EP0870872B1 - One-side impregnated printing paper support - Google Patents

Abstract

Laminating sheet consisting of base paper with pigment marking on the printing or varnishing side, which is impregnated from the other side of the paper with an impregnating resin. Preferably the pigment marking is applied in amounts of 1-8 g/m<2>; it contains 1-30 wt% melamine resin, urea resin, phenolic resin or glyoxal resin, and shows a pigment to binder ratio of (1:0.05)-(1:2.00) based on solid substance. The base paper shows a resin uptake of 5-30% of its wt., based on solid contents.

Description

The invention relates to pigment coated on one side Thin film based on prepregs.

Decorative films with a finish surface are decorative Surface materials for chipboard and MDF boards (medium density fibreboard) in furniture making. This Decorative films are soaked in synthetic resin or resin-impregnated and afterwards surface treated, decoratively printed or unprinted paper webs in one under pressure and warmth state that can no longer be reactivated. Depending on the type of Impregnation process is between thermosetting decorative films with fully impregnated core (off line process) and Decorative films based on pre-impregnated materials (online process) distinguished on which subsequently one Finish coating can be made. Consequently creates a decorative film that has a finished surface has.

Decorative films based on pre-impregnates already inside the paper machine, immediately after leaf formation, depending on a resin mixture of the area-related mass of the base paper more or less soaked. After drying, the paper needs to be or the film should be gap-proof so that the subsequent processing steps of the finish coating and lamination on appropriate supports there is no fiber separation within the decorative film.

By adding white or colored pigments the desired opacity and coloring become the paper pulp and possibly also lightfastness Pre-impregnated.

Pre-impregnates or decorative films with a mass per unit area of between 20 and 80 g / m ² are referred to as thin-film films. These thin-film films are usually characterized by good flatness and thus easy laminating, while the printability with water-based or solvent-based gravure inks only satisfies moderate demands due to the limited smoothability due to the synthetic resin content.

Also known are non-impregnated thin-film films, so-called Japanese papers, with mass per unit area between 20 and 50 g / m ² , which are increasingly being used as decorative surface materials.

In contrast to pre-impregnates, these contain white or dyed paper no or little Pigment components and therefore have untreated Condition only low opacity. That's just what they are able to limit the surface of chip and Cover MDF boards sufficiently. These Japanese papers have a very good internal strength and one-sided Smoothness out, which is a very good gravure printability and Enable paintability. On the other hand, they do not tend impregnated with synthetic resins, but only on the surface with an unpigmented polymer film treated Japanese papers during the lamination process Use mostly aqueous adhesives very strongly for Roll up on the edges. Generally common continuous process using roll lamination systems is therefore their fixation and drying on chipboard or MDF boards only possible with difficulty. The one with it covered plates can then also be used as easily as when using pre-impregnates edit, since the laminated paper only a short Fiber tear shows.

GB-A-1 455 461 relates to decorative laminates which are pigmented on the surface. To produce the surfaces, a non-impregnated paper is coated with a mixture of pigment and thermosetting resin, which is pressed under the influence of heat and pressure with other layers of paper soaked with thermosetting resin. According to a preferred embodiment, the paper provided with pigment on one side can be coated on the other side with a thermosetting resin. The basis weight of the paper to which the mixture of pigment and thermosetting resin is applied is 100 g / m ² .

DE-B-1 187 120 relates to a re-impregnated classic decorative base paper without a pigment coat, the base paper used having a weight per unit area of 150 g / m ² .

The object of the invention was therefore to provide thin-film films mass as low as possible to provide that with sufficient gap strength good flatness and equally good or even Faster roll lamination with aqueous adhesives exhibit, but also by a very good Characterize deep printability and paintability.

In addition, the thin film should be comparable area-related mass, if possible a higher one Lightfastness and opacity than normal Japanese papers and have better strengths than known pre-impregnates.

