DE2222401B2 - Process for the production of paper webs impregnated with aminoplastic binders for surface coating - Google Patents

Description

2. The method according to claim 1, characterized in that after treatment with the Aminoplast precondensate intermediate drying.

3. The method according to claim 1, characterized in that after applying the Copolymer dries and pressed in the heat.

4. The method according to claim 1, characterized in that an aminoplast precondensate Melamine-formaldehyde precondensate is used.

5. The method according to claim 1, characterized in that the acrylic ester copolymer as aqueous solution or dispersion is applied.

6. The method according to claim 1, characterized in that the further olefinically unsaturated Monomer d) at least

a) a polymerizable compound with carboxamide groups or one of its N-methylol groups or N-methylol ether derivatives or

b) a polymerizable ester of (methacrylic acid with 2 to 10 carbon atoms at least dihydric alcohol or one of its reaction products with at least one a compound having an epoxy group

is used.

The invention relates to an improved process for the production of impregnated carrier materials for surface coating, in which paper or a paper-like material is impregnated with an aqueous aminoplast condensate and a one-sided layer of an acrylic ester copolymer is applied to the impregnated material, preferably without intermediate drying.
It is known to be monochrome or with decorative

ίο Patterns of printed paper, fleece or textile webs with thermosetting aminoplasts or phenoplasts from aqueous or aqueous-alcoholic Soak the solution and then dry the webs obtained. The obtained materials are used for the production of laminates (laminates in the narrower sense) and for the production of surface coatings used for wood-based materials. The resin-impregnated material webs are applied to a appropriate document, such as B. a chipboard, a Fibreboard or plywood, a carrier layer soaked in phenolic resin or on mineral carriers such as Asbestos panels applied and connected to the base- This type of material production possesses big meaning.

It is also known to use aminoplasts and phenoplasts in the manner described one after the other in the so-called Double impregnation process or in a reciprocal manner Apply mixture to carrier webs.

Similar developments (mostly in the form of unsupported films or foils) based on thermoplastic polymers such as polyvinyl chloride have been tried but are of no importance attained.

It is now known that aminoplastic coatings are characterized by high gloss and great hardness when suitable processing techniques are used distinguish. Surfaces consolidated with aminoplastic binders, even if as an aminoplast Melamine resin is used, but do not have a longer exposure to the open atmosphere than consistently proven. So it is B. not possible, materials coated with melamine resin for outdoor applications to use. Phenolic binders that largely meet these requirements are however, as is known, not light-colored and therefore ruled out for decorative outdoor applications.

It is therefore an object of the invention to propose a method with the aid of which paper webs impregnated with aminoplastic binders can be produced for surface coating which, because of their weather resistance, are also suitable for outdoor use.
Coatings whose binder is made up of melamine-formaldehyde condensates cannot be produced with the short pressing times that would be possible on the apparatus side; above all, the gloss of the surfaces decreases as the pressing times become shorter. A recooling of the press plates is with short

bo press times not possible. So it was another The object of the invention to propose impregnation systems that are largest in terms of processing methods Allow economy (i.e. short pressing times, correspondingly low heating and cooling energy

b ^r > wall) and still achieve the highest known quality standard of coated surfaces (high gloss, hardness, crack resistance, cohesion).

According to the invention, the tasks set

solved by

a) in a manner known per se, paper webs with an aqueous preparation of a thermosetting aminoplast precondensate treated,

b) optionally intermediate drying and

c) on one side of the carrier substances treated in this way, a solution or dispersion of a certain, with Applying formaldehyde condensates compatible and heat-curable acrylic ester copolymer as

d) if appropriate, drying and, if appropriate, pressing while hot

In addition to urea resins, preferred aminoplast precondensates for the purposes of the invention Melamine-formaldehyde precondensates are understood. Melamine-formaldehyde precondensates are used z. B. obtained in a known manner that melamine and formaldehyde in alkaline aqueous The solution is subjected to condensation, the molar ratio between melamine and formaldehyde being im is generally chosen between 1: 1.8 and 1: 3. Melamine can be wholly or partially replaced by urea be replaced, with appropriate adjustment of the molar ratio and the manufacturing conditions.

