A ground cover mulch comprising carbon fiber

Field of invention

The present invention relates to a ground cover mulch comprising carbon black fibers. Also a method for its manufacture and use thereof is disclosed together with use of carbon black fibers. In particular the present invention relates to an improved paper mulch composition and more preferably a biodegradable paper mulch made of renewable materials .

Background

It is known from prior art to make paper mulch for agricultural production. Such paper comprises various components whereas its mechanical properties, cost and safety are important. Biodegradability is also an important feature whereas also the temporarily weather resistance is too .

One of the problems with making fiber based paper mulch is to dye the substrate black. This can be done using e.g. carbon black as disclosed below. The carbon black could either be added via a surface treatment step or steps such as coating or impregnation, or then in the wet end, or a combination of both.

The problem with the carbon black is that chemicals are needed to improve its retention. Higher amount of carbon black will also reduce strength. The use of carbon black as coating or surface sizing additive will partly solve the problem, but higher amounts of carbon black will then cause a very dense structure. The carbon black listed in the prior art are often made from petroleum based sources, which means that the raw material is not from a renewable resource.

In US3896585 there is disclosed a furnace or thermal black used in degradable agricultural mulch. The degradable agricultural mulch comprises a degradable film of

polybutene-1 or polypropylene which is at least about 40% isotactic, which film is about 0.4 to 20 mils thick and has a TALU rating of less than about 75,000 TALU, the

improvement which comprises incorporating therein about 0.04 to 2% by weight of a stabilizer and about 0.05 to 5% by weight of furnace or thermal black having a particle size of about 200 to 800 A.

In JP2003284435 a coating liquid for black colored paper mulch is disclosed together with a method for

producing black colored paper mulch. It is said to provide inexpensive and practical black colored paper mulch to be laid on the ground surface of a cultivated land so as to prevent weeds from growing from the ground surface by attenuation effect of transmitted light of sunshine to the ground surface and free from problems on safety and health.

The coating liquid for the black colored paper mulch is said to be obtain by dispersing powder active carbon in water containing a water-soluble binder. The method for producing the black colored paper mulch and the black colored paper mulch are each provided

In JP2000166398 a paper mulch sheet for paddy field is disclosed. A paper mulch sheet for a paddy field capable of improving water absorption at both ends of the sheet and raising adhesiveness to the paddy field by making Cobb water absorption per unit width at both end parts in the sheet laying direction have a specific value is disclosed. The paper mulch sheet for paddy field comprises a cellulose pulp as a main component has >=400 g/m2/min Cobb water absorption per unit width of 10-15 cm at both end parts in the sheet laying direction. In this case, preferably both the end parts contain a surfactant. The paper mulch sheet for paddy field can contain at least one kind of humic acid, a humate and carbon black.

In GB1236855 a method for the manufacture of fungus- resistant paper is disclosed. Fungus-resistant paper is made by adding to the pulp slurry from which the paper is to be made a solution of a hydroxyquinoline and a solution of a metallic salt and then forming paper from the slurry. The hydroxyquinoline may be 8-hydroxyquinoline , its dibromo- and diohloro-deri atives , 2-hydroxyquinoline, a salt of any of these or a mixture of two or more of these or their salts, and may be added in alkaline Cr acid solution. The metallic salt may be a salt of Cu, Zn, Al, Co, Mn, Ni , Fe or a mixture of at least two of these. In the examples: (8) 8- hydroxyquinoline is dissolved with sodium hydroxide in water and added to a slurry of kraft softwood fibres, a solution of copper sulphate is then added, followed by clay, carbon black and papermakers' alum, the slurry is then hydrated in a Jordan engine, and rosin sizing and urea- formaldehyde added, followed by polyacrylamide, the furnish is sheeted out on a Fourdrinier machine, pressed, partially dried, creped, and dried; (21) the paper in one example is

laminated to aluminium foil, using an acrylic latex

adhesive. The papers of the invention may be used as mulches, which may be worked into the soil after harvesting. The life of such sheets can be varied by varying the

proportion of quinolinolate, their soil-heating effect may be varied by varying their pigmentation and trace elements may be supplied to the soil by the use of appropriate quinolinolates . The paper in one of the examples may also be used as mulch, and moreover repels aphids .

