EP2158096A1

EP2158096A1 - Pre-impregnated product

Info

Publication number: EP2158096A1
Application number: EP08761274A
Authority: EP
Inventors: Martina Wicher; Mirko Standke
Original assignee: Technocell Dekor GmbH and Co KG
Current assignee: Schoeller Technocell GmbH and Co KG
Priority date: 2007-06-28
Filing date: 2008-06-20
Publication date: 2010-03-03
Anticipated expiration: 2028-06-20
Also published as: AR067037A1; US20100183890A1; CA2692288C; CA2692288A1; DE102007030102B4; ES2382085T3; CN101743132B; PL2158096T3; JP2010531376A; DE102007030102A1; US8349464B2; RU2431572C1; ATE544614T1; WO2009000769A1; PT2158096E; CN101743132A; BRPI0813753A2; CL2008001931A1; EP2158096B1

Abstract

Preimpregnated product obtainable by impregnating a decorative base paper with a solution of impregnating resin which comprises at least one polymer latex and at least one modified starch having a specific molecular weight distribution.

Description

prepreg

The invention relates to prepregs and from materials avai ^¬ che Dekorimprägnate or decorative Beschichtungswerk-.

Decorative coating materials, so-called Dekorpa ^¬ piere or decorative films, are preferably chenbeschichtung for surface in furniture manufacture and interior fittings, in particular laminate floors, are used. Under de ^¬ korpapier / decorative film is meant resin impregnated or resin-impregnated and surface-treated, printed or unprinted papers. Decorative papers / decorative foils are glued or glued with a carrier plate.

Depending on the type of impregnation, a distinction Zvi ^¬ rule decorative papers / decorative films with durchimprägniertem paper core and so-called prepregs in which the paper is impregnated in the paper machine online or offline only partially. None of the previously known prepregs, the formaldehyde-containing thermosetting Har ^¬ ze or low-formaldehyde of acrylate binder contained ^¬ th, meets all the demands placed on them such as good printability, high resistance to splitting, good Verklebbar- resistance and ease of painting.

For gluing the decorative films on wood materials such as chipboard or MDF board usually urea glues or polyvinyl acetate (PVAC) glues are used. The bonding of the decorative films is not always guaranteed.

Laminates (High Pressure Laminates) are ^¬ lamina te caused by compressing several impregnated, of stacked papers. The structure of these laminates generally consists of a highest surface resistance producing transparen ^¬ th overlay sheet (overlay), a resin-impregnated Dekorpa ^¬ pier and one or more phenolbeharzten kraft papers. As a basis for example Hartfa ^¬ ser- and chipboard and plywood are used.

The polymers prepared according to the short-cycle method laminates (low pressure laminates), the resin-impregnated decorative paper ge ^¬ is compressed directly with a substrate, wherein ^¬ play, a chipboard, using low pressure.

The decorative paper used in the above-mentioned coating materials is used white or colored with or without additional imprint.

With regard to the performance properties, the so-called decorative base papers serving as starting materials must fulfill certain requirements. These include high opacity for better coverage of the substrate, uniform formation and grammage of the sheet for a uniform resin absorption, high light resistance, high purity and evenness of the color for good re ^¬ producibility of the pattern to be printed, high wet ^¬ strength for a smooth impregnation, corresponding absorbency to obtain the requis ^¬ chen resin saturation level, dry strength, which is important in Umroll processes in the paper machine and printing in the printing press. Furthermore, the Spaltfes ^¬ ACTION is of particular importance as it is a measure of how well the decorative base paper can be processed. So the glued on decorative paper / decorative film should not unravel at Bear ^¬ beitungsschritten such as sawing or drilling.

To create a decorative surface, the decorative base papers are printed. Primarily, the rotogravure so-called ^¬ is used, in which the print image by means of several gravure rollers on the pier Pa ^¬ is transmitted. The individual pressure points are to be completely and as intensively as possible transferred to the Papieroberflä ^¬ che. But just in Dekortiefdruck only a small portion of the existing on the gravure screen dots is transferred to the paper surface. There are ent ^¬ so-called missing dots, ie defects. Often, the ink penetrates too deeply into the paper texture, reducing color intensity. Voraussetzun ^¬ gen for a good printed image with few defects and high color intensity are as smooth as possible and homoge ^¬ ne surface topography and a coordinated Farbannah ^¬ meverhalten the paper surface.