The production conditions for aminoplast impregnating resins required to carry out the invention are generally known. In this respect, reference can therefore be made to the relevant publications will.

The specific acrylic ester copolymers to be used according to the invention are as follows to say the following:

Thermosetting acrylic ester copolymers compatible with formaldehyde condensates - as well as the aminoplast condensates already mentioned - are known per se; Descriptions of suitable copolymers are z. B. contained in Hölscher, Reinhard, dispersions of synthetic plastics (series: chemistry, -to Physics and technology of plastics in individual representations, Vol. 13 and 14, Berlin, Heidelberg, New York 1969). It is advantageous to choose those copolymers which are water-dilutable or water-dispersible; in principle, however, there are also such copolymers usable, which can be applied from organic solution.

As indicated by the name acrylic ester copolymers, it is an essential component of these copolymers in each case at least one ester of acrylic acid; Methacrylic acid esters are used as equivalents to acrylic esters regard. Polymerizable or copolymerizable esters of (meth) acrylic acid (a) with monohydric, e.g. B. 1 to Alkanols containing 8 carbon atoms accordingly form the essential component of the invention usable copolymers. In detail z. B. methyl acrylate, methyl methacrylate, ethyl acrylate, Butyl acrylate, called 2-ethylhexyl acrylate. the mentioned esters can be partially replaced by their technical equivalents, such as. B. styrene or Acrylonitrile or other polymerizable vinyl compounds, which also form hard films and are used to Structure of such copolymers are suitable. For economic reasons, the aforementioned monomers form a proportion of 50 to 90 percent by weight in b5 the copolymers.

The copolymers to be used according to the invention become water-dilutable or water-dispersible by polymerizing in from 2 to 15% by weight of, for example, up to 10 carbon atoms, ct-olefinically unsaturated carboxylic acid or one basic group-containing copolymerizable, olefinically unsaturated monomers (c) imparted. These ionizable monomers often also give the copolymers according to the invention a corresponding compatibility with aminoplast condensates. Examples of monomers of the last mentioned Type are about acrylic acid, methacrylic acid, crotonic acid, maleic acid half-esters, also vinylpyridine, vinylimidazole, Diethylaminoethyl acrylate, etc. The copolymers formed with these monomers are polyelectrolytes and are generally dispersible or soluble in water by appropriate salt formation, depending according to the number of their ionizable groups and the composition of the aqueous liquor.

The copolymers also contain monomers that are present with themselves or with them at the same time Aminoplast condensates can form crosslinks; such monomers (b) are functional Groups, a carboxamide group optionally substituted by methylol or methylol ether groups, or es are esters of acrylic or methacrylic acid with a more than monohydric alcohol, such as. B. Butanediol monoacrylate and its homologues.

The above-mentioned group "monomers with reactive substituents" forms in the inventive For economic reasons, copolymers have a weight fraction of about 5 to 35%.

In contrast to acrylate resins, the z. B. methylolamide groups contain and are referred to as self-crosslinking, require acrylic resins with alcoholic Hydroxyl groups for crosslinking, i.e. heat curing, usually a low molecular weight auxiliary substance. A methylolated, optionally etherified, aminoplast-forming compound is used as the reaction partner. Practically, hexamethoxymethylmelamine and dimethylurea are in use as crosslinking auxiliaries.

Copolymers containing the aforementioned special monomer in a suitable combination and which are crosslinkable with themselves or with aminoplast precondensates in the heat, should for the implementation of the invention described here z. B. Molecular weights between 500 and 2500 exhibit. They allow relatively concentrated liquors to be produced. In general it succeeds namely, the second layer according to the invention on the carrier materials previously impregnated with aminoplasts in a single Apply operation when using relatively low molecular weight copolymers and ensures that this is transformed into correspondingly high-polymer, ignore infusible connections.

Dispersible copolymers of the type mentioned can also contain other minor amounts Monomers (d) which form hard films, such as acrylonitrile, optionally also styrene and other vinyl compounds contain. However, experience has shown that the last-mentioned monomers sometimes cause yellowing and are in some cases less recommended.

