US20250051982A1

US20250051982A1 - Hemp hurd-based nonwoven material and related production method

Info

Publication number: US20250051982A1
Application number: US18/721,724
Authority: US
Inventors: Alessandro Gagliardini; Carmine Cimini; Renzo Marcello ODOARDI
Original assignee: Texol Srl
Current assignee: Texol Srl
Priority date: 2022-01-13
Filing date: 2023-01-12
Publication date: 2025-02-13
Also published as: EP4463589B1; ZA202404418B; WO2023135548A1; CO2024008394A2; MX2024008770A; CA3239945A1; EP4463589A1

Abstract

A non-woven material containing hemp hurd powders and/or fibrils and synthetic or natural fibers or a combination thereof is disclosed. The hemp hurd powders and/or fibrils are cohesive with the synthetic or natural fibers or a combination thereof. A method of making the same is also disclosed. The non-woven material has good absorbent power for biological liquids and is cheaper and a more sustainable material than the currently used materials such as cellulose pulp, synthetic fibers, cotton fibers, viscose fibers or superabsorbent polymers.

Description

FIELD OF THE INVENTION

The present invention relates to a non-woven material, and to the related preparation method, which allows to guarantee a good absorbent power towards biological liquids, by using a cheaper and more sustainable material than the currently used materials such as cellulose pulp, synthetic fibers, cotton fibers, viscose fibers or superabsorbent polymers. In particular, the invention relates to a non-woven material having absorbent properties and to the related production method, comprising a portion of hemp hurd powders and/or fibrils and a portion of synthetic or natural fibres or a combination thereof, characterized in that the hemp hurd powders and/or fibrils are cohesive with said synthetic or natural fibers or a combination thereof.

STATE OF ART

In the search for natural and environmentally friendly materials, hem, a renewable raw material, becomes increasingly important. Hemp fibers are mainly used, which can be processed for the production of hemp fiber fabrics, felts or thin sheets.
The hurd represents the wood part of the hemp plant at harvest time. In the stalk external portion there are fibers which originally can be even few-meter long. Such fibers, actually, consist of much smaller fibers adhesive through pectin. Generally, such type of fibers is called “Bast fibers”. Similarly to hemp, other plants are capable to provide Bast fibers and in particular they are: linen, kenaf, ramie and jute.
The composition of hurd and fibers varies mainly depending upon the hemp cultivar and the cultivation methods. In particular, by harvesting the plant before flowering, as generally one proceeds with cultivars from fiber, hurds and fibers with less amount of lignin are obtained; vice versa, in case of the seed variety, a much more lignified material is obtained. Even the processes thereto the plant is subjected after harvest, could influence the hurd features. In particular such processes are mechanical but even deriving from the prolonged contact of the hemp stalks with water or however under conditions of humidity presence, the so-called retting. During retting the stalk portions swell again, by making more labile the bonds among the various portions. Moreover, phenomena due to microbic and enzymatic activity appear. After a retting period, it is noted that the subsequent mechanical procedures for extracting and separating the fibers become easier.
Generally, during the procedures for separating the fibres from the hurd and during the subsequent procedures aimed at refining the fibers more and more (cottonization), ashes in relevant percentages are produced (around 10% by weight with respect to the obtained fibers) which currently are not used and generally are dispersed in the grounds.
By way of example, two analyses are reported relating the composition of the fibers and of the hurds from examples in literature:

TABLE 1

Typical composition of fibers
(Fibers 2019, 7, 106; doi: 10.3390/fib7120106)

				Hemi-				Micro-
		Cellulose	Lignin	cellulose	Pectin	Wax	Ash	fibrillary
Fiber	Origin	(%)	(%)	(%)	(%)	(%)	(%)	angle (°)

Hemp	Bast	70-74	3.5-5.7	15-20	0.8	1.2-6.2	0.8	2-6.2
Jute	Bast	61-72	12-13	18-22	0.2	0.5	0.5-2	8
Sisal	Leaf	78	8	10	—	2	1	—
Linen	Bast	64-72	2-2.2	18-20	1.8-2.3	—	—	5-10
Ramie	Bast	69-91	0.4-0.7	5-15	1.9	—	—	7.5
Harakeke	Leaf	56-64	7.8	23-31	—	—	—	—
Coconut	Fruit	36-43	0.15-0.25	41-45	3-4	—	—	30-49
fiber
Kenaf	Bast	45-57	22	8-13	0.6	0.8	2-5	2-6.2