In DE431565A1 a mixture for use as a mulch is

disclosed. This is used for protecting crop plants. It is also disclosed the use of carbon black and paper material.

In US3839139A a light-occluding sheet is disclosed whereby carbon black is used as a component therein.

In JP2013-176314 a mulching sheet material is disclosed where activated carbon is used.

These three disclosures all disclose carbon black, but not fibers thereof.

In WO2012101329 additionally a ground-cover mulch is disclosed, which includes a web-formed vegetable fibre- bearing pulp, and wood distillate. The wood distillate includes birch-wood distillate. In addition, the invention also relates to a method for manufacturing a ground-cover mulch and the use of birch-wood distillate in ground-cover- mulch applications.

There is thus a need for improved mulch comprising a carbon black material, which preferably emanates from a renewable resource.

Summary of Invention The present invention solves one or more of the above problems, by providing according to a first aspect a ground cover mulch, which includes a web-formed vegetable fibre- bearing pulp, and a carbon black wherein the carbon black contains one or more carbon black fibres.

Also provided according to a second aspect of the invention is a method for manufacturing a mulch according to the first aspect comprising the following steps: a) providing a never-dried pulp or dried pulp, and b) adding carbon black fibre (s) either at the wet end of a paper/board production line, or through surface sizing, or through coating, or through impregnation, or through spraying, or through spinning, or through foaming, or through dusting in said line.

Also provided according to a third aspect of the invention is a mulch obtainable by the method according to the second aspect.

Also provided according to a fourth aspect of the invention is the use of carbon black fiber in a mulch wherein preferably said fibre is of non-fossil origin, most preferred emanating from a wood material such as lignin, and especially preferred used in a mulch, especially according to the first aspect .

Also provided according to a fifth aspect of the invention is use of a mulch according to the first aspect or third aspect in cultivation.

Detailed description of the invention

It is intended throughout the present description that the expression "carbon black fiber" embraces any carbon black fiber that could be useful in a mulch context. Said carbon black fiber may have its origin from a fossil source or a non-fossil source.

The expressions "fiber" and "fibre" are used

interchangeably in the present specification.

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. 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 dissolved type. The pulp may also comprise textile fibers. The pulp may also come from agriculture (e.g. potato, bamboo or carrot) . The pulp may also be nanopulp (MFC) . 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) .

According to a further preferred embodiment of the product, i.e. mulch, according to the first aspect of the invention the carbon black fibre (s) has/have a length of up to about 6 mm. Said length may also be from about 3 to about 6 mm, which also includes about 4 mm. The fibers may also be part of a powder and thus provide a mixture.

According to a further preferred embodiment of the product, i.e. the mulch, according to the first aspect of the invention the carbon black is a mixture of fibres in nano and/or microsize. With this unit it is referred to the diameter of the particle or fiber as determined in dry form.

According to a further preferred embodiment of the product, i.e. mulch, according to the first aspect of the invention the carbon black fiber (s) emanates from lignin, cellulose or hemi-cellulose, preferably lignin. The lignin may also be an un-purified fraction of lignin from a process and thus it may also contain various amounts of salts and ashes. The carbon black fiber (s) may also emanate from lignin and cellulose/hemi-cellulose or lignin and molasses. According to a further preferred embodiment of the product, i.e. the mulch, according to the first aspect the carbon black fibre (s) emanates from a non-fossil source, preferably from a wood material, most preferred from lignin (which may e.g. have been obtained through the so called

LignoBoost-process as set out in WO2006031175 or through a process of Virdia as e.g. set out in WO2014179777 ) . The lignin may be an organosolv lignin.

According to a further preferred embodiment of the second aspect the carbon black fibre (s) emanates from a non- fossil source, preferably from wood material, most preferred from lignin, cellulose or hemi-cellulose , preferably lignin. The lignin may also be an un-purified fraction of lignin from a process and thus it may also contain various amounts of salts and ashes. The carbon black fiber (s) may also emanate from lignin and cellulose/hemi-cellulose or lignin and molasses .

The mulch according to the first aspect of the

invention may also contain additionally one or more other fillers. Calcium carbonate, talc, kaolin, precipitated carbonate, fly ash, carbonated fly ash, silica, Al-oxides (or mixtures thereof) are plausible as additional fillers.