The copolymers or their dispersions or solutions can, if necessary, have a crosslinking effect Compounds are added. For example, the precondensates of aminoplast-forming compounds are with formaldehyde called like

Ν, Ν'-dimethylol-ethylene urea,
Ν, Ν'-dimethylol propylene urea,
N-methylol ^ -methoxy-ethylene-carbonate,
Hxamethylolmelamine,
Ν, Ν'-dimethyloluron,

as well as etherified or partially etherified methylolated Aminoplasts, e.g. B.

Ν, Ν'-dimethoxymethylene urea,
Ν, Ν'-dimethoxymethylpropyleneurea,
N, N ', N "-hexa- (methoxymethyl) melamine, among others

In addition, emulsifiers are generally required to produce the dispersions; belong here Compounds such as salts of long-chain fatty acids or sulfonic acids, sulfuric acid half-esters of polyoxyalkylenes and their ethers, esters and phenolic ethers.

The emulsifiers are generally used in amounts of up to 5% of the dispersion

For the purposes of the invention, as further auxiliaries in both solutions such as dispersions, for. B. Lubricants and release agents, such as natural and artificial waxes and leveling agents such as certain phosphoric acid esters to be useful.

The production of the copolymers is not part of the invention. It can be done in the usual way happen, for example by polymerizing the components in organic or aqueous solutions or dispersants, generally at elevated temperature and in the presence of polymerization initiators, which provide free rakicals. The use of others is included in the above compilation Monomers not listed are possible in minor amounts without affecting the range of Invention is abandoned.

It is of course also possible to add polycondensable resins to the polymer preparations, in particular, for. B. Mix in urea or melamine resins.

The desired degree of polymerization of the polymers can be achieved in a customary manner by using Regulators or correspondingly effective monomers are adjusted, which accordingly also constituents of the polymer molecules.

For - at least twice - soaking the carrier substances in the manner according to the invention, the the following notices of concern:

As described above, a solution or dispersion is first used in the usual manner Aminoplast precondensate soaked. It is practically exclusively continuous on an industrial scale the carrier web passed through an appropriately concentrated liquor of the impregnating agent and stripped off excess quantities of the liquor. The order (resin weight, based on paper weight) is generally 80 to 140%.

An aqueous-alcoholic solution or aqueous dispersion is now possible even without intermediate drying one as described constructed acrylic resins on one side z. B. by pouring, doctoring or by To apply roller application, provided that the application device is suitably adjusted, in general there is no need to fear that back-mixing of the various resin applications will occur. The one in the second The amount of resin applied to the coating process is between about 10 to 50%, based on the weight of the paper. The finished coated carrier web is then exposed to hot air, e.g. B. in a flotation dryer, the solvent or solvents removed.

To distinguish the invention from similar processes, the following should be said in 7U:

It is already known from the German Auslegeschrift 12 93 017, laminated body made with polycondensed Resin-impregnated papers to produce that the paper in a first stage with a Polymerization plastic dispersion containing solution of a polycondensable resin is impregnated, whereby, in order to obtain a certain residual absorbency of the paper, only about 5 to 15% polymerisation plastic and about 10 to 15% polycondensable resin im

ίο be applied first pass; then closes Intermediate drying takes place and then the web is once again in a second stage with a solution containing polycondensable resin soaked, dried and further processed accordingly According to a particular embodiment of this process, the resin solution is also used in the second stage Another addition of a polymer dispersion was added. This method is intended as described solve the task of producing particularly hard, scratch- and abrasion-resistant layers that are resistant to weathering and temperature influences show no tendency to form cracks.

Another method is described in German Auslegeschrift 14 69 570. Even with this one The process is impregnated in two layers, with two melamine resin solutions in succession with intermediate drying are applied, of which the binder of the first layer has a relatively long pouring time and the binder body of the second layer have a relatively short curing time. A similar one The German patent specification 10 53 303 makes a proposal to which the aforementioned German interpretation document 14 69 570 expressly refers.

Finally, it should be noted that in the industries that deal with the manufacture of resin-impregnated Papers employ procedures that are used after the application of aminoplastic Impregnating agents and their drying a technique to be described as a painting process is used the surface of the impregnated and dried papers subsequently z. B. with a layer of one Nitrocellulose lacquer is provided. This is also usually followed by drying.

