CA2445100C - Multilayered fibrous product and a process for the production thereof - Google Patents
Multilayered fibrous product and a process for the production thereof Download PDFInfo
- Publication number
- CA2445100C CA2445100C CA2445100A CA2445100A CA2445100C CA 2445100 C CA2445100 C CA 2445100C CA 2445100 A CA2445100 A CA 2445100A CA 2445100 A CA2445100 A CA 2445100A CA 2445100 C CA2445100 C CA 2445100C
- Authority
- CA
- Canada
- Prior art keywords
- layer
- fibre
- top layer
- fibrils
- filler
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 title claims abstract description 15
- 238000004519 manufacturing process Methods 0.000 title description 11
- 239000000945 filler Substances 0.000 claims abstract description 53
- 239000000835 fiber Substances 0.000 claims abstract description 52
- 239000000463 material Substances 0.000 claims abstract description 36
- 238000000149 argon plasma sintering Methods 0.000 claims abstract description 23
- 239000002245 particle Substances 0.000 claims abstract description 23
- 239000000049 pigment Substances 0.000 claims abstract description 16
- 229920002678 cellulose Polymers 0.000 claims abstract description 11
- 239000001913 cellulose Substances 0.000 claims abstract description 11
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 39
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 14
- 239000011248 coating agent Substances 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 13
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims description 10
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 8
- 239000011121 hardwood Substances 0.000 claims description 5
- 239000011122 softwood Substances 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- QXDMQSPYEZFLGF-UHFFFAOYSA-L calcium oxalate Chemical compound [Ca+2].[O-]C(=O)C([O-])=O QXDMQSPYEZFLGF-UHFFFAOYSA-L 0.000 claims description 4
- 239000001175 calcium sulphate Substances 0.000 claims description 4
- 235000011132 calcium sulphate Nutrition 0.000 claims description 4
- 238000009826 distribution Methods 0.000 claims description 4
- 238000001556 precipitation Methods 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- 239000012736 aqueous medium Substances 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 abstract description 6
- 229910052500 inorganic mineral Inorganic materials 0.000 abstract description 4
- 239000011707 mineral Substances 0.000 abstract description 4
- 230000006735 deficit Effects 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 110
- 239000000047 product Substances 0.000 description 45
- 235000010216 calcium carbonate Nutrition 0.000 description 16
- 229960003563 calcium carbonate Drugs 0.000 description 14
- 239000000123 paper Substances 0.000 description 12
- 230000003247 decreasing effect Effects 0.000 description 9
- 229920001131 Pulp (paper) Polymers 0.000 description 8
- 235000012211 aluminium silicate Nutrition 0.000 description 8
- 230000014759 maintenance of location Effects 0.000 description 8
- 239000005995 Aluminium silicate Substances 0.000 description 7
- 239000003795 chemical substances by application Substances 0.000 description 7
- 238000007670 refining Methods 0.000 description 7
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 6
- 230000000875 corresponding effect Effects 0.000 description 6
- 229910021653 sulphate ion Inorganic materials 0.000 description 6
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 4
- 238000010411 cooking Methods 0.000 description 4
- 229940088417 precipitated calcium carbonate Drugs 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 235000018185 Betula X alpestris Nutrition 0.000 description 3
- 235000018212 Betula X uliginosa Nutrition 0.000 description 3
- 229920003043 Cellulose fiber Polymers 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 239000012752 auxiliary agent Substances 0.000 description 3
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 3
- -1 carbonate compound Chemical class 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 235000010755 mineral Nutrition 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 2
- 229910021502 aluminium hydroxide Inorganic materials 0.000 description 2
- PZZYQPZGQPZBDN-UHFFFAOYSA-N aluminium silicate Chemical compound O=[Al]O[Si](=O)O[Al]=O PZZYQPZGQPZBDN-UHFFFAOYSA-N 0.000 description 2
- 229910000323 aluminium silicate Inorganic materials 0.000 description 2
- 239000008346 aqueous phase Substances 0.000 description 2
- 238000004061 bleaching Methods 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- 239000008199 coating composition Substances 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000002655 kraft paper Substances 0.000 description 2
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 description 2
- 239000000391 magnesium silicate Substances 0.000 description 2
- 229910052919 magnesium silicate Inorganic materials 0.000 description 2
- 235000019792 magnesium silicate Nutrition 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 description 1
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 206010016807 Fluid retention Diseases 0.000 description 1
- 239000004354 Hydroxyethyl cellulose Substances 0.000 description 1
- 229920000663 Hydroxyethyl cellulose Polymers 0.000 description 1
- 235000008331 Pinus X rigitaeda Nutrition 0.000 description 1
- 235000011613 Pinus brutia Nutrition 0.000 description 1
- 241000018646 Pinus brutia Species 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000001099 ammonium carbonate Substances 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 239000002518 antifoaming agent Substances 0.000 description 1
- 238000010009 beating Methods 0.000 description 1
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 238000003490 calendering Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 229920006184 cellulose methylcellulose Polymers 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000010961 commercial manufacture process Methods 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- JYIMWRSJCRRYNK-UHFFFAOYSA-N dialuminum;disodium;oxygen(2-);silicon(4+);hydrate Chemical compound O.[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[Na+].[Na+].[Al+3].[Al+3].[Si+4] JYIMWRSJCRRYNK-UHFFFAOYSA-N 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 235000019447 hydroxyethyl cellulose Nutrition 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000007645 offset printing Methods 0.000 description 1
- 239000011049 pearl Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004848 polyfunctional curative Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920002689 polyvinyl acetate Polymers 0.000 description 1
- 239000011118 polyvinyl acetate Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000003755 preservative agent Substances 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 239000001040 synthetic pigment Substances 0.000 description 1
- 239000000454 talc Substances 0.000 description 1
- 229910052623 talc Inorganic materials 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
- D21H27/30—Multi-ply
- D21H27/38—Multi-ply at least one of the sheets having a fibrous composition differing from that of other sheets
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
- D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H15/00—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution
- D21H15/02—Pulp or paper, comprising fibres or web-forming material characterised by features other than their chemical constitution characterised by configuration
- D21H15/10—Composite fibres
- D21H15/12—Composite fibres partly organic, partly inorganic
Landscapes
- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Paper (AREA)
Abstract
The multi-layer fibrous product and a process for producing it. According to the present invention the fibre product comprises at least two overlapping fibre layers, whereby the one that forms the top layer of the product contains filler and is lighter than the layer under it and is at least essentially opaque. According tothe present invention the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated. The present invention can be used, for example, to produce white surface liner with a lighter top layer without impairment of the strengthof the surface. Thus, the grammage of the layer can be at least about 5% by weight less than a top layer, which has the corresponding opacity and formation, and which has been produced from the same fibre material and mineral pigments.
Description
Multilayered Fibrous Product and a Process for the Production Thereof The present invention concerns a multi-layer fibrous product for use in making paper.
This kind of a product comprises at least two overlapping fibrous layers, of which at least the layer forming the operating surface of the product is light and essentially opaque (non-transparent), covering the fibre layer under it. The top layer contains filler and possibly conventional additives and auxiliary agents for paper.
The present invention relates also to a process for producing a multi-layer fibrous product for use in making paper.
A multilayered fibrous product usually consisting of two or three layers is called a "liner".
