WO2006008037A1

WO2006008037A1 - Use of melamine resin foils and/or films for 3d coating

Info

Publication number: WO2006008037A1
Application number: PCT/EP2005/007578
Authority: WO
Inventors: Marta Martin-Portugues; Günter Scherr; Tina Einfeld; Ralph Lunkwitz; Jakob Decher
Original assignee: Basf Aktiengesellschaft
Priority date: 2004-07-15
Filing date: 2005-07-13
Publication date: 2006-01-26
Also published as: DE102004034528A1

Abstract

The invention relates to the use of melamine resin foils and/or films for coating three-dimensionally structured surfaces and/or shaped bodies, produced from cellulose-containing fibrous materials, which are pre-impregnated or post-impregnated with an aqueous solution containing: (i) one or more non-etherified melamine formaldehyde condensates; (ii) one or more etherified melamine formaldehyde condensates with a ratio of formaldehyde to amino groups ranging from 1.0 to 1.8: 1 and a degree of alkylation ranging from 40 to 80 %, and; (iii) one or more polymer dispersions.

Description

Use of melamine resin films and / or films for 3D coating

description

The present invention relates to melamine resin films and / or films produced from cellulosic fibrous materials containing an aqueous solution containing

(i) one or more non-etherified melamine-formaldehyde condensates; (ii) one or more etherified melamine-formaldehyde condensates having a ratio of formaldehyde to amino groups of 1.0 to 1.8: 1 and an alkylation having a degree of from 40 to 80%, and (iii) one or more polymer dispersions,

after or before and after impregnation, for the coating of three-dimensionally structured surfaces and / or molded bodies.

Usually for the coating of three-dimensionally structured substrates (3D coating) thermoplastic films are used, for. B. for coating Holzwerk¬ materials in the furniture industry. The significant advantage of these thermoplastic films is until now their elasticity, disadvantageous are the high costs in the production u.a. caused by the additional use of adhesives, and the expected costs for disposal.

It is desirable to use the self-adhesive low-cost melamine resin films, which are used for example in the furniture industry for the finishing of smooth surfaces, as well for the coating of three-dimensionally structured surfaces. Pure melamine resins are too brittle for this application. Improved flexibility could be achieved according to DE-A 23 09 334 with etherified methylol melamine resins. These are mainly used for the production of composite materials such as melamine resin films. For this purpose, for. As papers, fabrics or nonwovens impregnated with the melamine resin and cured at temperatures of 100 to 18O ⁰ C. These melamine resin films are mainly used for surface treatment of wood-based materials such as chip-hardboard and blockboard. For this purpose, the melamine resin films are glued to the surfaces or edges of the wood-based materials using a suitable adhesive, if appropriate using heat and pressure. By coating with melamine resin films, the resistance of the wooden materials to mechanical stresses and their water resistance should be improved.

In order to achieve the flexibility and elasticity required for coating, for example, rounded edges, the melamine resins have been modified, e.g. B. by adding guanamine to DE-A 44 39 156 or by adding small amounts of an aqueous resin dispersion according to DE-A 38 37 965. A combination of Aminoplast resins with acrylate dispersions brings about a certain elasticity of the films produced according to DE-A 37 00 344. The patents described above disclose exclusively the production of so-called soft edges. When coating the soft edges with these melamine resin films, adhesives are needed as described in the examples to secure the resin films to the edges.

The known melamine resin films are, as far as the property of ductility, still capable of improvement. In particular, for the uniform coating of surfaces with three-dimensional structures, such as e.g. may be found in some styles (rustic furniture), and / or formkör¬ pern desired that melamine resin or melamine resin films can be used, which have an improved elasticity over the known with improved ver¬ or at least as good other properties. In addition, there is the desire to be able to coat three-dimensional structures with sharp-edged elements from a material surface. By modification, self-adhesive melamine resin films which hitherto were only suitable for coating smooth surfaces should be indicated for 3D coating. The coating should be done for aesthetic reasons and at the same time to simplify the production in a single pressing process. The main feature of such films or films lies in the deformability during the pressing process.

It is an object of the present invention to provide melamine resin films and / or films which are suitable for the planar coating of three-dimensionally structured surfaces, shaped articles and three-dimensionally structured articles with sharp-edged elements and which nevertheless have the usual quality features of a melamine resin film or film.

