EP1036881B1 - Base paper for decoration having improved dry strength - Google Patents

Abstract

The raw lamination paper is composed of cellulose fibers and filling materials from a paper mass of a cellulose mixture containing an unmodified and a cationic modified cellulose. The modified cellulose has a cation charge of 20-300 mmol/kg. The cellulose fibers are modified with a quaternary ammonium compound with a glycidyl function. The cationic modified cellulose forms at least 5 wt% of the cellulose mixture, using a short fiber cellulose for modification. The paper mass contains a wet strength agent in a vol. of 0.3-2.0 wt% of the cellulose. The filling material is titanium oxide, calcium carbonate, kaolin, talcum or a mixture of them.

Description

The invention relates to a decorative base paper and under Using the same produced decorative films or decorative laminates.

Decorative coating materials, so-called Decorative papers or decorative films, are preferably for Surface coating in furniture manufacturing and in the Interior fitting used. Under decorative film is understood a resin impregnated or resin impregnated and surface treated, printed or unprinted Paper web. Decorative foils are provided with a carrier plate glued or glued.

Depending on the type of impregnation one differentiates between decorative films with impregnated paper core and prepreg-based decorative films in which the Paper in paper machine on-line only partially is impregnated. Laminates (High Pressure Laminates) are laminates made by pressing several impregnated, stacked papers arise. The structure of these laminates consists in general from a highest surface resistance generating transparent overlay sheet (overlay), a resin-impregnated decorative paper and a phenolbeharztem Kraft paper. As a basis for this example Hardboard and chipboard as well as plywood used.

In the case of the laminates (low pressure laminates) produced by the short-cycle method, the decorative paper impregnated with synthetic resin is pressed directly with a base, for example a chipboard, using a low pressure.
The decorative paper used in the above-mentioned coating materials is used white or colored with or without additional imprint.

To so-called decorative base papers as starting materials for Production of the above-mentioned coating materials special requirements are made such as high opacity for better coverage of the pad, even Formation and grammage of the sheet for a uniform Resin absorption, high light resistance, high purity and uniformity of color for good Reproducibility of the pattern to be printed, high Wet strength for a smooth impregnation process, appropriate absorbency to obtain the required resin saturation, dry strength, in Umrollvorgängen in the paper machine and the Printing in the printing press.

Decorative base papers generally consist of highly white Sulphate pulps, mainly of hardwood pulp, to 45% pigments and fillers and wet strength agents, Retention aids and fixatives. decorative base paper differ from usual papers by the very much higher filler content and the absence of a Paper with standard sizing or surface sizing with the known sizing agents such as alkylketene dimers.

Opacity is one of the most important properties of Decorative base. This characterizes the opacity opposite the pad. To secure sufficient Opacity become the pulp fillers in high quantities added. To ensure good retention of the fillers in the sheet to reach the paper pulp are different Retention agent added. On the other hand, with rising Pigment content and filler content deteriorate the Strength and the impregnation behavior of the paper.

The strength of the decorative base paper, especially the Dry strength, but is for further processing, during transport through the printing press or at Rewinding processes in the paper machine important.

When using water-soluble resin systems for Imrägnierung of decorative papers is the wet tensile strength of great importance. Under wet tensile strength is the mechanical resistance in the wet state too understand. It becomes common in papermaking influenced by the addition of wet strength agents.

Because it is difficult to put those on decorative base papers Meeting requirements simultaneously are well known Decorative base papers can still be improved. this applies especially with regard to the properties of opacity and strength of the base paper.

US 4 505 775 relates to the production of cationic cellulose and its use in the Papermaking. By the cationic cellulose becomes the retention of dyes and fillers, in particular organic additives, in papermaking improved.

DE 197 28 796 A1 describes a paper for decorative Surfaces with a pigment content of 2 to 3% by weight, provided on the surface with a varnish layer and is glued to a workpiece. This paper had one Experience engine sizing and is considered an alternative to thought of classic decorative papers or decorative films.

The object of the invention is therefore, a decorative paper with high mechanical strength, high opacity and sufficient absorbency (impregnation ability) provide.

This task is solved by a decorative base paper, the from a pulp fiber and filler containing Paper pulp is formed, the pulp a Pulp mixture of a non-modified and a contains cationically modified pulp and the cationically modified pulp is an effective cationic charge of 20 to 300 mmol / kg and in the pulp mixture in an amount of at least 5% by weight is included.

Surprisingly, an improvement in the Dry strength noted, although the Paper suspension no dry strength agents were added. Other important features of the Decorative base paper such as impregnating ability or opacity be prepared by adding the cationically modified Pulp not affected.

Cationically modified pulps are for example from THE PAPER, Issue 12 (1980) p.575-579. their Use in decorative base papers and the resulting Strength increase can not be done in the prior art remove. Particularly advantageous is a proportion of 10 to 50 wt.%, In particular 10 to 20 wt.% Of the cationic modified pulp in the pulp mixture proven.