A liner can be completely brown (kraft-liner) or partially white (white-lined liner) or its top layer can be coated. The liner can be made of virgin fibre or recycled fibre or both.
A liner is used as a surface of a background liner in a corrugate board package. The special characteristics of kraft-liners are strength, uniform quality and product safety.
Strength is with kraft-liners a very important competitive advantage when comparing with recycled fibre-based products. The advantages of using test liners that contain recycled fibre are low price and the ecological values that support recycling.
The products called "Kemiart Graph" and "Kemiart Lite" and the uncoated "Kemiart Brite" of Oy Metsa-Botnia Ab can be mentioned as examples of commercial coated liners.
The liner product of Oy Metsa-Botnia Ab is a kraft-liner that has two fibre layers, the base layer being high yield softwood sulphate pulp and the top layer of bleached birch and softwood sulphate pulp. The fillers are used in the top layer to give the surface more brightness and smoothness, which improves the printability properties. Other chemicals, such as retention agents, are also used in production of liner, in order to retain the noil material and filling agents in the product instead of cycling it in the water cycle, and AKD
adhesives to improve water resistance. The coating is added to the coated products with an on-line coating unit. The coating is, for example, a combination of kaolin, carbonate and latex which improves significantly the printability of the product. The final gloss and smoothness of the final product are obtained with calendering.
The method of producing the top layer of the white lined linerboard (cover layer) is considerably more expensive than the method of producing brown back layer. The product can be optimised by changing, for example, the strengths of the fibre layers.
In that case it would be reasonable to produce the liner the top layer of which is as lightweight as possible. So far, however, the attempts to reduce the weight of the cover while maintaining a sufficient brightness of a liner without making the cover too weak, have been unsuccessful.. The amount of the white fibre cannot be decreased easily, without the brown fibre showing through.
The top layer does also need to have a good formation, which shows directly as good printability. Thus bad formation is visible especially well in grey scales of offset printing and as mottled print quality.
It is an object of the present invention to eliminate the problems involved with the known methods and to provide a novel solution for producing multi-layer fibre products, such as liners.
The present invention is based on the idea that a composite filler consisting of fibrils and mineral pigments is used as a filler of the top layer of the fibre product mentioned in the introduction.
Finnish Patent Specification No. 100729 discloses a papermaking filler comprising porous aggregates formed by precipitated calcium carbonate particles on the surface of fines.
What characterises this new kind of filler is that, according to the patent specification, the calcium carbonate is precipitated on fine fibrils produced by refining cellulose fibres and/or mechanical pulp fibres. The size distribution of the fines fraction corresponds mainly to the wire screen fraction P 100.
According to the present invention, it has been found that when the top layer of a multi-layer product is filled with the filler described above, the opacity of the surface increases so drastically that the grammage of the cover can be reduced significantly.
The top layer containing the new filler covers very efficiently the brown background despite the lower grammage.
Furthermore, within the scope of the present invention it has been found that also other similar fillers consisting at least partly of cellulose or lignocellulose fibrils, over which light scattering material particles has been precipitated, can be used as fillers. These particles are typically inorganic salts precipitating in an aqueous phase, such as calcium carbonate, calcium sulphate, barium sulphate and calcium oxalate.
According to the present invention it is, thus, possible to reduce the thickness of the multi-layer paper without impairing the opacity by using a filler that comprises fibrils over which calcium carbonate has been precipitated. GB Patent No. 628603 describes a multi-layer paper or board, the top layer of which contains modified fibre bulk. The bulk has been produced by impregnating the pulp with calcium chloride, after which the manipulated bulk is put in contact with carbonate compound, which causes the calcium carbonate to precipitate on the fibres - not on the fibrils. In the case corresponding to that described in the GB Patent, the bulk has considerably poor strength properties. It is stated in the publication, that it would not be possible to produce paper from this material. Moreover, the bulk has very poor retention.
In particular, in a preferred embodiment, the invention comprises a multi-layer fibrous product comprising of a top layer which overlaps one or more lower layers, wherein the top layer a) contains filler; b) is less dense than the one or more lower layers; and c) is at least essentially opaque; characterised in that the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils on which light scattering material particles have been precipitated; wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils; and wherein said fibrils on which said light scattering material particles are attached: i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.01 to 5 m and an average length of 10 to 1500 m.
3a In another preferred embodiment, the invention comprises a process for producing a multi-layer product, comprising the step of. a) fitting a fibre layer, which contains a filler and which forms the surface of the multi-layer product, on top of a backing layer that consists of at least one fibrous layer, wherein the fibre layer which is fitted on top of the backing layer is formed from a slush of fibre material which includes the filler which is comprised of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated, wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils, and wherein said fibrils on which said light scattering material particles are attached: i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.1 to 10 ,um and an average length of 10 to 1500 ,um.
The present invention provides considerable advantages. Thus, a white-lined liner can be prepared with a lighter top layer without compromising the strength of the surface. With the help of a new kind of a composite filling agent, the proportions of the white and brown layers can be changed much more easily. As the filler content can be increased and as the filler is extremely white, the amount of the white layer can be significantly decreased. By decreasing the white fibre layer, the commercial manufactures of liners can also decrease the total grammage of the liner. For example, it should be mentioned, that the grammage of the top layer according to the present invention can be at least about 5 %
by weight, preferably at least 10 % by weight smaller than a top layer that has a corresponding opacity and formation and is prepared from the same fibre material and mineral pigment.
The filler has been found to improve the formation and stiffness of the top layer. The filler described in the Fl Patent Specification No. 100729, referred hereinafter with its product name "SuperFill", retains well, which makes it possible to reduce the dosage of retention agents and still maintain a purer process. The better retention helps also to optimise/decrease the dosage of other paper making additives. Purity helps the operation of the machine and generally the operation efficiency of the machine improves, as the frequency of breaking down is smaller.
The present invention will be examined below in greater detail with the help of a detailed description and some examples.
Figure 1 present a side view of the principal structure of a two-layer fibre product and' Figure lb the corresponding four-layer fibre product, Figure 2 shows the light scattering factor of a two-layer fibre product produced according to the present invention and two reference products as a function of the Mullen indices with two different filling factors, Figure 3 shows corresponding results as a function of the bonding power (ScottBond), Figure 4 shows corresponding results as a function of the tensile index, and The figure 5 uses bar graphs to present the brightness of four two-layer fibre products, wherein two has top layers that contain filler according to the present invention, and two other contain reference filler.
Filler and its preparation As stated above, according to the present invention, composite filler comprising cellulose fibrils, on which light scattering pigments have been precipitated, is added as filler to the top layer of the multi-layer fibre product. Fibrils can originate from chemical pulp or mechanical pulp or mixtures thereof. By chemical pulp reference is herein made to a pulp, which has been treated with cooking chemicals to delignify cellulose fibres.
According to a preferred embodiment the fibrils are obtained by refining pulps produced with the sulphate process or with some other alkaline cooking method. In addition to chemical pulps, fibrils can originate also from chemi-mechanical or mechanical pulps.
Typically, the average thickness of cellulose or lignocellulose fibrils is smaller than 5 m, 5 conventionally smaller than 1 m. The fibrils are characterized by at least one of the following criteria:
a. they correspond to a fraction which passes a 100-mesh screen; and b. their average thickness is 0.01-10 m (preferably at maximum 5 m and in particular at maximum 1 m) and their average length is 10 - 1500 m.
