Patent Application
20130068409
The present invention relates to core paper, in particular to core paper as used for the production of decorative paper laminates. In addition, the invention relates to a method for producing the core paper and the use of the core paper as a carrier material for and/or on the layer structure(s) such as for example on boards of any kind
Core paper is known from prior art and is mostly used as a carrier for decorative paper to produce laminates, which are often used, for example, in the form of laminate boards and countertops, floor covering, etc.
The structure of such laminate consists of several interconnected two-dimensional layers which are made from the same or different materials in order to fulfill the specific functions and properties. In the production of decorative paper laminates, for example, core paper is used as one of these layers. Adhesive bonding of these layers is usually performed by pretreatment of the individual layers, for example, by prior capillary impregnation and subsequently pressing the layers in the stack subject to temperature and pressure.
Core paper known to prior art is produced from a virgin fiber mix as its raw material, which fulfills the demanding requirements for the required strength, impregnating and paper properties.
In addition to the consumption of natural resources, the drawback of using virgin fiber mix inter alia is the high raw material costs. Reconstituted fiber material, however, such as recovered paper, often does not satisfy the demanded requirements regarding strength, impregnation and paper properties.
The enormous cost pressure in today's paper industry leads to continuous production optimization and to the demand with respect to saving raw material and transportation costs. This entails the trend towards low grammage, while demanding unchanged quality parameters such as unchanged strengths, i.e. for lower grammage the requirements regarding strength increase accordingly.
With conventional impregnation methods, such as dip impregnation with impregnating resins, the entire paper web is passed through the liquid. In order to not have any tears of the paper web in the production with this method or any other disruptions of production, a certain wet strength of the core paper web is a prerequisite. This wet strength is usually achieved by adding chemical additives, so-called wet sealers, where they should be optimally adapted to the chemistry in the system.
The object of the present invention is to at least partially overcome the drawbacks known in prior art. The above object is satisfied by a core paper according to claim 1 according to the invention, a method for producing the core paper, and the use of the core paper.
Particularly preferred embodiments are the subject matter of the dependent claims.
The present object is satisfied by the core paper according to the invention containing the fiber material and possibly containing recovered paper. The core paper according to the invention comprises at least one proportion of a reconstituted fiber material mixture and a wet sealer as a first additive. The core paper according to the invention is characterized by adding at least one active substance active on the boundary surface as a second additive for increasing capillarity. The added amount of the second additive is in the range of 0.05% to 2% relative to the atro material.
According to the present invention, the core paper according to the invention is understood to be carrier paper as it is used for example in laminating decorative paper. In manufacturing this paper from reconstituted, so called recycled fiber material, at least one substance active on the boundary surface is used in addition to conventional wet sealers.
Laminable within the meaning of the present invention is understood, according to the Latin root word “lamina” meaning layer, as being all kinds of binding of various material layers. The term carrier material refers to the layers of material on which or under which one (or more) additional layer (s) can be laminated. Laminates are often referred to as layer composites.
Reconstituted fiber material according to the present invention is understood to be all kinds of fiber materials that is reconstituted for the production of paper, paperboard and cardboard, in particular of core paper and used in particular for the production of paper, paperboard and cardboard in particular of the core paper. These kinds of recovered paper are in particular specified according to the CEN European Standard EN 643.
Wet sealers within the meaning of the present invention are understood to be all additives which increase the strength of paper, paperboard and cardboard and core paper, inter alia in the wet state. In addition to the mechanical interlocking of the fibers and the formation of hydrogen bonds during the sheet forming process, which are responsible for the strength of the paper, wet strength agents connect inter alia the fibers at the points of contact and intersection. If the paper now becomes moist or wet, by which the hydrogen bonds and hereby also the strength is lost, then the wet strength agent maintains a part of the strength of the paper in the wet state. The wet strength is determined, for example, by means of a tensile load on a wet paper strip in a tensile testing machine, which during constant feeding leads to a tear of the wet paper strip. The use of wet strength agents is necessary in all areas of application in which paper becomes wet or very moist, such as in the field of hygiene or decorative paper. In the field of decorative paper, the wet strength is a prerequisite for the method step of resin impregnation, in which the paper web is passed through a liquid bath. Many wet sealers or wet strength agents, respectively, must condense out and polymerize in the internal paper structure. This occurs only in part in the drying section of a paper machine. For complete formation of wet strength, additional or curing time is usually necessary.
