DE2228936A1 - COATING FOR WOOD-BASED MATERIALS - Google Patents

Description

Badische Anilin- & Soda-Fabrik AG 2228936

Our sign; o.Z. 29 223 MuAiii

6700 Ludwigshafen, June 12, 1972

Coating for wood materials

The invention relates to a coating agent for wood materials based on carrier webs with amino or Phenoplasts pre-impregnated and with an additional layer of another hardenable resin to improve the performance properties are provided.

It is known to use carrier webs, in particular monochrome or decoratively printed papers with thermosetting aminoplasts or to impregnate phenoplasts from aqueous or aqueous-alcoholic solution and then the films or coatings obtained to dry. The films are intended to be used with each other or with wood-based materials such as chipboard, fiberboard and plywood sheets to be joined under the action of pressure and heat.

The one applied to the carrier web by the impregnation process The amount of resin is usually sufficient to create a firm bond with the substrate; in some cases will be additional For the resin impregnation, a glue line or glue film is applied between the substrate and the hardenable synthetic resin film.

It is also already known that it is possible to impregnate with aminoplasts or phenoplasts in two or more consecutive Steps to carry out, whereby the various stages of impregnation with regard to the composition, Viscosity and reactivity of different resins can be made.

With high-quality coatings, especially with coated ones It is also customary for wood-based materials to build up the coating from several layers, with aminoplast or phenoplast impregnated Paper layers are applied one after the other or at the same time. The various papers are after this

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Processes differentiated according to underlay, decor paper and overlay.

The coating of wood-based materials with synthetic resin films applied to a carrier is not based on the use of aminoplasts and phenoplasts remained limited. Rather, other polycondensable or polymerizable resins are already available used or suggested; in particular, the impregnation of papers with polymerizable compounds, e.g. B. with diallyl phthalate (prepolymers) or with crosslinkable polymers of the unsaturated polyester resin type are already known. These coatings too can be bonded to suitable wood-based materials under the influence of pressure and heat. A suitable one Overview of the possibilities of the prior art is z. B. in: Modern coating processes for wood-based materials, by W. Enzensberger, published in "Wood as Raw and Material", Volume 27, Issue 12, included.

The well-known options for surface finishing of wood-based materials are extremely versatile. The already known resin preparations and their processing techniques are sufficient but in many cases not yet if the available machine options for processing are optimally used should be. Rather, the machine processing options in many cases constrained by the inadequacies of the materials and their auxiliaries themselves.

For example, it is not possible to laminate wood-based materials with films that are built up on the basis of aminoplasts or phenoplasts to obtain surfaces that have the have high gloss painted surfaces. For this reason coated, i. H. under pressure and heat with Materials provided with a protective layer are provided with a suitable lacquer layer in a second step and, if necessary additionally polished to obtain the desired high gloss.

The possibilities for achieving this are particularly severely limited of surface gloss when coatings are aminoplastic or phenoplastically bound carrier substances

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be taken and thereby the economic so-called short-cycle process, in which apart from a recooling of the press plates, is used.

Films made from unsaturated polyester resins or diallyl phthalate polymers or their mixtures have a lacquer-like gloss even without recooling; Coatings with such synthetic resin films where relatively large amounts of material are required in contrast to painting, however, are due to the high costs such resins, and the need for organic solvents is a technical disadvantage of coating processes, based on the use of unsaturated polyester resins or diallyl phthalate.

In addition, polyester resins adhere to paper-like carrier materials not good, which is why in the German Offenlegungsschrift 2 I36 378 is recently proposed, decorative panels with the help of such resinated papers, their fibers - possibly already at the papermaking stage - with z. B. melamine or urea resins have been pretreated and then impregnated with a polyester or diallyl phthalate resin. In contrast to the present invention, the proposal of the above-mentioned publication is therefore the creation of a rough one spoken - polyester resin coating with improved Adhesive properties. This proposal is not comparable with the present invention because it is essentially is an aminoplast resin coating, the surface structure of which is improved.

It was namely a coating for wood-based materials on the Founded on the basis of a carrier material impregnated with a curable synthetic resin, the economic viability of aminoplastic or phenolic synthetic resin films. The coating can be described as one in a manner known per se impregnated with a curable aminoplastic or phenolic binder and, after drying, on one side with a Film of an unsaturated curable polyester resin or a diallyl phthalate preparation coated carrier web. As

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Resin preparation used in coating also becomes easy in the following referred to as "polyester resin".