In a particular embodiment of the invention, the in the pulp cationically modified Pulp has an effective cationic charge of 20 to 300 mmol / kg pulp, determined by the internal method No. 4 of the TU Darmstadt. Preference is given to pulp fibers with a charge density of 30 to 200 mmol / kg, in particular 30 to 100 mmol / kg. Under the term effective cationic charge "is a charge density too understand that with the charge density of not cationized pulp was calculated. The Density of pulp depends on the amount of pulp to be used cationic agent. The amount of cationizing agent may be 0.005 to 200 g / 1 kg Pulp amount.

The cationic modification of the pulp fibers can by reaction of the fibers with epichlorohydrin and a tertiary amine or by reaction with quaternary ammonium chlorides, such as Chlorohydroxypropyltrimethyl-ammonium chloride or Glycidyltrimethyl ammonium chloride.

Furthermore, the cationization of the pulp fibers by radical grafting of charged monomers, for example [2- (methacryloyloxy) ethyl] trimethyl ammonium chloride (TMAEMA) with neutral comonomers such as acrylamide respectively.

In a preferred embodiment of the invention Pulp fibers used by a Addition reaction of quaternary, glycidylfunktionelle Group containing ammonium compounds with Hydroxyl groups of the cellulose cationically modified are.

The unmodified pulp and the cationic modified pulps are preferably short fiber pulps with a mean fiber length of 0.5 to 0.7 mm, but also long-fiber pulps or blends Both types of pulp can be used. Short fiber pulps are, for example, hardwood pulps of aspen, beech or eucalyptus, of which last is particularly preferred. The pulp has preferably a freeness of 30 to 45 ° SR.

Suitable fillers are, for example, titanium dioxide, in particular of the rutile type, zinc sulfide, calcium carbonate, kaolin, talc or mixtures thereof. Particularly preferred is a rutile type titanium dioxide surface treated with Al ₂ O ₃ . The proportion of the filler in the decorative base paper can be up to 55% by weight, in particular 20 to 45% by weight.

As a wet strength agent can melamine / formaldehyde resins, Polyamine derivatives or polyamide derivatives in amounts of 0.3 up to 2% by weight, based on the weight of the pulp, be used.

The decorative paper may contain other substances such as organic and inorganic colored pigments, dyes, optical brighteners and dispersants used in the preparation of the decorative base paper added to the paper suspension become.

The decorative base papers according to the invention are produced in a known manner in a paper machine in a grammage range of 50 to 200 g / m ² . For this purpose, the pulp mixture of cationically modified pulp and unmodified pulp at a pulp density of 2 to 4 wt.% Milled to a freeness of 30 to 45 ° SR. In a mixing chest, filler and wet strength agent are added and mixed well with the pulp mixture. The thick stock thus obtained is diluted to a stock consistency of about 1% and, if necessary, further auxiliaries such as retention aids, defoamers, aluminum sulfate and, optionally, wet strength agent admixed. This thin material is fed to the wire section via the headbox of the paper machine. It is formed a nonwoven fabric and obtained after dewatering the decorative base paper, which is then dried.

For the production of decorative papers, the Decorative base papers with customary for this purpose Resin dispersions impregnated or impregnated. For this purpose are common synthetic resin dispersions for example, those based on polyacrylic or Polyacrylmethyl esters, polyvinyl acetate, polyvinyl chloride or synthetic resin solutions based on phenol / formaldehyde, Urea / formaldehyde or melamine / formaldehyde precondensates or their compatible mixtures.

The impregnation can also be done in the size press of the Paper machine done. The decorative paper can be so be impregnated, that the paper is not complete is impregnated by. Such decorative papers are also referred to as prepregs. The proportion of in the Decorative base paper by impregnation of incorporated resin is in this case 25 to 30 wt.%, Based on the Weight of the paper.

After drying, the soaked papers can still be painted and printed and then on a Substrate can be applied as a wooden board. The lacquered and optionally printed products generally referred to as decorative films.

The invention will be further elaborated in the following examples explained. Data in percent by weight refers to the weight of the pulp, if nothing else is specified.

example 1

A pulp mixture of 16.7% by weight of glycidyl trimethyl ammonium chloride (Quab® 151) modified eucalyptus pulp having a charge density of 34.8 mmol / kg and 83.3% by weight of a standard eucalyptus pulp having an average fiber length of 0.7 mm was ground at a stock density of 3% to a freeness of 33 ° SR. 100% by weight of TiO ₂ (rutile, d = 3.9 g / m ³ ) and 2% by weight of polyamide / polyamine-epichlorohydrin resin were then added to the pulp suspension and a base paper having a basis weight of 97 g / m ^{2 was} produced therefrom.

Example 2

A pulp blend of 50% by weight of a glycidyl trimethyl ammonium chloride modified eucalyptus pulp with a charge density of 34.8 mmol / kg and 50% by weight of a standard eucalyptus pulp was milled at a stock consistency of 3% to a freeness of 33 ° SR. The pulp suspension, the other substances were added as in Example 1 and made from a base paper with a basis weight of 95 g / m ² .

Example 3

A pulp mixture of 16.7% by weight of glycidyl trimethyl ammonium chloride (Quab® 151) modified eucalyptus pulp having a charge density of 65.5 mmol / kg and 83.3% by weight of a standard eucalyptus pulp was used at a consistency of 3% to milled to a freeness of 38 ° SR. The pulp suspension was then added to the other materials as in Example 1 and made of base paper with a basis weight of 95 g / m ² .