A substance active on the boundary surface according to the present invention is understood to be all kinds of substances that reduce the surface or boundary surface tension between two phases. A boundary surface is understood to be the surface between the two immiscible phases. A surface on the other hand is spoken of when one of the phases is a gas, such as air. The phase boundaries can be characterized by boundary surface or surface tension describing the tendency to reduce the boundary surface. Depending on their chemical composition and application, substances active on the boundary are also referred to as wetting agents, detergents (surfactants, soaps) or emulsifiers. Such materials are characterized by their polar structure in that the fact that they accumulate preferably at boundary surfaces of a disperse system. While “substance active on the boundary surface” refers to all such substances, the term “substance active on the surface” refers to substances that accumulate on the “surface” of a liquid at the boundary to the gas phase, for example, at the surface of water, which can for instance cause formation of foam.
Capillarity according the present invention refers to an effect which occurs as a result of the surface tension of liquids, preferably in cavities. Basically the effect of capillarity is based of the molecular forces that occur within a substance (cohesion forces) and at the boundary surface between a liquid, a solid body (vessel wall) and a gas (e.g. air) (adhesion forces).
Based on capillarity is inter alia the capillary effect of sponges, wicks, cleaning rags, cloth and paper. The larger the inner surface (by volume), the greater the capillary effect. The impregnating properties of the core paper according to the invention and the capillarity specified in accordance with the present invention are influenced or characterized by the capillary behavior, the capillary rise, the liquid absorption capacity, wetting, the edge angle, the surface tension.
Atro is the term for absolutely dry. Atro is also often referred to as otro (oven-dry). This term is the benchmark for measuring the dry content of paper and pulp. The specification is, for example, according to the standard: BS EN ISO 638 Paper, cardboard and fiber material—Determination of dry content—Oven-drying process. Dosage of additives is commonly based on the dry substance.
In a further embodiment of the core paper according to the invention, the proportion of reconstituted fiber material mixture is greater than 25%, furthermore, between greater than 40 and 100%, preferably between 50 and 95%, particularly preferably between 70 and 90%, preferably in the range of 75%, more preferably above 80%, most preferably above 95% and especially up to 100% and the fiber material is in particular selected from a group comprising for example Kraft pulp and/or Kraft liner in particular from department store waste from corrugated paper and cardboard with at least 70% corrugated paper and residues of solid cardboard and or packaging paper, used corrugated cardboard boxes, shreds of unused cardboard with layers of Kraft or test liner, used corrugated cardboard boxes with Kraft liner and/or corrugated medium on pulp and/or thermo-chemical pulp, used corrugated cardboard with layers of test or Kraft liner and at least one layer of Kraft liner, used bags from Kraft pulp equipped as tear-resistant or non-tear-resistant, unused bags of Kraft pulp equipped as tear-resistant or non-tear-resistant, used cardboard and paper from Kraft pulp naturally colored and/or white, shreds from unused pulp paperboard and paper from Kraft pulp uncolored, new carrier bags from Kraft pulp with or without wet tensile strength resistant paper containing envelopes made of Kraft paper repeatedly covered and/or coated and/or used, magazine paper, newspapers, in particular daily newspapers, combinations thereof and the like.
The proportion of reconstituted fiber material relative to the total fiber material is given as a percentage. Components of the total fiber material can also contain so-called virgin fiber material as well as artificial fiber material. In this, virgin fiber material, obtained by means of chemical and/or mechanical extraction processes, in contrast to the reconstituted fiber material usually show higher strengths, but is also more expensive.