The object was achieved by the use of melamine resin films and / or films, produced from cellulosic fibrous materials or fabrics containing an aqueous solution containing

(i) one or more non-etherified melamine-formaldehyde condensates, (ii) one or more etherified melamine-formaldehyde condensates which have a ratio of formaldehyde to amino groups of from 1.0 to 1.8: 1 and an alkylation - have degrees of degree (etherification) of 40 to 80%, and

(iii) one or more polymer dispersions,

after or before and after impregnation, for the coating of three-dimensionally structured surfaces and / or moldings.

The term "3D coating" is to be understood as the partial or complete coating of bodies, structures, reliefs, profiles, embossings and the like. These have three-dimensionally structured surfaces, that is to say shapes, configurations or structures which extend in all three spatial directions. The changes in shape can be both fluid and abrupt, as for example in sharp-edged structures, such as edges, corners and / or points, which describe a defined angle, which results from two or more converging planes. Furthermore, "three-dimensional deformation" is also understood to mean the full coating, or simultaneous / simultaneous coating of fronts and edges, of regular or irregular shaped bodies, profiles and the like.

It has been found that aqueous solutions for post- or pre-soaking and impregnation of cellulose-containing fibers are particularly suitable if they

(i) from 5 to 80% by weight, preferably from 5 to 50% by weight, in particular from 10 to 30% by weight, of one or more non-etherified melamine-formaldehyde condensates, (ii) from 5 to 80% by weight , preferably 5 to 50 wt .-%, in particular 10 to 40 wt .-% of one or more etherified melamine-formaldehyde condensates, a ratio of formaldehyde to form amino groups of 1.0 to 1, 8: 1, preferably 1 , 1 to 1, 7: 1, in particular 1.2 to 1, 6: 1, and a degree of alkylation of 40 to 80%, preferably 45 to 70%, in particular 50 to 70%, and (iii) 15 to 90 Wt .-%, preferably 20 to 80 wt .-%, in particular 30 to 70 wt .-% of one or more polymer dispersions

contain. The quantities of the components (i), (ii) and (iii) are complementary to 100 wt .-% and relate to the liquid resin mixture. The degree of alkylation describes the number of etherified methylol groups.

Auxiliaries and additives may also be added to the melamine resin mixture according to the invention, for example from 0.1 to 50% by weight, preferably from 0.2 to 30% by weight, in particular from 0.5 to 20% by weight, of urea, caprolactam, Phenyldiglycol, butanediol and / or saccharose, based on 100 wt .-% of the mixture (i) to (iii). Furthermore, it may contain conventional additives such as wetting agents, curing agents and catalysts.

In particular, the following is to be explained with regard to the structural components:

As constituent component (i), non-etherified melamine-formaldehyde condensates are used. The preparation of the building component (i) is well known. As a rule, first 1 mol of melamine with 1, 4 condenses to 2 moles of formaldehyde at a pH of from 7 to 9 and at temperatures of 40 to 100 ⁰ C, until the appropriate con- densationsgrad achieved. Melamine is usually used in solid form. Normally, formaldehyde is used in the form of concentrated aqueous solutions, for example as an aqueous solution of from 30 to 70 percent by weight, preferably as a 40 to 60 percent by weight solution.

In the synthesis component (ii), melamine-formaldehyde condensates are etherified with C ₁ -C ₄ -alcohols, such as methanol, ethanol, propanol, isopropanol, butanol and / or isobutanol. Preferred are methanol and ethanol. The preparation of the Aufbaukom¬ component (ii) is well known. The production is usually carried out in two stages. First, melamine is typically hydroxymethylated in a basic medium with formaldehyde. Then the pH is lowered and C 1 to C ₄ alcohols, for example methanol, fed to carry out the alkylation. The condensation conditions depend on the water dilutability desired for the resin, which is at least 1: 6. After condensation, the melamine resins are freed from excess alcohol and formaldehyde by distillation.

As synthesis component (iii), copolymer dispersions are used whose copolymers preferably contain carboxyl, hydroxyl, amide, glycidyl, carbonyl, N-methylol, N-alkoxymethyl, amino and / or hydrazo groups, in particular carboxyl groups. , Hydroxy, amide, glycidyl, carbonyl, N-methylol, N-alkoxymethyl, amino and / or hydrazo-containing acrylates. The abovementioned functional groups in the copolymer are obtained in the customary manner by copolymerizing corresponding monomers which carry these functional groups.

