DE2316289B2 - Process for producing fast-curing coatings - Google Patents

Description

The invention relates to a method / for producing fast-curing coatings on surfaces of wood, wood-based materials and hardened or unhardened woven fabrics impregnated with impregnating resins or non-woven carrier materials made of paper. Fleece or fabric. Liquid coating agents are used here on the basis of etherified aminopiast resins, polyester resins and acids, as well as common additives applied to the surface and cured with the application of heat.

From DE-OS 16 44 764, DE-OS 18 05 193 and DE-AS 18 05 182 are coating agents with a content of more than 50% low molecular weight Polyester resins and less than 50% low molecular weight aminoplast resins are known. They make conventional ones Stoving enamels that are produced in organic solvents. An addition of small amounts, For example, 0.5% p-toluenesulfonic acid accelerates the crosslinking, which lowers the baking temperatures or means burn-in times. Coating agents made from amino resins and alkyd resins or After the addition of acids, polyester resins can be used as so-called "acid-hardening paints" at room temperature to be cured. Such acid-curing paints are used for the production of coatings on wood or Wood materials used. They are also used as impregnating resins for impregnating paper, fleece or Fabric used. The hardening takes place through acidic catalysts with the application of heat and possibly pressure.

The acidic catalysts are in the form of acid-releasing compounds, organic and / or inorganic

Tonic acids are dimensioned in such a way that a sufficient pot life of the liquid coating agent is guaranteed. If p-toluenesulphonic acid is used as the acid catalyst, it is known that between 0.5 and a maximum of 3% are proposed, depending on the composition and reactivity of the coating agent. If larger amounts are used, the pot life (pot ^: ve) of the coating agent is reduced to a few minutes or coatings are obtained which have acid damage in the form of reduced adhesion, discoloration or other technological disadvantages. The stoving times when using the usual amounts of p-toluenesulphonic acid are as a rule 10 to 120 minutes at stoving temperatures between 120 ° C. and 200 ° C. The production of coatings on surfaces of wood and wood-based materials usually requires longer drying and / or hardening times. The same applies to the production of coatings on surfaces of unhardened or hardened carrier materials impregnated with impregnating resins made of paper, fleece or fabric, whereby adhesion problems can also occur after joint hardening when applied to unhardened surfaces and processing with the application of pressure leads to adhesion to the press plates and press belts made of plastic or Il Me ¹ does not avoid with certainty. in these cases, therefore, it jr necessary to perform a subsequent painting of the cured Trägcrmatcrialien in a special operation.

The object of the invention is to find a method that the disadvantages described above of reduced usability of the liquid coating agent does not have, and also provides technologically excellent coatings. The

■ »5 possibility of manufacturing coated foils or Laminated materials through the application of heat and pressure in one operation when using the usual facilities.

Another object of the invention was to reliably eliminate the disadvantages outlined above and self-hardening coatings on surfaces of wood and wood-based materials as well as hardened or uncured woven or non-woven carrier materials made of paper, fleece and impregnated with impregnation resin or to produce fabric that is also applied to unhardened surfaces in the same operation the application of heat and pressure results in perfect paintwork and thus a subsequent make additional painting unnecessary.

The object was surprisingly achieved by a method for producing fast-curing Coatings on surfaces of wood, wood-based materials, hardened or unhardened, with impregnating resins impregnated, woven or non-woven carrier materials made of paper, fleece or fabric Application and hardening of a liquid, optionally water-thinnable coating agent based on etherified amino resins and polyester resins,

15th

with p-toluenesulfonic acids as a curing catalyst, as well as if necessary, thinners, plasticizers, matting agents ^ fillers, coloring substances, Additives and additives, characterized in that a coating agent is used which is based on 100 Parts of low molecular weight aminoplast resin, whose methylol groups are monovalent and / or polyvalent Alcohols with at least one functional group are largely etherified

3–50% low molecular weight, linear and / or branched, predominantly low-viscosity polyester resins made from dicarboxylic acids and alcohols with two or more hydroxyl groups with a molecular weight between 200 and 6000 and a hydroxyl number up to 450,

4-30% of a polyvalent alcohol with at least two primary and / or secondary hydroxyl groups and

6 - 20% p-ToluolsuM ^ acid containing, with all Percentages on the amount of aminoplast resin are related.