TABLE 2

Typical composition of the hurd (Naithani et al. (2020). “Ecofriendly
prod. Hemp fibers”, Bioresources 12(1), 706-720)

					Hemicellulose
Raw	Cellulose	Lignin	Extractives	Ash	and
material	(%)	(%)	(%)	(%)	Pectin (%)*

Hemp hurd	42.0	27.4	2.2	1.4	27.0
Hardwood	44.2	26.9	3.7	1.1	23.7²

¹The content of Pectin and Hemicellulose was calculated by subtracting the sum of the content of cellulose, lignin, extractives and ashes from 100%;
²Hemicellulose only

As it can be noted from the above tables, the hemp fibers have a low lignin tenor whereas the hurd would have a lignin tenor similar to the hardwood wood (for example eucalyptus). Therefore, from these data one could expect a low absorption of liquids by the hurd. Moreover, it is known that products apparently similar to hurd, such as cuttings of wheat stalks, rice hull or corn stalks, are not hydrophilic. This due to the high content in lignin, to the presence of wax and of cutin.
The patent application WO 9965535 shows the use of ground hemp hurd as absorbent material for biological fluids, however it does not provide any indication about how obtaining a non-woven material by using ground hemp hurd.
Then, there is the need for providing a non-woven material and the related production method, allowing to guarantee a good absorbent power towards biological liquids, by using a cheaper and more sustainable material than the currently used materials such as cellulose pulp, synthetic fibers, cotton fibers, viscose fibers or superabsorbent polymers.

BRIEF DESCRIPTION OF THE INVENTION

The technical problem of providing a non-woven material allowing to guarantee a good absorbent power towards biological liquids, by using a cheaper and more sustainable material than the currently used materials such as cellulose pulp, synthetic fibers, cotton fibers, viscose fibers or superabsorbent polymers, is solved by the present invention, which provides a non-woven material comprising a portion of hemp hurd powders and/or fibrils and a portion of synthetic or natural fibers or a combination thereof, characterized in that said hemp hurd powders and/or fibrils are cohesive with said synthetic or natural fibers or a combination thereof, and the related preparation method.
The method, the invention relates to, provides to integrate hemp hurd powders or fibrils in the most common methods for manufacturing non-woven materials such as spunlace, air-laid, wet-laid, coform or combinations thereof.
The presence of hemp hurd powders or fibrils confers high adsorbent properties to the non-woven material, comparable to those of the most common absorbent materials used for products for hygienic-sanitary use such as the cellulose pulp, by allowing to reduce considerably the production costs, generally being waste obtained from the production and refining of hemp fibers. Moreover, the use of hemp hurd as replacement of conventional absorbent materials, such as the cellulose pulp or other absorbent fibers used in the implementation of the absorbent layers of the hygiene products represents an advantage form the point of view of sustainability and environment preservation. In fact, the hemp-based products used in the present development do not require the use of transformation chemical processes (such as for example in case of the wood or viscose cellulose pulp), on the contrary only of extraction mechanical processes, separation from the plant and reduction of sizes of hurd fragments (for example through grinding). Moreover, the hemp plant cultivation is a spring crop which, typically performed in the countries with temperate climate such as Italy, Central Europe and East Europe, does not require water supply, use of chemical fertilizers and pesticides, thus resulting to be a particularly sustainable crop.
The materials used in the present invention preferably come from plantations of so-called industrial hemp, plants which contain amounts of Tetra Hydro Cannabinol contained within the threshold established by the law, that is between 0.2% and 0.6% by weight.
Therefore, the present invention relates to a non-woven material comprising hemp hurd powders and/or fibrils and synthetic or natural fibers or a combination thereof, characterized in that said hemp hurd powders and/or fibrils are cohesive with said fibers.
A method for preparing a non-woven material comprising a portion of hemp hurd powders and/or fibrils and a portion of synthetic or natural fibers or a combination thereof, characterized in that is comprises a step of cohesion of said hemp hurd powders and/or fibrils with said fibers.