The copolymers generally contain the abovementioned functional groups in such amounts that they contain from 0.1 to 50% by weight, preferably from 0.3 to 20% by weight, based on the copolymer, of these monomers having functional groups. may contain lymerisiert.

As main monomers of the comonomers with the above-mentioned groups are the customary copolymerizable therewith olefinically unsaturated monomers, for example C ₁ - to C ₁₂ -alkyl esters of acrylic acid and methacrylic acid, preferably C ₁ - to C ₈ -alkyl, such as methyl acrylate, methyl methacrylate, ethyl acrylate, Ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate and lauryl methacrylate; Vinyl esters of C ₂ - to C ₄ -carboxylic acids, for example vinyl acetate and vinyl propionate, C ₁ - to C ₄ -dialkyl esters of maleic acid and fumaric acid, vinylaromatics such as styrene, α-methylstyrene, vinyltoluene; Acrylonitrile, methacrylonitrile, acrylamide, methacrylamide and vinyl ethers having 3 to 10 Kohlenstoffato¬ men, vinyl halides such as vinyl chloride and vinylidene chloride; multiply olefinically unsaturated compounds such as butadiene and isoprene and mixtures of the abovementioned monomers, provided that they are copolymerisable with one another. To prepare the resin mixture, the pH of the polymer dispersion is usually adjusted to 7.5 to 10 before the addition of the other components.

The components (i), (ii) and (iii) are usually for preparing the Harzmi- research for 2 to 30 minutes, advantageously for 10 to 20 minutes, mixed ver¬ at 15 to 30 ⁰ C.

Before impregnation, the resin mixture is usually mixed with one or more hardeners. Bronsted acids such as organic sulfonic acids and carboxylic acids and their anhydrides, e.g. Maleic acid, maleic anhydride and formic acid, ammonium compounds, e.g. Ammonium sulfate, Am¬ moniumsulfit, ammonium nitrate, ethanol ammonium chloride, dimethylethanolammonium sulfite and hardener combinations such as morpholine / p-toluenesulfonic into consideration.

The hardeners can be added in amounts of from 0 to 2.5% by weight, based on the aqueous impregnating resin. The skilled worker is aware that the hardener dosage can be adapted to the respective application requirements, wherein the reactivity of the impregnating resin / hardener mixtures z. B. can be adjusted according to the measurement of turbidity times and gel times.

In addition, auxiliary agents such as wetting agents may be added to the resin mixtures of components (i), (ii) and (iii). Suitable wetting agents are, for example, ethoxylated fatty alcohols or alkylphenol ethoxylates which can be added in amounts of from 0 to 1% by weight, based on the resin solution.

The melamine resin film and / or film used according to the invention has the required high elasticity without loss of the remaining quality properties, which is necessary for the coating of three-dimensionally structured surfaces and / or shaped articles and / or structured articles with sharp-edged elements. Among sharp-edged elements u.a. Edges, corners and points ver¬ stood, which describe a defined angle, which results from two or more converging planes.

For the preparation of the melamine resin films or films to be used according to the invention, absorbent cellulosic fibrous materials or fabrics or decorative paper are used in a manner known per se.

The manner in which the resin mixtures of components (i), (ii) and (iii) are further processed into melamine resin impregnates and how the coating of wood-based materials takes place with these impregnates is known to the person skilled in the art. As a rule, impregnation takes place in such a way that the paper is impregnated with the aminoplast resin solution. For example, papers with a basis weight in the range from 60 to 200 g / m ² with 120 to 150 wt .-%, based on the paper weight of Im¬ impregnating liquor, impregnated at room temperature. The impregnated paper is subsequently dried to a residual moisture content of about 5 to 10% by weight. For impregnation, the customary impregnation systems are suitable which bring about the desired amount of resin onto and into the papers in the so-called one-stage or two-stage process. The advantage of the two-stage process is that, if appropriate, different aminoplast resins can be used for the initial and post-impregnation.

The aminoplast films or films made in this manner are then hot formed. Advantageously, the films or films are pressed at elevated temperatures of for example 150 to 21O ⁰ C and / or elevated pressures of for example 7 to 30 bar during a pressing time of for example 10 to 60 s with the substrate.

Preferred substrates are wood-based materials, e.g. Country-style furniture, and "Oriented Strand Board" (OSB) panels. The bonding preferably takes place flat in a single work step, i. The three-dimensionally structured surface is coated with a single melamine resin film or film over the entire structure in a single pressing process.