It was surprising and completely unexpected that the specified composition of the coating agent used, in particular because of the high amount of p-toluenesulfonic acid, resulted in fast-curing coatings which require only a fraction of the curing times of the acid-curing coating agents known to date. Such coating agents can be cured ^{at 200 ° C. in 5 seconds.} The curing temperatures can be reduced, the curing times then having to be extended accordingly. It was also surprising that the liquid coating agents have a pot life of several days despite the high content of p-toluenesolphonic acid. After curing, the coatings obtained are flawless, full-bodied coatings with excellent technological properties, such as high hardness. Scratch resistance and stackability. No damage to the cured coating caused by the acid catalyst could be determined.

The liquid coating agent is like this according to the invention composed that it turns up to 95% of its weight into the solid state after hardening. That Liquid coating agents therefore have the character of a liquid plastic, which is only indistinct May contain amounts of water or other organic solvents. It is so in many cases possible, with a single application of the coating agent, the previously customary multi-layer applications substitute.

Apparently the reason for this lies in the fact that the simultaneous presence of etherified amino resins, low molecular weight, linear and / or branched, predominantly low viscosity polyester resins with a molecular weight between 200 and 6000 and a hydroxyl number up to 450, a polyvalent one Alcohol with at least two primary and / or secondary hydroxyl groups and a high content on p-toluenesulphonic acid to form film-forming crosslinking agents leads actions that were previously unknown.

Since there is no or only very little solvent or reaction cleavage products during hardening are liquid coating materials of this type, especially in connection with the Immission protection law is important.

The method according to the invention enables, for the first time, the production of fast-hardening coatings on surfaces of wood and wood-based materials, for which until today much longer drying or curing times were necessary. In addition, the Production of fast-curing coatings on foils or laminates in the existing machine Systems by applying the coating agent to the surface of the hardened and / or unhardened Impregnated carrier material containing impregnating resins: - rials take place, so that the subsequent hardening process, if necessary by means of the application of pressure and Heat can be done in one operation together with the production of the laminates.

The liquid coating agent according to the invention can also be used as an impregnating resin for Impregnation of wood and wood-based materials and of woven or non-woven carrier materials Paper, fleece or fabric can be used. This makes it possible for the coating and impregnating resin to come out consist of one and the same material, which results in the joint curing to form laminates leads to a particularly close bond between the impregnated carrier materials and the coating.

In the context of this invention, under "wood materials" Refinement products of wood are understood, such as chipboard, pressed board, paper, Paperboard and other molded cellulosic materials.

The carrier materials for holding the impregnating resins consist essentially of cellulose-containing materials Materials such as paper, cardboard, fabric or nonwovens made of cellulose. However, you can also use whole or partly made of woven or nonwovens made of natural or synthetic, inorganic or organic Be composed of fibers, such as glass fibers, asbestos fibers, cotton fibers, wool fibers, Polyamide fibers, polyester fibers, etc.

"Laminates" are impregnating resins that have hardened under the application of pressure and heat Materials that are made from several of the above-described ones, placed one on top of the other, impregnated with impregnating resins Support materials are made.

Other compounds which form amino resins are urea and its substitution products Aminotriazines that contain at least two amino groups, such as melamine, ammeline and thioammeline and benzoguanamine are used. The most common aldehyde is formaldehyde. The ones made with this Condensation products are produced in the customary manner, with elimination of water and removal of the water from the reaction mixture and etherification with a monohydric and / or polyhydric alcohol with at least one functional group produced. Suitable alcohols are, for example, methanol, Ethanol, propanol, isopropanol, butanol, secondary butanol, Isobutanol, allyl alcohol, glycol, diglycol, polyglycol. Glycerine, pentaerythritol, sorbitol, mannitol. It has It turned out that in the context of the present invention, in particular, the etherification of the Hexamethylol melamine with the monohydric alcohols is to be given preference. Particularly preferred and giving the best results, the hexamethoxy Suggested methyl melamine. The diluted amino resins are easily soluble in alcohols and leave it produce stable aqueous emulsions from these solutions. Some aminoplast resins, especially the Methyl ethers, also form solutions in water.