For this reason, base papers are usually smoothed calendering with so-called soft calenders ^¬, sometimes called Janus. This treatment can lead to pinching of the paper surface and thus to its compression, which has a detrimental effect on the resin receptivity. The abovementioned properties are substantially influenced by the impregnation of the decorative base paper, ie by the type of impregnating agent used.

The impregnating resin solutions customarily used for the impregnation of decorative base papers are resins based on urea, melamine or phenolic resins and containing formaldehyde and lead to brittle products having poor tear strength and printability.

It has recently become increasingly important to ensure that the impregnating resin solutions used for the impregnation of decorative base papers are free of harmful substances, in particular formaldehyde-free.

DE 197 28 250 A1 describes the use of formaldehyde-free resins based on a styrene / acrylic acid ester copolymer for producing yellowing-free prepregs. A disadvantage of this material is that it leads to a product with poor splitting resistance.

Formaldehyde-free impregnating resin solutions for impregnating decorative base papers are also described in EP 0 648 248 A1 and EP 0 739 435 A1. These preferably consist of a styrene-acrylic acid ester copolymer and polyvinyl alcohol. However, the paper impregnated with such an impregnating resin solution can still be improved in terms of the splitting strength.

In WO 01/11139 is a formaldehyde-free Zusammenset ^¬ pollution, consisting of a binder, an aqueous Polymer dispersion and glyoxal proposed, which allows the production of splitting resistant decorative papers. However, the paper impregnated with this composition does not laminate well.

The invention is therefore based on the object to provide a formal maldehydfreies prepreg which does not have the abovementioned disadvantages and is characterized in particular by good printability and high interlaminar strength from ^¬.

This object is achieved by a pre-impregnate, which is ^¬ it is by impregnation of a base paper with a Tränkharzlösung containing at least one polymer latex and at least one modified starch having a molecular weight distribution, expressed by a polydispersitätsindex Mw / Mn of at least 6. Be ^¬ vorzugt are starches which have a polydispersity index 6 to 23

In a particular embodiment of the invention, the impregnating resin solution contains at least one polymer latex and at least one modified starch, which preferably has the following molecular weight distribution of the starch molecules:

- not more than 6% by weight of molecules having a weight Molekularge ^¬ 0-1000 g / mol.

From 5 to 20% by weight of molecules having a molecular weight of from 1,000 to 5,000 g / mol,

20 to 40% by weight of molecules having a molecular weight of 5,000 to 25,000 g / mol, 20 to 45% by weight of molecules having a molecular weight from 25,000 to 200,000 g / mol,

5 to 22% by weight of molecules having a molecular weight of 200,000 to 1,000,000 g / mol,

0.5 to 5% by weight of molecules having a molecular weight of more than 1,000,000 g / mol.

The polydispersity index is usually the ratio ^¬ nis of weight and number average molecular weight Mw / Mn specified. It gives information about the width of the molecular weight distribution curve.

The molecular weight distribution of the modified starches was determined by gel permeation chromatography (GPC) in the usual way from the starch manufacturer. GPC analysis was performed using a chromatograph with säu ^¬ len Shodex KS. The eluent was 0.05 M NaOH at a flow rate of 1 ml / min. Calibration was carried out with pullulan standards with ^¬ be known molecular weights.

All modified starches used according to the invention are commercially available. These are in particular thermally and oxidatively degraded corn and potato starches.

Under prepreg ^¬ impregnated papers are understood in the present invention resin part. The amount of Tränkhar ^¬ zes is preferably 10 to 35 wt.%, But especially 12 to 30 wt.%, Based on the basis weight of the decorative base paper. It has been found that the impregnating ^resin solution according to the invention is particularly well suited, since it not only leads to improving the nip strength of the paper impregnated therewith, but also with respect to other properties such as printability, paint level or yellowing comparably good or even better results than the state the technology allows. In addition, the otherwise usual when using hydrophilic binder problems when laminating (gluing or gluing with the pad) of the impregnated papers do not occur. This means that the impregnating resin solution according to the invention allows Her ^¬ position of prepregs with good lamination ability. Another advantage is that the prepreg can be inexpensively manufactured at high machine speeds.

