A GROUND COVER MULCH COMPRISING MINERALS AND FUNCTIONAL AGENTS

Abstract

The invention relates to a ground cover in the form of a mulch, comprising a paper substrate originating from fibre-bearing pulp, preferably emanating from lignocellulosic material, which has been web-formed or sheet-formed. Paper based mulches face problems with biodegradability and microbial attacks, mechanical strength and cost. The solution according to the invention is that the fibres have been coated with one or more minerals, e.g., calcium carbonate, and the mulch comprises one or more functional agents, e.g., a colorant. Further, the mineral coated onto or into the fibres predominantly show up when precipitated in the form of one or more metal carbonates.

Claims

1. A ground cover in the form of a mulch, providing an environmentally sound solution for enabling re-using of minerals and at the same time providing a controlled biological degradation and fertilizing effect, which comprises a paper substrate originating from fibre-bearing pulp, which has been web-formed or sheet-formed, wherein the fibers have been coated with one or more minerals, and the mulch comprises one or more functional agents.

2. A cover according to claim 1 wherein the minerals are one or more carbonized minerals.

3. A cover according to claim 1 containing additionally one or more fillers.

4. A cover according to claim 3, wherein the filler is selected from the group consisting of talc, kaolin, lime, silica and aluminum oxides or combinations thereof.

5. A cover according to claim 1 wherein the functional agents are one or more colorant(s)colorants and/or one or more performance chemicals.

6. A cover according to claim 5 wherein the performance chemicals are selected from the group: strength additives, hydrophobic agents and retention chemicals or combinations thereof.

7. A cover according to claim 5 wherein the colorants include one or more UV absorbents and/or a carbon black.

8. A cover according to claim 1 further comprising one or more biocides and/or one or more nutrients.

9. A cover according to claim 7 wherein the carbon black emanates from a non-fossil source.

10. A cover according to claim 1 further comprising one or more additional layers.

11. Method for manufacturing a ground cover according to claim 1 comprising the following steps: a) providing a fiber suspension, b) providing one or more minerals, c) coating the minerals onto or into said fibres, d) forming a paper/board web substrate, thus providing a web substrate or sheet, and e) adding one or more functional agent(s) to the web substrate, thus providing a cover.

12. Method for manufacturing a cover according to claim 11 wherein the forming is made with a dry or wet laid process.

13. Method for manufacturing a cover according to claim 11 wherein step c) is performed at the wet end of a paper/board production line.

14. Method for manufacturing a cover according to claim 11 wherein step e) also comprises adding one or more biocide(s) and/or nutrient(s).

15. A ground cover in the form of a mulch, obtainable by the method of claim 11.

16. (canceled)

17. A cover according to claim 1, wherein the fibre-bearing pulp emanates from lignocellulosic material.

18. The cover according to claim 2, wherein the one or more carbonized minerals emanates from one or more metal hydroxides.

19. The cover according to claim 2 wherein the one or more carbonized minerals have been recycled.

20. A cover according to claim 9 wherein the non-fossil source is from biomass or organic waste residues of non-fossil origin.

21. The method according to claim 11, wherein the minerals are precipitated in the form of one or more metal carbonates.

22. The method of claim 21, wherein metal carbonates include calcium carbonate that is precipitated by using water and/or gaseous CO.sub.2 and/or sodium carbonate, or mixtures thereof.

23. The method according to claim 11 further comprising adding at least one filler, to the fibres with precipitated minerals after step c).

24. The method according to claim 11 further comprising a drying step after step d).

25. The method according to claim 11 further comprising providing one or more additional layers to the web substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0026] It is intended throughout the present description that the expression coated embraces in the context of fibres, useful in the context of ground covers (such as mulches), that said fibres may not be fully coated but also partly coated. It also in this context embraces lumen loaded, i.e. that the fibres may be lumen loaded.

[0027] The expressions fibre and fiber are further used interchangeably in the present description meaning the same thing.

[0028] The pulp mentioned in the present description, may be chemical pulp, mechanical pulp, thermomechanical pulp or chemi(thermo)mechanical pulp (CMP or CTMP). Said chemical pulp is preferably a sulphite pulp or a Kraft pulp.

[0029] The pulp may consist of pulp from hardwood, softwood or both types. The pulp may e.g. contain a mixture of pine and spruce or a mixture of birch and spruce. The chemical pulps that may be used in the present invention include all types of chemical wood-based pulps, such as bleached, half-bleached and unbleached sulphite, Kraft and soda pulps, and mixtures of these. The pulp may be of dissolving pulp type. The pulp may also comprise textile fibers, polymers or synthetic fibres. The pulp may also come from agriculture (e.g. potato, bamboo, wheat, bagasse or carrot). The pulp may also be nanocellulose, microfibrillated cellulose or cellulose whiskers. Said nanocellulose, microfibrillated cellulose or cellulose whiskers may also be chemically modified. Also combinations of said pulp types are possible in the context of the present invention. The pulp may also contain synthetic fibers or biofibers such as PLA (Poly-lactic acid). The pulp may also emanate from broke, recycled pulp, and sludge.