DETAILED DESCRIPTION OF FIGURES

FIG. 1 . Preparation of the absorption test of samples A and B

The tests for evaluating the absorption of the hurd-based material were of two types: the evaluation of the so-called free absorption and the under-pressure absorption.

FIG. 1 shows the scheme of the absorbent structure which is used to carry out the under-pressure absorption test. In the base 4 layers of cellulose filter paper are placed, each one having sizes of 10×10 cm and grammage of 150 g/m2. Above such layers a non-woven fabric (air-through bonded—ATB technology) based on polyester-polyethylene (PET-PE) two-component fibers. The dimensions are of 10×10 cm and the grammage of 20 g/m2. Above such layer the wet hurd powder coming from the free absorption test is placed and at last above such later an ATB non-woven fabric of the same type, dimensions and grammage of the underlying one is placed.

FIG. 2 . 20× and 100× images by optical microscope of the tested samples A and B. From the morphological point of view the two samples A and B were analysed in the optical microscope. In particular, it is noted that the morphology of the samples apparently is similar (sample B appears more agglomerated, but after contact with water it disperses completely in smaller portions) and they result to consist of a mixture of fibrils and particles with various dimension. The following photos are obtained at 20× and 100×.

FIG. 3 . Photo of the first part of the free absorption test wherein the hurd powder is placed in contact with saline solution in a beaker.

FIG. 4 . Photo of the second phase of the free absorption test wherein the wet hurd powder is separated from the excess of not absorbed saline solution by filtration on paper filter whatman.

FIG. 5 . Photo wherein the absorbent web containing the wet hurd powder is subjected to Edana 151.3-02 test modified as reported in the section “Examples”.