The polymer latex may preferably be a styrene copolymer such as a styrene-acrylic acid ester copolymer, a styrene-vinyl acetate copolymer, a styrene-butadiene or a styrene-maleic acid copolymer. But mixtures of these copolymers can be used. Particular preference is given to polymers which have a high degree of self-crosslinking. But not self-Po ^¬ mers are suitable.

In a particular embodiment of the invention, the impregnating resin solution used to prepare the prepreg according to the invention contains an ethyl-free styrene-acrylic ester.

The ratio starch / polymer latex in the impregnating resin solution ^¬ is preferably 80/20 to 20/80, forthcoming However, a quantity ratio of 45/55 to 65/35 and in particular 50/50 to 60/40, in each case based on the mass of the impregnating resin (atro), is added.

In a further embodiment of the invention, the impregnating resin solution contains pigments and / or fillers. The amount of the pigment and / or filler may be from 1 to 30% by weight, in particular from 2 to 20% by weight. The quantity refers to the binder mass (atro). The term binder is understood to ^{mean the} mixture containing the polymer latex and the modified starch.

The impregnating resin solution used for producing the prepregs according to the invention has a total solids content ^¬, based on the dry mass of from 9 to 40 wt.%, Preferably 20 to 35 wt.% And especially preferably 26 to 30 wt.%.

In the preparation of the impregnating resin solution, the starch is first set, either cold that is dissolved at room temperature to a maximum of Tempe ^¬ 60 ⁰ C in the water or is cooked at about 120 to 145 ⁰ C. In this case, an about 40 to 45% suspension with a pH of about 5 to 6 is generated. In the next step, the addition of about 50% is carried out taking into ^¬ supply of the desired solids content and the Mengenver ^¬ holds isses starch / latex weight La ^¬ tex dispersion at a pH value of 5 to 10. In a further step, a pigment made or filling material ^¬ addition. The decorative base papers to be impregnated are those which have undergone neither a sizing in the mass nor a Oberflächenlei- mung. They consist essentially of pulps, pigments and fillers and conventional additives. Typical additives may be wet strength agents, retention aids and fixatives. Divorce decorative base paper under ^¬ to sizing usual papers by the much higher filler or pigment content and the lack of a usual in paper sizing or surface.

The invention to be impregnated base paper may contain egg ^¬ nen high proportion of a pigment or a filler. The proportion of the filler in the base paper can be up to 55% by weight, in particular 8 to 45% by weight, based on the weight per unit area. Suitable pigments and fillers are for example titanium dioxide, talc, zinc sulfide ^¬, kaolin, alumina, calcium carbonate, corundum, aluminum and magnesium silicates or mixtures thereof.

The pulps used for the manufacture of the base papers Na ^¬ delholzzellstoffe (long fiber pulps) and / or deciduous wood pulps ^¬ (short fiber pulps) may be used. The use of cotton fibers and mixtures thereof with the aforementioned types of pulp can also be used. For example, a mixture of softwood / hardwood pulps in the ratio of 10:90 to 90:10, in particular 20:80 to 80:20, is particularly preferred. But also the use of 100% by weight hardwood pulp has proven to be advantageous. The quantities are based on the mass of the pulps (atro). Preferably, the pulp mixture may contain a proportion of cationically modified pulp fibers of at least 5% by weight, based on the weight of the pulp mixture. A proportion of 10 to 50% by weight, in particular 10 to 20% by weight, of the cationically modified pulp in the pulp mixture has proved to be particularly advantageous. The cationic modification of the cellulose fibers can be carried out by reaction of the fibers with an epichlorohydrin resin and a tertiary amine or by reaction with quaternary ammonium chlorides such as chlorohydroxypropyltrimethylammonium chloride or glycidyltrimethylammonium chloride. Cationically modified pulps and their preparation are known for example from DAS PAPIER, Issue 12 (1980) p.575-579.