From the description of the structure of the track, its production follows: Paper, nonwoven fabric, fabric or a similar carrier is impregnated with a commercially available impregnating resin solution in a manner known per se based on an aqueous urea or phenol-formaldehyde precondensate, dries the impregnated web and after drying brings a film on one side from a preparation of a Polyester resin.

"Coating" is therefore both within the meaning of the invention the process for the production of surface protection films, in particular for wood-based materials, as well as the one provided for this purpose Surface protection film - the coating agent - in unprocessed To understand form itself.

For the production of the coatings, aminoplastic or phenoplastic binders are used in a manner known per se, which are im generally exist in aqueous solution and are widely known as "impregnating resins" are used. So are those to be soaked Carrier materials, especially papers, generally known as to watch. One uses z. B. papers with particularly high absorbency, which, depending on the intended use, have weights per square meter between 20 and 200 g and generally already from Manufacturers recommended for certain uses. In the present sense, “various purposes” is primarily used as an underlayer paper (Underlay), as decor paper (medium to heavy grades) and as top layer paper (overlay; low square meter weight = light qualities).

In a broader sense, however, the invention also includes the use of nonwovens and woven fabrics as carrier materials, as they are often used in the manufacture of laminates.

Corresponding to the objective of the invention is the aftertreatment of the aminoplast or phenoplast-impregnated carrier

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with a synthetic resin based on an unsaturated polyester or of the diallyl phthalate, however, is generally limited to those carriers which are the outermost or topmost To form a layer of the future material.

Various systems are suitable as polyester resins, which are to be applied in a suitable manner and which differ in their processing partly differ.

So you can polymerized polyesters with a solid crosslinking agent Apply ("crosslinker") from an organic solution to impregnated, predried paper webs Drying with removal of the solvent gives solid, tack-free surfaces that are equal to or after a certain amount of time Storage time can be processed.

Likewise, unsaturated polyesters, which are in a liquid crosslinker, such as. B. styrene, are dissolved and a thickener, such as magnesium oxide, are applied to an impregnated and pre-dried paper web. You get one soft, somewhat sticky surface, which is generally intended for immediate further processing. If such films are to be stored, the surface must generally be covered with a release film, such as polyethylene. the Manufacturing and storage technology of such films is of the so-called Known from prepregs.

If there is no thickener present, otherwise one obtains same composition of unsaturated polyester liquid Surfaces; Films made in this way are intended for immediate further processing.

When the polyester preparations are applied to pre-dried paper webs containing melamine-formaldehyde condensates are pre-soaked, as they are known as decorative synthetic resin films, and the films produced in this way on carrier materials, in particular on chipboard, applied under pressure and heat, one obtains surfaces that are characterized by high

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Characterized by transparency, particularly good closeness and tear resistance.

It is a particular advantage of the coatings according to the present invention Invention that these coatings or films already can be pressed onto chipboard and fibreboard with pressing times of around 30 seconds using a temperature of about 160 ° C can be cooled back without the pressing plates after completion of the pressing process. With this so-called short cycle process high-gloss surfaces are achieved according to the invention; with conventional aminoplastic binders this has not been possible so far.

The advantage here is that the applied pressure is

2 is moderately low, e.g. B = in the range between 7.5 to 10 kgf / cm This low pressure is gentle on the board material, especially with low-density chipboard, and also allows it to be applied particularly thin surface protection layers, since the tendency of the material, the structure, corresponds to the low pressure to map the wooden substrate on the surface ("to be telegraphed through"), is low. In this way it is possible to produce single-layer coated chipboard particularly economically.

The well-known good adhesive effect of aminoplastic or phenoplastic Binder on wooden substrates works against the polyester resin layer, which forms the outermost surface of the future material, as an adhesion promoter and barrier layer. It are therefore not only economic advantages over the use of pure polyester resin coatings, the present Process has, but also technical advantages, particularly in the possibility of particularly fast processing and can be seen in the good composite effect.

If one intends to produce coatings that are called "primer films" are known, it is appropriate to proceed as follows?

It is advisable to choose a paper weight between 60 and 140 g / m and to use the aminoplastic binder (solid substance,

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absorbed on paper weight) in an amount between 55 and 90 % . After drying, the polyester or diallyl phthalate film is applied as follows; The primer film is allowed to run on one side over a roller which is immersed in the corresponding polyester or diallyl phthalate resin. The amount applied can be regulated by doctor blades, grooved rollers or similar devices. Films that only consist of a primer film layer with a relatively low resin content are expediently provided with an additional adhesive layer (glue film or underline) and in about 20 to 40 seconds under relatively low pressure (8 to 10 kp / cm) at a temperature between 150 and 170 ⁰ C applied to carrier materials, in particular chipboard.