DETAILED DESCRIPTION

The present invention relates to a non-woven material comprising hemp hurd powders and/or fibrils and synthetic or natural fibres or a combination thereof, characterized in that said hemp hurd powders and/or fibrils are cohesive with said fibres.
In the present description, under the term “cohesive” one relates to the powders and/or fibrils which can be cohesive physically, preferably through an entanglement or cohesive thermally, for example through a thermal treatment which allows to melt the hemp hurd powders and/or fibrils with the synthetic or natural fibers.
In an embodiment of the invention, said hemp hurd powders and/or fibrils are obtained by a process for pulverizing or decreasing dimensions of hemp hurd in a range from 1 μm to 2000 μm, preferably by grinding.
During the process for separating the hemp fibers form the plant (scutching), the separation of the wood portion (hurd) is obtained too, both as fragments which can be sent to an additional grinding process or as powders which are generated during the process itself and then separated from the fibers. Such powders could be suitable as material for the present development.
Moreover, during the processing and refining of the hemp fibers (process often called “cottonization” of the hemp fibers) obtained by subjecting the raw fibres to the action of the so-called “wool” cards, fractions under the form of powders are obtained which can result to be suitable for the present development.
Another embodiment of the invention consists in subjecting to grinding the whole plant coming, for example, from the “retting” process. In this case the product will be a mixture of hurd and fibers having length of around 1-10 mm so that such product results to be processable in the processes which will be described hereinafter as air-laid, wet-laid, coform and similar or correlated processes.
In an embodiment, said hemp hurd powders and/or fibrils are present in a range from 1% to 100% w/w.
In a preferred embodiment, said hemp hurd powders and/or fibrils are present in a range from 10% to 50% w/w.
In an additional embodiment, said powders have a dimension from 1 μm to 2000 μm, and said fibrils have dimensions from 1 to 20 cm.
In a preferred embodiment, said powders have a dimension from 10 μm to 600 μm, and said fibrils have dimensions from 50 to 2000 cm, preferably from 100 to 1000 μm.
In an embodiment, according to any one of the herein described embodiments, said synthetic or natural fibers are selected from a list consisting of nylon, polyester, polypropylene, polyethylene, cotton, linen, ramie, jute, cellulose pulp, viscose, superabsorbent polymers, thermoplastic fibers, Cellulose acetate, acrylic fibers.
According to an embodiment of the invention, said synthetic or natural fibers or a combination thereof, are present in a range from 0 to 95 w/w, preferably from 20% to 80% w/w.
In a preferred embodiment, said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof, are in a weight ratio therebetween (hurd/other fibers) from 5:95 to 95:5.
According to an additional embodiment, according to all herein described embodiments, said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof, are in a weight ratio therebetween from 80:20 to 20:80, preferably from 30:70 to 50:50.
In another embodiment, the non-woven material, the invention relates to, further comprises a binding agent.
Generally, the binding agent is a latex of the types known to the state of art. Such latices are mainly used in manufacturing air-laid non-woven fabrics. Generally, such latices are based on emulsions of polyacrylate polymers. In a preferred embodiment, said binding agent is selected among a list of binding agents which can be found in the application US 20070167096. In the present invention one tends to prefer the use of binding agents of natural origin such as those commercialized by the Swedish firm OrganoClick (www.organoclick.com) and in particular the biobinders called OC-Biobinder Lily and OC-Biobinder Clover.
Apart from the above-mentioned OC-Biobinder Lily, OC-Biobinder Clover, in the present development the “latex binders” can be used, known to the state of art as polymeric dispersions based on polyvinyl esters such as polyvinyl acetate or acrylics or vinyl acrylics.
Such latices generally include crosslinkable comonomers and they can include additives specific to the purpose such as the addition in the polymeric emulsion of crosslinking resins in combination with catalysts.
In the US application Nr. 20070167096 such latex binders are described more in details.
In an embodiment, such binding agent is present in a range from 0% to 30% w/w.
In a preferred embodiment, such binding agent is present in a range from 2% to 10% w/w.
According to an embodiment, the non-woven material of the invention is obtained by a process providing the deposition of a layer of said hemp hurd powders and/or fibrils between two layers of synthetic or natural fibers or a combination thereof.
In a preferred embodiment, the non-woven material, the invention relates to, is obtained by a spunlace, wet-laid, coform process or combinations thereof.
The traditional spunlace process is characterized by an entanglement of the fibers through under-pressure very thin water jets (hydro-entanglement). An example of such process is described in the Canadian patent Nr. 841,938. More generally, the process uses staple fibers, typically with title of 1-10 dtex and length approximately around 40 mm. Such fibers are sent to a card which orients the fibers and produces a carded product which is subsequently subjected to the cohesion by entanglement with water jets. At this point the non-woven fabric has to be dried up, a procedure which is performed by sending the non-woven fabric in an oven. At the end, the material is wound in coils which subsequently can be subjected to subsequent cutting or winding procedures.