The source material for the fibrils, i.e. the fines based on cellulose or other fibers, is fibrillated by beating it in a pulp refiner. The desired fraction may, when necessary, be separated by using a screen, but fines need not always be screened. Suitable fibril fractions include wire screen fractions P50 - P400. Preferably refiners with grooved blades are used.
The light-scattering material particles in the filler are inorganic or organic salts that can be formed from their source materials by precipitation in an aqueous medium. Such compounds include calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate, and mixtures thereof. The material particles are deposited on the fibrils. The amount of an inorganic salt compound in proportion to the fibril amount is approx. 0.0001 -95 % by weight, preferably approx. 0.1- 90 % by weight, most suitably approx. 60 - 80 % by weight, calculated from the amount of filler, and approx. 0.1- 80 % by weight, preferably approx. 0.5 - 50 % by weight, of the paper.
In the following, the present invention is examined with particular reference to a product according to FI Patent Specification No. 100729, but it is clear that the present invention can be adapted for other products mentioned hereinbefore by changing appropriately the source materials of the light scattering pigment.
The filler is produced by precipitating a mineral pigment on the surface of fine fibrils prepared from cellulose fibres and/or mechanical pulp fibres. For example, the precipitation of calcium carbonate can be carried out by feeding into an aqueous slush of fibrils an aqueous calcium hydroxide solution which possibly contains a solid calcium hydroxide, and a compound which contains carbonate ions and is at least partly dissolved "~t O1X3 ! FI0200341 in water (e.g. sodium carbonate or ammonium carbonate). It is also possible to introduce into the aqueous phase carbon dioxide gas that, in the presence of calcium hydroxide, pro-duces calcium carbonate. There are formed string-of-pearls-like calcium carbonate crystal aggregates, which are held together by fibrils, i.e. fine strands, and in which the calcium carbonate particles are deposited onto the fine fibrils and attached to them.
The fine fibrils together with calcium carbonate form string-of-pearls-like strands, and the calcium car-bonate aggregates primarily resemble strings of pearls in a pile. In water (slush) the ratio of the effective volume of the aggregates to the pulp is very high compared with the corre-sponding ratio of conventional calcium carbonate used as filler. By "effective volume" is meant, in this case, the volume required by the pigment.
The diameter of the calcium carbonate particles in the aggregates is about 0.1 to 5 m, typically about 0.2 to.3 m. In particular, the fibrils correspond to wire screen fractions P50 (or P100) to P400.
1 to 90 % by weight (dry weight), typically about 5 to 50 % by weight, of this kind of filler is added to the top layer of a multi-layer product. Usually the filler described forms at least 5 % by weight, most suitably from 10 to 100 % by weight of the filler of the base web and respectively 10 to 50 % by weight of the fibre material of the base web. In principle it is also possible to produce a base web the fibre material of which consist totally of fibrils of the filler, so, in general, the present filler can form 1 to 100 % by weight of fibre material of the base web.
In the slush used in the production of the top layer, part of the filler can consist of con-ventional fillers, such as calcium carbonate. However, preferably at least 80 %, especially preferably at least 90 % of the precipitated light scattering pigment particles are attached into the fibrils.
Multi-layer structure Figures la and lb illustrate the structures of the multi-layer products containing two and four layers, respectively. Figure I a illustrates a typical white lined liner board and Figure lb illustrates so called test liner.
This kind of a product comprises at least two overlapping fibrous layers, of which at least the layer forming the operating surface of the product is light and essentially opaque (non-transparent), covering the fibre layer under it. The top layer contains filler and possibly conventional additives and auxiliary agents for paper.
The present invention relates also to a process for producing a multi-layer fibrous product for use in making paper.
A multilayered fibrous product usually consisting of two or three layers is called a "liner".
A liner can be completely brown (kraft-liner) or partially white (white-lined liner) or its top layer can be coated. The liner can be made of virgin fibre or recycled fibre or both.
A liner is used as a surface of a background liner in a corrugate board package. The special characteristics of kraft-liners are strength, uniform quality and product safety.
Strength is with kraft-liners a very important competitive advantage when comparing with recycled fibre-based products. The advantages of using test liners that contain recycled fibre are low price and the ecological values that support recycling.
The products called "Kemiart Graph" and "Kemiart Lite" and the uncoated "Kemiart Brite" of Oy Metsa-Botnia Ab can be mentioned as examples of commercial coated liners.
The liner product of Oy Metsa-Botnia Ab is a kraft-liner that has two fibre layers, the base layer being high yield softwood sulphate pulp and the top layer of bleached birch and softwood sulphate pulp. The fillers are used in the top layer to give the surface more brightness and smoothness, which improves the printability properties. Other chemicals, such as retention agents, are also used in production of liner, in order to retain the noil material and filling agents in the product instead of cycling it in the water cycle, and AKD
adhesives to improve water resistance. The coating is added to the coated products with an on-line coating unit. The coating is, for example, a combination of kaolin, carbonate and latex which improves significantly the printability of the product. The final gloss and smoothness of the final product are obtained with calendering.
The method of producing the top layer of the white lined linerboard (cover layer) is considerably more expensive than the method of producing brown back layer. The product can be optimised by changing, for example, the strengths of the fibre layers.
In that case it would be reasonable to produce the liner the top layer of which is as lightweight as possible. So far, however, the attempts to reduce the weight of the cover while maintaining a sufficient brightness of a liner without making the cover too weak, have been unsuccessful.. The amount of the white fibre cannot be decreased easily, without the brown fibre showing through.
The top layer does also need to have a good formation, which shows directly as good printability. Thus bad formation is visible especially well in grey scales of offset printing and as mottled print quality.
It is an object of the present invention to eliminate the problems involved with the known methods and to provide a novel solution for producing multi-layer fibre products, such as liners.
The present invention is based on the idea that a composite filler consisting of fibrils and mineral pigments is used as a filler of the top layer of the fibre product mentioned in the introduction.
Finnish Patent Specification No. 100729 discloses a papermaking filler comprising porous aggregates formed by precipitated calcium carbonate particles on the surface of fines.
What characterises this new kind of filler is that, according to the patent specification, the calcium carbonate is precipitated on fine fibrils produced by refining cellulose fibres and/or mechanical pulp fibres. The size distribution of the fines fraction corresponds mainly to the wire screen fraction P 100.
According to the present invention, it has been found that when the top layer of a multi-layer product is filled with the filler described above, the opacity of the surface increases so drastically that the grammage of the cover can be reduced significantly.
The top layer containing the new filler covers very efficiently the brown background despite the lower grammage.
Furthermore, within the scope of the present invention it has been found that also other similar fillers consisting at least partly of cellulose or lignocellulose fibrils, over which light scattering material particles has been precipitated, can be used as fillers. These particles are typically inorganic salts precipitating in an aqueous phase, such as calcium carbonate, calcium sulphate, barium sulphate and calcium oxalate.
According to the present invention it is, thus, possible to reduce the thickness of the multi-layer paper without impairing the opacity by using a filler that comprises fibrils over which calcium carbonate has been precipitated. GB Patent No. 628603 describes a multi-layer paper or board, the top layer of which contains modified fibre bulk. The bulk has been produced by impregnating the pulp with calcium chloride, after which the manipulated bulk is put in contact with carbonate compound, which causes the calcium carbonate to precipitate on the fibres - not on the fibrils. In the case corresponding to that described in the GB Patent, the bulk has considerably poor strength properties. It is stated in the publication, that it would not be possible to produce paper from this material. Moreover, the bulk has very poor retention.