Example 4

A pulp mixture of 16% by weight of a modified by 3-chloro-2-hydroxypropyldimethyldodecyl-ammonium chloride (Quab® 342) eucalyptus pulp with a charge density of 56.5 mmol / kg and 84 wt.% Of a standard eucalyptus pulp was at a consistency of 3 % ground to a freeness of 39 ° SR. The pulp suspension was then added the further materials as in Example 1 and made from a 95 g / m ² heavy paper.

Example 5

A pulp mixture of 16.7% by weight of a 2- (methacryloyloxy) ethyltrimethylammonium chloride and acrylamide-modified eucalyptus pulp having a charge density of 153.7 mmol / kg and 83.3% by weight of a standard eucalyptus pulp was prepared according to Example 1 and processed with the same materials (pigment and wet strength agent) to a base paper with a basis weight of 96 g / m ² .

Comparative example

A pulp suspension of 100% by weight of standard eucalyptus pulp having a consistency of 3% and a degree of pulp grinding of the pulp fibers of 36 ° SR was added to the materials of Example 1 and a base paper having a weight per unit area of 94 g / m ^{2 was} produced therefrom.

Testing according to the examples and the Comparative Example produced decorative base papers

To evaluate the manufactured decorative base papers were the following test methods are used:

Measurement of cationic charge in the pulp

The determination is made in accordance with Internal Method No.4 the TU Darmstadt. The for determination of cationic groups developed in pulps measuring method is a colorimetric method. The colorimetric method uses dye ions of the dye methyl orange for Neutralizing the charges in and on the fiber. The used solution thereby depleted of dye ions. This Concentration decrease is in a UV spectrometer detected. The amount of cationic groups adsorbed methyl orange is calculated from the Difference in the blank colorimetrically determined and colorimetrically in the sample supernatant determined amount of methyl orange. The content of cationic groups are given in mmol / kg pulp.

Resin absorption [%]

The purpose of the test is to assess the ability of one Decor paper to include a melamine resin. For this purpose were 2 test strips (15 x 100 mm) in melamine resin MW 550 dipped, over a flat area between two strips Blotting paper laid, with a coating weight 15 s long burdened and then weighed back. The calculation The resin absorption takes place in% of the weight.

opacity

The opacity is a measure of the light transmittance of the Paper. It was sized on paper test strips 8 x 8 cm using the Elrepho 2000 colorimeter measured.

Dry tensile strength

This test serves to determine the tensile strength and the extensibility of raw papers. She will Paper strip 15 x 200 mm in the train inspector of the company Lorentzen & Wettre according to DIN 53112 performed. The values are specified in N. The higher the number, the better is the dry strength.

wet breaking load

This test is used to assess the wet strength of the Raw papers carried out. For this purpose, test strips of 15 mm width in distilled water for 5 minutes immersed. Subsequently, the wet strips were in a tensile tester to its wet tensile load tested. The Measured values are given in N. The lower the Numerical value, the worse the wet strength.

ash content

1 g of paper in strip form is conditioned for at least 30 minutes at 23 ° C./50% relative humidity and then introduced into the ashing device and ashed. The ash is transferred to a porcelain crucible and weighed. The ash in% results from the weight in gx 100. The ash content can be converted into g / m ² .

The test results are summarized in Table 1. exam Examples comparison 1 2 3 4 5 Dry breaking load, N 30.0 32.0 29.6 25.1 29.6 24.4 Wet fracture load [N] 6.1 6.0 4.8 4.8 6.1 6.1 Ash content [g / m ² ] 33.2 34.0 32.4 32.0 32.4 32.0 Opacity [%] 91.4 91.0 91.7 91.4 91.0 91.1 Resin absorption [%] 85.5 85.5 84.6 84.8 85.0 85.4

The results show that the dry strength of the Decorative base papers by using cationic modified Pulp is improved, taking on the additional Use of dry strength agent can be dispensed with can. Impregnation ability and opacity of Decorative base papers according to the invention are very good. Also an improved retention of the filler used could be observed.

The deterioration observed in some experiments wet strength can be increased by increasing the proportion of Wet strength agent or by adding anionic substances be brought to the desired level.

Claims (4)

1. A decorative paper base formed out of paper pulp containing pulp fibers and filler, characterized by the fact that the paper pulp contains a pulp mixture comprised of a non-modified and a cationically modified pulp and that the cationically modified pulp exhibits an effective cationic charge of 20 to 300 mmol/kg and that the share of cationically modified pulp in the pulp mixture measures at least 5 wt.%.
2. A decorative paper base according to one of claims 1 to 4, characterized by the fact that the cationically modified pulp is a short-fiber pulp.
3. A decorative paper base according to one of claims 1 to 2, characterized by the fact that the filler is titanium dioxide, calcium carbonate, kaolin, talcum or a mixture thereof.
4. A decorative paper or decorative film, containing a decorative paper base according to one of claims 1 to 3.