Previously it was common to use primer films impregnated with aminoplastic binders and with an additional layer of adhesive had been applied to a coatable substrate, in an additional operation with a commercially available Treat the paint system and continue to buff and polish to achieve a high gloss »

With the new synthetic resin coatings one obtains in a single process, namely during the pressing process itself, i.e. without Post-treatment, high-gloss, lacquer-like surfaces in a quality that is comparable to the conventional multi-step process is.

In addition, thanks to their elasticity and their fluidity during pressing the surface was very crack-free and closed. In the so-called graphite test you get a very nice rating.

The pre-impregnation of the carrier web is carried out in a known manner. The viscosity of aminoplast or phenoplast impregnating resin solutions, which generally have a solids content between 45 and 55% , is generally between 30 and 65 cP. The reactivity of the impregnating resin solutions (liquors) can be adjusted by adding hardeners to the required or desired pressing

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speed can be adjusted. In general, the fleet still wetting agents to improve the penetration to the paper, and continue to "B for _5-foaming agent.

The intermediate drying which follows the impregnation of the carrier material webs is known. Since now, in general, continuously working coating processes are used, the intermediate drying is also continuously working Plants, e.g. B. in flotation dryers made.

According to the invention, the pre-impregnated and intermediate-dried carrier material web is now made with a preparation of an unsaturated polyester or diallyl phthalate. Such preparations generally contain not only the binder but also crosslinkers, catalysts and other additives. The application of the preparations is z. B. by pouring, rolling, spraying, doctoring or the like possible. The relevant processing techniques are widely known and therefore need not be mentioned exhaustively at this point. The quantities used vary from case to case, depending on the application technique; but it is sure it i _o a. by quantities of polyester that are lower than aminoplastic or phenolic binders and only rarely reach the same order of magnitude "

By adding metal oxides or hydroxides, such as. B. magnesium oxide, Calcium oxide, and the equivalent hydroxides, can make the polyester preparations strong before or after coating are thickened, possibly until almost tack-free gels are formed, which are stored for a long time without further change and can only be networked in the warmth. If suitable agents are selected, however, pre-crosslinking is also possible Ionic polymerisation triggering additives possible.

It is not absolutely necessary to apply the polyester resin in a solvent or solvent mixture. To achieve Non-tacky, later easily hardenable top layers, however, it is often advantageous to add the reactive monomer, which is normally

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wise forms the bulk of the solvent, still a volatile one Adding solvent and removing it after application by means of a heat treatment.

Suitable unsaturated polyesters are, for. B. those based on maleic acid, fumaric acid, tetrahydrophthalic acid as unsaturated dicarboxylic acids, phthalic acids, adipic acid, succinic acid, hexachloroendomethylenetetrahydrophthalic acid and other than saturated dicarboxylic acids and ethylene glycol, propylene glycol, the butanediols, neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, 1,6-hexanediol, hydrogenated P bisphenol A, dioxalkylated bisphenol A and other than diols. The resins can also contain mono- and polybasic carboxylic acids in minor amounts or alcohols, such as benzoic acid, oleic acid, trimellitic acid, Pyromellitic acid, ethylhexanol, trimethylolpropane, glycerine, Contain pentaerythritol and others.

As is well known, acids and alcohols are normally present in equivalent amounts, but there may also be deviations from the equivalence up to 20 % upwards or downwards. The unsaturated polyesters generally have acid or hydroxyl numbers between 20 and 70.

By the amount of double bonds in the unsaturated dicarboxylic acid in relation to the total amount of acid and by choice of the alcohol, the concentration of copolymerizable double bonds in the polyester can be varied within wide limits. There the conversion of these double bonds partly determines the crosslink density and, in general, a high crosslink density it is desirable that the polyester have a high degree of unsaturation. Those polyesters are particularly advantageous which are solid and tack-free at room temperature and those with a suitable choice of the components or the molecular weight of the Pre-polymers can be readily produced in a known manner can.

However, the non-tackiness and strength of the uncrosslinked prepolymers at room temperature can also be achieved by reaction with

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Metal salts, especially - as mentioned above - metal oxides or -hydroxides, creating salt-like bonds between the neighboring molecules and thus a momentary increase in molecular weight occurs. The often resinous or sticky products become hard and tack-free in this way.

