DE19525300A1 - Impregnated foils for coating wood-based materials - Google Patents

Abstract

The prodn. of impregnated film comprises (1) impregnating an initial base material (I) with an aq. soln. of polymer (P) derived from (a1) 50-100 wt% (meth)acrylamide and/or a N-methylol deriv. thereof, and (b1) 0-50 wt% comonomer, drying to a water content of less than 4 wt% opt., and (2) impregnating with an aq. soln. contg. a condensation prod. of (a2) 1 mole melamine, (b2) 1.4-2.5 moles formaldehyde and (c2) 0-0.2 mole of a cpd. which can undergo an addn. or condensation reaction with formaldehyde. Also claimed is impregnated film (IF) made by this process.

Description

The present invention relates to a method for manufacturing of impregnated foils, characterized by

• I impregnating a starting material (I) with an aqueous solution of a polymer (P) built up
  • a1) 50 to 100% by weight of acrylamide, methacrylamide and / or a derivative of acrylamide or methacrylamide, in which one or both hydrogen atoms on the nitrogen atom are substituted by a hydroxymethyl group (monomers a1)
  • b1) 0 to 50% by weight of a further monomer which can be copolymerized with acrylamide (monomers b1)
    and optionally subsequent drying of the impregnated starting carrier (I) to a water content of less than 4% by weight, based on the solids content of the impregnated starting carrier (I), if its water content is higher,
• II Impregnation of the impregnated and optionally dried carrier (I) (starting carrier material II) obtained in step I with an aqueous solution containing a condensation product
  • a2) Melamine
  • b2) 1.4 to 2.5 moles of formaldehyde per mole of melamine and
  • c2) 0 to 0.2 mol of a further compound which can react with form aldehyde in an addition or condensation reaction, per mol of melamine.

Furthermore, the invention relates to impregnated films which this method are available and their use for loading layering of laminates.

Especially in the furniture industry, foils are needed that can for coating wood-based materials such as chipboard, plywood and wood fiber boards are suitable and this a protective and decorative lend rative surface.  

It is generally known (cf. Ullmann's Encyklopadie der techni schen Chemie, 4th edition, Verlag Chemie GmbH 1973, Volume 7, p. 417 to 418) for this purpose carriers such as paper or fiber use nonwovens with a melamine-formaldehyde condensate sation product are impregnated.

Various requirements are imposed on the impregnated foils poses. They should give the laminates a surface hen that is insensitive to water and chemicals. Next the surface should be as hard as possible so that it is against mechanical stress such as scratching is insensitive.

In order for the foils to meet these requirements, the melamine Formaldehyde condensation product with which the films are impregnated are cured to a highly cross-linked polymer.

The impregnated films are generally cured at elevated temperature and should, so that the processing of the impregnated nated foils can be carried out as economically as possible, take only a short time. For this purpose, the Melamine formaldehyde condensation products with which the carrier impregnated fabrics, hardener added.

However, it was found that the surfaces thus produced coatings are too brittle and tend to form cracks.

To give the surface coatings a higher elasticity borrow was recommended in DE-A-20 49 378, the melamine form aldehyde condensation products N-methylolacrylamide or Add N-methylol methacrylamide.

From DE-A-24 60 994 it is known for the same purpose Mixtures of melamine-formaldehyde condensation products and use water-soluble copolymers. As a monomer position of the copolymers is u. a. also acrylamide and meth acrylamide recommended.

DE-A-21 35 072 proposes mixtures of polymer dispersions of acrylic esters and acrylamides for the production of use elasticized foils.

A disadvantage of the use of mixtures of those from the third copolymers and melamine Formaldehyde condensation products, however, is that with this manufactured surface coatings for graying and Aus tend to form white efflorescence. This effect is special otherwise recognizable if colored or black as carrier substances  Decorative papers are used. The colors then appear gray or cloudy.

The object of the present invention was therefore to create new ones impregnated foils and processes for their preparation places with which hard and at the same time elastic upper let surface coatings be made and where ins particular the graying effect described does not occur.

Accordingly, the manufacturing processes defined at the outset of the impregnated foils or the foils themselves.

All the usual materials come as starting materials used for the production of impregnated foils are used to coat layer materials in Consideration (see Ullmann's Encyclopedia of Industrial Chemistry, 4. Edition, Verlag Chemie GmbH 1973, Volume 7, pages 417 to 418). These are primarily nonwovens and papers, especially baking soda kraft papers and decorative papers.