The base papers can be on a Fourdrinier paper machine or a Yankee paper machine Herge ^¬ provides. For this purpose, the pulp mixture can be ground at a consistency of 2 to 5 wt.% To a freeness of 10 to 45 ⁰ SR. In a mixing vessel, the fillers such as titanium dioxide and talcum, and wet ^¬ solid can be added and mixed well with the pulp mixture. The thick stock thus obtained can be up to a consistency of about 1% and diluted as far erfor ^¬ sary further auxiliaries such as retention agents, defoamers Ent ^¬, aluminum sulphate and other auxiliary agents mentioned above can be admixed. This thin material is fed to the wire section via the headbox of the paper machine. It is formed and the base paper obtained by Entwäs ^¬ provement a nonwoven fabric, which is subsequently dried. The basis weights of Papie ^¬ re produced may be 15 to 300 g / m ² . Particularly suitable However, are base papers with a basis weight of 40 to 100 g / m ² .

The application of the impregnating resin solution to be used according to the invention can be carried out in the paper machine or offline by spraying, impregnating, roller application or brushing (doctor blade). Particularly preferred is an order for size presses or film presses.

The impregnation of the impregnated papers is carried out in the usual way with the aid of IR or drum dryers in a temperature range from 120 to 180 ^° C. up to a residual moisture content of 2 to 6%.

After drying, the thus impregnated papers may (pre- impregnates) be printed and lacquered and be laminated to ^¬ closing by conventional methods on different sub ^¬ strate, such as chipboard or fibreboard.

The following examples serve to further illustrate the invention. Data in percent by weight relate to the weight of the pulp, unless otherwise indicated ^¬ . Quantity ratio means ratio of masses or weight ratio.

Examples

example 1

A pulp suspension was prepared by mixing a pulp mixture of 80% by weight of eucalyptus pulp and 20% by weight of pine sulfate pulp at a pulp density of 5 % to a freeness of 33 ⁰ SR (Schopper-Riegler) was ground. Subsequently, 1.8% by weight of epichlorohydrin resin was added as a wet strength agent. These cell ^¬ pulp suspension was adjusted with aluminum sulphate to a pH of 6.5. Thereafter, a mixture of 30% by weight of titanium dioxide and 5% by weight of talc, 0.11% by weight of a retention aid and 0.03% by weight of an antifoam was added to the pulp suspension and a decorative base paper having a basis weight of about 50 g / m ² and an ash content of about 23% by weight. The Gewichtsanga ^¬ ben refer to the weight of the pulp (absolutely dry).

This base paper was obtained in a size press with an aqueous resin solution of about 25th% solids content, containing modified starch C-FiIm 07324 (starch I, table 1) and n-butyl acrylate-styrene copolymer (Acronal ^® S 305 D) in a proportion of 80 20 on both sides in pregnated ^¬. For this purpose, first a 45% starch formulation was prepared and diluted with water to a concentration of 25 wt.%. Then the appropriate amount of the 50% aqueous polymer dispersion was added and the resulting polymer solution was diluted to a solids content of 25% by weight with water.

The impregnated paper was then dried at a temperature of about 12O Tem ^¬ ⁰ C to a residual moisture content of 2.5%. The order amount after drying was 10 g / m ² . At game 2

The raw paper from Example 1 was purified by size press with an aqueous resin solution containing modified starch I and n-butyl acrylate-styrene copolymer (Acronal ^® S 305 D) in a proportion of 60:40, impregnated with three Various ^¬ NEN order quantities. The solids content of the resin solution was 26% by weight.

The impregnated papers were then dried at a temperature of about 12O ⁰ C to a residual moisture content of 2.5%. The application rates after drying were 7 g / m ² (Example 2A), 10 g / m ² (Example 2B) and 14 g / m ² (Example 2C).

Example 3

The raw paper from Example 1 was blended by means of a size press with an aqueous resin solution having a solids content of 27.% Impregnating the modified starch I and n-butyl acrylate-styrene copolymer (Acronal ^® S 305 D) in a proportion of 50:50.