Depending on the extraction process used, fiber material can basically be divided into fiber material containing lignin and free of lignin. For reconstituted fiber material, this distinction is frequently no longer given due to the mixing of recovered paper or even recovered paper types, respectively. By means of strength parameters, static and dynamic strengths can be distinguished. Static strength is understood to be the force that a paper can withstand under a slow and steady tension load. For example, breaking force, tear length, tension length, modulus of elasticity are among the static strength parameters. Dynamic strength is understood to be the force that can a paper can withstand under a fast and unsteady tension load. For example, specific tear growth resistance, burst strength, number of double folds (buckling strength) are among the dynamic strength parameters.
Examples of general paper properties are paper smoothness, porosity, roughness, permeability to air, formation, stiffness, flatness and opacity.
With the respective proportions of reconstituted fiber material, the properties of the core paper according to the invention can in particular also be influenced. The achievable strength parameters and with respect to the impregnation method, the impregnation behavior of the core paper according to the invention, are of particular important in connection with the trend to reduce grammage mentioned in the introduction. The respectively necessary proportions of the overall fiber material are compiled according to the required strengths and properties of the final product. A total fiber material from 100% reconstituted fiber material mixture requires optimized production methods and special technical know-how. Reconstituted fiber material can also be referred to as recovered paper. Depending on properties and origin, the CEN European Standard EN 643 lists the types of recovered paper in various classes. In particular types of waste paper from class II are of importance for the present invention.
In a further embodiment of the core paper according to the invention, the wet sealer is selected as the first additive from a group comprising in particular compounds of epichlorohydrin resins, urea-, melamine-formaldehyde resins, phenol resins, acrylic resin dispersions, synthetic resin dispersions based on acrylic acid esters and/or styrene-butadiene, polyurethane-, polyolefin dispersions, polyamidoamine resins, polyamidoamine-epichlorohydrin resins, combinations thereof and the like. The mode of operation of these listed wet sealer groups in relation to the connection of fibers at the points of contact and intersection was described above.
In a further embodiment of the core paper according to the invention, the substance active on the boundary surface is selected as the second additive from the group comprising compounds which, strongly accumulate in particular at the boundary surfaces. According to their functional chemical groups, the additives are divided into bifunctional, anionic, nonionizable and cationic compounds. The characteristic feature of all the substances active on the boundary surface is their polar structure, mostly due to at least one lipophilic hydrocarbon radical, and at least one hydrophilic functional group, making them accumulate preferably at the boundary surfaces of a disperse system.
Examples of substances active on the boundary surface, such as surfactants, are: amphiphilic (bifunctional) compounds with at least one hydrophobic and one hydrophilic part of the molecule, where a hydrocarbon chain comprises eight to twenty-two carbon atoms, (dimethyl) siloxane chains, perfluorinated hydrocarbon chains.
Examples of anionic surfactants are in particular soaps, linear alkylbenzene sulfonate, alkane sulfonates, alkyl sulfates, alkyl ether sulfates, fatty alkyl polyethylene glycol ether sulfates, fatty alkyl sulfates.
Examples of nonionic surfactants are in particular fatty alkyl polyethylene glycol ether, fatty alcohol ethoxylates, fatty acid condensates, ethylene oxide/propylene oxide copolymers (EO/PO), alkyl phenol ethoxylates, sorbitan fatty acid ethers, sorbitan mono-(di, tri) laurate, -oleate, -palmitate, -stearate, polysorbates, sorbitan sesquioleates, alkylpolyglucosides N-methylglucamides, alkylphenol polyethylene glycol ethers, fatty alcohols, oxo-alcohols, Ziegler alcohols, alkyl phenols and ethylene oxide
Examples of cationic surfactants are in particular quaternary ammonium compounds containing hydrophobic groups, salts of long-chain primary amines
Examples of amphoteric surfactants are, in particular betaine, amino acid surfactants, N-(acylamidoalkyl) betaine, propylene oxide.
