paper can be> 1 m / s, preferably> 2 m / s, preferably a speed of> 5 m / s, such as> 8 m / s, and even more preferably a speed> 10 m / s.

In another embodiment, the photocatalytic nanoparticles are applied as a wet-on-dry spray coating to the upper and / or lower surface of the cover and / or decorative paper, after a first or a second impregnation of the paper with resin and resistant particles. wear, preferably aluminum oxide. Normally, the paper dries after each impregnation.

In a preferred embodiment of the invention, the photocatalytic nanoparticles can be mixed with a wetting agent and / or an alcohol prior to the spray coating step to improve the wettability of the impregnating fluid on the cover and / or decorative sheet.

In another embodiment of the invention, the photocatalytic nanoparticles can be applied as a combination of wet-wet and wet-dry spray coating.

In another embodiment of the invention, the photocatalytic nanoparticles are applied as a polymeric mixture in the resin impregnation step.

In another embodiment of the invention, the photocatalytic nanoparticles are incorporated into a cover sheet, e.g. For example, on the decorative paper itself before impregnation with polymer resin. Therefore, using such a photocatalytic cover sheet or the decorative paper, a photocatalytic layer can be easily introduced by applying the existing methods used to make laminated boards or panels, that is, impregnation with polymeric resin of the photocatalytic cover sheet or decorative paper followed by the manufacture of the laminated board in a lamination stage by hot ironing.

Said stages of impregnation with photocatalytic nanoparticles and drying / curing can be incorporated into an existing production line immediately before impregnation with polymeric resin of said cover sheet or decorative paper, or said cover sheet or photocatalytically impregnated decorative paper and cured can be stored until needed.

One type of nanoparticle suitable for use in the coating fluid composition is titania. The titania nanoparticles may further comprise, according to some aspects of the present invention, other elements. In some embodiments, said elements can be introduced into said nanoparticles with the aim of improving the photocatalytic activity of said nanoparticles by altering the absorption range of said titania photocatalytic nanoparticles.

The solvent in said coating fluid composition may comprise water, methanol, ethanol or isopropanol or combinations thereof or it may be only water.

The particle concentration of said photocatalytic nanoparticles in the manufactured board or panel can be increased by repeating said coating step several times.

A preferred embodiment of the impregnated paper produced comprises discrete photocatalytic nanoparticles on and in said cover sheet or decorative paper. Said nanoparticles or groups of nanoparticles may have, in many applications according to the present invention, substantially the same size as the effective particle size in said impregnating fluid composition.

The impregnated paper produced, comprising the photocatalytic nanoparticles, can be used in all known processes to produce laminated building panels, preferably flooring, wall panels and kitchen countertops.

The photocatalytic composition to be dispersed in the polymeric resin may preferably comprise photocatalytically active nanoparticles of titania (TiO2). In a preferred embodiment, said nanoparticles comprise the anatase and / or rutile and / or brookite crystalline form of titania or a combination thereof. Furthermore, the photocatalytically active nanoparticles are, according to the present invention, predominantly present in their final crystalline form in said composition, that is, no heat treatment is required to transform said nanoparticles to their active form. The primary average particle size or the crystallite size of the nanoparticles, e.g. ex. titania, expressed as an equivalent spherical diameter may preferably be less than 30 nm, such as less than 20 nm, and preferably less than 15 nm, such as less than 10 nm. Primary average particle size or crystallite size can be measured by X-ray Diffraction (XRD) using Scherer's formula. It is further preferred that the particle size distribution of said nanoparticles is relatively narrow.

The photocatalytic composition to be dispersed in the polymeric resin, whether it is introduced in the form of a powder or as a paste or suspension, can be added to the polymeric resin at any given time. In one embodiment of the invention, the photocatalytic composition is dispersed in the polymeric resin immediately prior to impregnation of the cover sheets or decorative papers with the polymeric resin. Said dispersing process can be facilitated by a specially designed machine or apparatus.

Examples

Having described the basic aspects of the invention, the following examples are provided to illustrate specific embodiments thereof.

Example 1 Wet on wet

This example illustrates the production of a polymeric surface containing embedded nanoparticles. The particles were applied as a dispersion by a spray system onto the freshly impregnated polymeric surface while it was still wet.

The following dispersion was used as a raw material. 30% TiO2 dispersion in water containing agglomerates of particles of size not greater than 80 nm, as determined by Nanotrack NPA 252 Particle Matrix. The stock solution was then dispersed on freshly impregnated melamine paper just after the paper would have come off the impregnation roller. The dispersion was applied to the paper using an Autojet spray system, pumping the fluid to the nozzles through a low pressure reservoir with a pressure of 1.8 bar. The nozzles were pulsating jet nozzles with air atomizing tips (1.5 bar air pressure) located 35 cm above the freshly impregnated paper in front of the inlet of the first drying oven.