It is also possible to use webs of Use paper pulp from which by pressing and drying Paper can be made.

The impregnated films according to the invention are produced by soaking the starting carrier substances with a water in step I. solution of a polymer (P), built up from

• a1) 50 to 100, preferably 75 to 100, particularly preferably 100 % By weight of acrylamide, methacrylamide and / or a derivative of Acrylamids or methacrylamids, in which one or both Hydrogen atoms on the nitrogen atom by a hydroximethyl group substituted (monomers a1)
• b1) 0 to 50, preferably 0 to 25 wt .-% of another with acrylic amide copolymerizable monomers (monomers b1)

impregnated.

The monomers (b1) are preferably 80 to 100 % By weight, particularly preferably 90 to 100% by weight, of monomers (b1.1), which in addition to a C = C double bond, which they use for copolymerization enabled with acrylamide, a hydroxyl group, a carboxyl group, a sulfonic acid group, optionally with C₁ to C₄ alkyl groups mono- or disubstituted carbamoyl groups or a carbonyl wear dioxy group and preferably 0 to 20, particularly preferred to 0 to 10 wt .-% different from the monomers (a1) and (b1.1)  those monomers (monomers b1.2) that copoly with acrylamide are meritable.

The monomers (b1.1) also include those monomers in which the carboxyl group or the sulfonic acid group in the salt form is transferred. The cations here include, for example Alkali metal ions prefer sodium and potassium and that Ammonium ion into consideration.

Examples of the monomers (b1.1) are acrylic acid, methacrylic acid, maleic acid, citraconic acid (methyl maleic acid), itacon acid (methyl succinic acid), fumaric acid, the (C₁- to C₄-hydroxy alkyl) esters of acrylic acid, e.g. B. hydroxyethyl acrylate, hydroxy propyl acrylate and hydroxybutyl acrylate, (C₁ to C₄ hydroxy alkyl) esters of methacrylic acid, e.g. B. hydroxypropyl methacrylate and hydroxybutyl methacrylate, C₁ to C₁₀ sulfonic acids with a C = C double bond, e.g. B. vinyl sulfonic acid, allylsulfonic acid, meth allylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrofoam sulfonic acid, 3-sulfopropyl acrylate, 3-methacrylic acid sulfopropyl ester, N-vinyl pyrrolidone, N-vinyl caprolactam, N-vinyl formamide, N-vinyl acetamide, N-vinyl methylacetamide.

It has proven to be particularly useful to include such monomers (b1.1) put in water a solubility of at least 100 g / l (measured at 25 ° C).

The monomers (b1.2) are mainly styrene, acrylonitrile, meth acrylonitrile, vinyl acetate, vinyl propionate, the (C₁ to C₄-alkyl) esters of acrylic acid, the (C₁ to C₄-alkyl) esters of Methacrylic acid and the (C₁ to C₄ alkyl) mono- and diesters of Maleic and fumaric acid into consideration.

The K value of the polymers (P) is usually 6 to 300, be preferably 7 to 150, particularly preferably 8 to 50, the K values on those in Encyclopedia of Chemical Technology, Third Edition, John Wiley and Sons, Inc 1983, Volume 23, pages 967 and Obtain the specified measurement method.

Polymers with K values from 6 to 300, preferably 7 to 150, be particularly preferably 8 to 50, the K values being based on those in H. Fikentscher, Cellulose-Chemie, Volume 13, pages 58 to 64 and 71 to 74 (1932) described measurement method are also suitable. K = k × 10³. It is measured in the K value Range from 6 to 20 as 5% by weight, in the K value range from 20 up to 100 as 1% by weight and with K values of more than 100 as 0.1 selected % solutions.  

The polymers (P) are generally prepared according to be known methods of radical polymerization, e.g. B. the Solution, precipitation, emulsion or suspension polymerization, solution polymerization in water is preferred.

All are suitable for initiating the radical polymerization common radical donor, e.g. B. per compounds, azo connections and redox systems.

In solution polymerization in water, water is preferred soluble initiators such as hydrogen peroxide, sodium, potassium and ammonium persulfates and all water-soluble azo initiators used. Soluble iron, copper, Vanadium salts and reducing agents such as sodium hydrogen sulfite, Sodium dithionite, ascorbic acid and glucose, for example in Consideration.

The person skilled in the art knows that it is particularly easy to settle down can produce molecular polymers (P) if he the polymeri sation in the presence of a controller.