However, resin-impregnated paper webs cannot be produced using the known processes described above produce which, after pressing, result in coatings on a corresponding substrate which wood-based materials can be sustainably protected from the effects of the weather. You allow

neither the use of shortened pressing times nor working without recooling on the press.

Production that can be used according to the invention
Acrylic ester copolymers

a) 2200 parts by weight of water with 20 parts by weight of a 15% aqueous solution of a Na salt of lauryl sulfonic acid and 35 parts by weight of ammonium persulfate in a polymerization vessel heated to 80 ° C

A mixture of 2200 parts by weight of water and 247 parts by weight of a 15% strength mixture is allowed to do so aqueous solution of an Na salt of lauryl sulfonic acid, 100 parts by weight of a 50% aqueous Solution of a mixture of saturated and

b5 unsaturated alkyl sulfates, with 12 to 18 carbon atoms, 4580 parts by weight of methyl methacrylate, 120 parts by weight of acrylic acid and 120 parts by weight of acrylic acid amide within

run into the polymerization vessel for about 2 hours.

After completion of the polymerization is cooled and a mixture of 300 parts by weight of a 20% ester wax emulsion, 35 parts by weight, 25% aqueous ammonia solution and 20 parts by weight a surface-active leveling agent added.

b) 1200 parts by weight of water, 10 parts by weight of a 15% aqueous solution of Turkish red oil, 10 parts by weight of a 15% aqueous solution of a sodium salt of lauryl sulfonic acid and 18 parts by weight of ammonium persulfate are in a Given the reaction vessel and heated to 85 ° C.

A mixture of 1380 parts by weight of water, 300 parts by weight of a 15% strength aqueous solution of a sodium salt of lauryl sulfonic acid, 100 parts by weight of a 15% strength aqueous solution of Turkish red oil, 135 parts by weight of a 45% strength aqueous solution of N-methylol methacrylamide is obtained from a second vessel , 60 parts by weight of acrylamide, 2700 parts by weight of methyl methacrylate, 120 parts by weight of 3-chloro-2-hydroxypropyl acrylate and 60 parts by weight of acrylic acid fed within 3 hours. The heating is then carried out for a further 30 minutes, any remaining monomer residues are removed and then cooled.
270 parts by weight of a 20% strength aqueous wax emulsion, 5 parts by weight of 25% strength ammonia and 5 parts by weight of 3η defoaming and leveling agent are stirred into the cold dispersion. A 45-50% dispersion is obtained.

c) 2400 parts by weight of water, 20 parts by weight of a 15% aqueous solution of Turkish red oil, 20 Parts by weight of a 15% aqueous solution of a sodium salt of lauryl sulfonic acid and 36 Parts by weight of ammonium persulfate are placed in a reaction vessel and heated to 85.degree.

A mixture of 2760 parts by weight of water, 500 parts by weight of in a 15% aqueous solution of a sodium salt of lauryl sulfonic acid, 300 parts by weight of a 15% aqueous solution of Turkish red oil, 5700 parts by weight of methyl methacrylate, 120 parts by weight of acrylic acid and 180 parts by weight Acrylamide supplied within 3 hours. Then heat up for another 30 minutes, removes any remaining monomer and then cools.

The cold polymerization is 540 parts by weight of a 25% aqueous wax emulsion, 10 parts by weight of ammonia 25%, 600 parts by weight of a 50% strength aqueous solution of Ν, Ν'-dimethylolethylene urea and 8 parts by weight Defoaming and leveling agents mixed in.

A 45-50% strength stable dispersion is obtained with a pH between 4 and 5 and with a good spreadability.

d) 300 parts by weight of water, 2 parts by weight of a 15% aqueous solution of Turkish red oil, 2 Parts by weight of a 15% strength aqueous solution of a sodium salt of lauryl sulfonic acid and 2.5 Parts by weight of ammonium persulfate are placed in a reaction vessel and heated to 85 ° C. From b5 A second vessel is a mixture of 260 parts by weight of water, 35 parts by weight of a 15% strength aqueous solution of a sodium salt of lauryl sulfonic acid, 25 parts by weight of a 15% strength aqueous solution of Turkish red oil, 450 parts by weight of methyl methacrylate, 60 parts by weight Butyl acrylate, 12 parts by weight acrylic acid, 18 parts by weight acrylamide and 60 parts by weight Diallyl phthalate supplied within 3 hours. Then it is heated for another 30 minutes after, removes any remaining monomer residues and then cools.