The impregnated paper was then dried at a temperature of about 12O Tem ^¬ ⁰ C to a residual moisture content of 2.5%. The order amount after drying was 10 g / m ² .

Example 4

The raw paper from Example 1 was blended by means of a size press with an aqueous resin solution having a solids content of 25.% Impregnating the modified starch I and n-butyl acrylate-styrene copolymer (Acronal ^® S 305 D) in a ratio of 20:80.

The impregnated paper was then heated at a temperature of about 12O Tem ^¬ ⁰ C to a residual moisture content of 2.5% dried. The order amount after drying was 10 g / m ² .

Example 5

The raw paper from Example 1 was blended by means of a size press with an aqueous resin solution having a solids content of 25.% Impregnating the modified starch C-FiIm 07311 (starch II, s. Table 1) and n-butyl acrylate styrene copolymer (Acronal ^® S 305 D ) in a quantity behaves ^¬ nis of 60:40.

Example 6

The raw paper from Example 1 was blended by means of a size press with an aqueous resin solution having a solids content of 25.% Impregnating the modified starch C-FiIm 07302 (thickness III, s. Table 1) and n-butyl acrylate styrene copolymer (Acronal ^® S 305 D ) in a quantity behaves ^¬ nis of 60:40.

Example 7

The raw paper from Example 1 was purified by size press with an aqueous resin solution containing a modified starch I and a hydrophobized styrene-butyl acrylate copolymer (B Cartacoat ^® 641) in a quantitative ratio of 60:40, impregnated. The solids content of the resin solution was 26% by weight. The impregnated paper was dried subsequently ^¬ ßend at a temperature of about 12O ⁰ C to a residual moisture content of 2.5%. The order amount after drying was 10 g / m ² .

Example 8

The raw paper from Example 1 was purified by size press with an aqueous resin solution containing modified starch I and a styrene-n-butyl acrylate copolymer (Acronal ^® S 305 D) is present in a quantitative ratio of 60:40, and titanium di ^¬ oxide in an amount of 15 .% (Based on the binder content (atro)), impregnated. The solid content of the resin solution was 28% by weight. The impregnated paper was then dried at a temperature of about 12O ⁰ C to a residual moisture content of 2.5%. On ^¬ amount applied after drying was 10 g / m ^2.

Comparative Example VI

The raw paper from Example 1 was purified by size press with an aqueous resin solution containing a dextrin (s. Table 1) and n-butyl acrylate-styrene copolymer (Acronal ^® S 305 D) in a proportion of 60:40, impregnated. The solids content of the resin solution was about 26% by weight. The impregnated paper was then dried at a temperature of about 12O Tem ^¬ ⁰ C to a residual moisture content of 2.5%. The order amount after drying was 10 g / m ² .

Comparative Example V2

The base paper from Example 1 was size-reduced with an aqueous resin solution containing modified starches. ke C-FiIm 07380 (starch IV, s. Table 1) and styrene-butyl acrylate copolymer (Acronal ^® S 305 D) in a proportion of 60:40, impregnated. The solids content of the resin solution was about 26% by weight.

Comparative Example C3

The raw paper from Example 1 was purified by size press with an aqueous resin solution containing polyvinyl alcohol (Mowiol ^® 4-98) and styrene-butyl acrylate copolymer (Acronal ^® S 305 D) in a proportion of 20:80, impregnating ^¬ defined. The solid content of the resin solution was about 27% by weight.