Suitable regulators are, for example, 2-mercaptoethanol, Mercaptopropanol, thioglycolic acid, thiolactic acid, dodecyl mercaptan and sec. Alcohols such as isopropanol and sec. The controllers are usually in amounts of 0.1 to 50 wt .-%, based on the total amount of monomers (a1) and (b1) in the polymerization of the monomers added.

Polymers (P) with a K value of 8 to 50 using a regulator are produced, particularly suitable.

To impregnate the starting carrier material (I) are aqueous Solutions of the polymer (P) used, preferably 5 to 25, 3 particularly preferably contain 10 to 20% by weight of the polymer (P).

The starting carrier material (I) is usually 4 to 8.5, be preferably with 5.5 to 7.5 g of the polymer (P), per 100 grams of the Starting carrier material (I) impregnated by adding 100 g each gang carrier material (I) an aqueous solution which the polymer (P) contains in the specified amounts, can act.

The way of impregnation is not critical. The end Gear carrier material (I) can, for example, in an aqueous solution 3 of the polymer (P) are immersed or the aqueous solution of the  Polymers (P) can be sprayed onto the starting material (I) will.

It is necessary that the with the aqueous solution of the poly meren (P) impregnated starting material (I) has a water content of less than 4 wt .-%, based on the solids content of the output impregnated with the aqueous solution of the polymer (P) carrier (I), if in the following step II impregnated with the melamine-formaldehyde condensation product becomes. The water content is preferably less than 3% by weight.

The solids content can be determined, for example, by one from a sample of the with the aqueous solution of the polymer (P) impregnated starting carrier material (T) determines the weight, dry the sample in a forced air drying cabinet at 150 ° C for 1 hour net, weighs the dried sample again and based on the weight difference calculated the water content.

To accelerate the drying, they are usually carried out at a temperature of 120 to 180 ° C, for example by the impregnated starting carrier materials (I) in a drying tunnel Dry contact-free on air cushions.

The carrier materials obtained in step I (starting carrier substances II) are in a subsequent step II with a aqueous solution of a melamine-formaldehyde condensation pro product impregnated.

The melamine-formaldehyde condensation products (in the following text D for short "condensation products") are generally known (cf. Ullmann's Encyclopedia of Technical Chemistry, 4th Edition, Volume 7, Pages 403 to 422 or Kunststoff-Handbuch, 2nd edition, 1988, Volume 10, pages 41 to 49.

As starting compounds for the production of the condensation pro become products

• a2) Melamine
• b2) 1.4 to 2.5, preferably 1.5 to 1.6 mol of formaldehyde per mol melamine  
• c2) 0 to 0.2, preferably 0 to 0.1 mol of a further compound, those with formaldehyde in an addition or condensation reaction can react, per mole of melamine

used.

In particular, the amounts of components (a2), (b2), (c2) chosen so that the molar ratio of the components (a1), (a3) and (a4) originally present -NH₂ groups for the component (a2) 0.1: 1 to 0.8: 1, preferably 0.4: 1 to 0.6: 1.

The melamine (component a2) is preferably used in solid form puts.

The formaldehyde (component b2) is preferably in the form of a 30- up to 50% by weight aqueous solution or in the form of paraform aldehyde used.

Component (c2) are urea and guanamines such as benzoguanamine and acetoguanamine. Bisguanamines such as adipo-, glutaro- or methylolglutarobisguanamine and compounds which meh rere, e.g. B. contain condensed aminotriazine nuclei are even if appropriate.

The urea is preferably in the form of a concentrated water solution of urea and formaldehyde (component a2), the are known from DE-A-24 51 990 and EP-A-0083427 puts. These solutions from 3.0 to 6.0, preferably 3.5 to 4.5 mol Formaldehyde per mole of urea, preferably have a solid content according to DIN 12605 from 50 to 85, preferably from 60 to 80 % By weight. They contain some of the urea and formaldehyde in free monomeric form, partly in the form of reaction products such as methy lolureas or low molecular weight condensation products.

The implementation of the starting compounds to the condensation products usually take place at a pH of 7 to 10, preferably from 8.5 to 9.2 and a reaction temperature of 60 to 110, preferably from 90 to 100 ° C. The implementation can be finished by lowering the reaction mixture to temperatures below cools at half 50 ° C, preferably to 20 to 30 ° C. It is generally mean worked at normal pressure.