45 parts by weight of a 20% strength aqueous wax emulsion and 2 parts by weight are added to the cold dispersion Ammonia 25% and 1.2 parts by weight of defoaming and leveling agents and 60 parts by weight of a 50% aqueous solution of N, N-Dimethyloläthylenurea stirred in. An approximately 45% strength, stable polymer dispersion is obtained.

example 1

With a - based on the dry content - 55% aqueous solution with a viscosity of 35 mPa s of a storage-stable melamine-formaldehyde condensate with a molar ratio of melamine to formaldehyde of 1: 1.8, a 110 g / m ² heavy decorative paper is made from high-grade cellulose in an impregnation system with 110% - based on the weight of the paper - resinified.

Without intermediate drying, 30 g / m ^{2 of} an impregnation solution consisting of

5 kg of a 50% butanolic solution

Acrylic resin solution
0.5 kg of dimethylethanolamine
7.5 kg of water
5 kg melamine impregnation resin (55% in

aqueous solution)

Applied homogeneously on the top. Subsequently, in a flotation dryer (air circulation temperature ^c C 150) dried to 6% volatile contents. The surface protection film produced in this way is pressed onto both sides in a known manner for 6 minutes on both sides of a chipboard glued together in a weatherproof manner at a pressure of 18 bar and a temperature of 145 ° C.

Example 2

Decorative paper weighing 110 g / m ² is pre-impregnated with a mixed condensate produced by the condensation of phenol, melamine and formaldehyde. After leaving the first impregnation unit, the resin application, based on the weight of the paper, is 120%. It is then dried to a volatile content of 12%.

30 g / m ^{2 of} a thermally crosslinkable 55% strength aqueous butanolic solution of a methacrylic ester copolymer are applied to the top using an intermediate impregnation unit. At 140 ^° C., volatile components are then dried down to 6%.

The surface protection film produced in this way is attached to a fungus-proof, weatherproof glued chipboard a pressure of 18 bar and a temperature of 145 ° C for 6 minutes in a known manner on both sides pressed on.

A release paper against the pressure plates (brass, nickel-plated and chrome-plated) is not required.

Example 3

The pre-impregnation of a 110 g soda kraft paper is with a mixed condensate of melamine, phenol and formaldehyde as in Example 2 carried out.

Without intermediate drying, 30 g / m ^{2 of} a thermally curable aqueous dispersion of a methacrylic ester copolymer (55%) are applied to the top. The further treatment and pressing of the film corresponds to example 2.

Comparative experiment to example 3

With a - based on the dry content - 52% aqueous solution of a melamine-formaldehyde condensate (molar ratio to melamine to formaldehyde 1: 1.8; viscosity 30 m Pa s) is a UO g / m ² heavy decorative paper made of high-grade cellulose in a Impregnation system with 145% - based on paper weight - resinated.

This is followed by drying in a flotation dryer with a circulating air of 150 ° C up to 5.4% volatile components. The melamine resin film thus prepared is applied to a weather-resistant chipboard at a pressure of 20 bar ίο and a temperature of 145 ⁰ C pressed for 5 minutes in a known manner.

The following table shows the improved properties of the surface protection films:

Synthetic resin film
example

Water vapor permeability of the
cured
Synthetic resin films ¹ )
(g per square meter and day) Atlas weatherometer test
Test result ² )

Outdoor exposure under
45 ° incline ³ )

Yellowing

Chalks

Comparative experiment 11.6

6.5
5.0
4.5

beginning
Area damage
unchanged
unchanged
unchanged

') The impregnated films are pressed using the data given for the lamination examples without a chipboard carrier.
Measurement conditions:
Measuring temperature: 20 ⁰ C, moisture gradient 85% rel / 0%. F. according to DIN 53 122.