Further examples of anionic surfactants are polyelectrolytes, emulsifiers, wetting and dispersing agents, humectants, and polysaccharides, in particular sorbitol.
In a further embodiment of the core paper according to the invention, the material suspension can comprise further additives which are added in a controlled manner as so-called chemical expedients or additives in the paper production process to achieve certain properties, effects, and process conditions, or are included already in a modified form in the reconstituted fiber material or recovered paper, respectively. This can be, in particular retention agents, drainage aid agents, retention agents dual systems or microparticle systems, wet and dry sealers, fillers and or pigments, in particular selected from a group of talc, titanium dioxide, aluminum hydroxide, bentonite, barium sulfate, calcium carbonate, kaolin, gypsum, be binding agent components, color coating components, defoamers, deaerators, biocides, enzymes, bleaching aid agents, optical brighteners, dyes, shading dyes, fixatives, precipitating agents (fixing agents), wetting agents, pH regulators combinations thereof and the like. In addition to the desired functions of the additives, interactions, however, can also result in adverse effects, which then have the additives negatively influence the method processes as so-called “trash”.
In a further embodiment of the core paper according to the invention, the active substance active on the boundary surface is added in particular in a proportion of weight of 0.1% to 3%, preferably from 0.5% to 1 25%, more preferably from 0.1% to 1.5% and 0.5% to 1%, respectively, particularly preferably in the range of 0<x̂2% and preferably from 1%, 1, 5% or 2% based on atro dry material. The dosage range presently shown of the active substance active on the boundary surface was determined from experiments and represents an optimized active range for obtaining the optimum paper properties, in particular for increasing capillarity.
Core paper can be produced as follows: In a so-called stock preparation process, an aqueous fiber material suspension is provided. The fiber material suspension preferably has passed screening which includes in particular a two-stage pressure screening and a 3-stage cleaner system process, where the pressure screening preferably uses slotted screeners which comprise slots in particular having slot widths between 0.2 to 0.3 mm and preferably 0.25 mm. Additional process steps can be dispersing stages and/or ash removal processes. In addition to other chemical agents or additives, respectively, which influence the paper production process as well as the paper properties, a wet strength agents and a substance active on the boundary surface, a so-called surfactant, are added to this fiber material suspension. The aqueous fiber material suspension, after the addition of all the raw materials/additives and just prior to the paper machine, is also referred to as a so-called finished stock. With the paper machine process steps of drainage/sheet forming, pressing, drying, possibly smoothing and rolling-up, the base-core paper is produced. After any possibly required ripening time, in which the final wet strength is achieved, the core paper is ready for the method step of impregnation. In the method of capillary impregnation, the core paper is for example guided through an immersion bath and impregnated with resin.
In a further preferred embodiment, the passivation of carbonates, which inter alia entered the core paper by the use of recovered paper, are protected so that release of CO2 is preferably prevented in the event of shifts in pH-value. For example, carbonate content can be passivated by the addition of small amounts of phosphoric acid. In addition, the fiber material can also be added suitable buffer systems in order to prevent a pH shift.
Finally, a further aspect of the invention comprises the addition of hydrophobic agents, thereby in particular influencing and adjusting the penetration behavior of the core paper specifically by the addition of two oppositely-acting agents, i.e. especially between surfactants and hydrophobic agents.
Thereby, the addition of a hydrophobic agent leads to reducing the rate of wetting and can in particular dampend the wetting behavior possibly abruptly caused by adding surfactants.
The object of the present invention is further also satisfied by a method for producing a core paper according to claim 1. The method in detail comprises the following steps of:
Furthermore, the above-described method according to the invention can also comprise the additional step of
Furthermore, the above-described method according to the invention can also comprise the additional step of
The present invention further comprises the use of the core paper as a material component in composite materials, in particular in laminate materials, in particular compact boards (sometimes having a thickness of up to 10 mm), fiber composites, and particle composites and interpenetrating composites. This covers the use of the core paper for all geometries of the composite.