Under the term “card” one relates to a machine for carding the textile fibers, consisting of a rotating drum (called big drum), coated with tips (teasels), at the periphery thereof two types of smaller rotating cylinders are arranged, with alternated arrangement, provided too with teasels, and respectively called workers, which allow to card the fiber when this passes therebetween and the bid drum, and cleaners, which have the function of stripping the workers and bringing the fibers back on the big drum; the carded fiber is then ceased to another cylinder, called discharger, therefrom it can be collected in form of veil.
The traditional air-laid process uses short fibers such as the fibers of cellulose pulp (length about 1-4 mm). The process consists in dispersing the fiber in an air current by transporting the fibers through perforated rotary cylinders (or other distribution systems) and depositing them above the perforated surface (mat) by forming a web. Generally, the vacuum through the perforated surface is used to help and facilitate the process for depositing the fibers. Upstream of this process, in particular when cellulose pulp is used, which usually is commercialized in sheets or compact tapes, such material is sent to apparatuses such as, for example, a hammer mill which performs a break of the sheet by forming as output discrete fibers which are captured by the air current and enter the air-laid formation process. In order to increase the resistance, to the cellulose fibers two-component synthetic fibers or synthetic latices can be mixed which, after a passage in oven, will constitute additional bonds in the web capable to increase the resistance thereof. A description of the air-laid process with discussion of the various systems to perform a cohesion can be found in the site: http://www.dan-web.com/what-is-airlaid.html.
In the wet-laid traditional process, staple fibers with a length up to 12 mm, are very often mixed with viscose and cellulose pulp which are suspended in water, by using big tanks. Subsequently, the water-fiber or water-cellulose pulp dispersion is pumped and deposited continuously on a forming wire. The water is sucked, filtered and recycled.
The traditional coform process provides to obtain a composite material comprising a mixture consisting of a stabilized matrix of thermoplastic fibers and of a second material. In particular, the second material generally includes absorbent fibers such as cellulose pulp, cotton, rayon and even superabsorbent polymers. Examples of coform materials are shown in the U.S. Pat. Nos. 5,350,624, 4,100,324, 4,818,464 and WO 03/052191A1. In the coform process the stabilized matrix is obtained by extruding continuously hot-melt polymers such as polypropylene, polyethylene terephthalate or polylactic acid.
According to an embodiment, said hemp hurd powders and/or fibrils and said synthetic or natural fibers are cohesive by hydroentanglements, thermal bonding, melting of hot-melt fibers, calender bonding, needle punching. Then, it is possible, during the veil carding process, to incorporate hot-melt fibers such as for example two-component fibers which, once reached the drying oven, tend to melt the low melting polymeric component and then to bind the veil fibers. Examples of such fibers can be polyester-polyethylene (PET-PE), polyester-copolyester (PET-CoPET), polyester-polypropylene (PET-PP) and polypropylene-polyethylene (PP-PE).
The hydroentanglement is a gluing process for moist or dry fibrous tapes implemented by carding, air-laid or wet-laid, wherein the resulting bound fabric is a non-woven fabric. It uses thin and high-pressure water jets which penetrate in the tape, they hit the conveyor belt (or “thread” as in the conveyor for manufacturing paper) and bounce back by entangling the fibers.
According to an embodiment, the non-woven material, the invention relates to, is characterized by the fact that said hemp hurd powders and/or fibrils confer to said non-woven material absorbent properties. In the Examples of the following chapter data are shown which demonstrate the absorbent power of the hemp hurd powders and/or fibrils included in the non-woven material of the present invention.
In an embodiment, the non-woven material, the invention relates to, is provided under the form of absorbent wipes, cloths for cleaning or drying surfaces, tablecloths and napkins, absorbent core for hygienic products such as panty liners, menstrual pads, baby diapers, adult diapers, absorbent mats. Moreover, the subject material can be used as absorbent material of products for medical use such as plasters, bandages and as part of laminates for use as medical gowns. In the cosmetic field the material, the invention relates to, can be used as substrate for beauty masks.
An additional object of the present invention is represented by a method for the preparation of a non-woven material comprising a portion of hemp hurd powders and/or fibrils and a portion of synthetic or natural fibers or a combination thereof, characterized in that is comprises a step of cohesion of said hemp hurd powders and/or fibrils with said fibers.
In a preferred embodiment, the method comprises the following steps:

- i) arrangement of a first layer of natural or synthetic fibers or a combination thereof;
- ii) deposition of a layer of hemp hurd powders and/or fibrils on said first layer of natural or synthetic fibers or a combination thereof obtained in step i);
- iii) cohesion of said first layer of fibers with said layer of hemp hurd powders and/or fibrils;
- iv) deposition and subsequent cohesion of a second layer of natural or synthetic fibers or a combination of them with the product obtained in step iii);
- v) drying in an oven at a temperature from 90 to 250° C. for a period of time from 5 to 60 seconds of the product obtained from step iv) to obtain a non-woven material with absorbent properties.
  Currently the cellulose pulp is inserted in coils, before mills, on the contrary as to the replacement of the cellulose pulp with the hemp hurd powders and/or fibrils of the present invention, this can be provided in several ways:
- a) compressed in balls and then opened,
- b) directly ground by the mills,
- c) already in powder and then by-passing the mills and using pneumatic suction systems.

In an embodiment, said hemp hurd grinding process at step i) is performed, for example, by using hammer mills.
In an embodiment of the method of the present invention, said hemp hurd powders and/or fibrils are present in a range from 1% to 100% w/w.
In a preferred embodiment of the method of the present invention, said hemp hurd powders and/or fibrils are present in a range from 20% to 50% w/w.
In an embodiment of the method of the present invention, said powders have a dimension from 1 μm to 2 mm and said fibrils have dimensions from 100 μm to 20 cm.
In a preferred embodiment of the method of the present invention, said powders have dimensions from 10 μm to 600 mm and said fibrils have dimensions from 200 μm to 1000 cm.
In an embodiment of the method of the present invention, said synthetic or natural fibers are selected from a list consisting of nylon, polyester, polypropylene, polyethylene, cotton, linen, ramie, jute, cellulose pulp, viscose, superabsorbent polymers, thermoplastic fibers, cellulose acetate fibers, acrylic fibers.
According to another embodiment of the method, the invention relates to, said synthetic or natural fibers or a combination thereof, are present in a range from 20% to 80% w/w.
In a preferred embodiment of the method of the present invention, said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof, are in a weight ratio therebetween (hurd/fibers) from 90:10 to 10:90.
In an embodiment, said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof, are in a weight ratio therebetween from 30:70 to 50:50.
According to an embodiment, said step ii) of obtaining a first layer of natural or synthetic fibers or a combination thereof is carried out in a spunlace process by a first card (Card A).
In an additional embodiment, said step iii) for depositing a layer of hemp hurd powders and/or fibrils is carried out by means of an air-laid formation head or an application system based on wet-laid technology. Both the air-laid and wet-laid technology are suitable to deposit and create webs consisting of particles and short fibres (such as the cellulose pulp or the hurd or other types of fibres having length from 1 mm up to 10 mm). These processes can exploit an aerodynamic principle where the particles are dragged by an air current (air-laid) or can exploit a hydrodynamic principle where the particles are dragged by a liquid such a water (wet-laid).
According to an embodiment, said step iv) of obtaining a second layer of natural or synthetic fibers or a combination thereof is carried out in a spunlace process by a second card (Card B).
In another embodiment, according to any one of the herein described embodiment, said cohesion of said layer of hemp hurd powders and/or fibrils with said layer of natural or synthetic fibres or a combination thereof, is obtained by hydroentanglement, thermal bonding, melting of hot-melt fibers, calender bonding, needle punching.
In an embodiment, the method described in the present invention further comprises at least a step of adding a binding agent.
In an embodiment, said binging agent is present in a range from 0% to 30% w/w. In a preferred embodiment, said binding agent is present in a range from 2% to 10% w/w.
Generally, the binding agent is a latex of the types known to the state of art. Such latices are mainly used in the manufacture of the air-laid non-woven fabrics. Generally, such latices are based upon emulsions of polyacrylate polymers. In a preferred embodiment, said binding agent is selected among a list of binding agents which can be found in the application US 2007016796. In the present invention one tends to prefer the use of binding agents of natural origin such as those commercialized by the Swedish firm OrganoClick (www.organoclick.com) and in particular the biobinders called OC-Biobinder Lily and OC-Biobinder Clover.
Apart the above-mentioned OC-Biobinder Lily, OC-Biobinder Clover, in the present development the “latex binders” can be used, known to the state of art as polymeric dispersions based on polyvinyl esters such as polyvinyl acetate or acrylates or vinyl acrylates.
In any part of the present description and the claims, the term comprising can be replaced by the term “consisting of”.
Hereinafter examples are shown which have the purpose of illustrating better the methods disclosed in the present description, such examples are in no way to be considered a limitation of the preceding description and of the subsequent claims.

EXAMPLES

Absorbent Power of the Hurd-Based Materials

Tests are reported in which the absorbent power of hurd-based powders coming from two different sources was measured: sample A comes from fiber hemp cultivated in Emilia and sample B comes from hemp cultivated in the area of Taranto. Such samples were compared to the cellulose pulp collected from a female pad.
The absorption of the samples was measured in two ways: the free absorption was evaluated by putting 1 g of sample in contact with 50 ml of 0.9% NaCl saline solution. After 10 minutes the sample was filtered by using Whatman paper and leaving to drop for 10 minutes. At the end, the sample was weighed and the absorbance calculated with the following formula:
Absorption(g/g/=(wet weight−dry weight)/dry weight
The liquid retention was measured by distributing the previously obtained wet sample above 4 layers of absorbent paper (12×12 cm each) and by placing above the sample 2 layers (20 g/m2 each one) of PET-PE non-woven fabric (obtained with Air-Through-Bond technology). The test preparation is shown in FIG. 2 .
Afterwards, such absorbent web is subjected to pressure through “Lenzing Wetback” apparatus by operating according to the Edana 151.3-02 method, modified since a test piece as the described one is prepared. After executing the test, the hurd powder is recovered weighed and one determines again the absorption which at this time assumes the name of retention, measured as g/g.
Retention(g/g)=(wet weight after wet back−dry weight)/dry weight