In particular, in a preferred embodiment, the invention comprises a multi-layer fibrous product comprising of a top layer which overlaps one or more lower layers, wherein the top layer a) contains filler; b) is less dense than the one or more lower layers; and c) is at least essentially opaque; characterised in that the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils on which light scattering material particles have been precipitated; wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils; and wherein said fibrils on which said light scattering material particles are attached: i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.01 to 5 m and an average length of 10 to 1500 m.
3a In another preferred embodiment, the invention comprises a process for producing a multi-layer product, comprising the step of. a) fitting a fibre layer, which contains a filler and which forms the surface of the multi-layer product, on top of a backing layer that consists of at least one fibrous layer, wherein the fibre layer which is fitted on top of the backing layer is formed from a slush of fibre material which includes the filler which is comprised of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated, wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils, and wherein said fibrils on which said light scattering material particles are attached: i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.1 to 10 ,um and an average length of 10 to 1500 ,um.
The present invention provides considerable advantages. Thus, a white-lined liner can be prepared with a lighter top layer without compromising the strength of the surface. With the help of a new kind of a composite filling agent, the proportions of the white and brown layers can be changed much more easily. As the filler content can be increased and as the filler is extremely white, the amount of the white layer can be significantly decreased. By decreasing the white fibre layer, the commercial manufactures of liners can also decrease the total grammage of the liner. For example, it should be mentioned, that the grammage of the top layer according to the present invention can be at least about 5 %
by weight, preferably at least 10 % by weight smaller than a top layer that has a corresponding opacity and formation and is prepared from the same fibre material and mineral pigment.
The filler has been found to improve the formation and stiffness of the top layer. The filler described in the Fl Patent Specification No. 100729, referred hereinafter with its product name "SuperFill", retains well, which makes it possible to reduce the dosage of retention agents and still maintain a purer process. The better retention helps also to optimise/decrease the dosage of other paper making additives. Purity helps the operation of the machine and generally the operation efficiency of the machine improves, as the frequency of breaking down is smaller.
The present invention will be examined below in greater detail with the help of a detailed description and some examples.
Figure 1 present a side view of the principal structure of a two-layer fibre product and' Figure lb the corresponding four-layer fibre product, Figure 2 shows the light scattering factor of a two-layer fibre product produced according to the present invention and two reference products as a function of the Mullen indices with two different filling factors, Figure 3 shows corresponding results as a function of the bonding power (ScottBond), Figure 4 shows corresponding results as a function of the tensile index, and The figure 5 uses bar graphs to present the brightness of four two-layer fibre products, wherein two has top layers that contain filler according to the present invention, and two other contain reference filler.
Filler and its preparation As stated above, according to the present invention, composite filler comprising cellulose fibrils, on which light scattering pigments have been precipitated, is added as filler to the top layer of the multi-layer fibre product. Fibrils can originate from chemical pulp or mechanical pulp or mixtures thereof. By chemical pulp reference is herein made to a pulp, which has been treated with cooking chemicals to delignify cellulose fibres.
According to a preferred embodiment the fibrils are obtained by refining pulps produced with the sulphate process or with some other alkaline cooking method. In addition to chemical pulps, fibrils can originate also from chemi-mechanical or mechanical pulps.
Typically, the average thickness of cellulose or lignocellulose fibrils is smaller than 5 m, 5 conventionally smaller than 1 m. The fibrils are characterized by at least one of the following criteria:
a. they correspond to a fraction which passes a 100-mesh screen; and b. their average thickness is 0.01-10 m (preferably at maximum 5 m and in particular at maximum 1 m) and their average length is 10 - 1500 m.
The source material for the fibrils, i.e. the fines based on cellulose or other fibers, is fibrillated by beating it in a pulp refiner. The desired fraction may, when necessary, be separated by using a screen, but fines need not always be screened. Suitable fibril fractions include wire screen fractions P50 - P400. Preferably refiners with grooved blades are used.
The light-scattering material particles in the filler are inorganic or organic salts that can be formed from their source materials by precipitation in an aqueous medium. Such compounds include calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate, and mixtures thereof. The material particles are deposited on the fibrils. The amount of an inorganic salt compound in proportion to the fibril amount is approx. 0.0001 -95 % by weight, preferably approx. 0.1- 90 % by weight, most suitably approx. 60 - 80 % by weight, calculated from the amount of filler, and approx. 0.1- 80 % by weight, preferably approx. 0.5 - 50 % by weight, of the paper.
In the following, the present invention is examined with particular reference to a product according to FI Patent Specification No. 100729, but it is clear that the present invention can be adapted for other products mentioned hereinbefore by changing appropriately the source materials of the light scattering pigment.
The filler is produced by precipitating a mineral pigment on the surface of fine fibrils prepared from cellulose fibres and/or mechanical pulp fibres. For example, the precipitation of calcium carbonate can be carried out by feeding into an aqueous slush of fibrils an aqueous calcium hydroxide solution which possibly contains a solid calcium hydroxide, and a compound which contains carbonate ions and is at least partly dissolved "~t O1X3 ! FI0200341 in water (e.g. sodium carbonate or ammonium carbonate). It is also possible to introduce into the aqueous phase carbon dioxide gas that, in the presence of calcium hydroxide, pro-duces calcium carbonate. There are formed string-of-pearls-like calcium carbonate crystal aggregates, which are held together by fibrils, i.e. fine strands, and in which the calcium carbonate particles are deposited onto the fine fibrils and attached to them.
The fine fibrils together with calcium carbonate form string-of-pearls-like strands, and the calcium car-bonate aggregates primarily resemble strings of pearls in a pile. In water (slush) the ratio of the effective volume of the aggregates to the pulp is very high compared with the corre-sponding ratio of conventional calcium carbonate used as filler. By "effective volume" is meant, in this case, the volume required by the pigment.
The diameter of the calcium carbonate particles in the aggregates is about 0.1 to 5 m, typically about 0.2 to.3 m. In particular, the fibrils correspond to wire screen fractions P50 (or P100) to P400.
1 to 90 % by weight (dry weight), typically about 5 to 50 % by weight, of this kind of filler is added to the top layer of a multi-layer product. Usually the filler described forms at least 5 % by weight, most suitably from 10 to 100 % by weight of the filler of the base web and respectively 10 to 50 % by weight of the fibre material of the base web. In principle it is also possible to produce a base web the fibre material of which consist totally of fibrils of the filler, so, in general, the present filler can form 1 to 100 % by weight of fibre material of the base web.
In the slush used in the production of the top layer, part of the filler can consist of con-ventional fillers, such as calcium carbonate. However, preferably at least 80 %, especially preferably at least 90 % of the precipitated light scattering pigment particles are attached into the fibrils.
Multi-layer structure Figures la and lb illustrate the structures of the multi-layer products containing two and four layers, respectively. Figure I a illustrates a typical white lined liner board and Figure lb illustrates so called test liner.
The grammage of the fibre product according to the present invention is preferably about 50 to 500 g/m2, typically about 80 to 350 g/m2. Usually its grammage is over 125 g/m2, but products having a granimage below 100 g/m2 qualify for small packages.