Low molecular weight polyester resins with molecular weights of 200-6000 can be both linear and be branched. The production takes place in the usual

Way by reacting dicarboxylic acids, such as. B. phthalic acid, isophthalic acid, hexahydroterephthalic acid, Tetrahydrophthalic acid, maleic acid, fumaric acid, itaconic acid or citraconic acid, with alcohols, the two or carry more hydroxyl groups, such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, Trimethyloipropane, glycerin, pentaerythritol, sorbitol, ur'd many other compounds that are about the existing alcoholic hydroxyl groups can be esterified with dicarboxylic acids. Acids and Alcohols can be used alone or in mixtures. The molecular weight can be found in simpler Regulate the proportion of polyol and dicarboxylic acid.

The low molecular weight polyester resins should also have hydroxyl numbers of up to 450. To do this too achieve, an excess of alcoholic component is used in the production, so that products arise that carry hydroxyl end groups. The technical production is carried out in a known manner Esterification of the components at higher temperatures with removal of the water of reaction formed performed. The polyhydroxyl compounds obtained in this way can be mixed with ethylene oxide or propylene oxide be implemented so that partial ethereal products are obtained.

Also condensation products that are obtained by using ethylene oxide or propylene oxide with ethylene dianiine or ethanolamine can be used for polyester production. Also are applicable epoxidized oils, castor oil, tall oil and other products containing hydroxyl groups. All of the foregoing Polyester types can be used alone or in mixtures. In the liquid middle of the coating! are 3–50% low molecular weight, linear and / or branched polyester resins, based on the amount of Aminoplast resins. The preferred amounts are between 11 and 25%. The appropriate ones As a rule, polyester resins are liquid or at least predominantly of low viscosity.

The liquid coating agent contains p-toluenesulphonic acid as hardener in an amount between 6 and 20%. based on the amount of aminoplast resin. The preferred amount is 8-18%. p-toluenesulfonic acid is usually used as an aqueous solution, but can also be dissolved in solvents. Even though other acids can also be used as hardeners, p-toluenesulphonic acid provides the best Results.

The liquid coating agent contains as a further component 4 - 30%, based on the amount of Aminoplast resin, a polyvalent alcohol with at least two primary and / or secondary hydroxyl groups. The preferred amounts are between 12 and 24%. Examples of suitable alcohols are Ethylene glycol, propylene glycol, butylene glycol. Ethyl diglycol. Glycerine, sorbitol, monoester of glycerine mil monovalent fatty acids. However, preferred glycerin is suggested because it is used along with dun others Components of the liquid coating agent particularly good results in terms of technological properties of the cured coating results.

For the correct setting of the appropriate processing consistency the liquid coating agent can also be mixed with water or other common diluents, such as alcohols, glycols, glycol esters, glycol ethers and other solvents are further diluted will.

If the technological properties of the film require it in terms of its elasticity, the liquid coating agents also the usual plasticizers such as esters of phthalic acid, z. B.

Dimethyl phthalate, diallyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate and other plasticizers compatible with the coating agent can be used.
Fillers can also be added, if necessary

ίο be, so z. B. silica, silicates, barium sulfate, etc. Matting agents such as highly disperse silica can also be added.

In order to color the coating, the coating agent can also contain the usual coloring substances. Additives and auxiliaries such as leveling agents, antifoam agents, Thixotropic agents can also be used. Other binders can also be used be contained in the coating agent, such as ζ Β. Epoxy resins. Polyurethane Har . Polyvinyl chloride resins

7 " etc.

The coating agent is produced in the usual way by mixing the components. So the components aminoplast resin, polyester resin and polyvalent alcohol are mixed homogeneously.

Sometimes it is advisable to use a component if it is in is not present in liquid form, first to dissolve in a solvent and this solution with the to mix other components. The p-toluenesulfonic acid is usually before the coating agent

jo processing added. To be as uniform as possible To achieve distribution in the coating agent, the p-toluenesulfonic acid is usually as a solution in Water or an organic solvent is used. 10-40% solutions are common, with good

S5 stirring can be mixed into the coating agent. The coating agent is applied using the spraying method customary in the paint industry, Stre ^; chen '> diving. Pouring. Rolling applied to the surfaces to be coated. The hardening times are very short

ί " and are dependent on the baking temperature. For example, at a temperature of 200 C only 5 seconds are required, while the curing time is extended to approx. 60 minutes at 60 C. All temperatures in between are between ^{60 0 C and 200 ° C}

■ <5 applicable. The curing times are within Limit from 5 seconds to 60 minutes, the curing time becoming shorter the higher the temperature.