	Absorbance	Retention
	g/g	g/g

Reference (cellulose	15.2	3.0
collected from female pad)	13.2	2.9
	14.5	2.85
Hurd sample A	10.0	4.0
	10.6	4.3
	8.7	4.0
Hurd sample B	6.0	2.3
	6.3	2.55
	6.1	2.4

In particular the hurd sample A provides very good and improved saline solution retention values with respect to the reference cellulose pulp.

Incorporation of the Hurd-Based Materials in Non-Woven Fabrics

The hurd-based products can be incorporated in the non-woven fabrics in particular by using the following technologies.

Spunlace Process.

The spunlace process is characterized by an entanglement of fibers through under pressure very fine water jets (hydro-entanglement). An example of such process is described in the Canadian patent N. 841,938. More generally the process uses staple fibres, typically with title of 1-10 dtex and length roughly around 40 mm. Such fibers are sent to a card which orients the fibers and produces a carded product which is subsequently subjected to cohesion through entanglement with water jets. At this point the non-woven fabric has to be dried, a procedure which is performed by sending the non-woven fabric in an oven. In the end, the material is wound in coils which subsequently can be subjected to subsequent cutting or winding procedures.
The use of a spunlace process with a configuration with two cards (card A and card B), having an air-laid formation head therebetween (the air-laid process is described hereinafter), appear to be very convenient within the present development. Practically a first veil consisting of long fibres (about 40 mm-staple fibers) is produced by the card A, on such veil, after undergoing a first cohesion through waterjets (water entanglement station), a layer of hurd powder or short fibers (less than 2 mm) is deposited. Afterwards, the card B puts a veil of long fibers (about 40 mm-staple fibers) above the hurd layer, which veil, after entanglement with water jets and drying in oven, will produce a non-woven fabric incorporating the stabile hurd.
A variation in such scheme could consist in using, as replacement of the air-laid head, a system for applying the hurd fiber or short fibers based on wet laid technology. The wet-laid is a process similar to the paper manufacturing and substantially would deposit on a filter the powder or the hurd fibrils transported through water.

Air-Laid Process.

The air-laid process uses short fibers such as the cellulose pulp fibers (length about 1-4 mm). The process consists in dispersing the fibers in an air current by transporting the fibers through perforated rotary cylinders (or other distribution systems) and by depositing them above the perforated surface (mat) by forming a web. Generally, the vacuum through the perforated surface is used to help and facilitate the process of depositing the fibers. Upstream of this process, in particular when cellulose pulp is used, which usually is commercialized in sheets or compact tapes, such material is sent to apparatuses such as, for example, a hammer mill which performs a break of the sheet by forming as output discrete fibers which are captured by the air current and enter the air-laid formation process. In order to increase the resistance, to the cellulose fibers two-component synthetic fibers or synthetic latices can be mixed which, after a passage in oven, will constitute additional bonds in the web capable to increase the resistance thereof. A description of the air-laid process with discussion of the various cohesion systems can be found in the site: http://www.dan-web.com/what-is-airlaid.html.
Currently, the cellulose pulp is inserted in coils, before mills, on the contrary as to the replacement of the cellulose pulp with the hemp hurd powders and/or fibrils of the present invention, this can be dosed in several ways:

- a) compressed in balls and then opened,
- b) directly ground by the mills,
- c) already in powder and then by-passing the mills and using pneumatic suction systems.

Coform Process.