Preferably the liner according to the present invention comprises a two-layer product (see Figure 1 a), that has a surface of a cover layer 1 and a back layer 2. The top layer covers the back layer so that the back layer cannot be seen through the top layer.
It is also possible to produce three-layer or four-layer products. In principle the number of layers in a layer product has no upper limit, there can be even up to 5, 6 or 7 layers. What is essential in the present invention, is that the top layer contains filler described more precisely hereinbefore, so that the top layer covers the layers under it, the layers that can be produced from raw materials of cheap costs.
Among multi-layer products, the test liner type four-layer products of Figure lb, having a top layer 3, a layer 4 under the top layer, intermediate layer 5 and a back layer 6, are to be mentioned.
Different raw materials can be used for production of a fibre product according to the purpose of use. Both virgin fibres and recycled fibres can be used. The virgin fibre can originate from softwood or hardwood (wood chips) or it can originate from cuttings.
Especially preferably virgin pulp is used in the top layer. This is most suitably produced by sulphate cooking (kraft pulp), because sulphate cooking gives a mass having especially good strength properties, as the name suggests. The recycled fibre can originate e.g. from used corrugated board packages (OCC) or mixed fibres. Recycled fibres are used especially for the production of test liners. The surface and back layer(s) can be produced from similar raw materials or from different source fibres. If virgin fibre, such as kraft pulp, is used for both, then the mass of the back layer can be cooked in high yield, after which a mild refining is performed on it. Mass that has been cooked to a lower kappa and also refined more than mass of the back layer, is used for the top layer.
Typically the pulp of the back layer is cooked to a kappa value of 30 to 70 and the pulp of the top layer to lower kappa value of 25 (the kappa number of the unbleached pulp). Bleaching can be performed in a manner known per se, e.g. as ECF of TCF bleaching.
Retention agents can be added to the slush e.g. in about 0.5 to 3 % of the amount of the fibre material. However, it has been found in connection with the present invention that the filler described here gives such a good retention that no retention agents are needed for the layer the and amount of the retention agents can be significantly decreased.
The liner is stuff or surface sized to improve the moisture resistance. If a low quality recycled fibre is used as raw material, it is preferable to use a surface-size press to produce a product that has sufficient strength. According to the machine the distribution of the base weight between the top and the back layer is about 20/80...40/60, typically about 30/70. Thus the grammage of the top layer is generally about 20 to 125 g/m2 (see below). When operating according to the present invention, the grammage of the top layer can be decreased over 10 %, up to 20 % or more, without deteriorating the optical or mechanical properties of the cover.
The layer product is produced in a manner known per se. According to one preferred embodiment both or all layers are produced first from slush of their own and spread on the Fourdriner wire. After this, the layers are couched fastened into each other.
With regard to the production process, a reference is made to a text by Ari Kiviranta "Board Grades", in a book series Paper-Making Science and Technology, Book 18, Paper and Board Grades, Fapet Oy, Jyvaskyla 2000, pages 68 and 69.
A planar fibre product according to the present invention can be used as a top layer of different corrugate board packages. The solution according to the present invention is especially preferably suitable for white lined top liner and coated white lined liner, both of which are used for demanding printing works. In these objects the fact that the surface of the liner according to the invention is extremely smooth and uniform, and has at the same time high opacity and brightness can be made use of. Generally the grammage of the top layer is about 20 to 125 g/m2, most suitably about 50 to 80 g/m2, especially preferably about 55 to 70 g/m2, and bleached chemical cellulose pulp is used of the top layer. In order to obtain a very good formation in the preferred embodiment of the present invention, mainly hardwood is used in the top layer. Thus e.g. over 60 % by weight, typically over 80 % of fibre material of pulp is hardwood and the rest softwood. The fibre material of pulp can consist totally of hardwood.
Conventional coating mixtures can be used for coating of the coated white lined top layer product. Precipitated calcium carbonate, ground calcium carbonate, calcium sulphate, calcium oxalate, aluminium silicate, kaolin (hydrous aluminium silicate), aluminium hydroxide, magnesium silicate, talc (hydrous magnesium silicate), titanium dioxide and barium sulphate, and mixtures thereof can be used as pigments. Synthetic pigments can also be used. Of the pigments mentioned above, the main pigments are kaolin, calcium carbonate, precipitated calcium carbonate and gypsum, which in general constitute over 50 % of the dry solids in the coating mix. Calcined kaolin, titanium dioxide, satin white, aluminium hydroxide, sodium silicoaluminate and plastics pigments are additional pigments, and their amounts are in general less than 25 % of the dry solids in the mix.
Special-quality kaolins and calcium carbonates, as well as barium sulphate and zinc oxide of the special pigments should be mentioned as examples.
Any known binders generally used in paper production can be used as binders in the coating composition. Besides the individual binders, it is also possible to use mixtures of binders. Examples of typical binders include synthetic latexes made up of polymers or copolymers of ethylenically unsaturated compounds, e.g. copolymers of the butadienestyrene type, and polyvinyl acetate having comonomers that contain carboxyl groups. Together with the materials mentioned above, it is possible to use , for example, water-soluble polymers, starch, CMC, hydroxyethyl cellulose and polyvinyl alcohol as binders. Furthermore, conventional additives and auxiliary agents, such as dispersants, agents affecting the viscosity and water retention of the mix, lubricants, hardeners used for improving water-resistance, optical auxiliary agents, anti-foaming agents, pH
control agents, and preservatives can be used in the coating composition.
The coating mix can be applied to the material web in a manner known per se.
The coating can be done before couching. Preferably it is done after forming the multi-layer structure.
The method according to the present invention for coating paper and/or board can be carried out with a conventional coating apparatus, in other words by blade coating, or by film coating or JET application. Coating can be done on-line or off-line.
The amount of grammage of the coating layer varies from 5 to 30 g/m2.
It has also been found in the context of the the present invention, quite surprisingly, that the above-described filler does not only improve opacity of the top layer but the filled layer is also very easy to be coated. The amount of pigment or amounts of coatings required for the desired brightness can be decreased with the filler.
According to the present invention, the opacity is significantly improved with the filler.
The following non-restrictive examples illustrate the present invention. The measurement results indicated for the paper properties in the examples have been determined by the 10 following standard methods:
Surface roughness: SCAN-P76:95 Porosity:. SCAN-P60 Resistance of air permeability: SCAN-M8,P 19 Example 1 Production of filler Re of chemical gulp Birch sulphate pulp was refined with a Valmet JC-01 refiner to produce pulp that is suitable for production of filler. The consistency of refining was about 4 %
and the total energy consumption was 343 kWh/t and specific edge load was 0.5 J/m.
Properties of the product are presented in Table 1.
Table 1. Fibre properties before and after refining Before refining After refining Fibre length (length), mm 0.86 0.58 Fibre length (weight), mm 1.00 0.77 Carbonating of pulp Carbonating was performed in tap water according to the FI Patent Specification No.
100729. Water slurry that has dry matter content of 2.22 % was produced. The final product had CaCO3 content of 69.7 % and a specific surface area of 10.6 m2/kg.