This task is solved by a thin film, those on the top of the paper, the print or Paint side, has a pigment coat and outgoing from the bottom, the lamination side, with a Impregnation resin is impregnated, the ratio of Pigment to binder in the pigment coat 1: 0.05 to 1: 2.00, based on the solid, and Resin absorption of the base paper 5 to 30% by weight, based on the raw paper weight.

For the production of the thin-film films according to the invention are pulp fiber mixtures with high absorbency and Strength, for example from eucalyptus pulp and Pine wood sulfate pulp. A Ground sizing is not essential and that Cellulose fiber mixture can vary depending on the desired Intended use contain white pigments or color pigments.

The pigment coating formed on one side of the thin film has a mass of 1 to 8 g / m ² , for example 3, 5 or 7 g / m ² . In a preferred embodiment, the ratio of pigment to binder in the pigment coat can be 0.05 to 1: 2 or 1: 0.08 to 1: 0.35, based on the solids content.

To produce the pigment coat, white pigments, such as kaolin, calcium carbonate, aluminum hydroxide, talc, Titanium dioxide or color pigments, such as iron oxide pigments, Carbon black, copper, aluminum, other metal pigments or organic color pigments used alone or in a mixture optionally with the addition of liquid dyes. The Pigment coat can be natural or synthetic Binders such as starch, polyvinyl alcohol, Carboxymethyl cellulose, polymer dispersions based of acrylic acid, acrylic acid ester, styrene, butadiene, Contain vinyl acetate or acrylonitrile. According to one In a preferred embodiment, the pigment line contains 1 up to 30% by weight, based on the pigment content, melamine resin, Urea resin, phenolic resin or glyoxal resin. usual Crosslinking agents and penetration aids can be in the Pigment line can be included.

The pigment line has barrier properties aqueous or solvent-containing substances, such as Varnishes and printing inks. To be as thin as possible Pigment lines a good smoothability and thus sufficient barrier properties are to be achieved flaky pigments, such as kaolin, aluminum hydroxide or talc is particularly preferred.

The lowering of the mass per unit area pigment-coated on one side according to the invention However, thin film films are limits with regard to the Strength and opacity of the decorative film set. On the one hand, by adding opacity-increasing, lightfast white or color pigments to the pulp mass, the opacity are increased, but what at the same time negatively affects paper strength. The The addition of dry and wet strength agents can do this negative influence on paper strength in some Reduce dimension. On the other hand, it is in the manufacture of colored paper is possible, partly or complete these pigments by aqueous dyes less light fastness to replace, since the Pigment coating has the disadvantage of lower light fastness such colored papers is able to compensate. By the Addition of, for example, anionic or cationic Direct dyes to the fiber material is the desired one Coloring of the paper achieved without loss of strength, but at the same time through the one-sided training Pigment coat still the opacity and lightfastness improved.

Aqueous can be used to impregnate the base paper Polymer dispersions based on the above Monomers and melamine, urea, phenol or Glyoxal resins and their mixtures with polymer dispersions be used. By adding a maximum of about ten parts by weight (solid) of white pigment Impregnating liquid can reduce the opacity of white pre-impregnates can still be increased. The resin intake can be 5 to 30 % By weight, based on the weight of the base paper, preferably 5 up to 15% by weight.

Furthermore, the impregnation mixtures can be further Auxiliaries, such as wetting agents, viscosity regulators, Non-stick and penetration aids, pigments, Dyes and defoamers can be added.

The pigment coat can preferably by means of so-called thin-layer technology within the Paper machine can be applied to the base paper. This procedure is described in Das Papier, 1991, Issue 10 A, p. V120-V124 and Wochenblatt für Papierfabrikation, 1993, Issue 10, pp. 390-393 and 1994, Issue 17, pp.671-676.

For the production of the invention Thin film has the so-called differential Coating style of driving proved to be particularly advantageous in "Wochenblatt für Papierfabrikation (1992) No. 6, S.198-205 ". When using this Application technology becomes thin on one side Pigment coat using the aforementioned Thin coating technology applied to the paper web and at the same time the other is impregnated Paper side in the roller nip (swamp formation).