[0030] The minerals mentioned in the present description may be one or more minerals, such as carbonized minerals emanating from one or more metal hydroxides, for example calcium hydroxide, magnesium hydroxide and/or fly ash, preferably wherein said mineral(s) has/have been recycled and thus said minerals are re-used.

[0031] It is intended throughout the present description that the expression minerals also embraces in the context of ground covers (such as mulches), non-carbonized metal hydroxides, such as calcium hydroxide, magnesium hydroxide. In the context of the present invention also fly ash is included in the expression mineral(s) even though this normally comprises different mineralogical compounds.

[0032] Said minerals may also be present in the form of particles (fines), which may comprise one or several metal hydroxides. Said minerals may also be calcined. This provides a low brightness material. Said fly ash could be derived from bottom ash, textile filters, electrostatic precipitators. Said ash may also be of different types e.g. it may be derived from biomasses, or coal.

[0033] There are also different mineralogical phases in fly ash from the paper industry which are e.g. quartz, calcite, lime, calcium silicate, anhydrite, merwenite, magnesite and gehlenite. The major chemical elements are CaO, SiO.sub.2 and Al.sub.2O.sub.3 (in order high to low). The size distribution of the fly ash varies between type of boiler, incineration conditions etc. A typical paper mill ash has all particles <500 m. 50% <30 m. Other possible fly ashes could also be, in the context of the present invention, coal fly ash and wood fly ash (on condition that the CaO content is high enough). Fly ash from waste incineration is also possible, but may be polluted and therefore might need extra treatment. Fly ash from different steps in the flue gas treatment could also be used in this context. Different kinds of treatment methods to improve the properties may also be used such as fractionation and/or grinding. The fly ash may also be purified.

[0034] Said coating procedure in step c) (which may involve nucleation, precipitation and/or crystallization on the fiber) may further be made according to an in-line technique alternatively to an at-site or off-line method.

[0035] Said coating procedure can also be made on part of the fiber fraction (which may be done before said fraction is added to the rest of the fibres which in turn is treated) and also at different fiber concentrations. The coating procedure can also take place in presence of other functional agents (such as performance chemicals).

[0036] It is intended throughout the present description that the expression thermoplastic embraces any thermoplastic polymer (which may be of fossil origin) that may be useful in the context of the manufacturing of ground covers, such as mulches. Said polymer may be, but is not limited to acrylates such as PMMA, PP (Polypropylene), PE (Polyethylene) such as HDPE (high density PE), MDPE (medium density PE), LDPE (low density PE), PA (Polyamide) such as nylon, PS (Polystyrene), Polyvinylchloride (PVC), polysulfone, ether ketone or polytetrafluoroethylene (PTFE). The PE may further be cross-linked (PEX). It may further be co-polymers comprising two or more of said polymers or mixtures comprising two or more of said polymers. Preferably PP (Polypropylene) or PE (Polyethylene) is used.

[0037] According to a further preferred embodiment of the first aspect of the invention the ground cover contains additionally one or more fillers.

[0038] According to a further preferred embodiment of the first aspect of the invention the filler is selected from the group comprising talc, kaolin, lime, silica and aluminum oxides or combinations thereof.

[0039] According to a further preferred embodiment of the first aspect of the invention the functional agent(s) is (are) one or more colorant(s) and/or one or more performance chemical. Said functional agents may improve the opacity and reduced brightness. Said substrate of the first aspect may also be surface sized, impregnated or surface treated to provide features such as controlled mechanical properties, biodegradability and/or hydrophobicity.

[0040] According to a further preferred embodiment of the first aspect of the invention the performance chemical(s) is (are) selected from the group: strength additives, hydrophobic agents and retention chemicals or combinations thereof. Said performance chemical(s) may also be one or more of the following:

[0041] Wet strength chemicals which can be e.g. UF resins (urea-formaldehyde), melamine-formaldehyde resins (MF), polyamide-amine epichlorohydrine (PARE), Epichlorohydrine (ECH), polyacryl amide/glyoxal, starch/glyoxal

[0042] Water soluble polymers such as fixing agents (PDADMAC, CPAM, PEI, PVAm, cationic starch), retention chemicals (Cationic

[0043] PAM, PAM, Anionic PAM, PEI, cationic starch, amphoteric starch, PEO, etc.), dry (cationic starch, different gums, acrylamide based polymers (PAM), polyvinyl amine (PVAm), CMC, chitosan, etc.) and wet strength agents (see above). Sizing dispersions such as alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosins.

