EP1036881A1 - 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 Use of the same made decorative films or decorative laminates.

Decorative coating materials, so-called Decorative papers or decorative films are preferably used Surface coating in furniture manufacturing and in Interior fittings used. Decorative foil is understood a resin-impregnated or resin-impregnated and surface treated, printed or unprinted Paper web. Decorative films come with a backing plate glued or glued.

A distinction is made depending on the type of impregnation process between decorative foils with impregnated paper core and pre-impregnated decorative foils, where the Paper in the 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 producing transparent overlay, one resin-soaked decorative paper and a phenolic resin Kraft paper. As a basis for this, for example Hardboard and chipboard as well as plywood used.

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

On so-called decorative base papers as starting materials for Manufacture of the above coating materials there are special requirements such as high opacity for better coverage of the underlay, even Formation and grammage of the sheet for an even 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 degree of resin saturation, dry strength, which during rewinding operations in the paper machine and at Printing in the printing press.

Decorative base papers generally consist of bright white Sulphate pulps, mainly from hardwood pulp, up to 45% pigments and fillers as well as wet strength agents, Retention aids and fixatives. Decorative base papers differ from usual papers by the very much higher filler content and the lack of one when Paper with normal mass sizing or surface sizing the known sizing agents such as alkyl ketene dimers.

Opacity is one of the most important properties of the Decorative base paper. This characterizes the covering ability towards the document. To ensure sufficient The fiber is filled with fillers in large quantities added. For good retention of the fillers in the sheet To achieve this, the pulp will be different Retention agent added. On the other hand, with increasing The pigment content and filler content deteriorate 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 operations important in the paper machine.

When using water-soluble resin systems for Impregnation of decorative papers is the wet tear resistance of great importance. That is under wet tensile strength mechanical strength when wet understand. It becomes common in papermaking influenced by the addition of wet strength agents.

Because it is difficult to apply the decorative raw paper Meeting requirements at the same time are known Decorative base papers can still be improved. this applies especially with regard to the properties of opacity and strength of the base paper.

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

This task is solved by a decorative base paper, the from a cellulose fiber and filler containing Paper pulp and, if necessary, customary aids is formed and a mixture of cellulose fibers unmodified and cationically modified Contains pulp.

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

Cationically modified pulps are for example known from DAS PAPIER, Issue 12 (1980) p.575-579. Their Use in decorative base papers and the resultant Strength increase can not be the prior art remove.

The pulp mixture preferably contains a proportion of cationically modified cellulose fibers of at least 5 % By weight, based on the weight of the pulp mixture, contains. A portion has proven to be particularly advantageous from 10 to 50% by weight, in particular 10 to 20% by weight, of cationically modified pulp in the pulp mixture proven.

wirksame kationische Ladung" ist eine Ladungsdichte zu verstehen, die mit der Ladungsdichte des nicht kationisierten Zellstoffs verrechnet wurde. Die Ladungsdichte des Zellstoffs hängt von der Menge des einzusetzenden kationischen Mittels ab. Die Menge des kationisierenden Mittels kann 0,005 bis 200 g/1 kg Zellstoff betragen.In a particular embodiment of the invention, the cationically modified cellulose contained in the paper pulp has an effective cationic charge of 20 to 300 mmol / kg cellulose, determined according to the internal method No. 4 of the TU Darmstadt. Cellulose fibers with a charge density of 30 to 200 mmol / kg, in particular 30 to 100 mmol / kg, are preferred. Under the term

effective cationic charge "is understood to mean a charge density which has been offset against the charge density of the non-cationized pulp. The charge density of the pulp depends on the amount of the cationic agent to be used. The amount of the cationizing agent can be 0.005 to 200 g / 1 kg of pulp .

The cationic modification of the pulp fibers can by reaction of the fibers with epichlorohydrin and a tertiary amine take place or by reaction with quaternary ammonium chlorides, such as Chlorhydroxypropyltrimethyl ammonium chloride or Glycidyl trimethyl ammonium chloride.

The cationization of the pulp fibers can also be carried out 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, glycidyl-functional Groups containing ammonium compounds with Hydroxyl groups of cellulose modified cationically are.

The unmodified pulp and the cationic modified pulp are preferably short fiber pulps with an average fiber length of 0.5 to 0.7mm, 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 the latter 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. A rutile-type titanium dioxide surface-treated with Al ₂ O ₃ is particularly preferred. The proportion of the filler in the decorative base paper can be up to 55% by weight, in particular 20 to 45% by weight.

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 base paper can contain other substances such as organic and inorganic colored pigments, dyes, optical brighteners and dispersants included in the manufacture 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 from 50 to 200 g / m ² . For this purpose, the pulp mixture of cationically modified pulp and unmodified pulp with a consistency of 2 to 4% by weight is ground to a freeness of 30 to 45 ° SR. Filler and wet strength agent are added in a mixing chest and mixed well with the pulp mixture. The thick material obtained in this way is diluted to a consistency of about 1% and, if necessary, further auxiliaries such as retention aids, defoamers, aluminum sulfate and, if appropriate, wet strength agents are added. This thin material is fed through the headbox of the paper machine onto the wire section. A nonwoven fabric is formed and the decorative base paper is obtained after dewatering, which is then dried.

For the production of decor papers, the Decorative base papers with the usual for this purpose Impregnated or impregnated synthetic resin dispersions. For this purpose are conventional synthetic resin dispersions for example those based on polyacrylic or Polyacrylic methyl 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 Paper machine done. The decorative base paper can be such be impregnated that the paper is not complete is impregnated by. Such decorative papers are also known as pre-impregnates. The share of that in that Decorative base paper by impregnation of the resin in this case is 25 to 30% by weight, based on the Weight of the paper.