Example 2 Fibre layers suitable for cover layer of two-layer white lined liner was produced from chemical pulp that contained 70 % by weight of birch pulp and 30 % by weight of pine pulp. Filler was added from the pulp in the slush in various amounts: 13 and 20 % by weight, respectively, of filler described in example 1(SuperFill),14 and 16 %
by weight, respectively, precipitated calcium carbonate (PCC, Albacar LO, ref. 1) and 14 % by weight of mixture of chalk and calcined kaolin (ref. 2).
Figures 2 to 4 illustrate the light scattering ability of the obtained fibre layers as a function of mechanical strength properties. The figures show that the light scattering factor is at least 25 % and about 20 % greater with the SuperFill filler when compared with references 1 and 2 in constant strengths.
Consequence of this is that the grammage of the surface can be decreased by about 20 %, which decreases significantly production costs of liner.
Figure 5 shows a result in which the above presented results are substantiated. The result is from a liner test run made by pilot machine (FEX) of STFI in Stockholm, wherein the grammage of the surface was decreased from the normal level of 75 g/m2 to a level of 65 g/m2. A two-layer fibre structure was produced for the test. The ISO
brightness of the product was determined.
Figure 5 shows that the top layer lightened 10 g/m2 with Superfill, generates brightness which is 4 brightness units greater as compared with the reference 2, in which the grammage is 75 g/m2. The result is extremely good and it suggests that the grammage of the surface can be decreased even lower than 10 g/m2.
Preferably the liner according to the present invention comprises a two-layer product (see Figure 1 a), that has a surface of a cover layer 1 and a back layer 2. The top layer covers the back layer so that the back layer cannot be seen through the top layer.
It is also possible to produce three-layer or four-layer products. In principle the number of layers in a layer product has no upper limit, there can be even up to 5, 6 or 7 layers. What is essential in the present invention, is that the top layer contains filler described more precisely hereinbefore, so that the top layer covers the layers under it, the layers that can be produced from raw materials of cheap costs.
Among multi-layer products, the test liner type four-layer products of Figure lb, having a top layer 3, a layer 4 under the top layer, intermediate layer 5 and a back layer 6, are to be mentioned.
Different raw materials can be used for production of a fibre product according to the purpose of use. Both virgin fibres and recycled fibres can be used. The virgin fibre can originate from softwood or hardwood (wood chips) or it can originate from cuttings.
Especially preferably virgin pulp is used in the top layer. This is most suitably produced by sulphate cooking (kraft pulp), because sulphate cooking gives a mass having especially good strength properties, as the name suggests. The recycled fibre can originate e.g. from used corrugated board packages (OCC) or mixed fibres. Recycled fibres are used especially for the production of test liners. The surface and back layer(s) can be produced from similar raw materials or from different source fibres. If virgin fibre, such as kraft pulp, is used for both, then the mass of the back layer can be cooked in high yield, after which a mild refining is performed on it. Mass that has been cooked to a lower kappa and also refined more than mass of the back layer, is used for the top layer.
Typically the pulp of the back layer is cooked to a kappa value of 30 to 70 and the pulp of the top layer to lower kappa value of 25 (the kappa number of the unbleached pulp). Bleaching can be performed in a manner known per se, e.g. as ECF of TCF bleaching.
Retention agents can be added to the slush e.g. in about 0.5 to 3 % of the amount of the fibre material. However, it has been found in connection with the present invention that the filler described here gives such a good retention that no retention agents are needed for the layer the and amount of the retention agents can be significantly decreased.
The liner is stuff or surface sized to improve the moisture resistance. If a low quality recycled fibre is used as raw material, it is preferable to use a surface-size press to produce a product that has sufficient strength. According to the machine the distribution of the base weight between the top and the back layer is about 20/80...40/60, typically about 30/70. Thus the grammage of the top layer is generally about 20 to 125 g/m2 (see below). When operating according to the present invention, the grammage of the top layer can be decreased over 10 %, up to 20 % or more, without deteriorating the optical or mechanical properties of the cover.
The layer product is produced in a manner known per se. According to one preferred embodiment both or all layers are produced first from slush of their own and spread on the Fourdriner wire. After this, the layers are couched fastened into each other.
With regard to the production process, a reference is made to a text by Ari Kiviranta "Board Grades", in a book series Paper-Making Science and Technology, Book 18, Paper and Board Grades, Fapet Oy, Jyvaskyla 2000, pages 68 and 69.
A planar fibre product according to the present invention can be used as a top layer of different corrugate board packages. The solution according to the present invention is especially preferably suitable for white lined top liner and coated white lined liner, both of which are used for demanding printing works. In these objects the fact that the surface of the liner according to the invention is extremely smooth and uniform, and has at the same time high opacity and brightness can be made use of. Generally the grammage of the top layer is about 20 to 125 g/m2, most suitably about 50 to 80 g/m2, especially preferably about 55 to 70 g/m2, and bleached chemical cellulose pulp is used of the top layer. In order to obtain a very good formation in the preferred embodiment of the present invention, mainly hardwood is used in the top layer. Thus e.g. over 60 % by weight, typically over 80 % of fibre material of pulp is hardwood and the rest softwood. The fibre material of pulp can consist totally of hardwood.
Conventional coating mixtures can be used for coating of the coated white lined top layer product. Precipitated calcium carbonate, ground calcium carbonate, calcium sulphate, calcium oxalate, aluminium silicate, kaolin (hydrous aluminium silicate), aluminium hydroxide, magnesium silicate, talc (hydrous magnesium silicate), titanium dioxide and barium sulphate, and mixtures thereof can be used as pigments. Synthetic pigments can also be used. Of the pigments mentioned above, the main pigments are kaolin, calcium carbonate, precipitated calcium carbonate and gypsum, which in general constitute over 50 % of the dry solids in the coating mix. Calcined kaolin, titanium dioxide, satin white, aluminium hydroxide, sodium silicoaluminate and plastics pigments are additional pigments, and their amounts are in general less than 25 % of the dry solids in the mix.
Special-quality kaolins and calcium carbonates, as well as barium sulphate and zinc oxide of the special pigments should be mentioned as examples.
Any known binders generally used in paper production can be used as binders in the coating composition. Besides the individual binders, it is also possible to use mixtures of binders. Examples of typical binders include synthetic latexes made up of polymers or copolymers of ethylenically unsaturated compounds, e.g. copolymers of the butadienestyrene type, and polyvinyl acetate having comonomers that contain carboxyl groups. Together with the materials mentioned above, it is possible to use , for example, water-soluble polymers, starch, CMC, hydroxyethyl cellulose and polyvinyl alcohol as binders. Furthermore, conventional additives and auxiliary agents, such as dispersants, agents affecting the viscosity and water retention of the mix, lubricants, hardeners used for improving water-resistance, optical auxiliary agents, anti-foaming agents, pH
control agents, and preservatives can be used in the coating composition.
The coating mix can be applied to the material web in a manner known per se.
The coating can be done before couching. Preferably it is done after forming the multi-layer structure.
The method according to the present invention for coating paper and/or board can be carried out with a conventional coating apparatus, in other words by blade coating, or by film coating or JET application. Coating can be done on-line or off-line.
The amount of grammage of the coating layer varies from 5 to 30 g/m2.
It has also been found in the context of the the present invention, quite surprisingly, that the above-described filler does not only improve opacity of the top layer but the filled layer is also very easy to be coated. The amount of pigment or amounts of coatings required for the desired brightness can be decreased with the filler.