In the context of this invention, the term "melamine resin film" is to be understood as meaning a non-self-adhesive film, the term "melamine resin film" describing a self-adhesive film.

Advantageously, adhesion takes place during coating by the aminoplast resin, i. it is advantageous self-adhesive Aminoplastharzfilme used for 3D deformation.

The preserving surfaces are clear and well closed with good deformability.

The advantages of the invention are also in the avoidance of costs for the aufwi¬ ge production and disposal of the thermoplastic films used so far.

Examples

Component (i): melamine-formaldehyde condensate

A mixture of aqueous formaldehyde (40 wt .-%, 758 g) and water (358 g) was heated to 30 ⁰ C and adjusted with 2 molar aqueous sodium hydroxide solution to a pH of about 9. Melamine (821, 6 g), diethylene glycol (78 g), and caprolactam (38 g) were added, the mixture was heated at 98 to 100 ⁰ C and stirred for about 70 minutes at a pH of 8.8 , Component (ii): etherified melamine-formaldehyde condensate of melamine (120 g) and formaldehyde (40% wt .-%, 455 ml) at a pH of 8 to 8.5 and temperatures of 60 to 7O ⁰ methylolated C , Methanol (910 ml) was added at a pH of 4, and the reaction mixture was held for a STUN de at temperatures of 5O ⁰ C. Subsequently, the pH of the mixture was adjusted to 8 to 9 and the reaction mixture was concentrated.

Comparison component (ii) etherified melamine-formaldehyde condensate of melamine (95 g) and formaldehyde (40 wt .-%, 455 ml) at a pH of 8 to 8.5 and temperatures of 60 to 7O ⁰ C. methylolated. Methanol (910 mL) was added at pH 4 and the reaction mixture was held at 60 ° C for one hour. Subsequently, the pH of the mixture was adjusted to 8 to 9 and the reaction mixture was concentrated.

Component (iii): polymer dispersion

Copolymer of an aqueous, hydroxyl-containing dispersion of a copolymer based on acrylic and methacrylic acid esters and styrene

Example 1 20 g of component (i), 30 g of component (ii) and 40 g of component (iii) were mixed at a pH of 7 to 9 at a temperature of 20 to 25 ° C for 10 to 20 minutes , The resulting resin mixture had a viscosity of 55 mPas.

Comparative Example 20 g of the component (i), 30 g of the comparative component (ii) and 40 g of the component (iii) were at a pH of 7 to 9 at a temperature of 20 to 25 ⁰ C for 10 to 20 minutes mixed. The resulting resin mixture had a viscosity of 57 mPas.

Example of use:

The resin mixtures of Example 1 and Comparative Example were after addition of 0.5 wt .-% hardener based on the resin mixture (eg organic salt of para-toluenesulfonic acid) on decorative paper with a basis weight of 80 g / m ² so impregnated and then dried that the decorative papers had a solids content of 120 to 130% and had a residual moisture content of 6 to 10%.

3D coating and characterization:

The obtained melamine resin films were pressed on a MDF (Medium Density Fiber) plate having a diameter of 16.5 cm including a 3D structure. 3D structures are to be understood as contours with round and straight surfaces and / or edges with a defined angle. The pressing process took place in a laboratory press at 150 to 16O ⁰ C under a force of 45 kN and in a time of 30-60 s instead. Characterization:

Deformability: The deformability and the adhesion of the melamine resin film on the MDF board including a 3D structure were evaluated. With good deformability, the coating should rest completely against the structure and firmly adhere to it without tearing, breaking or folding.

Evaluation:

0 = free of cracks or wrinkles

1 = free from cracks, occasional wrinkles

2 = isolated cracking, low wrinkling

3 = low cracking, moderate wrinkling 4 = moderate cracking, severe wrinkling

5 = severe cracking, very strong wrinkling

6 = broken and destroyed surface

Characterization of the surface: The obtained melamine resin film was formed on a smooth MDF board at a temperature of 160-165 ⁰ C under a pressure of 25 Kp and in a time of 110 s pressed. The following tests were carried out:

Curing: The quality of the cure was determined by exposing the coated MDF board to a 0.2N hydrochloric acid stained with 0.004 wt.% Rhodamine B solution for 16 hours. With good curing, the surface is not attacked by the acid. The strength of the attack can be judged by the strength of the red color.