The impregnation turns the paper structure into Depends on the later processing requirements measurable in its elasticity or brittleness / flatness changed. In addition, the invention is distinguished Decorative film with the impregnated paper back a fast and firm connection with the laminating chipboard or MDF board. This also contributes the physico-chemical surface design of the Thin film significantly.

The impregnated and surface-pigmented thin-film films can be smoothed on one side, with one on-line smoothing using a soft or machine calender Preserving the opacity of the paper as special has proven advantageous.

The one-sided pigment-coated Thin film based on prepregs have a sufficiently good flatness and Gap resistance and on the pigment-coated side very good printability and paintability. With Synthetic resin impregnated back of the paper allows a quick and easy gluing on Fiberboard.

The thin-film film according to the invention is also for other applications where paper backing is suitable excellent one-sided printability or Coatability with aqueous or solvent-based Media are desired and also very good ones Can be glued or laminated to the back of the paper with different substrate materials becomes. Examples include wall coverings, Poster materials and special cover papers for Called packaging.

The following examples illustrate the invention. All Quantities refer to the solid or Solids content unless otherwise stated.

example 1

A light brown colored base paper of 45 g / m ² with a fiber composition of 80% eucalyptus and 20% pine sulfate pulp without bulk sizing and with a filler insert of 25 was placed on an approximately 2.30 m wide paper machine with a machine speed of 400 m / min kg of titanium dioxide per ton of fibrous material produced and provided on one side with a clay pigment coat of high binder content of 3 to 4 g / m ² on a two-roll applicator (film press) using the differential coating method and impregnated on the back with a synthetic resin mixture of acrylic dispersion and urea resin. The resin absorption was about 10%, based on the weight of the base paper. The paper was then smoothed off line on one side on the pigment-coated side on a technical soft calender. The properties of the paper according to the invention achieved in this way are compared with the paper properties of conventional Japanese films and pre-impregnates of comparable mass per unit area and color.

The single-layer pigment-coated thin-film film according to the invention based on "pre-impregnate" of 45 g / m ² showed in the laboratory test compared to conventional furniture pre-impregnates of 53 g / m ² better printability in gravure printing and a higher gloss after coating with aqueous acrylate lacquer (9 g / m ² varnish application) on the pigmented paper top as well as a faster knocking away of the aqueous laminating adhesives (based on acrylate or urea) on the back of the paper (see also water absorption values). This suggests that the paper according to the invention can be better bonded / laminated to the fiberboard. The somewhat worse flatness should not have a negative impact on the laminating process. In contrast, the coverage of the fiberboard is somewhat poorer due to the lower ash content and the slightly lower opacity associated with it. In addition, the light fastness is worse.

Compared to conventional Japanese films, the thin film according to the invention a slightly better Printability in gravure, a significantly better one Paint level and faster knocking away of the adhesive on the back of the paper (improved stickability / laminability).

In addition, the cover of the fiberboard is due to the somewhat higher opacity of the paper according to the invention better. The light fastness is compared to the conventional one Japanese film light due to the surface pigmentation better.

Example 2

Analogously to Example 1, a white (bleached) base paper of 47 g / m ² with a fiber composition of 80% eucalyptus and 20% pine sulfate pulp and with a filler insert of 50 kg titanium dioxide per ton of fiber was produced on the paper machine and analogously to Example 1 Apply the pigment coating (clay) on one side using the "differential coating" method and impregnate on the back.

The paper was then used online of a soft calender smoothed.

Comparative example

Analogous to Examples 1 and 2, a white (bleached) base paper of 80 g / m ² with a fiber composition of 80% eucalyptus and 20% pine sulfate pulp and with a filler insert of 250 kg clay and 50 kg talc per t fiber was used on the paper machine manufactured. In contrast to the papers according to Examples 1 and 2, the paper stock was fully sized in size (resin size) in order to limit the penetration into the paper structure of the impregnating or coating compositions subsequently applied by means of the “differential coating” method.