The Autojet system was configured to deliver 30 ml of fluid / m2 of paper; then the paper was dried in two consecutive heating ovens. This produced a melamine paper with integrated TiO2 agglomerates of a very small size, penetrating about the first couple of hundred microns of the melamine paper.

Example 2 Wet on dry

This example illustrates the production of a polymeric surface containing embedded nanoparticles. The particles were applied in the form of a dispersion by means of a spraying system on the polymer surface after it had been dried in the heating oven.

The same liquid and spray system as in Example 1 was used in this experiment.

Example 3 Wet on raw paper

This example illustrates the production of a polymeric surface containing embedded nanoparticles.

The particles were applied as a dispersion by a spray system on raw paper before impregnating the paper with melamine.

Test results

The following table shows the result of different methods to apply the photocatalytic particles:

• Test I: Apply a photocatalytic top coat by impregnating the cover paper wet in wet by spraying.

• Test II: Apply a photocatalytic top coat by impregnating the cover paper wet on dry by spraying.

• Test III: Apply a photocatalytic top coat by impregnation of the cover paper wet on dry by spraying on the raw cover paper, before impregnation with melamine.

Appearance, stability and distribution were evaluated.

Treatment Aspect (a) Stability (b) Distribution (c)

White - Reference 1 1 -Test I: Wet in wet 1 1 1

Test II: Wet on dry 2 1 3

Test III: Wet in dry 4 4 2

a) The appearance, on a scale of 1-5, evaluated according to transparency and turbidity, was 1 if there were no visible differences with a non-integrated laminate and 5 is very cloudy.

b) The stability of the process was evaluated on a scale of 1-5, evaluated according to the useful life and flexibility of the material, where 1 is that there are no differences with the non-integrated laminate, and 5 is very sensitive to changes in the process .

c) The distribution of the integrated particles was evaluated on a scale of 1-5, where 1 is a completely homogeneous distribution of photocatalytic nanoparticles.

Claims (12)

i. Method for manufacturing a sheet comprising photocatalytic nanoparticles, the method comprising the steps of: • impregnating (41, 42) a sheet (10) of paper with a polymeric resin, comprising wear resistant particles; • drying the polymeric resin; • spraying (43, 40) the paper sheet (10) with the dried polymeric resin with an impregnating fluid composition comprising dispersed photocatalytic nanoparticles; • drying and / or curing (44, 45) at least partially said impregnated paper sheet comprising the polymeric resin and the impregnating fluid, wherein the photocatalytic nanoparticles comprise photocatalytically active TiO2 nanoparticles, wherein said nanoparticles have a primary particle size <50 nm, wherein the concentration of said photocatalytic nanoparticle impregnation fluid is> 1% by weight, and wherein the amount of impregnating fluid composition per square meter of the applied surface is in the range of 1-200 ml / m2. 2. The method according to claim 1, wherein the impregnating fluid composition comprises a solvent comprising water. The method according to claim in any one of the preceding claims, wherein said photocatalytic nanoparticles have a crystallinity of at least 50%. The method according to claim in any one of the preceding claims, wherein said nanoparticles have a primary particle size <30 nm, preferably a primary particle size of <20 nm such as <10 nm. The method according to claim in any one of the preceding claims, wherein the concentration of said photocatalytic nanoparticle impregnation fluid is> 5% by weight, preferably a concentration of said nanoparticles> 10% by weight such as> 15% by weight and even more preferably a concentration of said nanoparticles> 20% by weight such as> 25% by weight. 6. The method according to claim in any one of the preceding claims, wherein the amount of impregnating fluid composition per square meter of the applied surface is in the range of 5-100 ml / m2 and preferably in the range of 10 -50 ml / m2 such as 20-40 ml / m2. The method according to claim in any one of the preceding claims, wherein the photocatalytic nanoparticles have a group or aggregate size of <100 nm. A method for producing a laminated board or panel (1) by laying a sheet produced according to any one of the preceding claims, on a core, preferably a HDF panel and applying heat and pressure. The method according to claim 8, wherein the board is a pallet. The method according to claim 8 or 9, wherein the paper sheet is a cover sheet. 11. Board or laminated panel produced according to any one of claims 8-10, wherein said photocatalytic nanoparticles are homogeneously integrated in the uppermost layer of the panel, wherein the photocatalytic nanoparticles comprise photocatalytically active TiO2 nanoparticles, wherein said nanoparticles have a primary particle size of <50 nm, wherein the concentration of said photocatalytic nanoparticle impregnation fluid is> 1% by weight, and wherein the amount of impregnating fluid composition per square meter of the applied surface is in the range of 1-200 ml / m2. 12. The laminated board or panel produced according to claim 11, wherein said photocatalytic nanoparticles are homogeneously integrated into the final panel with a thickness of> 0.1 pm; > 1 pm; > 10 pm; > 50 pm; > 100 pm; > 500 pm; > 1000 pm.