If non-hardened or at most pre-gelled, woven or non-woven fabrics impregnated with impregnating resins

V) th carrier materials made of paper, fleece or fabric coated on one rope with the liquid coating agent, this carrier material can be the top layer of a stack of several other carrier materials impregnated in the same way with impregnating resins.

By applying pressure and heat, find! here both the production in one operation a laminate as well as the curing of the applied "coating agent to one with the Laminate firmly anchored coating instead. The for impregnation of the above Impregnating resins serving as carrier materials are known aqueous or alcoholic solutions of phenolic, urea or melamine resins or of mixed condensation products made of urea and melamine

(V-, resin. Fs it has now been found that the according to the invention Liquid coating agents used can also be used as impregnating agents /. DasTiiir.lo-n des to impregnating carrier material with the; crfindunes

Depending on the liquid coating agent used, this can be done in various ways. These methods are known and are not claimed here. For example, the carrier material can be fed continuously with the aid of rollers through a container which contains the liquid coating agent. The coating agent can, however, also be sprayed onto the carrier material or a web of the carrier material can be passed through rollers which are moistened with the emulsion. The working temperature can fluctuate within wide limits, it is preferably between room temperature and about JO ⁰ C. As soon as the carrier material is impregnated. according to one drain the excess or squeeze it off.

The hardening of the impregnated carrier materials is to insoluble and infusible plastics is only carried out after they have been stacked in multi-stage presses under heat and pressure, the formation of a uniform surface through the ι iicuVcinälten the binder combination described above is made possible.

The papers used for the impregnation are all suitable soda power or Cellulose papers. To produce decorative panels, the surface of which has colorful, light or decorative patterns should have, an impregnated decorative paper, colored or printed in color or with a Wood grain pattern printed cellulose paper is used.

In another possible way of working, the carrier materials impregnated with the usual impregnating resins are used after squeezing off the excess, first passed through a drying tunnel, which is at 100 up to 120 "C causes a pre-gelation of the impregnation;> rze. Thereafter, the coating is either coated directly with the liquid coating agent used according to the invention and cured or it is first an intermediate layer by applying a polyvinyl acetate or polyacrylate dispersion. Such an intermediate layer is then used with the invention · »<> further coated and cured according to the liquid coating agent used.

Those produced by the process according to the invention Coatings are characterized by excellent technological properties. It was surprising. · * 5 that a coating agent, which consists predominantly of low molecular weight components, even in thin ones Layers of a few microns under the action of higher temperatures in a short time crosslinking reactions enters, which lead to a hard thermosetting coating. The speed of reaction is running unexpectedly quickly. So far, such thermoset coatings could only be obtained through use of binder components with a high molecular weight that are already sufficiently pre-crosslinked. However, this result was surprising. The cured coatings are hard, high gloss, and excellent resistant to yellowing. They are also resistant to organic solvents such as xylene and mixtures from aliphatic hydrocarbons and benzene, & o Esters and ketones. In addition, they have excellent acid and alkali resistance. at Salt spray tests, tropical tests and tests in the Weatherometer do not show the coatings to be worth mentioning Impairment of their technological properties. Pigmented coatings have a positive "ring test"; h, if a metal part over the Coating is pulled, this leaves no discoloration

exercise in the surface.

The following examples are intended to explain the invention without restricting it. Specified parts are parts by weight, percentages are percentages by weight, unless expressly stated otherwise.

Example I.

A hydroxamelhylolmelamine which has been largely etherified with methanol is obtained, for example, by reacting

I part by weight of dry methyl alcohol with 5 parts by weight of methyl alcohol and OJ parts by weight of hydrochloric acid.

The clear solution is neutralized after 8-10 minutes. After the alcohol has evaporated, the methylamine-hexamethylol-methyl ether becomes crystals

riiitit. ii.

Of this

118 parts as an 85% aqueous solution with 17.6 parts of a polyester resin, produced by esterification of 1 mole of phthalic acid and 1.5 moles of ethylcnglycol with a hydroxyl content of about 8.5% and a viscosity of 330 ± 30 centipoise and a density at 20 ^° C. DIN 51 757 from approx. 1.3. and 19.2 parts of glycerin

well mixed.

Then you give

16 parts of p-toluenesulfonic acid. dissolved in 40 parts of ethyl glycol mono-butyl ether.

lies
6.9 parts of highly disperse silica.

After thorough mixing, the coating agent has a viscosity of 365 centistoccs at 25 ° C. the Pot life amount, depending on the temperature, multiple days.