Crosslinkers, some of which are also used in suitable quantities as solvents Ethylenically unsaturated copolymerizable compounds which have one or more double bonds are suitable contained in the molecule, such as styrene, chlorostyrene, methyl methacrylate, butyl acrylate, diallyl phthalate, diviny! benzene and prepolymers of the polyfunctional crosslinkers with free double bonds, such as. B. prepolymers of diallyl phthalate, the also have film-forming properties for themselves or can be cured with known agents.

Suitable catalysts are those compounds which give free radicals under the pressing conditions, eg. B. azo compounds, Peroxides and others.

As additives to both aen impregnating resins, as well as to the present invention applied polyesteroberfläohenharzen for example, inorganic fillers are suitable, such as chalk, dolomite, talc, inorganic or organic pigments such as titanium dioxide, silica gels, organic, slightly cross-linked, powdery substances, which greatly to swell capable such as B. partially crosslinked unsaturated polyester resins, leveling aids, thixotropic auxiliaries and others.

Manufacture of various polyester resin preparations

a) 400 parts of an 60 # strength acetone solution of an unsaturated polyester having a softening point (KSN) of up 8O ⁰ C, consisting of maleic acid, dimethyl terephthalate and 1,2-propylene glycol in a molar ratio of 1: 2 (acid value about 20): 1 are mixed with 10j5 parts of a diallyl phthalate prepolymer and homogenized by stirring at room temperature for 24 hours.

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6 % tert-butyl peroctoate is added to the mixture. A precipitate separates out of this on standing, but it can be easily stirred up. 2.5 # of a powdery, partially crosslinked polyester resin is added to the resin mixture with stirring.

b) 80 parts of a 50% solution of diallyl phthalate prepolymers in monomeric diallyl phthalate and 400 parts of a 60% acetone solution of the unsaturated polyester described under a) are stirred for 24 hours at room temperature. A precipitate settles out of this mixture (viscosity 56 DIN sec) on standing. The resin mixture is mixed with 2.5 % of a powdery, partially crosslinked polyester resin while stirring.

Before the paper laminates are coated, 6 % tert-butyl peroctoate is added and the mixture is shaken vigorously, the mixture becoming homogeneous.

c) The unsaturated polyester resin consists of a 60% styrene solution of an unsaturated polyester of maleic acid, o-phthalic acid and 1,2-propylene glycol in a molar ratio of 2 «1 s 3. This resin stabilized with 0.01% hydroquinone (acid number about 33) 6% tert-butyl peroctoate is added before the laminate is coated.

d) 3ooo parts of the unsaturated polyester resin as described under c) are performed at room temperature under stirring with 35 * 6 parts of magnesium oxide were added and then kept at 55 ° C until the homogeneous mixture after being cooled to 20 ⁰ C a viscosity of about I09 000 has cp; 6% tert-butyl peroctoate is added before coating.

Production of coated carrier material webs

example 1

A white, highly filled decorative paper based on ^ -cellulose with

on 110 g / m ² becomes 309851 / 1U2

A weight per unit area of 110 g / m 2 is used in a 55 # aqueous

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Solution of a melamine-formaldehyde condensation resin with a molar ratio of melamine to formaldehyde of 1: 1.8 and a viscosity of 50 cP soaked in catfish that a resin absorption of about 120 %, based on the weight of the paper, is achieved. The thus-impregnated paper is so far dried at 120 to 150 ⁰ C, that after 5 minutes post-drying at l60 ° C a weight loss of about 5% occurs. In a directly connected second impregnation unit, a solution of an unsaturated polyester-crosslinker mixture prepared as described under a) is applied to the top. It is then dried in a dryer to a volatile content of 7.5 %. Of the

ρ dry resin order from the second order stage is 35 g / m Subsequently, has a 19 mm thick chipboard in a so-called short-cycle press with the product prepared as described paper and 60 seconds at 150 ⁰ C and a pressure of 8 kgf / cm pressed. The chipboard coated in this way is removed from the hot press without recooling. Under these conditions, surfaces are obtained which have a high degree of gloss and are characterized by excellent cohesion and crack resistance.

Example 2

A printed decorative paper with a weight per unit area of 100 g / m 2 is impregnated as in Example 1 with an aqueous solution of a melamine-formaldehyde condensation resin. The resin absorption, based on the weight of the paper, is approx. 100 %. The residual moisture content, determined by drying for 5 minutes at 160 ° C, is about 4.5 %. In a second impregnation unit, the solution of an unsaturated polyester / crosslinker mixture prepared as described under b) is applied to the top and dried to 6.7% volatile constituents in a flotation dryer. The dry resin application from the second stage is 60 g / m. The film is processed as in Example 1, but with a pressing time of 20 seconds at 160 ° C. and

a pressure of 10 kp / cm obtained high-gloss and pore-free surfaces which could be removed from the mold without problems.