In contrast to Examples 1 and 2, the one-sided pigment coating of the paper web with a Mixture of acrylic latex and urea resin in the Ratio 70:30 (solid) of 20% titanium dioxide on the total amount of latex / urea resin (solid) added were made.

The back of the paper web was, however, with a Latex / synthetic resin mixture analogous to Examples 1 and 2 partially impregnated. The impregnation resin absorption was therefore only 5% of the raw paper weight.

This paper, which is referred to as printing base paper and is slightly pigmented on the basis of “pre-impregnate”, was compared with the thin-film film according to the invention, which was pigment-coated on one side and impregnated on the back, in the same way as in Example 2, and customary 45 g / m ² Japanese paper and furniture pre-impregnates of 53 g / m ² .

• beste Bedruckbarkeit im Tiefdruck
• höchster Lackstand
• schnellstes Wegschlagen des Kaschierklebstoffes auf der Papierrückseite, d. h. beste Verklebbarkeit/Kaschierbarkeit mit anderen Materialien.

Again, the one-sided pigment-coated thin-film film based on pre-impregnate according to the invention proves qualitatively superior to the other papers with regard to the following properties:

• best printability in gravure printing
• highest paint level
• Fastest knocking away of the lamination adhesive on the back of the paper, ie best bondability / lamination with other materials.

In contrast, opacity and light fastness are compared usual prepregs and the printing base paper worse out.

The opacity must influence the influence of the higher mass per unit area of printing base paper become.

This connects the thin-film film according to the invention both the positive properties of conventional Pre-impregnated and as well as those of the Japanese papers.

Example 4

According to Example 1, a light brown colored base paper with a weight per unit area of about 45 g / m ^{2 was} produced, the coloring not being carried out using a liquid dye but using iron oxide pigments.

In contrast to Examples 1 to 3, the one-sided pigment coating of the paper web with a Mixture of styrene / butadiene latex and urea resin in the Ratio 25:75, based on the solids content of the twice the amount of clay (solid) based on the Total amount of latex / urea (solid) was added, performed.

The back of the paper web was, however, with the impregnated with the same latex / synthetic resin mixture as in the Examples 1 to 3. The impregnation resin absorption was 30% of the Raw paper.

In comparison to those according to Examples 1 and 2 manufactured paper, the paper stood out higher lightfastness (grade 3-4), higher opacity (93%) and higher brittleness with a 30% lower tear-through factor.

Example 5

A colored base paper with a basis weight of about 45 g / m ^{2 was} produced in accordance with Example 4. In contrast to Example 4, however, the one-sided pigment coating of the paper web was carried out with a mixture of acrylic latex and urea resin in a ratio of 90:10 (solid), to which about twice the amount of clay (solid) was added. The back of the paper web was impregnated with the same latex / synthetic resin mixture as in Examples 1 and 2.

The impregnation resin absorption was about 10% of the Raw paper.

Compared to the papers produced according to Examples 1, 2 and 4, the product has slightly better printability and varnishability and higher elasticity.

Claims (3)

1. A thin film with a basis weight between 20 and 80 g/m² comprising a raw paper with a pigment coating on the printing or lacquering side of the raw paper, which is impregnated with an impregnating resin starting from the side opposite the pigment coating, whereby the ratio of pigment to a binder in the pigment coating is 1:0,05 to 1:2,00, based on the solid, and wherein the resin uptake of the raw paper is 5 to 30 wt% based on the weight of the raw paper.
2. A thin film according to claim 1, characterized in that the pigment coating is formed in a thickness of 1 to 8 g/m².
3. A thin film according to claim 1 or 2, characterized in that the pigment coating contains 1 to 30 wt% melamine resin, urea resin, phenolic resin or glyoxal resin.