² ) After 400 hours:

Yellowing: 0 no yellowing - 5 severe yellowing.
Chalking: 0 no chalking - 5 heavy chalking.

3) After 1 year.

Example 4

A white decorative paper of 100 g / m ² is soaked in a, based on the dry content, 55% strength aqueous solution of a melamine-formaldehyde condensation resin with a molar ratio of melamine: formaldehyde 1: 2.5 and a viscosity of 35 mPa s. The dry resin application after leaving the first impregnation bath is 110% based on the weight of the raw paper atro. The resin application increases asymmetrically towards the rear.

Without intermediate drying, a 50% strength dispersion according to a) is applied to the top in a directly connected 2nd impregnation unit. The applied layer is homogeneously distributed over distribution rollers. This is followed by drying in a flotation dryer with circulating air to a proportion of volatile constituents of 5.5%. The dry resin application from the 2nd application stage is 30 g / m ² .

The processing of the film is then shown in Example 6

Example 5

A white decorative paper of 100 g / m ² is impregnated as in Example 3

After brief drying with an infrared radiator, a 50% dispersion according to c) is applied to the top. The applied layer is homogenized over distribution rollers and then dried to 4.5% volatile constituents. The dry resin application from the second. Level is 25 g / m ² .

Example 6

A decorative paper of 100 g / m ² filled with 25% titanium dioxide is now, as described in Example 5, but with a resin application of 115%, based on the weight of the raw paper, impregnated.

After intermediate drying in the flotation dryer to a volatile content of 25%, a Mixture consisting of 75 parts by weight of the dispersion from b) and 25 parts by weight of the melamine-formaldehyde impregnating resin from Example 3 applied on top.

The applied layer is smoothed over distribution rollers; then the web is guided plane-parallel through a flotation dryer and dried to 5.0% volatile constituents. In the second application stage, 35 g / m ^{2 of} solid resin from the mixture referred to above were applied

The following table shows the processing data and the quality characteristics of the end faces

11 22 22 401 6th 12th 45 Synthetic resin films
4th 45 190 35 example
5 170 20th Pressing time, sec. 170 35 15th Melamine resin film ¹ ) no Press plate temperature, ⁰ C 15th 170 no 240 + 180 frosted Pressure, bar no 15th glittering 150 slightly porous Recooling high gloss no non-porous 20th 1 shine non-porous high gloss 0 Yes Unity 0 non-porous glittering Susceptibility to cracking 0 slightly porous visible impact load 1 DIN 53 799 no attack Acid test with 1N salt acid based on DIN 53 799

') Decorative paper of 100 g / m ² resin application based on atro paper 140% melamine-formaldehyde impregnating resin in a molar ratio

1: 2.2, modified residual volatile content 4.8%.
^J ) Level 0: decorative surface unchanged up to level 4: sample is torn through.

Claims (1)

Patent claims: 1. Process for the production of paper webs impregnated with aminoplastic binders for surface coating, characterized in that the paper web is in on known way with an aqueous solution of a melamine and / or urea-formaldehyde precondensate treated and a solution or dispersion on one side of the carrier substances treated in this way of a formaldehyde condensate compatible and heat-curable acrylic ester copolymer brings up a) 50 to 90 percent by weight of units with at least one ester of (meth) acrylic acid a monohydric alcohol containing 1 to 8 carbon atoms, b) 5 to 35 weight percent polymerized units of the bi) N-methylol (meth) acrylamide or one of its ethers with a 1 to 10 Monohydric alcohol containing carbon atoms or b ₂ ) a polymerizable monomer which has free alcoholic hydroxyl groups and which was obtained by reacting acrylic acid or methacrylic acid with an at least dihydric alcohol having 2 to 20 carbon atoms c) up to 2 to 15 percent by weight of units either of 3 to 10 carbon atoms polymerizable -olefinically unsaturated carboxylic acid or or and a basic one Group-containing copolymerizable, olefinically unsaturated monomers and d) up to 88 percent by weight of units of a further olefinically unsaturated copolymerizable Monomers.