The following Table 2 shows the results of the tests of the papers treated according to the invention in comparison with the prior art. The following properties were checked:

z-strength (as a measure of the interlaminar strength) The z strength thereof (tensile strength) perpendicular to the paper surface was ^¬ by TGL 25290/11 (Institute of Techno logy ^¬ the EPH in Zurich), a standard for decorative papers method determined. For this purpose, specimens with a diameter of 20 mm were first punched out of the prepreg to be tested and placed individually between two cylinder Surfaces brought and glued to these surfaces and cured. The test specimens thus produced were mounted in the holder perpendicular to the film plane is ^¬ and subjected to an increasing load until it breaks. The tensile strength was calculated as follows: σ ~ IB = F _max / A σ «IB - tensile force perpendicular to the film plane in

MPa (N / mm ² )

F max - force at test specimen break in NA - specimen area in mm ² (314 mm ² at d = 20mm)

printability

The visual evaluation was carried out according to the reference catalog,

Grades: 1 (very good) to 6 (very bad)

Paint booth (visual evaluation)

The evaluation was conducted by the comparison with the prior art (prepreg from Arjo Wiggins, comparative example ^¬ 3). For this purpose, the pre-impregnate samples were coated with an SH coating (SH primer / water-resistant, paint with built-in acid hardener) customary for this purpose in an amount of 12 g / m ² . The lacquered surfaces were then evaluated in oblique light and compared with each other.

Yellowing (determination Δb value)

The yellowness index was determined according to DIN 6167. It indicates the change in yellowness of a sample under the influence of temperature during a certain period of time. It is the difference between the so-called yellow values Δb of the treated and untreated sample. The b-values were measured with the colorimeter SF 600 (Datacor- lor) at D65 10 °.

As apparent from Table 2, the invention ^shown SEN prepregs to a higher strength in the z-direction and better printability. The yellowing behavior, in particular at elevated temperatures, is likewise improved in the case of the prepregs according to the invention. The paint level is better or comparably good compared to the usual prepregs.

Table 1 Modified starches

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Table 2 Test results

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Claims

PATENT APPLICATIONS

1. pre-impregnate, which is obtainable by impregnating a decorative base paper with a Tränkharzlösung, characterized in that the Tränkharzlösung contains at least one polymer latex and at least one modi ^¬ fected starch having a polydispersity index of 6 to 23.

2. A prepreg, obtainable by impregnating a decorative base paper with an impregnating resin, characterized in that the impregnating resin comprises at least one polymer latex and at least one modi ^¬ fied starch having a specific Molekularge ^¬ weight distribution, wherein the Molekularge ^¬ weight of the starch molecules distributed as follows: at most 6 wt.% of molecules having a molecular weight of 0 ^¬ to 1000 g / mol,

5 to 20 wt.% Of molecules having a Molekularge ^¬ weight of 1,000 to 5,000 g / mol, 20 to 40 wt.% Of molecules having a molecular weight of 5,000 to 25,000 g / mol, 20 to 45 wt.% Of molecules having a molecular weight of , 5 to 22 wt 25,000 to 200,000 g / mol% molecules with a Molekularge ^¬ weight from 200,000 to 1,000,000 g / mol, -. 0.5 to 5% by weight of molecules having a molecular weight of more than 1,000,000 g / cc. mol.

3. Vorimprägnat according to any one of claims 1 and 2, characterized in that the polymer latex is a styrene- (meth) acrylic acid ester copolymer.

4. Vorimprägnat according to one of claims 1 to 3, characterized in that the polymer latex is a styrene rol-butyl acrylate.

5. Vorimprägnat according to one of claims 1 to 4, characterized in that the quantitative ratio of starch ^¬ ke / polymer latex 20/80 to 80/20, based on the Mas ^¬ se of the impregnating resin (atro), is.

6. Vorimprägnat according to claim 5, characterized in that the ratio of 45/55 to 65/35, based on the mass of the impregnating resin (atro), is.

7. Vorimprägnat according to one of claims 1 to 6, characterized in that the impregnating resin solution contains 1 to 30 wt.% Of a pigment and / or filler, based on the binder composition (atro).

8. Vorimprägnat according to claim 7, characterized in that the pigment may be titanium dioxide, kaolin, bentonite and / or calcium carbonate.

9. Vorimprägnat according to one of claims 1 to 8, characterized in that the impregnating resin solution has a solids content of 9 to 40 wt.%.

10. Vorimprägnat according to one of claims 1 to 9, characterized in that the amount of the impregnating resin is 10 to 35% of the basis weight of Dekorohpapier.

11. decorative paper or decorative coating material, obtainable from a pre-impregnate according to one of claims 1 to 10.