According to the present invention, the opacity is significantly improved with the filler.
The following non-restrictive examples illustrate the present invention. The measurement results indicated for the paper properties in the examples have been determined by the 10 following standard methods:
Surface roughness: SCAN-P76:95 Porosity:. SCAN-P60 Resistance of air permeability: SCAN-M8,P 19 Example 1 Production of filler Re of chemical gulp Birch sulphate pulp was refined with a Valmet JC-01 refiner to produce pulp that is suitable for production of filler. The consistency of refining was about 4 %
and the total energy consumption was 343 kWh/t and specific edge load was 0.5 J/m.
Properties of the product are presented in Table 1.
Table 1. Fibre properties before and after refining Before refining After refining Fibre length (length), mm 0.86 0.58 Fibre length (weight), mm 1.00 0.77 Carbonating of pulp Carbonating was performed in tap water according to the FI Patent Specification No.
100729. Water slurry that has dry matter content of 2.22 % was produced. The final product had CaCO3 content of 69.7 % and a specific surface area of 10.6 m2/kg.
Example 2 Fibre layers suitable for cover layer of two-layer white lined liner was produced from chemical pulp that contained 70 % by weight of birch pulp and 30 % by weight of pine pulp. Filler was added from the pulp in the slush in various amounts: 13 and 20 % by weight, respectively, of filler described in example 1(SuperFill),14 and 16 %
by weight, respectively, precipitated calcium carbonate (PCC, Albacar LO, ref. 1) and 14 % by weight of mixture of chalk and calcined kaolin (ref. 2).
Figures 2 to 4 illustrate the light scattering ability of the obtained fibre layers as a function of mechanical strength properties. The figures show that the light scattering factor is at least 25 % and about 20 % greater with the SuperFill filler when compared with references 1 and 2 in constant strengths.
Consequence of this is that the grammage of the surface can be decreased by about 20 %, which decreases significantly production costs of liner.
Figure 5 shows a result in which the above presented results are substantiated. The result is from a liner test run made by pilot machine (FEX) of STFI in Stockholm, wherein the grammage of the surface was decreased from the normal level of 75 g/m2 to a level of 65 g/m2. A two-layer fibre structure was produced for the test. The ISO
brightness of the product was determined.
Figure 5 shows that the top layer lightened 10 g/m2 with Superfill, generates brightness which is 4 brightness units greater as compared with the reference 2, in which the grammage is 75 g/m2. The result is extremely good and it suggests that the grammage of the surface can be decreased even lower than 10 g/m2.
Claims (10)
1. A multi-layer fibrous product comprising of a top layer which overlaps one or more lower layers, wherein the top layer a) contains filler;
b) is less dense than the one or more lower layers; and c) is at least essentially opaque;
characterised in that the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils on which light scattering material particles have been precipitated;
wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils;
wherein said fibrils on which said light scattering material particles are attached:
i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.01 to 5 µm and an average length of 10 to 1500 µm;
wherein said multi-layer fibrous product has a grammage of about 80 to 350 g/m2 and said top layer has a grammage of about 20 to 125 g/m2; and wherein the distribution of the grammage between the top layer and the one or more layers is between about 20/80 and 40/60.
b) is less dense than the one or more lower layers; and c) is at least essentially opaque;
characterised in that the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils on which light scattering material particles have been precipitated;
wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils;
wherein said fibrils on which said light scattering material particles are attached:
i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.01 to 5 µm and an average length of 10 to 1500 µm;
wherein said multi-layer fibrous product has a grammage of about 80 to 350 g/m2 and said top layer has a grammage of about 20 to 125 g/m2; and wherein the distribution of the grammage between the top layer and the one or more layers is between about 20/80 and 40/60.
2. The multi-layer fibrous product according to claim 1, wherein the light scattering material particles are inorganic salts that can be formed from source materials by precipitation in an aqueous medium.
3. The multi-layer fibrous product according to claim 2, wherein the light scattering material particles are calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate or mixtures thereof.
4. The multi-layer fibrous product according to any one of claims 1-3, wherein the multi-layer fibrous product comprises a white lined top liner or a coated white lined liner.
5. The multi-layer fibrous product according to claim 1, wherein said top layer has a grammage of about 50 to 70 g/m2.
6. The multi-layer fibrous product according to any one of claims 1-5, wherein the top layer is produced from chemical cellulose pulp comprising hardwood pulp, softwood pulp or a mixture thereof.
7. The multi-layer fibrous product according to any one of claims 1-6, wherein the one or more lower layers comprise 1 to 5 layers that have been produced from virgin fibre or recycled fibre.
8. A process for producing a multi-layer product which consists of a top layer and a backing layer, comprising the step of:
a) fitting a fibre layer, which contains a filler and which forms the top layer and a surface of the multi-layer product, on top of the backing layer that consists of one or more fibrous layers to produce the multi-layered product, wherein the fibre layer is formed from a slush of fibre material which includes the filler which is comprised of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated, wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils, wherein said fibrils on which said light scattering material particles are attached:
i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.1 to 10 µm and an average length of 10 to 1500 µm;
wherein said multi-layer fibrous product has a grammage of about 80 to 350 g/m2 and said top layer has a grammage of about 20 to 125 g/m2; and wherein the distribution of the grammage between the top layer and the one or more fibrous layers is between about 20/80 and 40/60.
a) fitting a fibre layer, which contains a filler and which forms the top layer and a surface of the multi-layer product, on top of the backing layer that consists of one or more fibrous layers to produce the multi-layered product, wherein the fibre layer is formed from a slush of fibre material which includes the filler which is comprised of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated, wherein at least 80 % of the precipitated light scattering material particles are attached to said fibrils, wherein said fibrils on which said light scattering material particles are attached:
i) correspond to a fraction of fibrils that pass through a 50 mesh screen; or ii) have an average thickness of 0.1 to 10 µm and an average length of 10 to 1500 µm;
wherein said multi-layer fibrous product has a grammage of about 80 to 350 g/m2 and said top layer has a grammage of about 20 to 125 g/m2; and wherein the distribution of the grammage between the top layer and the one or more fibrous layers is between about 20/80 and 40/60.
9. The process according to claim 8, wherein the fibre layer which is fitted on top of the backing layer is coated in a paper machine with a pigment-containing coating mixture.