[0044] Pigments CaCO3, etc. and organic pigments such as starch pigments.

[0045] Surface sizing or coating chemicals that includes [0046] latexes such as styrene/butadiene, styrene/acrylate, or SMA, SMI, PE emulsions, nanostarch [0047] cross-linkers [0048] chemicals to control electrical or dielectric properties such as electrolytes [0049] binders to control surface strength and e.g. dusting

[0050] According to a further preferred embodiment of the first aspect of the invention the colorant(s) include one or more UV absorbents and/or a carbon black.

[0051] According to a further preferred embodiment of the first aspect of the invention said ground cover comprises also one or more biocide(s) and/or nutrient(s). The biocides may be a fungicide or a bactericide or a combination thereof. The nutrient may also be a stimulant for photosynthesis.

[0052] According to a further preferred embodiment of the first aspect of the invention the carbon black emanates from a non-fossil source, preferably from biomass or organic waste residues of non-fossil origin. The source is preferably lignin.

[0053] According to a further preferred embodiment of the first aspect of the invention said cover comprises also one or more additional layers. Said layers may be formed by nanocellulose, microfibrillated cellulose and/or cellulose whiskers, or by a thermoplastic, or by a composite comprising both fibres of lignocellulosic origin and one or more thermoplastics. Said nanocellulose, microfibrillated cellulose or cellulose whiskers may preferably be added in an amount of 0.2-40 g/m.sup.2 or more preferably in an amount of 1-30 g/m.sup.2 or most preferably in an amount of 5-25 g/m.sup.2. Said nanocellulose, microfibrillated cellulose or cellulose whiskers may be added in the form of a suspension that may additionally comprise other process or performance chemicals suitable in said context. The additional layer may provide enhanced characteristics related to enhanced water barrier, fumigation, oxygen barrier etc. but it may also have an influence on strength properties and also dimensional stability which is of importance.

[0054] According to a further preferred embodiment of the method according to the second aspect of the present invention the forming is made with a dry or wet laid process, preferably a wet laid process.

[0055] According to a further preferred embodiment of the method according to the second aspect of the present invention steps c) and d) is performed at the wet end of a paper/board production line. The paper may, as said earlier, be a multi-ply paper.

[0056] According to a further preferred embodiment of the method according to the second aspect of the present invention step f) also comprises adding one or more biocide(s) and/or nutrient(s).

[0057] As said the present invention provides the use of a mineral coated fiber as a material when preparing a cost efficient ground cover, preferably in the form of a paper mulch. Further the synthetized mineral(s) may preferably be precipitated onto the fibers by using e.g. CO.sub.2. By this fixing approach, it is possible to reduce costs of the substrate, enhance the opacity and enhance the biocidic effect (control degradation). The approach requires also less binder and it will also act as a nutrient for the soil. In addition the present invention solves the problem with binding of fly ash from an environmental perspective. Thus the present invention also allows the re-use and spreading of fly ash (being part of a ground cover) in an efficient way, which is an ecologically sound solution.

[0058] The composition of the raw material (preferably involving fly ash) should preferably have high content of CaO (>30%), whereas the brightness is less significant. In fact, a lower brightness grade is more preferred in order to prevent light transmission. A dark pigment will enable less need for black pigment (filler) in the surface treatment step. By utilizing this approach, it is possible to control the dosing of functional agents and minerals to soil.

[0059] There may also be an amount of Fe, Mg, Na, K, Zn and so on in fly ash and they may more act like tracers.

[0060] The usage of fly ash (instead of lime) can also reduce CO.sub.2 emissions. In addition one can expect that fly ash in itself has also pesticide effects for the ground cover, in the form of a mulch. Also as fly ash is bound in the ground cover according to the first aspect of the present invention, less fly ash will be washed with waters to ground water (compared to normal addition methods of fly ash). The ground cover according to the first aspect of the invention, such as a mulch, may also be helpful (e.g. in greenhouse environments) for improving heat retention in winter and cooling in summer to extend the growing season. The ground cover may also be helpful for soil conditioning/soil amendment to improve poor soils, or to rebuild soils. Said ground cover may also be helpful for enhancing soil stewardship mechanism for locking carbon into soil. Said ground cover may also contribute in such a way that a lower amount of chemical fertilizers may be needed. Also precipitation might occur in the presence of additional fertilizing chemicals such as e.g. phosphates, urea, etc. that also could enhance said effect of the ground cover.

[0061] Preferred features of each aspect of the invention are as for each of the other aspects mutatis mutandis. The prior art documents mentioned herein are incorporated to the fullest extent permitted by law.

[0062] In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.