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

The invention is further illustrated in the following examples explained. Weight percentages refer to the weight of the pulp unless otherwise stated is specified.

example 1

A pulp mixture of 16.7% by weight of a eucalyptus pulp modified with glycidyltrimethylammonium chloride (Quab® 151) with a charge density of 34.8 mmol / kg and 83.3% by weight of a standard eucalyptus cellulose with an average fiber length of 0.7 mm was ground at a consistency 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 cellulose suspension and a base paper with a basis weight of 97 g / m ^{2 was} produced therefrom.

Example 2

A pulp mixture of 50% by weight of a eucalyptus pulp modified with glycidyltrimethyl ammonium chloride with a charge density of 34.8 mmol / kg and 50% by weight of a standard eucalyptus pulp was ground at a consistency of 3% to a freeness of 33 ° SR. The further substances were added to the cellulose suspension as in Example 1 and a base paper with a basis weight of 95 g / m ^{2 was} produced therefrom.

Example 3

A pulp mixture of 16.7% by weight of a eucalyptus pulp modified with glycidyltrimethylammonium chloride (Quab® 151) with a charge density of 65.5 mmol / kg and 83.3% by weight of a standard eucalyptus pulp was obtained with a consistency of 3% to ground to a freeness of 38 ° SR. The further substances were then added to the cellulose suspension as in Example 1 and raw paper with a basis weight of 95 g / m ^{2 was} produced therefrom.

Example 4

A cellulose mixture of 16% by weight of a eucalyptus cellulose modified with 3-chloro-2-hydroxypropyldimethyldodecylammonium chloride (Quab® 342) with a charge density of 56.5 mmol / kg and 84% by weight of a standard eucalyptus cellulose was obtained with a material density of 3 % ground to a freeness of 39 ° SR. The further substances were then added to the pulp suspension as in Example 1 and a 95 g / m ² paper was made therefrom.

Example 5

A cellulose mixture of 16.7% by weight of a eucalyptus cellulose modified with 2- (methacryloyloxy) ethyltrimethyl ammonium chloride and acrylamide with a charge density of 153.7 mmol / kg and 83.3% by weight of a standard eucalyptus cellulose was prepared in accordance with Example 1 and processed with the same substances (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 with a consistency of 3% and a degree of pulping of the pulp fibers of 36 ° SR was added to substances according to Example 1 and a base paper with a basis weight of 94 g / m ^{2 was} produced therefrom.

Checking according to the examples and the Comparative example produced decorative base papers

For the evaluation of the manufactured decorative base papers The following test methods were used:

Measurement of cationic charge in the pulp

The determination is made according to Internal Method No. 4 the TU Darmstadt. To determine cationic groups Measurement method developed in cellulose is a colorimetric method. The colorimetric method uses dye ions of the dye methyl orange to Neutralize the charges in and on the fiber. The used solution depletes of dye ions. This Decrease in concentration is in a UV spectrometer detected. The amount of by cationic groups adsorbed methyl orange is calculated from the Difference of colorimetric in the blank determined and that in the sample supernatant colorimetric determined amount of methyl orange. The content of cationic groups are given in mmol / kg pulp.

Resin absorption [%]

The purpose of the exam is to assess a person's ability Decor paper to incorporate a melamine resin. For this purpose 2 test strips (15 x 100 mm) in melamine resin MW 550 submerged, over a flat surface between two strips Blotting paper placed with a coating weight for 15 s loaded and then weighed back. The calculation the resin absorption takes place in% of the weight.

opacity

The opacity is a measure of the translucency of the Paper. It was on paper test strips of a size of 8 x 8 cm with the help of the Elrepho 2000 color measuring device measured.

Dry breaking load

This test is used to determine the tensile strength and the elasticity of base papers. It is on Paper strips 15 x 200 mm in the company's tensile tester Lorentzen & Wettre carried out according to DIN 53112. The values are given in N. The higher the numerical value, the better is the dry strength.

Wet breaking load

This test is used to assess the wet strength of the Raw papers carried out. Test strips from 15 mm wide in distilled water for 5 minutes immersed. Then the wet strips were in a tensile testing machine for its wet breaking load. 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 incinerated. The ashes are 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 2nd 3rd 4th 5 Dry breaking load, N 30.0 32.0 29.6 25.1 29.6 24.4 Wet breaking 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 cationically modified Pulp is improved, being on the additional Use of dry strength agents can be dispensed with can. Impregnability and opacity of the decorative base papers according to the invention are very good. Also an improved retention of the filler used could be observed.

The deterioration seen in some trials the wet strength can be increased by increasing the proportion Wet strength agents or by adding anionic substances brought to the desired level.

Claims (8)

Decorative base paper which is formed from a pulp containing pulp fibers and filler, characterized in that the pulp contains a pulp mixture of an unmodified and a cationically modified pulp. Decorative base paper according to claim 1, characterized in that the cationically modified cellulose has an effective cationic charge of 20 to 300 mmol / kg. Decorative base paper according to claim 1 or 2, characterized in that the cellulose fibers are modified with quaternary ammonium compounds with glycidyl function. Decorative base paper according to one of claims 1 to 3, characterized in that the proportion of the cationically modified cellulose in the cellulose mixture is at least 5% by weight. Decorative base paper according to one of claims 1 to 4, characterized in that the cationically modified cellulose is a short fiber cellulose. Decorative base paper according to one of claims 1 to 5, characterized in that the paper pulp contains wet strength agents in an amount of 0.3 to 2% by weight, based on the cellulose. Decorative base paper according to one of claims 1 to 5, characterized in that the filler is titanium dioxide, calcium carbonate, kaolin, talc or a mixture thereof. Decorative paper or foil containing a Decorative base paper according to one of claims 1 to 7.