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Example 3

A printed decorative paper with a basis weight of 100 g / m 2 is impregnated as in Example 1 with an aqueous solution of a melamine-formaldehyde condensation resin and dried in a flotation dryer to a volatile content of 5.5%. The resin application, based on the weight of the paper, is 120 %. In a directly connected second impregnation unit, the unsaturated polyester resin produced as described under c) is applied to the top. In the second order

In the first stage, 35 g / m of solid resin are applied.

The film is processed as in Example 1 and provides a high-gloss, crack-free and closed surface.

Example K

A white, slightly filled paper with a basis weight

of 100 g / m is soaked with a 50 $ aqueous solution of a urea-formaldehyde condensation resin with a molar ratio of urea to formaldehyde of 1: 1.8 and a viscosity of 35 cP so that a resin absorption of approx. 65 %, based on the weight of the paper. The impregnated paper is then dried to a volatile content of 2.0%. In a directly connected impregnation unit, the solution of an unsaturated polyester / crosslinker mixture prepared as described under b) is applied to the top and dried to 5.7% volatile constituents in a dryer. The resin application in the second stage is 60 g / m 2. This film was pressed with the workpiece by placing a film of glue between the film and the wood-based material, which after pressing for 30 seconds between highly polished, chrome-plated press plates at a temperature of 160 ° C, produced a perfect bond between the wood-based material and the decorative film . The surfaces are laok-like, high-gloss, excellently closed and do not require any further treatment.

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Example 5

A printed, lightly filled decorative paper based on οίο cellulose with a basis weight of 80 g / m 2 is impregnated with an aqueous solution of a mixed condensate of urea melamine and formaldehyde (the resin absorption, based on the paper weight, is approx. 90 %). The residual moisture content, determined by drying for 5 minutes at 160 ° C, is 5.6 %. In a second step, the unsaturated polyester resin produced as described under d) is applied on the top. The resin application from the second stage is

65 s / ro · Then a 19 mm thick chipboard is inserted into a so-called short-cycle press covered with a film of glue and the paper as described above and 30 seconds at 160 ° C below pressed at a pressure of 10 kp / cm. The chipboard coated in this way is removed from the hot press without recooling. Under Under these conditions, surfaces are obtained that have a high degree of gloss and are characterized by excellent cohesion and tear resistance.

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Claims (7)

- 15 - Point 29 patent claims 1. Coating agent for wood-based materials based on a carrier material impregnated with a curable synthetic resin, consisting of a curable in a manner known per se aminoplastic or phenolic binder impregnated and, after drying, covered with a film on one side a preparation of an unsaturated curable polyester resin coated carrier web. 2. A process for the production of coating compositions for wood-based materials based on a carrier material impregnated with a curable synthetic resin, characterized in that a carrier material web is impregnated in a manner known per se with a solution of an aminoplastic or phenolic binder, dried and the impregnated and dried web on one side coated with a preparation of an unsaturated, hardenable polyester resin and optionally dried again. 3. The method according to claim 2, characterized in that the polyester preparation used is an unsaturated polyester containing a solid crosslinker in organic solution and the solvent is removed so that the unsaturated polyester does not yet harden. 4. The method according to claim 2, characterized in that an unsaturated, dissolved in a liquid crosslinker polyester, which is mixed with a thickener, is used as the polyester preparation. 5. The method according to claim 2, characterized in that an unsaturated polyester dissolved in a liquid crosslinker without thickening additives is used as the polyester preparation. 6. Coating agent according to claim 1, characterized by a carrier web with a square meter weight between 309851/1142 - 16 - O. Z. 29 225 60 and 140 g / m, pre-impregnated with 8θ to Ι4θ % of an aminoplastic or ph.enoplastic binder (dry, based on the carrier weight) and with 20 to 60 %, based on the original carrier weight, of a mixture of an unsaturated polyester and at least is coated on one side with a crosslinker. 7. Coating agent according to claim 1, characterized by a carrier web with a square meter weight of 60 to 140gfn which is pre-impregnated with 55 to 90 %, based on the carrier weight, of an aminoplastic or phenolic binder and with 20 to 90 %, based on the original carrier weight, one Mixture of an unsaturated polyester and at least one crosslinker is coated on one side. Badische Anilin- & Soda / Fabrik AG 309851/1 1 42