It has as said surprisingly been found, that the use of carbon black fiber, preferably with length up to 50 mm, preferably up to 10 mm, most preferred up to 6 mm, can solve the above problems. The dosing of carbon fiber in the wet end is easier to retend than carbon black particles.

Moreover, the carbon fiber can also as said be a mixture of both nanosize fibers and microfibers, thus both contributing to the mechanical properties in different ways (mechanical vs optical) . The said carbon black fiber may also be applied on the web via coating as set out earlier. It is also possible to coat the carbon fiber by using e.g. surface sizing or blade coating, spraying or foaming or other methods known for a person skilled in the art. The carbon fiber is, as said, preferably made from lignin, most

preferred purified lignin using e.g. the Lignoboost process.

The lignin is a renewable material, and thus this solves the aforementioned problem with using a renewable resource. The carbon fiber may also be made from modified lignin in order to control its physical dimensions, mechanical properties or compatibility with cellulose fibers or fibrils or the components in the said matrix. It may also be engineered to provide anti-microbial properties or optimized thermal and optical properties.

The addition of the carbon black fiber is preferably, as said earlier, added at the wet end of a paper machine, such as a conventional paper making machine, e.g. as the Fourdrinier machine, where a stock of fibrous material is passed through a series of steps to form a paper web, or any other type of machine for providing a fibrous material such as a sheet of paper or board.

The mulch according to the first aspect of the

invention is preferably done with a wet-laid technique, but a dry laid technique is not excluded. Another option would be to spray it on the wire as set out earlier. Another option may be co-grinding or mixing with furnish. Another option may be using an impregnation step e.g. surface si zing .

The mulch according to the first aspect of the

invention may also contain various additives, which are needed for its performance and for process runnability, such as process chemicals e.g. retention chemicals, dewatering chemicals, strength chemicals etc. and performance chemicals e.g. dyes, strength chemicals, hydrophobi zing agents, etc.

The carbon black fiber, which may be coated as set earlier, may provide a surface hydrophobic nature, which even may be a selective hydrophobicity and degradability.

The carbon black fiber may also be surface treated / impregnated to provide dimensional stability.

The carbon black fiber (s) may also be selectively applied e.g. just on the edges.

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. The invention is further described in the following examples the only purpose of which is to illustrate the invention and are in no way intended to limit the scope of the invention in any way.

Brief description of figures

Fig. 1 discloses Basis Weight [ISO 536] (left) and Thickness [DIN 53105 Tl] (right) . Fig. 2 discloses bulk [DIN 53105 T2] .

Fig. 3 discloses Tear [ISO 53115] .

Fig. 4 discloses burst strength (ISO 2758) .

Fig. 5 discloses tensile force (ISO 1924-2) .

Fig. 6 discloses Tensile Index (ISO 1924-2) . Fig. 7 discloses tensile strength (ISO 1924-2^

Fig. 8 discloses Stretch at rupture (ISO 1924/2) Fig. 9 discloses Young's Modulus (ISO 1924/2) .

Example A test of carbon black fibres in paper furnish (for agricultural purposes) was done.

There were two different fiber lengths used, 3 and 6 mm (SIGRAFIL C C3 - 4.0 /240-GlO 0 376-003 and SIGRAFIL C C3- 4.0/240-G100 376-006 (both obtained from SGL Group)) .

7% of carbon fibers were mixed with the reference furnish from Kvarnsveden mill so that the ratio of the reference furnish remained. The pulp was a mix of TMP and Kraft ( frozen) .

Table 1: Trial points were:

Hot disintegration with TMP was used and 5 min standard disintegration at 2 % consistency with Kraft pulp. The carbon fibres were mixed in the pulp using 30 min. in an ultrasonic bath. The fibres were well separated and bundles could be minimized. The carbon fibres were pitched in a standard disintegrator. This gave 8 RK (Rapid Kothen - sheet forming equipment) sheets with 70 gsm.

Measurements were then done:

Breaking length, Tear Autoline and Burst resistance Table 2: results

The results are further highlighted through Figures 1 -

9.

It can e.g. be seen that tear index is improved at a fibre length of 6 mm.

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.