Evaluation:

0 = no attack

1 = pale pink color

2 = distinct red color

3 = strong red coloration 4 = strong red coloration with slight surface swelling

5 = strong red color with strong surface swelling

6 = destroyed surface Unity:

The closed nature or porosity of the coated surface serves to assess the sensitivity to dirt. The surface to be tested was rubbed in with black shoe cream and then cleaned again with a cloth. The remaining in the pores shoe polish allows an assessment of the closed nature of the surfaces.

The assessment of the surface closure is carried out in the following stages: 0 = free of pores 1 = isolated pores

2 = few pores

3 = frequent pores

4 = many vacancies

5 = very many vacancies 6 = no closure.

Black level:

The black level measurement was carried out according to D 3265 with a Tint Tester 527 with brightness measuring head Tint Sensor. The measuring range covers 0-99.99 brightness units, where zero is the lowest brightness level (absolutely black). With values> 0.8 a clear graying is already recognizable.

After calibration of the instrument with a standard, the test specimen was measured three times and the mean value was indicated as blackness.

The papers impregnated and pressed with the comparative example showed such sticky surfaces that further tests could not be carried out.

The results are presented in Table 1.

Table 1 :

Claims

claims

1. The use of melamine resin films and / or films, produced from cellulose-containing fibers, which with an aqueous solution containing

(i) one or more unetherified melamine-formaldehyde condensates, (ii) one or more etherified melamine-formaldehyde condensates having a ratio of formaldehyde to amino groups of 1.0 to 1.8: 1 and a degree of alkylation of 40 to 80%, and (iii) one or more polymer dispersions,

after or before and after soaked, for the coating of three-dimensionally structured surfaces and / or moldings.

2. Use according to claim 1, wherein the aqueous solution

(i) 5 to 80% by weight of one or more non-etherified melamine-formaldehyde condensates,

(ii) from 5 to 80% by weight of one or more etherified melamine-formaldehyde condensates which have a ratio of formaldehyde to amino groups of

1, 0 to 1, 8: 1 and have a degree of alkylation of 40 to 80%, and

(iii) 15 to 90% by weight of one or more polymer dispersions

contains, wherein the amounts of the components (i), (ii) and (iii) to 100 wt .-% complement and relate to the liquid resin mixture.

3. Use according to claims 1 or 2, wherein the etherified melamine-formaldehyde condensate (ii) has a ratio of formaldehyde to amino groups of 1, 1 to 1.7: 1 and a degree of alkylation of 40 to 80%.

4. Use according to claims 1 or 2, wherein the etherified melamine-formaldehyde condensate (ii) has a ratio of formaldehyde to amino groups of 1, 1 to 1, 7: 1 and a degree of alkylation of 45 to 70%.

5. Use according to claims 1 to 4, wherein the dispersion contains (iii) Copolyme- risate with carboxyl, hydroxy, amide, glycidyl, carbonyl, N-methylol, N-alkoxymethyl, amino and / or hydrazo groups ,

6. Use according to claims 1 to 5, wherein the aqueous solution also 0.1 to 50 wt.% Urea, based on 100 wt .-% of the mixture (i) to

(iii) contains.

7. Use according to claims 1 to 6, wherein the aqueous solution

(i) 5 to 50% by weight of one or more non-etherified melamine

Formaldehyde condensates, (ii) from 5 to 50% by weight of one or more etherified melamine-formaldehyde

Condensates having a ratio of formaldehyde to amino groups of 1, 0 to 1, 8: 1 and a degree of alkylation of 40 to 80%, and

(iii) 20 to 80% by weight of a polymer dispersion

containing the quantities of the components (i), (ii) and (iii)

100 wt .-% and relate to the liquid resin mixture.

8. Use according to claims 1 to 7 for coating objects with 3D surfaces and / or sharp-edged elements, wood materials and / or OSB boards.

9. Use according to claim 1, wherein the cellulose-containing fibers are impregnated with melamine-formaldehyde impregnating resins or a mixture of melamine-formaldehyde impregnating resins and coating resins or a mixture of urea-formaldehyde resins and melamine-urea-formaldehyde resins, and with the aqueous solution (i) to (iii) according to claim 1 nachge¬ impregnated.

10. A method for 3D coating, characterized in that melamine resin films and / or films of cellulosic fibrous materials, which were nach¬ with the wäßri¬ gen solution according to claims 1 to 7 or before and after, produces and these applied to the three-dimensionally structured surface and / or shaped body to be coated.