Furthermore, the present invention also comprises the use of the core paper as carrier material for a web-shaped layer structure and in particular for overlays, decorative paper, films and nonwoven materials and/or as a cover layer, in particular as an overlay and pre-impregnated paper and/or as a carrier material on carrier boards in particular of wood fiberboards, such as chip boards, oriented strand boards (OSB), fiberboards of high or medium density, plywood, mineral-bonded wood materials on a plastic base, solid wood panels, countertops, floor covering, and preferably for the production of fiber composite materials, such as natural fiber reinforced plastics, wood-plastic composites and fiber-ceramic composites, and/or in return thereof, in particular as regenerated paper for coating back sides such as in particular for laminates, surface-coated boards such as wood fiberboards, panels, and combinations thereof and the like. With the product examples listed, the core paper according to the invention covers the use as carrier material for all possible layer structures.
The main advantage of the core paper is that at least in part reconstituted fiber material is used, which allows saving costs for raw materials, increases the recycling rate and promotes the sustainable use of renewable resources.
Further advantages of the core paper according to the invention over prior art can inter alia be, that despite the use at least in part of the reconstituted fiber material, the demanding conditions regarding the required strength, impregnation and paper properties are fulfilled, and/or are possibly even exceeded.
The invention is explained below with reference to preferred embodiments, where it is pointed out that these examples comprise modifications or additions as they directly arise for the person skilled in the art. Furthermore, these preferred embodiments are no restrictions of the invention such that modifications and additions are within the scope of the present invention.
For the production of core paper in prior art, grammage is used in the range from 40 to 400 g/m2, preferably in the range between 140 to 300 g/m2, more preferably between 150 to 250 g/m2, most preferably above 150 g/m2 uses conventional Kraft liner virgin fiber mix, in particular also Kraft pulp. Ideally, the virgin fiber pulp comes from an upstream pulp production, so that there are no intermediate drying steps of the fiber material, so that there is in particular no hornification of the fiber material. Hornfication of the fiber material affects the surface properties of the fibers and can negatively impact strength properties and the capillarity or absorbency of the finished core paper. Other differences with respect to capillarity can be observed between fiber material containing lignin and not containing lignin. Fibers containing lignin unlike lignin-free fibers show reduced absorbency due to hydrophobic surface properties of fiber materials containing lignin.
In contrast to this, the production of the core paper according to the invention is effected with up to 100% reconstituted fiber material. According to a preferred embodiment, waste paper types from unbleached virgin pulp were mainly used as reconstituted fiber material. Sheet formation of the core paper with a grammage between 40 to 400 g/m2 takes place at the paper machine, for example, in a single layer on a Fourdrinier wire with an attached top wire drainage, in particular a hybrid former and/or a downstream dandy roll.
The quality criterion of the test series for the process steps in the production was the positive influence of capillarity of the core paper.
With the addition of an active substance active on the boundary surface, it was possible to achieved at least comparable capillarity for the core paper according to the invention, which is inter alia apparent from a similar capillary rise.
Simultaneously, it was possible to improve the wet strength, which is shown by an increase in tensile strength longitudinally (wet) in the range of 20% over prior art. Improved impregnatability is due to improved wet strength of the core paper. A comparison is described below in more detail with reference to values in the table.
Table 1 is a comparison of the reference parameters of the core paper. The paper parameters capillary rise, breaking force longitudinally (dry), tensile strength longitudinally (wet) and permeability to air are compared with prior art. (100% virgin fiber/0% recovered paper), with 100% recovered paper and with the core paper according to the invention. For the core paper according to the invention, the capillary rise and the permeability to air are at the prior art level, the breaking force longitudinally (dry) reduced by half and the breaking force longitudinally (wet) is improved over prior art by 20%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 016 864.5 | May 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/057250 | 5/5/2011 | WO | 00 | 11/7/2012 |