Aqueous solutions of the condensation products with a solids content of 45 to 55% by weight and a viscosity of 20 to 80 mPas (based on a temperature of 20 ° C. and a shear rate of 100 s ⁾ are particularly suitable for producing the impregnated films according to the invention ^{. 1} ).

The aqueous solutions of the condensation products are in all common with a component accelerating the hardening puts. These are, for example, the general be knew hardener or reaction products of aliphatic Amines such as dimethylethanolamine with SO₂. The hardener becomes water solution of the condensation product in general in quantities from 0.1 to 1 wt .-% added.

So that the properties of the aqueous solutions of Kon change the sealing products as little as possible during their storage, the hardener will be beneficial to you immediately before impregnation tion of the carrier materials (I) added.

Furthermore, the aqueous solution of the condensation products also commonly used tools of the prior art be set, m z. B. antifoam and wetting agents, e.g. B. polyethoxylated alcohols.

The impregnation of the carrier materials (I) is used moderately according to a procedure like that for impregnation tion of the starting support materials (I) with the aqueous solution of the polymer (P) is described.

The starting carrier material (II) is usually 100 to 130, preferably with 110 to 120 g of the condensation product, per 100 Grams of the starting carrier (II) impregnated by each 100 g of starting material (II) an aqueous solution that the Contains condensation product in the specified amounts leaves.

It is recommended that the impregnated films according to the invention, provided they have a water content of more than 7.0% by weight have their solids content before further processing drying to dry.

Impregnated have particularly favorable processing properties Films with a water content of 5 to 7 and especially 5.5 to 6.5% by weight.

The films impregnated according to the invention are suitable for the Coating of laminated materials such as chipboard, wood fiber boards, blockboards and for coating wood and Plastic.  

For this purpose, the impregnated foils, optionally in several layers on top of each other, at an elevated temperature Pressed on materials. The temperature is usually 120 up to 220 ° C, the pressure 8 to 22 bar and the pressing time 8 to 55 sec.

In this way you get shiny surface coatings, the crack-resistant, resistant to water vapor and diluted Alkali and acids are and have a high color brilliance.

example 1

A white decorative paper with a weight of 80 g / m² was used a 15 wt .-% aqueous solution of polyacrylamide with a K value of 17 impregnated by dipping and dried at 140 ° C, after previously removing excess polymer solution by doctor blade had been. The dried paper (carrier material) had one Water content of 3.5 wt .-% and contained 7.5 g of polyacrylamide per m². The paper treated in this way was then washed with a aqueous solution of a melamine resin (molar ratio Melamine: formaldehyde 1: 1.6), which has a viscosity of 42 mPa · s (20 ° C), impregnated and at 140-160 ° C in a dry channel dried on air cushions without contact. The resulting one Decorative film contained 98g solid melamine resin per m² and had one Water content of 6.5 wt .-%. To determine the solid the materials were kept in a circulating air at 120 ° C. for 2 h drying cabinet dried.

With the decorative film, sanded chipboard was ver different conditions:

• a) 1 layer of decorative film 190 ° C, 20 kp / cm², 35 s pressing time
• b) 1 layer of decorative film 230 ° C, 20 kp / cm², 11 s pressing time
• c) 2 decorative film layers 170 ° C, 20 kp / cm², 6 min pressing time with recooling.

Example 2

The procedure was analogous to Example 1, but for an order of 8 g polyacrylamide (100%) / m² on the decorative paper.  

Example 3 (comparative example)

Analogous to example 1, but without pretreatment with polyacrylamide.

The laminates produced were the following ge described subject to application tests:

• - Determination of the degree of hardening
  A 0.1 n HCL stained with Rhodamine B (0.0⁵ g / l) is poured into a glass dome, the support edge of which is ground flat.

The dome filled with solution is left to the limit for 15 hours act on the surface of the body to be tested.

After removing the glass dome, the surface of the test rinsed with water and the rest of the water dried with a cloth. It is assessed visually Acid attack and dye lift.

The rating scale for acid attack and color winding is ge to manufacture and depends on the test Surface type.

It is classified according to rating levels from 0-6.
0 = no acid attack; no dye lift
1 = change in gloss
2 = slight staining
3 = strong staining, but no structural change
4 = swelling of the surface
5 = blistering
6 = peeling of the resin

• - Determination of the gloss level
  The degree of gloss is determined with a Lange REFO 3 / REFO 3-M gloss meter at an angle of incidence of 20 °. The gloss level of the surface is expressed in% of the reflected light.
• - crack resistance
  The crack test is carried out on surfaces which are developed by pressing two layers of decorative paper onto a particle board at 170 ° C and a pressure of 20 kp / cm². The pressing time is 6 minutes with subsequent cooling to room temperature. The coated particle board is stored for 15 hours at 80 ° C. in a forced-air drying cabinet to generate tensions and, after cooling, is assessed for crack formation.