The so-called coform process designates a composite material comprising a mixture consisting of a stabilized matrix of thermoplastic fibers and a second material. In particular the second material generally includes absorbent fibers such as cellulose pulp, cotton, rayon and even superabsorbent polymers. Examples of coform materials are shown in the U.S. Pat. Nos. 5,350,624, 4,100,324, 4,818,464 and WO 03/052191A1.
The coform process and assimilable processes is very interesting since the stabilized matrix is obtained by extruding continuously hot-melt polymers such as polypropylene, polyethylene phthalate or the polylactic acid.
In the production scheme from FIG. 2 of the patent PCT/US02/13333, described as coform between melt blown microfibers and short fibers, a process is illustrated wherein short fibers such as cellulose pulp, suitably replaceable with the hemp hurd powders and fibrils of the present invention, can be inserted in the middle of a structure consisting of a melt blown microfibers. In particular, the insertion point of the hurd corresponds to 136 whereas the point 130 corresponds to the area wherein the impact between the microfibers and the hurd powder/fibers (impingement point) takes place.

Claims

1. A non-woven material comprising hemp hurd powders and/or fibrils and synthetic or natural fibers or a combination thereof, wherein said hemp hurd powders and/or fibrils are cohesive with said fibers.

2. The non-woven material according to claim 1, wherein said hemp hurd powders and/or fibrils are obtained by a process of pulverizing or reducing the dimensions of hemp hurd in a range from 1 μm to 2000 μm.

3. The non-woven material according to claim 1, wherein said hemp hurd powders and/or fibrils are present in a range from 1% to 100% w/w.

4. The non-woven material according to claim 1, wherein said powders have a dimension from 1 μm to 2000 μm, and said fibrils have dimensions from 50 μm to 2000 μm.

5. The non-woven material according to claim 1, wherein said synthetic or natural fibers are present in a range from 0% to 99% w/w.

6. The non-woven material according to claim 1, wherein said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof are in a weight ratio therebetween from 5:95 to 95:5.

7. The non-woven material according to claim 1, further comprising a binding agent present in a range from 0% to 30% w/w.

8. The non-woven material according to claim 1, obtained by a process providing the deposition of a layer of said hemp hurd powders and/or fibrils between two layers of synthetic or natural fibers or a combination thereof.

9. The non-woven material according to claim 1, wherein said hemp hurd powders and/or fibrils and said synthetic or natural fibers are cohesive by means of hydro-entanglement, thermal bonding, melting of hot-melt fibers, calender bonding, or needle punching.

10. The non-woven material according to claim 1, wherein said hemp hurd powders and/or fibrils confer absorbent properties to said non-woven material.

11. A method for preparing a non-woven material comprising a portion of hemp hurd powders and/or fibrils and a portion of synthetic or natural fibers or a combination thereof, comprising a cohesion step of said hemp hurd powders and/or fibrils with said fibers.

12. The method according to claim 11, comprising the following steps:

i) arranging a first layer of natural or synthetic fibers or a combination thereof;

ii) depositing a layer of hemp hurd powders and/or fibrils on said first layer of natural or synthetic fibers or a combination thereof obtained in step i);

iii) cohering said first layer of fibers with said layer of hemp hurd powders and/or fibrils;

iv) depositing and subsequent of cohering a second layer of natural or synthetic fibers or a combination thereof with the product obtained in step iii); and

v) drying in an oven at a temperature from 90 to 250° C. for a period of time from 5 to 60 seconds of the product obtained from step iv) to obtain a non-woven material with absorbent properties.

13. The method according to claim 12, wherein the hemp hurd powders in step ii) is are obtained by means of a hammer mill or equivalent systems.

14. The method according to claim 11, wherein said hemp hurd powder and/or fibrils are present in a range from 1% to 100% w/w.

15. The method according to claim 11, wherein said hemp hurd powder and/or fibrils and said synthetic or natural fibers or a combination thereof, are in a weight ratio of from 10:90 to 90:10.

16. The non-woven material according to claim 3, wherein said hemp hurd powders and/or fibrils are present in a range from 10% to 50% w/w.

17. The non-woven material according to claim 4, wherein said powders have a dimension from 10 μm to 600 μm, and said fibrils have dimensions from 100 to 1000 μm.

18. The non-woven material according to claim 5, wherein said synthetic or natural fibers are present in a range from 20% to 80% w/w.

19. The non-woven material according to claim 6, wherein said hemp hurd powders and/or fibrils and said synthetic or natural fibers or a combination thereof are in a weight ratio of from 30:70 to 50:50.

20. The non-woven material according to claim 7 where the binding agent is present in a range from 2% to 10% w/w.