60 g / m 2 of the coating agent are poured onto a chipboard using a pouring machine. The curing of the coating takes place at a circulating air temperature of z. B. approx. 100 ⁰ C or with infrared rays within 1-3 minutes. You get a silk gloss. transparent lacquer coating with good adhesion, which is scratch-resistant and has excellent elasticity.

Example 2

On top of one with an impregnating resin a-. ' Base of a melamine-formaldehyde condensation product soaked decorative paper with a wood grain print a coating agent is selected using a wire doctor

823 parts de: Hexamethylolmelamines largely etherified with methanol in Example 1 as an 85% aqueous solution,

0.6 parts of a non-ionic wetting agent (ethylene oxide adduct of a fatty acid),

9.8 parts of a polyester from 1 mole of trimethylolpropane, 1.5 moles of phthalic acid with a Hydroxyl content of approx. 11.5%, a viscosity at 25 ° C of 650 ± 100 centipoise and a density according to DIN 51 757 of approx. 1.03,

73 parts of glycerine,

to which 30 parts of a 40% strength aqueous p-toluenesulfonic acid solution are added, applied in an amount of approx. 5-50 g / m ² .

The pot life of the liquid coating agent is 36 hours.

It is carried out in the usual way at a temperature of 100 ° C. using a pressure of 3-5 kg / cm ² within 2 minutes or at a pressure of 17-20 kg / cm ² at 170-2OO "C within 20 seconds A film with a firmly adhering glossy coating is obtained.

Example 3

Instead of the polyester resin mentioned in Example 2 is the same amount of a polyester resin obtained by reacting 12 moles of 1,4 bis (Hydro * .yethyl) cyclohexane. 6 moles of phthalic anhydride and 5 moles of adipic acid was used. The resulting polyester has a molecular weight of 1660 and an lydroxy number of 63.1. It is easily soluble in glycerine.

After application to the surface of a paper web impregnated with impregnation resins, as in Example 2 continued working.

The result corresponds to the result obtained in Example 2.

Example 4

By heating at 150-180 ⁰ C under a protective gas, a polyester is prepared from the following components:

116OTeMe fumaric acid

Parts of phthalic anhydride
Parts 1.2 propylene glycol.
80 parts of this polyester are in
35 parts glycerin and

35 parts of ethylene glycol dissolved to form a homogeneous solution.

100 parts of an 85% aqueous solution of hexamelhoxymethylmelamine and

20 parts of a 70% solution of a bulanol-etherified mineral resin in bulanol will

gC I üiycSiC! Hill /.KlMIIIg

stirred in and then

21 parts of a 40% p-toluenesulfonic acid solution in Butyl diglycol added.

The pot life is approx. 48 hours.

As described in Example I, this coating agent is applied in an amount of 130 g / m 2 to a chipboard applied and cured in 3 minutes at 120 ° C.

A high-gloss, scratch-resistant coating is obtained that is largely resistant to solvents.

Claims (2)

Patent claims: 1. Process for producing fast-hardening coatings on surfaces of wood, wood-based materials, Hardened or uncured, impregnated with impregnating resins, woven or non-woven carrier materials made of paper, fleece or fabric by applying and hardening a liquid, if necessary water-thinnable coating agent based on etherified amino resins and polyester resins, with p-toluenesulfonic acid as suspension catalyst, and, if necessary, thinners, plasticizers, matting agents, fillers, Coloring substances, additives and admixtures, characterized in that one a coating agent used, which is based on 100 parts of low molecular weight aminoplast resin, its methylol groups with monohydric and / or polyhydric alcohols with at least one functional GrüppC WCiigChcnCj VCrSiiiCrt ΙΐΐΠυ, 3–50% low molecular weight, linear and / or branched, mainly low-viscosity polyester resins made from dicarboxylic acids and alcohols having two or more hydroxyl groups with a molecular weight / wipe 200 and faOOO and a hydroxyl number up to 450, 4 - 30% of a polyvalent alcohol with at least two primary and / or secondary hydroxyl groups and Contains 6-20% p-toluenesulfonic acid, with all Percentages are based on the amount of aminoplast resin. 2. The method according to claim I, characterized in that that the low molecular weight aminoplast resin consists of hexamethylol melamine, its Methylolgruppf.n with monohydric and / or polyhydric alcohols with at least one functional Group are largely etherified.