10. The process according to claim 8 or 9, wherein the fibre layer which is fitted on top of the backing layer and the backing layer is formed separately on a Fourdriner wire and couched when still wet.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI20010848A FI117871B (en) | 2001-04-24 | 2001-04-24 | Multilayer fiber product and process for its preparation |
FI20010848 | 2001-04-24 | ||
PCT/FI2002/000342 WO2002092910A1 (en) | 2001-04-24 | 2002-04-24 | Multilayered fibrous product and a process for the production thereof |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2445100A1 CA2445100A1 (en) | 2002-11-21 |
CA2445100C true CA2445100C (en) | 2012-12-18 |
Family
ID=8561048
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA2445100A Expired - Fee Related CA2445100C (en) | 2001-04-24 | 2002-04-24 | Multilayered fibrous product and a process for the production thereof |
Country Status (9)
Country | Link |
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US (1) | US20040168779A1 (en) |
EP (1) | EP1392923B1 (en) |
JP (1) | JP4582998B2 (en) |
CN (1) | CN100396848C (en) |
AU (1) | AU2002249300B2 (en) |
CA (1) | CA2445100C (en) |
FI (1) | FI117871B (en) |
NZ (1) | NZ529159A (en) |
WO (1) | WO2002092910A1 (en) |
Families Citing this family (25)
Publication number | Priority date | Publication date | Assignee | Title |
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GB0030132D0 (en) * | 2000-12-09 | 2001-01-24 | Arjo Wiggins Fine Papers Ltd | Security paper |
EP1426489A1 (en) * | 2001-06-06 | 2004-06-09 | Kemira Chemicals Oy | Method for manufacturing a multilayered pulp product comprising a charge between layers |
US7211171B2 (en) * | 2002-01-05 | 2007-05-01 | The Procter & Gamble Company | Multiply tissue product |
US20040168781A1 (en) * | 2002-08-05 | 2004-09-02 | Petri Silenius | Noil for use in paper manufacture, method for its production, and paper pulp and paper containing such noil |
FI115475B (en) * | 2002-10-24 | 2005-05-13 | M Real Oyj | Process for making paper and cardboard |
FI122074B (en) | 2002-10-24 | 2011-08-15 | M Real Oyj | Process for making a fiber product |
CN101031686A (en) * | 2004-07-14 | 2007-09-05 | 国际纸业公司 | Method to manufacture paper |
US7491293B2 (en) * | 2004-09-29 | 2009-02-17 | Meadwestvaco Corporation | White top paperboard |
FI20055380L (en) * | 2005-07-01 | 2007-01-02 | M Real Oyj | Method for coating cellulose particles, coated cellulose particles and their use in paper and cardboard manufacturing |
US20070202283A1 (en) * | 2006-02-27 | 2007-08-30 | John Meazle | Reducing top ply basis weight of white top linerboard in paper or paperboard |
FI118809B (en) * | 2006-09-11 | 2008-03-31 | M Real Oyj | Process for the manufacture of a fiber product |
WO2008052970A1 (en) * | 2006-10-31 | 2008-05-08 | Basf Se | Method for producing a multi layer fiber web from cellulose fibers |
FI20085767L (en) * | 2008-08-11 | 2010-02-12 | Kemira Oyj | Gypsum product |
JP5528760B2 (en) * | 2009-09-30 | 2014-06-25 | 日本製紙株式会社 | Paper made by adding cellulose nanofibers and method for producing the same |
CN102535251B (en) * | 2011-12-30 | 2013-11-06 | 淄博欧木特种纸业有限公司 | Dustless abrasion-proof paper and making method thereof |
CA2962292C (en) | 2014-10-10 | 2019-02-05 | Fpinnovations | Compositions, panels and sheets comprising cellulose filaments and gypsum and methods for producing the same |
JP6729205B2 (en) * | 2016-09-05 | 2020-07-22 | 王子ホールディングス株式会社 | White liner for corrugated board, manufacturing method thereof, and white corrugated board |
WO2018097324A1 (en) * | 2016-11-28 | 2018-05-31 | 日本製紙株式会社 | Method for producing composite body of fibers and inorganic particles, and laminate containing composite body of fibers and inorganic particles |
EP3604671B1 (en) | 2017-03-31 | 2021-05-05 | Nippon Paper Industries Co., Ltd. | Method for manufacturing inorganic particle composite fiber sheet |
BR102017028522A2 (en) * | 2017-12-28 | 2019-07-16 | Klabin S/A | SHORT CHEMICAL FIBER KRAFTLINER PAPER |
CN111819325B (en) * | 2018-01-05 | 2023-05-12 | 国际纸业公司 | Paper product with increased bending stiffness and transverse strength and method of making same |
CN111335067B (en) * | 2020-04-14 | 2022-05-13 | 联盛纸业(龙海)有限公司 | Craft paper capable of improving L-value brightness of paper surface, surface layer and production method thereof |
AT524998B1 (en) * | 2021-04-21 | 2023-02-15 | Mondi Ag | Printable multi-ply paper for packaging and method of making same |
AT526620A1 (en) | 2022-11-08 | 2024-05-15 | Mondi Ag | Process for producing a printable liner web for packaging and printable liner for packaging |
AT526619A1 (en) | 2022-11-08 | 2024-05-15 | Mondi Ag | Process for producing a printable liner web for packaging and printable liner for packaging |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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FR935128A (en) * | 1946-01-28 | 1948-06-10 | Vanderbilt Co R T | Improvements in papermaking |
SE7708115L (en) * | 1976-07-14 | 1978-01-15 | English Clays Lovering Pochin | PROCEDURE FOR PREPARING PAPER OR CARDBOARD |
US5223090A (en) * | 1991-03-06 | 1993-06-29 | The United States Of America As Represented By The Secretary Of Agriculture | Method for fiber loading a chemical compound |
FR2689530B1 (en) * | 1992-04-07 | 1996-12-13 | Aussedat Rey | NEW COMPLEX PRODUCT BASED ON FIBERS AND FILLERS, AND METHOD FOR MANUFACTURING SUCH A NEW PRODUCT. |
CA2195300C (en) * | 1995-05-18 | 2001-06-12 | Michael C. Withiam | Method for preparation of pigmented paper fibers and fiber products |
FI100729B (en) * | 1995-06-29 | 1998-02-13 | Metsae Serla Oy | Filler used in papermaking and method of making the filler |
FI100670B (en) * | 1996-02-20 | 1998-01-30 | Metsae Serla Oy | Process for adding filler to cellulose fiber based m assa |
FI106140B (en) * | 1997-11-21 | 2000-11-30 | Metsae Serla Oyj | Filler used in papermaking and process for its manufacture |
-
2001
- 2001-04-24 FI FI20010848A patent/FI117871B/en not_active IP Right Cessation
-
2002
- 2002-04-24 US US10/475,773 patent/US20040168779A1/en not_active Abandoned
- 2002-04-24 NZ NZ529159A patent/NZ529159A/en not_active IP Right Cessation
- 2002-04-24 JP JP2002590164A patent/JP4582998B2/en not_active Expired - Lifetime
- 2002-04-24 AU AU2002249300A patent/AU2002249300B2/en not_active Ceased
- 2002-04-24 WO PCT/FI2002/000342 patent/WO2002092910A1/en active IP Right Grant
- 2002-04-24 CA CA2445100A patent/CA2445100C/en not_active Expired - Fee Related
- 2002-04-24 CN CNB028121619A patent/CN100396848C/en not_active Expired - Fee Related
- 2002-04-24 EP EP02718226.0A patent/EP1392923B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
US20040168779A1 (en) | 2004-09-02 |
FI20010848A0 (en) | 2001-04-24 |
JP4582998B2 (en) | 2010-11-17 |
FI117871B (en) | 2007-03-30 |
JP2004525282A (en) | 2004-08-19 |
WO2002092910A1 (en) | 2002-11-21 |
CN1516770A (en) | 2004-07-28 |
CA2445100A1 (en) | 2002-11-21 |
EP1392923A1 (en) | 2004-03-03 |
AU2002249300B2 (en) | 2008-04-24 |
FI20010848A (en) | 2002-10-25 |
EP1392923B1 (en) | 2018-07-25 |
NZ529159A (en) | 2005-07-29 |
CN100396848C (en) | 2008-06-25 |
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