The test results are shown in Table 1 below lists.

Table 1

Example 4

A black decorative paper with a weight of 90 g / m² was used a 15 wt .-% aqueous solution of polyacrylamide with a K value of 11 impregnated by dipping and dried at 140 ° C, after excess polymer solution is removed by doctor blade had been. The dried paper (carrier material) had one Water content of 3.7% by weight and contained 7.5 g of polyacrylamide per square meter. The paper treated in this way was then used an aqueous solution of a melamine resin (molar ratio Melamine: formaldehyde 1: 1.6, solids content 55%, viscosity 48 mPa · s (20 ° C)), which additionally 0.2 wt .-% wetting agent (a po lyethoxylated alcohol (Kauropal (R) 930/931)) and 0.5% by weight Hardener (dimethylethanolamine with SO₂ (hardener 529 / BASF Aktiengesellschaft)) contained, impregnated.

The films thus obtained were as in Example 1, point 1.1. and 1.2. processed.  

Example 5 (comparative example)

The procedure was analogous to Example 4, but the black one Decorative paper with a mixture of the poly aqueous solution impregnated with acrylamids and melamine resin. The dosage he followed so that the impregnated film the same per square meter Chen amounts of polyacrylamide and melamine resin contained, as in Example 4 described.

The laminates produced according to Examples 3 and 4 were visually assessed for their graying and as follows classified.

1 = without any impairment of the brilliant deep black color
2 = brilliance slightly subdued
3 = light graying
4 = heavy graying
5 = formation of white islands

Table 2

Claims (9)

1. Process for the production of impregnated films, characterized by

• I impregnating a starting carrier material (I) with an aqueous solution of a polymer (P) built up from
  • a1) 50 to 100% by weight of acrylamide, methacrylamide and / or a derivative of acrylamide or methacrylamide, in which one or both hydrogen atoms on the nitrogen atom are substituted by a hydroxymethyl group (monomers a1)
  • b1) 0 to 50% by weight of a further monomer copolymerizable with acrylamide (monomers b1)
    and optionally subsequent drying of the impregnated starting carrier material (I) to a water content of less than 4% by weight, based on the solids content of the impregnated starting carrier material (I) g if its water content is higher,
• II Impregnation of the impregnated and optionally dried carrier (I) (starting carrier II) obtained in step I with an aqueous solution containing a condensation product
  • a2) Melamine
  • b2) 1.4 to 2.5 moles of formaldehyde per mole of melamine and
  • c2) 0 to 0.2 mol of a further compound which can react with formaldehyde in an addition or condensation reaction per mol of melamine.

2. Process for the production of impregnated films according to claim 1, characterized in that the monomers (b1)

• b1.1) 75 to 100% by weight of a monomer copolymerizable with acrylamide, which has a hydroxyl group, a carboxyl group, a sulfonic acid group, optionally mono- or disubstituted carbamoyl groups with C₁- to C₄-alkyl groups, a carbonyldioxy group or a (C₁- to C₄ -Alkoxy) carbonyl group and
• b1.2) 0 to 25 wt .-% preferably monomers copolymerizable with acrylamide.

3. Process for the production of impregnated films according to An saying 1 or 2, characterized in that a polymer (P) with a K value of 6 to 300. 4. Process for the production of impregnated films according to the Claims 1 to 3, characterized in that in Step I an aqueous solution containing 5 to 25% by weight of the polymer (P). 5. Process for the production of impregnated films according to the Claims 1 to 4, characterized in that the off Gait carrier material (I) per 100 grams of starting carrier material (I) with 4 to 8.5 g of the polymer (P), in the form of its aqueous Solution, impregnated. 6. Process for the production of impregnated films according to the Claims 1 to 5, characterized in that in Step II an aqueous solution containing 45 to 55% by weight of the condensation product. 7. Process for the production of impregnated films according to the Claims 1 to 6, characterized in that the off gear carrier material (II) per 100 g of starting carrier material (II) with 100 to 130 g of the condensation product, in the form of its water solution, impregnated. 8. Impregnated foils, obtainable by a method of An sayings 1 to 7. 9. Use of the impregnated films according to claim 8 for loading layering of laminates.